1.3 Technical conditions for the manufacture of welded structures

The technical conditions for the manufacture of a welded structure include technical conditions for basic materials, welding materials, as well as requirements for workpieces for assembly and welding, for welding and for welding quality control.

The main materials used for the manufacture of critical welded structures operating under dynamic loads should be alloy steels in accordance with GOST 19281-89 or carbon steels of ordinary quality not lower than grade St3ps in accordance with GOST 380-94.

Compliance of all welding materials the requirements of the standards must be confirmed by a certificate from the supplying factories, and in the absence of a certificate - by test data from the factory's laboratories.

When manual arc welding, electrodes of at least type E42A in accordance with GOST 9467-75 with a rod made of Sv-08 wire in accordance with GOST 22496-70 must be used.

The welding wire must be free of rust, oil and other contaminants.

Requirements for workpieces for welding stipulate that parts to be welded from sheet, shaped, rolled and rolled products must be straightened before assembly for welding.

After rolling or bending, the parts should not have cracks, burrs, tears, waviness or other defects.

The edges of parts cut with scissors should not have cracks or burrs. The cutting edge must be perpendicular to the surface of the part, the permissible slope in cases not specified in the drawings must be 1: 10, no more than 2 mm.

Dents after straightening and the curvilinearity of the welded edges should not exceed the established tolerances for the gaps between the parts being welded. Maximum deviations of angular dimensions, if they are not specified in the drawings, must correspond to the tenth degree of accuracy of GOST 8908-81.

Parts submitted for welding must be accepted by the quality control department.

The assembly of the parts to be welded must ensure the presence of a specified gap within the tolerance along the entire length of the connection. The edges and surfaces of parts at the locations of welds with a width of 25-30 mm must be cleaned of rust, oil and other contaminants immediately before assembly for welding.

Parts intended for resistance welding at the joints must be cleaned from scale, oil, rust and other contaminants on both sides.

Parts with cracks and tears formed. during manufacture, assembly for welding is not allowed.

The specified requirements are ensured by technological equipment and corresponding tolerances for assembled parts.

During assembly, force adjustment, which causes additional stress in the metal, is not allowed.

The permissible displacement of the welded edges relative to each other and the size of the permissible gaps should be no more than the values ​​​​set for the main types, structural elements and dimensions of welded joints in accordance with GOST 14771-76, GOST 235182-79, GOST 5264-80, GOST 11534-75, GOST 14776-79, GOST 15878-79, GOST 8713-79, GOST 11533-75.

Local increased gaps must be eliminated before assembly for welding. It is allowed to weld gaps by surfacing the edges of the part, but not more than 5% of the length of the seam. Filling enlarged gaps with pieces of metal and other materials is prohibited.

Assembly for welding must ensure the linear dimensions of the finished assembly unit within the tolerances specified in Table 3, angular dimensions according to the 10th degree of accuracy of GOST 8908-81 in the absence of other accuracy requirements in the drawings.

The cross-section of the tacks is allowed up to half the cross-section of the weld. Tacks should be placed at the locations of the welds. The applied tacks must be cleared of slag.

Tack welding of elements of welded structures during assembly must be performed using the same filler materials and requirements as when making welds.

Assembly for welding must be accepted by the quality control department. When transporting and tilting metal structures assembled for welding, measures must be taken to ensure that the geometric shapes and dimensions specified during assembly are preserved.

Only certified welders who have a certificate establishing their qualifications and the nature of the work to which they are authorized should be allowed to weld critical assembly units.

Welding equipment must be provided with voltmeters, ammeters and pressure gauges, except in cases where the installation of devices is not provided. The condition of the equipment must be checked by the welder and service technician daily.

Practical inspection of welding equipment by the department of the chief mechanic and power engineer must be carried out at least once a month.

The manufacture of steel welded structures must be carried out in accordance with the drawings and the assembly and welding process developed on their basis.

The technological process of welding must provide for such an order of seams, in which the internal stresses and deformations in the welded joint will be the smallest. It should provide maximum welding capability in the down position.

Perform welding work using methods not specified in technological process and this standard, without agreement with the chief welding specialist, it is prohibited. Deviation from the welding modes and sequence of welding operations specified in the process sheets is not allowed.

The surfaces of parts where welds are located must be checked before welding. The edges to be welded must be dry. Traces of corrosion, dirt, oil and other contaminants are not allowed.

It is prohibited to strike an arc on the base metal, outside the boundaries of the weld, or to create a crater on the base metal.

In appearance, the weld should have a uniform surface without sagging or sagging and with a smooth transition to the base metal.

Upon completion of welding work, before presenting the product to the quality control department, welds and adjacent surfaces must be cleaned of slag, sagging, metal splashes, scale and checked by a welder.

When resistance spot welding, the depth of indentation of the electrode into the base metal of the welding point should not exceed 20% of the thickness of the thin part, but not more than 0.4 mm.

The increase in the diameter of the contact surface of the electrode during the welding process should not exceed 10% of the size established by the technical process.

When assembling for spot welding, the gap between the contacting surfaces at the locations of the points should not exceed 0.5-0.8 mm.

When welding stamped parts, the gap should not exceed 0.2-0.3 mm.

When resistance spot welding parts of different thicknesses, the welding mode should be set in accordance with the thickness of the thinner part.

After assembling parts for welding, it is necessary to check the gaps between the parts. The size of the gaps must comply with GOST 14776-79.

The dimensions of the weld must correspond to the drawing of the welded structure in accordance with GOST 14776-79.

During the assembly and welding of critical welded joints, operational control must be carried out at all stages of their production. The percentage of parameter control is determined by the technological process.

Before welding, you should check the correctness of assembly, the size and quality of the tacks, compliance with the geometric dimensions of the product, as well as the cleanliness of the surface of the welded edges, the absence of corrosion, burrs, dents, and other defects.

During the welding process, the sequence of operations established by the technical process, individual seams and welding mode must be controlled.

After completion of welding, quality control of welded joints should be carried out by external inspection and measurements.

Fillet welds are allowed to be convex or concave, but in all cases the leg of the seam should be considered the leg of an isosceles triangle inscribed in the cross-section of the seam.

The inspection can be carried out without using a magnifying glass or using one with magnification up to 10 times.

Control of the dimensions of welds, points and identified defects should be carried out using a measuring instrument with a division value of 0.1 or special templates.

Correction of a defective section of a weld more than twice is not allowed.

External inspection and measurement of welded joints must be carried out in accordance with GOST 3242-79.

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