Willie71
Warren J. Krywko
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- Feb 23, 2013
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How big was the quench tank? I use 5 gallons in my tank. Heat the Canola to 130-140 as well.
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Help identifying steel
- Thread starter GrenfellsBrutalForge
- Start date
How big was the quench tank? I use 5 gallons in my tank. Heat the Canola to 130-140 as well.
- Joined
- May 23, 2016
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I usually quench the blade and 1" or so of tang for~30s then suspend the whole knife in the oil until it cools below 100f. I put the thermometer in as soon as I suspend the blade and it usually climbs up around 200f. I wouldn't have thought that would be enough to temper the hardness back, but looking at the tempering graph for 8670, it appears that it would. I'll give the water a try. Hoping to have a blade I've been working on ready to heat treat this weekend. I might get a chance to try then. I'll try the water after the oil and if that doesn't make a difference I'll try longer/ hotter soak.
Btw, went ahead and rough ground and sharpened the edge of the first test blade without changing the ht. The initial edge cut news print cleanly. Chopped through a 2x4 a few times with it and it still cut newsprint cleanly afterwards. I plan to do some more cutting tests with it but my initial impressions were pretty good even though it SEEMED to me like a file was cutting it too easily.
Thanks again
-Colin
Btw, went ahead and rough ground and sharpened the edge of the first test blade without changing the ht. The initial edge cut news print cleanly. Chopped through a 2x4 a few times with it and it still cut newsprint cleanly afterwards. I plan to do some more cutting tests with it but my initial impressions were pretty good even though it SEEMED to me like a file was cutting it too easily.
Thanks again
-Colin
- Joined
- May 23, 2016
- Messages
- 115
Warren, my tank is a piece of 4" rigid conduit about 21" tall. I think it holds something like 6 litres of oil.
I usually always quench with the oil around 130f but it cooled down to ~90f on me while I was soaking the steel.
Next time I'll try to have it in the 130-140 range
-Colin
I usually always quench with the oil around 130f but it cooled down to ~90f on me while I was soaking the steel.
Next time I'll try to have it in the 130-140 range
-Colin
Stacy E. Apelt - Bladesmith
ilmarinen - MODERATOR
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6 liters of oils should not rise 100 degrees from quenching one blade .... something is wrong. I have a 1" round bar of steel I heat to probably 1800F and plunge into the AAA tank ( about 3 gallons) to heat the oil, and it takes several repeats to bring the tank up even 50 degrees.
200F will definitely auto temper the blade as well as result in a high RA. If the steel is held at 200 while it slow cools to 100, that means it never fully hit Mf. You are stabilizing the austenite .... which is what austempering does. This will make a somewhat hard ( Rc upper 40's to low 50's) and incredibly tough steel structure. In industry, where RA is an attribute, this is regularly done. Big coil springs are done that way.
In knife blades, you want to cool the blade from 400F to room temperature is a smooth and continuous drop. After about 30-60 seconds in the oil it should be removed and hung in still air until it is at room temperature. Any hold or delay along this drop will make a less hard and more tough structure. Since normal tempering gains significant toughness in most knife blades, the loss of hardness is not desirable ... so quench, cool, temper in a continuous line.
200F will definitely auto temper the blade as well as result in a high RA. If the steel is held at 200 while it slow cools to 100, that means it never fully hit Mf. You are stabilizing the austenite .... which is what austempering does. This will make a somewhat hard ( Rc upper 40's to low 50's) and incredibly tough steel structure. In industry, where RA is an attribute, this is regularly done. Big coil springs are done that way.
In knife blades, you want to cool the blade from 400F to room temperature is a smooth and continuous drop. After about 30-60 seconds in the oil it should be removed and hung in still air until it is at room temperature. Any hold or delay along this drop will make a less hard and more tough structure. Since normal tempering gains significant toughness in most knife blades, the loss of hardness is not desirable ... so quench, cool, temper in a continuous line.
Last edited:
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- May 23, 2016
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- 115
Thanks Stacey, I was unaware of that. I had read somewhere that the blade should be left in the oil to cool so that's what I had been doing. The cupon I tried to harden was unbelievably tough. I wasn't able to break it the way I tried.
I'm not 100% positive that the oil raises to 200f but I'm fairly sure it was up around there. I'll double check next time I ht. Might get there tomorrow.
Thanks again
-Colin
I'm not 100% positive that the oil raises to 200f but I'm fairly sure it was up around there. I'll double check next time I ht. Might get there tomorrow.
Thanks again
-Colin
- Joined
- Dec 21, 2006
- Messages
- 3,158
Colin, just keep in mind that canola oil is not an engineered quenchant. AAA, P50, QK, and other oils are engineered to slow down the rate of cooling once the pearlite nose was reached. Canola doesn't. If you were using AAA or similar, you can leave it in the oil until toom temp. I asked Kevin Cashen about this very thing, whether you should leave it in the oil or let it air cool once the PN has been reached. He indicated that some auto tempering might occur using an air cool after oil quench, but in the end, after the oven tempers were said and done, the results are basically identical.
Stacy E. Apelt - Bladesmith
ilmarinen - MODERATOR
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My comment and recommendations were based on his assertion that the oil rose to 200F from the quench.
If the oil is only 120-130F, or at room temp as is done with #50, The quench should only raise it about 5-10 degrees. If it stays below 150F, then the blade could cool in the oil until it reached room temperature if you wished. This could take up to an hour, as the cooling rate of a tank of oil is pretty slow. No real harm would be done, but I like the blade to reach room temp ( and assure Mf) in less than 10 minutes after the quench. I also prefer a even and continuous drop.
If the oil is around 200F, Mf would not be reached in sufficient time to avoid auto-tempering, and higher RA would be likely. The steel would likely only have an Rc in the mid to upper 50s before the temper. If his quench oil warms up excessively, then removing the blade and allowing it to air cool to room temp would be advisable.
This is my quench procedure:
Austenitize in the oven or forge and soak for the necessary time. I assure that the edge and tip are evenly heated and at the correct temperature ( *the spine is not important). The quench is smooth and the tank is about three feet from the forge. I normally remove the blade after about 8-10 seconds in the oil to check and straighten any warp/curve while still austenitic. Sometimes I stick it back in the oil for up to another 30 seconds to let it drop to below 400F, but usually I just stick it on a magnetic bar near the forge to hang in the air. After all blades are quenched and cooled, I gently wash them off with soap and water and temper immediately in a pre-heated oven. Even though I have several HT ovens, I use the forge to HT most carbon steel blades, and do the tempering in the kitchen oven. Sometime easy is just as good as complicated
* The way many folks like Don Hanson and others get nice hamon on blades with no clay is that they HT for the edge temperature. The spine may barely be above the Curie point ... or below it. Even if the whole blade is at the same temperature in a HT oven, the spine is much thicker than the edge. That means the spine and upper bevel will not make the pearlite nose in fast quench steels like W2, 1095. The auto-hamon ( as it is often called) is the result.
When doing HT is a forge with a high carbon steel, the edge is all you need to watch. If you spend too much attention on getting the spine up to 1450, then you will likely have an edge that is 1550. I would far rather have the edge at 1450, and really don't care what the spine temp is. Any soak should be done while observing the edge and keeping it at the target temp. If the spine rises to that temperature, fine ... but, again ... the edge is what you are hardening.
If the oil is only 120-130F, or at room temp as is done with #50, The quench should only raise it about 5-10 degrees. If it stays below 150F, then the blade could cool in the oil until it reached room temperature if you wished. This could take up to an hour, as the cooling rate of a tank of oil is pretty slow. No real harm would be done, but I like the blade to reach room temp ( and assure Mf) in less than 10 minutes after the quench. I also prefer a even and continuous drop.
If the oil is around 200F, Mf would not be reached in sufficient time to avoid auto-tempering, and higher RA would be likely. The steel would likely only have an Rc in the mid to upper 50s before the temper. If his quench oil warms up excessively, then removing the blade and allowing it to air cool to room temp would be advisable.
This is my quench procedure:
Austenitize in the oven or forge and soak for the necessary time. I assure that the edge and tip are evenly heated and at the correct temperature ( *the spine is not important). The quench is smooth and the tank is about three feet from the forge. I normally remove the blade after about 8-10 seconds in the oil to check and straighten any warp/curve while still austenitic. Sometimes I stick it back in the oil for up to another 30 seconds to let it drop to below 400F, but usually I just stick it on a magnetic bar near the forge to hang in the air. After all blades are quenched and cooled, I gently wash them off with soap and water and temper immediately in a pre-heated oven. Even though I have several HT ovens, I use the forge to HT most carbon steel blades, and do the tempering in the kitchen oven. Sometime easy is just as good as complicated
* The way many folks like Don Hanson and others get nice hamon on blades with no clay is that they HT for the edge temperature. The spine may barely be above the Curie point ... or below it. Even if the whole blade is at the same temperature in a HT oven, the spine is much thicker than the edge. That means the spine and upper bevel will not make the pearlite nose in fast quench steels like W2, 1095. The auto-hamon ( as it is often called) is the result.
When doing HT is a forge with a high carbon steel, the edge is all you need to watch. If you spend too much attention on getting the spine up to 1450, then you will likely have an edge that is 1550. I would far rather have the edge at 1450, and really don't care what the spine temp is. Any soak should be done while observing the edge and keeping it at the target temp. If the spine rises to that temperature, fine ... but, again ... the edge is what you are hardening.
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Stacey, the edge is all I concern myself with when hardening blades.
I hardened another cupon this morning. The canola oil did indeed get up to 200f while quenching. This time I quenched for 30s in the canola and then cooled the blade the rest of the way in water. File seems not to bite in on this one but I still can't break the cupon clamped in a vice with a hammer.
Is this normal for this steel? I know with 1095 after hardening it breaks really easily, 5160 is harder to break but it does. The hardness testing files I ordered should be here this week, I'll see what kind of hardness I got when they get here
I hardened another cupon this morning. The canola oil did indeed get up to 200f while quenching. This time I quenched for 30s in the canola and then cooled the blade the rest of the way in water. File seems not to bite in on this one but I still can't break the cupon clamped in a vice with a hammer.
Is this normal for this steel? I know with 1095 after hardening it breaks really easily, 5160 is harder to break but it does. The hardness testing files I ordered should be here this week, I'll see what kind of hardness I got when they get here