Provided is a hot-dip plating method that achieves good plating wettability between a metal material and a hot-dip plating bath and that makes it possible to reduce the amount of consumed energy as compared to conventional techniques. In a plating step included in the hot-dip plating method, vibration is applied to a hot-dip plating bath such that the ratio of the average sound pressure level (excluding noise) over ranges each lying between sound pressure peaks at harmonic frequencies of a fundamental frequency to the average sound pressure level (excluding noise) over the measured frequency range in an acoustic spectrum is greater than 0.2.

A gas wiping nozzle manufactured from parts divided along the slit length direction and maintains a gap in the width direction over the length direction in high temperature atmospheres and a method for manufacturing a hot-dip metal strip. In a gas wiping nozzle, a first and a second nozzle member are each divided along the length direction X of a slit into a plurality of nozzle members. The dimension of a divided face of the first nozzle member is 1.5T1 or more in a section of the first nozzle member where T1 is the thickness of the first nozzle member in the width direction Z of the slit, and the dimension of a divided face of the second nozzle member is 1.5T2 or more in a section of the second nozzle member where T2 is the thickness of the second nozzle member in the width direction Z of the slit.

An apparatus for treating a metal strip after it has exited from a coating container with a liquid coating material, for example zinc is provided. The apparatus includes a blow-off device arranged above the coating container having an air outlet gap for blowing off excess parts of the still liquid coating material from the surface of the metal strip after the passing of the metal strip through the coating container. An electromagnetic stabilizer is arranged above the blow-off device and has a plurality of individual magnets for stabilizing the metal strip after leaving the coating container and the blow-off device. In order to further increase the efficiency of the apparatus, at least some of the magnets of the stabilizer are formed as pot magnets with pot coils.

The present invention provides a method for manufacturing more beautiful black coated steel sheets by uniformly blackening the coating layer. Specifically, the present invention provides a method for manufacturing black coated steel sheets, which brings Zn—Al—Mg alloy coated steel sheets (1) into contact with steam in a closed container (10), wherein said closed container (10) can maintain a predefined internal pressure through variable control of the amount of steam flowing into said closed container (10) and/or the amount of steam flowing out of said closed container (10), and in said closed container (10) that can maintain said predefined pressure, said Zn—Al—Mg alloy coated steel sheets (1) have contact with the steam introduced into said closed container (10).

Method of measuring the thickness of a layer by a light source irradiating the layer with a light beam, which light source is controlled by a sinusoidal control signal having a modulation frequency f.sub.m so that the light beam presents optical power that is sinusoidally modulated at the modulation frequency, the measurement method consisting in: using detector elements to determine a calibration phase shift (Δφ.sub.cal) between the optical power and the control signal; heating the layer with the light beam; using the detector elements to detect a sinusoidal component of a heat flux radiated by the layer; calculating a phase shift (Δφ.sub.th/opt) between the sinusoidal component of the radiated heat flux and the optical power of the light beam while taking account of the calibration phase shift; and determining the thickness of the layer of material as a function of the phase shift (Δφ.sub.th/opt).

Within a coating device, a metal strip first runs through a coating container with a liquid coating agent and then a stripping nozzle device for stripping off excess coating agent from the surface of the strip. After the stripping nozzle device, the strip runs through a strip stabilizing device with a plurality of magnets on both broad sides of the strip. A form control deviation is determined as the difference between an actual form of the strip and a desired form of the strip and this form control deviation is used for activating the magnets in order to transform the actual form of the strip into the desired form. The magnets of the strip stabilizing device may be moved in the widthwise direction of the strip into a traversing position in relation to the magnets on the respectively opposite broad side of the strip.

The present invention provides a cooling device for a hot-dip plating device provided on an upper side of a plating thickness control device in a conveyance route of a hot-dip plated steel sheet that is conveyed from a plating bath in a vertically upward direction. The cooling device includes: a main cooling device that vertically sprays a main cooling gas to the hot-dip plated steel sheet; and a preliminary cooling device that is provided in a preliminary cooling section between the main cooling device and the plating thickness control device in the conveyance route, and sprays a preliminary cooling gas to a plurality of gas collision positions which are set along the preliminary cooling section.

When a portion for measuring the plating adhesion amount reaches an upstream side position, plating adhesion amount estimation values are calculated by using a plating adhesion amount estimation expression at positions away from a position that faces the distance sensors, that is, the upstream side position, by strip-width direction distances, of the surfaces of the steel strip. When the portion for measuring the plating adhesion amount reaches a downstream side position, the strip-width direction distances of the plating adhesion amount meters are matched to the strip-width direction distances, and the plating adhesion amount actual measurement values are obtained. The plating adhesion amount estimation expression is corrected on the basis of the differences between the plating adhesion amount estimation values and the plating adhesion amount actual measurement values. Accordingly, the control accuracy of the plating adhesion amount is improved.

Provided is a hot-dip plating method that achieves good plating wettability between a metal material and a hot-dip plating bath and that makes it possible to reduce the amount of consumed energy as compared to conventional techniques. In a plating step included in the hot-dip plating method, vibration is applied to a hot-dip plating bath such that the ratio of the average sound pressure level (excluding noise) over ranges each lying between sound pressure peaks at harmonic frequencies of a fundamental frequency to the average sound pressure level (excluding noise) over the measured frequency range in an acoustic spectrum is greater than 0.2.

Provided is a zinc alloy-plated steel material used in automobiles, building materials, home appliances, or the like, and more specifically, to a zinc alloy-plated steel material having excellent corrosion resistance and surface quality, and a method for producing same.