SAPH400 Hot Rolled Steel Coil
SAPH400 Hot Rolled Steel Coil - Automotive Structural High-Strength Steel
SAPH400 is a hot-rolled high-strength steel for automotive structural applications. It offers good formability and weldability combined with minimum tensile strength of 400 MPa.
Cold forming, stamping, bending, roll forming, welding, shearing
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SAPH400 Hot Rolled Steel Coil Introduction
SAPH400 is a hot-rolled high-strength steel grade standardized under JIS G3113:2006 and Q/BQB 310-2009 (Baosteel). It belongs to the family of automotive structural steels designed for chassis and body-in-white components. Typical delivery condition is hot-rolled coil, often pickled and oiled to improve surface quality and corrosion resistance. The steel provides an excellent balance of strength and ductility, making it suitable for cold forming operations such as bending, drawing, and shearing. Its fine-grained microstructure, achieved through controlled rolling and microalloying, ensures consistent mechanical properties across a wide thickness range. The grade is widely adopted by automotive OEMs and tier-one suppliers for lightweighting and crashworthiness requirements.
SAPH400 Hot Rolled Steel Coil Chemical Composition
The chemical composition of SAPH400 is defined in JIS G3113 and Q/BQB 310. Tight control of carbon and manganese ensures good weldability, while low phosphorus and sulfur levels improve toughness and formability. Microalloying elements such as niobium or titanium may be added for grain refinement, but are not mandatory as per the standard.
| Element | Standard Value (wt%) | Remarks |
|---|---|---|
| C | ≤ 0.21 | Improves strength; higher values may reduce weldability |
| Si | ≤ 0.30 | Deoxidizer; aids in strength without significantly impairing ductility |
| Mn | ≤ 0.75 | Enhances strength and hardenability; promotes fine grain structure |
| P | ≤ 0.030 | Kept low to avoid cold brittleness and segregation |
| S | ≤ 0.030 | Kept low for good hot workability and toughness |
| Alt/Nb/Ti* | Trace additions* | *Optional grain-refining elements; not mandated by the standard but may be present |
SAPH400 Hot Rolled Steel Coil Physical Properties
The following physical properties are typical for SAPH400 steel and are not guaranteed by the standard. They are provided for design guidance. Slight variations may occur depending on actual chemical composition and processing history.
| Property | Typical Value | Unit | Conditions / Remarks |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | Room temperature |
| Elastic Modulus (E) | 205 | GPa | Room temperature |
| Shear Modulus (G) | 80 | GPa | Calculated from E and ν |
| Poisson's Ratio (ν) | 0.30 | – | – |
| Thermal Expansion Coefficient (α) | 11.7 × 10⁻⁶ | 1/K | 20 °C – 100 °C |
| Thermal Conductivity (λ) | 52 | W/(m·K) | At 20 °C |
| Specific Heat Capacity (cp) | 470 | J/(kg·K) | Room temperature |
| Electrical Resistivity (ρe) | 0.15 | μΩ·m | At 20 °C |
SAPH400 Hot Rolled Steel Coil Mechanical Properties
Tensile testing is performed according to JIS Z2241 (JIS G3113) or equivalent. Elongation is measured on JIS No.5 test pieces. The bending test requires crack-free 180° bending around the specified mandrel diameter. All values are minimum unless otherwise noted. For thicknesses outside the specified ranges, the standard provides additional requirements; consult the full standard.
| Property | Standard Requirement | Unit | Test Condition / Remarks |
|---|---|---|---|
| Yield Strength (ReH) | ≥ 235 | MPa | Thickness ≤ 6 mm |
| Yield Strength (ReH) | ≥ 225 | MPa | Thickness > 6 mm to 14 mm |
| Tensile Strength (Rm) | ≥ 400 | MPa | All thicknesses |
| Elongation (A) | ≥ 31 | % | Thickness 1.6 – 2.0 mm, JIS No.5 specimen |
| Elongation (A) | ≥ 32 | % | Thickness > 2.0 – 2.5 mm, JIS No.5 specimen |
| Elongation (A) | ≥ 33 | % | Thickness > 2.5 – 3.15 mm, JIS No.5 specimen |
| Elongation (A) | ≥ 34 | % | Thickness > 3.15 – 4.0 mm, JIS No.5 specimen |
| Elongation (A) | ≥ 35 | % | Thickness > 4.0 – 6.0 mm, JIS No.5 specimen |
| Elongation (A) | ≥ 31 | % | Thickness > 6.0 – 14 mm, JIS No.5 specimen |
| Bend Test (180°) | d = 0.5 a | – | Thickness ≤ 6 mm (a = specimen thickness) |
| Bend Test (180°) | d = 1.0 a | – | Thickness > 6 mm |
SAPH400 Hot Rolled Steel Coil Fully Equivalent Material Standards and Substitutable Grades
| Region | Standard | Grade | Remarks |
|---|---|---|---|
| Japan | JIS G3113:2006 | SAPH400 | Original standard; identical requirements |
| China | Q/BQB 310-2009 | SAPH400 | Baosteel enterprise standard; fully equivalent to JIS SAPH400 |
SAPH400 Hot Rolled Steel Coil Application Introduction
SAPH400 is engineered for automotive components that require a reliable combination of strength, formability, and weldability. The steel is typically supplied as hot-rolled coil and can be processed through conventional stamping, roll forming, or tube making. It is suitable for parts that undergo moderate cold deformation and are subjected to dynamic loads. Designers should consider the thickness-dependent mechanical properties for part optimization.
Product Applications: Automotive chassis frames and sub-frames, Cross members and longitudinal beams, Suspension arms and spring brackets, Wheel rims and disc wheel components, Reinforcement panels (floor, door, bumper), Engine cradles and transmission mounts, Trailer and container structural parts
Processed into products: Front/rear side members, Bumper reinforcement beams, Suspension lower/upper control arms, Cross car beam assemblies, Frame rails and reinforcements, Spring seats and shackle brackets, Mounting brackets for powertrain
Application industries: Automotive (passenger cars, commercial vehicles), Transportation (bus, truck, trailer frames), Construction & agricultural machinery (light structural parts), General engineering (pressings, welded assemblies)
SAPH400 Hot Rolled Steel Coil Similar / Alternative Materials with Close Properties
| Region | Standard | Grade | Remarks |
|---|---|---|---|
| Japan | JIS G3113:2006 | SAPH370 | Lower tensile strength (≥370 MPa), higher ductility; may substitute where lower strength is acceptable |
| Japan | JIS G3113:2006 | SAPH440 | Higher tensile strength (≥440 MPa), lower elongation; suitable for weight reduction but may require adjusted forming parameters |
| China | Q/BQB 310-2009 | SAPH370 | Equivalent to JIS SAPH370 |
| China | Q/BQB 310-2009 | SAPH440 | Equivalent to JIS SAPH440 |
| Europe | EN 10149-2:2013 | S315MC | High-yield steel for cold forming; minimum yield 315 MPa, tensile 390–510 MPa; slightly higher strength, good formability |
| Europe | EN 10149-2:2013 | S355MC | Minimum yield 355 MPa, tensile 430–550 MPa; higher strength than SAPH400, less ductile |
Notes:
Material ordering should specify the required standard, grade, dimensions, and surface condition (e.g., pickled and oiled). When welding, low-hydrogen processes are recommended, and a slight preheat may be beneficial for thick sections. Additional testing, such as Charpy impact or hardness, can be agreed upon between the supplier and the purchaser. For parts requiring enhanced fatigue performance, hot-rolled SAPH400 may be upgraded to fine-grained or microalloyed grades under the same standard family.
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