During the welding process of brass tubes, it is not only important to select the appropriate welding method but also to pay attention to the optimal welding temperature. Both excessively high or low temperatures can adversely affect the entire welding process.
The optimal welding temperature is not fixed and is influenced by factors such as the local ambient temperature and humidity. After considering these factors, the most critical consideration is the temperature of the flame.
Carburizing flame is currently the most widely used type of flame. It is the result of the chemical reaction between oxygen and acetylene gas. It can be used for metal cutting and welding and produces white oxide solids. When using a carburizing flame for welding, it is recommended to maintain a temperature of around 2700 degrees under normal conditions.
Neutral flames are increasingly less used. Their characteristic is that the flame core directly depends on the composition of the combustion gas, flow rate, and flame diameter. A neutral flame can be roughly divided into three layers: the flame core is conical in shape, white in color, with a blue inner flame, and the overall appearance ranges from light purple to blue. Under normal conditions, the temperature of a neutral flame should be controlled at least above 3000 degrees Celsius, with a maximum not exceeding 3400 degrees Celsius.
Oxidizing flames have high operational requirements and are gradually being replaced by other types of flames. They utilize oxygen and acetylene for combustion, with gas pressure strictly controlled around 0.5 MPa. The oxygen valve and acetylene valve are opened simultaneously for ignition, and the mixing ratio of the two gases is generally determined based on material properties and construction requirements. The flame temperature does not have a fixed value.
Notes on Welding Copper Tubes
First, during welding, it is strictly prohibited for the tungsten electrode to come into contact with the welding wire or the molten pool. This is an issue that many workers overlook. If "tungsten striking" occurs, the copper tube may develop cracks of varying sizes, and in severe cases, the copper tube may be rendered unusable. If "tungsten striking" occurs, welding should be stopped immediately, the copper tube should be ground and polished, and the tungsten electrode should be replaced promptly.
Second, control the temperature. Here, "temperature control" refers to the interlayer temperature between multiple layers of copper tubing. During actual construction, if the operator finds that melting is difficult, the preheating temperature should be increased. The copper tubing can be reheated, with the preheating temperature exceeding 520 degrees Celsius. Welding without reaching the required temperature can easily result in poor welding reactions, directly affecting the quality of the copper tubing weld.
Third, pay attention to some minor details after welding, which are often overlooked by operators. After extinguishing the arc, the welding gun should not be immediately removed or raised. Instead, wait for about 5 minutes to continue utilizing the lagging gas protection function to protect the molten material. This is beneficial for both the welding gun and the copper tubing itself.
The above three welding precautions are very minor but are often overlooked by construction operators.
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