JPS5827860A - Combination of cylinder liner and piston ring - Google Patents

Abstract

PURPOSE:To improve resistance to wear, scuff, heat and corrosion, by specifying the composition and the average grain size of chromium of a cylinder liner and a piston ring having a basic structure of tempered martensite. CONSTITUTION:A cylinder liner and a piston ring are made of a material having a basic structure of tempered martensite in which fine particles of chromium carbide having an average particle size of 3-30mu are dispersed uniformly by the area ratio of 3-20%. Here, the cylinder liner is made of a steel having a hardness of HV400-800 and containing 0.5-1.2% of C and 12-19% of Cr by weight, and similarly, the piston ring is also made of a steel having a hardness of HV400-800. Further, a soft nitrided layer having a surface hardness of HV800- 1,500 is applied over the surface of at least either one of the cylinder liner or the piston ring.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a combination of a cylinder liner and a piston ring in an internal combustion engine, and is particularly used in diesel engines, high lead gasoline engines, or supercharged engines under high temperature, corrosion, and high load conditions. The aim is to obtain the optimal combination of cylinder liner and piston ring.

Cylinder liners and piston rings are most commonly made of cast iron, and in high-load engines, they are subjected to surface coatings such as Cr plating and heat treatment, such as nitrocarburizing and quenching. . However, in high-lead gasoline engines and exhaust gas recirculation engines, surface coatings such as Cr plating undergo significant corrosion W1 wear due to the high potential difference with the other material, and in high-load engines, fatigue peeling of the surface coating occurs frequently. there were.

On the other hand, when heat treatment is used to harden the surface, embrittlement progresses as the thickness of the heat treatment layer increases, causing problems in terms of strength with thin piston rings and cylinder liners. Ta.

Piston rings made of steel have attracted attention as a solution to this problem with 8@steel.
Steel piston rings having wear resistance such as No. 94 have been devised. However, for these steel piston rings, only cast iron or surface-coated or heat-treated cylinder liners could be used.

This is because when a bending surface is formed between copper and steel, it is easy to cause fusion between the metals called scuffing.Furthermore, it is difficult to absorb vibrations in parts such as cylinder liners that are subject to large load fluctuations as a whole. was also required, and for this reason cast iron or sintered alloys were preferred.

However, due to the recent demand for better fuel efficiency, the cylinder liner has also become lighter due to the progress of engine weight reduction! Among the cylinder liners, the cylinder sleeve in particular must be thin enough to meet the strength limit for press-fitting into the engine block, so cast iron,
Sintered cylinder liners are no longer usable.

Therefore, steel cylinder liners have once again attracted attention, but conventional cylinder liners are combined with cast iron piston rings, and copper cylinder liners are also coated with Cr plating or other surface treatments or heat treatments. Normally, it was impossible to combine it with a furnace-made piston ring. The reason for this is not only that steel has poor self-lubricating properties, but also that similar materials such as steel tend to form intermetallic bonds and fuse together, and that minute irregularities on the contact surfaces are deformed and the contact area This is because excessive wear and scuffing are likely to occur as a result of increased wear. Increasing the hardness against such *a and scuffing can improve the effect to some extent, but if you simply increase the hardness (for example, hardened tool #l), the higher hardness will cause the mating material to have less *g. This caused significant wear on the copper, and the occurrence of scuffing was unavoidable.

The present invention makes it possible to combine a piston ring and a cylinder liner, which was previously considered impossible, and has excellent sg resistance and scuffing resistance. At the same time, it also has heat resistance and corrosion resistance, making it a cylinder liner and piston ring combination that is particularly suitable for high-load engines.

The present invention will be explained in detail below.

First, the gist of the present invention is a combination of a cylinder liner and a piston ring having the following five configurations as described in the claims.

■ It is a combination of #l~Koyoru cylinder liner and steel piston ring.

(2) The base structure of the cylinder liner is tempered martensite, and in the base structure, fine carbides mainly composed of Cr and having an average grain size of 3 to 30 microns are uniformly dispersed in an area ratio of 3 to 20%.

■The component composition of the cylinder liner is C005~1.
2%, Cr12-19% and surface hardness is HV4
Must be between 00 and 800.

■ The base structure of the piston ring is tempered martensite, and the surface hardness is HV 400 - fine carbide with an average grain size of 3 - 30μ is uniformly dispersed in an area ratio of 3 - 20%.
Must be 800 copper.

(2) At least one of the cylinder liner and the piston ring has a soft nitrided layer with a surface hardness of HV 800 to 1500.

The combination of the cylinder liner and piston ring of the present invention having these five configurations has the following features.

First of all, while the conventional combination of steel and steel was significantly inferior in S resistance and scuffing resistance, the combination of the cylinder liner and piston ring of the present invention has a large amount of fine carbide in the cylinder liner. By dispersing a large amount of fine carbide in the piston ring and having a piston ring with a highly hard surface treatment layer, it has outstanding wear resistance and scuffing resistance. This can have a positive effect.

The reason for this effect is that the fine carbonized tube used in the present invention is mainly made of Cr and has a hardness of Hv1800.
High P degree carbide tearing of ~2200, fine average particle size,
Moreover, it is uniformly dispersed, and by interposing it between the sliding surfaces, it prevents direct contact between the metals. Furthermore, the base structure must also be made into tempered martensite to increase the hardness. This is because when the hardness of the base structure is low, the extremely finely dispersed contact portion deforms elastically or plastically and the contact area increases, and the effect of carbide intervening between the sliding surfaces cannot be changed.

On the other hand, for relative sliding members such as a cylinder liner and a piston ring, the relative compatibility of their materials is a problem, and specifically, the hardness and surface characteristics are a problem. death))
In the invention, the copper that makes up the cylinder liner and the copper that makes up the piston ring have a hardness difference equal to the surface treatment layer provided on the piston ring, and fine carbides are uniformly dispersed in the base structure of each other. 1 between metals. Not only is it difficult to cause carp, but the presence of a surface treatment layer, specifically a nitride compound layer created by soft nitriding treatment, on the sliding surface causes fusion between metals, resulting in a synergistic effect. It is something that can be obtained.

Therefore, in order to obtain the effects of the present invention, the steels of the cylinder liner and piston ring must be selected for the following reasons.

The steel used as the cylinder liner must have a certain rigidity and support the fine carbide in order to move with the piston ring. Therefore, the surface hardness of the cylinder liner must be at least HV 400 or higher.6. On the other hand, if the cylinder liner hardness is too high, the cylinder liner itself becomes brittle, which can lead to damage and danger in high-load engines, etc.
Must be selected in the range less than or equal to 0, -10,000vm H force e! By uniformly dispersing H fine carbides, uniform wear resistance can be obtained.However, when the average particle size is large, it is not only difficult to obtain particle uniformity, but also the carbide particle groups @ phase-sensitive interface. Abrasive wear associated with peeling from the surface is also likely to occur. On the other hand, if the average particle size of the carbide particles is small, not only is it difficult to obtain the entire carbide area, but also the bearing effect that acts between the sliding surfaces is difficult to obtain, so it is difficult to obtain a bearing effect that acts between sliding surfaces. In other words, the desired effect cannot be achieved unless the average particle size is selected within the range of 3 to 30 microns.

If the area ratio of these carbides is too small, the effect of the presence of carbides cannot be reversed, and if it is too large, the strength of the structure will drop significantly. Therefore, in the cylinder liner of the present invention, the area ratio of the carbide must be selected in the range of 3 to 20%, taking into consideration the sliding conditions.

Furthermore, steel having a matrix structure and carbide as described above,
At least in weight %, C0.5-1°2%, Cr12
~19% steel is required. Cl11 is essential as a carbide forming element, and 0.5%
If it is less than 0.5%, not only will the amount of carbide be insufficient, but also the matrix structure will be difficult to turn into martensite.

On the other hand, if Cfi exceeds 1.2%, the carbide tube becomes too large and the base becomes brittle, resulting in a significant decrease in formability, workability, and hardness. It is necessary to Furthermore, er is 'f!' as Cr carbide is a carbide that achieves the effects of the present invention. ! It is selected for reasons of suitability and is necessary as a solid solution in the base to improve MS properties and corrosion resistance. If it is less than 42%, the size or amount of the carbonized tube will be too small, and if it exceeds 19% In this case, the base structure is not only significantly embrittled, but also the carbonized tube becomes coarse, so it must be selected in the range of 12 to 19%.

Furthermore, as a means of improving the effects of the present invention, carbide-forming elements other than cr, especially .
By adding 0.6 to 1.5% of one or more of these as dowels, the following effects can be obtained.

That is, in the present invention, it is necessary to improve the sliding conditions by nitrocarburizing, as will be explained later.
o, V) have the effect of preventing the deep part of the material from softening due to softening, and form a highly hard carbide,
If the content of O is less than 25%, this effect will not be obtained, and if it exceeds 1.5%, the base will become extremely brittle, so it is desirable to add O in a range of 0.5 to 1.5%.

Although the cylinder liner has been explained above, the present invention is achieved by a synergistic effect by combining the optimum screw and tongue rings for such a cylinder liner, and the piston ring has the same range as the above-mentioned cylinder liner. It is characterized by having a matrix structure, carbide, and component composition, and furthermore, it is a vermicelli that has an appropriate hardness difference with respect to the cylinder liner.

In other words, as mentioned in the explanation of the cylinder liner, the piston ring whose matrix structure is tempered martensite and has fine carbides with an average grain size of 3 to 30μ uniformly dispersed in an area percentage of 3 to 20% is due to the carbides. It must be selected within the above range in order to satisfy both the bearing effect and strength.

Also, the component composition is C096~1.2%, Cr12~1
9%, more preferably (Mo% vlW, T
It is also for the same reason as for the cylinder liner that it is necessary to contain 0.5 to 1.5% of one or more of i).

The present invention achieves remarkable effects by combining the piston ring and cylinder liner with the same structure and composition, but for this purpose, at least one of the piston ring and the cylinder liner must have a hardness of HV 800 to 150.
It is necessary to provide a soft nitrided layer with a surface hardness of 0.

The reason for this is that the cylinder liner and piston ring described above have high surface hardness due to the carbide dispersed in the martensite base structure, but they require a surface hardness of Hv400 or more by adjusting the weight of carbide and the base structure. This is because if the hardness is less than HV 400, not only will the frictional contact area on the TWIN surface be large, but also abrasion wear due to minute foreign particles such as ma powder is likely to occur. - If you try to use a material with a blade surface hardness exceeding HV 800, the piston ring and cylinder liner, which are thin-walled parts, will become brittle in terms of strength.
However, although the combination of high-hardness stone rings and cylinder liners significantly increases wear resistance against steady IIF+, scuffing occurs during the initial run-in operation. There remains a risk that this will occur. One of the reasons for this is to obtain the effect of reducing the coefficient of friction, and to give a hardness difference between the piston ring and cylinder liner as well as between metals! A nitrocarburizing treatment must be applied to at least one of the cylinder liner and piston ring as a means of preventing liquid contact to some extent.

This soft nitrided layer is relatively deep in ordinary tool steels and carbon steels, but in high carbon and high Cr alloy steels such as the present invention, the depth of the nitride compound layer is not so deep, and In order to prevent softening due to nitriding (Mo, V
% W % Ti). As described above, in the present invention, the nitrocarburized layer is relatively thin, but during the break-in period of the engine, the presence of the nitrocarburide layer sufficiently prevents scuffing, and after the nitrocarburide layer has broken in to a certain extent, the piston rings and Initial 111P of cylinder liner
When the hardness layer is completed, the hardness layer becomes smaller than the original one, and the occurrence of [11 wear] on either the piston ring or the cylinder liner is prevented.

If the hardness of this nitrided layer is less than HV 800, there will be insufficient difference in hardness from the other material and the nitrided depth will be small. If the difference in hardness between the two and

As described above, the combination of the piston ring and cylinder liner of the present invention improves the stiffness by combining steel and hooks, and can be made thinner and thinner than normal Th11g.
It not only has excellent scuffing resistance, but also heat resistance.
It also has excellent corrosion resistance.

Regarding corrosion resistance, for example, surface coatings such as Cr plating have a potential difference with the base metal and are therefore easily susceptible to chemical corrosion, whereas in the present invention, piston rings are resistant to such chemical corrosion. The base material of both the cylinder liner and the cylinder liner is made of a corrosion-resistant material with high chromium content, making them resistant to corrosion.

Regarding heat resistance, the piston ring and cylinder liner of the present invention with high Cr are not only heat resistant in their bases themselves, but also have high C#l, high hardness, and therefore high strength. It can also withstand thermal fatigue.

Furthermore, when carrying out the present invention, it is possible to combine the piston ring and the cylinder liner with completely different copper materials, but it is possible to make the components different depending on the engine and to give each one its own characteristics. Needless to say, this is desirable.

Specifically, since the load applied to the piston ring is larger at high temperature and high load M, the piston ring is made of steel containing 0.8-1.2% of CO and 16 to 19% of Cr in terms of electric charge, and the cylinder inner is made of steel with a heavy weight. Q% C005~0.75%, Cr
It is assumed that steel containing 12-15% is provided, a soft nitrided layer is provided on both sides, and a hardness difference of 100-250 HV is given.

Such a combination is relatively high in piston rings.
By making it 1 high Cr, heat resistance and heat damage are greatly reduced.
Cylinder liners that usually require surface roughness adjustment processing such as honing are relatively 80. The hardness is lowered by lowering Cr to improve workability, and other conditions are adjusted based on the difference in hardness between the piston ring and cylinder liner.

patent applicant Nippon Piston Ring Co., Ltd.

Claims (3)

[Claims] (1) In the combination of a cylinder liner and a piston ring according to Tsugu, the cylinder liner has a matrix structure of tempered martensite, and the matrix structure contains fine carbides mainly composed of Cr and having an average grain size of 3 to 30 μm in area ratio. 3-20%
A cylinder liner made of copper having a uniformly dispersed structure, further containing 0.5 to 1.2% Cr, 12 to 19% by weight of Cr, and a surface hardness of 400 to 800 Hv; The ring has a base structure of tempered martensite, and has a surface hardness of HV 400 to 800 in which fine carbides with an average particle size of 3 to 30 μ are uniformly dispersed by area % of 3 to 20%, and A combination of a cylinder liner and a piston ring, characterized in that at least one of the cylinder liner and the piston ring has a nitrocarburized layer having a surface hardness of HV 800 to 1500. (2) The component composition of the cylinder liner is C0 in weight%.
, 6-1.2%, Si 1.0% or less, Mn 1'0% or less, Cr 12-19%, 0.5-1.5% of -second or two or more of (MO, V SW , Ti) A combination of a cylinder liner and a piston ring as described in Patent No. 1, characterized in that the combination is made of steel containing. (3) The component composition of the piston ring is C in weight/%.
0.6. ~1.2%, Sil. 0% or less, Mnl. 0% or less, Crl2 ~ 19%, (Mol V s V
llTi) and 0.5 to 1.5% of one or more of these
Claim 1, characterized in that it is a steel containing
Combination of cylinder liner and piston ring as described in section.