High temperature furnace, as a kind of commonly used heating equipment, laboratory is widely applied in sintering, melting, heating, heat treatment, etc., for each main parts such as heat preservation material, high temperature furnace heating element, thermocouple, temperature control program, and the control method of a comprehensive understanding and mastering, help us rational selection, manufacture and use of energy-saving, intelligence, safety, high temperature furnace, better use of high temperature furnace, improve the quality of heating products. The following from the specific introduction of a number of aspects to explain the high temperature furnace in the manufacture and use of what characteristics:
1. Refractory for high temperature furnace
Refractory insulation materials commonly used to improve the performance of, and a new type thermal insulation materials such as carbon fiber, alumina fiber, such as the use of lightweight high temperature refractory materials in colleges and universities, greatly reduce the weight of the high temperature furnace, reducing the original 1/5 of the weight, to a high temperature furnace refractory insulation materials commonly used in general are: zirconia brick, alumina brick, corundum brick, corundum - mullite brick, etc., with the improvement of main refractories qualitative content, volume density increased gradually, using temperature is increased, the heat preservation effect is better.
The carbon fiber felt on the high temperature furnace is a high temperature thermal insulation material with excellent performance, which is made by carbon fiber acupuncture into felt, pre-oxidation, carbonization, graphitization and other production processes. Under vacuum and inert atmosphere, the zUI small operating temperature of carbon fiber felt can reach 2500℃ or even 3000℃. Carbon fiber felt, blanket and board made of carbon fiber, with high heat resistance, good insulation, light weight, soft texture, corrosion resistance and other characteristics are ideal thermal insulation materials for high temperature furnace.
Alumina fiber is a kind of AL2O3 content as high as 95% 97% of inorganic materials, the maximum temperature reached 1800 ℃, with excellent high temperature mechanical properties and chemical corrosion resistance, no special atmosphere condition, the aluminum silicate fiber generally use only at 1200 ℃, the effective service life of 4-5 years, polycrystalline alumina fiber can be used for 1200-1700 ℃, with excellent heat resistance and high strength, corrosion resistance of lightweight insulation of alumina fiber cloth, felt, bench refractory fiber, meet the requirements of laboratories for high temperature furnace temperature.
The heat preservation material has a very important influence on the temperature rise and maintenance of the furnace. It determines the heat energy utilization efficiency of the high-temperature furnace and the temperature difference of each part of the furnace. It also determines the energy consumption during heating of the high-temperature furnace, which is related to the safety and service performance of the refractory masonry and furnace structure. Therefore, the thermal conductivity of thermal insulation materials is required to be low, good thermal insulation performance, high resistivity, electrical insulation energy consumption, does not hinder the discharge of furnace gas, at high temperature does not react with products in the furnace, the price is cheap and easy to purchase in large quantities.
2. Heating element of high temperature furnace
The heating elements of high temperature furnace are: resistance wire, silicon carbon rod, silicon molybdenum rod; Their high thermal efficiency, strong corrosion resistance, long life, high temperature laboratory commonly used for iron chromium aluminum, nickel chromium wire, nickel chromium iron high resistance alloy wire, zui generally high temperature less than 1300 degrees Celsius, they have high resistivity, small temperature coefficient of resistance, oxidation resistance performance of machining and welding, with high strength at high temperature, can be processed into various size shape, good corrosion resistance at high temperature, especially suitable for use in the atmosphere containing sulfur and sulfide, and the price is low, suitable for special electric furnace, laboratory furnace and all kinds of box high temperature furnace, etc.
Silicon carbide is silicon carbide as the main raw material, processed to blocking, high temperature silicide, recrystallization and rod-shaped non-metallic high temperature electric heating element, compared with the metal resistance wire, high temperature, anti-oxidation, corrosion resistance, long service life, deformation, installation and maintenance is convenient wait for a characteristic, silicon carbon rod under the condition of open air, can be used in the temperature range of 1000-1500 ℃ for a long time.
The atmosphere in the high-temperature furnace has an important influence on the service life of the silicon carbon rod, and gradually oxidizes to produce SiO2 during use. The high-temperature furnace of SiC crystallization is generally composed of several parts such as furnace body, power supply system, temperature measuring and controlling system and corresponding auxiliary equipment or devices, etc. The local resistance increases and the volume expands, resulting in post-ZUI fracture. The continuous service life of the silicon carbon rod in dry and clean air can reach 7000h. The silicon carbon rod has good chemical stability, and the acid has no effect on it. However, the metal oxides of alkali and alkaline earth have erosion effect on it under certain temperature conditions.
3. Various control methods with high precision and dynamic characteristics
High temperature furnace temperature control belong to the big inertia, big lag system, the power of heating element change is far behind the thermocouple temperature measurement, lead to the high temperature furnace temperature deviates from the set temperature, temperature difference from several to dozens of degree, the serious influence product quality and performance of test, so all kinds of methods of controlling temperature gradually, make the temperature control precision is further.
High temperature furnace use of closed loop feedback control system, general compared with thermocouple measured temperature, set temperature controller for processing, the results of comparison and control the heating power, heating rods today and to regulate the temperature of the high temperature furnace, and digital display instrument, thermocouple measuring temperature change at the same time, and compared with the set temperature, forming a closed-loop feedback system.
On 2018-08-08 11:45:46
