In the No.3 hot rolling mill, Chiba Works of JFE Steel, the endless rolling process, in which roughly rolled bars are joined and rolled continuously in the finishing mill, has been put into operation for mild steels. On the other hand, this process is not applied to high-tensile-strength steels, because alloy elements contained in the high-tensile-strength steels, such as silicon and manganese, form oxide layers at the joining interface, disrupting the joining process. In laboratory joining tests, by heating until the joining surface melted, the oxides layer was discharged from the interface and steels that form oxide with a low melting temperature were successfully joined. FEM flow analysis revealed that the viscosity of oxide is the most important parameter for discharging. The low melting temperature of oxide leads to the low viscosity, resulting in the discharge of the oxide layer.

The appearance of an automobile is one of the appealing points to customers. Character lines in outer panels such as hood and door panels play an important role in making automobiles attractive, and a sharp character line with a ridge of small curvature radius is much more preferred to a blunt character line. However, a skid line, a type of cosmetic defect, is apt to be generated along the character line during the press forming of a sharp character line. The authors revealed the mechanism of skid line generation by finite element analysis, and reported the results in a previous paper. In this study, a method is developed to continuously measure the panel shape during press forming. The results of the shape measurement suggest that a convex shape formed on the die ridge should move to a flat area of the die that a wavy shape should generate there immediately before the convex shape is flattened at the bottom dead center and that the wavy shape should grow to a skid line through springback.

The effects of process parameters on room-temperature (RT) deep drawability were investigated for AZ31B magnesium alloy sheets, in which the formation of basal texture was suppressed by high-temperature rolling. When the blank holder force was set to the minimum value to prevent wrinkling, high RT drawability was obtained. In particular, a significantly high limiting drawing ratio (LDR) of 1.83 was obtained by the optimization of the process parameters of the servo-press machine. At higher punch speeds, the drawability tended to be deteriorated; however, a high LDR of 1.72 was obtained even at a high punch speed of 50mm/s by the optimization of the process parameters of the servo-press machine. Furthermore, when the punch speed in the initial stage of deep drawing was reduced, it was possible to perform deep drawing without fracture even if the punch speed in the later stages was increased. The results of the study of the effect of lubricants indicated that relatively high RT drawability was obtained when molybdenum disulfide was utilized. It was also suggested to be important to select a lubricant that reduces punch load and does not delaminate during deep drawing.