JP6250499B2 - Disappearance model and disappearance model casting method using the same - Google Patents

Description

  The present invention relates to a disappearance model that is buried in foundry sand and disappears by pouring molten metal to form a mold, and a disappearance model casting method using the same.

  2. Description of the Related Art Conventionally, as one of sand mold casting methods, a vanishing model casting method in which a vanishing model made of a synthetic resin foam such as expanded polystyrene is embedded in foundry sand and the vanishing model is used as a mold is known.

  The vanishing model casting method forms a cavity by supplying molten metal from below to the vanishing model embedded in the foundry sand and decomposing and disappearing the synthetic resin forming the vanishing model by the heat of the molten metal. In this technique, a casting having the same shape as the vanishing model is obtained using the cavity as a mold. According to the vanishing model casting method, since the vanishing model is formed by the synthetic resin foam, even a casting having a complicated shape can be easily cast without using a core.

  However, depending on the casting method, there is a problem that a residue defect occurs in which residues such as carbides generated when the synthetic resin forming the disappearance model is decomposed adhere to the casting surface. The problem is that the amount of gas generated when the synthetic resin is decomposed by the heat of the molten metal is large, and the gas layer formed on the molten metal becomes thick, so that the gas layer acts as a heat insulating material. This is probably because of this. When the gas layer acts as a heat insulating material, the heat of the molten metal becomes difficult to be transmitted to the disappearance model, and the disappearance model decomposes at a low temperature, resulting in an increase in residue.

Therefore, in the disappearance model casting method, it is necessary to remove the gas generated when the disappearance model disappears to the outside of the mold, and various means for removing the gas (hereinafter referred to as degassing) have been proposed. Yes. As the degassing means, for example, it has been proposed to form 500 to 500,000 through-holes per 1 m ³ in a lattice shape in the disappearance model (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 2003-25044

  However, when the through hole is formed in the disappearance model, there is a disadvantage that the supplied molten metal flows into the through hole and the decomposition of the disappearance model progresses rapidly, so that the degassing may be difficult. .

  An object of the present invention is to provide a vanishing model that can eliminate such inconvenience, perform gas venting efficiently, and obtain a casting without residual defects, and a vanishing model casting method using the same. .

  In order to achieve such an object, the present invention is a disappearance model made of a synthetic resin foam, in positions facing each other on the surfaces extending in the vertical direction of the synthetic resin foam coated with a coating material, A plurality of gas vent windows provided by exposing the synthetic resin foam are provided, and one gas vent window pair is disposed in a horizontal direction with respect to another gas vent window pair adjacent in the height direction. It is characterized by being shifted in position.

  In the disappearance model of the present invention, when the molten metal is supplied from the bottom surface embedded in the foundry sand, the synthetic resin foam is decomposed by the heat of the molten metal, but the mold material remains, so the interior surrounded by the mold material Becomes hollow. The cavity is filled with the molten metal, and the molten metal solidifies to obtain a casting. In the process of filling the molten metal, the synthetic resin foam that forms the disappearance model above the molten metal is decomposed. A layer of gas generated by the above is formed.

  Here, in the disappearance model of the present invention, when the coating material is applied to the synthetic resin foam, a portion where the synthetic resin foam is exposed is provided, and this portion is used as a venting window, so that the cavity is formed. If it does so, the said foundry sand will face this cavity in the part of this vent hole. Accordingly, the gas is removed to the outside through the gap between the foundry sands.

  In the disappearance model of the present invention, the gas vent window is formed by exposing the synthetic resin foam from the coating material as described above, and is not formed as an actual through hole. , It is possible to prevent a rapid decomposition of the disappearance model due to the inflow of the molten metal.

  The vanishing model of the present invention includes a plurality of pairs of the vent windows, and one pair of vent windows is shifted in the horizontal position with respect to another pair of vent windows adjacent in the height direction. Is provided. As a result, in the disappearance model of the present invention, the gas generated by the decomposition of the synthetic resin foam forming the disappearance model can be efficiently vented, and the thickness of the gas layer formed above the molten metal Can be reduced.

  Therefore, according to the disappearance model of the present invention, the heat of the molten metal is easily transmitted to the disappearance model, and the synthetic resin foam forming the disappearance model can be decomposed at a high temperature. Can be obtained.

  In the disappearance model of the present invention, it is preferable that the synthetic resin foam includes a rib, and the gas vent window is provided in a portion corresponding to the rib.

  When the synthetic resin foam includes ribs, the rib portion has a larger volume of the synthetic resin foam than other portions, and a large amount of gas is generated by the decomposition of the synthetic resin foam. Become. Therefore, by providing the gas vent window at the portion corresponding to the rib, the gas generated by the decomposition of the synthetic resin foam can be vented more efficiently.

  In addition, when the surface extending in the vertical direction of the synthetic resin foam is symmetrical in the horizontal direction, the gas venting is uneven in the horizontal direction if the gas venting window is provided at a position that is asymmetric. There is concern about becoming.

  Therefore, in the disappearance model of the present invention, when the surfaces extending in the vertical direction of the synthetic resin foam are symmetrical in the horizontal direction, a plurality of pairs of the venting windows provided at the same height are provided with the synthetic resin foam. It is preferably provided at a position that is symmetrical to the body. By doing in this way, the said degassing can be performed uniformly in the part where the surface extended in the up-down direction of the said synthetic resin foam becomes symmetrical in a horizontal direction.

  Further, in the portion where the gas vent window is provided, the molten metal solidifies in a state of being in direct contact with the foundry sand, so that the target casting may be roughened.

  Therefore, in the disappearance model of the present invention, the gas vent window is provided on an outer end surface of a projecting portion provided to project further outward from a portion having a shape corresponding to a target casting of the synthetic resin foam. It is preferable. According to the vanishing model in which the gas vent window is provided on the outer end surface of the protruding portion, the rough casting surface is formed on the outer end surface of the protruding portion. Therefore, after the molten metal has solidified, it is possible to reliably prevent the occurrence of casting roughness in the target casting by deleting the portion corresponding to the protruding portion of the obtained casting.

  Further, the disappearance model casting method of the present invention includes a step of forming a runner in foundry sand accommodated in a casting frame, and a synthetic resin foam, which is formed in the vertical direction of the synthetic resin foam coated with a coating material. A plurality of pairs of venting windows are provided by exposing the synthetic resin foam at positions facing each other on the extending surfaces, and one pair of venting windows is adjacent to another in the height direction. The vanishing model provided with the horizontal position shifted with respect to the pair of gas vent windows is fixed so as to close the opening of the runner opening in the casting frame, and is embedded with the foundry sand. A step of forming a sprue communicating with the runner in the casting sand, pouring a molten metal from the sprue, dissociating and disappearing the disappeared model, and the trace has the same shape as the disappeared model And a step of obtaining a casting.

  According to the vanishing model casting method of the present invention, by using the vanishing model provided with the gas vent window, the synthetic resin foam forming the vanishing model can be decomposed at a high temperature. No casting can be obtained.

The typical perspective view which shows one structural example of the vanishing model of this invention. The flowchart which shows each process of the vanishing model casting method of this invention. The typical sectional view showing the disappearance model casting method using the disappearance model shown in FIG. The typical perspective view which shows the 1st modification of the vanishing model of this invention. The typical perspective view which shows the 2nd modification of the vanishing model of this invention. The typical perspective view which shows the 3rd modification of the vanishing model of this invention. The structural example of the comparative example of the vanishing model of this invention is shown, (A) is a typical perspective view of the comparative example 1, (B) is a schematic perspective view of the comparative example 2. FIG. In the disappearance model of Example 1 of this invention and the comparative examples 1 and 2, the change of the thickness of the gas layer with respect to the elapsed time after a molten metal passes a gate is shown, (A) is the gas layer of the surface layer part of a disappearance model (B) is a graph which shows the thickness of the gas layer of the center part of a vanishing model. In the disappearance model of Example 1 and Comparative Examples 1 and 2 of the present invention, the change in gas pressure with respect to the height of the disappearance model is shown, (A) is a graph showing the gas pressure of the surface layer portion of the disappearance model, (B) is The graph which shows the gas pressure of the center part of a vanishing model.

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

  As shown in FIG. 1, the disappearance model 1 of the present embodiment has a coating material 3 applied to a synthetic resin foam 2 such as expanded polystyrene, and a plurality of pairs are disposed at positions facing each other on the surfaces extending in the vertical direction. Gas venting windows 4a and 4b. The degassing windows 4a and 4b are provided by exposing the synthetic resin foam 2 from the coating material 3, and one degassing window pair 4a and 4a is adjacent to another degassing window in the height direction. The horizontal positions of the pairs 4b and 4b are shifted (in FIG. 1, on the side surfaces adjacent to each other of the disappearance model 1).

  The degassing windows 4a and 4b are formed by attaching a mask (not shown) such as an adhesive tape to a portion of the synthetic resin foam 2 where the degassing windows 4a and 4b are formed, and applying the coating material 3 to the entire synthetic resin foam 2. After application, the mask can be peeled off. Alternatively, the gas vent windows 4a and 4b may be formed by applying the coating material 3 while avoiding the portions of the synthetic resin foam 2 where the gas vent windows 4a and 4b are formed.

  Next, with reference to FIG.2 and FIG.3, the vanishing model casting method using the vanishing model 1 is demonstrated.

  In the disappearance model casting method of this embodiment, first, in STEP 1 of FIG. 2, the runner 11 is connected to the disappearance model 1 as shown in FIG. Next, in STEP 2 of FIG. 2, the vanishing model 1 to which the runner 11 is connected as shown in FIG. 3 is fixed in the casting frame 12 and embedded in the foundry sand 13.

  Next, in STEP 3 of FIG. 2, a gate 14 communicating with the runner 11 is formed in the foundry sand 13 as shown in FIG. 3. Then, in STEP 4 of FIG. 2, the molten metal is poured from the gate 14.

  If it does in this way, the said molten metal will be supplied to the bottom part of the vanishing model 1 from the runway 11 through the opening part 15 where the coating material 3 of the lower part of the vanishing model 1 is not apply | coated. In the disappearance model 1, since the coating material 3 is applied to the synthetic resin foam 2 such as expanded polystyrene as described above, the synthetic resin foam 2 is decomposed by the heat of the molten metal and disappears. The gas generated by the decomposition of the body 2 forms a gas layer between the molten metal and the undecomposed synthetic resin foam 2 thereabove.

  At this time, if the thickness of the gas layer is excessive, the heat of the molten metal is difficult to be transmitted to the undecomposed synthetic resin foam 2, and the synthetic resin foam 2 is decomposed at a low temperature, so there is a concern about the generation of residues. The Regarding the concern, in this embodiment, the disappearance model 1 in which the synthetic resin foam 2 is exposed from the coating material 3 and the gas vent windows 4a and 4b are formed is used.

  In the disappearance model 1, when the synthetic resin foam 2 is decomposed and disappears, the coating material 3 remains, the inside surrounded by the coating material 3 becomes a cavity, and the foundry sand 13 is exposed to the gas vent windows 4a and 4b. Accordingly, the gas is released through the gaps in the foundry sand 13 exposed from the vent windows 4a and 4b.

  Further, the vanishing model 1 includes a plurality of pairs of the vent windows 4a and 4b, and one pair of vent windows 4a and 4a is in contrast to another pair of vent windows 4b and 4b adjacent in the height direction. The horizontal position is shifted. As a result, in the disappearance model 1, the gas can be efficiently degassed, the thickness of the gas layer formed above the molten metal can be reduced, and the synthetic resin foam 2 can be formed at a high temperature. Generation | occurrence | production of a residue can be prevented by making it decompose.

  Therefore, in the disappearance model casting method of the present embodiment, it is possible to obtain a cast that has the same shape as the disappearance model 1 and has no residual defects at the trace where the disappearance model 1 disappears. The obtained casting is taken out by demolding in STEP 5 of FIG.

  Next, a modified example of the disappearance model 1 will be described. In the vanishing model 1 shown in FIG. 1, one gas vent window pair 4 a, 4 a and another gas vent window pair 4 b, 4 b adjacent in the height direction are provided on side surfaces of the vanishing model 1 adjacent to each other. As a result, the position in the horizontal direction is shifted. However, the pair of gas vent windows 4a and 4a and the other gas vent window pairs 4b and 4b adjacent in the height direction may be provided on the same side as shown in FIG.

  Further, when the synthetic resin foam 2 forming the disappearance model 1 includes the rib 5, either one or both of the gas vent windows 4 a and 4 b may be provided in a portion corresponding to the rib 5. FIG. 4 shows a case where the gas vent window 4 a is provided in a portion corresponding to the rib 5.

  Further, as shown in FIG. 5, in the disappearance model 1, when the surfaces extending in the vertical direction of the synthetic resin foam 2 are provided with portions 6 and 6 that are symmetrical in the horizontal direction, a plurality of pairs provided at the same height are provided. The gas vent windows 4 a and 4 a may be provided in the symmetrical portions 6 and 6 of the synthetic resin foam 2.

  Further, in the cast body obtained by the vanishing model casting method of the present embodiment, the molten metal comes into direct contact with the foundry sand 13 at the portions corresponding to the gas vent windows 4a and 4b, so that casting roughness may occur. Therefore, as shown in FIG. 6, the disappearance model 1 includes a protruding portion 7 provided to protrude further outward from a portion having a shape corresponding to the target casting of the synthetic resin foam 2. It is preferable that a gas venting window 4a or a gas venting window 4b is provided on the outer end surface.

  In this case, casting roughness may occur in the portion of the protrusion 7 corresponding to the gas vent window 4a or the gas vent window 4b. However, since the protruding portion 7 is a dummy provided to protrude further outward from a portion having a shape corresponding to the target casting, the protruding portion 7 corresponds to the protruding portion 7 of the casting after demolding. By removing the portion, a casting with no casting roughness can be obtained.

  Next, the gas layer when the vanishing model casting method is performed using the vanishing model 1 (Example 1) illustrated in FIG. 1 and the vanishing models 21 and 31 illustrated in FIG. 7A or 7B. The thickness and gas pressure were measured.

  The disappearance model 21 shown in FIG. 7A is a comparative example 1 and has the same configuration as the disappearance model 1 shown in FIG. 1 except that the gas vent windows 4a and 4b are not provided at all. Therefore, the corresponding parts are denoted by the same reference numerals, and detailed description thereof is omitted.

  Moreover, the vanishing model 31 shown in FIG. 7B is a comparative example 2, and is exactly the same as the vanishing model 1 shown in FIG. 1 except that the gas vent windows 4a and 4b are provided at the same height. It has the composition of. Therefore, the corresponding parts are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 8 shows the change in the thickness of the gas layer with respect to the elapsed time after the molten metal passes through the gate in Example 1 and Comparative Examples 1 and 2 of the present invention.

  In Example 1, electrodes and gas sensors (not shown) are inserted at a predetermined depth from a plurality of positions in the height direction of the disappearance model 1 shown in FIG. 3 and detected after a predetermined time after the molten metal passes through the gate. The thickness of the gas layer was calculated from the position of the molten metal and the highest position of the gas layer.

  As the disappearance model 1, a bottom surface having a size of 50 mm × 50 mm and a height of 400 mm was used. The electrode and the gas sensor are inserted vertically at a depth of 5 mm or 25 mm from a surface extending in the vertical direction of the disappearance model 1.

  As a result, the electrode and the gas sensor detect the position of the melt and gas layer in the surface layer portion of the disappearance model 1 at a depth of 5 mm, and the position of the melt and gas layer in the center portion of the disappearance model 1 at a depth of 25 mm. Detect position.

  Further, the position of the molten metal was detected as being at the position of the electrode B when the electrode A provided on the gate and a certain electrode B were energized.

  On the other hand, in Comparative Examples 1 and 2, the thickness of the gas layer was calculated in exactly the same manner as in Example 1 except that the disappearance models 21 and 31 were used instead of the disappearance model 1 in FIG. In FIG. 8, a region where the thickness of the gas layer is negative indicates that the molten metal is detected before the gas, and means that the position of the molten metal is fluctuating up and down.

  From FIG. 8, according to the disappearance model 1 of Example 1, after 6 seconds after the molten metal passed through the gate, the disappearance models 21 and 31 of Comparative Examples 1 and 2 were observed in both the surface layer portion and the center portion. In comparison, it is clear that the thickness of the gas layer is small and the position of the molten metal does not rise and fall sharply.

  FIG. 9 shows the change in gas pressure with respect to the height of the disappearance model in Example 1 and Comparative Examples 1 and 2 of the present invention.

  In the first embodiment, pressure sensors (not shown) are inserted at a predetermined depth from a plurality of positions in the height direction of the disappearance model 1 shown in FIG. At the indicated time, the gas pressure was detected by each pressure sensor.

  As the disappearance model 1, a bottom surface having a size of 50 mm × 50 mm and a height of 400 mm was used. The pressure sensor is inserted at a depth of 5 mm or a depth of 25 mm vertically from a surface extending in the vertical direction of the disappearance model 1. As a result, the pressure sensor detects the gas pressure at the surface layer portion of the disappearance model 1 at a depth of 5 mm, and detects the gas pressure at the center portion of the disappearance model 1 at a depth of 25 mm.

  On the other hand, in Comparative Examples 1 and 2, the gas pressure was detected in exactly the same manner as in Example 1 except that the disappearance models 21 and 31 were used instead of the disappearance model 1 in FIG.

  According to the disappearance model 1 of Example 1 from FIG. 9, the gas pressure is lower than the disappearance models 21 and 31 of Comparative Examples 1 and 2 at both the surface layer portion and the central portion at a height of about 160 mm or more. It is clear that the gas layer is thin.

  DESCRIPTION OF SYMBOLS 1 ... Disappearance model, 2 ... Synthetic resin foam, 3 ... Coating type, 4a, 4b ... Degassing window.

Claims (5)

A disappearance model made of a synthetic resin foam,
A plurality of pairs of vent windows provided by exposing the synthetic resin foam at positions facing each other on the surfaces extending in the vertical direction of the synthetic resin foam coated with a coating material;
The vanishing model, wherein one pair of venting windows is provided with a horizontal position shifted with respect to another pair of venting windows adjacent in the height direction.   The disappearance model according to claim 1, wherein the synthetic resin foam includes a rib, and the gas venting window is provided at a portion corresponding to the rib.   The disappearance model according to claim 1 or 2, wherein when the surfaces extending in the vertical direction of the synthetic resin foam are symmetrical in the horizontal direction, a plurality of pairs of the vent windows provided at the same height are provided. Disappearance model characterized by being provided at a symmetrical position of the synthetic resin foam.   The vanishing model according to any one of claims 1 to 3, wherein the gas vent window is provided to protrude further outward from a portion having a shape that matches a target casting of the synthetic resin foam. A vanishing model provided on the outer end surface of the protruding portion. Forming a runner in the foundry sand accommodated in the casting frame;
A plurality of pairs of gases provided by exposing the synthetic resin foam to positions facing each other on the surfaces extending in the vertical direction of the synthetic resin foam, which is made of a synthetic resin foam and coated with a coating material A pair of gas vent windows is provided with a vanishing model provided in the cast frame so that a horizontal position is shifted with respect to another pair of gas vent windows adjacent in the height direction. Fixing the open end of the runner to be closed and burying with the foundry sand;
Forming a sprue communicating with the runner in the casting sand;
A disappearing model casting method comprising: pouring molten metal from the gate, dissociating and disappearing the disappearing model, and obtaining a cast having the same shape as the disappearing model at the trace.