JPH02121763A - Casting method - Google Patents

Abstract

PURPOSE:To easily and surely prevent mixture of foreign matter by dipping a basket-like porous member into molten metal in a crucible preceded to pouring of the molten metal and inserting a stoke into the porous member. CONSTITUTION:At the time of dipping the porous member 11 into the molten metal 3 in the crucible 2, the foreign matter of deoxidation products, etc., precipitated at bottom part of the crucible 2 or floated in intermediate zone of the molten metal 3, is pushed out to outside of the porous member 11 and only clean molten metal 3 is obtd. in the porous member 11. Successively, a base 7 setting a mold 4, etc., is shifted to the upper part of a melting furnace 1, and by the descendent movement thereof, the stoke 10 is submerged into the molten metal 3 in the crucible 2. At the same time of submerging the stoke 10, by supplying negative pressure in a chamber 8, the negative pressure is introduced to inner part of the mold 4, too and the molten metal 3 in the crucible 2 is sucked up into a cavity 4a in the mold 4 through the stoke 10 and a sprue part 4b. By this method, the foreign matter is rejected in the crucible and only clean molten metal can de poured into the mold and the casting product having excellent cleanliness can be stably obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an improvement in a casting method in which molten metal in a crucible is injected through a stalk into a mold placed above the crucible.

(Prior art) This type of casting method includes a low-pressure casting method in which the crucible is sealed and a low pressure is applied inside the crucible, and the molten metal in the crucible is pushed up into the mold through a stalk. A suction casting method is well known in which a negative pressure is introduced into the crucible and the molten metal in the crucible is sucked into the mold through a stalk.

In this casting method, in order to prevent inclusion defects caused by foreign substances such as oxides from occurring in the cast product, conventionally, a porous member such as a wire mesh or a ceramic filter has been installed at the M-shaped sprue. were installed to trap foreign matter and prevent it from entering the cavity. However, according to this method, since the porous member is incorporated into the cast product, it not only has to be removed from the cast product by weir folding or processing, but also a new porous member must be reset into the M-shape after each shot. This resulted in an increase in the number of work hours and an extension of the cycle time.

As a countermeasure against this, for example, Japanese Patent Application Laid-Open No. 62-89580 discloses that a wire mesh is fixedly placed in the sprue part through an insulator, and electricity is applied to it to wait for the molten metal in the cavity to solidify. A casting method is disclosed in which the unsolidified molten metal is dropped into a crucible after the molten metal has solidified. According to this method, since the wire mesh (porous member) can be used, it becomes possible to solve the various problems in the general-purpose casting method described above.

Although the scope is different from the present invention, a casting method has already been disclosed in which the molten metal is passed through a filter having a specific pore size before melting the Ni-Ti alloy into an ingot. Publication No. 81-182873).

(Problem to be Solved by the Invention) However, according to the countermeasure shown in the above-mentioned Japanese Patent Application Laid-Open No. 82-895H, extra processing must be performed on the mold to attach the wire mesh, resulting in an increase in mold cost. In addition to this, there is a risk of electrical wiring being routed around the mold, which may come into contact with other objects during mold transfer and be damaged, so M-type must be handled with care. The problem was that it required a lot of time. Furthermore, since a wire mesh is fixedly placed at the sprue of the mold, it cannot be applied to sand molds that collapse after each shot, and there is a problem that the range of application is narrow.

) The K invention was made with the aim of solving the above-mentioned conventional problems, and its purpose is to simply and reliably prevent foreign matter from entering the mold without installing a porous member in the mold. The object of the present invention is to provide a casting method D:.

(Means for Solving the Problems) In order to solve the above-mentioned conventional problems, the present invention provides a solution to the problem of the crucible by passing the molten metal in the crucible through the stalk. In a casting method that involves pouring into molds placed on two sides, prior to pouring the molten metal,
The gist is that a cage-shaped porous member is immersed in the molten metal in the crucible, and the stalk is inserted into the porous member.

In the present invention, the material of the porous member is not specified, and wire mesh, ceramic filter, etc. can be selected. In addition, if the mesh size of this porous member is too coarse, it will not have the effect of removing foreign matter, and if it is too fine, it will easily become clogged, so the mesh number is No. 18 (opening 1.0 mrs), No. , 10.5 (eye opening 1
．． It is desirable to select one with a rating of 7+ss+).
Furthermore, the overall size of this porous member is arbitrary, and for example, it may be large enough to almost cover the inner surface of the crucible, or may be large enough to surround the stalk.

In the present invention, the porous member is immersed in the crucible at any time before the start of casting, but when scouring is performed in the crucible, it is at an appropriate time after the end of scouring and immediately before the start of PI production.

(Operation) In the casting method configured as described above, foreign matter is removed within the crucible and only clean molten metal is poured into the mold.

Moreover, it is sufficient to mechanically immerse the porous member in the crucible, and unnecessary work on the mold can be eliminated.

(Example) Hereinafter, an example of the present invention will be described based on the accompanying drawings.

FIG. 1 shows a first embodiment of the present invention applied to suction casting of magnesium alloy. In the same figure, 1
is a permanently installed melting furnace, and a crucible 2 is installed inside the melting furnace 1. In this crucible 2, the raw materials are melted and their components are adjusted, and further scouring is performed by adding a deoxidizing agent and the like, and the obtained molten magnesium alloy 3 is held in the crucible 2.

A mold 4 consists of an upper mold 5 and a lower mold 6. The mold 4 is placed on the base 7 and its 1. '4 is covered by a chamber 8 which is detachably connected to the base 7. A pipe 9 connected to a negative pressure source (not shown) is routed through the chamber 8, and negative pressure is supplied into the chamber 8 through the pipe 9 during construction. Further, a stalk 10 that extends downward through the base 7 is connected to a sprue 7b of the mold 4 that communicates with the cavity 7a. The base 7 can be moved laterally by a conveyance means (not shown) and can be moved up and down by an elevating means (not shown). During casting, the base 7 is moved north of the melting furnace 1 to move the stalk LO into the crucible. It operates so as to be immersed in the molten metal 3 in 2.

Therefore, in the embodiment of Sui-Tei 1, a cage-shaped porous member 11 is separately prepared as shown in FIG.
It is immersed in the molten metal 3 in the crucible 2 at the timing described later.

This porous member 11 is.

Stainless steel (- JIS SOS 43G as an example)
It is made up of a frame 12 made of stainless steel and covered with a wire mesh 13 made of stainless steel, and is large enough to cover the inner surface of the crucible 2. A support arm 14.14 extends from one end of the porous member 11 in the left-right direction. Retained.

During casting, the porous member 11 is immediately immersed in the molten metal 3 in the crucible 2 after the above-mentioned scouring is completed. By this immersion of the porous member 11, foreign substances such as deoxidized products (schematically indicated by x marks in FIG. pushed to the outside.

Inside the porous member 11, only clean molten metal 3 gathers, and as shown in FIG.
is moved above the melting furnace 1, and its downward movement causes the stalk 1o to be immersed in the molten metal in the molten metal 3. At the same time as this immersion of the stalk IO, a negative pressure is supplied into the chamber 8. Then, negative pressure is introduced into the mold 4,
The molten metal 3 in the crucible 2 is sucked up into the cavity 4a in the mold 4 through the stalk 1G and the sprue 4b.

Then, after waiting for the molten metal in the cavity 4a to solidify, the chamber is returned to the atmosphere. The unsolidified molten metal below B4b falls into Luppo 2, and thereafter, the stalk 10 is raised by the operation of the base 7, and the mold 4 is conveyed to the mold breaking station, where the mold is broken and the series of steps are carried out. The casting work is completed.

According to the above-described casting method, only the clean molten metal 3 in the porous member 11 is sucked up into the mold 4, so that a cast product with few inclusions and excellent cleanliness can be obtained.

Here, the mesh size of the porous member 11 is determined by the mesh No.
, 10.5 (mesh opening: 1.7 mm), and the occurrence of inclusion defects was investigated for a cast product (Example 1) obtained by carrying out the #PI manufacturing method described above. In the investigation, 8 charges were continuously cast, with 10 shots being 1 charge, and the inclusion defect rate was determined for each charge. For comparison, the inclusion defect rate was similarly determined for a cast product (comparison amount) obtained by carrying out the above casting without using a porous member. The investigation results are shown in Figure 3. In the figure, 0 represents the product of this example, and Δ represents the comparison amount. From this, it can be seen that the defective rate increases linearly from 3 charges on as the number of charges increases. 100% defective after 7 charges, but the product of this example still did not generate inclusion defects even after 8 charges, indicating that water settling was extremely effective in preventing inclusion defects. It became clear.

Next, set the mesh size of the porous member 11 to 2.

, 3.5 (fl opening 5.6mm) , 5
(H opening g 4.0+m) 7 (opening 2.8mm)
, 10.5 (eyes open!, 7 meals), 1601 intervals 1. Omm), 2B (opening 1.7mm)
Casting was performed in the same manner as above, and the occurrence of inclusion defects was investigated. The yJR inspection results are shown in Figure 4. From the results shown in the same figure, when using a porous seal with a tl coarser than mesh No. 7, as the number of charges increases from 4 charges, the defects linearly increase. While the rate increases, Metush No.

When a porous member 11 with a fine mesh of 10.5 or more was used, no inclusion defects occurred even after 8 charges, and it was found that it is desirable to select a porous member as fine as possible. Ta. However, mesh No. 28
If the mesh is too fine, as in the case of mesh size, clogging is likely to occur, so it is ideal to select a mesh with a mesh number of about 18 or 10.5.

FIG. 5 shows a second embodiment of the present invention applied to suction casting of aluminum alloy. In this figure, the same parts as those shown in FIG. As shown in FIG. 6, a cage-shaped ceramic filter is selected, and its overall size is made large enough to surround the stalk IO. This porous member 21 also has a support arm 22 extending in the left-right direction from its upper end, and this support arm 22 is seated on the upper surface of the melting furnace l.
In the second embodiment, the porous member 21 is immersed in the molten aluminum alloy 23 in the crucible 2 by blowing an inert gas into the molten metal 23 to remove the porous member 21. After performing the gas treatment and immersing the porous member 21, casting is performed in the same procedure as in the first embodiment.

The clean molten metal 23 in the porous member 21 is sucked up into the mold, making it possible to obtain a cast product with fewer inclusions, similar to the first embodiment.

Here, the porous member 21 has a thickness t (FIG. 6) of 10 mm and a mesh size of 9.5 mm. Using No. 9°2, 50 shots were continuously cast using the above casting method, and the occurrence of inclusion defects was investigated for each charge. As a result, no inclusion defects were observed in the cast product. Incidentally, the sprue part 4b (first
Using the conventional general-purpose 'pI manufacturing method, in which a wire mesh (mesh No. 9.2) is set in a wire mesh (Fig. As a result of investigating the occurrence of defects, the inclusion defect rate was 10%.In the conventional method, such inclusion defects occurred because the wire mesh was displaced from its predetermined position by the flow of molten metal.
This is due to the occurrence of gaps, and the method of the present invention, which does not allow such defects to occur, greatly contributes to stabilizing the quality of #PI construction. In addition, the average cycle time during the same 50 shots was 1 minute and 30 seconds in the conventional method, but it was 1 minute and 3 seconds in this second embodiment, and the method of the present invention greatly contributed to improving productivity. It became clear that.

(Effects of the Invention) As described above in detail, according to the casting method according to the present invention, by immersing the cage-shaped porous member in the molten metal in the crucible, foreign matter can be removed in the crucible. Only clean molten metal can be injected into the mold, making it possible to stably obtain cast products with excellent cleanliness. In addition, since there is no need to make any special modifications to the mold, it is possible to reduce not only the number of work hours but also the cost of the mold.Furthermore, it can be applied to both molds and sand molds, and the effect is great. be.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing the first embodiment of the present invention, Fig. 2 is a perspective view of a porous member used in the first embodiment, and Fig. 3 is a cross-sectional view showing the first embodiment of the present invention.
FIG. 4, a graph showing the occurrence of inclusion defects in the castings obtained in the example in comparison with the comparative example, shows the influence of the size of the holes in the porous member on the incidence of inclusion defects in the first example. FIG. 5 is a sectional view showing the second embodiment of the present invention, and FIG. 6 is a perspective view of the porous member used in the second embodiment. 2 ... Crucible 3 ... Molten metal 4 ... Mold 10 ... Stoke 11 ... Porous member (and 2 others) 2nd [7I 3rd Kyodai 47 Charji Maki

Claims (1)

[Claims] (1) In a casting method in which molten metal in a crucible is injected through a stalk into a mold placed above the crucible, prior to pouring the molten metal, a cage-shaped porous member is immersed in the molten metal in the crucible, and the stalk is A casting method characterized by inserting a into the porous member.