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Generation and Prevention of Cracks in Carbide Cutters

Abstract: In this paper, the application of carbide cutting tools is summarized, and the generation of cracks in carbide cutting tools is classified. According to the two types of welding crack and sharpening, the causes of cracks are analyzed in detail. Combining theoretical knowledge And production practice, given reasonable and feasible preventive measures and methods, the processing of carbide cutting tools have some guiding significance.

Key words: Carbide; Cutting tool; Crack; Welding;

1. Classification of carbide cutting tools: Carbide is a commonly used production materials and tool materials, with some excellent physical and mechanical properties, hard alloy hardness, wear resistance and red hardness are high, so the carbide cutting tools in the cutting Widely used, carbide cutting tool is the use of brazing technology will be alloy head and tool steel body firmly connected together, the crack is the use of carbide cutting tools in the most commonly encountered problems, a direct impact on the normal use of the tool. According to the crack, it can be divided into macroscopic crack and microcrack. According to the appearance of the crack, the causes and preventive measures of the crack are discussed.

2. Analysis of the causes of welding cracks in cemented carbide cutting tools: Welding cracks are common welding defects of alloy cutting tools, the main reasons are the following: The Effect of Cemented Carbide Hardness on Crack Formation Generally, the higher the strength of the cemented carbide, the less likely it is to crack at the time of welding. However, the main properties of the cemented carbide are often inversely proportional to the strength and abrasion resistance, which means that when we require high hardness and high resistance Grinding of the carbide, it will face the possibility of low-intensity cracks caused by the possibility. Therefore, the higher the hardness requirements of the alloy tool, the more attention in the processing of cracks.

2.2 Effects of blade, blade and saddle shape on crack formation: If the welding surface is not flat, the blade and the shape of the groove does not match, will make the solder distribution is not uniform, so that in the welding process will produce a lot of stress concentration, resulting in cracks or cracks. If the saddle is closed or semi-closed groove, will be due to the welding area is too large, thermal differences in the welding layer at the greater stress to form a crack or crack. Therefore, in the case of welding strength requirements, as far as possible to reduce the welding surface and welding area.

2.3 The effect of heating on crack formation: Welding stress is the direct cause of welding cracks, which is mainly due to the hard alloy blade and rigid body arbor caused by the greater heat shrinkage caused. As the hard alloy (blade) and steel (arbor) linear expansion coefficient of a large difference, lower than the steel 1/3 to 1/2, rapid heating, the tool will produce a large internal stress, Stress is too large, that is, within the alloy that the tensile stress, when the tensile stress is large enough, the carbide blade in the welding layer will be cracked. The poor thermal conductivity of cemented carbide is also one of the important causes of welding stress, which made a very high demand for welding process, so the control of welding temperature and solder selection is essential. In general, the temperature should be controlled at a temperature greater than the melting point of the solder between 30 to 50 degrees is ideal, so the solder to choose its melting point is lower than the steel (argon) melting point of 40 to 60 degrees solder. Heating, the first to preheat the arbor, from the bottom up slowly warm up, even heating for welding, which can reduce the expansion coefficient caused by the difference between the internal stress, reduce the thermal stress so that the possibility of blade edge crack.

2.4 Effect of cooling process on crack formation: Due to the difference in heat shrinkage, the cooling process of the cemented carbide tool after welding is also an important reason for the occurrence of cracks in the cemented carbide. After the welding, the cooling is carried out, the cooling is too fast and the cooling is rapid. In addition, poor solder failure can also cause the emergence of cracks. Therefore, the welding to choose a good dehydration of the solder, after welding, do not quickly water or air cooling, to do insulation treatment, can choose to put dry asbestos powder, sand, limestone and other media in the slow cooling, when the slow cooling to 300 degrees , Then placed in the holding furnace temperature 6 hours, then with the furnace cooling.

3. Analysis of the causes of sharpening of carbide cutting tools: The physical properties of the cemented carbide determine the characteristics of its crack, due to its high hardness, brittle Large, poor thermal conductivity and poor resistance to vibration, so the grinding is easier to produce cracks, the main types of thermal cracking, cracking, cracking, burst, the main form of reticular cracks. Crack defects seriously affect the cutting performance of the tool, the intensity is reduced by about half.

3.1 sharpening crack: As the hardness of the carbide blade is very high, so in the grinding process is easy to make the wheel sand passivation, if the grinding wheel from the effect is not good, it will lose the required cutting capacity, increase the friction, grinding process Will be due to local high temperature to form additional thermal stress, resulting in thermal cracking. This type of crack is due to the combination of the properties of the carbide and the choice of the use of the wheel. Therefore, from the elimination of additional thermal stress factors to achieve the purpose of prevention of sharpening.

3.2 sharpening vibration: In the process of sharpening, the rigidity of the arbor is not good, the machine tool main axis beating, sharpening margin is too large, clamping instability and other factors will cause the grinding process vibration more than, so that the blade fracture phenomenon. Therefore, from the elimination of vibration to bring a variety of factors to achieve the purpose of prevention of sharpening.

3.3 sharpening: Grinding wheel, the wheel of the axial and radial runout is too large, the direction of rotation of the grinding wheel and the grinding direction of the cutting edge is different from the rake angle and the rear corner of the grinding order inappropriate, will make the edge of the crack, Tip arc, the main and vice cutting edge, the front and rear are likely to produce subtle chipping. So control the beating of the grinding wheel and the development of a reasonable chain of technology, is the key to control the grinding edge grinding.

4. crack prevention: According to the reasons for the occurrence of cracks, respectively, to identify preventive measures, the specific summary of the following aspects:

4.1 Identification of cracks: Cracks from this form can be divided into macroscopic cracks and microcracks two categories. You can first use the naked eye to identify the macroscopic cracks, microscopic cracks to use more than 10 times magnifying glass observation can also be used kerosene cleaning method, color detection method found cracks. Crack the identification of the time, to accurately with the crack of the tool selected to avoid entering the next process, affecting processing efficiency.

4.2 Prevention of welding cracks: Welding to the formation of a smooth, suitable, and the blade coincide with the welding surface, if necessary, do sandblasting treatment to reduce stress concentration; solder to choose high-strength solder, such as L104; welding available dehydrated borax, can also be used 70% dehydration Borax and 30% boric acid mixed solvent; welding, the first preheat the arbor, master the heating sequence and temperature; welding, carbide cutting tools should be low temperature tempering and cooling with the furnace.

4.3 Prevention of sharpening cracks: Select the 60 ~ 80 particle size, hardness of medium-sized silicon carbide wheel, and timely grinding grinding wheel surface, can choose to intermittent grinding has reached a good cooling effect; first with alumina grinding wheel rough grinding, and then silicon carbide grinding wheel grinding, grinding , To control the beating of the wheel, the direction of rotation and the direction of the grinding of the population to the contrary, to comply with the previous razor - chip breaker - vice chamfer - tip arc - repair light edge of the order, Fierce, his hands should take support measures to prevent the vibration, the blade is higher than the wheel centerline 1 ~ 2mm, as far as possible to reduce the contact area with the wheel, to prohibit the rapid cooling after grinding, the machine grinding, the machine beating should not be too large, with Sufficient coolant.

5. Summary: The factors that affect the cracking of carbide cutting tools are complex and diverse. To analyze the specific reasons, from the welding and sharpening process to start, and actively prevent and improve the performance of cutting tools to achieve savings and reduce efficiency and improve the efficiency of the purpose.

Asia's largest molybdenum deposit: Luanchuan molybdenum reserves of 2.2million tons

Luanchuan molybdenum reserves of 2.2 million tons, ranking first in Asia, the world's third. So, what is the molybdenum of Luanchuan? How is it formed? This has always been a fresh knowledge, mysterious test of a scientific issue. With a curiosity, the author after asking the experts to learn, access to relevant information, and gradually put aside its layer of mystery.

According to an authoritative magazine, the Yanshanian fault structure and granite intrusion in the eastern part of China were extensively developed during the Mesozoic Yanshanian period from 19500 to 67 million years. The crust and mantle in the eastern part of the Qinling orogenic belt are rich in copper, lead, zinc, gold, silver, tungsten and molybdenum in the East Qinling area between the North China plate and the Yangzi plate. After the multi-period, deep plate structure, magma eruption and strong activities, so that the region of copper, lead, zinc, gold, silver, tungsten, molybdenum complement the line, and finally superimposed mineralization, so that the East Qinling The area of ​​molybdenum deposits in the regional distribution, and the mineralization space and time to show it, so that the earth into a treasure house on the ground.

Zheng Yi in the "talk about molybdenum metal ABC," an article said: According to the classification of geology, Luanchuan molybdenum deposit mostly skarn type deposits, a small part of the vein-like type of porphyry molybdenum deposit The From the perspective of the formation of ore deposits, these two deposits are formed with ore-containing aqueous solution, so they belong to gasification hydrothermal deposits. The so-called gasification hydrothermal deposits, according to the geologist's argument, is due to the Earth's internal energy, including thermal energy, kinetic energy, chemical energy of the geological role, will produce a dissolved mineral water solution. This type of solution consists of magmatic water, metamorphic water, and atmospheric precipitation. Magma water refers to the earth's internal magma on the invasion of the crust on the shallow, due to reduced pressure to release the dissolved water; metamorphic water is in the rock's metamorphism from the sedimentary rocks in the hot water solution; To the precipitation, sea water will also penetrate into the depths of the ground. In the access to geothermal or magma heat, will become a high temperature hydrothermal fluid. As the magma contains sulfur and other mining metals, such as copper, lead, zinc, molybdenum, silver, etc., they in the process of magma crystallization, part of the separation into the magmatic water, the formation of mineral water containing hot water. In addition, hydrothermal fluids can also extract minerals from the rock they travel. In the flow of rocks, the ore-forming elements lead, zinc, molybdenum, silver and other trace with the presence of minerals in the general. Blazing hydrothermal fluids flow through rocks and react with rocks, and when these minerals dissolve or recrystallize, the ore-forming elements contain hydrothermal fluids.

Ore-containing hydrothermal fluids are gaseous and liquid, and are water-dispersed solutions with temperatures ranging from 50 ° C to 650 ° C. Under the enormous pressure of the deep crust, this dissolved mineral water solution flows along the rock fracture, and the fracture zone flows, and chemical changes occur in the solution. Although these chemical changes are extremely slow, but in the long years of tens of thousands of years it is endless, or very slowly led to the hydrothermal mineralization to saturation, so that a large number of concentrated precipitation, the formation of gasification hydrothermal deposit The The intense plate activity eventually sends these deposits to the strata that humans can exploit, which is the mysterious nature of the gift to the human nonrenewable mineral resources - molybdenum metal.

In the long history of mankind, although Luanchuan this ancient mountain deep occurred too much magnificent, twists and turns bizarre things, but the molybdenum deposit is hidden in the mountains unknown. Until April 1956, China and the former Soviet Union jointly organized by the South China Geological Bureau Qinling regional geological survey brigade (437 team) at the junction of Henan and Shaanxi to carry out geological survey, they found Luanchuan Nanning Lake and three village may be hidden large Of the molybdenum deposits. Once upon a time, the geologic players, after passing through the Jingxian spines, went to the followers. After 1988, after three years of arduous prospecting, only three mines in Luanchuan's Sandaozhuang, Nannihu and Shangfanggou were found to have molybdenum metal 206 Million tons. After the Luanchuan County in Taowan, stone temple, Sanchuan, clay, together Valley and other places to explore a number of molybdenum resources. Since then, a poor village of Luanchuan has become a shining pearl on the land of China.

In 2010, according to the authoritative department released the world of molybdenum resources, a news that: the world only the United States, China, Chile, Canada and a few other countries have a wealth of molybdenum and so on. The world's static molybdenum reserves of about 55 million tons, of which about 65% of molybdenum, or 36 million tons is available. The distribution of molybdenum reserves is: molybdenum reserves in North America and South America account for more than 80% of the total static reserves of molybdenum, accounting for more than 98% of the total reserves of Western countries. The total reserves of the United States, Canada and Chile are 43 million tonnes, accounting for more than 78% of the world's total static reserves. China has proven reserves of molybdenum 8.55 million tons, ranking second in the world. In 2006, China Mining Institute crowned Luanchuan as "China Molybdenum".

China's hardware tool mold market has entered the forefront of the world

At present, China's daily hardware industry has entered the forefront of the world. Has established a zipper, electric shaving device, stainless steel utensils, wok, blade, bicycle lock and other 14 technology development centers, pressure cookers, electric shavers, lighters and other 16 product centers. These centers are now the vast majority of the development of the industry vanguard, and some have become the world's vanguard, and achieved good economic returns. It is understood that China's hardware industry is now at least 70% for private enterprises, the main force for the development of China's hardware industry. China has gradually become the world's metal processing power and export power, and has become one of the world's largest hardware production, has a broad market and consumer potential.

Hand tools market: increasingly intelligent, humane, the international hardware market, Europe and the United States developed countries due to the rapid development of production technology and labor prices, the general product to the production of developing countries, only the production of high value-added products, And China has a strong market potential, so more favorable for the development of metal processing export power.

China's hand tool market is mainly distributed in Zhejiang, Jiangsu, Shanghai, Guangdong, Shandong and Taiwan and other places, including Zhejiang and Guangdong, the most prominent. Zhejiang Yongkang has always been known as the "handmade tool town", and Zhejiang people's market sense of operation is quite strong, from the original hot pot products, stainless steel insulation Cup to last year's rage skateboard, to bring them rolling resources. Guangdong is also about to become the world's hardware tools die center. At present, around the Shenzhen and the Pearl River Delta region gathered more than 6,000 mold enterprises, employing more than 200,000 people. Has been held in Shenzhen in five times the South China International Mold Exhibition, attracting 25 countries and regions, more than 1,000 enterprises to participate in China's most professional and international level of the mold industry exhibition.

DIY products become hardware-related industry market new darling. In recent years, in Europe and the United States with the developed countries of the architectural hardware products designed to easy installation and maintenance-based, self-assembly products and tools greatly welcomed by the market. According to the analysis, the next two years, the domestic architectural hardware products will also be intelligent, humane development path.

Taiwan hand tool industry to adjust the product structure. Taiwan hand tool industry with product quality and stability, delivery on time, complete product range, with the needs of customers in the world has certain advantages. And Taiwan hand tools sold to the island-based market, the current local manufacturers about 5000, mostly in the central area of ​​Taiwan Island, mainly to small and medium enterprises. According to the survey data show that the individual hand tools for the product category, the sleeve for the export bulk, followed by hand tools, the third for gardening tools, wrench class ranked fourth, clamp class ranked fifth.

Tool market: market competitiveness continues to increase, it is reported that the world tool market demand continues to grow. Among them, Europe and North America grew steadily, especially in Eastern European countries. The Asian market rebounded slightly, with great market potential and marked growth in Latin American countries, especially in Mexico. At present, the world's cutting tool sales of more than 10 billion US dollars, industrial development of Europe, North America, Japan and Australia three major market share of 75% - 80%.

In Asia, China is also an important market. It is predicted that China's tool demand between 70-88 million yuan, of which high-precision, high efficiency, high reliability of modern cutting tools, such as cemented carbide and ceramics and other super-hard tool material can be transferred to the amount of tooling 1.2 billion yuan, of which 80% - 85% dependent on imports, mold manufacturing tool imports accounted for more than 90%. In the past year, the demand for tool market is growing slowly, mainly because of increased tool life, and then the user for the entire manufacturing process requirements, replacing a lot of machine tools and tools. As well as the application of multi-function tool increases, replacing a lot of previous single-function simple tool. In the future, users will pay more attention to the research and development of the tool in the production plant, not only in the field of materials and surface coating technology, but also in the tool products and their production process focus on production practice, to help tool manufacturers increase in their familiar areas In the market competitiveness.

From the tool product technology, Japan's DIJET, BIG, OSG, Sumitomo Electric, Hitachi, Japan, the newly developed high-speed high-hardness tool can be processed to the hardness of HRC70, Toshiba Tyco's high-quality products TAC fast cutter series carbide cutting tools Gradually replace high-speed steel cutting tools, especially circular knives. The United States Kenner knives, Sweden SANDVIK, high-cutting tools SECO company, SPINNER companies such as coating applications more and more common. China's knives and measuring instrument of the well-known enterprises Zhuzhou diamond tools, Guilin Guanglu digital monitoring and control companies also provide a newly developed products, to participate in international competition. High-speed processing with new tool market share continues to grow. From the tool manufacturers to cooperate with the point of view, in the field of high-tech market will appear a lot of big companies strong combination.

Mold industry development overview and trends in recent years, industrialized countries increased labor costs, its positive to developing countries, especially Southeast Asian countries, the domestic production of high and fine mold-based, large amount of artificial labor to rely on imports of mold solve.

"Eleventh Five-Year" period, the overall trend of China's mold market steady upward. At present, the domestic market for high-end home appliances, automobiles, plastic products, a great demand for mold, but requires domestic mold must be in terms of quality, delivery and other aspects to meet the needs of users. China's accession to the WTO, along with the wave of world economic integration, the global manufacturing industry to accelerate the transfer to the Chinese mainland is the trend, China will gradually develop into a world-class manufacturing base. Middle and low mold international market potential is very large, as long as the quality of domestic mold can be improved, delivery time to ensure that the prospects for mold exports is very optimistic. The obvious advantages of Guangdong, especially the Pearl River Delta region, will be developed within ten years into the world mold production center. At the same time, in recent years, China's annual consumption of nearly 1 billion US dollars of molds, including precision, large, complex, long-life mold accounted for the majority, so from the perspective of reducing imports, such high-grade mold in the market share will gradually increase The Modern molds of its high-tech, talent-intensive, high-tech background of the characteristics of the process-intensive industries, is in the new road to industrialization in the front of the industry, mold as an important manufacturing equipment industry for all walks of life at the same time, Directly for the high-tech industry services, molds in the manufacturing product development, innovation and production has a unique important position, making the mold manufacturing capacity and level of the level of national innovation has become an important symbol.

In 2010, the economy gradually stabilized, the mold as a manufacturing industry to change the growth mode, the key support of industrial restructuring, undoubtedly has a pivotal position, communication manufacturing upstream and downstream industries, and jointly promote the development of mold manufacturing industry has become an important task of Shenzhen Die Technology Society.

Mold industry to support the upgrading of the automotive industry products, it is learned that in 2009 China's passenger car to change to 221 (of which 175 cars), more than 114 in 2008. Independent models of 120 models, and as a full range of midfielder Passat die value of more than 250 million yuan, large plastic mold worth about 35 million to 40 million; from the car's heart generator cylinder die to the automotive white body stamping parts, from the accelerated China's energy-saving environmentally friendly vehicle R & D process (such as automotive engine plastic intake manifolds accounted for 80% of foreign, injection molds to achieve), to the new material super steel plate hot forming die, need to drive the core parts of the automobile industry Localization, high-grade car cover mold, automotive lightweight new material forming mold and multi-station progressive die are to promote the development of independent brand car protection, mold equipment is an important part of automotive equipment.

Household appliances industry: home appliances parts to rely on sheet metal stamping, plastic, foam, adsorption and other molds, a refrigerator need 150-200 to pay the mold, an air conditioner needs 50 or so of the mold, a washing machine needs about 60 pay Of the mold, there are a lot of small appliances ... ... Haier company a year to buy 6000 or so die, the amount of more than 5 billion December 2009, the Ministry of Industry issued a "speed up the upgrading of China's household electrical appliance industry guidance", for product upgrades, upgrading the important task of technology to speed up the transformation and upgrading of home appliances. (Such as low noise, energy saving, multi-room, etc.) mold manufacturing level is also the level of home appliance manufacturing process to improve the performance. According to statistics, in 2009 China's plastics industry 600 billion in sales, driven by 1: 100, has been 6 million mold support.

Aviation equipment technology and mold manufacturing, sheet metal equipment: as an important basis for aviation manufacturing technology, aviation sheet metal equipment technology mold to provide the main equipment for its molding in the superplastic forming equipment, thermoforming equipment, spinning equipment, bending Forming equipment, etc., a large board three-dimensional surface of a product forming molds often need dozens or even hundreds of sets of sheet metal from the surface of the mold; in the multi-point forming, the mold manufacturing will be discrete into a series of regular rules, Tune the basic body to complete the envelope surface, and then multi-point forming technology development of multi-point forming machine and so on.

Aircraft interior parts mold technology research and development and industrialization: supporting the development of China's commercial aircraft to provide products, mold manufacturing technology, selection of strong, fire-retardant, anti-smoke, thermal engineering plastics, combined with aviation technical standards and requirements for Aircraft interior parts of the material selection, product structure analysis and design, mold design and manufacturing and final product assembly of the entire technology research and development to achieve the aircraft interior parts complete sets of industrial applications. In the aircraft interior parts, the use of plastic to improve the aircraft to help reduce the weight, saving fuel, reduce costs. According to incomplete statistics, aircraft interior parts in the mold about 200 sets, the output value of a billion, driving the output value of about 30 billion yuan.

Electronic special equipment and new industries supporting areas, equipment manufacturing industry restructuring and revitalization plan ", in the" nine key industries to seize the key projects, the implementation of equipment autonomy, "the content of the first eight" electronic information industry "will be electronic Equipment, equipment and die as the focus, to promote the autonomy of information technology equipment.

Large scale, very large scale integrated circuit with lead frame precision multi-station progressive die, integrated circuit precision packaging mold, electronic components and precision connectors with precision molds, chip precision stamping die, automotive electronic mold as the frontier, computer peripheral Mold, multimedia digital products die, photoelectric communications products die, network products, molds, watches and clocks, and so die with the development of IT and information technology will be more and more demand. China is already the main producer of OA equipment and consumables (photocopiers, fax machines, printers, etc.), more than 60% of copying equipment, more than 40% of the image printing equipment manufactured in China, while the world's major OA equipment manufacturers in China Parts also makes OA equipment plastic mold development rapidly.

Medical equipment, according to the calculation of 10,000 kinds of products, 34 categories, 4000 enterprises. Such as health care equipment, polymer plastic products is also part of it. Almost all of the parts involved in molds, large to high pressure oxygen chamber, small to hearing aids, heart pacemakers ... polymer composite materials, bio-life engineering, medical equipment parts and components supporting the production of precision, ultra-precision molds will be manufactured in medical equipment Has a pivotal position.

2009, 40 million investment in the country, the direct investment in rail transport is 7,000 million, while the EMU core components of ultra-high-speed (300 km / hour) precision bearing mold core technology, speed 200 - 350 km high-speed EMU, High-power AC drive power / diesel locomotive, load 100 tons of rail heavy truck and urban rail transit vehicle bearings, gear drives, high-speed EMU gearbox precision casting mold; heavy-duty 25T axle heavy forging die, cold pier mold And so will support the emerging industry services.

Progress of Tungsten Carbide Roll for Metalworking

Abstract: In this paper, the development history, raw material selection, grade and binder content, manufacturing method and process, quality control and application of the carbide indentation for metalworking are described and discussed in detail.

Key words: metal processing, carbide roll, progress

In the carbon steel, alloy steel, nonferrous metals and their alloys processed into the line, bar and sheet rolling, the past used in the rolling rods are mostly made of tool steel and cast iron. Since the 80s due to the development of rolling technology, the speed of its rolling stick has reached 95-112 m / s. Even higher. Because the use of heat-resistant tool steel and cast iron made of bar, can not meet the requirements of high-speed rolling production. In order to meet the needs of industrial development, in recent decades a number of advanced production technology countries, have developed the production of carbide lumps, and continue to improve in quality, there have been standardized and serialized brand. Formed a special production line.

According to the current information reported, the Swedish company produced by the company, CT, CR and CG carbide tire ring Up to 12 species; West Germany Hurt produced MN and a MNC carbide rolling ring series of 10; Luke Lin Boer Barker produced VG and YN series 5; Pulani metal company 5; Five kinds of US companies; five US carbide companies; three kinds of carbide companies; Japan's Mitsubishi Metal Company 3; the United States Kenya three kinds of metal companies.

In particular, the Swedish company has long established a complete alloy roll ring production workshop, the production of 12 roller ring grades, more than 30 kinds of specifications. The largest roller ring diameter of up to 445mm, the current annual output of more than 10,000, about 175 tons of carbide weight, roll ring sales to the rest of the world.

China due to reform and opening up. Iron and steel non-ferrous metal processing industry has been a high-speed development. According to the statistics. China's current introduction of the level of modern technology, high-speed wire rod mill about more than 20 production lines, coupled with the domestic design of more than 10 wire production lines, wire production capacity greatly increased. High-speed rolling mill rolling 05-12.5mm wire production capacity of more than 600 million tons, we can see, the demand for carbide roller ring will increase and expand. In order to reduce the import roll ring. So that the roller ring localization, the current carbide roll, roll ring production, improve quality and reduce costs is very necessary.

Vigorously promote the application of tungsten carbide roll its significance is very far-reaching. The use of tungsten carbide rolls can greatly improve productivity and achieve higher quality processing materials. It is said that in typical rolling applications, tungsten carbide rolls can be lifted more than 10 times longer than steel roll rings. Plants that use steel or cast iron bars often need to be equipped with one or more barbed manufacturing facilities, requiring extensive management and production of engineering and technical personnel. With the use of tungsten carbide roll rings, only a few management and assembly personnel are required. This can save a lot of labor and maintain at a lower cost.

In the metal processing process, the requirements of the tungsten carbide roll is very harsh and complex. Because rolling tungsten carbide roll ring is not only in high temperature and high pressure conditions, but also must be able to impact and corrosion resistance. Therefore, for the tungsten carbide roll ring, not only must have sufficient strength and wear resistance, and must have a high thermal fatigue strength, corrosion resistance and oxidation resistance. In addition tungsten carbide roll ring must also have a good processing surface, that is, the density should be high, porosity should be reduced, otherwise it will affect the quality of processed products. It can be seen that in the production of carbide ring rolling ring on how to choose the material, how to choose the production process and design a reasonable structure is to create high quality tungsten carbide roll ring an important part. Therefore, this paper discusses the development history, material selection and production process of different materials of cemented carbide, and gives an overview of its application prospect.

2.tungsten carbide roller material development history:

Tungsten carbide was developed by metal researchers in the early 1920s. The presence of tungsten carbide. The tool material has undergone epoch-making changes, the development of the industry and the improvement of productivity plays an important role in promoting. Tungsten carbide is first used in metal cutting, followed by mining tools, drawing die and wear-resistant corrosion parts, with the development of industrial technology, but also to further expand the application of tungsten carbide. Since the 80s, tungsten carbide roll ring in the rolling process occupies an increasingly important position. What is the reason for the tungsten carbide roll to flourish? The first is due to the emergence of modern production technologies and equipment, such as large presses and large sintering furnaces, especially HIP equipment applications, not only to make large-size alloy products made possible, but also to obtain a small porosity or no porosity Tungsten carbide (in this way, the alloy can improve the toughness, fracture stress and impact resistance of 1-2%), so that the production of rolling tungsten carbide roll from 5% to 95% pass rate, the cost of production Greatly reduced, to meet the requirements, such as Sen's roll that requires a perfect mirror finish. As the density and structure are improved, other properties have also been improved, which for the tungsten carbide as a roll material laid a good foundation. Second, the use of tungsten carbide roll than steel or cast iron roll life greatly extended, greatly enhance the productivity, maintenance roll costs greatly reduced, allegedly using tungsten carbide roll or steel bar than the life of iron to increase ten times, tens of times or even hundreds of times The

Again, the application of tungsten carbide in cutting tools and mining tools has largely reached saturation, so many tungsten carbide manufacturers have gradually shifted production targets to develop in mechanical parts and abrasives, and in just a few years Alloy hammer, disc scissors, sticks and other production is set off a climax. The current tungsten carbide roll is used in many different rolling processes. Tungsten carbide roll is extremely important and increasingly important for rolling foil, bar, wire and plate. The rolling mill with hot rolling and cold rolling are used in the hot rolling of the tungsten carbide roll: the wire rod is finished rolling rolling ring; the rod semi-finished rolling roll; the round ingot and the square Steel for the steel bar for the steel bar; the roll for the steel bar of the circular ingot, the steel bar, the roll of the clamping roll, the inlet guide of the roll, and the like. The tungsten carbide rolls used for cold rolling are: multi-roll mill rolls; 2-Hi narrow strip mill rolls; rolls for flat yarns and molding mills; ERW pipe rolling mills;

Due to the further improvement of the composition and microstructure of the tungsten carbide, such as the improvement of the composition, the pure use of pure WC-Co as the lacing ring has been basically used in the past, but its impact is limited due to its insufficient impact resistance, poor corrosion resistance and oxidation resistance The Recently, Co-Ni-Cr was used as a binder, and its corrosion resistance and oxidation resistance were greatly improved. On the other hand, due to the progress of the process technology, we can make a certain granularity of the uniform WC powder, which can control a certain grain structure and make the alloy performance to meet the rolling requirements, we can see, with the development of tungsten carbide, Production development, its application will continue to expand.

3 choice of raw materials: the production of tungsten carbide roll raw materials are mainly we and Co powder, in order to control the grain size and other special purposes also add a small amount of other elements additives. 3.1 WC powder The production of tungsten carbide is usually tungsten metal powder and carbon black in the rotary mixer for a certain time to make it evenly distributed. Because of the large difference in the specific gravity of aluminum and carbon black, it is difficult to obtain uniform powder when mixing. Therefore, some methods of wet mixing, regardless of the method of mixing, must strictly consider the increase and decrease of carbon and oxygen in order to get Requires WC powder. Mixed with a good powder, the general use of carbon tube furnace, key furnace or high-frequency furnace for carbonation. During the carbonation process, the mixture of pin and carbon black is compacted into the graphite boat and then placed in the furnace. Through a hydrogen-protected furnace, the furnace temperature is about 1375'C-1650'C. The correct temperature control should be based on the required particle size. The usual rule is that the higher the carbonization temperature, the greater the particle size. The purpose of carbonation is to make the carbon content of WC powder as much as possible to reach the theoretical content, where the free carbon, oxygen, nitrogen as low as possible. The total carbon content of the WC used for the production of tungsten carbide rolls is between 6. 1-6 and 15%. The grain size of WC has a significant effect on the quality of tungsten carbide roll. Because the grain size greatly affects the performance of the roll material. For the production of tungsten carbide rolls, the WC grain size is generally in the range of 0.1 to 0.40 m. For a certain amount of binder, increasing the grain size of WC reduces the abrasion resistance, but improves the toughness. Therefore, the hot-rolled rolls must be coarse-grained alloys of relatively high rigidity, and low Co fine grain alloys are generally used for cold bars. In order to control the alloy grain size to the required level, not only to carefully control the grain size of W, but also to control the grain size of tungsten carbide.

3-2 Co powder:The cohesive metal commonly used in the production of tungsten carbide is Co powder. The metal Co powder is obtained by hydrogen reduction with pure oxidized diamond. However, most tungsten carbide production plants have lost the chemical process of drilling, the purchase of high purity ultra-fine metal Co powder as a cemented carbide binder. WC-Co tungsten carbide, which is currently used as a binder for BT, is the main alloy for metal processing rolls because Co has good wetting properties for WC. In addition to Co, in order to further improve the performance of the alloy to achieve a special purpose and requirements, also used Co-Ni-Cr as a binder. It has been proved that the addition of Cr in Co - Ni can significantly improve the corrosion resistance and oxidation resistance of cemented carbide. Due to the better corrosion resistance and oxidation resistance of WC-Co than Co-Ni-Cr binder , While the strength and hardness and WC-Co and quite, so successfully used as a high-speed steel roll hot rolling ring material.

4 tungsten carbide roll grades and binder content: the application of the bar, the main need for a certain degree of strength and wear resistance, so the general choice of "standard grade" or "pure WC grade" as the basic bar Grade. However, in order to control the grain size of the alloy or for other special requirements, a small amount of other elements can be added, so the use of standard alloy grades for rolling applications is the most common. In order to meet the requirements of different uses, adding bonded metal powder is variable. The most commonly used bonding metal powder: Co powder (the best toughness and wear resistance); Ni powder (to improve the role of corrosion); Co-Ni-Cr alloy powder (to improve corrosion resistance and oxidation resistance) The.