JP2936696B2 - Pressurized die casting method and method for determining the quality of cast products - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure die casting method and a method for determining the quality of a cast product.

[Conventional technology]

In the pressure die casting method, the molten metal is introduced into the mold cavity from the injection port of the mold while applying primary pressure, and the molten metal in the introduced cavity is added from a different pressure port from the injection port. This is a die casting method in which a cast product having a high density can be obtained by subjecting to secondary pressurization.

In order to respond to the increasing need for higher quality die-cast products, Japanese Patent Publication No. 59-13942 discloses a die-casting device in which the structure of a pressing mechanism is specified so that a pressing effect can be reliably obtained. A device has been proposed.

However, even when the above-mentioned conventional apparatus is used, there is a problem that the pressurizing effect fluctuates due to a change in casting conditions, and shrinkage cavities are generated, and a difference occurs in the processing allowance of the pressurized portion.

[Problems to be solved by the invention]

The present invention solves the above-mentioned conventional problems, and provides a pressure die-casting casting method in which shrinkage cavities are prevented by controlling a pressing condition in accordance with a change in casting conditions, and a method of determining the quality of a cast product by using the method. The purpose is to do.

[Means for solving the problem]

In order to achieve the above object, the pressure die casting method of the present invention is to perform a first pressurization after introducing a molten metal into a mold cavity from an injection port of a mold, and to perform a first pressurization to melt the molten metal in the introduced cavity. In a pressure die casting method in which a secondary pressurization is additionally performed from a pressurization port different from the injection port, a mold temperature, a duration of the primary pressurization, a start time of the secondary pressurization, and pressurization. The relationship with the speed is determined in advance as an optimal relationship for preventing shrinkage cavities of a cast product, and the mold temperature and the duration of the primary press are measured during casting, and the optimal relationship is determined using these measured values. The secondary pressurization during the casting is performed at the secondary pressurization start timing and the secondary pressurization speed set based on the above.

In order to achieve the above object, the present invention also provides a first pressurization after introducing a molten metal into a mold cavity from an injection port of a mold, and the molten metal in the introduced cavity is defined as the injection port. In the pressure die casting method in which secondary pressurization is additionally performed from another pressure port, the time-dependent change in the pressure of the molten metal in the mold cavity during casting is determined in advance as a reference waveform that prevents the occurrence of shrinkage cavities in the cast product. In addition, there is also provided a pressure die casting method characterized by setting a start time and a pressing speed of the secondary pressing based on a comparison between an actually measured waveform during casting and the reference waveform.

Further, the method for determining the quality of a cast product according to the present invention is characterized in that after introducing the molten metal into the mold cavity from the injection port of the mold,
A method of judging the quality of a product cast by a pressure die casting method in which the molten metal in the introduced cavity is subjected to a secondary pressurization through a pressurizing port different from the injection port. The time-dependent change in the pressure of the molten metal in the mold cavity during casting is determined in advance as a reference waveform for preventing shrinkage cavities of the cast product, and based on a comparison between the measured waveform during casting and the reference waveform, the casting is performed. Is used to determine the quality of the product.

[Action]

The present inventor has set a mold temperature and a duration of the primary pressurization between a start time and a pressurization speed of the secondary pressurization,
It has been found that there is an optimal relationship to prevent shrinkage cavities in cast products. The present invention utilizes this previously determined optimum relationship to determine in real time the secondary pressurization start time and pressurization duration in the casting according to the mold temperature and the primary pressurization duration measured during casting. By applying feedback and pressurizing under optimal conditions, the occurrence of shrinkage cavities is extremely effectively prevented.

Instead of the mold temperature and the duration of the primary pressurization, the change over time in the pressure of the molten metal in the mold cavity during casting is determined in advance as a reference waveform for preventing shrinkage cavities of the cast product,
Based on the comparison between the measured waveform during casting and the reference waveform,
It is also possible to set the start time and pressurization speed of the secondary pressurization.

Furthermore, by using the above-mentioned reference waveform and comparing the measured waveform with the actually measured waveform during casting to determine the quality of the product by the casting, it is possible to quickly and accurately determine the quality of the product, which is extremely advantageous in actual operation. It is.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

〔Example〕

FIG. 1 shows an example of an apparatus for performing pressure casting according to the present invention.

The movable mold 4 and the fixed mold 5 constituting the mold define a cavity 10 forming a mold space corresponding to the product shape.

A pressure sensor 1 for detecting the pressurized state of the molten metal is provided on an ejector plate 9 in contact with an end face of an ejector pin 8 for pushing out a solidified product, and measures a pressure applied to a cavity 10 during casting. The pressure sensor 1 is, for example, of a strain gauge type, has a spherical tip, and receives vertical pressurization from an ejector pin 8.

The squeeze pin 19 is a pin for additionally secondary pressing the molten metal in the cavity 10 in order to perform pressure casting as disclosed in Japanese Patent Publication No. 59-13942. Squeeze pin 19
A hydraulic cylinder 20, a hydraulic pipe 21, and a flow control valve 18 are provided in order to move and perform pressurization.

FIG. 2 shows the operating state of the squeeze pin 19. Time elapses from right to left in the figure. t indicates the time from the start of primary pressurization by the injection plunger 7 to the start of pressurization by the squeeze pin 19 (primary pressurization duration time). P is a squeeze pin
19 indicates the operating pressure. S indicates the operating speed of the squeeze pin 19. In the present invention, these operating conditions of the squeeze pin 19 are controlled.

The sliding speed and displacement of the squeeze pin 19 are measured by the displacement sensor 22.
Is measured by

An injection plunger 7 that slides tightly inside the injection sleeve 6 to fill the melt 15 into the cavity 10 applies the pressure transmitted from the injection plunger rod 16 and the injection cylinder 14 to the melt 15. After the molten metal 15 is injected into the injection sleeve 6 from the hot water supply port 13, the injection plunger 7 fills the injection sleeve 6. The pressure applied to the injection plunger 7 is measured by a strain gauge 17 attached to the injection plunger rod 16.

The temperature sensor 2 measures one or more mold temperatures.

23 is an electromagnetic valve for controlling the forward and backward movement of the squeeze cylinder 20. The flow control valve 18 is installed on the return side of the hydraulic pressure and is connected to the hydraulic tank 24. 25 shows a hydraulic pump. 26 is a controller of the flow control valve 18 for controlling the speed of the squeeze pin 19.

Cavity 10 composed of movable mold 4 and fixed mold 5
Then, the molten metal 15 is filled by the advance of the injection plunger 7,
Apply primary pressure. Since the molten metal 15 filled in the cavity 10 is solidified and contracted, shrinkage cavities are generated inside the casting. In order to prevent this, an additional secondary pressurization is performed by the squeeze pin 19 in addition to the primary pressurization by the injection plunger 7.

The waveform shown in FIG. 3 is obtained by measuring the pressure applied to the squeeze cylinder 20 and the applied pressure applied to the cavity 10. Time elapses from right to left in the figure. At this point, the molten metal 15 filled in the cavity 10 is primarily pressurized by the injection plunger 7. In the process (period t) leading to the time point, the molten metal pressure decreases due to solidification shrinkage. The squeeze pin 19 operates at the timing t (time) to compensate for this, and the pressing force propagates into the cavity 10. At this point, the casting is completed, the mold is opened for product removal, and the pressure drops.

FIG. 4 shows a pressure waveform in the cavity 10 when the squeeze pressure does not sufficiently propagate. The larger the pressure waveform, the greater the effect of preventing shrinkage cavities. FIG. 5 shows the results obtained by using the specific gravity of the cast product and the average value of the pressure applied to the cavity 10. When the pressure in the cavity is lower than a certain level, the specific gravity of the product is reduced with the decrease.

Such a phenomenon is that squeeze pressurization (secondary pressurization) or pressurization by an injection plunger (primary pressurization) is inappropriate for solidification of a molten metal and compensates for a pressure drop due to solidification shrinkage. Is not enough.

Conventionally, the above phenomenon was qualitatively grasped to some extent, but because it was not quantitatively grasped, casting control based on the phenomenon could not be performed, and the squeeze pressure effect varied, causing shrinkage nests. The occurrence could not be sufficiently prevented.

The present invention solves this problem, detects the solidification and pressurized state in the mold during casting, and controls the squeeze pressurizing condition in real time using the result to prevent shrinkage cavities from occurring.

As shown in Fig. 6, the solidification rate in the mold differs depending on the mold temperature. The lower the mold temperature, the faster the solidification rate. And cannot prevent shrinkage nests. When the mold temperature is high, the solidification speed is low. If the squeeze pressurizing speed is not reduced, the pressurization ends before the solidification is completed, and then shrinkage cavities occur due to solidification shrinkage.

On the other hand, the amount of pressure propagation in the cavity 10 varies depending on the duration of the primary pressurization of the injection plunger 7. As shown in FIG. 7, when the pressure of the injection plunger 7 decreases, the pressure in the cavity 10 also decreases. FIG. 8 shows the relationship between the primary pressurizing duration of the injection plunger 7 and the shrinkage cavity generation amount (indicated by the coagulation contraction amount). The longer the primary pressurization duration, the smaller the amount of shrinkage cavities generated. However, as shown in FIG. 9, it is necessary to consider this relationship by further incorporating the relationship with the squeezing pressure start timing. That is, as can be seen from the figure, if the squeeze pressurization start timing is too early or too late, the shrinkage cavity generation amount is not sufficiently reduced even if the primary pressurization duration of the injection plunger 7 is long.

Therefore, the squeeze condition (secondary press start timing (squeeze timing), secondary pressurization speed (squeeze speed)) is determined in advance with respect to the variation of the mold temperature and the primary pressurization duration as shown in FIG. By controlling on an optimum curve for preventing shrinkage cavities, it is necessary to sufficiently transmit pressure to the cavity 10 and prevent shrinkage cavities from occurring.

 The control procedure will be described with reference to FIG.

(Step 1) When the casting preparation of the die casting machine is completed, the mold temperature is measured, and the primary pressurization waveform of the injection plunger 7 is measured, and the time until this pressure decreases (the primary pressurization duration time) ).

(Step 2) Using the actually measured mold temperature and the primary pressurizing duration, the optimum squeeze condition (secondary pressurizing speed and secondary pressurizing start timing) is calculated based on the optimal relation curve in FIG. .

(Step 3) The calculated secondary pressurization speed and secondary pressurization start timing are input to each control system. That is, the pressurization start timing is determined by the open / close signal of the solenoid valve 23, and the pressurization speed is
It is controlled by an opening control signal of the flow control valve 18.

FIG. 12 schematically shows pressure waveforms in the cavity when pressure control according to the present invention is performed and when pressure control is not performed. ADVANTAGE OF THE INVENTION According to this invention, compared with the conventional method, the amount of pressure reduction with the passage of pressurization time is significantly reduced, and a sufficient pressurizing effect can be obtained.

In FIG. 13, when the squeeze pressing condition is controlled according to the present invention, in the case of the conventional squeeze pressing method without control,
And the comparative example in which squeeze pressing is not performed shows variations in the specific gravity of the cast product. In the product according to the present invention, as a result of the occurrence of shrinkage cavities being extremely effectively prevented, the variation in specific gravity is significantly reduced as compared with the conventional squeeze pressing method.

Next, another casting method of the present invention will be described. That is,
The average value of the measured pressure waveform in the cavity as shown in FIG. 4 is obtained, and as shown in FIG. 16, an amount for changing the pressurizing speed is controlled from the difference ΔP from the value of the reference waveform. That is, when the value of the pressure waveform is smaller than the value of the reference waveform, the pressurizing speed is increased, and when it is larger, the pressurizing speed is decreased. Even when this casting method is used, the same effects as in the above embodiment can be obtained.

 Next, a pass / fail determination method will be described.

The waveform of the pressure in the cavity is measured during the entire casting process up to the mold opening.If the average pressure in the cavity does not satisfy the predetermined reference value, the product obtained by the casting is judged to be defective and stratified. Can be performed.
In other words, the quality of the product is determined on the figure in which the average value of the measured pressure waveform in the cavity is obtained as shown in FIG. 4 and the correlation between the quality and the average value of the pressure in the cavity is obtained in advance as shown in FIG. . That is, if it is within the allowable range predetermined in FIG. 14, it is determined to be a good product, otherwise it is determined to be a defective product. In addition,
As processing of the read value of the pressure waveform in the cavity, in addition to obtaining the above average value, as shown in FIG. 15, a pressure value at a point in time after a certain time t is detected and compared with a reference value to determine pass / fail. May be. With these methods, the quality of the product can be determined quickly and accurately.

〔The invention's effect〕

As described above, according to the present invention, it is possible to perform pressurization under optimal conditions in accordance with fluctuations in casting conditions,
Shrinkage cavities can be prevented extremely effectively, and a cast product that sufficiently meets the needs for high quality can be cast.

Further, according to the present invention, the quality of the cast product can be quickly and accurately determined, so that high productivity and stable high quality can be secured.

[Brief description of the drawings]

FIG. 1 is a layout view including a cross-sectional view showing an example of an apparatus for performing pressure casting according to the present invention. FIG. 2 is a squeeze pin for applying additional pressure to a molten metal in a mold cavity. FIG. 3 is a graph showing a pressure waveform of a squeeze cylinder for performing additional secondary pressurization of the molten metal in the mold cavity and a graph showing a molten metal pressure waveform in the cavity. FIG. 5 is a graph schematically showing a molten metal pressure waveform in a cavity when squeeze pressurization is insufficient, FIG. 5 is a graph showing a change in specific gravity of a cast product with respect to an average molten metal pressure in a cavity, and FIG. FIG. 7 is a graph showing the solidification rate with respect to the mold temperature as a function of time with respect to the amount of solidification shrinkage. FIG. 7 is a graph showing the decrease in primary pressurization by the injection plunger and the decrease in melt pressure in the cavity. The figure shows the injection FIG. 9 is a graph showing the change in the amount of shrinkage cavities (indicated by the amount of coagulation contraction) with respect to the primary pressurization duration by the plunger. FIG. 9 shows the squeeze pin when the primary pressurization duration by the injection plunger is changed. FIG. 10 is a graph showing the relationship between the start time of additional secondary pressurization (squeeze timing) and the amount of shrinkage cavities generated by the squeeze pin. And FIG. 11 is a flowchart showing a procedure for controlling an additional secondary pressurization by a squeeze pin according to the present invention. Fig. 12 is a graph showing (a) the pressure control according to the present invention and (b) the pressure control not performed. casting A graph showing the variation in the specific gravity of the product, FIG. 14 is a graph showing the correlation between the average value of the pressure in the cavity and the quality of the casting, FIG. 15 is a graph showing the read value of the pressure in the pressure waveform of the molten metal in the cavity, FIG. 16 is a graph showing the relationship between the difference ΔP between the average value of the pressure waveform in the cavity and the reference value and the amount of change in the pressurizing speed. 1 ... pressure sensor, 2 ... temperature sensor, 4 ... movable type, 5 ... fixed type, 6 ... injection sleeve, 7 ... injection plunger, 8 ... ejector pin, 9 ... ejector plate, 10 … Cavity, 13… Hot water supply port, 14… Injection cylinder, 15… Metal melt, 16… Injection plunger rod, 17… Pressure sensor, 18… Flow control valve, 19… Squeeze pin, 20 …… Squeeze cylinder, 21… Hydraulic piping, 22… Displacement sensor, 23 …… Solenoid valve, 24 …… Hydraulic tank, 25 …… Hydraulic pump, 26 …… Flow control valve controller, 27 …… Amplifier, 28… … AD converter, 29 …… CPU.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-183954 (JP, A) JP-A-58-9758 (JP, A) JP-A-57-171559 (JP, A) JP-A-1- 197052 (JP, A) JP-A-64-83360 (JP, A) JP-A-63-313644 (JP, A) JP-A-64-27158 (JP, U) (58) Fields investigated (Int. ⁶ , DB name) B22D 17/22 B22D 17/32

Claims (5)

(57) [Claims] 1. A metal melt is introduced into a mold cavity from an injection port of a mold and subjected to primary pressurization, and the molten metal in the introduced cavity is additionally added from a pressurization port different from the injection port. To 2
In the pressure die casting method, the relationship between the mold temperature, the duration of the primary press, the start time of the secondary press, and the press speed is optimized for preventing shrinkage cavities of cast products. The mold temperature and the duration of the primary pressurization are measured in advance during the casting, and the secondary pressurization start timing and the secondary pressurization set based on the above-mentioned optimal relationship using these measured values are measured. A pressure die casting method wherein the secondary pressurization during the casting is performed at a pressure speed. 2. If the duration of the primary pressurization is shorter than a set value, the secondary pressurization is started at that time, and if longer than the set value, the secondary pressurization is started from the set value. And if the mold temperature is higher than a set value, the secondary pressurizing speed is reduced, and if the mold temperature is lower than the set value, the secondary pressurizing speed is increased. Item 1. A pressure die casting method according to Item 1. 3. Introducing the molten metal into the mold cavity from the injection port of the mold and then performing primary pressurization, and adding the molten metal in the introduced cavity from an additional pressure port different from the injection port. To 2
In the pressurized die casting method, the time-dependent change in the pressure of the molten metal in the mold cavity during casting is determined in advance as a reference waveform to prevent shrinkage cavities in the cast product. A pressure die-casting method characterized by setting the starting time of the secondary pressurization and the pressurization speed based on the comparison with the above. 4. The casting is performed by increasing the pressing speed when the measured waveform is smaller than the reference waveform, and decreasing the pressing speed when the measured waveform is larger than the reference waveform. The pressure die casting method according to claim 3, wherein 5. A metal melt is introduced into the mold cavity from the injection port of the mold and subjected to primary pressurization, and the molten metal in the introduced cavity is additionally added from a pressurization port different from the injection port. To 2
In the method of judging the quality of the product cast by the pressurized die casting method, the time change of the pressure of the molten metal in the mold cavity during casting is determined in advance as a reference waveform to prevent shrinkage cavities of the cast product. A method for judging the quality of a press-cast die-cast product, based on a comparison between an actually measured waveform during casting and the above-mentioned reference waveform.