T.O. 33B-1-13-99Figure 3-53. Magnetic Particle Indication of a Seam on a Bar.b. Laminations. (See Figure 3-54.) Laminations in rolled plate or strip are formed when blowholes orinternal fissures are notfused during rolling, but are enlarged and flattened into sometimes quite largeareas of horizontal discontinuities. Laminations may be detected by magnetic particle testing on the cutedges of plate. The laminations do not give indications on plate or strip surfaces, since they are internaland parallel to the surface. Ultrasonic mapping techniques are used to define them.Figure 3-54. Magnetic Particle Indications of LaminationsShown on Flame-Cut Edge of Thick Steel Plate.c. Cupping. This is a condition created in drawing or extruding when the interior of the metal does notflow as rapidly as the surface. Segregation in the center of the metal usually contributes to thisoccurrence. The result is a series of internal ruptures that are severe defects whenever they occur. Theymay be indicated with magnetic particles if the ruptures are large and are near the surface of the part.The cupping problem can be minimized by changing die angles. (See Figure 3-55.)
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