用低Cr合金化提高球铁力学性能的试验及应用

Investigation on Increasing Mechanical Property of Nodular Iron By Low Cr-Alloying and Its Application

用低Cr合金化球墨铸铁浇注了Y型试块和制动器支架铸件,对它们的金相组织和力学性能进行了详细的试验研究。结果显示:(1)Cr在球墨铸铁中有促进珠光体形成的作用,使部分铁素体变成珠光体,因而能有效地提高球墨铸铁的抗拉强度;(2)只要铁液成分、浇注工艺和孕育工艺合理,低Cr合金化不会使球墨铸铁产生渗碳体,更不会影响石墨球圆整度;(3)用低Cr合金化球墨铸铁来替代Cu合金化球墨铸铁生产制动器支架,力学性能达到QT550-5的技术标准,每吨铸件生产成本可节省138元。

Y-type test blocks and brake bracket castings were cast with low Cr-alloyed nodular iron,and their microstructure and mechanical properties were investigated in detail. The results showed：（1）Cr has effect promoting pearlite formation that it could change a part of ferrite into pearlite and therefore it could effectively elevate tensile strength of nodular iron.（2）As long as the chemical composition of the iron melt,pouring process and inoculating process were rational,low-Cr alloying did not cause the nodular iron producing cementite,and much more did not decrease roundness of graphite nodules.（3）By using low Cr-alloying as the substitute for Cu-alloying to produce brake bracket,the mechanical properties reached requirements of QT550-5 grade nodular iron,and saved 138 yuan RMB per ton castings.