WO2004003246A1

WO2004003246A1 - Material for sliding parts having self-lubricity and wire material for piston ring

Info

Publication number: WO2004003246A1
Application number: PCT/JP2003/008309
Authority: WO
Inventors: Etsuo Fujita; Kunichika Kubota; Yoshiki Masugata; Yoshihiro Minagi
Original assignee: Hitachi Metals, Ltd.
Priority date: 2002-07-01
Filing date: 2003-06-30
Publication date: 2004-01-08
Also published as: AU2003244199A1; JPWO2004003246A1; US20060048865A1; DE60325602D1; KR100701812B1; CN1327025C; CN1665950A; EP1529852A1; KR20050014896A; JP4273462B2; EP1529852A4; EP1529852B1

Abstract

A material for sliding parts wherein it comprises a steel containing, in mass %, 0.4 % or more and less than 1.5 % of C, 0.1 to 3.0 % of Si, 0.1 to 3.0 % of Mn, 0 to 0.5 % of Cr, 0.05 to 3.0 % of Ni, 0.3 to 2.0 % of Al, 0.3 to 20 % of the sum (Mo + W + V) of one or more selected from the group consisting of Mo, W and V, and 0.05 to 3.0 % of Cu, and graphite particles observed in a structure face thereof have an average particle diameter of 3 μm or less. Preferably, the area of graphite particles observed in a structure face accounts for 1 % or more of the area of the structure face and the graphite particles have an average particle diameter of 3 μm or less. The steel may further contain 0.3 % or less of S and 0.01 % or less of Ca, and is preferably subjected to a nitriding treatment before use. The material for sliding parts is used as a wire material for a piston ring.

Description

Description Self-lubricating materials for sliding parts and wires for biston rings

The present invention relates to sliding parts such as piston rings, cylinder liners, and vanes mounted on internal combustion engines such as ordinary plain bearings, roller bearings, ball bearings, gears, dies, and automobile engines. Belongs to the material used. Background art

Conventionally, sliding parts such as cylinder liners and vanes are provided with materials having excellent wear resistance. Above all, the piston rings used in internal combustion engines, especially in automobile engines, are shifting from conventional iron-made to so-called steel piston rings, which are used by processing steel wires into rings. In other words, a wire obtained by subjecting an ingot having a predetermined composition to hot working such as forging and hot rolling is further drawn into a steel wire material corresponding to the small cross-sectional shape of the piston ring, and the hardness is adjusted. Biston rings are generally manufactured by bending into a ring with a fixed curvature.

At present, it is common for the top ring, the second ring, and the oil ring to be attached to one piston from the combustion chamber side, but in Japan, the top ring and the oil ring, which are severe parts, are The high functionality of Steeli-Dani is permeating. Against this background, in recent years, the results of research on post-internal combustion engines, such as electric vehicles, have become concretely visible. It has been found that diesel engines with higher internal cylinder pressures have lower environmental impact than gasoline-powered vehicles if gas oil quality is improved and exhaust gas filters are upgraded, so the sliding performance can be used for more severe diesel engines. May be called for improvement.

In recent years, scalpels have also been included in engine internal phenomena, and it has been pointed out that among the three rings, the second ring made of iron is the most severe at present. (See Non-Patent Document 1 below).

A further reason for the shift to steel is to reduce the frictional force loss by reducing the thickness of the ring structure to improve the environmental performance of the engine, and consequently the need to increase the mechanical strength. Behind them, or improved wear resistance. In addition, in terms of technology transfer in the ring manufacturing process, ease of expansion, and surface treatment, environmental regulations for Cr plating, which is the mainstream for iron, are becoming stricter, resulting in less harmful effects and nitriding. Another reason is that steelification is accelerating due to the necessity of conducting steelmaking.

In steel biston rings, a method has been proposed to impart abrasion resistance to seizure resistance by performing a surface treatment such as nitriding treatment on the contact surface with the cylinder liner (see Patent Document 1 below). A technique for improving wear resistance without using the same has also been proposed (see Patent Document 2 below).

Non-Patent Document 1: Hideki Saito and 2 others, "Study on Diesel Engine Wear Under Severe Operating Conditions", Japan Society of Mechanical Engineers, Kyushu Branch, 2001 Research Presentation Lecture (1 99 9 9) (Internet <URL:

http: //www.ns.kogakum.ac.jp/ wwal013 / EGR / nagasaki / nagasaki.html>) Patent Document 1: Japanese Patent Application Laid-Open No. H10-0-030726

Patent Document 2: Japanese Patent Publication No. 5-8-0 4 6 5 4 2

Steel piston rings 鎵 The mechanical properties of iron rings are overwhelmingly ゃ Although they are excellent in abrasion resistance, they are inferior in seizure resistance. It is one. As shown in Patent Document 1, this problem is being addressed by making full use of surface treatment such as nitriding on the contact surface with the cylinder liner. However, there is room for improvement in terms of surface treatment costs and prevention of aluminum adhesion at the contact surface with the piston.

In addition, there is an attempt to solve the problem without surface treatment.Patent Document 2 and the like mainly propose a composition design that increases the amount of Cr-based carbides in steel, which is excellent in terms of performance and cost, by adding Cr of 10% or more mainly. Suggest an area. However, although the wear resistance is dramatically improved by increasing the amount of carbide, there is concern that the effect of improving seizure resistance is insignificant and that the machinability is degraded and the productivity is adversely affected. You. Therefore, it is necessary to perform surface treatment such as PVD However, a rise in cost is inevitable.

In addition, even when gas oil is used as fuel or gasoline is used, the amount of sulfur (S) contained may be large depending on the quality. When using fuel often S content, so ₄ ² by containing sulfur (s) - occurs, piston Tonri packaging is exposed to sulfuric acid dew point environment. Therefore, sulfuric acid corrosion resistance has also been required, and strict characteristics not required in the past are also required in terms of corrosion resistance. Disclosure of the invention

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a sliding component material that has improved seizure resistance and also has excellent wear resistance by using a nitriding treatment, and is applied to a biston ring thereof. An object of the present invention is to provide a wire rod for a piston ring that has excellent sulfuric acid corrosion resistance and manufacturability in addition to dynamic characteristics and has a low coefficient of friction.

The present inventors have described in detail the sliding behavior of various applied sliding components, particularly sliding components exposed to a sliding environment under fluid lubrication such as a piston ring. We investigated and examined. As a result, we found the optimal morphology for improving seizure resistance and lowering the coefficient of friction, and by finding out the composition that is effective in achieving that structure while taking into account the sulfuric acid corrosion resistance. Invented the invention.

Thus, according to the first aspect of the present invention, in mass%, C: 0.4% or more and less than 1.5%, Si: 0.1 to 3.0%, Mn: 0.3 to 3.0. %, Cr: 0 to 0.5%, Ni: 0.05 to 3.0%, A1: 0.3 to 2.0%, at least selected from the group consisting of Mo, W and V One type consists of steel containing 0.3 to 20% in total amount (Mo + W + V) and Cu: 0.05 to 3.0%. The average particle size of graphite observed in the microstructure section is 3 am A sliding component material having the following self-lubricating properties is provided.

According to the preferred form of the material for sliding parts, the area ratio of graphite observed in the tissue section is 1% or more, and the average particle size is 3 μπι or less. Further, it is preferable that no V-carbide is observed in the tissue section.

More preferably, at least one selected from the group consisting of Mo and W is 0.3 to 5.0% in total, and V: less than 0.1%. The preferred amount of A1 is 0.7 to 2.0%. The steel contains Mo: 1.5 to 3.0% and Co: 10% or less. Is preferred. In addition, the sulfur (S) and Ca content of the steel are preferably S: 0.3% or less, and Ca: 0.01% or less. It is preferable to use as.

According to a second aspect of the present invention, in mass%, C: 0.4% or more and less than 1.5%, S i: 0.:!-3.0%, M n: 0.1-3. 0%, Cr: 0 to 0.5%, Ni: 0.05 to 3.0%, A1: 0.3 to 2.0%, selected from the group consisting of Mo, W and V Contains at least one of 0.3 to 20% in total amount (Mo + W + V), Cu: 0.05 to 3.0%, and the average particle size of graphite observed on the tissue surface is 3 µm A wire for a piston ring made of the following steel is provided. In the biston ring made of this wire rod, the distribution state of the sulfide inclusions observed in the cross section of the structure parallel to the outer peripheral surface is determined by the parallelism between the straight lines passing over the maximum diameter of each sulfide inclusion. Within degrees. Preferably, the area ratio of graphite occupied in the cross section of the structure of the wire for a piston ring is 1% or more, and the average particle size is 3 μπι or less. The wire for a piston ring preferably contains Co: 10% or less, or further contains S: 0.3% or less, and Ca: 0.01% or less, and may be used after being subjected to nitriding treatment. preferable.

An important feature of the present invention is that, for sliding parts typified by piston rings, a steel structure in which fine and moderate graphite is precipitated has been realized as an optimal means for improving seizure resistance and reducing the friction coefficient. That is. In other words, it is intended to improve the durability performance by taking into account the peculiarity of the friction behavior between the piston ring and the cylinder, in order to compensate for it, and to improve the non-surface treatment material or surface treatment cost. Thus, even with the advantageous nitriding material, sufficient effects can be achieved with respect to the reduction in seizure resistance and friction coefficient, which were insufficient with conventional technologies.

In order to realize the graphite precipitation structure of the present invention as a means for industrial implementation thereof, it is possible to sufficiently rapidly precipitate graphite finely and to improve the workability and machinability. It was found that a certain component was found, and it was found that these effects could be further improved by adding sulfur (S) alone or in combination with sulfur (S) and Ca. Also, it has a great feature.

First, the graphite precipitation structure of the present invention will be described. The mainstream of sliding parts is a fluid lubrication design in which a fluid film of oil, water, etc. is constantly formed between the usually severely rubbing mechanical elements. This fluid film formation utilizes the buoyancy of a fluid that moves relative to each other like an airplane.If the viscosity and relative speed of the fluid increase, the fluid film interposed between the sliding parts becomes thicker. This protects the mechanical elements from friction.

However, in the case of internal combustion engines, since most of the current engines are of reciprocating motion type, the relative velocity between the piston ring and the cylinder near the top and bottom dead center is zero, and the fluid film is broken, wear and seizure Will occur and interfere with the normal operation of the internal combustion engine. Furthermore, since the goal of improving the performance of the biston ring is to prevent oil from entering the combustion chamber, that is, to enhance the effect of oiling, it is increasingly difficult to maintain the above-mentioned fluid film. It is in a situation.

Nevertheless, various fluid lubrication modes are working for such sliding motion, and the present inventors have tried to solve the problem by reviewing and utilizing these modes. In other words, there are three types of fluid lubrication mode: (1) wedge action, (2) expansion and contraction action, and (3) squeeze action. The squeeze action of (3) operates even when the relative speed is zero. There is work. To explain this, it is assumed that, for example, a plate-like solid is sliding on a substrate while interposing a fluid. In this case, the pressure distribution generated on the surface of the plate opposing the substrate has a boundary condition where the pressure is 0 at the edge of the plate, and in order to maintain lubrication, that is, to generate a positive pressure distribution, The pressure distribution must be a convex function and can be described by the following conditions.

P P <'Formula

Here, P is the pressure, X is the sliding direction, and y is the distance perpendicular to the sliding direction. The Reino 1ds equation, which is the basic equation of fluid lubrication, is expressed as follows.

dd (ph) ... formula dx

dt

Where, p is the density of the fluid, h is the thickness of the fluid film, 77 is the viscosity coefficient, t is time, and u is Indicates relative speed. Therefore, from the equations (1) and (2), the necessary conditions for generating a positive pressure in the fluid film are as follows.

ud {^ ₊ ph du ₊ d {ph) _<0 … Equation ₃

όχ 2 ϋχ dt

Equation (3) has three terms. The first and second terms include the relative velocity u, and correspond to the wedge action and the expansion / contraction action described above. And the third term that does not include u is the term indicating the squeeze action, which has the possibility of functioning even if the relative speed between the Biston ring Z cylinders becomes zero.

Explaining the physical meaning of the negative effect of the third term is that if the density of the fluid is constant, the thickness of the fluid film suddenly decreases over time. As a result, a positive pressure is generated in the fluid film. If this phenomenon is to be realistically attempted, a vertical load must be suddenly applied to the plate sliding on the substrate to squeeze out the fluid film. As a result, the fluid film is squeezed out, but at the same time, a high positive pressure is generated and the solid does not easily come into contact with each other. In other words, a squeeze effect can be expected.

Here, the present inventors have found that the effect can be further enhanced by forming a large number of hole-shaped structures on the sliding surface thereof. In other words, if a large number of fine holes are provided on the sliding surface, even if the relative velocity is zero and the fluid film is broken, the fluid in the holes will instantaneously elapse over the next time. It is squeezed out on the dead surface of the fluid, and a squeezing action can be obtained by a large decrease in the film thickness of the moved fluid. As a result, seizure in the vicinity of the vertical dead center of the reciprocating motion can be suppressed, and the friction coefficient can be reduced.

The graphite precipitate structure of the present invention has been determined by paying attention to this action and effect. That is, the graphite structure of the present invention first acts as a lubricating phase having a solid lubricating action, but at the same time, it is also important that the graphite film retains an oil film as pores when the graphite falls off. This is the above-mentioned squeezing action for improving the performance. As described above, the oil film is formed stably with respect to pressure fluctuations, and the effect is enhanced by arranging holes on the surface of the sliding surface. Get this effect For this reason, graphite precipitation is effective, and it is not only ordinary plain bearings, roller bearings, ball bearing members, but also large pressure fluctuations, piston rings, cylinder liners, shim surfaces of valve lifters, various cams, gears, It is also effective for sliding parts such as die members or cutting blades where it is difficult to form a continuous fluid lubricating film, such as sliding bearings.

Further, the graphite precipitate structure of the present invention is also effective in preventing adhesion wear with an aluminum piston, which has recently become a problem when applied to the piston ring. In other words, since aluminum has almost no solid solubility limit in carbon, the adhesion reaction is suppressed.

As described above, the sliding component material of the present invention disperses graphite on the surface of the structure. F It is important that the observed average particle size of graphite is 3 // m or less. This is because if the average particle size exceeds 3 im, the periphery of the graphite will be damaged during the sliding, and there is a concern that the fragments may enter the sliding surface. In order to obtain the effect of the graphite dispersion of the present invention, it is preferable that the area ratio of graphite observed on the tissue surface is 1% or more. More preferably, for relatively coarse graphite having a particle size of 1 μm or more, the average particle size is 5 or less, or the area ratio is less than 5%.

The lubrication effect due to the formation of holes causes the fluid film to decrease due to the above-mentioned effects, and any of them loses the effect. However, the means of the present invention is effective especially in reciprocating motion where it is difficult to form a continuous fluid lubricating film, such as with an internal combustion engine. Graphite deposition is effective in an environment where transient frictional behavior occurs, such as between a piston ring and a cylinder, where the area near the point is a temporary state and immediately shifts to an environment rich in lubricating oil. I do.

It is important to design a lubrication system capable of maintaining a fluid film only under conditions where a fluid film is temporarily broken, as represented by a piston ring and a cylinder liner. Even so, if the structure of the engine's rotation speed ゃ sliding parts is changed, solid contact is possible¾fe is increased, and these non-stationary sliding parts have solid lubrication like graphite steel. A wider range of slides can be obtained by applying a material with precipitated graphite Dynamic conditions.

Next, the component composition of steel constituting the sliding component of the present invention will be described.

Graphite steel itself has been reported for a long time, and these are mainly alloys to which Si and Ni have been added.However, there are a number of graphite precipitation treatments that maintain a temperature of 600 ° C or more. It took more than 10 hours. Thus, the present invention is characterized in that cementite is easily decomposed in order to complete precipitation of black tin at the level of several hours, and an appropriate amount of A1 is added to Ni.

Generally, carbon in iron is once precipitated as metastable cementite before the precipitation as graphite. For this reason, in the graphite precipitation treatment, it is necessary to decompose cementite and convert it to stable graphite. With conventional graphite steel, the decomposition of cementite was difficult to proceed, and it took a very long time. Therefore, in the present invention, by suppressing elements that hinder the decomposition of cementite, such as Cr, the aim is to design a component that can be decomposed immediately even when metastable cementite precipitates, and virtually no cementite is generated. It can be deposited as black holes at once.

A1 has a high diffusion rate in iron, and the addition of A1 increases the diffusion rate of vacancies and shortens the time required to form aggregates of vacancies where graphite is deposited. . By using such two effects in combination, the present invention has made it possible to precipitate graphite in a short time. It is also easy to deposit graphite only on the surface by carburizing or the like.

Further, A1 is also an element having nitriding hardening ability, which is advantageous in designing an alloy of nitrided hardened copper. In addition, Cr is also an element used as a nitriding hardening element. Since Cr not only inhibits graphite formation, which is the core technology of the present invention, but also significantly reduces sulfuric acid corrosion resistance. Avoid using as much as possible. Therefore, A1 used in the present invention is an important contained element.

In addition, it has been pointed out that if the nitride layer has a defect such as graphite with a particle size of 10 _m or more, such as the case of applying a nitriding treatment to graphite steel, the nitriding layer becomes brittle. Therefore, there were difficulties in depositing graphite on nitrided steel. Therefore, in the present invention, efforts were made to refine the precipitated graphite in order to realize the nitrided steel. For the miniaturization of the precipitation graphite, and (1) refining by processing strain, (2) the addition of A 1 ₂ 〇 ₃ like inclusions, (3) BN, deposited nuclei T i C, etc., three methods Are listed. However, (1) has limitations in the process, (2) has difficulty in the dispersion manufacturing method, and (3) has the effect achieved by controlling the trace components. There are difficulties in the manufacturing method for steel. Regarding these, for example, JP-A-11-246940 discloses a method of dispersing TiC. Takashi Iwamoto et al. In “Iron and Steel Vo 1.84 (1998) p. 57” show graphite precipitation using BN as a nucleus. However, in these, the second phase precipitates at a high temperature with a high diffusion rate of 1000 ° C or more, so it is difficult to maintain the fine uniformity of graphite, and it is difficult to use high alloys with severe component segregation. Difficult to apply. The present inventors have conducted various studies to achieve the miniaturization of graphite, and as a result, have found that the Cu—A 1 metal precipitate phase in the structure works effectively. This is a phenomenon in which the second phase acts as the nucleus of precipitated graphite, as described above.Since this Cu-A1 phase precipitates at a low temperature of 800 ° C or less, a fine graphite structure can be formed stably and quickly. . In the present invention, specifically, by adding Cu and A1 at a level at which the brittle phenomenon does not occur, it is possible to form a graphite structure with less strength deterioration and acting as a lubricating phase. In addition, Cu also contributes to the improvement of sulfuric acid corrosion resistance.

Many lubrication technologies based on the dispersion of graphite have been proposed in the field of iron.However, the usage environment for sliding parts in each field is becoming more severe every year. The change is progressing to. However, even in the case of cylinder blocks for internal combustion engines, for example, most of them are made of aluminum, but the inner wall of the cylinder liner still crystallizes lead, aiming at the above-mentioned effects. It is a situation where iron is used. The sliding parts of the present invention not only have the sliding properties, but also have the strength, abrasion resistance, and sulfuric acid corrosion resistance required due to severe environmental conditions. The purpose is to achieve the steel material taken in, and the alloy design for that purpose is characteristic. Hereinafter, the component composition will be described.

C is an important element that forms a solid solution in the matrix to impart strength, partially forms carbide, and the rest forms graphite to increase wear resistance and seizure resistance. For this there is little At least 0.4% is required. However, if the temperature exceeds 1.5%, the melting point decreases, making it difficult to homogenize the structure by diffusion annealing to eliminate solidification segregation, such as heating the ingot at around 1200 ° C for several tens of hours. Become. Therefore, C is set to 0.4% or more and less than 1.5%. Preferably, it is 0.5% or more and less than 1.3%.

Although Si is usually added as a deoxidizing agent, it is added here as an element for accelerating graphite precipitation and has an effect of improving the sulfuric acid corrosion resistance. Therefore, the lower limit is set to 0.1%. On the other hand, it also affects the tempering softening behavior of the steel, and the effect of Si is particularly important for low alloy steels. The preferable Si content for preventing temper softening and increasing the heat resistance is 1.0% or more. However, the point will rise if it is added excessively, so the upper limit of Si is set to 3.0%. Therefore, S U 0. Preferably, it is 0.5 to 3.0%, more preferably 1.0 to 3.0%.

Mn, like Si, is used as a deoxidizing agent, and at least 1% is required. However, excessive addition impairs graphite precipitation. Therefore, the upper limit was set at 3.0%. Therefore, Mn is set to 0.1 to 3.0%.

Although Cr is an effective nitridation hardening element, it is an element that suppresses the decomposition of metastable cementite, not only strongly inhibits the precipitation of graphite, but also significantly reduces sulfuric acid corrosion resistance. Need to be regulated. Therefore, in the present invention, it is 0 to 0.5%, preferably 0 to 0.3%.

Ni is an element that promotes the formation of graphite and is also a useful element in suppressing red hot embrittlement that occurs in the Cu-added steel, but on the other hand, in order to increase the solid solubility limit of C in Fe, the annealing state Is an element that inhibits workability in Therefore, it was set to 0.05 to 3.0%. Preferably, it is 0.6-1.5%.

One. Like 1-, it is an element that increases the hardness of nitriding, but in the present invention, the hardness of nitriding is secured by adding A 1 to the extent that Cr cannot be increased. Its characteristic feature is that it is a graphite-forming element, which aids in the diffusion of vacancies, and also serves as a Cu-A1 phase together with Cu to form graphite nuclei, causing rapid and fine precipitation. Since it is an effective element, it is necessary to add 0.3% or more. Here, A 1 is specified to be 2.0% or less in order to raise the point similarly to S i. Therefore, in the present invention, the addition range is limited to 0.3 to 2.0%. Preferably, 0.7 to 2. 0%.

Mo is a carbide forming element that does not inhibit graphite as compared with Cr, and is an element that imparts heat resistance. Carbides serve to enhance dimensional stability, for example, by constraining the matrix during thermoforming performed after bending in the piston ring manufacturing process. However, excessive amount of Mo-added rice cake suppresses the decomposition of cementite like Cr.

Even so, Mo has little effect of the above-mentioned inhibition, and on the other hand contributes significantly to the improvement of heat resistance and contributes to dimensional stability during heat treatment. Especially, in the manufacturing process of the piston ring, since the heat treatment process in the state of the fine wire is included, the importance of this property is high, and it is effective in suppressing the variation of the joint shape. On the other hand, the upper limit is set to 20% to prevent graphite precipitation. Here, since V and W have the same effect as that of Mo, in the present invention, at least one selected from the group consisting of Mo, W and V is 0.3 to 20% in total amount. It can be.

However, even when V is added, the formation of V carbide significantly inhibits the precipitation of graphite. Therefore, it is desirable that V carbide is not observed on the surface of the structure. Alternatively, it is preferable that the composite (Mo + W) of Mo and W or the single addition (Mo + W) is 0.3 to 5.0%, and V is less than 0.1%. Mo promotes the squeezing action of graphite and helps to form a fluid film under high pressure, thereby improving seizure resistance and reducing the coefficient of dynamic friction. In addition, from the viewpoint of improving the sulfuric acid corrosion resistance, it is preferable that the amount of Mo alone added is 1.5 to 3.0%.

Cu is an important element for the present invention together with A1, because Cu is effective in precipitating the metal phase of Cu—A1 and stably and rapidly forming a fine lead structure. It also has the effect of improving sulfuric acid corrosion resistance. Therefore, it is necessary to reciprocally adjust the content also serving as the amount of A1, and to obtain the effect, it is necessary to add 0.05% or more, and preferably 0.2% or more. On the other hand, if Cu is added excessively, the hardness at the time of annealing will increase, and workability will be impaired. Therefore, in the present invention, the composition range is 0.05 to 3.0%, and preferably 0.2 to 3.0%.

Furthermore, as a technology for improving lubricity, in the case of internal combustion engines, sulfur (S) is known as a technology for organizing and adding as an extreme pressure additive in engine oil to prevent seizure. On the other hand, the present inventors have found that the presence of MnS and red sulfide (sulfide) in the steel allows the sulfur (S) to form an in situ sulfide on the new surface created on the friction surface by frictional heating. They formed a film and found that this was effective in improving lubrication performance. According to this means, since the lubricating substance is scattered inside the material, it is not necessary to add a large amount of the lubricating substance to improve the lubricating performance at a necessary local portion. It can be expected to function semi-permanently because the effect does not disappear.

The conventional means for increasing the amount of Cr-based carbide in steel for piston rings is, in other words, the contact area with the cylinder liner is small, and the sliding energy per unit area is high. The aim is to increase the performance and balance with the cylinder liner. This improves the seizure resistance, but essentially increases the contact area by promoting wear on the cylinder liner side due to non-uniform contact, resulting in abnormal local surface pressure. The aim is to avoid rising. In other words, it is a technology that improves the familiarity of the piston ring at the beginning of installation, and has few functions as wear characteristics that require durability such as adhesive wear.

Excessive improvement in wear resistance will cause a situation where the cylinder liner will be attacked, and if it progresses extremely, it will increase the clearance, etc., and will increase the blow-by amount related to the amount of exhaust gas. The effect of sulfur (S) is to improve the seizure resistance by lowering the coefficient of friction without promoting the wear of the material, so it is highly effective in maintaining a small change in clearance even when the engine is running. .

Therefore, in the sliding component material of the present invention, seizure resistance can be further improved by adding an appropriate amount of sulfur (S). In other words, sulfur (S) is mostly combined with Mn to form MnS, which acts on lubricants such as engine oil to exert a lubricating effect, lowering the coefficient of friction and improving seizure resistance . Here, seizure is a phenomenon in which the frictional surface temperature rises due to frictional heat and the atoms move between the materials due to thermal vibrations, causing sticking. The frictional surface temperature is defined as the friction energy unit (= friction coefficient x surface pressure X (Slip speed). for that reason, When the coefficient of friction decreases, it becomes difficult to raise the temperature, and the seizure resistance improves. To achieve this effect, the content of sulfur (S) is effective, but if added excessively, the mechanical properties deteriorate, and for example, there is a concern that the wire may break during the drawing process of steel wires for steel biston rings. The upper limit is preferably 0.3%. The content is desirably 0.01 to 0.3%, and more desirably 0.03 to 0.3%.

Further, the present inventors have found that in order to obtain a material obtained by adding sulfur (S) to 0.3%, it is necessary to increase the forging ratio applied to the manufacturing process from the viewpoint of mechanical properties. I also found something desirable. In other words, it is effective for improving the mechanical properties of sliding parts, and in particular, for steel biston rings obtained by bending steel wires, it suppresses breakage and breakage in the bending process. It is also an effective means of doing so.

In this case, the forging ratio is defined as a reduction in area from an ingot to a piston ring product in the piston ring manufacturing process. In other words, compared to the cross section perpendicular to the direction in which the steel is forged and stretched, that is, the small cross section in the final biston ring product, (ingot cross-sectional area before forging) / (product cut after bending) Area). However, the reduction in area from steel wire to piston ring products due to bending is negligible for achieving the effects of the present invention, and is calculated by (ingot cross-sectional area before forging) / (before bending (forging * elongation). (After) steel wire cross-section). The higher the number of these forging ratios, the more the forging is progressing.

In a steel structure containing a sulfide such as Mn S, in the starting structure, a large number of spherical or spindle-shaped sulfides are present at the grain boundary triple point of the solidified cell structure, and the orientation is random. However, as the forging ratio to be applied increases, the orientation of the sulfide changes, and the mechanical properties are improved.

Increasing the forging ratio increases the orientation of the sulfide in the length direction of the steel wire.In other words, the sulfide expands along the circumferential stress that mainly acts on the piston ring, resulting in mechanical properties. Is hardly deteriorated. This effect is particularly remarkable for stretched sulfides, that is, salifides having an aspect ratio (maximum diameter / minimum diameter) of 3 or more. In other words, particularly, the circumference of a sulfide having an aspect ratio of 3 or more. Poor orientation in the direction leads to deterioration of mechanical properties.

Specifically, the sulphide observed on the tissue surface parallel to the outer peripheral surface of the biston ring The distribution of sulfide-based inclusions, especially the sulfide-based inclusions with an aspect ratio of 3 or more, is determined by the degree of parallelism (the angle on the acute angle side) between the straight lines passing over the maximum diameter of each sulfide-based inclusion. By setting the temperature to within 30 degrees, a material for sliding parts that is particularly effective as a wire for a piston ring can be obtained. For example, it is preferable to achieve a forging ratio of 500 or more.

Figure 5 shows a sketch of the microstructure of a forged steel with a forging ratio of 1 (as-forged) and 500 forged at a magnification of 400 times without corrosion, and a view of the sulfide-based inclusions at that time. The schematic diagram which performed the parallelism measurement is shown. Aspect ratio: Two optional sulfide-based inclusions of 3 or more are selected, and the straight line (A, B line) passing through the maximum diameter of each is measured, and the acute angle formed by each other is measured. Then measure it. This measurement is performed over at least 10 fields of view, and the maximum value of the angle is defined as parallelism. If there are no intersections in the field of view (for example, Figure 5—forging ratio 500), the A 'line parallel to the A line may be measured as an auxiliary line. The definition that one sulfide-based inclusion is regarded as one is defined as one that is considered to be connected by observation with a 400 × optical microscope, and a straight line passing through the maximum diameter is used as a measurement line.

In Fig. 5, it can be seen that the sulphide inclusions with a forging ratio of 1 exceeding 30 degrees are present, but those with a forging ratio of 500 are all less than 30 degrees. Specifically, the number 30 degrees is a number designed for fracture mechanics. Fig. 6 feG.i.Irwm (Analysis of Stresses and Strains Near the End of a Crack Transversing a Plate, Trans.ASME, Ser.E, J. Appl.Mech., Vol. 24, No. 3 (1957), pp. This figure shows how the stress intensity factor changes when an angle occurs in the stress direction and in the crack propagation direction, calculated analytically by It is. ((1 COS 'β ヽ · σ π τταα… Equation 4 where Κι is the stress intensity factor that is the driving force for crack propagation, jS is the angle between the stress direction and the crack direction, σ is the stress, π Is the pi, a is the crack length, and the crack is easy to propagate when it exists in a direction perpendicular to the stress (] 3 = 90 °), and there is a crack along the stress direction (= 0). ) And the crack does not progress, making it easier for the crack to progress (that is, The stress intensity factor increases sharply), which corresponds to more than 30 degrees. Considering that inclusions can be regarded as cracks due to poor mechanical bonding, it is clear that it is important to control the variation in the orientation of the inclusion distribution to 30 degrees or less. Then, it is understood that it is important to make the orientation of the elongated inclusions uniform.

Since sulfur (S) is a typical element that degrades the mechanical properties of steel, it is preferable to take measures for this strength in order to establish a steel piston ring. For example, Japanese Patent Application Laid-Open No. 07-258792, in which as much as 1% sulfur (S) can be added, covers cylinder liners that do not achieve a sufficient forging ratio, and basically covers steel. In fact, what makes the steel ring of the piston ring cost-effective is the plastic casting technology such as drawing, rolling and bending. In other words, if steel containing as much as 1% sulfur (S) is to be finished into a wire for piston rings using this process, the material strength required for the plastic working is insufficient, so the fracture in the drawing process Can occur, and it is difficult to reach a complete steel piston ring.

As described above, in the present invention, in order to further improve the seizure resistance, it is preferable to use a sliding component material containing 0.3% or less of sulfur (S). This is the only effective means for a piston ring wire rod, which is a material with extremely high ratio for sliding parts.

In order to further enhance the effect of S, it is effective to add Ca together with sulfur (S). Since Ca is present in Mn S, it easily flows out to the seizure surface. In addition, since it has a strong reducing action, it prevents oxide formation on the seizure surface and facilitates sulfide formation, thus improving lubricity. However, excessive addition of Ca impairs hot workability, so that 0.01% or less is preferable. To obtain the above effects, the content is preferably 0.0001% to 0.01%, more preferably 0.0005% to 0.01%.

The addition of S and Ca is effective in improving machinability and grindability in addition to seizure resistance. In particular, since the dispersion of MnS and the precipitation of graphite improve the machinability of steel, it is easy to form corners with a small radius of curvature, which are difficult to form by grinding. This makes it easier to manufacture an improved biston ring. Further, the sliding component material and the piston ring wire of the present invention can also contain Co for the effect of enhancing corrosion resistance, particularly sulfuric acid corrosion resistance. Further, like Mo, it promotes the squeezing action of graphite and helps to form a fluid film under high pressure, which has the effect of increasing seizure resistance and lowering the coefficient of dynamic friction. In this case, the content is preferably 0.5% or more.On the other hand, since it is not only an expensive element but no further effect is observed even if it is added excessively, the content is preferably set to 10% or less. desirable. More preferably, it is 2 to 5%.

The steel constituting the material for sliding parts and the wire rod for biston rings of the present invention is, for example, a steel that satisfies the content of each of the above-described element types, and that the remainder is substantially Fe. For element types other than the above, for example, the total amount should be 10% or less, and more preferably 5% or less. For this, steel with the remaining Fe and unavoidable impurities can be applied.

The following elements may be included in the steel of the present invention as long as they are within the following ranges, and are preferable ranges.

P≤0.1%, Mg≤0.01%, B≤0.01%, Zr≤0.1%

In addition, as a preferable condition of the present invention, by setting the area ratio of nonmetallic inclusions in the texture plane to 2.0% or less, it is possible to prevent breakage in a drawing step of processing into a steel wire rod and to reduce the wire rod. It is effective in preventing breakage when forming into a coil shape. In particular, it is effective for the production of piston rods that involve the production and processing of fine wire rods, and is desirable as a range that enables production with a high operating rate.

The nitriding treatment is effective in further improving seizure resistance and abrasion resistance as an effect added to the present invention, but in the case of the present invention, excellent seizure resistance is achieved regardless of the presence or absence of the surface treatment. And other surface treatments such as PVD and Cr plating may be combined. Also, taking piston rings as an example, these surface treatments are conventionally applied to the contact surface between the piston ring and the cylinder liner, which is the main sliding surface, but not to the friction surface with the piston. However, adhesion wear cannot be prevented. However, if the material of the present invention is used, sufficient seizure resistance is exhibited even without surface treatment, and the adhesion reaction is suppressed, so that the material is particularly effective for a piston ring.

In addition, since the graphite phase exists in the material of the present invention, it is immersed in, for example, a CuCl ₂ solution. Thus, a so-called intercalation treatment in which another molecule or ion is inserted between the molecular layers of the layered molecular structure of the black sharp can be performed, and the sliding characteristics can be further improved. Furthermore, since the graphite after the intercalation treatment also serves as a polymer polymerization catalyst, lubrication treatment with a polymer coat (polymer coating treatment) can be performed, or only the intercalation treatment is performed in advance to polymerize the lubricating oil. By making the state easy to slide, it is possible to obtain a sliding component that maintains a self-lubricated state by causing a polymerization reaction during sliding. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a photograph of a structure of a microphone opening showing a distribution state of graphite observed in a section of a structure of a material of the present invention (sample No. 3).

Fig. 2 is a photograph of the microstructure of the microphone opening showing the distribution of graphite observed in the microstructure section (different field of view) of the same material as that shown in Fig. 1.

FIG. 3 is a microstructure photograph showing the distribution state of graphite observed in the cross section of the structure of the comparative example material (sample No. 14).

Fig. 4 is a photograph of the microstructure of the microphone opening showing the distribution of graphite observed in the cross section of the same material as the material shown in Fig. 3 (another field of view).

FIG. 5 is a sketch diagram and a schematic diagram of a microstructure photograph illustrating the parallelism of the sulfide-based inclusions.

FIG. 6 is a diagram for explaining the effect of the angle between the stress direction and the crack propagation direction on the stress intensity factor.

FIG. 7 is a schematic diagram illustrating an ultra-high pressure friction and wear test method.

FIG. 8 is a schematic diagram illustrating a reciprocating wear test method.

FIG. 9 is a Stribeck diagram showing the relationship between the reciprocal of the load and the dynamic friction coefficient, and is a diagram illustrating a lubricated state.

[Example]

Hereinafter, the effects of the present invention will be described with reference to specific examples.

Example 1

Due to high frequency induction melting in the atmosphere, the residual Fe and inevitable impurities Ingots (cross-sectional dimensions: 22 OmmX 22 Omm) of each sample adjusted to the composition were obtained. Samples No .:! To 6 are examples satisfying the present invention, and samples No. 11 to 16 are comparative examples. Sample No. 16 is a material equivalent to JIS-SUS 440 B, and is a currently used piston ring material.

First, these ingots were subjected to hot working to obtain a linear material with a cross-sectional dimension of 9 mm × 9 mm (forging ratio: about 598). Sample No. 13 could be manufactured, but test pieces could not be manufactured because the steel material was destroyed in the subsequent hot working process.

Subsequently, a predetermined quenching and tempering treatment was performed after the annealing treatment to adjust the hardness to around 45 HRC. Then, the structure surface of the quenched and tempered linear material was observed without corrosion, and the distribution state of graphite (average particle size, area ratio to the structure) was examined. The distribution was investigated using image analysis from images in 10 visual fields observed with a 1000-fold optical microscope. The diameter of graphite used was the diameter of a perfect circle having the same area as the measured area of graphite. Regarding the distribution of graphite of the steel No. of the present invention:! To 6, the average particle size was about 0.3 to 2 im and the area ratio was 0.5 to 5%.

1 to 4 are micrographs showing the distribution of graphite in samples No. 3 and No. 14. FIG. Fine graphite is precipitated in the matrix structure of sample No. 3, but the graphite of sample No. 14 is coarse. This is because when an appropriate amount of Cu and A1 is included, a fine Cu-A1 phase is precipitated prior to graphite precipitation, and graphite is precipitated using the nucleus as a nucleus, resulting in a fine graphite distribution. If Cu or A1 is insufficient, this mechanism does not work, and graphite precipitates coarsely. Table 2 shows the distribution of graphite, including other samples. No graphite was observed in the structures of Sample Nos. 11, 12, 15, and 16.

These samples were subjected to ion nitriding at 530 ° C. for 5 hours at H ₂ : N ₂ = 1: 1 to obtain evaluation samples for seizure resistance and wear resistance. The test method for the evaluation of seizure resistance was carried out under the following conditions using an ultra-high pressure friction and wear tester shown in Fig. 7, and when the rotational torque of the mating material suddenly rose, the seizure was started. Was evaluated as a scuff load. The dynamic friction coefficient was determined from the rotational torque of the mating material when the load was l OMPa. In FIG. 7, reference numeral 1 indicates a sample, 2 indicates a mating material, and F indicates a load.

Sliding surface shape: 5 mm X 5 mm square

Friction speed: 2m / sec

Friction surface pressure; initial pressure 1.5MPa, 0.5MPa every minute

Lubricating oil; motor oil # 30

Drops only at initial pressure (10 cm ³ Z minutes), then stops supply Counterpart material: JIS FC 250 (mouse: iron) (Hardness: 100HRB)

Abrasion resistance was evaluated by a backward wear test. This method measures the wear width at the time by rubbing a separately prepared test piece of 8 mm in diameter and 20 mm in length with a counterpart material (FC250) of 2 Omm in diameter by reciprocating motion. Figure 8 shows the other test conditions. In FIG. 8, reference numeral 1 denotes a sample, 2 denotes a partner material, F denotes a load, and OIL denotes a lubricating oil.

Pressing load; 50 ON

Sliding distance per stroke; 1 30 mm

Maximum sliding speed: 0.5 m / sec

Lubricating oil (supplied by dripping); motor oil # 30

Mating material: JIS FC 250 (mouse: iron) (Hardness: 100HRB)

Table 2 shows the measurement results of the scuff load, kinetic friction coefficient and wear width together with the nitriding hardness.

Table 2

Graphite distribution V Carbide nitriding hardness Scuff load Dynamic friction coefficient Wear width

Remarks Average particle size m) Area ratio (%) (HV) (MPa) (mm)

0.4 0.8 None 853 12.5 0.11 0.55 The present invention

0.5 0.9 Yes 890 11.5 0.12 0.65 11

0.8 3.5 None 930 10.5 0.07 0.5 II

0.7 2.6 None 910 13.5 0.08 0.55 II

1.9 4.1 None 950 10.5 0.07 0.51 11

0.7 1.9 None 895 12.6 0.06 0.51 II Not observed 0 None 445 6.5 Measurement not possible 1.53 Comparative Example Not observed 0 None 773 7.0 Measurement not possible 0.71 〃

6.2 5.8 None 723 6.0 Measurement not possible 0.64 // Not observed 0 None 563 7.0 Measurement not possible 1.62 されず Not observed 0 None 1032 7.5 Measurement not possible 0.53 〃

From Table 2, it can be seen that Sample Nos .: to 6 satisfying the present invention have excellent scuff resistance and abrasion resistance because of high scuff load and narrow wear width. Samples Nos. 3 to 6 also have low values of the dynamic friction coefficient, and exhibit extremely excellent characteristics as sliding members. On the other hand, all the comparative samples which do not satisfy the graphite distribution of the present invention have poor seizure resistance. The lack of wear resistance of Samples Nos. 11 and 15 is due to the low content of both Cr and A1, which are elements having nitriding hardening ability, and low nitriding hardness. It is.

Further, the sample prepared in Example 1 was subjected to a seizure test under the same conditions without performing the nitriding treatment. Table 3 shows the results. Although the seizure resistance of Sample Nos. 1 to 6 satisfying the graphite distribution of the present invention is exhibited regardless of the presence or absence of the surface treatment, even if graphite is present, the scuff load of the coarse Comparative Sample No. 14 is low. Observation of the rubbing surface of this sample No. 14 after the test revealed that the periphery of the graphite had been damaged, and it was probable that the shards entered the friction surface and had poor sliding characteristics.

Table 3

Example 2

Sample No. 1 and Sample No. 15 in the composition shown in Table 1 were formed into coils with a diameter of 5.5 mm by hot rolling, and then drawn and cold-rolled to form a 1.5 mm X 3.1 mm flat wire. Finished in shape. Sample No. 1 could be processed without any problem, but Sample No. 15 had poor cold workability and broke during the drawing process. Image analysis of the area ratio of non-metallic inclusions occupying in both yarn and fabric surfaces in the state of the billet before drawing was performed on the structure plane perpendicular to the next drawing and rolling direction. 1 is 1.86%, sample No. 15 was 2.23%, and the cause of the fracture was that in addition to its high sulfur (S) content, the area ratio of nonmetallic inclusions exceeded 2.0%.

Example 3

Samples Nos. 1 to 6, 11, and 12 in Table 1 were finished in the process shown in Example 2 into a 1.5 mm X 3.1 mm flat wire shape, and quenched at 1 000 ° C for 30 minutes. And tempering were performed to a hardness of about 510HV. Thereafter, cutting was performed 10 times with a grinding wheel cutter at a rotation speed of 10,000 rpm and a feed speed of 1 mmZ seconds, and the occurrence of burrs was investigated. Table 4 shows the frequency of occurrence.

Table 4

Although burrs were observed in Sample Nos. 11 and 12, Sample Nos .:! To 5 in which an appropriate amount of sulfur (S) was added did not generate Paris, and the sulfur ( It can be seen that the addition of S) has a large effect on reducing burrs. This also improves manufacturability, especially in the manufacture of piston rings.

Example 4

Using an ingot of the same composition as that of sample No. 1 in Table 1 previously prepared separately, the hot working process was performed with a forging ratio of 1 to 10000, and the cross-sectional dimension of 3.OmmX 3.Omm A wire was produced. These are then quenched and tempered to have a hardness of 400 HV, and when the biston ring is formed, the outer peripheral surface of the wire rod is stretched. The parallelism in 3) was measured according to the above procedure. Then, a three-point bending test with a span of 3 O mm was performed on the wires after the hardness adjustment. This is to determine whether the quenched and tempered wire rod can be formed into a piston ring having a predetermined curvature by a roll bending method. Table 5 shows these results.

Table 5

A material with a high forging ratio and a parallelism of sulfide-based inclusions of 30 degrees or less has excellent mechanical properties and is effective in suppressing rupture, which is a concern during bending from a wire to a ring shape. Then, when these wires having excellent bending workability are bent and formed into a piston ring shape, the parallelism of the sulfide-based inclusions observed on the tissue surface parallel to the outer peripheral surface is obtained. In the case of the wire rod, there was no substantial change in the wire ratio.

The degree of parallelism of the sulfide inclusions observed in these wire states is also reflected in the piston ring state after bending. Regarding the shortage of fatigue rupture, which is a concern when such a biston ring with a small cross-section is mounted on an engine, the form of sulfide-based inclusions with a parallelism of 30 degrees or less depends on the mechanical properties. It is effective for improvement, and is particularly preferable for wires for biston rings.

Example 5

No. 21 to 23 ingots (cross-sectional dimension 22 Omm X 220) that satisfy the present invention and are adjusted to the composition of the remaining Fe and inevitable impurities shown in Table 6 by high-frequency induction melting in the atmosphere mm). In contrast to sample No. 21, sample No. 22 contains a large amount of M0, and sample No. 23 contains a large amount of Co. Table 6

• ¾W, V <0.01%, Ca <0.00001%

First, these ingots were subjected to hot working to obtain a linear material having a cross-sectional dimension of 9 mm X 9 mm (forging ratio: about 598). Subsequently, a predetermined quenching and tempering treatment was performed after the annealing treatment to adjust the hardness to about 40 HRC. Then, the microstructure surface of the quenched and tempered linear material was observed without corrosion, and the distribution state of graphite (average particle size, area ratio to the structure) was examined. The distribution situation was investigated by using image analysis from an image of 100 visual fields observed with a 100 × optical microscope.

Table 7

The graphite precipitation of all samples No. 21-23 was fine. Table 7 shows the distribution of graphite. The average particle size was 1 μm or less and the area ratio was 1 to 4%. The relatively coarse graphite having a particle size of 1 IX m or more has an average particle diameter of 1 to 1.5 / im and an area ratio of less than 1% in all samples. In each sample, the ratio of the area of relatively coarse graphite of 1 m or more to the total area of graphite was less than 1/4, indicating that fine graphite occupies most of the precipitated graphite. .

These samples were used as test pieces for evaluating the dynamic friction coefficient. The dynamic friction coefficient was evaluated using the ultra-high pressure friction and wear tester shown in Fig. 7 (the friction speed is different from that shown in Fig. 7) under the following conditions. Each time the load was stepped up, the dynamic friction coefficient was determined. Figure 9 shows the relationship between the reciprocal of the load and the dynamic friction coefficient.

Sliding surface shape: 5 mm X 5 mm square 1 m / s Friction surface pressure; initial pressure 1.5 MPa,

0.5MPa every minute

Lubricating oil Motor oil # 30

10 cm ³ / min constantly dropping the

Partner material: FC 250 (JIS mouse rat iron)

Fig. 9 is a curve called the Stribeck diagram, in which the "load characteristic" indicating the condition of the load applied to the friction sliding portion is plotted on the horizontal axis, and the friction coefficient is plotted on the vertical axis. This makes it possible to know the lubrication state. In the case of the present embodiment, since the friction speed is constant at 1 mZ second, the horizontal axis can be represented by the reciprocal of the load. In each curve in Fig. 9, the right side of the plot (extreme value) with the lowest coefficient of friction (low load side: the range indicated by the arrow) is the area where the lubricating film is not destroyed and fluid lubrication occurs. The left side (high load side) is the area where the fluid film is broken and the solid lubrication is mixed with the fluid lubrication due to the contact between the solids. Therefore, the lower the plot (extreme value) of the coefficient of friction shifts to the left side of the graph, the higher the load, the more the fluid film is not broken, indicating that fluid lubrication is possible. From the results in FIG. 9, it is found that the sample No. 22 having a higher Mo content than the sample No. 21 retains the fluid film even on the higher load side. In addition, it can be seen that in the sample No. 23 having a high Co content, the fluid film is retained even on the higher load side. This indicates that Mo and Co have the effect of promoting the squeezing action described above.

The leftmost plot of each curve corresponds to the load at which the test was stopped due to seizure. In Sample Nos. 22 and 23, the above plots shifted to the left (high load side) due to the addition of Mo and Co, and the seizure resistance was further improved. The kinetic friction coefficient is also low overall, and the addition of Mo and Co further improves good sliding characteristics due to graphite precipitation.

According to the present invention, self-lubrication imparts excellent seizure resistance even without surface treatment, has a low friction coefficient, and reduces energy loss due to friction, so that it can be applied to various sliding parts. By adjusting the morphology of the sulfide inclusions, it is particularly effective as a piston ring, reducing the aggression of cylinder liners and pistons, and improving the environmental performance and durability of the internal combustion engine. Big against Play a contribution. In addition, it has excellent workability such as machinability in the manufacturing process, and can reduce manufacturing cost and lead time, making it a material for sliding parts that is excellent in both performance and manufacturing, and is a very useful technology in industry. . Industrial applicability

The material of the present invention is used for sliding parts such as a piston ring, a cylinder liner, and a vane mounted on an internal combustion engine such as a plain bearing, a roller bearing, a ball bearing, a gear, a mold, and an automobile engine.

Claims

The scope of the claims

I. In mass%, C: 0.4% or more and less than 1.5%, S i: 0 .:! ~ 3.0%, M n ··· 0. 3.0%, Cr: 0 ~ 0 5%, Ni: 0.05-3.0%, A1: 0.3-2.0%, at least one selected from the group consisting of Mo, W and V in total amount (Mo + W (+ V): 0.3 to 20%, Cu: 0.05 to 3.0%, with self-lubricating properties with an average graphite grain size of 3 m or less observed on the structure surface Materials for sliding parts.

2. The self-lubricating sliding component material according to claim 1, wherein the area ratio of graphite observed on the texture surface is 1% or more and the average particle size is 3 μm or less.

3. The self-lubricating sliding component material according to claim 1 or 2, wherein no V carbide is observed on the tissue surface.

4. At least one member selected from the group consisting of Mo and W is 0.3 to 5.0% by mass (Mo + W), and V: less than 0.1% by mass%. 4. The sliding component material having self-lubricating properties according to any one of claims 1 to 3.

5. The self-lubricating sliding component material according to any one of claims 1 to 4, comprising a steel containing, by mass%, A1: 0.7 to 2.0%.

6. The self-lubricating sliding component material according to any one of claims 1 to 5, comprising a steel containing, by mass%, Mo: 1.5 to 3.0%.

7. The self-lubricating sliding component material according to any one of claims 1 to 6, comprising a steel containing, by mass%, Co: 10% or less.

8. The self-lubricating sliding member material according to any one of claims 1 to 7, comprising a steel containing, by mass%, S: 0.3% or less.

9. The self-lubricating sliding component material according to claim 8, comprising a steel containing, by mass%, C a: 0.01% or less.

10. The material for a sliding component having self-lubricating properties according to any one of claims 1 to 9, which is used after being subjected to a nitriding treatment.

I I. In mass%, C: 0.4% or more and less than 1.5%, S i: 0.1 to 3.0%, Mn: 0.1 to 3.0%, Cr: 0 to 0. 5%, Ni: 0.05 to 3.0%, A 1: 0.3 to 2.0%, at least one selected from the group consisting of Mo, W and V in a total amount (Mo + W + V) of 0.3 to 20%, Cu: 0.05 to This is a wire rod for a biston ring composed of steel containing 3.0% and having an average graphite particle size of 3 μm or less observed on the structure surface, and the structure surface parallel to the outer peripheral surface when used as a piston ring The wire for biston rings in which the distribution of the sulfide-based inclusions observed in (1) is within 30 degrees of the parallelism between straight lines passing over the maximum diameter of each sulfide-based inclusion.

12. The wire for a piston ring according to claim 11, wherein an area ratio of graphite observed on a tissue surface is 1% or more and an average particle diameter is 3 μm or less.

13. The wire for a piston ring according to claim 11 or 12, which is composed of steel containing, by mass%, Co: 10% or less.

14. The wire rod for a biston ring according to any one of claims 11 to 13, comprising a steel containing S: 0.3% or less by mass.

15. The piston ring material according to claim 14, comprising a steel containing, by mass%, C a: 0.01% or less.

16. The wire rod for a biston ring according to any one of claims 11 to 15, which is used after being subjected to a nitriding treatment.