JPS58179561A - Precision casting method of platelike hollow article - Google Patents

Abstract

PURPOSE:To produce a platelike part having a hollow part of high dimensional accuracy at a low cost in a precision casting method using a ceramic shell casting mold, by charging molten meta into the casting mold while insulating the heat in the extension part thereof and discharging the unsolidified metal in the mold after the inside wall surface solidified. CONSTITUTION:An expendable pattern 2 corresponding to a hollow platelike part of the nozzle vane or the like of a steam turbine is made and the extension part 2II having the same section as the section of a riser is provided in the upper part thereof. An extension part 2III is mounted in the lower part as well. A ceramic shell casting mold 3 is molded by using such expendable pattern and using ceramics as a material. A cylinder 5 of an exothermic material is set on the outside surface in the lower extension part 4 of the mold 3, and further a receptor 6 for molten metal is disposed so as to enclose the part 4. While the extension part is maintained at a high temp. by igniting the cylinder 5 in this state, the molten metal is charged into the mold 3. The molten metal solidifies from the inside wall surface of the mold 3 and the unsolidified metal 9 is discharged at the point of the time when the unsolidified metal 9 exists in the inside, and the casting having the hollow part is produced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a simple precision casting method for plate-like hollow products for ceramic shell mold pipes.

For example, 9J! Nozzle blades of medium and large steam turbines and guide vanes of water turbines for hydroelectric power generation (B) shown in Figures I1 and @2
In plate-shaped parts such as G#, high dimensional accuracy is required functionally, and at the same time, as shown in the figure, it is possible to provide a hollow part (1) within the wall thickness to achieve monomerization by I2. It is depicted.

In response to this sadness, the conventional manufacturing method uses two cores for casting. There are two methods: one is to integrally form the target hollow plate-like product, and the other is to mechanically assemble and form the target hollow product by bending plates, welding, etc.

However, in the former method, since a core is used, not only is it time-consuming to manufacture the mold and remove the core after casting, but the problem is that defects are easily caused by the gas generated from the core during casting. There is.

On the other hand, according to the latter method, the dimensional accuracy is poor, and therefore it is inevitable that the finishing process 1 is required and the processing cost increases. Furthermore, it cannot be denied that with this method, the products that can be manufactured are limited in terms of shape.

The present invention has developed a simple precision casting method using a ceramic shell mold as a new manufacturing method for plate-shaped crystals that require both dimensional accuracy and hollow weight reduction. And it can be provided at low cost.

That is, when the present invention casts a plate shape or a casting using a ceramic shell mold, an extended part is integrally formed in the mold, and the mold is pressure-poured with a heat-retaining shape of the extended part, and a predetermined amount is poured into the mold. After a period of time has elapsed, the mold wall of the extension arm 3 is damaged and the unsolidified molten metal in the mold is discharged.

This will be specifically explained using an example of casting a hollow nozzle as shown in FIG. In implementing the present invention,
First, a fugitive model corresponding to the target casting must be prepared, and then a ceramic shell cast for precision casting must be manufactured through a predetermined molding and firing set. The production of the ceramic shell mold is similar to the conventional process, except that an extension is integrally provided at one lower end of the mold, which is necessary for later draining of the molten metal.

and a feeder II (21) connected above and below it.
and an extension part (2 coils) with a circular cross section are integrally or separately welded. In the figure, tFi indicates the final product dimension of the nozzle blade (5).

In such a vanishing model WM zone, a shell layer of an appropriate thickness is formed according to a normal molding method, and then Kisei (2) disappears, and then a shell layer (casting, firing, drying,
Predetermined ceramic shell mold (!l) as shown in Figure 4
will be completed in

A target hollow casting is cast into such a ceramic shell mold (3) as follows. First, the ceramic shell mold (3) is made with the necessary holes (not shown), and its extension 5 (4) is made as shown in Fig. 4.
) A cylinder containing a pyrogenic substance (6) is set on the outer surface.
Further, a molten metal receiver (6) is arranged so as to surround the extension part (4) of the cast member (3), and at this time, the mold wall on the side of the extension part (4) is damaged in advance. A notch (7) for impact is provided on the inside of the receptor (6), and a protrusion (II) for impact is provided at a position facing the receptor (6), as shown in Figure S. Then, the exothermic substance (i%) is ignited and the extension part (4) is raised to a predetermined mold temperature, and then the melt is poured into the mold (3) at that temperature. In the mold, a JI solid shell (dotted line in the figure) of a constant thickness is formed and solidification progresses. At this time, the mold extension sK maintains the rice coagulation shape due to its heat retention effect. In this state, if the receptor (6) is struck as shown by the arrow S in the figure, the mold wall of the extension (4) will form the notch (
7) Unsolidified molten metal (9) in the mold (3) that is damaged at a certain point
is immediately expelled into the receptor (6). After that, once the casting has cooled down to a temperature where it will not deform, the mold is dismantled, the hollow casting is taken out, and the attachments are cut and other necessary post-finishing is carried out. Such plate-shaped hollow products are easily manufactured.

In the example in section E, the exothermic substance (5) is used as a heat insulating means for the mold extension (4), but this also applies to burner heating of that part or any other heat insulating means. Can be replaced. Furthermore, the damage method used in the extension section is not limited to the above example, and may be replaced with any other method as long as it is simple.

Examples of specific casting conditions and product results obtained by the method shown in the illustrated examples are listed below.

<Specific example> Product: 20-inch class steam turbine nozzle blade casting conditions Mold: Zircon-based Sekmikushiel & 6, Casting material: 5C5I3 equivalent type Temperature near 00°C ± 20°C (during casting) Casting temperature: 1550°C ± 20°C Casting Including time near M: Elapsed time from completion of pouring until completion: 15jeI:
Product results Hollowness ratio = 30 m Hollow part wall thickness = 3.5 ± 0.5 m As described in detail above, the present invention not only forms an extension part in the ceramic shell mold used, but also extends the extension part at a predetermined timing after pouring. This simple method allows for easy and reliable casting of products that have the excellent dimensional accuracy inherent to precision casting in terms of external shape, while at the same time forming hollow parts inside to reduce weight. can do.

The method of the present invention is advantageous in all aspects of product quality, dimensional accuracy, and manufacturing cost compared to conventional casting methods using cores, processing, and welding assembly methods.

Therefore, the present invention has particularly great technical value as a means for manufacturing hollow plate products such as steam turbine nozzle blades and water turbine guide vanes.

[Brief explanation of drawings]

FIG. 1 and gKz diagram are perspective views showing examples of shapes of plate-shaped hollow products, with FIG. 1 showing a hollow nozzle product and FIG. 2 showing a hollow vane product. Figure 3 shows an example of the shape of the evanescent model used in the present invention, (ml is its front view, (b) Fi
(C) shows its top view, and (C) shows its bottom view. Fig. 4 is a sectional view showing the casting process of the present invention, and Fig. 5 is a cross-sectional view showing the casting process of the present invention.
FIG. A...Steam turbine nozzle tail, B...Water wheel guide vane, (1)...Hollow part, (2)...Disappearance model,
(1) Ceramic shell mold, (4) Extension, (b) Pyrogen, (6) Molten metal receptor, (7) Notch, (8) ...protrusion, (9)...
・Unsolidified molten metal. JP-A-58-179561C3)'! g1 Figure ^'j21J Figure 4

Claims (1)

[Claims] 1. When casting a plate-shaped casting using the ceramic shell casting MM, an extension llK is integrally formed in the casting 11, and the metal is poured into the mold with a heat-retaining shape l of the chain extension s, and after a predetermined period of time has elapsed. After that, it will be extended! A precision casting method for a plate-shaped hollow product, characterized in that the casting wall of the mold is damaged and the hot water in the mold is forced out.