What are the typical preheating temperatures specified in API 1104 for carbon steel?

The specified preheating temperatures for carbon steel in API 1104 typically range from 50°F to 400°F. Preheating is an essential step in the welding process, particularly for carbon steel, as it helps reduce the risk of cracking and enhances the overall quality of the weld. The range provided in this option encompasses various factors such as the thickness of the steel, the carbon content, and the ambient temperature conditions, which can all influence the welding process.

Choosing preheat temperatures within this broader range allows for flexibility in different welding scenarios, making it easier to adapt to specific project requirements and material characteristics. While lower temperatures might be sufficient for thinner materials or less critical applications, higher preheating is often necessary for thicker sections or situations where higher restraint conditions might exist.

The other options do not match the complete range specified by API 1104, which is critical for ensuring proper weld integrity and performance in various environmental conditions.