Hardness testing measures a material’s resistance to deformation, particularly from scratching, indentation, or penetration. When testing steel, various methods can be used depending on the type of steel and the desired results. Here’s an overview of the common hardness testing methods:

1. Brinell Hardness Test (BHN):

  • A hard steel or carbide ball is pressed into the steel surface using a specific load.
  • The diameter of the indentation left by the ball is measured.
  • The Brinell Hardness Number (BHN) is calculated by dividing the applied load by the surface area of the indentation.
  • This method is best for testing softer steels and larger samples.

2. Rockwell Hardness Test (HR):

  • A steel or diamond cone (HRC), or steel ball (HRB), is pressed into the steel with two different loads: a minor load followed by a major load.
  • The depth of penetration under the major load is measured.
  • The Rockwell scale (e.g., HRC for hardened steel, HRB for softer steel) indicates hardness levels. This method is fast and suitable for most steel types.

3. Vickers Hardness Test (VHN):

  • A small diamond-shaped pyramid is pressed into the steel surface with a specific load.
  • The diagonal lengths of the resulting indentation are measured under a microscope.
  • The Vickers Hardness Number (VHN) is calculated, and this method is ideal for thin steel or very small parts.

4. Knoop Hardness Test:

  • Similar to the Vickers test but uses an elongated diamond-shaped indentation tool for testing small areas and thin steel sections.
  • Often used for microhardness testing.

Applications of Hardness Testing in Steel:

  • Assess wear resistance and durability.
  • Ensure quality in steel production for automotive, aerospace, and construction industries.
  • Determine material suitability for specific applications.

Each method has unique advantages depending on the size, shape, and type of steel being tested.