Method of making a hardened sheet metal article

Abstract

In a method of making a hardened sheet metal article, a blank is formed with at least one through-passage with a projecting collar. Thereafter, the blank is heated and hot-formed in a press mold to a sheet metal article. Still within the press mold, the sheet metal article is hardened. The shaping of the blank in the press mold is accompanied by a calibration of the through-passage to final shape.

What is claimed is:  
     
         1 . A method of making a hardened sheet metal article; comprising the steps of: 
 forming in a blank at least one through-passage with a projecting collar;    hot-forming and hardening the blank in a press mold to a sheet metal article; and    calibrating the through-passage to a final shape in the press mold.    
     
     
         2 . The method of  claim 1 , and further comprising the step of pre-forming the blank before the forming step.  
     
     
         3 . The method of  claim 2 , wherein the blank is pre-made with at least one hole.  
     
     
         4 . The method of  claim 1 , wherein the through-passage is formed with a circumferential collar.  
     
     
         5 . The method of  claim 1 , wherein the through-passage is formed with a discontinuous collar.  
     
     
         6 . The method of  claim 1 , wherein the blank is made of steel having a following composition, by weight percent: 0.19 to 0.25% carbon (C), 0.15 to 0.50% silicon (Si), 1.10 to 1.40% manganese (Mn), 0.020 to 0.050% titanium (Ti), 0.002 to 0.005% boron (B), 0.02 to 0.06% aluminum (Al), a maximum of 0.025% phosphorus (P), a maximum of 0.015% sulfur (S), a maximum of 0.35% chromium (Cr), and a maximum of 0.35% molybdenum (Mo), and the balance being iron (Fe) and other incidental impurities.  
     
     
         7 . A method of making a hardened sheet metal article; comprising the steps of: 
 forming in a blank at least one through-passage with a projecting collar;    heating the blank;    hot-forming the blank in a press mold to a sheet metal article;    hardening the sheet metal article in the press mold; and    calibrating the through-passage to a final shape in the press mold.