What Is Electric Welding?

Electric welding refers to a welding method that uses electrical energy, through heating or pressure, or a combination of both, with or without filling materials to achieve atomic bonding of the weldment. The processing equipment used for electric welding is called electric welding machine. ^[1]

Electric welding is a welding operation realized by using electrodes to melt the metal parts where they need to be connected by high temperature arc. Its working principle is: through the commonly used 220V or 380V voltage,

Electric welding was developed at the end of the 19th century with the development of the power industry.

In 1885, HH Benaldos of Russia discovered a carbon arc.

In 1887, American E. Thomson (Elihu Thomson) invented resistance welding for thin plate welding.

At the beginning of the 20th century, hand arc welding has entered a practical stage. In the 1920s, the automatic arc welding machine was made in the United States.

In 1930 the United States invented submerged arc welding.

In the 1940s and early 1950s, tungsten and fused electrode inert gas shielded welding, and carbon dioxide gas shielded welding were successively introduced in the United States and the Soviet Union, which promoted the application and development of gas shielded arc welding.

In 1951, the Soviet Union invented electroslag welding, which became an efficient welding method for large thickness weldments.

In the 1950s, ultrasonic welding, friction welding, and diffusion welding were successively introduced in the United States and the Soviet Union. The emergence of plasma arc welding, electron beam welding, and laser welding in the late 1950s and 1960s marked the development of high power density fusion welding, making many materials and structures difficult to weld by other methods.

Today, electric welding has been widely used in various industrial sectors such as machinery, electronics, construction, marine, aerospace, aviation, and energy. The weight of welded steel structural parts has accounted for about 45% of world steel production. The proportion of welded structures of aluminum and aluminum alloys is also increasing. Looking ahead, on the one hand, new welding methods, welding equipment and materials for welding will be further developed, and the welding process performance and welding quality will be improved and improved; on the other hand, the level of mechanization and automation of the welding process will be further improved. Welding robots will be further promoted. ^[1]

Welding methods are usually divided according to the heating and pressing conditions during welding.

The welding operation was observed and performed under a mask. Due to unclear vision and poor working conditions, to ensure the quality of welding, not only must have more skilled operating techniques, but also a high degree of concentration.

Before welding, the surface within 20mm of both sides of the workpiece joint should be cleaned (such as eliminating rust, oil, and moisture), and the metal at the end of the electrode core should be exposed for short-circuit arc starting. There are two methods of arc striking: percussion method and scratch method. The scratch method is easier to master and suitable for beginner arc operation.

I. Pilot Arc

(1) Wiping method. Align the electrode with the weldment first. Then wipe the electrode lightly like a match on the surface of the welding piece, ignite the arc, and then quickly lift the electrode 2 to 4 mm, and make it burn stably.

(2) Percussion. Align the end of the electrode with the welding piece, and then bend your wrist to make the electrode slightly touch the welding piece, and then quickly lift the electrode 2 to 4mm. After the arc is ignited, the wrist is flattened to keep the arc burning steadily. This arc starting method does not scratch the surface of the weldment, and is not limited by the size and shape of the surface of the weldment. Therefore, it is the main method used in the welding process. However, the operation of this arc ignition method is not easy to master, and it is necessary to improve proficiency.

Second, the article

Strip transport is the most important link in the welding process, and it directly affects the appearance and internal quality of the weld. After the arc is ignited, there are several basic movements of the electrode on the normal operating surface: gradually feeding in the direction of the molten pool, gradually moving in the direction of welding, and swinging laterally.

(1) Linear transport method. When welding by this method, the welding rod does not swing laterally and moves linearly along the welding direction. It is commonly used for butt-welding of -shaped grooves, the first layer welding of multi-layer welding or multi-layer multi-pass welding.

(2) Linear reciprocating strip method. When welding by this method, the end of the electrode swings back and forth along the longitudinal direction of the weld. It is characterized by fast welding speed, narrow welding seam and fast heat dissipation. It is suitable for the first layer of multi-layer welding with a large gap between the thin plate and the joint.

(3) Zigzag strip method. When welding by this method, the end of the electrode is continuously zigzag and moved forward, and it stops for a moment on both sides. The purpose of the swing is to control the flow of molten metal and obtain the necessary weld width to obtain better weld formation. This method of transporting bars is widely used in production, and is mostly used for welding of thick steel plates, butt joints of vertical welding, overhead welding, vertical welding, and fillet welding of vertical welding.

(4) Crescent strip method. When welding by this method, the end of the welding rod swings in a crescent shape along the welding direction. The speed of swing depends on the position of the weld, the type of joint, the width of the weld and the value of the welding current. At the same time, it is necessary to stay for a while on both sides of the joint. This is to make the edge of the weld have sufficient penetration to prevent undercuts. The characteristics of this strip transport method are that the metal melts well, has a longer holding time, the gas is easy to precipitate, and the slag is easy to float on the surface of the weld. The quality of the weld is higher, but the remaining temperature of the weld is higher. . The application range of this strip transport method is basically the same as the zigzag strip transport method.

(5) Triangle method. When using this method of welding, the end of the electrode performs a continuous triangle movement and moves forward continuously. According to the different forms of swing, it can be divided into two types: oblique triangle and regular triangle. The oblique triangle strip method is suitable for welding T-joint welds and beveled transverse welds at flat and overhead welding positions. Its advantage is that it can borrow Welding of the electrode to control the molten metal and promote good weld formation. The regular triangle strip method is only applicable to the vertical welding of butt joints and T-shaped joints with open bevels. It is characterized by the ability to weld thicker sections of welds at one time, and it is not easy to produce defects such as slag inclusion, which is conducive to improving production effectiveness.

(6) Circle-shaped strip method. When using this method of welding. The end of the electrode continuously moves in a circle or oblique circle, and moves forward continuously. The straight circle strip method is suitable for welding flat welds of thicker weldments. Its advantages are the long existence of the molten pool and the high temperature of the molten pool metal, which is conducive to the precipitation of oxygen, nitrogen and other gases dissolved in the molten pool. The slag floats up. The oblique circle method is suitable for horizontal and vertical T-joint welds and horizontal welds of butt joints. Its advantage is that it is beneficial to control the molten metal from being affected by gravity and cause the phenomenon of dripping, which is beneficial to the formation of welds.

Third, the welding seam ends

(1) Circle ending method: When the electrode moves to the end of the bead, use the movement of the wrist to make a circular motion until the arc crater is filled and then the arc is broken. This method is suitable for thick plate welding, and there is a danger of burning through for thin plate welding.

(2) Repeated arc breaking method: When the electrode is moved to the end of the weld bead, the arc is extinguished and the arc is repeated several times until the arc crater is filled. This method is suitable for thin plates and high current welding, but it is not suitable for alkaline electrodes, otherwise it will produce pores. ^[3]