Metallurgy of Copper

Presentation describes the metallurgy of Cu, briefly Physical metallurgy of Copper.

1. Metallurgy of Copper and alloys Raghavendra Darji Senior Research Fellow, ORSP/R&D/BRNS/2018/VB00, Dept. of Mech. Engg., School of Technology, Pandit Deendayal Petroleum University

2. Flow of the presentation Copper : Introduction Copper in History Effect of Alloying elements on Thermal Conductivity Selection of Copper Alloy Extraction of Copper Copper Alloy Designation Pure Copper Cu Zn system

3. Flow of the presentation Cu Sn system Cu Pb system Cu Al System Cu Ni System Cu Cr system Cu Be system Cu Cd system Ti Cu System Cu Ag system

4. Copper: Introduction Copper word came from the Latin word “cuprum”, which means “ore of Cyprus”. That is why the symbol for copper is “ Cu ”. The transition from the stone age to the metal age brought about by the discovery of copper in its native form around 8000 B.C. Around 4000 B.C. Egyptians learn to extract copper from its ores. Chalcopyrite CuFeS 2 , Chalcocite Cu 2 S, Bornite Cu 5 FeS 4 , Covellite CuS, Cuprite Cu 2 O are some of the ores of the copper from which copper can be extracted by “Pyrometallurgy, Hydrometallurgy or Electrometallurgy”.

5. Mesopotamia: Sumerians, Babylonians and Assyrians. Egypt and Syria, Aegean Sea: Crete, Mycenae, Greece. India, China, Roman Empire, Andean Culture: Vicu, Moche, Nazca, Tiwanaku, Chimu, Inca Central America. 3/3/2020 5 [1a]

6. Copper in History[1a] 3500 BC: Copper smelting, increased the supply of metal. 2500 BC: Bronze allowed the production of weapons, tools and cast object, 1500 BC – 700 BC: Bells, gongs came in to use as a source of sound , bronze was also used for the payments in the form of coins, Along with the passage of time copper was utilized to make the navigation instruments, in printing press, as screws and nuts, for optical telescope, table utensils, in steam engine , in various electrical and electronics equipment. 3/3/2020 6

7. Properties of pure copper FCC structure, Ductile, Malleable, Corrosion resistance, Electrical conductivity, Thermal conductivity, Formability, Cast ability,

8. Comparison of thermal conductivity between various elements

9. Selection of Copper Alloys Electrical conductivity : copper has the highest conductivity of the engineering metals. Silver or other elements may be added to increase strength, softening resistance or other properties without major loss of conductivity. Thermal conductivity : this property is similar to electrical conductivity. Alloys of copper may be used for this property, where good corrosion resistance compensates for loss of conductivity with increased alloying. Color and appearance : many of the copper alloys have a distinctive color, which may change as the object weathers. For most of alloys it is easy to prepare and maintain the surface to a high standard, even in adverse corrosion conditions.

10. Metallurgy The branch of science and technology concerned with the properties of metals, their production and purification . Includes the following areas Extraction and purification of metals, Processing of the material, Alteration of the properties of the metal, Heat treatments of the metals and alloys, Alloy design, Design of welding consumables, Advanced materials design

11. Copper Ores can be divide into Low grade and High grade ores.

12. Market Consumption Product Consumption 3/3/2020 13 Fig 3: Consumption of copper, Market and product wise.[4]

13. Various groups of the 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 Special alloys, which contain alloying elements to enhance a specific property or characteristic, for example, machinability.

14. Copper alloy designation Unified Numbering System (UNS) Alloy Designations, UNS System begun in 1974, Originally only 3 numbers for an alloy, Now C plus 5 numbers, Wrought and Cast alloys are included, CDA Administers UNS Copper Alloys System.

15. Wrought Copper alloys family C100xx-C150xx Commercially Pure Cu C151xx-C199xx Age Hardenable Cu (w/ Cd, Be, Cr, Fe) C2xxxxCu-Zn alloys – Brasses C3xxxxCu-Zn-Pb alloys – Leaded brasses C4xxxxCu-Zn-Snalloys – Tin bronzes C5xxxxCu-Snand Cu-Sn-Pb Phosphor bronze alloys C6xxxxCu-Al and Cu-Si Bronzes C7xxxxCu-Ni Copper Nickel and Cu-Ni -Zn Nickel Silver

16. Cast copper alloy family C800xx-C811xx Commercially Pure Coppers C813xx-C828xx 95-99% Copper C833xx-C899xx Cu-Zn alloys containing Sn, Pb, Mn, or Si C9xxxx Other alloys, including tin bronze, aluminum bronze, copper nickel

17. Figure.:1 Solubility of the elements with respect to the atomic size.

18. Effect of Alloying elements on the resistivity of copper

19. Figure.:2: Effect of the alloying additions on the critical resolved shear stress.

20. Fig.1: Comparison of the effect of cold working and subsequent annealing on the tensile mechanical properties and hardness of tough pitch copper and oxygen free copper , high conductivity copper.

21. Figure.2: Effect of oxygen content on the toughness (energy absorbed)

22. Typical Uses of C11000 - Copper Architectural § building fronts, downspouts, flashing, gutters, roofing, screening Automotive § gaskets, radiators Electrical § bus bars, conductivity wire, contacts, radio parts, switches, terminals Hardware § ball floats, butts, cotter pins, nails, rivets, soldering copper, tacks Miscellaneous § anodes, chemical process equipment, kettles, pans, printing rolls, rotating band, road bed expansion plates, vats

23. Cu Zn system Cu is having FCC structure while Zn is having HCP, The Atom size difference is only about 4 %. Solid Solution strengthening,

24. Cu Zn system Even though the increment in the CRSS due to Zn is lower compare to any other element. But the solubility of 39 % makes the Cu Zn much more useful than any other Cu alloy system. Cu Zn system divided into two major classification; 1) alpha brass and 2) alpha beta brass.

25. Cu Zn system Alpha can be considered as a copper rich phase and beta can be the Zinc rich phase. From the phase diagram the solubility of Zn in Cu can be estimated as around 38 %. Above this composition beta phase starting to appear and the percentage of the beta also increases. Further ahead of the composition various different phases started appearing such as gamma, eta and epsilon.

26. Cu Zn system Beta has a disordered BCC structure and can be called as an intermetallic compound, ẞ / is having ordered BCC structure and it is brittle. Below 250 C, ẞ / converted to α + γ can be considered as a eutectoid reaction. Small ordered layers can be called as a domain. The perfection of the order within a domain is referred to as the degree of order. Gamma is having complex cubic structure and it is electron compound Cu 5 Zn 8 .

27. Alpha Brasses Name Composition Applications Gilding Metal 95 % Cu, 5 % Zn Coins, Medals, Plaques, tokens, cheap jwellery. Commercial Bronze 90 % Cu, 10 % Zn Lip stick cases, Marine hardwares, screws. Red Brass 85 % Cu, 15 % Zn Heat exchanger tubes, Plumbing pipes, Name plates, Corrosion resistance tubes, bullet envelopes. Low brass/ Dutch brass 80 % Cu, 20 % Zn Musical Instruments, Ornamental works, Condenser tubes. Cartridge brass 70 % Cu, 30% Zn Cartridge cases, highest ductility with good strength, head light reflectors for automobiles, rivets, fasteners, ammunition parts Admiralty brass 70 % Cu, 29 % Zn, 1 % Sn Sn improves the corrosion resistance, Heat exchanger tubes. Aluminum Brass 76 % Cu, 22 % Zn, 2 % Al Al improves the corrosion resistance, marine and land power plants.

28. Alpha Beta brass Name Composition Applications Muntz Metal/ Yellow brass 60 % Cu, 40 % Zn Large nuts and bolts, Valves Steam. Free Cutting Brass 61.5 % Cu, 35.5 Zn, 3 % Pb Gears, Screws and Machine parts. Naval brass 60 % Cu, 39 % Zn, 1 % Sn Suitable for Sea water, piston rods, valve stems etc Architectural Bronze 57 % Cu, 40 % Zn, 3 % Pb Best forging properties. Manganese bronze 58 % Cu, 39 % Zn, 1.4 % Fe, 1 % Sn, 0.4% Al, 0.5 % Mn. Improves corrosion resistance and mechanical properties. Forging Brass 60 % Cu, 38% Zn, 2 % Pb Excellent hot working properties.

29. Fig : Cu-40 Zn quenched into ice water from 850 C Fig: Quenched Muntz Metal Fig: Cu-42Zn

30. Fig: Cu-43 Zn , (a): Furnace cooled, (b): Air cooled. Fig: Effect of Cooling rate on beta phase.

31. Typical Uses of C26000 - Cartridge Brass Architectural § grillwork Automotive § radiator and heater cores and tanks Electrical § flashlight shells, lamp fixtures, witches, reflectors, screw shells, socket shells Hardware § eyelets, fasteners, grommets, finish hardware articles (kick plates, lock sets, push plates, etc.)

32. Typical Uses of C26000 - Cartridge Brass Munitions § ammunition components Plumbing § plumbing accessories, plumbing brass goods Wire § fasteners, pins, rivets, screws, springs

33. Typical Uses of C36000 - Free Machining Brass Hardware § gears, pinions Industrial § automatic high speed screw machine parts (screws, bolts, nuts, miscellaneous fasteners)

34. Fig: Cu Sn system

35. Cu Sn System Alpha: Solid solution of Sn in Cu, Beta: Solid solution, Delta: Compound Cu 13 Sn 8 , 21/13 ratio, Epsilon: Compound Cu 3 Sn, 7/4 ratio, Gamma: Solid Solution of Cu in Sn.

36. Cu Sn system Cu Sn alloys are much stronger as compare to Cu Zn alloys. The alloy is single phase α up to 10 % Sn. The alloys of this systems are precipitation hardenable. But the precipitation process is very slow for this system. So the time is very long.

37. Fig: Effect of Sn content on Hardness and elongation at the fracture.

38. Comparison of Mechanical properties between Cu Zn and Cu Sn systems Fig: Comparison between the Cu Zn and Cu Sn systems mechanical properties.

39. Fig: Cu-10 Sn (a): Chilled structure, (b): sand cast structure

40. Effect of Lead Figure.3: Cu Pb phase diagram Cooling rate must be rapid

41. Effect of Lead It is used as a powerful deoxidizer during the melting practice, it removes oxygen from the liquid copper. This increases the soundness of the casting. Wrought phosphorous bronze (93.8 Cu, 6 Sn, 0.2 P): Good resistance to sea water corrosion . It is a single phase alpha bronze, having good ductility, can be rolled, strip, can be drawn into wires and rods.

42. Effect of Lead Cast phosphorous bronze (12 Sn, 0.3 – 1.0 P, Balance Cu): Higher phosphorous content forms Fe 3 P, increases hardness and strength of the alloys sacrificing the ductility . Hard and brittle particles in the soft matrix makes the material most suitable for the bearing applications. Alloy having good toughness along with good corrosion resistance to sea water. However for commercially pure copper the lead content must be controlled to as low as possible. Lead is having low solubility due to that it concentrates at the grain boundary and wets the surface between the two grains reducing the strength and sometimes it may cause the hot shortness .

43. Figure: Effect of lead content on machinability. Figure: Microstructure of the pure copper containing lead particles .

44. Typical Uses of C51000 - Phosphor Bronze Architectural § bridge bearing plates Hardware § beater bars, bellow, bourdon tubing, clutch disks, cotter pins, diaphragms, fuse clips, fasteners, lock washers, sleeve bushings, springs, switch parts, truss wire, wire brushes Industrial § chemical hardware, perforated sheets, textile machinery, welding rods

45. Cu Al system Figure : Cu Al phase diagram. Figure: Effect of alloying elements on hardness.

46. Cu Al system Figure: Equilibrium Phases in Cu Al phase diagram.

47. Cu Al system

48. Figure: Time Temperature and Transformation Diagram for Cu Al.

49. Figure : TTT diagram for mentioned chemical composition.

50. Cu Al system Cu Al, two alloys are most common 5 % Al and 8 % Al, required only homogenization after the as cast condition. 8 % Al alloys, undergoes the eutectoid transformation and transferors beta to alpha and gamma 2. The structure of alpha and gamma 2 is same as that of the Pearlite.

51. Figure: Cu- 11 % Al Microstructure. Homogenization followed by slow cooling from 800 degree C Figure: Cu – 11% Al microstructure, Homogenization followed by water quenching from 800 degree C Figure: Cu-10 % Al microstructure rapidly quenched from 750 degree C

52. Copper Nickel System

53. Copper Nickel System Isomorphous system, Having complete mutual solubility in liquid and solid state, Improve strength, Improve corrosion resistance, Improve creep properties.

54. Typical Uses of C70600 - Copper Nickel Industrial § condensers, condenser plates, distiller tubes, evaporator and heat exchanger tubes, ferrules, salt water piping

55. Copper Chromium Figure : Cu Cr phase diagram.

56. Copper Chromium Chromium copper alloys are high copper alloys, containing 0.6 to 1.2% Cr. The chromium copper alloys are used for their high strength, corrosion resistance and electrical conductivity. The chromium copper alloys are age hardenable, which, in this case, means that a change in properties occurs at elevated temperature due to the precipitation of chromium out of the solid solution. The strength of fully aged chromium copper is nearly twice that of pure copper and its conductivity remains high at 85% IACS, or 85% that of pure copper.

57. Copper Chromium It is used in applications such as resistance welding electrodes, seam welding wheels, switch gears, cable connectors, circuit breaker parts, molds, spot welding tips, and electrical and thermal conductors that require strength. Chromium copper has excellent cold formability and good hot workability . It is used in applications such as resistance welding electrodes, seam welding wheels, switch gears, cable connectors, circuit breaker parts, molds, spot welding tips, and electrical and thermal conductors that require strength. Figure: Cu Cr alloys microstructure.

58. Cu Be System Figure: Copper Beryllium Phase diagram .

59. Cu Be System The solubility is quite limited, so that the addition of beryllium for solid-solution strengthening is not favorable. However, alloys containing greater than 1.5% Be might be precipitation hardenable , since around 800 °C (1470 °F) they will be single phase (or), and at lower temperature, the (copper-beryllium) phase will precipitate from. Hardness values above 40 HRC . If these alloys are solution annealed, then cold worked prior to aging in the range 300 to 385 °C (570–725 °F), the precipitation process will occur before recrystallization (and hence softening) can occur.

60. Cu Be System Alloys contain some cobalt, which forms an insoluble beryllium contain some cobalt, which forms an insoluble beryllium cobalt compound that inhibits grain growth during solution annealing . Also, the cast alloys have additions that act as grain refiners to control the as-cast grain size. In heat treating, some precautions should be taken. One is to avoid using too high a solution temperature , as partial melting may occur, and upon cooling the phase will form, which is difficult to dissolve upon subsequent solution annealing.

61. Cu Be System Nominal Composition: Be 1.80-2.00, Co + Ni 0.20 min, Co + Ni + Fe 0.6 max, Pb 0.02 max, Cu + Sum of Named Elements 99.5 min Description: Solution annealed, cold rolled 37% to Hard temper and precipitation hardened at 315 C (600 F) for 2 h to achieve maximum hardness. Longitudinal section shows elongated grains of alpha phase and cobalt beryllides. Striations are caused by metastable precipitates, not resolved by optical microscopy.

62. Cu Be System Nominal Composition: Be 0.2-0.6, Ni 1.4-2.2, Cu + Sum of Named Elements 99.5 min Description: Solution annealed at 900 C (I 650 F), cold rolled 11%, and precipitation hardened at 480 C (900 F) for 2 h to achieve maximum hardness. Structure consists of slightly elongated grains of alpha phase, and small nickel beryllide particles. The strengthening metastable precipitates are not resolved.

63. Cu Cd system Figure : Copper Cadmium phase diagram .

64. Cu Cd system Cadmium copper alloys are considered high copper alloys, they contain approximately 98 - 99 % copper, 0.1 - 1.5% cadmium and sometimes minor amounts of other materials. When cadmium is added to copper the material becomes more resistant to softening at elevated temperatures. The more cadmium that is added the more heat resistant the material becomes. An extremely heat resistant cadmium oxide forms on the surface of the wire during arcing and protects it from eroding. This enables the cadmium copper wire to retain its strength under the high temperature conditions of the electric trains.

65. Cu Cd system Nominal Composition: Cu 99.8, Cd 0.7-1.2, Fe 0.02 Condition Cold Worked

66. Ti Cu system Figure: Ti Cu phase diagram

67. Ti Cu system Age hardenable alloy, Ti is soluble in Cu to little extent but Cu is not soluble in the Ti. Vast difference in the melting point, Behavior of both the metals are different; Ti is allotropic, Cu is not. Ti is having HCP; Cu is having FCC crystal structure, Ti is exotic while Cu is not. Corrosion resistance of Ti is superior to Cu and Monel (Ni Cu alloy).

68. Ti Cu system Nominal Composition Cu 4% Ti Alloy, Condition Cold worked and Aged

69. Effect of Addition of Silver Increase the recrystallization temperature while maintaining the conductivities. Other elements can also increase the recrystallization temperature but at the cost of conductivities.

70. List of companies producing copper in India Hindustan Copper Limited Hindalco Industries Limited (Birla Copper) Sterlite Industries Limited Jhagadia Copper Limited Nissan Copper Limited India Gujarat copper Alloys Limited

71. 3/3/2020 82

72. Challenges of copper welding Copper alloys posses properties that requires special attention in welding: 1. Thermal conductivity, (Lack of Fusion) 2. High thermal expansion coefficient, (Distortion) 3. Melting point temperature , (Quite moderate and higher than Al) 4. Hot short, (i.e. Brittle at elevated temp.) 5. Very fluid molten metal , (Less control of the weld pool) Pure Copper is not heat treatable as far as improvement in the mechanical properties are concerned 3/3/2020 83

73. 3/3/2020 84 (Hess et al. 2010) (Xie et al. 2012)

74. 3/3/2020 85 (Wang et al. 2017)

75. 3/3/2020 86 (A) : Microstructure at the Fusion line (B) : Microstructure at the weld (C) : Microstructure at base metal (Zhang et al. 2015)

76. 3/3/2020 87 (A) : Weld Microstructure comparison of DMIG and Laser hybrid process (B) : Fusion Line Microstructure comparison of DMIG and Laser hybrid process (C) : Base metal microstructure comparison of DMIG and Laser hybrid process

77. 3/3/2020 88 (A): Microstructure of the Weld obtained after GTAW of Copper. (B) : Microstructure along the fusion line after the GTAW of Copper. (Lin et al. 2014) Joint Efficiency obtained for the 3 mm thick pure copper was 79 % which was low considering the thickness.

78. Continue…… Micro cracking also found during the welding of copper using GTAW. 3/3/2020 89 Fig

79. Summary of the presentation Absorptivity, Thermal conductivity and fluidity in the liquid state are the main challenges of the Cu while welding. Absorptivity is increasing just above the melting temperature which causes the unstable weld pool, welding ejection and defects such as porosity and poor weld bead appearance. 3/3/2020 90

80. Continue…… Due to thermal conductivity the preheating becomes mandatory and higher welding current and slower welding speed required which result into very high heat input. Which ultimately produces the coarse grain structure. Multipass welding should be avoided to reduce the number of thermal cycles during the welding. 3/3/2020 91

81. References J. R Davis and Associates, ASM Specialty handbook : Copper and Copper Alloys. George F Vander Voort, ATLAS of Time Temperature Diagram. James Michel, Introduction to copper and copper alloys. Copper Development Association. M Ahlers, MARTENSITE AND EQUILIBRIUM PHASES IN Cu-Zn AND Cu-Zn-A1 ALLOYS.

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