Heavy-duty cold-rolling for mechanically descaling a hot-rolled steel strip before pickling

A method of mechanically descaling a hot rolled steel strip comprising, in the following order, the steps of:

• providing a hot-rolled steel strip having mill-scales adhered to a surface thereof;
• cold-rolling the hot rolled steel strip with work rolls at a rolling reduction of 30% or more, while supplying water or a water-soluble rolling oil to roll bites of the work rolls and said steel strip, said water or water-soluble rolling oil having a friction coefficient μ in the range of 0.05 to (0.15+α×D+β×R), wherein α is a constant (1/7500), β is a constant (−1/2500), R is a rolling reduction (%) and D is a diameter of a work roll;
• brushing the cold-rolled steel strip for removing said mill-scales from the surface of said steel strip;
• spraying hot water on said brushed steel strip;
• and
• pickling the hot water sprayed steel strip.

A method of mechanically descaling a hot rolled steel strip comprising, the in the following order the steps of:

• providing a hot-rolled steel strip having mill-scales adhered to a surface thereof;
• cold-rolling the hot rolled steel strip at a rolling reduction of 30% or more, while removing, with at least one selected from the group consisting of a polisher, a spray nozzle, and a scraper, scale fragments transferred from said hot-rolled steel strip to work rolls;
• spraying hot water on said cold-rolled steel strip;
• and
• pickling the hot water sprayed steel strip.

An apparatus for descaling a hot-rolled steel strip comprising:

• a cold-rolling mill for cold-rolling a hot-rolled steel strip having mill-scales adhered to the surface thereof at a rolling reduction of 30% or more;
• brush rolls provided downstream of said cold-rolling mill for removing scale fragments which are peeling off or adhesiveness of which has been weakened by the cold-rolling;
• a hot water spray nozzles downstream of said brush rolls;
• a pickling tank provided downstream of said hot water spray nozzles;
• and
• bridle rolls provided downstream of said pickling tank for applying a tension to said steel strip.

A method of descaling a hot rolled steel strip comprising, in the following order, the steps of:

• providing a hot-rolled steel strip having mill-scales adhered to a surface thereof;
• cold-rolling the hot rolled steel strip at a rolling reduction of 30% or more;
• brushing the cold-rolled steel strip, for removing scale fragments peeled off the surface of said steel strip;
• spraying hot water on said brushed steel strip;
• removing residual scales from the surface of the hot water sprayed steel strip in a pickling tank;
• and then
• annealing the pickled steel strip.