高强度低合金钢 Q420N 轧制工艺优化实践

试验高强度低合金钢Q420N(/%:0.16C,0.28Si,1.39Mn,0.015P,0.003S,0.11Cr,0.009N)的生产流程为120 t转炉-LF精炼-RH真空脱气-连铸300 mm×340 mm方坯-热连轧成Φ90 mm棒材。试验研究了普通轧制工艺(开轧1 100～1 150℃,终轧950～1 000℃,上冷床900～950℃,冷却速度0.5～1.0℃/s)和控轧控冷工艺(开轧1 100～1 150℃,终轧800～850℃,上冷床700～750℃,冷却速度5.0～15℃/s)对Q420N钢热轧显微组织和力学性能的影响。结果表明,随着终轧温度的降低和冷却速度的增大,Q420N钢材的显微组织得到改善,屈服强度明显增加;普通工艺轧制Q420N钢材屈服强度为325～340 MPa,晶粒度为6.0级,控轧控冷工艺轧制Q420N钢材屈服强度为495～515 MPa,晶粒度为9.0级,满足了标准要求,降低了生产成本。

Optimization Practice of Rolling Process for High-Strength Low-Alloy Steel Q420N

HSLA Steel Q420N ( /% ：0. 16C,0. 28Si,1.39Mn,0. 015P,0. 003S,0. 11Cr,0. 009N ) at production line is 120 t BOF-LF-RH-300 mm × 340 mm casting bloom-hot continuous rolling to Φ90 mm bar product. The effect of hot- rolled billet rolling to bar product processes by normal rolling ( beginning rolling at 1 100 ~ 1 150 ℃ , finishing rolling at 950 ~1 000 ℃ , to cooling bed at 900 ~950 ℃，cooling rate 0. 5 ~1.0 ℃/s ) and controlled rolling and controlled cooling (beginning rolling at 1 100 ~ 1 150 ℃ , finishing rolling at 800 ~850 ℃ , to cooling bed at 700 ~750 ℃ , cooling rate 5. 0 ~15 ℃/s ) on microstructure and mechanical properties of steel Q420N is tested and studied. The results show that the microstructure of Q420N steel is improved and yield strength is increased obviously with decreasing the finishing temperature and increasing the cooling rate. The yield strength of Q420N steel by normal rolling process is 325 ~340 MPa and the grain size rating is 6. 0, while the yield strength of Q420N steel by controlled rolling and controlled cooling process is 495 ~ 515 MPa and the grain size rating is 9. 0 which meets the standard requirements and reduces production cost.