CSP生产低碳钢的组织演变和析出物研究

Study on precipitation and microstructure evolution of low carbon steel produced by compact strip production

为了阐明EAF-LF-CSP工艺生产的低碳钢组织细化机理,在薄板坯和不同道次变形后的同一轧件上取样,利用金相、SEM、TEM、XEDS等技术研究了连轧过程中显微组织演变和钢中第二相析出物.结果表明:与普通连铸板坯相比薄板坯的凝固组织更加细小;随轧制道次增加,薄板坯表面和心部的组织差异逐渐减小,轧后室温组织细化;CSP生产的低碳钢中存在大量纳米尺寸的氧化物和硫化物,起到细化晶粒的作用.CSP生产中采用快速冷却和凝固工艺、单道次大压下连轧工艺和层流冷却工艺,是成品组织细化的主要原因.

An investigation has been carried out on the CSP low carbon steel and different rolling pass specimens of the same thin slab by metalloscope, SEM, TEM and XEDS methods, in order to study microstructural evolution and dispersive precipitation. It has been demonstrated that the solidification structure of thin slab is finer than that of conventional thick slab, the average grain size for the central area of the samples from 1st to 6th pass is reduced and microstructure difference between surface and central area of slab will be gradually decreased during rolling. Remarkable grain refinement effects can be attained by a large number of oxide and sulfide precipitates, which have been observed in low carbon steel. The rapid solidification rate during continuous casting, the great reduction of single rolling pass during continuous rolling and the laminar cooling system can be considered as the main reasons for grain refinement.