P91 steel welding method

Abstract

This invention provides welding method for P91 steel with basic steps of preheating, back welding with TGS-9CbªŽ2.4 solder wire, filler welding with C9MVªŽ2.5, C9MVªŽ3.2 welding rod and parameters of current 75-140A, welding time for every layer 6-21min, welding preheating temperature 150Deg and welding layer-to-layer temperature 200-300Deg, thermal insulation and thermal treatment. The technique progress can be found from: 1. increase welding current and speed about one times compared with generated method; 2. change layer bead arrangement, decrease welding bead and welding layer thickness convenient to operate, avoid dead angle, prevent welding bug; use layer-to-layer back fire effect to improve metal structure and performance of welding line; 3. come to welding operation standardization and process programming benefit for training and management to workers.

Description

technical field [0001] The invention relates to a P91 steel welding process method, which belongs to the technical field of special steel pipe welding. Background technique [0002] P91 steel is a new type of high-alloy heat-resistant steel, which is widely used for its excellent high-temperature lasting strength and creep rupture resistance. Compared with T22 steel, under the same temperature and pressure conditions, the wall thickness of the pipe is reduced by 50%. , reducing the structural weight; compared with austenitic steel, the expansion coefficient is small, and the thermal conductivity is improved, and the price is relatively cheap; both in terms of performance and economy, it shows its superiority, as a high temperature superheating It is the first choice and alternative steel grade for high temperature and high pressure pipelines such as headers and main steam pipelines. P91 steel is difficult to weld, mainly manifested in the easy occurrence of oxidation on the...

AI Technical Summary

Problems solved by technology

The welding of P91 steel is relatively difficult, which is mainly manifested in the problems of oxidation on the back of the weld, embrittlement of welded joints, cold cracks, and low impact toughness. The main reason is that during the welding process, the welding line energy is large and the interlayer temperature is high. As a result, the interlayer structure is overheated, resulting in Widmanstatten structure, large grains and network grain boundaries. These structures are prone to crack sources, forming cracks and expanding, resulting in a decrease in the impact toughness of the weld

In order to reduce the line energy, the common practice in the existing technology is to weld with low current and slow speed, the production efficiency is low, and the welder requires high technical level. The welding cycle of P91 steel pipe is about 24-30 hours

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