Development of Pre-hardened and Ultra-thick 1.2311 Steel Plate Used for Plastic Mold Steel

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）→860-890 ℃ 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.