CASE HARDENING STEELS
BS970: 1955 BS970: 1991 COLOUR CODE DESCRIPTION 
EN34665M17orange/redBlack 2% low carbon nickel molybdenum case hardening steel       
EN36B655M13orangeBright / black 3% nickel chromium case hardening steel       
EN39B835M15orange/light blueBright / black 4.1/4% nickel chromium case hardening steel       
EN41B905M39orange/blackBlack 1.1/2% chromium aluminium molybdenum nitriding steel       
EN351635M15orange/whiteBright / black 3/4% nickel chromium case hardening steel       
EN352637M17orange/yellowBright / black 1% nickel chromium case hardening steel       
EN353815M17orange/greenBright / black 1.1/4% nickel chromium case hardening steel