B440QZR Hot Rolled Steel Coil
B440QZR Hot Rolled Steel Coil - 440 MPa Yield Automotive HSLA Steel per Q/BQB 310-2009
Detailed material properties, chemical composition, mechanical and physical data for Baosteel B440QZR hot rolled steel coil under Q/BQB 310-2009.
Hot rolling, cold forming, stamping, bending, welding, machining
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B440QZR Hot Rolled Steel Coil Introduction
B440QZR is a hot-rolled high-strength low-alloy (HSLA) steel grade defined in Baosteel's Q/BQB 310-2009 standard for automobile structural applications. It is microalloyed with niobium and/or titanium to achieve a minimum yield strength of 440 MPa in the as-rolled or controlled-rolled condition. The steel offers a good combination of high strength, excellent formability, and reliable weldability, enabling weight reduction in vehicle components without sacrificing durability. Typical applications include chassis parts, suspension arms, wheel rims, and structural reinforcements. The product is supplied as hot-rolled coils or cut sheets with a hot-rolled surface; it can be subsequently cold formed, stamped, or welded in manufacturing processes. International similar grades include EN 10149-2 S460MC and JIS G 3134 SPFH590, although chemical and mechanical requirements may not be identical.
B440QZR Hot Rolled Steel Coil Chemical Composition , Heat Analysis
The chemical composition is based on the ladle analysis limits specified in Q/BQB 310-2009. Microalloying elements (Nb, Ti) are added to refine grain size and enhance strength through precipitation hardening. All values are maximum unless a range or minimum is indicated.
| Element | Standard Value (max or range) | Remarks |
|---|---|---|
| C | ≤ 0.12 | |
| Si | ≤ 0.50 | |
| Mn | ≤ 1.80 | |
| P | ≤ 0.025 | |
| S | ≤ 0.015 | |
| Alt | ≥ 0.015 | Total aluminium |
| Nb | ≤ 0.09 | May be partially or fully substituted by Ti |
| Ti | ≤ 0.15 | May be partially or fully substituted by Nb |
| N | ≤ 0.009 | For nitrogen binding |
B440QZR Hot Rolled Steel Coil Thermal and Electrical Physical Properties
Physical properties are representative for low-carbon microalloyed steel at room temperature unless otherwise noted. They are not specified by Q/BQB 310-2009 but are commonly used for design and simulation.
- Thermal conductivity, specific heat, and electrical resistivity are influenced by microstructure and temperature.
- The coefficient of thermal expansion is an average value for the range 20–200 °C.
| Property | Typical Value | Unit | Condition / Temperature |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | 20 °C |
| Elastic modulus (E) | 210 | GPa | 20 °C |
| Shear modulus (G) | 80 | GPa | 20 °C |
| Poisson's ratio (ν) | 0.3 | — | 20 °C |
| Coefficient of thermal expansion (α) | 12.0 | 10⁻⁶·K⁻¹ | 20–200 °C |
| Thermal conductivity (λ) | 50 | W/(m·K) | 20 °C |
| Specific heat capacity (cp) | 460 | J/(kg·K) | 20–100 °C |
| Electrical resistivity (ρe) | 0.20 | µΩ·m | 20 °C |
B440QZR Hot Rolled Steel Coil Mechanical Properties
Mechanical properties are based on transverse test pieces taken from hot-rolled strip/coil as per Q/BQB 310-2009. Properties are guaranteed for thickness range 1.6–6.0 mm (other thicknesses may be agreed upon).
- Yield strength and tensile strength values apply in the delivery condition.
- Elongation is measured on gauge length 50 mm (25 mm width specimen) or proportional gauge.
- Bend test mandrel diameter 'a' denotes specimen thickness.
| Property | Required Value | Unit | Test Condition |
|---|---|---|---|
| Yield strength (ReH) | ≥ 440 | MPa | Thickness 1.6–6.0 mm |
| Tensile strength (Rm) | 590 – 740 | MPa | Thickness 1.6–6.0 mm |
| Elongation (A80mm) | ≥ 19 | % | Thickness < 3.0 mm, transverse |
| Elongation (A5.65√S0) | ≥ 21 | % | Thickness 3.0–6.0 mm, transverse |
| Bend test (180°) | d = 0.5a | — | a = specimen thickness, no cracks |
B440QZR Hot Rolled Steel Coil Directly Equivalent Grades – No Exact International Counterpart; Closest Recommended Substitutes
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | Q/BQB 310-2009 | B440QZR | Original specification |
| Europe | EN 10149-2 | S460MC | Yield strength 460 MPa vs 440 MPa; similar microalloy concept. Slight overstrength; confirm with customer. |
| Japan | JIS G 3134 | SPFH590 | Tensile strength ≥590 MPa; yield typically ~400–450 MPa. Different property approach. |
| International | ISO 20887 | FeE460TM | Thermo-mechanically rolled; yield ≥460 MPa. |
B440QZR Hot Rolled Steel Coil Application Introduction
B440QZR is designed for structural applications requiring high strength, good cold formability, and excellent weldability. It is widely used in the automotive industry for weight-critical components. The steel can be formed by press braking, roll forming, and stamping. It is suitable for resistance spot welding, arc welding, and laser welding. Surface treatments such as painting, e-coating, and galvanizing are applicable.
- Typical industries: automotive, transportation, machinery manufacturing.
- Typical products: chassis frames, suspension arms, wheel rims, cross members, longitudinal beams, seat structures, brackets.
- Typical components: stamped and welded assemblies, structural tubes, formed reinforcements, energy-absorbing parts.
Product Applications: Chassis frames and subframes, Wheel rims, Suspension control arms, Axle beams, Trailer components, Cross members and longitudinal rails, Seat frames and mounting brackets, Structural body panels
Processed into products: Stamped structural brackets, Welded assemblies, Cold-formed channels and profiles, Hydroformed tubes (after heat treatment), Laser-welded blanks, Impact beams
Application industries: Automotive manufacturing, Commercial vehicle production, Agricultural machinery, Construction equipment, Rail transportation
B440QZR Hot Rolled Steel Coil Similar/Alternative Materials
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | Q/BQB 310-2009 | B420QZR | Lower yield strength (≥420 MPa). Same family. |
| China | Q/BQB 310-2009 | B500QZR | Higher yield strength (≥500 MPa). For heavier duty. |
| Europe | EN 10149-2 | S420MC | Yield ≥420 MPa, similar formability. |
| USA | SAE J1392 | 050XLK | HSLA hot rolled, yield ≥350 MPa; lower strength alternative. |
| Germany | DIN 1614-2 | QStE420TM | Thermo-mechanically rolled, yield ≥420 MPa. |
Notes:
Surface quality: Supplied with hot-rolled surface; may show slight mill scale. Surface protection with oil possible upon agreement. Edge condition: Mill edge or trimmed edge. Dimensional tolerances: In accordance with Q/BQB 301 or as agreed. Weldability: Equivalent carbon content (CEV) typically ≤0.35% ensures good spot and arc weldability without preheating. Cold formability: Minimum bend radius recommended: 0.5t (transverse direction). Data notice: The information provided is based on the standard Q/BQB 310-2009 and typical engineering data; exact properties should be verified with the mill certificate for each specific coil.
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