JPS6217141A - Grain refining method for eutectic si of al-si alloy - Google Patents

Abstract

PURPOSE:To uniformly disperse a grain refining agent into a molten Al-Si alloy at a high yield and to execute efficient grain refining of eutectic Si by continuously adding the grain refining agent contg. an eutectic Si improving element to the molten alloy in a casting spout leading to a casting device. CONSTITUTION:The prescribed molten Al-Si alloy 12 held and contained in a holding furnace 10 is conducted from a tap hole 14 to the casting spout 16 from which the molten alloy is dropped through a supply port 18 into a casting mold device 20, by which a cast ingot is continuously cast and an alloy billet 22 of eutectic or hypoeutectic Al-Si is obtd. A rod 26 for addition which consists of the grain refining agent including the eutectic Si improving element such as Na, Sr or Sb and is let off from a coil part 24 is continuously added via a feeder 28 such as feed roller into the molten Al-Si alloy 15 in the casting spout 16 in the above-mentioned method.

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to Aj? -Regarding a method for refining eutectic Si in Si-based alloys, in particular adding a eutectic St improving element to a eutectic or hypo-eutectic Al-Si alloy molten metal to make the eutectic Si produced during solidification uniform. The present invention also relates to an efficient method of miniaturization.

(Prior art and its problems) Hypoeutectic or eutectic AN-5i alloys are used to improve their mechanical properties, toughness, machinability, etc.
% S r , S b, etc. in the cast structure.
Improvement treatments are often performed to refine i, and conventionally, those improvement elements are the above-mentioned An! - When a predetermined ingot is continuously cast from a molten Si-based alloy, flux, a single metal, or an intermediate alloy has been directly poured into the molten alloy housed in a holding furnace.

However, because the refining agent containing the eutectic Si improving element is directly poured into a large amount of molten metal in the furnace and melted, it is difficult to uniformly disperse the improving element into the molten metal. This is difficult, and even if the molten metal in the furnace is stirred, the amount of the improving element added is extremely small compared to the amount of the molten alloy, so there is a problem that the concentration of the improving element tends to be uneven. Moreover, the added refiner containing the eutectic St improving element partially settles in the holding furnace or floats to the surface of the molten metal, making it no longer effectively utilized. There is also a problem that the yield of improved elements is poor due to oxidation loss.

Furthermore, since these improving elements are easily consumed by oxidation in the molten metal, their improvement durability is short and they are also consumed by degassing treatment. Therefore, as the molten metal retention time elapses, the eutectic S
There was a problem that the improvement effect of i changed. That is,
Although the eutectic Si in the ingot part cast in the early stage of casting is fine, its improvement effect decreases in the late stage of casting.
The problem arises that the eutectic Si becomes coarse and the quality of the product (ingot) changes accordingly.

(Solution Means) The present invention has been made to solve the above problems, and its gist is that a predetermined Al-
When molten Si-based alloy is introduced into a mold device through a casting trough and a predetermined A#-Si-based alloy ingot is continuously cast, a refining agent containing a eutectic St improving element is added to the casting trough. The object is to effectively refine the eutectic Si during solidification of the alloy by continuously adding it to the molten alloy that is guided through the alloy.

(Operation/Effect) That is, in the present invention, the eutectic Si improving element is added to the eutectic or hypoeutectic Aj2-Si alloy molten metal housed in the furnace in an amount corresponding to the total amount of the molten metal. The corresponding amount of eutectic Si improving element was continuously added to a portion of the molten metal that was gradually flowed out from the holding furnace etc. and led to the molding equipment. This makes it possible to uniformly disperse the eutectic Si improving element in the molten Al-Si alloy,
Moreover, the improving elements added to the molten metal can be effectively utilized, and the yield can also be effectively increased.

Furthermore, in the present invention, since the eutectic Si improving element is continuously added to the molten metal immediately before pouring, the eutectic Si refinement effect of the improving element is also greater (and Since the time from addition to casting is also constant,
Unlike conventional methods, the quality of the product does not change between the early and late stages of casting.

(Specific Description of Configuration) Next, the configuration of the present invention will be described more specifically in detail with reference to the drawings.

First, in FIG. 1, numeral 10 is a heat-retaining furnace as a molten metal holding furnace, inside of which there is eutectic or hypo-eutectic Al-S.
A molten i-based alloy (Si content of 14.0% or less) 12 is accommodated. The molten alloy 12 in the heat-insulating furnace 0 is led from the tap 14 to the casting trough 16, and further into the casting trough 16.
6 and is cast into a continuous casting mold device 20 through a supply port 18. As a result, a predetermined eutectic or hypoeutectic Al-Si alloy billet 22 is continuously produced.

The molten alloy 1 guided by the casting gutter 16
According to the present invention, eutectic S such as Na, Sr, Sb, etc.
A refiner containing a t-improving element will be added,
In this example, as shown in FIGS. 2 and 3, it is added to the molten alloy 12 in the form of a rod. That is, the addition rod 26 shown in FIG.
The addition rod 26 shown in FIG. 3 is made of AN-Si-Sr alloy, AN-Si-Sr alloy,
The loft is in the form of intermediate alloys such as Sr alloy, A11-Na alloy, and AN-Sb alloy, or in the form of single Sr and Sb.

The addition rod 26 is wound into a coil as shown in FIG. It is taken out and charged into the molten alloy 15 in the casting trough 16 from its tip side.

The rod 26 inserted into the molten alloy 15 is molten into the molten metal by the heat of the molten alloy 15, so that the improving elements are uniformly distributed in the molten metal 15. The rod 26 is continuously fed into the molten metal 15 according to the flow rate of the molten alloy 15, whereby the improving elements in the addition rod 26 are added to the molten alloy 15 at a predetermined ratio. That will happen.

The addition rod 26 is inserted into the molten metal 15 at such a position that the rod 26 is sufficiently melted into the molten alloy 15 in the casting gutter 16 and the eutectic Si improving element sufficiently exerts its refining effect. A possible location will be selected as appropriate. For example, in the illustrated example, the vicinity of the outlet 14 of the heat retention furnace 10, where the temperature of the molten alloy 15 is relatively high and the residence time until casting is relatively long, is suitably selected as the charging position. There is. However, in the case where a degassing device is provided in the middle of the casting trough 16, if degassing is performed by blowing chlorine gas, the improving elements Na and Sr will be significantly consumed. In such a case, it is desirable to add the rod 26 on the downstream side of the degasser, but in any case, the addition position can be freely selected.

As described above, in the method of this example, a eutectic Si improving element is charged in the form of a rod to the eutectic or hypoeutectic Al1-5i alloy molten metal 15 flowing out of the heat insulating furnace 10, and the eutectic Si improving element is melted. Since it is added step by step and continuously, the yield of the improving element is significantly improved. &8 of improved elements necessary for Kedashi and Insulation Furnace 10
This prevents the improvement elements from settling or floating in the heat insulating furnace 10 and becoming ineffective as a refining agent, unlike in the conventional case where a large amount is added simultaneously and all at once. be.

Furthermore, since the eutectic Si improving element is continuously added to the molten alloy 15 flowing through the pouring channel 16, the improving element is uniformly dispersed in the molten alloy 15, and the molten metal is The concentration of the improving element in molten metal 15 is also appropriate and constant.Moreover, the refiner containing such an improving element is in the form of a rod and added to the molten metal 1 immediately before casting.
Eutectic Si with improving elements to be added to 5
The eutectic S of the Al-Si alloy has a large refinement effect, and the time from when the improving element is added to the molten metal 15 until it is cast into the molding device 20 is always constant.
i is finely refined, and there is almost no difference in the degree of refinement between the early and late stages of casting.

Furthermore, as shown in FIG. 2, by charging the molten alloy 15 with the flux 30 containing improving elements covered with the A1 thin tube 32, heat etc. of the molten alloy 15 can be removed. It is possible to effectively prevent oxidation loss during the addition of improving elements due to their influence, and it is possible to further improve the yield.

Moreover, by adding the refiner containing the eutectic Si improving element to the molten metal in the form of a rod as in this example, depending on the rod size, existing grain refiner adding equipment can be used. There is also the advantage that the amount of the improving element added can be controlled freely and accurately by adjusting the loft diameter, shape, feed rate, etc. Furthermore, the addition rod 26 can be coiled. Since it can be stored in a container, it also has the advantage of being easy to handle.

In addition, when adopting the method of adding the improving element (refining agent) in the form of a rod in the present invention, the type and form of the flux 30 and rod alloy in the loft 26, the rod diameter, shape, feed rate, etc. can be appropriately selected depending on the casting method, casting amount, casting table mold type, distance from the rod addition position to the mold device, etc. Of course, the cross-sectional shape of the rod (26) may be not only circular but also band-like (plate-like) or irregularly shaped.
Furthermore, it is also possible to add it to the molten metal in a discontinuous form, for example in the form of a shot. and,
When using a granular improving element-containing refining agent instead of the rod-shaped addition method, it is also possible to add it in-line using a feeder or the like.

In addition to the specific examples illustrated, the present invention may be implemented in forms in which various modifications and improvements are made based on the knowledge of those skilled in the art without departing from the scope of the present invention. It goes without saying that the scope of the present invention includes such embodiments.

(Example) A/! - When continuously casting billets with a diameter of 254 mm using 8% Si alloy molten metal, S was added as an improving element.
was added in the form of an Aβ-10%Sr alloy.

That is, first, as a conventional method, an experiment was conducted in which the entire amount of Aβ-10%Sr alloy was added to the holding furnace 10 shown in FIG. 1 and casting was performed. On the other hand, in the method of the present invention, an AJ-10%Sr alloy rod (26) with a rod diameter of 1Q mm was used and cast by continuously charging it into the molten alloy 15 as shown in FIG. . In both cases, the amount of Sr added was 0.02%.

Then, regarding the alloy ingots (billet 22) obtained by the above two methods, the Sr addition yield was investigated for the ingots at the early stage of casting and the ingots at the later stage of casting, and the results are shown in Table 1 below. It was shown to. In addition, micrographs (x 1
00) are shown in FIGS. 4(a) to (bl).

Table 1 As is clear from Table 1, according to the method of the present invention, the yield of the eutectic Si improving element (Sr) is greatly improved, and the change is different between the early and late stages of casting. It is observed that there is no such difference, and furthermore, a comparison of the microstructures confirms that according to the method of the present invention, the eutectic Si is effectively refined.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing one embodiment of the present invention, and FIGS. 2 and 3 are cross-sectional explanatory diagrams showing different examples of the addition rod used in FIG. Figures (a) and 4 (bl are micrographs of micro-m weave of ingots according to the conventional method and the method of the present invention obtained in Examples, respectively. LO: Heat retention furnace 12.15: A1-3t system Molten base metal 16: Casting gutter 20: Mold device 22: Billet (ingot) 26: Addition rod 30: Refinement agent (flux) 327A1 Capillary tube Applicant: Sumitomo Light Metal Industries, Ltd. Figure 1 Figure 2 F 6

Claims (2)

[Claims] (1) When introducing a predetermined Al-Si alloy molten metal into a mold device through a pouring gutter to continuously cast a predetermined Al-Si alloy ingot, a refiner containing a eutectic Si improving element is used. A eutectic in an Al-Si alloy, characterized in that the eutectic Si is refined during solidification of the alloy by continuously adding to the molten alloy guided through the casting trough. A method for making Si finer. (2) The refining method according to claim 1, wherein the refining agent is in the form of a rod, and is fed in the longitudinal direction, charged into the molten alloy, and melted.