Importance

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Abstract

Deformation by camber recovery etc. due to non-uniform residual stress is suppressed, and occurrence of crack and burr is suppressed by improving press forming property of a roof side T-shaped portion, so that a reinforcing member having a predetermined shape accuracy is manufactured easily and inexpensively by pressing. A reinforcing member (12) is constructed by three members, i.e. an upper member (20), a lower member (22) and a central member (24). A tensile strength of the upper member (20) is selected lower than that of the central member (24), and is higher than that of the lower member (22). In comparison to a case where the upper member (20) and the central member (24) are constructed integrally by an ultra-high tensile steel plate, fluctuation of internally generated residual stress is made small. Shape accuracy is thereby improved by the reduced deforming amount due to camber recovery etc., thus press forming being facilitated. Also, a roof side T-shaped portion constructed by the upper member (20) is improved in the drawing property, and the door frame corner portions (30) and (32) are improved in the outer trimming property. Thus, the shape accuracy is improved, and yield and productivity is increased by suppression of crack generation.

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First Claim