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It is the distance between the external surface and the point on which Vickers hardness assumes the conventional value of HV = 685 (HRC ~ 59).It is determined as per point 2.1.1
The hardened surface may be approximately evaluated, with the help of a centisimal comparator with 20 magnification, considering the area (on a transversal section of the piece) including the external surface and the point on which the coloring of the surface etched by the reactive agent, change from blue to brown - yellow.
The section of the piece is polished and etched with reactive agent Nital 4% for about 30 seconds。 |
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