JPH0335865A - Method and apparatus for precision casting - Google Patents

Abstract

PURPOSE:To precisely cast a casting product having good dimensional accuracy and excellent quality by setting base metal for melting into position corresponding to a feeder head in a ceramic shell mold, melting this with induction magnetic field and dropping into casting space in the induction magnetic field. CONSTITUTION:The ceramic shell mold 3 is set in a refractory vessel 4 and in the position 3b corresponding to the feed head, the base metal 6 for melting is set. Successively, the base metal 6 for melting is melted with a coil 7 for forming the induction magnetic field arranged outside of the vessel 4 under melting atmosphere of Ar, etc., and dropped into the casting space 3a in the mold 3 and the induction magnetic field heating is executed with the coil 7. Then, power supplying rate for forming the induction magnetic field is made to 5kw/kg of the base metal 6 for melting. By this method, running of the molten metal is made good and preheating temp. of the mold 3 is drastically reduced at the time of manufacturing the casting product having thin part.

Description

[Detailed description of the invention] [Purpose of the invention]

(Industrial Application Field) The present invention relates to a precision casting method and a precision casting apparatus that are used for manufacturing precision casting products, and are particularly suitable for manufacturing precision casting products made of active metals. . (Prior art) Conventionally, in manufacturing precision casting products, a ceramic shell precision casting method represented by the Lost Fuchs method has generally been used. Metal Handbook” December 20, 1981
Published by Japan Institute of Metals, edited by Japan Institute of Metals, pp. 1513-1
It is described on page 518. (Problem to be solved by the invention) This precision casting method is a casting method that can obtain cast products with good dimensional accuracy and beautiful skin, and is of excellent quality. However, it is generally not applicable. Because the product is small, there are problems with casting efficiency and the number of man-hours required. In addition, when applying to cast products with many thin-walled parts, it is necessary to take measures to improve the flow of hot water, which requires complicated processes such as heating the mold to high temperatures and using vacuum suction casting. The problem was that there was a lot to do. (Object of the Invention) The present invention has been made in view of these conventional problems, and provides a ceramic shell precision casting method capable of obtaining cast products with good one-dimensional accuracy and beautiful casting surfaces and excellent quality. In addition, even when producing cast products with thin walled parts, it is possible to make full use of the advantages of this method, and it is also possible to improve the flow of hot water, making it possible to significantly reduce the preheating temperature of the mold. To provide a precision casting method and a precision casting apparatus which can simplify incidental equipment and precision process control without necessarily using vacuum suction casting which is expensive in equipment costs. It is an object.

[Structure of the invention]

(Means for Solving the Problems) The precision casting method according to the present invention is a precision casting method using a ceramic shell mold typified by the lost wax method, in which It is characterized by a structure in which the molten metal base material is melted by an induced magnetic field and cast into the casting space of a mold also placed within the induced magnetic field. The precision casting method according to the present invention uses a ceramic shell mold typified by the lost wax method, and is also called an investment casting method. Then, the molten metal base material is placed in a portion corresponding to the feeder or runner of the ceramic shell mold, and the molten metal base material is melted by an induced magnetic field. At this time, it is more desirable that the dissolution atmosphere be an inert gas atmosphere such as argon or nitrogen, or a reduced pressure (including vacuum) atmosphere.
Such a controlled atmosphere is particularly desirable when the casting is made of active metals. Next, the metal base material melted here falls into the casting space of the mold, which is also placed within the induced magnetic field, and is cast within this casting space. At this time, even after falling into the casting space of the mold, it is heated by the induced magnetic field, so that, for example, the cast metal that has solidified on the wall of the mold in the casting space is remelted, resulting in extremely good running properties, and thin-walled parts Even if a cast product has a large number of parts, its shape can be made with high precision. In addition, since the hot water runnability is good, vIyJ and preheating temperature can be significantly reduced, and vacuum suction casting does not necessarily have to be used in combination. In the embodiment of this R1 light, the amount of power supplied for forming the induced magnetic field is 5 per kg of the molten metal base material.
kW or more, to speed up the melting of the molten metal base material placed in the riser or runner equivalent part of the mold, and to improve the flowability of the molten metal that has fallen into the casting space of the mold. It is particularly desirable to improve the quality. A precision casting apparatus according to the present invention includes a ceramic shell mold having a casting space and a portion corresponding to a riser or runner that communicates with the casting space, and a ceramic shell mold that is arranged outside the ceramic shell mold and has a riser or runner of the mold. A configuration comprising an induction magnetic field forming coil that melts a molten metal base material disposed in a portion corresponding to the path by an induction magnetic field, and heats the molten metal that has melted and fallen into the casting space by the induction magnetic field. It is characterized by the following. In the precision casting apparatus according to the present invention, the ceramic shell mold having a casting space and a feeder or runner equivalent portion communicating with the casting space is a single ceramic shell mold having only one casting space. In addition, it can also be an assembly mold that has multiple casting spaces and is suitable for simultaneously casting multiple cast products. Then, the molten metal base material disposed outside the ceramic shell mold and corresponding to the riser or runner of the mold is melted by the induced magnetic field, and the molten metal base material is melted into the casting space. The coil for forming an induced magnetic field that heats the molten metal that has fallen into the mold by an induced magnetic field must have a capacity that outputs an induced magnetic field of 5 kW or more per 1 kg of molten metal base material, and be installed in the mold riser or the equivalent part of the runner. It is particularly desirable to quickly melt the molten metal base material, and to improve the flowability of the molten metal that has fallen into the casting space. Further, it is preferable that the coil for forming the induced magnetic field is shaped according to the mold envelope shape along the outer shape of the ceramic shell mold. It is also desirable, if necessary, to have a configuration in which a magnetic concentrator is arranged inside the forming induction coil. It is also desirable that the segments have a water-cooled structure, if necessary, and the arrangement of such magnetic concentrators makes it possible to efficiently melt small-weight molten metal base materials that can be used to make smaller castings. You will be able to perform well. Furthermore, the outside of the ceramic shell mold is made fireproof so that the melting atmosphere of the molten metal base material placed in the feeder or runner part of the ceramic shell mold is an inert gas atmosphere such as argon or nitrogen or a reduced pressure atmosphere. It is also desirable to surround it with a container or the like, if necessary. (Function of the invention) Since the precision casting method and precision casting apparatus according to the present invention have the above-described configuration, the molten metal base material disposed in the riser or runner portion of the ceramic shell mold is heated by induction. When melted and dissolved, the riser or runner phase,
Since the molten metal will fall into the casting space of the mold in the immediate vicinity of this part, even if the molten metal base material belongs to the so-called active metals, the chance of causing external contamination is extremely small. Since the molten metal that has fallen into the casting space of the mold is further heated by the induced magnetic field, sufficient water circulation is ensured and the feeder effect is significantly improved. Therefore, since the hot water flowability is sufficiently good, it is possible to reduce the preheating humidity of one mold, omit the preheating of the mold, and even without using vacuum suction casting together, the molten metal can fill especially the thin parts. As a result, the dimensional performance and shape accuracy are extremely good, and the casting surface is also very good, making it possible to cast products with excellent quality in a short time and efficiently. (Embodiment) In this embodiment, a small turbine wheel is cast using the precision casting apparatus shown in FIG. 1. This precision casting apparatus 1 has a turbine-shaped casting space 3a on a refractory mold table 2 connected to a gas supply pipe 2a, and a feeder equivalent part 5b (or a conventional runner) directly above the casting space 3a. At the same time, a refractory container 4 is installed on the upper surface side of the refractory mold stand 2 and outside the ceramic shell mold 3. There is a gas outlet 4a at the top of the
At the same time, an observation port 4b and an observation window 5 are provided at the top to cover the observation port 4b, and a coil 7 for forming an induced magnetic field is provided on the outside of the refractory container 4.
The molten metal base material 6 disposed in the feeder equivalent part 3b (or the conventional runner equivalent part) of the kusiel mold 3 is melted by the induced magnetic field, and the molten metal base material 6 melts and falls into the casting space 3a. The structure is such that the molten metal can be heated by the same induced magnetic field, and in this case,
The induced magnetic field forming coil 7 is shaped to match the mold envelope shape along the outer shape of the ceramic shell mold 3. When performing precision casting using such a precision casting apparatus 1, a molten metal base material 6 made of a Ni-based heat-resistant alloy with the components shown in Table 1 is used, and this molten metal base material 6 is pressed into the ceramic shell mold 3. It is located in the employment department 3b. Next, a refractory container 4 is placed on the outside of the ceramic shell mold 3.
A from the gas supply pipe 2a connected to the refractory mold table 2 with the induced magnetic field forming coil 7 positioned.
While supplying r gas, Ar gas is discharged from the gas discharge port 4a to make the dissolution atmosphere Ar atmosphere, and then the induced magnetic field forming coil 7 is supplied with a frequency of 8000 Hz and a maximum output of 60.
kW high frequency power was supplied. As a result of this energization, the molten metal base material 6 fell into the casting space 3a about 30 seconds after the start of energization. Subsequently, by energizing the induced magnetic field forming coil 7 for 5 seconds, the metal that has partially solidified in the casting space 3a is remelted, and the molten metal is poured into the details of the casting space 3a, especially the blade tips of the turbine blades. The high-frequency power supply was stopped after the tank was completely filled. In this fine vB casting, the weight of the molten metal base material 6 is 24
The weight of the cast product was 200 g, and the casting yield was 83%, which was significantly higher than the yield of 40 to 50% when manufactured by ordinary precision casting. In addition, the obtained cast product was precisely cast to a predetermined shape in every corner of its thin wall portion, and a good quality cast product was obtained with no occurrence of defects such as shrinkage cavities. Example 2 In this example, the precision casting equipment shown in FIG.
This shows the case of casting. This precision casting apparatus 11 has a hot chamber-shaped casting space 13. a, and a ceramic shell mold 13 having a feeder equivalent part 13b (or a conventional runner equivalent part) directly above this casting space i3a, and on the upper surface side of the refractory mold table 12 and with the ceramic shell mold 13 A magnetic concentrator 18 is installed on the outer circumferential side of the shell mold 13, and a refractory top cover 14 is installed above the ceramic shell mold 13 and the magnetic concentrator 18, and a gas outlet 14a is provided between them. The refractory upper lid 14 has an observation port 14b.
An observation window 15 is provided at a position covering this, and a coil 17 for forming an induced magnetic field is arranged on the outer circumferential side of the magnetic concentrator 18.
Molten metal base material 16 arranged in b (or the runner equivalent part)
is melted by an induced magnetic field and the molten metal base material 16
The structure is such that the molten metal that has melted and fallen into the casting space 13a can be similarly heated by the induced magnetic field. In one precision casting apparatus IT in this embodiment, the hot chamber that is the cast product is small with an outer diameter of 30 mm and a unit weight of 60 g, so in order to efficiently melt it, the magnetic concentrator
8 is used. As shown in FIG. 3, this magnetic concentrating body 18 consists of a plurality of copper segments 18a...18h that are insulated and divided by an insulator 19 in the circumferential direction, and each segment 18a...18h supplies cooling water. It has a water-cooled structure that is cooled by cooling water flowing through piping 20 and cooling water discharge piping 21. This magnetic concentrator 18 is arranged inside the induction magnetic field forming coil 17 through which a large current flows, and the segments 1 are insulated from each other.
This takes advantage of the fact that the skin alternating current flows at 8a◆ and 18h, and as shown in Figure 3, a coil current Ic, a segment internal cage current Is, and a melted base material skin current If are formed, and each Segment) 18a...18h A high-density magnetic field is formed inside the magnetic concentrator 18 by the intra-segment cage flow Is flowing in the segments 18a...18h, and even the molten metal base material 16 with a small diameter and small weight is efficiently melted. You will be able to do this. When performing precision casting using such a precision casting apparatus 11, a molten metal base material 16 made of high Cr heat-resistant cast steel with the components shown in Table 2 is used, and this molten metal base material 16 is poured into the ceramic shell mold 13. It was arranged in the riser equivalent part 13b. Next, a magnetic concentrator 1 is placed outside the ceramic shell mold 13.
8 and the induced magnetic field forming coil 17 are positioned, and the gas supply pipe 12a is connected to the refractory mold table 12.
At the same time, NZ gas is supplied from the gas outlet 14a and N2 gas is discharged from the gas outlet 14a to make the dissolving atmosphere an N2 atmosphere.Also, cooling water is flowed inside the magnetic concentrator 18, and the coil for forming an induced magnetic field is 17 with a frequency of 8000Hz
, supplied high-frequency power with a maximum output of 60kW. As a result of this energization, the molten metal base material 16 fell into the casting space 13a about 14 seconds after the start of 1 energization. Subsequently, by energizing the induced magnetic field forming coil 17 for 3 seconds, the metal that has partially solidified in the casting space 13a is remelted, and the molten metal is completely filled in every detail of the casting space 13a. The supply of high frequency power was stopped. In this precision casting, the casting yield of the product was 80%, which was considerably higher than that produced by ordinary precision casting. In addition, the obtained cast product was precisely cast in every corner according to the predetermined shape, and it was possible to obtain a good cast product without any defects such as shrinkage cavities.

【Effect of the invention】

The precision casting method according to the present invention is a precision casting method using a ceramic shell mold, typified by the lost wax method, in which a molten metal base material placed in a portion corresponding to the riser or runner of the mold is melted by an induced magnetic field. The precision casting apparatus according to the present invention, which is directly used for carrying out such a precision casting method, has a configuration in which the casting is performed in the casting space of a mold that is also placed within an induced magnetic field. A ceramic shell mold having a communicating feeder or runner equivalent part, and a molten metal base material placed outside the ceramic shell mold and placed in the mold's riser or runner equivalent part are melted by an induced magnetic field. At the same time, since the molten metal base material is melted and the molten metal falling into the casting space is equipped with an induction magnetic field forming coil that heats the molten metal by an induction magnetic field, the dimensional accuracy is good and the casting surface is beautiful. In addition to making full use of the advantages of the ceramic shell casting method, which allows for the production of cast products with excellent quality, it also prevents contamination of the molten metal base material as much as possible, eliminating impurities. It is possible to prevent as much as possible the deterioration of material properties due to It is possible to significantly lower the preheating temperature of the mold or eliminate the need for preheating itself, and it is not necessary to use vacuum suction casting, which is expensive in equipment costs, simplifying the ancillary equipment and controlling the process. This has the remarkable effect of making it possible to achieve high precision, and to efficiently cast and mold cast products with excellent quality such as mechanical properties and dimensional accuracy of the material in a short period of time. .

[Brief explanation of drawings]

Fig. 1 is an explanatory longitudinal cross-sectional view of a precision casting apparatus used in Example 1 of the present invention, Fig. 2 is an explanatory longitudinal cross-sectional view of a precision casting apparatus used in Example 2 of the present invention, and Fig. 3 is an explanatory longitudinal cross-sectional view of a precision casting apparatus used in Example 2 of the present invention. FIG. 3 is an explanatory plan view of a magnetic concentrator of the precision casting apparatus shown in the figure. 1.11...Precision casting equipment. 3.13...Ceramic shell mold. 3a, 13a...casting space, 3b, 13b...portion equivalent to riser (or portion equivalent to runner). 6.16... Molten metal base material. 7.17... Coil for forming induced magnetic field, 18... Magnetic concentrator.

Claims (9)

[Claims] (1) A precision casting method using a ceramic shell mold, typified by the lost wax method, in which the molten metal base material placed in the mold feeder or runner is melted by an induced magnetic field. A precision casting method characterized by casting in a casting space of a mold placed in a (2) The precision casting method according to item (1), wherein the melting atmosphere is an inert gas atmosphere such as argon or nitrogen or a reduced pressure atmosphere. (3) The precision casting method according to item (1) or item (2), wherein the amount of power supplied for forming the induced magnetic field is 5 kW or more per 1 kg of molten metal base material. (4) A ceramic shell mold having a casting space and a portion corresponding to a riser or runner that communicates with the casting space, and a ceramic shell mold that is disposed outside the ceramic shell mold and is disposed in the riser or runner equivalent portion of the mold. Precision casting characterized by comprising an induction magnetic field forming coil that melts the molten metal base material by an induction magnetic field and heats the molten metal that has melted and fallen into the casting space by the induction magnetic field. Device. (5) The precision casting apparatus according to claim (4), wherein the ceramic shell mold is an assembly mold having a plurality of casting spaces. (6) The precision casting apparatus according to claim 4 or 5, wherein the induction magnetic field forming coil has a capacity to output an induction magnetic field of 5 kW or more per 1 kg of molten metal base material. (7) Claim (4) wherein the induction magnetic field forming coil is shaped to match the mold envelope shape of the ceramic shell mold.
The precision casting apparatus according to any one of Items 1, 5) and 6). (8) Claim No. (4), wherein a magnetic concentrator is disposed outside the ceramic shell mold and inside the induction coil for forming a magnetic field.
The precision casting apparatus according to any one of Items 1, 5, 6, and 7. (9) The precision casting apparatus according to claim (8), wherein the magnetic concentrator is constituted by a plurality of segments that are insulated and divided in the circumferential direction, and each segment has a water-cooled structure.