Austenitic steel alloy

Abstract

An austenitic steel alloy includes manganese in an amount of from 25 wt % to 31 wt %, aluminum in an amount of from 7 wt % to 10 wt %, carbon in an amount of from 1.2 wt % to 1.6 wt %, molybdenum in an amount of more than 0 wt % and less than 6 wt %, and a balance of iron.

What is claimed is: 
     
         1 . An austenitic steel alloy comprising:
 manganese in an amount of from 25 wt % to 31 wt %;   aluminum in an amount of from 7 wt % to 10 wt %;   carbon in an amount of from 1.2 wt % to 1.6 wt %;   molybdenum in an amount of more than 0 wt % and less than 6 wt %; and   a balance of iron.   
     
     
         2 . The austenitic steel alloy according to  claim 1 , wherein said manganese is in an amount of from 26 wt % to 30 wt % and said aluminum is in an amount of from 8 wt % to 10 wt %. 
     
     
         3 . The austenitic steel alloy according to  claim 2 , wherein said manganese is in an amount of from 27 wt % to 29 wt % and said molybdenum is in an amount of from 2 wt % to 6 wt %. 
     
     
         4 . The austenitic steel alloy according to  claim 3 , wherein said aluminum is in an amount of from 8 wt % to 9 wt %. 
     
     
         5 . The austenitic steel alloy according to  claim 1 , wherein said carbon is in an amount of from 1.4 wt % to 1.6 wt %. 
     
     
         6 . The austenitic steel alloy according to  claim 1 , wherein said molybdenum is in an amount of from 2 wt % to 6 wt. 
     
     
         7 . The austenitic steel alloy according to  claim 1 , further comprising chromium in an amount of less than 0 wt %. 
     
     
         8 . The austenitic steel alloy according to  claim 1 , further comprising cobalt in an amount of less than 5 wt %. 
     
     
         9 . A method for making an austenitic steel, comprising steps of:
 a) smelting the austenitic steel alloy of  claim 1  to obtain a molten steel alloy;   b) casting the molten steel alloy to obtain a cast piece;   c) subjecting the cast piece to a hot-working treatment at a temperature of from 1100° C. to 950° C. to obtain a hot-worked body;   d) subjecting the hot-worked body to an initial water-quenching treatment to obtain a water-quenched body; and   e) subjecting the water-quenched body to an aging treatment at a temperature of from 480° C. to 600° C. to obtain an aged body.   
     
     
         10 . The method according to  claim 9 , wherein the temperature for the aging treatment is from 480° C. to 500° C., and the aging treatment is implemented for a period of from 5 hours to 12 hours. 
     
     
         11 . The method according to  claim 9 , wherein the temperature for the aging treatment is larger than 500° C. and up to 600° C., and the aging treatment is implemented for a period of from 1 hour to 4 hours. 
     
     
         12 . The method according to  claim 9 , further comprising a step of subjecting the aged body to a further water-quenching treatment. 
     
     
         13 . The method according to  claim 9 , wherein in step c), the hot-worked body has a thickness of less than 25% of that of the cast piece. 
     
     
         14 . An austenitic steel made by the method according to  claim 9 , wherein said austenitic steel has a fully austenitic phase, a yield strength at 25° C. of from 1200 MPa to 1400 MPa, a Rockwell C hardness at 25° C. of from 45 to 55, an ultimate tensile strength at 25° C. of from 1200 MPa to 1500 MPa, and an elongation at 25° C. of from 20% to 40%. 
     
     
         15 . The austenitic steel according to  claim 14 , wherein said austenitic steel has an ultimate tensile strength at 300° C. of larger than 1000 MPa. 
     
     
         16 . The austenitic steel according to  claim 14 , wherein said austenitic steel has a yield strength at 300° C. of larger than 970 MPa. 
     
     
         17 . The austenitic steel according to  claim 14 , wherein said austenitic steel has a yield strength at 500° C. of larger than 650 MPa and an ultimate tensile strength at 500° C. of larger than 700 MPa. 
     
     
         18 . The austenitic steel according to  claim 14 , wherein said austenitic steel has a yield strength at 700° C. of from 410 MPa to 420 MPa and an ultimate tensile strength at 700° C. of from 440 MPa to 449 MPa.