HEAT TREATMENT TEMPERATURES FOR CARBON STEEL
         
Temperature Colour of Glowing Steel                                    
Fahrenheit Centigrade    
       
2350 1288   Dazzling White
2200 1204   White
1975 1079   Light Yellow
1825 996   Lemon
1725 941   Orange
1650 899   Salmon and Scaling
1550 843   Bright Red and Scaling
Note that Steel becomes non-magnetic while heating at about 780-820 deg C but while cooling at a different temperature
1375 746   Cherry Red
1250 677   Medium Cherry Red                
1075 579   Dark Cherry Red
1050 566   Blood Red
900 482   Faint red (GLOW)
                   
Temperature Surface colour of polished Steel HARDNESS TYPICAL APPLICATIONS
Fahrenheit Centigrade        
750 400   Grey    
610 321   Pale blue 53Rc  
567 297   Bright Blue 55Rc Cheap Kitchen knives
550 287   Dark Blue 56Rc Springs
531 277   Purple 57Rc Cold Chisels, punches
509 265   Brown & Purple 58Rc  
491 255   Brown 59Rc Taps and Scribers
469 243   Gold Yellow/Straw 60Rc  
428 220   Pale Yellow 61Rc  
400 200   Very Pale Yellow 62Rc Woodturning tools