The top 10 issues most easily overlooked in welding

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During welding, attention is not paid to selecting the optimal voltage; whether it is for root pass, fill pass, or finish pass, and regardless of the size of the groove, the same arc voltage is used. In this case, it may not be possible to achieve the required penetration and width, leading to issues such as undercutting, pores, and spatter. Generally, depending on the specific situation, either a long arc or a short arc should be chosen to achieve better welding quality and efficiency. During welding, the welding current is not controlled; in order to speed things up, no bevel is used for the butt joints of medium-thick plates. The strength parameters decrease, sometimes not even meeting the standard requirements, and cracks appear during bending tests; this results in an unguaranteed performance of the welded joints, posing a potential risk to the structural safety. During welding, the welding current should be controlled in accordance with the process evaluation; a variation of 10–15% is allowed. The size of the root bevel should not exceed 6 mm. During docking, when the plate thickness exceeds 6 mm, a groove must be made for welding. Failing to pay attention to the welding speed and welding current, as well as to using the electrode diameter appropriately; not controlling the welding speed and welding current during welding, and failing to coordinate the electrode diameter with the welding position. When performing a root pass weld on fully penetrated corner joints, due to the narrow size of the root area, if the welding speed is too high, there is not enough time for gases and slag to be expelled from that area, which can lead to defects such as lack of penetration, slag inclusions, and pores at the root ； When welding the cover, if the welding speed is too fast, pores are also likely to form ； If the welding speed is too slow, the weld bead height will be too high and its shape will not be regular ； When welding thin plates or welds with a small root face, a too slow welding speed can easily lead to burn-through and similar issues. The welding speed has a significant impact on welding quality and production efficiency. When selecting it, an appropriate welding speed should be chosen in conjunction with the welding current, the position of the weld (root pass, fill pass, cap pass), the thickness of the weld, and the groove dimensions. A higher welding speed can be utilized to improve production efficiency, provided that full penetration is achieved, gases and slag can be easily removed, the weld does not suffer from burn-through, and good weld shape is obtained. Failure to control the arc length during welding; not adjusting the arc length appropriately based on factors such as the groove shape, number of welding layers, welding method, and electrode type. Due to improper use of the welding arc length, it is difficult to obtain high-quality welds. To ensure weld quality, short-arc welding is generally used during welding. However, the appropriate arc length can be selected depending on the specific circumstances in order to achieve the best welding quality. For example, in V-groove butt joints and fillet joints, a shorter arc should be used for the first layer to ensure full penetration without undercutting; the arc length can be slightly longer for the second layer in order to fill the weld completely. When the weld gap is small, a short arc should be used; when the gap is large, the arc can be slightly longer to increase the welding speed. The overhead welding arc should be as short as possible to prevent the molten iron from flowing downward ； When welding in the vertical or horizontal position, to control the pool temperature, it is also necessary to use a low current and a short arc. Lack of attention to controlling welding deformation: During welding, no effort is made to control deformation by considering factors such as the welding sequence, personnel arrangement, groove design, selection of welding parameters, and operating methods. As a result, significant deformation occurs after welding, making correction difficult and increasing costs. This is especially true for thick plates and large workpieces, where correction is particularly challenging; mechanical correction methods can easily cause cracks or layered tearing. Flame correction is costly, and improper operation can easily cause the workpiece to overheat. For workpieces with high precision requirements, failing to implement effective measures to control deformation can result in the installation dimensions not meeting the required standards, which may even lead to rework or scrap. Measures: Adopt a reasonable welding sequence, select appropriate welding specifications and procedures, and also implement counter-deformation and rigid fixation measures. During multi-layer welding, if welding is not carried out discontinuously and attention is not paid to controlling the interlayer temperature, thick plates are prone to develop cold cracks at the interface layers when interlayer temperature control is neglected; for example, if too much time passes between layers and welding continues without re-preheating ； If the interval between layers is too short or the temperature between layers is too high, it will also affect the properties of the weld and the heat-affected zone; this can lead to coarse grains, resulting in a decrease in toughness and ductility, and it creates potential risks for the joint. Measures: When welding thick plates in multiple layers, it is necessary to strengthen the control of the interlayer temperature. During the continuous welding process, the temperature of the base material being welded should be monitored, so that the interlayer temperature can remain as close as possible to the preheating temperature; the maximum interlayer temperature must also be controlled. In multi-pass welding, if slag is not removed and surface defects are not addressed before proceeding with the next pass, it can lead to defects such as slag inclusions, pores, and cracks in the weld, thereby reducing its strength. Additionally, this practice may cause spatter during the subsequent welding passes. This situation often occurs when welding thick plates; after each layer is welded, slag and defects are left unaddressed before moving on to the next layer. Procedure: When welding thick plates in multiple layers, each layer should be welded continuously. After each layer of welding is completed, the slag, surface defects on the weld, and spatter should be removed promptly. Any defects such as inclusions, pores, or cracks that could affect the quality of welding must be completely eliminated before continuing with welding. In joint butt or fillet weld combinations that require full penetration, insufficient dimensions of the weld corners are a problem. For T-joints, cross joints, fillet joints, and other types of butt or fillet weld combinations that need full penetration, inadequate dimensions of the weld roots can result in welding strength and stiffness that do not meet the design requirements. The same issue applies to the weld roots at the junctions between the web and the upper flange of crane beams or similar components, where fatigue analysis is required in the design. For butt joint combinations such as T-joints, cross joints, and corner joints that require full penetration, sufficient weld leg dimensions must be provided in accordance with the design requirements; generally, the weld leg size should not be less than 0.25t. For crane girders or similar webs designed with fatigue checks, the root size of the welds connecting them to the upper flange is 0.5t, and shall not exceed 10 mm. The allowable deviation for welding dimensions is 0–4 mm. Plugging weld rod ends or iron blocks into the joint gap during welding: Since it is difficult to fuse these weld rod ends or iron blocks with the workpiece during welding, this can lead to welding defects such as lack of fusion and incomplete penetration, thereby reducing the strength of the joint. Using rusty welding rod ends or iron blocks for filling makes it difficult to ensure consistency with the base material’s composition ； Using welding rod ends or iron pieces contaminated with oil, impurities, etc. as fillers can cause defects such as pores, slag inclusions, and cracks in the weld. All these situations will **reduce** the quality of the weld at the joint, failing to meet the quality requirements for welds specified in the designs and standards. Measures: (1) When the assembly gap of the workpiece is large but within the specified allowable range, and when this gap exceeds twice the thickness of the thin plate or is greater than 20 mm, the undercut areas should be filled using surfacing methods in order to reduce the assembly gap. It is strictly prohibited to use filled electrode tips or iron blocks for patch welding in the joint gaps. (2) When marking lines for part machining, care should be taken to leave sufficient cutting allowance and weld shrinkage allowance after cutting. The dimensions of the parts must be controlled properly; do not rely on increasing gaps to ensure the overall dimensions. For components with intersecting welds, if care is not taken in determining the welding sequence, and if the welding order is not arranged properly by analyzing the effects of weld stress release and weld stress on component deformation, welding is carried out randomly in various directions. As a result, the welds in different directions restrict each other, generating significant thermal contraction stresses that cause the plate to deform and become uneven; this can also lead to cracks in the welds. Measurements: For components with intersecting welds, a reasonable welding sequence should be established. When several intersecting welds need to be welded, the transverse welds that are prone to greater shrinkage and deformation should be welded first, followed by the longitudinal welds. This way, when welding the transverse welds, they won’t be restricted by the longitudinal welds; thus, the shrinkage stress in the transverse welds can be released without any constraints. This helps to minimize welding deformation and ensure weld quality. Alternatively, butt welds can be welded first, followed by fillet welds.