45# Steel CNC Machining

45# steel is a high-quality medium-carbon structural steel with excellent mechanical properties and processing characteristics. Before heat treatment, its hardness generally does not exceed 197 HB. After quenching, the hardness can be significantly increased to HRC 55–62, and after tempering, it stabilizes at HRC 42–46. The main mechanical properties include a tensile strength of ≥600 MPa, yield strength of ≥355 MPa, elongation ≥16%, and a reduction of area ≥40%. 45# steel also demonstrates outstanding impact toughness, reaching Akv ≥39 J or akv ≥49 J/cm².

Through a standard quenching and tempering process—normalizing (850°C), quenching (840°C), and tempering (600°C)—its comprehensive mechanical performance can be further optimized. This makes it ideal for medium-load components such as shafts, gears, automotive chassis parts, and building structural elements, and it is widely recognized and applied across the machining industry.

Mechanical Properties

Tensile Strength (σb): ≥600 MPa

Yield Strength (σs): ≥355 MPa

Elongation (δ5): ≥16%

Section Shrinkage (ψ): ≥40%

Impact Toughness: Akv ≥39 J, akv ≥49 J/cm²

Hardness:

   ① ≤197 HB (without heat treatment)

   ② HRC 55–62 (after quenching, without tempering)

   ③ HRC 42–46 (after tempering)

Heat Treatment Process

Normalizing: 850°C

Quenching: 840°C

Tempering: 600°C The quenching and tempering treatment significantly enhances the steel’s overall mechanical properties, including toughness and strength.

Applications

45# steel is commonly used for mechanical components that bear medium loads, such as shafts, gears, automotive chassis parts, and construction structural elements.