B380CL Hot-Rolled High-Strength Steel
B380CL Hot-Rolled High-Strength Steel for Automotive Structural Cold Forming
B380CL is a hot-rolled high-strength low-alloy steel grade designed for cold forming applications in the automotive sector. It offers minimum yield strength of 380 MPa with good formability and weldability, compliant with Baosteel enterprise standard Q/BQB 310-2009.
Hot rolling, pickling, oiling, cold forming (stamping, bending, roll forming), welding (resistance, arc), cutting (shearing, laser, plasma)
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B380CL Hot-Rolled High-Strength Steel Introduction
B380CL is a titanium/niobium microalloyed hot-rolled steel sheet and strip grade developed by Baosteel under the enterprise standard Q/BQB 310-2009. It belongs to the cold forming high-yield strength family and is primarily used for automobile structural components that require a balance of strength, toughness, and press formability.
Key characteristics:
- Minimum yield strength of 380 MPa guarantees reliable structural performance.
- Excellent cold formability for stamping and bending operations, with guaranteed elongation and bending properties.
- Good weldability simplifies assembly processes.
- Uniform mechanical properties across the strip width and length due to controlled rolling and cooling.
- Supplied as hot-rolled, often pickled and oiled to improve surface quality and corrosion protection during storage.
The grade is equivalent to HR380F in the Chinese national standard GB/T 20887.1, ensuring interchangeability with other domestic automotive steel specifications.
B380CL Hot-Rolled High-Strength Steel Chemical Composition
Typical chemical composition limits for B380CL according to Q/BQB 310-2009. Microalloying elements niobium, titanium, and vanadium are optional and may be added to achieve the required mechanical properties. If added, their contents must be reported in the inspection certificate. The combined Nb+V+Ti content is typically restricted to ≤0.22%.
| Element | Standard Value (max unless noted) | Remarks |
|---|---|---|
| Carbon (C) | ≤0.10% | Ladle analysis |
| Silicon (Si) | ≤0.50% | |
| Manganese (Mn) | ≤1.00% | May be adjusted for strength |
| Phosphorus (P) | ≤0.025% | Low for good formability |
| Sulfur (S) | ≤0.015% | Controlled for cleanliness |
| Total Aluminum (Alt) | ≥0.015% | Minimum requirement for deoxidation |
| Niobium (Nb) | ≤0.09% (optional) | Grain refiner; if added ≤0.09% |
| Titanium (Ti) | ≤0.22% (optional) | Precipitation strengthener; if added ≤0.22% |
| Vanadium (V) | ≤0.15% (optional) | Microalloying element; if added ≤0.15% |
| Nb+V+Ti | ≤0.22% (if added) | Combined limit |
B380CL Hot-Rolled High-Strength Steel Thermal and Electrical Physical Properties
The following physical property values are typical for hot-rolled high-strength low-alloy steels in the as-rolled condition and are provided for design guidance. They are not guaranteed minima or maxima but represent commonly accepted engineering data.
| Property | Typical Value | Unit | Test Conditions |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | Room temperature |
| Elastic modulus (E) | 210 | GPa | Room temperature |
| Shear modulus (G) | 80 | GPa | Room temperature |
| Poisson's ratio (ν) | 0.3 | – | Room temperature |
| Thermal expansion coefficient (α) | 12.2 × 10⁻⁶ / K | 1/K | 20–100 °C |
| Thermal conductivity (λ) | 42 | W/(m·K) | 20 °C |
| Specific heat capacity (cp) | 470 | J/(kg·K) | 20 °C |
| Electrical resistivity (ρ_e) | 0.23 | μΩ·m | 20 °C |
B380CL Hot-Rolled High-Strength Steel Mechanical Properties
Mechanical properties are determined on transverse test pieces according to GB/T 228.1. Elongation is measured on gauge length A80 for thickness <3.0 mm and on A5 (5.65√S0) for thickness ≥3.0 mm. Bend test is performed according to GB/T 232 with the indicated bend diameter; no cracks allowed on the outer surface of the bend.
| Property | Standard Requirement | Unit | Test Conditions |
|---|---|---|---|
| Yield strength (ReH) | ≥380 | MPa | Room temperature, transverse direction |
| Tensile strength (Rm) | 450–590 | MPa | Room temperature, transverse direction |
| Elongation (A80) | ≥23 | % | Thickness <3.0 mm, gauge length 80 mm |
| Elongation (A5) | ≥28 | % | Thickness ≥3.0 mm, gauge length 5.65√S0 |
| Bend test, 180° | d = 1a (no crack) | – | Thickness ≤3.0 mm |
| Bend test, 180° | d = 2a (no crack) | – | Thickness >3.0 mm |
B380CL Hot-Rolled High-Strength Steel Fully Equivalent Materials – Standards and Substitute Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB/T 20887.1 | HR380F | National standard equivalent; identical chemical and mechanical requirements |
| China | Q/BQB 310-2009 | B380CL | Original Baosteel enterprise specification |
B380CL Hot-Rolled High-Strength Steel Application Introduction
B380CL is optimized for structural parts that are cold formed and then assembled by welding or bolting. It delivers a robust combination of strength and ductility, enabling weight reduction while maintaining crashworthiness. Typical uses are in the automotive industry, but it can also be applied in light truck frames, trailer components, and agricultural machinery where similar requirements exist.
Product Applications: Chassis side rails, Cross members and reinforcements, Suspension control arms, Wheel rims and wheel discs, Bumper reinforcements, Engine cradles & subframes, Truck body panels
Processed into products: Stamped and bent structural brackets, Longitudinal beams for passenger car frames, Spring seats and hanger brackets, Differential housing supports, Steering knuckle supports, Torsion beam cross members, Roll-formed profiles for bus bodies
Application industries: Automotive (passenger cars, light commercial vehicles), Transportation (bus frames, truck cabin supports), Agricultural machinery (structural frames, implements), Construction machinery (light/medium duty components)
B380CL Hot-Rolled High-Strength Steel Similar or Alternative Material Recommendations
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Japan | JIS G3113 | SAPH440 | Hot-rolled structural steel; similar tensile strength (≥440 MPa) but lower minimum yield (≥275 MPa); suitable for many automotive parts but may require thickness increase if 380 MPa yield is mandatory |
| EU | EN 10149-2 | S355MC | High-strength low-alloy for cold forming; minimum yield 355 MPa, slightly lower; often used in similar applications if design allows |
| Japan | JIS G3134 | SPFH540 | Hot-rolled high-tensile steel; tensile ≥540 MPa, typical yield around 355 MPa; higher strength but not directly interchangeable for yield-critical designs |
| China | GB/T 20564.3 | CR420LA | Cold-rolled equivalent (if thinner gauge is acceptable); yield ≥420 MPa, but cold-rolled formability differs |
Notes:
1. B380CL is supplied with guaranteed weldability; however, for critical welded joints, welding procedure qualification is recommended.
2. Surface quality: pickled and oiled surface provides temporary corrosion protection and clean surface for subsequent forming and painting.
3. Dimensional tolerances comply with Q/BQB 301 or relevant GB/T standards.
4. The steel is not intended for low-temperature impact service; for such requirements, consider grades with specified Charpy impact energy.
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