Conventional expressions include Brinell hardness (HB), Rockwell hardness (HRC), Vickers hardness (HV) and Richter scale hardness (HL), among which HB and HRC are commonly used.
HB has a wide range of applications, and HRC is suitable for materials with high surface hardness, such as heat treatment hardness. The difference between them is that the probe of the hardness tester is different. The probe of Brinell hardness tester is steel ball, and the probe of Rockwell hardness tester is diamond.
HV- Suitable for microscope analysis. Vickers hardness (HV) is the value of Vickers hardness (HV) when the diamond square cone press with the load less than 120kg and the apex angle of136 is pressed into the surface of the material, and the surface area of the indentation pit of the material is divided by the load value.
HL portable hardness tester, easy to measure, bounces after hitting the hardness surface with the impact ball head; At the distance of 1mm from the sample surface, the hardness is calculated by the ratio of the rebound speed and impact speed of the punch. The formula is Richter hardness HL= 1000×VB (rebound speed) /VA (impact speed).
Portable Richter scale hardness (HL) can be converted into Brinell hardness (HB), Rockwell hardness (HRC), Vickers hardness (HV) and Shore hardness (HS). Or directly use Brinell hardness (HB), Rockwell hardness (HRC), Vickers hardness (HV), Richter scale hardness (HL) and Shore hardness (HS) to measure the hardness value according to the Richter scale hardness principle.
2.h B- Brinell hardness;
Brinell hardness (HB) is usually used in soft materials, such as nonferrous metals, steel before heat treatment or after annealing. Rockwell hardness (HRC) is generally used for materials with high hardness, such as hardness after heat treatment and so on.
Cloth hardness (HB) is to press a hardened steel ball or cemented carbide ball with a certain diameter into the surface of the measured metal under a certain test load, keep it for a specified time, and then unload it to measure the indentation diameter of the measured surface. The cloth hardness value is the quotient of the load divided by the surface area of the indentation ball. Generally speaking, a hardened steel ball with a certain size (generally diameter 10mm) is pressed into the surface of the material with a certain load (generally 3000kg) and kept for a period of time. The ratio of load to indentation area after unloading is Brinell hardness (HB), and the unit is kilogram force/square millimeter (N/mm2).
3. Rockwell hardness is an index to determine the hardness value according to the plastic deformation depth of indentation. Take 0.002 mm as the hardness unit. When HB & gt450 or the sample is too small, the Brinell hardness test cannot be used, and Rockwell hardness measurement can be used instead. It uses a diamond cone with a vertex angle of120 or steel balls with diameters of 1.59 and 3. 18mm to press into the surface of the measured material under a certain load, and the hardness of the material can be obtained from the indentation depth. According to the hardness of the test material, it can be expressed in three different scales:
HRA: It is the hardness measured by a diamond cone press under a load of 60kg. Used for extremely hard materials (such as cemented carbide).
HRB: Hardness is obtained from hardened steel balls with a load of 100kg and a diameter of 1.58mm, and is used for materials with low hardness (such as annealed steel and cast iron).
HRC: It is the hardness measured by a diamond cone press with a load of 150kg. Used for materials with high hardness (such as hardened steel).
In addition:
Supplementary question: If the hardness is higher than this range, use the Rockwell hardness A HRA.
If the hardness is lower than this range, use the Rockwell hardness B HRB.
The upper limit of fabric hardness HB650 cannot be higher than this value.
4. The indenter of the C scale of Rockwell Hardness Tester is a diamond cone with the vertex angle of 120 degrees, and the test load is a certain value. China standard is 150 kg force.
The indenter of Brinell hardness tester is hardened steel ball (HBS) or cemented carbide ball (HBW), and the test load varies with the diameter of the ball, ranging from 3000 to 31.25 kg force.
5. Rockwell hardness indentation is very small, and the measured value is local, so it is necessary to average the measured points, which is suitable for finished products and sheets and belongs to the category of nondestructive testing.
Cloth hardness indentation is large and the measured value is accurate, which is not suitable for finished products and sheets, and generally does not belong to nondestructive testing.
6. The hardness value of Rockwell hardness is an unknown without unit. So it is not correct to say how many degrees of Rockwell hardness is. )
The hardness value of fabric hardness is unit, which has a certain approximate relationship with tensile strength.
7. Rockwell hardness can be displayed directly on the dial or digitally, which is convenient, quick and intuitive to operate and suitable for mass production.
The hardness of cloth needs to measure the indentation diameter with a microscope, and then look up the table or calculate it, which is complicated to operate.
8. Under certain conditions, HB and HRC can be exchanged by looking up the table. Its mental arithmetic formula can be roughly written as:1HRC ≈110hb.
Hardness test is the simplest test method in mechanical properties test. In order to replace some mechanical properties tests with hardness tests, more accurate conversion relationship between hardness and strength is needed in production.