1、Copper-nickel Welding and FabricationHandling | Welding | PropertiesResistance to Corrosion and Biofouling | Important ApplicationsCopper Development Association Publication 139, Revised February 2013Copper Development Association Inc Publication A7020-99/13, Revised February 2013Nickel Institute Pu
2、blication 12014, Second Edition, February 2013Cover page picture acknowledgement: TIG welding 90-10 copper-nickel straight pipe to a bend (Courtesy Eucaro Buntmetall GmbH)Copper Development Association, based in the UK, is a non-trading organisation that promotes and supports the use of copper based
3、 on its superior technical performance and its contribution to a higher quality of life. Its services, which include the provision of technical advice and information, are available to those interested in the utilisation of copper and copper alloys in all their aspects. The Association also provides
4、 a link between research and the user industries and is part of an international network of trade associations, the Copper Alliance.Copper Development Association Inc is a U.S-based, not-for-profit association of the global copper industry, influencing the use of copper and copper alloys through res
5、earch, development and education, as well as technical and end-user support. CDA is committed to promoting the proper use of copper materials in sustainable, efficient applications for business, industry and the home.The Nickel Institute is an international, non-profit organisation which promotes th
6、e production, use and re-use (through recycling) of nickel in a socially and environmentally responsible manner. They offer free technical knowledge about nickel, its properties and uses to ensure optimum performance, safe handling and use. They are supported by most of the worlds producers of nicke
7、l and have offices in Belgium, Canada, China, Japan and U.S.A.Copper-nickel Welding and FabricationContentscoPPer-nIckel WelDIng anD fabrIcatIon | 1 tables and figures 21.0 Introduction 32.0 the alloys 4 2.1 Standards 4 2.2 Composition 4 2.3 Mechanical and Physical Properties 43.0 general Handling 6
8、 3.1 Cutting and Machining 6 3.2 Forming 7 3.3 Heat Treatment 7 3.4 Descaling 7 3.5 Painting 74.0 Welding 8 4.1 Preparation for Welding 8 4.2 Tack Welding 8 4.3 Weld Preparations 9 4.4 Welding Consumables 9 4.5 Manual Metal Arc (MMA or SMAW) 10 4.6 Gas-shielded Tungsten Arc (TIG or GTAW) 10 4.7 Gas-
9、shielded Metal Arc (MIG or GMAW) 11 4.8 Post-weld Treatment 12 4.9 Inspection 12 4.10 Mechanical Properties of Welds 125.0 clad Plate 13 5.1 Cutting 13 5.2 Welding 136.0 brazing 147.0 tube to tubesheet fabrication 158.0 sheathing and cladding of offshore structures 179.0 linings 1910.0 Desalination
10、Plants 2011.0 seawater corrosion resistance 21 11.1 Flow Rates 21 11.2 Sand Abrasion 21 11.3 Localised Abrasion 21 11.4 Galvanic Behaviour 22 11.5 Handling Sulphides 2312.0 biofouling resistance 2413.0 checklist 2514.0 bibliography 26 14.1 General 26 14.2 Fabrication 26 14.3 Piping Systems, Heat Exc
11、hangers and Condensers 26 14.4 Offshore Sheathing 26 14.5 Boat Hulls 27 14.6 Biofouling 2715.0 further Information and advice 28 Disclaimer: Whilst this document has been prepared with care, Copper Development Association, Copper Development Association Inc and Nickel Institute can give no warranty
12、regarding the contents and shall not be liable for any direct, incidental or consequential damage arising out of its use. For complete information on any material, the appropriate standard should be consulted.2 | coPPer-nIckel WelDIng anD fabrIcatIontablesTable 1 Designations in Standards for 90-10
13、and 70-30 AlloysTable 2 UNS Chemical Composition (%) of 90-10 and 70-30 Alloys for Welding ApplicationsTable 3 Typical Mechanical Properties of Annealed Copper-nickel Sheet and Plate (taken from EN1652:1997)Table 4 Typical Physical Properties of Copper-nickels and SteelTable 5 Welding Consumables -
14、Specifications Table 6 Typical All-weld Metal Mechanical Properties (based on 70-30 consumables)Table 7 Biofouling Mass on Copper-nickel Sheathed Test Pilings After 5 and 10 Years ExposurefiguresFigure 1 Examples of weld preparations for joining copper-nickel plateFigure 2 Examples of run sequence f
15、or welding copper-nickel clad plateFigure 3 Typical tube weld joint preparations for tube to tubesheet fabricationFigure 4 Typical attachments for platform sheathingFigure 5 Copper-nickel boat landing stageFigure 6 Galvanic seriesFinished weld showing root penetration on pipe bore(Courtesy Eucaro Bu
16、ntmetall GmbH)Tables and FiguresCopper-nickel alloys have a remarkable combination of good resistance to both corrosion and biofouling in seawater. As they are also readily welded and fabricated, they are an obvious choice for pipe systems, heat exchangers and structures engineered for marine use. C
17、opper-nickels have been specified for seawater use for over 50 years; they are the materials of first choice for seawater pipework and condenser/heat exchanger service for many of the worlds navies, floating production storage and offloading vessels and merchant ships. They are used in desalination,
18、 power plants and offshore fire water systems, and for the sheathed splash zone protection of oil and gas platform legs. In all such applications, their durability is proven. Fabrication of copper-nickels is not difficult, although a higher degree of cleanliness is required than for steel. They are
19、ductile and easily formed. Their machinability is similar to that of aluminium bronzes, phosphor bronzes and other copper alloys that do not have special free-cutting additions. Copper-nickels can be welded by most standard processes. The core of this book is welding and fabrication. General enginee
20、ring properties, corrosion and biofouling resistance and applications are included only where they influence decisions on fabrication. It provides an informed understanding of the two primary copper-nickel alloys, to allow good fabrication and operation. 21.0 IntroductioncoPPer-nIckel WelDIng anD fa
21、brIcatIon | 3TIG (GTAW) welding a 90-10 copper-nickel assembly32.0 The AlloysThere are two main grades of copper-nickel alloy used in marine service - 90-10 (10% nickel) and 70-30 (30% nickel). The 70-30 alloy is stronger and has greater resistance to seawater flow; but 90-10 will provide good servi
22、ce for most applications and, being less expensive, tends to be more widely used. Both alloys contain small but important additions of iron and manganese, which have been chosen to provide the best combination of resistance to flowing seawater and to overall corrosion. 2.1 standardsTable 1 gives som
23、e of the more common international designations for both alloys. 2.2 composition The chemical composition ranges for the two alloys vary between the different standards. When materials are intended for welding applications, the maximum limits for some specific impurities need to be restricted becaus
24、e of their effects on hot ductility, and thus on weldability. Examples of preferred limits for Zn, C, Pb, S and P are shown in Table 2. table 1 Designations in standards for 90-10 and 70-30 copper-nickel alloysalloyastm/UnsIsocen90-10C70600C70620*CuNi10Fe1MnCW352H70-30C71500C71520*CuNi30Fe1MnCW354H*
25、C70620 and C71520 are intended for products that will be subsequently welded4 | coPPer-nIckel WelDIng anD fabrIcatIontable 2 Uns chemical composition (%) of 90-10 and 70-30 alloys for Welding applicationsalloyUns nocumin. nifemnmax.Znmax.cmax.Pbmax.smax.Pmax.othermax.90-10C7062086.5 9-1111.8 1.00.50
26、.050.020.020.020.570-30C7152065.029-330.4-11.00.50.050.020.020.020.5table 3 typical mechanical Properties of annealed copper-nickel sheet and Plate (taken from en1652:1997)alloy0.2% Proof strength min. n/mm2*tensile strength min. n/mm2*elongation min.%Hardness HV90-10100300309070-3012035035100* 1N/m
27、m2 is equivalent to 145 psi2.3 mechanical and Physical PropertiesCopper-nickels are stronger than copper but lower in strength than steels. Their ductility, toughness and formability are all excellent. They do not embrittle at low temperatures and retain their mechanical strength and ductility down
28、to cryogenic temperatures. Table 3 below gives typical annealed mechanical properties for copper-nickel plate; strength can be increased by cold working but not by heat treatment. Heat exchanger tubing is normally produced and ordered in the light drawn rather than annealed condition. For design pur
29、poses, precise values should be taken from relevant international standards based on product form and size. 90-10 copper-nickel pipe fabrication for ship seawater systemcoPPer-nIckel WelDIng anD fabrIcatIon | 5table 4 typical Physical Properties of copper-nickels and steel Units90-1070-30Plain carbo
30、n steelDensitykg/dm38.908.957.85Melting range C1100-11451170-12401460-1490Specific heatJ/kgK377377485Thermal conductivityW/mK402950Coefficient of linear expansion 10-300C10-6/K171612Electrical resistivity at 20oCmicrohm/cm193430Modulus of elasticityGPa135152210Modulus of rigidityGPa505681Table 4 com
31、pares various physical properties with those of steel. Additionally, the 70-30 alloy is essentially non-magnetic and has a magnetic permeability very close to unity. The 90-10 alloy has a higher iron content and can have a permeability between 1.01 and in excess of 1.2, depending on the final heat t
32、reatment condition. A fast cool from the solution heat treatment temperature of 750oC is normally required to achieve a low permeability.An example of a copper-nickel application designed to benefit from its fabricability and corrosion properties is shown here. It is a flanged strainer to be used as
33、 part of the seawater system for a 110m yacht. It is made from 90-10 copper-nickel and separates larger debris and hard fouling such as mussels, barnacles, stones and weeds which would otherwise enter, block and cause obstructions in the system. The strainer has good resistance to the seawater with
34、an added benefit of deterring biofouling growth on its interior.(Courtesy Eucaro Buntmetall GmbH)5 36 | coPPer-nIckel WelDIng anD fabrIcatIon3.0 General Handling The precautions required for handling copper-nickels will be familiar to any fabricator who routinely handles materials like stainless ste
35、els and aluminium alloys, but may be new to those used to dealing with only carbon steels. Cleanliness is paramount: contamination can cause cracking and porosity during heat treatment or welding and may affect the corrosion resistance of the alloy. Ideally, fabrication should be done in an area dev
36、oted solely to copper-nickel alloys. Where this is impracticable, the standard of care of the material should be well above that necessary for carbon steels. Sheets should remain in their packing until needed and should be separated - normally by protective material - to avoid abrasion. Plates and s
37、heets are best stored vertically in covered racks. Walking over sheets should be avoided. Plastic film may be interposed between the sheet and rolls when roll forming. Grease and paint should be kept away from the surface, particularly near edges of weld preparations; all trace of marking crayons mu
38、st be removed before making a joint. Stainless steel brushes should be used, and tools such as grinding discs should not be interchanged between copper-nickel and other materials. Openings of pipes and fittings must be protected on completion of fabrication to prevent ingress of dirt etc. before ins
39、tallation.3.1 cutting and machining Copper-nickels can be cut using most conventional cutting processes, with the exception of oxy-fuel cutting. High-speed abrasive wheels work well for bevelling edges and trimming material. Band saws or shears may be used for cutting, but allowance made for the all
40、oys relative softness and ductility. Plasma-arc cutting is fast, accurate and economical. Laser and abrasive water jet cutting are also possible.Although copper-nickels are not as readily machined as free-cutting brass, they are much easier to machine than materials, such as stainless steels, which
41、work harden rapidly: they can be ranked with aluminium bronze and phosphor bronze alloys. More details and recommendations are given in Recommended Machining Parameters for Copper and Copper Alloys, DKI Monograph i.18. Plasma cutting copper-nickel plate (Courtesy Eucaro Buntmetall GmbH)6 4coPPer-nIc
42、kel WelDIng anD fabrIcatIon | 73.2 formingCopper-nickels can be hot or cold formed, although cold working is preferred; a maximum of 50% reduction is achievable before a full inter-stage anneal becomes necessary. A 20% cold reduction approximately halves the as-annealed elongation and doubles the pr
43、oof strength. Hot working is carried out at 850-950C (90-10) or 925-1025C (70-30) but can lead to hot cracking in inexperienced hands. Tubes can be bent by a range of methods, including rotary draw bending, 3-roll bending, compression bending and ram bending (press bending). When bending copper-nick
44、el, a mandrel and wiper die are also applied for support (mandrel bending). Care must be taken to get smooth bends and avoid wrinkling, because liquid turbulence in service can lead to impingement attack. Bends with a tube bend radius of twice the tube diameter can be produced. Smaller radii require
45、 prefabricated bends. 3.3 Heat treatment The work piece should be clean and free from any contamination before and during heating. Copper-nickels can embrittle if heated in the presence of contaminants such as sulphur, phosphorus, lead and other low melting point metals, sources of which include pai
46、nts, marking crayons, lubricating grease and fluids. Fuels used must be low in sulphur; normally, fuel oils containing less than 0.5% by weight of sulphur are satisfactory. Oxidising atmospheres cause surface scaling and therefore furnace atmospheres should be between neutral and slightly reducing a
47、nd must not fluctuate between oxidising and reducing conditions. Flame impingement must be avoided.For a full anneal, soaking times of 3-5 minutes per mm thickness are appropriate. The recommended temperatures are: 90-10 750-825C 70-30 650-850C. Stress relieving is seldom applied but, if required, t
48、he recommended temperatures are: 90-10 250-500C 70-30 300-400C. 3.4 Descaling Surface oxide films on both alloys can be very tenacious. Oxides and discolouration adjacent to welds can be removed with very fine abrasive belts or discs. If pickling is required, a hot 5-10% sulphuric acid solution cont
49、aining 0.35g/l potassium dichromate is satisfactory. Before pickling, oxides can be broken up by a grit blast. The pickled components should be rinsed thoroughly in hot, fresh water and finally dried in hot air. 3.5 Painting Painting copper-nickel is strictly unnecessary as the alloys inherently res
50、ist corrosion and biofouling. However, it is sometimes desirable, perhaps for aesthetic reasons, or to reduce the exposed metal area in a bimetallic couple, and so reduce the risk of galvanic corrosion.A thorough roughening by grit or sand blasting is crucial before paint is applied. Compared with t
