JPS63264242A - Production of mold for investment casting - Google Patents

Abstract

PURPOSE:To reduce the residue of wax and to prevent the defect in a product shape by heating a tree like wax pattern formed by a refractory layer under rotating in the state of inclining it at a specified angle. CONSTITUTION:A mold 14 is arranged on a driving roller 18 inside the appropriate heating furnace 16 of an autoclave, etc., so that the runner forming part 2 of a wax pattern 6 is inclined by the specified angle alpha for the horizontal plane and the gate forming part 8 of the pattern 6 becomes down. The mold 14 is then rotated around the tree like center part 2 with the rotary movement of the driving roller 18. On the other hand the model 6 buried inside the mold 14 is melted by heating it up to the specified temp. by the heating furnace 16 and flowed out of the gate forming part 8 to the external part to form a casting cavity 20. Consequently the casting cavity 20 having the numerous product cavities 24 communicating to the runner 22 around the runner 22 and in the shape that the lower part end of the runner 22 becomes of a gate 26 is formed.

Description

[Detailed description of the invention] (Technical field) The present invention relates to a method of manufacturing a mold for investment casting,
In particular, the present invention relates to an effective method for dewaxing wax constituting a wax model when manufacturing molds for investment casting.

(Prior art and its problems) Investment casting method has traditionally been known as a precision casting method under the name of lost wax casting method, and is the most complex casting method among various precision casting methods. It is accepted that it can be made using the method that can produce it with the highest precision.

In this investment casting method, (a
(b) The mold is highly fire-resistant, and almost all materials can be cast. It has the characteristics of good quality, good casting surface, and (c) mass production of mass-produced products with reduced machining costs.
Especially when making products that have complex shapes or hard materials that require a large number of man-hours for machining or cannot be machined, or when making several pieces to make one complex part. It can be advantageously used when making a product made by assembling or welding small parts into an integral cast product.

When molding the mold used in this investment casting method, first, as is well known, a tree-like mold is formed, which provides a form in which a large number of product casting parts (product cavities) are arranged around the runner. A wax model is manufactured, and then a predetermined refractory layer is formed around the wax model by coating using slurry, stucco, etc., and then the wax model is melted by heating (dewaxing). By subsequent firing, a predetermined casting cavity is formed in the refractory layer; that is, by removing the wax model, a mold is obtained in which a correspondingly shaped casting cavity is formed in the refractory layer. It becomes.

By the way, the dewaxing operation in such a molding method, that is, the operation of eluting the wax model from a mold with a refractory layer formed around the wax model, is disclosed in, for example, Japanese Patent Publication No. 60-59007. This process is carried out by heating the wax model while the tree-shaped base is placed vertically with the part corresponding to the sprue facing down. Generally, it has a tree shape with a trunk-shaped runner forming part located at the center and a number of product cavity forming parts provided around it.
Heating depending on the shape of the product cavity forming part, such as
The molten wax cannot completely flow out of the casting cavity of the mold being formed, and even after this dewaxing step, some portion of the wax model remains within the casting cavity of the mold. It is recognized that

For this reason, conventionally, such residual wax is burnt out at the same time as the firing process of the refractory layer forming the mold, but if the amount of residual wax becomes large, It is true that the firing time for such a mold is long, and therefore, in order to improve the productivity of the desired mold manufacturing, it is necessary to reduce the amount of residual wax as much as possible and shorten the firing time. It is desired to do so.

Furthermore, since the wax that forms the wax model generally contains various impurities, even if the wax is burned away by the above-mentioned firing operation, wax residue will remain in the casting cavity. Moreover,
The amount of such wax residue increases when low-grade wax is used, and when casting is performed with such wax residue adhering to the inner surface of the casting cavity, the shape of the resulting product deteriorates. This causes problems such as deterioration and defects, resulting in deterioration of quality.

Therefore, from the standpoint of this wax residue, the greater the amount removed in the wax dewaxing process, in other words, the smaller the amount of wax remaining in the mold, the better.

(Solution Means) Here, the present invention has been made to solve the above-mentioned conventional problems, and its gist is to form a refractory layer around a tree-shaped wax model. The wax model with the refractory layer formed thereon is then melted and then fired to produce an investment casting mold in which a predetermined casting cavity is formed with the refractory layer. The wax model is heated while being rotated around the axis of the tree shape with the part corresponding to the sprue at the base of the tree shape facing down and the axis of the tree shape inclined at a predetermined angle with respect to the horizontal plane. The reason is that the elution operation is carried out.

To solve this problem, in the present invention, in the dewaxing process, which is one of the manufacturing processes of investment casting molds, the mold with a refractory layer formed around the wax model is placed vertically as in the conventional method. The dewaxing operation is not carried out by heating the wax while rotating it around its axis while tilting it at a predetermined angle. As the mold rotates, the wax remaining in the casting cavity that is being formed is gradually guided downward through the runner to the sprue side, thereby effectively increasing the amount of wax removed. .

(Specific Configuration/Example) Hereinafter, the configuration of the present invention will be explained in more detail with reference to the drawings showing a specific example of the present invention.

First, the tree-shaped wax model used in the present invention is obtained by molding using compounded wax or the like in the same manner as in the past, and assembling it as necessary, for example as shown in FIG. As shown, there is a trunk-shaped runner forming part 2 located in the center, and a plurality of product cavity forming parts 4 arranged around this runner forming part 2 and having a shape corresponding to the intended cast product. Therefore, the wax model 6 is integrally formed into a so-called tree-shaped wax model 6.

In this wax model 6, the tree-shaped base corresponds to the sprue forming part 8.

And around this tree-shaped wax model 6,
A refractory material 1'ilO is formed according to a conventional method, and a cylindrical frame body 12 is formed to back up the refractory material layer 10.
is provided. In addition, in order to form the refractory layer 10 around the tree-shaped wax model 6, for example, tetraethyl orthosilicate, ethyl silicate 40. It consists of immersion in a slurry obtained by mixing a refractory binder such as colloidal silica or silicate with a suitable refractory fine powder such as alumina, zircon 1, or zirconia, and a refractory powder such as alumina, zircon, or zirconia. A coating layer of a predetermined thickness is formed by combining with sprinkling of stucco material, and a back-up layer is formed by filling refractory powder as necessary on top of the coating layer, thereby forming the mold 14. It is.

Next, in the mold 14 containing this wax model 6,
A dewaxing operation is performed by heating in a suitable heating container such as an autoclave or a heating furnace, but in the present invention, in such a dewaxing operation, the mold 14 is tilted. In other words, refractory IJ
With the sprue forming part 8 at the base of the tree shape of the wax model 6 in which the IO is formed facing down, the shaft (2) of the tree shape
The wax model 6 is melted and melted by heating it while rotating the mold 14 around the axis (2) of the tree shape in a state where the mold 14 is tilted at a predetermined angle (α) with respect to the horizontal plane. That's what I did.

An example of a dewaxing operation according to the present invention is shown in FIG.
The runner forming part 2 is inclined at a predetermined angle: α with respect to the horizontal plane, and the wax model 6 is placed on the drive roller 18 so that the runner forming part 8 is at the bottom. The mold 14 is rotated around the tree-shaped center (2) by the rotation of the driving roller 18, while the mold 14 is buried in the mold 14 by being heated to a predetermined temperature by the heating furnace 16. The wax model 6 is melted and allowed to flow out from the sprue forming part 8 of the wax model 6, thereby forming a casting cavity 20 corresponding to the wax model 6 in the mold 14. be. That is, the casting cavity 20 has a runner 22 in the center, a number of product cavities 24 around the runner 22 communicating with the runner 22, and a lower end of the runner 22 (see FIG. ) is sprue 2
6 is formed as a tree shape.

As described above, in the dewaxing operation according to the present invention, since the mold 14 is rotated in an inclined state, the wax could not be removed in the conventional vertical dewaxing operation. The wax that accumulates in the bottom (lower) part of the product cavity 24 is removed by rotating the mold 14. As shown in FIG. 2, when the casting cavity 24 is located above the runner 22, it flows down into the runner 22 as shown by the arrow, and then flows in a spiral shape inside the runner 22, and then 26 to the outside, thereby significantly reducing the amount of wax remaining in each product cavity 24 of the mold 14, so that the subsequent firing operation removes such residual wax. Even if it is burnt down,
This makes it possible to effectively reduce wax residue adhering to the inner surface of the product cavity 24.

In this dewaxing operation, the heating temperature for melting the wax model in the mold 14 is appropriately determined to be a temperature suitable for melting and pouring out the wax model, for example, 90°C. The temperature is approximately 180°C, and the inclination angle of the mold 14 is:
As α and rotation speed, the tree shape of wax model 6,
In particular, the most effective angle and rotational speed for pouring out the wax are determined as appropriate depending on the shape of the product cavity forming part 4, in other words, the shape of the casting cavity 20 to be formed, the type of wax, etc. For example, the mold 14 is tilted and rotated at an angle of about α=20° and at a rotational speed of about 1 revolution/minute.

Then, the mold 14 that has been subjected to such a dewaxing operation is then subjected to a firing operation in the same manner as in the past, and by this firing operation, the casting cavity 2 is heated.
The wax that still remains or adheres inside the casting cavity 2 will be burnt out, but as described above, by performing the dewaxing operation according to the present invention,
Since the amount of wax remaining in the 0 is effectively reduced, the time required to remove the wax by this firing operation is shortened, and as a result, the firing time can be effectively shortened. The casting cavity 20,
In particular, since the amount of wax residue adhering to the inner surface of the product cavity 24 can be reduced, problems such as deterioration of the shape of the cast product to be cast in subsequent casting operations and generation of defects can be effectively suppressed. , the quality of the resulting cast product could be advantageously improved.

Furthermore, the thus obtained fired mold is subjected to a casting operation using a prescribed molten metal according to a well-known ordinary casting method, thereby producing the intended casting product, especially a precision casting product. It will be cast with high quality C1.

Although the configuration of the present invention has been explained in detail based on an example of the present invention, the present invention is not to be construed as being limited to the above-mentioned specific configuration; It should be understood that the present invention may be implemented with various changes, modifications, improvements, etc. based on the knowledge of those skilled in the art, without departing from the above.

- For example, in the above specific example, a cylindrical or cylindrical mold with a back-up layer formed thereon is used as the mold 14 to which the dewaxing operation is performed, thereby preventing rotation during the dewaxing operation. Although this can be done easily, the present invention can of course be applied to mold structures that do not have such a backup layer, as long as they can be rotated.

Furthermore, it goes without saying that various known rotation mechanisms can be used for the rotation structure of the mold 14 in the dewaxing process, in addition to the one illustrated.

Furthermore, when forming a wax model, various known methods are adopted, and in addition to forming the entire model with wax as shown in the example, a product cavity forming part made of wax around a sprue rod is formed with wax. It is also possible to form it by a method of attaching it.

(Effects of the Invention) As is clear from the above description, the present invention differs from the conventional method in which the mold is placed vertically and performs the dewaxing operation.
By heating the mold while rotating it in an inclined state, more wax can be effectively removed by performing a dewaxing operation. In particular, it effectively suppresses adhesion to the inner surface of the product cavity and causes defects in the product shape, making it possible to use low-grade wax, shortening the firing time, and improving productivity. This can be advantageously improved, and this is where the present invention has great industrial significance.

[Brief explanation of the drawing]

FIG. 1 is an explanatory sectional view showing the mold before dewaxing, and FIG. 2 is an explanatory sectional view illustrating the state of the dewaxing operation. 2: Runway forming section 4: Product cavity forming section 6: Wax model 8: Sprue forming section 10: Refractory layer 12: Frame 14: Mold 16: Heating furnace 18: Drive roller 20: Casting cavity 22: Runway 24 :Product cavity 26: Sprue

Claims (1)

[Claims] After forming a refractory layer around a tree-shaped wax model, the wax model is melted and then fired to create an investment casting mold in which a predetermined casting cavity is formed in the refractory layer. When manufacturing, the wax model on which the refractory layer is formed is placed with the part corresponding to the sprue at the base of the tree shape facing down, and the axis of the tree shape is tilted at a predetermined angle with respect to the horizontal plane. A method for producing a mold for investment casting, characterized in that the elution operation of the wax model is carried out by heating the wax model while rotating the wax model.