Method for evaluating material reheating crack sensitivity through stress relaxation test

Abstract

The invention relates to a method for evaluating material reheating crack sensitivity through a stress relaxation test. The method comprises the following steps: integrating welding thermal simulation and stress simulation, simulating a welded HAZ coarse-grain region microstructure by simulating different welding process parameters, and simulating a residual stress state of a sample by taking certain measures; performing destressed heat-treatment simulation until the sample is fractured or the set heat insulation stage is ended so as to obtain a change relationship between the temperature, the stress and the like along with time; characterizing the material reheating crack sensitivity by using a fracture temperature-fracture time curve. According to the method disclosed by the invention, the material reheating crack sensitivity is directly evaluated on a thermal simulated testing machine through weld simulation and stress relaxation testing. The whole testing process is very close to the actual situation, the testing cycle is very short, high-efficiency and accurate, and the material loss is less during the test. The method disclosed by the invention can be used for various weld and stress simulation process parameters. The method has great significance in the actual material reheating crack sensitivity prediction and has progressiveness.

Description

technical field [0001] The invention relates to a method for evaluating material reheating crack sensitivity by stress relaxation test. The invention belongs to the technical field of iron and steel physical and thermal simulation analysis. Background technique [0002] In recent years, with the development of pressure vessels to extreme conditions of high parameters such as high pressure, cryogenic temperature, high corrosion, and large size, in order to meet higher and higher service requirements, post-weld heat treatment has been used as a means to improve the quality of welded pressure vessel products Included in many standards. The occurrence of reheat cracks is due to the fact that the strain generated during the relaxation of welding residual stress exceeds the plastic deformation capacity of the coarse-grained zone in the heat-affected zone under post-weld heat treatment or high-temperature work. Therefore, it is very important to try to reflect the plastic or cree...

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Problems solved by technology

[0003] There are mainly the following methods for evaluating the reheating crack sensitivity of steel grades: one is to use small iron research samples to conduct tests at different heat treatment temperatures, but the accuracy of this method is very low, and the obtained data often have large errors. The guiding significance for the actual post-weld heat treatment is not very great; the second is to use the plug test, use the actual welded joints to make samples, and conduct tests under different loads to obtain some quantitative data, but the shortcoming of the plug test is that the test period is long , the processing of the sample is difficult, and the consumption of test materials is relatively large; the third is to use the method of physical simulation to first simulate the microstructure of the welded HAZ, and then undergo high-temperature tensile tests under different heat treatment conditions until the sample breaks. The stress relaxation sensitive temperature range can be obtained by the change of the reduction of area. The "Measurement Method for Stress Relaxation Crack Sensitivity Temperature of Quenched and Tempered High-Strength Steel for Large Spherical Tanks" disclosed in the application number 2016110298872 belongs to this type of method.

However, this method can only reflect the strain resistance ability of the material at high temperature, and cannot reflect the stress relaxation deformation ability of the material under constant strain conditions during the actual stress relaxation process.

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