Spring steel 65Mn hot-rolled coil Q235B, sold from one sheet.

65Mn is a high-carbon manganese alloy spring steel with excellent elasticity and wear resistance, widely used in the field of mechanical manufacturing. The following is a detailed analysis of its key characteristics and applications:

1. Material Characteristics

• Chemical Composition:
  Carbon (C) 0.62%-0.70%, Manganese (Mn) 0.90%-1.20%, Silicon (Si) 0.17%-0.37%, Sulfur and Phosphorus content ≤0.035%14.
• Mechanical Properties:
  • Tensile Strength: 825-925MPa (hot-rolled state)25
  • Hardness: Can reach HRC 38-6013 after heat treatment.
• Heat Treatment Process:
  Quenching (830°C oil cooling) + Tempering (540°C), forming a troostite structure to enhance overall performance24.

2. Core Advantages

• Hardenability: Sizes below φ12mm can be fully oil-quenched, with decarburization tendency lower than that of silicon steel26.
• Fatigue Performance: After quenching and tempering, the fatigue limit approaches that of alloy spring steel14.
• Cost-Effectiveness: Lower cost compared to high-alloy spring steel, suitable for mass production35.

3. Typical Applications

• Spring Components:
  • Automotive clutch reed springs, brake springs25
  • Mechanical spiral springs, spring washers16
• Wear-Resistant Parts:
  • Grinding machine spindles, precision lead screws49
  • Mining machinery hammer heads, screen plates7
• Tools:
  • Cold stamping die punches, fitter chisels69

4. Processing Considerations

• Overheating Sensitivity: Quenching temperature must be strictly controlled (±20°C) to avoid cracking37.
• Poor Weldability: Argon arc welding is recommended with preheating at 150-300°C9.
• Alternative Materials: For high dynamic load scenarios, 60Si2Mn (higher fatigue strength) can be selected8.