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
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
GOST 8732-78GOST 8731-74GB/T 8162-2018GB/T 8163-2018ASTM A106/A106MEN 10216-110204509G2S20#45#Q355BA106 Gr.B
Parameters
| Parameters | |
|---|---|
| Outside diameter | 32–426 mm; per GOST 8732 the size range is 20–550 mm |
| Wall thickness | 3–40 mm |
| Length | random length 4–12.5 m; fixed and multiple length to specification |
| Steel grade | 10, 20, 45, 09G2S; 20#, 45#, Q355B per GB |
| Supply group under GOST 8731 | V — with controlled chemical composition and mechanical properties |
| Heat treatment | without heat treatment or normalized to specification |
| Testing | hydrostatic test of every pipe, mechanical tests per heat |
Sizes and weight
| Size, mm | Weight, kg/m | Metres per tonne |
|---|---|---|
| 32×3 | 2.15 | 466.1 |
| 42×3 | 2.89 | 346.6 |
| 57×3.5 | 4.62 | 216.6 |
| 76×4 | 7.1 | 140.8 |
| 89×4 | 8.38 | 119.3 |
| 108×4 | 10.3 | 97.5 |
| 133×5 | 15.8 | 63.4 |
| 159×5 | 19 | 52.7 |
| 219×6 | 31.5 | 31.7 |
| 273×8 | 52.3 | 19.1 |
| 325×8 | 62.5 | 16 |
| 426×10 | 102.6 | 9.75 |
Theoretical weight at steel density 7.85 g/cm³. Actual batch weight is by scale and mill certificate.
Description
Seamless hot-finished pipe is rolled from a round billet: an ingot or continuously cast billet is heated, pierced into a hollow shell on a piercing mill and elongated to the required diameter and wall. There is no weld, so the metal works uniformly across the whole section, and such pipe is used for pressure, temperature and alternating load: boiler circuits, steam lines, hydraulics, pump and compressor piping, machine parts for machining. Size range to GOST 8732-78, technical requirements to GOST 8731-74; mills in China roll to GB/T 8162-2018 for structural use and GB/T 8163-2018 for fluid transport, for export to ASTM A106/A106M and EN 10216-1.
The grades differ in carbon and alloying content. Steel 10 and 20 are quality carbon steels, the main choice for pipelines and boiler plants: steel 20 goes into circuits with elevated medium temperature when supplied to group V of GOST 8731 with heat treatment per the specification. Steel 45 contains more carbon, is harder and is used for machining: shafts, bushings, sleeves. 09G2S is a low-alloy steel with manganese and silicon, works at sub-zero temperatures and is chosen for cold-climate design and critical structures. At mills in China steel 20 corresponds to grade 20#, 45 to 45#, 09G2S to Q355B; ASTM A106 Gr.B is the nearest equivalent of steel 20 by composition and strength, but with different test requirements.
During inspection at the mill, the outside diameter and wall thickness of seamless pipe are measured with a micrometer and callipers at both ends of the sampled pipes in two mutually perpendicular directions; this checks ovality and wall-thickness variation, which GOST 8732 limits by the wall tolerance. The inside surface is examined for laminations, laps and cavities, the ends for squareness of cut. The heat number in the pipe marking is matched against the mill test certificate (MTC): chemical composition, mechanical properties, heat treatment regime and hydrostatic test result. The bundle tag and strapping are checked. Rejects recorded in the report are replaced; the replacement is supplied by the manufacturing mill under its contract with the bureau.
Applications
- steam lines and boiler circuits
- pressure pipelines for steam, water and gas
- hydraulic systems and pump piping
- oil and gas piping, downhole equipment
- blanks for machining: shafts, bushings, sleeves
- critical steel structures in 09G2S
Packing and shipment
Bundles strapped with steel band in three or more places, diameters from 219 mm — loose, piece by piece; ends with protective caps per the specification; every pipe carries the mill marking with grade, size and heat number, the bundle carries a tag.
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
AISI 304 · 316L · 08Kh18N10 · 03Kh17N14M3 · Ø10–325 · GOST 9941 · ASTM A312
Stainless steel pipe
Pipe in austenitic 304 and 316L steel, welded and seamless. Food, chemical and water media
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
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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