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Common Problems in Steel Structure Welding

Foshan Steel refers to the structure mainly composed of steel materials, is one of the main types of building structures. Structure is mainly made of steel and steel plate, such as steel beams, steel columns, steel trusses and other components, the components or components are usually used between the weld, bolt or rivet connection. Because of its light weight, and the construction is simple, widely used in large factories, venues, high-level and other fields.
Steel structure in the welding process, there are many matters needing attention, once negligent, there may be a big mistake.

1. Welding construction does not pay attention to choose the best voltage
【phenomenon】
Welding, whether it is rendering, filling, cover, regardless of groove size, are selected the same arc voltage. This may not meet the requirements of the penetration, melting wide, undercuts, stomatal, splash and other defects.
【Measures】
Generally should be selected for different situations corresponding to the long arc or short arc to get a better welding quality and efficiency. For example, primer welding in order to be able to get a better penetration of short arc operation should be used, filled with welding or cover surface welding in order to get higher efficiency and melting width can be appropriately increased arc voltage.

2. Welding does not control the welding current
【phenomenon】
Welding, in order to grab the progress of the butt weld for the plate to take not open groove. Strength index decreased, or even less than the standard requirements, bending test cracks, so that the weld joint performance can not be guaranteed, constitute a potential hazard to structural safety.
【Measures】
Welding process according to the assessment of the welding current control, allowing 10 to 15% floating. Beveled edge of the groove size should not exceed 6mm. Butt joint, the thickness of more than 6mm, to open the groove for welding.

3. Do not pay attention to welding speed and welding current, electrode diameter in coordination.
【phenomenon】
Welding does not pay attention to control the welding speed and welding current, electrode diameter, welding position coordination to use. Such as the full penetration of the angle seam backing welding, due to the root size is narrow, such as welding speed too fast, the root gas, slag does not have enough time to discharge, easy to root imperfect penetration, slag, porosity and other defects ; Cover surface welding, such as welding speed too fast, but also easy to produce pores; welding speed is too slow, the weld residual height will be too high, irregular shape; welded sheet or blunt edge size of the small weld, the welding speed too Slow, prone to burn through and so on.
【Measures】
Welding speed, welding quality and welding production efficiency have a significant impact, when used with the welding current, weld location (bottoming, filling welding, cover welding), the thickness of the weld, groove size selection of the appropriate welding speed, To ensure penetration, gas, welding slag easy to discharge, do not burn through, under the premise of forming a good selection of larger welding speed, in order to improve productivity efficiency.

4. Do not pay attention to control arc welding length
【phenomenon】
Welding is not based on the groove form, the number of welding layers, welding forms, electrode type and so appropriate to adjust the length of the arc. Due to improper use of welding arc length, it is difficult to obtain high quality weld.
【Measures】
In order to ensure the quality of the weld, welding generally use short-arc operation, but according to different situations to choose the appropriate arc length to obtain the best welding quality, such as V-shaped groove docking, corner of the first layer should be used Short arc to ensure penetration, and does not happen undercurrent phenomenon, the second layer can be slightly longer to fill the weld. Weld gap time is appropriate to use short arc, the arc can be a little longer when the arc, welding speed. Up welding arc should be the shortest to prevent molten iron downstream; vertical welding, horizontal welding in order to control the bath temperature, but also with small current, short arc welding. In addition, no matter what welding, in the course of the movement should pay attention to always keep the arc length is basically the same, in order to ensure that the entire weld melting width and penetration consistent.

5. Welding does not pay attention to control welding deformation
【phenomenon】
Welding not pay attention to the welding sequence, staffing, groove form, selection of welding methods and methods of operation and other aspects of control deformation, resulting in large deformation after welding, correction difficulties, increase costs, especially heavy plate and large parts, the correction is difficult , With mechanical correction can cause cracks or lamellar tear. Flame correction with high cost and poor operation easily lead to overheating of the workpiece. For the workpiece with high precision, it does not take effective control deformation measures, will lead to the workpiece installation size can not meet the requirements, or even cause rework or scrap.
【Measures】
The use of reasonable welding sequence and use the appropriate welding specifications and methods of operation, but also the use of anti-deformation and rigid fixation measures.