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SCM440H High-Strength Chromium-Molybdenum Alloy Steel
SCM440H is a high-strength chromium-molybdenum alloy steel classified as a structural steel with guaranteed hardenability (H-grade steel); in its designation, "SCM" denotes the chromium-molybdenum steel series, while "H" indicates the guaranteed hardenability band. In the quenched and tempered state, this material exhibits high strength, good toughness, and excellent fatigue properties, making it suitable for the manufacture of critical components subjected to heavy loads and high stress.
SCM440H Chemical Composition and the Role of Alloying Elements:
Carbon content: approximately 0.38%–0.44%,
Chromium: 0.85%–1.25%,
Molybdenum: 0.15%–0.35%,
Harmful elements (phosphorus and sulfur) are strictly limited to 0.03%.
The synergistic effect of the key alloying elements—chromium and molybdenum—significantly enhances the material's hardenability, high-temperature strength, and resistance to tempering-induced softening.
The typical mechanical properties of SCM440H in the quenched and tempered state are as follows:
Tensile strength: 930–1080 MPa (varies by cross-sectional size; e.g., 1100–1300 MPa for diameters ≤16 mm)
Yield strength: ≥785 MPa (≥900 MPa for diameters ≤16 mm)
Elongation: ≥12%
Reduction of area: ≥45%
Impact toughness: ≥50 J (at 20°C)
Hardness: HRC 28–36 (or HB 280–320)
Key performance advantages of SCM440H include:
Combination of high strength and good toughness: Capable of withstanding high loads and impact loads.
Excellent fatigue resistance: Suitable for manufacturing components subject to high-frequency vibration, such as gears and shafts.
Good hardenability: Ensures consistent performance even in large-section workpieces.
Uniform microstructure and excellent hardenability: Stable response to heat treatment and controllable hardness.
SCM440H Properties:
Quenching: Heat to 830–860°C, hold, and then cool in oil or water to transform austenite into martensite.
Tempering: Temper at 500–650°C to achieve the desired hardness, relieve internal stresses, and stabilize the microstructure.
Annealing: Heat to 680–700°C, hold, and cool slowly to improve machinability.
Strict control of temperature and cooling rates during heat treatment is essential to ensure microstructural uniformity. SCM440H exhibits no significant temper brittleness and minimal distortion during quenching, making it suitable for the manufacture of precision components.
SCM440H Chemical Composition and the Role of Alloying Elements:
Carbon content: approximately 0.38%–0.44%,
Chromium: 0.85%–1.25%,
Molybdenum: 0.15%–0.35%,
Harmful elements (phosphorus and sulfur) are strictly limited to 0.03%.
The synergistic effect of the key alloying elements—chromium and molybdenum—significantly enhances the material's hardenability, high-temperature strength, and resistance to tempering-induced softening.
The typical mechanical properties of SCM440H in the quenched and tempered state are as follows:
Tensile strength: 930–1080 MPa (varies by cross-sectional size; e.g., 1100–1300 MPa for diameters ≤16 mm)
Yield strength: ≥785 MPa (≥900 MPa for diameters ≤16 mm)
Elongation: ≥12%
Reduction of area: ≥45%
Impact toughness: ≥50 J (at 20°C)
Hardness: HRC 28–36 (or HB 280–320)
Key performance advantages of SCM440H include:
Combination of high strength and good toughness: Capable of withstanding high loads and impact loads.
Excellent fatigue resistance: Suitable for manufacturing components subject to high-frequency vibration, such as gears and shafts.
Good hardenability: Ensures consistent performance even in large-section workpieces.
Uniform microstructure and excellent hardenability: Stable response to heat treatment and controllable hardness.
SCM440H Properties:
Quenching: Heat to 830–860°C, hold, and then cool in oil or water to transform austenite into martensite.
Tempering: Temper at 500–650°C to achieve the desired hardness, relieve internal stresses, and stabilize the microstructure.
Annealing: Heat to 680–700°C, hold, and cool slowly to improve machinability.
Strict control of temperature and cooling rates during heat treatment is essential to ensure microstructural uniformity. SCM440H exhibits no significant temper brittleness and minimal distortion during quenching, making it suitable for the manufacture of precision components.
