JPH0452261A - Production of hot-dipped strip-like metal - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing hot-dip plated metal strips by spraying molten metal.

[Conventional technology]

In such a plating method, a means is required to smooth the plating layer after spraying the molten metal.
As one of the methods for this purpose, for example,
Publication No. 1456 discloses spraying molten metal atomized with pressurized gas onto a steel plate whose surface has been cleaned, and then spraying the pressurized gas with a gas wiping nozzle.

[Problem to be solved by the invention]

However, compared to other plating methods such as electroplating and hot-dip plating, spraying of molten metal still cannot produce plated metal strips with sufficient surface smoothness depending on the subsequent break-in process such as gas wiping. You can't get it.

An object of the present invention is to provide a means for achieving a surface smoothness equivalent to dip plating in the production of plated metal strips by spraying molten metal.

[Means to solve the problem]

The present invention has achieved its object by spraying molten metal to produce a hot-dip plated metal strip using molten metal particles having a weight average particle diameter of 15 times or less the thickness of the plating to be formed.

Here, the weight average particle diameter is defined as, when the volume of one non-spherical molten metal particle is Vp, the diameter d of a sphere equal to the volume is obtained as follows. This d is called the spherical equivalent diameter.

At that time, dm obtained from the following formula is weight average M: total weight of particles (kg) Vp: volume of particles with spherical equivalent diameter d (m3) ρ: specific gravity of particles (kg/m3) Nd: spherical equivalent diameter is the number of particles with d, that is, in a set of particles with a certain particle size distribution,
Add up the weight starting from the small particles, and the weight is 50% of the total.
% particle size.

In order to increase the adhesion efficiency of the sprayed hot-dip plated metal to 90% or more, the spraying device should be installed within a distance range shown by the following formula from the metal strip.

However, L distance between the spray device and the metal strip (m) θ Spray spread angle of the spray (rad) ρ Specific gravity of the molten metal to be sprayed (kgf/m") d Weight average particle diameter of the molten metal to be sprayed (m) V Maximum speed of molten metal to be varnished (m/5ec) α Surface tension of molten metal to be varnished (kgf/m) 1.75: Coefficient Also, by performing the above spraying in multiple stages, it is possible to The plating thickness can be controlled over a wide range, and a smoother surface can be achieved.

Furthermore, after spraying, the belt-shaped metal is heated and held for one hour at a temperature expressed by the following formula, making it possible to further smooth the surface.

That is, S is the retention time (seconds), d is the particle diameter (μm), and T
Hold the temperature (1), further T, the plating metal melting point (1)
When, S2O,095X ("Manira 11") T/T.

The conditions shall be maintained. However, T>T.

It is.

The belt-shaped metal referred to here refers to anything made of metal such as iron plates, copper plates, and aluminum plates.

[Effect]

In the present invention, the weight average particle diameter is 15% of the plating thickness.
Use hot-dip plated metal particles less than twice as large. Even if the diameter of the metal particles is larger than the plating thickness, as shown in Figure 2, due to the wetting of the plating metal particles and the strip metal, the particle size of the plating metal does not directly correspond to the plating thickness, and the plating is larger than the plating thickness. This is because metal may be used.

Moreover, the reason why it is set to 15 times or less is as follows.

That is, FIG. 3 shows the relationship between (weight average particle diameter/target plating thickness) of hot-dip plated metal and the rate of non-plating. As shown in the figure, if (weight average particle diameter/target plating thickness) exceeds 15, non-plating will occur no matter what heating conditions are used.
The target plating thickness) needs to be 15 times or less.

Further, if larger particles are used, extra time is required for smoothing, and a larger heating and holding furnace is required, which increases the equipment cost.

Further, after spraying, by maintaining the above-mentioned specific temperature for a specific time, the adhering particles and the steel strip are further wetted and smoothed, and the surface smoothing is further improved.

Further, in the present invention, when the treated strip metal is an iron material, using electroplated strip metal as the base plating such as nickel has the effect of further improving smoothing.

It is known that the distance between the spray device and the metal strip is expressed by: Here, FIG. 4 shows the change in adhesion efficiency when the coefficient k is changed. Based on this result, it is preferable to set the coefficient k to k<1.75 in order to increase the adhesion efficiency of hot-dip plated metal to 90% or more.Thereby, the distance was set to the following relationship.

〔Example〕

FIG. 1 shows an example in which the present invention is applied to galvanizing a steel plate.

A continuous plating device 1 is disposed on the exit side of a continuous annealing furnace (not shown), and the steel plate S moving in the direction shown by the arrow is annealed in the continuous annealing furnace (not shown) and then transferred to a deflector.
At the position of roll 2, the temperature was 450°C. Next, molten zinc was sprayed in a plating chamber provided with nozzles 3 in two stages. The particle size of the molten metal at this time is determined by the gas atomization method, that is, the molten metal is made of nitrogen.

The particle size was adjusted to a weight average particle size of 25 μm by atomization using a non-oxidizing gas such as argon. 4
is a heating furnace that is connected to the plating chamber. The heating furnace 4 may be any type of heater that does not contact the steel plate, such as an electric heater, high-frequency induction heating, or radiant tube heating. The atmosphere may be an oxidizing atmosphere or a non-oxidizing atmosphere.

In each of the above-mentioned spraying operations, the maximum amount of molten metal ejected from the nozzle 4 was 160 g/sec/m (radius), and the control range was 160 to 80 g/sec/rn (width).

Using this equipment, 160g/sec per light emission
Zinc was sprayed onto the annealed steel plate at a temperature of 450° C. using two stages of nozzles having a spray amount of /m (width). Zinc contains 0.2% aluminum. Zinc temperature is 460℃
, the atmosphere temperature is 450℃, the atmosphere composition is 100% nitrogen,
The action of the heating device was to maintain the steel plate at 450°C for 0.5 seconds.

Regarding the relationship between the particle size and initial velocity of the molten metal to be sprayed, the spray spread angle, and the distance between the spraying device and the steel plate, in order to reduce the adhesion efficiency of the sprayed molten metal to 90% or less, the spraying distance should be as follows: It was made a condition.

At the same university, each symbol is as described above.

In the above equipment, the number of seven nozzles used is varied, and the spraying is shown in FIG. 5, which shows the number of nozzle stages and the area weight/line speed control range. In the figure, the horizontal axis shows the line speed (m/min), the left vertical axis shows the amount of adhesion per unit area on the steel plate, and the right vertical axis shows the cumulative spray amount of each nozzle. As a result, as the number of nozzle stages increases, the coating weight and line speed can be controlled over a wide range.

Although the total number of stages can be reduced by increasing the amount of spray per one light emission, the uncontrollable range indicated by A becomes wider. However, if it is made too small, the number of stages will increase and the equipment will become expensive. It is important to set the number of stages that is economically suitable based on the line speed and maximum basis weight of the equipment.

FIG. 6 shows the residence time in the heating furnace 5 and the aforementioned X=(0,
5+d/200)/(T/Tm) and surface smoothness. In the figure, it can be seen that there is a linear relationship between the above equation and the smoothness.

FIG. 7 shows the results of a salt spray test to determine the durability of a plated steel plate with a zinc coating of 80 g/m' on one side obtained under the above conditions using a two-stage nozzle. For comparison, the characteristics of a plated steel sheet obtained by conventional immersion plating under the conditions of galvanizing bath temperature of 450° C., pre-immersion steel sheet temperature of 453° C., and galvanizing bath components of Zn 99.8% and AIo 2% are shown. As shown in the figure, it can be seen that the plated steel sheet obtained by the present invention has the same durability as the plated steel sheet obtained by conventional dip plating.

〔Effect of the invention〕

The following effects can be achieved by the present invention.

(1) It is possible to produce a plated strip with a smoothness comparable to that of conventional immersion plating.

(support)) Spraying allows for faster plating.

(3) Both single-sided and double-sided plating is possible.

(4) Different plating can be applied to the front and back surfaces.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of equipment for carrying out the present invention;
Figure 2 is an explanatory diagram showing the state of adhesion of plated metal particles, Figure 3 is a graph showing the relationship between (weight average particle diameter of plated metal/plating thickness) and non-plating occurrence rate, and Figure 4 is a graph showing the rate of non-plating. Graph showing the relationship between conditions and adhesion efficiency of hot-dip plated metal. Figure 5 is a graph showing the relationship between the number of spraying steps and smoothness. Figure 6 is a graph showing the relationship between holding temperature, time and smoothness. The figure is a graph showing the characteristics of the plated strip obtained by the present invention. 1: Continuous plating equipment 2: Deflector roll 3: Nozzle for spraying 4: Heating furnace S: Steel plate patent applicant Nippon Steel Corporation (and one other person) representative
Rihito Kobori Masu i11 Figure @ 3 Figure 4 Figure 1! 2 (k IS '17 Hun (-11 huan) Figure S pm Tanzu drawer ~ 1 O〈@θ Month 5& Water a * Mulberry θ call (h ``)

Claims (5)

[Claims] 1. In a method of manufacturing a hot-dip plated metal strip by spraying molten metal, the weight average particle diameter is 15 times the thickness of the plating.
A method for producing a hot-dip plated metal strip, characterized by using hot-dip plated metal particles of twice the size or less. 2. In a method of manufacturing a hot-dip plated metal strip by spraying molten metal, the weight average particle diameter is 1.
A hot-dip plated strip characterized by spraying hot-dip plated metal particles of 5 times or less onto the metal strip, then heating and holding the strip metal under the temperature and time conditions expressed by the following formula to smooth the surface. Method of manufacturing metals. s≧0.095×{0.5+(d/200)}/(T/
T_m) However, T>T_m S: Holding time (seconds) d: Weight average particle diameter (μm) T: Holding temperature (°C) T_m: Plating metal melting point (°C) 3. A method for producing a molten plated metal band, characterized in that spray devices for spraying molten metal particles having the particle size as set forth in claim 1 onto the metal band are provided in a plurality of stages in the direction of movement of the metal band, and the spraying is performed in multiple stages. Production method. 4. 2. A method of manufacturing a hot-dip plated metal strip according to claim 1, characterized in that a metal strip electroplated with nickel is used. 5. 1. A method for producing a hot-dip plated metal strip, which comprises installing a spray device at a distance from the metal strip less than or equal to the distance expressed by the following formula. L< (1.75/θ) Specific gravity (Kgf/m^3)d
: Weight average particle diameter of molten metal to be sprayed (m) V: Maximum speed of molten metal to be sprayed (m/sec) α: Surface tension of molten metal to be sprayed (Kgf/m) 1.75:
coefficient