Uses and applications of tungsten and molybdenum materials
Beginning in the 20th century, a number of chemical elements that previously found no use began to play an important role in industry and are collectively referred to as rare elements or rare metals. Most of the rare metals were discovered in the late 18th and early 19th centuries, so their industrial applications were later than those of other commonly used metals, but many of the rare metals have now long since become commonly used in modern industrial technology.
Tungsten (W), molybdenum (Mo) and their alloy materials are rare high melting point metal materials in the subgroup VI of the periodic system of Mendeleev elements. Tungsten and molybdenum are widely used in electronics, medical, glass, iron and steel metallurgy and other industries because of their unique high melting point, good electrical and thermal conductivity and superior corrosion resistance and ray resistance as boats, heat insulation screens, high temperature furnace structural parts, ray targets, etc.
01 Tungsten and molybdenum reserves in China
The proven rare metal resources in China are abundant and large in scale. The reserves of many rare metals are the first in the world, among which molybdenum, tungsten and other mineral resources are even more abundant. According to statistics, by 2020 China's tungsten reserves will have reached 2.22 million tons and molybdenum reserves will be about 3.73 million tons.
China's molybdenum reserves are abundant and widely distributed, relatively concentrated in five provinces: Henan, Jilin, Guizhou, Shaanxi and Hunan. Tungsten resources are relatively concentrated in four provinces, namely Jiangxi, Henan, Hunan and Fujian. In recent years, the mining, smelting, processing and trading enterprises of China's tungsten industry have been gradually conglomerated.
The distribution of molybdenum, tungsten and other rare metal resources in China is very regional. They are facing a huge demand and a crisis of decreasing resources, so it is inevitable to increase prospecting efforts and reduce waste. At the same time, on the production side, the integration of enterprises should be carried out, and the winners and losers should be eliminated. In terms of exports, but also consciously increase the added value of products, for greater profits. Rather than simply selling related metal powder raw materials to obtain meager benefits, the technological upgrading of these must rely on scientific and technological innovation to support.
02 Characteristics of tungsten, molybdenum and tungsten-molybdenum alloys
Tungsten and molybdenum belong to Group VIIB elements in the periodic table, and are typical high melting point metals, their basic properties are similar, but also have their own characteristics. The surface of tungsten and platinum metal are silvery gray luster, the powder is dark gray, high melting point, high strength, high elastic modulus, small expansion coefficient, low vapor pressure, excellent electrical and thermal conductivity, but tungsten and molybdenum have the common disadvantage of high temperature oxidation and low temperature brittleness.
Tungsten, molybdenum alloying purpose is to further improve its high-temperature strength, improve oxidation resistance and improve welding properties, the preparation of heat-resistant alloys or thermal strength alloys applied to high temperatures of 1000-2000 ℃, requiring high strength when applied at high temperatures under certain loads, without plastic deformation and fracture. Therefore, the high temperature resistance to reading is one of the important indicators of high temperature alloys.
03 The use of tungsten and molybdenum and their application areas
Currently, the world of refractory materials research has evolved from the traditional "high purity, ultra-fine, and uniform" to "nano, composite design and integrated manufacturing. Through these advanced technologies, refractory tungsten alloys can not only retain their high melting point and corrosion resistance, but also greatly improve their comprehensive mechanical properties. At present, the research and application of refractory metals are still far behind other metal materials. Therefore, it is the focus of current research to further optimize and improve the processing process of various tungsten alloy materials through technical transformation and according to the requirements of different application fields.
And tungsten alloys have been widely used in many fields such as aviation/aerospace, military equipment, electronics and chemical industry due to their comprehensive properties such as high density, high strength, low coefficient of thermal expansion, corrosion resistance and good machinability.
Its main uses include: (1) Carbide for cutting, welding and spraying, such as tungsten carbide. (2)Used in the electronic industry for a large number of filaments and cathodes for electron tubes, heat generating elements for high temperature resistance furnaces, such as impact resistant tungsten wires and composite rare earth tungsten electrodes. (3) Armor-piercing bullets, liners, etc. Used in high-temperature fields, even in the military.
Improving the plasticity of tungsten and tungsten alloy materials, lowering their plastic-brittle transition temperature, and further improving their high-temperature thermal strength properties have been the hot spots of research in the field of tungsten alloys. Therefore, the plastic-brittle transition behavior, high-temperature strength properties, welding and compounding, and manufacturing process optimization of tungsten are the main elements of tungsten research and development. Technology development around these elements includes purification, refinement, toughening, and compounding.
Molybdenum is used predominantly in the steel industry, accounting for about 80 percent of total molybdenum consumption, followed by the chemical industry, which accounts for about 10 percent. In addition, molybdenum is also used in electrical and electronic technology, medicine and agriculture, accounting for about 10 percent of total consumption.
The addition of other elements (such as titanium, zirconium, hafnium, tungsten and rare earth elements) to molybdenum as a substrate constitutes a non-ferrous alloy. These alloying elements not only play a role in solid solution strengthening and maintaining low-temperature plasticity for molybdenum alloys, but also form a stable, diffusely distributed carbide phase that increases the strength and recrystallization temperature of the alloy. Molybdenum-based alloys are used in high heat generating components, extruded abrasives, glass melting furnace electrodes, spray coatings, metalworking tools, parts for spacecraft, etc. because of their good strength, mechanical stability, and high ductility.
After decades of rapid development, especially since the reform and opening up, China's tungsten and molybdenum industry as a whole has reached a high level, and has formed a complete industrial system from geological exploration, mining, beneficiation to smelting and processing and economic and trade, design, scientific research, education, etc., which can produce thousands of product varieties and basically meet the needs of the national economy, and some of the process technology and products have approached or reached the international advanced level. The reserves, production, trade and consumption of tungsten and molybdenum rank first in the world. However, we should also see that the rapid development of the tungsten and molybdenum industry has also revealed many problems, including serious waste of resources, low level of technology and equipment, disorderly competition in the industry, unreasonable structure of export products, low prices, etc. Tungsten and molybdenum resources have been facing the danger of depletion.
China is a large country of tungsten and molybdenum resources, tungsten and molybdenum production and exports are among the world's top, but far from being a tungsten and molybdenum economic powerhouse, tungsten and molybdenum deep processing technology, equipment and product quality compared with foreign countries is still very backward, to effectively control the scale of tungsten and molybdenum mining and primary smelting and processing products investment, to stop low-level duplication of construction; to market-oriented, vigorously integrate and ban high energy consumption, high pollution and low product We should increase the investment in scientific research, improve the technology and equipment level of mining and smelting, improve and promote new equipment and technology, optimize the product structure, vigorously develop deep processing products and high value-added end products, encourage the development of products with independent intellectual property rights, and fully develop products with independent intellectual property rights. The company will encourage the development of products with independent intellectual property rights, fully develop tungsten and molybdenum deep processing products, improve the efficiency of tungsten and molybdenum resources utilization, and enhance the economic benefits of the industry; increase the export share of deep processing products with high technical content and high added value, such as high specific gravity tungsten alloy, cemented carbide, molybdenum wire, molybdenum sheet and strip, molybdenum shaped parts, molybdenum alloy, etc., and optimize the product structure of tungsten and molybdenum system in China is the future development direction of tungsten and molybdenum deep processing industry.
