Various heat treatment methods for carburizing and carbonitriding gears
Various heat treatment methods for carburizing and carbonitriding gears
Grade | No | Gear type | Heat treatment process |
20CrMnTi 20SiMnVb 20CrMo 20CrMnMo | 1 | Most gears that have been carburized with gas or liquid (or carbonitriding) | Carburizing (920-940℃) or carbonitriding (840-860℃) → pre-cooling in the furnace, soaking (830-850℃), (not pre-cooling for carbonitriding) → direct quenching (oil quenching) Or hot oil martensite graded quenching)→tempering (180℃, 2h) |
2 | 1) Gears whose distortion does not meet the requirements after direct quenching and need to be quenched by a press or a mandrel 2) Gears that need to be machined after carburizing 3) Solid carburized gear | Carburizing or carbonitriding→cooling→reheating (850-870℃)→quenching (oil quenching or hot oil martensitic quenching)→tempering | |
3 | Gears with higher accuracy requirements (level 7) | The gear is rough-processed and formed before carburizing; after carburizing, it is cooled down at a slower cooling rate to perform semi-finishing of the gear; then the high-frequency or intermediate-frequency induction heating device is used to heat the tooth part and the vicinity of the tooth root for quenching. After tempering, finish the tooth profile (honing or grinding) and use the push knife to finish the inner hole of the spline | |
20,20Cr
| 4 | Carburized gear | Quench directly after carburizing, if the crystal grains are coarse, it is advisable to use the heat treatment process of No. 2 for treatment |
12CrNi3A 20CrNi3A 12Cr2Ni4A 20CrNi2Mo 17CrNi2Mo 20Cr2Ni4A 18Cr2Ni4WA | 5 | Carburized gear | Carburizing (900-920℃)→cooling→reheating (12CrNi3A, 20CrNi3A, 12Cr2Ni4A, 20Cr2Ni4A: [800±10℃); 18Cr2Ni4WA: 850±10℃) → quenching (oil or (200±30℃) alkaline bath , After keeping for 5-10min, air cooling)→cold treatment (-70～ -80℃×1.5-2h)→tempering |
6 | Gears that need to be cut after carburizing | Carburizing→cooling→high temperature tempering (650±10℃)×5.5-7.5h, air cooling, 18Cr2Ni4WA should be discharged with furnace cooling below 350℃, air cooling→reheating→quenching→tempering | |
7 | Gears whose core hardness is too high after general quenching | Quenching can be carried out according to the following specifications: 18Cr2Ni4WA: After heat preservation at 850±10℃, quickly put it into an alkali tank at 280-300℃, keep it for 12-20min, then transfer it to 560-580℃ nitrate bath and keep it oil-cooled for 30-50min 12CrNi3A: After keeping the temperature at 820-850℃, keep oil cooling for 8-12min in the alkali tank at 230±50℃ | |
8 | Carbonitriding gear | Carbonitriding (830-850℃)→direct quenching (oil or alkali bath, martensite graded quenching, 18Cr2Ni4WA can be air quenched)→cold treatment→tempering | |
9 | Gears that need to be cut after carbonitriding | Carbonitriding→cooling→quenching→tempering |