For various methods of welding requirements for structural elements to prepare edges and seams are governed by the size of the relevant state standard. Welded joints to lock their constituent parts relative to each other and keeping the necessary clearance before welding gather in assembly tools, or by means of tack. The length of tack depends on the thickness of the metal. Tack cross-sectional area is approximately 1 / 3 of the cross stitch, but not More than 25 ... 30 mm2. Tack is usually carried out with coated electrodes or semi-automatic in carbon dioxide. It is recommended to apply by the inverse of the imposition of the basic single-pass weld, or the first layer in the multi-pass joints.

When welding, tack should melt completely, since they can form cracks due to the high rate of heat transfer. Therefore, before welding, tack thoroughly cleaned and inspected. If you have a tack crack her cursed or removed by other means. In the electroslag welding parts, usually set with a gap, widening at the end of the seam. Relative position of parts is fixed braces set at 500 ...

1000 mm from each other and are disposed of as suture. The automatic arc welding and electroslag welding in the beginning and end of the suture set input and output plates for welding seam from the beginning steady-state thermal cycle (the required weld size) and output from the main crater suture electrodes. Weld butt joints gas, hand-coated electrodes or semi-automatic gas shielded and powder wire is usually performed on the weight. In automatic welding techniques involve the use of providing warning and burn-through high-quality root pass penetration. To prevent the formation of seams pores, cracks, fusions and other defects of welded edges thoroughly cleaned before welding of the slag remaining after the thermal cutting, rust, oil and other contaminants. Arc welding important structures is best done with both sides. More favorable results are obtained with multilayer welding. In this case, especially on thick metal, achieved a more favorable structure in the weld metal and heat affected zone. However, the method filling in a multilayer cutting welding depends on the thickness of the metal and heat treatment of steel prior to welding. When you see the seams of defects (pores, cracks, penetration, undercutting, etc.) in place of metal is removed by mechanical defect by gas-flame, and air-arc gouging and plasma or after stripping podvarivaetsya. Keep in mind that when welding low alloy steels selection of welding equipment and affect the shape of penetration, the share of participation base metal electrodes in the formation of the joint, as well as on its composition and properties. Gas welding. Low-carbon and low carbon steel low alloy satisfactorily welded gas welding. For welding using normal fire. The use of flux is required. As the filler metal used welding wire and electrodes brands Sv-08, S-08A, Sv-08GS, 12GS-S, S-08G2S. Power of the flame at the left of the welding 100 ... 130 l / mm, right 120 ... 150 l / mm. The weld metal contains a small amount of nitrogen. This is due to its low concentration in the flame. Hydrogen remains in the seam in significant amounts and can cause pores in them. Oxidation of FeO by carbon formation of CO can also lead to the porosity of the joint. It is therefore recommended to use filler metal of low carbon content. Burnout silicon and manganese can lead to lower ductility of the weld metal - mechanical properties of weld metal may be somewhat improved hot forging or heat-treated (normalized or low-temperature annealing).