WEBVTT

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welding.

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Welding, the joining of two metals with a strong permanent bond. Welding is one of the major

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construction techniques used in steel fabricating. The heavy construction industry and builders of

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modern high-rise structures are among the many industries that have switched from

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shielded metal arc electrodes to the gas shielded metal arc or flux cord process. The gas shielded

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flux cord process is widely used in heavy weldments of mild and low alloy steels. The flux

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cord electrode is an arc welding process for single and multiple pass welding of steels of

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various alloy content and physical properties. Spooled or coiled electrodes convey the electric

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current or amperage for the arc which fuses the material to be welded and at the same time

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provides the filler metal for the weld. Both the 332nd inch and 1 16th inch wire are shipped

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by pallet. For our work in the flat position we'll be using the 332nd electrode. The 1 16th

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is an all position wire. First check the carton for damage. A punctured carton could mean a

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plastic inner liner and a damaged roll. Then roll the coil free and you're ready to mount it on the

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wire feed. We'll also be working with a relatively simple welding system involving a wire feeder,

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drive rolls, gas and welding gun. Line up all the holding clamps on the wire feed, mount the coil,

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and lock the holding clamps into position. Then cut the first tie wrap. But be careful not to

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cut all four tie wraps or you'll get a bird's nest. That's another way of saying costly downtime. Line

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up the loose end of the electrode, trim the end with a wire clipper, cut the second tie wrap,

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and insert the wire into the drive roll. Start feeding the wire through the feed cable to the

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end. Next, cut the third and fourth tie wraps on the coil. After tightening the drive roll tension

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screws, remove the contact tip from the gun. Load the gun through the inching switch on the

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wire feed unit or by brief squeezes on the gun trigger to a point where the electrode protrudes

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from the gas cup by three-quarters of an inch. Now replace the contact tip. Remember to set the

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wire feed speed control to between 38 and 40 inches per minute. Then check your drive roll

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tension. Too much tension and you'll get a file action on the electrode. Tighten the tension nut

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with your fingers and feel the wire as it runs. Your fingers should drag on the wire. Checking

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your gas flow is a simple procedure of squeezing the welding gun trigger and checking the meter.

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Make necessary adjustments on the flow control so that the meter reads 45 cubic feet per hour.

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That's the recommended setting for 332nd wire. Welding amperage and wire feed speed depend upon

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the particular application and specification established by the welding engineer. Adjust your

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feed speed to these guidelines. If in doubt, check your consumable catalog. The area you are

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welding, the weld zone, is protected from atmospheric contamination by carbon dioxide

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shielding gas and a molten blanket of dense but easily removed slag. The electrode stickout should

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be three-quarters to one inch beyond the gas cup and one and a quarter inches beyond the contact

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tube. Excessive electrode stickout could cause poor gas shielding and pinholes in the weld.

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Correct guide tube placement and proper positioning of the nozzle results in x-ray

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sound welds. A leading angle to the gun of two to fifteen degrees gives a lagging gas

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shield. The same leading angle technique is used in fillet welds as with flat welds. When making

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fillet welds, position the electrode 35 to 40 degrees from the vertical plane. Now you're ready

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to begin welding with this five-step sequence. After you've turned on the power source and

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adjusted the voltage range, turn on the CO2 shielding gas. Adjust the regulator and flow

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meter and set the wire drive speed. Lower your helmet, position the gun, squeeze the trigger,

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and start an arc. Bead size is determined by the welder's rate of travel on the workpiece. It has

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a marked effect on weld penetration and bead appearance. Here's what happens when speed is

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reduced to the point where the molten metal, the weld metal, and slag flow into a crater

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beneath the arc giving an insulating effect between the arc and base metal. Note the bead

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appearance and shallow penetration. In this instance, the rate of travel was adjusted to

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give the best combination of bead shape and penetration. Deposit a bead too fast and

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penetration is reduced while bead appearance is smaller with a slightly convex surface. There is

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also the possibility of undercut. Remember, deep penetration of the flux-cored electrode reduces

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your edge preparation for butt joints. But deep penetration also means less welding time to achieve

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comparable strength and load carrying capacity. To these features, add simplicity and you have

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one of the most popular welding processes today.