US20130291463A1

US20130291463A1 - Evaporative pattern for casting and casted product

Info

Publication number: US20130291463A1
Application number: US13/823,804
Authority: US
Inventors: Yumi Kobayashi
Original assignee: Individual
Current assignee: Toyota Motor Corp
Priority date: 2011-01-28
Filing date: 2011-01-28
Publication date: 2013-11-07
Also published as: CN103338877A; WO2012101824A1; JPWO2012101824A1; JP5445680B2

Abstract

An evaporative pattern having a high strength is provided. An evaporative pattern 102 is a pattern for an evaporative casting. In the evaporative pattern 102, a reinforcing member 30 which is made of a non-evaporative material that does not evaporate by heat of a molten metal is embedded in a joint 114 which is made of an evaporative material that evaporates by the heat of the molten metal. The evaporative material is typically foam polystyrene. The strength of the foam polystyrene is low. Since the reinforcing member which is made of a material having strength higher than that of the evaporative material is embedded in the evaporative pattern 102 which is made of the foam polystyrene, the strength of the evaporative pattern 102 improves.

Description

TECHNICAL FIELD

The present invention relates to an evaporative pattern for casting and a casted structure that is casted by using the evaporative pattern.

BACKGROUND ART

An evaporative pattern casting is a kind of casting method, and may be called a lost-foam casting or a full mold casting. This method may be generally described as below. First, a pattern is made of an evaporative material which evaporates by heat of a molten metal. The pattern is called an evaporative pattern. Next, a sand mold is made by burying the evaporative pattern therein. The molten metal is poured into a cavity of the sand mold. Here, the ‘cavity’ means a space which is occupied by the evaporative pattern. When the molten metal is poured into the cavity, the evaporative pattern evaporates by the heat of the molten metal, and the space which has been occupied by the evaporative pattern is filled with the molten metal. When the sand mold is broken down after the molten metal is cooled and solidified, a casted structure perfectly having the same shape as that of the evaporative pattern is obtained. As the evaporative material, foam polystyrene or wax is typically used.
Since the evaporative material has a characteristic feature of evaporating by the heat of the molten metal, it has a disadvantage of a low strength. That is, the strength of the existing evaporative pattern is not high. Therefore, for example, patent document 1 proposes to attach a disk-like reinforcing member to a hollow space inside a pipe-like evaporative pattern. In the patent document 1, the evaporative pattern to which the reinforcing member is attached is buried in a sand mold. The reinforcing member is provided with a through hole which is formed in the axial direction, and sand comes into the pipe via the through hole. The reinforcing member is removed after a casted product is formed.

CITATION LIST

Patent Document

Patent document 1: Japanese Patent Application Publication No. 07-22301

SUMMARY OF INVENTION

Technical Problem

In the technique of the patent document 1, the reinforcing member is buried in sand in addition to the evaporative pattern. Therefore, although the through hole which allows the passage of sand is provided, sand is not likely filled at the back side of the reinforcing member. Accordingly, when the periphery of the evaporative pattern is not sufficiently filled with sand, a desirable casted product may not be obtained. For this reason, a frequent check whether sand is sufficiently filled at the back side of the reinforcing member is required. Further, the technique of the patent document 1 cannot be applied to shapes other than the pipe. The present invention provides a technique which can be applied to shapes other than the pipe, does not need to bury a reinforcing member separated from an evaporative pattern, and compensates the insufficient strength of the evaporative pattern.

Solution to Technical Problem

According to the technique disclosed in the present description, a reinforcing member is embedded in an evaporative pattern. That is, strength of the evaporative pattern itself is improved. Accordingly, there is no need to bury a member other than the evaporative pattern into the sand mold as in the case of the technique of the patent document 1. Further, this method may be applied to any shape of evaporative pattern. The reinforcing member may be made of a non-evaporative material which does not evaporate by heat of a molten metal. Typically, the reinforcing member nay be made of steel, titanium, or other metals having a high strength.
In the meanwhile, in the novel technique disclosed in the present description, the reinforcing member remains inside a casted product. That is, the reinforcing member improves not only the strength of the evaporative pattern but also the strength of the casted product. It is desirable that the reinforcing member be made of a material having strength higher than that of a casting material.
In another aspect of the technique disclosed in the present description, the entire reinforcing member may be covered by the evaporative material. This means that a molten metal flowing space may be ensured in a periphery of the reinforcing member.
In still another aspect of the technique disclosed in the present description, there may be a wire extending from the reinforcing member to outside the evaporative pattern. The exposure portion of the wire may be fixed by the sand of the mold. This means that the reinforcing member is supported by the sand mold through the wire. Since the wire is used, even when the molten metal flows into and the evaporative material evaporates, the reinforcing member does not move because the reinforcing member is supported by the wire. In the evaporative pattern which adopts the wire, the reinforcing member may be allocated at a desirable position inside the casted product.
The technique disclosed in the present description also provides a novel casted product. The casted product may be obtained by a casting with the evaporative pattern. That is, the casted product is characterized in that a reinforcing member made of a material different from that of the casting material is embedded therein. As described above, it is desirable that the reinforcing member be made of a material having strength higher than that of the casting material. In this technique, it is desirable that the casting material be iron. That is, one casted product disclosed in the present description may be a casted iron structure in which the reinforcing member having the strength higher than that of iron is embedded.
One embodiment of the casted product may include a plurality of rod members that configures a frame with a Rahmen structure, a truss structure, or a combination structure of the Rahmen structure and the truss structure. Furthermore, in the casted product, the reinforcing member may be embedded in the joint of the frame. Hereinafter, for simplifying the description, the ‘structure which is made of the plurality of rod members configuring the truss structure, the Rahmen structure, or the combination structure of the truss structure and the Rahmen structure’ will be simply referred to as a ‘frame structure’. In the frame structure, a large force is loaded at the joint. Accordingly, when the reinforcing member is embedded in the joint, the strength of the entire structure may be improved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic side view illustrating a press machine.

FIG. 2A is a plan view illustrating a die (evaporative pattern).

FIG. 2B is a side view illustrating the die (evaporative pattern).

FIG. 3 is an enlarged view illustrating a joint of the evaporative pattern.

FIG. 4 is an enlarged view illustrating a joint of an evaporative pattern of a modified example.

FIG. 5 is an enlarged view illustrating a joint of an evaporative pattern of another modified example.

DESCRIPTION OF EMBODIMENTS

To begin with, a subject which is casted by an evaporative pattern of an embodiment will be described. In the embodiment, a die for machine press is a casted product which corresponds to the subject. In order to help with understanding, the usage example of the die for machine press will be described first. FIG. 1 is a schematic side view illustrating a press machine 50 equipped with dies 2 and 42. FIG. 2A is a plan view illustrating the die 2, and FIG. 2B is a side view illustrating the die 2. Furthermore, in FIG. 2B, the die 42 which faces to the die 2 is also illustrated. The die 2 is fixed to a bolster 51, and the die 42 is fixed to a slider 52. The slider 52 can be moved up and down by an actuator 55 while being guided along a support column 53.
The die 2 includes a design block 20, positioning blocks 24, and a support block 26. The design block 20 includes a design surface 20 a which is used to transfer a desired shape to a work plate. The die 2 of this example is a die which is used to press-mold a fender of a vehicle. The design surface 20 a is formed based on the shape of the fender. The positioning blocks 24 are disposed at four corners of the die 2. In the drawing, it is noted that the reference numeral 24 is given to only one positioning block and is not given to the other positioning blocks.
When the work plate W is interposed between the design block 20 of the die 2 and the design block 40 of the die 42 and the actuator 55 moves the slider 52 down so as to apply a load to the work plate W. The work plate W is deformed according to the shape of the design surface 20 a. That is, the shape of the design surface 20 a is transferred to the work plate W.
At the time of matching the die 2 and the die 42, guide pins 25 of the die 2 are fitted to guide bushes 45 of the die 42, so that the die 2 and the die 42 are positioned to each other. That is, the design surface 20 a of the die 2 and a design surface 40 a of the die 42 are positioned to each other. The guide pins 25 are provided in the positioning blocks 24. As illustrated in FIG. 2A, the positioning blocks 24 are disposed at four corners of the die 2 so as to surround the design block 20. Since the positioning blocks 24 are disposed at four corners of the design block 20, the relative position between the design surface 20 a of the die 2 and the design surface 40 a of the die 42 may be accurately determined.
The support block 26 is used to attach various tools that utilize a press load. As the type of tool, for example, a bending tool which rounds the end of the work, a punching tool which punches the work in the horizontal direction so as to make a through hole, and the like may be exemplified. A support block 46 which faces to the support block 26 is attached to the die 42. The tool which is disposed between the support blocks 26 and 46 is configured to operate the tool by utilizing a load, which is generated when the support blocks 26 and 46 move close to each other, as a driving force.
The design block 20, the positioning blocks 24, and, the support block 26 are connected to each other through a plurality of rods 12 (rod members). A connection portion between the rods is referred to as a ‘joint 14’. In the drawing, it is noted that the reference numerals are given to only some of the rods and the joints and are not given to all of the rods and joints. The plural rods 12 are combined with each other vertically, horizontally, and obliquely so as to form a frame 10. In a case where the lattice window surrounded by the plural rods 12 is rectangular, the rods 12 form a Rahmen structure. In the portion in which the lattice window surrounded by the plural rods 12 is triangular, the rods 12 form a truss structure. That is, the frame 10 has the above-described frame structure. Furthermore, the truss structure means a frame structure in which only an axial force is exerted in the rods, but a moment is not exerted therein, and the Rahmen structure means a frame structure in which both the axial force and the moment are exerted in the rods. Since the Rahmen structure and the truss structure are both formed only by the rods, an appropriate flexibility can be obtained as an entirety thereof with a high strength ensured.
The die 2 is a casted product which is made by a full mold casting or a lost-foam casting. Although it will be described in detail later, a reinforcing material which is made of metal having strength higher than that of the casting material is embedded in the joints 14 of the die 2.
As illustrated in FIG. 2A, the design block 20 is supported by the rods 12 at four sides in the top view. Further, the design block 20 is also supported by the rods 12, which are arranged in the perpendicular direction, from the rear surface thereof. Since the design block 20 is supported by the rods 12 at the four sides and the rear surface, the design block may be flexibly and slightly moved even when receiving a load. That is, when a biased press load is applied to the design block, the design block 20 slightly moves so that the distribution of the press load becomes uniform. Accordingly, a deviation in the press load is solved by such a small movement. The relative position between the entire die 2 and the die 42 is accurately determined by the positioning blocks 24 at the four corners. On the other hand, since the design block 20 is supported by the rods 12 at the four sides and the rear surface, the design block can slightly move so as to solve the deviation in the press load. Since no biased press load concentrates on the design surface 20 a, abrasion of the die is suppressed and the high work molding precision is maintained.
Rigidity of the design block 20 is higher than rigidity of the frame 10 which is assembled by the rods 12. Further, rigidity of the positioning block 24 is also higher than the rigidity of the frame 10. Thus, when the press load is applied, the deformation amounts of the design block 20 and the positioning block 24 are small compared to the deformation amount of the frame 10. That is, although the entire frame 10 is deformed, the deformation of the design block 20 and the deformation of the positioning block 24 are suppressed. Since the deformation of the design block 20 is suppressed, the high work molding precision may be maintained.
The die 2 is made by an evaporative pattern casting (a full mold casting or a lost-foam casting). Thus, it is needed to prepare an evaporative pattern having the same shape as that of the die 2 illustrated in FIGS. 2A and 2B. Hereinafter, the evaporative pattern having the same shape as that of the die 2 of FIGS. 2A and 2B may be referred to as an evaporative pattern 102. Further, hereinafter, the components of the evaporative pattern corresponding to the respective components of the die 2 are indicated by three-digit numbers including double-digit numbers representing the components of the die 2. For example, the number 112 is allocated to the evaporative rod corresponding to the rod 12 of the die 2. The evaporative pattern 102 is made of an evaporative material which evaporates by the heat of a molten metal. The evaporative material is typically foam polystyrene.
The large evaporative pattern may be easily bent. The die 2 which is used to manufacture the fender of a vehicle has several meters of sizes in length and width. When the evaporative pattern 102 of such a size is made of foam polystyrene, the evaporative pattern may be bent easily. In particular, the die 2 of FIGS. 2A and 2B includes the frame 10 having the plural rods 12. Furthermore, the diameter of the rod 12 is several tens of centimeters. When the frame 10 of several meters is made of the foam polystyrene, the frame may be easily broken down. Especially, the joints 14 may be easily broken down. Typically, there is a concern that the joints may be damaged when carrying the evaporative pattern and burying it into a sand mold. Therefore, in the technique of the embodiment, a reinforcing member is embedded into the evaporative pattern 102.
FIG. 3 is an enlarged view illustrating a joint of the evaporative pattern 102. In FIG. 3, a joint 114 of the evaporative pattern which is formed by connecting four rods 112 of the evaporative pattern is illustrated. The joint of FIG. 3 may appear in various portions of the evaporative pattern 102. Furthermore, although the evaporative pattern 102 has a joint which is formed by connecting rods other than four, it has a similar structure as illustrated in FIG. 3.
A reinforcing member 30 made of steel may be embedded in each joint 114. The reinforcing member 30 extends passing through the joint 114 so as to connect the end portions of the adjacent rods 112. The relative position between the joint 114 and the group of the adjacent rods 112 is held by the reinforcing member 30. That is, the reinforcing member 30 enhances the strength of the evaporative pattern 102.
The rods are also connected to the design block or the positioning blocks of the evaporative pattern 102. The reinforcing member 30 may also be embedded in the connection portion between the block and the rod. That is, the reinforcing member 30 may be embedded at various locations of the evaporative pattern 102. The reinforcing member 30 is completely covered by the evaporative material. In other words, this means that a passage for molten metal is ensured between sand and the reinforcing member when burying the evaporative pattern in the sand mold. Thus, at the time when the molten metal is poured into the sand mold, the molten metal is not blocked by the reinforcing member 30 serving as a dam and the molten metal flows over the reinforcing member 30.
The casting process using the evaporative pattern 102 will be described. First, the sand mold is made by burying the evaporative pattern 102 (or an evaporative pattern 202 or 302) having the shape illustrated in FIGS. 2A and 2B. Next, the molten metal (casting iron) is poured into a cavity of the sand mold. The cavity means a space which is occupied by the evaporative pattern 102. The evaporative pattern 102 is melted by the heat of the molten metal, so that the space occupied by the evaporative pattern 102 is filled with the molten metal. The periphery of the reinforcing member 30 is also filled with the molten metal. Here, the reinforcing member 30 which is at the normal temperature promotes the cooling of the molten metal. As the cooling speed becomes faster, the hardness of the casted product becomes higher. That is, there is an advantage that the strength of the casted product is improved by embedding the reinforcing member 30. Especially, the casting iron is brittle (toughness thereof is not high). For this reason, the strength against a tensile force is not particularly high. When the reinforcing member is made of a material having a high toughness, for example, rolled steel for a general structure (JIS standard, SS400, SS490, SS540, and the like), the toughness of the entire casted product may be improved.
When the sand mold is removed after the molten metal is cooled and solidified, the casted product, that is, the die 2 perfectly having the same shape as that of the evaporative pattern 102 is obtained. As for the obtained die 2, the reinforcing members 30 are embedded in the joints 14. More specifically, in the die 2, the plurality of rods 12 includes the frame 10 configuring the Rahmen structure, the truss structure, or the combination structure of the Rahmen structure and the truss structure, and the reinforcing members 30 are embedded in the joints 14 of the frame 10. The reinforcing members 30 reinforce the evaporative pattern, and also reinforce the die 2 as the casted product.
FIG. 4 illustrates a modification example of the evaporative pattern 102. In an evaporative pattern 202 of FIG. 4, a metal wire 234 extends from a reinforcing member 230, which is perfectly covered by the evaporative material, to outside of the evaporative pattern 202. In other words, the evaporative pattern 202 includes the wire 234 of which one end is fixed to the reinforcing member 230 and the other end is exposed from the evaporative pattern 202. When the evaporative pattern 202 is buried in the sand mold, the end portion of the wire 234 is fixed to the sand mold. That is, the reinforcing member 230 is directly supported by the sand mold through the wire 234. Thus, the reinforcing member 230 does not move when the evaporative pattern 202 is melted by the heat of the molten metal. For this reason, the reinforcing member 230 may be disposed at the accurate position inside the casted product.
The evaporative pattern may be made of a plurality of types of evaporative materials. For example, the rod may be made of a paper pipe, and the joint may be made of foam polystyrene. FIG. 5 is an enlarged view illustrating the joints of the evaporative pattern 302. Since the evaporative pattern 302 includes plural joints, it is noted that a part or the entirety thereof has the same structure as that of FIG. 5. In the evaporative pattern 302, the joints 314 are made of the foam polystyrene. The reinforcing members 30 made of steel is embedded in the joints 314. The joints are connected to each other by the paper pipes 312. Furthermore, in the present description, it is noted that the paper pipes 312 are a kind of rods which connects two adjacent joints to each other. The joints 314 and the paper pipes 312 are connected to each other by an adhesive. The evaporative pattern 302 uses the paper pipes 312 as the rods constituting the frame. The evaporative pattern 302 has an advantage that the molten metal flows smoothly when the molten metal is poured into the sand mold.
In the evaporative pattern of the embodiments, the reinforcing member is embedded in the relevant joint portion of the frame that is configured of the rods. The embedding location of the reinforcing member is not limited to the joint. For example, the reinforcing member may be embedded in the design block 20 or the positioning block 24. The reinforcing member to be embedded in the evaporative pattern may be made of a metal which is not melted or burned by the heat of the molten metal. The reinforcing member may be made of a metal such as steel, titanium, or tungsten. It is desirable that the reinforcing member be made of a material having strength higher than that of the casting material.
While the specific examples of the invention have been described in detail, these are merely examples of the invention, and are not considered as limiting the claims. The description of the claims includes various modifications and changes of the above-described embodiments. The technical elements described in the description or the drawings exhibit the technical utility solely or by various combinations, and are not limited to the combination of the claims of the application. Further, the techniques exemplified in the description or the drawings may attain multiple purposes at the same time, and the technical utility may be obtained by attaining one of the purposes.

LIST OF REFERENCE SIGNS

2: die, 10: frame, 12: rod, 14: joint, 20: design block, 20 a: design surface, 24: positioning block, 25: guide pin, 30: support block, 50: press machine, 51: bolster, 52: slider, 53: column, 55: actuator, 102: evaporative pattern, 112: rod of the evaporative patterns 114: joint of evaporative pattern

Claims

1. An evaporative pattern for casting, wherein a reinforcing member made of a non-evaporative material that does not evaporate by heat of a molten metal is embedded in the evaporative pattern made of an evaporative material that evaporates by the heat of the molten metal; and

a wire extends from the reinforcing member to outside of the evaporative pattern.

2. The evaporative pattern of claim 1, wherein the entire reinforcing member is covered by the evaporative material.

3. A casted product made by a casting using the evaporative pattern of claim 1, wherein the reinforcing member made of a metal that is different from a casting material is embedded in the casted product.

4. The casted product of claim 3, wherein the casted product includes a plurality of rod members that configures a frame configured by any one of a Rahmen structure, a truss structure, and a combination structure of the Rahmen structure and the truss structure, and the reinforcing member is embedded at a joint of the frame.

5. A casted product made by a casting using an evaporative pattern, wherein:

the evaporative pattern includes a reinforcing member embedded therein, the reinforcing member being made of a non-evaporative material that does not evaporate by heat of a molten metal, and the evaporative pattern being made of an evaporative material that evaporates by the heat of the molten metal; and

the casted product includes a frame, configured by any one of a Rahmen structure, a truss structure, and a combination structure of the Rahmen structure and the truss structure and constructed by a plurality of rod members, and the reinforcing member is embedded at a joint of the frame.