Project 2 from DaveO: Firecracker Welding

[DaveO]

Years ago I recall my Dad telling a story about Japanese shipbuilders using a tripod SMAW setup, where one leg of the tripod is the electrode, to weld steel plates together. According to the story this allowed an untrained worker to perform the task. My recollection of the story is the worker struck an arc and gravity fed the electrode into the arc. I seem to recall that one of the details of the story is that late in WWII Japan was running low on trained workers, and this was the only way to maintain production. This has been one of those "Dad" stories that has stayed with me, so I decided to look into it further and try it myself.

Turns out that story is only partially true: firecracker welding does exist, of course, and was tested for use in the shipbuilding industry. However it was developed in the 1960's, not in WWII, so either my Dad was way off or my recollection of his story is way off. The tripod part of the story is wrong, for instance.

In researching the story, I found a paper published by Bethlehem Steel (http://www.dtic.mil/cgi-bin/GetTRDoc...f&AD=ADA451495) for the Naval Surface Warfare Center. The paper cites a number of reasons to implement it: it allows welding in tight spots that are typical to shipbuilding, for instance. The idea was to increase productivity: the paper says a trained operator could get multiple arcs established simultaneously and put down a lot more welds than a typical welder. For this study they also developed special tapes to hold the electrode in place, and developed long electrodes: 28 inches long and even 72 inches long (yup, 6 feet!). Bethlehem Steel performed methodical tests for different weld types and many electrode types: 7024 worked the best for them.

In my attempt I decided on a 7018 rod (for its drag capabilities) on a horizontal butt weld of 3/32 mild steel. Photo 1 shows the butt weld. Photo 2 shows the setup: this is a dry run I set up while the 7018s baked. The Beth Steel paper doesn't divulge the mechanics of starting the weld, and I felt that turning on the welder and leaping from "off" to "full welding" would not be good for something somewhere. So I decided to forego the securing tape suggested by Beth Steel and drop the electrode onto the plate. The Beth Steel paper did mention they used steel wool to help initiate an arc- photo 3 shows my intended drop setup with a little wisp of steel wool on the end of the electrode.


NONE of those ideas worked. I started out at about 75 amps, got no results, and cranked the heat up to about 100 amps thinking it would help start the arc. The drop technique was useless, with or without steel wool. Finally I wound up picking up the striker, starting the arc as in normal welding, and then setting the striker down and holding it still. This actually worked! But the heat was too high and the weld completely burned through (photo 4)- I didn't realize it until the rod had burned to the end of the steel. I flipped the steel around so I could start from the other direction and turned amps down to about 75. This resulted in a tolerable weld, for maybe an inch or so. Photo 5 shows the results of two different successes. I tried to hold the striker still but it waved around- probably why Beth Steel used tape. Photo 6 shows the opposite side of the weld.


I wish I could have experimented more, but I was running out of play time and my wife was already torqued that I used a kitchen appliance to recondition the electrodes. Firecracker welding is a dead science these days, replaced by processes that are actually automated. But here's to you, Dad-