There're many problems in quality of steel # 45 produced by LD-LF-CC in Laigang,such as surface pores and upset cracks.

Through hydrogen determination online during manufacturing process,analyzing inclusions element in 20CrMnTiH by SEM and EDAX analysis,and observing defects on the surface of casting blanks,mechanism of upset cracks of 20CrMnTiH smelted by converter in Laiwu steel is found.

A1N in Steel and its Affect on Forging Crack;

Through experiment found that the producing cause of forging cracks was oxide inclusions and composition segregation of Si、Mn element in original steel and non-suitable heating time for forging steel.

This paper describes how the conclusion has been drawn from the metallurgical analysis that cracking in the bracket of hydraulic prop stand of 160t railway crane is not the quenching cracks caused by inapt quenching but rather micro forge cracks caused by non-metallic inclusion in forging blank before the bracket being heat-treated.

By analyzing of the quality of material and heat treatment in detail through chemical and metallographic examination,the whole processing of causing crack and decarbonization was discussed and demonstrated and simulation test was made,the results proved that crack of bearing outer ring was wet crack after forging.