Hardness Testing

1. Rockwell hardness: the index to determine the hardness value based on the indentation plastic deformation depth. Take 0.002 mm as a hardness unit. When HB > 450 or the sample is too small, it is not allowed to use Brinell hardness test instead of Rockwell hardness measurement. It uses a diamond cone with a top angle of 120 ° or a steel ball with a diameter of 1.59 and 3.18mm to press into the surface of the tested material under a certain load, and the hardness of the material is calculated from the depth of the indentation. According to the hardness of the test material, there are three different scales:
(1) HRA: the hardness obtained by using 60kg load and diamond cone indenter for materials with extremely high hardness (such as cemented carbide, etc.); (2) HRB: the hardness obtained by using 100kg load and 1.58mm diameter hardened steel ball for materials with low hardness (such as annealed steel, cast iron, etc.); (3) HRC: the hardness obtained by using 150kg load and diamond cone indenter, for very hard materials High quality materials (such as quenched steel, etc.);
2. Brinell hardness: Brinell hardness (HB) is generally used for soft materials, such as non-ferrous metals, steel before heat treatment or after annealing.
Brinell hardness (HB) is to press a certain diameter of hardened steel ball or cemented carbide ball into the surface of the metal to be tested with a certain amount of test load, keep it for a specified time, and then unload it to measure the diameter of the indentation on the surface to be tested. The Brinell hardness number is the quotient of the load divided by the spherical surface area of the indentation. Generally: press a certain size of hardened steel ball into the surface of the material with a certain load and keep it for a period of time. After the load is removed, the ratio of the load to the indentation area is Brinell hardness number (HB), and the unit is kilogram force / mm2 (n / mm2). The test load and the diameter of the test ball need to be determined according to the actual performance of the material;
3. Vickers hardness: the Vickers hardness test method was proposed by Smith and cedrand in 1925. Vickers Armstrong, a British company, developed the first hardness tester tested by this method. Compared with Brinell and Rockwell hardness tests, Vickers hardness test has a wide measurement range, covering almost all kinds of materials, from softer materials to superhard materials. The measurement principle of Vickers hardness is basically the same as that of Brinell hardness, and the hardness value is calculated according to the load on the unit area of indentation. The difference is that the indenter of the Vickers hardness test is the regular pyramid of diamond. During the test, under the action of a certain load, a square conical indentation is pressed out on the sample surface, and the diagonal length of the indentation is measured to calculate the surface area of the indentation. The value of load divided by the surface area is the hardness value of the sample, which is represented by the symbol HV;
4. Leeb hardness: Leeb hardness is expressed in HL. Leeb hardness test technology was invented by Dr. dilma of Switzerland. It uses a certain mass of impact body with tungsten carbide ball head to impact the surface of the test piece under a certain force, and then rebound. Because of the different hardness of the material, the rebound speed after impact is also different. A permanent magnet material is installed on the impact device. When the impact body moves up and down, its peripheral coil senses an electromagnetic signal proportional to the speed, and then converts it into a Leeb hardness value through an electronic circuit;
5. Shore hardness: HS for short, a standard for hardness of materials, first proposed by scholl, a British. The elastic rebound method is used to drop the impact pin from a certain height to the surface of the material under test. The striker is a small cone with a tip, which is often inlaid with a diamond. The test value is 1000x striker return speed / striker initial speed (i.e. velocity ratio before and after collision multiplied by 1000);
6. Barcol hardness: Barcol hardness (hereinafter referred to as Barcol hardness) was first proposed by American barber Colman company. It is a kind of hardness category widely used in the modern world. A certain shape of hard steel press pin is pressed into the surface of the sample under the action of standard spring test force. The hardness of the material is determined by the press depth of the press pin. Each press 0.0076mm is defined as a Barcol hardness unit. The hardness unit of Babbitt is expressed as HbA;
7. Knoop hardness: Knoop hardness is the hardness measured as an absolute value, which is mainly used in processing. Generally speaking, the Knoop hardness of diamond is 7000-8000 kg / mm2;
8. Vickers hardness: a certain shape of hard steel press pin is pressed into the surface of the sample under the action of the standard spring test force. The material hardness is determined by the press depth of the press pin. The press depth of 0.01mm is defined as a Vickers hardness unit. The unit of Vickers hardness is hw.