Bearing bushing for toggle link mechanism and manufacturing method thereof

Abstract

Provided is a sliding material that has excellent fatigue resistance even in a usage environment where a strong impact load occurs. [Solution] A sliding material used in a sliding environment where impact loads occur, comprising a base made of a Cu-Zn-Al brass casting alloy, an intermetallic compound of Mn silicide or Cr silicide contained in the base, the compound having a nanoindentation hardness of 15 GPa or more, and a solid lubricant-embedded portion exposed on the sliding surface of the sliding material, and the embedding rate of the solid lubricant-embedded portion on the sliding surface of the sliding material is 15.8% or less.

Description

[Technical Field]

[0001] The present invention relates to a sliding material and a manufacturing method thereof. [Background technology]

[0002] Oil-less sliding materials with graphite embedded as a solid lubricant have been used in severe mixed lubrication conditions where shock loads occur.

[0003] It has been known that bearings in environments where boundary lubrication or mixed lubrication occurs can maintain their lubrication by incorporating embedded graphite to assist lubrication (see, for example, Patent Document 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5342882 [Patent Document 2] Patent No. 7105522 [Patent Document 3] Patent No. 6331835 [Patent Document 4] Japanese Patent Application Publication No. 10-159851 Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Document 1 discloses a graphite-embedded sliding material containing an Fe-Mn-Si intermetallic compound in a brass alloy. However, the composition of the Fe-Mn-Si intermetallic compound is not specified, and the sliding performance of this compound is not disclosed.

[0006] Patent Document 2 discloses a sliding material having a base made of a brass alloy and a Cr-Fe-Si intermetallic compound contained in the base and having a nanoindentation hardness of 20 GPa to 28 GPa. However, Patent Document 2 does not disclose any findings related to the embedding rate of the graphite embedded portion.

[0007] Patent Document 3 proposes a toggle bearing bushing having a plurality of circular holes filled with a solid lubricant. However, Patent Document 3 does not disclose any findings related to the embedding rate of the graphite embedded portion.

[0008] Patent Document 4 discloses a sliding bearing used in link mechanisms, etc. However, Patent Document 4 does not disclose anything about intermetallic compounds.

[0009] In recent years, there has been an increasing demand for the use of hard high-tension steel in graphite-embedded sliding plates used in press die-related equipment, and strong impact loads are generated under reciprocating sliding. 7 Repeated impacts exceeding 100 times occur, and the number of impacts is also increasing, so measures are being required in sliding materials.

[0010] The present invention has been made to solve such conventional problems, and has as its object to provide a sliding material that has excellent fatigue resistance even under a usage environment where a strong impact load occurs. [Means for solving the problem]

[0011] The present invention is a sliding material used in a sliding environment where impact loads occur, which has a base made of a Cu-Zn-Al brass cast alloy, an intermetallic compound of Mn silicide or Cr silicide contained in the base, the compound having a nanoindentation hardness of 15 GPa or more, and a solid lubricant-embedded portion exposed on the sliding surface of the sliding material, and the embedded rate of the solid lubricant-embedded portion on the sliding surface of the sliding material is 15.8% or less. [Effects of the Invention]

[0012] The present invention can provide a sliding material that has excellent fatigue resistance in a sliding environment where an impact load occurs. [Brief explanation of the drawings]

[0013] [Figure 1] 1A and 1B are diagrams showing the configuration of a sliding member using the sliding material of the embodiment as a substrate; [Figure 2] 5A and 5B are diagrams showing impact loads generated in a cam slider; [Figure 3] 1 is a diagram showing a wear curve that occurs when an impact load occurs. [Figure 4] FIG. 1 is a graph showing the elongation of the fatigue limit when the solid lubricant-embedded portion is eliminated in the S / N curve of a brass alloy. [Figure 5] FIG. 1 is a graph showing the fatigue limit elongation when extrusion processing is performed in the S / N curve of a brass alloy. [Figure 6] 1 is a schematic diagram showing an intermetallic compound Cr silicide according to an embodiment; [Figure 7] 1 is a schematic diagram showing an intermetallic compound Mn silicide according to an embodiment. [Figure 8] FIG. 1 is a diagram showing a reciprocating sliding test device. [Figure 9] FIG. 2 is a graph showing the progress of friction performance of materials containing a Cr—Fe—Si compound in Examples 1 and 2 with and without graphite embedded therein. [Figure 10] FIG. 10 is a graph showing the progress of friction performance of materials containing an Mn—Fe—Si compound in Examples 3 and 4 with and without embedded graphite. [Figure 11] FIG. 2 is a graph showing the progress of friction performance of Cu-Zn-Al-based brass alloys containing no intermetallic compound according to Comparative Examples 1 and 2, with and without embedded graphite. [Figure 12] S / N curves for each burial rate [Figure 13] Diagram of analysis to determine bearing stiffness. [Figure 14] Graph of bearings with different solid lubricant embedment rates. [Figure 15] FIG. 10 is a diagram showing the relationship between embedment rate and stiffness. [Figure 16] A diagram showing the S / N curves of sand-cast material and extruded material. [Figure 17] FIG. [Figure 18] A graph showing the friction coefficient of a material coated with a resin containing MoS2. [Figure 19] FIG. 2 is a schematic diagram of a cam device used in a press die device. [Figure 20] FIG. 1 is a schematic diagram of a toggle device used in a molding machine. DETAILED DESCRIPTION OF THE INVENTION

[0014] The sliding member of the embodiment will be described in detail below, but the present invention is not limited to this embodiment.

[0015] 1 is a diagram showing the configuration of a sliding material used in a sliding environment where an impact load occurs according to an embodiment, showing a cylindrical sliding material (bearing type) having a plurality of solid lubricant-embedded portions.

[0016] As shown in FIG. 1, the sliding material 1 of the embodiment has, on the sliding surface 1A, a plurality of solid lubricant-embedded portions 4 that exhibit self-lubricating properties at a predetermined embedding rate or less. When the embedding rate is 0%, the sliding material does not have any solid lubricant-embedded portions 4. The sliding material 1 may be cylindrical or plate-shaped. For the solid lubricant-embedded portions 4 of the embodiment, for example, graphite-based, PTFE-based, MoS2-based, Pb alloy-based, or other solid lubricants can be used. The embedding rate is more preferably 0% or more and 12% or less.

[0017] An example of an impact load applied to the sliding material of the embodiment is a case in which a load of 45 MPa or more occurs in 0.1 seconds, as shown in Fig. 2. The present invention is not limited to this, but refers to a case in which the load increases suddenly in a short period of time. The sliding material of the embodiment is a sliding material used in such a severe sliding environment, and includes a base material 2 made of a Cu-Zn-Al-based brass cast alloy, and an intermetallic compound 3A or 3B of Mn silicide or Cr silicide having a nanoindentation hardness of 15 GPa or more, and an embedding ratio of a solid lubricant (such as graphite) 4 of the sliding material is 15.8% or less.

[0018] Figure 3 shows the wear curve that occurs when an impact load occurs. Generally, wear due to sliding is proportional to the sliding distance and load (σ). However, when an impact load occurs, wear does not progress linearly, but rather progresses exponentially after a certain stable state.

[0019] The following basic equation for Engel's impact wear was obtained from the literature, PAEngel Impact wear of multiplated electrical contacts. W=f(N.σ)=kNσ n Where W: wear amount N: Number of impacts k: constant σ: stress is.

[0020] This basic formula shows that the amount of wear caused by impact is a function of the number of impacts N and the stress generated σ, and that the amount of wear is proportional to the nth power of the stress and the number of repeated impacts, resulting in extremely destructive wear.

[0021] The process leading to impact failure can be divided into three stages.

[0022] Initial wear stage Rapid wear (n>1), which corresponds to the so-called running-in state, progresses and a running-in surface is formed. In other words, rapid wear increases the true contact area, disperses the surface pressure, and reduces the effective σ.

[0023] Zero Wear Stage The steady wear state is reached at a gentle and stable condition of n = 1. In this state, no noticeable wear occurs, but repeated impact loads cause accumulation of dislocations just below the surface, which leads to the next fracture.

[0024] Measurable wear stage When the limit point N0 is reached, wear failure of n>1 begins, and wear failure progresses exponentially. Normally, in this final process, the impact load causes surface collapse, and the wear particles released onto the sliding surface adhere to the mating material, leading to the so-called seizure phenomenon (Fig. 3).

[0025] When we follow the sliding phenomenon accompanied by impact in this way, we can see that, unlike the process in which a fracture phenomenon progresses on the outermost surface as seen in simple sliding friction phenomena, this is a process in which the material structure itself just below the surface is destroyed, resulting in extremely serious fracture phenomena that expand exponentially. Therefore, the biggest issue is how to reduce the generated stress σ, which is the impact load.

[0026] As such, it is important to reduce the stress (σ) generated by impact wear. Figure 4 shows the effect on the fatigue curve (S / N curve) of reducing the amount of solid lubricant embedded in the material, thereby extending the fatigue limit.

[0027] In other words, the vertical axis indicates stress (σ) and the horizontal axis indicates the number of repetitions (N). Generally, for crystal structures with face-centered cubic (fcc) structures, 6 More than 10 times 7 For this reason, the fatigue strength of cam slides and toggle bushings is 6 ~10 7 Under operating conditions where the number of cycles reaches as many as 1000, it is important to reduce the stress (σ) generated. By reducing the embedded ratio of the solid lubricant embedded section, the stress generated in the bearing decreases from σ1 to σ2. This increases the fatigue limit from N1 to N2, improving fatigue resistance.

[0028] On the other hand, Figure 5 shows what happens when the fatigue resistance of the material itself is improved. By improving fatigue resistance, the fatigue curve of the material shifts from line A to line B. Therefore, even with the same stress (σ), the fatigue limit increases from N1 to N2, improving fatigue resistance.

[0029] 6 shows the three-dimensional structure of the intermetallic compound as seen from a cross section perpendicular to the sliding surface 1A of the sliding material 1 of the embodiment. The sliding material 1 has a base material 2 and a Cr-Fe-Si based intermetallic compound 3A.

[0030] The substrate 2 is made of a Cr-Zn-Al brass alloy and provides the sliding material 1 with a shape and mechanical strength suited to its intended use.

[0031] In the embodiment, Cr silicide refers to a Cr-Fe-Si based intermetallic compound 3A, and Mn silicide refers to a Mn-Fe-Si based intermetallic compound 3B.

[0032] The Cr-Fe-Si intermetallic compounds 3A are compounds composed of Cr, Fe, and Si. The Cr-Fe-Si intermetallic compounds 3A of the embodiment have a structure of (Cr,Fe)3Si. Each of the Cr-Fe-Si intermetallic compounds 3A has a rounded curved outer shape.

[0033] A large number of Cr-Fe-Si intermetallic compounds 3A contained in the base material 2 are bonded to each other, thereby forming a three-dimensional structure in which a large number of Cr-Fe-Si intermetallic compounds 3A are linked together. The Cr-Fe-Si intermetallic compounds 3A contained in the slide material 1 of this embodiment have a nanoindentation hardness of 28 GPa.

[0034] The hardness of the Cr-Fe-Si intermetallic compound 3A and the Mn-Fe-Si intermetallic compound 3B can be measured by hardness measurement using a nanoindenter.

[0035] Hardness measurements using a nanoindenter conform to "ISO 14577-1 Metallic materials - Instrumented indentation test for hardness and materials parameters -" and its supplement, "Annex A (normative) Materials parameters determined from the force / indentation depth data set." A BRUKER HYSTRONT1980 device was used for hardness measurements using a nanoindenter.

[0036] The hardness measurement conditions were a test load of 800 μN, loading for 1 s, holding for 0.4 s, and unloading for 1 s. In ISO notation, the measurement conditions are HIT8x10 -4 The hardness was set to / 1 / 0.4 / 1. To measure the particles of Cr-Fe-Si intermetallic compound 3A crystallized in the alloy, a grid pattern was set up over the measurement area including the particles of Cr-Fe-Si intermetallic compound 3A, and multi-point measurements were performed by indenting the lattice points of the grid pattern. The maximum value of the hardness measured by a nanoindenter, which is characteristic of Cr-Fe-Si intermetallic compound 3A, was taken as the nanoindentation hardness of intermetallic compound 3A.

[0037] Even when the Mn-Si binary intermetallic compound Mn5Si3 is converted into a ternary compound like the Mn-Fe-Si intermetallic compound 3B, the basic structure remains Mn5Si3, and some of the Mn is replaced (Mn x ,Fe y ) (where x + y = 1). In other words, by introducing the concept of determining chemical structure through SEM atomic ratio measurement, it has become possible to determine the exact chemical structure.

[0038] Figure 7 is a schematic diagram of the three-dimensional cross-section of a sliding material containing Mn-Fe-Si intermetallic compound 3B. Mn-Fe-Si intermetallic compound 3B has the chemical structure of (Mn,Fe)3Si. Like Mn-Si intermetallic compounds, Mn-Fe-Si intermetallic compound 3B has a preferential growth crystal direction and grows individually separated into a granular or dendritic shape.

[0039] It was found that a part of the petal-like structure of Mn-Fe-Si intermetallic compound 3B was transformed into a eutectic structure and changed into a granular structure. The nanoindentation hardness of Mn-Fe-Si intermetallic compound 3B measured by the above-mentioned method was 18.5 GPa.

[0040] Brass-based casting alloys are evaluated for their wear resistance and low friction (low μ) according to the basic tribological equation (1). μ=τ0 / P H ···(1) where μ is the coefficient of friction, τ0 is the shear force of the lubricant, and P H : Hardness (load / area).

[0041] The coefficient of friction μ is proportional to the shear force of the lubricant and inversely proportional to the hardness of the substrate. H is the load divided by the contact area. The friction coefficient μ can be reduced by increasing the hardness of the intermetallic compound that becomes the load point during friction, or by reducing the contact area of ​​the intermetallic compound.

[0042] The effects of the Cr-Fe-Si intermetallic compound 3A and the Mn-Fe-Si intermetallic compound 3B of the embodiment are obtained by the following formula (1) of tribology: P H An increase in hardness reduces the coefficient of friction, and the presence of a lubricant reduces the frictional work expressed as μ x load x speed, which reduces the generation of frictional heat and provides a low-friction effect. In other words, brass alloys containing hard intermetallic compounds such as Cr silicide and Mn silicide can be expected to improve friction characteristics.

[0043] (Example) Examples will be described below, but the present invention is not limited to these Examples. First, the sliding properties of the sliding material depending on the embedding rate of the solid lubricant embedded portion were confirmed.

[0044] The embedding rate of the solid lubricant-embedded portions 4 is the ratio, expressed as a percentage, of the total surface area of ​​the solid lubricant-embedded portions 4 appearing on the sliding surface 1A divided by the area of ​​the sliding surface 1A (Fig. 1).

[0045] As shown in Table 2, Example 1 contains a Cu-Zn-Al substrate 2 containing Cr-Fe-Si intermetallic compound 3A and has a 12% embedded graphite 4 ratio, Example 2 contains a Cu-Zn-Al substrate 2 containing Cr-Fe-Si intermetallic compound 3A and has a 0% embedded graphite 4 ratio, Example 3 contains a Cu-Zn-Al substrate 2 containing Mn-Fe-Si intermetallic compound 3B and has a 12% embedded graphite 4 ratio, Example 4 contains a Cu-Zn-Al substrate 2 containing Mn-Fe-Si intermetallic compound 3B and has a 0% embedded graphite 4 ratio, Comparative Example 1 contains a Cu-Zn-Al substrate containing no hard compounds and has a 12% embedded solid lubricant ratio, and Comparative Example 2 contains a Cu-Zn-Al substrate containing no hard compounds and has a 0% embedded solid lubricant ratio. The wear amounts of these sliding materials were compared. The volume ratio of the intermetallic compounds on the friction surface is in the range of 3% to 15%.

[0046] 8 is a diagram showing a reciprocating sliding test device. The reciprocating sliding test device 4 applies a load N (surface pressure 30 N / mm in this test) to the sample 5. 2 ) was applied and the sliding was performed on the mating material 6. The test conditions are shown in Table 1. The poor lubrication conditions were set to be closer to the usage conditions in which each sliding material is used.

[0047] [Table 1]

[0048] [Table 2]

[0049] [Table 3]

[0050] The state of change in the friction coefficient and the amount of wear resulting from this reciprocating sliding test are shown in Table 3, and the changes in the friction coefficient are shown in Figures 9, 10, and 11.

[0051] As outlined in Table 3, Examples 1 and 2 containing Cr-Fe-Si intermetallic compound 3A and Examples 3 and 4 containing Mn-Fe-Si intermetallic compound 3B have low maximum friction coefficients of 0.10 to 0.13 and small wear volumes of 0.7 μm to 2.6 μm. In contrast, Comparative Examples 1 and 2, which do not contain hard compounds, have high maximum friction coefficients of 0.14 to 0.15 and large wear volumes of 6.0 μm to 6.8 μm. As such, the sliding materials of the Examples can reduce the friction coefficient and wear volumes under high loads.

[0052] Figure 9 shows the change in the friction coefficient of Examples 1 and 2, which contain the Cr-Fe-Si intermetallic compound 3A as the intermetallic compound. A comparison of Example 1, in which the solid lubricant embedded portion 4 is embedded at a rate of 12%, and Example 2, in which the solid lubricant embedded portion 4 is embedded at a rate of 0% (no graphite), reveals a similar trend, with a gradual decrease in the friction coefficient. This is a characteristic of materials containing the Cr-Fe-Si intermetallic compound 3A, and it can be seen that the exposure of this compound on the friction surface contributes to the reduction in friction.

[0053] 10 shows the change in the friction coefficient of Examples 3 and 4, which contain the Mn-Fe-Si intermetallic compound 3B as the intermetallic compound. A comparison of Example 3, in which the embedding rate of the solid lubricant embedded portion 4 is 12%, and Example 4, in which the embedding rate of the solid lubricant embedded portion 4 is 0% (no graphite), shows almost the same tendency, remaining stable throughout.

[0054] Figure 11 shows the change in the friction coefficient over time for Comparative Examples 1 and 2, which do not contain intermetallic compounds. The materials of Comparative Examples 1 and 2 experience mixed lubrication (partial metal-to-metal contact causes an increase in the friction coefficient), resulting in an unstable friction coefficient. Therefore, if the solid lubricant-embedded area that provides lubrication is eliminated, the fluctuations in the friction coefficient become even greater. In other words, this shows that eliminating the solid lubricant-embedded area that assists lubrication results in an extremely unstable sliding state. As such, the sliding materials of Comparative Examples 1 and 2, which do not contain intermetallic compounds, require the presence of a solid lubricant-embedded area, while the materials of Examples 2 and 4, which contain intermetallic compounds, can maintain a stable sliding state even without the presence of a solid lubricant-embedded area.

[0055] In Examples 1 and 2, the Cu-Zn-Al-based base material 2 contains 22 to 26% Zn and 4 to 6% Al, but the base material 2 may contain 20 to 32% Zn and 3 to 8% Al. In order to strengthen the base material 2, it is also possible to add 1 to 5% Mn and 1 to 5% Ni.

[0056] On the other hand, Cr-Fe-Si intermetallic compound 3A is a compound with a weight ratio of Cr:Fe:Si of 4.8:0.85:1. It is a stable compound with a melting point of 1770°C and is preferentially formed in the molten metal. Silicide formation is rate-determined by the amount of Si; for example, 0.8% Si consumes 3.9% Cr and 0.7% Fe as compounds. Similarly, Mn-Fe-Si compound 3B is a compound with a weight ratio of 3.1:2.8:1. It is a stable compound with a melting point of 1270°C and is preferentially formed in the molten metal. Therefore, if the amount of Si is determined according to the weight ratio, it is possible to form Cr-Fe-Si intermetallic compound 3A by adding the appropriate amounts of Cr and Fe. Similarly, in the case of Mn-Fe-Si intermetallic compound 3B, adding the appropriate amounts of Mn and Fe makes it possible to form Mn-Fe-Si intermetallic compound 3B. In other words, silicide is a compound whose rate is determined by Si, and the appropriate amount of Si is 0.2 to 1.5%; any increase in silicide beyond this makes the material brittle.

[0057] To cast these components, a high-frequency melting furnace is used, and after melting Cu at 1150°C, Zn and Al metals are added, and then Mn, Ni, Fe, Cr, and Si are added in the form of alloys with Cu in specified amounts. After melting, the mixture is degassed, allowed to settle, and the slag is removed, and the molten metal is poured into a sand mold or metal die to obtain the casting material of the specified shape.

[0058] From the above test results, it was found that in the materials containing the intermetallic compounds 3 such as Cr silicide and Mn silicide of the examples, the friction conditions are relaxed and lubricity is maintained even when the lubrication assistance from the solid lubricant embedded portion 4 is low.

[0059] Next, for the sliding material of Example 1, the embedding rate was changed to 10 7 The limit of the embedding rate was determined when the fatigue limit was set at 1000 times.

[0060] The fatigue curve was obtained under the following conditions (Table 4).

[0061] [Table 4]

[0062] Figure 12 shows the fatigue curves for each embedment ratio. The top curve shows the fatigue curve for a material with a 0% embedment ratio, i.e., no solid lubricant embedded portion. When the practical load is 130 MPa, the fatigue limit for a 0% embedment ratio is 10 7 On the other hand, the number of times that the burial rate is 28% is 10 6 ~10 7 It can be seen that the fatigue limit lies between 10 7 It can be seen that the embedding rate of embedding materials that do not fatigue up to 10 times is 15.8%. 7 It was found that in order to maintain the fatigue limit for 1000 cycles, the embedment rate must be kept below 15.8%.

[0063] From the results of the above examples, it was found that a sliding material 1 used in a sliding environment where impact loads occur, which has a base material 2 made of a Cu-Zn-Al brass cast alloy and contains an intermetallic compound 3A or 3B of Mn silicide or Cr silicide having a nanoindentation hardness of 15 GPa or more, and in which the embedded ratio of the solid lubricant embedded portion 4 of the sliding material is 15.8% or less, has excellent fatigue resistance even in a usage environment where strong impact loads occur.

[0064] 2.Sliding material structure In this embodiment, in a sliding environment where impact loads occur, the Cu-Zn-Al-based base material 2 of the sliding material 1 contains an intermetallic compound 3A or 3B, such as Mn silicide or Cr silicide, with a nanoindentation hardness of 15 GPa or more, to improve friction performance and provide sliding characteristics that complement the solid lubricant-embedded portion 4, which is responsible for friction performance. Furthermore, the amount of the solid lubricant-embedded portion 4, which has been conventionally used, is reduced, increasing rigidity, reducing the amount of deformation occurring in the bearing, lowering generated stress, and enabling the sliding material to withstand large impact stresses occurring in the cam sliding portion and toggle bushing.

[0065] To investigate the relationship between the embedded rate of solid lubricant and the rigidity of the sliding material, an FEM analysis was performed using configuration 7 shown in Fig. 13. Rigid body 10 was completely restrained, and rigid body 8 was restrained so that it could only move up and down, and a load of 1 kN was applied vertically downward to investigate the rigidity of bushing 9.

[0066] Figure 14 shows the sliding materials (bearing materials) that were compared using FEM analysis. 11 is a commonly used buried state with an burial rate of 28%, 12 is two buried in a row with an burial rate of 20%, 13 is one buried in a row with an burial rate of 12%, 14 is the embodiment with no burial and an burial rate of 0%, 15 is buried according to the specifications of Patent Document 3 with an burial rate of 25%, and 16 is one with no burial in part with an burial rate of 22%.

[0067] Table 5 shows the relationship between the embedment rate and stiffness.

[0068] [Table 5]

[0069] Figure 15 shows a graph of the relationship between the burial rate and stiffness in Table 5. The vertical axis represents stiffness, and the horizontal axis represents burial rate. As shown in Figure 15, there is an inversely proportional relationship between the burial rate and stiffness, and it was found that greater stiffness can be obtained by reducing the burial rate.

[0070] In this way, increasing the rigidity of the sliding material reduces the amount of deformation that occurs in the sliding material, lowering the stress that occurs, and enabling the sliding material to withstand large impact stress that occurs in the cam sliding part and toggle bushing. In other words, in order to avoid wear and damage to the sliding material due to repeated impact forces, reducing the stress that occurs as described above has the effect of extending the fatigue limit of the sliding material.

[0071] Therefore, the sliding material 1 used in a sliding environment where impact loads occur has a base material 2 of a Cu-Zn-Al brass cast alloy and contains an intermetallic compound 3A or 3B of Mn silicide or Cr silicide having a nanoindentation hardness of 15 GPa or more, and the embedded ratio of the solid lubricant embedded portion 4 of the sliding material is 15.8% or less, and preferably has a rigidity of 7.5 MPa / mm or more.

[0072] 3. Effect of extrusion materials The sliding material of the embodiment is used in a sliding environment where impact loads occur, and friction performance is improved by including intermetallic compounds such as Mn silicide and Cr silicide with a nanoindentation hardness of 15 GPa or more in the Cu-Zn-Al-based base material 2 of the sliding material 1, and rigidity is increased by reducing the embedded ratio of the solid lubricant embedded portion 4 below a predetermined value. This reduces the amount of deformation occurring in the sliding material, lowering the generated stress, making it possible to withstand large impact stresses occurring in cam sliding portions and toggle bushings, and improving fatigue resistance. Furthermore, in the embodiment, a sliding material with improved fatigue resistance is provided by casting the sliding material and then extruding it.

[0073] The manufacturing method of the sliding material of the embodiment is as follows: A Cu-Zn-Al-based base material 2 contains, by mass, 25% Zn and 5% Al, and to strengthen the base material 2, 2% Mn and 3% Ni are added to the base alloy, and 4.8% Cr, 0.85% Fe, and 1.0% Si are added to generate a Cr-Fe-Si-based compound 3A, or 3.1% Mn, 2.8% Fe, and 1% Si are added to generate a Mn-Fe-Si compound 3B.

[0074] To cast these components, a high-frequency melting furnace is used. After melting Cu at 1150°C, Zn and Al metals are added, and then Mn, Ni, Fe, Cr, and Si are added in predetermined amounts in the form of alloys with Cu. After melting, the mixture is degassed, allowed to settle, and the slag is removed before the molten metal is poured into a cylindrical mold 10 inches in diameter and 600 mm long to create an extrusion billet. The riser portion of the billet is cut off, heated to 800°C, and loaded into an extrusion device where the billet is hot-extruded into a ring shape at an extrusion ratio of 35.

[0075] The ring-shaped material thus obtained was subjected to the fatigue test described above. Figure 16 shows the S / N curves of the material containing Cr silicide of Example 2, a normal sand mold material, and the extruded material obtained by extruding this material. As shown in Figure 5, by extruding a material containing an intermetallic compound with excellent friction performance, it is possible to withstand high loads and extend the fatigue limit.

[0076] 3. Effect of resin coating containing MoS2 Materials containing intermetallic compounds can reduce the embedded rate of solid lubricant, which improves rigidity and reduces deformation, reducing the stress generated even when high loads are repeatedly applied, and making it possible to extend the fatigue limit.In addition, considering cases where lubricant cannot be used for such materials due to temperature rise, the effect of coating the surface of the sliding material with a resin containing MoS2 was demonstrated.

[0077] First, the surface of a brass alloy containing Cr silicide was coated with a resin containing MoS2 under the following conditions. The resin coating material (2) is as follows: Resin components Solid lubricant MoS257% Gr.17% Epoxy resin, balance Resin coating thickness: 20~30μm Resin coating method: spray coating Firing conditions: 200℃ x 0.5h in air Next, this coating material was heated to 150°C and subjected to a surface pressure of 6.0 N / mm 2 The friction coefficient was monitored over a 190m sliding distance. A bronze sintered material containing 10% graphite (trade name: deva.metal) (1) was used as a comparison material.

[0078] An outline of the rotary sliding test device is shown in Figure 17. Reference numeral 17 denotes the test device, 18 denotes a housing, 19 denotes a bushing, and 20 denotes a shaft. A load N is applied to the housing 18, and the shaft 20 is rotated.

[0079] Figure 18 shows the friction coefficients of materials coated with resin containing MoS2. (1) is a sintered bronze material containing 10% graphite, and (2) is Example 2 from Table 2 coated with resin containing solid lubricant. The friction coefficient of (2) remains stable at the 0.1 level, confirming that the resin-coated material containing solid lubricant has superior friction characteristics to (1) even in the absence of an oil film.

[0080] 4. Application Examples Oil-free sliding materials with embedded solid lubricant graphite have been used in harsh mixed lubrication conditions where shock loads occur, particularly as sliding members for cam devices used in molds and as bearings for toggle link mechanisms in molding machines.

[0081] Figure 19 shows a cross-sectional view of a cam device according to an embodiment. Reference numeral 21 denotes the cam device, 24 denotes a cam holder, 25 denotes a cam slider, 26 denotes a cam driver, 22 denotes an upper die portion, 23 denotes a lower die portion, 27 denotes a plate material, and 28 denotes a sliding material. Cam device 21 is composed of cam holder 24, cam slider 25, and cam driver 26. Cam device 21 is installed between upper die portion 22, which moves up and down, and fixed die portion 23, and pierces the side of plate material 27 to be formed. As shown in Figure 12, impact loads are generated when piercing is performed under reciprocating sliding motion of the press die head. Furthermore, steel plates processed in recent years have become harder and higher tensile strength, resulting in greater impacts. High precision is required for the relative positioning of the processing tool and the workpiece, so minimal wear is required on the sliding surfaces of the cam holder and cam driver, and greater durability is required.

[0082] In general, an injection molding machine produces a resin molded product of a desired shape by injecting high-pressure resin from the injection unit into the cavity of the mold while the mold is closed by the mold clamping unit and a large clamping force is applied to the mold, and then removing the resin molded product from the mold that is wide open after cooling and solidifying.Such a mold clamping unit is required to be able to open and close the mold in a short time and to apply a large mold clamping force to the mold, and toggle-type mold clamping units with a toggle link mechanism as a boosting mechanism that rapidly increases the load by tracing a tangent curve under reciprocating sliding are widely used.

[0083] A schematic diagram of a toggle device is shown in Figure 20. The toggle link mechanism in toggle-type mold clamping unit 29 has multiple joints between the fixed platen and movable platen 30. The bearing bushing 31 used in these joints does not necessarily have an equal load acting on the entire cylindrical inner surface. At the beginning of mold closing by the movable platen, i.e., from mold opening to mold closing, the speed of the movable platen is fast and the mold closing force is small, so no large load acts on the cylindrical inner surface of the bearing bushing. However, as mold closing nears completion, the speed of the movable platen decreases rapidly, but instead the mold closing force by the movable platen increases significantly, so that a large load acts on the cylindrical inner surface of the bearing bushing 31. The range of the cylindrical inner surface on which this large impact load acts is approximately one-eighth of the entire circumference of the inner surface of the bearing bushing 31. In recent years, injection molding machines have been required to perform high-cycle, high-speed molding, and bearings have come to be subjected to repeated impact loads in a short period of time.

[0084] Although examples of applications where impact loads are generated include sliding materials for press dies and bushings for toggle mechanisms in molding machines, sliding materials with embedded solid lubricants have also been used in other applications, such as bushings for side rolls in hot rolling mills, to reinforce boundary to mixed lubrication. In the present embodiment, by reducing the number of embedded holes and making the sliding material tougher, it is possible to provide a sliding material with increased fatigue resistance and excellent durability. Therefore, the present invention is not limited to the above examples and can be applied to many impact-resistant sliding parts.

[0085] The present embodiment provides a technology for suppressing fatigue failure of sliding materials due to impact loads by reconsidering the very existence of solid lubricant embedded parts. For example, in sliding materials used in press dies, an impact load of 45 MPa occurs for 0.1 seconds as shown in Figure 2. The present embodiment is applicable to cases where such a sudden load occurs.

[0086] Even under harsh sliding conditions where the sliding surface falls into boundary lubrication due to the occurrence of impact loads, the use of low-friction materials maintains a fluid lubrication state, reduces the amount of solid lubricant embedded that impairs bearing rigidity, reduces the deformation of the sliding material and reduces the generated stress, and the addition of extrusion molding increases the fatigue load, and reciprocating sliding is repeated in a short period of time, resulting in a repeated impact load of 10 6 This makes it possible to maintain a healthy state even under sliding conditions of more than 100 times.

[0087] Although the embodiment has been described above, this embodiment is presented as an example and is not intended to limit the scope of the invention. This novel embodiment can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. This embodiment and its modifications are included within the scope and spirit of the invention, and are also included in the inventions and their equivalents as set forth in the claims. [Explanation of symbols]

[0088] 1.Sliding material, 1A.Sliding surface, 2.Base, 3A.Cr-Fe-Si intermetallic compound, 3B.Mn-Fe-Si intermetallic compound

Claims

1. A sliding material used in a sliding environment where impact loads occur, A base material made of a Cu-Zn-Al brass casting alloy, an intermetallic compound of Mn silicide or Cr silicide, which has a nanoindentation hardness of 15 GPa or more, contained in the base material; a solid lubricant-embedded portion exposed on the surface of the sliding material, A sliding material, wherein the embedded ratio of the solid lubricant embedded portion on the sliding surface of the sliding material is 15.8% or less.

2. 2. The sliding material according to claim 1, wherein the sliding material has a rigidity of 7.5 MPa / mm or more.

3. 2. The sliding material according to claim 1, wherein the surface of the sliding material has a resin coating containing a solid lubricant.

4. 2. The method for producing a sliding material according to claim 1, comprising the steps of: casting a material; forming a billet from the cast material; and extruding the billet.

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