Life Time of Tungsten Heater of Kinescope Evaporation - Heat Treatment

In the process of kinescope evaporation, surface of wire would change and produce crystalline structure because of temperature, it would greatly shorten the life of the heater when the crystal structure increase to a certain number. Therefore, manufacturers should pay attention to control the number of crystal structure of wire surface in the deposition process. In addition, the more the amount of aluminum insertion, the shorter the tungsten heater life time, so the amount of aluminum insertion should not exceed the amount of theory evaporation.

In addition to these two reasons, the fluidity of aluminum has a great impact on the life time of tungsten heater in vapor deposition process. The fluidity of aluminum tungsten is measured by the amount of coil wetted on wolfram twisted spiral surface. The greater the number of spiral turns soaked, the better the fluidity of aluminum. If the Al liquidity is better, aluminum on the surface of the screw would be less after each deposition, the chance of reaction with tungsten would be less, which can prolong life time of tungsten heater. On the contrast, if the liquid of aluminum is poor, then residual aluminum would be deposited on tungsten surface for a long-term after each deposition. Thereby shortening the life time of the heater element.

The heat treatment temperature has a great impact on the life time of heater element. In order to increase its service life, tungsten heater would be placed in the furnace, keep warm for 10 minutes under the conditions of 1400 ℃, and then do heat treatment. When the heat treatment temperature is higher than 1450 ℃, the wire would completely recrystallized, so the spiral would become very brittle, it would break once it is to be touched and cannot be used again. If the heat treatment temperature is lower than 1350 ℃, then it cannot eliminate interior stress generated in the process of wire deformation, which would also reduce its life time. Therefore, control heat treatment temperature is essential for life time of wolfram heater.

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