The main processing methods of
large-diameter steel pipes are:
Forging steel: Pressure processing method that uses the reciprocating impact of a forging hammer or the pressure of a press to change the bank into the shape and size we need.
Extrusion: It is a processing method in which the steel is enclosed in a closed extruder and pressure is applied at one end to extrude the metal from a prescribed die hole to obtain a finished product with the same shape and size. It mostly uses to produce non-ferrous metal materials.
Rolling: A press working method in which a steel metal blank passes through a gap between a pair of rotating rolls (various shapes), and the cross-section of the material is reduced due to the compression of the rolls and the length is extended.
Drawing steel: It is a processing method that draws rolled metal blanks (forms, tubes, products, etc.) through a die hole to reduce the cross-section and increase the length. Most of them use for cold working.
Large-diameter steel pipes are mainly finished by continuous rolling of hollow base material without mandrel by tension-reducing. Under the premise of ensuring the spiral steel pipe, the spiral steel pipe is heated to a high temperature above 950℃ and then rolled into various specifications of seamless steel pipes through a tension reducer. The standard formulation and production of large diameter steel pipe documents show that deviations are allowed when manufacturing large-diameter steel pipes: allowable length deviation: the allowable deviation of the length of the steel bar when delivered according to the fixed-length shall not be more than +50mm. Bending degree and end: the bending strain of the straight steel bar does not affect normal use, and the total bending degree is not more than 40% of the total length of the steel bar; the end of the steel bar should be cut straight, and local deformation should not affect the use. Length: Steel bars are usually delivered in a fixed-length length, and the specific delivery length should be indicated in the contract; when the steel bars are delivered in coils, each reel should be one steel bar, and 5% of the number of reels per batch is allowed to consist of two steel bars composition. The disk weight and disk diameter shall be negotiated and stipulated by the supplier and the buyer.
