Brazed composite steel blades

52 Ford

52 Ford

Well-Known Member
I was looking at a Kershaw knife with a "composite" blade. 2 types of steels joined with a copper braze joint.

I was looking at the melting temp of copper and it's plenty high enough to be able to braze a blade, then do all of your heat treating. Phosphor bronze has a fairly high melting temp, too. That'd be a little stronger than pure copper braze.

The first thing that comes to my mind would be to mill a slot in the "spine" material and have a piece of the "edge" material that slots into it with maybe 10 thou clearance on the sides, shim it to get it even, then braze it up with either pure copper or phosphor bronze wire (both easy to get online).

After that, you could either forge it a little to give some sort of pattern to the braze joint, or just go straight to stock removal.

Then heat-treat as normal.


Am I missing something or do you think that'd work?
 
This method could also work for adding a carbide edge and it'd be fairly easy to replace it if it gets chipped. I'd leave the spine fairly soft in the case of a carbide edge though.
 
Well, this knife isn’t quite topical but it’s the closest any thread has ever been to it, so here’s an odd composite knife. I bought it off an itinerant welder who was here for a year welding at the local nuke. The blade body is non-HTd 440c. The tang is a 303 rod and guard is welded on and matches 303 butt cap. The cool part is that he cut the edge out and then used stellite rod to hard face the edge onto the body. The photo sucks but it’s the best i can do for now. What looks like a hamon is the stellite line. I believe the fellow’s name was Stan Freiberg and he was from the Houston area. He’d easily be in his 70s now. Anyway, my composite knife story.

8A4BB9A6-8B05-4EDC-8D44-83CD0F23E5BB.jpeg
 
There is a knife company or two that does carbide or similar edges that are soldered on. I reckon it does work.
 
fitzo said:
Well, this knife isn’t quite topical but it’s the closest any thread has ever been to it, so here’s an odd composite knife. I bought it off an itinerant welder who was here for a year welding at the local nuke. The blade body is non-HTd 440c. The tang is a 303 rod and guard is welded on and matches 303 butt cap. The cool part is that he cut the edge out and then used stellite rod to hard face the edge onto the body. The photo sucks but it’s the best i can do for now. What looks like a hamon is the stellite line. I believe the fellow’s name was Stan Freiberg and he was from the Houston area. He’d easily be in his 70s now. Anyway, my composite knife story.

View attachment 80450
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That's cool.
 
Stellite is the same stuff they put on the end of hardnose (as opposed to sprocket nose) chainsaw bars. That stuff is TOUGH.

I think a HSS or carbide cutting edge with a Damascus body would look awesome. Especially with the line of copper braze. You could play off that with a copper guard, bolsters, pins, and a dark handle material.
 
I've been following thread, but haven had a chance to comment, and glad I didn't. I had no idea what the "composite blade" was. I'd looked a bit at the kersaw knives but thought it was simply San Mai. Nope, not at all. Watching the video
makes me think it's all about marketing.
 
It l
J. Doyle said:
What is the advantage to this? Why would one want to do this or want to own this? I'm genuinely curious
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On this scale - as in folders knives and smallish fixed blades - it's just for looks. Just like Damascus (don't try and tell me Damascus is for anything but looks - LOL)

On a bigger scale, you could make a blade that performs sorta like a bi-metal hacksaw blade. Flexible spine and a hard edge, especially so if you use carbide for the edge.
 
52 Ford said:
It l

On this scale - as in folders knives and smallish fixed blades - it's just for looks. Just like Damascus (don't try and tell me Damascus is for anything but looks - LOL)

On a bigger scale, you could make a blade that performs sorta like a bi-metal hacksaw blade. Flexible spine and a hard edge, especially so if you use carbide for the edge.
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I could be wrong but I bet a soft copper or brass layer in the blade matrix is more detrimental than two steels that both weld and harden the same and have matching thermal properties.

Properly made Damascus is no worse than either of the parent materials. Likewise it's no better than it's parent materials either.

But add soft non ferrous metals in the mix? I bet it's inferior to pattern welded steel. Probably totally fine in a small light use blade as you suggest.

Personally, I'll pass.
 
Shouldn't be an issue. Not saying it's better than pattern welding, but phosphor bronze (and nickel-silver, for that matter) have plenty of tensile strength. Especially with those patterns that Kershaw introduces. It adds a lot of surface area to the braze joint.

Something like 60Ksi tensile strength. So the same as a 6010 welding electrode.

They have less wear resistance, since they're softer, but if you take a look brazed carbide lathe tooling for example, it holds up fine, since the braze joint is just there to hold it to the shank. Obviously they braze that with silver solder, not phosphor bronze, but still. Roughly the same tensile strength.

I'll try and get around to making one and I'll post it to The Forum.
 
When you do make one be sure to take plenty of photos and do a write. I'd LOVE to read it, or follow a WIP.
 
Can do. Not sure what I'd do... maybe Damascus (which I'm admittedly not good at) for the body and HSS for the edge? I bet that could end up looking awesome. Especially with the copper for contrast.

Another interesting combo to try would be an aluminum body and a steel edge. I know I can braze aluminum to steel. I'm not sure how well copper would work as the brazing filler. It SHOULD work, since copper sticks to steel and I know that you can alloy copper with aluminum.

I think for the aluminum/steel combo, I'd heat treat the steel as usual, then maybe shot peen the aluminum.

It could make for a SUPER light weight knife.
 
Be sure you check the melting temp of aluminum. The HT temp for most of the high carbon steels is around 1500F or so and aluminum melts below 1300F. Copper is better around 1900F. That's why you can make Go Mai with a copper layer. Rather than the normal "welding" of outer layer of steel to inner steel core, the copper layer provides more of a "brazing" effect to hold the layers together.
 
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