Method for softening a selected portion of a steel object by heating

Abstract

A method and apparatus for tempering the shank portion only of die blocks which comprises subjecting the shank portion of a die block or other large metal part to electrical energy derived from induction heating or infrared heating to a controlled depth, preferably just sufficiently deep to temper the shank portion but not sufficiently deep to temper the hardened working portion of the part.

What is claimed is:  
     
         1 . In a method of reducing the incidence of cracking at the shank-body junctions of hardened die blocks, the steps of 
 placing an electric heat source in close, operative proximity to the shank-body junction of a die block to be softened,    directing the heat generated by the electric heat source only to the body-shank portion of the die block, and    terminating the operation of the electric heat source after the body-shank portion of the die block has been drawn.    
     
     
         2 . The method of  claim 1  further characterized in that 
 the electric heat source is in abutting contact with the shank-body junction surfaces formed in the die block.  
 
     
     
         3 . The method of  claim 2  further characterized in that 
 the thickness of the electric heat source equals the height of the shank of the die block.  
 
     
     
         4 . The method of  claim 3  further characterized in that 
 the electric heat source is induction heating coils.  
 
     
     
         5 . The method of  claim 1  further characterized in that 
 the electric heat source is spaced from the body-shank portion of the die block.  
 
     
     
         6 . The method of  claim 5  further characterized in that 
 the electric heat source is infrared heating means.  
 
     
     
         7 . The method of  claim 6  further characterized in that 
 the infrared heating means are tungsten halogen lamps arranged to direct infrared energy onto a defined area of a die block to be softened.  
 
     
     
         8 . The method of  claim 6  further characterized in that 
 the tungsten halogen lamps operate in the short wave division of the electromagnetic spectrum.  
 
     
     
         9 . Apparatus for reducing cracking at the body-shank junctions of a hardened die block, said apparatus including, in combination 
 an electric heat source in close proximity to the body-shank junction portion of the die block,    said electric heat source being arranged to direct heat to the body-shank junction portion of the die block, and in an amount such that the body-shank portion, only, of the die block is softened to a level at which subsequent cracking at a shank-body junction of the die block is substantially eliminated, and    means for confining the heat from the electric heat source to the body-shank junction portion of the die block.    
     
     
         10 . The apparatus of  claim 9  further characterized in that 
 the electric heat source is induction heating coil means.  
 
     
     
         11 . The apparatus of  claim 10  further characterized in that 
 the means for confining the induction heating currents generated by the induction heating coil means includes at least partial envelopment by non-magnetic material of those portions of the induction heating coil means which are not in operative relationship with the shank or body portion of the die block.  
 
     
     
         12 . The apparatus of  claim 11  further characterized in that 
 the means for confining the induction heating currents are substances selected from the group consisting essentially of non-magnetic rock, rock-type and ceramic materials which are capable of withstanding, without substantial distortion, the temperatures generated during treatment by the induction heating coil means.  
 
     
     
         13 . The apparatus of  claim 12  further characterized in that 
 the induction heating coil means are in abutting contact with the shank-body junction surface of a die block.  
 
     
     
         14 . The apparatus of  claim 13  further characterized in that 
 the thickness of the induction heating coil means equals the height of the shank of a die block.  
 
     
     
         15 . The apparatus of  claim 9  further characterized in that 
 the infrared heating means are tungsten halogen lamps.  
 
     
     
         16 . The apparatus of  claim 14  further characterized in that 
 the tungsten halogen lamps are spaced closely to the body-shank junction portion of the die block.  
 
     
     
         17 . The apparatus of  claim 15  further characterized in that the tungsten halogen lamps are arranged to operate in the short wave division of the electromagnetic spectrum.