Steel Hardness by Heat Treatment

Achievable hardness for common Czech / EN steels · delivery · quenched · tempered

← Back to Engineering

Hardness Reference Table 20

Category:
Treatment:
🔍
Czech / EN grade Category Delivery
HB		 Quenched
max HRC		 Low temper
150–250 °C		 QT / High temp.
550–650 °C		 Surface
(case/nitride)		 Hardness bar
(max)		 Notes
Categories: Structural Through-hardening Case-hardening Nitriding Tool Stainless — = not applicable / no significant hardening
Notes & References

Reading the table

  • Delivery HB: hardness in normalised/annealed delivery state
  • Quenched max HRC: maximum achievable after quenching (no tempering)
  • Low temper (150–250 °C): maintains most hardness, reduces brittleness
  • QT/High temper (550–650 °C): quench + high temper (zušlechťování)
  • Surface: case or nitriding surface hardness; core remains tough

Hardenability factors

  • Carbon content is the primary factor (min. ≈ 0.30% for through-hardening)
  • Alloying (Cr, Mo, Ni, Mn) increases hardenability — deeper through-hardening
  • Quenching medium: water > oil > air — faster cooling = higher hardness, more distortion
  • Section size: large sections may not harden fully through without high-alloy steel

HRC ↔ HB approximate conversion

  • HRC 20 ≈ HB 241
  • HRC 30 ≈ HB 286
  • HRC 40 ≈ HB 371
  • HRC 50 ≈ HB 481
  • HRC 60 ≈ HB 613
  • HRC 65 ≈ HB 721

Related pages

Heat treatment methods overview:

🔥 eng-037 — Heat Treatment Overview