JP4541062B2 - Functional member and manufacturing method thereof - Google Patents

Description

  The present invention relates to functional members such as machine parts and jigs, and more particularly to functional members suitable for improving tribological performance between surfaces.

  A functional member refers to a member as an element for constituting some mechanism by combination, and the surface property is a function when a plurality of functional members are brought into contact with each other to be fixed, fitted, or mutually moved. It has a big impact. Among the surface properties, the surface roughness has a great influence on the above-mentioned functionality, and particularly the tribological performance has a great influence on the frictional resistance, efficiency, life and the like of the entire apparatus composed of functional members. Also, in the field of micromachines and nanotechnology that has been attracting attention in recent years, there is a possibility that the device itself may not operate depending on the degree of surface roughness, and the effect of surface roughness is extremely significant. It is.

  In order to solve the problems related to the surface of such a functional member, various surface treatments have been attempted in the past, and particularly for the purpose of smoothing the surface and improving fatigue strength, Shot peening that hits particles and imparts high compressive residual stress in the vicinity of the surface to increase the hardness is widely known.

However, shot peening causes damage to the grain boundaries on the surface of the member due to the hitting of the particles, and this causes numerous irregular irregularities to be formed on the surface. May fall. Moreover, there is a possibility that the dimensional accuracy of the workpiece may be distorted and the contact surface strength of tribology may be significantly reduced. In order to improve this point, Japanese Patent Application Laid-Open No. 11-48036 (Patent Document 1) proposes that after carburizing and quenching machine parts, shot peening is performed, and then barrel treatment is performed to finish the surface.
JP 11-48036 A

  However, since this method uniformly cuts the machining marks formed on the machined surface, the oil retention effect (pool effect) by the machining marks is lost after barrel polishing. Therefore, among functional members, there is a problem that the intended effect cannot be obtained if a tribological effect is expected, regardless of the purpose of fitting or fixing where friction with the counterpart member does not matter so much. .

  Furthermore, in this prior art, excessive grinding of the surface is prevented by quenching and hardening the machine parts. However, assuming quenching, the materials that can be surface-treated are limited, and the surface roughness that can be achieved. There is also a limit.

  An object of the present invention is to solve the above problems and to further improve the functionality of the functional member.

  In order to achieve the above object, the functional member according to the present invention has a surface-modified layer having a surface compressive stress and is refined by a peening process, and the surface of the surface-modified layer is made of fine particles. By the collision, the surface is flattened while leaving the concave portion derived from the processing mark of the peening process, and the surface modified layer remains after the planarization. In this case, on the surface of the planarized surface modification layer, a portion (including both a shaved portion and a plastically deformed portion) lost due to collision with fine particles or a smooth surface and a concave portion that are aggregates thereof are included. Is formed.

  Thus, since the surface of the functional member of the present invention is flattened, rolling resistance and sliding resistance can be suppressed. In addition, as the flattening progresses, the parts disappeared by collision with the fine particles (including both the shaved part and the plastically deformed part) gather to have a certain size (smooth surface). Since a recess derived from the processing mark of the peening process is formed adjacent to the contact area when the functional members are brought into contact with each other, and air can be sent to the contact surface by the recess, Even in a non-lubricated state, adhesion between functional members can be prevented. When machining is performed before the peening process, burrs and burrs are formed at the corners of the material, which may adversely affect the tribological effect. This kind of trouble is also avoided because it is completely removed by the injection.

  In addition, the surface of the functional member has a surface-modified layer with surface compressive stress and refined crystal grains, resulting in a dense, high-hardness and tough structure, and high fatigue strength. Further, it is possible to ensure wear resistance, impact resistance and the like.

  In this configuration, it is desirable to set the area ratio (A / B) between the area A of the smooth surface and the area B of the recesses within a range of 2 to 20 (more preferably within a range of 5 to 15). When this ratio is less than 2, the concave area increases more than necessary. As a result, the convex portion (smooth surface or the like) of the mating member is easily fitted into the concave portion of the functional member, and the convex portion bites into the concave portion. This may adversely affect the tribological effect. On the other hand, if this ratio exceeds 20, the area of the concave portion is remarkably reduced, so that when the lubricant is interposed on the contact surface, the effect of retaining the lubricant is reduced, and the tribology is similarly adversely affected. This area ratio can be adjusted according to the elasticity, plasticity, frictional characteristics, etc. of each material, so that the required tribological performance can be obtained arbitrarily and the restrictions imposed on the usage conditions of the functional members can be reduced. Can do.

  As a pre-process of the peening treatment, in addition to material removal processing (for example, cutting processing or grinding processing), molding processing such as forging and casting, or surface treatment such as super hard coating can be employed. Of course, heat treatment can also be performed before and after these previous steps.

  The peening treatment here is for hitting particles having an average particle size of about 30 to 300 μm on the surface at high speed. If the particles are sprayed on the surface with high hardness by heat treatment, the processed surface is rapidly heated by the spray energy of the particles and then rapidly cooled, and this is repeated thereafter, so that the residual austenite structure is recrystallized or refined. A martensite structure can be formed, and the surface hardness can be further increased. Therefore, the fatigue strength can be improved by ensuring high surface hardness and compressive residual stress.

  The functional member described above has a first step of forming a refined surface modified layer having a surface compressive stress by raising the surface temperature to the A3 transformation point or higher by peening treatment, and injecting fine particles. By doing so, the surface of the surface modification layer can be planarized while leaving a recess derived from the processing marks of the peening treatment, and the second step of remaining the surface modification layer after planarization can be produced. it can.

  At this time, as the fine particles used in the second step, those obtained by attaching abrasive grains to a porous carrier can be used. In this case, processing marks formed by plastic deformation due to the collision of the fine particles may remain on the smooth surface, but the impact at the time of the fine particle collision is mitigated due to the use of a porous carrier. The diameter and depth are generally smaller than hard particles of the same size that do not have the same type of structure.

  In the production of the functional member, it is possible to adjust the area ratio between the smooth surface and the recess by controlling the spraying time of the fine particles, and finish the surface roughness as required. This is because, when the spraying ability of the fine particles is constant, the irradiation time of the fine particles and the removal ratio of the ridges that determine the surface roughness are almost proportional, and the cross-section of the ridges (direction perpendicular to the surface) It uses the shape of a cone or a truncated cone. If the injection time is short, only the top of the peak is removed, whereas if the injection time is long, it reaches the bottom of the peak (the valley bottom). This is because, as a result of the removal, the concave portion is reduced and the smooth surface is increased.

  In the mechanism in which the lubricant is interposed between the surface of any one of the above functional members and the surface of the mating member in contact with the functional member, when the members are slid relative to each other, the volume of the recesses changes. Since the lubricant subjected to the pumping action is supplied to the contact surface, a high tribological effect can be obtained. The “mating member” here includes not only a functional member to which the present invention is applied but also other members to which the present invention is not applied.

  As a material capable of interposing a lubricant on the contact surface as described above, a sintered metal impregnated with a lubricating oil is known, but in this oil-containing sintered metal, a capillary phenomenon due to a combination of continuous pores and spherical particles is known. Although the lubrication performance can be improved by its own wettability, the contact stress is extremely limited due to the weak interparticle bonding force. As is clear from this example, conventionally, it was considered difficult to achieve both self-lubricating properties and contact stress.

  On the other hand, in the functional member of the present invention, the corner portion of the boundary portion composed of the smooth surface and each ridge line of the recess is rounded as if chamfered by injection of fine particles, and the smooth surface is also a flat surface or surface. Finished in a substantially arc-shaped cross section convex in the direction away from. As described above, the surface modified layer remains, and burrs and burrs that impair the self-lubricating property are completely removed by the injection of fine particles. Therefore, it is possible to provide a functional member that has excellent self-lubricating properties and can withstand a large contact stress, and both can be achieved.

  As described above, according to the present invention, good tribological characteristics can be obtained due to the oil reservoir effect on the contact surface of the functional member, and further, an effect of improving wear resistance and impact resistance can be expected. Therefore, these synergistic actions can significantly improve the durability life of the functional member. Further, the processing can be performed without selecting the shape of the functional member, the processing can be completed in a short time, and the processing cost can be suppressed at a low cost.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  In this invention, a 1st process and a 2nd process are given to the functional member which passed through previous processes, such as cutting and forging. As will be described later, the first step is a step of performing a peening process, and the second step is a step of performing injection processing with fine particles. FIG. 1 is a diagram conceptually showing a change in the cross-sectional shape of the surface of the functional member 1 until the second step is completed after passing through the first step. FIG. 1 (a) is after the peening process in the first step. FIG. 5B shows the second process during the injection process, and FIG. 4C shows the end of the injection process.

  In this invention, you may heat-process before performing the peening process which is a 1st process to the functional member which passed through the previous processes, such as cutting and forging. This “heat treatment” means a heat treatment mainly performed for the purpose of improving the surface hardness. In addition to quenching (tempering) treatment such as sub-quenching, induction hardening, carburizing and quenching, heat treatment such as nitriding treatment and carbonitriding treatment is widely used. included. In addition to this heat treatment, a heat treatment can also be performed between the peening treatment of the first step and the fine particle injection step of the second step as necessary.

  The peening process in the first step is to select and use shots that have the same or higher hardness as the functional material material, such as silicon carbide (Carborundum), high-speed steel, and ceramics, depending on the type of material. Is done. The average particle diameter of these shots is about 30 to 300 μm. By injecting this shot onto the surface of the workpiece together with compressed air at a speed of, for example, 100 m / s or more, preferably about 300 m / s, a compressive residual stress is generated in the surface layer due to plastic deformation due to the impact. In addition, due to the energy of the particles that collide at high speed, the temperature of the surface layer portion rises, transformation occurs in the surface layer structure, and the metal structure is refined. That is, as a result of a part of the energy being converted into thermal energy by collision with the particle surface, the surface layer is heated to the A3 transformation point or higher (recrystallization temperature or higher for non-ferrous metals) and martensitic transformation occurs in the steel structure. Arise. This is a phenomenon similar to a type of isothermal transformation, and in the surface layer, retained austenite is transformed into martensite. Therefore, a structure having high hardness and high toughness can be obtained. According to the experiment results of the present inventors, it was confirmed that the compressive residual stress after the peening treatment is about 700 to 1500 MPa, and the surface hardness is about 50 to 400 Hv higher than that before the processing.

  In FIG. 1A, the surface modified layer 13 having a compressive residual stress and a fine structure formed by the peening process is represented by cross-hatching. The depth of the surface modification layer 13 is within 15 μm (generally 7 to 12 μm). Thus, by forming the surface modification layer 13 limited to the extreme surface, it is possible to solve various problems of tribology. On the other hand, in the normal shot peening process, the depth of the influence layer exceeds 100 μm (usually about 200 μm), which is the most different point from the peening process in the first step. Further, in normal shot peening, the crystal grains on the outermost surface are not refined unlike the peening process.

  On the surface of the functional member 1 after the peening treatment, a large number of processing marks having a size corresponding to the size of the shot are formed by plastic deformation due to the collision of the shot. Thereby, as shown to Fig.1 (a), it comes to have the initial surface roughness which the peak part 4 became high with respect to the valley bottom 3 of the valley part 2 (In addition, the height of an unevenness etc. is exaggerated. Drawn). The shape of the initial surface roughness and the depth of the unevenness depend on the processing method performed in the previous process such as cutting and forging.

  The member 1 that has undergone the previous process is subjected to injection processing as the second process. In this injection processing, as shown in FIG. 1 (b), by injecting fine particles 6 from the injection port 5, the crest 4 of the initial surface roughness is mainly scraped or plastically deformed to flatten the surface. Is. The injection port 5 is arranged aiming at the side surface 41 (the surface from the valley bottom 3 up to the top) of the peak portion of the initial surface roughness, but the member surface of the injection port 5 (when approximated to a flat surface) The inclination angle α with respect to the surface is preferably an acute angle and as small as possible. Specifically, it is good to set in the range of 5 degrees or more and 45 degrees or less. If the surface of the member 1 is wide, the crest 4 can be similarly removed on the wide surface by moving the injection port 5 in the direction of the arrow while keeping the inclination angle α of the injection port 5 constant. it can.

  As the fine particles 6, elastic fine particles in which a large number of abrasive grains 15 are attached to a porous carrier 14 are used as shown in FIG. 4. In this case, the carrier 14 is softer than the member 1, has a certain degree of plasticity, and is lightweight and has a size of about 0.1 to 5 mm, and can be produced from natural fibers such as plant fibers. As the abrasive 15, a material obtained by processing an abrasive such as silicon carbide, alumina, diamond powder, iron oxide or the like to 1 to 20 μm is used. The abrasive grains 15 are not limited to the materials and sizes exemplified above, but can be selected according to the type of the member 1 from among abrasives made of various materials and sizes used in polishing and lapping processes. Moreover, when using the product from a vegetable fiber as the support | carrier 14, the fat content or sugar content can be functioned as an adhesive material at the time of making the abrasive grain 15 adhere. The carrier 14 is not limited to natural fibers such as plant fibers, but may be artificially composed on the condition that the above properties are provided.

  The fine particles 6 are impregnated with 20 to 70% by weight of water or oil in advance to increase the weight, and are sprayed on the surface of the member 1. In this case, since a soft porous body is used as the carrier 14 for the fine particles 6, the fine particles 6 sprayed on the surface of the member 1 collide with the surface and at the same time deform according to the surface shape. The deformed fine particles 6 are elastically repelled and separated from the surface of the member, but slide on the surface until they are repelled.

  By injecting the fine particles 6 toward the side surface 41 of the peak portion 4, the peak portions 4b protruding from the other peak portions 4a always collide with the fine particles. Therefore, if the fine particles 6 are blown continuously for a certain period of time, each peak 4 is sequentially scraped or plastically deformed by impact, and eventually, as shown in FIG. Alternatively, the smooth surface 8 smoothed by the aggregate is formed. On the other hand, of the valleys 2 having the initial surface roughness, those remaining after the formation of the smooth surface 8 constitute the recesses 10 having the valley bottoms 3 as the groove bottoms. The concave portion 10 has a shape corresponding to the valley portion 2 having the initial surface roughness. However, since the valley portion 2 itself is shaved or plastically deformed by the fine particles 6, the shape becomes smoother than that of the valley portion 2.

  Thus, unlike the shot peening, the surface processing with the fine particles 6 is intended to scrape the ridges 4 by sliding on the surface, rather than causing the fine particles to collide with the surface of the member. Therefore, compared with shot peening, it is possible to create a smooth surface 8 that is polished on the surface by reducing the influence of formation of processing traces due to plastic deformation and application of compressive residual stress to the member 1. Further, in the existing polishing method such as barrel polishing, the surface modification layer 13 formed in the first step is all removed, but in the above-described injection processing, as shown in FIG. The surface modification layer 13 remains. Accordingly, the characteristics (fatigue strength, wear resistance, impact resistance, etc.) peculiar to the surface modified layer 13 are not lost.

  In addition, innumerable concave portions 10 derived from processing marks of the peening process are formed on the surface of the functional member 1 on the order of microns. Since the processing marks are generally formed smaller than the oil film thickness of the lubricating oil, the lubricating oil retention force on the surface is improved, the oil film can be easily formed, and the friction coefficient can be reduced.

  By these synergistic actions, the functional member 1 has high tribological performance and high fatigue strength, wear resistance, impact resistance, and the like.

  1 is formed when the injection time of the fine particles 6 is short, the horizontal line 9b of FIG. 1 is formed when the injection time is longer than that, and the horizontal line 9c of FIG. 1 is formed when the injection time of the fine particles 6 is longer. Represents the height level of the smooth surface 8 to be applied. As is apparent from this drawing, if the injection time of the fine particles 6 is controlled, it is possible to easily adjust the height level of the smooth surface 8 and thereby adjust the area ratio between the smooth surface 8 and the recess 10. Become. FIG. 1 (c) shows a state where the machining is completed at the level of the horizontal line 9b in FIG. 1 (b).

  FIG. 3 shows a sectional structure of the mechanism in which the functional members 1 are combined. The smooth surfaces 8a and 8b of the functional members 1a and 1b that have undergone the second step are brought into contact with each other to form the contact surface 11, and both members A state in which the lubricating oil 12 is interposed in the recesses 10 of 1a and 1b is shown. In this state, the members 1a and 1b are relatively slid along the contact surface 11, so that the lubricating oil 12 is supplied to the contact surface 11 by being pumped by the volume change of the recess 10 to form an oil film. .

  In this case, if the area ratio of the concave portion 10 with respect to the smooth surface 8 of one functional member (for example, 1a) is too large, the smooth surface 8b of the other functional member (for example, 1b) is fitted into the concave portion 10, and as a result, lubrication characteristics. Cause a decline. On the other hand, if the area ratio of the concave portion 10 is too small, the oil pool effect in the concave portion 10 is reduced, and thus the lubrication characteristics are similarly lowered. From the above viewpoint, the area ratio (A / B) between the area A of the smooth surface 8 and the area B of the recess 10 is preferably 2 or more and 20 or less (preferably 5 or more and 15 or less).

  In addition, in FIG.1 (c), although the smooth surface 8 is represented planarly, as long as this smooth surface 8 is a surface formed by removing the original peak part 4 (it shows with a broken line), the shape is For example, as shown in FIG. 2, an arc-shaped cross section having a slightly convex direction away from the surface may be used.

  By these synergistic effects, according to the present invention, it is possible to improve the durable life of each element (guide block, rail, ball, etc.) of a machine part that makes rolling contact or sliding contact under high surface pressure, such as a linear motion guide bearing. At the same time, a reduction in sliding resistance can be achieved. The present invention can be applied not only when the processing target surface is a flat surface but also when the processing target surface is a curved surface or a spherical surface. Of course, the present invention can be applied not only to machine parts but also to other metal products such as dies and jigs, thereby ensuring excellent moldability and machinability and improving the durability life. Can be obtained.

  It is a figure which shows the process for obtaining the surface of the functional member concerning this invention, and is an enlarged view showing the cross-sectional shape image of a functional member.   It is sectional drawing which shows the other shape example of a smooth surface.   It is an enlarged view showing the cross-sectional shape image of the contact surface in the mechanism which made the functional members contact.   It is an expanded sectional view showing an example of the structure of fine particles.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Functional member 2 Valley part 3 Valley bottom 4 Mountain part 41 Side surface 5 Injection port 6 Fine particle 7 Removal part 8 Smooth surface 10 Recessed part 11 Contact surface 12 Lubricant 13 Surface modification layer

Claims (5)

A method for producing a functional member having a surface comprising a smooth surface and a recess adjacent to the smooth surface,
The material surface of the functional member is peened using particles selected from the group consisting of hydrocarbon, high-speed steel, and ceramic, and the surface temperature of the material is raised to the A3 transformation point or higher, whereby the surface of the material A first step of applying a compressive stress and forming a refined uneven surface modification layer;
While leaving the concave surface modified layer derived from the processing marks of the peening process by colliding the fine particles having abrasive grains attached to the porous carrier with the uneven surface modified layer formed on the surface of the material, and abolished a part of the convex portion surface modification layer is planarized to form a smooth surface and a surface comprising a recess adjacent thereto, by controlling the injection time of the fine particles, the area a and the recess of the smooth surface Adjusting the area ratio (A / B) with the area B to a range of 2 to 20 and including the second step of leaving the surface modified layer after planarization;
The manufacturing method of the functional member characterized by the above-mentioned.   The method for producing a functional member according to claim 1, wherein the first step is a peening treatment in which particles having an average particle diameter of 30 to 300 μm are sprayed onto the material surface of the functional member at a speed of 100 m / s or more.   The manufacturing of the functional member according to claim 1 or 2, wherein the second step injects fine particles within a range of an inclination angle of 5 ° or more and 45 ° or less with respect to a surface when approximated to a flat surface of the functional member. Method.   The functional member according to any one of claims 1 to 3, wherein the fine particles include a plant fiber porous carrier and a grinding material selected from the group consisting of silicon carbide, alumina, diamond powder, and iron oxide. Manufacturing method. The heat treatment selected from submerged quenching, induction quenching, carburizing quenching, nitriding treatment, and carbonitriding treatment is performed before and / or between the first step and the second step. 5. The method for producing a functional member according to any one of 4 above.

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