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厚规格 35CrMo 预硬型模具钢板的回火组织与硬度研究张兴锦 吴会亮 张兆萍 陈永南(莱钢集团宽厚板事业部)摘 要 通过扫描电镜的分析手段，研究了莱钢生产 35CrMo 预硬型模具钢板厚度方向显微组织对硬度分布的影响。结果表明:80 mm 厚度钢板经过 900 ℃淬火和 550 ～560 ℃回火后，钢板近表面硬度为 HＲC32 ～36，心部硬度超过 HＲC28，厚度方向硬度波动控制在 HＲC5 以内;120 mm 厚度钢板经过 920 ℃淬火和 570 ℃回火后，钢板近表面硬度为 HＲC32 ～34，心部硬度下降到 HＲC28 ～ 30。回火态钢板表面硬度下降幅度大于心部硬度的下降幅度，钢板近表面处组织中的回火马氏体呈板条状，原始奥氏体被晶界不同取向的板条马氏体分割细化，组织中碳化物呈短棒状，数量相对较少;板厚 1/2 处组织为回火贝氏体和数量较多的碳化物。随着钢板厚度增加和回火温度升高，显微组织中回火马氏体体积分数逐渐减少，回火贝氏体体积分数逐渐增多，组织中的碳化物析出量逐渐增加，聚集长大趋势明显。关键词 预硬型模具钢 35CrMo 回火 显微组织Ｒesearch on Tempering Microstructure and Hardness of LargerThickness Pre － hardened Die Steel Plate 35CrMoZhan Xinggjin，Wu Huiliang，Zhang Zhaoping and Chen Yongnan(Heavy Plate Division of Laiwu Iron and Steel Group Corp． )Abstract The effect of through － thickness microstructure on hardness distribution of pre － hardened die steelplate 35CrMo produced by Laigang has been studied by means of scanning electronic microscopy in this paper． The re-sults show that after 900 ℃quenching and 550 ～560 ℃ tempering，the near surface hardness of 80 mm thickness platereaches HＲC32 ～36，the center hardness exceeds HＲC28 and the variation of through － thickness hardness is con-trolled to a value less than HＲC5;after 920 ℃quenching and 570 ℃ tempering，the near surface hardness of 120 mmthickness plate reaches HＲC32 ～34，the center hardness decreases to HＲC28 ～30． After tempering，the surface hard-ness decreases more than the center hardness，the microstructure show that the near surface microstructure consists oftempered lath martensite，the prior austenite are segmented and refined by the lath martensite of different orientation，the carbides in microstructure are in the shape of short bar with less quantity． The microstructure at 1/2 plate thicknesscomposes of tempered bainite and more carbides． With increasing of plate thickness and tempering temperature，thefraction of tempered martensite decreases，the fraction of tempered bainite gradually increases，the carbide content alsoincreases gradually with significant tendency of aggregation and growth．Keywords Pre － hardened die steel，35CrMo，Tempering ，Microstructure0 前言模具是工业产品批量生产的基础工艺装备，其生产技术水平的高低已成为衡量一个国家制造水平的重要标志之一。近年来，我国模具行业正在向大型、精密、复杂、高效、长寿命和多功能方向迅猛发展［1］ ，产量已跃居世界前列，用量较大的塑料模具钢主要有40Cr、35CrMo、P20 和718 等预硬化钢。35CrMo 钢是用于制造大型模具的预硬化塑料模具钢，经过调质处理后硬度为 HＲC28 ～36，具有硬度均匀、加工性能好、模具畸变小的特点［2］ 以及加工后不需要再进行热处理的优点，可以避免模具加工后热处理变形开裂的问题，因此