JPH10158771A - Aluminum alloy for casting, excellent in pressure resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an aluminum alloy for casting, in which shrinkage cavities are dispersed and pressure resistance is improved. SOLUTION: This alloy has a composition which consists of, by weight, 4-12% Si, 0.5-5% Cu, 0.1-0.6% Mg, 20-250ppm Ca, 0.1-1.0% Zn, and the balance aluminum with inevitable impurities and in which, as to the ratio of weight concentration between Si and Ca, the ratio of Si to Ca is 1 to >=0.005.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an aluminum alloy for castings having excellent pressure resistance.

[0002]

2. Description of the Related Art Conventionally, Al-Si-Cu alloys have been widely used as casting alloys because of their relatively good castability and good mechanical strength. However, this alloy system has a large amount of shrinkage and tends to concentrate shrinkage cavities. Accordingly, when pressure resistance is required, there is a problem that the pressure medium leaks through the shrinkage cavity. Also, in order to obtain a sound casting, in order to prevent shrinkage cavities that easily occur from entering the product, it is necessary to take a large riser, and the yield of the casting, which is the ratio of the weight of the casting to the weight of the casting, is reduced. There is an economic problem of getting worse. Also, depending on the casting method, solidification shrinkage generated in the riser tends to appear on the casting surface of the cast product due to changes in casting conditions such as melting temperature, mold temperature, etc., and at that time, shape defects and appearance defects referred to as shrinkage are caused. .

[0003]

In order to solve this problem, conventionally, Ca has been added to disperse shrinkage cavities to improve pressure resistance. However, with Ca alone, the pressure resistance is not sufficiently improved, and when the Ca concentration is too high, the degassing property and the fluidity are reduced. Therefore, there is a limit in improving the pressure resistance with Ca.

[0004] In particular, in the case of a recycled aluminum alloy, Fe mixed in from the scrap as a raw material and A in the molten metal.
1, Al-Si-Fe intermetallic compound crystallized by reacting with Si inhibits the filling of the molten metal due to solidification shrinkage near the final solidification part, so that shrinkage cavities and continuous linear shrinkage cavities are formed. There is a problem that aggregates are easily generated and the pressure resistance of the casting is deteriorated.

[0005] Recently, the addition of Ca to an Al-Fe-Si intermetallic compound, which increases the amount of crystallization when the Fe concentration is high, suppresses the amount of crystallization and prevents the occurrence of linear shrinkage cavities. An aluminum alloy that ensures pressure resistance has been proposed (JP-A-1-156446). However, in the present invention, although the pressure resistance impaired by the high Fe concentration can be restored to the level where the Fe concentration is low, further improvement in the pressure resistance cannot be expected. Further, in an alloy having a low Fe concentration, the effect of Ca is small because the above-mentioned intermetallic compound itself to be made harmless is small.

[0006]

The present invention has been made as a result of various studies in view of these problems. That is, the means for achieving the present invention is that Si is 4 to 12 (wt.
%), Cu is 0.5 to 5 (wt%), Mg is 0.1 to
0.6 (wt%), Ca is 20 to 250 (ppm), Z
n 0.1 to 1.0 (wt%), and Si and Ca
Is characterized in that Ca is 0.005 or more times the weight concentration of Si1 and the balance consists of aluminum and unavoidable impurities.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is intended to greatly reduce the eutectic temperature while simultaneously containing an appropriate amount of Ca, Mg, and Zn in an Al--Si--Cu alloy, Is focused on because the solidification temperature range, which is the difference between the liquidus temperature and the eutectic temperature, expands because it is hardly affected by the inclusion of. That is, it has been found that the solidification temperature range, which is the coexistence region of the liquid phase and the solid phase, greatly affects the pressure resistance of the cast product, and the pressure resistance improves as the region becomes larger.

Hereinafter, the reasons for limiting the components of the aluminum alloy according to the present invention will be described. Si is a component that improves fluidity in an Al—Si—Cu alloy. At 4 wt% or less, the effect is small, and at 12 wt% or more, primary crystal silicon is crystallized at the time of casting, and the toughness is reduced due to an internal notch effect.

[0009] Cu hardens an alloy matrix (hereinafter abbreviated as a matrix) in a solid solution and precipitates Al or a precipitate of Al and Mg by aging treatment to increase mechanical strength and hardness. If the content is 0.5 wt% or less, it is not enough to increase the mechanical strength and hardness of the matrix, and 5 w
Even if t% or more is added, improvement in mechanical strength cannot be expected so much.
Conversely, hot cracking occurs during casting, impairing the soundness of the casting.

It has been found that adding Mg together with Ca and Zn lowers the eutectic temperature and improves the pressure resistance. Further, Mg contains Si and the intermetallic compound Mg ₂
Although Si is formed and imparts a heat treatment property to the material and contributes to an improvement in mechanical strength, when the content is more than appropriate, the toughness is reduced. Therefore, the content is desirably 0.6% or less. If the content is 0.1% or less, the effect of improving the pressure resistance due to the coexistence with Ca cannot be expected.

It has been found that by containing Ca together with Mg and Zn, the eutectic temperature is lowered and the pressure resistance is improved. However, the Ca concentration for obtaining sufficient pressure resistance is set to 1 for the Si concentration. Case, 0.0005 times or more by weight of Ca
Concentration is required. If the Ca concentration is less than this ratio, there is no effect on the pressure resistance. The Ca concentration is 250 (ppm)
In the above case, the degassing property and the fluidity of the aluminum alloy melt are deteriorated, so that the molten metal cannot be sufficiently spread in the mold, which causes poor running of the molten metal and a boundary of the molten metal.

It has been found that when Zn is contained together with Mg and Ca, the eutectic temperature is lowered and the pressure resistance is improved. In addition, being contained together with Mg is effective in improving mechanical properties. However, if the content is less than 0.1%, the effect cannot be expected. If the content is 1.0% or more, the effect of deteriorating the toughness is large. Therefore, the concentration of Zn is 0.1
To 1.0%.

[0013]

EXAMPLES Examples of the present invention will be described below together with comparative examples. An aluminum alloy having the composition shown in Table 1 was melted, and FIG.
The mold shown in (1) was poured into the mold and observed for shrinkage cavities.

(1) Shrinkage cavity test conditions Pouring temperature 720 ± 5 ° C Mold Molded shell sand having the inner dimensions shown in Fig. 2 Mold temperature Room temperature Melt treatment Degassing treatment with ethane hexachloride

(2) Result of shrinkage cavity observation Shrinkage cavity observation is performed by dividing the alloy casting cast in the mold shown in FIG. The volume was measured. The pipe depth was measured at the portion A shown in the schematic view of the cross section of the alloy casting shown in FIG. The pipe volume is determined by dividing the pipe portion on both split surfaces (Fig. 1
Of Part B) was embedded with clay, the weight was measured, and the result was divided by the specific gravity of the viscosity. Table 2 shows the results. Examples 1 to 8 of the present invention have a smaller pipe depth than Comparative Examples 1 to 6,
It is clear that the pipe volume and the amount of shrinkage are small, and the pressure resistance is improved.

(3) Mechanical test results Aluminum alloys having the compositions shown in Table 1 were melted, and JIS H5 at a mold pouring temperature of 700 ± 5 ° C and a mold temperature of 200 ± 10 ° C.
A strength test piece was prepared by casting into a boat bottom mold 202. In the strength test, the test piece was subjected to a solution treatment at 500 ° C. for 8 hours.
After water quenching with warm water at 0 ° C., aging treatment was performed at 160 ° C. for 6 hours, and then performed. The results of the mechanical test are shown in Table 3. Table 2
As can be seen from the results of this example,
_It is clear that _B , σ _0.2 , and δ are all excellent, and that the mechanical strength is excellent in addition to the pressure resistance.

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

[Table 3]

[0020]

As described above, in the alloy of the present invention, Al
0.1-0.6 (wt%) Mg and 20-250 (ppm) Ca, 0.1-1.
By containing Zn (0% by weight), shrinkage cavities are dispersed, and this has an advantage of excellent pressure resistance.

[Brief description of the drawings]

FIG. 1 is a schematic view of an alloy casting subjected to shrinkage cavity measurement.

FIG. 2 shows the inner dimensions of a mold.

[Explanation of symbols]

 A Indicates the pipe depth. B shows the part where the pipe volume was measured.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Noboru Seki 1-13-9 Shiba-Daimon, Minato-ku, Tokyo Inside Showa Denko K.K.

Claims (1)

[Claims] 1. A method according to claim 1, wherein 4 to 12 (wt%) of Si and 0.
5 to 5 (wt%), Mg is 0.1 to 0.6 (wt%),
20 to 250 (ppm) of Ca, 0.1 to 1.0 of Zn
(Wt%), and the weight ratio of Si to Ca is at least 0.005 times that of Si1, with the balance being aluminum and unavoidable impurities. Aluminum alloy for castings.