JPH0151538B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to a cylinder sleeve (including cylinder liner) made of a sintered alloy that has high airtightness and excellent wear resistance and is used in internal combustion engines and compressors. . The cylinder sleeve according to the present invention is used as an insert type cylinder sleeve. (Prior Art) Most insert-type sleeve materials conventionally used are cast iron materials manufactured by melting and casting. Manufacturing cylinders and sleeves using the melt-casting method inevitably requires a large amount of processing costs, which goes against the need for resource conservation and also has the inherent problem of environmental pollution.
Problems such as segregation and formation of cavities are also likely to occur. Furthermore, the recent trend has been to narrow the bore spacing between cylinders due to lighter and more compact engines, and this has inevitably led to a need for thinner sleeve materials, resulting in higher rigidity than cast iron materials. There is a growing demand for cylinder sleeves with In order to meet this demand, the current practice is to apply expensive chrome plating to high-rigidity steel materials. In order to improve the current state of the prior art, the present applicant has published a patent application in Japanese Patent Application Laid-Open No. 54-20911,
2.0% C, 0.1-5.0% Mo and/or Cr, 0.1
~3.0% Ni and/or Cu, 0.01-0.5% S,
We provided a cylinder liner material made of sintered alloy, the remainder of which is Fe, and which has a large number of independent pores inside. Generally, sintered materials have many pores, and these pores open on the material surface, and these pores become oil pools, so sintered alloy materials have favorable effects as wear-resistant sliding members. demonstrate. 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 problems such as an increase in blow-by gas. produces no results. Although it is possible to seal gas by filling these pores by forging after sintering or Cu infiltration treatment, this method is uneconomical and has poor mass productivity, and furthermore, such treatment is difficult. When applied, the pores formed on the surface also disappear, so the above-mentioned oil pool effect cannot be expected. The sintered alloy cylinder liner material proposed by the present applicant is characterized in that, in order to eliminate this drawback, the continuous pores are made independent through the action of S, in particular. (Problems to be solved by the invention) The cast iron materials currently used for cylinders and sleeves have the problem that there is a large machining allowance, and similarly, steel materials require expensive chrome plating. Since sintered materials have continuous pores, such sintered materials are not suitable for thin-walled cylinder sleeves. In addition, the above-mentioned JP-A-Sho
Regarding the cylinder liner material made of sintered alloy described in Publication No. 54-20911, the present inventors researched its properties and found that it did not have sufficient rigidity and had sufficient mechanical properties as a thin material. I found out that there is a problem. (Means and effects for solving the problem) The present invention aims to correct the above-mentioned defects of the conventional general sintered material by separating a large number of interconnected pores existing in the sintered material into individual pores. This blocks the gas passage, leaving open pores on the surface to act as oil pools, and the shape of the pores is appropriate in order to obtain high rigidity. This solves the above problems, and
The feature of the present invention is that the weight ratio is 0.5 to 1.5.
%C, 0.1 to 0.6% P, and 0.1 to 0.5% S, the remainder being substantially iron, and having a large number of spheroidal independent pores inside, the alloy having 6.7 to 7.3%
The cylinder sleeve material is constructed from a sintered alloy having a density of g/cm ³ and a porosity of 5-15%. First, the reason for limiting the composition and physical properties of the sintered alloy will be explained. C (carbon) is an element necessary to combine with Fe to form a pearlite matrix that is desirable for wear resistance and rigidity, but if the C content is less than 0.5%, a large amount of ferrite remains in the resulting alloy. This is not preferable due to the above properties. In addition, if the C content exceeds 1.5%, cementite will precipitate coarsely and the material will become brittle, so the range should be limited to 0.5% to 1.5%.
The rate shall be 1.5%. S (sulfur) has the effect of making the interconnected pores in the sintered material independent from each other, and acts as a chip breaker during machining to improve machinability. However, if its content is less than 0.1%, the above effects will be poor,
Also, if the content exceeds 0.5%, it will cause the material to become brittle and also promote damage to the sintering furnace.
The content must be within the range of 0.1-0.5%. Generally, P (phosphorus) in sintered iron is often used to improve wear resistance by forming a Fe-C-P eutectic. However, unlike the above, P in the present invention is added in a small amount to generate minute liquid phases in many places during sintering, and locally eliminates pores in the sintered material.
S causes the shape of the isolated pores to become spheroidal. That is, P plays an important role in optimizing the shape of the pores, which is the object of the present invention, by interacting with S, which has the effect of turning continuous pores into independent pores. By making the pore shape spherical in this manner, the rigidity of the sintered alloy is increased.
This is thought to be because high strength is obtained by spheroidizing weak parts of the material, like the spheroidization of graphite in ductile cast iron. Furthermore, since P directs dimensional changes during sintering in the direction of contraction due to solidification of the liquid phase, a high-density material can be obtained. Moreover, phosphorus is dissolved in the matrix,
Helps strengthen the matrix. P content is 0.1
If P is less than 0.6%, the effect of making the pores spheroidized and denser and increasing the strength will be poor. On the other hand, if P exceeds 0.6%, the amount of Fe-P-C eutectic liquid phase will decrease during sintering. This is not preferable because it becomes too large and becomes brittle. Phosphorus can be obtained by blending and mixing ferroalloy powder in a predetermined ratio, but in order to achieve uniform distribution by minimizing segregation that would lead to eutectic formation, ferroalloy fine powder of 10μ or less is used. is desirable. Next, regarding 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, these relationships are unique, but the density is 6.7 to 7.3 g/cm It is necessary to be within the range of ³ . If the density is less than 6.7 g/ ^cm3 , the strength of the material will be insufficient, and even if the pores are made independent, gas sealing will tend to be insufficient mainly due to enlargement of the pores. If it exceeds 7.3 g/cm ³ , the porosity on the sliding surface will decrease, the oil retention will be insufficient, and there will be a tendency to accelerate wear of the material. On the other hand, the porosity needs to be 5 to 15%. When the porosity is less than 5%, oil retention tends to be poor due to the oil pooling effect on the sliding surface, and when the porosity exceeds 15%, the pores become coarse and the material weakens and gas There is a tendency for poor sealing. The sintered alloy according to the present invention may also contain small amounts of alloying elements. In other words, the spheroidization of the pores is possible even when wear resistance improving elements such as Cr and Mo are added, and the effect of spheroidization is
Not damaged by Mo etc. However, a major feature of the present invention is that only the above-mentioned C, P, and S provide the properties required for a cylinder sleeve material. In this respect, alloying elements such as Cr, Mo, and Ni in the sintered alloy work to strengthen the alloy and satisfy the above required properties, but the shape, amount, and density of pores are also equal to or higher than those of the alloying elements. It is thought that this is because it affects the above-mentioned required characteristics. The sintered alloy material of the present invention can be produced by pressure forming and sintering by a conventionally used method. The internal structure and physical properties of the material of the present invention will be explained in detail with reference to the following Examples and Comparative Examples. Example 1 -150 mesh atomized iron powder, 1% -325 mesh graphite powder, 1.8% FeP powder (P25%) of 10μ or less, and 0.25% -250 mesh sulfur powder. Add zinc stearate to this
0.8% was added and mixed, and a tensile strength test piece ( ^JSPM2-65 ) and an abrasion test piece (size 70
mm x 17 mm x 7 mm) and cylinder sleeve material (80 mmφ x 74 mmφ x 100 mm) were each molded and sintered at 1160°C for 30 minutes in a reducing gas atmosphere. Comparative Example 1 To -150 mesh atomized iron powder, 1% -325 mesh graphite powder and 1.8% FeP powder (P25%) of 10μ or less were added, and zinc stearate was added to this. Add 0.8% and mix, 6ton/
The same tensile strength test piece and abrasion test piece as in Example ¹ were molded at a molding pressure of cm2, and then molded in a reducing gas atmosphere.
Comparative material 1 was obtained by sintering at 1160°C for 30 minutes. Comparative Example 2 A test piece was manufactured under the same conditions as Comparative Example 1 except that Fep powder among the additives in Comparative Example 1 was not added. Comparative Example 3 A tensile strength test piece, an abrasion test piece, and a cylinder sleeve having the same dimensions as in Example 1 were manufactured using cast iron, which is currently commonly used as a cylinder sleeve material. Comparative Example 4 -100 mesh atomized iron powder, 1% -325 mesh graphite powder, 1.8% FeP powder (P25%) with a particle size of 10μ or less, -250 mesh sulfur powder 0.23 % and 0.8% zinc stearate were added and mixed, and molded into tensile strength test pieces, wear test pieces, and cylinder sleeves at a low molding pressure of 4 ton/cm ² , and then molded at 1130°C in a reducing gas atmosphere. Sintered for 30 minutes. Comparative Example 5 -250 mesh atomized iron powder, -325 mesh graphite powder 1%, FeP powder (P25%) with a particle size of 10μ or less 1.8%, -250 mesh sulfur powder 0.23 % and 0.8% zinc stearate were added and mixed, and a tensile strength test piece, an abrasion test piece, and a cylinder/sleeve material were each molded at a molding pressure of 7 ton/cm ² in a reducing gas atmosphere.
It was sintered at 1200℃ for 30 minutes. Table 1 shows various properties of the materials obtained in Example 1 and Comparative Examples 1 to 5 above.

【table】

[Table] As shown in Table 1, Example 1 according to the present invention
High strength and high Young's modulus have been obtained. Comparative example 1
is the case in which sulfur is removed from Example 1, but the strength is
Comparative Example 2, in which both the rigidity and the rigidity are significantly reduced, is a case in which phosphorus is removed along with sulfur, but the strength and the rigidity are further decreased. These data show that the high strength and high Young's modulus of the material of the present invention (Example 1) are due to the synergistic effect of the addition of sulfur and phosphorus. Comparative Example 4 has a low density and high porosity, so its strength is low, and Comparative Example 5 has a high density and a low porosity, so it has sufficient strength, but as described below, its wear resistance is poor. Not very good. Next, micrographs of cylinder sleeves manufactured in Example 1 according to the present invention and Comparative Example 1 are shown in FIGS. 1A and B and FIGS. 2A and B, respectively. From this, the pores are continuous in the materials with only phosphorus added in FIGS. 2A and 2B, but in Example 1 according to the present invention, the pores are independent and spherical.
These spherical pores are the cause of the high Young's modulus and are a feature of the material of the present invention. Next, using the wear test pieces obtained in Example 1 according to the present invention and Comparative Example 3, which is a currently commonly used cast iron sleeve, a wet wear test was conducted using a reciprocating wear tester under the following conditions. The wear coefficient and amount of wear were determined. (i) Lubrication: Wet diesel oil (SAE10#) (ii) Stroke: 50mm x 2 (reciprocating) (iii) Load, speed, time: 10Kgf−600C.Pm−60
(iv) Measuring method of wear A rod-shaped chrome-plated material is used as a mating material and is slid against the specimen material (sleeve material), and then the wear scar depth (microns) of the specimen material is determined. The wear scar diameter (mm) of the material was determined. The measurement results are shown in the table below.

[Table] As is clear from Table 2, Example 1 according to the present invention
It can be seen that the material of Comparative Example 3 has a smaller wear coefficient and a smaller amount of wear than the material of Comparative Example 3. Furthermore, the opponent
It was confirmed that the Cr plating has less wear and is an excellent sliding member. Further, an engine test was conducted using the cylinder sleeves obtained in Example 1 and Comparative Examples 3 to 5 in a 4-stroke gasoline engine (4 cylinders, 1500 c.c., bore 74 x stroke 80).
The experimental conditions were a 500 hr durability test at 5500 rpm and full load. Table 3 shows the experimental results.

[Table] From the results of this engine test, it is clear that the blow-by of the material of Example 1 according to the present invention in an actual engine is at the same level as the result of the cast iron sleeve of Comparative Example 3. This is the result of the addition of phosphorus and sulfur, which makes the pores connected inside the sintered material independent and improves gas sealing properties. Furthermore, the material of Example 1 resulted in a significant reduction in sleeve and ring wear compared to the co-cast iron sleeve material. This is because the lubrication state of the worn surface is improved because the holes are formed on the sleeve surface. Comparative example 4 has a density of 6.4 and a porosity of
In this case, the density was intentionally lowered to 19%, but due to the coarsening of the pores, the gas sealing performance deteriorated and the amount of blow-by increased abnormally. Furthermore, in Comparative Example 5, the amount of liquid phase was intentionally increased during sintering to collapse the pores, but due to the lack of oil retention, both the sleeve and ring suffered abnormal wear with a slight stubble. was. (Effects) As described above, the cylinder liner and sleeve according to the present invention have gas sealing properties equivalent to those of melt-molded materials, have excellent wear resistance, and reduce wear of the mating material, thereby extending the life of the engine. Furthermore, since it is a material with high strength and a high Young's modulus, it can sufficiently withstand the thinning of the sleeve required for lighter and more compact engines. For these reasons, the material of the present invention has sufficient characteristics of a sleeve material required for new engine designs. Furthermore, rotary compressor vanes and the like can be considered as applications that exhibit the above-mentioned characteristics, and the sintered alloy of the present invention can also be used in these applications.

[Brief explanation of drawings]

Figures 1A and 1B are micrographs of the metallographic structure of the sintered alloy of Example 1 (100x and 500x magnification, respectively), and Figures 2A and 2B are micrographs of the metallographic structure of the sintered alloy of Comparative Example 1. (Each magnification
100x and 500x).

Claims (1)

[Claims] 1 0.5-1.5% carbon and 0.1-0.6% by weight
of phosphorus and 0.1 to 0.5% sulfur, the remainder being substantially iron, and having a large number of spheroidal independent pores inside, the cylinder sleeve material comprising the sintered alloy. A cylinder sleeve material having a density of 6.7 to 7.3 g/cm ³ and a porosity of 5 to 15%, and having a high rigidity.