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"Work Hardening of Stainless Steel Sheet"

An ongoing discussion beginning back in 2002 ...


Q. Please can anyone advise me as to whether 0.7mm thick 304 grade stainless steel sheet will undergo surface hardening as a result of brushing to a finish of approximately 1.5 microns. If so, are there any techniques that can be employed to minimise the hardening, without the use of additional processes such as annealing?

Paul Hambelton
- Southend-on-Sea, Essex, England


A. 304 is not considered to be a hardenable grade of SS. You will see a warpage of the material because you are removing material from one side which normally reduces the surface stress causing it to bow.

James Watts
- Navarre, Florida


A. As a quick, unscientific answer, the answer is that the surface will probably not be effected. Reasons are many and dependent on type of wheel used. The harder and the stiffer the wheel material the more possible the effect. Meaning, if you use steel wire, it might be possible. Soft cotton buffs with abrasive is not likely. Work hardening with mechanical processes involves compacting the surface molecules and this can only be done with pressure.

tony kenton
AF Kenton



A. Paul:

First Q: Absolutely yes. You can harden almost any commercial metal by mechanical work. Even nonferrous metals such as copper and aluminum (who has not bent a piece of copper wire and see it become stiffer?). Only difference with heat treatment is penetration of this effect.

Second Q: A possibility is to avoid micro surface deformation (flowing of the metal) and shift to micro surface elimination (cutting of the metal). In other words: sandpapering and low speed hand polishing will leave less hardening effect than high speed brushing.

Guillermo Marrufo
Monterrey, NL, Mexico

January 15, 2009

Q. We're still looking for the right stainless steel to make flexible pen nibs, or nibs that bend under hand pressure but snap back to the original position when the hand pressure is release. We tried 400 series, but couldn't heat treat for sufficient hardening. Someone who made nibs told us to use 316 and work harden, then anneal. What's the best way to work harden without overworking? Is stamping the blanks sufficient? Does rolling further work harden? If we can heat treat for annealing, why doesn't that count as heat treating for hardness? Thanks - CKA

Chares Ackerman
pens - Berkeley, California

January 19, 2009

A. You can harden by heat treatment those of the 400 series that are martensitic stainlesses, but not those of the 400 series that are ferritic stainlesses. Which 400-series grade(s) did you trial?

You cannot harden 316 by any heat treatment. You can harden it by cold-work (deformation). Subsequent annealing will totally destroy any work-hardening and will return the material to the previous soft condition that existed before you deformed it.

I believe that stamping blanks will not change the hardness of the material, as it does not deform the material. Cold rolling is all that is available to you, and the more you deform it the harder it will get, up to a point. You control the final hardness by controlling the amount of cold rolling.

Bill Reynolds
Bill Reynolds [dec.]
consultant metallurgist - Ballarat, Victoria, Australia
We sadly relate the news that Bill passed away on Jan. 29, 2010.


January 20, 2009

A. Charles,

As Mr. Reynolds explained, austenitic stainless steels like Type 316 don't respond to typically quench hardening treatments. I think what the manufacturer was trying to recommend was an austenitic stainless steel like Type 301 or Type 302 that is cold rolled (if in strip form) or cold drawn (if in wire form), then form the desired shape, then perform a low temperature aging treatment (sometimes referred to as stress relieving, annealing, or tempering although none of them is technically correct). I encourage you to contact a supplier of cold rolled stainless steel strip to discuss the application in detail.

Toby Padfield
Automotive supplier - Michigan, USA

February 3, 2009

Q. Thank you for your information regarding heat hardening stainless steel. We will try the 420 and 430 grades, which are martensitic 400's.

If we decide to return to the 316 and work harden it, would simple deformation work, such as forming the curvature of the nib by pressing it on a block? Or would you recommend more deformation, such as rolling the blank in between rollers to get the desired radius on the length?

Thank you in advance,

Charles Ackerman [returning]
- Berkeley, California, USA

February 4, 2009

A. The more cold deformation, the higher the hardness. The small amount of deformation just from curving the nib would give a small increase in hardness. Whether that increase is enough for your application, is for you to determine by trial.

My expectation would be that you would need to cold roll for hardness and expect no significant benefit from curving the nib - but that's my expectation, not the result of any trial that I've carried out.

Bill Reynolds
Bill Reynolds [dec.]
consultant metallurgist - Ballarat, Victoria, Australia
We sadly relate the news that Bill passed away on Jan. 29, 2010.


February 7, 2009

A. Try using 410 SS. If you cannot heat treat that to a desired hardness, I seriously doubt if you would ever be able to work harden 316 enough.

James Watts
- Navarre, Florida

February 25, 2012



March 7, 2012

A. Hi Ben!

No, 304 and 316 are almost identical when it comes to mechanical properties. Those are going to be determined by the amount of cold working the material has seen, so you can get annealed, quarter-hard, half hard, full hard, etc with both rods and sheet. Thick things like plate are going to be annealed, and low hardness.

Stronger non-magnetic stainless steels would include the Nitronic series (Nitronic 40, Nitronic 50, Nitronic 60) and A286 precipitation hardenable stainless steel.

Good luck!

lee gearhart
Lee Gearhart
metallurgist - E. Aurora, New York

November 14, 2012

A. A hard austenitic stainless steel alloy would work nice for you.

chris postle
- cleveland ohio usa

September 17, 2017

Q. I have blow needle made out of stainless steel 304. In one operation they are getting bent as they are in 1/8" Dia outside .062" inside hole. Can we harden it?

Amarjit jajwan
Dieco-tech mfg - Brampton, Ontario, canada

February 14, 2019

Q. I've been reading about A4 stainless steel fasteners.
I understand that A4-50 is soft, A4-70 is stronger due to 'cold-working' ... but what makes A4-80 a hardened type of 316 stainless steel? What gives it the greater tensile strength?

Zara Lou
- Leeds, Yorkshire, UK.

February 2019

A. Hi Zara. Per BSAA, '80' is just cold worked harder than '70' :-)


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