Tool steel for plastic molds

Abstract

A pre-hardened and pre-tempered tool steel is used for producing molds for plastic parts, in particular matrices of large dimensions. In order to make possible high core hardness without qualitative disadvantages even at large diameters, a tool steel is proposed, which has a composition in weight-% of C=0.25 to 0.30, SI=0.04 to 0.20, Mn=1.2 to 2.0, Cr=1.0 to 2.0, Ni=0.9 to 1.5, Mo=0.3 to 0.8, V≦0.2 and Al=0.01 to 0.03, wherein the remainder consists of iron and the unavoidable impurities. The addition of boron for increasing hardness was intentionally omitted since it has been shown that with larger diameters boron results in non-reproducible hardness, in particular in the core area.

1 . Use of a tool steel for producing molds for plastic parts, having the following composition (in weight-%): 
 C=0.25 to 0.30    Si=0.04 to 0.20    Mn=1.2 to 2.0    Cr=1.0 to 2.0    Ni=0.9 to 1.5    Mo=0.3 to 0.8    V≦0.2    Al=0.01 to 0.03    wherein the remainder consists of iron and the unavoidable impurities.    
     
     
         2 . Use of a tool steel in accordance with  claim 1 , characterized by an Ni content between 0.9 and 1.2 weight-%.  
     
     
         3 . Use of a tool steel in accordance with  claim 1  or  2 , characterized by an Si content between 0.004 and 0.15 weight-%.  
     
     
         4 . Use of a tool steel in accordance with one of the preceding claims, characterized by an Mn content between 1.2 and 1.6 weight-%, an Mo content between 0.4 and 0.6 weight-%, and a V contents between 0.05 and 0.15 weight-%.  
     
     
         5 . Use of a tool steel in accordance with one of the preceding claims, characterized by an S content between 0.008 and 0.15 weight-%.  
     
     
         6 . Use of a tool steel in accordance with one of the preceding claims, characterized in that it is water- or polymer-hardened and tempered and has a maximum hardness of 40 HRC.  
     
     
         7 . Use of a tool steel in accordance with one of the preceding claims, characterized in that, following hardening, it is tempered at a tempering temperature of approximately 620° C. for approximately 30 HRC.  
     
     
         8 . Use of a tool steel in accordance with one of the preceding claims, characterized in that it is pre-hardened and pre-tempered with a diameter of at least 400 mm.  
     
     
         9 . Use of a tool steel in accordance with  claim 8 , characterized in that it is pre-hardened and pre-tempered with a diameter of at least 1000 mm.