A plan view pattern control method for plate rolling called the Mizushima Automatic Plan View Pattern Control System (MAS) or Dog Bone Rolling (DBR) was developed. In this method, the slab is given a non-uniform thickness pro le in the width direction to obtain non-uniform elongation at following at rolling. In order to make the plate more rectangular under various rolling conditions, prediction of elongation at following at rolling is necessary. In this research, the in uence of the width of the dog-bone (overly thick part at the slab width edge) on the sh-tail length (over-elongation at the slab end) is investigated. The sh-tail length increases as the dog-bone width increases and the dog-bone width ratio decreases. These phenomena are related to the following behavior of the restriction of excessive elongation in the dog-bone because of existence of unrolled volume before roll gap entrance: As the dog-bone width increases and the dog-bone width ratio decreases, the working length of restricting stress increases. Hence, restricting stress is released earlier and the rolling length for sh-tail formation increases. As a result, the sh-tail length increases. Therefore, in prediction of the plan view pattern, not only the dog-bone thickness, but also the dog-bone width and dog-bone width ratio should be considered. [ : rolling, plate rolling, deformation behavior, model simulation, FEM, plan view pattern control, dog-bone width, crop length, mizushima automatic plan view pattern control system (MAS), dog bone rolling (DBR) Keywords

Synopsis : In rolling of ultra thin stainless steel foil, there are two rolling limits. One is owing to elastic deformation of work rolls, and the other is owing to edge crack of rolled foil. In this paper, fundamental investigation was conducted about the basic characteristic of the rolling limits of ultra thin stainless steel foil. The influence of several rolling conditions on minimum thickness and behavior of edge crack were investigated experimentally. This paper provides new formula to predict the minimum thickness in ultra thin foil rolling. The relation between the edge crack depth and the rolling conditions is also discussed. The edge crack expands with rolling passes. However, the degree of the edge crack at same foil thickness shows different behavior depending on rolling conditions. The depth of edge crack rolled by small diameter work rolls is shallower than that of same thickness foil rolled by large diameter work rolls. Moreover, when Young's modulus of work rolls is high, it turns out that the edge crack is small. Based on detailed observation of the foil edge phenomenon, good correlation between edge crack depth and foil thickness at extreme edge portion is found. From those experimental results, it is suggested that the rolling conditions advantageous to control edge drop are effective to suppress edge crack expansion.

For the purpose of edge crack control in hot rolling of 36%Ni-Fe alloys, a high temperature tensile test and laboratory-scale hot rolling experiment were carried out. Intergranular oxidation has been considered to be one of the major factors in edge cracking. Edge cracks which initiate from intergranular oxidation grow to the inner side along coarse grain boundaries as the thickness reduction ratio increases. The depth of intergranular oxidation increases at higher reheating temperatures. However, recrystallization occurs at the crack tip, and this has the effect of suppressing crack growth. This suggests that promoting recrystallization during hot rolling by increasing the reheating temperature, rather than inhibition of intergranular oxidation as such, is effective for suppressing edge cracking.

A plan view pattern control method for use in plate rolling called Mizushima Automatic Plan View Pattern Control System (MAS) or Dog Bone Rolling (DBR) was developed. In this method, slab is given a nonuniform thickness profile in the width direction to obtain nonuniform elongation. In order to make the plate more rectangular under various rolling conditions, the prediction of elongation is necessary. In this research, the influence of the width of the dog-bone (overly thick part at the slab width edge) on the fish-tail length (over-elongation at the slab end) is investigated. The fish-tail length increases as the dog-bone width increases and the dog-bone width ratio decreases. These phenomena are related to the following behavior of the restriction of excessive elongation at the dog-bone. As the dog-bone width increases and the dog-bone width ratio decreases, the working length of restricting stress increases. Hence restricting stress is released earlier and the rolling length of fish-tail formation increases. As a result, the fish-tail length increases. Therefore, in the prediction of the plan view pattern, not only the dog-bone thickness, but also the dog-bone width should be considered.

Synopsis :For the purpose of edge crack control in hot rolling of 36%Ni-Fe alloys, a high temperature tensile test and laboratory-scale hot rolling experiment were carried out. Intergranular oxidation has been considered to be one of the major factors in edge cracking. Edge cracks which initiate from intergranular oxidation grow to the inner side along coarse grain boundaries as the thickness reduction ratio increases. The depth of intergranular oxidation increases at higher reheating temperatures. However, recrystallization occurs at the crack tip, and this has the effect of suppressing crack growth. This suggests that promoting recrystallization during hot rolling by increasing the reheating temperature, rather than inhibition of intergranular oxidation as such, is effective for suppressing edge cracking.