#weld defects

[weldingtheway]

Burn through and melt through occur when a welder melts through the metal they are trying to weld. Burn through creates an unsightly hole or gap. Melt through causes a raised area along the back of the material being welded. Both defects are particularly troublesome with sheet metal and thin plates. It is generally a result of too much penetration caused by having too much heat input in the weld zone. This problem can be corrected, with MIG, by reducing the wire-feed speed, which, in turn lowers the welding amperage. Travel speed may also be increased. Excessive penetration often causes burn through. While melt through is not necessarily bad, it is unsightly and the welded part may be rejected.

[weldblog]

Another visual on pipeline installation. The process of pipeline installation is a bit difference from pipe welding which is often performed in shops. Several welding techniques has been developed for fabrication and manufacturing of static equipment and structures. Welding with downhill progression is one popular technique used for installation of long pipelines. Joint type used for this process is Butt joint in which two pipe pieces are butted each other. 

In this case weld deposition rate is a bit higher than ordinary shop welds.  Stick welding is best process to produce pipeline welds. 

Joint Preparation:

In this process two pipe pieces are brought together with the help of clamps and then two welders are required to make welds from either sides. 

As stick process (also named as shield metal arc welding), is used where an arc is produced between piece and coated electrode. There may be possibility of several weld defects like: partial point penetration, undercuts, crater cracks, inclusion of slag, hydrogen induced cracking due to incorrect usage of stick rods. In order to avoid this re qualify the welders and build up are the common practices to make completely fused welds. 

[weldblog]

Structural welding is common joining technique, primarily using in construction, oil and gas, maritime and fabrication industries. Structural welding needs same level of weld quality assurance as compared to pressure welding. It’s common practice to weld a pipe either round or square geometry with a flat plate or to weld a plate to plate joint. Such weld joints are mostly referred to as  T-joints because of the shape they produce. All types of arc processes including TIG, MIG and FCAW (flux core arc welding) are employed in joining of these joints. 

Like other joint types, there are also some critical weld defects that ought to be avoid in case of T-joints. Common weld imperfections are lack of fusion, blow holes, burn through etc.