Конструкциялық материалдар және термоөңдеу Конструкционные материалы и термообработка Constructional materials and heat treatment Учебное пособие для специальности: 5В071200– «Машиностроение»
Influence of heat treatment on the mechanical
жүктеу/скачать 1,99 Mb. Pdf көрінісі
|
| Influence of heat treatment on the mechanical
properties of steel. Heat treatment is carried out for change of mechanical properties of steel (durability, hardness, plasticity, viscosity). These properties depend on steel structure after heat treatment. After annealing, drawback, normalization (drawback with cooling on air) the structure of steel consists of plastic ferrite and cementite, possessing the high hardness and fragility. Inclusions of carbides have strengthening effect on steel. At small number of cementite inclusions of steel are plastic and have low hardness. Crushing of cementite particles leads to steel hardening at heat treatment. When strengthening cementite particles ability of steel to plastic deformation increases. Temperature increase of drawback of the tempered products, conducting to integration of cementite particles, reduces durability. Durability decreases at reduction of speed of cooling in the course of training or temperature increase from thermal disintegration. 204 After training the structure of steel consists of marten site and residual austenite. Hardness is defined by the hardness of marten site and its quantity. Plasticity of the tempered steel depends not only on the content of marten site, but also on its dispersion (the size of needles). For providing a high complex of mechanical properties seeks to receive after training fine-needled structure that is reached at fine-grained structure of austenite before transformation. Hardness of steel depends on temperature of isothermal disintegration of austenite. The temperature of isothermal disintegration of austenite is lower, the dispersion of pearlitic phases and there of the hardness of steel is higher is higher. Final operation of heat treatment is drawback. At drawback the steel product gains the final properties. The drawback temperature is higher, the durability is lower and plasticity of steel is higher. The greatest plasticity corresponds to drawback at a temperature 600-650zs. Mechanical properties of steel after hardening and high drawback are higher in comparison with the annealed or normalized steel. The double heat treatment consisting in hardening with the subsequent high drawback, conducting to significant improvement of the general complex of mechanical properties, is called as improvement and is a main type of heat treatment of constructional steel. жүктеу/скачать 1,99 Mb. Достарыңызбен бөлісу:
|