| 摘要 |
PURPOSE:To manufacture a steel plate having high magnetic flux density by a method in which finish rolling during the hot rolling is completed at specific temperature, while the subsequent cooling until the strip is rolled up is made by a control cooling method, and then rolled up at a low temperature in the manufacture of a cold-rolled lower electromagnetic steel plate. CONSTITUTION:A roughly rolled steel slab, containing <0.06% C, <0.50% Si, and <0.120% P, is reheated at 1,180 deg.C, and then hot-rolled at a finishing temperature between the transformation points Ac1 and Ac3. Then, the slab is gradually cooled at a cooling rate of 20 deg.C/sec or less for at least 5 seconds or more immediately after the rolling in order to coarsen the crystal grains of the hot-rolled plate, raising the magnetic flux density of the rolled steel product. The winding temperature is set up to a temperature between 500 and 600 deg.C to prevent the lowering of iron loss value after rolling and also to make the acid-washing operation efficient. Lastly, the slab is washed with an acid, cold-rolled, and then annealed by the usual procedure to obtain a cold-rolled lower electromagnetic steel plate having a high magnetic flux density. |
