forging multiple pieces of "rod"

S

scherar

Well-Known Member
Hi,

I am new to the forging part of knife making, but I have a source for some carbon steel (round) bands out of concrete pipe. Is there a way to get pieces of these 'bands' and forge them together? They are about 1/4" to 5/16" in diameter. I have some experience making pattern welded steel, so I was wondering if you could fit them closely together and possibly put some sort of nickel content rods with it and make some sort of Damascus?? I know inclusions are always a concern, so I didn't know if the small gaps when putting the rounds together would pose a problem? Any Ideas??

Thanks
 
I'm not a pattern welding making at all, but I'd think the biggest concern would be what steel do you have? Is it a mild steel? Something like rebar? OR - is it actually a good steel? I guess you could hammer a piece to a knife shape, then HT and see how it works. Grain size, how hard, etc and go from there.

Ken H>
 
It should be some sort of high carbon stuff. It is used in pre-stressed 66" concrete water pipe made in the 1960's. when you cut these bands in the concrete, it blows apart. When we've been cutting them with the angle grinder, they put off showering sparks. I'm assuming they are at a spring temper now. I don't know how many varieties of steel there were in the 60's, so that might narrow it down some.
 
At best it's a crapshoot as to what they are made of. The reason the concrete "blows apart" is due to the tension created as the concrete cured and shrank slightly....where as the rods did not.

As far a welding them together, it certainly can be done. The cleaner they are the better before starting. Were it me, I would stack as many as I could handle together....MIG weld one end, then heat and start twisting. Once I got the "bundle" as tightly twisted as possible, I'd then start welding in sections, overlapping until everthing was solid. The reason for twisting everything to together is two fold......first and foremost it keeps the rods from "slipping" past each other when you're trying to weld them......secondly, it may not seem like it. but in a straight bundle of round rods, there is a huge amount of air space that must be eliminated through forging. Personally, I wouldn't put nickel into something like this.....just too many unknown factors....and with nickel being so expensive, it could be a very costly mistake if thing fail. (I'm talking about pure nickle).
 
Here's something relative to your steel, a few years back, Florida power has a nuclear power plant and the reactor walls had a few cracks. instead of having a company that works on reactors repair it they took it upon themselves to do it. they were supposed to put tension bands around the reactor before they cut into it, apparently they screwed that up because when they cut into it, { the reinforcing steel } the reactor cracked all over from expanding, destroying the thing. that reactor has been permanatly shut down now, with millions in fines and going back to coal burners, raising electric prices, and losing jobs. that place is a bad topic in Fl. Anyways, I never heard exactly what the composition of that steel was but I imagine it's a pretty strong alloy of some type.
 
I was thinking they used a cable in pre-stressed concrete? Pull the cables really really tight, then pour concrete in form and let dry? I just read a bit and find there is both "pre-stressed" and "post-stressed" concrete. I remember seeing beams brought to construction site with a big bow in beam due to the pre-stressing of cables/concrete. Pre-stressed concrete is much different than ferrocement used in boat construction.

The bars used were described in one article as "rebar" - that is hard stuff, but not good knife making material.

Ken H>
 
These are definitely rings of solid steel, about 1/4" in diameter.

So I did an experiment tonight with a piece of a ring. I ground two sides flat & tested on the Rockwell tester and got about 42-43Rc. I then heat treated a piece @ 1500 for ten minutes and quenched in an 11 sec oil. Rockwell was 66. I broke a piece and it looks light grey and fine grained(without a microscope). So, definitely a hardenable steel.

Ed, if you stack the pieces & tack weld them, would you have to use flux when twisting them & then forging them into a knife shape?
 
Yes, you'd need to use flux of some variety. You might need more or less depending on how clean the rods are when you forge them......Make sure you remove any/all concrete from the rods.
 
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