Chen Yufeng,Zhang Junfen,Xue Qihe,et al.Effect of Nitrogen Content and Final Rolling Temperature on Low-temperature Impact Toughness of Titanium Microalloyed High-strength Steel CGLC700[J].Special Steel,2024,45(03):40-48.
Chen Yufeng,Zhang Junfen,Xue Qihe,et al.Effect of Nitrogen Content and Final Rolling Temperature on Low-temperature Impact Toughness of Titanium Microalloyed High-strength Steel CGLC700[J].Special Steel,2024,45(03):40-48. DOI: 10.20057/j.1003-8620.2023-00215.
Effect of Nitrogen Content and Final Rolling Temperature on Low-temperature Impact Toughness of Titanium Microalloyed High-strength Steel CGLC700
Aiming at the problem of poor low-temperature impact toughness of titanium microalloyed high-strength steel CGLC700, by thermodynamic calculations and high-temperature in-situ observations, as well as the use of electron backscattering diffraction, transmission electron microscopy, scanning electron microscopy, and optical microscopy have been used to investigate inclusions, second-phase particles, fracture morphology, and low-temperature impact toughness of the Ti-bearing high-strength steel. The results show that the reasons for the poor low-temperature impact toughness of Ti-bearing high-strength steel are related to the large-size brittle inclusions and the precipitation phase of Ti(C,N) and TiN in the steel. When the nitrogen content in steel is reduced from 0.004 9% to ≤0.003 5%, the number and size of brittle inclusions in steel can be effectively reduced, and the impact toughness of steel can be improved. Reducing the final rolling temperature from 885-895 ℃ to 875-885 °C can promote the precipitation of nanoscale TiC second phase particles and the formation of large-angle grain boundaries, and reduce the effective grain size, thereby significantly improving the low-temperature impact toughness of steel. Compared with experimental steel 1#, when the nitrogen content was reduced to ≤0.003 5% and the final rolling temperature was 875-885 °C, the average grain size in titanium microalloyed high-strength steel decreased from 3.1 μm to 2.7 μm, the proportion of small-size effective grains was higher, the large-size inclusions and number density decreased, the proportion in the large-angle grain boundary increased by 16.6%, and the low-temperature impact energy of steel could be increased from 14.75 J to 37.35 J.
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