JPS5896871A - Vacuum deposition furnace - Google Patents

Abstract

PURPOSE:To make the responsiveness of the rate of evaporation fast and to prevent splashing by installing a heater which is a heating source in the upper part in a vacuum deposition furnace, and projecting carbon fins from the bottom plate of the furnace to above the bath surface. CONSTITUTION:When a shutter 4 is opened in the stage of vapor deposition, zinc vapor is plated through an opening 6 on a steel strip 10 which travels in, for example, a right direction, above the body 1 of the vapor deposition furnace. Here, molten zinc 7 is heated directly with the heater 8 in the upper part of the inside of the furnace or is heated with carbon fins 11, and evaporates successively from the surface layer. Therefore, the rate of evaporation responds quickly to the change in the rate of heating from the heater 8. Since the formation of the oxide film on the liquid surface of the zinc is suppressed by the reducing power of the carbon, splashing is difficult to arise and the sticking of liquid drops on the steel plate 10 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vapor deposition furnace that has quick response in vapor deposition rate and good plating performance in a continuous vacuum vapor deposition apparatus for, for example, galvanizing copper strips.

As a method of continuously forming a galvanized film on a copper strip,
In addition to the conventional molten zinc bath method and electroplating method, the vacuum evaporation plating method is attracting attention because of its advantage over plating on only one side. A conventional vapor deposition furnace is one in which heating is performed from the bottom of the furnace, as shown in FIG.

In FIG. 1, numeral 1 denotes a furnace body housed in a vacuum atmosphere, and molten zinc 7 is held inside the furnace body. There is an opening 6 in a part of the ceiling 5, which is covered with a shutter 4 that is rotated around a hinge 5. Heater 8 as a heating source below the furnace
is installed, and both the furnace body 1 and the heater 8 are covered with a heat insulating material 9.

During deposition, the shutter 4 is open, and the molten zinc 7 is heated through the bottom plate of the furnace body 1 by the heater 8, vaporized and plated onto the copper strip 10 running through the opening 6 above the deposition furnace. Molten zinc is continuously supplied from the supply duct 2 in an amount equal to the amount of evaporation.

Such conventional vapor deposition furnaces have the following drawbacks.

(1) In the plating process line, for example, if the thickness of the supplied copper strip changes, the amount to be plated on the steel strip,
In other words, there are times when it is desired to instantaneously change the amount of basis weight per unit area, but in conventional vapor deposition furnaces, the heat capacity of the molten zinc in the vapor deposition furnace and the furnace body itself is large, so it is difficult to change the heating amount of the heating source. Even if the change is made instantaneously, there is a drawback that the response of the zinc evaporation rate is slow and a large amount of products with a non-standard basis weight are produced before it stabilizes.For example, when the line speed is 50 Vmin and the basis weight is 70 g/ It is expected that the vapor deposition furnace planned for the 2 m2 line will take about 6 minutes to settle, and during this time a 180 m product will be out of specification.

(2) Since the zinc bath is heated from the bottom, bubbles are generated by boiling at the bottom of the zinc bath, which rise upward in the liquid and exit from the liquid surface. At this time, a so-called splash occurs in which the liquid scatters. In addition, an oxide film is likely to form on the liquid surface, and if a film is formed, air bubbles will accumulate under the film, and if they grow to a certain size, the film will be instantly destroyed, making the splash harsh. If splash occurs, there is a risk that droplets will stick to the copper strip, resulting in product defects.

The present invention has been made to solve the above-mentioned drawbacks and realize a heating method with a fast response speed. It is a vapor deposition furnace characterized by carbon fins that protrude above the zinc bath surface, and has a quick response.
Moreover, it is possible to realize a vapor deposition furnace that prevents splashing.

Hereinafter, one embodiment of the present invention will be described in detail with reference to FIG.

In FIG. 2, a heater 8 as a heating source is a molten zinc 7 in a furnace.
A large number of carbon fins 11 protrude from the bottom plate at appropriate intervals to above the zinc bath surface. The rest of the structure is the same as the conventional structure shown in FIG. 1, so a description thereof will be omitted.

In FIG. 2, when the shutter 4 is open and the steel strip 10 is running above the vapor deposition furnace, for example to the right in the figure, the molten zinc 7 is directly heated by the heater 8 above, or the carbon fin 11 is heated and evaporated through the opening 6
The copper strip 10 is plated through it.

With such a configuration, the following effects are achieved.

■ If simply heated from above, the heat absorption coefficient of the surface of molten zinc is very small, approximately 0.1, so direct radiant heating from above would result in the heater temperature being too high, so carbon If the fins are made to protrude above the surface of the zinc bath, the absorption rate of the carbon surface is as large as about 1.0, so the overall absorption rate can be improved and a method of heating from above can be realized.

(2) According to the present invention, since zinc is heated from above, it evaporates from the surface layer, so it quickly responds to changes in the amount of heat from the heating source.

For example, line speed 30 m/min, basis weight 70-g
/m2 line, the settling time is about 30 seconds to 1 minute.

In other words, the time required for stabilization becomes extremely short, and the occurrence of non-standard products is reduced.

At the same time, since carbon has a reducing power, it suppresses the formation of an oxide film on the surface of the zinc liquid, making splash less likely to occur and preventing droplets from adhering to the product.

■ In the conventional method, the zinc bath surface is 550℃ and the furnace bottom plate is 600℃.
Therefore, if a steel plate was used for the bottom of the furnace, the corrosion rate would be extremely high, and for industrial use it would have been necessary to use ceramic instead of steel plate. However, according to the present invention, the zinc bath surface can also be Since the temperature at the bottom of the furnace is almost the same at 550°C, steel plates can be used, which is inexpensive.

■ Since the contact area between carbon fins and zinc is large,
Improves heat transfer.

[Brief explanation of drawings]

FIG. 1 shows the configuration of a conventional vacuum deposition furnace, and FIG. 2 shows the configuration of an embodiment of the vacuum deposition furnace of the present invention. Sub-agents 1) Meifuku agent Ryo Hagiwara -

Claims (1)

[Claims] A vacuum evaporation furnace characterized in that a heating source heater is installed in the upper part of the furnace, and carbon fins are made to protrude from the furnace bottom plate to above the bath surface.