42CRMO4

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Introduction

42CrMo4 is a high-grade alloy steel known for its outstanding combination of high strength, toughness, good hardenability, and excellent fatigue resistance. Belonging to the family of low-alloy steels, 42CrMo4 is widely used for critical mechanical engineering components requiring high tensile strength and impact resistance, particularly after quenching and tempering. It is also known as AISI 4140 or EN19 in other standards.

Standards and Equivalent Grades:

42CrMo4 Alloy Steel is typically used in:

  • Crankshafts
  • Gears and pinions
  • High-load machine parts
  • Connecting rods
  • Axles and shafts
  • Bolts and studs
  • High-stress forged parts
  • Tool holders and molds
  • Automotive and aerospace components

Properties of the Grade:

  • High tensile strength and yield strength
  • Excellent toughness and impact resistance
  • Good hardenability and wear resistance
  • High fatigue strength
  • Good machinability in tempered condition
  • Good dimensional stability after heat treatment
  • Moderate corrosion resistance when surface protected
  • Suitable for nitriding and induction hardening

Chemical Composition:

Element Content (%)
Carbon (C) 0.38 – 0.45
Silicon (Si) 0.10 – 0.40
Manganese (Mn) 0.60 – 0.90
Phosphorus (P) ≤ 0.025
Sulfur (S) ≤ 0.035
Chromium (Cr) 0.90 – 1.20
Molybdenum (Mo) 0.15 – 0.30

Mechanical Properties:

(Typical values after quenching and tempering)

Property Typical Value
Tensile Strength 850 – 1000 MPa
Yield Strength ≥ 700 MPa
Elongation ≥ 13%
Reduction of Area ~ 45%
Impact Strength (Charpy V-notch at room temp.) ≥ 35 J
Hardness (Quenched & Tempered) 28–32 HRC

Physical Properties:

Property Typical Value
Density 7.85 g/cm³
Modulus of Elasticity 210 GPa
Thermal Conductivity (at 20°C) ~ 42.6 W/m·K
Specific Heat Capacity ~ 460 J/kg·K
Coefficient of Thermal Expansion (20–100°C) ~ 12 × 10⁻⁶ /°C

Forging:

Forging Temperature Range: 850°C – 1150°C

Procedure:

  • Preheat to 850°C.
  • Final forging temperature should not fall below 850°C.
  • After forging, cool slowly in sand, dry ash, or furnace to avoid cracking.

Heat Treatment:

  1. Annealing:
    • Heat to 680°C – 720°C.
    • Hold for sufficient time, then cool slowly in the furnace.
    • Result: Soft structure for easy machining.
  2. Hardening:
    • Heat to 830°C – 860°C.
    • Quench in oil or water depending on required properties.
  3. Tempering:
    • After hardening, temper between 540°C – 680°C depending on desired mechanical properties.
    • Air cool after tempering.
  4. Nitriding (Optional):
    • Can be nitrided to achieve a hard, wear-resistant surface (~ 60–65 HRC).

Dimensional Tolerances:

  • Hot Rolled Bars: As per EN 10060 or ASTM A29 standards.
  • Bright Drawn or Peeled Bars: Tolerances as per ISO h9/h11.
  • Ground Bars: Precision tolerances to ISO h6 or finer.

Machinability:

  • Good machinability in normalized and tempered condition.
  • Use high-speed steel or carbide tooling for best results.
  • Employ cooling/lubrication to prolong tool life and achieve better surface finishes.

Corrosion Resistance:

  • Moderate corrosion resistance in untreated condition.
  • Better resistance when nitride, plated, or coated.
  • Not suitable for highly corrosive environments unless additional surface protection is applied.

Weldability:

  • Fair weldability but requires care.
  • Preheating to 200°C – 300°C is recommended before welding.
  • Post-weld stress-relieving is advisable to reduce residual stresses.
  • Suitable for standard welding processes with proper procedures.

Available Form:

42CrMo4 is available in:

  • Hot Rolled Bars
  • Peeled and Turned Bars
  • Bright Bars
  • Ground Bars
  • Forged Bars
  • Cut Pieces and Plates

Supplied in annealed, normalized, quenched, and tempered conditions as per customer specification.

Conclusion:

42CrMo4 Alloy Steel Bar stands out for its superior combination of strength, toughness, and fatigue resistance, making it an ideal choice for demanding engineering applications. It can be readily heat-treated, machined, and adapted for a wide range of heavy-duty mechanical components. With proper processing and surface treatments, 42CrMo4 delivers reliable performance and long service life across multiple industries.

Related Products :   16MnCr5, EN19, 42CrMo4, 20MnCr5, EN353, EN31, EN24, EN47, EN41B, SAE4140, SAE52100, SAE 8620, SCM420, EN36C, Maps