JPH0941050A - Method for melting aluminum or aluminum alloy scrap - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reutilize Al scrap as an Al alloy free from problems in strength and toughness without depending on the kinds of Al alloy series by suppressing the contents of Pb, Bi and V in molten metal obtd. by remelting Al scrap to prescribed ones or below. SOLUTION: At the time of melting Al or Al alloy scraps, the concn. of Bi in the molten metal is suppressed to >=0.10wt.%, the concn. of Pb to <=0.10% and the concn. of V to <=0.15% respectively. Namely, the concns. of Bi, Pb and V in the molten metal are measured, and the Al or Al alloy molten metal is refined so as to regulate the content of each element to prescribed one or below. For example, it is diluted by the other Al or Al alloy small in the content of their each element, or it is refined, e.g. by extracting the concentrated unsolidified molten metal of the impurity elements in the final period of the solidification with a phenomenon that the impurity elements are concentrated in the final unsolidified molten metal applicated. Thus, Al or Al alloy scrap can be reproduced into reproduced Al or Al alloy products without causing any troubles.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of melting Al or Al alloy scrap, and in particular, using Al or Al alloy scrap as a raw material without any problem in strength, toughness, electrochemical characteristics, corrosion resistance and the like. The present invention relates to a melting method capable of obtaining Al or an Al alloy capable of being processed.

[0002]

2. Description of the Related Art Al or Al alloys (hereinafter, represented by Al alloys) have excellent properties such as lightness, workability, corrosion resistance, and surface appearance, and therefore, they are used for home electric appliances, automobile parts, It is widely used in various fields including building materials. On the other hand, the electric energy required for remelting and recovering the Al alloy scrap is about 1/1 of the electric energy for newly manufacturing the Al alloy by electrolytic refining.
It is a material with extremely high recycling merits because it requires an extremely small amount of about 30, and various studies have been conducted on its recovery and reuse technology.

In the recovery and remelting of Al alloy scrap, various impurity elements derived from the pigment contained in the overcoat paint and the foreign metal mixed and taken into the scrap are mixed. For example, in a case where a paint using lead oxide or the like is applied as a pigment, Pb is mixed as an impurity element, and the JIS 2011 alloy has 0.2 to
Since 0.6% by weight of Pb and Bi are added,
If the 2011 alloy is mixed in the scrap, Pb
And Bi are contained in the molten metal as impurity elements. In some cases, the element added to remove these impurity elements may remain in the molten metal and cause reverse contamination. As such an element, an element added for the purpose of removing Si may be used. Some V etc. correspond to this.

When recovering and remelting Al alloy scrap and using it, with respect to elements such as Fe, Mg, and Si that have a relatively large mixing frequency and a relatively large mixing amount, the effects of the mixing on the physical properties are confirmed. Although various studies have been conducted on methods for removing these impurity elements, since the amount of Pb, Bi, and V mentioned above is relatively small, these impurity elements affect the physical properties of recycled Al alloy products. There is no example in which even such effects were pursued.

[0005]

According to the present invention, when Al alloy scrap is recovered and reused under the above-mentioned conventional technique, a small amount of P may be mixed therein.
Attention is paid to b, Bi, and V to clarify the obstacles caused by these impurity elements, and to establish a technique that can be utilized as a regenerated Al alloy without any trouble without causing the obstacles of those elements.

[0006]

The melting method according to the present invention, which has been able to solve the above problems, involves melting the Al or Al alloy scrap with a Bi concentration of 0.10% by weight in the molten Al or Al alloy. % Or less, the Pb concentration is 0.
The gist lies in suppressing the V concentration to 10% by weight or less and the V concentration to 0.15% by weight or less, respectively. In addition, as a specific means for suppressing the content of the above three elements to be less than the specified amount, A
Bi or P in molten metal consisting of l or Al alloy scrap
The content of each of b and V is measured, and other Al or Al alloys having a small content of each element (for example, pure Al ingot) so that the content of each element becomes the above concentration or less.
Method, or measuring the contents of Bi, Pb and V in the molten metal consisting of Al or Al alloy scrap, so that the contents of these respective elements are below the above concentrations,
A method for purifying the molten Al or Al alloy may be adopted. As a specific method for the purification, an element or a compound that binds to the above-mentioned elements in the molten metal to form an insoluble compound or the like in the molten metal is used. Concentration of impurity elements at the final stage of solidification by utilizing the method of addition and removal, or the fact that high-purity Al solidifies first and the impurity element concentrates in the last unsolidified melt when the melt solidifies by cooling. It is possible to employ a method of refining by extracting the unmelted molten metal thus prepared, or the like.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Under the conventional techniques as described above, the present inventors have found that Pb and B which may be mixed in scrap of Al or Al alloy (represented by Al alloy again).
Regarding i and V, the content of these impurity elements is regenerated Al
We pursued the effect on the physical properties of alloy products. As a result, P
b and Bi segregate in the grain boundaries in the Al base material in a concentrated state, and as the content thereof increases, the concentrated grains become coarse, and the physical properties of the regenerated Al alloy product, particularly the toughness, are small. If the Pb and Bi contents are 0.10, respectively, the deterioration of the physical properties due to the coarsening of the thickened grains is caused.
It was confirmed that when the content exceeded the weight percentage, it appeared remarkably.

By the way, FIGS. 1 and 2 are graphs showing the results of examining the effect of each concentration of Pb or Bi contained in the regenerated Al alloy on the average grain size of impurities concentrated and segregated at the grain boundaries. As is clear from these graphs, when the concentration of Pb or Bi contained as impurities is up to 0.10% by weight, the particle size of the segregation portion derived from these impurities is not so large, and as a result, The adverse effect on the toughness of the recycled Al alloy product is hardly a problem, but if they exceed 0.10% by weight, the average grain size of the impurities concentrated and segregated at the grain boundaries increases rapidly,
It was confirmed that this remarkably appears as deterioration of the toughness of the recycled Al alloy product. Therefore, such Pb and B
In order to avoid the trouble caused by the mixture of i, at the stage of recovering and remelting the Al alloy scrap, the contents of Pb and Bi should be 0.10% by weight or less at the most by the method described later. It is necessary to limit it.

Further, V which may be mixed in the recycled Al alloy molten metal is Fe, Si, Mg, Cr, etc., which are other elements often mixed in the Al alloy, and further the base metal. Which has a property of forming an intermetallic compound with Al, and when the V concentration in the regenerated Al alloy exceeds 0.15% by weight, the intermetallic compound abruptly coarsens, and the coarse intermetallic compound becomes As a result of being the starting point of fracture, the strength and toughness of the regenerated Al alloy are remarkably lowered, and the coarse intermetallic compound also has a great difference in electrochemical characteristics from the matrix phase, so that the corrosion resistance is extremely deteriorated. It was confirmed.

By the way, FIG. 3 shows the particle size distribution and the number of intermetallic compounds generated in Al alloys with V contents of 0.10% by weight, 0.15% by weight and 0.20% by weight. Is a graph showing the results of examining the relationship between
When the V content is up to 0.15% by weight, the particle size and the number of intermetallic compounds formed in the Al alloy do not change so much, but when the V content is 0.20% by weight or more, It is clear that the grain size and the number of the intermetallic compounds are rapidly increasing, and this has a significant adverse effect on the physical properties of the regenerated Al alloy. Therefore, it is understood that the V content in the recycled Al alloy should be suppressed to 0.15% by weight or less in order to avoid the deterioration of the physical properties due to the V content.

The present invention was made on the basis of the above knowledge, and when the Al alloy scrap is recovered and remelted to be effectively utilized as a regenerated Al alloy, the remelting step of the Al alloy scrap is performed. Then, the Bi concentration in the molten metal is set to 0.1
0% by weight or less, Pb concentration of 0.10% by weight or less, and V concentration of 0.15% by weight or less to prevent deterioration of strength, toughness, corrosion resistance, etc. due to intermetallic compounds derived from these elements. As a regenerated Al alloy product, it has succeeded in establishing a technology capable of being regenerated as an Al alloy product having substantially no trouble.

Al or A regenerated by the present invention
The l-alloy pays attention to Pb, Bi, and V, which have hardly been noticed as harmful impurities, and regulates the upper limit values of those impurity elements mixed in with the use of scrap. The above-mentioned obstacles caused by these elements are not only caused by regeneration as pure Al, but also a 2000 series Cu-containing Al alloy and a 3000 series Mn.
Containing Al alloy, 4000 series Si-containing Al alloy, 500
It can be similarly utilized for regeneration as all Al alloys such as 0-based Mg-containing Al alloy, 6000-based Mg / Si-containing Al alloy, and 7000-based Zn-containing Al alloy.

As described above, the method for controlling the content of Pb, Bi, V in the Al alloy remelted molten metal to the specified amount or less is not particularly limited, but as a general method, Al alloy scrap is used. Measure the content of each element in the molten metal obtained by remelting, dilute by adding other Al alloy scrap or Al metal with a small content of each element, and the impurity element concentration below the specified value. To measure the content of each element in the molten metal obtained by remelting Al alloy scrap, and when the content of each impurity element exceeds the specified concentration, forms an insoluble compound with that element. A method of adding other possible elements or compounds to separate and remove the impurity element as an insoluble matter from the molten metal. When solidifying the molten aluminum alloy scrap, the unsolidified molten metal at the final stage of solidification is removed. However, include a method of removing and concentrating said impurity element in yet-solidified metal, they alone in some cases may be conducted by combining them appropriately, short eventually Play A
lPb, Bi,
Each content of V may be reduced to the specified concentration or less.

[0014]

EXAMPLES Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to the following Examples as far as the present invention is concerned. It is, of course, possible to implement the present invention with appropriate modifications, and all of them are included in the technical scope of the present invention.

EXAMPLE By selecting several kinds of Al alloy scraps, appropriately changing their compounding amounts, and diluting them with an appropriate amount of pure Al ingot, as shown in Table 1, Pb, Bi, 2000 series, 3000 series, 5000 series with different V contents
Regenerated into 6000 series and 7000 series Al alloys. The obtained ingot is rolled at a final rolling rate of 80% to a plate thickness of 2 mm, and H
18 materials were used. 2000 series, 6000 series and 70 series
For the 00 series, 490 ° C, 515 ° C and 4 respectively
After heating at 90 ℃ for 30 minutes, quenching with water, 190 ℃ ×
Heat treatment was performed for 9 hours, 180 ° C. × 8 hours, and 120 ° C. × 24 hours to obtain a T6 material. Each of them was evaluated for strength and toughness according to the following criteria, and the results shown in Table 1 were obtained.

The strength was evaluated by the tensile strength using JIS No. 5 tensile test pieces, and those satisfying the JIS standard values were evaluated as ◯, and those not satisfying them were evaluated as x. The toughness evaluation is JI
The S4 No. impact test piece was used to evaluate the Charpy impact value. When the impact value was 20% or less lower than that of the comparative material containing no Pb, Bi or V, it was evaluated as ◯, and when less than that, it was evaluated as x. .

[0017]

[Table 1]

As is clear from Table 1, when the Bi concentration exceeds 0.10% by weight or the Pb concentration exceeds 0.10% by weight, regardless of the kind of the regenerated Al alloy system. Also has poor toughness, and when the V concentration exceeds 0.15% by weight, both strength and toughness are very poor,
Although there is a problem in utilization as a recycled Al alloy, when the content of each of the above three kinds of elements is below the specified concentration, there is no problem in strength and toughness in any alloy system, and Al of each alloy system is used. It can be seen that it can be used as a recycled alloy product without any problems.

[0019]

The present invention is configured as described above.
1 or Pb, Bi, V in the molten metal obtained by remelting when recovering and recycling 1 or Al alloy scrap
By controlling the content of the three elements below to a predetermined amount or less, it was possible to reuse as an Al alloy having physical properties with no problem in strength and toughness regardless of the type of Al alloy system.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the Pb concentration in a molten metal obtained by remelting an Al alloy scrap and the average grain size of impurities concentrated in the crystal grain boundaries of the Al alloy.

FIG. 2 is a graph showing the relationship between the Bi concentration in the molten metal obtained by remelting Al alloy scrap and the average grain size of impurities concentrated in the crystal grain boundaries of the Al alloy.

FIG. 3 is a graph showing the relationship between the V concentration in a molten metal obtained by remelting an Al alloy scrap, the particle size of an intermetallic compound formed in the Al alloy, and the number of the intermetallic compound per unit area. Is.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazutaka Kunii 1-5-5 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo Kobe Steel Co., Ltd. Kobe Research Institute (72) Inventor Kenji Osumi Takatsuka, Nishi-ku, Kobe-shi, Hyogo 1-5-5 stand, Kobe Steel, Ltd. Kobe Research Institute

Claims (3)

[Claims] 1. When melting Al or Al alloy scrap, Bi concentration in the Al or Al alloy molten metal is 0.10 wt% or less, Pb concentration is 0.10 wt% or less,
A method for melting Al or Al alloy scrap, characterized in that the V concentration is suppressed to 0.15% by weight or less, respectively. 2. The contents of Bi, Pb and V in the molten metal made of Al or Al alloy scrap are measured, and the contents of each of these elements are adjusted so that the contents are not more than the concentrations described in claim 1. The melting method according to claim 1, wherein the melting is performed by diluting with another Al or Al alloy having a small element content. 3. The respective contents of Bi, Pb and V in a molten metal made of Al or Al alloy scrap are measured, and the contents of the respective elements are controlled so as to be equal to or less than the concentration according to claim 1. Alternatively, the melting method according to claim 1, wherein the molten Al alloy is purified.