For arc spot welds qualified at a base metal temperature of 100 degrees F or lower, by how much percent shall the weld time be increased at a temperature of 32 degrees F?

When welding at lower temperatures, such as 32 degrees F, additional considerations must be taken into account to ensure the quality and integrity of the weld. Specifically, the electrical resistance of the base metal and the characteristics of the welding process may change under cooler conditions. This is particularly relevant for arc spot welding, where the energy required to achieve a proper weld is influenced by both temperature and metal properties.

In this case, increasing the weld time by 20 percent is necessary to compensate for the lower temperature. At 32 degrees F, the base metal behaves differently than at 100 degrees F, and extending the weld time increases the likelihood of achieving adequate fusion and penetration. Insufficient time could lead to poor weld quality, which may ultimately compromise the strength and reliability of the welded joint. Adjusting the weld time appropriately is essential for maintaining the structural integrity of the weld in adverse temperature conditions.

Other options reflect lower percentage increases, which would not provide sufficient adjustment for the drop in temperature, potentially leading to ineffective welds. Thus, the 20 percent increase is the correct and necessary adjustment to ensure high-quality welds in colder conditions.