JP6242424B2 - Copper-based sliding member - Google Patents

Description

  The present invention relates to a copper-based sliding member used for a reciprocating sliding portion of various industrial machines.

  Conventionally, a copper-based sliding member to which graphite is added as a lubricating component has been used. For example, in the copper-based sliding member coated with the copper alloy layer of Patent Document 1, the number of graphite powder in the copper alloy layer is reduced by adding graphite having a large particle size of 75 to 900 μm to the copper alloy layer. The copper alloy forms a network, so that it becomes a sliding member having higher strength than a conventional copper alloy to which graphite having a small particle size is added. Moreover, in the copper-type sliding member which coat | covered the copper alloy layer of patent document 2, solid lubricants, such as graphite, are contained in Bi by including solid lubricants, such as Bi and graphite, as a lubrication component in a copper alloy layer. It is said that it is dispersed in the sintered copper alloy as a phase that is taken in and coexists, thereby increasing the strength of the sliding member.

JP 2000-309807 A JP 2002-285262 A

  In the copper-based sliding member of Patent Documents 1 and 2 described above, as shown in FIG. 4A, a metal part such as a copper alloy forms a network, and a solid lubricant is surrounded by the metal part. Are dispersed in the metal in the form of When the copper-based sliding member of Patent Documents 1 and 2 is applied to the reciprocating sliding portion, first, at the moment when the sliding direction of the mating member that reciprocally slides changes, the surface of the mating member and the copper-based sliding member are changed. The relative speed with the sliding surface of the moving member is zero. At this time, only the load parallel to the thickness direction of the sliding layer is applied from the mating member to the sliding layer of the copper-based sliding member.

  Next, as shown in FIG. 4B, a dynamic friction state (sliding (sliding) occurs between two surfaces of the sliding surface of the copper-based sliding member and the counterpart member from the moment when the counterpart member starts to move. In the meantime, the sliding layer of the copper-based sliding member is elastically deformed by a load in the direction of movement of the mating member, and no sliding (sliding) occurs between the two surfaces. In this case, the force (starting force) for causing sliding (sliding) between the two surfaces of the copper-based sliding member and the mating member includes the force required for elastic deformation of the sliding layer. And when the copper alloy of a sliding layer forms a network like patent document 1, 2, since a deformation | transformation is easy to propagate to the whole copper alloy network as shown to Fig.4 (a), a sliding layer The amount of elastic deformation increases, so that the starting force increases. In other words, the coefficient of static friction between the sliding surface of the copper-based sliding member and the mating member increases. For this reason, at the moment when sliding (sliding) occurs between the two surfaces of the copper-based sliding member and the mating member, a large frictional force is applied between the two surfaces, and the surface of the sliding layer is worn. Is likely to occur.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a copper-based sliding member that has a low coefficient of static friction with a counterpart member and is suitable for use in a reciprocating sliding portion. It is in.

  In order to achieve the above-described object, in the invention according to claim 1, a copper-based sliding member in which a sliding layer having a sliding surface is provided on the surface of a steel back metal, wherein the sliding layer is made of copper. An alloy and 20 to 40% by volume of graphite, wherein the copper alloy contains 1 to 15% by mass of Sn, and the balance is made of copper and inevitable impurities. The sliding layer includes the graphite Including an island-shaped copper alloy phase dispersed in the sliding layer in the form of a sea-island structure surrounded by the island-shaped copper alloy phase having a length in the direction parallel to the sliding surface of 25 to 500 μm The ratio of the island-shaped copper alloy phase having a length in the direction parallel to the sliding surface with respect to the sliding layer is 25 to 500 μm is 5 to 40% by volume.

  In the invention which concerns on Claim 2, the copper-type sliding member of Claim 1 WHEREIN: The island-shaped copper alloy phase whose length of a parallel direction to the said sliding surface is 25-500 micrometers is parallel to the said sliding surface. The aspect ratio defined by the ratio (x / y) of the length x in the direction and the length y in the direction perpendicular to the sliding surface is 1.2 to 5 and is 50% by volume or more. And

  In the invention which concerns on Claim 3, in the copper-type sliding member of Claim 1 or Claim 2, the said copper alloy is further 1-15 mass% of Ni, and 0.01-0.5 mass% of P. It contains at least one of the above.

  In the invention which concerns on Claim 4, in the copper-type sliding member in any one of Claim 1 thru | or 3, the said copper alloy is further 1-10 mass% of at least 1 or more types of Pb and Bi. It is characterized by containing.

  In the invention according to claim 1, as shown in FIG. 1, the sliding layer includes an island-like copper alloy phase dispersed in the sliding layer in the form of a sea-island structure surrounded by graphite. It has been found that the static friction coefficient with the mating member is lowered when the ratio of the island-like copper alloy phase having a length in the direction parallel to the sliding surface of 25 to 500 μm is 5 to 40% by volume. This is presumed to be performed by the following mechanism.

  When the copper-based sliding member of the present invention is applied to the reciprocating sliding portion, first, at the moment when the sliding direction of the mating member that reciprocates is changed, the surface of the mating member and the copper-based sliding member slide. The relative speed with the surface becomes zero. And, from the moment when the movement of the mating member starts, until the transition to a dynamic friction state (a state where sliding (sliding) occurs between the sliding surface of the copper-based sliding member and the mating member), Although the sliding layer of the copper-based sliding member receives a load in the direction of movement of the mating member, as shown in FIG. 1, the island-shaped copper alloy phase is taken in by the surroundings, so at the interface with the graphite Since slip occurs, only a slight elastic deformation occurs in the island-like copper alloy phase itself. In addition, even if a slight elastic deformation occurs in the island-like copper alloy phase, it is blocked by the surrounding graphite, and other island-like copper alloy phases and copper alloy phases other than the island-like copper alloy phase (partly network) It does not propagate to the copper alloy phase). In addition, the island-like copper alloy phase existing between the copper alloy phases other than the island-like copper alloy phase (copper alloy phase partially forming a network) and the surrounding graphite are other than the island-like copper alloy phase. It suppresses that the elastic deformation of the copper alloy phase of a form (copper alloy phase which formed the network partially) propagates to the copper alloy phase of forms other than other island-like copper alloy phases. For this reason, the amount of elastic deformation of the sliding layer is reduced, and the frictional force at the time of activation applied to the sliding layer is reduced. In other words, the sliding layer of the copper-based sliding member of the present invention has a low coefficient of static friction with the counterpart member.

  Moreover, in the invention which concerns on Claim 1, although the ratio of the island-like copper alloy phase whose length of a parallel direction with respect to the sliding surface with respect to a sliding layer is 25-500 micrometers is 5-40 volume%, the island shape When the ratio of the copper alloy phase is less than 5% by volume, the effect of reducing the elastic deformation amount of the sliding layer becomes insufficient, and the static friction coefficient with the mating member increases. On the other hand, when the ratio of the island-like copper alloy phase exceeds 40% by volume, the strength of the sintered layer after the primary sintering described later becomes too low, so the sintered layer is destroyed during rolling, and the present invention A copper-based sliding member cannot be produced. In addition, the island-shaped copper alloy phase contained in the sliding layer of the copper-based sliding member is not only an island-shaped copper alloy phase having a length in the direction parallel to the sliding surface of 25 to 500 μm, but also parallel to the sliding surface. A small amount (5% by volume or less with respect to the sliding layer) of an island-shaped copper alloy phase having a length in the direction of less than 25 μm or an island-shaped copper alloy phase having a length exceeding 500 μm may be included.

  Although the volume ratio of the island-shaped copper alloy phase to the sliding layer is difficult to directly measure, the island-shaped copper area relative to the area of the sliding layer in the cross-sectional structure of the sliding layer perpendicular to the sliding surface. This can be confirmed by measuring the ratio of the area of the alloy phase. In the invention according to claim 1, the length in the direction parallel to the sliding surface of the island-shaped copper alloy phase is the sliding of the island-shaped copper alloy phase in the cross-sectional structure of the sliding layer perpendicular to the sliding surface. It is the length in the direction parallel to the surface.

  Further, graphite is contained in the sliding layer as a lubricating component, and is further involved in the formation of island-like copper alloy phases dispersed in the sliding layer in the form of a sea-island structure surrounded by graphite. If the content of graphite in the sliding layer is less than 20% by volume, the island-shaped copper alloy phase dispersed in the sliding layer in a form surrounded by graphite becomes insufficient. On the other hand, if the content of graphite in the sliding layer exceeds 40% by volume, the sliding layer becomes brittle.

  Moreover, the copper alloy in a sliding layer contains 1-15 mass% of Sn. Sn has the effect of increasing the strength of the copper alloy, but if the Sn content is less than 1% by mass, the effect is insufficient. On the other hand, if the Sn content exceeds 15% by mass, the copper alloy becomes brittle.

  In the invention according to claim 2, the island-shaped copper alloy phase having a length in the direction parallel to the sliding surface of 25 to 500 μm has a length x parallel to the sliding surface and a direction perpendicular to the sliding surface. When the aspect ratio defined by the ratio (x / y) to the length y is 1.2 to 5% is 50% by volume or more, the static friction coefficient between the copper-based sliding member and the mating member is Found lower. This is due to the fact that the shape of the island-shaped copper alloy phase grains has a slightly long anisotropy in the direction parallel to the sliding surface. That is, since the mating member reciprocates horizontally in the horizontal direction with respect to the sliding surface of the copper-based sliding member, the island-shaped copper alloy phase should be slightly longer in the direction parallel to the sliding surface. Sliding between the island-like copper alloy phase and graphite is likely to occur. For this reason, the coefficient of static friction with the counterpart member is lowered.

  Further, as in the invention according to claim 3, the copper alloy may further contain at least one of Ni in an amount of 1 to 15% by mass and P in an amount of 0.01 to 0.5% by mass. Even if these elements are contained in the copper alloy, the effect of reducing the coefficient of static friction with the counterpart member is sufficiently exhibited by the island-like copper alloy phase in the sliding layer.

  Further, as in the invention according to claim 4, the copper alloy may further contain 1 to 10% by mass of at least one of Pb and Bi. Pb and Bi are lubricating components and have the effect of lowering the dynamic friction coefficient during the dynamic friction of the sliding layer. However, when the content of at least one or more of Pb and Bi is less than 1% by mass, the effect Is insufficient. On the other hand, if the content of at least one of Pb and Bi exceeds 10% by mass, the sliding layer becomes brittle.

It is a schematic diagram which shows the copper-type sliding member containing an island-like copper alloy phase. It is a figure for demonstrating formation of the copper alloy phase in the manufacturing process of the copper-type sliding member in case the porosity at the time of dispersion | spreading is large. It is a figure for demonstrating formation of the copper alloy phase in the manufacturing process of a copper-type sliding member when the porosity at the time of dispersion | spreading is small. It is a figure for demonstrating the friction generation | occurrence | production mechanism of the copper-type sliding member which added the conventional solid lubricant.

  A copper-based sliding member made of a copper alloy and graphite according to this embodiment will be described with reference to FIGS. The manufacturing process of the copper-type sliding member which concerns on this embodiment is performed in order of powder preparation, powder mixing, dispersion | distribution, primary sintering, primary rolling, and secondary sintering. First, a copper alloy powder having an average particle diameter d50 of 25 to 50 μm is prepared by a water atomization method. The average particle size d50 means a particle size having a cumulative volume of 50% in the particle size distribution measurement using a laser diffraction / scattering method. Moreover, the powder produced by water atomization becomes irregular shaped powder (powder having a non-spherical shape).

Next, the copper alloy powder is mixed with a scaly graphite powder having a flat shape (manufactured by Nippon Graphite Industry Co., Ltd.) using a general mixer. The scaly graphite powder has a particle size of 45 to 75 μm and occupies 60% by mass or more of the entire graphite powder, and the maximum particle size is 300 μm or less. The particle size of the flaky graphite powder is measured using a sieve. The particle size of the scaly graphite powder is the dimension of the longest part of the particles having a flat shape. At this time, the porosity of the mixed powder of copper alloy powder and scaly graphite powder (porosity: 1-AD / TD, AD: apparent density (g / cm ³ ), TD: theoretical density (g / cm ³ )) is 60 to 76%.

  And this mixed powder is spread | dispersed on a steel strip (steel back metal), and a spreading layer is formed. As shown to Fig.2 (a), the porosity (60-76%) of the said mixed powder is maintained for the porosity of a spreading | diffusion layer. The back metal layer is not limited to steel, but may be made of a copper alloy or other metal. The back metal may be made of steel and copper or a copper alloy coated on the surface of the steel.

  After the spraying process, a primary sintering process is performed. In the primary sintering step, it is necessary to perform sintering at a sintering temperature lower by 50 ° C. or more than the temperature (melting point) at which the liquid phase is generated in the copper alloy in order to maintain the porosity of the spray layer during spraying. Thereby, it can prevent that a liquid phase generate | occur | produces in a copper alloy. For example, when sintering a copper alloy containing 10% by mass of tin, sintering is performed at a sintering temperature of 700 to 740 ° C. And after heating of a copper alloy is started and it becomes sintering temperature, it hold | maintains at the sintering temperature for 2 to 10 minutes, and cools after that. In the primary sintering step, sintering is performed so that the shrinkage ratio (shrinkage ratio: 1-sintered layer thickness (mm) / spreading layer thickness (mm)) is 3 to 10%. Thus, when sintering was performed such that the shrinkage rate during primary sintering was 3 to 10%, the porosity of the sintered layer was 55 to 75 as shown in FIG. %become. In addition, when sintering is performed at a sintering temperature at which a liquid phase is generated in the copper alloy, the porosity of the sintered layer is reduced, and the shrinkage rate during primary sintering exceeds 10%. And when the cross section of the sintered layer when the shrinkage rate during primary sintering exceeds 10%, the neck formation between the copper alloy powders is often observed as in the structure shown in FIG. As a result, the amount of island-shaped copper alloy phase formed in the sintered layer (sliding layer) is reduced. On the other hand, if the shrinkage rate during primary sintering is less than 3%, the strength of the sintered layer is too low, and the sintered layer is destroyed during rolling described later.

  After the primary sintering step, a rolling step for densifying the sintered layer is performed using a rolling mill. When the porosity of the sintered layer before rolling is 55 to 75% (FIG. 2 (b)), the crushing allowance during rolling (the thickness of the sintered layer having pores before rolling and the void after rolling) There are many differences between the thickness of the sintered layer that has been eliminated and the holes have been densified. For this reason, as shown in FIG.2 (c), the direction of the major axis of scaly graphite powder aligns after rolling. Further, in the primary sintering process, as shown in FIG. 2 (b), since there is little neck formation between the copper alloy powders, in the subsequent rolling process, the scaly graphite powder enters the gaps between the copper alloy powders, Many island-like copper alloy phases surrounded by the graphite powder are formed. On the other hand, when the porosity of the sprayed layer is less than 60% (FIG. 3A), the porosity of the sintered layer is also lowered. And when the porosity of the sintered layer before rolling is less than 55%, as shown in FIG. For this reason, as shown in FIG.3 (c), the direction of the major axis of scaly graphite powder does not align after rolling. Further, in the primary sintering process, as shown in FIG. 3 (b), there is much neck formation between the copper alloy powders. The island-like copper alloy phase surrounded by the scaly graphite powder cannot be formed.

  After the rolling process (primary rolling process), a secondary sintering process is performed. In this secondary sintering process, sintering is performed under the same conditions as the primary sintering process, and a secondary rolling process is performed as necessary. .

  When a copper alloy powder having an average particle diameter d50 of less than 25 μm is used, the porosity of the sintered layer after the primary sintering becomes greater than 75%, so that the strength of the sintered layer is lowered, and the sintered layer is sintered during rolling. The stratification is destroyed. On the other hand, when the average particle diameter d50 of the copper alloy powder exceeds 50 μm, the porosity of the sintered layer after the primary sintering becomes smaller than 55%, so the island-shaped copper alloy phase surrounded by the scaly graphite powder is Little formed.

  As shown in FIG. 2 (c), the porosity of the sintered layer after primary sintering is 55 to 75%, and when the crushing allowance during rolling is large, the long axis of the flake graphite powder Although the orientations are uniform, the use of flaky graphite powder with a small particle size makes it difficult to align the major axes as compared with flaky graphite powder with a large particle size. For this reason, the smaller the particle size of the scaly graphite powder, the smaller the contribution to the formation of the island-like copper alloy phase surrounded by the scaly graphite powder. If the amount of scaly graphite contained in the sliding layer is constant, the larger the particle size of scaly graphite powder, the smaller the number of powders, and the island-like copper alloy phase surrounded by scaly graphite powder. Becomes difficult to form. Thus, the island-like copper alloy phase surrounded by the flaky graphite powder is less likely to be formed when the particle size of the flaky graphite is too small or too large. Specifically, the flaky graphite powder having a particle size of less than 45 μm has a small contribution to the formation of the island-like copper alloy phase surrounded by the flaky graphite powder, and the flaky graphite powder having a particle size exceeding 75 μm is also used. The contribution to the formation of the island-shaped copper alloy phase surrounded by the scaly graphite powder is small. Therefore, unless a scaly graphite powder containing 60% or more of particles having a particle size in the range of 45 to 75 μm is used, the island-like copper alloy phase surrounded by the scaly graphite powder is not formed. For the reasons described above, even when scaly graphite powder having a maximum particle size exceeding 300 μm is included, the island-shaped copper alloy phase surrounded by scaly graphite powder is difficult to form.

  Next, Examples 1 to 14 and Comparative Examples 1 to 6 according to this embodiment were produced, and the form of the copper alloy phase was measured, and a reciprocating sliding test was performed. Table 1 shows the measurement results of the components of Examples 1 to 14 and Comparative Examples 1 to 6, the form of the copper alloy phase, and the static friction coefficient in the reciprocating sliding test.

  For the cross-sectional measurement of the copper-based sliding member, the composition image (magnification: 50 times) was taken in the range of 2.3 mm × 0.7 mm by cutting in the direction perpendicular to the sliding surface. In addition, the obtained composition image is obtained by using a general image analysis method (analysis software: Image-Pro Plus (Version 4.5); manufactured by Planetron Co., Ltd.) having a length in the direction parallel to the sliding surface of 25 to 25. The sum of the area of the island-shaped copper alloy phase which is 500 μm was measured, and the proportion of the island-shaped copper alloy phase whose length in the direction parallel to the sliding surface was 25 to 500 μm was calculated from the area of the entire sliding layer. . Moreover, the ratio of this area calculated | required the average using the composition image of six visual fields (six different arbitrary cross sections). This result is shown in the column “25 to 500 μm island-shaped copper alloy phase (volume%)” in Table 1.

  In addition, the aspect ratio is obtained by using the above analysis software for the obtained composition image when the length in the thickness direction of the sliding layer is set as the Y axis and the length in the vertical direction is set as the X axis. The length (y) in the Y-axis direction and the length (x) in the X-axis direction of the island-shaped copper alloy phase were measured, and the ratio (x / y) of these lengths was calculated and determined. The sum of the areas having an aspect ratio of 1.2 to 5 was measured, and the aspect ratio was 1 from the total area of the island-shaped copper alloy phase having a length in the direction parallel to the sliding surface of 25 to 500 μm. The ratio of the island-like copper alloy phase of 2 to 5 was calculated. The results are shown in the column “Aspect ratio: 1.2 to 5 (volume%)” in Table 1.

  The reciprocating sliding test was performed under the conditions shown in Table 2. The static friction coefficient was measured by measuring the friction coefficient immediately after the sliding direction was changed and repeating this for 4 hours to obtain the average value. In addition, in the measurement of the friction coefficient in the reciprocating sliding test, the peak of the friction coefficient when the sliding direction changes is measured as the static friction coefficient. The test time was 4 hours, but when the amount of wear exceeded 50 μm, it was judged as abnormal wear and the test was terminated.

  In Examples 1 to 3 and 6 to 11, an irregularly shaped copper alloy powder having an average particle diameter d50 of 35 μm and a particle diameter in the range of 45 to 75 μm produced by using the water atomization method is 80% by mass. Occurred and the flaky graphite powder having a maximum particle size in the range of 106 to 150 μm was mixed using a general mixer so as to be the components shown in Table 1 to prepare a mixed powder. The components of Sn, Ni, P, Pb, and Bi are alloyed and contained in the copper alloy powder. And the mixed powder produced on the steel strip (steel back metal) was spread | dispersed, the spreading layer was formed, primary sintering was performed at the sintering temperature of 700-740 degreeC, and the sintered layer was formed. Next, rolling to densify the sintered layer and secondary sintering at a sintering temperature of 700 to 740 ° C. were performed to produce a copper-based sliding member. In addition, in the column of “graphite 45 to 75 μm (mass%)” in Table 1, the mass ratio of the raw graphite powder having a particle size in the range of 45 to 75 μm is shown. "Porosity (%)" column shows the porosity of the spray layer, and "Shrinkage (%)" column shows the shrinkage ratio (shrinkage ratio: 1- after primary sintering) in the primary sintering step. Sintered layer thickness (mm) / spreaded layer thickness (mm)), and the “sintered layer porosity (%)” column shows the porosity of the sintered layer after primary sintering.

  Example 4 was prepared in the same manner as in Example 1 except that an irregularly shaped copper alloy powder having an average particle diameter d50 of 50 μm produced using a water atomization method was used as the copper alloy powder.

  Example 5 uses a scaly graphite powder having a particle size in the range of 45 to 75 μm occupying 60% by mass and a maximum particle size in the range of 106 to 150 μm as the scaly graphite powder. Except for the above, it was produced in the same manner as in Example 1.

  In Example 13, a copper alloy powder having an average particle diameter d50 of 25 μm and produced using a water atomizing method was used as a copper alloy powder, and the other than that, it was produced in the same manner as in Example 1.

  In Example 14, a scaly graphite powder having a particle size in the range of 45 to 75 μm occupies 95% by mass and a maximum particle size in the range of 106 to 150 μm is used. Except for the above, it was produced in the same manner as in Example 1.

  In Examples 1 to 11, 13, and 14, 5 to 40% by volume of an island-like copper alloy phase having a length in the direction parallel to the sliding surface of 25 to 500 μm was formed, resulting in a low coefficient of static friction. In Examples 3, 13, and 14, the length in the direction parallel to the sliding surface is 25 to 500 μm by controlling the sintered layer to have a higher porosity (spreading layer porosity). Many island-like copper alloy phases are formed. In particular, in Example 3, the length in the direction parallel to the sliding surface with respect to the sliding layer is 25 to 500 μm by controlling so that the porosity of the sintered layer (the porosity of the spreading layer) is increased. The ratio of a certain island-like copper alloy phase is formed as much as 40% by volume. In such Examples 3, 13, and 14, among the island-like copper alloy phases whose length in the direction parallel to the sliding surface is 25 to 500 μm, those having an aspect ratio of 1.2 to 5 are 50% by volume or more. In particular, the coefficient of static friction was low.

Example 12 was produced in the same manner as in Example 1, but hard particles (Mo ₂ C) were also added and mixed at the same time in the powder mixing step. The component amount of the hard particles was added as shown in Table 1. Even when hard particles were added, the same results as in Example 1 were obtained.

  Comparative Example 1 was prepared in the same manner as in Example 1 except that the same scaly graphite powder as in Example 1 was used, and the graphite content in the sliding layer was 15% by volume. In Comparative Example 1, since the graphite content in the sliding layer was as low as 15% by volume, the ratio of the copper alloy surrounded by the scaly graphite powder was low. For this reason, the island-like copper alloy phase surrounded by graphite was hardly formed in the sliding layer, and the static friction coefficient was higher than that of Example 1.

  Comparative Example 2 is a flaky graphite powder having a particle size in the range of 45 to 75 μm occupying 50% by mass, and in the range of 75 to 300 μm occupying 50% by mass. Other than this, it was produced in the same manner as in Example 1. Since this comparative example 2 contains only 50% by mass of scaly graphite powder having a particle size in the range of 45 to 75 μm, the number of scaly graphite powder is small, and the copper alloy is hardly surrounded by the scaly graphite powder. . For this reason, the island-like copper alloy phase surrounded by graphite was hardly formed in the sliding layer, and the static friction coefficient was higher than that of Example 1.

  Comparative Example 3 was produced in the same manner as in Example 1 except that an irregularly shaped copper alloy powder having an average particle diameter d50 of 55 μm produced using a water atomization method was used as the copper alloy powder. In Comparative Example 3, since the average particle diameter d50 of the copper alloy powder was as large as 55 μm, the porosity of the spray layer was low, and the porosity of the sintered layer was also low. For this reason, the island-like copper alloy phase surrounded by graphite was hardly formed in the sliding layer, and the static friction coefficient was higher than that of Example 1.

  Comparative Example 4 was prepared in the same manner as in Example 1 except that a copper alloy powder having an average particle diameter d50 of 35 μm prepared using a gas atomization method was used as the copper alloy powder. When copper alloy powder is produced using the gas atomization method, the powder has a spherical shape. In Comparative Example 3, since the spherical copper alloy powder was used, the porosity of the spray layer was low, and the porosity of the sintered layer was also low. For this reason, the island-like copper alloy phase surrounded by graphite was hardly formed in the sliding layer, and the static friction coefficient was higher than that of Example 1.

  In Comparative Example 5, sintering was performed at a sintering temperature of 850 ° C. in which a part of the copper alloy was in a liquid phase, and the others were produced in the same manner as Example 1. In Comparative Example 5, the porosity of the spray layer was 67%, but a liquid phase of the copper alloy was generated during the primary sintering, and the porosity of the sintered layer was reduced to 51%. For this reason, the island-like copper alloy phase surrounded by graphite was hardly formed in the sliding layer, and the static friction coefficient was higher than that of Example 1.

  Comparative Example 6 was prepared in the same manner as in Example 1 except that a mixed powder of copper powder and tin powder was used as the copper alloy powder. In this comparative example 5, in the temperature raising process during primary sintering, first, the tin powder becomes a liquid phase, and a part of the copper powder is made into a liquid phase by the liquid phase of tin, and the porosity of the sintered layer is 51. %. For this reason, the island-like copper alloy phase surrounded by graphite was hardly formed in the sliding layer, and the static friction coefficient was higher than that of Example 1.

Claims (4)

A copper-based sliding member provided with a sliding layer having a sliding surface on the surface of the steel back metal,
The sliding layer is made of a copper alloy and 20 to 40% by volume of graphite, the copper alloy contains 1 to 15% by mass of Sn, and the remainder is made of copper and inevitable impurities.
The sliding layer includes an island-shaped copper alloy phase dispersed in the sliding layer in the form of a sea-island structure surrounded by the graphite,
The island-shaped copper alloy phase includes one having a length in a direction parallel to the sliding surface of 25 to 500 μm,
The ratio of the island-like copper alloy phase whose length in a direction parallel to the said sliding surface with respect to the said sliding layer is 25-500 micrometers is 5-40 volume%, The copper-type sliding member characterized by the above-mentioned.   The island-shaped copper alloy phase having a length parallel to the sliding surface of 25 to 500 μm is a ratio of a length x parallel to the sliding surface and a length y perpendicular to the sliding surface ( 2. The copper-based sliding member according to claim 1, wherein one having an aspect ratio defined by x / y) of 1.2 to 5 is 50% by volume or more.   The copper-based slide according to claim 1 or 2, wherein the copper alloy further contains at least one of Ni in an amount of 1 to 15 mass% and P in an amount of 0.01 to 0.5 mass%. Moving member.   The copper-based sliding member according to any one of claims 1 to 3, wherein the copper alloy further contains 1 to 10% by mass of at least one of Pb and Bi.