5160 Ninjato/Chokuto Sword

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xenocomics

Joined
Jan 12, 2025
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Hey guys. Today I just quenched my first sword. I used hot rolled annealed 5160 spring steel, just cut out and rough shaped before quenching. No forging or hammering.

I clayed the blade in an attempt for a hamon (3 to 1 refractory cement and iron oxide), although I did not know before hand that 5160 is such a deep hardening steel. Heated it to where it was non-magnetic, and into warm parks 50 oil. No audible cracking sounds or visible cracks, and no fireballs. Problem is, I forgot to count so, after watching the video I realized I left it in the quench oil for 14 seconds...,.bit too long lol

Tempered at 400 for one hour, air cool then again for 45 minutes. Waiting on some Rockwell files to arrive before doing it again.

There is no left and right warping, but the spine curved a little, but the "right" way just making it a bit more like a katana than a ninja sword. It very slight.

Two questions. I think I almost for sure through hardened it with a quench like that right? And, is there any prayer of getting a hamon out of this? I've already whetstoned up to 8000 with traditional Japanese water stones and tried lemon juice with a drop of soap.
 
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Welcome xenocomics. Fill out your profile so we know a bit about you and where you live.

Parks #50 is used at room temperature, not warmed. The normal work range is 50-90°F.

Your quench for 14 seconds would affect a hamon on a low alloy steel, but with the 5160 steel you used a hamon was unlikely from the start. You want a steel with low alloy content and especially low manganese for hamon formation. 5160 has .80-1% chromium and .75-1.00% manganese. A perfect hamon steel has less than .35% manganese and no other alloying beyond trace elements. Most steels have more than this, but using a steel that is as low as possible will yield the best hamon results. W2 is a favorite of many hamon enthusiasts.

Your summation that it through hardened is likely correct. Your summation that there will not be a hamon is also correct.
 
Stacy E. Apelt - Bladesmith said:
Welcome xenocomics. Fill out your profile so we know a bit about you and where you live.

Parks #50 is used at room temperature, not warmed. The normal work range is 50-90°F.

Your quench for 14 seconds would affect a hamon on a low alloy steel, but with the 5160 steel you used a hamon was unlikely from the start. You want a steel with low alloy content and especially low manganese for hamon formation. 5160 has .80-1% chromium and .75-1.00% manganese. A perfect hamon steel has less than .35% manganese and no other alloying beyond trace elements. Most steels have more than this, but using a steel that is as low as possible will yield the best hamon results. W2 is a favorite of many hamon enthusiasts.

Your summation that it through hardened is likely correct. Your summation that there will not be a hamon is also correct.
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Thanks for the reply! I chose 120 degrees for the parks 50 actually based on wonderfully researched article specifically on 5160, and the effects in different times/temperature ranges. Stating that the optimal range they found was 1525 target temp, 7-9 seconds quench 120 degree parks 50, and tempering done at 400. Both for balance of hardness and flexibility, as well as crystalline structure. I am currently wasting every drill bit I own trying to get through the tang.....even after spot torch tempering. Rockwell harness = 1,000,000.…..I'll see when the files arrive haha
 
Can you post a link to that research article?

Try carbide bits.


BTW, flexibility is not a factor of HT. Young's Modulus determines flexibility and is unrelated to hardness. It is related to geometry.
 
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Also, parks 50 has a temp range from 57-120 according to their data sheet. I chose the upper end range to hopefully alleviate some stress, and to actually minimize the temperature gap between the steel and the quenchant. This was an effort to put a little bit less stress on the steel, as I was scared of cracking it on my first go. Basically I chose the lowest temp I could where it was non-magnetic, and the highest temp for the oil, because I don't have a good way yet to measure temperatures too well. My target hardness I hope is in the 55-60 HRC range.
 
All your numbers are good. I think your sword should be fine.
While that seems like a reasonable attempt to reduce the shock of the quench, the shock is a product of the structure conversion from austenite to martensite that starts at 400°F and is effectively done by 200°F (in 5160).

I agree that the temperature of Parks#50 can be up to 120°F, but when quenching a sword, the temperature will rise a good bit, thus starting a bit lower would-be good insurance.
In the real world, anywhere from 50° to 120° should get the same results with a simple lower carbon steel like 5160.

Questions/Notes:
Did you do cryo in LN immediately after the quench as Larrin did?
Retained austenite is a thing folks like Larrin look at, but is simple steels is not really an issue for the average knifemaker.

As far as toughness in a sword, a little RA is a good thing.
Swords are not long knives. They have very different geometry and stress points. Hardness is usually much lower than a knife ... and toughness is the most important attribute the HT is designed to fit. I make a sword with high toughness as my main target for HT parameters, and around Rc 55-57 as my hardness target.

I have read that 5160 article several times in the past and scanned over it again. It does not state what temperature Larrin used for the parks #50.
IIRC, Larrin (and the folks he has do the tests for him) often warm their Parks #50 above room temp with good results ... but they are usually quenching 2" x.2" test coupons.

I have had no issues with quenching 5160 in room temp Parks.5160 is not prone to cracking due to it being hypoeutectoid, and having 1% chromium and 1% manganese.

Spot torch tempering may not work well on 5160, as it can re-harden to some degree in air. Carbide bits are the answer to drilling a hardened tang.
 
No, I did not cryo. Thank for the advice and input. I will have a better idea of hardness this evening when my files arrive. Picked up some harder bits gonna drill at low speed, etc. pics soon!
 
Well, I think I landed between 50-55 HRC. The 55 file is where I can feel the teeth start to catch. Bit low but....hey, first try? Maybe shouldn't have done the second tempering cycle. Bit more polish and voila! How do I do pictures on here?
 
Best way I've found for posting photos here is to put them somewhere else and use the insert image button

How did you control heat for the temper? The clay could have left the blade colder, leaving it softer, and you then tempered hotter than expected. That could give you a softer than expected result
There are a lot of variable here so it's hard to say what it is. ~55HRC is fine for a sword IMO

Edit: oh, and the lack of cryo compared to Dr Larrin's numbers
 
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Don't skip the second temper on knife blades. It has a metallurgical function.

In the first temper the Brittle Martensite is converted to Tempered Martensite. At the same time, Retained Austenite is converted into new brittle martensite. The second temper converts that into tempered martensite. Without the second temper the edge may be chippier. Done with good temperature control, the second temper should not appreciably affect final hardness. Maybe 1 Rockwell point at most.
 
Stacy E. Apelt - Bladesmith said:
Don't skip the second temper on knife blades. It has a metallurgical function.

In the first temper the Brittle Martensite is converted to Tempered Martensite. At the same time, Retained Austenite is converted into new brittle martensite. The second temper converts that into tempered martensite. Without the second temper the edge may be chippier. Done with good temperature control, the second temper should not appreciably affect final hardness. Maybe 1 Rockwell point at most.
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TY for the input. I just finished hack at a piece of wood like an axe. no chipping, folding, or even scraches really. I did some level of research into triple quench/triple temper. But, decided against it for this piece
 
Alex Topfer said:
Best way I've found for posting photos here is to put them somewhere else and use the insert image button

How did you control heat for the temper? The clay could have left the blade colder, leaving it softer, and you then tempered hotter than expected. That could give you a softer than expected result
There are a lot of variable here so it's hard to say what it is. ~55HRC is fine for a sword IMO

Edit: oh, and the lack of cryo compared to Dr Larrin's numbers
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Really just with a magnet. I also had an infrared heat gun but....that didn't seem to be giving accurate numbers. I am very open to suggestions on better heat control. Other than some super expensive oven for swords.
 
The IR heat guns aren't very accurate; the emissivity is different for different materials. You can get a thermocouple and a ceramic cover for it (very important if using a propane forge!!) and use that to see what temp the forge is running? Use a metal tube as a baffle, too so it's not in direct contact with the flame. Getting an even heat in a forge can be difficult and judging the temperature by eye is difficult.

Salt typically melts around 1475, some people use that to get an idea. There are tempilstiks that melt when the temp is reached; that is a better option and you can get a variety of temperatures!
 
xenocomics said:
Really just with a magnet. I also had an infrared heat gun but....that didn't seem to be giving accurate numbers. I am very open to suggestions on better heat control. Other than some super expensive oven for swords.
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Forge design can help, you don't want direct flames onto the blade. Instead use radiant heating inside the forge, combined with getting a good turbulent gas flow. Or a charcoal forge designed for and even fire. You can also build PID controlled gas forges, but you'll have to consider thermocouple location
Baffles can help with this, basically a big piece of steel tube
Practice will also help

By the time you're considering a customised forge and the like an electric heat treatment oven might not be that much more expensive

FB doesn't like making data available to other sites, because they are dickheads. I use my mastodon, imgur is also a common image hosting place
 
IR pyrometers don't work well above 1000°. The steel starts glowing and the emissivity doesn't read right. There are settings on lab grade units to compensate for that, but it is still a lab type tool and not suited to a forge. I have a $1500 laser pyrometer and don't use it for forge HT because the reading isn't reliable. With experience and lots of practice, you can control a forge and heat a sword to a "good enough" temperature control for hardening sufficiently. Most of my hamon quenches for swords are done in the forge.

If a sword blade will fit my 24" HT oven, it usually gets done there, but if it is too long, I use the forge.

One good method of working a sword in a forge is using a muffle. I put a 3X3" section of square tube in the forge that is the length of te forge floor, and let it heat with the forge until it is the same color as the forge lining. I usually stick a TC connected to a reader in it from one end and can monitor the temp pretty close. I have a PID controlled forge that will run the forge so the muffle stays at a specific target temp. It works OK, but is shorter than the forge I do swords in.

What is most important in doing a forge HT of a sword is that it requires constant moving of the sword blade. I "pump" the blade slowly in and out of the muffle spo the entire blade gets evenly heated, checking with the magnet regularly. Once it is non-magnetic all over, I try for even color end to end and when happy with it, I quench.

Tips:
Cutting a small thin slot in the lower portion of the HT oven door so the tang sticks out allows a sword with a 20" blade edge to be HTed in the electric kiln. Stuff and wrap kaowool around the tang while heating the sword. When not in use, plug the slot with a slice of firebrick or a wad of kaowool.

The stickys have good info on building a forge as well as forge HT methods. There is also my plans for a PID controlled forge the stickys

If building a dedicated long gas forge, 24" is usually sufficient. At 30" it gets problematical to keep the chamber evenly heated without a lot of adjustment and multiple individually controlled burners. If you need a BIG forge, the best method is what we call a "Drum" forge. It is a large vertical forge. Most have a single blown burner at the bottom. Some have a central muffle down the middle. If this idea intrigues you, search "Don Fogg drum forge".
Caveat - A big forge can cost a lot, and may not have even heating ... plus takes lots of experience to run right.

In most cases, a large electric HT oven is a more reasonable option. They make them up to 48" with pretty good chamber heating control.
 
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