Quenching 1084 at 1500f and it won't harden!

SkagSig40

SkagSig40

Joined
Feb 1, 2001
Messages
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I bought a Paragon SC2 and used it for the first time to heat my steel(1084). After letting the Paragon warm up for 30 minutes, I Normalized at 1600F for 10 minutes, let air cooled. Then did thermal cycling at 1550, 1500 and 1450 for about 5-6 minutes each and air cooling between each cycle. Then I put it back in to the Paragon that was at 1500 and let the knife sit for 15 minutes(5 to fully heat and 10 to soak). I quickly opened the door and dunked the knife for 15+seconds into my 130f canola oil quench tank of 5 gallons and moved around spine to edge. The blade was a nice cherry red when it when in but is still soft as butter! A file grabs easily! I tried a 2nd time(not the full normalizing and thermal cycling) heating to 1500f and quenching with no success.
Any ideas what might have happened? I have made 3 knives total before this and used a gas forge to heat to non-magnetic and quenched and the steel hardened right up! I bought this Paragon so I could have very accurate temperatures but it appears something is not right. I have pictures and a short 45 second video I could send to anyone wanting to see what I did. I just can't post it here as I'm not sure how to. Email me at codamonster@gmail.com and I'll send you a video showing the shade of red hot steel coming out of the Paragon. Thanks for any help!
 
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Willie71 said:
Are you 100% sure you didn’t mix up your steel? That’s the most obvious error.
Click to expand...

I bought it from New Jersey Steel Baron and it is marked 1084. The digital read out on the Paragon flashed from 1490ish to 1505 or so.
 
Sounds like a good layer of decarb is on the blade. Your parameters show that you heated the blade for at least 45 minutes. I suspect that if you ground into the blade to finish it, you will hit hard steel. A file will grab the decarb easily.

1084 is the eutectoid. It needs only enough time at austenitization to equalize. No soak time is required. Normalization is a good idea if you forged it, but unnecessary if it was stock removal.
 
I think JT, and Stacy are right. I had a similar problem with W-2 steel and it was the decarb.
 
Thanks guys! So I'm not exactly sure what "decarb" is? Does this decarb happen when you heat in a forge and quench? That is how I did my first 3 blades and the file skated right off. I noticed after taking the blade out of the Paragon for the first time after normalization it was covered in a kind of puffy flaky skin that brushed off with a steel brush. As I went through the thermal cycling and finally the heat treat I brushed off the skin each time but the blade was still black. So if I grind off the black with say 400 grit and file test, the blade will be hard most likely? What is the best way to avoid the decarb?

Also I did my heat treating and 10 minutes soak based on what the Cashen site said to do for 1084. It said to hold the 1500f for 10 minutes. It did not mention anything about thermal cycling and I did that based on a recommendation here on the forum. I appreciate the help gentlemen! I was so upset last night after about 6 hours of trying to figure out what I was doing wrong I was about to put my head through the wall! Haha!
 
Google decarb and you'll see this is a common issue when people think that their steel didn't harden in HT. The carbon migrates out of the steel leaving the black HT scale on the surface. Just below that is a thin layer that is starved of carbon which won't harden well. Grind past that decarb layer and you'll hit the hardened steel. The longer you soak in nonreducing atmosphere, the thicker the decarb, so quick heat to austenitizing temp in a forge would be less decarb than 10 minute soak in your kiln which is probably why you didn't encounter this before.
 
If you file it with a good file a few times, you will notice it starting to skate. Sanding/grinding down with 220 then 400 will quickly remove the decarb layer. Decarb is a normal process in HT and the longer the steel is exposed to air at HT temps the more carbon goes out of the surface. This does not harm the blade, but does put a thin layer of plain iron on the surface ... only a few thousandth thick. You have to sand/grind the surface after HT on all knives, so this isn't any real problem.

To prevent, or lessen decarb, coat a carbon steel blade with a thin layer of satanite or ATP36. Stainless steel must be wrapped in stainless HT foil and sealed airtight.
 
When you used your forge the gas was burning all or most of the O2 out. If you use a electric oven your knife is exposed to 20ish% 02. Carbon and 02 kinda have a thing going. Sometimes it's great when they get together and well... Sometimes not.
 
I really appreciate the help gentlemen! It was 3am when I gave up on my last 1500f attempt to harden and I left the blade on the work bench and did not temper, thinking I failed again. I'll check it for cracks and if all looks good, I'll re-harden one more time and immediately start 2, 400 degree temper cycles. I'll keep you posted how it turns out this week.
 
Unless you think you overheated after thermal cycling and grew the grain, you could just temper once, grind away the decarb, and file test the clean steel, no need to reheat treat. Or like Stacy and kuraki said, if you simply keep filing with your file, you'll probably hit the hardened steel after cutting though the decarb. 1084 doesn't need any fancy triple quench, North-South facing, hocus pocus magic nonsense. :)

If it didn't harden then I would question whether the temperature control or readout on your oven is malfunctioning.
 
Stacy E. Apelt - Bladesmith said:
Sounds like a good layer of decarb is on the blade. Your parameters show that you heated the blade for at least 45 minutes. I suspect that if you ground into the blade to finish it, you will hit hard steel. A file will grab the decarb easily.

1084 is the eutectoid. It needs only enough time at austenitization to equalize. No soak time is required. Normalization is a good idea if you forged it, but unnecessary if it was stock removal.
Click to expand...
It was stock removal, so next time I'll just heat to 1500 and quench and skip the normalization and thermal cycles. I was thinking I should do all of that even for stock removal blades. So what are your thoughts on just tempering this blade after it has sat for 4 days since being heat treated? I have seen articles saying you need to temper right away or it won't come out right and also that you can temper 1084 any time after heat treat no matter how long? I was planing on re-heating it to 1500f and quenching again and tempering right away at 400f. Thanks!
 
If you have a kiln/forge and the time, you should thermal cycle your steel, even if you are a stock remover. But hey, I'm the kinda guy that still rinses off the packaged, "triple-washed" lettuce from the grocery store. Not that I don't trust the sweaty disgruntled worker on the line at the produce facility. I'm sure food safety is the only thing on his mind after lunch break, Friday afternoon.

Your 1084 is like a monk in a strip club... decarb is his robe.

:cool:
 
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All it takes is one finished knife with big spheroids and grain to begin normalizing and thermal cycling everything I'm not positive of the condition of. That's all it took for me anyway.
 
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