比较了大截面塑料模具钢中460 mm×800 mm×3 200 mm非调质预硬型SWFT钢和500 mm×800 mm×2 900 mm调质预硬型3Cr2MnNiMo钢的截面硬度以及心部和表层的显微组织,测试了两种钢的奥氏体连续冷却转变曲线.结果表明:两种钢都具有较好的淬透性,强烈推迟了块状先共析铁素体的出现;两种钢截面硬度波动均在±1.5 HRC内;3Cr2MnNiMo钢表层显微组织为回火马氏体,心部为回火贝氏体,反映出其淬火后的回火工艺调整了截面硬度;而SWFT钢有较宽的贝氏体相变范围,使得其心部和表层在锻造空冷后都得到均匀的贝氏体组织.

The hardness and microstructure of the 460 mm×800 mm×3 200 mm non-quenched & tempered prehardened (SWFT) steel and the 500 mm×800 mm×2 900 mm quenched & tempered prehardened 3Cr2MnNiMo steel for plastic moulds were compared and studied.The continuous cooling transformation curves of the two steels were measured.The results show that the two steels both had good hardenability,which strongly put off the appearance of massive proecutectoid ferrite.The surface microstructure of 3Cr2MnNiMo steel was tempered martensite and center microstructure was tempered bainite,which reflected that the tempering process adjusted the uniformity of its hardness.While the broad bainitic transformation zone made the microstructure of SWFT steel obtained uniform bainite through the whole mould.