112 



Tables 49 and 50 

 MECHANICAL PROPERTIES 



TABLE 49. — Carbon Steels — Commercial Experimental Values 



S. A. E. (Soc. of Automotive Eng., U. S. A.) classification scheme used as basis for steel groupings. First 

 two digits S. A. E. Spec. No. show steel group number, and last two (or three in case of five figures) show 

 carbon content in hundredths of one per cent. 



The first lines of properties for each steel show values for the rolled or forged metal in the annealed or nor- 

 malized condition. Comparative heat-treated values show properties after receiving modified S. A. E. heat 

 treatment as shown below (Table 50). The P-limit and ductility of cast steel average slightly lower and the 

 ultimate strength 10 to 15 per cent higher than the values shown for the same composition steel in the annealed 

 condition. The properties of rolled steel (raw) are approximately equal to those shown for the annealed con- 

 dition, which represents the normalized condition of the metal rather than the soft annealed state. 



The data for heat-treated strengths are average values for specimens for heat treatment ranging in size 

 from 5 to i£ in. diameter. The final drawing or quenching temperature for the properties shown is indicated 

 in degrees C with the heat treatment letter, wherever the information is available. In general, specimens 

 were drawn near the lower limit of the indicated temperature range. 



Structural Steel: Rolled: S max. 0.05; P-Bess. max. 0.10; -O-H. max. 0.06. 



Tension: Yield Point min. = 0.5 ultimate; ultimate = 38.7 to 45.7 kg/mm 2 or 55,000 to 65,000 lb/in- 

 with 227c min- elongation in 50.8 mm (2 in.). 



* Average carbon contents: steel castings, C 0.30 to 0.40; structural steel, C 0.15 to 0.30 (mild carbon or medium 

 hard steel). 



TABLE 50. — Explanation of Heat Treatment Letters used in Table of Steel Data 



Motor Transport Corps Modified S. A. E. Heat Treatments for Steels. (S. A. E. Handbook, Vol. 1, pp. 

 9d and ge, 1915, q. v. for alternative treatments.) 



Heat Treatment A. — After forging or machining (1) carbonize at a temperature ^tween 870 and 930° C 

 (1600 and 1700° F.); (2) cool slowly; (3) reheat to 760 to 820 C (1400 to 1500 F.) and quench in oil. 



Heat Treatment D. — After forging or machining: (1) heat to 820 to 840° C (1500 to 1550 F.); (2) quench; 

 (3) reheat to 790 to 820° C (1450 to 1500° F.); (4) quench; (5) reheat to 320 to 650^ } (600 to 1200° F.) 

 and cool slowly. 



Heat Treatment F. — After shaping or coiling: (1) heat to 775 to 800° C (1425 to 1475° F.); (2) quench; 

 (3) reheat to 200 to 480° C (400 to 900 F.) in accordance with degree of temper required and cool slowly. 



Heat Treatment H. — After forging or machining: (1) heat to 820 to 840° C (1500 to 1550° F.); 

 (2) quench; (3) reheat to 2^0 to 650 C (450 to 1200° F.) and cool slowly. 



Heat Treatment L. — After forging or machining: (1) carbonize at a temperature between 870 and 

 950° C (1600 and 1750 F.), preferably between 900 and 930 C (1650 and 1700 F.); (2) cool slowly in car- 

 bonizing material; (3) reheat to 790 to 820° C (1450 to 1500 F.); (4) quench; (5) reheat to 700 to 760 C 

 (1300 to 1400 F.); (6) quench; (7) reheat to 120 to 260 C (25010500 F.) and cool slowly. ' 



Heat Treatment M. — After forging or machining- (1) heat to 790 to 820 C (1450 to 1500 F.); 

 (2) quench; (3) reheat to between 260 and 68o° C (500 and 1250° F.) and cool slowly. 



Heat Treatment P. — After forging or machining: (1) heat to 790 to 820 C (1450 to 1500 F.); (2) 

 quench; (3) reheat to 750 to 770 C (1375 to 1425 F.); (4) quench; (5) reheat to 260 to 650 C (500 to 

 1200 F.) and cool slowlv. 



Heat Treatment T. — After forging or machining: (1) heat to 900 to 950 C (1650 to 1750 F.); (2) quench; 

 (0 reheat to 260 to 700 C (500 to 1300° F.) and cool slowly. 



Heat Treatment U. — After forging: (1) heat to 830 to 870 C (1525 to 1600° F.), hold half an hour; 

 (2) cool slowly; (3) reheat to 900 to 930° C (1650 to 1700° F.); (4) quench; (5; reheat to 180 to 290 C 

 (350 to 550° F.) and cool slowly. 



Heat Treatment V. — After forging or machining. (1) heat to 900 to 950° C (1650 to 175° F-)l 

 (2) quench; (3) reheat to between 200 and 650 C (400 and 1200 F.) and cool slowly. 



Editor's Note: Oil quenching is recommended wherever the instructions specify "quench," inasmuch as 

 the data in the table are taken from tests of automobile parts which must resist considerable vibration and 

 which are usually small in section. The quenching medium must always be carefully considered. 

 Smithsonian Tables. 



