1Cr13钢闸板毛坯锻件开裂原因分析

Damper Slug Cracks Analysis of 1Cr13 Steel

从断口、金相和显微硬度等方面1Cr13钢闸板毛坯锻件在加工中开裂形成贯穿性裂纹,对此进行检验和分析。结果表明,裂纹源区断口近表面一定深度内具有沿晶断裂特征,而裂纹扩展区断口则是韧窝特征;金相分析表明源区组织是保留马氏体位向的回火索氏体+粒状碳化物,基体组织则是铁素体+颗粒状珠光体。分析认为,闸板在气刨加工去除表层金属的反复受热和冷却过程中表层组织发生了淬火和回火转变,由于表层和次表层的马氏体相变存在异步现象,最终在组织应力和热应力作用下导致表层萌生裂纹源,并在热应力和组织应力的共同作用下扩展进而形成贯穿性开裂。

Penetrating cracks in damper slug were found during machining.The cracking cause was analyzed by metallographic,fracture and micro hardness.The intergranular fracture formation was observed in cracks original area at some depth near surface,but dimples observed in fracture extending area by means of SEM.The metallographic examination shows that,the microstructure is temper sorbite and granular cementite with keeping martensite orientation,and the matrix is ferrite and granular pearlite.Base on above,it is believed that quenching and temper was taken place during heating to high temperature to remove melting metal,and finally the microstructure was transformed from original ferrite to temper sorbite.In which these changes occurred in different time step in surface and subsurface,the stress resulted from microstructure transformation and heat transitions led in pregnant cracks and finally formed a penetrating crack.