Abstract:  Effect of (/% ：) 0.023Al_sol, 0.035Al_sol、, 0.018~0.019Al_sol-0.012~0.014Ti and 0.019~0.020Al_sol-0.031 ~0.032Nb microalloying on mixed grain size of Φ120 mm case hardened steel ZF7 (% ： 0.18~0.20C, 0.22~0.25Si, 1.22~1.30Mn, 0.008~0.016P, 0.019~0.029S, 1.19~1.25Cr, 0.0018~0.0022B) produced by 60 t BOF-LF-VD-300 mm x 360 mm CC-continuous rolling process and heated at 930 °C has been studied. Results show that with heat treatment condition at 930 °C for 7.5 h, as Al_sol content in steel is 0.035% , there is no mixed grain size occurred in steel ZF7, but in steel ZF7 microalloying with (/% ：) 0.023Alsol, 0.018 〜0.019Al_sol-0.012~0.014Ti or 0.019~0.020Al_sol-0.031 ~0.032Nb the phenomena of mixed grain size occurs in steel, it is indicated that the steel has sufficient Al_sol content is key factor to avoid mixed grain size occurring in steel ZF7.

摘要： 研究了(/%)0.023Al_sol、0.035Al_sol、0.018～0.019Al_sol-0.012～0.014Ti和0.019～0.020Al_sol-0.031～0.032Nb微合金化对60 t BOF-LF-VD-300 mm×360 mm CC-连轧工艺生产的Φ120 mm ZF7渗碳钢(/%:0.18～0.20C、0.22～0.25Si、1.22～1.30Mn、0.008～0.016P、0.019～0.029S、1.19～1.25Cr、0.001 8～0.002 2B)930℃加热时晶粒度混晶的影响。结果表明,在930℃ 7.5 h热处理条件下,当Al_sol为0.035%时ZF7钢未发生混晶现象,当钢中(/%)0.023Al_sol或0.018～0.019Al_sol-0.012～0.014Ti或0.019～0.020Al_sol-0.031～0.032Nb微合金化时,ZF7钢均发生了混晶现象,说明钢中有足够的Al_sol含量是防止ZF7钢发生混晶的关键因素。 

关键词: ZF7渗碳钢, Al_sol、Ti、Nb, 微合金化, 混晶