Let you know about vacuum furnace process gas

Design principles of vacuum furnace:
The principle of vacuum furnace design is to extract the ambient air in the furnace at the beginning of heat treatment, and at the same time, process gas can be introduced to reach a specific pressure below atmospheric pressure. Therefore, the vacuum furnace can well control the amount of gas passing through the furnace during the entire process. , type and quality. Gas quenching with inert gases is a widely used technique for controlling quenching rates and results. Additionally, as temperatures increase within the hot zone, the addition of specific process gases can provide additional benefits, improving results for a variety of heat treatment applications. The first step in the vacuum heat treatment process is to remove the air from the furnace.
Heated metal parts are particularly susceptible to reacting with elements commonly found in the air, such as water vapor or oxygen, so removing the air can significantly reduce unnecessary harmful reactions. However, the introduction of specific process gases can also produce reactions or conditions required as part of the process. Backcharging process gas during the heating process can bring many benefits. Some processes may require the introduction of a very small amount of gas (0.01 Torr to 10 Torr), such as hydrogen to help remove oxides, or the addition of elements such as carbon for surface carburizing hardening, or the addition of other inert gases to limit the use of elements such as Cr in high-temperature processes in the volatilization. Other processes may require the introduction of sufficient process gas (1 atmosphere or higher) to achieve convective heating by operating an internal fan to evenly heat parts with complex geometries or large cross-sections.

Partial pressure process of vacuum furnace: maintaining reaction control at a pressure close to vacuum. The partial pressure process means that after the furnace reaches a vacuum state, a very small flow of process gas is filled into the furnace to generate or control the reaction when the temperature rises. . The process gas can be an inert gas such as argon or nitrogen, or a reactive gas such as hydrogen or acetylene. The partial pressure heat treatment process can be used as a purge in the furnace, that is, by adding inert gas to remove most of the remaining gas atoms and molecules in the furnace. When inert gas (such as argon) is added to the furnace during the heating process, it can drive the movement of smaller atoms or molecules such as hydrogen, oxygen, and nitrogen, forcing them to be quickly discharged out of the furnace when the system is evacuated for the second time.
Inert gas can also slow down the volatilization of elements such as Cr, which easily precipitate from the surface of the workpiece at high temperatures and extremely low pressures. After filling with inert gas, even a very low partial pressure of the inert gas can help prevent the precipitation of elements in Cr-containing materials. Some materials of steel are particularly susceptible to oxidation, and oxides may even form on their surface before heat treatment. Therefore, sometimes we need to introduce hydrogen into the heat treatment process at a specific temperature to promote the reaction of certain metal oxides with the introduced hydrogen, thereby reducing the oxidation of the workpiece. (While it is common sense from a safety perspective to be very careful when introducing hydrogen into any system, its use in heat treating processes involving parts containing titanium or certain copper alloys is generally not recommended.) In AvaC low-pressure carburizing, etc. In the process, the addition of process gases such as acetylene at low pressure helps provide case hardening solutions that meet specific requirements. This is particularly effective for parts with very complex geometries: components made from powder metal, for example. In addition to these processes, partial pressure gas systems can be used to avoid diffusion bonding between parts and tooling and provide a temporary cooling step, thereby increasing the efficiency of vacuum cooling.

Vacuum furnace convection heating process: The convection process is to fill the furnace with inert gas in a vacuum state until the pressure in the container is equal to or higher than one atmosphere. It may not seem like much sense to evacuate a furnace to a near vacuum and then backfill it with another gas to the same pressure as it was before the vacuum was evacuated, but by controlling the elements present in the recharged gas, you can ensure that you are dealing with The parts do not react with harmful elements that may be present in the ambient air, such as water or oxygen.
Vacuum furnaces mainly transfer heat through thermal radiation. In a vacuum environment, since there is no ambient air, heat is not transferred by convection. As a result, operators have effective control over process temperature and uniformity throughout critical steps of heat transfer. However, because thermal radiation transfers energy in a linear direction, geometries such as complex curved surfaces and deep holes can significantly affect the consistency of the heat treatment process. Filling the furnace with an inert gas at atmospheric pressure or higher can better control the heating uniformity of complex components. And at lower temperatures, convective heating is more efficient than radiant heating. Airflow generated by internal convection fans ensures efficient heat transfer throughout all geometries of the complex components. Airflow can provide more consistent heat transfer to deep holes or sharp corners, ensuring that the entire part heats up evenly and reaches the desired holding temperature faster. This effectively reduces process time and speeds up the production cycle of complex parts while ensuring temperature uniformity. Conclusion Although the main function of a vacuum furnace is its gas quenching capability, the addition of process gas during the heating and holding processes adds more functions and a wider range of uses to the equipment. Partial pressure and convection heating allow the vacuum furnace to control the working environment in the furnace more accurately, making the vacuum furnace an ideal tool for stable production and clean workpieces.

Vacuum furnace