Abstract：In order to improve the quality stability of 316H stainless steel under the condition of sodium cold fast reactor high temperature and strong neutron radiation environment,the ferrite area percent of 316H stainless steel must be lower than 1%,which is much lower than 2%-8% in 316H stainless steel plates produced by conventional production process. The purpose is to reduce the ferrite area percent by the following method. The ratio of equivalent Cr and Ni was controlled below 1.3 and the ferrite content was controlled below 7% according to the phase diagram calculation combined with analysis of C,Cr,Ni,Mo and N in 316H stainless steel. The molten steel should be cooled rapidly at the initial stage of solidification to make the molten steel pass quickly δ-Fe phase region according to the phase transformation process. The cooling rate should be slowed down after the temperature of molten steel lower than δ-Fe phase zone,so that the δ-Fe can be transformed into austenite through peritectic reaction and high-temperature diffusion as much as possible. According to the above analysis,the highest ferrite content was decreased from more than 15% to about 10% by reducing the superheat of molten steel from (45±5) ℃ to (35±5) ℃,the increasing of cooling water intensity from 2 700 L/min to 3 000 L/min can reduce the ferrite area percent from 10% to 7% continually. Finally,the amount of secondary cooling water is reduced from 0.75 L/kg to 0.55 L/kg,and the ferrite area percent of whole continuous casting slab section can be reduced to less than 7%. The steel plate rolled with low ferrite content slab obtained by adjusting the three process parameters of continuous casting production superheat,mold cooling intensity and secondary cooling water distribution step by step still cannot meet the technical requirements. For eliminating residual ferrite thoroughly,the cross test of different holding temperature and holding time were test,the optimal homogenization technology for eliminating residual ferrite holding was that 1 250 ℃ holding for 24 h. Ultimately,the 316H stainless steel containing residual ferrite less than 0.1% was obtained by the above measures.
李建民, 庄迎, 尹嵬. 316H不锈钢铁素体的形成与控制[J]. 钢铁, 2022, 57(11): 123-130.
LI Jian-min, ZHUANG Ying, YIN Wei. Ferrite formation and control in 316H stainless steel[J]. Iron and Steel, 2022, 57(11): 123-130.
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2022, Vol. 57 
