Introduction

20Mn2 is a low-carbon manganese steel grade known for its excellent strength, good toughness, and high hardenability. With moderate carbon content and enhanced manganese levels, 20Mn2 exhibits good mechanical properties, particularly after heat treatment such as carburizing or quenching and tempering. It is widely used for manufacturing engineering components that require high strength and wear resistance.

Properties of 20Mn2 Grade

  • Moderate to high tensile strength
  • Good toughness and impact resistance
  • High hardenability due to manganese content
  • Good wear resistance after heat treatment
  • Excellent machinability in annealed condition
  • Good weldability when proper procedures are followed
  • Suitable for surface-hardening processes like carburizing

Uses/Applications of 20Mn2 Grade:

  • Gears and gear shafts
  • Crankshafts and camshafts
  • Automotive transmission parts
  • Connecting rods
  • Fasteners such as bolts and studs
  • Construction machinery components
  • Sleeves, couplings, and pinions
  • General engineering parts requiring wear resistance and toughness

Chemical Composition (Typical):

Element Content (%)
Carbon (C) 0.17 – 0.23
Manganese (Mn) 1.30 – 1.60
Silicon (Si) 0.15 – 0.35
Sulfur (S) ≤ 0.035
Phosphorus (P) ≤ 0.035
Iron (Fe) Balance

Mechanical Properties (Typical, in Heat Treated Condition):

Property Value
Tensile Strength 500 – 700 MPa
Yield Strength ≥ 280 MPa
Elongation (in 50 mm gauge length) ≥ 16%
Impact Strength (Charpy V-Notch at room temp) ≥ 27 Joules
Hardness (HB) 140 – 190 HB (as rolled or normalized)

After quenching and tempering, tensile strength can increase significantly depending on conditions.

Physical Properties:

Property Value
Density 7.85 g/cm³
Modulus of Elasticity 210 GPa
Thermal Conductivity ~46 W/m·K
Specific Heat Capacity ~460 J/kg·K
Electrical Resistivity ~0.16 µΩ·m

Forging:

Forging of 20Mn2 steel should be carried out between 1150°C and 850°C:

  • Begin forging at approximately 1150°C.
  • Do not forge below 850°C.
  • After forging, parts should be cooled slowly in sand, ashes, or a controlled furnace environment to avoid cracking.

Dimensional Tolerances

Manufactured according to standard specifications:

  • Hot Rolled Bars: EN 10060, EN 10058 standards.
  • Cold Drawn Bright Bars: EN 10277 standards for tighter tolerances and improved surface finishes.
  • Custom tolerances can be provided upon request for specialized applications.

Heat Treatment:

20Mn2 responds well to a range of heat treatments:

  • Annealing: Heat to 650°C – 700°C, hold for suitable time, then cool slowly in the furnace to soften the material and improve machinability.
  • Normalizing: Heat to 860°C – 900°C and cool in air to refine grain structure and improve mechanical properties.
  • Hardening: Heat to 830°C – 870°C, quench in oil or water depending on part size and requirements.
  • Tempering: Tempering after quenching is critical. Typical tempering temperatures range from 400°C to 650°C depending on desired mechanical properties.
  • Carburizing: For enhanced surface hardness, parts can be carburized at around 880°C – 920°C followed by hardening and tempering.

Machinability:

  • Good machinability in normalized or annealed conditions.
  • Cutting speeds should be moderate.
  • Use high-speed steel (HSS) or carbide cutting tools for optimal performance.
  • Adequate lubrication during machining is recommended to improve surface finish and tool life.

Machinability Rating: Approximately 60% – 65% compared to free-cutting steel.

Corrosion Resistance:

  • 20Mn2 has low inherent corrosion resistance.
  • Must be protected by painting, oiling, galvanizing, or other coatings if used in corrosive environments.

Not suitable for marine or high-humidity environments without protection

Weldability:

  • 20Mn2 is weldable with standard procedures.
  • Preheating at 150°C – 250°C may be required for heavy sections or critical welds.
  • Low-hydrogen electrodes are recommended to minimize the risk of hydrogen-induced cracking.
  • Post-weld heat treatment (stress relieving) may be advised to optimize mechanical properties and reduce residual stresses.

Available Form:

  • Hot Rolled Round Bars
  • Cold Drawn Bright Bars (Round, Square, Hexagonal, Flats)
  • Forged Bars and Shafts
  • Wire Rods
  • Custom sizes and lengths available upon request
  • Supplied in black, bright, normalized, annealed, or hardened and tempered conditions

Conclusion:

20Mn2 carbon steel bar is a versatile, high-performance material widely used across multiple industries for manufacturing medium-strength parts with good toughness and wear resistance. It combines excellent forging, machining, and heat treatment capabilities, offering cost-effective solutions for engineering and automotive applications. When protected appropriately, 20Mn2 provides reliable service life even under challenging operational conditions.

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