1, steel additive
As an alloy additive of steel, molybdenum is the most important use. According to the statistics of 1986, it accounts for 83% of the total molybdenum consumption in the world. Molybdenum-containing steel accounts for110 of the world crude steel output. Therefore, the ratio of molybdenum to steel is often regarded as one of the signs of a country's industrial development. The ratio of molybdenum to steel in the world is 0.0 1 1%, that in the United States is 0.0 14%, and that in China is only 0.004%, which is less than half of the world average. Adding molybdenum to steel is often divided into the following aspects:
Alloy steel: the consumption of molybdenum is the largest, accounting for 44% of the total consumption of molybdenum in the world, accounting for more than half of the added molybdenum in steel.
Among them, the molybdenum content of structural steel (or general molybdenum steel) is about 0. 1% ~ 0.2%, which is widely used as large steel members such as skyscrapers and bridges, which can improve the hardness, strength and toughness of steel and prolong the life of these large facilities.
Molybdenum steel containing 0.3% molybdenum is often used as load-bearing parts and transmission parts in transportation and automobile manufacturing. High strength alloy steel usually contains less than 0.3% molybdenum, 0.5% ~ 3.5% nickel and 0.5%~ 1.0% chromium to improve the hardness, strength and toughness of steel, and has good weldability and corrosion resistance. At the end of 1970s, the Soviet Union was used to develop Tyumen Oilfield in Siberia, and the construction of 4300km natural gas pipeline in alpine region consumed molybdenum 18kt. When the second Siberian railway was built, the consumption of molybdenum was also great.
Stainless steel: accounting for about 22% of the total molybdenum consumption, usually containing 4%~5% molybdenum, which is often used in places with erosion resistance and corrosion resistance. Such as oil refining, natural gas wells and oil wells, aircraft engines, marine equipment, chemical equipment and other places with serious corrosion.
High speed steel and tool steel: about 8% of the total molybdenum consumption. High speed steel usually contains 3.75%~9.5% molybdenum, with an average of 4.8%, and metals such as tungsten, vanadium and chromium are often added at the same time. At present, 90% of the high-speed steel used in the world contains molybdenum. About 6000 tons of molybdenum is used to produce high-speed steel every year in the world.
The molybdenum content of tool steel is usually 0.6% ~ 2.95%, and the molybdenum used in tool steel in the world is 2000~2500t every year.
Cast iron and rollers: their consumption accounts for 6% of the total molybdenum consumption. Adding 0.3% ~ 1.0% molybdenum to cast iron will greatly improve the tensile strength, bending strength and fatigue strength, and improve the structural uniformity of castings, which is especially important for large castings and widely used in automobile manufacturing, pressure pipes and molds.
2, molybdenum and molybdenum-based alloys
Their consumption accounts for about 6% of the total molybdenum consumption in the world. Molybdenum has the advantages of high melting point and boiling point, good high-temperature strength, friction corrosion resistance, high thermal conductivity, small thermal expansion coefficient and good hardenability, and is widely used in aerospace, weapons, electronics, chemical industry and other fields.
When the recovered satellite re-enters the atmosphere, it must overcome the erosion of hot air. Therefore, it is required to withstand vibration, impact, vacuum, radiation and temperature alternation. Molybdenum-based alloy is often used to make the skin of the stable skirt of satellite recovery cabin. TZM molybdenum alloy is also used to manufacture the nozzle of solid fuel rocket engine of space rocket or space shuttle, the nose cone of rocket, the leading edge of aircraft, rudder, heat shield, honeycomb structure and so on.
Molybdenum steel is not only used as tank armor in weapon industry, but also used as integral turbine impeller of cruise missile and helium turbine impeller which is not easy to react with high temperature gas-cooled atoms by using the corrosion resistance of TZM and TZC molybdenum alloys.
In the electronic industry, molybdenum is often used as the grid, screen electrode of various electron tubes and the power lead-out line of advanced electric light sources by taking advantage of its high melting point, low expansion coefficient and low secondary electron emissivity. Now it is considered that adding a small amount of silicon, aluminum and potassium to molybdenum can make its secondary crystallization temperature 700℃ higher than that of pure molybdenum, reaching 1800~ 1900℃.
The chemical industry often uses the corrosion resistance of molybdenum. Molten glass can corrode most metals, but only molybdenum and platinum can resist it. Platinum is too expensive, and now molybdenum or molybdenum alloy containing 30% tungsten is often used instead of platinum as the electrode of glass melting furnace. Melting and maintaining molten metal: lead 1059℃, bismuth 1430℃, lithium 999℃, mercury 599℃, potassium and sodium 899℃, zinc 850℃. At this time, molybdenum has become the best material choice because of its corrosion resistance and high temperature strength, and has been widely used. Molybdenum and molybdenum-based alloys are widely used to manufacture sulfuric acid heat exchangers and valves.
Molybdenum is widely used in processing industry. The die used at high temperature is heated, and the mechanical alternating stress leads to fatigue cracking of the material. Using molybdenum or molybdenum-based alloy with small thermal expansion coefficient, strong thermal conductivity and good high temperature strength can greatly prolong the life of the die. When the British G.K.N company dies-casts delicate parts such as watchcases, the service life can reach 5000 times, generally 3000 times. The service life of molybdenum alloy die used for bearing production is 15 times longer than that of original high-speed steel and bearing steel die. Molybdenum alloy die can be used at 1200℃ when forging refractory superalloys at isothermal temperature. Molybdenum-based alloy is often used as the plug and die of seamless steel pipe piercer because of its high hardness and strong cold and hot fatigue resistance, and its life is several hundred times longer than that of 3Cr2W8V die steel.
The annual consumption of molybdenum used in automobile piston rings and cylinder inner walls abroad has reached more than 600 t, and molybdenum has high reflectivity to laser and is not easy to be damaged by laser. The United States is using it to develop a laser mirror with a diameter of 2.5m and a thickness of 13mm. Jouns said that the thermal conductivity and thermal expansion of molybdenum are very close to that of the time, and it is very suitable for manufacturing the packaging shell of silicon wafer, the heart of a supercomputer. Molybdenum is also a good spraying material, which can greatly improve the corrosion resistance of spraying parts and prolong the service life.
3. Molybdenum chemical products
This item accounts for about 10% of the total molybdenum consumption, of which about half is used as lubricant, followed by catalyst, pigment, corrosion inhibitor and reagent.
(1) Lubricant: High-purity molybdenum disulfide powder is widely used as the king of solid lubrication because of its advantages of wide temperature adaptability, heavy load resistance, direct air resistance and radiation protection.
Aerospace field: the high vacuum of the high-altitude universe and the strong radiation of cosmic rays are beyond the reach of conventional lubricating materials such as grease or graphite. Molybdenum disulfide has excellent lubrication efficiency under high vacuum, radiation, weightlessness, high temperature and ultra-low temperature, so it is widely used in spacecraft, such as antenna orientation mechanism of international communication satellite, and its aluminum pivot sleeve is lubricated by molybdenum disulfide friction film; Yuyun meteorological satellite and OAO-I orbiting astronomical observation satellite use 88Ag- 12MoS2 as electric contact brushes; Both the universal joint bearing of synchronous meteorological satellite and the spherical bearing of TRIAD satellite use molybdenum disulfide as lubricant.
Molybdenum disulfide is the best choice of lubricating material in high temperature and strong radiation environment of nuclear industry. Molybdenum disulfide is usually used to lubricate the transmission parts and friction pairs in foreign high temperature atomic reactors. The transport mechanism of high temperature liquid sodium-cooled fast breeder reactor works in nitrogen and sodium vapor. When lubricated with molybdenum disulfide, a layer of wear-reducing Na2 MoO 4 film is formed on the surface of the parts. The transmission mechanism of the British "Dragon" high temperature gas-cooled reactor is sealed in a dry sleeve filled with nitrogen. After spraying molybdenum disulfide on the ball and raceway surfaces of its bearings, the working friction coefficient can be kept at 0.003. The transmission mechanism of AVR high temperature pebble bed reactor in Germany and St. Frenburg high temperature gas cooled reactor in the United States is also lubricated with dry film containing molybdenum disulfide.
Automobile internal combustion engine can only convert 25% of the thermal energy of gasoline combustion into useful work, and the friction loss is 10.5%. In 1979, Akaoka reported that the average driving distance per liter of gasoline increased by 7.9% after adding molybdenum disulfide to automobile engine oil. In 1975, Reston reported that adding more than 1% molybdenum disulfide to automobile engine oil can reduce fuel consumption by 4% ~ 8% on average.
The American Railroad Association (R.A.R) used 28 kinds of lubricants in one year, and three of the five suitable lubricants contained molybdenum disulfide. Canada's state-owned railways and Pacific railways have been using lubricating paste containing 50% molybdenum disulfide and 50% mineral alcohol for many years.
Molybdenum disulfide is mixed with plastic, bronze, cast iron and other substrates to make self-lubricating gears, bearings and bearing shells, which are used in high-temperature environments such as textiles, printing and dyeing, paper making, food, rubber and so on, to realize oil-free or oil-less lubrication.
Molybdenum disulfide is added into lubricating oil and grease to make composite lubricating oil, grease and paste, which are widely used in various fields: Molybdenum disulfide calcium-based lubricating grease is applied to the coupling of cold rolling mill, Molybdenum disulfide gear film-forming paste is applied to the crown block gearbox in steel rolling workshop, and Molybdenum disulfide dry film or film-forming paste is used to lubricate the bearing bush and gear of large ball mill.
(2) Catalyst: Molybdenum compound is one of the most widely used catalysts. As early as 19 10, British Badishe published the patent of molybdenum compound as catalyst for ammonia synthesis process. Up to now, nCo2O3mMoO is still widely used in ammonia synthesis industry as a catalyst for hydrodesulfurization of feed gas and oil.
Acrylonitrile is the raw material for synthesizing polypropylene fiber, and ammonia oxidation of propylene is the main method for mass production of acrylonitrile at present. The first industrial catalyst used in this reaction is bismuth phosphomolybdate-silica catalyst, which has evolved several times, but molybdenum is the main component of this kind of catalyst.
Nickel oxide-molybdenum oxide catalyst has high activity and selectivity, and is used as the catalyst for propylene oxidation to acrylic acid at 435℃. The conversion of propylene is 84% and the yield of acrylic acid is 79%.
Formaldehyde is an important raw material in modern chemical industry, which is mainly produced by methanol oxidation. The catalyst for this reaction is silver or iron molybdenum oxide. In contrast, the service life of silver (2~6 months) is not as good as that of iron-molybdenum oxide (1~2 years). The conversion rate of silver (60%~73%) is not as good as that of iron-molybdenum oxide (99%). The reaction temperature of silver (635℃) is higher than that of iron-molybdenum oxide (
Molybdenum disulfide is the main component of hydrodesulfurization catalyst (such as sulfurized Co2O3? MoO3/Al2O3 catalyst). It has great catalytic activity in hydrogenation of olefins or benzene rings or hydrogenolysis of C-S bonds.
Ammonium paramolybdate is a particularly effective catalyst for coal liquefaction with alumina as the carrier. At 450℃ and 7MPa hydrogen pressure, the conversion rate of coal liquefaction is as high as 95%, and the yield of artificial oil is 63%.
The United States has successfully developed a catalyst containing 6%~20% molybdenum and 5%~4% potassium. It is not afraid of the corrosion of hydrogen sulfide and can be used as a catalyst for Fischer-Tropsch synthesis. When the inlet gas contains (10~25)× 10-6H2S sound, it can produce liquefied petroleum gas containing 70% hydrocarbons without interference.
(3) Pigments: The most commonly used inorganic yellow pigments in the world today are chrome yellow and cadmium yellow. Lead, chromium and cadmium are highly toxic. In the voice of environmental protection, the development of non-toxic pigments is very important.
BSD—- Molybdenum has bright yellow color and good light and thermal stability. It is suitable for manufacturing common coatings, high-temperature coatings, architectural coatings and other products. It can also be used to prepare civil and engineering plastic products. You can also make colored wax products and colored graphite.
The structural formula of molybdenum orange is about 25PbCrO4? 4PbMoO4？ Since 1960s, lead sulfate has become a widely used inorganic pigment. Molybdenum orange is bright orange red, with strong light stability and good hiding power, and has certain anti-corrosion and anti-rust properties. Therefore, it is widely used in transportation, large-scale outdoor devices, agricultural machinery, printing ink, plastics and so on. For example, the antenna tower of Shanghai TV Station is painted with molybdenum orange paint. Now many inorganic pigment manufacturing companies in the world produce molybdenum orange. 1970 British molybdenum orange 10000t or more, 1982 world molybdenum orange production reached 35000t. However, as a country rich in molybdenum resources, China only produces them in small batches.
(4) Micro-fertilizer: Plant organisms are composed of more than 60 elements, and nitrogen, phosphorus and potassium are the three major fertilizers for plants. A few elements such as boron, manganese, zinc, copper, cobalt, molybdenum and iodine are called seven micronutrients, which have been used in more than 20 countries such as the United States and Japan, and began to be used in China in the late 1950s. At present, there are more than ten kinds of micro-fertilizers, including molybdenum.
The American Fertilizer Supervision Association suggested that 0.2kg of boron, 0.5kg of zinc, 0.5kg of manganese, 0.5kg of copper, 0.005kg of iron 1t of common fertilizer should be added.
Seed dressing with ammonium molybdate in Nanhua Township, Changsha County, Hunan Province increased peanut yield by 32.2%, and spraying molybdenum fertilizer in Dezhuang County, Guangdong Province increased early rice yield by 25.6%. From 1957, the experiment of applying molybdenum fertilizer to soybean developed to large-scale aerial spraying seed dressing, and the soybean yield increased by about 10%.
(5) Others: Black molybdenum film is used as a dark mirror for solar energy conversion. Effective photothermal solar energy conversion needs to match high solar energy absorption rate and high infrared reflectivity, and black molybdenum film is the best material at present.
Flame retardants and smoke suppressants for organic polymers; British research shows that adding 3% ~ 4% molybdenum trioxide to halogenated polyester can increase the critical oxygen index (the lowest O/N of organic matter combustion) by 3% ~ 4%, increase the carbon production during combustion by about 4%, and reduce the smoke production by 3%.
Water corrosion inhibitor: Molybdenum heteropoly acid salt can be used as water corrosion inhibitor. At 50℃ and pH 8.13 ~ 8.25, the corrosion rate of carbon steel sheet before adding molybdenum salt was 1.24 1 mm/year, and after adding molybdenum heteropoly acid salt, the corrosion rate decreased to below 0. 15 mm/year. Sodium phosphomolybdate was the best.
The composite ion exchange material of recycled 137Cs, ammonium phosphomolybdate (AMP) ion exchange material can be used to recycle 135Cs, which has high selectivity and corrosion resistance to 137Cs. Compared with other ion exchange materials, the exchange capacity and elution performance are superior.
Molybdenum and molybdenum compounds have a wide range of other uses.