Copper alloy for sliding members, casting, sliding member and manufacturing method thereof

Abstract

Provided are: a copper alloy which is to be used in a sliding member and contains tin, sulfur, iron and phosphorus as main components thereof, and has sliding properties which are equal to or better than that of the prior art even when containing no iron or having a low iron content; or a method for producing a sliding member by casting. A copper alloy to be used in a sliding member according to the present invention is characterized by containing tin in the amount of 3.0-16.0 mass%, inclusive, sulfur in the amount of 0.3-1.0 mass%, inclusive, iron in an amount less than 0.3 mass%, and phosphorus in the amount of 0.04-0.5 mass%, inclusive, with the remainder constituting copper and inevitable impurities.

Description

[Technical field]

[0001] The present invention relates to a copper alloy for use in slide members, which does not contain lead as a main component. [Background technology]

[0002] Conventionally used copper alloys contain a certain amount of lead to improve sliding properties and machinability, and CAC603 was used as a sliding material. However, in recent years, due to the RoHS Directive and other environmental considerations, copper alloys that use less lead or are lead-free have been developed.

[0003] For example, Patent Document 1 describes in examples a copper alloy for slide members that contains 5.14 mass% or more and 15.54 mass% or less of tin, 0.42 mass% or more and 1.04 mass% or less of sulfur, 0.31 mass% or more and 3.43 mass% or less of iron, 0.012 mass% or more and 0.033 mass% or less of phosphorus, and the balance being copper and unavoidable impurities.

[0004] Patent Document 2 describes a copper alloy with improved machinability, which is a wrought copper alloy material containing tin, phosphorus, and sulfur, with the balance being copper and unavoidable impurities, and which contains dispersed sulfides having an average diameter of 0.1 to 10 μm in a cross section (transverse cross section) perpendicular to the longitudinal direction of the wrought copper alloy, and in which the area ratio of the sulfides is 0.1 to 10%. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4658269 [Patent Document 2] Patent No. 5916464 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the copper alloy described in Patent Document 1 has a problem in that the sliding properties are insufficient when the iron content is lower than the specified value.

[0007] In addition, Patent Document 2 describes the effect of machinability in copper alloys containing tin, sulfur, and phosphorus other than iron, but does not describe the sliding properties. Generally, copper alloys that are suitable for cutting due to their good machinability are not suitable for sliding applications.

[0008] Furthermore, copper alloys with a high iron content are prone to casting defects, and there has been a problem in that many defective products are produced when producing copper alloys by casting.

[0009] Therefore, an object of the present invention is to provide a copper alloy for sliding members, the main components of which are tin, sulfur, iron and phosphorus, which has sliding properties equal to or greater than those of the prior art even when it does not contain iron or contains only a small amount of iron, and to provide a copper alloy for sliding members which has sliding properties and good castability. [Means for solving the problem]

[0010] In order to solve the above problems, a copper alloy for a slide member according to the present invention is characterized in that it is a first embodiment that contains 3.0 mass % or more and 16.0 mass % or less of tin, 0.3 mass % or more and 1.0 mass % or less of sulfur, less than 0.3 mass % of iron, 0.04 mass % or more and 0.5 mass % or less of phosphorus, and the balance being copper and unavoidable impurities.

[0011] The copper alloy for a sliding member according to the present invention may further select a second embodiment that further limits the first embodiment by containing 6.0 mass % or more and 15.0 mass % or less of tin and 0.005 mass % or more and less than 0.3 mass % of iron.

[0012] Furthermore, the copper alloy for a slide member according to the present invention can select a third embodiment, which further limits the first embodiment and contains 9.0 mass % or more and 11.0 mass % or less of tin, 0.5 mass % or more and 1.0 mass % or less of sulfur, and 0.005 mass % or more and less than 0.05 mass % of iron.

[0013] As the present invention, a casting made of the copper alloy for a sliding member according to any one of the first to third embodiments can be selected.

[0014] In the present invention, a slide member made of a casting made of the copper alloy for slide members according to any one of the first to third embodiments can be selected.

[0015] The method for producing a slide member according to the present invention is characterized in that it is a method for producing a slide member by melting and casting a copper alloy containing 3.0 mass% or more and 16.0 mass% or less of tin, 0.3 mass% or more and 1.0 mass% or less of sulfur, less than 0.07 mass% of iron, and 0.04 mass% or more and 0.5 mass% or less of phosphorus.

[0016] Furthermore, in the method for producing a slide member according to the present invention, an embodiment in which tin is contained in an amount of 6.0 mass % or more and 15.0 mass % or less, and iron is contained in an amount of 0.005 mass % or more and less than 0.05 mass % can be selected. Effect of the Invention

[0017] According to the present invention, even if the iron content is reduced, the sliding properties can be equal to or greater than those of conventional copper alloys for sliding members by appropriately adjusting the phosphorus content. In addition, good castability can be achieved with the same metal composition. [Brief description of the drawings]

[0018] [Figure 1A] Cross-sectional photograph of fracture evaluation of Example 9 in the castability test [Figure 1B] Cross-sectional photograph of fracture evaluation of Example 10 in castability test [Figure 1C] Cross-sectional photograph of fracture evaluation of Comparative Example 6 in castability test DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The copper alloy for a sliding member according to the present invention is a copper alloy containing predetermined amounts of tin, sulfur, iron and phosphorus, with the balance being copper and unavoidable impurities.

[0020] The copper alloy must contain 3.0% by mass or more of tin. Tin has the effect of improving the matrix strength of the copper alloy, improving the wear resistance, and maintaining good sliding properties, but if the content of tin is less than 3.0% by mass, these effects become insufficient. On the other hand, the content of tin must be 16.0% by mass or less. If the content of tin exceeds 16.0% by mass, the mating material may be significantly worn, and good sliding properties may not be obtained. Furthermore, in order to obtain a copper alloy with a good balance of properties required for a sliding member, such as strength, elongation, hardness related to wear resistance, and wear amount, the content of tin is preferably 6.0% by mass or more and 15.0% by mass or less, and more preferably 9.0% by mass or more and 11.0% by mass or less.

[0021] The copper alloy must contain 0.3% by mass or more of sulfur. Sulfur reacts with copper, iron, or both to form sulfides. This sulfide has solid lubricity, reduces the friction coefficient, improves conformability, and imparts good sliding properties in a sliding state. If the sulfur content is less than 0.3% by mass, these effects are not obtained or are insufficient, so it is preferable that the sulfur content is 0.5% by mass or more. On the other hand, the sulfur content must be 3.0% by mass or less. If the sulfur content exceeds 3.0% by mass, there is a high risk that the sulfur will reduce the strength. Furthermore, in order to exhibit sufficient sliding performance, the sulfur content is preferably 1.0% by mass or less, and more preferably 0.7% by mass or less.

[0022] The copper alloy must contain less than 0.3% by mass of iron. If the iron content is 0.3% by mass or more, the hardness of the copper alloy will be too high, and when used as a sliding member, there is a high possibility that the mating material will be attacked and worn, or the elongation will decrease, resulting in a decrease in product performance. On the other hand, the smaller the iron content, the worse the wear resistance tends to be. Since iron forms Fe-S compounds together with sulfur to improve the sliding properties of the copper alloy, it is better to contain iron in order to form a necessary amount of Fe-S compounds to ensure the necessary sliding properties. Therefore, in order to obtain a copper alloy with a good balance between hardness and sliding properties, the iron content is preferably 0.005% by mass or more and less than 0.3% by mass, and more preferably 0.005% by mass or more and 0.05% by mass or less.

[0023] From the viewpoint of castability, the copper alloy must contain less than 0.3% by mass of iron. If the iron content is 0.3% by mass or more, there is a high possibility that casting defects will occur in the cast product. In order to have sufficient castability, the iron content is preferably 0.07% by mass or less.

[0024] The copper alloy must contain 0.04% by mass or more of phosphorus. Phosphorus forms a Cu-P compound with copper, which has the effect of increasing the hardness of the entire copper alloy. In the copper alloy of the present invention, even if the iron content is reduced, the above-mentioned phosphorus content ensures the sliding properties. On the other hand, the phosphorus content must be 0.5% by mass or less. If phosphorus is present in an amount exceeding 0.5% by mass, the hardness of the entire copper alloy increases too much, resulting in a decrease in seizure resistance.

[0025] The copper alloy may contain copper and unavoidable impurities other than the above elements. The content of the elements contained as the above unavoidable impurities is preferably as low as possible, and more preferably below the detection limit. Examples of such elements include molybdenum and nickel.

[0026] Examples of sliding members using the copper alloy of the present invention include rolling bearings, linear bushes having sliding bearings, and cylinder liners. By using the copper alloy of the present invention in the parts of these sliding members that require slidability, well-balanced sliding performance is exhibited. As a manufacturing method for manufacturing the sliding member of the present invention, casting methods such as gravity casting, centrifugal casting, and die casting are preferably mentioned. The casting obtained by any of these casting methods suppresses the occurrence of casting defects as described above, and exhibits a good balance of strength, elongation, hardness related to wear resistance, and wear amount, and can be suitably used as the above-mentioned sliding member. EXAMPLES

[0027] (Mechanical property test) Raw materials were adjusted so that the composition after casting would be the mass % of each component of the Examples and Comparative Examples listed in Table 1, with the remainder being copper and unavoidable impurities. The raw materials were heated to 1200°C and melted, and a copper alloy was cast by gravity casting using a mold.

[0028] (Tensile and elongation tests) The cast copper alloys after the heat treatment were subjected to a tensile test (Instron 5982, manufactured by Instron Corporation) using No. 14A test pieces having a parallel part diameter of 5 mm as specified in JIS Z2241, and evaluated based on the tensile strength and elongation at the time of breakage of the test pieces.

[0029] (Tensile test evaluation criteria) ◎: 300MPa or more ○: 200MPa or more and less than 300MPa △: 100MPa or more and less than 200MPa ×: Less than 100MPa

[0030] (Elongation test evaluation criteria) ◎: 24% or more ○: 16% or more but less than 24% △: 8% or more but less than 16% ×: Less than 8%

[0031] (Hardness test) The cast copper alloy after the heat treatment was subjected to a Brinell hardness test (BO3, manufactured by Imai Seiki Co., Ltd.) and evaluated based on the Brinell hardness. The test conditions were a test force of 500 kgf and a 10 mm diameter cemented carbide ball as an indenter.

[0032] (Hardness test evaluation criteria) ◎: 80HB or more and less than 120HB 〇: 60HB or more and less than 80HB △: 40HB or more and less than 60HB ×: Less than 40HB or more than 120HB

[0033] (Wear volume confirmation test) The cast copper alloy after the heat treatment was machined to prepare a disk with an outer diameter of 70 mm and a thickness of 6 mm. The friction surface was finished with #80 waterproof paper.

[0034] Next, a friction test was performed on the disk friction surface of each of the examples using a friction tester (UMT-TriboLab, manufactured by Bruker). In the friction test, a ball with a diameter of 10 mm made of high oxygen chromium bearing steel (SUJ2) was brought into contact with the disk, and the ball was pressed against the contact surface with a load of 10 N while reciprocating at a friction speed of 20 mm / s for 15 minutes with an amplitude of 2 mm (±1 mm). After the friction test, a 3D shape measuring instrument (VR-5200, manufactured by Keyence Corporation) was used to calculate the amount of wear from the width and depth of the worn part on the disk friction surface.

[0035] (Wear volume confirmation test evaluation criteria) ◎: 0.15mm 3 below 〇: 0.16mm 3 More than 0.30mm 3 below △:0.31mm 3 More than 0.45mm 3 below ×:0.46mm 3 End

[0036] (Mechanical property test overall evaluation criteria) ◎:All◎ 〇: Contains one or more 〇, others are ◎ △: Contains one or more △, others are ◎ or 〇 ×: Contains at least one ×

[0037] [Table 1]

[0038] As shown in Table 1, since the contents of the components in Examples 1 to 8 are within the ranges of the present invention, it is understood that the materials have good performance in terms of tensile strength, elongation, hardness, and wear resistance required for use as sliding members. In particular, Examples 2, 7, and 8 show that as long as the phosphorus content is 0.04% by mass or more, which is higher than the amount described in the examples of Patent Document 1, the materials have very good performance even if the iron content is less than 0.05% by mass.

[0039] In Comparative Example 1, the iron content is higher than the range of the present invention, so the elongation performance is reduced. In Comparative Example 2, the tin content is lower than the range of the present invention, and in Comparative Example 3, the tin content is higher than the range of the present invention, so the hardness performance and the elongation and hardness performance are reduced. Furthermore, in Comparative Example 4, the sulfur content is lower than the range of the present invention, and in Comparative Example 5, the sulfur content is higher than the range of the present invention, so the wear resistance, tensile strength, and elongation performance are reduced.

[0040] (Castability test) The raw materials were adjusted so that the composition after casting was the mass % of each component of the Examples and Comparative Examples shown in Table 2, with the remainder being copper and unavoidable impurities, and tensile test pieces were prepared by the same melting, casting, and processing steps as in the above tensile test, and then a tensile test was performed under the same conditions. Evaluation was performed by observing the fracture surface after the tensile test.

[0041] (Castability test evaluation criteria) ○: No casting defects on the fracture surface ×: Casting defects present on fracture surface

[0042] [Table 2]

[0043] As shown in Table 2, the iron contents of Examples 9 and 10 are within the range of the present invention, but the iron content of Comparative Example 6 is higher than the range of the present invention. As a result, as shown in Figures 1A and 1B, Examples 9 and 10 have no casting defects and have good castability, but Comparative Example 6 has casting defects and has poor castability, as shown in Figure 1C.

[0044] In this way, in a copper alloy for a sliding member whose main components are tin, sulfur, iron, and phosphorus, the iron and phosphorus contents are adjusted, i.e., the iron content is not contained or the iron content is reduced compared to the conventional technology, while the phosphorus content is increased, thereby making it possible to realize a copper alloy for a sliding member having sliding properties equal to or better than those of the conventional technology. Also, by reducing the iron content, it is possible to realize a good cast copper alloy for a sliding member.

Claims

1. A copper alloy for a sliding member comprising: 3.0 mass% or more and 16.0 mass% or less of tin; 0.3 mass% or more and less than 1.0 mass% of sulfur; 0.005 mass% or more and less than 0.05 mass% of iron; 0.04 mass% or more and 0.5 mass% or less of phosphorus; and the remainder being copper and unavoidable impurities.

2. 2. The copper alloy for a sliding member according to claim 1, comprising 6.0% by mass or more and 15.0% by mass or less of tin.

3. A casting made of the copper alloy for sliding members according to claim 1 or 2.

4. A sliding member comprising a casting made of the copper alloy for sliding members according to claim 1 or 2.

5. A method for producing a slide member, comprising the steps of melting a material adjusted to have, after casting, components of 3.0 mass % or more and 16.0 mass % or less of tin, 0.3 mass % or more and 1.0 mass % or less of sulfur, less than 0.07 mass % of iron, 0.04 mass % or more and 0.5 mass % or less of phosphorus, with the remainder being copper and unavoidable impurities, and casting the molten material.

6. 6. The method for producing a slide member according to claim 5, wherein the alloy contains 6.0% by mass or more and 15.0% by mass or less of tin and 0.005% by mass or more and less than 0.05% by mass of iron.

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