Steel article

Abstract

A steel article consists of an alloy which consists in weight- %: 1.7-2.5; 0.1-2.0 Si; 0.1-2.0 Mn; max 0.2 N; max 0.2 S; 12 16 Cr; 2.1-3.5 (Mo+W/2); 5-8 V; max 0.1 Nb, balance essentially only iron and unavoidable impurities. The steel has a micro-structure obtainable by a manufacturing of the steel which comprises spray forming of an ingot, the micro-structure of which contains 14-25 vol-% carbides of mainly MC-type, where M substantially consists of vanadium, of which carbides at least 80 vol-% have a substantially rounded shape and a size in the longest extension of the carbides amounting to 1-10 μm, and M 7 C 3 -carbides, where M substantially consists of chromium, which carbides typically have a more elongated shape than the MC-carbides, of which MC-carbides at least 80 vol-% have a maximal extension amounting to 3-50 μm.

1 . Steel article, characterised in that it consists of an alloy which contains in weight-% 
 1.7-2.5 C    0.1-2.0 Si    0.1-2.0 Mn    max 0.2N    max 0.2 S    12-16 Cr    2.1-3.5 (Mo+W/2)    5-8 V    max 0.1 Nb    balance essentially only iron and unavoidable impurities, and that the steel has a micro-structure obtainable by a manufacturing of the steel which comprises spray forming of an ingot, the micro-structure of which contains 14-25 vol-% carbides of mainly MC-type, where M substantially consists of vanadium, of which carbides at least 80 vol-% have a substantially rounded shape and a size in the longest extension of the carbides amounting to 1-10 μm, and M 7 C 3 -carbides, where m substantially consists of chromium, which carbides typically have a more elongated shape than the MC-carbides, of which MC-carbides at least 80 vol-% have a maximal extension amounting to 3-50 μm.    
     
     
         2 . Article according to  claim 1 , characterised in that the micro-structure contains 3-8 vol-% MC-carbides and 10-20 vol-% M 7 C 3 -carbides.  
     
     
         3 . Article according to  claim 2 , characterised in that it after hardening and tempering has a hardness of 55 to 64 HRC.  
     
     
         4 . Article according to  claim 3 , characterised in that the martensitic matrix of the steel after hardening and tempering contains 0.2-0.7 weight-% C in solid solution.  
     
     
         5 . Article according to any of claims  1 - 4 , characterised in that the total content of C in the steel is at least 1.8%.  
     
     
         6 . Article according to any of claims  1 - 4 , characterised in that the total content of C in the steel is max 2.3%.  
     
     
         7 . Article according to any of claims  1 - 6 , characterised in that the steel contains 0.2-1.0% Si.  
     
     
         8 . Article according to any of claims  1 - 7 , characterised in that the steel contains 0.2-1.0% Mn.  
     
     
         9 . Article according to any of claims  1 - 8 , characterised in that the steel contains at least 13% Cr.  
     
     
         10 . Article according to any of claims  1 - 9 , characterised in that the steel contains max 15.5% Cr.  
     
     
         11 . Article according to  claim 10 , characterised in that the steel contains 13.2-14.5% Cr.  
     
     
         12 . Article according to any of claims  1 - 10 , characterised in that the steel contains at least 6.1% V.  
     
     
         13 . Article according to any of claims  1 - 11 , characterised in that the steel contains max 7.5% V.  
     
     
         14 . Article according to claims  12  and  14 , characterised in that the steel contains 6.3-7.3% V.  
     
     
         15 . Article according to any of claims  12 - 14 , characterised in that the steel does not contain more than max 0.04 Nb.  
     
     
         16 . Article according to any of claims  1 - 15 , characterised in that the steel contains at least 2.3% Mo.  
     
     
         17 . Article according to any of claims  1 - 15 , characterised in that the steel contains max 3.0% Mo.  
     
     
         18 . Article according to any of claims  1 - 17 , characterised in that the steel does not contain more than max 1.0% W, preferably max 0.5% W.  
     
     
         19 . Article according to any of claims  1 - 18 , characterised in that the steel does not contain more than max 0.1% S, preferably max 0.05% S.  
     
     
         20 . Article according to any of claims  3 - 19 , characterised in that it after hardening and tempering at a temperature between 180-220° C. has a hardness of 55-62 HRC, preferably at least 59 HRC.  
     
     
         21 . Article according to any of claims  3 - 19 , characterised in that it after hardening and tempering at a temperature between 380 and 450° C. has a hardness of 55-62 ARC, preferably at least 59 ARC.  
     
     
         22 . Article according to any of claims  3 - 19 , characterised in that it after hardening from a temperature between 480 and 520° C. has a hardness of 60-63 HRC.  
     
     
         23 . Article according to any of claims  3 - 19 , characterised in that it after hardening from a temperature between 510 and 530° C. has a hardness between 61 and 64 HRC.