The selection of gear processing materials depends on the application requirements

The selection of gear processing materials depends on the application requirements. Commonly used gear materials are steel (cast steel and forged steel), cast iron and non-metallic materials.The descriptions are as follows, for reference.

XNUMX. Cast steel

Cast steel is often used for larger sizesgear.

Cast steel has good wear resistance and strength, but it should be annealed and normalized, and quenched and tempered if necessary.

XNUMX. Forged steel

The steel has good toughness and impact resistance. It can also be heat treated or chemical heat treated to improve its mechanical properties and increase the hardness of the tooth surface, so it is most suitable for making gears.

Except for those whose size is too large (da>400-600m) or those with complex structures and shapes that are only suitable for casting, forged steel is generally used to make gears, and carbon steel or alloy steel with a carbon content of (0.15-0.6)% is commonly used.

Forged steel for manufacturing gears can be divided into:

1. Hard tooth surface (hardness>350HBS):

The main gear transmissions used in forged steel high-speed, heavy-duty and precision machines (such as precision machine tools, aero engines) for gears that need to be processed, in addition to requiring excellent material performance, gear teeth with high strength and tooth surface with high hardness (such as In addition to 58-65HRC), finishing such as gear grinding should also be carried out.

Gears that need to be finished are mostly cut first, then surface hardened, and finally finished, the accuracy can reach 5 or 4.

This kind of gear has high precision and relatively expensive price, so the heat treatment methods include surface quenching, carburizing and nitriding, soft nitriding and cyanidation.

So the material depends on the specific requirements and heat treatment method.

2. Soft tooth surface (hardness≤350HBS):

After heat treatment, the forged steel used for gear cutting gears does not require high strength, speed and accuracy. It should be used to facilitate gear cutting and prevent the tool from being quickly worn and dull.

Therefore, the gear blank should be cut after normalizing (normalizing) or quenching and tempering.After cutting, it is the finished product.Its precision is 8 grades, and it can reach 7 grades for fine cutting.

This kind of gear is easy to manufacture, economical and highly productive.

3. Alloy steel:

For high-speed, heavy-duty aerospace gears that require small size and small quality, alloy steels with excellent performance (such as 20Crmnti, 20Cr2Ni4A, etc.) are used.

According to the composition and performance of the metal contained in alloy steel, the toughness, impact resistance, wear resistance and adhesion resistance of the material can be improved respectively, and the mechanical properties of the material and the hardness of the tooth surface can also be improved by heat treatment or chemical heat treatment. .

Three, cast iron

Gray cast iron gears are often used in occasions where the work is stable, the speed is low, and the power is not high.

Gray cast iron is more brittle in nature, poor in impact resistance and wear resistance, but has better resistance to bonding and pitting corrosion.

Fourth, non-metallic materials

For high-speed, light-load and low-precision gear transmissions, in order to reduce noise, non-metallic materials (such as cloth bakelite, nylon, etc.) are often used as small gears.

The big gear is still made of steel or cast iron.In order to make the large gear have sufficient anti-wear and anti-pitting ability, the hardness of the tooth surface should be 250-350HBS.

The tooth surface of the gear should have a high resistance to wear, pitting, adhesion and plastic deformation, and the tooth root should have a high resistance to breaking.

Therefore, the basic requirements for the selection of gear tooth material performance are: the tooth surface should be hard and the tooth core should be tough.If there are any unclear points or related processing requirements in the above description, you can consult EP free of charge.