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In Search of Better Welds

October 3, 2008
By: Sara Schafer, Farm Journal Media Business and Crops Editor
 
 
Welding technology has advanced since the 1930s, when stick (electrode) welders, using AC power sources, began making their way to farm country. Today there are other options, such as TIG and wire welding, but stick welders remain the go-to form of welding to tackle farm tasks. Here are several tips from experts to help you use your stick welder more effectively.

What Electrode Numbers Mean
A numbering system—for example, E6011—established by the American Welding Society identifies electrodes, explains Mike Crawford, Hobart Brothers stick electrode product manager. The numbers are printed on the side of each electrode. The "E" at the beginning of the numbers simply means "electrode."

The first two numbers indicate the minimum tensile strength, in thousands of pounds per square inch (psi), that the rod will produce. For example, the E6011 rod has a tensile strength of 60,000 psi.

If the third digit is 1, the electrode is designed for use in all positions. If it's 2, the rod is designed for flat and horizontal welding. A 3 means the rod is for flat welding.

The fourth digit represents the coating type and the type of welding current (AC, DC or both) that can be used with the electrode.

Don't spend too much time trying to memorize the system. As the adjacent story explains, you probably only need two to four different electrodes for farm repairs.



AC or DC?

If you inherited your stick welder from your father, chances are it uses AC power. Once, that was the only kind of stick welder available.

You certainly can stick weld with AC power. "Some guys I grew up with are very good with an AC welder,” says John Leisner, product manager for Miller Electric Manufacturing Company. "But it took them a lot of welding rod to get to that point, as well as a lot of frustration.”

Today, AC/DC welders cost a bit more but provide substantial benefits compared with AC-only machines. So, if high commodity prices have left you with a few extra dollars to spend on shop equipment, buying an AC/DC welder might be a good place to upgrade.

As a ballpark figure, Leisner says, you can buy an entry-level stick welder with AC and DC power for $600, about $200 more than a straight AC version. "If you opt for a welder/generator, most of them come with AC and DC,” Leisner adds.

There are numerous reasons to use DC power, says Cary Urka, who repairs and fabricates equipment for his family's strawberry farm in Brethren, Mich., and teaches welding classes through The Farmer's Workshop. "It makes welding easier, especially for poor fit-ups and out-of-position work. Most electrodes run best on DC-positive, and there's a wider selection of electrodes to use.”

Leisner adds: "The biggest misconception in the industry is that stick welding is difficult. That misconception originated with people who grew up using AC ‘buzz boxes.'”

The reason DC makes welding easier lies in the nature of AC power. AC, of course, stands for alternating current, which means the power is not continuous.

"With standard wall power, the welding current changes direction approximately 120 times per second,” Leisner explains. "Each time it changes direction, the current stops flowing between the electrode and the work piece. This can cause your welding rod to stick to the piece you're working on and the arc to extinguish.

"AC also requires you to hold the tip of the welding rod farther away from the work piece, which makes welding more difficult,” Leisner continues. "If you get too close, the arc can go out when the current changes direction.”

"Many machines in this class have low, open-circuit voltage, which results in poor arc stability,” Urka says.

With direct current, there are fewer arc outages and less sticking, making it easier to weld vertically and overhead and resulting in better-looking welds, Leisner adds. DC reverse polarity (meaning the electrode is positive and the current is traveling from the work piece to the electrode) provides about 10% more penetration at a given amperage, which makes it easier to weld thicker metals. It also does a better job of welding thinner metals.

Stick welding, technically called shielded metal arc welding, is still the most preferred form of welding for most general farm fabrications and repairs.

"AC power may be used with alloys, such as nickel for cast iron repairs,” Urka says. Another use is for welding magnetized metal, says Leisner's colleague, Miller Electric product manager Chris Wierschke.
"A common source of magnetized metal,” Wierschke says, "is old well pipe, sometimes called sucker pipe, which farmers use to fabricate things around the farm. When you weld magnetized pipe with DC power, the pipe sometimes becomes polarized, resulting in ‘arc blow'—the molten metal in the joint tends to gravitate to one side of the welded joint.

"Arc blow doesn't make welding impossible, but it does make it more difficult,” Wierschke says. "There are several ways to deal with it, but switching to AC power is the easiest because it eliminates the problem.”
If you ever need to use a thicker rod to weld thin material, AC power makes the job easier without causing warping, burn-through or other problems, Wierschke adds. That's because, with half the cycle being positive and half negative, the weld puddle has a chance to cool, resulting in less heat to the work piece. (Another option is to use a 6013 rod, which performs better on thin metal, Wierschke says.)
Some welding rods are AC-only and others are DC-only, Leisner notes.

Always read the instructions on the package before using.

What Electrode?

Successfully executing a stick weld largely depends on choosing the right electrode for the material to be welded.

Choosing the right electrode may not be as complicated as you think. "Two electrodes—the 6011 and 7018—will handle 90% of the welding jobs on a farm,” says Caleb Krisher, manager of market and product development for Hobart Welding Products.

Suitable for carbon and galvanized steel, "the 6011 electrode is a great all-around farm rod because it can do the job when conditions are less than ideal,” Krisher says. "It's very forgiving if you're working on metal that has not been perfectly prepared, as you may encounter with in-field repairs.

"Because the weld puddle solidifies, or freezes, quickly, 6011 electrodes work well for out-of-
position repairs,” Krisher continues. "The electrode is deep-penetrating and great for metal 1⁄8" or thicker.”

The 7018 electrode is also suitable for material 1⁄8" or thicker. It works with low-, medium- and high-carbon steels and is excellent for out-of-position welding and tacking. It is not recommended for low-voltage AC welders.

"The 7018 electrode is good for welding very thick metal [like a hitch] when you need to make multiple passes,” says Bruce Morrett, product manager for Hobart Brothers. "It's a good choice if you have a ½" groove to fill.”

"Use the 6011 for dirty metal and thin metal and the 7018 for clean metal and thick metal,” Krisher says.

Another electrode you may occasionally use is a 6013. Like the 6011, the 6013 is an all-purpose electrode. Offering medium penetration, it works well for joints with poor fit-up and for thinner metals. "Because it is very fast-freezing, it works well for overhead welding,” Krisher says.

"6013 electrodes are easy to use, making them a good choice for less-skilled welders,” Morrett says. "But don't use a 6013 when you are dealing with rusty or painted metal—it can't penetrate surface contamination.”

If you hard-surface implements, Krisher recommends purchasing "hard- surfacing buildup (or overlay) rod.” He explains, "It costs more, but the hard-surfacing job will last three to five times as long as it will with a standard electrode.”

All of these electrodes work with both AC and DC power. "With the 7018, there's a version that is specially formulated to work with AC power,” explains Michigan farmer Urka. "So, if you're limited to AC, make sure you buy that type of 7018 rod.”

What Size Electrode?
As a rule of thumb, use an electrode similar in diameter to the size of the base metal you're welding, Krisher says. "As a maximum, the thickness of the metal should not be more than twice the diameter of the rod.”

You can weld a larger piece of metal with a smaller-diameter rod, Krisher adds, but you'll have to make multiple passes and it will take much longer.

For More Information
  • For additional tips on improving your stick welding technique, log on to www.millerwelds.com/education/articles/articles16.html.
  • For more about specialized electrodes, visit www.hobartwelders.com/elearning/#stick. Click on "Stick Welding.

You can e-mail Darrell Smith at dsmith@farmjournal.com.

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FEATURED IN: Farm Journal - October 2008
RELATED TOPICS: Machinery, Contests, Shops

 
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