Hardness Measurement
Application of hardness measurement: hardness measurement is simple and fast; no damage to the sample (non-destructive test); hardness can comprehensively reflect other mechanical properties such as the strength of the material; hardness is directly related to wear resistance, the higher the hardness, the more wear-resistant Sex is better. Therefore, the hardness measurement is widely used, and the hardness is often marked on the drawings as the main basis for parts inspection and acceptance.
Measurement method: measurement methods such as indentation method, bombardment method and scratch method can be used. The pressing method is commonly used in production (Brinell hardness method, Rockwell hardness method, Vickers hardness method, etc.).
Brinell Hardness: HB (Brinell-hardness) (HBS, HBW)
Brinell hardness measurement principle: use a spherical indenter with a diameter of D, press into the surface of the material with the corresponding test force F, remove the test force after a specified holding time, measure the average diameter d of the residual indentation with a reading microscope, and use a ball The pressure on the unit surface area of the crown indentation represents the hardness value. The actual measurement can obtain the hardness value by looking up the table after measuring the d value.
HBS ( HBW ) = F/S = 2F/ π D[D - (D2-d2)1/2]
- HBS - Indicates the Brinell hardness value measured with a hardened steel ball indenter. Scope of application: less than 450;
- HBW - Indicates the Brinell hardness value measured with a carbide indenter. Scope of application: 450~650
Brinell hardness measurement principle
Brinell hardness representation method: the numbers before the symbol HBS or HBW represent the hardness value, and the numbers after the symbol represent the sphere diameter, load and load holding time respectively in sequence. For example: 120HBS10/1000/30 means that the Brinell hardness value measured when a steel ball with a diameter of 10mm is kept under a load of 1000kgf (9.807kN) for 30s is 120.
Features of Brinell hardness
The measurement value is stable and accurate, and can reflect the average hardness of the material more realistically; Disadvantages: The indentation is large, the operation is slow, and it is not suitable for mass-produced finished parts and thin parts.
Brinell hardness measurement range: used for hardness measurement of raw materials and semi-finished products, and can be used to measure cast iron; non-ferrous metals (non-ferrous metals), steels with lower hardness (such as annealed, normalized, quenched and tempered steel).
Rockwell Hardness
Rockwell hardness measurement principle: use a diamond cone or quenched steel ball indenter, press the indenter into the surface of the material under the action of the test pressure F, after a specified time, remove the main test force, keep the initial test force, use the residual pressure The hardness value is calculated by the increment of the trace depth. During the actual measurement, the Rockwell hardness value can be directly read through the dial of the testing machine.
HR = K - h/0.002; K——constant, the value of diamond indenter is 100, and the value of spherical indenter is 130.
Rockwell Hardness Measurement Principle
Rockwell hardness measurement conditions: Rockwell hardness can measure a wide range of hardness values from soft to hard. Different indenters and test forces can be used according to the hardness value of the measured object.
Rockwell Hardness Features
Rapid and simple measurement, small indentation, and large hardness measurement range; Disadvantages: data accuracy, stability, and repeatability are not as good as Brinell hardness.
Rockwell hardness measurement range: It can be used for finished products and thin parts, but it is not suitable for measuring materials with coarse and uneven structure (as shown in the table above).
Vickers hardness: HV (diamond penetrator hardness)
Vickers hardness measurement principle: similar to Brinell hardness. A diamond regular square pyramid indenter with an angle of 136 degrees is used to press into the surface of the material with the specified test force F, and the test force is removed after the specified time, and the hardness is expressed by the average pressure on the unit surface area of the regular square pyramid indentation value.
Vickers hardness measurement principle
Vickers hardness characteristics: large measuring range, can measure materials with hardness in the range of 10~1000HV; small amount of indentation.
Vickers hardness application: It can measure thinner materials and surface hardened layers such as carburizing and nitriding.
For more information on this source, please visit TITLTEST.COM If you need to know more details, please contact support@titltest.com