Method and device for producing hardened steel components

Abstract

The invention relates to a method for press hardening sheet steel components in which a blank is detached from a sheet steel band composed of a hardenable steel alloy and the blank is then austenitized, in that it is heated to a temperature greater than Ac 3 and is then inserted into a forming tool and formed in the forming tool, and during the forming, is cooled at a speed greater than the critical hardening speed, characterized in that in order to inhibit microcracks of the second type from being produced during the forming and hardening process in the sheet metal blanks that are to be formed, oxygen is supplied adjacent to the positive radii and/or drawing edges; the invention also relates to a device for performing this method.

1 . A method for press hardening sheet steel components comprising: cutting a blank out from a sheet steel band composed of a hardenable steel alloys; austenitizing the blank, by heating it to a temperature greater than Ac 3 , inserting it into a forming tool, and forming in the forming tool, and during the forming, cooling it at a speed greater than the critical hardening speed; characterized in that in order to avoid microcracks of second type from forming in the sheet metal blank to be formed during the forming and hardening process, oxygen is supplied
 in and/or adjacent to the positive radii and/or drawing edges and/or   in contact regions.   
     
     
         2 . The method according to  claim 1 , characterized in that the entry of oxygen by means of inserts ( 1 ) made of oxygen-storing materials are provided in the forming tool adjacent to or in the region of the drawing edges and/or positive radii, which are dimensioned so that deep drawing is not negatively affected and the inserts ( 1 ) form a reservoir for oxygen. 
     
     
         3 . The method according to  claim 2 , characterized in that inserts ( 1 ) made of sintered metals, porous ceramics, or impervious ceramics are used. 
     
     
         4 . The method according to  claim 2 , characterized in that the inserts ( 1 ) are supplied with oxygen or oxygen-containing fluids from the forming tool side, or the inserts ( 1 ) or mold cavity are flooded with oxygen or an oxygen-containing fluid between two forming procedures. 
     
     
         5 . A device for the press hardening or hot forming and hardening of sheet steel components, having two forming tool halves; the two forming tool halves cooperate in order to deep-draw a blank and are embodied so that they can move toward and away from each other; depending on a desired forming contour, at least one positive radius or one drawing edge region is provided with a drawing edge ( 2 ), a ceramic insert being positioned in lieu of a metallic drawing edge ( 2 ), wherein the it is inserted into the respective forming tool half in a form-fitting way. 
     
     
         6 . The device according to  claim 5 , characterized in that in the ceramic insert, a recess ( 7 ) is provided, which is dimensioned so that the remaining thickness of the drawing edge ( 2 ) between a surface, which adjoins the drawing edge ( 2 ), and the recess ( 5 ) corresponds approximately to its radius. 
     
     
         7 . The device according to  claim 6 , characterized in that the recess ( 5 ) between the drawing edge ( 2 ) and a forming tool surface ( 4 ) has a height, which corresponds to approximately 25 to 35 mm at a depth of 5 to 9 mm or is embodied as a groove ( 8 ), which has a height between the surface ( 4 ) and the drawing edge ( 2 ), which totals approximately 8 to 12 mm, with a depth of 5 to 9 mm or in the region of the wall ( 4 ) adjacent to the drawing edge ( 2 ), a plurality of recesses in the form of slots ( 9 ) extending in the drawing direction; and the slots ( 9 ) have a slot width of 4 to 8 mm and a slot spacing of 7 to 11 mm so that remaining bridge pieces have a width of 1 to 5 mm. 
     
     
         8 . The device according to  claim 7 , characterized in that the recess ( 7 ), the groove ( 8 ), or the slots ( 9 ) are supplied from the rear, i.e. from the tool side, with an oxygen-containing fluid by means of supply openings and correspondingly drilled lines. 
     
     
         9 . The method according to  claim 3 , characterized in that the inserts ( 1 ) are supplied with oxygen or oxygen-containing fluids from the forming tool side, or the inserts ( 1 ) or mold cavity are flooded with oxygen or an oxygen-containing fluid between two forming procedures.