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Heat treat 5160

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I'm about to heat treat a 5160 Bowie/Fighter. I did a little research, and found temps between 1575F to 1600F for normalizing temps. That seems a little high to me, but that's the numbers I keep running into. For annealing and Hardening 1525F seems to be the temps. I'll be using an electric furnace for the first time. Now for my question, if I get the temp up to 1525 or 1575 or whatever, I open the door and put the blade in, the temp. drops when the door was opened, then it climbs back to the set temp. How long do I leave the blade in, once the temp. reaches the set point again? 1 minute, 2, 3? Also I read, I think its the Montana way, calls for 3 normalizes, 3 anneals, and 3 quench's. Is this a little over kill. I though we did the 3 normalizes to reduce the grain size, therefore eliminating the multiple quench's. I was planing on 3 normalizing heats, followed by one anneal, and one quench, and then 3 tempers. I don't mind the 3 anneals, what scares me is the 3 quench's. Thanks for any help.

 

Tony G

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As far as I know the temps are right. I don't understand what you mean by "normalize" vs "anneal". A true anneal in 5160 is a process like bring the piece to non-magnetic, hold for some length of time, reduce to ambient 50 degrees an hour. Which would soften it to it's max softness. If you have the controls to really do an anneal, you can skip the normalize steps, you are accomplishing the same thing.

 

The HT process I have used for 5160, which is good enough to make an ABS test knife out of, is: 3 normalize after forging, 3 normalize after grinding, single hardening in oil, 3 temper cycles of 4 hours each at 400F. That worked for me.

 

Geoff

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Don't anneal after normalizing; that's just going to grow back the big grain that you just reduced through normalizing. And there's no need for multiple quenching cycles if you have the ability to soak at an accurately held temp. Three normalizing cycles, soak at 1525 for ten minutes or a little more (meaning start counting when the steel hits 1525), one quench, three one-hour tempers.

Edited by Matt Bower

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Don't anneal after normalizing; that's just going to grow back the big grain that you just reduced through normalizing. And there's no need for multiple quenching cycles if you have the ability to soak at an accurately held temp. Three normalizing cycles, soak at 1525 for ten minutes or a little more (meaning start counting when the steel hits 1525), one quench, three one-hour tempers.

 

I don't understand how you would enlarge the grain by annealing after normalizing, if you normalize at 1575f 3 times, and then anneal at 1525F.You heated the steel to a higher temp. normalizing then you did for the anneal. If 1575F reduces the grain size, heating to 1525F shouldn't enlarge them, should it?

 

Tony G

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It's all in the cooling cycle. Normalizing refines the grain by relatively fast cooling in air. Annealing enlarges the grain by a very slow cooling in the furnace, and every minute spent above critical grows the grain. 5160 is a right bugger to truly anneal without that 50 degrees per hour ramped cooling anyway, so I don't bother trying. It'll almost air harden in thin section, so make sure when you normalize you leave it in warm still air, no cold breezes or cold anvils.

 

The chromium in it retards grain growth to some extent, which is why you soak it before quenching, to get all the chromium into solution.

 

Don't overthink it though, 5160 is pretty easy and forgiving stuff in HT. B)

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If you're only heating to 1525 to anneal, you might not in fact grow the grain any during an annealing cycle. But assume that you didn't. What would you gain by that cycle, except maybe an extra chance at decarb and scale? What's it supposed to do for you?

 

BTW, I personally wouldn't normalize three times at 1575. I'm not sure I see the point of that (which doesn't mean there is no point). I shoot for one cycle up near around 1600 or a little hotter, one around 1550, and one around 1500. Given that at the moment I'm working with Tempilaq and Tempilstiks in either a coal forge, or a propane forge that won't tune down as far as it should, this is a lot easier said than done. I envy your access to an electric furnace.

Edited by Matt Bower

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Ok, So I do 3 normalize heats in decending temperatures ( 1600, 1550, 1500 ). Heat to 1525, soak for 10 min. then quench. Temper 3 times. Questions: do I soak when normalizing? If so, how long? Is 10 min soak before the quench to long? I don't want to grow the grain again. :blink:

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Questions: do I soak when normalizing? If so, how long?

 

That's a great question! I know it's great, because the same question once occurred to me! I asked some guys I consider metallurgy gurus, and the basic response seemed to be "no" -- it isn't really necesary to soak when normalizing. I understand that the higher temps of the first heat reduces the need to soak (achieving full solution is a time-temp thing, and temp is much more important than time). I'm not sure I fully understand why it's not necessary on the lower heats.

 

Is 10 min soak before the quench to long? I don't want to grow the grain again. :blink:

 

If you can accurately hold at 1500 F, no, ten minutes of soak shouldn't hurt your grain. I hate to direct anyone away from Don's wonderful forum, but these two threads are really, really worth reading:

 

http://www.bladeforums.com/forums/showthread.php?t=394824

http://www.bladeforums.com/forums/showthread.php?t=398842

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as i understand it you probably want to soak a little on the first normalising heat, to put as many of the carbides into solution as possible, evening out their distribution. at the lower normalising temps, it may not be needed as you should already have everything distributed as you want, and depending on the alloy, the carbides may not dissolve at these temps anyway. that said, if you can hold an even temp, soaking will do no harm (in 5160 i think the chromium acts sorta like vanadium in that it pins the grain size), and will ensure that you get full transformation to austenite (it is the transformation to and from austenite which refines the grain, so full transformation is desirable), which is also the reason you want a bit of a soak before quenching. i think.

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Tony,

 

1600F is industry normalizing temp. for 5160, and 1525 is quench temp. Stepping down the normalizing temp. is what I've been taught. I'd normalize three times at 1600, 1575, 1550, then heat to 1525 and soak 10 minutes before quench. Heat Treaters Guide doesn't specify a soak for 5160 but I always soak for awhile... if the temp. is controlled, soaking steels that don't need it won't hurt them.

 

You asked 'how long from return to set point before steel reaches set point'. I peek in the oven looking to see the blade being the same color as the kiln interior. I always forget to time the process so I can do it that way, but maybe you will... =]

 

Tempering two times at two hours each is what I do. I learned it from "Mete"...

 

Mike

Edited by Mike Krall

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5160 is a right bugger to truly anneal without that 50 degrees per hour ramped cooling anyway, so I don't bother trying. It'll almost air harden in thin section, so make sure when you normalize you leave it in warm still air, no cold breezes or cold anvils.

 

So, maybe like hang it in a warmed steel pipe with a cover on it?

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If by warmed you mean glowing red hot, that would help, yes. A bucket of vermiculite is good too, especially if you put another piece of larger hot steel in with it.

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From Alan's quoted response: "It'll almost air harden in thin section, so make sure when you normalize you leave it in warm still air, no cold breezes or cold anvils."

 

 

So, maybe like hang it in a warmed steel pipe with a cover on it?

 

 

I'm guessing, Andrew... You are looking to normalize and not run into any air hardening aspect. HTG says, "In the thermal sense, normalizing is an austenitizing heating cycle, followed by cooling in still or agitated air." The "agitated air" is a controlled aspect... like sticking the piece in a tube with a fan blowing air through it. No matter if still or agitated, air is considered fast cooling... still air being a slower fast. It's drafts that can cause problems... still air is consistent... agitated air is consistent... drafts are not consistent.

 

I keep the doors to the shop closed (no windows). I've heard of others using tubes of various materials, sheet metal, casing, multiple layered tubes of metal window screen, cardboard even, and hanging the blade in it to avoid potential drafts. I'm pretty sure breathing hard does not fall into the "draft" category, though... =]

 

Mike

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Arise necro thread......

I've been struggling to find info on normalizing 5160, at least info that makes sense.

Came to the conclusion that I'm mixing up normalizing and annealing........although I still struggle to understand a normalizing temp higher than the quench temp....oh well, those are the facts. 

I have 3 large cleavers in 5160 that I treated rather badly with a hammer, and I would like to normalize them properly before HT.

I'll be using the digital kiln because it's accurate and has proven to be rather economical as far as electricity is concerned.

the only logical way I can think to do this is set the kiln to 870C, wait till it's up to temp and then put the blades in 1 at a time (they won't all fit)......but for how log?

 

BTW the first 5160 blade I heat treated in the kiln looked like a carbon balloon when I peeked at 820C, I was worried about decarb, but it came out hard and I've never before had such nice even temper colour.

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However long it takes to get to heat.  I don't have a kiln yet, but I suspect a couple of minutes at least.

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Gerhard,

Heat Treaters Guide (my "HTG" from post before yours)... that is, "the book" from the American Society of Metallurgists... says under 5160,5160H, 5160RH, under normalize: "Heat to 870 C (1600 F). Cool in air".  Here, they do mean still air.  

You have a kiln, and when the kiln stabilizes (less and less on time for the amount of off time, to a point where the on and off times don't change... not to say equal amounts of time, mind you), a piece of steel of the sections you are dealing with placed in the oven for 10 minutes or so will likely be through-heated to kiln temperature.  Taking a narrow peak into the kiln and looking for a piece of steel that is the same color as the kiln walls will give a pretty good verification of steel and kiln temperature being equal.  I have to say... a thick piece of steel can show exterior color same as kiln and NOT be at that temp. internally.  Sometimes (sometimes) a thicker piece will show light shadows (slightly darker) areas even if predominantly kiln temp. color.  I've always read that as "piece not temperature equalized"... but that's me  guessing at things.   

I don't know what you know... 

For steels of this general type, grain growth temps. are 1650 F to 1750F... closer to the lower is my guess for this steel.   For knife like structures, finer grain (within reason, please) is better.  Part of the aspect of normalizing is causing all grains to be the same size.  Bigger grains are not wanted here (or maybe any where, but ???).  A temp. close to grain growth temp. for the steel will cause the grain size to equalize quicker. (An awful lot of steel stuff is time and temp. dependent... less time, less temp. less happens, and then the opposite... with constraints on both ends). So for 5160, through-heating to 1600 F and cooling in air will make grain size equal.  

If the blade has been forged, and/or had other high temp and/or time excursions applied to it, a single normalizing process with leave a person with equal but LARGE gains. Many forging knife makers (and others who are not heat treating professionals) normalize 2 (usually, at least) or 3 times (that's what I learned from the more knowledgeable).  Each following normalizing cycle causes the grains to get smaller.  I was also taught to step down the normalizing temps... all being above the temp. a person wants (needs) for quench.  "The book" for 5160 says 1600 F to normalize and also says 1525 F to quench.  That's a small range.  Me, I'd use 1650 F, 1600 F, 1550 F for the normalize.  I have used 25 F steps in normalizing a number of times and feel (feel) I'm right and proper with the world,  so it could be 1600 F, 1575 F, 1550 F.  I'm sure there is a difference in those two, but I don't know what... or if it would make a use-find-able difference. 

Is that enough?

Mike 

Edited by Mike Krall
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On 2/9/2019 at 7:41 AM, Mike Krall said:

Is that enough?

Mike 

@Mike Krall thank you very much for the advice and additional information, much appreciated!

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You're welcome, Gerhard...

Mike 

Edited by Mike Krall

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