1095 home heat treat

[claybuster5]

I bought some 1095 from Aldo and I've researched home heat treats. I realize I should have bought 1084. :/ So, I've decided to use canola oil after reading up but I see that some people say to heat the oil to 100-120 before the quench. My question is do you have to? What good does it do? Doesn't it make it more prone to catching fire?
Thanks guys I appreciate all the help

 

[PocketEdge]

Yes, you really should heat the oil to around 120f or so. By doing so you increase the viscosity of the oil making it more effective in cooling the blade. When you plunge the blade in the oil a vapor barrier is formed and a more viscous oil works faster at getting the blade wet and cooling it. Do you have to? No. But you are not getting the most out of the steels hardness if you don't. I use an old crock pot I got from a second hand store. I don't think temperature has anything to do with fire but I could be wrong.

 

[silver_pilate]

When I first started and used canola oil, I only had very momentary flames if any as the blade transitioned the surface. Heating to 120 isn't going to make you any more prone to flashing. However, what it will do is decrease the viscosity of the oil and allow it to better cool the steel by faster dissipation of the vapor jacket. Agitation is important when using any oil. Make sure you agitate tip-butt or edge to spine, not side to side. This will also help dispel the vapor jacket and create a more uniform and faster cooling.

It sounds like you know that this isn't the ideal situation for 1095, but I can't blame you for trying it out. For a thin blade in 1095, canola will probably work ok, though not as good as a brine or fast oil (though it is a lot less risky than brine also). A thicker blade will have trouble cooling fast enough. As important or more is the temperature control during heating. You'll need to hold at proper temperature (around 1500F) for 5 minutes or so to get the results you want. The problem is, 1500F is a good bit above the curie point where the steel turns non-magnetic at 1414F, so it's hard to judge by eye, and then it can be hard to maintain. You might try heat-treating a few sample coupons in a darkened space, paying close attention to the color and shadows within the steel and see what works for you.

--nathan

 

[claybuster5]

Thank you both for your ideas, you have no idea how much your help means to me. I will heat it up now for sure, either in a crock pot like Grant said or in a pot on my gas grill stove outside. I will let you know how they come out. Thanks again.
- Patrick

 

[daizee]

Good luck, Claybuster. I've had reasonable (though uncalibrated) success with 1/8" 1095 and warm canola. The most complicated part of doing your first quench, IMO, is getting a heatable oil vessel the right size and shape.

Lately we've been using a tall 'tank' of stainless and simply heating the outside with a torch and checking with a thermometer. The temp of the oil takes a bit to stabilize, or you can stir it around to speed that up. This is quite fast. I also have a cheap electric turkey roaster which holds quite a bit of canola. This takes longer to heat up, but has its own temp control. I put a meat thermometer through the lid to get the actual temp, which comes out about half the set-point on the dial.

 

[Drew Riley]

Doesn't it make it more prone to catching fire?

Considering you're going to be plunging a piece of 1500F steel into the oil, I don't think the fact that it's slightly above room temperature should make it any more or less flamable. It does make a difference, however, where cooling/vapor barrier is concerned. It does seem a little counter intuitive that hotter oil cools faster than colder oil, but it's much more about viscosity than temperature.

 

[me2]

Just as a little extra information, canola oil and vegetable oils in general don't tend to form a vapor jacket. Beyond that, I've only tried 1095 with a Mapp torch and water. Don't use water if you can help it, but it will give you a harder blade than canola oil. I used water for my kiridashi, but I hardened it before grinding. Came out pretty good though. Every time I've tried hardening 1095 after grinding, it either warped or cracked.

 

[Rick Marchand]

You can minimize flare-up by plunging fully, quickly and agitating. Most flare-ups occur due to overheating the blade. If you heat slowly and check with a magnet often, you can do an acceptable job. Don't use a torch or attempt heat treat in the light. The darker the better. When I have people in the shop, I like to stress that point. I'll turn off all the lights but one lamp and heat a blade in the forge. Even with only one light on, the blade will look black.... then I shut the last light off and BING... I'm suddenly holding a glowing RED blade. Slow, steady heat.... keep the blade moving. Look up "decalescence". If your room is dark enough, you can actually see visual cues that the blade is going into solution.

You can do a low-tech heat treat with 1095. It might not be optimal... 1084 would definately be the better choice but don't let that put a damper on having fun making knives. I'm glad to hear that you've researched enough to know what steel your should be using. It isn't going to happen overnight and I personally think that low-tech heat treating gives you a solid start as a new maker. You may later choose to farm out HT or dive in deeper on your own but you will have a greater understanding of it, IMO.

 

[claybuster5]

Thank you for all of that information Rick, I was planning on using my charcoal grill as a forge so I will have to do this at midnight! I think I'm going to use some scrap 1095 before I ruin my 1st blade.

 

[Salem Straub]

The main thing I've seen cause flare-up when quenching is having red-hot steel sticking out of the oil. If the tang is that hot, and is not fully plunged into the oil, the fact that the oil is getting that hot at the surface where it can burn in atmospheric oxygen will cause a flare-up. Edge-quenching causes big time flare up as well.

It's less about the vapor jacket with vegetable oil, than thermal conductivity. The oil, when preheated, becomes less viscous, and more efficient at pulling the heat out of the steel and dissipating it. Preheating the oil past 130 degrees or so, I have read, can actually begin to have a negative effect on cooling efficiency.

Another way to heat the oil is to preheat a good sized bar of steel (for two gallons oil, try some 1" round 5" long or so, heated to very low red) in the forge, and quench/stir it around in the oil. You should have a kitchen thermometer in the oil and be watching it. Take the heat bar out of the oil 10 degrees or so below your target temperature, it will continue to rise a bit.

 

[fadugleman]

It sounds like you know that this isn't the ideal situation for 1095, but I can't blame you for trying it out. For a thin blade in 1095, canola will probably work ok, though not as good as a brine or fast oil (though it is a lot less risky than brine also). A thicker blade will have trouble cooling fast enough. As important or more is the temperature control during heating. You'll need to hold at proper temperature (around 1500F) for 5 minutes or so to get the results you want. The problem is, 1500F is a good bit above the curie point where the steel turns non-magnetic at 1414F, so it's hard to judge by eye, and then it can be hard to maintain. You might try heat-treating a few sample coupons in a darkened space, paying close attention to the color and shadows within the steel and see what works for you.

--nathan

Is brine for heat treating literally just salt water?

 

[Stacy E. Apelt - Bladesmith]

Yes, brine is salt water with a little less than one pound salt per gallon water.

I find the main cause of a tank flare up ( and burning/charing of the quenchant) is red hot tongs. If you leave the tongs and the tang out of the oil, it will ignite the oil on them. Just submerge the whole thing. A deep enough tank is the trick here.