Ceramic composite pipes are manufactured using self propagating high-temperature synthesis centrifugal method* It is to place a seamless composite tube in the tube mold of a centrifuge, and add a mixture of iron red and aluminum powder to the composite tube. This mixture is called an thermite in chemistry.
After the centrifuge tube mold reaches a certain speed of rotation, a spark ignites the thermite, which immediately burns on its own. The combustion wave rapidly spreads, causing intense chemical reactions and releasing a large amount of heat during the spread. These heats can reach temperatures of 3860K and 3600K under thermal conditions, causing both the original materials in the ceramic composite pipe and the products after the reaction, namely alumina (commonly known as corundum) with a melting point of 2045 ℃, to become molten.
Due to the rapid reaction, which takes only a few seconds, the molten reactants are quickly separated according to their specific gravity under the action of centrifugal force. The specific gravity of iron in the product (7.85g/cm3) is twice that of aluminum oxide (3.95g/cm3). The heavier iron is thrown onto the inner wall of the steel pipe by centrifugal force, while the lighter aluminum oxide is distributed in the inner layer of the iron. Due to the rapid absorption and heat transfer of ceramic composite pipes, alumina and iron quickly reach the solidification point and solidify in layers. The ceramic composite pipe formed afterwards consists of a corundum ceramic layer, a transition layer mainly composed of iron, and an external steel pipe layer from the inside out. The high-temperature molten iron and aluminum oxide liquid come into contact with the composite pipe wall, causing the inner wall of the composite pipe to be in a semi molten state, forming a metallurgical bond between the iron layer and the composite pipe, and a solid bond between the iron layer and the corundum ceramic layer. The bonding shear strength (i.e., the strength when the ceramic layer is pressed out axially) is ≥ 15MPa; The crushing strength of ceramic composite pipes (i.e. the strength when crushing the ceramic inside the pipe from the outside) is ≥ 350MPa.
