Application Practice of New Mould to Improve Black Line Defects in Wide and Thick Plates

ZHOU Ping; ZHAO Lifeng; DONG Hui; HUANG Shaowen; LI Xiangqian

Abstract：The black line defect at the edge of wide and thick plates,also known as"edge straight cracking",is closely related to factors such as the state of the casting slab corner and rolling process.It usually appears in different forms such as wider single strips or thinner multiple"wire drawing"strips.It is a common problem faced by medium and thick plate production enterprises in the industry.Constructing a finite element calculation model for thermal/mechanical coupling in the rolling process,studying the temperature field and metal flow deformation law of casting slabs with different narrow surface slab structures during the rolling process.By reserving a widening amount on the narrow surface of the casting billet,the widening amount in the middle of the narrow surface during the rolling process is equivalent to the widening amount on the upper and lower surfaces in the last pass,in order to achieve the goal of controlling the distribution range of black lines.After on-site implementation verification,the new mould has achieved significant results in improving the black line defects of wide and thick plates,and the distance between the black line and the side edge of the steel plate can be reduced by 10 mm.