JIS G3444

JIS G3444:1994 – Carbon Steel Tubes for General Structural Purposes

1. Standard Definition and Background

JIS G3444 is the standard of carbon steel tubes for general structural purposes, established by JISC, The Japanese Industrial Standards Committee. (Note) The JIS G3444:1994 standard has been added to this standard. This Standard specifies the carbon steel tubes (hereafter referred to as “tubes”) used for civil engineering, architecture and other structures. The code promotes structural safety and economy, through the appropriate use of materials and workmanship.

Key Technical Features:

Manufacturing Flexibility: We produce plates, seamless, ERW (Electric Resistance Welded), FW (Furnace Welded), and fully continuous arc-welded (spiral and longitudinal) pipe.

Not Heat Treated:Manufacturing typically does not include heat treating to save on production costs

Size: For welded tubes of ≤318.5mm OD and for all seamless tubes; For piles ≥318.5mm OD JIS A5525 is applied

Note the above: The JIS system is technically not compatible with ANSI/ DIN; the JPI standards gives the ANSI equivalent for interchangeability.

2. نطاق التطبيق

2.1 التطبيقات الأساسية

2.2 Limitations

Load Type: Static loading only (dynamic loads require additional verification)

درجة الحرارة: -30°C to 120°C (low-temp applications need toughness validation)

Environment: Neutral soils (pH 4-10); corrosive environments require protective coatings

3. Material Technical Requirements

3.1 Grade Classification and Chemical Composition

Table 1: Chemical Composition (Ladle Analysis, wt%)

Key Controls:

Strict P/S limits (≤0.040%) to minimize cold brittleness

STK490’s low carbon (C≤0.18%) optimizes weldability

Micro-alloying (V, Nb) permitted for grain refinement

3.2 Mechanical Properties

Table 2: Mechanical Requirements

Special Provisions:

Thin-Wall Adjustment: For t<8mm, elongation may decrease 1.5% per 1mm thickness reduction

Weld Strength: Welded tube joints must achieve ≥95% of base metal strength

4. Dimensions and Tolerances

4.1 Size Ranges

القطر الخارجي (OD): 10.2–318.5 mm (welded tubes)

Wall Thickness (t): Agreement-based (refer to JIS G3454 Sch series)

4.2 Key Tolerances

Table 3: Geometric Tolerances

Special Cases:

Welded tubes >350mm OD: End tolerance ±0.5mm; body tolerance ±0.5%

Large-diameter measurement: Use circumference method (π=3.14)

5. Testing and Quality Control

5.1 Mandatory Tests

Mechanical Tests:

Tensile Test: 2 samples per ≤100-tube batch (weld excluded)

Flattening Test: Mandatory for welded tubes; compress to H≤0.85D without cracking

Bend Test (Optional): 90° bend with mandrel radius ≤8t upon request

Non-Destructive Testing:

100% UT or RT for welded tubes (RT acceptance: JIS Z3104)

5.2 Defect Handling

Surface Defects: Repair/remove if depth >12.5% wall thickness

Weld Defects: No lack of fusion or through-thickness cracks permitted

6. Engineering Applications and Evolution

6.1 Grade Selection Guide

6.2 Limitations and Development

Wall thickness series: No standard series, depends on agreements

Compatibility and interoperability International Working : Technically NOT compatible with ANSI/DIN, but acceptable for use with JPI standards

Future Prospects: High strength steels (STK600) and environment-friendly weathering steel

7. Conclusion and Implementation

JIS G3444 serves as Japan’s cornerstone standard for structural tubing through:

Strength-Graded Design: Five grades for optimized material selection

Process Efficiency: No-heat-treatment requirement reduces costs

Safety Assurance: Strict P/S controls (≤0.040%) ensure low-temperature toughness

Critical Implementation Notes:

Avoid STK290 for dynamic loads (e.g., seismic bracing); use STK400+

Specify weld inspection method (UT/RT) and acceptance criteria in orders

Measure large-diameter tubes (OD>350mm) via circumference method

Standard Transition:

For piles ≥318.5mm: Use JIS A5525

For pressure piping: Apply JIS G3454 (Sch thickness series)