1. State Key Laboratory of Metal Matrix Composite, Shanghai Jiaotong University, Shanghai 200240, China 2. Research Institute, Baoshan Iron and Steel Co. , Ltd. , Shanghai 201900, China
The composition of MgO-Al2O3-SiO2 complex inclusion, which formed by adding different quantity of Ni-Mg alloy to steel in MgO crucible induction melting furnace, had a huge effect on the solidification structure of 430 stainless steel. The experimental results show that with the increase of the content of magnesium in steel ingot, the ECR (equiaxed crystal ratio) can be increased at first and decreased subsequently, while the equiaxed crystal size and the width of the columnar should be first decreased then increased, and there exist an optimal range of magnesium content, (5-13)×10-6, in which the equiaxial crystal ingot is more than 70%. By connecting inclusion observation with thermodynamic calculation, when Mg content is less than 13×10-6, with the increase of [Mg], there will precipitate more MgO·Al2O3 phase around MgO-Al2O3-SiO2 complex inclusions; besides, when [Mg] is more than 13×10-6, there is 2MgO·SiO2 phase around the inclusions. The planar disregistry calculation shows that the planar disregistry between the MgO·Al2O3 and δ-Fe is 1. 2%, while the 2MgO·SiO2 vs δ-Fe is 13%. It can be concluded that the MgO·Al2O3 around the MgO-Al2O3-SiO2 complex inclusion could promote the formation of equiaxed grains and refine the solidification structure of 430 stainless steel while the 2MgO·SiO2 are unable to promote the nucleation, explaining the trend of the ECR and grain size of the ingot along with Mg content.
TIAN Yue-mei,,CHEN Zhao-ping,XU Ying-tie,GONG Mao-tao,,SHU Da.
Effect of MgO-Al2O3-SiO2 Complex Inclusion on the Solidification Structure of 430 Stainless Steel[J]. Journal of Iron and Steel Research, 2014, 26(6): 61-66
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