Mounting joints of steel structures are welded, bolted and especially responsible - on rivets. If necessary, steel structures are connected with reinforced concrete, welding the connecting elements to embedded parts of reinforced concrete structures or connections are carried out on bolts.
Welded joints are used for rigid joining of supporting structures and, if necessary, to have a tight, water-tight joint of elements. Such structures include sheet constructions of the housings of blast furnaces, dust collectors, tanks, gas holders. Hard joints include joints between columns, columns and crane girders, columns and roof trusses.
The welded joints of the mounting elements are initially fastened together with coarse mounting bolts, and since the strength obtained is insufficient for strength calculations, the elements are welded together. Depending on the type of structures to be connected, the elements can be welded directly or with the help of additional butt plates.
Column joints. Columns 18 m or more in height before transportation are divided into dispatch elements, based on the dimensions of the vehicles. During installation, these parts of the columns are joined together, welding can be performed directly or with the help of steel plates, which are mounted on bolts and welded to the elements being joined. The joints of columns of one-story industrial buildings are usually made in the nadkranovoy part above the crane girders. The milled ends of the supracrane and main parts of the column are joined to each other and welded along the joint plane. For greater rigidity, both parts are interconnected with a butt sheet lining.
Connection crane girders with columns. The crane beam is supported by the edge of a vertical sheet directly on the base plate of the column and is connected to it by bolts. Additionally, the crane beam is attached to the above-crane part of the column with brake structures, which are attached to the columns and beams on the bolts and additionally boil with a long seam.
The connection of farms with columns . When hinging truss on the column, the upper chord of the truss is attached to the column, connecting the fastener with bolts and assembly weld seam to the plates welded to the column. In the rigid connection of the truss with the top of the column in the interface, the butt plate is additionally placed, which is connected to the base plate of the end of the column and the truss belt with bolts and welding. The bottom belt of the truss with the molding rests on the mounting table and is attached to the column with bolts and welding.
Quality control of welded joints. Welds are checked by external inspection, revealing irregularities in height and width, lack of penetration, undercuts, cracks, large pores. In appearance, the welds should have a smooth or fine-flaked surface, the weld metal should be dense along the entire length of the weld. Tolerances in the dimensions of the cross sections of welds and welding defects should not exceed the values specified in the relevant standards.
To control the mechanical properties of the weld metal and the strength of welded joints, test connections are welded from which test specimens are cut. The tests are carried out for tensile strength, hardness, elongation, etc. To check the quality of the welding, x-ray and γ-radiation scanning on the film is used, ultrasonic flaw detectors have been used.
Defects in the welds are eliminated in the following ways: breaks in the seams and craters are welded; the seams with cracks, incomplete penetration and other defects are removed and brewed again; base metal undercuts are trimmed and brewed, providing a smooth transition from the weld metal to the base metal.
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