JPS5817251B2 - Sintered metal cylinder liner material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cylinder liner (including a cylinder sleeve) made of a sintered alloy that has high airtightness and excellent wear resistance and is used in internal combustion engines and compressors.

Conventional cylinder liners and sleeves are mostly made of cast iron and manufactured using the melt-casting method.The production of cylinder liners using the melt-casting method inevitably results in high machining costs, which is difficult to achieve in recent years. In addition to meeting resource requirements and the inherent problem of environmental pollution, the materials obtained using this method also have problems such as segregation and formation of cavities.Furthermore, the recent trend is toward higher output engines. , high rotation speeds, exhaust gas countermeasures, etc., there is a tendency for cylinder liners and sleeves with higher quality than cast iron materials to be required. The current situation is that

In view of the above, an object of the present invention is to save resources and to provide a cylinder liner and sleeve material made of sintered alloy that is inexpensive to manufacture, is made of a homogeneous material, has high airtightness, and has excellent wear resistance. It is about providing.

Generally, there are many pores in sintered materials, and these pores
The sintered alloy material exhibits a favorable effect as a wear-resistant member because it has pores on the surface of the material and these pores become oil pools.

However, in materials such as cylinder liners and sleeves that are subject to high explosion pressure and require advanced gas sealing properties, the continuous pores inherent in the sintered material become gas passages, resulting in undesirable effects such as an increase in blow-by gas. produce results.

Although it is possible to seal the gas by filling these pores by forging after sintering or Cu infiltration treatment, for example, this method is uneconomical and has poor mass productivity. When such a treatment is applied, the pores formed on the surface also disappear, so there is a drawback that the above-mentioned oil pool effect cannot be expected.

The present invention corrects the deficiencies of the conventional sintered materials described above.

In other words, a large number of interconnected pores that generally exist in a sintered material are made to become independent pores, thereby blocking the gas passage and leaving open pores on the surface to form an oil pool. This effect is further enhanced by the hard particles uniformly distributed in the material.

That is, the cylinder liner material of the present invention has a weight ratio of C0.5.
~2.0%, Mo and Cr or both 0.1 to 5.0%, Ni and Cu or both o, i to 3.0%, and the use of sulfur powder. The matrix of this alloy is mainly made of pearlite, does not contain martensite, and contains hard particles in this matrix. and sulfide particles are dispersed and precipitated, and the sintered alloy has a large number of independent pores inside, and the porosity thereof is 5 to 20.

This sintered alloy has a density of 6.6 to 7.3 g/C1
ft, and the porosity is preferably 5 to 20.

C is an element necessary to combine with Fe to form a pearlite matrix, but if the C content is less than 0.5%, ferrite remains in the resulting alloy, which is disadvantageous for wear resistance. It becomes too much, which is not desirable.

Furthermore, if the content of C exceeds 2.0, cementite precipitation increases in the resulting alloy, and at the same time, the amount of free graphite remaining increases, both of which cause embrittlement of the material. The content is limited to 0.5 to 2.0% by weight.

Both Mo and Cr precipitate hard particles in the matrix of the obtained alloy, and when this alloy material is put into practical use, the hard particles are separated from the secondary sliding surface of the matrix on the sliding surface. It is a necessary element to perform a bearing action as a primary sliding surface, further promote the oil pooling effect of the holes opened in the sliding surface, and improve the wear resistance of the material.

The content of at least one of Mo and Cr is o, 1%
If the content is less than 5.5%, the above effects will be poor, and if the content is less than 5.
When the coefficient exceeds 0, precipitation of hard particles becomes excessive, resulting in embrittlement of the material and also deterioration of formability of the material.

For this reason, the content of one or both of Mo and Cr must be in the range of 0.1 to 5.0% by weight.

Both Ni and Cu are elements that form a solid solution in the matrix, improve the toughness of the material, and impart heat resistance.

However, if the content of at least one of Ni and C'u is less than 0.1%, the above effects will be poor, and if the content exceeds 3.0%, some of the Cu will remain undissolved. Particles remain, and in the case of Ni, the diffusion of Fe becomes non-uniform, so the uniformity of the structure decreases in both cases, and furthermore, the effect reaches a ceiling compared to the amount of addition, impeding economic efficiency.

Therefore, the content of either or both of Ni and Cu must be within the range of 0.1 to 3.0.

The addition of S powder has the effect of making the pores that are continuous inside the material member independent from each other, and in addition,
Combined with Fe, Mo and Cr, sulfide particles are dispersed and precipitated in the matrix, and these sulfide particles act as a solid lubricant and improve the wear resistance of parts that are easily exposed to boundary lubrication conditions, such as cylinder liners and sleeves. Furthermore, it serves as a chip breaker during machining to improve rigidity.

However, if the content is less than 0.01%, the above effects will be poor, and if the content exceeds 0.5%, it will cause embrittlement of the material and promote damage to the sintering furnace.
The content of S must be within the range of 0.01 to 0.5 parts.

The sintered alloy material of the present invention can be produced by pressure forming and sintering using conventional methods.

Next, the relationship between the density and porosity of the cylinder liner or sleeve material according to the present invention having the above-mentioned component composition is unique, and the density is within the range of 6.6 to 7.3 g/~. It is preferable that the

If the density of the sintered material is less than 6.6 g/ff1, the strength of the material is insufficient, and even if the pores are made independent, gas sealing tends to be insufficient mainly due to coarsening of the pores, and the density is 7.3 f! If it exceeds /cyyt, the porosity on the sliding surface decreases, the oil retention becomes insufficient, and there is a tendency to accelerate wear of the material.

On the other hand, the porosity of the sintered alloy is between 5 and 20.

When the porosity of the sintered material is less than 5 coefficients, oil retention tends to be poor due to the oil pool effect on the sliding surface, and when the porosity exceeds 20%, the pores tend to become coarser. embrittlement of materials,
The internal structure and physical properties of the material of the present invention will be explained in more detail with reference to the following Examples and Comparative Examples.

Examples 1 to 6 and Comparative Examples 1 and 2 In each of the Examples and Comparative Examples, the amount of atomized iron powder shown in Table 1 was added to the amount of graphite powder shown in Table 1, FeCr powder (
Cr content: 62%), FeMcm (Mo content: 72%), Ni powder, Cu powder, and S powder were added, and to this, 0.8% of zinc stearate was added in the amount listed in Table 1. Mixed and formed into a tensile strength test piece (8
, 7X96.5X5, parallel part 5.7X25X8.7),
Abrasion test piece 19.6φ x 16φ x 15, air permeability test piece (19.6φ x 16φ x 15), workability test piece 36φ x
Molding 20φ×10 and cylinder sleeves,
Sintering was performed at 1130° C. for 30 minutes in a reducing gas atmosphere to create a sintered material.

Table 2 shows the composition and properties of the sintered materials obtained in Examples 1 to 6 and Comparative Examples 1 to 2.

Next, micrographs of cylinder sleeves manufactured in Example 2 according to the present invention and Comparative Example 2 are shown. show.

From this, in the conventional material shown in FIG. 2, many pores are continuous, but in the cylinder liner and sleeve according to the present invention shown in FIG. 1, the many pores existing inside are rounded. It can be seen that the pores exist as independent pores.

Next, using the wear test pieces obtained in Examples 1 to 6 and Comparative Examples 1 to 2, a surface pressure of 33 kg/cr was measured using a precious wood type abrasion tester.
it, friction speed 0.10, 0.47, 0.95 m/S,
A wear test was conducted under the conditions of a friction distance of 600 m, a dry method, and Cr plating of the mating material to determine the friction coefficient and amount of wear.

The results of the friction coefficient obtained are shown in Figure 3, and the amount of wear is shown in Figure 4.
As shown in the figure.

As is clear from this, the materials of Examples 1 to 6 according to the present invention have smaller coefficients of friction and less wear than the materials of Comparative Examples 1 and 2.

In the materials of Examples 1 to 6 according to the present invention, Mo or Cr sulfides are formed by the addition of S powder, and these sulfides exhibit a self-lubricating effect, but this effect is due to the hard particles of Mo or Cr. is further promoted by forming the primary sliding surface relative to the secondary sliding surface of the matrix.

It can be seen that due to these synergistic effects, the material of the present invention has a small friction coefficient, a small amount of wear, and excellent wear resistance.

Next, a gas sealing property test was conducted using the air permeability test pieces obtained in Examples 1 to 6 and Comparative Examples 1 to 2.

Seal both ends of the test piece and apply a pressure of 1 kg/c from one side.
wt of air was pumped, the test piece was immersed in water, and the generated air bubbles were collected and weighed to determine the gas sealing properties of each material.

The results are shown in Table 3.

As is clear from this, the amount of air leakage of the materials of Examples 1 to 6 and Comparative Example 1 according to the present invention is significantly smaller than that of Comparative Example 2, which is a comparative material.

In other words, as shown in Fig. 2, the pores that normally connect inside the sintered material and reduce the gas sealing properties of the sintered material become rounded and independent pores by adding a predetermined amount of S powder, improving the gas sealing properties. Processing experiments were conducted using the workability test pieces obtained in Examples 1 to 6 and Comparative Examples 1 to 2, which were found to be improved.

The outer diameter of the test piece was cut using a lathe at a cutting speed of 52 m/
Fig. 5 shows the state of wear of the tool when machining was performed under the following conditions: m1n1 feed rate 0.15 mrn7' rev, depth of cut 2φ, tool carbide, dry process.

As is clear from this, in the materials of Examples 1 to 6 according to the present invention, the added S forms sulfides with Fe, Mo, and Cr,
In addition to working as a chip breaker, the sulfides, especially Mo and C'r, have lubricating properties, which also improves machinability. It can be seen that material No. 1 has S powder added, but because it does not form sulfides with lubricating properties, no significant improvement in rigidity is observed.

That is, in Examples 1 to 6 according to the present invention, it can be seen that the synergistic effect of Mo or Cr and S acts to improve the rigidity as well as to improve the wear resistance.

Furthermore, using the cylinder sleeves obtained in Examples 1 to 6 and Comparative Example 2, a 4-stroke diesel engine (6 cylinders, 600, 1 bore 108 and 1 stroke
13) was used to conduct an engine test.

Experimental conditions were 2000 rpm, 100 Hr at full load.
It was an endurance test.

Prior to this experiment, a similar test was conducted on the currently assembled cast iron sleeve, and the results are also shown in Table 4.

0 (*marked average value for 6 cylinders) From this, the materials of Examples 1 to 6 according to the present invention have improved gas sealing properties by making the pores connected inside the sintered material independent by adding S powder. As a result, the blow pie in an actual engine was improved to the same level as the result with a conventional cast iron sleeve, and the sulfide of Mo or Cr and S was improved.
It can also be seen that a synergistic effect is exerted with the bearing action of the hard Cr particles, significantly reducing not only the wear of the single cylinder sleeve but also the wear of the mating piston ring.

As described above, the cylinder liner and sleeve according to the present invention have excellent gas sealing properties equivalent to those of cast material, have excellent wear resistance, and also reduce wear of the mating material and extend the life of the engine. It also has excellent machinability, so it can save resources and provide products of stable quality economically.

[Brief explanation of drawings]

FIG. 1 is a 100 times larger microscopic structure photograph of the material of Example 2 according to the present invention, and FIG. 2 is a 100 times larger microscopic structure photograph of the material of Comparative Example 2 with comparison. Fig. 3 is a graph showing the friction coefficient of Examples 1 to 6 according to the present invention and Comparative Examples 1 and 2 with a precious wood type abrasion tester, and Fig. 4 is a graph showing the amount of wear at that time. . Furthermore, FIG. 5 is a graph showing tool wear obtained in processing experiments of Examples 1 to 6 and Comparative Materials 1 and 2 according to the present invention.

Claims (1)

[Claims] 10.5 to 2.0% by weight of carbon, 1 to 5.0% by weight of at least one of molybdenum and chromium, and 0.1 to 2.0% by weight of carbon.
3.0% by weight of at least one of nickel and copper;
0,01 obtained using sulfur powder as sulfur source
The matrix of this alloy consists of a sintered alloy containing ~0.5% by weight of sulfur, with the remainder consisting essentially of iron.
It is mainly composed of pearlite and does not contain martensite.
In this matrix, hard particles and sulfide particles are dispersed and precipitated, and the sintered alloy has a large number of independent pores inside, and the porosity is 5 to 20. Liner material 02 The cylinder liner material 0 according to claim 1, wherein the sintered alloy has a density of 6.6 to 7.3 g/i.