1. Material and blank manufacturing factors
(1) poor adhesion between the liner and the backing
This is a major problem with sliding bearings that cast tin-based or lead-based bearing alloy liners. A good combination enhances the tin-based and lead-based bearing alloys and contributes to heat dissipation from the bearing surface. For good bonding, tin must be placed on the backing joint before casting the tin-based and lead-based bearing alloys, and the temperature of the backing and bearing alloys is strictly controlled.
When the size of the bearing bush is allowed, the tin bath method should be used to hang the tin. The temperature of the tin bath in the pure tin bath should be kept at 280-300 ° C. The temperature of the tin bath in the solder bath should be kept at 270-300 ° C. The bush is immersed in the tin bath. The temperature can reach the tin liquid temperature and can be taken out. Large bushings can be tinned by tinning, first heating the bush with flame, and then applying pure tin or solder to the surface to be tinned.
It has been found that making a wedge groove on the surface of the backing cast lining not only does not contribute to the combination of the backing and the lining, but at the sharp corners of the shoulder of the groove, stress concentration will cause cracks.
(2) stomata
For large bushings with tin-based or lead-based bearing alloy linings, when the casting temperature is too low or the backing is insufficiently preheated, air bubbles will appear on the lining joint surface. These bubbles are not conducive to heat dissipation from the surface of the bearing pad and also weaken the tin- or lead-based bearing alloy lining. When casting a cast copper-based alloy, looseness is caused by the release of hydrogen from the copper alloy.
(3) Large grain size
This is a peculiar problem for tin-based and lead-based bearing alloy liner bushings. In the cooling and solidification process of the cast bearing alloy, if the cooling rate is very slow, the size of the tin-bismuth crystal grains will exceed 0.1 mm, which can be observed by the naked eye. Such intermetallic compounds are easily broken, break off the friction surface after being broken, and become particles entering the lubricating oil circulation system, causing bearing damage.
(4) Uneven distribution of lead
Copper and lead are not co-dissolved, so when the bearing bush is made of copper-lead alloy which is a copper-based bearing alloy, uneven distribution of lead may occur. Rapid cooling of the copper-lead alloy after casting can prevent uneven distribution of lead. The production of copper-lead alloy bearing bush by powder metallurgy can completely solve the problem of uneven distribution of lead in copper-lead alloy.
2. Installation and operation factors
(1) Poor alignment
The support of the shaft requires at least two fulcrums. If the two sliding bearings are poorly aligned and the coaxiality error is large, the distribution of the load on the width of the bearing bush will be uneven, and the edge contact phenomenon will occur, causing the lubricating oil film to rupture and causing adhesive wear.
(2) improper matching of bearing bush and bearing housing hole
If the bearing bush is improperly fitted with the bearing housing hole, the bearing bush may be loose and cause fretting wear. After loose or fretting wear, it is unfavorable for heat transfer, which may cause the friction surface temperature of the bearing pad to be too high.
The mating surface of the bearing bush and the bearing housing is not clean, and there are particles and dirt, which will also cause poor conduction.
In summary, checking the damaged bearing surface may provide important information about bearing failure, so you should not forget to check the back of the bearing.
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