Thread: Quenching Oils and Hardening Steels

Thanks for that link DW. It certainly confirms what I learnt by trial & error (mostly the latter) that when it comes to quenching, "oils ain't just oils" & that there's a bit more than specific heat & thermal conductivity involved!

It also confirmed what I thought, based on limited experience, that you can get an alloy less than its maximum hardness by using different quenching fluids or wrong technique. Someone asked about this on another forum & was told very firmly that if it's at the critical temperature, a steel either hardens to its maximum hardness on quenching, or it doesn't harden at all. That didn't match my own experience. On my last episode of hardening I twice got a blade hard for half its width, while the other half remained dead soft, even though I swear the colour was even across the full width of the blade. I find that very hard to explain with my very limited understanding, but the phenomenon was real enough...

The science of metallurgy is so complex & the hardening/tempering process so susceptible to minute changes in composition of steels and quenching processes it's no wonder so much mystique has developed around it all. The Greeks & the Norse had special gods who looked after smithing, & I've often felt that although I go through the physical motions of heat-treating, the results are determined by some power outside my control!

I'm grateful there are a few steels available to the (very) occasional smith like myself that behave reasonably predictably & yield decent blades if Hephaestus or Thor are feeling magnanimous on the day. One good thing about heat-treating is that it's easy to do it again if you don't succeed on the fist try (or the second, or the third.... ).
Cheers,

I've learned a lot about how NOT to quench from watching "Forged in Fire" show on TV......

"It will kill"......but only some of the time !

Originally Posted by Mr Brush

I've learned a lot about how NOT to quench from watching "Forged in Fire" show on TV......

"It will kill"......but only some of the time !

They seem to intentionally get less experienced participants. Early on, they closed the first season with Murray Carter and another pro guy who beat him (the other guy made a sword that was all solid, and murray's clad sword bent just a tiny bit).

The stages were uneventful because both guys are pros - they both easily finished everything and made gorgeous examples. No super bright orange knives going into a quench, and nobody checking with magnets before knives cooled. For the average person not making anything, it made for a boring show.

Reality TV always follows a format:
* Zany start, introduce you to the people (character building), define the mission, start, some goes to plan, then...oh no!! chaos!! Deadline will not be met, and suspense, and in the end the show comes together and someone comes out on top.

With the pro guys end of season 1, there wasn't much potential for chaos - it was really a matter of how little was it going to take for one guy's wares to come out on top of the other.

I was super impressed -I know murray is a pro, but he's always been *Very* proud of himself. Good to see him prove it in a neutral environment. I"ll bet the audience was bored, because the last thing you want to do with a TV show that's a "I could do that too!" kind of theme is show people who are so good at what they're doing that you think "I couldn't do that" .

Originally Posted by IanW

Thanks for that link DW. It certainly confirms what I learnt by trial & error (mostly the latter) that when it comes to quenching, "oils ain't just oils" & that there's a bit more than specific heat & thermal conductivity involved!

It also confirmed what I thought, based on limited experience, that you can get an alloy less than its maximum hardness by using different quenching fluids or wrong technique. Someone asked about this on another forum & was told very firmly that if it's at the critical temperature, a steel either hardens to its maximum hardness on quenching, or it doesn't harden at all. That didn't match my own experience. On my last episode of hardening I twice got a blade hard for half its width, while the other half remained dead soft, even though I swear the colour was even across the full width of the blade. I find that very hard to explain with my very limited understanding, but the phenomenon was real enough...

The science of metallurgy is so complex & the hardening/tempering process so susceptible to minute changes in composition of steels and quenching processes it's no wonder so much mystique has developed around it all. The Greeks & the Norse had special gods who looked after smithing, & I've often felt that although I go through the physical motions of heat-treating, the results are determined by some power outside my control!

I'm grateful there are a few steels available to the (very) occasional smith like myself that behave reasonably predictably & yield decent blades if Hephaestus or Thor are feeling magnanimous on the day. One good thing about heat-treating is that it's easy to do it again if you don't succeed on the fist try (or the second, or the third.... ).
Cheers,

I had some trouble figuring out what people were talking about heat treating on the forums, but some experience has cleared a lot of it up. I don't use anything that requires a complex cycle and dissolving of high temperature carbides - all of those types of steels come with grain enlargement and decarb if you don't have a wrap or vacuum environment and a furnace. But the following are all easy with parks just heating a color past nonmagnetic:
* 1080/84, 1095, O1, 52100, XHP (V11) - though I heat quickly to much higher - closer to 1900F, but I don't know that it does anything because I can't hold the steel there in open atmosphere - longer time would normalize it and dissolve all of the chromium and carbon, 26c3, most old files

Those are all fair game. There are probably others. You can cheat with the chromium PMs (like D2, XHP/V11, etc) because the powder structure prevents you from having to normalize and melt all of the chromium carbides in the steel, but in reality, I don't like those better than the plainer steels for everyday work since lucking into tip modification with the buffer.

At any rate, the pet schedules that people have and the claims of 67 hardness 52100 from black heat in cold canola - who knows. Maybe someone is heating something really thin and only testing the thin part.

What I do know with parks is it hardly feels any different than canola, but the nickel ball test shows how much better it stays in contact with something being hardened and it transfers the heat better. I've not had a single item fail to harden or underharden (1095 was marginal in canola, and I guess it's worth giving it ano

Another shot now because it probably wasn't the steel that was "just OK"). No heating needed for parks and the critical part of the process is transitioned faster. From color to the eye to in the quench has to be about a second, and then the oil has to be able to transition the first 500 degrees in 1 second for some things like 1095 (White steel would probably be worse - and I'd guess it's always done in cladding - though I've done some thin knives of prelaminated white in canola and it turned out OK (but they are ground mostly before heat treatment so that whatever is going to be the cutting edge going into the oil is very thin. Once there's a hot core that doesn't cool right away, then it's a fight between the oil and the heat coming from the core slowing the transition at the surface.

Which points back to why O1 is probably one of the best ideas for beginners - if you get it in spheroidized good quality stock, it doesn't really need to be cycled to make a very good iron - it just needs to be heated just past critical and quenched in any decent oil and it will fully harden. Add a jar of icewater at the tail end of the cool and toss the blade in the freezer and it'll get harder than you ever need and still have high hardness at straw temper.

The knife community is so infatuated with microstructure when 2/3rds of perfect for microstructure is fine with us that they end up growing the grain on some steels sometimes chasing thermal cycles and recommending things that aren't that easy to execute (If you'd had parks - which everyone is always hesitant to recommend because it's expensive - and heated to nonmagnetic plus a little past, you can just uneventfully plunge the item being heated into it (not past the slot is probably a good idea for many steels as if the steel is heated past the slot, it can warp there), and toss whatever it is in to the freezer for half an hour and then temper. But without the parks, I'm not sure the 1084 recommendation is as good as the knife folks like to make it out to be (but they also have a much greater tolerance for stuff that's a little soft, because a little soft is tough, and you can use a knife that's got a little bit of deflection at the edge. Woodworking tools, not so much.

At any rate, it's get the first 500 degrees off or so in a second if possible and then the rest off in a continuous drop if possible in the next 30 seconds or so and get the tail end temperature as low as possible to maximize the amount of martensite (but that last bit is only if you're chasing lots of headroom).

Someone asked me for details of my “coffee can forge” a couple of weeks ago. I thought rather than start a new thread, I’d put it here along with D.W.’s post & the link to heat-treatable steels & their quirks.

The idea of this type of forge or furnace is to provide a bit of insulation around a small space so a butane (or preferably MAP-gas) torch can get enough of a small chunk of steel to conversion point without taking forever & using an entire bottle of gas. So you need a material that is both refractory to heat deterioration (i.e. totally non-combustible) and has a relatively low heat conductance (i.e. an insulator). There are several materials that can do the job, and a search on the topic will turn up a few alternatives, but I chose to use ash as my main refractory material. I had lots of the stuff after numerous fire-pit fires this Winter (getting rid of the dead radiata pines from our yard).

For my first attempt I opened the can at one end, and made "legs" with 8mm bolts. I added a strip of thicker plate between each pair of legs to stiffen the thin plate of the can. I just mixed the ash to a paste & tamped it in an old 4L olive oil can around an (empty!) wine bottle to form the chamber:
1 Making furnace.jpg

I made the paste too wet, and it took ages to dry out: 2 ash only.jpg

But dry it did, eventually, and although the straight ash was a bit friable, my forge worked pretty well for a while, but eventually the ash started to flake away, particularly over where the flame entered the main chamber.

So I tried another suggestion I’d read somewhere years ago. I mixed up ash & plaster of paris (somewhere around 60/40 by volume, but it could’ve been 5% either way). I added enough water to make a stiff paste and packed it in around the bottle as before. It was a bit difficult to get the bottle out, I had to twist & pull hard ‘til the bottle got above the torch vent, after which it slid out pretty well.

I think I made the paste a bit too wet, because it took a long time for the p. of p. to start going off & my nice clean chamber slumped a bit before that happened, but not too badly, it remained pretty straight where it matters:
3 Forge.jpg

I made a couple of cakes from the excess mix which dried to a nice hard & light consistency over the next few days. I hit one with a hammer & it took a good sharp blow to break it in half:
5 Mix broken.jpg

So lookin’ pretty good, but it took a couple of weeks for the mix in the can to dry enough that I was game to fire it up (I hefted it every few days to feel the weight, but p’raps I should’ve been more scientific & weighed it until it stopped getting any lighter).
5 working.jpg

I only ran it for a short burst the first time. I’ll give it a few more bursts every few days, gradually getting it hotter & getting the last vestiges of water out of it. But I ran it long enough to prove it’s doing the job, & with luck this one should do me long enough to cook the few blades I’m likely to want in the next few years.

Cheers,

You'll like having concentrated heat.

I've got a couple of thoughts. I have three "forges", only one is really a quality unit, and the others are a paint can and a long section of stainless exhaust pipe with refractory blanket (about $22 on ebay for a big square of it - enough for a couple of forges).

I've made most things in the black can forge - the pipe forge is for longer things like paring chisels (I kid you not, I had a ghetto setup of a pinched soup can that I stuck out of the end of the can forge and covered with a section of blanket, but if I bumped the can - it fell off. orange can, orange chisel - not great).

The black paint can has two holes in the side and one in the back - each about the size of a mapp torch nozzle and with a single mapp torch, it can bring the whole cutting area of an XHP iron to temp (1900F or so), and easily heat anything that has a lower critical temp.

Any forge is better than none. Aside from that, it's nice to have some room behind the burner as well as in front of it so you can move a tool in and out to get it to heat evenly, and it's nice if the heat is really high at the point where it is so that you can get things heated quickly.

I thought the large forge would be good, but for making most things related to tools, it's way too much. It isn't as hot as the small can forges, but it's hot enough - but the volume of heat is excessive. I think it's around 50k btu with the two burners and once the insides of the forge are really hot, the radiant heat coming out of it (along with the wash of heat coming just from the burners) is really hard to be in front of and you don't get the control that you get with a smaller forge with higher points of heat and easier view. So it sits, used at this point only once in a while - usually if there's a need to anneal something large.



I use two TS4000 style torches for heat for both of the smaller forges - usually propane, but have a gaggle of mapp cans around (the temp charts show it only slightly hotter, but it's significant for something that needs faster heating or a higher temp - like small bits of powdered stainless, etc) - and I use a cutting torch with oxy/mapp to heat small areas that need forge welding (there's no reason to get into trying that kind of thing unless there's a very specific need - I only do it for chisel bolsters).

In terms of making chisels, small knives and plane irons (as long as they're not parers), the can forge is all I'd need.

20210914_062323.jpg20210914_062313.jpg20210914_062256.jpg


The large forge has started to accumulate a mess on it (broken refractory bricks that block the small forges while they heat, and borax). I should keep a neater area but the forges are on the floor as is my anvil - and nothing will stay clean near an anvil, anyway.

About the heat source - if one is going to use torches (I prefer them to larger higher output burners that are really more appropriate for farriers and knife makers), the TS4000 type here is one that advertises that its "Swirls" gases. It gets to a higher temperature than a similar torch from the same company that makes twice the BTU. The simlilar torch makes more BTUs, but because it's forcing more gas through at a lower flame temp, it doesn't actually make the forge as hot (the heat is pushed out of the ends of the forge faster with the gas volume instead).

Any of the self-igniting torches stuck into these forges will soon lose its ability to self ignite, but otherwise continue to work fine.

I now know how I’m going to blue my machine parts rather than putting them in the kitchen oven for hours.

Originally Posted by riverbuilder

I now know how I’m going to blue my machine parts rather than putting them in the kitchen oven for hours.

(electric heat guns aren't a bad idea in a forge or in any small heat housing - like the ones used for paint removal).

Just putting this out there for the craic, never tried any of this on steel,
but recently annealed some copper to make a gasket the lawnmower.
Can any of you lads tell me if it would be possible to harden an inch of this chisel
I only would need an inch of the business end.

Would this be possible to do with a cheap chefs blowtorch, and gas refil cannister on hand?
I don't have any equipment otherwise, but I could try rigging some things up, like a few nice stones or
a big steel plate.

Would I be able to do something that could be able disassembled to nothing, as I don't have the space for this.

I don't need to do anything this chisel, but sure would be nice to know if it might be possible to make use of a few bars of buried farm bits with what I have now.
I have a kerosene weed burner at the folks which I might make use of, instead of the chefs thing if that would be a better idea.
As you can see not big deal that I need it done anytime soon.

16.JPG15.JPG


Thanks
Tom

A small torch would easily do that - you could probably heat it without housing heat, but even a small corner put together to hold heat would do far better. You can also use an old steel soup can or something without lining it, just to hold some of the heat in.

Heat the end to red and if you have a small magnet near by (like one of those pickup tools, or even glue the cheapest magnet you can find to something metallic), test what you're heating with the magnet - when it loses magnetism, heat it quickly another color brighter (if it's red looking to you, heat it to a moderate orange. If it's moderate orange, heat it a step brighter) and then quench in cooking oil - straight in and then slowly up and down (not side to side, that'll induce warping).

The only thing I don't know is how small the chef's torch is that you're talking about - the smaller the torch, the smaller the heat space and the less mass and better insulation in the space. If it's similar to a plumbing type torch (the ones with 14 oz of gas and a flame about 1/2" wide), that's plenty.

A propane weed burner is relatively low temp and really high output, and hard to use (it'll radiant heat you and burn you before the steel gets hot unless you have some kind of protection from radiant heat).

Thanks David
Going to read you're reply a few times to understand what you're saying better.

So I cannot just blast the chisel out in the open without a housing to hold in the heat.
The tool is something like this wee thing.
Chefs blowtorch .jpeg
Plenty of magnets, sounds like a good idea to make a pick up tool with a bit of old coathanger.
I was going to revise some colour charts before I even considered this also.

So I'd ideally need a sealed unit to hold in the heat,
I have a stainless double insulated wine bottle holder, or an old stainless pot which was a kettle
for the wee thing if it would work.

Think I remember reading the warping comment before, maybe from yourself, I would most certainly be attempting to do the same and dipping vertically.

What I'm a bit unclear about is, if you're mentioning things like cooking oil for example,
for best results, as I don't know what I'd do with a bottle of oil afterwards.
i.e
I do however have some old motor oil which is abundant, and presumably could be used for wiping tools afterwards,
maybe with some straining.
I might have read that it's harder to extinguish, is this why, or is it a plethora or reasons I need vegetable oil.

Oh and can I make the steel worse, as this steel has the biggest wire edge I've ever encountered.
I take it I might have a few goes at this.
It'll be some time before I would go about doing this, as I'd want to have some other things to do at the same time,
maybe a router cutter from an allen key or another specialist chisel should I have need.

Thanks
Tom

i'm not familiar with those torches - the listings say a 2500F flame temp for some of them, but that doesn't make sense against butane's published burn temp that's about the same as propane. Assuming that the btu rating on the listings is right at 4000F and the flame temp is 3500F, it should be enough to do what you want - but there's one way to tell.

I wouldn't get fancy on the heat housing, just use a steel can and put it on something that won't have any water in it - like on top of another can, and stick the end of the torch in and the end of the chisel in. if you can get the end of the chisel bright red to lower orange levels, you'll be good to go (this is inside without sunlight interfering with the ability to see the color, and no bright lights toward the chisel).

I have one of those torches and they easily melt copper wire (melting point 1083C/1981F).
Mine's an Iroda and it claims a flame temp of 1300ºC and when used with a heat shield it can heat a small bit of steel to just over 1200ºC as measured by my pyrometer.
My heat shield is a half dozen fire bricks set up to make up a little cave.
When operating from room temp the cave acts as a heat sink and takes some time to heat up but I don't do that with the Iroda, instead I use a propane torch and then when the cave is nice and hot I insert the steel and use teh Iroda.
As DW says a metal can will be better than nothing.

Don't use old motor oil - its full of heavy metals and carcinogens and best disposed of in a suitable manner.
Used Cooking oil can be used as bar and chain oil in a chainsaw if you have one.
I've put about 40L of the stuff through my saws before I found a cheap mineral oil replacement.
It's best mixed at least 50:50 with regular oil because If you leave pure cooking oils like Canola in a chainsaw for couple of years it can polymerize/gel and gum up the oil pump.

I dunno, I'm familiar with a couple of chef's torches & the ones I know I think would struggle, but would probably get the end of a thin chisel like that to conversion temp if you use some form of heat containment. If you could borrow the sort of typical torch used for soldering plumbing fixtures etc, it would do the job easily, probably without any containment, though I think it's always better to have that because you get it to temp quicker (less scale formation, which is important on an already-finished item like your chisel) and more evenly heated.

I am a total neophyte when it comes to heat-treating, it's something I've dabbled with ever since I was a kid on the farm. We had an old forge with a cranked blower & I loved cooking up steels & quenching them (in straight water) to see what happened. It was quite a while before I leaned there is a difference between high C & mild steel, so at first I was mystified as to why some got hard & some didn't ( ). Fast forward a few decades & my early attempts at heating small items in the open on the bench top were very hit & miss - no problems with something tiny like a marking-gauge cutter, but I struggled (with two torches) to get the blade for this travisher properly heated in open flames:
T3.jpg

As to the quenching, as DW says, try the old engine oil & see what happens, it may work or it may not, but it won't do any harm other than stinking up your shed.

The little bit of heat-treating I did over the last 25 years or so was done using either water (old car leaf-springs to make a couple of draw-knives) or used oil for O1 (like the travisher blade). But when I tried using engine oil to quench some 1080 steel a little while back, nothing happened! The blades came out of the quench as soft as they began. So I bought a couple of litres of the cheapest canola oil (which the supplier of the steel had recommended, cost me all of $8 & I've used it multiple times now, so I think I got my money's worth), & that did the trick, once I learnt that it needs to be quite warm to work properly.

Sometimes, reading the instructions really helps, but in your case you have no instructions, so you just have to suck it & see.

Cheers,