The common materials for gears

The common materials are forged steel, cast steel and cast iron.

Forged steel:

According to the hardness of tooth surface, it can be divided into two categories

When HB < 350, it is called soft tooth surface

When H8 > 350, it is called hard tooth surface

Hardness of tooth surface HB < 350

Process: forging blank → normalizing — rough turning → tempering and finishing

Common materials: 45 × 45, 35SiMn, 40Cr, 40crni, 40MnB


It has better comprehensive performance, higher strength and hardness of tooth surface, and better toughness of tooth core.

After heat treatment, the cutting accuracy can reach 8 grades.

Manufacturing is simple, economic, high productivity, and the requirement for accuracy is not high.

Hardness of tooth surface HB > 350

When medium carbon steel is used:

Technological process: forging blank → normalization → rough cutting → tempering → fine cutting → high and medium frequency quenching → low temperature tempering → honing or grinding agent running in, electric spark running in.

Common materials: 45, 40Cr, 40crni.


High hardness of tooth surface HRC = 48-55, high contact strength, good wear resistance.

The tooth core maintains the toughness after quenching and tempering, has good impact resistance and high bearing capacity.

The accuracy can be reduced by half to 7 levels.

Suitable for mass production, such as: automobile, machine tools and other medium speed medium load gearbox gear.

When using low carbon steel:

Forging blank → normalization → rough cutting → tempering → fine cutting → carburizing and quenching → low temperature tempering → gear grinding. Up to level 6 and 7.

Common materials: 20Cr, 20CrMnTi, 20mnb, 20crmnto