The connection issue between the heat exchange tubes and the tube sheet

Manual TIG welding should work as well; since there is no automatic welding machine, manual welding is the only option, though automatic welding yields better results

Tube sheet thickness: 20 mm. Tubes: 14, wall thickness: 1 mm; arranged in a triangular pattern with a spacing of 1.25

Manual TIG welding can be used; the key is that the welder’s skills must be up to standard. The surface quality after manual TIG welding is not as good in appearance as that of automatic welding.

What should I pay attention to when welding? :loveliness:

Strictly adhere to the specified welding current and welding speed, use argon gas for protection, ensure the groove is thoroughly cleaned, and be careful when ending the weld to avoid shrinkage cavities

If the drawing specifications or the contract stipulate the use of automatic TIG welding, then it must be carried out in accordance with those requirements; otherwise, it is not necessary. However, whether it is manual TIG welding or automatic TIG welding, a welding procedure qualification is required, and welders must have the appropriate certifications to work.

:$ Go and find out what welding processes are

Welding process parameters for TIG welding I. Electrical parameter 1. Welding current The welding current in TIG welding is usually determined based on the material of the workpiece, its thickness, and the spatial position of the joint. As the welding current increases, the depth of penetration increases, while the width and height of the weld increase slightly, but by only a small amount. Either too high or too low a welding current can result in poor weld formation or welding defects. 2. Arc voltage: The arc voltage in tungsten inert gas welding is primarily determined by the arc length; as the arc length increases, the arc voltage rises, the weld width increases, and the penetration depth decreases. When the arc is too long and the arc voltage is too high, it can easily lead to incomplete welding and undercutting, as well as poor shielding effect. However, the arc length cannot be too short either. When the arc voltage is too low and the arc is too short, the welding wire is likely to come into contact with the tungsten electrode, causing a short circuit that can damage the tungsten electrode; in addition, tungsten inclusion is likely to occur. Therefore, the arc length is usually set to be approximately equal to the diameter of the tungsten electrode. 3. Welding speed: As the welding speed increases, the penetration depth and width decrease. If the welding speed is too high, lack of fusion and incomplete welding can occur; if it is too low, the weld seam becomes wide, and defects such as porosity and burn-through may arise. In manual TIG welding, the welding speed is usually adjusted as needed, depending on the size of the weld pool, its shape, and the fusion condition on both sides. II. Other parameters 1. Nozzle diameter: As the nozzle diameter (referring to the inner diameter) increases, the flow rate of the protective gas must be increased; this results in a larger protection area and better protection effects. However, when the nozzle is too large, it not only increases argon consumption but also makes it difficult to observe the welding arc and the welding process. Therefore, the commonly used nozzle diameter is generally preferably in the range of 8 mm to 20 mm. 2. Distance between the nozzle and the workpiece The distance between the nozzle and the workpiece refers to the gap between the nozzle’s end face and the workpiece; the smaller this distance, the better the protection effect. Therefore, the distance between the nozzle and the workpiece should be as small as possible, but too small a distance makes it difficult to observe the molten pool; hence, the distance between the nozzle and the workpiece is usually set between 7 mm and 15 mm. 3. Tungsten electrode protrusion length: To prevent the arc from overheating and damaging the nozzle, the tip of the tungsten electrode should generally extend outside the nozzle. The distance from the tip of the tungsten electrode to the nozzle surface is the length to which the tungsten electrode extends. The shorter this extension, the closer the distance between the nozzle and the workpiece, resulting in better protection; however, if it is too short, it will hinder the observation of the molten pool. When welding butt joints, it is advisable for the tungsten electrode to extend 5 mm to 6 mm ； When welding fillet welds, it is better for the tungsten electrode to extend 7 mm to 8 mm. 4. Gas protection method and flow rate: In TIG welding, in addition to using a circular nozzle to protect the welding area, the nozzle can also be made flat depending on the welding space (such as in narrow-gap TIG welding) or taken on other shapes. When welding the root weld, the weld on the back side of the workpiece can be oxidized due to exposure to air; therefore, back-gas shielding must be used. Argon and helium are the safest gases for back-gassing when welding all materials. Nitrogen is the safest gas for back-gassing protection during the welding of stainless steel and copper alloys. The gas flow rate range for back inflation protection using general inert gases is 0.5 to 42 L/min. As the nozzle diameter and the length of the tungsten electrode protruding increase, the gas flow rate should also increase accordingly. If the gas flow rate is too low, the protective gas flow becomes weak, resulting in poor protection; this can lead to defects such as pores and oxidation of the weld seam ； If the gas flow rate is too high, turbulence is likely to occur, the protection effect will be poor, and it will also affect the stable combustion of the arc. When inflating the pipe fitting, an appropriate gas outlet should be provided to prevent excessive gas pressure inside the pipe during welding. When 25 to 50 millimeters remain before the completion of welding at the root pass, it is necessary to ensure that the pressure of the gas filled inside the pipe is not too high, in order to prevent the welding pool from being blown out or the root from becoming concave. When using argon for backside shielding in pipe fitting welding, it is best to introduce the gas from below so that air can be expelled upward, and to position the gas outlet away from the weld.

Yes, it is best to use automatic welding, as it ensures good weld quality

Manual welding is also an option, but automatic welding offers better quality and efficiency