ASTM A213 is the standard specification for seamless ferritic and
austenitic alloy-steel boiler, superheater, and heat-exchanger
tubes. Grade : T2, T5, T5b, T5c, T9, T11, T12, T17, T21, T22, T23,
T24, T36, T91, T92, T122, and T911. The tubing sizes and thickness
usually furnished to this specification are 1/8″(3.2 mm) in inside
diameter to 5″(127 mm) in outside diameter and 0.015″ to
0.500″(0.4-12.7 mm) in minimum or average wall thickness. ASTM A213
tubes of custom-diameter may be furnished, provided such tubes
comply with all other requirements of the standard specification.
GRADE
| Standard | Low-Alloy Steel Grade |
| ASTM A213 | T2 T5 T5b T5c T9 T11 T12 T17 T21 T22 T23 T24 T36 T91 T122 T911 |
CHEMICAL COMPOSITION
| Element | C | Mn | Si | P | S | Cr | Mo |
| T2 | 0.10~0.20% | 0.30~0.61% | 0.50~0.81% | 0.025% | 0.025% | 0.50~0.81% | 0.44~0.65% |
| T5 | 0.15% | 0.30~0.60% | 0.50% | 0.025% | 0.025% | 4.0~6.0% | 0.44~0.65% |
| T5b | 0.15% | 0.30~0.60% | 1.00~2.00% | 0.025% | 0.025% | 4.0~6.0% | 0.44~0.65% |
| T5c | 0.12% | 0.30~0.60% | 0.50% | 0.025% | 0.025% | 4.0~6.0% | 0.44~0.65% |
| T9 | 0.15% | 0.30~0.60% | 0.25~1.00% | 0.025% | 0.025% | 8.0~10.0% | 0.90~1.10% |
| T11 | 0.05~0.15% | 0.30~0.60% | 0.50~0.10% | 0.025% | 0.025% | 1.0~1.5% | 0.44~0.65% |
| T12 | 0.05~0.15% | 0.30~0.61% | 0.50% | 0.025% | 0.025% | 0.8~1.25% | 0.44~0.65% |
| T17 | 0.05~0.25% | 0.30~0.61% | 0.15~0.35% | 0.025% | 0.025% | 0.8~1.25% | - |
| T21 | 0.05~0.15% | 0.30~0.60% | 0.50~0.10% | 0.025% | 0.025% | 2.65~3.35% | 0.80~1.06% |
| T22 | 0.05~0.15% | 0.30~0.60% | 0.50% | 0.025% | 0.025% | 1.9~2.6% | 0.87~1.13% |
| T23 | 0.04~0.10% | 0.10~0.60% | 0.50% | 0.03% | 0.010% | 1.9~2.6% | 0.05~0.30% |
| T24 | 0.05~0.10% | 0.30~0.70% | 0.15~0.45% | 0.02% | 0.010% | 2.20~2.60% | 0.09~1.10% |
| T36 | 0.10~0.17% | 0.80~1.20% | 0.25~0.50% | 0.03% | 0.025% | 0.30% | 0.25~0.50% |
| T91 | 0.07~0.14% | 0.30~0.60% | 0.20~0.50% | 0.02% | 0.010% | 8.0~9.5% | 0.85~1.05% |
| T92 | 0.07~0.13% | 0.70% | 0.50% | 0.02% | 0.010% | 8.5~9.5% | 0.30~0.60% |
| T122 | 0.07~0.14% | 0.30~0.60% | 0.50% | 0.02% | 0.010% | 10.0~11.5% | 0.25~0.60% |
| T911 | 0.09~0.13% | 0.30~0.60% | 0.10~0.50% | 0.02% | 0.010% | 8.5~9.5% | 0.09~1.10% |
ALLOYING ELEMENTS
The addition of Molybdenum (“Moly”) increases the strength of the
steel and its elastic limit, enhance the steel resistance to wear,
its impact qualities, and the hardenability. It also improves the
resistance to softening, makes chromium steel less prone to
embrittlement and prevents pitting.
Chromium, a key element also for stainless steel alloys, prevents
steel oxidation at elevated temperatures and increases the
resistance of steel to corrosion. It enhances the tensile, yield, and hardness properties of
low-alloy pipes at room temperatures.
Other alloying elements, present in various degrees in pipes of all
grades are:
- Aluminum: decreases oxygen from steelmaking
- Boron: used to produce fine grain size and enhance steel hardness
- Cobalt: used to enhance the steel’s heat and wear-resistance
- Manganese: gives better steel hardenability
- Nickel: Enhances toughness, hardenability and impact strength at low
temperatures
- Silicon: decreases oxygen, enhances hardenability and toughness
- Titanium: prevents precipitation of chromium carbide
- Tungsten: refines steel grain size and enhance the steel hardness,
especially at high temperatures
- Vanadium: gives steel enhanced fatigue resistance
As mentioned, low-alloy steels have a total amount of alloying
elements below 5%; high alloy steel has a higher percentage of
these elements.
