Development and application of hot forming steel CR300MB for high-end vehicle

doi:10.13251/j.issn.0254-6051.2022.07.019

Abstract

Abstract: After smelting, continuous casting, hot rolling, pickling and cold rolling, the cold-rolled coil of CR300MB steel was produced. In order to develop the hot forming steel CR300MB for high-end vehicle, the spesimens cut from the cold-rolled CR300MB steel coil were simulated by continuous annealing and batch annealing process. The results show that the mechanical properties of the two kinds of specrmens simulated by continuous annealing and batch annealing can satisfy the requirement of the high-end vehicle enterprise standards, however, for the specrmens simulated by continuous annealing, the yield strength and tensile strength are too high and the elongation is too low compared with that of the imported material, and the grains are coarse, most of them are elongated rolling deformed grains and there is banded segregation, while the mechanical properties of the specrmens simulated by batch annealing are closer to that of the imported material, and the grains are fine and most of them are equiaxed. Comprehensive analysis shows that the mechanical properties and microstructure of the specrmens simulated by 680 ℃ batch annealing process are the best, and the batch annealing process with annealing at 680 ℃ and holding for 10 h is adopted to develop the CR300MB cold rolled hot forming steel. The yield strength, tensile strength and elongation of the CR300MB steel before hot stamping meet the standard requirements, and the microstructure and mechanical properties are better than that of the specrmens simulated by batch annealing, basically reaching the level of the imported material. The developed CR300MB steel adopts the hot stamping process of heating temperature 930 ℃ with holding time 300 s, holding pressure 8000 kN with holding time 10 s to trial produce the parts for a high-end automotive company and gets success. The mechanical properties, microstructure and decarburization layer depth of the parts are qualified, which shows that the development and application of the CR300MB hot forming steel for high-end vehicle is successful.

Key words: hot forming steel, CR300MB steel, batch annealing, mechanical properties

CLC Number:

Chen Bo, Zhany Jiguo, Hua Yongxing, Yin Shuchun, Wu Lei, Liang Zhenwei, Sun Kuo. Development and application of hot forming steel CR300MB for high-end vehicle[J]. Heat Treatment of Metals, 2022, 47(7): 107-113.

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