Reasons Analysis on Cracks of ZG45 Cast Steel Axle Sleeves

Cracks were found on ZG45 cast steel axle sleeves surface during manufacturing, and cracks formation causes were analyzed by means of chemical compositions analysis, macro examination, metallographic examination and scanning electron microscope analysis, etc. The results show that as a result of inappropriate smelting and casting procedure, the content of silicon and manganese in the steel was below the standard requirement, which led to coarse grains forming in the steel and low-melting-pointed non-metallic inclusions gathering along the grain boundaries at the last solidified areas. Therefore, the grain boundaries became the weak positions and cracks formed and extended along the grain boundaries under action of the following thermal stress.