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I have recently been commissioned to make a stainless steel knife for a local veterinarian. It is essentially a full tang 4 1/2" hunting knife with a 440C blade, and I am planning to finish it with stainless steel fittings and a micarta handle so that it can be safely dunked in sanitizers several times a day.

This is my first time working with 440C, and I have found the hardening process quite troublesome (in fact, the blade does not seem to have hardened at all.)

My process so far has been as follows:

I forged the blade in my coal forge using wood as my fuel, forging in the red to orange range.

I then annealed the blade in my new heat treating oven, heating to 1650ºF, holding for 15 minutes, cooling at 100ºF/hour to 1200º, and then air cooling the blade.

After rough grinding, I heated the blade to 1850ºF, soaked for 45 minutes, and tried to plate quench with 1/4" thick steel plates.

I checked the blade hardness with a chainsaw file, and it still seemed really soft. Thinking that the blade had not hardened because I used steel plates instead of aluminum, I reheated to 1850º, and soaked for 30 minutes in the oven. This time, I performed a point down quench in linseed oil, but only quenched the blade and ricasso. To my dismay, the file still cut the steel easily.

Does anyone have any idea what I have done wrong, or better yet, how to fix it?

Jordan

Jordan,

1850 degrees should be right for this blade and it shouldn't need more than an air quench. Do you have a programmable oven? If so, then I would suggest a 10 minute soak at 1200 and another at 1400 before coming to 1850 for 10 minutes. (Be sure to have an air tight seal on your stainless foil package.)

Another thought. Are you taking the blade out of the foil pack when quenching? If not then you might be delaying the quench too long. Either take it out of the pack & air quench or quench the entire pack in a quenching oil for 1-2 seconds and immediately do a press quench.

Let us know how you progress.

Gary

Actually, you brought up an interesting point: I haven't been using a foil package. Could that be why the hardening hasn't worked? Is it possible that I lost carbon due to the oxidizing atmosphere?

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Actually, you brought up an interesting point: I haven't been using a foil package. Could that be why the hardening hasn't worked? Is it possible that I lost carbon due to the oxidizing atmosphere?

Very possible. Did you get much scale? Try grinding the blade and see if it is harder below the surface.

Gary

There was a fair bit of scale, more than there usually is from the forge. I could try grinding it, but the file cut pretty deeply, and, as I grind pretty close to the finish dimensions before the heat treat, there is not much material that I can afford to lose.

Seems like I might be forging another stainless blade.

Third time's the charm??!!

Gary, do you have a good source for heat treating foil? Everywhere I look seems awfully expensive. So far, Jantz seems to have the best price, at $50 for a 25 foot roll of 321 foil. Does that sound about right?

Jordan,

I'm afraid that you have let yourself get talked into quite a project. Your biggest problem is that high chromium steels like 440C just don't lend themselves well to being forged.

I think that if I were you, the first thing that I would do is to ask the customer why he wants 440C. If it is simply because he heard that it makes a good knife then I would explain how he could get a better knife by letting you use your own choice of steels and why. Take the time to talk steel(s) with him. Explain the differences in them. Often times after hearing the why, the customer will understand and agree.

Gary

Gary,

440c was my choice of steel for his knife. As the customer is a large animal veterinarian, the blade needs to be able to withstand some powerful sanitizing agents and cleaners on a daily basis. I didn't think that a carbon steel knife would hold up well in those conditions.

I read in Jim Hrsoulas's books that both 440c and 154cm can be forged in a clean, reducing fire, so I figured I would give it a try.

I suppose I could forge the full tang for the knife, and then go the stock removal route for the blade. However, I haven't ruled out that it was the annealing and austintizing in the oxidizing atmosphere of the oven that caused the blade not to harden, so I might still end up ruining a stock removal blade using my previous heat treating methods.

Would you suggest getting the heat treat foil just in case?

Also, will 321 foil work, or should I go for the higher temperature 309 type? The 321 is supposedly rated for 2000ºF, and I am only going to 1850º, but I am not sure how much to trust such ratings.

If you end up using the 440C then either type of foil will work. I wouldn't be afraid of using carbon steel for the blade however. <img src=' http://www.americanbladesmith.com/ipboard/public/style_emoticons//wink.gi f' class='bbc_emoticon' alt=';)' /> People used it with good success for many years before there was stainless.

Gary

When I have used 440c I have heated it to 1950 and held for 10 minutes then quenched in oil. I have not had any problems with not hardening that way. I have not tried forgeing any yet I will have to give it a try sometime.

David

I'm going to chime in here and reiterate what Gary said about not forging the 440C. I read Jim H's books as well and while I agree he has a lot of great information, I also believe he left as much out. Case in point, forging stainless steels is possible, just not practical. Forging high grade stainless has to be done at very low heats and over a very long time, or you risk creating a piece of jewelry. I have made several knives from 440C and it's one of my preferred stainless steels for customers who request or require a stainless steel knife. I never forge it, but go back to the stock removal method. I would also recommend getting a serious quenching oil for your stainless knives. Loose the linseed and the plate method. If you are worried about blade warp during the oil quench,(or in an air quench) get a couple of sticks of 3/8"x1"x12" copper bars. Drill them to replace the jaws in your vise. Arrange the vise so the jaws run vertically and position it close to the quenching pot. Give that steel a quick submersion in the oil (like 3-5 seconds) and put it into the copper jaws and clamp it down along the spine. The copper will finish the quench and keep the blade straight.

Gary also mentioned using a carbon steel for this veterinarian's knife, and either O-1 or 52100 should resist the chemicals he cleans the blade with. You can also patina the blade to provide a little extra oxide layer to help.

I don't use the foil wrap on my stainless blades. I found that unwrapping them took too much time and effort. I either wrapped them so tightly to avoid scaling that I bent them during the unwrapping or I wrapped them loosely to make unwrapping easier, so I got the scale. In the end I just resigned myself to more grinding.

I tried not to get into this one, but here goes anyway. As an experiment, with a small piece of 440, I ground a small blade. To keep down scale I coated it with a thin layer of satanite. After heating it to a little over 1900, I quenched it in oil and tempered it three times at 450, I think. Very little scale and it cuts like crazy. That's the one and only time I've tried it, so I don't know if it would work again or not.

Dale

I'm not sure of a veterinary setting but I use a W-2 blade daily in a commercial kitchen. It does require a bit of extra care, I keep it clean and dry when not in use and have not had a problem in almost 3yrs.

If you do feel like you need to go with stainless I would go with stock removal.

Hi all,

Just got some tool wrap, and tried the hardening on knife number three....It worked!

The knife was forged in the medium forging ranges, not getting too hot. I did not forge very close, so as to leave plenty of steel on the edge in case of slight decarburization. I will temper the knife today, and will post some pictures. Of the knife once it is finished.

Thanks everyone so much for your help!

Jordan