JPH04164218A - Detecting method for gas pressure in casting mold - Google Patents

Abstract

PURPOSE:To detect the gas pressure in a casting mold by inserting a test piece into an electric furnace, by taking out the gas generated along with heating, by measuring the pressure of the gas and by estimating the gas pressure in a casting mold when molten metal is poured with an actual core incorporated. CONSTITUTION:A test piece 1 comprises a container 10 made of stainless steel, sand mold section 11 and pressure in-take pipe 12 made of stainless steel. The test piece 1 fitted in a mold is inserted in the furnace chamber of a pipe-like electric furnace 4 and heated with the pressure in-take pipe 12 and a manometer 3 connected to a tube 3a. The gas generated in the sand mold section 11 caused by heating is introduced into the manometer 3 through the air flowing pass 12a of the pressure in-take pipe 12 and the tube 3a to be measured. The actual gas pressure in a casting mold when molten metal is poured with an actual core incorporated can be estimated from the value of gas pressure thus measured.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a method for detecting gas pressure in a mold for detecting the pressure of gas generated from a sand mold containing a shell core and an organic or inorganic binder. .

[Prior Art] A binder contained in a sand mold such as a shell core decomposes during casting and generates gas. This gas greatly affects the quality of castings, especially gas defects such as blowholes and pinholes. For example, when the gas pressure generated in the mold during casting is higher than the molten metal pressure, the above gas defects are likely to occur. -Therefore, as a conventional method to measure the gas pressure generated in the mold during casting, a gas pressure sensor is installed in the main mold in which the shell core is placed, and molten metal is poured into the cavity of the main mold. A method is known in which the gas pressure of gas generated from the core is detected using a gas pressure sensor (Castance Vol. 54, No. 2, pp. 125 to 127, published by Japan Foundry Association).

[Problems to be Solved by the Invention] However, the method described above requires actually pouring the molten metal, and it is difficult to use a high-frequency melting furnace or a low-frequency melting furnace for metal melting, as well as a main mold forming machine, a core forming machine, etc. It requires casting equipment and is difficult to measure in general laboratories that do not have such equipment.

The present invention was developed in view of the above-mentioned circumstances, and an object of the present invention is to provide a method for detecting gas pressure in a mold that can detect gas pressure without pouring molten metal.

[Means for Solving the Problems] The in-mold gas pressure detection method of the present invention includes a container having a predetermined cross-sectional shape with at least one open end, and a container filled with a viscous material corresponding to the binder content of the actual core. A step of obtaining an eggplant 1 to piece having a sand mold part having a binding agent content and a pressure outlet pipe having one end inserted into the sand mold part through the opening of the container and having an air passage projecting from the sand mold part at the other end. , Using a gas pressure detection means and an electric furnace, the test piece is charged into the furnace chamber of the electric furnace, and the test piece is heated to a temperature higher than the decomposition temperature of the binder in the sand mold part of the test piece. The generated gas is introduced into the gas pressure detection means through the air passage of the pressure extraction pipe, the gas pressure is measured by the gas pressure detection means, and from the measured value of the gas pressure, it is possible to determine when pouring with a real core installed. This method is characterized in that the steps of estimating the actual gas pressure in the mold are sequentially performed.

At least one end of the test piece container used in the present invention is open. This container can be pipe-shaped. If it is made into a pipe shape, it is preferable that the inner diameter is about 10 to 15 mm and the length is about 100 to 150 mm. If the inner diameter is too small, it will be difficult to create the sand mold, and if the inner diameter is too large, the central area of the sand mold will be damaged. Inconveniences such as poor firing treatment are likely to occur. Furthermore, if the length of the container is too short, it will be difficult to detect the gas pressure, and if it is not long, the temperature distribution during measurement will tend to vary. One end of the pressure extraction tube of the test piece is inserted into the sand mold part through the opening of the container. The pressure extraction pipe preferably has an inner diameter of about 2 to 3 mm; if the inner diameter is too small, the sand mold section may be clogged with sand, and if the inner diameter is too large, it becomes difficult to create the sand mold section.

Considering the length of the electric furnace, etc., the length of the pressure extraction pipe is 25
Approximately 0 to 300 mm is preferable.

The amount of binder compounded in the sand mold part of the test piece is set in accordance with the amount of binder compounded in the actual core.

The gas pressure detecting means used in the present invention may be a manometer, a semiconductor diaphragm type gas pressure gauge, or the like.

Further, a known electric furnace can be used.

In the present invention, the temperature at which the test piece is heated is appropriately selected depending on the type of sand mold part, and is, for example, 250 to 300'C.
It can be done.

[Example] Hereinafter, the method for detecting gas pressure in a mold according to the present invention will be explained according to each example.

(Example 1) First, a test piece 1 shown in FIG. 2 is manufactured.

The test piece 1 is a stainless steel container 10 and a sand mold part 1.
1 and a pressure outlet pipe 12 made of stainless steel. The container 10 has a pipe shape with openings 10a and 10b at both ends, and has an inner diameter of 13 mm and a length of 150 mm. The pressure extraction pipe 12 has a ventilation passage 12a, one end 12b is inserted into the sand mold 11 through the opening 10b, and the other end 12G protrudes from the sand mold 11. The pressure outlet pipe 12 has an inner diameter of 2.5 mm and a length of 250 mm. The sand mold section 11 is formed from shell sand loaded into the container 10.

The sand mold part 11 has a binder compounding amount corresponding to the binder compounding amount of the actual shell core used in the actual casting line.

Test piece 1 of Example 1 was manufactured as follows. That is, 160 g of novolac type phenolic resin was added to 8 kg of Fuqua sand heated to 160'C, stirred for 25 seconds, and an aqueous solution consisting of 32 g of hexamethylenetetramine (hereinafter referred to as hexamine) and 12 oz of water was added.
The mixture was stirred for 5 seconds, and further 8 q of calcium stearate was added and stirred for 20 seconds to obtain resin coated sand.

Then, the pressure outlet pipe 12 is passed through the center of the container 10, and the resin coated sand is filled into the container 1O.

Further, FIG. 3 shows a mold 2 used in the firing process.

The mold 2 includes a pair of mold parts 21 having a groove part 20 and a mold part 21.
It consists of a hinge part 22 that holds the holder so that it can be opened and closed. Then, with the test piece 1 fitted into the groove 20, the mold 2 was set at 300'C±2C using a temperature controller, and the resin coated sand was fired for 2 minutes.

Thereafter, using a manometer 3 as a gas pressure detection means and a tubular electric furnace 4 in which a quartz tube 40 is arranged, the test piece 1 is charged into the furnace chamber of the electric furnace 4 as shown in FIG. 1, and the pressure is taken out. Test piece 1 was heated with tube 12 and manometer 3 connected through tube 3a. The heating temperature was 1300±10°C. Note that the temperature of the electric furnace 4 was set using a thermocouple 45 and a thermocouple thermometer 46. Furthermore, water 3C is injected into the manometer 3. The electric furnace 4 was a silico three-top tubular electric furnace.

Then, the gas generated from the sand mold part 11 due to heating is introduced into the manometer 3 through the air passage 12a of the pressure extraction pipe 12 and the tube 3a, and the manometer 3 increases the gas pressure by 30°C.
Measured for minutes.

The measurement results are shown in characteristic line A1 in FIG. As shown in characteristic line A1, the gas pressure increased relatively slowly in the initial stage of heating, but after about 60 seconds, the gas pressure reached approximately 25 CI/art, and then the gas pressure increased. The pressure gradually decreased.

(Example 2) A resin-coated sand according to Example 2 was obtained under the same conditions as in Example 1 except that the novolac type phenol resin was 144 CI and the hexamine was 28.8 g. and,
As in Example 1, a test piece 1 having a sand mold part 11 was formed from this resin-coated sand, and the gas pressure was measured. The measurement results are shown in characteristic line A2 in FIG. As shown in characteristic line A2, the gas pressure increased relatively slowly in the initial stage of heating, but when approximately 60 seconds had elapsed, the gas pressure was approximately 16 to 17C1/cffl, and then the gas pressure decreased. It gradually decreased.

(Example 3) A resin coated sand according to Example 3 was obtained under the same conditions as in Example 1 except that hexamine was changed to 240. A test piece 1 having a sand mold part 11 was formed using this resin coated sand, and the gas pressure was measured. The measurement results are shown in characteristic line A3. As shown in characteristic line A3, the gas pressure increased relatively slowly in the initial stage of heating, but when approximately 60 seconds had passed, the gas pressure increased to approximately 23 Q/crtr.
After that, the gas pressure gradually decreased.

(Comparative Example 1) Using the resin coated sand obtained in Example 1, 3
The product was fired at 00'C for 2 minutes to obtain the actual core 7 shown in FIGS. 6 to 8. This actual core 7 has a sand mold part 70 and a sand mold part 70.
It consists of a pressure extraction pipe 71 inserted into. Note that the sand mold part 70 has a size of 22 mm x 22 mm x 200 mm. The pressure extraction pipe 71 has an inner diameter of 2.5 mm and a length of 250 mm.
It is mm.

Then, as shown in FIGS. 6 to 8, the actual core 7 is placed in the main mold 6 having a cavity 60, and the pressure outlet pipe 71 is connected to a gas pressure gauge, and in this state, the high temperature molten metal is poured into the cavity 60. Gas pressure was measured for 1 minute using a gas pressure gauge.

The measurement results are shown in characteristic line B1. The material of the molten metal is F.
At e12, the pouring temperature is 1400°C. As shown in characteristic line B1, gas pressure rises rapidly at the initial stage of pouring.
After about 20 seconds, the gas pressure was approximately 23 g/crir.

(Comparative Example 2) Using the resin coated sand obtained in Example 2, an actual core 7 was obtained in the same manner as in Comparative Example 1, and the molten metal was poured into the cavity 60 with the core 7 placed in the main mold 6. flowing,
Gas pressure was measured. The measurement results are shown in characteristic line B2.

As shown in characteristic line B2, the gas pressure rises rapidly at the initial stage of pouring, and after about 20 seconds, the gas pressure reaches approximately 16 to 1
It was 7q/cd.

(Comparative Example 3) Using the resin coated sand obtained in Example 3, a real core 7 was obtained in the same manner as in Comparative Example 1, and with the real core 7 placed in the main mold 6, molten metal was poured into the cavity 6O. was flown through the pipe, and the gas pressure was measured. The measurement results are shown in characteristic line B3. As shown in characteristic line B3, the gas pressure rises rapidly at the initial stage of pouring, and after about 20 seconds, the gas pressure reaches approximately 22q/cm.
Met.

(Evaluation) As explained above, when comparing Examples 1 to 3 and Comparative Examples 1 to 3, it is found that although the increase form of the gas pressure (increased) at the initial stage of heating is different, looking at the highest value of gas pressure, 1 is comparative example 1
, Example 2 corresponds to Comparative Example 2, and Example 3 corresponds to Comparative Example 3. Therefore, the gas pressure when molten metal is actually poured can be estimated from the measurement results of Examples 1 to 3.

[Effects of the Invention] According to the method for detecting gas pressure in a mold of the present invention, gas pressure can be measured without actually pouring molten metal, and therefore gas pressure in a mold can be measured even in a place without casting equipment such as a melting furnace or a molding machine. Can detect pressure.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram showing the measurement method, Figure 2 is a sectional view without the test piece, and Figure 3 is a perspective view of the resin coated sand of Death 1 to Piece being fired in a mold. . FIG. 4 is a graph showing the measurement results according to the example,
FIG. 5 is a graph showing the measurement results of the comparative example. 6, 7, and 8 show the main mold used in the comparative example, with FIG. 6 being a plan view, FIG. 7 being a front view, and FIG. 8 being a side view. In the figure, 1 is a test piece, 10 is a container, 11 is a sand mold part,
12 is a pressure extraction pipe, 3 is a manometer, and 4 is an electric furnace (not shown). Patent applicant Aisin Kako Co., Ltd.

Claims (1)

[Claims] (1) A container with a predetermined cross-sectional shape with at least one open end, a sand mold part loaded into the container and having a binder content corresponding to the binder content of the actual core, and one end with an open end of the container. A step of obtaining a test piece having a pressure extraction pipe inserted into the sand mold part through the sand mold part and having a ventilation passage whose other end protrudes from the sand mold part, using a gas pressure detection means, and an electric furnace, the test The test piece is charged into the furnace chamber of the electric furnace, and the test piece is heated to a temperature higher than the decomposition temperature of the binder in the sand mold part of the test piece, and the gas generated during heating is passed through the air passage of the pressure extraction pipe. The gas pressure is introduced into the gas pressure detection means through the gas pressure detection means, and the gas pressure is measured by the gas pressure detection means, and from the measured value of the gas pressure, the actual gas pressure in the mold when pouring into which the actual core is installed is determined. A method for detecting gas pressure in a mold, characterized in that the steps of estimating are carried out in order.