Q235B ERW welded round pipes
Q235B ERW Steel Pipe Description
Q235B ERW welded round pipes are straight-seam tubes made from Q235B carbon structural steel, joined by high-frequency electric resistance welding (ERW) and supplied to GB/T 3091 (low-pressure liquid delivery) or GB/T 13793 (longitudinal welded tube). The base steel carries a minimum yield strength of 235 MPa (≤16 mm) and a tensile band of 370–500 MPa, with a guaranteed Charpy impact of 27 J at +20 °C. They are the default choice for building structures, scaffolding, and non-critical low-pressure fluid lines where cost and weldability matter more than pressure rating.
Despite the name sometimes used on the market, Q235B carbon steel ERW pipe is a plain carbon structural steel under GB/T 700-2006 - not an alloy steel. The "Q" denotes the yield strength, "235" the 235 MPa minimum yield for sections up to 16 mm thick, and "B" the quality class that adds a room-temperature impact test. That combination is what makes Q235B the workhorse grade for fabricated and welded structures across China and its export markets.
As a Q235B electric resistance welded pipe, the product starts as hot-rolled strip, is cold-formed into a round profile, and is welded along a single longitudinal seam with no filler metal. GNEE supplies Q235B ERW welded steel pipe in outside diameters from 21.3 mm to 610 mm (DN15–DN600, ¾ in–24 in) and wall thicknesses from 0.6 mm to 20 mm, in lengths of 6 m, 9 m or 12 m, plain-end, beveled, or hot-dip galvanized. Send your OD × wall, quantity and destination.
Technical Specifications
| Parameter | Capability |
|---|---|
| Product form | Q235B ERW welded round pipes (straight-seam, longitudinal weld) |
| Base steel standard | GB/T 700-2006 (carbon structural steel) |
| Pipe standards | GB/T 3091-2015 (low-pressure liquid); GB/T 13793-2016 (longitudinal welded tube) |
| Outside diameter (OD) | 21.3–610 mm (DN15–DN600, ¾ in–24 in) |
| Wall thickness (WT) | 0.6–20 mm |
| Length | 6 m / 9 m / 12 m; cut-to-length on request (up to ~14 m) |
| Ends | Plain end, beveled end, or threaded with coupling |
| Surface / coating | Black (as-rolled), oiled, painted, or hot-dip galvanized (GB/T 13912) |
| Weight | weight = 0.02466 × WT × (OD − WT) kg/m |
| Certification | Mill test certificate per GB/T 2101 / EN 10204 3.1; third-party inspection (SGS, BV) available |
The Q235B ERW pipe OD WT range is 21.3–610 mm outside diameter and 0.6–20 mm wall, covering DN15–DN600. Q235B ERW pipe weight per metre follows the standard formula 0.02466 × WT × (OD − WT) kg/m - a worked example is in the FAQ.
Chemical Composition
The Q235B ERW pipe chemical composition is controlled by GB/T 700-2006 as ladle (heat) analysis maximums. Low carbon and moderate manganese are what give the grade its weldability; tight sulfur and phosphorus keep toughness and weld quality up.
| Element | Q235B (max %) |
|---|---|
| Carbon (C) | 0.20 |
| Silicon (Si) | 0.35 |
| Manganese (Mn) | 1.40 |
| Phosphorus (P) | 0.045 |
| Sulfur (S) | 0.045 |
Mechanical Properties
The Q235B ERW pipe mechanical properties are thickness-dependent for yield and elongation; tensile strength stays in a fixed 370–500 MPa band at every thickness. Because ERW pipe walls are usually ≤20 mm, the 235 MPa / 225 MPa values are the ones most orders design to.
| Property | Value |
|---|---|
| Yield strength, min | 235 MPa (≤16 mm); 225 MPa (16–40 mm); 215 MPa (40–60 mm) |
| Tensile strength | 370–500 MPa (all thicknesses) |
| Elongation, min (A) | 26 % (≤16 mm); 25 % (16–40 mm); 24 % (40–60 mm) |
| Charpy impact (Class B) | ≥27 J at +20 °C (V-notch, longitudinal) |
| Density | 7.85 g/cm³ (0.284 lb/in³) |
Note: some purchasing specs round the 60–100 mm yield band to 215 MPa; the GB/T 700-2006 value is 205 MPa. Confirm the exact band against the mill test certificate for thick-wall orders.
Grade Ladder and Welding Route
Two comparison tables settle the two questions buyers ask most: which Q235 sub-grade, and which welding route.
| Grade | Impact test | Typical use |
|---|---|---|
| Q235A | None | General structures, no toughness requirement |
| Q235B | ≥27 J at +20 °C | Welded structures, most export orders |
| Q235C | ≥27 J at 0 °C | Cold-climate structures |
| Q235D | ≥27 J at −20 °C | Low-temperature structures |
| Route | Size suitability | What it is best at |
|---|---|---|
| ERW (electric resistance welded) | OD ≤610 mm (24 in) | Uniform wall, high dimensional accuracy, low cost, thin-to-medium wall |
| Seamless (SMLS) | All sizes | No longitudinal seam; higher cost, used where seam is unwelcome |
| SAW (LSAW / SSAW) | OD >610 mm, heavy wall | Large-diameter, thick-wall line and structure pipe |
Q235B ERW welded round pipes cover the small-to-medium diameter range; once you exceed about 610 mm OD you move to a submerged-arc route, not to a bigger ERW mill.
Q235B vs S235JR vs ASTM Equivalents
On the process question first: HFW vs ERW is not a real choice - they name the same high-frequency resistance weld, with HFW simply stating the frequency qualification. For export orders the same tube is ordered against different standards. Q235B vs S235JR is usually a non-issue: S235JR (EN 10025-2) has the same 235 MPa yield and the same +20 °C / 27 J impact, so the two are treated as equivalent in most projects. The closest US ASTM A53 equivalent is ASTM A53 Type E Grade B; the closest plate equivalent is ASTM A36/A36M; and JIS G3101 SS400 covers the same strength class.
| Standard | Equivalent grade | Use note |
|---|---|---|
| GB/T 700 / GB/T 3091 | Q235B | Base grade of this page |
| EN 10025-2 / EN 10219 | S235JR | European structural tube; same yield and impact |
| ASTM A53 | Type E Grade B | Closest US pipe-form equivalent |
| ASTM A36 / A36M | A36 | US plate equivalent |
| JIS G3101 | SS400 | Japanese strength-class equivalent |
Applications
Q235B ERW pipe applications cluster in jobs where the pipe carries load or low-pressure media rather than high pressure or temperature. Five fields account for most orders:
Building Structures and Scaffolding
As a Q235B ERW pipe for construction, it is cut, bent and welded into columns, purlins, handrails, guardrails and temporary scaffolding. Its weldability and formability keep fabrication fast and cheap on site.
Low-Pressure Fluid Delivery
Under GB/T 3091, Q235B ERW welded steel pipe carries water, air, and non-critical low-pressure gas. It is not a high-pressure pipeline grade and must be sized by the applicable code rather than treated as a fixed pressure-rated pipe.
Machinery and Equipment Frames
Rollers, conveyor supports, machine bases and agricultural equipment use the tube for its straightness, uniform wall and easy machinability.
Greenhouses, Fences and Furniture Tube
Light-wall Q235B ERW tube is the structural backbone of greenhouses, fences, display racks and tubular furniture where appearance and cost dominate.
Galvanized Outdoor Service
Q235B ERW pipe galvanized by hot-dip zinc (GB/T 13912 / ISO 1461) serves outdoor handrails, streetlight poles and fencing that must resist weathering without painting.
Quality Control and Testing
Chemical and mechanical verification. Each heat is checked against GB/T 700; the mill test certificate records composition and the tensile/impact results.
Hydraulic test. GB/T 3091 requires hydrostatic pressure testing of every pipe (or an agreed NDT substitute).
Nondestructive testing. Eddy-current or ultrasonic inspection of the seam verifies integrity without destroying the pipe.
Dimensional checks. OD, wall thickness and straightness are measured to the supply tolerance before bundling.
Coating inspection. Galvanized orders are checked for coating mass and uniformity per GB/T 13912.
Q235B ERW Pipe
Send your OD × wall, quantity, length, end type and destination port - our technical team will confirm the specification against GB/T 3091 or GB/T 13793 and return a quotation with lead time within 24 hours.
Request a Q235B ERW Welded Round Pipe Quote
Why Source Q235B ERW Welded Round Pipes from GNEE
As a Q235B ERW pipe supplier we support both standard stock and custom specifications.
Stock and lead time. Common OD × wall sizes are held in stock; mill orders ship within about 25 days after deposit.
Documentation. Every lot ships with a mill test certificate and supports third-party inspection (SGS, BV, Intertek).
Export handling. FOB/CIF/CFR from Tianjin/Xingang, with bundle or bulk packing per destination.
FAQ
Is Q235B ERW pipe an alloy steel?
No. Q235B carbon steel ERW pipe is a plain carbon structural steel under GB/T 700-2006. It contains only residual alloying levels of Mn, Si, P and S and is not an "alloy steel." Any listing that titles it "Q235B alloy steel pipe" is using the wrong term and should be corrected.
What is the difference between GB/T 3091 and GB/T 13793 for Q235B ERW pipe?
GB/T 3091-2015 covers welded steel pipes for low-pressure liquid delivery (water, air, gas); GB/T 13793-2016 covers longitudinal electric-resistance-welded steel tubes for structural and mechanical use. Same Q235B base steel, different end-use scope - pick GB/T 3091 for fluid lines and GB/T 13793 for structures.
Q235B vs S235JR - are they the same?
For most projects yes. Q235B (GB/T 700) and S235JR (EN 10025-2) share a 235 MPa minimum yield and a +20 °C / 27 J Charpy impact, so they are treated as equivalent. The US pipe-form equivalent is ASTM A53 Type E Grade B.
What pressure can Q235B ERW pipe withstand?
In short, the Q235B ERW pipe pressure rating is not a fixed catalogue number. Q235B ERW pipe is a low-pressure fluid pipe (GB/T 3091), not a fixed pressure-rated ASME pipe. Working pressure depends on OD, wall thickness and the design code, so it must be calculated per the applicable standard rather than quoted as a single bar rating. For non-critical low-pressure water/air lines it is the standard choice.
How is the weight of Q235B ERW pipe calculated?
Use the standard steel-pipe weight formula: weight = 0.02466 × WT(mm) × (OD(mm) − WT(mm)) kg/m. For a 48.3 mm OD × 3.5 mm wall tube that is 0.02466 × 3.5 × 44.8 ≈ 3.87 kg/m. Confirm with the actual measured wall before pricing.
Can Q235B ERW pipe be hot-dip galvanized?
Yes. Q235B ERW pipe galvanized by hot-dip zinc is common for outdoor handrails, fencing and poles, coated to GB/T 13912 / ISO 1461. Galvanizing is a finish applied after welding and does not change the base grade.
Does Q235B ERW pipe need preheating for welding?
No. At ≤0.20 % carbon, Q235B ERW pipe welding by manual arc, CO₂ or resistance methods needs no preheat or post-weld heat treatment. That is the main reason it is so widely fabricated on site.
Q235B vs Q235A - which should I buy?
Q235B adds a guaranteed +20 °C impact test that Q235A lacks. For any welded or load-bearing structure, Q235B is the safe default; choose Q235A only for non-critical parts with no toughness requirement. For colder service move up to Q235C (0 °C) or Q235D (−20 °C).
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