Metal hardness measuring

To measure hardness of metals we use a Vexus SHR 150D desktop hardness meter.

Hardness - is a mechanical property which is important in the technical practice especially for cast pieces used for rock crushing.

Our laboratory performs hardness tests according to Rockwell, or Brinell.

Hardness is determined on a hardness meter as a difference of the depth of impression of a penetrating body (a diamond cone, a steel ball) between two stages of the equipment (preliminary and total). The cone has a peak angle of 120° and a round part radius of 0.2 mm (HRA, HRC). A ball has the diameter of 1.5875 mm (HRB).

The hardness test according to Rockwell, or Brinell, is fast, easy and punches are very small (the maximum depth of 0.2 mm). It is suitable for common checks of large series of products.

The scale selection (i.e. the type of penetrating body) mainly depends on the presumed hardness of the tested material.

HRA

Harness determined by a diamond cone at the total load of 600 N.

For sintered carbides and thin surface films

HRB

Harness determined by a steel ball (B = ball) at the total load of 1,000 N.

For softer metals (25 - 100 HRB)

HRC

Harness determined by a diamond cone (C = cone) at the total load of 1,500 N.

It is recommended for the range of HRC = 20 – 67

In addition to the desktop harness meter, our company also uses a TH 140 digital hardness meter, especially for easy measuring of hardness in the field, e.g. on large cast pieces.

Measurement principle

A striker of a certain weight hits the tested object at the given speed and given testing force. The impact and rebound force of the striker are measured at the distance of 1 mm from the tested surface. Leeb hardness degree is expressed as an average of rebound speed of the hit.

Manner of calculation:

HL=1000 x VB/VA

HL – Leeb harness degree

VB – rebound speed of the striker

VA – impact speed of the striker

The TH 140 digital hardness meter measures hardness using the Rockwell, Brinell and Vickers methods. This enables us to measure materials of various hardness.