St3sp · Q235B · Ø57–530 · GOST 10704
Longitudinally welded pipe
Round pipe from strip with a high-frequency weld. Structures, fencing, low-pressure water and gas
St3sp · 17G1S · K42–K52 · Ø530–2020 · GOST 8696 · GOST 20295
Large-diameter spiral-welded pipe
Pipe with a submerged-arc spiral weld, diameters 530–2 020 mm. Water mains, trunk lines, piles, casings
GOST 8696-74GOST 20295-85GB/T 9711-2017GB/T 3091-2015API Spec 5LEN ISO 3183St3sp09G2S17G1S17GSK42K52Q235BL245L360API 5L Gr.BX52
Parameters
| Parameters | |
|---|---|
| Outside diameter | 530–2 020 mm |
| Wall thickness | 6–16 mm |
| Length | 10–12 m; to specification |
| Steel grade and strength class | St3sp, 09G2S, 17G1S; K42–K52 per GOST 20295; L245–L360 per GB/T 9711 |
| Weld | spiral, double-sided submerged arc welding |
| Ends | bevelled for welding; without bevel to specification |
| Testing | hydrostatic test; ultrasonic and X-ray weld inspection per the acceptance standard |
Sizes and weight
| Size, mm | Weight, kg/m | Metres per tonne |
|---|---|---|
| 530×7 | 90.3 | 11.1 |
| 630×8 | 122.7 | 8.15 |
| 720×8 | 140.5 | 7.12 |
| 820×9 | 180 | 5.56 |
| 920×10 | 224.4 | 4.46 |
| 1 020×10 | 249.1 | 4.01 |
| 1 220×12 | 357.5 | 2.8 |
| 1 420×14 | 485.4 | 2.06 |
| 1 620×16 | 632.9 | 1.58 |
| 2 020×16 | 790.7 | 1.26 |
Theoretical weight at steel density 7.85 g/cm³. Actual batch weight is by scale and mill certificate.
Description
Spiral-welded pipe is formed from hot-rolled coil: the strip is fed at an angle to the pipe axis and coiled in a helix, and the edges are joined by automatic submerged-arc welding from both sides, outside and inside. This way one mill produces any diameter from strip of one width, so spiral-welded pipe covers diameters from 530 mm, where longitudinal forming would require very wide plate. Size range and requirements to GOST 8696-74 for general-purpose pipe and GOST 20295-85 for trunk oil and gas pipelines up to 820 mm in diameter; at mills in China this is GB/T 9711-2017 and GB/T 3091-2015, for export API Spec 5L and EN ISO 3183.
For water mains, piles and casings St3sp to GOST 8696 is taken, at mills in China Q235B. For trunk pipelines GOST 20295 specifies not a grade but a strength class by tensile strength: K42, K50, K52 and higher, covered by steels 17G1S, 17GS and 09G2S; at mills in China under GB/T 9711 these are L245, L290, L360, under API 5L — Gr.B, X42, X52. A spiral weld is longer than a straight one per metre of pipe, so for pressure pipe the standard requires full non-destructive testing of the weld: ultrasonic, and radiographic at the ends. Ends are supplied bevelled for welding; the type and shape of the bevel are written into the specification.
During inspection at the mill, the outside diameter of spiral-welded pipe is measured with a circumference tape around the perimeter at both ends, the wall thickness with an ultrasonic thickness gauge and a micrometer at the end face, end ovality by two mutually perpendicular measurements. The weld is examined outside and inside for undercut, offset and reinforcement height; the bevel angle and root face are checked, as is the curvature of the pipe along its length. The heat number and pipe number in the marking are matched against the mill test certificate (MTC): chemical composition, mechanical properties, hydrostatic test result and the non-destructive weld test record. Rejects recorded in the report are replaced; the replacement is supplied by the manufacturing mill under its contract with the bureau.
Applications
- trunk water mains and collectors
- oil and gas pipelines to GOST 20295
- piles and foundation shells for bridges
- casings under roads and railways
- ventilation and flue ducts
- pressure pipelines of pumping stations
Packing and shipment
Loose, piece by piece, without bundles; ends with protective rings or caps per the specification; every pipe carries the mill marking with pipe number, heat, strength class and size.
Grade equivalents
| GOST | GB (China) | ASTM | EN | Note |
|---|---|---|---|---|
| Steel 20 | 20# | A106 Gr.B | P235GH | Seamless pipes. Nearest equivalents by composition and strength; test requirements differ between the standards |
| Steel 45 | 45# | 1045 (A519) | C45 | Seamless pipes for machining, nearest equivalents. A519 is a standard for mechanical tubing; C45 under EN 10083 is a steel grade, tubes in it are made to EN 10297-1 |
| 09G2S | Q355B | A572 Gr.50 | S355J2H | Low-alloy steel, nearest equivalents. Before GB/T 1591-2018 the grade was designated Q345B; A572 is a standard for rolled products, not for pipe; S355J2H is a hollow section grade under EN 10219 |
| St3sp | Q235B | A53 Gr.B | P235TR1 | Welded pipes. A53 Gr.B is the nearest equivalent: its tensile strength is higher than that of Q235B |
| St3sp | Q235B | A500 Gr.B | S235JRH | Hollow sections. A500 specifies a higher yield strength than Q235B; structural design uses the standard stated in the specification |
| St2sp, St3sp | Q195, Q235 | A53 Gr.A | S195T | Water and gas pipes. GOST 3262 does not specify mechanical properties, so the grade comparison is nominal |
| K42 (GOST 20295) | L245 (GB/T 9711) | API 5L Gr.B | L245NB | Spiral-welded pipes. A strength class by tensile strength, not a steel grade |
| 08Kh18N10 | 06Cr19Ni10 | TP304 | 1.4301 | Stainless pipes. Austenitic 18-10 steel; 03Kh17N14M3 corresponds to TP316L and 1.4404 |
Equivalents are the closest match, not identical: chemistry and tolerances differ between standards. The exact grade and standard are written into the contract.
Related items
Steel 20 · 09G2S · Ø32–426 · GOST 8732
Seamless hot-finished pipe
Pipe without a weld from a solid billet for pressure, steam and hydraulics. Steel 10, 20, 45, 09G2S
Buyer questions
How to read a mill test certificate for pipe
The certificate (MTC) states the standard, steel grade, size, heat number, chemical composition by element, mechanical properties of the test specimens (yield strength, tensile strength, elongation), the hydrostatic test result and, for welded pipe, the result of non-destructive testing of the weld. The heat number in the certificate is matched against the marking on the pipe and the bundle tag: this is the only link between the document and the metal. The bureau checks this match at the mill before shipment and attaches the certificate to the inspection report.
How a seamless pipe differs from a welded one and when each is needed
A seamless pipe is rolled from a solid billet, it has no weld, and it goes where there is pressure, temperature or alternating load: boiler plants, steam, hydraulics, machine parts. A welded pipe is formed from strip and welded by high-frequency current; at the same size it is simpler to produce, and the weld passes a hydrostatic test and non-destructive testing. For structures, fencing, water lines and low-pressure gas lines a welded pipe does the job. The choice is fixed in the specification by the project, not by price.
How the tonnage of a pipe batch is calculated
The theoretical weight per metre of round pipe is calculated as 0.02466 · (D − t) · t, where D is the outside diameter and t the wall thickness in millimetres, steel density 7.85 g/cm³. For a hollow section: 0.0157 · t · (a + b − 2.86 · t). The actual weight is determined by weighing at the mill and is stated in the packing list. Whether settlement is by theoretical or actual weight is fixed in the specification before the order is placed: on thin walls the difference between them is noticeable.
What is checked during batch inspection of pipes at the mill
Outside diameter and wall thickness with a micrometer and callipers at both ends of the sampled pipes, ovality, wall-thickness variation, straightness, condition of the ends and bevel, the weld of welded pipe from outside and, where accessible, from inside, marking on every pipe, the bundle tag and matching of the heat number against the mill test certificate. The results are entered in a report with photo documentation. Rejects recorded in the report are replaced; the replacement is supplied by the manufacturing mill under its contract with the bureau.
What quantity can be ordered
The batch is sized to your quantity — send a specification with sizes, grades, acceptance standard and lengths. The manufacturing mill confirms the batch for a specific size range; the bureau agrees the inspection and acceptance procedure in the contract. Several sizes in one batch are sourced from one mill or from several if their size ranges differ.
Price request
Send your specification and we will quote your batch
Steel pricing depends on grade, size, tonnage and delivery terms on the day of contract. A number on the page would be wrong by the time you read it.
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