GB/T 3091 Q195 is a standard and fully established material specification for manufacturing Spiral Submerged Arc Welded (SSAW) steel pipes [citation:2, citation:6, citation:10]. This combination represents the most basic, entry-level product for low-pressure fluid transmission and general structural applications under the Chinese national standard [citation:2, citation:4].
The designation "GB/T 3091 Q195 Spiral Submerged Arc Pipe" combines the most economical carbon steel grade (Q195) with the spiral welding process for large-diameter, low-cost applications where high strength is not required .
📋 Key Specifications for GB/T 3091 Q195 SSAW Pipe
The table below summarizes the primary specifications for this product, based on comprehensive industry data [citation:2, citation:3, citation:6, citation:10].
| Attribute | Description |
|---|---|
| Standard | GB/T 3091: "Welded steel pipes for low pressure liquid delivery" (latest version: GB/T 3091-2015) [citation:2, citation:4, citation:6]. |
| Scope | Applicable to water, air, heating steam, gas, and other low-pressure fluid transmission [citation:2, citation:3, citation:4, citation:6]. |
| Steel Grade | Q195: The entry-level carbon structural steel grade. The "Q" stands for "屈服强度" (yield strength), and "195" indicates the minimum yield strength in MPa . |
| Base Material Standard | GB/T 700: Carbon Structural Steels [citation:2, citation:6]. |
| Manufacturing Process | Spiral Submerged Arc Welding (SSAW/HSAW) : Formed from hot-rolled steel coil at room temperature, with the weld seam running continuously in a spiral. Welded using double-sided automatic submerged arc welding (inside and outside) [citation:2, citation:6]. |
| Chemical Composition | Per GB/T 700 requirements for Q195. Typically low carbon and manganese content for maximum formability and weldability at the expense of strength. |
| Mechanical Properties (min) [citation:2, citation:3, citation:6] | Yield Strength: 195 MPa (for thickness ≤ 16mm); 185 MPa (for thickness > 16mm) Tensile Strength: 315 MPa Elongation: 15% (for OD ≤ 168.3mm); 20% (for OD > 168.3mm) |
| Typical Size Range [citation:2, citation:6, citation:10] | Outside Diameter: 168 mm to 4064 mm (approx. 6" to 160") Wall Thickness: 5 mm to 50 mm (common range 5-25 mm) Length: 3 m to 18 m standard; up to 50 m available for specific applications |
| Key Testing Requirements [citation:2, citation:3, citation:6] | Chemical analysis; tensile test; flattening test; bend test; hydrostatic test (each pipe); non-destructive testing (ultrasonic or X-ray of weld seam - standard practice). |
| Common Applications [citation:2, citation:3, citation:4, citation:6, citation:10] | Low-pressure water transmission; irrigation systems; drainage lines; ventilation ducts; fencing; temporary pipelines; non-critical structural supports; general utility piping where cost is the primary driver. |
| Certification | Mill Test Certificate typically to EN 10204 Type 3.1 or equivalent, with test results and traceability records . |
📊 GB/T 3091 Grade Comparison
Q195 is the entry-level strength grade in the GB/T 3091 specification. The table below shows its position relative to other common grades [citation:2, citation:3, citation:6]:
| Grade | Yield Strength (MPa) min (t ≤ 16mm) | Tensile Strength (MPa) min | Elongation % (OD > 168.3mm) | Relative Strength vs. Q195 | Typical Application |
|---|---|---|---|---|---|
| Q195 | 195 | 315 | 20 | Baseline | Most economical, non-critical applications |
| Q215 | 215 | 335 | 20 | +10% | Light structural, general purpose |
| Q235 | 235 | 370 | 20 | +21% | General construction - MOST COMMON |
| Q275 | 275 | 410 | 18 | +41% | Higher strength requirements |
| Q345 | 345 | 470 | 18 | +77% | High-strength structural applications |
📏 Dimensional Specifications
GB/T 3091 specifies the following typical tolerances for SSAW pipes [citation:3, citation:7]:
| Parameter | Tolerance |
|---|---|
| Outside Diameter (OD ≤ 508mm) | ±0.75% of specified diameter |
| Outside Diameter (OD > 508mm) | ±1.0% of specified diameter |
| Wall Thickness | ±10% of nominal |
| Straightness (OD > 168.3mm) | ≤ 0.2% of total length |
| Length (fixed lengths) | +100mm / -0mm |
Standard Diameter Range: 168mm to 4064mm (6" to 160") [citation:2, citation:6, citation:10]
🔍 Key Points to Understand
What "GB/T 3091 Q195" Means: This is the Chinese national standard for low-pressure fluid transmission pipes using the most basic carbon steel grade. Q195 has minimum yield strength of 195 MPa and is the most economical steel grade available for pipe manufacturing .
Historical Significance: Q195 was added to GB/T 3091 starting with the 2008 version, which introduced several key changes including adding Q195 grade, incorporating spiral welded pipes, and tightening quality requirements [citation:1, citation:4, citation:5, citation:7, citation:8].
Q195 vs. Q235: Q195 offers approximately 17% lower yield strength than Q235 (195 MPa vs. 235 MPa) and is correspondingly less expensive. It is the most cost-effective choice when minimum strength requirements are very low .
SSAW Advantages for Q195: The spiral welding process is ideal for large-diameter, low-cost Q195 pipes :
Large Diameter Capability: Can economically produce pipes up to 160" diameter
Cost Efficiency: Lowest cost manufacturing method for large diameters
Long Lengths: Up to 50m lengths reduce field joints
🔧 Manufacturing Process for GB/T 3091 Q195 SSAW Pipe
The manufacturing process follows standard SSAW production methods with quality controls suitable for low-strength applications :
Raw Material Preparation: Hot-rolled steel coils meeting Q195 chemistry requirements are leveled, inspected, and edge-milled.
Spiral Forming: The steel strip is continuously formed into a cylindrical shape at a specific helix angle at room temperature .
Submerged Arc Welding: Double-sided automatic submerged arc welding (inside and outside) creates the spiral seam with full penetration [citation:2, citation:6].
Non-Destructive Testing: 100% ultrasonic or X-ray inspection of the weld seam is standard practice.
Hydrostatic Testing: Each pipe individually tested to verify pressure integrity .
Mechanical Testing: Tensile tests, flattening tests, and bend tests to verify properties [citation:2, citation:3].
End Finishing: Ends prepared (plain or beveled) for field welding.
Coating: Optional external coatings (varnish, bitumen, epoxy) and galvanizing available (OD ≤ 508mm) [citation:2, citation:6].
🏭 Applications
GB/T 3091 Q195 SSAW pipes are used in the most cost-sensitive applications [citation:2, citation:3, citation:4, citation:6, citation:10]:
| Application | Description |
|---|---|
| Low-Pressure Water Transmission | Rural water supply, temporary water lines, irrigation systems |
| Drainage Lines | Storm water drainage, culverts, waste water systems |
| Ventilation Ducts | Air handling systems, exhaust ducts, ventilation shafts |
| Fencing and Barriers | Agricultural fencing, temporary barriers, guard rails |
| Temporary Pipelines | Construction site water supply, dewatering lines |
| Structural Applications | Non-critical supports, light structural frames, scaffolding |
📝 Important Considerations
Standard Version: The current version is GB/T 3091-2015 [citation:2, citation:4, citation:6]. When ordering, specify the required version year.
Q195 vs. Higher Grades: Q195 is the most economical grade but has the lowest strength. For most applications requiring even moderate pressure, Q235 is the more common and recommended grade [citation:2, citation:9, citation:10].
Coating Options: Pipes can be supplied with various coatings [citation:2, citation:6, citation:10]:
Galvanized: For corrosion protection (OD ≤ 508mm only) [citation:2, citation:6]
Black (bare): Standard mill finish
Varnish/Anti-rust oil: Temporary protection
Bitumen coating: For buried service
Pressure Limitations: Q195 pipes are suitable only for very low-pressure applications. Always verify design pressure against the material's yield strength.
Complete Specification: When ordering, specify [citation:2, citation:6, citation:10]:
GB/T 3091, Grade Q195, SSAW (spiral welded), Size (OD x WT), Length, End Finish
Standard version: [e.g., GB/T 3091-2015]
Coating requirements: [e.g., bare, galvanized, varnish]
📝 Summary
GB/T 3091 Q195 Spiral Submerged Arc Welded pipes are the most economical, entry-level product for large-diameter, low-pressure fluid transmission and non-critical structural applications under the Chinese national standard [citation:2, citation:4, citation:6]. With minimum yield strength of 195 MPa, these pipes offer the lowest cost solution for applications where strength requirements are minimal .
Available in diameters from 168mm to over 4000mm with wall thicknesses to 50mm and lengths up to 50m, these pipes are produced using the cost-effective SSAW manufacturing process while meeting the requirements of the GB/T 3091 specification [citation:2, citation:6, citation:10].
Q195 is the most basic grade in the GB/T 3091 family, suitable for non-critical, low-pressure applications where cost is the primary driver. For applications requiring even moderate strength, consider upgrading to Q235 – the most common and recommended grade for general service [citation:2, citation:9, citation:10].
When ordering, ensure you clearly indicate the complete standard with version year, grade Q195, manufacturing process (SSAW), required dimensions, and any coating requirements based on your specific application [citation:2, citation:6, citation:10].
