ASTM A335 ALLOY STEEL SEAMLESS PIPE
ASTM A335 is often called as chrome moly pipe because of the chemical contain of Molybdenum (Mo) and Chromium (Cr). Molybdenum increases the strength of steel and Chromium (or chrome) is the essential constituent of stainless steel. The composition chrome moly alloy steel pipe make it ideal for use in power plants, refineries, petro chemical plants, and oil field services where fluids and gases are transported at extremely high temperatures and pressures.
- Strong resistance to rupturing at high temperatures and high pressures
- May be used for Hydrogen Sulfide Corrosion Services
- Resistant to cracking from hydrogen attack and embrittlement
- Resistant to hot sulfide corrosion cracking
- Can be used for NACE Applications where sour environments are under high temp and pressure
- Can be used in NACE-MRO 175 Sour Service
- Ideal for creep rupture applications
- Can handle high temperatures with very low elasticity
CHEMICAL COMPOSITION OF ASTM A335 ALLOY STEEL SEAMLESS PIPE
The types of alloy steel covered by the ASTM A335 – ASME SA335 specification are designed with a “P” prefix, from P5 to P92. Grades P11/P22 and P91/92 are typically found in power stations, whereas grade P5 and P9 are more common for application in the petrochemical industry. Grades P9, P91 are, in the list, the more expensive (a P91 seamless pipe may cost approx 5€ per kg.).
| ASTM A335 Low-Alloy Steel (Grades) |
UNS equivalent |
C≤ | Mn | P≤ | S≤ | Si≤ | Cr | Mo |
| P1 | K11522 | 0.10~0.20 | 0.30~0.80 | 0.025 | 0.025 | 0.10~0.50 | – | 0.44~0.65 |
| P2 | K11547 | 0.10~0.20 | 0.30~0.61 | 0.025 | 0.025 | 0.10~0.30 | 0.50~0.81 | 0.44~0.65 |
| P5 | K41545 | 0.15 | 0.30~0.60 | 0.025 | 0.025 | 0.5 | 4.00~6.00 | 0.44~0.65 |
| P5b | K51545 | 0.15 | 0.30~0.60 | 0.025 | 0.025 | 1.00~2.00 | 4.00~6.00 | 0.44~0.65 |
| P5c | K41245 | 0.12 | 0.30~0.60 | 0.025 | 0.025 | 0.5 | 4.00~6.00 | 0.44~0.65 |
| P9 | S50400 | 0.15 | 0.30~0.60 | 0.025 | 0.025 | 0.50~1.00 | 8.00~10.00 | 0.44~0.65 |
| P11 | K11597 | 0.05~0.15 | 0.30~0.61 | 0.025 | 0.025 | 0.50~1.00 | 1.00~1.50 | 0.44~0.65 |
| P12 | K11562 | 0.05~0.15 | 0.30~0.60 | 0.025 | 0.025 | 0.5 | 0.80~1.25 | 0.44~0.65 |
| P15 | K11578 | 0.05~0.15 | 0.30~0.60 | 0.025 | 0.025 | 1.15~1.65 | – | 0.44~0.65 |
| P21 | K31545 | 0.05~0.15 | 0.30~0.60 | 0.025 | 0.025 | 0.5 | 2.65~3.35 | 0.80~1.60 |
| P22 | K21590 | 0.05~0.15 | 0.30~0.60 | 0.025 | 0.025 | 0.5 | 1.90~2.60 | 0.87~1.13 |
| P91 | K91560 | 0.08~0.12 | 0.30~0.60 | 0.02 | 0.01 | 0.20~0.50 | 8.00~9.50 | 0.85~1.05 |
| P92 | K92460 | 0.07~0.13 | 0.30~0.60 | 0.02 | 0.01 | 0.5 | 8.50~9.50 | 0.30~0.60 |
MECHANICAL PROPERTIES OF ASTM A335 ALLOY STEEL SEAMLESS PIPE
| Hardness | ||||||
| A335 Low-Alloy Pipe | UNS Number | Yield Strength ksi | Tensile Strength ksi | Elongation % | Rockwell | Brinell |
| P1 | K11522 | 30 | 55 | 30 | – | – |
| P2 | K11547 | 30 | 55 | 30 | – | – |
| P5 | K41545 | 40 | 70 | 30 | – | 207 max |
| P9 | S50400 | 30 | 60 | 30 | – | – |
| P11 | K11597 | 30 | 60 | 20 | – | – |
| P12 | K11562 | 32 | 60 | 30 | – | 174 max |
| P22 | K21590 | 30 | 60 | 30 | – | – |
| P91 | K91560 | 60 | 85 | 20 | – | – |
HEAT TREATMENT
Alloy Steel pipe are heat treated to achieve mechanical properties as per the desired alloying element. Below are some of the types of heat treatment.
- Normalize Quench and Tempering
- Quench and Tempering
- Normalizing & Hardening
TESTING REQUIREMENTS
- Transverse/longitudinal: tension and flattening, hardness, bend tests- for material which has been heat-treated in batch furnaces, these tests shall be made on the 5% of the pipes from each heat lot number. For smaller lots, one pipe at a minimum has to be tested
- ASTM A335 Gr. P91 shall have a hardness of 250 HB / 265 HV (25 HRC)
- Hydro testing: shall be applied to every length of pipe
- The non-destructive electric test is optional
TOLERANCES
DIAMETER
| A335 Pipe | Over | Under | ||
| NPS [DN] | in. | mm | in. | mm |
| 1/8 to 1 1/2 / DN 6 to 40 | 1/64 (0.015) | 0.4 | 1/64 (0.015) | 0.4 |
| Over 1 1/2 to 4 / DN 40 to 100 | 1/32 (0.031) | 0.79 | 1/32 (0.031) | 0.79 |
| Over 4 to 8 / DN 100 to 200 | 1/16 (0.062) | 1.59 | 1/32 (0.031) | 0.79 |
| Over 8 to 12 / DN 200 to 300 | 3/32 (0.093) | 2.38 | 1/32 (0.031) | 0.79 |
| Over 12 / > DN 300 | +/- 1% of the specified outside diameter | |||
WALL THICKNESS
The tolerances in WT, in %, from specified are:
- 1/8 to 2 1/2 [6 to 65] incl., all t/D ratios: over 20%, under 12.5%
- Above 2 1/2 [65], t/D < or = 5%: over 22.5%, under 12.5%
- Above 2 1/2 [65], t/D > 5%: over 15%, under 12.5%
t = Specified Wall Thickness; D = Specified Outside Diameter)
