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I Forge Iron

Annealing Stainless Steel


Fe-Wood

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300 series? 1950F and quench in cold water! Yes, really.


Quench for anneal? Really? Why is that Grant? I had been thinking about messing around welding some stainless. I know you have to exclude oxygen in the weld usually via a capsule but why would you quench the anneal?
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I`m listening closely here as I used to heat it and then throw it in the corner.
I`m looking forward to learning something new.
How about it Grant? "We`re all in our places with bright shining faces" as my kindergarten grade teacher would say. :)

Man that woman was annoying!That is far too young an age to be exposed to the "kill `em with kindness" technique.Gives me the willies just thinkin` about it.

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Had a minute yesterday so I tried to anneal the stainless with the quench method (to impatient to wait). I'm using propane and oxy for heat. Got it to a nice bright orange almost yellow heat. I think it is 20g - heats fast and cools fast. It softened right up. Now about that carbon layer. Man that stuff is tough! Any backyard techniques to avoid this? Tricks for removal?

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Passivation? enlighten my simple mind :huh:


Citric and nitric (and I think acetic) acids will etch the iron, but leave the chromium, causing a layer of chrome oxide to form, and removing free iron from the surface making a durable rust-resistant coating. Acids containing chlorine like hydrochloric (muriatic) will strip the chromium oxide and promote rusting.

Hope this helps.

Phil
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Citric and nitric (and I think acetic) acids will etch the iron, but leave the chromium, causing a layer of chrome oxide to form, and removing free iron from the surface making a durable rust-resistant coating. Acids containing chlorine like hydrochloric (muriatic) will strip the chromium oxide and promote rusting.

Hope this helps.

Phil


What kind of solution should I use?
Thanks Phil :D
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I would be cheap and try the vinegar first. If it does not perform well, I would then try citric acid as it is safer than nitric acid. If you Google "passivation of stainless steel" there are some articles.

This explains what is going on rather well.
http://www.iftworldwide.com/white_paper/passivation.pdf

Phil

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You can do passivation on SS using electrolysis. Use baking soda and water for the electrolyte, hook the pos lead from a trickle charger to the SS and the NEG lead to a SS scrap. Put them both in the electrolyte and turn the charger on. It'll be clean in a while, just check occasionally. If you use dilute sulphuric acid for electrolyte you can clean up the heat scale in minutes depending on the concentration but you'll have to rinse, neutralize, dry and dispose of the acid safely.

Whatcha spinning?

Frosty the Lucky.

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a friend asked if I could spin a set of dinner plates out of stainless... Of course I said yes.... and just to complicate it I thought I would add a set of bowls. So I'm teaching myself how to spin a 7" dia. X 3" deep bowl. I almost got it without needing to anneal. That last 3/4" at the rim is a bugger ;)

Heres a picture of the finished continental kit for the trailer I did a while back

post-6253-0-63155100-1291338939_thumb.jp

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I would be cheap and try the vinegar first. If it does not perform well, I would then try citric acid as it is safer than nitric acid. If you Google "passivation of stainless steel" there are some articles.

This explains what is going on rather well.
http://www.iftworldwide.com/white_paper/passivation.pdf

Phil



Good Article Phil- Thanks!
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  • 3 weeks later...

Be aware that not all stainless is anneal by quenching, the martensetic grades are normally a subcritical anneal (heat to 650 deg C hold for up to 12 hours allow to air cool to ambient).
If you pickup some stainless from the scrap yard you need to identify it before you go messing with it. Martensetic grades are normally magnetic.
It can be a bugger to anneal, we just had to have 3 goes at annealing 2 24"od x 3" x 18"id rings out of 431 stainless last week. They kept on coming out at 416 HB, we had to go back right to the start and begin again. We finally got them down to 255HB and our customer was finally able to machine them.

Merry christmas to everyone.
Its 8.30 in the morning here, and I'm sitting on the verandah typing this wearing a tee shirt and shorts and its already 25 deg C. Seen the pickys of up north and all I can say have a nice white christmas.

Phil

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