A large-diameter pipe dissimilar steel welding process applied to advanced ultra-supercritical boiler materials

By combining manual tungsten inert gas welding (TIG) and shielded metal arc welding (SMAW), the problem of welding dissimilar steels such as UNS S31035 and SA-335P92 large-diameter pipes was solved, resulting in a welded joint with stable performance at high temperatures, suitable for the manufacture of advanced ultra-supercritical boilers.

CN116275401BActive Publication Date: 2026-07-21HARBIN BOILER CO LTD
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Patents(China)
Current Assignee / Owner
HARBIN BOILER CO LTD
Filing Date
2023-03-30
Publication Date
2026-07-21

AI Technical Summary

Technical Problem

There is a lack of relevant manufacturing experience in welding dissimilar steels such as UNS S31035 and SA-335P92 large-diameter pipes in the existing technology. In particular, exploration and experimental research are needed in aspects such as the selection of welding materials, bevel preparation, preheating temperature, temperature control between weld layers, and post-weld heat treatment.

Method used

A combination of manual tungsten inert gas welding (TIG) and shielded metal arc welding (SMAW) was used to weld SA-335P92 alloy steel pipes and UNS S31035 new austenitic heat-resistant steel pipes. This included pre-weld beveling, preheating control, multi-layer welding, and post-weld heat treatment to ensure the mechanical properties and aesthetics of the welded joints.

Benefits of technology

It effectively avoids problems such as cold cracking, hot cracking and poor fusion during the welding process, and forms a welded joint with excellent mechanical properties. It is suitable for high-temperature long-term aging tests with stable performance and meets the evaluation standard of NB/T 47014-2011.

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Abstract

A large-diameter pipe dissimilar steel welding process applied to advanced ultra-supercritical boiler materials belongs to the technical field of welding. The process comprises the following steps: S1. Pre-welding preparation, preparation of a groove, and cleaning of the groove and the inner and outer walls on both sides thereof, water removal, oil removal, and impurity removal treatment; S2. First welding by using manual tungsten argon arc welding; S3. Second welding by using shielded metal arc welding; S4. Post-welding treatment, post-welding and welding interruption 200-250 DEG C / 1-2h post-heat treatment, and then 755+ / -15 DEG C / 4h stress relief annealing heat treatment of the welded joint. The process solves the problems of P92 side heat affected zone cold cracks, weld zone hot cracks, and poor fusion between welds and between welds and base metal during welding of UNS S31035 and SA-335P92 large-diameter pipes by controlling the welding material selection, groove preparation, type and flow of protective gas, and welding specification parameters, and ensures that a welded joint with excellent mechanical properties and good appearance is formed.
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