What is and what causes Incomplete Fusion in welding?

Answer 1

You have to clean the beak of the soldering iron with a sandpaper before pressing the tip of the welder on the wire. Heat it up (the wire) first, by pressing the tip of the welder on it) and only afterwards place the tin on the wire. [This answer pertains to soldering not welding.] In the welding process incomplete fusion occurs when the weld does not fuse with the base metal and can be caused by #1 travel speed too slow which allows the weld to roll over the edges trapping slag between the weld and the base metal. #2 amperage set too low which doesn't allow complete melting of the base metal, the weld deposit, and/or the flux/coating/slag. #3 electrode angle wrong which pushes the weld metal over the slag. #4 amperage setting too high and/or travel speed too fast which undercuts the edge of the base metal allowing slag to be trapped there and subsequent passes to bury the slag. #5 incorrectly placing the beads in multiple passes leaving voids along the edges that subsequent passes do not penetrate and remove. #6 arc length too long allowing weld to be deposited randomly. These answers relate to SMAW (stick welding) but some can be addressed in other processes. Other factors may apply to this problem in any of the welding processes. If you are reffering to a different process please ask again and specify which process.