汽车车轴管调质开裂原因分析及探讨

某批次的汽车车轴管在调质后存在开裂现象,分析该开裂材料的性能、非金属夹杂物、金相组织和扫描电镜形貌。分析认为:汽车车轴管开裂的原因是由于材料局部(Fe,Mn)S复合夹杂物聚集,在后续轧制过程中沿轧制方向延伸,密集夹杂物破坏了组织的连续性,恶化了组织的横向性能,导致材料在横向变形最大的外弯角处开裂,并在调质过程中的组织应力作用下发生扩展。建议在炼钢过程中降低钢中硫含量,改善硫化物的尺寸、形态和分布,杜绝卷渣,减少材料中夹杂数量和局部聚集。

Analysis and Discussion of Reason for Cracking of Automobile Axle Pipe as Developed during Quenching&Tempering Process

Cracking is found with a certain batch of automobile axle pipes as quenched and tempered.Accordingly the cracking material is overall analyzed in terms of mechanical property,non-metallic inclusion,metallographic structure and SEM morphology,etc.The test results reveal that the reason for the cracking is that the local(Fe,Mn)S composite inclusions aggregate,and extend along the rolling direction in the subsequent rolling process;the dense inclusions destroy the continuity of the structure,and deteriorate the transverse performance of the structure,leading to the cracking of the material at the outer comer with the largest transverse deformation,and the expansion under the effect by the structural stress during the quenching-tempering process.Accordingly it is suggested to reduce S content in the steel during the melting process,and improve the size,shape and distribution of the sulfide,and eliminate the entrapped slag,so as to reduce the quantity and local aggregation of the inclusions in the steel.