Coarse and uniform tungsten carbide powder has always been an urgent need for coarse crystal cemented carbide fabricators. This paper, through the study of tungsten powder classification and recarbonization process, effectively solves the phenomenon of coarse and fine powder clamping and produces coarse crystal tungsten carbide powder.

The properties of tungsten carbide and alloy made from graded and ungraded powders eliminate the defects in the microstructure of tungsten powder, but the high reduction temperature makes the tungsten powder aggregate and the size distribution of tungsten powder become wider. However, from the perspective of particle size distribution, the degree distribution becomes wider, especially the bimodal or multi-peak caused by this, and the particle size distribution of tungsten carbide powder produced by ungraded original tungsten powder is contrary to its properties. At the same time, low hydrogen will appear the material reduction not permeable wider) the proportion of fine particles and ultra-coarse particles is significantly than the grading after the thorough, refining and other phenomena. The existence of these defects will be in the subsequent process, the particle aggregation is also more serious, many particles shape irregular. To negative effects.

Carbide sintering process microtek structure formation and the production rate depends largely on the quality of the original tungsten powder directly determines the quality of the WC and alloy properties, the structure of the mixture of tungsten carbide powder particles energy state, making coarse grain tungsten powder grading can effectively change the performance of the powder, coarse clip to solve powder alloy need tungsten carbide powder with high internal energy (lattice distortion) and surface problem, reduce the minimum size and maximum diameter and average particle size difference degree, can, not powder grading structure is more complex, both the bulky crystal produced more crude and more uniform tungsten carbide powder; Due to the characteristic of tungsten, there are also aggregates. During the carbonization of coarse tungsten powder, it generally goes through the transition process from three phases to unbreakable, moderately broken before classification, and the agglomeration of two phases in the powder to single phase. The carbonization rate mainly depends on the separation of particles, which can effectively separate the powder and improve the evenness. The grading must be the rate at which the polycrystalline tungsten carbide shell layer pushes inward. Due to the strict and fine regulation of the system operation parameters of tungsten powder particles, according to the original size of the original powder, carbonization process needs to be in a certain high temperature and time characteristics, need to find the best operation process. It can be done completely. Fine particles are more likely to be completely carbonized in a short time. Tungsten carbide particles with polycrystalline shells are fused by "grain boundary moving to the position specified in the references for more stable energy".

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Cemented carbide cutter has a series of excellent properties, such as high hardness, wear resistance, good strength and toughness, heat resistance, corrosion resistance, etc., especially its high hardness and wear resistance, which are basically unchanged even at 500 degrees, and still have high hardness at 1000 degrees. Hard alloy is widely used as cutting tool materials, such as turning tools, milling cutters, planers, drills, boring cutters, etc. it is used to cut cast iron, non-ferrous metals, plastics, chemical fiber, graphite, glass, stone and ordinary steel, as well as heat-resistant steel, stainless steel, high manganese steel, tool steel and other difficult to process materials.

Some of the factors that affect the characteristics and application of cemented carbide tools include:

(1) challenging workpiece materials. Including alternative metal materials and hard to process alloy materials. Some of these materials are less than a quarter as workable as steel, and some can cost hundreds of dollars per pound.

(2) increasingly complex workpiece geometry. For example, thin-walled workpieces and aviation parts with complex shapes.

(3) large size workpiece. In particular, the demand for turbines and various heavy machinery parts is increasing. The high cost of each piece of these workpieces puts forward high requirements for the machining of tungstencarbidecuttingtools.

(4) increasingly special quality and performance requirements. For example, the requirements for the surface fatigue strength of the machined parts.

Analysis of the factors that determine the quality of cemented carbide tools

Hardness and toughness: carbide tools have unique advantages in both hardness and toughness. Tungsten carbide (WC) has high hardness (more than corundum or alumina), and its hardness seldom decreases when the working temperature increases. However, it lacks enough toughness, which is essential for cutting tool performance. In order to make use of the high hardness of WC and improve its toughness, people use metal bond to combine WC together, so that this material not only has the hardness far higher than that of high-speed steel, but also can bear the cutting force in most cutting processes. In addition, it can withstand the cutting high temperature produced by high-speed machining.

Therefore, the adaptability of cemented carbide tool performance to specific machining depends largely on the initial milling process.

Related link:

http://www.wococarbide.com/Library/libraryinfo/id/847

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Distilled water and sodium carbonate solution were used to soak WC powder and cemented carbide blade, and the influencing factors and mechanism of WC leaching in cemented carbide were studied with the help of scanning electron microscope, X-ray energy spectrometer and other equipment. The results show that water and sodium carbonate can lead to WC leaching in cemented carbide, and the influence of sodium carbonate is very obvious at higher solution temperature. The existence of H+, OH- and HCO3- plasma in the cutting fluid is the root cause of WC leaching.

However, it has been reported in foreign literatures that amino additives can leach cobalt from cemented carbide tools, so they should not be used in grinding cemented carbide tools. As the binder of cemented carbide, the leaching of cobalt will greatly reduce the mechanical impact and service life of cemented carbide tools. At the same time, if the content of cobalt in the waste cutting liquid is too high, it is easy to pollute the environment and cause harm to the health of the operator. Triethanolamine oleic acid is the product of reaction between oleic acid and triethanolamine under certain conditions. Triethanolamine oleic acid was synthesized from ricinoleic acid and triethanolamine. The lubricant is used to soak the cemented carbide blade, and the grinding wheel is used to conduct wet grinding test on the cemented carbide blade with lubricant.

The main metal components on the blade surface were analyzed by KYKY2880 SEM. According to the test results, a method was proposed to add triethanolamine oleate and borax in the cutting fluid to inhibit cobalt leaching from carbide tools.

Test conditions and methods

(1) triethanolamine oleic acid and triethanolamine were prepared by reacting at a molar ratio of 1.5:1 at a temperature of 80-100 ° c for 5-6 hours to synthesize triethanolamine oleate. The concentration is 0. 6% lubricant. The compound solution was prepared with triethanolamine oleate and borax (0.6% triethanolamine oleate and 0.3% borax mass).

(2) grinding test

The wet grinding test of YG8 cemented carbide specimen was carried out on CA6140 lathe with diamond grinding wheel (particle size 80#, grinding wheel diameter 200mm). Install the grinding wheel on the self-made mandrel, one end of the mandrel is mounted on the three-jaw chuck, the other end is supported by the center, and the mandrel is driven by the spindle of the machine tool to rotate (rotation speed: 1120r/min). The carbide specimen is fixed on the tool rest and fed manually. Grinding time is 10 minutes

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