Aluminum has been applied in various fields because of its light weight, corrosion resistance, good electrical conductivity and other characteristics, with the rise of new energy, the application of aluminum has been strengthened, and the connection of aluminum in addition to riveting, bonding is welding, for the connection of aluminum plate resistance welding is an important process, application scenarios in addition to conventional industrial applications, It is widely used in new energy vehicles, aerospace and other fields.
Principles of Aluminum Welding
The advantages of aluminum plate resistance spot welding are obvious, without adding auxiliary materials, only by the base metal melting can form a strong solder joint. Aluminum in the air often has a layer of oxide film, aluminum melting point is 660 degrees Celsius, and the oxide film is aluminum oxide, its melting point is about 2000 degrees, and melt the base material to form the core first to break the oxide layer, which is also the aluminum spot welding process is considered to be more difficult reason.
Welding Equipment Selection
The selection of aluminum plate spot welding machine, intermediate frequency inverter DC power supply because of its output current is DC, with higher thermal efficiency, so it is the first choice for aluminum plate spot welding. The traditional three-phase secondary rectifier power supply is half-wave rectifier, capacitive energy storage power supply although the output is DC but the time is very short, so its comprehensive performance is not as good as the intermediate frequency inverter DC spot welder, these power supplies have applications in the early stage, the future application scenario will be less and less.
Points To Note When Aluminum Spot Welding
Aluminum plate spot welding process, aluminum plate conductivity and thermal conductivity ratio is high, so the need for greater current and appropriate welding time, which requires attention to the following points:
1. The power of the equipment should be large enough to ensure that the current output can be maximum in a short time, generally 2-3 times the current of carbon steel spot welding;
2. The electrode needs strong water cooling, and the heat can be taken away quickly after welding;
3. The spherical diameter of the front end of the electrode should be matched, and different plate thickens should have different spheres, and the principle should not be lower than SR25;
4. The electrode diameter should match the thickness of the plate, and the electrode diameter below 1.0MM of the plate is ¢13; Sheet thickness 1.0-1.5 Electrode diameter is ¢16; Sheet thickness 1.5-2.0 Electrode diameter is ¢20; Plate thickness above 2.0 electrode diameter is not less than ¢25;
5. The electrode material is made of copper alloy with high conductivity or hardened copper, and the conductivity is not less than 80%IACS;
6. To meet the high quality solder joints, the surface of the aluminum plate should be deoxidized, pickling or polishing, and the surface resistance of the A-level joint of aviation/military products should be controlled at 50 microohm-100 microohm;
Welding Quality Inspection
Aluminum plate spot welding after the test mainly non-destructive testing and damage detection two categories, non-destructive mainly through visual, X-ray and ultrasonic detection, damage detection mainly stretching, low times and other detection, the specific detection methods are as follows:
1. Appearance inspection, including the shape of solder joint, solder joint color, indentation depth, etc.;
2. X-ray detection, film detection of the diameter of the weld core, whether the weld core cracks, shrinkage and other defects;
3. Low-power detection, 15-25 times after slice corrosion of solder joints, to detect welding permeability, welding defects, etc.;
4. Tensile test, the main test solder joint strength;
5. Stripping test, stripping or tearing test of solder joints, mainly used for on-site strength detection and confirmation of core diameter.
6. Ultrasonic detection, with the upgrade of ultrasonic detection technology, the application of spot welding detection continues to strengthen, through the comparison of reflected waveform, as well as the maturity of digital imaging technology, polycrystalline head ultrasonic detection will be a good choice for non-destructive testing of aluminum spot welding.
Summary
With the mature application of MFDC welding machine, as well as the improvement of welding process and detection means, the threshold of aluminum plate spot welding will be lower and lower, and it will also promote the aluminum plate spot welding in industrial lightweight, as well as new energy, aerospace and more widely used.
Post time: Aug-07-2024
