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Carbon Steel Rectangular Tube – ASTM A500 Structural RHS & ERW Tubing
Xi'an Dongmeng Group Co., Ltd. supplies carbon steel rectangular tubes, also known as Rectangular Hollow Sections (RHS), for structural engineering, steel fabrication, industrial equipment frames and construction projects.
Our rectangular steel tubing solutions cover cold-formed ERW structural sections in carbon and low-alloy structural steel grades. Product specifications can be matched to ASTM A500, EN 10219, JIS G 3466 and applicable GB/T requirements, subject to material grade, dimensions and manufacturing availability.
We support project-based sourcing, customized cutting, surface protection, dimensional inspection, material traceability and export packaging. Whether you require standard RHS sizes for steel frameworks or specified rectangular tubing for industrial fabrication, Dongmeng Group can help coordinate the material, processing and documentation requirements for your purchase order.
Request a Rectangular Steel Tube Quotation – Send Us Your Grade, Size, Wall Thickness, Quantity and Destination Port.
What Is a Carbon Steel Rectangular Tube?
Carbon steel rectangular tubing is a hollow steel section with four flat external faces, rounded corners and unequal overall side dimensions. In structural engineering, it is commonly designated as a Rectangular Hollow Section (RHS), while in North America it is frequently classified as rectangular Hollow Structural Section (HSS) tubing.
Compared with open structural profiles, an RHS provides a closed cross-section suitable for structural members subject to specified combinations of axial force, bending and torsion. Its flat surfaces also facilitate welding, bolted connections, bracket attachment and fabrication of equipment frames.
The load-bearing capacity depends on steel grade, section geometry, wall thickness, member length, connection details and design conditions. Product selection should therefore follow the relevant structural design code rather than relying on external dimensions alone.
Carbon Steel Rectangular Tube Technical Specifications
| Item | Specifications |
| Product | Carbon Steel Rectangular Tube / RHS / Rectangular HSS |
| Standards | ASTM A500; EN 10219-1/-2; JIS G 3466; GB/T 6728-2025 |
| Materials | Carbon and low-alloy structural steel |
| Grades | A500 B/C; S235JRH; S275J0H; S355J2H; STKR400/490; Q235/Q355 subject to availability |
| Production | Cold-formed ERW; alternative processes upon review |
| Wall Thickness | 0.8–12 mm listed on current page; confirm per size |
| Lengths | 5.8 m, 6 m, 12 m, custom cut subject to confirmation |
| Surface | Black, oiled, painted, pre-galvanized, or post-fabrication hot-dip galvanized as specified |
| Inspection | Chemical, mechanical, dimensional and weld inspection as required |
| Documents | Mill Test Certificate; EN 10204 3.1 when available and specified |
| Packing | Strapped bundles with protective arrangements for shipment |
| MOQ | 3 MT indicated on existing page; confirm at quotation |
| Delivery | Subject to grade, dimension, stock, processing and order quantity |
Material Standards & Steel Grades
Rectangular steel tubing is manufactured under different structural and mechanical tubing specifications. Choosing the correct standard is essential because mechanical properties, manufacturing requirements, dimensional tolerances and intended use vary between specifications.
| Standard | Typical Grades | Product Category | Typical Selection |
| ASTM A500/A500M | Grade B, Grade C | Cold-formed structural tubing | North American structural HSS |
| EN 10219-1/-2 | S235JRH, S275J0H, S355J2H | Cold-formed welded structural hollow sections | European structural RHS |
| JIS G 3466 | STKR400, STKR490 | Square and rectangular structural tubing | Japanese structural projects |
| GB/T 6728-2025 | Grade per applicable material specification | Cold-formed structural sections | Chinese standard projects |
| ASTM A513/A513M | Grade and type per purchase order | ERW mechanical tubing | Equipment and mechanical fabrication |
ASTM A500 Grade B & Grade C
ASTM A500 is widely specified for cold-formed carbon steel structural tubing. Grade selection should consider the project design strength, applicable code, product availability and required certification.
EN 10219 S235JRH & S355J2H
These grades are selected for cold-formed welded structural hollow sections. S355J2H may be considered where higher specified strength and low-temperature impact requirements are relevant.
JIS G 3466 STKR400 & STKR490
These designations apply to carbon steel square and rectangular tubes for general structures. The applicable edition should be identified in the purchase order.
Important Engineering Note: Different ASTM, EN, JIS and GB grades must not be represented as exact equivalents without checking their chemical composition, yield and tensile properties, impact requirements and dimensional tolerances.
Standards reference: ASTM International, Steel Tube Institute and JIS G 3466 published scope and grade information.
Rectangular Hollow Section Sizes & Wall Thickness
Dongmeng Group's existing product schedule lists a range of rectangular steel tube sizes, from light fabrication sections to larger structural RHS. The following selections are reorganized from the published dimensional chart for easier procurement reference.
| External Size (mm) | Listed Wall Thickness (mm) |
| 50 x 30 | 1.0–3.0 |
| 60 x 40 | 1.5–3.5 |
| 75 x 50 | 1.5–4.0 |
| 80 x 40 | 1.5–4.0 |
| 100 x 50 | 2.0–6.0 |
| 100 x 60 | 2.0–6.0 |
| 120 x 60 | 3.0–6.0 |
| 120 x 80 | 3.0–6.0 |
| 150 x 100 | 4.0–12.0 |
| 175 x 100 | 4.0–12.0 |
| 200 x 100 | 4.0–12.0 |
| 200 x 150 | 4.0–12.0 |
| 250 x 150 | 5.0–12.0 |
| 300 x 200 | 5.0–12.0 |
| 400 x 200 | 5.0–12.0 |
The table reproduces selected size/thickness combinations from the existing website. It is a sourcing reference, not a confirmed in-stock catalogue. Grade, dimensional tolerances and actual supply capability must be checked for each combination.
Understanding RHS Dimensions
RHS sections are typically specified by their outside dimensions and nominal wall thickness.
For example, RHS 150 × 100 × 5 mm indicates a rectangular hollow steel section with a nominal outside height of 150 mm, outside width of 100 mm and wall thickness of 5 mm.
Specifying the correct outside dimensions alone is not sufficient for close-fit assemblies. Buyers should also define thickness tolerance, corner radius or profile, straightness, internal weld bead requirements and cutting tolerance where applicable.
Dimensional Tolerances & Quality Requirements
For engineered applications, dimensional control affects structural fit-up, connection accuracy and fabrication efficiency.
The applicable product standard should determine acceptance limits for external dimensions, wall thickness, corner profile, squareness, twist and straightness.
For illustration, EN 10219-2 provides dimensional tolerances according to side length and thickness. The standard includes a ±10% thickness tolerance for rectangular sections with nominal thickness up to 5 mm, subject to its stated conditions. Other tolerances apply to thicker sections and different dimensions.
Our technical review can cover:
Outside height and width measurement
Wall thickness at defined measurement positions
Corner radius and profile evaluation
Straightness, twist and squareness
Weld seam appearance and condition
Cut length and end squareness
Identification, surface condition and packaging
Buyer Tip: For precision assembly, telescoping components or automated welding fixtures, specify actual mating dimensions and tolerances rather than ordering structural tubing solely by nominal size.
ERW Manufacturing Process
Carbon steel rectangular hollow sections are commonly produced using electric resistance welding and cold-forming technology.
01. Steel Strip Selection
Hot-rolled or suitably prepared steel strip is selected according to the specified grade, chemistry, thickness and manufacturing route. Incoming material identification and documentation are reviewed.
02. Roll Forming & ERW Welding
The strip passes through a forming and welding line. An electric-resistance-welded longitudinal seam is produced, followed by the appropriate weld bead treatment and dimensional forming operations.
03. Rectangular Shaping & Sizing
The tube is formed into the specified rectangular section. The production route, roll tooling and size control determine its final flatness, corner geometry and dimensional consistency.
04. Cutting & Inspection
Finished sections are cut to the specified lengths, inspected according to the order requirements and prepared for marking, protection and shipment.
Cold-formed ERW is the primary manufacturing route discussed here. Cold-drawn precision rectangular tubes and hot-finished structural hollow sections are separate product specifications that require their own process and technical verification.
Key Product Advantages
Closed-Section Structural Efficiency
A rectangular hollow profile can provide efficient bending performance about its principal axes and useful torsional stiffness for engineered structural applications.
Suitable for Welded Fabrication
Flat exterior faces facilitate attachment of plates, brackets, stiffeners and welded connections, subject to the steel grade and approved welding procedure.
Multiple Dimensional Configurations
Buyers can select different side ratios and wall thicknesses to match structural geometry, fabrication space and load requirements.
Optional Surface Protection
Black, oiled, painted and galvanized configurations can be evaluated based on the intended exposure conditions and fabrication sequence.
Project-Oriented Export Supply
Custom cutting, inspection documentation, product identification and export packing can be coordinated to meet approved order requirements.
Surface Finish & Corrosion Protection Options
Black / Mill Finish
Uncoated carbon steel rectangular tubing for general structural fabrication and subsequent surface treatment. Mill scale and normal production surface characteristics may be present.
Anti-Rust Oiled Finish
A temporary protective oil film may be applied for handling and short-term storage. It is not a substitute for a qualified outdoor corrosion-protection system.
Galvanized Finish
Galvanized options can be evaluated according to the tube manufacturing and fabrication route. Pre-galvanized strip and post-fabrication hot-dip galvanizing require different coating specifications and inspection criteria.
Painted / Primer-Coated Finish
Shop primers or protective paint systems may be specified for selected projects. Coating compatibility, surface preparation, dry-film thickness and exposure requirements must be agreed before processing.
For post-fabrication hot-dip galvanizing, standards such as ASTM A123/A123M or ISO 1461 may apply according to the article and processing scope. They should not automatically be applied to every continuously galvanized tube product.
Custom Rectangular Tubing Fabrication Services
Dongmeng Group supports purchasing projects that require more than standard mill lengths. Processing options are evaluated according to drawings, tube dimensions, grade and selected coating route.
Precision Cutting & Cut-to-Length
Specified fixed lengths for fabrication and assembly, with cut tolerances and deburring requirements confirmed before production.
Drilling, Slotting & Hole Preparation
Customized connection holes and slots for bracket assembly or bolted construction, subject to approved drawings and minimum edge-distance requirements.
Mitre Cutting & Weld-End Preparation
Prepared ends for angled tube connections, fabricated frames and structural assemblies. Cut geometry and weld preparation must be matched to the joint design.
Surface Finishing & Packaging
Protective oiling, painting, galvanizing coordination, bundle marking and export packing according to the project's specifications.
Important: Any cutting, punching, welding or galvanizing performed after the base tube has been produced may affect dimensions, mechanical performance or corrosion protection. Requirements should be reviewed before processing.
Industrial Applications of Rectangular Steel Tubing
Steel Structures & Building Frames
RHS members for engineered columns, bracing, secondary frames and structural supports.
Machinery & Equipment Frames
Rectangular steel tubing for machine bases, support frames and fabricated equipment structures.
Solar & Industrial Support Structures
Engineered frames, braces and mounting supports where the selected grade and coating are suitable.
Vehicle & Trailer Fabrication
Rectangular mechanical or structural tubing for specified vehicle frames and fabricated subassemblies.
Stairs, Railings & Architectural Steelwork
Rectangular tubing for fabricated stair frames, handrails and architectural metalwork.
Storage Platforms & Material Handling
Structural frames and supporting members for approved industrial storage and handling equipment.
Inspection, Traceability & Quality Documentation
Quality requirements for structural rectangular tubing should be based on the specified manufacturing standard and project conditions.
| Inspection Item | Purpose | Verification |
| Chemical Analysis | Confirm grade chemistry | Mill material records / analysis |
| Tensile Properties | Verify specified grade strength | Test report under applicable standard |
| Wall Thickness | Confirm specified thickness | Measurement against standard tolerances |
| External Dimensions | Confirm section geometry | Height, width and profile measurements |
| Straightness & Twist | Support fabrication fit-up | Measurement under specified standard |
| Weld Seam | Review seam condition | Visual / supplementary testing as specified |
| Surface & Coating | Check surface or corrosion protection | Visual inspection / specified coating test |
| Traceability | Link delivered product to records | Heat, batch or bundle identification |
| Third-Party Inspection | Independent acceptance when required | Agreed inspection scope |
| Documentation | Confirm compliance | MTC / EN 10204 3.1 if available |
Inspection records and certification should be agreed before order confirmation. Not all standards require the same tests, and optional testing should not be represented as mandatory for every shipment.
Export Packaging & Delivery
Carbon steel rectangular tubing can be packaged into appropriately secured bundles for handling, storage and international transportation.
Packing arrangements may include steel straps, identification labels, protective separators, supports and additional moisture protection where required. The method depends on tube dimensions, bundle mass, surface finish and transportation mode.
For export orders, buyers may specify container loading requirements, marking information, inspection hold points, preferred shipping ports and supporting commercial documents.
Delivery lead time depends on material sourcing, dimensional availability, fabrication requirements, order quantity and inspection arrangements.
Why Choose Dongmeng Group?
Industrial Steel Supply Experience
Dongmeng Group focuses on sourcing and delivering industrial steel materials for international projects, including carbon steel tubing and other structural steel products.
Specification-Based Procurement
We help clarify material standards, steel grades, structural applications and dimensional requirements before final quotation.
Flexible Processing Coordination
Project-specific cutting, finishing, marking and packing options can be discussed against approved drawings and manufacturing capability.
Documentation & Quality Support
Material traceability, mill documentation and third-party inspection arrangements may be coordinated according to the purchase order.
International Project Supply
We support B2B buyers seeking consistent commercial communication, documented specifications and export-oriented shipment arrangements.
Frequently Asked Questions
1. What is the difference between rectangular steel tubing and RHS?
RHS means Rectangular Hollow Section. It is a standard industry designation for rectangular structural hollow steel sections. Rectangular steel tubing is a broader commercial term that may also include mechanical tubing.
2. Is ASTM A500 suitable for structural rectangular tubing?
Yes. ASTM A500 covers cold-formed structural tubing in round and shaped sections, including rectangular sections. The selected grade and section must still satisfy the project design requirements.
3. What is the difference between ASTM A500 and ASTM A513 rectangular tubing?
ASTM A500 is a structural tubing specification. ASTM A513 covers ERW mechanical tubing. The two standards have different intended applications and requirements, so substitution should be evaluated and approved before ordering.
4. What steel grades can be supplied?
Depending on material availability, options may include ASTM A500 Grade B/C, EN 10219 S235JRH/S355J2H, JIS G 3466 STKR400/STKR490 and suitable Chinese structural steel grades. Exact grades and sizes require confirmation.
5. What rectangular tube sizes are available?
The existing Dongmeng Group size schedule includes common dimensions such as 60×40, 100×50, 150×100, 200×100 and 300×200 mm. Larger or non-standard dimensions should be confirmed individually.
6. Can rectangular tubing be cut to custom lengths?
Custom lengths and specified cutting tolerances can be evaluated. Buyers should include the cut length, permitted deviation, end condition and quantity in the RFQ.
7. Do rectangular steel tubes have a visible longitudinal weld?
ERW rectangular tubing normally contains a longitudinal weld seam. Weld bead appearance, internal bead condition and inspection requirements depend on the manufacturing process and selected specification.
8. Can rectangular steel tubing be hot-dip galvanized?
Yes, suitable products can be galvanized, subject to size, fabrication configuration and galvanizing capability. Pre-galvanized steel strip and hot-dip galvanizing after fabrication are different production routes.
9. Are rectangular steel tubes suitable for pressure pipelines?
Structural rectangular tubing should not be assumed suitable for pressure service. Pressure-retaining applications require a specification, design assessment and testing regime appropriate to the operating conditions.
10. How is the weight of rectangular steel tubing calculated?
The mass per metre depends on outside dimensions, actual wall thickness, corner geometry and steel density. Square-corner calculations provide only an estimate; certified section-property tables or agreed manufacturing data should be used for purchasing and structural design.
11. Can you provide an EN 10204 3.1 Mill Test Certificate?
EN 10204 3.1 documentation can be requested when supported by the supplying mill and agreed at the time of order. The document must relate to the delivered material and its traceability records.
12. What information is needed to quote rectangular steel tubing?
Please provide the applicable standard, steel grade, outside dimensions, wall thickness, length, surface finish, quantity, certification requirements and delivery destination. Drawings should be included for customized parts.
Request a Quote – Carbon Steel Rectangular Tube
Looking for a reliable carbon steel rectangular tubing supplier for your next project?
Xi'an Dongmeng Group Co., Ltd. supports international buyers sourcing ASTM A500 structural RHS, EN 10219 rectangular hollow sections and customized carbon steel rectangular tubing.
Send us your required standard, grade, dimensions, wall thickness, quantities, surface finish and destination port for a specification-based quotation.
Copy an RFQ Template
Product: Carbon Steel Rectangular Tube (RHS)
Standard:
Grade:
Outside Dimensions (H × B):
Wall Thickness:
Length:
Surface Finish:
Quantity:
Cutting / Processing:
Inspection / MTC:
Destination Port:
Required Delivery Date:
Office Information
Phone
+86 157 6921 4734
+86 157 6921 4734
Office Address
Room 4107, Runfeng Building, Sanqiao New Street, Weiyang District, Xi'an City, Shaanxi Province, China
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