JPS6012268A - Method and device for suction casting - Google Patents

Abstract

PURPOSE:To obtain a defectless casting having excellent cleanliness in the stage of evacuating the inside of the cavity of a casting mold to suck a molten metal up into the cavity and casting said metal by immersing a sprue into the molten metal while maintaining the inside of the cavity in the pressurized state for the beginning thereby preventing intrusion of slag. CONSTITUTION:Air or inert gas is supplied from a pressure control device 6 into the cavity 4 of a casting mold 1 and is pressurized. A sprue 5 is then dipped to the prescribed depth into a molten metal 9 while the pressurized gas is allowed to flow out through the sprue 5. The flow rate of the pressurized gas is changed over to a low flow rate when the top end of the sprue 5 arrives at the surface of the molten metal. The cavity 4 is then evacuated to suck the molten metal 9 therein. Said device 6 is connected via a conduit 7 to the mold 1 and is formed of a pressurizing device 11, an evacuating device 12, a pressurizing valve 13 and a reducing valve 14 provided in combination therewith, a pressure switch 17 and a pressure setter 18 which regulates the working pressure thereof.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to an improvement in the suction casting method in which the pressure inside the mold cavity is reduced and the molten metal is sucked up and cast. (Prior art) Suction casting in which the molten metal is sucked up and cast. This method is used as an excellent method for producing sound castings because there is little turbulence in the molten metal filling the cavity, good molten metal circulation, and a large pouring effect at the sprue. This suction casting method also has the advantage of a high yield because the unsolidified molten metal is quickly discharged from the product solidification layer and sprue.

However, when the sprue is immersed in the molten metal during casting, the surface of the molten metal is usually covered with slag and flux, and this slag may get mixed into the sprue. There was a problem that inclusions increased.

Of course, this problem can be solved by removing slag, etc., but slag, etc., protects the molten metal from the atmosphere,
It is essential to ensure the specified quality,
Furthermore, even if an attempt was made to remove it mechanically for a time, it was only moderately difficult in actual operation.

(Object of the Invention) In view of the above-mentioned problems of the prior art, the present invention provides a means for preventing quality inspection of the molten metal, and locally removing slag etc. from the sprue insertion part on the surface of the molten metal, thereby making it possible to remove the slag from inside the mold. An object of the present invention is to provide a suction casting method and device that prevents slag etc. from entering the mold.

(Structure of the Invention) This purpose is to pressurize the cavity of the mold with air or inert gas before casting, and to cause the pressurized gas to flow out from the sprue. The sprue is immersed in the molten metal to a predetermined depth. This is achieved by a suction casting method and apparatus thereof, in which the pressure in the cavity is then switched to reduced pressure to suck the molten metal.

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

FIG. 1 shows the basic aspect of the suction casting method. In the figure, reference numeral 1 denotes an air-permeable mold such as a sand mold or a shell mold, which is made up of an upper mold 2 and a lower mold 3, and the periphery thereof is usually covered with a PVC film or a metal chamber. The mold 1 is supported by a lifting device (not shown), and a sprue 5 extending downward from the lower mold 3 communicates with the cavity 4.

Further, a pressure control device 6 is connected to the casting ff11 via a conduit 7. Conventionally, the pressure control device 6 plays the role of exhausting the inside of the cavity 4 and the sprue 5 communicating therewith, but in this embodiment, the pressure control device 6 has a ladle 08 which has various functions described later, and is separately melted. The mold 1 is set under the mold 1 to accommodate the molten metal 9 produced in the furnace.

The surface of the molten metal 9 is usually covered with slag (including flux) to prevent atmospheric oxidation of the molten metal and absorption of hydrogen from the atmosphere.
Ten layers are formed. Note that, in some cases, the mold 1 is placed above the melting furnace itself without using the ladle 8, and the mold 1 is lowered by driving a lifting device (not shown). At this time, conventionally, the pressure in the cavity 4 and the sprue 5 would have been reduced by the operation of the pressure control device 6. If the mold 1 is then lowered and the sprue 5 is immersed in the molten metal 9, the molten metal 9 will be released from the sprue. 5 into the cavity 4, whereby a product of a predetermined shape is cast.In this embodiment, however, by installing the pressure control device 6 as shown in FIG. , which undergoes a unique casting process as shown in FIG.

That is, in FIG. 2 showing the pressure control device 6, 11
is a pressurizing device that is a source of air or inert gas, 1
Reference numeral 2 denotes a pressure reducing device containing a vacuum pump, etc., which are connected in parallel to the conduit 7. Furthermore, the pressurizing device 11 and the pressure reducing device 12 each have a pressurizing valve (electromagnetic valve) 1.
3 and a pressure reducing valve (IIt magnetic valve 14) are connected to the pressure sensor (not shown) in the conduit 7 by a pressure signal system 15, and a pressure signal system 15 is connected to the pressure sensor (not shown) in the conduit 7, and a control signal A pressure switch 17 connected through the system 16 is provided.This pressure switch 17 detects the back pressure of the pressurized gas in the conduit 7, and opens and closes the pressurizing valve 13 and the pressure reducing valve 14 based on it. Its operation timing is determined by the pressure setting device 18.
It is designed to be adjusted by.

In addition, a stop signal system 19 is connected from the pressure switch 17 to a stop mechanism of the lifting device (not shown).
3 is opened, and the pressure reducing valve 14 is closed to introduce a predetermined pressurized gas into the cavity 4 of the mold 1 and the sprue (Fig. 1). When the device is driven to lower the mold 1, the sprue 5 approaches the surface of the molten metal 9, and at this time, the pressurized gas flowing out from the sprue 5 causes the 10 layers of slag in the insertion part of the sprue 5 to move toward the outer periphery. The water is removed and the clean surface of the hot water is exposed on the other side (a). Thereafter, as the mold 1 descends, the sprue 5 passes through the exposed portion of the molten metal surface and immerses into the molten metal 9, gradually increasing the immersion depth.

During this time, as shown in Figure 4, the back pressure of the pressurized gas rises slightly just before the sprue 5 is immersed (point A in the figure), and then gradually fluctuates up and down due to bubbling. It shows the property of increasing the pressure.

In this embodiment, the pressure setting device 18 sets the set pressure of the pressure switch 17 to a pressure corresponding to a predetermined immersion depth (point B in FIG. 4). When the sprue 5 reaches a predetermined immersion depth, the pressure valve 15 closes and the pressure reducing valve 14 opens, conversely reducing the pressure inside the cavity 4 and the sprue 5.At the same time, the pressure switch 17 turns the lifting device up and down. A stop signal is sent to the mechanism, and the lifting device and therefore the mold 1 stop descending. Under this condition, the molten metal 9 in the ladle 8 is sucked up into the cavity 5 through the sprue 5, Predetermined casting is completed (c).

As described above, according to the method, when the sprue 5 is immersed in the molten metal, the slag 10 is removed from the insertion part, and the slag 10 is removed.
0 into the sprue 5 and therefore into the cavity 4 is prevented.

FIG. 5 shows a pressure control device according to another embodiment of the present invention. Here, the same components as those shown in FIG. 2 are given the same reference numerals, and their explanations are omitted.
A first pressurizing valve 20 and a second pressurizing valve 2 are provided in the conduit 7 connecting to the first pressurizing valve 2.
2 are interposed in parallel, and a flow rate regulating valve is interposed between the second pressurizing valve 22 and the pressurizing device 11.
A first pressure switch 23 and its pressure setting device 24 and a second pressure switch 25 and its pressure setting device 26 are provided.The first pressure switch 23 is connected to the first and second pressurizing valves 20. The pressure value at point A in Fig. 4 is set there, and the pressure value at point A in Fig. 4 is set there.
The pressure switch 25 is used to switch between the second pressurizing valve 21 and the pressure reducing valve 14, and the pressure value at point B in FIG. 4 is set there. The first and second pressure switches 25, 25 may be replaced.

With this configuration, first, the first pressurizing valve 2° is opened, the second pressurizing valve 21 is closed, and the mold 1 is lowered while supplying pressurized gas at a relatively high flow rate to the cavity 4. At this stage, when the sprue 5 approaches the hot water surface (FIG. 3 (al), the slag 10 is removed from the insertion part of the sprue 5 as in the first embodiment).
is excluded. However, just before the sprue 5 is immersed in the molten metal 9, the back pressure increases slightly and reaches point A, as shown in FIG. The first pressurizing valve 2o is activated based on the signal of
is closed and the second pressurizing valve 21 is opened.

As a result, a relatively low flow rate of pressurized gas is supplied into the cavity 4 via the flow rate regulating valve 22, and at the same time, valve control is transferred from the first pressure switch 27 to the second pressure switch.

After that, when the mold 1 is further lowered and the sprue 5 reaches a predetermined immersion depth (Fig. 3(b)), the back pressure reaches B shown in Fig. 4.
The second pressure switch 25 closes the second pressurizing valve 21 and opens the pressure reducing valve 14 by reducing the back pressure. From then on, the same operation as in the first embodiment is performed. be exposed.

In this way, in the embodiment of the end chain 2, pressurized gas is supplied at a relatively high flow rate until the sprue 5 comes into contact with the molten metal surface to facilitate the removal of the slag 1o, and then the sprue 5 flows into the molten metal 9. During immersion, a relatively low flow rate of pressurized gas is supplied to suppress bubbling in the molten metal.

Figure 6 shows the inclusion results of products cast according to the first and second examples above, in comparison with the results of products obtained by the conventional wicking casting method17. It is something.

The melting conditions are: melted material: 5usso4, melting furnace τ
High frequency furnace, melting amount: 50C Casting conditions: mold = CO2
Mold, casting amount: 2kf, immersion depth: 100+IIwI, pressurizing conditions: pressurized gas: argon gas, first example:
+ 200, Hg, second example: + 200 m
+Hg (1st stage), +100. Hg (second stage),
The test conditions were as follows: - For each 10 shots, the cut layer, cross-section polishing, microscopy at 50x magnification, and the frequency of inclusions observed were checked.

From FIG. 6, inclusions were observed in 8 out of 10 shots using the conventional method, 2 out of 10 shots using the first embodiment, and 1 out of 10 shots using the second embodiment. Only inclusions were observed in the shot, confirming the effectiveness of slag removal in water droplets.

Here, the reason why the second embodiment is slightly better than the first embodiment is that the flow rate of the pressurized gas is 2.
This is because bubbling of the molten metal was suppressed as much as possible by the stage switching. Furthermore, by using argon gas as the pressurized gas, the inside of the cavity 4 is replaced with an inert gas, and the molten metal is protected from the atmosphere, and this effect is added to that of this example. It is.

In the above two embodiments, the air-permeable mold 1 was used, but it goes without saying that water droplets can also be applied to a suction casting method using a mold equipped with an exhaust means.

(Effects of the Invention) As described above in detail, the present invention effectively eliminates slag when initially pressurizing the inside of the cavity and immersing the sprue in the molten metal, and then reducing the pressure inside the cavity to drain the molten metal. We have realized a suction casting method and device that can draw suction into the cavity.This prevents slag and other substances from getting into the cavity, making it possible to manufacture healthy castings with excellent cleanliness.

In addition, water droplets can be eliminated by simply switching between pressurization and depressurization, and it is also possible to set the sprue depth by detecting pressure17, making it extremely easy to automate the entire suction casting process. It worked.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the basic aspect of the suction casting method, Fig. 2 is a block diagram showing an example of the structure of a pressure control device according to the present invention, and Fig. 5 fa) to (cl are according to the present invention). A schematic diagram showing the suction casting method in chronological order, FIG. 4 is a back pressure characteristic diagram of pressurized gas, and FIG. 5 is a block diagram showing the structure of a pressure control device as another embodiment of the present invention. Figure 6 is a frequency distribution diagram showing the results of inclusions in cast products obtained by water droplet in comparison with the conventional method. 1... Mold 4... Cavity 510. Sprue, 6, 6' ...Pressure control device 7...
Conduit 9... Molten metal 11... Pressure device, 12... Pressure reduction device 13.20
．． 21...Pressure valve, 14...Pressure reducing valve 17.23.2
5...Pressure switch 18.24.26...Pressure setting device

Claims (4)

[Claims] (1) Before casting, the cavity of the mold is pressurized with air or inert gas, the pressurized gas is allowed to flow out from the sprue, and the sprue is immersed in the molten metal to a predetermined depth, and then the cavity is depressurized. A suction casting method characterized by switching to molten metal and sucking the molten metal. (2) The suction casting method according to claim 1, characterized in that the flow rate of the pressurized gas is changed from a high flow rate to a low flow rate when the tip of the sprue reaches the hot metal surface. (3) A pressure device that is a source of air or inert gas, a pressure reducing device that is a source of low pressure, a pressurizing valve and a pressure reducing valve that are attached to each of the pressurizing device and the pressure reducing device, and A pressure control device comprising a pressure switch that detects the back pressure of pressurized gas and switches between the pressurizing valve and the pressure reducing valve and stopping the lifting device, and a pressure setting device that adjusts the operating pressure of the pressure switch. 1. A suction casting device comprising: a pressure control device connected to a mold via a conduit. (4) One of the two pressure reducing valves is connected to a pressurizing device via a flow rate adjustment valve, and the opening and closing of the two pressure reducing valves is controlled by two pressure switches or a two-stage pressure switch and a pressure setting device attached to it. The suction casting apparatus according to claim 3, characterized in that the apparatus is configured to: