Corrosion resistant metals and metal compositions

Abstract

A metal article including an at least partially heat treated metal composition, and a method for treating the metal article are provided. The method for treating the metal article may include heating the metal article to a first holding temperature of about 690° C., and holding the metal article at the first holding temperature for at least about 10 hours. The method may also include cooling the metal article from the first holding temperature to a first cooling temperature of about 65° C. or less. The method may further include heating the metal article to a second holding temperature of about 615° C., and holding the metal article at the second holding temperature for at least about 10 hours. The method may also include cooling the metal article from the second holding temperature to a second cooling temperature of about 65° C. or less.

We claim: 
     
         1 . A metal composition, comprising:
 about 0.03 wt % or less of carbon;   about 1.00 wt % or less of manganese;   about 0.015 wt % or less of sulfur;   about 0.03 wt % or less of phosphorus;   about 1.00 wt % or less of silicon;   about 3.50 wt % to about 4.50 wt % of nickel;   about 11.50 wt % to about 14.00 wt % of chromium;   about 0.40 wt % to about 1.00 wt % of molybdenum;   about 0.50 wt % or less of copper;   about 0.06 wt % or less of cobalt;   about 0.10 wt % or less of tungsten;   about 0.05 wt % or less of vanadium;   about 0.02 wt % or less of nitrogen; and   a balance of iron and impurities.   
     
     
         2 . The metal composition of  claim 1 , wherein the metal composition comprises about 0.50 wt % of the impurities. 
     
     
         3 . The metal composition of  claim 1 , wherein the metal composition comprises about 0.30 wt % of the impurities. 
     
     
         4 . The metal composition of  claim 1 , wherein the metal composition comprises:
 about 0.02 wt % or less of the carbon;   about 0.01 wt % or less of the sulfur;   about 0.02 wt % or less of the phosphorus;   about 0.05 wt % or less of the cobalt; and   about 0.015 wt % of the nitrogen.   
     
     
         5 . The metal composition of  claim 1 , wherein the metal composition comprises:
 about 0.015 wt % or less of the carbon;   about 0.005 wt % or less of the sulfur;   about 0.015 wt % or less of the phosphorus;   about 0.04 wt % or less of the cobalt; and   about 0.01 wt % of the nitrogen.   
     
     
         6 . A metal article, comprising:
 an at least partially heat treated metal composition, wherein, prior to at least partially heat treating, the metal composition comprises:
 about 0.03 wt % or less of carbon; 
 about 1.00 wt % or less of manganese; 
 about 0.015 wt % or less of sulfur; 
 about 0.03 wt % or less of phosphorus; 
 about 1.00 wt % or less of silicon; 
 about 3.50 wt % to about 4.50 wt % of nickel; 
 about 11.50 wt % to about 14.00 wt % of chromium; 
 about 0.40 wt % to about 1.00 wt % of molybdenum; 
 about 0.50 wt % or less of copper; 
 about 0.06 wt % or less of cobalt; 
 about 0.10 wt % or less of tungsten; 
 about 0.05 wt % or less of vanadium; 
 about 0.02 wt % or less of nitrogen; and 
 a balance of iron and impurities. 
   
     
     
         7 . The metal article of  claim 6 , further comprising a Rockwell hardness C of about 23 HRC or greater. 
     
     
         8 . The metal article of  claim 6 , further comprising a Rockwell hardness C of about 20 HRC or greater. 
     
     
         9 . The metal article of  claim 6 , further comprising a Brinell hardness of about 255 HBW or greater. 
     
     
         10 . The metal article of  claim 6 , further comprising a Brinell hardness of about 240 HBW or greater. 
     
     
         11 . A method for treating a metal article, the method comprising:
 heating the metal article to a first holding temperature of about 690° C., wherein the metal article comprises carbon, manganese, sulfur, phosphorus, silicon, nickel, chromium, molybdenum, copper, cobalt, tungsten, vanadium, and iron;   holding the metal article at the first holding temperature for at least about 10 hours;   cooling the metal article from the first holding temperature to a first cooling temperature of about 65° C. or less;   heating the metal article to a second holding temperature of about 615° C.;   holding the metal article at the second holding temperature for at least about 10 hours; and   cooling the metal article from the second holding temperature to a second cooling temperature of about 65° C. or less.   
     
     
         12 . The method of  claim 11 , further comprising:
 cooling the metal article from the first holding temperature to ambient temperature; and   holding the metal article at ambient temperature for at least about 24 hours.   
     
     
         13 . The method of  claim 12 , wherein:
 the metal article has a thickness of about 12.7 cm or greater; and   holding the metal article at ambient temperature for at least about 24 hours further comprises holding the metal article at ambient temperature for an additional five hours for each 2.54 cm of the thickness greater than about 12.7 cm.   
     
     
         14 . The method of  claim 11 , wherein:
 the metal article has a thickness of about 12.7 cm or greater; and   holding the metal article at the first holding temperature for at least about 10 hours further comprises holding the metal article at the first holding temperature for an additional one hour for each 2.54 cm of the thickness greater than about 12.7 cm.   
     
     
         15 . The method of  claim 11 , wherein:
 the metal article has a thickness of about 12.7 cm or greater; and   cooling the metal article from the first holding temperature to the first cooling temperature further comprises cooling the metal article at a rate of about 55° C. per hour or lower.   
     
     
         16 . The method of  claim 11 , wherein:
 the metal article has a thickness of about 2.54 cm or less; and   cooling the metal article from the first holding temperature to the first cooling temperature further comprises cooling the metal article at a rate of about 275° C. per hour or lower.   
     
     
         17 . The method of  claim 11 , wherein:
 the metal article has a thickness of about 2.54 cm to about 12.7 cm; and   cooling the metal article from the first holding temperature to the first cooling temperature further comprises cooling the metal article at a rate of about 275° C. per hour divided by the thickness of the metal article or lower.   
     
     
         18 . The method of  claim 11 , wherein:
 the metal article has a thickness of about 10.16 cm or greater; and   heating the metal article to the first holding temperature further comprises heating the metal article at a rate of about 55° C. per hour or lower.   
     
     
         19 . The method of  claim 11 , wherein:
 the metal article has a thickness of about 10.16 cm or less; and   heating the metal article to the first holding temperature further comprises heating the metal article at a rate of about 225° C. per hour or lower.   
     
     
         20 . The method of  claim 11 , wherein the metal article comprises:
 about 0.03 wt % or less of the carbon;   about 1.00 wt % or less of the manganese;   about 0.015 wt % or less of the sulfur;   about 0.03 wt % or less of the phosphorus;   about 1.00 wt % or less of the silicon;   about 3.50 wt % to about 4.50 wt % of the nickel;   about 11.50 wt % to about 14.00 wt % of the chromium;   about 0.40 wt % to about 1.00 wt % of the molybdenum;   about 0.50 wt % or less of the copper;   about 0.06 wt % or less of the cobalt;   about 0.10 wt % or less of the tungsten;   about 0.05 wt % or less of the vanadium;   about 0.02 wt % or less of the nitrogen; and   a balance of the iron and impurities.