Beginner welding should pay attention to what problems

Welding problems
Beginner welding should pay attention to what problems
[Phenomenon]
During welding, the same arc voltage is selected regardless of the size of the groove, whether it is bottoming, filling or covering. In this way, the required penetration depth and width may not be reached, and defects such as undercut, pores and splash may occur.
[Measures]
Generally, the corresponding long arc or short arc should be selected for different situations to get better welding quality and work efficiency. For example, in order to obtain a better penetration depth during bottoming welding, short arc operation Ⅲ filling welding or cover surface welding should be used to increase the arc voltage appropriately in order to obtain higher efficiency and melting width.
2. Welding without control
[Phenomenon]
During welding, in order to catch up with the progress, the butt weld of medium and heavy plate shall not be beveled. The strength index decreases, even fails to meet the standard requirements, and cracks appear during bending test, which will make the performance of weld joints can not be guaranteed and pose potential hazards to structural safety.
[Measures]
The welding shall be controlled according to the welding current in the process qualification, and 10 ~ 15% floating is allowed. The size of the blunt edge of the groove should not exceed 6mm. When butt joint, when the plate thickness exceeds 6mm, the groove shall be opened for welding.
3, do not pay attention to the welding speed and welding current, the diameter of the electrode is used in coordination
[Phenomenon]
When welding, do not pay attention to control the welding speed and welding current, the diameter of the electrode and the welding position are used in coordination. For example, when backing welding the full penetration corner seam, due to the narrow root size, if the welding speed is too fast, the root gas and slag inclusion do not have enough time to come out, which is easy to cause defects such as incomplete penetration, slag inclusion and pores at the root. When welding the cover surface, if the welding speed is too fast, it is also easy to produce pores. If the welding speed is too slow, the weld surplus height will be too high and the appearance will not neat; when welding thin plates or small welds with blunt edges, the welding speed is too slow and burn through is easy to occur.
[Measures]
Welding speed has a significant impact on welding quality and welding production efficiency. When selecting, appropriate welding speed is selected according to welding current, weld position (backing welding, filling welding, cover surface welding), weld thickness and groove size. On the premise of ensuring penetration, easy discharge of gas and welding slag, no burning through and good forming, larger welding speed is selected to improve productivity and efficiency.
4. Do not pay attention to control arc length during welding
[Phenomenon]
During welding, the arc length shall not be properly adjusted according to the groove form, welding layer number, welding form, welding rod type, etc. Due to the improper use of welding arc length, it is difficult to obtain high-quality welds.
[Measures]
In order to ensure the weld quality, C short arc operation is generally adopted during welding, but appropriate arc length can be selected according to different situations to obtain the optimal welding quality. For example, shorter arc should be used for the first layer of V-shaped groove butt joint and angle joint to ensure penetration and no undercut. The second layer can be slightly longer to fill the weld. Short arc should be used when the weld gap is small, and the arc can be slightly longer when the gap is large, and the welding speed is accelerated. The overhead welding arc should be the shortest to prevent the molten iron from flowing down; 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 welding is adopted, attention should be paid to keeping the arc length basically unchanged during the movement, so as to ensure that the melting width and penetration depth of the whole weld are consistent.
5, welding does not pay attention to control welding deformation
[Phenomenon]
During welding, the deformation is not controlled from the aspects of welding sequence, personnel arrangement, groove form, welding specification selection and operation method, etc., which leads to large deformation after welding, difficulty in correction and increased cost, especially for thick plates and large workpieces, which are difficult to correct and easy to cause cracks or lamellar tearing by mechanical correction. The cost of flame correction is high and the operation is not good, which is easy to cause the workpiece to overheat. For workpieces with high precision requirements, if effective deformation control measures are not taken, the installation size of the workpiece will not meet the use requirements, and even cause rework or scrap.