Welding process of UNS N07208 superalloy pipe for boiler at 700 DEG C or above

Abstract

The invention discloses a welding process of a UNS N07208 superalloy pipe for a boiler at 700 DEG C or above. The welding process comprises the following steps that (A) groove processing before welding is performed, a welding area is cleared, and preheating is performed; (B) assembling and welding are performed as required; (C) nondestructive flaw detection is performed after welding; and (D) post-welding heat treatment is performed after flaw detection is qualified. Welding materials adopted in the step (B) are SFA-5.14 ERNiCrCoMo-2 and an improved type thereof or SFA-5.14 ERNiCrCo-1 and an improved type thereof, and mixed gas of (60-80)% argon and (40-20)% helium is adopted as protective gas of a welding molten pool; and through the welding process, the defects such as slag inclusion, microcrack and incomplete fusion inside a welded seam can be eliminated, the welding quality and performance of a joint are ensured, the qualification rate of one-time flaw detection is increased, and conditions are created for future development of boilers at 700 DEG C and at the higher level and engineering application of a superalloy UNS N07208.

Description

technical field [0001] The invention relates to a welding process for UNS N07208 superalloy pipe. Background technique [0002] UNS N07208 is an aging-strengthened superalloy developed by Hastelloy International Corporation of the United States, and its typical chemical composition is well known. Due to its excellent high-temperature mechanical properties, corrosion resistance and good cold and hot processing properties, it is considered to be the most potential material for manufacturing key components such as high-temperature heating surfaces and headers of ultra-supercritical boilers at 700 °C and higher. [0003] The superalloy UNS N07208 is considered to be the most potential material for the development of high-temperature key components of 700°C and higher ultra-supercritical boilers. Many experiments have been carried out at home and abroad. Welding process research, especially the welding research of large-diameter and thick-walled pipes is relatively small, and th...

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Problems solved by technology

[0003] The superalloy UNS N07208 is considered to be the most potential material for the development of high-temperature key components of 700°C and higher ultra-supercritical boilers. Many experiments have been carried out at home and abroad. Welding process research, especially the welding research of large-diameter and thick-walled pipes is relatively small, and there is no mature welding process for reference. With the existing welding process methods, the qualified rate of post-weld joint flaw detection is low, and there are slag inclusions, micro Cracks, lack of fusion and other defects, quality and joint performance cannot be guaranteed

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