Method for producing a motor vehicle component and motor vehicle component

Abstract

A method for producing a motor vehicle component having two regions, with different strength is disclosed. A first one of the two regions has a high strength and a second one of the two regions has a higher ductility and lower strength relative to the first region. In a motor vehicle component produced with the method, the first region has a strength between 1400 and 1600 MPa at a breaking elongation A5>13% and the second region has a tensile strength between 950 and 1050 MPa at a breaking elongation A5>16%.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims and includes equivalents of the elements recited therein: 
     
         1 . A method for producing a motor vehicle component having two regions with different strength properties, comprising the steps of:
 providing a blank made from hardenable steel sheet;   heating the blank to at least 800 to 1100° C.;   transferring the heated blank into a furnace with two temperature zones, so that a first region of the blank is arranged in a first one of the two temperature zones and a second region of the blank is arranged in a second one of the two temperature zones, wherein the first zone has a first temperature essentially corresponding to an austenization temperature, and the second zone has a temperature between 300 and 600° C.;   cooling the second region of the blank to a second temperature between 300 and 450° C.;   holding the first region at the first temperature and the second region at the second temperature for a defined period of time; and   hot forming and press hardening the blank into the motor vehicle component, thereby establishing a tensile strength between 900 and 1300 MPa and a breaking elongation A5 of more than 16% in the second region.   
     
     
         2 . The method of  claim 1 , wherein the blank is heated in the heating step to 900 to 1000° C. 
     
     
         3 . The method of  claim 1 , wherein the blank is heated in the heating step to austenization temperature +/−100° C. 
     
     
         4 . The method of  claim 1 , wherein the hardenable steel is an alloy comprising the following alloy components in weight percent: 
       
         
           
                 
                 
                 
               
                     
                     
                 
                     
                   Carbon (C) 
                    0.14-0.3% 
                 
                     
                   Manganese (Mn) 
                     0.8-2.5% 
                 
                     
                   Silicon (Si) 
                     1.5-2.5% 
                 
                     
                   Chromium (Cr) 
                   max. 0.4% 
                 
                     
                   Aluminum (Al) 
                   max. 0.1% 
                 
                     
                   Nickel (Ni) 
                   max. 0.3% 
                 
                     
                   Boron (B) 
                   0.0008-0.005% 
                 
                     
                   Titanium (Ti) 
                    0.005-0.1% 
                 
                     
                   Niobium (Nb) 
                   max. 0.1%, 
                 
                     
                     
                 
             
                
               
               
                
                
                
                
                
                
                
                
                
                
               
            
           
         
       
       Remainder Iron and smelting related contaminations. 
     
     
         5 . The method of  claim 3 , wherein in the cooling step the second region is cooled from the austenization temperature to between 300 and 450° C. at a cooling rate of between 100K/s and 10K/s. 
     
     
         4 . The method of  claim 1 , wherein the hot forming and press hardening step establishes a bainitic structure in the second region and an essentially martensitic structure in the first region. 
     
     
         5 . The method of  claim 4 , wherein the bainitic structure is a lower bainitic structure. 
     
     
         6 . The method of  claim 1 , wherein the period of time is between 5 and 400 seconds. 
     
     
         7 . The method of  claim 1 , wherein in the first region in the hot formed and press hardened plank has a tensile strength between 1200 and 1700 MPa and a breaking elongation A5 greater than 13%. 
     
     
         8 . The method of  claim 7 , wherein the tensile strength is between 1300 and 1600 MPa. 
     
     
         9 . The method of  claim 7 , wherein the tensile strength is between 1450 and 1550 MPa. 
     
     
         10 . The method of  claim 1 , wherein the second region in the hot formed and press hardened plank has a tensile strength between 950 and 1050 MPa and a breaking elongation A5 of more than 17%. 
     
     
         11 . The method of  claim 1 , wherein the second region in the hot formed and press hardened plank has a yield point Rp0.2 between 550 and 800 MPa. 
     
     
         12 . The method of  claim 11 , wherein the yield point is between 600 and 700 MPa. 
     
     
         13 . The method of  claim 1 , wherein the heating step and the holding step are performed in a continuous furnace system or in a heating station with downstream furnace. 
     
     
         14 . The method of  claim 13 , wherein the downstream furnace is constructed as continuous furnace. 
     
     
         15 . The method of  claim 14 , wherein the continuous furnace comprises three temperature zones. 
     
     
         16 . A motor vehicle component produced according to the method of  claim 1  and comprising first and second regions, said first and second regions differing in strength, wherein the first region has a strength between 1400 and 1600 MPa and a breaking elongation A5 of greater than 13% and the second region has a tensile strength between 950 and 1050 MPa, a yield point Rp0.2 of between 600 and 700 MPa and a breaking elongation A5 of greater than 16%. 
     
     
         17 . The motor vehicle of  claim 16 , wherein the first region has a martensitic structure and the second region has a bainitic structure. 
     
     
         18 . The motor vehicle of  claim 17 , wherein the bainitic structure is a lower bainitic structure.