Tungsten, Silver and Copper Alloys, UK

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Material:	Elkaloy 05 and 00

Type of Product:	Phosphorus containing brazing alloys.

Applications:	The outstanding feature of these alloys is their ability to braze copper in air without the use of a flux. When a flux is used the alloys are suitable for brazing all copper-base alloys except those containing iron and nickel.

	Nickel, nickel-base alloys, ferrous metals and copper alloys containing nickel and iron should not be brazed with these phosphorus-bearing alloys. Although the brazing alloys will wet and flow on such materials, the brazed joints obtained are inherently brittle due to the formation of intermetallic compounds.

Elkaloy 05	With a 6% phosphorus content, Elkaloy 05 provides the best combination of flow and ductility for pipe joints. It is free flowing alloy that will produce joints that can be moderately deformed without suffering cracking. It is used in joining electrical assemblies and in plumbing and air conditioning applications.

Elkaloy 00	This is the standard copper-phosphorus alloy used where ductility is not a critical consideration. Its high phosphorus content makes it free flowing and since it contains no silver it is economical to use. This combination of properties gives the alloy a wide use in refrigeration, air conditioning and heat exchanger applications as well as general fabrication of copper items.

Nominal Composition:	Ag Cu P Melting Range o C

Alloy
Elkaloy 05	5 89 6 644-815
Elkaloy 00	- 93 8 714-810

	The upper melting point is the true liquidus of the alloy. Brazing is usually carried out at temperatures significantly below those shown.

Workshop Practice:	The best results are obtained where the joint gap is controlled within the range 0.05 - 0.125mm. Joint gaps less than 0.05mm will not allow full capillary flow of the molten alloy and, whilst gaps up to 0.2mm can be filled adequately, gaps larger than this may create problems.

	These brazing alloys have relatively long melting ranges, and the parent metals brazed almost invariably have high values of thermal conductivity. For these reasons the work should be heated quickly to brazing temperature, and oxy-acetylene is preferable to either natural gas/compressed air or propane.

	When brazing copper to copper in air these alloys are self-fluxing but when joining copper base alloys e.g. brasses or bronzes the use of a suitable flux like Elkaflux powder is necessary. (See Data Sheet 1300 : 153)

	When tough-pitch copper is being brazed, it should be remembered that this material is subject to deterioration if heated to a high temperature in reducing conditions. Tough-pitch copper contains dissolved cuprous oxide, which may be reduced by a reducing flame or atmosphere to leave small cavities in the metal. This effect is known as hydrogen embrittlement. When brazing these materials a neutral or slightly oxidising flame is therefore recommended.

Special Considerations:	Phosphorus containing brazing alloys should not be used in cases where they will be exposed to heavily sulphurised gases at elevated temperatures. In air the maximum continuous service temperature is about 200^oC. At higher temperatures selective oxidation of the phosphorus in the alloy occurs, with consequent joint deterioration.

	The alloys are widely used in plumbing applications and since they do not contain zinc, they cannot suffer from dezincification.

	The alloys produce somewhat rough-textured braze fillets of greyish colour, and when permitted to run uncontrolled over the work will roughen the surface.

	They are not the best brazing alloys to use in cases where good appearance is desired, or where subsequent tinning, soft soldering or electroplating operations are necessary. Where good appearance is a prime requirement, then consideration should be given to the use of silver brazing alloys Elkaloy 55, 42, 38 or 30. (See Data Sheets 1300 : 150 and 1300 : 151).

Forms of Supply:	The main forms of supply are 2.0mm and 2.5mm dia. rod but wire and rings are also available.

All Mallory Alloys Group products conform to, if not exceed, the relevant standards as assured by the Quality Management System

Quality Management System - ISO 9002, EN 29002, BS5750-2