激冷铸铁凸轮轴铸造工艺及断裂分析

某批次激冷铸铁HT300CrMoCu汽车凸轮轴装配时,近1/4的凸轮轴在中间轴颈处发生断裂,采用宏观、微观对凸轮轴进行了理化检测,并对凸轮轴的铸造工艺进行分析.结果表明,凸轮轴致裂的原因首先是由于Cr含量超标,强烈阻碍铸铁的石墨化,形成合金碳化物；再就是冬天气温下降快,浇注温度低,冷铁未作及时调整,引起凸轮部分全白口,轴颈也出现了白口组织.通过控制合金成分、浇注温度、孕育处理、过热温度和保温时间、冷铁的尺寸等因素,来控制石墨的形成,改善和提高凸轮轴的性能.

Fracture Analysis of Chilled Nodular Iron Camshafts

A batch of chilled nodular iron camshafts were broken during assembling.The reasons of broken were analyzed on the cracking position,fracture observation by SEM and microstructure inspection.The results show that Cr exceed content and low pouring temperature created large amount of carbide,even whole cam became white iron.They also weaken the mechanical properties of camshafts production,causing a batch of camshafts broke.Some technical measures were taken,on the control of chemical and pouring temperature ...