What should be removed at 20 minutes after the pour?

At 20 minutes after the pour, it is important to remove alignment tools. This timeframe allows sufficient time for the thermite weld to begin cooling and solidifying, ensuring that the weld has formed properly and the alignment tools can be safely removed without disturbing the integrity of the weld. Alignment tools are used during the setup to ensure that the pieces being welded are positioned correctly. If they are left in place for too long, they could interfere with the final quality of the weld.

Removing supports, excess material, or cooling elements typically occurs at different intervals. Supports provide stability during the welding process and may not need to be removed until the weld has fully cooled and set. Excess material is often trimmed after sufficient cooling to ensure proper fusion and finish. Cooling elements are necessary to manage temperature during the welding process and often remain in place longer to help maintain appropriate temperatures post-weld. Thus, the emphasis at this point is on ensuring the correct alignment is preserved, making the removal of alignment tools the focus.