Cracks in forged 52100

pedervisti

pedervisti

Joined
Oct 31, 2008
Messages
249
Hello, i have recently been having some issues with what i believe are cracks in some of my blades!
The steel is 15mm round 1.3505 (52100), the treatment i give it is after forging i normalize 3 times before hardening at 830c into warm canola oil then temper twice at 230c for 45 minutes. It was finished by sanding to 800 grit, after that an etch in ferric chloride for 10 minutes and a quick polish with tormek paste.
I already have a thread on bladesmithsforum (Here is the full thread with several extra photos: http://www.bladesmithsforum.com/index.php?showtopic=30331), and the conclusion there was that the steel was flawed from the mill, however i am hesitant to contact my supplier since i don't quite think the cracks on the raw bar look anything like the cracks i see on my blades. The reason i am also posting a thread here is to see if anyone here can relate to the issue and/or have an explanation, maybe the conclusion here will be the same, but i would like to be 100% sure before going to my supplier, the last thing i want, is to have me being the problem, while i think it is the material! (i hope you can relate to that!)

So some pictures to explain what i mean:

The first blade i noticed cracks on:


Then i did a second test-blade to see if it was a consistent thing: (it was!)


I then broke the blade to see how the grain looked like:




I then decided to grind a blade from the bar rather than forge it, just to see if it was my forging process that was the issue, this blade was cleaned up to 800 grit and etched in ferric, mind you this blade had not been heat treated yet!:


I found something that could look like cracks along the spine of the blade, which would then be the surface of the rough bar:




So do anyone have any idea what it is? i dont think the cracks on the raw bar look anything like the cracks on the initial blades :confused:
Another thing to note, i just hardened that ground blade, and it has not developed anymore cracks during ht.

Best regards
Peder Visti
 
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it is from too fast of a quench. Canola oil is about the same as parks 50 in speed maybe faster for the first fiveish hundred degrees. I got this same look quenching 52100 in Parks 50. same steel quenched into parks AAA or Texaco type A no problems. the grain looks good so it probably wasn't overheated.
 
Bill...you have WAY more experience than myself in ALL of it....but I quench 52100 in canola and Parks 50, and have never run into this phenomenon. Both are technically too fast for 52100, for sure. Maybe I got lucky, tho!!! Also, he showed a pic of a knife that he polished out....but did NOT heat treat...and the "cracks" are visible along the spine. Very interesting scenario here.
 
samuraistuart said:
Bill...you have WAY more experience than myself in ALL of it....but I quench 52100 in canola and Parks 50, and have never run into this phenomenon. Both are technically too fast for 52100, for sure. Maybe I got lucky, tho!!! Also, he showed a pic of a knife that he polished out....but did NOT heat treat...and the "cracks" are visible along the spine. Very interesting scenario here.
Click to expand...
I was thinking those cracks along the spine of the blade was simply scores from the rolling process, since the spine of that blade is the actual edge of the bar of material.
Bill, that all makes perfect sense, the outer steel cools faster than the inner, and so cracks when it has nowhere to shrink! I think i will see if i can get some proper quench oil.
Thanks
Peder Visti
 
Oh...OK....I am certainly at a loss here. I didn't know canola was that fast of an oil. I always heard it was maybe a 9-11 second oil, while Parks 50 being a 7 second oil. But like I said....Bill has TONS more experience than myself....and I defer to his opinion for sure.
 
Canola is kind of a "funny" for lack of a better term, oil for quenching knives. It has a very fast initial cooling rate but then because it lacks any of the additives that true quenching oils has it kind of stalls in the finish making it an overall slower oil than it should/could be. there is a good bit of information somewhere on the WWW and I believe there was a discussion on this forum about it a year or so ago could have been longer though.

Stuart, I have no doubt that you have done this successfully. I know of guys that have had good results quenching 52100 in water. For me 52100 and water spells disaster. I one time used water to quickly cool areas of a 52100 blade while forging. I was just passing the piece through the water just to slightly cool it total time in the water was possibly 1/2 second. quenched in Texaco type A while finishing I found lots of tiny almost imperceptible cracks similar to the above pictures that really popped out when the blade was etched. I knew it wasn't the steel or the oil so I did a test, again with the water and sure enough same results. another time I was hammering the choil area on a knife when it slipped out of the tongs I was holding the blade with and landed in a quench tank of P50 that I had been quenching some W2 in this one look almost Identical to Peder's blade.
 
From some experience ... these cracks resulted from anvil-quenched (rest the yellow hot blade too long on cold anvil face). And couple with possibly forge heat was too high for that thin cross section a heat or 2 prior to grinding (crack zone looks like a direct flame bloom).

pedervisti said:
Click to expand...

Crack line looks to me like it's just folded over burr from rolled or sheared. Try grind 1-2mm off that spine to see if the crack goes away.
Click to expand...

I concur with Bill - In common scenarios: too fast quenchant speed and or aust temp too high can lead to surface cracks.
 
Whit that steel also you can have issues if you let it cool to much when forging or get to hot...the proper range for forging 52100 is about 1100 to 950 °C; upper and the steel may crumble, lower and the steel could crack, especially the thin section get cool very quick on the anvil.
The grain looks fine, a slower oil may be better for the 52100 as suggested. Nice blades, by the way :thumbup:
 
Thank you for all the good info! Bluntcut, the crack in the spine was only a surface crack, or burr as you suggested!
I will see if i can find any proper quench oil here in europe!
Best regards Peder Visti
 
I also have had problems of too high a heat in the forge. 52100 likes a moderate heat. Too high and it turns to mush. Even at moderately high heats you get cracks that cannot be repaired and will show up in the HT. Just another possibility.
 
So an update to this thread.
I decided that i would invest in some proper quenching oil and do a final test blade.
And so i did, and what do you know, it was all because of too fast quench oil. :)

This test blade was done the same way as the others, but this time quenched in "Durixol w25"

The blade is at a dirty etch, and not a single crack is showing this time!










Thanks to everyone for their inputs!
Best regards
Peder Visti
 
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