SEM420

SEM420 Alloy Steel Product Overview

SEM420 is a low-alloy, chromium-molybdenum steel standardized under JIS G4105, known for its excellent strength, toughness, and case-hardening properties. This steel is widely used as an engineering steel due to its high hardenability, good weldability, and excellent cold-strain plasticity. SEM420 is typically supplied in the annealed or normalized condition (max 229 HB) and is ideal for applications requiring a hard, wear-resistant surface with a tough, ductile core after carburizing and quenching. Its balanced alloy content ensures stable composition, low harmful elements, and high purity, making it a reliable choice for precision components.

Applications

SEM420 is primarily used in case-hardened components for automotive, industrial, and engineering applications:

Automotive:

• Gears, pinions, and gear shafts for transmissions and differentials.
• Camshafts, crankshafts, and drive shafts.
• Axle shafts, steering knuckles, and clutch components.

Industrial:

• Heavy-duty bushings, bearings, and sprockets.
• Machine tool spindles, arbours, and spline shafts.
• Forged components like couplings and connecting rods.

Other Uses:

• Agricultural and construction machinery components.
• High-pressure fasteners and bolts.
• Oil and gas industry parts requiring high surface hardness and core toughness.

Chemical Composition

The chemical composition of SEM420 ensures its case-hardening properties and core toughness:

• Chromium (Cr): Enhances hardenability and surface wear resistance after carburizing.
• Molybdenum (Mo): Improves strength, toughness, and resistance to tempering.
• Manganese (Mn): Contributes to hardenability and strength.
• Carbon (C): Low content ensures weldability and core toughness, with carburizing adding surface hardness.

Supply Size

SEM420 is available in various forms and sizes to meet industrial requirements:

• Round Bars:
  Diameter 16 mm to 700 mm.
• Flat Bars:
  Minimum: 10 mm thickness x 80 mm width.
  Maximum: 500 mm thickness x 2000 mm width.