Common hardness test method

1. ROCKWELL HARDNESS

The test method is to use a diamond cone with a vertex angle of 120 degrees or a steel ball with a diameter of 1.5875mm/3.175mm/6.35mm/12.7mm to press into the surface of the material to be tested under a certain load, and then calculate the hardness of the material from the indentation depth.

The three most commonly used scales are A, B, and C, namely HRA, HRB, and HRC. According to the hardness of the experimental material, scales with different hardness ranges are used to represent:

HRA is the hardness obtained by using a 60Kg load and a diamond cone indenter, and is used for materials with higher hardness. For example: steel sheet, hard alloy.

HRB is the hardness obtained by using a 100Kg load and a hardened steel ball with a diameter of 1.5875mm, and is used for materials with lower hardness. For example: mild steel, non-ferrous metals, annealed steel, etc.

HRC is the hardness obtained by using a 150Kg load and a diamond cone indenter, and is used for materials with higher hardness. For example: hardened steel, cast iron, etc.

2. SHORE HARDNESS

The Shore hardness is to use a steel with a certain shape to press it vertically into the surface of the sample under the action of the test force. When the surface of the presser foot is completely attached to the surface of the sample, the tip of the indenter has a certain extension relative to the plane of the presser foot. Length L (see Figure 1), the Shore hardness is characterized by the L value, the larger the L value, the lower the Shore hardness, and vice versa.

Shore hardness testers are mainly divided into three categories: Type A, Type C and Type D. Their measurement principle is exactly the same, the difference is that the size of the measuring needle is different.

Type A has a needle tip diameter of 0.79mm. The Shore A hardness tester is used to measure soft plastics, rubber, synthetic rubber, felt, leather,

The tip diameter of Type D is 0.2mm. That is, the radius is R0.1. The Shore D hardness tester is used to measure the hardness of hard plastic and hard rubber, such as floor materials, bowling balls and other on-site hardness measurements.

The C-type stylus is a ball with a diameter of 5mm. Shore C hardness tester is used to measure soft materials such as foam and sponge.

3. INTERNATIONAL RUBBER HARDNESS

According to the depth of the ball indenter indented into the material to be tested, the performance of elastic materials or rubber against indenter indentation is measured. Apply an initial contact force on the 1, 2.5 or 5mm ball indenter and set the indentation depth to zero. Then increase the force value to the specified total load, at which point the depth of material penetration is measured. The IRHD value is related to the depth of the indenter.

This measurement method is usually applied to test smaller components and O-rings

4. VICKERS HARDNESS

Vickers hardness refers to the use of a diamond pyramidal indenter with an angle of 136 degrees between opposite surfaces to press into the surface of the tested sample under the action of a specified load F, remove the load after holding for a certain period of time, and measure the indentation diagonal Length d, and then calculate the indentation surface area, and finally calculate the average pressure on the indentation surface area, which is the Vickers hardness value of the metal, expressed by the symbol HV. In the actual measurement, no calculation is required, but the measured hardness value is directly obtained by looking up the table according to the measured d value.

5. BRINELL HARDNESS

Brinell hardness (HB) Use a steel ball or carbide ball of a certain diameter to press into the surface of the sample with the specified test force (F), remove the test force after the specified holding time, and measure the indentation diameter on the sample surface ( L). The Brinell hardness value is the quotient obtained by dividing the test force by the spherical surface area of the indentation. Expressed in HBS (steel ball), the unit is N/mm2 (MPa).

The symbol of Brinell hardness is represented by HBS or HBW

HBS means that the indenter is a hardened steel ball, which is used to measure materials with a Brinell hardness value below 450, such as mild steel, gray cast iron and non-ferrous metals.

HBW means that the indenter is cemented carbide, which is used to measure materials with a Brinell hardness value below 650.

6. WEBSTER HARDNEDD

Webster hardness refers to a hard steel indenter of a certain shape, which is pressed into the surface of the sample under the standard spring test force, and the indentation depth of the indenter is used to determine the hardness of the material. The indentation depth of 0.01mm is defined as a Webster hardness unit . The Webster hardness unit is expressed as HW.