Metal Hardening..the home way?

[Billy Golightly]

OK guys, putting the group collective knowledge to the test here. Lets suppose I want to harden something, like a transmission gear, or shaft, in my shop. What are my options, and courses of action?

[Jason Hall]

when I was younger I read that you could harden Gm turbo 350 Intermediate spraggs In your oven. I think the article I read was In a car craft magazine :lol: :lol: It needed to be heated to 500 degree's for 30 minute's. I can find out more Info If you want, I have a couple friends that make some crazy stuff, and have lots of parts heat treated right here In town.

[Billy Golightly]

That would be very helpful Jason, thanks! :beer:

[Jason Hall]

What are you trying to do? I'm sure I could get It done CHEAP!!! This part of the world Is kinda slow because of the Economy.

[dizasterzrfun69]

buy a "curing oven" or whatever its called like my shop teacher had and cook it for a few hours, you can heat it up and drop it into some motor oil too but that will make it "fragile", yet very hard i think.... :confused:

Hey jason CALLL ME

[Thorpe]

Heat it with a torch and put it in oil a few times... Acts as more of a case hardening... wont make it brittle... We have done it a few times in our shop... Not a heavy duty enough procedure for something like the wheels on our english wheel with a hardness near 55, What are you trying to harden?

[beets442]

+1 on case hardening with heat and oil. To get it deeper, I've preheated hard steel and then welded hard surface rod (very hard to do without undercut or cracking) to it then turned, milled it to size. Beets

[Billy Golightly]

For the sake of discussion, lets say a connecting rod :)

I have no idea on the hardness scale what that would need to be. I have heard of "oil quenching" before, but didn't really know wht it was before you guys mentioned it here, thats very interesting. So if the whole part was cherry red for a bit, and then threw it in a bucket of oil (wonder what weight and viscosities, how that effects it? I'd assume that thicker stuff would be a longer cool down time?) thats an effective way to harden a part?

[WIkid500]

Oil quenching is a great way to harden a part with out making it brittle like when you quench with water. If you want to case harden something you need to heat it for a length of time in carbon. I can dig out a book from last semester and find formulas if need be for this kind of stuff.

In your case with a connecting rod I would heat it to a dull orange, not cherry red and dunk it in USED motor oil. The used oil has much more carbon in it and this acts like case hardening.

[LonesomeTriZ]

I thought freezing engine internals was batter. That is what I am having done when get get started on my 7.3 twin turbo biuld.

[Daddio]

Work hardening is another way to harden steel. Get yourself some basic info on blacksmithing. I love working with metal. My specialty is sheetmetal.

[1BFC]

Here you go Billy..

http://www.google.com/url?sa=U&start=3&q=http://www.countryplans.com/vintage_farm//machineshop/hardeningsteelMIJun51.pdf&ei=Y0jhSfWUEZT0nQev4_StCQ&usg=AFQjCNGyV9D0JRrGVTuxadkkkOAVK0giQw

Careful how you heat up the item you want to harden. If you don't heat it evenly you can induce some twisting and other nasty things.

If you really want to make something special, harden it and then send it out for cryo treatment.

From experience, Cryo treatment works all by itself too. Story to follow..

Several years ago a friend of mine raced a highly modified E Production Mazda Miata in the SCCA on a national level. Very competitive field with very restrictive rules on what you can and can not do. One of the areas they restricted heavily was brakes...(go figure, such a dumb area to restrict). Anyway, he used to go through a set of rotors every other race and TWO sets of rotors every time they ran Sebring....

After trying everything else we sent the rotors out to get Cryo treated. After treating the rotors they would go an entire season....and still not be beyond usable.

Anyway, that's my contribution there Billy. The crystal structure of various types of alloys is very unique between them all. Read as much as you can before testing anything out on an expensive part!! :)

Good luck!

[Billy Golightly]

I appreciate all the input guys, hopefully I might get to put this to the test sometime soon :)

[SWIGIN]

i just read about this in my machinist book..... i'll post what it says when im not on the ps3

[cheaptecate]

It depends on the metal. The big difference is how you cool it down. some metals you need to quench in water, some in oil, and some just air cool. If you have a metal that needs to be water quenched and you air cool it it will not harden. it might actually aneal it and be softer. If you water cool a metal that needs to be air cooled you WILL crack it(been there, done that, spent the money:cry: ).
For something as important as a rod I would go to a pro. Also, would you want to harden a rod. I would think it would break faster because it compresses and stretches every cycle. Maybe case harden it but like stated before, that needs to be packed in carbon and air tight.

[Billy Golightly]

Sweet, thanks SWIGIN. Oddly enough I have a machinist handbook here and I never thought to look in it. Didn't expect it to have any steps or directions I could possible do without having an entire factory at my disposal :lol:

[Billy Golightly]

It depends on the metal. The big difference is how you cool it down. some metals you need to quench in water, some in oil, and some just air cool. If you have a metal that needs to be water quenched and you air cool it it will not harden. it might actually aneal it and be softer. If you water cool a metal that needs to be air cooled you WILL crack it(been there, done that, spent the money:cry: ).
For something as important as a rod I would go to a pro. Also, would you want to harden a rod. I would think it would break faster because it compresses and stretches every cycle. Maybe case harden it but like stated before, that needs to be packed in carbon and air tight.


I was using the rod mostly just as an example and for the sake of discussion. The practice in general interests me in a lot of ways. Mostly for engine stuff. Rods being one, and things like transmission shafts and gears being another. I think it'd be just good information to know and have off hand for any future endeavors :)

[Daddio]

This is something I remember hearing a lot about as far as use in increasing durability of engine parts and welds etc.
http://en.wikipedia.org/wiki/Shot_peening

[SWIGIN]

ok this is from south bends ''how to run a lathe'' 40th edition

to case harden carbon tool steel

heat the end of a bit slowly to a bright cherry red them immerse the end 1 1/2'' in cold water.... but do not cool the shank. pull it out when cool and polish the tip with emry cloth.
the tool is now hardened and as the heat from the shank passes into the tip it will discolor the polished surface indicating the amount of temper being drawn.
when a light straw color appears, cool the entire tool quickly and it will have the correct strength for turning.

for hachets, scew drivers, chiseles ect...wait to cool the entire thing till it draws a brown/yellow color. for springs dark purple.



case hardening

heat cherry redand apply cyinide of potassium to the surface you wish to case harden. the cyinide will disolve slowly into the surface, after a good coating return the steel to the fire and heat slowly for about a minute then remove from fire and quench in water.


anneal tool steel


heat slowly to cherry red and place in a box of lime or ashes to cool slowly. when its at room temp its ready to be machined.



the quenching in oil thing seems to be a old way of putting a finish on bare metal to protect it

[Brockey]

I have seen this done by heating up the steel red hot and dipping it in pickled water or a salt water. My father had his students make cold cuts in school this way.

Now I am a stress reliever/ heat technician in the oil field and know that if you can get a procedure of the steel you just have to preheat, soak, anneal or bakeout the materail according to the specs provided from the manufacture and it become hardened.

Of course most people figure just get it red hot and cool it down immediately but this doesnt always work. The preheat time and temperture increase affects it aswell as the soak. The soak is how long you hold it at the required temp and then the cool down procedure. How long that takes and what methods use.

Interesting job! We had a 48 inch bung on a big steam drum that was 6 inches thick steel. It was cracking so we had to ramp it up within 12 hours to 2150 degrees farenheight. And then soak it for X amount of hours and then strip it at 2150 and use force blowers to cool it quickly. We had to wear radiant suits and all at that temperture. Was really cool, the metal was starting to become translucent. Then they had no problem with cracks.

[300rman]

be careful heating anything up to red-hot, especially things like connecting rods.....metal likes to warp when undergoing heating and cooling like that.

[Dirtcrasher]

We did allot of hardening when I worked with the toolmaker. But, we always knew what metal it was 01 tool steel. You'd make your part, throw it in the oven till it was cherry read, quench it in quenching oil and then put it on a heat plate that slowly brought the temperature up again. Then we would have to finish grind the piece as some dimensions changed during hardening.

I would think it would be very hard to do reliably without knowing exactly what type of metal it was.

[The Goat]

Billy I posted up a link maybe a few weeks after I got here about liquidmetal

www.liquidmetal.com

the things they are doing are quite interesting

[honda250sx]

Be careful hardening anything threaded or tapped. It will change its size indefinetly and make it unusable. When machining you run an oversize tap prior to hardening.