Summary of common technical knowledge points of 2013 New Rockwell hardness tester
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First, the Rockwell hardness tester accuracy adjustment method: first open the upper cover If the indication value is lower than the standard block, first fix the screw with a screw, loosen the nut, rotate the adjusting screw clockwise, if the measured value is high , then rotate the screw in the opposite direction.
Second, the surface Rockwell hardness tester load change mechanism: it consists of knobs, bushings, chucks, cards, cams, brackets, camshafts, forks and so on. The load is turned clockwise to the desired load position when the hardness tester is unloaded.
Third, Rockwell hardness tester operating error factors: 1, sample selection, poor preparation, placement is not strong; 2, the head is not well installed; 3, test conditions are selected, improper control; 4, unskilled operation, such as loading and unloading Impact; 5, reading error.
Fourth, the use of surface Rockwell hardness tester to detect the T-scale detection of thin parts Note: There will be small marks on the back of the sample, at this time on the sample, material rheology will occur. This can be avoided if a small diamond work area with a diameter of approximately 4.5 mm is used. This diamond table cannot be used for Rockwell and N scales. Moreover, when using such a workbench, it must be noted in the report. 5. The mechanical composition of the Rockwell hardness tester: Rockwell hardness tester is a special equipment for measuring the hardness of materials. It has many types, but the structure is roughly the same, generally The body, the loading mechanism, the sounding mechanism and the indenter are composed. The working principle is: adding a predetermined load to the indenter through the loading mechanism, pressing it into the surface of the sample, measuring the indentation depth, and giving the hardness value.
Sixth, the surface Rockwell hardness test principle: the surface Rockwell hardness tester is based on the secondary application of test force (initial test force and total test force), the diamond indenter or 1.588mm diameter steel ball The indenter is pressed into the surface of the sample or the product. After the total test force is maintained for a certain period of time, the main test force is removed, the initial test force is retained, and the indentation depth is measured. The difference between the depth of penetration and the depth of penetration under the initial test force indicates that the depth of the Rockwell hardness is higher, and the hardness value is lower. The unit of measurement for depth is 0.001 mm for 1 degree. It can be read directly from the Rockwell indicator.
7. Rockwell hardness tester's requirements for accuracy: The tolerance of the Rockwell hardness tester is ±2%, the variation is not more than 2%; the tolerance of the total load is ±0.5%, and the variation is not more than 0.5. %.
Eight, Rockwell hardness tester in the hardness test application characteristics: Rockwell hardness test using the method of measuring the depth of penetration, the hardness value is directly read through the indicator or projection screen, so the operation is simple and rapid, high efficiency, adapt to batch zero Inspection of components; Rockwell hardness test method can use diamond indenter and steel ball indenter, can measure hard and soft samples, and has a wide range of use; in addition, this method is easy to operate and easy to grasp. Due to the above reasons, the Rockwell hardness test has been widely used in production, and has become the main means for testing the quality of products and determining a reasonable processing technology. More than 70% of the hardness testers are Rockwell hardness testers. However, this method has many factors affecting the measurement results due to the indenter and the measuring mechanism, so its accuracy is not as high as that of Vickers and Brinell.
Nine, Rockwell hardness tester B scale use: Rockwell hardness tester B scale is the hardness value obtained by using 1.588 steel ball indenter plus 100KG test force, mainly used to measure the softer metal material of Rockwell B hardness, when the Rockwell B hardness is higher than 100HRB or lower than 20HRB, this scale is not applicable. When the hardness is low, creep phenomenon will occur. When the hardness is high, the steel ball will be deformed, which will cause the hardness value to be inaccurate.
X. The influence of the load rate of the Rockwell hardness tester on the measured value: The Rockwell hardness test is a static load test, and the load application should be stable without impact. There should be sufficient time from the contact of the indenter to the surface of the sample to the load, and the loading speed should not be too fast, so as to avoid the load exceeding the specified value due to the impact force, resulting in an increase in the indentation depth. When the preload is accelerated, the indentation depth difference is reduced, and the hardness value is increased; when the main load application speed is increased, the hardness value is generally lowered, and the influence on the high hardness is large, and the low hardness is not significant. The effect of speed is closely related to the material.
11. Measurement range of plastic Rockwell hardness tester: The standard hardness tester of HRE scale has a measurement range of 70~94HRE, the standard hardness tester of HRL scale has a measurement range of 100~120HRL, and the standard hardness tester of HRM scale has a measurement range of 85~110HRM. The standard hardness tester for the HRR scale measures from 114 to 125 HRR.
12. Surface Rockwell hardness tester symbol: The surface Rockwell hardness tester symbol is represented by HR, and is marked with the scales N and T used, such as HRN, HRT, etc., for example, the hardness value symbol is HR15N and its hardness range is 70. ~94.
Thirteen, Rockwell hardness tester load and pressure head coordination: Rockwell A scale: with 60KG test force + diamond indenter; Rockwell B scale: with 100KG test force + steel ball indenter; Rockwell C ruler: Test force + diamond indenter with 150KG.
Fourteen, Rockwell hardness tester load: a, initial load: there is friction between the spring and the main shaft, the lever and the dial indicator, resulting in an increase or decrease of 100N. Adjust the screws loosely, adjust the movement, and the top rod is not in the proper position. There is a difference in the starting line, causing the initial load to be incorrect. If the initial load is not correct, adjust the spring, spindle, lever, dial indicator, etc. After the position of the adjustment block is moved properly, tighten the adjusting screw and tighten the position of the jack. The tolerance of the initial load should be less than ±2%. b. Main load: The leverage ratio is wrong, the weight of the boom and the weight is wrong; the main shaft, the lever and the weight are skewed, which will cause errors in the main load. The leverage ratio is wrong and should be adjusted. If the knife edge is worn, it should be repaired or replaced, and the spindle deformation should be straightened. The spindle, lever and weight skew should be positive. The tolerance of the main load of various scales is less than ±0.5%.
Fifteen, Rockwell hardness tester buffer refueling method: If the main test force is applied, the indicator hand starts to rotate rapidly, and then slowly rotates, indicating that the oil in the buffer is too small, at this time using the oil can with the extended nozzle slowly Inject the clean No. 32 oil and turn the loading and unloading handle several times at the same time to move the piston up and down several times to completely remove the air in the buffer until the oil sinks to the bottom and the oil slightly overflows from above.
16. The hardness tester shall periodically perform the indication error test during use. The method is as follows: according to the test conditions marked by the standard block, five hardness tests are performed on different positions on the surface of the standard block, and the arithmetic mean value is taken. The ratio of the difference between the value and the standard block value to the standard block value should not exceed Provisions. If the indication error measured by the hardness tester exceeds the specified value, first check the indenter or replace the indenter, and use the standard sensor to check whether the test force of the hardness tester is correct. The test force tolerance should not exceed 1%.
Seventeen, Rockwell hardness tester head installation method is as follows: the pressure head is installed in the spindle hole, when installing the pressure head, it must ensure that the spindle hole, end face, indenter tail handle and shoulder are clean and free of foreign matter. When installing, firstly press the ram tightening screw to the top of the shank, and then load the main test force. When the total test force is added, the ram tightening screw is tightened while maintaining the total test force. Finally unloaded, the indenter is installed.
Eighteen, Rockwell hardness value is calculated as follows:
N-constant, for A, C, D, N, T scales, N = 100; other scales, N = 130;
H- residual indentation depth, mm;
S-constant, for Rockwell hardness, S = 0.002 mm, for surface Rockwell hardness, S = 0.001 mm. The depth of indentation corresponding to each Rockwell hardness unit is Rockwell hardness of 0.002 mm and surface Rockwell hardness of 0.001 mm. The lighter the indentation, the higher the hardness. The Rockwell hardness test is divided into two types, one is the ordinary Rockwell hardness test, and the other is the surface Rockwell hardness test. Rockwell hardness test uses 1200 diamond cone and 1.588mm, 3.175mm steel ball three indenters, using 60kg, 100kg, 150kg three test forces, they have a total of nine combinations, corresponding to the Rockwell hardness of nine scales, namely HRA , HRB, HRC, HRD, HRE, HRF, HRG, HRH, HRK. The surface Rockwell hardness test uses two kinds of indenters: 1200 diamond cone and 1.588mm steel ball. It adopts three test forces of 15kg, 30kg and 45kg. They have six combinations, corresponding to the six scales of surface Rockwell, namely HR15N, HR30N. , HR45N, HR15T, HR30T, HR45T. The Rockwell hardness test conditions are shown in Table 2-1. The selection of the Rockwell hardness scale is shown in Table 2-2.
Nineteen, Rockwell hardness tester classification: according to the application method: general Rockwell hardness tester, surface Rockwell hardness tester, comprehensive Rockwell hardness tester; according to the operation method: manual Rockwell hardness tester, electric Rockwell hardness According to the display mode: pointer type, digital display Rockwell hardness tester; according to the loading method: the code is loaded by the principle of leverage, the sensor is directly loaded.
20, Rockwell hardness tester for sheet thickness requirements: Rockwell hardness tester is only suitable for measuring the thickness of the sheet must be more than 1mm, the diameter of the round bar is 3mm, small products can not be measured. View the summary of common technical knowledge points of 2013 New Rockwell hardness tester (1)