In copper joint production, internal porosity defects are a key issue affecting product quality. They not only reduce the mechanical properties of the joint but can also lead to safety hazards such as leaks. Porosity primarily arises from incomplete gas escape during welding or casting, or from the decomposition of impurities within the material at high temperatures. Therefore, reducing internal porosity defects requires a comprehensive approach encompassing material preparation, process control, and environmental management.
Material preparation is the foundation for reducing porosity. The purity of the copper directly affects the probability of porosity formation; high-purity copper has a low impurity content, reducing the gas generated by impurity decomposition at high temperatures. Simultaneously, the copper surface must be rigorously cleaned to remove oil, oxide layers, and other contaminants. These contaminants decompose at high temperatures, producing gases such as hydrogen and oxygen, increasing the risk of porosity. Furthermore, the selection of welding wire is crucial; wires with matching base metal composition and good deoxidation properties should be used to minimize gas generation during welding.
Process control is the core element in reducing porosity. In the casting process, smelting parameters, such as smelting temperature and holding time, need to be optimized to ensure that the molten copper is fully melted and that gases have sufficient time to escape. Simultaneously, a well-designed gating system, including venting channels and risers, helps gases escape smoothly during pouring. In the welding process, welding parameters, such as welding current, voltage, and speed, must be strictly controlled to avoid excessive heat input leading to violent boiling of the molten pool and increasing the risk of gas entrapment. Furthermore, using appropriate welding methods, such as argon arc welding and laser welding, can reduce the need for gas shielding during welding and lower the probability of porosity.
Environmental management is equally important for reducing porosity. Humidity, dust, and other contaminants in the production environment can adhere to the copper surface and decompose at high temperatures, generating gases. Therefore, it is necessary to maintain a clean and dry production environment to minimize the impact of contaminants on the copper. At the same time, for the welding process, it is essential to ensure the purity and stable flow rate of the shielding gas to prevent insufficient shielding gas from causing air entrapment into the molten pool and increasing the risk of porosity.
In specific process implementation, some auxiliary methods can also be used to reduce porosity. For example, degassing the molten copper before casting can remove dissolved gases by introducing inert gases or adding degassing agents. During welding, preheating and post-heat treatment are employed. Preheating reduces welding stress and porosity, while post-heat treatment promotes gas escape from the weld, reducing residual porosity. Furthermore, for critical components, non-destructive testing techniques such as X-ray and ultrasonic testing can be used to comprehensively inspect the interior of the copper joint, promptly identifying and addressing porosity defects.
Strict operational procedures during production are also crucial. Workers must undergo professional training and be familiar with the process flow and operating procedures to avoid porosity caused by improper operation. For example, during welding, the welding torch must be kept stable to prevent molten pool fluctuations; during casting, pouring speed and temperature must be controlled to prevent gas entrapment due to excessively fast pouring or high temperatures.
Quality traceability and continuous improvement are long-term guarantees for reducing porosity. A comprehensive quality traceability system needs to be established, with detailed records of the production process of each batch of copper joints, including material batches, process parameters, and test results. Once porosity defects are discovered, the cause can be quickly traced and corrective measures taken. Simultaneously, the production process needs to be regularly evaluated and optimized, new technologies and equipment introduced, and the production quality of copper joints continuously improved.
