A335 P91 Pipes

A335 P91 Pipes

Standard: ASTM A335 Standard Specification for Seamless Ferritic Alloy-Steel Pipe for High-Temperature Service;
Size Range: OD: 88.9~1422mm (3''~56''); WT: 2.11~140mm (Sch10 and above);
Tensile Strength min.: 85ksi / 585MPa
Yield Strength min.: 64ks / 415MPa

Product Details

P91 pipe is a kind of chrome moly pipes lsted in ASTM A335, a standard in the power generation industry and the petrochemical industry. We have the most advanced manufacturing technology. Our piercing and rolling technology possesses a number of patents in designing and manufacturing the equipment, and has improved in lots of areas targeting better performance and efficiency.

1. Reference Documents

ASTM A999/A 999M Specification for General requirements for Alloy and Stainless Steel Pipe.

ASTM E 213 Practice for Ultrasonic Examination of metal Pipe and Tubing

ASTM E 309 Practice for Eddy-Current Examination of Steel Tubular Products Using Magnetic Saturation

ASTM E 381 Method of Macroetch testing Steel Bars, Billets, Blooms, and Forgings

ASTM E 570 Practice for Flux Leakage Examination of Ferromagnetic Steel Tubular Products

ASME B26.10M Welded and Seamless Wrought Steel Pipe

2. Manufacture

Hot Rolled for 8'' and above or Cold Drawn for 6'' and below


3. Manufacturing Process

Raw Material Inspection → Cold Centering → Heating → Piercing & Rolling → SIzing → Heat Treatment → Testing → Finishing → NDE → Visual & Dimension Inspection → Marking → Storing & Shipping


4. Supplementary Requirements

S1. Product Analysis

S2. Transverse Tension Tests

S3. Flattening Test

S4. Metal Structure and Etching Tests

S5. Photomicrographs

S6. Photomicrographs for Individual Pieces

5. Chemical Requirements

Chemical Requirements



Composition, %
P91K915600.08-0.120.30-0.600.0200.0100.20-0.508.00-9.500.85-1.05V 0.18-0.25
N 0.030-0.070
Ni 0.40max
Al 0.02max
Cb 0.06-0.10
Ti 0.01 max
Zr 0.01max

6. Heat Treatment
Normalizing for all product forms shall be performed within the temperature range of 1040-1080°C. Once the surface temperature of the component has exceeded 1040°C, the minimum time at temperature shall be specified in the table below.
The product shall be air cooled outside of the furnace and away from any source of heat or other conditions that would retard the rate of cooling or cause non-uniform cooling. Cooling shall be continuous down to at least 95°C at the metal surface before tempering.
The rate of cooling shall be at least 5°C/min from the normalization temperature to 600°C. Note that for components greater in wall thickness than 75mm, forced air-cooling or oil quenching or the equivalent from the normalizing temperature to a surface metal temperature below 600°C may be necessary to achieve the required mechanical properties.

Section or Wall ThicknessMinimum Hold Period After Metal Surface Temperature has Exceeded 1040°C
≤50mm (2 inch)10 minutes
>50mm (2 inch), ≤75mm (3 inch)30 minutes
>75mm (3 inch), ≤100mm (4 inch)45 minutes
>100mm (4 inch), ≤125mm (5 inch)75 minutes
>125mm (5 inch), ≤150mm (6 inch)90 minutes

Tempering for all product forms is to be performed within the temperature range of 770-790°C. Time at the tempering temperature shall be at least one hour per 25mm of thickness, with a minimum tempering time of 10 minutes. The product may be furnace cooled or cooled in still air from the tempering temperature, so long as excessive distortion, excessive thermal stresses, and over-tempering are avoided.