Welding Defects and How To Prevent Them
by Martin Rice
This article covers some welding defects that are sometimes overlooked or not considered. Each welding project requires careful considerations. They include:
- The process, the type of welding i.e. stick, MIG, TIG.
- The composition of the base metal and thickness.
- The welding position, i. e. flat, vertical, horizontal, overhead.
- The weld joint and type.
- Electrical supply and equipment.
- And finally, the welding techniques to be used.
To minimize the chance of welding defects be sure to consider 1) the travel speed of the pass; 2) the size and type electrode; 3) machine settings; 4) make sure the welding is done in accordance with the plan and the current conditions.
Most of, or a great deal of, welding defects can be identified by the "naked eye." By knowing what is likely to produce welding defects you will learn how to avoid them. Production without defects saves time, materials, repair costs, and a decrease in productivity.
The two following causes for weld rejection should not be but are often overlooked 1) is the weldor proficient with the process being used? 2) is the welding rod supply up to standards? Use only properly stored, dried, and maintained welding rods.
Welding defects include poor penetration. It's the failure of the welding rod and base metal to fuse together. It's caused by a root face that is too big; a root opening that is too small; an electrode that's too large; slow travel speed or a machine setting that's too low.
Poor fusion is the failure to blend the layers of weld metal together with the base metal. A lack of fusion is caused by " . . . failure to raise to the melting point of the base metal or the deposited weld metal," (Miller Electric Mfg. Co.) It's caused by improper fluxing; dirty plate surfaces; improper electrode size or type; wrong current settings. Electrodes that do not meet the storing, drying and maintenance specifications also cause it. Poor fusion is common with spot welding and mig welding when welding settings are incorrect.
Undercutting is another problem that causes welding defects. It burns away the base metal at the toe of the weld. It's caused by a current adjustment that is too high; an arc gap that is too long or failure to fill up the crater completely with weld metal.
Porosity looks "sponge like," or like tiny "bubbles" in the weld. It's caused by gases being released by the cooling weld because a current setting is too high or arc is too long.
Slag inclusion occurs when the slag is not chipped and cleaned properly and then another pass is made over the top. To avoid, 1) prepare the groove and weld properly before each pass; 2) thoroughly clean in between passes; check the machine settings against those suggested by the manufacturer; 3) hold a smaller weld puddle.
About the Author
Martin Rice teaches college level welding, in addition to writing articles for www.RodOvens.com, where you can purchase Welding Rod Ovens online.