I. Classification of Welded Steel Tubes
i. Classification by welding process
a. Arc-welded steel pipes
Suitable for applications in oil drilling equipment, mechanical manufacturing, and other fields.
b. Resistance-welded steel pipes
Includes high-frequency welding and low-frequency welding.
Among these, ERW carbon steel pipes belong to resistance-welded steel pipes and are widely used in structural and fluid conveyance applications.
c. Gas-welded steel pipes
A traditional process, now largely replaced by arc welding.
d. Furnace-welded steel pipes
Typically used for low-pressure water and gas pipelines, as well as large-diameter LSAW steel pipes for high-pressure oil and gas transportation.
ii. Classification by weld structure
a. Straight-seam welded pipes
Features: Simple process, low cost, and fast production speed. Suitable for small-diameter steel pipes (e.g., DN < 500 mm).
Applications: Commonly used in building structures and low-pressure fluid conveyance (water, gas).
b. Spiral welded steel pipes
Advantages: Higher strength than LSAW steel pipes, enabling the production of large-diameter steel pipes (e.g., DN > 500 mm) using narrow-band steel.
Limitations: Weld length increases by 30% to 100%, with lower production speed.
c. Subcategories
Submerged arc welded pipes:
Classified by pressure rating:
Class A (Q235/16Mn, high pressure);
Class B (Q195/Q235, low pressure).
Double-sided submerged arc welded pipes are commonly used in oil and gas pipelines.
High-frequency welded pipes:
No unified international standard; primarily uses Q235 material.
Suitable for non-pressure applications, such as ERW black steel pipe production.
iii.Classification by functional application
a. General-purpose welded steel pipes
Used for conveying water, gases, and other low-pressure fluids.
Made of Q195A/Q235A material, they must pass hydrostatic pressure and bending tests.
b. Welded galvanized steel pipes
Divided into hot-dip galvanized and electrogalvanized types.
Suitable for humid or corrosive environments.
c. Oxygen blowing welding tubes
Used in steelmaking processes, resistant to high temperatures.
Made of 08~20 steel, some undergo aluminum treatment.
d. Electrical conduit
Thin-walled carbon steel tubes, requiring galvanization or coating treatment.
Used in building electrical distribution systems.
e. Mechanical structural tubes
Including metric welded tubes and special-shaped tubes.
f. Special-industry pipes
Such as transformer cooling pipes and spiral welded pipes.
iv. Classification by end shape
a. Round welded pipes
Highly standardized, with the largest market share.
b. Special-shaped welded pipes
Including square, rectangular, elliptical, and other cross-sections.
Mainly used for frame structures, mechanical components, and special design requirements.
v. Classification by material and standard
| Standard | Application Field | Material |
|---|---|---|
| GB/T 3091 | Low - pressure fluid transmission | Q235 |
| API 5L | Petroleum and natural gas pipelines | L245, etc. |
| GB/T 12771 | Corrosive fluid transmission | 0Cr18Ni11Nb, etc. |
| ASTM A312 | International standard for austenitic stainless steel pipe | 304, 316L, etc. |
II. Welded steel tube material table
| Material Code | Material Name | Chemical Composition (mass fraction, %) | Characteristics | Application Scope |
|---|---|---|---|---|
| Q195 | Low Carbon Steel | C: 0.05-0.12 Mn: 0.20-0.50 P: ≤0.045 S: ≤0.045 |
Low strength, good plasticity, high toughness, excellent welding performance | General low-pressure fluid conveying pipes, building structural components, etc. |
| Q215A | Low Carbon Steel | C: 0.14-0.22 Mn: 0.30-0.60 P: ≤0.045 S: ≤0.050 |
Moderate strength, good welding performance, good machinability | Low-pressure fluid conveying, building structures, mechanical manufacturing, etc. |
| Q235A | Low Carbon Steel | C: 0.14-0.22 Mn: 0.30-0.70 P: ≤0.045 S: ≤0.050 |
Higher strength, good toughness, excellent welding performance | Widely used in construction, machinery, chemical industry, petroleum, and other fields |
| Q235B | Low Carbon Steel | C: 0.14-0.22 Mn: 0.30-0.70 P: ≤0.045 S: ≤0.045 |
Higher strength and toughness, stricter quality control | Important structural components, high-pressure vessels, bridges, etc. |
| Q235C | Low Carbon Steel | C: 0.14-0.22 Mn: 0.30-0.70 P: ≤0.035 S: ≤0.035 |
High strength and toughness, good low-temperature performance, superior quality | Structural components in low-temperature environments, pressure vessels, etc. |
| 16Mn | Low Alloy High Strength Steel | C: 0.12-0.20 Mn: 1.20-1.60 P: ≤0.035 S: ≤0.035 |
High strength, good toughness, excellent welding performance, good low-temperature performance | High-pressure pipelines, bridges, building structures, mechanical manufacturing, etc. |
| Q345 | Low Alloy High Strength Steel | C: 0.12-0.20 Mn: 1.20-1.60 P: ≤0.035 S: ≤0.035 |
High strength, good toughness, excellent welding performance, good low-temperature performance | High-pressure pipelines, bridges, building structures, mechanical manufacturing, etc. |
| 0Cr13 | Stainless Steel | C: ≤0.12 Cr: 12.00-14.00 Mn: ≤1.00 P: ≤0.035 S: ≤0.030 |
Good corrosion resistance, higher strength, magnetic | Food processing, medical devices, chemical equipment, etc. |
| 1Cr17 | Stainless Steel | C: ≤0.12 Cr: 16.00-18.00 Mn: ≤1.00 P: ≤0.035 S: ≤0.030 |
Good corrosion resistance, higher strength, magnetic | Chemical equipment, decorative materials, etc. |
| 00Cr19Ni11 | Stainless Steel | C: ≤0.03 Cr: 17.00-19.00 Ni: 9.00-12.00 P: ≤0.035 S: ≤0.030 |
Excellent corrosion resistance, moderate strength, non-magnetic | Food processing, chemical equipment, medical devices, etc. |
| 1Cr18Ni9 | Stainless Steel | C: ≤0.08 Cr: 17.00-19.00 Ni: 8.00-11.00 P: ≤0.035 S: ≤0.030 |
Good corrosion resistance, moderate strength, non-magnetic | Food processing, chemical equipment, medical devices, etc. |
| 0Cr18Ni11Nb | Stainless Steel | C: ≤0.08 Cr: 17.00-19.00 Ni: 9.00-13.00 Nb: 0.40-0.70 P: ≤0.035 S: ≤0.030 |
Excellent corrosion resistance, moderate strength, non-magnetic, strong resistance to intergranular corrosion | Food processing, chemical equipment, medical devices, etc. |
III. Welded steel tube standard table
| Standard Number | Country/Region | Scope of Application | Main Technical Requirements | Notes |
|---|---|---|---|---|
| GB/T 3091-2015 | China | Welded steel tubes for low-pressure fluid conveyance | Nominal diameter: DN6-DN600 Material: Q195, Q215, Q235, etc. Test methods: Hydrostatic test, bending test, flattening test, etc. Delivery condition: Hot-rolled, cold-rolled |
Widely used for conveying water, gas, air, oil, and other low-pressure fluids |
| GB/T 14291-2006 | China | Welded steel tubes for mine fluid conveyance | Nominal diameter: DN50-DN300 Material: Q235, Q345, etc. Test methods: Hydrostatic test, bending test, impact test, etc. Delivery condition: Hot-rolled |
Used for mine air compression, drainage, gas extraction, etc. |
| GB/T 12770-2008 | China | Welded stainless steel tubes for mechanical structures | Nominal diameter: DN6-DN200 Material: 0Cr13, 1Cr17, 00Cr19Ni11, etc. Test methods: Hydrostatic test, bending test, intergranular corrosion test, etc. Delivery condition: Hot-rolled, cold-rolled |
Used in machinery, automobiles, bicycles, furniture, etc. |
| GB/T 12771-2008 | China | Welded stainless steel tubes for fluid conveyance | Nominal diameter: DN6-DN200 Material: 0Cr18Ni11Nb, 1Cr18Ni9, etc. Test methods: Hydrostatic test, bending test, intergranular corrosion test, etc. Delivery condition: Hot-rolled, cold-rolled |
Used for conveying low-pressure corrosive media |
| ASTM A53 | USA | Welded steel tubes for low-pressure fluid conveyance | Nominal diameter: 1/8 inch - 24 inches Material: Grades A, B, C Test methods: Hydrostatic test, bending test, tensile test, etc. Delivery condition: Hot-rolled, cold-rolled |
Widely used for conveying water, gas, air, oil, and other low-pressure fluids |
| ASTM A500 | USA | Welded steel tubes for structural use | Nominal diameter: 1 inch - 24 inches Material: A500 Grade A, B, C, D Test methods: Tensile test, bending test, impact test, etc. Delivery condition: Hot-rolled, cold-rolled |
Used in building structures, mechanical manufacturing, etc. |
| ASTM A240 | USA | Welded stainless steel tubes | Nominal diameter: 1/8 inch - 24 inches Material: 304, 304L, 316, 316L, etc. Test methods: Hydrostatic test, bending test, intergranular corrosion test, etc. Delivery condition: Hot-rolled, cold-rolled |
Used in chemical, food processing, medical devices, etc. |
| EN 10217-1 | Europe | Seamless and welded steel tubes (non-alloy steel) | Nominal diameter: DN6-DN600 Material: S235JR, S235J2, S235J2G3, etc. Test methods: Hydrostatic test, bending test, tensile test, etc. Delivery condition: Hot-rolled, cold-rolled |
Used for conveying water, gas, air, and other low-pressure fluids |
| EN 10217-2 | Europe | Seamless and welded steel tubes (alloy steel) | Nominal diameter: DN6-DN600 Material: S355J2, S420J2, S460N, etc. Test methods: Hydrostatic test, bending test, impact test, etc. Delivery condition: Hot-rolled, cold-rolled |
Used for high-pressure fluid conveyance, mechanical manufacturing, etc. |
| EN 10217-3 | Europe | Seamless and welded steel tubes (stainless steel) | Nominal diameter: DN6-DN600 Material: 1.4301 (304), 1.4404 (316L), etc. Test methods: Hydrostatic test, bending test, intergranular corrosion test, etc. Delivery condition: Hot-rolled, cold-rolled |
Used in chemical, food processing, medical devices, etc. |
| JIS G 3444 | Japan | Ordinary welded steel tubes | Nominal diameter: DN6-DN600 Material: SS400, SM490, etc. Test methods: Hydrostatic test, bending test, tensile test, etc. Delivery condition: Hot-rolled, cold-rolled |
Used for conveying water, gas, air, and other low-pressure fluids |
| JIS G 3445 | Japan | Welded steel tubes for high-pressure fluid conveyance | Nominal diameter: DN6-DN600 Material: STPG40, STPG45, etc. Test methods: Hydrostatic test, bending test, impact test, etc. Delivery condition: Hot-rolled, cold-rolled |
Used for high-pressure fluid conveyance |
| JIS G 4305 | Japan | Welded stainless steel tubes | Nominal diameter: DN6-DN600 Material: SUS304, SUS316, etc. Test methods: Hydrostatic test, bending test, intergranular corrosion test, etc. Delivery condition: Hot-rolled, cold-rolled |
Used in chemical, food processing, medical devices, etc. |
