Nema Enclosure Manufacturers-Welding Issues
13 Issues Easily Ignored While Welding Electrical Box Enclosure-Phenomenon + Solutions
How to make a certified NEMA rated, UL listed or IP rated Electrical Enclosures?There are many manufacturing process from material selection,metal laser ,cutting,bending,turning,folding,punching, stamping,Welding,Surface treatment and Assembly.There are details that we should focus on.But today,Zhongfeiya Tech are going to share with us the 13 issues easily ignored while welding electrical box enclosure.The relative phenomenons and solutions may help you a lot.
1. Do not pay attention to choosing the best voltage during welding construction of electrical cabinet.
[Phenomenon] When welding, no matter it is bottoming, filling, covering, no matter the size of the groove,we usually use the same arc voltage . In this way, the required penetration depth and penetration width may not be reached, and defects such as undercuts, pores, and splashes may occur.
[ Solutions 1] Generally, the corresponding long arc or short arc should be selected for different situations to obtain better welding quality and work efficiency. For example, short arc operation should be used in order to obtain better penetration in bottom welding, and the arc voltage can be appropriately increased in order to obtain higher efficiency and melting width in fill welding or cover welding.Wall Mount Electrical Enclosure Without Welding Undercuts, pores, and splashes.
[ Solutions 2]Use welding robots, automated mechanical equipment used for welding operations. Welding robots can realize production automation and effectively to achieve transformation and upgrading.Zhongfeiya Tech is equipped with welding robots machine while manufacturing metal electric enclosures.Find qualified NEMA electrical enclosures such as NEMA 1 enclosure, NEMA 2 enclosure, NEMA 3 enclosure,NEMA 3R enclosure,NEMA 4 electrical enclosure,NEMA 4x rated box,NEMA 12 enclosures,,NEMA 13 from Zhongfeiya Tech.
2. Welding not control welding current
[Phenomenon] During welding, in order to speed up the mass production of electric cabinets progress, the butt weld of the medium and thick plates shall not be grooved. The strength index drops, or even fails to meet the standard requirements, and cracks appear during the bending test. This will make the performance of the weld joint not guaranteed and pose a potential hazard to the structure safety of the sheet metal enclosure.
[ Solutions] When welding, the welding current should be controlled according to the process qualification, and 10-15% fluctuation is allowed. The size of the blunt edge of the groove should not exceed 6mm. When butt joints, when the plate thickness of metal sheet exceeds 6mm, grooves should be opened for welding.
3. Do not pay attention to the welding speed and welding current, and the diameter of the welding rod is used in coordination.
[Phenomenon] When welding, do not pay attention to controlling the welding speed and welding current, and use the electrode diameter and welding position in coordination. For example, when the bottom welding is performed on a fully penetrated corner seam, due to the narrow root size, 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 defects such as infusion, slag inclusions, and pores in the roots. ; During cover welding, if the welding speed of electrical box enclosure is too fast, it is easy to produce blowholes; if the welding speed is too slow, the weld reinforcement will be too high and the shape will be irregular; when welding thin plates or welds with small blunt edges, the welding speed is too high. Slow and easy to burn through.
[Solutions] Welding speed has a significant impact on welding quality and welding production efficiency. Choose appropriate welding according to welding current, welding seam position (bottom welding, filling welding, cover welding), welding seam thickness, and groove size. Speed, on the premise of ensuring penetration, easy discharge of gas and welding slag, no burning through, and good forming, a larger welding speed should be selected to improve productivity and efficiency.
4. Do not pay attention to controlling the arc length when welding weatherproof electrical enclosures.
[Phenomenon] When welding, the arc length is not adjusted appropriately according to the groove form, the number of welding layers, the welding form, and the electrode type. Due to improper use of the welding arc length, it is difficult to obtain high-quality welds.
[ Solutions] In order to ensure the quality of the weld, short arc operation is generally used when welding, but the appropriate arc length can be selected according to different situations to obtain the best welding quality, such as V-groove butt joints and corner joints. A shorter arc should be used for the layer to ensure penetration without undercutting. The second layer can be slightly longer to fill the weld. The 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 can be increased. The arc of the overhead welding should be the shortest to prevent the flow of iron water; in order to control the temperature of the molten pool during vertical and horizontal welding, small current and short arc welding should also be used. In addition, no matter what kind of welding is adopted, it is necessary to keep the arc length basically unchanged during the movement, so as to ensure that the melting width and penetration depth of the entire weld are consistent.
5. Welding does not pay attention to controlling welding deformation of electrical enclosure box.
[Phenomenon] When welding, we do not pay attention to control deformation from welding sequence, personnel arrangement, groove form, welding specification selection and operation method, etc., resulting in large deformation after welding, difficulty in correction, and increased costs, especially for thick plates and large workpieces. The correction is difficult, and it is easy to cause cracks or laminar tears with mechanical correction. The cost of flame correction is high and poor operation can easily 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 requirements for use, and even cause rework or scrap.
[ Solutions] Adopt a reasonable welding sequence, select appropriate welding specifications and operation methods, and adopt anti-deformation and rigid fixation measures.
6. Multi-layer welding is not continuous welding, and care is not taken to control the temperature between layers
[Phenomenon] When welding thick plates with multiple layers, do not pay attention to the temperature control between layers. If the interval between layers is too long, welding without reheating will easily cause cold cracks between the layers; if the interval is too short, the temperature between layers Too high (over 900°C) will also affect the performance of the weld and the heat-affected zone, and will cause coarse grains, resulting in a decrease in toughness and plasticity, and will leave potential risks to the joint.
[ Solutions] In the multi-layer welding of thick plates, the temperature between layers should be strengthened. The temperature of the base metal should be checked during the continuous welding process, so that the temperature between the layers can be as consistent as the preheating temperature. The maximum temperature should also be controlled. The welding time should not be too long. In case of welding interruption, appropriate post-heating and heat preservation measures should be taken. When welding is applied again, the re-heating temperature should be appropriately higher than the initial pre-heating temperature.
7. Multi-layer welds do not remove weld slag and weld defects on the surface of the weld, and then perform the lower layer welding
[Phenomenon] When welding thick plates with multiple layers, the lower layer is welded directly without removing the welding slag and defects after each layer is welded, which is likely to cause defects such as slag inclusion, pores, and cracks in the weld, which reduces the connection strength and also causes the lower layer welding. Time splash.
[ Solutions] When welding thick plates with multiple layers, each layer should be welded continuously. After each layer of welds is welded, the slag, weld surface defects and spatters should be removed in time, and slag inclusions, pores, cracks and other defects that affect the welding quality should be thoroughly removed before welding.
8. The size of the weld angle of the joint butt or corner butt combined weld that requires penetration is not enough
[ Phenomenon] T-joints, cross joints, corner joints and other butt joints or corner butt combined welds that require penetration, and the size of the weld feet is not enough, or the web and upper wing of crane beams or similar components designed with fatigue check requirements The size of the welding foot of the welding seam of the plate edge is not enough, and the strength and rigidity of the welding will not meet the design requirements.
[ Solutions] T-shaped joints, cross joints, corner joints and other butt joint welds that require penetration must be in accordance with the design requirements, and there must be sufficient welding foot requirements. Generally, the size of the welding foot should not be less than 0.25t (t is the joint Thinner plate thickness). The size of the weld leg of the crane beam or similar web plate and the upper flange that is designed with fatigue check requirements is 0.5t, and should not be greater than 10mm. The allowable deviation of welding size is 0～4 mm.
9. Welding the electrode head or iron block in the joint gap
[ Phenomenon] Because it is difficult to fuse the electrode head or iron block with the welded part during welding, it will cause welding defects such as infusion and infusion, which will reduce the connection strength. If it is filled with rusty electrode heads and iron blocks, it is difficult to ensure that the material is consistent with the material of the base material; if it is filled with electrode heads or iron blocks with oil stains, impurities, etc., it will cause pores, slag inclusions, cracks and other defects in the weld. These conditions will greatly reduce the weld quality of the joint and fail to meet the quality requirements of the design and specifications for the weld.
[ Solutions] When the assembly gap of the workpiece is large, but does not exceed the specified allowable range, and the assembly gap exceeds 2 times the thickness of the thin plate or greater than 20mm, the surfacing method should be used to fill in the recessed part or reduce the assembly gap. It is strictly forbidden to use filler welding rod head or iron block repair welding method in the joint gap. When the parts are processed and scribed, pay attention to the cutting allowance and the welding shrinkage allowance after cutting, and control the size of the parts. Do not increase the gap to ensure the overall size.
10. When plates of different thickness and width are used for butting, the transition is not smooth
[Phenomenon] When using plates of different thicknesses and widths for butt joints, do not pay attention to whether the thickness difference of the plates is within the standard allowable range. If it is not within the allowable range and no gentle transition treatment is performed, the welding seam will easily cause stress concentration and welding defects such as unfusion at the place higher than the thickness of the sheet, which will affect the welding quality.
[ Solutions] When the relevant regulations are exceeded, the weld shall be welded into a slope, and the maximum allowable value of the slope shall be 1:2.5; or one or both sides of the thickness shall be processed into a slope before welding, and the maximum allowable value of the slope shall be 1:2.5 , The slope of the structure that directly bears the dynamic load and requires fatigue calculation should not be greater than 1:4. When panels of different widths are butted, thermal cutting, mechanical processing or grinding wheel grinding should be used according to the factory and site conditions to make the transition smoothly, and the maximum allowable slope of the connection is 1:2.5.
11. Do not pay attention to the welding sequence for components with cross welds
[Phenomenon] For components with crossed welds, we do not pay attention to the reasonable arrangement of the welding sequence by analyzing the welding stress release and the influence of welding stress on the deformation of the components. Instead, the vertical and horizontal welds are randomly applied. The temperature shrinkage stress caused by the deformation of the board, the board surface is uneven, and may cause cracks in the weld.
[ Solutions For components with cross welds, a reasonable welding sequence should be established. When there are several vertical and horizontal cross welds to be welded, the transverse welds with larger shrinkage deformation should be welded first, and then the longitudinal welds, so that the transverse welds will not be constrained by the longitudinal welds and the shrinkage stress of the transverse welds Released under unconstrained conditions, can reduce welding deformation and ensure the quality of the weld, or weld the butt weld first and then the fillet weld
12. When the lap joint of section steel rods is welded by surrounding welding, continuous welding is applied at the corners
[Phenomenon] When the lap joint between the profiled steel rod and the continuous plate adopts surrounding welding, the welding seams on both sides of the rod shall be welded first, and the end welding seams shall be welded later, and the welding shall be discontinuous. Although this is beneficial to reduce welding deformation, stress concentration and welding defects are likely to occur at the corners of the rod, which affects the quality of the welded joint.
[ Solutions] When the lap joint of section steel rods is welded, it should be welded continuously at the corner at one time. Do not weld to the corner and then run to the other side to weld.
13. Equivalent strong butt joints are required, and the arc ignition plate and lead-out plate are not provided at both ends of the crane beam wing plate and the web plate.
[Phenomenon] When welding butt welds, full penetration fillet welds, and the welds between the flange plate and the web of the crane beam, the arc striking plate and lead plate are not added at the arc starting and lead-out points, so that when welding the start and end ends, Since the current and voltage are not stable enough, and the temperature at the start and end points is not stable enough, it is easy to cause defects such as unfusion, infusion, cracks, slag inclusion, and pores in the start and end welds, which reduces the weld strength and fails to meet the design requirements.
[ Solutions] When welding butt welds, full penetration fillet welds, and the welds of crane beam wing plates and web plates, pilot arc plates and lead plates should be set at both ends of the weld. After the defective part is led out of the workpiece, the defective part is then divided to ensure the quality of the weld.
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