[Phenomena] During welding, the same arc voltage is selected regardless of the size of the groove, whether it is priming, filling, covering, or the size of the groove. In this way, the required penetration depth and width may not be achieved, and defects such as undercuts, pores, and splashes may appear.
[Measures] Generally, according to different situations, the corresponding long arc or short arc should be selected respectively to obtain better welding quality and work efficiency.For example, short arc operation should be used in order to obtain better penetration during bottom welding, and the arc voltage can be appropriately increased in order to obtain higher efficiency and penetration width during filler welding or cover welding.
[Phenomena] During welding, in order to speed up the progress, the butt weld of the medium and heavy plate is not grooved. The strength index decreases, or even fails to meet the standard requirements, and cracks appear during the bending test, which will make the performance of the welded joints unable to be guaranteed and pose a potential hazard to the structural safety.
[Measures] During welding, the welding current should be controlled according to the welding current in the process evaluation, allowing 10-15% to float, and the size of the blunt edge of the groove should not exceed 6mm. When butt joint, when the thickness of the plate exceeds 6mm, bevel must be opened for welding.
[Phenomena] When welding, do not pay attention to control the welding speed and welding current, and use the electrode diameter and welding position in harmony.For example, when bottom welding is performed on a fully penetrated corner seam, due to the narrow size of the root, if the welding speed is too fast, the root gas and slag inclusions do not have enough time to discharge, which is easy to cause incomplete penetration, slag inclusions, pores and other welding at the root. Defects; during cover welding, if the welding speed is too fast, it is easy to generate pores; if the welding speed is too slow, the weld height will be too high, and the shape will be uneven; when welding thin plates or welds with small blunt edges, the welding speed Too slow, prone to burn through and so on.
[Measures] Welding speed has a significant impact on welding quality and welding production efficiency. The selection should be based on welding current, weld position (backing welding, filler welding, cover welding), weld thickness, and groove size to select appropriate welding On the premise of ensuring penetration, easy discharge of gas and welding slag, no burning through, and good forming, a larger welding speed is selected to improve productivity and efficiency.
[Phenomena] During welding, the arc length is not properly adjusted according to the groove form, the number of welding layers, the welding form, and the electrode type. It is difficult to obtain high-quality welds due to improper use of the welding arc length.
[Measures] In order to ensure the quality of the welding seam, short arc operation is generally used during welding, but the appropriate arc length can be selected according to different situations to obtain the best welding quality, such as V-groove butt, fillet joint first The first layer should use a shorter arc to ensure penetration without undercutting, and the second layer can be slightly longer to fill the weld. When the weld gap is small, a short arc should be used. When the gap is large, the arc can be slightly longer and the welding speed can be accelerated. The overhead welding arc should be the shortest to prevent molten iron from flowing; in order to control the temperature of the molten pool during vertical welding and horizontal welding, small current and short arc welding should also be used.
In addition, no matter what kind of welding is adopted, attention should be paid to keep the arc length basically unchanged during the movement process, so as to ensure that the fusion width and penetration depth of the entire weld are consistent.
[Phenomena] During welding, we do not pay attention to controlling the deformation in terms of welding sequence, personnel arrangement, groove form, welding specification selection and operation methods, etc., resulting in large deformation after welding, difficulty in correction, and increased cost, especially for thick plates and large workpieces. Correction is difficult, and mechanical correction can easily cause cracks or laminar tearing. The cost of straightening with flame is high and the operation is not easy to cause the workpiece to overheat.For workpieces with high precision requirements, failure to take effective measures to control deformation will cause the installation size of the workpiece to fail to meet the requirements for use, and even cause rework or scrap.
[Measures] Adopt a reasonable welding sequence and select appropriate welding specifications and operation methods, and also adopt anti-deformation and rigid fixing measures.