JPH04276031A - Method for removing phosphorus in aluminum - Google Patents

Abstract

PURPOSE:To efficiently remove and reduce phosphorus in aluminum. CONSTITUTION:Molten aluminum or aluminum alloy containing a considerable amt. of phosphorus is filtered at <=750 deg.C. The filtering size of the filter is 150-450mum. By this method, the amt. of phosphorus in aluminum or aluminum alloy is easily and effectively decreased so that P-contg. scraps and returned material can be used and limits for the use of aluminum or aluminum alloy material can be eliminated.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing phosphorus from aluminum, and an object of the present invention is to provide a method for efficiently removing phosphorus from molten aluminum.

[0002] In recent years, in the aluminum industry, it has become unavoidable to use recycled scraps and recycled materials rather than primary metals, and pure aluminum used for foils, printing boards, etc. is also used for building materials and utensils. In order to reduce costs, there is a tendency to incorporate a large amount of commercial scrap into aluminum alloys used for rolling out products.

However, the above-mentioned municipal waste includes copper product scrap containing P, scrap material of Ni-P plating on Al plate, scrap and return material of hypereutectic Al-Si alloy containing P, and ink. It is unavoidable that household waste coated with chemicals, photosensitizers, resins, etc. will also be included.

On the other hand, hypoeutectic Al-Si alloys containing 4 to 10% Si, such as AC4A, AC4B, AC4C
, AC8A, AC8B, etc. have good castability, high strength, and wear resistance.
is added and subjected to improvement treatments such as eutectic silicon refinement, and is used in automobile parts such as brake drums, crankcases,
It is used in large quantities in pistons, etc. However, the permissible range of component elements of such Al-Si alloys is wider than that of other alloys, so when it is melted, commercial scraps and return materials of various alloys are added, and the above-mentioned Si :4~1
A 0% Al-Si alloy may contain 5 ppm or more of P.

[0005]

[Problems to be Solved by the Invention] From the above-mentioned circumstances, if a pure Al material contains 5 ppm or more of P, uniform etching will not be achieved when chemically treated, resulting in disadvantages such as deterioration of surface quality. Come.

[0006]Also, in the above-mentioned Al-Si alloy containing 4 to 10% Si, although the allowable amount of P varies depending on the type of alloy, when the P content exceeds 5 to 10 ppm, the eutectic Si The refinement, that is, the improvement treatment effect is inhibited, and the desired strength and wear resistance cannot be obtained, and there are also disadvantages such as a large amount of shrinkage during casting.

[0007]Therefore, although various studies have been made to remove P from Al or Al alloys as described above, no suitable removal method has been found, and in the field Measures have been taken to reduce the amount of P by mixing materials, but since the P itself is not removed, the operation is complicated and has disadvantages such as requiring a large amount of energy and processing operations.

[0008]

[Means for Solving the Problems] The present invention was created after repeated studies in view of the above-mentioned circumstances. According to the results of the study, the size of the compound is highly dependent on the temperature of the molten metal, and it was discovered that P can be effectively removed by filtration under specific conditions of the molten metal temperature, and this led to the completion of the present invention. Ta. That is, the present invention is as follows.

(1) A method for removing phosphorus from aluminum, which comprises filtering a molten aluminum or aluminum alloy containing 5 ppm or more of phosphorus at a temperature of 750° C. or lower to remove phosphorus. (2) The method for removing phosphorus in aluminum as described in item (1) above, wherein the molten aluminum alloy is a hypoeutectic or eutectic Al-Si alloy molten metal. (3) The method for removing aluminum as described in either (1) or (2) above, characterized in that the filtration particle size of the filter for filtering at a molten metal temperature of 750° C. or lower is 150 to 450 μm. How to remove phosphorus.

0010

[Operation] By filtering a molten aluminum or aluminum alloy containing 5 ppm or more of phosphorus at a molten metal temperature of 750° C. or lower, the AlP compound in the molten metal is filtered in an appropriately enlarged state and is appropriately removed.

[0011] The inventors have carefully studied the morphology and behavior of AlP compounds in molten metal containing 20 ppm of P in pure Al, and have found that the size of the AlP compounds in the molten metal is highly dependent on the molten metal temperature. , and that it changes reversibly. That is, this is the micrograph of Figure 1.
~ As shown in Figure 5, Figure 1 relates to filter residue when filtered at 720 °C, Figure 2 at 740 °C, Figure 3 at 760 °C, Figure 4 at 780 °C, and Figure 5 at 800 °C. However, in Figures 3 to 5, the AlP compound is extremely fine, whereas in Figures 2 and 1, it is extremely large, and its size hardly changes even when the temperature is below 720°C. It was confirmed that there was no problem.

Furthermore, the results of X-ray analysis of the compound shown in FIG. 1 show that detection peaks appear at positions corresponding to Si detection, indicating that AlP has almost the same crystal structure as Si. known and as mentioned above pure A
Since this is the case when l is used, there is no Si,
It is obvious that it is AlP. It has also been confirmed that such P exhibits the same behavior in a hypoeutectic Si alloy as in this pure Al molten metal.

Furthermore, the present inventors investigated the filtration characteristics of such AlP compounds, and found that this AlP compound
If the P compound is a fine particle of 1 μm or less, the AlP compound is likely to aggregate, and as a result, the filtration speed becomes extremely slow and clogging occurs even with a small amount of filtration, that is, the filtration mechanism becomes completely closed and cannot be filtered. In contrast, in Figure 1,
As shown in Figure 2, when the AlP compound is 2 to 3 μm or larger, it is filtered by a cake filtration mechanism on the filter, which can effectively avoid a decrease in filtration speed and prolong the filtration time, and reduce the amount of filtrate on the filter. Removal allows continuous use of the filter.

That is, by performing filtration at a molten metal temperature of 750° C. or lower, efficient filtration and advantageous filtration can be achieved by repeatedly using the filter, and the P content in the molten metal can be appropriately reduced.

[0015] Filtration particle size of the filter used for filtration (
According to a measuring method according to JIS B8356), if the diameter is less than 150 μm, clogging tends to occur and productivity is inhibited, while if it is more than 450 μm, the filtration efficiency becomes poor. That is, by setting the diameter to 150 to 450 μm, filtration can be performed while appropriately avoiding these disadvantages.

[0016] As the above-mentioned filter material, an alumina filter made of ceramics has excellent strength and high durability. However, if a phosphoric acid binder is used, P may be mixed into the molten metal from the filter, so it is preferable to use a boric acid binder or a sintered filter.

Regarding filtration pressure and filtration weight, as an example, in the case of molten metal at 720°C, the filtration pressure rises instantaneously to nearly 0.9 kgf/mm2 at the beginning of filtration, but after about 3 minutes has passed, 0.7kgf/m
It was confirmed that a stable filtration pressure of about m2 was exhibited, and that appropriate filtration could be carried out for at least ten minutes or more. Regarding the amount of filtration, if the molten metal temperature is 760°C or higher, it will become clogged in about 2 to 6 minutes and become almost impossible to filter, whereas if the temperature is 750°C or lower, it will be at least 15 to 15 minutes.
Filtration can be continued for 20 minutes or more.

[0018]

[Embodiments] Specific embodiments of the present invention will be described below. In addition, all analyzes of P were performed by chemical analysis. Example 1 P in AC4C (Al-7%Si-0.3%Mg)
Prepare a molten metal containing 15 ppm of
0.4 kg/cm2 using an alumina tube filter with a filtration particle size of 250 μm at a temperature of 0.4 kg/cm2.
When the filtration treatment was performed at a filtration rate of ・hr, it was confirmed that the P content of the filtered molten metal had decreased to 3 ppm.

Example 2 AC8B (Al-9%Si-3%Cu-1%Mg-0.
A molten metal containing 20 ppm of P in 5% Ni) was prepared, and this molten metal was heated at a temperature of 700°C and at a weight of 0.2 kg/c.
When the product was filtered in the same manner as in Example 1 using an alumina tube filter with an average pore size of 350 μm at a filtration rate of m2·hr, the P content was reduced to about 4 ppm.

Example 3 Pure aluminum with a purity of 99.7% and containing 10 ppp of P.
The molten metal containing m was heated to 710°C and the filtration rate was 0.
When filtered in the same manner as in Examples 1 and 2 using a filter with an average pore diameter of 250 μm at 3 kg/cm 2 ·hr, the P content was 2 ppm or less (2 ppm is the detection limit of the analytical instrument).

[0021]

[Effects of the Invention] According to the present invention as explained above, the P value in aluminum or aluminum alloy can be easily and effectively reduced, thereby making it possible to appropriately utilize P-containing scraps and return materials. It also has industrial effects such as eliminating the limitations on the use of aluminum materials or aluminum alloy materials, making it possible to use filter materials continuously or repeatedly, and being able to carry out advantageous and low-cost processing. This is a great invention.

[Brief explanation of the drawing]

FIG. 1 is a micrograph (400x magnification) showing the microstructure of the metal on the filter filtered at a molten metal temperature of 720°C.

FIG. 2 is a micrograph (400x magnification) showing the microstructure of the metal on the filter filtered at a molten metal temperature of 740°C.

FIG. 3 is a micrograph (400x magnification) showing the microstructure of the metal on the filter filtered at a molten metal temperature of 760°C.

FIG. 4 is a micrograph (400x magnification) showing the microstructure of the metal on the filter filtered at a molten metal temperature of 780°C.

FIG. 5 is a micrograph (400x magnification) showing the microstructure of the metal on the filter filtered at a molten metal temperature of 800°C.

Claims (3)

[Claims] Claim 1: Aluminum or aluminum alloy molten metal containing 5 ppm or more of phosphorus is heated to a molten metal temperature of 750
A method for removing phosphorus from aluminum, characterized by removing phosphorus by filtration treatment at a temperature below ℃. 2. The removal method according to claim 1, comprising:
A method for removing phosphorus from aluminum, characterized in that the molten aluminum alloy is a hypoeutectic or eutectic Al-Si alloy molten metal. 3. The method for removing phosphorus in aluminum according to claim 1, wherein the filtration particle size of the filter that is used for filtering at a molten metal temperature of 750° C. or lower is 150 to 450 μm. Removal method.