The effect of 0. 000 5% ~Q. 001 2% Mg on inclusion formation and solidification structure of ferrite stainless steel 430 (/% : 0.04C

0.25-0.32Si

0.28-0.38Mn

16.5-16.9Cr) melting by a 60 kg vacuum induction furnace has been tested and studied. Results show that with adding magnesium alloy in liquid steel 430 the size of MgO compound inclusions in steel decreases while their number and density are increase； adding magnesium alloy is available io improve the solidification structure of steel 430 and the lower the casting temperature the more obvious the improved effect

for instance with casting at 1 580 ℃ the equiaxed zone ratio of magnesium-treated steel increases to 88.5% from 30.8% of non-treated normal steel while the correspondent equiaxed grain size decreases to 945.3 μm from 1741.6 μm. The planar dis-registry between inclusions containing MgO and δ phase is minor

it is an effective heterogeneous nucleation agent to promote the formation of equiaxed crystal and inhibit the growth of columnar crystal

finally fine the solidification structure of casting steel 430.