18 May 2020
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To help we’ve put together some tips associated with common undercutting, lack of fusion, slag inclusions and penetration problems.
Undercutting causes a weaker area at the toe of the weld and often leads to cracking.
Failure of the weld metal to fuse completely with the base metal.
Slag inclusions occur when the slag generated by the molten flux in the wire’s core becomes trapped inside of the weld. There are four major causes of slag inclusions.
Incorrect weld bead placement
Provide sufficient space in the weld joint for additional passes, particularly on joints requiring multiple passes.
Maintain the correct travel angle and travel speed. In flat, horizontal, and overhead positions your drag angle should be between 15 and 45 degrees. In the vertical up position, your drag angle should be between 5 and 15 degrees. If you still experience slag inclusions increase your drag angle slightly. Maintain a steady travel speed; if you travel too slowly, the weld puddle will get ahead of the arc and create slag inclusions.
Incorrect weld heat input
Maintain proper weld heat input, too low of welding heat input can cause slag inclusions. Use the manufacturer’s recommended parameters for a given wire diameter. If slag inclusions still occur, increase the voltage until the inclusions cease.
Clean thoroughly between weld passes, removing any slag with a chipping hammer, wire brush or grinding before beginning your next weld pass.
Excessive penetration occurs when the weld metal melts through the base metal and hangs underneath the weld. It often results from too much heat.
Using these valuable tips should result in good welding technique, and your ability to prevent these problems—or identify and rectify them quickly without sacrificing time or quality.