Continuous annealing line, continuous hot-dip galvanizing line, and steel sheet production method

A steel sheet production method comprising, in the following order:

• a step (A) of uncoiling a cold-rolled coil to feed a cold-rolled steel sheet by a payoff reel;
• a step (B) of passing the cold-rolled steel sheet through an annealing furnace in which a heating zone, a soaking zone, and a cooling zone are arranged in said order in a sheet passing direction, to continuously anneal the cold-rolled steel sheet by a step (B-1) of annealing the cold-rolled steel sheet in a reducing atmosphere containing hydrogen in the heating zone and the soaking zone and a step (B-2) of cooling the cold-rolled steel sheet in the cooling zone;
• a step (C) of continuously passing the cold-rolled steel sheet discharged from the annealing furnace, the step (C) including a step (C-1) of immersing the cold-rolled steel sheet in a hot-dip galvanizing bath located downstream of the annealing furnace in the sheet passing direction to apply a hot-dip galvanized coating onto the cold-rolled steel sheet;
• and
• a step (D) of coiling the cold-rolled steel sheet by a tension reel to obtain a product coil,
• wherein the steel sheet production method comprises
• a sound wave irradiation step of irradiating the cold-rolled steel sheet being passed downstream of the hot-dip galvanizing bath after the step (C-1) and before the step (D) with sound waves so that a sound pressure level at a surface of the cold-rolled steel sheet will be 30 dB or more.