JPH038546A - Centrifugal casting method - Google Patents

Abstract

PURPOSE:To solidify molten metal with directional solidification, to push out impurity onto inner surface and to cast a sound product by injecting cooling fuid on outer surface of a mold while rotating the mold to execute casting while forcedly cooling the mold. CONSTITUTION:The molten metal is poured in the mold 1 and the cooling fluid is injected from each nozzle 4 while rotating the mold 1 at high velocity. At this time, the cooling fluid made to collid to the outer surface of the mold 1 under condition of making fine water drips with compressed air, is instaneously made to steam with heat of vaporization by conducting the heat of the mold 1 to effectively cool the mold 1. Therefore, excessive temp. raising of the mold 1 is restrained, and even if the thickness of the mold 1 is not thick, the rigidity, which can bear to high velocity, is given, and also solidification of the molten metal layer in the mold 1 is progressed from outer layer side to inner layer side and impurity contained in the molten metal is pushed out onto the inner surface in the molten metal layer and accumulated. After casting, the inner surface of casting tube body is machined to manufacture the sound product.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a centrifugal casting method.

(Prior art and its problems) As is well known, in the horizontal centrifugal casting method, a cylindrical mold is rotatably supported in a substantially horizontal position, molten metal is poured into the mold from the end of the mold, and the mold is rotated at high speed. The pipe body is formed by solidifying the molten metal.

In the centrifugal casting described above, directional solidification of the molten metal layer is established. Directional solidification in this case means that the solidification of the molten metal layer within the mold progresses from the portion that is in contact with the inner surface of the mold, that is, from the outer surface side of the molten metal layer toward the inner surface side.

Due to the above-mentioned directional solidification, the impurities contained in the molten metal are successively pushed out to the inner surface of the molten metal layer, and at the end of solidification, no segregation or shrinkage occurs in the wall thickness of the cast pipe, and the impurities are pushed out inside the cast pipe. It will accumulate on the surface.

After casting is complete, the inner surface of the cast tube is milled to remove impurity build-up, thereby producing a sound product.

When solidification progresses from both the outer and inner surfaces of the molten metal layer,
Impurities accumulate inside the cast product, causing segregation, and shrinkage is present, and unless the inner surface of the cast tube body is cut and removed to a considerable thickness, it will not be a sound product and the yield will be reduced.

Conventionally, in order to achieve directional solidification of the molten metal layer, the thickness of the mold was increased to increase the heat removal effect, but since it was a natural cooling method, the cooling rate was slow and the molten metal layer was drawn from the inner surface side. It was not possible to sufficiently suppress coagulation.

Additionally, if the wall thickness of the mold is thin, the temperature of the mold will rise excessively during the casting process, reducing its rigidity and causing vibration during rotation, which is dangerous, so it is necessary to increase the wall thickness of the mold. there were.

The present invention provides centrifugal casting that can effectively solidify the molten metal layer in the mold from the outer surface to the inner surface without increasing the wall thickness of the mold by forcibly cooling the rotating mold. It clarifies the law.

(Means for Solving the Problems) The centrifugal casting method of the present invention cools the mold (1) by injecting cooling fluid onto the surface of the mold (1) from outside the mold (1) while rotating the mold. It is characterized by performing casting.

(Functions and Effects) Since the mold (1) is forcibly cooled by the cooling fluid, excessive temperature rise of the mold (1) is suppressed.

Therefore, sufficient rigidity to withstand the high-speed rotation of centrifugal casting can be provided without increasing the wall thickness of the mold (1).

As mentioned above, the mold (1) is forcibly cooled with cooling fluid.
) removes heat from the molten metal layer in the mold (1) sequentially from the outer layer, solidifying the molten metal layer from the outer surface side to the inner surface side, and due to this directional solidification, impurities contained in the molten metal are sequentially removed from the molten metal. The impurities are extruded to the inner surface side of the layer, and at the end of solidification, no segregation or shrinkage occurs in the wall thickness of the cast tube, and impurities are accumulated on the inner surface of the cast tube.

After casting is complete, simply by shallowly cutting the inner surface of the cast tube, the accumulation of impurities can be removed, and a product with a high slug and a healthy product can be manufactured.

(Example) A cylindrical mold (1) of a horizontal centrifugal casting device is rotatably supported horizontally by a rotation support roller (not shown), and is connected to a rotation drive device (not shown).

A plurality of injection nozzles (4) are arranged on the outside of the mold (1) at equal intervals along the axial direction of the mold (1) with their tips facing the mold (1).

Each injection nozzle (4) is arranged perpendicularly to the axis of the mold (1) in the same plane that includes the axis of the mold (1), and each injection nozzle (4) has a fan-shaped souboulet pattern P. Inject cooling fluid.

The cooling fluid of the embodiment is one in which water is injected together with pressurized air in the form of as fine water droplets as possible.

The reason for this is that the finer the water droplets, when they collide with the outer surface of the mold, the shorter the time it takes to absorb the heat of the mold and turn into steam, preventing the formation of a film of water on the mold surface and allowing the cooling fluid to cool. This does not prevent continuous direct collision with the mold surface and improves cooling efficiency.

If you simply drop a water shower onto the mold, a film of water will form on the surface of the mold, preventing the low-temperature water that drops one after another from coming into direct contact with the mold surface. When the water is turned into fine droplets and sprayed onto the surface of the mold, the cooling efficiency is low.

The outer diameter of the mold (1) is approximately 800 mm, the effective length (product length) is approximately 3500 mm, the arrangement pitch of the nozzles (4) is approximately 1000 mm, from the surface of the mold (1) to the tip of each nozzle (4). The distance is approximately 300 mm.

When the cooling fluid is injected from each nozzle (4), the injected cooling fluid impinges on the surface of the cooling mold (1) in the form of one narrow band extending in the axial direction.

Thus, the molten metal is poured into the mold (1) from the pouring hole (21) of the end plate (2) of the mold (1), and cooling fluid is injected from each nozzle (4) while rotating the mold (1) at high speed. .

The cooling fluid that collides with the outer surface of the mold in the form of fine water droplets by the pressurized air takes away the heat of vaporization from the mold and instantly turns into water vapor, effectively cooling the mold.

Since the mold (1) is forcibly cooled by the cooling fluid, excessive temperature rise of the mold (1) is suppressed. Therefore, without increasing the wall thickness of the mold (1), it is possible to provide the necessary and sufficient rigidity to withstand the high-speed rotation of centrifugal casting.

As mentioned above, the mold (1) is forcibly cooled with cooling fluid.
) removes heat from the molten metal layer in the mold (1) sequentially from the outer layer, solidifying the molten metal layer from the outer layer side to the inner layer side, and due to this directional solidification, impurities contained in the molten metal are sequentially removed from the molten metal layer. At the end of solidification, no segregation or shrinkage occurs in the wall thickness of the cast tube, and impurities are accumulated on the inner surface of the cast tube.

After casting is complete, the inner surface of the cast tube is milled to remove any impurity build-up, resulting in a healthy product.

The present invention is not limited to the configuration of the above embodiment,
Various modifications are possible within the scope of the claims.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the implementation status of the present invention, Figure 2 is Figure 1 ■
It is a cross-sectional view along the -■ line.

Claims (1)

[Scope of Claims] [1] In a centrifugal casting method in which a molten metal is poured into the mold from the end of a cylindrical mold and the mold is rotated at high speed to form a tube body, while the mold (1) is being rotated, A centrifugal casting method characterized by performing casting while forcibly cooling the mold by injecting cooling fluid onto the outer surface of the mold. [2] The centrifugal casting method according to claim 1, wherein the cooling fluid is a mixture of pressurized air and water, and is injected as fine water droplets.