Hardness tester type - Hardness tester must read

- Jan 16, 2019-

Cloth hardness | HB(HBW\HBS): Cloth hardness (HB) is a test load of a certain size, pressing a hardened steel ball or carbide ball of a certain diameter into the surface of the metal to be tested for a specified time, then Unloading, measuring the diameter of the indentation of the surface to be tested. The cloth hardness value is the quotient obtained by dividing the load by the spherical surface area of the indentation. Generally: a certain size (usually 3000kg) of a hardened steel ball of a certain size (typically 10mm in diameter) is pressed into the surface of the material for a period of time. After the load is removed, the ratio of the load to the area of the indentation is Brinell. Hardness value (HB) in kilograms of force per mm2 (N/mm2). Rockwell hardness | HR (commonly used Rockwell scale HRA, HRB, HRC): Rockwell hardness is the hardness value of the indentation plastic deformation depth. Use 0.002 mm as a unit of hardness. When HB>450 or the sample is too small, the Brinell hardness test cannot be used instead of the Rockwell hardness measurement. It uses a diamond cone with a apex angle of 120° or a steel ball with a diameter of 1.588mm. It is pressed into the surface of the material to be tested under a certain load, and the hardness of the material is determined from the depth of the indentation. According to the hardness of the test material, it is expressed in three different scales: HRA: is the hardness obtained by 60kg load and diamond cone indenter, used for extremely high hardness materials | HRB such as cemented carbide: Yes Hardness obtained with 100kg load and 1.58mm diameter hardened steel ball for lower hardness materials | such as cast iron HRC: is the hardness obtained with 150kg load and diamond cone indenter for high hardness Materials | Hardness testing such as hardened steel is the simplest and most convenient test method in mechanical properties testing. In order to be able to replace some mechanical properties tests with hardness tests, a relatively accurate conversion relationship between hardness and strength is required for production. Practice has proved that there is an approximate relationship between the hardness values and the strength values of various hardness 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 and the higher the hardness value. Vickers hardness | HV: Vickers hardness (HV) is pressed into the surface of the material with a load of 120 kg and a diamond square cone presser with a apex angle of 136°. The surface area of the material indentation pit is divided by the load value. Vickers hardness value (HV). It is suitable for the hardness measurement of larger workpieces and deeper surface layers. Vickers hardness has a small load Vickers hardness, test load 1.961~49.03N, it is suitable for the hardness measurement of thin workpieces, tool surfaces or coatings; micro Vickers hardness, test load less than 1.961N, suitable for metal foil, Determination of the hardness of very thin surface layers. Shore hardness | HA/HD: A steel press pin with a certain shape is pressed vertically into the surface of the sample under the test force. When the surface of the press foot is completely fitted to the surface of the sample, the tip end surface of the press pin is opposite to the plane of the presser foot. A certain extension length L, the size of the Shore hardness is characterized by the value of L. The larger the L value, the lower the Shore hardness, and vice versa. Shore hardness | HS: Shore hardness test is a dynamic load test method. The principle is to reduce the weight of a steel ball with a certain quality of diamond steel or hardness tester from a certain height to the surface of the sample. The measured hardness value is characterized according to the height of the hammer rebound. The symbol is HS. The higher the profile of the hardness tester, the harder the surface measurement is. A90 is the hardness of the diamond and D45 is the hardness of the hardened steel. Hardness tester error: The hardness tester itself produces two kinds of errors: one is the error caused by the deformation and movement of its parts; the other is the error caused by the hardness parameter exceeding the specified standard. For the second error, the hardness tester is calibrated with a standard block before measurement. For the Rockwell hardness test results, the difference is within ±1. A stable value with a difference of ±2 can give a correction value. When the difference is outside the range of ±2, the hardness tester must be repaired or replaced by other hardness test methods. Rockwell hardness scales have a de facto scope of application and should be selected correctly according to the regulations. For example, when the hardness is higher than HRB100, the HRC scale should be used for testing; when the hardness is lower than HRC20, the HRB scale should be used for testing. Because the accuracy and sensitivity of the hardness tester are worse than the specified test range, the hardness value is not accurate and should not be used. Other hardness testing methods also stipulate corresponding calibration standards. The standard block used to calibrate the hardness tester cannot be used on both sides because the standard surface and the back surface hardness are not necessarily the same. The standard block is generally valid for one year from the date of calibration.