kumudmetal@yahoo.in 022-26790450 / 9823374318 S.V. Road, Near Syndicate Bank,opp.Crystal Apartment, Jogeshwari (w), Mumbai -400102
Ultra Bronze Castings, Manufacturer, Supplier, Mumbai, India

U Bronze Castings

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U Bronze Castings

U Bronze is a Zn-Al-Cu-Sn alloy, Silver in colour and has unparalleled bearing properties. U Bronze Bearings can be replaced for Phos. Bronze, Gun Metal, Leaded Bronze, Leaded Tin Bronze, etc to obtain better results at a lower cost.

It has unusual anti-friction properties that brings about a very fine running surface and low temperature, whereby pivots and shafts are protected. Frictional load dissipation of energy is reduced in the use of bushings made of U Bronze, therefore this alloy is suitable and qualifies for bushings for low and high speeds with light and/or heavy loads.

U Bronze can stand extreme conditions of shaft deflections and emergency starting and stopping conditions. It is an ideal bearing material for heavy and light load pressures with low and high surface speeds.

Another major advantage of U Bronze alloy that makes it economical is the fact that it has a specific gravity of 4.8 only as compared to 8.9 of other bronzes, which gives a considerable savings.

U Bronze has all the qualities of bearing alloy i.e.

COMPATIBILITY CONFORMABILITY THERMAL DISSIPATION
LOAD CAPACITY FATIGUE STRENGTH HARDNESS

Hence U Bronze is a technically superior and economically cheaper Anti-Friction alloy as compared to Gun metal, Phos. Bronze, Leaded Bronze, Aluminium Bronze, Other Traditional Bronzes, Brasses, White Metal and Nylon.

Advantages :

U Bronze is technically superior to the traditional bronze because of the following properties.

  • Higher Tensile Strength.
  • Double thermal conductivity.
  • Lower specific weight.
  • Easy machinability.
  • Four to Five times longer life than Phos. Bronze.

U Bronze is cheaper even at initial purchase as its specific gravity is only 4.8. Thus if a particular bush in Phos. Bronze or Gun Metal weighs 100 Kg then the identical bush in U BRONZE will weigh only 56 Kgs. Over and above the above stated fact U Bronze is economical as its working life is 4 to 5 times longer than Phos. bronze.

Microstucture : U BRONZE has a heterogeneous structure i.e. hard particles in soft matrix In this case the hard ternary eutectic Cu-Al-Zn etc is in a soft binary matrix of Zn/Al. The microstructure is similar in form to the tin bronzes.

In case of U BRONZE the question of diffusion of copper into journal does not arise as :-

  • a. It has a low content of copper.
  • b. Copper is not present in free state as it forms intermetallic compound with Zn and Al.
  • c. Easily oxidised surface of U BRONZE prevents diffusion.

It is claimed that in the event of lubrication failures, bushings of U BRONZE will not score the shaft, no welding of bearing to the shaft will occur and the shaft will not suffer any embrittlement due to copper penetration.

There is no change in the texture even when U BRONZE is re-melted several times, borings, turnings, scrap pieces can be re-melted and recast without under going any deterioration in quality.

U BRONZE is less sensitive to load fluctuations thus suggesting its suitability as a bearing material for heavy static loads and those subjected to sudden and high impact loadings as are found in the case of cranes, road rollers, tractors, earth moving machinery, etc.

Mechanical and Physical Properties.

Ultimate Tensile Strength MPa. 420-490
Yield Strength MPa. 378
Elongation % in 51mm. 2-8
Hardness BHN 90-120
Shear Strength MPa. 290-305
lmpact Strength Joules (6.35 x 6.35mm. Un notched bar) 15.2
Creep Strength MPa. (Stress to produce Creep rate of 0.01%/1000 Hrs. at 25º C) 70
Creep rate at 138 MPa. Stress (%1000 Hrs. at 20º C) 0.04
Density gms/Cm 3  at 20° C. 4.7-4.9
Solidification Shrinkage % 1.26
Solidification Temperature range ° C. 480-580
Thermal Conductivity mm/mm/° C at 20-100° C (x 10 -6 .) 136
Thermal expansion W/m/°C at 70-140°C. 25
Electrical Conductivity %IACS 30.2
Endurance Limit (Fatigue Strength) MPa. 59
Fracture Toughness MPa. m½ 22
Energy to Fracture N M -1 . 11x10 3
Stress to Fracture MPa. 149
Co-efficient of friction. 0.01-0.30

(This table indicates the maximum bearing pressure permissible at specific sliding speeds with gravity drip feed lubrication)

Sliding Speeds Bearing Pressure
Metric British Metric British
1 Metre/Sec 200 Ft/Min 400 Kgs/Cm2 5690 Lbs/Sq. In.
2 Metre/Sec 400 Ft/Min 360 Kgs/Cm 2 5120 Lbs/Sq. In.
3 Metre/Sec 600 Ft/Min 230 Kgs/Cm 2 3270 Lbs/Sq. In.
4 Metre/Sec 800 Ft/Min 140 Kgs/Cm 2 2000 Lbs/Sq. In.
5 Metre/Sec 1000 Ft/Min 40 Kgs/Cm2 570 Lbs/Sq. In.
6 Metre/Sec 1200 Ft/Min 25 Kgs/Cm2 350 Lbs/Sq. In.
7 Metre/Sec 1400 Ft/Min 14 Kgs/Cm2 200 Lbs/Sq. In.

The above table indicates that U BRONZE can be used in preference to Phosphorus Bronze, Gun Metal, Leaded Bronze and other alloys for both low and high speed applications and goes to prove its economy and efficiency in heavy and light engineering services.

Stress - Strain characteristic (CREEP).

The ASME Boiler Code defines the allowable design stress as the load required to produce a secondary creep rate of 1%. in 1,00,000 Hrs. (11.4 Years). On this basis the design stress for U BRONZE is 70 MPa and thus U BRONZE can be recommended for many stressed applications at temperatures upto 150 ºC.

U BRONZE is ideally suited as a bearing alloy as the brinell hardness fails gradually with increase in temperature. This insures longer life due to reduced wear.

Temperature Brinell Hardness
50 ºC 90 Min
100 ºC 80 Min.
140 ºC 60 Min.
200 ºC 33 Min.
  • ==>  U BRONZE has better castability, lower density, improved strength, less wear in service, with regard to Brass and Bronze alloys.
  • ==> U BRONZE has an as Cast U. T. S. of @ 425 MPa at room Temp. and drops to 380 MPa at 80 ºC and to 200 MPa at 150 ºC.
  • ==> Temp. ageing also has no effect on the U.T.S. ageing at 95 ºC for 10,000 Hrs. (425 Days) results in a decrease to 370 MPa.
  • ==> Elongation of U BRONZE shows a gradual rise with increase in Temp. and increases sharply above 100 ºC.

Applications of U BRONZE

  • Cement and Building industry
  • General Engineering Industries
  • Paper & Pulp Industries
  • Heavy Engineering Industries
  • Mining, Iron and Steel Works
  • Machine Tools
  • Presses
  • Textile Industries
  • Agricultural Machinery
  • Smelters
  • Internal Combustion Engines
  • Oil Lubricated Pumps
  • Generators
  • Rubber Industries
  • Refineries
  • Power Plants
  • Transport Industry
  • Oil Industries
  • Chemical Industries
  • Railways
  • Aeronautics