Anti-Bacterial & Anti-Microbial Uses for Copper & Copper Alloys
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EN Standards for Copper & Copper Alloys
Fabrication of Copper & Copper Alloys
Material Safety for Copper & Copper Alloys
RoHS Copper & Copper Alloys
General Information for Phosphor & Leaded Bronze
Phosphor Bronzes Overview
Phosphor bronzes and tin bronzes are an alloy group with the primary content of copper, tin and phosphorous.
Usually, this balance is divided into 0.5 to 11% tin, and 0.01 to 0.35% phosphorous.
The tin element increases both the corrosion resistance and material strength of the alloy, while the phosphorous influence increases wear resistance and rigidity.
Phosphor bronze has excellent spring qualities, high resistance to fatigue, high corrosion resistance, and are superb to solder and form.
Primarily used in electricals, other uses can extend to spring washers and corrosion resistant bellows, bolts, bearings, dental bridges, ships propellers, and the reed components of organs and pipes.
The leaded phosphor bronzes combine this strength with high wear resistance, good thermal properties, substantial load-bearing capacity and better machinability, and are used for sleeve bearings, nuts, screws, electrical plugs and wiring, and doorknobs.
A phosphor bronze composition of 94.8% copper, 5% tin and 0.2% phosphorous is also used for cryogenic applications. Its combination of low thermal conductivity and electrical conductivity enables it to make electrical connections to devices at extremely low temperatures without adding heat.
Phosphor Bronze Product Forms
Phosphor Bronze Sheet and Plate
Phosphor bronze sheets and plates are available in a range of thicknesses and are an ideal choice for welding projects.
Use is most common where wear resistance, high fatigue resistance, and superb forming characteristics are required such as electrical environments.
Phosphor Bronze Continuous Cast Bar
Cast bar is mostly used in electrical applications, but when continuously cast it can also be applied to decorative railings, furniture, springs, fasteners, and welding rods.
Centrifugally Cast Rings
This process creates a densely structured alloy, free from blowholes and inclusions.
Superb mechanical properties make centrifugally cast rings an ideal production process for spigot bearings, rings, tubes, flanges and hollow cylindrical bars.
Continuous Cast Bespoke and Hollow Sections
Continuous casting is a process whereby molten metal is placed into a mould that rapidly chills the metal to a solid state. This rapid cooling ensures a fine grain structure in the solid metal with higher performance characteristics than sand casting.
The cast shaped bar can then be cut as desired.
Phosphor Bronze grades PB1 and PB2 are both suitable materials for continuous casting.
PB1 has high mechanical strength, excellent corrosion and wear resistance and is an ideal choice for heavy loads
While PB2 contains higher tin and lower phosphor than PB1, it is suitable for heavy loading, as well as environments where high-sliding velocity and high-impact loading are essential.
Phosphor Bronze History
Throughout the history of phosphor bronze there have been dedicated programs for the research and development of its capabilities and fine-tuning of its properties.
Much of this has been driven towards electrical connectors and switches because, while they performed well, they still lacked a crucial coveted property for electrical components - springiness in high-temperature environments.
A product was therefore still needed that could tick all the essential boxes of high electrical conductivity, strength retention at required temperatures, excellent inherent material strength, and yet still be easily fabricated to strip form while maintaining low-cost output.
So, experiments in making tiny changes to the structural composition began.
Around 2001, an alloy was developed at the Olin Corporation based in Clayton, Missouri, which could remove this final hurdle. They made two significant changes that ultimately provided the answers:
- The first step was to add iron to the solution, thus needing less tin for the strength element.
- The final piece of the puzzle came in the form of zinc, also as a substitute for some of the tin, zinc is much cheaper than tin to manufacture.
Its composition consisted of:
- Zinc 9.9%
- Phosphorous – 0.03%
- Copper 85.97%
- Iron 1.9%
- Tin 2.2%
This composition created that springiness while retaining all its other ideal electrical characteristics, and also proved to be cheaper than initial phosphor bronzes.
So when we refer to ‘Phosphor Bronze’ today it is predominantly this newer version that has become the standard in electrical working.
Fascinatingly it is not strictly a phosphor bronze in the metallurgical sense, but more of an iron modification of tin brass.
