【作者】 魏代斌；

【导师】 杨华；

【作者基本信息】 山东大学 ， 材料加工工程， 2008， 硕士

【摘要】 Cr12冷作模具钢属于高碳高铬类莱氏体钢,这类钢含有较高的C(1.4～2.1%)和大量的Cr(11～13%)。晶界上粗大网状共晶碳化物存在使钢的强度和韧性明显降低,严重缩短了模具使用寿命。因此,破碎沿晶界连续分布的网状碳化物是提高Cr12钢综合性能的有效途径。本文在实验室条件下,采用Al-Fe-Zn-Si复合变质剂对Cr12钢进行复合变质处理,并运用高倍视频显微镜(HSVM)、SEM、XRD等测试手段分析了复合变质处理对Cr12钢的组织及性能的影响。实验结果表明:复合变质处理能够提高碳的活度,生成异质核心,并能增大过冷,降低氧、硫及磷含量,从而使Cr12钢枝晶明显细化,粗大板条状碳化物减少,碳化物网络产生破碎倾向,且碳化物分布均匀性得到提高;复合变质剂加入量为0.8%时,Cr12钢的组织最好。高温热处理表明,普通Cr12钢中共晶碳化物在1080℃以下很难断网和粒化,Al-Fe-Zn-Si复合变质剂的加入提高了Cr12钢中C元素的活度,使其扩散能力增强,促使淬火过程中长条状碳化物熔断及加速其尖角部分的溶解,从而使孤立块状、粒状碳化物数量增加,碳化物形态及分布均得到明显改善。经1080℃加热即可实现铸态下的断网,并弥散分布。性能测试结果表明:复合变质处理后,Cr12钢硬度变化不明显,而韧性有较大提高,使其耐磨性能也明显改善。更多还原

【Abstract】 As a kind of high-carbon high-chromium ledeburite steel, Cr12 steel contains higher content of C(1.4-2.1%) and amount of Cr(11-13%). The network eutectic carbides existing in the casting steel is harmful for the strength and ductility of it which seriously shortens the using time of the steel. So breaking this network carbide is one of methods to improve the performance of this steel.In our work, the Al-Fe-Zn-Si modifier was used to modify the Cr12 steel. The microstructure and performance of it were studied by HSVM, SEM, XRD and so on. The results show that the Al-Fe-Zn-Si modifier can effectively refine the dendrite of the steel, reduce the amount of the coarse plate-like carbide, break the net-like carbide and improve it distribution. It is because that the addition of the modifier improves the activity of the carbon and provides the nuclei. In addition, it can also increase the under cooling and decrease the content of O,S and P. It is found that the microstructure of steel is the best when the addition level of the modifier is 0.8%.The high temperature heat-treatment results show that the common Cr12 steel is difficult to change the network eutectic carbide into dispersed particle-like carbide under the 1080℃treatment. But the net-like eutectic carbide can be easily broke and become the particle-like under the same heat-treatment after being modified by the Al-Fe-Zn-Si. It is considered that the improvement of the activity of C with the addition of the modifier is the reason for this transformation. The diffusion of C is boosted as the activity being improved which accelerates the burn out of the net-like carbide and the solution of the acuate part.The properties experiment results show that the rigidity is not improved very much but the ductility and wear-resistance are obviously improved.更多还原