Production Standard of High Frequency Straight Seam Welded Pipe

High frequency straight seam welded pipe can be divided into straight seam high frequency resistance welded steel pipe(ERW steel pipe) and straight seam high frequency induction welded steel pipe (LSAW steel pipe) according to different high frequency welding process. The forming process generally adopts roll bending cold forming. The high-frequency straight seam welded pipe is generally produced with a small diameter, and the outer diameter is generally less than 660mm or 26 inches. Its characteristics are: fast welding speed, for example, for steel pipes with an outer diameter of less than 1 inch, the maximum welding speed can reach 200 meters / minute. For a 25-inch outer diameter steel pipe, the welding speed can also reach more than 20 meters / minute. The welding method is pressure welding instead of fusion welding. Compared with fusion welding, the welding heat affected zone is relatively small and has little effect on the structure of the base material. The strength and toughness of the weld after welding are different from the parent. According to the use requirements, the internal and external welding burrs can be cleaned or not. Welding can not clean the workpiece, can weld thin-walled pipes, weldable metal pipes. High frequency straight seam welded pipe process: slitting-uncoiling-strip steel leveling-head and tail shearing-strip steel butt welding-looper storage
Forming — Welding — Deburring — Sizing — Flaw Detection — Flying Cut — Initial Inspection — Steel Pipe Straightening — Pipe Section Processing — Hydrostatic Test — Flaw Detection — Printing and Coating — Finished Product. High frequency straight seam welded pipe is mainly used in water supply engineering, petrochemical industry, chemical industry, power industry, agricultural irrigation, urban construction.

Uses: For liquid transportation: water supply and drainage. For gas transportation: coal gas, steam, liquefied petroleum gas. For structural use: for piling pipes, for bridges, docks, roads, pipes for building structures, etc.

Performance characteristics of high frequency straight seam welded pipe:
1. The biggest feature is high production efficiency, fast heating speed, no filler metal.
2. ERW welded pipe is easier to achieve quality control. The produced steel pipe has high dimensional accuracy and small deviations in outer diameter and wall thickness.
3. Excellent toughness, excellent anti-extrusion and anti-explosion performance, low carbon, sulfur and phosphorus content, greatly improved impact toughness.
4. ERW casing adopts hot-rolled coiled sheet, the grain size and microstructure density of the tube blank are higher than that of seamless tube.
5. In terms of price, ERW steel pipes are also quite competitive and have a long service life.

Specification of high frequency straight seam welded pipe: Steel pipe outer diameter: φ88.9-φ508mm (3 1 / 2inch -20inch)
Length of steel pipe: 8-12.5m
Steel pipe material: API 5L A, B, X42-X80
Executive standards: API 5L, ISO3183, GB / T9711 and other standards and additional technical conditions for users.

In the production process of high-frequency straight seam welded pipes, because the actual size is difficult to meet the nominal size requirements, that is, it is often larger or smaller than the nominal size, so the standard specifies that there is a difference between the actual size and the nominal size. A positive value is called a positive deviation, and a negative value is called a negative deviation. The sum of the absolute values ??of the positive and negative deviations specified in the high-frequency straight seam welded pipe standard is called tolerance, also known as "tolerance zone". The deviation of high-frequency straight seam welded pipe is directional, that is, it is represented by "positive" or "negative"; the tolerance is not directional, so the deviation value is called "positive tolerance" or "negative tolerance". wrong.

The delivery length of the high-frequency straight seam welded pipe is also called the length required by the user or the contract length. The standard has the following provisions for the delivery length. The usual length of high-frequency straight seam welded pipe (also called non-fixed length): where the length is within the length specified by the standard and there is no fixed length requirement, it is called the normal length. For example, the structural tube standard stipulates: hot-rolled (extruded, expanded) steel pipe 3000mm ~ 12000mm; cold-drawn (rolled) steel pipe 2000mmm ~ 10500mm. Fixed Steel Length of Permanent Steel Manufacturing Co., Ltd. Steel Pipe Factory: The fixed length should be within the normal length, which is a fixed length required by the contract. However, it is not possible to cut out the absolute length of the fixed scale in actual operation, so the standard specifies the allowed positive deviation value for the fixed length.

The high-frequency straight-seam welded pipe produces a fixed-length pipe with a larger drop in the yield rate than the usual length pipe. It is reasonable for the manufacturer to request a price increase. The rate of price increase varies from company to company. Generally, the price increase is about 10%.

The double-length length of the high-frequency straight seam welded pipe should be within the normal length, and the single-length length and the multiple of the total length should be indicated in the contract (for example, 3000mm × 3, that is 3 times 3000mm, the total length is 9000mm). In actual operation, the allowable positive deviation of 20mm should be added to the total length, plus the length of each single ruler The cut margin should be left. Take the structural tube as an example, the margin of the cut is specified: the outer diameter ≤159mm is 5 ^ 10mm; the outer diameter> 159mm is 10 ^ 15mm. If there is no double length length deviation and cutting allowance specified in the standard for high-frequency straight seam welded pipe, it shall be negotiated by the supplier and the buyer and indicated in the contract. The double-length length is the same as the fixed-length length, which will bring a substantial reduction in the production rate of the production enterprise. Therefore, it is reasonable for the production enterprise to raise the price, and the price increase range is basically the same as the fixed-length length.