Solid phase sintering and liquid phase sintering in MIM process

Sintering is a very important step in metal injection molding, which is the densification of porous blank after degreasing.

The control of temperature and time in the sintering process directly affects the performance of the final product. In this process, it is this link that really needs to be mastered.

When the blank after degreasing is sintered, the powder completes the connection between the powder particles at the temperature lower than its main components by passing through the front of the atom, reducing the space between the particles, thus achieving the purpose of densification.In the MIM process, after densification, the blank will still have the shape designed in advance to match the injection mold, but after sintering, it will become with a certain strength and performance, can withstand a certain external force, and will not be as porous and fragile as the blank just removed the fat.

Some people have summarized the characteristics of MIM sintering from two aspects. From the macro perspective, the porosity of the blank as a whole decreases and the density of the blank increases. From the micro perspective, particle transfer occurs in the atoms of the powder particles, so that the powder can produce a bond between particles to maintain a certain shape and performance without the action of binder.

The principle of sintering is that at a certain temperature, the use of heat force to activate the atoms of the powder so that the physical location of the migration, the powder shape of the blank into the particles closely connected to the block of the blank.From this, we can see the importance of temperature for sintering. Theoretically, the higher the temperature, the faster the migration of atoms generated in the sintering process, the more atoms from one position to another, and the faster the

sintering process.

In actual production application, people will often mention two words: solid phase sintering and liquid phase sintering, actually this not what of, about the difference between the two, a little bit more simple said is according to the different sintering temperature, sintering temperature solid phase sintering is lower than the melting point of all components, and the liquid phase sintering is sintering temperature below the melting point of main components.At the same time, these two sintering methods have one thing in common: they are carried out without external pressure.

Therefore, solid-phase sintering and liquid-phase sintering are called non-pressure sintering, which is mainly relative to the methods of pressure sintering such as hot pressing, hot forging and hot isostatic pressing.In MIM process, the blank is usually sintered by non-pressure sintering.