हार्डनेस कन्वर्टर

Each scale uses a different indenter and load:

• HRC (Rockwell C) — Diamond cone, 150 kgf. For hardened steels (20–70 HRC).
• HRB (Rockwell B) — 1/16" steel ball, 100 kgf. For softer materials (20–100 HRB).
• HV (Vickers) — Diamond pyramid, variable load. Universal range, very precise.
• HB (Brinell) — 10 mm carbide ball, 3000 kgf. For castings, larger test areas.

General guidance:

• HRC — Hardened and tempered steels, tool steels, case-hardened parts
• HRB — Annealed steels, brass, aluminum, softer metals
• HV — Thin sheets, coatings, micro-hardness, wide range of materials
• HB — Castings, forgings, raw stock, weld HAZ testing

When in doubt, use HRC for hardened steels and HV for everything else.

Different hardness tests measure different physical properties:

• Rockwell measures depth of penetration
• Vickers measures area of indentation
• Brinell measures diameter of indentation

Since these are fundamentally different measurements, the relationships between them are empirical (based on testing), not mathematical. Results vary by material type, microstructure, and heat treatment condition.

ASTM E140 provides accepted approximate conversions based on extensive testing of carbon and alloy steels.

For carbon and alloy steels, the approximate relationship is:

• Rm (MPa) ≈ 3.45 × HB
• Rm (psi) ≈ 500 × HB

This is valid for the range of approximately 100–400 HB. Above ~55 HRC, this relationship breaks down as materials become brittle.

Do not use this for stainless steels, cast irons, non-ferrous metals, or materials with unusual microstructures.

Rockwell (ASTM E18): Apply preload (10 kgf), then major load (60/100/150 kgf). Measure depth increase. Quick (~10s), portable, minimal surface preparation.

Vickers (ASTM E92/E384): Force a diamond pyramid into the surface. Measure both diagonals under microscope. Very precise, works for micro-hardness (HV 0.01) to macro (HV 120).

Brinell (ASTM E10): Press a 10 mm ball into the surface with 3000 kgf (for steel). Measure indentation diameter. Averages over a large area — ideal for heterogeneous materials like castings.