At present, the main production processes of large-diameter steel pipes in my country are hot-rolled large-diameter steel pipes and hot-expanded large-diameter steel pipes. The largest specifications of hot-expanded seamless steel pipes are 325 mm-1220 mm and the thickest is 120mm. Hot-expanded seamless steel pipes can produce non-national standard sizes. Hot-expanded seamless pipes are what we often call hot-expanded pipes. Steel pipes with relatively low density but strong shrinkage are expanded by oblique rolling or drawing. A rough pipe finishing process. It is a process of thickening steel pipes in a short period, producing non-standard and special types of seamless pipes, and it is low in cost and high in production efficiency. It is the current development trend in the field of pipe rolling.
Large-diameter steel pipes are also called large-diameter galvanized steel pipes, which refer to welded steel pipes with hot-dip or electroplated zinc layers on the surface of large-diameter steel pipes. Galvanizing can increase the corrosion resistance of steel pipes and extend their service life. Galvanized pipes are widely used. In addition to being used as pipeline pipes for general low-pressure fluids such as water, gas, and oil, they are also used as oil well pipes and oil pipelines in the petroleum industry, especially offshore oil fields, oil heaters, condenser coolers, coal distillation, and oil exchanger pipes for chemical coking equipment, as well as pier pipe piles and support frames for mine tunnels.
First, large-diameter steel pipe forming methods:
1. Hot push expansion method: The push expansion equipment is simple, low-cost, easy to maintain, economical, and durable, and the product specifications are flexible. If you need to prepare large-diameter steel pipes and other similar products, you only need to add some accessories. It is suitable for the production of medium and thin-walled large-diameter steel pipes, and can also produce thick-walled steel pipes that do not exceed the capacity of the equipment.
2. Hot extrusion method: The blank needs to be machined before extrusion. When extruding pipes with a diameter of less than 100mm, the equipment investment is small, the material waste is small, and the technology is relatively mature. However, once the diameter of the pipe increases, the hot extrusion method requires large-tonnage and high-power equipment, and the corresponding control system must also be upgraded.
3. Hot piercing rolling method: Hot piercing rolling is mainly longitudinal extension and oblique extension. Longitudinal extension rolling mainly includes limited mandrel continuous tube rolling, less-frame limited mandrel continuous tube rolling, three-roller limited mandrel continuous tube rolling, and floating mandrel continuous tube rolling. These methods have high production efficiency, low metal consumption, good products, and control systems, and are increasingly widely used.
Second, large-diameter steel pipe processing method:
1. Rolling; the large-diameter steel pipe metal billet passes through the gap (various shapes) of a pair of rotating rollers, and the pressure processing method that reduces the material cross-section and increases the length due to the compression of the rollers is a common production method for producing large-diameter steel pipes. It is mainly used to produce large-diameter steel pipe profiles, plates, and pipes. It is divided into cold rolling and hot rolling.
2. Forging; a pressure processing method that uses the reciprocating impact force of the forging hammer or the pressure of the press to change the billet into the shape and size we need. Generally divided into free forging and die forging, it is often used to produce large-scale materials, blanks, and other materials with large cross-sectional dimensions.
3. Drawing: It is a processing method that draws the rolled metal billet (profile, tube, product, etc.) through the die hole to reduce the cross-sectional area and increase the length. It is mostly used for cold processing.
4. Extrusion: It is a processing method in which a large-diameter steel pipe puts the metal in a closed extrusion cylinder, applies pressure at one end, and squeezes the metal out of the specified die hole to obtain a finished product with the same shape and size. It is mostly used to produce non-ferrous metal large-diameter steel pipes.
Third, large-diameter steel pipe connection type:
1. Large-diameter steel pipe quick-connect flange type: perform annular argon arc welding on the flange and the matching, and use quick clamps to compress the sealing gasket between the flanges to play a sealing role and complete the matching connection.
2. Large-diameter steel pipe welding type: perform annular argon arc welding on the usual socket-type pipe fittings and matching, which plays a sealing role and completes the matching connection.
3. Compression type of large-diameter steel pipe: insert the pipe into the pipe fitting, the two ends of the pipe fitting are protruding U-shaped grooves, and the built-in sealing ring is connected by the socket part of the special pipe fitting tool.
4. Compression type of large-diameter steel pipe: insert the pipe into the pipe mouth of the pipe fitting, tighten it with a nut, and use the spiral force to compress the sleeve of the pipe mouth through the sealing ring to seal and complete the pipe connection.
5. Cone thread type of large-diameter steel pipe: perform annular argon arc welding on the external thread sleeve and the matching, and the internal thread pipe fitting is connected with a cone to seal and complete the matching connection. It can be used in harsh environments such as foundation sinking, high temperatures, and high pressure.
6. Limit compression type of large-diameter steel pipe: the pipe adopts a flanging or port welding ring, and the connection method is a flexible or semi-flexible connection. After the rubber sealing ring limit seal is compressed by 20%-30%, it enters the metal sealing groove, and the limit seal is used to protect the sealing element. It can be used in harsh environments such as foundation sinking, high temperatures, and high pressure.
7. Heat-shrinkable fittings for large-diameter steel pipes: On-site welding can be used when connecting pipes. If the welding points cannot be handled on-site, heat-shrinkable fittings can be used for supplementary sealing, which shrinks under the action of heat to achieve shrinkage sealing.
Post time: Jan-16-2025