bluuebunny/crossref_metadata_2025 huggingface dataset:
The Development of New Materials for Nonmagnetizable Retaining Rings and Other Applications in the Power Generating Industry
Authors: Stein G
Published: December 2008

Long before the first forged retaining rings were manufactured, our company, Schmiedewerke Krupp-Klöckner, was concerned with the development of nonmagnetizable steels for the manufacture of retaining rings. In addition to our company, only a few manufacturers are manufacturing rings that meet the requirements of present-day specifications.

As various steel brands developed beginning early in this century, the requirements of our customers concerning the mechanical properties and the corrosive environmental conditions became greater and greater. This led us in the late seventies to a material that meets present and future requirements regarding both mechanical properties and full corrosion resistant behavior.

This paper will show the main steps in the development of retaining ring production by our company. Today we use as starting material for our retaining rings cast electrodes of electric furnace steel which are remelted in our electroslag remelting plant. The ingot undergoes several forging and reheating operations to produce a ring blank. The blanks are rough turned, solution heat-treated, and then work-hardened so as to obtain the desired 0.2% proof stress. This operation is followed by a stress-relieving heat treatment and a finish-machining operation. This production requires continuous monitoring of the production procedure as well as extensive in-process and final tests.

In the last 30 years, about 18 000 retaining rings have been manufactured from a material with 0.5% carbon, 18% manganese, 4.5% chromium, and 0.1% nitrogen. Physical and mechanical properties could be met with this material even in customers' advanced specifications. There is only one disadvantage: The material is susceptible to stress corrosion cracking. Some failures of retaining rings in recent years were due to the occurrence of stress corrosion cracking. The best way to avoid stress corrosion cracking is to use a nonsusceptible material. Such a material has been developed for the manufacture of retaining rings in our company. Up to now we have produced more than 400 rings with 0.2% proof stresses up to 1250 N/mm2.

This paper will show the chemical analysis, mechanical properties, residual stresses, stress corrosion properties, susceptibility to hydrogen-induced cracking, fracture toughness properties, sensitization at elevated temperatures, and stress relaxation behavior.

Even with this extraordinary material, we have not stopped the development of retaining ring material. Three years ago our company installed the only full-size pressure electroslag remelting equipment in the world. With this equipment we can increase the nitrogen content of any material above the normal solubility limit. This will lead to higher 0.2% proof stresses and more homogeneous mechanical properties without losing the corrosion-resistant behavior of the new retaining ring material.
Optimizing Mechanical Properties of Specialty, Stainless, and Heat-Resistant Alloy Steel Forgings by Thermomechanical Processing
Authors: Kuhlman GW , Pishko R , Darden WS , Krubsack WL
Published: December 2008

Ferrous alloy forgings typically are used at the critical points in any given application, and thus it is incumbent upon the forger to select optimum melting technology and design processing techniques to provide specialty, stainless, and heat-resistant steels that possess the full extent of the grade's mechanical properties. Thermomechanical processing techniques can be employed to achieve such goals. In specialty steels such as HP310, HP9Ni-4Co-0.20C, and AF1410, combinations of working practices and thermal treatments have been examined to maximize the ductility and/or fracture toughness of these ultra-high strength steels. In stainless steel Grades 15-5PH and PH13-8Mo in forgings, critical fracture-toughness requirements can be enhanced by careful selection of forging parameters. Finally, for heat- and corrosion-resistant materials, including A286 and Inconel 625, relationships between forging and thermal treatments have been studied that optimize grain size, strength, and toughness.
Integral Forged Pump Casing for the Primary Coolant Circuit of a Nuclear Reactor: Development in Design, Forging Technology, and Material
Authors: Austel W , Körbe H
Published: December 2008

Developments in the forging of large casings for primary circuit coolant pumps for light water reactors in Germany are demonstrated beginning with the multiple forging fabricated version and ending with the integral forged type. This version is the result of the joint efforts of the pump manufacturer and the forgemaster after a cost-gain evaluation and represents an optimum solution in view of its functional and economical performance and also considering the high requirements for mechanical-technological properties, including homogeneity of the material. The development from 22 NiMoCr 3 7/A 508 Class 2 to 20 MnMoNi 5 5/A 508 Class 3 and their optimization will be demonstrated. This development is based mainly on minimizing the sulfur content and on vacuum carbon deoxidation (VCD), which results in a reduction of the A-segregations, in improving fracture toughness and isotropy, and in the desired fine-grain structure.
Manufacturing of Large and Integral-Type Steel Forgings for Nuclear Steam Supply System Components
Authors: Kawaguchi S , Tsukada H , Suzuki K , Sato I , Onodera S
Published: December 2008

Forgings for the reactor pressure vessel (RPV) of the pressurized heavy water reactor (PHWR) 700 MWe, which is composed of seven major parts and nozzles totaling about 965 tons, were successfully developed. These forgings are: 1. Flanges: an outside diameter of 8440 mm and a weight of 238 tons max, requiring an ingot of 570 tons. 2. Shells and torus: an outside diameter of about 8000 mm with large height. 3. Cover dome: a diameter of 6800 mm and a thickness of 460 mm, requiring a blank forging before forming of 8000 mm in diameter and 550 mm thick.

The material designation is 20Mn-Mo-Ni 5 5 (equivalent to SA508, Class 3).

Even with greater dimensions and weight than the current largest forgings, the manufacture and the qualities achieved were satisfactory. These successful results were obtained by recent developments in the manufacturing technology of steels, such as steel making, metal-working processes, and heat treatment, which are vital to the quality of large-sized and heavy-walled steel forgings.

In this paper, the manufacturing of and the properties of such large and integral forgings are discussed, including an overview of manufacturing processes for ultralarge-sized forgings over the last two decades.
Advanced Technology of Heavy-Section Tube Sheets for Nuclear Power Generation
Authors: Skamletz TA , Grimm WW
Published: December 2008

Considered in particular were the toughness requirements at low temperatures, the safe weldability, and the minimum sensitivity against temper embrittlement at stress-relieving temperatures of Steel 20 MnMoNi 5 5, corresponding to ASTM A 508 Class 3. High-temperature tensile and creep properties up to 450°C had to be met.

These targets were achieved by applying the production steps as follows: 1. The steelmaking was done according to the Buderus calcium-argon blowing (CAB) process. The low sulfur contents of 0.002% and lower and the special pouring technology to achieve low segregation rates are the basic reasons for the outstanding toughness and the isotropy of the material properties. 2. The forging technology, in particular the temperature range and the deformation rate, was designed to produce fine-grain structure already in the as-forged condition. 3. A newly developed, three-step, quality heat treatment is most important for the hardening through and the toughness level of the heavy section. 4. The report submits a discussion of the dimensional limits for 20 MnMoNi 5 5 forgings produced according to different technologies.
Survey of New Developments in Forging Techniques and Equipment
Authors: Kramarow NM
Published: December 2008

This paper discusses the introduction into commercial practice of a number of new forging press and control technologies developed by press builders for the forging of high-temperature alloys and special stainless steels.

The paper categorizes forging technologies by forging characteristics and press characteristics. A number of specific fields are then surveyed: 1. Warm die forging to produce finished gear profiles without further machining. 2. Isothermal and hot die forging, in which the die temperature and the billet temperature are identical or very close, for forging high-temperature materials used in gas turbine engines and similar applications. The presses and controls required for these different applications are described in some detail. 3. Precision forging, also known as draftless forging in the aircraft industry, is described. The sophisticated controls needed for this type of forging are discussed. 4. Multiaxis forging, not a new technique, used for the production of items weighing several tons for severe duty. Again, modern controls and press design make these forging technologies commercial practice. 5. Automation is now moving into the forge shop; items such as the ring preforms for ring mills, which formerly were hammered to shape, are now produced at high speeds on automatic ring preform presses. 6. Computer controls have now been applied to preform forging to eliminate the open die in the hand shaping of preforms before finishing. This operation now can be fully programmed at great savings in labor and energy.

The paper concludes with a discussion of a very large installation for the production of thick-walled forged tubes and a new mechanical screw press which can deliver very large amounts of energy on each blow.The paper concludes with a discussion of a very large installation for the production of thick-walled forged tubes and a new mechanical screw press which can deliver very large amounts of energy on each blow.
Forging Force Requirements with Special Regard to Shear Resistance of the Forge Material
Authors: Javorik LJ
Published: December 2008

The purpose of this development project was to precalculate forging forces. This is important not only to design the most economical machine to do the job, but also because knowledge of the exact forging force enables us to carry out the desired metallurgical change in the material.

While the work on strength, work hardening, the effect of speed on the virtual strength of the material, temperature, and friction offers little novelty and serves mostly as a summary, the formulas developed are still the results of a new and independent theoretical and experimental work; emphasis was put on developing a theory to calculate shear resistance offered by the forge material because the author found no publication dealing with this subject in spite of the fact that such forces by shear characteristically range around one third of the total forging force requirement.

The author faced the difficulty that all regular (bidirectional) shear formulas are strongly restricted in their range of validity, and, if this limited range is exceeded, the formulas suffer greatly in accuracy. Therefore, the author briefly explains existing shear theories and their ranges of validity and gives new and revised formulas for the ordinary bidirectional shear that no longer are restricted by location thickness, or by other dimensions of the material. Then the author uses the newly developed general shear theory, converting the theory to monotool shear calculation as is the case in forging.
Hydrogen—Its Occurrence, Determination, and Control in Steel Forgings
Authors: Murphy EL , Steiner JE
Published: December 2008

The history of hydrogen-related problems in heavy steel forgings is traced. Hydrogen embrittlement and its manifestation as “fisheyes” and lowered ductility in tension specimens is discussed. Flaking, its occurrence, detection, and control, past and present, is reviewed. Recommendations for hydrogen control in specifications of ASTM Subcommittee A01.06 on Steel Forgings and Billets are presented.
Failure Analysis of Hot Forging Dies
Authors: Ebara R , Kubota K
Published: December 2008

Impact failure of hot forging dies occurs frequently from surface cracks due to mechanical or thermal fatigue. However, useful information regarding failure analysis of hot forging dies is scarce because few data exist on the fracture behavior and fractography of hot forging die steels.

In this paper, what is mainly described is dynamic fracture toughness, low cycle fatigue behavior, and fracture surface appearances of hot forging die steels. A couple of quantitative analyzed examples of fracture toughness and temperature by use of stretched zone width measurement for hot forging die failure are described.
An Application of Fracture Mechanics to a Ship Controllable Pitch Propeller Crank Ring
Authors: Hilton PD , Mayville RA , Peirce DC
Published: December 2008

A fracture mechanics analysis was conducted to establish the fracture toughness of a controllable pitch propeller crank ring material required to prevent a fracture mode in which loss of a propeller blade occurs. Loss of the propeller was assumed to be prevented if fracture instability could not occur before the fatigue crack grew to a size beyond which crack growth would proceed radially through the flange of the crank ring and not around the circumference. The fracture analysis was conducted by modeling the cracked crank ring as a plate with a part-through crack in bending. Numerical solutions for part-through cracks in bending were combined with results for large crack length-to-plate width geometries for through cracks in bending to determine KI for the large crack size of interest. Values of KI with plastically adjusted crack lengths were converted to values of JI and crack driving force curves were generated. Estimates of the plastic collapse moment for the crank ring were made as an alternative method of determining fracture conditions. The results of the analysis are a minimum acceptable value of yield strength and curves of yield strength versus minimum acceptable values of JIR and Tmat at a crack extension of 1.27 mm as determined by a J-R curve test.
Variable Flaw Shape Analysis for a Reactor Vessel under Pressurized Thermal Shock Loading
Authors: Yang CY , Bamford WH
Published: December 2008

A study has been conducted to characterize the response of semi-elliptic surface flaws to thermal shock conditions which can result from safety injection actuation in nuclear reactor vessels. A methodology was developed to predict the behavior of a flaw during sample pressurized thermal shock events. The effects of a number of key variables on the flaw propagation were studied, including (1) fracture toughness of the material and its gradient through the thickness, (2) irradiation effects, (3) effects of warm prestressing, and (4) effects of the stainless steel cladding.

The results of these studies show that under thermal shock loading conditions the flaw always tends to elongate along the vessel inside surface from the initial aspect ratio. However, the flaw shape always remains finite rather than becoming continuously long, as has often been assumed in earlier analyses. The final shape and size of the flaws were found to be rather strongly dependent on the effects of warm prestressing and the distribution of neutron flux.

The improved methodology results in a more accurate and more realistic treatment of flaw shape changes during thermal shock events and provides the potential for quantifying additional margins for reactor vessel integrity analyses.
Effect of Loading Rate on Dynamic Fracture of Reaction Bonded Silicon Nitride
Authors: Liaw BM , Kobayashi AS , Emery AF
Published: December 2008

Wedge-loaded, modified tapered double cantilever beam (WL-MTDCB) specimens under impact loading were used to determine the room temperature dynamic fracture response of reaction bonded silicon nitride (RBSN). The crack extension history, with the exception of the terminal phase, was similar to that obtained under static loading. Like its static counterpart, a distinct crack acceleration phase, which was not observed in dynamic fracture of steel and brittle polymers, was noted. Unlike its static counterpart, the crack continued to propagate at nearly its terminal velocity under a low dynamic stress intensity factor during the terminal phase of crack propagation. These and previously obtained results for glass and RBSN show that dynamic crack arrest under a positive dynamic stress intensity factor is unlikely in static and impact loaded structural ceramics.
Interactive Effects of High and Low Frequency Loading on the Fatigue Crack Growth of Inconel 718
Authors: Petrovich A , Bessler W , Ziegler W
Published: December 2008

The effect of a loading profile containing a high frequency (200 Hz) loading component superimposed on a low frequency (∼0.05 to 0.5 Hz) loading component on fatigue crack growth of Inconel 718 at 650°C was investigated. The high frequency sinusoidal loading was added during the upper level hold period of the low frequency trapezoidal waveform.

Fatigue crack growth tests were carried out on Inconel 718 with a constant low frequency ΔK and an increasing high frequency ΔK in such a manner that the regimes in which crack growth is low frequency cycle and high frequency cycle dominated were investigated. Particular attention was devoted to the interaction of the two loading components in the low frequency dominated crack growth regime and the dependence of the transition to high cycle domination on factors such as low frequency cycle ΔK and hold time. The effects of hold times in the range of 2 to 180 s and low frequency ΔK in the range of 15 to 40 MPa√m were investigated.

In the high cycle dominated regime, the relationship between crack growth rate and high frequency ΔK had the characteristics of threshold crack growth data. In the low cycle dominated regime the high frequency cycle retarded crack growth under certain circumstances.
Creep Crack Growth under Non-Steady-State Conditions
Authors: Saxena A
Published: December 2008

The problem of characterizing crack growth under small scale creep and transition conditions is of great practical significance. This paper defines a crack tip parameter Ct for characterizing creep crack growth behavior under wide range creep conditions from small scale creep to steady-state creep. Under steady-state creep conditions, Ct is shown to reduce to the familiar C∗-integral. The physical basis for the Ct parameter is also provided. Wide range creep crack growth data on A470 Class 8 steel using two specimen geometries were obtained and correlated with the Ct parameter in the temperature regime of 482 to 538°C. The levels of creep deformation in the various specimens tested to obtain the crack growth rate data ranged from small scale creep to essentially steady-state creep conditions.
JIc Testing Using Arc-Tension Specimens
Authors: Kapp JA , Bilinsky WJ
Published: December 2008

JIc was determined in two materials (6061-T651 aluminum and ASTM A-723 Grade 1, Class 4 pressure vessel steel) using arc-tension (A(T)) and compact tension (C(T)) specimens. The J-R curves were determined by using the multispecimen method and the compliance unloading method. J was determined for the A(T) specimen by the Merkle-Corten method of analysis as modified by Clarke and Landes. A correction factor was included to account for the tensile loading component, and both the plastic and elastic components of J were necessary when using the A(T) specimen. With the proper formulas for J in the A(T) specimen, the same J-R curves were determined in both materials using either A(T) or C(T) specimens. This preliminary study suggested that the A(T) specimen was totally adequate for JIc testing and should be included in subsequent versions of ASTM Test for JIc, A Measure of Fracture Toughness (E 813).
Mode II Fatigue Crack Growth Specimen Development
Authors: Buzzard RJ , Gross B , Srawley JE
Published: December 2008

A novel Mode II test specimen has been developed that has potential application in understanding phenomena associated with mixed-mode fatigue failures in high performance aircraft engine bearing races. The attributes of the specimen are as follows: it contains one single-ended notch, which simplifies data gathering and reduction; the fatigue crack grows in-line with the direction of load application; a single axis test machine is sufficient to perform testing; and the Mode I component is vanishingly small.
A Single Specimen Determination of Elastic-Plastic Fracture Resistance by Ultrasonic Method
Authors: Hirano K , Kobayashi H , Nakazawa H
Published: December 2008

A single specimen ultrasonic determination procedure of the empirical measure of elastic-plastic fracture resistance under monotonic and multiple unloading conditions was proposed. It was shown that the elastic-plastic fracture toughness JIc and the tearing moduli TJ (Δamax) calculated from the slope of the determined J-Δamax curves are independent of specimen size and side groove depth. It was also found that the advancing crack tip opening displacement δa is nearly constant during the stable crack growth. The multiple unloading R-curve was successfully determined and corresponded to the monotonic R-curve. In addition, the transition behavior from low cycle fatigue to monotonie stable crack growth characteristics was experimentally clarified.
Evaluation of Environmentally Assisted Cracking of a High Strength Steel Using Elastic-Plastic Fracture Mechanics Techniques
Authors: Hackett EM , Moran PJ , Gudas JP
Published: December 2008

The objective of this investigation was to assess the feasibility of determining the environmentally assisted crack growth characteristics of a high strength 4340 steel during cathodic polarization in seawater using J-integral techniques. A secondary objective was to demonstrate the capability of using these techniques for investigating stress corrosion cracking-hydrogen embrittlement mechanisms in high strength steels.

It was concluded that stress corrosion-hydrogen embrittlement crack growth behavior in a high strength steel can be characterized using techniques developed for the study of stable elastic-plastic crack growth. In the case of environmentally assisted cracking, an added dimension results from the rate dependence of the process, giving results which are displacement-rate dependent. Cathodic polarization of 4340 steel specimens in seawater resulted in up to a four-fold decrease in the energy required for fracture initiation (JIc). The extent of this decrease was a strong function of both pre-exposure time and displacement rate. A good correlation was obtained between fracture morphology changes predicted from the material J-R curves and actual fracture surface measurements. The technique should therefore be a useful tool in mechanistic studies of environmentally assisted crack growth in high strength steels.
Stress Intensity Factors for a Circular Ring with Uniform Array of Radial Cracks of Unequal Depth
Authors: Pu SL
Published: December 2008

The plane problem of a uniform array of unequal depth radial cracks originating at the internal boundary of a pressurized circular ring is considered. The 12-node quadrilateral isoparametric elements with collapsed singular elements around crack tips are used to compute stress intensity factors at crack tips.

In a previous study of equal depth radial cracks, the weakest configuration (having highest values of stress intensity factors) was a ring with two diametrically opposed cracks. The current study shows that if for any reason one of the two cracks should grow a little faster than the other, the stress intensity factor at the tip of the longer crack increases at a much faster rate to enhance the faster growth of the longer crack.

Numerical results are also obtained for cases of three and four radial cracks. They show the same trend: that once one or two cracks grow a little more than the rest, the stress intensity factors at these deeper cracks will be increased progressively higher to keep the faster pace of growth. This explains why failure caused by a single major crack has been observed most frequently.

The finite element results show that the relationship between the stress intensity ratio and the crack depth ratio is approximately linear. This approximation enables us to estimate stress intensity factors at unequal depth cracks by a simple numerical method. The estimations thus obtained are close to stress intensity factors computed from the finite element method.
Extension of Surface Cracks During Cyclic Loading
Authors: Müller HM , Müller S , Munz D , Neumann J
Published: December 2008

The extension of semielliptical surface cracks in plates under cyclic tension and cyclic bending loading has been investigated. The analytical results compared different assumptions, applying local and weighted averaged ΔK values and the effect of crack closure. The experimental results showed that the developing crack front can be described fairly accurately by semiellipses. Applying local ΔK values for the prediction underestimates the developing crack aspect ratio a/c. Applying the weighted averaged ΔK or a crack closure factor improves the prediction.
Comparison of Predicted Versus Experimental Stress for Initiation of Crack Growth in Specimens Containing Surface Cracks
Authors: Reuter WG
Published: December 2008

Fracture mechanics concepts were used to evaluate the ability to predict the stress for crack initiation for specimens containing surface cracks. The comparison is made between the predicted stress (σpred) and the experimentally determined stress (σexp). The predictions were made for conditions ranging from elastic to plastic. The predictions were based on suggestions by P. Paris for modifying an equation developed for center-cracked panels. Acoustic emission techniques were used to detect the load corresponding to crack initiation.
Comparison of Ductile Crack Growth Resistance of Austenitic, Niobium-stabilized Austenitic, and Austeno-ferritic Stainless Steels
Authors: Balladon P , Heritier J
Published: December 2008

Fracture toughness and ductile crack growth properties are compared at room and elevated temperatures by using the J integral concept for three grades: (1) an austenitic stainless steel water-quenched from different temperatures, (2) a niobium-stabilized austenitic stainless steel containing niobium carbides and niobium carbonitrides in an austenitic matrix, and (3) an austeno-ferritic stainless steel that contains about 50% ferritic phase in an austenitic matrix and shows higher tensile properties compared with the two other grades.

The J-R curves of the two austenitic grades are mainly dependent upon the inclusion content and the direction of the crack growth plane. Some results show the influence of residual stress level on J-R curves.

The JIc and dJ/da values for the austeno-ferritic grade cannot be explained only by the roles of the inclusion content and the crack growth plane direction; a specific behavior of the ferritic phase in this duplex steel may decrease JIc compared with the two austenitic grades.
Minimum Time Criterion for Crack Instability in Structural Materials
Authors: Homma H , Shockey DA , Hada S
Published: December 2008

Cracks in 4340 steel, 1018 steel, and 6061 aluminum specimens were loaded by short pulses of various amplitudes and durations of about 20 to 80 μs to generate experimental results of critical stress amplitudes for crack instability. Stress intensity histories experienced by the cracks at instability were calculated by a finite element method. The results showed that it is necessary to introduce time effect into the instability criterion, such as in the minimum time theory proposed by one of the authors. Correlation between the minimum times obtained for the three materials and their mechanical properties was discussed to clarify the physical meaning of the minimum time. The experimental results showed that the minimum time becomes long for the ductile material.
Boundary Layer Effects in Cracked Bodies: An Engineering Assessment
Authors: Smith CW , Epstein JS , Olaosebikan O
Published: December 2008

Experimental methods of analysis and corresponding algorithms for converting data into fracture parameters were reviewed. Results obtained from applying the methods to an analysis of boundary layer effects in compact bending specimens and in moderately deep surface flaws under Mode I loading were presented. Finally, a means for incorporating the new results into linear elastic fracture mechanics (LEFM) design rationale was suggested.
Advanced Ultrasonic Examination Methods for Corrosion Detection and Assessment in Industrial Components
Authors: Meredith WR , Lamping GA
Published: December 2008

Ultrasonic examination techniques and equipment have been improved in recent years and have become indispensable in many industrial applications where undetected corrosion can result in unscheduled downtime. Likewise, microprocessor technology has advanced in versatility and cost efficiency so that many practical applications have become possible. The resulting combination of improved examination hardware and microprocessor-based data acquisition and analysis devices has revolutionized nondestructive examination as applied to the detection and assessment of corrosion. This paper presents information concerning three recently developed ultrasonic systems which have been proven effective in the detection of thinning, pitting, and methane-type hydrogen damage. Each of these systems utilizes manual placement of the ultrasonic search unit, as opposed to totally automated systems which rely on complicated electromechanical systems for movement and position readout. As a result, greater versatility, reliability, and speed are achieved with no loss in accuracy.
Fundamental Aspects of Acoustic Emission Applications to the Problems Caused by Corrosion
Authors: Yuyama S
Published: December 2008

This paper describes the utility of acoustic emission (AE) for the detection and monitoring of corrosion, stress corrosion cracking (SCC), and corrosion fatigue (CF). It comprehensively surveys laboratory studies and field applications that have been made to date. How to apply the technique to fundamental studies in the laboratory and continuous monitoring in engineering structures are discussed in detail. Various microprocesses that can produce detectable AE are shown and their relative energy levels, emanated as AE, are discussed in terms of peak amplitudes measured on laboratory specimens by a conventional piezoelectric sensor. All the available information clearly demonstrates the potential usefulness of the AE technique.
Monitoring Stress-Corrosion Cracking by Acoustic Emission
Authors: Martin P , Dickson JI , Baïlon J-P
Published: December 2008

Acoustic emission (AE) is well suited for laboratory studies of stress corrosion cracking (SCC) since the crack velocity is often approximately proportional to the AE rate. For 7075-T651 and 2024-T351 aluminum alloys, this proportionality is shown to be particularly good. For 7075-T651, less scatter is obtained in SCC crack velocity when these are based on the cumulative AE counts than on surface crack length measurements. The curve of AE rate versus time after addition of fresh solution into the crack depends on the type of transducer employed. Using either a broad-band or a resonant transducer, it was possible to distinguish between SCC and corrosion signals from their frequency spectrum.

The applicability of employing AE to detect SCC in an industrial environment is considered. Possible solutions to some of the difficulties expected in cases where SCC produces low-amplitude AE signals are discussed.
Corrosion Monitoring of Underwater Steel Structures
Authors: Birring A
Published: December 2008

Deterioration of underwater steel structures due to corrosion is of serious concern because it reduces thickness in structural components, which can degrade structural strength. Inspection programs are necessary to determine the remaining thickness so that action can be taken to repair the damage if required.

An ultrasonic technique using a focused transducer has been developed to find the thickness of steel plates or structures corroded from both sides and having pit sizes as large as 15 mm in diameter and 4 mm deep. The technique was implemented into a system that acquires and processes ultrasonic waveforms reflected from the corroded area and determines the thickness. The system was tested and successfully operated in a harbor environment.
Overview of Corrosion Monitoring in Modern Industrial Plants
Authors: Dean SW
Published: December 2008

A number of procedures and devices used to monitor corrosion damage and metal loss are discussed. The advantages and drawbacks of these methods are reviewed. The factors which need to be considered in selecting a corrosion monitoring system include the purpose of the program, the cost and availability of the equipment, reliability of the system, and the nature of the corrosive stream. The problems which accompany a plant corrosion program, including safety, potential for leaks, and misleading data, are discussed. Various commercial devices employing polarization resistance, electrical resistance, polarization behavior, and alternating current (AC) are included. Problem areas in corrosion monitoring are discussed, together with needs for future development.
Oil Production Corrosion Inhibitor Optimization by Laboratory and Field Application of Electrochemical Techniques
Authors: Cameron GR , Coker LG
Published: December 2008

A multifaceted approach was used to address the corrosion inhibition program in Esso Resources Canada Limited's Redwater field. In the laboratory, inhibitor performance was measured by linear polarization and film persistency wheel tests. Both techniques produced similar inhibitor ranking, although the percent protection results were consistently higher for the linear polarization technique. In the field, corrosion rates were monitored by several devices. Metal loss measurements from flush strip electrical resistance probes best correlated to weight-loss coupons, although the instrument's calculated corrosion rates did not agree with the indicated metal loss. Inhibitor and tracer concentrations were monitored during batch-circulation well treatments to improve application efficiency. The concentration measurements showed that circulation time is the controlling factor in effectively batch-treating wells that have high annular fluid levels. The foregoing investigations, which provided vital information for corrosion control in a specific field, also point the way to improvements in corrosion inhibition technology.
Techniques for the Evaluation of Cooling Water Corrosion and Scale Inhibitors in the Laboratory and at the Industrial Plant Site
Authors: Labine P , Norman W , King D , Minalga J
Published: December 2008

Polyphosphate based chemical treatment programs were evaluated in experimental cooling towers using linear polarization and potentiodynamic polarization techniques to monitor uniform corrosion and pitting corrosion rates. Correlations between laboratory and field corrosion rates are quite good. Relative heat transfer data indicate that two synthetic polymers are more effective than five phosphonates in minimizing calcium phosphate deposition.
Waterside Corrosion Control During Operation of Drum-Type Utility Boilers
Authors: Gabrielli F , Mohn NC
Published: December 2008

The water and steam side surfaces of a high pressure fossil fuel boiler are subject to a variety of potential corrosion problems. Construction materials include copper alloys, carbon steels, ferritic alloys, and austenitic stainless steels. Assessing the degree of corrosion of components is important to allow planning for maintenance during scheduled outages and to avoid unscheduled downtime. Corrosion control programs recommended by Combustion Engineering, Inc. (CE) include two areas of corrosion monitoring. First, on-line monitoring of the water and steam side environment is used to evaluate the duration and degree of exposure to corrodents, and to provide feedback information to assist in minimizing corrosion. In addition, both nondestructive testing and destructive testing during unit outages is used to assess corrosion damage. Typical operational corrosion problems in a high pressure (1241 kPa [ > 1800 psi]) fossil fuel utility boiler are detailed and recommended corrective measures are presented.
Dependence of Stress Corrosion Cracking of Parent, Heat-Affected Zone, and Weld Metal of HSLA Line-Pipe Steel on Potential
Authors: Hoey GR , Ramsingh RR , Bowker JT
Published: December 2008

Potentiostatically controlled slow-strain-rate tension tests (∼ 10-6s-1) were conducted on the parent steel, simulated heat-affected zone, and weld metal specimens obtained from a sample of Canadian grades 483 and 414 high-strength low-alloy (HSLA) line pipe. All stress corrosion cracking (SCC) tests were conducted in 0.5 mmol/cm3 Na2CO3 + 1.0 mmol/cm3 NaHCO3 solutions at 75°C in a stressed-electrode cell. Percentage reduction in area and apparent secondary cracking velocity were used as measures of SCC susceptibility. The potentials at which cracking occurred were correlated with fast and slow scan anodic potentiodynamic polarization curves in the same environment.

Secondary cracks occurred along the gage length normal to the stress in a narrow potential range with crack growth rate reaching a maximum in the range from — 700 mV to — 650 mV versus saturated-calomel electrode. This maximum in the crack depth versus potential curves occurred near the primary passive potential. Scanning electron microscopy provided unambiguous evidence for the presence or absence of SCC in the parent steel, HAZ and weld metal samples in a CO3-2/HCO3-1 environment.

The results support a mixed dissolution-hydrogen embrittlement model for SCC of HSLA line-pipe steel.
Harmonic Impedance Spectroscopy for the Determination of Corrosion Rates in Cathodically Protected Systems
Authors: McKubre MCH , Syrett BC
Published: December 2008

The nonlinear current-voltage response which is characteristic of a corroding metal/electrolyte interface prohibits the use of corrosion resistance measurements in conjunction with the Stern-Geary relationship, to provide an in situ determination of corrosion rates, at potentials removed from the free corrosion potential.

In this paper we describe the development of a technique for the electrochemical measurement of the anodic corrosion current (“corrosion rate”) under conditions of an applied cathodic protection potential. Our effort has been directed towards a simplified theoretical treatment of the harmonic current response at frequencies of 1f, 2f, 3f, 4f… to a 20 to 50-mV AC voltage perturbation at frequency f.

Experimental verification of the theoretical treatment was obtained by comparing the results of harmonic analysis with those obtained by mass loss determinations for copper : nickel alloy specimens of varying geometries, in oxygenated synthetic ocean water, at various levels of applied cathodic polarization.
Electrochemical Noise as an Indicator of Anaerobic Corrosion
Authors: Iverson WP , Heverly LF
Published: December 2008

Anaerobic (bacterial) corrosion is an important cause of failures of underground structures such as pipelines. Pipeline failures could be prevented if better methods for determining the presence and location of areas of bacterial corrosion existed. A technique was developed which permits the detection and recording of rapid potential fluctuations (noise) produced in a corroding metal. It is believed that this noise is mainly caused by the breaking of protective films on the metal surface. Anaerobic bacterial corrosion also produces a type of noise, probably due to the breaking of iron sulfide films.

Preliminary evidence indicates that detection and production of this noise on pipelines may offer promise in locating areas of microbial corrosion as well as other types of corrosion. Differences in the type of noise signal could enable differentiation between biological and nonbiological corrosion. Continuing studies should verify or reject these premises.
Gas Chromatographic/Mass Spectrometric Analysis of Paraho Shale Oil < 260°C (500°F)
Authors: Gallegos EJ
Published: December 2008

Paraho shale oil <260°C (500°F) was analyzed by gas chromatography/mass spectrometry (GC/MS) with the intent of establishing a preliminary set of guidelines and conditions under the auspices of ASTM for the GC/MS analysis of shale oil. A 60-m DURABOND-1, DB-1, fused silica capillary column coupled directly to our fast scanning 7070H double-focusing mass spectrometer was chosen. GC/MS operating parameters were selected so that the total ion monitor (TIM), GC trace would match that of a flame-ionization detector (FID) GC trace obtained previously under optimized conditions for a DB-1 column. Preliminary results show the presence of homologs of n-alkanes, isoalkanes, alkenes, or cyclic alkanes, alkylbenzenes, naphthalenes, indanes, tetralins, thiophenes, pyridines, indoles, phenols, and so forth. The data were reduced using an automatic quantitation INCOS computer procedure designed by J. Karnofsky specifically for this laboratory.
Characterization of Nitrogen Compound Types in Hydroprocessed Shale Oil Products with Mass Spectrometry and Potentiometric Titration
Authors: Heppner RA , Holmes SA , Weber JH
Published: December 2008

High-resolution mass spectrometry and potentiometric titration have been applied to the analysis of nitrogen-containing fractions from fuel products derived from hydroprocessed shale oil. Both low and high ionizing voltages were used to obtain the mass spectrometric data. Data obtained with high ionizing voltage was analyzed using the Peters and Bendoraitis method. For chemically stable fractions, this method yielded good agreement with results from potentiometric titration. Agreement was worse for fractions containing reactive pyrrole and arylamine species. Low ionizing voltage data indicated that dimerized species had been produced in these reactive fractions after their isolation. Semiquantitative determination of nitrogen compound types in fuel products from hydroprocessed shale oil is possible using high-resolution mass spectrometry, potentiometric titration, and absorption chromatography.
Pyrolysis Mass Spectrometry and Multivariate Analysis of Several Key World Oil Shale Kerogens and Some Recent Alginites
Authors: Meuzelaar HLC , Windig W , Futrell JH , Harper AM , Larter SR
Published: December 2008

To demonstrate the potential of modern pyrolysis/mass spectrometry (Py-MS) for rapid characterization of oil shale kerogens and alginites of different geological and depositional origin, four key world oil shale kerogens and three alginites were analyzed by Curie-point Py-MS in combination with multivariate analysis methods such as factor and discriminant analysis.

The pyrolysis mass spectra of the algal coal torbanite and the two recent alginites coorongite and botryococcus rubber reveal similar structural characteristics as observed in previous pyrolysis gas chromatographic/mass spectrometric (GC/MS) studies, including signatures of specific aliphatic hydrocarbon moieties produced by Botryococcus braunii. Moreover, application of a new time-resolved Py-MS technique reveals the rather heterogeneous nature of the two recent alginites coorongite and botryococcus rubber which contain several types of oxygen functionalities and exhibit complex thermal decomposition reactions, as opposed to the much more homogeneous nature of torbanite which shows a rather simple thermal decomposition behavior. The thermal decomposition patterns of the four kerogens derived from Green River, kukersite, tasmanite, and messel oil shales show an overall resemblance with torbanite. Factor and discriminant analysis of the pyrolysis mass spectra, however, reveal the existence of relatively minor but highly characteristic differences. For instance, the messel shale kerogen shows a significant hydroxyaromatic component, presumably reflecting contributions of terrestrial plant materials to the depositional environment. In contrast, the high sulfur signals of the tasmanite shale kerogen reveal a strong marine influence.

The relationship between the Py-MS patterns in the discriminant analysis plot shows an overall resemblance with the relative positions of the kerogens in a Van Krevelen diagram. Consequently, it appears feasible to classify oil shale kerogens into the proper Tissot types (I–IV) on the basis of direct Py-MS results.

It is concluded that computerized Py-MS techniques offer a highly promising approach to rapid structural characterization and classification of a potentially broad range of oil shale kerogens and alginites.
An Evaluation of Triple Quadrupole Mass Spectrometry/Mass Spectrometry (MS/MS) for On-Line Gas Analysis of Trace Sulfur Compounds from Oil Shale Processing
Authors: Wong CM , Crawford RW , Yost RA
Published: December 2008

To reduce effectively sulfur gas content from shale processing to environmentally acceptable levels, hydrogen sulfide (H2S), carbonyl sulfide (COS), sulfur dioxide (SO2), and methanethiol (CH3SH) plus trace sulfur compounds must be removed. Of these, the trace sulfur compounds have not been well characterized but should be known to ppm levels in order to optimize gas cleanup procedures. Most techniques for analysis of trace sulfur components in oil shale gases have limitations. The applications we describe using triple quadrupole mass spectrometric techniques (TQMS) appear to have overcome many problems of trace sulfur analysis.

Basically, a TQMS produces a mass spectrum of a mass spectrum and is, therefore, highly sensitive, selective, and specific. Tests on a Finnigan TQMS at the University of Florida and on a totally computerized TQMS designed at Lawrence Livermore National Laboratory (LLNL) using pure standards, mixed gas standards, and Fisher assay gas grab samples show that we can quantitatively as well as qualitatively detect the following components:

1. methanethiol = < 1 ppm

2. ethanethiol = 3 ppm

3. n-propanethiol = < 1 ppm

4. isopropanethiol = 4 ppm

5. carbonyl sulfide = 1 ppm

6. carbon disulfide = 4 ppm

7. dimethyl sulfide = 10 ppm

8. dimethyl disulfide = < 1 ppm

9. thiophene = < 1 ppm

10. 2 or 3 methyl thiophene = < 1 ppm

For a rapidly changing gas stream, timing studies on the LLNL TQMS show that analytical results for 10 sulfur compounds (1000 readings on each parent and key daughter ions) can be acquired and quantitatively calculated in ∼ 30 s. For kinetics studies, data on selected daughters for ten compounds can be acquired in a total of 540 ms.
Application of Mass Spectrometry to Petroleum Exploration
Authors: Seifert WK , Moldowan JM , Gallegos EJ
Published: December 2008

Compounds significant to the petroleum chemist concerned with petroleum exploration are those hydrocarbons possessing biological marker characteristics, that is, possessing intact steroid, terpenoid, and isoprenoid skeletons. These hydrocarbons are so closely related to the compounds occurring in the living organism from which petroleum was formed that they are capable of yielding very specific information regarding source, maturation, migration, and biodegradation of petroleum. Examples how source shales can be related to petroleum reservoirs using computerized gas chromatography/mass spectrometry, (GC/MS) are shown. The terpane GC/MS multiple array processor (MAP) approach can be used to differentiate source shales of different degrees of maturity and, thus, to determine source rock quality. Heavily biodegraded oils can be characterized and correlated by GC/MS fragmentograms of steranes and terpanes. Ratios of specific biomarkers obtained by quantitation from GC/MS data are used to differentiate oils of different degrees of migration. Examples from the exploration arena worldwide are given to illustrate these applications.