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Design manual Design manual Success with aluminium profiles

Cover picture: The aluminium profile on the front cover fits snugly into the plastic casing shown above. The whole is part of the GH2 ceilingmounted lift produced by Guldmann A/S in Denmark. In use, the lift facilitates the safe handling of patients. By reducing the physical exertion demanded of care staff, it also provides a safer working environment. The lifting unit runs in rails (also aluminium profiles) and the whole assembly weighs only 8.7 kg. Its lifting capacity is 200 kg. Besides low weight and high strength, aluminium profiles have many other design advantages. The profile on the cover is 284 mm wide and has three compartments for housing the lift motor and batteries. The profile’s various channels are purpose-designed to guarantee the rapid and easy fitting of all the lift’s components. Once the profile has been extruded, the only machining required is cutting to length and the milling of the holes for cables and the lift mechanism. The profile shown here has a natural anodised finish.

Production: Sapa Profiler AB, Sapa Profiles Ltd and Jonsson & Lindén. 1st UK edition: 2000 copies, current as of May 2007. This manual can be quoted from provided that the source is clearly stated. Illustrations and pictures may only be reproduced with the consent of Sapa Profiler AB.

Design manual

Sapa Profiles Ltd is a part of an international industrial group developing, manufacturing and marketing aluminium products with high added value. The company has operations throughout Europe and in the USA and China. The building, automotive and engineering industries are the company’s largest customer segments. For further details, see www.sapagroup.com. 1

CONTENTS

1. Aluminium profiles – the possibilities

4–5

2. Aluminium – the properties Physical properties of some of the most commonly used metals and plastics

6–9

3. From bauxite to recycled metal

8 10 – 11

4. Environmental impact 12 – 17 4.1 The environmental impact of extrusion, surface treatment and machining 13 4.2 Product examples 14 – 16 4.2.1 Cars 14 – 15 4.2.2 Underground railway carriages 15 – 16 4.2.3 Window frames 16 – 17 4.3 Health 17 5. Aluminium profiles – the applications Statistics – use by industry Statistics – total consumption

18 – 19 18 19

6. Extrusion principles Solid profiles and hollow profiles

20 – 21 21

7. Choosing the right alloy Alloying elements, alloy codes and types At-a-glance alloy selection Heat treatment recommendations Common construction alloys Special alloys

22 – 27 22 24 25 26 27

8. Wide profiles with tight tolerances

28 – 29

9. General design advice Recommended wall thickness – guidelines 9.1 Uniform wall thickness 9.1.1 Exceptions 9.2 Soft lines 9.3 Solid profiles if possible 9.4 Fewer cavities in hollow profiles 9.5 Profiles with deep channels 9.6 Heat sinks 9.7 Decorate!

30 – 34 30 31 31 31 32 32 32 – 33 33 34

10. Jointing 35 – 73 10.1 Screw ports 35 – 36 10.2 Jointing – nuts and bolts 37 10.3 Snap-fit joints 38 – 39 10.4 Jointing profile to profile 39 – 51 10.4.1 Longitudinal jointing 39 – 40 10.4.2 Telescoping 41 – 42 10.4.3 Latitudinal jointing 42 – 44 10.4.4 Hinges 44 – 46 10.4.5 T-joints 47 – 48 10.4.6 Corner joints 49 – 51 10.5 Jointing with other materials 52 – 53 10.6 Riveting 54 – 55 10.7 End caps 55 – 56 10.8 Adhesive bonding 57 – 63 Essential knowledge 57 Joint design 58 Choice of adhesive 59 – 62 Pre-treatment operations in bonding 63 Literature 63 10.9 Fusion welding 64 – 67 Most aluminium alloys can be welded 64 2

10.10

Methods – MIG, TIG and robot welding 65 Welding economy 66 Filler metals 66 Strength 67 Profile design with regard to fusion welding 67 Friction Stir Welding 68 – 73 An established technology 68 The principle of FSW – illustrations 69 FSW welds – a comparison with MIG 70 Strength, Leakproofness, Repeatability, Corrosion resistance, Limitations 71 Strength of FSW joints, Comparison with MIG and TIG – Reference: The Royal Institute of Technology, Sweden 72 – 73

11. Profile tolerances Tolerances on dimensions EN 755 -9 Cross-sectional dimensions Alloy groups Tolerances on dimensions other than wall thickness Tolerances on wall thickness of solid and hollow profiles Length Squareness of cut ends Tolerances on form Straightness Convexity – Concavity Contour Twist Angularity Corner and fillet radii EN 12020-2 Cross-sectional dimensions Tolerances on dimensions other than wall thickness Tolerances on wall thickness of solid and hollow profiles Length Squareness of cut ends Length offset for profiles with a thermal barrier Tolerances on form Straightness Convexity – Concavity Contour Twist Angularity Corner and fillet radii

74 – 86 75 – 78 75 75 76 77 78 78 78 – 81 79 79 80 80 81 81 82 – 86 82 82 82 83 83 83 83 – 86 83 84 84 85 85 86

12. Surface classes Visible surfaces – important information Review profile design carefully The effects of surface treatment Handling and stocking Surface classes 1 – 6, Area of application, Suitable Sapa alloys

87 – 89 87 88 88 88

13. Thermal break profiles Sapa’s method Single or double insulation Insulated profile design

90 – 91 90 90 91

89

CONTENTS

14. Machining General 14.1 Stock cutting 14.1.1 Punching/cutting 14.2 Stock removal 14.2.1 Turning 14.2.2 Drilling 14.2.3 Milling 14.2.4 Cutting to length 14.3 Plastic forming 14.3.1 Draw bending 14.3.2 Roller bending 14.3.3 Stretch bending 14.3.4 Press bending 14.4 Threading 14.5 Tolerances Product examples – stock cutting, stock removal and plastic forming 14.6 Hydroforming The principle Example product 15.

Surface treatment Profile design Mechanical surface treatment Anodising Coloured oxide layers 15.4 Painting 15.4.1 Powder coating Product examples – powder coating 15.4.2 Decoral 15.4.3 Wet painting 15.5 Sapa HM-white 15.6 Screen printing 15.7 Function-specific surfaces 15.8 At-a-glance guide for choice of surface treatments 15.9 Colour guide for anodising

15.1 15.2 15.3

16. 16.1 16.2 16.2.1 16.2.2 16.2.3 16.2.4 16.2.5 16.2.6 16.3 16.4 16.5 16.6 16.7 16.8 16.9

16.10

Corrosion Aluminium’s corrosion resistance The most common kinds of corrosion Galvanic corrosion Preventing galvanic corrosion Pitting Preventing pitting Crevice corrosion Preventing crevice corrosion Aluminium in open air Aluminium in soil Aluminium in water Corrosion at the water line Aluminium and alkaline building materials Aluminium and chemicals Aluminium and dirt Aluminium and fasteners At-a-glance guide for choosing fasteners Corrosion checklist

17. Cost-efficiency 17.1 How you, the designer, can influence cost-efficiency

92 – 103 92 – 93 94 94 95 – 96 95 96 96 96 97 – 98 97 97 98 98 99 99 100 – 101 102 – 103 102 103 104 – 122 104 105 106 – 109 108 110 – 115 110 – 111 112 – 113 114 – 115 115 116 – 117 118 – 119 120 121 122 123 – 134 123 123 – 127 124 125 126 126 127 127 128 129 129 130 131 131 131 132 – 133 133 134

17.2 17.3

How you, the purchaser, can influence cost-efficiency Sapa’s vision

18.1 18.2 18.2.1 18.2.2

Knowledge banks 139 – 141 The Profile Academy 139 Further sources of knowledge 140 – 141 Sapa Technology 140 Colleges, industry organisations, etc. 141

18.

19. Design 19.1 General 19.2 Design literature 19.3 Key considerations in aluminium design 19.4 Cross-sectional shape 19.4.1 Asymmetrical profiles – the shear centre 19.4.2 Solid or hollow profiles? 19.5 Design using the partial coefficient method – general 19.6 Material 19.6.1 Material values 19.6.2 Partial coefficients 19.7 Designing 19.7.1 General 19.7.2 Buckling 19.7.3 Effective thickness 19.7.4 Reinforced elements 19.7.5 Axial force Torsional buckling and lateral-torsional buckling 19.7.6 Bending moments Lateral buckling 19.7.7 Transverse force 19.7.8 Torsion 19.7.9 Combined loads Bending instability 19.7.10 Concentrated force and support reaction 19.8 Joints 19.8.1 General 19.8.2 Force distribution in joints 19.8.3 Types of failure in joints using fasteners 19.8.4 Nuts and bolts 19.8.5 Self-tapping screws 19.8.6 Screw ports Open screw port Closed screw ports 19.8.7 Tracks for nuts and bolts 19.8.8 Rivet joints 19.8.9 Welded joints 19.8.10 Miscellaneous jointing methods 19.9 Fatigue 19.9.1 General 19.9.2 Scope 19.9.3 Fatigue load 19.9.4 Designing for fatigue 19.9.5 Detail types

136 – 137 138

142 – 163 142 142 142 – 143 143 – 145 143 – 144 144 – 145 145 145 – 146 145 – 146 146 146 – 151 146 146 – 147 147 – 148 148 148 – 149 149 149 – 150 149 – 150 150 150 151 151 151 – 155 151 151 152 152 – 153 153 153 – 154 153 – 154 154 154 154 154 – 155 155 155 – 163 155 155 155 155 – 156 156 – 163

135 – 138 135 – 136 3

“It is what we remember that makes us wise.” Remember to keep this manual readily to hand!

4

1. THE POSSIBILITIES

1. Aluminium profiles

– the possibilities Aluminium profiles help designers to create unique solutions that satisfy all expectations, hopes and demands. The tooling costs are reasonable, there are few technical limitations and a whole new world of possibilities is opened up for exploration. It is at the design stage that there are so many opportunities to incorporate features that will make the profile easier to machine and easier to fit. Low weight combined with high strength, excellent corrosion resistance and superb finishes are just some of the properties the designer can fine-tune to ensure that the final product meets all specifications. On top of all this, aluminium is easy to recycle and the extrusion process is simple – applying considerable pressure, a heated billet is forced through a die. The resultant profile is shaped exactly like the aperture in the die. This manual is primarily intended for those who would like to gain further insight into success with aluminium profiles. Whenever there is a need for greater help or guidance, Sapa is happy to provide advice and expertise. Few manufacturers can match our depth of knowledge and experience. Contact us and find out for yourself!

5

2. THE PROPERTIES

2. Aluminium

– the properties Low weight, high strength, superior malleability, easy machining, excellent corrosion resistance...

After iron, aluminium is now the second most widely used metal in the world. This is because aluminium has a unique combination of attractive properties. Low weight, high strength, superior malleability, easy machining, excellent corrosion resistance and good thermal and electrical conductivity are amongst aluminium’s most important properties. Aluminium is also very easy to recycle. Weight With a density of 2.7 g/cm3, aluminium is approximately one third as dense as steel. Strength Aluminium alloys commonly have tensile strengths of between 70 and 700 MPa. The range for alloys used in extrusion is 150 – 300 MPa. Unlike most steel grades, aluminium does not become brittle at low temperatures. Instead, its strength increases. At high temperatures, aluminium’s strength decreases. At temperatures continuously above 100°C, strength is affected to the extent that the weakening must be taken into account. Linear expansion Compared with other metals, aluminium has a relatively large coefficient of linear expansion. This has to be taken into account in some designs. Malleability Aluminium’s superior malleability is essential for extrusion. With the metal either hot or cold, this property is also exploited in the rolling of strips and foils, as well as in bending and other forming operations. Machining

Easy to mill, drill, cut, punch, bend, weld, bond, tape...

6

Aluminium is easily worked using most machining methods – milling, drilling, cutting, punching, bending, etc. Furthermore, the energy input during machining is low. Jointing Features facilitating easy jointing are often incorporated into profile design. Fusion welding, Friction Stir Welding, bonding and taping are also used for jointing.

2. THE PROPERTIES

Aluminium combines low density and high strength. These properties are here being used in the decking of a bridge.

These heat sinks exploit aluminium’s high thermal conductivity.

Aluminium has superior malleability. 7

2. THE PROPERTIES

Conductivity Aluminium is an excellent conductor of heat and electricity. An aluminium conductor weighs approximately half as much as a copper conductor having the same conductivity. Reflectivity Aluminium is a good reflector of both visible light and radiated heat. Screening – EMC Tight aluminium boxes can effectively exclude or screen off electromagnetic radiation. The better the conductivity of a material, the better the shielding qualities. Corrosion resistance

The oxide layer is dense and provides excellent corrosion protection.

Aluminium reacts with the oxygen in the air to form an extremely thin layer of oxide. Though it is only some hundredths of a μm thick (1 μm is one thousandth of a millimetre), this layer is dense and provides excellent corrosion protection. The layer is self-repairing if damaged. Anodising increases the thickness of the oxide layer and thus improves the strength of the natural corrosion protection. Where aluminium is used outdoors, thicknesses of between 15 and 25 μm (depending on wear and risk of corrosion) are common. Aluminium is extremely durable in neutral and slightly acid environments. In environments characterised by high acidity or high basicity, corrosion is rapid. Further details are given in chapter 16, “Corrosion”. Non-magnetic material Aluminium is a non-magnetic (actually paramagnetic) material. To avoid interference of magnetic fields aluminium is often used in magnet X-ray devices. Zero toxicity After oxygen and silicon, aluminium is the most common element in the Earth’s crust. Aluminium compounds also occur naturally in our food. For further details, see chapter 4, “Environmental impact”. Physical properties of some of the most commonly used metals1) and plastics

2)

8

®

Fe

Cu

Zn

Density, g/cm3

2.7

7.9

8.9

7.1

1.1

1.4

Melting point,°C

658

1 540

1 083

419

255

175

Thermal capacity, J/kg, °C

900

450

390

390

1 680

1 470

Thermal conductivity, W/m, °C

230

75

390

110

0.23

0.23

24

12

16

26

70 – 100

80 – 90

Coeff. of linear expansion, x 10 -6/°C

1)

®

Al

Nylon

Delrin

(Polyamide 6–6)

(Polyacetal)

El. conductivity, % I.A.C.S. 2)

60

16

100

30

–

–

El. resistance, x 10 -9 7m

29

105

17

58

–

–

Modulus of elasticity, GPa

70

220

120

93

3

3

Table values are for commercially pure metals. 100% I.A.C.S. (International Annealed Copper Standard) is the conductivity that, at 20°C, corresponds to 58 m/7, mm2.

2. THE PROPERTIES

Aluminium is easy to work using most machining methods.

Aluminium has excellent resistance in neutral and slightly acid environments.

Weight and strength – aluminium is approximately one third as dense as steel. Aluminium alloys have tensile strengths of between 70 and 700 MPa. 9

3. THE RAW MATERIAL

3. From bauxite to

recycled metal The Earth’s crust is 8% aluminium.

There is plenty of raw material for the production of aluminium. In a variety of forms, aluminium compounds make up a full 8% of the Earth’s crust. Bauxite Bauxite is the main starting point in the production of aluminium. It has been estimated that, given the present rate of aluminium production, there is enough bauxite to last another 200 to 400 years. This assumes no increase in the use of recycled aluminium and no further discoveries of bauxite. Bauxite forms when certain aluminium bearing rocks decompose. Its main constituents are aluminium oxides, iron and silicon. The largest and most lucrative bauxite deposits are located around the Equator. Major producers include Australia, Brazil, Jamaica and Surinam. Alumina (Al2O3) Normally in close proximity to the mine, bauxite is refined into alumina. The next stage, production of aluminium by molten electrolysis of the alumina, is concentrated in countries with good supplies of electricity. The production of 1 kg of aluminium requires around 2 kg of alumina. The production of 2 kg of alumina requires about 4 kg of bauxite. The metal Due to aluminium’s chemistry, relatively large amounts of energy (primarily electricity) are required to reduce alumina to aluminium. Around 47 MJ (approx. 13 kWh) goes into the molten electrolysis of 1 kg of the metal. However, this investment gives excellent dividends. The energy expended in aluminium production is often recouped several times over. By reducing the weight of vehicles, the use of aluminium reduces fuel consumption (see also chapter 4). Similarly, energy losses in aluminium power lines are comparatively small. Recycling

Aluminium scrap – a valuable raw material.

10

Scrap aluminium is a valuable resource that is set to become even more important. In principle, all scrapped aluminium can be recycled into a new generation of products. With appropriate sorting, scrap aluminium can advantageously be recycled to produce the same sorts of products over and over again. Furthermore, recycling requires only 5% of the original energy input.

3. THE RAW MATERIAL

In today’s environment-conscious society, the recycling of used aluminium products is becoming ever more important and ever more common.

The aluminium cycle

THER MECHANICAL

PAC K AG I N G

AP

PL

IC

A

S

PRODUCTS

DO

ON

TR

S

R PO

N TA

TI

AN

B

In the aluminium cycle, the metal can be reused for the same purposes over and over again. Unlike many other materials, aluminium does not lose its unique properties.

E CT R I C A L A P P ND EL LI C GA AT I N I ON D L S UI

CASTING

REMELTING

PRIMARY ALUMINIUM

Al2O3 Al2O3

So easy to recycle: Aluminium is the perfect “eco-metal”. Very little aluminium is lost in the remelting process. Increased recovery, dismantling and sorting of spent products has led to even greater recycling of aluminium.

11

4. THE ENVIRONMENT

4. Environmental

impact All industrial activity consumes natural resources and has an impact on the environment. The aluminium industry is no exception to this. However, using aluminium in preference to other products often has a positive impact. Thus, to gain a true assessment of an aluminium product from the environmental point of view, a life cycle analysis is essential. Several examples are given later in this chapter. Absolute recycling

Absolute recycling – repeatable recycling with maintained quality and high yield.

Aluminium collected for recycling enters an almost never-ending “eco-circle”. This is because very little metal is lost in remelting. On average, losses through oxidation during remelting amount to a few per cent only. Furthermore, the quality of the remelted material is so high that it can be used for the same product over and over again. Hence our use of the term “absolute recycling” – repeatability with maintained quality and high yield. Extrusion As mentioned in chapter 3, producing aluminium from bauxite requires comparatively large amounts of energy. The manufacture of aluminium profiles, on the other hand, requires relatively little energy. At the web site of EAA (the European Aluminium Association) you can obtain further information on profile manufacturing and a number of other subjects connected with the use of aluminium and profiles. The address: www.aluminium.org

The remelting works in Sjunnen, Sweden.

12

4.1 EXTRUSION – ENVIRONMENTAL IMPACT

4.1 The environmental impact of extrusion, surface treatment and machining Cutting to length is the main source of noise in factories producing aluminium profiles. This noise has been reduced by screening. Changing the lubricants used on billet end faces has not only improved the quality of air in workshops, but also given cleaner profiles that require less post-extrusion cleaning. A further measure to reduce potentially negative environmental impact is the increased use of gas nitriding for the hardening of dies. Dies are now stored with residue aluminium on them, thus minimising the need for cleaning. Similarly, the mineral oil based cooling and cutting fluids previously used in the machining of semi-finished goods have been replaced by water-based products. This has reduced the need to use organic degreasing agents. Sapa no longer uses trichloroethylene for degreasing. The alkaline water solutions used today produce a semi-stable emulsion containing droplets of grease and oil. Drawing off this emulsion extends the life of the degreasing bath and gives a product that can be recycled as, for example, a lubricant for machining operations. The etching process in anodising has been improved by the use of “neverdump” baths. These consume minimum quantities of chemicals and produce less waste. Used etching baths are neutralised. This precipitates the aluminium content as a hydroxide, which is then refined into chloride. To an increasing extent, the chloride is being used as a flocking agent in water treatment plants. Copper and cobalt salts were previously used for dyeing profiles during anodising. Again to lessen any potentially negative impact on the environment, these have been replaced by tin salts.

Die cleaning – a closed process producing no waste water.

13

4.2 ENVIRONMENT – ALUMINIUM IN EVERYDAY USE

4.2 Product examples 4.2.1 Cars More and more car manufacturers are using aluminium in preference to steel. It is perfectly possible to replace 182 kg of steel components with 82 kg of aluminium – 100 kg less strain on the engine. If no recycled metals are used, aluminium components require 2,740 MJ more energy to produce than the steel parts they replace. However, with a typical lifetime of use, the lighter car will require 640 litres less fuel. This is the equivalent of 23,000 MJ. Furthermore, when the content of recycled metal reaches 90%, an aluminium component actually consumes less production energy than its steel counterpart. Environmental benefits Assuming no recycled steel or aluminium is used: – During the car’s lifetime, the extra energy used in producing aluminium is recouped a good eight times over. – Production of the aluminium components emits 100 kg more CO2 than is the case for steel. This higher impact on the environment is made good many times over during the car’s lifetime – the reduced petrol consumption reduces CO2 emissions by 1,500 kg. Total life cycle analysis

The production of a steel bonnet presents a 60% greater total load on the environment than the production of an aluminium bonnet.

Total life cycle analyses underline the energy and environmental benefits resulting from the use of aluminium. Car manufacturers make extensive use of such analyses. In this sector of industry, the Swedish EPS method1) is the most widely used analytical tool. An example is given below. A steel car bonnet is replaced by an aluminium one. This reduces the weight from 18 to 10 kg. Applying the EPS method, the total load on the environment presented by the steel bonnet is around 60% greater than the load presented by the aluminium bonnet. 1)

EPS = Environmental Priority Strategies in product design is a practical method for calculating “environmental load”. The method takes into account what happens throughout the manufacture, use and eventual disposal of a product. Calculations are based on the following formula: Environmental load index x Quantity = ELU (Environmental Load Unit) An environmental load index is a numerical value corresponding to the load on the environment considered to be presented by a defined quantity/amount of a substance, product or activity.

14

4.2 ENVIRONMENT – ALUMINIUM IN EVERYDAY USE

Space Frame One of the modern technologies used in the manufacture of car bodies is the Space Frame, a skeleton of aluminium profiles. Covering the frame with aluminium sheets gives weight reductions of up to 200 kg per car. This is double the saving cited on the previous page. As in other applications, replacing steel with aluminium reduces weight. Here, this leads to reductions in petrol consumption and emissions. Other plus points are improved crash-safety, reduced risk of corrosion and decreased environmental load.

4.2.2 Underground railway carriages Nearly all modern underground railways use carriages with bodies constructed of longitudinally welded aluminium profiles. In Japan, analyses of real energy consumption have been carried out on the Chiyoda line. The analyses compared the line’s steel-carriaged trains with those having aluminium-bodied carriages. In the latter, 9,450 kg of steel is replaced by 4,000 kg of aluminium. 4,000 x 37.2 2) 9,450 x 9.5 2)

Energy consumption in the production process 1)

Aluminium Steel Difference

Energy consumption during two years of operation

Steel carriages Aluminium carriages Difference

1)

2)

No recycled metal used.

3)

= 148,800 kWh = 89,775 kWh 59,025 kWh

3)

561,200 kWh 489,900 kWh 71,300 kWh

Consumption as estimated by Sapa Technology. 1 kWh = 3.6 MJ.

15

4.2 ENVIRONMENT – ALUMINIUM IN EVERYDAY USE

Energy savings in less than two years Assuming no use of recycled aluminium or steel, the Chiyoda example shows that, in less than two years, aluminium carriages represent an “energy saving”. Similar real-life analyses in Atlanta (USA) and Germany have given figures of 3 and 1.6 years respectively as the times in which the extra energy used in production is recouped. When the use of recycled metals is taken into consideration, aluminium carriages are clearly more “energy-efficient” even at the production stage. The recycling of aluminium consumes far less energy than the recycling of steel.

4.2.3 Window frames In Austria, there has been a study in 1991 of the environmental aspects of the use of various materials (aluminium, PVC coated steel, wood and aluminium clad wood) in window frames. The results obtained using the EPS method are summarised below. – Calculated over the entire life cycle of the product, aluminium clad wooden frames present the lowest load on the environment. – In the production phase, wooden frames present unquestionably the lowest environmental load. However, this is more than nullified by the need for regular maintenance/replacement. – Aluminium frames are far superior to plastic coated steel frames. – Frames of plastic coated steel present the largest load on the environment. – The possibility of recycling aluminium with very little energy consumption is a significant factor in aluminium’s good performance.

16

4.3 HEALTH ASPECTS

Conclusion The use of aluminium in products such as window frames has clearly demonstrable benefits for the environment.

4.3 Health All normal forming and cutting of aluminium has no consequences for human health. However, if worksite ventilation is inadequate, lengthy periods of gas welding can have an effect on the respiratory organs. Before undertaking gas welding, current recommendations and regulations should be studied. Local health and safety bodies are usually able to provide help here. Friction Stir Welding (see pages 68 – 73 of this manual) does not use filler metals or shielding gases. This avoids the problem outlined above. Aluminium is non-toxic All life on Earth is adapted to its presence – aluminium has always been a natural part of the environment. The soil contains, on average, 7% aluminium (by weight). The use of aluminium products, whether untreated or anodised, presents no health hazards. As an illustration of this, aluminium has been used for decades in kitchen pots and pans. At one time, aluminium was cited as a possible cause of Alzheimer’s disease. However, the leading medical scientists of today consider that there is no such link. It is also worth mentioning that our normal diet includes aluminium. Food and food additives account for roughly 97% of our daily intake of approximately 12 mg. The remaining 3% comes from aluminium products such as kitchen foil and cooking vessels.

Aluminium in the diet: 97% from foodstuffs, 3% from food preparation.

17

5. THE APPLICATIONS

5. Aluminium profiles

– the applications The purpose of this manual is to give its readers an insight into optimum design using aluminium profiles. Further details and concrete advice are readily available from Sapa. Whatever the field Whatever the field of operation, it seems that aluminium profiles have something to offer. The transport industry makes extensive use of aluminium profiles in lorries, buses, cars, trains, ships, etc. With increasing demand for lighter vehicles that consume less fuel and place less strain on the environment, the use of profiles is constantly rising. The benefits are clear. Other sectors of industry have also seen the advantages. Profiles are being used in all types of design solutions. Examples include machine parts, a wide range of products for everyday home and office use and equipment used in free time activities. In the electronics industry, aluminium profiles are used in heat sinks, casings, front plates and so on. The building industry uses aluminium profiles in, amongst other things, doors, windows, fascias and glass roofs. The list of Furniture/office Other Transport 39% sectors and applications is long. equipment 8% 10% In all sectors, the demand for recyclability is Building growing ever stronger. No structural material can 24% be more profitably recycled than aluminium. This Electronics Machine parts factor is sure to acquire increasing significance. 10% 9% Aluminium profiles will become more common End use of the aluminium profiles in all industries. In some respects, the use of produced in the Nordic countries in 2000. aluminium and extrusion has really only just begun.

18

5. THE APPLICATIONS

The advantages of aluminium and extrusion More and more constructors and designers are realising the advantages of extrusion – the freedom it gives them to create precisely the shape that solves the problem, low tooling costs, easy machining, purpose-tailored surface treatment, etc. Furthermore, extrusion technology continues to develop and new production methods such as Friction Stir Welding and hydroforming are adding still further to the possibilities opened up by aluminium profiles. On top of all this, aluminium has a host of unique structural properties. Simply put, aluminium profiles facilitate the creation of efficient designs at competitive prices – exactly the right conditions for new products on new markets.

Profile use is increasing in line with the demand for reduced energy consumption and minimum stress on the environment.

Young metal, young industry The electrolysis of alumina to produce aluminium was first achieved in 1886. This was the major breakthrough that eventually led to the commercial production of aluminium products. By the turn of the century, world production of primary aluminium had reached around 5,700 tons. In 2001, highlighting the importance of aluminium in modern industrial production, the figure was approximately 24.5 million tons. To give some idea of scale, 24.5 million tons is the combined weight of something over 18 million Volvo S40s. In Sweden, the first attempts to extrude aluminium were made in the middle of the 1920’s. Still in Sweden, it was in 1937 that Metallverken, a company in Finspång, started regular production of profiles. At the same time, Saab began production of aeroplanes in Linköping. Over the next few years, and reaching a peak at the end of the Second World War, Saab made extensive use of aluminium. Since the late 1940’s, the consumption of aluminium and aluminium profiles has risen steadily as shown in the graph below.

MIO Tonnes 30

25

World Production of Primary Aluminium 1950 – 2002

20

15

10

5

0

1950

2002

19

6. EXTRUSION PRINCIPLES

6. Extrusion principles Extrusion starts with aluminium alloy logs. These are cut into billets, which then go into an induction furnace for heating to the right extrusion temperature of 450 – 500°C. Next, applying considerable pressure, each heated billet is forced through a die, the profile emerging rather like toothpaste from a tube. The profile emerges at a speed of 5 – 50 metres per minute and length is normally between 25 and 45 metres. Cooling in air or water commences immediately the profile leaves the die. After cooling, the profile is stretched. This is both to relieve any stress and to give the profile the desired straightness. At the same time, all functionally important dimensions and surface quality are checked. The profile is then cut to a suitable length or to the exact length requested by the customer. The final strength of the material is controlled through natural or artificial ageing. Dies Dies are made of tool steel (normally SIS 2242). The die aperture, which corresponds to the desired cross section of the profile, is produced by spark erosion. Sapa both makes its own dies and buys in from independent manufacturers.

Billets are heated to the right temperature in an induction furnace.

20

6. EXTRUSION PRINCIPLES

Two main classes There are two main classes of profile – solid and hollow: Solid profiles are produced using a flat, disc-shaped die. Hollow profiles are produced using a two-part die. In hollow dies, the mandrel (the part that shapes the cavity in the profile), is supported on a bridge. During extrusion, the metal separates around the bridge. The other part of the die shapes the outer contour of the profile. Large and medium-sized profiles are pressed through a die with only one aperture. Smaller profiles can be advantageously pressed through multi-apertured dies – there may be as many as 16 apertures. Die lifetime depends on the shape and desired surface quality of the profile. The cost of replacement dies is covered in the price of the profile.

Dies for solid profiles.

A hollow die.

A profile emerging onto the cooling table.

Stretching relieves profiles of any stress or twisting.

21

7. ALLOYS

7. Choosing the

right alloy Pure aluminium is relatively soft. To overcome this, the metal can be alloyed and/or cold worked. Most of the aluminium reaching the marketplace has been alloyed with at least one other element. Sapa uses a long-established international system for identifying aluminium alloys (see the table below). The first digit in the four-digit alloy code identifies the major alloying element. The European standard uses the same codes. The table below gives the broad outline of the systems.

The 6000 series is by far the most widely used in extrusion.

Alloying element

Alloy code

Alloy type

None (pure aluminium)

1000 series

Not hardenable

Copper

2000 series

Hardenable

Manganese

3000 series

Not hardenable

Silicon

4000 series

Not hardenable

Magnesium

5000 series

Not hardenable

Magnesium + silicon

6000 series

Hardenable

Zinc

7000 series

Hardenable

Other

8000 series

As cold working is the only way to increase the strength of the alloys that cannot be hardened, most of these go for rolling. In extrusion, on the other hand, hardenable alloys are the most commonly used. The 6000 series, which has silicon and magnesium as the alloying elements, is by far the most widely used in extrusion. In Sapa’s 7021 alloy, zinc and magnesium are responsible for the hardening effect. Some alloys use manganese, zirconium or chrome to increase toughness. Iron, which is found in all commercial aluminium, can have a negative effect on toughness and finish (amongst other things) if present in high quantities.

22

7. ALLOYS

Heat treatment Apart from 1050A, all Sapa alloys are hardenable. Their final strength is thus determined by solution heat treatment and ageing (precipitation hardening). Solution heat treatment is normally carried out during extrusion by carefully controlling the temperature of the emerging profile. Precipitation hardening, which takes a few hours, occurs afterwards in special furnaces. In some circumstances, it may be necessary for the customer to carry out heat treatment. Sapa’s recommendations in these cases are given in the table on page 25. Natural ageing is the spontaneous hardening of solution treated aluminium at room temperature (refer to the table on page 25). Choosing the right alloy Amongst the factors affecting the choice of the right alloy for an extruded product are: – Strength, finish, suitability for decorative anodising, corrosion resistance, suitability for machining and forming, weldability and production costs. The at-a-glance table on the next page should only be used as a rough guide. In cases of doubt, contact Sapa for advice and guidance. For example, optimum cost-efficiency may sometimes be gained by choosing a comparatively lower strength alloy with higher extrudability.

In cases of doubt, contact Sapa for advice.

Logs being prepared for extrusion.

23

7. ALLOYS

At-a-glance alloy selection Relative grading: 3 = top mark

Sapa Sapa Sapa Sapa Sapa 6063 6063A 6005 6005A 6082

Sapa 7021

Sapa Sapa 1050A 6101

Sapa 6463

Tensile strength

1

1

1

2

2

2

3

0

1

1

Impact strength

3

3

3

1

2

2

2

3

3

3

Surface finish

3

3

3

2

2

2

1

3

3

3

Suitability for decorative anodising

3

3

3

2

2

1

1

2

3

3

Corrosion resistance

3

3

3

2

2

2

1

3

3

3

Machinability: cutting forming

1 3

2 3

2 2

2 2

2 2

2 2

3 2

0 3

2 3

2 3

Weldability

3

3

3

3

3

3

3

3

3

3

Price

3

3

3

2

2

2

2

3

3

3

Suitable alloys for anodising Refer to 15.3, “Anodising”.

24

Bright anodising

Sapa 6060

Electrical conductors

Common construction alloys

Property

High-strength constructions

Special alloys for

7. ALLOYS

10 50 Sa A pa 61 01 Sa pa 64 63

70 21

Sa pa

380

400- 380- 380-

(380-

420

420

420

450

420)

a)

b)

420

Sa pa

82

A 60

05 Sa pa

380- 380- 380- 380-

420

420

Sa pa

60

05

A 60

63

380-

420

Sa pa

60

63 60

Sa pa

Sa pa

Soft annealing: Rapid full through heating, followed by approx. 30 min. at stated temperature. Cooling should be slow and, down to 250°C, preferably in a furnace. After that, free cooling.

Sa pa

60

60

Heat treatment recommendations

420

c)

Solution heat treatment: Rapid full through heating, followed by 15 – 30 min. (depending on wall thickness) at stated temperature. Forced air-cooling (fan) if wall thickness under 6 mm. Water cooling where over 6 mm. Cooling speed, 1 – 2°C per sec.

510

510

530

530

530

535

460

–

530

(510

±10

± 10

± 10

± 10

± 10

± 10

± 10

–

± 10

± 10)

d)

e)

Natural ageing: Occurs spontaneously at room temperature. Temper T4 achieved in stated number of days.

2

2

30

Artificial ageing: Heat to the stated age hardening temperature (°C). Hold there for approx. 8 hours. After that, free cooling.

2

2

2

2

175

175

175

175

175

175

±5

±5

±5

±5

±5

±5

c) –

– f) g)

2

2

175

175

±5

±5

a) Cool to 220 – 230°C in a furnace. Hold at this temperature for 4 – 6 hours. After that, free cooling. b) Coarse grain structure may form (a coarse-grained structure decreases strength and gives a poorer finish after anodising). c) Sapa 6463 should not be soft annealed and subjected to solution heat treatment. This lessens the material’s suitability for bright anodising. d) To be cooled quickly (usually in water). When cooling, the material must be moved quickly from furnace to water (approx. 10 sec.). e) The cooling rate in the critical range, 400 – 200°C, should be at least 1°C per sec. It must not exceed 5°C per sec. Rates above this may cause stress corrosion. f) Artificial ageing can be 100°C (± 5°C) for 4 hours + 150°C (± 5°C) for 8 hours. g) For maximum strength, a break of at least 72 hours between solution heat treatment and artificial ageing is required.

Heat treatment alters alloy properties. The picture above shows temperature control during solution heat treatment. 25

7. ALLOYS

Common Construction Alloys Alloy data as per EN-755-2 Alloy designations European standards: numerical notation chemical notation 1) USA: Aluminum Association Swedish standards:

Sapa 6060

Sapa 6063

Sapa 6063A

Sapa 6005

Sapa 6005A

EN-AW-6060 AlMgSi

EN-AW-6063 AlMg0.7Si

EN-AW-6063A AlMg0.7Si(A)

EN-AW-6005 AlSiMg

EN-AW-6005A AlSiMg(A)

AA 6060

AA 6063

AA 6063A

AA 6005

AA 6005A

SS-EN-AW6060

SS-EN-AW6063

SS-EN-AW6063A

SS-EN-AW6005

SS-EN-AW6005A

Alloy data Temper

T4 2)

T6

T4 2)

T6

T66 F25

T4 2)

T6

t a 25 60

ta3 150

t a 25 65

t a 10 170

t a 10 200

t a 25 90

t a 10 190

ta5 225

ta5 215

ta5 225

ta5 215

10 < t a 25 160

10 < t a 25 180

10 < t a 25 180

5