How to use the vacuum brazing furnace?
The following is how to use the vacuum brazing furnace:
**1. Preparation before use**
1. Equipment inspection
- Check whether the appearance of the vacuum brazing furnace is damaged, whether the furnace door is well sealed, and whether the connection parts are tight. Ensure that the equipment has no obvious physical damage to avoid safety problems or affect the vacuum degree during use.
- Check the heating system, including whether the heating elements, thermocouples, etc. are working properly. Check whether the heating elements are broken, short-circuited, etc., and whether the thermocouples accurately measure the temperature in the furnace.
- Check whether the vacuum system, including the vacuum pump, vacuum valve, vacuum gauge, etc., is normal. Start the vacuum pump, check whether its exhaust speed and ultimate vacuum degree meet the requirements, whether the vacuum valve is flexible, and whether the vacuum gauge accurately displays the vacuum degree.
2. Clean the furnace
- Before use, the debris, dust, etc. in the furnace should be cleaned up to avoid contaminating the workpiece or affecting the vacuum degree during the brazing process. You can use a vacuum cleaner, a clean rag and other tools for cleaning.
- For newly installed or long-unused vacuum brazing furnaces, it is also necessary to bake the furnace to remove moisture and other volatile substances in the furnace. The oven temperature is generally 100℃ to 200℃, and the duration depends on the size of the equipment and the usage, usually a few hours to more than ten hours.
3. Prepare the workpiece and brazing material
- Prepare the workpiece and brazing material for brazing according to the welding requirements. The surface of the workpiece should be cleaned to remove impurities such as oil and rust, and can be treated with cleaning agents, sandpaper, etc.
- Select the appropriate brazing material, and determine the type, specification and amount of the brazing material according to the workpiece material and welding requirements. The brazing material should be kept dry and clean to avoid moisture or contamination.
4. Install the workpiece
- Put the prepared workpiece and brazing material into the furnace, and pay attention to the reasonable placement to avoid contact between the workpieces or contact with the furnace wall. Special fixtures or trays can be used to fix the workpiece to ensure that the workpiece does not move or deform during the brazing process.
- For some workpieces with special shapes or where local heating is required, auxiliary heating devices such as induction coils, resistance wires, etc. can be used to install them in appropriate positions.
**II. Operation steps**
1. Vacuuming
- Close the furnace door, start the vacuum system, and start vacuuming. First, use a mechanical pump to pump the pressure in the furnace to a low vacuum state (generally 10Pa to 100Pa), and then start a Roots pump or diffusion pump to further pump the pressure in the furnace to a high vacuum state (generally 10⁻³Pa to 10⁻⁵Pa).
- During the vacuuming process, closely observe the reading of the vacuum gauge to ensure that the vacuum degree meets the requirements. If the vacuum degree rises slowly or abnormally, check whether there are leaks or other problems in the vacuum system in time and deal with them.
2. Heating and heating
- When the vacuum degree meets the requirements, start the heating system and start heating. According to the characteristics of the workpiece material and the brazing material, set the appropriate heating rate and brazing temperature. The heating rate is generally controlled between 5℃/min and 20℃/min to avoid deformation of the workpiece or uneven melting of the brazing material due to excessive heating.
- During the heating process, the temperature in the furnace should be monitored in real time by thermocouples, and the heating power should be adjusted according to the temperature changes to ensure that the temperature is controlled within the set range. At the same time, pay attention to the state of the workpiece to avoid abnormal conditions such as overheating and discoloration.
3. Insulation
- When the temperature in the furnace reaches the brazing temperature, it enters the insulation stage. The insulation time depends on the size, shape, material and characteristics of the workpiece, generally ranging from tens of minutes to several hours. The purpose of insulation is to fully melt and diffuse the brazing material to form a firm welded joint.
- During the insulation process, the temperature in the furnace should be kept stable to avoid excessive temperature fluctuations. At the same time, continue to observe the changes in the vacuum degree to ensure that the vacuum degree always remains within the required range.
4. Cooling
- After the insulation is completed, turn off the heating system and start cooling. The cooling method can be natural cooling, forced air cooling or water cooling, etc., depending on the workpiece material and requirements. The cooling speed should be properly controlled to avoid stress or deformation of the workpiece due to excessive cooling.
- During the cooling process, the vacuum state should be maintained until the temperature in the furnace drops to a certain level, and then inert gas (such as nitrogen) is slowly filled in to restore the pressure in the furnace to normal pressure. The purpose of filling in inert gas is to prevent the workpiece from being oxidized during the cooling process.
5. Out of the furnace
- When the temperature in the furnace drops to room temperature, open the furnace door and take out the workpiece. Be careful when taking out the workpiece to avoid collision or damage to the workpiece. At the same time, check the workpiece to see if the quality of the welded joint meets the requirements.
- If defects are found in the welded joint, such as incomplete penetration, pores, cracks, etc., the reasons should be analyzed and corresponding measures should be taken to improve them. For example, process parameters can be adjusted, brazing filler metal can be replaced, and workpiece surface treatment can be improved.
**Three, maintenance after use**
1. Cleaning equipment
- After use, the furnace chamber and furnace door seal of the vacuum brazing furnace should be cleaned in time to remove residual brazing filler metal, oil stains and other impurities. Special cleaning agents and tools can be used for cleaning to ensure that the equipment is clean and tidy.
- Clean the vacuum system, including vacuum pumps, vacuum valves, vacuum gauges, etc. Regularly replace the vacuum pump oil, clean the vacuum valves and pipes to ensure the normal operation of the vacuum system.
2. Check the equipment
- Carry out a comprehensive inspection of the equipment, including the heating system, vacuum system, control system, etc. Check whether the heating elements are damaged, whether the thermocouples are accurate, whether there are leaks in the vacuum system, and whether the control system is working properly.
- If problems are found in the equipment, repair or replace parts in time. For some wearing parts, such as thermocouples, heating elements, etc., they should be replaced regularly to ensure the performance and reliability of the equipment.
3. Maintain the equipment
- Regularly maintain the vacuum brazing furnace, including lubricating mechanical parts, checking electrical connections, calibrating temperature and vacuum, etc. Maintenance work can extend the service life of the equipment and improve the performance and stability of the equipment.
- For equipment that has not been used for a long time, moisture-proof and dust-proof treatment should be carried out, and power-on test runs should be carried out regularly to ensure that the equipment can work normally when needed.
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