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Performance Characteristics of SCM822H Constituents
SCM822H is a representative chromium-molybdenum alloy structural steel within the Japanese JIS standard system, belonging to the "H-steel" series. The "H" suffix denotes "Hardenability," signifying that—in addition to controlled chemical composition—the steel's end-quench curve (Jominy curve) is constrained within a specified band. Consequently, fluctuations in hardenability between batches or even across different heats are significantly lower than those of standard SCM822; this characteristic is the fundamental reason for its widespread adoption in mass-produced automotive carburized parts.
SCM822H Chemical Composition:
SCM822H Mechanical Properties and Heat Treatment Characteristics:
The typical processing route for SCM822H involves carburizing, quenching, and low-temperature tempering; it can also be used for medium-load shafts following a quench-and-temper treatment. Due to controlled hardenability (Jominy end-quench band), bars with diameters of 30–80 mm generally yield a mixed martensite-bainite core microstructure after oil quenching. Surface hardness reaches HRC 58–62 after carburizing, while core hardness is adjustable within the HRC 30–40 range. Tensile strength typically falls between 900 and 1100 MPa (higher values are achievable in the quenched-and-tempered state, depending on cross-section and tempering temperature).
Grain size is generally required to be finer than ASTM No. 5–6. JIS G 4052 imposes austenite grain size constraints on H-grade steels to prevent grain coarsening at carburizing temperatures—which would otherwise compromise impact toughness—a factor critical to the bending fatigue life of automotive gears.
Applications of SCM822H steel:
Automotive transmission gears, differential bevel gears, and planetary gears (highest volume application);
Slewing bearings, track link pins, and bushings for construction machinery;
High-strength automotive bolts (Grades 10.9–12.9), steering knuckle arms, and axle shafts;
Drive shafts and chain drive pins for motorcycles and light trucks.
SCM822H Chemical Composition:
| C | Si | Mn | P | S | Cr | Mo | Ni | Cu |
| 0.19 | 0.15 | 0.55 | 0.03 | 0.03 | 0.85 | 0.35 | 0.25 | 0.30 |
SCM822H Mechanical Properties and Heat Treatment Characteristics:
The typical processing route for SCM822H involves carburizing, quenching, and low-temperature tempering; it can also be used for medium-load shafts following a quench-and-temper treatment. Due to controlled hardenability (Jominy end-quench band), bars with diameters of 30–80 mm generally yield a mixed martensite-bainite core microstructure after oil quenching. Surface hardness reaches HRC 58–62 after carburizing, while core hardness is adjustable within the HRC 30–40 range. Tensile strength typically falls between 900 and 1100 MPa (higher values are achievable in the quenched-and-tempered state, depending on cross-section and tempering temperature).
Grain size is generally required to be finer than ASTM No. 5–6. JIS G 4052 imposes austenite grain size constraints on H-grade steels to prevent grain coarsening at carburizing temperatures—which would otherwise compromise impact toughness—a factor critical to the bending fatigue life of automotive gears.
Applications of SCM822H steel:
Automotive transmission gears, differential bevel gears, and planetary gears (highest volume application);
Slewing bearings, track link pins, and bushings for construction machinery;
High-strength automotive bolts (Grades 10.9–12.9), steering knuckle arms, and axle shafts;
Drive shafts and chain drive pins for motorcycles and light trucks.
