1. Classification of Welding Methods
With the continuous development of production and science and technology, there are many types of metal welding methods at present. If they are distinguished according to the characteristics of the welding process, they can be classified into three categories: fusion welding, pressure welding, and brazing.
● Fusion Welding - Definition: The welding method of melting the base metal at the place to be welded to form a weld without the application of pressure is called fusion welding. Arc Welding: Melting Electrode Melting Electrode Not Melting Electrode. The common feature of this type of welding method is that the joint of the weldment and the filler metal material is melted by a local heat source, fused with each other without pressure, and cooled and solidified to form a firm joint. Arc welding and electroslag welding belong to this category. one type.
● Pressure welding - Definition: During the welding process, pressure must be applied to the weldment to complete the welding process called pressure welding. Resistance welding; cold pressure welding. The common feature of this type of welding method is that whether the weldment is heated or not, a certain pressure is applied to make the two joint surfaces come into close contact to produce a bonding effect so that the two weldments are connected together. Contact welding and friction welding belong to this category kind.
● Brazing - Definition: Using a metal material with a lower melting point than the base metal as the solder, heating the weldment and the solder to a temperature higher than the melting point of the solder and lower than the melting temperature of the base metal, using the liquid solder to wet the base metal, filling The welding method in which the joint gap and the mutual diffusion with the base metal to connect the weldment is called brazing. Brazing is similar to fusion welding, but there are essential differences. It uses a metal material with a lower melting point than the base metal as the solder and heats the weldment and the solder to a temperature higher than the melting point of the solder but lower than the melting point of the base metal. The method of using liquid brazing material to wet the base metal, filling the joint gap, and interdiffusion with the base metal to realize the method of connecting the weldment.
2. Welding method of copper
Common Welding Methods
The methods of welding red copper include gas welding, manual carbon arc welding, manual electric arc welding, and manual argon arc welding, and automatic welding can also be used for large structures.
● Gas Welding of Copper
The most commonly used copper is the butt joint, and the lap joint and the T-joint are used as little as possible. Gas welding can use two kinds of welding wires, one is the welding wire containing deoxidizing elements, such as wire 201, 202; the other is the general copper wire and the cutting strip of the base metal, using gas agent 301 as the flux, gas welding copper should be used. Neutral flame.
● Manual Arc Welding of Copper.
When the thickness of the weldment is greater than 4 mm, it must be preheated before welding, and the preheating temperature is generally around 400-500 °C. For welding with copper 107 electrode, the power supply should be reversed by DC. A short arc should be used during welding, and the electrode should not swing laterally. The reciprocating linear motion of the electrode can improve the formation of the weld. For long welds, the gradual de-welding method should be adopted, and the welding speed should be as fast as possible.
When multi-layer welding, the slag between the layers must be completely removed. Welding should be carried out in a well-ventilated place to prevent copper poisoning. After welding, use a flat hammer to strike the weld to relieve stress and improve weld quality.
● Manual Argon Arc Welding of Red Copper
In the manual argon arc welding of red copper, the welding wires used are wire 201 and wire 202, and copper wire, such as T2, is 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. The cleaning methods include mechanical cleaning and chemical cleaning. When the thickness of the butt joint plate is less than 3mm, the groove shall not be opened;
When the plate thickness is 3~10mm, open a V-shaped groove, and the groove angle is 60°~70°; when the plate thickness is greater than 10mm, open an X-shaped groove, and the groove angle is 60°~70°; in order to avoid unwelded Transparent, generally leaving no blunt edges. According to the thickness of the plate and the size of the groove, the assembly gap of the butt joint is selected within the range of 0.5 to 1.5 mm.
Manual argon arc welding of red copper usually adopts 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 at the root of the weld, it is necessary to increase the welding speed, reduce the consumption of argon gas, 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.
● Carbon Arc Welding of Copper
The electrodes used in carbon arc welding include carbon electrodes and graphite electrodes. The welding wire used in carbon arc welding of red copper is the same as that used in gas welding. The base metal can also be used to cut strips, and the flux for gas welding of red copper, such as gas agent 301, can be used.