Microwave sintering technology is a new science and technology. With the characteristics of high efficiency, energy saving, environmental protection and flexible control, it has been increasingly widely used in industrial, agricultural and high-tech fields, and has formed a new industry. Hunan Province Zhongsheng Thermal Energy Science and Technology Co., Ltd. has adopted Microwave pusher kiln High temperature sintering control technology has built an automatic production line of vanadium nitride with a daily output of one ton at the end of June 2012. At present, the operation condition is good, the product quality is stable, and the production of vanadium nitride has the advantages of short sintering time, high energy utilization rate, excellent product quality, automatic control of production process, safety and pollution-free, short equipment maintenance time, on-line replacement of vulnerable parts without stopping production, etc.  

1． microwave heating Principle

Materials are divided into conductors, semiconductors and insulators. Insulators are also called dielectric materials, which are composed of polar molecules and non-polar molecules. Microwave is a high-frequency electromagnetic wave with a frequency ranging from 300 MHz to 300 GHz and a wavelength of 1-1mm. These dielectric materials composed of polar molecules and non-polar molecules, under the action of microwave high-frequency electromagnetic field, the polar molecules change from the original random distribution state to the orientation in accordance with the polarity of the electric field, and the polar molecules in the medium change from the original thermal movement state to the orientation in accordance with the alternating microwave electromagnetic field, generating intense friction and heat. In this microscopic process, microwave energy is converted into heat energy in the medium, which makes the medium temperature rise in a macroscopic way, which is the basic principle of microwave heating. Microwave heating is caused by the loss of electric field energy of dielectric materials. For conductive metal materials, the electric wave cannot penetrate into the interior and be reflected, and metal materials cannot absorb microwave.  

2.  Microwave equipment --The heating methods of microwave sintering furnace and traditional resistance sintering furnace are different:

There are essential differences in heating methods between microwave sintering furnace of vanadium nitride and traditional resistance sintering furnace of vanadium nitride. The conventional radiation conduction heating method adopted by ordinary vanadium nitride resistance sintering furnace is to rely on the heating element to transfer the heat energy to the heated object through convection, conduction and radiation to reach a certain temperature. The heat is transferred from outside to inside, so the sintering time is long and the energy consumption is large. The heating method of microwave sintering furnace is based on the fact that the absorption of microwave by materials is realized by coupling microwave electric field or magnetic field to convert microwave energy into heat energy. Its heating method is to heat from the inside of the heated object, with short heating time, low energy consumption, high material density and high yield.  

3． Microwave high temperature Advantages of sintering in the industrial application of vanadium nitride (silicon nitride manganese):

3.1. Simple operation and easy control

According to the control principle of microwave sintering, the control system of microwave sintering equipment is highly integrated, easy to operate and maintain. Temperature control can be achieved by adjusting the power control knob. According to the process requirements of vanadium nitride production, the computer program can be modified in time to facilitate automatic production control.  

3.2 Energy saving and efficient, compact products

Microwave is directly coupled with the material, leading to the overall heating of the material. Microwave energy is directly absorbed by materials and converted into heat energy. The energy utilization rate is extremely high, saving more than 30% energy than conventional sintering. Microwave sintering has fast heating speed and short sintering time, which reduces the internal thermal stress of materials, thus reducing the tendency of cracking and deformation, and the density of products is high.  

3.3 Microwave source adopts special isolator, which can realize Magnetron It can be replaced online without stopping the machine, so as to ensure that the microwave leakage does not exceed the standard and does no harm to human body. The microwave leakage is less than 0.5mw/cm2 (national standard is less than 5mw/cm2), and the replacement speed is fast.

3.4 The thermal insulation materials of microwave equipment are made of microwave special materials owned by ZHUANLI in modular assembly, which can greatly reduce the annual maintenance time of equipment (generally, the annual maintenance time is not more than one week).

4. Improvement in practical application

As the sintering temperature of vanadium nitride reaches about 1200 ℃, the vanadium nitrogen alloy is being formed. At this time, the microwave absorption ability decreases and the microwave reflection is reflected. If we use our own zhuanli microwave/electric hybrid heating high temperature push kiln technology, the energy saving effect will be significantly improved.

5. Pictures in industrial applications

five point one Microwave high-temperature pusher kiln (Figure 1)

5.2 Microwave high-temperature pusher kiln sintering vanadium nitride (Figure 2)