Effect of Process Conditions on Residual Stress in Laser-MAG Welding of High Strength Steel

2020 ◽  
Vol 831 ◽  
pp. 71-77
Author(s):  
Zhong Feng Tian ◽  
Jun Feng Li ◽  
Zhi Xuan Chen ◽  
Zhao Nan Wang
Keyword(s):  
Residual Stress ◽  
High Strength Steel ◽  
High Strength ◽  
Welding Residual Stress ◽  
Process Conditions ◽  
The Finite Element Method ◽  
Test Plate ◽  
Thick Cylinder ◽  
Actual Test ◽  
Good Agreement

In this paper, the finite element method is used to simulate and analyze the laser-MAG composite welding of 4mm thick cylinder of high strength steel 30CrMnSiA, and the variation law of welding residual stress under different technological conditions is obtained. By comparing and analyzing the welding residual stress of the actual test plate by blind hole method with theoretical calculation value, the two methods are in good agreement, and the rationality of the model is verified.

Formation Mechanism of Hydrogen-Induced Delayed Cracking in Weld Center of High-Strength Steel

2012 ◽  
Vol 557-559 ◽  
pp. 1304-1307 ◽  
Author(s):  
Jing Qiang Zhang ◽  
Jian Guo Yang ◽  
Jia Jie Wang ◽  
Xue Song Liu ◽  
Zhi Bo Dong ◽  
...  
Keyword(s):  
Residual Stress ◽  
Formation Mechanism ◽  
Welded Joints ◽  
High Strength Steel ◽  
Hydrogen Pressure ◽  
High Strength ◽  
Welding Residual Stress ◽  
Cracking Behavior ◽  
Hydrogen Damage ◽  
Delayed Cracking

Based on the estimation of the critical hydrogen pressure and concentrations required for hydrogen-induced delayed cracking in high-strength steel, the conclusion that welded joints are hydrogen pressure microcracks body can be drawn under certain conditions. Through the analysis of the relationship between the microstructure evolution of welded joints, diffusion enrichment of hydrogen and cracking behavior, the formation mechanism of hydrogen-induced delayed cracking in weld center of high-strength steel joints is analyzed and the mechanism that stress induced the residual diffusion hydrogen gathered to promote the hydrogen pressure microcracks propagation is proposed. The research shows that the initation and propogation of hydrogen-induced delayed cracking in weld center can be divided into two stages, i.e. irreversible hydrogen damage stage and reversible hydrogen damage stage. In irreversible stage hydrogen pressure is the main causes of the initation of microcracks, while in reversible stage welding residual stress and residual diffusible hydrogen are necessary conditions for microcracks growth. The microcracks growth can be controlled by regulating welding residual stress.

Effect of Welding Residual Stress and Plastic Constraint on Brittle Fracture of a High Strength Steel

2009 ◽  
Author(s):  
Masaki Torigoe ◽  
Yoichi Yamashita ◽  
Takehisa Yamada
Keyword(s):  
Residual Stress ◽  
Brittle Fracture ◽  
High Strength Steel ◽  
Crack Tip ◽  
High Strength ◽  
Fracture Initiation ◽  
Parent Material ◽  
Welding Residual Stress ◽  
Cross Sectional ◽  
Plastic Constraint

This paper investigates the effect of welding residual stress and plastic constraint on brittle fracture of a 780 MPa class high-strength steel (HT780). In order to investigate the effect of welding residual stress, three point bend (3PB) fracture toughness tests were conducted using the parent-material specimens and groove-welded specimens which were prepared to have the same cross-sectional proportion; i.e., a ratio of thickness to width of 0.5. Crack length was determined so that the crack tip was located in the base-metal zone far from the heat-affected zone of the welded specimen to eliminate the effect of any degradation of the parent-material property on fracture resistance. Also, in order to investigate the effect of constraint, tensile loading tests in which the plastic constraint was expected to be less than 3PB were conducted using welded specimens as the same as employed in the 3PB test. Three dimensional finite element (FE) analyses were performed to evaluate the stress state near the crack tip at the point of brittle fracture initiation for each test condition. From the results of experiments and FE analyses, it is confirmed that the fracture test results can be evaluated using J or KJ – Q theory, by considering enhancement or reduction due to residual stress.

Effect of Heat Treatment on Corrosion and Fracture Behavior of SPV50Q High Strength Steel Weldment in H2S-Containing Environment

2008 ◽  
Author(s):  
Jianqun Tang ◽  
Jian-Ming Gong ◽  
Luyang Geng ◽  
Jiang Yong
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Residual Stress ◽  
High Strength Steel ◽  
Fracture Behavior ◽  
High Strength ◽  
Optical Microscope ◽  
Welding Residual Stress ◽  
Liquefied Petroleum Gas ◽  
Steel Weldment

SPV50Q high strength steel is often used to fabricate liquefied petroleum gas (LPG) spherical tanks with larger capacity, and tanks are expected to free post weld heat treatment (PWHT) for avoiding the possible reduction in strength. Sulfide stress corrosion cracking (SSCC), however, has been found in weldment, especially the heat-affected zone (HAZ), in LPG environment contaminated by wet H2S. The failure analysis showed that the existence of welding residual stress in weldment is one of the major factors in the occurrence of cracking. Post welding heat treatment (PWHT) is a feasible method of reducing welding residual stress. Therefore, in order to investigate the effect of heat treatment on mechanical properties, corrosion and fracture behavior of SPV50Q steel weldment, the difference in mechanical properties of the weldment with and without heat treatment at 590°C for 160 min after welding was measured using tensile test and impact test. The corrosion behaviors of base metal (BM), weld metal (WM) and HAZ metal in the weldment were investigated by potentiodynamic polarization in H2S-containing solution. In the same solution, the susceptibility to environmental cracking was evaluated by slow strain rate testing (SSRT). The feature of fracture and the morphologies of cracks were observed by scanning electrode microscope (SEM) and optical microscope (OP). The results indicate that the execution of heat treatment does not greatly change the properties of SPV50Q steel weldment, which can provide technology support for the remanufacturing of the LPG tanks having suffered from SSCC by repair welding following local or integral heat treatment.

Study on Laser Welding Residual Stress of High Strength Steel

2015 ◽  
Vol 42 (6) ◽  
pp. 0603007
Author(s):  
伍强 Wu Qiang ◽  
徐兰英 Xu Lanying ◽  
杨永强 Yang Yongqiang ◽  
孔春玉 Kong Chunyu
Keyword(s):  
Residual Stress ◽  
Laser Welding ◽  
High Strength Steel ◽  
High Strength ◽  
Welding Residual Stress

Evaluation of Cracking Behavior of SPV50Q High Strength Steel Weldment in Wet H2S Containing Environment

2005 ◽  
Vol 297-300 ◽  
pp. 951-957 ◽  
Author(s):  
Jian Ming Gong ◽  
Jian Qun Tang ◽  
Xian Chen Zhang ◽  
Shan Tung Tu
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
High Strength Steel ◽  
High Strength ◽  
Post Weld Heat Treatment ◽  
Welding Residual Stress ◽  
Cracking Behavior ◽  
Steel Weldment ◽  
Hydrogen Induced Cracking ◽  
Weld Heat

JIS-SPV50Q high strength steel is often employed in construction of liquid petroleum gas (LPG) spherical tanks due to its high strength and good ductility. In general, post weld heat treatment is not performed after welding of SPV50Q high strength steel and welding residual stress will be retained in weldment. Service experience and inspection indicate that higher H2S concentration and welding residual stress result in the environmental failure, such as blistering or hydrogen induced cracking (HIC), sulfide stress corrosion cracking (SSCC) and stress oriented hydrogen induced cracking (SOHIC). In the present paper, the cracking behavior of SPV50Q high strength steel weldment by manual electric arc welding has been investigated in various saturate solutions with different concentrations of H2S. The results of slow strain rate testing, performed at a strain of 1×10-6s-1, reveal the presence of SSCC and HIC in the base metal adjacent to HAZ. The ffects of the different temperatures of post weld heat treatment on cracking are discussed. The suitable post weld heat treatment could increase the resistance of SPV50Q weldment on SSCC or HIC and does not decrease the mechanical properties of SPV50Q weldment.

Dynamic Response Analysis of Butt Joint of HTS-A Steel Considering Welding Residual Stresses

2013 ◽  
Vol 423-426 ◽  
pp. 944-950
Author(s):  
Wei Shen ◽  
Ren Jun Yan ◽  
Lin Xu ◽  
Kai Qin ◽  
Xin Yu Zhang ◽  
...  
Keyword(s):  
Residual Stress ◽  
Dynamic Response ◽  
Hot Spot ◽  
Time History ◽  
High Strength ◽  
Simulation Method ◽  
Butt Joint ◽  
Welding Residual Stress ◽  
Response Analysis ◽  
Hull Structure

This paper uses both numerical simulation method and experimental research method to study on welding residual stress of high-strength steel of the cone-cylinder hull. Welding is often accompanied by a larger welding residual stress, which directly affects the safety and service life of the hull structure. In order to obtain the distribution of the welding residual stress, the welding procedure was developed by its parameter language by using FE analysis software in this paper. Then the welding residual stress of hot spot region was measured through X-ray nondestructive testing method, and compared it with simulation results. Finally, considering the residual stress as the initial stress, this paper analyzed dynamic response process of the welding structure under combined actions of the welding residual stress and multiaxial loads, which could more accurately determine the stress of welding structure and the location of fatigue risk point. According to the amplitude of damage parameters and strain time-history curve, we can estimate the fatigue life of structure by selecting the corresponding damage models.

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