WELDING OF COPPER AND COPPER ALLOYS

Prepared by: Gowrish

Copper Properties

• Face centre cubic structure• High electrical and thermal conductivity• Density three times higher than aluminum

about 8.94 mg/m3• Good machine ability and malleability

Applications

• Electrical conductors• Thermal insulation• Cosmetics• Fresh and salt water environments• Alkaline solutions environments

Classification of Copper and Copper Alloys

Welding consumables

Copper alloys To improve the properties of copper and make it suitable for

industrial applications, some alloys are added in different proportions

Major alloys added are, Aluminum Nickel Tin Silicon Iron Boron Chromium Manganese Zinc

Copper Aluminum(Aluminum Bronze)

UNS number C95200-C95900(CAST product)C60600-C64400(Wrought product)Aluminum added in the proportion of 3 to 15%Aluminum increase strength, yield strength and hardness but decrease the elongationAluminum up to 7.5% are single phase and have only alpha phaseAluminum above 7.5% to 15% exhibits dual phase alpha and beta phase ( Hard and martenstic structure)

Copper Aluminum(Aluminum Bronze) Conti’..

Precautions in welding Aluminum Bronze• Dual Phase Aluminum Bronze shall be

preheated to avoid HAZ due to Beta phase• Aluminum oxide shall be cleaned prior to

welding which is hygroscopic and creates porosity in weldment

Copper Nickel Alloys

UNS numberC70100-C72950 ( Wrought Alloys)C96200-C96900 (Cast Alloys)• Copper can completely dissolve Nickel in any

proportions• Addition of Ni from 3% to 30%• Ni increase strength and toughness• Ni retains some austentic structure at room temp• Titanium added as deoxidizer in weld consumables

Copper Nickel Alloys(Contin’..)

Precautions• Sulfur and Lead embrittlement is usual and

such impurities is restricted to 0.02% max• Preheating and post heating is not

recommended due to room temp austenitic structure

• This alloys cannot hardened by heat treatment

Copper Tin Alloys

UNS numberWrought Alloys – C40400-C49080Cast Alloys – C94700-C94900• Tin added in range of 2%-10% in addition to deoxidizer

Phosphorus(0.03%-0.04%)

• This alloy also known as Phosphorus Bronze

• Tin increase fatigue resistant, wear resistance and hardness in cold worked condition

Copper Tin Alloys(Conti’…)

Precautions • Tin melting point is about 480deg cel and upon

further melting, tin will start to boil off and cause porosity

• Copper tin alloys with addition of Lead as a deoxidizer shall not welded due to radioactive emission

• Cast form Copper Tin alloys have dendrites formation issue

Copper Zinc Alloys

UNS numberWrought Alloys – C20500-C49080,C66400- C69950Cast Alloys – C83300-C86800• Zinc added in the range of 20% -36 % are single phase • Zinc above 36% are dual phase and exhibit hardest micro

structure• Dual phase can be hardened by heat treatment (Q&T)• Zinc addition increase strength, coefficient of thermal expansion• Mainly used for fresh water transport system and decorative

purpose• Preheat and post weld is recommended for dual phase copper

zinc alloys

Some other alloying elements in Copper

Manganese• Added in range of 0.05%-3.0%• Improves the hot working characteristicsIron• Maximum solubility of iron in copper is 0.1%• Iron increase solid solution strength and

precipitation hardening

Some other alloying elements in Copper (contin’…)

Silicon• Solubility of silicon in copper is 3% max at room

temp• Silicon acts as a deoxidizer and improve

malleability and ductilityChromium• Copper can dissolve max of 0.55% Cr at room

temp• Cr increase electrical conductivity

Issue of welding Copper with other materials

• Copper to Stainless steel welding Copper can’t dissolve Chromium and welding

this dissimilar combination, Stainless steel shall be buttered with 99%Ni alloy and welded by Copper alloy consumable

FILLER METAL SELECTION FOR DISSIMILAR WELDING

Suggested Shielding gas selection

Joint Design

References

• Copper Development Association (CDA)• BOC world of welding• TWI Global Knowledge