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Heat Treating and Metallurgy Discussion of heat treatment and metallurgy in knife making.

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  #1  
Old 08-04-2019, 11:01 AM
Rasmus Kristens Rasmus Kristens is offline
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sawblade. How to work and ht?

Hi guys

I just got a hold of this beauty:


Its 0,12" thick and 25" in diameter.

There are no marking on the blade and its possible to file it down.

How should i go about using this steel? Should i anneal if first before working it?
Should i HT as "normal" 3 normalization cycles and then try to see which hardness I get when quenchin around nonmagnetic?

Last edited by Rasmus Kristens; 08-04-2019 at 11:53 AM.
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  #2  
Old 08-04-2019, 03:26 PM
jimmontg jimmontg is offline
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Remember you have a mystery steel Rasmus so I hope you didn't pay much for it.

That said you don't need to normalize it as it isn't forged, just anneal a piece and ht and see how it does. Hi speed saw blades like that tend to be made of either an L6 type tool steel or a shock absorbing steel like S5 and ht like you would 1080. Newer made in China saw blades are junk as far as I'm concerned.

I wouldn't be surprised if it was 1060 with some nickel. Does the file bite into it easily or is it tough to file? If it files easily most likely it's probably has a 0.5-0.6% carbon content, but don't let that scare you a tool steel like S5 are 0.5 and can get pretty hard, like Rc 63 as quenched., but S5 wouldn't file too easily because I believe it has a .3+ vanadium content and that would make it a little more abrasion resistant. It's actually a pretty nice knife steel if you can find it. I have no idea how it forges so wouldn't bother when there's better known steels I could use, but if I had a piece of 1/8 flat bar I'd give it a try. As a shock absorbing steel it, like L6 make pretty good ax heads.

But just experiment with some coupons and test them.
My mistake Rasmus S5 has 0.2% vanadium which only inhibits grain growth and imparts no hardness. It is S7 that has 0.35 vanadium, but it makes a nice knife too. Has 1.4% molybdenum in it. Heat it to 1750 and air quench gives RC60 and oil give 62. Guessing 1800 degrees in a forge isn't hard, it's doggone bright yellow. lol

Last edited by jimmontg; 08-04-2019 at 03:52 PM. Reason: mistaken identity
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  #3  
Old 08-04-2019, 04:08 PM
Rasmus Kristens Rasmus Kristens is offline
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Thanks for the detailed explenation. I got it for free since my neighbour disassembled and old lumber saw.
It was hooked up to a very Nice 7.4 hp motor! It was a pretty cool old DIY build.
It does file easily.
I wil do some tests and see if i can get some coupons ht nicely.
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  #4  
Old 08-05-2019, 02:54 AM
jimmontg jimmontg is offline
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Hmmm I wonder if you might have an L6 type alloy with nickel in it to make it less liable to break since its definitely a very old sawmill blade. Try to heat a coupon to around 1700/950c degrees bright reddish orange and air cool it with an air blast from canned air if you don't have an air compressor. If it gets hard you'll have some nice bush crafting knives that are tough. Temper at 400 for two hours should put you around Rc 57, if you oil quench its even harder. Don't forget the break test. I bet if you cut a small strip off it would bend 90 degrees plus before it breaks. They didn't like those big expensive blades breaking when a log might twist.

I have the ability to see what material is by laser/spectrometer analysis. It isn't very expensive, see if you can find a heat treater in Germany who can do it. Heck I'd be interested, some of those old blades were just 1075 with 1.5 to 2% nickel added. L6 has other alloying metals than just plain 1075/nickel which would not air quench.
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  #5  
Old 08-07-2019, 01:07 AM
Rasmus Kristens Rasmus Kristens is offline
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Quote:
Originally Posted by jimmontg View Post
Try to heat a coupon to around 1700/950c degrees bright reddish orange and air cool it with an air blast from canned air if you don't have an air compressor.
I'w been reading through your post a few times now. And i have a question.
This temperature seems quite high compared to the temeratures i aim for when heat treating the carbon steels i work with.
Is this because the L6 steel is an alloysteel or what is the reason for this temperature?

One more thing. I have never annealed steel before.
How is this done? Get it to critical temperature (which i don't know) and slowly cool?`
Is that it?
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  #6  
Old 08-07-2019, 08:47 AM
Doug Lester Doug Lester is offline
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I would avoid annealing unless I had a regulated oven to do it in. If I had one I would heat the steel to about 1400 and slow cool to help spherodize the carbides. Critical annealing, which you were describing, can cause the carbides to clump into plates which can cause problems with drilling and grinding later. I would stick to normalizing the steel.

Doug


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  #7  
Old 08-07-2019, 04:12 PM
jimmontg jimmontg is offline
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L6 is indeed an alloy.

It has 1.75 nickel, .75 carbon, .90 chrome, .35 molybdenum and .75 manganese. L6 has enough nickel to use for making Damascus. I did not know you didn't know how to anneal. As Doug Lester said that is best done in a controlled oven. I used to do it in a smaller forge my brother and I made mostly just for annealing, but the forge must be able to be closed off on both ends. As Doug said best to normalize.

But in case you wanted to know how we annealed in the forge is we would heat the forge until the wall was glowing brightly. Then we would put the blades in we wanted to anneal, heat to nonmagnetic then close the door and shut off the forge. It took 24 hours to cool down from the extra thick walls and door. Perfect anneal every time. We mostly used it for old Nicholson files we found a huge stash of.

1700 isn't the best temp, 1650 is if you are air quenching L6, but I just gave you that process to see if it would air quench at all. To my way of thinking there are so many more and better steels than 1080 to use and L6 like O1 forge or oven I would use those instead, but the caveat is that they are more expensive, but I don't care because they are easier to ht and are better, especially L6, but just try and find it in thin sizes. Old saw blades are one possible source. Here is a link to L6 and it properties and ht.

http://http://cintool.com/documents/...rdening/L6.pdf
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  #8  
Old 08-08-2019, 03:24 AM
Rasmus Kristens Rasmus Kristens is offline
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This forum is pure gold!
Thanks for sharing your knowledge both of you😄
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  #9  
Old 08-09-2019, 02:50 PM
Rasmus Kristens Rasmus Kristens is offline
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Okay! I just did some testing and the coupons are in the oven right now at 400 F.
I took 2 of the coupons to bright orange, maybe a bit to hot, and quenched one i brine and one i canola oil. Both quenching mediums at room temperature.
Bouth coupons became extremely hard.

The 3rd coupon I gave a bevel at 40 grid, i made it very thin for the sake of the test. I took this to a bit above nonmagnetic but not as hot as the 2 other coupons. I quenched this in oil. I wanted to see if the edge would "bacon warp", crack or deform. No deformation and the edge is rock hard.

I will follow up after the "breakening"! :-)
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  #10  
Old 08-09-2019, 04:21 PM
Rasmus Kristens Rasmus Kristens is offline
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Everything broke. But not in the best way i think.
Grain looked very good, I will post pictures tomorrow.

All of the tests seemed very britte still after tempering.
I tempered at 400 F for 1 hour and cooled down slowly to room temperature before breaking.
There was no bending in the coupons before they broke.

The brine test seemed the most brittle.

Could this be a sign that the temper temperatur was to low? Or that i needed longer in the oven?
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  #11  
Old 08-10-2019, 01:34 AM
Doug Lester Doug Lester is offline
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Your a brave man trying a brine quench with that steel. I would go with canola oil instead. You could try tempering for two cycles of 400 for two hours each and see if that does the trick. If they still seem a little brittle you could increase the tempering temperature at 25 increments until you find the point that you want.

Doug


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  #12  
Old 08-10-2019, 03:15 AM
jimmontg jimmontg is offline
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Still brittle after temper?

Try tempering at 435. I always tempered L6 at 435 for TWO hours and that gave me Rc59/60 and I used an oil quench. It was still a little brittle, but the edge wouldn't chip. In other words standard for a knife unless it's deferentially ht. The quenching oil we had was a slower oil, it was a Chevron made oil and was bought for O1 and other slower quench steels. I couldn't give you the specifics on it other than it was a higher viscosity oil. Actually Parks 50 is too fast for O1 and other alloys like the S series shock absorbing steels. L6 also takes a slower oil too. That's why canola oil works well for these steels as does automatic transmission fluid as they are thicker, just avoid any smoke or fumes from ANY quench oil. By the way, canola oil goes bad if used often. Takes about a year and you'll start getting inconsistent results is how it starts. This is just something I have heard here on knife Network.

Now lets take a look at your results.
Even the bright orange grain looked fine, good.
Every thing was brittle, indeed your temper is to low and too short, two hours is standard Rasmus and don't worry about going too long, it's about temperature more than time except the two hours or going too short.
The one beveled coupon didn't warp, good sign that you have an alloy steel versus a plain 1075 steel. How long was the beveled edge?
The brine quenched one would be the most brittle as it quenched the fastest. I wouldn't count on a brine quenched knife not cracking based on a single coupon 3.2 mm thick.

Go ahead and grind out a knife and and coupon, then take the bevel down to within 0.5 to 1 mm on the edge, heat to above magnetic for a minute and quench in warm oil like 120 degrees. Temper for two hours at 435 and start cutting and finally see how much flex the coupon has.
Another test is if you have any ferric acid or cold gun blue like Birchwood Casey Super Blue. Put a few drops of the acid on it and wipe off. If it doesn't darken then you have a high nickel steel. If you can't get the acid try the gun blue and if it won't blue consistently, but is very blotchy same as before, lots of nickel. If it air hardens under an air blast and is brittle you most likely have L6.
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  #13  
Old 08-10-2019, 07:27 AM
Rasmus Kristens Rasmus Kristens is offline
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Left: Brine quench
Middle: Oil quench (high temp)
Right: Oil quench lower temp

Looking at te grain today in better light, it does look a bit large.
But it also looks inconsistent. I don't know if the break can fool the eye?
The grain at the cross section af the bevel looks very smooth and uniform but other areas the grain looks larger.


Ferric etch.
The steel turned dark very fast.

I don't have any canned air or a compressor. So the air quench must wait.
I will make a small knife blank and test with a longer and hotter temper.

Last edited by Rasmus Kristens; 08-10-2019 at 07:32 AM.
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  #14  
Old 08-10-2019, 07:24 PM
jimmontg jimmontg is offline
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Well the ferric acid turning dark fast means if there is nickel in it it's less than 1%. I couldn't tell very well, but the grain looks good in the high temp center one. Looks like it broke consistently too. You might have some chrome in it. Try what Doug said, but since you have a limited amount of material try two hours at 425 which I have found to be good for a lot of Nicholson files which are basically W2 steel. If it's still brittle try 2 2 hour tempers.

If you decide to use brine heat it up to 80C+ to help, note help prevent cracking, but it's no guarantee. You have oil use it at 45-54C (115-130F) as oil should be heated up some and not used at room temp, because too cold oil will also make some steels brittle and/or warp. You have a mystery steel and it could be 5160 for all we know without spectral analysis.

Last edited by jimmontg; 08-10-2019 at 07:29 PM.
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