Effect of quenching and tempering process on microstructure and properties of automobile large beam steel 700L
LI Guan-nan1,2, SHANG Zhi-qiang2, LI Hong-jun1
1. Technical Center, Handan Iron and Steel Group Co., Ltd., Handan 056015, Hebei, China; 2. College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China
Abstract:The effects of different quenching and tempering processes on the microstructure and mechanical properties of 700L automobile beam steel were studied by means of metal pendulum impact test and microhardness test with the methods of OM, SEM, TEM. The results showed that with the increase of quenching temperature, the granular bainite (GB) structure decreased, the number of lath bainite ferrite (BF) increased gradually, the width of lath increased, and the number of white precipitates on the ferrite matrix and boundary increased. With the increase of tempering temperature, the massive ferrite grew up, the M/A structure and the decomposition of residual austenite were obvious, and a small number of equiaxed ferrite appeared. The number of tempering precipitates increased, and particle coarsening and growing phenomenon occurred when the tempering temperature exceeded 600 ℃. The low temperature impact energy fluctuated at different quenching and tempering conditions, which was mainly related to the change of microstructure regularity for the second phase particles and the matrix. The experimental steel had the best low temperature impact toughness after tempering at 600 ℃, which was mainly due to the presence of a large number of bainite ferrite (BF) with high density dislocation and the second phase nanoparticles with appropriate size and uniform distribution in the steel matrix.
李冠楠, 商志强, 李红俊. 调质工艺对汽车大梁钢700L组织性能的影响[J]. 中国冶金, 2022, 32(4): 41-46.
LI Guan-nan, SHANG Zhi-qiang, LI Hong-jun. Effect of quenching and tempering process on microstructure and properties of automobile large beam steel 700L[J]. China Metallurgy, 2022, 32(4): 41-46.
CHEN K, JIANG Z, LIU F, et al. Effect of quenching and tempering temperature on microstructure and tensile properties of microalloyed ultra-high strength suspension spring steel[J]. Materials Science and Engineering A-Structural Materials Properties Microstructure and Processing, 2019, 766:1.
Deng X, Wang Z, Misra R D K, et al. Precipitation behavior and mechanical properties of Ti-Mo medium-carbon steel during austenite to bainite transformation[J]. Journal of Materials Engineering and Performance, 2015, 24(2): 1072.