Superfine cemented carbide is known as "three high alloys" for its high toughness, high strength and high hardness at the same time. It is widely used in the manufacture of microdrill, dot matrix printer, precision die, glass precision cutting, textile cutting and so on. However, in order to obtain high-performance ultra-fine cemented carbide and further improve the mechanical properties of WC cemented carbide, it is necessary to control the grain size of WC. Therefore, how to obtain uniformly distributed ultra-fine WC powder or wc-co composite powder has become a hot spot of current research. Tungsten carbide can be produced in various ways. The traditional tungsten carbide production method is made from solid carbon tungsten carbide powder, which can produce tungsten carbide powder with particle size of 1 ~ 30 m. Direct reduction carbonization technology is a kind of technology to prepare WC powder, which has the advantages of low production cost, simple process and high purity of the product. Japan sumitomo electric co., ltd. USES WO3+C powder to directly and continuously reduce carbon in a hydrogen-atmosphere rotary furnace to produce ultra-fine WC powder. Ultrafine WC powder 0.1 m was prepared by direct reduction carbonization of WO3 and carbon black. In this paper, WO3 and carbon black are used as raw materials to prepare ultra-fine WC powder by direct reduction carbonization technology, and the reaction temperature and holding time in the process of reduction carbonization are studied.

Ultra-fine grain cemented carbide has high hardness and high strength, and is widely used in the manufacture of microdrill bits, dot matrix printer needles and precision tools for the drilling of integrated circuit boards. Ultrafine tungsten carbide powder is an important raw material for the preparation of ultrafine cemented carbide. At present, the reports of preparing nanometer, ultrafine tungsten carbide powder, or the way of the composite powder is more, there are mainly tungsten oxide reduction carbonization method (that is, the traditional process), directly carbonized tungsten oxide method, plasma chemistry carbonation method, halide tungsten carbide method, since the reducing amine salt, high frequency plasma method, gas solid instead should method, freeze drying, etc. These methods, the traditional process is simple and easy, reasonable, stable and reliable, large production capacity and advanced products are of good quality, low cost and efficiency higher advantages, and is closely related with tungsten carbide production in our country, is a kind of conform to China's national conditions, more province industrial production method, the traditional process made BET size is less than 0.2 microns ultrafine tungsten carbide powder as the U.S. DOW company is the quality of the production of the tungsten carbide powder. However, other methods still have disadvantages such as complicated process, high production cost, low efficiency and many impurities, which are suitable for industrial scale production.

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Wear is one of the three major failure modes (wear, corrosion and fracture) of metal mechanical parts. Modern industry urgently needs workpieces that can work effectively under severe wear conditions (such as high temperature, high speed friction and wear, etc.). Compared with traditional metal abrasion resistant materials, ceramic particle reinforced metal matrix surface composites effectively combine the high strength and toughness of metal materials with the high hardness of ceramic particles to form a high-performance material with overall impact resistance and surface abrasion resistance, which has attracted extensive attention. Among them, tungsten carbide particle reinforced steel matrix surface composite has the advantages of price, performance and technology. This paper reviews the research and application of tungsten carbide particle reinforced steel-based wear-resistant composites at home and abroad. Tungsten carbide (WC) is hexagonal crystal, with high hardness, high melting point, small thermal expansion coefficient, good wear resistance, and so on. Moreover, the wetting Angle of the liquid iron and steel encapsulates the tungsten carbide particles, which can support and protect the tungsten carbide particles. Almost all steel materials can be used as the matrix of casttungsten carbide reinforced particles due to the good forming properties of molten steel and complete wetting of tungsten carbide particles. However, the specific choice of steel or iron matrix should be based on the corresponding operating conditions (temperature, stress, wear resistance, etc.) to choose.

At the same time, tungsten carbide granule reinforced local composite material of steel matrix was designed and prepared. Low chromium cast iron, nodular cast iron, cast steel, gray cast iron and other steel materials were selected as bulk materials to study their composite effect. The composite process and casting process were improved and optimized, and were applied to the local composite of the worn surface of the flow parts of slurry pump. The microstructure and formation mechanism of the composite layer were analyzed, and the erosion wear properties of the composite material were investigated and compared with that of high chromium cast iron (Cr15Mo2).

It turns outthat the water glass sand mold (core) plus negative die casting infiltration technology can achieve complex surface (surface) the preparation of particle reinforced composites, pouring method is simple and reliable, in less than 10 mm, base material thickness of composite layer thickness can reach 3 ~ 7 mm, and the composite layer less casting defects, the composite effect is good, high density and interface bonding strength, material organization is divided into the base material area, transition area and complex area, uniform distribution in composite layer of tungsten carbide particles in high chromium cast iron substrate and grain shape intact. The pump chamber and inner cover of the 4' slurry pump produced by the module compaction pulverization process have basically realized the local composite of the whole worn surface. Grey cast iron with low chromium cast iron casting temperature is 1550~ 1600degreescan get composite good surface composite material, relatively ideal effect.

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Thermosetting hammer thermal spray powder coatings is also called the art type of powder coating, because coating can form as a hammer blow after the metal surface decorative pattern, this type of powder coatings not only has many advantages of thermosetting powder coating commonly, smooth and beautiful decorative pattern, coating, adornment sex is strong, also can make up and covered the surface rough, uneven defects, such as hammer powder coatings has the colour and lustre downy, coating flexibility, solid and durable, so widely used in instruments and meters, power distribution cabinets, security doors, home appliances furniture, lighting, medical equipment and other fields of metal surface coating.

Hammer pattern powder coating is prepared by using the principle of curing powder coating's melting viscosity, surface tension and curing speed, etc. There are usually several ways to produce hammer pattern powder coatings.

Add packing in the production of hammer powder coatings principle: increase the dosage of packing, or the use of high oil absorption packing, to obstruct the normal flow when the resin melt, the resin can not fully inclusive or just package appearance filler particles, no excess resin to fill the space between the fillers particles, thus forming the skeleton of the three-dimensional structure for fillers particles.

Using this method need to pay attention to is: different filler oil absorption is different, generally to achieve the same volume concentration, small density, small particle size than the surface area and large oil absorption yan filler amount. The advantage of the hammer grain produced by this method is that its cost is low, but if the amount of filling is not controlled properly, the powder coating construction performance, coating film mechanical properties, chemical resistance properties will be affected. In general to use this method to produce high efficiency and good stability of the product, the production process can be made some adjustments.

Join incompatible material production hammer powder coating is to point to: add some incompatible polymer inthermal spray powdercoating, its melting point higher than the melting temperature of powder coating resin binders, powder coating containing incompatible premixed by melt extrusion with other resin curing agent are incompatible, curing film when constitute the basic material of resin coating on the polymer particles, forming a texture. This method should pay attention to the need to strictly control the types of incompatible substances and the amount of additives, otherwise the mechanical properties of the coating will be affected. The hammer pattern powder coating produced by this method has good chemical and corrosion resistance.

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Anodic oxidation, electrophoretic coating and powder spraying are the main surface treatment methods of aluminum profiles. Each method has its own advantages and occupies a considerable market share. But if you want to divide the high and low, personally think or spraying powder dominant, what are the advantages?

Advantage 1

The process is relatively simple, mainly due to the improvement of the automatic precision of the main equipment in the production process, some of the main technical parameters have been able to achieve microcomputer control, effectively reducing the difficulty of process operation, while greatly reducing the auxiliary equipment;

Advantage 2

High yield, in general, if the appropriate measures, can maximize the control of nonconforming products;

Advantage 3

The energy consumption is obviously reduced. In the production process of ordinary anodic oxidation and electrophoretic coating, the consumption of water and electricity is quite large, especially in the oxidation process. The output current of the rectifier can reach 8000~11000A, and the voltage is between 15~ 17.5v. In addition, the heat consumption of the machine itself needs to be constantly cooled by circulating water. The power consumption per ton is usually around 1000 degrees.

Advantage 4

The pollution degree of water and air is reduced, the use of flake alkali, sulfuric acid and other liquid organic solvents is no longer used, reduce water and air pollution, but also effectively improve the competitive strength of aluminum profile and as an environmental protection product of plastic steel profile, reduce some production costs accordingly;

Advantage 5

The labor intensity of workers has been significantly reduced, because the use of automated assembly line operations, feeding methods and the use of fixture has been significantly simplified, improve the production efficiency, but also reduce the labor intensity;

Advantages 6

The requirements for the surface quality of raw materials are significantly reduced. The powder coating can completely cover the extrusion lines on the profile surface, cover up some defects on the surface of aluminum profiles, and improve the surface quality of aluminum profiles.

Advantages 7

Some of the physical indicators of the coating film than other surface treatment film has significantly improved, such as hardness, wear resistance, acid resistance, can effectively extend the service life of aluminum profiles.

Powder spraying is powder coating, process is used is electrostatic spraying, the use of electrostatic spray gun, under the influence of accelerating wind, so that the powder particles ejected gun body carrying a positive charge, and with a negative charge profile contact, electrostatic adsorption, and then through high temperature curing. It also enhances the adsorption strength of the coating and prevents the paint film from falling off.

Look from craft itself, have quite tall science and technology composition, allocate the coating of each different color, produce the adornment effect of different color department, accord with the need of indoor adornment more, also be with the application of aluminous profile in bldement to indoor development trend photograph is consistent. In particular, the combined use of spraying profiles and thermal insulation bridge, so that it has a more fashionable trend, thermal spray powder profiles with a greater space for development, but also other processing methods produced by the profile can not be replaced.

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Nanomaterials with grain size ranging from 20 nm to 100nm can be used to prepare nanomaterials, but there are still many technical problems in the wide application of nanomaterials in thermal sprayingpowder. The research on it is not deep enough. At present, the coating particles of nanostructure prepared by thermal spraying are mostly submicron particles of 100 ~ 200nm. Did not really reach the nanometer level, coating density is not high enough. The particle size that produces the small-size effect at room temperature is less than 100nm, and the particle strength generally abides by the hall-petch relationship, the smaller the particle is. The higher the intensity. In this sense, there is no breakthrough in the performance of nano-coating at present, and there is still a lot of room for development.

Another important problem is that nano powder cannot be directly used in thermal spraying. Because too fine powder will produce burning and flying problems, and powder delivery is very difficult, deposition efficiency is also affected. Generally, the particle size range of spraying powder is -140 ~ +500 mesh. The solution is to prepare nanomaterials into micron-scale nano-structures that can be directly thermally sprayed. At present, liquid dispersion spray method and mechanical grinding synthesis method are mainly used to prepare nano-structure feedstock. But it also brings the problem of complicated process and increasing cost. Therefore, the study of high quality, high performance or with special structural properties of nano powder or nano composite powder is a very important direction of nano thermal spraying research, but also the power of thermal spraying technology development.

The research time of nano thermal spraying technology is not long, there are many topics need further research and discussion. Such as:

(1) study on the structure and characterization of nano thermal spraying powders;

(2) research on quality control of thermal spraying structure coating;

(3) study on the melting, cooling process and corresponding mechanism of nanomaterials in spraying;

(4) research on the behavior characteristics of nano thermal spraying coating during use;

(5) research on computer control of nano thermal spraying.

As an important application field of nanomaterials, the research level of thermal spraying technology in China is still far behind that in the United States, Japan and other developed countries. The research ofthermal sprayingpowdersis still in the experimental stage. But from the results of existing research. Nano-structure coating prepared by thermal spraying technology has excellent antisepsis and wear resistance, and has a good application prospect. Although the cost of coating preparation and some technical problems still limit the wide application of this technology, its application has a broad prospect. With the development of nanomaterials, advanced thermal spraying equipment, advanced thermal spraying technology development, nano thermal spraying technology will be developed and widely used.

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For micro/nano particles in the process of the thermal spraying processcontrol measures, according to the principle of similarity, in thermal spraying workshop for prototype, combining the theory of gas-solid two-phase flow, thermal spraying workshop similar experimental model is established, under the condition of different ventilation and dust removal of micro/nano powder in thermal spraying workshop movement and the diffusion regularity of experiment research. The results show that mechanical ventilation can significantly reduce the concentration of micro-nano dust particles in thermal spraying workshop. The higher the ventilation flow per unit time, the lower the concentration of micro-nano dust particles in the respiratory layer of the workshop, and the shorter the removal time. Under the condition of the same ventilation rate, the combination of the bottom and the side of the workshop is more beneficial to the removal and settlement of the respirable layer micro-nano dust particles than the side strong ventilation alone.

The diffusion process of micro-nano dust inthermal sprayingpowderworkshop is essentially gas-solid two-phase flow. According to the motion law of gas-solid two-phase flow and the analysis of basic motion equation, the physical quantities involved mainly include air density, gas pressure, airflow velocity, aerodynamic viscosity coefficient, particle size, particle density, particle velocity, particle movement time, gravity acceleration, geometric size, etc.

Based on the principle of dimensional analysis, seven similarity criterion Numbers are derived: stokes criterion number, homogeneity criterion number, euler criterion number, froude criterion number, Reynolds number number, gas-solid phase density criterion number, and motion criterion number.Generally limited by actual experimental conditions, it is often difficult or difficult to realize that similar model and prototype meet all similar criteria at the same time. Therefore, under the condition of ensuring sufficient accuracy, the number of similar criteria is simplified according to the actual situation, that is, the approximate similar model is established.

Considering the actual movement of micro/nano dust particles in thermal spraying workshop, the similarity criterion number can be simplified as the geometric similarity criterion number and the ventilation rate ratio of the exhaust outlet.

The layout of similar experimental model (referred to as "experiment box") in the thermal spraying workshop is consistent with the actual workshop structure. There are 8 air inlets on the upper end and 3 air outlets on the side, and the remaining surfaces are sealed. All sides of the experiment box are made of colorless transparent acrylic sheets (commonly known as "plexiglass"), and all sizes are designed according to similar models. Micro-nano particle dispersion device is installed on the left side of the experiment box to simulate the dust source in the process of thermal spraying. Honeycomb floor is adopted at the bottom of the workshop, and the whole system is relatively complex, so it is simplified. 9 air outlets are set at the bottom of the experimental box, and centrifugal fan is adopted at one end as the negative pressure source.

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Die Matching Guidelines - Four Steps of Drawing Die Matching and Calculation Method of Key Data

Summary: Wire drawing die matching is the work of determining drawing pass, die hole size and shape according to blank size and wire size during wire drawing. It is also called drawing procedure or drawing route formulation. It can be divided into single-pass drawing die and multi-pass drawing die. The main steps of drawing die include the following four steps: 1. Selecting blanks; 2. Determining the number of intermediate annealing; 3. Determining the number of drawing passes and the elongation coefficient of distribution passes; 4. Calibration of die matching. This paper introduces the steps and calculation methods of wire matching for circular and special section metal drawing.

Mould matching principle and calculation example of sliding wire drawing machine

Summary: Wire drawing die matching refers to the method of selecting each drawing die in our drawing process. There are two main points in reasonable die matching: one is machinery; the sliding wire drawing machine has its fixed pulling wheel speed ratio. The correlation number of 7.2mm copper rod to 1.6mm copper wire is calculated by calculating the die matching example of the real wire drawing machine.

Uses of various drawing dies. Detailed classification

See how you classify it? The purpose of drawing dies is to reduce the material to be drawn.

According to size: micro-hole drawing die (inner hole size below 0.2), conventional drawing die.

According to the material of wire drawing die: diamond drawing die (natural diamond and artificial diamond, also known as polycrystalline drawing die), generally used for drawing small size wire and cable; carbide drawing die (YG3, YG6, YG8, YG10 and many other brands), mainly drawing large specifications of steel, copper, aluminum, and other products.

According to the materials and products drawn, they can be divided into ordinary drawing die, aluminium clad steel drawing die, prestressing steel wire drawing die, wire rope drawing die, steel cord drawing die, welding wire drawing die, welding rod drawing die, wire drawing die and so on. After using tungsten carbide steel wire drawing die for a period of time, its internal parts will gradually wear out and be damaged, resulting in the reduction of working performance and accuracy of the carbide wire drawing die. Due to carelessness of operators and improper maintenance and use, the tungsten steel wire drawing die will be damaged or the product quality will decline, and even cause shutdown. How to eliminate and avoid these failures? The number of cemented carbide die fitters is required to master the relevant die repair technology, so that failure can occur at any time, can be handled and repaired at any time, so that it can resume normal use as far as possible, and has given full play to the maximum potential of the die.

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Starting in 1893, German scientists used tungsten trioxide and carbon heated together in an electric furnace to a high temperature to make tungsten carbide, and tried to use their high melting point,High hardness and other characteristics to make drawing die, etc., in order to replace the diamond material.ButWC spraying powderhas not been used in industry because of its high brittleness, easy cracking and low toughness.

In the 1920s, German scientist Karl Schroter found that pure tungsten carbide could not adapt to the drastic stress changes formed in the drawing process. Only by adding low-melting metal into WC could the roughcast have certain toughness without reducing its hardness.

Schroter first proposed in 1923 the patented method of powder metallurgy, in which tungsten carbide is mixed with a small amount of ferrous metals (iron, nickel, cobalt), then pressed into shape and sintered in hydrogen at temperatures above 1300 to produce a hard alloy.

So far, the development oftungsten carbide sprayingpowdergenerally spans three stages. The first phase consists of powders and wires with metals and alloys as the main components, including aluminum, zinc, copper, nickel, diamond and iron metals and their alloys. These materials are made into powders, produced by primary grinding methods such as crushing and mixing, and manufactured by drawing wire or alloy wires of a certain diameter. These materials are mainly used in flame powder spraying, line spraying and arc spraying processes. Coating function is relatively simple, general corrosion resistance, wear resistance, small application surface; The second phase began in the mid-1950s. It has been found that it is necessary to improve the spraying process of tungsten carbide to obtain a more wear-resistant coating in order to solve the problem of mass wear in industrial equipment. After several years of efforts, the introduction of self-fusion alloy, the development of flame spray welding process. This is known as "hard surface technology". Self-fusion alloy is made by adding B, Si and Cr into the metal of Ni, Co and Fe groups, which can form eutectic alloying elements and antioxidant elements with low melting point. After tungsten carbide is sprayed, it is heated and remelted to obtain a hard coating. This technique was inspired in part by the welding surface treatment process.

Thanks to their high hardness, high metallurgical bonding and excellent oxidation resistance, these coatings have taken a big step forward in terms of wear resistance and oxidation resistance. The appearance of self-fusion alloy greatly promoted the development of tungsten carbide spraying technology. Another technological breakthrough at this stage is the emergence of plasma spraying equipment. Plasma flame up to 10,000 degrees, almost all materials can be sprayed. As a result, people began to think and develop a series of ceramic materials and metal ceramic materials. In fact, only after the mid-1970s, after the 8th international thermal spraying conference held in Miami in 1976, with the rapid development of the aviation industry, these materials really found a way to be applied, and high-performance, are gradually emerging. Technical wear-resistant, high temperature resistant, anti-gas corrosion and heat insulation surface engineering coating materials, so that thermal spraying technology from the simple maintenance workshop began to enter the aerospace and aircraft and other high-tech industries, and solve the headache of many metallurgical engineers. Not only did aircraft designers worry about the technology dropping planes from the sky, but since then, aircraft engines with more than 100 parts have been included in the specifications and must be sprayed with tungsten carbide to meet the designer's requirements. In the third stage, a series of composite powders and self-adhesive primary spraying powders appeared in the mid-1970s. It was not until the 1980s that sandwich lines were introduced to the market as arc sprayed materials.

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Using the parallel light projection method and the high precision linear CCD as the measuring sensor, combined with the mechanical scanning method, the hole diameter of the drawing die nibs was quickly detected. The circuit design of anti - spot interference in CCD aperture detection is proposed.

High-speed wire drawing production line is an important production equipment in the metal products industry. The quality of each process in wire-drawing production depends on whether the aperture of the wire-drawing die in the process is qualified. The axial section of the die hole is shown in figure 1, which is composed of four parts: inlet area, working area, sizing area and outlet area. Die diameter is the diameter of the specified diameter zone. Because the die hole is a cone Angle change hole, it is difficult to directly measure its minimum diameter, currently in the metal products industry is usually put silicone injection die hole to silicon gel solidification and then pull out, through the measurement of silicon punch die to obtain the die diameter. This kind of measurement method has low efficiency and is not suitable for the requirement of mass production. The range of the instrument:Φ 2 ~ 10 mm, accuracy < 0.01 mm.

The instrument adopts the method of parallel light projection and USES the high-precision linear CCD as the measuring sensor to extract the dimension information of thedrawing die nibshole. As shown in FIG. 2, the light source 1 forms parallel light through the condenser 2, the light column 3 and the collimating lens 4. Under the irradiation of parallel light, the wire-drawing die hole is imformed on the photosensitive surface of CCD through the imaging objective 6 and the light column 7. Optical system using remote fangyuan's heart light path, lighting and material can be reduced when installing drawing die sizing with position deviation, the measuring error caused by the light source to choose 6 v, 25 w halogen tungsten lamp step-down use, in order to improve the life and collimating mirror, choose standard photographic lens imaging lens, CCD and the use of Toshiba TCD106C, 5000 photosensitive pixels, center distance of adjacent pixels of 7 microns, the total size of 35 mm.

Measuring aperture with linear CCD is different from measuring diameter of outer circle. If the axis of measured rod and optical axis of measuring system are perpendicular to each other, the outer diameter can be measured by projection method. When measuring the inner diameter, the axis of the measured hole must be parallel to the optical axis. After the hole passes through the optical path imaging, the linear array CCD cannot directly measure the aperture. What the CCD cuts is the string of the hole. As long as the sampling frequency of CCD and the motion speed of the mechanical scanning mechanism are reasonably set, the scanning error can be controlled within the range that does not affect the accuracy.

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In order to improve the surface hardness and wear resistance of parts, a layer of tungsten carbide wear-resistant coating was applied on 45# steel by vacuum melting method. Hardness distribution and wear resistance change data ofwear-resistant coating for WC spraying powder at different depths were obtained through microhardness tester and wear test. The results show that the hardness of the diffusion layer of the coating is the lowest, and the hardness of the coating is higher than that of the matrix and the diffusion layer. In the condition of dry friction, the outer layer of the coating has the best wear resistance, the middle layers have the same wear resistance, and the coating near the diffusion layer has the worst performance.

Wear is one of the three main failure forms of materials, it is very huge economic losses, adhesion wear is one of the most common forms of wear, its development is very fast, easy to make parts or machine accident, causing huge losses. Wear failure of all kinds of parts caused by adhesive wear accounts for about 15%, and one of the main factors affecting the solid material adhesive wear is the hardness of the material, for the friction pair material hardness, the higher the hardness of the material, the better the wear resistance, therefore, the study of the hardness and wear resistance of parts material has important practical significance. In addition, the use of surface engineering technology, can make the material surface is not get it and hope to have a special performance (such as requirement surface wearability, heart good toughness), and the surface layer is very thin, material very little, high performance price ratio, saving material and saving energy, reducing environmental pollution, is an important measure to realize the sustainable development of the material. It is in this context that this paper attempts to make some research on the hardness and wear resistance of WC wear-resistant coating prepared by vacuum melting and burning method by means of test.

Sample preparation

Nickel-based tungsten carbide alloy powder fn15-wc35 and Ni45B were mixed in a ratio of 3:1 (mass ratio). Then saturated turpentine was added. The mixed WC spraying powder was prepared into paste for later use. Powder composition is shown in table 1. Clean the 45 steel surface to be coated with kerosene and dry it in an electric oven to check for defects in the abrasion resistant coating. If there is insufficient coating or coating loss, be sure to reapply, to ensure that the coating is relatively flat, there can be no defects. Coating is good and then into the oven for drying, baking temperature of 110degrees, drying time should be greater than 8 h, make not easy peeling off coating.

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The rapid development of high technology requires new materials with superior properties, and puts forward higher requirements for the hardness, strength and wear resistance of materials. Tungsten carbide base ultra fine cemented carbides have showed excellent mechanical properties, when WC spraying powder grain size decreases to 0.5 mu m, alloy shows excellent comprehensive performance, especially of ultrafine alloy treated by HIP, due to eliminate the residual pore in the alloy, the alloy properties (tensile strength) was further improved. There are many methods to prepare ultrafine tungsten carbide powder, but they can be divided into chemical method and mechanical method. Chemical methods mainly include spray heat transfer, organic salt thermal decomposition, one-step reduction carbonization, etc. The mechanical methods include high energy ball grinding, vibration ball grinding and mechanical alloying. Israeli g. r. graen-muginstein et al. obtained nanometer tungsten carbide powder with powder size of 0.6 m after 300h ball grinding, and dry grinding powder size was more uniform (5 ~ 10nm), while wet grinding powder size was wider (1 ~ 50nm). In this study, the submicron tungsten carbide powder was prepared by vibrating ball milling method.

Ultra-fine grain cemented carbide has high hardness and high strength, and is widely used in the manufacture of microdrill bits, dot matrix printer needles and precision tools for the drilling of integrated circuit boards. Ultrafine WC sprayingpowderis an important raw material for the preparation of ultrafine cemented carbide. At present, the reports of preparing nanometer, ultrafine tungsten carbide powder, or the way of the composite powder is more, there are mainly tungsten oxide reduction carbonization method (that is, the traditional process), directly carbonized tungsten oxide method, plasma chemistry carbonation method, halide tungsten carbide method, since the reducing amine salt, high frequency plasma method, gas solid instead should method, freeze drying, etc. These methods, the traditional process is simple and easy, reasonable, stable and reliable, large production capacity and advanced products of good quality, low cost and efficiency higher advantages, and is closely related with tungsten carbide production in our country,whichis a kind of conform to China's national conditions, more province industrial production method, literature, points out that the traditional process made BET size is less than 0.2 microns ultrafine tungsten carbide powder as the U.S. DOW company is the quality of the production of the tungsten carbide powder. However, other methods still have disadvantages such as complicated process, high production cost, low efficiency and many impurities, which are suitable for industrial scale production.

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Tungsten carbide ball is consists of cobalt alloy ball (YG6X YG6 and YG8 YG10, YG13), while the back of the figure represents the cobalt content, such as: YG6 refers to the CO content is 6%, the remaining 94% WC, there is another kind of tungsten nickel alloy ball (YN6 YN8, YN10, YN12), in the same way at the back of the Numbers represent a nickel. The proportion of two kinds of alloy ball in front of the 14.6 15.1, and those for titanium carbide alloy ball ball, weight is lighter.

Ball tooth bit is a kind of rock drill bit which appears with the development of hydraulic rock drill. It has high working efficiency, fast drilling speed and saves auxiliary working time. It is suitable for fast driving of high-power rock drill. Ball tooth drill bit in the drilling of brittle rock, with the use of high power hydraulic drill, the biggest characteristic is fast and stable chisel, drill bit grinding cycle is long. Since the 1970s, porter company has been researching and developing ball-tooth bit as its main product. Now, the sales volume of various ball-tooth bit accounts for 60% ~ 70% of the total production of the ball-tooth bit. In 1968, after adopting the precision hot-setting technology, sandvik company developed a series of ball-tooth drill bits with large and small diameter for percussion drilling, and recommended the ball-tooth drill head as the "ideal supporting drilling tool for hydraulic rock drill". In the next few years, ball tooth bit will take more and more proportion in rock drilling bit market.

After the 1980s, China began to pay attention to the research and development of ball-tooth bit. In the 1990s, the quantity and quality of domestic ball-tooth drill bits have been greatly developed (table 5), and the export volume is also increasing year by year. A batch of ball tooth bit manufacturers with larger output and better quality appeared, such as lianhuashan, chengtan, changsha mining institute, changjiang river, shaodong and so on. Among them, the ball tooth bit produced by lianhuashan takes a large proportion in the export bit.In the production process of ball tooth bit, high quality carbides of shell steel, high precision processing equipment, reasonable processing technology and heat treatment technology are the preconditions to ensure product quality. The ball tooth bit steel used in foreign brazing tool factory mainly USES chrome-nickel-molybdenum steel or silicon-manganese chrome-nickel-molybdenum steel. In the hard alloy aspect, each factory selects the high quality tungsten carbide ball, like Sweden DP series alloy, Germany GT series alloy and so on.

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The wear resistance of different particle sizes of tungsten carbide powder was compared and analyzed. The wear resistance of spray welding layer increased with the decrease of casting tungsten carbide particle size. The reason is: with the decrease of the particle size of cast tungsten carbide, its distribution in the spray welding layer is improved, and the microstructure of the spray welding layer becomes more uniform. On the contrary, the larger the cast tungsten carbide particles are, the larger the gap between them is, and the more easily the abrasive particles invade the base metal and wear it out. The casting tungsten carbide particles are widely spaced, and the scraping action of polygonal quartz sand edges and angles on the soft matrix phase on the surface of the spray welding layer will result in serious wear and tear of the matrix phase, and finally the hard phase particles will fall off due to the loss of the maintenance of the matrix phase. The cast tungsten carbide particles are small and the distance between the particles is small.

Casting tungsten carbide powderplays a key role in abrasion resistance during the process of wear and tear, and the shielding and protection of the softer matrix phase in turn leads to the matrix playing a good holding role relative to casting tungsten carbide alloy powder, so that it will not fall off. In this way, they rely on each other and play their respective roles.

Different kinds of tungsten carbide have great differences in hardness, toughness, cladding performance and so on. One or more mixtures can be reasonably selected as hard ceramic phases according to the working conditions.

Single crystal tungsten carbide can be prepared by mixing tungsten powder with carbon black in a high temperature carburizing furnace. The hardness and toughness of tungsten carbide are between cast tungsten carbide and sintered tungsten carbide. At the same time, it has good wetting property to iron group metals. However, the content of monocrystalline tungsten carbide in the surface composite material should not be too high, otherwise, the phenomenon of bridging monocrystalline tungsten carbide is extremely easy to occur, especially in the laser cladding process. The bonding force between the bridge surfaces is very weak, and it is easy to be damaged from the bridge surface under external load, resulting in spalling of tungsten carbide and reducing wear resistance.

Precautions for health protection of personnel in tungsten carbide powder production workshop

Due to the fact that tungsten carbide powder is a micro powder, the following matters should be noted by relevant personnel in the tungsten carbide powder production workshop:

1. Tungsten carbide dust can cause bronchitis, bronchiolitis, atresic bronchiolitis and atrophic emphysema.

2. Tungsten carbide can cause the proliferative reaction of lymphocytes in the lungs and gradually harden. The walls of the blood vessels thickened and homogenized.

3. Gastrointestinal dysfunction, renal irritation and catarrh inflammation of the upper respiratory tract occurred in people exposed to tungsten carbide dust at work.

Therefore, in the environment with access to tungsten carbide powder, it is necessary to use a gas mask, dust suit, gloves and glasses that meet the requirements. Tungsten carbide powder production in all stages to prevent dust leakage, workers to do pre-employment physical examination, a regular examination every year. When worker upper respiratory tract appears apparent symptom, want to transfer work temporarily, disengage from contact with tungsten. When appear lung sclerosis or outside respiratory function maladjusted, should transfer from the post.

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Posted by: hannahgwendolyn at 10:01 AM | No Comments | Add Comment
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The thermal expansion of wire drawing diesdiameter has a significant impact on the increase of steel wire diameter. In order to measure the distribution of wire drawing die temperature, drill 4 holes in the wire drawing die and insert thermocouples. The distance between each hole and the steel wire surface is respectively 1.5, 4.5, 11.3, 19.3 mm. The thermal conductivity of mold core and mold sleeve is 97,90 W/mK, respectively. Thermal expansion coefficient are: 4.7 x 10-6 / degrees, 12 x 10-6 / degrees. Lubricants are calcium based SCM 435.

Wire drawing die work half cone Angle 4 degrees~ 10 degrees, drawing speed is 10 ~ 110 m/min. Partial compression rate 11.6% (from 7.90mm to 7.42mm).

Half Angle is 7.5 degrees, the entrance of the wire drawing die wire drawing rate of 110 m/min, wire drawing die temperature within the original 2.5 min grew rapidly and stable 10 min later start, A, B, C, D of each hole temperature: 160150138130 degrees; Surface, 110 degrees.

The increase ratio of wire diameter is defined as h= (d-d)/d * 100, where d is the diameter of the drawing wire and d is the diameter of wiredrawing dies. When h is positive, the diameter of the drawn wire is larger than that of the drawing die. When h is negative, the diameter of the drawn wire is smaller than that of the drawing die. Hd =h-h0. In the production process, the difference between the original diameter of the wire before drawing and the diameter of the stable state is very important, so the diameter increase ratio is defined as hd. In drawing speed 110 m/min, working under the condition of half cone Angle is 7.5 degrees, relationship between hd and quality of wire drawing parameters as follows: the quality of steel wire before 200 kg, with the increase of quality, diameter enlargement ratio gradually increases to 0.1%, quality of steel wire after more than 200 kg of steady at 0.1%.

The temperature of hole A decreases gradually with the increase of the working cone half Angle in the steady state of wire drawing. Work half cone Angle is 4 degreesand 5.5 degreesand 7.5 degreesto 10 degrees, hole respectively A temperature: 175170165160 degrees. The diameter increase ratio was 0.15%, 0.12%, 0.10% and 0.08%, respectively.

Drawing under steady state corresponding,40,70,110 10 m/min, drawing speed, hole are A average temperature: 90120150170 degrees. When the drawing speed is lower than 80 m/min, the diameter ratio increases faster with the increase of speed. When the drawing speed exceeds 80 m/min, the diameter increases slowly as the speed increases. When the drawing speed is 10 m/min, diameter enlargement ratio closer to 0%, when the work is half cone Angle of 10 degrees, the diameter increased more than 0.1%.

Related link:
http://www.wococarbide.com/Transaction/en_article_info/id/661.html

Posted by: hannahgwendolyn at 09:37 AM | No Comments | Add Comment
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