Abstract: In view of the low qualified flaw detection rate caused by X80M inclusions，the steelmaking process was investigated and found that the effective calcium content in the silicon-calcium wires used for calcium treatment was low. By changing the types of silicon-calcium wires and optimizing the process of calcium treatment，such as controlling w(S) below 25×10-6，increasing the feeding speed of silicon-calcium wires from 1.8 m/s to 2.5 m/s，reducing the bottom blowing flow rate from 180~200 L/min to 120~150 L/min，w(Ca) in molten steel was controlled at (13~25)×10-6，Al2O3 inclusions couuld be modified into calcium aluminate inclusions in the low melting point zone of CaO-Al2O3-CaS ternary Phase Diagram，and their sizes were all below 50μm. The qualification rate of flaw detection for X80M steel increased from 94.60% to 99.69% on average，which ensures the quality of products.

Key words: X80M, flaw detection, inclusion, calcium treatment