I'm stumped with 440c

csalt09

Well-Known Member
I'm stumped. I have been lurking here for some time now and usually find answers that were already asked. I have a evenheat oven and just getting into stainless (440c). I followed the evenheat info for 440c, foil packet at 1900 for 15min. I used 1" aluminum quench plates. I did not let the knives get below 150f and did x2 tempers at 325 for 1hr each. My testing showed edge chipping on a brass rod. I also did a knife bend test and it broke at about 10 to 20degrees. The edge started dulling after about 4 cuts on 1/2" manila rope. I realize the I need to increase my termpering temp but stumped on the lack of edge holding. Oh, the grain on the broken knife seemed ok. Any ideas? My tempering temps may not be as accurate as they should as a side note.
 
Much has to do with the geometry you grind...... there's a reason that the old Buck 110 folders had that overly excessive edge bevel....it was because in the beginning, the engineers chose 440C for the steel, and didn't give much thought to type the grind.....the first couple runs of those knives (way back when), had terrible issues with blades chipping badly and breaking.....because they were trying to do a flat grind, which simply wasn't strong enough for the combination of Rc and steel. Rather then change steels, they chose to change the grind to "sorta" (semi) hollow grind that left a huge amount of material thickness at the edge, which traded off sharpness and cutting reistance in favor of durability.

Most stainless steels have a VERY narrow target Rc hardness, meaning that you have to be pretty much right on to get a usable end product. They are not like carbon/alloy steels....you can can't widely differ the tempering temp and have it come out "right". What I have found is that staying close to the target hardness that is recommeded, and modifying the grind geometry is the best course of action when dealing with most SS.

I followed the evenheat info for 440c, foil packet at 1900 for 15min. I used 1" aluminum quench plates. I did not let the knives get below 150f and did x2 tempers at 325 for 1hr each.

When I read that, it prompted me to think about my own experiences when I first started experimenting with SS. There are so many variables when it comes to heating a blade, theres no way I could cover them here. Just think about what you're doing, and look at each step. I've come to understand that the recommeded heat treat procedures should be used as a Starting Point, and not absolute. When I first started using CPM154, I had issues with it not fully hardening.....using the recommended formula. What happened to me was I wasn't taking into consideration that the formula of 1900F for a 15min soak meant that the time started when the entire blade had reached that temp. DUH! After several trial and error runs, I settled on 1950F for 20 mins. That solved my issues with that particular steel.

Compared to carbon/alloy steels, SS is going to be "chippy", its just the nature of the beast. Personally I only use a limited amount of SS, simply because it sells, and customers want it. Personally, the only "advantages" I can see of SS over a carbon/alloy blade are.... (1.) Very low maintenance, due to the SS factor, and (2.) Bragging rights about having a blade made of the "latest and greatest" steel. In the end, I doubt you will ever get any SS to perform like a carbon/ally blade will....they are two totally different animals. What you mentioned about your testing (the chipping and the 10-20 degree break) sound about right for a 440C blade.
 
Thanks Ed, that makes since about the flat grind. The knife I tested was a full flat ground blade and fairly thin. I'm glad to know that 440c is normally chippy because even when I increased the tempering temp it still chipped and has not so great edge retention.
 
What Ed said is very spot on about stainless.
What i can suggest, if you still want a stainless blade, is to switch to steels like sandvik 14c28n, or AEB-L, because those are steel that behave very similar to carbon steels in terms of edge stability.
Bear in mind that with any SS you'll have to fight with the residual austenite, and you do that by cooling the steel well under room temperature following the manufacturer instructions. Tempering the steel before freezing will stabilize the RA a lot, so the cooling, from the moment you quench, has to be continuos until the selected under zero temp it's reached...then you can temper.
You are also right, you need to be sure about your oven temperatures, and if you have a way to be sure of them it will definitely help ht'ing SS.
 
OK, I'm going to go WAY out on a limb here a disagree a bit with the master. He's right, if you want 440C at RHC 59, you have to nail it, but it has a wide range of tolerance both in hardening and in tempering that will give you different results, but still way superior to the results you are getting. 440C can harden at 1850 for an hour - 1875 for 1/2 hour - 1900 for 15-20 minutes or even 1950 for 10 minutes (not recommended). With most of those, it will end up around 59-60 without cryo and 60-61 with cryo. It needs to be tempered back at least a point or two and many commercial knives have been tempered back into the 55 range. That will still outperform your results.

I get it that you wanted to get to temper real quick and that is critical with carbon and tool steels but not so much stainless. By all means, go ahead and do a flash temper in the kitchen or toaster oven to take the stress out, but they are so inaccurate, you have to keep the temp just enough to take the stress out - think 250 for 440C - and later you can use the evenheat to get to where you really want to be.

440C can make some awesome knives (Ask Lawrence @ Rhino).

Now I am going to completely agree with the master. There has to be something wrong with your edge geometry. No heat treat on it's own would lead to results as bad as you are getting. Hoping Lawrence will chime in with some edge advice.

Don't bend test stainless. It's made for awesome knives - not prybars

Rob!
 
I did change the geometry on another knife and got better results, not great but better. To snap temper, would I temper at 250 for 1 hour? I have a fluke ir temp gun to check temps on the blade and when I pull the blade out of the oven and immediately check the temp it reads in the 150 degree range but 350 when checked in the oven. Any idea why that is?
 
Yes, I think that snap temper would buy you lots of time. An old data sheet from Crucible actually showed a usable temper for 440C at 212F. No, I'm not recommending that, but 250 should easily take the major HT stresses out, and even if the oven is way out, it is less likely to wreck your blade. I don't have much experience with IR testers, but you don't need one to tell 150 from 350. 150 can be handled (gingerly) with a bare hand. Uncomfortable but doable. For 350, think of taking the casserole dish out of the oven without pot holders. :what!:

I'm not suggesting 440C is a great steel - or a bad steel for that matter. Someone above suggested AEB-L. Nice stuff! Elsewhere on the web, someone compares it to 440B. That simply isn't the case. It is a purpose defined fine slicer steel. Hardens to the mid 60's - tempers back predictably to 55 - 62 depending on what you want out of it - and takes a scary sharp edge if that's what you want too. Probably not recommended for chopping. Often even cheaper than 440C.

Also, be careful of recipes. I think the one you followed on the Evenheat site included Cryo. While HT can certainly be done without cryo, the results are significantly different - particularly with stainless.

Rob!
 
I agree with the recommendations for AEB-L and also for subzero. I would think retained austentite is your issue. When I do stainless, I only use two steels, AEB-L and S35VN. AEB-L for a fine edge at Rc62, and S35VN at Rc60 for edge holding.
 
I've been hearing a lot of good things about AEB-L. I want to pick one stainless to work with for now was thinking about cm154 but AEB may be a better choice for my experience level.
 
I use both CPM154 and AEB-L.

They feel and respond pretty much the same to me when I'm working them. I grind post-heat treat, so that's probably why.

There is a huge cost difference. You can buy a lot of AEB-L for the price of a stick of CPM154.


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I've been hearing a lot of good things about AEB-L. I want to pick one stainless to work with for now was thinking about cm154 but AEB may be a better choice for my experience level.

Different animals and depends on what you want out of the knife. AEB-L is purpose specific - and very good at slicers indeed. Maybe not so good for a camp or utility knife that might see some 'extra' duties. CPM154 is a bit more expensive, but there is very little it won't do extremely well. If you're firm on using just one steel, I'd choose the CPM 154 for its versatility. - and for the value that a 'super steel' adds to your knife.

Both of these have a solid place for blade steel choices.
 
don't chime in too much with heat treats but been doing a lot of flat ground 440-c small hunters of late.
I have been doing foil wrapped 1880 for 15 min plate quench then temper at 325 degrees for 2 hrs with a edge at .020 to .017and never had problems with being chippy. I have had tested and they come out to 58 rc almost every time. I like 440-c thought it was nice to work hope you figure it out. good luck. http://www.alphaknifesupply.com/zdata-bladesteelS-440C.htm thought I would add this link hope it helps.
 
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I actually have three 440c knives in the oven now. I just picked up a few lbs of dry ice and will be trying cryogenic for the first time.
 
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