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Metal Casting Technologies : March 2005
38 METAL Casting Technologies March 2005 Two readings of each impression should be taken and the results averaged. The readings should be at 90° to each other and at 45° to the surface preparation grind marks. The average diameter of the impression is converted to a Brinell hardness number using the appropriate conversion chart for the load and ball diameter used. SUMMARY AND PRECAUTIONS The testing site on each casting should be designated so that all tests are carried out in the same location. The surface of the test piece should be properly prepared. Grinding should be flat and deep enough to ensure casting structure. The test piece should be well supported so that it doesn't move during loading. Castings should be comfortable to the touch before testing. If the surface is too hot, results will be inaccurate. The testing machine should be used according to the manufacturer's instruction with the correct load and ball size and type for the test piece. Load dwell times should be consistent. Two readings should be made of each impression. The reading should be at 90o to each other and the results averaged. Each reading should be at 45o to the surface preparation grinding marks. Testing sites should be at least one ball diameter away from edges of the test piece. References 1. ASM -- Source Book on Ductile Iron, The Brinell Hardness Test as a Practical Metallurgical Control Tool by R. F. Marande & J. K. Kearns -- 2. AS 1816-1990 -- Metallic Materials -- Brinell Hardness Test 3. Newage Testing Instruments Inc -- Web Site 7. Test Block 8. Measuring impression with illuminated portable microscope BacktoBASICS