|Title of Invention||
A PLAIN BEARING AND A METHOD OF PRODUCING THE SAME
|Abstract||The present invention relates to a plain bearing for the spigots of rolling mill rolls with a bearing bush (1) of metal and slide bearing alloy (2), on a tin basis with antimony and copper, disposed therein, characterised in that the slide bearing alloy (2) consists of6.8 to 7.2 weight percent of antimony, 6.3 to 6.7 weight percent of copper, 0.5 to 0.7 weight percent of zinc, 0.05 to 0.15 weight percent of silver and the rest tin. The invention also relates to a method of producing the bearings.|
|Full Text||The invention relates to a plain bearing for the spigots of the rolls of rolling mills and a method of producing the same. The bearings comprise a bearing bushing of metal and a plain bearing alloy introduced into it and based on tin with antimony and copper.
Such bearings have been produced for many years, for example, as oil film bearings. The employed plain bearing alloy, however, is relatively soft so that it flows easily when under load. This flowing results in a loss of shape stability and requires a relatively quick exchange of the bearings for new or reworked bearings. Moreover, the resistance to pressure of the plain bearing alloy is relatively small.
It is also known to add cadmium to the known plain bearing alloys by which measure it was possible to increase the resistance to pressure. Cadmium-containing alloys, however, are no longer used as a result of their toxicity despite their advantages with respect to the resistance to pressure. Therefore, the known plain bearing alloys have been used again.
From EP 0 717 121 Bl plain bearing alloys are known which, by addition of silver and zinc, have the advantage of a higher compression limit and an improved repeated impact flexural load.
These new alloys are used primarily in turbines, compressors, pistons and expansion engines. The advantage is that no toxic components are added to the plain bearing metal. The use of these alloys for necks of rolls, however, has not been easily possible in the past because the alloy components according to this prior art fluctuated widely so that the required minimal flow properties and the great resistance to pressure could not be realized in the desired way.
It is an object of the invention to improve a known plain bearing as well as a method for producing the plain bearing such that an excellent shape stability is provided as a result of minimal flow tendency and a high resistance to pressure so that, as a result, the bearings experience a long service life.
For this purpose, features of the present invention are proposed. It was found that the use of such a plain bearing alloy significantly increases the shape stability and the resistance to pressure.
It is however advantageous when in the production of the plain bearings the plain bearing alloy is applied onto the inner mantle of the pre-heated bearing bushing in the form of a rough layer thickness of 4 to 7 mm by centrifugal casting. In the past, rough layer thickness of 8 to 12 mm have been required in order to obtain a finished layer thickness of 1.25 mm. By reducing the rough layer thickness, on the one hand, a significantly reduced amount of alloy material must be employed so that a more cost-efficient manufacture of the bearing is possible; on the other hand, a significantly reduced amount of alloy material must be cooled. Accordingly, faster cooling periods and thus optimized microstructure transformations can be achieved which have a positive effect on the shape stability and the resistance to pressure of the bearing material.
Moreover, during machining of the plain bearing by a cutting machining process, less material must be removed from the rough layer thickness in order to reach the final thickness so that the working step is shortened. Fewer cuttings which must be disposed off are produced, and the machining device becomes shorter and thus less loaded.
The reduced flow tendency and the higher resistance to pressure have the effect that the bearing in operation will not wear as easily and quickly so that a longer service life can be achieved. The bearings have to be reworked less frequently, respectively, must be replaced less frequently with new bearings. Also, in the reworking process the inventive alloy can again be used so that the advantages of the reduced flow tendency and higher resistance to pressure also apply to reworked bearings.
The invention will be explained with the aid of a drawing. In this connection, the Figure shows a bearing bushing 1 into which the plain bearing alloy 2 comprised of 7 percent by weight antimony, 6.5 percent by weight copper, 0.6 percent by weight zinc, 0.1 percent by weight silver, and tin as the remainder is introduced and which has been turned from the rough layer thickness of 4 to 7 mm to a finished layer thickness of 0.5 to 1.2 mm.
1. A plain bearing for the spigots of rolling mill rolls with a bearing bush (1) of metal
and slide bearing alloy (2), on a tin basis with antimony and copper, disposed therein,
characterised in that the slide bearing alloy (2) consists of 6.8 to 7.2 weight percent of
antimony, 6.3 to 6.7 weight percent of copper, 0.5 to 0.7 weight percent of zinc, 0.05
to 0.15 weight percent of silver and the rest tin.
2. The plain bearing according to claim 1, wherein the slide bearing alloy (2) consists
of 7 weight percent of antimony, 6.5 weight percent of copper, 0.6 weight percent of
zinc, 0.1 weight percent of silver and the rest tin.
3. The plain bearing according to claim 1 or 2, wherein the finished layer thickness of
the slide bearing alloy (2) amounts to between 0.5 and 1.2 mm.
4. A method of producing slide bearings for the spigots of rolling mill rolls according to any one of claims 1 to 3, wherein the slide bearing alloy (2) is applied in a raw layer thickness of 4 to 7 mm by centrifugal casting on the inner circumference of the preheated bearing bush.
5. The method according to claim 4, wherein the cooling of the bearing bush (1) takes place at at least 0.5° C/sec after the centrifugal casting has been carried out.
|Indian Patent Application Number||IN/PCT/2001/1089/CHE|
|PG Journal Number||13/2008|
|Date of Filing||01-Aug-2001|
|Name of Patentee||SMS SCHLOEMANN-SIEMAG AKTIENGESELLSCHAFT|
|Applicant Address||Eduard-Schloemann-Strasse 4, 40237 Dusseldorf,|
|PCT International Classification Number||C22C 13/02|
|PCT International Application Number||PCT/EP00/00488|
|PCT International Filing date||2000-01-22|