ASTM A213 Stainless Steel Tubing: Full Specification Guide
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What Is ASTM A213?
ASTM A213 is the standard specification for seamless ferritic and austenitic alloy-steel boiler, superheater and heat-exchanger tubes. It covers tubes intended for high-temperature and high-pressure service, and is one of the most widely referenced standards for power generation and petrochemical furnace tubing. The specification includes ferritic grades such as T5, T11, T12, T22 and T91, and austenitic stainless grades such as TP304, TP304L, TP316, TP316L, TP321 and TP321H. The ASME edition of the same document is ASME SA213, which is used in code-stamped boiler and pressure vessel work.
A213 tubes are always seamless, which means they are produced from a solid billet without a longitudinal weld, giving them the highest integrity for pressure-retaining duty. The standard also sets out the manufacturing, heat treatment, testing and marking requirements that must be met before the tubing is released for service.
Chemical Composition of Common Grades
The table below shows the composition limits for the austenitic stainless grades most often supplied to A213.
| Grade | C, max | Mn, max | P, max | S, max | Si, max | Cr | Ni | Mo |
|---|---|---|---|---|---|---|---|---|
| TP304 | 0.08 | 2.00 | 0.045 | 0.030 | 1.00 | 18.0-20.0 | 8.0-11.0 | - |
| TP304L | 0.035 | 2.00 | 0.045 | 0.030 | 1.00 | 18.0-20.0 | 8.0-13.0 | - |
| TP316 | 0.08 | 2.00 | 0.045 | 0.030 | 1.00 | 16.0-18.0 | 11.0-14.0 | 2.00-3.00 |
| TP316L | 0.035 | 2.00 | 0.045 | 0.030 | 1.00 | 16.0-18.0 | 10.0-14.0 | 2.00-3.00 |
| TP321 | 0.08 | 2.00 | 0.045 | 0.030 | 1.00 | 17.0-19.0 | 9.0-12.0 | - |
Mechanical Properties and Solution Annealing
The table below lists the minimum tensile requirements and solution annealing temperatures for the austenitic grades.
| Grade | Tensile, MPa min | Yield, MPa min | Elongation, % min | Hardness, HRB max | Solution temp, C min |
|---|---|---|---|---|---|
| TP304, TP316 | 515 | 205 | 35 | 90 | 1040 |
| TP304L, TP316L | 485 | 170 | 35 | 90 | 1040 |
Austenitic grades are solution annealed at a minimum temperature of 1040 C and then rapidly cooled, so that carbides remain in solution and the material keeps full corrosion resistance.
Manufacturing Process and Dimensional Tolerances
The manufacturing sequence for A213 seamless tubing consists of heating the round billet, piercing, sizing, cold drawing or cold rolling, solution annealing, straightening, inspection and packaging. Dimensional tolerances depend on whether the tube is hot-finished or cold-finished. For cold-drawn tubes, the outside diameter tolerance is plus or minus 0.10 mm for diameters below 25 mm, plus or minus 0.15 mm for 25 to 40 mm, and up to plus or minus 0.38 mm for diameters between 75 and 100 mm; wall thickness tolerance is plus 20 percent for tubes up to 38.1 mm outside diameter and plus 22 percent above that, with no minus tolerance. Hot-finished tubes allow wider variation, for example plus 0.4 mm and minus 0.8 mm on outside diameter for tubes up to 100 mm.
Heat Treatment Procedures
Ferritic alloy grades such as T5, T11, T22 and T91 are normally normalized and tempered; for example grade T91 requires a normalizing temperature above 1040 C followed by tempering above 730 C to develop the required creep strength. Austenitic stainless grades are solution annealed above 1040 C and rapidly cooled, as described above. The heat treatment must be recorded on the mill certificate so that the thermal history of the tube is fully traceable.
Inspection and Applications
Inspection requirements under A213 include chemical analysis, tensile testing, hardness testing, flattening, flaring and hydrostatic or non-destructive electric testing. Tubes are primarily used in boilers, superheaters and heat exchangers in power plants, in petrochemical furnaces, in refinery heater tubes, and in process coolers and condensers where the combination of temperature, pressure and corrosive media demands a seamless product with verified properties.
Frequently Asked Questions
What is the difference between ASTM A213 and ASME SA213?
They are the same specification: ASME SA213 is the edition adopted into the ASME Boiler and Pressure Vessel Code. The requirements are identical, and SA213 is referenced when the tubing is used in code-stamped equipment.
Is A213 tubing available in welded form?
No. A213 covers only seamless tubing. Welded and welded-and-cold-drawn tubing for general service is covered by other specifications such as A249 and A688.
Why are the low carbon grades TP304L and TP316L used?
The lower carbon limit prevents chromium carbide precipitation at grain boundaries during welding, so the heat-affected zone keeps its corrosion resistance without post-weld heat treatment.
What is the difference between TP321 and TP304H?
TP321 is stabilised with titanium, which prevents sensitisation and gives good resistance to intergranular corrosion and creep strength in the 500 to 900 C range; TP304H is a higher-carbon version of TP304 with improved high-temperature strength but no stabilising element.
What tests are mandatory before A213 tubing is shipped?
The standard requires chemical analysis, tensile and hardness testing, flattening and flaring tests, and hydrostatic or non-destructive electric testing, all documented on the mill certificate with the heat number.
