Provided is a hot-band annealing method comprising subjecting a Si-containing hot rolled steel sheet, having an oxidized scale formed on a surface of the steel sheet by hot rolling, to hot-band annealing with a hot-band annealing equipment provided with a heating zone, a soaking zone, a cooling zone, and a rapid heating device at an upstream side of the heating zone and/or in an inlet side of the heating zone, wherein the hot rolled steel sheet is heated by not lower than 50° C. at a heating rate of not less than 15° C./s by using the rapid heating device to improve a descaling property. Also, provided is a descaling method characterized by subjecting the Si-containing hot rolled steel sheet, after the hot-band annealing, to descaling only by pickling without requiring mechanical descaling or heating the steel sheet in the pickling process.

Provided is a hot-band annealing method comprising subjecting a Si-containing hot rolled steel sheet, having an oxidized scale formed on a surface of the steel sheet by hot rolling, to hot-band annealing with a hot-band annealing equipment provided with a heating zone, a soaking zone, a cooling zone, and a rapid heating device at an upstream side of the heating zone and/or in an inlet side of the heating zone, wherein the hot rolled steel sheet is heated by not lower than 50° C. at a heating rate of not less than 15° C./s by using the rapid heating device to improve a descaling property. Also, provided is a descaling method characterized by subjecting the Si-containing hot rolled steel sheet, after the hot-band annealing, to descaling only by pickling without requiring mechanical descaling or heating the steel sheet in the pickling process.

Provided is a hot-band annealing method comprising subjecting a Si-containing hot rolled steel sheet, having an oxidized scale formed on a surface of the steel sheet by hot rolling, to hot-band annealing with a hot-band annealing equipment provided with a heating zone, a soaking zone, a cooling zone, and a rapid heating device at an upstream side of the heating zone and/or in an inlet side of the heating zone, wherein the hot rolled steel sheet is heated by not lower than 50° C. at a heating rate of not less than 15° C./s by using the rapid heating device to improve a descaling property. Also, provided is a descaling method characterized by subjecting the Si-containing hot rolled steel sheet, after the hot-band annealing, to descaling only by pickling without requiring mechanical descaling or heating the steel sheet in the pickling process.

Provided is a hot-band annealing method comprising subjecting a Si-containing hot rolled steel sheet, having an oxidized scale formed on a surface of the steel sheet by hot rolling, to hot-band annealing with a hot-band annealing equipment provided with a heating zone, a soaking zone, a cooling zone, and a rapid heating device at an upstream side of the heating zone and/or in an inlet side of the heating zone, wherein the hot rolled steel sheet is heated by not lower than 50° C. at a heating rate of not less than 15° C./s by using the rapid heating device to improve a descaling property. Also, provided is a descaling method characterized by subjecting the Si-containing hot rolled steel sheet, after the hot-band annealing, to descaling only by pickling without requiring mechanical descaling or heating the steel sheet in the pickling process.

Provided is a hot-band annealing equipment provided with a heating zone, a soaking zone and a cooling zone for subjecting a Si-containing hot rolled steel sheet to hot-band annealing, wherein when the Si-containing hot rolled steel sheet is subjected to hot-band annealing with the hot-band annealing equipment provided with a rapid heating device at an upstream side of the heating zone and/or in an inlet side of the heating zone, the hot rolled steel sheet is heated by not lower than 50 C. at a heating rate of not less than 15 C./s by using the rapid heating device to improve a descaling property, whereby descaling can be performed only by pickling without requiring mechanical descaling or heating the steel sheet in the pickling process. Also provided are a hot-band annealing method and a descaling method using the above equipment.

The method includes determining an oxide layer removal energy density threshold from a section of the product, including transmitting, to a segment of the section, analyzing pulses of wavelength and of pulse duration equal to those of the stripping lasers to form a stripped region, capturing an image of the segment, determining, from this image, a dimension representative of the stripped region and evaluating, from the dimension, the removal energy density threshold; transmitting stripping pulses to the section, the energy density of the stripping pulses being higher than the removal energy density threshold, the stripping laser being controlled in such a way that every point of the section is exposed to an energy density higher than the removal energy density threshold.