The refractory materials and insulation materials are used for the structure materials of most heat treatment furnaces. This is because the heat treatment furnaces are usually in a high temperature state. All non-metallic materials that can withstand high temperatures and withstand the physical and chemical effects generated at high temperatures are collectively called refractory materials. When designing and constructing a heat treatment furnace, the rational selection of refractory materials and insulation materials is of great significance to meet the requirements of the heat treatment process, increase the service life of the heat treatment furnace, save energy and reduce costs. Here we first understand the commonly used refractories. Refractory materials commonly used in heat treatment furnaces include clay bricks, high alumina bricks, lightweight refractory clay bricks, silicon carbide refractory products, aluminum silicate refractory fibers, and refractory concrete.
(1) The main raw materials of clay bricks are refractory clay and kaolin. Clay bricks are the most widely used in heat treatment furnaces and can be used to build furnace tops and bottoms. However, due to its weak acidity, it has a corrosive effect on iron and aluminum heating elements. It cannot be used as a brick for electric heating elements and as a lining for high-carbon atmosphere furnaces.
(2) High-alumina bricks and corundum products, with high refractoriness, maximum service temperature up to 1500 degrees Celsius, high-temperature structural strength, good chemical stability, mostly used for lining of high-temperature heat treatment furnaces and salt bath furnaces, bricks for electric heating components . Corundum products are high-alumina bricks with high high-temperature structural strength and refractoriness. They are commonly used in resistance wire rods, brick thermocouple bushings, and high-temperature furnace bottom bricks.
(3) Light-weight refractory clay bricks and ultra-light refractory clay bricks. Their load softening starting point is low, that is, the high-temperature strength is low, the chemical stability is poor, and the volume change is large. It should be used as a protective layer for heat treatment furnace lining. In the case where the high-temperature structural strength and refractoriness meet the requirements, light-weight refractory clay bricks should be selected as much as possible.
(4) Silicon carbide refractory products, whose refractoriness can reach more than 2000 degrees Celsius, high temperature structural strength is high, abrasion resistance, good thermal conductivity. According to the different manufacturing processes, it can be used in electric heating components of high-temperature furnaces and furnace bottom plates of high-temperature furnaces.
(5) Aluminum silicate refractory fiber is a new type of soft fibrous refractory material, which has the effect of refractory and heat preservation. According to different raw materials, it can be divided into silicate road, quartz, alumina and graphite refractory fiber. It has the characteristics of light weight, good thermal stability and low thermal conductivity. It is easy to process and easy to install. It can also be made into prefabricated blocks or prefabricated plates sandwiched between two layers of refractory materials. Generally, aluminum silicate fiber is used for heat treatment furnace, and graphite fiber is used as refractory material in vacuum furnace, hot pressing furnace and atmosphere furnace. However, some atmospheres in the heat treatment furnace have a corrosive effect on the refractory fiber, which affects its range of use.
(6) Refractory concrete is a refractory material obtained by cementing, shaping and hardening cement bauxite with a certain particle size as aggregate. The advantage is that it can increase the speed of furnace repair and furnace building, and the service life is similar to that of refractory bricks, so the cost is low. The disadvantage is low fire resistance.