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Classification of metal working conditions

2020-04-20
Metal working conditions include deformation temperature, deformation speed and deformation mode.  Deformation temperature: increasing the temperature of metal during deformation is an effective measure to improve the malleability of metal. in the heating process, as the heating temperature increases, the mobility of metal atoms increases, the attraction between atoms weakens, and slippage is easy to occur. therefore, the plasticity increases, the deformation resistance decreases, and the malleability is obviously improved. therefore, forging is generally carried out at high temperature.  Heating of metal is an important link in the whole production process, which directly affects productivity, product quality and effective utilization of metal.  The requirements for metal heating are: under the condition of uniform heat penetration of the blank, the required temperature for processing can be obtained in a short time while maintaining the integrity of the metal and minimizing the consumption of metal and fuel. One of the important contents is to determine the forging temperature range of the metal, i.e. the reasonable initial forging temperature and final forging temperature.  The starting forging temperature is the starting forging temperature. In principle, it should be high, but there should be a limit. If the limit is exceeded, the steel will suffer from heating defects such as oxidation, decarburization, overheating and overburning. The so-called overburning refers to the fact that the heating temperature of the metal is too high, oxygen permeates into the metal, oxidizes the grain boundaries and forms brittle grain boundaries. During forging, it is easy to break, and the starting forging temperature of the carbon steel scrapped by forgings should be about 200℃ lower than the solid phase line.  The final forging temperature is the stop forging temperature. In principle, it should be low, but not too low. Otherwise, the metal will undergo work hardening, which will significantly reduce its plasticity and increase its strength. The forging will be laborious and even crack for high carbon steel and high carbon alloy tool steel.  Deformation speed: deformation degree within unit time of deformation speed level. The influence of deformation speed on the malleability of metal is contradictory. On the one hand, with the increase of deformation speed, recovery and recrystallization cannot be carried out in time, so that the phenomenon of work hardening cannot be overcome in time. The plasticity of metal decreases, the deformation resistance increases, and the malleability deteriorates. On the other hand, during the deformation of metal, some of the energy consumed in plastic deformation is converted into heat energy, which is equivalent to heating the metal, so that the plasticity of metal increases, the deformation resistance decreases, and the malleability becomes better. The larger the deformation speed, the more obvious the thermal effect becomes.

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