What is the minimum preheat temperature required for a prequalified WPS when welding #18 ASTM A706 reinforcing steel without test reports?

In the context of welding #18 ASTM A706 reinforcing steel, the minimum preheat temperature for a prequalified Welding Procedure Specification (WPS) is indeed 200°F (90°C). This requirement is in place to help reduce the risk of hydrogen-induced cracking in the heat-affected zone and ensure better weld quality.

Preheating the base metal before the welding process allows for a more controlled cooling rate, which is crucial for preventing undesirable microstructural changes that can lead to cracks. This specific preheat temperature has been determined based on the properties of the material being welded and is part of the guidelines outlined to ensure safety and integrity in welding practices.

Adhering to this specified preheat temperature also aligns with industry best practices intended to safeguard against common welding issues when using high-strength reinforcing steel. Lower or higher preheat temperatures may not effectively mitigate these risks, which is why the specified 200°F is significant for this type of steel under these specific conditions.