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Brett Hurt
12-25-2010, 01:55 AM
So if I heat up some steel to red hot with a torch and then put in 30W oil what well happen, does it get hard Brett

rebel54
12-25-2010, 02:02 AM
Only if it is oil harden tool steel.

Walter
12-25-2010, 02:03 AM
Brett, depends on the steel. long and short, there are steels that will / can be hardened in a fashion similar to what you describe, and there are those that cannot. I'm not gonna make any assumptions on what you have. drop some details on what you have and people here can give a better answer.

doctor demo
12-25-2010, 02:12 AM
So if I heat up some steel to red hot with a torch and then put in 30W oil what well happen, does it get hard Brett

Open a window first:D

Steve

Brett Hurt
12-25-2010, 02:14 AM
I have some mild steel do no know the number but machines very easily. So what I have done is make a holder that lets me screw in the screws Iam making so I can slot them, Iam doing a lot of them. And I thought that if I make a holder want it to last a long time make it hard. I would post a picture but Iam not good at that.

doctor demo
12-25-2010, 02:41 AM
The odds of getting any benefit from heat treating a unknown mild steel are not in Your favor.
See if You can pick up some O1 or drill rod if You want a harden-able fixture.

Steve

dp
12-25-2010, 02:53 AM
It won't be the same after as it was before. Test it before and test it after to see what changed. It may be what you need or it may not. You will learn something, though, and can share it here.

Black_Moons
12-25-2010, 03:23 AM
Hardening tends to warp things like threads.. Your generaly better off leaving it soft unless you are truely mass producing something. (Day in, day out, weeks on end)

djc
12-25-2010, 03:35 AM
...I thought that if I make a holder and want it to last a long time make it hard...

Perhaps what you are seeking is not hardness, but toughness. As others have said, it may not be a good idea to harden threads in your fixture, hence if you do go the hardening route, perhaps case harden (with the holes blocked).

If you want something that is tough (and can be hardened if necessary), a large grade 10.8 or 12.9 bolt or capscrew (sorry, don't know the US equivalent grade - better than grade 5 or 8 anyway) provides a good starting point.

Walter
12-25-2010, 03:50 AM
Brett, more than likely the steel your using won't harden via the method you describe. a great choice for doing what you describe is 1144, or stressproof steel. heat it until red and hold it there for 15-30 seconds (I'm assuming it's not a huge item) then quench it in an oil / water mix 25/75% respectively. 1144 hardens easily. It's also wonderful stuff to machine. O1 is good stuff but more touchy and harder to machine. once it's hard go back and temper it, slowly and as evenly as possible heat it until it starts to go straw - purple colored. once you have it to that color quench it again and yer good to go.

*heat till red* = evenly until it's a bright cherry red in low light, you can also nicely judge by using a magnet and holding the heat when the steel loses it's magnetism. just touch the magnet to the steel and then get the mag away from the heat quickly. Mag's don't seem to like alot of heat.

SGW
12-25-2010, 09:08 AM
To amplify a bit on what Walter said:

"Red hot" is really more like "carrot orange." When it's hot enough, corners and edges will visually lose their sharpness, but the best way to tell is with a magnet.

#30 oil may be a bit heavy for your purposes, you probably want something a bit lighter weight.

If the steel is water-hardening, for best results boil the water first, to drive out dissolved air, then let it cool before using.

cuemaker
12-25-2010, 10:21 AM
grade 10.8 or 12.9 bolt or capscrew (sorry, don't know the US equivalent grade - better than grade 5 or 8 anyway) provides a good starting point.

Grade 10.8 is roughly the same as SAE grade 8 and 12.9 is close to grade 9, although there is not an official grade 9 bolt..... but people make them.

brian Rupnow
12-25-2010, 10:27 AM
If its ordinary 1018-1020 mild steel, nothing much will happen except it will turn a nice uniform black colour. If its material sold as "drill rod" or "silver steel" it will harden to a much harder state and become very brittle.

tdmidget
12-25-2010, 01:31 PM
Brett, then quench it in an oil / water mix 25/75% respectively.
.

That sounds like the hard part. How do you "mix" oil and water?

mochinist
12-25-2010, 01:56 PM
If its a low carbon steel you'll just color it, if it is a higher carbon steel, whether air or oil hardening, it will make it hard if you get it to the critical temp(use the mag trick, easier than color in my opinion). When it is at the critical temp, plunge it(straight and or evenly as possible to prevent warpage) into the oil and swirl it in a figure eight for about a minute. After that wipe off the oil and immediately toss it in the oven at around 425 for two hours.

You can figure out if it is a high or low carbon steel by doing a spark test(google it).

GNO
12-25-2010, 02:23 PM
heat treating & tempering & cold treating is a skill/science all its own, however,folks who work with/at it do some amazing projects,black.& knife smithing come to mind. There are air,oil,& water quenching steels & I have seen mild steel [chisel] quenched in brine, that could cut the parent metal. The oil on top of water is sometimes used to cut back the shock of straight water

Dr Stan
12-25-2010, 04:23 PM
2X on what others have said. Without knowing the composition of the steel its a crap shot. You may want to experiment a bit with some small pieces. Try oil, brine, water, and air quenching to see what happens. You could also try case hardening the material with Kasenite. A Google search will give you the details of the product including sources, just make sure you have good ventilation as it stinks to high Heaven.

rohart
12-25-2010, 08:46 PM
Sounds like you've got an ordinary low carbon mild steel. And it also sounds like you want a thin hard layer to reduce the wear as you work with your threaded components.

Case hardening would normally be the way to go, but getting case to work on an internal thread would be difficult. One way to do the job I think you are doing is to tap your threads and then slice your component down the middle, to create half threads as it were. If you did this, case hardening would work.

Case hardening means getting kasenit or material containing carbon and nitrogen I believe - bone does the trick - into direct contact with the steel surface at high temperature. That's why split threads can be hardened, but not proper internal threads.

Nitriding is gas based, so that would work too, but I don't know if the gas diffuses up a threaded hole well enough. And I don't think nitriding is a home shop procedure.

Terry L
12-25-2010, 09:03 PM
That sounds like the hard part. How do you "mix" oil and water?

Soluble oil. :D

lazlo
12-25-2010, 10:20 PM
FWIW: I lost a bet with Will Bastas (famous blacksmith) about hardening mild steel.

I was trying to drill a rivet hole in the backstrap of a complicated rack we had made. The drill was skidding across the surface of the "mild steel", like it was hardened tool steel. I flattened the strap from a piece of 1/2" round bar in a power hammer, so I thought I had work-hardened the surface. So I keep drilling, and half-way through the backstrap, it's no better.

Will swings by the drill press and tells me to anneal the strap. Anneal mild steel?! So I heat the strap back up to forging temperature, and just sit it under a tool rack and let it cool in ambient air over an hour or so.

Go back to the drill press, same bit, and it goes through the strap, and several other mounting holes, like butter.

We start discussing with the class why mild steel shouldn't harden, and Will takes a piece of 3/8" round bar, forges it into a punch, and then water quenches it. He proceeds to drift several holes in a flat forged from the same stock.

The only theory we could come up with is that there's so much recycled crap in modern steel that alloy contaminants (vanadium, manganese, tungsten, ...) are forming carbides instead of pearlite (iron carbide) formation in medium-to high-carbon steel.

Peter S
12-25-2010, 10:30 PM
I take it our American members don't use the term mild steel, but we do in this part of the world. You can do what you like with heat and oil and it will not harden - insuffcient carbon.

lazlo
12-25-2010, 10:43 PM
I take it our American members don't use the term mild steel, but we do in this part of the world.

I take it our Australian members don't read the previous posts. ;)


You can do what you like with heat and oil and it will not harden - insuffcient carbon.

Unless the mild steel is made from scrap and has low carbon, but a considerable alloy content...

Edit: by the way, I have several 1/4" rods of the same stock left over from that class. If anyone has access to a x-ray fluorescence gun, I would love to see the alloy analysis!
This stock came from Metals4U, which is a rather sizable national chain.

madman
12-25-2010, 11:13 PM
I am guilty of using motor oil(only Old Stinky stuff) to heat treat steels. Firstly the steel should have .30 carbon content red hot stick in stinky oil yup its hard all right. if thats what you want there you go Merry xmas mike

The Artful Bodger
12-25-2010, 11:35 PM
I take it our Australian members don't read the previous posts. ;)


???????????:cool: :cool:

Peter S
12-26-2010, 12:31 AM
I take it our Australian members don't read the previous posts. ;)

Lazlo,

Your knowledge of geography and mild steel are pretty similar :D

lazlo
12-26-2010, 12:35 AM
Lazlo,

Your knowledge of geography and mild steel are pretty similar :D

LOL, guilty as charged Peter! My apologies to the Aussie members. :)
I was being sarcastic about your sweeping generalization of Americans knowing what "mild steel" is when you clearly didn't read my post.

I know exactly what mild steel is. In fact, I'll bet you the cost of shipping a rod of this "mild steel" to New Zealand that when you water quench it, it will be hard as glass.

oldtiffie
12-26-2010, 12:38 AM
P'raps he means Australasia or Oceania AB.

http://en.wikipedia.org/wiki/Australasia

http://en.wikipedia.org/wiki/Oceania

The Antipodes perhaps?

http://en.wikipedia.org/wiki/Antipodes

Brett Hurt
12-26-2010, 12:55 AM
Thanks for all help, so how do I Case harden it maybe thats the way to go for me Brett

lazlo
12-26-2010, 01:08 AM
Case hardening is dirt simple: you heat the part up to cherry red, brush or dip the Kasenite (or Cherry Red, or whatever) onto the part. The powder melts and forms a glassy shell. Then re-heat the part to cherry red again, hold for a couple of minutes, then quench in cold water.

If you need a deeper case, you can pack the part in a metal container covered in the Kasenite. Then you heat the whole container up to cherry red, and soak for:


Case depth .005, Time 15 minutes
Case depth .010, Time 30 minutes
Case depth .015, Time 40 minutes
Case depth .020, Time 50-55 minutes

Peter S
12-26-2010, 08:23 AM
P'raps he means Australasia or Oceania AB.

Well yes, I suppose after overcoming surprise that we speak English down here, explaining to Americans why we haven't put a bridge between our two adjacent countries is a tricky one. I put it down to Aussie reluctance to being known as the "West Island", lets face it there are good blokes on both side of the "ditch" who could do the job with a few concrete pipes and a bit of fill! :)

Lazlo,

I believe the simple answer to your experience is that it was not mild steel! :)

lazlo
12-26-2010, 10:56 AM
I believe the simple answer to your experience is that it was not mild steel! :)

Yes, but the problem is that it isn't/wasn't an isolated incident. We had several thousand pounds of that mild steel from Metals4U in various sizes and shapes, and it all exhibited the same hardening characteristics.

Will was careful to point out that you can't harden old-stock mild steel, which is presumably much purer than modern "mongrel" steel. (Thanks Bruce! ;))

So Will (and other modern smiths) now teach their students to water quench "mild" steel for a temporary/expedient punch or chisel.

Brett Hurt
12-29-2010, 12:59 AM
I case hardened it with kasnit! and it worked very well first time I have ever had done this thanks so much Brett