Thread: Quenching Oils and Hardening Steels

I preheat the quenching oil (new, left over, light weight engine oils from a variety of sources) in a metal tank (a 5L olive oil can) on an old electric fry pan.

Originally Posted by D.W.

.......All of these variables are why it's hard for the average garage person to beat buying decent O1 rolled stuff and heating it once and quenching it in pretty much anything.

Amen to that!

Yesterday, my heat-treating career took a bad setback! I fired up my new "forge" in earnest to harden a new blade I'd just made for my half-rebate infill. The Luban blade that I built it around is a perfectly good blade, but it's too short for convenient setting. The first two dunks (in canola) didn't do nuthin', the heated end remained stubbornly soft & easily filed. Yes, I had pre-heated the oil this time, and it was the same oil & the blade is from the the same length of 1084 I had managed to harden nicely just a few weeks ago in the 'old' furnace, which was essentially the same. I had tested the blades with a magnet & there was absolutely no 'stick' back to where I wanted it hardened, put it back in the fire a bit longer & raised the colour a smidgin, but to no avail.

On the third attempt, I got the steel as hot as my single torch could get it, and in my haste to get it from furnace to the quench, I knocked the tin of oil over!

Have you ever seen how quickly & how far 2 litres of hot oil can spread over a bench & floor?!! I spent the last hour of my day cleaning up the mess, shut the shed up & went inside & had a calming beer. Needless to say, I didn't even bother to test the blade, it never made it into the oil. On Monday, I'll get another bottle of canola and try again (with the oil can inside a steel bucket, just in case).

I had also made a new blade for my panel plane - this one is a whopper and 5mm thick. It is O1, which I have had no trouble with in the past (though much smaller blades) & I had visions of trying to harden it with my 'new' furnace, but I have decided that plan needs a rethink. So I'm thinking I'll drill a hole in the other side of the furnace for a second torch, which ought to both increase the number of effective BTUs and even-up the temperature in the chamber. Well, that's the theory, anyway....

The story will continue.

This is my small quench tank - a piece of 6mm thick x 100mm diameter x 300mm long steel pipe with a 6mm thick steel based welded onto the bottom.
Its quite heavy so a bit harder to tip over than the olive oil can.

QuenchT.jpg

Originally Posted by IanW

Amen to that!

Yesterday, my heat-treating career took a bad setback! I fired up my new "forge" in earnest to harden a new blade I'd just made for my half-rebate infill. The Luban blade that I built it around is a perfectly good blade, but it's too short for convenient setting. The first two dunks (in canola) didn't do nuthin', the heated end remained stubbornly soft & easily filed. Yes, I had pre-heated the oil this time, and it was the same oil & the blade is from the the same length of 1084 I had managed to harden nicely just a few weeks ago in the 'old' furnace, which was essentially the same. I had tested the blades with a magnet & there was absolutely no 'stick' back to where I wanted it hardened, put it back in the fire a bit longer & raised the colour a smidgin, but to no avail.

On the third attempt, I got the steel as hot as my single torch could get it, and in my haste to get it from furnace to the quench, I knocked the tin of oil over!

Have you ever seen how quickly & how far 2 litres of hot oil can spread over a bench & floor?!! I spent the last hour of my day cleaning up the mess, shut the shed up & went inside & had a calming beer. Needless to say, I didn't even bother to test the blade, it never made it into the oil. On Monday, I'll get another bottle of canola and try again (with the oil can inside a steel bucket, just in case).

I had also made a new blade for my panel plane - this one is a whopper and 5mm thick. It is O1, which I have had no trouble with in the past (though much smaller blades) & I had visions of trying to harden it with my 'new' furnace, but I have decided that plan needs a rethink. So I'm thinking I'll drill a hole in the other side of the furnace for a second torch, which ought to both increase the number of effective BTUs and even-up the temperature in the chamber. Well, that's the theory, anyway....

The story will continue.

Oil will go far - and it will just keep going. Imagine also tipping over a gallon can of shellac and not noticing that it was tipped until the next morning - to find that it all leaked out onto the floor (it goes a little bit, less spread out than oil, and turns into a not-hard-not liquid layer). The key to solving things like oil spills and shellac spills is not having a floor so clean in the rest of the shop that they will drastically change the ambience.

I started with a mason jar quench of peanut oil, which was a waste of time (Because someone told me that only peanut oil would work - they were from the south here, where that's the cheapest oil - soy oil is that here and it solidifies at a lower temperature and I like it better. It's in containers labeled "vegetable oil" where the seller doesn't want to be obligated to keep the vegetable the same. Or, in short, for people who don't want to pay for "canola oil".

Anyway, i became enamored with how without mixing, the top layer of oil would get really hot if you quenched two things. And then found that the mason jar (Which is meant to be boiled while canning) would explode if the differential was too great. Oops (I guess the top layer got hotter than boiling water and the top third or so of the jar exploded off with a "clink" (not flying far, just breaking off in all directions in a bunch of pieces)).

I have two holes in my paint can forge and a small hole in the back - if the front is bricked, the thing will generally get hot evenly, but it's easier to heat something evenly quicker (if it's a little longer) with two torches. When making paring chisels, since the backs are thick and the ends aren't, I heat with the torches facing into the "exhaust pipe forge" and there is no exhaust out of the back of the forge. I guess with everything, it's whatever works, but plane irons are nice because you don't often have to heat more than an area of 2.5"x2.5"

O1 is a good choice for 5mm thick steel - it'll through harden fine. if you did a 1084 iron 2mm thick and another 5mm thick, even in parks, there would probably be some difference in hardness and if you snapped it, it may not have extremely fine grain in the center (due to slower quenching or thermal effects when thermal cycling). I'd guess O1 initially made its mark by being lots easier to get uniformly hardened so that it would have stability in large cross sections (to make measuring tools or precise machine parts), but I don't know that for sure. I have knives of clad material that will warp when they're finish ground and then go back to straight when they're cool. Nobody would ever notice it in the kitchen because the whole knife will never get warm, and the warping is subtle. It'd be a real problem in manufacturing causing a requirement for the machine parts to remain the same temperature through production vs. something not needing that if it had better temp stability.