Bubbles Separation Behaviour of Cr12N Steel during High Pressure Solidification Process

Considering the some bubbles separation during smelting Cr12N ferritic stainless steel,the ingot had been examined by an optical microscope,and the optical image had been analysed by using a microimage analysis & process software. It is found out that when the melting pressure is 0.6 MPa and solidification pressure is increased from 1.0 MPa to 1.6 MPa,the average number of bubbles per square millimeter decreases from 46.37 to 9.46,among them the number of bubble with diameter greater than 20 μm reduces down to 17.4% of origin number,while the number of bubble with diameter less than 5 μm increases by 37.7%. With increasing solidification pressure,the bubble area percentage becomes smaller. When the ingot is produced at a combined conditions of 0.3 MPa melting pressure and 1.6 MPa solidification pressure,the average bubble area percentage on lower surface is 23.9% of that on the upper surface,and average bubble area percentage at the edge position is 25.9% of that at the center position.