S440L Hot Rolled Steel Coil for Automotive Structural Parts
GB/T 3273-2005 S440L Hot Rolled Coil – High-Strength Automotive Beam Steel with Superior Formability
S440L thermomechanically rolled steel coil for automobile frames and structural parts, offering minimum 440 MPa tensile strength and excellent cold forming capability.
Cold forming, bending, stamping, drawing, welding, phosphating, painting
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S440L Hot Rolled Steel Coil for Automotive Structural Parts Introduction
S440L is a hot-rolled high-strength low-alloy (HSLA) steel defined in GB/T 3273-2005 for automotive frame and beam applications. It combines a minimum tensile strength of 440 MPa with good ductility and weldability, making it ideal for chassis and structural components subjected to dynamic loads. The steel is supplied in coil, strip, or cut sheet form, typically in the as-rolled or controlled-rolled condition, and can be further processed by pickling and oiling.
- Minimum yield strength up to 305 MPa depending on thickness
- Excellent cold bending and forming characteristics
- Can be microalloyed with Nb, V, or Ti for grain refinement
- Widely used in truck frames, bus chassis, and trailer beams
S440L Hot Rolled Steel Coil for Automotive Structural Parts Chemical Composition per GB/T 3273-2005
The ladle analysis for S440L steel ensures consistent mechanical properties and weldability. Grain-refining elements such as niobium, vanadium, or titanium may be added upon agreement. When these microalloying elements are used, the minimum aluminum requirement may be waived.
| Chemical Element | Standard Value (wt%) | Remarks |
|---|---|---|
| Carbon (C) | ≤ 0.18 | Controlled for weldability and toughness |
| Silicon (Si) | ≤ 0.50 | Deoxidizer and strength contributor |
| Manganese (Mn) | ≤ 1.60 | Primary solid-solution strengthener |
| Phosphorus (P) | ≤ 0.025 | Maximised to avoid embrittlement |
| Sulfur (S) | ≤ 0.015 | Low level for improved formability |
| Acid-soluble Al (Alₛ) | ≥ 0.015 | Grain refinement; requirement may be omitted if Nb, V, Ti are added |
| Niobium (Nb)* | Optional | Microalloying for grain refinement and precipitation strengthening |
| Vanadium (V)* | Optional | Optional microalloying element |
| Titanium (Ti)* | Optional | Optional microalloying element |
S440L Hot Rolled Steel Coil for Automotive Structural Parts Thermal and Electrical Physical Properties
The physical constants are representative for low-carbon manganese-microalloyed steels. They are not specified in GB/T 3273 but are provided for design calculations. Variations may occur depending on the actual chemistry and processing route.
| Property | Typical Value | Unit | Reference Condition |
|---|---|---|---|
| Density (ρ) | 7.85 | kg/dm³ (g/cm³) | Room temperature |
| Modulus of elasticity (E) | 210 | GPa | Room temperature |
| Shear modulus (G) | 80 | GPa | Room temperature, calculated |
| Poisson's ratio (ν) | 0.30 | — | Room temperature |
| Thermal expansion coefficient (α) | 12.0 × 10⁻⁶ | K⁻¹ | 20 – 100 °C |
| Thermal expansion coefficient (α) | 12.8 × 10⁻⁶ | K⁻¹ | 20 – 200 °C |
| Thermal expansion coefficient (α) | 13.5 × 10⁻⁶ | K⁻¹ | 20 – 300 °C |
| Thermal conductivity (λ) | 50 | W/(m·K) | Room temperature |
| Specific heat capacity (c) | 460 | J/(kg·K) | Room temperature |
| Electrical resistivity (ρₑ) | 0.20 | µΩ·m | Room temperature |
S440L Hot Rolled Steel Coil for Automotive Structural Parts Mechanical Properties
The mechanical properties are determined on transverse test pieces according to GB/T 228. S440L exhibits a well-balanced combination of strength and ductility. The values depend on the sheet thickness and are valid for the hot-rolled condition without further heat treatment. Bending tests are performed with a 35 mm wide strip bent through 180°.
| Property | Standard Requirement | Unit | Test Conditions / Thickness (t) mm |
|---|---|---|---|
| Upper yield strength (ReH) | ≥ 305 | MPa | t ≤ 6.0 |
| Upper yield strength (ReH) | ≥ 295 | MPa | 6.0 < t ≤ 8.0 |
| Upper yield strength (ReH) | ≥ 275 | MPa | 8.0 < t ≤ 14.0 |
| Tensile strength (Rm) | 440 – 590 | MPa | All thicknesses |
| Elongation after fracture (A) | ≥ 26 | % | t ≤ 6.0, gauge length L₀ = 50 mm (or 80 mm as agreed) |
| Elongation after fracture (A) | ≥ 25 | % | 6.0 < t ≤ 8.0 |
| Elongation after fracture (A) | ≥ 24 | % | 8.0 < t ≤ 14.0 |
| 180° cold bending | d = 0.5a | — | t ≤ 6.0; bend width = 35 mm, a = sample thickness |
| 180° cold bending | d = a | — | 6.0 < t ≤ 8.0; bend width = 35 mm |
| 180° cold bending | d = 1.5a | — | 8.0 < t ≤ 14.0; bend width = 35 mm |
S440L Hot Rolled Steel Coil for Automotive Structural Parts Equivalent Standards and Substitutable Grades
| Country / Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB/T 3273 | S440L (440L) | Original grade |
| Japan | JIS G3113 | SAPH440 | Nearly identical mechanical properties; commonly substituted |
| Europe | EN 10149-2 | S420MC | Slightly higher yield; strength range overlaps |
| International | ISO 6930-2 | FeE420 | Equivalent to S420MC |
| USA | ASTM A1011/A1011M | HSLAS Grade 50 Class 1 | Comparable strength level, similar applications |
| India | IS 1079 | Fe440 | Close match in tensile properties for hot-rolled carbon steel |
S440L Hot Rolled Steel Coil for Automotive Structural Parts Application Introduction
S440L is engineered for cold-formed structural parts in automotive engineering. Its balanced strength and ductility facilitate complex forming without cracking, and its weldability allows integration into heavy assemblies. Typical applications include:
Product Applications: Truck chassis frames, Trailer longitudinal beams and cross members, Bus body structural profiles, Automotive bumper and impact beams, Dumper bodies and container frames
Processed into products: Main longitudinal frame rails, Transverse cross members and engine mount brackets, Suspension control arms and leaf-spring supports, B-pillar reinforcements and rocker panels, Tow hooks, hanger brackets, and gusset plates
Application industries: Automotive Manufacturing, Commercial Vehicle & Trailer, Bus & Coach Building, Agricultural Machinery, Construction Machinery
S440L Hot Rolled Steel Coil for Automotive Structural Parts Materials with Similar Performance
| Country / Region | Standard | Grade | Remarks |
|---|---|---|---|
| Europe | EN 10149-2 | S315MC / S355MC | Lower strength but very similar processing; for less demanding parts |
| South Korea | KS D 3560 | SAPH440 | Korean version identical to JIS SAPH440 |
| Germany | DIN EN 10149-2 | QStE420TM | Thermomechanically rolled, good formability |
| Russia | GOST 1050 | St5ps / St5sp | Carbon structural steel with comparable strength, but less formability |
| China | GB/T 912 | Q345B | Broader structural grade; may be used with thicker sections |
Notes:
Special agreements: S440L may be ordered with restricted carbon equivalent (CEV) to improve weldability. Microalloying additions (Nb, V, Ti) must be stated at inquiry. Surface quality classes and dimensional tolerances follow GB/T 3273-2005. The steel is normally supplied with a mill scale finish; pickled and oiled surface is optional. For applications requiring high fatigue life, stress-relief annealing after forming is not mandatory but can be applied by agreement.
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