The Use Of Molybdenum

Jun 28, 2020

Alloy steel: it consumes the largest amount of molybdenum, accounting for 44% of the world's total molybdenum consumption and more than half of the steel molybdenum added.

Among them, structural steel (or general molybdenum steel) containing about 0.1%~ 0.2% molybdenum is widely used as large steel components such as skyscrapers, Bridges, etc., which can improve the hardness, strength and toughness of steel, and extend the life of these large facilities.

Molybdenum steel containing 0.3% molybdenum is used in load-bearing and transmission components in transportation and automobile manufacturing. High strength alloy steels usually contain less than 0.3% molybdenum, 0.5%~ 3.5% nickel and 0.5%~1.0% chromium to improve the hardness, strength and toughness of the steels, as well as good weldability and corrosion resistance. In the late 1970s, the Soviet Union used the Tyumen oil field in Siberia to build a 4300km natural gas pipeline in the alpine region, which consumed 18kT of molybdenum alone. The construction of the second Siberian railway also consumed a large amount of molybdenum.

Stainless steel: it accounts for about 22% of the total molybdenum consumption, usually add molybdenum for 4%~5%, often used in corrosion prevention, corrosion resistance place. Such as petroleum refining, natural gas Wells and oil Wells where corrosion is severe, aircraft engines, Marine equipment, chemical equipment... And so on.

High speed steel and tool steel: it accounts for about 8% of the total molybdenum consumption. High speed steel usually contains 3.75%~9.5% of molybdenum, with an average of 4.8%. Tungsten, vanadium, chromium and other metals are often added. Molybdenum is contained in 90% of the world's high-speed steel. Worldwide, about 6,000 t of molybdenum is used to produce high-speed steel each year.

The molybdenum content of tool steel is usually 0.6 %~ 2.95%, and the molybdenum used in tool steel is 2000~2500t worldwide every year.

Cast iron and rollers: they account for 6% of the total molybdenum consumption. When 0.3%~ 1.0% molybdenum is added to cast iron, tensile, bending and fatigue strength will be greatly improved, and the uniformity of casting structure will also be improved, which is especially important for large castings, which are widely used in automobile manufacturing, pressure piping and casting molds.

Molybdenum and molybdenum base alloys

They account for about 6% of the world's total molybdenum consumption. Molybdenum has the advantages of high melting point, high boiling point, high temperature strength, anti-friction and corrosion resistance, high thermal conductivity, small thermal expansion coefficient, good hardenability, etc., which make it widely used in aerospace, weapons, electronics, chemical and other fields.

When the recovered satellite reenters the atmosphere, it must overcome thermals. Molybdenum based alloys are commonly used to make the skin of the stable skirt of the satellite recovery module. TZM molybdenum alloy is also used to make the nozzle of solid fuel rocket engine of space rocket or space shuttle, nose cone of rocket, leading edge of aircraft, rudder, heat shield, honeycomb structure, etc.

In weapon industry, not only molybdenum steel is used as tank armor, but also TZM and TZC molybdenum alloy are used as integral turbine impeller of cruise missile and helium turbine impeller with high temperature gas-cooled atom reaction difficulty.

The advantages of high melting point, low expansion coefficient and low secondary electron emissivity of molybdenum are often used in the electronic industry, which is widely used as the gate, screen and power outlet of advanced electric light source of various electronic tubes. It is believed 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, up to 1800~1900℃, which is widely used as heating element and heat insulation screen.

The corrosion resistance of molybdenum is often used in the chemical industry. Molten glass corrode most metals, but only molybdenum and platinum are resistant to corrosion. Platinum is so expensive that molybdenum or molybdenum alloys containing 30% tungsten are now often used instead of platinum as electrodes in glass furnaces. Smelting and storage of molten liquid metal: lead at 1059 ℃, bismuth at 1430℃, lithium at 999℃, mercury at 599℃, potassium and sodium at 899℃, zinc at 850℃. At this time, the corrosion resistance and high temperature strength of molybdenum determine that it is the best material choice, and has been widely used. Molybdenum and molybdenum-based alloys are widely used in the manufacture of sulphuric acid heat exchangers and valves.

Molybdenum is more widely used in the processing industry. Under high temperature, the die is subjected to heat and mechanical alternating stress, which results in the fatigue crack of the material. The mold life is greatly extended by small thermal expansion coefficient, strong thermal conductivity and high temperature strength of molybdenum or molybdenum base alloy. British G.K.N company die casting hand watchcase and other delicate parts, the life can be up to 5000 times, generally 3000 times, bearing production using molybdenum alloy mold life than the original high-speed steel, bearing steel mold life increased 15 times. Molybdenum alloy dies can be used at 1200℃ when isothermal forging refractory superalloy. Because of the high hardness of molybdenum base alloy and the high fatigue strength of cold and heat resistance, it is often used as the top and mould of seamless pipe punch, and its life is hundreds of times longer than that of 3Cr2W8V mold steel.