High strength alloy steels and methods of making the same

Abstract

A method for producing alloy steel is provided. An alloy mixture may be melted to produce a melted alloy mixture. The alloy mixture comprises 2 to 4 weight % chromium (Cr), 12 to 16 weight % manganese (Mn), at most 4 weight % silicone (Si), 1 to 3 weight % aluminum (Al), at most 0.3 weight % carbon (C) and iron (Fe). The melted alloy mixture may be formed into a product. The product may be heated to produce a thermally homogenized product. The thermally homogenized product may be hot rolled into a plate with a first thickness. The plate may be warm rolled at a warm rolling temperature until the plate has a second thickness. The warm rolling temperature may be configured such that a crystal structure of the plate has 30 to 70 volume % austenite. The warm rolling temperature may be between 350° C. and 550° C.

What is claimed is: 
     
         1 . An alloy steel, comprising:
 2 to 4 weight % chromium (Cr);   12 to 16 weight % manganese (Mn);   at most 4 weight % silicone (Si);   1 to 3 weight % aluminum (Al);   at most 0.3 weight % carbon (C); and   iron (Fe).   
     
     
         2 . The alloy steel of  claim 1 , having a nickel (Ni) content of at most 1.5 weight %. 
     
     
         3 . The alloy steel of  claim 1 , having a copper (Cu) content of at most 3 weight %. 
     
     
         4 . The alloy steel of  claim 1 , wherein:
 the chromium is present at 2.9 to 3.1 weight %;   the manganese is present at 13.9 to 14.1 weight %;   the silicone is present at 0.9 to 1.1 weight %;   the aluminum is present at 1.9 to 2.1 weight %; and   the carbon is present at 0.09 to 0.11 weight %.   
     
     
         5 . The alloy steel of  claim 4 , having at least one of:
 a tensile strength of at least 1765 megapascals (MPa), a yield strength of at least 1476 MPa and a total elongation of at least 13%;   a tensile strength of at least 1508 MPa, a yield strength of at least 978 and a total elongation of at least 27.8%;   a tensile strength of at least 1696 MPa, a yield strength of at least 907 and a total elongation of at least 27.8%;   a tensile strength of at least 1538 MPa, a yield strength of at least 1029 and a total elongation of at least 25%; or   a tensile strength of at least 1481 MPa, a yield strength of at least 335 and a total elongation of at least 24.8%.   
     
     
         6 . The alloy steel of  claim 4 , having a copper content of 1.5 to 2.5 weight %. 
     
     
         7 . The alloy steel of  claim 6 , having at least one of:
 a tensile strength of at least 1515 MPa, a yield strength of at least 1099 MPa and a total elongation of at least 41%;   a tensile strength of at least 1368 MPa, a yield strength of at least 1029 MPa and a total elongation of at least 44.8%;   a tensile strength of at least 1353 MPa, a yield strength of at least 986 MPa and a total elongation of at least 39.3%;   a tensile strength of at least 1414 MPa, a yield strength of at least 753 MPa and a total elongation of at least 42%; or   a tensile strength of at least 1268 MPa, a yield strength of at least 392 MPa and a total elongation of at least 42%.   
     
     
         8 . The alloy steel of  claim 1 , having a nickel content of 1.0 to 1.6 weight % and a copper content of 0.5 to 1.1 weight %, wherein:
 the chromium is present at 2.4 to 2.6 weight %;   the manganese is present at 13.9 to 14.1 weight %;   the silicone is present at 2.6 to 2.8 weight %;   the aluminum is present at 1.9 to 2.1 weight %; and   the carbon is present at 0.19 to 0.21 weight %.   
     
     
         9 . The alloy steel of  claim 8 , having at least one of:
 a tensile strength of at least 1628 MPa, a yield strength of at least 1485 MPa and a total elongation of at least 25.8%;   a tensile strength of at least 1698 MPa, a yield strength of at least 1584 MPa and a total elongation of at least 37%;   a tensile strength of at least 1700 MPa, a yield strength of at least 1499 MPa and a total elongation of at least 39.4%;   a tensile strength of at least 1657 MPa, a yield strength of at least 1482 MPa and a total elongation of at least 41%; or   a tensile strength of at least 1649 MPa, a yield strength of at least 547.2 MPa and a total elongation of at least 40.1%.   
     
     
         10 . A method for producing an alloy steel, comprising:
 melting an alloy mixture to produce a melted alloy mixture;   forming the melted alloy mixture into a product;   heating the product to produce a thermally homogenized product;   hot rolling the thermally homogenized product into a plate with a first thickness; and   warm rolling the plate at a warm rolling temperature until the plate has a second thickness, wherein the warm rolling temperature is configured such that a crystal structure of the plate has 30 to 70 volume % austenite.   
     
     
         11 . The method of  claim 10 , wherein at least one of:
 the warm rolling temperature is between 350° C. and 550° C.;   the second thickness is between 0.9 millimeters (mm) and 1.1 mm; or   a thickness reduction of the first thickness to the second thickness is 60% to 70%.   
     
     
         12 . The method of  claim 10 , wherein at least one of:
 the thermally homogenized product is hot rolled at one or more hot rolling temperatures between 800° C. and 1200° C.;   the first thickness is between 2 mm and 4 mm; or   a thickness reduction of a thickness of the thermally homogenized product to the first thickness is 70% to 90%.   
     
     
         13 . The method of  claim 10 , wherein the product comprises at least one of one or more slabs, one or more ingots or one or more billets. 
     
     
         14 . The method of  claim 10 , wherein the product is heated at 1000° C. to 1200° C. for 3 to 5 hours to produce the thermally homogenized product. 
     
     
         15 . The method of  claim 10 , comprising:
 prior to warm rolling the plate and responsive to hot rolling the plate, cooling the plate until the plate reaches a second temperature between 500° C. and 900° C.; and   responsive to the plate reaching the second temperature, maintaining a temperature of the plate for 45 min to 75 min at a third temperature between 500° C. and 900° C.   
     
     
         16 . The method of  10 , comprising:
 responsive to warm rolling the plate, heat treating the plate at a heat treatment temperature, wherein the heat treatment temperature is configured such that at least one of:   15 to 25 volume % austenite is formed;   40 to 60 volume % austenite is formed;   70 to 90 volume % austenite is formed; or   at least 95 volume % austenite is formed.   
     
     
         17 . A method for producing an alloy steel, comprising:
 melting an alloy mixture to produce a melted alloy mixture, wherein the alloy mixture comprises:
 2 to 4 weight % chromium (Cr); 
 12 to 16 weight % manganese (Mn); 
 at most 4 weight % silicone (Si); 
 1 to 3 weight % aluminum (Al); 
 at most 0.3 weight % carbon (C); and 
 iron (Fe); 
   forming the melted alloy mixture into a product;   heating the product to produce a thermally homogenized product;   hot rolling the thermally homogenized product into a plate with a first thickness; and   warm rolling the plate at a warm rolling temperature until the plate has a second thickness, wherein the warm rolling temperature is configured such that a crystal structure of the plate has 30 to 70 volume % austenite.   
     
     
         18 . The method of  17 , comprising:
 responsive to warm rolling the plate, heat treating the plate at a heat treatment temperature for a specified duration of time, wherein:
 the chromium is present at 2.9 to 3.1 weight %; 
 the manganese is present at 13.9 to 14.1 weight %; 
 the silicone is present at 0.9 to 1.1 weight %; 
 the aluminum is present at 1.9 to 2.1 weight %; and 
 the carbon is present at 0.09 to 0.11 weight %; and 
   at least one of:
 the heat treatment temperature is between 180° C. and 220° C. and the specified duration of time is between 15 minutes and 25 minutes, wherein the plate has a tensile strength of at least 1508 MPa, a yield strength of at least 978 and a total elongation of at least 27.8%; 
 the heat treatment temperature is between 430° C. and 470° C. and the specified duration of time is between 15 minutes and 25 minutes, wherein the plate has a tensile strength of at least 1696 MPa, a yield strength of at least 907 and a total elongation of at least 27.8%; 
 the heat treatment temperature is between 500° C. and 540° C. and the specified duration of time is between 15 minutes and 25 minutes, wherein the plate has a tensile strength of at least 1538 MPa, a yield strength of at least 1029 and a total elongation of at least 25%; or 
 the heat treatment temperature is between 800° C. and 900° C. and the specified duration of time is between 5 minutes and 15 minutes, wherein the plate has a tensile strength of at least 1481 MPa, a yield strength of at least 335 and a total elongation of at least 24.8%. 
   
     
     
         19 . The method of  17 , comprising:
 responsive to warm rolling the plate, heat treating the plate at a heat treatment temperature for a specified duration of time, wherein:
 the alloy mixture has a copper content of 1.5 to 2.5 weight %; 
 the chromium is present at 2.9 to 3.1 weight %; 
 the manganese is present at 13.9 to 14.1 weight %; 
 the silicone is present at 0.9 to 1.1 weight %; 
 the aluminum is present at 1.9 to 2.1 weight %; and 
 the carbon is present at 0.09 to 0.11 weight %; and 
   at least one of:
 the heat treatment temperature is between 270° C. and 310° C. and the specified duration of time is between 15 minutes and 25 minutes, wherein the plate has a tensile strength of at least 1368 MPa, a yield strength of at least 1029 MPa and a total elongation of at least 44.8%; 
 the heat treatment temperature is between 430° C. and 470° C. and the specified duration of time is between 15 minutes and 25 minutes, wherein the plate has a tensile strength of at least 1353 MPa, a yield strength of at least 986 MPa and a total elongation of at least 39.3%; 
 the heat treatment temperature is between 560° C. and 600° C. and the specified duration of time is between 15 minutes and 25 minutes, wherein the plate has a tensile strength of at least 1414 MPa, a yield strength of at least 753 MPa and a total elongation of at least 42%; or 
 the heat treatment temperature is between 800° C. and 900° C. and the specified duration of time is between 5 minutes and 15 minutes, wherein the plate has a tensile strength of at least 1268 MPa, a yield strength of at least 392 MPa and a total elongation of at least 42%. 
   
     
     
         20 . The method of  17 , comprising:
 responsive to warm rolling the plate, heat treating the plate at a heat treatment temperature for a specified duration of time, wherein:
 the alloy mixture has a copper content of 0.5 to 1.1 weight %; 
 the alloy mixture has a nickel content of 1.0 to 1.6 weight %; 
 the chromium is present at 2.4 to 2.6 weight %; 
 the manganese is present at 13.9 to 14.1 weight %; 
 the silicone is present at 2.6 to 2.8 weight %; 
 the aluminum is present at 1.9 to 2.1 weight %; and 
 the carbon is present at 0.19 to 0.21 weight %; and 
   at least one of:
 the heat treatment temperature is between 280° C. and 320° C. and the specified duration of time is between 15 minutes and 25 minutes, wherein the plate has a tensile strength of at least 1698 MPa, a yield strength of at least 1584 MPa and a total elongation of at least 37%; 
 the heat treatment temperature is between 450° C. and 490° C. and the specified duration of time is between 15 minutes and 25 minutes, wherein the plate has a tensile strength of at least 1700 MPa, a yield strength of at least 1499 MPa and a total elongation of at least 39.4%; 
 the heat treatment temperature is between 530° C. and 570° C. and the specified duration of time is between 15 minutes and 25 minutes, wherein the plate has a tensile strength of at least 1657 MPa, a yield strength of at least 1482 MPa and a total elongation of at least 41%; or 
 the heat treatment temperature is between 800° C. and 900° C. and the specified duration of time is between 5 minutes and 15 minutes, wherein the plate has a tensile strength of at least 1649 MPa, a yield strength of at least 547.2 MPa and a total elongation of at least 40.1%.