266 



HANDBOOK OF MECHANICAL DESIGN 

 FLAME HARDENING DATA 



0.2 



04 



0.6 



1.4 



r.6 



1.8 



0.8 1.0 1.2 



Carbon, Per Ceni 



RELATION BETWEEN BRINELL HARDNESS AND CARBON CONTENT WHEN STEEL IS COOLED SLOWLY 



AND WHEN WATER QUENCHED 



600 

 500 



]400 



i- 300 



200 



I 



; 100 



0.04 



0.16 



Q20 



Q08 0,12 



Depth, Inches 



DEPTH HARDNESS CURVES OF FLAME 

 HARDENED S.A.E. 4140 ANNEALED STEEL 



008 0.16 Q24 Q3Z Q38 



Depf h Below Surface, Inches 



HARDNESS FROM SURFACE TO CORE OF FLAME 

 HARDENED S.A.E. 1045 STEEL 



Flame Hardening Specifications 



Material. — Cast iron, malleable iron, and any alloy steels other than tool steels, 

 with carbon content equal to S.A.E. 1040 or higher, depending on the hardness 

 desired. 



Preparation. — In order to assure freedom from surface cracking, the steel should 

 be stress-reheved bj^ anneahng or normahzing before flame hardening. 



Hardness Obtained. — Surface hardness of the case will depend on the carbon 

 content of the steel, as shown by the accompanying curves. 



Depth of Hardness. — Hardness varies with depth below the surface as shown by 

 the curves. 



Precautions. — Avoid overheating, which is one of the prime causes of surface 

 checking and cracks. 



Reference Literature. — "Flame Hardening by the Oxy-Acetylene Process," 

 published by the International Acetylene Association, 30 East 42nd Street, New York, 

 N. Y. 



