A335 P1 / A182 F1
UNS K11522
½Mo carbon-molybdenum grade — the entry chrome-moly for moderate elevated-temperature steam and process piping where plain carbon steel runs out of creep strength.
Alloy Steel — Chrome-Moly & Low-Alloy Grades
Chromium-molybdenum and low-alloy steels for elevated-temperature pressure service, hard-wearing components and high-strength engineering parts.
Alloy Steel — Material Overview
Alloy steel adds chromium, molybdenum, nickel and vanadium to carbon steel to raise creep strength at temperature, hardenability and toughness. The chromium-molybdenum ("chrome-moly") family — P1, P11, P12, P22, P5, P9, P91 and P92 — is the backbone of power-plant, refinery and boiler service, where it resists hydrogen attack and holds strength at temperatures carbon steel cannot.
The low-alloy AISI/SAE grades — 4130, 4140, 4340 and their EN equivalents — are through-hardening steels for shafts, gears, high-strength fasteners and machinery parts. ACERO ALLOYS supplies alloy steel pipes, fittings, flanges, plates, bars and fasteners to ASTM/ASME specifications with mill test certification.
11grades listed
7,850 kg/m³typical density
6product forms
Available Grades
The grades below are the ones most often asked for. Each grade stays on this page — the material-first way to browse.
A335 P11 / A182 F11
UNS K11597 EN / W.Nr. 1.7335
1¼Cr-½Mo grade for steam lines and process piping to about 540 °C — the entry grade of chrome-moly service.
A335 P12 / A182 F12
UNS K11562
1Cr-½Mo grade between P1 and P11 — the standard steam-superheater and process-piping steel for service around 500 – 550 °C.
A335 P22 / A182 F22
UNS K21590 EN / W.Nr. 1.7383
2¼Cr-1Mo grade — the classic refinery and power-plant grade for headers, steam piping and hydrogen service to about 600 °C.
A335 P5 / A182 F5
UNS K41545 EN / W.Nr. 1.7362
5Cr-½Mo grade with resistance to sulphidation and hydrogen corrosion — furnace tubes and refinery hot service.
A335 P9 / A182 F9
UNS K90901
9Cr-1Mo grade for higher-temperature furnace and boiler duty with good sulphidation resistance.
A335 P91 / A182 F91
UNS K91560 EN / W.Nr. 1.4903
Modified 9Cr-1Mo-VNb grade with martensitic microstructure — the modern grade for ultra-supercritical power-plant main steam lines to about 620 °C.
A335 P92 / A182 F92
UNS K92460
9Cr-2W-VNb martensitic grade with boron and nitrogen — higher creep strength than P91 for ultra-supercritical main steam and reheat lines to about 650 °C, with a smaller wall thickness than lower grades.
AISI 4130
UNS G41300 EN / W.Nr. 1.7218
½Cr-½Mo low-alloy steel with good weldability — structural tubing, pressure fittings and automotive/aerospace parts.
AISI 4140 / EN19
UNS G41400 EN / W.Nr. 1.7225
1Cr-½Mo medium-carbon steel with high hardenability — the standard grade for shafts, spindles, bolts and machinery components in the quenched-and-tempered condition.
AISI 4340 / EN24
UNS G43400 EN / W.Nr. 1.6582
Ni-Cr-Mo steel with very high hardenability and toughness in thick sections — heavy-duty shafts, gears and landing-gear-type components.
Available Product Forms
Alloy Steel is offered in the product forms below. Availability varies by grade and size — confirm the exact combination with our sales desk.
Pipes & Tubes
Seamless and welded pipes and tubes to ASTM/ASME, IS and BS specifications — including boiler, air-preheater and corten tubes.
Sheets, Plates & Coils
Hot-rolled and cold-rolled sheets, plates, coils, circles and flats in standard and cut sizes.
Pipe Fittings
Butt-weld, forged and socket-weld fittings — elbows, tees, reducers, caps, stub ends, olets and nipples.
Flanges
Weld neck, slip-on, blind, lap joint, socket weld, threaded, spectacle, ring joint, orifice and deck flanges to ASME B16.5, 150# – 2500#.
Bars, Rods & Wires
Bright and black round bars, square and hex bars, flats and wires in stainless, duplex, alloy, carbon and nickel-alloy grades.
Fasteners
Bolts, nuts, studs, washers and threaded rods in alloy and stainless grades.
Chemical Composition & Mechanical Properties
Chemical composition: nominal ranges as published in the common product standards — indicative and for comparison only. Mechanical properties: typical minimum values for the common product forms in the annealed / solution-treated condition. Always purchase against the current ASTM/EN specification and the mill test certificate.
A335 P1 / A182 F1
| Element | Content |
|---|---|
| Molybdenum (Mo) | 0.44 – 0.65 |
| Carbon (C) | 0.10 – 0.20 |
| Manganese (Mn) | 0.30 – 0.80 |
| Silicon (Si) | 0.10 – 0.50 |
| Phosphorus (P) | ≤ 0.025 |
| Sulphur (S) | ≤ 0.025 |
| Property | Value |
|---|---|
| Tensile strength (min) | 380 MPa |
| Yield strength (min) | 205 MPa |
A335 P11 / A182 F11
| Element | Content |
|---|---|
| Chromium (Cr) | 1.00 – 1.50 |
| Molybdenum (Mo) | 0.44 – 0.65 |
| Carbon (C) | 0.05 – 0.15 |
| Manganese (Mn) | 0.30 – 0.60 |
| Property | Value |
|---|---|
| Tensile strength (min) | 415 MPa |
| Yield strength (min) | 205 MPa |
A335 P12 / A182 F12
| Element | Content |
|---|---|
| Chromium (Cr) | 0.80 – 1.25 |
| Molybdenum (Mo) | 0.44 – 0.65 |
| Carbon (C) | 0.05 – 0.15 |
| Manganese (Mn) | 0.30 – 0.61 |
| Silicon (Si) | ≤ 0.50 |
| Phosphorus (P) | ≤ 0.025 |
| Sulphur (S) | ≤ 0.025 |
| Property | Value |
|---|---|
| Tensile strength (min) | 415 MPa |
| Yield strength (min) | 205 MPa |
A335 P22 / A182 F22
| Element | Content |
|---|---|
| Chromium (Cr) | 1.90 – 2.60 |
| Molybdenum (Mo) | 0.87 – 1.13 |
| Carbon (C) | 0.05 – 0.15 |
| Manganese (Mn) | 0.30 – 0.60 |
| Property | Value |
|---|---|
| Tensile strength (min) | 415 MPa |
| Yield strength (min) | 205 MPa |
A335 P5 / A182 F5
| Element | Content |
|---|---|
| Chromium (Cr) | 4.00 – 6.00 |
| Molybdenum (Mo) | 0.45 – 0.65 |
| Carbon (C) | ≤ 0.15 |
| Property | Value |
|---|---|
| Tensile strength (min) | 415 MPa |
| Yield strength (min) | 205 MPa |
A335 P9 / A182 F9
| Element | Content |
|---|---|
| Chromium (Cr) | 8.00 – 10.00 |
| Molybdenum (Mo) | 0.90 – 1.10 |
| Carbon (C) | ≤ 0.15 |
| Property | Value |
|---|---|
| Tensile strength (min) | 415 MPa |
| Yield strength (min) | 205 MPa |
A335 P91 / A182 F91
| Element | Content |
|---|---|
| Chromium (Cr) | 8.00 – 9.50 |
| Molybdenum (Mo) | 0.85 – 1.05 |
| Vanadium (V) | 0.18 – 0.25 |
| Niobium (Nb) | 0.06 – 0.10 |
| Carbon (C) | 0.08 – 0.12 |
| Property | Value |
|---|---|
| Tensile strength (min) | 585 MPa |
| Yield strength (min) | 415 MPa |
A335 P92 / A182 F92
| Element | Content |
|---|---|
| Chromium (Cr) | 8.50 – 9.50 |
| Molybdenum (Mo) | 0.30 – 0.60 |
| Tungsten (W) | 1.50 – 2.00 |
| Vanadium (V) | 0.15 – 0.25 |
| Niobium (Nb) | 0.04 – 0.09 |
| Nitrogen (N) | 0.03 – 0.07 |
| Boron (B) | 0.001 – 0.006 |
| Carbon (C) | 0.07 – 0.13 |
| Manganese (Mn) | 0.30 – 0.60 |
| Silicon (Si) | ≤ 0.50 |
| Phosphorus (P) | ≤ 0.020 |
| Sulphur (S) | ≤ 0.010 |
| Property | Value |
|---|---|
| Tensile strength (min) | 620 MPa |
| Yield strength (min) | 440 MPa |
AISI 4130
| Element | Content |
|---|---|
| Chromium (Cr) | 0.80 – 1.10 |
| Molybdenum (Mo) | 0.15 – 0.25 |
| Carbon (C) | 0.28 – 0.33 |
| Manganese (Mn) | 0.40 – 0.60 |
| Property | Value |
|---|---|
| Tensile strength (Q&T, typical) | 670 – 900 MPa |
| Yield strength (Q&T, typical) | 435 – 700 MPa |
AISI 4140 / EN19
| Element | Content |
|---|---|
| Chromium (Cr) | 0.80 – 1.10 |
| Molybdenum (Mo) | 0.15 – 0.25 |
| Carbon (C) | 0.38 – 0.43 |
| Manganese (Mn) | 0.75 – 1.00 |
| Property | Value |
|---|---|
| Tensile strength (Q&T, typical) | 850 – 1080 MPa |
| Yield strength (Q&T, typical) | 650 – 950 MPa |
AISI 4340 / EN24
| Element | Content |
|---|---|
| Nickel (Ni) | 1.65 – 2.00 |
| Chromium (Cr) | 0.70 – 0.90 |
| Molybdenum (Mo) | 0.20 – 0.30 |
| Carbon (C) | 0.38 – 0.43 |
| Property | Value |
|---|---|
| Tensile strength (Q&T, typical) | 980 – 1180 MPa |
| Yield strength (Q&T, typical) | 780 – 1000 MPa |
Physical Properties
| Property | Value |
|---|---|
| Density | 7.85 g/cm³ (7850 kg/m³) |
| Thermal conductivity (P22, 100 °C) | ≈ 37 W/m·K |
| Modulus of elasticity | ≈ 200 – 210 GPa |
Industrial Applications
- Power-plant steam piping, headers and boiler tubes (P11–P91)
- Refinery furnace tubes and hot hydrocarbon service
- Hydrogen and sulphidation-corrosion service
- High-strength shafts, gears and machinery parts (4140, 4340)
- High-strength bolting and fasteners
- Pressure-vessel and exchanger components
Applicable Standards
| Standard | Scope |
|---|---|
| ASTM A335 / ASME SA335 | Seamless ferritic alloy-steel pipe for high-temperature service |
| ASTM A234 / ASME SA234 | Piping fittings of wrought carbon and alloy steel |
| ASTM A182 / ASME SA182 | Forged or rolled alloy-steel flanges, fittings and valves |
| ASTM A387 / ASME SA387 | Chromium-molybdenum pressure-vessel plates |
| ASTM A193 B7 / B7M / B16 | Alloy-steel bolting for high-temperature service |
| ASTM A320 | Alloy-steel bolting for low-temperature service |
| EN 10083 | Quenched and tempered steels (EN grades) |
Quality & Documentation
Alloy steel is supplied against ASTM/ASME or EN specifications with EN 10204 Type 3.1 certification, heat-number traceability and, for chrome-moly grades, the applicable hardness and microstructure controls. NDE, impact testing and third-party inspection can be arranged with the enquiry.
Related Engineering Calculators
Pipe Weight Calculator
Theoretical weight of pipe from outside diameter, wall thickness, length and material.
Round Bar Weight Calculator
Theoretical weight of round bars from diameter, length and material.
Sheet & Plate Weight Calculator
Theoretical weight of sheets and plates from length, width, thickness and material.
Technical Flange Calculator
ASME B16.5 dimensions, bolting pattern and weight estimates for 14 flange types.
Unit Conversion Calculator
mm ↔ in, m ↔ ft, kg ↔ t, kg/m ↔ lb/ft and MPa ↔ psi conversions.
Frequently Asked Questions
What does the P-number in A335 grades mean?
The number series (P5, P9, P11, P22, P91) reflects the chromium-molybdenum balance: higher numbers generally mean higher alloy content and higher allowable service temperature — P11 (1¼Cr) to about 540 °C, P22 (2¼Cr) to about 600 °C and P91 (9Cr-VNb) to about 620 °C.
Why is P91 different from other chrome-moly grades?
P91 is a modified 9Cr-1Mo steel with controlled vanadium and niobium. Its martensitic structure and fine precipitates give roughly double the creep strength of P22, allowing thinner walls in ultra-supercritical power-plant piping. It requires careful welding and heat treatment.
What is the difference between AISI 4140 and 4340?
4340 adds about 1.65–2% nickel to the 4140-type Cr-Mo chemistry, giving deeper hardenability and higher toughness in thick sections. 4140 covers most general high-strength parts; 4340 is chosen for heavy-duty shafts and critical components.
What bolting suits alloy-steel flanges?
ASTM A193 Gr. B7 studs with A194 Gr. 2H nuts are the standard pairing for F11/F22 flanges — the recommended combination is shown by our flange calculator.
Can you supply A387 plates in normalized-and-tempered condition?
Plate is normally supplied in the normalized-and-tempered or quenched-and-tempered condition required by the specification. Confirm the wall thickness, class and heat-treatment condition with the enquiry.
Need Alloy Steel Priced?
Send the grade, product form, size and quantity — our sales desk replies with an offer and lead time within one business day.