GB/T 5310 Steel Tube Buyer’s Guide: 20G, 15CrMoG, 12Cr1MoVG, T91 & T92 Seamless Pipe for High-Pressure Boilers and Mill-Direct Sourcing

This guide is for procurement engineers, boiler designers, EPC sub-contractors, and QA managers qualifying a gbt 5310 steel tube supplier — and shows how EZ Steel Industrial, a mill-direct Chinese manufacturer with sites in Cangzhou, Yangzhou, and Lishui, fits into a defensible supply chain for both boiler tubing and adjacent heat exchanger tube orders.

GB/T 5310 is the Chinese national standard for seamless steel tubes used in high-pressure boilers and similar high-temperature pressure equipment. It is not a general-purpose seamless standard, and it is not a structural standard. Low-pressure fluid conveyance uses GB/T 8163; high-temperature pressure-bearing service uses GB/T 5310; refinery hydrocracking, ethylene cracking, and steam-methane reforming all reference 5310 as the primary Chinese alternative to ASME SA-213 / SA-335.

Scope: carbon steel 20G / 20MnG / 25MnG; alloy 15MoG / 20MoG / 12CrMoG / 15CrMoG / 12Cr2MoG / 12Cr1MoVG / 12Cr3MoVSiTiB / 07Cr2MoW2VNbB (T23/P23) / 10Cr9Mo1VNbN (T91/P91) / 10Cr9MoW2VNbBN (T92/P92); stainless 07Cr19Ni10 (TP304H) / 10Cr18Ni9NbCu3BN (Super304H) / 07Cr25Ni21NbN (HR3C) / 07Cr18Ni11Nb (TP347H) / 08Cr18Ni11NbFG (TP347HFG). OD 16–824 mm, wall 2–65 mm. Outside the scope: welded tubes (GB/T 13296 / GB/T 14976), line-pipe (GB/T 9711 / ISO 3183), structural hollow sections (GB/T 6728 / EN 10210).

GB/T 5310-2023 was published on 2023-09-07 and replaced the 2017 edition on 2024-04-01. For most projects already designed against GB/T 5310-2017 or the older GB/T 5310-2008, the 2023 ｕｐｄａｔｅ is evolutionary rather than disruptive. The changes you are most likely to encounter in a procurement specification are:

• Normalized heat-treatment language for alloy grades — clarifying the relationship between normalizing, tempering, and the optional full-anneal delivery condition. This matters for creep-resistant grades where an incorrect tempering window will sink the long-term creep strength of the tube.
• Tightened grain-size and inclusion rating requirements for martensitic grades (T91/P91, T92/P92), bringing the cleanliness expectation closer to ASME SA-213.
• Extended chemical envelope for 10Cr9Mo1VNbN and 10Cr9MoW2VNbBN to align more closely with the ASME T91/T92 specification limits, which removes a long-standing source of confusion when a Chinese heat is dual-certified to both GB/T 5310 and ASME SA-213.
• Hydrostatic test hold-time language for large-diameter tubes harmonized with the requirements in GB/T 5310-2017 Annex, reducing ambiguity at the receiving dock.

For teams that have been buying 15CrMoG, 12Cr1MoVG or T91/P91 for years, the 2023 ｕｐｄａｔｅ mostly tightens language rather than changing the grades themselves — but it does require refreshing the reference standard on existing POs.

The grade list in GB/T 5310 is long because it serves the entire thermal power generation envelope — from 300 MW subcritical units up to 1,000 MW ultra-supercritical units, plus petrochemical cracking furnaces and refinery high-pressure service. For most international buyers, the practical decision comes down to five families: carbon steel (20G family), 1Cr-½Mo (15CrMoG / T11 / T12), 2¼Cr-1Mo (12Cr2MoG / T22), 9Cr-1Mo-V-Nb-N (T91/P91) and 9Cr-1Mo-W-V-Nb-B-N (T92/P92).

Carbon Steel Family — 20G, 20MnG, 25MnG

20G is the workhorse of subcritical waterwall, economizer, and low-temperature superheater tube, and the Chinese equivalent of SA-210C. 20MnG and 25MnG are higher-manganese variants. Above 450°C, 20G begins to show pearlite spheroidization and graphitization, so it should be specified only where the metal temperature is reliably below 450°C.

1Cr-½Mo Family — 15MoG, 20MoG, 12CrMoG, 15CrMoG

15CrMoG is the Chinese equivalent of T11/T12 (ASME SA-213) / P11/P12 (SA-335), used in the 500–550°C superheater and reheater range. The 0.8–1.1% Cr addition stabilizes carbides.

2¼Cr-1Mo Family — 12Cr1MoVG, 12Cr2MoG

12Cr1MoVG is the dominant alloy grade in Chinese subcritical and supercritical boiler construction (the Chinese equivalent of T22/P22), approved for service up to 580°C wall temperature. The "V" denotes a small vanadium addition (0.15–0.30%) that pins carbides. 12Cr2MoG is the higher-Cr variant used in ethylene cracking furnace tubes.

Modified 9Cr-1Mo — T91/P91 (10Cr9Mo1VNbN)

10Cr9Mo1VNbN, dual-certified to ASME SA-213 T91 / SA-335 P91, is the backbone of the supercritical and ultra-supercritical boiler header and main steam piping market. Its low thermal expansion coefficient and high thermal conductivity make it the preferred material for thick-wall headers and steam piping at 580–600°C wall temperature. The martensitic microstructure is sensitive to heat-treatment parameters.

T92/P92 (10Cr9MoW2VNbBN)

10Cr9MoW2VNbBN (the Chinese equivalent of ASME T92/P92) is the highest-strength ferritic grade. The W and B additions push allowable stress roughly 30% above T91/P91 in the 600–650°C range, the default for the hottest reheater and superheater tubes in 660 MW and 1,000 MW ultra-supercritical units.

Stainless & Heat-Resistant — TP304H, TP347H, Super304H, HR3C

For the highest-temperature superheater and reheater surfaces in ultra-supercritical units, austenitic stainless grades enter the picture. 07Cr19Ni10 is the GB/T 5310 designation for TP304H; 07Cr18Ni11Nb is TP347H, stabilized with niobium. Super304H (10Cr18Ni9NbCu3BN) and HR3C (07Cr25Ni21NbN) are the creep-strength-enhanced austenitic grades for 600°C+ service, produced in EZ Steel's Lishui stainless facility.

20G: Rm 410–550 / ReL ≥245 / A ≥24 (waterwall, economizer, ≤450°C).
20MnG: Rm ≥415 / ReL ≥240 / A ≥22 (economizer, header piping).
15CrMoG: Rm 440–640 / ReL ≥235 / A ≥21 (superheater, 500–550°C).
12Cr1MoVG: Rm 470–640 / ReL ≥255 / A ≥21 (header, main steam, ≤580°C).
12Cr2MoG: Rm 450–600 / ReL ≥280 / A ≥20 (cracking furnace tube).
07Cr2MoW2VNbB (T23/P23): Rm ≥510 / ReL ≥400 / A ≥20 (reheater, 580–600°C).
10Cr9Mo1VNbN (T91/P91): Rm ≥585 / ReL ≥415 / A ≥20 (header, main steam, ≤600°C).
10Cr9MoW2VNbBN (T92/P92): Rm ≥620 / ReL ≥440 / A ≥20 (reheater, 600–650°C).
07Cr19Ni10 (TP304H): Rm ≥515 / ReL ≥205 / A ≥35 (superheater, 600°C+).
07Cr18Ni11Nb (TP347H): Rm ≥515 / ReL ≥205 / A ≥35 (superheater / reheater, 600°C+).
10Cr18Ni9NbCu3BN (Super304H): Rm ≥590 / ReL ≥235 / A ≥35 (USC, 600–650°C).
07Cr25Ni21NbN (HR3C): Rm ≥655 / ReL ≥295 / A ≥30 (USC, 650–700°C).

GB/T 5310 tubes are made by hot piercing followed by hot rolling or hot extrusion; cold drawing is reserved for smaller diameters and tighter wall tolerances. The standard requires delivery in the heat-treated condition — never as-rolled — and the heat-treatment cycle is grade-specific:

20G / 20MnG / 25MnG: normalizing, optional tempering. 15MoG / 20MoG / 12CrMoG / 15CrMoG: normalizing + tempering. 12Cr1MoVG / 12Cr2MoG: normalizing + tempering (narrow tempering window). T23/P23 (07Cr2MoW2VNbB): normalizing + tempering; W and B require tight process control. T91/P91 (10Cr9Mo1VNbN): austenitizing 1040–1080°C + tempering 730–780°C → tempered martensite. T92/P92 (10Cr9MoW2VNbBN): austenitizing + tempering; the W+B package makes the tempering window even more sensitive. Austenitic stainless (TP304H, TP347H, Super304H, HR3C): solution annealing, rapid quench.

For 12Cr1MoVG and T91/T92, the tempering temperature and hold time are the most consequential parameters: a temper too hot or long sacrifices creep strength; one too cold leaves untempered martensite and risks brittle behavior. EZ Steel's Yangzhou furnaces are calibrated against documented SA-213 reference heats, and every T91/P91 and T92/P92 lot is hardness-mapped before release.

EPC teams that maintain dual specifications — a Chinese GB/T 5310 spec for the Chinese-supplied portion of a project and an ASME SA-213 / SA-335 spec for the rest of the world — use the cross-reference below. Most modern 5310 mills, including EZ Steel, can dual-certify to both standards if the heat analysis is within both chemical envelopes.

Carbon steel: GB/T 5310 20G / 20MnG ↔ ASME SA-210C / SA-106B ↔ EN 10216-2 P235GH ↔ JIS G3462 STB410.
½Cr-½Mo: 15MoG ↔ SA-213 T1 ↔ EN 16Mo3 ↔ STBA12; 12CrMoG ↔ SA-213 T2 ↔ STBA20; 15CrMoG ↔ SA-213 T11/T12 ↔ EN 13CrMo4-5 ↔ STBA22/23.
1Cr-½Mo / 2¼Cr-1Mo: 12Cr1MoVG ↔ SA-213 T22 / SA-335 P22 ↔ EN 10CrMo9-10 ↔ STBA24; 12Cr2MoG (Cr+) ↔ SA-213 T22 (Cr+).
Modified 9Cr-1Mo: 10Cr9Mo1VNbN ↔ SA-213 T91 / SA-335 P91 ↔ EN X10CrMoVNb9-1 ↔ STBA27.
9Cr-1Mo-W-V: 10Cr9MoW2VNbBN ↔ SA-213 T92 / SA-335 P92.
Austenitic stainless: 07Cr19Ni10 ↔ SA-213 TP304H ↔ EN X6CrNi18-10 ↔ SUS304HTB; 07Cr18Ni11Nb ↔ SA-213 TP347H ↔ EN X7CrNiNb18-10 ↔ SUS347HTB.

Two notes: the 5310 martensitic grades (T91/P91, T92/P92) require stricter process control than their ASME equivalents, so a mill that delivers these grades cleanly usually delivers every other grade on the list as well. EN 10216-2 is the pressure-purpose European standard, while EN 10216-5 covers stainless; for boiler tube work the 10216-2 column is the more relevant cross-reference.

Grade selection is driven by steam pressure, metal temperature, and the inner fluid. The simplified map below is the practical short-list in a vendor quotation; it is not a substitute for a detailed ASME B31.1 or EN 12952 calculation.

Waterwall: subcritical 20G; supercritical and ultra-supercritical 15CrMoG / 12Cr1MoVG.
Economizer: 20G (or SA-210C) at all pressure classes.
Superheater: subcritical 15CrMoG / 12Cr1MoVG / T23-T92; supercritical and USC add 12Cr1MoVG, T23-T92, TP347H / TP347HFG, Super304H, HR3C.
Reheater: subcritical 12Cr1MoVG / T23-T92; supercritical and USC add TP347H, Super304H, HR3C.
Header and main steam piping (thick-wall): subcritical 20G / 15CrMoG / 12Cr1MoVG / P12; supercritical and USC 12Cr1MoVG / P91 / P92.

EZ Steel has seen the same five procurement mistakes cause avoidable project delays; each is fixable with a tighter specification before the PO is released.

Pitfall 1 — Specifying "to GB/T 5310" without a year

The 2017 and 2023 editions of GB/T 5310 are functionally similar but not identical. Always pin the year in the PO. If you have an existing design that referenced 2017, the 2023 edition is the current accepted reference; if you have a legacy design, keep the 2017 reference on the PO. EZ Steel holds documentation for both.

Pitfall 2 — Mixing up "GB/T 5310" with "GB/T 8163"

GB/T 8163 is the seamless tube standard for low-pressure fluid conveyance. It is not interchangeable with 5310. If you receive 8163 tube on a 5310 PO, the metallurgy is wrong and the receiving inspection will catch it. The most common source of the mix-up is a trading company that quotes a 8163 price for a 5310 inquiry to win the order, then "upgrades" to 5310 — or quietly delivers 8163 with a paper conversion. A mill-direct quotation is the simplest safeguard.

Pitfall 3 — Assuming all "T91" is the same

The 9Cr-1Mo-V-Nb-N specification has tight chemistry and tight heat-treatment windows. Two heats, both nominally T91, can have very different creep-strength margins depending on austenitizing temperature, tempering temperature, austenitic grain size and inclusion rating. Always review the MTC's actual mechanical test results (Rm, ReL, A, hardness, impact) before signing off on the delivery, not just the grade name.

Pitfall 4 — Forgetting the matching pipe fittings and pipe flanges

A boiler tube order almost always comes with a downstream order for matching pipe fittings, pipe flanges, gasket, stud bolt & nut sets, and industrial valves. Sourcing tube from one supplier and fittings from another introduces two MTC systems and two inspection regimes. EZ Steel produces alloy tube, butt-weld fittings, forged steel flanges, spiral-wound gaskets, stud bolt sets, and API 600 gate / globe / check valves under a single QA umbrella.

Pitfall 5 — Underestimating lead time on T91/P91 and T92/P92

The T91/P91 and T92/P92 grades are not stock items at most tube mills. A mill-direct order from EZ Steel typically requires 8–14 weeks for a new production slot, plus 2–3 weeks for heat treatment, NDT, MTC preparation and container loading. Repeat orders on standing alloy can be faster, but a new specification should always be planned on a 12-week horizon.

EZ Steel Industrial Co., Ltd. has produced high-pressure seamless tube since 1994, with three production sites — Cangzhou (alloy inventory and custom fittings), Yangzhou (large-scale carbon & carbon alloy steel tube), Lishui (stainless and copper-nickel corrosion-resistant materials) — 500+ employees, 480,000-ton annual capacity, ISO 9001, API 5L, API 5CT, and PED certified.

The mill-direct workflow runs: specification review (PO + MTC + dual-cert needs) → fixed-price quotation valid 30 days → production (hot piercing, rolling / drawing, heat treatment, hydrotest, NDT, dimensional inspection) → EN 10204 3.1 MTC in English and Chinese → optional buyer-witnessed or third-party inspection (SGS, BV, TÜV) → seaworthy packing, bundle marking per heat number, FOB / CFR / CIF from Shanghai, Ningbo, or Qingdao.

For projects that bundle tube, fittings, flanges, gaskets, stud bolts, and industrial valves into a single mill-direct package, QA cost is meaningfully lower and schedule risk collapses to one production plan.

Is GB/T 5310 equivalent to ASME SA-213 / SA-335?

Functionally yes at the chemistry level; most mills can dual-certify to both. The differences are in test methodology, MTC format, and heat-treatment cycle language. Dual certification is the cleanest approach and is available from EZ Steel on request.

What is the maximum size available in GB/T 5310?

OD 16–824 mm, wall 2–65 mm. For very large OD beyond 824 mm the project typically moves to GB/T 14976 (welded stainless) or to plate-rolled seam-welded pipe under ASME SA-672 / SA-691.

Can a mill-direct carbon & carbon alloy steel order ship with third-party inspection?

Yes. SGS, BV, TÜV, Lloyd's Register, and DNV are all commonly used for EZ Steel shipments. The inspector attends hydrotest, NDT, and dimensional inspection, reviews the MTC draft, and signs off on the release — standard procedure for international EPC orders.

Does EZ Steel also supply matching condenser tube and heat exchanger tube?

Yes. The Lishui stainless facility supplies GB/T 13296 stainless heat exchanger tube and condenser tube in austenitic (304/304L/316/316L), duplex (2205/2507) and super-austenitic (254 SMO, AL-6XN) grades, plus copper & nickel alloy tubes for seawater and marine & ship-building condenser service.