镁处理对430铁素体不锈钢夹杂物形成和凝固组织的影响

试验研究了0.000 5%～0.001 2%Mg对60 kg真空感应炉熔炼的430铁素体不锈钢(/%:0.04C、0.25～0.32Si、0.28～0.38Mn、16.5～16.9Cr)夹杂物形成和凝固组织的影响。结果表明,430钢液中添加镁合金后,钢中形成平均粒径更小,数量密度更大的含MgO复合夹杂物;镁合金的加入可以改善430钢的凝固组织,且浇铸温度越低,改善效果越明显,在1 580℃浇铸时,等轴晶率由常规钢的30.8%提高至镁处理钢的88.5%,相应等轴晶尺寸由1 741.6μm降至945.3μm。含MgO夹杂物与δ相二维错配度极小,可作为430钢有效异质形核剂,促进等轴晶的形成,抑制柱状晶的生长,细化凝固组织。

Effect of Magnesium Treatment on Inclusion Formation and Solidification Structure Ferrite Stainless Steel 430

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.