The microstructure,mechanical property and hole expansion property of 800 MPa-level hot-rolled acid-pickled hole expansion steel at different coiling temperatures were analyzed by optical microscope,scanning electron microscope,ten-sile tester and hole punching expansion tester.The results showed that the microstructure was mainly composed of ferrite+bainite when the coiling temperature was 450-600 ℃.With the increase of coiling temperature,the ferrite grains in-creased,while the volume fraction of bainite decreased gradually.The yield strength and tensile strength of the material were improved,the elongation had no significant change,and the hole expansion rate was reduced obviously.With overall consideration,when the coiling temperature was 450-500 ℃,the tensile strength was higher than 780 MPa,and the hole expansion rate was above 50％.
关键词
高扩孔钢/卷取温度/组织与性能/扩孔率
Key words
high hole expansion steel/coiling temperature/microstructure and property/hole expansion rate
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