JP2593745B2 - Flux for aluminum alloy plating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flux for plating an aluminum alloy on a steel material. More particularly, when the hot dipping an aluminum alloy containing aluminum steel material by one-step process by a wet method, the flux floated on the molten metal, to a flux for use in a molten state.

[0002]

2. Description of the Related Art In general, hot-dip plating on steel materials is performed by the following method in order to obtain good plating appearance and adhesion. (1) Wet method: For example, in a method disclosed in Japanese Patent Publication No. 31-8366, a zinc chloride-ammonium chloride-based flux is put into a molten metal bath and then a thickness of about 100 to 200 mm is applied.
A molten layer (Blanket) is formed at a thickness of 1 mm, and a steel material is inserted into a metal bath from above the layer, whereby a flux is first acted on, and the molten metal is reacted with the molten metal. This is a hot-dip plating method in which the flux is taken out while removing the flux with a squeezing roll, or taken out from a surface without a flux layer. This method can cope with steel materials of various shapes, and can perform reliable plating at low cost. (2) Dry method: For example, in the method disclosed in Japanese Patent Application Laid-Open No. 1-283353, a steel material is immersed in an aqueous solution of an ammonium chloride-based flux and then immersed in a molten metal plating bath not covered with the flux. This is a hot-dip plating method for plating. The disadvantage of this method is that since the surface of the molten metal is covered with a thin oxide film, oxide is involved when steel is inserted, and surface defects such as unplating, bumps, pinholes, and uneven plating occur. It is. (3) Sendzimer method: After reducing a steel material with a gas such as hydrogen or ammonia in a high-temperature closed furnace, a snout (Snow) is used.
This is a gas reduction method in which plating is performed by dipping in a molten metal plating bath through t). This method has the advantage that it can be continuously processed at high speed in a lined facility. However, the equipment is very expensive, and the object is limited to continuous steel plates, steel wires, etc., and it is not possible to process steel pipes, mold steels, and molded steel products with complicated structures. The disadvantage is that it is difficult to do so.

[0003]

However, a problem of the wet method is that since the flux is used for a long period of time on a high-temperature molten metal, components that easily evaporate escape more and more. Therefore, the flux composition changes with the passage of time, and the effect thereof is not stable. In particular, metals with relatively high melting points, such as aluminum alloys
When plating, the higher the ratio of aluminum, the more alloy
The melting point of the flux further increases , the melting point of the flux rises with the change in composition, the flux solidifies and forms a shelf, and a cavity is created between the molten metal and the flux, which hinders the plating operation. . Accordingly, the present invention is, A
Smell of molten aluminum alloy plating containing luminium
Aluminum alloy
Depending on the melting point and plating operation temperature of the metallic, acting with the flow of the flux to provide a flux that can be stably maintained.

[0004]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a flux used for floating on a high-temperature molten aluminum alloy when the aluminum alloy is hot-dip plated. The main component, zinc chloride 1-8 mol, sodium chloride 26-36 mol, potassium chloride 14-20 mol
A fluxing aluminum alloy plating containing aluminum, which comprises a. The addition ratio of potassium chloride to sodium chloride is preferably 1.8 to 1.9 in terms of molar ratio of sodium chloride to 1.0 in order to obtain the effects of the present invention. According to the present invention, the melting point of the flux can be arbitrarily determined and adjusted according to the working temperature of the metal to be plated. In other words, since components that easily evaporate are hardly contained, the flux composition can be stably maintained, and the melting point can be increased without forming a shelf. That is, the ratio of aluminum is
High working temperature for large aluminum alloys
The function as a flux is maintained by the degree.

[0005]

In general, as an important component which easily evaporates but has a strong flux action, for example, ammonium chloride can be mentioned from the properties of the compounds shown in Table 1. Ammonium chloride removes oxides on the surface of the steel material and the surface of the molten metal in the form of chloride to remove the oxides, and helps wettability. However, since it is easy to evaporate, it is good if the working temperature is relatively low and the melting point is low, such as plating of tin, lead, zinc or alloys thereof, but it is not suitable for aluminum alloy plating because the working temperature is too high. Ammonium chloride forms a double salt or complex salt with other components to improve the flux stability to a certain extent. However, increasing the amount of added ammonium chloride has the disadvantage of impairing fluidity, and its proportion in the total flux is usually about 30 mol% or less. Is preferred.

On the other hand, important components that are difficult to evaporate and have a strong flux action include, for example, zinc chloride and lithium chloride based on the properties of the compounds shown in Table 1. These, like ammonium chloride, remove oxides on the surface of the steel material and the surface of the molten metal in the form of chloride to remove them, and assist in wettability and fluidity. Both form double salts and complex salts with other compounds, and are deliquescent. Therefore, they retain water moderately. During plating, the molten flux helps to boil and agitate, and enhances the reduction reaction. In particular, the addition of a large amount of lithium chloride, Anne
Ammonium alloy plating with high ratio of monium (for example,
For example, a combination of 55 wt% Al and 45 wt% Zn
It has been newly found that it is particularly excellent as a flux for high-temperature plating work ( gold plating) . The addition ratio of zinc chloride is completely different from the conventional technology of adding a large amount of 50% or more, and the addition ratio of lithium chloride having a high melting point is suppressed to a very small amount of 1 to 8 mol%. 40 to 60 mol%, which far exceeds the amount
Improved to be suitable for high temperature plating workability. The lower limit of the proportion of zinc chloride was 1 mol% is less in is because weakens the synergistic effect of the flux effect of 4 components, of the upper limit was made 8 mol%, the proportion in particular of aluminum Outside the range This is because the aluminum alloy plating with high hardness lacks the working temperature aptitude and the plating appearance deteriorates.

[0007] On the other hand, used for flux
As a component for, for example, sodium chloride, potassium chloride and the like from the properties of the compounds of Table 1. The main function is to control the role of the filler and the melting point of the flux. Increasing these amounts increases the melting point of the bath flux, and decreasing them decreases the melting point of the bath flux. Both are not usually added much to the bath flux when the working temperature is relatively low such as galvanizing,
When working temperature is high such as aluminum alloy plating
It plays an important role. Both are typical stable compounds of alkali metals and do not eutect into the plating metal.
However, there is a drawback that there is no water retention because there is no deliquescence, and it adheres to the upper wall of the plating bath during the plating operation, so that a flux shelf can be easily formed. The molar ratio of sodium chloride to sodium chloride is about 1.8. This addition ratio is also shown in the examples.
As described above, the range may be set to 1.8 to 1.9. And
The addition ratio of sodium chloride in the whole flux is 2
6 to 36 mol%, potassium chloride addition ratio is 14 to 2
0 mol% is most preferable in terms of working temperature suitability. The lower limit of the ratio of sodium chloride in the whole flux is 26
mol%, the upper limit was made 36 mol%,: 14 mol% the lower limit of the proportion of potassium chloride, the upper limit was set to 20 mol% is again a large amount of aluminum is outside this range
The reason for this is that the aluminum alloy plating containing the aluminum alloy lacks the working temperature suitability, and the plating appearance is deteriorated . As other ingredients,
Alkaline earth chlorides, such as MgCl ₂ , CaCl
₂ , SrCl ₂ etc. may be added little by little,
A great effect according to the purpose of the invention cannot be expected only by complicating the composition.

[0008]

[Table 1]

Although the individual actions and roles have been described above, the features of the present invention will be described again. The conventional flux component contains zinc chloride as a main component, for example, 50 mol%.
The flux contained a large amount of zinc chloride as described above, which has an important effect as a flux, and has been used well (for example, JP-A-58-136759). The component is 40m
ol% or more of lithium chloride, and a very small amount of zinc chloride.
Flux of the present invention, in terms of melting point and boiling points, since the high but other properties than zinc chloride are similar, Al
High melting point of aluminum alloy due to high ratio of minium
At higher working temperatures
No flux formation and flow without shelf formation due to solidification
It was confirmed that plating work with stable properties was possible, and that the utility was extremely high. The flash comprising the composition of the present invention
The above-mentioned stable aluminum alloy plating
Business is possible, the ratio of aluminum exceeds 50%
Al 55% -Zn 45% aluminum alloy plating
An example is shown below.

[0010]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but it goes without saying that the present invention is not necessarily limited only to these Examples. The steel material is previously immersed in a commercially available alkaline degreasing agent (60 to 70 ° C.), degreased and washed with water, washed with a 15 wt% hydrochloric acid aqueous solution, washed with hot water, and dried. Subsequently, as shown in Example 1 of Table 2, the steel material was 8 mol of ZnCl ₂ .
1%, 52 mol% of LiCl, 26 mol of NaCl
%, An aluminum alloy (Al55-Zn45, wt.) Melting bath flux consisting of 14 mol% of KCl.
/ Wt%), gradually inserted into the plating bath through a bath flux, and pulled up after immersion for 30 seconds. As a result, a beautiful aluminum-zinc alloy-plated steel material free from surface defects such as unplating, bumps, pinholes, and uneven plating was obtained, and the workability was found to be extremely good. Further, Examples 2 to 5 also showed excellent results. Next, the ratio of zinc chloride, lithium chloride, sodium chloride, and potassium chloride in the flux in the examples and the difference in the performance will be described. In Example 1, the proportion of ZnCl ₂ was the largest, 8 mol%, in Example 2, 4 mol%, and in Example 3, 1 m
ol%, the proportion of LiCl is accordingly 52 mol
%, 56 mol%, 59 mol%
The ratio between aCl and KCl is constant. This means that the melting point of the bath flux becomes higher in order, and is suitable for the case where the plating operation temperature is higher in order. And Na
In Examples 4 and 5, the proportions of Cl and KCl were as described in Examples 1 and 2,
The melting point is set higher than 3 and higher. The proportion of each of these components is more than due to differences in their flux action
The emphasis is on plating workability due to differences in melting points. On the other hand, in Comparative Examples 1 to 4, the proportions of ammonium chloride and zinc chloride, which are easily evaporated, are large, so that the easily evaporated components evaporate over time, the flux components change, and the fluidity decreases. Therefore, the stability as a bath flux was lacking, and a stable reducing action and a good plating appearance could not be obtained. That is, it is shown that the composition of the comparative example is not suitable for aluminum alloy plating having a high plating operation temperature. Hot-dip galvanized alloy composition (melting point about 52
(0 ° C.), the working temperature was set at 610-630 ° C., but when the ratio of aluminum is large, the melting point of the alloy is further increased, so that the working temperature is also increased. The lower the proportion of aluminum, the lower the melting point and the lower the operating temperature.
Also, even if the alloy component is a metal other than zinc, or a plating alloy with another metal added,
Needless to say, it can be diverted according to the plating operation temperature.

[0011]

[Table 2]

[0012]

[Effects of the Invention] From Table 55 Al-45% Zn-45% Zn
As is clear from the examples of aluminum alloy plating, the use of the bath flux of the present invention containing lithium chloride as a main component increases the aluminum ratio as in the examples.
Aluminum alloy plating by solidifying the flux
It is possible to provide a beautiful steel material having good corrosion resistance and good workability without forming a shelf with good workability, and the industrial advantage is great.

Claims (2)

(57) [Claims] 1. A flux used for floating on an aluminum alloy at a high temperature when hot-dip-plating an aluminum alloy, the main component of which is 40 to 60 mol of lithium chloride, which contains 1 to 8 mol of zinc chloride and 26 to 26 mol of sodium chloride. 36 mol, potassium chloride 14-20 mol
Aluminum alloy plating flux containing aluminum, which comprises a. 2. The aluminum containing aluminum according to claim 1, wherein the molar ratio of potassium chloride to sodium chloride is 1.0 to 1.0 for potassium chloride and 1.8 to 1.9 for sodium chloride. Flux for alloy plating.