ASTM A335 Seamless ferritic alloy steel pipe for high temperature use

ASTM A335 is a standard specification for seamless ferritic alloy steel tubes for high-temperature service. The pipe is suitable for bending, welding, flanging and other forming operations, widely used in electric power, petrochemical, oil refining and other industries, especially suitable for boiler and superheater pipeline and other high temperature and high pressure conditions.

Common ASTM A335 grades include P1, P2, P5, P9, P11, P22, and P91. The chemical composition and mechanical properties of each grade are different.

Chemical composition:

Grade	C（%）	Mn（%）	P（%）	S（%）	Si（%）	Cr（%）	Mo（%）
P1	0.10-0.20	0.30-0.80	≤0.025	≤0.025	0.10-0.50		0.44-0.65
P2	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	≤ 0.15	0.30-0.60	≤0.025	≤0.025	≤0.50	4.00-6.00	0.44-0.65
P9	≤ 0.15	0.30-0.60	≤0.025	≤0.025	0.50-1.00	8.00-10.00	0.44-0.65
P11	0.05-0.15	0.30-0.61	≤0.025	≤0.025	0.50-1.00	1.00 - 1.50	0.44-0.65
P22	0.05-0.15	0.30-0.60	≤0.025	≤0.025	0.50-1.00	1.90 - 2.60	0.87-1.13
P91	0.08-0.12	0.30-0.60	≤0.020	≤0.010	0.20-0.50	8.00 - 9.50	0.85-1.05

Mechanical properties:

Grade	Yield Strength（MPa）	Tensile Strength（MPa）
P1	≥ 205	≥ 380
P2	≥ 205	≥ 380
P5	≥ 205	≥ 415
P9	≥ 205	≥ 415
P11	≥ 205	≥ 415
P22	≥ 205	≥ 415
P91	≥ 415	≥ 585

Application of ASTM A335 pipe

Because of the addition of chromium and molybdenum elements in ASTM A335 pipe, the tensile strength, high temperature resistance and corrosion resistance of the steel pipe are significantly improved. Due to its high temperature and high pressure resistance, ASTM A335 tubes are commonly used in power plants, refineries, petrochemical plants and oilfield services. The fields of application of different grades of steel are also different. The most common uses of P11, P22 and P91 tubes are in the power industry and petrochemical plants, and P5 and P9 tubes are usually used in refineries.

ASTM A335 tube test method

ASTM A335 has strict test requirements for the quality and performance of steel pipes, and the common test methods are as follows:

Hydrostatic test: The curved inner diameter should be 1 inch [25 mm]. Each pipe shall be hydraulically tested, and non-destructive electrical testing may be used optionally during manufacturing.

Ultrasonic test: Through ultrasonic detection of whether there is damage in the pipe body, and to detect whether the element content in the steel pipe meets the specifications.

Hardness test: The hardness of P91 shall not exceed 250 HB/265 HV [25HRC].

Dimensional check

Size range: Nominal pipe diameters (NPS) are available from small to large diameters, with various wall thickness standards such as SCH 40, SCH 80, SCH 160.

Heat treatment requirement

According to different grades and applications of steel pipes need to be subjected to corresponding heat treatment (such as annealing, normalizing, or quenching and tempering).

Grade	Heat treatment method	Heat treatment temperature range
P1	Full annealing or normalizing plus tempering	650 - 700
P2	Normalizing plus tempering	650 - 700
P5	Normalizing plus tempering or quenching plus tempering	675 - 750
P9	Normalizing plus tempering or quenching plus tempering	700 - 780
P11	Normalizing plus tempering	675 - 775
P22	Normalizing plus tempering	675 - 775
P91	Quenching plus tempering	Quenching: 1040 - 1080 Tempering: 730 - 780