Thin Section Heat Treating

[geoffriong]

I am interested in a standard process for the carburizing and oil quenching of a thin section steel (10B21). The part is a pinion with section sizes varying from 2.1mm to 4mm. Other than part geometry, what else can be done to avoid cracking in the quench? Thanks in advance for any information.

 

[TVP]

The following are causes for distortion and cracking during quenching:

1. Nonuniform agitation/circulation
2. Mechanical handling damage
3. Water contamination
4. Quenchant that has too fast of a cooling rate
5. Bath temperature too low
6. Oxidation of oil
7. Decarburization
8. Furnace overheating

Houghton has an excellent guide called "Houghton on Quenching" that describes the various technical aspects of quenching. I highly recommend that you contact them. For the best technical assistance, ask for D. Scott MacKenzie (Technical Specialist).

 

[Goahead]

From the description of the problem it seems that quenching is performed from carburizing temperature. If this is the process used, one could try to first reduce the temperature to about 850 C and equalize, and only then quench in hot oil. Another procedure would be to furnace cool and then reheat for quenching.

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