Various Situations and Analysis of Incomplete Welding in Welding Process

Incomplete penetration during welding refers to the defects caused by the base metal not melting and the weld metal not entering into the root of the joint. According to the welding method of the weldment, it can be divided into incomplete penetration at the root and incomplete penetration in the middle. The liquid weld metal does not enter into the root blunt edge. The one-sided welding of V-shaped or U-shaped groove is incomplete penetration at the root and the liquid metal does not enter into the middle blunt edge, In double V-groove or double U-groove, double side welding is incomplete in the middle.

Incomplete penetration defect of weld

Incomplete penetration in the weld will reduce its effective area, which will seriously reduce the strength and other mechanical properties of the weldment. Incomplete penetration will also cause stress concentration, which will seriously reduce the fatigue strength of the weld. Under the condition of bearing stress, the incomplete penetration of weldment will develop into crack, which is more harmful than porosity, slag inclusion, tungsten inclusion and other defects.

Causes of incomplete penetration

1.Low welding current

2.groove size is not suitable

3.The influence of magnetic bias blow

4.The deviation of the electrode is too large

5.Poor cleaning of interlayer and welding root

The use of large current for welding is the basic method to prevent incomplete penetration. When welding fillet weld, using AC instead of DC to prevent magnetic bias blowing, strengthening cleaning, reasonable groove design and other measures can effectively prevent incomplete penetration.

Image characteristics of incomplete solder film

The image of incomplete penetration is a thin straight black line, and the contour of both sides of the defect is very neat. The width of incomplete penetration image is the width of the gap between blunt edges, and the image contour becomes irregular. As long as the linear defect at the root of the weld can be judged, it is incomplete penetration.

The non welded bottom plate is located in the projection position of the weld root, generally in the middle of the weld, and it is intermittent or continuous distribution, sometimes it can run through the whole negative.

Incomplete penetration under radiation

The incomplete penetration defect is located in the center of the weld, and it is a straight black line on the negative film. There are many circular defects in the center of the weld. The black line in the center of the weld connects the circular defects in series and runs through the whole weld. The outline is clear and the blackness is uniform. It is a typical incomplete penetration defect.

Incomplete penetration and incomplete fusion image

The profile of the weld center is very straight, and the defect contour close to the base metal is irregular.

Basic knowledge about welded pipe