Claims:WE CLAIM:
1. A metal composition for a bushing , the metal composition comprising:
iron powder in an amount of 84% to 93% by weight;
copper powder in an amount of 6% to 15% by weight.
2. The metal composition for the bushing as claimed in claim 1, wherein the metal composition further comprises carbon in an amount of 0.10% to 0.80% by weight
3. The metal composition for the bushing as claimed in claim 1, wherein the composition further comprises tramp elements.
4. A process for preparing the metal composition for the bushing as claimed in claim 1, wherein the process involves the steps of mixing the iron powder and the copper powder in required weight ratio for a pre-determined time, forming said mixture by subjecting the same to tonnage of press and specified air pressure, sintering formed mixture by subjecting to specified temperature and soak time and machining and oil impregnation by soaking at predetermined soaking temperature and specified soaking time.
, Description:FIELD OF THE INVENTION
[001] The invention relates to a bushing. More specifically, the invention relates to a bushing that is self-lubricating.

BACKGROUND OF THE INVENTION
[002] A bushing is a device that supports a rotating or sliding or oscillating shaft, and is designed to withstand load and minimize friction. Bushings are usually used over an extended period of time under extreme power and adverse conditions. Lubrication plays a vital role in performance and life of the bushing. Generally a groove is provided on internal surface of the bushing for internal lubrications. However, inclusion of these grooves requires machining operation, which disturbs the porous structure in adjacent area leading to inhomogeneous tribological properties. Also, addition of grooves reduces the surface contact area hence more Hertzian stress is borne by the bushing component.
[003] Bushings are available in different designs and materials. One known type of bushing is a bimetallic bushing, which is a self-lubricating bushing. However, such bushings are costly and complex to manufacture. Another type is a powder-based bushing, which is also a self-lubricating bushing. However, such bushings are costly and complex to manufacture. This type of bushes will have limited crushing strength making them unusable under high load condition.
[004] Another type is an alloy-based bushing which requires external lubrication. However, frequent lubrication is required for such bushes, making it less user friendly since there are chances of overfilling and also requires additional serviceability time, incurs extra costs and labour. Additional mechanism is required for enabling lubrication at predefined frequency by user. Such mechanism provided to enable lubrication externally often leads to contamination by foreign particles, leading to loss of function.
[005] Thus, there is a need in the art for improved bushing with improved wear resistance and mechanical properties.

SUMMARY OF THE INVENTION
[006] Accordingly, the present invention in one aspect provides a metal composition for a bushing , the metal composition comprising iron powder in an amount of 84.00% to 93.00% by weight and copper powder in an amount of about 6.00% to about 15.00% by weight.

BRIEF DESCRPTION OF DRAWING
[007] Reference will be made to embodiments of the invention, examples of which may be illustrated in accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.
FIG. 1 illustrates a bushing in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION
[008] The present invention is directed towards a metal composition for a bushin . The bushing thus formed is self-lubricating, has high wear resistance, high compressive strength, and good mechanical properties.
[009] In an embodiment, the invention relates to a metal composition for a bushing, said metal composition comprising of iron powder and copper powder.
[010] The metal composition for bushing comprises iron powder in an amount of about 84% to about 93% by weight and copper powder in an amount of about 6.00% to about 15.00% by weight.
[011] The combination of iron-copper powder metal renders porosity to the bushing which results in excellent tribological properties and also provides optimum crushing strength.
[012] The metal composition further comprises carbon in an amount of about 0.10 % to about 0.80% by weight. This carbon further aids in controlling the porosity at desired level.
[013] The metal composition may optionally comprise miscellaneous elements which are not added intentionally but present as tramp elements.
[014] In an embodiment, the bushing of the invention is self-lubricating. The bushing is soaked in specific grade of oil, such as mineral based oil for a pre-determined time. This oil is absorbed into the bush due to its porous nature. During the usage, when contact pressure is applied on bush, this pre-soaked oil oozes out of the bushing system thereby generating a lubrication condition.

[015] In another embodiment, the invention relates to the process of manufacturing said bushing composition comprising the steps of mixing of raw material, compacting the mixture formed; sintering the compacted mixture, sizing and oil impregnation. Thus, the stepwise process includes the following:
Process Important process characterstics
Mixing % Weight control for each element, mixing time, apparent density
Forming Tonnage of press, air pressure, rate of compaction
Sintering Zone wise temperature, Soaking time in each zone
Machining To control critical dimensions
Oil impregnation Oil soaking temp, Oil soaking time

[016] Advantageously, the metal composition of bushing of the present invention has high wear resistance, high compressive strength, and good mechanical properties for high wear and tear applications. The combination of iron-copper powder metal with controlled porosity yields excellent tribological properties and optimum crushing strength.

[017] While the present invention has been described with respect to certain embodiments, it will be apparent to those skilled in the art that various changes and modification may be made without departing from the scope of the invention as defined in the following claims.