A single-sided welding and double-sided forming welding method for thick-walled vertical welding joints of centralized downcomers

Abstract

The invention provides a single-face welding and dual-face forming welding method of a thick-wall vertical weld bond of a common downcomer. The method of combining a carbon dioxide flux-cored wire with inert gas tungsten electrode shielded welding is adopted, bottoming weld is firstly carried out to form a bottoming layer, then filling layer welding is carried out above the bottoming layer, and uniform heating of the bottoming layer, an upper groove and a lower groove is kept; and multiple thickened layers are welded to a filling layer, the welding joint of the previous layer is remolten during welding, the multiple thickened layers are arranged in a staggered manner, and a capping layer is welded above the thickened layers. The method of the carbon dioxide flux-cored wire and inert gas tungsten electrode shielded welding is adopted, slag and gas dual-layer protection at the weld bond during welding is achieved, and multiple welders can synchronously achieve welding at multiple positions; and the welding efficiency and welding quality of the common downcomer are effectively improved, waste, generated by a large amount of repair after welding, of production equipment, resources andwork hours is avoided, the construction period is greatly shortened, and meanwhile the construction cost is reduced.

Description

technical field [0001] The invention relates to the technical field of welding and forming of concentrated descending pipes, in particular to a welding method for single-sided welding and double-sided forming of thick-walled vertical welds of concentrated descending pipes. Background technique [0002] In the water circulation system, when the flow pressure head remains constant, the smaller the resistance of the downcomer, the higher the circulation flow rate, which can make the state of the water wall tube more stable, easy to improve the stability of the water wall tube and extend the water wall tube life. However, as the working pressure of the boiler increases, the density difference between water and steam decreases. In order to ensure a certain circulation flow rate so that the water-cooled wall tube can be well cooled, many measures have been taken to reduce the flow resistance of the circulation loop in the existing process. Large diameter centralized downpipe is o...

AI Technical Summary

Problems solved by technology

[0004] 1) Solid argon arc welding wire has a large amount of molten metal and a large amount of welding shrinkage. When the bottom layer is welded to three-quarters of the overall welding thickness, the weld gap at the welding port at this time is already smaller than the diameter of the welding wire at this time. Then, in the welding process of the last quarter thickness, unmelted and uneven phenomena are prone to occur at the root of the back of the down-groove weld;

[0005] 2) In the existing welding process, it is required that the first three drops of molten iron melted by the electrode cannot exist in the weld seam during the welding process, because it is very easy to produce pores and / or dense pores during welding; on the other hand, In the welding process of the prior art, due to the limitation of the length of the electrode, there are too many welded joints during the welding process, which will also cause dense pores and even slag inclusions during welding. The above-mentioned pores and / or Dense porosity will accompany the melting of the weld until the welding of the entire electrode is completed, and then further affect the overall welding quality of the downcomer. The pass rate after ultrasonic testing usually does not exceed 60%, and then a large number of repairs occur

[0006] Based on the above reasons, it is difficult to ensure the quality of the overall project with the centralized downcomer welding process under the existing technology, and because of the large number of repairs, the welding process and the repair process cause a large lag in the overall project

At the same time, based on the above reasons, the welding process of the centralized downcomer in the prior art also consumes a lot of man-hours, resulting in a great waste of construction resources such as equipment, labor, and materials.

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