The pressure control system consists of a pressure/vacuum sensor (inlet), a pressure control instrument, and an adjustable-diameter throttle valve in parallel with the main valve at the inlet of the vacuum pump system. The furnace pressure is obtained by the vacuum pressure sensor and sent to the pressure control instrument. After comparing with the set point value of the instrument, the instrument outputs the control signal to control the opening and closing degree of the throttle valve (the main valve in parallel with it is closed at this time). (Adjustment of opening and closing degree also has good PID control function), so as to maintain the degree of vacuum in the furnace stable within the specified pressure range. After the pre-commissioning of the equipment installation was completed, the main performance indicators were identified. The results are as follows.
(1) In the clean, empty furnace, after vacuum degassing, the vacuum degree refers to the identification of the vacuum sintering furnace: ultimate vacuum [011Pa, pressure rise rate 3Pa/h.
(2) temperature control by the temperature controller (set the maximum heating rate of 15e/min): maximum heating rate of 15e/min (01250e), 10e/min (12501550e); maximum test temperature of 1600e; good temperature following performance (can be Adjust PID parameters for optimization).
(3) Put 4kg of pure paraffin in the furnace for the dewaxing test. According to the test technology provided by the factory (since pure paraffin is different from compact, the conditions are more severe), the test result is: the wax collection rate (wax up to 3192kg in wax collection tank) is about 98%, better than the design requirements .
(4) Put 15 billets of the same brand number and the same lot number in the furnace and place them in the upper, middle, lower, left, right, front and back positions of the work area. After normal sintering, measure each sample piece. The coercive force, the extreme value does not exceed 016kA/m, that is, the uniformity of 013kA/m, which can be identified at the sintering temperature in the furnace temperature uniformity better than 5e, fully meet the high quality carbide sintering requirements .
(5) There is no strict acceptance criteria for carbon atmosphere control. Using a common vacuum furnace for sintering, severe decarburization (plum-shaped decarburized bamboo-like phase) of the sample compact, using different atmosphere control parameters (H2 and CH4 ratios, different carburizing temperatures) in the furnace, Sintered samples with neither carburization nor decarburization and severe carburization can be obtained, respectively. Therefore, the furnace atmosphere control is flexible and reliable.
(6) In dewaxing atmosphere control and partial pressure sintering, the control precision of furnace pressure is within 100Pa, which is stable and reliable.
(7) When the pressure in the furnace is 80kPa, rapid cooling is performed. From 900e to [100e, it takes about 3h in the empty furnace, and not more than 415h in the full furnace. Therefore, for the general product, one furnace product is completed within 24h. The sintering work (including the loading and unloading time of the furnace) is not a problem.
(8) This equipment adopts a continuous directional (from the hearth to the interior) to remove PEG by hydrogen gas. After testing, it shows that PEG pollution in the furnace is greatly eliminated. No trace of PEG is found in the furnace, and the product quality is good. , And to avoid the operation of the more dangerous operation of Tovar.