Method for producing a component by hot forming a pre-product made of steel

Abstract

A method for producing a component by hot forming a pre-product made of steel is disclosed. The pre-product is heated to a forming temperature and is then reshaped, said component having a bainitic microstructure with a minimum tensile strength of 800 MPa after the forming process. In the process, the pre-product with the specified alloy composition is heated to a temperature below the A c1 transformation temperature, said pre-product already consisting of a steel with a microstructure made of at least 50% bainite.

What is claimed: 
     
         1 .- 15 . (canceled) 
     
     
         16 . A method for producing a component by hot forming a pre-product made of steel, comprising:
 providing a pre-product made of steel having a microstructure of at least 50% bainite and having the following alloy composition in weight %:   
       C: 0.02 to 0.3 
       Si: 0.01 to 0.5 
       Mn: 1.0 to 3.0 
       P: max 0.02 
       S: max 0.01 
       N: max 0.01 
       Al: up to 0.1 
       Cu: up to 0.2 
       Cr: up to 3.0 
       Ni: up to 0.2 
       Mo: up to 0.2 
       Ti: up to 0.2 
       V: up to 0.2 
       Nb: up to 0.1 
       B: up to 0.01;
 heating the pre-product to forming temperature below Ac1 transformation temperature; and 
 forming the pre-product into the component, wherein the component after the forming has a bainitic microstructure with a minimal tensile strength of 800 MPa. 
 
     
     
         17 . The method of  claim 16 , wherein the microstructure of the pr-product is composed of at least 70% bainite and a content of residual austenite+martensite is<10% and the remainder is ferrite. 
     
     
         18 . The method of  claim 16 , wherein the pre-product has the following alloy composition in weight %: 
       C: 0.02 to 0.11% 
       Si: 0.01 to 0.5% 
       Mn: 1.0 to 2.0% 
       P: max 0.02% 
       S: max 0.01% 
       N: max 0.01% 
       Al min : 0.015 to 0.1% 
       B: max. 0.004% 
       Nb+V+Ti: max 0.2%. 
     
     
         19 . The method of  claim 16 , wherein the pre-product has the following alloy composition in weight %: 
       C: 0.05 to 0.11% 
       Si: 0.01 to 0.5% 
       Mn: 1.0 to 2.0% 
       P: max. 0.02% 
       S: max 0.01% 
       N: 0.003 to 0.01% 
       Al min : 0.03 to 0.1% 
       B: max 0.004% 
       Mo: 0.04 to 0.2 
       Ti: 0.04 to 0.2 
       Nb+V+Ti: 0.1 to 0.2%. 
     
     
         20 . The method of  claim 16 , wherein during the heating step only portions of the pre-product are heated to forming temperature, and optionally above the Ac 1  transformation temperature. 
     
     
         21 . The method of  claim 16 , wherein the pre-product is heated to a temperature below 720° C. 
     
     
         22 . The method of  claim 21 , wherein the pre-product is heated to a temperature in a ranged from 400 to 720° C. 
     
     
         23 . The method of  claim 22 , wherein the pre-product is heated to a temperature in a ranged from 500 to 700° C. 
     
     
         24 . The method of  claim 16 , further comprising prior to the heating step, is providing the pre-product with a metallic or lacquer-like coating. 
     
     
         25 . The method of  claim 24 , wherein the metallic coating contains Zn and/or Mn and/or Al and/or Si. 
     
     
         26 . The method of  claim 16 , wherein the heating to forming temperature is accomplished inductively, conductively, or by means of radiation. 
     
     
         27 . The method of  claim 16 , wherein the pre-product is a metal plate or a tube. 
     
     
         28 . The method of  claim 27 , wherein the metal plate is made of hot strip or cold strip. 
     
     
         29 . The method of  claim 27 , wherein the tube is a seamlessly hot rolled tube or a welded tube made of hot strip or cold strip. 
     
     
         30 . The method of  claim 29 , wherein the tube is subjected to one or multiple further drawing and/or annealing processes.