Method And Device for Energy-Efficient Hot Forming

Abstract

The invention relates to a method for hot forming of steel parts, in particular blanks or semi-finished products of steel, in which the steel parts are heated in a furnace for at least partial austenitisation to a temperature above the Ac1 temperature and hot formed in a forming tool. The object of providing a method for hot forming of steel parts which allows an energy-efficient performance of the hot forming while at the same time reducing the cycle times for producing a hot formed component, is achieved in that the waste heat from the furnace is used for further heat treatment steps of the steel part before and/or after the at least partial austenitisation of the steel part.

1 . Method for hot forming of steel parts, in particular blanks or semi-finished products of steel, in which the steel parts are heated in a furnace for at least partial austenitisation to a temperature above the AC1 temperature and hot formed in a forming tool, comprising using waste heat from the furnace in a heat treatment step for the steel parts occurring at least one of before and/or after the at least partial austenitisation of the steel parts. 
     
     
         2 . Method according to  claim 1 , wherein a continuous furnace is used for the at least partial austenitisation of the steel parts. 
     
     
         3 . Method according to  claim 1 , wherein the furnace for at least partial austenitisation of the steel parts is at least partially heated by gas and the waste heat from the combustion exhaust gases from the furnace is used for the heat treatment step. 
     
     
         4 . Method according to  claim 1 , wherein using the waste heat from the furnace in a heat treatment step is achieved in a preheating furnace to pre-alloy the steel parts. 
     
     
         5 . Method according to  claim 1 , wherein the forming tool for hot forming is at least partially heated with the waste heat from the furnace for at least partial austenitisation of the steel part. 
     
     
         6 . Method according to  claim 1 , wherein using the waste heat from the furnace in a heat treatment step includes tempering of the formed steel parts. 
     
     
         7 . Method according to  claim 1 , wherein the heat treatment step on the steel parts are performed by forced convection. 
     
     
         8 . Method according to  claim 1 , wherein the steel parts are heated in the preheating furnace to a temperature of 200° C. to Ac1 temperature. 
     
     
         9 . Device for performing a method according to  claim 1 , comprising:
 a furnace for heating steel parts to above the Ac1 temperature in order to form an at least partially austenitic structure;   a forming tool for hot forming of the steel parts;   means for transporting the steel parts from the furnace to the forming tool;   means for using the waste heat from the furnace in a heat treatment step in at least one of before and/or after the at least partial austenitisation of the steel parts.   
     
     
         10 . Device according to  claim 9  wherein the means using the waste heat are provided for heating at least one of a preheating furnace, the forming tool, and/or a tempering furnace. 
     
     
         11 . Device according to  claim 9 , wherein the furnace is a continuous furnace. 
     
     
         12 . Device according to  claim 10 , wherein as means for heating the preheating furnace, the forming tool, and the tempering furnace, at least one of medium supply lines and fans are provided for guiding the combustion exhaust gases from the furnace for the at least partial austenitisation. 
     
     
         13 . Method according to  claim 2 , wherein the continuous furnace is a roller hearth furnace and is used for the at least partial austenitisation of the steel parts. 
     
     
         14 . Method according to  claim 1 , wherein the steel parts are AlSi-coated steel parts. 
     
     
         15 . Method according to  claim 1 , wherein the steel parts are heated in the preheating furnace to a temperature of about 250° C. to about 700° C. 
     
     
         16 . Device according to  claim 11 , wherein the continuous furnace is a roller hearth furnace.