Steel Pipe & Tube & Alloy Steel Pipe,GB/T 5310-2023、GB/T 8162、ASTM A335、ASME SA213
1. Product Overview
Alloy steel pipes are seamless pipes manufactured via hot rolling, cold drawing or hot extrusion processes. They take high-quality carbon steel as the base material and are added with alloy elements including Chromium (Cr), Molybdenum (Mo), Nickel (Ni), Manganese (Mn) and Vanadium (V). Compared with ordinary carbon steel pipes, they feature high strength, excellent high-temperature resistance, superior corrosion resistance and good low-temperature toughness. They are widely used in harsh working conditions with high temperature, high pressure and severe corrosion.
2. Material & Chemical Composition
2.1 Functions of Main Alloy Elements
| Alloy Element | Main Functions |
|---|---|
| Chromium (Cr) | Improve oxidation resistance, corrosion resistance and hardenability; form dense oxide film above 600℃ |
| Molybdenum (Mo) | Enhance high-temperature strength and creep resistance, suitable for long-term high-temperature pressure-bearing applications |
| Nickel (Ni) | Optimize low-temperature toughness and corrosion resistance, improve material stability |
| Manganese (Mn) | Boost strength and hardenability, and serve as deoxidizer and desulfurizer |
| Vanadium (V) | Refine grain structure and greatly improve strength and toughness |
| Titanium (Ti) | Stabilize carbides and prevent intergranular corrosion |
| Niobium (Nb) | Increase high-temperature strength and creep resistance |
2.2 Common Steel Grades & Relevant Standards
2.2.1 Domestic Standards (GB)
15CrMoG: Chromium-molybdenum steel, maximum operating temperature ≤550℃, applied to medium-pressure boilers and steam pipelines.
12Cr1MoVG: Chromium-molybdenum-vanadium steel with outstanding high-temperature strength, maximum operating temperature ≤580℃, used for high-pressure boilers and superheaters.
10Cr9Mo1VNb (T91): High-alloy heat-resistant steel, maximum operating temperature ≤625℃, applicable to supercritical boilers and nuclear power pipelines.
Q345D (16Mn): Low-alloy high-strength steel, used for low-temperature pipelines and structural supports.
2.2.2 International Standards (ASTM/ASME)
SA-213 T12 (Equivalent to 15CrMoG), SA-213 T22 (Equivalent to 12Cr2MoG), SA-213 T91
SA335 P11/P12/P22/P91: Seamless ferritic alloy pipes for high-temperature service, outer diameter: 60.3-1067mm, wall thickness: 2-150mm.
3. Product Classification
3.1 By Alloy Content
Low-alloy Steel Pipes: Total alloy content <5%, such as Q345D and 15CrMo. Cost-effective, mainly used for medium and low-pressure boilers and pressure vessels.
Medium-alloy Steel Pipes: Total alloy content ranges from 5% to 10%, represented by 12Cr1MoV. Excellent resistance to high temperature and pressure, widely used in power stations and petrochemical equipment.
High-alloy Steel Pipes: Total alloy content >10%, including T91 and nickel-based alloy pipes. Stable performance under extreme conditions, applied to aerospace and nuclear industries.
3.2 By Production Process
Hot-rolled Seamless Alloy Pipes: Produced by heating pipe billets followed by piercing and rolling. High production efficiency, suitable for large-diameter and thick-walled pipes. Outer diameter: 57-630mm, wall thickness: 3.5-100mm.
Cold-drawn Seamless Alloy Pipes: Formed by cold drawing from hot-rolled pipe blanks. Featured with high dimensional accuracy and smooth surface, ideal for small-diameter and thin-walled pipes. Outer diameter: 10-159mm, wall thickness: 1-20mm.
3.3 By Application
High-pressure Boiler Pipes: Comply with GB/T 5310-2023. Used for boiler drums and superheaters, working pressure ≥9.8MPa, operating temperature: 480-620℃.
Petroleum Cracking Pipes: Applied to high-temperature cracking pipelines in refineries, working temperature: 450-550℃, resistant to hydrogen sulfide corrosion.
High-pressure Chemical Fertilizer Pipes: Used for conveying high-pressure media in chemical fertilizer plants, featuring low-temperature resistance and hydrogen corrosion resistance.
Mechanical Structural Pipes: Applied to engineering machinery and hydraulic systems with high strength and high dimensional precision.
4. Mechanical Properties (Typical Values)
| Steel Grade | Tensile Strength (MPa) | Yield Strength (MPa) | Elongation after Fracture (%) | Operating Temperature |
|---|---|---|---|---|
| 15CrMoG | 440-640 | ≥295 | ≥22 | ≤550℃ |
| 12Cr1MoVG | 470-640 | ≥255 | ≥21 | ≤580℃ |
| T91 | ≥585 | ≥415 | ≥20 | ≤625℃ |
| Q345D | 490-620 | ≥345 | ≥21 | -40℃ ~ 450℃ |
5. Dimensions & Specifications
Outer Diameter: 10-1067mm (Common sizes: 57, 76, 89, 108, 159, 219, 273, 325, 426, 530, 630mm)
Wall Thickness: 1-150mm (Common sizes: 3.5, 4, 6, 8, 10, 12, 14, 16, 20, 25, 30mm)
Length: Standard fixed length 6-12m; custom multiple lengths and short lengths are available.
Tolerance: Outer diameter tolerance ±0.5%~±1%, wall thickness tolerance ±10%~±12.5%; high-precision pipes reach ±5%.
6. Production Process
Pipe Billet Preparation: Adopt high-quality alloy steel ingots or continuous casting billets, inspect surface defects and chemical composition.
Heating: Heat pipe billets in furnace to 1100-1250℃ for uniform plasticity.
Piercing: Process heated billets with piercing mill to form hollow shell pipes.
Rolling / Cold Drawing:
Hot Rolling: Roll shell pipes to control outer diameter and wall thickness.
Cold Drawing: Conduct pickling and phosphating on hot-rolled blanks before cold drawing to improve precision and surface finish.
Heat Treatment: Normalizing plus tempering (for T91), annealing (for 15CrMo) to optimize microstructure and eliminate internal stress.
Finishing: Straightening, cutting, chamfering, non-destructive testing (UT/MT/RT) and surface treatment (anti-rust oil, black paint coating).
Inspection: Dimensional measurement, mechanical property test, hydrostatic test (test pressure ≥10MPa) and chemical composition analysis.
7. Core Advantages
High-temperature Resistance: Long-term operating temperature ranges from 450℃ to 625℃, maintaining stable strength without deformation at high temperature.
High-pressure Resistance: Excellent pressure bearing capacity, maximum working pressure up to 32MPa, suitable for high-pressure vessels and pipelines.
Corrosion Resistance: Resist oxidation, hydrogen sulfide and hydrogen corrosion, fit for corrosive environments in chemical and refining industries.
Good Low-temperature Toughness: Grades like Q345D keep excellent toughness at -40℃ and avoid brittle fracture.
Long Service Life: Stable metallographic structure and fatigue resistance, service life is 2-3 times that of ordinary carbon steel pipes.
8. Application Fields
Power Industry: Supercritical / Subcritical boiler superheaters, reheaters and main steam pipelines.
Petrochemical Industry: High-temperature furnace tubes for cracking, pipelines for hydrogenation units, high-pressure reactors and long-distance oil & gas transmission pipelines.
Coal Chemical Industry: Pipes for high-pressure gasifiers and coal-to-hydrogen plants, resistant to high pressure and hydrogen corrosion.
Machinery Manufacturing: Hydraulic cylinders, high-pressure gas cylinders and structural parts for engineering machinery with high strength and precision.
Shipbuilding Industry: Boiler pipes and high-pressure pipes for power systems, featured with high temperature resistance and impact resistance.
9. Delivery Status & Packaging
Delivery Status: Normalizing + Tempering, Annealing, Quenching and Tempering (per steel grade and customer requirements).
Packaging: Bundled packing (2-5 tons per bundle) with sealed pipe ends and moisture-proof film wrapped outside. Small-diameter pipes are packed in wooden cases; large-diameter pipes are delivered in bulk with anti-rust treatment.
Delivery Cycle: 5-7 working days.
10. Quality Standards & Certifications
Executed Standards: GB/T 5310-2023, GB/T 8162, ASTM A335, ASME SA213
Certifications: ISO9001, CE, API 5L. Material certificates, mechanical property reports and non-destructive testing reports can be provided.
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