Basic operation of a welding rod

Basic professional terms, welders or to know. You can’t just burn. You don’t know anything else. A electrode from head to tail, there are several steps, in case the film is not qualified to find the problem, know the problem in which step. One question three do not know, dry for many years or a general welding, still welding reinforcement, in situ. If you want to improve your skills, your professional knowledge should also improve. The basic operation of electrode arc welding is arc starting, strip moving and ending. Whether these three actions are standard or not is the key to determine the welding quality. (1) arc ignition Arc initiation is the production of electric arc. Electrode arc welding is to use low voltage, high current discharge to generate an arc, relying on the electrode instantaneous contact with the workpiece. When starting the arc, the electrode end must contact the surface of the welding piece to form a short circuit, and then quickly lift the electrode up 2 ~ 4mm distance, at this time the arc is ignited. There are two ways to start the arc: the collision method and the scratch method. Arc method (1) touch attack Also known as point contact method or percussion method. Bump method is the welding rod and the workpiece to maintain a certain distance, and then vertical fall, so that gently knock on the workpiece, short circuit, and then quickly lift the electrode, arc starting method. This method is suitable for welding in various positions. Wipe HuaFa (2) Also known as line contact method or friction method. Scratch method is to slide the electrode on the groove, into a line, when the end contact, short circuit, because of the contact surface is very small, the temperature rises sharply, before melting, the electrode will be raised, arc starting method. This method is easy to master, but easy to stain the groove, affecting the welding quality. The two arc-starting methods mentioned above should be applied flexibly according to the specific situation. Although it is easy to start the arc with the scratch method, it will scratch the surface of the weldment if it is not used properly. In order to minimize the surface damage of the welding parts, the welding groove should be scratched, the length of the scratched with 20 ~ 25mm is appropriate. In the narrow place welding or welding parts surface is not allowed to have scratches, should use the impact method of arc starting. It is difficult to master the collision arc starting method, the lifting action of the electrode is too fast and the electrode is too high, the arc is easy to extinguish; Moving too slowly may cause the electrode to stick to the workpiece. When the electrode is stuck to the workpiece, the electrode should be quickly swung around, so that it is separated from the weldment; If it still cannot be separated, immediately loosen the welding clamp to cut off the power supply, so as not to damage the welding machine for too long short circuit. (3) Technical requirements of arc ignition At the arc starting, due to the low temperature of the steel plate, electrode skin has not fully played its role, will make the welding seam at the arc starting point is higher, the depth of penetration is shallow, easy to produce pores, so usually should be in the weld starting point behind 10mm arc starting, after the ignition arc elongated arc, and quickly move the arc to the starting point of the weld for preheating. After preheating, the arc will be short, the arc length of the acidic electrode is about equal to the diameter of the electrode, the arc length of the alkaline electrode should be about half of the diameter of the electrode, normal welding. Even if the air hole is produced at the arc starting point, this part of metal can be remelted when the arc passes through for the second time, so that the air hole is eliminated and the arc starting scar will not be left. In order to ensure that the starting point of the weld can be welded through, the electrode can be made appropriate lateral swing, and a little pause on both sides of the root of the groove, to form a certain size of the pool. Arc initiation has a certain influence on welding quality, often because of arc initiation is not good and caused by the initial welding defects. To sum up, the following points should be done when starting the arc: (1) The workpiece groove is free from oil and rust, so as not to affect the conductivity and prevent the molten pool from producing oxide. (2) in contact, the electrode lift time should be appropriate. Too fast, the gas is not ionized, the arc may be extinguished; Too slow, so that the electrode and the workpiece bonding together, unable to ignite the arc. (3) the end of the electrode should have a bare part in order to start the arc. If the electrode end is unevenly exposed, the file should be used before the use of processing, to prevent in arc starting, hit too hard so that the drug skin off into a block, causing arc blowing and arc starting instant protection. (4) the arc setting position should be selected appropriately, starting arc or re-starting arc due to welding interruption, generally should be 10 ~ 20mm from the beginning of the solder joint behind the arc, and then move to the beginning of the solder joint, to molten pool to continue to move the electrode, in order to eliminate the possible arc setting defects. (2) Shipment After the arc is ignited, the normal welding process begins. For good welding and seam forming, the electrode must be in constant motion. The movement of the electrode is called the transport. Transport strip is the specific performance of welder operation skill level. The quality of the weld and the shape of the weld are mainly determined by the strip. The strip is composed of three basic movements, which are the feeding movement of the electrode, the transverse swing movement of the electrode and the movement of the electrode along the weld. Three basic movements of the electrode 1 – electrode feed 2 – electrode swing 3 – moving along the weld (1) welding rod feeding movement It is mainly used to maintain the required arc length. As the heat of the arc melts the electrode end, the arc becomes longer and tends to extinguish. To keep the arc burning, the electrode must be sent to the pool until the whole electrode is welded. In order to ensure a certain arc length, the electrode feeding speed should be equal to the melting speed of the electrode, otherwise it will cause the change of arc length, affect the weld width and depth. (2) the electrode swings and moves along the weld These two movements are closely related, and are more varied and difficult to master. A certain width, height and depth of weld can be obtained through the joint action of the two. The so-called welding speed is the length of welding seam completed per unit time. Welding speed is too slow, will be welded into a wide and local uplift of the weld; Too fast, will be welded into intermittent slender weld; When the welding speed is moderate, the welding surface can be smooth, the welding wave is careful and uniform. (3) Method of shipment In order to control the temperature of the molten pool and make the weld have a certain width and height, the following methods are often used in production. 1) Straight line conveyor method When using the linear strip welding method, it should keep a certain arc length, and the electrode does not swing and moves along the welding direction. Because the electrode does not swing horizontally at this time, the welding depth is larger, and the width of the weld is narrow. Under normal welding speed, welding wave is full and smooth. This method is suitable for plate thickness 3 ~ 5mm without opening groove butt flat welding, multi-layer welding of the first layer and multi-layer multi-channel welding. 2) Straight-line round-trip conveyor method This method is the end of the electrode along the longitudinal weld line swing back and forth, mainly suitable for thin plate welding and joint gap larger weld. It is characterized by fast welding speed, narrow weld and fast heat dissipation. 3) Zigzag movement method This method is to make the end of the electrode zigzag continuous swing and move forward, on both sides of the pause for a moment, to prevent the occurrence of edge defects. This technique is easy to operate and widely used for the welding of thick steel plates. It is suitable for flat welding, vertical welding, vertical welding butt joint and vertical welding corner joint. 4) Crescent-shaped moving strip method This method is to make the electrode end along the direction of the welding crescent shape swing left and right, and on both sides of the appropriate position for a moment to stop, so that the edge of the weld has enough depth to prevent defects bite. This method is suitable for inverted, vertical, flat welding position and the need for full weld. The scope of application is basically the same as the zigzag strip method, but the weld residual height is larger. Its advantage is that it can make the metal melt well, and has a longer holding time, and the gas and slag in the molten pool easily float to the surface of the weld, which is conducive to obtaining high quality weld. 5) Triangular stripe method This method is to make the electrode end for continuous triangular movement, and constantly moving forward. According to the different scope of application, it can be divided into oblique triangle and regular triangle. The oblique triangle strip method is suitable for welding T – shaped joint inverted weld and transverse weld with groove. It is characterized by the swing of the electrode to control the melting of metal, and promote the formation of a good weld. Equilateral triangle strip method is only applicable to the vertical welding of butt joint and T-joint with groove opening. It is characterized by a thick weld section, which is conducive to improving productivity, and it is not easy to produce defects such as slag inclusion. 6) Circular movement Move the electrode end in a continuous circle and keep moving forward. This kind of conveyance method divides positive circle and oblique circle two kinds. The circular moving strip method is only suitable for welding thick workpiece flat weld, its advantage is that it can make the molten metal has a high enough temperature, conducive to gas escape from the molten pool, can prevent the weld porosity. Oblique circle moving strip method is suitable for T – shaped joint transverse welding (flat fillet welding) and inverted welding as well as butt joint transverse weld, which is characterized by the control of molten metal from gravity, can prevent metal liquid dripping, contribute to weld forming. (3) Closing When the arc is interrupted and the welding is finished, the arc pit at the end shall be filled. If the arc is terminated immediately, an arc pit lower than the surface of the weldment will be formed. The phenomenon of loose, crack, porosity, slag inclusion and so on often appear in the arc pit, so the ending action when the weld is completed is not only to extinguish the arc, but also to fill the arc pit. The closing actions are as follows: (1) Circle ending method When the electrode is moved to the end of the weld, it moves in a circle until the arc pit is filled and then the arc is broken. It is mainly used for finishing thick plate welding. (2) Repeated arc breaking end method At the end, the electrode in the arc pit repeatedly quenching, arc several times, until the arc pit is filled. This method is generally suitable for thin plate and high current welding, but alkaline electrode should not be used, because it is easy to produce pores. (3) Backweld ending method Move the electrode to the end of the weld immediately stop, and change the electrode Angle back welding a short section. This method is suitable for alkaline electrode. When changing electrode or temporary arc stop, the arc should gradually lead to the inclined front of the groove, and slowly raise the electrode, so that the molten pool is gradually reduced. 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