Product Overview
Mitech MHR-150DT Electronic Rockwell Hardness Tester, based on the mechanical principle of conical diamond or hard alloy indenter pressing into the sample surface to produce indentation, realizing the material hardness measurement by measuring the depth of the indentation. Capable of inspecting the finished or semi-finished parts of the machined sample, it is suitable for high accuracy hardness testing for batches parts with various metal or non-metallic materials. According to statistics, Rockwell hardness testing is the most widely used hardness testing method in metal processing industry, which utilization ratio is more than 70%. With stable performance, convenient visual reading, electric loading and operation more convenient, it is widely used in metal processing and manufacturing, various metal material’s failure analysis and other fields like colleges and research institutions. It is the new type Brinell hardness testing instrument for testing the hardness of the materials like cast iron, steel, soft alloy and so on.
Function & application
l Used for quality control in metal processing manufacturing
l Used for failure analysis testing of metallic materials;
l Demonstration experiment for education and teaching in Colleges and Universities;
l Hardness testing of materials in scientific research institutions
Working Principle
The Rockwell hardness test is taking the diamond cone with 120°apex angle or the hardened steel ball with specified diameter as the indenter to press into sample surface with specific test force, then get the Rockwell hardness of the measured metallic materials according to the sample surface indentation depth.
The Rockwell hardness measurement principle is shown as below figure. 0-0 is the position that the diamond indenter is not yet in contact with the sample. 1-1 figure is the indenter position under the affect of the preliminary test force, the indentation depth is h1. The preliminary test is to eliminate the influence to the testing result accuracy caused by the roughness of the sample surface. 2-2 in the figure is the indenter position under the influence of the testing force (the preliminary test force and the main test force). The depth is h2. 3-3 in the figure is the indenter position after dismounting the main test force. As the metal elasticity will recovery some degree after deformation, the really indentation depth of the indenter is h3. The plastic deformation caused by the main test force make the indenter pressing into the depth is h＝h3－h1. Rockwell hardness value is determined by the size of h, the greater the depth h, the lower the hardness, otherwise, the higher the hardness.
In the traditional concept, usually use a constant C minus h to represent the level of hardness, while the depth of indentation per 0.002mm as a unit of hardness. The hardness value obtained is called the Rockwell hardness value, denoted by the symbol HR.
In the formula, c is a constant (for HRC, HRA, c is 0.2; for HRB, c is 0.26). The Rockwell hardness value HR obtained is an unknown number which is usually read directly on the test machine indicator when testing.
It should be noted that the measured hardness values would be different with different indenter and test force. Therefore, the Rockwell hardness testing specifies 15 different hardness test scales according to the different indenter specification and test force sizes. And the HRB, HRC, HRA are the most widely used.
Working Conditions
l Operation Temperature：10～30℃；
l Relative Humidity：≤65％；
l The surrounding environment should avoid of vibration, strong magnetic field, corrosive medium and heavy dust.
Instrument Features
l Widely used for high-precision hardness testing for parts with a variety of metal and non-metallic materials;
l Adopt automatic loading and unloading test force mechanism, variable hand wheel can control the size of the test force,
easy to operate;
l Equipped with potentiometer to ensure their own load time;
l Option for various specifications of the indenter, support 15 types of Rockwell hardness scales testing;
l With multi-level test force, a wider range of tests, and higher accuracy;
l With high-precision mechanical dial structure shows hardness values, simple operation, easy to read
l With modeling novel, strong structure, high reliability, simple operation, intuitive readings, and high test efficiency;
l The stability of the main unit is good. Tthe surface quality of the workpiece and the human operation factors have little
influence on the hardness test results;
l Equipped with excellent performance of the carbide indenter, high hardness, wear
resistance, good toughness, meanwhile with high temperature and corrosion resistance to ensure the accurate,stable and
reliable instrument test value ;
l With the function of error value correction, and the hardness value of the error can be corrected by key input, to make
the hardness value more accurately meet the tests’requirements;
l Consistent with GB/T230.1、GB/T230.2、JJG112 and other relevant domestic and foreign standards.
Instrument Maintenance
l Before using this instrument, please read the instruction manual carefully, and learn more about the steps and
precautions to avoid damage due to improper operation or the occurrence of personal safety accident;
l The test personnel should follow the operating procedures.Before and after the test,it should be repeated with standard
block calibration equipment. If a long time idle, it should be re-booted after several proofreading, when it is stable after the
test results, and then test its parts;
l If the specimen has visible deformation marks on the back and edges, the test result would be useless. It should choose
the intender or test force to test again;
l Normally, the first point is only used to offset the gap of each support surface without needing to record the test result.
Record the statistical test result from the second point;
l To ensure the accuracy of the test, and the pressure should be kept clean when used, such as indentation of oil or dust
and other stains.It can be used with absorbent cotton (industrial) or carefully wipe the ether at the top of the indenter;
l Pay attention to palm the instrument for carrying to forbid falling across. Please fix well the measuring lever,
counterweight and boom before carrying;
l It is strictly prohibited to turn the variable loading handwheel when the instrument load or unload the test force. Rotating
the handwheel forcibly will cause the internal gear dislocation, test force in chaos and even damage the internal parts of
the instrument;
l The using period of hardness block is one year. And the distance between the two adjacent indentation or indentation
center to the edge is more than 3mm. If too close,it will affect the measured results;
l Long time after the re-enabled,it should be preheated the electrical components before test;
l When not in use for a long time, please cover the dust cover to prevent dust into the instrument interior. And the
hardness block, indenter should be coated with antirust oil to prevent rusting after using;
l Please regularly put a small amount of oil on the screw and the handwheel interface;
l The power should first be cut off when the fuse is replaced or the weight is removed;The hardness tester should be
calibrated at least once a year to ensure its accuracy.
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