What can be a cause of insufficient penetration in welding?

Insufficient penetration in welding can occur when there is too tight of a gap or too heavy of a land. A tight gap means that there is not enough space for the weld pool to adequately flow into the joint, which can prevent the weld from penetrating deeply into the base materials. This inadequate flow can lead to a weak joint that does not meet strength requirements. Similarly, a heavy land, which refers to the thickness of the edges of the materials being joined, can also restrict the penetrative capacity of the weld. The welding arc may only melt the outer edges instead of reaching the base material effectively, leading to insufficient penetration.

In contrast, excessive heat input, incorrect filler material, and insufficient shielding gas are more likely to relate to different issues in the welding process, such as distortion or porosity, rather than an immediate lack of penetration.