Seamless Carbon Steel Pipe (20#, 45#, A106 Gr.B)
Seamless carbon steel pipe with no weld seam, from OD 10 mm to 610 mm and wall 1.5 mm to 60 mm, in 20#, 45# and ASTM A106 Gr.B. Hot-rolled and cold-drawn, to GB/T 8163 and GB/T 3087, for pressure, boiler, hydraulic and high-temperature service. Hydro test and mill certificate supplied.
Product Overview
Seamless pipe is produced by piercing a solid round billet and then rolling or drawing it into a tube, so the wall is continuous all the way round with no weld seam anywhere. That construction is why seamless pipe is the default choice wherever the pipe has to hold pressure, work at elevated temperature, or survive a reversing load — a weld seam, however well made, remains the point at which a pressure line is most likely to fail first.
Two production routes give you a choice of size and tolerance. Hot-rolled seamless pipe covers the large sizes and heavier walls, typically from about OD 32 mm to 630 mm with walls from 3 mm up, and is the workhorse for process, boiler and structural pipe. Cold-drawn seamless pipe starts from a hot-rolled tube and is drawn down to a smaller diameter with a thinner wall, giving better dimensional accuracy and a smoother bore, typically from OD 10 mm to about 200 mm — the route used for hydraulic cylinders, instrument lines and precision components.
We supply 20# quality carbon steel as standard (equivalent to AISI 1020 and the usual basis for A106 Gr.B supply), 45# where a higher-strength, machinable and hardenable material is needed, and material certified to ASTM A106 Gr.B where the project calls for the ASTM certificate. Standard lengths are 6 m and 12 m.
Specifications & Size Range
Size ranges for the hot-rolled and cold-drawn routes, grouped by outside diameter. Heavier walls, intermediate diameters and non-standard lengths are made to order. State the service, the design pressure and the standard on the enquiry so the wall thickness is selected rather than guessed.
| Outside diameter | Common OD × wall (mm) | Production route | Standard length | Typical service |
|---|---|---|---|---|
| Small, OD 10 – 38 mm | 10×2, 14×2, 18×3, 22×3, 25×3, 32×3.5, 38×4 | Cold-drawn | 6 m, cut to order | Hydraulic and instrument lines, precision parts, small heat exchangers |
| Medium, OD 42 – 108 mm | 42×4, 48×4, 57×4, 76×4, 89×5, 108×5 | Cold-drawn / hot-rolled | 6 m / 12 m | Process piping, boiler tubes, cylinder barrels, general pressure lines |
| Large, OD 114 – 273 mm | 114×6, 133×6, 159×6, 194×7, 219×8, 273×8 | Hot-rolled | 6 m / 12 m | Steam and process mains, heat exchangers, structural tubular members |
| Extra large, OD 299 – 630 mm | 299×9, 325×10, 377×12, 426×12, 530×10, 630×12 | Hot-rolled | 6 m / 12 m, made to order | Large process lines, boiler headers, high-temperature steam pipework |
| Heavy wall | Any OD above, wall to 60 mm | Hot-rolled | 6 m, cut to order | High-pressure headers, hydraulic cylinders, machined tubular parts |
Tolerances
Dimensions, wall thickness, length and straightness follow the applicable standard for the route used: GB/T 8163 for liquid service pipe and GB/T 3087 for low and medium pressure boiler pipe, with ASTM A106 where that specification governs. Cold-drawn pipe is produced to a tighter diameter and wall tolerance than hot-rolled pipe and is normally supplied with a smoother bore. Hydrostatic testing and ultrasonic or eddy-current wall inspection can be specified.
Steel Grades & International Equivalents
All grades below are supplied with a mill test certificate. The right-hand column shows the material type and the Chinese standard the grade is produced to; the middle columns give the nearest recognised equivalent in other national standards. Exact equivalence for a specific project should be confirmed on the enquiry.
| GB (China) | ASTM / AISI (US) | EN (Europe) | JIS (Japan) | DIN (Germany) | Type / Standard |
|---|---|---|---|---|---|
| 20# seamless (A106 Gr.B equivalent) | A106 Gr.B / A53 Gr.B | P235GH (EN 10216-2) | STPG370 (JIS G3454) | St37.0 | Seamless carbon steel pipe (GB/T 8163 / GB/T 3087) |
| 20# (20 carbon steel) | AISI 1020 / ASTM A29 1020 | C22 (EN 10083) | S20C (JIS G4051) | CK22 | Quality carbon structural steel (GB/T 699) |
| 45# (45 carbon steel) | AISI 1045 / ASTM A29 1045 | C45 (EN 10083) | S45C (JIS G4051) | CK45 | Quality carbon structural steel (GB/T 699) |
Grade Notes
- 20# seamless (A106 Gr.B equivalent) — High-temperature service seamless pipe for steam, water and process lines. Supplied with mill test certificate.
- 20# (20 carbon steel) — Low-carbon quality steel with good weldability and cold formability. Standard material for seamless pipes, boilers and machined parts.
- 45# (45 carbon steel) — Medium-carbon steel for shafts, gears and axles. Responds well to quenching and tempering.
Chemical Composition (%, ladle analysis)
Typical specification limits. Actual heat values are reported on the mill test certificate supplied with every shipment.
| Grade | C | Si | Mn | P max | S max | Other elements |
|---|---|---|---|---|---|---|
| 20# seamless (A106 Gr.B equivalent) | ≤0.30 | ≥0.10 | 0.29–1.06 | ≤0.035 | ≤0.035 | — |
| 20# (20 carbon steel) | 0.17–0.24 | 0.17–0.37 | 0.35–0.65 | ≤0.035 | ≤0.035 | — |
| 45# (45 carbon steel) | 0.42–0.50 | 0.17–0.37 | 0.50–0.80 | ≤0.035 | ≤0.035 | — |
Mechanical Properties
Minimum values at room temperature unless stated. ReL = yield strength; Rp0.2 = 0.2% proof stress; Rm = tensile strength; A = elongation after fracture.
| Grade | Yield (ReL) | Proof (Rp0.2) | Tensile (Rm) | Elongation A | Impact / others | |
|---|---|---|---|---|---|---|
| 20# seamless (A106 Gr.B equivalent) | ≥240 MPa | — | ≥415 MPa | ≥22% | — | — |
| 20# (20 carbon steel) | ≥245 MPa | — | ≥410 MPa | ≥25% | — | — |
| 45# (45 carbon steel) | ≥355 MPa | — | ≥600 MPa | ≥16% | — | — |
Standards & Documents
- GB/T 8163 — seamless steel pipes for liquid service
- GB/T 3087 — seamless steel pipes for low and medium pressure boilers
- ASTM A106 Gr.B — seamless carbon steel pipe for high-temperature service
- ASTM A53 Gr.B and EN 10216-2 P235GH — equivalent pressure pipe specifications
- GB/T 699 — quality carbon structural steels, covering 20# and 45#
- Testing: hydrostatic pressure test, ultrasonic or eddy-current inspection, EN 10204 3.1 mill test certificate
Typical Applications
| Industry / Application | Typical use |
|---|---|
| High-temperature steam & boiler plant | Boiler tubes, superheater and economiser tubes, steam mains and header pipework where the material must retain strength at temperature. |
| Oil, gas & petrochemical lines | Process piping, gathering lines, heat-exchanger tubes and reactor pipework, in A106 Gr.B or 20# as the specification requires. |
| Hydraulic & pneumatic systems | Hydraulic cylinder barrels, high-pressure oil lines and pneumatic cylinders, normally in cold-drawn 20# or 45# for bore accuracy. |
| General pressure pipework | Compressed air, water and process lines where a leak at a seam would be unacceptable and seamless construction is specified. |
| Precision machined tubular parts | Bushes, sleeves, spacers, rolls and machined components produced from cold-drawn tube in 20# or 45#, often with a honed bore. |
| Structural & mechanical tube | Machine frames, rollers, drive shafts and structural members where the seamless wall and uniform properties are wanted. |
| Automotive & machinery components | Drive shafts, axle tubes, shock absorber bodies and engine components in 45# where strength after heat treatment is required. |
Common Problems Buyers Face — and How We Prevent Them
These are the issues that most often cause claims on steel imports. Each one is controlled in our process before shipment.
Wall thickness varies around the circumference, so the pressure rating is uncertain
Why it happens: The piercing and rolling process naturally produces some eccentricity, and if the wall is checked at one point only, a thin area elsewhere is missed.
Our control: Wall thickness is measured at multiple points around the circumference and reported, and ultrasonic wall inspection can be specified for pressure duty. For any pressurised application, state the minimum wall you need so the tube is selected and inspected against that figure rather than against a nominal average.
Pipe will not machine or hold a tolerance on the bore
Why it happens: Hot-rolled seamless pipe carries mill scale on the surface and a wider tolerance, and it is sometimes used for a precision component where a cold-drawn tube was the right product.
Our control: For machined parts and cylinder barrels, order cold-drawn seamless tube, which gives a better diameter tolerance, a smoother surface and less eccentricity. Where a truly accurate bore is needed, specify honed tube so the inside diameter is finished to size before delivery.
Hardness too high for machining
Why it happens: 45# and some 20# material can arrive in a hard as-rolled condition and will not machine cleanly at the planned cutting speed.
Our control: State the machining operation on the enquiry. We supply 20# and 45# in the annealed or normalised condition with a hardness limit stated on the certificate, normally 156 HBW maximum for 20# and 229 HBW maximum for 45#, so the tool life you planned is achievable.
Surface rust on pipe stored before installation
Why it happens: Seamless pipe is supplied without a protective coating, and humid air or a long sea voyage will produce surface oxidation on both the outside and, to a lesser extent, the bore.
Our control: Pipe is shipped dry with desiccant and VCI paper on request, and for demanding routes we supply oiled pipe or hot-dip galvanized seamless pipe. For storage on site, keep the pipe under cover and off the ground rather than relying on the mill’s temporary protection.
Documentation is rejected because the certificate does not name the standard the project requires
Why it happens: The same physical pipe can be certified to GB/T 8163, GB/T 3087 or ASTM A106, and a certificate issued against the wrong standard is rejected even though the material is sound.
Our control: State on the enquiry which standard the project will enforce. The pipe is then produced, tested and certified to that specification, and where an ASTM certificate is required we confirm before the order is accepted that the material can be certified to it.
Our Supply & Manufacturing Advantages
- No weld seam — Continuous wall all the way round, which is why seamless pipe is specified for pressure, elevated temperature and fatigue duty.
- Hot-rolled and cold-drawn — Large diameters and heavy walls by hot rolling, and precise diameters with a smooth bore by cold drawing, from one supplier.
- Three grades to match the duty — 20# for general quality-carbon service, 45# for strength and hardenability, and A106 Gr.B where the ASTM certificate governs.
- Testing matched to the application — Hydrostatic pressure test, ultrasonic or eddy-current wall inspection and mechanical property testing arranged according to the service.
- Bore finishing options — Cold-drawn, honed or machined bore for hydraulic cylinders, instrument lines and precision tubular components.
- Documented and traceable — EN 10204 3.1 mill test certificate for every heat with composition, mechanical properties and, where required, hardness and test pressure.
Packaging, Delivery & Payment
- Packing: loose in bulk vessel, or bundled and containerised to your requirement. Galvanized and coated products get VCI paper, waterproof wrapping and edge protection. See our export packaging methods.
- Availability: both stock and custom production. Tell us the specification and we will confirm the route.
- MOQ: no strict minimum — one ton can ship.
- Lead time: stock dispatched to port within 3 days; orders needing export packaging about 1 week; custom production quoted per product.
- Payment: stock — 10% deposit, balance before shipment; custom production — 50% deposit, balance before shipment.
- Documents: EN 10204 3.1 mill test certificate with every shipment; third-party inspection (SGS / BV) on request.
Frequently Asked Questions
What is the Chinese equivalent of ASTM A106 Gr.B seamless pipe?
20# quality carbon steel to GB/T 699, with the pipe produced to GB/T 8163 or GB/T 3087, is the normal Chinese basis for A106 Gr.B supply, and the two are close on carbon, manganese and mechanical properties. We can also supply pipe certified to ASTM A106 Gr.B itself where the project requires the ASTM certificate. Tell us which standard the project will enforce.
Should I specify hot-rolled or cold-drawn seamless pipe?
Choose hot-rolled for larger diameters, heavier walls and general pressure or process service, where cost per metre is the deciding factor. Choose cold-drawn when the pipe must hold a tight diameter and wall tolerance, when the bore has to be smooth for flow or for machining, or when the component will be machined after delivery. Cold drawing costs more but removes machining allowance.
Which grade should I use for a hydraulic cylinder barrel?
Use 20# cold-drawn seamless pipe for general hydraulic and pneumatic cylinder barrels, or 45# where the barrel will be machined and hardened or where higher strength is required. For accurate bores, specify honed tube so the inside diameter is finished to size. Send the working pressure, bore and tolerance and we will confirm the grade and wall.
What testing comes with a seamless pipe order?
Every pipe can be hydrostatically tested to the standard or to your specified pressure, and ultrasonic or eddy-current wall inspection is available to verify wall thickness and detect internal defects. Mechanical properties are tested per heat and reported on the mill certificate, which also carries the composition and the heat number.
At what temperature can A106 Gr.B pipe be used?
ASTM A106 Gr.B is specified for high-temperature service and is widely used for steam and process lines up to around 425 degrees C, subject to the design code that governs your plant. Above that range, alloy steels such as 12Cr1MoV are normally required. Give us the design temperature and pressure and we will confirm the grade and the standard to apply.
How is seamless pipe different from ERW welded pipe in price and performance?
Seamless pipe costs more per ton because it is pierced and rolled from a solid billet rather than formed from strip and welded. In return it has no seam, a more uniform structure and better performance in pressure, high-temperature and fatigue service. For water, drainage and ordinary structural work, ERW pipe is the more economical and entirely adequate choice.
Who supplies seamless carbon steel pipe from China for export?
We do. Dayang supplies seamless pipe to process plant contractors, boiler and heat-exchanger manufacturers, hydraulic equipment builders and steel stockists worldwide, in 20#, 45# and A106 Gr.B, hot-rolled or cold-drawn, with hydrostatic test records and mill certificates issued with each shipment.
Do you have a minimum order quantity and what is the lead time?
No strict minimum and a trial order of one ton can ship. Common sizes are dispatched to the port in about three days; orders requiring hydrostatic testing, ultrasonic inspection, honing, a specific standard certificate or cutting to length take around a week. Non-standard sizes are quoted with their own production lead time.
What documents accompany a seamless pipe shipment?
An EN 10204 3.1 mill test certificate showing heat number, chemical composition, mechanical properties and, where specified, hardness; a hydrostatic test report; and ultrasonic or eddy-current inspection reports where these were ordered. Commercial invoice, packing list and certificate of origin complete the set.
Request a Quotation Export Packaging
Live Stock & Indicative Price
The table below lists live stock at the time of publication, with indicative EXW China reference prices in USD per tonne (converted at 6.70 CNY/USD). Steel prices move with the mill market every week — send us your size, quantity and destination and we will confirm availability and issue a firm FOB or CIF quotation.
| Product | Size / Model | Grade | Price (USD/t, EXW) | Stock (t) |
|---|---|---|---|---|
| Seamless Steel Pipe | Ø10 × 2 mm | — | $1,299 | 17 |
| Seamless Steel Pipe | Ø12 × 2 mm | — | $1,269 | 11 |
| Seamless Steel Pipe | Ø14 × 2 mm | — | $1,134 | 26 |
| Seamless Steel Pipe | Ø14 × 3 mm | — | $1,090 | 2 |
| Seamless Steel Pipe | Ø16 × 3 mm | — | $948 | 15 |
| Seamless Steel Pipe | Ø18 × 3 mm | — | $925 | 536 |
| Seamless Steel Pipe | Ø20 × 3 mm | — | $873 | 405 |
| Seamless Steel Pipe | Ø22 × 3 mm | 20# | $743 | 332 |
| Seamless Steel Pipe | Ø22 × 4 mm | 20# | $743 | 953 |
| Seamless Steel Pipe | Ø25 × 2.5 mm | 20# | $721 | 448 |
| Seamless Steel Pipe | Ø25 × 3 mm | 20# | $706 | 232 |
| Seamless Steel Pipe | Ø25 × 4 mm | 20# | $706 | 127 |
| Seamless Steel Pipe | Ø25 × 5 mm | 20# | $706 | 301 |
| Seamless Steel Pipe | Ø27 × 3 mm | 20# | $706 | 1080 |
| Seamless Steel Pipe | Ø27 × 4 mm | 20# | $706 | 1194 |
| Seamless Steel Pipe | Ø28 × 3 mm | 20# | $706 | 226 |
| Seamless Steel Pipe | Ø28 × 4 mm | 20# | $706 | 182 |
| Seamless Steel Pipe | Ø30 × 3 mm | 20# | $676 | 182 |
| Seamless Steel Pipe | Ø32 × 3 mm | 20# | $615 | 1016 |
| Seamless Steel Pipe | Ø32 × 3.5 mm | 20# | $615 | 1101 |
| Seamless Steel Pipe | Ø32 × 4 mm | 20# | $615 | 1000 |
| Seamless Steel Pipe | Ø32 × 5 mm | 20# | $615 | 912 |
| Seamless Steel Pipe | Ø32 × 3 mm | — | $709 | 717 |
| Seamless Steel Pipe | Ø34 × 3 mm | 20# | $615 | 577 |
| Seamless Steel Pipe | Ø34 × 3.5 mm | 20# | $615 | 775 |
| Seamless Steel Pipe | Ø34 × 4 mm | 20# | $615 | 640 |
| Seamless Steel Pipe | Ø34 × 5 mm | 20# | $615 | 211 |
| Seamless Steel Pipe | Ø38 × 3 mm | 20# | $615 | 459 |
| Seamless Steel Pipe | Ø38 × 3.5 mm | 20# | $615 | 408 |
| Seamless Steel Pipe | Ø38 × 4 mm | 20# | $615 | 389 |
| Seamless Steel Pipe | Ø38 × 5 mm | 20# | $615 | 417 |
| Seamless Steel Pipe | Ø40 × 3 mm | 20# | $615 | 312 |
| Seamless Steel Pipe | Ø42 × 3 mm | 20# | $610 | 149 |
| Seamless Steel Pipe | Ø42 × 3.5 mm | 20# | $600 | 117 |
| Seamless Steel Pipe | Ø42 × 4 mm | 20# | $600 | 327 |
| Seamless Steel Pipe | Ø42 × 5 mm | 20# | $600 | 383 |
| Seamless Steel Pipe | Ø42 × 3.5 mm | — | $679 | 266 |
| Seamless Steel Pipe | Ø45 × 3 mm | 20# | $610 | 81 |
| Seamless Steel Pipe | Ø45 × 3.5 mm | 20# | $600 | 372 |
| Seamless Steel Pipe | Ø45 × 4 mm | 20# | $600 | 333 |
| Seamless Steel Pipe | Ø45 × 5 mm | 20# | $600 | 187 |
| Seamless Steel Pipe | Ø48 × 3 mm | 20# | $609 | 298 |
| Seamless Steel Pipe | Ø48 × 3.5 mm | 20# | $597 | 36 |
| Seamless Steel Pipe | Ø48 × 4 mm | 20# | $597 | 261 |
| Seamless Steel Pipe | Ø48 × 5 mm | 20# | $597 | 289 |
| Seamless Steel Pipe | Ø50 × 3.5 mm | 20# | $601 | 309 |
| Seamless Steel Pipe | Ø50 × 3 mm | 20# | $609 | 332 |
| Seamless Steel Pipe | Ø50 × 4 mm | 20# | $597 | 317 |
| Seamless Steel Pipe | Ø50 × 5 mm | 20# | $597 | 114 |
| Seamless Steel Pipe | Ø51 × 3 mm | 20# | $609 | 78 |
| Seamless Steel Pipe | Ø51 × 3.5 mm | 20# | $601 | 174 |
| Seamless Steel Pipe | Ø57 × 3 mm | 20# | $601 | 175 |
| Seamless Steel Pipe | Ø57 × 3.5 mm | 20# | $582 | 222 |
| Seamless Steel Pipe | Ø57 × 4 mm | 20# | $582 | 76 |
| Seamless Steel Pipe | Ø57 × 5 mm | 20# | $582 | 2 |
| Seamless Steel Pipe | Ø57 × 6 mm | 20# | $582 | 58 |
| Seamless Steel Pipe | Ø57 × 8 mm | 20# | $591 | 69 |
| Seamless Steel Pipe | Ø60 × 3 mm | 20# | $601 | 51 |
| Seamless Steel Pipe | Ø60 × 3.5 mm | 20# | $582 | 69 |
| Seamless Steel Pipe | Ø60 × 4 mm | 20# | $582 | 46 |
| Seamless Steel Pipe | Ø60 × 5 mm | 20# | $582 | 86 |
| Seamless Steel Pipe | Ø60 × 6 mm | 20# | $582 | 71 |
| Seamless Steel Pipe | Ø60 × 8 mm | 20# | $591 | 261 |
| Seamless Steel Pipe | Ø63.5 × 3.5 mm | 20# | $601 | 133 |
| Seamless Steel Pipe | Ø70 × 4 mm | 20# | $594 | 133 |
| Seamless Steel Pipe | Ø70 × 5 mm | 20# | $594 | 230 |
| Seamless Steel Pipe | Ø70 × 6 mm | 20# | $594 | 30 |
| Seamless Steel Pipe | Ø73 × 5 mm | 20# | $593 | 220 |
| Seamless Steel Pipe | Ø76 × 3.5 mm | 20# | $601 | 38 |
| Seamless Steel Pipe | Ø76 × 4 mm | 20# | $587 | 27 |
| Seamless Steel Pipe | Ø76 × 6 mm | 20# | $585 | 416 |
| Seamless Steel Pipe | Ø76 × 4.5 mm | 20# | $597 | 198 |
| Seamless Steel Pipe | Ø76 × 5 mm | 20# | $593 | 263 |
| Seamless Steel Pipe | Ø76 × 8 mm | 20# | $585 | 190 |
| Seamless Steel Pipe | Ø89 × 3.5 mm | 20# | $601 | 44 |
| Seamless Steel Pipe | Ø89 × 4 mm | 20# | $593 | 39 |
| Seamless Steel Pipe | Ø89 × 4.5 mm | 20# | $590 | 1 |
| Seamless Steel Pipe | Ø89 × 5 mm | 20# | $590 | 676 |
| Seamless Steel Pipe | Ø89 × 6 mm | 20# | $585 | 47 |
| Seamless Steel Pipe | Ø89 × 8 mm | 20# | $585 | 331 |
| Seamless Steel Pipe | Ø89 × 7 mm | 20# | $585 | 223 |
| Seamless Steel Pipe | Ø95 × 5 mm | 20# | $593 | 343 |
| Seamless Steel Pipe | Ø95 × 6 mm | 20# | $585 | 392 |
| Seamless Steel Pipe | Ø95 × 8 mm | 20# | $585 | 60 |
| Seamless Steel Pipe | Ø102 × 8 mm | 20# | $585 | 71 |
| Seamless Steel Pipe | Ø102 × 10 mm | 20# | $585 | 94 |
| Seamless Steel Pipe | Ø102 × 5 mm | 20# | $593 | 89 |
| Seamless Steel Pipe | Ø102 × 6 mm | 20# | $585 | 105 |
| Seamless Steel Pipe | Ø108 × 4 mm | 20# | $593 | 1101 |
| Seamless Steel Pipe | Ø108 × 4.5 mm | 20# | $590 | 1415 |
| Seamless Steel Pipe | Ø108 × 5 mm | 20# | $593 | 139 |
| Seamless Steel Pipe | Ø108 × 6 mm | 20# | $585 | 180 |
| Seamless Steel Pipe | Ø108 × 10 mm | 20# | $585 | 115 |
| Seamless Steel Pipe | Ø114 × 5 mm | 20# | $578 | 35 |
| Seamless Steel Pipe | Ø114 × 6 mm | 20# | $570 | 32 |
| Seamless Steel Pipe | Ø114 × 10 mm | 20# | $570 | 38 |
| Seamless Steel Pipe | Ø114 × 4 mm | 20# | $601 | 20 |
| Seamless Steel Pipe | Ø114 × 4.5 mm | 20# | $585 | 29 |
| Seamless Steel Pipe | Ø114 × 8 mm | 20# | $570 | 45 |
| Seamless Steel Pipe | Ø121 × 10 mm | 20# | $570 | 66 |
Showing 100 of 173 listed sizes (lowest prices first). Price range USD 570–1,299 per tonne (EXW China). MOQ from 1 tonne; stock dispatched to port within 3 days. Mill test certificate (EN 10204 3.1) and third-party inspection available on request.