First broken blade (heat treat)

I cannot argue with the points you make Stacy. That is good advice for newbies. I would however add, maybe a newbie could experiment with blanks or sacrificial blades, to see for himself how a particular steel reacts to different proceedures. That is how I learned what could be done, and what should not be. Of course, I am still learning. Sorry for any confusion.
 
Patrice Lemée;8959137 said:
Well, it looks like I won't be passing my JS test anytime soon...

broken2.jpg


By the way, is Park 50 suppose to smoke that much?
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Patrice, both the ease of fracture and the heavy smoking are explained by your photo of the end grain (far too coarse). The blade was probably overheated. In a proper full quench Parks #50 or any oil should not smoke at all, upon removal from the oil in an interrupted attempt at marquenching there should be light wisps of smoke from the blade. Overheating the blade will lead to flashing the oil or the heavy smoke you describe. If your oil is smoking heavily you are shortening its working life, so it is important to get ahead of this and alleviate the issue with better temperature.

If you wish to straighten the blade before tempering it needs to be done with a carefully timed interrupt. It is best to interrupt the cooling as close to Ms as possible (in this case 400F would be fine). If you interrupt the quench too much above Ms the auto-tempering effects will be too extreme. The window for straightening will occur as the blade is cooling from Ms to around M50% this will give you around three to five minutes (all depending on room temperature and air flow) to straighten any kinks that you see developing. Around 300F things will begin to get stiffer and when you feel heavy resistance to you hand correction, you stop.

I will just give the facts as I know them, and my experience about the different steels. Carbon content and alloying determine both Ms and Mf, the more you have of either will lower them, so if you interrupt both 1084 and O1 at around 450F the O1 will reach a given martensite percentage much later than the 1084. I normally get from three to five minutes out of a 10xx series steel and have worked O1/L6 blades with ease after eight minutes out of the interrupt. So you have both chemistry and temperature, cooling or airflow considerations in the given shop, as well as how much the insulating gloved hands are all over the blade. There really is no basis for disagreement on a plethora of heat treating issues if we remember that each individual chemistry will require us to step back and reassess the process.
 
I have to agree with Kevin and LRB on this one.

An interupted quench will work on either type of steel, but there is less time with the simple steels.

"If you interrupt the quench too much above Ms the auto-tempering effects will be too extreme." Cashen
 
Nothing like a little validation to start the day. I was starting to think that maybe there was something wrong my HT process. Thanks guys.
 
I could add that knowing the smoke point of your quenching medium can be helpful in doing an interrupted quench, as Kevin sort of touched on. I don't know what the smoke point of Parks #50 is, but it can vary quite a bit with different types of oils. However, it's usually in the neighborhood of an interrupted quench, between 300-500 degrees.

"upon removal from the oil in an interrupted attempt at marquenching there should be light wisps of smoke from the blade." Cashen
 
LRB said:
Nothing like a little validation to start the day. I was starting to think that maybe there was something wrong my HT process. Thanks guys.
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I believe the misunderstanding probably originated with some confusion about what you meant by O1 being ductile several minutes after the quench. I think most people would read that as meaning the steel is still largely soft for some *time* after a finished quench. But I think you must have meant some *time* after pulling the blade from the oil, *while still very hot and still somewhat austenitic*. Meaning an interrupted quench of sorts. I believe it was reasonable to read what you wrote as meaning that a nearly room temperature piece of O1, a few minutes after quench, can still be tweaked - which didn't jive.


Internet communication is a fickle thing. :thumbup:
 
Good point Nathan. I want to say that it's more a matter of temperature than time, but the two are obviously connected.

With the interrupted quench, if you pull it out to soon (too hot), the auto temper may be too extreme. If you pull it out to late (too cool), you may not have enough time to straighten it.
 
Patrice, was it smoking when you pulled it out or just while it was in the Parks?

It kind of sounds like the Parks might have a much lower smoke point than the vegetable oil, which would give you less time if using smoke as a guide for an interrupted quench.

I think there's some confusion over the smoking. Kevin says it shouldn't smoke during a proper full quench (when it's totally immersed), but others are saying it does. I'm assuming Kevin means smoking on the surface of the quenching medium, because the vapor jacket down in the medium, usually contains some smoke which is released into the air as the “vapors“ escape from the surface.

Maybe also some confusion about when the quench ends.

Aside from that, the grain does look a bit course.
 
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Tai, it started smoking after the blade had been in it for a little while so like Kevin said I overheated it. And when I pulled out the blade it was still so hot that it was flaming. :eek:
I have to get an oven.

Thanks again for all your help. I could not do it without you guys.
 
Lets talk about the smoke for a bit....

I have never had my quenchant (HQ-K) NOT smoke while heat treating. It doesn't flame up or anything but I get a blanket of smoke over the surface of the oil. Its about 1" thick and white like a fog. The smoke never rises out of the tank until I blow it out. My tank is a 6" vertical tube 36" long. Are you saying that I consistantly overheat my blades? I really don't think I am.

Rick
 
It takes a small amount of "time" for vapors/smoke to form and escape from the surface of the medium.

If you pulled it out and it was flaming, it was too hot. You need to look at smoke points and flash points.
 
I think that would be a no, Nathan. When I take one out of quench It is done, not really interrupted. I keep them in the oil for about 45 seconds moving. They are hot, but not hot enough to cause a serious burn, only too hot for comfort with bare hands. I figure that would be well below 400°.
 
The flash point of canola is around 600, which is a bit too hot for an interrupted quench, IMO. The smoke point is closer to 400 for refined canola.
 
Flash Point for P50 is 280 deg F.
Working range is 50-120 deg F. :confused:
I Could not find info about smoke point.
 
Patrice Lemée;8964377 said:
Flash Point for P50 is 280 deg F.
Working range is 50-120 deg F. :confused:
I Could not find info about smoke point.
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Yes Wally Hayes uses P50 and doesn't preheat at all during the warmer months.


My Houghton Quench K has a Flashpoint of 178C and a Firepoint of 208C... I can't find a Smokepoint.... I would guess around 160C (325-340F)?


Just for fun...

Smoke Points
Safflower 265 degrees C
Sunflower 246 degrees C
Soybean 241 degrees C
Canola 238 degrees C
Corn 236 degrees C
Peanut 231 degrees C
Sesame 215 degrees C
Olive 190 degrees C
Lards 183 to 205 degrees C
 
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LRB said:
I think that would be a no, Nathan. When I take one out of quench It is done, not really interrupted. I keep them in the oil for about 45 seconds moving. They are hot, but not hot enough to cause a serious burn, only too hot for comfort with bare hands. I figure that would be well below 400°.
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I have to think it must be austenite converting to martensite as the blade continues to cool towards Mf (meaning a cooling and temperature thing, not a timing thing exactly), I just can't think of anything else that would cause that.

My trouble with that reasoning is I think an approximate Mf for O1 ought to be hotter than that. Even D2, with an Mf generally given around -100f, still gives me fits once it is cool enough to touch. I'm not disputing your observations, they're just different than I would have expected and don't align well with my understandings of O1.

No matter. Congratulations on 1000 posts. If you do a give away - I want number 42...
 
Not too sure how on-topic this might be, but since Patrice is a new knifemaker (like me) and we're talking about straightening blades during the quench/temper cycles I thought I might throw this in.

After breaking my first blade from trying to straighten after quenching but before tempering (and Bladesmth's correpsonding slap on the wrist for doing so ;) ) I thought about how I would get the tempering blade (which is in my lower oven in my kitchen) into my garage to my vice and bending jig while it was still 300 to 400degF. Obviously if I pulled the blade out of the even and ran to the garage the temp would be below 300deg.

What I thought I might do (which thankfully I haven't had a warped blade in awhile so I haven't tested it yet) is put a cake-pan filled with clean sand into the tempering oven and let it come up to temp. When it was time to temper I would submerge the freshly-quenched blade in the sand and perform the tempering cycles (2hrs + 2hrs for my 1095 steel). After the final tempering cycle I would grab the whole cake pan and run to the garage to straighten the blade if needed. The sand will A) allow a consistant tempering heat over the whole blade, and B) retain a lot more heat allowing me to pull the blade out and straighten it while it's still 300 to 400degF.

I'm sure some other bladesmith has already thought of this though ;) so I might be reinventing the wheel.

Jesse
 
A piece of Kaowool works, too. Place the hot blade in it and fold over. Cary to the vise and straighten.

Steel doesn't cool all that fast in air, so no need to rush. Once it contacts the vise or other metal surface ( anvil and hammer) it cools rapidly. Using a wooden mallet and a board on the anvil to straighten blades, or wooden dowels in the vise jig helps slow down things a bit.
I agree with the others that there is more time than most would think when straightening with gloved hands.My experience has shown a one or two minutes at most. My concern with post-quench straightening advise is new makers who haven't gained the experience to know when to stop straightening. In my opinion, for an inexperienced smith, it is best done in the first minute or after tempering.

LRB, I apologize for sounding as I did. On re-read it was poorly stated the first time.
I should not have made the comment to an experienced maker in the way I did.My point was to advise a newbie against the procedure, not to tell others who know how to do it that it shouldn't be done by them. Again, I apologize.

To make one additional point for a newbie to take from this thread......
Kevin uses salt pots and controlled ovens. He has great experience with long hot blades and straightening them. He can slip on and off a pair of HT gloves with a shake of his hand.He knows just where and how hard to bend a blade to straighten a warp or bend. I would suspect LRB and Tai can do it in their sleep,too. How did they attain this super-skill? Experience - doing it on hundreds (maybe thousands?) of blades. The fact that they have gained this skill is commendable, and their experience is good information to study.......but new makers should not expect to have their first attempts at straightening in this fashion go as smoothly. Many knifemaking skills are second nature to old timers, and seem impossible to new makers. It will take time to gain the eye-hand-brain connection to know when to bend and when not to. Until then, going heavy on the safer side is good practice.
 
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