Blade not hardening

J

Jak Epp

Joined
Dec 27, 2023
Messages
204
So I just heat treated a small bowie today, but after 4 attempted quenches, the blade would not harden. I did three normalizing cycles and quenched it, but the back 1/5 of the edge was not hard. So, I quenched again, and this time none of the blade was hard. A file bit right in. I quenched for a third time (which, looking back, was not a smart move) and the file still bit in. I then redid my normalizing cycles and quenched, and it got harder than before, but still not hard enough. Any ideas what is happening or what I can do?
I'm using 1084 and canola.
 
What temperature did you austenitize at? How long did you hold at temp? Did you grind away the decarb from all the heat and cool cycles you ran the blade through?
 
We need a lot more info to help:
1) Method of heating and method of quench.
2) Temperatures of austenitization and "normalizing" as well as how you determined those temperatures.
3) Quench oil used, quantity, and temperature.
4) Post quench decarb removal before testing for hardness.
5) Steel type and source.

It is almost sure that the answer is in one or two of those questions.
 
Back when I was using heated canola oil I had a batch of 1095 blades that just wouldn't harden. I did a water quench (knowing the danger of cracks) and the blade would harden just fine. Now I use Parks 50 that works good for me. Not sure if I had any 1084 blade problems with canola oil, but think I did.
 
Stacy E. Apelt - Bladesmith said:
We need a lot more info to help:
1) Method of heating and method of quench.
2) Temperatures of austenitization and "normalizing" as well as how you determined those temperatures.
3) Quench oil used, quantity, and temperature.
4) Post quench decarb removal before testing for hardness.
5) Steel type and source.

It is almost sure that the answer is in one or two of those questions.
Click to expand...
I heated the blade in a gas forge to just above nonmagnetic, and let cool, then heated to nonmagnetic and cooled, then heated to just below nonmagnetic and coiled. For austenization, I heated to just above nonmagnetic and quenched in canola. I held it in the oil for 7-10 seconds and then straightened by either clamping in a vice or gently tapping with a hammer on my anvil. I quenched on two gallons of canola. I had heated it up to about 130 beforehand, but I was heat treating a batch so the oil was probably higher temp than when I began. I didn't grind before testing with a file, bit I did file down the edge a little bit and it was still soft. The Steel is 1084 from Pop's.
 
Jak Epp said:
I heated the blade in a gas forge to just above nonmagnetic, and let cool, then heated to nonmagnetic and cooled, then heated to just below nonmagnetic and coiled. For austenization, I heated to just above nonmagnetic and quenched in canola. I held it in the oil for 7-10 seconds and then straightened by either clamping in a vice or gently tapping with a hammer on my anvil. I quenched on two gallons of canola. I had heated it up to about 130 beforehand, but I was heat treating a batch so the oil was probably higher temp than when I began. I didn't grind before testing with a file, bit I did file down the edge a little bit and it was still soft. The Steel is 1084 from Pop's.
Click to expand...
Did you forge the blade?

Hoss
 
The more testing we do, the more I think 1084 is not a good beginner steel.

It’s hard to guess at the problem with your blades. It could be over heating, too much time in the forge, excessive decarb, wrong quench temp, wrong quench oil, forging outside where it’s hard to judge the temperature, oxidizing flame, too many thermal cycles, don’t know without watching you work.

If possible, switch to a better steel for young smiths.

80crv2, 8670, or 5160 might be better choices. Start with thinner stock and make smaller knives at first.

You’re doing lots of things right, just can’t say why the blades aren’t getting hard.

Hoss
 
DevinT said:
The more testing we do, the more I think 1084 is not a good beginner steel.

It’s hard to guess at the problem with your blades. It could be over heating, too much time in the forge, excessive decarb, wrong quench temp, wrong quench oil, forging outside where it’s hard to judge the temperature, oxidizing flame, too many thermal cycles, don’t know without watching you work.

If possible, switch to a better steel for young smiths.

80crv2, 8670, or 5160 might be better choices. Start with thinner stock and make smaller knives at first.

You’re doing lots of things right, just can’t say why the blades aren’t getting hard.

Hoss
Click to expand...
The most confusing part is that this was the fourth 1084 blade in the batch I heat treated, and the first three hardened perfectly, the file refuses to bite at all. I do wonder if the quench oil was too hot, seeing as that was the 4th blade I'd quenched in already warm oil. I'll try grinding it down a little to see if I get past the decarb, but if that doesn't work, would it be unwise to attempt another heat treat?
 
Do you have a way to heat treat one in an oven for comparison purposes? Maybe send a coupon out for hardening if not?
 
Jak Epp said:
I do wonder if the quench oil was too hot, seeing as that was the 4th blade I'd quenched in already warm oil.
Click to expand...
This is sounding likely to me. You're only using ~8L of oil, that's not a very big quench tank. Especially if it's a deep tank and a cold layer can form in the bottom so you're effectively dealing with even less oil
 
weo said:
What kind of forge did you use to forge the blade?
Click to expand...
I use a Hell's Forge propane forge; I know, not the best option, bit I didn't do enough research before I bought one.

Still, I've successfully heat treated 7 knives with it, and my more recent ones hold a pretty good edge and are quite tough.
 
I see you are from Nebraska J Jak Epp

In case you didn't know and aren't too far away there is a forging expo/competition happening in North Platte in October. Should be some good fun and learning to do there. I will likely be checking it out myself.
 
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