Du Pengju,Yu Xinyun,Sun Xianjin,et al.Effect of Tempering Process on Microstructure and Mechanical Properties of Dual Phase High Strength Bridge Steel with Low Yield Ratio[J].Special Steel,2025,46(06):122-128.
Du Pengju,Yu Xinyun,Sun Xianjin,et al.Effect of Tempering Process on Microstructure and Mechanical Properties of Dual Phase High Strength Bridge Steel with Low Yield Ratio[J].Special Steel,2025,46(06):122-128. DOI: 10.20057/j.1003-8620.N250531.
Effect of Tempering Process on Microstructure and Mechanical Properties of Dual Phase High Strength Bridge Steel with Low Yield Ratio
In high strength steel, tempering process is usually used to improve toughness, but at the same time, the yield ratio which reflects the material's deformability, also increases sharply after tempering treatment. This study systematically investigated the effects of tempering on the microstructure evolution, tensile deformation behavior and low-temperature impact toughness of Q500qE dual phase high strength bridge steel with low yield ratio by means of DSC, SEM, EBSD, tensile test and oscillographic pendulum impact tester, which has guiding significance for realizing the matching of yield ratio and toughness of high strength steel. The results showed that during the heating process M/A islands decomposed first and then cementite precipitated at about 240
o
C-420
o
C. After tempering, the yield behavior changed from continuous type to discontinuous type, and the yield ratio increased sharply to 0.85 after tempering at 500
o
C. Low temperature tempering at 350
o
C can improve the crack arrest ability by decreasing work hardening ability and relieving the probability of strain localization at interfaces during deformation, which can balance the yield ratio and toughness well.
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