[China Aluminum Industry Network] 1. Outline low-pressure thin-walled containers for mass production. Most of the parts use ZL115 differential pressure casting blanks. Although the castings were examined by X-ray inspection, due to the limitations of structural features and the different size and distribution of the casting defects, some defects were not clearly visible on the X-ray film. They were often found after mechanical processing, and some had small diameter penetrations. Stomata can only be found after stress testing. This has seriously affected the quality of products and production schedules, and even caused huge economic losses. Some conventional welding repair methods do not meet the technical requirements well. In order to verify the effectiveness of this new process in solving the problems of sealability and appearance defects repair after cast aluminum parts were machined, a new way of repairing defects in cast aluminum parts was found. We conducted a large number of process tests and necessary tests. And form a set of correct procedures for the repair of defects in cast aluminum parts.
2, metal surface repair machine defect repair mechanism Because aluminum and its alloys are very strong chemical reactivity, the surface is easy to form oxide film, and mostly refractory properties (such as Al2O3 melting point of about 2050 °C, MgO melting point is about 2500°C) In addition, aluminum and its alloys have high thermal conductivity, and they tend to cause no fusion during welding. Since the specific gravity of the oxide film is extremely close to that of aluminum, it is also likely to become an inclusion in the weld metal. At the same time, the linear expansion coefficient of aluminum and its alloys is large and the thermal conductivity is strong, and warpage and deformation are easily generated during welding. This is a difficult problem when welding aluminum and its alloys. At present, the more commonly used argon arc welding in fusion welding is based on “cathode atomization†to crush the oxide film and protect the oxide film from being regenerated under the protection of argon gas. However, when the heat-treated aluminum alloy is heat treated by welding, the strength in the near-slit region is greatly weakened, and warpage is unavoidable. The metal surface repairing machine is mainly used for repairing casting defects. It has an inverter high-frequency + pulse power supply, a welding torch which can make the wire rotate at a high speed, and a control part. The mechanism of repairing defects is: using high-frequency + pulse voltage to break down the gas to form plasma gas, thus generating an electric spark with a temperature up to 6000° C., and the electric spark will melt the rotatable electrode (wire) instantly (10-5 -10-6 seconds) and the base metal with which it is in contact are melted at the same time, relying on the combination of the instantaneous high temperature and the mechanical friction of the rotating wire and the base metal and the rotating electric field force, the oxide film is broken, and the oxidation is performed under the protection of the argon gas. The film cannot be regenerated to complete the metallurgical bond between the wire and the base metal. Because of the short spark action time, the base metal that is in direct contact with the welding wire is partially melted. The heat conductivity of aluminum is very good, and the input heat is diffused and dissipated into the air instantly, and the substrate hardly generates temperature rise, so the substrate will not be deformed. Cast aluminum parts are repaired after machining, without affecting the dimensional accuracy. After repair, the surface is repaired or machined. The appearance can be consistent with the substrate.
3, repair experimental materials:
ZL115 heat treatment state: Quenching + incomplete artificial aging wire: S311 standard aluminum silicon wire Sample form: test plate slotted, open hole with a cast aluminum defect repair machine for repair after the preparation of metallographic specimens.
