Final answer:
The preheat temperature required for welding the specified pipes depends on the applicable welding code or standard. Consult the code or standard for the exact preheat temperature based on factors such as carbon equivalent, thickness, and welding process.
Step-by-step explanation:
The preheat temperature required for welding an ASTM A106 grade B, NPS 8, s40 pipe to an ASTM A335 grade P9, NPS 8, s40 pipe can be determined based on the applicable welding code or standard. In general, the preheat temperature is determined to minimize the risk of hydrogen-induced cracking, ensure proper heat input during welding, and improve the integrity of the weld joint.
For this specific case, you would need to consult the welding code or standard such as AWS D1.1 (for structural steel) or ASME Section IX (for pressure vessels) to determine the exact preheat temperature required for the specific combination of materials. The preheat temperature would depend on factors such as the carbon equivalent of the materials, thickness of the pipes, and the welding process being used.
It is important to consult the welding code or standard and follow the recommended preheat temperature guidelines to ensure a successful and safe welding operation.