¡¡Factors affecting the performance of the steel pipe 3PE coating more, such as layout, equipment selection, surface quality, heating, coating temperature, cooling, transmission accuracy, material properties and testing each process, etc., will result in poor control of coating layer adhesive force is small, too thin, cracks or bubbles and other defects, job specifications and strict implementation of scientific methods of control deficiencies and ensure yield corrosion control is essential [3-8].
China Patent CN200710057236 [1] .9 (water-cooling method for a steel pipe corrosion) discloses a steel outer annular cooling device, the cooling effect is improved, but still can not overcome the external cooling measures resulting from quality defects and weld fundamentally coating thickness decreases. [2] pointed out that the ideal way to reduce the coating thickness thinning is cooled from the inside of the pipe.
U.S. Patent US6270847B1 discloses a pipe coating internal cooling method within the pipe into the pump, the water in the pipe wall during the rotation of the steel pipe, steel pipe coating and cooling of the order of: steel, FBE layer, an adhesive layer, and PE layer. Pipe heat and speed enables fast cooling pipe and coatings, and due to the cooling process of the coating from the inside out, coating the wall in the cooling contraction and better bonding, coating of small hoop stress , weld bead coating thinning is very small, thus improving the quality of anti-corrosion and reduce raw material costs. However, this method difficult to achieve internal cooling.
[9] and [10] of the HPCC (high performance composite coating) coating system was introduced. The epoxy powder process, and the adhesive layer PE / PP layer through the electrostatic spray coating on the surface of the steel pipe, forming a continuous transition between the layers of one kind of "hierarchical structure", there is no apparent interface between the layers, sticky Relay stronger, more uniform coating thickness, and can eliminate the top welding and soldering foot hole, reduce stress coating ring. U.S. Patent US5178902 published in 1993. This HPCC process, and have achieved good results in engineering applications, but due to the heat conduction slow powder body, HPCC process is difficult to obtain a thick coating, mechanical performance than 3PE.
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