精炼渣对双相钢化学成分和非金属夹杂物的影响

Effect of refining slag on chemical composition and non-metallic inclusions of dual phase steel

为了明晰精炼渣与双相钢之间反应对渣、钢成分及非金属夹杂物的影响,基于双相钢的精炼生产,用MgO质坩埚进行了50%CaO-45%Al_(2)O_(3)-5%MgO顶渣分别与A、B两种成分双相钢反应的渣-钢平衡试验。结果表明,未加渣时钢中主要夹杂物为MgO-Al_(2)O_(3)类,部分含少量MnS,呈黑色不规则块状,绝大多数尺寸在4μm以下,A、B钢中夹杂物数量密度分别为9.19个/mm^(2)和6.19个/mm^(2)。渣-钢反应后,A、B钢中Al含量显著降低,Ti含量降低;渣中CaO含量降低,MgO含量升高;夹杂物中MnS消失,MgO组分增加,夹杂物数量密度显著降低,尺寸变化不大。所用顶渣可以降低钢中S含量、TO含量和夹杂物数量密度,提高钢的洁净度。试验结果和热力学分析表明,双相钢的Al含量较高,其对渣-钢反应前后钢、渣的化学成分和夹杂物有较大影响。结合MgO/MgO-Al_(2)O_(3)/Al_(2)O_(3)的相稳定图,解释了在本试验条件下渣-钢反应前后钢中主要夹杂物类型为MgO-Al_(2)O_(3)的原因。研究结果可为优化双相钢的成分和洁净度控制提供理论指导。

In order to clarify the effect of reaction between refining slag and dual phase steel on chemical compositions of slag and steel as well as non-metallic inclusions,slag-steel equilibrium experiments were carried out between 50%CaO-45%Al_(2)O_(3)-5%MgO top slag and two dual phase steels(named as A and B)using MgO crucible,which was based on industrial refining of dual phase steel.The results show that the main inclusions before slag-steel reaction are MgO-Al_(2)O_(3) type,and some containing small amount of MnS.Most inclusions are black irregular lumps,with size below 4μm.The number density of inclusions in steel A and B is 9.19/mm^(2) and 6.19/mm^(2),respectively.After slag-steel reaction,Al content of both steel A and B is reduced significantly and Ti content is reduced.The content of CaO in slag decreases and MgO increases.The component of MnS in inclusions disappears and MgO content increases.The number density of inclusions decreases greatly while the size changes little.After refining by the top slag used in present study,the S content and TO content of steel as well as the number density of inclusions are reduced,and the cleanliness of steel is improved.Both experimental results and thermodynamical analysis indicate that the high content of Al in dual phase steel has large effect on chemical composition of steel and slag as well as inclusions both before and after the slag-steel reaction.Combined with the phase stability diagram of MgO/MgO-Al_(2)O_(3)/Al_(2)O_(3),the reason for main inclusion type of MgO-Al_(2)O_(3) in steel before and after slag-steel reaction under present experimental conditions is explained.The research results can provide theoretical guidance for optimizing the composition and cleanliness control of dual phase steel.