Machinery's Handbook, 31st Edition
GEAR MATERIALS
2323
Steels for Industrial Gearing
Hardness a
Case RC
Core BHN
Material Specification
Typical Heat Treatment, Characteristics, and Uses
Case-Hardening Steels
Carburize, harden, temper at 350 ° F. For gears that must be wear-resistant. Normalized material is easily machined. Core is ductile but has little strength. Harden, temper at 900 ° F, Nitride. For parts requiring greater wear resistance than that of through-hardened steels but unable to tolerate the distortion of carburizing. Case is shallow, core is tough. Carburize, harden, temper at 350 ° F. For gears requiring high fatigue resistance and strength. The 86xx series has better machinability. The 20 point steels are used for coarser teeth. Carburize, harden, temper at 300 ° F. Primarily for aerospace gears that are highly loaded and operate at high pitch line velocity and for other gears requiring high reliability under extreme operating conditions. This material is not used at high temperatures. Harden, temper at 1200 ° F, Nitride. For gears requiring high strength and wear resistance that cannot tolerate the distortion of the carburizing process or that operate at high temperatures. Gear teeth are usually finished before nitriding. Care must be exercised in running nitrided gears together to avoid crazing of case-hardened surfaces. Through-Hardening Steels Harden and temper to required hardness. Oil quench for lower hardness and water quench for higher hardness. For gears of medium and large size requiring moderate strength and wear resistance. Gears that must have consistent, solid sections to withstand quenching.
AISI 1020 AISI 1116 55-60 160-230
AISI 4130 AISI 4140 50-55 270-370
AISI 4615 AISI 4620 } 55-60 170-260 AISI 8615 AISI 8620 } 55-60 200-300
AISI 9310 58-63 250-350
Nitralloy N and Type 135 Mod. (15-N)
90-94 300-370
AISI 1045 AISI 1140 24-40
…
AISI 4140AISI 4340 Harden (oil quench), temper to required hardness. For gears requiring high strength and wear resistance, and high shock loading resistance. Use 41xx series for moderate sections and 43xx series for heavy sections. Gears must have consistent, solid sections to withstand quenching. a Hardness value scales are: RC for Rockwell C scale, BHN for Brinell Hardness Numbers. Worm Gears: For bronze worm gears, two alternative analyses of phosphor bronze are recommended, SAE No. 65 and No. 63. 24-40 … SAE No. 65 (called phosphor gear bronze) has the following composition: Copper, 88 to 90; tin, 10 to 12; phosphorus, 0.1 to 0.3; lead, zinc, and impurities (max) 0.5 percent. Good castings made of this alloy should have the following minimum physical charac teristics: Ultimate strength, 35,000 pounds per square inch; yield point, 20,000 pounds per square inch; elongation in 2 inches, 10 percent. The composition of SAE No. 63 (called leaded gun metal) follows: copper, 86 to 89; tin, 9 to 11; lead, 1 to 2.5; phosphorus (max), 0.25; zinc and impurities (max), 0.50 percent.
Copyright 2020, Industrial Press, Inc.
ebooks.industrialpress.com
Made with FlippingBook - Share PDF online