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.).

Product Tags:

A335 P9 Alloy Steel Pipe ASTM A335/ASME SA335 Gr. P5, P9, P11, P22, P91

Standard: ASTM A335

grade:P1, P2,P5,P9,P11,P91,P92

OD:10.3-660mm

WT:1.6-60mm

Length:5.8m-12m or random legth

Technical: Quenching & Tempering

Application: Gas fire power plant, coal fire power plant, headers and steam lines, Feed water pipes,

super heaters and reheaters.

A335 P9 Alloy Steel Pipe that covers “chrome-moly” seamless pipes with remarkable resistance to

corrosion and good tensile strength at high-temperature service. Generally, ASTM A335 P11, P22,

and P91 pipes are used in power generation and in downstream oil and gas, P5 and P9 grades are

for refinery applications.

How to define alloy pipes?

Alloy pipes are tubular with higher percentages, than standard carbon steel pipes, of alloying elements

as Molybdenum (Mo), Chromium (Cr), Nickel, etc. Actually, the ASTM A335 covers “low-alloy” steel pipes,

i.e. pipes that have a total amount of alloying elements below 5%. The addition of higher percentages of

alloying elements (example Nickel and Chromium) transforms the steel into higher alloys, like stainless steel,

duplex, up to super-alloyed materials like Inconel, Hastelloy, Monel, etc.

Alloy steel pipes are used in the energy industry for high temperature and very low-temperature service

(cryogenic), or for applications with very high pressures.

ASTM A335 alloy steel pipes fit ASTM A234 WPx series buttweld fittings (WP5, WP9, WP91) and A182 Fx

forged fittings and flanges (A182 F5, F9, F11, F22, F91). All these materials have similar chemical and mechanical

properties and can be joined or welded.

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:

1. Aluminum: decreases oxygen from steelmaking

2. Boron: used to produce fine grain size and enhance steel hardness

3. Cobalt: used to enhance the steel’s heat and wear-resistance

4. Manganese: gives better steel hardenability

5. Nickel: Enhances toughness, hardenability and impact strength at low temperatures

6. Silicon: decreases oxygen, enhances hardenability and toughness

7. Titanium: prevents precipitation of chromium carbide

8. Tungsten: refines steel grain size and enhance the steel hardness, especially at high temperatures

9. 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.

CHEMICAL COMPOSITION
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.).

Product Tags:

carbon steel seamless tube

carbon steel seamless pipes

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