Forged steel and cast steel are the common materials for gear manufacturing, followed by cast iron. In special cases, non-ferrous and non-metallic materials can also be used.
Steel: steel with carbon content of 0.1% – 0.6% is commonly used because of its best performance (mechanical properties can be improved by heat treatment).
Forged steel: the steel is forged and its performance is improved. The most commonly used steel is 45 steel.
Soft tooth surface gear (HB ≤ 350): blank → hot (positive, adjusting) → gear cutting (general level 8, fine cutting level 7).
Hard tooth surface gear (HB ≥ 350): blank → hot (positive) → gear cutting → surface hardening treatment (quenching, cyaniding, nitriding) → finishing (grinding teeth, general grade 6, finishing grade 5).
The strength of forged steel is better than that of rolled steel. Forged steel is used for important gears. According to the hardness of tooth surface and manufacturing technology, the steel gear can be divided into soft tooth surface and hard tooth surface gear. The soft tooth surface gear is refined after tempering or normalizing. The hardness of the tooth surface is small and the bearing capacity is not high, but its manufacturing process is simple and suitable for general mechanical transmission. Hard face gear is heat treated after finishing. It has higher hardness and larger bearing capacity than soft face gear. However, its manufacturing process is complex and it is generally used in high-speed and heavy-duty machines with compact structure requirements.
Cast steel: when the diameter of the gear is greater than 500mm, the wheel blank is not suitable for forging. Cast steel can be used, but normalizing treatment shall be carried out before finishing to eliminate the residual stress of the casting and make the hardness uniform, which is conducive to cutting.
Cast iron: cast iron has good casting performance, but poor bending strength and impact resistance, and its graphite can play a certain role in lubrication. Therefore, cast iron gear is often used in open gear drive.
Non metallic materials: commonly used are wood tape, engineering plastics, etc. The non-metallic material has small elastic modulus, the gear is easy to deform, which can reduce the dynamic load and noise. It is generally suitable for high-speed light load and low precision gear transmission.