The welding joint created by welding two workpieces of metal together is only as strong as the procedure used to create the weld in the first place. Welding defects types are typically caused by improper welding procedure. Defects increase the chance that the weld will not hold. Defects, it means that every discontinuity which overshadows welding tolerance limit cause quality of welding decline. Once a welder understands the defect his or he is causing, the welder can assess what welding procedure he is using and fix the errors. There are many types of welding defects that most occur in the welding process, among them such as lack of fusion, undercutting, cracking and pinholes.
Welding Defects Types
The first type of welding defect is lack of fusion. It is caused by base metals imperfectly heating during the welding process. If the base metals’ heat was not high enough nearly the melting point, the metals being welded together may have no become good molten weld metals during the welding process and the two pieces of base metal did not join well. Imperfectly heating possibility caused by improper travel speed of welding, using the welding current too low, faulty joint preparation, using too large an electrode diameter, magnetic arc blow and wrong electrode angle. Lack of fusion is characterized by edges that are still flat and smooth and show no signs of having once been molten metal.
The next type of welding defect is undercutting. Undercutting is looked like a groove or a slight ditch in the weld metal right along the weld line. It is produced by several faulty of welder during the welding process. Welder does the faulty electrode manipulation. The welder also does absolutely wrong in using welding current setting; it is too high current in use. Another faulty is an arc length that too long because electrode distance from base metal is too high. Finally, too fast travel speed welding and arc blow also can produce welding defect that called undercutting. The size of the groove deepens the faster the arc travels along the weld line. Decreasing the arc speed reduces the depth of the groove and eventually eliminates it. Using proper electrode angles or proper welding current for electrode size and welding position also can eliminate undercutting. Other ways also can decline of producing undercutting by reducing arc length, the travel speed of welding and effect of arc blow.
Another type of welding defects most produced during the welding process is cracking. Cracking looks like ridges in the weld line that resemble an earthworm’s body. Many cracking types depend on the causing it, such as arc strike cracking, cold cracking, crater cracking, hat cracking and hot cracking. In general, cracking typically occurs because unprepared well such as insufficient weld size, excessive joint restraint, poor joint design and/or preparation, base metal surface covered with oil, grease, moisture, rust dirt or mill scale.
Besides, cracking also is caused by faulty on choosing the filler wire metal does not match with base metal, or also caused by rapid cooling rate. Reducing joint restraint through proper design or reducing cooling rate through preheating can eliminate cracking. Other ways also can decline of producing cracking by adjusting weld size to part thickness, select the proper joint design, use more ductile filler metal, and properly clean base metal prior to the welding process.
The last type of welding defect is pinholes. Pinholes refer to a welding defect caused by high welding temperatures. If the temperature of the arc making the weld is too high, tiny holes resembling pinholes may appear on the surface of the weld. High temperatures of welding are possibly caused by lower travel speed of welding and using the welding current too high.
Keep reading: Basic Principles of Non-Destructive Testing (NDT)
In brief, welding defects types that are lack of fusion, undercutting, cracking and pinholes most was produced by improper welding procedure. It is can causes quality of welding decline.