Method of producing a tool steel

Abstract

In a method of producing a tool steel, in particular a hot-work tool steel, a steel of the following analysis: C: 0.25-0.6 weight-%, Si: max 0.15 weight-%, Mn: max. 0.3 weight-%, Mo: 2-5 weight-%, Cr: 0-2 weight-%, W: 1-3 weight-%, V: 0-2 weight-%, Ni: 0-3 weight-%, and a residue of iron and unavoidable impurities due to smelting is smelted and alloyed, wherein a workpiece of this steel is heated up and austenitized at temperatures >Ac 3 and then cooled down, wherein the cooling is effected down to a temperature of 330° C. to 360° C. and the workpiece is held isothermally at this temperature, until the workpiece is completely bainitically transformed, followed by cooling down to room temperature, together with a hot-work tool steel for this purpose and its use.

1 . Method of producing a tool steel, in particular a hot-work tool steel, wherein
 a steel of the following analysis
 C: 0.25-0.6 weight-% 
 Si: max 0.15 weight-% 
 Mn: max. 0.3 weight-% 
 Mo: 2-5 weight-% 
 Cr: 0-2 weight-% 
 W: 1-3 weight-% 
 V: 0-2 weight-% 
 Ni: 0-3 weight-% 
   
       and a residue of iron and unavoidable impurities due to smelting is smelted and alloyed, wherein a workpiece of this steel is heated up and austenitized at temperatures >Ac 3  and then cooled down, wherein the cooling is effected down to a temperature of 330° C. to 360° C. and the workpiece is held isothermally at this temperature, until the workpiece is completely bainitically transformed, followed by cooling down to room temperature. 
     
     
         2 . Method according to  claim 1 , 
       wherein
 after complete through heating for a period of 20 to 40 min., austenitizing takes place. 
 
     
     
         3 . Method according to  claim 1 , 
       wherein
 isothermal holding takes place for a period of 30 to 90 min. 
 
     
     
         4 . Method according to  claim 1 , wherein
 cooling from the austenitizing temperature down to the isothermal holding temperature is conducted at cooling rates from λ=0.4 to λ=2.   
     
     
         5 . Method according to  claim 1 , wherein
 after cooling to room temperature, the workpiece is tempered to set the hardness.   
     
     
         6 . Method according to  claim 1 , wherein
 the tempering temperature lies between 580° C. and 660° C., while the duration of tempering lies between 1 and 2 hours.   
     
     
         7 . Hot-work tool steel produced by a method according to  claim 1  and with an analysis as follows:
 C: 0.25-0.6 weight-% 
 Si: max 0.15 weight-% 
 Mn: max. 0.3 weight-% 
 Mo: 2-5 weight-% 
 Cr: 0-2 weight-% 
 W: 1-3 weight-% 
 V: 0-2 weight-% 
 Ni: 0-3 weight-% 
 
       and a residue of iron and unavoidable impurities due to smelting, wherein the hot-work tool steel has a residual austenite content <1% with an otherwise completely bainitic structure, wherein hardness lies between 46 and 53 HRC and notch-bend impact energy 4.5 and 8.5 joules. 
     
     
         8 . Use of a tool steel according to  claim 7  for hot-work tools such as injection moulds, hot-working tools, press hardening tools, forging dies, hammer dies, hot-piercing punches, hot-extrusion punches.