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Rusty found on SS 420 material with Heat Treatment

March 6, 2008

I'm facing a complaint from customer of rusty issue on my part which using SUS420 material.
The part process is after turning, heat treatment, grinding and degreasing.

Could you help on my queries below.
1) Is the rusty due to heat treatment process? but before that we did not see any rust problem.
2) if add in another passivation process will it help to solve the rusty issue?
3) or it might turn to rusty after a period of time ?
4) any other material can recommend which will not have rusty problem with my process above.

Hope you can help me above.

thanks,

Lim BL
Engineer - Penang, Malaysia

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PROBLEM
You have a problem of CLEANING parts.
Review your solutions
Use too hot water to rinse
Finally, dry your parts

Jose Castellanos
- Minneapolis, MN, USA
March 18, 2008

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Heat treatment of the 420 will increase the probability of rusting.
Rust is caused by the environment that it is subjected to. It takes moisture and oxygen for a part to rust. A number of other items will accelerate the rusting process, like salt from any source.
Contact with iron or steel parts will promote rust of the SS.
If the parts are cleaned and died, properly and immediately, something else is causing the rust.
Consider that acids and sulfides in some paper and cardboard will promote rust. Some vinyl packages will promote rust.

So, there is a great deal that you have not told us about your situation.

James Watts
- Navarre, Florida
March 19, 2008

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March 30, 2008

Dear Lim Bl
I think following reasons for rusting of sus420 grade.
before heat treatment you clean the parts because in turning process so many free iron particle,oil,dust,other reactive chemical found on the surface.your heat treatment process are controlled atomasphere or batch annealing.if possible after finishing all operations you put some oil on the surface of the parts because sus420 grade not behave like sus304 grade. this problems due to improper passivation after all operations.

Umashankar Gupta
- Hyderabad