Heat Treatment of Steel Machinery's Handbook, 31st Edition
489
Table 5a. Typical Heat Treatments for SAE Alloy Steels (Carburizing Grades) Table 5a. (Continued) Typical Heat Treatments for SAE Alloy Steels
Carburized
Reheat
Temper, d
Cycle Anneal b
SAE No.
Normalize a
Deg. F
Deg. C
Deg. F Deg. C
Deg. F Deg. C
yes 1650–1700 899–927 E 1425–1475 e 774–802 e E 250–350 121–177 yes 1650–1700 899–927 E 1475–1527 f 802–831 f E 250–350 121–177 yes 1650–1700 899–927 C 1425–1475 e 774–802 e E 250–350 121–177 yes 1650–1700 899–927 C 1475–1525 f 802–829 f E 250–350 121–177
yes yes yes yes yes yes yes yes i yes i yes i yes i yes yes yes yes yes yes yes yes yes yes yes yes i
4317 & 4320 4608 to 4621
yes 1650–1700 899–927 E g yes 1650–1700 899–927 E g
… … … 250–350 121–177 … … … 250–350 121–177 … … … 250–350 121–177
816–899 h E
… 1500–1650 h
yes 1650–1700 899–927 E 1375–1425 e 746–774 e E 250–350 121–177 yes 1650–1700 899–927 E 1450–1500 f 788–816 f E 250–350 121–177 yes 1650–1700 899–927 C 1375–1425 e 746–774 e E 250–350 121–177
4812 to 4820
yes 1650–1700 899–927 C 1450–1500 f 788–816 f E 250–350 121–177 … … 1650–1700 899–927 E g … … … 250–350 121–177
… 1650–1700 899–927 E 1425–1475 e 774–802 e E 250–350 121–177 … 1650–1700 899–927 E 1500–1550 f 816–843 f E 250–350 121–177 … 1650–1700 899–927 C 1425–1475 e 774–802 e E 250–350 121–177 … 1650–1700 899–927 C 1500–1550 f 816–843 f E 250–350 121–177 yes 1650–1700 899–927 E 1475–1525 e 802–829 e E 250–350 121–177 yes 1650–1700 899–927 E 1525–1575 f 829–857 f E 250–350 121–177 yes 1650–1700 899–927 C 1475–1525 e 802–829 e E 250–350 121–177 yes 1650–1700 899–927 C 1525–1575 f 829–857 f E 250–350 121–177 … 1500–1650 h 816–899 h E … … … 250–350 121–177
5115 & 5120
8615 to 8625 8720
yes 1650–1700 899–927 E g
… … … 250–350 121–177 … … … 250–350 121–177
yes 1500–1650 h
816–899 h E
… 1650–1700 899–927 E 1400–1450 e 760–788 e E 250–350 121–177
9310 to 9317
yes i … 1650–1700 899–927 C 1500–1525 816–829 E 250–350 121–177 a Normalizing temperatures should be not less than 50°F (28°C) higher than the carburizing temperature. Follow by air cooling. b For cycle annealing, heat to normalizing temperature; hold for uniformity; cool rapidly to 1000–1250°F (538–677°C); hold 1 to 3 hours; then air or furnace cool to obtain a structure suitable for machining and finishing. c Symbols: C = cool slowly; E = oil. d Tempering treatment is optional and is generally employed for partial stress relief and improved resistance to cracking from grinding operations. e For use when case hardness only is paramount. f For use when higher core hardness is desired. g Treatment is for fine-grained steels only, when a second reheat is often unnecessary. h Treatment is for activated or cyanide baths. Parts may be given refining heats as indicated for other heat-treating processes. i After normalizing, reheat to temperatures of 1000–1200°F (538–649°C) and hold approximately 4 hours. Metallography.— The science or study of the microstructure of metal is known by most metallurgists as “metallography” or sometimes “crystallography”. The examination of metals and metal alloys by the aid of the microscope is one of the most effective methods of studying their properties and is also a valuable means of controlling the quality of man ufactured metallic articles and of testing the finished product. In preparing the specimen, a flat surface is first formed by filing or grinding and then given a high polish, which is later etched in order to clearly reveal the internal structure under the microscope. This process clearly shows an experienced observer the effect of variation in composition, heat treatment, etc., and in many cases it has proved a correct means of determining certain properties of industrial products that a chemical analysis has failed to reveal.
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