Aluminum vacuum brazing furnace and tehcnology introduction

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1. Principle
Selection of vacuum brazing equipment and process selection for small aluminum plate-fin heat exchangers

2.Technical characteristics of vacuum brazing furnace:

2.1 The effective heating zone size of the big furnace is 1200×800×800 mm (length×width×height); the effective heating zone size of the small furnace is 1200×600×600 mm (length×width×height);
2.2 The highest temperature of the furnace: 700℃;
2.3 Furnace temperature uniformity ±3℃;
2.4 Ultimate vacuum: maximum 8.0×10-4Pa, small furnace 6.7×10-4Pa;
2.5 Commonly used vacuum degree 10-1～10-3Pa;
2.6 Total furnace load: 800Kg for big furnace, 500Kg for small furnace;
2.7 Pressure rise rate: 0.5Pa/h;
2.8 Heating power: 240KW for large furnace, 150KW for small furnace;

3. Requirements for furnace maintenance

3.1 The condition of the furnace should always be kept in good condition;
3.2 When the furnace is shut down, the furnace door should be closed to prevent humid air from entering the interior and maintain a proper vacuum;
3.3 Measuring instruments should be checked regularly in accordance with the management of instruments and meters, to ensure the correctness and reliability of the measured values, and avoid the loss of waste due to instrument failure;
3.4 The furnace should be regularly or irregularly brushed to remove magnesium powder and clean up dirt to prevent contamination of the workpiece surface;
3.5 Water and gas pipelines should be kept unobstructed, with flexible opening and closing of valves;
3.6 Good electrical insulation and furnace sealing performance;
3.7 The brazing furnace should be kept in good condition, and the equipment should be inspected once a month. The vacuum degree is 2×10-2Pa; 5×10-3Pa. The water pressure is 0.1~0.3MP a;

4. Matters needing attention in loading furnace
4.1 Pay attention to bumps when the workpiece enters and exits the furnace;
4.2 Attention should be paid when loading the furnace according to the size of different workpieces:
4 2.1 The placement of the workpiece should be as horizontal as possible;
4 2.2 The distance between the six sides of the workpiece and the heating element in each direction should be roughly the same;
4 2.3 Pay attention to safety when loading the workpiece;

5. Vacuum brazing equipment operation

5.1 After the workpiece enters the furnace, close the furnace door, first start the mechanical vacuum pump, open the bypass valve, and then start the Roots pump after vacuuming for about 10 minutes, open the main valve to start the diffusion pump, and the diffusion pump works for 80-90 minutes. During the time, you can preheat the temperature below 360 degrees while pumping the vacuum. After the diffusion pump works, the vacuum degree reaches above 10-2Pa and continue to heat until the end of the brazing (Note: The vacuum degree drops to a certain degree during heating , The heating rate can be adjusted according to the degree of vacuum);

5.2 The heating rate of the furnace temperature should be slow before 520℃ to avoid a large temperature difference between inside and outside. According to the temperature difference and the size of the workpiece, the heat preservation section can be accelerated or added in the middle. The purpose is to minimize the temperature difference between the inside and the outside and increase the vacuum. Generally small workpieces can heat up faster (see brazing-process diagram);

5.3 When the center temperature of the workpiece reaches or approaches the brazing temperature, it can be advanced or delayed depending on the size of the workpiece. When the brazing temperature is reached, the heating should be stopped, so that the workpiece is brazed at a constant temperature at the brazing temperature (see Brazing-Process);

5.4 The temperature of the brazing workpiece is 575-605 degrees for the heat exchanger, and the heat sink is 560-605 degrees. For large workpieces, the core temperature should be controlled, and the brazing time should be determined according to the size of the workpiece;

5.5 After the workpiece is out of the furnace, it is naturally cooled in the air. At this time, check whether the brazing seam is full, check the brazing quality and external dimensions and other items, and then mark the brazing steel stamp on the workpiece (including: brazing date, or number);

5.6 The parameters of the brazing process should be well recorded in detail, and the records should be included in the product quality file for examination when analyzing and researching product quality issues;

learn More : Aluminum Vacuum Brazing Furnace