Hydrogen Assisted Cracking of a Low Alloy Steel-pressure, Temperature and Yield Strength Effects on the Threshold Fracture Toughness PDF Download

Author: Grosvenor Cook Story (III.)
Publisher:
ISBN:
Category :
Languages : en
Pages : 432

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Author: Grosvenor Cook Story
Publisher:
ISBN:
Category : Strength of materials
Languages : en
Pages : 199

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Author: William Donald Needham
Publisher:
ISBN:
Category : Naval architecture
Languages : en
Pages : 554

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An experimental study was conducted to evaluate the corrosion performance of weldments of a high strength low alloy(HSLA) steel in a simulated seawater environment. This steel, designated HSLA80, was developed by the United States Navy for use in ship structural applications. Stress corrosion CRACKING(SCC) and hydrogen embrittlement(HEM) were investigated by conducting 42 Wedge-Opening load(WOL) tests as a function of stress intensity and corrosion potential and 33 Slow Strain Rate(SSR) tests as a function of strain rate and corrosion potential. The corrosion potentials were chosen to simulate the environmental conditions of free corrosion, cathodic protection and hydrogen generation. The results from this investigation indicated that HSLA 80 base metal and weldments were susceptible to hydrogen assisted cracking(HAC) in a seawater environment under conditions of continuous plastic deformation and triaxial stress in the presence of hydrogen. The heat-affected zone of the weldment was found to be the most susceptible portion of the weld joint. A lower bound was established for the critical stress intensity for stress corrosion cracking for HSLA 80 base metal and weldments.(Theses).

Author: Ryan Buntain
Publisher:
ISBN:
Category : Dissimilar welding
Languages : en
Pages : 275

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This research investigated the HAC susceptibility of LAS butter welds joined to F65 steel pipes using nickel based Alloy 625 filler wire in the as-welded condition. Four different weld mock ups were investigated in this work. Each of the weld mock ups utilized slightly different closure welding procedures. Metallurgical characterization along with environmental testing using the Delayed Hydrogen Cracking Test (DHCT) was used to investigate the hydrogen assisted cracking behavior of the different interfaces.

Author: John C. Lippold
Publisher: John Wiley & Sons
ISBN: 1118230701
Category : Technology & Engineering
Languages : en
Pages : 418

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Describes the weldability aspects of structural materials used in a wide variety of engineering structures, including steels, stainless steels, Ni-base alloys, and Al-base alloys Welding Metallurgy and Weldability describes weld failure mechanisms associated with either fabrication or service, and failure mechanisms related to microstructure of the weldment. Weldability issues are divided into fabrication and service related failures; early chapters address hot cracking, warm (solid-state) cracking, and cold cracking that occur during initial fabrication, or repair. Guidance on failure analysis is also provided, along with examples of SEM fractography that will aid in determining failure mechanisms. Welding Metallurgy and Weldability examines a number of weldability testing techniques that can be used to quantify susceptibility to various forms of weld cracking. Describes the mechanisms of weldability along with methods to improve weldability Includes an introduction to weldability testing and techniques, including strain-to-fracture and Varestraint tests Chapters are illustrated with practical examples based on 30 plus years of experience in the field Illustrating the weldability aspects of structural materials used in a wide variety of engineering structures, Welding Metallurgy and Weldability provides engineers and students with the information needed to understand the basic concepts of welding metallurgy and to interpret the failures in welded components.

Author: William Moss
Publisher: CRC Press
ISBN: 0429565925
Category : Technology & Engineering
Languages : en
Pages : 63

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This document defines the types of cracking and the conditions under which each can occur in carbon and low alloy steels in wet H2S-containing environments, specifies materials requirements necessary to prevent such cracking, and presents test methods for evaluating materials performance.

Author: James R. Rule
Publisher:
ISBN:
Category : Dissimilar welding
Languages : en
Pages : 217

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This work builds upon the previous research regarding hydrogen assisted cracking (HAC) of low alloy steel to nickel-base filler dissimilar metal welds (DMWs). In particular, this work is focused on DMWs commonly experienced in offshore oil and gas production systems in subsea use. The HAC tendency of these welds has been attributed to formation of susceptible microstructures at the fusion boundary during welding. As such, a post-weld heat treatment (PWHT) is utilized to temper these microstructures as well as relieve residual stresses. However, these microstructures can persist even after PWHT due to the steep compositional gradient driving migration of carbon from the base metal toward the fusion boundary and into the partially mixed zone (PMxZ) of the weld. The degree to which this migration occurs is a function of materials selection (base metal and filler metal) as well as weld and PWHT procedure. Due to this phenomenon, there is a balance that must be found to provide tempering of the susceptible microstructures that form during welding and limiting the formation of new susceptible microstructures during PWHT. Previous research has established a test method in the form of the delayed hydrogen cracking test (DHCT) which can delineate the effects of materials combination, weld procedure, and PWHT on HAC of DMWs. This test's qualitative ranking of susceptibility agreed well with industry experience. The current study worked towards refining the test methodology investigating the effects of test parameter influence on realized results. Of the investigated variables, it was found that how the test samples are coated is of primary importance where a consistently exposed fusion boundary scheme providing the most repeatable result in test. Additionally, a comparison was made between the test hydrogen charging condition which uses a dilute acid and constant current density of 10mA/cm2 and the service environment which is seawater with a constant potential (-850 to -1100mVAgIAgCl). Through this comparison it was understood that the dilute acid is indeed an accelerated charging environment where the level of acceleration scales with nascent hydrogen concentration differences as indicated by pH and charging current density differences with the dilute acid providing roughly a 1000x acceleration factor. Further work focused on establishing a pass/fail criterion which would transform the DHCT method from qualitative to quantitative. This was done by measuring the diffusible hydrogen content of each DMW at various charging times to find the saturation time. This diffusible hydrogen saturation time was then compared with DHCT results from previous and current work to show that samples which sustain load beyond saturation do not fail due to HAC. This methodology proved successful for sound welds without prior defects and correlated well with service experience. The final focus of the work related to modeling and prediction of DMW microstructures towards predicting HAC susceptibility. The modeling involved thermodynamic and kinetic simulations to model the diffusion of alloying elements both during weld and PWHT thermal cycles. The model was validated using quantitative measurements of the composition through electron probe microanalysis as well as through hardness and microstructural evaluation. The results were correlated with HAC experience to provide a microstructural/character map to facilitate identifying trends which led to susceptibility. The findings confirmed previous research showing fresh martensite to be the main driver for behavior followed by precipitation of M7C3 carbides. This model was applied to a previously untested DMW to predict the microstructure and gauge the relative HAC susceptibility. The predictions proved to be accurate and aligned with both microstructure and HAC susceptibility. The framework of the model can be used as an engineering tool early in the design stage for materials selection and weld procedure development. The final focus of the work related to modeling and prediction of DMW microstructures towards predicting HAC susceptibility. The modeling involved thermodynamic and kinetic simulations to model the diffusion of alloying elements both during weld and PWHT thermal cycles. The model was validated using quantitative measurements of the composition through electron probe microanalysis as well as through hardness and microstructural evaluation. The results were correlated with HAC experience to provide a microstructural/character map to facilitate identifying trends which led to susceptibility. The findings confirmed previous research showing fresh martensite to be the main driver for behavior followed by precipitation of M7C3 carbides. This model was applied to a previously untested DMW to predict the microstructure and gauge the relative HAC susceptibility. The predictions proved to be accurate and aligned with both microstructure and HAC susceptibility. The framework of the model can be used as an engineering tool early in the design stage for materials selection and weld procedure development.

Author: Anthony W. Thompson
Publisher: John Wiley & Sons
ISBN: 1118803272
Category : Technology & Engineering
Languages : en
Pages : 1090

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Proceedings of the Fifth International Conference on the Effect of Hydrogen on the Behavior of Materials sponsored by the Structural Materials Division (SMD) Mechanical Metallurgy and Corrosion & Environmental Effects Committees of The Minerals, Metals & Materials Society held at Jackson Lake Lodge, Moran, Wyoming, September 11-14, 1994.

Author: T. A. Auten
Publisher:
ISBN:
Category : Steel, Structural
Languages : en
Pages : 28

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Author: Samerjit Tantaseraneewat
Publisher:
ISBN:
Category :
Languages : en
Pages : 298

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