Abstract: Based on domestic and abroad market demands，this article introduces the development process of pre-hardened and ultra-thick 1.2311 steel plate used for plastic mold steel.Experimental study on continuous phase transformation behavior of 1.2311 steel was conducted，and a static continuous cooling transformation curve was drawn.By KR pretreatment→120 t converter （smelting using slag retention method can control carbon content within 0.20%-0.30%）→LF（refining argon blowing time ≥60 minutes）→VD （vacuum degree ≤67 Pa，vacuum holding time≥20 minutes）→450 mm slab continuous casting（low superheat of 8-15 ℃，low pulling speed of 0.45 m/min）→Slab heating→5 000 mm mill rolling （the sum of the last three pass reductions is ≥140 mm for rough mill）→870-890 ℃ normalizing process→ACC controlled cooling （combination of water cooling and air cooling）→550-610 ℃ tempering process，the pre-hardened and ultra-thick steel plate for plastic mold 1.2311 with a specification of ≥150 mm was successfully developed.The results show that a Brinell hardness deviation of ≤15HBW across the entire thickness，resulting in good uniformity of hardness，the ultrasonic testing of the plates meets the requirements of Level I in GB/T2970―2016.All comprehensive performance indicators meet the development requirements.

Key words: 1.2311 steel, Pre-hardened, CCT Curve, Hardness

摘要： 基于国内外市场需求，介绍了塑料模具用1.2311预硬化特厚钢板的研制过程。对1.2311钢进行了连续相变行为试验研究，并绘制出静态连续冷却转变曲线。经KR预处理→120 t转炉（留渣法冶炼控制碳含量0.20%~0.30%）→LF（精炼吹氩时间保持≥60 min）→VD（真空度不高于67 Pa，真空保持时间≥20 min）→450 mm板坯连铸（过热度8~15 ℃、拉速0.45 m/min）→板坯加热→5 000 mm轧机轧制（粗轧末3道次压下量之和≥140 mm）→-870~890 ℃正火→ACC控制冷却（水冷、空冷结合）→550~610 ℃回火，成功研制出≥150 mm规格塑料模具用1.2311预硬化特厚钢板。结果表明，全厚度布氏硬度偏差≤15HBW，硬度均匀性良好，钢板超声波探伤符合GB/T2970―2016中I级要求。各项综合性能指标满足研制要求。

关键词: 1.2311钢, 预硬化, 连续冷却转变曲线, 硬度