ASTM A213 / A213M — Seamless Alloy Steel and Stainless Steel Boiler, Superheater and Heat-Exchanger Tubes
ASTM A213/A213M (latest edition: A213M-22a) is the primary specification for seamless tubes used in boilers, superheaters, and heat exchangers at elevated temperatures and pressures. ASME SA-213 is adopted in BPVC Section II Part A. A213 covers two broad grade families: ferritic and martensitic Cr-Mo alloy steels (T-designations) and austenitic stainless steels (TP-designations), together spanning service temperatures from ambient to over 650 °C.
1. Scope and Related Standards
| Standard |
Scope |
| ASTM A213 / ASME SA-213 |
Seamless ferritic and austenitic alloy steel boiler, superheater, and heat-exchanger tubes |
| ASTM A335 / ASME SA-335 |
Seamless ferritic alloy steel pipe for high-temperature service (T11→P11, T22→P22, T91→P91) |
| ASTM A312 / ASME SA-312 |
Seamless and welded austenitic stainless steel pipe (TP grades, same alloys as A213) |
| ASTM A269 / ASME SA-269 |
Seamless and welded austenitic SS tubing for general service (companion light-gauge tube spec) |
| ASTM A789 / ASME SA-789 |
Seamless and welded duplex stainless steel tubing |
2. Grade Families
Family 1: Ferritic and Martensitic Cr-Mo Alloy Steel Grades (T-series)
| Grade |
UNS No. |
Alloy |
Max Service Temp. |
Key Application |
| T5 |
K41545 |
5 Cr – ½ Mo |
650 °C |
Refinery heater tubes, high-temperature corrosive gas |
| T9 |
S50400 |
9 Cr – 1 Mo |
650 °C |
Refinery, high-temperature oxidising atmospheres |
| T11 |
K11597 |
1¼ Cr – ½ Mo |
580 °C |
Boiler superheater and reheater tubes |
| T22 |
K21590 |
2¼ Cr – 1 Mo |
620 °C |
High-temperature/high-pressure superheater headers |
| T91 |
K91560 |
9 Cr – 1 Mo – V – Nb – N |
650 °C |
USC boiler superheater, reheater, main steam lines |
| T92 |
K92460 |
9 Cr – 0.5 Mo – 1.8W – V – Nb – B |
650 °C |
A-USC boilers; superior creep to T91 above 600 °C |
| T122 |
K91271 |
11 Cr – 0.4 Mo – 2W – Cu – V – Nb – N |
650 °C |
Advanced A-USC boilers; highest ferritic grade creep strength |
Family 2: Austenitic Stainless Steel Grades (TP-series)
| Grade |
UNS No. |
Key Feature |
Max Service Temp. |
| TP304 |
S30400 |
18Cr-8Ni; general purpose austenitic |
800 °C |
| TP304H |
S30409 |
C 0.04–0.10%; higher creep strength than 304 |
816 °C |
| TP316 |
S31600 |
16Cr-12Ni-2Mo; corrosion + moderate high-temp |
800 °C |
| TP316H |
S31609 |
C 0.04–0.10%; BPVC high-temperature creep credit |
816 °C |
| TP321 |
S32100 |
Ti-stabilised; no sensitisation 425–900 °C |
816 °C |
| TP321H |
S32109 |
Higher C + grain size control; maximum creep strength |
816 °C |
| TP347 |
S34700 |
Nb+Ta stabilised; higher creep than 321 |
816 °C |
| TP347H |
S34709 |
Higher C (0.04–0.10%); ASME highest allowables for stabilised grades |
816 °C |
| TP310S |
S31008 |
25Cr-20Ni; outstanding oxidation resistance >900 °C |
1100 °C (oxidation) |
3. Chemical Composition — Ferritic Grades
| Grade |
C |
Mn max |
Cr |
Mo |
Others |
| T11 |
0.05–0.15 |
0.60 |
1.00–1.50 |
0.44–0.65 |
Si 0.50–1.00 |
| T22 |
0.05–0.15 |
0.60 |
1.90–2.60 |
0.87–1.13 |
Si ≤0.50 |
| T91 |
0.08–0.12 |
0.60 |
8.00–9.50 |
0.85–1.05 |
V 0.18–0.25, Nb 0.06–0.10, N 0.03–0.07, Al ≤0.02 |
| T92 |
0.07–0.13 |
0.60 |
8.50–9.50 |
0.30–0.60 |
W 1.50–2.00, V 0.15–0.25, Nb 0.04–0.09, B 0.001–0.006 |
4. Mechanical Properties
| Grade |
UTS min (MPa) |
YS min (MPa) |
Elong. min (%) |
Hardness max |
| T11 |
415 |
205 |
30 |
163 HBW |
| T22 |
415 |
205 |
30 |
163 HBW |
| T91 |
585 |
415 |
20 |
265 HBW (min 196) |
| T92 |
620 |
440 |
20 |
265 HBW (min 196) |
| TP304H / TP316H |
515 |
205 |
35 |
192 HBW |
| TP321H / TP347H |
515 |
205 |
35 |
192 HBW |
5. Heat Treatment Requirements
| Grade |
Required Condition |
Temperature (°C) |
Notes |
| T11 / T22 |
Full anneal or N+T |
900–960 / temper 650–780 |
Subcritical anneal also permitted |
| T91 / T92 |
Normalize + Temper (mandatory) |
1040–1080 / temper 730–800 |
Hardness 196–265 HBW mandatory; no anneal permitted |
| TP304H / TP316H |
Solution anneal |
1040–1150 |
Grain size requirement: ASTM No. 7 or coarser for TP304H in ASME service |
| TP321H / TP347H |
Solution anneal + stabilise |
SA: 1040–1150; stabilise: 845–900 |
Stabilising anneal maximises Ti/Nb carbide precipitation for high-temperature service |
Grain size note (austenitic H-grades): For TP304H, TP321H, TP347H used in ASME BPVC high-temperature service, a minimum grain size of ASTM No. 7 (or coarser) is often specified. Coarser grain improves creep resistance at elevated temperatures. The solution-anneal temperature must be sufficient to achieve this grain size — lower anneal temperatures (close to 1040 °C) may produce finer grains. Specify grain size in purchase order when required by BPVC design.
6. Testing Requirements
| Test |
Requirement |
| Tensile |
One per heat or heat-treatment lot |
| Hardness |
Each tube for T91/T92 (HBW window 196–265); spot check for other grades |
| Hydrostatic or NDE |
Each tube — hydrostatic or ET (eddy current) as agreed |
| Flattening (ferritic) |
Flattening test per A213 for T11/T22 to check for lack of fusion in welded rounds used as starting stock |
| Grain size (TP H-grades) |
ASTM E112 — when specified; typically for BPVC superheater applications |
7. Grade Selection Guide — Temperature vs Grade
| Service Temperature |
Recommended Grade |
Reason |
| Up to 425 °C |
T11, ASTM A106 Gr.B (carbon steel) |
Carbon steel sufficient; T11 for slightly corrosive media |
| 425–580 °C |
T11, T22, TP304H / TP316H |
Cr-Mo for low cost; 304H/316H for corrosion + creep |
| 580–620 °C |
T22, T91, TP321H, TP347H |
T91 for low weight; TP321H/347H for corrosion resistance |
| 620–650 °C |
T91, T92, TP347H, TP347HFG |
T92 best ferritic creep above 620 °C; TP347HFG austenitic option |
| >650 °C (oxidising) |
TP310S, TP310H |
25Cr-20Ni for oxidation resistance; creep is secondary |
8. How to Order
| # |
Item |
Example |
| 1 |
Standard |
ASTM A213M-22a or ASME SA-213 |
| 2 |
Grade |
T91 or TP347H |
| 3 |
OD × Wall |
50.8 mm OD × 5.0 mm wall (or inch equivalent) |
| 4 |
Length |
6 m random or 12 m fixed |
| 5 |
Heat treatment |
Normalized + Tempered (T91 mandatory) |
| 6 |
Test |
Hydrostatic test + hardness 100% (T91) |
| 7 |
Certificate |
EN 10204 3.1 MTR |
HT PIPE supplies ASTM A213 boiler tubes in T11, T22, T91, TP304H, TP316H, TP321H, and TP347H grades with full EN 10204 3.1 traceability.
9. Frequently Asked Questions
Q1: Can T91 boiler tubes be annealed instead of normalized + tempered?
No. ASTM A213 and ASME SA-213 explicitly require T91 (and T92) to be normalized at 1040–1080 °C followed by tempering at 730–800 °C. The normalize + temper cycle is what creates the tempered martensitic microstructure responsible for T91's creep strength. Annealing T91 produces a ferritic/bainitic structure with substantially lower creep strength and is not acceptable for pressure service. The mandatory hardness window (196–265 HBW) is the primary acceptance criterion for correct heat treatment.
Q2: What is the difference between TP347H and TP347HFG?
TP347HFG (Fine Grain) is a proprietary/enhanced version of TP347H with controlled grain size (ASTM grain size 8 or finer) and specific thermo-mechanical processing. TP347HFG is used in ultra-supercritical boiler tubes at 620–700 °C and has higher allowable stress in ASME BPVC than standard TP347H because the finer grain structure promotes better steam-side oxidation resistance and higher creep-fatigue resistance — critical in cycling power plants. Standard A213 TP347H does not specify grain size.
