JIS G3444 Structural Steel Tube

JIS G3444 Structural Steel Tube

JIS G3444 is a special standard in the Japanese Industrial Standard (JIS) for carbon steel and alloy steel pipes for structural use. It is mainly used in scenarios with requirements for strength and formability, such as building frames, mechanical supports, and bridge load-bearing structures. With its precise dimensional tolerances and stable mechanical properties, it has become a commonly used pipe in the industrial and infrastructure fields.

Grade:STK290,STK400,STK490,STK500,STK540

Outer diameter: 33.4-660mm

Wall thickness:2.1-22mm

Length:0.8-18m

Manufacture Method: Hot Rolled.

Surface Treatment: Coating, Painting, Galvanized, etc.

JIS G3444 structural steel tube chemical composition:

JIS G3444 structural steel tube mechanical property:

Manufacturing Process and Quality Control
1. Manufacturing Processes
JIS G3444 Structural Steel Tube is primarily produced using two processes, tailored to meet varying dimensional and precision requirements:

Electrical Resistance Welding (ERW): Suitable for pipes with an outer diameter ≤ 609.6mm. High-frequency current is used to weld the edges of the pipe. The weld strength is ≥ 90% of the base material strength, resulting in high production efficiency and manageable costs. This process is commonly used for mass-produced standard-sized pipes.

Seamless Steel Sintering (SMLS): Suitable for pipes with an outer diameter greater than 219.1mm or requiring higher pressure and fatigue resistance (such as heavy machinery load-bearing pipes). This process involves hot-rolled piercing followed by cold drawing/rolling, eliminating weld seams and ensuring more uniform overall strength.

2. Mandatory Quality Inspection
To ensure safe use of the structure, each batch of pipes must pass the following inspections:
1. Appearance Inspection: No cracks, folds, scars, or delamination on the surface. Rust depth ≤ 10% of the wall thickness.

2. Dimensional Inspection: Measure the outer diameter, wall thickness, and ovality of each pipe to ensure compliance with tolerance requirements.

3. Mechanical Property Inspection: Three specimens are sampled from each batch and subjected to tensile and bend tests (bend angle 180°, bend diameter = 3 x wall thickness). Only specimens free of cracks are considered acceptable.

4. Hydraulic Pressure Testing: ERW pipes must undergo a hydrostatic test (test pressure = 2 MPa, hold pressure for 30 seconds, no leakage). Seamless pipes may also undergo hydrostatic or ultrasonic testing as needed.

5. Weld Inspection (ERW pipes only): Eddy current testing or X-ray testing is used to detect internal weld defects and ensure weld quality. III. Core

Application Scenarios and Selection Recommendations
1. Typical Applications

Construction: Steel structure columns, beams, scaffolding support tubes, and seismic supports;

Machinery: Machine tool base support tubes, construction machinery (excavator/crane) supports, and conveyor equipment frames;

Infrastructure: Small bridge guardrail tubes, municipal streetlight poles, and temporary enclosure support columns;

Other Applications: Warehouse rack columns, agricultural machinery frames, and light-load conveyor pipes.

2. Selection Guide

Light-Duty Scenarios (Load Capacity ≤ 5kN): Select STK 400 with ERW technology for the best cost-effectiveness.

Medium-Duty Scenarios (Load Capacity 5-15kN): Select STK 490, preferably with ERW technology (OD ≤ 219.1mm). Seamless technology is available for OD > 219.1mm.

Heavy-Duty/Seismic Scenarios (Load Capacity > 15kN): Select STK 540 with seamless technology for enhanced strength and fatigue resistance.

Corrosive Environments (e.g., Outdoor and Humid Environments): Hot-Dip Galvanized or Painted JIS G3444 Steel Pipe is recommended for improved corrosion resistance and extended service life.

JIS G3444 Structural Steel Tube, with its advantages of "strong strength adaptability, high dimensional accuracy, and controllable costs," have become the preferred pipe material in the construction and machinery fields. We can accurately match the grade and process to specific load-bearing and environmental requirements to ensure a balance between structural safety and economic efficiency.