TS 
 
_- 1900 c 
 
 
 HEAT-TREATING CHA 
 
 TO REFINE CARBON STEEL 
 Heat evenly to just above 
 the critical temperature, 
 shown by the red curve 
 line, in relation to the car- 
 bon content. 
 
 
 Carbon 
 
 1300° 
 
 .20 .30 .40 
 
 REMARKS 
 
 1. 
 
 Always use a rising 
 Check temperatures 1 
 Heat colors observed 
 Use as a guide only. 
 
 5 V 
 
 ^ 1 9 oil 
 
 QotV'lbl »9;n (> x V.S.Ya 
 
 ■55883 
 
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Digitized by the Internet Archive 
 in 2011 with funding from 
 The Library of Congress 
 
 http://www.archive.org/details/heattreatingcharOOyarn 
 
CENT. FAHR. 
 
 _— 1900 c 
 
 HEAT-TREATING CHART— Showing Critical Temperatures for Carbon Steel 
 
 
 TO REFINE CARBON STEEL 
 Heat evenly to just above 
 the critical temperature, 
 shown by the red curve 
 line, in relation to the car- 
 bon content. 
 
 AFTER HEATING TO REFINING TEMPERATURE 
 
 1 . TO ANNEAL-AIlow to cool in the furnace, 
 
 in ashes, or in the air, depend- 
 ing on the carbon content, sec- 
 tion and degree of softness 
 required. 
 
 2. TO HARDEN— Quench in water or oil, de- 
 pending on the carbon content, 
 section and degree of hardness 
 required. 
 
 TO DRAW BACK AFTER HARDEN- 
 ING, reheat to any temperature 
 under 1350° F., depending on 
 properties required. 
 
 TO TEMPER FOR TOOLS,— 
 after hardening, draw temper 
 between 430° F. (light yellow) 
 625° F. (peacock green) tem- 
 per color, depending on the 
 use, and degree of hardness 
 required. 
 
 HEAT TREATING CARBON STEEL 
 
 REFINING 
 
 Heating carbon steel evenly to just above the 
 critical temperature (shown on chart by red curve 
 line in relattorrto the carbon content) will refine 
 the grain structure, to the best possible condition. 
 This refinement can be retained in the steel when 
 cool to a great extent, either in the annealed, 
 hardened, drawn or tempered condition, by the 
 methods suggested. 
 
 TO DETERMINE RESULTS OF TREATMENT 
 
 Fractures of the treated steel will show the grain __L 
 structure and indicate to what extent the refine- 
 ment has been accomplished, 
 
 TO DEtERMINE THE CRITICAL TEMPERATURE 
 
 To find the critical temperature, when the car- 
 bon content is not known, overheat a small bar 
 several hundred degrees above its possible critical 
 temperature, and quench in water, break off 
 a small piece and observe the grain structure, 
 which should be coarse. Then reheat, as near as 
 possible to 1382° F-, for refining, quench in water 
 and fracture. If the grain is not refined, repeat 
 the operation at a little higher temperature until a 
 refined grain structure is obtained, which will in- 
 dicate that the critical temperature has been 
 reached. 
 
 l.OO 1.10 1.20 1.30 1.40 1.50 1.60 1.70 
 
 Use as a guide only. 
 
 REMARKS 
 
 Always use a rising temperature, in arriving at the critical point, for refining steel. 
 
 Check temperatures by pyrometer wherever possible. 
 
 Heat colors observed in moderate-diffused daylight approximate thi temperatures shown. 
 
 1.90 
 
 
 
 
 
 #sl p»B 
 
 V. S. YARN ALL, 1914