Torch hardening question

deadin

deadin

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What temperatures can a standard propane torch heat a5/16 to 3/8th dia. drill rod up to? (How about a small propane/oxygen torch?)

I need to harden and temper a piece of either W1 or A2 rod. The W1 requires 1450-1600 degrees and the A2 is 1700-1900.

(I'm making a spanner to remove the hammer stud from a 32 top-break and those little blades are going to have to be tough.)
 
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I make a lot of punches and tools for my engraving & restoration work and have done so for the last 40yrs. Drill rod gets the call quite often.

I use a simple propane torch for the task.
You can use Mapp, or Propane/O2, or even OA. But it's really easy to get carried away with these. Plain propane will work into the 1400 range in my experience.
I'm guessing you could use it on small dia air hardening rod if it needs to get to 1900F,,but I've never used the stuff.
I'm no machinist/metal guy. The air hardening stuff I've run accross is a pain to work with as I can't draw it back. I just don't now enough about all the tech science of it all. I get along OK with what I know and do.

Most I make from 1/8, 3/16 and 1/4 d/rod. A few slightly bigger hand stamps when needed use bigger dia mat'l. But I use the same propane cyl torch. (Old Chev push rods make great punches and hand stamps!)

If you can't bring it up to temp just holding it in the flame,,lay the part on a piece of charcoal (brickette works OK). It'll reflect the heat back, glow red and heat things up in a hurry. Asbestos paper works well too but thats not PC anymore of course.

Water hardening or Oil hardening...Heat to red,,quench. Books say 'cherry red',,who the heck knows what cherry red is. Red

Polish the part bright so you can see the temper colors change for the next step.

(To avoid heat scale on small parts like this that you are torch hardening,,you can coat them with an alcohol/Boric Acid slurry.
The alcohol burns right off leaving a crust of boric acid on the part. Handled carefully (it's brittle) it'll protect the part from the outside oxygen in the air when you heat it up red so it won't 'scale'.
When you quench it,,the boric acid crust disintegrates leaving a dull light grey colored clean steel surface. Easy to polish up for tempering. Especially good when making stamps and the like, but saves work on any job. Cleaning the tough adhearing heat scale from the new work is a pain. )

Draw the temper. You can use the same propane flame,,carefully.
I draw the punches out to a yellow color. I need them quite hard but don't want them to shatter.

For a screw driver,,the good ones are drawn to 'spring temper blue' which is a bright sky blue color.
Tease the color change up on the part. Don't over heat any one area.
It'll want to change quicker on the thin areas,,slower on the thicker areas.
If you go past what you want,,anneal it (soften it).
Re-harden it (first step)
Then re-draw the temper.

Another way to draw the temper and safer way to avoid overdoing it is to place the part on a piece of thick steel. 3/8,,even 1/4 will do,,something of mass. You heat the steel piece from underneath.
The heat is conducted to the part more evenly than the direct flame in the first process and though slower,,results in a more even and controlled tempering.
You should be just be able to cut the new screw driver with a sharp fine file when tempered correctly.
Just like a new mainspring.
Good Luck on your project.
 
I do heat treating but use a digital oven. But her is some help

A small propane torch might work but you can up your odds of success by making a small forge. Get a either 4 soft fire bricks and make a long box or just one and bore a 1 1/4 hole length wise in it and then a small side hole for the torch. Soft bricks carve easily. Hard fire bricks do not and do not insulate as well and take forever to heat.

Steel goes no magnetic at about 1414f so have a magnet close by and as the steel turns red start touching it with mag, when it quits sticking go a couple shades lighter red. Dim lighting helps. In your case I would go with the O1 or W1 drill rod as the A2 has more alloy and really needs to soak at the critical temperature for about 30 min to achieve the best results. After you harden it you will need to temper it or it will be extremely brittle. For what you describe I would go to around 600f for 2 hours in the kitchen oven. A knife would be about 400-450, but that would still be brittle for a striking or prying instrument. Springs are about 800f. Tempering is time critical.

The reply above was sent while I was typing tempering with a torch will work but it is called a snap temper for a reason. The time factor is even more critical in air harden steels because they all have an increased amount of chrome which slows down carbon movement and is why it fails to temper (draw) with short heats. Most of it also has a secondary temp where the hardness actually goes back up with more heat instead of continuing down like most simpler carbon steels.

If your not in a hurry I would harden and temper a couple for you in either material.
 
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Sorry, but, I would never harden A2 with a torch.

Because it really needs to soak at temperature for 30 minutes and because it needs to be at least 1800. It is impossible to hold a good temperature for any period of time with a torch and because it needs to be at least 1800f. At that temp oxegen will attack it and you will get decarbonation. I Heat treat all air hardening steels in a stainless steel foil packet to keep this from happening. Also because of its carbon content (1%) it tends to be brittle as it forms carbides which set up in the grain boundaries.. Industrially it is used do punches and dies, but they are square face punches designed for use in rigid equipment like punch presses. Not good for side loading.
O1 would work better than W1 or A2 as it is an oil hardening steel. O1 is a standard drill rod and is available at most Fastenal stores

Probably the best steal for his application would be 5160. Spring steel. It is slightly carbon poor (.60) and forms no carbides.

Iron can only use approx .85% carbon and excess carbon will seek something to bond with and from carbides. While carbides are extremely hard they are not tough. Toughness and hardness are not the same and typically at odds with each other. There is a reason guns and tools (except things like dies) are made from lower carbon steels and have relatively low hardness.



and yea I am a steel nut who studies steels and HT. I am a custom knife maker. I use a variety of steels including A2, D2, 5160, W1, O1, 1095, 15N20, 5160 and now some of the higher end stainless.

I will repeat my offer to harden the tool and would even donate the 5160 as I have a hundred lbs or so of it laying around. Just don't know what shape the tool is.
 
After careful consideration of all factors, I'd say take steelslaver's offer. ;)
 
2152hq:
(To avoid heat scale on small parts like this that you are torch hardening,,you can coat them with an alcohol/Boric Acid slurry.
Click to expand...
Are you talking about something like Kasenit?

Steelslayer,
That's a generous offer! I have an example made up from plain cold-roll and will post a picture later today. (I know it can't be properly hardened, but I wanted to see if I could even fabricate what I needed.)
 
Here is a picture of what I'm trying to make. Thoseblades are only about .050 x .050 x .050, so they're going to have to be pretty strong. (The stud had been in the gun for 134 years.)

studwrench.jpg
 
What id the OD of the part where the pegs protrude? Is the hole in the center necessary and if so what size. I have a mill and a lathe. Pretty simple tool. I would be soaking the part in a 50/50 mix of kerosene and transmission fluid to help free it up.
 
Mill and lathe here also.:) Just no experience with heat treating.....:o
The OD at the pegs is .3125. The center hole is necessary (it fits over the hammer shaft) and is .144 dia. (#27 drill), 0.5" deep. The pegs are .056 wide, .045 thick and .058 protrusion from the body of the tool.
I've been soaking the parts in Kroil, alternating with Ballistol.
Wiil kerosene & ATF be any better?
 
Kroil is good, tranny fluid and kerosene maybe a little better. I think time is makes a bigger difference though.

OK, Just checking is the thick from toward center to OD? or following circumference.?
 
I forgot to mention, the distance between the pegs (across the center) is .201. The thickness is following the circumference and the width is across the center.
Here are a couple more pictures that might make it clearer....
stud.jpg
 
2152hq:

Quote:
(To avoid heat scale on small parts like this that you are torch hardening,,you can coat them with an alcohol/Boric Acid slurry.

Are you talking about something like Kasenit?


No not a hardening compound,,,but a heat scale shield instead.
When you do torch hardening in the open air, the part will get a nasty crust of dark grey heat scale adhearing to it after it is quenched.

The scale needs to be removed and the part polished bright so you can see the temper color change in the next stepof the process.
One way is to polish the scale off. It's a difficult job especcialy on small parts.
Another is to soak the part(s) in weak muriatic acic for an hour or more (2 tbps acid//gal water @ room temp).

The other is to mix the boric acid powder with a little alcohol to make a paste. Cover the part with the paste and light it to burn the alcohol off. It leaves the part inside a hard but brittle sheel of the borric acid sealed off from the outside O2.
So when it's heated,no scale forms.
The Borric acid shell glows as brightly red as the part inside. The shell disintegtrates on contact with the quench medium leaving a clean grey steel part ready for tempering.

Boric acid is solid in Home improvement and Garden stores as ant and roach poision. Comes in a plastic sqeeze bottles usually w/a spout used to squirt the contents which are a dry dust consistancy chemical into cracks an crevices.
For our purposes,,just mix enough of the boric acid powder with plain rubbing or ispropal alcohol to make a paste and cover the part in a thick coat. Light up the alcoholand burn it off,.
wear eyr protection.

FWIW,,I'd make up a small punch to fit into one of the spanner slots in the nut stuck in the frame. Shape it careful to sit down into the slot and up against the side wall of the notch at a slight angle,
Give it a few gentle and educated taps in the un-loosening direction. You may be rewarded with loosening it and the spanner need do nothing more than light weight work from there.
 
Got it, I'll make one up and harden and temper it. If it is a little tight you might have to adjust it with a diamond file.

Various compounds will work and do a decent job helping prevent scale and decarb during HT. I started out using a torch then a forge to harden, and although it will work, trust me a digital oven is way way better. Plus good tempering is very time dependent. Although a snap temper will draw the hardness it does not do much to reform the martensite structure of hardened steel. Most heat treating charts call for at least one two hour cycle to temper. Two cycles are preferred because the first cycle will cause any unconverted austensite to convert to untempered martensite that needs the second cycle to temper properly. Very few of the anti scale compounds work well above the 1500r range needed for air hardening steels. Stainless foil or an inert atmosphere is the way to go on those steels. I can flood my furnace with inert gas butt, prefer the foil.

Yes, simple torch methods can get you serviceable results, but it is not the optimum. The saying goes in the knife makers world that if God provided you with the perfect steel it would still need the proper heat treat to become the perfect blade.
 
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Wow! I'm getting an education here. :D I want to try some of this out myself to see if I can do it. (SS, I really appreciate your efforts on this. I will use your piece as a model to see if I can duplicate it.)

A Question.... In reading the various instructions on tempering (drawing??) I understand the reason for polishing the part in order to see the color change when heating to the desired temperature. My question is, If using a kitchen oven at, say 400 deg. for an hour , is the polish still needed or can it be done after tempering? (for appearance sake.)
 
Been reading through this thread and I now have more knowledge about heat treating then I ever thought I would.

I just wanted to say its threads like this that keep me coming back to this forum. And people like Steelslaver offering to make a punch for a fellow forum member is above and beyond.

Its nice to see common decency is not dead and most gun owners are stand up guys.
 
You are correct that the polishing is so that one can see the color changes in the steel. While this works it is difficult to accurately gauge temp this way and control it with a torch. there is also the depth of the heat in the piece. While it will work it also does not really allow a complete temper. Your piece is in my oven and about ready to quench then I will temper it. I am going to temper it to 650f for more toughness. 400f would be for something like a knife blade. Harder but more apt to break under a side load. I used O1 tool steel because I have it in round stock. Main industrial use is drill bits.

You want an heat treating education go read and ask here. hypefreeblades forums ? Index page

Want to know more about metal? Read this book
Metallurgy Fundamentals
Daniel Brandt
ISBN: 0-87006-922-5
 
Nice work, SS.
Also, I'm glad I'm not the only one here familiar with using 50/50 Dexron/Kerosene for a penetrating lube.
It works amazingly, and doesn't smell like Pine Sol.
I have a can of Kroil, if I can find it, and it's great stuff.
It's also expensive stuff for something that doesn't work any better than Dexron/Kerosene.
 
I just made a tool such as this from W-1, 3/8 O.D. with nearly the same dimensions on the business end. Mine was to use on a 44 HE 2nd model hammer stud. The stud on my gun was staked in place with a circular tool. The staking strike was not evenly centered and I could see that metal was displaced into one of the slots of the stud. I worked on this slowly with a square needle file and when loosening the stud could feel the part working against the staking. My gun was from the early '20s and had seen hard use but the stud was not frozen in place with rust, it just was quite solidly locked with the staking.

The tool worked just fine. I had hardened and drew to light blue as 2152hq wrote above using a propane torch. I had drilled the tool through so there was not so much material to heat and yet I probably should have used acetylene as it was a bit slow heating.

Dan
 
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