Numerical Simulation of Welding Residual Stress and Post-Weld Heat Treatment for Dissimilar Steel Welded Joint

2008 ◽  
Vol 575-578 ◽  
pp. 747-752 ◽  
Author(s):  
Guo Dong Zhang ◽  
Chang Yu Zhou
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Thermal Expansion ◽  
Thermal Expansion Coefficient ◽  
Base Metal ◽  
Expansion Coefficient ◽  
Welded Joint ◽  
Welding Residual Stress ◽  
Dissimilar Steel ◽  
Welding Line

By the finite element analysis software ABAQUS and the function of coupling process between heat and stress, the welding residual stress of Cr5Mo and 20 steel joint was analyzed. In addition the heat treatment of dissimilar steel welded joint was simulated. The residual stress distributions of dissimilar steel welding and heat treatment after welding were obtained. The comparison of welding residual stress between the homogenous steel and dissimilar steel was carried out. The results indicate that the welding residual stress of the same steel is lower than that of dissimilar steel welded joint obviously. Because of the difference of thermal expansion coefficient for base metal and welding microstructure, the relatively higher residual stress is produced due to the bigger thermal expansion coefficient of base metal. The highest annular residual stress is in welding line root of internal wall, while the highest axial residual stress is in welding line surface of outer wall. The welding residual stress of dissimilar welded joint is reduced obviously after heat treatment. The research results provide the possibility for optimizing the welding procedure and improving the reliability of dissimilar steel welding joint.

Effects of Heat-Treatment Temperature on the Properties of Negative CTE Eucryptite Ceramics

2010 ◽  
Vol 105-106 ◽  
pp. 123-125 ◽  
Author(s):  
Yong Li ◽  
Qi Hong Wei ◽  
Ling Li ◽  
Chong Hai Wang ◽  
Xiao Li Zhang ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Thermal Expansion ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Heat Treatment Temperature ◽  
Bending Strength ◽  
Sol Gel ◽  
Negative Thermal Expansion ◽  
Treatment Temperature ◽  
Heat Treated

In this paper, negative thermal expansion coefficient eucryptite powders were prepared by sol-gel method using silica-sol as starting material. The raw blocks were obtained by dry pressing process after the powder was synthesized, and then the raw blocks were heat-treated at 600º, 1150º, 1280º, 1380º, 1420º and 1450°C, respectively. Variations of density, porosity and thermal expansion coefficient at different heat treatment temperatures were investigated. Phase transformation and fracture surface morphology of eucryptite heat-treated at different temperatures, respectively, were observed by XRD and SEM. The results indicate that, with the increasing heat- treatment temperature, the grain size and the bending strength increased, porosity decreased, thermal expansion coefficient decreased continuously. Negative thermal expansion coefficient of -5.3162×10-6~-7.4413×10-6 (0~800°C) was obtained. But when the heat-treatment temperature was more than 1420°C, porosity began to increase, bending strength began to decrease, which were the symbols of over-burning, while the main crystal phase didn’t change.

Compositional Design of Ceramic Extrusion Die Materials Based on the Residual Stress Analyses in the Die Manufacturing Process

2011 ◽  
Vol 291-294 ◽  
pp. 1709-1712
Author(s):  
Chong Hai Xu ◽  
Jing Jie Zhang ◽  
Zhen Yu Jiang ◽  
Ming Dong Yi
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Thermal Expansion ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Extrusion Die ◽  
Element Simulation ◽  
Die Material ◽  
Longitudinal Cracks ◽  
Ceramic Extrusion

In the die manufacturing process of ceramic extrusion die, the residual stress was produced resulted from the thermal expansion coefficient mismatch between ceramic die and die core of graphite. As a result, the longitudinal cracks were formed in the ceramic extrusion die. The thermal residual stress formed in the cooling process was analyzed by finite element simulation method. The result indicated that the thermal expansion coefficient was the primary factor which could affect the tensile stress of ceramic extrusion die. Then, the thermal expansion coefficient, elastic modulus and poisson's ratio of ceramic extrusion die material were selected as design variables, and the largest tensile stress that less than allowable stress of ceramic die material was determined as the objective function, the material component were optimized according to the finite element simulation. The longitudinal cracks were eventually avoided.

Effects of Post Weld Heat Treatment Residual Stress on the Creep of Elbow Welded Joint

2009 ◽  
Author(s):  
Changyu Zhou ◽  
Guodong Zhang
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
High Temperature ◽  
Internal Pressure ◽  
Creep Strain ◽  
Welded Joint ◽  
Post Weld Heat Treatment ◽  
Welding Residual Stress ◽  
Creep Analysis ◽  
Boiler Tubes

It is well known that type IV crack emerges in the high temperature welded components. Although the welding residual stress will drop after post weld heat treatment (PWHT), the PWHT residual stress still remains in the welded joint. When the joint is in service at high temperature and under high pressure, the PWHT stress and pressure will induce the creep strain in the welded joint of the elbow of T91 boiler tubes. Usually, it is considered that the PWHT stress will relax at high temperature environment and is ignored by many researchers. In this paper, by the finite element analysis codes ABAQUS and the function of RESTART, a sequential coupling calculating program for creep based on welding residual stress has been developed by establishing the model of temperature field, residual stress and creep analysis. The welding residual stress and creep of elbow welded joint for T91 boiler tubes was simulated by the program. According to the finite element calculation results, the PWHT stress has a great influence on the T91tube creep. This method established the basis of calculating the effects of welding residual stress on the creep of welded joint. Firstly, the welding residual stress and the PWHT stress was simulated by ABAQUS. Based on the work, the stress distribution of the T91 tube elbow can be obtained under internal pressure and the PWHT stress. Secondly, for the elbow welded joint the creep under the internal pressure only and the creep under internal pressure and PHWT stress can be simulated by the ABAQUS codes. Then comparison of creep strain in the elbow welded joint with PWHT stress and with internal pressure is made in the paper. Although the stress induced by the PWHT and internal pressure would relax in a short time, the creep strain of the elbow welded joint is still influenced by initial stress state. The results shown that the PWHT stress can not be ignored for the creep analysis of the elbow welded joint. So it can be considered that the PWHT residual stress is one of possible failure factors for the elbow welded joint. The design of high temperature elbow welded joint need to consider the influence of the PWHT residual stress. This paper will provide a more comprehensive means for life assessment of the welded joint in service.

Research on Welding Repair for Reheating Hot Pipe Elbow of 325MW Station Boiler

2012 ◽  
Vol 516-517 ◽  
pp. 414-418 ◽  
Author(s):  
Xiang Feng Zheng ◽  
Qing Wang ◽  
Yan Ting Feng ◽  
Xiao Guang Niu ◽  
Xiao Jun Hao ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Base Metal ◽  
Heat Input ◽  
Welding Residual Stress ◽  
Fusion Line ◽  
Metallographic Examination ◽  
Microscope Analysis ◽  
Metal Material ◽  
Pipe Elbow

Through methods, such as microscope analysis, metallographic examination, the crack located nearby the fusion line between reheating hot pipe elbow and blocking valve is reheat crack. The base metal material and excessive welding residual stress are the primary inducement of crack. In replacing pipe elbow, the measures of reducing residual stress, such as hammer blowing ,lower welding heat input, post welding heat treatment and so on, were taken. The welding repair succeeded greatly.

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