JPS6143154B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a pouring control method for a pressurized automatic pouring furnace, which effectively prevents air from entering the molten metal poured into the mold during automatic pouring into the mold. At the same time, the sprue cup of the mold is constantly filled with molten metal during pouring, so that the molten metal does not overflow outward, and the pouring can be performed at the most effective pouring speed pattern. The purpose is to provide a control method.

As is well known, pressurized automatic pouring furnaces are used in casting lines, and their basic structure:
The operation is as shown in FIGS. 1a, b, and c. The furnace body 1 includes a molten metal chamber 2, a tapping passage 3 and a molten metal receiving passage 4 which are provided in communication with the bottom area of the molten metal chamber 2 in a siphon type, respectively, and a lid 5 that hermetically seals the molten metal chamber 2. 3a and 4a are an outlet and a receiving outlet, respectively. A pressurizing conduit 6 opening into the lid 5 faces into the molten metal chamber 2 and communicates with an external pressure source. The pouring operation of such a pouring furnace is as follows. First, when waiting for pouring, a base pressure P is applied to the upper surface of the molten metal in the molten metal chamber 2, as shown in FIG. 1a. The base pressure P pushes down the molten metal level in the molten metal chamber 2, and maintains the molten metal level in the tapping passage 3 at a pre-level, reaching the level immediately before tapping. From this state, as shown in FIG. 1b, a shot pressure ΔP is applied which is added to the base pressure P and causes the molten metal to pass over the weir of the tap outlet 3a. As a result, the supply pressure inside the furnace increases to the pouring pressure of P+△P,
The molten metal is tapped out from the tap 3a and poured into a mold (not shown). When the predetermined amount of molten metal is poured, the first
As shown in Figure c, the pressure inside the molten metal chamber 2 is released to below the base pressure P. Therefore, the level of hot water in the hot water tap passage 3 decreases, hot water tap stops, and one pouring operation is completed.
Replenishment of molten metal is performed through the molten metal inlet 4a. The furnace pressurization control in each step of the pouring operation as described above is all performed automatically, and the conventional control system diagram is as shown in FIG. That is, a volume booster 8 for controlling the supply pressure in the furnace is inserted in a pressurizing pipe 6 that communicates and connects the pouring furnace 1 and the compressed air source 7. As is well known, the volume booster 8 is a pilot-controlled large-capacity pressure reducing valve, and is constructed so that the output side pressure is controlled in a constant ratio relationship with the pilot pressure. Control circuit 9 of this volume booster 8
A booster relay 10 for setting the base pressure and a shot pressure setting device 11 are connected in cascade between the pressure source 7 and the pressure source 7, respectively. The shot pressure setting device 11 is a pressure reducing valve that can be adjusted manually, for example, so that the set value can change the pouring speed according to the volume of the mold, etc., and is connected to the booster relay 10 via a solenoid valve 12. The booster relay 10 is connected to the base pressure P set as described later, and also to the shot pressure setting device 1.
The shot pressure ΔP set in step 1 is added, and this value is applied to the volume booster 8 as a control signal pressure, and is connected to the control end plug of the volume booster 8 via the solenoid valve 13. To set the base pressure P, a servo motor 1 is connected to a load cell 14 that detects the weight of molten metal in the furnace 1 and a variable throttle part of a booster relay 10.
5. A potentiometer 16 and an adjuster 17 are provided which are variably operated in conjunction with the servo motor 15. That is, as the amount of molten metal in the furnace changes, the base pressure for keeping the molten metal at a pre-level must be changed every moment, and the target value of this base pressure P is determined according to the output signal of the load cell 14. On the other hand, the base pressure set value of the booster relay 10 by the servo motor 15 is fed back via the potentiometer 16, and the deviation value outputted from the regulator 17 after being compared with the target value is used to operate the servo motor 15 and automatically The booster relay 10 is then set to the new predetermined base pressure. On the other hand, an exhaust valve 18 is connected to the pressurizing pipe 6 for releasing pressure when the hot water tap is stopped, and the exhaust valve 18 is connected to the solenoid valve 1.
Opening/closing is controlled by compressed air via 9. 20
is a relief valve.

In the above control system, in the pre-level holding state before tapping, the solenoid valve 12 is closed, 13 is open, and 19 is closed, and the pressure inside the furnace body 1 is controlled by the booster relay 10.
The base pressure P is increased through the volume booster 8, which is controlled by the base pressure signal pressure. When hot water is tapped, valves 12 and 13 are open and valve 19 is closed, and the shot pressure setting device 1 is set to the base pressure P mentioned above.
The volume booster 8 is controlled by the signal pressure to which the shot pressure ΔP set in step 1 is added, and the pressure inside the furnace is increased to the pouring pressure P+ΔP. Valve 1 when hot water stops
Only 9 is open, and 12 and 13 are closed. Therefore, the pressure inside the furnace is released to the outside through the exhaust valve 18. Immediately thereafter, the pressure inside the furnace is increased to a pre-level holding state until the next pouring process. Each of the above solenoid valves 1
Controls 2, 13, and 19 are program-controlled by a timer (not shown) in conjunction with the casting line.

Now, in the conventional pouring control method described in Figure 2,
When pouring molten metal, the molten metal is tapped at (base pressure P) + (constant shot pressure ΔP), and the relationship between the molten metal pouring pattern into the mold and the molten pouring pressure is as shown in FIG. When pouring into the mold for the first time, set the specified base pressure.
During pouring, a constant shot pressure ΔP is applied to _P1 . The second time, the base pressure is slightly higher than _P1 because the amount of molten metal is reduced by the amount of melt released.
Set to P ₂ . It should be noted that it takes a short time for the molten metal to reach the outlet after the shot pressure is increased, and pouring of the molten metal starts with a slight delay. Considering the operation of pouring molten metal into the mold, as shown in FIG. 4, the casting electrode 21 is provided with a sprue cup 23 at the sprue 22, and molten metal is poured as shown by arrow A. In this case, if the pouring speed is slow and the sprue 22 is not filled with molten metal, the air around the outside gets caught up in the molten metal and cannot escape, causing the formation of cavities inside the casting. becomes. For this reason, especially in the early stages of pouring, the molten metal must be poured at a fast speed so that the sprue cup 23 is completely filled, and consideration must be given to prevent air from entering the molten metal from the outside. In this state, the molten metal slowly flows down into the mold cavity due to its own weight. However, if a predetermined amount of molten metal is poured at a fast enough speed to fill the sprue cup 23, the molten metal may overflow from the sprue cup 23 and spill outward depending on how the molten metal flows down into the cavity. There is a risk of it being stored away. In the conventional method where the pouring pressure, which is the sum of the shot pressure and the base pressure, is kept constant, that is, at a constant pouring speed, the pouring speed and pouring time are set and the pouring is performed automatically. Molten metal often overflowed from the mold, resulting in insufficient amount of metal poured into the mold, resulting in casting losses.

The present invention eliminates the drawbacks of the above conventional method,
The purpose of this invention is to provide a method for controlling the pouring of molten metal into a pressurized automatic pouring furnace, which enables the pouring of molten metal into a mold effectively without overflowing, even though it uses an automatic pouring method. be. The purpose of this is to use the method of the present invention to set the pouring speed of the pouring furnace high in the first half of the pouring process and slow in the second half when pouring the metal into the mold. This is achieved by controlling the magnitude of the shot pressure applied for a predetermined period of time so that it is large in the first half of the shot pressure application period and small in the second half.

Furthermore, as an apparatus for carrying out the method of the present invention,
The shot pressure setting device sets the shot pressure setting value to be large or small, and is switched and controlled during pouring.
It is equipped with a pressure reducing valve for setting the shot pressure.

The method of the present invention will be explained in detail below with reference to the drawings. Fig. 5 shows that during pouring pressurization from time _t1 to time _t3 , the furnace is heated so that the pouring speed is fast in the first half up to time _t2 , and slow in the second half after time _t2 . The pouring pressure of internal pressurization is controlled to be high in the first half and low in the second half. With this control method, the molten metal that is tapped from the pouring furnace and poured into the mold is
In the first half of pouring, the sprue cup is filled to the brim to prevent air from getting mixed in, and in the second half, the speed to the sprue cup is gently controlled to correspond to the molten metal flowing slowly from the mold sprue into the cavity. This prevents the molten metal from overflowing and allows the molten metal to be poured into the mold effectively.

As the above-mentioned pouring pressure control means, in the method shown in FIG. 5, the shot pressure is controlled to be changed to a large shot pressure ΔPa in the first half of pouring, and to a shot pressure ΔPb smaller than ΔPa in the second half. As a result, the pouring pressure, which is the sum of the base pressure P and the shot pressure △Pa or △Pb, changes stepwise as shown in the figure.
Pouring can be performed at a desired pouring speed pattern.

An apparatus for carrying out the control method shown in FIG. 5 can be constructed as shown in FIG. 6 according to the present invention. The illustrated embodiment differs from the control system circuit shown in FIG. 2 in the shot pressure setting device. The other circuit configurations are the same. That is, in the embodiment of the present invention shown in FIG. 6, two pressure reducing valves 11a and 11b for setting shot pressure are connected in parallel via pipes via electromagnetic switching valves 24a and 24b, respectively. However, one pressure reducing valve 1
1a is set to shot pressure ΔPa in FIG. 5, and the other pressure reducing valve 11b is set to ΔPb. Each pressure reducing valve 11a, 11b is switched and controlled by a program timer 25 at time _t2 in FIG. According to the above circuit configuration, in the first half of pouring, the valve 24a is open and the valve 24b is closed, and the shot pressure △Pa is added to the base pressure P set in the booster relay 10 to control the volume booster 8. . Therefore, the pouring pressure in the furnace is P+△Pa, and the pouring speed is fast. then time t ₂
When this happens, the valve 24a is closed and the valve 24b is opened, so the shot pressure is set to ΔPb. Therefore, the pouring pressure in the furnace is reduced to P+△Pb via the volume booster 8, and the pouring speed is slowed down to effectively pour the metal into the mold according to the pouring pattern shown in FIG. can be done.

As described above, according to the present invention, the pouring speed pattern when pouring metal from a pressurized automatic pouring furnace into a mold is controlled to be fast in the first half of pouring and slow in the second half. Therefore, the sprue cup of the mold is constantly filled with molten metal to effectively prevent air from entering from outside, and the molten metal can be poured effectively without overflowing from the sprue cup to the outside. Since the shot pressure is adjusted to control the pouring speed, the error in the pouring amount is smaller and the configuration of the control device is simpler than when the pouring speed is controlled by adjusting the base pressure. The practical effects are extremely large.

[Brief explanation of the drawing]

Figures 1a, b, and c are cross-sectional views of the pressurized pouring furnace showing different operating states, Figure 2 is a conventional pouring control system circuit diagram, and Figure 3 is the conventional pouring control system shown in Figure 2. A diagram showing the relationship between the pressure inside the furnace and the pouring speed into the mold according to the control method, Figure 4 is an explanatory diagram of the pouring situation into the mold, and Figure 5 is a diagram explaining the pouring control method according to the present invention. A line diagram corresponding to FIG. 3 and FIG. 6 are circuit diagrams of essential parts showing a pouring control device for carrying out the control method shown in FIG. 5, respectively. 1: Pouring furnace, 2: Molten metal chamber, 3a: Tapping port, 5:
Lid, 6: Pressure pipe line, 7: Pressure source, 8: Volume booster, 9: Volume booster control circuit, 1
0, 10a, 10b: Booster relay, 11, 1
1a, 11b: Pressure reducing valve for shot pressure setting, 1
2, 13, 19, 24a, 24b, 26a, 26
b: Solenoid switching valve, 18: Exhaust valve, 25: Program control timer, P: Base pressure, △P, △
Pa, △Pb: Shot pressure.

Claims (1)

[Claims] 1. Equipped with a tap that communicates with the bottom area of the molten metal chamber in a siphon style with a sealed lid, and before pouring the molten metal, base pressure is applied in the molten metal chamber to maintain the height of the molten metal in the tap path at a pre-level just before pouring. At the same time, when pouring molten metal using a pressurized automatic pouring furnace that taps the molten metal at a pouring pressure that is the base pressure plus shot pressure and pours it into the mold, the shot pressure that is applied to the furnace in addition to the base pressure is used. By controlling the magnitude of the shot pressure so that it is large in the first half of the application period and small in the second half, the pouring speed is large in the first half of pouring and becomes small in the second half. Method for controlling pouring in a pressure-type automatic pouring furnace.