JPH0239572B2 - OOBAREIYOMETSUKIGOKIN - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an overlay alloy,
More specifically, the present invention relates to a quaternary overlay alloy that is applied by plating to Kelmet bearings used in internal combustion engines. (Prior art) Sliding bearings used in internal combustion engines are constructed by depositing Kelmet alloy on a steel plate processed into a cylindrical bushing, half-split metal, or ring-shaped metal shape, and coating the top with an overlay alloy. It is well known that this has been done. The main function of the overlay alloy is to improve the compatibility between the bearing and the shaft of the crankshaft, etc., and eliminate poor contact between the shaft and bearing caused by shaft misalignment caused by the machining accuracy of the internal combustion engine housing. However, foreign matter mixed into the lubricating oil may be buried in the overlay alloy. One of the overlay alloys that has been widely used until now is a Pb-Sn binary alloy. However, due to the recent increase in the output of internal combustion engines, the above-mentioned Pb-Sn binary alloy cannot meet the severe load capacity required for overlays.
Therefore, Pb-based ternary overlay alloys whose load capacity has been improved in recent years are now widely used. Examples include Pb- containing Cu1-10% and Tl5-80%
There is a Tl-Cu alloy. Such ternary overlay alloys have insufficient wear, corrosion and fatigue resistance. In particular, as the output of internal combustion engines has increased in recent years, the load applied from the shaft to the bearings has increased, so the thickness of the oil film between them has decreased, and direct contact between the shaft and the bearings has become more difficult. ternary alloys cannot adequately meet the high degree of wear resistance required when the bearing is subjected to wear by the shaft. moreover,
Pb-Sn-Sb and Pb-Sn-Cu ternary alloys have a problem of insufficient compatibility. on the other hand,
Ternary alloys of Pb-Sn-In not only have the disadvantage of not being able to obtain the desired conformability unless indium is added in large amounts, even though indium is expensive, and also suffer from insufficient load capacity and wear resistance. However, premature damage to the overlay occurs. In U.S. Pat. No. 4,309,064, the applicant
(1) 5-20% Sn, (2) 0.05-10% one or more of In and Tl, (3) 0.05-5% Mn, Bi, Ni, Cu,
We proposed a quaternary overlay alloy consisting of one or more of Ca and Ba, and (4) the balance Pb and impurities. In the process of technology progressing from conventional general ternary overlay alloys to the above quaternary overlay alloys,
The five properties of fatigue resistance, corrosion resistance, load capacity, wear resistance, and conformability are interrelated, and if one property is not excellent, the other properties will also be adversely affected, reducing the reliability and service life of the overlay. In recent years, the mechanical load on the overlay has increased due to the high output of internal combustion engines, and the lubrication condition of the overlay has worsened due to the extension of the lubricating oil replacement period. It has been revealed that the above-mentioned
This led to the development of a quaternary overlay alloy containing elements that improve wear resistance such as Mn. The present invention uses such prior art as a starting point to further improve the fatigue resistance of overlay alloys. Here, it is important to note that the fatigue resistance of overlay alloys is improved by the denseness and uniformity of its structure, that simultaneous quaternary plating is not preferable in order to form a quaternary overlay alloy with a dense structure, and that It is known from the above-mentioned US patent that a dense and homogeneous structure can be obtained by diffusing the components. The US patent disclosing the above-mentioned quaternary overlay alloy reveals that the five properties of the overlay alloy are interrelated, as mentioned above, and that the five properties can be comprehensively improved by improving wear resistance in particular. Improving measures were adopted. Furthermore, according to the method of diffusing the components in order to obtain an overlay alloy with excellent fatigue resistance disclosed in the above-mentioned U.S. patent, the plating structure is It is thought that tissue densification is achieved while the micropores inside disappear or shrink. However, since the diffusion method is essentially a heat treatment process,
Due to melting or softening of low melting point metals such as In and Sn,
Coarsening of phases such as In may also occur. In the known diffusion method, the effect of improving fatigue resistance due to disappearance or shrinkage of micropores in the plating structure is greater than the deterioration of fatigue resistance due to coarsening of crystal grains or phases.
It can be said that fatigue resistance has improved overall. (Problems to be Solved by the Invention) The present invention seeks to improve the fatigue resistance resulting from the composition of the quaternary overlay alloy disclosed in the above-mentioned US patent. That is, the present inventors
After intensive research into how the four components of Pb, Sn, In, and Cu affect fatigue resistance and plating structure, we surprisingly found that Cu, a high melting point metal, had the strongest effect. I found it. The present inventors investigated in detail the plating structure of the above-mentioned known quaternary overlay, and found that in addition to the density represented by the size and degree of the micropores, there are two factors: the homogeneity of the metal parts other than the micropores. We found that the properties of the Metsuki tissue can be expressed by its properties. The latter homogeneity can be detected by a secondary electron image of the fractured surface of the plating layer using an electron microscope. however,
This homogeneity cannot be expressed quantitatively depending on the size (more or less), but can only be expressed by comparing the degree of homogeneity by comparing the secondary electron images of the fractured surface. The present inventors investigated the relationship between Cu and the homogeneity of the plating structure, and found that when Cu exceeds 0.05%, the plating structure becomes non-homogeneous, resulting in poor fatigue resistance under severe bearing usage conditions. I found it. (Means for Solving the Problems) The present invention comprises tin of 2 to 20% by weight and 0.05% tin by weight.
The overlay plating alloy has a composition of from 1 to 15% indium, from 0.01 to less than 0.05% copper, with the remainder being lead and impurities. The overlay alloy composition of the present invention will be explained. Tin added to the lead-based overlay alloy of the present invention is an element that primarily imparts corrosion resistance and wear resistance. In lead-tin binary alloys, tin is dispersed in the alloy in metallic form, and this makes it easy for tin to diffuse into the lining layer beneath the overlay, resulting in a disadvantage that the wear resistance decreases with the use of the overlay. There is. However, in the alloy of the present invention in which indium and copper are added, tin has a greater tendency to form intermetallic compounds, and is stabilized to the extent that the above diffusion does not occur, resulting in poor reliability in conformability, corrosion resistance, wear resistance, etc. enhance sexuality. Additionally, tin increases the corrosion resistance of the overlay against certain corrosive organic acids that form in lubricating oils. If the tin content is less than 2%, it is not very effective, while if it exceeds 20%, the hardness of the overlay at high temperatures decreases, causing a problem of decreased performance during use (decreased wear resistance). Note that the preferred tin content is 5 to 10%. Indium increases the chemical corrosion resistance of the overlay to corrosive organic acids in lubricating oils, and also forms intermetallic compounds with tin to stabilize the tin and improve compatibility, as described above. If the indium content is less than 0.05%, there will be no effect, and if it exceeds 15%, the overlay layer will become soft and the abrasion resistance and cavitation and erosion resistance will decrease. This content is preferably 4 to 7%. The most distinctive feature of the present invention is that the structure of the overlay alloy is made dense by containing copper in an amount of less than 0.05% and more than 0.01%. Hereinafter, changes in the structure of the overlay alloy depending on the copper content will be explained with reference to FIGS. 1 to 5. In addition, Figures 1 to 5 are 7
Secondary electron image (magnification) of an overlay alloy of %Sn, 5.5%In, 0~0.015%Cu, balance lead
3000x). 1 to 5 show a fractured surface structure in which a nickel barrier layer and an overlay layer are laminated on Kelmet, and the uppermost layer corresponds to the overlay layer. Cu=0% (Figure 1) and Cu=0.15
% (Figure 5), the overlay layer is Cu0.01%
(Figure 2), Cu0.03% (Figure 3) and Cu0.04%
Compared to the case shown in FIG. 4, the filling state of the metal particles is coarser. On the other hand, in the overlay layer shown in FIGS. 2 to 4, in which the metal particles are densely packed, the grain boundaries of the electrodeposited grains are relatively clearly arranged. As mentioned above, a homogeneous structure cannot be obtained either when the copper content in the overlay alloy is zero or high (0.15%). Corresponding to such structural changes, if the copper content is less than 0.01%, the wear resistance will be low, while if the copper content is 0.05% or more, the fatigue resistance will be insufficient. Therefore, the copper content of the overlay alloy of the present invention was set to less than 0.01% to 0.05%. In the quaternary overlay alloy of the present invention, by determining the composition as described above, a homogeneous structure is formed in the plating state to improve fatigue resistance, and the wear resistance is also improved by the action of a small amount of Cu. It has characteristics. These characteristics of overlay alloys are manifested in improved bearing performance, such as less wear and less fatigue in high-speed, high-load internal combustion engines, compared to conventional quaternary overlay alloys. (Function) The inventors of the present invention obtained the following findings by observing secondary electron images of bearings after using them under various conditions. In other words, we found that in overlays with a Cu content of less than 0.05% and a homogeneous plating structure, the diffusion of Sn into the bearing alloy during bearing use becomes inactive. As is well known, in order to prevent the above-mentioned diffusion of Sn
Although a Ni barrier is used, it is a new finding that Sn diffusion is suppressed by the overlay structure itself. Therefore, the present inventors assumed that the plating structure became homogeneous, making it difficult for Sn to move, but as a result of experiments using various equipment including EPMA, it was found that Cu was 0.01% to 0.05% (less than 0.05%). It is assumed that if there is Sn, Sn will be captured by Cu and difficult to diffuse, which is a strong cause of suppressing Sn diffusion. From the above, Cu from 0.01 to 0.05% (less than)
Considering the effect of improving fatigue resistance and wear resistance by using (b) Fatigue resistance improves because the plating structure becomes homogeneous within the above-mentioned Cu content range. (b) Sn is captured by Cu in the above Cu range, improving fatigue resistance. On the other hand, Cu content is 0.05%
If the amount exceeds that amount, the amount of Sn captured by Cu becomes too large, and the inherent corrosion resistance improvement effect of Sn is lost, resulting in a ripple effect of lowering fatigue resistance. (c) When Cu exceeds 0.05%, the density of the plating structure is impaired, minute pores become numerous or large, the strength of the overlay decreases, and the fatigue resistance decreases as a result. Cu content from 0.01% to 0.05%
When Cu increases, the density is similarly impaired, but Cu
In the range of =0.01% to 0.05% (less than), the ripple effect of strength reduction on fatigue resistance is small. (d) The influence of Cu on wear resistance does not change even if Sn is captured. That is, Cu and Sn have a relative capture relationship, and Cu captured by Sn is effective in improving wear resistance. The corrosion resistance mentioned in section (b) above is rather an electrochemical phenomenon;
Wear resistance is more of a mechanical phenomenon, and the features of the two can be expressed in contrast.
There may be a difference in the effects of Sn and Cu as described above. Therefore, when Cu is added in an amount of 0.01% or more, the wear resistance of the overlay is improved. Micro-alloying (micro-
To show the effect of alloyed Cu, below:
The influence of Cu content on fatigue resistance and wear resistance will be explained with reference to Table 1 showing the experimental results of the present inventor. In Table 1, fatigue condition A is a repeated load
The general conditions are 200Kg/cm ² , rotation speed 5600rpm, and test time 10Hr, and fatigue condition B is 300Kg/cm ² repeatedly.
The rotation speed is 7300 rpm, the test time is 10 Hr, and the fatigue condition C indicates the severe conditions of 300 Kg/cm ² repetition, the rotation speed is 7300 rpm, and the test time is 100 Hr, and both are fatigue resistance test conditions that were conducted using an actual engine test. shows. In addition, the lubricant used in all conditions is SAE
Equivalent to #30, the oil temperature was 120℃. Also, ◎, 〇,
△ and × are both indications of observation results of the slip surface of the overlay alloy, and are respectively good (◎),
Indicates locally slight fatigue or drag (○), slight fatigue surface detection (△), and significant fatigue and drag surface detection (×). The wear test conditions were as follows. (a) Testing machine - Soda type dynamic load tester (b) Rotation speed - 2000rpm (c) Surface pressure - 130±130Kg/cm ² (d) Time - 1.5 hours (e) Lubricating oil used - SAE#30 ( F) Oil temperature -120℃ (G) Mating shaft - S55C circular rod (H) Kelmet - Composition - Pb-Sn-Cu (thickness
(0.25μm) (li) Ni barrier layer - 2.5μm The composition of the overlay alloy other than Cu is Sn7%, In5
%, and the thickness was 15 μm.

[Table] From Table 1, if the fatigue conditions are not severe (A),
The Cu content has little effect on the fatigue resistance of the overlay, but under severe conditions (B) and (C)
It can be seen that fatigue resistance deteriorates significantly when the Cu content exceeds 0.5%. The effect of Cu on wear resistance is that the Cu content is 0.01
When it exceeds %, it almost disappears. On the other hand, fatigue resistance decreases with Cu of 0.1% or more, which has an inferior cross-sectional structure even if the wear resistance is the same. Cu content is 0.01%
In the case of , wear resistance is not so good, but good fatigue resistance is obtained. As mentioned above, the present inventors used EPMA etc. to suppress the diffusion of Sn, and the micro-alloyed Cu suppresses the diffusion of Sn.
We believe that this is the most powerful effect of Cu on improving fatigue resistance. Note that the homogeneity and density of the plating structure also directly and indirectly affect the fatigue resistance, so this point will be explained below. Comparing and considering Table 1 and Figures 1 to 5, we can see that the effect of Cu on wear resistance is composition dependent, and when the amount exceeds a certain amount (0.01%), an alloy with excellent wear resistance becomes Therefore, it can be said that the shadow of the Cu content has diminished. From another point of view, the wear resistance is more dominantly influenced by its surface hardness in contact with the mating material than by the entire overlay cross section, and the overlay surface hardness is influenced by the surface hardness of the overlay.
The presence of Cu improves wear resistance due to its hardening effect. On the other hand, fatigue resistance is due to the very small amount of Cu content (0.005%).
If this is the case, the direct effect of Cu itself will be more likely than the effect of wear resistance. For example, Cu=0.01%
Although the wear resistance is not very good (3 mg), the overlay structure is homogeneous, and
Since the Ni barriers are also in close contact (Figure 2),
Despite poor wear resistance, fatigue resistance is good (marked with ◎ in Table 1). When Cu further increases to Cu=0.04%, wear resistance improves (1
mg), but the fatigue resistance is marked with a circle (condition B), showing a decreasing tendency. As can be seen from the trend in Figure 4 (0.04%), when Cu approaches 0.05%, micropores are generated in the overlay and the overlay is further reduced.
Since areas that appear to be plating defects also occur between the Ni barriers, it is presumed that such pores, defects, etc. are the starting point of fatigue. When the Cu content increases further (0.05-1%
Cu), the coarse structure as shown in FIG. 5 becomes more prominent, and the entire overlay becomes a state in which coarse particles are loosely combined, and it is thought that the entire overlay becomes the starting point of fatigue. These trends are remarkable in condition (C). However, the above-mentioned fatigue becomes less sensitive to the plating structure when the conditions are mild (condition A). The greatest feature of the present invention is that it provides a quaternary overlay plating alloy with Cu content of less than 0.01 to 0.05% based on the above-mentioned findings and considerations. Furthermore, the feature of the present invention is the above-mentioned 2 to 20% Sn,
The composition of 0.05 to 15% In is also determined from the viewpoint of improving fatigue resistance. When the Sn content exceeds 20%, the structure of the quaternary overlay alloy becomes coarse and the high temperature strength decreases, and when it is less than 2%, its corrosion resistance decreases, and in either case, the fatigue resistance decreases. Furthermore, if the In content is less than 0.05%, the corrosion resistance will decrease, and if it exceeds 15%, the structure will become coarse and the high temperature strength will decrease, so in either case, the fatigue resistance of the quaternary overlay plating alloy will decrease. . A method for manufacturing an overlay alloy according to the present invention will be described below. Lead borofluoride 150-200 g/, tin borofluoride 5-5 as known from the above US Pat. No. 4,309,064
When plating is performed by adjusting the plating time using a plating bath containing 15g/, copper borofluoride 1-3g/, gelatin about 2g/, and hydroquinone about 2g/
Pb-Sn-low Cu ternary plating with different Cu contents is formed. Similarly, indium plating is performed using known flash plating or a cyan alkali bath, and finally, diffusion is performed between the In layer and the Pb--Sn--Cu layer. The thickness of the overlay varies from 2 to 2 depending on the usage conditions.
Set to 30 μm. As for the diffusion temperature conditions and time, flash plating, alkali plating bath composition and other conditions, those known in the above-mentioned US Pat. No. 4,309,064 can be used. (Example) Below, the fatigue resistance is the best at Cu = 0.03%,
Examples will be described in which the fatigue properties of quaternary overlay alloys with varying Sn and In contents were investigated. The test conditions were the above-mentioned condition B for samples 1 to 22, with the test time varied to 10, 50, and 200 hours, and sample 23
-29 was measured under condition D (test time 50 hours, oil temperature 140°C, other conditions same as condition A). The test results are shown in Table 2.

【table】

[Table] In Table 2, the overlay alloys of Comparative Examples Nos. 13, 14, and Nos. 27 to 29 have poor fatigue resistance.
In addition, the Sn content is 2 to 20%, preferably 5 to 10%,
It can be seen that the fatigue resistance of the overlay alloy is particularly good when the content is 5.5 to 9%. In this Sn content range, the ratio of Sn captured by Cu to Sn not captured by Cu is considered to be in a favorable balance. Example 2 A 2.5 μm thick Ni barrier layer and a 15 μm thick overlay were formed on Pb-Sn-Cu Kelmet (0.25 mm thick). Overlay composition is 7%
The composition consisted of Sn, 5% In, Cu in the percentage shown in Table 3, and the balance lead. The bearing having the Kelmet, Ni barrier layer, and overlay was subjected to an actual engine test under the severe conditions B and C.

[Table] In Table 3, the fracture surface structure is the result of observing the fracture surface of the overlay with an electron microscope before the actual engine test, and evaluated under the same conditions as explained in Figures 1 to 5. . The surface condition was obtained by removing the bearing from the engine after the test and observing the sliding surface of the overlay. 〇 indicates slight localized fatigue, △ indicates slight fatigue throughout, and × indicates fatigue occurred. The degree of severity is indicated respectively. Wear amount is condition B
By measuring the difference in weight before and after the test. From Table 3, according to the present invention, the wear resistance is superior to that of the conventional ternary overlay (Cu = 0%).
It can also be seen that an overlay with wear resistance equivalent to that of the conventional quaternary overlay (Cu = 0.15%) and excellent fatigue resistance can be obtained. (Effects) According to the present invention, it has wear resistance equal to or higher than conventional quaternary overlay plating alloys in high-speed, high-load internal combustion engines, and has superior fatigue resistance than conventional quaternary overlay plating alloys. An overlay alloy is provided having.

[Brief explanation of drawings]

Figures 1 to 5 are metallurgical micrographs (3000x magnification) of bearings in which a nickel barrier layer and an overlay layer are laminated on Kelmet, and the Cu content of each overlay alloy is 0% (the first
Figure), 0.01% (Figure 2), 0.03% (Figure 3), 0.04%
(Figure 4) and 0.15% (Figure 5).

Claims (1)

[Claims] 1. 2 to 20% tin by weight and 0.05 to 15% tin
% indium and 0.01 to less than 0.05% copper,
An overlay metal alloy containing lead and impurities. 2. The plating alloy for overlay according to claim 1, wherein the tin content is 5 to 10%. 3. The plating alloy for overlay according to claim 1, wherein the indium content is 4 to 7%.