I. Welded steel tube classification system
i. Classified according to the welding process
Welding method directly affects the performance and scope of application of steel pipe, mainly divided into the following types:
Electric arc welding pipe: applicable to oil drilling equipment, machinery manufacturing and other fields.
Resistance welding pipe: including high-frequency welding (high efficiency, low cost) and low-frequency welding (specific industrial scenarios).
Gas welded pipe: traditional process, now mostly replaced by arc welding.
Furnace Welded Pipe: Typical applications include low-pressure water and gas pipes and large diameter LSAW pipes for high-pressure oil and gas transportation.
ii. Classification according to weld seam structure
Welded seam form determines the strength and productivity of steel pipe, divided into twomainstream types:
a. Straight seam welded pipe
Characteristics: simple process, low cost, fast production speed, suitable for small diameter steel pipe (e.g. DN < 500 mm).
Applications: building structures, low-pressure fluid transportation (water/gas), etc.
b. Spiral Welded Pipe
Advantages: Higher strength than LSAW pipes, large diameter pipes (e.g. DN > 500 mm) can be produced from narrow strip, high flexibility.
Limitations: 30% to 100% increase in weld length, lower production speed.
Subcategory:
Submerged arc welded pipe: divided into Category A (Q235/16Mn, high pressure) and Category B (Q195/Q235, low pressure) according to pressure level.
High-frequency welded pipe: no uniform international standards, commonly used Q235 material, suitable for non-pressure-bearing scenarios.
iii. Classification by functional use
Different application scenarios have differentiated needs for steel pipe performance, the main types include:
General-purpose welded pipe (black pipe): conveying water, gas and other low-pressure fluids, material Q195A/Q235A, need to pass water pressure and bending test.
Galvanized welded pipe: hot-dip galvanized (high corrosion resistance) and electro-galvanized (low cost), for wet or corrosive environments.
Oxygen blowing welded pipe: high-temperature resistant pipe for steelmaking process, made of 08~20 steel, partially aluminized.
Wire casing: thin-walled carbon steel tubing, to be galvanized or coated, for building power distribution systems.
Mechanical Structural Tubes: including metric welded tubes (OD x wall thickness labeling), roller tubes (conveyor components) and profiled tubes (square/rectangular cross section).
Tubes for special industries: e.g. transformer cooling tubes (subject to flattening/flaring tests), spiral welded tubes (oil and gas long-distance pipelines).
iv. Classification according to end shape
Round welded pipe: high degree of standardization, accounting for the mainstream of the market.
Shaped welded pipe: including square, rectangle, oval, etc., used for building frames, mechanical parts and other special design needs.
v. Classification by material and standard
The global mainstream standard system corresponds to different material requirements:
Carbon steel series:
GB/T 3091: low pressure fluid transportation (Q235).
API 5L: Oil and gas pipeline (L245, etc.).
Stainless steel series:
GB/T 12771: corrosive fluid transportation (0Cr18Ni11Nb, etc.).
ASTM A312: International Standard for Austenitic Stainless Steel Pipe.
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. |
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