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65Mn chemical composition and mechanical properties
Introduction to the Chemical Composition, Mechanical Properties, and Main Applications of 65Mn Steel
65Mn is a high-carbon manganese steel known for its excellent mechanical properties and versatility in industrial applications. The addition of manganese enhances the hardenability of the steel, allowing it to be effectively hardened even in oil quenching for components with a diameter of up to 12mm. Compared to silicon steel, 65Mn exhibits less surface decarburization, making it a preferred choice for precision parts. After heat treatment, 65Mn offers superior comprehensive mechanical properties over carbon steel, although it is prone to overheating sensitivity and temper embrittlement.
This type of steel is widely used in the production of small springs such as flat springs, round springs, seat springs, valve springs, clutch reeds, brake springs, cold-drawn coil springs, and spring rings. Its excellent overall performance includes high elastic limit, strength limit, yield ratio, anti-relaxation characteristics, fatigue resistance, and good hardenability. Additionally, 65Mn demonstrates favorable physical and chemical properties, including heat resistance, low-temperature resistance, oxidation resistance, and corrosion resistance. To achieve these properties, spring steel must have high metallurgical quality, uniform composition, minimal surface defects, and precise dimensions.
In comparison to standard carbon steel No. 65, 65Mn steel plates offer higher strength, hardness, elasticity, and hardenability. However, they are more susceptible to overheating and temper embrittlement, and water quenching can lead to cracking. The material has acceptable formability in the annealed state, but its cold deformation plasticity is limited, and weldability is poor. It is commonly used for medium-loaded leaf springs, coil springs with diameters between 7–20 mm, spring washers, spring rings, wear-resistant parts like grinding machine spindles and spring chucks, precision machine tool screws, cutting tools, bearing collars, and railway rails.
Chemical Composition:
- Carbon (C): 0.62–0.70%
- Silicon (Si): 0.17–0.37%
- Manganese (Mn): 0.90–1.20%
- Sulfur (S): ≤0.035%
- Phosphorus (P): ≤0.035%
- Chromium (Cr): ≤0.25%
- Nickel (Ni): ≤0.30%
- Copper (Cu): ≤0.25%
Mechanical Properties:
- Tensile Strength (σb): ≥980 MPa (100 kgf/mm²)
- Yield Strength (σs): ≥784 MPa (80 kgf/mm²)
- Elongation (δ10): ≥8%
- Area Reduction (ψ): ≥30%
- Hardness: Hot rolled ≤302 HB; Cold drawn + heat treated ≤321 HB
Heat Treatment:
- Quenching: 830°C ± 20°C, oil-cooled
- Tempering: 540°C ± 50°C (or ±30°C if specified)
The steel is typically delivered in either heat-treated or non-heat-treated condition for hot-rolled products, while cold-drawn materials are supplied in a heat-treated state.
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Editor: Hardware Business Network Information Center