CN1665950A - Material for sliding parts having self-lubricity and wire material for piston ring - Google Patents

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 mum 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 mum 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

Be used to have the material and the piston ring wire rod of self lubricity slide unit

Technical field

The present invention relates to as the slide unit that is installed in motor car engine or other oil engines for example material of piston ring, cylinder sleeve and blade, and the material that is used as sliding surface bearing, roller bearing, ball bearing, gear and mould.

Background technology

So far, the material with the wear resisting property excellence is used for slide unit, as cylinder sleeve and blade.At oil engine, especially the piston ring material that uses in the motor car engine has become the wire rod steel by cast steel, and above-mentioned materials is processed to annular shape.Usually, the preparation method of piston ring is that the ingot casting that will have predetermined composition is thermally processed into wire rod by forging, hot rolling etc., again the wire rod that is obtained is carried out moulding by drawing etc., make it to have and the corresponding given cross-sectional shape of the small cross-section form of piston ring, wire rod after the moulding is adjusted, made it to have given hardness, subsequently, wire rod is carried out bending machining, make it to become annular shape with predetermined bend radius.

At present, three kinds of piston ring being arranged, is respectively slubbing ring, second road ring and the oil ring.Above-mentioned piston ring is fixed on the piston according to said sequence from combustion chamber one side of oil engine.Because slubbing ring and oil ring are worked under special harsh conditions, therefore, in Japan, have developed the use steel, so that obtain advanced function.Using steel is to having required further to improve the response of oil engine since nearest.That is: in order to respond for example electric vehicle progress of research of back oil engine, require oil engine to have advanced function.For the diesel engine of under mal-condition, working, also emphasize to require to improve sliding capability, because diesel engine has higher internal pressure, as long as lightweight oil upgrading and emission gases filter function is stronger, then compare with petrol motor, the environmental pressure that is brought is less.

Point out that in passing nearest research is also at the inside phenomenon of engine, and show: the wearing and tearing that the second road ring of cast steel system is subjected in three kinds of rings are the most serious, non-patent literature described as follows 1 is described.

Other reason that piston ring adopts steel to replace cast iron is: in order to use the fine work plug ring that can make engine have advanced environmental performance, reduce the power loss of bringing because of frictional force, the material of physical strength and wear resisting property excellence must be provided; And, use harmless nitriding to handle and also can promote the application of steel loop, handle because adopt this processing to replace main chromium plating as the processing of cast iron ring surface, meet strictness control requirement to environment, and the transfer and the development that realize encircling manufacturing technology easily.

According to a proposal,, prepare wear-resistant and piston ring (referring to patent documentation 1) bite-resistant by for example nitriding of surface treatment is carried out on the surface that contacts with cylinder sleeve.The another kind of method (referring to patent documentation 2) of not improving wear resistance by surface treatment has also been proposed.

* non-patent literature 1:Hideki Saitoh etc. " Researches on abrasion ofdiesel engines under severe driving conditions ", Research reportlectures (1999), Kyushu Branch of Japan Society of MechanicalEngineers (Internet＜URL: Http:// www.ns.kogakuin.ac.jp/-wwa1013 / EGR/nagasaki/nagasaki.htm1＞)

* patent documentation 1:JP-10-030726 A

* patent documentation 2:JP-58-046542 B2

The mechanical property of steel piston ring and wear resisting property are more more excellent than cast-iron piston ring, and still, their bite-resistant performance is relatively poor.This is that the steel second road ring does not obtain one of fine reasons of development always.The research that improves the bite-resistant performance is based on so that the surface is transformed, and the steel loop surface carburization to contacting with cylinder sleeve for example is as described in patent documentation 1.But because surface-treated cost and the problem that occurs aluminium adhesion between piston and piston ring at the interface, above-mentioned open question still exists.

The another kind of method of not improving the bite-resistant performance by surface treatment has been proposed, as described in patent documentation 2.According to this patent, alloy contains and is not less than 10% chromium, to improve the ratio of the carbide of chromium in the steel matrix.Although can significantly improve wear resisting property by the carbide that increases chromium,, the problem that exists some to relate to productivity comprises the little and machinability decline of bite-resistant performance improvement degree.In order to overcome these weak points, patent documentation 2 proposes to carry out for example PVD of surface treatment, and adopts this surface treatment can not avoid the raising of manufacturing cost.

In addition, use lightweight oil or even gasoline situation about acting as a fuel under, according to the quality grade difference, contain many sulphur sometimes in the fuel oil.When in oil engine, using the high fuel of this sulphur content, because the sulphur that exists in the fuel forms SO ₄ ^2-, piston ring can be exposed in sulphur dew point (dewing) atmosphere.Therefore, also require the piston ring sulfuric acid corrosion resistant, the result, compared with the past, the requirement that piston ring is had the corrosion resistance nature of improvement just becomes strict more.

Disclosure of the Invention

Based on the problems referred to above, the present invention has been proposed, and, the purpose of this invention is to provide the material and the piston ring wire rod that are used for slide unit, wherein, slide unit is handled by improving bite-resistant performance and nitriding with material, should have the excellent abrasive energy, and wherein, described wire rod should have excellent corrosion resistance to sulfuric acid, excellent productivity and low frictional coefficient.

The inventor studies and tests the sliding motion of slide unit, and it is being in the slip atmosphere under the Liquid Lubrication Condition of representative that described slide unit is exposed to the piston ring environment.As a result, the inventor has found a kind of best metal tissue that is suitable for improving the bite-resistant performance and reduces frictional coefficient, and a kind of chemical constitution that is suitable for obtaining the metal structure of sulfuric acid corrosion resistant.

The result, according to a first aspect of the invention, a kind of material as the self-lubricating slide unit is provided, these parts are made of a kind of steel, this steel contains, in mass: be not less than 0.4% to the C (carbon) that is lower than 1.5%, 0.1-3.0%Si, 0.1-3.0%Mn, 0 (comprising 0)-0.5%Cr, 0.05-3.0%Ni, 0.3-2.0%Al, (Mo+W+V) total amount is the Mo that is selected from of 0.3-20%, W (tungsten) and at least a element of V (vanadium), and 0.05-3.0%Cu, wherein, can observe the graphite granule that average particle size particle size is not more than 3 μ m in the cross section of described steel metal structure.

According to a preferred embodiment, the metal structure cross-section to graphite granule organizing to occupy in the total area in cross section and be not less than 1% area ratio, and have and be not more than 3 μ m average particle size particle size.More preferably in organizing the cross section, do not observe the carbide of vanadium.

And preferred described steel contains at least a element that is selected from Mo and W that total amount is 0.3-5.0%, and is lower than 0.1%V.The preferred 0.7-2.0% of Al content.Preferably, described steel can also contain 1.5-3.0%Mo and/or not be higher than 10% Co.Preferably, S in the steel (sulphur) and Ca content are controlled at respectively and are not higher than 0.3% and be not higher than 0.01%.Preferred described steel carries out nitriding to be handled, to be used as slide unit.

According to a second aspect of the invention, a kind of wire rod as piston ring is provided, this piston ring is made of a kind of steel, this steel contains, in mass: be not less than 0.4% to the C (carbon) that is lower than 1.5%, 0.1-3.0%Si, 0.1-3.0%Mn, 0 (comprising 0)-0.5%Cr, 0.05-3.0%Ni, 0.3-2.0%Al, (Mo+W+V) total amount is the Mo that is selected from of 0.3-20%, at least a element of W (tungsten) and V (vanadium), and 0.05-3.0%Cu, wherein, can observe the graphite granule that average particle size particle size is not more than 3 μ m in the cross section of described steel metal structure.In the metal structure of the piston ring of making by described wire rod, parallel with piston ring periphery organize cross-section to the distribution of sulfide inclusion be such: the angle of cut when each straight line by each sulfide inclusion major axis intersects mutually is not more than 30 °, and the described angle of cut can be regarded as a kind of parallelism degree.According to a preferred embodiment, the metal structure cross-section to graphite granule organizing to occupy in the total area in cross section and be not less than 1% area ratio, and have and be not more than 3 μ m average particle size particle size.

Wire rod as piston ring preferably contains the Co that is not higher than 10% quality, and contains S (sulphur) that is not higher than 0.3% quality and the Ca that is not higher than 0.01% (quality).Preferably it is carried out nitriding and handle, to be used as piston ring.

A critical aspects of the present invention is to obtain specific steel metal structure, and in this tissue, tiny graphite granule is separated out in steel matrix with suitable ratio, with the bite-resistant performance of improving steel and the frictional coefficient that reduces slide unit such as piston ring.That is: target of the present invention is to improve its weather resistance taking into full account on the fricting movement basis special between piston ring and cylinder.According to metal structure of the present invention, can obtain gratifying advantageous effects to the bite-resistant performance of improving steel that proposes previously and the target that reduces frictional coefficient, and non-finish materials of the prior art, perhaps the material of nitriding is for realizing that above-mentioned target all can not be satisfactory, and its surface treatment cost is favourable.

Has a metal structure that graphite is separated out about of the present invention, the inventor has studied and can separate out tiny graphite granule fully fast and can effectively improve the processing characteristics of steel and the chemical constitution of machinability, so that adopt industrial feasible means to obtain described metal structure.Fruitful achievement is: by add single-element sulphur or sulphur and Ca in steel, can further improve above-mentioned effect.This is another key feature of the present invention.

At first, introduction has the metal structure of the present invention that graphite is separated out.

Slide unit mainly is designed for hydrodynamic lubrication, and wherein, fluid film for example oil film or moisture film can be stable formation between the mechanical organ of mutual sliding contact under the mal-condition.As the aerial relative movement of aircraft, the formation of fluid film can cause the fluid of relative movement to produce buoyancy.Along with the increase of fluid viscosity or the raising of speed of relative movement, the fluid film between the slide unit becomes thicker, and like this, mechanical organ is protected, and can not wear and tear.

But most of oil engine is a reciprocating motion type, makes that the speed of relative movement between piston ring and the cylinder is zero near upper and lower stop, the result, and wearing and tearing and/or interlock often take place because of fluid film breaks in slide unit, thereby cause the improper motion of oil engine.In addition, flow into the combustion chamber owing to forbid oil, promptly so-called " frizing " become an important factor of high-performance piston ring, and therefore, the state being fit to this purpose will be difficult to keep fluid film.

But, the inventor still looks back the various hydrodynamic lubrication patterns during the sliding motion that effectively uses hydrodynamic lubrication, so that overcome the problems referred to above.In brief, the hydrodynamic lubrication pattern comprises three kinds of effects, that is: (1) wedging, (2) expansion and (3) extruding.Squeezing action (3) is even be that zero state is also effective at speed of relative movement.Suppose that solid board slides existing under the fluidic condition on substrate, then can carry out description below squeezing action.Under this hypothesis, the final condition that acts in the face of the pressure distribution on the solid plate surface of substrate is: the pressure of solid board edge is zero.Pressure distribution will change according to a kind of semisphere function, keep lubricated necessary positive pressure distribution so that produce.The expression formula of this pressure distribution is:

$\frac{{\&PartialD;}^2}{\&PartialD;x^2}P+\frac{{\&PartialD;}^2}{\&PartialD;y^2}P<0$

Formula 1

In formula 1, P is a pressure, and x is a slip direction, and y is edge and the vertical distance of slip direction.Reynolds is equation now, and the formula below promptly the fundamental equation of hydrodynamic lubrication adopts is represented:

$\frac{\&PartialD;}{\&PartialD;x}\left(\frac{\mathrm{\&rho;}{h}^3}{12\mathrm{\&eta;}}\frac{\&PartialD;P}{\&PartialD;x}\right)+\frac{\&PartialD;}{\&PartialD;y}\left(\frac{\mathrm{\&rho;}{h}^3}{12\mathrm{\&eta;}}\frac{\&PartialD;P}{\&PartialD;y}\right)=\frac{u}{2}\frac{\&PartialD;\left(\mathrm{\&rho;h}\right)}{\&PartialD;x}+\frac{\mathrm{\&rho;<figure-callout\; id="2"\; label="h"\; filenames="A0381563100331.png"\; state="\{\{state\}\}">h</figure-callout>}}{2}\frac{\&PartialD;u}{\&PartialD;x}+\frac{\&PartialD;\left(\mathrm{\&rho;h}\right)}{\&PartialD;t}$

Formula 2

In the formula 2, ρ is a fluid density, and h is a fluid film thickness, and η is a viscous modulus, and t is the time, and u is a speed of relative movement.According to formula 1 and 2, the requirement that produces positive pressure in fluid film can be written as formula 3.

$\frac{u}{2}\frac{\&PartialD;\left(\mathrm{\&rho;h}\right)}{\&PartialD;x}+\frac{\mathrm{\&rho;<figure-callout\; id="2"\; label="h"\; filenames="A0381563100331.png"\; state="\{\{state\}\}">h</figure-callout>}}{2}\frac{\&PartialD;u}{\&PartialD;x}+\frac{\&PartialD;\left(\mathrm{\&rho;h}\right)}{\&PartialD;t}<0$

Formula 3

Formula 3 has three, and first and second comprises respectively and foregoing wedging and the corresponding speed of relative movement u of expansion.The 3rd does not relate to speed of relative movement u, its correspondence be squeezing action, be that zero state is also effective even this effect is expected between piston ring and cylinder speed of relative movement.

The 3rd is keeping under the constant condition of fluid density for the physical significance that condition had of negative value is, fluid film thickness reduces fast, thereby causes producing in the fluid film positive pressure.In fact this phenomenon can realize by the solid board of sliding on substrate is applied a vertical load suddenly, so that the extrusion fluid film.As a result, produce high positive pressure simultaneously, and sliding panel is difficult to directly contact with substrate by the extrusion fluid film.In brief, realized squeezing action.

The inventor finds: by changing sliding surface, make it to have the structure that comprises many tiny holes, can strengthen squeezing action.Tiny hole in the sliding surface wherein keeps fluid, and, even be zero at speed of relative movement, under the fluid film destructive situation, also can at once from hole, provide fluid to desiccated surface.The fluid film thickness that causes by liquid motion obviously reduce to cause compressional movement.As a result, restrained and near the upper and lower stop interlock has taken place during the to-and-fro movement, and, frictional coefficient also reduced.

In order to obtain above-mentioned effect and effect, determined graphite according to the present invention to separate out tissue.That is: graphite granule is not only as solid lubricant, and also helps the formation that oil keeps hole after it comes off.Hole has realized being suitable for keeping the squeezing action of oil film.Squeezing action guarantees to stablize the formation of oil film, and irrelevant with the fluctuation of pressure.As mentioned above, exist hole to strengthen squeezing action on the sliding surface.Separating out of graphite granule can be strengthened squeezing action definitely effectively, and, for common slide unit, as sliding surface bearing, roller bearing or ball bearing, can guarantee this validity, and, be difficult to the stable slide unit that forms this hydrodynamic lubrication film for obviously fluctuating because of pressure, as piston ring, cylinder sleeve, valve tappet pad, cam, gear, mould or cutting tip, also can guarantee this validity.

Graphite is separated out to organize also and can effectively be restrained adhesive wear, and recently, under the situation of piston ring attached to the aluminium piston, adhesive wear has become a problem.Because aluminium seldom is dissolved in the carbon, therefore restrained adhesion reaction.

The tissue that has the graphite granule that wherein distributing as the material of the present invention of slide unit.Importantly will organize cross-section to the mean sizes of graphite granule be controlled at and be not more than 3 μ m.If mean sizes is greater than 3 μ m, then during sliding motion, the graphite granule that is positioned at periphery can often damage, and the graphite bits can very be invaded slide plane unfriendly.The metal structure cross-section to graphite granule organizing and occupying in the total area in cross section under the situation that is not less than 1% area ratio, the distribution of graphite granule is more effective.Be not less than the relatively large graphite granule of 1 μ m for size, more preferably graphite granule has the mean sizes that is not more than 5 μ m, and perhaps its area ratio in organizing the cross section total area is no more than 5%.

The formation of hole still can cause the minimizing of fluid film because of above-mentioned effect, and it is invalid finally to become for lubricated very effective.The formation hole has not been considered to an important factor in the hydrodynamic lubrication design.Yet method of the present invention is effective especially for the oil engine that relates to to-and-fro movement, is difficult to form continuously fluid film.For example, graphite is separated out in irregular rubbing characteristics and become more effective under the situation that repeats between piston ring and the cylinder sleeve, in the described situation, near fluid film destructive transient state approaching zero the upper and lower stop of speed of relative movement is transformed into the state that has a large amount of lubricating oil.

The Lubrication Design that can keep fluid film relative movement between with piston ring and cylinder sleeve be representative because of the temporary transient disruptive situation of structure reason fluid film under be even more important.Irrelevant with Lubrication Design, the possibility of solid contact increases along with the variation of the speed of rotation of engine or slide unit structure.In this case, the material of the graphite granule of effective solid lubrication that wherein is scattered here and there being applied to this irregular slide unit can guarantee to realize sufficient lubrication under various sliding conditions.

From following explanation, will understand that the alloy designs of the steel of the present invention of making slide unit.

Just relevant for the report of graphitized steel, still most of this class report all is about Si or Ni steel alloy since ancient times.In addition, this class steel need spend tens hours or longer time keeps being not less than under 600 ℃ the high temperature, so that the indigenous graphite particle.According to the present invention, adopt the element al that quickens the cementite decomposition with Ni, according to the suitable proportion alloying, so that graphite granule is separated out fully at several hrs.

Before graphite was separated out, because carbon is generally separated out in steel matrix as semistable cementite, therefore, cementite should decompose and become stable graphite in graphitizing process.The shortcoming of conventional graphite steel is the cementite little disintegration, and therefore, the indigenous graphite particle just needs considerable time.On the other hand, the present invention adopts a kind of alloy designs, and wherein, control hinders element that cementite decomposes such as the content of Cr so that even separating out under the situation of semistable cementite, can finish the decomposition of cementite at short notice.As a result, carbon is separated out with the graphite form at once, and does not form a large amount of cementites.

By being added on the high Al of velocity of diffusion in the steel, can improve the velocity of diffusion of hole.The velocity of diffusion height can quicken to separate out as graphite granule the gathering of the hole in site.As a result, because the influence of Al and the quick gathering of hole, separating out of graphite granule can be finished at short notice.And processing such as nitriding help only at upper layer indigenous graphite particle.

Interpolation Al also is suitable for the alloy designs of nitriding hardening steel, because Al is a kind of nitriding hardening element.Another kind of element Cr with same nitriding hardening effect can hinder unfriendly as the separating out of the graphite granule of basic fundamental main points of the present invention, and can cause the remarkable decline of corrosion resistance to sulfuric acid.Therefore, should avoid adding Cr as far as possible, still, Al is as being used for the most important element of this purpose by alloying.

The nitriding of graphitized steel has been considered to be not suitable for the material of indigenous graphite, because the disadvantage of bringing of separating out of graphite granule is in nitriding steel: the nitrided case meeting becomes fragile because of the graphite granule that the size that has wherein had the defective effect is not less than 10 μ m.According to the present invention, can restrain this disadvantage by graphite being separated out become fine particle.

Adopt any following method can realize that graphite is separated out becomes the change of fine particle: (1) is introduced the processing strain and is separated the graphite precipitate, (2) Al ₂O ₃Deng be mingled with and (3) disperse to separate out as graphite the BN in site, TiC etc.But method (1) is restricted to creating conditions, and disperses Al in the method (2) ₂O ₃Deng technology be difficult to.Remaining method (3) also is difficult to for the required technology of high carbon steel, can obtain BN, the suitable dispersion of TiC because have only by strictness control trace components.As for known change, the dispersion of TiC is disclosed among the JP-11-246940, Iwamoto etc. disclose the separating out of BN of separating out the site as graphite on " Iron and Steel " (1998,84 volumes, the 57th page).But, any method all requires the thermal treatment of separating out second phase 1000 ℃ or higher high-temperature zone, to improve velocity of diffusion, therefore, be difficult to be applied to the easily a large amount of accumulative high quality steel of alloying element, reason is the uniform distribution that is difficult to realize tiny graphite granule.

The inventor has studied separating out of tiny graphite granule from many aspects, and finds: separate out the Cu-Al intermetallic compound for realizing that above-mentioned purpose is very effective in steel matrix.The Cu-Al intermetallic compound, promptly a kind of second phase plays graphite and separates out the site.This intermetallic compound is separated out not being higher than under 800 ℃ the relative low temperature, thereby can form the stabilizing tissue with tiny graphite granule at short notice.Owing to according to the present invention the content of Cu and Al is controlled at and restrains the level that embrittlement takes place, therefore, formed as mutually lubricated but can not reduce the graphite structure of physical strength.And, add element Cu and also can effectively improve corrosion resistance to sulfuric acid.

Although up to now about many proposals that are distributed with of the graphite granule of lubricate in the cast steel,, become surface treated steel by cast steel as the deterioration of the material of slide unit for the environment that is suitable for various slide unit and exposed.But, for the cylinder body that great majority all comprise aluminium parts, have graphite and separate out the cast steel of tissue and still be used as the inboard wall of cylinder liner material, to obtain aforementioned effect.Slide unit of the present invention is characterised in that the alloy designs principle of the steel that is suitable for still having cast steel characteristic, so that obtain physical strength, wear resisting property and the necessary corrosion resistance to sulfuric acid of competent environmental degradation, and sliding capability.

From following explanation, will understand that the chemical constitution of slide unit:

Carbon is a kind of important element, its a part of solution strengthening steel matrix, and another part is separated out as carbide, and remaining part is separated out as graphite.Carbide and graphite are separated out and are improved wear resistance and bite-resistant performance.In order to reach above-mentioned effect, carbon content must be at least 0.4% (quality).But the excess carbon that is not less than 1.5% (quality) can reduce the temperature of fusion of carbide unfriendly, and like this, metal structure is difficult to realize homogenizing by diffusion annealing, for example heats ingot casting down at about 1200 ℃ and eliminates solidifying segregation in tens hours.In this case, determine that the carbon content scope is: be not less than 0.4 (quality) but be lower than 1.5% (quality), be preferably 0.5% (quality) or higher but be lower than 1.3% (quality).

Si is as traditional reductor and also separate out the accelerator interpolation as graphite.Si also can effectively improve corrosion resistance to sulfuric acid.For this reason, determine following 0.1% (quality) that be limited to of Si.In addition, add elements Si and can restrain steel softening during annealing, and Si's influences particularly important in low alloy steel.Preferred definite Si content is not less than 1.0% (quality), so that improve hot strength, avoids annealing softening.But, because excessive Si can improve A unfriendly ₁Temperature is so be controlled to be 3.0% (quality) with the upper limit of Si.Therefore, determine that the Si content range is 0.1-3.0% (quality), preferred 0.5-3.0% (quality), more preferably 1.0-3.0% (quality).

Mn is the same with Si, adds as reductor.For deoxidation, Mn content must be at least 0.1% (quality), and still, excessive Mn can hinder separating out of graphite.For this reason, be limited to 3.0% (quality) on the control Mn, and, determine that the Mn content range is 0.1-3.0% (quality).

Cr is a kind of element of effective nitriding hardening, but it can restrain the decomposition of semi-stability cementite and separating out of strong obstruction graphite unfriendly.Cr also can the grievous injury corrosion resistance to sulfuric acid.Therefore, control Cr upper content limit is 0.5% (quality).For this reason, determine that the Cr content range is 0-0.5% (quality), preferred 0-0.3% (quality).

Ni is that a kind of graphite is separated out accelerator and can effectively be restrained red shortness (red shortness often appears in the steel of Cu alloying), still, has improved the solubleness of carbon in Fe unfriendly, causes the processing characteristics of annealed state relatively poor.Therefore, determine that the Ni content range is 0.05-3.0% (quality), preferred 0.6-1.5% (quality).

Al is the same with Cr, also is a kind of element of effective raising nitriding hardness.Because in alloy designs of the present invention, must avoid increasing Cr content, therefore, guarantee for this purpose suitable nitriding hardness by adding Al.Element al plays graphite and forms the agent effect, promotes the diffusion of hole, and and Cu together, form and separate out the Cu-Al phase in site as graphite.That is: Al is a kind of effective element of separating out tiny graphite granule in short-term, and therefore, Al content should be not less than 0.3% (quality).The upper limit of Al is controlled to be 2.0% (quality), and reason is the same with Si, and the increase of Al content can improve A ₁Temperature.Therefore, determine that the Al content range is 0.3-2.0% (quality), is preferably 0.7-2.0% (quality).

Mo is that a kind of carbide forms agent, compares with Cr, and the degree that its obstruction graphite is separated out is less, but can improve the resistance toheat of steel.The carbide of molybdenum is the constraint steel matrix in thermoforming step (carrying out after the bending step in the piston ring manufacturing processed), thereby improves dimensional stability.But the same with Cr, excessive Mo can hinder the decomposition of cementite.

In addition, Mo to graphited inhibition a little less than, still, add the dimensional stability during elements Mo is significantly improved thermotolerance and thermal treatment.Particularly in comprising the heat treated piston ring manufacturing processed of thin wire, Mo is very important for the deviation of restraining butt joint shape (abutment profile) to the influence of dimensional stabilizing.For this reason, the addition of Mo is 0.3% (quality) or higher.On the other hand, the upper limit of Mo is controlled at 20% (quality), and reason is that separating out of graphite hindered along with Mo content increases.V has the effect identical with Mo with W.Therefore, at least a Mo that is selected from, the element addition summation of W and V is 0.3-20% (quality).

Be preferably formed a kind of metal structure, wherein, even also do not observe the carbide of vanadium on the structure of steel cross section of vanadium alloying, reason is that the carbide of vanadium can significantly hinder separating out of graphite.If add V together separately or with Mo and W, then the ratio of V is preferably controlled and is lower than 0.1% (quality), and the total amount of Mo and W is 0.3-5.0% (quality).Elements Mo has been strengthened the squeezing action of graphite and has been promoted that fluid film under high pressure forms, thereby improves the bite-resistant performance and reduce kinetic friction coefficient.In addition, add Mo and can improve corrosion resistance to sulfuric acid.Therefore, the preferred content range of single interpolation elements Mo is controlled to be 1.5-3.0% (quality).

Cu is the same with Al, is a kind of Cu-Al of separating out intermetallic compound has the stabilizing tissue of tiny graphite granule mutually with quick formation important element.Add element Cu and also effectively improve corrosion resistance to sulfuric acid.For this reason, must control the ratio of Cu with respect to Al, and, determine that Cu content is not less than 0.05% (quality), preferably be not less than 0.2% (quality), so that Cu plays a role mutually with Cu-Al.But the too high meeting of excessive Cu causes the raising of annealed state hardness, and reduces the processing characteristics of steel, therefore, the upper limit of Cu is controlled to be 3.0% (quality).So, determine that the Cu content range is 0.05-3.0% (quality), preferred 0.2-3.0% (quality).

By the way, sulphur is added in the machine oil as organic extreme-pressure additive usually.Described additive is applied in the oil engine, in order that improve lubricated and prevent interlock.On the contrary, the inventor chances on and is mingled with sulfide M nS in the steel matrix.This sulfide form a kind of original position sulfide film on the unsalted surface that exposes because of heat of friction, and this sulfide film can effectively improve lubricity as the sulphur source.The method according to this invention, excellent lubricating property almost can for good and all be guaranteed, reason is need not add a large amount of lubricants that improves oilness at predetermined parts, perhaps under the situation of not losing lubricity, just can realize the distribution of lubricant in steel, contain the situation that then often occurs the forfeiture lubricity during the engine oil of extreme-pressure additive in replacing.

The another kind of traditional method target that is used as the carbide of chromium in the steel of piston ring that increases is to reduce the surface-area that piston ring contacts with cylinder sleeve, and improve the wear resisting property of piston ring, like this, slide energy with high per unit area proportional action on piston ring, so that the wearing and tearing between equalizing piston ring and the cylinder sleeve.Although the distribution of carbides by chromium can be improved the bite-resistant performance,, the purpose of the distribution of carbides of chromium is to prevent the unusual rising of part carrying, this situation is caused by non-homogeneous contact basically.As a result, increase the wearing and tearing that aggravate cylinder sleeve because of contact area.In brief, the distribution of carbides of chromium can make piston ring and cylinder sleeve be complementary in the initial stage of contact, still, for the polishing machine relevant with the life-span, for example not influence of adhesive wear.

Excessively improve the situation that wear resistance can cause occurring the piston ring scuffing cylinder sleeve.If barrel wear is serious, then the gap becomes greatly unfriendly, causes leak rate to increase, and the leak rate correspondence the amount of emission gases.On the other hand, it is influential to the improvement of bite-resistant performance to add elementary sulfur, and reason is at the situation decline low-friction coefficient that does not quicken the steel wearing and tearing, the result, and oil engine can work long hours, and the gap does not have noticeable change.

That is: by adding the sulphur of adequate rate, can further improve bite-resistant performance as the material of the present invention of slide unit.Elementary sulfur in most cases reacts with Mn, form MnS, and reaction product MnS and engine oil effect as lubricant, shows oilness.As a result, reduced frictional coefficient, and, the bite-resistant performance improved.

To be friction surface adhere to together phenomenon because of atom transfer takes place therebetween in interlock.In heat of friction friction surface is heated under the pyritous state, the thermal vibration of atom has promoted atom transfer.The temperature of friction surface is a frictional energy, i.e. the monotone increasing function of frictional coefficient * carrying * sliding velocity.In other words, if frictional coefficient reduces, then temperature is difficult to raise, thereby has improved the bite-resistant performance.Add sulphur and can effectively reduce frictional coefficient, but excessive sulphur can damage mechanical property, steel wire rod probably can be disrumpent feelings in the drawing step of making the steel pistons ring.Therefore, control sulphur on be limited to 0.3% (quality).Preferred definite sulphur content scope is 0.01-0.3% (quality), more preferably 0.03-0.3% (quality).

The inventor also finds: in the manufacturing processed of sulphur content up to the material of 0.3% (quality), increase forging ratio, can effectively improve the mechanical property of slide unit.In other words, mechanical property raises along with the increase of forging ratio.Particularly work as the steel pistons ring and add man-hour, improve forging ratio and help preventing that steel wire rod from cracking and disrumpent feelings taking place during bending by the bent steel wire rod.

Forging ratio is defined as the section ratio of ingot casting and product design in the piston ring manufacturing processed.The steel cross section of just vertical forging or drawing direction, perhaps as the piston ring small cross-section of the finished product, forging ratio adopts the ratio value representation of (not forging the sectional area of ingot casting)/(sectional area of crooked back product).But, depress to the cross section of piston ring product by steel wire rod and to be compared to that to reach above-mentioned effect effect very little, can ignore, therefore, forging ratio can adopt ratio (not forging the sectional area of ingot casting)/(forging also drawing but unbent steel wire rod sectional area) expression.Forging ratio is higher, and the forging degree that material is subjected to is bigger.

Wherein distribute in the initial as-cast structure of steel of sulfide M nS, have many spherical or fusoid sulfide inclusions, these are mixed in born of the same parents' shape solidified structure three crystal grain contact place random orientations at crystal boundary.Along with forging ratio increases, the orientation of sulfide inclusion gradually changes, thereby has improved mechanical property.

Along with forging ratio increases, sulfide inclusion is machine-direction oriented along steel wire rod more, and, under the hoop stress effect that mainly acts on piston ring, elongate.As a result, basically eliminate the disadvantageous effect of sulfide inclusion to mechanical property.Typically, have 3 or bigger aspect ratio (major axis dimension/minor axis dimension), can prevent that mechanical property from descending by the shape that makes sulfide inclusion.In other words, if having 3 or the sulfide inclusion orientation along the circumferential direction of bigger aspect ratio unfavorable, then also can cause mechanical property to descend.

Particularly, adopt the circumferentially parallel surface structure of microscopic examination and piston ring can obtain the distribution of sulfide inclusion.Control the distribution of above-mentioned sulfide inclusion, particularly have 3 or the distribution of the sulfide inclusion of bigger aspect ratio, so that each makes by the parallelism between the straight line of each sulfide major axis (angle of acute angle one side) and remains in the scope that is not more than 30 °, so that steel wire rod that can be used as piston ring or the material that can be used as slide unit are provided.For this reason, determine that preferably forging ratio is 500 or higher.

Fig. 5 is a cover synoptic diagram, explanation be that observed forging ratio is that 1 not forged steel (as cast condition) and forging ratio are the microstructure that 500 forged steel does not corrode attitude under the opticmicroscope, and the synoptic diagram of explaining the sulfide inclusion parallelism measurement method.Selecting arbitrarily two aspect ratios is 3 or bigger sulfide inclusion, measures each by the acute angle between the straight line (line A and line B) of single sulfide major axis, and, in the whole field range of microscope, repeat this measurement.In at least ten microscopic fields of view, repeat same measurement again.Maximum value during employing respectively takes measurement of an angle is as parallelism.When there not being (shown in the forged steel that forging ratio among Fig. 5 is 500) when intersecting, the line A ' parallel with line A can think an auxiliary line.Here, 400 show the sulfide grain that the observation conduct connects together under little visual field is considered to an individual particle, and, will be decided to be measuring line by the straight line of this individual particle major axis.

Among Fig. 5, forging ratio is in the tissue of 1 not forged steel, and the parallelism that sulfide inclusion distributes is greater than 30 °, and still, forging ratio is that any parallelism all is controlled in and is not more than 30 ° in the tissue of 500 forged steel.In fact, numeral is a design load of determining according to fracture mechanics for 30 °.Fig. 6 is a graphic representation, what its illustrated is the analytical results of G.R.Irwin, so that explain at crackle during along the direction expansion different with stress direction, how to change stress intensity factor (referring to " Analysis of Stresses and Strains Near the End of a CrackTransversing a Plate ", Trans.ASME, Ser.E, J.Appl.Mech., Vol.24, No.3 (1957), pp.361-364).Analytical results is used as shown in the formula representing:

${\mathrm{<figure-callout\; id="1"\; label="K"\; filenames="A0381563100321.png,A0381563100331.png"\; state="\{\{state\}\}">K</figure-callout>}}_1=(1-\mathrm{<figure-callout\; id="2"\; label="co\; s"\; filenames="A0381563100331.png"\; state="\{\{state\}\}">co</figure-callout>}{s}^{}{}^2\mathrm{\&beta;})\&CenterDot;\mathrm{\&sigma;}\sqrt{\mathrm{\&pi;a}}$ Formula 4

In the formula 4, K ₁Be stress intensity factor, β is the angle between stress direction and the direction of crack propagation, and σ is a stress, and a is a crack length.Formula 4 shows: the crackle of vertical with stress direction (β=90 °) is expanded easily, and the crack propagation degree of extending along stress direction (β=0 °) is less.Be easy to expansion (that is: stress intensity factor increases suddenly) and equal 30 ° corresponding to angle.Because dynamically poor bonding strength can be regarded inclusion as crackle, therefore, be understood that making inclusion distribute to have is not more than 30 ° controlled orientating deviation, promptly the orientations of extended inclusion is very important for the supression crack propagation.

Because sulphur is a kind of to the deleterious representative element of steel mechanical property, therefore, need the suitable method of improving intensity, so that steel is suitable for piston ring.For example, maximum 1% (quality) of JP-07-258792A suggestion permissible sulfur, it relates generally to the cast steel that adopts inadequate forging ratio to be processed into cylinder sleeve etc.But,, can obtain the low-cost manufacturing process of practicable piston ring by for example drawing of metal forming, rolling and crooked.If by metal forming the steel of this sulphur content maximum 1% (quality) is processed into wire rod as piston ring, then owing to do not reach the necessary strength of materials of metal forming, this steel may be disrumpent feelings in the drawing step.As a result, be difficult to produce the high piston ring of reliability.

According to aforesaid the present invention, preferred sulphur content is not higher than the material of 0.3% (quality) as slide unit, with the further bite-resistant performance of improving.Typically, as in the material (this material is processed to have the shape of product of high forging ratio) of piston ring, control and add sulphur highly significant.

By adding Ca together, can further put forward the doctor positive effect with sulphur.Elements C a reducing power is very strong, and it is contained among the MnS, the result, and Ca oozes out into engagement surface easily.The prevention of oozing out of Ca forms oxide compound in engagement surface, but helps to form the sulfide with lubricity.Yet excessive Ca is unfavorable for hot workability, therefore, preferably control Ca on be limited to 0.01% (quality).In order to reach above-mentioned effect, determine that preferably the Ca content range is 0.0001-0.01% (quality), more preferably 0.0005-0.01% (quality).

Add sulphur and Ca simultaneously and also can effectively improve machinability and grinding performance except that the bite-resistant performance.Particularly, the distribution of MnS and graphite granule separates out the machinability that can improve steel.Because the machinability that improves can be processed into the target shape with small curvature radius with the angle of steel, therefore, can easily produce the high piston ring of frizing ability.

Material of the present invention as slide unit and piston ring can contain Co, to improve erosion resistance, and corrosion resistance to sulfuric acid particularly.Elements C o and Mo can strengthen the extrusion effect of graphite, and promote the formation of oil film under the high pressure, thereby improve the bite-resistant performance and reduce kinetic friction coefficient.When content was not less than 0.5% (quality), this effect of Co was more remarkable.But Co is a kind of noble element, and excessive Co can not make performance further improve.Therefore, preferably control Co content and be not higher than 10% (quality), more preferably 2-5% (quality).

The steel of the present invention that is used as slide unit and piston ring contains the above-mentioned element of specified proportion, and surplus person mainly is an iron.Control other element total amount and be not higher than 10% (quality), more preferably no higher than 5% (quality).

Steel of the present invention can further contain one or more following elements, and concrete content is as follows:

P≤0.1% (quality), Mg≤0.01% (quality), B≤0.01% (quality), Zr≤0.1% (quality).

Optimum condition of the present invention is to make metal structure contain area in organizing the whole area in cross section than the non-metallic inclusion that is not higher than 2.0%, thus, prevent to be shaped to and fracture takes place in the drawing process of wire rod and prevent from during wire rod is made coiled material, to take place disrumpent feelings in steel.This particular organization typically is suitable for the piston ring manufacturing process, and this manufacturing process is attended by the moulding and the processing of thin wire simultaneously, so that set up the high manufacturing process of a kind of productivity.

As additional effect of the present invention, nitriding further improves bite-resistant performance and wear resistance.Nitriding can be carried out together with other surface treatments such as PVD or plating Cr, no matter reason is whether surface treatment of steel, all has excellent bite-resistant performance.With the piston ring is example.This surface treatment is applied on the main slipping plane of the piston ring that contacts with cylinder sleeve usually, but is not suitable for being applied to the friction surface that contacts with piston.In a word, can not expect to restrain the generation of adhesive wear by traditional surface treatment.But material of the present invention needn't carry out surface treatment and just have excellent bite-resistant performance, can prevent the generation of adhesion reaction, and is therefore, particularly useful as piston ring.

Because material of the present invention has the metal structure that has the graphite phase, it can carry out intercalation processing, thus, and by for example being immersed in CuCl ₂In the solution, foreign molecules or ion are embedded in the layer molecule tissue of graphite, further improve sliding properties.In addition, the graphite granule that is in the intercalation processing state plays the polymerization catalyzer.Therefore, this material is changed to become to be adapted to pass through polymeric coating (coated polymer film) or change as pretreated intercalation and makes the state of lubricating oil polymerization, so that be provided at the slide unit of the maintenance self lubricity that the polymerization reaction causes during the sliding motion.

The accompanying drawing summary

Fig. 1 is the Photomicrograph of observed graphite granule distribution situation on the cross section of material of the present invention (sample 3);

Fig. 2 is the Photomicrograph of observed graphite granule distribution situation on the different cross section of the same material of another Zhang Zaiyu Fig. 1;

Fig. 3 is the Photomicrograph of observed graphite granule distribution situation on the cross section of control material (sample 14);

Fig. 4 is the Photomicrograph of observed graphite granule distribution situation on the different cross section of the same material of another Zhang Zaiyu Fig. 3;

Fig. 5 is the microstructure synoptic diagram that a cover is used for explaining the sulfide inclusion parallelism.

Fig. 6 is the graphic representation that is used for illustrating the influence of the angle counter stress intensity factor between stress direction and the direction of crack propagation;

Fig. 7 is the synoptic diagram of the frictional wear experiment of explanation under ultra-high voltage;

Fig. 8 is the synoptic diagram of the reciprocal wear test of explanation;

Fig. 9 is used to explain lubricated Stribeck figure, explanation be the inverse of load and the relation between the kinetic friction coefficient.

Embodiment

Will be expressly understood further feature of the present invention by the following examples.

Embodiment 1

In high frequency furnace, several steel of melting under the atmospheric environment, adjustment makes it have the chemical constitution shown in the table 1, and is cast into the ingot casting that sectional dimension is 220mm * 220mm.In the table 1, sample 1-6 satisfies qualification of the present invention.Sample 11-16 be the contrast steel, wherein, sample 16 correspondences be the JIS SUS440B that is used for the conventional piston ring.

Table 1

Specimen coding	Chemical constitution [% (quality)]
																	????C	????Si	????Mn	????Cr	????Al	????S	??Mo	????W	????V	????Mo+W	??Mo+W+ ????V	????Ca	????Ni	????Cu	????Co	????Fe
	????1 ????2 ????3 ????4 ????5 ????6 ????11 ????12 ????13 ????14 ????15 ????16	????0.42 ????0.66 ????0.79 ????0.98 ????1.42 ????0.88 ????0.55 ????1.00 ????0.55 ????0.78 ????0.55 ????0.80	????1.85 ????0.93 ????1.52 ????2.32 ????2.78 ????1.55 ????1.49 ????0.25 ????1.51 ????1.23 ????1.35 ????0.31	????2.83 ????1.21 ????1.98 ????1.03 ????1.01 ????1.05 ????0.71 ????0.31 ????0.72 ????0.46 ????0.55 ????0.40	????0.25 ????0.45 ????0.31 ????0.21 ????0.01 ????0.03 ????0.21 ????1.48 ????1.01 ????0.03 ????0.60 ????17.5	????0.31 ????0.78 ????1.48 ????1.03 ????1.91 ????1.03 ????＜0.01 ????1.53 ????＜0.01 ????1.34 ????＜0.01 ????＜0.01	????0.29 ????0.13 ????0.06 ????0.12 ????0.03 ????＜0.01 ????＜0.01 ????＜0.01 ????0.35 ????0.06 ????0.31 ????＜0.01	??0.5 ??2.0 ??7.2 ??7.5 ??2.9 ??1.05 ??1.0 ??1.8 ??4.8 ??4.2 ??0.9 ??1.0	????＜0.01 ????2.9 ????5.1 ????10.0 ????3.0 ????＜0.01 ????2.0 ????3.4 ????9.9 ????2.1 ????0.9 ????＜0.01	??＜0.01 ??1.2 ??＜0.01 ??0.5 ??＜0.01 ??＜0.01 ??＜0.01 ??＜0.01 ??＜0.01 ??＜0.01 ??＜0.01 ??＜0.01	????0.5 ????4.9 ????12.3 ????17.5 ????7.9 ????1.05 ????3.0 ????5.2 ????14.7 ????6.3 ????1.8 ????1.0	????0.5 ????6.1 ????12.3 ????18.0 ????7.9 ????1.1 ????3.0 ????5.2 ????14.7 ????6.3 ????1.8 ????1.0	????0.0002 ????0.0010 ????0.0030 ????0.0060 ????0.0098 ????＜0.0001 ????0.0003 ????＜0.0001 ????0.0002 ????0.0050 ????＜0.0001 ????＜0.0001	????2.96 ????0.2 ????0.3 ????0.5 ????2.1 ????0.8 ????＜0.05 ????＜0.05 ????＜0.05 ????2.53 ????1.44 ????＜0.05	????0.1 ????2.8 ????1.1 ????1.3 ????0.8 ????0.8 ????＜0.05 ????＜0.05 ????0.8 ????＜0.05 ????＜0.05 ????＜0.05	????＜0.01 ????＜0.01 ????＜0.01 ????＜0.01 ????＜0.01 ????＜0.01 ????＜0.01 ????＜0.01 ????＜0.01 ????＜0.01 ????＜0.01 ????＜0.01																	Surplus surplus surplus surplus surplus surplus surplus surplus surplus surplus surplus surplus

Except that sample 13, the forging ratio with about 598 is thermally processed into the wire rod that sectional dimension is 9mm * 9mm with each ingot casting.Sample 13 is forged, but fail to be processed into sample because of rupturing during the hot-work of after forging, carrying out in succession.

Under predetermined condition, wire rod is annealed, and quench afterwards and tempering, so that its hardness is adjusted to about 45HRC.Adopt observation by light microscope to quench and the surface structure of tempered wire rod under etch state not, with the distribution of the graphite granule in the surface measurements tissue, that is: the average particle size particle size of graphite granule and area ratio.By image analysis is carried out in ten visual fields observing, the distribution of research graphite granule under 1000 times of opticmicroscopes.The size of graphite granule represents that with the diameter of proper circle described proper circle is identical with the area of the graphite granule that is detected.In the tissue of sample 1-6, mean sizes is that the area ratio that the graphite granule of 0.3-2 μ m distributes is 0.5-5%.

Fig. 1-the 4th illustrates the Photomicrograph of the distribution situation of graphite granule in sample 3 and 14.In the matrix of sample 3, detect and separated out tiny graphite granule and separate out, and in the matrix of sample 14, have thick graphite granule.The reason of discrepancies of sample 3 and 14 on particle size can be done description below: because sample 4 contains the Cu and the Al of an amount of ratio, tiny Cu-Al intermetallic compound particle was separated out before graphite is separated out, and, obtain tiny graphite granule as the site of separating out of graphite.On the other hand, owing to lack Cu or Al, the Cu-Al intermetallic compound can't play a role mutually in the sample 14, and graphite is grown up into big particle as a result.Table 2 has provided the distribution situation of graphite granule in all samples that comprise sample 3 and 14.At sample 11,12, do not detect the distribution of graphite granule in 15 and 16 the matrix.

At H ₂: N ₂In=1: 1 the atmosphere, under 530 ℃ to each sample ion nitriding 5 hours, and as the sample of estimating bite-resistant performance and wear resistance.The bite-resistant performance is used friction wear testing machine shown in Figure 7, estimates by the ultra-high voltage frictional wear experiment.Actual conditions is as follows: measure the rotary torque to the mill part that keeps wearing and tearing to contact with sample.Regard the time that rotary torque increases suddenly as interlock begin, the load of this moment is be evaluated as scuffing load.Calculate kinetic friction coefficient by the rotary torque to the mill part under the 10MPa load.Among Fig. 7, numeral 1 is a sample, and numeral 2 is that symbol F is a load to the mill part.

The size shape of sliding surface: size 5mm * 5mm's is square

Friction velocity: 2m/ second

Act on the pressure of friction surface: original pressure 1.5MPa

The 0.5MPa/ branch of advancing the speed

Lubricating oil: #30 machine oil

Lubricating oil only the initial stage with 10cm ³/ minute speed drip, but just stop afterwards.

To mill part: JIS FC250 (grey cast iron of hardness 100HRB)

Adopt reciprocal wear testing machine to estimate wear resistance, wherein, the sample of diameter 8mm, long 20mm rubs to mill part (FC250) by to-and-fro movement and diameter 20mm's, to measure the wearing and tearing width of sample.Fig. 8 is the synoptic diagram of reciprocal wear testing machine.Introduce other abrasive conditions below.Among Fig. 8, numeral 1 is a sample, and numeral 2 is that symbol F is a load to the mill part, and symbol OIL is a lubricating oil.

Pressure load: 500N

Every round-robin sliding distance: 130mm

Maximum slip velocity: 0.5m/ second

Lubricating oil (drippage): #30 machine oil

To mill part: JIS FC250 (grey cast iron of hardness 100HRB)

Table 2 shows the measuring result that scratches load, kinetic friction coefficient and wearing and tearing width and nitrided case hardness.

Table 2

Specimen coding	Graphite Distribution		The carbide of vanadium	Nitrided case hardness (HV)	Scratch load (MPa)	Kinetic friction coefficient	Wearing and tearing width (mm)	Remarks
									Average particle size particle size (μ m)	Area is than (%)
	????1 ????2 ????3 ????4 ????5 ????6	????0.4 ????0.5 ????0.8 ????0.7 ????1.9 ????0.7									????0.8 ????0.9 ????3.5 ????2.6 ????4.1 ????1.9	Not having to have or not does not have	????853 ????890 ????930 ????910 ????950 ????895	????12.5 ????11.5 ????10.5 ????13.5 ????10.5 ????12.6	????0.11 ????0.12 ????0.07 ????0.08 ????0.07 ????0.06	????0.55 ????0.65 ????0.5 ????0.55 ????0.51 ????0.51	The embodiment of the invention
????11 ????12 ????14 ????15 ????16			Not detecting 6.2 does not detect	????0 ????0 ????5.8 ????0 ????0	Do not have	????445 ????773 ????723 ????563 ????1032	????6.5 ????7.0 ????6.0 ????7.0 ????7.5	Do not detect	????1.53 ????0.71 ????0.64 ????1.62 ????0.53	Reference examples

Table 2 result confirms: all the sample 1-6 scuffing load height and the wearing and tearing width that satisfy the present invention's definition are little, so all have excellent bite-resistant performance and wear resistance.Particularly, sample 3-6 has low kinetic friction coefficient and the performance that is suitable as slide unit.On the other hand, the control sample bite-resistant performance that distributes of the specific graphite granule of all discontented unabridged versions inventions is relatively poor.Sample 11-15 is owing to the Cr and the Al that lack as the nitriding hardening element, and their nitriding hardness deficiency causes wearing no resistance.

The sample of the embodiment 1 that nitriding is not handled carries out the interlock experiment under above-mentioned similarity condition.The result is as shown in table 3.The sample 1-6 that satisfies the specific graphite granule distribution of the present invention needn't carry out surface treatment, just has excellent bite-resistant performance.On the other hand, the scuffing load of control sample 14 is less.When examining under a microscope the sliding surface of interlock experiment control sample 14 afterwards, fracture has taken place in the graphite granule that can detect the periphery place.This observations means that graphite bits have invaded sliding surface, causes sliding properties to descend.

Table 3

Specimen coding	Graphite Distribution		Scratch load (MPa)	Remarks
					Average particle size particle size (μ m)	Area is than (%)
	????1 ????2 ????3 ????4 ????5 ????6	????0.4 ????0.5 ????0.8 ????0.7 ????1.9 ????0.7					????0.8 ????0.9 ????3.5 ????2.6 ????4.1 ????1.9	????11.5 ????10.5 ????11.0 ????13.0 ????12.0 ????11.5	The embodiment of the invention
????11 ????14			Do not detect 6.2	????0 ????5.8	????6.5 ????6.0	Reference examples

Embodiment 2

In sample in the table 11 and 15 each is rolled into the coiled material of diameter 5.5mm, then, by drawing with cold rollingly be processed into the flat wire rod shape that sectional dimension is 1.5mm * 3.1mm.Sample 1 is shaped to described target shape without any difficulty, but sample 15 is disrumpent feelings in the drawing step because cold-forming property is poor.At microscopically, along with the vertical direction of rolling direction observe sample 1-15 not the as-drawn blank metal structure and analyze, to measure the area ratio of non-metallic inclusion.The area of non-metallic inclusion ratio is 1.86% in the sample 1, and sample 15 is 2.23%.The comparative observation result can think that the disrumpent feelings reason of sample 15 except that excessive sulphur, also is area than the excessive non-metallic inclusion that is higher than 2.0%.

Embodiment 3

Under condition similarly to Example 2, with sample 1-6, each in 11 and 12 is processed into the flat wire rod shape that sectional dimension is 1.5mm * 3.1mm, 1000 ℃ of heating 30 minutes down, quenches and is tempered to the hardness of about 510HV.Sample after handling is adopted milling cutter, with the amount of feed machining of 10000 rev/mins rotation frequencys and 1mm/ second ten times, so that the frequency of occurrences of research overlap.Table 4 has provided the experimental result of the overlap frequency of occurrences.

Table 4

Specimen coding	The overlap frequency of occurrences	Remarks
			????1 ????2 ????3 ????4 ????5 ????6	????0 ????0 ????0 ????0 ????0 ????7	The embodiment of the invention
????11 ????12	????8 ????10	Reference examples

In sample 11 and 12, all detect the appearance of overlap, still, add among the sample 1-5 of an amount of S and overlap all do not occur.This result confirms: it is obvious for restraining the overlap effect to add S.As a result, piston ring can the high-level efficiency manufacturing.

Embodiment 4

Prepare the identical ingot casting of sample in chemical constitution and the table 11 separately.Ingot casting is thermally processed into the wire rod that sectional dimension is 3.0mm * 3.0mm, and wherein the variation range of forging ratio is 1-10000.By quenching and tempering is adjusted into 400HV with the hardness of hot-work wire rod.According to abovementioned steps, the parallelism of sulfide inclusion in the surface measurements tissue (aspect ratio 3 or bigger), described surface structure is parallel with the length direction of elongate wire, and as the periphery of piston ring.

The adjusted wire rod of hardness is carried out the three-point bending experiment that span is 30mm.Not disrumpent feelings sample is evaluated as A up to 10mm with Bending Deviation, and disrumpent feelings sample is evaluated as B.This experimental result is for judging whether quenching and tempered wire rod may be to have the piston ring of predetermined curvature highly significant by rolling brake forming.Table 5 shows experimental result.

Table 5

Specimen coding	Forging ratio	Parallelism (degree)	Disrumpent feelings evaluation
				????1-1 ????1-2 ????1-3 ????1-4 ????1-5	????1 ????10 ????500 ????2000 ????10000	????84.5 ????45.2 ????27.8 ????11.5 ????3.5	????B ????B ????A ????A ????A

Can be understood by table 5 result: the metal structure that the parallelism that wherein distributing is not more than 30 ° sulfide inclusion has excellent mechanical property, can restrain effectively during bending wire is circularized shape, take place disrumpent feelings.The surface structure parallel with piston ring periphery observed show: the parallelism and the aspect ratio of the sulfide inclusion between wire rod and the piston ring made by bent wire do not have considerable change.

The parallelism of the sulfide inclusion of observing on the wire rod surface structure has reflected the tissue of the piston ring of making by bent wire.Parallelism is not more than the mechanical property of 30 ° sulfide inclusion distribution can effectively improvement piston ring, does not worry taking place the often repeated stress failure of appearance in the conventional engines again.For this reason, it is suitable especially for the wire rod as piston ring parallelism to be carried out specific control.

Embodiment 5

In high frequency furnace, several steel of melting under the atmospheric environment are adjusted it and are had the chemical constitution shown in the table 6, and are cast into the ingot casting that sectional dimension is 220mm * 220mm.Compare with sample 21, sample 22 contains proportional higher relatively Mo, and sample 23 contains proportional higher relatively Co.

Table 6

W, V＜0.01% (quality), Ca＜0.0001% (quality)

Specimen coding	Chemical constitution [% (quality)]
													????C	??Si	??Mn	????P	??S	??Ni	??Cr	??Mo	??Co	??Cu	??Al	??Fe
	????21 ????22 ????23	??0.86 ??0.86 ??0.86	??1.75 ??1.69 ??1.68	??0.30 ??0.30 ??0.31	??0.008 ??0.010 ??0.008	??0.020 ??0.022 ??0.022	??0.30 ??0.30 ??0.31	??0.001 ??0.001 ??0.001	??0.98 ??1.97 ??0.99	??0.01 ??0.01 ??3.99	??0.82 ??0.76 ??0.87	??1.22 ??1.20 ??1.18													Surplus surplus surplus

Forging ratio with about 598 is thermally processed into the wire rod that sectional dimension is 9mm * 9mm with each ingot casting.Wire rod is annealed, and, hardness is adjusted to about 40HRC afterwards by quenching and tempering.Afterwards, observe to quench and the surface structure of tempered wire rod under etch state not, with the distribution of measuring graphite granule (average particle size particle size of the graphite granule in the surface structure and the area of graphite granule than).By ten images observing are analyzed the distribution of research graphite granule under 1000 times of opticmicroscopes.

Table 7

Specimen coding	Graphite granule mean sizes (μ m)	The area of graphite granule in organizing the cross section total area is than (%)	Be of a size of 1 μ m or the bigger area of graphite granule in organizing the cross section total area than (%)	The mean sizes (μ m) of 1 μ m or bigger graphite granule
					????21 ????22 ????23	????0.55 ????0.50 ????0.75	????1.69 ????2.05 ????3.50	????0.41 ????0.14 ????0.70	????1.15 ????1.20 ????1.33

Sample 21-23 all has the tissue that exists tiny graphite to separate out.As shown in table 7, the area ratio that the size that is distributed is not more than the graphite granule of 1 μ m is 1-4%.In sample 21-23 in any, the average particle size particle size that is of a size of 1 μ m or bigger big graphite granule is 1-1.5 μ m, and area is than less than 1%.That is to say, be understood that it is fine particle that most of graphite is separated out, and the area ratio of big graphite granule and all graphite granules is controlled in and is lower than 1/4.

With the sample of each sample with the kinetic friction coefficient that judges.The evaluation employing of the kinetic friction coefficient friction wear testing machine (friction velocity except) identical with Fig. 7 carries out.Experiment condition is as described below.By acting on moment of torsion on the mill part and loadometer are calculated each kinetic friction coefficient constantly that load progressively increases.Fig. 9 shows the inverse of load and the relation between the kinetic friction coefficient.

The shape of sliding surface: 5mm * 5mm's is square

Friction velocity: 1 meter per second

Act on the pressure of friction surface: starting stage 1.5MPa

The 0.5MPa/ branch of advancing the speed

Lubricating oil: #30 machine oil

With 10cm ³/ minute speed drip continuously

To mill part: JIS FC250 (grey cast iron)

Fig. 9 is so-called " Stribeck ' s figure ", representative be the load-up condition that is applied on the friction sliding members, reflected the relation between load character (X-coordinate) and the frictional coefficient (ordinate zou).Lubricating status can be estimated by this figure.For embodiments of the invention, because friction velocity keeps 1m/ invariable second, axis of abscissa is represented with the inverse of load.In every curve of Fig. 9, from frictional coefficient minimal data point (extreme value) to the right a side (low-stress one side, i.e. arrow institute how) corresponding be that lubricant film does not damage, reach the zone of hydrodynamic lubrication.What left side (a heavily stressed side) was corresponding is because of solid components directly contacts together, occurs the zone of fluid and solid lubrication simultaneously.Relation among Fig. 9 shows: along with frictional coefficient minimal data point (extreme point) among the figure is moved to the left, even under condition of high ground stress, also can reach the unspoiled Liquid Lubrication Condition of fluid film easilier.

Be understood that by Fig. 9 result Mo content can more keep fluid film under the high-load than sample 21 high samples 22, and Co content still can keep fluid film than sample 21 high samples 23 under the load that further increases.The raising of fluid film hold facility has proved the effect of Mo and Co, promptly above-mentioned extrusion effect.

The data point correspondence of every curve left end be because the load when the interlock frictional wear experiment occurring and stopping.Compare with sample 21, sample 22 and 23 is owing to be added with Mo and Co, and its leftmost side data point is moved to the left (shifting to the higher side of stress), causes the further improvement of bite-resistant performance.And kinetic friction coefficient also descends in general.In a word, by adding Mo and/or Co, further strengthened graphite and separated out influence sliding properties.

According to the present invention, obtained need not surface treatment, it is low and have the steel of self lubricity just to have excellent bite-resistant performance, a frictional coefficient, the result, described steel is suitable for various slide units, has reduced the energy waste that friction causes.In addition, owing to simultaneously the distribution of sulfide inclusion is controlled, described steel can be processed into cylinder sleeve and the lighter piston ring of piston wear degree.As a result, the present invention helps significantly to improve the environmental performance and the weather resistance of oil engine.And because described steel processing characteristics and machinability excellence, it can be processed into slide unit or piston ring with low manufacturing cost, and pre-set time is also shorter.In other words, consider, the present invention is to provide use properties and all excellent material of processing characteristics, so it is a kind of real useful technology as slide unit from industrial point of view.

Industrial applicability

Material provided by the invention can be used as slide unit and for example is installed in piston ring, cylinder sleeve or blade in motor car engine etc. and sliding surface bearing, roller bearing, ball bearing, gear and mould.

Claims (16)

1. material as the self-lubricating slide unit, these parts are made of a kind of steel, this steel contains, in mass: be not less than 0.4% to the C (carbon) that is lower than 1.5%, 0.1-3.0%Si, 0.1-3.0%Mn, 0 (comprising 0)-0.5%Cr, 0.05-3.0%Ni, 0.3-2.0%Al, (Mo+W+V) total amount is the Mo that is selected from of 0.3-20%, at least a element of W (tungsten) and V (vanadium), and 0.05-3.0%Cu, wherein, can observe the graphite granule that average particle size particle size is not more than 3 μ m in the cross section of described steel metal structure.

2. according to the material of claim 1, wherein, organize cross-section to graphite granule organizing to occupy in the total area in cross section and be not less than 1% area ratio, and have and be not more than 3 μ m average particle size particle size.

3. according to any one the material in claim 1 and 2, wherein, in organizing the cross section, do not observe the carbide of vanadium.

4. according to any one the material among the claim 1-3, wherein, described steel contains in mass: (Mo+W) total amount is at least a element that is selected from Mo and W of 0.3-5.0%, and the V that is lower than 0.1%.

5. according to any one the material among the claim 1-4, wherein, described steel contains the Al of 0.7-2.0% in mass.

6. according to any one the material among the claim 1-5, wherein, described steel contains the Mo of 1.5-3.0% in mass.

7. according to any one the material among the claim 1-6, wherein, described steel contains in mass and is not higher than 10% Co.

8. according to any one the material among the claim 1-7, wherein, described steel contains in mass and is not higher than 0.3% S (sulphur).

9. material according to Claim 8, wherein, described steel further contains and is not higher than 0.01% Ca in mass.

10. according to any one the material among the claim 1-9, wherein, described steel has been carried out the nitriding processing, with as slide unit.

11. wire rod as piston ring, this piston ring is made by a kind of steel, this steel contains, in mass: be not less than 0.4% to the C (carbon) that is lower than 1.5%, 0.1-3.0%Si, 0.1-3.0%Mn, 0 (comprising 0)-0.5%Cr, 0.05-3.0%Ni, 0.3-2.0%Al, (Mo+W+V) total amount is the Mo that is selected from of 0.3-20%, at least a element of W (tungsten) and V (vanadium), and 0.05-3.0%Cu, wherein, can observe the graphite granule that average particle size particle size is not more than 3 μ m in the cross section of described steel metal structure, and wherein, parallel with piston ring periphery organize cross-section to the distribution of sulfide inclusion be such: the angle of cut when each straight line by each sulfide inclusion major axis intersects mutually is not more than 30 °, and the described angle of cut can be regarded as a kind of parallelism and measures.

12. according to the wire rod of claim 11, wherein, the metal structure cross-section to graphite granule organizing to occupy in the total area in cross section and be not less than 1% area ratio, and have and be not more than 3 μ m average particle size particle size.

13. according to any one the wire rod in claim 11 and 12, wherein, described steel contains the Co that is not higher than 10% quality.

14. according to any one the wire rod among the claim 11-13, wherein, described steel contains the S (sulphur) that is not higher than 0.3% quality.

15. according to the wire rod of claim 14, wherein, described steel further contains the Ca that is not higher than 0.01% quality.

16. any one the wire rod according among the claim 11-15 wherein, has carried out the nitriding processing to described steel, with as piston ring.

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