Alloy and a method of making an alloy

Abstract

A bainitic steel alloy and a method for making such an alloy are disclosed, in which the bainite plates are particularly small, less than 50 nanometres in width. In preferred embodiments of the invention, each bainite plate is surrounded by a film of retained austenite; the level of retained austenite in the alloy is greater than 10%; and the alloy is substantially free of blocky unstable austenite and cementite.

1 . A bainitic steel alloy having the following composition in weight percent:
 carbon 0.6-1.0;   silicon 1-2;   manganese 0.5-2.5;   phosphorous 0-0.01;   sulphur 0-0.008;   chromium 0-1.3;   molybdenum 0.2-0.4;   nickel 0-1.3;   aluminium 0.01-0.06;   cobalt 0-4;   copper 0-0.07;   nitrogen 0.005-0.06;   niobium 0-0.01;   tin 0-0.07;   vanadium 0-0.3;   
       the remainder being iron save for incidental impurities. 
     
     
         2 . A bainitic steel alloy having the following composition in weight percent:
 carbon 0.7-0.85;   silicon 1-2;   manganese 0.5-2.5;   phosphorous 0-0.01;   sulphur 0-0.008;   chromium 1-2;   molybdenum 0.2-0.4;   nickel 0-0.08;   aluminium 0.01-0.06;   cobalt 1.4-5;   copper 0-0.1;   nitrogen 0.005-0.06;   niobium 0-0.005;   tin 0-0.1;   vanadium 0.1-0.3;   
       the remainder being iron save for incidental impurities. 
     
     
         3 . A bainitic steel alloy as claimed in  claim 2 , and having the following composition in weight percent:
 carbon 0.75-0.8;   silicon 1.3-1.4;   manganese 1.9-2.2;   phosphorous 0.005-0.008;   sulphur 0-0.005;   chromium 1.2-1.25;   molybdenum 0.3-0.35;   nickel 0-0.06;   aluminium 0.02-0.04;   cobalt 1.65-1.75;   copper 0-0.05;   nitrogen 0.01-0.04;   niobium 0-0.001;   tin 0-0.05;   vanadium 0.14-0.16;   
       the remainder being iron save for incidental impurities. 
     
     
         4 . A bainitic steel alloy having the following composition in weight percent:
 carbon 0.7-0.85;   silicon 1.2-2;   manganese 0.5-2.5;   phosphorous 0-0.01;   sulphur 0-0.008;   chromium 0-0.35;   molybdenum 0.2-0.4;   nickel 0.9-2;   aluminium 0.01-0.06;   cobalt 0-1.5;   copper 0-0.1;   nitrogen 0.005-0.06;   niobium 0-0.005;   tin 0-0.1;   vanadium 0-0.3;   
       the remainder being iron save for incidental impurities. 
     
     
         5 . A bainitic steel alloy as claimed in  claim 4 , and having the following composition in weight percent:
 carbon 0.75-0.8;   silicon 1.3-1.4;   manganese 1.9-2.2;   phosphorous 0.005-0.008;   sulphur 0-0.005;   chromium 0.2-0.25;   molybdenum 0.3-0.35;   nickel 1-1.1;   aluminium 0.02-0.04;   cobalt 0-0.05;   copper 0-0.05;   nitrogen 0.01-0.04;   niobium 0-0.001;   tin 0-0.05;   vanadium 0-0.01;   
       the remainder being iron save for incidental impurities.