Method for producing sliding member, sliding member, and substrate material of sliding member

Abstract

In a method, in which a plain bearing alloy layer is bonded to a surface of a backing steel sheet, and, a Bi-based overlay layer is then deposited on the plain bearing alloy layer by electroplating, replacement of Bi with the backing steel sheet and deposition of Bi on the backing steel sheet are prevented. Prior to the step of electroplating of the Bi-based overlay layer, the following metals and the like are formed on at least the back surface of the backing steel sheet. An electrochemically more noble metal than Bi, an electrochemically more base metal than Bi and capable of forming a passivation state, or resin.

Claims

1. A method of producing a sliding member, said method comprises the steps of: bonding a plain bearing layer over a first surface of a backing steel sheet, opposite to a second surface of the backing steel sheet; subjecting the plain bearing layer and the first protecting layer defined below to an electroplating, thereby depositing a Bi based overlay layer on the plain bearing layer, but neither depositing Bi on nor roughening a first surface of the first protecting layer facing away from the backing steel sheet; and prior to the step of electroplating of the Bi-based overlay layer, said method further comprises a step of forming a first protecting layer on the second surface of the backing steel sheet, said first protecting layer consisting of a noble metal, wherein said electroplating comprises a step of immersing the whole of a substrate material comprising the backing steel sheet, the plain bearing layer, and the first protecting layer into a Bi-ion containing plating liquor, and the noble metal of the first protecting layer is electrochemically more noble than Bi.

2. The method according to claim 1, wherein said method consists of said bonding step, said forming of the first protecting layer step, and said electroplating step, and said substrate material consists of the backing steel sheet, the plain bearing layer and the first protecting layer.

3. The method according to claim 1, wherein the noble metal is Cu.

4. A method of producing a sliding member, said method comprises the steps of: bonding a plain bearing alloy layer over a first surface of a backing steel sheet, opposite to a second surface of the backing steel sheet; electroplating to subject the plain bearing alloy layer and the first protecting layer defined below to the electroplating, thereby depositing a Bi based overlay on the plain bearing alloy layer but not depositing Bi on the first protecting layer on a surface away from the backing steel sheet; and prior to the step of electroplating of the Bi-based overlay layer, said method further comprises the steps of forming a first protecting layer on the second surface of the backing steel sheet, said first protecting layer consisting of a noble metal; and forming a second protecting layer consisting of a noble metal on the first surface of the backing steel sheet, wherein said electroplating comprises a step of immersing the whole of a substrate material comprising the backing steel sheet, the plain bearing alloy layer, and the first and second protecting layers into a Bi plating liquor, and the noble metal of the first and second protecting layers is electrochemically more noble than Bi.

5. The method according to claim 4, wherein the noble metal is Cu.

6. A method of producing a sliding member, said method comprises the steps of: bonding a plain bearing alloy layer over a first surface of a backing steel sheet, opposite to a second surface of the backing steel sheet; electroplating to subject the plain bearing alloy layer and the first protecting layer defined below to the electroplating, thereby depositing a Bi based overlay on the plain bearing alloy layer, but not depositing Bi on the first protecting layer on a surface away from the backing steel sheet; and prior to the step of electroplating the Bi-based overlay layer, said method further comprises the steps of: forming a first protecting layer on the second surface of the backing steel sheet, said first protecting layer consisting of a noble metal; forming a second protecting layer consisting of a base metal on the first surface of the backing steel sheet; passivating a surface of the second protecting layer on a surface of the second protecting layer away from the backing steel sheet; and pickling the passivated surface of the second protecting layer, thereby removing passivated material prior to the step of electroplating, wherein said electroplating comprises a step of immersing the whole of a substrate material comprising the backing steel sheet, the plain bearing alloy layer, and the first and second protecting layers into a Bi plating liquor, and wherein the noble metal of the first protecting layer is electrochemically more noble than Bi, and the base metal of the second protecting layer is electrochemically less noble than Bi, capable of forming a passivated state on a surface thereof and selected from the group consisting of Al, Cr and Ni.

7. The method according to claim 6, wherein the noble metal is Cu.

8. The method according to claim 6, wherein the base metal is selected from the group consisting of Cr and Ni.

9. The method according to claim 6, wherein the base metal is Al and the passivation is carried out by anodizing.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 A cross sectional view of a plain bearing according to an embodiment of the present invention. This illustration is referred to for describing a method for providing a noble-metal or oxide layer on both surfaces of a backing steel sheet.

(2) FIG. 2 A cross sectional view of a plain bearing according to an embodiment of the present invention. This illustration is referred to for describing a method for providing a noble-metal or oxide lay on the back surface of a backing steel sheet.

(3) FIG. 3 A cross sectional view of a plain bearing according to an embodiment of the present invention. This illustration is referred to for describing a method for providing a resin coating on the back surface of a backing steel sheet.

EMBODIMENTS OF INVENTION

(4) FIGS. 1 through 3 show a cross section of a sliding member produced by the method according to the present invention. The reference numerals denote as follows: 1a backing steel sheet (hereinafter referred to as backing metal); 1aa top surface of the backing metal, i.e., a surface on the lining side; 1bback surface, i.e., a surface on the side opposite the lining; 2a protecting layer (hereinafter referred to as a noble metal layer); 3a plain bearing alloy layer (hereinafter referred to as lining); and 10a Bi-based overlay layer. In FIG. 1, prior to bonding the lining 3 on the surface 1a of a backing metal 1, the noble metal layers 2a and 2b are deposited on both the top surface 1a and the back surface 1b of a backing metal 1, by electroplating, sputtering, pressure-bonding, or the like. The thickness of layer 2a, 2b is preferably 0.2 to 10 m, more preferably 0.5 to 3 m. Subsequently, the lining 3 is deposited on the noble metal layer 2a on the top-surface 1a side of a backing metal. In this stage, a substrate material 12 of a sliding member is obtained.

(5) Finally, the substrate material 12 of sliding member is connected to a cathode and is immersed entirely in a plating liquor, thereby depositing a Bi-based overlay layer 10 by electroplating. Since Bi of the Bi-based overlay 10 is base as compared with the metal of the noble metal layer 2, neither substitution nor precipitation occurs between the noble metal layer 2b and Bi (alloy). Specifically, although the noble metal layer 2b is lightly etched by plating liquor, electrolytic precipitation of Bi (alloy) does not occur. The noble metal layer 2a between the lining 3 and top surface (1a) of backing metal 1 does not participate in corrosion prevention of the back surface of a backing metal 1 but enhances adhesion between 3 and 1a.

(6) Preferable conditions of Bi electroplating are as follows. Alkanesulfonate 70 g/L Bi ions 10 g/L pH approximately 0 Temperature 25 degrees C. Current Density 2 A/dm.sup.2 Time 20 minutes

(7) In FIG. 2, a lining 3 is bonded directly to the top surface 1a of a backing metal 1. Subsequent to or prior to bonding of the lining, the noble metal layer 2 is deposited on the back side 1b of a backing metal by electroplating, sputtering, pressure-bonding or the like. A sliding member substrate material 12 is obtained in this stage. Subsequently, the substrate material 12 is connected to a cathode and is immersed entirely in a plating liquor, thereby depositing a Bi-based overlay layer 10 by electroplating. Since Bi of the Bi-based overlay 10 is more base as compared with the metal of the noble metal layer 2, neither substitution nor precipitation occurs between the noble metal layer 2 and Bi (alloy). That is, Bi (alloy) does not electrolytically deposit on the noble metal layer 2.

(8) Such elements as Al, Ti, Cr and Ni are base metals as compared with Bi. Surfaces of these metals change to Al.sub.2O.sub.3, TiO.sub.2, Cr.sub.2O.sub.3, NiO or the like and are thus passivated. Bi (alloy), therefore, does not electrolytically precipitate on the passivated surface. Thus, these base metals can be used for the layer 2 instead of the noble metal. A layer of these base metals is formed on a desired surface through vapor deposition of Al, Ti or the like, or vapor deposition or electroplating of Cr, Ni or the like. Passivation treatment is then carried out by a known method, such as anodizing of Al. In this case of Cr, Ti or Ni, heat treatment causes passivation. Passivation also occurs, when these metals are allowed to stand at room temperature for a few days, the so-called native oxide is formed. As a result, no artificial treatment is necessary. Since these oxides are electrically non conductive, these oxides and Bi (alloy) are not substituted with each other. Specifically, such substitution does not occur on the opposite side 2b of a backing metal. Bi (alloy) does not precipitate on the opposite side 2b. Among the oxides mentioned above, the oxides of stainless steel such as FeCr, and of Al-based material are known as a passivation film component and attain stable protecting effect.

(9) Referring to FIG. 3, a lining 3 is bonded to the top surface 1a of a backing metal 1. Subsequent to or prior to the bonding, a resin layer 4 having a thickness of preferably 1 to 500 m, more preferably 2 to 100 m, is bonded to the back surface 1b on the backing metal 1 mentioned above. Epoxy resin, polyimide resin, phenol resin and the like can be used as resin. The resin is applied and then baked to form a resin layer 4. A sliding member substrate material 12 is obtained in this stage. The substrate material 12 is subsequently connected to a cathode and its entire surface is immersed in the plating liquor, so as to have a Bi-based overlay layer 10 deposited by electroplating. Since resin is electrically non conductive, a substitution between the resin layer 4 and Bi (alloy) does not occur. Namely, Bi (alloy) does not electrolytically precipitate on the resin layer 4.

(10) Next, the present invention is described in more detail with reference to experimental examples.

COMPARATIVE EXAMPLE

(11) A 1.3-mm thick SPCC steel sheet was used as a backing metal 1 (FIG. 1), on which no noble metal layers 2a, 2b were deposited. A 0.2-mm thick Cu alloy layer (composition: Cu-5% Sn) as a lining 3 was bonded to the top surface side (1a) of the backing metal 1. The substrate material 12 was manufactured as described above and was connected to a cathode, and its entire surface was immersed in a Bi electroplating bath having a composition described above. A 7-m thick Bi-based overlay layer was plated under the current condition described above. After plating, the surface of the backing metal's back side (1b) was inspected. Surface roughness was observed. Roughness Rz of the backing metal's back side surface (1b) was 25 m.

Example 1

(12) A 1.3-mm thick SPCC steel sheet was used as a backing metal 1 (FIG. 1). A 0.2-mm thick Cu alloy layer (composition: Cu-5% Sn) was used as a lining 3. First, the noble metal layers 2a, 2b are deposited on the both sides of a backing metal 1 by electroplating. 2-um thick Cu was deposited in a cyanate bath under a current density of 2 A/dm.sup.2. Then, rinsing with water and drying were carried out. A lining 3 was subsequently bonded to the top surface side (1a) of a backing metal 1. The substrate material 12 was manufactured as described above and was connected to a cathode, and its entire surface was immersed in a Bi electroplating bath having a composition described above. A Bi-based overlay layer was plated to a thickness of 7 m under the current condition described above. After plating, the surface of the backing metal's back side 1b was observed. The surface was virtually not different from the one which had undergone electroplating, with neither surface roughening nor Bi deposition being observed.

Example 2

(13) In FIG. 2, the backing metal 1 and lining 3 were of the same types as in FIG. 1. The same type of Bi-based overlay layer 10 was deposited by electroplating. However, the noble metal layer 2 was deposited only on the back surface 1b of a backing metal 1. After plating, the surface of the backing metal's back side was observed. This surface was virtually not different from the one which had undergone electroplating, with neither surface roughening nor Bi deposition being observed.

Example 3

(14) The same type of backing metal 1 and the same type of lining 3 were formed to provide a layer structure as shown in FIG. 1. However, a Cr layer 2 was deposited on a work piece by electroplating. An Ni layer 2 was deposited on another work piece. After the work pieces were allowed to stand at room temperature, the surface 2 was converted to Cr.sub.2O.sub.3 and NiO and thus passivated. Subsequently, a Bi-based overlay layer 10 was deposited by electroplating. After plating of the Bi-based overlay layer 10, the surface of the Cr.sub.2O.sub.3 layer and NiO layer 2 on the back side of a backing metal was observed. This surface turned out to be virtually not different from a surface obtained from electroplating and subsequent standing at room temperature. Neither surface roughening nor electrolytic deposition of Bi were observed.

Example 4

(15) The backing metal 1, lining 3 and Bi-based overlay 10 were all of the same types as in FIG. 1. Instead of using noble metal layers 2a, 2b, a Cr layer 2 was deposited on a work piece. Also an Ni layer 2 was deposited on another work piece. These layers were electrolytically deposited on the both sides of a backing metal (electroplating). When the Cr or Ni layer 2b on the backing metal side was allowed to stand at room temperature, the surface of the Cr layer was converted to Cr.sub.2O.sub.3 and thus passivated, while the surface of the Ni layer was converted to NiO and thus passivated. The lining was sintered on the Cr or Ni layer 2a in a reducing protective sintering atmosphere. The Cr.sub.2O.sub.3 layer and NiO present on the Cr and Ni layers 2a were reduced to Cr and Ni, respectively, during sintering. After plating of the Bi-based overlay layer 10, the surfaces of the Cr.sub.2O.sub.3 layer and NiO layer 2 on the back side of a backing metal were observed. The surfaces turned out to be virtually not different from those obtained through electroplating and subsequent standing at room temperature. Neither surface roughening nor electrolytic deposition of Bi were observed.

Example 5

(16) The backing metal 1 and the Bi-based overlay layer 10, which are the same as those in FIG. 1, as well as an epoxy resin layer 4 constructed a structure shown in FIG. 3. After applying a 3-m thick epoxy resin layer 10, baking was carried out at 100 degrees C. After plating of the Bi-based overlay layer 10, the surfaces of the Cr.sub.2O.sub.3 layer and NiO layer 2 on the back side of a backing metal were observed. The surfaces were found to be virtually not different from a surface obtained through electroplating and subsequent standing at room temperature. Neither surface roughening nor electrolytic deposition of Bi were observed.

INDUSTRIAL APPLICABILITY

(17) When a Bi-based overlay is deposited on backing steel sheet in a conventional production method of plain bearing, the performance of a backing steel sheet inevitably deteriorates. The present invention enables to prevent such performance deterioration and greatly contribute to industry.