变质处理对铅黄铜铸态组织及凝固方式的影响

Effects of Modification on As-cast Microstructure and Properties as well as Solidification Mode of Lead Brass in Permanent Mold

研究了变质处理对金属型铸造铅黄铜铸态组织和力学性能的影响,用倾出法试验验证了变质处理对铸造铅黄铜凝固方式的影响和壳杯试样凝固组织的变化。结果表明,未变质处理壳杯试样凝固组织为粗大的α和β枝晶,壳杯内表面凝固结晶面粗糙,变质处理能够细化铸态组织和提高金属型铸造铅黄铜的力学性能,凝固方式由逐层凝固变为逐层+体积凝固方式,变质处理后壳杯试样的凝固组织为表面细等轴晶+窄枝晶区+等轴晶,壳杯内表面结晶面由粗糙变为光滑,组织从枝状晶变为细小的等轴状晶。

Effects of modification on as-cast microstructure and mechanical properties of lead brass in permanent mold were investigated,and the solidification mode and solidification structure transformation of slush cup were observed by pouring testing.The results reveal that solidification structure of un-modified slush cup with coarse inner face consists of coarse α and β dendrite,and solidification mode is evolved from sequential solidification into mixing solidification of sequential solidification with mushy solidification,while that of modified one in which the inner face is transformed from coarse into smooth is composed of fine equiaxed grain in surface and narrow dendrite zone as well as equiaxed grain in inner.Microstructural observation shows that the microstructure is converted from dendrite into fine equiaxed grain.