Final answer:
Cluster porosity typically occurs perpendicular to the weld face and involves a group of small gas pockets. It's important to use clean materials, correct techniques, and parameters to prevent it.
Step-by-step explanation:
The type of porosity that usually occurs with an orientation perpendicular to the weld face is cluster porosity. This happens when small gas pockets form within the weld metal, creating a cluster of holes that are often aligned perpendicular to the direction of welding. This issue can be caused by several factors including contamination, improper welding techniques, or incorrect choice of filler material. To reduce the risk of cluster porosity, it's crucial to ensure clean base and filler materials, proper shielding gas coverage, and appropriate welding parameters.