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Thread: Case hardening

  1. #1
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    Default Case hardening

    A while ago Bob asked me about case hardening and just reminded me. Rather than simply emailing him I thought I'd also share it with other members in case it's of any interest. I have no idea if it's the "correct" way, but it seems to work for me.

    The parts are a couple of 1214 hex bar nuts I made up to fit on trailer jockey wheels that will be used to jack and roll machines around. The top winding handle was of course unsuitable so I quickly made these up to replace the handle, that way I can use a ratchet on it. Normally I wouldn't case harden something like this, but I find 1214 is a little soft, so thought I'd harden them.

    This is what is needed; the part (shown with stainless wire I was initially going to suspend it by, Kasenit or Cherry Red hardening compound, MAPP or other high temperature heat source, foil pie trays (very cheap and will contain the compound, finally water to quench.



    Sorry this one is a little out of focus, but heat the part until it's bright red, if it's not hot enough the compound won't stick to it. I find it often needs quite a few trips to the "pie tray" until the part is sufficiently coated.



    As the compound begins coating the part note how the flame is now quite yellow. When the compound gets quite hot it will eventually flow like thick paint and coat the entire part, however as mentioned it often takes quite a few trips to get to that point.



    As it gets more coverage the flame will become increasingly yellow



    More to follow ...

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  3. #2
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    Once the part is completely covered in compound you're ready for the quench. I think the longer it's held at temperature the deeper the case hardening, however I'm typically just after a light coating so don't waste too much gas on the process. Get the part evenly heated and then straight into the water. This what you're left with.



    Sorry, these photos also aren't great, but after quenching I just remove the compound and crud with a fine scotchbrite belt on my linisher. I wouldn't go too crazy here however as the hard case will be quite thin. I'd suggest doing all the surface finishing before hardening and just use this stage to clean things back up.




    That's it. Since it's just a thin case I don't do anything other than leaving it as this. The core of the part is still quite soft. I have no idea just how hard this layer is, but it truly does feel very much like glass to the touch.

    Just out of interest (or not) this is the part on the jockey wheel. When I go down to pick up another jockey wheel I'll get some more suitable steel and weld up a bracket that actually does the lifting of the machines. Unfortunately I have (yet again) run out of steel so that will be in a couple of days and I'll put that up as a sperate post.



    Hopefully that was of some interest to those who haven't done it. For those who have/do I'd appreciate any thoughts or feedback as any instructions are pretty thin on the ground and I just bumbled my way through it the first time I tried. However now it doesn't take long at all.

    The Kasenit I bought from Enco in the US and had it sent out. I believe it's NOT toxic (according to the MSDS anyway) but the stuff stinks so I'd definitely suggest doing it in a well ventilated area. An alternative is Cherry Red, which I believe is essentially just the same.

    Pete

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    It would seem that Kasenit isn't available any more, however "Cherry Red" is easily available and costs just US$23.40 from Enco. I forgot to mention that any excess in the pie tray can simply be tipped back into the tin, so it lasts a very long time.

    As far as the toxicity, apparently trace toxic fumes are released, hence why it should be done in a ventilated area ... for those contemplating doing their case hardening in a broom closet! However no reparatory equipment is recommended and I think it's a case of common sense if using in normal circumstances. Nevertheless I'm no expert and that's just what I'd read, the MSDS is available by search for others to make up their own minds.

    Here is a much better video than I've been able to show, demonstrating the use of Cherry Red. [ame=http://www.youtube.com/watch?v=9tlsq2ESQz0]Instant Steel Case Hardening: demonstration - YouTube[/ame]

    Once I have a proper heat treating oven I will try case hardening in that. The process is effectively the same except the part is placed in a container with the compound. The compound melts and becomes liquid. Given the amount of time it can be held at the appropriate temperature, and the consistency of the coating, I'd expect far greater case depths doing it that way. Nevertheless, as mentioned above, a really thick case is often not especially important to me as the parts are already finish machined.

    Pete

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    Pete, thanks for the info. Must try that one day. BTW are you aware you can buy side-winder jockey wheels? Swivel Jockey wheel with side winder | eBay

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    Thanks Bryan, I'd done a number of searches on ebay and hadn't found that link. I think he listed this just after the last time I checked, and his previous listing was just before. Typical

    Anyway, as it's turned out it's been a blessing in disguise as this way I'll be able to use the two top winding wheels in areas where space is tight, and use the side winders on the other end. The nuts didn't take long to make so no drama, but still, given how long I've been trying to get sidewinders seeing that listing was very much a case of ...

    Pete

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    Hi Pete,

    Thanks for posting that write up, I've bought Rose Mill (the makers of Cherry Red) PBC anti-scaling powder from knife making suppliers..

    They also sell Cherry Red.. Cherry Red Case Hardening Power 1lb [Cherry Red 1lb] - $23.25 : USA Knife Maker Supply, Operated by a knifenaker for knifemakers!

    They also sell stainless foil and other handy bits for heat treating.

    Regards
    Ray

  8. #7
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    Hi guys,
    I have a tub of this in the shed(since 6/2010 infact).
    1 KG Case Hardening Compound REPLACEMENT FOR KASENIT
    I'm yet to try it out.
    One tip I have read that might help someone is that if you dont quench. You can then machine the case off parts you dont want hard(so of course the area to be hardened has to be finished to size and the area you dont want hardened needs to be a little over size). Then heat and quench and its hard where you need and and soft where you dont. Havent tried it of course, but its a great story.

    Stuart

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    Thank you Pete.

    I have a nasty looking 2 kilogram unopened tin of Hardite. Nasty because the contents warrant a large skull and cross bones TOXIC warning and because the tin is rusting away from the inside. Barium is one of the constituents of the compound. Maybe this stuff is too dangerous to use?

    Does the process differ, timewise, if a variety of steels are treated ie, 1020,1030,1045,4140.....?
    Is there any dimensional change resultant from case hardening? The ability to transform 1214 would be reason enough for me to have a go at the process.

    Regards
    Bob.

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    As I understand it Bob, some of the earlier case hardening compounds were quite nasty, but with their replacements quite cheap, very long lasting, and far less toxic, I'd be donating your can to the museum

    There's no difference time wise in terms of the type of steel used, at least at the level I'm doing it, that may well be a different story if getting more technical with it. I believe there is a difference in the rate at which different steels can take up carbon, but this is such a thin layer I honestly can't see any real difference. Cherry Red market their product as "instant" hardening, and that's basically what it is.

    It does require quite a lot of heat to get the part hot enough though, and the one MAPP torch struggles a little even with a part the size I showed above. It's not that it needs a hotter heat, it simply needs MORE heat, so if I were doing this often I'd probably try using a couple of LPG torches instead of the MAPP. If it's not hot enough it takes a while to get the compound to stick to the metal, so it's really false economy to try to get by with less heat. If it's quite hot the process is literally just as fast as in the video above, though I'm puzzled at to why the guy didn't just flip the part to coat the other side instead of pouring compound from a scoop, never mind.

    With regard some of the steels you mentioned, I think you'd have to be a little careful. At least the 4140 and 1045 you mentioned will harden by themselves, especially the 4140, so that may mean putting a little more thought into tempering the 4140. Either way, I'd guess the case hardening compound is somewhat superfluous in at least these 2 cases. I believe products such as Cherry Red and Kasenit use a carburising technique, so if you wanted to check on suitability compare that to the material's datasheets. However I think Cherry Red also contains other products within it to help steels that don't contain all the necessary elements to harden properly under simple carburising techniques. I believe Kasenit is nothing more than sodium ferrocyanide (yellow prussiate of soda) and carbon black (the latter certainly explaining the smell). I expect it would be simple to home make just using the sodium ferrocyanide if you could find a source cheaply. BTW, I think many people (myself included) see the "cyanide" in that name and freak out. As best I can ascertain, it's actually completely harmless, indeed is a food additive (E535), although when heated it does produce a small amount of toxic gas, just how much I can't say. Again that's just my uneducated understanding of it. Just reading through and researching this it's quite remarkable the reaction the word "cyanide" causes, so it's quite difficult to filter through the copious amounts of BS out there to find credible information. I do know however that it's quite a different product to those that may be used commercially, sodium cyanide for example, which are real nasty and possibly the active ingredients of earlier case hardening compounds (???).

    There may be some dimensional changes Bob, in addition to distortion, as the steel needs to above the austenitizing temperature, so by definition that may cause distortion. However in practice I haven't noticed anything. The 2 holes you see in the part above were tapped for M6 grub screws, they were well tapped, yet they screwed in just as easily after treatment as before. If you recall the drawbars I made up for the mill, I also case hardened them, but did them far more thoroughly. They were from the same 1214 hex bar and I also didn't notice any changes whatsoever. I agree, the ability to harden this is gold, as it machines beautifully, yet can be made quite wear resistant in use.

    Pete

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    Thank you again Pete.

    I do very much appreciate your informative response. The advice regarding additional heat will be heeded. Another barbeque gas bottle might be the answer and would have the additional benefit of serving as a backup because when does a bottle usually runout!

    BT

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    My pleasure Bob, hopefully that's of some interest. I think a big gas bottle with appropriate size burner would be a good solution. The whole process really is so dead simple, it's not much more difficult than simply painting for example. I've read that the extra chemicals in Cherry Red leave a nicer, more interesting, finish. May not be as big a deal for us here as I don't think there's any keen gunsmiths or knife makers, but still, given the choice I think the nicer finish would be better.

    Pete

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    I've just been watching the video again and they seem to be saying that with their product it will air harden, so what I said about being able to machine the case off may not apply.

    Stuart

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