JPH0790538A - Hot dip spray coating method for band-shaped metallic sheet - Google Patents

Abstract

PURPOSE:To provide a high-quality coated steel sheet having a good coating thickness and coating appearance by maintaining the temp. of a ban-shaped metallic sheet, as an objected to be coated before being sent to a coating stage, lower than the m.p. of a hot dip coating metal. CONSTITUTION:The particulates of the hot dip coating metal are sprayed by nozzles 4 in a non-oxidizing atmosphere to the surfaces of the continuously fed band-shaped metallic sheet S after pretreatments, by which the surfaces are coated. Before the band-shaped metallic sheet S heated in a treating furnace 1 in this method is introduced into a coating chamber 2, the temp. of the metallic sheet S is measured by a thermometer 6 and this temp. is maintained at the temp. lower than the m.p. of the coated metal. As a result, the coated metal immediately solidifies on the metallic sheet S and sticks to the steel sheet without flowing. This metallic sheet S is reheated to melt the solidified coating layers in a remelting and heating section 10, by which the good coating layers having no holes and having the desired thickness are obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for hot-spray plating a strip-shaped metal plate such as a steel plate, and more particularly to a method for atomizing a molten metal to be plated such as Zn and Al by spraying and spraying.

[0002]

2. Description of the Related Art Examples of the melt spray plating method of this type include, for example, JP-A-53-99047 and JP-A-1.
As disclosed in JP-A-2014456, when attention is paid to the temperature of a strip-shaped metal plate as an object to be plated in this plating method, it is necessary that this temperature be equal to or higher than the melting point of the plating metal. It is explained that the reason is that the molten metal adhering to the strip metal does not reflow and solidify on the surface of the strip metal plate.

[0003]

However, if the flowability of the molten metal is good, the collision pressure of the spray fluid causes the molten plated metal to reflow or re-spray on the surface of the object to be plated, which is good. It is difficult to obtain a good plating thickness and plating appearance. If the wettability between the object to be plated and the plated metal is not good, the molten plated metal on the surface of the object to be plated will be aggregated in the form of drops, and as a result, the molten plated metal that has aggregated in the form of drops will be covered. Dispersed on the surface of the plated body, a good plated product cannot be obtained.

According to the present invention, the temperature of the strip-shaped metal plate, which is naturally set higher than that of the plated metal in the conventional melt spray plating, is set lower than that of the plated metal. An object of the present invention is to provide a hot-dip spray plating method that has a plating thickness and a plating appearance and that enables obtaining a high-quality plated steel sheet.

[0005]

SUMMARY OF THE INVENTION The gist of the present invention is to spray fine particles of molten metal in a non-oxidizing atmosphere onto the surface of a strip-shaped metal plate which has been pretreated and continuously fed. During spray plating, the temperature of the strip-shaped metal plate before it is sent to the plating process is lower than the melting point of the hot-dip plated metal, then spray-plated, and then the plated metal is solidified and then reheated to solidify. A method for melt spray plating a strip-shaped metal sheet, characterized in that the plating layer is melted to form a good plating layer having no void and a desired plating thickness.

In the present invention, the temperature of the strip-shaped metal plate during the above-mentioned spray plating is 20.degree.
It is preferable that the temperature is lowered in the range of 300 ° C., and the reheating temperature of the solidified metal is in the range of the melting point of the plated metal or higher to the melting point + 200 ° C.

[0007]

[Function] By lowering the temperature of the strip-shaped metal plate before plating to be lower than the melting point of the hot-dip plated metal, the plated metal sprayed during the spray plating is quickly cooled and solidified on the strip-shaped metal plate having a temperature lower than the melting point. By solidifying the plating metal, the flow of the plating metal on the surface of the metal plate after plating is suppressed, and as a result, it is easy to achieve the target plating thickness and at the same time a good plating appearance is obtained. However, as it is solidified, there are holes in the plated part and the surface is uneven, so it is unacceptable as a product, so the band-shaped metal containing the solidified plated metal is melted in the next step. By performing the reheating treatment as described above, it is possible to dissolve the plating metal and obtain a plated steel sheet having a smooth surface without voids.

The temperature of the strip-shaped metal plate at the time of plating may be lower than the melting point of the hot-dip plated metal, but is preferably the melting point -2.
It is desirable to set the temperature in the range of 0 ° C to the melting point of -300 ° C. If the temperature of the strip-shaped metal plate is too close to the melting point of the plating metal, the plating metal may fluidize.
If the temperature is lower than 0 ° C, the adhesion of the plated metal will be deteriorated and the plating operation will be hindered.

The temperature at the time of reheating is preferably in the range of the melting point of the plating metal to the melting point + 200 ° C. If this temperature is not higher than the melting point, it is meaningless because the plating metal will not dissolve, and if it exceeds the upper limit temperature, it will be too high and lead to excessive fluidization, or it will react with the strip metal to obtain the desired plating quality. It is not practical because it causes problems such as lack of energy and increases energy cost. Note that this reheating step may be continued online after the plating step, or the once solidified steel sheet may be wound up and performed in another line.

Specific examples of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of a case where a plating metal such as hot-dip galvanizing is spray-plated on both surfaces of a strip-shaped metal plate continuously fed in a non-oxidizing atmosphere. Reference numeral 1 is a heat treatment furnace for heating the strip-shaped metal plate S to a desired temperature for heat treatment, 2 is a spray plating chamber for plating the heat-treated strip-shaped metal plate S, and 3 is a deflector roll for holding and guiding the metal plate S. . In the plating chamber 2, spray nozzles 4 facing each other are arranged in a substantially symmetrical position with a metal plate sandwiched between them, and hot-dip metal is applied from one side through a pipe branched to the nozzle 4 and non-oxidizing pressure is applied from the other side. By supplying gas, atomized plating metal is sprayed on the surface of the metal plate. Reference numeral 5 is a molten metal tank for feeding the hot-dip metal. The above structure is conventionally known.

According to the present invention, in such a spray plating line, the strip metal plate S heated in the heat treatment furnace 1 is always maintained at a temperature lower than the melting point of the plating metal before being introduced into the plating chamber 2. This is the first feature. Therefore, the temperature of the metal plate is measured by a thermometer 6 (for example, a radiation thermometer) immediately before the plating chamber, and the temperature can be maintained within a preset temperature range (below the melting point of the plating metal). For example, a cooling or heating device 7 for the strip-shaped metal plate S is installed at an appropriate position until it is introduced into the plating chamber 2, and the temperature of the metal plate is controlled. By maintaining the strip metal at a temperature below the melting point of the plated metal, the spray-plated metal immediately solidifies on the surface of the metal plate and adheres without flowing. The adhesion amount is appropriately determined by the spray pressure, the plating metal supply amount, the line speed of the strip-shaped metal plate, and the like.

FIG. 2 is a schematic view showing a cross section of a steel plate during spray plating in the plating chamber 2 based on a micrograph. When the plating layer 8 collides with the surface of the metal plate, it immediately begins to solidify and becomes an uneven surface. It is also recognized that the holes 9 are formed inside the plating layer.

Next, the second feature of the present invention is to reheat the strip-shaped metal plate to which the solidified plating metal is attached to dissolve the plating metal. In the illustrated case, a heating unit 10 of a temperature controllable type is arranged at the rear of the plating chamber 2 to heat the continuously fed strip-shaped metal plate S to a temperature equal to or higher than the melting point of the solidified plating metal. To dissolve the plating metal.
By this melting, the plating layer 8 having pores and exhibiting an uneven surface becomes a smooth surface without pores, and a beautiful hot-dip plated plate can be obtained. This state is shown in the schematic diagram of FIG. Specific examples of the heating equipment include an electric heating means and a means such as a burner. This heating means can be separately provided outside the line when there are restrictions in terms of equipment or space.

[0014]

【Example】

Example 1 A hot-dip galvanized steel sheet was produced under the following plating conditions using the spray plating equipment of the present invention shown in FIG. The plated steel sheet thus obtained was treated under the reheating conditions shown in Table 1, and the quality of the plated steel sheet after the treatment was also investigated.・ Strip-shaped metal: 0.75 mm × 1300 mm, cold-rolled steel plate of general carbon steel ・ Pretreatment: Heated in a continuous annealing furnace at 800 ° C., N ₂ +
After reducing in an H ₂ (H ₂ = 8%) gas atmosphere, it is cooled.・ Steel plate temperature at the entrance of plating room: 320 ℃ ・ Line speed: 150m / min ・ Plating metal: zinc, zinc bath component Zn 99.8%,
Al 0.2% Molten zinc temperature 460 ° C

[0015]

[Table 1]

Example 2 An aluminum plated steel sheet was produced under the following plating conditions using the spray plating equipment of the present invention shown in FIG. The plated steel sheet thus obtained,
The treatment was performed under the reheating conditions shown in Table 2, and the quality of the plated steel sheet after the treatment was also investigated.・ Strip-shaped metal: 0.75 mm × 1300 mm, cold-rolled steel plate of general carbon steel ・ Pretreatment: Heated in a continuous annealing furnace at 800 ° C., N ₂ +
After reducing in an H ₂ (H ₂ = 25%) gas atmosphere, it is cooled.・ Steel plate temperature at the entrance of plating room: 450 ℃ ・ Line speed: 100m / min ・ Plating metal: Aluminum bath component Al 90%, Si 1
0% molten aluminum temperature 650 ℃

[0017]

[Table 2]

Example 3 Using the spray plating equipment of the present invention shown in FIG. 1, a turn (Pb-
Sn alloy) plated steel sheet was manufactured. The plated steel sheet thus obtained was treated under the reheating conditions shown in Table 3,
In addition, the quality of the plated steel sheet after the treatment was investigated.・ Strip-shaped metal: 0.75 mm × 1300 mm, cold-rolled steel plate of general carbon steel ・ Pretreatment: Heated in a continuous annealing furnace at 800 ° C., N ₂ +
After reducing in an H ₂ (H ₂ = 8%) gas atmosphere, it is cooled. -Temperature of steel plate at the entrance of plating chamber: 150 ° C-Line speed: 100 m / min-Plating metal: Pb-Sn bath component Pb 92%, Sn
8% Pb-Sn temperature 350 ° C

[0019]

[Table 3]

[0020]

As described above, according to the hot-spray plating method of the present invention, it is possible to prevent the hot-dip metal from reflowing or re-scattering on the surface of the strip-shaped metal. A beautiful and high-quality strip-shaped metal plate having a plated appearance can be obtained.

[Brief description of drawings]

1 shows an outline of a plating line suitable for carrying out the method of the present invention.

FIG. 2 is a schematic view showing an enlarged surface state of a strip-shaped metal plate immediately after melt-spray plating by the method of the present invention.

FIG. 3 is an enlarged schematic view of the surface state of the strip-shaped metal plate after the solidified plated metal is melted, following FIG.

[Explanation of symbols]

 S band-shaped metal plate 1 heat treatment furnace 2 plating chamber 3 deflector roll 4 spray nozzle 5 hot-dip metal tank 6 thermometer 7 cooling or heating device 8 plating layer 9 holes 10 remelting heating section

Claims (2)

[Claims] 1. When performing spray plating by spraying fine particles of a molten metal in a non-oxidizing atmosphere onto the surface of a strip-shaped metal plate which has been pretreated and continuously fed, before being sent to a plating step. After the temperature of the strip-shaped metal plate is lower than the melting point of the hot-dip galvanized metal, spray plating is performed, then after the plated metal is solidified, it is reheated to dissolve the solidified plated layer, and it is possible to obtain a hole-free and desired A method for melt-spray plating a strip-shaped metal plate, which comprises forming a plating layer having a good plating thickness. 2. The temperature of the strip-shaped metal plate during spray plating is set to be lower than the melting point of the hot-dip plated metal in the range of 20 ° C. to 300 ° C., and the reheating temperature of the solidified metal is equal to or higher than the melting point of the plated metal to the melting point. The hot-dip spray plating method according to claim 1, wherein the temperature is set to + 200 ° C.