Most of the industrial pipelines in petrochemical equipment are high temperature, high pressure and pipelines that transport corrosive media. During the working process, because the media transported by industrial pipelines are corrosive to a certain extent, the toughness and corrosion resistance of the pipes should be improved. In order to meet the requirements of industrial pipeline work, many heat treatment manufacturers use medium frequency induction heating equipment to heat treat it, with good results.
1. Heat treatment process flow of industrial pipelines
Industrial pipeline semi-finished products - quenching and heating - forced cooling of the inner and outer walls, quenching - tempering - thermal straightening - cooling bed cooling - hardness testing - electromagnetic ultrasonic flaw detection - pipe end magnetic particle testing - grinding and inspection.
2. Heat treatment process
1) The purpose of heat treatment using medium frequency induction heating equipment is to improve the material toughness and corrosion resistance of the process pipeline, and give full play to the strength and toughness of the material. C90 grade process pipelines generally use alloy steel for quenching and tempering heat treatment in order to ensure the process Pipes have sufficient strength, toughness and corrosion resistance. The heat treatment process is: using medium frequency induction heating equipment for heat treatment, the heating temperature is 910-930°C, water cooling, the tempering temperature is 710-720°C, and then cooled to 480°C for heat straightening.
2) Post-weld heat treatment temperature has a certain impact on the performance of low-alloy heat-resistant steel welded joints. Heat treatment and tempering specifications are the main factors affecting the weld. Experience shows that each low-alloy heat-resistant steel has a better temper. Parameter range. When selecting the post-weld heat treatment temperature, we should not only consider reducing the hardness of the weld and the heat-affected zone, but also consider other factors to obtain better welding joint performance and achieve the true purpose of post-weld heat treatment. Because the high content of diffusible hydrogen in the weld is one of the causes of cold cracks, when the structural stress of 13CrMo44 pipes is not large and the pipe wall is thin, the occurrence of cracks can be avoided by preheating before welding and heat treatment after welding. Perform subsequent heat treatment. In order to fully escape hydrogen and reduce the content of diffusible hydrogen in the weld, it is correct to adopt a process of 250-350°C and heat preservation for 30-60 minutes.
3) To improve the corrosion resistance of C90 oil pipes, in addition to preventing temper brittleness, quenching non-martensite and its transformation products should also be reduced. Quenching and high-temperature tempering can eliminate the formation of oil pipes during rolling deformation and heating. Thermal straightening can eliminate the residual internal stress of uneven deformation caused by repeated roller pressure during straightening. The temperature of hot straightening is controlled within the range of 400-500°C.
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GS-ZP-1200
