What should be noted when converting between steel and plastic?

　　 Steel-plastic transition Pipe-to-flange connections are primarily used to join PE pipes with pipes and pipe fittings made of other materials, offering easy and rapid installation. Steel-plastic transition pipes consist of a PE end and a metal pipe end, and are available in various configurations, including straight sections, bends, threaded connections, and welded joints.

　　Flanged connectors consist of PE flanged connectors and steel flange components, and are suitable for connecting PE pipelines to pipelines made of other materials, as well as to pumps, valves, fire hydrants, and other pipeline accessories. The metal components of all types of steel-to-plastic transition connectors undergo special anti-corrosion treatment, ensuring a service life comparable to that of PE pipes.

　　Steel-plastic conversion exhibits excellent wear resistance, corrosion resistance, impact resistance, resistance to direct sunlight, and resistance to photoaging.

　　 Steel-plastic transition Anti-corrosion heat-shrink sleeves are used for underground and wall-mounted corrosion protection of DN steel gas pipelines. They are specifically designed to meet the requirements for corrosion protection, sealing, wear resistance, and aesthetic appeal at weld joints of both buried and overhead steel pipelines, as well as at the transition sections where steel meets plastic. These sleeves can also be applied to seal and protect pipeline flange connections, insulated flanges, and clamp (lock) coupling sections.

　　It forms a highly corrosion-resistant coating with excellent wear resistance, corrosion resistance, impact resistance, resistance to direct sunlight, and resistance to photoaging.

　　PE steel-plastic transition to an integral structure or “closed cover” exhibits excellent performance in terms of shrinkage resistance, creep resistance, aging resistance, impact resistance, and heat resistance.

　　The hot-melt adhesive used in anti-corrosion heat-shrink sleeves exhibits exceptionally high shear and peel strength, with strong adhesion and excellent sealing performance on steel pipes, epoxy coatings, and PE coatings. In addition, it demonstrates outstanding fire resistance, water-immersion resistance, and resistance to water-vapor permeation, ensuring a service life that matches that of the pipeline itself.

　　For steel-to-plastic transition and corrosion protection, heat-shrinkable sleeves with an anti-corrosion coating can be configured as a three-layer structure consisting of a heat-shrinkable circular sleeve coated with an adhesive applied over a two-component liquid epoxy primer. The sleeve is made of a radiation-crosslinked polyolefin substrate and a special sealing hot-melt adhesive. This sealing hot-melt adhesive exhibits excellent adhesion to the polyolefin substrate, the steel pipe surface, and solid epoxy coatings.

　　It is used to protect steel-to-plastic transition connectors. During heat-shrink installation, the circular sleeve radially contracts while the internal composite adhesive layer melts, firmly enveloping the steel-to-plastic transition joint to form a robust anti-corrosion barrier. It exhibits excellent resistance to abrasion, corrosion, impact, direct sunlight, and photo-aging.

　　 Steel-plastic transition The assembly process for the pipe fittings is characterized by: directly injecting polyethylene into the reducer PE pipe; turning a portion of the steel pipe on a lathe; using a horizontal hydraulic press to advance the reducer PE pipe; leveraging the reaction force to extrude the fixed pressure sleeve from the end of the steel pipe into the PE end; and, by adjusting the length of the pipe connection section via the hydraulic press’s die platen, completing the assembly as follows:

　　(1) Polyethylene raw material is injection-molded using an injection molding machine to produce tapered PE pipes. The injection pressure is maintained between 70 and 90 MPa, the barrel temperature is controlled between 200 and 220°C, and the mold temperature is maintained between 40 and 50°C.

　　(2) Turn the front face of the steel pipe to form several anti-separation grooves, then place it on the die platen of a horizontal hydraulic press after turning.

　　(3) Start the horizontal hydraulic press; the press’s hydraulic pusher will move the reduced-diameter PE pipe onto the mold tray.

　　(4) Press the constant-pressure sleeve against the upstream end of the reducing PE pipe; the reaction force generated by the constant-pressure sleeve compresses the inner surface of the reducing PE pipe against the outer surface of the steel pipe at the connection end. The compression process is controlled by adjusting the length of the pipe connection section via the die platen of the hydraulic press, thereby completing the assembly.

　　Technical Overview

　　The assembly process for steel–plastic transition fittings involves directly injecting polyethylene into a reducing PE pipe, turning the steel pipe section on a lathe, and using a horizontal hydraulic press to advance the reducing PE pipe. The reaction force then presses a fixed-pressure sleeve from the end of the steel pipe into the end of the PE pipe. By adjusting the length of the pipe connection section via the hydraulic press’s die platen, the assembly is completed. This inventive process eliminates the waste of PE raw material that would otherwise result from using small-diameter steel pipes within large-diameter PE pipes. It also removes the time and effort required to locate a powerful forging hammer and to make reducing cuts, as well as the need for repeated welding, thereby saving substantial labor, materials, and time, significantly boosting productivity and reducing production costs by 15%. Moreover, since welding poses certain risks to fitting performance and can generate dust pollution during the process, this method alleviates the urgent demand for skilled welders.