Tempering bath: canola oil

[peter johnsson]

Yes, that looks like a good one.

 

How even temperature do you think that bath has?

How well could you maintain a set temperature during, say a 40 min tempering?

 

Perhaps I shall have to look for old heating coils, like the one you have inside at the bottom. That is smart use of old parts.

[Bennett]

I used a torch, with a small rose bud for fine tuneing the temp. I could hold it within 5 degrees, once the target temp was reached, weather considered, as long as I had fuel. My probe is about a foot long, and took readings before, and after stirring. The 3 heating points kept the range very nominal, within 10 degrees of each zone, as far as I can measure.

Edited February 17, 2009 by Bennett

[Sam Salvati]

I used a simple system like yours for a while, Sam. Nothing beats it for simplicity but I felt I was getting a hotspot where the flame was especially without a large volume of oil so I housed it in an insulated drum to even out the heat along the whole length. The horizontal burner arrangement matt describes sounds good too for an even heat.

 

I had the same suspicions, thanks for confirming it Paolo. I extended a piece of flat bar in the tank, and would occasionally stir by lifting it (it had a scoop bend at the end) which seemed to keep things even. But your idea of using the drum forge as an oven for the tank is a GREAT idea!

 

Thank you Peter!

Edited February 18, 2009 by Sam Salvati

[kb0fhp]

Just be carful to keep a lid on it when you aren't using it to keep out moisture. my old rig(6" pipe 3' tall, basically a gas forge around a tube) ended up getting a significant amount of waterin it, even with a (loose fitting)lid. OIl float on water, and water has a lower boiling point, and really likes to expand when it turns into a gas, so one day while I was heating it up, the water at the bottom started boiling, making my quench tank into makeshift oil cannon/volcano that shot hot oil everywhere, got on the insulation, caught fire and wouldn't go out. I emptied my extinguisher on it to no avail.

 

Now, I would marquench/temper in it, so the temps were pretty high, but still......

 

 

I am glad you weren't hurt. Water in oil is DANGEROUS. Any water greater than 0.1% (1000 ppm) is asking for just the thing that Jesse experienced. In addition - water at lower levels can cause spotty hardness, soft spots and cracking.

 

The Saginaw Steering Plant lost nearly 1/3 of its plant because of 1 gallon of water in a 1000 gallon quench tank. BE VERY VERY CAREFUL!

[kb0fhp]

Hey man,

 

I found that vibrating the quench was the quickest, easiest way to agitate. It doesn't take much. in a pinch, we've done it by holding a palm sander on the tube. The results are remarkably effective. I don't think it helps past the vapor phase, but before that, there is a marked difference in the quantity of smoke produced. vitually zero. I would usually try to slow the cooling rate down once it got past that point anyhow, so it was ideal. Truthfully, I wouldn't do it any other way with this type setup. the anti scale compound I used to use would cake on in a normal oil bath, and flake off with a water quench, and the astounding thing was that it would make the compound flake off like it was water quenched when we vibrated it

 

Tai Goo gave me the idea to try it, and there is an ASM article that was floating around touting vibrations as being superior to conventional agitation protocol, but I can't seem to find it.

 

The idea of using vibrations is an old one. It was originally thought to be Russian and in one of their Journals - mid 1970s. There are some articles in Heat Treating Progress in the past year or so that describe the process. It works by breaking up a stagnant vapor phase. It works very well and in just the way you observed.

[Ken Burns]

Well - a little late to get in on this, but.... my tempering tank is 6" x app 48", peanut oil. Have 2 1200W (short) hot water elements in bottom. Units wired in series so use 220v. Wrapped with insulation then put stove pipe around that to hold it in place. Using a 'stove' type variable control. Seems to be good for abt 480*f. max. Have lid. Also put faucet at bottom so I can draw out a bit of oil for other quenching jobs ( and h20 too ).

ksb

[Jack Alvin]

The idea of using vibrations is an old one. It was originally thought to be Russian and in one of their Journals - mid 1970s. There are some articles in Heat Treating Progress in the past year or so that describe the process. It works by breaking up a stagnant vapor phase. It works very well and in just the way you observed.

 

I think its great idea