Method and apparatus for producing steel-plastic composite pipe

Abstract

The composite steel / plastic pipe producing process includes longitudinally bending or spirally winding steel plate with holes and welding to form metal pipe skeleton, separating the welded metal pipe skeleton from atmosphere with inert air, extruding the core layer plastic pipe inside the metal pipe skeleton, extruding the outer layer plastic pipe outside the metal pipe skeleton and making the inner layer and the outer layer of plastic pipe combined into one integral via the holes in the metal skeleton. The present invention also provides one composite steel / plastic pipe producing line. The produced composite steel / plastic pipe has high bearing capacity and firm combination of the inner and outer plastic layers.

Description

Technical field: [0001] The invention relates to a production method of a steel-plastic composite pipe, in particular to a method of using an inert gas protection device to isolate the welding seam from the outside air at the welding place of a cylindrical metal skeleton with holes from the welding point along the welding seam to prevent Oxidized layers are formed on the inner and outer surfaces of the welding seam, and the production method and device of compounding the adhesive layer, the core layer tube and the outer layer tube on the inside and outside of the cylindrical metal frame with holes respectively. Background technique: [0002] There are many methods and devices for the production technology of steel-plastic composite pipes, as well as corresponding patents, which use a metal skeleton with holes as a reinforcement, and extrude a composite polymer material on the skeleton as a continuum to wrap the skeleton to form a steel-plastic composite pipe. The reports and...

AI Technical Summary

Problems solved by technology

This kind of pipeline not only has the higher pressure bearing capacity of metal pipelines, but also has a plastic inner and outer wall and connects the inner and outer walls through the holes of the metal skeleton, so it has better anti-corrosion performance and pipeline connection performance. It is compatible with metal pipelines and Compared with pure plastic pipes, it has better comprehensive performance, and has been widely used in chemical industry, oil transportation, gas transportation, pressure transportation and corrosive media. It is a better structural composite pipe, but according to the above patents In the technical schemes, the molten polymer continuum passes through the holes of the metal skeleton to form the inner and outer pipe walls at the same time. This molding method has great defects. The molten polymer continuum turns over to The other side is melted and combined with each other. The turbulent flow of the polymer over the metal skeleton will leave a lot of residual stress in the cooled plastic pipe wall, which will lead to easy cracking during the use of the pipe and reduce the service life of the pipe. And this flow mode will destroy the thin layer of adhesive layer that is extruded or sprayed or covered on the inner and outer surfaces of the metal skeleton, especially in the pores, resulting in a direct bond between the polymer continuum and the metal skeleton surface rather than through bonding. The agent layers are firmly combined with each other, while the polymer continuum is a non-polar surface, and the metal skeleton surface is a polar surface, the two cannot really be firmly combined with each other, resulting in mutual delamination during transportation or installation or use , In addition, the temperature of the polymer mutual fusion bonding surface is lowered due to the crossover of the metal skeleton, which also affects the reliability and strength of mutual fusion bonding

Patent 00100446.8 discloses a steel-plastic composite pipe forming device, including an inner pipe extruder, an outer pipe extruder, a glue coating device, a steel strip coil forming device and a steel strip coil welding machine. The device can produce There is a steel-plastic composite pipe with inner and outer plastic pipe walls and metal steel plates bonded together. However, there is a big defect in the welding method of the steel plate seams in this technical solution, that is, the temperature of the weld seam is very high after welding, and no measures are taken to close it. The weld seam is isolated from the outside air, and the weld seam is in direct contact with the air, resulting in a layer of oxide layer around the weld seam. Due to the existence of this oxide layer, the inner and outer plastic pipe walls and the cylindrical metal skeleton cannot be firmly combined. Together, even if the adhesive layer is coated on the inner and outer surfaces of the cylindrical metal skeleton, such as my patent application 03117307.1 "Continuous production device for steel-plastic composite pipe with adhesive coating on the inner and outer surfaces of the steel skeleton with holes", but due to the oxide layer The barrier effect of this layer of adhesive cannot firmly combine the inner and outer plastic pipe walls with the cylindrical metal skeleton, and it is easy to remove the inner and outer plastic pipe walls and the adhesive layer together with the oxide layer from the weld. The surface of the metal skeleton is torn apart, causing the steel-plastic composite pipe to often cause delamination between the steel and plastic during use, and the conveyed medium penetrates from the steel-plastic delamination to tear the pipe and corrode the pipe, destroying the integrity of the entire piping system normal work

The existing technical scheme also includes installing a grinding wheel mechanism or a scraper on the welded seam of the steel plate to remove the oxide layer on the surface of the welded seam, but this method can only remove the oxide layer on the outer surface of the cylindrical metal skeleton, and has no effect on the oxide layer on the inner surface of the skeleton. The oxide layer cannot be removed, and it pollutes the environment. The oxide layer on the outer surface cannot be removed cleanly, and the polymer compounded on the metal skeleton contains impurities and metal cutting

The equipment for manufacturing multi-layer composite pipe disclosed in patent 99801833.3 is also the same as the above-mentioned technical solution, and no measures are taken to isolate the weld seam from the outside air, and this patent is aimed at the lap welding technology of metal plates. The thickness and height are different, the inner and outer surfaces of the metal skeleton are uneven, and the inner and outer plastics, especially the adhesive layer, are not firmly bonded at the dead corners of the overlap, or even cannot be bonded to each other at all, which may easily cause delamination between steel and plastic.

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