Product Introduction: Alloy Steel Pipe
Alloy steel pipe is a type of steel tube manufactured from carbon steel, alloy structural steel, or stainless heat-resistant steel through hot-rolling or cold-drawing processes. It is classified by material composition, and its defining characteristic—unlike carbon steel pipe—is the addition of specific alloying elements.
Core Definition:
An alloy steel pipe is a tube made from alloy steel. By adding alloying elements such as chromium (Cr), molybdenum (Mo), vanadium (V), and nickel (Ni), the steel gains enhanced physical and chemical properties.
Key Features:
100% Recyclable: Fully recoverable and reusable, supporting environmental protection and energy-saving policies.
Lightweight & High Strength: The hollow cross-section design makes it lighter than solid steel under equivalent bending/torsional strength — an economical structural material.
High Temperature & Pressure Resistance: Alloying elements like Cr and Mo provide excellent high-temperature strength and oxidation resistance.
Corrosion Resistance: Alloying improves resistance to corrosion in specific media.
By Manufacturing Process:
| Category | Process Description | Typical Product |
|---|---|---|
| Hot-rolled (extruded) seamless pipe | Round billet heated, then pierced, rolled or extruded | Large-diameter thick-wall pipe |
| Cold-drawn (rolled) seamless pipe | Cold-worked based on hot-rolled pipe for higher dimensional accuracy | Small-diameter precision pipe |
By Cross-Section Shape:
Round Pipe: Most common — uniform stress distribution, high fluid delivery efficiency, widely used in fluid transport.
Shaped Pipe: Special cross-sections for specific structural needs.
Relationship Between Alloy Steel Pipe and Seamless Pipe:
Alloy steel pipe is defined by material, while seamless pipe is defined by manufacturing process. Alloy steel pipes are typically produced using seamless processes, but seamless pipes include both alloy and carbon steel types.
Grade designation follows: "Carbon content + Alloy element symbols (with content)"
The first two digits indicate average carbon content (in ten-thousandths of a percent).
Common Material Grades:
| Category | Representative Grades | Main Alloying Elements |
|---|---|---|
| Carbon-Manganese Steel | 16Mn, 20G, 25MnG, 27SiMn | Mn, Si |
| Chromium-Molybdenum Steel | 15CrMo, 12Cr1MoV, 12Cr2Mo, 10CrMo910 | Cr, Mo |
| Cr-Mo-Vanadium Steel | 12Cr1MoV, 12Cr2MoWVTiB | Cr, Mo, V |
| Cr-Mo Steel (ASTM) | T11, T12, T22, T91, T92 | Cr, Mo |
| Chromium Steel | Cr5Mo, Cr9Mo | Cr |
| Superalloy | GH2747, GH4169 | Ni, Cr, Fe |
| Other Alloy Steels | 40Cr, 30CrMo, 35CrMo, 42CrMo | Cr, Mo |
Alloy Content Notation Rule:
If average alloy content < 1.5% → only element symbol (no number)
If ≥ 1.5%, 2.5%, 3.5%... → number (2, 3, 4...) after the symbol
Example: 12Cr1MoV
Average carbon: 0.12%
Chromium: 0.9–1.2%
Mo and V: < 1.5%
GB/T 5310 (Seamless steel tubes for high-pressure boilers):
| Grade | Tensile Strength (MPa) | Yield Strength (MPa) | Elongation (%) |
|---|---|---|---|
| 20G | 410–550 | ≥245 | ≥24 |
| 15CrMoG | 440–640 | ≥235 | ≥21 |
| 12Cr1MoVG | 470–640 | ≥255 | ≥21 |
| 12Cr2MoG | 450–600 | ≥280 | ≥20 |
| 12Cr2MoWVTiB | 540–735 | ≥345 | ≥18 |
ASME SA213 (Boiler pressure vessel code):
| Grade | Tensile Strength (MPa) | Yield Strength (MPa) | Hardness (HB) |
|---|---|---|---|
| T11 | ≥415 | ≥205 | ≤163 |
| T22 | ≥415 | ≥205 | ≤163 |
| T91 | ≥585 | ≥415 | ≤250 |
| T92 | ≥620 | ≥440 | ≤250 |
| Standard | Title | Application |
|---|---|---|
| GB/T 8162 | Seamless steel tubes for structural purposes | General structural & mechanical use |
| GB/T 8163 | Seamless steel tubes for fluid transport | Engineering & equipment fluid pipelines |
| GB/T 3087 | Seamless steel tubes for low/medium pressure boilers | Industrial & domestic boilers |
| GB/T 5310 | Seamless steel tubes for high-pressure boilers | Power plant & nuclear boiler pipelines |
| GB/T 6479 | Seamless steel tubes for high-pressure chemical fertilizer equipment | Fertilizer equipment |
| GB/T 9948 | Seamless steel tubes for petroleum cracking | Oil refineries, boilers, heat exchangers |
| GB/T 15062 | Wrought superalloy seamless tubes | Superalloy pipes (effective Mar 1, 2026) |
| YB/T 6122 | Large-diameter corrosion-resistant alloy seamless pipes | OD 219–610mm (effective Jul 1, 2024) |
| ASME SA210 | Seamless steel tubes for boilers & superheaters | US boiler code |
| ASME SA213 | Seamless ferritic & austenitic alloy tubes for boilers | US boiler code |
| DIN 17175 | Seamless steel tubes for heat-resistant service | German standard |
Standard Update:
GB/T 9948-2025 integrates four previous standards (GB/T 9948-2013, GB/T 6479-2013, GB/T 33167-2016, GB/T 24592-2009), applicable to seamless steel tubes for petrochemical furnace tubes, heat exchangers, and pressure pipelines — working pressure ≤ 360 MPa, temperature ≤ 350°C.
Power Industry: High-pressure boilers, superheaters, reheaters in power & nuclear plants
Petrochemicals: Cracking units, heat exchangers, fertilizer equipment, chemical pipelines
Energy Transport: Oil, natural gas, and coal gas transmission pipelines
Mechanical Engineering: Drive shafts, drilling rods, scaffolding, bearing rings
Military: Gun barrels, artillery tubes
General Engineering: Pipelines for water and solid material transport
