Hardness refers to the ability of a material to resist the pressing of a hard object into its surface. It is one of the important performance indications of metal materials. Generally, the higher the hardness , the better the abrasion resistance. Common hardness indicators are Brinell hardness , Rockwell hardness , and Vickers hardness.
Brinell hardness (HB)
A certain load (generally 3000kg) is used to press a hardened steel ball of a certain size (generally 10 mm in diameter ) into the surface of the material for a period of time. After unloading , the ratio of the load to the indentation area is the Brinell hardness value (HB).
Rockwell hardness (HR)
When HB> 450 or the sample is too small , the Brinell hardness test cannot be adopted and the Rockwell hardness measurement is used instead. It is a diamond cone with a vertex angle of 120° or a steel ball with a diameter of 1.59/3.18 mm. It is pressed into the surface of the material under a certain load , and the hardness of the material is obtained from the depth of the indentation. According to the hardness of the test material , it is expressed in three different scales:
HRA: It is a hardness obtained by using a 60kg load and a diamond cone indenter. It is used for extremely hard materials (such as cemented carbide).
HRB: It is a hardened steel ball with a load of 100kg and a diameter of 1.58mm. The hardness is determined for materials with lower hardness (such as annealed steel and cast iron).
HRC: It is a hardness obtained with a 150kg load and a diamond cone indenter. It is used for very hard materials (such as quenched steel).
Vickers hardness (HV)
The diamond square cone indenter with a load within 120kg and a vertex angle of 136°is pressed into the surface area of the material indentation pit is divided by the load value to obtain the Vickers hardness value (HV).
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