Commonly used materials are forged steel, cast steel, and cast iron.
XNUMX. 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
常用材料;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 level 8
Simple manufacturing, economical, high productivity, low precision requirements
2.Tooth surface hardness HB>350
When using medium carbon steel:
Process: forging blank → normalization → rough cutting → quenching and tempering → fine cutting → high and intermediate 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 the 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
Features:
Tooth surface hardness and strong load-bearing capacity.
Good core toughness and impact resistance
It is suitable for high-speed, heavy-duty, overload transmission or occasions with compact structure requirements, locomotive main transmission gears, aviation gears.
XNUMX. Cast steel
When the gear diameter d>400mm, the structure is complicated, and the forging is difficult, cast steel can be used
Material ZG45.ZG55, normalizing treatment.Normalization, quenching and tempering.
Three, cast iron
Strong resistance to adhesion and pitting corrosion, but poor resistance to impact and abrasion.
It is suitable for stable work, low power and low speed, or large size and complicated shape.It can work under oil shortage conditions and is suitable for open transmission.
Fourth, non-metallic materials
Fabric, wood, plastic, nylon, suitable for high speed and light load.
When selecting materials, consider:
Non-standard gearDifferent working conditions and different forms of damage to the gear teeth are the basis for determining the strength of the gear and the selection of materials and heat treatment.
1.When the gear teeth are easily broken under impact load, materials with better toughness should be selected, and low carbon steel can be used for carburizing and quenching.
2.For high-speed closed transmission, the tooth surface is prone to pitting. Materials with better tooth surface hardness should be selected, and medium carbon steel surface hardening can be used.
3.For low-speed and medium-load, when gear tooth fracture, pitting, and wear can occur, materials with good mechanical strength, tooth surface hardness and other comprehensive mechanical properties should be selected, and medium-carbon steel quenched and tempered can be selected.
4.Strive to have a small variety of materials, easy to manage, and consider resources and supply.
5.When the structure size is compact and the wear resistance is high, alloy steel should be used.
6.The equipment and technology of the manufacturing unit.