Maraging steel article and method of manufacture

Abstract

A fully dense, powder-metallurgy produced maraging steel alloy article of prealloyed powder for use as a tool for high temperature applications. The article in the as-produced condition having a hardness less than 40 HRC to provide machinability and thereafter the article upon maraging heat treatment having a hardness greater than 45 HRC. A method for producing this article comprises compacting prealloyed powder to produce a fully dense article having a hardness less than 40 HRC and thereafter maraging heat treating to a hardness greater than 45 HRC.

1 . A fully dense, powder-metallurgy produced maraging steel alloy article of prealloyed powder for use as a tool for high temperature applications comprising, in weight percent: 
 C 0.08 max., Mn 1.0 max., Si 1.0 max., Cr 2.5-6.0, Mo 6.0-10.0, Ni 1.0-4.0, Co 9.0-14.0, sulfur up to 0.3 and balance iron and incidental elements and impurities;    said article as-produced having a hardness of less than 40 HCR to provide machinability; and    thereafter said article upon maraging heat treatment having a hardness greater than 45 HRC.    
   
   
       2 . The article of  claim 1 , comprising, in weight percent, C 0.05 max., Mn 0.1 to 0.05, Si 0.01 to 0.5, Cr 4 to 5.75, Mo 7 to 9, Ni 1.5 to 3, Co 10 to 13,S 0.005 to 0.05 and balance iron and incidental elements and impurities.  
   
   
       3 . The alloy article of  claim 1  comprising, in weight percent, C 0.01 to 0.04, Mn 0.2 to 0.4, Si 0.15 to 0.4, Cr 4.7 to 5.3, Mo 7.5 to 8.5, Ni 1.7 to 2.3, Co 10.75 to 12, S 0.01 to 0.03 and balance iron and incidental elements and impurities.  
   
   
       4 . The article of claims  1 ,  2  or  3  in the solution-annealed condition.  
   
   
       5 . The article of claims  1 ,  2  or  3 , wherein said article is in the form of a die.  
   
   
       6 . The article of claims  1 ,  2  or  3 , wherein said article is in the form of a container for liquid metal.  
   
   
       7 . A method for producing an article for use in processing of hot metal comprising: 
 compacting prealloyed powder of a maraging steel to produce a fully dense article having a hardness of less than 40 HRC to provide machinability;    thereafter maraging heat treating said article to achieve a hardness greater than 45 HRC; and    said prealloyed powder comprising, in weight percent, C 0.08 max., Mn 1.0 max., Si 1.0 max., Cr 2.5-6.0, Mo 6.0-10.0, Ni 1.0-4.0, Co 9.0-14.0, sulfur up to 0.3 and balance iron and incidental elements and impurities.    
   
   
       8 . The method of  claim 7 , wherein said prealloyed powder comprises, in weight percent, C 0.05 max., Mn 0.1 to 0.05, Si 0.01 to 0.5, Cr 4 to 5.75, Mo 7 to 9, Ni 1.5 to 3, Co 10 to 13, S 0.005 to 0.05 and balance iron and incidental elements and impurities.  
   
   
       9 . The method of  claim 7 , wherein said prealloyed powder comprises, in weight percent, C 0.01 to 0.04, Mn 0.2 to 0.4, Si 0.15 to 0.4, Cr 4.7 to 5.3, Mo 7.5 to 8.5, Ni 1.7 to 2.3, Co 10.75 to 12, S 0.01 to 0.03 and balance iron and incidental elements and impurities.  
   
   
       10 . The method of  claim 7 ,  8  or  9 , wherein maraging heat treatment is performed at temperatures within a range of 540 to 700 degrees C.