DIRECT HARDENING STEELS
BS970: 1955 BS970: 1991 COLOUR CODE DESCRIPTION 
EN16T605M36Tblue/redBright / black manganese molybdenum steel       
EN16MT606M36Tblue/greenBright drawn semi freecutting manganese molybdenum steel       
EN19T709M40Tblue/yellowBright / black 1% chromium molybdenum steel       
EN24T817M40TblueBright / black 1.1/2% nickel chromium molybdenum steel       
EN24 ANNEALED817M40 ANNEALEDblue/brownBright drawn 1.1/2% nickel chromium molybdenum steel       
EN30B835M30blue/purpleBlack 4.1/4% nickel chromium (with/without) molybenum steel       
EN31535A99blue/whiteBright 1% carbon chromium steel       
EN40BT722M24Tblue/blackBlack 3% chromium molybdenum nitriding steel