Method of making a sheet-metal part

Abstract

The invention relates to a method for producing components from sheet metal, wherein at least one patch sheet (2) is placed on a base sheet (1) to form a material doubling and is positionally securely fixed, the component unit thus formed, comprising base sheet (1) and patch sheet (2), is heated to a temperature suitable for hot forming and is then hot-formed to form the component and, preferably subsequently or simultaneously, is subjected to partial or total cooling or quenching for the purpose of a specific structure conversion, wherein, for the purpose of improved corrosion protection, the base of sheet (1) in the contact region of the patch sheet (2), or the patch sheet (2) on the side thereof facing the base sheet (1), or both base sheet (1) and patch sheet (2) in the corresponding area are coated with an anti-corrosion coating (6) that is resistant to the temperatures occurring during the hot forming, before the patch sheet (2) is placed on the base sheet (1).

1 . A method of making a sheet-metal part from sheet steel, the method comprising the steps of:
 coating at least one face of the base sheet and/or at least one face of the patch sheet with an anticorrosion paint able to withstand predetermined temperatures at which the steel of the sheets is hot workable;   fixing the coated patch sheet on the coated base sheet with the faces juxtaposed at a joint to form a subassembly of double thickness;   heating the subassembly of the base sheet and the patch sheet to the predetermined temperatures of hot working;   hot-working the heated subassembly to form the part; and   cooling or quenching the part for targeted structural transformation, whereby the coating protects the joint and thereby prevents penetration of corrosion-promoting substances into the joint of the part.   
     
     
         2 . The method according to  claim 1 , wherein one of the following paints is used as the corrosion paint:
 silicon carbide with a suitable solvent,   polysiloxanes or silanes with a suitable solvent.   
     
     
         3 . The method according to  claim 2 , wherein
 xylenes,   benzenes,   alcohols, or   tetrahydrofuran   
       is used as solvent in the anticorrosion paint. 
     
     
         4 . The method according to any one of  claim 1 , wherein the base sheet and the patch sheet are of 22MnB5 grade steel. 
     
     
         5 . The method according to any  claim 1 , wherein galvanized steel sheet or sheet steel with a zinc-nickel coating or with an aluminum-silicon coating is used as a starting material for the base sheet and the patch sheet. 
     
     
         6 . The method according to  claim 1 , further comprising the step of:
 coating the part with another anticorrosion paint after cooling or quenching.   
     
     
         7 . The method according to  claim 6 , wherein the part is coated with an electrophoretically deposited coating as the other anticorrosion paint. 
     
     
         8 . The method according to  claim 1 , wherein the anticorrosion paint is annealed by the predetermined temperatures applied to the subassembly for hot working. 
     
     
         9 . The method according to  claim 1 , wherein the patch sheet is fixed to the base sheet by a joining process. 
     
     
         10 . The method according to  claim 9 , wherein the joining process is a clinching in which the materials of the patch sheet and base sheet are interconnected by local deformation. 
     
     
         11 . The method according to  claim 9 , wherein the joining process is carried out by weld points in one or more areas of the subassembly. 
     
     
         12 . The method according to  claim 11 , wherein the weld points are subsequently treated by a laser beam after hot working in such a way that they are invisible on the subassembly after quenching or cooling. 
     
     
         13 . A part made according to the method according to  claim 1 . 
     
     
         14 . The part according to  claim 13 , wherein the part is a structural body part for a vehicle.