Steel article

Abstract

The invention concerns an article of a steel which is characterized in that it consists of an alloy which contains in weight-%: 1.2-2.0 C, 0.1-1.5 Si, 0.1-2.0 Mn, max. 0.2 N, max. 0.25 S, 4-8 Cr, 0.5-3.5 (Mo+W/2), 5-8 V, max. 1.0 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 8-15 vol-% carbides of essentially only 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 1-20 μm.

1 . Steel article, characterized in that it consists of an alloy which contains in weight-%; 
 1.2-2.0 C    0.1-1.5 Si    0.1-2.0 Mn    max 0.2 N    max 0.25 S    4-8 Cr    0.5-3.5 (Mo+W/2)    5-8 v    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 8-15 vol-% carbides of essentially only 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 1-20 μm.    
     
     
         2 . Article according to  claim 1 , characterized in that it consist of an alloy which contains in weight-%: 
 1.2-2.0 C    0.1-1.5 Si    0.1-2.0 Mn    max 0.2 N    max 0.25 S    4-8 Cr    0.5-3.5 (Mo+W/2)    5-8 V    max. 1.0 Nb    balance essentially only iron and unavoidable impurities.    
     
     
         3 . Article according to  claim 2 , characterized in that it contains max. 0.5 Nb.  
     
     
         4 . Article according to  claim 3 , characterized in that it contains max. 0.3 Nb.  
     
     
         5 . Article according to  claim 4 , characterized in that it contains max. 0.1 Nb.  
     
     
         6 . Article according to  claim 5 , characterized in that it has not contain any intentionally added niobium.  
     
     
         7 . Article according to  claim 1 , characterized in that the micro-structure contains 10-14.5 vol-% MC-carbides, of which the main part with reference to volume has a size in the longest extensions of the carbides larger than 3.0 μm and max. 10 μm.  
     
     
         8 . Article according to  claim 7 , characterized in that it after hardening and tempering has a hardness of 45-60 HRC.  
     
     
         9 . Article according to  claim 8 , characterized in that the martensitic matrix of the steel after hardening and tempering contains 0.1-0.5 weight-% C in solid solution.  
     
     
         10 . Article according to any of claims  1 - 9 , characterized in that the total content of C in the steel is at least 1.3%, preferably at least 1.4%.  
     
     
         11 . Article according to any of claims  1 - 10 , characterized in that the total content of C in the steel is max. 1.9%, preferably max. 1.8%.  
     
     
         12 . Article according to any of claims  1 - 11 , characterized in that the steel contains 0.1-1.0 Si, preferably max. 0.65% Si.  
     
     
         13 . Article according to any of claims  1 - 12 , characterized in that the steel contains 0.2-1.5 Mn.  
     
     
         14 . Article according to any of claims  1 - 13 , characterized in that the steel contains at least 4.2% Cr.  
     
     
         15 . Article according to any of claims  1 - 14 , characterized in that the steel contains max. 6.5% Cr.  
     
     
         16 . Article according to  claim 15 , characterized in that the steel contains 4.5-5.5% Cr.  
     
     
         17 . Article according to any of claims  1 - 15 , characterized in that the steel contains at least 6.0% V.  
     
     
         18 . Article according to any of claims  1 - 17 , characterized in that the steel contains max. 7.8% V.  
     
     
         19 . Article according to  claim 17  and  18 , characterized in that the steel contains 6.8-7.6% V.  
     
     
         20 . Article according to any of claims  1 - 20 , characterized in that that steel does not contain more than max. 0.04 Nb.  
     
     
         21 . Article according to any of claims  1 - 20 , characterized in that the steel contains at least 1.5% Mo.  
     
     
         22 . Article according to any of claims  1 - 21 , characterized in that that steel contains 1.8-2.8% Mo.  
     
     
         23 . Article according to any of claims  1 - 22 , characterized in that that steel does not contain more than max. 1.0% W, preferably max. 0.5% W.  
     
     
         24 . Article according to any of claims  1 - 23 , characterized in that the steel does not contain more than max. 0.15 S, preferably max. 0.08 S.  
     
     
         25 . Article according to any of claims  8 - 24 , characterized in that it after hardening from an austenitising temperature in the temperature range 1000-1150° C. and tempering at a temperature in the temperature range between 590-640° C., 2×2 h, has a hardness of 48-53 HRC.  
     
     
         26 . Article according to any of claims  8 - 24 , characterized in that it after hardening from an austenitising temperature in the temperature range 1000-1150° C. and tempering at a temperature in the temperature range between 540-610° C., 2×2 h, has a hardness of 54-58 HRC.  
     
     
         27 . Article according to any of claims  8 - 24 , characterized in that it after hardening from an austenitising temperature in the temperature range 1050-1150° C. and tempering at a temperature in the temperature range between 540-580° C., 2×2 h, has a hardness of 58-60 HRC.