JPH0358825B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to casting systems, particularly low pressure casting systems, and methods for automatically controlling low pressure casting cycles.

Low-pressure casting is a well-known casting technique in which a metallic or non-metallic mold is placed in a sealed furnace, the bottom of the mold is filled with metal or a liquid alloy, and the metal or liquid alloy is solidified. To fill the mold, a pressurized fluid of several decibar is fed into the furnace to transport molten metal into the mold via an injection tube. After filling the mold, the pressure inside the furnace is increased further, during which time the metal solidifies. Once the metal has solidified, the supply of pressurized fluid is stopped and the unsolidified metal is recovered.

For low-pressure casting, metal molds, molds made of sand or graphite, zircon, carborundum, etc. bonded with a binder (mainly synthetic resin), and ceramic or plaster end molds can be used.

Metal molds are durable but expensive, so they are only used for mass production.

On the other hand, non-metallic molds are relatively inexpensive and
By adjusting the permeability, there is an advantage that the recesses in the mold can be filled more reliably.

Low pressure casting using inexpensive sand molds meets today's demands in industry, particularly in the aircraft industry, which requires high quality and tightly toleranced alloy parts.

The main technical problems affecting such cast articles are listed below.

Control of the turbulence that occurs as molten metal rises through the mold. This turbulence is related to the flow rate of the molten metal and is a factor that determines the degree of oxidation.

Ram knotting occurs when excessive pressure is applied to the excess head of the mold. When this ram knotting occurs, the intergranular spaces in the mold are covered with metal.

Coagulation started earlier than expected.

Metal flow (configuration,
displacement, cooling, etc.).

Reproducibility of operations to maintain uniform quality.

Improving manufacturing efficiency.

In order to better understand the working principle of the method according to the invention, when the tip of the metal is located almost stationary at a height H above the level of the metal in the crucible, the driving pressure into the crucible is P = Hρg (ρ It is useful to note that g is the density of the metal and g is the dynamic acceleration). The movement of liquid spreads the braking force between the metal and the wall.

Experience and calculations show that the differential law of driving pressure change defined by the following formula can be obtained.

dP/dt=KρgdH/dt=KρgV (V is the rising vertical velocity of the metal tip, K≧1 is a coefficient considering the mold shape and frictional resistance depending on V) When the value of the speed t, that is, dP/dt is small , K=1. When the value of V is large, K and V tend to asymptotic values.

Subsequently, the most common case with small V occurs, in the filling phase P = ρgH and dP / dtρgV, and in the high pressure phase, P = ρgH + △P, where △P is the high pressure experienced by the metal at the top of the mold.

When the metal is in the high pressure phase, this high pressure depends on the height H of the metal in the crucible, which changes with successive castings.

In order to obtain the conditions for the theoretical relationship regarding casting mentioned above, we need the following. This means, on the one hand, that the metal tip advances regularly and acts on the metal drive pressure in such a way that it follows a precise velocity profile. Whatever the shape and sharpness of the cavity to be filled, this advancement of the metal must occur without any attenuation that would cause the liquid to solidify rapidly and be interrupted before it is completed, and without casting. It must be carried out without agitation, which tends to cause oxidation which can cause local weakening and discontinuities in the product. On the other hand, a sufficiently high pressure is applied rapidly so that the metal after filling the mold cavity does not recede during the solidification process. However, it must be within variable conditions such that no metal infiltration occurs between the particles of the mold. Furthermore, these effects must take into account unstable fluctuations such as the drop in the height of the metal in the crucible and the evacuation of gases.

Prior art techniques developed to relatively solve these problems have not been successful. In some systems in use today, the casting cycle follows a phase limited by elevation marks located in the mold. Actuation is caused by the introduction of a predetermined amount of air into the crucible. The metal drive speed is a largely unpredictable result of this quantity, the shape of the article, and the inevitable emissions of gas. Other systems impose a constant rate of pressure variation for every cycle, or even make adjustments in multiple pressure steps until a determined final pressure is achieved. This system does not provide pressure correction to account for metal height reduction. This allows reproducibility of all castings. Additionally, some systems specifically make corrections from the representation given at the beginning of the analog calculator sequence. However, this requires prior adjustment and eliminates the possibility of casting different parts in each cycle, as is often done in the aerospace industry. Furthermore, corrections made admit inaccuracies in the estimate, and errors generally only increase as casting continues.

The purpose of the present invention is to comprehensively solve the above problems in low pressure casting methods. The present invention provides a cycle during the filling of the cavity of the mold, adapted to its development, with precise predetermined velocity and acceleration characteristics, and a high-pressure phase is created at a predetermined height after filling the mold and before solidification. It is equipped with a method that makes it possible to provide the following information.

The method according to the invention focuses on directly taking into account unstable variations such as mold metal height reduction and outgassing in order to provide these features.

Another object of the invention is to describe a method and a device which, by providing such material for implementing this general method, allows a theoretical and automatic development of the method of the invention.

In particular, the present invention automatically controls metal pressure through valves controlled by its pilot or controller.

The provided system essentially includes: namely, conventional low-pressure casting machines, automatic pilots, valves controlled by the pilot, pressure sensors in the furnace containing the crucible that convey pilot information, and pressure sensors located on the metal rise path at process change points in the mold that also convey pilot information to it. A number of sensors detect the presence of metal and a metal temperature sensor in the crucible is connected to the pilot.

According to the method of the invention, the continuous production of articles takes place in two stages.

The first stage is the following processing stage. After the casting system design has been determined, a pressure change curve is drawn that leads to a high pressure that will yield a metal drawing rate and an article with sufficient metallurgical properties. According to a preferred feature of the invention, a cycle divided into eight phases is selected. The first three phases correspond to mold filling. During each phase process, the metal is given a constant rate of rise appropriate to the shape of the article. To do this, a constant casting pressure variation rate is set during the process of these phases.

The first phase corresponds to the rise of the metal from the resting height of the crucible towards the mold and takes place inside the tube leading to the mold. During this phase of the process, the speed is high enough to depend only on the casting equipment. During the second phase, filling of the conical entrance of the mold takes place. The third phase takes place where the injection tube is connected to the mold. This phase takes place at different speeds depending on the type of article.

During the fourth phase, metal fills the mold. This phase is sometimes further divided. The optimum speed is related to the shape of the article, especially its thickness and height. Upon exiting the fourth phase, the metal must fill the mold.

To control the drive pressure during this dynamic portion of the casting, four metal presence detectors are installed at the points where the mold shape changes and communicate phase change commands to the pilot. . A particular sensor, in particular the one that first hits the metal, makes it possible to set the relationship between the driving pressure and the pressure outside the casting spout. To this end, the sensor commands the pilot to record the height of the driving pressure at the moment the metal moves to that height. Therefore, the pilot only takes into account the relative pressure, which considers the measured value recorded as zero pressure when the operation is initiated by the sensor. Therefore, the problem caused by the reduction in the height of the metal in the crucible is solved. Sometimes it can be used to divide the replenishment capture into dependent phases.

The next three steps take place after mold filling. During phase 5, the pressure △ for the height of the final pressure of mold filling
Set P1. It takes place for a time ΔT1. The speed and acceleration of the driving pressure are chosen in such a way as to avoid ram shock. This is because fine sand molds can be used.

Through phase 6, a pressure ΔT2 is established for a very short time ΔT2. The sum of ΔP1 and ΔP2 represents the mouth pressure that must be exerted before the article begins to solidify. ΔP1 and ΔP2 and ΔT1 and ΔT2 depend on the properties of the article, especially the nature of the alloy, thickness, length and height.

Phase 7 corresponds to high pressure maintenance. This phase is interrupted by a pilot following the information transmitted by the thermocouple at the end of solidification at the bottom of the article. This thermocouple is located in the hottest part of the casting system.

Phase 8 is the release phase. The parameters given to the casting in the testing process are in phase 8. namely temperature and rate of metal rise during the phase 2, 3, and 4 process. These rates are proportional to the rate of pressure variation during the process of these phases and give their final values. That is, the values are the values of high pressure ΔP1 and time ΔT1, and the values of high pressure ΔP2 and time ΔT2.

All these dimensions are given via the driving pressure. These parameters include various oxidation, bubbles, growth, water injection, micropositories, shrinkage pores,
Controlling micro-shrinkage porosity greatly affects the metallurgical properties of the article.

Generally, a large number of tests of this type are repeated and used statistically, varying the parameters of the casting system and also affecting the mold temperature. These tests are continued until satisfactory metallurgical properties are obtained. The pilot records the previous specific values effectively obtained during the casting and release strokes. Furthermore, it fills in and releases the duration of the mold filling phase. After each casting, the properties of the resulting article are tested.

According to this test series, eight castability characteristic values are isolated. The times of phases 5, 6 and 7 are associated with them. Introducing into the pilot memory the type of article (or its code), the eight cycle characteristics and the interrelationships that exist between the three periods of the corresponding phases 5, 6 and 7.

Subsequently, the second or manufacturing stage begins. The mold is placed in a low pressure machine and a single manual operation is used to mark the article and temporarily start the cycle. With these independent indications, the pilot adjusts the casting and temperature according to the optimum characteristics possessed by the memory.

According to a preferred embodiment of the invention, the equipment utilized in the manufacturing phase is simplified to possess only a single presence sensor, which will be described below. This sensor is located, for example, at the outlet of the metal injection tube. The mold is then removed from the cabinet. In this case, it is conceivable to use this cabin simultaneously to interrupt the first phase and to limit the height of the casting reference pressure. This criterion makes it possible to take into account the reduction in metal height.

In the casting of this mold, also in a series of steps, phase 2,
The time information corresponding to the changes of 3 and 4 is no longer given by the mold presence sensor, but by the pilot itself according to its suitability value.

According to the invention, means are provided for making it possible to make articles with very small thickness sections. In this case, a low pressure is created at the inner cavity end of the mold which is to form the narrow part of the article. During the casting process, the metal traps air bubbles in the voids. According to the invention, the formation of a vacuum in this cavity is programmed. This action is carried out by grooves that cross the side walls of the mold in the areas in question. This low pressure is achieved according to the same mold parameters that form the mold high pressure. In this case, the narrowness of the cavities associated with the outflow of metal is not disturbed and it is therefore possible to obtain a complete filling of these zones in a very satisfactory manner. The technique therefore consists in achieving a vacuum automatically and in small areas of cross-section according to the shape of the article.

Furthermore, according to the invention, means are provided for avoiding leakage of liquid metal under the mold. In fact, it is necessary to support the mold in place against the pressing action of the metal directed from the bottom upwards.

Other features and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings. This description is an example and does not limit the invention.

In FIG. 1, a crucible 1 is shown located inside an insulated furnace 2 in relation to the various machines making up the casting machine. The furnace is closed by a fixed lid 3. There is metal 4 inside the crucible. The cavity of the mold 5 is supplied with liquid metal via an injection pipe 6 and a casting system 7.

A small amount of driving gas (air or natural gas) is introduced into the furnace via conduit 8. The illustrated mold is applied to a processing stage with three metal presence sensors E2, E3, E4. This presence sensor is an electron that is grounded by passing through the metal. A fourth sensor E1 is fixedly located at the top of the injection tube 6. In order to avoid any clinker formation of eroded features due to continuous casting operations, a system consisting of a transmitter, a receiver, a generator and a wave beam analyzer was preferably chosen as the presence sensor.
The preferred form of this system will now be described in detail.

Auxiliary valve 9 for controlling the arrival of driving fluid to the mold
, a thermocouple 10 located 20 mm above the hottest contact of the casting system, and a thermocouple 11 located inside the metal crucible. A pressure sensor 12 is placed inside the crucible of the furnace. The furnace is reheated by resistor 13.

The power distribution includes ten setting devices 14 to 23 above it. The center of the switchboard has 12 scale plates 24 above it.
a to 24l, and a display scale plate 25 whose lower part embodies a polygonal line interrupted by nine small lamps. The lower part of the switchboard is equipped with a setting device 27 on the left, followed by a three-stage switch 28, a switch 29, and a pusher 30 with a light-emitting display.

4 presence sensors E1, E2, E3, E4, thermocouples 10 and 11, pressure sensor 12 are connected to cable 31
It sends information to the pilot via 37. The pilot then commands the opening and closing of the auxiliary valve 9 via the cable 38 and the installation of the resistor 13 under voltage via the cable 39.

Next, we will describe the adjustment and development of a pilot casting system during a test process to process articles of a given type.

This control consists in providing a continuous fluctuating phase at the driving pressure P, the curve of which is shown in FIG.

In FIG. 2, the four phases labeled 1, 2, 3, and 4 correspond to the stages of dynamic progress of the metal in the mold.
Phases 5 and 6 correspond to the high pressure achieved after the mold has been filled with metal. Phase 7 maintains high pressure at the sprue during solidification. Phase 8 performs system release. During this phase of the process the metal falls back into the crucible.

One test consists of varying the rate of metal rise into the mold from a specified pressure during phases 2, 3, and 4 (as noted above, they are proportional) to selected values V2, V3, and V.
Including giving a height such that it is set to 4. In this test step, the period T1 and the high pressure P1 of phase 5 are further
Similarly, period T2 and phase 6 high pressure P2 are applied.

Before every test of this type, setter 14 to
0, V2, V3, V4, P1, T1, P
2. Adjust the values selected for this test of T2. Further, the setting device 21 fixes the temperature T of the metal during the casting process. All fixed values are presented on the front surface of the setter.

The pilot considers and stores these eight values.

Test casting development is carried out as follows.

First, the related molds are installed. The machine is supported and installed on the switch 30. A red light on the switch indicates the end of the system's stationary phase and casting begins. The auxiliary valve, which was initially closed during the first phase, is opened by the pilot.

The pressure increases and the metal, which was initially stationary at that level in the crucible, rises into the tube 6 at the speed set during machine construction. It reaches the presence sensor E1.
The sensor communicates metal path information to the pilot at that height. Therefore, the pilot installed pressure sensor 12.
Based on. A pressure sensor transmits an indication of the pressure level to the furnace. The pilot memorizes this value and therefore considers it as the reference pressure.

From this moment on, the pilot is responsible for all drive of the system and controls the pressure changes to set the characteristics applied and stored during the processing of subsequent phases, according to the principles described further below.

Phase 2 then begins. Metal fills the inlet groove of the mold. During this phase of the process, the pilot acts on the auxiliary valve to effectively set the rate of variation of the feed pressure which provides the metal rise rate V2. As a rule, this velocity V2 is lower than the rate of rise of the metal in the tube V1. This phase 2 is interrupted when metal passes in front of the presence sensor E2. Information is sent to the pilot, which changes the phase.

During phase 3, metal is charged into the casting system.
At that time, the pilot gives a rising speed V3 rather than the feed pressure.

During phase 4, metal is filled into the mold. The pilot adapts to the change in feed pressure to raise the metal at speed V4, and the metal eventually reaches the electrode E.
4, which tells the pilot that the metal has completely filled the mold.

The following phase is the high pressure phase. In phase 5, the pilot applies a pressure increase ΔP1 during time ΔT1. In phase 6, the pilot applies a pressure increase ΔP2 during time ΔT2. During phase 7, the pilot stabilizes the high pressure. During this phase metal solidification occurs, generally from top to bottom. A thermocouple 10 analyzes the temperature level below the mold in the casting system. When the temperature reaches the end of the solidification stage,
That is, when the metal has completely solidified in the mold, information is sent to the pilot. At the end of Phase 7, the pilot reduces the pressure in the furnace and Phase 8 begins. The unsolidified liquid metal descends into the crucible again.

During the test process, the operator receives information regarding the height of the casting via the scale plate 25. In fact, lamp 26
a, 26b...26i are ignited continuously after each phase changes. At the end of each step, the pilot estimates and stores the effectively obtained characteristics. At the end of casting, cycles V2, V3, V4, △P1, △T
1, the characteristics of △P2, △T2, the characteristics of the times △t2, △t3, △t4 of phases 2, 3, 4, and the characteristics of the effectively obtained cycle temperature are shown on the scale plates 24a, 24.
b, 24c...presented during 24k. Workers can use them for inspection.

Next, the principle of operation of the pilot will be explained.

It has three basic functions: namely, an input/output function connecting the pilot to the measuring device on the one hand and to the display mechanism provided on its display board on the other hand, a calculation-comparison-decision function, and a memory function.

For example, consider the development of the second phase. The phase begins with presence sensor E1. The working rhythm of the pilot is caused by a clock system that divides the time scale into successive elementary pitches.

From the stored cycle characteristics, the pilot knows that a lift rate V2 must be applied during this phase of the process. Comprehensive calculations estimate that each time interval of this phase must be increased by a theoretical increment ΔPt=ρgV2Δt during the process. A pressure sensor mounted within the furnace then communicates to the pilot the true increase in pressure ΔPr during each time interval. The pilot therefore implements the comparator shown in FIG. 3 between ΔPt and ΔPr. If ΔPt is greater than ΔPr, ie, the true pressure increase during the time interval is less than the theoretical pressure increase, the pilot opens the auxiliary valve 9 via its input/output assembly. Similarly, △
If Pt is lower than or equal to ΔPr, the pilot closes the auxiliary valve 9 and this is repeated step by step during the evolution of the time scale before each time pitch.

When the pilot is connected to the adjustment or continuous position by switch 28, the end of the phase is transmitted to it from the outside by the presence sensor or from the inside by the memorized phase duration, giving the number of time pitches for each phase. .

The plotter visualizes the real curve resulting from the overall control of the casting. These curves, as seen in FIG. 2, include a series of successive small steps surrounding the theoretical curve. Each small step corresponds to a time interval Δt and a pilot actuation of the auxiliary valve 9.

Therefore, the four actions on the mold during the time interval process are calculation of ΔPt, measurement of ΔPr, comparison between ΔPt and ΔPr, and activation of the electronic valve.

The system includes a microprocessor that performs these four functions and allows complete control of the casting.

The device provides these pressure control characteristics to each article with satisfactory and constant accuracy.
It can be applied to cast the above articles. Therefore, the pressure range is set by setting 22 at the beginning of each casting. The pilot divides this pressure range into 2 to the 12th power = 4096 stages. However, the precision of the control, ie the fineness with which the pilot follows the theoretical curve, is expressed by the relationship ΔPt/Δt of the jump in the increase in extrusion pressure over the period Δt of the corresponding time pitch.

Similarly, during range selection, the pilot selects the duration of each pitch to maintain constant accuracy. These periods vary from 50/1000 seconds in the lowest range to about 200/1000 seconds in the highest range.

Six areas are accessed into the device by sensors 22. For each of these ranges, the period of each elementary step increase in pressure and pitch in time is stored in the microprocessor during pilot configuration.

Typically, at the end of such testing, the article is observed and its mechanical characteristics estimated. These tests are repeated many times, taking into account previous tests. At the end of successive adjustments, the appropriate characteristics of the cycle according to which the article is cast are statistically established. Those 11 values exhibiting excellent mechanical properties are displayed on dials 24a, 24b, 24c...24k. The operator presents the reference of the related article through the sensor 27 and sets the switch to the recording state. The eleven specific values of the casting are presented at 27 and stored by the pilot in correlation with the references of the articles presented at 27.

The sequence of operations of the previous test was described when switch 29 was in the automatic position. That is, as described above, phase 7 is automatically interrupted at the command of thermocouple 10. According to another option, when switch 29 is in the manual position, phase 7 period D is provided prior to casting during the characterization of the cycle. It is presented to sensor 23.

In this case, when recording aptitude characteristics, the existence value D is always
241 visualized, memorized in the characteristics and given by the pilot for the phase of the series.

In order to begin the series phase with articles of a given type that have been previously adjusted and have the appropriate characteristics memorized, the multi-stage switch is placed in the series condition and actuator 3 is activated.
It is sufficient to present the code of the article by the sensor 27 to support the zero. Therefore, the pilot selects 11 values t2, t3, t4, △P1, △T1, △P2, △ for the type test phase of range G and period D.
Call T2, Δt2, Δt3, Δt4, and ΔT. These values are in memory, the casting is performed and the resulting parameters are visualized in 24.

Due to series stage casting, it is no longer necessary to use a mold containing a presence sensor. Only sensor E1 is retained. In fact, during the test phase, the time indications transmitting the sensors E2, E3, E4 are replaced by the stored data Δt2, Δt3, Δt4.

Other than these simplifications, series stage casting is performed similarly to test stage casting.

FIG. 4 shows a preferred presence sensor E1 according to the invention.
is shown. It is ultrasonic type. It includes an oscillator/decoder assembly 40 outside the system;
It consists of a probe 41 located inside the outer fixed plate 42 with respect to the connecting nozzle 43 and drawn on the left side of the nozzle.

An oscillator/decoder assembly 40 emits a signal in the ultrasound band that is transmitted to the transducer by a conductor 44;
It is oscillated by the probe. The generated ultrasonic reflected beam is collected by the probe 41 and sent to the conductor 45.
is sent to assembly 40 and analyzed by a decoder.

If the molten metal tip 46 is located at a lower height than the probe 41, the action of the device is illustrated by the curve 4a. The probe emits an ultrasound beam,
Its effect is illustrated by peak E. This beam is first reflected on the left inner side 43a of the connecting nozzle,
Next, it passes through the inner path to the connecting nozzle while being slightly weakened, and is further reflected onto the right inner surface 4b of the same connecting nozzle 43.

Continuous reflection is characterized by reflection from the peak R1 to the left side of the nozzle and from peak R2 to the right side of the nozzle. It is noted that peaks E, R1, and R2 decrease individually, but peaks R1 and R2 are equally large. The two peaks R1 and R2 represent the phase difference and energy of the beam simultaneously reflected and received by the probe 41 and directed to the decoder portion of the assembly 40.

When the metal tip 46b is at a height above the probe 41, the behavior of the system is shown by curve 4b. It is embodied by the reflection peaks R'1 and R'2 on the respective left and right faces of the coupled nozzle, and the oscillation peak is denoted by E'. In this case, the peak
R'2 is very weak compared to peak R'1. These information are sent to the decoder portion of assembly 40 as before.

During operation, the role of this decoder is to distinguish between the placement of the 46a and 46b metal tips. Therefore, this decoder is of R2 type and R'2 type.
It has a mechanism that allows you to distinguish peaks from types.

The decoder sends information to the pilot via cable 48 regarding the metal position relative to the probe position.

In FIG. 5 a small portion of the article of casting is shown. This article is the trailing edge of a turbomachine blade during casting. The metal 49 advances inside the nest left inside the mold 51. Inside this nest, there is a small groove 52 with a height of 1 mm and a width of 2 mm. This groove communicates via an auxiliary valve 55 with a tube 53 connected to a vacuum source 54 .

Means, particularly a cable 56, is provided for sending pressure instructions to the pilot and for providing low pressure control as the metal progresses through the nest. These means are of the same type as those used to suppress the drive pressure previously described. The pilot in this case suppresses the vacuum pressure so that during its deployment it sucks in the gas bubbles trapped by the metal in the cavity 40, leading to a satisfactory surface condition on the entire surface of the mold and improving the quality of the metal. make possible intrusions.

In some cases, an electrode 57 is installed,
It acts as a presence sensor and allows entry into the vacuum pressure phase induced by the pilot. In the series phase, 56 and 57 are removed and the release is effected by the time stored in the pilot.

In FIG. 6, the mold conditioning device used in the conditioning phase is shown. The device essentially comprises a metal box 58, inside of which a core of gravel 59 is located. Due to the pressing action of the metal 60 rising into the mold of the mold, this mold supports the stress against the fixed plate 61 that tends to pull it up. Means are provided to keep it in place. For this purpose, the scale 62 is fixed across the upper span 63 of the box 58 by a wedge. A screw 64, which is integral with the aforementioned scale, presses the mold core downwards into the box, via a wedge 65, against the forehead. The mold and box are connected. To attach them to the fixed plate 61, bars 67 and 68 transmit the vertical stress exerted by the movable plate 69 from top to bottom. Different types of wedges 70 and 71 are provided to adapt the system to molds and boxes of different sizes.

FIG. 7 shows the adjustment system used during the manufacturing stage. It is adapted to successively position molds of different dimensions. For this purpose, different molds are installed in boxes 72 or 73 by scale-screw-wedge systems of the type shown in FIG.
A pair of jacks 74 are integral with the movable plate 69.
Means are provided for moving these two jacks relative to each other symmetrically to the axis of the casting machine. Arrows f1 and f'1 symbolize this movement. Furthermore, the shaft 75 moves perpendicularly to each of the jacks and reaches the shoulder 76. Arrows f2 and f'2 illustrate these movements. Upon installation of each mold, the corresponding article mold is determined by pilot 40.
The pilot stores in memory the position of the jack corresponding to the type of article. This automatically commands, via the motor 77, the movement of the two jacks according to the axis f1 and directs them against the upper span of the two metal boxes. The pilot then commands the deployment of the two jacks 74. Two shoulders 76 are fixed plate 6
Box 73 is placed over 1. When the casting is finished, the pilot moves the two jack shafts 75.
commands reentrancy. Molds and boxes containing newly cast articles can be removed from the system.

It will be appreciated that the method and apparatus described above allow for complete control of the kinetic, static and thermal conditions of each casting according to adjustable predetermined characteristics. The conditions given in the casting process take into account various accidental deformations that occur during mold filling. in this case,
Casting development is independent of crucible metal height reduction, development gas leakage and heat loss. The casting conditions are completely reproducible and lead to a series of articles of completely identical quality.

Similarly, it will be appreciated that the method described above streamlines the sequential development of a series of articles of a given type. A solution adapted to the adjustment stage and production stage is provided. Each start of the series therefore requires only very limited human intervention.

Furthermore, it will be appreciated that although the material described above is simple, its operation is precise and effective. Ultrasonic sensing systems avoid the problem of clinker formation. The regulated vacuum pressure method allows the production of very fine articles that have heretofore been difficult to obtain with molds. Finally, the adjustment system makes mold installation very easy.

It is noted that the above method is applicable to all castable materials, such as magnesium, steel or plastic materials, and the above described apparatus is applicable to all low pressure casting equipment. The metal transfer source driven by the gas flow can be completely replaced by a liquid, rotating electric field or electromagnetic pump. In fact, it is sufficient to recognize the relationship between the height of the metal of the injection tube and the element that initiated its movement. This relationship is established mathematically or empirically in all cases.

Although the present invention has been described in detail by way of examples, this is not intended to limit the scope of the invention.

[Brief explanation of drawings]

Fig. 1 is a schematic sectional view of a low-pressure casting machine implementing the method of the invention and a pilot that automatically controls its operation; Fig. 2 is a graph showing a typical casting cycle according to the invention; Fig. 3; 4 is a schematic diagram of the valve control device and cycle automation device, FIG. 4 is a schematic diagram of the ultrasonic pressure sensor used in the method of the present invention on the upper part of the metal injection pipe in the mold, and FIG. 5 is a diagram of the horizontal thickness. A schematic representation of the apparatus according to the invention used when casting articles with small parts; FIG. 6 is a sectional view showing the type of mold conditioning applied in the conditioning step; FIG. FIG. 3 is a cross-sectional view showing a solution to the adjustment problem. 1... Crucible, 2... Furnace, 4... Metal, 5...
Mold, 6... Injection pipe, 7... Casting system, 8...
...Driving gas conduit, 9...Driving fluid control auxiliary valve, 1
0, 11...Thermocouple, 12...Pressure sensor, 14
~23... Setting device, E1, E2, E3, E4...
Presence sensor.

Claims (1)

[Claims] 1. A casting system comprising: a furnace; a crucible placed in the furnace for supplying metal to be heated and melted by the furnace; a mold placed above the furnace; an injection pipe located in the crucible and having an upper end communicating with the mold to transfer the heated and molten metal from the crucible to the mold; and the heated and molten metal is injected into the mold. at least one metal presence sensor disposed proximate to the casting cycle for determining the start time of the casting cycle; one end opening into the furnace above the crucible and the other end connected to a fluid source to supply the fluid to the furnace; a conduit for feeding fluid from a fluid source into the furnace; a flow rate adjustment means for adjusting the flow rate of the fluid fed into the furnace; and a pressure sensor communicating with the furnace to detect the pressure inside the furnace. and a controller that controls the flow rate adjusting means so that the pressure in the furnace becomes a function of a predetermined time based on the operation start time. 2. A method for automatically controlling a casting cycle, comprising: setting an optimum pressure in a furnace in a casting system as a function of time based on a predetermined start-up time; and supplying pressurized fluid into the furnace to control the molten metal. injecting the molten metal into the mold; sensing the molten metal as it passes near a location where the molten metal is injected into the mold; and continuously sensing the actual pressure in the furnace; A method for automatically controlling a casting cycle, comprising: comparing the pressure with the optimum pressure; and continuously adjusting the amount of the fluid to match the pressure in the furnace with the optimum pressure.