WO2007117079A1

WO2007117079A1 - Lubricative copper alloy

Info

Publication number: WO2007117079A1
Application number: PCT/KR2007/000997
Authority: WO
Inventors: Yeon-Soo Kim
Original assignee: K E & C Co., Ltd.
Priority date: 2006-04-11
Filing date: 2007-02-27
Publication date: 2007-10-18
Also published as: KR100640273B1

Abstract

The present invention relates to a lubricative copper alloy, and more particularly to a Iubricative copper alloy, which is produced at a low cost to have high strength, high hardness, high shock resistance and high tensile force, so that various industrial machine components, to which the alloy is applied, is produced at a reduced cost, thereby offering competitive machine equipment, and which reserves its inherent functions for a long period while assuring a drastically prolonged service life, resulting in reduction of maintenance cost. For this purpose, the lubricative copper alloy according to the present invention is produced by melting silicon (Si), aluminum (Al), nickel (Ni), manganese (Mn), zinc (Zn), iron (Fe), tin (Sn), phosphorous (P) and copper (Cu), and is capable of assuring high strength, high load bearing ability, high tensile force and excellent lubricating property. In addition, the lubricative copper alloy comprises silicon (Si) of 0.5-7wt%, aluminum (Al) of 0.5-3wt%, nickel (Ni) of 0.1-3wt%, manganese (Mn) of 0.5-5wt%, zinc (Zn) of 3-16wt%, iron (Fe) of 0.5-3wt%, tin (Sn) of 0.5-5wt%, phosphorous (P) of 0.1-0.15wt% and the balance of copper (Cu).

Description

Description LUBRICATIVE COPPER ALLOY

Technical Field

[1] The present invention relates to a lubricative copper alloy, and more particularly to a lubricative copper alloy, which is produced by melting silicon (Si), aluminum (Al), nickel (Ni), manganese (Mn), zinc (Zn), iron (Fe), tin (Sn), phosphorous (P) and copper (Cu), and which is capable of assuring high strength, high load bearing ability, high tensile force and excellent lubricating property. Background Art

[2] A lubricative copper alloy has been widely used as material for various industrial machine components such as metal bearings, gears, reduction worm gears, aircrafts, ships and automobiles, which require wear resistance, corrosion resistance, thermal shock resistance and lubricity.

[3] Typically, bronze, which is an alloy consisting of copper and tin, has been dominantly used as a copper alloy. However, since the Cu-Sn-based alloy includes a large amount of expensive tin, the cost of producing the alloy is increased, com- petiveness of plant for production is lowered. Furthermore, since our country must buy tin itself from foreign countries because of lack of tin resource, the cost of producing a copper alloy is further increased.

[4] In order to overcome the above problems, a bronze alloy has been commonly used, which is produced by alloying technology of adding domestically available elements such as Pb, Sn or Zn, and optionally adding Ni to offer the bronze alloy mechanical properties and abrasion resistance superior to those of conventional copper alloy.

[5] The abrasion-resistant copper alloy such as bronze incurs high production cost and has low hardness and strength. Consequently, when the copper alloy is used in machine components such as bushes and metal bearings which require high hardness and strength, the machine components have a problem with a short service life.

[6] Meanwhile, a copper alloy, which includes Pb, Zn, Mn, Ni and Sn for the purpose of solving the above-mentioned problems, has been developed and used. However, the copper alloy has still problems in that brittleness thereof is increased, thereby the copper alloy is apt to be damaged. Disclosure of Invention

Technical Problem

[7] Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a lubricative copper alloy, which is increased in strength and hardness so as to offer high shock resistance and thus high tensile force.

[8] Another object of the present invention is to provide a lubricative copper alloy, which can be produced at a reduced cost, so that various industrial machine components, which require abrasion resistance, corrosion resistance, thermal shock resistance and lubricity, are produced at a low cost, thereby offering competitive machine equipment.

[9] A further object of the present invention is to provide a lubricative copper alloy, which has all of high strength, high load bearing ability and high tensile force, thus fulfilling its inherent functions for a long term. Technical Solution

[10] In order to accomplish the above object, a lubricative copper alloy according to the present invention is configured as follows.

[11] According to a first embodiment of the present invention, the present invention provides a lubricative copper alloy, which is produced by melting silicon (Si), aluminum (Al), nickel (Ni), manganese (Mn), zinc (Zn), iron (Fe), tin (Sn), phosphorous (P) and copper (Cu), and which is capable of assuring high strength, high load bearing ability, high tensile force and excellent lubricating property.

[12] According to a second embodiment of the present invention, the present invention provides a lubricative copper alloy, which comprises silicon (Si) of 0.5-7wt%, aluminum (Al) of 0.5-3wt%, nickel (Ni) of 0.1-3wt%, manganese (Mn) of 0.5-5wt%, zinc (Zn) of 3-16wt%, iron (Fe) of 0.5-3wt%, tin (Sn) of 0.5-5wt%, phosphorous (P) of 0.1-0.15wt% and the balance of copper (Cu).

Advantageous Effects

[13] As described above, the present invention provides a lubricative copper alloy, which is produced at a low cost to have high strength, high hardness, high shock resistance and high tensile force, so that various industrial machine components, which require abrasion resistance, corrosion resistance, thermal shock resistance and lubricity, is produced at a reduced cost, thereby offering competitive machine equipment.

[14] In addition, the lubricative copper alloy according to the present invention is capable of reserving high strength, high load bearing ability and high tensile force for a long period while assuring a drastically prolonged service life. Consequently, the present invention produces advantageous effects in that a labor cost and a maintenance cost required for replacement of worn or damaged components can be reduced. Best Mode for Carrying Out the Invention

[15] Production and component composition of a lubricative copper alloy according to the present invention will now be described in detail. [16] The lubricative copper alloy according to the present invention is produced in such a way that a Cu-Si mother alloy consisting of Cu of 93% and Si of 7%, a Cu-Ni mother alloy consisting of Cu of 97% and Ni of 3%, a Cu-Al mother alloy consisting of Cu of 97% and Al of 3%, a Cu-Mn mother alloy consisting of Cu of 95% and Mn of 5%, a Cu-Fe mother alloy consisting of Cu of 97% and Fe of 3%, and a Sn-P mother alloy consisting of Sn of 85% and P of 15% are first prepared, the mother alloys are put in molten copper, and then zinc is added to the resulting molten copper. A component composition of the lubricative copper alloy produced according to the present invention is represented in Table 1 below.

[17] Table 1

[18] In the lubricative copper alloy according to an embodiment of the present invention, where the copper alloy includes Si of 5wt%, Mn of 2.5wt%, Zn of 14.5wt%, Sn of 2.5wt%, Fe of 1.5wt%, Al of 1.9wt%, Ni of 1.4wt%, P of 0.12wt% and the balance of Cu, the copper alloy had measurements of a tensile strength of 81kg/mm , a Brinell hardness of 270 or more and an elongation percentage of 12% or more.

[19] The reason for limiting the component composition of the copper alloy to the above values is explained as follows. If Si is less than 0.5wt%, lubricity is deteriorated, whereas if Si is more than 7wt%, the copper alloy suffers cracking. Hence, a content of Si is limited to a range of 0.5 to 7wt%.

[20] If Ni is less than 0.1wt%, toughness is increased, resulting in decrease in hardness and strength, whereas if Ni is more than 3wt%, toughness is drastically decreased. Hence, a content of Ni is limited to a range of 0.1-3wt%.

[21] If Al is less than 0.5wt%, strength, tensile strength and elongation percentage are de creased, whereas if Al is more than 3wt%, brittleness is increased, resulting in poor impact resistance. Hence, a content of Al is limited to a range of 0.5-3wt%.

[22] If Mn is less than 0.5wt%, tensile strength is decrease, whereas if Mn is more than 5wt%, the copper alloy is liable to be broken. Hence, a content of Mn is limited to a range of 0.5-5wt%.

[23] If Fe is less than 0.5wt%, hardness and strength are decreased, whereas if Fe is more than 3wt%, a lot of pores form in the copper alloy, which leads to an increased brittleness and thus poor impact resistance. Hence, a content of Fe is limited to a range of 0.5-3wt%.

[24] If Sn is less than 0.5wt%, there is no effect of densifying structure of the copper alloy and thus increasing strength and hardness, thereby decreasing strength and hardness, whereas if Sn is more than 5wt%, a density of the copper alloy structure is increased beyond a desired value, thus the copper alloy suffers cracks and breakages. Hence, a content of Sn is limited to a range of 0.5-5wt%.

[25] P is an element, which serves to improve flowability and workability in a casting operation, and serves to eliminate impurities in a process of producing alloy, thus enhancing a tensile strength. Therefore, a content of P is limited to 0.1-0.15wt% so as to allow the element P to properly fulfill functions thereof.

[26] If Zn is less than 3wt%, an elongation percentage of the copper alloy is decreased, whereas if Zn is more than 16wt%, strength, hardness and lubricity are decreased. Hence, a content of Zn is limited to a range of 3- 16wt%.

[27] The applicant deposited the lubricative copper alloy, which is applied to an oilless bearing, to KRISS (Korea Research Institute of Standard and Science), in order to measure a friction coefficient of silicon lubricative material for low speed and high load operation. Hereinafter, experimental results obtained from the test will be described in detail.

[28] According to a test data report from KRISS, the test was conducted as follows.

[29] Test Purpose

[30] An oilless bearing refers to a bearing, which is designed to remove the necessity of oil refill in the case where it is difficult or undesirable to refill oil or there is no effect, even though oil is refilled, owing to high or low temperature, corrosive atmosphere, infiltration of foreign substances, shock load, vibration and inaccessible structure for oil, thereby realizing improvement in machine performance, reduction in labor force and cost required for oil refill, and improvement in productivity. Further, the oilless bearing, which is silicon lubricative material for low speed and high load operation, is adapted to serve to minimize deformation of displacement of a bridge slab, which is in turn transmitted to lower structure for supporting the bridge. Excellence in frictional ability of an oilless bearing according to its frictional coefficient occupies an important place in displacement and stability of a bridge. According to this test, a method of measuring a frictional coefficient of a bearing and results obtained from the method will be described.

[31] Test Specimen

[32] A friction test specimen, which is comprised of a disc-shaped piece having a diameter of 50mm and homogeneously alloyed with silicon lubricative material, was submitted by the applicant. The test specimen was held by a hydraulic grip of a shaft device, which has a diameter of 30mm and includes a holding part having a length of 25mm. The test specimen is configured such that the surface alloyed with silicon lubricative material is formed to have excellent perpendicularity with respect to a shaft for test specimen. [33] A comparative test specimen was made from an iron alloy with a surface coated with Cr. The coated surface of the comparative test specimen was ground so as to assure intimate contact with the test specimen alloyed with silicon lubricative material and to minimize a surface roughness thereof. The comparative specimen was prepared to have the same shape and dimensions as those of the friction test specimen.

[34] Test Method

[35] As test machine used in this test, a biaxial test machine was used, which is capable of concurrently applying tensile load (or compressive load) and torsional load, and having an axial load capacity of 10OkN and a maximum torsional load capacity of 1000Nm, thus enabling measurement of both an axial load and a torsional load.

[36] The test specimen was formed into a cylindrical shape at a part to be gripped by the test machine. Therefore, there is a need to provide a remarkably reliable holding grip so as not to allow a relative movement between the test specimen and the grip. In this test, a hydraulic grip, which has remarkably excellent holding power, was used to hold the test specimen.

[37] Since perpendicularity between the frictional surface and a holding shaft for test specimen has a significant influence on test results, there is a need to check perpendicularity of the specimen prior to the test.

[38] A normal pressure was applied to exert a surface load of 350kgf/cm (34.28 MPa).

The test specimen used in this test has a diameter of 50mm, and thus a nominal pressure of 67.4kN was correspondingly applied.

[39] A torsional movement was employed as a relative movement for measuring a frictional coefficient. In this case, an angular movement between +10 degrees and -10 degrees was conducted at a test frequency of 0.5Hz to measure a frictional force due to the relative movement. The angular movement was conducted while the test specimen was linearly moved at an average linear velocity of 5.82mm/s.

[40] Prior to the test, dimensions of the specimen were measured and recorded. From the friction test, the torsional load and the normal pressure are measured, and maximum and minimum torques are periodically measured using a peak detector at regular intervals. After the test, the maximum and minimum torques are measured, and then changes in the torques are recorded.

[41] From the measured torsional load and the normal pressure, and the dimensions of the specimen, a momentary frictional coefficient was determined using the following equation:

[42] μ = 3T/2rP

[43] wherein, μ represents a frictional coefficient, T represents a torsional load (Nm), r represents a radius (m) of a friction surface of the test specimen, and P represents a normal pressure (N). [44] Test Procedure

[45] Dimensions of a frictional specimen and a comparative specimen were measured and recorded; [46] the frictional specimen and the comparative specimen were held by grips, and whether proper perpendicularity between the frictional surface of the specimen and the shaft for specimen was obtained, was determined; [47] a normal pressure is gently applied up to a nominal pressure, after the application of the nominal pressure, and whether the frictional specimen properly coincided with the comparative specimen, was determined; and [48] torsional displacement within an angular range of + 10 degrees to -10 degrees was periodically imposed while recording torsional loads. [49] Test Results and Analysis

[50] The changes in torsional load and frictional coefficient with the number of test repetitions were represented in Table 2 below. [51] Table 2

[52] From the results obtained by conducting the test for measuring frictional coefficient of silicon lubricating material for low speed and high load under the above conditions at KRISS, it was observed that the oilless bearing, to which the lubricative copper alloy according to the present invention is applied, showed a relatively low and steady frictional coefficient of about 0.06, even though repetitive torsional loads were applied.

[53] Such low frictional coefficient, which has been obtained from the test, signifies that friction between the oilless bearing and other structural components is decreased, and it is possible to prevent excessive frictional heat. Therefore, when the lubricative copper alloy according to the present invention is applied to an oilless bearing, the oilless bearing may require a small amount of lubricating oil or may eliminate the necessity of applying lubricating oil. Furthermore, even if only a small amount of lubricating oil is supplied, consumption of the lubricating oil due to boiling of the lubricating oil caused by frictional heat can be reduced, which leads to cost saving. As a consequence, since wear or damage to an oilless bearing can be reduced, it is expected that cost necessary for replacement, maintenance and the like is reduced.

[54] In addition, since there is almost no change in frictional coefficient with increased numbers of repetitions, it is possible to realize a durable oilless bearing which can be efficiently used for a long period time. Consequently, it is also expected that labor cost required for replacement and maintenance is reduced.

[55] Although the present invention has been described for illustrative purposes, those skilled in the art will be apparent that various substitutions, modifications, and application to various components are possible, without departing from the scope and spirit of the invention.

[56]

Claims

[1] A lubricative copper alloy, which is produced by melting silicon (Si) of l-7wt%, aluminum (Al) of 0.5-3wt%, nickel (Ni) of 0.1-3wt%, manganese (Mn) of 0.5-5wt%, zinc (Zn) of 3-16wt%, iron (Fe) of 0.5-3wt%, tin (Sn) of 0.5-5wt%, phosphorous (P) of 0.1-0.15wt% and the balance of copper (Cu), and which is capable of assuring high strength, high load bearing ability, high tensile force and excellent lubricating property.