In the process of welding, the total action of the weld is called transport rod. The transport rod includes three actions: feeding along the electrode axis, longitudinal movement of the weld axis and transverse swing.
1) The basic action of the transport rod
After the electrode is sent along the axis to the melt tank to melt the electrode, the length of the arc can be maintained unchanged, so the feeding speed of the electrode to the melt tank is equal to the melting speed of the weld rod. If the welding rod feeding speed is less than the melting speed of the welding rod, the length of the arc will gradually increase, resulting in arc breaking; If the welding rod feeding speed is too fast, the arc length is quick to shorten.
The welding rod does not move vertically in the welding direction, which causes the welding rod to form a weld between the molten metal and the molten base metal.weaving. The lateral swing of the welding rod is to obtain a certain width of the weld, and to ensure the good fusion of both sides of the weld. The swing range shall be determined according to the wide bottom of the weld and the electrode diameter. Lateral swing to be uniform, to obtain the required wide bottom and speed weld. The normal weld width generally does not exceed 2- -5 times of the electrode diameter.
2) The beginning of the weld: the beginning of the weld refers to the weld at the first place. The residual height of this part of the weld is easy to increase, which is because the temperature of the welding parts is low at the beginning of welding, and the temperature of this part of the metal can not be quickly increased after the arc induction, so the melting depth is shallow, and the residual height is large. In order to avoid this situation, the arc can be slightly longer after igniting the arc, the necessary preheating of the welding parts, and then appropriately lower the arc into normal welding.
(3) Application of arc welding method and arc welding method: as the electrode arc welding double-sided forming base welding process,it can be divided into Continuous arc welding method Broken arc welding method.
1) Continuous arc welding method: It is small welding current and smaller diameter of welding rod, in the welding process, the arc keep stable combustion, to the groove gap forward evenly swing, make the welding back form uniform welding method, the method is simple operation, small changes, easy to master, and the weld back form dense, neat, good internal quality, excellent mechanical properties, is widely used for the international and domestic, its disadvantage is due to the limitation of groove gap. The problem of difficult joint of acid electrode is more prominent. Arc welding method is mainly used for alkaline welding rod welding and vertical welding and elevation welding of acid welding rod centre.
2) Broken arc welding method: In the welding process by rhythmic to control the arc in and arc out, so as to control the pool temperature, get good welding joint and internal quality of welding method, the advantage is can use large groove gap, using large welding current, for thin welding double forming, welding current is not greatly restricted, arc welding welding method is mainly used for acid rod flat welding, horizontal welding and pipe plate thin wall welding, this welding method is more practical in production and maintenance, but, compared with arc welding method, arc welding method is difficult to master, the welder basic skills The requirements are also high.
(4) Weld joint: the connection between the rear weld and the first weld is called the weld joint. Due to the limitation of the long bottom of the welding rod, the front and back of the welding joint is inevitable, but the weld joints should be uniform, and prevent the weld joint is too high, disconnect, inconsistent width and other defects. There are four kinds of welding joint: intermediate joint: after welding weld welding from the end of the first welding, the arc pit about 10mm, the arc length should be slightly longer than the normal welding, and then move back to the arc pit, lower the arc and slightly swing, and then forward normal welding. This joint method is one of the most used, Suitable for single layer welding and multilayer welding surface joint.
1) Back joint: the head of the two welds, the head of the first weld is slightly lower, the rear welding weld must be slightly ahead of the beginning of the front weld, and then slightly elongate the arc will gradually lead the arc to the beginning of the forward weld, and cover the end of the front weld, after the welding is flat, and then move to the welding direction.9
2) Opposite joint: this is the final connection of two welds. When the rear welding weld reaches the first welding weld, the welding speed should be slightly slower. After filling the pit of the first weld, then weld a little forward at a faster speed, and then extinguish the arc.
3) Section welding head: this is the beginning of the welding weld and the first welding, the welding to the beginning of the front welding weld, the welding Angle should be changed, so that the electrode points to the back end of the front weld, elongate the arc, after the formation of the melting pool, then lower the arc, move back, and finally return to the original melting pool to close the arc. The smoothness of the joint connection or not is related to the operation technology of the welder, as well as to the temperature of the joint. High temperature, the more smooth of the connection. Therefore, the middle joint requires the arc to be short, and the welding rod should be fast. During multilayer welding, the layer should be staggered to improve the tightness of the weld. In addition to the weld When the indirect head, the welding slag can not be cleaned. Before the other joints, the welding slag at the joint must be removed first, otherwise the joint can not be connected. If necessary, the joint can be polished into an inclined plane before the joint.
(5) The end of the weld: the end of the weld refers to how to finish arc after welding.
1) At the end of the welding, the weld should be finished. At the end, also maintain the normal temperature of the molten pool to facilitate the weld joint. There are many kinds of ending methods, including repeated arc breaking ending method, circle ending method, back welding ending method and transfer ending method. For single-sided welding and double-sided forming, the welding ending mainly adopts repeated arc breaking ending method and back welding ending method. This small repeated arc breaking method is generally used for the weld ending of acid welding rod, and the back welding ending method is mostly used for the weld ending of alkaline welding rod. If the arc is suddenly extinguished, the weld will have a sunken arc pit on the welding surface, reducing the strength of the weld end, and easy to cause arc pit crack . If the arc is quickly pulled off at the end, the gas in the liquid metal has too late to escape, and it is easy to produce pores and other defects. In order to overcome the defects of the arc pit, the following methods can be used to end, repeated arc closing method: when the electrode is moved to the end of the weld, the arc pit is repeated for several times until the arc pit is filled. This method is suitable for the weld ending of sheet and high current welding, but not for alkaline welding electrode.
2) Ring ending method: when the electrode is moved to the end of the weld, the circle movement is made at the arc pit until the arc pit is filled and then the arc is broken. This method is suitable for the ending of the thick plate.
3) Transfer ending method: when the electrode is moved to the end of the weld, stop at the arc pit, slowly raise the arc, and then lead to the base groove at the edge of the weld. At this time, the molten pool will gradually shrink, and generally no defects after solidification. Suitable for the ending of electrode replacement or temporary arc stop.
