Large diameter steel pipe forming method:
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 producing medium and thin-walled large-diameter steel pipes, and can also produce thick-walled pipes that do not exceed the equipment’s capacity.
2. Hot extrusion method: The blank needs to be machined and pre-processed before extrusion. When extruding pipe fittings with a diameter of less than 100mm, the equipment investment is small, the material waste is less, 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 based on longitudinal rolling extension and cross-rolling extension. Longitudinal rolling and extension rolling mainly include continuous tube rolling with limited moving mandrel, continuous tube rolling with limited-stand mandrel, three-roll continuous tube rolling with limited mandrel, and continuous tube rolling with the floating mandrel. These methods have high production efficiency, low metal consumption, good products, and control systems, and are increasingly widely used.
Qualification standard parameters for flaw detection of large-diameter steel pipes: In the production of large-diameter steel pipes, a single circular inclusion and pore with a weld diameter not exceeding 3.0mm or T/3 (T is the specified wall thickness of the steel pipe) is qualified, whichever is the larger of the two. Small ones. Within the range of any 150mm or 12T weld length (whichever is the smaller value), when the distance between a single inclusion and a pore is less than 4T, the sum of the diameters of all the above-mentioned imperfections that are allowed to exist alone should not exceed 6.0mm or 0.5 T (whichever is smaller). A single bar-shaped inclusion with a length not exceeding 12.0mm or T (whichever is smaller) and a single bar-shaped inclusion with a width not exceeding 1.5mm is qualified. Within the range of any 150mm or 12T weld length (whichever is the smaller value), when the interval between individual inclusions is less than 4T, the maximum cumulative length of all the above-mentioned imperfections that are allowed to exist individually should not exceed 12.0mm. A single undercut of any length with a maximum depth of 0.4mm is qualified. A single undercut with a maximum length of T/2 a maximum depth of 0.5mm and no more than 10% of the specified wall thickness is qualified as long as there are no more than two in any 300mm weld length. All such undercuts should be ground. Any undercut that exceeds the above range should be repaired, the offending area removed, or the entire pipe rejected. Undercuts of any length and depth that overlap each other longitudinally on the same side of the inner and outer welds are unacceptable.
Post time: Jan-05-2024