The development status of 3PE anti-corrosion spiral steel pipe industry is still good at home and abroad, it also plays a relatively large role in the anti-corrosion industry. 3PE anti-corrosion steel pipe base material includes seamless steel pipe, spirally submerged arc welding pipe and longitudinally submerged arc welding pipe. The three-layer polyethylene (3PE) anti-corrosion coating has been widely used in the petroleum pipeline industry for its good corrosion resistance, water vapor permeability and mechanical properties.
The 3pe anti-corrosion steel pipe treatment process includes several steps of preheating, heating and cooling: (1) The preheating of the rail head uses the power frequency power supply to inductively heat the rail head to 550~600 °C, the purpose of which is to improve the electrical efficiency during the late induction heating. For example, if the power supply and frequency are properly configured, the price of the spiral welded pipe can be directly inductively heated without being required. (2) The rail head is heated to the quenching temperature. The head of the rail is heated to 850~900T by the IF power source frequency of Hz. The short-time diathermy is heated and the head metal is completely austenitized. Then, immediately enter the rapid quenching and cooling. (3) After the rail head quenching and cooling the rail head reaches the austenitizing temperature, it is immediately cooled by compressed air injection or pressure spray quenching. The cooling rate is controlled in the high temperature section of the C curve, and the cooling rate is maintained to obtain a fine interlamellar pitch pearlite structure. During the quenching phase, when the head temperature drops to 450~500 °C, the compressed air or water mist should be stopped and cooled to air temperature until normal temperature.
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