Four welding methods of copper

【Summary Description】 The color of copper is purple-red, so it is called copper. In the humid air copper surface will produce a layer of basic copper carbonate, commonly known as patina (patina). Copper often contains a small amount of bismuth, lead, sulfur, oxygen, phosphorus, antimony, arsenic and other impurity elements, all impurities will reduce the conductivity of copper, especially phosphorus is the most obvious, but phosphorus is a good deoxidizer of copper, so phosphorus is still a beneficial element in copper. Copper has high plasticity in both cold and hot states, but its strength and hardness are low. The strength of copper can be improved by cold working. But at this time, the plasticity is significantly reduced (about 6%), and the conductivity is also reduced by 1-3%. After cold working of copper by 550-600 ℃ annealing, the plasticity can be completely restored. Copper still has high plasticity at low temperatures, but at high temperatures of 400-700 ℃, the strength and plasticity are greatly reduced. The thermal conductivity of copper is much better than that of steel, and the thermal conductivity of copper is 7 times that of steel. As the temperature rises, the gap is even larger. A large amount of heat is conducted out, and the base material is difficult to melt locally. A heat source with high power and concentrated heat must be used, and sometimes preheated, and the heat affected zone is very wide. Welding copper (commonly known as industrial pure copper) methods include gas welding, manual carbon arc welding, manual arc welding and manual argon arc welding, and automatic welding can also be used for large structures. 1. Gas welding of copper Butt joints are most commonly used for welding 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 the welding wire containing deoxidizing elements, such as wire 201 and 202, and the other is the general copper wire and the cutting strip of the base metal, using the gas agent 301 as the flux. Neutral flame shall be used for gas welding of copper. 2, Manual arc welding of copper In manual arc welding, red copper electrode copper 107 is used, and the welding core is red copper (T2, T3). The edge of the welding place shall be cleaned before welding. When the thickness of the weldment is greater than 4mm, it must be preheated before welding, and the preheating temperature is generally about 400~500 ℃. With copper 107 electrode welding, the power supply should be DC reverse connection. When welding, short arc should be used, and the welding rod should not be swung laterally. The reciprocating linear motion of the welding rod can improve the forming of the weld. Long welds shall be welded by step-back method. The welding speed should be as fast as possible. During 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, flat head hammer should be used to knock the weld to eliminate stress and improve the quality of the weld. 3. Manual argon arc welding of copper When red copper manual argon arc welding, the welding wire used is wire 201 (special red copper welding wire) and wire 202, and red copper wire, such as T2. 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 inclusion. Cleaning methods are mechanical cleaning and chemical cleaning method. When the thickness of the butt joint plate is less than 3mm, no groove is opened; When the plate thickness is 3~10mm, open a V-shaped groove with a groove angle of 60 ~ 70o; When the plate thickness is more than 10mm, open an X-shaped groove with a groove angle of 60 ~ 70o; In order to avoid incomplete welding, generally no blunt edge is left. According to the plate thickness and groove size, the assembly clearance of the butt joint is selected in the range of 0.5~1.5mm. 4, red copper manual argon arc welding DC is usually connected, 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 argon 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. There is also carbon arc welding of copper. The electrodes used in carbon arc welding are carbon electrodes and graphite electrodes. The welding wire used for carbon arc welding of red copper is the same as that used for gas welding. It can also be cut from the base metal and flux used for gas welding of red copper, such as gas 301, etc.

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