Low ni-containing steel alloys with hydrogen degradation resistance

Abstract

The present invention provides steel alloys with hydrogen degradation resistance comprising controlled amounts of Mn and C, as well as Al, Cr, Cu, Ni and Si. The steel alloys have an austenite microstructure and relatively high stacking fault energies, which avoid the formation of martensitic phases that reduce hydrogen resistance.

What is claimed is: 
     
         1 . A hydrogen degradation resistant steel alloy comprising from 15 to 30 weight percent Mn, from 0.15 to 1 weight percent C, and from 0.05 to 3 weight percent Al, wherein the steel alloy has a microstructure comprising at least 99 percent volume austenite, and possesses a relative reduction in area of no more than 20 percent. 
     
     
         2 . The steel alloy of  claim 1 , wherein the C is greater than 0.2 weight percent. 
     
     
         3 . The steel alloy of  claim 1 , wherein the Mn is greater than 18 weight percent. 
     
     
         4 . The steel alloy of  claim 1 , wherein when the Mn is less than 18 weight percent, the C is greater than 0.2 weight percent. 
     
     
         5 . The steel alloy of  claim 1 , wherein when the C is less than 0.3 weight percent, the Mn is greater than 18 weight percent. 
     
     
         6 . The steel alloy of  claim 1 , wherein the Mn comprises from 18 to 25 weight percent, and the C comprises from 0.3 to 1 weight percent. 
     
     
         7 . The steel alloy of  claim 1 , wherein the Mn comprises from 20 to 24 weight percent, and the C comprises from 0.4 to 0.6 weight percent. 
     
     
         8 . The steel alloy of  claim 1 , further comprising from 0.8 to 2.5 weight percent Ni. 
     
     
         9 . The steel alloy of  claim 1 , further comprising at least 0.2 weight percent Cu. 
     
     
         10 . The steel alloy of  claim 1 , further comprising from 0.8 to 2.5 weight percent Ni, and from 0.2 to 2 weight percent Cu. 
     
     
         11 . The steel alloy of  claim 10 , further comprising at least 0.5 weight percent Si. 
     
     
         12 . The steel alloy of  claim 10 , further comprising at least 1 weight percent Cr. 
     
     
         13 . The steel alloy of  claim 10 , further comprising from 0.5 to 4 weight percent Si, and from 1 to 3.5 weight percent Cr. 
     
     
         14 . The steel alloy of  claim 1 , further comprising at least 0.02 weight percent Ti. 
     
     
         15 . The steel alloy of  claim 1 , wherein the Mn comprises from 20 to 24 weight percent, and the C comprises from 0.3 to 0.6 weight percent. 
     
     
         16 . The steel alloy of  claim 15 , further comprising from 0.8 to 2.5 weight percent Ni, and from 0.2 to 2 weight percent Cu. 
     
     
         17 . The steel alloy of  claim 16 , further comprising from 0.5 to 4 weight percent Si, and from 1 to 3.5 weight percent Cr. 
     
     
         18 . The steel alloy of  claim 17 , wherein the Al comprises from 1.4 to 1.8 weight percent, the Ni comprises from 1.2 to 1.5 weight percent, the Cu comprises from 0.6 to 1.2 weight percent, the Si comprises from 2 to 3.2 weight percent, and the Cr comprises from 2 to 3.2 weight percent. 
     
     
         19 . The steel alloy of  claim 18 , further comprising from 0.08 to 0.2 weight percent Ti. 
     
     
         20 . The steel alloy of  claim 1 , wherein the microstructure comprises at least 99.5 volume percent austenite. 
     
     
         21 . The steel alloy of  claim 1 , wherein the relative reduction in area is less than 15 percent. 
     
     
         22 . The steel alloy of  claim 1 , wherein the steel alloy possesses an ultimate tensile strength of greater than 700 MPa, and a total elongation of greater than 50 percent. 
     
     
         23 . A method of producing the steel alloy of  claim 1 , comprising hot rolling the steel alloy to form a slab and cooling the slab. 
     
     
         24 . The method of  claim 23 , further comprising subjecting the steel alloy slab to electrochemical charging to generate nascent atomic hydrogen.