JPH0313940B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method and apparatus for adding a desired inoculant to molten metal (hereinafter referred to as "molten metal") in centrifugal force casting.

[Prior Art] The addition of an inoculant to molten metal during casting is generally widely practiced, but it is said to be the most popular and most effective for cast iron (including spheroidal graphite cast iron). In other words, adding an inoculant (Fe-Si type, Ca-Si type, etc.) to the molten metal suppresses the generation of cementite, induces the crystallization of primary graphite, and increases the number of graphite eutectic cells, thereby improving the quality of the material. It has a great effect on improving. Research and development on the inoculant itself to be added is active, and there are several reports on the method of adding it. For example, "Inoculant addition device" (Japanese Patent Application Laid-Open No. 1983
120347) and "Method and Apparatus for Adding Inoculant" (Japanese Unexamined Patent Publication No. 59-215247). However, these techniques are all related to so-called static casting, and are difficult to apply to centrifugal casting.

Methods (and devices) for adding inoculants to centrifugal casting can be broadly classified into two conventional methods. In FIGS. 2 and 3, a long cylindrical mold 12, which is rotated at high speed by the operation of a centrifugal casting machine 11, approaches a ladle 13 and extends relatively into the mold. A pouring gutter 5 with a diameter of 100 mm is inserted, and the tip of the gutter reaches near the rear end of the mold, the ladle 13 is tilted, and the molten metal is poured into the mold through the pouring gutter.

Among the conventional methods of adding inoculant, one is to add the inoculant stored in a container 1a to the molten metal using a vibrating feeder or screw feeder near the starting end of the pouring gutter, as shown in Fig. 2. It is sprayed on the surface and flows down a long pouring gutter to the tip of the gutter.

In another conventional example, as shown in FIG. 3, the inoculant cut out from the container 1b into the hopper 2b is guided by pressure air fed from the outside through a thin tube 4b attached along the pouring gutter. The liquid is ejected from the blow-off nozzle 6b at the tip toward the casting surface. In this case, the usual method is to insert an even thinner inner tube 14 into the thin tube 4b and allow the primary pressure air to pass through the inner tube, or conversely, to pass the primary pressure air through the thin tube 4b and fill the inner tube 14 with powder. There is a method of transportation.

Furthermore, when the diameter of the casting tube is large, it is also possible to construct a screw feeder built in a thin tube attached to the pouring gutter to convey the inoculant to the tip.

[Problem to be solved by the invention] Let us consider the prior art example listed above. The method of spraying the inoculant at the starting point where the ladle is tilted and the molten metal is transferred to the pouring gutter as in the first example has the advantage of being easy to operate and simplifying the equipment, but the inoculation effect is not immediately effective after treatment. is the largest, and the phenomenon of the inoculation effect disappearing (usually referred to as ``fading''), which weakens over time, cannot be ignored. Particularly in the case of spheroidal graphite cast iron, this poses a major problem in terms of quality control. Although slight fading occurs while pouring down the long pouring gutter (for 3 to 5 seconds), it is a sign of casting defects (breaks, melting holes, spills, etc.), especially if the inner surface of the mold is not coated. etc.) This results in a reduction in the effectiveness of the substance added for prevention purposes.

The second example has no problem in terms of inoculation effect, but has a problem in transporting the inoculant within the tubule. As mentioned above, since the gap between the thin tube and the inner tube inserted therein must become narrow, there is a great concern that the inoculant will become clogged near the supply port. In addition, if the pressure of the air is increased to prevent this, the force of the air flying from the blowing nozzle is strong, causing the coating on the inner surface of the mold to peel off, and this scattering reduces the effective yield of melting into the molten metal. The problem is that it significantly degrades the working environment.

For example, if the conventional thin tube length is 5 m (this is the conventional technology for normal centrifugal cast iron tubes)
If the additive is not sent under a pressure of at least 3 kg/cm ² , it will almost certainly be Fe, which has a high specific gravity.
- Problems such as Si and other substances clogging the pipes were unavoidable.

However, from the point of view of the molten metal receiving the addition, if it is directly hit by an air jet without protection, the more violent the jet, the more the molten metal will scatter, and it will be exposed to severe oxidation, which will deteriorate the quality of the product. There is a high concern that it may cause

Several technical means can be considered to solve this problem, but for example, in Fig. 4 of JP-A-55-70458, inoculant powder is filled in a metal hoop, avoiding the feeding of additives by air. The wire is inoculated by being fed while contacting the molten metal along the molten metal path from the pouring ladle to the inner surface of the centrifugal casting mold.

It is true that this method can prevent the oxidation effect due to molten metal scattering, but it requires some additional equipment and work requirements.

In addition, it is difficult to convey the inoculant by incorporating a screw feeder inside the capillary tube without using pressurized air, and it is difficult to apply it to cast tubes with small diameters. It was twisted and could not be used for practical purposes.

In order to solve the above-mentioned problems, the present invention is capable of adding an inoculant for centrifugal casting that does not impair the inoculum effect, can be applied to small diameter casting pipes, and has fewer troubles associated with addition. The purpose is to provide a method and apparatus.

[Means for Solving the Problems] The inoculant addition method for centrifugal force casting according to the present invention involves transporting the inoculant in fixed amounts at a time by low static pressure to the starting end of a thin tube attached to a pouring gutter; By injecting low dynamic pressure in the direction of movement within the capillary and adding it to the molten metal from the tip of the capillary, and by keeping the total of the static pressure and dynamic pressure at a maximum of 1.5 kg/cm ² or less, the above-mentioned effect can be achieved. Solved the problem.

In addition, the devices used only for carrying out this method include a thin tube that is attached to the pouring gutter and opens a blow-out nozzle near its tip, an airtight container that stores the inoculant, and a fixed amount of the inoculum that is cut out from the airtight container. A pressurized air source that evenly pressurizes both sealing members is connected to the sealed hopper, and the sealed hopper and the thin tube are connected by a flexible tube with a relatively large diameter. disclosed a configuration in which a secondary pressure air outlet is opened to direct in the direction of flow of flowing air.

[Operations and Examples] For convenience, the operations of the present invention will be described through a description of the device.

FIG. 1 shows an embodiment of the device of the present invention, in which a closed container 1 for storing an inoculant and a closed hopper 2 are juxtaposed, and a quantitative cutting device 3 (in this example) is used to supply the inoculant from the container to the hopper in fixed amounts. The two are connected by the Scryufida). Static pressure is applied equally to the sealed container 1 and the sealed hopper 2. Specifically, an air supply pipe 7 connected to a pressure air source (not shown) is opened to the sealed hopper, thereby bypassing the sealed container and the sealed hopper. They are connected with a tube 8 to maintain equal pressure.

The pressurized air is usually compressed air, but other gases, such as inert gases, may be used depending on the purpose.

This pressurized air uniformly pressurizes both containers and applies static pressure to the additives moving between them, leading them from the closed hopper 2 to the flexible tube 9 having a relatively large diameter. Although the pressure of the air is much lower than in the past, since the diameter of the flexible tube is large, the additive moves through the tube without clogging on the way, and reaches the starting end of the thin tube 4 attached to the pouring gutter 5. Since the diameter of the thin tube is small, there is a high probability that it will get clogged midway due to the static pressure that has been pressurized up to this point. This increases the force and allows it to be delivered to the tip without clogging.

Although the pressure of the secondary air itself is much lower than in the past, it works effectively because the inner diameter of the thin tube is small, achieving air transport that effectively utilizes the entire cross-sectional area of the tube.

Therefore, when the additive is discharged from the nozzle 6 at the tip of the thin tube, ideally it is desirable that the energy of the conveying air be completely used up and be close to zero, but in practice In order to convey long thin tubes, it is necessary to suppress the total static pressure and dynamic pressure to 1.5Kg/ ^cm2 .
More specifically, for example, good results can be obtained by setting the static pressure to 0.7Kg/cm ² and the dynamic pressure to 0.8Kg/cm ² which is 0.1Kg/cm ² higher than this, and in the best example, the static pressure is 0.3Kg/cm 2 .
Kg/cm ² , dynamic pressure 0.4 Kg/cm ² , total expulsion of the additive at the tip of 0.7 Kg/cm ² was recorded.

Since the device of the present invention has such a configuration and function, a method is realized in which the inoculant powder is jetted out in a constant amount at low pressure near the tip of the pouring gutter and added to the molten metal.

[Effects of the Invention] As described above, the present invention sprays a fixed amount of inoculant in a low-pressure air stream from the tip of the pouring gutter in a closed state. Since this transports the powder using the entire cross-sectional area of the capillary, it is possible to reach the tip without clogging the pores at a much lower pressure in a capillary with a much smaller diameter than in conventional techniques. Therefore, this method can also be applied to the manufacture of small diameter cast pipes, which has not been possible in the past. Low-pressure powder ejection at the tip of the pouring trough can solve several conventional problems. In particular, it prevents the occurrence of causes that lead to product defects, such as scattering of molten metal, oxidation due to turbulent flow, and contamination of nonmetallic inclusions. Furthermore, since the structure is in a sealed state, the working environment is improved and work safety is also increased, which is a unique effect.

[Brief explanation of drawings]

FIG. 1 is a front view of an embodiment of the device of the present invention, and FIGS. 2 and 3 are front views showing different conventional techniques.
FIG. 4 is a perspective view showing still another conventional technique. 1... Sealed container, 2... Sealed hopper, 3... Fixed amount cutting device, 4... Thin tube, 5... Pouring gutter, 6
... Blowout nozzle, 7 ... Air supply pipe, 8 ... Bypass pipe, 9 ... Air supply pipe, 10 ... Second air supply pipe,
...Inoculant.

Claims (1)

[Claims] 1. A long pouring gutter is inserted into a long cylindrical mold that rotates at high speed, and molten metal is poured into the mold through the pouring gutter and the molten metal is poured into the mold. In the centrifugal force casting inoculant addition method, in which the desired inoculum powder is added to the pouring trough, the inoculant is conveyed in a fixed amount at a time by low static pressure to the starting end of a thin tube attached to a pouring gutter, and then An inoculant for centrifugal casting, characterized in that it is added to the molten metal from the tip of a thin tube by increasing the injection force in the direction of movement, and that the total of the static pressure and dynamic pressure remains at a maximum of 1.5 Kg/cm ² or less. Addition method. 2. Consists of a thin tube that is attached to the pouring gutter and opens a blow-out nozzle near its tip, an airtight container that stores the inoculant, and an airtight hopper that receives the inoculum by cutting out a fixed amount of the inoculant from the airtight container. A pressurized air source that evenly pressurizes the inside of the sealing member is connected to the sealing hopper, the sealing hopper and the thin tube are connected by a flexible tube with a relatively large diameter, and a second tube is provided in the middle of the thin tube pointing in the direction of flow of air. An inoculant addition device for centrifugal casting, characterized by an open spout for subpressure air.