KR20110110179A - Composition of particulate materials for forming self- lubricating products in sintered steel, product in self- lubricating sintered steel and process for obtaining self-lubricating products in sintered steel - Google Patents

Abstract

The composition comprises iron as the main particulate metal material; At least one particulate alloy element having a function of curing a structural matrix of iron; Formed by chemical elements that stabilize the ferrite phase during sintering, and with additional alloying elements included in the composition, when formed with chemical elements that stabilize the ferrite phase of the structural matrix of iron, they are easily formed by the precursor compound itself. It is equipped with the precursor of the particulate compound which is carbide or a carbonate. The composition is adapted by compaction or powder injection molding. The process of the present invention can yield a self-lubricating sintered steel product with the composition.

Description

COMPOSITION OF PARTICULATE MATERIALS FOR FORMING SELF-LUBRICATING PRODUCTS IN SINTERED STEEL, PRODUCT IN SELF-LUBRICATING SINTERED STEEL AND PROCESS FOR OBTAINING SELF-LUBRICATING PRODUCTS IN SINTERED STEEL}

The present invention relates to a special technique for producing finished products (parts) and semi-finished products (multiple objects) formed from a composition of particulate matter (in the form of metal and nonferrous metal powders) designed to be sintered, wherein the product is In addition to the constituent elements of the metal structural matrix of the product being formed, the microstructure of the self-lubricating product exhibits a low coefficient of friction applied to the high strength and high mechanical strength of the sintered part or product, a continuous metal matrix that can give the sintered product. It has a precursor phase of a solid lubricant that produces a precipitate of solid lubricant in the volume of the metal matrix that is guided to form and forms particles by decomposition during the sintering step.

The present invention is directed to other techniques or processes for obtaining said parts or articles by powder metallurgy and said metal compounds for forming self-lubricating materials in situ during sintering to sintered steel parts or articles obtained from said compounds.

Given the earlier stages of technology development, there is a need to develop high performance functional materials that are specifically designed for each particular group of applications. In many mechanical engineering applications, there is a need for materials having both high mechanical strength and high wear resistance with a low coefficient of friction.

It is estimated that 35% of the total mechanical energy produced in the universe is lost by lubrication efficiency and converted to heat by friction. Apart from energy loss, the heat generated degrades the performance of the mechanical system by heating. Therefore, the low coefficient of friction of mechanical parts under friction is not only very important, but also important for the energy economy, but not only increases the durability of the parts within the mechanical system, but also contributes to environmental conservation because of the reduced waste material.

The method used to reduce friction and resistance between relative moving surfaces is to keep them separate and separated from each other. In the possible lubrication method, the hydrodynamic (fluid lubrication) method is most often used. In the hydrodynamic lubrication method, an oil film is formed which completely separates the relative moving surfaces. However, the use of fluid lubricants has been pointed out that applications at very high or very low temperatures typically have problems and the application of fluid lubrication may react chemically when the fluid lubricant acts as a contaminant. In addition, in situations where the cycle is stopped and lubrication is limited, or in the case where continuous formation of the oil film is impossible, contact between the two parts occurs and eventually the parts wear out. Dry lubrication, ie the use of solid lubricants, is a traditional lubrication method, but since the solid lubricant acts, there must be no contact between the part surfaces but no rupture of the formed layer.

Solid lubricants have been well applied in the area of lubrication in question. They can be used at very high temperatures under high load conditions and chemically reactive environments where conventional lubricants cannot be used. Moreover, dry lubrication (solid lubricant) is on the one hand environmentally clean.

Solid lubricants may be applied to tribologically paired parts which are applied to the volume of material of the parts in the form of a film or in the form of a second phase particle which is produced or deposited on the surface of the part. When a particular film or layer is applied and they wear out, metal to metal wear occurs and rapid wear of the unprotected contact surfaces of relatively movable parts occurs. Under these circumstances, a film or layer is applied, replacement of lubricant is difficult and oxidation and deterioration must be further considered. Therefore, a more suitable solution to increase the life of the material is to combine a solid lubricant in the volume of the component material of the part to form the elemental structure in a synthetic material with a low coefficient of friction. This is possible through powder metallurgy techniques, in order to obtain a continuous composite material which already has dimensions and geometries close to the final product (semi-finished product) or final geometry and dimensions (final product), ie compacted by pressing, rolling, extrusion and injection molding To form a powder composition, which is then sintered.

Self-lubricating mechanical parts with low coefficients of friction, such as self-lubricating bushings, are manufactured using powder metallurgy techniques from metal powders that form the metal structure matrix of sintered parts mixed with solid lubricant powders. The parts have been used in various household appliances and small equipment such as printers, electric shavers, drills, blenders and the like. A well known prior art solution for structural matrices is to use brass, copper, silver, pure metals. As the solid lubricant, molybdenum sulfide (MOS2), silver (Ag), polytetrafluoroethylene (PTFE) and diselenide molybdenum are used. Bushings made of a self-lubricating material with a copper matrix and mainly brass, including low melting point desulfurized molybdenum and selenium, graphite powder solid lubricant particles, have been manufactured and used for several decades in many engineering applications. However, these parts do not exhibit high mechanical strength as a function of the high volumetric capacity (25-40%) of the solid lubricant particles because of the microstructural factors on the mechanical strength of the parts. These high capacity solid lubricants are not optimized for the applications required for the part to have high mechanical strength and microstructural parameters such as the average free path between particles in the formed synthetic material and the size of the solid lubricant particles dispersed in matrix form. It has been considered that it is necessary to have a low coefficient of friction both in the mechanical strength of the metal matrix (strength and hardness). The high volume percentage of solid lubricants that have inherently low strength to shear does not contribute to the mechanical strength of the metal matrix. Moreover, solid lubricant particles are easily sheared and function as a function of shear forces that occur during the step of further reducing the continuity of the metal structural matrix of the self-lubricating composition formed, compacting the composition and mechanically homogenizing the powder composition (running with a mixer). The shape is changed. Moreover, the low hardness of the metal matrix allows gradual blockage of solid lubricant particles to occur at the contact surface of the sintered material or article. Therefore, in order to maintain a sufficiently low coefficient of friction, high volume percentages of solid lubricants with the construction of dry self-lubricating compound materials have been commonly used.

A partially differentiated and more developed scenario compared to what has already been described is disclosed in US 6890368A, which is used at temperatures in the range of 300 to 600 degrees Celsius, with sufficient traction resistance (Rm ≥ 400Mpa) and a friction coefficient of 0.3 or less. A self lubricating composition that can be used has been proposed. The document forms a metallic structural matrix and comprises solid lubricant particles in its volume and mainly comprises hexagonal boron nitride, graphite or compositions thereof, wherein the material has a temperature of 300 to 600 degrees Celsius and a sufficient traction resistance (Rm? A solution for obtaining low friction coefficient parts or products is sintered from a composition of particulate matter in a state of 400 MPa) and a small coefficient of friction of 0.3 or less.

Hexagonal nitriding with structural brittleness and low mechanical strength after sintering, as disclosed in the Brazilian patent application (temporary application number 018080057518) dated September 12, 2008, in the name of the applicant and the same applicant. It is possible to obtain a part or a product obtained by solidifying a powder composition having both a solid lubricant powder such as boron and graphite and a structural matrix malvale at the same time.

This drawback occurs as a result of inadequate dispersion (scattering) of the solid lubricant phase by shearing the powder particles of the structural matrix during the mixing (compensation) step of the part or product to be produced.

Solid lubricants tend to surround the particles during the mixing and adaptation step where they are dispersed by shear between the particles in the structural matrix sphere and the solid lubricant yields to stresses that exceed low shear stresses.

On the other hand, the presence of a solid lubricant between the particles of the structural matrix formed by shear inhibits the formation of metal contacts between these particles forming the structural matrix of the composition during sintering, which structurally The embrittlement saki contributes to reducing the continuity of the structural matrix phase of the composite material.

These problems can be largely solved through the solution proposed in the Brazilian patent application described above by obtaining a composite material with greater mechanical strength than the prior art solutions.

However, in the solution proposed in the above patent application of the same applicant as the applicant of the present invention, for example, hexagonal boron nitride, graphite or non-ferrous metal particles such as these are metallic materials forming the structural matrix of the composite product to be sintered. The addition of at least one particle alloying element to the mixture is required, and thus the liquid phase bonds into discrete particles between the structural matrix of the solid lubricant and the particulate matter forming the nonferrous metal particles during the sintering step of the adapted metallurgical composition. To prevent the particulate solid lubricant from being dispersed to embrittle and surround them during the mixing and adapting (densifying) part or product to be made. In view of the above drawbacks, it is desirable to provide a solution that does not require premixing of solid lubricant particles in the metallurgical composition to be sintered, as well as the addition of alloying elements of the metallic composition to form a liquid phase during sintering. .

Therefore, it is an object of the present invention during the sintering to form a finished or semi-finished product of self-lubricating sintered steel which is finely dispersed in the solid lubricant phase resulting from the sintering treatment, exhibiting high hardness and high mechanical strength and having high continuity of the structural matrix. There is provided a composition of particulate matter for forming sintered steel with a structural matrix of metals.

It is an object of the present invention to finely distribute the phase of solid lubricants produced during sintering, exhibit high hardness and high mechanical strength and have a high degree of continuity of the structural matrix to sinter to form semifinished or finished products of self-lubricating sintered steel. It is to provide a composition of particulate matter for forming sintered steel that allows a metal structural matrix during.

It is an object of the present invention to apply pressure rolling and other methods after sintering the above-described composition which is finely decomposed to the solid lubricant phase of graphite produced during sintering and has a high hardness, high mechanical strength and low friction coefficient and exhibits high continuity of the metal structural matrix. It is to provide a self-lubricating sintered steel obtained by fitting through powder compaction through injection molding.

It is a further object of the present invention to provide a process as described above from the composition of particulate matter in a process which does not involve premixing of solid lubricant particles in the metal composition to be sintered and does not add alloying elements in the metal composition to form a liquid phase during sintering. To provide a process for obtaining lubricated sintered steel products.

In the first aspect of the present invention, the object of the present invention described above is iron; At least one particulate alloy element having a function of curing iron forming a matrix of an iron structure; Through a composition of particulate matter for producing a self-lubricating sintered steel product that is preformed by compacting and injecting a composition comprising a non-ferrous metal composition that is a precursor to a solid lubricant phase of graphite to be formed in the product during sintering. Obtained.

In the method of practicing the present invention, the nonferrous metal particulate composition is a carbide or carbonate type composition comprising a chemical element that stabilizes the ferrite phase of the iron structure matrix.

In another method of practicing the invention, the nonferrous metal particulate composition is derived from a chemical element that stabilizes the ferrite phase, and additional particulate alloy elements having a function of stabilizing the ferrite phase need to be included in the metal composition.

In the present invention, graphite particles are formed by separation of precursor phases during sintering of parts or articles. Examples of precursor phases implemented in the present invention are silicon carbide (SiC), molybdenum carbide (Mo ₂ C), chromium carbide (Cr ₃ C ₂ ), and the like. In preparing the powder mixture constituting the new composition,

In preparing the powder mixture constituting the new composition material, the carbide in the form of fine powder particles (preferably 5 to 25 μm) is mixed with iron powder (main element) and other powders of alloying materials present in the powder mixture. do.

Most designated carbides for causing precipitation of graphite nodules in the iron matrix forming self-lubricating sintered steel have, in their molecular formula, chemical elements that strongly stabilize the ferrite phase present, for example, in silicon carbide (SiC). During sintering, ie at the sintering temperature of the part or product, silicon carbide (SiC) dissociates and the chemical element silicon becomes a solid solution in iron, ie in the structural matrix of iron. As in the process in which SiC dissociates, the amount of soluble Si results in an increase in the iron matrix surrounding the dissociated SiC particles. As can be seen in the iron-silicon equilibrium diagram, the chemical element silicon strongly stabilizes the ferrite phase: the peak of loop a ← → (a + γ) in the Fe-Si diagram is dependent on the weight of Si (4.2% at). By 2.15%. Therefore, during the sintering of the sintered steel between 1125 and 1250 degrees Celsius, the concentration of silicon dissolved in iron around the dissociated SiC particles reaches the gamma phase dissolution limit and transition of gamma ions in ferrite occurs. In the first case of the SiC dissociation process, on the other hand, the Si concentration does not reach the value required to stabilize the alpha phase around the dissociated SiC particles, and the particles produced by dissociation also become a solid solution and into the interior of the matrix. The iron matrix around the dispersed but dissociated SiC particles is transferred to the ferrite phase, and the process for stabilizing carbon is due to the very low solubility of carbon in the ferrite phase (when the maximum is 0.022% by weight at 727 degrees Celsius). It stops. Therefore, the released carbon as a result of carbide dissociation forms graphite nodules, which are surrounded by a layer of ferrite even though the remainder of the matrix may continue to exhibit a gamma image.

The present invention will be described in detail below with reference to the accompanying drawings by way of illustration of an embodiment of the invention.
Figures 1A, 1B and 1C schematically illustrate the evolution of the microstructure during the sintering step in which the carbide particles mixed with the iron powder (matrix) dissociate, while Figure 1A shows that the carbide particles have not yet reacted. The two phases of the microstructure of the initial stage of the non-processing process are shown, and FIG. 1B shows a state in which a partial dissociation of carbide has already occurred, and FIG. 1C shows a state in which dissociation is already completed.
FIG. 2 shows that in an ideal situation the solid lubricant should be in the form of individual particles or nodules that have a regular mean free path (λ) between the particles and the nodules and are evenly distributed in the volume of the material, and the high precision of the matrix of the composition material It is a schematic illustration of the preferred and ideal state of the distribution of solid lubricant particles or nodules in the volume of the compositional material in steel with a low coefficient of friction and maintaining a figure.
3 is a photograph of the microstructure of the material of the present invention in a state in which carbide particles are dissociated and already sintered, showing a matrix of graphite nodules and a composition material surrounded by a clear layer formed by ferrite phase.
4 is a photograph obtained at high resolution (20000 times) with a field emission gun (FEG-SEM) of an electron microscope as evidence of the structure in the form of nano-thickness graphite skin or flakes. It is a figure which shows the structure in detail.
FIG. 5 is a schematic simplified diagram of an example of compaction in the formation of a part or article to be sintered later, the compaction being made to provide a self-lubricating layer on two opposing sides of the product to be sintered; The process can be used when only one self-lubricating layer is required on one or more sides of the part to be sintered.
6A, 6B and 6C show a bar having a core of a metal alloy coated on its outer layer with a self-lubricating material, and obtained by compacting by extrusion of a tube of self-lubricating composition material and a bar of the self-lubricating composition material. It is a figure which shows the example of adaptation of a product.
FIG. 7 is a schematic simplified diagram of an example of compaction in the formation of a part or article to be subsequently sintered, which compaction is achieved by rolling the self-lubricating composition material on opposite sides of the plate or strip of the metal alloy.

As already mentioned above, one object of the present invention is to provide a composition of particulate matter which can be extruded or injection molded or compacted (press, rolled) to uniformly mix and form (densify), It is possible to have defined geometries (parts) in which the sintering operation can be carried out to obtain a product exhibiting a reduced coefficient of friction, high hardness and mechanical strength for a product obtained by the prior art.

The composition of the present invention comprises: a particulate major metallic material predominant in forming the composition, and at least one particulate alloying element having a function of curing the predominant material, the components comprising a structural matrix in the synthetic product in the steel to be sintered; During sintering it contributes to form particulate precursor material for obtaining solid lubricant nodules by dissociation.

According to the present invention, as shown in FIG. 2, the main particulate metal material forms the structural matrix 10 of iron is a precursor for producing a nod 20 of solid lubricant by dissociation during iron and sintering. Phase, and sintering is based on carbides or carbonates that are preferably formed with chemical elements that stabilize the ferrite phase in the structural matrix 10 of iron. When the precursor phase used does not have a composition, chemical elements capable of stabilizing the ferrite phase in the matrix 10 of iron and certain additional alloying elements sufficient to stabilize the ferrite phase are also added to the composition of the present invention. Should be.

Alloying elements having the function of curing the structural matrix of iron are formed of one element selected from, for example, chromium, molybdenum, carbon, silicon, phosphorus, manganese and nickel, but other elements such as vanadium and copper may be used. It should be noted that they can simultaneously perform the same function in the structural matrix with more elements than one alloy element.

The present invention needs to have an alloy hardening element capable of performing the function of curing the structural matrix of iron to be formed during sintering by fusion of the components (chemical homogenization), but this is limited to the alloying elements exemplified herein. It should be noted that it is not.

1A, 1B, 1C and 2 schematically illustrate the various stages in which the microstructure of the composition develops as a dissociation function of carbide (SiC) during sintering. FIG. 3 is an optical micrograph of the microstructure of the composition material formed after sintering, and FIG. 4 shows the structure of the deposited graphite present inside the nodules in the form of λλ skins or leaves of nano-thickness. This structure is positive for the formation of a tribological layer at the interface of the relative moving surface of the tribological pair which increases the efficiency of solid lubrication. The parallel addition of other alloying elements to stabilize the ferrite phase in the powder mixture to be formed of the composition has a tendency to increase the production of graphite nodules 20 by dissociation of the carbide particles mixed into the volume of the material while sintering the matrix Accelerate the increase in the alpha phase within.

The alloying elements that dissociate the carbides and stabilize the ferrite phase prevent carbon from solutioning in the matrix and form a layer of alpha phase 12 around the particles 11 in dissociation so that they are in a solid solution. When this contributes to increasing the hardness of the matrix, and if the hardness increased by the presence of these alloying elements in a solid solution in iron is not sufficient, then another alloying element must be added additionally to the powder mixture, which is why During this process, the matrix is liquefied and this achieves the hardness and mechanical strength required for the application. Therefore, in the present invention, the metal structural matrix of the material stabilizes the ferrite phase such as silicon and molybdenum dissolved in the iron matrix as a result of dissociation of the carbide mixed with the iron powder in the treatment of the material by powder metallurgy. It is automatically cured and formed by a solid solution with alloying elements.

In addition to those that must be present to stabilize the alloying elements, other alloying elements have the ability to control the hardness and mechanical strength of the matrix to achieve high performance against the tribological and mechanical behavior of the dry self-lubricating composition material produced during sintering. It can be added to the powder mixture with. Examples of other alloying elements which are preferably used to increase the hardness and mechanical strength of the matrix in the present invention replace Cr, Ni, Mn, W, V and C in addition to Si, No, P elements that strongly stabilize the ferrite phase. You may. In the present invention it is formed by two alternatives to the type of carbide used in the powdered mixture composition formulated for making products by powder metallurgy:

Alternative 1: Iron powder + particles of carbide powder (11) formed by a chemical element that stabilizes the ferrite phase (mixed at ≤10% in volume ratio) at sintering temperature to dissociate to produce graphite nodules (20) Powder particles of another chemical element called an alloying element having the function of increasing the hardness and strength of the structural matrix 10 of

Alternative 2: Carbon coining from carbide dissociation of particles of carbide powder (11) formed by a chemical element that stabilizes the iron powder + ferrite phase (mixed at ≦ 10% by volume) + carbide matrix Powder particles of other chemical elements called alloy elements having the function of increasing the hardness and strength of the structural matrix 10 of iron to prevent them, and other alloying elements present to adjust the mechanical properties of the structural matrix of the composition.

Since the structural matrix 10 of iron of the metal is the only microstructural element of the composition which contributes to the mechanical strength in the composition material to be formed, the high continuity of the matrix of the composition is the mechanical strength of the sintered part or component manufactured with the material. Will be raised. The maintenance of the high continuity of the metal structural matrix of the dry self-lubricating sintering composition material does not contribute to the mechanical strength of the product being sintered because the latter does not contribute to the mechanical strength of the material, in addition to low porosity and low volume ratio on the solid lubricant. In addition, the solid lubricant present in the volume of the material is uniformly distributed in the volume, i.e. having a regular mean free path (λλλ ") inside the structural matrix of iron 10 (see also FIG. 2) as separate particles or nodules. It must be dispersed in the form of 20. This results in a large lubrication efficiency and at the same time ensures a high continuity of the matrix, which ensures a high mechanical strength in the composition material. To prevent the solid lubricant particles from dispersing within the interface forming the layer of the solid lubricant as well as the support as well as the part being actuated (when rubbing in relative motion) and to prevent the solid lubricant particles from being covered by plastic deformation of the structural matrix. Play a role.

According to the invention, the additional alloying component which stabilizes the ferrite phase is formed of at least one element selected from phosphorus, silicon, cobalt, chromium and molybdenum. Although these elements are considered to be best suited to act separately or to interact with iron alpha phase stabilization at sintering temperatures (about 1125 degrees to 1250 degrees Celsius), the present invention is not only required to harm carbon dissociation but also as an illustration herein. It is to be understood that the alloying components used are also stabilized. When the composition of the present invention is adapted for compaction, the main particulate metal material (iron) preferably has an average particle size of between about 5 μm and about 90 μm. The curable element and the precursor component of the solid lubricant phase (compound) having the function of curing the structural matrix must have a particle size of less than about 45 μm; It should be noted that the average particle size of the main particulate metal material, ie iron, must always be larger than the average particle size of the precursor component (compound) on the alloying element and the solid lubricant.

When the composition of the present invention is adapted by injection molding, it is preferred that the main particulate metal material (iron) has a particle size between about 5 μm and about 25 μm.

In the same way, the alloying element and precursor component on the solid lubricant preferably have a particle size of about 5 μm and about 25 μm. When the composition is found to be compatible by injection molding or extrusion before sintering, the composition is shaped by extrusion from about 40 to 45% by being adapted by injection molding of paraffins and other waxes, EVA, low melting point polymers. Thereby further comprising at least one organic binder selected from low melting polymers in formulations ranging from about 15 to 45% of the total volume of the metallurgical composition. The organic binder is extracted from the composition, for example by evaporation, after the adaptation step and before the sintering step is carried out. The composition described above is obtained by mixing an appropriate amount of particulate matter selected for the continuous acquisition of the self-lubricating sintered product and for the formation of the composition. Mixtures of other particulate materials are homogenized and compacted, i.e., densification is carried out by pressing, rolling or extruding, or by injection of powder, resulting in this operation, not only densifying powder objects but also desired products of the obtained by sintering You can also get the shape.

When adapted by powder casting by extrusion or injection, the mixture of the composition containing the organic binder is homogenized at a temperature not below the melting point of the organic binder and the homogenized mixture is granulated and injected for easy handling and storage. It is supplied to the molding machine.

After fitting the part, this is done by extrusion of the organic binder, which is generally done in two steps, the first being chemical extraction in solvent (eg hexane) and the second being thermal degradation Or a CD plasma related thermal treatment. The composition proposed herein has a hardness of 230 HV to 700 HV, a coefficient of friction μ ≤ 0.15, a mechanical traction resistance of 350 to 750 MPa (depending on the processing parameters used and the alloying components present) and forms a solid lubrication layer and moves. It is also possible to obtain self-lubricating sintered parts or articles in which porous carbon nodules with an internal structure in the form of a skin with nano-thickness which facilitate the dispersion of graphite within the possible surface are also dispersed. 5, 6A, 6B, 6C, and 7 are present in a compact form in any desired amount that adapts to a shape that approximates the required final part or desired shape from which a self-lubricated final part or product can be obtained. It is a figure for the purpose of showing the example of the other possibility which can adapt the composition to make.

In many applications, however, self-lubricating properties are only required for one or more surface areas of a mechanical part or element that are in frictional contact with another moving element.

Thus, the desired self-lubricating product may be a surface layer composed of a structural substrate 30, one or more opposing surfaces 31, and a composition 40 of the present invention, suitably adapted to particulate matter, as shown in FIG. 41). In the illustrated embodiment, the two opposing surface layers of the structural substrate 30 and the composition 40 form two opposing punches P forming a compact and adapted composite article 1 in which the sintering step is carried out afterwards. It is compact in the inside of the appropriate mold M. In this embodiment, the two opposing surfaces 31 of the structural substrate 30 exhibit desirable self-lubricating properties. 6A and 6B show examples of products in the form of tubes 3 and bars 2 respectively obtained by extrusion of the composition 40 in a suitable compression matrix (not shown). In this case, the fitting by compacting the composition 40 is done in a later extrusion step. The bar 2 and the tube 3 are combined with the reliably dispersed particles of the particulate solid lubricant 20 and a sintering step is carried out for the formation of the structural matrix 10 based on iron.

FIG. 6C illustrates another example of an article formed by a composite bar 4 having a structural core 35 of particulate matter enclosed around its outer periphery by a surface layer 41 formed from the composition 40 of the present invention. Illustrated. As in the present case, the adaptation and compactness (high density) of the outer layer 41 and the structural core 35 of the composition 40 are obtained by co-compression of two parts of the composite bar 4 to be subjected to the sintering step.

When compaction of the composition 40 is done by extrusion, it can occur, for example, by the formation of the bars 2, 3 of FIGS. 6A, 6B, 6C, the composition being sintered by known techniques for removal It may further comprise an organic binder that can be thermally removed from the composition before the step and after formation of the composition. The organic binder can be, for example, one selected from the group consisting of paramin and other waxes, EVA, low crystalline polymers.

7 schematically illustrates another method of obtaining a composite article from sintered steel having one or more surface areas having self-lubricating properties. In this embodiment, the product 5 obtained is in the form of particles already formed in the form of a strip on at least one of the opposing surfaces of the structural substrate 30 in a continuous strip by rolling the surface layer 41 of the composition 40 of the present invention. Represents a structural substrate 30 formed of a material. The composite product 5 is subjected to a sintering step.

Although the present invention is described herein by some embodiments of possible compositions and associations with other structural substrates, such compositions and associations may be applied to the matrix during the sintering step, as defined in the claims appended to the present specification. It should be understood that modifications or variations will be apparent to those skilled in the art without departing from the permanent tendency of the solid lubricant to dissolve in and the concept of controlling the distribution in the solid lubricant separate particles in the structural matrix. .

2: bar 3: tube
5: product 10: matrix
35 core 40 composition
41: surface layer

Claims (24)

In a composition of particulate matter for forming a self-lubricating product in sintered steel adapted by compaction or powder injection,
Iron as the main particulate metal material; At least one particulate alloy element having a function of curing iron forming a structural matrix of iron; A composition comprising a non-ferrous metal that is a precursor to a solid lubricant of graphite to be formed in a compound product during sintering.
The method according to claim 1,
The non-ferrous metal, which is a precursor to the solid lubricant phase of graphite, is a compound of the carbide or carbonate type, which composition comprises a chemical element that stabilizes the ferrite phase of the structural matrix of iron in the composition.
The method according to claim 2,
The chemical element for stabilizing the ferrite phase is selected from silicon carbide, molybdenum carbide and chromium carbide.
The method according to claim 1,
And wherein said nonferrous metal particulate compound further comprises an additional particulate alloying element for stabilizing said ferrite phase, which is a carbide or carbonate from the composition of all chemical elements for stabilizing the ferrite phase of said iron matrix.
The method of claim 4,
And wherein the additional particulate alloying element that stabilizes the ferrite phase of the iron structural matrix is at least one selected from silicon, phosphorus, molybdenum and chromium.
The method according to any one of claims 2 to 5,
Wherein said non-ferrous metal particulate compound, which is a precursor of a solid lubricant phase of graphite, has a volume percentage of less than about 10% of the mass of the metallurgical composition of the particulate material to be adapted.
The method according to any one of claims 1 to 6,
The particulate alloy element having a function of curing the iron of the structural matrix of iron is formed by at least one of elements selected from nickel, chromium, molybdenum, vanadium, manganese, copper, silicon, phosphorus and carbon. Composition.
The method according to any one of claims 1 to 7,
The composition is adapted by powder compaction (pressing, rolling, double pressing or compacting) and the particles of the main particulate metal material (iron powder) have an average size lying between about 5 μm and about 90 μm, and A particle of a particulate alloy element having a function of curing iron and a particle of a nonferrous metal particulate compound are precursors of a solid lubricant phase of about 45 μm or less.
The method according to claim 8,
And wherein the average particle size of said primary particulate metal material, ie iron, is larger than the average particle size of said primary particulate alloy element and said non-ferrous metal particulate compound that is a precursor to said solid lubricant.
The method according to any one of claims 1 to 7,
Wherein the composition is adapted by extrusion and injection molding, wherein the major particulate metal material, the particulate alloy element and the nonferrous metal particulate compound, which is iron, has a particle size between about 5 μm and about 25 μm.
The method according to claim 10,
Paraffin and other waxes, EVA, metallurgical compositions are provided with an organic binder system selected from the group consisting of low melting polymers in proportions ranging from about 40 to 45% of the total volume.
In a self-lubricating sintered steel product obtained from a composition of particulate matter as defined in any of claims 1 to 11, wherein the adaptation is carried out before sintering,
A self-lubricating sintered steel product characterized by having a hardness between 230 HV and 700 HV, having a friction coefficient of μ ≤ 0.15 and exhibiting traction resistance between 350 and 900 MPa.
The method of claim 12,
Self-lubricating sintered steel article, characterized in that at least one surface layer (41) of said metallurgical composition (40) is bonded to a structural substrate (30).
The method according to claim 13,
Self-lubricating sintered steel product, characterized in that the structural substrate (30) is associated with the surface layer (41) of the metallurgical composition (40) to form a particulate material to be sintered.
The method according to claim 14,
Self-lubricating sintered steel product, characterized in that the structural substrate (30) is in the form of a strip plate with at least one of the opposing surfaces engaging the surface layer (41) of the metallurgical composition (40).
The method according to claim 14,
The structural substrate (30) is a self-lubricating sintered steel product, characterized in that it is in the form of a structural core (35) of the composite bar (4) bonded to the outer periphery of the surface layer (41) of the metallurgical composition (40).
A method for obtaining a self-lubricating sintered steel article from the composition of particulate matter as defined in claim 8 or 9.
-Mixing a predetermined amount of particulate matter forming a metallurgical composition,
Homogenizing the mixture of particulate matter,
Compacting the particulate material mixture to provide a mixture in the shape of the product to be sintered,
Self-lubricating sintered steel products comprising a process of sintering compacted and adapted mixtures at temperatures of about 1125 to about 1250 ° C. during graphite nodules sintering by dissociation of precursor compounds in the volume of the structural matrix. How to get.
18. The method of claim 17,
Compacting the particulate material mixture forming the composition comprises rolling the composition into a plate or strip to be continuously sintered.
18. The method of claim 17,
The process of compacting the particulate material mixture forming the composition 40 opposes the structural substrate 30 in the form of a plate or strip of particulate material compatible with the main particulate metal material forming the structural matrix 10. And a process for rolling the composition over at least one of the faces.
The method according to claim 18 or 19,
And an additional step of cold rolling a plate or strip to reduce the residual porosity leading to final annealing after sintering the particulate material.
The method according to claim 18 or 19,
The process of compacting the particulate material mixture forming the composition 40 is for obtaining a self-lubricating sintered steel product, which is extruded into one of the shapes formed by the bar 2 and the tube 3. Way.
18. The method of claim 17,
Compacting the particulate material mixture forming the composition 40 may comprise a structural core in the form of a bar of particulate material that is compatible with the primary particulate metal material forming the structural matrix 10 to form the compound bar 4. (35) A process for obtaining a self-lubricating sintered steel product, comprising the step of extruding the composition in the form of a tubular sleeve (42) around it.
The method according to claim 21 or 22,
And said composition (40) is an organic binder that is thermally removed from the product prior to the sintering process.
A method for obtaining a self-lubricating product in sintered steel from a composition of particulate matter as defined in claim 10 or
-Mixing a predetermined amount of particulate matter forming a metallurgical composition,
Homogenizing the mixture of particulate matter at a temperature at which the organic binder does not melt,
Granulating the composition to facilitate feeding into a handling, storage and infusion machine,
Injection molding the particulate material mixture to provide the mixture in the shape of the product to be sintered,
Removing the organic binder from the cast part,
A process for sintering the parts obtained by the adaptation of the powder at temperatures of about 1125 and 1250 ° C.

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