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Hydrogen Bake - How Long and When?

June 26, 2008

We buy a part that is made from medium carbon steel heat treated to RC 29-37. It is zinc electroplated per ASTM B633, Type II (yellow zinc dichromate supplementary treatment). With the change in requirements in B633 in the 2007 version this part now requires hydrogen embrittlement relief for 10 hours minimum at 190-220 °C and that it occur prior to the dichromate. By specification my next order of parts will require this change in HE relief is applicable. My questions are;
- How important is the 10 hours for HE relief vs. the 3 hours that was in the previous B633 version for a part this hard?
- How important is it that the HE relief occur before the dichromate treatment. This will require a significant change in processing at the vendor if we have to do the HE bake between these steps.

Thanks,

Charles Wiese
Buy plated parts - Carbondale, Illinois

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June 28, 2008

Take a look at the spec. In the old days, it was an optional post plate bake at the hardness of your parts and required at Rc39.
The longer bake will cost you more.
The bake should come after plate and before chromate as the chromate dries out too fast and looses some of its effectiveness.

James Watts
- Navarre, Florida