Abstract: The present invention provides a new high-strength and Si—Cr containing hot rolled steel plate provided with higher strength as well as excellent workability and a method for manufacturing the steel plate. The high-strength steel plate can be obtained by controlling the particle size of prior austenite to be 10 ?m or less, and properly selecting the coiling temperature. The steel plate obtained includes a retained austenite phase in a volume fraction of 5% to 20%; a martensite phase in a volume fraction equal to or less than 10%; and a bainite phase in the remaining volume fraction. The particle size of the retained austenite particle is 1 ?m or less and the retained austenite particles are dispersed uniformly.

Abstract: The hot rolling apparatus of the present invention has a mill arranged on the preceding stage, mills of a plurality of stands arranged on the later stage which are different-diameter roll mills including a pair of different-diameter work rolls having an equivalent roll diameter of less than 600 mm or minimum-diameter roll mills including a pair of work rolls having a diameter of less than 600 mm, and a cooling unit for cooling steel to be rolled which is arranged on each exit side of the mills of at least two stands on the later stage. The hot rolling apparatus can smoothly manufacture hot rolled plates of fine-particle steel.

Abstract: The hot rolling apparatus of the present invention has a mill arranged on the preceding stage, mills of a plurality of stands arranged on the later stage which are different-diameter roll mills including a pair of different-diameter work rolls having an equivalent roll diameter of less than 600 mm or minimum-diameter roll mills including a pair of work rolls having a diameter of less than 600 mm, and a cooling unit for cooling steel to be rolled which is arranged on each exit side of the mills of at least two stands on the later stage. The hot rolling apparatus can smoothly manufacture hot rolled plates of fine-particle steel.