Hardening Metal and annealling?
  Re: (...)
Can anyone give a quick primer/recommendations on hardening and then tempering O1 steel? I’ll give you what I plan and would appreciate any feedback/hints you can offer.

I have a piece of 1/8th” O1 steel 2”x3”. It was purchased annealed and now I want to harden and then temper it to serve as a plane blade (kind of). I have the following steps in mind:

1. Rough shape the bevel.

2. Place on a ‘heat brick’ and use a MAPP torch to heat to a uniform ‘cherry red’. I would use something like this. http://www.lowes.com/pd_34454-215-600448___I would try and heat the blade uniformly and slowly to the desired color.

3. Immediately quench in some kind of oil (I would probably use vegetable oil or motor oil- does it matter)

4. Once cooled, heat in an oven set at 300 F for about 2 hours to anneal.

5. Reflatten and hone the bevel.

Does this sound about right?


I miss nested quotes..........
  Re: Hardening Metal and annealling? by PedroOhare (Can anyone give a qu...)
Don't sweat the petty things and don't pet the sweaty things. -- G. Carlin
  Re: Hardening Metal and annealling? by PedroOhare (Can anyone give a qu...)
Vegetable oil won't stink up your house like motor oil will. The oil will catch on fire. Make sure nothing flammable is close by. As the blog mentions, he learned by trial and error. It may not work out perfectly the first time, but you'll learn something. When you're heating the iron, sunlight can diminish the glow of the steel. Having some sort of shade to let you see the color will really help.
  Re: Re: Hardening Metal and annealling? by Daniel S (Vegetable oil won't ...)
I was actually planning on doing it outside at night to see the color of the steel as it heats. I guess I can also use a magnet to check the temp which sounds more accurate. That was a very helpful article.

I miss nested quotes..........
  Re: Re: Hardening Metal and annealling? by PedroOhare (I was actually plann...)
Annealing is softening the steel to a very soft state by extremely slow cooling after heating above the critical temperature. We anneal so we can file and saw the steel easily.

Tempering is softening and toughening the steel after quenching, and involves heating to an intermediate temperature.
  Re: Hardening Metal and annealling? by PedroOhare (Can anyone give a qu...)
The Hock method is pretty concise, and it works for O1 tool steel. That works for your application. It will not necessarily work for any of the other tool steels, because their constituent alloying elements are different or in different proportions, and the temperature control to get desired properties needs to be more precise. Aside from carbon, alloying elements in steel are more about controlling how an item responds in heat treating.

One correction on terminology. The heat treat in the oven post-quenching is called tempering, not annealing. Annealing is when you put the steel in a furnace above the critical temperature for a relatively long time to reorganize the microstructure (sort of a reset to zero). An annealed steel is normally air cooled or allowed to remain in a turned off furnace without quenching to cool down. Annealed steel is very ductile, so annealing is typical prior to working or shaping the steel.

Tempering happens after a steel is quenched. (In a typical cycle, it's anneal - work/shape - anneal - quench - temper). It's purpose is to relieve internal stresses and convert some of the undesirable microstructures to less brittle ones. Tempering actually makes the steel softer, but you're trading a hard brittle steel for one that's less hard and not so brittle.
Still Learning,

Allan Hill
  Re: Re: Hardening Metal and annealling? by PedroOhare (I was actually plann...)
You have the general idea OK...I would use two fire bricks...lay the steel on one and use the other brick like a "wall" to reflect the heat back onto the steel..otherwise you may come up short of BTUs..but you "could" use two torches to get it hot enough...OR instead of firebrick, use a bed of charcoal..{even better}..but dont trust your eye alone...use a magnet.....far more accurate..

Your tempering method should work fine......ANY type of oil will work...use what you have..
"If you don't read newspapers you're uninformed...If you do read newspapers, you're misinformed.....Mark Twain

Jack Edgar, Sgt. USMC Korean War 51/52
Get off my lawn ! Upset

  Re: Re: Hardening Metal and annealling? by Timberwolf (You have the general...)
Sounds good. I actually knew the difference between annealing and tempering. I just wrote it wrong in my 'Subject' line. I guess the only other question would be, if two bricks are better than one, would four bricks (making a little house open on the two ends) be better than two and then using two MAPP torches one from either end?

I miss nested quotes..........
  Re: Hardening Metal and annealling? by PedroOhare (Can anyone give a qu...)
This is how I do it, and it works well.
1 Rough grind the bevel. Do not get close to sharp. If the steel is too thin it will burn and be ruined
2 Get it bright cherry/non magnetic. You're piece is only 1/8", don't worry about going slow.
3 Don't quench the whole thing, just the first half or so. Move it around in the oil to keep from forming air pockets. Wait for it to stop sizzling. It should be fairly cool.
4 Remove from oil and immediately sand, wire wheel/brush, whatever to get the back clean. Move fast.
5 Watch the colors run up to the edge in light, when straw gets to your edge (or very close) quench the whole thing in oil, moving it around until completely cool. No need for an oven soak/stinking up the house.
5b If the colors didn't make it to the edge before you ran out of heat in the steel, heat the other end with your torch until they do. Quench.
6 Sharpen
7 Reharden if you ever grind past what you have just hardened.
  Re: Re: Hardening Metal and annealling? by MikeLemon (This is how I do it,...)
Pedro, I use 4 bricks, one on the bottom, two resting on top of the first brick forming a v, with the narrow part of the v at the far end, and one block on top. You need a ton of air for the flame on the torch, so gaps are not a problem, you are just trying to hold in some of the heat so the metal isn't sitting in 70F air and instead is in air that is pretty hot. If you are using a decent MAPP torch, you won't need two torches for 1/8 inch steel, but two would not hurt.

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