Vacuum furnace is mainly used for sintering of metal powder products, metal injection molding products, cemented carbide, ceramics, NdFeB, stainless steel non-woven fabrics, etc. The structure of high-temperature vacuum sintering furnace is basically the same as that of vacuum heat treatment furnace, but appropriate changes are made according to the sintering process. The vacuum sintering furnace is divided into double vacuum sintering furnace and single outdoor circulating pressurized cold vacuum sintering furnace. The double vacuum sintering furnace has two identical sintering furnaces, sharing a set of vacuum pumping system and electrical control system; During operation, the two furnaces are used for heating and cooling respectively and are used alternately. The furnace has the functions of degreasing, pre sintering and sintering in the same furnace. The degreasing system includes external pipes, vacuum valves, condensers, collectors, mechanical pumps, etc. The single outdoor circulating pressurized air cold sintering furnace needs to be equipped with a vacuum unit with high vacuum and high pumping speed to meet the requirements of NdFeB sintering process. The furnace structure is the same as that of single outdoor circulating pressurized air quenching vacuum furnace.
1. Preparation before furnace opening ① Check whether there are tools or other conductive substances in the electrical control box. If there are forgotten workpieces in the furnace, they should be removed in time. ② Check whether the electrical switch contacts normally after closing. ③ Check whether the temperature control instrument works normally, and turn on its switch to make it work. 2. Open furnace production ① Set the temperature of the automatic temperature control instrument according to the process requirements. ② Place the control "handle" at the automatic control position to raise the temperature. ③ When the cold furnace heats up, the workpiece can be loaded for 2h after the temperature is reached, and continuous production is allowed. ④ The workpiece shall be placed evenly and stably in the furnace, and it is not allowed to contact with the heating wire. ⑤ Operate in strict accordance with the process procedures. 3. Shut down the boiler, turn on the instrument switch, and turn off and turn off the power knife switch. 4. Precautions for box type resistance furnace operation ① When the furnace temperature is higher than 400 ℃, it is not allowed to open the furnace door for intense cooling. ② The maximum operating temperature shall not exceed 950 ℃. ③ The charging quantity shall not be too large, and the temperature drop caused by it shall not be greater than 50 ℃. ④ Do not exert too much force during charging to avoid damaging the furnace bottom. ⑤ Always pay attention to whether the electrical appliances of the instrument and electrical control box work normally. ⑥ The newly installed or overhauled furnace shall be placed at room temperature for 2~3 days and nights after decoration. The electrician shall check with a 500V tramegger that the resistance of the three-phase electric heating element to the ground (furnace shell) shall be greater than 0.5M Ω before power transmission. Power supply and baking shall be conducted according to the following process. 100~200 ℃, 15~20h, open the furnace door, 300~400 ℃, 8~10h, open the furnace door, 550~600 ℃, 8h, close the furnace door, 750~800 ℃, 8h, close the furnace door, remove the cover plate of the furnace shell, so that the water vapor in the masonry is easy to disperse. ⑦ After the newly overhauled or newly installed furnace has been used for one month, the state of diatomite at the furnace top should be checked, and if it sinks, it should be filled again. 5. Maintenance of box type resistance furnace ① Always pay attention to furnace lining and resistance wire support plate bricks, and repair in time in case of damage. ② Check the condition of the heating wire frequently. If there is contact between the two wires, they should be separated in time. ③ Check the clamping head fastening of the resistance wire lead out rod every month, remove the oxide skin and tighten the clamping head in time. ④ Clean the furnace every week to remove oxides and workpieces left in the furnace. ⑤ Frequently check the use of furnace door hoisting steel wire, and replace it in time in case of damage.
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