METHOD FOR MEASURING SURFACE CLEANLINESS OF COLD ROLLED STEEL PLATE

摘要

PURPOSE:To indirectly determine the cleanliness of steel plate surface by inserting a metal test piece of less than specific thickness between coil layers at the time of winding a cold rolled steel plate to a tight coil and recovering the test piece and measuring the amount of the carbon adhered on the surface at the unwinding of the coil after annealing. CONSTITUTION:A shooter 3 for test pieces which makes use of compressed air or the like is provided below the steel plate 2 out from the final stand 1 of cold rolling mills, in proximity to the winding position, and a test piece 4 of =100 micron thickness is shooted horizontally toward the winding start part of a coil 5 so that said piece is inserted between the coil layers. To recover the test piece 4, the test piece 4 appearing from between the layers of the coil 5 is forcibly sucked and attracted by an electromagnet 7. After the electromagnet 7 is inverted by a drive unit, the test piece is released and is recovered into a lower vessel 9. The carbon amount of the recovered test piece 4 is measured by a conventional method.