Effects of Absorbed Hydrogen on Fracture Toughness of Welded SA516 Grade-70 Steel PDF Download

Author: Mohamad Haidir Maslan
Publisher:
ISBN:
Category : Pressure vessels
Languages : en
Pages : 64

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Author: Sebastian Dayou
Publisher:
ISBN:
Category : Fracture mechanics
Languages : en
Pages : 43

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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 15

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The effects of hydrogen on the fracture toughness properties of upset welded Type 304L stainless steel were measured and compared to those measured previously for as-received and as-welded steels. The results showed that the upset welded steels had good fracture toughness properties, but values were lower than the as-received material. The fracture toughness value of the base material was 6420 in-lbs/sq. in., while the welded steels averaged 3660 in-lbs/sq. in. Hydrogen exposure lowered the fracture toughness values of the as-received steel by 43 % to 3670 in-lbs/sq. in. and the welded steels by 21 % to 2890 in-lbs/sq. in. The fracture morphologies of the unexposed steels showed that ductile fracture occurred by the microvoid nucleation and growth process. The size of the microvoids on the fracture surfaces of the welded steels were much smaller and more closely spaced that those found on the base material fracture surfaces. The change in the size and spacing of the microvoids indicates that the fracture toughness properties of the welded steels were lower than the base steels because of the higher concentration of microscopic precipitates on the weld plane. The welds examined thus far have been {open_quotes}good{close_quotes} welds and the presence of these precipitates was not apparent in standard {open_quotes}low{close_quotes}-magnification metallographic sections of the weld planes. The results indicate that hydrogen did not weaken greatly the solid-state welds but that other inclusions or impurities present prior to welding did. Improvements in surface cleaning and preparation prior to welding should be explored as a way to improve the strength of solid-state welded joints.

Author: Ellis E. Fletcher
Publisher:
ISBN:
Category : Steel
Languages : en
Pages : 82

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This report deals with the deleterious effects of hydrogen gas on steel at elevated temperatures and/or pressures. Hydrogen attack on steels is manifest as decarburization, intergranular fissuring, or blistering. These conditions result in lowered tensile strength, ductility, and impact strength. The reaction of hydrogen with iron carbide to form methane is probably the most important chemical reaction involved in the attack on steel by hydrogen. Attack of steel at elevated temperatures and pressures is limited or prevented by the following measures: (1) use of steel alloyed with strong carbide-forming elements, (2) use of liners of resistant alloy steels, and (3) substitution of resistant nonferrous alloys.

Author: Deon Johan De Beer
Publisher:
ISBN:
Category :
Languages : en
Pages :

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In the petrochemical industry, carbon steels exposed to H2S environments may be susceptible to stress-corrosion cracking. A tensile residual stress and high hardness increases the risk of cracking in H2S environments. NACE SP 0472 limits weld metal hardness to 210 HV10 (200 HB) and heat-affected zone hardness to 250 HV10 to prevent stress-corrosion cracking of carbon steel welds in H2S. The hardness is controlled by the weld thermal cycle or by a post-weld heat treatment. In this project, the effect of hardness on the susceptibility to stress-corrosion cracking was investigated by increasing electrode strength systematically and measuring residual stress in the weld metal in the as-welded state. Samples were manufactured from SA 516 Gr 70, a carbon steel used extensively in the petrochemical industry. Heavily clamped plates were welded to minimise distortion and to maximise residual stress. The weld metal hardness was increased by using E6013, E7018-1, E8018-B2 and E9018-B3 electrodes without a post-weld heat treatment. Mechanical tests included all-weld and transverse tensile tests, impact strength and hardness testing. As the nominal strength of the weld metal increased, the all-weld tensile strength increased from 512 to 829 MPa, while the yield strength increased from 443 to 659 MPa. The average weld metal hardness increased from 177 to 317 HV10. The transverse tensile strength was between 511-517 MPa, while the yield strength (in the transverse direction) was between 360 and 382 MPa. Residual stresses of the welded joint were measured by neutron diffraction in the through-thickness, longitudinal and transverse direction. The Von Mises theorem evaluated the principle residual stress. Results indicate that the residual stress in the weld metal may be up to 99% of the yield strength. For stress-corrosion cracking, the samples were submerged in the standard TM0177-2005 test solution for 30 days. The only sample to crack was the E9018, with an average weld metal hardness of 317 HV10. The study results were consistent with the NACE SP0472 specification and earlier publications.

Author: A. R. Elsea
Publisher:
ISBN:
Category : Steel
Languages : en
Pages : 42

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This memorandum introduces the problem of delayed, brittle failures associated with hydrogen in steel, particularly high-strength steel. It is intended to help the steel user determine if he has such a problem. The effects of hydrogen on the mechanical properties of steel are dealt with, and the behavior of material susceptible to delayed, brittle failure is described. Also, the effects of such factors as strength level, magnitude of applied stress, hydrogen content, steel composition, test temperature, and strain rate on hydrogen embrittlement and the susceptibility to hydrogen-induced, delayed, brittle failure are discussed. Possible sources of hydrogen in steel and the types of tests useful in determining the susceptibility to delayed failure are outlined. (Author).

Author: James Edward Campbell
Publisher:
ISBN:
Category : Alloys
Languages : en
Pages : 30

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On the basis of the information available, steels(ferritic, martensitic, and bainitic), nickel-base alloys, and titanium alloys become embrittled in pure-hydrogen-gas environments at ambient temperature. The embrittling effect is detected by making tension tests on sharp-notched specimens in an environment of high-purity hydrogen gas and, for comparison, tests on similar specimens in an inert gas at the same temperature and pressure. If the material is embrittled by hydrogen, its notch tensile strength will be reduced. The effect is more pronounced as the hydrogen-gas pressure is increased, but in some cases the embrittling effect has been observed at 1 atmosphere of pressure. The effect is more pronounced for the high-strength steels and high-strength nickel and titanium alloys than for the low-strength alloys. In unnotched specimens exposed to a pure-hydrogen environmental, hydrogen embrittlement manifiests itself as a decrease in ductility. Results of tests on stable austenitic stainless steels such as Types 310 and 316, or certain aluminum alloys such as 6061-T6, 2219-T6, and 7075-T73, and beryllium copper indicate that there is no significant evidence of embrittlement of these alloys in hydrogen gas at pressures up to 10,000psi.

Author: Thomas J. Watson
Publisher:
ISBN:
Category : Carbon steel
Languages : en
Pages : 194

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Author: P. F. Timmins
Publisher: ASM International(OH)
ISBN:
Category : Technology & Engineering
Languages : en
Pages : 216

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This book is designed to help metallurgical, chemical, mechanical and reliability engineers responsible for the safe operation and maintenance of equipment made of steel.

Author: Cedric D. Beachem
Publisher: ASM International(OH)
ISBN:
Category : Science
Languages : en
Pages : 432

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