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Welding of copper alloys
The document discusses the welding characteristics and processes of various copper alloys, highlighting their excellent conductivity, corrosion resistance, and challenges such as hot cracking and porosity. It details specific welding techniques, filler materials, and preheating requirements for different copper and copper-zinc alloys, as well as the influence of alloying elements on weldability. Various welding methods, including gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW), are described along with best practices for achieving optimal weld quality.
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Welding of copper alloys
- 1. Welding of CopperAlloys JABIN MATHEW BENJAMIN 13MY04
- 2. Copper And CopperAlloys • Excellent electrical and thermal conductivities • Outstanding resistance to corrosion • Ease of fabrication • Good strength and fatigue resistance 2 Dept. of Metallurgical Enng 10/16/2014
- 3. Copper Alloys •COPPERS, WHICH CONTAIN A MINIMUM OF 99.3% CU • HIGH-COPPER ALLOYS, WHICH CONTAIN UP TO 5% ALLOYING ELEMENTS • COPPER-ZINC ALLOYS (BRASSES), WHICH CONTAIN UP TO 40% ZN • COPPER-TIN ALLOYS (PHOSPHOR BRONZES), WHICH CONTAIN UP TO 10% SN AND 0.2% P • COPPER-ALUMINUM ALLOYS (ALUMINUM BRONZES), WHICH CONTAIN UP TO 10% AL • COPPER-SILICON ALLOYS (SILICON BRONZES), WHICH CONTAIN UP TO 3% SI • COPPER-NICKEL ALLOYS, WHICH CONTAIN UP TO 30% NI • COPPER-ZINC-NICKEL ALLOYS (NICKEL SILVERS), WHICH CONTAIN UP TO 27% ZN AND 18% NI 3 Dept. of Metallurgical Enng 10/16/2014
- 4. Alloying Elements andweldability • Zinc • reduces the weldability of all brasses • Tin • increases the hot-crack susceptibility • Beryllium, aluminum, and nickel • Oxide entrapment, which may reduce the strength of the weldment. • Formation of these oxides prevented by shielding gas or by fluxing • Silicon • beneficial because of its deoxidizing and fluxing actions. • Low thermal conductivity makes silicon bronzes the most weldable of the 4 copper Dept. of Metallurgical Enng alloys for any arc process. 10/16/2014
- 5. • Phosphorus •does not adversely affect or hinder welding • Chromium • inert protective atmosphere to prevent formation of chromium oxides. • Cadmium • no serious effect on the weldability of copper • Oxygen • cause porosity and reduce the strength of welds • Deoxidizing elements--usually phosphorus, silicon, aluminum, iron, or manganese. 5 Dept. of Metallurgical Enng 10/16/2014
- 6. Factors Affecting Weldability Effect of Thermal Conductivity. Cu has high thermal conductivities the type of current and shielding gas must be selected to provide maximum heat input to the joint preheating may be decided based on thickness Counteracts the rapid head dissipation Cold worked Cu alloys tend to become weaker and softer at HAZ hot cracking may occur in heavily cold worked Welding Position highly fluid nature flat position is used whenever possible Vertical, overhead and the horizontal position- seldom used 6 Dept. of Metallurgical Enng 10/16/2014
- 7. Precipitation-Hardenable Alloys Beryllium, chromium, boron, nickel, silicon, and zirconium. Care must be taken to avoid oxidation and incomplete fusion. Reduction in mechanical properties due to overageing Should be welded in the annealed condition, followed by precipitation hardening treatment Hot Cracking copper-tin and copper-nickel, are susceptible to hot cracking wide liquidus-to-solidus temperature range Severe shrinkage stresses produce interdendritic separation during metal solidification 7 Dept. of Metallurgical Enng 10/16/2014
- 8. Porosity zinc, cadmium, and phosphorus have low boiling points. Vaporization of these elements during welding may result in porosity. Higher travel speed and filler metals with less volatile element content Surface Condition Oxides formed are difficult to remove Cleaning and shielding helps to avoid oxide formation 8 Dept. of Metallurgical Enng 10/16/2014
- 9. Welding of Cu Difficulties: High oxygen content and impurities Electrode: Ecu and filler: ERCu Preheating : thickness, conductivity 9 Dept. of Metallurgical Enng 10/16/2014
- 10. Preheating 10 Dept.of Metallurgical Enng 10/16/2014
- 11. Effect of shieldinggas 11 Dept. of Metallurgical Enng 10/16/2014
- 12. GTAW Upto 3.2mm thickness but more for flat position Shielding: upto 1.6mm Ar and over 1.6mm He, deeper penetration Pulsed current can be used GMAW Shielding: Ar or mixture of Ar and He Filler: ERCu Spray transfer and pulsed current SMAW ECuSi, ECuSn-A DCEP Flat position 12 Dept. of Metallurgical Enng 10/16/2014
- 13. Welding of Copper-ZincAlloys (Brass) • C20500, C49080, C83300 • Evolution of zinc fumes is a problem • Low-zinc brasses are shown to have good weldability using GTAW • High-zinc brasses, tin brasses, special brasses, and nickel silvers have only fair weldability • Preheating is not normally required • Leaded brasses are unweldable 13 Dept. of Metallurgical Enng 10/16/2014
- 14. • Shielding: He-foralloys having higher thermal conductivities. • Filler should not contain zinc • Low zinc- ERCuSn-A GMAW 14 • Unleaded brasses can be welded using GMAW.- low-zinc alloys (red brasses) and the high zinc alloys • Filler should not contain copper-zinc- Silicon bronze (ERCuSi-A)- good fluidity • DCEP • Preheat: 95 to 315 °C- low zinc alloys • High zinc alloys- more porosities • Filler ERCuAl-A2 strength or ERCuSn-A colour match Dept. of Metallurgical Enng 10/16/2014
- 15. • SMAW •Covered electrodes- ECuSi, ECuSn-A, ECuSn-C, ECuAl-A2, ECuAl-B • Low zinc- ECu-Sn-A and ECuSn-C • Preheating of the base metal from 200 to 260 °C • High zinc copper alloys can be welded with aluminum bronze (ECuAl-A2) electrodes • Preheat and interpass temperatures are 260 to 370 °C 15 Dept. of Metallurgical Enng 10/16/2014
- 16. Welding of Copper-Tinalloys (Phosphor Bronzes) • C50100-C52400 • GTAW • Up to approximately 13 mm • DCEN or a stabilized alternating current • Shot peening each layer of multi-pass welds reduces cracking and stresses • Shielding- Argon- restricts the size of the HAZ. • Thicker sections, helium shielding gas • Filler metal- ERCuSn-A • Preheating: not required for thin sections, Thick sections require preheating to 175 or 200 °C • Interpass temperature should not exceed 200 °C 16 Dept. of Metallurgical Enng 10/16/2014
- 17. • GMAW •Thicknesses of 9.5 to 13 mm. • 90° single-V grooves are used • Filler Metal- ERCuSn-A 17 • Preheating of the phosphor bronzes helps in obtaining complete fusion, less porosity, but columnar grains and hot cracking • SMAW • Covered electrodes: ECuSn-A and ECu-Sn-C • Preheating is required in the range of 150 to 200 °C • Maximum ductility, the welded assembly should be postweld heat treated to 480 °C (900 °F) and Dept. of Metallcurogicoalle Endn grapidly. 10/16/2014
- 18. Welding of Copper-NickelAlloys (C70000-C79900) • GTAW • Preferred for copper-nickel alloys with section thicknesses up to 1.6 mm • Electrode- EWTH-2 • Ar shielding gas- provides better arc control and stability, • DCEN, Alternating current can be employed for automatic welding • Preheating is not necessary and backing strips or rings can be used 18 • Filler Metals: Deoxidized- ERCuNi- minimize porosity and the possibility of oxygen embrittlement • Autogenous welds can sometimes be made on sheet thicknesses up to 1.6 mm Dept. of Metallurgical Enng 10/16/2014
- 19. • GMAW 19 • Preferred welding process for non-leaded copper-nickel alloys thicker than approximately1.6 mm (0.06 in.). • Preferred welding position: Flat position • Preferred shielding gas: Ar • Argon-helium mixes give better penetration on thick sections. • Direct current electrode positive is recommended. • Spray or short-circuiting transfer • Filler Metals. ERCuNi- 0.15 to 1.00% Ti, which serves as a deoxidizer • No preheating or postheating • Interpass temperatures should be maintained below 65 °C Dept. of Metallurgical Enng 10/16/2014
- 20. • SMAW •Both wrought and cast forms • Copper-nickel electrode- ECuNi • DCEP • Special care is needed to ensure complete slag removal • Vertical and overhead positions 20 Dept. of Metallurgical Enng 10/16/2014
- 21. Other processes forwelding of Cu Laser beam welding Difficulties: high reflection of laser beam and high thermal conductivity Absorption increases with temperature Shorter wavelength has better welding Electron beam welding Thin and thick sections Resistance spot welding Lower conductivity alloys readily spot welded Not practical for unalloyed Cu 21 Dept. of Metallurgical Enng 10/16/2014
- 22. Flash welding Leaded Cu (upto 1% Pb) can be flash welded Rapid upsetting at minimum pressure Low melting point and narrow plastic range Premature termination of current: lack of fusion Delayed termination: over heating Solid state welding Annealed Cu can be welded at room temperature: good malleability Diffusion welded or explosive welding 22 Dept. of Metallurgical Enng 10/16/2014
- 23. Reference Weldingof copper and copper alloys, AWS welding handbook, Volume 3, Ed. 8, 1997 ASM metal handbook, volume 6, 1993 23 Dept. of Metallurgical Enng 10/16/2014
- 24. THANK YOU 24 Dept. of Metallurgical Enng 10/16/2014