Past about 425°C, carbon steel starts giving its strength back, and that is the exact address where chrome moly lives. Metinox Overseas is an alloy steel pipes manufacturer and supplier in Mumbai, stocking ASTM A335 seamless chrome moly in grades P11 and P22 with P5, P9 and P91 against order, shipping to power and refinery buyers across India, the USA, the Middle East and Africa with 3.1 certification on every heat. The chromium buys oxidation resistance, the molybdenum buys creep strength, and together they carry steam lines that would slowly stretch carbon steel apart. The full catalogue sits under Pipes & Tubes.
Two neighbours to know before ordering. The tube side of this same family, the T-grades that live inside boilers, is covered on Alloy Steel Tubes. And below the temperature threshold, Carbon Steel Pipes & Tubes does the job for less; nobody should pay for chromium the service never uses.
Table of content
- The A335 P-Grade Ladder
- Chrome Moly Pipe Chemistry
- Alloy Steel Pipe Mechanical Properties
- Alloy Steel Pipes Products
- Welding Chrome Moly: The Honest Part
- AS Pipe Sizes, Schedules & Companion Grades
- Alloy Steel Pipe Applications
- AS Testing, Certification, IBR & Export to USA, Middle East & Africa
- Explore Related Ranges
- Alloy Steel Pipes: Frequently Asked Questions
The A335 P-Grade Ladder
The grades are rungs on a temperature ladder, and each rung is priced accordingly. Climb only as high as the metal temperature demands.
| Grade | Nominal Alloy | Climbs to (typical design zone) | Where it gets specified |
|---|---|---|---|
| P1 / P12 | C-0.5Mo / 1Cr-0.5Mo | The first step past carbon steel | Moderate-temperature steam and process lines |
| P11 | 1.25Cr-0.5Mo | Main steam and hot reheat into the mid-500s °C | The mainstay of Indian and African power plants |
| P22 | 2.25Cr-1Mo | A step above P11 in both creep and hydrogen duty | High-pressure steam, hydroprocessing lines |
| P5 / P9 | 5Cr-0.5Mo / 9Cr-1Mo | Refinery heater and transfer duty | Furnace outlets and sulfur-bearing refinery streams |
| P91 | 9Cr-1Mo-V-Nb | The 600°C class, where P22 runs out | Supercritical boilers, HRSGs, main steam on modern units |
Where the enemy is corrosion rather than temperature, the ladder is the wrong tool; that decision belongs to Stainless Steel Pipes and its grade table.
Alloy Steel Pipes Products
Alloy Steel P1 Pipes
Alloy Steel P5 Pipes
Alloy Steel P9 Pipes
Alloy Steel P11 Pipes
Alloy Steel P12 Pipes
Alloy Steel P22 Pipes
Alloy Steel P91 Pipes
Alloy Steel P92 Pipes
Welding Chrome Moly: The Honest Part
Every grade on this page is air-hardenable to some degree, so the weld rules are not suggestions. Preheat before the arc strikes, matching filler, and post weld heat treatment after it stops; skip the PWHT on P11 or P22 and the joint carries a hard, brittle zone into service. P91 is stricter again: its performance lives in a precise tempered martensite structure, so interpass temperatures, PWHT windows and even dissimilar-metal joints to austenitic pipe are engineered decisions, not site improvisations. None of this is a reason to avoid the family. It is the reason to buy it from people who will say it out loud before the order, not after the first cracked joint.
Alloy Steel Pipe Applications
- Power Generation: main steam, hot reheat and header piping across Indian and African utility projects.
- HRSG & Combined Cycle: P91 where the 600°C class earns its fabrication discipline.
- Refining: P5 and P9 furnace and transfer lines on Gulf and Indian sites.
- Fertilizer & Petrochemical: hydrogen and high-temperature process duty where P22 holds the line.
AS Testing, Certification, IBR & Export to USA, Middle East & Africa
Pipes are hydrostatically tested or NDE examined per A335, with hardness checks where the grade demands them and transverse or longitudinal tensiles per lot. Every order ships with an EN 10204 3.1 mill test certificate, heat-number traceable, with IBR Form III-A certification arranged for boiler duty in India and 3.2 witnessing through BV, SGS or TUV for project specs. Metinox Overseas is ISO 9001 and PED certified; the program is on our Quality Policy page. Export consolidations run from Mumbai to the USA, the Middle East and Africa, bundled and end-protected per Packing and Dispatch. Ex-stock dispatches in 7 to 14 working days; made-to-order grades take 4 to 6 weeks.
Explore Related Ranges
- Alloy Steel Tubes – the T-grades that live inside the boiler
- Carbon Steel Pipes & Tubes – the economical floor of the ladder
- Stainless Steel Pipes – when corrosion, not temperature, is the enemy
- Pipes & Tubes – the full catalogue, one level up
Alloy Steel Pipes: Frequently Asked Questions
One rung of the ladder. P11 carries 1.25 percent chromium and half a percent molybdenum; P22 roughly doubles both, buying more creep strength and better hydrogen service. P11 covers most conventional power piping; P22 takes over where pressure and temperature climb past it. Price follows the alloy content.
Because its strength lives in a precise heat-treated microstructure: normalized at 1040 to 1080 degrees C and tempered at 730 to 800. Weld it or heat it outside the rules and the creep strength you paid for quietly disappears while the pipe looks fine. P91 rewards discipline and punishes improvisation, so the fabrication spec matters as much as the material spec.
Yes. For boiler and steam service under the Indian Boiler Regulations, A335 material ships with IBR Form III-A certification arranged at order stage. State IBR in the enquiry and the paperwork is priced in from the start.
Yes, on regular consolidations from Mumbai, with the 3.1 documentation and any IBR or 3.2 papers travelling with the cargo. Gulf refinery orders clear on our existing approvals, and African utility shipments are bundled and end-protected for the inland leg.
When sustained metal temperature passes roughly 425 degrees C, where carbon steel loses strength and long exposure risks graphitization. Below that line, carbon steel is the better money; above it, the P-grade ladder starts. Quote both boundaries in the enquiry and the grade picks itself.
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