What is the maximum temperature a pulling force can be applied to the closure weld?

The maximum temperature at which a pulling force can be effectively applied to a closure weld is crucial for ensuring the integrity and strength of the weld. Applying too much force at excessive temperatures can lead to deformation, weakening the weld joint.

The correct answer indicates that a pulling force can be applied up to 700° F. This temperature is carefully determined based on the materials used in thermite welding and the specific characteristics of the weld. At this temperature, the weld has cooled sufficiently to achieve a stable bond but remains malleable enough to allow for safe handling and application of forces without risking structural failure.

Maintaining this maximum temperature helps in preventing detrimental changes in the material's properties, such as loss of strength or ductility, which can occur at too high temperatures. Each of the other options represents temperatures that could compromise the weld's integrity if a pulling force were applied, either causing physical damage to the weld or leading to potential failure during operation.