材料期刊网

在使用 CSP 工艺生产低碳或超低碳钢时，在铸坯中，特别是铸坯宽面的中心经常观察到相当数量的微米级碳覆夹杂物.通过对 CSP 流程不同的钢种铸坯取样，研究了这类夹杂物的结构特点和析出机制.指出碳覆夹杂物呈双层结构，外面包裹一层富碳层、中心为钙铝酸盐或含 CaO 的复合夹杂物.热力学计算结果显示这层富碳物质并非 CaC2.通过对比球墨铸铁中球状石墨的形成条件，指出 CSP 铸坯中存在冷却速度快、S 元素含量低、加钙处理后促球化元素 Ca、Mg 含量相对较高，有大量夹杂物作为形核核心等促进碳覆夹杂物析出的有利条件.C 为易偏析元素，在低碳或超低碳钢铸坯凝固过程中液芯中 C 含量的升高，能够析出球状的碳覆夹杂物.并指出由于碳覆夹杂物的析出，中心钢基体 C 含量降低，碳覆夹杂物析出能够减轻铸坯凝固过程中 C元素的偏析程度.

A kind of carbon bearing inclusion was frequently detected in the slab,in particular in the central part of a slab,of low carbon or ultra-low carbon steel produced by compact strip production (CSP)process.The struc-ture and the formation mechanism of carbon bearing inclusion was studied in different kinds of steel grades pro-duced by CSP process.It finds that the carbon bearing inclusion presents a duplex structure,in which the outer layer composes of graphite rich material and the inner core composes of calcium aluminates or CaO rich multi-com-ponent oxide.Thermodynamic analysis shows that the precipitation of carbon bearing inclusions are not CaC2. In addition,by comparing with spherical graphite formation conditions in spheroidal graphite cast iron,it finds that during the CSP slab solidification,the cooling rate is relative high,the sulfur content is very low,the Ca and Mg content which are beneficial to spherical inclusion formation are relative rich after Ca-treatment and there are a lar-ger number of modified inclusions as nucleation core,thus it is likely to form the carbon rich layer surrounding the inclusion core in the liquid core of a slab with carbon content increase and temperature decrease.Furthermore,it is found that the C content in the central part of a slab decrease due to the precipitation of carbon bearing inclusion, thus it indicate the precipitation of carbon bearing inclusions is beneficial to ease the segregation of carbon in a slab during solidification.