DE1421830B - Lubricants for bearings - Google Patents

Description

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The invention relates to the use of lead oxide as a lubricant for bearings.

Lead oxide has such a coefficient of friction at elevated temperatures that it can be used as a lubricant or lubricant is suitable for bearings. For this purpose, solid film coatings made of lead oxide are applied to special Materials, for example also applied to steel. A warehouse constructed in this way is only useful, however, as long as the thin film of lead oxide is present on the steel running surfaces of the bearing. Because the coating must be very thin, it rubs off for a fairly short time, so that the life of a such camp is short. This is disadvantageous for many purposes.

Lubricants and lubricants for bearings need to be used depending on the intended use and the Ambient conditions different requirements are made. For example, the In addition to the lowest possible coefficient of friction, in many cases a certain sliding surface of a bearing Have embedding capacity for dirt. Regardless of whether the lubricant is supplied from the outside Whether or not they are used in the warehouse, corrosion and oxidation must not occur. the Wear or abrasion should be low, especially if the bearing has been running for a long time should be operated. If the warehouse is only used once for a short time, for example in a Missile, then the abrasion speed is of secondary importance. Also the ambient temperature and the mode of operation of the warehouse, for example continuous operation or short-term operation, have to do with Requirements placed on a bearing lubricant influence. It is also required that a bearing be insensitive is against temperature fluctuations, has good thermal conductivity and that the thermal Extension of its running surface is adapted to that of the adjacent parts. More general Aspects are a low storage weight and volume as well as easy workability of the Storage areas.

The object of the invention is to create a lubricant which guarantees a long service life for the bearing and which satisfies a wide variety of requirements with regard to its lubricity (\ ^{ability. <;}

This object is achieved according to the invention through the use of a material consisting of lead oxide as the main ingredient and from at least one other oxide, with which one on the surface a bearing formed porous carrier layer is impregnated, the free energy of oxide formation is more positive than that of lead oxide, as a lubricant for bearings.

The lead oxide is one or more oxides for the formation of the material used as a lubricant of the elements silicon, aluminum, bismuth, vanadium, arsenic, molybdenum, tungsten, antimony, titanium, Tin, copper, boron, iron and chromium mixed in. This results in a large group of Bearing lubricants that meet a wide variety of requirements. By the choice and amount of the dem Lead oxide admixed oxide or the admixed oxides can be made according to the requirements work out some lubricant properties and suppress others.

The porous carrier layer impregnated with the oxide mixture is preferably made of copper or silver. % In order to ensure a long service life for the bearing, a relatively large amount of the Oxide mixture introduced into the carrier layer, so that on the running surfaces of the bearing always a fairly there is a large amount of lubricant.

One difficulty in introducing the oxide mixture containing lead oxide as the main constituent into the very small pores of the carrier layer is that the lead oxide can be reduced to lead. In order to impregnate the carrier layer with the oxide mixture, the impregnating agent must wet the material of the carrier layer to a certain extent. If the carrier layer consists of copper, the oxide mixture must be composed in such a way that it wets the surface of the copper at the soaking temperatures and flows into the small pores and spaces in the carrier layer. The impregnation temperature and other conditions are to be chosen so that the lead oxide is not reduced to lead to any significant extent. For this, the oxide mixture must have a certain liquid solubility in copper. Molten lead oxide wets copper very well at or above a temperature of 888 ^{° C. and}

therefore easily penetrates a porous copper mass at this temperature. However, lead oxide has one fairly high coefficient of friction, so that it is compared to other substances as a lubricant for Warehouse only has limited use. To reduce the coefficient of friction and in numerous Cases to decrease the viscosity at higher temperatures are the other mentioned Oxides added to lead oxide. In order to improve the lubricant property considerably, in in all cases the other oxides are added to the lead oxide in such an amount that the mixture has a lower melting temperature than lead oxide. '· ·

Often the oxide material added to the lead oxide has a higher melting temperature than lead oxide. the Mixtures that can be used as lubricants or lubricants, however, always have a lower one Melting temperature than the individual oxides. Almost all oxides added to lead oxide form with it one or more eutectics. The proportions used, however, are not limited to those used to form a eutectic required amount limited. Many mixtures can be referred to as ceramics. Other form glasses, some of which have a finely divided, glassy phase and others a devitrified phase be able.

For the lubricant according to the invention you do not need a support body, for example steel, aluminum, Plastic or the like, however, if such is used, a carrier layer is on the support body made of copper or silver. Stand to form a carrier layer with or without a support body methods known per se are available. U.S. Patent 2,902,748 is an example of a Method for applying a carrier layer made of sintered copper on a strip Material, for example steel, described. There is an essential property of the carrier layer in that its surface material must have an oxide free energy which is more positive than that of lead oxide, so that the carrier layer does not reduce the lead oxide when it is in the form of the oxide mixture is introduced into the carrier layer. Copper and silver meet this requirement. But it can other materials can also be used as a backing if certain precautionary measures are followed. So For example, sintered iron or aluminum particles can form the carrier layer if the powdered iron or aluminum particles with a material, e.g. B. copper or silver plated so that the carrier layer in contact with the impregnating agent has a free energy to form oxide which is more positive than that of lead oxide.

After the carrier layer is formed in a manner known per se, the oxide mixture is in the Introduced spaces and pores. The oxide added to the lead oxide must always be selected in such a way that that the mixture has a lower melting point than lead oxide even if the melting point of the additional oxide is above the lead oxide melting point.

The oxide mixture can be introduced into the carrier layer by a hot casting process or in Powder form is applied and then heated until it melts and enters the pores of the carrier layer flows into it.

For a better understanding of the invention, refer to

the figure noted showing the relationship between the test duration and the storage temperature of a copper-lead bearing and Fig. 11 shows a bearing in which the lubricant of the invention is used.

Table I also contains the data for a large number of mixtures according to the invention. At the top of Table I are reference data for lead oxide for comparison purposes.

For all oxide additives, the amount added to the lead oxide, the eutectic points, the melting temperature of the mixture at the eutectic points, the melting conditions and the coefficient of friction of the various mixtures are given. '

Table I Pb O masters

Additive Area
0 / Eutectic
0 / Enamel
temperature Molten state Coefficient of friction (lowest) / 0 / 0 ° C (middle) PbO 888 viscous 0.60 SiO ₂ 1 to 28 8th 733 fluid 0.27 0.23 15th 733 viscous 0.27 28 733 very viscous - 0.45 Al ₂ O ₃ 1 to 4 4th 865 very viscous 0.68 - Bi ₂ O ₃ 1 to 49 28 580 fluid 0.38 0.22 PbO - CrO ₃ 1 to 25 8th 785 viscous 0.31 0.28 V ₂ O ₅ 1 to 49 13th 759 fluid 0.38 - 45 482 viscous 0.93 - As ₂ O ₅ 1 to 49 5 804 fluid 0.96 - 17th 815 fluid - 0.14 33 787 fluid 0.24 0.45 PbO-MoO ₃ 1 to 33 18th 787 fluid 0.73 0.16 PbO - WO ₃ 1 to 45 29 725 fluid 0.22

continuation

Additive Area
O/ Eutectic
O/ Enamel
temperature 496 Molten state Coefficient of friction (lowest) /O Yo ■ -C 815 (middle) 0.17 Sb ₂ O ₃ 1 to 49 (incomplete ändiges 855 fluid 0.23 Phase diagram) 815 0.31 B ₂ O ₃ 1 to 49 12th 844 fluid 0.44 - TiO ₂ 1 to 3 3 815 fluid 0.70 • - SnO ₂ 1 to 2 1.5 682 very viscous - - P ₂ O ₅ 1 to 7.5 5 fluid 0.39 - 9 - - - 25 to 49 25th fluid 0.50 0.18 Cu ₂ O 1 to 30 18th very viscous 0.31

Table I (continued) Pb O masters

composition SiO ₂ Enamel Melted Coefficient of friction (lowest) PbO AI ₂ O ₃ % temperature
⁰ C Status 0.22 % % 28 (middle) 71 1 16 721 fluid 0.33 83 1 13th 705 fluid 85 2 9 705 fluid 40 1 4th 692 fluid 91 5 6th 771 fluid 93 1 692 /fluid

PbO B ₂ O ₃ SiO ₂ 482
532 fluid
fluid 0.30
0.33 0.19 85
93 11
5 4th
2

PbO V ₂ O ₅ TiO ₂ 872 fluid 0.32 0.17 -1
89.5 -10
7.3 1-5
3.2
(no eutectic)

PbO SiO ₂ P ₂ O ₅ 755 viscous 0.38 0.36 ι
85 -30
12.5 1-30
2.5
(no eutectic)

PbO SiO ₂ Fe ₃ O ₄ thin 0.34 0.27 85 10 5
(no phases
diagram available)

In order to obtain reproducible test results, the samples that provide the information according to Table I, made from sintered copper without a

Support element made of steel or the like. Is used. The copper powder from which the mold is made, is a homogeneous mixture with a wide

Particle size range that is cold-solidified at a pressure of 840 kg / cm ² and sintered in hydrogen at a temperature of 1000 ^{° C.} The resulting shape has about 30% voids per unit of space.

ι The impregnating agent is used in the desired proportions

mixed and heated to its melting temperature, whereupon the porous copper mold into the molten one Oxide mixture is immersed until the pores of the mold are filled. All samples will be Quenched with water immediately after leaving the weld pool.

The friction tests are carried out at room temperature and at a sustained level of 40% Humidity run without lubricant, apart from the lubricant that is from the Sliding surface material itself is supplied. A test device according to Falex is equipped with a test mandrel made of steel with a low carbon content, rotating at 192 revolutions / min, and with weights between 31.5 and 256 kg is loaded. During the, · testing process, the weight is on for 5 minutes FY held a predetermined height and then enlarged.

Although some mixtures based on lead oxide (PbO) have a coefficient of friction, which is probably too high to be usually used for the sliding surface of a bearing can, they have compensating properties and can also be used as friction materials be used in clutch plates and the like. All materials have the advantage of being out of the curve the figure can be seen.

If the temperature of a typical copper-lead bearing rises above a critical point, the bearing will fail (solid line). A warehouse with ^; a carrier layer according to the invention can initially exhibit a higher temperature due to friction than the copper-lead bearing; shortly after its temperature reaches a given point, it drops and is held roughly constant over time. This shows a very important property of the group of storage materials according to the invention.

Because of this property, the material can under certain conditions as a result of the formation of a Glaze or an oxidic surface coating on the attacking rotating shaft without lubrication to run. As long as this surface film remains intact and is not destroyed by pressing etc., the coefficient of friction is lower than when the shaft is running on a non-glazed surface would. Hence, one can expect that the interacting material will not have a great effect on the Exerts friction with this bearing material. In fact, some tests have shown that this glaze-forming Property of the copper permeated with oxides even a perfect rubbing on one revolving body made of stainless steel. In this case, the coefficient of friction is as low as the one observed on a low carbon steel shaft. This observation is extremely significant in view of the fact that most metals are unusable when they should slide unlubricated on stainless steel; the components usually eat or weld together considerably stuck together.

As can be seen, the group of mixtures based on lead oxide has a higher one Temperature stability than copper-lead materials.

Another advantage that results from tests on a copper mold in which a mixture is based penetrated the base of lead oxide and other oxides is that the sliding surface material can run unlubricated in an unreactive atmosphere and in air. While running argon has a lower coefficient of friction than running in air. Lots of fabrics seem better in Air than running in an unreactive atmosphere, which may indicate the formation of an oxide film during operation. An oxidation of the copper seems, however, to reduce its coefficient of friction to enlarge.

If the coefficient of friction is also an important factor, one chooses for a given one Occasionally use a material with a higher coefficient of friction when that other is desirable Has properties. In many cases, the sliding surface material should be resistant to corrosion. When also only a limited number of tests in a standardized bath to evaluate the corrosion have been carried out from xylene, lauric acid and nitrobenzene, it turns out that the tested Oxide mixtures stand out in comparison to the reference material made of copper and lead.

Table II

Results of the corrosion evaluation

material Weight
modification
g / h [square inch] 40
Cu-Pb -0.120
-0.005
-0.005 Cu - (PbO - 10% SiO ₂ - 5% A1 ₂ O ₃ )
Cu - (PbO - 12% B ₂ O ₃ )

Mechanically, lead oxide-based materials seem to have an advantage over a copper form that is impregnated with lead. For example, sintered copper soaked in lead with 30% has a tensile strength of 910 kg / cm ² and a compressive strength of 2870 kg / cm ² . The same sintered copper form, into which a mixture of 85% PbO, 10% SiO ₂ and 5% Al ₂ O _{3 has} penetrated, has a tensile strength of 1190 kg / cm ² and a compressive strength of 6020 kg / cm ² . The greatly increased compressive strength is a great advantage in bearings that are supposed to run quickly under heavy loads. An impregnating agent made of 85% PbO, 10% SiO ₂ and 5% Al ₂ O ₃ in an unsintered copper form brings the same tensile strength and a somewhat increased compressive strength compared to the sintered copper, into which lead has penetrated; so it turns out that it does not matter to use a sintered mold.

1 sheet of drawings

109 584/365

Claims (2)

Patent claims: 1. Use of a material with which a formed on the surface of a bearing porous support layer made of copper or silver or another layer coated with copper or silver Fabric is impregnated, consisting of 1. Lead oxide as the main ingredient and 2. one or more oxides of the elements silicon, phosphorus, aluminum, bismuth, Vanadium, arsenic, molybdenum, tungsten, antimony, titanium, tin, copper, boron, and iron chrome as a lubricant for bearings. 2. Use of a material according to claim 1, consisting of 20th 1. Lead oxide as the main ingredient and 2. a) I to 28% SiO ₂ or b) 1 to 49% Bi ₂ O ₃ , V ₂ O ₅ , As ₂ O ₅ , Sb ₂ O ₃ or B ₂ O ₃ or c) 1 to 4% Al ₂ O ₃
or d) 1 to 25% CrO ₃ or e) 1 to 33% MoO ₃
or f) 1 to 45% WO ₃ or g) 1 to 3% TiO ₂
or h) 1 to 2% SnO ₂ or
i) 1 to 30% Cu ₂ O or
k) 1 to 7.5 or 25 to 49% P ₂ O ₅ as a lubricant for bearings.