New shop, first sword, want HT feedback

T

Tom Kinder

Joined
Jun 14, 2014
Messages
7
So I finally got my shop put together enough I can make swords.

My first sword was originally intended to be a XIIIb but I had trouble keeping everything even and lined up and the only way to save it was to grind the profil into a type XIV. I feel it works ok I just ended up with a light duty thin XIV due to the distal taper.
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I want to talk about my heat treat process, the results I got, and what I can do better.
First my rig:

My ovens are horizontal made of stacked soft fire brick on top of ceramic fiber duraboard by Fiberfrax with a line of hard firebrick down the center to support the sword. Heated by two 24" half round ceramic fiber heaters (back to back for 48" of heat centered over a 52" chamber) made by Watlow and rated for continuous operation up to 2200 degrees F. The heaters are covered by half round ceramic fiber board and blankets on top for the high temp oven. The low temp tempering oven is the same thing but no blankets. My ovens and quench tube are controlled by Watlow 93 microprocessor controllers with K type thermocouples. When I put a cold blade (20 degree ambiant temp in shop) the oven loses about 80 degrees and takes about ten minutes to ramp back up. My controllers are set up to bring it up slow and soft. Once it gets to temp I start the timer for soak. All temperatures I talk about in my process where hit and held + or - 10 degrees F.

The idea was to get a bainite structure with as much martensite as I could manage for the edges and thin areas

steel is 1095

I normalized:
Heated to 1575 with a ten minute soak cooled to black in still air
Heated to 1525 with ten minute soak and cooled in air
Heated to 1475 with ten minute soak and cooled in still air

Austenitized at 1475 with a ten minute soak
Quenched into McMaster Carr fast quench oil heated to 320 degrees and held in quench for five seconds with some slight agitation (oil temp rose to about 380)
I moved the sword from oil to tempering oven in about two to three seconds to prevent air cooling
Tempering oven was preheated to 550 degrees sword was held there for just over three hours

I don't have access to salt pots so I'm hoping heat is heat and there's no magic in salt other than rapid transfer of heat through contact and that bainite will have formed in the tempering oven where I did not get martensite.
One concern I had right away was that my tempering oven rose to about 565 degrees when I put the quenched blade in making me think I should have held it in quench longer

So after I cleaned it up a little just to knock the little bit of scale off I took it to work to put in the hardness tester
The thin parts below the fuller ranged from 52 to 57 HRC
The thicker parts around the fuller and tang ranged from 46 to 49 HRC with the softest part in the center of the tang just behind the fuller and that one actually hit 44

The sword can be flexed just over ninety degrees and will return to true

So those of you with more experience how did I do, what have I likely got and what can I do better?

Thank you
 
Looks like nice work.
The bainite thing seems to be coming back again. I had in the past been part of a serious discussion and I certainly tried to explain that getting bainite was not really worth the trouble as much of the reason was not much more than rumor. You have the equipment there to do a very finely controlled martensite .Do you really need more than that ??

Welcome to the forum Tom !!
 
Thanks. Been lurking for years finally got around to registering last summer as my shop started to come together. I have been working with and learning from Gus Trim for years. He doesn't really talk about it but his sword are martensite and bainite mix and I've always loved his swords so yeah I think I want to see what I can get in bainite.
 
So, You believe that the fuller is primarily bainite? It seems that, because of the differences in hardness you had a certain conversion to martensite towards the edge. On your next sword you could try something similar but heat to 450 and hold after the quench? Not certain if you can see the difference between the structures with a light microscope but you can certainly discern the surface grain size upon polishing and staining.
 
Bo T, yeah I'm hoping the thick area around the edges of the fuller are bainite. Holding at 450 would take longer to form the bainite but it would be harder bainite and by the chart it looks to not be a lot longer so I may try a lower temp hold next time for sure.

I'm gonna have to check my notes, I may have written the wrong hold temp on my write up. I wrote it all from memory and as I recall I was waffling about doing a 500 or 550 degree hold. Now I'm not sure.

So have you polished a bainite martensite mixed blade before? Is the grain difference as obvious as a hamon? I understand that bainite is made of the same basic stuff as pearlite and under the microscope it is the same color but has a needle shaped structure ( I think I got that right just rote memory from reading) so maybe it will look similar to a pearlite / martensite boundary. Is that correct? Guess I'll see when I get it polished up. I've always been bad at revealing hamon though
 
BTW the very fine structure found in some of the Japanese swords is there due to HAND polishing ! I wouldn'twant to predict what these things look like as the polishing and HT details are quite variable as far as what you get.If you want a hamon go slowly by hand.
 
I'm glad you linked those posts, I now have more questions for Gus. Either he has changed what he does in the past couple years or some of the details got lost in his post stroke state and never made it to me. The process that has been telling me about in last couple years has been a modified marquench and is a textbook example of how to get bainite and martensite mix.
I do know the formula has been tinkered with during the time he was making the 60 HRC blades for a bit there and I know he tuned the process about five years ago but I don't know the full scope of changes
 
That last link is interesting and shows things are still the same!! [I'm Robert C with my miniature bronze leaf sword ! ] The written and published HT recipies are really guides , not absolutes.
As for the martensite/baintite thing show it's best not to assume because small changes in time or temperature ,or composition can make you a liar LOL. To repeat my word from one of the threads--"experiment !"
 
Well, you might chat up Tink and also note Darksword now claims their 5160 is getting ht to 60 at the edge and 50 for the body. At any rate, I thought Gus was still outsourcing, which means anyone with that steel and formula might succeed. Don't overlook the old alloy banding and ghost polishing "hamon".

Kevin checks in here every now and then but the makers and smith areas might be a place for crossposting. Keep in mind Don Fogg's board as well

http://www.bladesmithsforum.com/

nevermind, you are already there;)

Cheers

GC
 
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Well it seems I was wrong about Gus's treatment. You see he told me everything but either he forgot a part or I did. And it made the difference between forming lower bainite and tempered martensite. So yup, Gus's swords are all lath martensite and that is very hard to distinguish from bainite in a lot of applications or so I understand. It is going to require a good bit of testing but I think I like this treatment for 1095. Not sure how 5160 would react to this, I think I'll start with Gus's formula and work from there.

Is there any definitive way to identify bainite from tempered martensite without needing special equipment?
 
Bainite is a diffusion process as is pearlite. Martensite is a shear type crystallographic change taking place very quickly. Similar to martensite is twinning.

http://www.msm.cam.ac.uk/phase-trans/newbainite.html

This is the second version of the bainite book .It should tell you everything you'd ever wanted to know about it !!!

X-ray crystallogrophy should do it as it would pick up the martensite crystal and the ferrite one also.
 
An optical microscope can get @ 1000X. Take a ruler and look at the distance between the mm graduations. This is the size that 1 micrometer can be clearly seen under an optical microscope. If the bulk properties of bainite are enough different (due to the formation mechanisms) than tempered martensite, you might have a chance. There isn't any way, that I know of, for you to look at the micro structure of your sword without cutting it up. I am not certain of the x-ray crystallography, but the machines that I have seen require a small sample. You could run samples with the same cross sectional profile several inches long through the same HT.
 
Tom Kinder said:
Is there any definitive way to identify bainite from tempered martensite without needing special equipment?
Click to expand...

Another guy on one of the forums in years past talked about how differently martensite & bainite reacted to his polishing stones. This was one way he could verify that the heat treat did what it was supposed to, without expensive micrographs. The other was destructive testing, since the two phases fail in different manners, though I doubt you want to try that on every blade.
 
Okay, silly question. Why not take your best effort and put it to a field test? I know a guy can get carried away with grain analysis, etc. So test it. Is there a better way to test a blade than cutting stuff?
 
I will certainly be testing it once I finish it. Still needs a lot of little detail work. Thing is, I've never had a sword made this way before so I want to make sure I understand what I observe. I'll be able to tell if it will hold a decent edge right away as I sharpen it and I can already tell it is going to handle nicely and I'm pretty sure it should cut well.

In the end either it is going to cut well, hold an edge, and stand up to hard use or it won't. I'll be able to identify that. I am just looking for a way to confirm that I did get some bainite in the blade and if I can figure out generally where that would be great. I just hate to assume and I'm no fan of guessing.

I would love to figure out the depth of martensite I can get with this treatment, that way I can assign an area to be martensite or bainite by controlling thickness or I can adjust my process to get the thickness I want. I understand this may be an unreasonable expectation but I'm trying to figure it out all the same
 
To me, Tom, it's simple, do the best you can, record what you can, and cut. It will work itself out very quickly. I believe you are over thinking this a bit. Do your best, record, and have fun cutting every damned thing you can down. At least, that's what I did. You will compensate as you go along. Best of luck to you, my friend. It's a long and fascinating journey you are on, and there are no scientific certainties, it's an art.
 
I do tend to over think things, honestly I enjoy it. But you can bet I'll put this sword through its paces. I have done a lot of cutting in my time
 
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