Method for forming high tensile strength metal sheet

Abstract

A method for forming a high tensile strength metal sheet (HTSMS), which is performed in a power press machine composed of a die, a punch and a blank holder, is disclosed. The HTSMS is placed between the die and punch with blank holder. A step portion appears at both an outer side of the punch and a pressing portion of the blank holder. The step portion is corresponding to a predetermined bent portion of the HTSMS. A step will be formed at an edge of the HTSMS by progressively pressing of the step portion to avoid recoil of the HTSMS after forming process.

1 . A method for forming a high tensile strength metal sheet, which is performed in a power press machine composed of a die, a punch and a blank holder, wherein a step portion appears at both an outer side of the punch and a pressing portion of the blank holder, the method comprising the steps of:
 a) setting the blank holder at a predetermined position which is coplanar with the punch, and the high tensile strength metal sheet (HTSMS) being placed on a plane formed by the punch and the blank holder;   b) driving the punch to ascend to a first position to make the HTSMS roughly deformed;   c) driving the punch to ascend to a second position to make the HTSMS sequentially deformed; and   d) driving the punch to ascend to a third position to make the HTSMS finally deformed with a step formed by the step portion.   
   
   
       2 . The method for forming a high tensile strength metal sheet as  claim 1 , wherein the steps b), c) and d) are continuously performed.