Can overheating stainless steel make it weaker?

Hello, All!
Could someone please explain how overheating a piece of stainless steel can weaken it?
The piece of steel would be 12" long, by 1" high, by 2.9mm thick.
The method of overheating would be by grinding the steel on a grinder and using heavy pressure and multiple passes.
Thanks With best regards, dukecola. E-mail: snipped-for-privacy@adelphia.net
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
A true stainless is only hardenable by cold working. Heat anneals out the cold work making it weaker. For grinding this should be a near surface effect.
Heating can also cause an embrittlement problem called carbide sensitization. Happens at high temperatures such as welding.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Duke:
The dimensions of the piece sound like maybe a knife or a skate blade.
If the material is a martensitic stainless steel, then overheating can cause what is known as grinding burn. A thin (less than 0.01" thick) layer just below the surface can be altered in the same ways as for a high strength alloy steel like AISI 4340.
See Figures 1 and 2 of the 30 year old article on surface integrity at: http://www.shotpeener.com/library/pdf/1974003.pdf
There are two possible different effects of overheating,depending on how high of a local temperature was reached near the surface. In both cases the material will have its previous heat treatment altered.
If the local temperature just exceeded the tempering temperature used in heat treatment, then just below the surface the steel will be overtempered and will be softened compared to the material below it. It will be weaker.
If the local temperature also exceeded the critical temperature of the steel, then austenite can also have formed and been transformed to produce fresh martensite on cooling. Then just below the surface the material will be harder, perhaps both as hard as glass (but also as brittle as glass). Further below the surface the steel will again be overtempered and softer, as previously described.
Pittsburgh Pete ------------------------------------------------------------------ DISCLAIMER
We don't believe what we write, and neither should you. Information furnished to you is for topical (external) use only. This information may not be worth any more than either a groundhog turd, or what you paid for it (nothing). The author may not even have been either sane or sober when he wrote it down. Don't worry, be happy.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Hello, Pittsburgh!
Yes, I'm talking about skate blades. I'm a skate sharpener. I was taught long ago not to overheat the blades while grinding. Many of my customers who have had their skates sharpened at other shops, however, have soon found their blades cracked for no apparent reason, just from skating. I believe this was caused by overheating while sharpening, especially when the skates are new and the first radius of hollow between the edges is ground in. Most shops give a "free" sharpenening when skates are purchased, yet they rush to do the job, applying too much pressure on the grinding stone and too many consecutive passes. This leaves blue/bronze hues in the steel. At my shop, I take my time sharpening the steel, allowing it to cool, and using light pressure. I just don't have any of my customers returning with broken blades. The other shops are telling the customers that the steel is "defective", and that's why it broke. I was looking for some kind of layman's rebuttal to set the record straight... it's actually the poor skate sharpener who is making the steel brittle.
Thanks, Duke
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.