20# carbon steel seamless pipe is the Chinese standard medium-carbon seamless tube (GB/T 699 grade 20 steel, roughly equivalent to AISI 1020 / S20C in chemistry) manufactured in fluid-service and boiler-tube executions under GB/T 8163, GB 3087 and GB/T 8162. It is the default choice in Chinese plant engineering for process piping, boiler water walls, superheaters, hydraulic circuits and mechanical tubing where 20-class carbon steel properties, full-seamless integrity and export documentation are required. Huaxia-Steel supplies 20# seamless pipe factory direct: outside diameters from 21 mm to 720 mm, wall thicknesses 2.5–80 mm, hot-rolled and cold-drawn manufacturing routes, hydrostatic testing, UT inspection and EN 10204 3.1 mill certificates as standard.
Product Overview
Grade 20 steel carries a nominal 0.17–0.24 percent carbon with manganese 0.35–0.65, silicon 0.17–0.37, and tight sulfur and phosphorus (≤ 0.035 each) — the classic medium-low carbon composition that balances strength, weldability and cold-working capability. Delivered hot-rolled, the tube runs in the 410–550 MPa tensile range with 235 MPa minimum yield (for the common sizes) and elongation ≥ 24 percent, giving a strength-toughness combination well suited to pressurized service at moderate temperatures. The seamless route — rotary piercing of a round billet followed by mandrel rolling or Pilger rolling (hot-rolled), or drawing over a mandrel from hollows (cold-drawn) — leaves no weld seam, which is the decisive property for boiler and pressure work and the reason 20# tube is specified where ERW alternatives are prohibited.
Three standard executions cover most orders. GB/T 8163 (seamless steel pipe for fluid transport) is the general process-piping version with hydrostatic or eddy-current verification. GB 3087 (seamless steel tubes for low and medium pressure boilers) adds the elevated-temperature discipline for boiler service, with flatter-tolerance walls and verified high-temperature behavior. GB/T 8162 (seamless pipe for structural purposes) covers mechanical and construction duty where pressure verification is not required. International buyers frequently cross-qualified these against ASTM A106 Gr B (pressure service) and ASTM A179 / A192 (boiler tubes) — the chemistries and property classes are close cousins, and dual-certified MTCs are available on request.
Specification Table
| Parameter | Range | Notes |
|---|---|---|
| Outside diameter (hot-rolled) | 57 – 720 mm | common: 57, 76, 89, 108, 133, 159, 219, 273, 325, 377, 426 mm |
| Outside diameter (cold-drawn) | 10 – 108 mm | tighter tolerances, smoother ID |
| Wall thickness | 2.5 – 80 mm | schedule equivalents SCH 20–160 on request |
| Length | 3 – 12 m random; fixed lengths ±500 mm | exact cutting to 6 m / 9 m / 12 m standard |
| Manufacturing | hot-rolled (HR), cold-drawn (CD) | CD preferred for ≤ 108 mm OD precision |
| Chemistry (grade 20) | C 0.17–0.24, Mn 0.35–0.65, Si 0.17–0.37, S ≤ 0.035, P ≤ 0.035 | per GB/T 699 |
| Mechanical (HR) | YS ≥ 235 MPa, TS 410–550 MPa, EL ≥ 24% | size-dependent bands per execution standard |
| Tolerance (OD) | ±1% hot-rolled; ±0.5% cold-drawn | per GB/T 8163 / 3087 tables |
| Test | hydrostatic, eddy current, UT, flattening, tensile, impact (opt) | scope by standard and order |
| Certificates | EN 10204 3.1 MTC, third-party inspection on request | SGS / BV / TUV witnessed |
Available Grades and Cross-References
While this page focuses on grade 20, the same production line covers the full GB carbon seamless family, and orders can be split across grades from one mill heat program:
| GB grade | Close equivalent | Typical use |
|---|---|---|
| 20# (GB/T 699) | AISI 1020 / S20C / C22E | fluid, boiler, general pressure piping |
| 10# (GB/T 699) | AISI 1010 / S10C | lower strength, better cold formability |
| 45# (GB/T 699) | AISI 1045 / C45 | mechanical tubing, cylinders |
| Q345B (GB/T 1591) | S355JR territory | structural seamless |
| 20G (GB 5310) | A106 Gr B / A192 territory | high-pressure boiler tubes |
For buyers certifying to ASTM, the most requested pairings are 20# / GB/T 8163 against A106 Gr B and 20# / GB 3087 against A192. Chemistry is compatible; the property classes align; the difference sits in test frequency and tolerance conventions, which dual-certified certificates resolve by testing to the stricter of the two scopes.
Manufacturing Standards
- GB/T 8163 — seamless steel pipe for fluid transport: the baseline process-pipe standard, verified by hydrostatic pressure test or eddy-current examination.
- GB 3087 — seamless tubes for low and medium pressure boilers: tighter wall tolerances, verified at elevated temperature, standard for boiler water walls and economizers.
- GB/T 8162 — structural seamless pipe: mechanical duty, dimensional emphasis, no pressure verification.
- GB/T 699 — the grade chemistry standard defining 20# steel itself.
- ASTM A106 Gr B / A179 / A192 — available as dual-certification targets for American-spec projects.
Heat treatment is by manufacturing route: hot-rolled tube normally ships as-rolled (or normalized on request), while cold-drawn tube ships stress-relief annealed or normalized to restore ductility after drawing. Both conditions are confirmed on the MTC with actual hardness and mechanical results.
Applications
- Process piping: steam, water, oil and gas distribution inside plants at moderate pressure and temperature — the GB/T 8163 workhorse.
- Boiler components: water wall panels, economizer and superheater elements in low/medium pressure boilers under GB 3087.
- Hydraulic and pneumatic circuits: cold-drawn 20# tube as the feedstock for honed cylinder tube and precision ID requirements.
- Mechanical and structural members: shafts, rollers, frames and supports under GB/T 8162 where a seamless section carries load.
- Heat exchanger tubing: cold-drawn execution with closer ID control for shell-and-tube bundles.
Quality Assurance
Every order runs a documented test plan: ladle chemistry per heat, tensile and flattening tests per lot, hydrostatic pressure verification (or eddy-current per GB/T 7735 where agreed), dimensional sampling against the tolerance tables, and visual/surface inspection with grinding limits per the standard. UT longitudinal examination to GB/T 5777 is available for pressure-critical walls. Third-party inspection (SGS, BV, TUV, or your nominated agency) is welcomed and witnessed at our works, with the inspector’s stamp appearing on the final MTC set. Marking follows GB conventions — grade, size, standard, heat number stenciled or banded along the pipe — and heat traceability is preserved from billet to bundle.
Packaging and Shipping
- Standard: bundles with steel strapping, end caps on request, HDPE sleeves for surface protection on ODs ≤ 219 mm.
- Export upgrade: seaworthy bundles in containers with timber cradles, or loose in 20 ft/40 ft with dunnage; breakbulk and bulk vessel loading for large OD above 325 mm.
- Coating options: bare (mill scale), varnish or anti-rust oil internal/external, black paint, 3PE/FBE via partner coating line for pipeline service.
- Documents: commercial invoice, packing list, EN 10204 3.1 MTCs, CO/FORM where applicable, and container weight distribution plans for heavy steel loading.
Typical lead time is 15–30 days for stock-range sizes and 30–60 days for production heats on large OD or special walls, with FOB, CFR and CIF quotations to your port.
Ordering Notes and Size Selection
Size selection on 20# tube follows a few rules of thumb that prevent over-engineering: choose the smallest standard wall that passes the pressure calculation plus corrosion allowance, because non-standard walls price at rolling minimums; prefer the common OD list above, where stock and tooling exist in depth; and specify random lengths where the cutting plan allows, since fixed-length tolerancing adds processing cost on both sides. When the bill of material mixes walls on one OD, we quote each wall as its own line — mixing walls inside one nominal size creates tolerance and certificate confusion downstream.
- Stock-range sizes (57–426 mm OD common walls) ship fastest; check the stock list before committing a project schedule — mill heats on odd walls add 2–4 weeks.
- Schedule conversion: supply your schedule number (SCH 40, SCH 80, SCH 160) and we map it to the exact metric OD × wall with tolerance band stated on the quote.
- Cold-drawn preference: for ID-sensitive service (hydraulics, heat exchanger bundles), order CD execution — the smoother bore and tighter OD tolerance save machining later.
- Pressure verification: state the design pressure and temperature; we confirm the hydro test pressure per GB/T 8163 tables and flag where wall upgrades are needed.
- Mixed heats: for long material lists we consolidate sizes across heats to fill containers efficiently while keeping each size single-heat where the project requires it.
For repeated annual programs we also offer frame-agreement pricing against published billet indices, releasing sizes against your monthly call-offs — the standard structure for EPC and distributor customers who need price stability across a project year.
FAQ
What is the difference between 20# pipe and 20G pipe?
Both are grade-20 chemistry carbon steel, but 20G is the high-pressure boiler execution under GB 5310 with stricter chemistry, elevated-temperature property verification and more rigorous test scope. 20# under GB/T 8163 or GB 3087 serves general fluid and low/medium pressure boiler duty. Choose 20G when the design code is a high-pressure boiler code.
Can 20# seamless pipe replace ASTM A106 Grade B?
In chemistry and property class, yes — grade 20 matches 1020-class chemistry and meets A106 Gr B-class strength. For formal substitution, order dual-certified material where the mill tests to the A106 scope (including the high-temperature yield minimums and the A106 sampling rules) and names both standards on the 3.1 MTC.
What tolerances should I expect on cold-drawn tube?
Cold-drawn 20# tube runs about ±0.5% on OD and ±7.5–10% on wall per GB tables, with better ID finish than hot-rolled. For honed or SRB cylinder tube, we supply downstream-processed products with H8/H9 ID tolerances from the same feedstock.
Which surface protections are standard for export?
Bare with mill scale is standard; varnish or anti-rust oil is the common export upgrade; black paint and 3PE/FBE coatings are available for buried or pipeline service. End caps and HDPE wrap are added per request at nominal cost.
Need 20# seamless pipe with GB/T 8163, GB 3087 or dual A106 certification, hydro and UT test records and 3.1 MTCs? Send OD, wall, length and quantity — Huaxia-Steel replies with stock availability, per-ton pricing and lead time within 24 hours.
