Grain Refinement

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Pyromaniac

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May 13, 2013
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I know a lot of people have done extensive research on this topic and have shared their results but everything I have been able to find on it has been very specific regarding temperatures. Sadly I do not have a temperature regulated oven, only a propane forge and it is hard to be able to get it to exact temperatures needed. I was wondering if there is an better way to do this in a forge than simply trying to guess.

Thanks
 
I posted a similar question on a different forum. I was told, that for simple steels, any type of controlled thermal cycling will result in an improvement of the grain structure. This is in regared to using a forge. What type of steel are you using?
 
Just guess acurately! A magnet stops sticking at about 1414, you start seeing color at about 1000, and from there you have to just use color. Someone showing you is worth TONS! Find someone within driving distance, or a hammer in, be respectful, and ask questions! Most in this trade are willing to help.

Start by filling in your profile, some one might live 5 miles from you and you might not know it.

It's a long journey, but rewarding!
 
I deal with the same issue with my propane farriers forge. I over heated a 5160 blade and then tried to re heat treat it and got cracks. I suggest keeping a magnet close to your forge and also heat at night or in a dark shop to see the heat colors in the steel.
 
Currently I am using a mystrey steel I found on a rail road that I am hoping is high carbon. Currently I'm just making a test knife of of it. Normally I use 1095 and 5160. And thanks Ballew, I never thought to do it at night. I've just been doing it with all my lights off in my shop.
 
Within a budget. I'm only in high school so I don't have a steady source of income beside what knives I sell in my town and the few jobs doing yard work for some of the elderly.
 
Pyromaniac said:
Currently I am using a mystrey steel I found on a rail road that I am hoping is high carbon. Currently I'm just making a test knife of of it. Normally I use 1095 and 5160. And thanks Ballew, I never thought to do it at night. I've just been doing it with all my lights off in my shop.
Click to expand...

1095 is about the simplest steel you can get. Go ahead and experiment. Thin out and flatten some pieces of steel to about 1/4". Soften them in different ways. Spherzoid (?) pearlite is supposed to be the easiest to grind and machine. Keep notes. Grind them, file them, drill a couple of holes and see which softening method worked best (if any).

Now run each piece of steel through slightly different normalizing steps, doing your best to stay in the color range for the given temperatures. Marquench and break your steel to look at the grain structure. It was suggested to me to break a Nicholson file in half and use that as a comparison.

You could do the same with a piece of your mystery steel.

Many have suggested that a smith should do the same with any new steel they acquire, to help maximize the results of working that steel.

Did I mention, keep good notes.
 
Actually my mystery steel is already at about 1/4 inch give or take. Me a fried were walking along the railroad one day and saw a grate with spikes on it. I got the grate he got the spikes. The grate is actually very large(about 100 pounds) and from the welds I do not belive it was factory welded. When you say Marqeunch what do you mean, I'm not familar with that term. Typically to soften I just bring it to critical and set it in a tub of vermicultie for a few days. If you know a more effiecnt way that is not to complex I would love to hear it.
 
Marquenching would be using a tempering medium such as molten salts or quench oil that can be maintained at the target tempering temperature, then quenching into it. A somewhat advanced technique, not really necessary for what you are doing.

To find out whether your steel is hardenable, a good preliminary test is to grind the steel and observe the sparks thrown off. Low carbon will be a longer, less bushy or sparkly spark stream. High carbon will have many sparkly exploding sparks, nice and bright.

Then, if it sparks fairly high carbon, heat to non-magnetic, then just a little past, a barely discernible shade brighter, and quench in oil. If you do not have commercial quench oil, canola or veg oil pre heated to 130 degrees or so will work fine. Snap the test coupon in a vise, it should be quite brittle. If not, try again with your quenching temp just a little higher. IF you can, try to hold it at your quench temp carefully without overheating it for a few minutes- five is optimal, but even two minutes is better than 10 seconds.

If still not hardening, try quenching in brine. If it won't harden in brine, it's probably no good for knives.

If your steel got hard in the quench, after breaking, look at the grain in the break. It should be velvety. If it looks coarser than that, try bringing your quenching temp down a little bit.

To get the finest grain possible, once you have determined a good quenching temp a little above non-magnetic, bring it to a little higher than that, air cool. Bring it to your quenching temp, air cool. Bring it up to just the low side of your quench temp, air cool. Heat to quench temp, and quench. These are normalizing cycles for grain refinement.

Upon breaking this test coupon, the grain should be nice and velvety.

A good alternative to slow cooling in vermiculite, which can be fairly ineffective in higher carbon and alloy steels, is to bring the steel up to low red (below critical) and let it air cool to black, then water or oil quench. Do this three times in a row. This should leave your steel in a very workable and relaxed condition. I do this after forging a blade, so it will saw, grind, and drill easily. Normalize once or more after grinding for further stress relief, then quench.
 
"Marquenching would be using a tempering medium such as molten salts or quench oil that can be maintained at the target tempering temperature, then quenching into it. A somewhat advanced technique, not really necessary for what you are doing."

Thanks Salem, I've been reading too many papers on bainite. :)
 
Several things:
1) The steel plate could be many types of steel, but it would be unlikely that it is a knife steel. If you have 100 pounds and really want to know, send a 2"X2" piece off for analysis and then you know what the steel is. Other than that, you can guess for a year and never know.

2) Annealing in vermiculite is not the best way. It will cause the steel to cool into the pearlite range, and then slowly form coarse pearlite which can be very hard to drill, file, and sand. Heating to a bit above non-magnetic and quenching, followed by heating to just BELOW non-magnetic , holding at that temp for 5-10 minutes, cooling to black (900F), and then quenching will give you a spheroidal carbide structure in fine pearlite that is easy to work with.
If you don't have the ability to hold at 1250F for 5-10 minutes, just hold just below critical for a minute or two and let cool to black, then quench.

3) The way to refine grain without controlled equipment is the standard thermal cycling.
Heat to around 1600-1650F and quench (cherry red, but not orange)
Heat to just a bit above non-magnetic and quench
Heat to just below non-magnetic, cool to black, and quench
The steel is now fine grained, and ready to be hardened.
 
Do not even try.
Really - without move gear you will be just guessing in so many places you wont know anything more.
Try to work simple routine for a single steel first.
 
Ok. Thanks everyone. I did like you siad Salem and spark tested it and it spit plenty of bright sparks. Though I think I'm just going to forget about it and go back to using 1095/5160 and the files and few leaf springs i have left. Anybody got any ideas for which i could use it for? Thanks for all the info on grain refinement.
 
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