scholarly journals A Study on Microstructure, Residual Stresses and Stress Corrosion Cracking of Repair Welding on 304 Stainless Steel: Part I-Effects of Heat Input

Materials ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2416
Author(s):  
Yun Luo ◽  
Wenbin Gu ◽  
Wei Peng ◽  
Qiang Jin ◽  
Qingliang Qin ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Stainless Steel ◽  
Residual Stresses ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Heat Input ◽  
Corrosion Cracking ◽  
304 Stainless Steel ◽  
Sensitivity Index ◽  
Repair Welding

In this paper, the effect of repair welding heat input on microstructure, residual stresses, and stress corrosion cracking (SCC) sensitivity were investigated by simulation and experiment. The results show that heat input influences the microstructure, residual stresses, and SCC behavior. With the increase of heat input, both the δ-ferrite in weld and the average grain width decrease slightly, while the austenite grain size in the heat affected zone (HAZ) is slightly increased. The predicted repair welding residual stresses by simulation have good agreement with that by X-ray diffraction (XRD). The transverse residual stresses in the weld and HAZ are gradually decreased as the increases of heat input. The higher heat input can enhance the tensile strength and elongation of repaired joint. When the heat input was increased by 33%, the SCC sensitivity index was decreased by more than 60%. The macroscopic cracks are easily generated in HAZ for the smaller heat input, leading to the smaller tensile strength and elongation. The larger heat input is recommended in the repair welding in 304 stainless steel.

scholarly journals A Study on Microstructure, Residual Stresses and Stress Corrosion Cracking of Repair Welding on 304 Stainless Steel: Part II-Effects of Reinforcement Height

Materials ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2434 ◽  
Author(s):  
Xiaodong Hu ◽  
Hao-Yong Jiang ◽  
Yun Luo ◽  
Qiang Jin ◽  
Wei Peng ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Residual Stresses ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Structural Integrity ◽  
Great Influence ◽  
Steel Part ◽  
Corrosion Cracking ◽  
304 Stainless Steel ◽  
Repair Welding

The repair reinforcement height is an important parameter of repair welding, which may have a great influence on structural integrity. In this paper, the effects of repair welding reinforcement height on the microstructure, microhardness, residual stresses and stress corrosion cracking (SCC) behavior of a 304 stainless steel-repaired joint were investigated by experimentation and simulation. With an increase of the repair weld reinforcement height, the δ ferrite content in weld and fusion zone is obviously reduced, and the ferrite shape is gradually changed from the skeleton to the worm shape. With the increase of repair welding reinforcement height, the microhardness and residual stresses decrease gradually. The tensile strength and elongation for higher repair weld reinforcement height are larger than those with lower repair weld reinforcement height. The higher the repair weld reinforcement height, the harder it is for SCC to occur. The repair welding in 304 stainless steel is recommended to be repaired no more than two times.

Mitigation of Stress Corrosion Cracking in Nuclear Weldments Using Low Plasticity Burnishing

2008 ◽  
Author(s):  
Jeremy E. Scheel ◽  
Douglas J. Hornbach ◽  
Paul S. Prevey
Keyword(s):  
Stainless Steel ◽  
Residual Stresses ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
304 Stainless Steel ◽  
Surface Enhancement ◽  
Low Plasticity Burnishing ◽  
Water Reactors ◽  
Compressive Residual Stresses

Stress corrosion cracking (SCC) has been observed for decades in austenitic alloy weldments such as type 304 stainless steel as well as in Ni based alloy weldments including Alloy 600 and 690. SCC continues to be a primary maintenance concern for many components in both pressurized water reactors (PWR) and boiling water reactors (BWR). SCC is understood to be the result of a combination of susceptible material, exposure to a corrosive environment, and tensile stress above a threshold. Tensile residual stresses developed by prior machining and welding can accelerate SCC. A surface treatment is needed that can reliably produce deep compressive residual stresses in austenitic and Ni based alloy weldments in order to prevent SCC. Post-weld surface enhancement processing via low plasticity burnishing (LPB) can be used to introduce deep compression into tensile fusion welds thereby mitigating SCC. LPB has been developed as a rapid and inexpensive surface enhancement method adaptable to existing CNC machine tools or robots. Deep compressive residual stresses produced by LPB are designed to reduce the surface, and near surface stress state to well below the SCC threshold. Residual stress results are shown for 304 stainless steel, Alloy 22 and Alloy 718. SCC test results comparing LPB treated and un-treated 304 stainless steel weldments are presented. Results show that the deep compression produced by LPB eliminates SCC in austenitic weldments.

Effect of Ultrasonic Impact Treatment on the Stress Corrosion Cracking of 304 Stainless Steel Welded Joints

2008 ◽  
Author(s):  
Gang Ma ◽  
Xiang Ling
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Stainless Steel ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Welded Joints ◽  
Corrosion Cracking ◽  
Coarse Grained ◽  
304 Stainless Steel ◽  
Ultrasonic Impact Treatment

High tensile weld residual stress is an important factor contributing to stress corrosion cracking (SCC). Ultrasonic impact treatment (UIT) can produce compressive stresses on the surface of welded joints that negate the tensile stresses to enhance the SCC resistance of welded joints. In the present work, X-ray diffraction method was used to obtain the distribution of residual stress induced by UIT. The results showed that UIT could cause a large compressive residual stress up to 325.9MPa on the surface of the material. A 3D finite element model was established to simulate the UIT process by using a finite element software ABAQUS. The residual stress distribution of the AISI 304 stainless steel induced by UIT was predicted by finite element analysis. In order to demonstrate the improvement of the SCC resistance of the welded joints, the specimens were immersed in boiling 42% magnesium chloride solution during SCC testing, and untreated specimen cracked after immersion for 23 hours. In contrast, treated specimens with different coverage were tested for 1000 hours without visible stress corrosion cracks. The microstructure observation results revealed that a hardened layer was formed on the surface and the initial coarse-grained structure in the surface was refined into ultrafine grains. The above results indicate that UIT is an effective approach for protecting weldments against SCC.

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