With the continuous development of production and science and technology, there are currently many types of metal welding methods. If distinguished according to the characteristics of the welding process, they can be summarized into three major categories: (classification family method) fusion welding, pressure welding, and brazing.
1) Fusion welding - definition: The welding method in which the base metal to be welded is melted to form a weld without the application of pressure is called fusion welding. Arc welding: melting electrode, melting electrode (rod arc welding, submerged arc welding, gas metal arc welding, screw melting pole welding), non-melting electrode (tungsten arc welding, plasma arc welding, carbon arc welding, atomic hydrogen non-melting Electrode welding, gas welding, oxygen hydrogen, oxyacetylene, air acetylene, thermite welding, electroslag welding, electron beam welding, laser welding). The common feature of this type of welding method is that it uses a local heat source to melt the joints of the weldment and the filler metal material (sometimes without the filler metal material), fuse with each other without applying pressure, and form a strong joint after cooling and solidification. Arc welding , electroslag welding all belong to this category.
2) Pressure welding - Definition: During the welding process, pressure must be applied to the weldment (heated or not) to complete the welding, which is called pressure welding. Resistance welding (spot welding, seam welding, projection welding, butt welding, high frequency welding); cold pressure welding (ultrasonic welding, explosion welding, forge welding, diffusion welding, friction welding, air pressure welding). The common feature of this type of welding method is that a certain pressure is applied to the weldment regardless of whether it is heated or not, so that the two joint surfaces are in close contact to produce a bonding effect, thereby connecting the two welding parts together. Contact welding and friction welding all fall into this category. kind.
3) Brazing - Definition: Using a metal material with a lower melting point than the base metal as the filler metal, heating the weldment and the filler metal to a temperature higher than the melting point of the filler metal and lower than the melting temperature of the base metal, and using liquid filler metal to moisten the base metal The welding method that fills the joint gap and mutually diffuses with the base metal to connect the weldments is called brazing (flame, induction, furnace, dipping, electron beam, infrared, etc.). Brazing is similar to welding, but there are essential differences. It uses a metal material with a lower melting point than the base metal as the filler metal, and heats the weldment and the filler metal to a temperature higher than the melting point of the filler metal but lower than the melting point of the base metal. This method uses liquid solder to wet the base metal, fill the joint gaps and diffuse with the base metal to connect the weldments.
Common welding methods of copper
Methods for welding copper include gas welding, manual carbon arc welding, manual arc welding and manual argon arc welding. Automatic welding can also be used for large structures.
1) Gas welding of copper
Butt joints are most commonly used for copper, and lap joints and T-joints are used as little as possible. Two kinds of welding wires can be used for gas welding. One is a welding wire containing deoxidizing elements, such as wire 201 and 202; the other is a general copper wire and cutting strips of the base material, using gas agent 301 as a flux. When gas welding copper, it should be used Neutral flame.
2) Manual arc welding of copper
When the thickness of the weldment is greater than 4 mm, it must be preheated before welding. The preheating temperature is generally around 400-500°C. Use copper 107 welding rod for welding, and the power supply should be DC reverse connected. A short arc should be used during welding, and the welding rod should not swing laterally. The reciprocating linear motion of the welding rod can improve the formation of the weld. The stepless welding method should be used for long welds, and the welding speed should be as fast as possible.
When welding multiple layers, the slag between layers must be completely removed. Welding should be performed in a well-ventilated area to prevent copper poisoning. After welding, use a flat-head hammer to tap the weld to eliminate stress and improve weld quality.
3) Manual argon arc welding of red copper
In manual argon arc welding of copper, the welding wires used include wire 201 (special copper welding wire) and wire 202. Copper wires such as T2 are also used.
Before welding, the oxide film, oil and other dirt on the welding edge of the workpiece and the surface of the welding wire must be cleaned to avoid defects such as pores and slag inclusions. Cleaning methods include mechanical cleaning and chemical cleaning. When the thickness of the butt joint is less than 3mm, no beveling is required.
When the plate thickness is 3 to 10 mm, a V-shaped groove is made, and the groove angle is 60° to 70°; when the plate thickness is greater than 10 mm, an X-shaped groove is made, and the groove angle is 60° to 70°; in order to avoid unwelded Transparent, generally leaving no blunt edges. According to the plate thickness and groove size, the assembly gap of the butt joint is selected in the range of 0.5~1.5mm.
Manual argon arc welding of red copper usually uses DC positive connection, that is, the tungsten electrode is connected to the negative electrode. In order to eliminate pores and ensure reliable fusion and penetration of the weld root, it is necessary to increase the welding speed, reduce argon gas consumption, and preheat the weldment. When the plate thickness is less than 3mm, the preheating temperature is 150~300℃; when the plate thickness is greater than 3mm, the preheating temperature is 350~500℃. The preheating temperature should not be too high, otherwise the mechanical properties of the welded joint will be reduced.
4) Carbon arc welding of red copper
The electrodes used in arc welding include carbon electrodes and graphite electrodes. The welding wire used in carbon arc welding of copper is the same as that used in gas welding. You can also use the base metal to cut strips, and you can use flux for gas welding copper, such as gas agent 301, etc.
