GB/T 34201-2017 Seamless Hot-Rolled Square and Rectangular Structural Steel Tubes

TORICH manufactures seamless hot-rolled square and rectangular steel tubes for structural applications in accordance with GB/T 34201-2017. These hollow steel sections are designed for load-bearing structural components requiring specified mechanical strength, dimensional consistency, and controlled cross-sectional geometry.

Available materials include carbon structural steels, quality carbon steels, and low-alloy high-strength steels such as Q235B, Q345B, Q390, Q420, and Q460. The seamless hot-rolled manufacturing process eliminates longitudinal weld seams, while the selected steel grade and delivery condition determine the required mechanical properties.

Square sections are specified from 40 × 40 mm to 500 × 500 mm, rectangular sections from 50 × 30 mm to 600 × 400 mm, and nominal wall thicknesses from 3 mm to 60 mm. Custom lengths, dimensional tolerances, heat treatment, and surface preparation can be arranged according to project requirements.

1. Product Specifications

Note: The dimensional ranges reflect the scope of GB/T 34201-2017. Actual production availability depends on the steel grade, cross-section, wall thickness, and manufacturing feasibility. Dimensions and tolerances outside the standard requirements must be agreed upon before production.

2. Main Features

Seamless Structural Construction

The tubes are manufactured by a hot-rolled or hot-expanded seamless process without a longitudinal welded joint.

This construction provides continuous parent metal around the cross-section, eliminating longitudinal weld-seam defects as a separate inspection concern. Structural performance must still be verified through the specified mechanical properties, dimensional inspection, and material quality requirements.

Defined Dimensional Accuracy

GB/T 34201-2017 establishes measurable tolerances for side dimensions, wall thickness, straightness, squareness, and corner geometry.

The standard specifies a maximum external corner radius of 3S, where S represents nominal wall thickness.

For a tube with a nominal wall thickness of 10 mm, the maximum permitted external corner radius is therefore 30 mm.

The permitted twist over the full tube length is:

V ≤ 2 + 0.5 × L/1000 mm

Where L is the tube length in millimeters.

For a 6,000 mm tube, the maximum permitted twist is 5 mm.

These requirements allow structural fabricators to assess dimensional suitability before cutting, positioning, and welding operations.

Grade-Dependent Mechanical Strength

The mechanical properties are determined by the steel grade and nominal wall thickness.

For Q235 steel with wall thickness up to 16 mm, the minimum yield strength is 235 MPa, while Q345 provides a minimum yield strength of 345 MPa under the same thickness condition.

The nominal yield-strength difference is approximately 46.8%. However, structural loading capacity must be determined from the complete section geometry, applicable design code, buckling conditions, and connection details rather than yield strength alone.

Controlled Surface and Internal Quality

The inside and outside surfaces must be free from unacceptable cracks, folds, scabs, rolling laps, and delamination.

Under the applicable provisions of GB/T 34201-2017, non-metallic inclusions are evaluated according to GB/T 10561-2005, Method A. Individual inclusion ratings for the specified A, B, C, D, and DS classifications must not exceed Grade 2.5.

Surface cleaning, protective coatings, or additional nondestructive examination can be specified when required by the structural fabrication process.

3. Our Manufacturing Advantages

1. Dimensional Verification for Structural Assembly

A common issue during fabrication is inconsistent section geometry, particularly corner radius, side flatness, and angular accuracy. These variations can affect the fit-up of end plates and connecting components.

TORICH addresses this through dimensional inspection of the outside side lengths, wall thickness, corner geometry, and straightness.

The standard permits side concavity or convexity up to 1% of the corresponding side dimension and specifies adjacent-side perpendicularity of 90° ±1°.

When tighter assembly requirements apply, inspection points and acceptance limits can be defined from the customer's technical drawing before production.

2. Steel Grade and Weldability Control

Purchasing steel sections solely by nominal yield strength can create problems when the components require extensive welding or operation at reduced temperatures.

TORICH supports material selection according to the required strength, wall thickness, delivery condition, and impact toughness.

For example, GB/T 34201-2017 limits the carbon equivalent (CEV) of hot-rolled Q345 grades, except quality class A, to 0.44%.

The carbon equivalent is calculated as:

CEV = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15

This requirement supports welding procedure evaluation, although suitable preheating and welding parameters must still be determined from section thickness, restraint, consumables, and applicable fabrication standards.

3. Material Traceability and Documented Inspection

Inconsistent inspection records and incomplete material identification can delay incoming inspection and structural fabrication approval.

TORICH supports heat-number traceability, chemical composition verification, tensile testing, and dimensional examination according to the agreed inspection plan.

Inspection documentation can include material grade, heat number, dimensional results, chemical composition, and mechanical test values. EN 10204 3.1 certification and additional testing can be arranged when specified in the purchase order.

This enables purchasing and quality teams to verify material conformity before fabrication begins.

4. Applicable Standards

GB/T 34201-2017 is the primary manufacturing and acceptance standard for this product. Other regional standards may be considered for separately specified orders.

Important: These standards have different manufacturing, dimensional, material, and inspection requirements. They are not automatically interchangeable. Compliance with ASTM, EN, GOST, or JIS must be evaluated and specified separately; supplying a tube under GB/T 34201-2017 does not establish conformity with another standard.

5. Application: Load-Bearing Columns for Industrial Steel Warehouses

Seamless hot-rolled square and rectangular steel tubes can be used to manufacture load-bearing hollow steel columns for industrial warehouse structures.

In this application, the columns transfer vertical loads from the roof structure to the foundation while also resisting bending moments introduced by lateral loading and frame connections.

Q235B can be considered for conventional structural loading conditions, while Q345B provides a higher nominal yield strength for designs requiring greater material strength.

Rectangular sections can be selected where bending resistance differs between the two principal axes. Square sections are useful when similar geometric properties are required in both directions.

When specifying tubes for warehouse columns, the design engineer should verify section strength, overall buckling resistance, local wall slenderness, connection design, and the applicable building code. Material certification and dimensional conformity are particularly important for welded base-plate and beam-to-column connections.

6. Chemical Composition

7. Mechanical Properties