Forge Welding Barrel

[David R. Pennington]

We started our gun barrel welding project yesterday. After looking over the available stock we settled on a wagon tire that wasn't quite as heavy and wide as we wanted. We had one that was wide and heavy but was heavily pitted with rust, so we settled on the narrower tire and welded two sections of it back to back. Any one done it this way? We cut two sections from the tire each 36" long. We straightend them and then forge welded them together. The tires were rounded off a good bit on the edges where they ran on the road and we positioned them with rounded sides together and forge welded together to get a good thick skelp. We then worked down the skelp to thin it out and get more width. Power hammer helped out a lot. We now have a skelp about 3 1/2" by 1/2" by 44" long. I suppose next session we will work on shaping the blank and begin the weld to start the tube. I put handles in some of the tools we might need today,a fuller and couple different sizes of top swages. The material appears to be good wrought iron and welds very nicely. You fellows that have done this, are we going in the right direction?

[whetrock]

David,
I've not yet tried my hand at this. Keep us posted at how it goes. Post pics if you can. Keep notes and share them if you will.
Whet

[Hungry Horse]

What did you use to clean up these old wagon tires? I have seen these around old farms, and thought they were a good source of wrought iron, but as you say, many are very rusty, and would need extensive cleaning.

                   Hungry Horse

[keweenaw]

I have heard from some with good knowledge that most wagon tires are a low grade of wrought iron (wasn't wrought all that many times) that isn't necessarily appropriate for making a barrel.

Tom

[James Wilson Everett]

Guys,

This really sounds like an interesting project, for sure.  I have forge welded several full length barrels from wrought iron, but have never had to weld two sections together to get the proper size skelp, that one is beyond my experience.  My skelps were the approximate width and thickness as above, but were only about 36" long.   When finished the welded barrels were about 44" long.  The forging does elongate the rough barrel quite a bit.

As to using wagon wheel rims, of the dozen or so that I have used, only two were refined enough to make a good barrel, and of the two only one was wide and thick enough.  If the slag streaks are very fine to the point of being difficult to see, then the iron is well refined.  If the slag streaks are larger, then it may not be good to use that material.  Coarse and refined wrought iron have about the same ratio of iron to slag (97% iron to 3% slag) but the refined stuff has the slag as very fine filaments in the iron rather than heavier bands.  Here is a photo of a forged wrought iron barrel, see the tiny slag streaks, not very big - so a nicely refined piece of wrought iron here.



I certainly hope that the barrel forging work will result in a great success and a beautiful barrel.

Jim

[James Wilson Everett]

Guys,

Here is a photo of a gunlock where the lockplate was made from an old barn hinge.  Look at the larger slag streaks in this less refined piece of wrought iron - probably not the quality that would be used for a barrel, but for a lockplate it is OK.


Jim

[TMerkley]

James,

Do you by chance have a comparison photo that would depict the granular structure differences between the two?

Just curious

[James Wilson Everett]

Guys,

Here is a professionally done photo of good wrought iron showing the elongated grain structure and the slag streaks.  The slag is really integral and beneficial to the metal as it provides very good corrosion resistance and a very high resistance to both shock and fatigue failures.  When we break wrought iron, the break shows these fibers, a lot like hickory wood.



Here is another photo showing steel, no fibers here at all.



And just as a comparison, here is cast iron - very brittle and cannot be forged.



Jim

[TMerkley]

Awesome!!!

Thank you!

[Dphariss]

I would have to wonder how inclusions in the iron are beneficial for a gun barrel. They certainly are not in steel.
If this was the case then why did Springfield Armory use "best iron" for rifle musket barrels rather than the inclusion riddled stuff used for wagon tires?
Lots of dug up trade gun barrels show really poor iron and one examined in "Colonial Frontier Guns" had a piece of better iron for about 10" at the breech then poorer iron welded to it for the bulk of the length.

Dan

[keweenaw]

Every time the iron is folded and wrought some percentage of the slag is ejected so not only are the slag stringers getting smaller there is a lower percentage of slag overall.  If you do this enough and there was a high enough percentage of carbon in the starting iron, which would have been high in charcoal smelted iron, you get an unalloyed carbon steel - think Japanese swords.

As for the the slag stringers adding to the ductile nature of the iron you need to remember that straight cast iron is essentially a crystalline structure with scattered inclusions. These show well in the cast iron photomicrograph.  Cracks are easily propagated along the crytalline boundaries where almost every crystal touches another crystal.  Think breaking ice.  In wrought iron the slag stringers break up the continuity of the crytalline boundaries and stop the cracks.  This is just like drilling a hole at the end of a crack in a piece of aluminum or any other metal to keep a crack from spreading.

Tom

[whetrock]

Dan's comment and Snyder's reply. Both very helpful.

I have "0" experience in welding up barrels, so I'm just chatting here... 
Seems to me that the particular issue in this thread isn't just about strength. It's also about 18th C technology.  If a guy needs to weld up a skelp with a hammer, then (as I understand it) the combination of low carbon content and slag in the wrought iron helped that forge welding process go smoothly without burning the skelp. (Am I right? Again, just asking.)

In a different thread Jim E told about about patents for "cast" barrels, in which the barrel maker started with solid (no weld) tube, which he then elongated over a mandril. This (presumably) yielded a stronger barrel. It also allowed the barrel maker to start with material of superior strength, since he did not need to weld it.

Please interpret this as an open ended question, rather than a comment.

[Jim Kibler]

With all due respect, there is quite a bit of misinformation here...

First, about silicate inclusions being beneficial for the performance of skelp welded barrels.  The answer is no.  They may contribute to slightly better corrosion resistance, but that point is minor.  They do not enhance the mechanical properties of a skelp welded barrel.  With all this said, wrought iron of sufficient quality has been thoroughly proven satisfactory for the application.  You must understand a couple of points.  First, silicate inclusions offer little mechanical strength in comparison to the iron matrix.  Since they are long and stretched out, they in some ways mimic a crack.  The second point to consider is how the load is applied to a gun barrel.  A barrel with wrought iron grain, or inclusions, running longitudinally is actually the worst oriention relative to the load a barrel experiences. The stress is such that it is trying to make the barrel bigger, or I beleive what is refered to as a hoop stress.  So the mechanical properties of wrought iron are quite different in different orientions (anisotropy).  This is why one can start a cut and then tear wrough iron along the grain wih a hammer.  Again, if the quantity and size of inclusions is small enough wrought iron will work given a barrel of suficient size.

About the idea of a crystaline structure being prone to cracking.  This is not necessarily the case.  There are many structures with very low inclusion content that are very ductile.  As was mentined, inclusions are generally viewed as a negative attribute in terms of mechanical performance.  Cracks can run along crystaline boundaries, but don't have to.  This is the idea of ductile versus brittle fracture.  An example is low carbon ferritic steel or iron.  This will typically break in a very ductile manner.  Now, to be clear, the inclusions in wrought iron MAY (though I'm not sure about this) slow down crack growth that is perpendicular to their longitudinal axis, but this is not the direction one would encounter a crack in a skelp welded barrel.  A  The primary reason flake iron or gray cast iron is brittle is the lack of mechanical strength of all the free graphite and it's pointy thin nature (much like a crack). The example shown is particuarly bad in that it has a lot of small flakes refered to as spiky graphite as well.  Not a desirable attribute. 

There may be more I've missed, but this is what comes to mind based on what has been said.  This sort of stuff was once a big part of my life, but hasn't been for a while.  Guns are more fun!

[Dphariss]

Every time the iron is folded and wrought some percentage of the slag is ejected so not only are the slag stringers getting smaller there is a lower percentage of slag overall.  If you do this enough and there was a high enough percentage of carbon in the starting iron, which would have been high in charcoal smelted iron, you get an unalloyed carbon steel - think Japanese swords.

As for the the slag stringers adding to the ductile nature of the iron you need to remember that straight cast iron is essentially a crystalline structure with scattered inclusions. These show well in the cast iron photomicrograph.  Cracks are easily propagated along the crytalline boundaries where almost every crystal touches another crystal.  Think breaking ice.  In wrought iron the slag stringers break up the continuity of the crytalline boundaries and stop the cracks.  This is just like drilling a hole at the end of a crack in a piece of aluminum or any other metal to keep a crack from spreading.

Tom

While repeated hammering, hot, is a way to purify iron there is little of this in making a gun barrels  from  wagon tires unless its hammered out, folded and welded again to regain the thickness. All this hammering as done in making the iron for the most part rather than in the making of finished products.
The English used to like horseshoe stubs for gun barrel so long as they were wrought iron. By remelting the stubs with some steel and pounding out the resulting bloom they removed the majority of impurities. This is described in "The Gun" by W. Greener  1831 or so. Which can be found on the WWW for download, after sifting though the "The Gun and It Development" by WW Greener that comes up in all such searches.
Impurities in the damascus barrels caused "greys" and these were frowned upon in the better guns since, if they passed proof, they would show in the final finish of the barrels.


Dan

[whetrock]

I, for one, appreciate the helpful, patient explanations you guys have just posted.

So, ... does the slag actually have any benefit at all in regard to the forge welding process, or is it just the absence of carbon that we are looking for when trying to find material that takes a good weld???

My point is this:  Even if I find a good skelp that has low slag content, that may or may not imply that it will be weldable.  The thread has already generated some helpful info on slag in relation to strength. I'm hope it will also generate some info on on slag & carbon in relation to welding itself.  Thanks in advance.

[bgf]

I think that unless I did it full-time for a living, I'd take the hand forged barrel all the way through proofing (remotely), rifling, etc. then bore it out and line it. Even a "good" wagon tire was probably not the quality of wrought iron used for barrels -- I don't think I've ever seen slag inclusions on an original barrel.

Dan,
The horseshoe thing is interesting.  My brother was a full-time farrier for a good while (until his back went out beyond continuing), and there was all sorts of lore about the properties of used horse-shoes being "worked" (on the horse) into something better than they were made from.  Now they are just mild steel, so I can't see them improving significantly from wear (perhaps a little hardening), but I wonder if the idea with wrought iron ones was that they were continuously "hammered" while in use.  Of course, it could have just been a plentiful source of wrought iron!

[Canute Rex]

The range of quality of wrought iron was wide. I have seen bridge parts that had coarse grain and wagon parts that were quite fine. The heavy forging of the wagon tires in question might improve the grain structure a bit, but the slag percentage would also have something to do with that.

The main advantage of low carbon is high burning temperature. You can get wrought iron hundreds of degrees hotter than tool steel without damage. The problem that goes with the benefit is that you have to get it hotter to melt the slag inclusions in order to weld it. It does act somewhat as a flux, but I'd recommend using a flux anyway.

If I ever forge welded a barrel out of wrought I'd spiral weld it. Jim Kibler's comments on hoop stress are important to consider. I'd tend to go with bgf and line it as well, but that kind of makes the whole exercise moot.

If 18th century barrel makers could have gotten their mitts on mild steel they would have flung their hats in the air and cheered.

[Old Bob]

I think that unless I did it full-time for a living, I'd take the hand forged barrel all the way through proofing (remotely), rifling, etc. then bore it out and line it. Even a "good" wagon tire was probably not the quality of wrought iron used for barrels -- I don't think I've ever seen slag inclusions on an original barrel.

Dan,
The horseshoe thing is interesting.  My brother was a full-time farrier for a good while (until his back went out beyond continuing), and there was all sorts of lore about the properties of used horse-shoes being "worked" (on the horse) into something better than they were made from.  Now they are just mild steel, so I can't see them improving significantly from wear (perhaps a little hardening), but I wonder if the idea with wrought iron ones was that they were continuously "hammered" while in use.  Of course, it could have just been a plentiful source of wrought iron!

Many rifles made by Cook & Brother during the Civil War have noticeable slag inclusion in them. It was said that due to a lack of good iron during some of the production they resorted to inferior iron. Supposedly, to make the barrels stronger they twisted them to lay the inclusions in a spiral around the axis of the barrel. I don't know whether that had any positive effect or not, but it's obvious in pictures.

I have a bit of wrought here but so far I've not found any good "Norway Iron" in the bunch. Some of it's so bad you can't even forge a point on a bar without it brooming out. I did turn one sample from a piece and it looked promising, but it's not big enough for a barrel.

[David R. Pennington]

This may well be an exercise in futility but it sure is fun. If we end up with a shootable barrel it will be great, but if not,  at least we will have deepened our respect for the early craftsmen while honing our forge welding skills and enjoying some great fellowship in the smokey ole blacksmiths shop! We had several old wagon tires to choose from. The one that was closest to the right size we rejected because it appeared to be of a low grade and showed signs thereof. The one we chose appears to be of a better grade iron and the two pieces have welded together beautifully. If we get to that point of course we will proof the barrel well before it is ever stocked.

[David R. Pennington]

Sorry I missed addressing a question or two. Hungry horse, we just hit them a little with a grinder. They only had a small amount of surface rust. James, there were no visible inclusions in these tires and we had to look hard to find the original forgeweld on them. I'm no expert on wagons but due to their uniform shape I would say they were factory made. After welding the two pieces up I can only see one small separation streak on one edge.

[doug]

     the barrel below is signed by John Moll and has conspicuous grain or streaks in it.  When I bought the gun, the barrel looked like it had been used for a hammer (many times).  I draw filed it and rerusted it and to my surprise the pattern came out.  I think that my point in part is that we often do not see the pattern in wrought iron barrels because over time, patina obscures it.  Often it is only when badly abused barrels are resurrected and refinished, that the pattern becomes apparent.  By comparison with the coarse conspicuous grain of this barrel, I had a Enfield percussion pistol barrel in which the grain was so fine it could hardly be seen.   A similar example of something which is not often apparent would be the barrel of an 1842 which allegedly was refinished and apparently then left in a damp garage where it became quite rusted and shallow pits.  In cleaning that one up and re rusting it, it turned out to have a longitudinal forge weld seam down the bottom of the barrel.  Both because of patina and location that is a feature that would not be apparent on most guns

cheers Doug

[Dphariss]

The horseshoe stubs should have read horseshoe NAIL stubs.
Gotta proof read better. What I get for drive by posting.....

Dan

[Hungry Horse]

 I own a small all metal Deringer type pocket pistol, that has a smooth bore barrel. It has what is either, the welding seam, or the grain of the wrought iron on the bottom of the barrel.

                          Hungry Horse

[Canute Rex]

Horseshoe *nail* stubs makes total sense. A small diameter product like that would have to be made out of the finest grain wrought iron.