Aluminium Extrusions - Technical Design Guide

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ALUMINIUM EXTRUSIONS

—

_a

_{technical design guide}

For

free,

_{objective advice}

on

all

matters relating

to

aluminium extrusions

contact:

The

Shapemakers Information Service Broadway House Calthorpe Road Birmingham

B151TN

Tel: 021

4562276

Fax: 021

4562274

ALUMINIUM EXTRUSIONS

—

_a

_technical

design guide

PUBLISHED

BY THE

SHAPEMAKERS

—

_the

_{information arm of the UK Aluminium Extruders Association}

©

The _Shapemakers Broadway House Calthorpe Road Birmingham B151TN DISCLAIMER

This book

is

intended _{for use by technically} skilled personnel. The use

of

the information contained herein _{by such technically skilled personnel,} is at the risk of the user. While all reasonable skill and care has been exercised in the _preparation of this book, there are no warranties, express or _implied, as

to

the _accuracy or completeness

of

this _{work, either by the} author or the _{publisher, both}

of

whom _deny responsibility

or

liability for any results _{obtained or damages} caused as

a

_consequ- ence

of

the use _{thereof .The publisher and} the author hereof _{grant no} licence with this book and disclaim all _liability

_for

_{suitability, practicability, infringement} of _property rights

of

third parties

or

non-conformance with any codes, standards

or

regulations.

ACKNOWLEDGEMENT TO BSI

Extracts from British _{Standards are reproduced} with

the

permission of BSI. Com- plete copies

of

the Standards can be obtained _{by post from BSI Sales, Linford Wood,} Milton Keynes, MK1

4

6LE.

First published October _{1989 Reprinted July} 1991 _{Reprinted August} 1994

Printed

in

Great Britain _by

St

Edmundsbury Press Ltd

PREFACE

to

the 1994

_reprint

—

_{by Howard Spencer}

Since this manual was _{originally published, British Standards} have _published

a

new aluminium structural code, BS 8118 1991, which _supersedes BS CP118 1969:

— _{Part 1: Code of} Practice

for

Design

— _Part

_2:

_{Specification for Materials, Workmanship and Protection}

There _{is at present}

a

_change-over period where both design codes are valid, but at some time

in

the future BS CP118 will be withdrawn. This new code is intended to bring aluminium structural design into line with other metals and also with European standard codes, which will simplify future preparation of an overall European structural code for aluminium.

I intend here to _{give users}

of

the manual

a

_very brief outline

of

how the new codes will

affect the use

of

aluminium. It is impossible to go into too much detail. Those requiring additional information should refer to the codes themselves, available from British Standards (see address below).

The New Code

The new code is based around

a

new design approach, based on the principle of 'limit state design'. This principle is concerned with ensuring that any given structure can _carry the loads and forces placed upon

it

without failure, up

to

a pre-determined limit. The factored resistance

of

a

structure must therefore never be less than the factored loading. The _{following equation can be applied:}

Y12R

=

Y4S

=

overall resistance factor R

=

calculated resistance

=

_{overall loading factor}

S

=

maximum _design load

The resistance is calculated from the effective sectional properties, the limiting stress and

a

material and connection factor. The loading effect is factored for type of load, i.e. dead load, imposed load, wind load and temperature induced forces. The new code also covers the calculation of elastic instabilities. Aluminium sections with _very wide, thin elements are susceptible

to

local buckling under _{high compres-} sive stresses. The relevant calculations have been simplified in the new code by adopting

a

classification system based upon a factored relationship between the width or _depth

of

the element and the thickness. Three categories are listed for moment resistance — _{compact, semi-compact and slender.} For _{compact sections,}

no further check is _{required as they will} not suffer from _{local buckling. (For example,} afl the sections listed in BS 1161 "Aluminium _{Structural Sections" are compact.)} Semi-compact resistance is obtained by using

the

quoted limiting stress

of

the material. Sections defined _{as slender,} however, are assessed on the basis

of

a reduced effective wall thickness and the extent

of the

reduction can be obtained from a series

of

curves. Only the _{compact and slender categories} are allowed when calculating the axial resistance

of

struts.

The recommendation

for

deflection levels has not _changed, but

a

word of caution is included in the _{specification against imposing} too tight

a

standard on aluminium structures _{when the particular application} does not merit it.

The section on _welding has _{been greatly extended} from that

in

the _{original code.} Guidance is provided on

the

design of welds taking into account the strength

of

the weld metal and a _{partial reduction in strength in} the heat affected zone of the parent metal. The _limiting stresses for both filler _{and parent metal} are _{given with} factors for designing butt and lap joints for both traverse and longitudinal welds.

Adhesively bonded joints are only recommended for _{secondary stressed connec-} tions. The factored resistance

of

a

bonded joint can be calculated from _{an expres-} sion containing

a

failing standard, obtained from testing, and a material connection factor for bonded joints, If validated test data is available,

it

can be used in the _joint resistance expression.

The section on _fatigue has _{also been greatly extended, incorporating information} from both UK _{and European research.} The tables for both welded and non-welded structures contain detailed sketches illustrating the type of construction, direction of stress, fluctuation and possible crack locations. The tables are based upon BS 5400 Part 10: Bridges and give

the

classification for

a

range

of

structural detail.

Full supporting data _{including mathematical formulae} relevant

to

the _{design calcula-} tions and curves used in the code are set out in the _appendices of the new code and can be used to assist _{computer aided design.}

All references in the manual to BS CP1 18 now apply to BS 8118 and, as

the

new code does not cover _permissible stress levels, table 3.2 and figure 3.3 are not applicable. Tables 3.4 and 6.11 have also been modified as the standard elastic modulus for all _wrought aluminium _{alloys is} now 70,000 N/mm2

Reviewing the worked examples given in the manual,

the

pedestrian balustrade (pages 113—122) results

in

marginal modifications to some sections when worked to the new _{code but gives} similar overall results. In the case

of

the _{unloading ramp,} however (pages 111—112) there could be

a

slight saving

in

the thickness

of

the section when meeting the new code. The _{column example (pages 123—125) refers} to alloy 2014 AT6 which is _{no longer}

a

standard material

in

the new _{code. Although it} can _{be used,} the limit state stresses would have

to

be _{established and,}

in

this case, the section thickness would have

to

_{be slightly} increased.

Competently used, the old code should still give an acceptable level of design. It should be noted, however, that if the calculations are to be officially approved then only the new code is valid. Furthermore, the up-dated information

in

the new code can result in

a

more economical structural use

of

the material.

Codes referred to: BS 8118 Part 1: 1991 Code

of

Practice for _Design BS _{8118 Part 2: 1991 Specification} for Materials,

Workmanship and Protection These are available from:

Sales Dept, BSI, Linford Wood, Milton Keynes, MK14 6LE, or any HMSO.

INTRODUCTION

Aluminium is a _{highly versatile, light and} strong material which can be _produced

in

a variety

of

alloys and extruded into an almost infinite number

of

shapes. This powerful combination of factors enables the user to be more innovative and facilitates cost- effective design.

Comprising 8%

of

the earth's crust, aluminium

is

a plentiful resource. It is a modern material, first used

in

commercial production

in

1886. Since then, the list of applications has grown immensely. Now, designers working in

a

whole range of different sectors, including general engineering, construction, transport, packaging and _{consumer products,} are _reaping the _{benefits gained} by using aluminium extrusions.

The _Shapemakers was established _{by the} Aluminium Extruders Association (AEA) in 1984 to provide independent guidance on all matters relating

to

extruded aluminium. Representing

the

UK's top extrusion companies, The _{Shapemakers is} able

to

draw _upon these _{companies' considerable resources and expertise.}

This _{technical design guide contains}

a

wealth of information on aluminium itself, as well as _{giving details} on the _{extrusion process, fabrication and finishing. Also} included is

a

comprehensive design section, which outlines

the

important design considerations and shows

a

number

of

_{worked examples.}

For reasons

of

_clarity, only

six

alloys have been incorporated into

the

main body of the manual. These _{have been carefully selected}

to

illustrate the various uses of alloys — from general purpose

to

high strength. Additional alloys are listed

in

the appendices. For details

of

the availability

of

any alloy listed in this _{manual, please} contact the Shapemakers Information Service

in

Birmingham, Tel: 021 456 2276.

The AEA would like

to

thank The _{Shapemakers' technical consultant, Howard} Spencer, for all his work in compiling this design guide.

A

special thanks also goes to The _{Shapemakers' members, Hugo Ravesloot,} Jim Peach and Chris Forman.

Derek Phillips

CONTENTS

PRINCIPLES

OF

EXTRUSION

1

MATERIAL SPECIFICATIONS

25

MECHANICAL PROPERTIES

33

DURABILITY

45

SURFACE FINISHING

55

FABRICATION

63

CONDUCTIVITY

87

TEMPERATURE

93

FIRE

97

CARE AND CONTROL

101

DESIGN

105

GLOSSARY

OF

TERMS

127

ALUMINIUM EXTRUSIONS

—

a

_{technical design guide}

SECTION 1

-

PRINCIPLES OF EXTRUSION

CONTENTS

Title _{Page No.}

EXTRUSION PROCESS 4 Direct Extrusion 4 Indirect Extrusion 5 Hollow Sections 6 EXTRUDABILITY 7 Extrusion Ratio 7 Shape Factor 7 SIZE 8 THICKNESS 8 SLOTS 10 SECTION CLASSIFICATION 11 CORNERS 11 TOLERANCES 12

List

of

Figures

Fig No. Title _{Page No.}

1.1 The Direct Extrusion Process 4 1.2 The _Differing Operating

Principles of Direct

and Indirect Extrusion 5

1.3 Extrusion of a Hollow Section 6

1 _{.4 Thick to Thin Transitions} in

Extrusion Cross Section 10

1.5 _{Pressure Hinge} 10

1.6 Slot _{Aspect Ratios} 10

1.7 _{Standard Section Types} 11

List of

Tables

No. Title _{Page No.}

1.1 _{Shape Factor} Value 8

1.2

A

Guide to Minimum Thickness 9 1.3 Tolerances on Diameter of Round

Bar Intended for use on

Automatic Lathes 12 1.4 Tolerances on Widths Across

Flats

of

Hexagonal Bar for the

Manufacture

of

Nut & Bolts 13 1.5 Tolerances on Diameter of

Round Bar in the Controlled

Stretched Condition 13

List of

Tables (contd.)

No Title _{Page No.}

1.6 Tolerances on Diameter or Width

Across Flats of Bars for General Purposes and on Width

of

Solid or Hollow Regular Sections 14

1 .7 _{Angular Tolerances for}

Extruded Regul& Sections 15 1.8 Permitted Corner Radii 15

1 .9 _{Tolerances on Wall Thicknesses}

of Extruded Round Tube

(classes A, B and C). 16

1.10 Tolerances on Thickness of

Bars and Regular Sections 17

1.11 _{Tolerances on Open End of}

Channels and L Beams 18/19

1.12 Tolerances on the Outside

Diameter of All Extruded Round

Tube and on the Inside Diameter

of Class

A

and Class B Extruded

Round Tube 20

1.13 Tolerances on Thickness of

Hollow Sections (classes A and B) 21

1 .14 _{Tolerances on Straightness for}

Extruded Bar, Regular Sections

and Extruded Round Tubes 22

1.15 _{Tolerances on Length} for All

Materials Supplied in Fixed

Cut Lengths 23

1 .16 _{Tolerances on Concavity}

and Convexity for Extruded

EXTRUSION PROCESS Direct Extrusion

The direct extrusion process can be clearly seen in the schematic diagram in Fig. 1.1.

Cylindrical aluminium alloy billets of cast or extruded manufacture are heated to between 4500 and 500° before being loaded into

a

container and the billet squeezed through a die orifice using ram _pressures of _up to 68OMPa. The die is _{supported by} a

series of back dies and bolsters so _{that the main press load is transferred} to

a

front

platen.

Fig. 1.1

-

The Direct Extrusion Process

4

Platen Ram cross head

Stem Liner Die slide Dummy block Container Billet Die Backer Sub bolster Extruded section

On _leaving the die _{the temperature} of the section is more than 500°C and with heat

treatable afloys the _quenching, or solution heat treatment, takes _{place in} the

production line. This can be by water bath, water spray or forced-draught air, with the latter being particularly useful for thin sections. The _{approximate temperature drop} during the traverse of the quench box is 250°C. To avoid distortion care has to be exercised in handling sections with extreme aspect ratios and large variations in

thickness.

After extrusion the section is guided down the table _{by a puller on} to a slatted moving

belt. Modern Pullers are based on linear motor _{s,stems and operate} on _{tables up to} 40 _{metres long. On completion} of _{an extruded length,} the section is sheared at the press end and lifted from the slatted table by eccentric pivoted arms. It is then transferred _{by a walking beam} or multi-belt transfer table to the _{stretcher bay where} it is given

a

controlled stretch to _{straighten and remove minor mis-alignments. The} section is then taken and cut

to

ordered lengths on _{high speed tungsten carbide} tipped saws.

If the material is _{required in} the _{solution heat treated condition (T4) it} is released at this stage. If the full _{strength aged material (T6)} is _{required, it is given} a _{precipitation} treatment before release. In the case of _{the T5 temper, there} is _{limited cooling} at the press exit and the material goes directly to _{precipitation treatment.}

Indirect Extrusion

In the traditional direct method of extrusion, as described above, the die is _stationary and the _{press ram applies pressure on} to the billet. In the indirect method, the ram

carries the die _{and applies pressure on} to the _{stationary billet, in} the _{opposite direction} of extrusion. There can be variation to _{this basic concept, but in every case the} billet

remains stationary in relation to the _{container, thereby keeping friction loss} to a bare minimum. See Fig. 1.2. Die

-

Extrusion Die Billet Extrusion Indirect extrusion Die Billet

Hollow Sections

A _bridge or _'port-hole die' _{is usually used} to make hollow sections. A solid billet is forced, under pressure, through a _composite die tool that first divides the metal into two or more separate streams which then flows down under the bridge to be pressure welded together and emerge, as an extruded section, through the orifice formed between the mandrel nose and the outer section shape which has been cut in the die. See Fig. 1.3.

Any sample taken across the section would show an integral material quality with no reduction

of

_{strength in} the _{weld areas. Inspection methods are usually by} destructive test _sampling

in

line with that laid down by the British Standards for scaffold tubing in

specification BS 1139. Production methods for this kind of section are well established and extruders will be _pleased to advise on the _feasibility of _{producing any hollow}

section.

Some caution must be exercised, however where thin hollow sections are required in

the stronger alloys, particularly from the _bridge or _{port-hole production methods. Hollow} sections are usually produced in these alloys by using centre mandrels that are not

connected

to

the die _{but are passed through} a bored

or

pierced hole in the centre of the billet and either connected or _{supported by the press} rod. _{In this type} of _{production, the}

metal flow around the _{mandrel is not interrupted and} there are no extrusion weld planes in the _{section. There may} be some restriction in the _availability

of

this type of _production and in the range of sections obtainable from it. As the standard of _{tolerances may} also

be wider further information and advice should be _{sought from the extruder}

for

_strong

alloy hollow sections.

Pressure

Fig. 1.3

-

Extrusion

of

a

Hollow Section

6

area

EXTRUDABILITY

Aluminium alloys offer

a

wide range

of

performance characteristics and important amongst these is its extrudability. Linked with modern die-making facilities and

traditional expertise the metal offers a _{virtually unlimited variety} of section shapes. The feasibility of any extrusion has both technical and commercial considerations and most extruders use a number of methods to _{evaluate extrusion complexity. These} methods

are usually based upon a combination of _{extrusion theory and} experience.

Extrusion Ratio

Extrusion ratio is the value obtained _{by dividing the cross-section} area of the extrusion

billet _{by the} cross-section area of the extrusion to _{be produced.} It _{depends very} much

on the size and type of press available and is

a

factor that can only be considered by the extruder. Optimum extrusion ratios for _{direct extrusion are usually between} 30 and 50.

With low values of 7 or under, there is very little working of the material during extrusion. This gives a _{corresponding drop in mechanical properties and} the _possibility of coarse

grain bands. Values

of

80 and above require high breakthrough pressures which are

likely

to

cause die distortion and possible breakage.

In some cases the extrusion ratio can _{be improved by using} a multi-hole die. In the case of _{indirect extrusion much higher extrusion ratios are possible because} of the relatively

low frictional force developed in the system.

Shape Factor

The resistance of a section to extrusion can be influenced _{by the shape factor. This is} the _{relationship between the periphery and cross-section} area

of

the section being extruded. It is usual for extruders

to

_modify the _{shape factor value, in terms} of extrusion

weight, by dividing the periphery by the cross sectional area and multiplying by .0027.

The _{shape factor of} a _proposed extrusion is _{usually compared with that} of

a

similar

existing extrusion

to

obtain

a

measure of extrudability. This is not a precise method, however, as any large difference in wall thickness can _{alter the ratio substantially.} In

general, the higher the value the more difficult the extrusion and the more limited the alloy choice thereby restricting some high strength alloys. Table 1 .1 sets out some

Table 1.1

-

_Shape Factor Values

Section _Type CCD Thickness _{Shape Factor}

mm mm

L

142 2.5 300

L

70 1.5 500

I

112 5.0 152

O

142 solid 15

O

70 solid 30

©

50 3.0 247

©

50 1.5 494

ltiiiiiil

_{210 3.0 190} 210 2.0 285

Iii

11J 140 2.0/6.0 183 I-

I

40 2.0/1.5 430 SIZE

The size of an extruded shape is determined by the diameterof the circumscribing circle (CCD) required to enclose the cross-section. The maximum CCD for _any die size is

governed by the need to _{keep an unbroken structural ring around} the die orifice.The minimum width

of

_{that ring can vary from 20 mm on an average size solid} die

to

60 mm

or more on dies for _{large hollow sections. Most average sections}

fit

into CCDs below 155 mm with

a

medium range of _{250 mm and very large sections up}

to

400 mm.

The section, should, as far as _{possible, be distributed around} the centre of the CCD. In _{any extrusion, metal} flow _{is slower towards the outside edge} of the die so _{the placing} of _{thicker parts} of the _{section away} from the centre results in a more even metal flow. THICKNESS

Factors that dictate thickness are influenced _{by section shape, alloy,} die face _pressure, extrusion speed and section stability during solution heat treatment and post-extrusion handling.

A

general guide to minimum thickness is given in Table 1.2 which is based

on 6063 material.

E E I- 0) 0) C-)

r

0) 0)

Table 1.2

- A

Guide

to

Minimum Thickness

C C D in mm

a) Values for 6082 should be increased by 25%

b) These thickness

-

GCD ratios represent average values based upon good working

practice.

c) The values up to 1 .25 mm thick are for _{small specialised presses with very high}

die _{face pressure} levels.

d) When ratios below those shown are required contact extruders.

The _{extrusion process will tolerate variations} in section thickness but it is important to avoid abrupt change. Acceptable transition between thicknesses can be _{obtained by} using radii or blending curves, see Fig. 1 .4. Short spans

of

local thinning can also be

incorporated in most sections. This is

a

useful method

of

introducing pressure hinges in section elements which will be _{deformed during subsequent fabrication, see Fig.} .5.

p

p

I

Thin hinge

Radius / —

Fig. 1.4

-

Thick

to

Thin Transitions in _Fig. 1.5

-

Pressure _Hinge Extrusion Cross-Section

SLOTS

The formation

of

slots,

or

open box channels, in a section requires a finger or box spigot

to be retained on the die. As

it

is _{not possible} to _{reinforce these spigots, which} act as local cantilevers under extrusion pressure,

a

practical limit must be placed on the size and type of _{slots available. Fig.} 1.6 details the normal method of calculating slot aspect ratios although where gaps are below 3 mm these ratios are even further reduced. The

maximum ratios are 3:1. Higher values are possible, particularly in 6063 alloy. Screw

ports and bolt slots are detailed under these headings in section 6 Fabrication.

—

Gap

—

Depth

___

_____

Width

Area Depth

Aspect Ratio =

—

Aspect Ratio =

—

Gap2 Width

Fig. 1.6

-

Slot Aspect Ratios.

SECTION CLASSIFICATION

There are three _{standard types} of section

-

solid, semi-hollow and hollow. The first and

last are self-explanatory. Semi-hollow describes those solid sections which have _open

box recesses with aspect ratios (depth/width) less than three. In general, the tooling and production costs increase with section categories from solid

to

semi-hollow and then hollow.

Solid Semi-hollow Hollow

Fig. 1.7

-

Standard Section _Types

CORNERS

All corners are normally broken by a radius but _{where absolutely necessary, sharp} corners can _{be incorporated in}

a

_{section either internally} or _{externally but the} life of the

die and the _speed

of

extrusion are both markedly reduced. Such corners also introduce problems where painted finishes are specified, introducing obvious sight lines. The

breaking of the corners, even by 0.5 mm radii is helpful in overcoming these problems

but for ideal extrusion conditions, radii should be related to the overall size of the

TOLERANCES

Tolerance levels for regular sections are laid down in BS 1474, however as the bulk of extrusions are non-standard they are not covered in the standard. The extrusion

industry regards BS 1474 as a target level and is prepared

to

accept

if

for all general business, apart from very thin or _{complex sections which} will be the subject of special

enquiry. Closertolerances can be obtained for some sections but, again, this is

a

matter between customer and extruder.

In _{line with most production methods, tolerances are necessary}

_to

cover variations in

the actual process and wearing of tools and dies.

Most tolerances are quoted as _{plus or minus around} a datum value but,

if

required,

unilateral tolerance can be obtained, either all positive or all _negative. It is essential, however, to _{agree this requirement before} die manufacture is commenced as the

dimensional datum of the die will be altered.

All tolerances should be measured at 160G. This is _{particularly significant} forthe length

tolerances

of

long bars.

There is no laid-down standard for the surface smoothness or texture

of

mill finished extruded sections.

Table 1.3

-

Tolerances

on

Diameter

of

Round Bar Intended for use

on

Automatic Lathes

Diameter

Plus and minimum tolerances on diameter Over Up

to

and including mm 10 18 30 40 60 80 100 mm 18 30 40 60 80 100 160 +mm -mm 0.05 0.10 0.08 0.13 0.14 0.14 0.20 0.20 0.30 0.30 0.40 0.40

±

0.5% of _{specified diameter} 12

Table 1.4

-

Tolerances on Width Across Flats

of

_Hexagonal

Bar

for

the

Manufacture

of

Nuts

&

Bolts

Width across flats

Tolerance on width across flats (all minus) Over Up

to

and Including mm mm mm

-

4.0 0.08 4.0 19.0 0.10 19.0 36.0 0.13 36.0 46.0 0.15 46.0 80.0 0.20

Table 1.5

-

Tolerances

on

Diameter

of

Round Bar

in

the Controlled Stretched Condition*

Diameter

Tolerances on diameter (plus and minus) Over Up

to

and including mm mm +mm -mm 10 18 0.05 0.20 18 30 0.08 0.26 30 40 0.14 0.28 40 60 0.20 0.40 60 80 0.30 0.60 80 100 0.40 0.80 100 180 0.5% of 1.0 % of specified specified diameter diameter

* The controlled stretch procedure reduces the level of any residual stresses in a bar and is ideal for _{machining stock. Special Tempers T6510 and T6511} refers.

Table 1.6

-

Tolerances on Diameter or Width Across Flats

of

Bars

for General _{Purposes and} on Width

of

Solid

or Hollow _{Regular Sections}

Diameter, width or

width across flats

Tolerances _{(see notes} 1 and 2)

Over Up

to

and including mm mm ±mm - _{3 0.16} 3 10 0.20 10 18 0.26 18 30 0.32 30 40 0.40 40 60 0.45 60 80 0.50 80 100 0.65 100 120 0.80 120 140 0.90 140 160 1.00 160 180 1.10 180 200 1.20 200 240 1.30 240 280 1.50 280 320 1.70

NOTE 1: Tolerances in this table apply to solid materials other than:

(a) round bar for use on automatic lathes (see table 1.4)

(b) controlled stretched bar (see table 1.6)

(c) hexagonal bars for the manufacture of nuts and bolts (see table

1.5)

NOTE 2: Tolerances _{in this table apply} to hollow regular sections

having a wall thickness not less than 1.6mm or 3% of the overall width,

whichever is the greater. In the case of non-heat-treated material or

1.6mm or 4% of the overall width, whichever is the greater, in the case

of heat treated material. The tolerance should be applied to the width

measured at the corners.

Table 1.7

-

Angular Tolerances

for

Extruded Regular Sections

Nominal thickness of

thinnest leg Allowable deviation from angle

specified (measured at

the

ex- tremitles

of the

section)

j- Over Up

to

and including mm mm - _1.6 2° 1.6 5.0 1.5° 5.0 - 1°

Table

1.8-

Permitted Corner Radii For square and _rectangular sections

Minor dimension

Radius on corner _(max.) Over Up

to

and Including mm mm mm - ₅ 0.4 5 10 0.8 10 25 1.6 25 50 2.5 50 120 3.0 120 - 5.0

For regular sections (e.g. angle, channel, I- and

I

-

sec- tions)

Thickness of

section Radius

on

corner (max.)

mm Up

to

and including 5 Over5 mm 0.8 1.5

Table 1.9

-

Tolerances on Wall Thickness

of

Extruded Round Tube (classes

A, B

and C) (see note 1)

Nominal

wall

thickness

of tube

Class A _{Class B Class C}

Toleranc on mean wall thickness Wall thickness at any point (Max.) (Mm.) Tolerano on mean wall thickness Wall thickness at any point Tolerance on mean Wall thickness at any point . (Max.) (Mm.) (Max.) (Mm.) . wall thickness mm 1.0 1.5 2.0 2.5 3.0 4.0 5.0 6.0 7.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 25.0 ±mm 0.15 0.16 0.17 0.18 0.20 0.23 0.26 0.28 0.31 0.34 0.40 0.46 0.53 0.58 0.63 0.68 0.74 0.81 mm 1.20 1.71 2.23 2.74 3.27 4.30 5.34 6.38 7.43 8.47 10.52 12.61 14.71 16.76 18.82 20.90 23.00 26.10 mm 0.80 1.29 1.77 2.26 2.73 3.70 4.66 5.62 6.57 7.53 9.48 11.39 13.29 15.24 17.18 19.10 21.00 23.90 ±mm - 0.18 0.20 0.22 0.27 0.31 0.37 0.43 0.51 0.56 0.65 0.77 0.88 1.00 1.13 1.22 1.35 1.49 mm - 1.74 2.27 2.80 3.36 4.42 5.49 6.58 7.67 8.76 10.85 13.03 15.24 17.34 19.44 21.63 23.81 27.00 mm - 1.26 1.73 2.20 2.64 3.58 4.51 5.42 6.33 7.24 9.15 10.97 12.76 14.66 16.56 18.38 20.19 23.00 ±mm - - - - 0.65 0.70 0.75 0.82 0.89 0.94 1.03 1.15 1.30 1.40 1.50 1.60 1.73 1.88 mm - - - 3.87 4.93 6.00 7.09 8.18 9.27 11.36 13.54 15.75 17.88 20.00 22.13 24.32 27.50 mm - - - - 2.13 3.09 4.00 4.91 5.82 6.73 8.64 10.46 12.25 14.12 16.00 17.88 19.68 22.50

NOTE 1: BS tolerance classes A,B and C for round tube denote a descending order of

tolerance standard. All classes applicable to 6063, 6063A, 6082, 6101A,

6463, Only Classes B & C are applicable to 2014A

NOTE 2: _{The tolerances given in this table apply} to non-heat-treated tube of wall

thickness not less than 1.6mm or 3% of the outside diameter, whichever is the

greater and to heat treated tube of wall thickness not less than 1.6mm or 4%

of the outside diameter, whichever is the _greater.

NOTE 3: These tolerances on wall thickness do not apply where tolerances on both

outside and inside diameter are required in which case the eccentricity

tolerance on the resultant wall should be agreed between the purchaser and

the supplier at the time of the enquiry and order.

NOTE 4: Mean thickness is defined as the sum of the wall thicknesses measured at the

ends of any two diameters at right angles, divided by four.

NOTE 5: The tolerance on the wall thickness of intermediate nominal wall thickness

should be taken as those of the next lower size.

Table 1.10- Tolerances on Thickness of Bars and Regular Sections Width across flats of bar or width of section Over Up to and Including Tolerances on specified thickness (plus and minus) Up to and Over Including 1.6mm 1.6mm up to and thick including 3mm thick Over 3mm up to and including 6mm thick Over 6mm up to and including 10mm thick Over 10mm up to and including 18mm thick Over 18mm up to and including 30mm thick Over 30mm up to and including 40mm thick Over 40mm up to and including 60mm thick Over 60mm up to and including 80mm thick Over 80mm up to and including 100mm thick Over 100mm up to and including 120mm thick Over 120mm up to and including 140mm thick Over 140mm up to and including 160mm thick mm - mm 10 mm 016 ± mm 018 ± mm 020 ± mm 022 ± mm - + mm - + mm - + mm - + mm - ± mm mm - + mm - mm - 10 18 018 020 022 024 026 . 18 30 022 024 026 028 030 032 - - - - - - . 30 60 0 24 0 26 0 28 0 30 0 33 0 36 0 40 - - . . 60 80 0 28 0 30 0 32 034 0 37 0 40 043 0 45 0 50 - - - - 80 120 032 034 036 039 042 045 048 052 057 065 080 - - 120 180 - 036 040 045 050 055 060 065 070 075 082 090 100 180 240 - - 050 055 060 065 070 075 080 085 090 095 105 240 320 - - 060 065 070 075 080 085 090 095 100 105 1 10 NOTE:- For sections over 160 mm thick, the tolerances on thickness are those shown for comparable widths (see Table 1.6)

Table 1.11 Tolerances on Open End Channels and L Beams Overall width Wof channel or i-beam Minimum thickness of web or flange Inlernal or exte,nai tolerance on open end dimension for various deplhs of opening D(pius and minus) For 0 For 0 For 0 ForD ForD For 0 For 0 For 0 For 0 For 0 For 0 up to and over over over over over over over over over over including 10mm 18mm 30mm 40mm 60mm 80mm 100mm 120mm 140mm 160mm 10mm up to and up to and up to and up to and up to and up to and up to and up to and up to and up to and deep including including including including including including Including including including including 18mm 30mm 40mm 60mm 80mm 100mm 120mm 140mm 160mm 180mm deep deep deep deep deep deep deep deep deep deep Over Up to and including Over Up to and including mm - mm 10 mm - 1.5 3.0 mm 1.5 3.0 - * mm 026 0.23 0 22 + mm 032 0.28 0.26 ÷ mm 0.41 0.34 0.30 + mm - • - * mm - • - + mm - • - + mm - - - * mm - - - + mm - - - + mm - - - + mm - - - 10 18 - 1.5 3.0 1.5 3 0 - 0.31 0 29 0.28 038 0.34 0.32 0.47 0 40 0.36 0.56 0.46 0.41 070 0.55 0.47 - - - - - - - - - - - -' - - - - - - 18 30 - 3.0 6.0 3.0 6.0 - 037 0.37 0.35 047 044 0.41 0.57 053 048 0.68 0.62 055 0.84 076 0.64 1.05 _{093 0} 78 126 1.11 091 - - - - - _- - - - - - - 30 40 - 3.0 6 0 3.0 6.0 - 0.45 0.45 0 43 0.55 0.52 0.49 0.65 0.61 0 56 0 76 0.70 0 63 0 92 0.84 0.72 1.13 1.01 ₀ 86 1 34 1.19 0.99 1.55 1.36 1.12 1 76 1,54 1.26 - - - - - - 40 60 - 3 0 6.0 3.0 6 0 - - - - 060 0.57 0.54 0.70 0 66 061 081 0.75 0.68 097 0 89 0,77 1.18 1 06 0.91 1.39 1 24 1.04 1.60 1.41 117 181 1 59 1.30 2.02 1.76 1 43 - - - 60 80 - 3.0 6.0 3.0 6.0 - - - - 0.65 0.62 0.59 0 75 0.71 0.66 0.86 0.80 073 1.02 0.94 0.82 1 23 1.11 0.96 1 44 1.29 1.09 165 1.46 1.22 1.86 164 1.35 2.07 1.81 148 2.28 1.99 161 80 100 - 6 6 - - - - - 0.90 086 1.01 ₀₉₅ 1.17 1.09 1.38 1.26 1 59 1.44 1.80 1.61 2.01 1 79 2.22 1.96 2.43 2.14 100 120 - 6 6 - - - - - 1.05 1.01 1.16 1.10 1 32 1.24 1.53 1.41 1 74 1 59 1.95 1.76 2.16 1.94 2.37 2.11 2.58 2.29 120 140 - 6 6 - - - - - 1.15 1.11 126 120 1,42 134 1.63 1,51 1.84 1.69 206 1.86 2.26 2.04 247 221 265 2.39 140 160 - 6 6 - - - - - 1.25 1.21 1 36 1.30 1.52 1.44 1 73 1.61 1.94 1.79 2.15 1.95 2.36 2.14 2.57 2.31 2.78 2.49

Table 1.11 (continued) Depth of Open end dlmens!on Flonqe Web Open 0 Depth of opeeng Overall width Wof Minimum thickness internal or external tolerance on open end dimension for various depths of opening D (plus and minus) channel or I-beam of web or flange or D For D For D For D For 0 For 0 For D For D For 0 For 0 For 0 Over Up to and Over Up to and up to and over over over over over over over over over over Including including IncludIng 10mm 18mm 30mm 40mm 60mm 80mm 100mm 120mm 140mm 160mm 10mm up to and up to and up to and up to and up to and up to and up to and up to and up to and up to and deep Including Including including including including including including including including including 18mm 30mm 40mm 60mm 80mm 100mm 120mm 140mm 160mm 180mm deep deep deep deep deep deep deep deep deep deep mm 160 mm 180 mm - 6 mm 6 - mm - - + mm - - + mm 1.35 1 31 + mm 146 1.40 + mm 162 1.54 + mm 183 1 71 + mm 204 1.89 + mm 225 2.06 + mm 246 2.24 + mm 2.67 241 + mm 288 259 180 200 - 6 6 - - - - - 1.45 141 1 56 150 1.72 1.64 1.93 181 214 199 2.35 2.16 256 2.34 277 251 298 269 200 240 - 6 6 - - - - - 1 55 151 1 66 160 1 82 1.74 2 03 191 2,24 209 2 45 2.26 2 66 2.44 2 87 261 3 08 279 240 280 6 - - - 1 71 180 194 211 229 246 264 281 299 280 320 6 - - - 1.91 2.00 2 14 232 2.40 2.66 284 3.01 3.19

Table 1.12

-

Tolerances on

the

Outside Diameter

of All

Extruded Round Tube and

on the

Inside Diameter

of

Class

A

and class B

Extruded Round Tube _(see note 1)

Outside _diameter,

or

inside diameter Tolerance on the actual diameter _(see notes 5 _{and 6)} Tolerance on

the

mean diameter _(see notes

5

and 6) Over Up

to

and Including mm 12 18 30 40 50 60 80 mm 18 30 40 50 60 80 300 ±mm 0.25 0.30 0.36 0.45 0.54 0.60 1%of diameter ±mm 0.19 0.23 0.27 0.34 0.40 0.45 314%of diameter NOTE 1. For _{details concerning}

the

applicability

of

tolerance class (A

or

B)

to

alloy, see 1.9.

NOTE 2. The tolerances are _applicable

to

non-heat-treated tubing

of

wall thickness

not

Iessthan 1.6mm or 3% ofthe out- side _diameter, whichever is

the

greater, and

to

heat-treated tubing

of wall

thickness not less than 1.6 mm

or

4

%

of

the outside _diameter, whichever Is the _greater.

NOTE 3. In the case

of

_tubing

in

straight lengths,

the

above tolerance

limits

are Inclusive

of

ovality.

NOTE 4. Where

a

tolerance on wall thickness

is

_{required, the} tolerances

on

diameter are

to

be applied either

to

the outside diameter

or

to

the Inside _diameter, but

not to

both.

NOTE 5. Tolerances

on

the actual diameter Indicate the amount by which the diameter _(inside

or

outside, as appro-

priate

measured

in

any direction may depart from

the

speci- fied diameter. Tolerances

on

the mean _{diameter (inside or} outside, as _appropriate) Indicate the amount by which the mean

of

two

diameters measured In

two

directions

at

right angles

in the

same plane may depart from the specified diameter.

NOTE _{6. The given tolerances}

on

the actual diameter

do

not apply

to

annealed _{tube, coiled tube,}

or

tube having a wall thickness less than 2.5 %

of

outside diameter. The toler- ances

of

these products and

of

controlled stretched tube are subject

to

agreement between purchaser and supplier.

Table 1.13- Tolerances on Thickness of Hollow Sections (classes A and B( Width or widlh across flats Tolerances on specified thickness Class A Class B Over Up to and Including Up to and including 1.6 mm thick Over 1.6mm up to and including 3.0mm thick Over 3.0mm up to and Including 6.0mm thick Over 6.0mm up to and including 10mm thick Over 10mm up to and including 18mm thick Over 18mm up to and Including 30mm thick Up to and including 1.6mm thick Over 1.6mm up to and including 3.0mm thick Over 3.0mm up to and including 6.0mm thick Over 6mm up to and including 10mm thick Over 10mm up to and including 18mm thick Over 18mm up to and including 30mm thick mm mm 10 10 18 18 30 + mm - 0.20 026 * mm . 0.22 0.28 * mm . - 032 + mm . . - * mm - - . mm - - - * mm - 022 0.28 + mm - 0.28 036 * mm - - 0.54 mm - . - mm - . + nm - 30 60 60 80 80 120 032 0,36 . 036 041 0.48 0.41 048 0 58 048 058 0.68 . 062 0 82 - - 1 00 036 045 - 0.45 055 0.65 065 075 0 80 090 095 1 00 1 40 145 1.50 - - 2 00 120 180 180 240 240 320 . - - 0.65 - - 075 095 - 0.85 1 05 1 25 0.95 1 20 1 45 110 1 40 1 80 . - - 075 - - 0.85 1 00 - 110 1 20 1 40 1 60 1 80 2 00 2.20 240 2 60 NOTE 1. For details concerning the applicability of tolerance class (A to B) to alloy, see Note 1 of Table 1,9 NOTE 2. The tolerances apply to non-heat-treated sections of wall thickness not less than 1.6 mm or 3% of the overal width, whichever is the greater, and to heat-treated sections of wall thickness not less than 1.6mm or 4% of the overall width, whichever is the greater.

Table 1.14

-

Tolerances on Straightness for Extruded Bar, Regular Sections and

Extruded Round Tubes _{(see below)}

For bars, tubes

or sections

within a

circumscribing circle

Temper Nominal length

of

bar, tube or section L Maximum derivation S _{from straightness} of length L (metres) (see below) Maximum localized kink in any 300 mm portion mm Up to and including 100 All tempers m over 0.4 mm 1.5 L mm 0.6 Over 100 F All other tempers over 0.4 over 0.4 2.0 L 2.5 L 0.8 1.0

NOTE 1. The straightness is measured _by determining the maximum deviation from

straightness S over length 1, when the bar, section or tube is supported on a flat table such that the deviation is minimized by Its own mass.

NOTE 2. Kink Is measured _using a _{straight edge} 300 _{mm in length (see below).}

NOTE 3. Tolerances _{on straightness for} annealed and controlled stretched materials

should be subject to agreement between the purchaser and the supplier at the time

of

the

enquiry and order.

Localized kink _{300mm straightedge} Bar, tube or section ot length L

V

7/

/ /

/

///V/

////4//

//

///

//

/

//

Maximum Section through - deviation S tiatness measuring table Length L 22

Table 1.15

-

Tolerances on Length for All Materials Supplied in Fixed Cut Lengths

Diameter, width

across flats or overall width

Tolerances _{on length} for _{given length (plus and} minus)

(see notes 1 and 2)

Over Up

to

and including Over 300 mm up

to

and including 1000 mm long Over 1000 mm up to and including 1500 mm long Over 1500 mm up to and including 5000 mm long Over 5000 mm up to and including 7000 mm long Over 7000 mm up to and including 10000 mm long Over 10000 mm long mm - 60 100 140 180 mm 60 100 140 180 240

jmm

2.0 2.0 3.0 3.5 4.5 jmm 2.5 2.5 3.5 4.0 5.0 jmm 2.5 3.5 4.0 5.0 6.5

jmm

3.5 4.0 5.0 6.5 8.0

jmm

4.0 5.5 6.5 8.0 9.5

jmm

6.5 7.5 8.0 9.5 11.0

NOTE 1. Tolerances on length are measured at a temperature of 16 5

C.

They provide

for out-of-squareness

of

cut to the extent of 10.

NOTE 2. Total tolerances (i.e. the sum

of

the plus and _{minus limits) may be applied}

unilaterally by agreement between the supplier and the purchaser.

Table 1.16

-

Tolerances on Concavity and

Convexity for Extruded Solid and Hollow Sections

Width of section W Maximum allowable

deviation D _(see figure)

mm mm

Up to and

including 25 0.125

Over25 _0.l2Sper2Smm

increment in width

(e.g. for 150 mm width

maximum deviation D

permitted is 0.75 mm)

Under 20

20 _up

to

_{and including 40}

Over _{40 up}

to

and including 80

Over 80:

Lengths upto and including 8000 mm Lengths over 8000 mm degrees 3 0.5 degrees 7 5 3

Table 1.17- Tolerances on Twist for Extruded Solid and Hollow Sections

Twist T

ALUMINIUM EXTRUSIONS

—

a

_{technical design guide}

SECTION

2-

MATERIAL SPECIFICATIONS

CONTENTS

Title _{Page No.}

ALLOYS 27

TEMPER 29

Solution Heat Treatment 30 Precipitation Heat Treatment 30

List

of

Figures

Fig No. Title Page No.

2.1 _{Temper Cycles} 29

2.2 _{Solubility Diagram} 31

List of

Tables

No. Title _{Page No.}

2.1 _{Chemical Composition} 27

2.2 _{Alloy Characteristics and Uses} 28

ALLOYS

High purity aluminium, 99.00% and above, has excellent durability together with high thermal and electrical conductivity. It is easily worked and afthough

it

can be strengthend by cold working

it

remains a _{low stength} material.

For more general use, alloying elements are introduced, _{producing materials that}

retain the general characteristics of pure aluminium but have greater structure strength (refer to Table 2.2). In the extrusion industry, the _{alloys most widely} used

throughout the world are in the International Standards 6000 series, to which the British Standards alloys also conform. The _{main alloying constituents} in this series are silicon and magnesium (refer to _{Table 2.1).}

Table 2.1

-

_{Chemical Composition}

COMPOSITION (%) ALLOY BS 1474 Others (1987) SI Fe Cu Mn Mg Cr NI Zn TI Each Total Al 0.20- 0.45- 6063 0.60 0.35 0.10 0.10 0.90 0.10 - 0.10 0.10 0.05 0.15 REM 0.30- 0.15- 0.60- 6063A 0.60 0.35 0.10 0.15 0.90 0.05 - 0.15 0.10 0.05 0.15 REM 0.70- 0.40- 0.60- 6082 1.30 0.50 0.10 1.00 1.20 0.25 - 0.20 0.10 0.05 0.15 REM * _{0.30- 0.40-} 6101A 0.70 0.40 0.05 - 0.90 - -

-

- 0.03 0.10 REM 0.20- 0.45- 6463 0.60 0.15 0.20 0.05 0.90 - - 0.05 - 0.05 0.15 REM 0.50- 3.90- 0.40- 0.20- 0.15- 2014A 0.90 0.50 5.00 1.20 0.80 0.10 0.40 0.25 0.20 0.05 0.15 REM

*

_{6101A comforms to BS 2898 ** T + Zr}

Table 2.2

-

_Alloy

CharacteristIcs and Uses

BS CHARACTERISTICS TYPICAL USES

6063 Suitable for intricate extruded sections of _{mid-strength.} Forms

well in T4 condition. High

corrosion resistance. Good surface finish.

6063A

A

stronger version

of

6063 but

retaining most

of

that alloy's good

surface finish and formability. 6082 The _{recommended alloy for}

structural purposes with good strength and general corrosion resistance.

6101A The best combination of electrical and mechanical conductor properties with conductivity of 55% of the International Annealed Copper

Standard.

6463 Based on _{high purity (99.8%)} aluminium, this alloy was developed

to

respond well to

chemical or electro-chemical

brightening or anodizing. It has

excellent formability.

2014A A _{high strength alloy with} moderate corrosion resistance.

28

The _{most widely used alloy. Architectural} members i.e. glazing bars and window frames; windscreen sections, road trans- port.

Road and rail transport, general engi- neering, ladders and light structures.

Road and rail transport, scaffolding, bridges, cranes and heavy structures.

Busbar, electrical conductors and fittings

Motor car trim and other applications requiring

a

bright finish.

Structures, aerospace, general engineering.

TEMPER

The _properties of _{alloys in} the _{6000 and 2000 range can} be _{improved by} heat treatments after extrusion.

These alloys, although available in the _{F, "as manufactured", condition, are} more

usually produced in one of the following three tempers:- T4

-

solution heat treated

T5 - _{precipitation treated (artificially aged)}

T6 - _{solution heat treated and precipitation treated (fully heat treated)}

T5 PRECIPITATION HEAT ___________ SOLUTION TREATMENT EXTRUSION_F (QUENCHING) (AGEING)

:

F

Fig. 2.1 - Temper Cycles

The current _procedure for _producing the T4 temper is _usually 'on-line". An _extrusion,

emerging from the die at about 500°C, is rapidly cooled _by air, water spray or water

immersion, depending upon the section _shape and extrusion speed. The _temper,

although stronger than in the F condition, is still of _relatively low _strength and, with its

high elongation value,

it

is an excellent choice where severe _forming is _required. Some

natural _ageing or _hardening will _{occur which will, in some alloys, curtail} the time

available for _forming.

For thin sections a _{stronger temper, T5,} is _{available. T5 is given greater strength by} carrying out precipitation treatment without any solution heat treatment. This is provided by heating the material up to about 180°C and soaking for several hours in an oven.

The _{final and strongest temper available (without the application} of _{cold work)} is T6 which combines both the solution heat treatment and the _{precipitation treatment.} The _{relationship between mechanical properties and heat treatment} of

a

_range of aluminium alloys was first discovered _by Wilm in 1906. Overthe _years, the _{process has} been developed with improvements and innovations being introduced which have

helped to make the "heat treated" alloys the most widely used extrusion materials in

the world.

in recent years, much greater use has been made

of

reheat treatment following low temper or heat induced fabrication operations such as bending and welding. This is

a _property of aluminium that is well worth considering at the design and material

selection stage of _{fabricated components.}

It is _{not the purpose}

of

this manual to _{deal with detailed metallurgical aspects} of aluminium and its alloys, but the following simplified explanation of _{heat treatment may} be

of

_{background interest:-}

The thermal treatment consists of _{two phases:}

a) solution heat treatment

b) precipitation heat treatment Solution Heat Treatment

The chemical constituents

of

_{aluminium alloys are} to

a

_greater or lesser extent soluble in aluminium. The degree

of

absorption varies with the amount and type

of

constituent and _{temperature. The higher} the _temperature, the _{greater the amount dissolved.} Fig.

2.2 shows

a

_{typical solubility diagram where,} at _{temperatures above point}

A

, (the

Solvus temperature) the _{atoms are in solid solution and designated by the prefix} "solute". These atom phases of constituents are thus dissolved in solid solution and a rapid temperature drop, through quenching, will prevent the solute atoms from diffusing

out

of

_{solution. This condition, however, is not totally stable and} a _{natural ageing} will

take _{place, varying from several days}

to

_{several weeks depending upon} the _alloy. During the ageing process a fine dispersion

of

clusters

of

solute atoms will occur. The final stable condition is defined as _{T4 temper.}

Precipitation Heat Treatment

The precipitation heat treatment process, also known as artificial ageing, speeds up and greatly increases the rate of _{precipitation and fine dispersion}

of

the constituent atoms, which are distributed in clusters over the whole matrix. The _{alloy will now tend} to _{resist material dislocation, resulting in} a marked improvement in both strength and hardness, usually to

a

level well above that obtained by natural ageing.

0 U) CU U) 0 E U) I— Liquid % Constituent

Figure 2.2

-

Solubility Diagram

Liquid

-

solid

5 Solid

Page blank

ALUMINIUM EXTRUSIONS

—

_a

_{technical design guide}

SECTION

3-

MECHANICAL PROPERTIES

CONTENTS

Title _{Page No.}

INTRODUCTION 35 STRESS ₃₆ Axial _{Loading 38} STIFFNESS 41 HARDNESS ₄₃ FATIGUE 43

List of

Figures

Fig No. Title Page No.

3.1 Yield Point 36

3.2 _{Typical Stress} Strain

Curves 37

3.3 Permissible Compressive

Stresses in Struts 39 3.4 _{Relationship Between}

Hardness Number and

Tensile, Yield Strengths 42

3.5 Fatigue Curves For Some Aluminium Alloys

(Rotating Cantilever Tests) 44

List

of

Tables

No. Title Page No.

3.1 _Properties

to

BS 1474 35

(1987)

3.2 Permissible Stresses 38

3.3 Effective Lengths

of

Struts 40 3.4 Moduli of Elasticity 41

INTRODUCTION

A

wide range

of

mechanical properties is available from aluminium and its alloys with the level of _{performance varying with} the _degree of _{alloying and temper. The property} range for the more generally available commercial alloys is given in Table 3.1.

Table 3.1

-

Properties

to

BS 1474(1987)

ALLOY TEMPER MAX

THICKNESS mm 0.2% Ps N/mm2 ULT. STRESS N/mm2 %ELONGATION b) 5.65y' 50

mm

6063 Fe) T4 T5 16 200 150 25 150 - 70 110 160 100 130 150 195 13 16 8 8 12 14 7 7 6063A T4 15 T6 25 25 25 90 160 190 150 200 230 14 8 8 12 7 7 6082 Fe) T4 15 T6 200 150 6 20a) - 120 230 255 110 190 270 295 13 16 - 8 12 14 8 7 6lOlAd) T6

-

170 200 10 8 6463 T4 T6 50 50 75 160 125 185 16 10 - - 2014A 14 T6 20a) 20a) 230 370 370 435 11 7 10 6

a) Thicker sections are possible and give higher mechanical properties. For

details contact extruder.

b) The elongation is obtained from a tensile test _sample on which a _gauge length

is marked _prior

to

testing. The gauge length is specified, being either 50 mm long or 5.65

/

cross-sectional area. (So)

C) The properties of aluminium vary with temperature outside an approximate

range

of

-50°C

to

+80°C. _{They will increase} at low temperatures and decrease

at _{high temperatures.} The values vary with the alloy, see Table 8.2. d) Alloy 6101A conforms

to

BS 2898.

e) Values given for F condition are not specified properties in British Standards and are given for _{information only.}

STRESS

Aluminium does not exhibit a _{yield point. Stress/strain behaviour} is similar to that

of

a

numberof other metals, including some alloy steels. It _{is necessary, therefore,}

to

advise a _{recognisable point} of _{departure from elastic}

to

_{plastic behaviour. In} the method

chosen, the _{stress level registered} at _{0.2%. Permanent strain is regarded} as the _yield point. The yield point can be obtained from the stress/strain curve _{by drawing} the offset

of

O.2% _{strain parallel to the elastic line for the alloy under consideration. The 0.2%}

proof stress can be read at the _point

of

intersection of the two lines, see _{Fig. 3.1.} Alloy

curves will have

a

_{different point} of _departure for _{each temper} condition.

E E

z

0, CO U)

Fig. 3.1

-

Yield Point

36

0.70 200

/

/

_{0.2 Ordinate}

NB. for reasons of clarity

the alloy curve is

exaggerated

/

/

/

20

/

0.50 0.60 % Strain

500- 2014A T6 Mild Steel 400 ——

/

/

/

E 300-

//'7

6082 T6

z

a, / ci)

/

'—'—I (I) 200- 100- I I I 0 5 10 15 20 % Strain

Table 3.2

-

Permissible Stresses ALLOY TEMPER AXIAL _e) N/mm2 Pt Pc BENDING N/mm2 Pbt Pbc SHEAR N/mm2 BEARING N/mm2

s

6063 6063 6082 2014A 2014A 15 T6 16 T4 16 62 87 139 135 124 154d) 20 69 96 154 153 142 154d) 224 37 52 83 81 108 117 139 222 239 278 106 81 61 71 49 Pt AXIAL TENSION Pc AXIAL COMPRESSION Pbt BENDING TENSION Pbc BENDING COMPRESSION

s SLENDERNESS RATIO AT EULER BLEND POINT SEE FIG. 3.3

a) Permissible stress levels are laid down in BS CP1 18 The Structural Use of

Aluminium".

b) 6063 values are applicable to 6101A and 6463.

C) 6063A is a new alloy, not yet allocated

a

value but from experience it should

be _{slightly in excess} of _{6063 values (8%).}

d) Arbitrarily reduced values

to

allow for inferior crack-propagation resistance. e) Applies only when buckling is not the criterion.

AxIal Loading

For _{axial loading, in columns and struts, the permissible compressive stress} is obtained by inserting the appropriate slenderness ratio into the alloy/temper curves given in

Fig. 3.3, and using the effective length factor from Table 3.3.

CM E E

z

'a CM a) (1) a) > U) (a a) 0. E 0 0 a) .0 0) 0) E a)

Fig. 3.3

-

Permissible Compressive Stresses

in

Struts = _K!.

whore = slenderness ratio

K = _{end fixity factor (effective length)} L = _spaninmm

r = radius of _gyration of section in mm

also r =

= inertia

A = cross sectional area

100 1

Table 3.3

-

_{Effective Lengths}

of

Struts

End Condition _{Effective Length}

of

Strut

Effectively held in position and restrained

in direction at both ends 0.7 L

Effectively held in position at both ends

and restrained in direction at one end 0.85 L

Effectively held in position at both ends,

but not restrained in direction L

Effectively held in position and restrained

in direction at one end and _partially

restrained in direction but not held in

position at the other end

1.5 L

Effectively held in position and restrained

in direction at one end, but not held in

position or restrained at other end

2.0 L

NOTE. L is the length of strut between points of lateral support.

The _{extensive range}

of

shapes and, over the last few years, the ability of the industry to _{produce thinner extrusions} has _encouraged the use of slender sections. Because of _{low aspect ratios (width/depth) and high element thickness ratios (width/thickness)} of the _{thinner extrusions they require examination} for _{possible modes}

of

elastic instability. The modes of failure listed below are particularly relevanttothin-walled open sections of _{asymmetrical shape} in _{aluminium alloys.}

a) Torsional warping

b) Lateral instability

C) Local buckling

All the factors are influenced _{by the shape and dimensions}

of

the section and, whilst (a)

and (b) are also relevant

to

span, (C) is not.

Although safe values are often quoted in simple terms for aspect and element thickness ratios, they are not entirely reliable and should not be used. If there is _{any doubt about} the robustness of

a

section in the form

of

failures list above,

it

should be checked, using

appendices F, G, H and Kin BS CP 118- The Structural Use of Aluminium". The _design approach uses equivalent slenderness ratios

in

conjunction with alloy compression curves. The strut curves in Fig. 3.3 can be used for _{torsional warping} but will give pessimistic values for lateral instability and local buckling, where the equivalent slenderness ratio falls on the _{straight line parts}

of

the _{graphs: See} BS CP1 _{18 Fig.} 2 for modified compression curves suitable for _{solving lateral instability and local buckling.}

STIFFNESS

The stress/strain relationship is _{given by} Hooke's Law which states that intensity of stress is proportional to strain. This is _applicable to aluminium alloys to a level _just below the _{0.2% proof stress,} the slope

of

the line being obtained from:

Table 3.4

-

Modull

of

Elasticity

E = Stress where E is the modulus of _elasticity Strain

ALLOY MODULUS OF ELASTICITY E

N/mm2 6063 65,500 6063A 65,500 6082 68,500 6101A 65,500 6463 65,500 2014A 72,000

These values are approximately one third of that

of

mild steel, 210,000 N/mm2.

Aluminium under elastic bending will therefore give deflections three _{times greater} than those obtained from mild steel under similar loading conditions. This is not true

for _{self weight loading where} the _{light weight}

of

aluminium counteracts the effect

of

the lower elastic modulus of aluminium. _{The advantage} to be obtained from

a

low modulus are greater impact absorption with shock loads and lower imposed stress

levels from movement in static structures caused by temperature variation or support settlement. The modulus of _elasticity will _{vary with temperature, see Table} 8.2.

In applications where deflection is the _{controlling design factor,} the _{performance of} aluminium can be _{dramatically improved by utilising the advantages}

of

the extrusion process to position materials strategically around the section. The geometric proper-

ties can also be increased _by small additions

to

section depth.

This modification applies to all materials but can be more readily incorporated into

extruded aluminium sections. Examples are given in Section 11, Design.

The _{relationship between lateral and longitudinal strain, within} the elastic limit, is given by Poisson's Ratio which, for aluminium alloys, is usually 0.34.

30 x E E 25

z

-c 0) c 20 )2) (0 D .; 15- (0 C 10 a I-

HARDNESS TESTER SETTINGS

Brinell

lOmm.Steel ball penetrator

-

500kg.load

Vickers

Diamond _penetrator

-

various loadings

Rockwell 'F'

1.6mm Steel ball penetrator - 6Okg.load

Rockwell 'E'

3.2mm, Steel ball penetrator

-

lOOkg.load

Rockwell 'B'

1.6mm Steel ball penetrator

-

lOOkg.load

Rockwell 'K'

3.2mm Steel ball penetrator

-

l5Okg.load Webster

Model 'B'

Note:

As this

table shows, a hardness value covers

a

range of stress levels and must

not therefore be used to _{give precise measurements}

of

_strength.

Fig. 3.4

-

Relationship Between Hardness Number and _{Tensile, Yield Strengths}

42

35

Tensile

Relationship between

hardness number and

tensile strength

for magnesium

-

silicide

alloy extrusions in

the artificially aged

condition Yield (1/6063 T5 & T6 6082 T6 F j"1 i'• •1 Brinell 6063A

_T6

Vickers 45 055 6065 707580 85 9095100105110 46 51 56 61 66 71 76 82 87 92 98103 109115 Rockwell 'F' Rockwell

'E'

54 61 67 71 76 79 82 85 87 89 91 - Rockwell

'B'

47 55 62 68 I I I 72 77 80 83 86 88 90 92 94 96 Rockwell

'K'

-

- - -

12 23 32 39 45 50 55 60 63 66 — 15253441485358826670737678 Webster 5 7 9 10 11 12 13131414—151515161616—1717 Hardness number