There are many types of materials for gear forgings. The commonly used materials for gear forgings are: 40Cr, 42CrMo4, 20CrMnMo, 20CrMnTi, etc.

42CrMo4 forged and 40Cr forged gears are mostly the most large-scale gear forgings in the lifting industry.

The small piece has no owner (reference). Most gears require gears to improve quality. The heat treatment hardness of the gears can reach the best performance at 38-42HRC. The toughness of 42CrMo4 is much better than 40Cr, because the former has better heat treatment hardenability, which is closely related to its material. Also, the strength at the same hardness is very close. In the best performance, the tensile strength of 40Cr is 60 ~ 75 kg / mm ;the yield strength is 35 ~ 55 kg / mm; the tensile strength of 42CrMo4 forged is 110 kg / mm;the yield strength is 95 kg / mm, obviously 42CrMo4 performance is much better than 40Cr performance.

Hardness

40Cr material has good hardenability, it can be hardened to 28 ~ 60mm in diameter when water quenching, and 15 ~ 40mm in diameter when oil quenching. After tempering, the material has good comprehensive mechanical properties, and has good low notch sensitivity and low temperature impact toughness. After 40Cr gear forgings are quenched and tempered, they are often subjected to surface induction hardening or nitriding. When the hardness is 174 ~ 229HBS, the cutting performance is better, the relative cutting workability is 60%, the carbon content of 40Cr forgings is maintained at about 0.40%, to ensure that the steel has a good combination of strength and toughness. The addition of Cr element is mainly to improve the hardenability of steel. When quenching and heating, Cr element is completely dissolved in austenite, which improves the hardenability of steel. After quenching, Cr element solid solution strengthens the matrix structure and improves the tempering stability of the matrix structure. During high temperature tempering, some Cr elements diffuse from the matrix structure to the precipitated cementite Fe3C to form alloy cementite (Cr, Fe) 3C.

Chemical components

The main chemical components of 40Cr steel for gear forgings are: 0.37% ~ 0.44% C, 0.17% ~ 0.37% Si, 0.50% ~ 0.80% Mn, 0.80% ~ 1.10% cr, ≤0.035% P, ≤0.035% S

The phase transition points are: Ac1770 ℃, Ac3805 ℃, Ms328 ℃.

The initial forging temperature of 40Cr gear forgings is 1100 ~ 1150 ℃, and the final forging temperature is 800 ℃. After forging, the size needs to be cooled slowly when the size is more than 60mm.

-To be continued

Ms Sharon Wan

Mobile/WhatsApp: 0086-13580960968

Tel: 0086-769-23190193

Fax: 0086-769-88705839

Email: Sharon@otaisteel.com