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by Curtis Von Fange
Part One of this series can be found here
We are still dealing with arc welding on our broken bushog in this series. Our welder of choice for this project will be an AC arc welder since it seems to be relatively common on farm sites and will also give us the heat we need for a good penetrating weld. We've also amassed our protective gear and decided on our location for work. The onlookers have been chased away for their own protection. So what else do we need to know before we start welding?
I suppose we should probably take a look at the electrodes, or welding rods, and see what they are all about. The welding rod is where the action takes place. This is where the heat is concentrated, the puddle of metal is manipulated, and the repairing weld is created. Professional welders consider many factors when picking out a rod for a job. The types of material being welded play a large part in this choosing process. Is the metal a mild, low alloy, or nickel steel? Does it have other melted components like chromium, manganese, or vanadium in it? Is it aluminum, copper mix bronze or lead? There are almost too many types of metals to choose from, each using a different rod to ensure proper metal bonding. So for our bushog repair we'll just settle for a mild steel type of rod.
Next we have to have a basic understanding of what all those gazillion numbers imprinted on the rod mean. Most rods that one runs across at the farm supply store will be labeled something like this: E 6011 or, perhaps, E 7020. The 'E' means that it is an electrode suitable for arc welding. The following two numbers indicate the tensile strength of the material in the rod when the weld is stress relieved. '60' stands for 60,000 psi, '70' for 70,000 psi, etc. The next number, a one, two, or three, indicate the position of the joint the electrode is designed to weld. For example, an electrode numbered XX1X will weld in all positions. A XX2X will weld butt and fillet joints in the flat or horizontal position. XX3X is recommended for flat position welds only. The last number is an indicator of the power supply, type of covering, type of arc penetration and presence of iron powder. Once again, since thoroughly understanding all these numbers, metal types, and flux compounds won't get our bushog repaired we'll simply settle for some general guidelines.
Now that we've selected our welder, our safety equipment, and rod lets get an idea of the current level to use. The thickness of the metal to be welded and the diameter of the corresponding rod will pretty much determine the amperage setting. Pick out a rod that is about the same size as the metal. An 1/8 inch rod will have a setting between 30 and 80 amps. The higher the setting the more heat generated; consequently, the weld will have to be faster or the metal will burn out; there may also be more splatter to contend with. The lower the setting the more sluggish the arc will be, there will be poorer weld penetration, and the arc may flame out more often. Experimenting on a piece of scrap metal will help determine the setting you are most comfortable with. If you are using a 3/16 inch rod the settings can be between 100 amps and 200 amps. Again, it is determined by the welders skill and comfort in performing his work.
Metal preparation is the key to making a good weld. The surfaces must be clean of rust, dirt, grease and grime. Grabbing that wire brush and scrubbing away like brushing your teeth will go a long way to cleaning the area to be worked on. If there is a stress crack which is being welded take a hand grinder and grind a 'V' the length of the crack in order for the weld to penetrate both sides of the break. After each pass chip off the slag and debris and wire brush the area before another weld is made. Cracked areas hiding under splatter, rusty metal flakes and/or layered metallic garbage should have the debris ground off so the weld will be made against the parent metal or the most basic of structure. If there are multi levels of paint on the piece then take a grinder and work out the paint so the arc will strike easier and so the weld will have better integrity.
One last note, when the final weld has been cooled and the slag and debris cleaned off of it inspect it carefully to make sure it did what you wanted it to. Look for undercutting of the parent metal as this can form a weak spot in the repair. Make sure you followed the crack and didn't wander off to the side in the excitement of keeping a good arc and metallic bead. Check to make sure there is ample bead on the repair and that any repair plates have good penetration on their edges. Finally drop a good coat of primer and paint on the repair to protect the bare metal from the elements. Welded repairs seem to rust quicker than any other type of exposed metallic areas. Besides a good coat of paint will look good and make the repair look complete.