JP2011110573A - Lost foam pattern casting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lost foam pattern casting method capable of filling a high temperature melt into an entire pattern without increasing the number of gates and of effectively suppressing scum defects. <P>SOLUTION: In the lost foam pattern casting method, the melt is poured into a mold formed by embedding a pattern comprising a resin foaming body in casting sand and a product is cast while losing the pattern by the melt. The position of gate of the melt to the pattern installed in casting sand is set at the height of the centroid position of the product that is cast or in the vicinity of the centroid position. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a disappearance model casting method, and more particularly to a technique for reducing residual defects in a model.

  The above disappearance model casting method is known, for example, in Patent Document 1. In this method, due to a decrease in the temperature of the molten metal poured into the mold, there may be a residual defect in which the unmelted portion of the model sticks to the surface of the product, particularly at the final filling site. In general, since the molten metal enters the model from the bottom to the top, residue defects are likely to occur on the upper surface of the cast product. Therefore, Patent Document 1 discloses a measure in which an upper runner and a lower runner are provided to prevent the turbulent flow of the molten metal and the molten metal in a high temperature state quickly reaches the upper part.

JP-A-7-308734

  However, in the measure described in the above-mentioned Patent Document 1, the number of gates increases as the runners increase, so it is troublesome to produce a mold or when cutting a gate when obtaining a product after casting. There is an inconvenience that labor is increased, workability is lowered, and processing cost is increased.

  Therefore, an object of the present invention is to provide a disappearing model casting method that can fill a high temperature molten metal throughout the model without increasing the number of gates and can effectively suppress residual defects.

  In the disappearance model casting method according to claim 1 of the present invention, a molten metal is poured into a mold in which a model made of a resinous foam is embedded in foundry sand, and the product is removed while the model is lost by the molten metal. In the vanishing model casting method for casting, the gate of the molten metal to the model installed in the foundry sand is set to the height of the center of gravity of the product to be cast.

  Further, in the disappearance model casting method according to claim 2 of the present invention, molten metal is poured into a mold in which a model made of a resinous foam is embedded in foundry sand, and the model is lost by the molten metal. In the vanishing model casting method for casting a product, the gate of the molten metal to the model installed in the foundry sand is set downward from the center of gravity within a range of 120 mm from the center of gravity of the product to be cast. And

  Further, in the disappearance model casting method according to claim 3 of the present invention, molten metal is poured into a mold in which a model made of a resinous foam is embedded in foundry sand, and the model is disappeared by the molten metal. In the disappearing model casting method for casting a product, when the center of gravity of the product cast in the foundry sand is within a range of 440 mm above the lower end of the product, The molten metal gate is installed above the center of gravity of the product within a range of 440 mm above the lower end of the product.

  According to the present invention, the final filling temperature of the molten metal filled in the model region can be made as high as possible by setting the gate at the height of the center of gravity position of the product or in the vicinity of the height of the center of gravity position. Defects are less likely to occur.

  In the vanishing model casting method of the present invention, the product obtained is a press die (claim 4).

  According to the present invention, since the gate is set at the height of the center of gravity position of the product, or near the height of the center of gravity position, the hot melt can be filled in the entire model without increasing the number of gates, There exists an effect that a residue defect can be suppressed effectively.

It is sectional drawing of the casting_mold | template which showed the vanishing model casting method of this invention notionally. It is sectional drawing which shows the state which cast the casting (product) in which an important part exists in a part of upper surface by the casting_mold | template (side gate type | mold) which concerns on this invention. It is sectional drawing which shows the state which cast the casting (product) which has an important part in a part of upper surface by the casting_mold | template (bottom gate type | mold) which is not this invention. It is a figure which shows the concept of the gate height setting in this invention. It is a graph which shows the relationship between the molten metal temperature of the important part of a casting bottom face, and the gate height from a casting bottom face. It is a graph which shows the relationship between the molten metal temperature of the important part of a casting upper surface, and the gate height from the gravity center position of a casting.

Embodiments according to the present invention will be described below with reference to the drawings.
FIG. 1 shows a cross section of a mold 1 conceptually showing a vanishing model casting method according to an embodiment. The mold 1 is configured by burying a model 3 in foundry sand 2 filled in a casting frame (not shown).

  A gate 4 connected to the model and a runner 5 connected to the gate 4 are formed around the model 3 in the foundry sand 2. The runner 5 is provided with a plurality of openings (two in FIG. 1) to the upper surface of the mold 1, and a gate 6 is provided in one (right side in FIG. 1). Further, the runner 5 on the other opening side is particularly a gas vent passage 7, and a filter 8 for releasing only the combustion gas to the atmosphere outside the mold 1 is provided in the gas vent passage 7.

  The mold 1 is manufactured according to the following procedure. First, a mold-forming agent having graphite as a main component and having excellent fire resistance is applied to the surface of the model 3 and sufficiently dried. On the other hand, the runner 5 (including the gas vent passage 7) 5 and the gate 4 are formed in the cast frame by a method such as assembling a paper tube, and the model 3 is arranged and supported at a substantially central portion in the cast frame. At this stage, a filter 8 is also disposed in the gas vent passage 7. Thereafter, the casting sand 2 is filled in the casting frame, the model 3 is buried, and the gate 6 is installed.

  As the foundry sand 2, new sand or old sand such as zircon sand, chromite sand, and synthetic ceramic sand is used in addition to quartz sand mainly composed of quartz. A binder and a curing agent are added to the foundry sand 2 as necessary.

  The runner 5 and the gate 4 are formed with commercially available products having a diameter of 30 to 70 mm (for example, Kao's quaker casting runner pipes: EG runners CF-30S, CF-50S, CF-70S, etc., the main component is recycled pulp. ) Etc. are used. The filter 8 is made of a porous material or the like formed by mixing an appropriate binder with sand equivalent to No. 2 silica sand and having a thickness of about 40 mm.

The model 3 is obtained by hand-molding a synthetic resin foam such as expanded polystyrene into a desired shape. As the coating agent, for example, Kao Quaker PC260 manufactured by Kao Corporation is used, and is applied to the surface of the model with a thickness of 1.5 to 3.5 mm and an air permeability of about 10 mm ² .

  Thus, the mold 1 is manufactured. According to this mold 1, when molten metal (molten metal material) is poured from the gate 6, the molten metal reaches the model 3 through the runner 5 and the gate 4, and the model 3 disappears by being melted with the molten metal. The molten space is filled in the disappearing space. That is, the model 3 is replaced with molten metal. A large amount of combustion gas is generated at the initial stage of pouring in which the model 3 burns, and the combustion gas is discharged to the atmosphere through the filter 8 in the gas vent passage 7 at the most downstream side of the runner 5. A part of the combustion gas passes through a coating film formed by applying a coating agent to the surface of the model 3, and further passes through the foundry sand 2 and is discharged to the atmosphere.

  Now, in the casting_mold | template 1 of one Embodiment, the height position of the gate 4 in the foundry sand 2 is set to the position which satisfies either of the following conditions (a)-(c).

(A) The height of the center of gravity of the product to be cast.
(B) Downward from the center of gravity within a range of 120 mm from the center of gravity of the cast product.
(C) When the position of the center of gravity of the cast product is within a range of 440 mm above the lower end of the product, the position is 440 mm above the lower end of the product and above the position of the center of gravity of the product.

  In the present invention, the above (1) is the best mode. However, in actual manufacturing, the gate may not be set at the height of the center of gravity due to design circumstances. In that case, the above condition (b) or (c) is adopted. That is, the gate height in the present invention is set so that the height of the center of gravity of the product is the best, and when it is difficult, the gate height is set above or below the center of gravity of the product.

  Here, the superiority of the present invention when there is an important part on the upper surface of the casting will be described with reference to FIGS. 2 and 3 (the hatched portion in FIGS. 2 and 3 is the casting portion by filling with molten metal). First, FIG. 2 shows a state in which a casting (product) 10 having an important part 10A on a part of the upper surface is cast according to the present invention. The important part 10A is a part where casting defects such as the above-mentioned residue defects are not allowed and a sound casting filled with the molten metal is to be performed. As shown in FIG. 2, the gate 4 is arranged on the side of the casting 10 (side gate type), and an important part is located immediately above the gate 4. When the gate 4 is at a height position that satisfies any of the above conditions (a) to (c), the important portion 10A is filled with the molten metal in advance, and thereby the important portion 10A has a residual defect. It is hard to happen.

  On the other hand, FIG. 3 shows a bottom gate type in which the gate 4 is arranged on the bottom surface of the casting 10, and in this case, the completion of the filling of the molten metal on the upper surface is almost entirely simultaneous, and residue defects are likely to occur on the entire upper surface. Therefore, a residue defect tends to exist in the important part 10A.

  Now, the gate height affects the degree of filling of the molten metal into the model area to be replaced by the casting. If the gate is too high, the above-mentioned residue defects are likely to occur on the bottom side of the casting, and if the gate is too low, the top side of the casting Residue defects are likely to occur. The present invention solves this problem, and the upper and lower limits of the gate height are set as shown in (b) and (c) above.

First, the upper and lower limits of the gate height are
H (upper limit): upper limit of the gate height from the bottom of the casting (mm)
H (lower limit): Lower limit of the gate height from the bottom of the casting (mm)
Hgate: Gate height from the bottom of the casting (mm)
Is expressed by the following formula (1).
H (upper limit) ≧ Hgate ≧ H (lower limit) (1)
When the condition of the formula (1) is satisfied, the entire product which is a casting can be filled with a high-temperature molten metal, and residue defects can be reduced. Here, the upper limit of gate height: (upper limit) and the lower limit: H (lower limit) are determined from casting data as follows.

Ha: Bottom (lower end) height position of casting (mm)
Hb: Height position of the center of gravity of the casting (mm)
Hc: Upper surface (upper end) height position (mm) of casting
a, b: constants (when using a handmade model with a pouring temperature of 1380 ° C. and a foaming ratio of 50 times mainly composed of expanded polystyrene, a = 440, b = 120)
When Hb <440, H (upper limit) = Ha + a (2)
H (lower limit) = Hb−b (3)
The concept of the above Ha, Hb, Hc, “H (upper limit) = Ha + a”, and “H (lower limit) = Hb−b” is shown in FIG.

  The constants a and b are obtained from Table 1 and the graphs of FIGS. These tables and graphs are casting data showing the results of examining the formability of the bottom surface of the casting and the top surface of the casting for the casting samples 1 to 7 whose gate height positions were changed. It is assumed that the important parts are present on the bottom and top surfaces of the casting.

  First, looking at the moldability of the bottom surface of the casting in Table 1, it is confirmed that the moldability is good up to a maximum of 440 mm in Hgate (gate height). FIG. 5 is a graph showing the relationship between the molten metal temperature at the critical part of the bottom of the casting and the gate height from the bottom of the casting. As is clear from this, the gate height from the bottom of the casting is 440 mm or less. In this case, the important part of the bottom surface can be cast without residual defects. Therefore, a = 440.

  Further, when the formability of the upper surface of the casting is seen in Table 1, a residue defect occurs when Hgate-Hb (gate height from the center of gravity of the casting) is within -120 mm. FIG. 6 is a graph showing the relationship between the molten metal temperature of the important part on the upper surface of the casting and the gate height from the center of gravity of the casting. As is clear from this, the gate height from the center of gravity of the casting is −120 mm. In the case of the following, the important part of the upper surface can be cast without any residue defects. Therefore, b = 120.

  As described above, by setting the height position of the gate in the foundry sand to a position that satisfies any of the above conditions (a) to (c), the bottom surface and the top surface of the casting (product) It is possible to carry out a disappearing model casting method that has good moldability and that is unlikely to cause residue defects particularly in important portions of the upper surface. In Table 1, cast samples 1 to 4 are examples of the present invention, and 5 to 7 are comparative examples outside the present invention.

  A coating agent (60 to 65 Baume) is applied to the surface of a model molded from foamed polystyrene with an external dimension of 750 × 800 × 430 (mm), dried, and then configured in the same manner as shown in FIG. A mold was formed and cast. The gate height in the foundry sand in the mold was 435 mm from the bottom of the model according to the center of gravity of the casting. In this case, the upper limit of the gate height: H (upper limit) was 440 mm, and the lower limit: H (lower limit) was 380.7 mm. The casting material was FC300 (flaky graphite cast iron), the temperature of the molten metal during pouring (casting temperature) was 1365 ° C., and the casting weight was 13 tons. As a result of casting, no casting defects such as residue defects were found on the bottom and top surfaces of the casting, and a good product could be obtained.

DESCRIPTION OF SYMBOLS 1 ... Mold 2 ... Foundry sand 3 ... Model 4 ... Gate 5 ... Runway 6 ... Spout 7 ... Degassing passage 8 ... Filter 10 ... Casting (product)

Claims (4)

In the disappearance model casting method in which a molten metal is poured into a mold in which a model made of a resinous foam is embedded in foundry sand, and the product is cast while the model is lost by the molten metal,
A vanishing model casting method, wherein a molten metal gate to the model installed in the foundry sand is set at a height of a center of gravity of a product to be cast. In the disappearance model casting method in which a molten metal is poured into a mold in which a model made of a resinous foam is embedded in foundry sand, and the product is cast while the model is lost by the molten metal,
A vanishing model casting method, characterized in that a molten metal gate to the model installed in the foundry sand is set downward from the center of gravity within a range of 120 mm from the center of gravity of a product to be cast. In the disappearance model casting method in which a molten metal is poured into a mold in which a model made of a resinous foam is embedded in foundry sand, and the product is cast while the model is lost by the molten metal,
When the position of the center of gravity of the product cast in the foundry sand is within 440 mm above the lower end of the product, the molten metal gate to the model installed in the foundry sand is placed from the lower end of the product. A vanishing model casting method characterized by being installed above the center of gravity of the product within a range of 440 mm above.   The vanishing model casting method according to claim 1, wherein the product is a press die.

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