JP2015199975A - Slide member and manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve abrasion resistance in a slide member having an Fe-based sinter layer without hardening.SOLUTION: A slide member has a back metal and a lining layer formed on the back metal, the lining layer contains 9 to 22.5 wt.% of Cu, 1.0 to 2.5 wt.% of Sn, 0.5 to 2.0 wt.% of C, 0.8 to 1.6 wt.% of P and Fe, and has a first phase with a porous shape and a second phase formed in the first phase and having higher P concentration than that of the first phase.

Description

  The present invention relates to a sliding member having an Fe-based sintered layer.

  A bearing (so-called bush) used in a working machine such as a construction machine is required to operate with less oil supply from the viewpoint of simplifying maintenance. Therefore, it is known that a bearing lining layer is formed of a porous material and lubricating oil is held in the hole.

  Patent Document 1 discloses a technique for improving wear resistance and seizure resistance by finely dispersing special carbides in martensite in an Fe-based sintered bush.

Japanese Patent No. 4842283

  In the technique described in Patent Document 1, in order to ensure wear resistance, it is necessary to perform quenching in order to increase the hardness of the Fe matrix phase.

  On the other hand, the present invention provides a technique for improving wear resistance without quenching in a sliding member having an Fe-based sintered layer.

  The present invention has a backing metal and a lining layer formed on the backing metal, the lining layer comprising 9-22.5 wt% Cu, 1.0-2.5 wt% Sn 0.5 to 2.0% by weight of C, 0.8 to 1.6% by weight of P, and Fe, and a porous first phase is formed in the first phase, Provided is a sliding member having a second phase having a higher P concentration than the first phase.

  In the cross section perpendicular to the surface of the back metal, the area ratio of the second phase in the lining layer may be in the range of 3 to 20%.

  In the cross section, the area ratio may be in a range of 3 to 10%.

  The composition of Cu in the lining layer may be 13.5 to 22.5% by weight, and the composition of Sn may be 1.5 to 2.5% by weight.

  The composition of C in the lining layer may be 1.5 to 2.5% by weight.

  The porosity of the lining layer may be 25 area% or less.

  The oil content in the lining layer may be 25% by volume or less.

  The porosity of the lining layer may be 15 area% or more.

  The oil content in the lining layer may be 15% by volume or more.

  The present invention also includes a step of preparing a mixed powder containing iron powder, bronze powder, graphite powder, and a phosphorus-containing additive, a step of spraying the mixed powder on a back metal, and a lining on which the mixed powder is sprayed. There is provided a method for manufacturing a sliding member, comprising a step of sintering a layer, a step of rolling down the sintered lining layer, and a step of sintering the pressed lining layer.

  According to the present invention, wear resistance can be improved without quenching in a sliding member having an Fe-based sintered layer.

The figure which shows the structure of the sliding member 1 which concerns on one Embodiment. 4 is a schematic diagram showing a cross-sectional structure of the sliding member 1. FIG. The figure which illustrates the structure | tissue photograph of the lining layer 12. FIG. 3 is a flowchart showing a method for manufacturing the sliding member 1. The figure which illustrates the characteristic of the produced test piece. The figure which shows P composition dependence of wear depth. The figure which shows the bronze powder compounding ratio dependence of wear depth. The figure which shows the graphite powder compounding ratio dependence of wear depth. The figure which shows the oil content dependency of wear depth. The figure which shows the oil content dependency of a friction coefficient.

1. Structure FIG. 1 is a diagram illustrating a structure of a sliding member 1 according to an embodiment. The sliding member 1 is, for example, a bush used as a bearing in various devices such as an engine drive unit, a transmission, an excavator, a crusher, and a crushing mill of a construction machine. The sliding member 1 may be other than a cylindrical bush.

  FIG. 2 is a schematic diagram showing a cross-sectional structure of the sliding member 1. FIG. 2 shows an AA cross section (cross section perpendicular to the surface of the back metal 11) in FIG. The sliding member 1 has a back metal 11 and a lining layer 12. The backing metal 11 is a layer for reinforcing the mechanical strength of the lining layer 12. The back metal 11 is made of, for example, steel. The lining layer 12 is provided along the sliding surface of the bearing (the surface in contact with the shaft), and is a layer for imparting characteristics as a bearing, for example, characteristics such as friction characteristics, seizure resistance, and wear resistance. .

  In this example, the lining layer 12 is an Fe-based sintered layer. The lining layer 12 preferably contains Cu, Sn, C, and P, and the balance is substantially Fe. The composition of Cu is preferably 9 to 22.5% by weight, and more preferably 13.5 to 22.5% by weight. The composition of Sn is preferably 1.0 to 2.5% by weight, and more preferably 1.5 to 2.5% by weight. The composition of C is preferably 0.5 to 2.0% by weight, and more preferably 1.0 to 2.0% by weight. The composition of P is preferably 0.8 to 1.6% by weight, and more preferably 0.8 to 1.2% by weight.

  FIG. 3 is a diagram illustrating a structural photograph of the lining layer 12. The lining layer 12 has a matrix phase 121, pores 122, a Cu—Sn phase 123, and a P concentrated phase (P rich phase). Note that the P-enriched phase is too small to be seen in FIG. The matrix phase 121 is a matrix phase mainly composed of Fe—C—P. Since the lining layer 12 is formed by powder sintering, a large number of holes 122 are formed. That is, the matrix phase 121 has a sponge shape having a large number of pores 122 inside. When the Fe—Cu—Sn—C—P based alloy is sintered, the low melting point Cu—Sn based alloy first becomes a liquid phase and penetrates into the pores in the matrix phase 121 to form the Cu—Sn phase 123. . Further, the P-concentrated phase oozes out from the matrix phase 121 as a liquid phase and spreads into the voids of the powder. Thus, the P-concentrated phase is dispersed in a matrix in the matrix phase 121.

2. Manufacturing Method FIG. 4 is a flowchart showing a manufacturing method of the sliding member 1. In step S1, an alloy powder to be the lining layer 12 is prepared. Specifically, iron powder, bronze powder, graphite powder, and phosphorus-containing additive are mixed. As the iron powder, for example, one having an average particle diameter of 100 to 120 μm is used. As the bronze powder, for example, a composition having a composition of Cu10Sn (Cu: 90% by weight, Sn: 10% by weight) and an average particle diameter of 60 to 70 μm is used. As the graphite powder, for example, one having an average particle diameter of 20 μm or less is used. As the phosphorus-containing additive, for example, iron phosphide powder having a composition of Fe20P (Fe: 80 wt%, P: 20 wt%) and an average particle diameter of 10 to 20 μm is used.

  In step S2, alloy powder is sprayed on the back metal. As the back metal, for example, a rolled steel strip is used.

  In step S3, first sintering is performed. For example, the first sintering is performed in a nitrogen atmosphere at a holding time of 950 ° C. for 15 minutes. At this time, it is considered that the Cu—Sn alloy melts and forms the Cu—Sn phase 123.

  In step S4, intermediate reduction is performed. Intermediate pressure is a step of applying pressure to the sintered layer. The application of pressure is performed by rolling, for example. The intermediate reduction is performed until the lining layer 12 has a predetermined thickness (for example, a plate thickness including the back metal 11 and a half immediately before step S4).

  In step S5, second sintering is performed. The second sintering is performed, for example, in a nitrogen atmosphere at 1000 ° C. for 15 minutes. At this time, it is considered that a P-concentrated phase is precipitated from the matrix phase 121.

  In step S6, the plate including the back metal 11 and the lining layer 12 is formed into a predetermined shape (for example, a cylindrical shape). In addition, quenching after sintering is not performed.

3. Examples Test pieces of sliding members were prepared under various conditions, and these test pieces were evaluated. As evaluation items, wear depth and friction coefficient were used.

  As the backing metal 11, a rolled steel strip corresponding to SAE (Society of Automotive Engineers) 1009 (C: 0.15 wt% or less, Mn: 0.60 wt% or less, P: 0.03 wt% or less, S: 0 0.05% by weight or less, other impurities: 0.15% by weight or less, Fe: remainder). As raw materials for the lining layer 12, iron powder, bronze powder, graphite powder, and phosphorus-containing additives were used. These powders were mixed at a blending ratio that provides a desired composition.

  FIG. 5 is a diagram illustrating characteristics of the produced test piece. Here, five test pieces in which the addition amount of P was changed to 0.4% by weight, 0.8% by weight, 1.2% by weight, 1.6% by weight, and 2.0% by weight in the cross section. The distribution of P concentration, the area ratio of the P-concentrated phase, the porosity, and the oil content are shown.

  The distribution of P concentration in the cross section was measured by EPMA (Electron Probe MicroAnalyser). In this figure, a bright gradation part has a high P density, and a dark gradation part has a low P density. As can be seen from the EPMA image of the test piece having P of 0.8 to 2.0% by weight, the P-concentrated phase 124 spreads through the voids of the matrix and is dispersed in a network.

  The area ratio of the P-concentrated phase was measured using an image analysis apparatus (manufactured by Nireco Corporation, LUZEX) in the cross section of the lining layer 12 observed with an electron microscope at a magnification of 200 to 500 times. Here, the area ratio of the P-concentrated phase was measured at a plurality of portions other than the pores 122 in the lining layer 12. Since the pore 122 portion is not measured, when looking at the entire lining layer 12, the product of the non-porosity (1-porosity) and the measured area ratio is the area ratio of the P-concentrated phase. It seems to be equivalent.

  The porosity was measured using image processing software in the lining layer 12 observed with an optical microscope at a magnification of 50 to 100 times.

  The oil content indicates the volume ratio of the oil impregnated in the lining layer 12 with respect to the lining layer 12. Since the oil is retained in the pores 122, the oil content has a correlation with the porosity. Here, the ratio (VO / VL) of the volume VO of the impregnating oil to the volume VL of the lining layer 12 was calculated as the oil content. The volume of the impregnated oil was obtained by dividing the weight change of the lining layer 12 before and after soaking the oil by the oil density. The volume of the lining layer 12 was obtained by multiplying the surface area of the lining layer 12 by the thickness. In the test piece having P of 1.2% by weight or less, the condition of intermediate pressure reduction (step S4) was adjusted so that the oil content was in the range of 20 ± 3%.

  FIG. 6 is a diagram showing the P composition dependence of the wear depth. The vertical axis represents the wear depth obtained as a result of the wear test, and the horizontal axis represents the composition of P in the lining layer 12. The mixing ratio of iron phosphide (Fe20P) powder is 0, 2, 4, 6, and 8 wt% (0.04, 0.8, 1.2, and 1.6 wt% with P composition) To the same condition). The composition other than P was constant, and the alloy composition was Fe-18Cu-2Sn-1.5C- (0.4 to 1.6) P. Note that the test piece having a mixing ratio of iron phosphide powder of 10 wt% (corresponding to 2 wt% in the composition of P) has few holes and cannot be impregnated with oil, and an oil-impregnated bearing can be produced. There wasn't.

Three or more test pieces were produced under each condition. About the produced test piece, the wear depth was measured on the following test conditions.
Testing machine: Cylindrical flat plate testing machine (block-on-ring)
Lubrication: Dry (oil-impregnated only)
Load: 137N
Sliding speed: 0.04m / sec
Mating material: S45C (Induction hardening)
Counterpart material hardness: HRC60
Test time: 5 minutes

  From FIG. 6, it can be seen that the wear resistance is improved by adding 0.4 wt% or more of P. In particular, the test piece to which 0.8 to 1.6% by weight of P is added has a wear depth suppressed to less than half compared to the test piece to which P is not added, and the wear resistance is greatly improved. Yes. It can be said that the ratio of the P-concentrated phase 124 to the entire lining layer 12 in these test pieces is preferably 3 to 20% from FIG.

  FIG. 7 is a diagram showing the dependence of the abrasion depth on the blending ratio of bronze powder. The vertical axis represents the wear depth obtained as a result of the wear test, and the horizontal axis represents the blending ratio of the bronze powder in the alloy powder. In addition, as a bronze powder, the thing whose composition is Cu10Sn was used.

  The compounding ratio of the bronze powder was changed under the conditions of 10, 15, 20, and 25% by weight. The composition other than Cu and Sn was constant, and the alloy composition was Fe- (9-22.5) Cu- (1-2.5) Sn-1.5C-1.2P. Three or more test pieces were produced under each condition. About the produced test piece, the wear depth was measured on the same conditions as FIG.

  From FIG. 7, for example, when the target value of the wear depth is 6 μm or less, the blending ratio of the bronze powder is 15% by weight or more (that is, Cu is 13.5% by weight or more and Sn is 1.5% by weight or more). Then, it can be seen that the target value can be achieved. That is, it can be seen from FIG. 7 that, in addition to adding P by 0.4% by weight or more, further adding 13.5% by weight or more Cu and 1.5% by weight or more Sn further improves the wear resistance. .

  FIG. 8 is a graph showing the dependency of the wear depth on the graphite powder blending ratio. The vertical axis represents the wear depth obtained as a result of the wear test, and the horizontal axis represents the blending ratio of the bronze powder in the alloy powder. The compounding ratio of the graphite powder was changed under the conditions of 0.5, 1.0, 1.5, and 2.0% by weight. The composition other than C was constant, and the alloy composition was Fe-18Cu-2Sn- (0.5-2.0) C-1.2P. Three or more test pieces were produced under each condition. About the produced test piece, the wear depth was measured on the same test conditions as FIG.

  From FIG. 8, for example, when the target value of the wear depth is set to 6 μm or less, the target value is set when the mixing ratio of the graphite powder is 1.0 wt% or more (that is, C is 1.0 mass% or more). You can see that it can be achieved. That is, it can be seen from FIG. 8 that the wear resistance is further improved by adding 1.0 wt% or more of C in addition to adding 0.4 wt% or more of P.

  FIG. 9 is a diagram showing the oil content dependency of the wear depth. The vertical axis represents the wear depth obtained as a result of the wear test, and the horizontal axis represents the oil content. The alloy composition was Fe-18Cu-2Sn-1.5C-1.2P. The amount of oil impregnated into the lining layer 12 was changed, and the wear depth was measured under the same conditions as in FIG.

  FIG. 9 shows that, for example, when the target value of the wear depth is 6 μm or less, the target value can be achieved if the oil content is 25% or less. That is, in addition to adding P by 0.4% by weight or more, it can be seen that if the oil content is 25% or less, the wear resistance is further improved. Since the oil content has a correlation with the porosity of the lining layer 12, an oil content of 25% or less corresponds to a porosity of 25% or less.

FIG. 10 is a diagram showing the oil content dependency of the friction coefficient. The vertical axis represents the friction coefficient obtained as a result of the friction test, and the horizontal axis represents the oil content. Although the result of FIG. 9 suggests that a lower oil content is better, there is a concern that the friction coefficient increases when the oil content is low. Therefore, the oil content dependency of the friction coefficient was measured. The alloy composition was Fe-18Cu-2Sn-1.5C-1.2P. The amount of oil impregnated into the lining layer 12 was changed, and the friction coefficient was measured under the following conditions.
Tester: Reciprocating sliding tester Lubrication: Dry (oil-impregnated only)
Load: 1300N
Sliding speed: 0.04m / sec
Stroke: 10mm
Operation time: 120min
Mating material: S45C (Induction hardening)
Counterpart material hardness: HRC60

  FIG. 10 shows that, for example, when the target value of the friction coefficient is 0.17, the target value can be achieved if the oil content is 15% or more. That is, it can be seen that if the oil content is 15% or more, the m book coefficient is improved. Since the oil content has a correlation with the porosity of the lining layer 12, an oil content of 15% or more corresponds to a porosity of 15% or more. In the test piece of FIG. 5, it can be said that the ratio of the P-concentrated phase 124 to the entire lining layer 12 is preferably 3 to 10% from FIG. 5 in order to make the porosity 15% or more. .

DESCRIPTION OF SYMBOLS 1 ... Sliding member, 11 ... Back metal, 12 ... Lining layer, 121 ... Matrix phase, 122 ... Hole, 123 ... Cu-Sn phase, 124 ... P concentration phase

Claims (10)

With the back metal,
A lining layer formed on the backing metal,
The lining layer is
9-22.5 wt% Cu,
1.0-2.5 wt% Sn,
0.5-2.0 wt% C;
0.8 to 1.6% by weight of P and Fe,
A porous first phase;
A sliding member having a second phase formed in the first phase and having a higher P concentration than the first phase. 2. The sliding member according to claim 1, wherein an area ratio of the second phase in the lining layer is in a range of 3 to 20% in a cross section perpendicular to the surface of the back metal. The sliding member according to claim 2, wherein the area ratio is in a range of 3 to 10% in the cross section. The composition of Cu in the lining layer is 13.5 to 22.5% by weight,
The sliding member according to any one of claims 1 to 3, wherein the composition of Sn is 1.5 to 2.5 wt%. The sliding member according to any one of claims 1 to 4, wherein the composition of C in the lining layer is 1.5 to 2.5 wt%. The sliding member according to any one of claims 1 to 5, wherein a porosity of the lining layer is 25 area% or less. The oil content in the lining layer is 25% by volume or less. The sliding member according to any one of claims 1 to 6, wherein: The sliding member according to claim 4, wherein a porosity of the lining layer is 15 area% or more. The sliding member according to claim 4, wherein the oil content in the lining layer is 15% by volume or more. Preparing a mixed powder comprising iron powder, bronze powder, graphite powder, and a phosphorus-containing additive;
Spraying the mixed powder on a backing metal;
Sintering the lining layer dispersed with the mixed powder;
Rolling the sintered lining layer;
And a step of sintering the pressed lining layer.