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Han dynasty bronze ring hilted dao


Jeroen Zuiderwijk

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5 hours ago, Kevin Colwell said:

I have made so many handles and scabbards out of rosewood, I am allergic to it now. I only use it for my good friends. Everyone else gets maple that gets died!

I have no idea about wood on the really old ones, but I think wrapped handles were standard. Textile/cord wraps, not wood at all, was common in the earliest iron swords. I presume it would have been in the bronze. You probably already knew that, though :).

kc

When looking at jians from the Warring States onwards, cord over wood seems to be the norm. Bronze daos seem to be different with the wrapping directly on the tang. It may be that the textile was placed under the wood (as shown on the iron example above), to provide more friction between the wood and tang. The pommel doesn't keep the wood in place, so either the wood has to be glued or enough friction should be achieved to keep it in place. Not using glue means the hilt can be quickly disassembled and maintenance performed, and put back together. That's my guess at the moment. I'll probably just glue the wood directly onto the tang though. 

 

I'm not tempted to use rosewood, considering the terrible health problems I've had with toxic wood before (yew).

Jeroen Zuiderwijk

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I thought you probably already knew more than I could contribute :).

Thanks for teaching me and the rest of us this bit.

I don't know anything directly about the bronze swords. But, I am happy to be along for the ride.

 

I haven't used yew, but thanks for the warning about it. 

 

I have decided to just use soft or hard maple and dye it for a lot, depending upon how hard the wood needs to be. It can be beautiful, and I don't have to deal with the other problems. 

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“Years ago I recognized my kinship with all living things, and I made up my mind that I was not one bit better than the meanest on the earth. I said then and I say now, that while there is a lower class, I am in it; while there is a criminal element, I am of it; while there is a soul in prison, I am not free.” E. V. Debs

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I've found a piece of peach wood in my stock that was given to me years ago by (sorry, can't remember who that was). Apparently peach is native to China, so I'll see if I can use that for the hilt. It's got drying cracks, so I have to see if I can salvage large enough pieces that are crack free. I've also ordered some madder dyed silk yarn to be used for the cord. 

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Jeroen Zuiderwijk

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On 5/14/2023 at 5:44 PM, Kevin Colwell said:

You probably already knew that, though :).

Still good info for those of us who didn't know.

 

The only times I have made a wood scabbard, I have used Basswood. It is lightweight and strong, with a very dense grain. So dense that it wouldn't stain easily with commercial stains. I have to add the dye to a cellulose lacquer and use that to seal and color the wood.

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Yesterday I heat treated the blade. Heat treating this type of bronze is quite the reverse of what you'd expect with steel. 20% tin bronze is hard and brittle if cooled slowly, but becomes very tough without loosing much of its hardness if quenched from above 600. I'm enough out of the loop to know what the different phases mean, but this is the (rather complex) phase diagram of tin bronze just for info:

 

Binary phase diagram of copper-tin under non-equilibrium ...

With regular tin bronze (at around 10%), there isn't much difference between cooling fast or slow. There is a small increase in the amount of cold working you can do if quenching after annealing. But at 20% tin, the difference is very notable. 

 

I don't actually know the alloy used in these Han Dynasty bronze daos. But 20% tin bronze was often used in earlier Chinese swords. They did some interesting things with bronze in China: some swords were bimetallic, with a high tin bronze edge cast around a lower tin bronze core. Another thing that was done was infusing tin into the surface, so the edge and surface layer were very hard, but under the surface the blade had a lower tin content. The bronze jians of the Terracotta army are also 20% tin bronze. Whether these were actual weapons, or bronze representations of steel weapons to be included in the burial is a matter of debate. Officially it seems to be the conclusion that these were the latter, as it's said that they were not quenched so extremely brittle and non functional. But I've seen one of the swords with a bend tang, which would be impossible if it had not been quenched. 

 

I remember I first started experimenting with 20% tin bronze (also known as bell bronze), I found that it was extremely brittle. But I also found out that cymbals are made from it, and they are cold hammered from sheet metal. So I wondered how that was possible. Apparently, by quenching from red hot, that brittleness is removed. As I cast this blade 15 years ago, I don't remember if I had already done this. Just to be on the safe side, I heated it up and quenched it yesterday. I was questioning I would do this and risk the blade at this stage, but eh, got to live on the edge a bit sometimes :) 

 

I don't have a heat treating facility, certainly not for blades of this size, so I cobbled something together from what I could find in the shed, with the aim I can take it apart again to have as little waste as possible. Well, this seems to have worked :)

 350447056_625385046320119_2575972727419820277_n.jpg

Still straight:

350540007_147688504967557_3823319803172540555_n.jpg

I had to guess the temperature. As I was working in broad daylight, I had to consider that it would look much colder at the required temperature. So no visible glow could already be hot enough. I also didn't want to get it too hot, as it will be quite soft and bend under gravity. Above 800C, and it will fall into pieces. After some time in the glowing coals, I saw the oxidation colors dancing on the blade, which happens when it's just starting to glow and evenly across the entire length. I carefully picked it up at the center of gravity with the tongs and quenched in water. I hope this was sufficient. I'm not going to test the blade, so I probably will never know if it worked as well as I hope it did. But in theory it should have worked based on earlier experience. 

 

Since I had some glowing charcoal left, I used that up in a little bit of forging. 

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Jeroen Zuiderwijk

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I always perk up when I see phase diagrams.  So good.  

 

I would bet Jeroen already knows this, but for those that don't I thought I would add a little context to the phase diagram he posted and what is going on.  Keep in mind my specialty is ferrous metallurgy, so we are definitely on the edge of things I know.  Fortunately I have good resources and my base knowledge is such that if there are further questions I can probably dig a little bit and get answers if anyone has any.  Fun fact: my quick go-to reference book (copyright 1993) uses a Cu-Sn phase diagram from 1948 that is different from the one Jeroen posted.  While they look similar at a glance, there are definite differences, especially around the vertical section around the 38% Sn region.  I am sure the one Jeroen has posted is more accurate.  

 

As with any binary (2-element) phase diagram, the amount of each phase present can be determined with the lever rule.  Since Jeroen talks about the differences between 10% Sn and 20% Sn, we'll go with those 2 compositions for the examples.  In the 586C to 799C range we see that we have alpha and beta phases present.  Without measuring too closely, it looks to me like at 586C 10% Sn is about 15% of the way between the alpha and beta zones, and 20% Sn is about 75% away.  Therefore at 586C an alloy with 10%Sn would be 85% alpha phase and 15% beta phase.  Likewise, the 20% Sn would be 25% alpha and 75 beta.  As we heat up to 798C we see that the beta section gets more prominent, to the point that 20% Sn is about 90% beta.  Both alpha and beta phases are solid solutions of Cu and Sn.  I'm pretty sure the nomenclature for bronze follows that of brass, and therefore the alpha phase is FCC and the beta phase is BCC.  We can also see that the alpha phase is present from solidification all the way down, though the proportions do change.  Phases will generally form as indicated in the phase diagram, but when a sample is quenched, that can alter how things go (just like with steel).  Bronzes can harden in a few ways, but I am pretty sure the pure Cu-Sn alloys we are looking at here really only precipitation harden.  This is why quenching is so effective, nothing has a chance to precipitate out to harden it.  

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Great stuff!  I wonder what the people passing by out on the street thought, if they even noticed.  Some guy heat-treating a bronze sword, not your everyday sight. :lol: In cities around here, if you smell charcoal you follow your nose in anticipation of good grilled food. I guess in your town you find a homemade forge and quench trough? 

 

Am I correct in thinking that most European bronze tools were in the 10% tin range, sometimes with a little arsenic to make it harder?  

 

Thanks for the phase diagram as well.  That makes sense.  I know most nonferrous metals are quenched to anneal, I just never thought much about the phase changes behind that idea OR precipitation hardening.  I have age-hardened sterling silver by holding it at 500F, though.  Only because a jewelry handbook told me that would work, no idea of the science behind it.  

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1 hour ago, Jerrod Miller said:

I always perk up when I see phase diagrams.  So good.  

 

I would bet Jeroen already knows this, but for those that don't I thought I would add a little context to the phase diagram he posted and what is going on.  Keep in mind my specialty is ferrous metallurgy, so we are definitely on the edge of things I know.  Fortunately I have good resources and my base knowledge is such that if there are further questions I can probably dig a little bit and get answers if anyone has any.  Fun fact: my quick go-to reference book (copyright 1993) uses a Cu-Sn phase diagram from 1948 that is different from the one Jeroen posted.  While they look similar at a glance, there are definite differences, especially around the vertical section around the 38% Sn region.  I am sure the one Jeroen has posted is more accurate.  

 

As with any binary (2-element) phase diagram, the amount of each phase present can be determined with the lever rule.  Since Jeroen talks about the differences between 10% Sn and 20% Sn, we'll go with those 2 compositions for the examples.  In the 586C to 799C range we see that we have alpha and beta phases present.  Without measuring too closely, it looks to me like at 586C 10% Sn is about 15% of the way between the alpha and beta zones, and 20% Sn is about 75% away.  Therefore at 586C an alloy with 10%Sn would be 85% alpha phase and 15% beta phase.  Likewise, the 20% Sn would be 25% alpha and 75 beta.  As we heat up to 798C we see that the beta section gets more prominent, to the point that 20% Sn is about 90% beta.  Both alpha and beta phases are solid solutions of Cu and Sn.  I'm pretty sure the nomenclature for bronze follows that of brass, and therefore the alpha phase is FCC and the beta phase is BCC.  We can also see that the alpha phase is present from solidification all the way down, though the proportions do change.  Phases will generally form as indicated in the phase diagram, but when a sample is quenched, that can alter how things go (just like with steel).  Bronzes can harden in a few ways, but I am pretty sure the pure Cu-Sn alloys we are looking at here really only precipitation harden.  This is why quenching is so effective, nothing has a chance to precipitate out to harden it.  

I really appreciate that information, thanks! I really should make time to delve into this subject more (or again, since I had it at university nearly 30 years ago).

Jeroen Zuiderwijk

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1 hour ago, Alan Longmire said:

Great stuff!  I wonder what the people passing by out on the street thought, if they even noticed.  Some guy heat-treating a bronze sword, not your everyday sight. :lol: In cities around here, if you smell charcoal you follow your nose in anticipation of good grilled food. I guess in your town you find a homemade forge and quench trough? 

Well, you can find both actually, since my neighbour often has the BBQ on :) But yeah, whenever f.e. a postman walks by, it often gets a lot of interest, and occasionally even pictures taken :)

 

1 hour ago, Alan Longmire said:

Am I correct in thinking that most European bronze tools were in the 10% tin range, sometimes with a little arsenic to make it harder?  

On average 10% tin (but can vary quite a bit), and with later bronzes also a some lead. But lead IMO doesn't improve anything, which is also why lead content was lower in swords. Arsenic and antimony were mainly included in the early coppers/bronzes, when there was little or no tin around. It's said that arsenic wasn't added, but arsenic containing ores were used to produce the arsenic bronzes.

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Jeroen Zuiderwijk

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Still need to do the final polishing, but the blade is looking better and better. I'm going to cast the scabbard mouthpiece and slide some time in the future. I'll have to start making models/moulds for those. The mouthpiece will be a tricky cast, as they seem to be of very thin metal. I may do it in a soapstone mould, by which I can make the thinnest casts from my experience.

P1330075.JPG

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Jeroen Zuiderwijk

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  • 2 weeks later...

oh man, that is lovely.

Thanks for the diagram, too. This is just great.

 

please visit my website http://www.professorsforge.com/

 

“Years ago I recognized my kinship with all living things, and I made up my mind that I was not one bit better than the meanest on the earth. I said then and I say now, that while there is a lower class, I am in it; while there is a criminal element, I am of it; while there is a soul in prison, I am not free.” E. V. Debs

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