JPS5961564A - Method and device for controlling cooling time for casting in die casting - Google Patents

Abstract

PURPOSE:To enable removal of a casting at an optimum temp. by calculating the heat energy that a die absorbs from a molten metal in accordance with the temp. gradient between the two points in the die, and determining die opening by the heat energy. CONSTITUTION:Two temp. detecting elements 8, 9 spaced at different distances from the inside wall of a cavity 7 are provided near the casting plane of a movable die 4 in the direction where the heat flux from a molten metal flows. The electrical signals corresponding to the temp. from the elements 8, 9 are changed to voltage signals by input conversion circuits 10, 11. The signals are subjected to a subtraction by a subtractor 12 which outputs the temp. difference thereof. The temp. difference is integrated in an integration circuit 13, and the integrated value is multiplied by a correction factor (k) by a multiplier 14. The value set by a setter 16 in accordance with the die 4 and the casting condition and the output signal of the multiplier 14 are compared in a comparator 17. When the output signal of the multiplier 14 exceeds the set value, the comparator issues an ON-OFF signal to a die operation device 18 which performs the die opening operation of the die 4.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for controlling casting cooling time in mold casting, which controls the mold opening time from mold casting to mold opening in a mold casting apparatus such as a die casting machine. and equipment.

In mold casting, the casting must be removed from the mold when the temperature of the materials in the mold has fallen to a certain ideal temperature determined by the solidification characteristics of the molten metal used. No. If you open the mold and take out the casting when the temperature is higher than this ideal blackness, the casting will not easily separate from the mold, damaging the mold and shortening the life of the mold. The distortion rate and shrinkage rate of castings are large, resulting in an increase in dimensional accuracy, an increase in the defective rate, and an increase in the range of quality variations. Of course, opening the mold when the molten metal in the mold has not sufficiently solidified is dangerous, as it may cause the casting to burst or the mold to burn. Also.

On the other hand, leaving the casting in the mold at any time after the temperature of the casting in the mold has fallen to the ideal temperature will only unnecessarily increase the casting cycle time and reduce the casting rate per unit time. This results in a decrease in the number of pieces.

Currently, the most ideal and reliable way to determine whether the temperature of the casting inside the mold has fallen to the ideal temperature is to directly determine the temperature of the casting inside the mold.

There is no suitable means for directly measuring this.

Therefore, in the past, the time required for the molten metal injected into the mold to absorb heat from the mold, solidify, and drop to the ideal temperature was determined through a preliminary test, and a timer was set to set that time. Start with the molten metal injection signal.

This is used as a guideline for mold opening and casting removal time. Alternatively, the temperature change of the mold after the molten metal U=1 is discharged is detected by a heat-sensitive element, and the indicated temperature change is monitored to indirectly estimate the cooling state of the casting in the mold. The following methods have been adopted.

However, when using the timer, the initial temperature of the mold at the time of molten metal injection in each casting cycle gradually rises as castings are repeated, and the temperature of the mold in each casting cycle gradually increases. The cooling rate characteristics of the molten metal in the mold vary depending on the initial temperature of the mold, and as the initial temperature of the mold increases, the cooling rate of the molten metal decreases. There is a discrepancy between the time and the actual desired opening time, and the discrepancy gradually increases, making it impossible to open the mold and take out the objects in good condition. Rough management is not possible.In addition, the above mold temperature monitoring method is
Although the control accuracy is relatively better than the timer method, it cannot go beyond the standard control based on the LA of two workers, and the actual temperature control range is wide, ranging from ideal crystallinity ±50 to 150°C.

Not enough.

The present invention aims to eliminate these drawbacks, and calculates the thermal energy that gold 7q2 absorbs from the molten metal based on the temperature gradient between two points in the mold, and calculates the thermal energy of the mold based on the thermal energy. The opening side 1 is set to 11 so that the casting can be opened and the casting can be taken out, and the cooling time for the casting is more sufficient.

This allows for satisfactory mold opening and casting removal.

Next, the invention will be explained in detail with reference to an embodiment shown in two drawings.

In Fig. 1, 1 is a fixed plate, 2 is a movable plate, 4 is a fixed mold, 4 is a movable mold, 5 is an injection nose, 6 is an injection plunger, 7 is a cavity, and an injection sleeve 5 is shown. The molten metal supplied into the chamber is cast into the chamber 7 by the action of the injection planer 7 to obtain the desired casting of the cedar 4.

For example, in the vicinity of the casting wall surface of the mold filter 4, within the movable mold 4, the tN distance from a part of the inner wall surface of the cavity 7 is approximately 10.
Two temperature detection elements 8+9f are placed at a distance of about
:, MSk was assigned to two points with different distances from the inner wall surface of the carrier in the flow direction of the heat flux from the molten metal. The temperature detecting elements 8 and 9 measure the mold humidity at two points near the casting wall surface of the mold 4, and measure the humidity at 7! It was made possible to output an electrical signal according to ll'+ degree.

10.11 is an input conversion circuit that converts these electrical signals into voltage signals or current signals, and 12 is two manual conversion circuits 1.
A subtraction circuit outputs the temperature difference between two points near the casting wall surface by subtracting the output signal of 0.11, 1B is the output signal of the subtraction circuit 12, that is, an integration circuit that integrates the temperature difference, 14 is A multiplier multiplies the output signal 12 of the integrating circuit by a correction coefficient k, and 15 is a correction coefficient setting device. A reset signal R is manually input to the integrating circuit 1. 16 is a setting device for presetting setting values based on the mold 4 and casting conditions; 17;
is a comparator which compares this set value with the output signal of the multiplier 14 and outputs an OFF signal when the output signal of the 2 multiplier 14 exceeds the set value.

Reference numeral 18 denotes a mold operating device which opens the mold in response to the ON-OFF signal from the comparator 17. Since the integrating circuit 13 integrates the value of the temperature difference, a value corresponding to thermal energy is obtained. Therefore, the setting device 16 also sets a value corresponding to the thermal energy.

19.20 depends on the sign of the value reduced by the energy reducer 12,
This is a comparator that determines whether the temperature difference between the two points is positive or negative, and 21 and 22 are display devices that display the results.

In the present invention, in the vicinity of the casting wall surface of the mold 4, the distance from the casting wall surface is made different in the flow direction of the heat flux from the molten metal.
The temperature gradient in the vicinity of the barrier of the mold 4 was measured using two temperature detection elements 8°9 provided at the points.

Heat flux 1 flowing from the molten metal into the mold 4 due to this temperature gradient
Then, the thermal gradient is calculated by a subtraction circuit, and the thermal energy absorbed by the mold from the molten metal is calculated from the integral value of the heat flux from the point when the molten metal starts being pressurized into the mold 4, and this value is set in advance. When the set value is reached, the mold operating device 1
By the operation of 8.

Open the mold.

The heat flow rate passing through a unit area near the casting wall in the mold is as follows:
Let λ be the thermal conductivity, T be the humidity temperature, and let X be the thickness 11 from the casting wall surface.

θ・r q−λ〜 δX It is expressed as

Therefore, the heat Fa q passing through the above unit area in the time elapsed from the time when the molten metal was placed in the mold is.

becomes. Therefore, in the present invention, two
The temperature TI+12 at the point was measured and the above equation was approximated as follows, and the total amount of heat absorbed by the mold from the molten metal was approximated to be proportional to the amount of heat q passing through the unit area.

As shown in the block diagram of FIG. 1, the casting cooling time in die casting, ie.

Appropriately control mold opening time.

However, if cooling is performed from the casting wall surface by a cooling operation such as spraying during mold opening, the temperature gradient near the casting wall surface may be significantly reversed. Since the mounting positions of the temperature detecting elements 8 and 9 are important, such as the distance Δt between the temperature detecting elements 8 and 9, the positive or negative temperature difference 'r, -, T2, that is, is used as a function to confirm this.

Tl-T2) 10α+ TI T2 <-α(α,-
α is the allowable temperature difference) was determined by comparators 19 and 20, and the results were displayed.

Note that in the present invention, the number of temperature detection elements 8 and 9 may be two or more.

Furthermore, the accuracy can be improved by attaching the temperature detection elements 8, 9 near the mold barrier m1 at several locations and using the average value of the temperature gradients at the multiple locations. In the block diagram, the correction coefficient setter 15 and the multiplier 14 may be omitted depending on the case.

In the present invention, even if the temperature of the mold immediately before pouring the molten metal into the mold fluctuates, the amount of heat absorbed by the mold as it rises from the molten metal is calculated from the temperature gradient near the casting wall surface, and this total amount of heat is Since the mold opening operation is performed when the amount of heat absorbed by the mold reaches the optimal cooling state, a similar effect can be obtained.

(1) Rupture and seizure of the casting can be prevented, and the υJ removal resistance can be reduced, significantly extending the life of the mold.

(2) Appropriate casting cooling time can always be obtained, and υ
There is no variation in the number of nails of the j-made cycle, j-monitori IL, and the fourth degree. In addition, the dimensional accuracy of the casting is stabilized, and the quality can be improved.

(3) Cooling time will not be longer than necessary.

The number of pieces cast per unit time increases, improving efficiency.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of an apparatus for carrying out the method of the present invention. 1...Fixed plate, 2...Movable plate, Ro...Fixed mold. 4...Movable mold, 8, 9...Temperature detection element, 1
0゜11...Input conversion circuit, 12...Subtraction circuit. 1ro...integrator circuit, 14...multiplier, 16...
...Setter, 17.191 20...Comparator, 18
...Mold operating device. Patent applicant: Ube Industries, Ltd.

Claims (4)

[Claims] (1) By measuring the thermal gradient near the casting wall of the mold and integrating it over time. Calculates the thermal energy key absorbed by the mold from the molten metal. A method of controlling the casting cooling time in mold casting in which the mold is opened when the calculation result reaches a preset value. (2) Two temperature detection elements installed near the casting wall surface of the mold at two points with different distances from the casting wall surface in the flow direction of the heat flux from the molten metal, detect the mold wall surface. 6 near the wall
1□ Measure the W degree gradient, calculate the heat flux flowing from the molten metal into the mold based on the temperature gradient, and use the integral value of the heat flux from the time when the molten metal starts to flow into the mold to determine whether the mold is flowing into the molten metal. A special i/mouth 11 request is made in which the absorbed thermal energy is calculated and the mold is opened when this value reaches a preset value based on the mold, casting conditions, etc. A method for controlling casting cooling time in mold casting according to item 1. (3) A temperature detection element that outputs an electric signal corresponding to the mold temperature at two points near the casting wall surface of the mold with a distance difference from the barrier surface in the flow direction of the heat flux from the molten metal; an input conversion circuit that converts an electrical signal into a voltage signal or a current signal; a subtraction circuit that outputs the temperature difference between two points near the casting wall surface by subtracting the output signals of the two input conversion circuits; The output signal of the subtraction circuit, that is, the integration circuit that integrates the temperature difference, is compared with the output signal of the integration circuit and a preset value based on the mold and casting conditions, and the output signal from the integration circuit is calculated. A control device for casting cooling time in mold casting, comprising a comparator that outputs a signal when the set value is exceeded, and a mold operating device that opens the mold according to the signal from the comparator. (4) A comparator that determines whether the 61h degree difference between two points near the casting wall surface of the mold with a distance difference from the casting wall surface in the flow direction of the heat flux of the molten metal is positive or negative. A control device for cooling time of mold casting in mold casting as claimed in claim 1, comprising a display device for displaying the result.