What factor could result in a lack of fusion or penetration in a weld?

A too fast travel speed during the welding process can indeed lead to a lack of fusion or penetration in a weld. When the welder moves the electrode too quickly across the workpiece, the heat generated may not be sufficient to melt the base material adequately or to fuse the weld bead into the base material. This can create weak areas where there is inadequate bonding between the materials. Proper travel speed is critical in ensuring that the weld puddle has enough time to heat and penetrate into the base material for a strong connection.

In contrast, factors like insufficient electrode angle may affect the quality of the weld, but they do not directly correlate to the lack of penetration. Using a higher current generally increases heat input, which may enhance penetration. Overlapping of the weld is an issue that pertains more to the weld's profile and appearance rather than direct penetration or fusion, but it can also lead to weakness in the joint. Therefore, the travel speed is the primary factor in this context that can cause insufficient fusion and penetration in a weld.