Hardness test is the most simple and feasible test method in mechanical property test. In order to replace some mechanical properties tests with hardness tests, a more accurate conversion relationship between hardness and strength is needed in production.
Dietmar leeb: The leeb hardness is designed according to the latest principle of the Leed hardness test using the most advanced microprocessor technology.
Brinell hardness (HB) with a certain load (generally 3000kg), the hardened steel ball of a certain size (generally 10mm in diameter) is pressed into the surface of the material and kept for a period of time. After the load is removed, the ratio of the load and the indentation area is the Brinell hardness value(HB), the unit is kg force/mm2.
Rockwell hardness (HR) when HB>450 or the sample is too small, the Brinell hardness test can't be used instead of Rockwell hardness measurement. It is to use a diamond cone with a top angle of 120℃ or a steel ball with a diameter of 1.59 or 3.18mm to press into the surface of the measured material under a certain load, and the hardness of the material can be calculated by the depth of the indentation. According to the hardness of the test materials, there are three different cases.
HRA: hardness obtained with a 60kg load and a diamond cone press for extremely hard materials such as hard alloys.
HRB: the hardness is obtained by using 100kg load and 1.58mm diameter hardened steel ball, used for low hardness materials (such as annealed steel, cast iron, etc.)
HRC: hardness obtained by 150kg load and drill cone press for very hard materials such as hardened steel.
Vickers hardness (HV), Vickers hardness is obtained by dividing the load value by the surface area of material indentation pit with a load value within 120kg and a square cone diamond indenter with a tip. Angle of 136°.
Nou hardness (HK), suitable for hardness testing of high hardness materials (hardness measurement above HV1000).
And shore hardness tester.
Webster's hardness tester (HW), it is suitable for measuring wechsler hardness of aluminum alloy products.
Gypsum hardness tester, it is suitable for the hardness measurement of building gypsum. The steel ball is placed on the specimen to measure the depth of ball mark under the action of fixed load, and the hardness of gypsum specimen is calculated.
The above hardness is just a few commonly used, there are shore (HS) hardness, Shore (HS) hardness, barb hardness, Mohs hardness and so on. It has been proved by practice that there are approximately corresponding relations between hardness values and strength values of metal materials. Because the hardness value is determined by the initial plastic deformation resistance and the continued plastic deformation resistance, the higher the strength of the material, the higher the plastic deformation resistance, the higher the hardness value.