Jfe Steel Corporation

Kawasaki Steel Corporation

Takahiro Sugano

Nobuyuki Sato

Satoshi Yoneda

Takashi Yamauchi

Sachihiro Iida

Eiko Yasuhara

Hiroki Yamagami

Takayuki Fukui

An apparatus for manufacturing a molten zinc coated steel sheet includes a molten zinc coating device, a temper rolling mill, an acid solution contacting device, and a cleaning device connected in tandem, wherein the acid solution contacting device and the cleaning device are separated from each other with a region therebetween and an absolute humidity controller is disposed in the region between the acid solution contacting device and the cleaning device.

Apparatus for manufacturing molten zinc coated steel sheet

Cleaning of a hot dip galvanized steel sheet is conducted by bringing a strip-shaped steel sheet which was treated by surface oxidation in advance into contact with a cleaning liquid for 1 second or more, and then bringing the hot dip galvanized steel sheet into contact with pure water, while continuously transferring the hot dip galvanized steel sheet. The method allows efficiently and fully washing off the acidic solution adhered to the surfaces of the hot dip galvanized steel sheet treated by surface oxidation. The invention also provides an apparatus for cleaning the hot dip galvanized steel sheet to carry out the above cleaning method.

Method for cleaning hot dip galvanized steel sheet and cleaning apparatus therefor

A method of controlling the concentration of P of cleaning solution waste water starts by providing a waste water buffer tank capable of either sending the waste water to a waste water treatment plant or storing the waste water after the waste water is accepted. The concentration of P in the cleaning solution is set within a target concentration range, and matter to be treated is treated. The concentration of P in the waste water is measured in the waste water buffer tank. When the measured value of the concentration of P is less than a selected upper limit, the waste water is sent from the waste water buffer tank to the waste water treatment plant. When the measured value of the concentration of P is higher than the selected upper limit, sending the waste water to the waste water treatment plant is stopped, and the waste water is stored in the waste water buffer tank. The concentration of P is reduced to a value within the target concentration range, and the matter to be treated is treated.

Method for controlling a waste water concentration of cleaning solution containing phosphorus

Continuous annealing equipment contains: a heating zone, a soaking zone, and a rapid cooling zone, the rapid cooling zone having gas jet cooling equipment and is provided with at least one pair of seal rolls at each of an inlet and an outlet thereof and bridle roll units each composed of two or more bridle rolls in front of and behind itself; the bridle roll unit behind the rapid cooling zone having two or more heating rolls each having an induction heater thereinside; and the heating roll having a winding angle of 100&#xb0; or more per heating roll and 380&#xb0; or more in total of all the heating rolls.

Continuous annealing equipment

A molten metal is deposited on the surfaces of a metal strip by continuously dipping the metal strip in a coating bath. The metal strip is lifted at a constant speed while supported with a pair of upper and lower support rolls in the coating bath. The coating weights of the molten metal deposited on the surfaces of the metal strip are adjusted by wiping the molten metal with gases from gas wiping nozzles disposed above the surface of the coating bath. The metal strip is advanced while supported with a pair of upper and lower touch rolls, wherein the metal strip is advanced by setting the distance L between the upper support roll disposed in the coating bath and the lower touch roll disposed outside the coating bath within the range determined by a formula L&lE;80&times;T&times;W,/V, where L: distance between the upper support roll in the coating bath and the lower touch roll outside the coating bath (mm), V: line speed of the metal strip (m/min), T: tension imposed on the metal strip (kgf/mm,), and W: target coating weight per one side of the metal strip (g/m,). The stable quality of the metal strip can be obtained by reducing the variation of the coating weights of the molten metal deposited on the surfaces of the metal strip at all times regardless of the change of the operating conditions under which continuous hot dip galvanizing operation is carried out. Further, a coating cost can be greatly reduced by preventing the excessive deposition of the molten metal.

Growing community of inventors

Tokyo, Japan

Takahiro Sugano