Stress relaxation crack sensitivity temperature testing method for hardened and tempered high-strength steel used in large-size spherical tank

Abstract

The invention relates to a stress relaxation crack sensitivity temperature testing method for hardened and tempered high-strength steel used in a large-size spherical tank. In the method, firstly, simulation of weld thermal cycle is carried out to a test sample, wherein the test sample is heated according to preset steps so as to simulate structure status of HAZ, and then a high-temperature tensile test under a thermal treatment condition is carried out until the test sample is broken. The stress relaxation crack sensitivity temperature of the steel material is acquired on the basis of change on the reduction of area of the test sample. In the method, welding thermal simulation technology is employed to carry out a welding test, so that the method has short test period and can simulate the structures of all welding zones. Because temperature and loading control of a test machine are quite accurate, accurate test data can be acquired. The method has low working load and is high in testing efficiency, and is a simple method for testing the stress relaxation crack sensitivity temperature. The method is applied to test of the stress relaxation crack sensitivity temperature of steel materials and provides evidence for making a post-weld heat treatment process for a hardened and tempered high-strength steel pressure vessel.

Description

technical field [0001] The patent of the invention relates to a stress relaxation sensitive temperature detection method for quenched and tempered high-strength steel plates for pressure vessels. Background technique [0002] After the pressure vessel is welded, there will inevitably be a large welding residual stress. The welding residual stress of the pressure vessel made of quenched and tempered high-strength steel is even greater. If it is allowed to exist, it will bring hidden dangers to the safe operation of the pressure vessel. For this reason, the general pressure vessel must be subjected to post-weld heat treatment after welding to eliminate welding residual stress. However, as the strength of quenched and tempered steel is getting higher and higher, the problem of stress relaxation cracks generated in the post-weld heat treatment process has attracted more and more attention. It has been found that all kinds of steel have a temperature sensitive to stress relaxatio...

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Problems solved by technology

[0003] The traditional methods for obtaining the sensitive temperature range of stress relaxation cracks in steel mainly include the following: one is to use small iron research samples to conduct tests at different heat treatment temperatures to detect the sensitive temperature of stress relaxation cracks in steel plates, but this method is limited The accuracy is very low, the data obtained are often too large in error, and have little guiding significance for the actual post-weld heat treatment process; another method is to use the pin test to measure the sensitive temperature of stress relaxation cracks, which uses actual welded joints to make samples. Then conduct tests under different loads to obtain some quantitative data. The disadvantage of the plug test is that the test period is long, the sample processing is complicated, and the consumption of test materials is relatively large.

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