Increasingly demanding material requirements found in piping and boiler construction for industries such as power generation and petrochemical processing have made a specific type of chromium-molybdenum steel pipe-referred to as grade P91-a frequent choice because of its ability to withstand high pressures and high temperatures. Alloy P91 is used in many critical applications that require significant strength at high temperatures, including superheaters, headers, and steam lines. However, P91 is a higher-cost material that presents some challenges in fabrication. Achieving sound welds with P91 pipe requires operator skill; careful control of heat input before, during, and after welding; and appropriate low-hydrogen filler metals.
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