I. Rockwell Hardness (HR) 1. Principle
A diamond cone (120° apex angle) or a steel ball (1.59mm or 3.18mm diameter) is used as an indenter. Under initial and main loads, the indentation depth is pressed into the material surface. The hardness value is calculated based on the indentation depth. The deeper the indentation, the lower the hardness value. 2. Features: Rapid testing and easy operation make it suitable for batch testing; it can test medium- and high-hardness materials; and various scales are available depending on the material hardness: HRA: 60kg load, diamond indenter, suitable for extremely hard materials such as carbide; HRB: 100kg load, steel ball indenter, suitable for mild steel, copper alloys, and aluminum alloys; HRC: 150kg load, diamond indenter, suitable for hardened steel and high-hardness alloys. 3. Typical Applications
Widely used for rapid hardness testing of metal products (such as cutting tools, bearings, gears, and cast iron). II. Brinell Hardness (HBW) 1. Principle
A carbide ball of a certain diameter (usually 10 mm) is pressed into the material surface under a specified load. The hardness value is calculated based on the indentation diameter. Common types of Brinell hardness are: HBS (steel ball indenter), suitable for materials with a hardness of ≤450 HB, such as mild steel, gray cast iron, and non-ferrous metals; HBW (carbide ball indenter), suitable for materials with a hardness of ≤650 HB, and the mainstream modern standard. 2. Features: Stable and repeatable results; suitable for soft to medium-hard metals; large indentation, not suitable for thin-walled or small parts. 3. Typical Applications: Hardness testing of raw materials and rough-machined parts, such as annealed steel, cast iron, non-ferrous metals, and their alloys.
III. Vickers Hardness (HV) 1. Principle
A diamond indenter, a regular square pyramid with a 136° apex angle, is pressed into the material surface under a specified load. The hardness value is calculated based on the diagonal length of the indentation. 2. Features: High precision, capable of testing extremely small areas; wide application range, from soft metals to ultra-hard materials; extremely small indentation, suitable for thin-walled parts, coatings, and micro-area testing. 3. Typical Applications: Hardness testing of precision parts, coatings, and thin plates (such as mobile phone housing coatings), as well as hardness analysis of microscopic areas (grain boundaries and phase boundaries) in scientific research.
V. Test Method Selection Recommendations: Production site and batch testing: Use Rockwell hardness. Raw materials and high precision requirements: Use Brinell hardness. Coating, micro-area, and scientific research testing: Use Vickers hardness.
