JPH0617558B2 - Method for removing inclusions of molten metal - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for removing inclusions of molten plated metal.

(Prior art) In a molten plated metal bath such as zinc or aluminum, the iron powder or the like brought into the bath by the steel strip, which is the material to be plated, reacts with the plated metal to form inclusions (generally dross and (Referred to as) occurs, and this adheres to the steel strip and causes deterioration of quality.

Then, in order to remove such inclusions, it is possible to mechanically remove the dross located on the surface of the plating bath (Act No. 60-122358) or to scoop up the dross deposited on the bottom of the bath. Although disclosed, in reality, in addition to the dross thus generated, there are fine dross floating in the bath, which also causes deterioration of the quality of the plated steel strip. Most of the dross located on the surface of the bath and the dross deposited on the bottom of the bath are caused by the dross floating in the bath, and it is strongly required to remove such dross reliably. .

(Problems to be Solved by the Invention) The present invention has been made to solve such conventional problems and to reliably remove dross in a plating bath.

(Means and Actions for Solving Problems) The present invention is to filter molten metal powder with a ceramic filter, blow a gas in opposition to the flow of metal powder,
The gas is passed through the filter to form fine bubbles,
It is a method for removing inclusions of molten metal powder, which is characterized by floating in the metal powder.

That is, in the present invention, the molten plated metal is filtered with a ceramic filter to remove the dross in the metal, and the gas is blown to pass the gas through the filter.
Prevents clogging of the filter, and when the gas passes through the filter, the gas becomes finer, which floats up in the bath.
The fine dross is quickly pushed up to the surface of the bath by the effect of fine bubbles and can be separated and removed.

That is, the metallurgical metal from which the fine dross has been removed is further filtered by a ceramic filter to remove dross that cannot be removed due to the floating of fine bubbles.

As the ceramic filter in the present invention, there are materials such as Al ₂ O ₃ system, ZrO ₂ system, and CaO system, and the porosity of the filter is 40 to 80 vol%.
The pore diameter is preferably 0.4 to 2.0 mm, and the thickness is 10 to 30 mm, and those formed in a plate shape or a cylinder shape can be used.

The blowing gas is preferably an inert gas such as nitrogen gas.

As the molten metal, it is preferable to remove inclusions such as zinc and aluminum.

Thus, in one example of the molten metal plating line, when the iron concentration in the metal plating metal during operation becomes 0.03% or more, the occurrence of inclusions (dross) becomes remarkable, but according to the present invention as described above, the iron concentration is It can be removed to 0.025% or less, and the occurrence of dross can be reliably prevented.

Next, an example of the method of the present invention will be described with reference to the drawings.

Example 1 In FIG. 1, a cylindrical ceramic filter 2 is arranged in a container 1 as shown in the drawing, and a gas blowing pipe 3 is exposed in the filter 2. Then, the molten metal plating 4 is guided through the inlet 5, passes through the filter 2, removes inclusions (dross) in the metal metal 4, and is discharged through the outlet 6.

On the other hand, an inert gas (nitrogen gas) is blown from the gas blowing pipe 3 to pass through the filter 2 and float in the bath of the metal plating 4 to prevent clogging of the metal 2 and to prevent fine particles in the metal metal 4. The inclusions are floated and the inclusions (dross) 7 are positioned on the surface of the bath.

Reference numeral 8 in the drawing denotes a burner which preheats the inside of the container 1 before the treatment and, at the same time, heats when the temperature of the plated metal 4 greatly decreases.

Example 2 In FIG. 2, a container 1 is divided into an upper chamber 9 and a lower chamber 10 through a plate-shaped ceramic filter 2, and a molten metal plate 4 is introduced from an inlet port 5 and passed through the filter 2 to form a metal plate. The inclusions (dross) in 4 are removed and discharged from the outlet 6.

On the other hand, an inert gas is blown from the plug 11 provided in the lower chamber 10 to pass through the filter 2 to prevent clogging, and air bubbles of the blown gas are floated in the bath of the metal plating 4 to reach the bath surface. The inclusion (dross) 7 is positioned.

Reference numeral 8 in the drawing is a burner for preheating the inside of the container 1 before the treatment and heating it when the temperature of the plated metal 4 greatly decreases.

(Example) Next, the Example of this invention is given.

In the apparatus shown in FIG. 2, the upper chamber (height 4
50mm, width 400mm, length 600mm), lower chamber (height 10
0 mm, width 400 mm, length 600 mm) ceramic filter (material Al ₂ O ₃ 90%, residual SiO ₂ , MgO, etc., porosity 50
%, Average porosity 0.8 mm, thickness 20 mm), flow rate from the continuous molten zinc plating line plating bath 300 kg /
Minute zinc bath (temperature 470 ° C, component Fe0.05%, Al
0.2% ± 0.02%, residual zinc and impurities) were continuously introduced into the upper chamber through the inlet, and the bottom of the lower chamber (plug area 900c
Nitrogen gas was blown at a flow rate of 0.2 m ³ / min (blow pressure 0.8 Kg / cm ² ) from m ² , porosity 30%, average pore diameter 0.2 mm) to form fine bubbles through the filter. , Raised the zinc bath in the upper chamber.

On the other hand, zinc that had moved from the upper chamber to the lower chamber via the filter was taken out from the outlet and circulated in the bath of the above-mentioned plating line. Zinc extracted from the outlet has a temperature of 460 ° C Fe
The content was 0.023%, and inclusions were reliably removed.

(Effect of the Invention) By the method of the present invention, inclusions (dross) in the metal powder
Can be reliably removed, and deterioration of the quality of the plated product due to inclusions can be reliably prevented.

[Brief description of drawings]

FIG. 1 shows an example of the method of the present invention, (a) is a side view, (b) is a view taken along the line AA of (a), and FIG. 2 is another example of the method of the present invention. FIG. 1 ... Container 2 ... Ceramic filter 3 ... Gas injection tube 4 ... Molten metal

Claims (1)

[Claims] 1. A method for filtering molten metal with a ceramic filter, blowing a gas in opposition to the flow of the metal, allowing the gas to pass through the filter to form fine bubbles, and floating in the metal. And a method for removing inclusions of molten metal.