Alloy and properties

• The Alloy
• Mechanical and physical properties
• Economic efficiency
• Standardisation

Why is Carobronze^®(CuSn8 P) that plain bearing material since many years

• cost saving by reduced wear, low material costs and longer life
• high operational safety by approved product quality, profound advice and excellent material properties
• high service level by an extensive range of stock dimensions (special dimensions are produced on customers' request)

The alloy

CAROBRONZE^® has the following composition: approx. 8 % Sn, 0.3 % P, balance copper (reference analysis). Our internal tolerances for the alloy composition are considerably narrower than specified in the international standards. This guarantees a high-purity alloy which permits us to achieve improved antifriction properties and reduced variations of mechanical properties compared with traditional CuSn alloys. A further advantage is the high phosphorus content which on the one hand helps to suppress wearing processes and on the other improves the lubrication film adhesion on the surface and - as can be proven - favours the emergency running property.

Mechanical and physical properties

By means of cold working and heat treatment CAROBRONZE^® can be produced with a wide range of mechanical properties. The spectrum of tempers ranges from soft (R380) to spring hard (R620).For most applications the stock temper R450 or R460 is used. On request, the material can also be supplied with specified Brinell hardness (e. g. H125 to DIN EN 12163).

The achievable degree of hardness is influenced by diameter and wall thickness. For a wall thickness of up to 11 mm and the temper R460 or R550 tube outside diameters of 120 or 110 mm respectively can be supplied. The temper R460 combines good values for proof stress and tensile strength with high values of elongation. If particular requirements are made on impact and shock load we recommend the tempers R550 and R620.

Economic efficiency

Material consumption
The use of Carobronze^® permits thin-walled, slim and compact dimensions. Therefore, in cost comparisons the corresponding application and the design possibilities using Carobronze^® should always be taken into consideration, a bearing bush of Carobronze^® having a material content up to five times less than a bush of RG7 (red bronze). Therefore, an exclusive comparison of the absolute kilogram price would lead to a wrong conclusion.

Machining allowances
For almost every final dimension (e. g. O.D. of the bush) Carobronze^® tubes are available, the dimensions of which only deviate from the final dimension of the bush by a few tenths of a millimetre.In this way, the processing expenditure and the swarf cost is minimised. For certain applications our program comprises precision tubes (see page 8) from which bushes can be pressed in H7 bores without processing of the outside diameter.

Life
Thanks to the above described properties, Carobronze^® has, based on the same conditions ofuse, a considerably longer life than other copper alloys. Trials carried out at the German Aerospace Research Institute have confirmed these properties.

Standardisation

The differentiation between CuSn8 and CuSn8P, carried out for the first time in DIN EN 12449, is based on the special antifriction properties of CAROBRONZE^®/CuSn8P in the mixed friction application.

The CAROBRONZE^® (CuSn8P) alloy also covers the CuSn8 - however, with superior antifriction properties.