Development of lead-free plain bearing for heavy-duty
Yoshio Kumada(TAIHO KOGYO CO.,LTD), Souji Kamiya(TAIHO KOGYO CO.,LTD), Katsuyuki Hashizume(TAIHO KOGYO CO.,LTD), Takashi Tomikawa(TAIHO KOGYO CO.,LTD), Hiroshi Kanayama(TAIHO KOGYO CO.,LTD)
Fig. 1 shows a structure and characteristics of the developed material, in comparison with a conventional Cu-Pb alloy. In order to avoid bearing failures caused by a poor resistance of Pb to corrosion, Pb is actively excluded from a bearing material, though Pb is an extremely useful material for bearings. Addition of Ag, in place of Pb, gives good seizure resistance and anti-adhesive property to a Cu lining. In addition, a newly developed lead-free overlay consisted of solid lubricant and resin is applied to the Cu-Sn-Ag alloy lining, therefore, Pb free bearing is completed.
The reasons behind a higher load-carrying capacity of the alloy are the
preventing metal transfer of bearing material to the shaft during the
operation. Less transfer is originated by following roles of Sn and
Ag added to the alloy.
Fig. 2 shows the correlation between the detected amounts of Sn and Ag on the bearing surface. From this analysis there are a lot of spots showing more than twice value as high as that of Sn and Ag at the initial stage. Fig. 3 shows the smaller and stable friction coefficient of Sn-Ag thin layer in verifying experiments.
Load-carrying capacity of the developed bearing is shown in Fig. 4 as P-V performance chart. Each plot means the Cu-Sn-Ag alloy bearing endures to be used in each P-V condition, resulting from endurance tests in each P-V. As results, the Cu-Sn-Ag alloy bearing is possible to use under loads of 120 MPa and more, which is about 1.5 times as many loads as that of conventional Cu-Pb alloy bearings.
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