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Brinell hardness method and Rockwell hardness method. Hard and brittle casting alloys are usually measured by the Rockwell hardness method, and other casting alloys are generally measured by the Brinell hardness method. For cast alloys with uniform metallographic structure such as cast steel, there is a certain conversion relationship between Rockwell hardness, Brinell hardness and tensile strength. Refer to GB/T112-199 "Ferrous Metal Hardness and Strength Conversion Value" and GB /T3771-1983 "Copper alloy hardness and strength conversion value".
The Brinell hardness method uses a cemented carbide ball with a certain diameter to press it into the surface of the sample with the corresponding test force.
After the specified holding time, remove the test force, measure the indentation diameter on the surface of the sample, and divide the test force by the test force. The quotient obtained from the spherical surface area of the indentation represents the Brinell hardness value, and the symbol is HBW, which is suitable for materials with the Brinell hardness value less than or equal to 650. The instruments, samples, test methods and test results of the Brinell hardness test shall comply with GBT231.1-2002 "Metal Brinell Hardness Part I: "Test Method". The Brinell hardness test can be carried out on tensile specimens, impact specimens, castings or specially cast hardness test blocks. The test surface should be smooth and flat, free of scale and foreign dirt. The test location should meet the requirements of the corresponding casting standard or be negotiated by the supplier and the buyer. The Rockwell hardness method is to press the diamond cone indenter or the steel ball indenter into the surface of the sample under the action of the initial load and the total load (equal to the initial load plus the main load), and then remove the main load, and measure at the initial load. The indentation depth under load increases the e value, and the e value is used to calculate the Rockwell hardness.
The Rockwell hardness varies according to the scale used.
The most commonly used scales are HRA, HRB and HRC. HRB adopts steel ball indenter with hardness value=130-c; HRA and HRC adopt diamond cone indenter with hardness value=100-e. The main load of HRA is 490.3N, and the measurement range is 60~85HRA; the main load of HRC is 1373N, and the measurement range is 20~67HRC. The instruments, specimens, test conditions and test methods used in the Rockwell hardness test, as well as the treatment of the test results shall comply with GB/T 230.1-2004 "Metal Rockwell Hardness Part 1: Test Method (A, B, C, D, E, F, G, H, K, N, T Scale)". The selection of the specimen, the test location and the technical requirements for the test surface of the Rockwell hardness test are the same as those of the Brinell hardness test.
In addition to Brinell hardness and Rockwell hardness, the hardness of metals can also be represented by Shore hardness (HS) and Vickers hardness (HV). Measuring the Shore hardness of metals should meet the requirements of GB/T4341-2001 "Metal Shore Hardness Test Method". The determination of the Vickers hardness of metals should meet the requirements of GB/T4340.1-1999 "Metal Vickers Hardness Test Part 1: Test Method". Various types of hardness testers should be periodically verified by the national metrology department in accordance with relevant standards
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