I need to harden some cuts of steel. This is the grade known as 'guage plate' which AIUI is a low-medium carbon content steel. All I know is that it has to be heated to a certain fairly high temperature, then quenched in oil, water or watever. Then it has to be re-heated to a somewhat lower temperature and allowed to cool back *slowly* again to room temperature. This second stage is called 'tempering' I believe. But that's as much as I know. Does anyone know what the correct temperatures should be for each stage and the best mediums for the quenching part and the slow cooling part? Any info would leave me slightly less ignorant than I am at present! Thanks, p.
What you have there is probably O1 tool steel, which is actually a relatively high carbon steel (0.85% to 1%), but it's important to be sure. Water quenching is dicy, oil works better on the higher carbon alloy steels, although this will depend on the tool size.
so far you've more or less got yout heat treating tempering terms correct ...... heat to around 800C and hold it there for a while, how long depends on the size, and then quench in hand warm oil, vegetable oil works fine for this. Tempering should be done immediately and temperatures depend on what qualities you want on the steel, hardness or toughness. What exactly is the steel for and what size are the pieces?
I'm sorry, Simon. I did answer your post last night but for some reason it hasn't appeared. I've got two principal sizes and shapes to harden. The guage plate is 8mm thick and is in small chunks of a few square inches each. Could these be done with a blow lamp and if so, how will I tell when it gets to 800 degrees? The other part is a shaft of 28mm diameter and weighs about 3 kilos. It's got a long tapered point at one end. I do have access to a forge if necesary for this piece. It's a slightly different carbon contenct to the plate but not by enough to worry about. Any ideas? (thanks for the references youa and the other chap provided, btw).
Sorry, I should have also mentioned, the shaft needs to be hardened in such a way as that it won't bend; the plates need to have the quality of 'teeth' so they will penetrate other softer metals without bluntning or gouging. Thanks again.
"Paul Burridge" wrote in message news: snipped-for-privacy@posting.google.com...
That's ok ... I wasn't being serious :-)
how much is a few inches? and how long is the shaft? it sounds to me like you are making some kind of axe for a robot wars machine now that i put your
2 posts together :-D
I wouldn't say that you are looking for fine tolerances like if you were making a knife blade, blade makers can be very anal about their HT methods ;-) and you could end up with loads of normalising and cycling and you don't really need that. you'll never get your "teeth" hot enough with a blow lamp unless you build a forge around it out of fire brick to insulate it, or maybe a large diameter metal tube that you can insulate with refractory wool (available from pottery suppliers, etc.) place your "teeth" inside, block the ends up with more wool and leave an aperture you can fire the torch inside, this should retain enough heat. A good plumber's torch should get you by as long as you keep the cavity as small as possible. From then on, keep checking on the "teeth" and look for the orange glow in the steel, when it gets close, take them out (with tongs) and test them with a magnet ( a good idea is not to be holding the magnet at this point, but to have it stuck to a metal object) ......when the right temperature is reached, your "teeth" will lose their magnetic qualities, at this point, just check that you have a uniform colour (best to do this somewhere with reasonably low light) and then plunge it in to warm oil, hold it there with the tongs untill all the fuss has died down and then quickly get it to your preheated to 200C tempering oven ( a kitchen oven will do at a push) and leave it there for a couple of hours, this will work fine for the shaft too as long as you get a uniform heat prior to quenching. your shaft will require further tempering at a hotter heat though which you could do with your plumbers torch, but do this after the initial oven tempering, heat until blue and leave to cool...... there's a lot more I could go into ... but the subject is huge and i am still learning (aren't we all?)
The other option is to find someone to do it for you and remove the hit and miss factor. there are plenty of heat treating services out there or you could even find a college that has a smitthing course and see if a student fancies taking it on (cheap option)
So what are you building? ... go on ..... and if I am right ... you need to look in to certain steel restrictions that they have on robot wars ;-)
Correct. How remarkably perceptive of you. :-) I always avoid making overt references to it as it generally draws a lot of spurious interest from lurkers and such like and I don't have the time to answer all the various off-topic questions they tend to ask about the show. Shaft lenght is about 750mm.
Many thanks indeed. That's the most complete explanation I've yet read on the subject and fits in perfectly with everything else I've seen written on it.
Well, one of my co-teamsters has a close friend who's a farrier and who does similar stuff. But I prefer us to do as much as possible for ourselves. As you say, it's all about *learning*!
Not really. I'm aware of the restrictions. It's not the first time we've competed. I have some provisional pix of the MkII on the web at the moment. If you want to take a look, e-mail me for the URL. I'm not putting it in the public domain until the site's properly sorted out but since you've been so helpful and informative I'll extend the offer to you alone. :-)
Look for the Curie point (this works for all (sic) steels, some of which want different temperatures). Heat it up until a magnet stops sticking to it, then you're there.
The "O" in "O-1" stands for oil-hardening. An "A" would be an air-hardening steel. Other letters are less obvious.
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