USACERL TR 96/104

17

MILD CARBON STEEL

COPPER-BEARING STEEL

WEATHERING!STEEL

AVE, PENETRATION PER SIDE , mile

° 4 6 12 16
EXPOSURE TIME, YEARS

(Adapted from Horton, not dated).

Figure 4. Comparison of atmospheric corrosion behavior of several steel types.

corrosion penetration of several steels exposed to an industrial environment
(Horton, not dated). Corrosion nearly stops after 3 years in the weathering steel;
however, corrosion continues in both the plain carbon and copper-bearing steel,
although the copper-bearing steels corrode at about half the rate of the plain carbon
steels.

Unfortunately little data is available on the atmospheric corrosion behavior of the
A710 type steels. Although their compositions are similar to weathering steels, it
is not clear how the higher copper and finer microstructure affect the A710 steels’
corrosion behavior. However, most steelmakers agree that the corrosion rates
should be a least similar to the copper-bearing steels. Corrosion research has been
performed for the U.S. Navy and has concentrated on marine environments and
stress corrosion cracking susceptibility. These results indicate these steels have
good resistance to stress-corrosion cracking in marine environments (Aylor et al.,
May 1990).

Weldability

The weldability of the HSLA steels has been extensively studied over the past 10
years (Wilson, March 1987; Lundin, Menon, and Lawson, December 1989; Kvidahl,
July 1985; Deb, Challenger, and Burna, November 1985; Wallace and Heid,



38 USACERL TR 96/104

References

Abe, T., M. Kurihara, and H. Tagawa, “Thermo-Mechanically Processed High Copper Bearing Steel
Plates,” Microalloyed HSLA Steels, Proceedings of Microalloying ’88/1988 World Materials
Congress, Chicago, IL (American Society for Metals [ASM] International, Materials Park, OH,
September 24-30, 1988), pp 581-588.

Anderson, T.L., J.A. Hyatt, and J.C. West, “The Benefits of New Higher Strength Low-Alloy (HSLA)
Steels,” Welding Journal, vol 66, no. 9 (September 1987), pp 21-27.

Aylor, D.M., R.A. Hays, R.E. Rebis, and E.J. Czyryca, Corrosion and Stress Corrosion of HSLA-100
Steel, DTRC/SME-90/17 (David Taylor Research Center’ [DTRC], May 1990).

Baker, H., ed., “Alloy Phase Diagrams,” ASM Handbook, vol 3 (ASM International, Materials Park,
OH, 1992), p 2.168.

Balaguer, J.P., Z. Wang, and E.F. Nippes, “Stress-Relief Cracking of a Copper Containing HSLA
Steel,” Welding Research (Supplement to Welding Journal), vol 68, no. 4 (April 1989), pp
121s-131s.

Bollinger, W., R. Varughese, E. Kaufmann, W.-F. Qin, A.W.Pense, and R.D. Stout, “The Effect of
Welding and Fabrication Operations on the Toughness of A710 Steel,” Microalloyed HSLA
Steels, Proceedings of Microalloying 88/1988 World Materials Congress, Chicago, IL (ASM
International, Materials Park, OH, September 24-30, 1988), pp 277-290.

Castner, H.R., T. Jutla, V. Linse, and J. Smith, “Welding Procedures for Tough HAZ’s in Copper-
Strengthened HSLA Steels,” Abstracts of Papers Presented at 74th American Welding Society
Annual Meeting, Houston, TX (American Welding Society, Miami, FL, April 25-29, 1993), pp
112-114.

Churchill, R.K., J.H. Devletian, and D. Singh, High Yield Strength Cast Steel with Improved
Weldability, Program Report No. 0326 (National Shipbuilding Research Council [NSRC], May

1991).

Davis, O.J., “Welding Research for Shipbuilding, The SP-7 Panel Program from 1972 to 1992,”
Program Report No. 0364 (NSRC, November 1992).

* Now Naval Surface Warfare Center, Annapolis, MD.


34

USACERL TR 96/104

approach-and perhaps a more near-term solution—is welding with undermatched
weld metals. This is the current approach the U.S. Navy has taken on some of its
HSLA-100 decking weldments. This approach generally requires a case-by-case
evaluation in which the joint geometry and configuration are examined to determine
the ability of the constraint offered to raise effectively the yield strength of the
confined weld metal similar to the effect noted in braze joints.

Considerable work is ongoing to develop better high strength weld metal. Currently
the National Center for Excellence in Metal Working Technology (NCEMT) in con-
junction with the Naval Surface Warfare Center (formerly David Taylor Research
Center) is directing a three-phase program to develop advanced welding consum-
ables for high strength steels. The first phase, which involved participation from the
Oregon Graduate Institute and the Ohio State University, evaluated 15 experimen-
tal compositions at two heat inputs. The results from these experiments have lead
to the development of 10 additional wire compositions that are targeted to meet the
program goals of strength and toughness. These experimental gas metal are
welding wires are being produced by Alloy Rods. Delivery of these wires has been
made for Phase 2 testing of the weld metals at NCEMT. After Phase 2 testing, a
decision will be made on the viability of a commercialization phase, Phase 3.
Preliminary testing of the experimental weld metals on HSLA-100 at three different
heat inputs and no preheating have shown no cracking.

Other weld metal development work sponsored by the National Shipbuilding
Research Program is ongoing at the Colorado School of Mines. The objective of this
project is the development of shielded metal arc electrodes for HSLA-100. Titanium
and other microalloy additives are being used to produce desirable fine grain ferritic
structure to modify the basic martensitic/bainitic metallurgy. This approach is
aimed at meeting the yield strength and toughness requirements for HSLA-100 and
to improve resistance to hydrogen-assisted cracking (Davis, November 1992).

The relatively severe sensitivity of the base materials to reheat cracking has lead
to at least one major failure. Potential users of the HSLA steels are generally aware
of this problem and in some instances appear to have become conservative in their
approach to fabrication of these steels. The ability to refine the coarse grained HAZ,
and thus significantly reduce the potential for reheat cracking, has lead some to
consider the application of what is now termed controlled-deposition techniques for
HSLA steel fabrication. There has been some concern that the sensitivity to reheat
cracking could lead to interbead HAZ cracking as a result of the reheating of a
coarse grained HAZ from subsequent passes; however, no failures have been
attributed to this mechanism. The probability of this mechanism occurring is small
unless associated with an interbead discontinuity such as lack of fusion. The
application of a controlled deposition technique has been considered to avoid the
possibility of interbead cracking. This approach appears to be overly conservative.


USACERL TR 96/104

43

Hackett, E.M., L.R. Link, and J.M. Blackburn, Metallurgical, Mechanical Property, and Weldability
Evaluation of Commercial Accelerated Cooled (AC) /Direct Quenched (DQ) Steels, DTRC/SME-
89/56 (March 1990).

Knight, D.E., and J.R. Carlberg, Shock Performance Evaluation of HSLA-100 Foundation Structures,
DTRC/SSPD-90-172-1 (October 1989).

Link, L.R., Fatigue Crack Growth of 5456-H116 Aluminum and HSLA-80 Weldments,
DTRC/SME-88/39 (July 1988).

Link, L.R., and R.W. Armstrong, Microstructural and Mechanical Properties of Two Candidate HSLA-
65 Controlled Rolled Steels, DTRC/SME-88/29 (June 1988).

Link, R.E., and E.J: Czyryca, Mechanical Property Characterization of HSLA-100 Steel Plate, DTRC/
SME-88/38 (December 1988).

Lukens, W.E., Mechanical Properties of Buried Gas Tungsten Arc HY-100 and HSLA Steel Weldments,
DTNSRDC/SME-84/124 (January 1985).

McCaw, R.L., and R.T. Brenna, A Preliminary Evaluation of Weldments Produced in Thick-Section
NICOP HSLA Steel, DINSRDC/ TM-28-82-151 (September 1982).

McCaw, R.L., and R.J. Wong, Welding of HSLA-80 Steel, DINSRDC/SME-85/32 (June 1985).

Montemarano, T.W., R.T. Brenna, T.E. Caton, D.A. Davis, R.L. McCaw, L.J. Roberson, T.M.
Scoonover, and R.J. Wong, Results of the Evaluation of ASTM A710, Grade A Steel Under the
“Certification of HSLA Steels for Surface Ship Construction Program,” DINSRDC/TM-28-84-17
(January 1984).

Morton, A.G.S., and T.E. Caton, Status Report on Corrosion Testing of High-Strength Low-Alloy Steels,
DTNSRDC/SME-84/02 (May 1984).

Natishan, M.E., Micromechanisms of Strength and Toughness in a Microalloyed, Precipitation
Hardened Steel, DTRC/SME-89/04 (May 1989).

Novack, M.R., Metallurgical and Mechanical Evaluation of HSLA-80 Steel Structural Tubing,
DTNSRDC/ SME-86/60 (August 1986).

Scoonover, T.M., Heat-Affected Zone Toughness and Tensile Properties in ASTM A710 Steel
Weldments, DTRC/SME-88/18 (September 1988).

Sutton, G.E., An Evaluation of the Mechanical and Corrosion Behavior of Thin Section High-Strength
Low-Alloy (HSLA) Steels, DINSRDC/SME-83/67 (November 1983).

Vassilaros, M.G., E.J. Czyryca, and H.I. McHenry, An Evaluation of the Feasibility of Developing High
Strength Low Alloy Commercial Steels for Naval Applications, DINSRDC/TM-28-81-207
(September 1981).



USACERL TR 96/104

abl

Table 1. Chemical composition requirements of low-carbon age-hardenable alloy.

ASTM* ASTM ASTM MIL-S-24645**

A710/736 A710 A710/736

Grade A Grade B Grade C HSLA-80 HSLA-100
Carbon 0.07 0.06 0.07 0.06 0.06
Manganese 0.40-0.70 0.40-0.65 1.3-1.65 0.40-0.70 0.75-1.05
Phosphorus 0.025 0.025 0.025 0.020 0.020
Sulfur 0.025 0.025 0.025 0.006 0.006
Silicon 0.40 0.15-0.40 0.40 0.40 0.40
Nickel 0.07 0.06 0.07 0.06 0.06
Chromium. 0.60-0.90 = = 0.60-0.90 0.45-0.65
Molybdenum 0.15-0.25 = 0.15-0.25 0.15-0.25 0.55-0.65
Copper 1.00-1.30 1.00-1.30 1.00-1.30 1.00-1.30 1.45-1.75
Niobium 0.02 min 0.02 min 0.02 min 0.02-0.06 0.02-0.06
* ASTM specifications.
**Military specifications.

Momic Percent Copper

a0 40 0 0. m
Weeveenpedecreesyesdeeeeentendesessepabess

Temperature °C

sore

(Source: Baker 1992).

ELL 5 ee

Te

40 30 60 70
Weight Percent Copper

80

inp i

1084.87°C

Figure 1. Copper-iron equilibrium phase diagram.



USACERL TR 96/104

49

Acronyms and Abbreviations

ATLSS
CCT
CERF
COMAT
CTOD
CVN
ft-lb

HSLA

kip
kJ/in.

LBZ
MPa
NCEMT
PWHT
SRC

Vp

Advanced Technology for Large Structural Systems (Center for)
continuous cooling transformation

Civil Engineering Research Foundation

construction materials program

crack tip opening displacement

Charpy V-notch

foot pound

heat-affected zone

high-strength low-alloy

high yield

kilopound

kilojoules per inch

kilopounds per square inch

local brittle zones

megapascals

National Center for Excellence in Metal Working Technology
post weld heat treatment

stress relief cracking

plastic limit load



USACERL TR 96/104

21

Recently a railcar designer/fabricator considered fabricating a railcar truck from A710
steel plate. As part of the evaluation, because of the close tolerances required for the
axles and other machine parts, it was determined to be necessary to PWHT the
assembly. Subsequent studies of the reheat cracking susceptibility of A710 steels
caused the company to reject these steels as a candidate material for railcar trucks.

Heat-Affected Zone Softening

Because HSLA steels are age-hardened, there always is the possibility that sub-
sequent thermal cycles, such as experienced during welding, can change the size and
distribution of strengthening precipitates. Thus in the HAZ of a weld one might
expect to find zones in which: (1) the epsilon-copper has been dissolved and the
copper put back into a supersaturated solution, or (2) the epsilon-copper precipitate
has overaged and provides little strengthening. Tempering of the dislocation struc-
tures also will be experienced in the HAZ. These conditions would be expected to
create a softened region in the HAZ; this is observed in some situations.

The occurrence of softened zones has been reported by numerous researchers
(Jesseman and Schmid, November 1983; Kim and Choo, September 1988; Lundin
et al., December 1990; Abe, Kurihara, and Tagawa, September 1988). Figure 7

400
WM PL AZ BM
HSLA-89-1
300 4
2
=
=
a
a
a >
Zz
6 s
c
—
~ 200 4
15 kUfin; 18/5=2.5s
67 kKJ/in; 18/5=15.0s
112 kJ/n; 18/5=39.6s
100 T T T T T T T T T
5 “3 -1 1 3 5 7 9 VW 13 15

DISTANCE, mm

(Source: Lundin et al., December 1990).

Figure 7. Typical microhardness distribution across heat-affected zones (HAZ) for HSLA-
80/A710 at three different cooling times (800 °C to 500 °C).



USACERL TR 96/104

39

Deb, P., K.D. Challenger, and R.F. Burna, “Microstructural Characterization of Shielded Metal Arc
Weldments of a Copper-Bearing HSLA Steel,” Materials Science and Technology, vol 1
(November 1985), pp 1000-1006.

Dexter, R.J., J.W. Fisher, and J.E. Beach, “Fatigue Behavior of Welded HSLA-80 Members,”
Proceedings of the International Offshore Mechanics and Arctic Engineering 12th Conference,
June 1993, Glasgow, Scotland.

Fisher, J.W., and R.J. Dexter, “Weld Improvement and Fatigue Life Extension,” Proceedings of the
International Offshore Mechanics and Arctic Engineering 12th Conference, June 1993, Glasgow,
Scotland.

Graville, B.A., “Cold Cracking in Welds in HSLA Steels,” Welding of HSLA (Microalloyed) Structural
Steels, Proceedings International Conference on Welding of HSLA (Microalloyed) Structural
Steels, Rome, Italy (ASM International, Materials Park, OH, November 9-12, 1976), pp 85-101.

Hamburg, E.G., and A.D. Wilson, "Producton and Properties of Copper, Age Hardened Steels,"
Proceedings of an International Conference on Processing, Microstructure and Properties of
HSLA Steels, November 3-5, 1987, Pittsburgh, PA, A.J. DeArdo, ed. (Sponsored by the Ferrous
Metallurgy Committee of the Minerals, Metals, and Materials Society, Warrendale, PA, 1988),
pp. 241-259.

Hettich, D.L., “Application of A710 Steel in a Beam-to-Column Weak-Axis Connection,” Master's
Thesis, Lehigh University, Bethlehem, PA, June 1990.

High-Performance Construction Materials Planning Committee, “High-Performance Construction
Materials: An Essential National Program for America and Its Infrastructure,” Draft of
Executive Report, February 17, 1993, Civil Engineering Research Foundation.

Horton, J.B., “The Rusting of Low-Alloy Steels in the Atmosphere,” Booklet 2385-A (Bethlehem Steel
Corporation, Bethlehem, PA, not dated).

Jesseman, R.J., and G.J. Murphy, “Mechanical Properties and Precipitation Hardening Responses in
ASTM A710 Grade A and A736 Alloy Steel Plates,” Journal of Heat Treating, vol 3, no. 8 (June
1984), pp 228-236,

Jesseman, R.J., and G.C. Schmid, “Submerged Arc Welding a Low-Carbon, Copper-Strengthened Alloy
Steel,” Welding Research (Supplement to Welding Journal), vol 62, no. 11, (November 1983), pp
321s-330s.

Kapadia, B.M., Y. Adonyi, J.D. Defilippi, and W.F. Domis, “Development of HSLA Steel with 80-ksi
Yield Strength for Offshore Tubular Applications,” presented at Welding Research Council
Weldability Committee, March 1993, New York, NY.

Kim, H.J., and W.Y. Choo, “Application of TMCP Steels for Shipbuilding and Offshore Structures,”
Microalloyed HSLA Steels, Proceedings of Microalloying ’88 / 1988 World Materials Congress,
Chicago, IL (ASM International, Materials Park, OH, September 24-30, 1988), pp 205-213.



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1. AGENCY USE ONLY (Leave Blank) | 2. REPORT DATE 3, REPORT TYPE AND DATES COVERED
September 1996 Final
4. TITLE AND SUBTITLE 5. FUNDING NUMBERS
Low-Carbon, Age-Hardenable Steels for Use in Construction: A Review 4A162784
AT41
CB2
6. AUTHOR(S)

Robert A. Weber, Bruce R. Somers, and Eric J. Kaufmann

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION
U.S. Army Construction Engineering Research Laboratories (USACERL) REPORT NUMBER
P.O. Box 9005 TR 96/104

Champaign, IL 61826-9005

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Headquarters, U.S. Army Corps of Engineers AGENCY REPORT NUMBER
ATTN: CEMP-ET

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Washington, DC 20314-1000

11, SUPPLEMENTARY NOTES
Copies are available from the National Technical Information Service, 5285 Port Royal Road, Springfield, VA 22161.

12a. DISTRIBUTION / AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE

Approved for public release; distribution is unlimited.

13, ABSTRACT (Maximum 200 words)
High-strength low-alloy (HSLA) steels are being used extensively in U.S. Naval shipbuilding and are being substituted for
quenched and tempered HY-80 steel plate. This report examines other applications for the use of HSLA steels. They were
studied to determine possible uses in U.S. Army Corps of Engineers construction projects, the current technology gaps, and
the research necessary to fill those gaps.

HSLA steels offer some benefits over conventional steels of the same strength level. They are virtually immune to
hydrogen-assisted cracking in the heat affected zone of welds, which allows HSLA steel to be welded without preheating.
However, at higher strength levels the weld metals used may require preheat to prevent weld metal hydrogen-assisted
cracking.

The low-carbon, fine grained microstructure that results from typical processing yields a favorable combination of
excellent fabricability, strength, and toughness to HSLA steel that adds to its usefulness and gives it clear advantages over
quenched and tempered construction steels. However, fatigue and buckling may limit direct design substitutions of HSLA
steel in Corps new construction application. HSLA steel is resistant to hydrogen-assisted cracking but susceptible to reheat
cracking, and applications requiring post weld heat treatment are not recommended. Also, local brittle zones may result in
low toughness.

14, SUBJECT TERMS 15. NUMBER OF PAGES
high-strength low alloy steels 52
steel in construction 16. PRICE CODE
17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION 20. LIMITATION OF
OF REPORT OF THIS PAGE OF ABSTRACT ABSTRACT
Unclassified Unclassified Unclassified SAR
NSN 7540-01-280-5500 Standard Form 298 (Rev. 2-89)

Prescribed by ANSI Std 239-18
298-102



32 USACERL TR 96/104

Hydrogen-assisted cold cracking requires a tensile residual stress, a susceptible
microstructure, and hydrogen. In a weldment the tensile residual stress results
from the weld shrinkage strains and is proportional to the amount of restraint. The
susceptible microstructure generally is accepted to be martensite. As mentioned
previously, the principal microconstituent in the coarse grain HAZ in the A710 steel
is bainite, thus resistance to hydrogen-assisted cracking is high. Hydrogen is
commonly present in varying amounts in the atmosphere surrounding the arc; the
amount that ends up in the HAZ depends on the quantity present as well as the
transformation characteristics of the weld metal and base metal. When welding a
typical structural steel (yield strength approximately 40 ksi), the weld metal
typically is a low-carbon, relatively-lean alloy composition. As the molten pool
moves along, the on-cooling transformation of the weld metal usually occurs before
that of the base metal HAZ directly beneath. Thus, for a short distance, untrans-
formed austenite is beneath the weld metal that has transformed, most typically to
a ferrite-pearlite mixture (Figure 12). Because the solubility of hydrogen is higher
in austenite than the transformed product and the diffusivity of hydrogen is faster
in the transformed products, the hydrogen dissolved in the weld metal tends to get
pumped across the fusion line into the HAZ.

The composition of the weld metal must be richer to match higher strengths.
Wrought base metal can develop high strength though complex aging reactions and
thermal-mechanical treatments, but the weld metal typically can develop strength
only through alloy additions. PWHT can age the weld metal. However, PWHT
generally is not used specifically for weld metal strengthening, and the procedure

tae

1

HHHHH SY. m4

Figure 12. Schematic representation of hydrogen movement during weld deposition of typical structural
steel.


18

USACERL TR 96/104

November 1990; Bollinger et al., September 1988; Balaguer, Wang, and Nippes,
April 1989; Kim and Choo, September 1988; Lundin et al., December 1990; Abe,
Kurihara, and Tagawa, September 1988; Scoonover, November 1990; Kapadia et al.
unpublished; Churchill, Devletian, and Singh, May 1991; Stuart, January 1991;
West, May 1987; Anderson, Hyatt, and West, September 1987; Kvidahl unpublished;
Castner et al., April 1993; Dexter, Fisher, and Beach, unpublished). A710-type
steels are readily weldable under almost all shop and field conditions using a wide
variety of welding processes and procedures. Generally no preheat is required for
these materials, primarily because of the very low carbon content.

Hydrogen-Assisted Cracking

The potential for excellent weldability in HSLA steels is illustrated in Figure 5.
This diagram, proposed by Graville (Wilson et al., September 1988), relates
susceptibility to hydrogen-assisted cold cracking to carbon content and carbon
equivalent. The A710-type of materials are in zone I of the Graville diagram
because of their low carbon content, thus they are expected to be relatively
hydrogen-crack free under most welding conditions. Studies have shown that A710

GRAVILLE DIAGRAM
ZONES OF HAZ CRACKING SUSCEPTIBILITY

0.6:
0.55
ZONE II ZONE III
HIGH UNDER
DEPENDS ON
ALL CO! IS.
0.45 CONDITIONS NOITION

0.34

0.25

CARBON CONTENT, WT. PERCENT

0.15

HSLA-100

0: T T T T T. T T 4
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 14 1.2
CARBON EQUIVALENT

CE = C+(Mn+Si)/6-+(Ni+Cu)/15+(Cr+Mo+V)/5

(Source: Wilson et al., September 1988).

Figure 5. Weldability of steel as a function of carbon content and carbon equivalent.


24 USACERL TR 96/104

3 Applications

U.S. Navy

The U.S. Navy has conducted extensive evaluations of the advantages of HSLA
steels (Kvidahl, July 1985); and broad application of these steels has occurred in the
shipbuilding program. The prime benefit generated by HSLA steels is the ability
to weld without preheat. Sustained preheat and interpass controls needed when
welding high yield (HY)-80 and HY-100 steels cost nearly $1.5 million for a typical
ship, and can cost up to $15 million for larger units. Thus significant savings
accrue when the A710-type materials are substituted for the HY steels. Most of the
HSLA tonnage used in the 80 grade material is as hull plate and is 3/4 in. thick or
less. The 100 grade plate is used up to 3 in. thick, mainly in deck plating.

The Appendix is a bibliography of U.S. Navy reports (compiled by E. Czyryca of the
Naval Surface Warfare Center) that deals with HSLA steels.

Offshore Drilling Equipment

Bethlehem-Beaumont fabricated a critical connection in a column leg-to-mat deck
joint of an offshore oil platform jacking rig using 5.5-in. thick A736 plate (West, May
1987; Anderson, Hyatt, and West, September 1987). The plate was purchased in the
quenched (not aged) condition. The lower yield strength of this condition permitted
easier rolling to the required diameter. The subassembly was welded then precipita-
tion hardened to attain the desired strength level. Figure 8 shows the connection
detail for this rig. The steel was supplied by Kawasaki Steel at a delivered cost of
$0.58/lb in 1986.

Ingalls Shipbuilding Division of Litton Industries has had significant experience
with A710-type steels for construction of offshore oil drilling platforms (Kvidahl,
May 1983). This experience was partly responsible for the U.S. Navy’s introduction
of A710-type steels in the construction of U.S. Navy cruisers (Kvidahl, July 1985).
Recently USX introduced a new seamless pipe product for offshore tubular
applications (Kapadia et al., March 1993).


20

USACERL TR 96/104

cracks are intergranular in nature, typical of high-temperature, stress-rupture
failures. The failed specimens exhibit low ductility, and show little or no evidence
of deformation. Reheat cracks usually are confined to the coarse-grain region of the
HAZ, thus cracking is directly related to prior exposure to extremely high tempera-

tures.

Evaluations of the susceptibility of the A710-type materials to reheat cracking have
shown the A710 steels to be one of the most vulnerable of all steels known to be
prone to this type of cracking (D. Chen, E.J. Kaufman, B.R. Somers, and A.W. Pense,
unpublished data) Figure 6 shows the reheat cracking response of an A710 plate
compared to an A517F (T-1) plate, a material known to be quite susceptible to
reheat cracking. Figure 6 shows a low critical stress for reheat cracking for this
A517F plate, 107 MPa (15.3 ksi), but an even lower critical stress for the A710 plate,
74 MPa (10.7 ksi).

One major service failure due to this type of cracking is known to the authors. It
involved a large vessel used to contain molten metal. The vessel was fabricated
from a thick A710 alloy plate. The cracking occurred because of exposure to an
elevated service temperature. Fortunately the cracking was discovered before a
major catastrophe occurred.

500
Isothermal Test

Temperature: 621°C
Heat Input: 2K]/mm

400 +

O ASITF
A710

~ 3004

a

a

=

» 200-4

PA

S

7)

100 5

oS

0 T T T T i
al 1 10 100 1000 10000

‘Time to Rupture (MIn.)

(Source: Balaguer, Wang, and Nippes, April 1989.)

Figure 6. Comparison of reheat cracking susceptibility in A710 and A517F as revealed by the
stress rupture implant test at 1150 °F (621 °C).


USACERL TR 96/104

frequently is impractical because of size restrictions, e.g., in large structures. In
situations with extremely lean high strength alloys, the transformation characteris-
tics of the weld metal-base metal combination may be as shown in Figure 13.
Because of the higher alloy content of the weld metal, the dissolved hydrogen in the
weld metal remains in the weld metal, and there is a tendency to pump hydrogen
from the base metal into the weld metal.

When the A710-type materials are welded without preheat, in situations with high
restraint and perhaps stress raisers, hydrogen-assisted cracking may be expected
to occur in the weld metal. Weld metals in these higher strength ranges typically
have not been used without preheat in the past. Additionally, the transformation
characteristics of the typical base metals used with these weld metals have been
such that the hydrogen was not driven into the weld metal as may be the case with
the lean A710-type steels. In some instances the result is that cracking occurs in the
weld metal. Improved weld metals are needed for full utilization of the no preheat
benefit in A710-type materials and all the newer family of high-strength, low-
carbon, low-alloy steels that develop strength via thermomechanical controlled
processes.

There are two approaches to a solution to the high strength weld metal problem.
The most straight forward is the development of new and better high strength weld
metals that resist hydrogen cracking when welded without preheat. A second

Figure 13. Schematic representation of hydrogen movement during weld deposition of new high
performance low-carbon, lean-alloy steels.



USACERL TR 96/104

15

Class 3—Quenched and Precipitation Heat Treated. Austenitizing at 1600 to 1700
°F (870 to 930 °C) and water quenching provides a fine supersaturated microstruc-
ture with a yield strength of about 65 ksi (450 MPa). Precipitation hardening at
1000 to 1200 °F (540 to 650 °C) causes copper-rich precipitates to form. The
strength increase provided by this age hardening more than offsets the microstruc-
tural softenng (tempering) that occurs simultaneously at the precipitation heat
treatment temperatures. To a certain extent, a tempering reaction, precipitation,
and/or growth of carbides may be seen in all three classes; however, it is more pro-
nounced in Class 3 because the more rapid cooling develops a finer microstructure
in a lower temperature transformation product.

Except for the lower allowable sulfur level in the military specification, the military
specification HSLA-80 composition is essentially identical to Grade A of the ASTM
specification. This low sulfur level is achieved by calcium treatment, and generally
the steel makers supply both the military and the ASTM materials with this
treatment. The HSLA-100 grade is supplied only in the Class 3 condition. The
military specification allows for HSLA-80 up to 1/2 in. thick to be supplied in the
Class 1 condition.

Figure 3 shows the range of yield and tensile strengths and Charpy V-notch (CVN)
results typical from production heats of A710. These materials are capable of
superior combinations of strength and toughness, with yield strengths nearly 100 ksi
and -120 °F CVN values averaging over 100 foot-pounds (ft-lb). When more
stringent dynamic tear toughness requirements are imposed, controlled rolling prior
to reaustenitizing, quenching, and aging has been found to be helpful in achieving
additional toughness (Hamburg and Wilson, November 1987).

The CCT diagram for A710 steels (Figure 2B), shows that a range of microstructural
constituents can be formed in this low carbon steel; but in practice, proeutectoid
ferrite is the primary microstructural component. Small amounts of acicular ferrite,
bainite, and martensite also might be formed. The carbon content of A710 steel is
typically restricted to less than 0.07 percent so high toughness levels can be
developed, and cold cracking problems essentially can be eliminated, even if the
welding consumables can generate a hydrogen potential.

Typically, because of the limited hardenability of the A710 composition, the plate
thickness is restricted to 1.25 in. for high toughness applications. However, thick-
nesses up to 5 in. are possible if only modest toughness is required (Wilson et al.,
September 1988). A modified A710 with higher manganese (1.4 percent) and
molybdenum (0.45 percent) content has been found capable of achieving 80 ksi yield



USACERL TR 96/104

1

Introduction

Background

Over the past decade, ASTM A710-type, low-carbon, age-hardenable steels have
been used increasingly in manufacturing and construction because of their excellent
weldability and fracture toughness. The largest tonnage of this type of steel
probably is used in U.S. Naval shipbuilding, and these steels are covered by Military
Specification MIL-S-24645, which includes both an 80 kips per square inch (ksi) and
a 100 ksi minimum yield strength material. Shipbuilding steels have become known.
as high-strength low-alloy (HSLA) steels, although they are not truly within the
confines of the conventional definition of HSLA steels because their total alloy
content generally is about 4 percent.

The use of microalloyed steels for construction and pressure vessel applications goes
back to the 1940s when critical material shortages made the use of only small
amounts of alloys in steel products mandatory. In the 1950s, a number of companies
introduced construction steels that contained manganese and other alloys as well
as vanadium, titanium, and niobium. Most of these steels are now covered by ASTM
A588 and A572, and are considered the early microalloyed steels, although they
were not originally identified as such. In the 1970s microalloyed steels with low
carbon content, high manganese levels, and microalloy carbide and nitride formers
became identified as construction materials with high strength, good weldability,
and good low temperature toughness. These materials allow control of grain size
and microstructure, either as-rolled or specially processed, to provide a good
combination of properties for a number of applications.

Some of the first uses of intentional additions of copper to steels were provoked by
the appreciable atmospheric-corrosion resistance developed. The ASTM A242 and
A588 steels possess at least four to as much as eight times the atmospheric-corrosion
resistance of structural carbon steel, which has a low copper content. When properly
exposed to the atmosphere, such bare steels will develop a tight, adherent, protec-
tive-oxide coating during the first several months of weathering. Thereafter, little
additional steel corrosion occurs.



30

USACERL TR 96/104

Sp Shear Link

is I

(a) Eccentrically-Braced Frame

Knee Brace

NS

(b) Knee-Braced Frame

Figure 11. Applications for A710 high-performance steel which are required to undergo cyclic
plastic deformation in an earthquake.

The improved weldability of HSLA steels should allow the use of thicker flanges in
welded girders. This permits the use of members that are the same depth as
conventional steel girders to achieve greater strength and stiffness. Thicker web
and flange plates may reduce or eliminate the need for stiffeners in some instances.
Elimination of the stiffeners, welds, and their distortion problems could improve the
fatigue strength of the girder.

The excellent toughness and weldability of the HSLA steels should result in their
applications involving repairs and retrofitting of bridges and other structures.
Retrofitting may be done to improve resistance to fatigue or seismic loading. The
use of these steels in repairs and retrofitting may be driven by the ability to weld in
the field under poor conditions, possibly even from one side only. For example, the
knee bracing shown in Figure 11b could be installed in existing frames using
one-sided welding. High performance steel plates also are ideal for one-sided weld-
ing as doubler plates on existing structure. These doubler plates could be used to
add capacity to or to repair damage caused by collision of vehicles or fatigue crack-
ing. When repairing, if the original failure was due to loads higher than expected
and the level of these loads cannot be changed, a replacement of the area or detail


USACERL TR 96/104

27

Discussion

The A710-type materials provide an excellent combination of strength, toughness,
and weldability unavailable in any conventional structural steel. Because these
materials can be welded without preheat, there is a potential for significant
fabrication cost savings. Because of the high strength, there is a potential for weight
saving design applications. Because of the high toughness, new structures fabri-
cated from A710-type materials will be more defect tolerant and will provide an
inherently safer structure. Another benefit that can be expected is reduced repair
cycles because of the improved weldability.

The foregoing benefits must be weighed against the higher costs of HSLA steels.
Because of the additional heat treatments and higher alloy content, these steels are
more expensive than conventional micro-alloyed structural steels. However, when
used by the U.S. Navy, these HSLA materials provide significant savings and
improved performance. But in this instance HSLA materials are being used to
replace a quenched and tempered steel of higher alloy content and relatively poor
weldability. The cost savings projected by the U.S. Navy will not occur if A710-type
materials are used to replace conventional structural steels. The current price for
A710-type steels ranges from $0.75 to $1.00 per pound; the price for conventional
structural steels ranges from $0.45 to $0.65 per pound. If the A710-type steels are
to replace conventional structural steels successfully, then there must be significant
design, fabrication and operational benefits to justify the added material costs.

One factor that causes high strength materials to be less able to take full advantage
of the higher strength is that the fatigue life in large, welded structures is princi-
pally a function of the weldment geometry rather than the base metal strength
(Dexter, Fisher, and Beach, June 1993). This means any implementation of HSLA
materials that attempts to use the benefit of the higher strength by reducing section
size and weight, and at the same time raising the operating stress, will have reduced
fatigue capacity. The fatigue S-N curves for A710-type large scale weld details are
not significantly different than S-N curves from similar weld details fabricated from
lower strength, carbon-manganese steels. To a certain degree, the fatigue capacity
of these weld details may be improved by auxiliary treatments such as peening or
gas tungsten arc remelting of weld toes (Fisher and Dexter, June 1993). Obviously



USACERL TR 96/104

Contents
5S) 2: |: ce 1
FOreWOrd 221. e EEE ene enn nee 2
List of Tables and Figures ........... 00. c ccc cece cece eee nen nee enn ene 4
1 Introduction 0.0.0.0... cece ene ene nent eens 7
Background 2.0... 6c ccc cece eee n tenner e eee n enn eee 7
Objectives 8
Approach . 8
Scope ..........2.0005 8
Mode of Technology Transfer . 8
Metric Conversion Factors 9
2 High-Strength Low-Alloy Materials ............. 5.0. c eee eee eee teers 10
Metallurgy 10
Weldability 17

U.S. Navy

Offshore Drilling Equipment .

Mining Industry ..........

Oil and Pipeline Applications . o

Water Systems 20.0... eee teen e eee ene etn eens
4 Discussion ........ 2.0. c cece eee ete een teeter ene 27
5 Conclusions and Recommendations ................0ecee cece eee eens 36
References .... 20.6... c cece n teen een n entree nee 38
Appendix: Bibliography of HSLA Steel Research Publications .......... 0.6.0 eeeeeee 42
Acronyms and Abbreviations .............. 66 ec e cece eee cence n en enene 49

Distribution



2 USACERL TR 96/104

Foreword

This research was conducted for the Directorate of Military Programs, Head-
quarters, U.S. Army Corps of Engineers (HQUSACE), under Project 4A162784AT41,
“Military Facilities Engineering Technology’; Task MA, Work Unit CB2,
“Assessment of HSLA Steels for Construction.” The technical monitor was Charles
Gutberlet, CEMP-ET.

The work was performed by the Materials Science and Technology Division (FL-M)
of the Facilities Technology Laboratory (FL), U.S. Army Construction Engineering
Research Laboratories (USACERL). The USACERL principal investigator was
Robert A. Weber. Bruce R. Somers and Eric J. Kaufmann are researchers with the
Center for Advanced Technology for Large Steel Structures, Lehigh University,
Bethlehem, PA. Ilker R. Adiguzel is Acting Chief, CECER-FL-M, and Donald F.
Fournier is Acting Operations Chief, CECER-FL. The technical editor was Agnes
E. Dillon, Technical Information Team.

Special acknowledgement is due to Ernest Czyryca, Naval Surface Warfare Center,
Annapolis, MD; James Snyder, Bethlehem Steel Corporation, Bethlehem, PA; Alex
Wilson, Lukens Steel, Coatesville, PA; Sam Manganello, USX, Monroeville, PA;
Robert Dexter and Le-Wu Lu, Lehigh University, Bethlehem, PA.

COL James T. Scott is Commander of USACERL, and Dr. Michael J. O’Connor is
Director.


16

USACERL TR 96/104

Distribution of Tensile Results
A710A Class 3, 0.75 in. Thick

Number of Occurances
80

60

40

20
IF

80 a4 88 92 96 100 104 108 112
Strength, ksi
MM Yiold Strength LI Ulimate Tensio Strongth

Distribution of CVN Results
A710A Class 3, 0.75 in. Thick

Nanber of Occurances
60

50

40

30

20

40 60 80 100 120. 140160 160 200-220
Ful-Size CVN Specinen Energy, ft-b
M Zero F Test Terrperalure 1) ~120 F Test Temperature

(Source: Wilson et al., September 1988).

Figure 3. Distribution of properties in 0.75 in. (19 mm) thick HSLA-80/A710 Grade A Class 3
plates.

strength up to 8 in. thick with a modest toughness level, 73 ft-lbs at -50 °F (Wilson
et al., September 1988).

Because of the copper content, can these A710-type steels exhibit good atmospheric
corrosion resistance—weathering behavior-similar to that of the ASTM A588 and
A242 weathering steels? These weathering steels develop a tightly adherent,
protective rust after 3 to 4 years of wet-dry atmospheric exposure. This behavior
stems from a carefully balanced composition with typically 0.35 percent copper, 0.50
percent chromium, and 0.50 percent nickel. Figure 4 shows a comparison of the


USACERL TR 96/104

1

13

Applications for A710 high-performance steel which are required to
undergo cyclic plastic deformation in an earthquake ...............0- 30

Schematic representation of hydrogen movement during weld
deposition of typical structural steel .. 0.6.6... ese c eee c eee eee eee 32

Schematic representation of hydrogen movement during weld
deposition of new high performance low-carbon, lean-alloy steels ...... 33


22

USACERL TR 96/104

shows the microhardness distributions across several HAZ in an HSLA-80 weldment
(Lundin et al., December 1990). The longer cooling times imposed by the higher
heat inputs tend to produce larger and softer soft zone regions. Jesseman and
Schmid (November 1983) found the softened region became wider as the energy
input was raised. However, a detrimental effect of such a softened region is not
always present. Transverse tensile tests showed that this softened region did not
affect the joint strength at heat inputs up to 125 kilojoules per inch (kJ/in.) on 2.25
in. thick plates. Recent work at Lehigh University has confirmed that low heat
input weldments in thick section steels may not provide sufficient time for softening
to occur. The softened zone is more apparent in thinner sections or at higher heat
inputs. If the welded section is small enough it may be possible to soften the entire
section by the heat of welding.

Heat Input Restrictions

The necessity for maximum heat input controls when welding some high strength
quenched and tempered steels stems primarily from two motivations. It is desirable
to avoid low toughness microstructures that develop in the slowly cooled HAZ. Also
the low strength and toughness that can develop in weld metals deposited at high
heat inputs should be avoided. Currently heat input restrictions are imposed by
military standard 1689 for welding U.S. Navy ship structures. The requirements
state that a maximum of 45 kJ/in. is permitted when welding HSLA-80 less than
1/2-in. thick, and a maximum of 55 kJ/in. is permitted when welding HSLA-80 1/2
in. thick or greater. The standard also allows the possibility of exemption from these
requirements. Several shipyards have qualified procedures that allow extensions
of these heat input limitations.

Some concern for limiting the heat input comes from the occurrence of local brittle
zones (LBZs) that are known to occur in HSLA steels. Typically these LBZs are
associated with the coarse-grained HAZ or intercritically reheated coarse-grained
HAZs. Scoonover (November 1990) suggested that the typical heat inputs used in
shipbuilding result in small, discontinuous LBZs. Probabilistic fracture mechanics
models incorporating LBZs indicate only a small increase in the probability of
service failure caused by the presence of LBZs (Scoonover, November 1990).

Suppliers

Four major domestic steel companies supply A710-type plate: Armco, Bethlehem,
Lukens, and USX. All four supply principally the Grade A composition, most often
in Class 3 condition. USX indicated they occasionally also have supplied some of the


US Army Corps
of Engineers

Construction Engineering USACERL Technical Report 96/104
Research Laboratories September 1996

Low-Carbon, Age-Hardenable Steels for
Use in Construction: A Review

by
Robert A. Weber, Bruce R. Somers, and Eric J. Kaufmann

High-strength low-alloy (HSLA) steels are being
used extensively in U.S. Naval shipbuilding and
are being substituted for quenched and tem-
pered HY-80 steel plate. This report examines
other applications for the use of HSLA steels.
They were studied to determine possible uses in
U.S. Army Corps of Engineers construction pro-
jects, the current technology gaps, and the re-
search necessary to fill those gaps.

HSLA steels offer some benefits over conven-
tional steels of the same strength level. They
are virtually immune to hydrogen-assisted crack-
ing in the heat affected zone of welds, which
allows HSLA steel to be welded without preheat-
ing. However, at higher strength levels the weld
metals used may require preheat to prevent weld
metal hydrogen-assisted cracking.

The low-carbon, fine grained microstructure that
results from typical processing yields a favorable
combination of excellent fabricability, strength,
and toughness to HSLA steel that adds to its =
usefulness and gives it clear advantages over wae ny

quenched and tempered construction steels. a

However, fatigue and buckling may limit direct anne eaenes riageenetration beam-to-column weld with beam
design substitutions of HSLA steel in Corps new
construction application. HSLA steel is resistant

to hydrogen-assisted cracking but susceptible to
reheat cracking, and applications requiring post weld
heat treatment are not recommended. Also, local
brittle zones may result in low toughness.

19961216 016

Approved for public release; distribution is unlimited.

(DTIC QUALITY LNEYSCTED 8



USACERL TR 96/104

Hicho, G.E., C.H. Brady, L.C. Smith, and R.J. Fields, Effects of Varying the Austenitizing and
Precipitation Hardening Temperatures and Times on the Ability of HSLA-80 To Achieve a Yield
Strength of 100 ksi, DIRC/SME-CR-03-88 (March 1988).

Hicho, G.E., R.J. Fields, and S. Singhal, Effects of Variations in Heat Treatment on the Mechanical
Properties and Microstructure of ASTM A710, Grade A, Class 3 Steel, DINSRDC/SME-CR-22-83
(May 1983).

Howell, P.R., Microstructural Development in HSLA-100 Steel Weld Metals, Ist Annual Progress
Report, ONR Grant No. N00014-89- J-1958 (The Pennsylvania State University, University
Park, PA, 1990).

Matlock, D.K., and G.R. Edwards, Initial Study: Characterization of HSLA Weld Metal Microstructures
for Development of Welding Consumables, DINSRDC/SME-CR-24-83 (October 1983).

Matlock, D.K., and G.R. Edwards, The Metallurgy of HSLA Steel Weld Metal Produced by the
Submerged Arc Process, DINSRDC/SME-CR-01-85 (September 1984).

Matlock, D.K., and G.R. Edwards, The Metallurgy of HSLA Steel Weld Metal Produced by the
Submerged Arc Process - Phase II, DTINSRDC/SME-CR-12-86 (August 1986).

Matlock, D.K., and G.R. Edwards, The Metallurgy of HSLA Steel Weld Metal Produced by the
Submerged Arc Process - Final Report, DINSRDC/SME-CR-13-86 (August 1986).

Nichting, R.A., and E.L. Brown, A Physical Metallurgical Basis for Heat-Affected Zone and Base-Plate
Properties of a Microalloyed HSLA Steel, DINSRDC/SME-CR-24-86 (December 1986).

Paules, J.R., J.G. Speer, and S.S. Hansen, Production Trial of Ultra-Low Carbon “BETHSTAR 80”
Steel Plates for Naval Shipbuilding Applications, DINSRDC/SME-CR-25-86 (April 1986).

Siewert, T.A., State of the Art in Ferritic Electrode Technology, DTRC/SME-CR-08-86 (July 1986).

DTRC Publications

(Publications on HSLA steels from Navy programs, including Navy-sponsored studies.)

Abeln, S.P., et al., “The Microstructure and Properties of Selected High Strength Ferritic Weld
Metals,” Microstructural Science, vol 14 (ASM International, Materials Park, OH, 1986), pp
99-114.

Blicharski, M.R., C.I. Garcia, S. Pytel, and A.J DeArdo, "Structure and Properties of ULCB Plate
Steels for Heavy Section Applications" in A.J. DeArdo, ed., Proceedings of an International
Conference on Processing, Microstructure and Properties of HSLA Steels, November 3-5, 1987,
Pittsburgh, PA (The Ferrous Metallurgy Committee of the Minerals, Metals, and Materials
Society, Warrendale, PA, 1988), pp 317-329.



USACERL TR 96/104

Metric Conversion Factors

U.S. standard units of measure are used throughout this report. A table of metric
conversion factors is presented below.

Tin.
1ft

1 sqft
1 sq ft/min
1cuft
1 mi
1Ib

1 gal
1 psi
1 um
°F

25.4 mm
0.305 m
0.093 m?
0.093 m/min
0.028 m®
1.61 km
0.453 kg
3.78L

6.89 kPa
1x10%m

(°C x 1,8) +32



8 USACERL TR 96/104

The use of copper in amounts over 0.2 percent to strengthen structural steels also
goes back to at least the 1940s, when it was used in some ships. Structural steels
with copper additions for precipitation strengthening, forerunners of the current
A710-type grades, were introduced in the 1960s but generated little interest among
engineers and the construction industry at that time. However, engineering needs
change, and now there is considerable interest in the combination of properties that
copper age-hardening steels of the A710 type provide.

The current interest in these materials by the U.S. Army Corps of Engineers
(USACE) raises questions about the utility of the materials for Corps construction
projects. Can this material reduce the section thicknesses required for common con-
struction applications and still provide the required service life? This and similar
types of questions prompted an investigation of the A710 steels for possible applica-
tion in Corps construction.

Objectives

The objectives of this work were to study the high-strength low-alloy ASTM A710-
type steels to determine possible uses in USACE construction projects, the current
technology gaps, and the research necessary to fill those gaps.

Approach

This report comprises information compiled from the technical literature and inter-
views with fabricators, steelmakers, and researchers involved with the use, supply,
and evaluation of HSLA steels.

Scope

The scope of this work was limited to HSLA steels and their application to the
construction of civil structures typical of the U.S. Army Corps of Engineers military
construction programs.

Mode of Technology Transfer

The pertinent information in this report will be incorporated in the next update of
the Technical Manual TM5-805-7, Welding: Design, Procedures, and Inspection.


USACERL TR 96/104 41

Wilson, A.D., E.G. Hamburg, D.J. Colvin, S.W. Thompson, and G. Krauss, “Properties and Micro-
structures of Copper Precipitation Aged Plate Steels,” Microalloyed HSLA Steels, Proceedings
of Microalloying ’88 / 1988 World Materials Congress, Chicago, IL (ASM International, Materials
Park, OH, September 24-30, 1988), pp 259-275.



USACERL TR 96/104

29

W14 x 257 Column

be
t

H

H

a

1

it

ma

\ Flange Connection Plate

Material: A710 Steel

aN

aN

ly We7 x 94 Beam

Material For Beam and
Column: ASTM A572
Grade 50

J
Ty
SS

Figure 9. Beam-to-column weak axis connection test details with A710 steel.

1.25

A

‘A572 (50) Steel Plate

ie) 0.50

1.00

4 i
1.50 2.00
alap

Figure 10. Load-deflection curves of beam-to-column weak axis connections.


46

USACERL TR 96/104

Czyryca, E.J., “Development of Low-Carbon Copper-Strengthened HSLA Steel Plates for Ship
Construction” in R. Pradhan, ed., Metallurgy of Vacuum Degassed Steel Products, conference
proceedings (The Metallurgical Society [TMS], American Institute of Mining Engineers [AIME],
Warrendale, PA, January 1990), pp 469-484.

Czyryca, E.J., “Development, Qualification, and Certification of HSLA-80 and HSLA-100 Steels for
U.S. Navy Ship Construction,” in J.T. Hickey, P.G. Howden, and M.D. Randall, eds.,
Proceedings International Conference on the Metallurgy, Welding, and Qualification of
Microalloyed (HSLA) Steel Weldments (American Welding Society, Miami, FL, November 6-8,
1990), pp 553-572.

Czyryca, E.J., RE. Link, R.J. Wong, D.M. Aylor, T.W. Montemarano, and J.P. Gudas, “Development
and Certification of HSLA-100 Steel for Naval Ship Construction,” Naval Engineers Journal,
vol 2, no. 3 (May 1990), pp 63-82.

Garcia, C.1., and A.J. DeArdo, “Structure and Properties of ULCB Plate Steels for Heavy Section
Applications,” Microalloyed HSLA Steels, Proceedings of Microalloying ’88/1988 World
Materials Congress, Chicago, IL (ASM International, Materials Park, OH, September 24-30,
1988), pp 291-299.

Gudas, J.P., R.B. Pond, and G.R. Irwin, “Metallurgical Aspects of Plastic Fracture and Crack Arrest
in Two High-Strength Steels,” Nonlinear Fracture Mechanics: Volume II - Elastic-Plastic
Fracture, ASTM STP 995 (American Society for Testing and Materials [ASTM], Philadelphia,
PA, 1989), pp 497-536.

Hamburg, E.G., and A.D. Wilson, “Production and Properties of Copper, Age Hardened Steels,”
Proceedings of International Symposium on Processing, Microstructure and Properties of HSLA
Steels (The Minerals, Metals, and Materials Society, Warrendale, PA, 1988).

Hicho, G.E., et al., “Effect of Thermal Processing Variations on the Mechanical Properties and
Microstructure of a Precipitation Hardening HSLA Steel,” Journal of Heat Treating, vol 3, no. 3
(June 1984), pp 205-212.

Hicho, G.E., et al., “Effects of Heat Treatment on the Mechanical Properties and Microstructures of
Four Different Heats of a Precipitation Hardening HSLA Steel,” Journal of Heat Treating, vol
5, no. 1 (February 1987), pp 7-19.

Holsberg, P.W., and R.J. Wong, “Welding of HSLA-100 Steel for Naval Applications” in R.A. Patterson
and K.W Mahin, eds., Weldability of Materials (ASM International, Materials Park, OH, 1990),
pp 219-239.

Montemarano, T.W., B.P. Sack, J.P. Gudas, M.G. Vassilaros, and H.H. Vanderveldt, “High Strength
Low Alloy Steels in Naval Construction,” Journal of Ship Production, vol 2, no. 3 (August 1986).


USACERL TR 96/104

these extra steps increase the cost and lower the economic benefits of the use of.
HSLA material.

In many structures (e.g., ship hulls and storage tanks) if the allowable stress is
increased to take advantage of high strength steel, compression stability is more
likely to become a governing design consideration. If the design becomes overly
thin, local buckling may occur at service load levels and lead to fatigue cracking
from repeated out-of-plane deformations. Factors that influence buckling include
residual stress, geometrical imperfections, and the steel elastic properties. Unfor-
tunately, these factors are to a large degree independent of the steels’ tensile
strength. Therefore, design configurations and details with improved stiffness and
fatigue life are required for efficient use of high strength steel.

One area that holds promise for the application of HSLA materials is in structural
details that can significantly benefit from the superior toughness of these materials.
Recently the feasibility of such a benefit was shown when an A710 was substituted
for an A572 in small attachment tabs in a beam-to-column weak axis connection
(Figure 9). When tested with the A572 connection, the joint failed prematurely due
to fracture of one of the A572 connecting plates. The failure was attributed to
unavoidable strain concentrations caused by this design detail. When tested with
A710 connection tabs, this design showed a significant increase in connection
capacity. The nondimensional load-deflection curves of the two tests are shown in
Figure 10. The A572 test did not reach the plastic limit load (Vp) of the beam. The
A710 test ultimate load exceeded Vp by about 20 percent and the connection showed.
good ductility. Final failure of the A710 connection was caused by a fracture of the
beam tension flange; the failure of the A572 connection was in the top flange
connection tab (Hettich, June 1990).

For structures designed for seismic applications, the steel must be able to develop
fully plastic hinges and absorb energy. This behavior is limited by either exhaustion
of ductility or, more likely, ductile tearing of the material, especially at the welded
or bolted connections. Therefore, the superior ductility and toughness of the A710-
type steels make them ideal for such uses. These qualities make the HSLA steel
ideal for applications involving biaxial tension, e.g., gusset plates. Structural
shapes, particularly “I” beams, rolled or fabricated from A710 steel could make
excellent shear links in eccentrically braced frames (Figure 11a). These frames are
gaining acceptance as a means of dissipating energy by cyclic plastic deformation of
the short center shear link. Obviously, this use puts extreme demands on the mate-
rial’s ductility. Figure 11b shows knee bracing, which could be used to dissipate

energy.


4 USACERL TR 96/104

List of Tables and Figures

Tables

1 Chemical composition requirements of low-carbon age-hardenable

Fo) W
2 Mechanical property requirements per ASTM: low-carbon age-

hardenable alloyS ...... 0... c cece cece center n ene neee 14

Figures

1 Copper-iron equilibrium phase diagram ........ +... essence eee eee on
2 Continuous cooling transformation diagrams ........... 60s eee eens 13
3 Distribution of properties in 0.75 in. (19 mm) thick HSLA-80/A710

Grade A Class 3 plates
4 Comparison of atmospheric corrosion behavior of several steel

TYPOS eee eee enn e ene eee eens 17
5 Weldability of steel as a function of carbon content and carbon

equivalent .... 00... c eee c eee eee cette ete e tne enna es 18
6 Comparison of reheat cracking susceptibility in A710 and A517F as

revealed by the stress rupture implant test at 1150 °F (621 °C) ........ 20
7 Typical microhardness distribution across heat-affected zones (HAZ)

for HSLA-80/A710 at three different cooling times (800 °C to

£5100 id ©) aa val
8 Joint detail of column leg-to-mat deck from offshore oil platform

jacking rig
9 Beam-to-column weak axis connection test details with A710 steel ..... 29

10 Load-deflection curves of beam-to-column weak axis connections ...... 29


USACERL TR 96/104

19

steel has a very low potential for martensite formation in the grain-coarsened heat
affected zone (Lundin, Menon, and Lawson, December 1989). A710 steel is expected
to posses superior resistance to hydrogen-assisted cracking. As a testament to this
excellent weldability, one U.S. Navy investigation conducted more than 100 weld-
ability tests over a range of processes and heat inputs, no test showed any heat-
affected zone (HAZ) cracking (Kvidahl, July 1985).

There have been some concerns for the cracking resistance of the weld metal (Deb,
Challenger, and Burna, November 1985; Wallace and Heid, November 1990),
especially when matching strength in the higher strength modifications of these
A710-type materials. If preheat is not used, the hydrogen cracking problem may
move to the weld metal portion of the joint when the strength levels begin to
approach 100 ksi, this is particularly true for the processes that are more prone to
hydrogen pick-up. Tests at Newport News Shipyard have suggested that a preheat
of 125 °F (51.6 °C) minimum is necessary to avoid weld metal cracking in HSLA-100
weldments over 3/4-in. (19-mm) thick welded with matching strength shielded metal
arc electrodes (Wallace and Heid, November 1990).

Reheat Cracking

Another area of concern in the HSLA alloys is their susceptibility to reheat cracking.
Reheat cracking, also referred to as stress-relief cracking (SRC) and post weld heat
treatment (PWHT) cracking, is defined as cracking that occurs in the HAZ during
the exposure of welded assemblies to post weld heat treatment (PWHT) or high
temperature service. This type of cracking has been found to be predominantly
located in the coarse-grained HAZ and is intergranular in nature (Balaguer, Wang,
and Nippes, April 1989).

Meitzner (November 1975), in a comprehensive review of SRC in weldments, stated
that SRC was associated with: (1) precipitation-hardening materials, (2) intergranu-
lar failure with little or no evidence of deformation, and (8) the coarse grained region
of weld HAZ. Most SRC cracking has been associated with alloy systems that under-
go precipitation hardening, e.g., some low-alloy steels, ferritic creep-resistant steels,
austenitic stainless steels, and nickel-based alloys.

Although the exact mechanism has not been clearly established, the basic character-
istics of cracking are similar for all the HSLA materials. No external stress is
necessary, the crack driving force is derived from residual stress in sound weldments
that are heated to elevated temperatures after welding. Therefore, cracks most
often are found in thicker sections with high levels of self-restraint, but they may
occur even in sheet details if the restraint from fabrication is high enough. The HAZ



36

USACERL TR 96/104

Conclusions and Recommendations

Corps of Engineers steel construction requires fatigue and seismic strength, but not
necessarily high tensile strength. These requirements therefore rule out using
ASTM A710 steels for typical new construction projects. Retrofit and repair applica-
tions could benefit from the use of A710 steel, but additional work on joint and con-
nection designs would be required.

The HSLA steels have the potential to provide significant savings in fabrication
costs as well as increased reliability and safety for high tensile strength applica-
tions. However, some applications should be avoided because of the metallurgical
characteristics of the HSLA steels; specifically, PWHT should be avoided because of
the reheat cracking susceptibility. Technology gaps need to be fully investigated so
confident application of the HSLA steels can occur. Some of the work required to
close these gaps is currently underway; additional work may be needed in some

situations.

Metallurgically three problem areas have inhibited the application of the HSLA

steels:

* the inability of currently available weld metals to match the weldability of the
ASTM A710-type steels,

. the sensitivity of these materials to reheat cracking,

* the toughness degradation due to LBZ as measured by CTOD.

Several research initiatives currently are under way for the first problem area.
Additional efforts in this area may not be required. No additional recommendations
should be made until the direction the current programs are headed is clear. Most
of the need for this work is required by the application of higher strength—100 ksi
yield strength and above-type steels and is not as critical for the application of the
80 ksi A710 steel.

The need for additional work in the area of reheat cracking susceptibility is not a
high priority at this time. The problem is not expected to be encountered in struc-
tural applications because no PWHT is required. The question of interbead HAZ
cracking due to reheat cracking sensitivity does not appear significant based on the


USACERL TR 96/104

37

fabrication experience to date. If reheat cracking occurs it would be associated with
other welding discontinuities that would require removal and repair regardless of
the reheat crack sensitivity.

The problem of LBZs and their effect on overall structural fracture has not been
satisfactorily resolved, and there is some question about whether a problem exists.
Newer A710 modifications appear to have improved the resistance to the apparent
HAZ toughness degradation measured by CTOD (Scoonover, November 1990).
There is a discrepancy between the results of CVN and CTOD testing. Full-scale
testing of actual weldments will resolve this question. It is recommended that after
a complete literature survey of this question, full-scale tests in conjunction with
CVN and CTOD tests should be conducted to determine the effect of LBZ on the
overall performance of a full-scale structure.

From the structural engineering standpoint, two areas require further examination
to allow the application of the HSLA steels and utilize them to their maximum
benefits. These are the buckling stability and the fatigue life of structures. Both
properties are not improved by increases in yield strength and will be degraded if
existing designs substitute thinner sections to take advantage of the higher
strengths available with these materials. Novel approaches to designs for utiliza-
tion of higher strength steels are needed. However, recommendations for additional
work should be delayed until the extensive COMAT plan develops into its final
format.



USACERL TR 96/104

25

X = FILLET
WELD OF
SUFFICIENT
SIZE TO
GRIND 1-374"
RAD.

tL
~~ —at- 2
x o 3" x
30 et
X = FILLET |
WELD OF
SUFFICIENT y
SIZE TO b x
GRIND |" a
RAD. “Y-
100% 30°
UT
45°
tou =
Nw | IN
a1 ¢ I
to \ |
\
\
45°
/ Q°
A, 30° >
wo
a.
3.
| | 28

a
TT

The 5.5 in. thick section was fabricated from an A710-type alloy.
(Source: Anderson, Hyatt, and West, September 1987).

Figure 8. Joint detail of column teg-to-mat deck from offshore oil platform jacking rig.

H.R. Castner of the Edison Welding Institute recently reported on some weld
development work using an A710-type material for tendons and riser pipe for what
will be the world’s deepest tension leg platform in 2,860 ft of water (Castner et al.,
April 1993). Three steel grades with nickel content varying from approximately 1
to 2 percent were evaluated over a range of heat inputs from 30 to 75 kJ/in., and pre-
heat and interpass temperatures from 75 to 700 °F. Optimum procedures based on
HAZ toughness results were found to be at heat inputs between 45 and 50 kJ/in.,
with preheats of 75 °F and maximum interpass temperatures of 375 °F. These
procedures are based on welding 26-in. diameter pipe with a wall thickness of 1.3 in.



i. General Comments. (Indicate what you think should be changed to make this report and future reports
of this type more responsive to your needs, more usable, improve readability, etc.)

5. If you would like to be contacted by the personnel who prepared this report to raise specific questions or
discuss the topic, please fill in the following information.

Name:

Telephone Number:

Organization Address:

6. Please mail the completed form to:

Department of the Army

CONSTRUCTION ENGINEERING RESEARCH LABORATORIES
ATTN: CECER-TR-I

P.O. Box 9005

Champaign, IL 61826-9005


44 USACERL TR 96/104

Werchniak, W., E.J. Czyryca, and D.M. Montiel, Fatigue Properties of HSLA-100 Steel and Weldments,
DTRC/SME-89/113, September 1990.

Wong, R.J., Weld Process Development and Weldability of HSLA-100 Steel, Interim Report, DINSRDC/
TM-28-87-09 (March 1987).

Wong, R.J., Weldability and Welding Procedure Development for HSLA-100 Steel Non-pressure Hull
Structures, DIRC/SME-90/40 (September 1990).

Xirk, M.T., Applicability of ASTM A710 Grade A Class 3 (HSLA-80) Steel for Use As Crack Arresters,
DTNSRDC/SME-87/54 (June 1987).

DTRC Contractor Reports

Brown, E.L., and R.A. Nichting, A Physical Metallurgical Basis for Heat-Affected Zone and Base-Plate
Properties of HSLA Steels for Naval Applications, DINSRDC/SME-CR-20-84 (December 1984).

Coldren, A.P., and T.B. Cox, Development of 100 ksi Yield Strength HSLA Steel, DINSRDC/SME-
CR-07-86 (July 1986).

Coldren, A.P., and T.B. Cox, Phase II Report and Phase III Commercial Plate Documentation for
Development of 100 ksi Yield Strength HSLA Steel, DINSRDC/SME-CR-07-87 (June 1987).

Crooks, M.J., L.C. Smith, and R.C. Reno, Microstructural Evaluation of Explosion Bulge Tested HSLA-
80 Plates, DTRC/SME-CR-02-88 (March 1988).

Fiselstein, L.E., D.O. Harris, C.A. Rau, D.D. Dedhia, and R.A. Sire, Probabilistic Fracture Mechanics
Evaluation of Local Brittle Zones in HSLA-80 Steel Weldments, DTRC/SME-CR-05-90

(December 1989).

Fleck, N.A., The Effect of Filler Wire and Flux Compositions on the Microstructure and Properties of
Microalloyed Steel Weld Metal, DINSRDC/SME-CR-17-84 (January 1985).

Fletcher, E., Review of Status, Properties, Weldability and Producibility of High-Strength Steels for
Naval Surface-Ship Construction, DINSRDC/SME-CR-23-83 (May 1983).

Garcia, C.I., and A.J. Deardo, Study of the Bs Temperature in a Molybdenum-Containing Ultra-Low
Carbon Bainitic Steel for Heavy Plate Applications, DINSRDC/SME-CR-22-86 (December 1986).

Gray, J.M., J.T. Hickey, and A.M. Gilroy-Scott, Report on Effects of Nitrogen on the Weldability of
Microalloyed Steels, DINSRDC/SME-CR-05-87 (January 1987).

Hicho, G.E., C.H. Brady, L.C. Smith, and RJ. Fields, Effect of Heat Treatment on Mechanical
Properties and Microstructure of Four Different Heats of ASTM A710 Steel, DINSRDC/
SME-CR-05-85 (March 1985).


42 USACERL TR 96/104

Appendix: Bibliography of HSLA Steel Research
Publications

David Taylor Research Center* (DTRC) Reports

Caton, T.E., Corrosion Testing of High Strength, Low Alloy Steels, DINSRDC/SME-84/99 (David
Taylor Naval Ship Research and Development Center’ [DTNSRDC], Annapolis, MD, April
1985).

Czyryca, E.J., Trial Production of HSLA-100 Steel Plate, DTRC/SME-87/83 (February 1988).
Czyryca, E.J., HSLA-100 Steel Plate Production: 2nd Production Heat, DTRC/SME-89/19 (July 1989).

Czyryca, E.J., Development of Copper-Strengthened HSLA Steels for Naval Construction, DTRC/
SME-90/21 (June 1990).

Czyryca, E.J., G.L. Franke, E.M. Hackett, P.W. Holsberg, T.W. Montemarano, R.J. Wong, and M.G.
Vassilaros, Advances in High Strength Steel Technology and Fabrication for Future Naval Hull
Construction, DTRC/SME-90/12 (November 1991).

Czyryca, E.J., and R.E. Link, Physical Properties, Elastic Constants, and Metallurgy of HSLA-100
Steel Plate, DTRC/SME-88/62 (December 1988).

Czyryca, E.J., and R.E. Link, Fracture Toughness of HSLA-100, HSLA-80, and ASTM A710 Steel
Plate, DTRC/SME-88/64 (January 1990).

Czyryca, E.J., and R.E. Link, Intermediate Composition HSLA-100 Steel for Ship Structural
Applications in Light Gages, DTIRC-TM28-90-01 (May 1990).

Czyryca, E.J., R.E. Link, and R.J. Wong, Certification of HSLA-100 Steel for Structural Applications,
Status Report, DIRC-TM-28-88-03 (January 1988).

Czyryca, E.J., R.E. Link, and R.J. Wong, Evaluation of HSLA-100 Steel for Surface Combatant
Structural Certification, DIRC/SME-89/15 (August 1989).

Gudas, J.P., Micromechanics of Fracture and Crack Arrest in Two High Strength Steels, DINSRDC/
SME-87/20 (May 1987).

* Now Naval Surface Warfare Center, Annapolis, MD.


12

USACERL TR 96/104

Nickel also provides toughness. Chromium and molybdenum are added to control
the epsilon-copper precipitate nucleation and growth so consistent properties can be
developed. Chromium and molybdenum also provide additional hardenability that.
helps promote a fine ferritic/bainitic/martensitic microstructure. Niobium helps
retard austenite recrystallization during hot rolling and makes grain refinement
possible. Niobium also provides some precipitation hardening. Grain size control
during austenitizing is provided by the niobium carbo-nitride precipitates.

Figure 2 shows continuous cooling transformation (CCT) diagrams for an A710 com-
position and an HSLA-100 composition (Wilson, et al., September 1988). The
increased hardenability of the HSLA-100 alloy is evidenced by the displacement of
the proeutectoid ferrite field to longer times or slower cooling. The A710 CCT
diagram consists of proeutectoid ferrite, acicular ferrite, martensite, and upper
bainite. Figure 2B shows an extensive martensitic region, with granular bainite and
proeutectoid ferrite at slower cooling rates. Granular bainite contains packets of
ferrite laths with noncementite, interlath, second-phase particles. These particles
have been identified as retained austenite or a combination of retained austenite
and martensite (Hamburg and Wilson, November 1987). These structures are
difficult to distinguish from upper bainite, which consist of ferrite and cementite.
Granular bainite occasionally is observed in A710 compositions (Wilson et al.,
September 1988).

Table 2 summarizes the mechanical properties available via various processing
conditions as allowed by ASTM and military specifications. The ASTM materials
can be furnished in one of three conditions or classes as they are termed in the
specifications.

Class l—As-rolled and Precipitation Heat Treated. The ferritic microstructures
formed by conventional hot-rolling or controlled rolling typically have yield
strengths from 65 to 75 ksi (450 to 525 MPa). Reheating in the range of 1000 to
1200 °F (540 to 650 °C) causes the supersaturated copper to precipitate and raises
strengths. Controlled rolling is often used to achieve adequate toughness in thicker
Class 1 plates. The thickness limits are based on mill capacity. The rolling mill
must introduce sufficient strain at low rolling temperatures to achieve grain refine-
ment. Currently, the maximum Class 1 plate thickness in ASTM is 3/4 in. (19 mm)
and 1/2 in. (18 mm) in the military specification.

Class 2—Normalized and Precipitation Heat Treated. This process requires a
normalization at 1600 to 1700 °F (870 to 930 °C) followed by reheating at 1000 to 1200
°F (540 to 650 °C) to precipitate epsilon-copper in the ferrite and raise strengths.


USACERL TR 96/104

Table 2. Mechanical property requirements per ASTM: low-carbon age-hardenable alloys.

Grade Yield strength | Tensile strength Charpy V-notch
Specification |_condition* (ksi) (ksi) %E
Grade A 85, t<5/16" 90, t<3/4" 20 20ft-lb@-50F, Long.**
Class 1 80, 5/16<t<3/4" 15ft-lb@-50F, tran
Grade A 65, t<1" 72, t<2" 20 50ft-Ib@-50F***
Class 2 60, 1"<t<2” 65, 2"<t<4"
A710 55, 2"<1<4" 60, t>4"
50, t>4"
Grade A 75,t<2" 85, t<2" 20 50ft-lb@-80F***
Class 3 65, 2"<t<4" 75, 2"<t<4"
60, t>4" 70, t>4"
Grade B 85, t<5/16" 90, t<1/2" 18 20ft-lb@-25F, long
82, 5/16<t<3/8" 88, 1/2<t<3/4" 15ft-lb@-25F, tran***
80, 3/8<t<1/2"
75, 1/2<t3/4"
Grade C 90,t<3/4" 100, t<3/4" 20 20ft-lb@-50F, long
Class 1 15ft-lb@-50F, tran**
Grade C 85, t<3/4" 95, t<1/2” 20 50ft-lb@-80F***
Class 3 80, 3/4"<t<2" 90, 1/2"<t<2"
Grade A 80, t<3/4" 90-110, t<3/4" 20 20ft-Ib@-50F, long
Class 1
Grade A 65, t<1" 72-92, t<2" 20 20ft-Ib@-50F, long
Class 2 60, 1"<2" 65-85, 2"<t<4"
A736 55, 2"<t<4" 60-80, t>4”
50, t>4"
Grade A 75, t<2" 85-105, t<2" 20 20ft-Ib@-50F, long
Class 3 65, 2"<t<4" 75-95, 2"<t<4"
60, t>4" 70-90, t>4"
Grade C 90, t<3/4" 100-120, t<3/4" 20 20ft-Ib@-50F, long
Class 1
Grade C 85, t<3/4" 95-115, t<3/4" 20 20ft-Ib@-50F, long
Class 3 80, 3/4<t<2" 90-110, 3/4"<t<2"
MIL-S HSLA-80 80-100, t<1.25" 110, t<1/2" 14,t<1/4" 60ft-lb@-1 20F
24645 Info only, t>1/2"__| 20,t>1/4" 35% shear@-120F
HSLA-100 100-130, t<3/4" Info only 12,t<1/4" 80ft-lb@-80F
100-125, 3/4<t<4" 17,1/4<t<3/4" | 90% shear@-80F
18,3/4<t<4" | 60ft-lb@-120F

35% shear@-120F

*Class 1, as-rolled and precipitation heat treated; Class 2, normalized and precipitation heat treated;
Class 3, quenched and precipitation heat treated.
“On agreement, transverse tests may be specified instead of longitudinal.
*““Optional supplementary test requirements.



USER EVALUATION OF REPORT

REFERENCE: USACERL Technical Report 96/104, Low-Carbon, Age-Hardenable Steels for Use in
Construction: A Review

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USACERL TR 96/104

35

Controlled deposition requires a buttering of the base metal with a low heat input
first layer followed by a higher heat input second layer with sufficient heat to refine
the coarse grained HAZ of the first layer. Obviously this deposition technique re-
quires significant additional attention and eliminates most of the economic incentive
to utilize HSLA steels. The initiation of reheat cracking in the HAZ requires a
stress raiser to initiate or trigger the cracking. The authors have never experienced
reheat cracking in HSLA steels when normal butt joints with typical reinforcement
are subject to PWHT. Only when stress raisers are present, does the coarse grained
HAZ crack. :

The occurrence of local brittle zones in the HAZ of the HSLA steels also has played
some part in the hesitancy of fabricators to use A710-type materials. There is a
discrepancy between the results of CVN and crack tip opening displacement (CTOD)
tests of HAZs. Generally the CVN testing shows some toughness degradation, but
not to unacceptable levels. The CTOD test, with a sharper notch and larger speci-
men, may sample more of the LBZ and thus reveal the larger toughness degradation
of these zones. The question of how LBZ affects the fracture behavior of full-scale
structures has not been answered adequately.

Corps construction, which includes water control structures and buildings, fre-
quently is governed by needs for fatigue and earthquake-resistant designs. New
construction would not benefit by the use of A710 steels because larger section
thicknesses still are required for fatigue resistance. Retrofitting and repair projects
may receive some benefit from the use of the A710 steels by strengthening the
members and improving the fatigue and seismic strength. Corps projects will not
benefit from the weldability characteritics of the A710 steels because the materials
normally used have fairly good welding characteristics.



USACERL TR 96/104

23

low chromium grades (Grade B and C) to the oil drilling industry. Bethlehem
supplies plate rolled from ingots furnished by Armco.

Recently USX announced the availability of seamless piping produced from a modi-
fied A710 composition. This modification adds approximately 0.015 percent titani-
um and eliminates the chromium. This composition apparently has increased the
resistance to toughness degradation in the HAZ as well as lowered the sensitivity
to reheat cracking (Kapadia et al., March 1993).

Only limited structural shapes are currently produced in any of the A710 composi-
tions. The only.commercially available shape known to the authors are rectangular
tubular welded beams supplied by Bull Moose Tube Company. Ingalls Shipyard has
evaluated built-up structural shapes for stiffeners for ship hulls. These shapes were
“T” shapes welded from A710-type wrought strip.

No casting alloys have been successfully produced commercially in the HSLA type
of composition. ESCO Foundry conducted a research project in the casting area
under the auspices of the National Shipbuilding Research Program (Churchill,
Devletian, and Singh, May 1991). ESCO Foundry discovered that the desired
properties—excellent strength and toughness—possible in the wrought condition
could not be developed in a casting of the low-carbon, copper age-hardenable type
of compositions. ESCO Foundry has had some success in developing a nonage-
hardening steel casting composition that approaches the combination of properties
exhibited by the A710-type wrought alloys. There has been some application of an
age-hardenable cast steel in cast nodes for offshore platforms (Stuart, January
1991). These are not copper age-hardening alloys but attain their properties
through a double normalizing treatment and take advantage of vanadium and
niobium additions to control grain size and provide some precipitation hardening.
Castings have not replaced fabricated nodes on a large scale mainly because of the
experience that already exists for fabricated nodes. The long delivery time that
inhibits design changes also has limited the application of these castings.

Some work currently is underway at Lehigh University’s Advanced Technology for
Large Structural Systems (ATLSS) Center evaluating the feasibility and properties
of some experimental A710-type castings for special beam-to-column connection
assemblies. These castings have exhibited strengths similar to the wrought A710
materials with some degradation of the toughness properties. Nevertheless, the
toughness is superior to the A572 beams and columns being connected.



The contents of this report are not to be used for advertising, publication
or promotional purposes. Citation of trade names does not constitute ar.
official endorsement or approval of the use of such commercial products.
The findings of this report are not to be construed as an official

Department of the Army position, unless so designated by other authorized
documents.

DESTROY THIS REPORT WHEN IT IS NO LONGER NEEDED

DO NOT RETURN IT TO THE ORIGINATOR


USACERL TR 96/104

47

Speich, G.R., and T.M. Scoonover, “Continuous-Cooling Transformation Behavior and Strength of
HSLA-80 (A710) Steel Plates,” Proceedings of International Symposium on Processing,
Microstructure and Properties of HSLA Steels (The Minerals, Metals, and Materials Society,
Warrendale, PA, 1988).

Wilson, A.D., “High Strength, Weldable Precipitation Aged Steels,” Journal of Metals, vol 39, no. 3
(March 1987), pp 36-38.

Wilson, A.D., C.R. Roper, and E.G. Hamburg, “Improved Plate Steels for Structural Applications,”
SAE Paper 870790, Proceedings of the Earth Moving Industry Conference (Society of Automotive
Engineers, Warrendale, PA, April 1987).

Wong, R.J., and M.D. Hayes, “Arc Welding Consumables for HSLA Steels with Yield Strengths of 80
ksi and Above” in J.T. Hickey, D.G. Howden, and M.D. Randall, eds., Proceedings International
Conference on the Metallurgy, Welding, and Qualification of Microalloyed (HSLA) Steel
Weldments, (American Welding Society, November 6-8, 1990), pp 450-489.

Naval Postgraduate School Publications

Bissot, D.M., Development of a Constitutive Equation for HSLA-100 at Cryogenic Temperatures, Naval
Postgraduate School, Thesis Report (December 1987).

Burna, R.F., Effects of Preheat on Weldments of NI-COP Steel, Naval Postgraduate School, Thesis
Report (September 1983).

Hamilton, J.E., The Effect of Temperature on the Tensile Properties of HSLA-100 Steel, Naval
Postgraduate School, Thesis Report (June 1987).

Heinze, M.H., The Effect of Aging Treatment on the Microstructure and Properties of Copper-
Precipitation Strengthened HSLA Steel, Naval Postgraduate School, Thesis Report (December

1988).

McNutt, S.A., Stress Relief Cracking in Copper-Precipitation Strengthened HSLA-100 Steel, Naval
Postgraduate School, Thesis Report (December 1988).

Mickelberry, K.D., Microstructural Characterization of HSLA-100 Steel GMA-Weldments, Naval
Postgraduate School, Thesis Report (September 1987).

Potkay, G.P., Microstructural Characterization of the Heat Affected Zone of HSLA-100 Steel GMA-
Weldment, Naval Postgraduate School, Thesis Report (December 1987).

Other Publications

These publications are related to Navy HSLA-80 and HSLA-100 and steels in Navy research
programs.



USACERL TR 96/104

31

in question could be made with a new A710 detail. Even if the original problem
stemmed from fatigue, the increased flaw tolerance of the A710 steel will allow
longer life.

Significant research activity designed to efficiently and effectively use the new high
performance steels is developing. In 1991, the Civil Engineering Research Founda-
tion (CERF, Washington, DC) recommended that top priority be placed on research
and development to exploit the potential of high performance concrete and steel for
the nation’s infrastructure. In response, a planning committee made up of experts
from industry, academia, and government are planning and formulating a high-
performance construction materials program (COMAT). Industrial leadership for
studies of high performance steel will be provided by the High-performance Steel
Coordinating Committee to be organized by the American Iron and Steel Institute
and the American Institute of Steel Construction. Required Federal support for
COMAT is envisioned at $2 to $4 billion over a 10-year plan (CERF draft planning
document, not dated).

A recently initiated Federal Highway Administration project (Project DTFH61-
93-R-00007) focuses on the feasibility of using HSLA steels in highway bridges.
Specifically, the research is supposed to investigate the potential for using the HSLA
steels in present bridge design criteria, and then extending the research into new
bridge design criteria.

New bridge designs should be the result of innovative concepts that make more
efficient use of the high performance steels. The project team—composed of Modjeski
and Masters, Inc., and the primary consultant, Lehigh University’s ATLSS Center—
is directing its efforts toward innovations through specification change and
variations in the basic structural form. Another focus of this work will include
attempts at developing designs that take advantage of the extraordinary fracture
toughness of HSLA steels. And, because of the reduced need to preheat, field
welding may be considerably more attractive to many designers than it has been in
the past. The project team believes the ability to capitalize on the fracture
toughness and weldability of the HSLA steels will be the key to finding “better ways
to build safer, more efficient bridges....the bridge of tomorrow” (Modjeski and
Masters, October 1992).

A significant difficulty in trying to take advantage of the ability to be welded with-
out preheat is the lack of reliable weld metals with similar capabilities. Hydrogen-
assisted cracking is sometimes experienced in the weld metal when the HSLA steels
are welded without preheat.



40

USACERL TR 96/104

Kvidahl, L.G., “Shipyard Experience in Welding ASTM A710,” paper presented at Copper in Steel
Conference, Luxembourg, May 27, 1983.

Kvidahl, L.G., “An Improved High Yield Strength Steel for Shipbuilding,” Welding Journal, vol 64,
no. 7 (July 1985), pp 42-48.

Lundin, C.D., T.P.S. Gill, C.Y.P. Qiao, Y. Wang, and K.K. Khan, “Weldability of Low-Carbon
Micro-Alloyed Steels for Marine Structures,” Bulletin 359, Welding Research Council Bulletin
(December 1990).

Lundin, C.D., R. Menon, and J.M. Lawson, “HAZ Transformation and Toughness in A710 Grade A
Class 3 Precipitation Strengthened Steel,” Welding Research (Supplement to Welding Journal),
vol 68, no. 12 (December 1989), pp 467s-472s.

Meitzner, C-F., “Stress-Relief Cracking in Steel Weldments,” Bulletin 211, Welding Research Council
Bulletin (November 1975).

Modjeski and Masters, Inc., “Innovative Bridge Designs Using Enhanced Performance Steels,”
proposal to Federal Highway Administration, Department of Transportation, Washington, DC.,
submitted in association with ATLSS Center at Lehigh University, Bethlehem, PA (October
1992).

Scoonover, T.M., “Evaluation of Local Brittle Zones in HSLA-80 Weldments,” Proceedings
International Conference on The Metallurgy, Welding, and Qualification of Microalloyed (HSLA)
Steel Weldments, J.T. Hickey, D.G. Howden, and M.D. Randall, ed. (American Welding Society,
Miami, FL, November 6-8, 1990), pp 276-305.

Speich, G.R., and R.M. Scoonover, "Continuous Cooling Transformation Behavior and Strength of
HSLA-80 (A710) Steel Plates,” Proceedings of an International Conference on Processing,
Microstructure and Properties of HSLA Steels, November 3-5, 1987. A.J. DeArdo, ed., Sponsored
by The Ferrous Metallurgy Committee of The Minerals, Metals, and Materials Society,
Warrendale PA, 1988, pp 263-286.

Stuart, H., “The Properties and Processing of Microalloyed HSLA Steels,” Journal of Metals, vol 43,
no. 1 (January 1991), pp 35-40.

Wallace, D.T., and Heid, R.W., “Weldability Testing and Qualification of HSLA-100,” Proceedings
International Conference on the Metallurgy, Welding, and Qualification of Microalloyed (HSLA)
Steel Weldments, J.T. Hickey, D.G. Howden, and M.D. Randall, ed. (American Welding Society,
Miami, FL, November 6-8, 1990), pp 695-722.

West, J.C., “The Benefits of a Modified-Chemistry, High-Strength Low-Alloy Steel,” Journal of Ship
Production, vol 3, no. 2 (May 1987), pp 111-118.

Wilson, A.D., “High Strength, Weldable Precipitation Aged Steels,” Journal of Metals, vol 39, no. 3
(March 1987), pp 36-38.


26 USACERL TR 96/104

Mining Industry

Some heavy duty truck bodies designed for coal hauling have been fabricated with
NI-COP®, the trade name for an A710-type alloy produced by Armco Steel Corp.,
Middleton, OH. Both the heavy box frame and bed of these off-road trucks were
made from the A710-type steel. Some dredging equipment has used A710-type alloy
fabrications. These steels were chosen because of requirements for high reliability
and the ability to be successfully welded in cold, harsh environments.

Oil and Pipeline Applications

Grade C and B compositions are used in the oil industry in the form of electric
resistance welded tube and pipe. Armco also reports that some 17 ton check valve
assemblies used in the Alaskan pipeline have been manufactured from NI-COP*.

Water Systems

A recent fabrication of a large penstock specified an HSLA-80 material of the
straight sections and an A736 (the pressure vessel grade of A710) 4-in. thick plate
for some bifurcations in the line. Currently there is litigation concerning this fabri-
cation, thus information about this application is not freely available. However, the
thick sections were welded without preheat. Unfortunately, the high strength weld
metal selected for this application apparently was not amenable to welding without
preheat. Significant transverse weld metal cracking developed.

Application of HSLA steels to water and oil storage tanks has not yet occurred.
Discussions with several fabricators indicate that there are possible needs for HSLA
steels. Several large tanks recently were fabricated with 80 and 100 ksi yield
strength plates (A537 Class 2 and A514). The use of the A710-type materials most
likely would have provided lower fabrication costs in those instances. However, the
owners, designers, and fabricators have been hesitant to use A710-type steels
because they are not specifically permitted by the applicable design specifications
of the American Water Works Association or the American Petroleum Institute.


10 USACERL TR 96/104

2 High-Strength Low-Alloy Materials

Metallurgy

Low-carbon, copper precipitation-aged plate steels were introduced in the late 1960s
by the International Nickel Company as IN-787. The current ASTM specification
(A710) for structural applications was developed more than 10 years ago. For
pressure vessel applications, this material is covered by ASTM specification A736.
Both A710 and A736 steels can be supplied in three different classes: Class 1, as-
rolled; Class 2, normalized; and Class 3, quenched. All three classes are precipita-
tion heat treated at 1000 to 1300 °F (540 to 705 °C) for 30 to 60 minutes. They
exhibit a wide range of tensile strength, 65 to 120 ksi (450 to 650 MPa) as well as
good impact toughness at low temperatures.

Table 1 lists the compositions of the three ASTM grades of these A710-type steels
and the HSLA-80 and HSLA-100 of the MIL-S-24645. These are extremely low
carbon steels (<0.07 percent carbon) with moderate alloy additions of manganese,
nickel, molybdenum, and chromium and with significant copper, which provides the
age-hardening characteristic.

Copper has a high solubility in austenite at typical austenitizing temperatures, 1600
to 1750 °F (870 to 950 °C), as shown in Figure 1. Ferrite formed at high tempera-
ture also has a relatively high solubility for copper, slightly over 2 percent
maximum. However, due to the sloping solvus line, the copper solubility drops
significantly at lower temperatures. Thus, a rapidly cooled alloy contains copper in
a supersaturated condition. When reheated, copper-rich precipitates form as fine
spherical particles and cause the precipitation-hardening of the steel. These par-
ticles usually are referred to as epsilon-copper. Steels containing more than 0.60
percent of copper are capable of exhibiting precipitation hardening of the ferrite.

Copper is known to have the potential to cause hot shortness problems due to molten
iron-copper phases at the scale interface during heating in oxidizing atmospheres
(Jesseman and Murphy, June 1984). The addition of nickel prevents this problem.


48 USACERL TR 96/104

Heid, R., and T. Wallace, "Weldability Testing and Qualification of HSLA 100,” Proceedings of an
International Conference on The Metallurgy, Welding and Qualification of Microalloyed (HSLA)
Steel Weldments, Microalloying International and AWS (American Welding Society, Houston,

TX, November 6-8, 1990), pp 695-722.

Irving, R.R., “A Cost Effective Replacement for HY-80?” Iron Age, vol 229, no. 10 (May 16, 1986), pp
78-85.

Krishnadev, MLR. et al., “Effect of Low Temperatures on Fracture Behavior of Copper-Precipitation
Strengthened HSLA Steel,” Microstructural Science, vol 15 (ASM International, Materials Park,
OH, 1987), pp 89-111.

Krishnadev, M.R., et al, “Fracture-Microstructure-Mechanical Property Relations in an Advanced
HSLA Steel,” Microstructural Science, vol 14 ASM International, Materials Park, OH, 1986),

pp 189-203.

Krishnadev, M.R., J.T. McGrath, J.T. Bowker, S. Dionne, and A. Lassravini, “HAZ Microstructure and
Toughness of Precipitation Strengthened HSLA Steels and Conventional HY-Grade High
Strength Steels,” Welding Metallurgy of Structural Steels (The Metallurgical Society,
Warrendale, PA, 1987), pp 137-155.

Kvidahl, L.G., “An Improved High Yield Strength Steel for Shipbuilding,” Welding Journal, vol 64,
no. 7 (July 1985), pp 42-48.

Romhanyi, K., et al., “Comparison of Simulated HAZ Microstructure and Toughness for Two
High-Strength Steels,” Microstructural Science, vol 14 (ASM International, Materials Park, OH,
1986), pp 115-126.

Smith, N.J., J.T. McGrath, J.A. Gianetto, and R.F. Orr, “Microstructure/ Mechanical Property
Relationships of Submerged Arc Welds in HSLA-80 Steel,” Welding Research (Supplement to
Welding Journal), vol 68, no. 3, (March 1989), pp 112s-120s.


USACERL TR 96/104

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13

1000

TEMPERATURE, C

HSLA-80 (A710) STEEL

M, = Martensite Start.

400 OPH: 250 225 211 203 193 178 169 163 168 163
6 eee wut wt
10° 40° 107 19° 10°
TIME, Secencs
a

A= Austenite, PF = Proeutectic Ferrite, AF = Acicular Ferrite, UB = Upper Bainite,

o
wi J
fed
s
2 4
& ea \ , we
= «ool v
= \ M.
300+ \
100+ X
OPH: 383-380 ‘) \\ 300 4
0 1
40° 10° 107 40 10
TIME, Seconds
b

Figure 2. Continuous cooling transformation diagrams.