Welding rod arc welding operation technology

【Summary Description】 Electrode arc welding operation technology. In all kinds of welder training materials or welder manual, the operation technology of welding rod arc welding is introduced in detail, and the main points are briefly described here. 1 Arc striking, transportation and closing. (1) Arc strike The arc is ignited by the end of the electrode near the starting point of the weld. Usually used to ignite by scratching and tapping. The scraping method is to scrape the end of the electrode on the surface of the weldment. Similar to strike a match. Scraping must be carried out in the groove, and the arc starting point is preferably selected on the welding part about 10mm away from the arc starting point of the welding seam. Immediately after ignition, normal welding is carried out in the welding direction. The welding passes through the origin fire point and is remelted, thereby eliminating the arc scar or ball drop weld metal that may remain at this point. The tapping method is to make the electrode perpendicular to the arcing point on the weldment, gently touch the arcing point at the end, and immediately lift it. The operation method after ignition is the same as the scraping method described above. The impact force should not be too strong, otherwise the coating will fall off into pieces, causing arc instability and affecting the welding quality. Once the arc is extinguished during the welding process, the arc must be reignited. It is best to hit the weldment again immediately before the end of electrode cooling, which is conducive to reburning, because the hot drug skin is easy to become a conductor, especially for electrodes containing a large amount of metal powder. The starting point of the reignition arc shall be on or near the crater to be welded. The arc must be restarted when the electrode is replaced. Arc starting point should be selected on the front weld crater or before the front weld. After ignition, move the arc backward to fill the crater, and then continue to weld forward. Arc striking at non-welding parts is not allowed, otherwise defects such as pits, welding beading or cracks will be left during arc striking. (II) transport conditions; When welding, the shape and size of the molten pool can be controlled by correct conveying, so as to obtain good fusion and weld formation. There are three basic movements in the process of conveyor belt, namely, forward movement, swing movement and feeding movement. 1) The forward action is the action of moving the electrode end forward along the axis of the weld. Its speed represents the welding speed and can affect the welding heat input and the cross-sectional area of the weld metal. 2) The swing action is to make the electrode terminal swing horizontally in the vertical direction. The way, amplitude and speed of the swing directly affect the width and penetration of the weld, as well as the fusion on both sides of the groove. 3) The feeding action is the action of continuously feeding the electrode to the molten pool along its own axis. When the electrode feed speed is the same as its melting speed, the arc length is stable. If the wire feeding speed is slower than the melting speed, the arc length becomes longer, the melting depth becomes shallower, the melting width increases, the arc drift is unstable, the protection effect becomes worse, and the spatter is large. Therefore, in general, it is desirable to weld at a feed rate equal to or slightly greater than the melting rate and at an arc length equal to or less than the electrode diameter. Skilled welders can continuously change and coordinate these three actions according to the form of welded joint, weld position, weldment thickness, electrode diameter and welding current, as well as changes in the shape and size of the molten pool during the welding process, so as to control the molten pool within the required shape and size range. Table 3 lists the commonly used modes of transport and their scope of application. (3) End the arc. At the end of welding, if the arc is broken immediately, a crater will be formed at the end of the weld, which will reduce the working section of the weld, thereby reducing the strength of the joint, generating crater cracks, and also causing stress concentration. Therefore, the crater must be closed after it is filled. Commonly used arc closure methods are:. 1) Arc closure method When the arc moves to the end of the weld, the end of the electrode moves in a circular motion until the crater is filled, and then the arc is disconnected. This method is suitable for thick plate welding. 2) Return welding arc closing method When the arc moves to the end of the weld, stop for a while, and change the angle of the electrode to make it flow back for a short period of time, and then pull the arc off. This method is suitable for the welding of alkaline electrodes. 3) Repeated arc extinguishing reignition method The arc is extinguished and restarted several times at the end of the welding until the arc pit is filled. Suitable for high current or thin plate welding occasions.

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