Advantages of vacuum sintering of tungsten cobalt carbide

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A typical representative of commonly used cemented carbide, tungsten-cobalt cemented carbide (YG-type cemented carbide) refers to an alloy composed of tungsten carbide as a hard phase and metal cobalt as a binder phase. In terms of use, tungsten-cobalt carbide can not only be used to make cutting tools, drawing dies, cold punching dies, nozzles, rolls, top hammers and other wear-resistant tools and mining tools, but also can be used to cut cast iron, non-ferrous metals and Non-metallic materials; From the perspective of production process, the preparation steps of YG-type cemented carbide include batching of tungsten carbide powder and cobalt powder, wet grinding, drying, granulation, compression molding, mold removal, sintering, etc. Note: Two kinds of WC powder, coarse and fine, are used for batching. The particle size of the coarse WC powder is (20-30) μm, and the particle size of the fine-grained WC powder is (1.2-1.8) μm.

There are two basic methods for sintering cemented carbide: one is hydrogen sintering, in which the composition of parts is controlled by phase reaction kinetics in hydrogen and atmospheric pressure, and the other is vacuum sintering, which uses a vacuum environment or reduces the ambient gas pressure, through Slow down reaction kinetics to control carbide composition. Vacuum sintering has a wider range of industrial applications.

The atmosphere control capability of the hydrogen sintering process is sufficient for tungsten-cobalt-based cemented carbides, but for alloys containing titanium carbide, tantalum carbide or niobium carbide for steel cutting tools, the oxidation potential of the atmosphere is too high, resulting in the composition of the alloy. Variations, vacuum sintering is usually used to reduce these, alloy oxide content, hydrogen sintering is generally done by means of mechanical push boats, through continuous sintering, a separate pre-burning furnace can be used to remove lubricants to prevent high sintering after volatile contamination process. Pre-sintering can also increase the green strength and enable rough cutting, for example, turning and drilling. Embryo strength.

Vacuum sintering: Compared with hydrogen sintering, vacuum sintering has several advantages. First, vacuum sintering can control the product composition extremely well. Under the pressure of 1.3~133pa, the exchange rate of carbon and oxygen between the atmosphere and the alloy is very low. The main factor affecting the composition change is the oxygen content in the carbide particles, not the reaction rate of carbon and the rarefied gas in the vacuum, so in the industrial production of sintered cemented carbide, vacuum sintering has an advantage.

During hydrogen sintering, the oxidation potential of the atmosphere gas in the furnace increases due to the infiltration of hydrogen and the reaction between hydrogen and the ceramic furnace components. Vacuum sintering does not have these problems, and the oxidation potential in the furnace is lower than that of hydrogen sintering. Therefore, the vacuum sintering process is more suitable for alloys containing titanium carbide, tantalum carbide and niobium carbide, which are sensitive to oxidation.

Secondly, vacuum sintering can flexibly control the sintering system, especially the heating rate in the heating and heating stage, to meet the needs of production. For example, when sintering alloys containing titanium carbide, tantalum carbide, and niobium carbide, the temperature must be raised slowly. There is – a holding stage at an intermediate temperature to get a high-quality product. Vacuum sintering is a batch operation, which can flexibly adjust the required sintering system, while hydrogen sintering is mostly a continuous sintering process, which can accurately control the temperature of each sintering stage.

SIMUWU provides carbide vacuum sintering furnaces with stable equipment quality, advanced technology, temperature uniformity during vacuum and process gas operation to ensure high-quality products and well-designed safety concepts and systems, by which makes the furnace operation reliable and fully automated.

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