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.

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

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)

A335 steel pipe Heat Treatment:

A335 pipes shall be reheated and furnished in the full-annealed, isothermal annealed,or normalized and tempered condition. If furnished in the normalized and tempered condition, the minimum tempering temperature for Grades P5, P5b, P9, P21, and P22 shall be1250°F [675°C], the minimum tempering temperature for Grades P1, P2, P11, P12, and P 15 shall be 1200°F [650°C].
 Pipe of Grades P1, P2, and P12, either hot finished or cold drawn, may be given a final heat treatment at 1200°F[650°C] to 1300°F [705°C] instead of heat treatments