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• Name and Nature: JIS G3466 is a technical specification in the Japanese Industrial Standards for "carbon steel square and rectangular tubes for general structural purposes". The full name is "Carbon steel square and rectangular tubes for general structure".

• Latest version: Revised on February 22, 2021 (JIS G3466:2021), replacing the old version standard.

• Scope of application: Mainly used for square and rectangular carbon steel pipes in fields such as civil engineering, building structures (such as steel beams and columns), and mechanical manufacturing.

• Applicable scenarios:

Steel structures such as building frames, bridge supports, and roof structures.

Photovoltaic support systems (in compliance with JIS C8955 standard), automotive parts, agricultural greenhouses, etc.

• Material classification:

It is classified into two types based on strength: STKR400 (tensile strength ≥400 MPa) and STKR490 (tensile strength ≥490 MPa).

The material is common carbon steel, similar to Q235 and Q345 of Chinese standards, or ASTM A500 of American standards.

Manufacturing method:

• Welded steel pipes: Formed by resistance welding (ERW), forging or arc welding, and then cold-bent into square or rectangular shapes.

• Seamless steel tubes: Made from hot-rolled or cold-drawn seamless tubes through forming processes (less common).

Performance requirements:

• Mechanical properties: Tensile strength, yield strength, elongation and other indicators must be met (in accordance with JIS Z 2241 tensile test).

• Corrosion resistance: It can be enhanced by hot-dip galvanizing (refer to JIS G 3302) or oiling treatment.

• Dimensional tolerance: Bending degree ≤2mm per meter, total bending degree ≤ 0.2% of the total length.

The following table summarizes the main technical parameter requirements:

JIS G3466 is often used in conjunction with or benchmarked against the following standards:
• China: GB/T 6728 (Cold-formed Hollow steel sections for structural purposes).

• USA: ASTM A500 (Cold-formed square and rectangular carbon steel tubes for structural purposes).

• Europe: EN 10210/10219 (non-alloy structural steel hot/cold formed hollow sections).

• Building structure: High-rise building steel beam and column support system (due to high cross-sectional rigidity and strong compressive resistance).

• Photovoltaic support frame: Support frame for ground-mounted power stations (designed in accordance with JIS C8955 wind load resistance).

• Machinery and Transportation: Container frames, automotive chassis components, guardrails, etc.

• Special Requirements: Some enterprises customize short-length pipes (≥2000mm) or interface pipes for non-standard projects.

JIS G3466 is one of the key standards for structural engineering in East Asia, and is widely used especially in export projects to Japan and China. Its core advantage lies in:

1. Strict quality control: covering chemical composition, mechanical properties and non-destructive testing requirements;

2. High compatibility: In line with international standards such as ISO and EN, it supports project certifications in multiple countries;

3. Cost-effectiveness: The welding process is mature, and the price is lower than that of similar seamless pipes (such as ASTM A500).

STKR400:

Tensile strength ≥400 MPa,

yield strength ≥245 MPa (refer to the yield strength of similar material STK490 ≥315 MPa).

Applicable scenarios:

• Building structure: Medium-load structures such as ordinary factory steel beams, roof trusses, and shaft supports.
• Photovoltaic support frame: Ground photovoltaic power station support frame (needs to be designed in accordance with JIS C8955 wind resistance).
• Light machinery: agricultural greenhouse frames, furniture frames, small shelves, etc.

Advantages: Good weldability, easy cold bending and forming, and relatively low cost (about 4,500 to 4,930 yuan per ton).

STKR490:

Tensile strength ≥490 MPa,

yield strength ≥315 MPa (approximately 28% higher than STKR400).

Applicable scenarios:

• Heavy-duty structures: main beams of Bridges, core tubes of high-rise buildings, and support frames for large industrial equipment.
• Transportation: Container frames, railway vehicle chassis, heavy truck chassis components.
• Energy facilities: Internal structure of wind power towers, pressure vessel supports, etc.

Advantages: High strength reduces the self-weight of the structure (such as in large-span designs), but the welding and cold bending processes have higher requirements. The price is 10% to 15% higher than that of STKR400.

Common uses of STKR400

• Construction engineering: Support for residential floor slabs, framework for shopping mall canopies (such as 50×30×2.0mm small-sized pipes).

• Municipal facilities: guardrails, street lamp brackets, bus stop canopies.

• Mechanical manufacturing: Conveyor frames, small machine tool guards.

Typical applications of STKR490

• Heavy structure:

Bridge cantilever beams (such as 200×200×11.0mm large-sized pipes).

Port crane track support frame.

• Special fields:

Auxiliary supports for nuclear power equipment (requiring non-destructive testing).

Anti-roll frame for military vehicles (high impact resistance).

Scenarios where STKR400 is selected:

Medium and low-load projects with limited budgets.

• Scenarios that require rapid welding processing (such as on-site construction).

Structures with low sensitivity to weight (such as fixed shelves).

Scenarios where STKR490 is selected:

• High dynamic loads or impact environments (such as vehicle chassis, hoisting equipment).

• When weight reduction is required for large-span designs (such as the roofs of sports venues).

Heavy engineering projects that strictly meet seismic and wind resistance standards.

Note: The actual selection should be comprehensively evaluated in combination with the design load, environmental corrosiveness and processing conditions. For instance, galvanized STKR400 can be selected for photovoltaic brackets in humid coastal areas, while STKR490 should be given priority for the skeletons of cross-border logistics containers to cope with stacking impact.

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