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Precautions for selecting vacuum sintering furnaces

There are many factors that influence the vacuum sintering process, from the size and material of the hot zone in the furnace to whether the debinding and sintering processes are performed in the same furnace. However, all sintering processes must also consider one thing: how to effectively remove the binder from the material.
This article will discuss how to remove binder from the sintering process without the risk of contamination. Proper operation is crucial, and there are many ways to do this. Let’s start with a key question – when the binder is released due to the heat in the furnace, should it be burned or captured.

Which method is best for your vacuum sintering furnace?
When binder is released during sintering, there are two ways to deal with it: capture or burn it off. Each has its own advantages and disadvantages and is suitable for different situations. The first factor to consider is pressure. Sintering can be carried out at subatmospheric pressure (partial pressure) or at slightly positive pressure. The pressure level in the furnace largely determines the binder removal method to be used. If the sintering furnace is used at partial pressure, any gases generated during the process need to be extracted from the sintered material. In this case, it should be avoided that the extracted binder vapor enters the vacuum pump, which can only be achieved by using a condenser. A burner may still be arranged after the vacuum pump, but its purpose is not to burn off the binder, but to burn off the combustible gases used in the process. If sintering is carried out at slightly positive pressure, the situation will be very different. In this case, the user has a choice of binder removal methods. On the one hand, condensation and capture methods may be applicable. Condensation can be used at different gas flow rates and binder contents, so it is a flexible method. On the other hand, it is important to note that the condensate still needs to be captured and disposed of, thus increasing the cost of the sintering process. In situations where labor and disposal costs are strict, burning off the binder may be a more appropriate approach. However, it also has potential problems. From an equipment perspective, it is necessary to ensure that the burner settings are efficient so that the binder does not condense before reaching the burner. Sometimes there may be an imbalance between the gas flow rate and the burner’s ability to handle the process gas, so close monitoring is required. If the binder content in the material being processed is too high, residues may accumulate in the burner’s pipeline, causing a high probability of failure. In addition to this, the cost of using the burner must also be added to the total cost of the sintering process. In some cases, users will choose to use built-in burners on vacuum furnaces to remove binder gases instead of installing additional removal devices. However, the flames seen at the air outlet of vacuum sintering furnaces are usually intentionally generated for a specific purpose: to prevent the accumulation of hydrogen in the environment and eliminate the risk of explosion. They are neither designed to treat emissions to remove toxic gases nor to effectively remove binder in the furnace. Therefore, it is necessary to install a special combustion chamber to handle the released binder gas. This combustion chamber can be accurately designed for different gas flow rates and binder contents to ensure that the binder is fully oxidized within the appropriate combustion time.

How to Choose the Right Condenser for Your Vacuum Furnace
If you have decided to install a condenser to meet your binder removal needs, you must ensure that you select the right one. The most important thing is whether you should choose a liquid or solid condensing unit. Your choice will depend on the chemical composition of the binder used. These substances have very different liquefaction points and solidification temperatures, so when they are removed from the furnace, liquid or solid residues may be produced. Different types of residues require different types of condensers.
The situation with solid residues is the most complicated. Here, the problem is to prevent the binder from condensing before it reaches the trap (to avoid line blockage or valve failure). To do this, the condenser lines and components need to be properly heated to keep the binder at a certain temperature before it reaches the trap. These condensers usually have larger lines to capture solid residues, which can reduce their heat exchange efficiency. However, because the binders used are easy to condense, solid residue condensers often do not require a large surface area and do not need to be cooled to a low temperature. However, they do require cleaning, which is a disadvantage of solid residue systems. Solid residue can be heated, liquefied, and removed automatically or manually. The first system is preferred as it is faster and requires less manpower. If the sintering process produces liquid residue, the condenser is likely to be much simpler. It requires a large, cooled surface area to condense more binder in the shortest possible time. The condensate generally flows down to a removable collection container and may also pass through a filter to remove dust particles. Liquid condensate is easier to handle automatically, so this type of condenser is usually much more efficient.

Make the right investment decision
It is also important to invest in the key components of the vacuum sintering furnace. From the right high temperature zone insulation to efficient and easy to clean rotary pumps, there are many different factors that need to be weighed. By making the right decisions in these areas, users can reduce costs, reduce workload, improve efficiency, and most importantly, ensure the success of their products.

Vacuum Sintering Furnace