Vacuum Furnace Differential Pressure Dewaxing Technology

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The overall design of the vacuum dewaxing and sintering furnace requires dewaxing, pre-burning, sintering and rapid cooling to be completed at one time. In terms of structure, the difference from the general vacuum sintering furnace is that a graphite inner tank is added, and inner tank doors (covers) are set at both ends of the inner tank. And adopt the low-pressure carrier gas dewaxing process, the carrier gas flow is furnace → liner → wax collection system → vacuum exhaust system. The vapour of the binder (molding) agent removed from the product is extracted from the lower part with the carrier gas, and after the binder (molding) agent is separated by the wax collecting device, the residual gas is discharged to the atmosphere in various ways.​​

Vacuum dewaxing means that in the vacuum furnace, without any carrier gas, during the heating dewaxing period, the volatilized paraffin vapor is discharged out of the furnace by the vacuum system to achieve the purpose of dewaxing. There are many factors that affect product quality during sintering, among which paraffin removal is a very important part. In the process of cemented carbide press forming, it is necessary to add an appropriate amount of paraffin wax. These paraffin waxes only work on the forming process and have no effect on the internal quality of the final product. If the removal method is improper, the paraffin is not removed completely, and the residual paraffin exists in the product in the form of carbon or its compounds in the subsequent sintering process, which will affect the total carbon control of the product, and the effect of total carbon control will affect the quality of alloy products. have an important role. Therefore, the use of advanced technology to remove forming agent in vacuum/pressure sintering technology is of great significance to improve production efficiency and ensure stable product quality.

The advantages of differential pressure dewaxing technology:

(1) During the whole dewaxing process, a fixed pressure difference is formed inside and outside the graphite box, and gas is continuously filled into the furnace from the outside of the thermal insulation layer, and the vacuum system is continuously pumped from the graphite box to the outside of the furnace. A directional airflow from the outside of the thermal insulation layer to the inside of the thermal insulation layer, from the outside of the graphite box to the inside of the graphite box, this airflow will take the paraffin evaporated in the product out of the furnace from the exhaust pipe, which greatly reduces the pollution of the paraffin to the furnace body.

(2) With the directional flow of gas, the heat transfer in the furnace is mainly based on convection, which promotes the uniformity of the temperature of the furnace, reduces the temperature difference of the product, and improves the uniform dewaxing process.

(3) Since the furnace is filled with argon gas, the use of argon gas is safe and stable.

(4) The system is equipped with a complete wax trap, a cooling/heating device for the wax trap and its pipes, and the general heating temperature is 70 °C, especially the use of cold and hot water conversion control technology to make argon and The paraffin vapor is completely separated and the contamination of the vacuum system by the paraffin is avoided.

(5) The application of this technology makes the dewaxing rate reach more than 98%.