Nitro V heat treat and grinding. My first rodeo with this steel.

G

godogs57

Joined
Apr 16, 2004
Messages
754
I was given two bars of this steel recently and I know it’s quite a departure from my usual CPM154 in many ways. I cut out two filet knives and one standard plain vanilla hunter. They are profiled But not ground at this point. Given all the talk about AEB-L AND Nitro V’s tendency to warp, do you think I’d be better served to grind (hollow grind) post heat treat?

Just wondering since this is my first time with Nitro V.

Thanks in advance!
 
I’ve worked with aebl some and I know nitro v is very similar, id definitely grind post heat treat especially if hollow grinding. In my opinion aebl grinds as easy as carbon steels so I see no point in grinding while it’s soft. Most ceramic abrasives do better on hardened steel anyway. Just my two cents but I think it’s much easier to address warps on full thickness stock.
 
Especially the filet knives.....those are thin (or should be) blades to begin with. Like Joshua said, AEBL/Nitro V are relatively simple stainless steels that grind pretty easily even when hard. I find that adding a stress relief cycle prior to hardening really helps with those warp issues. Once the blades are profiled AND straight, do a 1200°F 2 hour cycle prior to hardening.
 
Grind post heat treat.

To help stop warping as soon as I come off the clamped plate quench I clamp to some angle iron and it stays clamped through cold treat and first temper. I've made 7 inch fillet knives from 070 stock this way and not had major issues with warping.
 
Follow up: Great results! I followed Nerd’s advice for “freezer” cryo instead of LN just to see what happened.

1900 for 15 minutes, aluminum plate quench. 24 hours in my deep freeze, temper twice @ 300 degrees. Came out 60 on the nose and zero warpage. Ground the blades this morning and straight as an arrow.
 
FYI, nerd says you only need 60 minutes, not 24 hours!

How long should the cryo treatment be?

Martensite forms basically instantly so it only needs to reach the temperature of the freezer, cold bath, etc. Some studies have recommended extended times for increased wear resistance but those studies are questionable. Usually 60 minutes is fine for cryo or cold treatment.
 
godogs57 said:
Follow up: Great results! I followed Nerd’s advice for “freezer” cryo instead of LN just to see what happened.

1900 for 15 minutes, aluminum plate quench. 24 hours in my deep freeze, temper twice @ 300 degrees. Came out 60 on the nose and zero warpage. Ground the blades this morning and straight as an arrow.
Click to expand...
How did you test hardness? With cryo and only a 300F temper you should be closer to 64. I’d check your calibration if using a rockwell tester or your oven it may be running cooler than what the PID is saying or your temper was significantly higher than you thought
 
With 14C28N, which is very similar to Nitro V, I ran a series of coupons and at 1900 F oven with 15 minute soak I got 61 Rc for both freezer and Cryo treatment. This was with a 300F temper 2x2h
 
Just to point out, he did not use cryo. He used his deep freezer.
With a 1900°F austenitization followed by a freezer cold treatment, the as-quenched would be around Rc62.5 at best. With a 300°F temper it would drop to around Rc61. His Rc60 could be easily in the +/- range of error.
 
So with 14C28N at 1950 F oven and 300 temper the cryo coupons were 64 Rc and freezer were at 62.5 Rc.

Below about 1925 F for austenetizing the tempered hardness was the same for freezer and cryo.
 
Just realized this thread is from a year ago, my brain read the date and forgot what year we are in.
 
You must log in or register to reply here.
Back
Top