Commonly Used Materials For Gears
Gears rely on their own structural dimensions and material strength to withstand external loads, which requires materials to have high strength, toughness and wear resistance; due to the complex shape of the gears, the gears require high precision, and the materials also require good manufacturability.
Commonly used materials are forged steel, cast steel, and cast iron.
1. Forged steel
According to the hardness of the tooth surface, it is divided into two categories
When HB＜350, it is called soft tooth surface
When H8>350, it is called hard tooth surface
l. Tooth surface hardness HB＜350
Process: forging blank → normalizing – rough turning → quenching and tempering, finishing
Commonly used materials; 45#, 35SiMn, 40Cr, 40CrNi, 40MnB
Features:
It has good overall performance, the tooth surface has high strength and hardness, and the tooth core has good toughness.
After heat treatment, the precision of gear cutting can reach 8 levels.
The manufacturing is simple, economical, and the productivity is high, and the accuracy requirements are not high.
2. Tooth surface hardness HB＞350
When using medium carbon steel:
Process: forging blank → normalization → rough cutting → quenching and tempering → fine cutting → high and medium frequency quenching → low temperature tempering → honing or abrasive running-in, electric spark running-in.
Commonly used materials: 45, 40Cr, 40CrNi.
Features:
The tooth surface hardness is high HRC=48-55, the contact strength is high, and the wear resistance is good.
The tooth core maintains toughness after quenching and tempering, has good impact resistance and high load-bearing capacity.
The accuracy is reduced by half, up to 7 levels of accuracy.
Suitable for mass production, such as medium-speed and medium-load transmission gears for automobiles, machine tools, etc.
When using low carbon steel:
Forging blank → normalization → rough cutting → quenching and tempering → fine cutting → carburizing and quenching → low temperature tempering → tooth grinding. Up to level 6 and level 7.
Common materials: 20Cr, 20CrMnTi, 20MnB, 20CrMnTo.