Within what temperature range must the rails be preheated for thermite welding?

In thermite welding, preheating the rails is a crucial step to ensure a successful bond and prevent thermal shock to the materials being welded. The ideal preheating range is between 1100° - 1800° F. This temperature range is effective because it helps to bring the rail material up to a suitable temperature where the thermite reaction and the subsequent melting of the metal can occur more efficiently.

When the rail reaches this temperature range, it allows for proper fusion between the molten thermite metal and the rail itself, resulting in a strong and durable weld. This preheating minimizes the risk of cracking and improves the overall integrity of the weld, ensuring that it can withstand the stresses and strains of heavy rail use.

Proper control of the preheating temperature is essential, as temperatures that are too low could lead to weak welds, while excessively high temperatures might lead to distortion or other defects in the rail materials. Thus, the specified range is designed to optimize the welding process and promote the best possible outcome for the joint.