JPS6316455B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to brass alloys, particularly brass alloys useful in applications where wear resistance is required. Brass alloys have good corrosion resistance, wear resistance, and castability, and are cheaper than high-strength brass or bronze. However, although brass alloys have excellent wear resistance, they are inferior to high-strength brass in high-load areas and inferior to bronze under high-speed sliding conditions. Therefore, if the desired lubricating effect cannot be obtained with the brass alloy alone, adding a solid lubricant may be considered for the purpose of improving wear resistance. Solid lubricants include graphite, lead or copper sulfide;
Examples include sulfides and fluorides such as lead sulfide and molybdenum disulfide. Methods for incorporating these solid lubricants include a sintering method, an impregnation method, and a casting method. For example, when dispersing and containing graphite using these methods, particular attention is paid to the particle size and content of graphite particles due to problems with uniform mixing and restrictions on manufacturing methods. However, the alloys obtained by these methods, despite the appropriate grain size and content of graphite, and despite the reinforcement of the base alloy,
The desired wear resistance could not be obtained. In general, the main properties required for a sliding body are that it does not cause wear or damage to the mating material, and that the sliding body itself has wear resistance. An object of the present invention is to provide a brass alloy with a low coefficient of friction and excellent wear resistance, particularly for use in high-pressure oil-free bearings and sliding plates. . The present invention is characterized in that wear resistance is significantly improved by dispersing graphite, a solid lubricant, in a brass alloy, which is the cheapest among copper alloy ingots and has excellent castability and machinability. Also, the coexistence of lead and graphite provides a mutually lubricating effect, and the addition of Sn makes it possible to prevent stress corrosion cracking. Furthermore, it is based on the discovery that by adding two or more selected from Cr, Si, Ce, and La, it is possible to obtain a brass alloy that is significantly tougher. That is, the present invention has a weight ratio of Cu60.0 to 88.0.
%, pb0.1~20.0%, Ti0.1~2.0%, p0.1~1.0%,
Consisting of 1.0-10.0% graphite and residual Zn, 0.5-2.0% Sn added to this alloy, and 0.5% or more of two or more selected from Cr, Si, Ce, and La.
It is characterized by the addition of ~2.0%,
The aim is to provide a brass alloy that has significantly better wear resistance than conventional brass alloys. Next, details of the present invention will be described. First, when adding graphite to brass alloys, if the amount exceeds 10%, the flowability of the molten metal will deteriorate, especially in casting methods, making it difficult to obtain sound castings, so it should be in the range of 10% or less. Should. 1.0
If it is less than that, the desired lubrication effect cannot be obtained. Further, the amount of lead added is 0.1 to 20.0%. If it exceeds 20.0%, no significant improvement in wear resistance will be achieved with respect to the amount added, and the strength of the sliding material itself will decrease, and if it is less than 0.1%, the desired lubricating effect will not be obtained. Addition of Ti has the effect of improving the wettability between graphite and the metal matrix and improving toughness by refining the crystal grains of the metal matrix. If the amount of Ti added is less than 0.1%, the above effects will not be obtained, and if the amount of Ti added is less than 0.1%, then 2.0%
If it exceeds 100%, it will not be completely dissolved in the metal matrix and will remain. However, the amount added is proportional to the surface area of the graphite particles, and for example, when 6% of graphite particles with an average particle size of 250 μm (60 mesh) are added, a suitable range of Ti is 0.6 to 0.8%. Ti combines with oxygen in the molten metal and in the atmosphere when the molten metal temperature in the atmosphere is around 950℃, forming titanium oxide, and its effect disappears, but as mentioned above, the amount added is
If it is 0.8% or more, it not only precipitates as titanium carbide on the surface layer of graphite particles, but also may remain in the metal matrix without being dissolved as a solid solution. It is not desirable to add more than 0.8% to graphite with an average particle size of 250 μm (60 mesh), as it will also stake the mating material. P is added primarily for the purpose of deoxidizing, but in the present invention it is added to ensure sliding wear resistance. If the amount added is less than 0.1%, there will be no effect, and if it exceeds 1.0%, compounds will be formed with other blended elements, resulting in poor flowability of the molten metal, which is not appropriate. In another aspect of the present invention, Sn is added to members that will be used for a long period of time, and its purpose is to prevent stress corrosion cracking. The amount added is 0.5 to 2.0%; if it is less than 0.5%, there is no effect, and if it exceeds 2.0%, it is slightly effective in improving sliding wear resistance, but no significant lubricating effect is obtained. Moreover, in another invention of the present invention,
0.5 to 2.0 of two or more selected from Cr, Si, Ce, and La
% added. Mitsushi Metal (MM) and the like are used as metals containing these. If the amount added is less than 0.5%, no effect on high-temperature oxidation resistance can be expected, and if it exceeds 20%, it becomes impossible to improve wear resistance without reducing high-temperature oxidation resistance. For example, the solubility limit of Cr in Cu is approximately 0.7 at 1070℃.
%, a large amount of coarse Cr compounds will precipitate into the copper substrate, making it impossible to obtain the desired high-temperature oxidation resistance properties. That is, if it exceeds 2.0%, the high temperature oxidation resistance properties will be extremely deteriorated and it is not appropriate. Furthermore, the wear resistance of graphite is significantly improved when 15 to 50% of the area ratio is exposed on the sliding surface. As a shape in which graphite is easily exposed on the sliding surface, a lump or spherical shape is more suitable than a foil shape or a scale shape. Conventionally, in general graphite-dispersed sintered alloys, attention has been paid to the particle size distribution and addition amount of the dispersed graphite particles for the purpose of uniform mixing, and according to this sintering method, the smaller the particle size is than 100 μm, the better. It is said that there are. On the other hand, in the casting method, the larger the particle size, the better. Further, as a result of studying details regarding graphite particles for the purpose of the present invention, it was found that, for example, 6% by weight of graphite particles were added to base alloy molten metal in foil-like, scale-like, lump-like or spherical shapes, respectively. After dispersion and casting, the wall side of the mold is approximately 2
When the sliding surface is made by cutting mm, the ratio of exposed area of graphite particles to sliding area is 13.1 for foil graphite particles.
%, 14.7% for flaky graphite and 23.1% for massive (spherical) graphite particles, indicating that the graphite exposed area is large in massive or spherical graphite particles. On the other hand, the results of the sliding property test showed that wear resistance was proportional to the size of the graphite exposed area. In other words, the sliding properties are significantly affected not only by the amount of graphite added but also by the ratio of the graphite particle exposed area to the sliding surface area. It has been found that lump-like or spherical forms are better than foil-like or scale-like forms. Therefore, the shape of the graphite particles used is lumpy or spherical, and the exposed area of the graphite particles relative to the sliding area is:
It is desirable to set it to 15-50%. As described above, the alloy having the chemical composition of the present invention provides excellent wear resistance with a low coefficient of friction under high pressure. Next, embodiments of the present invention will be described. Example 1 Commercially available copper and zinc ingots were placed in a graphite crucible and melted to have the same composition as a foundry brass alloy ingot (YBsCIn), and then Pb, P, and Ti were added and melted. Homemade massive graphite (-16
After 0.3 kg of 80 mesh) was added and stirred and dispersed, it was poured into a mold and solidified under pressure (600 kg/cm ² ) to obtain an ingot having the composition shown in Table 1. Example 2 An ingot having the composition shown in Table 1 was obtained in the same manner as in Example 1 except that Sn was further added when adding Pb, P, and Ti in Example 1. Examples 3 and 4 Same as Example 2 except that Cr+Si+MM (Example 3), Si+MM (Example 4a), or Cr+MM (Example 4b) was added when adding Pb, P, Ti, and Sn in Example 2. In the same manner, ingots having the compositions shown in Table 1 were obtained. Comparative Examples 1 and 2 Comparative Example 1 was an ingot of a commercially available brass alloy ingot for casting (YBsCIn3). In addition, in Example 1, Pb
An ingot having the composition shown in Table 1 was obtained in the same manner as in Example 1, except that no ingot was added, and Comparative Example 2 was obtained. The obtained ingot was cut approximately 2 mm from the mold wall surface, a test piece was cut out with the sliding surface, and the mating material was cut out.
SAE4620 (HRC; 58 to 63), dimensions and shape: outer diameter
35 mm, width 8.15 mm, and surface roughness of 0.13 to 0.28 μRMS, press it with a surface pressure of 10 to 300 Kg/ ^cm2 , and set the sliding speed (circumferential speed) to 0.03 m/S under dry conditions (no lubrication).
A sliding test was conducted. The test results are shown in Table 1.

[Table] As is clear from Table 1, the critical surface pressure and PV value of the brass alloy of the example are 10 times that of the commercially available brass alloy of Comparative Example 1, and 1.7 times that of the graphite-dispersed brass alloy of Comparative Example 2. It is shown that it has excellent abrasion resistance. Furthermore, compared to Comparative Example 2, the wear coefficient, temperature rise, and amount of wear on the mating material are smaller. Although data has been omitted, the Sn-added material of the present invention has no stress corrosion cracking, and no cracking occurred during processing. Furthermore, it was confirmed that Cr, Si, and MM additives have excellent high-temperature oxidation resistance, and when used in current collectors, excellent wear resistance can be obtained. The brass alloy of the present invention has a low coefficient of friction and excellent wear resistance, and is used for oil-free bearings for high temperatures and high loads, sliding plates, etc.

Claims (1)

[Claims] 1. Cu60.0~88.0%, Pb0.1~20.0%,
A wear-resistant brass alloy consisting of 0.1-2.0% Ti, 0.1-1.0% P, 1.0-10.0% graphite, and the balance Zn. 2 Cu60.0~88.0%, Pb0.1~20.0% by weight,
Ti0.1~2.0%, P0.1~1.0%, graphite 1.0~10.0%,
A wear-resistant brass alloy consisting of 0.5-2.0% Sn and the balance Zn. 3 Cu60.0~88.0%, Pb0.1~20.0% by weight,
Ti0.1~2.0%, P0.1~1.0%, graphite 1.0~10.0%,
A wear-resistant brass alloy consisting of 0.5 to 2.0% Sn, 0.5 to 2.0% of two or more selected from Cr, Si, Ce, and La, and the balance Zn.