Nippon Steel Corporation

Yoichi Sashihara

Tetsuya Miyazaki

Isao Nakamura

Kunitoshi Watanabe

Masahiro Masuda

Kazuhiro Sekimoto

A method of calculating heat input to an alloying furnace which includes heat input means for use in the production of hot galvanized band steel comprising conveying a band steel of a selected steel variety through the alloying furnace and forming a plated deposition on the band steel in the alloying furnace comprising an alloyed layer of iron and zinc, establishing a formula defining a correlation between heat input and at least the steel variety, the plated deposition and the conveying speed of the band steel, inputting information which relates at least to the steel variety, the plated deposition, and the conveying speed, determining the heat input on the basis of the information inputted, and using the determined heat input to control the heat input means of the alloying furnace thereby controlling the formation of the iron and zinc alloyed layer plated deposition.

Method of controlling heat input to an alloying furnace for

A plate temperature and an emissivity are determined at the outlet of an insulated heated zone, and compensations are established which reduce deviations between the respective measured values and the respective target values. A heat input is compensated for in accordance with the greater one of the compensations relating to the plate temperature and the emissivity, respectively. For a U-pattern material, .DELTA.Q is previously added to the heat input for the leading and the trailing end portion of the material. The band steel is irradiated by laser radiation at the outlet of the heating zone in order to detect the degree of alloying on the basis of the intensity of reflected radiation. When an unalloyed surface is detected, a target value of the heat input is modified. ITV camera is used to determine the optical reflectivity of the surface of the band steel at the outlet of a cooling zone in order to detect the degree of alloying. After the process has been stabilized, the heat input is gradually decremented, and when any slight insufficiency in the degree of alloying is detected, a fixed compensation is added to the heat input under that condition, subsequently ceasing to update the heat input.

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Otemachi, Japan

Yoichi Sashihara