3 steel grades suitable for making gear
Gear steel is the general name of steel used in gear manufacturing. Gear is one of the most widely used mechanical components, and is widely used in mechanical transmission. There are many types of gears, such as spur gear, chain gear, synchronous pulley, helical gear, internal gear, rack, straight bevel gear, arc bevel gear, zero bevel gear, staggered spiral gear, worm gear, etc.
Gear steel is a key material with high requirements for special alloy steel used in automobile, railway, ship and engineering machinery. Gear material needs strong bending fatigue strength and contact fatigue strength, and the tooth surface should have enough hardness and wear resistance, and the tooth core should have certain strength and toughness. Gears are usually made of forged steel, except for foundry plants with too large size (Dia > 400-600mm) or suitable for complex structures and shapes.
Carbon steel or alloy steel with carbon content of 0.15-0.6% is usually used in gear applications. The Microalloy Elements in gear steel can improve the toughness, impact resistance, wear resistance and adhesion of the material, and the mechanical properties of the material can also be improved by heat treatment or chemical heat treatment. Alloy gear steel usually does not include low carbon alloy steel, such as 15CrMo, 20Cr, etc. and medium carbon alloy steel: 40Cr, 42CrMo, 35CrMo, etc.
15CrMo
Carburizing surface quenching treatment is generally used to pay attention to the strength or toughness of parts or parts that need to bear a lot of friction, such as cylinder piston, spindle, gear, bolt, shaft, etc. It is used to make profile less than 30mm under high speed, medium load or heavy load, impact and friction of important parts; for example, crosshead of gear, ring gear and gear shaft.
In the automotive industry, the cross-section used is less than 30mm; important carburizing parts bear high speed or heavy load and impact; for example, gears, shaft gear rings, gear shafts, sliding bearing spindles, crossheads, claw clutches, worm, etc
25CrMo4
The alloy structural steel 25crmo4 (ASTM 4118) has high hardenability, no temper brittleness, good weldability, little cold crack tendency, good machinability and cold strain plasticity.
25CrMo4 gear steel is used in general conditions or under carburizing quenching conditions, which is used for manufacturing corrosive medium with working temperature lower than 250 ℃, high pressure pipe and various fasteners working with medium containing hydrogen nitrogen mixture, higher carburizing parts and automobile gears, various special wear-resistant parts, such as aircraft, shaft, high pressure pipe and various fasteners.
42CrMo4
42CrMo4 (ASTM 4140) is a medium carbon chromium molybdenum alloy steel. Chromium content provides good hardness permeability, molybdenum element provides hardness uniformity and high strength. The alloy well balances strength, toughness and wear resistance. It has the following advantages: stable composition, less harmful elements, high purity of steel, small decarbonization layer, less surface defects, etc., and easy to process under heat treatment conditions, with good ductility and high temperature stress resistance. This material is widely used in the production of high-strength steel fasteners, such as engine, mould, motor, gear, transmission parts, shaft, gear, arm, cold forging, screw products.
In addition, ASTM 4320, 4340, 8615, 8617, 8620, 8622, 9840 (https://otaialloysteel.com/products/alloy-steel/)and so on can also be used for gear purposes. As common alloy carburizing and bearing steel, they are mainly used as materials for automobile bearings, transmission shafts, gears, screws, tool parts and other impact resistant and wear-resistant parts. The surface after carburization has high hardness, wear resistance and contact fatigue strength, while the core still maintains good toughness and can bear high impact load.
