Does stainless steel need a heat treat to be rust resistant?

eyeeatingfish

eyeeatingfish

Joined
Dec 9, 2003
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Ok, sort of knife related. Recently I purchased scrap stainless damascus from Chad Nichols to try my hand at some jewelry. So I cut out a bunch of crosses and I noticed they would rust some after sitting on the workshop bench. The guy on the phone had told me that stainless damascus will rust quickly if not heat treated so after cleaning them up I used my coffee can forge to heat treat them. They didn't soak for a long time, maybe 5 minutes when they were at a bright color. Pulled them out and threw them in new motor oil (5w20 I think?) Sanded the black oxidation off and I noticed that rust would still start to form if left on my work bench for a week or two. Even after the acid etch and the buffing them to a decent sheen they would still have a small amount of rust form. A coating of the polishing compound might have reduced this a little though?

So now I am wondering a couple of things, is it true that stainless steel isn't rust resistant unless heat treated? And if so did I not heat treat it properly? This was the first time I was using the forge and I realize these forges are better suited to the carbon steels but as I wasn't trying to get a high performing knife I figured it wouldn't need to be so precise. I am in Hawaii so the humidity and salt content in the air doesn't help but I have a stainless steel damascus wedding ring and have never had a problem with it. Or is it that the knife steels used in stainless damascus just aren't that rust resistant as compared to whatever was used in my ring?

On a side note for heat treating a carbon knife blade I read about the cherry red color being about the right color. If I pull a knife of 1095 out of the forge and it is past cherry red to orange or higher do I just have to wait for it to air cool to cherry red and then quench or do I have to let it cool all the way and start over?

Thanks for the input! I will have to post pictures when I have finished them.
 
Blade steels do need to be heat treated to become stainless.

Stainless steels require very specific soak temps and cant be properly HT in a forge.

Also you wont have any luck HT 1095 in a forge. Its a hypereutectoid steel and like stainless needs very specific HT times and temps. 1084 can be easily HT in a forge. You should pick some up from New Jersey Steel Baron.

Also NEVER quench in motor oil. It gives off highly toxic fumes. Use warm canola oil or Parks 50 instead.

I hope this helps and good luck with your project
 
First you need to know what type of stainless is involved. But NO! Stainless Steels do NOT require heat treating to be rust resistant.

Now, remember, the Damascus you have might have stainless steel as well as carbon steel to make the Damascus.

You said your Damascus is showing rust - is it showing rust on the bright SS portion of Damascus? OR - is it the high carbon portion that's showing rust?

OR - is your Damascus supposed to be totally stainless steel? If so, that would be a new one for me.

Again, Heat Treating has nothing to do with rust resistant of SS.

As a general rule and you know about ROT, Damascus that has been etched tends to rust less than normal high carbon steels.

Of course, I've been wrong before, and will be wrong again. So, if anyone dis-agrees with my statements please comment.

Ken H>
 
I've met a number of bladesmiths who normalize and heat treat hypereutectoid steels in a forge (solid and gas) with good results. But, it requires more practice than eutectoid steels and the caveat is it needs to be in a location where the ambient light is right. I have to agree that, for a beginner, 1084 and a magnet are the way to go.
 
hyperutectoid steels have been heat treated in forges, coal, coke, charcoal, and other fuel types for hundreds of years. WHAT HAS CHANGED?

Also some alloys of stainless steel definitely need to be heat treated before they are resistant to rusting.

actually let me rephrase this a bit some alloys become more resistant to rust after heat treatment than the same alloy was in an annealed state.
 
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Bill, you are MUCH MUCH more experienced than I am with knife making with a MUCH MUCH higher level of knowledge that I have. Just which SS alloy requires HT'ing to improve resistance to rust? As we both know, SS is rust "resistant" not rust "proof". Do you have links for these SS alloys?

Even some SS blade steels can be HT'd in a forge providing you've got a TC to monitor temp and using a hand valve to trim level of flame. Such as Sandvik steel which require only 5 minute soak for 1/8" and less, it's not too hard to hold required temp for 5 minutes in a forge. Best to use a muffer pipe.

Thank you, Ken H>
 
For those who use one of the stainless steels that can be tempered at 400 F or 900 F -- the 400 F temper will be more corrosion resistant !.
 
Ken H> said:
Bill, you are MUCH MUCH more experienced than I am with knife making with a MUCH MUCH higher level of knowledge that I have. Just which SS alloy requires HT'ing to improve resistance to rust? As we both know, SS is rust "resistant" not rust "proof". Do you have links for these SS alloys?

Even some SS blade steels can be HT'd in a forge providing you've got a TC to monitor temp and using a hand valve to trim level of flame. Such as Sandvik steel which require only 5 minute soak for 1/8" and less, it's not too hard to hold required temp for 5 minutes in a forge. Best to use a muffer pipe.

Thank you, Ken H>
Click to expand...

Here you go Ken, this is just one of several government agency papers I found.

http://www.google.com/url?sa=t&rct=...o4H4AQ&usg=AFQjCNHkLuuVsLFf45eBswcB77XUD7QKsQ

I didn't bother reading the whole paper.

this one is by nasa.

http://www.google.com/url?sa=t&rct=...o4H4AQ&usg=AFQjCNF8BETq1dI9seNoXHeERfkGPzXTxg
 
Bill, you sure came up with the documentation for sure. I skimmed thru some of the paper but didn't read the whole thing by any means.

Now, I must ask the question the OP asked - should HT'ing be required for SS not to develop rust just laying on table for a week in the shop? While I admit, I do NOT have the experience of many of ya'll folks, I have fooled around with SS (304 and 316 mostly) for many years and have NEVER seen those rust from lying on shop table for a week or so, and they were NEVER HT'd.

Ken H>
 
Ken H> said:
I have fooled around with SS (304 and 316 mostly) for many years and have NEVER seen those rust from lying on shop table for a week or so, and they were NEVER HT'd.

Ken H>
Click to expand...

You can't HT 304 and 326, they're austenitic. They also have practically no carbon. High carbon stainless need to be heat treated to dissolve the carbon (makes martensite) and free up chrome (makes corrosion resistant). Annealed, the carbon and the chrome is in carbides.
 
I myself have had 410, 416 and 420 lightly rust in the annealed state, but not just lying on the bench. these steels also seem to me to finish way nicer and be more scratch resistant after hardening and tempering.
 
The problem is that if the cromium is bounded into carbides it can't perform it's magic; that's how a great part of the Cr is in the annealed steel state.
When the steel is hardened, the Cr carbides let go the Cr into solution, leading to free Cr substituting Fe atoms within the matrix. That free Cr will ready react with the oxygen, developing a passive oxyde that protects the steel from rusting.
Of course any stainless steel, even annealed, has a big portion of free Cr, but surely less then the hardened one.
 
Thanks for all the input!
Ok, so the consensus of most here seems to be that the heat treat will increase the rust resistance.
While my heat treat clearly isn't a proper knife heat treat I am still getting it very hot and quenching it so it should be getting harder right? Just not in the optimal knife range? I could have left it to soak longer but I don't feel like grinding off oxidization again...
I thought about just putting a very light coat of wax to protect it. I don't know the content of the SS damascus. The chad nichols website doesn't say but I assumed it was all SS. I haven't noticed a pattern of the rust being on one layer more than the other. The rust isn't near as bad as the bar of 1095 I have lying around so it definitely is more rust resistant. I just don't want to sell or give some jewelry item to someone only to have it rust a little from sitting around. Again I am in Hawaii and that only makes things worse. I am thinking maybe I need to find another source of SS damascus marketed towards jewelers that is very rust resistant?

Thanks for the warning on car oil but it is all I got for now so I will avoid the fumes.

As for 1095 in a home made forge I have read about people doing it all the time so now I am just confused about that.

I am still confused about my last heat treating question. If I am heat treating a metal and I realize that based on the color I went too high do I need to let it cool slowly and start over or do I just wait till it cools to the cherry color and then quench? I realize that too high the heat makes the grains grow so once you realize you went too hot then what?
 
I use 440c and while grinding before HT, it will get a little surface rust from dipping it in the bucket to cool it off. After HT, when polishing, it never shows any rust. As mete said, tempering at 400 or so does make it more corrosion resistant. I made a knife for my brother-in-law who is a hydraulic engineer. He works in and around water all day everyday. The knife maker who does my HT told me that tempering around 400 would be best. He normally tempers at 925 or so for a higher RC.
 
I called Chad Nichols damascus and he explained the steels used are a 300 series and AEB-L or AEV-L (couldn't tell exact letters pronounced) but both are stainless. He suspected that maybe the steel did not have a long enough soak at the temperature. I was at about 5-10 minutes and he suggested 20 minutes. I will have to try a test piece at 20 minutes and see how it works. He said to use plate quence but he said the oil was ok for my purposes.
 
So was still wondering what happens when you pull a blade out of the oven and realize it got too hot. Do you have to let it cool completely and start over or do you wait for it to cool to the right temperature and then quench?
 
You need to let it air cool and then redo HT. When it air cools the steel will go back to its annealed state.

If you overheat it you will get bad grain growth and it will become brittle and also have a higher probability of cracking when you quench it.
 
eyeeatingfish said:
So was still wondering what happens when you pull a blade out of the oven and realize it got too hot. Do you have to let it cool completely and start over or do you wait for it to cool to the right temperature and then quench?
Click to expand...

if it got too hot I personally would quench in oil and then thermal cycle at least twice and then reheat and quench again probably twice.

as far as hardening these are both stainless steels 304 is a non hardening alloy and aeb-l should not need more than 10 minutes at 1925. but it is likely that you never got it hot enough in your forge
 
If making jewels, i won't be concerned about grain growt at all, also as Bill pointed out you probably didn't overheat it to start with...AEBL is air hardening, but just dunking into oil after soaking at temp (orange yellow, not cherry red for SS) for ten minutes will drive you home :)
 
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