JPH0724564A - Parts made of spheroidal graphite cast iron and its manufacture - Google Patents

Abstract

PURPOSE:To realize the lightweight construction and to improve the wear resistance of a sliding part by forming a cylinder block or the like by spheroidal graphite cast iron of high strength CONSTITUTION:In a cylinder block or the like, the body part except the cylinder bore part is made of spheroidal graphite cast iron consisting of the mixed structure of spheroidal graphite, ferrite and pearlite, and only the cylinder bore part is made of the metal whose structure is composed of flake graphite 3, pearlite 4, and cementite 5. Thus, in pouring the molten metal added with spheroidal graphitizing agent into the mold, the copper foil is used to promote the pearlitization and precipitation of cementite, the powder of iron sulfide is coated on one side of this copper foil as the promoting agent for flake graphitization, this copper foil is coiled around the corresponding surface to the sliding part of the core with the coated surface of the copper foil being inside, and the molten metal is poured into the mold.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention realizes weight reduction by forming a cylinder block of an engine from high-strength spheroidal graphite cast iron and improves wear resistance of sliding portions such as cylinder bores. For technology.

[0002]

2. Description of the Related Art Conventionally, attempts have been made to reduce the weight of an engine cylinder block or the like by forming it from high-strength spheroidal graphite cast iron (ductile cast iron) to reduce the weight. However, although spheroidal graphite cast iron has high strength, it is inferior in wear resistance. Therefore, if the cylinder block is formed of spheroidal graphite cast iron alone, the wear resistance of the sliding portion cannot be secured. Therefore, conventionally, as an application of the conventional technique described in, for example, Japanese Patent Laid-Open No. 58-212550, the cylinder bore portion is formed by a separate member (liner member) made of flake graphite cast iron having high wear resistance. A method of casting around spheroidal graphite cast iron is adopted.

[0003]

In the production of parts such as cylinder blocks, when a small amount of Mg or the like is added to the molten metal to form a toughened spheroidal graphite cast iron part, the conventional method is as follows. Although a method of improving wear resistance by taking the moving part as a separate member of flake graphite cast iron has been taken, this method requires a separate member such as a liner member,
That was a factor of high cost. Further, when using a separate member in this way, for example, when the spheroidal graphite cast iron part is a cylinder block body, and the separate member is a liner,
There is also a problem that the cooling effect is deteriorated because the gap between the liner and the block body is a heat insulating layer.

The present invention has been made in view of the above problems, and provides a spheroidal graphite cast iron component capable of improving the abrasion resistance of a sliding portion while reducing the weight thereof, and a method of manufacturing the same. The purpose is to

Another object of the present invention is to improve the wear resistance of the cylinder bore portion without using a separate member while reducing the weight by forming the cylinder block from spheroidal graphite cast iron.

[0006]

The spheroidal graphite cast iron according to the present invention is a spheroidal graphite cast iron part such as a cylinder block having a sliding portion, and the texture of the sliding portion such as a cylinder bore is flake graphite and pearlite. It is characterized by comprising precipitates such as cementite that are harder than pearlite. Further, the method for producing spheroidal graphite cast iron according to the present invention is a method for producing a spheroidal graphite cast iron part having a sliding portion, and suppresses the ferritic transformation of the cast iron matrix structure by contact with the molten metal to promote pearlite formation. Along with this, a foil material such as copper foil, which has a melting point lower than the temperature of the molten metal that promotes the precipitation of cementite, which is harder than pearlite, is used, and one side of the foil material suppresses the spheroidization of graphite by contacting with the molten metal to form flakes. After applying a graphite flaking promoting material such as iron sulfide that promotes, the foil material is placed on the mold surface corresponding to the sliding part with the surface coated with the graphite flaking promoting material facing inside, and then in the mold It is characterized by injecting molten metal into.

When the cylinder block is manufactured by the above manufacturing method, copper foil is used as the foil material, and the thickness of the copper foil is 0.8 to 1.6% by weight of copper with respect to the molten metal volume of the cylinder bore portion. It is better to set

[0008]

In the spheroidal graphite cast iron component of the present invention, the component body is spheroidal graphite cast iron, and its structure is generally a mixture of flake graphite, ferrite and pearlite, and has high strength. Therefore, it is possible to reduce the thickness by reducing the thickness of the main body portion such as the cylinder block. Further, the sliding portion such as the cylinder bore portion has a structure composed of flake graphite, pearlite, and precipitates such as cementite, and has excellent wear resistance.

Further, according to the manufacturing method of the present invention, a graphite flaking promoting material such as iron sulfide is applied to one surface of a foil material such as a copper foil, and the foil material is applied to the inside of the sliding surface of a component. It is arranged on the mold surface corresponding to the moving part. Then, when the molten metal is poured into the mold, a substance such as copper forming the foil material is suppressed from ferritization of the cast iron matrix structure by contact with the molten metal to promote pearlite formation, and is harder than pearlite. The precipitation of cementite etc. is promoted. Also, after a while, the foil material melts and the graphite flaking promoting material such as iron sulfide contacts the molten metal, whereby spheroidization of graphite is suppressed and flaking is promoted. At that time, by setting the thickness of the copper foil so that the copper content is 0.8 to 1.6% by weight with respect to the molten metal volume of the cylinder bore, the precipitation amount of cementite is increased and the wear resistance is reliably ensured. improves. As a result, a spheroidal graphite cast iron such as a cylinder block in which the sliding part has a structure composed of flake graphite, pearlite, cementite, etc., and the main body part surrounding the sliding part has a structure in which spheroidal graphite, ferrite and pearlite are mixed Parts are obtained.

[0010]

1 is a cutaway perspective view of a cylinder block for a diesel engine according to an embodiment of the present invention. In the figure, 1 is a cylinder block, and 1a is a cylinder bore. Reference numeral 2 is a piston that reciprocates in the cylinder bore 1a.

The cylinder block 1 has a main body portion excluding the peripheral portion (referred to as a cylinder bore portion) of the cylinder bore 1a made of spheroidal graphite cast iron, and has a mixed structure of spheroidal graphite, ferrite and pearlite. Further, the cylinder bore portion is, as shown in FIG. 2, a flake graphite 3 and a pearlite 4.
And a cementite 5 structure.

The cylinder block is cast by pouring a molten metal containing a predetermined amount of a graphite spheroidizing agent such as Mg into a mold. And at that time, the copper foil 1 as shown in FIG.
1 is used, and iron sulfide powder 12 is applied to one surface of the copper foil 11 as shown in FIG. And this copper foil 1
1 with the surface coated with iron sulfide powder 12 inside
Wrap around the surface portion corresponding to the cylinder bore 1a of 3,
The core 13 is set and the molten metal is poured into the mold by a usual method.

The thickness of the copper foil 11 is set so that the copper content is 0.8 to 1.6% by weight with respect to the molten metal volume of the cylinder bore.

When the molten metal is poured into the mold as described above, the copper foil 11 comes into contact with the molten metal to suppress the ferritic transformation of the cast iron matrix structure to promote the pearlite formation and the precipitation of cementite. Be promoted. Then, after a while, since the molten metal temperature is higher than the melting point (1083 ° C.) of the copper foil 11, the copper foil 11 is melted and the copper foil 11 comes into contact with the iron sulfide powder 12, whereby the spheroidizing of graphite occurs. It is suppressed and the flaking is promoted. As a result, the cylinder bore has a structure composed of flake graphite 3, pearlite 4 and cementite 5 as shown in FIG. 2, and the main body has a structure in which spherical graphite, ferrite and pearlite are mixed.

The copper foil 11 contributes to the formation of pearlite and cementite, prevents the iron sulfide powder 12 from being exposed and flows out during pouring, and makes the black smoke flakes caused by iron sulfide uniform throughout the bore. Let

Although the cylinder block has been described in the above embodiment, the present invention can be applied to other parts made of spheroidal graphite cast iron and a manufacturing method thereof.

The foil material that can be used in the production method of the present invention can suppress the formation of ferrite and promote the formation of pearlite, and can promote the precipitation of carbides (not limited to cementite) having a hardness of 600 Hv or more, and Any material may be used as long as it satisfies the condition that the melting point is lower than the molten metal temperature, and is not limited to copper foil. It is also possible to use a material other than iron sulfide powder as the graphite flaking promoting material.

[0018]

EFFECTS OF THE INVENTION Since the present invention is configured as described above, it is possible to reduce the weight by forming parts such as a cylinder block from spheroidal graphite cast iron and to improve the wear resistance of the sliding portion. it can. And since it is possible to improve the wear resistance of the sliding portion without using a separate member,
It is possible to reduce the manufacturing cost and improve the cooling performance.

[Brief description of drawings]

FIG. 1 is a cutaway perspective view of a cylinder block for a diesel engine according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a structure of a cylinder bore portion according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram illustrating a manufacturing method according to an embodiment of the present invention.

[Explanation of symbols]

 1 Cylinder Block 1a Cylinder Bore 3 Flake Graphite 4 Perlite 5 Cementite 11 Copper Foil 12 Iron Sulfide Powder 13 Core

Claims (4)

[Claims] 1. A spheroidal graphite cast iron part having a sliding part, wherein the structure of the sliding part is composed of flake graphite, pearlite and a precipitate harder than pearlite. 2. The spheroidal graphite cast iron component according to claim 1, wherein the component is a cylinder block, and the sliding portion is a cylinder bore portion. 3. A method for producing a spheroidal graphite cast iron part having a sliding portion, which suppresses ferritic transformation of a cast iron matrix structure by contacting with molten metal to promote pearlite formation and precipitation of harder precipitates than pearlite. Using a foil material having a lower melting point than the molten metal temperature to promote, one side of the foil material is coated with a graphite flaking accelerating material that suppresses spheroidization of graphite by promoting contact with the molten metal and promotes flaking, A spheroidal graphite cast iron part characterized in that the foil material is placed on the surface of the mold corresponding to the sliding part with the surface coated with the graphite flake accelerating material inside, and then molten metal is injected into the mold. Production method. 4. The component is a cylinder block, the sliding portion is a cylinder bore portion, copper foil is used as the foil material, and the thickness of the copper foil is such that the copper volume is 0. The method for producing a spheroidal graphite cast iron component according to claim 3, wherein the content is set to 8 to 1.6% by weight.