大截面非调质预硬塑料模具钢FT600与SDP1相变特性的对比研究

Comparative Study of Phase Transition Properties of FT600 and SDP1 Steels for Large Cross-section Non-quenched and Tempered Prehardening Plastic Mould

以FT600及SDP1两种大截面非调质预硬化塑料模具钢为研究对象,采用热膨胀仪、扫描电镜和XRD等手段分析讨论了合金成分、冷却速度等对两种试验钢相变行为的影响。结果表明,在FT600成分基础上,通过降Si增Mn的合金优化设计,SDP1钢的贝氏体临界冷速可降低至0. 015℃/s,在试验冷速范围内残留奥氏体的体积分数均低于5%,因此空冷就可获得均匀的组织,其硬度均匀性也优于FT600钢。通过充分发挥Mn和Si等廉价合金元素的作用,SDP1钢更适合于制造更大截面尺寸的非调质预硬化塑料模具。

Two large cross-section non-quenched and tempered prehardening plastic mould steels,named FT600 and SDP1,were studied.The effects of alloy compositions and cooling rate on the phase transformation of the two steels were analyzed and discussed by using the thermal expansion instrument,scanning electron microscope(SEM)and X-ray diffraction(XRD).The results showed that based on the composition of FT600 steel,the optimized alloy design of decreasing Si and increasing Mn was carried out,so the critical cooling rate for bainite transformation of SDP1 steel was reduced to 0.015℃/s and the volume fraction of retained austenite was less than 5%for all the cooling rates.This implied that the uniform microstructure can be obtained by air cooling,and its hardness fluctuation was smaller than that of FT600 steel.It turned out that the SDP1 steel was more suitable to the production of non-quenched and tempered prehardening plastic dies with larger cross-section size by full playing a role of the cheap alloying elements such as Mn and Si.