Hot-rolled steel sheet manufacturing method and manufacturing device

Abstract

Provided are a hot-rolled steel sheet manufacturing method and manufacturing device, by which a hot-rolled steel sheet having excellent surface properties and fine texture can be manufactured. Specifically provided is a hot-rolled steel sheet manufacturing method, wherein a heating unit, a descaling unit, a finishing rolling mill line, a cooling unit disposed in the finishing rolling mill line, and a quenching unit disposed just behind the finishing rolling mill line are used, and by controlling the operations of the heating unit, the cooling unit, and the quenching unit, the temperature (T1) of a material to be rolled on the finishing rolling mill line entrance side, the temperature (T2) of the material to be rolled on the final stand entrance side of the finishing rolling mill line, and the temperature (T3) of the material to be rolled on the quenching unit exit side are controlled. Also provided is a hot-rolled steel sheet manufacturing device which is provided with a heating unit, a descaling unit, a finishing rolling mill line, a cooling unit disposed in the finishing rolling mill line, a quenching unit disposed just behind the finishing rolling mill line, and a control means, and controls T1, T2, and T3 by controlling the operations of the heating unit, the cooling unit, and the quenching unit by the control means.

Description

technical field [0001] The present invention relates to a method and device for manufacturing hot-rolled steel sheets. In particular, the present invention relates to a manufacturing method and manufacturing apparatus of a hot-rolled steel sheet focusing on temperature control of a workpiece rolled by a finishing mill. Background technique [0002] Hot-rolled steel sheets are produced by rough-rolling a slab heated in a heating furnace in a rough-rolling mill to produce a rough-rolled material (hereinafter sometimes referred to as "rough section bar (Japanese: rough バ 1)"), after that, in the finishing mill, the rough section delivered to the finishing mill by using the conveying table is rolled to the specified size, and after the cooling process of cooling under the specified conditions, it is finally rolled in the coiler for winding. [0003] Among the hot-rolled steel sheets produced in this way, steel sheets used for automobiles, structural materials, etc. are required...

AI Technical Summary

Problems solved by technology

[0015] However, in the technology disclosed in Patent Document 2, as a method of efficiently controlling the temperature of the steel sheet, the thickness of the rough section and the finish rolling speed are corrected, but in order to manufacture a steel sheet with a fine grain structure, it is necessary to Accumulated strain, therefore, it is not desirable to slow down the finish rolling speed. In this method, the finish rolling speed cannot be freely changed only for the purpose of temperature control.

[0016] Moreover, the cooling of the steel plate after finish rolling requires a strong cooling capacity, so a quenching device with a high flow density is used, and the quenching device sprays a large amount of cooling water to a narrow range, but it is difficult to increase the cooling capacity in a short period of time. Reducing the amount of cooling water requires a minimum adjustment of the cooling capacity, so it is difficult to cope with changes in the finishing rolling speed such as accelerated rolling

However, in the technology of Patent Document 2, only the heating device is used to compensate for the temperature drop of the tail end of the rough bar that stays at the entrance side of the finish rolling mill during the finish rolling process. In order to suppress the energy required for heating to a small , it is necessary to shorten the time spent staying at the entrance side of the finish rolling mill, so it is necessary to implement accelerated rolling that gradually increases the finish rolling speed, so that the change of the finish rolling speed cannot be avoided

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