Carburizing, Carbonitriding Gear Heat Treatment Methods
| Steel grade | Item | Gear type | Heat treatment process |
|
20CrMnTi 20SiMnVb 20CrMo 20CrMnMo |
1 |
Most gears that have been carburized (or carbonitriding) by gas or liquid |
Carburizing (920-940℃) or carbonitriding (840-860℃) → furnace pre-cooling, soaking (830-850℃), (carbonitriding is not pre-cooling) → direct quenching (oil quenching or hot oil martensite grading quenching) → tempering (180℃,2h) |
|
2 |
1) After direct quenching, the gear whose distortion does not meet the requirements needs to be quenched by pressing bed or sleeve bar
2) Gears that need to be machined after carburizing 3) solid carburizing gear |
Carburizing or carbonitriding → cooling → reheating (850-870℃) → quenching (oil quenching or hot oil martensite grading quenching) → tempering |
|
|
3 |
High precision requirements (7) gear |
The gear is roughed before carburizing.After carburizing, it is cooled down at a slower cooling rate, and the semi-finishing of gear is carried out.The diathermic tooth and the part near the tooth root are quenched by high frequency or medium frequency induction heating device. After tempering, the tooth shape is finished (honing or grinding) and the inner hole of the spline is finished by pushing knife | |
|
20,20Cr |
4 |
Carburized gear |
Direct quenching after carburizing, such as coarse grain, it is appropriate to use the No. 2 heat treatment process for processing |
|
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℃) alkali tank, after holding 5-10min, air cooling) → cold treatment (-70 ~ -80℃×1.5-2h) → tempering |
|
6 |
Gears that need to be machined after carburizing |
Carburizing → cooling → high temperature tempering (650±10℃) × 5.5 ~ 7.5h, air cooling, 18Cr2Ni4WA should be with the furnace cooling below 350℃ air cooling → reheating → quenching → tempering | |
|
7 |
Generally, after quenching, the core of the gear is too high hardness |
Quenching can be carried out according to the following specifications:
18Cr2Ni4WA: 850±10℃ after insulation, quickly put into the 280-300℃ alkali tank, keep 12-20min, into the 560-580℃ saltsalt bath for 30-50min oil cooling 12CrNi3A: After heat preservation at 820-850℃, it was kept in an alkali tank at 230±50℃ for 8-12min in oil cooling |
|
|
8 |
Carbonitriding gear |
Carbonitriding (830-850℃) → direct quenching (oil or alkali tank, martensite grading quenching, 18Cr2Ni4WA available air quenching) → cold treatment → tempering | |
|
9 |
Gears that need to be machined after carbonitriding |
Carbonitriding → cooling → quenching → tempering |
① Too much austenite or too high core hardness in the infiltration layer can reduce the quenching temperature to 760℃, while the core hardness is too low and the amount of ferrite is too much, and the quenching temperature can be increased to 850℃.
② The hardness after tempering should not be higher than 35HRC.If the hardness of individual parts is high, it can be tempered once again at 680-700℃.
The above process curve is summarized based on the actual process of many customers’ products and the reference heat treatment design manual, which can be used for the reference of the majority of industrial furnace enthusiasts and users.More heat treatment equipment design information, welcome to inquire!
Editing by Francis Lee
Copyright: RQ Furnace
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