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Carbide removal from 300 series stainless steel

Hello,
I work with a metal stamping company. Since few days, I have seen that our 300 series stainless steel parts are showing yellow coloration. (Part size is 0.225" to 0.200" approximately). We did scanning electron microscopic analysis and have seen traces of carbon! Can someone tell me how to remove carbide from stainless steel?

Anvita Chitnis
Metal Stamping - Goleta, California, US
2007

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Possibly, contamination from the tooling. Maybe from the stainless: 302 may have 0.15% C, 304 0.08%, 305 0.12%, 309 0.20%, although 304L & 316L have no more than 0.03% (all %C values are maximums). Carbide can form from improperly annealing -- austenitic SS should be quenched (rather than slow cooled) from the annealing temperature to avoid carbide formation. Heating in air can also cause a yellow oxide.

Try passivation per ASTM A967, 'Standard Specification for Chemical Passivation Treatments for Stainless Steel Parts.'

Ken Vlach [deceased]
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.
2007