Hydrogen Induced Mechanical Property Behavior of Dissimilar Weld Metal Interfaces

2011 ◽  
Author(s):  
Jamey A. Fenske ◽  
Martin W. Hukle ◽  
Brian D. Newbury ◽  
J. R. Gordon ◽  
Rick Noecker ◽  
...  
Keyword(s):  
Weld Metal ◽  
Strain Rate ◽  
Crack Growth ◽  
Alloy Steel ◽  
Slow Strain Rate ◽  
Low Alloy Steel ◽  
Hydrogen Charging ◽  
Curve Crack ◽  
Metal Interfaces ◽  
Tearing Resistance

A series of catastrophic failures between alloy 625 weld metal (referred to as ‘A625’) and AISI 8630 low alloy steel forgings (referred to as ‘8630’) on cathodically-charged subsea equipment demonstrate the need to gain a better understanding of the hydrogen-induced tearing resistance of these interfaces as well as similar types of interfaces also currently used in the field. Other dissimilar metal weld interfaces in use include ASTM A182 F22 (referred to as ‘F22’) welded with A625. Similar metal alternatives are also in use, including F22 welded with low alloy steel (referred to as ‘LAS’). Slow strain rate single-edge notched bend tests under hydrogen charging conditions were used to establish ‘R-curve’ crack growth resistance trends for the F22-A625 and F22-LAS weld metal interfaces. Differences in ‘R-curve’ crack growth behavior between the different weld metal interfaces have been observed and compared to R-curve results from 8630-A625 interfaces. The F22-LAS interface demonstrates the most tearing resistance under slow strain rate after hydrogen charging followed by the F22-A625 and then the 8630-A625 interface. Subtle differences between the weld metal microstructures are described and provide a possible explanation regarding the difference in ‘R-curve’ behavior.

Study on High Temperature Flow Stress Model of As-cast SA508-3 Low Alloy Steel

2020 ◽  
Vol 831 ◽  
pp. 25-31
Author(s):  
Pan Fei Fan ◽  
Jian Sheng Liu ◽  
Hong Ping An ◽  
Li Li Liu
Keyword(s):  
High Temperature ◽  
Flow Stress ◽  
Strain Rate ◽  
Alloy Steel ◽  
Flow Behavior ◽  
Peak Stress ◽  
Stress Model ◽  
Low Alloy Steel ◽  
Two Stage ◽  
Flow Stress Model

In order to obtain the high temperature flow behavior of as-cast SA508-3 low alloy steel, the stress-strain curves of steel are obtained by Gleeble thermal simulation compression test at deformation temperature 800°C-1200°C and strain rate 0.001s-1-1s-1. Based on Laasraoui two-stage flow stress model, a high temperature flow stress model is established by multiple linear regression method. The results show that the peak stress characteristics are not obvious at low temperature and high strain rate, which is a typical dynamic recovery characteristic. Meanwhile, the peak stress characteristics are obvious at high temperature and low strain rate, which is a typical dynamic recrystallization characteristic. By means of the comparisons between experiments and calculations, the Laasraoui two-stage flow stress model can truly reflect flow behavior of steel at high temperature, which provides theoretical guidance for the hot deformation of the steel.

Further Development of a Model for Predicting Corrosion Fatigue Crack Growth in Reactor Pressure Vessel Steels

1987 ◽  
Vol 109 (3) ◽  
pp. 340-346 ◽  
Author(s):  
J. D. Gilman
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Alloy Steel ◽  
High Stress ◽  
Time Dependent ◽  
Crack Advance ◽  
Low Alloy Steel ◽  
Time Rate ◽  
Paris Law

Analysis of fatigue crack growth data for low-alloy steel shows that the influence of cyclic frequency in simulated LWR environments can be interpreted as the superposition of a time-dependent, corrosion-assisted crack growth rate upon an increment predicted by a Paris law. The time-dependent component increases monotonically to a maximum of about 6×10−5 mm/s as stress cycling becomes more aggressive. A useful measure of aggressiveness is the average time rate of crack advance due to the Paris law component alone; i.e., AΔKn × frequency. The result suggests that current ASME Code methods for flaw assessment are highly conservative in some regimes of stress and frequency, but there is a possibility of growth rates well above the ASME XI, Appendix A curves in a very low-frequency, high-stress regime. An upper bound to the time rate of corrosion-assisted crack growth in low-alloy steel is well supported by the data. The threshold conditions for the onset of this high rate are less well defined and require further investigation.

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