Abstract: Production flowsheet of steel 420M (/% ： 0.18 〜0.23 C, ≤1.00Si, 0.25 ~ 1.00Mn, ≤0.020P, ≤ 0.005S, 12.0 ~ 14.0Cr, ≤ 0.50Mo, ≤ 0.50Ni) is 20 t EAF-AOD-LF-3 t ingot-Φ190 mm tube shell-Φ193 mm x29 mm shell-rolled by ASSEL mill to Φ158.75 mm x25.4 mm tube. Because of poor hot plasticity of steel 420M the piercing point consumption is large in piercing process, the inner wall of shell easily produces overlap and the tube surface cracks easily form after rolled by ASSEL mill. With optimized process including decreasing tube shell heating temperature from original 1 240 ~ 1 280 °C to 1 150 ~ 1 250 °C，using bearing molybdenum piercing point to replace medium carbon CrMo steel piercing point, improving tube rolling parameters and slow cooling or annealing after rolling the surface quality of tube improved markedly and the qualified rate of first nondestructive test increases from original less than 50% to more than 95% .

摘要： 420M钢(/%:0.18～0.23C,≤1.00Si,0.25～1.00Mn,≤0.020P,≤0.005S,12.0～14.OCr,≤0.50Mo,≤0.50Ni)的生产工艺流程为20 t EAF-AOD-LF-3 t锭-Φ190 mm管坯-Φ193 mm×29 mm毛管-ASSEL机组轧成Φ158.75 mm×25.4 mm管。因420M钢热塑性差,穿孔时顶头耗损大,毛管内壁易产生折叠,ASSEL轧管后易产生表面裂纹等缺陷。通过优化工艺,管坯加热温度从1 240～1 280℃降至1 150～1 250℃,采用含钼顶头代替中碳CrMo钢顶头,改进轧管工艺参数,轧后缓冷和退火,显著提高钢管表面质量,一次探伤合格率由不足50%提高至95%以上。