JP2857568B2 - Composite cylinder liner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tough cylinder liner.

[0002]

2. Description of the Related Art A cylinder liner used in an internal combustion engine basically requires abrasion resistance and seizure resistance because a piston ring slides at a high speed. For this reason, various types of cast irons for cylinder liners have conventionally been made of A-type graphite as a material of cylinder liners for securing seizure resistance and containing wear resistance improving elements such as Cr, B, P, V, Mo, and Nb. Wood is used.

[0003]

However, in recent years,
While the size of internal combustion engines has been increasing, their weight and fuel economy have been required, and conventional materials have insufficient strength, and improvements in strength are desired. In order to improve the strength, a higher-strength cast iron material may be selected as the liner material. However, there is a possibility that the wear resistance and seizure resistance inherently provided in the cylinder liner may be impaired. It is also effective to increase the thickness of the liner, but in this case, weight reduction is hindered.

The present invention has been made in view of the above problems, and has as its object to provide a cylinder liner which has high strength and can be reduced in weight.

[0005]

A cylinder liner according to the present invention is a composite cylinder liner in which an inner layer made of a cast iron material for a cylinder liner having A-type graphite is welded and joined to an inner surface of an outer layer made of a tough cast iron material, The outer layer has a chemical composition in weight%, C: 2.0-2.5%, Si:
0.6-3.0%, Mn: 0.2-1.0%, N
i: 2.5% or less, Cr: 1.0% or less, M
o: Contains essentially 1.0% or less, with the balance being substantially F
e, and the structure is formed of a high carbon adamite material mainly composed of pearlite matrix and crystallized graphite.

[0006]

Since the inner layer of the cylinder liner of the present invention is formed of a cast iron material for cylinder liner having A-type graphite, the abrasion resistance and the seizure resistance on the inner surface portion in contact with the piston ring are excellent. On the other hand, the outer layer is made of high-carbon adamite material with a specific chemical composition and structure,
It has good weldability to the inner layer, has a high strength at the outer surface portion which is the starting point of breakage of the liner, and furthermore, the crystallized graphite in the structure inhibits the progress of cracks, so that it is not easily broken.

Although it is conceivable to use a steel-based tough material such as cast steel as the outer layer material, welding and joining with the inner layer are extremely difficult, and the composition change of the inner layer material after welding is large, so that the liner material may be used. Organization and function deteriorate. The outer layer material according to the present invention has the advantage that the strength is more than twice that of the conventional liner material, the weldability and the bondability with the inner layer material are good, and the composition fluctuation of the inner layer material is small.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, the composite cylinder liner of the present invention has a structure in which an outer layer 1 and an inner layer 2 are combined. The outer layer 1 is formed of a high-carbon adamite material having excellent toughness as described below, while the inner layer 2 is formed of a conventional cast iron material for cylinder liners having A-type graphite having excellent seizure resistance and wear resistance. The inner layer 2 is welded to the inner surface of the substrate. In addition, 3 is a mixed layer generated at the time of welding,
It has an intermediate composition between the outer layer 1 and the inner layer 2.

Outer layer 1 of composite cylinder liner of the present invention
Is formed of a graphite-crystallized high-carbon adamite material having the following composition. C: 2.0 to 2.5% C is mainly contained for obtaining strength and crystallized graphite.
If it is less than 2.0%, solidification shrinkage cracks are liable to occur during casting, resulting in insufficient strength and difficulty in crystallization of graphite. Meanwhile, 2.
If it exceeds 5%, the amount of cementite crystallized at the time of casting increases, and the material becomes brittle.

Si: 0.6-3.0% Si has a close relationship with the crystallization of graphite, and if it is less than 0.6%, crystallization of graphite becomes almost difficult, resulting in deterioration of toughness. On the other hand, if it exceeds 3.0%, the material is liable to be embrittled by Si dissolved in the matrix. Mn: 0.2 to 1.0% Mn combines with S and is effective in removing the adverse effects of S. If it is less than 0.2%, the effect is too small. on the other hand,
If it exceeds 1.0%, the material becomes hard and brittle.

Ni: 2.5% or less Ni effectively acts on graphitization and strengthening of the matrix. But,
If it exceeds 2.5%, the effect is saturated, and it becomes minus below the diameter surface. In addition, bainite, martensite, and an untransformed structure are easily generated, and may be rather brittle. Cr: 1.0% or less Cr has a strengthening effect on the matrix and a stabilizing effect on cementite. However, if it exceeds 1.0%, crystallization of graphite becomes difficult, and the toughness is deteriorated.

Mo: 1.0% or less Mo has the effect of improving toughness like Ni, but if it exceeds 1.0%, it becomes hard and the toughness is rather deteriorated. The tough cast iron material of the outer layer essentially contains the above alloy components, and the balance is formed of Fe and impurities. Essentially means to allow the addition of other alloying elements that can improve the material without impairing the action of the above alloy components. For example, in addition to the above alloy components, Ti, Al, Zr One or more kinds may be contained in a total of 0.1% or less. By containing such an element, the occurrence of a casting cavity can be prevented, and a sounder material can be obtained. Since these elements are powerful deoxidizing agents, if the total amount exceeds 0.1%, the molten metal is in a peroxidized state, and the fluidity is lowered. Although P and S, which are impurities, are inevitably mixed in from the raw material, the smaller the amount, the better.

The microstructure of the outer layer is mainly composed of crystallized graphite and matrix, and may contain a small amount of eutectic cementite. Since cementite is brittle, it is desirable to suppress the crystallization as much as possible. The base is mainly pearlite, partly ferrite, bainite, martensite,
Retained austenite may be observed. Ferrite is excellent in toughness, and depending on the purpose, it may be desirable to precipitate it. However, since bainite, martensite, and retained austenite deteriorate the material, it is necessary to avoid the generation of ferrite.

On the other hand, as a material for forming the inner layer 2 of the composite cylinder liner, an appropriate material is selected from various cast iron materials for cylinder liners having A-type graphite, which are described in a handbook relating to iron and steel materials, data books and the like. Can be used. The composite cylinder liner described above can be easily manufactured by centrifugal casting. That is, first, after the outer layer is cast, the inner layer material is cast at an appropriate timing, and the two are welded and integrated. As the centrifugal casting method, any of a horizontal type, an inclined type, and a vertical type can be applied.

In general, inoculation is effective for reducing the size of the cast structure and promoting graphitization. As for the outer layer material, if the inoculation technique is applied, a material in which graphite is more finely and uniformly distributed can be obtained. At this time, the inoculation amount was 0.1 as Si content.
1 to 1.0% is appropriate. If it is less than 0.1%, the effect of inoculation cannot be expected, while if it exceeds 1.0%, a corresponding effect cannot be obtained. CaSi and FeSi are suitable as inoculants. In addition, the S of the outer layer material melt was adjusted so that the Si content of the outer layer after inoculation was in the range of 0.6 to 3.0%.
The i content is adjusted.

In addition, when the outer layer and the inner layer are welded, melting from the outer layer to the inner layer inevitably occurs. To prevent such melting, an outer layer is cast, an intermediate layer is cast on the inner surface, and then the inner layer is cast. Just cast it in. After casting, strain relief annealing at about 400 ° C. to 600 ° C. is performed to remove residual stress. Further, if necessary, the toughness of the outer layer material is further improved by subjecting the network-like cementite to fragmentation by heating at or above the A ₁ transformation point and subjecting the pearlite to a heat treatment for granulation.

Next, specific examples will be described. Inner diameter φ120
Using a 0 mm centrifugal force casting mold, the molten outer layer material (cast thickness 250 mm) shown in Table 1 was centrifugally cast, and after the outer layer was solidified, the inner layer molten material shown in the same table (cast thickness 100 mm) was solidified therein. )
Was centrifugally cast.

[0018]

[Table 1]

When the mechanical properties of the outer layer of the obtained composite cylinder liner were examined, it was as follows. No. 1: Tensile strength 52.3Kg / mm ² , elongation
1.21% No. 2: Tensile strength 48.9 Kg / mm ² , elongation
The general mechanical properties of the conventional single-layer cylinder liner are as follows: tensile strength 18 to 25 kg / mm ² , elongation 0.2 to
It is about 0.8%.

[0020]

According to the composite cylinder liner of the present invention, the outer layer of the liner, which is a starting point of fracture and particularly requires toughness, is formed of the above-described graphite-crystallized high-carbon adamite material, while the inner layer of the liner is formed according to its use characteristics. It is made of a conventional cast iron material for cylinder liners having A-type graphite with excellent seizure resistance and abrasion resistance, and both are welded and joined, which impairs the original use characteristics of the inner surface of the liner. Without increasing the strength of the cylinder liner by the tough outer layer, the cylinder liner can be made thinner and lighter.

[Brief description of the drawings]

FIG. 1 is an explanatory cross-sectional view of a composite cylinder liner according to the present invention.

[Explanation of symbols]

 1 outer layer 2 inner layer

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁶ , DB name) C22C 37/00 B22D 19/08 B22D 19/16 F02F 1/00 F02F 1/08

Claims (1)

(57) [Claims] 1. A composite cylinder liner in which an inner layer made of a cast iron material for a cylinder liner having A-type graphite is welded and joined to an inner surface of an outer layer made of a tough cast iron material, wherein the outer layer has a chemical composition of C: 2.0 to 2.5%, Si: 0.6 to 3.0
%, Mn: 0.2-1.0%, Ni: 2.5% or less, Cr: 1.0% or less, Mo: 1.0% or less, and the balance substantially consists of Fe A composite cylinder liner characterized in that the structure is formed of a high-carbon adamite material mainly composed of pearlite matrix and crystallized graphite.