Heat Treating 410 Stainless Steel - Too Much Scale!

[vtcnc]

I'm normally in the other subforums on HM: machining, Atlas, Taig, Sherline, etc. so I feel like I'm trespassing on hallowed ground...I'm on a quest and need some help from the knifemakers on HM...if I am knocking on the wrong door, please redirect me...

We manufacture "crown" punches for our semi-automated can opening systems. Think big cans, #10 size for food preparation. www.edlundco.com

We bevel the edges of the knives, roll and weld them to fit just inside the can. Then we heat treat the knives to give them some life after having opened hundreds of cans per day.

Our heat treat oven recently died and we replaced it with a heat treat oven that had a gas control. We used to pack and wrap our knives to prevent scaling. We were under the impression that we could avoid the pack and wrap by purging the chamber with gas and turning the gas 4-5 times per hour during the cycle to avoid scaling.

We are using argon, purging the chamber at 60 CFM and then running at about 5CFM during the cycle. We think we are turning 5 times per hour. The scaling is less, but we are still having to work hard to remove it afterwards.

Our next step is to try nitrogen and we are wondering if it makes sense to try to seal up the chamber, but I think this has safety problems written all over it...unless we were to create a vacuum chamber of some type, and then we are looking at just scrapping what we have and starting over...I'd like to work with what we have.

So, couple of pointed questions...is it possible to minimize, if not eliminate scale on 410 using the typical heat treat oven with a gas shield/purge?

If so, has anybody any experience in that sort of cycle and what can you share with me? We are sort of lost and feeling like we are missing something fundamental - any help or insight is very much appreciated!

 

[vtcnc]

Nothing??


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[Tony Wells]

I have no knife heat treatment experience, but what I have had done commercially that had to be decarb/scale free was done in a vacuum. I have always been of the opinion that an atmosphere controlled furnace would or could produce acceptable results. That said, I would expect some interaction with even traces of residual air unless a virtual flood of an inert gas was injected. The nature of the hot gas would need to be known, whether it was heavier or lighter than air, for example, to control where in the furnace to place the objects to be heat treated to minimize contact with any residual air.

Just offhand, without really thinking about it, I would believe that nitrogen could be absorbed to some degree at elevated temperatures. I know in carbon/alloy steels nitriding is one mean of case hardening, and it is done in a nitrogen atmosphere. Not sure it would apply to 410 though.

 

[vtcnc]

I have no knife heat treatment experience, but what I have had done commercially that had to be decarb/scale free was done in a vacuum. I have always been of the opinion that an atmosphere controlled furnace would or could produce acceptable results. That said, I would expect some interaction with even traces of residual air unless a virtual flood of an inert gas was injected. The nature of the hot gas would need to be known, whether it was heavier or lighter than air, for example, to control where in the furnace to place the objects to be heat treated to minimize contact with any residual air.

Just offhand, without really thinking about it, I would believe that nitrogen could be absorbed to some degree at elevated temperatures. I know in carbon/alloy steels nitriding is one mean of case hardening, and it is done in a nitrogen atmosphere. Not sure it would apply to 410 though.

Tony thanks for the thoughtful reply. We ran the oven with Nitrogen this week. Slightly, almost no less scaling than with argon. I think we need another solution. I've got another trick up my sleeve, it includes a vacuum chamber and induction coil. I'll share a video with you once we try it.thanks again. Also, it looks like Tapatalk is working great with the site this evening, not surely OT is intermittent or maybe Nels flipped the switch for me! Thanks!

 

[Matthew Gregory]

Is there any reason you don't want to return to using foil? I'm assuming the idea was to use the gas inlet on the new oven, but it sounds as if that's not quite cutting it for you...

Another product that I've got some experience with is antiscale coatings from Advanced Technical Products. They make a liquid coating that can be applied to parts, allowed to dry, and then heat treated. Upon quench, the vast majority of the coating blows off, and the rest can be washed off with soapy water. The liquid has the consistency of ceramic slip, goes on pretty easily (I just dip parts right into the bucket the anti-scale compound came in), and parts come out pretty darn clean.

Here's their website: http://www.advancedtechnicalprod.com/index.html

My contact there was Tim Conner - really nice guy. 1 (513) 851-6858

Not sure if this is what you're thinking about, but give him a call and see if they have a product that he could suggest to you for the material and process you're using. For the record, I've never seen a heat treat oven outside of a modern vacuum furnace that would eliminate scaling entirely - unless you can eliminate the atmospheric effects entirely, it's going to happen. Hope this helps!

 

[vtcnc]

Thanks Matthew, this is precisely what I'm thinking in terms of trying to reduce or eliminate scaling...I put the call into Tim this a.m., I'll let you know how it works out! Thanks again!

 

[ex_isp]

There are also powders that (I use them for knives) are applied to warmed steel. It melts and leaves a glass-like coating, sealing out all the atmospheric gases just as the liquid does. Made by rosemill dot com. I use the PCB product that goes up to 1650 F as I am doing tool steel (O1). For stainless you need higher heat and they have a high temp product called WillCarbo. Same folks that make Cherry Red. Might be worth a call.

Sorry I had to use the "dot com" instead of a URL but being new, I can't insert links yet.

Ex