Gear Material Steels for Industrial Gearing

Gear Design & Engineering | Engineering Materials

Gear Material Steels for Industrial Gearing: These engineering materials are typical steel used within industrial applications. This list is by no means exhaustive however does provide a baseline in the section of engineering gear materials

Material
Hardness
Typical Heat Treatment,
Case
Core
Specification
Rc
Bhn
Characteristics, and Uses
Case-Hardening Steels

AISI 1020 
AISI 1116

55–60 160–230 Carburize, harden, temper at 350°F. For gears that must be wear-resistant. Normalizedmaterial is easily machined. Core is ductile but has little strength.
AISI 4130
AISI 4140
50–55 270–370 Harden, temper at 900°F, Nitride. For parts requiring greater wear resistance than that of through-hardened steels but cannot tolerate the distortion of carburizing. Case is shallow, core is tough.
AISI 4615
AISI 4620
AISI 8615
AISI 8620
} 55–60 } 55–60 170–260 200–300 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.
AISI 9310 58–63 250–350 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.
Nitralloy N and Type 135 Mod. (15-N) 90–94 300–370 For gears requiring high strength and wear resistance that cannot tolerate the distortion of thecarburizing 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
AISI 1045
AISI 1140
24–40 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.
      Harden (oil quench), temper to required hardness.
AISI 4140
AISI 4340
24–40 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.

Worm Gears: For bronze worm gears, two alternative analyses of phosphor bronze are recommended, SAE No. 65 and No. 63.

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 per cent.

Good castings made of this alloy should have the following minimum physical characteristics: Ultimate strength, 35,000 pounds per square inch; yield point, 20,000 pounds per square inch; elongation in 2 inches, 10 per cent.

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 per cent.

Good castings made of this alloy should have the following minimum physical characteristics: Ultimate strength, 30,000 pounds per square inch; yield point, 12,000 pounds per square inch; elongation in 2 inches, 10 per cent.

These alloys, especially No. 65, are adapted to chilling for hardness and refinement of grain. No. 65 is to be preferred for use with worms of great hardness and fine accuracy. No. 63 is to be preferred for use with unhardened worms.

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