First back yard HT done, need some help

Hengelo_77

Hengelo_77

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This weekend I did my first HT together with an other knife maker.
We've used a BBQ filled with charcoal and a hair drieer for air supply.

The blade got heated to a nice orange and checked with a large magnet.
Then we quenced it in sun flower oil.
We annealed the blade two times an hour at 200C (390F)

The steel is 1.2519 a carbon steel.

I tried prying in a block of wood, afterwards.
Without much effort the point broke off. It does show a fine grain.
The rest of the edge seems pretty good. It can take some chopping.

The bevels show marks where the hot coals touched the steel. Is that OK?

So why did the point broke off?
The point was quite slimm. What I can think of is that the point got over heated.
Can that be the case?

Or did something else go wrong?
 
My guess is that you need to raise your tempering temperature a bit (by the way, that step at 200C is tempering, not annealing. Annealing is heating to austenization temperature, followed by a very slow cooling that will leave the steel as soft as it can be). I'm not certain of the composition of 1.2519, but since it's European standard name is 110WCrV5 I'm guessing that it's a hypereutectoid (110) steel containing Tungsten (W), Chromium (Cr), and Vanadium (V). You likely need a bit more tempering heat to get the properties you're looking for. Try re-tempering twice at around 220C and test it again. Keep going up in increments of 20C or so until you get where you want to be.

Overall it sounds as if you did quite a good job on the heat treatment.

-d
 
Hard to say without being there but I would guess that it was overheated.

Start with a less destructive test at first. After the first temper at 390, I would sharpen the blade and test the edge for chipping on a brass rod. If it chips, it needs a slightly higher temper.

When you say it does show a fine grain, what does it look like exactly?
 
Not sure what 1.2519 carbon steel is, but if you heated it above austenitizing temp and held it there for too long, you could have grain growth which will basically result in a weaker blade.
 
69_knives said:
Hard to say without being there but I would guess that it was overheated.


When you say it does show a fine grain, what does it look like exactly?
Click to expand...

Well it is hard to describe and I'm not in the position to post a photo.
It has the structure of fine grit sandpaper. Maybe 220gritt (very rough guess)
It has a gray color of a normal pencil.

The point was quite slim so it would have absorbed more heat than the edge with the backing of a thicker spine.

The brass rod test, it is done with a sharpened edge, right?
 
flatgrinder said:
Not sure what 1.2519 carbon steel is, but if you heated it above austenitizing temp and held it there for too long, you could have grain growth which will basically result in a weaker blade.
Click to expand...

Could 5 minutes be to long?
 
Hengelo_77 said:
Could 5 minutes be to long?
Click to expand...

No, 5 min isn't too long. If it has the alloys mentioned by Deker they will retard grain growth and it probably needs a bit of a soak.

A fine grain fracture will look smooth, perhaps wavy, but smooth. If you're seeing texture like 220 sandpaper you might have overheated it a bit. Tips are really bad about that.

390 is a fairly low temper. Try sharpening the blade and flexing the edge on a brass rod hard enough to see the very edge flex. If you get chipping you probably need to bump up your temper a bit.
 
hengelo, I think you overheated the tip and tempered too low.
Try 220 for 2 hours and then do a brass rod test.

1.2519 is a bit on the tricky side for a rudimentary HT.

Why don't you post this question on weapons.be?
There is more experience with it there then overhere.
 
This is the knife. How does the grain size look?

Foto-HBJF437O.jpg
 
Hengelo_77 said:
This is the knife. How does the grain size look?
Click to expand...

Judging by the fact that it looks like the height of the broken off section is about .250" or so, it's not bad. Not great, but I've certainly seen worse. It likely got a bit overheated, but not dramatically so.

I usually leave the tip section out of the fire (if working with coal or charcoal)until the rest of the blade is up to heat and then start working it back and forth to bring the tip to temp last.

I still thing the major issue was your low tempering temp. I'd re-temper and re-test the same blade and see what difference it makes.

-d
 
Correct me if I am wrong, but even correctly HT'd and Tempered blades will chip if enough pressure is placed on them. Don't we want a hard Tip/Edge so that it holds a sharpened edge better? Or Should the tip bend in this scenario? I saw a video somewhere recently that showed a Brass rod test on an edge that when pressure was placed the edge Flexed then went back to the original shape (If it stayed bent it would be too soft) but when he put too much pressure on the edge test it chipped, but the grain was fine...
 
Ryan your right on all accounts. Being unfamiliar with this steel, I'd guess it's similiar to O1 Modified. which requires a precise heat treatment. your best best would be to do the heat treating in low light conditions as you'll see the steel get red a few hundred degrees sooner. More than likely though this type of steel needs to be held at it's austenizing temp ( probably around 1500ºF) for about 15-45 minutes to let all those carbide formers get happy and into solution. then ramped up another 50ºF and oil quenched.

my .02 worth
Jason
 
Thnx
Should a poit brake or bend?
Personally I'd prefer a blade that needs sharpening ofter, but won't brake.
 
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