Can 35CrMo Achieve 600HV After Heat Treatment?

35CrMo steel can reach 600HV (≈55HRC) hardness after proper heat treatment, but strict control of process parameters is required. Below is a detailed analysis:

 

 

Key Heat Treatment Processes

Quenching

Temperature: 850–880°C (full austenitization)

Cooling medium: Oil quenching (preferred) or water quenching (with crack risk)

Expected hardness: 50–55HRC (≈500–600HV), depending on section size and cooling rate.

Tempering

Low-temperature tempering (150–200°C): Maintains high hardness (550–600HV) but with lower toughness (suitable for wear-resistant parts).

Medium-temperature tempering (300–400°C): Slightly reduced hardness (450–550HV) but improved toughness.

To consistently achieve 600HV, low-temperature tempering must be selected, and full quenching must be ensured.

 

Critical Influencing Factors

Carbon content (0.32–0.40%): Near the lower limit requires stricter quenching conditions.

Section thickness: Core hardness may be insufficient for thicknesses >50mm.

Cooling rate: Oil quenching may require forced agitation; water quenching risks distortion/cracking.

 

Typical Applications

Cases achieving 600HV:

High-strength bolts (surface quenching + low-temp tempering)

Gear teeth (case hardening can exceed 60HRC on the surface)

Punch dies (through-hardening + low-temp tempering)

 

Key Considerations

Preferential surface hardening: For >600HV surface hardness, carburizing/nitriding is recommended.

Testing verification: Microhardness (HV) testing is necessary to avoid Rockwell (HRC) conversion errors.

 

Conclusion

35CrMo steel can reach 600HV via optimized quenching + low-temperature tempering, but adjustments may be needed based on actual working conditions. Small-batch trials are strongly advised!