JP2015183237A - Slide member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a slide member having high anticorrosion and strong joint between a slide layer and steel back metal.SOLUTION: A porous sinter layer 4 forming a slide layer 3 is formed of a Ni-P alloy phase 7 and a granular Fe or Fe alloy phase 8 and includes no Cu component, so that the porous sinter layer 4 has high anticorrosion to an organic acid and sulfur constituent. The Ni-P alloy phase 7 functions as a binder connecting the granular Fe or Fe alloy phases 8, and coats a surface of a steel back metal layer 2 serving as an interface between it and the slide layer 3. On a surface of the steel back metal layer 2, a low pearlitic phase part 8 having a ratio of pearlitic phase lower by 50% or more with respect to a pearlitic phase in a tissue on a center part of the steel back metal layer 2 in a thickness direction, is formed, so that shear on the interface between the slide layer 3 and the low pearlitic phase part 8 of the steel back metal layer 2, hardly occurs, and joint between the slide layer 3 and steel back metal layer 2 can be reinforced.

Description

  The present invention relates to a sliding member having high corrosion resistance and strong bonding between a resin composition of a sliding layer and a steel backing metal.

  Conventionally, a sintered copper-based material having a porosity of about 5 to 25% is used for a sliding member for a fuel injection pump. This sliding member supplies the liquid fuel from the outer peripheral surface side to the inner peripheral surface (sliding surface) side of the cylindrical sliding member through the pores existing inside the sliding member. A fluid lubricating film of liquid fuel is formed on the surface (sliding surface), and a shaft that rotates at high speed is supported. Such a sintered copper-based material has a problem that corrosion of a copper alloy occurs due to an organic acid and a sulfur component contained in the fuel, and this copper-based corrosion product is mixed into the fuel. For this reason, in order to improve corrosion resistance, the sintered copper-type sliding material containing Ni, Al, and Zn is proposed (for example, refer patent documents 1-3).

  Conventionally, a porous sintered layer made of a copper alloy has been provided on the surface of the steel back metal via a copper plating layer, and further, a multi-layer in which pores and surfaces of the porous sintered layer are impregnated and coated with a resin composition The sliding member which consists of these sliding materials is used (for example, refer patent document 4, 5). And what applied such a multilayer sliding material to the sliding member for fuel-injection pumps is proposed (for example, refer patent document 6).

JP 2002-180162 A JP 2013-217493 A JP 2013-237898 A JP 2002-61653 A JP 2001-355634 A JP2013-83304A

  By the way, although the sintered copper-type sliding material of patent documents 1-3 contains Ni, Al, and Zn and has improved corrosion resistance, corrosion of the copper alloy by the organic acid contained in fuel, and a sulfur component is carried out. It cannot be completely prevented. In addition, the sintered copper-based sliding material of Patent Documents 1 to 3 is low in strength to form pores in the entire inside of the sliding member, and is particularly suitable for a common rail fuel injection pump as shown in Patent Document 6 and the like. As the sliding member used, the load capacity is insufficient.

  Moreover, in the multilayer sliding material of patent documents 4-6, since it has the structure of a steel back metal, intensity | strength is high. However, the porous sintered layer made of a copper alloy is corroded by an organic acid or sulfur component contained in the fuel or lubricating oil. Further, without providing a copper plating layer as in Patent Documents 4 to 6 on the surface of the steel back metal, a powder of Fe or Fe alloy is simply sprayed on the surface of the steel back metal and sintered to form a porous sintered layer. Furthermore, it has been found that the sliding material in which the porous sintered layer is impregnated with the resin composition has weak bonding at the interface between the sliding layer and the steel backing metal.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a sliding member having high corrosion resistance and strong bonding between the sliding layer and the steel back metal.

  In order to achieve the above object, in the invention according to claim 1, in the sliding member in which a sliding layer comprising a porous sintered layer and a resin composition is provided on a steel back metal layer, the porous member The sintered layer is composed of a Ni-P alloy phase and a granular Fe or Fe alloy phase, and the steel back metal layer is a carbon steel having a carbon content of 0.05 to 0.3 mass%, and has a structure. Is composed of a ferrite phase and a pearlite phase, and the surface of the steel back metal layer serving as an interface with the sliding layer is compared with the pearlite phase in the structure in the center in the thickness direction of the steel back metal layer. A low pearlite phase portion in which the proportion of the pearlite phase is reduced by 50% or more is formed, and the Ni-P alloy phase of the porous sintered layer connects the granular Fe or Fe alloy phases to each other, and Surface of the steel back metal layer serving as an interface with the dynamic layer Characterized in that it covers the whole.

  According to a second aspect of the present invention, in the sliding member according to the first aspect, the Ni component of the Ni-P alloy phase is diffused in the low pearlite phase portion.

  According to a third aspect of the present invention, in the sliding member according to the first or second aspect, the thickness of the low pearlite phase part is 1 to 50 μm.

  In the invention which concerns on Claim 4, in the sliding member in any one of Claim 1 thru | or 3, the area ratio of the said pearlite phase in the surface of the said low pearlite phase part is 0 to 10%. It is characterized by.

  In the invention which concerns on Claim 5, in the sliding member in any one of Claim 1 thru | or 4, the composition of the said Ni-P alloy phase is 9-13 mass% P, remainder Ni, and an unavoidable impurity It is characterized by comprising.

  In the invention which concerns on Claim 6, in the sliding member in any one of Claim 1 thru | or 5, the ratio of the said Ni-P alloy phase in the said porous sintered layer is the said porous sintered layer. The said Ni-P alloy phase is 5-40 mass parts with respect to 100 mass parts of this, It is characterized by the above-mentioned.

  In the invention according to claim 1, the porous sintered layer constituting the sliding layer is composed of a Ni-P alloy phase and a granular Fe or Fe alloy phase, and does not contain a Cu component. High corrosion resistance to sulfur components. The Ni-P alloy phase of the porous sintered layer functions as a binder that connects the granular Fe or Fe alloy phases, and covers the entire surface of the steel back metal layer serving as an interface with the sliding layer. The resin composition constituting the sliding layer is not in contact with the steel back metal layer. The steel back metal layer is carbon steel having a carbon content of 0.05 to 0.3% by mass, and the structure is composed of a ferrite phase and a pearlite phase, but the carbon content is 0.05% by mass. When using less carbon steel, the strength of the steel back metal layer is low and the strength of the sliding member becomes insufficient. On the other hand, when carbon steel having a carbon content exceeding 0.3 mass% is used, the ratio of the pearlite phase in the low pearlite phase portion of the steel back metal layer is increased. Furthermore, on the surface of the steel back metal layer serving as the interface with the sliding layer, the ratio of the pearlite phase to the pearlite phase in the structure at the center in the thickness direction of the steel back metal layer is reduced by 50% or more. By forming the pearlite phase portion, shearing at the interface between the sliding layer and the low pearlite phase portion of the steel back metal layer is difficult to occur, and the bonding between the sliding layer and the steel back metal layer can be strengthened.

  In addition, as in the invention according to claim 2, the Ni component of the Ni-P alloy phase is diffused in the low pearlite phase portion, thereby strengthening the bonding between the sliding layer and the steel back metal layer. it can.

  Moreover, like the invention which concerns on Claim 3, the thickness of a low pearlite phase part shall be the range of 1-50 micrometers. Since the thickness of the steel back metal layer is at least 0.3 mm in a general sliding member, if the thickness of the low pearlite phase part is 50 μm or less, the strength of the steel back metal layer is not affected. In addition, when the thickness of the low pearlite phase portion is less than 1 μm, the low pearlite phase portion may not be partially formed on the surface of the steel back metal layer serving as an interface with the sliding layer.

  Further, as in the invention according to claim 4, the area ratio of the pearlite phase on the surface of the low pearlite phase part is 0 to 10%. When the area ratio of the pearlite phase on the surface of the low pearlite phase is 10% or less, the effect of increasing the bonding strength between the sliding layer and the steel back metal layer is enhanced.

  Further, as in the invention according to claim 5, the composition range of the Ni-P alloy phase is composed of 9 to 13% by mass of P, the balance Ni and inevitable impurities, so that the melting point of the Ni-P alloy is lowered. It can be. In addition, as for the composition of a Ni-P alloy phase, it is more desirable to consist of 10-12 mass% P, remainder Ni, and an unavoidable impurity. In the temperature rising process when the porous sintered layer is sintered on the steel back metal layer, all the Ni-P alloy phase components of the porous sintered layer are made into a liquid phase, and the Ni component is converted into the surface of the steel back metal layer. To diffuse. The diffusion of the Ni component to the surface of the steel back metal layer is related to the formation of a low pearlite phase portion on the surface of the steel back metal layer. In the composition of the Ni—P alloy phase, when the P content is less than 9 mass% or exceeds 13 mass%, the melting point of the Ni—P alloy becomes high. This reduces the amount of Ni-P alloy liquid phase generated during sintering, makes it difficult for the Ni component to diffuse to the surface of the steel backing metal layer, and makes it difficult to form a low pearlite phase on the surface of the steel backing metal layer. .

  As in the invention according to claim 6, the proportion of the Ni-P alloy phase in the porous sintered layer is 5 to 40 parts by mass of the Ni-P alloy phase with respect to 100 parts by mass of the porous sintered layer. And The Ni-P alloy phase of the porous sintered layer functions as a binder that connects the granular Fe or Fe alloy phases, and covers the entire surface of the steel back metal layer that serves as an interface with the sliding layer. When the proportion of the Ni-P alloy phase is less than 5 parts by mass, the strength of the porous sintered layer and the bonding between the porous sintered layer and the steel back metal layer become insufficient. On the other hand, if the proportion of the Ni-P alloy phase exceeds 40 parts by mass, the portion to be vacant is filled with the liquid phase of the Ni-P alloy during sintering. The rate is too small.

It is a schematic diagram which shows the cross section of the sliding member which formed the low pearlite phase part on the surface of the steel back metal layer. It is an enlarged view which shows the structure | tissue near the center part of the thickness direction of a steel back metal layer. It is an enlarged view which shows the structure | tissue near the surface of a steel back metal layer. It is a schematic diagram which shows the conventional sliding member.

  The sliding member 1 in which the low pearlite phase portion 8 is formed on the surface of the steel back metal layer 2 according to the present embodiment will be described with reference to FIGS. 1 to 3. FIG. 1 is a schematic view showing a cross section of a sliding member 1 in which a low pearlite phase portion 8 is formed on the surface of a steel back metal layer 2. FIG. 2 is an enlarged view showing the structure near the center of the steel backing metal layer 2 in the thickness direction, and FIG. 3 is an enlarged view showing the structure near the surface of the steel backing metal layer 2.

  As shown in FIG. 1, the sliding member 1 includes a steel backing metal layer 2 and a sliding layer 3, and the sliding layer 3 is composed of a porous sintered layer 4 formed on the steel backing metal layer 2 and a resin composition. It consists of thing 5. The porous sintered layer 4 is composed of granular Fe or Fe alloy phase 6 and Ni—P alloy phase 7. The Ni—P alloy phase 7 is a binder that connects the Fe or Fe alloy phase 6 grains or the Fe or Fe alloy phase 6 grains and the surface of the steel back metal layer 2. Further, the sliding layer 3 is formed with a layer of Ni-P alloy phase 7 so as to cover the entire surface of the steel back metal layer 2 which becomes an interface with the sliding layer 3, and the resin composition of the sliding layer 3. The object 5 is not in contact with the steel back metal layer 2 by the layer of the Ni-P alloy phase 7. Further, as shown in FIG. 1, the grains of Fe or Fe alloy phase 6, or the grains of Fe or Fe alloy phase 6 and the surface of steel back metal layer 2 are bonded via Ni—P alloy phase 7. ing. The Fe or Fe alloy phase 6 grains, or the Fe or Fe alloy phase 6 grains and the surface of the steel back metal layer 2 are formed with portions that are directly contacted or joined by sintering. May be. Further, the Fe or Fe alloy phase 6 grains may be formed such that a part of the surface is not covered with the Ni-P alloy phase 7. However, even in this case, it is necessary that the resin composition 5 of the sliding layer 3 does not come into contact with the surface of the steel back metal layer 2 that is an interface with the sliding layer 3. The porous sintered layer 4 has pores for impregnating the resin composition 5, and the porosity is 10 to 60%. More preferably, the porosity is 20 to 40%.

  The composition of the Ni-P alloy phase 7 consists of 9 to 13% by mass of P, the balance Ni and unavoidable impurities. The composition of the Ni—P alloy phase 7 is a composition range in which the melting point of the Ni—P alloy is lowered. The composition of the Ni-P alloy phase 7 is more preferably composed of 10 to 12% by mass of P, the remaining Ni and inevitable impurities. In the temperature rising process when the porous sintered layer 4 is sintered on the steel back metal layer 2, as described later, all of the seven components of the Ni-P alloy phase of the porous sintered layer 4 are made into a liquid phase, The Ni component is diffused on the surface of the steel back metal layer 2. The diffusion of the Ni component to the surface of the steel back metal layer 2 is related to the formation of the low pearlite phase portion 8 on the surface of the steel back metal layer 2. Further, in the composition of the Ni—P alloy phase 7, when the P content is less than 9 mass% or exceeds 13 mass%, the melting point of the Ni—P alloy becomes high. As a result, the amount of the liquid phase of the Ni—P alloy is reduced during sintering, and the layer of the Ni—P alloy phase 7 is not formed on the entire surface of the sliding layer 3 serving as the interface with the steel back metal layer 2. Thus, a portion where the Ni—P alloy phase 7 is not formed is likely to be generated, and the Ni component is difficult to diffuse to the surface of the steel back metal layer 2, and the low pearlite phase portion 8 Is difficult to form.

  In addition, the Ni-P alloy phase 7 further contains one or more of B component in the range of 1-4% by mass, Si component in the range of 3-12% by mass, and Cr component in the range of 7-14% by mass. It may be a composition.

  The ratio of the Ni—P alloy phase 7 in the porous sintered layer 4 is 5 to 40 parts by mass with respect to 100 parts by mass of the porous sintered layer 4, more preferably 10 ˜20 parts by mass. The ratio of the Ni-P alloy phase 7 is such that the Ni-P alloy phase 7 is composed of Fe or Fe alloy phase 6 grains, or a binder that binds the Fe or Fe alloy phase 6 grains to the surface of the steel back metal layer 2. In addition, the range is suitable for forming the porous sintered layer 4 in a form covering the entire surface of the steel back metal layer 2. When the proportion of the Ni-P alloy phase 7 is less than 5 parts by mass, the strength of the porous sintered layer 4 and the bonding between the porous sintered layer 4 and the steel back metal layer 2 are insufficient. On the other hand, when the proportion of the Ni-P alloy phase 7 exceeds 40 parts by mass, the portion to be vacant is filled with the Ni-P alloy during sintering, so the porosity of the porous sintered layer 4 Is too small.

  The granular Fe or Fe alloy phase 6 in the porous sintered layer 4 may have an average particle diameter of 45 to 180 μm. The composition of the granular Fe alloy is not limited. Generally commercially available grains such as pure iron, hypoeutectoid steel, eutectoid steel, hypereutectoid steel, cast iron, high speed steel, tool steel, austenitic stainless steel, ferritic stainless steel and the like can be used. Whichever Fe alloy is used, the corrosion resistance to organic acids and sulfur components is superior to that of conventional copper alloys. The granular Fe or Fe alloy phase 6 constituting the porous sintered layer 4 reacts with the components of the Ni—P alloy phase 7 on its surface (surface that becomes an interface with the Ni—P alloy phase 7). A phase may be formed. And since the porous sintered layer 4 is comprised from such granular Fe or the Fe alloy phase 6 and the Ni-P alloy phase 7, and Cu component is not contained, it has the corrosion resistance with respect to an organic acid or a sulfur component. Are better.

  The resin composition 5 is impregnated and coated on the pores and the surface of the porous sintered layer 4. As shown in FIG. 1, the resin composition 5 is not in contact with the surface of the steel back metal layer 2. As the resin composition 5, a general sliding resin composition can be used. Specifically, any one or more of fluororesin, polyetheretherketone, polyamide, polyimide, polyamideimide, polybenzimidazole, epoxy, phenol, polyacetal, polyethylene, polypropylene, polyolefin, polyphenylene sulfide, and solid As the lubricant, a resin composition containing any one or more of graphite, graphene, graphite fluoride, molybdenum disulfide, fluororesin, polyethylene, polyolefin, boron nitride, and tin disulfide can be used. Further, the resin composition 5 may further contain one or more of granular or fibrous metals, metal compounds, ceramics, inorganic compounds, and organic compounds as fillers. In addition, the resin, the solid lubricant, and the filler constituting the resin composition 5 are not limited to those exemplified here.

  For the steel back metal layer 2, carbon steel (hyeutectoid steel) having a carbon component content of 0.05 to 0.3% by mass is used. The structure of the steel back metal layer 2 is composed of a ferrite phase 9 and a pearlite phase 10 as shown in FIG. When carbon steel having a carbon component content of less than 0.05% by mass is used, the strength of the steel back metal layer 2 is low, and the strength of the sliding member 1 is insufficient. On the other hand, when carbon steel having a carbon content exceeding 0.3 mass% is used, the proportion of the pearlite phase 10 in the low pearlite phase portion 8 of the steel back metal layer 2 is increased.

  The steel back metal contains the carbon component, and any one of Si of 0.1% by mass or less, Mn of 1% by mass or less, P of 0.04% by mass or less, and S of 0.04% by mass or less. One or more of them may be contained, and the composition may be composed of the remaining Fe and inevitable impurities. The structure of the steel back metal layer 2 is composed of a ferrite phase 9 and a pearlite phase 10, but contains fine precipitates (precipitate phases that cannot be detected even if the structure is observed at 1000 times using a scanning electron microscope). Is acceptable.

The ferrite phase 9 in the steel back metal layer 2 is a phase having a composition close to that of pure iron with a maximum carbon component content of 0.02% by mass. On the other hand, the pearlite phase 10 in the steel back metal layer 2 is a lamellar structure phase in which a ferrite phase and a cementite (Fe ₃ C) phase that is an iron carbide are alternately arranged in a thin plate shape. The pearlite phase 10 has a larger amount of carbon component than the ferrite phase 9. As shown in FIG. 3, the surface of the steel back metal layer 2 serving as the interface with the sliding layer 3 has a pearlite phase with respect to the pearlite phase 10 in the structure in the center in the thickness direction of the steel back metal layer 2. A low pearlite phase portion 8 in which the ratio of 10 is reduced by 50% or more is formed.

  In the present embodiment, in the cross-sectional structure cut in the direction parallel to the thickness direction of the sliding member 1 using an electron microscope, the vicinity of the central portion of the steel back metal layer 2 in the thickness direction, and the sliding layer 3 and An electron image was taken at a magnification of 500 times each near the surface of the steel back metal layer 2 serving as the interface of the steel, and the image was analyzed using a general image analysis method (analysis software: Image-Pro Plus (Version 4.5); The area ratio of the pearlite phase 10 in the structure was measured. And the ratio of the pearlite phase 10 in the structure in the vicinity of the surface of the steel back metal layer 2 serving as the interface with the sliding layer 3 with respect to the pearlite phase 10 in the structure in the central portion in the thickness direction of the steel back metal layer 2 ( It can be confirmed that the low pearlite phase portion 8 is formed on the surface of the steel back metal layer 2 serving as an interface with the sliding layer 3 by reducing the (area ratio) by 50% or more. In addition, the observation part of the area ratio of the pearlite phase 10 in the vicinity of the center part in the thickness direction of the steel back metal layer 2 may not be located at the center part in the thickness direction of the steel back metal layer 2 in a strict sense. This is because the structure between the center position in the thickness direction of the steel back metal layer 2 and the low pearlite phase part 8 has substantially the same structure (the area ratio of the same pearlite phase 10). .

  The thickness of the low pearlite phase portion 8 is 1 to 50 μm from the interface with the sliding layer 3. Furthermore, it is preferable that the thickness of the low pearlite phase part 8 shall be 1-10 micrometers. Since the thickness of the steel back metal layer 2 is at least 0.5 mm in a general sliding member, the strength of the steel back metal layer 2 is not affected if the thickness of the low pearlite phase portion 8 is 50 μm or less. Further, if the thickness of the low pearlite phase portion 8 is less than 1 μm, the low pearlite phase portion 8 may not be partially formed on the surface of the steel back metal layer 2 that serves as an interface with the sliding layer 3.

Further, the low pearlite phase portion 8 of the steel back metal layer 2 serving as an interface with the sliding layer 3 contains a Ni component diffused from the Ni—P alloy phase 7 in the porous sintered layer 4. This Ni component is contained in the low pearlite phase portion 8 in the form of a solid solution in the ferrite phase 9 near the surface of the low pearlite phase portion 8. Although the Ni component diffused from the Ni-P alloy phase 7 of the porous sintered layer 4 to the low pearlite phase portion 8 of the steel backing metal layer 2 is extremely small, the low pearlite phase portion 8 is measured by EPMA (Electron Probe Microanalyzer). The Ni component diffused in is confirmed. Further, the Ni component in the low pearlite phase portion 8 exists in a form dissolved in the ferrite phase 9, and gradually from the surface serving as the interface with the sliding layer 3 of the low pearlite phase portion 8 toward the inside. It can be confirmed that the concentration of the Ni component is decreased. Note that a phase of Ni ₃ P (intermetallic compound) is not formed in the low pearlite phase portion 8.

  Further, the surface of the low pearlite phase portion 8 of the steel back metal layer 2 is particularly reduced in the pearlite phase 10 due to the diffusion of the Ni component. The area ratio of the pearlite phase 10 on the surface of the low pearlite phase portion 8 is preferably 0 to 10% in order to increase the bonding strength between the sliding layer 3 and the low pearlite phase portion 8 of the steel back metal layer 2.

  Next, the joining of the resin composition 15 of the sliding layer 13 and the steel back metal layer 12 in the conventional sliding member 11 will be described with reference to FIG. FIG. 4 is a schematic view showing a sliding member 11 in which a porous sintered layer 14 is formed on a conventional steel back metal layer 12.

  When the pearlite phase is large on the surface of the steel back metal layer 12 serving as an interface with the sliding layer 13, the bonding of the sliding layer 13 with the resin composition 15 becomes weak. As shown in FIG. 4, when such a steel back metal layer 12 is used as the sliding member 11, shear may occur locally at the interface between the resin composition 15 of the sliding layer 13 and the steel back metal layer 12. is there. This is because, when the temperature at which the sliding member 11 is used increases, the thermal expansion amount of the resin composition 15 of the sliding layer 13 is larger than that of the steel back metal layer 12, so that the resin composition 15 of the sliding layer 13 and the steel This is because shear stress is generated at the interface with the back metal layer 12.

Specifically, the thermal expansion coefficient differs between the ferrite phase and the pearlite phase in the steel back metal layer 12, and the pearlite phase contains cementite (Fe ₃ C), which is an iron carbide, and therefore has a smaller thermal expansion coefficient than the ferrite phase. . For this reason, when the temperature of the sliding member 11 rises, the shearing force due to the difference in thermal expansion between the resin composition 15 of the sliding layer 13 and the steel back metal layer 12 becomes non-uniform at the interface. And the difference of thermal expansion amount is large at the interface between the resin composition 15 of the sliding layer 13 and the pearlite phase of the steel backing metal layer 12, and a micro shearing portion is formed by the shear stress due to the difference of the thermal expansion amount. In addition, as the area of the pearlite phase on the surface of the steel back metal layer 12 increases, the area where micro shearing occurs increases, and the interface between the resin composition 15 of the sliding layer 13 and the ferrite phase of the steel back metal layer 12 also increases. It is thought that shear propagates. On the other hand, in this embodiment, a layer of the Ni-P alloy phase 7 is formed on the sliding layer 3 so as to cover the entire surface of the steel back metal layer 3 which becomes an interface with the sliding layer 3, Since the resin composition 5 of the dynamic layer 3 does not come into contact with the steel back metal layer 2, the above problem is prevented. Moreover, the low pearlite phase part 8 in which the ratio of the pearlite phase 10 is reduced by 50% or more with respect to the inside of the steel back metal layer 2 is formed on the surface of the steel back metal layer 2 serving as an interface with the sliding layer 3. Thus, shearing at the interface between the Ni—P alloy phase 7 of the sliding layer 3 and the steel back metal layer 2 due to the difference in thermal expansion coefficient between the ferrite phase 9 and the pearlite phase 10 is difficult to occur.

  Next, a method for producing the sliding member 1 according to this embodiment will be described. First, a mixed powder of Fe or Fe alloy powder and Ni-P alloy powder is prepared. When preparing the mixed powder, it is necessary to include a component that becomes the Ni-P alloy phase 7 of the porous sintered layer 4 in the form of a Ni-P alloy powder. And after mixing the prepared mixed powder on a steel plate at room temperature, it sinters in 930-1000 degreeC reducing atmosphere using a sintering furnace, without pressurizing a powder spreading layer.

  At the time of sintering, when the temperature reaches 880 ° C. in the middle of the temperature rise, Ni—P alloy grains composed of 9 to 13% by mass of P and the balance Ni 2 begin to melt. The liquid phase flows between the Fe or Fe alloy grains or between the Fe or Fe alloy grains and the surface of the steel back metal layer 2 so as to cover the entire surface of the steel back metal layer 2. Formation of the binder layer 4 is started. The Ni—P alloy grains composed of 9 to 13% by mass of P and the balance Ni 2 are completely in a liquid phase at 950 ° C. In addition, the grain of Ni-P alloy which consists of composition of 10-12 mass% P which reduced the content range of P, and remainder Ni becomes completely a liquid phase at 930 ° C.

  The sintering temperature is set to be equal to or higher than the temperature at which the Ni—P alloy grains are completely melted. Moreover, although the composition of the Ni-P alloy will be described later, it is a composition that completely melts at a temperature (A3 transformation point) or higher at which the structure of the steel back metal layer 2 becomes a complete austenite phase.

  When the steel back metal layer 2 reaches 727 ° C. (A1 transformation point) in the temperature rising process during sintering, the structure composed of the ferrite phase 9 and the pearlite phase 10 starts to transform into the austenite phase, and the carbon content is increased. The steel back metal layer 2 of 0.05 to 0.3% by mass has a structure composed entirely of an austenite phase at 900 ° C. Since the austenite phase has a larger gap (distance) between Fe atoms than the ferrite phase 9, the Ni atoms of the Ni—P alloy phase 7 in the porous sintered layer 4 are likely to diffuse into the gap. It becomes a state. As described above, the composition of the Ni-P alloy is such that it completely melts at a temperature higher than the temperature (A3 transformation point) at which the structure of the steel back metal layer 2 becomes a complete austenite phase, and the sintering temperature is Ni The temperature is set to be equal to or higher than the temperature at which the grains of the -P alloy are completely melted. This is because the Ni atoms in the Ni—P alloy phase 7 in the liquid phase state are more diffused into the austenite phase on the surface of the steel back metal layer 2 than the Ni atoms in the Ni—P alloy phase 7 in the solid phase state. It is easy to happen.

  In combination, the Ni-P alloy is completely in a liquid phase during sintering to cover the entire surface of the steel back metal layer 2 and the steel back metal layer 2 is in a complete austenite structure. Ni atoms diffuse on the surface of the back metal layer 2. As a result of this Ni atom being dissolved in the austenite phase, the carbon atoms dissolved in the gaps between the Fe atoms in the austenite phase are diffused so as to be expelled to the inner side of the steel back metal layer 2. The Ni atoms in the liquid phase are diffused into the austenite phase on the surface of the steel back metal layer 2 and become a solid phase at the same time as being dissolved, so that the Ni atoms are near the pole surface of the steel back metal layer 2. Only spread.

  If it becomes 727 degreeC (A1 transformation point) in the cooling process after sintering, the structure | tissue of the steel back metal layer 2 will become a structure | tissue which consists of the ferrite phase 9 and the pearlite phase 10 again. By the above mechanism, the inside of the steel back metal layer 2 becomes a normal structure composed of the ferrite phase 9 and the pearlite phase 10 (the ratio of the pearlite phase 10 is a normal structure determined by the content of the carbon component), and the sliding layer 3 is a structure in which the ratio of the pearlite phase 10 is reduced with respect to the surface of the steel back metal layer 2 on the side that becomes the interface with the steel 3 (the surface of the steel back metal layer 2 is a structure substantially composed of the ferrite phase 9). It is presumed that a low pearlite phase portion 8 is formed. The Ni component is contained in the steel back metal layer 2 in a state where it is dissolved in the ferrite phase 9 near the surface of the low pearlite phase portion 8.

  As described above, the resin composition 5 (which may be diluted with an organic solvent) prepared in advance is applied to the member in which the porous sintered layer 4 is formed on the surface of the steel back metal layer 2. The pores of the binder layer 4 are filled and impregnated so as to cover the surface of the porous sintered layer 4. The member is heated for drying and firing the resin composition 5, and the sliding layer 3 composed of the porous sintered layer 4 and the resin composition 5 is formed on the surface of the steel back metal layer 2. Is done. As the resin composition 5, the resin composition described in paragraph 0027 can be used.

  In addition, it is desirable to use a cold-rolled steel plate (or a strip) as the material for the steel back metal layer 2 of the present embodiment. In a cold rolled steel sheet, strain (atomic vacancies) is introduced into the crystal structure of the steel in the rolling process. This strain is a defect part in which an atomic level gap in which Fe atoms do not exist is formed in a site where Fe atoms should exist in the crystal structure of the steel back metal. The crystal strain in the steel back metal layer 2 gradually moves to the surface side of the steel back metal layer 2 and disappears during the temperature rising process during sintering, but Ni atoms in the Ni-P alloy phase 7 are replaced by this strain. However, it diffuses to the part which was distorted in the crystal on the surface side of the steel back metal layer 2. On the other hand, when a hot-rolled steel sheet is used, since the hot-rolled steel sheet has very little crystal distortion, Ni atoms hardly diffuse into the surface of the steel back metal layer.

In the present embodiment, the mixed powder of Fe or Fe alloy powder and Ni-P alloy powder was used as described above, but Fe-Ni-P-based alloy powder produced by an atomizing method or the like was used. In this case, or when a mixed powder of Ni powder and Fe-P alloy powder is used, only a part of the Ni and P components of the powder composition becomes liquid phase during sintering, and the amount of liquid phase generated is small. The diffusion of Ni atoms to the surface of the steel back metal layer hardly occurs. For this reason, the low pearlite phase part in which the ratio of the pearlite phase decreased is not formed on the surface of the steel back metal layer. Further, since this liquid phase is mainly composed of Ni ₃ P, it is formed so that the Ni ₃ P phase (intermetallic compound) is present at the interface between the sintered porous sintered layer and the steel back metal layer. This Ni ₃ P phase is hard but brittle, and the bonding between the porous sintered layer and the steel back metal layer becomes very weak.

Moreover, it should be avoided to contain Sn having a low melting point as the alloy composition of the porous sintered layer 4 in the present embodiment. Sn has a low melting point and becomes a liquid phase at an extremely initial temperature of about 232 ° C. in the temperature rising process during sintering. However, the Sn atom that has become the liquid phase reacts with the Fe atoms in the steel back metal layer, resulting in porous firing. It is formed so that an Fe ₂ Sn phase or an Fe ₃ Sn phase (intermetallic compound) is present at the interface between the bonding layer and the steel back metal layer. This Fe ₂ Sn phase and Fe ₃ Sn phase are hard but brittle, and the bonding between the porous sintered layer and the steel back metal layer becomes very weak. By including Cu in the alloy composition of the porous sintered layer containing Sn (for example, by containing 3 to 4 times as much Cu by mass as the Sn content), a liquid phase was obtained during sintering. The Sn component diffuses into Cu, and the formation of the Fe ₂ Sn phase and the Fe ₃ Sn phase at the interface between the porous sintered layer and the steel back metal layer can be prevented or alleviated. However, since the Cu component is contained in the porous sintered layer, the corrosion resistance against organic acids and sulfur components is lowered.

Moreover, in this embodiment, although the low pearlite phase part 8 is formed in the surface of the steel back metal layer 2, when using the steel plate which previously formed the Fe plating layer and Ni plating layer on the surface, a sliding member Is expensive. Furthermore, when using a steel plate having an electroless Ni—P alloy plating layer formed on the surface in advance, a large amount of Ni is present at the interface between the steel back metal layer and the Ni—P alloy plating layer during the temperature rising process during sintering. ₃ P phase (intermetallic compound) is precipitated, and the bonding between the sliding layer and the steel back metal layer becomes weak. This is related to the fact that the crystal structure of the electroless Ni—P alloy plating layer is amorphous. In the electroless Ni—P alloy plating layer, the crystal structure changes from amorphous to crystalline in the temperature rising process during sintering, but at the same time, a large amount of Ni ₃ P phase (intermetallic compound) precipitates. When the crystal structure of the electroless Ni—P plating layer changes from amorphous to crystalline, a shearing force is generated at the interface with the surface of the steel sheet, and a minute shear portion is formed. It is considered that a large amount of Ni ₃ P phase (intermetallic compound) was deposited in the vicinity of the shearing portion. In this embodiment, the step of forming the plating layer on the surface of the steel sheet is omitted, and the low pearlite phase portion 8 is simultaneously formed in the sintering step of the porous sintered layer 4. Can be manufactured at low cost.

DESCRIPTION OF SYMBOLS 1 Sliding member 2 Steel back metal layer 3 Sliding layer 4 Porous sintered layer 5 Resin composition 6 Fe or Fe alloy phase 7 Ni-P alloy phase 8 Low pearlite phase part 9 Ferrite phase 10 Pearlite phase

Claims (6)

In a sliding member provided with a sliding layer comprising a porous sintered layer and a resin composition on a steel back metal layer,
The porous sintered layer comprises a Ni-P alloy phase and a granular Fe or Fe alloy phase,
The steel back metal layer is carbon steel having a carbon content of 0.05 to 0.3% by mass, and the structure is composed of a ferrite phase and a pearlite phase,
On the surface of the steel back metal layer serving as an interface with the sliding layer, the ratio of the pearlite phase is reduced by 50% or more with respect to the pearlite phase in the structure at the center in the thickness direction of the steel back metal layer. Low pearlite phase is formed,
The Ni-P alloy phase of the porous sintered layer connects the granular Fe or Fe alloy phases to each other and covers the entire surface of the steel back metal layer serving as an interface with the sliding layer. A sliding member characterized by that.   The sliding member according to claim 1, wherein a Ni component of the Ni-P alloy phase is diffused in the low pearlite phase portion.   The sliding member according to claim 1 or 2, wherein the low pearlite phase part has a thickness of 1 to 50 µm.   The sliding member according to any one of claims 1 to 3, wherein an area ratio of the pearlite phase on a surface of the low pearlite phase part is 0 to 10%.   5. The sliding member according to claim 1, wherein the composition of the Ni—P alloy phase comprises 9 to 13% by mass of P, the remaining Ni, and inevitable impurities.   The ratio of the Ni-P alloy phase in the porous sintered layer is 5 to 40 parts by mass of the Ni-P alloy phase with respect to 100 parts by mass of the porous sintered layer. The sliding member according to any one of claims 1 to 5.

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