Cold-Working Steel

Abstract

The invention relates to a cold-working steel having a chemical composition, in % by weight, of 1.3-2.4 (C+N), whereof at least 0.5 C, 0.1-1.5 Si, 0.1-1.5 Mn, 4.0-5.5 Cr, 1.5-3.6 (Mo+W/2), but max 0.5 W, 4.8-6.3 (V+Nb/2), but max 2 Nb, and max 0.3 S, in which the content of (C+N) and of (V+Nb/2) are balanced in relation to each other such that the contents of these elements are within an area that is defined by the coordinates A, B, C, D, A in the system of coordinates in FIG. 11 , where the coordinates of [(C+N), (V+Nb/2)] for these points are A: [1.38, 4.8], B: [1.78, 4.8], C: [2.32, 6.3], D: [1.92, 6.3], and a balance essentially only iron and impurities at normal contents.

1 . A cold-working steel, comprising, in % by weight:
 1.3-2.4 (C+N), whereof at least 0.5 C,   0.1-1.5 Si,   0.1-1.5 Mn,   4.0-5.5 Cr,   1.5-3.6 (Mo+W/2), but max 0.5 W,   4.8-6.3 (V+Nb/2), but max 2 Nb, and   max 0.3 S,   in which the content of (C+N) and of (V+Nb/2) are balanced in relation to each other such that the contents of these elements are within an area that is defined by the coordinates A, B, C, D, A in the system of coordinates in  FIG. 11 , where the coordinates of [(C+N), (V+Nb/2)] for these points are:   A: [1.38, 4.8]   B: [1.78, 4.8]   C: [2.32, 6.3]   D: [1.92, 6.3], and   balance essentially only iron and impurities at normal contents.   
     
     
         2 . A steel according to  claim 1 , wherein the content of (C+N) and of (V+Nb/2) are balanced in relation to each other such that the contents of these elements are within an area that is defined by the coordinates E, F, G, H, E in the system of coordinates in  FIG. 11 , where the coordinates of [(C+N), (V+Nb/2)] for these points are:
 E: [1.48, 4.8]   F: [1.68, 4.8]   G: [2.22, 6.3], and   H: [2.02, 6.3].   
     
     
         3 . A steel according to  claim 2 , wherein the content of (C+N) and of (V+Nb/2) are balanced in relation to each other such that the contents of these elements are within an area that is defined by the coordinates K, L, M, N, K in the system of coordinates in  FIG. 11 , where the coordinates of [(C+N), (V+Nb/2)] for these points are:
 K: [1.62, 5.2]   L: [1.82, 5.2]   M: [2.05, 5.8], and   N: [1.85, 5.8].   
     
     
         4 . A steel according to  claim 1 , wherein the content of (C+N) and of (V+Nb/2) are balanced in relation to each other such that the contents of these elements fulfil the condition 0.32<(C+N)/(V+Nb/2)<0.35. 
     
     
         5 . A steel according to  claim 1 , comprising 0.1-1.2% Si. 
     
     
         6 . A steel according to  claim 5 , comprising 0.4% Si. 
     
     
         7 . A steel according to  claim 1 , comprising 0.1-1.3% Mn. 
     
     
         8 . A steel according to  claim 7 , comprising 0.4% Mn. 
     
     
         9 . A steel according to  claim 1 , comprising 4.5-5.1% Cr. 
     
     
         10 . A steel according to  claim 9 , comprising 4.8% Cr. 
     
     
         11 . A steel according to  claim 1 , comprising 1.5-2.6% (Mo+W/2). 
     
     
         12 . A steel according to  claim 11 , comprising 1.6-2.0% (Mo+W/2). 
     
     
         13 . A steel according to  claim 12 , comprising 1.8% (Mo+W/2). 
     
     
         14 . A steel according to  claim 1 , comprising max 0.3% W. 
     
     
         15 . A steel according to  claim 1 , comprising max 0.3% Nb. 
     
     
         16 . A steel according to  claim 1 , comprising max 0.15% S. 
     
     
         17 . A steel according to  claim 1 , comprising a hardness in the range 58-63 HRC, achieved after hardening from a temperature of between 980 and 1050° C. and tempering at a temperature of between 500-560° C./2×2 h. 
     
     
         18 . A steel according to  claim 1 , wherein the steel has a microstructure after hardening from 1050° C. and tempering that contains 8-13% by volume of MX-carbides, -nitrides and/or carbonitrides that are evenly distributed in the matrix of the steel, where M is essentially vanadium and X is carbon and/or nitrogen, of which carbides, nitrides and/or carbonitrides at least 90% by volume have an equivalent diameter, D e kv, of less than 3.0 μM, and is essentially free from MyC 3 -carbides, -nitrides and/or carbonitrides. 
     
     
         19 . A steel according to  claim 18 , wherein at least 90% by volume of said MX-carbides have a maximum extension of 2.0 μm. 
     
     
         20 . A method for at least one of cutting, shearing, punching and forming working of a metal working material in the cold condition, by a tool comprising a steel according to  claim 1 . 
     
     
         21 . A method for the pressing of a metal powder by a tool comprising a steel according to  claim 1 . 
     
     
         22 . A method of manufacturing a steel, comprising:
 a) production of a metal powder from a metal melt, b) hot isostatic pressing of the powder at a temperature of between 950 and 1200° C. and a pressure of between 90 and 150 MPa to form a consolidated body,   c) hot working of the consolidated body at a temperature of initially between 1050 and 1150° C.,   d) soft-annealing at about 900° C., and   e) hardening from a temperature of between 980 and 1050° C. and tempering at a temperature of between 500 and 560° C. to a hardness in the range of 58-66 HRC, wherein the metal powder has a composition according to  claim 1 .   
     
     
         23 . A steel according to  claim 5 , comprising 0.2-0.9% Si. 
     
     
         24 . A steel according to  claim 7 , comprising 0.1-0.9% Mn. 
     
     
         25 . A steel according to  claim 14 , comprising max 0.1% W. 
     
     
         26 . A steel according to  claim 15 , comprising max 0.1% Nb. 
     
     
         27 . A steel according to  claim 17 , comprising a hardness in the range 59-62 HRC, achieved after hardening from a temperature of between 980 and 1020° C. 
     
     
         28 . A method according to  claim 22 , wherein the hardness is in the range of 61-63 HRC.