DE102010000450B4 - A method of making a hollow casting and method of making a void-forming member for use therefor - Google Patents

Abstract

A method of making a hollow casting (30) having an internal cavity, comprising:
Disposing a void-forming member (10) having a partially open hollow portion (12) and a microporous member (15) integrally attached thereto in a mold (50), the hollow portion (12) having the same shape as the trainee Cavity, and wherein the microporous member at least (15) at the open portion of the hollow portion (12) has a number of micropores (15a) permitting the passage of air but not the passage of a molten parent metal casting material (20); and
Pouring the molten parent metal casting material (20) into the mold (50) such that the cavity-forming element (10) is enclosed by the cast-in parent metal casting material (20).

Description

BACKGROUND OF THE INVENTION

Field of the invention

The present invention relates to a method of manufacturing a hollow casting having an internal cavity used for insulation purposes and the like, for example, a heat-insulated piston for an internal combustion engine.

Technical background

In order to produce a hollow casting having an internal cavity for heat insulating purposes and the like, for example, a heat-insulating bulb for an internal combustion engine, a manufacturing method is considered which comprises: pre-introducing a cavity-forming member having a hollow portion of the same shape as cavity to be formed, into a mold, and pouring a molten parent metal casting material into the mold, whereby the cavity-forming member introduced into the mold is enclosed by the parent metal casting material.

For example, a void-forming member is provided that includes: a main body made of, for example, sintered Fe / Mn, and a part has an open hollow portion, and a shutter member made of, for example, a stainless steel plate and integrally fixed to the main body so as to hermetically seal the open part of the hollow portion. However, if a void-forming member having such a structure is used, air in the hollow portion constituting a hermetic space may suddenly expand during casting due to the heat of the molten metal, causing the hollow portion to deform and swell could.

As a void-forming element which overcomes this disadvantage, reference 1 ( JP H02-36350 B2 ) or document 2 ( JP H03-9821 B2 ), each a member of the family EP 0 209 090 B1 are a cavity-forming member obtained by converting a solid substance which is solid at room temperature and convertible into gas or liquid at a temperature below the melting point of a parent metal casting material having the same shape as the cavity to be formed is formed and the solid substance is covered with a porous body, which is resistant to a molten parent metal casting material. In the formation of a hollow casting, the cavity-forming member is placed in a mold, and a molten parent metal casting material is poured into the mold and press-molded, thereby obtaining a casting enclosing the cavity-forming member. Then, in the casting, an opening is formed which communicates with the solid substance, and a heat treatment is performed at a temperature lower than the melting point of the casting of the base metal casting material and which is at least as high as the melting point of the casting solid substance, whereby the solid substance is converted into gas or melted, so that they can flow out through the opening and thus can be removed. After the solid substance has been removed, the opening is closed with a screw or the like, thereby obtaining a hollow casting having an internal cavity.

The DE 100 03 821 C2 also discloses a light metal piston for an internal combustion engine having a roof-shaped bottom bounded by a combustion bowl and having a cavity at least partially disposed around the combustion bowl. The soluble core for the production of the cavity is fastened with fastening means on an outer casting insert.

SUMMARY OF THE INVENTION

With the method of manufacturing a hollow casting according to any of the cited references 1 and 2, without the risk of inflation, which otherwise would be due to heat during casting, a hollow casting having a cavity whose shape corresponds to the intended value can be obtained. However, since each of the methods of the references 1 and 2 involves providing the casting with an opening to remove a gaseous or molten substance, the low-melting substance embedded in the hollow portion becomes a gas in a reheating process or a melt is transferred and that the opening is closed again after the removal of this substance, the process is quite complicated on the whole.

The present invention was carried out before the background described. The primary object of the present invention is to disclose a new method for producing a hollow casting, with which a hollow casting having a cavity whose dimensions correspond to the intended values can be produced by a simpler machining process. A second object of the present invention is the disclosure of a method for producing a Cavity-forming element, which is used for such a method.

A method for producing a hollow casting having an internal cavity according to the present invention includes: introducing a cavity-forming member having a partially open portion and a microporous member integrally attached thereto into a mold, the hollow portion having the same shape as that cavity to be formed and wherein the microporous member has at least at the open part of the hollow portion a number of micropores permitting the passage of air but not the passage of a molten parent metal casting material, and pouring the molten parent metal casting material into the mold; that the void-forming element is enclosed by the cast-in base metal casting material.

According to the manufacturing method of the present invention, molten metal is poured into a mold into which the void-forming member has been inserted. Thus, although the void-forming member is heated and air in the hollow portion expands, this air may escape through the micropores of the microporous member. Thus, it can not happen that the hollow section inflates. Further, the molten metal does not get into the hollow portion through the microporous member. Therefore, the shape of the hollow portion formed in the cavity forming member can be kept unchanged, and a cavity whose dimensions correspond to the intended values is formed in the thus produced hollow casting. In addition, since the main manufacturing method involves only one step of introducing a void-forming member into a mold and a step of molding a molten parent metal casting material into the mold, the manufacturing method can be greatly simplified.

The present invention may be applied to methods of making any hollow castings. For example, the present invention can be applied to the production of a heat-insulating piston of an internal combustion engine, in which case the cavity is used as a heat-insulating portion.

The present invention also discloses a method for producing a void-forming member for use in the above-mentioned method of manufacturing a hollow casting, including: introducing the microporous member into a mold, positioning an object to be removed (hereinafter also referred to as an object, which is to be removed) having the same shape as the hollow portion to be formed and adapted to disappear under the influence of heat, on the microporous member, casting a metallic material into the mold and performing a heat treatment such that the object To be removed disappears to form a hollow section.

By the above-mentioned manufacturing method, a cavity-forming member having a hollow portion of arbitrary shape can be easily produced. The material for the object to be removed may be any material and is not particularly limited as long as it can be rendered to be gaseous by the heat with which a metallic material is melted, and thus made to disappear. Examples of the object to be removed include paper, plastic and the like.

The main body of the void-forming member may be formed with any metallic material whose melting point is higher than the temperature of the molten parent metal casting material when a hollow casting is produced using the void-forming member and which is resistant to the molten parent metal -Gusswerkstoff. For example, when the base metal casting material is an aluminum-based metal, the main body of the void-forming member may be formed with an iron-based metal powder. Examples of a molding method are a sintering method and the like. Further, a material such as Fe / Mn alloy powder and titanium alloy powder may also be used.

The material for the microporous element of the cavity-forming member may also be any material whose melting point is higher than the temperature of the molten parent metal casting material when a hollow casting is formed using the cavity-forming member and which is resistant the molten parent metal casting material. Examples of materials include metallic materials such as stainless steel or low alloy steel and ceramic materials. The material for the microporous member may be suitably determined in consideration of the size of the micropores to be formed in the microporous member, the viscosity of the molten parent metal casting material, and the like. If the base metal casting material is an aluminum-based metal, approximately 60 to 200 mesh should be provided.

According to the present invention, a hollow casting having a cavity, the Dimensions correspond to the intended values are generated by a simple machining method.

BRIEF DESCRIPTION OF THE DRAWING

In the attached drawing show:

1A and 1B an embodiment of a void-forming member used for a method of manufacturing a hollow casting according to the present invention;

2A to 2D an embodiment for the production of a void-forming element;

3 another embodiment for the production of a cavity-forming element;

4 another embodiment for the production of a cavity-forming element;

5 an embodiment in which the method for producing a hollow casting according to the present invention with reference to the in 1A and 1B shown cavity-forming element is executed;

6 a test piece used for a test;

7 the way of carrying out the experiment; and

8th a heat-insulating piston, which is produced by the method for producing a hollow casting according to the present invention.

LIST OF REFERENCE NUMBERS

10

Cavity-forming element

11

Main body of a cavity-forming element

12

hollow section

15

microporous element of a void-forming element

15a

Micropores of a microporous element

16, 16a, 16b

Material to be removed

17

mold

18

metallic material

20

Base metal casting material

21

molten metal

30

hollow casting

50

mold

60

A heat-insulating piston of an internal combustion engine, which was formed by a method for producing a hollow casting according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be described by way of embodiments with reference to the accompanying drawings. 1A and 1B show an embodiment of a void-forming member used for the method of manufacturing a hollow casting according to the present invention. 2A to 2D show an embodiment for the production of a void-forming element. 3 shows a further embodiment for the production of a cavity-forming element. 4 shows a further embodiment for the production of a cavity-forming element. 5 shows an embodiment in which the method for producing a hollow casting according to the present invention with reference to the in 1A and 1B shown cavity-forming element is executed. 8th shows an example of a heat-insulating piston, which is formed by the method for producing a hollow casting according to the present invention.

A cavity-forming element 10 has a main body 11 and a microporous element 15 on, as in the lateral perspective view of 1A and in the cross-sectional view of 1B shown. In this example, the main body 11 of cylindrical shape, and a hollow section 12 , which is also cylindrical in shape, is in the main body 11 formed so that the downwardly directed side of the hollow section 12 is open. It should be noted that the shape of the hollow section 12 Overall, any shape can be as long as part of the hollow section 12 open and the other part of the hollow section 12 from the main body 12 is enclosed airtight.

The microporous element 15 has a number of micropores 15a on and is on the side on which the open surface of the hollow body 11 is integral with the main body 11 connected. In the drawing shown here has the microporous element 15 essentially the same size as the bottom of the main body 11 , However, the microporous element can 15 have any size, as long as it is at least part of the hollow section 12 can cover.

As in 5 shown is the size of the micropores 15a that are in the microporous element 15 are formed, designed so that a molten metal 21 made of base metal cast material 20 , the for casting a hollow casting 30 on the basis of the cavity-forming element 10 is not used by the micropores 15a can pass through. The size of the micropores 15a can range from 60 to 200 mesh when the molten metal 21 is an aluminum-based metal as described above.

Both the main body 11 as well as the microporous element 15 the void-forming element 10 can be formed from a suitable material whose melting point is higher than the temperature of the molten metal 21 from the base metal cast material 20 , to pour the hollow casting 30 on the basis of the cavity-forming element 10 is used, and the opposite of the parent metal casting material 20 is stable. For example, the main body exists 11 made of a parent metal, and the microporous element consists of a stainless steel grid plate.

2A to 2D show a method for producing the void-forming element 10 , In this method, first, the microporous element mentioned 15 prepared, and a material to be removed 16 (hereinafter also referred to as material 16 which is to be removed, for example) made of paper, as in 2A represented arranged at it. The material 16 which is to be removed has the same three-dimensional shape as a cavity formed in the hollow casting 30 which is to be obtained should be trained. After the microporous element 15 with the material to be removed arranged thereon 16 in a suitable mold 17 was used, as in 2 B is shown, powder of a suitable metallic material described above 18 supplied from above to fill the mold as in 2C and then the powder is molded. Then, the molded element becomes the mold 17 taken out, and a sintering treatment is performed. The heat of the sintering treatment burns the material to be removed 16 and the resulting fuel gas passes through the micropores 15a of the microporous element 15 issued. Thus, as in 2D shown, the cavity-forming element 10 get that the main body 11 and the microporous element 15 and that the inner hollow section 12 having. It should be noted that the metallic material 18 does not have to be metal powder, as long as it can be brought into a desired shape by heating. In addition, a sintering treatment does not necessarily have to be performed.

3 shows another method for producing the void-forming element 10 , Here are two to be removed materials 16a and 16b , which are shaped differently than the material to be removed 16 on the microporous element 15 arranged. When the in 2 B to 2D illustrated steps using the materials to be removed 16a and 16b can be performed, a cavity-forming member may be formed, which has two hollow portions which are shaped differently. Of course, it is also possible a variety of pieces of materials to be removed 16 to use with the same shape or three pieces of materials to be removed 16 to use with different shapes. As a result, the production of the void-forming element 10 with any number of hollow sections 12 of any shape facilitated by the application of this manufacturing process.

4 shows another method for producing the void-forming element 10 , This becomes the main body 11 with the aforementioned hollow section 12 one side of which is open, formed by a suitable, conventionally known shaping method or machining method as in the left-hand illustration of FIG 4 is shown. Then, the mentioned microporous element becomes 15 integral with the underside of the main body by a suitable method 11 attached, whereby the cavity-forming element 10 is finished as in the right representation of 4 is shown.

5 shows an embodiment in which the hollow casting 30 using said void-forming element 10 is formed. In this example, the void-forming element becomes 10 so in a mold 50 used that microporous element 15 is placed at the top, and the molten metal 21 of the base metal casting material 20 gets into the mold from above 50 cast. The microporous element 15 has, as already described, a number of micropores 15a on, the passage of air, but not the passage of the molten metal 21 from the base metal cast material 20 enable. Air in the hollow section 12 which has expanded due to the heat of the molten metal is passing through the micropores 15a from the hollow section 12 issued. Thus, the hollow section does 12 no change in shape. Furthermore, it can not happen that the molten metal 21 in the hollow section 12 penetrates.

The pouring of molten metal 21 from the base metal cast material 20 causes the cavity-forming element 10 from the parent metal casting material 20 is enclosed, causing the hollow casting 30 is obtained. In the hollow casting thus produced 30 a cavity is formed which is shaped in the same way as the hollow section 12 that in the cavity-forming element 10 is trained. There are cases where the joining plane is not alloyed if an aluminum-based metal having a sintered body embedded therein is poured. To solve this problem, the cavity-forming element 10 preferably subjected to a aluminizing treatment with molten aluminum for about one to two minutes before it enters the mold 50 is used.

The inventors have made a trial to investigate whether the microporous element 15 allowed the passage of a molten metal. 6 shows a test piece TP, which is used for the experiment, and 7 shows the procedure of the experiment. As the test specimens, TPs, two types of thin SUS304 plates (60 mesh and 200 mesh) were used as microporous elements 15 used, and each plate was between iron rings 19a and 19b arranged. As in 7 Each of the two test specimens, TPs, was placed in the mold 50 used, and aluminum melt (AC8A) 21 was poured at a temperature of 720 ° C so that it enclosed the test piece TP. After cooling, the resulting casting was removed and its backside was observed. It was found that the region within the iron ring 19b which was below the test specimens, the TPs, was hollow, and the microporous element 15 was visible from the bottom. Thus, the experiment could confirm that the presence of the microporous element 15 the passage of a molten metal 15 does not allow.

8th shows a thermally insulated piston 60 an internal combustion engine having a cavity as a heat-insulating portion, which communicates with the hollow portion 12 the void-forming element 10 was trained. The thermally insulated piston 60 is made by casting the base metal casting material 20 formed in a mold (not shown), while the cavity-forming element 10 is arranged in the mold. The hollow section (cavity) 12 the void-forming element 10 serves as a heat-insulating section.

Claims (9)

Method for producing a hollow casting ( 30 ) with an internal cavity, comprising: arranging a cavity-forming element ( 10 ) with a partially open hollow section ( 12 ) and a microporous element integrally attached thereto ( 15 ) in a mold ( 50 ), wherein the hollow section ( 12 ) has the same shape as the cavity to be formed, and wherein the microporous element at least ( 15 ) at the open part of the hollow section ( 12 ) a number of micropores ( 15a ), but not the passage of a molten parent metal casting material ( 20 ) allow; and casting the molten parent metal casting material ( 20 ) in the mold ( 50 ), so that the cavity-forming element ( 10 ) from the cast base metal casting material ( 20 ) is enclosed. Method for producing a hollow casting ( 30 ) according to claim 1, wherein the cavity-forming element ( 10 ) a main body ( 11 ) with the hollow section ( 12 ) and on the side where the open area of the hollow section ( 12 ), integrally attached to the main body microporous element ( 15 ) and wherein both the main body ( 11 ) as well as the microporous element ( 15 ) is formed with a material whose melting point is higher than the temperature of the molten parent metal casting material ( 20 ), when the hollow casting ( 30 ) using the void-forming element ( 10 ) and that is resistant to the molten parent metal casting material ( 20 ) Method for producing a hollow casting ( 30 ) according to claim 2, wherein the base metal casting material ( 20 ) is an aluminum-based metal, the main body ( 11 ) of the cavity-forming element ( 10 ) is formed with a material selected from the group consisting of iron-based metal, Fe / Mn alloy and titanium alloy, and wherein the microporous element ( 15 ) with a metallic material selected from the group consisting of stainless steel and low alloy steel, or formed with a ceramic material. Method for producing a hollow casting ( 30 ) according to one of claims 1 to 3, wherein the base metal casting material ( 20 ) is an aluminum-based metal and the size of the in the microporous element ( 15 ) formed micropores ( 15a ) is in the range of 60 to 200 mesh. Method for producing a hollow casting ( 30 ) according to one of claims 1 to 4, forming a thermally insulated piston ( 60 ) for an internal combustion engine, wherein the cavity serves as a heat-insulating section. Process for the preparation of the cavity-forming element ( 10 ), which is used for the method for producing a hollow casting ( 30 ) according to one of claims 1 to 4, comprising: arranging the microporous element ( 15 ) in a mold ( 17 ); Position an object to be removed ( 16 ) on the microporous element ( 15 ), whereby the material to be removed ( 16 ) has the same shape as the hollow portion to be formed and is designed to disappear under the influence of heat; Casting a metallic material ( 18 ) in the mold ( 17 ); and performing a heat treatment so that the material to be removed ( 16 ) disappears to form the hollow section. Process for the preparation of the cavity-forming element ( 10 ) according to claim 6, wherein the object to be removed is paper or plastic. Process for the preparation of the cavity-forming element ( 10 ) according to claim 6 or 7, wherein the metallic material ( 18 ) is a powder of metallic material and a sintering treatment is carried out after a press molding, so that the object to be removed ( 16 ) disappears. Process for the preparation of the cavity-forming element ( 10 ) according to one of claims 6 to 8, wherein two or more objects to be removed ( 16a . 16b ) on the microporous element ( 15 ), whereby the objects to be removed ( 16a . 16b ) have the same or different shapes.

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