Deviation and Forming Method of Large-Diameter Steel Pipe in Production

Deviation of large-diameter steel pipes in production:
Common large-diameter steel pipe size range: outer diameter: 114mm-1440mm wall thickness: 4mm-30mm. Length: according to customer requirements can be made in fixed length or indefinite length. Large-diameter steel pipes are widely used in various industrial sectors such as military, energy, electronics, automobiles, and light industry, and are important welding processes.

The main processing methods of large-diameter steel pipes are:
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 blank into the shape and size we need.
Extrusion: It is a processing method for steel to place metal in a closed extrusion box and applies pressure at one end to make the metal extrude from the specified die hole to obtain a finished product with the same shape and size. It is mostly used for the production of non-ferrous metal steel.
Rolling: A pressure processing method in which the steel metal billet passes through the gap between a pair of rotating rolls (various shapes), and the cross-section of the material is reduced and the length is increased due to the compression of the rolls.
Pulling steel: It is a processing method in which the rolled metal blank (type, pipe, product, etc.) is pulled through the die hole to reduce the cross-section and increase the length. Most of them are used for cold working.

Large-diameter steel pipes are mainly completed by tension reduction and continuous rolling of hollow base metal without a mandrel. On the premise of ensuring the spiral steel pipe, the whole spiral steel pipe is heated to a high temperature above 950°C and then rolled into seamless steel pipes of various specifications through a tension-reducing machine. The standard-setting documents for the production of large-diameter steel pipes show that there are allowable deviations in the manufacture and production of large-diameter steel pipes: length allowable deviation: the length allowable deviation of steel bars when delivered according to the specified length shall not exceed +50mm. Bending degree and end: The bending deformation of the straight steel bar should not affect normal use, and the total bending degree should not exceed 40% of the total length of the steel bar; the end of the steel bar should be cut straight, and the local deformation should not affect the use. Length: steel bars are usually delivered according to the fixed length, and the specific delivery length should be specified in the contract; when the steel bars are delivered in coils, each coil should be one steel bar, and 5% of the coils in each batch are allowed to consist of two steel bars composition. The weight and diameter of the plate are negotiated and stipulated by the supply and demand sides.

The forming method of large diameter steel pipe:
1. Thermal push expansion method: Push expansion equipment is simple, low in cost, easy to maintain, economical and durable, and flexible in product specification change. 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-wall thick large-diameter steel pipes, and can also produce thick-wall pipes that do not exceed the capacity of the equipment.
2. Hot extrusion method: Before extrusion, the blank needs to be machined and pretreated. 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 be upgraded.
3. Hot piercing and rolling method: hot piercing and rolling are mainly longitudinal rolling and cross rolling. Longitudinal rolling and extension rolling are mainly limited-moving mandrel tube rolling, few-stand limited-moving mandrel tube rolling, three-roller limited-moving mandrel tube rolling, and floating mandrel tube rolling. These methods have high production efficiency, low metal consumption, good product, and control system, and are increasingly widely used.