Expert Yogi
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| In 1910, molybdenum products were produced by powder metallurgy process. Until 1945, powder metallurgy process has been the only industrial production method for manufacturing molybdenum sheet, wire and bar. In the mid-1940s, rparke and j.l.ham developed a method for preparing high-performance molybdenum and molybdenum alloy ingots by consumable arc smelting process. From the late 1940s to the mid-1960s, in order to meet the needs of atomic energy, aviation and aerospace technology, molybdenum alloy and related processes were widely studied, and mo-0.5ti-0.02c alloy and mo-0.5ti-0.1zr-0.02c (TZM) alloy were developed. From the late 1960s to the early 1970s, mo-hf-c alloys with higher strength were made. China began to produce molybdenum products from powder metallurgy billets in the late 1950s. Later, molybdenum and its alloy bars, wires, plates, foils, pipes and rectangular pipes were produced by powder metallurgy and melting.1.4308 Varios tipos de chapa de acero inoxidable 304l
Molybdenum alloys produced in industry can be divided into mo-ti-zr, Mo-W and Mo Re alloys, as well as mo-hf-c alloys strengthened by hafnium carbide particle precipitation. TZM alloy has excellent comprehensive properties and is the most widely used molybdenum alloy. TZC (mo-1.25 ti-0.15 zr-0.15c) alloy has higher high temperature strength and recrystallization temperature than TZM, but its processing is difficult and its application is limited.
Molybdenum alloys have the disadvantages of low temperature brittleness, welding brittleness and high temperature oxidation, so their development is limited. It is difficult to improve the high temperature oxidation resistance of molybdenum alloy by alloying. At present, only protective coating is used to improve this performance. The main problem in the research of molybdenum alloy is to improve the high temperature strength, recrystallization temperature and low temperature plasticity. The main problem in the research of pure molybdenum is to improve the low temperature plasticity, that is, to reduce its plastic brittle transition temperature.
The main strengthening ways of molybdenum alloys are solution strengthening, precipitation strengthening and work hardening (see metal strengthening). Titanium, zirconium and hafnium are the main alloying elements of molybdenum. The effect of alloying elements on the hardness of molybdenum rolled bars is shown in the figure on the next page. Titanium, zirconium and hafnium can not only strengthen and maintain the low-temperature plasticity of materials, but also form stable and dispersed carbide phase, and improve the strength and recrystallization temperature of materials.201 Tubo de acero inoxidable de diámetro grande 100mm soldado
Interstitial impurities carbon and nitrogen, especially oxygen, have a serious effect on the plastic brittle transition temperature. Their solubility in molybdenum is very low (no more than 1ppm at room temperature), and the excess interstitial elements are distributed on the grain boundary in the form of molybdenum compounds, which reduces the grain boundary strength and leads to intergranular brittle fracture. Adding trace boron to molybdenum alloy can refine grains, purify grain boundaries and change grain boundary morphology, so as to improve the plasticity of molybdenum: adding trace elements such as iron and yttrium can also improve the low-temperature plasticity (see interface). In 1955, G. Geach and J. Hughes found that rhenium can significantly improve the plasticity of molybdenum and tungsten and reduce the plastic brittle transition temperature of molybdenum to - 200 ?.
Acero Inoxidable Del óxido Del Cromo
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Industrial production alloy series
