First, deviations in the manufacturing of large-diameter steel pipes.
Common large-diameter steel pipe size range: Outer diameter: 114mm-1440mm; Wall thickness: 4mm-30mm. Length: Can be made to a fixed length or a non-fixed length according to customer requirements. Large-diameter steel pipes are widely used in various industrial sectors such as aviation, aerospace, energy, electronics, automobiles, and the light industry, and are one of the important welding processes.
The main processing methods for large-diameter steel pipes are:
(1) Forging steel: A pressure processing method that uses the reciprocating impact force of a forging hammer or the pressure of a press to change the billet into the required shape and size.
(2) Extrusion: A processing method in which metal is placed in a closed extrusion cylinder, pressure is applied to one end, and the metal is extruded from a specified die to obtain a finished product with the same shape and size. It is mostly used in the production of non-ferrous metals and steel.
(3) Rolling: A pressure processing method in which steel billets (of various shapes) are passed through the gap between a pair of rotating rolls, resulting in a reduction in cross-section and an increase in length due to compression by the rolls.
(4) Drawing: A processing method in which rolled metal billets (shapes, tubes, products, etc.) are drawn through a die to reduce their cross-section and increase their length. This method is mostly used for cold working.
Large-diameter steel pipes are mainly produced through tension reduction rolling of hollow base material without a mandrel. While ensuring the quality of the spiral steel pipe, the entire spiral steel pipe is heated to a temperature above 950℃ and then rolled into seamless steel pipes of various specifications using a tension reduction mill. Standards for the production of large-diameter steel pipes indicate that the following deviations are permissible during manufacturing:
(1) Permissible length deviation: The permissible length deviation of reinforcing bars delivered in fixed lengths shall not exceed +50mm.
(2) Bending and Ends: The bending deformation of straight reinforcing bars should not affect normal use, and the total bending should not exceed 40% of the total length of the reinforcing bar; the ends of the reinforcing bars should be cut straight, and local deformation should not affect use.
(3) Length: Reinforcing bars are usually delivered in fixed lengths, and the specific delivery length should be specified in the contract; when reinforcing bars are delivered in coils, each coil should contain one reinforcing bar, and 5% of the coils in each batch are allowed to consist of two reinforcing bars. The coil weight and coil diameter shall be agreed upon by the supplier and the buyer.
Second, Forming Methods for Large-Diameter Steel Pipes.
1. Hot Push Expansion Method: The push expansion equipment is simple, inexpensive, easy to maintain, economical, and durable, and allows for flexible product specification changes. If it is necessary to produce large-diameter steel pipes or similar products, only some accessories need to be added. It is suitable for producing medium and thin-walled large-diameter steel pipes, and can also produce thick-walled steel pipes not exceeding the equipment capacity.
2. Hot Extrusion: Pre-processing of the billet before extrusion is required. For extruding pipes with diameters below 100mm, equipment investment is low, material waste is minimal, and the technology is relatively mature. However, as the pipe diameter increases, hot extrusion requires high-tonnage and high-power equipment, necessitating upgrades to the control system.
3. Hot Piercing Rolling: Hot piercing rolling primarily involves longitudinal and skew rolling. Longitudinal rolling includes limited-stand mandrel continuous rolling, few-stand limited-stand mandrel continuous rolling, three-roll limited-stand mandrel continuous rolling, and floating mandrel continuous rolling. These methods offer high production efficiency, low metal consumption, good product quality, and sophisticated control systems, leading to their increasingly widespread application.
Post time: Dec-10-2025