Chrome Moly JIS SCM420 Alloy Steel Bars

Product Description

JIS SCM420 is a classic chromium-molybdenum alloy steel specified under the Japanese Industrial Standards (JIS G4053).

Designed primarily as a case-hardening (carburizing) steel, SCM420 features a low carbon content (around 0.20%) combined with targeted additions of chromium and molybdenum. This chemistry makes it the ideal choice for heavy-duty components requiring a surface that can withstand massive abrasion alongside an exceptionally tough core that absorbs sudden operational impacts without snapping.

Global Equivalents

When sourcing internationally or switching manufacturing prints, SCM420 lines up directly with these prominent national standards:

• USA (AISI/SAE): AISI 4120 / UNS G41200

• Germany (DIN / WNr): 20CrMo4 / 1.7321

• Europe (EN): 22CrMoS4 / 20CrMo4

• France (AFNOR): 20CD4

• China (GB): 20CrMo

Chemical Composition (Typical %)

The precise allocation of chromium provides excellent hardenability, while the molybdenum refines the grain structure to prevent core embrittlement during prolonged high-temperature carburizing cycles.

Mechanical Properties (Core Properties Post-Heat Treatment)

Because SCM420 is typically used in a case-hardened state, the bulk bar material properties are measured after quenching and tempering to represent the tough internal core supporting the hardened outer case.

• Tensile Strength ($R_m$): ≥ 980 MPa (N/mm²)

• Yield Strength ($R_{e}$): ≥ 785 MPa

• Elongation ($A$): ≥ 14%

• Reduction of Area ($Z$): ≥ 40%

• Impact Toughness (Charpy V-Notch): ≥ 59 J

• Surface Hardness (Post-Carburization): Typically 58 – 62 HRC

• Delivery Condition Hardness: ≤ 217 HBW (Annealed for effortless machining)

Key Technical Characteristics

• Outstanding Carburizing Performance: It behaves reliably in gas, liquid, or vacuum carburizing environments, creating a highly predictable hardened case depth.

• Excellent Dimensional Stability: Molybdenum ensures that complex machined geometries experience minimal distortion during the intense oil quenching phase.

• Cold Shear & Workability: In its soft-annealed delivery state, SCM420 displays highly favorable cold workability, making it well-suited for cold drawing, peeling, or complex milling before undergoing the final heat-treat phase.

Common Industrial Applications

JIS SCM420 bars are widely specified across automotive drivetrain assemblies, heavy machinery, and precision power transmission setups:

• Automotive Transmission: High-stress transmission gears, synchronizer sleeves, input shafts, and differential pinions.

• Heavy Machinery: Hydraulic piston rods, crane pivot pins, high-torque industrial drive shafts, and universal joints.

• Fasteners & Tooling: High-durability anchor bolts, case-hardened clamping hardware, and structural wear rings for industrial machinery.