EoW September 2010

technical article

r/s BadWay

Tin content in %

Figure 5 ▲ ▲ : Bendability of various phosphor bronzes as a function of strength

composites is described. The combination of a newly developed, low-alloy phosphor bronze with a tin coating is a worth- while alternative to tin-coated copper- iron alloys, also from an ecological and economic point of view, and yields a similar properties profile. An approach to generating added value for customers by reducing the amount of material used is made feasible by the new development of a 10% phosphor bronze. This has a similar properties profile to an 8% copper-tin alloy but has superior bendability. Moreover, the new alloy facilitates resource-saving design, as it can withstand higher levels of stress. Material savings of 20% appear to be realisable. n This paper was first presented at the 58 th International Wire & Cable and Connectivity Symposium held in Charlotte, NC 8 th –11 th November 2009, and is reproduced with the generous permission of the organisers.

The difference in electrical conductivity between BB95 and an 8% tin bronze is approximately 1% IACS (International Annealed Copper Standard), ie the tin has a negligible conductivity-reducing influence when present in the alloy at this level. At SH (spring hard) temper, BB95 exhibits the same softening properties as an 8% phosphor bronze; a significant reduc- tion in hardness is first observed at about 280 °C. In addition, the relaxation of the new material (<20% at a temperature of 100°C for a test duration of 10,000h) is comparable to that of the above mentioned reference alloy (provided the stress level is identical). Given the above mentioned contact force, these results suggest that it should be possible to achieve a reduction in the thickness of the material, and therefore a reduction of about 20% in the amount of material needed, by using BB95. 3 Summary Steep increases in the prices of raw materials, and especially in the price of copper, have drastically changed the relationship between the value added and the metal value in the manufacture of semi-finished copper-alloy products. Savings in recycling and in the materials used have a greater impact, looked at in the round, than the total finishing expenditure. Using low-alloy copper materials as an example, the influence of a well-planned choice of alloys and

Ralf Hojda, Dr Michael Köhler Sundwiger Messingwerk GmbH & Co KG – Germany Website : www.sundwigermessingwerk.com James Schraml The Miller Company – USA Website : www.themillerco.com

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EuroWire – September 2010