May 31, 2017

Technological measures for preventing carbide inserts from grinding crack defects

Carbide inserts has high hardness,high brittleness, poor thermal conductivity, heat shrinkage rate, usually should be grinding with diamond grinding wheel with diamond grinding wheel. But the price is expensive, not easy to wear after repair, so many factories still use the ordinary grinding wheel for grinding.In the grinding process, the higher in hardness. Ordinary wheel, abrasive easily passivated, sharp blade surface friction to produce local high temperature, the formation of additional thermal stress caused by thermal deformation and cracks, directly affect the service life of the cutter and machining quality.Therefore,we should take the necessary measures to prevent grinding cracks. Through processing practice, summed up the technological measures the following can effectively prevent or reduce the grinding crack.

1.negative edge grinding method

Negative grinding method refers to a sharpening tool, first in the rake face or flank grinding out a negative edge. The hard alloy belongs to brittle materials, the grinding wheel vibration due to the cutting tool by impact load, prone to crack; at the same time, the instant heating and cooling the grinding zone the thermal stress may exceed the strength limit of cemented carbide and hot cracks. The negative edge grinding method can improve the strength ofcarbide inserts, blade to enhance anti vibration and impact load bearing capacity, and increase the heating area, to prevent the grinding heat large guide blade, so as to reduce or prevent cracks.

2.wheel with molybdenum infiltration

At room temperature, the powder and ethanol mixed solution made of molybdenum disulfide, then in a sealed container (to prevent evaporation of ethanol) will be the new ordinary wheel soaked in the mixed solution, removed after 14 hours, natural dry for 18 to 20 hours, the grinding wheel grinding wheel dry completely.By the treatment with internal voids of molybdenum disulfide the abrasive grains can lubricates the grinding wheel chip is good, is not easy to be blocked. The test proved that the grinding hard alloy blade with molybdenum wetted, sharp grinding, abrasive easily passivated, the deformation of the workpiece is small,smooth chip, chip shape with a band, take away most of the grinding heat. In order to improve the grinding effect, improve the blade yield.

3.reasonable selection of grinding parameters

If the excessive friction in the process of grinding, the grinding temperature can lead to a sharp rise, hard alloy blade is prone to burst, so the reasonable selection of grinding parameters is very important. The reasonable grinding parameters commonly used for circumferential speed of v=10 ~ 15m/min, =0.5 ~ 1.0m/min longitudinal feed f f =0.01 ~ 0.02mm/,horizontal stroke. Manual grinding. The longitudinal and transverse feed are not too large.

4.other technical measures

The knife rod rigidity tool holding spindle instability,beating can cause grinding cracks, therefore, by machine,grinding,machining system of fixture and tooling composition should have sufficient rigidity, and should control the grinding wheel axial and radial runout.

There are many factors caused by carbide inserts produce grinding crack,only choose the appropriate grinding wheel,the grinding process is reasonable,which can effectively avoid cracks, improve the grinding quality.

 

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May 27, 2017

Carbide dies as high-quality dies are developing towards high-end market

The cemented carbide dieshas basically been serialized and standardized. From the development of recent years, the research and design theory of cemented carbide die in China has been further, more scientific and more widely applied. Along with the rapid development of social economy and science and technology, with the tide of economic globalization, China on equipment manufacturing industry especially the high-end equipment manufacturing industry put forward new requirements, the development of high-end equipment manufacturing industry in China, the corresponding mold and the equipment manufacturing industry is closely connected to the standard industry, high-end hard alloy mould products market needs and requirements attendant. Industrial developed countries attach great importance to the development of standard parts for high-end cemented carbide die, especially high quality carbide mould standard parts. Mold standard parts can guarantee the quality of industrial products. As China's economy has entered a stable period, the gradual optimization of industrial structure, the quality of industrial products like requirements is also more and more high, this to the standard mold requirements are increasingly high, hard alloy mould China mold standard parts to the high-end market is the inevitable trend of development.

Cemented carbide dies is a very important alloy product. It can be used in many places, such as cutting tools, and it is also used in mining and road engineering. It has a very good hardness, and very wear-resistant, but in the process of use, there are many places to pay attention to. Before using the carbide die, read the relevant information in detail, and be proficient in the operation so as not to panic in case of an emergency. Secondly, in the process of normal operation of the machine, it is necessary to make good monitoring of the equipment status, and if it fails, it can be found and eliminated as soon as possible. It is also important to note that the operator should wear overalls and work caps to prevent accidents. In the process of machine operation, especially in the process of moving, you should pay attention to the surrounding environment, and avoid trees such as trees, wires and so on.

Uninterrupted operation of cemented carbide dies in practical applications often has a long time, so the equipment in use for a long period of time even after the failure should be suspended for a period of time, and do a good job of equipment inspection and maintenance work to ensure the normal operation of the machine.

Forming manufacturing technology and processing technology, mold manufacturing process of modern hard alloy has been very simplified,the standard mold parts, not only the accuracy, quality has been able to meet the requirements of assembly, and can purchase from the market, forming a blank, including forging, rolling template, can also purchase from the market.

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May 26, 2017

Pay attention to the details of using tungsten carbide blade

All factories have a collection point for scrap blades. There is no such thing as more interesting than the study of scrap blades,which leads to the formation of a pragmatic view of how carbide blades are used (and misused) and can be used to reduce costs.

The considerations should be the following easy to measure factors:

How many different types of blades are used?

What is the average number of cutting edges that a blade has?

What percentage of the cutting edges used in relation to the length of the cutting edge?

What are the number of worn, damaged or unused cutting edges?

The content of this article is based on the study of a large customer of a mountain tool. The results of this study represent a similar study conducted by our company.

Blade difference

The first fact to be determined is that the carbide blades used are very different. In our sample, there are 638 different blades to maintain the operation of six CNC lathes. The good side is that each blade is the champion of every category. But the 638 blades are packed in 10 boxes each, meaning 6380 stock blades. All this is just to keep the six lathes running. The next fact is that each blade has a relatively small number of cutting edges. In many workshops, the blade is still triangular or diamond. The possibility of the best combination of the number of cutting edges (triangular blades) and the cutting edge strength (diamond blade) provided by the convex triangular blade is clearly not enough to be recognized in many workshops.

In 1970s, the best advice would be to use a large, robust blade. The hard alloy used in that period was tough but not good enough. The strength of tungsten carbide blades is guaranteed by their size (large blade = thick blade = high strength blade). A blade requires that its cutting edge be at least three times longer than the cutting depth. Two things have changed at the same time. On the one hand, the average cutting depth for turning has been obviously reduced.

A study carried out by seco showed that the average cutting depth of turning about 2.5~3mm. on the other hand, the fourth generation of hard alloy today (such as TP2500) has very good toughness, but also its hardness (higher wear resistance). This means that for today's cemented carbide blades, the relationship between the length of the cutting edge and the depth of the cut can be radically changed. The geometry of the blade of the latest generation (for example, MF5) is clearly suited to the new situation.

Unused cutting edge

The situation becomes really clear when you look at the blade according to the way they wear in use. The correct form of cutting edge wear is the safety, predictable and controlled wear of the flank.The cutting edge should not break. The cutting edge is broken because of incorrect use or improper selection of the cutting edge. The cutting edge must be "worn" before being thrown into the box that holds the worn cutting edge. The new cutting edge, which has not yet been discarded for processing, is always striking.

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May 25, 2017

How to improve the durability of carbide turning tools

In addition to good tools, coated cutting fluids, there is a new process for cutting off the thermal circuit.

As everyone knows, in the process of metal cutting and chip deformation due to friction, so that the cutting area had a high temperature, at the same time as the tool and the workpiece of different materials, a thermocouple poles caused thermal electromotive force, the DC current heat. It is easy to strengthen the oxidation process of surface of carbide turning tool,and accelerate the tool wear. Under certain conditions,a thermal electromotive force is also generated in the contact area between the tool and the machine tool, the contact area between the workpiece and the machine tool,and the friction pairs of the machine tool itself. During the cutting process, there is also a thermal magnetic effect and an electromagnetic effect. In the high temperature contact zone,the surface will also produce electron emission of discharge phenomenon.

In recent years, domestic and international science and technology researchers show that the heat caused by thermoelectric current generated in the cutting process and other factors, the two heat current is to form a loop through the machine tool workpiece tool system. At the same time, there is a local thermal current in the tool - workpiece limited contact area cycle, and therefore exacerbated the tool wear. So, to improve the cutting performance and improve tool life in addition to the above basic way, can also adopt a new approach,and the strengthening of carbide tool wear thermal flow effect to fight, to cut off the hot current loop.

Cutting method of heat current circuit is very simple, even if the tool insulation and machine tool or workpiece and machine tool, the thermal current loop cannot be formed by cutting area, so as to reduce metal affinity,reduce bue and scale production,so as to improve the cutting performance of carbide turning tool, improve the tool life and processing quality.

How to cut off the thermal current loop. On the lathe, in the various carbide turning tool with a bakelite pad knife plate or plastic pad knife plate, the knife rod under the plane, and the side of machine tool carriage of insulation; milling, planer, if the vise clamping the workpiece,and the workpiece between jaw pad of wood or rubber the insulation board,workpiece and cutter and clamp the drill; it can be made of high strength plastic and plastic handle shank drill cutter, the shank and the spindle hole insulation.

It has been proved by practice that cutting off the heat current circuit is especially suitable for the processing of high strength, high hardness and hard cutting materials to show the effect, and the durability of the tool is usually increased by 1~2 times. Therefore, it is one of the easiest and easiest methods to implement.

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May 24, 2017

Systematic development of tungsten carbide cutting tools

Due to the high impact of high speed and high impact load on high speed milling,tungsten carbide cutting toolscan withstand the risk of breakage and fatigue at high speed. It turns out that in the case of repeated rotating load, 30% of the stress can cause the carbide to be damaged. So in high-speed cutting applications, the strength of the blades, the toughness and the resilience are the primary considerations. In addition, the high speed cutting tool material requirements: the blade surface quality and overall material of very low density of defects, and consistent with the subtle structural and fine grain size is the same important. Cutting material containing Cobalt (Cobalt) component of the higher, the greater the toughness and the fracture resistance of materials, the smaller the grain size, the higher the wear resistance, but in the process of cutting when the temperature increases, deformation resistance will be reduced. In the above tests, a typical tungsten carbide material is suitable for the application of aluminum materials for aerospace applications. A microstructure of a tungsten carbide type, WC -6co, shows the compact structure of uniform and fine grinding without alloy square particles. The uniform grain is about 1 mu m, and the hardness is analysed to 1630 HV30.

Crater wear, flank wear, the devolop tumor, edge defect and gap abrasion are the blades in the early failure of the main topic, and reduces the surface quality of workpiece materials. A surface polishing process called "mircrofinish", which USES a mirror (surface polished) blade, can reduce the wear and tear of the crescent, the edge defect and the debris tumor. The tool series did not use a special coating in the test,and all the tungsten carbide cutting toolswere carried out under uncoated conditions.

It has to be said that a revolutionary carbide blade design method has improved the quality of the structural components of the space industry and the surface surface of similar artifacts. By the blade, blade, blade axial ready-made tolerance,and in the process of cutting tool deformation produced by the deviation, can be used to the elliptical structure to a certain degree of compensation, and at the same time avoid the sharp edge of blade structure and formed by two milling knife pitch. (chip breaker with large positive rake Angle trough) and V groove design can make the cutting speed and feed the ascent to 7000 cubic centimeter clearance volume per minute, and maintain the good surface quality and smoothness. The design of the v-shaped slot allows the blade to withstand a strong centrifugal force, at a high speed of 40, 000 RPM. To achieve the reliable cutting process and the best surface finish, the additional factors such as the effect and vibration are also considered. Especially the analysis of the vibration, this is common in machining of tungsten carbide cutting toos and the spindle system of special natural resonance frequency excitation, increase the understanding of its technology application in the cutting tool performance and make a more correct guess. Light alloy aerospace applications thin-walled components, through the special design of carbide blade shape, selection of tungsten carbide and body set, make the processing application more effective, more productive, and at the same time to obtain a better surface quality. But in high performance (high quantity of chip removal) advances in the application of feeding and cutting speed, cutting tools, lathe spindle and manufacturers still faces from stability, the spindle design, process control system and security of each category of new challenge.

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May 22, 2017

Cold extrusion finishing with carbide turning tools

The size of the extrusion allowance determines the magnitude of the required extrusion force, and the magnitude of the extrusion force has a direct bearing on the extrusion effect.If the extrusion allowance is too large, the extrusion knife will wear rapidly, resulting in a lower surface quality; if the extrusion allowance is too small,it will not meet the expected processing goal. Therefore, the minimum extrusion allowance should be chosen as long as the extrusion accuracy is guaranteed. Generally, when extruding carbon steel and alloy steel material, the extrusion allowance can be selected from 0.025 to 0.04mm, and 0.03 to 0.05mm should be selected when squeezing the cast iron. When the workpiece material is soft (such as non-ferrous metal) can choose larger extrusion margin; workpiece size is small, should choose smaller extrusion margin, in order to prevent overall deformation. As the extrusion allowance is affected by extrusion, surface hardness, surface roughness of workpiece before extrusion and workpiece wall thickness, it is better to test extrusion before machining to determine the optimum extrusion parameters. High speed extrusion finishing can make extrusion cutter and workpiece surface contact zone temperature, workpiece surface yield strength decreased, the workpiece is easy to deformation and lower surface wave in the trough, thus improving the surface roughness of the workpiece. But if the extrusion speed is too high, it will destroy the lubricating oil film, which will easily cause burns or scratches on the surface of the workpiece. Therefore, there exists an optimum speed of light absorption (which can be obtained by experiment). When processing ferrous metal, the extrusion speed can be selected between 0.5 and 1m/ s, and the amount of the knife can be selected between 0.01 and 0.03mm/r. The bigger value is taken when machining the excircle, and the smaller value is selected when machining the inner hole. The following problems should be paid attention to in extrusion processfor carbide turning tools:

The working parts shall be the straight line of 3 to 5mm on the extrusion edge, and the tungsten carbide turning tools should be squeezed about 1mm higher than the center. Extrusion process should be adjusted according to the various phenomena produced by the workpiece surface. Such as the workpiece surface pitting or scratches, extrusion showed that blade surface roughness, burnishing speed; the surface peeling phenomenon indicates that the large amount of repeated extrusion, extrusion or workpiece material ductility. Lubrication and cooling in extrusion process are very important. Before extrusion workpiece surface does not allow the existence of rust, oil, iron, dust, lubricating and cooling fluid should be injected into the full extrusion process, to take the heat generated in the extrusion, prolong the service life of extrusion knife. Usually, the mixture of oleic acid and kerosene can be used to squeeze the cast iron. When it is used to squeeze carbon steel and alloy steel, oil can be used as a cooling lubricant.

The extrusion test and the processing practice show that the cold extrusion finishing of the workpiece with carbide turning toolson the surface has the advantages of reliable quality, simple operation, economical and practical, high efficiency and low cost. Before extrusion workpiece surface roughness is Ra3.2 ~ 1.6 m after extrusion surface roughness is Ra0.8 ~ 0.2 m, improve the rate of up to 70% ~ 90%; by extrusion can also reduce the size of the workpiece diameter tolerances; extruding after burnishing hardening layer of workpiece is 3mm, which can greatly improve the fatigue strength of the workpiece and anti corrosion ability. If the extrusion knife is mounted on a vertical lathe, extrusion of the oversize workpiece beyond the grinding range of the grinding machine can be carried out. The extrusion processing method has wide application range, and can be used for processing ferrous metal materials and processing non-ferrous metal materials.

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May 19, 2017

discusses how to select thermal spray materials for coating

 

Thermal sprayingis a series of process,in the process, fine and dispersed metal or non metal coating material in a molten or semi molten state, deposition to a substrate surface after preparation, forming a spray deposition layer. The coating material can be powdered, banded, filamentous or rod-shaped heat. Spray gun from fuel gas, arc or plasma arc with the necessary heat, the thermal spraying material is heated to a plastic state or molten state, and then subjected to acceleration of compressed air, the constrained particle beam impact onto the substrate surface. The impact to the surface of the particles, and the deformation by stamping, forming a laminate sheet. The adhesion after substrate surface preparation, then cooled and piled up, eventually forming a layered coating. The coating for different coating materials can realize high-temperature corrosion resistance, abrasion resistance, heat insulation, anti electromagnetic wave function.

The correct choice of thermal spray coatingmaterial is the key to ensure the work required for the properties of the coating. The coating materials selection, should first consider the working conditions and performance of workpiece coating required, but also consider the workpiece material, batch, economy and intends to adopt the method of thermal spraying coating. According to the function of the coating can be divided as the corrosion resistant coating, abrasion resistant coatings, friction reducing and sealing coating,high temperature resistant thermal barrier coatings, insulation or conductive coating, the size of repair coating.

The surface of the workpiece after coating in the rejection caused by failure reason is often not a single factor, so can meet the requirements of working conditions and performance of the coating does not necessarily exist simple relationship should be analyzed in detail. According to the working conditions,and reference and experimental data on the coating structure, physical, chemical, mechanical and other comprehensive performance consider, in order to determine one or several kinds of coating materials.

Wear resistant coating is one of the main fields of the application of surface coating technology. Although there is a general relation between the hardness and wear resistance, hardness and wear resistance but not entirely representative of the surface coating. Because of the different types of wear properties of material is not the same, and in the wear and often accompanied by shock, corrosion influence of fatigue, and temperature.

The choice of surface coating materials can not blindly pursue high performance or high price of the coating material, resulting in unnecessary waste of material price can not be used as selection of thermal spray coating quality standards, in order to meet the working conditions of reaction requirements, as far as possible the use of cheap coating materials, is particularly important in mass production when for example, can use the material of Ni based alloy coating without cobalt base alloy coating materials.

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May 18, 2017

market prospects of ungsten carbide powder is better off, steady and strong

A sound and effective market regulation mechanism and indirect regulation of tungsten industry policy will be conducive to environmental protection. To increase the production specification mining tungsten supply gap makes most of tungsten concentrate holding the goods cover Xishou mentality increasingly strong, tungsten concentrate prices high stalemate.

Downstream of the tungsten carbide alloy from the market performance in general, enterprises and products factory new orders is not much, but the cost is behind the leading price; tungsten materials market turnover flat. The price of tungsten carbide powderdespite a slight boost, but the downstream demand is not increased significantly, the market transactions to complete pre orders for the Lord, so the short-term market will be stable in tungsten carbide powderstrong. Indicates that the tungsten market will toward healthy and stable direction, the market will follow in the footsteps of tungsten carbide powder, the prospects for the better.

tungsten carbide powderwith tungsten oxide as raw materials, reduction with hydrogen in four tube muffle furnace or multi furnace, particle size from 0.6-30 microns. The main points of coarse, fine granularity, few, silver powder, impurity content based on the national standard.

Made by hydrogen reduction of tungsten trioxide or ammonium paratungstate. Prepared by hydrogen reduction process of tungsten carbide powderwas generally divided into two stages: the first stage in the 500 ~ 700oC temperature, were reduced to two tungsten oxide; second stage in the 700 ~ 900oC temperature, two tungsten oxide also into tungsten carbide powder. Redox reactions often in tubular furnace or rotary furnace.

The performance reduction of tungsten carbide powder(such as purity, particle size, particle size etc.) depends mainly on the reduction process. The reduction of tungsten carbide powderin tube furnace, the main parameters affecting the reduction rate is reducing temperature, loading amount of tungsten oxide in burning boat, boat speed, the water content in hydrogen flow and hydrogen gas. With the increase of reduction temperature, the particle size of tungsten carbide powderbecame thick.

Preparation of tungsten carbide powderin hydrogen reduction method, and early used tungsten oxide carbon reduction method, tungsten carbide powderpurity reduction temperature is higher than the 1050oC. obtained by this method is low. In addition, using aluminum, calcium, zinc and other working process of tungsten oxide is in progress. For the special use and high requirement purity, ultra fine grained tungsten carbide powder, tungsten chloride is the development of the hydrogen reduction of tungsten carbide powdersize to be less than 0.05 M.

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May 15, 2017

The manufacturing methods for tungsten carbide coating

Perhaps the definition of tungsten carbide coating and many people have some understanding, and for their production methods, it is a little strange. The tungsten carbide coating by HVOF spraying tungsten carbide cobalt based alloy powder or nickel tungsten carbide alloy powder and chromium based alloy powder of tungsten carbide hardness can reach HV1200 temperature of 850 degrees, so that the valve spare parts,wear resistance,corrosion resistance, high temperature resistance, oxidation resistance. More than manual welding, chrome, carburizing, quenching and tempering, process, production efficiency can be increased more than 2 times, the production cost is reduced by more than 50%, service life can be extended several times.

The tungsten carbide coating, interstitial carbon atoms embedded in tungsten metal lattice, does not destroy the original metal lattice, formed interstitial solid solution, so it is also called the interstitial (or insert) compound. Tungsten carbide by high temperature heating a mixture of tungsten and carbon, hydrogen or hydrocarbon can accelerate the reaction if. Oxygen containing compounds for preparation of tungsten products, and ultimately must be vacuum treatment at 1500 DEG C, to remove carbon dioxide. Tungsten carbide should be machined at high temperatures, making cutting tools, structural materials, kiln jet engine, gas turbine and nozzle.

The corrosion and corrosion of super hard coating, including those containing tungsten carbide coatingsare widely used in mechanical engineering used in the production of various products and tools. This coating has high corrosion resistance, high chemical resistance and high abrasion resistance, thus significantly prolonged mechanical engineering products in the harsh operating conditions and tool life.

However, the rate of synthesis of tungsten carbide is very low, and when the tungsten carbon layer growth, the internal stress of the coating increased sharply, resulting in coating delamination. So through the PVD method cannot produce a sufficiently thick coating. In addition, the nature of physical vapor deposition method is not suitable for coating deposition with complex shape parts, the it is unlikely that the coating is deposited on the covered part relative to the X-ray part.

Chemical vapor deposition (CVD) eliminates these disadvantages. The.CVD method can be used to deposit high wear resistance and high corrosion resistance coatings on substrates and components with complex shapes

In a typical CVD process for composite coating deposition, heating in the reaction chamber and the substrate, pre mixed gas phase reagent into a reaction chamber.The composition and process of change of the reaction mixture parameters (substrate temperature, the reaction mixture, the reaction mixture velocity, total pressure, the gas temperature), can be a variety of coatings.

In the CVD method of tungsten carbide coatingdeposition, only the fluoride method may form tungsten carbide with high quality at low temperature. In order to achieve this purpose, can be in the CVD process of six tungsten hexafluoride, a mixture of hydrogen and carbon containing gas by thermal decomposition.

A variety of reagents can be used as carbon containing gases such as two methyl ether, amine, propylene, etc. one or two kinds of tungsten carbide can be synthesized by one of them.

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May 12, 2017

High hardness cemented carbide rods subvert the traditional tungsten cobalt alloy material

Have to say,cemented carbide rods for light weight and high hardnesssubvert the traditional tungsten cobalt alloy material, reached the foreign advanced level and fill the gap. At the same time, than imported products in the market price low nearly doubled, greatly reduce the production cost and improve the competitive ability of products.

The rapid development of foundry machinery industry, requirements of cutting speed, feed volume, high precision, long service life, however, the traditional hard alloy cutting tools have been unable to meet the above requirements. In foreign countries, super cemented carbide rodshave as deep processing instruments. At present, Chinese cemented carbide industry structure is not reasonable, more in the low-end products and high-end product development is slow, heavily dependent on the United States, Europe,Japan imports, especially in the fields of research, related work is still in the stage of system modeling and simulation,which has not yet formed independent intellectual property products and mass production.

5 years ago, a research group in the study of a new generation of cold bit alloy bar products for a long time, the high speed dry cutting of stainless steel and other materials in the process of cutting red hardness and toughness of the poor, after testing hundreds of times, by adjusting the formula and sintering of powder and other measures, independent research and development of a titanium the base matrix, light weight and high strength alloy bars, the proportion of 7.2g/cm3, greatly improving the cutting tool materials such as stainless steel stem at high light in the process of the service cycle.

In order to overcome the defects of poor toughness of cemented carbide, by adding other elements, obviously improves the mechanical properties and physical properties of hard alloy, light alloy microstructure, fracture toughness and flexural strength improved, wear resistance, high temperature resistance, impact resistance, resistance to surface diffusion and antioxidant capacity were improved in different degree.

The above describes the difference between foreigncemented carbide rodsand China’s. I believe that we should word hard alloy rodare not unfamiliar, so we all know what are the use of hard alloy bar? For everybody here for detailsbelow:

1. It applies to micro drilling

2.Ithas good abrasion resistance and bending strength, mainly used for the production of extruded bars, suitable for general drill tool wear parts.

3.Ithas good abrasion resistance and bending strength, mainly used in the production of extruded bars, making small diameter micro drill tool, the use of clocks and other processing, whole reamer tools and wear parts.

4.Cemented carbide rodsfor a fine granular tungsten steel, tungsten steel bar has the high hardness, good bending strength, wear resistance and not easy to collapse, not easy to fracture. The micro drill is a special material, widely used in tungsten steel milling cutter, knife and wear parts.

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May 11, 2017

Theoretical basis of tungsten carbide density measurement

 

In recent years,new research has been focused on fine grained, ultra fine grained, even nanocrystalline tungsten carbide and gradient tungsten carbide. The gradient tungsten carbide has the gradient of the composition and the gradient of the structure. In addition, it can also be used to produce the gradient tungsten carbide, such as the gradient tungsten carbide anvil.

Fine grain and ultra-fine grain tungsten carbide has also come to market, such as the fine grain YGS drawing die in drawing LMM steel wire, is 3 times the general drawing die.

Density is an important quality index of tungsten carbide. Under certain conditions, the density reflects the structure of the alloy. When the porosity is larger or the free carbon exists, the density is low. ETA phase occurred in the alloy, high density.

Density is usually used in the tungsten carbide industry to determine the accuracy of a brand. Unlike conventional understanding, the porosity of modern tungsten carbides cannot be determined by density measurements. The density of tungsten carbide (WC) is 15.7 g/cm3, and the density of cobalt is about g/cm3. So for the WC-Co brand, with increasing cobalt content, the density decreases linearly, increase of titanium carbide leads to lower density because of pure titanium carbide tungsten carbide density is only 4.9 (WCWC, also abbreviated TC) density is 15.7 g/cm3, the density of cobalt is 4.9 g/cm3.

tungsten carbide density has a great relationship with the material composition, porosity and carbon content, and the density of tungsten carbide is extremely sensitive to the composition and the porosity of the alloy under the condition of certain composition.

Firstly,What is the relationship between density and material composition? Density is closely related to the content of material composition. For example, the density of tungsten cobalt alloy decreases with the increase of cobalt content.

Secondly,what is the relationship between density and porosity?There is a close relationship between density and pore size. The existence of pores and the size of pores directly affect tungsten carbide density. Because of the existence of pores, the actual density is less than the theoretical density. tungsten carbide in the process of compaction and sintering in the carburizing, burning, dirty, bubbling, peeling, not good pressure, etc., will result in reduced density.

Thirdly, what is the relationship between density and carbon content? In the case of a constant composition, porosity, and free carbon density ETA hard alloy and tungsten carbide has a direct relationship. In a WC+ + ETA three-phase zone, with the amount of carbon reduction, phase Co and phase increase, decrease, increase of W content, the density increases. In a WC+ + ETA three-phase region, with the increase of carbon content (free carbon is called the "C" class, pore density reduction). In a phase WC+ area, with the amount of carbon reduction, a phase of the increase of W content, the density increases. In general, the carbon content of normal tissue increased from 0.1 to 0.13%, and its density decreased by 0.1g/cm3. The density of tungsten carbide (WC, also abbreviated to TC) is 15.7g/cm3, and the density of cobalt is 8.9g/cm3.

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May 10, 2017

Application of thermal spraying in textile printing and dyeing industry

Modern textile machinery especially chemical machinery, light, energy saving is fast, the direction of development. The high-speed moving parts of many energy consuming general as far as possible the use of lightweight alloy matrix (such as aluminum) surface hardening and functional coating composite manufacturing.

Textile parts requirements have a well-defined surface shape, which is due to the contact with the fibers in these parts must be oriented, winding, spinning and drawing and winding required fiber effect. For the design requirements of the special surface tension, and the fiber does not cause hair pulling and scrapes, and must also have sufficient wear resistance, in order to meet the requirements of long time stable spinning work, especially the large-scale production of textile industry, this requirement is more prominent. The design and function of the system by thermal spraying coatingpreparation can meet.

The textile industry in the use of A12O3 TiO2 coating with a wide range, although this kind of coating has good resistance to corrosion resistance. But due to A12O3 and TiO2 and other oxides with different proportions of ceramic coating materials with new technology, such as polishing treatment, different after plasma spraying brush after grinding, grinding and sanding the processing method, the coating can obtain different hardness with different surface condition, in order to meet the needs of all kinds of textile properties of fiber. Its characteristics are as follows:

 

excellent wear resistance of high speed fiber, high hardness and low surface energy properties of oxide ceramic coating, determine its essential wear and friction reduction, which is not easily replaced by other materials

Different ceramic coating after the processing method to make the surface with different profiles, so there will be a different friction. The fiber can be applied to moderate "twist", so that the fiber to achieve the necessary strength and toughness.

 

the use of spray sprayed surface particles (raised by numerous appropriate processing to eliminate the sharp peak), provide an appropriate surface roughness, and the effect of fiber fiber surface to obtain the necessary "Cashmere", achieve good dyeing, have certain moisture absorption.

 

Cr2O3 than A12O3 with high hardness and chemical corrosion resistance. Carbide coatings mainly provide abrasion resistance, in the textile industry has a special role. Most parts of textile machinery needs to prepare the surface was smooth, delicate, uniform surface ceramic coating. The thermal spraying processmust grasp the following three aspects: one is the surface roughening sandblasting with fine grained corundum than 0.25mm: two is the particle size range of 5-45 m three powder spraying; coating thickness is generally 0.15-0.20mm. these applications has formed a system in our country, the scale and standardization. The application of textile and chemical fiber industry of ceramic coating ceramic coating accounted for most of the market.

The series of models of welding dryer, water roller, roller roller, ventilation; mercerizing machine under the camshaft roller, and various import cloth iron plate, gear, shaft; guide roller, performance decline in the use of the joint locomotive fabric shaft, the surface wear can by thermal spraying with high performance alloy, ceramic and polymer materials processing technology, improve and extend the mechanical components of the performance and service life.

Posted by: hannahgwendolyn at 09:25 AM | No Comments | Add Comment
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May 09, 2017

The cemented carbide wire drawing die is the most efficient one

With regard to the use of wire drawing die, there are many claims that the development of industrial production in China's mold industry is still strong momentum, especially in the mold of the drawing die use efficiency is very high. Because there are other die drawing die without the absolute advantage. Industrial machinery production of the mold above the size of a lot of models, each mold has its own unique efficacy. The advantage is that the mold can according to a model made numerous the same product, this can save a lot of manpower and working time, improve work efficiency, so the emergence of mold really accelerated the pace of industrial production.

1.high drawing efficiency. Wire drawing diein the use of the necessary maintenance of the life of the wire drawing die and the surface quality of the wire is very important, it is recommended that the customer polycrystalline diamond wire drawing die every 24 hours for a maintenance. Within 24 hours, the pore diameter of polycrystalline diamond wire drawing die is small, and the change rate of wire diameter is very small.

2.good wear resistance, long life. The life of the polycrystalline diamond drawing die is about 30~50 times of that of the cemented carbide die, so it is not necessary to change the die frequently during the drawing process. The variation of the diameter of the wire drawing die in the unit time is very small, and the size of the drawn wire is small.

3.save raw materials. If the drawing surface is coated with a metal wire, stop the electroplating process in the drawing process and did not stop, which leads are electroplating wire surface plating thickness exceed the standard required to start drawing, cut wire thickness exceed the standard, resulting in enormous waste, waste more more downtime.

The wire drawing mold is used in what areas? In the production or processing of high-precision materials, requires the use of wire drawing die, then drawing die in what area is used? And what are the steps of drawing technology of drawing die? These problems, we have a look.

Dies use a wide range, such as electronics, radar, television, appearance and aerospace and other fields, all kinds of alloy wire is drawn out by diamond wire drawing die, diamond wire drawing die because of the natural diamond as material, which has extremely strong abrasion resistance, high service life. Production technology of drawing die with set, contains several technical steps die, draft, turning etc..

Wire drawing dieis a metal wire through a mold to make it from coarse to fine, gradually reached the scale of the needs of everyone, this special mold that is drawing die. The die core of a wire drawing die is usually made of natural diamond, artificial diamond.

Wire drawing die includes diamond drawing die, plastic drawing die and so on. There are many uses.

Posted by: hannahgwendolyn at 09:16 AM | No Comments | Add Comment
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May 03, 2017

Improvement of heat treatment technology for cemented carbide inserts

By metallographic and hardness measurement shows that the cutter body by high strength after quenching, high frequency welding process in martensite with high hardness to Soxhlet size of pearlite and chunky ferritic low strength and hardness. In this transformation, the hardness and strength of the cutter body is greatly reduced. This shift is due to the cutter body high-frequency welding head, welding temperature is higher, generally 900 to 950 DEG C; this high temperature quenching after the knife body near the weld are normalized, resulting in the hardness, greatly reduced strength. From the crater near the area because of heat conduction welding, the region temperature, high temperature caused by tempering in the region, and also makes the area of strength, hardness decreased. The tool is used, the tool damage is also the most easy to appear in the welding position that the cutter body hardness welding, strength degradation is the tool Important cause of damage.

In order to find out the knife body first and then quenching on the cutter body causes high-frequency welding method of making hard alloy knife head has the above defects, we do the following test: first made the test to determine the shape and size of milling cutter, the test principle is easy to test metallographic sampling. The cemented carbide insert head at 900 DEG C the heating and cooling, the cutter head hardness does not change significantly.

cemented carbide insert in quenching, if the quenching medium is saline,cemented carbide insert and cracking due to rapid cooling; if the medium is oil, cooling, heating at 900 DEG C, cemented carbide insert without cracking. It is proved that the welding tool used in quenching, the knife should be used in alloy steel oil cooling can be hardened, but can not use oil quenching hard, carbon steel hardened to water, such as a knife body made of 45 steel or high carbon steel welding tool, after quenching, the knife body material should be changed into alloy steel.

In order to prevent the solder melting at the heating process of the cutter body position change welding, solder flow or the cutter head and the cutter, quenching temperature should not exceed 900 degrees, 850 degrees below the best quenching temperature. Most of the alloy steel are near 850 DEG C, and in general, high alloy steel quenching temperature is over 900 DEG C, so the whole appliance when quenching, the knife body material should be selected in small, high alloy steel, such as forming the previously mentioned flat drill, cutter body material is W18Cr4V, quenching temperature above 900 DEG C, the overall quenching cannot.

According to the above three, we first test for quenching cutter, cutter body materials, milling and quenching test before quenching after welding is the same as that of quenched from the knife body weld 1mm metallographic test, microstructure of martensite ferrite, hardness 52 ~ 54HRC metallographic cutter body quenching and when the cutter head weld hardness. Milling cutter, drill the whole quenching test and into the formal production and achieved good results.

Note that the whole milling cutter when quenching, the knife head is welded on the cutter body, and the cemented carbide hard and brittle, a little bump will cause the scrap off angle, quenching, tempering and sandblasting after all must be careful not to bump.With the overall quenching of the cutter, the hardness of the cutter body at the welding seam has been greatly improved compared with that of the original quenching tool.

Posted by: hannahgwendolyn at 09:23 AM | No Comments | Add Comment
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