JPS589946A - Purifying method for molten al and al alloy - Google Patents

Abstract

PURPOSE:To purify molten Al or a molten Al alloy by filtering it with >=2 kinds of fire resistant filters having different pore sizes to thoroughly remove inclusions in the molten metal. CONSTITUTION:Molten Al or a molten Al alloy contains inclusions such as refractory fragments mixed in the melting stage, Al oxide and Al nitride. The inclusions are divided roughly into beltlike inclusions (a) having about 1mum width and >=1,000mum length and fine particles (b) having about 1-10mum diameter. The molten metal contg. inclusions is first passed through a ceramic filter or a plurality of ceramic filters >=1 time to remove the inclusions (a) by filtration. After adding a grain refiner such as Ti or a Ti-B compound, the molten metal is further passed through a ceramic filter having a smaller pore size >=1 time to remove the fine particles (b). Thus, the molten Al or the molten Al alloy is purified without clogging the filters and reducing the yield of the grain refiner such as Ti.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cleaning treatment method for removing inclusions present in molten aluminum and aluminum alloy mixed or generated during the process of melting aluminum and aluminum. The present invention relates to a method for cleaning a molten alloy, in which multiple types of refractory filters are provided in multiple stages, and inclusions of different sizes are sequentially filtered.

In general, aluminum and molten aluminum alloy contain materials mixed with raw materials such as base metal, master alloy, scrap, etc.
Inclusions newly generated due to chemical reactions in melting process 1, or inclusions generated due to accumulated causes such as broken pieces of refractories that occur after melting process, and inclusions such as oxides and nitrides of these. things exist. Therefore, these inclusions are removed by Cts gas, flux, and sedation treatment, but they are not always completely removed, and they often get mixed into the product, causing various surface defects and deterioration of mechanical properties. However, there were drawbacks that adversely affected the quality of the product and reduced the commercial value.

In the past, inclusions that could not be removed by the above-mentioned treatment methods were usually formed from tubular or plate-shaped porous ceramics with excellent fire resistance before the melting process or casting process. This is removed by filtration using a porous filter.

However, this conventional method puts safety first and minimizes the filter cell size, since the intervention to be removed has various shapes, large and small, depending on the generation process and the difference in type S. However, the following problems could not be avoided.

In other words, the filtration load is large and clogging occurs in a short period of time, and the service life of the filter is shortened, resulting in poor workability.Furthermore, the filter is expensive, which is economically disadvantageous. there were.

Moreover, an even bigger problem is that the particles were added during the grain refinement process that is carried out prior to filtration and removal.耘? i-
This results in the trapping of grain refining agents such as 8 compounds at the same time, and as a result, the amount of the treatment agent added must be increased more than necessary. ′j However, based on the problems of the conventional method mentioned above, this.

As a result of investigating and analyzing the majority of fireproof filters discarded due to clogging in trenches, we found that among the various shapes of inclusions present in aluminum and molten aluminum alloys, especially coarse ones It was found that this was a major cause of the decrease in filtration efficiency because it obstructed the molten metal inlet side of the filter.

Therefore, the coarse inclusions covering the molten metal inlet side produce an effect similar to that of a filter mesh, and the T1 and! It is presumed that a part of the i-B compound is trapped by this, and as a result, the crystal grain refining effect corresponding to the trapped amount disappears.

In other words, the shapes of the inclusions present in the molten metal are diverse, but if you roughly classify them based on their shape, they are about 1μ in width and about 1000μ or more in length, as shown in the schematic diagram in Figure #I1. A band-like inclusion a with a diameter of 1 to 10 pi! In order to capture and prevent leakage, fine particles are used to match the size of the smallest inclusions that need to be removed. Before it enters the filter 〇, a band-like inclusion a adheres to the outer periphery of the filter, causing significant clogging, and a considerable amount of the band-like inclusion aK), T1 and T-i-B compounds are captured, This is due to the fact that the above-mentioned bad shadows are caused, and for this reason, before entering the filter with a large cell size, 1. Removal is considered to be extremely important.

This invention was made based on the above-mentioned circumstances, and uses one or more fire-resistant filters when removing inclusions present in molten aluminum and aluminum alloys. , carry out the filtration operation one or more times, using one or more fire-resistant filters with small pore size (cell size) installed either integrally with this filter or separately. By repeating the filtration operation once or more times, the filtration efficiency and filter life can be improved, and by adding a grain refining agent after passing through the first R filter, the above-mentioned filter can be improved. The present invention provides a method for cleaning molten alloy metal with particles and particles that are trapped at the inlet of the Luther molten metal and aimed at making effective use of grain refining agents.

Hereinafter, the method according to the present invention will be specifically explained with reference to Examples. Hereinafter, aluminum and aluminum alloy molten metal will be simply referred to as molten metal.

First, in an experiment, during the molten metal filtration process using additive-free materials such as T1 and B, band-shaped inclusions that remained attached to the outer periphery of the filter along with the molten metal were collected and redissolved, and the filter pore size and band-shaped inclusions were measured. Find the relationship with the filtration status alone.

Figure 2 shows the relationship between the cell size and the passing inclusions, which shows the density of band-like inclusions present in the molten metal that passed through the filters after conducting filtration tests using filters of various cage sizes. . Here, the density is defined as the number of clear fields of band-like inclusions when 100 fields of view are examined using an optical microscope at 200 times magnification. According to the above results, for band-like inclusions alone, the filter cell size is 6 pieces, 150
- The above was found to be sufficient.

Next, 1. The relationship between the cell size of each of these 11 filters and the time required for filtration is as shown in Figure 3. Significant clogging occurs when the cell size is 100 and 150 or more, and the filtration efficiency is It shows that the value decreases.

As a result of the above experiments, the cell size of the filter for removing band-like inclusions is 6 to 100,150 square meters (cell size: 14 seconds).
It has been found that a value of approximately 8 to 0.5 mm is optimal.

Therefore, when carrying out the molten metal filtration in this process, first, the T1, T1, Alternatively, a grain refining agent consisting of a Ti-B compound is added, and then a commonly used cell size, for example, 5o.

It is particularly preferable to remove fine inclusions by passing through a filter having a fine size of 150 mm.

That is, only the band-like inclusions in the molten metal are T1 and 'I'.
The number of filters having a large cell size in the first stage and the number of filters having a small cell size in the second stage in this invention is as follows: It is not limited to one sheet, but it is also possible to have two or more sheets as necessary.

FIG. 4 is an explanatory diagram of a cleaning treatment apparatus showing an embodiment according to the invention of (2008). Molten metal exiting the melting furnace 1 passes through the gutter 2,
After passing through a coarse filter 3, it passes through a normally used fine filter 4, passes through a molten metal retainer 5, and flows toward a casting machine 6.

Below, the molten metal temperature f760℃ of Mut-Mg series product number 5182,
Table 1 shows a comparison of the results of cleaning a sample of 30 tons using the cleaning treatment method according to the present invention and the conventional treatment method.

The filter used in the cleaning process according to the present invention is a coarse pore filter with a cell size of 20/50 cells.
m (2.5 cm per cell), the cell size of the microporous filter is 200 cells 150 cm (0.25 cm), the thickness of both is 50 cm, the filtration area is 5000 cm for both,
The filter used in the conventional treatment method was the above-mentioned microporous filter alone.

As explained in detail above, the method for cleaning molten metal of a metal alloy according to the present invention uses at least two or more types of refractory filters having different pore sizes in multiple stages. Since the filtration operation is performed sequentially, removing the inclusions, the time required for filtration of the molten metal can be shortened, the filtration efficiency can be improved, and the life of the filter can be extended. In addition, since the grain refining agent is added after filtering out the band-like inclusions in the first stage filter, the yield of the grain refining agent can be improved, resulting in significant industrial gains. .

[Brief explanation of drawings]

Figure 1 shows aluminum fII#I! Schematic diagram of IO filtration method, Figure 2, filter cell size and passing inclusions.
Figure 3 is a diagram showing the relationship between filter cell size and filtration time, and Figure 4 is a diagram showing the relationship between filter cell size and filtration time. It is an explanatory view of a cleaning processing device by AK. l...Melting furnace, 3...Coarse filter, 4...Fine pore filter〇

Claims (1)

[Claims] (1) In the method of filtering and removing inclusions such as oxides and nitrides present in molten aluminum and aluminum alloys using a fire-resistant filter, first, the molten metal is filtered one or more times using a fire-resistant filter with a large cell size. After the filtration operation, a multi-stage filtration method in which the filtration operation is performed one or more times using a refractory filter with a smaller cell size installed either integrally with the above refractory filter or separately is classified as 41. A cleaning treatment method for molten alloys.