Welding Techniques Using a DC Machine

DC Advantages

• DC current makes it easier to strike and hold a welding arc, produces less spatter, makes for easier welding of vertical and overhead surfaces and can handle a broad range of metal thicknesses. Successful DC welding requires the correct current setting, arc length, electrode angle, electrode manipulation and speed of travel. Most DC arc welding is done at power levels under 200 amps. The power level for a particular job will depend on the steel thickness and whether the weld is horizontal or vertical. Power level also will vary by the type of welding rod you use. In general, the lower the power level, the longer you can run the welding machine without overheating it.

Clean Area

• Before starting to weld, clean rust, grease and oil off the parts to be joined. Use a wire brush or grinder to remove loose rust. Be diligent in cleaning because poor preparation can lead to weak welded joints. Select the welding rod for the job and set the appropriate welding current. Clamp the welder leads to the workpiece and strike your arc. The arc’s length should be about equal to the diameter of the welding rod’s metal core. An arc that’s too short will be erratic and may end up welding the rod itself to the workpiece. An arc that’s too long will produce metal spatter, poor deposition rates and porous welds.

Rod Travel

• You strike the arc with the rod held perpendicular to the workpiece, then tilt it about 15 degrees of arc toward the direction of travel for horizontal surfaces and drag the molten metal along the joint. When welding vertical surfaces, tilt the rod about 15 degrees away from the direction of travel, in essence pushing the pool of molten metal up the joint. The proper travel speed produces a weld that’s slightly convex, about twice the width of your rod, is smooth and fills the joint completely. In general, keep the arc in the leading third of the molten weld pool. Going too slow produces a wide weld bead with little penetration. Moving too fast creates a narrow bead that doesn’t fully fill the joint.

Manipulating Rod

• When welding thicker steel, you can get a wider, penetrating weld bead by moving the rod slightly from side to side as you travel. Properly done, you will get a continuous series of overlapping circles. Limit side-to-side travel to 2.5 times the diameter of the metal welding rod core. Make sure you have a good view of the molten weld puddle at all times. Keep your head to the side and out of the smoke.