Nothing quite like breaking something and knowing it ought to be replaced, but it’s almost dark. A new part would probably have to be ordered in. The closest hope for a new part is two hours away. Plus, it’s Saturday evening. The cattle haven’t been fed, and the broken part needs fixed or replaced before the feed truck will feed the heifers.
In this situation, there is no “take it to town option.” I would venture that there are more people in the production end of agriculture that know how to do some welding than those who do not.
I would define welding as applying enough controlled heat to two pieces of metal so that the melted metal flows together to make one piece. Most of the time, additional material is added to the mix.
I’ll start by talking about stick welding iron and steel. Aluminum, titanium and stainless steel may be welded, but it’s not the same as welding iron or steel.
I asked a friend, who has had his own manufacturing and repair business in a rural area for about half a century, what he saw as the cause of failed welds brought to his shop to be welded “right.” He said it was usually lack of penetration or the weld material being contaminated with air pockets, slag or other debris, like oil and paint.
Penetration
This means making a repair that is 100% weld. It is possible to weld with enough heat to melt completely through the broken pieces, leaving no part cratered or still fractured. Heavier parts should be shaped, usually with a hand grinder, so that the weld will melt through to the backside of both pieces. Often this requires two or more passes to fill the void.
Contamination
The area to be welded should be cleaned of any oil, grease, dirt, paint or galvanization (or other coatings) before being welded.
Some will state that a good hot rod (electrode) will burn off the above contaminants. Yes and no. When a weld is finished, the “new” metal that is "created” by the electrode as you weld is now an alloy (mix) of the two pieces being welded together, and the rod, and any contaminants or coatings that remain, visible or not.
Air pockets
The shielding gas will prevent oxidation of the weld area. Welding in the wind can blow the shielding gas away from the weld and allow oxygenation of the weld, usually showing up as air pockets. Oil in the weld area will also cause air pockets.
What material are you welding? What rod should you use?
All steel is not the same. Almost all truck frames have stickers that say, “Do not drill or weld to frame rails.” You will notice that said truck frames have been drilled and welded as they were made. The manufacturer knows exactly what quality of steel that frame is made of and will match it with welding materials of the same strength.
Mild steel is the most common. A 6011 electrode should be adequate for mild steel. T-1 is a common high-strength steel. A 7018 rod is preferred here. (Note: The “60” and “70” refer to the tensile strength of a properly made weld.)
Welding mild steel to T-1 steel works, but the higher-strength rod should be used. A 7018 rod will alloy nicely with T-1 and also with mild steel. A lower-strength rod would not properly alloy with the higher-strength steel and would result in a weak weld.
6013 is the other popular welding electrode. Often called the “farmer’s rod,” this can be easier to run than a 6011, but it is much more difficult to achieve proper penetration with it. To simplify, the 6013 would be prone to lie down on top of the parent metals (the two pieces being welded together), while the 6011 and 7018 will burn into the parent metals easier.
Note that if your stick welding machine is AC only, you need a 7018 rod that states it is suitable for AC machines. (The lettering on each rod should be E7018 AC.) 6011 works best with AC current (running it on DC results in excessive spattering).
The heat setting should be hot enough for adequate penetration and low enough that you’re not spending all day filling holes burned through your work. Get the rod size, type and heat set by trying it on scrap metal so when your critical repair is first touched by your “sparks,” they are the right sparks.
Back to the feed truck breakdown. It was a 1-inch shaft that broke with a spiral break and, of course, inside a bearing.
The shaft was removed from the feed truck and taken to the farm shop. An angle grinder was used to open the areas of the broken shaft wide enough to reach for penetration with a 1/8-inch 7018 rod. The spiral break was about 3 inches long, diagonal to the shaft. This left about 1/8-inch of broken material toward the center of the break untouched by the grinder. Clamped together in the original position, it was welded with heavy tacks on one side, then the other.
This was followed by heavy penetration beads, alternating sides. After each pass, the area was chipped or wire brushed to remove the slag. Alternating sides, one pass at a time, the shaft was built up to at least its original diameter. Then came the tedious part of using the angle grinder to reduce the repaired area so the bearing and its keeper would fit more or less snugly on the shaft.
Reassembled, it worked with only minimal wobbling. The owners declined to spring for a new part.
