A welder is working on a critical structural component made of G40.21 350W steel. The welding procedure specification (WPS) calls for a preheat temperature of 100°C. However, the ambient temperature in the shop is 5°C. What steps must the welder take according to CSA W59 to ensure proper preheat application and prevent potential issues like cracking?

Question: A welder is working on a critical structural component made of G40.21 350W steel. The welding procedure specification (WPS) calls for a preheat temperature of 100°C. However, the ambient temperature in the shop is 5°C. What steps must the welder take according to CSA W59 to ensure proper preheat application and prevent potential issues like cracking?

Answer options:

• Proceed with welding, as the shop temperature is above freezing. ✅ Apply preheat to 100°C as specified, and ensure the temperature is maintained throughout welding.
• Increase the preheat temperature to compensate for the cold ambient conditions.
• Consult with the engineer to reduce the preheat requirement due to the cold environment.

Correct answer: Apply preheat to 100°C as specified, and ensure the temperature is maintained throughout welding.

Explanation: According to CSA W59, preheat temperatures specified in the WPS must be achieved and maintained throughout the welding process, regardless of ambient conditions, to prevent cracking and ensure proper metallurgical properties. Increasing preheat arbitrarily or reducing it without engineering approval is not permitted. Welding without meeting the specified preheat is a violation of the procedure.