304系不锈钢冶金过程硬质夹杂物形成机理分析

doi:10.13228/j.boyuan.issn0449-749x.20220547

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Abstract 304 stainless steel is widely used due to the excellent corrosion resistance and processing performance, while the hard inclusions in the steel have a great influence on the surface quality of the cold plate. The variation law of the size and quantity of various inclusions in the smelting process of 304 stainless steel was investigated in order to clarify the formation mechanism of hard inclusions in 304 stainless steel, through sampling in industrial production and using automatic scanning electron microscope ASPEX and statistical methods. The results show that the total oxygen content of steel casting decreases continuously with the bottom blowing and stirring, and the mass percent of T[O] decreases from 0.008 8% to 0.002 5% in the process from AOD steel production to casting. The main types inclusions at the end of AOD and LF are silicate, and contain a small amount of compound silicate and a small amount of magnesium aluminum spinel inclusions. From the end of LF to slab, The composition of the inclusions has undergone a partial transformation, the content of SiO₂ in the inclusions decreases, and the content of Al₂O₃ increases. From AOD to tundish, the hard inclusions of magnesium-aluminum spinel and Al₂O₃ in molten steel are very few, while the proportion increases significantly from tundish to slab, the ratio of magnesium-aluminum spinel increases by 28%, and the percentage of compound silicate inclusions in the deoxidation products of steel-slag reaction also increases significantly. However, the proportion of SiO₂-Al₂O₃in the deoxidized product of deoxidizer and the deoxidized product of steel-slag reaction decreased significantly. The largest proportions are composite silicate, magnesium-aluminum spinel and SiO₂ inclusions among the types of inclusions with a size of ≥10 μm in the slab. The phase transition behavior of CaO-SiO₂-Al₂O₃-MgO melts with different compositions was calculated by thermodynamic software. The melt will precipitate a high melting point phase of MgO-Al₂O₃when the temperature decreases, and the precipitation temperature of magnesia-aluminum spinel increased significantly and the magnesia-aluminum spinel phase was more easily precipitated with increase of the content of MgO and Al₂O₃ in the melt. The hard inclusions are mainly formed by the deoxidation products silicaluminate and composite silicate during the solidification process of continuous casting with the decreasing of temperature.

Key words： 304 stainless steel hard inclusions magnesium aluminum spinel surface quality deoxidation products

Received: 26 August 2022

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	ZHAI Jun
	WANG Wei
	LANG Wei-yun

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ZHAI Jun,WANG Wei,LANG Wei-yun. Analysis of formation mechanism of hard inclusions during metallurgical process of 304 stainless steel[J]. Iron and Steel, 2023, 58(4): 39-47.

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http://www.chinamet.cn/Jweb_gt/EN/10.13228/j.boyuan.issn0449-749x.20220547 OR http://www.chinamet.cn/Jweb_gt/EN/Y2023/V58/I4/39

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