| 摘要 |
PROBLEM TO BE SOLVED: To produce a hot-rolled steel plate having good surface characteristic, reduced in red scale flaw by jetting the high pressure water with a flat nozzle after jetting the high pressure water having a specific jetting energy with a straight nozzle having a specific width. SOLUTION: The hot-rolled steel plate containing >=0.1 wt.% Si is produced. In such a case, after ejecting the steel material from a heating furnace, descaling is executed with the high pressure water. At this time, after jetting the high pressure water having >=120 KJ/m2 jetting energy per unit area of the steel material 2 by using the straight nozzles 1 having <=10 mm jetting width, the high pressure water having >=40 KJ/m2 jetting energy per unit area of the steel material 2 is jetted with the flat nozzles 3. In such a way, the scale 4 on the upper layer is firstly removed with the straight nozzles 1 and successively, the scale 5 on the lower layer is removed with the disposed flat nozzles 3 to remove the whole scale. Relating to the straight nozzles 1 the opening angle of the jetting flow at the outlet of the nozzle is <=5 deg. so that the jetting flow is straightly jetted onto the steel material while scarcely dispersing the jetting flow in the width direction of the steel material.
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