JPH08108263A - Reduced pressure casting method of wire drum and wire drum - Google Patents

Abstract

(57) [Summary] [Purpose] A wire drum that is tough and has excellent dimensional accuracy
To propose a casting technology that can be manufactured as an integrally cast product without using mechanical cutting or the like. [Structure] A sand mold is embedded in foundry sand 4 filled in a decompression container 2 of an upper open type, and cast iron treated with a graphite spheroidizing agent and an inoculant is filled in a casting space in the sand mold under suction decompression condition. By pouring the molten metal and solidifying it, an integrally cast product made of non-cutting spheroidal graphite cast iron is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for vacuum casting a wire drum and a wire drum, and more particularly to a technique for manufacturing a wire drum which is tough and has excellent dimensional accuracy as an integrally cast product without mechanical cutting or the like. .

[0002]

2. Description of the Related Art In general, a wire drum supports a heavy load through a rope and therefore needs to be strong. This wire drum is conventionally manufactured by finishing the shape of the wire drum after casting, particularly by finishing the complicated winding portion of the rope winding portion by mechanical cutting or the like. Therefore, the wire drum manufactured by such a method has a drawback that the cost is high.

In order to overcome such drawbacks, by taking advantage of the characteristics of cast iron, which has a low melting temperature and excellent fluidity, and has a very small shrinkage at the time of solidification, a wire is formed as an integrally cast product without mechanical cutting or the like. A method of manufacturing the drum is conceivable. That is, this method combines the main mold and the core, and the core and the core model (wooden mold), and pours the molten metal into the sand mold that forms a casting space of the same shape as this product and solidifies it. This is a method of casting a wire drum.

[0004]

However, in such a casting method: The gas contained in the molten metal is released during solidification,
Defects such as blowholes and pinholes occur in castings. . When casting a casting having a thin-walled portion, the gas in the mold is pushed into the thin-walled portion and does not escape to the outside of the mold, and as a result, there is a defect called "poor hot water" in which hot water does not flow to the thin-walled portion. . During pouring, steam and other gases generated from the mold and gas pushed into the mold do not escape to the outside of the mold and resist the pouring pressure, so the sand mold partially expands and the casting product partially Various defects such as “tension” that swells in the inside occur. Therefore, the dimensional accuracy of the cast product is poor, and it is difficult to secure the roundness, especially for circular cast products such as wire drums.Therefore, it is essential to finish the wire drum cast by this method such as machine cutting. Met. further,
This method has a problem that even if it can be commercialized, it causes white pig iron in a thin portion, particularly in a winding portion having a complicated shape, and the mechanical strength of the thin portion is lowered. That is, the wire drum produced by this method has a fatal defect that the toughness, which is an essential characteristic, is not sufficient.

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and in particular, proposes a casting technique for manufacturing a wire drum, which is tough and has excellent dimensional accuracy, as an integrally cast product without mechanical cutting or the like. To do.

[0006]

Means for Solving the Problems As a result of intensive research aimed at achieving the above-mentioned objects, the inventors have focused on spheroidal graphite cast iron as a means for compensating for insufficient strength (toughness), and have carried out vacuum casting as means for eliminating defective casting. I focused on. That is, the sand mold is further embedded in the foundry sand, and the cast iron that has been treated and improved with the melt treatment agent while gently and uniformly depressurizing the gas inside the sand mold is cast, preferably as the sand mold. By performing vacuum casting using a sand mold constrained by a metal frame provided with a plurality of gas suction holes in place, it was found that the above-mentioned various drawbacks can be solved, and the contents of the following are the subject matter of the wire drum A new vacuum casting method was completed.

That is, according to the present invention, (1) a sand mold is buried in a molding sand filled in a decompression container of an upper open type, and a graphite spheroidizing agent and inoculation are applied to a casting space in the sand mold under suction decompression condition. It is a vacuum casting method for a wire drum, characterized in that an integrally cast product made of spheroidal graphite cast iron is obtained by pouring and solidifying cast iron treated with the agent. (2) In the invention described in (1) above, the sand mold is a sand mold in which a casting space having the same shape as the casting member is formed by shell sand, and further, a metal frame having a plurality of gas suction holes formed at appropriate places It is preferable that it is constituted by a member constrained from. (3) In the invention described in (1) or (2) above, the treatment with the inoculant is the primary inoculation in which the Bi-based inoculant is added to the molten metal immediately after the ladle is discharged, and the Fe-Si-based inoculant. It is preferable that the method comprises a secondary inoculation in which is added to the pouring flow when pouring into the sand mold. (4) And, as a wire drum manufactured by the above reduced pressure casting method, the present invention is a wire drum in which a rope winding portion is formed by connecting peaks and troughs in a body peripheral portion, a non-cutting type spherical graphite. We propose a wire drum that is an integrally cast product made of cast iron.

[0008]

[Function] In the conventional vacuum casting method, the pressure in the mold is reduced,
This is a casting method in which the molten metal is injected into the mold by atmospheric pressure to cast. By casting a wire drum having a winding portion of a complicated shape by this casting method, the thin space of the sand mold is decompressed, so that defects such as mixing of sand into the casting product, deformation of the mold, and insertion are caused. It caused the problem of being easy. Even if such a defect does not occur, the pressure inside the sand mold is reduced so that a dimensional change or the like is likely to occur. Therefore, for the wire drum reduced pressure cast by this conventional method, machining such as mechanical cutting was indispensable. .

On the other hand, according to the present invention, the entire sand mold is further embedded in foundry sand, and the cast iron is poured and solidified while performing gentle and uniform vacuum suction of the sand mold through the foundry sand. The point is characteristic. As a result, it is possible to reduce the pressure evenly in the sand mold, particularly in the casting space, under favorable conditions, so that defects such as sand inclusion, mold collapse, and insertion into the casting product (wire drum), and further casting product A wire drum having excellent dimensional accuracy can be stably vacuum-deposited as an integrally cast product without causing defects such as partial "bulging".

In particular, in order for the above effects to work effectively, the sand mold is a sand mold in which a casting space having the same shape as the casting member is formed by shell sand, and a metal frame in which a plurality of gas suction holes are formed at appropriate positions. It is preferable that it is constituted by a member constrained from the outside.

Furthermore, the present invention is an integrally cast article made of spheroidal graphite cast iron by pouring and solidifying cast iron, which has been treated and improved with a melt treating agent of a graphite spheroidizing agent and an inoculant, into a casting space in a sand mold to solidify the cast iron. Is characterized in that As a result, it is possible to effectively prevent white pig iron formation, particularly in a thin portion of the cast product, and to stably perform reduced pressure casting of a wire drum having excellent toughness.

The reason why the cast iron treated with the graphite spheroidizing agent and the inoculant is used is to replace the ordinary cast iron with the spheroidal graphite cast iron so as to improve the mechanical properties, and to inoculate the white pig iron. This is because it is possible to prevent it and obtain a material having excellent toughness.

Particularly, the treatment with the above-mentioned inoculant is performed by the primary inoculation in which the Bi-based inoculant is added to the molten metal immediately after the ladle is discharged,
It is preferably composed of a secondary inoculation in which the e-Si-based inoculant is added to the pouring flow when pouring into the sand mold. The reason why the double inoculation method is adopted in this way is to maintain the effect of inoculation, prevent white pig iron, and obtain a uniform spheroidal graphite cast iron structure to obtain a material having excellent toughness.

Since the graphite spheroidizing agent and the Bi-based inoculant are added to the ladle, the treatment amount of these is such that the Bi-based inoculant has a Bi content of 0.1 to 0.2% and the graphite spheroidizing agent has a Bi content of 0.1 to 0.2%. Since it is 0.3 to 0.5%, it is desirable that the amount of Bi added to the total molten metal in the ladle be 0.005 to 0.010%. In particular, in the case of graphite spheroidizing agent, if 1.5% is added to the total melt in the ladle, the Mg content is about 5.2% and the yield in the ladle is 70-80%. After all, the residual Mg in the total molten metal in the ladle was 0.030 to 0.06.
It becomes 0%. Further, in the case of the Fe-Si inoculant, the granular inoculant is directly inoculated into the pouring flow, so 0.05 to 0.
Addition of 2% is desirable.

As described above, according to the present invention, the cast iron treated with the graphite spheroidizing agent and the inoculant spreads to every corner including the thin portion of the wire drum, and the gas in the sand mold at the time of pouring is also increased. Since it is evenly discharged outside the frame, it is stable and pressure-reduced as a one-piece cast wire drum made of sound spheroidal graphite cast iron, which has excellent toughness without causing white pig iron and has excellent dimensional accuracy that does not require cutting. can do.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of an elevator wire drum cast in this example, and FIG. 2 is a diagram showing the dimensions and required accuracy of a rope winding portion provided on the body peripheral portion of the wire drum. That is, the wire drum to be cast is
The rope winding part has a narrow tip of 1.4 mm, and the roundness from the center is ± 1 mm, which is a tight tolerance product.

FIG. 3 is a schematic sectional view showing an example of a vacuum casting apparatus used in the method of the present invention. That is, this reduced pressure casting apparatus is a casting apparatus including a reduced pressure container 2 filled with the molding sand 4 and a sand mold embedded in the molding sand 4 filled in the reduced pressure container. In this device, each wall surface of the decompression container 2 except for the top portion is formed of a hollow double wall, and the inner wall surfaces thereof are formed of a porous ventilation plate (for example, a screen) 3 and The hollow portion is configured to communicate with the suction means 1 (for example, a pump), and the sand mold is a mold in which a casting space having the same shape as the wire drum (product) 15 is formed by shell sand. In particular, the sand mold in this embodiment has a shell mold 8, a core 7,
9. A combination of the feeder core 11 and the feeder core 12 forms a casting space having the same shape as the drum to be manufactured.
13 was closed with nylon film 5. further,
In this sand mold, the entire assembly components are constrained by a metal frame 10 in which a plurality of gas suction holes 6 are formed at appropriate places. The diameter of the foundry sand 4 is preferably larger than the hole diameter of the porous ventilation plate 3, for example, when a screen is used, for example, the diameter of the hole is 70 mesh peak sand. It is desirable to use a screen of 200 to 280 mesh.

According to the casting method of the present invention which is carried out by using such a vacuum casting apparatus, a sand mold is buried in a molding sand 4 filled in a vacuum container 2 of an upper open type, and the sand mold is under a suction depressurized state. This is a method of pouring and solidifying cast iron treated with a graphite spheroidizing agent and an inoculant into a casting space therein, for example, a wire drum as shown in FIGS. 1 and 2 was vacuum-cast by the following method. (1) First, the sand mold restrained by the metal frame 10 is placed in the decompression container 2
The molding sand 4 contained in the container is filled with dry molding sand 4 having good air permeability, and the container 2 is subjected to compaction while vibrating. Buried. (2) Next, at the time of pouring, use the original pressure of the vacuum pump -30.
The pressure was reduced to 0 mmHg to -500 mmHg. As a result, the gas at the time of pouring enters the molding sand 4 through the gas suction holes 6 of the metal frame 10,
It is sucked through the porous ventilation plate (screen) 3 and the inside of the sand mold is uniformly depressurized. (3) Then, the cast iron having the component composition shown in Table 1 treated with the melt treatment agent of the graphite spheroidizing agent and the inoculant shown in Table 2 is poured into the casting space in the sand mold under the suction decompression state. , A wire drum for an elevator was cast. In this casting method, the primary inoculation in which the Bi-based inoculant is added to the molten metal immediately after the ladle is discharged, and the secondary inoculation in which the Fe-Si-based inoculant is added to the pouring flow when pouring into the sand mold Due to 1.
We tried to prevent the white pig iron from winding the rope as thin as 4 mm.

The elevator wire drum thus cast has excellent dimensional accuracy even in the rope winding portion, which is a thin portion, and the roundness is within the tolerance, so that the elevator wire drum is commercialized without cutting. be able to. Moreover, when the hardness at the peak of the rope winding portion was measured by a Vickers hardness tester, uniform hardness was obtained at both the tip end portion and the central portion of the rope winding portion. As a result of microscopic observation of the cross section of the rope winding portion, as shown in the photograph of FIG. 4, spherical graphite was formed in every corner of the thin portion, and white pig iron could be effectively prevented. It is also clear from.

[0020]

[Table 1] * CE = C + 1/3 (Si + P)

[0021]

[Table 2]

[0022]

As described above, according to the present invention, the cast iron treated with the graphite spheroidizing agent and the inoculant spreads to every corner including the thin portion of the wire drum, and the cast iron is kept in the sand mold during pouring. Since gas is evenly discharged to the outside of the frame, it is an integrally cast product of a sound spheroidal graphite cast iron wire drum that has excellent toughness without causing white pig iron and excellent dimensional accuracy that does not require finishing such as machine cutting. As a result, stable pressure reduction casting can be performed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an elevator wire drum according to the present invention.

FIG. 2 is a diagram showing dimensions and required accuracy of a rope winding portion of an elevator wire drum.

FIG. 3 is a schematic sectional view showing an example of a vacuum casting apparatus used in the method of the present invention.

FIG. 4 is a micrograph showing a metal structure of a cross section of a rope winding portion of a wire drum according to the present invention.

[Explanation of symbols]

 1 Suction means 2 Decompression container 3 Porous ventilation plate 4 Foundry sand 5 Nylon film 6 Gas suction hole 7, 9 Core 8 Shell type 10 Metal frame 11 Core for hot water 12 Core for hot water 13 Hot water supply 14 Hot water 15 Product

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location C21C 1/10 103

Claims (4)

[Claims] 1. A sand mold is embedded in foundry sand filled in a decompression container of an upper open type, and cast iron treated with a graphite spheroidizing agent and an inoculant is filled in the sand casting space under a suction depressurized state. A vacuum casting method for a wire drum, characterized in that an integrally cast product made of spheroidal graphite cast iron is obtained by pouring and solidifying. 2. The sand mold is constituted by a sand mold in which a casting space having the same shape as the casting member is formed by shell sand, and further constrained from the outside by a metal frame having a plurality of gas suction holes formed at appropriate positions. The reduced pressure casting method according to claim 1, wherein 3. The treatment with the above-mentioned inoculant comprises the primary inoculation in which the Bi-based inoculant is added to the molten metal immediately after the ladle is discharged, and Fe-
The vacuum casting method according to claim 1 or 2, which comprises a secondary inoculation in which a Si-based inoculant is added to a pouring flow when pouring into a sand mold. 4. A wire drum, wherein a rope winding portion is formed by connecting peaks and troughs on the body circumference and is a non-cutting type spheroidal graphite cast iron integrally cast product.