08 Nov 2021
Arc ignition is the operating ability that must be mastered first to learn the welding technology of electrode arc welding. The arc ignition of the electrode arc welding machine generally adopts the contact short circuit ignition method, that is, the electrode and the workpiece are short-circuited when the arc is ignited, and then the electrode is opened to ignite the arc. The process of contacting a short circuit to ignite an arc ( Figure 1). According to different operating methods, the arc ignition type is divided into two types: percussion arc ignition and scratch arc ignition.
The first method is to strike to start the arc. Now align the end of the electrode with the weldment, and then bend your wrist down hard to make the electrode slightly hit the weldment and lift it up 2~4mm quickly to generate an arc. After igniting the arc, place your wrists flat and start welding with a certain arc length (Figure 2-a). The striking arc method is more difficult to master, and improper operation is likely to cause the welding rod to stick to the workpiece. The second method is to scratch the arc. The action is like drawing a match. First align the end of the electrode with the workpiece, and then twist the wrist to make the electrode scratch gently on the surface of the workpiece. Use gentle force and not too much, then lift the electrode by 2~4mm, and an arc will be generated at this time. . After the arc is ignited, the electrode should not leave the workpiece too high, and the arc length should be kept within a range that is compatible with the diameter of the electrode, so as to avoid arc failure caused by arc breaking. Flip your wrist quickly back to the original position, and then start welding (Figure 2-b). The scratch arc method is generally suitable for alkaline electrodes. Scratching arc ignition is relatively easy to master, but improper operation can easily damage the surface of the workpiece and cause arc scratches.
Precautions for arc ignition: First, if the welding rod sticks to the workpiece during arc ignition, do not panic. Do not swing the welding rod with excessive force, otherwise the end coating will fall off and the weld joint will be prone to pores and other defects. In the correct operation, swing the electrode from side to side for a few times, and then it can be separated from the workpiece. If it still cannot be separated, quickly loosen the welding tongs and cut off the power supply to avoid damage to the welding machine due to long short-circuit time. Second, when starting the arc, avoid direct welding from the original position. This is because the temperature of the steel plate is relatively low, and the electrode coating has not fully exerted its effect. When the arc is started, there will be a higher welding seam, a shallow penetration, and easy to produce pores, so the arc should be 10mm from the end. Start the arc at the place ( Figure 3). After ignition, lengthen the arc. Move to the end of the weld for preheating, and then lower the arc for welding after preheating. This arc ignition method can melt part of the metal when the arc passes through even if there are pores at the ignition arc, so that the pores are eliminated, and there is no arc ignition scratch. In order to ensure the penetration of the arc starting point, the arc can be properly swayed to ensure the residence time on both sides of the groove and form a molten pool of a certain size.
Knowing the method and precautions of arc ignition, we should also understand the arc closing technology. The arc closing of the weld bead refers to the arc closing method adopted at the end of a weld. If the arc is immediately broken when the arc is closed, an arc crater below the surface of the weldment will be formed. This not only reduces the strength of the weld joint, but also produces stress concentration, which leads to crater cracks. Here are a few ways to close the arc, which are also commonly used in electrode arc welding. The first is the reflow method. The welding arc moves to the end of the weld and stays there for a while, then changes the angle of the electrode and the welding direction to re-weld for a short period of time, and then break the arc after filling the arc crater. This method is suitable for welding with alkaline electrodes (Figure 4-a). The second method is to draw a circle to close the arc. When the welding arc moves to the end of the weld, the welding arc moves in a circular motion until the arc crater is filled, and then the arc is broken. This method is suitable for the arc closing of the weld when welding thick plates (Figure 4-b). The third method is repeated arc extinguishing and arc ignition. The welding arc extinguishes and ignites the arc at the end of the weld repeatedly until the arc crater is filled. This method is suitable for arc closing when welding thick or thin plates with high current. This method is not suitable for welding with alkaline electrodes (Figure 4-c).
The application of electrode arc welding welding technology is very wide, whether it is in construction projects or industrial production, it is extremely common, and it is also one of the most popular welding technologies in social development at this stage. It is used in the development of today's society. Plays an important role and meaning. The method of starting and closing the arc of electrode arc welding is the necessary knowledge to master the welding technology of electrode arc welding. It is very necessary to learn more welding knowledge and it is the foundation of becoming an excellent welder.
Keywords: welding machine
Originally published 08 Nov 2021, updated 08 Nov 2021.