JIS G3445 STKM13B Carbon Steel Seamless Tube
JIS G3445 STKM13B Carbon Steel Seamless Tube for Automotive and Structural Applications
Comprehensive data on STKM13B carbon steel seamless tube per JIS G3445: chemical composition, tensile and yield strength, elongation, bend test, typical physical properties, international equivalents, and applications in automotive and structural engineering.
Hot-finished or cold-drawn, with optional annealing, followed by straightening and cutting.
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JIS G3445 STKM13B Carbon Steel Seamless Tube Introduction
STKM13B is a carbon steel grade specified in Japanese Industrial Standard JIS G3445 for seamless steel tubes used in mechanical and structural applications, particularly in automobiles. It offers a minimum tensile strength of 490 MPa and yield strength of 305 MPa, with good ductility and weldability. The tubes are delivered in as-manufactured condition (hot-finished or cold-drawn) and are suitable for bending, machining, and other forming operations.
JIS G3445 STKM13B Carbon Steel Seamless Tube Chemical Composition
The chemical composition complies with JIS G3445. STKM13B is a general-purpose carbon steel with controlled carbon and manganese to ensure adequate strength and good weldability. Phosphorus and sulfur limits are set to maintain cleanliness.
| Element | Content (mass %) | Remarks |
|---|---|---|
| Carbon (C) | ≤ 0.25 | |
| Silicon (Si) | ≤ 0.35 | |
| Manganese (Mn) | 0.30 - 1.00 | |
| Phosphorus (P) | ≤ 0.040 | |
| Sulfur (S) | ≤ 0.040 |
JIS G3445 STKM13B Carbon Steel Seamless Tube Thermal and Electrical Physical Properties
These physical properties are not specified in JIS G3445. The values provided are typical for plain carbon steel (0.20-0.25% C) and may be used for engineering calculations. Actual values may vary slightly depending on manufacturing process and condition.
| Property | Typical Value | Unit | Condition |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | Room temperature |
| Modulus of Elasticity (E) | 205 | GPa | Room temperature |
| Shear Modulus (G) | 80 | GPa | Room temperature |
| Poisson's Ratio (ν) | 0.29 | - | — |
| Thermal Expansion Coefficient (α) (20–100 °C) | 11.5 × 10⁻⁶ | /K | 20 to 100 °C |
| Thermal Conductivity (λ) | 45 | W/(m·K) | Room temperature |
| Specific Heat Capacity | 486 | J/(kg·K) | Room temperature |
| Electrical Resistivity (ρe) | 0.19 × 10⁻⁶ | Ω·m | Room temperature |
JIS G3445 STKM13B Carbon Steel Seamless Tube Mechanical Properties
The following mechanical properties are specified in JIS G3445. Tensile and yield strength are verified at room temperature. Elongation requirements depend on specimen type and tube dimensions. A bend test is mandatory to assess cold formability.
| Property | Required Value | Unit | Test Condition |
|---|---|---|---|
| Tensile Strength (Rm) | ≥ 490 | MPa | Room temperature, per JIS Z2241 |
| Yield Point or 0.2% Proof Strength (ReH / Rp0.2) | ≥ 305 | MPa | Room temperature, per JIS Z2241 |
| Elongation (A) | ≥ 23 | % | Test piece No.11, for tube O.D. ≤50 mm, wall thickness ≤8 mm |
| Elongation (A) | ≥ 23 | % | Test piece No.12, for tube O.D. ≤50 mm, wall thickness >8 mm |
| Elongation (A) | ≥ 23 | % | Test piece No.11, for tube O.D. >50 mm, wall thickness ≤8 mm |
| Elongation (A) | ≥ 23 | % | Test piece No.12, for tube O.D. >50 mm, wall thickness >8 mm |
| Bend Test | No crack after 90° bend over mandrel of diameter 6 × O.D. | - | Room temperature |
JIS G3445 STKM13B Carbon Steel Seamless Tube Fully Equivalent Standards and Substitute Grades
No international standard provides a completely identical grade to JIS STKM13B. The following grades are considered similar in chemical composition and mechanical properties, and may serve as functional substitutes with appropriate verification.
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Europe | EN 10297-1 | E355 | Similar C-Mn steel for seamless tubes; yield 355 MPa, tensile 490-630 MPa |
| USA | ASTM A519 | 1026 | Chemical composition close, but may require adjustment for exact strength match |
| China | GB/T 8162 | 20 | Carbon structural steel tube; tensile ≥410 MPa, lower strength but commonly used |
JIS G3445 STKM13B Carbon Steel Seamless Tube Application Introduction
STKM13B tubes are widely used in automotive and general structural engineering due to their balance of strength, formability, and cost-effectiveness. Typical processing includes bending, cutting, welding, and machining. The mandatory bend test ensures reliable cold forming.
Product Applications: Automotive chassis components, Steel frames for bicycles and motorcycles, Structural tubing for buildings, Furniture tubing, Hydraulic cylinder barrels, Conveyor rollers, Agricultural equipment frames
Processed into products: Suspension arms, Steering columns, Drive shafts, Exhaust system pipes, Machine structural supports, Bicycle frame tubes, Handlebar stems
Application industries: Automotive, Construction, Machinery, Furniture, Bicycle manufacturing
JIS G3445 STKM13B Carbon Steel Seamless Tube Similar / Alternative Material Recommendations
These materials are not exact equivalents but share comparable mechanical and processing characteristics. They can be considered for design alternatives after checking specific requirements.
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Europe | EN 10297-1 | E355 | Roughly equivalent for mechanical tubing, widely available |
| USA | ASTM A519 | MT1015 | Lower carbon variant; tensile and yield values lower, suitable for less demanding structures |
| China | GB/T 8162 | Q345B | Higher strength low-alloy steel; may be used for heavier structural applications |
Notes:
The bend test is mandatory and requires the tube to withstand a 90-degree bend over a former of diameter six times the outside diameter without cracking. This ensures sufficient ductility for cold bending operations in fabrication. For welded structures, preheating is generally not required because of the moderate carbon content.
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