After the high-temperature electric kiln body is built in a large area, the furnace shall be dried. Before oven drying, megger shall be used to detect the insulation of equipment, which is generally not less than 2m Ω. Refractory fire brick furnace drying is divided into three stages: ① the moisture discharge period is 0 ~ 200 ℃, which is the discharge period of moisture in the mud and moisture in the masonry. The furnace door must be opened and the insulation time is long. ② The expansion period of masonry is the period when the masonry begins to expand and expand, and the temperature rise at this time shall not exceed 50 ℃ /h. ③ The insulation period is more than 600 ℃, and the masonry will be damaged if the temperature rises by 100 ~ 200 ℃.
Precautions for high temperature electric kiln drying and daily use
(1) Prepare operation procedures for use and maintenance, establish operation records and repair files, count the accumulated working hours of operation, strengthen daily maintenance, master the change trend of equipment technical status, find out the signs of failure and damage as soon as possible, avoid hot repair in the nature of emergency repair, prepare repair materials and prepare repair process in advance according to the furnace load and working conditions. For example, the service life of alloy components is related to many factors, such as working temperature, furnace medium, component quality and operation conditions. Its fluctuation life is 6000 ~ 10000h.
Vacuum furnaces generally have many leakage faults in spring and autumn, and leakage faults are easy to occur when they are idle for a long time. Take the pressure rise rate once a month (under normal temperature, close all vacuum valves, stop the operation of the vacuum system, read one number after 10min, and then read another number after 1h. The difference between the two numbers is the value of the pressure rise rate), and master the trend of equipment leakage. For example, if the vacuum equipment is shut down continuously for one worship, it should be idled once.
In the vacuum system leak detection, in addition to plugging with vacuum mud paste, you can also use a medical needle to suck the suspected leak point of ether sword shooting, and observe whether there is any change in the reading of the vacuum gauge. The blind plate with vacuum silicon tube hole can also be made to block the vacuum pipeline in sections for leak detection. The diffusion pump can be cleaned by chemical pickling if there is carbon deposit.
(2) After the brick furnace is repaired, it shall be checked frequently at the initial stage of use to check whether the furnace surface temperature and furnace temperature are too high, and whether the heating body is overheated, burnt out, uneven temperature or whitened. For three-phase high-temperature electric furnace and when the capacity of resistance furnace exceeds 100kW, ammeters shall be installed in each phase and each heating zone. If abnormal furnace temperature and instrument indication are found, timely analyze and deal with them.
(3) Do not overload the equipment. The maximum service temperature of the alloy element refers to the surface temperature of the element allowed in dry air, not the temperature of the heating material or the temperature around the electric heating element. Note that the temperature of the electric heating element itself is 100 ℃ higher than the surrounding medium temperature or the heated temperature.
(4) Avoid deleting products in hot places, especially copper, aluminum, zinc, tin, lead, etc. in contact with electric heating elements, whether it is fine powder, molten liquid or steam, to prevent the formation of "pockmarks" on the surface of electric heating body, which will reduce the cross section and finally burn out due to overheating.
(5) When measuring the uniformity of furnace temperature, pay attention to the positioning and binding mode of temperature measuring contact and the distance from the heating element. The furnace hearth and brick shelf shall be cleaned frequently (at least monthly) with a brush, broom, compressed air, vacuum cleaner, etc. to prevent impurities such as oxide skin in the furnace from falling on the electric heating elements, resulting in short circuit, or even burning the brick shelf. The bottom plate, crucible, furnace pot and other heat-resistant steel components should be hoisted and knocked to remove the oxide skin every time they are used for a period of time. If impurities such as iron oxide scale are not removed in time, they will melt and react with refractory bricks to melt the furnace wire.
(6) After the furnace is heated up, the furnace door cannot be opened for a long time. When the temperature is higher than 400 ℃, it shall not be cooled sharply. When the temperature of electric heating elements is high and the temperature changes greatly, it is easy to cause oxidation and scaling. For molybdenum heating furnace, EI shall be cooled to below 200 ℃ before stopping the supply of protective gas.