Electric heating tubes made of different steels are different, and you cannot blindly seek the cheapest and cause the life of the electric heating tubes to be short. What we need most is a greater price-performance ratio, so we must increase our professional knowledge to enrich ourselves. Here, we will introduce the commonly used material classification for the production of electric heating tubes: acid refractory steel, alkaline refractory steel, oxide materials, neutral refractory steel, refractory compound materials and high temperature compound materials. Usually we call it ordinary steel and special steel.
Introduction of ordinary steel:
The raw materials used are electric heating tubes made of silica and waste silica bricks. Its silica bricks have strong resistance to acid slag corrosion, but they are easily corroded by alkaline slags. The load softening temperature is very high, close to its refractoriness, and the volume does not decrease after repeated calcination. The larger amounts are silica bricks and clay bricks. Silica brick is a finished product containing more than 93% SiO2. It even expands slightly, but the thermal shock resistance is poor. Silica bricks are mainly used in thermal equipment such as coke ovens, glass melting furnaces, and acid steel furnaces. Clay bricks contain 30%～46% alumina, refractory clay is the main raw material, with a refractoriness of 1580-1770°C and good thermal shock resistance. It is a weakly acidic refractory material. It has corrosion resistance to acidic slag and is widely used. The refractory steel with the largest output belongs to common material steel.
Introduction of special steel:
The content of corundum increases with the addition of alumina content. The main crystal phases in the high-alumina product are mullite and corundum. The corundum product containing more than 95% alumina is a kind of high-quality special refractory steel with a wide range of uses. Chrome bricks are mainly made of chrome ore as the raw material, and the main crystal phase is chromite. The corrosion resistance to steel slag is good, but the thermal shock resistance is poor, and the high temperature load deformation temperature is low. Chrome magnesia bricks made of chrome ore and magnesia in different proportions have good thermal shock resistance and are mainly used as alkaline open-hearth roof bricks.
The electric heating tube is made with magnesia as the main crystal phase. The main raw materials for the production of magnesia bricks are magnesite, seawater magnesia, which is made by high-temperature calcination of magnesium hydroxide extracted from seawater) and so on. It has good resistance to alkaline slag and iron slag. The melting point of pure magnesia is as high as 2800℃, which is represented by magnesia products. Containing more than 80% to 85% of magnesium oxide. Therefore, the fire resistance of magnesia bricks is higher than that of clay bricks and silica bricks. Since the mid-1950s, due to the adoption of oxygen-blown converter steelmaking and the use of alkaline open hearth furnace tops, the production of alkaline refractories has gradually increased, while the production of clay bricks and silica bricks has been reduced. Alkaline refractories are mainly used for oxygen blowing converters, open hearth furnaces, electric furnaces, non-ferrous metal smelting, and some heat treatment equipment all use special steel materials.
