PRODUCT CATEGORIES

Vacuum Heat Treatment Furnace

Vacuum Sintering Furnace

Vacuum Brazing Furnace

How to choose vacuum furnace correctly

The vacuum degreasing and sintering integrated furnace series is mainly used for degreasing and sintering stainless steel, cemented carbide, high temperature alloys, high specific gravity alloys, magnetic materials, carbides and other products. It can realize the two production processes of continuous degreasing and sintering in the same furnace body. Degreasing and sintering in the same furnace body can eliminate repeated moving, heating and cooling of products, improve product quality, shorten production cycles, and improve production efficiency. The special degreasing and sealed furnace bladder and grease trap can reduce the contamination of the inner furnace wall, heat shield and heating element. The degreasing and grease collection are more effective. The special sealed furnace bladder is helpful to improve the uniformity of furnace temperature. Directional airflow degreasing strengthens the degreasing effect and makes the degreasing more thorough. It can be sintered at constant pressure to suppress metal volatilization and improve product density and quality.

Choose the best configuration for your vacuum sintering furnace
In addition to heat shields, high-temperature areas also require attention. The basic principle is to reduce the weight of the high-temperature zone as much as possible, find a system with a suitable temperature range, reduce operating costs, and improve operating efficiency at maximum power.
In terms of shape, the square cross-section can ensure that the air flow through the high-temperature area is optimized, and it is also conducive to reducing costs when the effective volume is the same. You have the flexibility to choose based on the parts you need to work on. However, if you need to reach extremely high temperatures, you don’t have many options. This is because, in such cases (above 2,000°C), usually only cylindrical resistive heating elements suspended by current feedthroughs can be used.
Airflow distribution is also a consideration. You have 3 options: use an air distribution box, not use an air distribution box, or not control air distribution at all.
Air distribution boxes give operators greater control over air flow. Maintaining a slightly higher pressure outside the box helps prevent the high temperature area from being contaminated by degreasing products. By passing gas directly into the box, users can keep the gas flowing through the sintered part as pure as possible, thereby reducing product defects and improving quality. This would be the best configuration if debinding and sintering are performed in the same furnace.
However, vacuum sintering can also be performed without the use of an air distribution box. In this case, the air flow can be distributed through a series of points on the furnace chamber, which can also ensure the uniformity of the sintering process. Compared with the solution using an air distribution box, such a system can expand the effective volume of the furnace chamber and heat and cool faster. It also means that the sintering furnace can be used for other processes such as tempering – an important advantage for smaller plants.
Finally, there are also systems that do not control airflow distribution. These basic systems can be obtained by modifying ordinary furnace types, but they are not suitable for very special sintering processes.

Choose the best loading method
If you choose a system that uses an air distribution box, charging is the last aspect to consider (otherwise, you can already start purchasing a vacuum furnace or arranging a vacuum furnace retrofit now). At this point, the main question is whether fixed or movable bins should be used to hold the parts.
The most appropriate option still depends on your needs. Movable bins are suitable for single airflow mode and for charges that can be cooled in still air. In this case, the material box can be placed on the frame, which is simple and safe to operate.
For more complex furnace models with multiple airflow patterns, movable bins may not be practical. At this time, the material box needs to be equipped with a movable shelf so that the charge can be taken out without moving the sintering material box. There are also combination solutions, that is, a movable frame is inserted into the fixed box to form an intermediate layer. However, these combined systems take up a lot of space in the furnace chamber and have an impact on thermal efficiency and effective volume, so they are not commonly used.

How to choose the correct vacuum sintering furnace equipment
The heat shield is one of the most important factors when choosing a vacuum furnace. There are two main types of heat shields to choose from: metal and graphite, each with their own characteristics.
Metal heat shields are usually made of molybdenum, tungsten or stainless steel, which have a wide range of applicable temperatures (tungsten is suitable for high-temperature processes, while molybdenum is best used at lower temperatures). The best thing about metal heat screens, though, is their cleanliness. Unlike graphite heat shields, metal heat shields have an extremely low risk of process contamination due to decarburization or degassing. Therefore, aerospace and medical device manufacturers often prefer metal heat shields – their products have strict requirements for cleanability.
Another advantage is cost. The initial cost of metal heat shields is usually higher, but is compensated by features such as short evacuation times, fast heating and cooling rates, and even temperature distribution. However, molybdenum has certain problems, the most important of which is that it becomes brittle at high temperatures and is easily oxidized and affects the vacuum degree. This factor needs to be considered when choosing.
Graphite is another option, which again has its own pros and cons. On the plus side, graphite is capable of use at extremely high temperatures (up to 3,000°C), has low density, is lightweight, has high emissivity, and has excellent temperature uniformity. You can easily replace and repair graphite heat shields if needed, and you can add carbon fiber composite laminate for extra protection. Although graphite is suitable for most conventional sintering processes, it does have disadvantages. On top of that, graphite is prone to vapor absorption and particle generation, especially if a tie coat is used. So, contamination can be a problem.