JPH03146255A - Reduced pressure suction casting method - Google Patents

Abstract

PURPOSE:To improve the yield of as cast product and to execute casting with simplified finish process by specifying opening hole diameter in a molten metal introducing passage and returning back the molten metal before the molten metal in this passage solidifies at the time of sucking the molten metal under reduced pressure in cavity in a mold through the molten metal introducing passage and gate. CONSTITUTION:The pressure in a chamber 11 is reduced with gas pressure reducing source 21 and the molten metal is sucked in the cavity 15 in the permeable mold 13 through the molten metal introducing passage 17 and gate 3. Then, the opening hole diameter in the introducing passage 17 is made to >=1.5 times the thickness in the casting near the gate 3 to make heat holding property in the introducing passage 17 large. At the time of solidifying the part of gate 3 after filling up the molten metal in the cavity 15, the mold 13 is ascended from the molten metal to drop the molten metal in the introducing passage 17 and return back this into a ladle 23. By this method, a product part 1 fitted with an attached material composed of the gate 3 and a part 5a of the introducing passage 17, is obtd., and by cutting and grinding this attached material, the product part 1 is manufactured. Further, by this method, cutting and removal of the attached material are facilitated and the product part 1 with simple work and high yield of as cast product, is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a vacuum suction casting method in which a casting is manufactured by sucking molten metal by reducing the pressure inside a surface mold.

[Prior art] Conventionally, as this type of vacuum casting method,
A technique disclosed in Japanese Patent No. 35227 is known. That is,
A shell mold or regular sand mold is held in a chamber,
In this method, after the mold is immersed in the molten metal, the pressure inside the chamber and the cavity is reduced, and the molten metal is introduced into the cavity through the molten metal introduction passage and weir to produce a casting. This casting method has the advantage that thin-walled castings with complex shapes can be produced relatively easily.

By the way, in this casting method, by appropriately setting the size and shape of the opening of the clear metal introduction passage and the suction holding time, the molten metal in the molten metal introduction passage is It is solidified to prevent molten steel from flowing out (flow pack) in the product section. For example, as shown in Fig. 10, 1: With the connection pipe (as-cast product) of the one-shaped water pipe manufactured by this method, the product is manufactured by introducing molten metal through the molten metal introduction part 102 and weir 104. In order to prevent the molten metal from flowing out, the molten metal introduction part 1 is cast.
A thin portion 108 is formed in 02, and solidification is performed there.

[Problems to be Solved by the Invention] However, since the molten metal is solidified integrally with such a large molten metal introduction section 1021 and product section 106, the following problems occur.

(2) The molten metal introduction section 102 after casting becomes a hindrance to handling in the finishing process.

■ Even if you try to cut and remove it with the weir 104, the molten metal introduction part 1
02 is a nuisance, and therefore not only is the work troublesome, but it is also an obstacle to automation.

■ The molten metal introduction part 102 is 1 to prevent flow pack.
: Although it is designed to be relatively small, it is therefore difficult to provide the molten metal introduction part 102 with a feeder function. (2) Since the molten metal introduction part 102 is large, the as-cast yield is low.

The present invention aims to solve the above-mentioned problems of the conventional technology, and by appropriately setting the size of the molten metal introduction part and the dimensions of the weir, it is possible to achieve a high as-cast yield and simplify the finishing process. The purpose is to provide a casting method.

[Means for Solving the Problems] In the vacuum suction casting method of the present invention 11, which has been made to solve the above problems, the pressure in the cavity of the mold is reduced and the molten metal is introduced into the cavity through the molten metal introduction passage and the weir. The opening diameter of the molten metal introduction passage should be at least 1.5 times the wall thickness of the casting to be cast in the cavity around the weir, and after filling the cavity with molten metal, the molten metal in the molten metal introduction passage should be It is characterized by raising the mold from the molten metal so that the molten metal returns before it solidifies, and stopping vacuum suction.

In addition, the opening diameter of the molten metal introduction passage (in relation to the thickness of the casting around the weir, it is necessary to change it variously depending on the solidification rate between the introduction passage and the area around the weir, but it is at least 1.5 times or more) More preferably, it is 3 times or more E.

[Operation] The vacuum suction casting method according to the present invention reduces the pressure inside the cavity of the mold, introduces the molten metal into the cavity from the molten metal introduction passage through the weir, raises the mold above the molten metal, and stops the vacuum suction. This is a method of manufacturing castings.

The opening diameter of the molten metal introduction passage in this invention (larger than 1.5 times the thickness of the casting around the weir).

Therefore, even after the molten metal is introduced into the cavity,
The heat retention of the molten metal introduction passage is great. Therefore, when the mold is lifted out of the molten metal while applying suction, the molten metal in the molten metal introduction passage returns and does not solidify integrally with the cast product.

Therefore, the cutting process such as cutting off the solidified portion of the molten metal introduction passage from the product body is easy, and the yield is high because this portion is not solidified.

[Example] An example of the present invention will be described below with reference to the drawings.

1 to 3 are perspective views showing an as-cast product (a 2-inch water pipe cheese) produced by the casting method of this embodiment.

In these figures, the weir 3 and a part 5a of the molten metal introduction part 5 are solidified in an annular shape on both sides of the product part 1 of the water pipe. That is, in the as-cast state, the weir 3 is integrated with the product part 1, and since the molten metal introduction part 5 is returned as molten metal, only the annular part 5a remains. Product part 1 of this water pipe
(Table Austenitic stainless steel (JIS standard: 5C)
313), and the dimensions of the casting etc. are as listed in Table 1. Here, the wall thickness of the product part 1 is 4 mm near the weir 3, and the diameter of the molten metal suction part 5 is φ30 mm, so the ratio thereof is 7.
5 (30/4).

Table 1 Next, a casting method in which the molten metal introducing portion 5 is not solidified into the product portion 1 will be described.

FIG. 4 shows a vacuum suction casting device. In the same figure, this device (see Figure 1) has an air-permeable mold 13 formed on the inner surface of a chamber 11, a molten metal introduction passage 17 communicating with a cavity 15 in the mold 13, and a cavity 15 connected to the chamber 11.
The molten metal introducing passage 17 is immersed in the molten metal in the ladle 23.

That is, in this device, the chamber 11 etc.
The molten metal introduction passage 17 is immersed in the molten metal by descending relative to the molten metal.

Then, when the gas decompression source 21 is activated, the cavity 5 of the mold 13 is brought into a negative pressure state via the chamber 11, and the molten metal in the ladle 23 is sucked into the cavity 5. When the cavity 15 is filled with molten metal and the part of the weir 3 has solidified, the mold is lifted out of the molten metal, and the molten metal in the molten metal introduction passage 17 falls and returns to the ladle 23. Subsequently, the chamber 11 is withdrawn to the demolding position, the operation of the gas decompression source 21 is stopped, and the sand is removed to obtain the as-cast product shown in FIG. Further, in a finishing step, the weir 3 and a part 5a of the molten metal introduction part 5 are cut and polished to complete the product part 1.

In the above embodiment, most of the molten metal in the molten metal introduction passage 17 is returned to the ladle 23, and only the base 3 and a part 5a of the molten metal introduction part 5a are attached to the product part 1. By casting the product part 1 having such a shape, there are the following effects, which are shown in comparison with the conventional example shown in FIG.

■ Figure 5 shows the time it takes to cut the molten metal introduction part 5 etc. from the product part 1 and polish it into a product. In comparison, we were able to shorten the finishing process time from 8 minutes to 1 minute.

■ Also, as shown in Figure 6, (:, in this example (A), (
The yield in the as-cast state was 96%, which was significantly higher than 52% in conventional example (B).

(2) Molten metal introduction passage 17 (It has a large capacity and a high heat retention effect, so it is difficult to solidify, so it can also serve as a riser function.

In addition, the quality of the cast product was examined by visual inspection and gamma ray inspection, but there were no casting defects in any of them, and it was not possible to produce a sound casting. 1 shows the shape of a casting according to another embodiment. In this embodiment, the position of the weir 3A is formed on the back surface of the product part 1.

This embodiment can also achieve the same effects as the above embodiment. In addition, the dimensions of the castings, etc. [A, b, C are the same, and e and f are designed to be 50 mm and 8 mm. Also, in this example, there is one weir 3A, so the finishing process can be further simplified. It can save time.

[Effects of the Invention] As explained above, according to the vacuum suction casting method of the present invention, by appropriately setting the shape and size of the molten metal introduction part and weir, it is possible to achieve a high as-cast yield and reduce the number of finishing steps. Castings can be manufactured with simple operations.

[Brief Description of the Drawings] Fig. 1 is a perspective view showing an as-cast product produced by the vacuum casting method of the present invention, Fig. 2 is a front view of the as-cast product shown in Fig.
FIG. 4 is a cross-sectional view showing the vacuum casting apparatus, FIGS. 5 and 6 are graphs showing the effects of the same embodiment, and FIG. 7 is a perspective view showing another embodiment. , FIG. 8 is a front view of another embodiment, FIG. 9 is a side view of another embodiment, and FIG. 10 is a perspective view of a conventional as-cast product.

Claims (1)

[Claims] In the vacuum suction casting method in which the pressure inside the cavity of the mold is reduced and the molten metal is introduced into the cavity through the molten metal introduction passage and weir, the opening diameter of the molten metal introduction passage is determined by the diameter of the opening of the casting to be cast in the cavity. The wall thickness is at least 1.5 times that around the weir, and after filling the cavity with molten metal, the mold is raised from the molten metal so that the molten metal is returned before the weir has completed solidification and the molten metal in the molten metal introduction passage has solidified. A vacuum suction casting method characterized by stopping vacuum suction.