High Performance Steels

Research Group on Steel Products
for Bridges
The Japan Iron and Steel Federation(For Bridge Construction)

Nippon Steel Corporation
JFE Steel Corporation
Kobe Steel, Ltd.
Secretariat:
Market Development GroupManagement Policy Planning Division
The Japan Iron and Steel Federation
Tekko-Kaikan Bldg., 3-2-10
Nihonbashi-Kayabacho, Chuo-ku
Tokyo 103-0025, JAPANTEL: 81-3-3669-4815 FAX: 81-3-3667-0245

Notice: While every effort has been made to ensure
the accuracy of the information contained within thispublication, the use of the information is at the reader's risk and no warranty is implied or expressed by
the Japan Iron and Steel Federation with respect tothe use of the information contained herein.
(Printed in Japan, March 2015)

Photo: Tokyo Gate Bridge

Research Group on Steel Products for Bridges
The Japan Iron and Steel Federation

High Performance Steels:

Strength, Toughness and Weldability, Corrosion Resistance, etc.

Materials

Steels for Bridge High Performance Structures"High Performance Steel" is the designation given to thesteel that offers higher performances in tensile strength,
toughness, weldability and cold formability and corrosion
resistance than those generally used in bridge construction.
Some of these high performance steels have alreadybeen specified in the Specifications for Highway Bridges of the Japan Road Association, revised in December
1996. High performance steels thus specified and thosefor which bridge application is being studied and whichhave already been put into practical use in fields otherthan bridge construction are introduced here.

High Performance Steels:

Standards
SBHS400
SBHS400W
SBHS500
SBHS500W
SBHS700
SBHS700W

Steel with constant yield point(Thicknesses: over 40 mm)

Steel with narrow rangeof yield point variation
Steel with low yield ratio
Low yield point steel
Ultrathick steel plate

2〜7

Strength

Materials

High-strength steel

Pages(Yield point 400 N/mm2 and over)(Yield point 400 N/mm2 and over, weathering steel)(Yield point 500 N/mm2 and over)(Yield point 500 N/mm2 and over, weathering steel)(Yield point 700 N/mm2 and over)(Yield point 700 N/mm2 and over, weathering steel)Standards

Pages(Tensile strength 690 N/mm2 and over)
HT690
HT780
(Tensile strength 780 N/mm2 and over)
HT950(Tensile strength 950 N/mm2 and over)(Yield point 215 N/mm2 and over)
SM400C(Yield point 235 N/mm2 and over)
SM400C-H
2
SM490C(Yield point 295 N/mm and over)(Yield point 315 N/mm2 and over)SM490C-H
2
SM520C*(Yield point 335 N/mm and over)(Yield point 355 N/mm2 and over)SM520C-H
SM570**(Yield point 430 N/mm2 and over)(Yield point 450 N/mm2 and over)
SM570-H
2
SMA400CW(Yield point 215 N/mm and over)(Yield point 235 N/mm2 and over)
SMA400CW-H
2
SMA490CW(Yield point 335 N/mm and over)(Yield point 355 N/mm2 and over)
SMA490CW-H
SMA570W**(Yield point 430 N/mm2 and over)(Yield point 450 N/mm2 and over)
SMA570W-H
2(Yield point variation 120 N/mm )
SN400
SN490
(Yield point variation 120 N/mm2)
SA440(Yield point variation 100 N/mm2)(Yield ratio=Yield point/Tensile strength 80%)
SN400
(Yield ratio=Yield point/Tensile strength 80%)
SN490
(Yield ratio=Yield point/Tensile strength 80%)
SA440
LY100
(Yield point 100 N/mm2-grade steel)
LY225(Yield point 225 N/mm2-grade steel)
Steel plates having high strength and excellent toughness in the range of thicknesses surpassing
those specified in the Specifications for Highway Bridges
2*75~100 mm: 325 N/mm and overHigh Performance Steels:8〜910 〜 1112 〜 13

14 〜 15
16 〜 172**75~100 mm: 420 N/mm and overToughness and Weldability

Materials

Standards

Pages❶ Cold forming

Steel with excellent toughness

Charpy absorbed energy*vE ≥150JvE ≥200J

Radius in cold forming (t: thickness)
7t and over
5t and over

18 〜 19❷ Meeting the specification required for low-temperature application

Low preheating steel
Steel for large heat-input welding
Steel with lamellar-tearing resistanceSteel having PCM lower than standard ones specified in the Specifications for Highway Bridges
Steel applicable to large heat-input welding
Z15, Z25, Z35 (Steel having guaranteed reduction of area in the thickness direction)

20
21
22 〜 23*The value at JIS-specified test temperature

High Performance Steels:● An important technology, which allows production of highperformance steels like high-strength steel grades
having tensile strengths of 500 and 600 N/mm2 widely
applied for steel bridges, is the Thermo-MechanicalControl Process (TMCP). TMCP adequately controls
reheating and rolling, and cooling after rolling in steel
plate production. The TMCP tech-nology imparts betterweldability, higher strength, excellent toughness andimproved properties to steel plates. (See pages 36-37)

Corrosion Resistance and Other Properties

Materials

Standards

Weathering steel

SMA400W
SMA490W
SMA570W

Steel for galvanizing

Steel that prevents dull gray surface and cracking due to galvanizing

Structural stainless steel
Clad steelLongitudinally-proﬁled (LP) steel plate
High-strength steel wire for bridge cables

SBHS400W
SBHS500W
SBHS700W(0.1% offset proof stress 235 N/mm2 and over, tensile strength 520 N/mm2 and over)
SUS304
SUS316(0.1% offset proof stress 235 N/mm2 and over, tensile strength 520 N/mm2 and over)
SUS304N2 (325 N/mm2 0.1% offset proof stress 440 N/mm2, tensile strength 690 N/mm2 and over)
Stainless-clad steel (base metal: carbon steel + clad material: stainless steel)
Titanium-clad steel (base metal: carbon steel + clad material: titanium)
Maximum difference in thickness 25~30 mm, maximum taper gradient 4 mm/m, total length 6~25 m
ST1770 (tensile strength 1,770 N/mm2 and over), ST1960 (tensile strength 1,960 N/mm2 and over)Pages

24 〜 27
28 〜 2930
31
32 〜 33
34 〜 36

1

SBHS

Material Characteristics(Steels for Bridge High Performance Structures)
Scope
SBHS (Steels for Bridge High Performance Structures) are high-performance steel
plates (JIS G 3140) for use in bridge construction. These steels were developed as aresult of a joint industry-academia research project and with the primary object of reducing the construction cost of steel bridges.
In terms of strength, toughness and weldability, the performance of SBHS exceedsthat of 490 N/mm2-, 570 N/mm2-conventional and 780 N/mm2-grade conventional steel.
A good understanding of the high performance offered by SBHS and their effective
application will enable the user both to produce rational bridge designs and to conduct
more streamlined member manufacturing.
In the revision of Specifications for Highway Bridges in Japan (2017), SBHS400,
SBHS400W, SBHS500 and SBHS500W were added as structural materials for bridges.

Features

Chemical Composition
Grade

C

Si

Mn

P

S

Cu

Ni

Cr

Mo

V

B

N

SBHS400≤ 0.15≤ 0.55≤ 2.00≤ 0.020≤ 0.006

—

—

—

—

—

—

≤ 0.006

SBHS400W≤ 0.150.15~0.55≤ 2.00≤ 0.020≤ 0.006 0.30~0.50 0.05~0.30 0.45~0.75

—

—

—

≤ 0.006

SBHS500≤ 0.11≤ 0.55≤ 2.00≤ 0.020≤ 0.006———≤ 0.006

SBHS500W≤ 0.110.15~0.55≤ 2.00≤ 0.020≤ 0.006 0.30~0.50 0.05~0.30 0.45~0.75

SBHS700≤ 0.11≤ 0.55≤ 2.00≤ 0.015≤ 0.006

SBHS700W≤ 0.110.15~0.55≤ 2.00≤ 0.015≤ 0.006 0.30~1.50 0.05~2.00 0.45~1.20

Yield point or
proof stress(N/mm2)

Grade

SBHS400W
SBHS500
SBHS500W

400 and over

500 and overTensilestrength(N/mm2)

SBHS700•490 N/mm2 grade [SBHS400(W)] : Yield strength—Improvement by 10~23% (+35~75 N/mm2)•570 N/mm2 grade [SBHS500(W)] : Yield strength—Improvement by 9~19% (+40~80 N/mm2)•780 N/mm2 grade [SBHS700(W)] : Nearly similar— Improvement by 2~5% (+15~35 N/mm2)

—

—

—

—

—

—

—

—

≤ 0.006≤ 0.60≤ 0.05≤ 0.005≤ 0.006≤ 0.60≤ 0.05≤ 0.005≤ 0.006490~640

Elongation

Charpy absorbed energy

Thickness
(mm)

Test
specimen%

Test specimen
CharpyTesttemperature absorbed energy* and its sampling
direction(˚C)(J)

6 ≤ t ≤ 16

JIS No. 1A

15 and over

16 < t ≤ 50

JIS No. 1A

19 and overt < 40JIS No. 4

21 and over

6 ≤ t ≤ 16

JIS No. 5

19 and over

570~720

Weld-crack Sensitivity Composition PCM (%)■ Higher Yield Strength than Conventional Steel—Yield Point or Proof Stress, Tensile Strength and Elongation, and Charpy Absorbed Energy

SBHS400

As steel plates produced using TMCP technology, SBHS high-performance steel plates
for bridge construction make high strength compatible with high weldability and workability. (For TMCP technology, refer to pages 36~37.)

Unit: %

SBHS700W

700 and over

780~930

t < 16

JIS No. 5

26 and overt < 20JIS No. 4

20 and over

6 ≤ t ≤ 16

JIS No. 5

16 and overt < 16

JIS No. 5

24 and overt < 20JIS No. 4

16 and over

0–5

100 and overV notchDirection perpendicular torolling direction–40*Average value of three test specimens■ Higher Workability and Weldability than Conventional Steel, and theAbility to Eliminate Preheating and to Lower Preheating Temperatures•490 N/mm2 grade [SBHS400(W)] : No need for preheating•570 N/mm2 grade [SBHS500(W)] : No need for preheating•780 N/mm2 grade [SBHS700(W)] : Lowering of preheating temperature (100~120˚C→50˚C)

Welding Materials
Standards of Welding Materials

Greater Contribution
toward Reduced Steel Weight and Construction Cost
■ Practical Effect Yielded at Tokyo Gate Bridge(Kanto Regional Development Bureau, Ministry of Land, Infrastructure, Transport and Tourism.
: Technoangle No. 38, October 2005)

Welding method

SBHS400,SBHS500,
SBHS700

SBHS400W,SBHS500W,
SBHS700W

Shielded metal arc welding

JIS Z 3211

JIS Z 3214

Solid wire

JIS Z 3312

JIS Z 3315

Flux cored wire

JIS Z 3313

JIS Z 3320

Gas metalarc welding○ Reduction of weight of steel products applied: About 3%○ Reduction of cost for member manufacturing: About 12%

490 N/mm2-grade steel
Property

Strength

Workability
Weldability
Corrosion
resistanceStrengthrating

SBHS400
SBHS400W

Conventional
steel
SM490Y
SMA490W

SBHS500
SBHS500W()

2

SBHS700

SBHS700W

Conventional
steel(HT780＊)

)

≥ 400

≥ 335

≥ 500

≥ 430

≥ 700

≥ 700

≥ 685

Constant
yield point

○

△

○

△

○

○

△

Excellent
toughness

○

△

○

△

○

○

△

Lowering of preheating
temperature

○

△

○

△

○

○

△

̶

○

̶

○
○
○
○
(SBHS400W) （SMA490W） (SBHS500W) (SBHS570W)○ Applicable by use of common-specification grade△ Inapplicable by use of common-specification grade

Steel grade

(˚C)

(J)

SBHS400(W)490 and over0

47 and over

SBHS500(W)570 and over–5

47 and over

SBHS700(W)780 and over–15

47 and overTesttemperature

Charpyabsorbed energy***No speciﬁcation of fracture position**Average value of three test specimens

Conventional
steel
SM570
SMA570W(

JIS Z 3351 (solid wire), JIS Z 3352 (flux cored wire),
JIS Z 3183 (deposited metal)

Charpy absorbed energy of
weld metal

Joint tensile
strength*(N/mm2)780 N/mm2-grade steel

Yield point(N/mm2)

Weathering
steel spec

Submerged
arc welding

Example in 50 mm-thick steel plate

570 N/mm2-grade steel

Required Performance of Weld Joints＊ HBS G3102 (HT780)

Example of Applicable Welding Materials (SBHS500)
Welding method
SMAW
CO2 gas
GMAW
Ar + 20%CO2 gas

JIS Speciﬁcation
JIS Z 3211

FCAW

CO2 gasJIS Z 3313

SAW

Deposited metal
Wire
Flux

JIS Z 3183
JIS Z 3351
JIS Z 3352

JIS Z 3312

Welding position
All position
Flat, Horizontal
All position
All position
Flat, Horizontal
Horizontal fillet
Flat

SymbolE57J16-XX
G57JA1UCXX
G57JA1UMXX
T57J1T1x-yCA-XX-U
S58J2-XX
YS-XX
SZXX1

Notes : · “XX” indicates the symbol of the chemical composition.
· Regarding the quality classiﬁcation of ﬂux-cored wire, “Tx” indicates the symbol of the application characteristics.
(Example–”T1”: Use of shield gas, DC (+), rutile type)· “y” indicates the symbol of the welding position. (Example–”0”: Flat and horizontal ﬁllet welding positions; “1”: All position welding)· Regarding the quality classiﬁcation of welding ﬂux, “Z” indicates the symbol of the production method.

3

Yield Strength

Toughness
Relation between Yield Strength and Steel Weight

Toughness of Base Metal for SBHS (Example)
SBHS toughness is higher than that of conventional steel and, further, is guaranteed in
the direction perpendicular to the rolling direction. SBHS manufactured according toweathering steel specifications have the same toughness as mentioned above.

2

For plate girder bridges, steel products with yield strengths of 500 N/mm and underare effective for economical design. This type of steel is also effective in reducing theplate thickness of heavy-gauge steel members.

Lowering of Preheating Temperatures
Effect of Lowering of Preheating Temperatures in Shielded Metal Arc Welding (SMAW)
Steel grade

For long-span suspension bridges and cable-stayed bridges, steel products with ayield strength of 700 N/mm2 are effective for economical design.

Conventional steel
490 N/mm
grade

2* T. Konishi, S. Miki et al: Possibility for Economical Design of Steel Bridge by Use of High-strength Steel, Proceedings ofJapan Society of Civil Engineers, No. 654/1-52, July 2000

Yield Strength of SBHS
SBHS are available in three yield strength grades (400, 500 and 700 N/mm2) anddemonstrate constant yield strength regardless of plate thickness. SBHS manufactured
according to weathering steel specifications have the same yield strength as mentioned
above.

Symbol570 N/mm2
grade
780 N/mm2
grade

SM490YClassiﬁcation
Standard PCM(preheating
temperature)*(SM490Y)(SMA490W)（SMA490W）

PCM requiring no preheating

SBHS400 (W)PCM (preheating temperature)

Conventional steel(SM570)

PCM requiring no preheating

Plate thickness (mm)t ≤ 2525 < t ≤ 40

40 < t ≤ 50

0.26 (no preheating)
0.26 (no preheating)—

50 < t ≤ 100

0.27 (80˚C)
0.27 (80˚C)

0.24

0.29 (100˚C)
0.22≦0.22 (no preheating)Standard PCM (preheating temperature)* 0.26 (no preheating)—

0.27 (80˚C)
0.24

0.29 (100˚C)
0.22

SBHS500 (W)PCM (preheating temperature)≤0.20 (no preheating)

Conventional steel(HT780)Standard minimum preheating
temperature (°C)**100

SBHS700 (W)Minimum preheating temperature (°C)

120
50 (t≤75)* Standard PCM, preheating temperature standard (Japan Road Association: Speciﬁcations for Highway Bridges, 2012 Ed.)** Standard minimum preheating temperature (Honshu-Shikoku Bridge Authority, Steel Bridge Manufacturing Standards, May 1993)

y-groove Weld-crack Test Results (JIS Z 3158)

45

Workability
Workability of SBHS500

Assessment of Workability of SBHS500

Dimension of Ⅰ-girder Used in Workability Test
Steel grade［1］Results of Assessment Test for Assembly Weldability

Dimension (mm)Application
sectionSteel gradePlatethickness

Width × Length

Upper flange30

500 × 6900

Web

20

2920 × 6900

Lower flange50

700 × 6900

Stiffener

12

SBHS500

Ⅰ-girder Manufacturing Drawing (Elevation)

unit (mm)Conventional steel≤ 0.20PCM

unit (mm)SM490YSBHS500≤ 0.22

Weld length

20 mm

50 mm

Assessment
resultNo
crackingNocracking

General

50 mm
80 mm
and over*and over
Provision in Specificationsfor Highway Bridges*In the case when heavier plate thickness is 12 mm and underConﬁrmation that no cracks occurred in welds with a weld length of
20 mm during assembly welding (conventional steel: 80 mm and over)［2］Assessment Results for Effect of Interpass Temperatures

Manufacturing of Ⅰ-girder(1) Example in x groove(2) Example of welding condition
Welding
methodWeldingside

SAW

1st sideand2nd sideunit (mm)Layer No.

ElectrodeHeat input(kJ/mm)Interpass temperature
(˚C)

1

−

≤5

2nd layer to
final layerL

3 grades
① 200 and under② 250 and under③ 300 and under≤ 10
T(3) Assessment of Weld Joint Performance

Outline of Workability Test Results
Assessment item

Application section

Comparison with
SM490Y

Assessment item/Manufacturing condition

Cuttingt = 50 mm○

Cut-surface roughness

Boringt = 50 mm○

Boring accuracyt = 20, 50 mm◎［1］

Available assembly weld length: 20 mm

Web

t = 20 mm○

No preheating; Maximum heat input: 6.1 kJ/mm·T-SAW

Upper flanget = 30 mm○

No preheating; Maximum heat input: 9.9 kJ/mm·T-SAW

Lower flanget = 50 mm○［2］

No preheating; Maximum heat input: 10 kJ/mm·T-SAW

Web-Flange○

No preheating
No preheating

Assembly welding
Butt welding

Fillet welding
Distortion
straightening

Site welding

Stiffener○

Press straightening○

Roller straightening○Webt = 20 mm○［3］

No preheating; Maximum heat input: 9.7 kJ/mm·EGW

Upper flanget = 30 mm○［2］

No preheating; Maximum heat input: 4.1 kJ/mm·CO2

Lower flanget = 50 mm○［2］

No preheating; Maximum heat input: 4.1 kJ/mm·CO2◎ Excellent○ Similar

In spite of being 570 N/mm2-grade high-strength steel, SBHS500 has workability similar to that of SM490Y.
6

Confirmation of appropriate
weld joint performance at
an interpass temperature of
300°C and under (conventional
steel: 230°C and under*)*Required performance of weld joint described in HBS(Standards of Honshu-Shikoku Bridge Authority)［3］Results of Assessment of Weld Joint Toughness

Applicability for large heatinput welding (10 kJ/mm
and under) similar to thatof SM490Y
7

High-Strength SteelApplication Beneﬁts
Trial calculation example based on AASHTO (composite plate girder)
Conditions: Simple girders having 33 m span

Scope
The thickness of plates to be applied can be reduced and structural weight can be
decreased through the use of high-strength steel. Many application advantages —such as longer spans, efficient transport and erection, and also efficient fabrication
and welding are brought about.

Dimensions of the Bridge Subjectedto the Study

Relationship between Yield Point
and Steel WeightMaterial Characteristics
Standards for High-Strength SteelStrength ratings

Stress-Strain Curves of Each Grade

Standards

Steel of 690 N/mm2 grade

HBS G3102
WES 3001

HT70
HW550

Steel of 780 N/mm2 grade

HBS G3102
WES 3001
JIS
G3128

HT80
HW685
SHY685

Steel of 950 N/mm2 grade

WES 3001

HW885

HBS : Honshu-Shikoku Bridge Standard
WES : Japan Welding Engineering Society Standards
JIS : Japanese Industrial Standards

Application Examples
High-strength steel of 690 and 780 N/mm2 grades is in wide use in long suspension,
cable-stayed, truss and other bridges.

Yield Point, Tensile Strength and Allowable Stress of Each Grade
Grade

Strength (N/mm2)
Yield point

Tensile strength

Allowable stresst ≤ 40

235

400

140

SM400
SMA400W

40 < t ≤ 75

215

400

125

75 < t ≤ 100

215

400

125

t ≤ 40

315

490

185

SM490

40 < t ≤ 75

295

490

175

75 < t ≤ 100

295

490

175

SM490Yt ≤ 40

355

490

210

SM520C40 < t ≤ 75

335

490

195

SMA490W

75 < t ≤ 100

325

490

190

t ≤ 40

450

570

255

40 < t ≤ 75

430

570

245

75 < t ≤ 100

420

570

240

HT690

t ≤ 100

590

690

355

HT780

t ≤ 100

685

780

—

HT950

t ≤ 100

885

950

—

SS400

SM570
SMA570W

8

Thickness (mm)Steel products used for upper and lower
chords of superstructure

Akashi Kaikyo Bridge

Source: Honshu-Shikoku Bridge Authority

9

Steel with Constant Yield Point(Thickness : Over 40 mm)
Scope

Comparison of Yield Point between SM520C and SM520C-H

As shown below, the applicable thickness has been increased up to 100 mm following the revision of the Specifications for Highway Bridges in December 2002. Underthe revision, it is possible to use steel plates of thickness exceeding 40 mm withguaranteed no variation in the lower limits in yield point or proof stress depending on
thickness. These steels are called “Steel with Constant Yield Point” and already haverich application records.

Selection Criteria for Steel Grades According to Thickness
Steel for non-welded structures

SS400

Steel for welded structures

GradesThickness(mm)

SM400A
SM400B
SM400C
SM490A
SM490B
SM490C
SM490YA
SM490YB
SM520C
SM570
SMA400AW
SMA400BW
SMA400CWSMA490AW
SMA490BW
SMA490CWSMA570W

6

8

16

25

32

40

50

100

Application Beneﬁts
The allowable stress of the steel with constant yield point conforms to the values
listed in the table below regardless of thickness, based on the yield point guarantee
in the table at left. Steel weight reduction provides an economic benefit and complexity in design can be avoided through the use of steel with constant yield point.
Bold line: Steel with constant yield point (-H) can be applied.
(Speciﬁcations for Highway Bridges-PartⅡ. Steel Bridges, Japan Road Association)

Material Characteristics

Allowable Tensile Stresses in Axial Direction and in Bending one (N/mm2)
Steel with constantyield point

The thickness range of steel with constant yield point is 40~100 mm. The steel guarantees the yield point specified for conventional JIS materials with thicknesses not
more than 40 mm and the steel designation has the suffix “-H” in addition to designation in JIS.

Comparison of Yield Point between Steel with Constant Yield Point and Conventional JIS Materials
2

Yield point or proof stress of steel with constant yield point (N/mm )10

2

Yield point or proof stress of conventional JIS steel (N/mm )Designation

Thickness (mm)40 < t ≤100

Designation

SM400C–H
SMA400CW–H

235 and overSM490C–H

Thickness (mm)16 < t ≤40

40 < t ≤75

75 < t ≤100

SM400CSMA400CW

235 and over

215 and over

215 and over

315 and overSM490C

315 and over

295 and over

295 and overSM520C–H
SMA490CW–H

355 and overSM520CSMA490CW

355 and over

335 and over

325 and over

SM570–H
SMA570W–H

450 and over

SM570
SMA570W

450 and over

430 and over

420 and overConventional
JIS steelThickness (mm)SM400C–H
SMA400CW–H

SM490C–H

SMA490YC-H
SM520C–H
SMA490CW–H

SM570–H
SMA570W–H

40 < t ≤100

140

185

210

255

Thickness (mm)SM400
SMA400W

SM490

SMA490Y
SM520CSMA490W

SM570–H
SMA570W–H

t ≤40

140

185

210

255

40 < t ≤75

125

175

195

245

75 < t ≤100

125

175

190

240

11

Steel with Narrow Range of Yield Point
Variation and Steel with Low Yield Ratio

Application Beneﬁts❶ Steel with Narrow Range of Yield Point Variation
In the case of using this type of steel in building construction, the entire building
structure can be expected to show the designed plastic deformation behavior.

Scope
The plastic design is adopted in steel-frame building construction in Japan, and thus
the building’s safety at a time of earthquake depends largely on the plastic deformation capability of the steel products applied.
Accordingly, for JIS-SN400 (B, C) and 490 (B, C) steels widely used in steel-framebuilding construction and high performance steel of the 590 N/mm2 grade (SA440)
for building structures, it is guaranteed that the margin between the upper and lower limits in yield point falls within a narrow range of 120 N/mm2 for the SN steel and
100 N/mm2 for the SA steel, and further that the yield ratio for both grades is lessthan 80%.
As a result, these steel products are expected to demonstrate excellent deformation capability at a time of earthquake.

Deformation Behaviors of Structures Employing the Steelwith Narrow Range of Yield Point Variation

Material Characteristics
Mechanical Properties of JIS-SN400 and 490, and SA440
Standards

Yield point or proof stress (N/mm2)

SN400B
SN400C

16 < t ≤ 40
235 to 355, incl.

40 < t ≤ 100
215 to 335, incl.

SN490B
SN490C

16 < t ≤ 40

40 < t ≤ 100

325 to 445, incl.

295 to 415, incl.

SA440B
SA440C

440 to 540, incl

Tensile strength (N/mm2)

Yield ratio (%)

400 to 510, incl

80 and under

490 to 610, incl

590 to 740, incl

80 and under

80 and underElongation (%)
No. 1A specimen
16 < t ≤ 50
22 and overNo. 4 specimen
40 < t ≤ 100

No. 1A specimen
16 < t ≤ 50

No. 4 specimen

21 and over

23 and overNo. 4 specimen
20 and overNo. 5 specimen
26 and over

24 and over

40 < t ≤ 100❷ Steel with Low Yield Ratio
In the structural members employing steel with low yield ratio, plastic deformation
occurs over a wider range, and as a result these members demonstrate excellent
deformation capability.

Notes❶ Omission of the standards for SN steel with thicknesses of 16 mm and under❷ Applicable thickness of SA440: 19 mm to 100 mm, incl.
❸ Yield ratio = (Yield point or proof stress/tensile strength)×100

Improvement in Deformation Capabilityof Structures Employing Steel with Low Yield Ratio

12

13

Low Yield Point SteelApplication Beneﬁts
Comparison of earthquake response between a structure equipped with seismic
damper and a conventional structure is shown below.

Comparison of Earthquake Response between Structure Equippedwith Seismic Damper and Conventional Structure

Scope
Low yield point steel features a low yield point, excellent elongation performance(high ductility) and is used in seismic dampers for building structures. Earthquake
input energy is absorbed by plastic deformation of seismic dampers employing thistype of steel, and thus oscillations of building structures can be reduced.

Material Characteristics
Steels of 100 and 225 N/mm2 yield point grades are used for seismic dampers ofbuilding structures.
❶ Mechanical Properties
Designation

Low yield point or
proof stress(N/mm2)Tensile strength Yield ratio(N/mm2)

(%)

LY100

80 〜 120

200 〜 300

≤60

LY225

205 〜 245

300 〜 400

≤80

Elongation
Test
specimen
JIS Z 2201
No.5

(%)
50≤
40≤

Application Examples
Building seismic damper application is shown below.

❷ Chemical Composition
Designation

C

Si

Mn

P

S

N

LY100

≤0.01

≤0.03

≤0.20

≤0.025≤0.015≤0.006

LY225

≤0.10

≤0.05

≤0.50

≤0.025≤0.015≤0.006

Buckling-restrained
brace

Brace supporttype shear panel

Stud-typeshear panel

Wall panel❸ Example of Stress-Strain Curves

Buckling-restrained brace

14

Wall panel

15

Ultrathick Plate

Application Beneﬁts● The application of ultrathick plate allows not only compact structural sections but

also a reduction in the number of main girders to be applied and the elimination of
stiffened girders. The end result is a large numerical reduction in the fabrication
processes of bridge members.
● The section’s plastic deformation can be expected, and therefore deformation
capacity becomes large.

Scope
Application of ultrathick plates allows construction of larger-size structures. Whenultrathick plates are used for bridge structures, the structures can be simplified due
to reduction in the number and sectional area of structural members applied.

Illustration of Applications of Ultrathick Plate Members

Material Characteristics
Examples of specified maximum thickness of steel plates in several specifications or
standards, and major application examples in steel structures are as follows:

Reduced numbers of main
girders to be applied

Bridge pier having a compact
section and reduced numbersof stiffened members

A standard covering ultrathick plates with thickness over 100 mm for bridge applications is prepared — Ultrathick Plates for Steel Superstructure of the Honshu-Shikoku
Bridge Standard (HBS G3107, Draft). This standard prescribes ultrathick plates formain tower base plates, splay saddles, tower links and other suspension bridge
members.

Application Examples
In the United States and Europe, steel plates with thickness over 100 mm are conventionally used in bridge construction.

Application Example in France

Example of application in minimum girder bridges in Japan(Tokai-Oobu viaduct: SM570, maximum plate thickness 75 mm)

Application in Base Plate ofSuspension Bridge Main Tower(SS400 t=180 mm)

Courtesy: Honshu-Shikoku Bridge Authority

16

17

Steel with Excellent Toughness
Scope
Application of steel with excellent toughness has such advantages as:❶ Cold forming is possible with smaller bending radius.
❷ Application of steel products can be expanded in cold regions.
Along with progress in production technology, it has recently become possible tomanufacture steel plates having excellent toughness.

❷ Application in Cold Regions
The toughness of steel products decreases at low temperatures, and therefore
countermeasures must be taken against brittle fracture. However, use of steel plates
having appropriate toughness poses no problems in their application in cold regions.

Application Examples in Cold Region(Distribution of Lowest Temperatures in Hokkaido)

Example of Comparison in Impact Properties
between Conventional Steel and Steelwith Excellent Toughness

Material Characteristics❶ Cold Bending
The section of steel products in which strain occurs due to cold bending poses the
problem of toughness decline, and accordingly the Specifications for Highway Bridges prescribe that as a basic rule the inside bending radius should be more than 15
times the thickness.
However, where sufficient toughness can be secured for the section of steel products subjected to cold bending, the Specifications stipulate cold bending within theinside bending radius more than 5 times the thickness. Practically, cold bending restrictions are eased for steel plate for which the following conditions are guaranteed.

Source: Guidelines for Design and Construction of Steel Highway Bridges in
Hokkaido, Research Committee on Steel Highway Bridges of Association for Civil Engineering Technology of Hokkaido

Application Examples
Cold Bending of the Corner Section

Steel bridge pierSteel main girder

Example of a truss bridge employing square steel tubes with bent
sections (Takishita Bridge, Hokkaido)

18

19

Low Preheating Steel

Steel for Large Heat-input Welding

Scope

Scope
2

As bridge length increases, high-strength steel of more than 570 N/mm in strength
rating is increasingly adopted for bridge girders. In bridge construction employing
high-strength steel and heavy-thick steel, steel products must be preheated justprior to welding in order to prevent cold cracking of the welds. However, on-sitepreheating at 100°C or higher presents a heavy burden not only with regard to work
control but also for the welding operators. Application of low preheating steel permits
reduction or elimination of preheating and incidental work.

Along with advancing automation in welding, large heat-input welding is increasingly used. In general, as weld heat-input is increased, weld quality tends to deteriorate.
Application of steel for large heat-input welding contributes to improved welding
quality as well as higher welding efficiency.

Material Characteristics
Examples of welding qualities are shown below.

Material Characteristics
Low preheating steel is designed with a low cracking parameter of material, andtherefore preheating temperature during welding can be lowered.

Application Examples
Application of steel for large heat-input welding allows greater reduction in the number of welding passes.

Example of on-site welding of main girder web(Electro-gas welding employing large heat-input
welding)

Application Beneﬁts
Application of low preheating steel (low PCM steel) allows considerable lowering of
the preheating temperature.

Example of Effect of Lowering of Preheating Temperature in Submerged Metal Arc Welding (SMAW)
Steel grade
SMA400
SMA400W
SMA490
SMA490Y
SMA520C
SMA570
SMA490W

Thickness (mm)PCMt ≤ 2525 < t ≤ 40

40 < t ≤ 50

50 < t ≤ 100

Standard PCM(preheating temperature)

0.24 (no preheating)

0.24 (50˚C)

PCM requiring no preheating

̶

0.22

Standard PCM(preheating temperature)

0.24 (no preheating)

0.26 (50˚C)

PCM requiring no preheating

̶

0.24

Standard PCM(preheating temperature)

0.24 (no preheating)

PCM requiring no preheating̶

0.26 (80˚C)

0.27 (80˚C)
0.22

0.27 (80˚C)
0.24

0.29 (100˚C)
0.22

Macroscopic photos showing comparisonof weld joint sections

Standard PCM, standard preheating temperature (Speciﬁcations for Highway Bridges, Japan Road Association, March 2012)20

21

Steel with Lamellar-tearing
Resistance

Reduction of Area measured by the Through-thickness Direction Tensile Test of Steelwith Lamellar-tearing Resistance Speciﬁed in JIS G 3199
Class

Average value of three specimens

Value of each specimen

S content (%)

Z15(S)

15% and over

10% and over0.010 and under

Z25(S)

25% and over

15% and over0.008 and under

Z35(S)

35% and over

25% and over

0.006 and under(

To be applied according
to agreement between
the user and the supplier)

Reference: Classiﬁcation according to WES 3008.
"S" is attached when S content is speciﬁed.

Scope
Along with recent trends in the scaling-up and complexity of steel structures, the useof structural members with welded joints that are subjected to large tensile stress inthe thickness direction is unavoidably increasing in steel bridge construction fromthe structural, functional and aesthetic viewpoints. These structural members may
suffer from lamellar-tearing after welding. Therefore, the application of steel withlamellar-tearing resistance is recommended in the Specifications for Highway Bridges in Japan.

Material Characteristics
Lamellar tearing is a phenomenon of cracking parallel to thesurface of steel plates and can occur in welded joints subjected
to tensile stress like cruciform, T- and corner joints. Non-metallic inclusions (mainly MnS) and root cracking can become theinitiation site of lamellar tearing.
Although lamellar-tearing resistance can be directly confirmedby the Z-window type restraint weld cracking test, it is generally
evaluated by the reduction of area measured by the through-thickness direction tensile test and S (sulfur) content in the steel.
Lamellar tearing-resistant steel that guarantees the value of the
reduction of area is specified in WES 3008 (Japan Welding Engineering Society Standards) and JIS G3199 (Japanese Industrial
Standards), in which the non-metallic inclusions contained in thesteel decreases and alloy segregation diminishes.

Illustration of Lamellar Tearing

Application Beneﬁts
For welded structural members in which lamellar tearing is suspected, the use oflamellar-tearing resistant steel and appropriate welding procedure can preclude
lamellar tearing.

Application Examples
Locations Where Lamellar-tearing Resistant Steel can be Applied

Relationship between Reduction of Area in the Through-thickness
Direction Tensile Test and S Content (WES3008-1990)

22

23

Weathering Steel

Cautions in the Use of Weathering Steel❶ Considerations to be made in the planning stage (effect of airborne salt)● In areas with airborne salt levels at 0.05 mdd (mg/100 cm2/day) or lower, weath-

ering steel can be applied in an unpainted state.

Scope
Weathering steel can dispense with painting because of its characteristics that thedevelopment of rust is controlled steadily with the lapse of time. As a result, maintenance costs can be significantly reduced.

● The following figure shows the standard areas where measurements of airborne

salt can be eliminated and unpainted weathering steel can be applied. (Airborne
salt measurement method: the dry gauze method specified in JIS Z2381 or the
method specified by Public Works Research Institute)

Unpainted Weathering Steel Applicable Areas

Schematic Drawing of Rust Layers of Weatheringand Ordinary Steels Exposed for Long Time❷ Diagram for Forecasting Plate Thickness Reduction
In areas where the amount of airborne salt is 0.05 mdd or lower, the forecasted reduction of plate thickness after 100 years of application is minimal.

Plate Thickness Reduction Forecast Curve (Airborne Salt Level: 0.05 mdd or lower)

Material Characteristics
Weathering steel for bridge construction is specified in JIS — JIS G3114 Hot-rolled
Atmospheric Corrosion Resisting Steels for Welded Structures (SMA series).

Hot-rolled Atmospheric Corrosion Resisting Steels for Welded Structures (JIS G 3114)
Designation

Yield point or proof stress (N/mm2)
t ≤ 16 mm 16 < t ≤ 40 40 < t ≤ 75 75 < t ≤ 100 100 < t ≤ 160 160 < t ≤ 200

SMA 400 AW/AP
SMA 400 BW/BP

245 and over 235 and over 215 and over 215 and over 205 and over 195 and over

SMA 400 CW/CP

245 and over 235 and over 215 and over 215 and over

SMA 490 AW/AP
SMA 490 BW/BP

365 and over 355 and over 335 and over 325 and over 305 and over 295 and over

SMA 490 CW/CP

365 and over 355 and over 335 and over 325 and over——

SMA 570 W/P

460 and over 450 and over 430 and over 420 and over

—

—

—

Tensilestrength(N/mm2)400 〜 540—
490 〜 610
570 〜 720

Charpy absorbed energy
Testing temperature Absorbed energy
—

—

0˚C

27J and over0˚C

47J and over

—

—

0˚C

27J and over0˚C

47J and over

-5˚C

47J and over

Reference: In general, "W" steel is used unpainted or with rust stabilization treatment, and “P” steel is used painted.

24

The curve in the above figure shows the range of forecasted plate thickness reduction,
based on the horizontal exposure of test specimens between main girders at 22 locations nationwide for 9 years. (The exposure results have also been proved by the
results of 17-year exposure tests.)25

Application Beneﬁts

Reference: (Example of secular change)
At the initial stage of construction, non-uniform rusting can be found, but this changes to a uniform dark brown tone as time passes.

Merits of Weathering Steel● Reduction of lifecycle costs: Repainting can be eliminated.
● Mitigation of environmental burdens: Unpainted steel can be applied.
● Environmental harmonization: The attractive stabilized rust that over time forms on(Example of unpainted use)

Completion

About 2nd month⇒

About 1st year⇒

About 28th year

weathering steel surfaces harmonizes well with the natural surroundings.

Image of Lifecycle Cost
Distant view

Close-range
view

Application Examples
Unpainted Weathering Steel in Bridge Structure (Japan)

26

Reference: (Ni-type weathering steel)
In contrast to conventional JIS weathering steel, the newly developed Ni-type weathering steel contains a quantity of nickel as a main element. Ni-type weathering steel
is more resistant to airborne salt and has already been put into practical use.

27

Steel for Galvanizing

Application Beneﬁts
When galvanizing is adopted as a corrosion protection method for steel bridges,
maintenance costs such as repainting are greatly reduced, thus leading to the reduction of the life-cycle cost (LCC) of steel bridges.

Scope

Example of LCC Assessment

Hot-dip galvanizing is widely applied as a method of corrosion protection of steel
products used for bridge construction. In hot-dip galvanizing, structural members are
immersed in a high-temperature galvanizing bath, which poses the following problems:● Dull gray surface due to galvanizing (surface discoloration)● Cracking due to galvanizing (cracking due to zinc embrittlement and high strains)
Steel for galvanizing is provided with measures to prevent dull gray surface due togalvanizing and cracking due to zinc embrittlement.

Material Characteristics❶ Dull Gray Surface due to Galvanizing
Dull gray surface due to galvanizing concerns galvanizing temperatures and theamount of Si included in the steel (see figure below).
The figure shows that control of Si amount to 0.02% and under or 0.15~0.25% will
improve the dull gray surface of the steel product during galvanizing.

Relationship between Evaluation Points
to Assess Dull Gray Surface and Si Content
Calculation Conditions of LCC Assessment
Model 1
Replacement cycle

Model 260 years

200 years

Painting (coating film)

Chlorinated rubber paint15 years

Repainting

Chlorinated rubber paint15 years

Zinc spraying

70 years

Slab

RC slab40 years

PC slab

200 years

Slab maintenancePartial maintenanceafter 20 years of service

20 years

Maintenance for joint section

50 years

SupportSteel support

30 years

Rubber support

100 years

Expansion device

Conventional specification

10 years

Minimized maintenance specification

20 yearsPavement

Ordinary asphalt365 and over

10 years

Modified asphalt

15 years

Water-proofing layer

Sheet water-proofing (pavement cycle)

10 years

Sheet water-proofing (pavement cycle)

15 years

Water-proofing layer
replacement

Paint water-proofing(pavement cycle)

10 years

Paint water-proofing(pavement cycle)

15 years

Galvanizing

130 years(K. Nishikawa: A Concept of Minimized Maintenance Bridges, Bridge and Foundation Engineering, Aug. 1997)❷ Cracking due to Galvanizing
In the process of hot-dip galvanizing, zinc sometimes penetrates into the grain boundary of the heat-affected zone due to weld residual stress and thermal stress, which
lowers the grain boundary’s strength and causes cracking. This phenomenon is calledcracking due to zinc embrittlement.
The relationship between zinc embrittlement of steel products and chemical composition was studied and clarified (see Equation 2). It became clear that in the caseof 570 N/mm2 grade steel, when the chemical composition parameter, SLM400, satisfies
Equation 1, cracking due to zinc embrittlement does not occur.

Application Examples
A Bridge Constructed Using Galvanized Members

In the case of 570 N/mm2 grade steel: SLM400≥53%̶̶̶̶ ①
SLM400 = 227– 320C –10Si –76Mn – 50Cu – 30Ni – 92Cr – 88Mo – 220V – 200Nb + 200Ti̶̶̶̶ ②In Equation 2, adjustment of chemical composition to satisfy Equation 1 allows
production of steel products in which zinc embrittlement is improved.
28

29

Structural Stainless Steel

Clad Steel

Scope

Scope
Clad steel refers to the product produced by joining steel with different kinds of metals in a layer state. The aim of clad steel is to reconcile excellent function and economy that are not obtainable from a single material.
Stainless steel, titanium and other corrosion-resistant materials are used as the
cladding material for steel, in which strength is borne by steel, thus realizing an extremely economical material.

Passive Film of Stainless SteelApplication of stainless steel makes possible constructionof structures having excellent corrosion resistance.
In stainless steel production, more than 12% of Cr, which
is liable to oxidize, is added to the steel, which forms a stable passive film on the steel surface. This passive film enhances corrosion resistance of stainless steel. If the passive
film is damaged due to surface flaw, it offers an advantagethat the film is recovered quickly due to Cr ions.

Illustration of Clad SteelMaterial Characteristics
There are three kinds of stainless steel, which are used as structural materials:❶ SUS304 (SS 400 grade strength)❷ SUS316 (SS 400 grade strength+High corrosion resistance)❸ SUS304N2 (SM 490 grade strength)

Stress–Strain Curve

Physical Properties of SUS304
Steel

SUS304 Mild steel SUS304/Mild steel

Density

7.93

7.86

1.01

Specific electric resistanceμΩ–cm (room temperature)

72

19.5

3.69

Magnetism

No

Yes

—

0.12

0.116

1.03

Linear thermal expansion coefficient ×10 / ˚C

17.3

11.7

1.48

Thermal conductivity
×10–2 cal/cm/sec/ ˚C(100˚C)

3.89

11.9

0.33

Specific heat

g /cm

3

cal /g / ˚C (0~100˚C)–6Young’s modulusE

tf /cm2

1970

2110

0.93

Modulus of rigidityGtf /cm2

758

840

0.90

0.3

0.3

1.00

Poisson’s ratio

Application Examples
Stainless-clad Steel

Titanium-clad SteelThis steel already has application records in dam andwatergate facilities, but in recent years its application
for bridge superstructure is being examined.

Titanium is an expensive material, but when titanium
is used in the form of titanium-clad steel, future
maintenance costs will be greatly reduced.

Full-scale pilot member of bridge box girder(Differences in surface luster are due to investigations
made on appearance differences by surface-treatment methods.)

Example of a steel pier partially covered with titanium clad steel
in the splash and tidal zone

In addition, dual-phase stainless steel (ASTM S82122, SUS329J3L, etc.) having an
austenitic and ferritic dual-phase structure has been put on the market. The stainlesssteel has corrosion resistance similar or superior to that of SUS304 and SUS316 andtensile strength twice that of SUS304 and SUS316.

Application Examples
In building construction, excellent corrosion resistance anddecorativeness inherent to stainless steel are attracting muchattention and thus stainless steel is finding increasing use
as structural members. In addition to building construction,
stainless steel is steadily being applied for bridge construction in Europe, the US, and Asian nations.

Courtesy: Aichi Steel Works, Ltd.

30

31

LP Steel Plate

Application Beneﬁts(Longitudinally-proﬁled Steel Plate)● Rationalized Thickness Composition in Compliancewith the Section Force Required

Scope
LP steel plates are produced by changing the thickness in the longitudinal direction.
Longitudinally profiled steel plates have become available due to recent developments
in plate rolling technology.
Application of LP steel plates allows cost reduction by eliminating welds and reducing structural weight.
LP steel plates have already been applied in the construction of more than 100
bridges in Germany and France, and are finding increasing applications in shipbuilding and bridge construction in Japan.

① Structural weight of LP steel plate girders can be reduced, compared to steel
girders of equal thickness.
② Application effect is greatly improved for large-section twin-girder bridge.
● Equal Thickness in Joints① Use of filler plates can be eliminated in bolt joints.
② Tapering process is not required for weld joints.

Material Performances❶ Production Process

LP Steel Plate Production by Rolling

Basic Conﬁguration of LP Steel Plate(Longitudinal-direction Section)

Application Examples
An illustration of application of LP steel plates in girder flanges is shown below.

❷ Size Availability of LP Steel Plates
Maximum thickness difference :Maximum gradient :Minimum thickness :Maximum thickness :Total length :Width :

25 – 30 mm
4 mm/m
10 – 15 mm
100 mm6〜25 m≥1.5 m❸ Applicable Steel Standards for LP Steel Plates
JIS G 3101 SS400, JIS G 3106

32

33

High-Strength Steel Wire for Bridge Cables
Scope
In long-span suspension bridge construction, as the span length increases, thedeadweight of the bridge increases, and cable section increases correspondingly incase of using steel wire of identical strength level.
When adopting high-strength steel wire for the main cables of long-span suspension
bridges, the cable section can be made smaller, and efficient erection work, reductionof main tower height and simplified stiffening structure are realized.
For the construction of Akashi Kaikyo Bridge having a center span of 1,991 m,
high-strength steel wire having a tensile strength of 1,770 MPa, 200 MPa higher thanconventional galvanized steel wire (1,570 MPa) for bridge cable, was developed andput into practical use. In recent years, high-strength steel wire with an even higher
strength grade of 1,960 MPa has been developed.

Application Beneﬁts
Trial Calculation of Span Length andCable Wire Strength for Suspension Bridges

Example of Change in Bridge Structure due toHigher Strength of Steel Cable(from 1,570 MPa steel wire to 1,770 MPa steel wire)

Increasing Strength of Steel Wire for Cables of Various Bridges

Material Characteristics
Cable Section
In producing steel wire with 1,770 MPa and 1,960 MPa
strength grade, low-alloy steel with higher levels of C and Si
was adopted as the base material, which improved the tensile strength by 200~400 MPa over the 1,570 MPa grade.
1,770 MPa and 1,960 MPa high-strength wire not only
possess high tensile strength, but also demonstrate toughness and fatigue strength, and also exhibit handling efficiency during cable erection that are similar or superior to thoseof 1,570 MPa grade wire.

Application Examples
For Akashi Kaikyo Bridge, 1,960 Mpa steel wire is adopted for the catwalk ropes in
addition to 1,770 Mpa steel wire for the main cables.

Akashi Kaikyo Bridge (main cables)

Kurushima Bridge (main cables)

Major Speciﬁcations of Steel Wire for Bridge Cables
Item
Material

Mainchemicalcompositions

1570 MPa strength grade

1770 MPa strength grade1960 MPa strength grade

C (%)

0.75 ~ 0.80

0.80 ~ 0.85

0.90 ~ 0.95

Si (%)

0.12 ~ 0.32

0.80 ~ 1.00

1.00 ~ 1.20

Mn (%)

0.60 ~ 0.90

0.60 ~ 0.90

0.30 ~ 0.60

1570 ~ 1770

1770 ~ 1960

Tensile strength (MPa)
Proof stress (MPa)
Mechanicalproperties
Galvanized
wire

Elongation (%)
Coils (3d)No. of twists
2

Amount of galvanizing (g/m )Zinc coat adhesion (5d winding)Free ring cast diameter (m)34Note: In the case of wire diameter of 5 mm

≥1160 (0.7% total elongation) ≥1370 (0.8% total elongation)

1960 ~ 2150

≥1470 (0.2% offset)

≥4

≥4

≥4

No breakage

No breakage

No breakage

≥14

≥14

≥14

≥300

≥300

≥300

No peeling off

No peeling off

No peeling off

≥4

≥4

≥4

35

TMCP (Thermo-Mechanical Control Process)Features
Because TMCP steel plates feature low carbon equivalent and high fracture toughness
through proper application of controlled rolling and cooling, these plates offer thefollowing features:

Scope● Features in Terms of Plate Fabrication● What Is TMCP?

① Outstanding improvement in weldability② Little change in material performances after gas flame straightening③ Improvement in notch toughness of HAZ (heat-affected zone) of weld joint④ Softening in HAZ by large heat-input welding — within the practically allowable range

TMCP refers to the Thermo-Mechanical Control Process —a steel plate rolling process
based on controlled rolling followed by controlled cooling. Application of TMCP
technology not only allows a greater reduction of the carbon equivalent (Ceq) and theweld crack sensitivity composition (PCM), two important parameters for weldability,
but also enables the production of high-strength, high-toughness and other high-performance steel plates.

Relationship between Carbon Equivalent and Strengthof Steel Plates Produced by the Conventional Rolling Method
and TMCP (thickness: 20~30 mm)● Feature of Microstructure

TMCP steel plates have fine ferrite and pearlite structure, compared to conventional steel plates.
● TMCP Equipment

Microstructure of 490 N/mm2 Grade Steel (× 400)

An outline of TMCP equipment is shown below.

Typical Arrangement of TMCP Equipment

TMCP(controlled rolling)

TMCP(controlled rolling + controlled cooling)

Conventional rolling*In certain plants, roughing mill is not used.

3637