Failed 80CRV2 Heat Treat

[duckie]

I heat treated a few stock removal 80CRV2 knives and then took them to the local tool/die shop to have them HRC tested. They tested between 48 and 53.

From what I've read, that's WAY too soft. The guy at the tool/die shop offered to re heat treat them for me with his heat treat oven. He just called and said he took the two softest ones and could only get them to 56HRC post-quench (no temper).

Do we need to anneal them first? What are we doing wrong?

 

[Gene Kimmi]

80CRV2 is known for heavy decarb. You need to do some grinding after heat treat to make sure you get down to the hard steel before testing.

 

[duckie]

80CRV2 is known for heavy decarb. You need to do some grinding after heat treat to make sure you get down to the hard steel before testing.

I did after my attempt. He tested clean steel. He said he ground away the decarb before he tested them after his attempt

 

[Rick Marchand]

Sometimes steel received from the mill is heavily, spheroidized/annealed. Not usually a big problem if you have the equipment to soak/hold the piece at the proper austenitizing temp... but more simple "heat and quench" methods just don't allow enough time for proper diffusion. With out knowing the process of the heat treater, it's difficult to troubleshoot.

 

[duckie]

Sometimes steel received from the mill is heavily, spheroidized/annealed. Not usually a big problem if you have the equipment to soak/hold the piece at the proper austenitizing temp... but more simple "heat and quench" methods just don't allow enough time for proper diffusion. With out knowing the process of the heat treater, it's difficult to troubleshoot.

I forge heated them just past magnetic, quenched in heated canola oil, tempered at 400 in a kitchen oven for 1 hour, then accidentally left them at 400 for 5 hours on the second temper (fell asleep). Ground them before testing.

The guy who heat treated them the second time soaked them at 1525 for 10 minutes then quenched them in motor oil. (Tested before temper at 52-55RC)

 

[Cliff Carter Knives]

Where did you get the steel?

 

[polish avenger]

What Cliff said.
And...motor oil is not a quenchant.

 

[duckie]

Where did you get the steel?

Waterjetknives.com

 

[Rick Marchand]

I suspect it’s a combination of coarsely spheroidized steel and inadequate austenitizing. Please please please stop using motor oil as a quenchant. It’s just a bad for you as it is for the steel. If you can’t get an engineered oil, canola will suffice.

In my opinion, that steel needs to be brought up to 1700-1900F to restore its hardenability. Then cycled at 1450-1500F to refine … THEN the final austenitizing at 1500-1550F and quench in warm oil.

 

[duckie]

What Cliff said.
And...motor oil is not a quenchant

I suspect it’s a combination of coarsely spheroidized steel and inadequate austenitizing. Please please please stop using motor oil as a quenchant. It’s just a bad for you as it is for the steel. If you can’t get an engineered oil, canola will suffice.

In my opinion, that steel needs to be brought up to 1700-1900F to restore its hardenability. Then cycled at 1450-1500F to refine … THEN the final austenitizing at 1500-1550F and quench in warm oil.

Thanks. I'm not the one using motor oil. That was the guy at the tool and die shop. My oil is also not great though. I'm using canola.

 

[Ken H>]

Your canola oil heated to around 120F will work pretty good as a medium speed quench. Rick said it just fine - take the blade and heat hot - you're using a forge with no temperature indication? Heat to really bright red and hold for a couple minutes. This puts every thing back in solution with big grain. Then as Rick says cycle 3 times around 1500 to refine the grain to a smaller size. I'll bet you'll find the steel gets hard as it should then.

 

[Britt_Askew]

In the future if you want steel that you can just heat to just past magnetic and quench Alpha knife supply would be a good place to shop.

 

[me2]

For hardening 80CrV2

Why canola isn’t a recommended quench oil for 80CrV2.

 

[me2]

The heat treating video covers hardening with a forge and with an oven with good temperature control.

 

[me2]

I heat treated a few stock removal 80CRV2 knives and then took them to the local tool/die shop to have them HRC tested. They tested between 48 and 53.

From what I've read, that's WAY too soft. The guy at the tool/die shop offered to re heat treat them for me with his heat treat oven. He just called and said he took the two softest ones and could only get them to 56HRC post-quench (no temper).

Do we need to anneal them first? What are we doing wrong?

Maybe several things or maybe just one or two. The steel may have too coarse a structure for hardening as it’s delivered to you. Higher temperatures and longer soak times are needed to get things rearranged for hardening.

The canola oil may not cool the steel fast enough depending on thickness and the starting microstructure before quenching. Motor oil definitely isn’t fast enough.