GB/T 11251 30CrMo Alloy Steel Plate Material
GB/T 11251 30CrMo Alloy Steel Plate - High-Strength Cr-Mo Structural Steel
Detailed material data for 30CrMo hot-rolled alloy steel plate per Chinese standard GB/T 11251, including chemical composition, mechanical and physical properties, international equivalents, and typical applications.
Hot forming, annealing, quenching and tempering, normalizing, stress relieving, welding, machining
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GB/T 11251 30CrMo Alloy Steel Plate Introduction
30CrMo is a chromium-molybdenum alloy structural steel plate defined under GB/T 11251 (Hot-rolled alloy structural steel plates). It belongs to the medium-carbon low-alloy quenched and tempered steel family, offering an excellent combination of high strength, toughness, and good hardenability.
- Typical delivery condition is hot-rolled, annealed, or quenched and tempered.
- Widely used for manufacturing critical mechanical components such as gears, shafts, bolts, and pressure vessels.
- Exhibits good weldability and machinability in the annealed or tempered state.
GB/T 11251 30CrMo Alloy Steel Plate Chemical Composition
The chemical composition of 30CrMo alloy steel plates according to GB/T 11251 is strictly controlled to ensure the desired mechanical properties and hardenability. The chromium and molybdenum additions provide improved strength and creep resistance, while the carbon content optimizes hardenability. Residual elements are kept at low levels to maintain ductility and toughness.
| Chemical Element | Standard Value (wt%) | Remarks |
|---|---|---|
| Carbon (C) | 0.28 - 0.34 | Primary hardening element |
| Silicon (Si) | 0.17 - 0.37 | Deoxidizer, improves strength |
| Manganese (Mn) | 0.40 - 0.70 | Improves hardenability and strength |
| Chromium (Cr) | 0.80 - 1.10 | Improves hardenability, wear and corrosion resistance |
| Molybdenum (Mo) | 0.15 - 0.25 | Enhances hardenability, high-temperature strength, and creep resistance |
| Phosphorus (P) | ≤ 0.030 | Impurity, limited for toughness |
| Sulfur (S) | ≤ 0.030 | Impurity, limited for ductility and weldability |
| Nickel (Ni) | ≤ 0.30 | Residual element, not intentionally added |
| Copper (Cu) | ≤ 0.30 | Residual element, may influence corrosion resistance |
GB/T 11251 30CrMo Alloy Steel Plate Thermal and Electrical Physical Properties
Physical properties are measured on fully heat-treated 30CrMo steel. These values are essential for design calculations involving thermal expansion, heat transfer, and electrical conductivity. The density and moduli are typical for low-alloy steels. Properties vary slightly with temperature; the values given are at room temperature unless otherwise specified.
| Property | Typical Value | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | At 20 °C |
| Modulus of Elasticity (E) | 210 | GPa | At 20 °C |
| Shear Modulus (G) | 80 | GPa | At 20 °C, calculated from E and ν |
| Poisson's Ratio (ν) | 0.3 | - | At 20 °C |
| Thermal Expansion Coefficient (α) | 12.2 | 10⁻⁶ /K | Between 20 °C and 100 °C |
| Thermal Expansion Coefficient (α) | 13.1 | 10⁻⁶ /K | Between 20 °C and 300 °C |
| Thermal Expansion Coefficient (α) | 13.9 | 10⁻⁶ /K | Between 20 °C and 500 °C |
| Thermal Conductivity (λ) | 42.7 | W/(m·K) | At 100 °C |
| Thermal Conductivity (λ) | 39.8 | W/(m·K) | At 400 °C |
| Specific Heat Capacity (c) | 460 | J/(kg·K) | At 20 °C |
| Electrical Resistivity (ρₑ) | 0.23 | µΩ·m | At 20 °C |
GB/T 11251 30CrMo Alloy Steel Plate Mechanical Properties
Mechanical properties of 30CrMo plates depend on heat treatment condition and section thickness. The values below are representative for quenched and tempered condition (typical for high-strength applications) as per GB/T 11251 for plate thickness ≤ 16 mm. For thicker sections, properties may be slightly lower. Impact energy is tested at room temperature using Charpy V-notch specimens.
- Quenching temperature: 880 °C (oil)
- Tempering temperature: 540 °C (water or oil)
| Property | Standard Requirement | Unit | Test Condition |
|---|---|---|---|
| Yield Strength (ReH) | ≥ 785 | MPa | Thickness ≤ 16 mm (Q+T) |
| Yield Strength (ReH) | ≥ 735 | MPa | Thickness 16-40 mm (Q+T) |
| Yield Strength (ReH) | ≥ 685 | MPa | Thickness 40-60 mm (Q+T) |
| Tensile Strength (Rm) | ≥ 930 | MPa | Thickness ≤ 16 mm (Q+T) |
| Tensile Strength (Rm) | ≥ 880 | MPa | Thickness 16-40 mm (Q+T) |
| Tensile Strength (Rm) | ≥ 835 | MPa | Thickness 40-60 mm (Q+T) |
| Elongation after Fracture (A) | ≥ 12 | % | Thickness ≤ 16 mm, gauge length 5.65√So |
| Elongation after Fracture (A) | ≥ 12 | % | Thickness 16-40 mm |
| Elongation after Fracture (A) | ≥ 13 | % | Thickness 40-60 mm |
| Impact Energy (KV2) | ≥ 63 | J | Charpy V-notch, 20 °C, thickness ≤ 60 mm |
| Bend Test (180°) | d = 3a | - | Thickness ≤ 16 mm, bending diameter = 3 × plate thickness (a) |
| Hardness (HBW) | ≤ 229 | - | Annealed condition (soft) |
GB/T 11251 30CrMo Alloy Steel Plate Internationally Equivalent Standards and Replaceable Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| USA | ASTM A29 / A29M | 4130 | Comparable chemical composition; properties may differ based on standard |
| Japan | JIS G4105 | SCM430 | Equivalent Cr-Mo steel with similar heat treatment response |
| Germany | DIN EN 10263-4 | 25CrMo4 (1.7218) | Close match in composition and mechanical properties |
| European Union | EN 10263-4 | 25CrMo4 (1.7218) | Harmonized European grade |
| International | ISO 683-1 | 25CrMo4 | ISO designation mirrors EN 25CrMo4 |
| Great Britain | BS 970 Part 1 | 708M25 | British equivalent, often used interchangeably |
GB/T 11251 30CrMo Alloy Steel Plate Application Introduction
30CrMo steel plates are utilized in industries requiring a balanced combination of high tensile strength, good impact toughness, and reliable heat treatment response. They are typically machined and welded in the annealed or quenched & tempered condition, then possibly case-hardened or nitrided for surface wear resistance. Below are typical application sectors and specific products.
Product Applications: Pressure vessels and boilers, High-strength bolts and fasteners, Crankshafts and connecting rods, Gears and pinions, Hydraulic cylinder tubes, Structural steel frameworks
Processed into products: Automotive axle shafts and steering knuckles, Flanges and valve bodies, Drill collars and tool joints, Turbine rotors and blades, Forged rolls and spindles, Welded shafts and gear wheels
Application industries: Automotive and transportation, Oil & gas (drilling equipment, pipelines), Power generation (turbine components), General mechanical engineering, Construction and structural engineering, Mining and heavy equipment
GB/T 11251 30CrMo Alloy Steel Plate Similar or Closely Related Materials
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB/T 11251 | 35CrMo | Higher carbon content for increased strength, slightly lower toughness |
| China | GB/T 11251 | 42CrMo | Higher carbon and chromium for superior strength and wear resistance |
| China | GB/T 11251 | 20CrMo | Lower carbon, better weldability, often used in carburized condition |
| USA | ASTM A29 | 4140 | Higher carbon and slightly higher Cr and Mo, more strength |
| Germany | DIN EN 10083-3 | 34CrMo4 | Similar properties, slightly different composition range |
| Japan | JIS G4105 | SCM435 | Higher carbon (0.33-0.38%) variant for higher hardenability |
Notes:
Additional remarks:
- 30CrMo plates may be ordered with various quality requirements (e.g., ultrasonic testing, impact testing at low temperature, or restricted chemical composition).
- The mechanical properties listed are based on typical values from GB/T 11251 for quenched and tempered condition. The standard also provides properties for normalized or annealed conditions; always refer to the applicable revision of the standard and the purchase specification.
- Welding of 30CrMo usually requires preheating (150-300 °C) and post-weld stress relieving to avoid cracking.
- Hardness in the hardened and fully tempered condition can range from 28 to 36 HRC depending on tempering temperature.
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