Mechanical Properties of Large Diameter Steel Pipes

The main processing methods of large-diameter steel pipes are:

①Forged steel: A pressure processing method that uses the reciprocating impact of a forging hammer or the pressure of a press to change the blank into the shape and size we require.

②Extrusion: It is a steel processing method in which metal is placed in a closed extrusion cylinder and pressure is applied on one end to extrude the metal from a specified die hole to obtain a finished product of the same shape and size. It is mostly used to produce non-ferrous metal materials. steel.

③Rolling: A pressure processing method in which the steel metal blank is passed through the gap between a pair of rotating rollers (in various shapes). Due to the compression of the rollers, the material section is reduced and the length is increased.

④ Drawing steel: It is a processing method that draws the rolled metal blank (shaped, tube, product, etc.) through the die hole into a reduced cross-section and increased length. Most of them are used for cold processing.

Large-diameter steel pipes are mainly completed through tension reduction and continuous rolling of the hollow base material without a mandrel. The documents for standard setting and production of large-diameter steel pipes show that deviations are allowed when manufacturing and producing large-diameter steel pipes:

① Allowable length deviation: The allowable length deviation of steel bars when delivered to fixed length shall not be greater than +50mm.

②Bending and ends: The bending strain of straight steel bars does not affect normal use, and the total curvature is not greater than 40% of the total length of the steel bars; the ends of the steel bars should be sheared straight, and local deformation should not affect use.

③Length: Steel bars are usually delivered in fixed lengths, and the specific delivery length should be specified in the contract; when steel bars are delivered in coils, each coil should be one steel bar, and 5% of the coils in each batch are allowed to be composed of two bars. Composed of steel bars. The disc weight and disc diameter are determined by negotiation between the supply and demand parties.

Mechanical properties of large diameter steel pipes:

1. Tensile strength: During the stretching process, the force (Fb) endured by the sample when it is broken is calculated by the stress (σ) obtained by the original cross-sectional area (So) of the sample, which is called tensile strength ( σb), the unit is N/mm2 (MPa). It represents the maximum ability of a metal material to resist damage under tension.

2. Yield point: For metal materials with yield phenomenon, the stress at which the sample can continue to stretch without increasing (remaining constant) force during the stretching process is called the yield point. If the force decreases, the upper and lower yield points should be distinguished. The unit of yield point is N/mm2 (MPa).

3. Elongation after breaking: In the tensile test, the percentage of the increased length of the gauge length of the sample after breaking to the original gauge length is called elongation. Expressed by σ, the unit is %.