JP5455008B2 - Centrifugal casting method - Google Patents

Description

  The present invention relates to a horizontal centrifugal casting method in which a molten metal based iron is cast into a casting mold that rotates about a horizontal axis.

  When manufacturing relatively long hollow castings such as cast iron pipes, a pouring tub is inserted from one end into a cylindrical casting mold that rotates around a horizontal axis, and these casting molds and castings are poured. The hot metal is moved relative to the axial direction, the molten metal is poured from the pouring bath, and the molten metal is cast from one end to the other using the centrifugal force on the inner peripheral surface of the casting mold. A horizontal centrifugal casting method is often employed (see, for example, Patent Document 1).

  In such a horizontal centrifugal casting method, in order to protect the casting mold from the molten iron-based metal at high temperature, a slurry-like coating solution in which powdered refractory material such as graphite, silica sand and diatomaceous earth is dissolved in water is used. Wet spray coating method that coats the inner surface of the mold in advance (see, for example, Patent Document 2), and a powdered inoculant such as ferrosilicon from a nozzle attached to a pouring bath that moves relative to the casting mold, A dry coating method (see, for example, Patent Document 3) in which the molten metal is sprayed and coated on the inner surface of the mold on the front side where the molten metal is poured is often employed. The dry coating method has an advantage that the casting material can be stabilized by the inoculation effect of the inoculum.

JP 2006-150432 A Japanese Patent No. 2555236 Japanese Patent Publication No.7-115145

  The centrifugal casting method employing the wet spray coating method described in Patent Document 2 can protect the casting mold from the molten metal by a refractory material pre-coated on the inner surface of the mold, but before the casting process. Since a separate coating process and drying process are required, there is a problem that production efficiency is inferior.

  On the other hand, the centrifugal casting method adopting the dry coating method described in Patent Document 3 coats the inoculum on the inner surface of the mold while casting, so the production efficiency is excellent, but ferrosilicon (Fe-Si) Inoculants such as heat resistance is inferior to refractory materials and has high thermal conductivity, so the casting mold cannot be adequately protected from the molten metal, and the mold tends to wear out due to the occurrence of cracks etc. There is a problem that the cooling rate at the time of casting is increased and casting defects such as hot water boundaries and pinholes are likely to occur. When cracks occur in the mold, the production efficiency is reduced due to the repair.

  Accordingly, an object of the present invention is to provide a horizontal centrifugal casting method that can ensure excellent production efficiency and can sufficiently protect the casting mold from the molten metal and suppress the occurrence of casting defects.

In order to solve the above-mentioned problems, the present invention pours molten iron metal into a cylindrical casting mold rotating around a horizontal axis while moving in the axial direction of the casting mold, and centrifugal force In a centrifugal casting method in which a molten metal is cast on the inner peripheral surface of the casting mold using a powder, a powdered refractory material having a melting temperature higher than the casting temperature of the molten metal is sprayed on the inner surface of the casting mold, spraying, simultaneously with the pouring of the molten metal, and to adopt a method of performing the casting mold inner surface of the front casting the molten metal while moving the pouring same said axial simultaneously and.

  That is, before casting the molten metal, it is possible to ensure excellent production efficiency by spraying a powdery refractory material having a melting temperature higher than the casting temperature of the molten metal on the inner surface of the casting mold, and Fully protected from the molten metal, it was possible to suppress the occurrence of casting defects.

The casting temperature of the molten iron-based metal is about 1350 ° C. or less, and as a refractory material having a higher melting temperature, alumina (Al ₂ O ₃ ), magnesia (MgO), molybdenum silicide (MoSi ₂ ), Forsterite (2MgO.SiO ₂ ), titanium carbide (TiC), zircon (ZrO ₂ .SiO ₂ ) and the like can be mentioned.

Insert a pouring bath for pouring the molten metal into the casting mold from one end side, and move the casting mold and the pouring bath relative to each other in the axial direction so that one end side and the other end side of the casting mold. The molten metal is poured from one of the above to the other side, and moved relative to the casting mold in the axial direction together with the molten metal and moved simultaneously in the same axial direction as the molten metal poured , A refractory material spraying means for spraying the refractory material on the inner surface of the casting mold is provided, and the refractory material is sprayed on the inner surface of the casting mold before casting the molten metal on the side before the molten metal is poured. Thus, the refractory material can be efficiently dispersed on the inner surface of the casting mold before casting the molten metal.

  By mixing the powdery refractory material with an inoculum and spraying the refractory material mixed with the inoculum on the inner surface of the casting mold, the casting material can be stabilized by the inoculation effect of the inoculum. .

  The mixing ratio of the refractory material is 2% by mass or more, preferably 5% by mass or more. This is because if the mixing ratio of the refractory material is less than 2% by mass, the mold protection effect of the refractory material cannot be sufficiently expected.

  By making the refractory material have a specific gravity greater than that of the inoculum, the refractory material having a higher specific gravity is segregated to the outer peripheral side by centrifugal force, increasing the protective effect of the mold, It can be segregated to the side and brought into contact with the molten metal to increase the inoculation efficiency.

  The refractory material may be alumina. Alumina can be obtained relatively inexpensively.

  In the centrifugal casting method according to the present invention, the powdered refractory material having a melting temperature higher than the casting temperature of the molten metal is sprayed on the inner surface of the casting mold before casting the molten metal. The casting mold can be sufficiently protected from the molten metal and the occurrence of casting defects can be suppressed.

Schematic notched front view showing a centrifugal casting apparatus employing a centrifugal casting method according to the present invention Sectional drawing which expands and shows the principal part of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a centrifugal casting apparatus employing a centrifugal casting method according to the present invention. This centrifugal casting apparatus is of a horizontal type that casts a ductile cast iron pipe. A cylindrical casting mold 1 is supported by a pair of rotary drive rollers 2 and rotates at a high speed around a horizontal axis. The ladle 3 is supplied with, and the molten metal A is introduced from the ladle 3 and the pouring rod 4 inserted into the casting mold 1 from one end side is moved in the axial direction of the casting mold 1 by the traveling carriage 5. It is supposed to be. Further, a refractory material spraying pipe 6 as a refractory material spraying means is arranged in parallel on the side of the pouring tub 4 so as to move in the axial direction together with the pouring tub 4.

The refractory material spray pipe 6 is connected to a pressure tank 8 through a flexible hose 7. The pumping tank 8, powdered alumina as refractory material (specific gravity: about 3.97 g / cm ³⁾ and, ferrosilicon as inoculant: Mixture B is determination of a (specific gravity of about 2.20 g / cm ³⁾ While being supplied from the feeder 9, compressed air C is supplied from the supply pipe 10, and the mixture B is sprayed from the nozzle 6a at the tip of the refractory material spray pipe 6 by air conveyance.

As shown by the arrows in FIG. 1, when casting the ductile cast iron pipe, the casting carriage 1 travels to the left of the casting mold 1 axial direction in which the traveling carriage 5 moves backward from the casting mold 1. Molten metal A is poured from the tip of the pouring tub 4 inserted into the casting duct, and a ductile cast iron pipe is cast from the right back side of the casting mold 1 toward the left front side. In this embodiment, the axial position of the casting mold 1 is fixed, and the pouring tub 4 is moved in the axial direction by the traveling cart 5. However, the axial position of the pouring tub 4 is fixed and the casting mold 1 is cast. The mold 1 may be moved in the axial direction.

As shown in an enlarged view in FIG. 2, the nozzle 6 a of the refractory material spray pipe 6 is provided at a position slightly retracted from the tip of the pouring tub 4 and is arranged side by side on the side of the pouring tub 4. when the Chuyutoi 4 to pouring the molten metal a with retraction to the left, at the same time as the pouring to the inner surface of the casting mold 1 of the front side while moving simultaneously pouring the same direction of the molten metal a A mixture B of alumina and ferrosilicon is dispersed. At this time, the mixture B sprayed on the inner surface of the casting mold 1 rotating at high speed segregates alumina having a large specific gravity toward the outer peripheral side and ferrosilicon having a small specific gravity toward the inner peripheral side due to centrifugal force. Therefore, the inner surface of the casting mold 1 is sufficiently protected from the molten metal A by alumina segregating to the outer peripheral side, and ferrosilicon segregating to the inner peripheral side is efficiently inoculated into the molten metal A.

  A ductile iron pipe was cast using the centrifugal casting apparatus described above. The mixing ratio of alumina as the refractory material in the mixture B was 10% by mass. As the alumina, powdered sintered alumina was used, and the particle size was 325 mesh or less. The bulk specific gravity of this powdery alumina is 3.62.

  The ductile cast iron pipe was cast repeatedly with the same casting mold 800 times, and the inner surface of the mold after use and the casting defect of the cast ductile cast iron pipe were examined. As a result, no wear such as cracks was observed on the inner surface of the mold, and almost no casting defects were found in the ductile cast iron pipe. From the above results, it was confirmed that the centrifugal casting method according to the present invention can sufficiently protect the inner surface of the casting mold from the molten metal, extend the repair period, and suppress casting defects. It was confirmed that the material of the ductile cast iron pipe was also stabilized.

  Further, when the mixing ratio of alumina in the mixture B was set to 2% by mass, the same casting was performed, but there was no problem with the wear of the mold and the casting defect of the ductile iron pipe, and a good casting result was obtained. It was. This is because the heat insulation effect on the mold by alumina is reduced and fine cracks are likely to occur on the inner surface of the mold, but the fine powdery alumina gets into the fine cracks and the inner surface of the mold is smoothed. It was considered that the cast iron pipe was not affected, and the cast iron pipe after casting could be smoothly pulled out from the mold.

  In the above-described embodiment, the inoculant is mixed and dispersed in the powdered refractory material, but only the refractory material can be dispersed. In this case, the inoculum can be mixed in the molten metal of the pouring bath.

DESCRIPTION OF SYMBOLS 1 Casting die 2 Rotation drive roller 3 Ladle 4 Pouring pot 5 Traveling cart 6 Fireproof material spray pipe 6a Nozzle 7 Flexible hose 8 Pressure feed tank 9 Metering feeder 10 Supply pipe

Claims (6)

The molten metal (A) is poured into the cylindrical casting mold (1) rotating around the horizontal axis while moving in the axial direction of the casting mold (1), and centrifugal force is used. In the centrifugal casting method in which the molten metal (A) is cast on the inner peripheral surface of the casting mold (1), a powder form having a melting temperature higher than the casting temperature of the molten metal (A) on the inner surface of the casting mold (1). The refractory material is sprayed, and the spraying is performed simultaneously with the pouring of the molten metal (A) and before the molten metal (A) is cast while simultaneously moving in the same axial direction as the molten metal. (1) A centrifugal casting method characterized by being performed on the inner surface. A pouring tub (4) for pouring the molten metal (A) into the casting mold (1) is inserted from one end, and the casting mold (1) and the pouring tub (4) are relative to each other in the axial direction. The molten metal (A) is poured from one end side or the other end side of the casting mold (1) to the other side, and the casting mold (4) is axially cast together with the pouring bath (4). Refractory material spraying means (6) which moves relative to the mold (1) and simultaneously moves in the same axial direction as the pouring of the molten metal (A), and sprays the refractory material onto the inner surface of the casting mold (1). 2) and the refractory material is sprayed on the inner surface of the casting mold (1) before casting the molten metal (A) on the side before the molten metal (A) is poured. The centrifugal casting method described in 1.   The centrifugal casting according to claim 1 or 2, wherein the powdery refractory material is mixed with an inoculum, and the refractory material (B) mixed with the inoculum is sprayed on the inner surface of the casting mold (1). Method.   The centrifugal casting method according to claim 3, wherein the mixing ratio of the refractory material (B) is 2 mass% or more.   The centrifugal casting method according to claim 3 or 4, wherein the refractory material (B) has a specific gravity greater than that of the inoculum.   The centrifugal casting method according to claim 1, wherein the refractory material is alumina.

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