What is the primary purpose of the slag pans in the thermite welding process?

The primary purpose of the slag pans in the thermite welding process is to contain the molten steel. During thermite welding, a reaction occurs that produces molten steel as the end product. This molten steel needs to be safely contained to ensure that it fills the joint properly without spilling out. The slag pans are designed to catch and hold this liquid metal while it cools and solidifies. This containment is crucial not only for the efficiency of the welding process but also for the safety of the operators and the surrounding environment, preventing any uncontrolled flow of molten material and potential hazards.

The other choices, while they might seem related to aspects of the thermite welding process, do not accurately capture the main function of the slag pans. Cooling, supporting molds, and collecting waste material do not align with the primary role, which is specifically to contain the molten steel produced during the weld.