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How to Anneal Stainless Steel to Soften It

 

Q. I have some stainless steel blanks that I use for POW/MIA bracelets; they are about 2 mm thick X 7" X .5". The stainless is extremely hard -- is there a way to anneal the stainless to soften it up? I have a ceramic kiln I can heat it in if this is possible? Can anyone help?

Thanks,

John Sissons
silversmithing - Tacoma, Washington


 

A. Hello John!

The stainless you have is likely in the cold rolled condition. Annealing is commonly done at 1900F or so, for roughly an hour. You want to cool it fairly fast, especially through the 1500° F to 800° F temperature range, to avoid 'sensitization'. In that temp range, the chromium and the carbon in the stainless tend to combine, which depletes your stainless steel of chromium, the magic element that makes it stainless. Water quenching is fine metallurgically, but it may give you additional distortion, causing your sheet to warp or bow.

If you do it in air you WILL get an ugly scale- will you be able to grind it off? I'd recommend trying a small piece to see if you can live with the discoloration. Alternatives include using small stainless steel bags offered by heat treat supply houses, or getting it done commercially in an inert atmosphere.

Good luck!

Lee Gearhart
metallurgist
East Aurora, New York

Heat Treatment


March 17, 2011

Q. You mentioned something about stainless bags or annealing bags. Could you please extrapolate as I have some silversmithing students who are working in stainless and I'd love to improve our annealing process. Currently we are just using a gas/air torch (silversmithing style) and heating up to orange and holding temperature for say 10 secs. I really wonder whether this has any benefit?

Regards,

chris maron
- Sydney, NSW, Australia

March 18, 2011

A. Hello Chris!

What I was talking about are small bags, or envelopes, made of stainless steel. You put your parts inside, fold the metal as tightly as you can to keep out air, and anneal the package. Nabertherm in Germany makes them, as does Sentry in the US under their Sen/Pak trade name. Google "annealing envelopes" or something similar and you'll see pictures of what I'm describing. They give reasonable protection at the high temperatures used for thorough annealing of 18-8 stainless steel grades. We use something similar when aging beryllium copper- I'll wrap parts in aluminum foil and flow nitrogen gas through the package, and it works like a charm. The parts go in shiny and come out shiny. Aluminum melts at too low a temperature for wrapping stainless steel, however.

Regarding your current practice, and looking at Uddeholm's temperature chart (www.uddeholm.com/files/Temperature_guide.pdf ) I see that orange is about 1700 °F, and that's pretty high. Ten minutes won't fully anneal stainless grades, as you won't get any carbide dissolution, but you will get a great reduction of the residual stress you put in from bending or cutting or other working. So it's worthwhile, and may be all you need, but if you want to heat higher for longer, try the annealing bags.

Good luck!

Lee Gearhart
metallurgist
East Aurora, New York


May 20, 2011appended

Q. Is it possible to do annealing on Stainless Steel 316 (ASTM A 213 TP 316) tube size 1/4" OD, 20 SWG or 16 SWG? Can you suggest how to do this?

Is it possible to do the same for a 3/8" OD tube of similar thickness?

These tubes are usually cold drawn tubes, and annealing is required for relieving stresses developed due to work hardening

Nitin Kirloskar
Manufacturing - Pune, Maharashtra, India

March 27, 2012

Q. I NEED TO ROLL 1" S/S ROUND BAR 304 INTO THE SHAPE OF AN S BUT IT WANTS TO SPRING BACK WOULD ANNEALING HELP? OR WHAT WOULD YOU SUGGEST?

ROWLAND STANTON
- PENSACOLA, FLORIDA, USA


April 1, 2012

A. Hi Rowland!

You could bend it part way, then anneal, then bend it some more. Maybe take more than two steps, if you have the luxury. That would certainly reduce the amount of residual stress in the bar, and allow it to retain the S shape.

Good luck!

Lee Gearhart
metallurgist
East Aurora, New York


April 9, 2012

Q. Is it possible to anneal 441 Stainless Steel Tubing?
How do you anneal 441 SS tubing?

Jim Austin
- Jackson, Michigan, USA


April 12, 2012

A. Yes it is possible to anneal Type 441 stainless steel tubing. Full annealing is performed by heating to a temperature between 760 and 830 C for 90 minutes per 25 mm of thickness, followed by air quenching. Stress relieving, e.g., after welding, can be performed in the range of 200-300 °C.

Toby Padfield
Automotive component & module supplier - Michigan, USA


July 28, 2012

Q. Hi. I would like to make jewelry and other decorative items from old stainless steel flatware. Although it's possible to hammer it flat and bend it into desired shapes, it's hardness makes it quite difficult. Years ago I worked in a jewelry store and used a gas torch to repair jewelry. Because of that, I am thinking that if I annealed the flatware before trying to bend it, it's malleability would be increased. Unfortunately, I don't remember what we used for annealing...seems like it was some sort of pickling solution, then, of course, flux for effecting the solder joint. I'd appreciate any suggestions for making these items easier to work with as well as suggestions for where to obtain the annealing material. Thanks so much for your help! Deborah

Deborah Galloway
- Roanoke, Virginia, USA


June 18, 2014

Q. Deborah, did you get any response to your question? I would really like to know the answer too.

Mary Morrison
Student of metal jewelry - Rock Hill, South Carolina


June 2014

A. Hi Mary. Annealing for softening can be done, but it's by no means simple to understand, let alone do :-)

For example you harden copper by cooling it slowly, and soften it by cooling it rapidly -- whereas with steel you do the exact opposite. And with stainless steel, you also have to be conscious of cooling at the right rate through critical temperature zones as explained by Lee Gearhart. And then you have the issue of oxidation (blackening) unless you are able to exclude air with a special furnace or the stainless steel bags that he talks about.

I would not want to discourage you at all, but annealing stainless steel is a challenge you'll really have to work at, not a quick trick. And if you read jewelry-making forums they'll all tell you to find sterling silver flatware, not stainless, for your designs :-)

Luck and Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


September 15, 2012

Q. What would be the procedure for annealing stainless rod for threading?

Paul Marshall
- Anchorage, Alaska


September 26, 2012

Q. What grade of stainless steel should be used for a mold to be used in a glass kiln? The temperature will not exceed 1700 degrees.

Fran King
- Fort Myers, Florida, USA


November 8, 2012

Q. We have a continuous annealing and pickling line for stainless steel. Can someone tell me the annealing cycle for 200 and 300 Series and low nickel of stainless steel with chemical composition.

R.K.Kushwah
- Angul, Orissa, India


May 8, 2013

Q. I need to drill an SS304 M8 stud. The material is very hard. Can any one tell me how can I soften the material?

NAZIR KHAN
Heavy Equipment - Mumbai , INDIA

January 21, 2014

Q. How can 202 Austenitic stainless steel be softened or annealed? Please advise for above grade annealing temp., soaking and cooling process. etc.
With regards,

Tonmoy kr Mitra
individual - Faridabad, Haryana, India


August 18, 2014

Q. Sir,
I want to bend a ss pipe of dia 1 inch and thickness of 0.95mm. Can annealing help me to bend that pipe easily without getting wrinkles?

Thanking you
Parag

Parag Chavan
Engineering Works - Ahmednagar, Mahrashtra, INDIA


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QAQAQQAQAQQAQQQQQQ, very similar to the code on many other pages -- a pattern of Q's balanced by A's at the beginning, devolving to a long string of Q's.

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Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
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