Method of producing press-hardened structural parts

Abstract

In a method, a blank of unhardened steel sheet is subjected in a press tool to a hot forming and press-hardening process to produce a structural part. After press-hardening, at least one linear zone of the structural part is heat treated in order to increase ductility and reduce strength in the linear zone in relation to adjacent regions of the structural part. After heat treatment, a bending or cutting operation is carried out on the structural part along the linear zone.

What is claimed is: 
     
         1 . A method, comprising the steps of:
 subjecting a blank of unhardened steel sheet in a press tool to a hot forming and press-hardening process to produce a structural part;   heat treating at least one linear zone of the structural part; and   subjecting the structural part after the heat treating step to a bending or cutting operation along the linear zone.   
     
     
         2 . The method of  claim 1 , wherein the structural part has a tensile strength of at least 700 MPa after undergoing press-hardening. 
     
     
         3 . The method of  claim 1 , wherein the structural part has a ductility which is increased in the linear zone in relation to a region adjacent to the linear zone. 
     
     
         4 . The method of  claim 3 , wherein the ductility in the linear zone is increased by at least 5% in relation to the adjacent region of the structural part. 
     
     
         5 . The method of  claim 1 , wherein the heat treating step is executed at a temperature between 100° C. and 700° C. over a time period of less than or equal to 30 seconds. 
     
     
         6 . The method of  claim 1 , wherein the heat treating step is executed inductively. 
     
     
         7 . The method of  claim 1 , wherein the heat treating step is executed through infrared radiation. 
     
     
         8 . The method of  claim 1 , wherein the heat treating step is executed while the structural part is clamped in a holding device. 
     
     
         9 . The method of  claim 8 , wherein the structural part is clamped in the holding device until the structural part has cooled down to a temperature level that does not cause distortion. 
     
     
         10 . The method of  claim 8 , wherein at least one area of the structural part is maintained in the holding device under elastic tension. 
     
     
         11 . The method of  claim 8 , wherein the structural part is secured in the holding device in such a way as geometrical changes of the structural part are compensated during the heat treating step so that the structural part has a desired geometry after undergoing heat treatment and/or removal from the holding device. 
     
     
         12 . The method of  claim 1 , further comprising the step of coating a surface of the structural part. 
     
     
         13 . The method of  claim 1 , further comprising the step of coating the blank before undergoing heat treatment and press-hardening. 
     
     
         14 . The method of  claim 1 , wherein the structural part is used for a body or component of a motor vehicle.