Comprehensive Guide to Baosteel Q/BQB 310
Comprehensive Guide to Baosteel Q/BQB 310-2009 B320L Hot Rolled Steel Coil
In-depth material datasheet of B320L hot rolled steel coil under Baosteel standard Q/BQB 310-2009, covering chemical composition, mechanical and physical properties, international equivalents, and applications.
Cold forming, bending, stamping, welding, plasma/laser cutting
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Comprehensive Guide to Baosteel Q/BQB 310 Introduction
B320L is a high-strength low-alloy (HSLA) hot rolled steel grade specified in Baosteel enterprise standard Q/BQB 310-2009 for cold forming. It delivers minimum yield strength of 320 MPa and provides excellent formability, weldability, and fatigue resistance. This grade is microalloyed mainly with manganese, ensuring fine-grain strengthening without complex microalloying elements. Supplied in as-hot-rolled condition, B320L is ideal for structural components that require bending, drawing, and moderate deformation. It is widely adopted in automotive and machinery industries for parts like beams, reinforcements, and brackets, offering a cost-effective balance between strength and workability.
Comprehensive Guide to Baosteel Q/BQB 310 Chemical Composition
The chemical composition of B320L, as per Q/BQB 310-2009, is designed to achieve a good combination of strength and formability. Manganese provides solid-solution strengthening, while low carbon ensures excellent weldability and cold formability. Aluminum is added for deoxidation and fine grain control. The limits are tight to guarantee consistent mechanical properties across coils.
| Element | Standard Value (wt%) | Remarks |
|---|---|---|
| C (Carbon) | ≤0.10 | Low carbon for weldability and formability |
| Si (Silicon) | ≤0.50 | Deoxidizer, contributes to strength |
| Mn (Manganese) | ≤1.50 | Primary solid-solution strengthener |
| P (Phosphorus) | ≤0.025 | Controlled for toughness |
| S (Sulfur) | ≤0.020 | Controlled for internal cleanliness |
| Alt (Total Aluminum) | ≥0.015 | Grain refinement and deoxidation |
Comprehensive Guide to Baosteel Q/BQB 310 Thermal and Electrical Physical Properties
The physical properties below represent typical data for low-carbon HSLA hot rolled steel. Actual values may vary slightly with processing conditions and temperature. These parameters are essential for design calculations involving thermal expansion, heat transfer, and electrical resistivity.
| Property | Typical Value | Unit | Test Condition |
|---|---|---|---|
| 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) | 12.0 × 10⁻⁶ | K⁻¹ | 20–100 °C |
| Thermal conductivity (λ) | 50 | W/(m·K) | Room temperature |
| Specific heat capacity | 460 | J/(kg·K) | Room temperature |
| Electrical resistivity (ρ_e) | 0.15–0.25 | μΩ·m | Room temperature |
Comprehensive Guide to Baosteel Q/BQB 310 Mechanical Properties
Mechanical properties for B320L hot rolled steel are evaluated at room temperature according to Q/BQB 310-2009. The yield and tensile strengths meet the minimum requirements, while the elongation ensures sufficient cold formability. Bending tests confirm the material's ability to withstand 180° bending without cracking.
| Property | Required Value | Unit | Test Condition |
|---|---|---|---|
| Yield Strength (ReL/ReH) | ≥320 | MPa | Transverse test specimens |
| Tensile Strength (Rm) | 390–510 | MPa | Transverse test specimens |
| Elongation after fracture (A80) | ≥19 | % | Gauge length 80 mm, thickness < 3.0 mm |
| Elongation after fracture (A5) | ≥23 | % | Gauge length 5.65√So, thickness ≥ 3.0 mm |
| Bend test (180° bending) | d = 0a | — | Bend diameter equals thickness, no cracks |
Comprehensive Guide to Baosteel Q/BQB 310 Fully Equivalent Material Standards and Substitute Designations
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Europe | EN 10149-2 | S315MC | Closest equivalent: yield ≥315 MPa, tensile 390–510 MPa, A80 ≥21% |
| International | ISO 6930-2 | S315MC | Harmonized with EN 10149-2 |
| Germany | DIN EN 10149-2 | S315MC | Identical technical delivery conditions |
| UK | BS EN 10149-2 | S315MC | Identical technical delivery conditions |
| China (Baosteel) | Q/BQB 310-2009 | B320L | Original specification; fully interchangeable with above |
Comprehensive Guide to Baosteel Q/BQB 310 Application Introduction
B320L is engineered for cold-formed structural components where high strength and reliable formability are required. Typical processing includes stamping, bending, rollforming, and welding. The material can be readily coated or painted after proper surface preparation. Designers benefit from its predictable mechanical properties and availability in various thicknesses.
Product Applications: Chassis longitudinal beams, Cross members and subframe components, Reinforcement panels and brackets, Engine mounting rails, Agricultural implement frames, Wheel rims and disc blanks (prior to forming)
Processed into products: Stamped and bent brackets, Welded tubular assemblies, Roll-formed sections (U-channels, C-profiles), Laser-cut blanks for subsequent forming, Deep-drawn cups and structural housings
Application industries: Automotive (passenger cars, light commercial vehicles), Agricultural machinery (tractor parts, harvester frames), Construction and infrastructure (structural hollow sections, scaffoldings), General engineering (brackets, supports, machinery housings), Energy and transportation (railway components, truck frames)
Comprehensive Guide to Baosteel Q/BQB 310 Similar/Comparable Material Recommendations
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Europe | EN 10149-2 | S340MC | Higher yield strength (≥340 MPa), formability slightly reduced |
| Japan | JIS G 3134 | SPFH490Y | Yield ≥325 MPa, tensile ≥490 MPa, used for automotive structural applications |
| Japan | JIS G 3113 | SAPH440 | Yield ≥305 MPa, tensile ≥440 MPa, commonly used for vehicle frame parts |
| Germany | DIN 1614 (withdrawn) | StW23 | Former standard; similar chemistry and strength, replaced by EN 10149-2 |
| China | GB/T 20887.1 (proposed) | HR420L/HR340LA | Potential national standard equivalents; slightly varied chemical and strength requirements |
Notes:
B320L is generally not supplied with guaranteed impact toughness at low temperatures; if required, additional agreement with the steelmaker is needed. Surface treatment (pickling and oiling) improves stamping lubricity and corrosion protection during transport. The grade can be supplied as slit strip or cut-to-length sheets. Because this is an enterprise standard, minor deviations from national or international standards may exist; cross-reference with EN 10149-2 S315MC for full equivalency when sourcing.
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