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High-Performance Blades Sharing ideas for getting the most out of our steel.

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  #1  
Old 12-01-2008, 01:33 AM
T. Hendrickson T. Hendrickson is offline
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1095 cracked

My 1095 steel blade formed 3 cracks 1/4" long on the edge.

Here's how I treated it:



Heated oven to 1450

Set blade in and left it for 5 minutes to heat up

Quenched in water

Tempered at 450 in oven


Is it because of the water quench? Should I use oil? I thought 1095 was water-hardening. Also the edge wasn't ground all that thin. About average for a hunter. It was hollow ground.


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  #2  
Old 12-01-2008, 07:48 AM
Kevin R. Cashen Kevin R. Cashen is offline
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Quote:
Originally Posted by T. Hendrickson
...Is it because of the water quench?
Yes

Quote:
Originally Posted by T. Hendrickson
Should I use oil?
Yes
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  #3  
Old 12-01-2008, 11:11 AM
T. Hendrickson T. Hendrickson is offline
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Thanks Kevin. I'm fairly certain I've read that 1095 should harden with water, that's why i was confused. Is vegetable oil OK then?


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  #4  
Old 12-01-2008, 02:05 PM
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chiger chiger is offline
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Hey T,

Not to call anyone out, but you can quench in water. Just have to be very particular as to how it's done.

Have a couple questions. First, did you do a tip first, edger down quench and does the blade have a weird shape? Next, did you do a single plunge and for how long. And last, how long after quenching did the blade get into the temper oven?

I ask because I've done a bunch of 10 series steels successfully and these are the things I worry about to get 'um to come out.

First odd shapes that have thick and thin areas side by side tend to set up stresses that will crack.

Next, An interrupted quench is the only safe way to quench in water no matter the steel. A 1-1 1/12 second initial quench...pull it out of a 2 count and then plunge it back in for another 2 or so seconds. Depends on size. About the time the steam and commotion stop pull it back out. Your just trying to get it down to 160-180 degrees.

Lastly, RUN, don't walk to a PRE-HEATED oven for temper. It WILL crack in as little as 5 minutes after quenching if you don't get it to the temper oven. You may get lucky and get longer, but why risk it.

If you did all that...never mind. Maybe I'm just a lucky old fart! ;~)

About everyone around here will agree with Kevin. And an oil quench is the safest way to do it, but NOT the only way. W and 10 series steels will only archive maximum hardness with a water quench according the the manufactures of these steels. A heated salt brine will also reduce the risk.

Also, I don't worry about what the temp is. I just take the grind to critical, checked with a magnet and quench. You'll probably do more damage than good trying to hold it at temp.

By the time the spine is critical, the edge grind will have been at critical for too long. It's the edge your wanting to get to maximum hardness anyway. A softer spine means tougher blade.

Sorry to hear you had a problem. Hope it wasn't on of my post that lead you astray! ;~)

chiger,
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  #5  
Old 12-01-2008, 08:49 PM
T. Hendrickson T. Hendrickson is offline
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Quote:
Originally Posted by chiger
Hey T,

Not to call anyone out, but you can quench in water. Just have to be very particular as to how it's done.

Have a couple questions. First, did you do a tip first, edger down quench and does the blade have a weird shape? Next, did you do a single plunge and for how long. And last, how long after quenching did the blade get into the temper oven?

I ask because I've done a bunch of 10 series steels successfully and these are the things I worry about to get 'um to come out.

First odd shapes that have thick and thin areas side by side tend to set up stresses that will crack.

Next, An interrupted quench is the only safe way to quench in water no matter the steel. A 1-1 1/12 second initial quench...pull it out of a 2 count and then plunge it back in for another 2 or so seconds. Depends on size. About the time the steam and commotion stop pull it back out. Your just trying to get it down to 160-180 degrees.

Lastly, RUN, don't walk to a PRE-HEATED oven for temper. It WILL crack in as little as 5 minutes after quenching if you don't get it to the temper oven. You may get lucky and get longer, but why risk it.

If you did all that...never mind. Maybe I'm just a lucky old fart! ;~)

About everyone around here will agree with Kevin. And an oil quench is the safest way to do it, but NOT the only way. W and 10 series steels will only archive maximum hardness with a water quench according the the manufactures of these steels. A heated salt brine will also reduce the risk.

Also, I don't worry about what the temp is. I just take the grind to critical, checked with a magnet and quench. You'll probably do more damage than good trying to hold it at temp.

By the time the spine is critical, the edge grind will have been at critical for too long. It's the edge your wanting to get to maximum hardness anyway. A softer spine means tougher blade.

Sorry to hear you had a problem. Hope it wasn't on of my post that lead you astray! ;~)

chiger,
Thanks for the informative reply. This knife was a 4" Clip point hollow ground hunter; fairly straightforward (it was actually my second try; I broke the first one).

I did a single plunge in the water (which was as hot as I could get it from the faucet) I also didn't temper for at least 20 minutes. I suppose either of these may have been the cause. Very interesting.

How much hardness would I sacrifice by using oil? I'm wondering if it would be worth it if it made things easier.

Also, you say that I shouldn't try to keep the blade at critical temp; problem is I'm using an electric kiln, so I have to leave it in there just long enough to reach temp, which I don't know. I left it for 5 minutes, maybe only 2-3 minutes?

Thanks for your help.

Thayer


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  #6  
Old 12-01-2008, 09:18 PM
Chris Meyer Chris Meyer is offline
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Hmmm, for hardening, the Heat Treater's Guide calls for heating 1095 to 1475 degrees F, and to oil quench sections under 3/16", but what do they know...

The Currie point for steel (non-magnetic) is 1414 degrees F (as the temperature is rising). 1095 needs to reach 1475, so you have to raise the temperature past non-magnetic for it to harden completely, if that's your goal.


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  #7  
Old 12-01-2008, 09:26 PM
T. Hendrickson T. Hendrickson is offline
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Ok, so it sounds like using oil wouldn't sacrifice any hardness (this steel was 1/8"). Do most of you use vegetable oil?


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  #8  
Old 12-01-2008, 09:50 PM
Kentucky Kentucky is offline
 
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I use peanut oil on 1095 with good results..Heated to about 130*..
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  #9  
Old 12-01-2008, 10:15 PM
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chiger chiger is offline
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Hey Thayer,

I'm going to post a pic of some 1984 that I watched crack in my hand about 30-45 minutes after quench. No interrupted quench just a single quench. Now I don't mess about. They all get the same treatment ever since. W1...whatever. But it's a cool pic. You can actually see how a clip right next to an anvil set up stresses that caused the crack! PING!

As to how much hardness. Not a lot really. I mean, W1 hardens to around 62 Rc in water and around 58 Rc in oil from what I've read. And you want the thing at 56-58 Rc after tempering anyway. But you still have to temper! The stress is still there even though it's not completely hardened. You just don't have to worry about it making that nasty little cracklin' sound. ;~)

Whatever quenching media you use, salt brine or oil, you really want it at least 160 and no more than 180. Tap water from your water heater is going to be 130 tops. Low but better than nothing. The important part is not cooling the blade below 160-180 during quench. And if you use oil you don't do the interrupted quench.

Can you open the kiln and test it with a magnet? I think what I would do is go to an auto parts store and get one of those telescoping magnets. Set the kiln to what the manufactures say critical is for 1095 and put in the blade when it's at temp. When you think the blade is nearly ready, open the door and test the blade about 2/3 up the bevel with the extended magnet. If it's nonmagnetic, don't wait for the spine to reach critical. Just go on and quench it. Probably be heated all the way up to the spine by the time you get it out to quench anyway. Never used an electric kiln, but that's what I'd try.

If you set the blade in edge up on the stand it should reach critical first. But be sure to put it so it's easy to reach and so that the magnet doesn't pull it over if it's still magnetic. Even if you have to slot some mild steel channel iron as a stand and let it heat with the kiln.

Oh, you said you broke the first one. How and where. If it's broken in the right place you can repair it and make a user/test knife out of it.

Anyway, here's the pic enjoy my pain. I had at least 20 hours in it when it went bad. GRRRR!

Almost forgot and I'm sure you know. Sand the blade to at least 220 before you try to heat treat. Don't really need more than that, but it does need to be well done. Wouldn't want to give those cracks a head start.

chiger,

Cracked.jpg
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  #10  
Old 12-01-2008, 10:35 PM
Kevin R. Cashen Kevin R. Cashen is offline
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Quote:
Originally Posted by T. Hendrickson
Thanks Kevin. I'm fairly certain I've read that 1095 should harden with water, that's why I was confused. Is vegetable oil OK then?
Some industry specs do indeed suggest water, but they are also aiming to for maximum hardness in parts that have thickness measured in inches, not fractions of an inch. Chris is correct that industry recommends fast oils for thinner sections. Many makers, particularly those working with Japanese style blades use water, but many good swordmakers will admit to losing a percentage of blades to it. To minimize this they often avoid total solution by intentional under-soaking. Water can destroy a blade in one of two ways, either through very uneven cooling due to a very problematic vapor jacket or by super cooling unnecessarily fast while the new high stress phase is forming. Cooling as fast as you can from 1475F (the lowest recommended temp to quench from for 1095) to 700F to 650F will be best to avoid forming fine pearlite or upper bainite (both will lower final hardness and strength), slowing the cooling in this range will invite the formation of these phases. Once 400F is achieved faster than necessary cooling, as with water, will drastically increase you chances of distortion or cracking if you avoided any other phases and get full hardness via martensite.

Many oils will allow some formation of fine pearlite with 1095, but there are oils specifically designed to do this task by industries that can not afford to lose parts to water or fail to achieve full hardness. I use one of them myself and consistently achieve total maximum hardness in all my 10XX series steels, and I have yet to lose any to cracking. Any steel above .8% carbon should reach 65HRC as quenched if total hardness was achieved. I have shared the oils I use with a few makers of Japanese style swords and after some practice they have managed to duplicate most of the hamon effects of water while eliminating the expense of lost blades. This thread is kind of caught between a rock and a hard place with water and vegetable oils, i.e. over cool or under cool. I happened to have found a tool to do the job just right but everybody must find their own way. I wish you luck with yours Mr. Hendrickson.

Last edited by Kevin R. Cashen; 12-01-2008 at 10:40 PM.
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  #11  
Old 12-01-2008, 11:00 PM
T. Hendrickson T. Hendrickson is offline
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Thanks for the info folks. Feel lucky to receive this stuff for free.

Chiger, maybe I'll try that with the magnet instead of just letting it sit there and overheat.

I tried flexing my blade after I finished the temper and PING it snapped right at the ricasso/tang joint. I had made my corners there sharp despite all i read about rounding them off, which I will ALWAYS do from now on. I'm not a bladesmith, so I couldn't see how I could possibly fix the knife. Maybe an arc welder? Any ideas?

thayer


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Old 12-01-2008, 11:30 PM
Chris Meyer Chris Meyer is offline
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Quote:
"...maybe I'll try that with the magnet instead of just letting it sit there and overheat."
If your oven has a reasonably accurate temperature gauge, why would you disregard it and use a magnet, which can only tell you that your blade is at 1414 F or above?! Also, how would the steel overheat if your oven is working properly?

Earlier, you asked what type of oil to use. The obvious answer is real heat treating oil if you can get it. You'll need a fast quenching oil for the 1095.

I believe that Kevin was alluding to Park Metallurgical's #50 quench oil. It's a very good and fast oil (and the one I use), however, as a practical matter it's unattainable at the moment because the manufacturer wants it that way.

Houghton is reportedly much more customer friendly than Park Metallurgical. They make a variety of oils, but I believe their Quench K oil is the one you'd want (best to double check that though).

Some of the guys on the forums are able to get Houghton oils, but I don't know exactly where they get them. However, here is the contact page for Houghton.

McMaster Carr carries some 11 second quench oil. I don't know exactly how that compares to the other two oils I mentioned, but it may be fast enough for 1095. (Perhaps someone will chime in with comparison numbers?)

Anyway, those are some suggestions for the oil you need.


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Old 12-02-2008, 12:52 AM
T. Hendrickson T. Hendrickson is offline
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Chris, I say that because I don't know how long the blade needs to sit there to reach temp. For all I know it could be 30 seconds or 5 minutes. I don't want the blades to sit at quench temp longer than necessary, I guess is what I'm trying to say. Perhaps you can fill me in on this? How long should I leave them in?

Thank you for the information on the oil, it helps very much.

Thayer


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Old 12-02-2008, 09:00 AM
Kevin R. Cashen Kevin R. Cashen is offline
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Thayer, you mentioned that you are working out of a kiln, if this is the case is your controller/thermocouple fairly accurate? If so then you can take advantage of your ability to soak at temperature. All hardenable steel will benefit greatly from a soak at temperature. The purpose of heating the steel before the quench is to put carbon into solution that was segregated by previous softening operations. At around 1335F-1350F the conditions will occur inside the steel for this to happen. At 1414F the steel will go nonmagnetic due an abrupt change in the spin of the electrons in the iron atoms, this is known as the Currie point and it has nothing to do with how much carbon is in solution. But in order for the carbon to travel throughout the metal you will have to go to a slightly higher temp than either of these and hold long enough for it to complete the journey. Each steel will have its own temperature that is the minimum you want to go to in order to get adequate solution, with steels that have carbon contents in excess of .85% that temperature will be on the lower side because putting more than .8% carbon into solution can lead to other issues. On the opposite side is the temperatures that you do not want to exceed since after all the carbon is in solution there will be no material left to define the walls of the grains and grain growth can commence, however this is much, MUCH, more a factor of temperature than of time. For our purposes, if you are in control of your temperature, one can say that time is almost irrelevant to grain growth since until you exceed a certain temperature there will be no grain growth.

As previously mentioned, the minimum temperature you want to go to for proper hardening of 1095 is 1475F. , if you were to go to 1475 and hold it for at least 10 minutes at that temperature before your quench into a fast oil you should see hardness of 65 Rockwell at the edge with lowering degrees towards the spine, how close to the spine things are still HRC 65 will depend on your oil. 10 minutes is a guideline, if the steel has seen no other heat treatment other than what it received at the mill then you would want at least 10 minutes. If you have done other heating operations to it that temperature could be adjusted down or perhaps up depending? You want to leave a few thousands thickness around the edge to be removed later due to a thin skin of oxide or decarburized steel, as that is the only thing you have to fear about leaving it in a well calibrated kiln for as long as you want.

Shooting low on the temp or undersoaking the steel will result in lesser amounts of carbon in solution and will leave multitudes of patches of soft iron within the blade that the carbon did not have time to reach and saturate once in motion. This condition will allow a file to skate over the hardened areas as if the whole blade were hard and not detect the soft areas between, but it will bury a Rockwell penetrator and show from 5 to 20 points less in hardness. If your 1095 did not have manganese you could put plenty of carbon into solution and quench into water more safely (as they did in the old days) but modern simple carbon steels have increased hardenability due to that alloying addition.

My advice is to get your hands on the best oil for quenching that you can and preheat it to around 130F, soak the steel at 1475F. for at least 10 minutes and then quench into that oil keeping the blade in motion under the surface (tip to tang, not side to side) to increase the cooling action. As soon as the blade reaches room temperature waste no time getting it into the temper, as even with oil, fully hardened steel left untempered may not survive the long haul.

With increased soaks you will find your tempering temperatures will increase. If proper solution occurred 400F will be your starting point for tempering and with 1095 you will be surprised at how close to 500F you may have to go to get below 60HRC. For a good little hunting knife 425F may be nice but for a large chopper 450 may be more like it. Folks who have never implemented a good soak will be aghast at these numbers, and no more shocked than I am when I hear tempering temps of 375F or below. But I have spent many hours looking at both blade results under the microscope (as well as using and other tests) and that is why I would recommend the soak.

Last edited by Kevin R. Cashen; 12-02-2008 at 09:06 AM.
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  #15  
Old 12-02-2008, 09:24 AM
Wade Holloway Wade Holloway is offline
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Thanks Kevin that was great, even I was able to understand that. Thanks allot, puts allot of things in perspective for me.
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