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The aim of this work is to develop a welded structure and a technology for manufacturing a smoke valve casing ID 2000 for use in a blast furnace to substitute the previously used cast design from 35L steel. The proposed large-size structure (3742 x 3020 x 3275 mm) should provide a strong and tight connection of three thick-walled (to 40 mm) rolled shells. The development of the structure and its elements was carried out using three-dimensional modelling in the Compass-3d software. The joining zones of the shells are designed as bent transition elements with a double curvature. It was found that the use of technological allowances when bending the cylindrical shells of sectors makes it possible to obtain parts with the required accuracy (a deviation in diameter not higher than 5 mm). The rolling of the shells having a complex curved line of joining can be performed on a rectangular workpiece. A curved joining line with the sections having a length of 150-170 mm and cross-connections of 50-70 mm is cut out on the workpiece using a computerized flame-cutting machine. It was shown that the removal of the cross-connections by manual gas cutting and preparation of edges for welding can be performed only after rolling and welding of the straight joint of the shell. Techniques for fitting the double-curved segments during assembling using special hydraulic struts were elaborated. These techniques were used to develop a technology for manufacturing a welded casing structure. Due to the optimization of the casing design, its weight was reduced by 5.5% compared to that produced by casting. Using the developed technology, two valves were manufactured to replace obsolete valves at the largest blast furnace (5500 m3) in Europe "Severyanka", PJSC Severstal. The described technical solutions provided a significant reduction in the labour intensity of manufacturing the presented structure, at the same time as ensuring its high quality and optimized weight compared to that produced by casting.

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