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Hardness testing


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  • 2. For more help contact meMuhammad Umair Bukhari 03136050151
  • 3. HardnessThe Metals Handbook defines hardness asResistance of metal to plastic deformation, usually by indentation. OR The dictionary of Metallurgy defines thehardness as the resistance of a material to indentation.
  • 4. Introduction to hardness testing.. Hardness has variety of meanings Metal Industry resistance to Metallurgist resistance to penetration Mineralogist resistance to scratching Machinist resistance to machining
  • 5. Purpose of hardness testing The principal purpose of hardness test is to determine the suitability of a material for a given application. The ease with which the hardness test is performed has made it the most common method of inspection for metals and alloys.
  • 6. General types of hardness testing….. Current practice in USA divides hardness testing into two categories: Macrohardness: Refers to testing with applied loads on the indenter of more than 1 kg and material being tested are tools, dies and sheet material in the heavier gages(in large scale) Microhardness: Refers to testing with applied loads are 1 kg or below, and material being tested is very thin (down to 0.0125 mm or 0.0005 inch).
  • 7. Hardness measuring mechanisms Hardness is measured in a variety if ways. Static indentation tests Rebound tests Scratch file tests Ultrasonic test etc. erosion test abrasion tests
  • 8. Static indentation test A ball, cone, or pyramid is forced into the surface of the metal being tested The relationship of load to area or depth of indentation is the measure of hardness, such as in brinell, knoop, Rockwell and Vickers hardness tests.
  • 9. Brinell hardness testingINTRODUCTION: A Swedish, J.A.Brinell, announced Brinellhardness test. He pressed an indenter with ahard ball to the surface of a metal. Duringtesting period, the weights were maintainedconstant in indicated time. A low-ordermicroscope measured the diameters ofindentations. The values of diameters will betransferred respectively into the value ofBrinell hardness, HB value.
  • 10. Standard procedure.. That the test be made with a ball of 10 mm diameter under a load of 3,000 kg for ferrous metals the loaded ball is pressed into the specimen for at least 10s. But for non-ferrous these parameter are different in which load of 500 kg is applied for 30s.
  • 11. Contd….. The diameter of the impression produced is measured by means of a microscope containing an ocular scale, usually graduated in tenths of a millimeter, permitting estimate to the nearest 0.05 mm.
  • 12. Brinell hardness numberThe Brinell hardnessnumber, or simply theBrinell number, isobtained by dividing theload used, in kilograms,by the actual surfacearea of the indentation, insquare millimeters.
  • 13. BHN = the Brinell hardness number F = the imposed load in kg D = the diameter of the spherical indenter in mm Di = diameter of the resulting indenter impression in mm
  • 14. A well structured Brinell hardnessnumber reveals the test conditions, andlooks like this, "75 HB 10/500/30" whichmeans that a Brinell Hardness of 75was obtained using a 10mm diameterhardened steel with a 500 kilogram loadapplied for a period of 30 seconds.
  • 15. Rockwell hardness testingINTRODUCTION: S.P. Rockwell announced hardness test in 1919.In the United States; however, it was used topractical by C.H. Wilson. Different weights composed of different materialindenters will inspire various usages. There aretwo kinds of indenters, one is with a steel headand the other is with a diamond head. Rockwellhardness test is the most popular hardness testnowadays.
  • 16. Types of Rockwell testing Rockwell testing: In Rockwell testing the minor load is 10 kg and major load (60, 100, or 150 kg) is used regardless of the type of indenter. Rockwell superficial testing: In Rockwell superficial testing minor load is 3 kg and major loads (15, 30 or 45 kg) are used.
  • 17. TEST PROCEDURE Apply a minor load of 10 kg. Then the dial is set to zero and then major load is applied. Then apply major load 60 to 150 kg according to the scale used for 4 to 5 seconds. Release the major load only. Machine will show the Rockwell Hardness Number HR on the machine. All these operation will be done by machine automatically. 100 number means most hard and 0 means least hard
  • 18. Rockwell test principle.. Itconsists of measuring the additional depth of heavy load indenter beyond the depth of previously applied light load (minor).
  • 20. Types of indenters used Diamond cone indenters are used for testing hard materials such as hardened steel and cemented carbides. Hardened steel ball indenter are used for testing softer materials such as fully annealed steel, softer grades of cast iron , wide variety of non-ferrous metals and some non0metallic materials
  • 21. Advantages of Rockwell hardness testing: The most widely used method for determining hardness. Simple to perform Highly skilled operators are not required. Different types of loads and indenters can be used. The entire operation completes within 10 sec. Results are displayed digitally on the screen
  • 22. Precautions During manual operation, the work piece should be raised very slowly with the screw as it approaches the indenter. The surface being tested must be perpendicular to the direction of the force on the indenter within 2-5 degree. Careless operation in applying load, not only result in accurate reading but can damage the indenter.
  • 23. THANKS…..