JPH06106331A - Spheroidal graphite cast iron parts and production thereof - Google Patents

Abstract

PURPOSE:To provide the cast iron parts having a cylinder block and sliding parts made of inexpensive cast iron with which the sufficient reduction in the thickness and weight is possible while specified strength and rigidity are assured and the process for production of these parts. CONSTITUTION:The melt of a ductile cast iron is poured into the casting mold DC formed with an iron sulfide layer 5 in the peripheral part of a second core 4 corresponding to the liner part of the cylinder block, by which the cylinder block is cast. The ductile cast iron is reformed to a flake graphite cast iron in the part (liner part) near the peripheral part of the second core 4 by iron sulfide layer 5, by which the wear resistance is enhanced. The body part of such cylinder block is formed of the ductile cast iron having the high strength and high rigidity and, therefore, the sufficient reduction of the thickness and weight is possible. Since there is no need for separately forming the liner part, the production cost is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spheroidized graphite cast iron part and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, weight reduction of automobile parts has been promoted, and there is also a strong demand for downsizing or weight reduction of cylinder blocks. Therefore, conventionally, a cylinder block mainly made of cast iron has been proposed in which only the cylinder liner, which is the sliding portion, is made of cast iron, and the other portions are made of an aluminum alloy (for example, JP-A-58). -21550). The aluminum alloy cylinder block is usually manufactured by casting a cast iron cylinder liner around an aluminum alloy.

[0003]

However, when the cylinder block is made of aluminum alloy as described above, the aluminum alloy material is expensive and the manufacturing process is complicated, which causes a problem that the cost is significantly increased. Therefore,
As a material, a relatively inexpensive cast iron that has been conventionally used may be used, and a method of reducing the weight by thinning each part of the cylinder block may be considered. However, if the cylinder block is made thin, its strength and rigidity are lowered, so there is a problem that if the predetermined strength and rigidity are to be ensured, it is not possible to expect such a significant reduction in thickness and weight.

On the other hand, it is conceivable to use a cast iron material having higher strength and rigidity than cast iron that has been conventionally used for a cylinder block to reduce the thickness and weight. That is, as the cast iron material for the cylinder block, flake graphite cast iron, which has better wear resistance than before, is used.
Although (FC) is used, for example, ductile cast iron (spheroidal graphite cast iron) having higher strength and rigidity than such flake graphite cast iron is used to achieve sufficient thinning and weight reduction.

However, such ductile cast iron is
Although excellent in strength and rigidity, there is a problem that the wear resistance is relatively low. Therefore, when the cylinder block is formed of ductile cast iron, only the cylinder liner portion needs to be separately formed of a cast iron material having high wear resistance, which causes a problem of increasing cost.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and is made of cast iron at a low cost, which can achieve a sufficient thinning and a light weight while ensuring a predetermined strength and rigidity. An object of the present invention is to provide a cast iron part provided with a cylinder block or a sliding part, and a manufacturing method thereof.

[0007]

To achieve the above object, the first invention is a method for manufacturing a spheroidized graphite cast iron part having a sliding portion, which corresponds to the sliding portion of a mold. A graphite spheroidization suppressing material is placed in a part, and then a molten metal of spheroidized graphite cast iron is poured into a mold to cast a spheroidized graphite cast iron part, and a method for producing a spheroidized graphitized cast iron part. I will provide a.

A second aspect of the present invention is the method for manufacturing a spheroidized graphite cast iron part according to the first aspect, wherein the spheroidized graphite cast iron part is a cylinder block having a liner portion as a sliding portion, and graphite Provided is a method for manufacturing a spheroidized graphite cast iron part, characterized in that the spheroidization suppressing material is iron sulfide.

A third aspect of the present invention is a spheroidized graphite cast iron part having a sliding portion, wherein the texture is modified into flake graphite cast iron only near the surface of the sliding portion. Provide graphite cast iron parts.

A fourth aspect of the present invention is the spheroidized graphite cast iron part according to the third aspect, wherein the spheroidized graphite cast iron part is a cylinder block having a liner portion which is a sliding portion, and a cylinder bore having a liner portion. Provided is a spheroidized graphite cast iron part characterized in that the structure is modified into flake graphite cast iron only in the vicinity of the surface.

[0011]

EXAMPLES Examples of the present invention will be specifically described below.
1 and 2 are respectively an elevation sectional view and a plan sectional view of a mold for manufacturing (casting) a cylinder block according to the present invention as shown in FIG. 3 by a manufacturing method according to the present invention. Hereinafter, a method for manufacturing such a cylinder block will be described with reference to FIGS. (1) Assembly of Mold As shown in FIGS. 1 and 2, in the process of manufacturing the cylinder block, the mold DC is first assembled.
The procedure for assembling the template DC is as follows. That is, the main mold 1 (sand mold) is placed at a predetermined position, and the main mold 1
A lower bulge for forming a crank chamber at a predetermined position in a cavity 2 formed in the first core 3 having a substantially cylindrical shape.
A (sand mold) and a cylindrical second core 4 (sand mold) for forming a liner portion are arranged.

Next, iron sulfide, which is a graphite spheroidization suppressing material, is applied to the peripheral surface of the cylindrical second core 4, that is, the position corresponding to the surface of the liner portion of the cast product (cylinder block). Layer 5 is formed. Here, iron sulfide is mixed with a binder having a proper adhesive property (for example, office glue) to form a paste, and the paste has a predetermined thickness (for example, 0. 5 mm) to form an iron sulfide layer 5. It should be noted that instead of applying the paste containing iron sulfide in this way, iron sulfide is glued to a thin plate of styrofoam, and the thin plate of styrofoam is attached to the second core 4
It may be arranged in the cavity 2 around the.

Then, at the position corresponding to the water jacket of the casting (cylinder block), the cavity 2
After the water jacket core 6 (sand mold) is placed inside, the upper end surface of the main mold 1 is closed by the upper mold 7, and the assembly of the mold DC is completed. In such a mold DC, the thickness of each part of the cavity 2 after assembly is set to be relatively thin so that the casting (cylinder block) can be made sufficiently thin.

(2) Pouring of molten metal Cavity 2 of the mold DC thus assembled
A melt of ductile cast iron (spheroidized graphite cast iron) is poured into the inside through the melt supply passage 8. After the cavity 2 is filled with the molten metal, the molten metal is naturally cooled and solidified. However, in the vicinity of the iron sulfide layer 5, that is, in the portion where the liner portion is formed, the ductile cast iron is sulfided during pouring and solidification. It is reformed by iron into flake graphite cast iron.

That is, although ductile cast iron contains magnesium (Mg) which is a spheroidizing element, this magnesium is combined with sulfur in iron sulfide during pouring and solidification to form magnesium sulfide (MgS). To generate. For this reason, the content of magnesium, which is a spheroidizing element, decreases near the iron sulfide layer 5, and flake graphite cast iron is produced. The molten metal of the ductile cast iron is solidified as it is into the ductile cast iron in the portion other than the vicinity of the iron sulfide layer 5.

(3) Removal of casting After the molten metal in the mold DC is solidified, the main mold 1 and each core 3,
4, 6 and the upper mold 7 are removed, and a casting or cylinder block 10 as shown in FIG. 3 is obtained. As described above, since each part of the cavity 2 of the mold DC is formed relatively thin, the cylinder block 10 is sufficiently thin and lightweight.

In this cylinder block 10, only the liner portion 11 (sliding portion) is made of flake graphite cast iron having high wear resistance, and the other portions are made of ductile cast iron having high strength and rigidity. The microstructure of the metal structure (ductile cast iron) of the main body and the microstructure of the metal structure (flake graphite cast iron) of the liner part 11 of the cylinder block 10 manufactured in this manner are respectively shown in FIG. And Fig. 5
And shown in. Therefore, the cylinder block 10 is sufficiently thin and lightweight, but sufficient strength and rigidity are ensured. Further, sufficient wear resistance is ensured in the liner portion 11, which is a sliding portion with respect to the piston.
Since the cylinder block 10 is made of cast iron, it goes without saying that the cost is low. Further, according to such a manufacturing method, since the liner portion 11 is integrally formed with the main body portion at the time of casting and it is not necessary to separately form the liner portion 11, the cost thereof is further reduced.

[0018]

According to the first aspect of the present invention, at the time of casting a spheroidized graphite cast iron part, the spheroidized graphite cast iron is reformed into flake graphite cast iron by the graphite spheroidization suppressing material at the portion corresponding to the sliding portion. To be done. Therefore, the spheroidized graphite cast iron structure having high strength and rigidity is formed in the main body of the spheroidized graphite cast iron part, while the flaky graphite cast iron structure having high wear resistance is formed in the sliding portion. Therefore, it is possible to enhance the wear resistance of the sliding portion while sufficiently securing the strength and rigidity of the main body portion.

According to the second invention, basically, the same operation and effect as those of the first invention can be obtained. Here, the spheroidized graphite cast iron part is a cylinder block, and the spheroidized graphite cast iron structure is formed in the main body portion to enhance strength and rigidity, while the flaky graphite is used in the liner portion that is a violent sliding portion with the piston. A cast iron structure is formed and wear resistance is enhanced. Therefore, it is possible to reduce the thickness and weight of the cylinder block while ensuring sufficient strength and rigidity, and it is possible to sufficiently enhance the wear resistance of the liner portion. Further, since the liner portion can be integrally formed with the main body portion during casting,
Since it is not necessary to separately form the liner portion, the manufacturing cost is reduced.

According to the third invention, in the spheroidized graphite cast iron part, the main body is made of spheroidized graphite cast iron, and the sliding portion is made of flake graphite cast iron. It is possible to improve the wear resistance of the sliding portion while sufficiently securing the above.

According to the fourth invention, basically, the same action and effect as those of the third invention can be obtained. , Here, the spheroidized graphite cast iron part is a cylinder block, while the main body is formed of spheroidized graphite cast iron to enhance strength and rigidity, while the cylinder bore (liner) that is a violent sliding portion with the piston is It is formed of flake graphite cast iron structure and has improved wear resistance. Therefore, it is possible to reduce the thickness and weight of the cylinder block while ensuring sufficient strength and rigidity, and it is possible to sufficiently enhance the wear resistance of the cylinder bore (liner portion).

[Brief description of drawings]

FIG. 1 is an elevational cross-sectional explanatory view of a mold used for casting a cylinder block according to the present invention.

FIG. 2 is an explanatory plan cross-sectional view of the mold shown in FIG.

FIG. 3 is a perspective view of a cylinder block according to the present invention.

FIG. 4 is a micrograph of a metal structure (ductile cast iron structure) of a main body of a cylinder block according to the present invention.

FIG. 5 is a micrograph of a metal structure (flake graphite cast iron structure) of a liner portion of a cylinder block according to the present invention.

[Explanation of symbols]

 DC ... Mold 1 ... Main mold 2 ... Cavity 3,4 ... First and second cores 5 ... Iron sulfide layer 10 ... Cylinder block 11 ... Liner part

Claims (4)

[Claims] 1. A method of manufacturing a spheroidized graphite cast iron part having a sliding portion, wherein a graphite spheroidization suppressing material is arranged at a portion of the mold corresponding to the sliding portion, and then spheroidized in the mold. A method for producing a spheroidal graphitized cast iron part, characterized by pouring a molten graphite cast iron to cast a spheroidized graphite cast iron part. 2. The method for manufacturing a spheroidized graphite cast iron component according to claim 1, wherein the spheroidized graphite cast iron component is a cylinder block having a liner portion as a sliding portion,
A method for manufacturing a spheroidized graphite cast iron part, wherein the graphite spheroidization suppressing material is iron sulfide. 3. A spheroidized graphite cast iron part having a sliding part, wherein the structure is modified into flake graphite cast iron only near the surface of the sliding part. 4. The spheroidized graphite cast iron component according to claim 3, wherein the spheroidized graphite cast iron component is a cylinder block having a liner portion that is a sliding portion, and the vicinity of the surface of a cylinder bore forming the liner portion. A spheroidized graphite cast iron part characterized in that its structure is modified into flake graphite cast iron.