Конструкциялық материалдар және термоөңдеу Конструкционные материалы и термообработка Constructional materials and heat treatment Учебное пособие для специальности: 5В071200– «Машиностроение»
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| Steel with special properties.
In the industry widely use steel and the alloys possessing special properties: the set conductivity, the low specific electrical resistance set by temperature factor of linear expansion, semi-conductor and magnetic properties, ability to get into condition set products. Wide application was found by metals and alloys of high conductivity: silver, copper, bronze and brass. Silver is applied to manufacturing of not oxidized conductors of electric contacts of responsible devices. Special methods from silver produce coverings on copper, brass and non conducting materials: ceramics, glass, polymers. Copper has wide application thanks to high conductivity, good mechanical characteristics, lower in comparison with cost silver. For protection of copper against oxidation current carrying elements to silver. In products with the raised mechanical characteristics use brass, cadmic and beryllium bronze. Cadmic bronze use for manufacturing of sliding contacts, membranes. Brass apply to manufacturing of various current-carrying details. Aluminum is characterized by rather high electrical- in a combination to plasticity and small density. It is more widespread in the nature, than copper, is more resistant to corrosion. Semi-conductor materials represent a class of materials with the electronic conductivity, being characterized a bigger specific electrical conduction, than metals, but smaller, than dielectrics. For receiving semiconductors with the set specific electrical resistance and type of conductivity carry out their alloying. According to chemical classification of semi-conductor materials, they are divided into two classes: 193 - the simple semiconductors incorporating one element., - the difficult semiconductors being chemical compounds and alloys. Magnetic steel and alloys characterize magnetic permeability, coercive force and a residual induction. Depending on values of these sizes magnetic materials divide on: - magnetic and soft materials (ferromagnetic), having small coercive force and big magnetic permeability. They are electro-technical iron and steel, iron-nickel alloys (permalloy)., - magnetic and firm steel and alloys having big coercive force. These are high- carbonaceous and alloyed became, special alloys. Alloys with high electric resistance are applied to manufacturing of electro- heaters and elements of resistance (resistors) and rheostats. In the industry wide application was received by the materials possessing high a limit of elasticity and a limit of endurance. These properties of materials are provided with their thermal processing - training and the subsequent water- tempering. Medium-carbon steel with elastic properties apply to manufacturing of springs, springs of general purpose. To manufacturing of elastic elements in instrumentation apply alloys with special elastic characteristics. Springs, membranes, bellows-produce from alloys 42НХТЮ, 17ХНГТ, 68НХВКТЮ, etc. These alloys in the tempered condition are rather technological in processing, and after aging gain high elasticity and durability. Alloys with set by factor of thermal expansion contain a large amount of nickel. The alloy 36Н-an invar, doesn't extend almost at temperatures from a minus 60 to +100?С, possesses good office characteristics, is technological and corrosion-resistant. Invar alloying cobalt receives a super invar. These alloys apply to manufacturing of details of the devices demanding the constant sizes in the range of climatic changes of temperatures. For connection of metal details of devices with the glass apply the alloys of Fe-Ni alloyed by cobalt or copper. To connections with heat-resistant glass apply an alloy 29НК (29 % of nickel and 18 % of cobalt) - cover. To not heat- resistant glasses apply an alloy 48Н-platynite. In instrumentation widely use the materials consisting of two layers of materials with various temperature factors of foundry expansion – thermo bimetals. Thermo bimetals apply to manufacturing of thermal relays, condensers and alarm fire devices. жүктеу/скачать 1,99 Mb. Достарыңызбен бөлісу:
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