Introduction
As a key process, the sintering process is the last major step in the production process of cemented carbide. The so-called sintering is to heat the powder compact to a certain temperature, keep it for a certain time, and then cool it, so as to obtain a product with the required properties. The purpose of sintering is to turn the porous powder compact into an alloy with certain structures and properties. The waste products produced by the sintering process generally cannot be processed by subsequent processes, so the selection of the process and equipment has a significant or even decisive influence on the structure and properties of the sintered carbide products. Various methods and equipment for promoting sintering continue to emerge. They have played a positive role in improving the sintering process, promoting the performance of cemented carbide products, and reducing energy consumption. Sintering equipment and sintering process are closely related. According to the development of cemented carbide sintering process and the actual situation of the current domestic cemented carbide sintering process equipment, it can be roughly divided into the following 3 equipment options.
Continuous Molybdenum Wire Sintering Furnace
The continuous molybdenum wire sintering furnace has the advantages of easy operation, long service life of the furnace tube, low power and continuous production. It has been widely used for a long time, and there are still a few manufacturers using it.
However, the sintering atmosphere of this sintering furnace is difficult to control, so the product is easy to carburize or decarburize, especially for large products. And because it is sintered under positive pressure, some oxide impurities cannot be well volatilized and eliminated, which affects product quality.
Horizontal vacuum sintering furnace
Sintering under the condition that the pressure in the furnace is lower than atmospheric pressure is called vacuum sintering. The horizontal vacuum sintering furnace has the characteristics of convenient loading and unloading and process operation, high reliability and good maintainability.
Due to the vacuum sintering process, oxide impurities can be effectively eliminated. Compared with the hydrogen sintering furnace, the purity and physical properties of the sintered products are significantly improved. However, because the vacuum degree is an important indicator of the vacuum sintering furnace, its control has a great influence on the product quality, making it difficult to control the vacuum degree. In addition, it has the disadvantage that the carbon content is difficult to control in actual production, and the production quality of low-cobalt cemented carbide with very strict requirements on the accuracy of carbon content control cannot be guaranteed.
Pressure sintering furnace
Pressure sintering furnace is also called air pressure sintering furnace. It is the highly advanced sintering equipment in the production of cemented carbide at present, also known as HIP sintering equipment.
The microprocessor-controlled program ensures full automation and reproducibility of the process, as well as consistent product quality. The computerized processing of the operation and related data can meet the requirements of highly reliable quality. This sintering furnace can set different sintering process input control systems according to different sintered products. The operator only needs to operate the furnace to open and close the furnace easily, which will not affect the specific sintering process, and completely eliminate human factors in the entire sintering process. The stability of the product is guaranteed.
The equipment is very suitable for the sintering of low cobalt cemented carbide with very strict carbon content control requirements. The physical and mechanical properties of WC-20% cemented carbide are shown in the Table.
| Name of Equipment | Hardness (HRA) | Flexural Strength (MPa) | Grain Size (μm) | Density (g·cm3) |
Horizontal vacuum sintering furnace | 85.5 | 2900 | 3.0 | 13.5 |
Air pressure sintering furnace | 87.4 | 3200 | 1.8 | 14.07 |
As can be seen from the above Table, the low-cobalt cemented carbide products produced by the gas pressure sintering furnace have significantly improved hardness and strength compared with the products produced by the vacuum sintering furnace. The pore defects have been greatly improved, and the density has been significantly increased, the sintered crystal grains are much finer, the structure is more uniform, and the properties are greatly improved.
With more than 10 years of export trading experience, our factory has always deeply understood the meaning of product quality to our customers, so our factory has always aimed to provide uncompromising quality, and attached great importance to the introduction and maintenance of advanced production equipment. ZZ Old Craftsman has introduced the latter two kinds of sintering equipment, especially the pressure sintering equipment to provide customers with premium products and more satisfaction.
