Tungsten trioxide (WO3) because of its unique nature has been widely applied in all aspects of industry and technology. Besides the morphology and structure of WO3 has a direct relationship with applications, now, people have many ways to prepare different pore size of the porous oxide, including large hole, mesoporous and microporous. But the porous foam structure material for fragile so little research and application.

After the expert study, they can produce tungsten trioxide dimensional network structure having a supporting force. Typical synthetic methods for producing tungsten trioxide dimensional network structure are as follows:
(1) 1g metal tungsten powder dissolved in mixed liquor which includes 15ml30% H2O2 and 15ml methanol. In this process to keep stirring then make it to form a clear solution.
(2) Put 0.12g polyvinyl pyrrolidone into clear solution which made from pervious task to form a transparent slightly viscous solution.
(3) The solution was concentrated under 333K, when the solution was concentrated to 5ml, foam-like structure of WO3 is begin to form.
(4) Calcining the foam-like structure at 773K for 6 hours, at a heating rate control at 1K / min.   

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Tungsten trioxide crystal structure satisfies stoichiometric ratio strictly should be distorted perovskite structure, namely the absence of cation A pattern appears in the ABO3 perovskite structure. Oxygen atom is octahedron, and a tungsten atom in the center of the octahedron. All single phases of tungsten are octahedral structure but the structural is different. Since tungsten trioxide varying degrees of oxygen vacancy and therefore the stoichiometric become more complicated, so that the tungsten trioxide chemical formula is usually written as WO3-X. With the increase in the number of oxygen vacancies, which are distributed in the crystals of WO3-X becomes ordered together, a so-called shear surface. When X <0.02 the shear surface is randomly distributed. When X≥0.02 shear surface become parallel arranged, with the increasing degree of reduction of the degree of ordering shear surface arrangement is also increasing. These compounds have different crystal structures, and vacancies, such that the tungsten trioxide having a variety of properties, photocatalytic activity which has not the same.

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 Non-sag tungsten wire(non-sag refers to the resistance of the wire against deformation (“sagging”) under its own weight at working temperature) is doped silicon, aluminum, potassium oxide tungsten wire, which is widely used in electronic devices and hot wire, such as high wire color temperature, thermal shock resistance wire and the cathode tube radiation.

In order to make clear the non-sag nature of tungsten lamp wire, its recrystallization behavior was studied by means of microscopic scrutiny and X-ray diffraction. Wire having sag nature begins the recrystallization in a preferred orientation related to initial fiber direction at temperature about 1000°C. This orientation is destroyed at about 1300°C, leading to an ordinary non-preferential polygon structure. The subsequent grain growth is very slow even at considerably higher temperatures. On the contrary, with non-sag wires this oriented recrystallization is maintained up to 2000˜2100°C, followed by the abrupt coarsening, in which the coarsened crystals encroach directly the remaining fiber structure. Thus, the coarsened crystals tend to occupy the whole cross-section of the wire, and the wire becomes finally to form a successive chain consisting of single crystals. This phenomenon was interpreted as the inhibition dependent coarsening advocated by Beck and others in 1949. This inhibiting action in tungsten wire is most likely caused by the minute quantities of doped materials.

 

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Under a low temperature condition, the recrystallization will occur by adding some metals (such as palladium, nickel, iron and others) to the wire surface. It is an important process when the wires act as reinforcement material in metal matrix composites because of its damage to the mechanical properties of non-sag tungsten wires.

Transmission Electron Microscope (TEM) observations about the initial stage of recrystallization of 0.18 mm doped tungsten wire showed that the formation, through dislocation rearrangement, of new grains with a relative disorientation could play a critical role in the recrystallizing process. The impeding effect of potassium bubbles both on dislocation rearrangement and boundary migration resulted in the abnormal recrystallized behavior of the heavily drawn doped tungsten wire. In addition, it was found that the non-<110> orientation of recrystallized tungsten grains could originate either from the grains with a non-<110> orientation in the starting material or from the newly nucleated grains. These observations could explain the recrystallizated features of tungsten wire which the current theory could not account for.

 

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Tungsten Carbide Rod Binder

Tungsten carbide rod is made up of two parts. One is the tungsten hardening phase which makes tungsten carbide rod be high wear resistance and high strength. The other part is the tungsten carbide rod binder like cobalt or nickel.

In 1923, Schroter from German add 10%-20% cobalt into cemented carbide as binder, invented the new alloy of cemented carbide and cobalt, and hardness is approximately the same as diamond. This is the first artificially synthesized tungsten carbide in the world. Tungsten carbide rod made by this method has high wear resistance and high strength and toughness.

Cobalt is by far the most widely used binder metal or "cement" in tungsten carbide rod because it most effectively wets tungsten carbide grains during liquid phase sintering. For this reason cobalt is believed to be superior to other binder metals in terms of eliminating residual porosity and achieving high strength and toughness values in sintered products.


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Tungsten Carbide Rod Producing Countries

About 50 countries manufacture tungsten carbide rod in the world and the total output can reach to 27000t-28000t. The main producing countries are America, Russia, Sweden, China, German, Japan, England and France. The tungsten carbide rod market has reached the saturated condition so the competition is really fierce. China started to make tungsten carbide rod in the end of 1950s. After a long time research, the technique and output improve a lot in the 1960s-1970s. In 1970s, the tungsten carbide rod producing capability reached to 6000t, the total output reached to5000t which is second only to Russia and America, ranked the third place in the world.

About 600-700 enterprises produce tungsten carbide rod in the world. Among which the most competitive ones are Sandvik in Sweden and Kennametal in America. In 2000, tungsten carbide rod total sale is 88.72 billion dollars and they accounted for 40% of it. 


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Tungsten Carbide Round Rod

Tungsten carbide round rod is a shape for round rod, and the main material for tungsten carbide round rod is tungsten carbide. Tungsten carbide, also known as cemented carbide, is an extremely hard alloy made from tungsten and carbon that offers high wear resistance as well as good corrosion resistance. These tungsten carbide round rods are used for the manufacture of cutting tools for the metal, wood, plastic and other industries where hardness and wear corrosion resistance is required. Tungsten carbide round rods are available in standard lengths of 310 and 330 mm.

Tungsten carbide round rod has been ground to achieve the precise shape and size, and has a precision tolerance. The tungsten carbide round rod provides high wear resistance, and good corrosion and heat resistance. Tungsten carbide round rod is mainly applied in making drills, end mills and reamers. And it is also used for cutting, punching and measuring tools.


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Tungsten Carbide Rod Corrosion Resistance in PH Value

Although tungsten carbide rod with cobalt binder has fairly good resistance to attack by acetone, ethanol, gasoline and other organic solvents as well as by ammonia, weak acids, and tap water. Exposure to formic, hydrochloric, hydrofluoric, nitric, phosphoric, sulfuric, and other strong acids, however, can result in a relatively rapid deterioration of the binder phase. Corrosion rates are affected also by temperature, the concentration and electrical conductivity of the corrosive agent, and by other environmental factors.

The following chart is the corrosion resistant details of tungsten carbide rod cobalt binder& tungsten carbide rod nickel binder in PH value. 

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International solid carbide cutting tools industry status is mainly reflected in the following two aspects:

First, international solid carbide cutting tools industry status is reflected in that the output value of international solid carbide cutting tools the international is about $ 1.3 billion, of which PCB drill and micro-milling of 600 million (about 20% of micro cutter), the average unit price of 1 USD / support, about $ 600 million; metalworking of solid carbide cutting tools around 25 million (60 million or more cutters), the average price is about $ 30, with a total of about $ 700 million.

Secondly, international solid carbide cutting tools industry status is reflected in that the forefront of the solid carbide cutting tools is Germany, accounting for 60% market share. Asia, China, Japan, South Korea accounted for about 25%, North America 15%.
 

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Tungsten carbide rod bending and deformation affecting factors includes carbon gradient, cobalt gradient, temperature gradient and density gradient.

1.Carbon gradient. During the dewaxing and sintering process the carbon gradient would change continuously. Due to the different parts of the tungsten carbide rod has different decarburization and carbon pick-up capability, carbon gradient then comes into being. Setting time in different parts also changes which causes liquid phase moves to the setting section first and cause the bending and deformation of tungsten carbide rod.

2.Cobalt gradient. During the vacuum sintering process of tungsten carbide rod, the wettability of the cobalt for different parts causes the liquid cobalt moves ups and downs.

3.Temperature gradient. During sintering process, liquid cobalt often moves to the high temperature section. The higher the temperature, the higher the cobalt contents will be, thus the deformation of tungsten carbide rod will be more serious.

4.Density gradient. Due to the insufficient pressure and uneven surface of rolled material, density gradient becomes another important factor. Normally, tungsten carbide rod with low density will bend and deform more easily.


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