贝氏体预硬型塑料模具钢大模块硬度与组织分析

HARDNESS AND MICROSTRUCTURE OF BAINITE PRE-HARDENED PLASTIC MOULD STEEL IN LARGE BLOCK

对860 mm厚非调质预硬型塑料模具钢(NQP钢)大模块进行解剖,测定了模块截面硬度、碳含量,并对不同部位的组织进行了金相观察,测定了该钢的CCT曲线。结果表明:整个模块截面碳偏析程度在0.04%～0.06%,碳含量分布规律与硬度分布规律一致;CCT曲线表明其具备良好的淬透性,在0.015～0.1℃/s的冷速范围内可获得完全的贝氏体。分析其截面硬度波动在±1.5 HRC内的原因在于此钢具有较好的贝氏体淬透性,大模块整个截面上都获得了均匀的贝氏体组织,能满足大截面塑料制品行业的使用要求。

The non-quenched pre-hardened （NQP） plastic mould steel large block with thickness of 860 mm was dissected. The hardness, carbon content and microstrueture over the section were tested and observed, also the CCT curve was tested. The results showed that the carbon content in the whole block was uniformity with the carbon segregation of 0.04% - 0.06%. The distribution of carbon and hardness was the same. The CCT curves showed the steel was of good hardenability, and bainite could be obtained within the cooling rate of 0. 015 -0.1 ℃/s. Good uniformity in hardness with a variation of ＋ 1.5 HRC throughout the section was due to the high hardenability of bainite. It was shown that the large mould block could meet the requirement of large scale plastic products industry.