JIS G3445 STKM13A Mechanical Structural Carbon Steel Tube
JIS G3445 STKM13A Mechanical Structural Carbon Steel Tube for Automotive & General Engineering
Comprehensive technical data for STKM13A carbon steel tube according to JIS G3445. Includes chemical composition, mechanical properties, physical properties, equivalent grades and application guidance.
Hot rolling, cold drawing, annealing, normalizing, welding (for ERW tubes)
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JIS G3445 STKM13A Mechanical Structural Carbon Steel Tube Introduction
JIS G3445 STKM13A is a carbon steel tube intended for mechanical and structural applications, including automotive components. It is manufactured by either seamless or electric resistance welding processes and is supplied in various conditions such as hot-finished, cold-finished, or annealed. The steel offers good weldability, machinability, and moderate strength, making it suitable for general structural and mechanical parts. Typical applications include vehicle frames, bicycle components, furniture structures, and machinery parts.
JIS G3445 STKM13A Mechanical Structural Carbon Steel Tube Chemical Composition
The chemical composition is based on heat analysis according to JIS G3445. The values are maximum limits unless a range is given. STKM13A is a simple carbon-manganese steel with no intentional addition of alloying elements. Residual elements such as Ni, Cr, Cu may be present but are not specified.
| Element | Standard Value (%) | Remarks |
|---|---|---|
| Carbon (C) | ≤0.25 | |
| Silicon (Si) | ≤0.35 | |
| Manganese (Mn) | 0.30 - 0.90 | |
| Phosphorus (P) | ≤0.040 | |
| Sulfur (S) | ≤0.040 |
JIS G3445 STKM13A Mechanical Structural Carbon Steel Tube Physical and Thermal-Electric Properties
Physical properties are average values for carbon steel and are not part of JIS G3445 requirements. They are provided for general engineering calculations. Thermal expansion and conductivity vary with temperature; room-temperature values are given unless noted.
| Property | Standard Value | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | Room temperature |
| Modulus of Elasticity (E) | 206 | GPa | Room temperature |
| Shear Modulus (G) | 79.3 | GPa | Room temperature |
| Poisson's Ratio (ν) | 0.29 | - | Room temperature |
| Thermal Expansion Coefficient (α) | 12.1 | 10⁻⁶/K | 20°C to 100°C |
| Thermal Conductivity (λ) | 51.9 | W/(m·K) | At 100°C |
| Specific Heat Capacity (c) | 486 | J/(kg·K) | Room temperature |
| Electrical Resistivity (ρ_e) | 0.15 – 0.20 | Ω·mm²/m | Room temperature |
JIS G3445 STKM13A Mechanical Structural Carbon Steel Tube Mechanical Properties
Mechanical properties are specified for tubes in the as-delivered condition. Requirements may vary with tube dimensions. Tensile testing is performed on longitudinal strip specimens according to JIS Z2241. Bend test applies to tubes with outside diameter ≤ 50 mm. Note: For wall thickness > 8 mm, elongation requirements differ. No impact test is required by the standard.
| Property | Standard Value | Unit | Condition |
|---|---|---|---|
| Yield Strength (ReH) | ≥215 | MPa | Room temperature; as-delivered |
| Tensile Strength (Rm) | ≥370 | MPa | Room temperature |
| Elongation (A) | ≥30 | % | Longitudinal; wall thickness ≤8mm, OD ≥22.4mm; JIS No.11 or No.12 test piece |
| Elongation (A) | ≥28 | % | Longitudinal; wall thickness >8mm; JIS No.11 or No.12 test piece |
| Elongation (A) | ≥17 | % | Transverse; wall thickness >8mm; JIS No.5 test piece |
| Bend Test (Bend Diameter) | 4 × wall thickness (for OD ≤50mm) | - | 180° bend; no cracking required |
| Bend Test (Bend Diameter) | 6 × wall thickness (for OD >50mm) | - | 180° bend; no cracking required |
JIS G3445 STKM13A Mechanical Structural Carbon Steel Tube Fully Equivalent Material Standards and Substitute Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Japan | JIS G3445 | STKM13A | Original specification |
JIS G3445 STKM13A Mechanical Structural Carbon Steel Tube Application Introduction
STKM13A tubes are widely used in structures requiring moderate strength and good formability. They are easily welded and machined, making them versatile for many industries. Typical processing includes bending, cutting, welding, and surface treatments like galvanizing or painting.
Product Applications: Automotive structural tubes (subframes, seat frames), Bicycle frame tubes, Metal furniture tubes, Construction scaffolding and support tubes, Machine guide rails and rollers, Handrails and guardrails
Processed into products: Welded automotive frames and sub-assemblies, Bent tubular handlebars, Machined spacers and bushings, Drill-and-tap mounting brackets, Welded structural frames (gates, racks)
Application industries: Automotive industry (chassis, suspension arms, roll cages), Bicycle and motorcycle frames, Furniture manufacturing (table legs, chair frames), Construction and civil engineering (scaffolding, handrails), Agricultural equipment, General machinery (conveyor rollers, hydraulic cylinders (low pressure), spacers)
JIS G3445 STKM13A Mechanical Structural Carbon Steel Tube Similar / Alternative Material Recommendations
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| European Union | EN 10305-1 | E235 | Similar strength and carbon content; cold drawn seamless tube. |
| International | ISO 2938 | TS 4 | Mechanical tubing with comparable tensile strength. |
| United States | ASTM A513 | Grade 1010 | ERW carbon steel tube; chemistry close but not identical. |
| China | GB/T 8162 | 20 | Seamless steel tube for structural purposes; mechanical properties approximate. |
| Germany | DIN 2391-1 | St 37-2 (E235) | Seamless precision steel tube; close mechanical values. |
Notes:
Additional information: JIS G3445 also covers grades STKM12A, STKM12B, STKM13B, and STKM14A, etc., with varying carbon content and mechanical properties. STKM13A represents a medium-strength option with balanced weldability and formability. For applications requiring higher strength or improved toughness, consider STKM13B or STKM14A. Always verify the latest standard revision for exact tolerances and testing requirements.
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