Tungsten and molybdenum materials
From the 20th century, some chemical elements that had no use before began to play an important role in industry. These chemical elements are collectively called rare elements or rare metals. Most rare metals were discovered in the late 18th and early 19th centuries, so their industrial application was later than that of other commonly used metals. However, many of the metals that are now rare metals have long since become common in modern industrial technology.
Tungsten (W), molybdenum (Mo) and its alloy materials are rare and high melting point metal materials. Tungsten and molybdenum are widely used in electronics, medical treatment, glass, iron and steel metallurgy and other industries because of their special high melting point, good electrical and thermal conductivity and excellent corrosion resistance and ray resistance.
Molybdenum reserves are abundant and widely distributed in China, mainly concentrated in Henan, Jilin, Guizhou, Shaanxi and Hunan provinces. Tungsten resources are concentrated in Jiangxi, Henan, Hunan and Fujian provinces.
Tungsten and molybdenum belong to Group Ⅶ in the periodic table. They are typical high melting point metals with similar basic properties, but also have their own characteristics. The surface of tungsten and platinum is silver 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 shortcomings of high temperature oxidation and low temperature brittleness.
The purpose of tungsten and molybdenum alloying is to further improve the high temperature strength, improve the oxidation resistance and improve the welding performance, and prepare the heat resistant alloy or heat strong alloy applied at the high temperature of 1000-2000 ℃, which requires high strength under a certain load and high temperature application without plastic deformation and fracture. Therefore, high temperature reading resistance is one of the important indexes of superalloy.
