What is Hardness

Under the specified applied load, the steel ball or diamond indenter is pressed vertically into the surface of the specimen to produce an indentation, and the indentation depth is tested, and the Rockwell hardness can be calculated by using the Rockwell hardness calculation formula hr=(k-h) c. To put it simply, the shallower the indentation, the greater the HR value, and the higher the hardness of the material. with"hrc"to represent.

For example, HRC60 means that when using a diamond cone indenter with a top angle of 120 degrees under a test load of 150kg, the indentation depth of the specimen is

Rockwell hardness: An index that determines the hardness value by the depth of plastic deformation of the indentation.

1.Rockwell hardness has no unit, it is a mechanical property index without a large quantity, and its most commonly used hardness scale is A, B, and C, which are usually recorded as HRA, HRB, HRC, and its expression method is hardness data plus hardness symbol, such as 50HRC.

It is a hardness calculated by using a 60kg load and a diamond cone press, and is used for materials with high hardness.

3.For example: cemented carbide.

It is a hardness obtained by using a 100 kg load and a hardened steel ball with a diameter of 58 mm, and is used for materials with low hardness.

5.For example: mild steel, non-ferrous metals, annealed steel, cast iron, etc.

It is a hardness obtained with a load of 150 kg and a diamond cone presser, and is used for materials with high hardness.

7.For example: quenched steel, etc.

8.There are three different standards of Rockwell hardness: HRA, HRB, and A, B, and C in HRC.

9.Called Ruler A, Ruler B, Ruler C.

10.The Rockwell hardness test is one of several common indentation hardness tests that are used today.

Rockwell hardness: An index that determines the hardness value by the depth of plastic deformation of the indentation.

The indenter (diamond cone, steel ball or cemented carbide ball) is pressed into the surface of the sample in two steps (initial experimental force and main experimental force), the main experimental force is discharged after the specified holding time, and the residual trace depth h. under the initial experimental force is measured

Generally, we do Rockwell hardness for metal bulk objects in our laboratory.

Metal sheet objects are made of thin sheets to make Vickers hardness.

Rubber and plastic are made of Shore hardness.

Rockwell and Vickers hardness can be calculated with each other!

Grading representation of Rockwell hardness:

Hardness is a material's ability to resist penetration by foreign objects. The most common way to test the hardness of steel is to file the edge of the workpiece with a file, and the hardness is determined by the depth of the scratch marks on its surface. This method is called the file method, and this method is less scientific.

The hardness tester is extremely accurate and is a common method for testing hardness in modern times. The most commonly used test method is the Rockwell hardness test. The Rockwell hardness tester uses the depth of the diamond to determine the hardness of the metal, and the greater the depth, the less hardness it is.

Rockwell hardness, which was proposed by Rockwell in 1921, is the hardness value of a metal material measured using a Rockwell hardness tester. The value is not a single friend, only with the code "HR" to dedicate, the measurement method is to press the steel ball or diamond indenter vertically into the surface of the material to be tested under the specified applied load, resulting in a dent, according to the depth of the dent after the load is released, the Rockwell hardness can be calculated by using the Rockwell hardness calculation formula hr=(k-h) c. The Rockwell hardness value is displayed on the dial of the hardness tester and can be read directly.

In the above formula, k is a constant, k= when the diamond indenter, and k= when the steel ball indenter is quenched; h is the indentation depth of the specimen after the main load is removed; c is also a constant, and in general c=.

It can be seen from this that the shallower the indentation, the greater the HR value and the higher the hardness of the material.

Generally, the code names HRA, HRB, HRC are used to represent the hardness of the material, in which HRA indicates that the test load is tested by a diamond cone indenter with a top angle of 120 degrees;

HRB indicates that the test load is tested using a quenched steel ball with a diameter;

HRC indicates that the test load is tested using a diamond cone head with a top angle of 120 degrees.

For the hardness of the knife making material, the knife making industry generally uses HRC to represent the hardness of the blade, such as HRC60, that is, when the test load is the use of a diamond cone indenter with a top angle of 120 degrees, the indentation depth of the tested material is.

In short, the higher the hardness, the higher the wear resistance, but the greater the brittleness. The maximum hardness is not more than 60HRC. Generally, the edge hardness of a good knife should be above 50hrc and below 60hrc.

Leeb and Rockwell are different hardness measurements, and the conversion relationship between them is complex. Conversions between different materials and hardness measurement methods require empirical formulas or calibration curves for calculations, often using specialized hardness measuring instruments and standard samples for measurement and calibration.

For common metallic materials, the conversion between Leeb and Rockwell can be calculated using the following empirical formula:

hrc = × hl +

According to this formula, when Kai socks return to HL650, the corresponding HRC hardness is about .

It should be noted that this conversion formula is only applicable to specific metal materials and hardness measurement methods, and the actual conversion results may be biased due to factors such as materials, hardness measurement methods, specimen shape and size, etc. Therefore, when performing hardness measurement and hardness conversion, it is necessary to follow standard methods and specifications, and use professional hardness measuring instruments and standard samples for calibration and comparison as much as possible. Keep an eye on hunger.

Hardness representation is generally divided into absolute hardness and relative hardness, absolute hardness is generally only used in the Kejia world, and rarely used in actual production, so usually we come into contact with the hardness unit system cover the mountain for relative hardness, often there are several ways to express it: Shore hardness (also known as: Shore hardness), do let Rockwell hardness, Brinell hardness (also known as:

Burnell hardness), Locke's hardness; The conversion relationship is detailed in the following formula:

1. Shore hardness (HS) = Brinell hardness (BHN) 10 + 12.

2. Shore hardness (HS) = Rockwell hardness (HRC) + 15.

3. Brinell hardness (BHN) = Rocknell hardness (HV).

Because the Shore hardness is the Shore hardness, there is no conversion relationship.

A, B, and C in HRA, HRB, HRC, etc., are three different standards.

Rockwell hardness is an index of hardness value determined by the depth of plastic deformation of the indentation, with millimeters as a unit of hardness. The use of different indenters and different forces in the Rockwell hardness test results in different combinations, corresponding to different scales of Rockwell hardness. There are 3 scales that are commonly used, and their applications cover almost all commonly used metal materials.

Rockwell hardness (HR) testWhen the sample to be measured is too small or the Brinell hardness (HB) is greater than 450, the Rockwell hardness measurement is switched to the test. The test method is to use a diamond cone with a top angle of 120 degrees or a steel ball with a diameter of 120 degrees to press into the surface of the measured material under a certain load, and the hardness of the material is calculated from the indentation depth. The three most commonly used scales are A, B, C, HRA, HRB, HRC, which should be represented by the scales with different hardness ranges according to the different hardness of the experimental materials

The HRA is a hardness obtained with a load of 60 kg and a diamond cone press, and is used for materials with higher hardness. For example: steel sheets, cemented carbide.

HRB is a hardness obtained with a 100 kg load and a diameter hardened steel ball for materials with lower hardness. For example: mild steel, non-ferrous metals, annealed steel, etc.

HRC is the hardness obtained with a load of 150 kg and a diamond cone presser for higher hardness materials. For example: quenched steel, cast iron, etc.

Rockwell hardness: An index that determines the hardness value by the depth of plastic deformation of the indentation.

Rockwell hardness is a type of press-in hardness, and there are 9 hardness standards instead of 3, which are:

HRA, HRB, HRC, HRD, HRE, HRF, HRG, HRH, and HRK

It is based on the test scale and load. A, B, C are just common hardness, and small bookshelves for engineering students |Press-in hardness – Brinell, Vickers, Rockwell.

Rockwell hardness has no unit, it is an undisciplined mechanical property index, and its most commonly used hardness scale is A, B, and C, which are usually recorded as HRA, HRB, HRC, and its expression method is hardness data + hardness symbol, such as 50HRC.

A, B, and C in HRA, HRB, HRC, etc., are three different standards in Rockwell hardness, which are called scale A, scale B, and scale C.

The Rockwell hardness test is one of several common indentation hardness tests used today, with an initial pressure of 10 kgf for all three scales) and a hardness value calculated based on the indentation depth. Scale A uses a ball cone diamond indenter, which is then pressurized to 60 kgF); Scale B uses a steel ball with a diameter of inches) as the indenter, and then pressurizes to 100kgf); Ruler C uses the same ball cone diamond as ruler A as the indenter, but the force after compression is 1471N (150kgf). Therefore, bar B is suitable for relatively soft materials, while bar C is suitable for harder materials.

It has been proved in practice that there is an approximate corresponding relationship between the hardness value and the strength value between the various hardness values of metal materials. Because the hardness value is determined by the initial plastic deformation resistance and the continuing plastic deformation resistance, the higher the strength of the material, the higher the plastic deformation resistance, and the higher the hardness value. However, the conversion relationship between the various materials is not consistent.

Rockwell hardness: An index that determines the hardness value by the depth of plastic deformation of the indentation.