JP3318747B2 - Method for measuring sodium equivalent and phosphorus content in aluminum alloy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for measuring the sodium equivalent and the amount of phosphorus in an aluminum alloy, and more particularly to a method for measuring the amount of sodium and phosphorus present in an aluminum alloy for casting. The present invention relates to a method for determining the shape of crystalline Si.

[0002]

2. Description of the Related Art Al- in aluminum alloys for castings
Si alloy crystallizes Si in a eutectic reaction. The shape of the crystal called eutectic Si is plate-like, and there is a defect that the cast product is easily broken when stress is applied from the outside, and the extensibility is small in terms of material mechanics.

[0003] In order to improve this drawback, conventionally, A
A trace amount of sodium (Na) is added to the melt of the l-Si alloy. That is, when Na is added to the molten Al-Si alloy, the crystallization of Si is delayed, the structure changes to an extremely fine structure, and the cast aluminum alloy does not easily break even when subjected to stress, Extensibility can be increased.

[0004] A typical aluminum alloy for castings, Japanese Industrial Standard (JIS) AC4C, usually contains 50 ppm of Na. However, when this content is reduced to 10 ppm or less, the elongation ratio becomes about 5% to 1%. It drops to below,
The cast product is a defective product that cannot be used.

[0005] As chemical components of aluminum alloys for casting, Cu, Si, Mg, Zn, Fe, Mn, Ni, T
Although i, Pb, Sn, Cr, Al, etc. are specified in JIS, N added to the aluminum alloy melt by the caster
The effect of a must be guaranteed by the trader himself. Therefore, at the casting site, it is necessary to measure the effect of adding Na to the molten aluminum alloy, that is, the shape of the crystallized Si by itself.

[0006] In recent years, the amount of phosphorus (P), which has not been a problem in the past, has been rapidly increasing in aluminum alloy ingots. This is because the use of waste aluminum alloy products in the production of aluminum alloy ingots causes the inclusion of P contained in the paint used for the products, and also hypereutectic Al-Si This is due to the fact that P is added for the purpose of refining the eutectic Si because the utilization factor of the alloy has increased.

However, if phosphorus (P) is present in the aluminum alloy base metal even to a small extent, Na added to the molten metal of the base metal is inhibited by the amount of P present. In particular, when P coexists in a large amount, for example, 10 ppm or more,
Even if a normal amount of Na is added, it is difficult to refine eutectic Si. Therefore, in order to cast a good quality aluminum alloy casting, it is important to measure the amount of P present in the molten metal before the furnace.

[0008] It is very difficult to analyze a trace amount of P in a molten aluminum alloy.
Emission spectroscopy, which observes the emission spectrum, or wet analysis, in which the sample is dissolved in a solvent and the precipitate is analyzed, or microscopic observation, must be relied on. It requires technology and is economically inconvenient, and it is impossible at all to perform this in front of the furnace.

Further, in the conventional emission analysis method, when Na is added to a molten aluminum alloy, that is, when a so-called improvement treatment is performed, the amount of added Na can be analyzed. It is not possible to analyze the trace amount of P added for conversion. Therefore, P
By the remaining amount of Na, other than the Na inhibited by this, which we will call the sodium equivalent (NaE),
The effect of the improved processing will appear.

In view of these problems, a main object of the present invention is to provide a method for thermally analyzing a molten aluminum alloy for casting and measuring the amounts of Na and P present in the molten metal from a cooling curve thereof. Is to do.

It is a further object of the present invention to provide a method for measuring the eutectic temperature of Si present in an aluminum alloy before a furnace to determine the amount of Na present in the molten metal.

Another object of the present invention is to provide a method for determining the shape of eutectic Si present in a molten aluminum alloy for casting.

[0013]

In order to achieve these objects, the method of the present invention comprises the following steps: (1) without performing an improvement treatment of adding Na to a molten Al-Si alloy for casting; Obtaining the eutectic temperature of the molten metal (hereinafter referred to as “non-improved eutectic temperature” (TEu)) as it is, and (2) performing an improved treatment of adding Na to the molten metal and subjecting it to thermal analysis (3) determining a temperature difference (ΔTE) between the non-improved eutectic temperature (TEu) and the improved eutectic temperature (Eu); And (5) determining the content of phosphorus (P) from the sodium equivalent (NaE) from the temperature difference (ΔTE).

[0014]

Description of the Invention As is known from the phase diagram of an Al-Si alloy, the eutectic temperature (TEu) in the case where the unmodified treatment is not performed is 577 ° C, and the shape of the eutectic Si is It is a so-called needle shape. When Na is added thereto (improvement treatment), the improved eutectic temperature (TEu) shows a temperature lower by about 10 ° C. than 577 ° C. When the unmodified eutectic temperature (TEu) of an Al-Si alloy contains standard elements such as Cu and Mg specified in the JIS standard in this alloy, it decreases in accordance with their contents.

The formula for determining the unmodified eutectic temperature (TEu) is given by BR Krohn.
"Modern Casting (Modern Casting)
ing), 1985.21, using the following equation (1).

Formula (1) TEu = 577-12.5 × [4.43 (% Mg) +
1.43 (% Fe) +1.93 (% Cu) +1.7 (%
Zn) +3.0 (% Mn) +4.0 (% Ni)] /% S
i

Therefore, in the present invention, the non-improved eutectic temperature (TEu) in the case where Na is not added to the supplied molten Al-Si alloy is calculated by using the above equation (1).

Next, the molten metal is subjected to an improved treatment of adding Na, and the improved eutectic temperature (TE) is measured by a usual thermal analysis method.

Therefore, the temperature difference (ΔTE) between the non-improved eutectic temperature (TEu) and the improved eutectic temperature (TE) is determined. That is, equation (2) ΔTE = TEu−TE

Further, the value of the temperature difference (△ TE) is multiplied by a coefficient 15 to determine the Na equivalent in the molten metal. The basis for calculating the coefficient 15 will be described as follows.

FIG. 2 is a graph showing the relationship between the Na content and the improved eutectic temperature (TE) when the AC4C alloy is subjected to the improvement treatment. In the figure, the vertical axis indicating the temperature indicates the position indicated by ■. Is the unmodified eutectic temperature (TEu). This unmodified eutectic temperature (TE
u) is 572 ° C. for the AC4C alloy,
Since the 4B alloy contains 2.3% of Cu, the temperature is 565 ° C., which is about 7 ° C. lower than that of the AC4C alloy.

The eutectic temperature of each of the AC4B alloy and the AC4C alloy decreases linearly from the non-improved eutectic temperature due to the increase in the amount of Na.
u) and the difference (ΔTE) between the improved eutectic temperature (TE), when the amount of Na increases, the temperature difference (ΔT
E) also increases. The relationship between the AC4B alloy and the AC4C alloy is very slightly different, but can be considered almost the same. When the ΔTE increases by 1 ° C., the amount of Na increases by about 15 ppm.

The improved eutectic temperature (TE) decreases linearly with the amount of Na added and increases by about 15 ppm each time the temperature difference (ΔTE) increases by 1 ° C.

Therefore, to determine the equivalent of Na (NaE) from the temperature difference (△ TE), the following equation (3) holds: NaE = △ TE × 15.

According to the present invention, according to the Na equivalent (NaE) obtained as described above, if the equivalent is 0 to 5, the shape of the eutectic Si is massive, and if the equivalent is 6 to 39, the needle is a needle. If the shape is 40 to 59, it can be determined that the shape is mesh, and if it is 60 or more, the shape can be determined to be granular.

Further, according to the present invention, after obtaining the Na equivalent (NaE) as described above, the content of phosphorus (P) present in the molten metal can be determined.

In examining the content of phosphorus (P), it should be noted that even if a normally specified amount of Na is added to the molten aluminum alloy, phosphorus in the molten metal has a value greater than the ordinary value. If it is contained, eutectic Si cannot be miniaturized.

That is, in the molten metal, Na is preferentially combined with P to become Na ₃ P. Its atomic weight ratio is 3Na: P,
That is, 68.96931: 30.97362 = 2.226.
7, the atomic weight ratio of Na ₃ P is 2.2.

From the above description, as shown in the following equation (4), after calculating the Na content (NaE) in the molten metal, the value obtained by subtracting the amount of added Na is used as the atomic weight of Na ₃ P. Dividing by the ratio 2.2 gives the P content. Formula (4) (NaE−Na) /2.2=P

[0030]

[Experimental example] A first sample obtained by melting 5 kg of a commercially available AC4C alloy ingot at a temperature of 720 ° C and adding Na thereto to improve the treatment, and the amount of P adding a Cu-8% P alloy and adding the same. Is 30
ppm, and further added Na to prepare a second sample.

The first sample and the second sample were analyzed by the emission analysis method, the wet analysis method, and the method of the present invention. The analysis results are as shown in Table 1.

[0032]

[Table 1]

Next, the sodium equivalent (NaE) and the amount of P of the first sample and the second sample were determined by the method of the present invention. The NaE of the first sample was 50 ppm. From this, it became clear that most of the contained Na was acting effectively.

The second sample, NaE, was similarly examined and found to be only 8 ppm. From the results, it was found that most of the Na added last was ineffective.

The fact that the shape of the eutectic Si of the first sample is reticulated, and that the shape of the eutectic Si of the second sample is reticulated or acicular is as estimated from the sodium equivalent contained. is there. It should be noted that P obtained by the method of the present invention is
Was identical to the value obtained by wet analysis.

As described in detail above, the present invention provides a method for measuring the sodium equivalent and the phosphorus content in an aluminum alloy. Therefore, when casting a casting of an aluminum alloy, the molten metal is subjected to an improved treatment. N required for
The addition amount of a can be easily determined in front of the furnace, and the evaluation and selection can be easily performed based on the content of phosphorus (P) present in the supplied alloy ingot. The shape of eutectic Si can be immediately determined.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the Na equivalent and the improved eutectic temperature (TE) when an AC4C alloy is subjected to an improvement treatment.

Claims (3)

(57) [Claims] (1) determining a non-improved eutectic temperature (TEu) by thermal analysis of a molten Al-Si alloy for casting; and (2) improving eutectic of the molten metal by adding Na to the molten metal. Temperature (Eu), and (3) a temperature difference (差) between the non-improved eutectic temperature (TEu) and the improved eutectic temperature (Eu).
TE) and (4) determining the amount of Na contained in the molten metal from the temperature difference (ΔTE) by measuring the sodium equivalent in the aluminum alloy. And (2) determining an improved eutectic temperature (Eu) of the Al-Si alloy for casting, (2) obtaining an improved eutectic temperature (Eu) of the molten metal, and (3). Calculating a temperature difference (△ TE) between the non-improved eutectic temperature (TEu) and the improved eutectic temperature (Eu); and (4) determining the temperature difference (△
And measuring the amount of Na contained in the molten metal from the TE), determining the content of phosphorus by dividing the amount of the numerical value obtained by subtracting the added atomic weight ratio of NaP ₃ of the Na from the content of the Na Measuring the amount of phosphorus in the aluminum alloy. 3. The eutectic Si has a massive shape when the sodium equivalent is 0 to 5, a needle-like shape when the sodium equivalent is 6 to 39.
The method for determining the shape of eutectic Si from the method according to claim 1, wherein the shape is eutectic Si if the value is 40 to 59, and the shape is eutectic if the value is 60 or more.