Basic knowledge of metal materials

Tungsten, a metallic element. The atomic number is 74 and the atomic weight is 183.85. Steel gray or silver white, high hardness, high melting point, not corroded by air at room temperature; the main purpose is to manufacture filament, high-speed cutting alloy steel, super hard molds, and also used in optical instruments and chemical instruments. China is the world's largest tungsten storage country.

Generally, metals with a melting point higher than 1650°C and a certain reserve and metals with a melting point higher than the melting point of zirconium (1852°C) are called refractory metals

Ferrous metals mainly refer to iron, manganese, chromium and their alloys, such as steel, pig iron, ferroalloys, cast iron, etc.

The strength and hardness of non-ferrous alloys are generally higher than that of pure metals, the resistance is larger than that of pure metals, the temperature coefficient of resistance is small, and it has good comprehensive mechanical properties.

Rare metals usually refer to metals that are less abundant or sparsely distributed in nature.

Tungsten is a rare high-melting-point metal that can increase the high-temperature hardness of steel. It belongs to the VIB group of the sixth period (the second longest period) of the periodic table. Tungsten is a silver-white metal that looks like steel. Tungsten has a high melting point, a very low vapor pressure, and a low evaporation rate. The chemical properties of tungsten are very stable. It does not react with air and water at room temperature. When it is not heated, any concentration of hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid and aqua regia will not have any effect on tungsten. When the temperature rises to 80°-100 At °C, among the above-mentioned acids, except for hydrofluoric acid, other acids have a weak effect on tungsten. At room temperature, tungsten can be quickly dissolved in a mixed acid of hydrofluoric acid and concentrated nitric acid, but it has no effect in alkaline solutions. In the presence of air, molten alkali can oxidize tungsten into tungstate. In the presence of oxidants (NaNO3, NaNO2, KClO3, PbO2), the reaction to form tungstate is more violent. It can be combined with chlorine, bromine, iodine, carbon, nitrogen, sulfur, etc. at high temperature, but not with hydrogenation

nickel

Nickel is a metallic element that is approximately silvery white, hard, ductile, and ferromagnetic. It is highly polished and resistant to corrosion. Nickel is a ferrophilic element, and its content in the earth is second only to silicon, oxygen, iron, and magnesium, ranking fifth. The highest nickel content in the core of the earth is a natural nickel-iron alloy. In the earth's crust, the nickel content of mafic rocks is higher than that of silicoaluminous rocks. For example, the nickel content of peridotite is 1,000 times that of granite, and the nickel content of gabbro is 80 times that of granite. It has good ductility and medium hardness. Nickel is a silver-white metal with magnetism and good plasticity. It has good corrosion resistance, nickel is similar to silver white, hard, ductile and ferromagnetic metal element, it can be highly polished and corrosion resistant. After being dissolved in nitric acid, it turns green. Mainly used in alloys (such as nickel steel and nickel silver) and as a catalyst (such as Raney nickel, especially as a hydrogenation catalyst.

molybdenum

The chemical properties of molybdenum are relatively stable. Molybdenum is stable in air or water at room temperature or at not too high temperatures. When molybdenum is heated in the air, the color begins to change from white (color) to dark gray; when the temperature rises to 520℃, the molybdenum starts to be slowly oxidized to produce yellow molybdenum trioxide (MoO3 becomes white after the temperature drops to room temperature); the temperature rises to 600 Above ℃, molybdenum is rapidly oxidized to MoO3. When molybdenum is heated to 700~800℃ in the water solar terms, MoO2 will be formed. When it is further heated, the molybdenum dioxide will continue to be oxidized into molybdenum trioxide. Molybdenum can ignite spontaneously in pure oxygen to produce molybdenum trioxide. Molybdenum oxides have been reported in many reports, but many of them are reaction intermediates, rather than thermodynamically stable phases.

Molybdenum is mainly used in the iron and steel industry, most of which are directly used for steelmaking or cast iron after industrial molybdenum oxide briquetting, and a small part is smelted into ferromolybdenum flakes, and then used for steelmaking. The molybdenum content in low-alloy steel is not more than 1%, but the consumption in this area accounts for about 50% of the total consumption of molybdenum. The addition of molybdenum to stainless steel can improve the corrosion resistance of steel. Adding molybdenum to cast iron can improve the strength and wear resistance of iron. The nickel-based superalloy containing 18% molybdenum has the characteristics of high melting point, low density and small coefficient of thermal expansion, and is used to manufacture various high-temperature parts for aviation and aerospace. Molybdenum metal is widely used in electronic devices such as electron tubes, transistors and rectifiers. Molybdenum oxide and molybdate are excellent catalysts in the chemical and petroleum industries. Molybdenum disulfide is an important lubricant

Molybdenum rods, used as electrodes for transistors, light-emitting diodes and solar cells

Pure molybdenum wire is used in high-temperature electric furnaces, electric discharge machining and wire cutting,

Molybdenum sheet is used to make radio equipment and X-ray equipment

Molybdenum is resistant to high temperature ablation and is mainly used in the manufacture of gun bores, rocket nozzles, and tungsten wire brackets for light bulbs. The addition of molybdenum to alloy steel can improve the elastic limit, corrosion resistance and maintain permanent magnetism. It is a non-ferrous alloy formed by adding other elements to molybdenum as the matrix. The main alloying elements are titanium, zirconium, hafnium, tungsten and the rare earth elements titanium and zirconium. The elements not only play a solid solution strengthening effect on the molybdenum alloy, maintain the low-temperature plasticity of the alloy, but also form a stable and dispersed carbide phase to improve The strength and recrystallization temperature of the alloy. Molybdenum alloy has good thermal conductivity, electrical conductivity and low expansion coefficient. It has high strength at high temperature (1100～1650℃) and is easier to process than tungsten. It can be used as the grid and anode of the electron tube, the support material of the electric light source, and used to make die-casting and extrusion molds, and parts of spacecraft.

titanium

    Titanium is a chemical element. The chemical symbol is Ti and the atomic number is 22. It is a silver-white transition metal. It is characterized by light weight, high strength, metallic luster, and good corrosion resistance (including sea water and aqua regia). And chlorine). [1] Because of its stable chemical properties, good high temperature resistance, low temperature resistance, strong acid resistance, strong alkali resistance, as well as high strength and low density, it is known as "space metal. The two most useful properties of titanium are corrosion resistance. It has the highest strength-to-weight ratio among metals. High melting point, small specific gravity, high specific strength, good toughness, fatigue resistance, corrosion resistance, low thermal conductivity, good high and low temperature resistance, low stress under rapid cold and hot conditions Features

graphite

 1. Used as refractory material: Graphite and its products have the properties of high temperature resistance and high strength. It is mainly used in the metallurgical industry to make graphite crucibles. In steelmaking, graphite is often used as a protective agent for steel ingots and as an inner lining of metallurgical furnaces.

2. As a conductive material: used in the electrical industry to make electrodes, brushes, carbon rods, carbon tubes, positive electrodes of mercury positive current devices, graphite washers, telephone parts, coatings for television picture tubes, etc.

3. As a wear-resistant lubricating material: Graphite is often used as a lubricant in the machinery industry. Lubricating oil is often not used under high-speed, high-temperature, and high-pressure conditions, while graphite wear-resistant materials can work at high sliding speeds at a temperature of 200 to 2000 ℃ without lubricating oil. Many equipment that transports corrosive media widely use graphite materials to make piston cups, seals and bearings. They do not need to add lubricating oil when they are running. Graphite emulsion is also a good lubricant for many metal processing (wire drawing, pipe drawing).

4. Graphite has good chemical stability. Specially processed graphite, which has the characteristics of corrosion resistance, good thermal conductivity, and low permeability, is widely used in the production of heat exchangers, reaction tanks, condensers, combustion towers, absorption towers, coolers, heaters, and filters , Pump equipment. It is widely used in petrochemical industry, hydrometallurgy, acid-base production, synthetic fiber, papermaking and other industrial sectors, which can save a lot of metal materials.

5. Used as casting, sand-finding, die and high-temperature metallurgical materials: Because graphite has a small thermal expansion coefficient and can withstand rapid changes in cold and heat, it can be used as a mold for glassware. After using graphite, ferrous metals can be used to obtain castings with precise dimensions and a high surface finish. It can be used without processing or a little processing, thus saving a lot of metal. The production of cemented carbide and other powder metallurgy processes usually use graphite materials to make porcelain boats for compression molds and sintering. Single crystal silicon crystal growth crucibles, regional refining vessels, support fixtures, induction heaters, etc. are all made of high-purity graphite. In addition, graphite can also be used for vacuum smelting graphite heat insulation boards and bases, high-temperature resistance furnace tubes, rods, plates, grid sheds and other components.

6. Used in the atomic energy industry and national defense industry: Graphite has a good neutron moderator used in atomic reactors. Uranium-graphite reactor is currently the most widely used type of atomic reactor. The deceleration material in the nuclear reactor used as power should have a high melting point, stability, and corrosion resistance. Graphite can fully meet the above requirements. The purity of graphite used in atomic reactors is very high, and the impurity content should not exceed dozens of PPM. Especially the boron content should be less than 0.5PPM. In the national defense industry, graphite is also used to make solid fuel rocket nozzles, missile nose cones, parts of aerospace equipment, heat insulation materials and radiation protection materials.

7. Graphite can also prevent boiler fouling. Tests by relevant units have shown that adding a certain amount of graphite powder (approximately 4 to 5 grams per ton of water) can prevent boiler surface fouling. In addition, graphite coating on metal chimneys, roofs, bridges, and pipes can prevent corrosion and rust.

8. Graphite can be used as pencil lead, pigment and polishing agent. After the stone mill has been specially processed, various special materials can be made for use in relevant industrial sectors.

9. Electrode: How can graphite replace copper as an electrode

Graphite is soft, dark gray; it has a greasy feel and can stain paper. The hardness is 1～2, and the hardness can increase to 3～5 with the increase of impurities in the vertical direction. The specific gravity is from 1.9 to 2.3. Under the condition of isolating oxygen, its melting point is above 3000℃, which is one of the most temperature-resistant minerals.

Nitinol

Nitinol is a shape memory alloy, which is a special alloy that can automatically restore its plastic deformation to its original shape at a certain temperature. Its expansion rate is over 20%, its fatigue life is up to 1*10 to the 7th power, its damping characteristic is 10 times higher than that of ordinary springs, and its corrosion resistance is better than the best medical stainless steel at present, so it can meet all kinds of engineering and It is an excellent functional material for medical application requirements.

In addition to the unique shape memory function, the memory alloy also has excellent characteristics such as wear resistance, corrosion resistance, high damping and super elasticity. Characteristics: 1 Form memory: 2 Super elasticity: 3 Sensitivity to changes in oral temperature: 4 Corrosion resistance: 5 Anti-toxicity: 6 Soft correction power: 7 Good shock absorption: