Something Old and Something New

[Aiden CC]

I had two opposite visions for the KITH this year, so I decided to make both, and let whoever gets my entry decide. The first one started out a bit rough:

 

I believe the first or second puck from the left is what ended up as the edge bar. I re-melted it from some wrought iron round bars. 
 

Meanwhile, the other knife needed somewhat more precise treatment. 
 

I chose to take a warikomi approach for this knife, the body is from a link of small anchor chain, opened with a chisel for the hearth steel edge. 
 

Here’s where the blades stand now, the right is made from MagnaCut. I don’t have as many pictures of it yet, but I have something a bit… different planned for the handle. 
 

That’s it for now, thanks for looking!

[Joshua States]

Man, your recent work with that hearth steel/iron stuff is truly impressive.

[Aiden CC]

On 5/22/2023 at 1:47 PM, Joshua States said:

Man, your recent work with that hearth steel/iron stuff is truly impressive.

Thank you! I’ve taken a bit of a break, but there are a few blades in the pipeline. 
 

There were a lot of things I was considering for a handle, and after seeing some lovely curly birch handles on gyuotos by several of the smiths I follow, I opted to use this piece. The blade is heat treated, but still needs to be ground. 
 

The other knife is pretty much finished! An herb chopper, so to speak . There was a warp from heat treatment that I ground out in the blade but persisted in the tang. I opted to use it to fit more greenery on one side as opposed to risking a break straightening it. The handle has dried thyme, rosemary, and Thai basil flowers. 
 

 

[Alan Longmire]

That's too cool! 

[Jaron Martindale]

That resin handle is gorgeous

[Joshua States]

Very cool handle.

I always draw back my tangs with a torch and can straighten them fairly easily.

[Aiden CC]

Thanks, all! I’ve wanted to do a clear handle for a while and KITH always seems like a good time to try new things. 
 

On 7/9/2023 at 9:06 PM, Joshua States said:

Very cool handle.

I always draw back my tangs with a torch and can straighten them fairly easily.

I thought about it with this one, but I’m not sure whether or not MagnaCut undergoes any secondary hardening. 

 

Now that one knife is done, I’ve been putting in some work on the other. 
 

I made a smaller practice blade and tried a stone finish. I couldn’t get good contrast with wrought and hearth steel with stones, so I decided to use the same finishing route I do for seaxes and etched it. 
 

Here it is after etching. This anchor chain is either extremely clear wrought or is some kind of very low carbon steel. It sparks like wrought and I thought one link had a fibrous break, but there’s not really grain showing here. A little polishing compound and final sharpening and this blade will just be waiting on the handle!

[Joshua States]

1 hour ago, Aiden CC said:

I’m not sure whether or not MagnaCut undergoes any secondary hardening

I've never worked with it either, so consider this uninformed rambling....

Maybe isolated heat and straighten hot? 
Don't mind me, I never worry about ruining a perfectly good pirce of steel  by pushing the envelope.

[Jerrod Miller]

16 hours ago, Aiden CC said:

I’m not sure whether or not MagnaCut undergoes any secondary hardening.

I took a quick look at Larrin's page on it and didn't see any results going over 400F, though it is implied that he tried some higher.  Given the chemistry I would not expect a significant secondary hardening due to the extensive presence of strong carbide formers (2% Mo, 4% V, and 2% Nb).  Secondary hardening around 1000F is typically the precipitation of carbides, which are not only hard themselves, but will cause a localized chemistry change that destabilizes retained austenite which then converts to martensite (which often remains untempered).  The one micrograph of Magnacut that is posted in the linked article does not state what the heat treat condition is, as it was presented to show a comparison of the carbides.  It looks to me like it could be a fully heat treated sample, and there are small sections of what I assume is retained austenite.  So there is a little room for retained austenite conversion, but there is already a strong carbide present so I wouldn't think much more precipitation would happen.  

 

Of course, a full hardness vs tempering temp plot would be the best way to know for sure.  Closest I could quickly find to that is posted at KnifeMaker.ca.  Their data goes up to 1000F and only shows hardness decreasing.  

[Aiden CC]

8 hours ago, Jerrod Miller said:

Of course, a full hardness vs tempering temp plot would be the best way to know for sure.  Closest I could quickly find to that is posted at KnifeMaker.ca.  Their data goes up to 1000F and only shows hardness decreasing.  

It looks like for the treatments with no cryo there is some increase in the hardness for the higher tempering temperatures, which would make sense if retained austenite is a significant factor. Is the idea that carbide precipitation reduces the austenite carbon content and destabilizes it? That would make sense, I've wondered how carbide precipitation on its own could make so much of a difference, especially at temperatures where tempering would reduce the hardness of other parts of the microstructure. A number of years ago I had some secondary hardening issues making springs from CP 154 (for the Swiss army knife project that's still gathering dust on a shelf ), but there are quite a few differences between the two alloys. If I recall correctly, I think I've seen that grade called a "high speed steel" somewhere, which seems like it would imply the secondary hardening is intended.

 

A bit of a digression, but I actually met Larrin at a conference a few weeks ago, steel metallurgy is a surprisingly small world! If this had been a bit earlier I guess I could have asked him about any potential higher tempering temperatures he had tried.

[Francis Gastellu]

On 7/9/2023 at 2:01 AM, Aiden CC said:

The handle has dried thyme, rosemary, and Thai basil flowers. 

 

I had missed this earlier post, that handle is really (really) lovely! 

[Jerrod Miller]

14 hours ago, Aiden CC said:

It looks like for the treatments with no cryo there is some increase in the hardness for the higher tempering temperatures, which would make sense if retained austenite is a significant factor. Is the idea that carbide precipitation reduces the austenite carbon content and destabilizes it?

 

I guess I was in a little too much of a rush and didn't look at the higher austenitizing temp columns and really, all of the data (but that is why I included the link).  There is indeed a slight bump in some scenarios.  It is indeed the destabilizing of the austenite, primarily through changing the carbon content - but of course there is more going on, too.  And it is important to note that the martensite doesn't really temper well until it is re-heated.  So if carbides are precipitated at 1000F, then the steel is cooled to room temp, you should temper again to temper the new martensite.  So in the instance here (straightening the tang), you would want to torch the tang to sub-critical temps, let it cool to room temp, then torch it again.  

 

This is a really good time to point out (to the forum at large) the importance of austenitizing temperature and that it can certainly have an effect on the final microstructure (beyond grain growth issues).  When you have carbide forming elements (besides iron carbide), time and (especially) temperature will have a big role to play in what the chemistry looks like in the steel.  Remember that we are really dealing with metal matrix composites.  The carbides in the matrix can form and dissolve, changing the chemistry of the matrix, as well as changing grain boundary characteristics (e.g. pinning them or not).  

[Aiden CC]

I managed to finally find some time to finish the second knife, so both are done now! My plan was for the person who draws my name to get to pick one of the two, they are certainly very different knives. I’m pretty sure that old chain isn’t wrought, but instead a very low C/Mn mild steel. I’ve found 1018 hardens a bit in water, and this one didn’t seem to at all. Also, very few sparks. Thanks everyone for following along, and I look forward to the drawing!

[Carlos Lara]

I really like the look of this one, wrought or no wrought!