Aluminium alloys used in bodywork

The choice of material and the condition in which

it is required must depend largely upon design

requirements and the manufacturing processes

within the factory. The alloys most commonly used

in vehicle body work are as shown in Table 4.9.

136Repair of Vehicle Bodies

Table 4.5General characteristics of all wrought forms of aluminium alloys

General characteristics

Inert-gas Welding

shielded resistance (spot,

Purity Temper or Cold arc (MIG seam, flash Metal

or alloy condition forming Machining Durability or TIG) butt or stud)b,c Oxy-acetylened arc

5251 F V G V Ve E Ge Fe

O V G

H22 G G

H24 G V

H28 G V

H39X F V F Ve E Ge Ge

5454 F V V V Ve E Fe N

O V V

H22 G G

H24 G G

5154 F V V Vf E E F N

O V Vf

H22 G Gf

H24 F Gf

H28

5083 F G E Vf E E F N

O G Vf

H22 F Ff

H24 G Ff

6082 F V G G Ve V Fe Ge

O E G G

T4 G V V

T6 F E G

T451

T651

1200 F E F V E V V G

O E F

H12 V F

H14 V F

H16 G G

H18 F G

3103 F E F V E E V G

O E F

H12 V F

H14 V F

H16 G G

H18 F G

(a) Materials are graded thus: E excellent; V very good; F fair; P poor; N not recommended.

(b) The mechanical properties of work hardened or heat-treated materials will be reduced in the vicinity of the weld.

(c) The weld zone is generally discernible after anodic treatment, the degree depending on the material and welding process.

(d) The oxy-acetylene process is normally recommended only for material thinner than 6–4 mm.

(e) Filler or electrode of other than parent metal composition is recommended.

(f ) Applicable at temperature of 70 °C and less.

Table 4.6Chemical composition limits1 and mechanical properties of unalloyed aluminium plate, sheet and strip (BS 1470)

Elongation on 50 mm

Elongation on

Others2 Thickness Tensile strength

Materials thicker than 5.65 over

Material Tolerance Silicon Iron Copper Manganese Magnesium Chromium Nickel Zinc Gallium Titanium Each Total Aluminium __ Min. Max. 0.5 mm 0.8 mm 1.3 mm 2.6 mm 3.0 mm 12.5 mm thick

designation category (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) min. (%) Temper4 (mm) (mm) (N/mm2) (N/mm2) min. (%) min. (%) min. (%) min. (%) min. (%) (min.) (%)

1080A A 0.15 0.15 0.03 0.02 0.02 – – 0.06 0.03 0.02 0.02 – 99.80(3) F 3.0 25.0 – – – – – – – –

O 0.2 6.0 – 90 29 29 29 35 35 –

H14 0.2 12.5 90 125 5 6 7 8 8 –

H18 0.2 3.0 125 – 3 4 4 5 – –

1050A A 0.25 0.40 0.05 0.05 0.05 – – 0.07 – 0.05 0.03 – 99.50(3) F 3.0 25.0 – – – – – – – –

O 0.2 6.0 55 95 22 25 30 32 32 –

H12 0.2 6.0 80 115 4 6 8 9 9 –

H14 0.2 12.5 100 135 4 5 6 6 8 –

H18 0.2 3.0 135 – 3 3 4 4 – –

1200 A 1.0 Si _ Fe 0.05 0.05 – – – 0.10 – 0.05 0.05 0.15 99.99(3) F 3.0 25.0 – – – – – – – –

O 0.2 6.0 70 105 20 25 30 30 30

H12 0.2 6.0 90 125 4 6 8 9 9 –

H14 0.2 12.5 105 140 3 4 5 5 6

H16 0.2 6.0 125 160 2 3 4 4 4 –

H18 0.2 3.0 140 – 2 3 4 4 – –

1 Composition in per cent (m/m) maximum unless shown as a range or a minimum.

2 Analysis is regularly made only for the elements for which specific limits are shown. If, however, the presence of other element s is suspected to be, or in the case of routine analysis is

indicated to be, in excess of the specified limits, further analysis should be made to determine that these other elements are not in excess of the amount specified.

3 The aluminium content for unalloyed aluminium not made by a refining process is the difference between 100.00% and the sum of all other metallic elements in amounts of 0.010% or more

each, expressed to the second decimal before determining the sum.

4 An alternative method of production, designated H2, may be used instead of the H1 routes, subject to agreement between supplier and purchaser and providing that the same specified

properties are achieved.

_So

Table 4.7Chemical composition limits1 and mechanical properties of aluminium alloy plate, sheet and strip (non-heat-treatable) (BS 1470)

Elongation on 50 mm

0.2% Elongation on

Other

Others2 Thickness

proof

Tensile strength

Materials thicker than 5.65 over

Material Tolerance Silicon Iron Copper Manganese Magnesium Chromium Nickel Zinc restrictions Titanium Each Total Aluminium __ stress min. Min. Max. 0.5 mm 0.8 mm 1.3 mm 2.6 mm 3.0 mm 12.5 mm thick

designation category (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) Temper3 (mm) (mm) (N/mm2) (N/mm2) (N/mm2) min. (%) min. (%) min. (%) min. (%) min. (%) (min.)

3103 A 0.50 0.7 0.10 0.9–1.5 0.30 0.10 – 0.20 0.10 – 0.05 0.15 Rem.* F 0.2 25.0 – – – – – – – – –

Zr _ Ti O 0.2 6.0 – 90 130 20 23 24 24 25 –

H12 0.2 6.0 – 120 155 5 6 7 9 9 –

H14 0.2 12.5 – 140 175 3 4 5 6 7 –

H16 0.2 6.0 – 160 195 2 3 4 4 4 –

H18 0.2 3.0 – 175 – 2 3 4 4 – –

3105 A 0.6 0.7 0.30 0.30–0.8 0.20–0.8 0.20 – 0.40 – 0.10 0.05 0.15 Rem. O 0.2 3.0 – 110 155 16 18 20 20 – –

H12 0.2 3.0 115 130 175 2 3 4 5 – –

H14 0.2 3.0 145 160 205 2 2 3 4 – –

H16 0.2 3.0 170 185 230 1 1 2 3 – –

H18 0.2 3.0 190 215 – 1 1 1 2 – –

5005 A 0.30 0.7 0.20 0.20 0.50–1.1 0.10 – 0.25 – – 0.05 0.15 Rem. O 0.2 3.0 – 95 145 18 20 21 22 – –

H12 0.2 3.0 80 125 170 4 5 6 8 – –

H14 0.2 3.0 100 145 185 3 3 5 6 – –

H18 0.2 3.0 165 185 – 1 2 3 3 – –

5083 B 0.40 0.40 0.10 0.40–1.0 4.0–4.9 0.05–0.25 – 0.25 – 0.15 0.05 0.15 Rem. F 3.0 25.0 – – – – – – – – –

O 0.2 80.0 125 275 350 12 14 16 16 16 14

H22 0.2 6.0 235 310 375 5 6 8 10 8 –

H24 0.2 6.0 270 345 405 4 5 6 8 6 –

5154A B 0.50 0.50 1.10 0.50 3.1–3.9 0.25 – 0.20 0.10–0.50 0.20 0.05 0.15 Rem. O 0.2 6.0 85 215 275 12 14 16 18 18 –

Mn _ Cr H22 0.2 6.0 165 245 295 5 6 7 8 8 –

H24 0.2 6.0 225 275 325 4 4 4 6 6 –

5251 A 0.40 0.50 0.15 0.10–0.50 1.7–2.4 0.15 – 0.15 – 0.15 0.05 0.15 Rem. F 3.0 25.0 – – – – – – – – –

O 0.2 6.o 60 160 200 18 18 18 20 20 –

H22 0.2 6.0 130 200 240 4 5 6 8 8 –

H24 0.2 6.0 175 225 275 3 4 5 5 5 –

H28 0.2 3.0 215 255 285 2 3 3 4 4 –

5454 B 0.25 0.40 0.10 0.50–1.0 2.4–3.0 0.05–0.20 – 0.25 – 0.20 0.05 0.15 Rem. F 3.0 25.0 – – – – – – – – –

O 0.2 6.0 80 215 285 12 14 16 18 18 –

H22 0.2 3.0 180 250 305 4 5 7 8 – –

H24 0.2 3.0 200 270 325 3 4 5 6 – –

* Remainder

1 Composition in per cent (m/m) maximum unless shown as a range or a minimum.

2 Analysis is regularly made only for the elements for which specific limits are shown. If, however, the presence of other elements is suspected to be, or in the case of routine analysis is

indicated to be, in excess of the specified limits, further analysis should be made to determine that these other elements are not in excess of the amount specified.

3 An alternative method of production, designated H2, may be used instead of the H1 routes, subject to agreement between supplier and purchaser and providing that the same specified

properties are achieved.

_So

Table 4.8Chemical composition limits and mechanical properties of aluminium alloy plate, sheet and str ip (heat-treatable) (BS 1470)

0.2%

Elongation on 50 mm

Elongation on

Other

Others2 Thickness

proof

Tensile strength

Materials thicker than 5.65 over

Material Tolerance Silicon Iron Copper Manganese Magnesium Chromium Nickel Zinc restrictions Titanium Each Total Aluminium __ stress min. Min. Max. 0.5 mm 0.8 mm 1.3 mm 2.6 mm 3.0 mm 12.5 mm thick

designation category (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) Temper3 (mm) (mm) (N/mm2) (N/mm2) (N/mm2) min. (%) min. (%) min. (%) min. (%) min. (%) (min.)

2014A B 0.50–0.9 0.50 3.9–5.0 0.40–1.2 0.20–0.8 0.10 0.10 0.25 0.20 0.15 0.05 0.15 Rem.* 0 0.2 6.0 110 – 235 14 14 16 16 16 –

Zr _ Ti T4 0.2 6.0 225 400 – 13 14 14 14 14 –

T6 0.2 6.0 380 440 – 6 6 7 7 8 –

T451 6.0 25.0 250 400 – – – – – 14 12

25.0 40.0 250 400 – – – – – – 10

40.0 80.0 250 395 – – – – – – 7

Clad B 0.50–0.9 0.50 3.9–5.0 0.40–1.2 0.20–0.8 0.10 0.10 0.25 0.20 0.15 0.05 0.15 Rem. T651 6.0 25.0 410 460 – – – – – – 6

2014A Zr _ Ti 25.0 40.0 400 450 – – – – – – 5

40.0 60.0 390 430 – – – – – – 5

60.0 90.0 390 430 – – – – – – 4

90.0 115.0 370 420 – – – – – – 4

115.0 140.0 350 410 – – – – – – 4

2024 B 0.50 0.50 3.8–4.9 0.30–0.9 1.2–1.8 0.10 – 0.25 – 0.15 0.05 0.15 Rem. O 0.2 6.0 100 – 220 14 14 16 16 16 –

T4 0.2 1.6 240 385 – 13 14 14 – – –

1.6 6.0 245 395 – – – – 14 14 –

T6 0.2 1.6 345 420 – 7 7 8 9 – –

1.6 6.0 355 420 – – – – 9 9 –

O 0.2 6.0 110 – 235 12 12 14 14 14 –

T3 0.2 1.6 290 440 – 11 11 11 – – –

1.6 6.0 290 440 – – – – 12 12 –

T351 6.0 25.0 280 430 – – – – – 10 10

25.0 40.0 280 420 – – – – – – 9

40.0 60.0 270 410 – – – – – – 9

60.0 90.0 270 410 – – – – – – 8

90.0 115.0 270 400 – – – – – – 8

115.0 140.0 260 390 – – – – – – 7

*Remainder

_So

Table 4.9Standard aluminium alloys: availability, physical properties, and applications

Nominal

composition:

% alloying Physical properties

elements

Related BS/GE (remainder Coefficient

specification aluminium Standard formsa of linear

Purity or (BS 1470–1475) and normal Melting expansion Typical road transport

alloy (new (old BS alloy impurities) Hollow Density range °C per °C applications

nomenclature) designation) Mg Si Mn Sheet Plate Extrusions extrusions Tube g/cm3 lb/in3 (approx.) (20–100°C)

Non-heat-treatable alloys

1200 IC – – – ___ _ _ 2.71 0.098 660 0.000 023 5 Vehicle panelling where panel

beating is required; mouldings

and trim. Tank cladding

3103 N3 – – 1.2 ___b _b _b 2.73 0.099 645–655 0.000 023 5 Flat panelling of vehicles and

general sheet metal work.

Tank cladding

5251 N4 2.25 – 0.4 ___ – _ 2.69 0.097 595–650 0.000 024 Body panelling. Head boards

and drop sides. Truss panels in

buses. Cab panelling. Tanker

shells and divisions

5154A N5 3.5 – 0.4 _ – _ – _ 2.67 0.096 600–640 0.000 024 5 Welded body construction.

Tipper body panelling. Truss

panels in buses

5454 N51 2.7 – 0.8 Tanker shells and divisions

5083 N8 4.5 – 0.5 ___ – _ 2.65 0.096 580–635 0.000 024 5 Pressurized bulk transport at

ambient or low temperature

Heat-treatable alloys

6082 H30 0.7 1.0 0.5 ___ _ _ 2.70 0.098 570–660 0.000 023 5– All structural sections in

0.000 024c riveted vehicle bodies.

Tipper body panelling.

Highly stressed underframe

gussets, truss panels

(a) Other forms may be available by special arrangement.

(b) Not covered by British Standard (general engineering) specification.

(c) Depending on condition.

Metals and non-metals used in vehicle bodies 141

Alloy 5154A is suitable for use in car panels

which are to be pressed into shape; it is supplied in

either annealed condition or H2 condition, which are

the most suitable for press work on vehicle bodies.

Of the other materials, 1200 is a commercial purity

sheet, and is widely used for exterior and interior

panelling where no great strength is required. Types

3103, 5251, 5154A and 5056A are non-heat-treatable

alloys of the aluminium-magnesium range with a

strength of 90–325 N/mm2. They come in sheet

form, and provide a range of mechanical properties

to suit different applications. They are used extensively

in panel work, and also for forming, pressing

and machining, and can be welded without much difficulty.

The plate material 5083 is a medium-strength

non-heat-treatable alloy particularly suitable for

welding. It can be used for parts carrying fairly high

stress loads and is often used in the form of patterned

tread plate for floor sections.

For internal structure members which need to be

stronger than the outer panels, the heat-treatable

alloys usually used are 6063 and 6082, and in

odd cases 2014A. Type 6082 is a heat-treatable

medium-strength alloy which combines good

mechanical properties with high corrosion resistance.

Permissible stresses in this alloy can be as

high as 200 N/mm2 under static loading conditions,

although some reduction below this would

normally be made for transport applications where

there is a considerable element of dynamic loading.

The alloy is weldable by the inert gas arc

process, but there is a considerable loss of strength

near the weld owing to the annealing effect of the

welding process. Type 6063 is also a heat-treatable

alloy but of somewhat lower strength, and is used

mainly in applications requiring good surface finish

or where the parts are required to be anodized.

Alloy 2014A contains a greater percentage of copper

than the others, is more expensive, is more difficult

to form and is less resistant to corrosion, but

has the advantage of a greater tensile strength.

Fastenings and solid rivets can be of commercial

purity material or of aluminium alloy 5154A, and

for smaller sizes 6082 is sometimes used. Rivets

are also available in 5056A material, but should

not be used in cases where high temperatures occur

in service. Bolts used in bodywork are normally of

the 6082 alloy.

The condition in which heat-treatable alloys are

supplied should be related to their application or

use in bodywork. For example, if a section is to

remain straight and is part of a framework which is

to be bolted, riveted or welded in place, it is obvious

that the material used should already be fully

heat treated so that maximum strength is provided

to support the framework or structure of the body.

On the other hand, if the section has to be shaped,

bent or formed in any way the material should be

used in the annealed condition and then heat

treated after the shaping operations have all been

carried out.

Aluminium alloys are now being accepted by the

automobile manufacturers as a standard material

for exterior and interior trim, and are used for all

normal bright trim applications such as radiator

grilles, headlamp bezels, wheel trim, instrument

panels, body mouldings and window and windscreen

surrounds. Alloys used for trimming can be

divided into two groups: high-purity alloys bright

finished on one side only, in which the majority of

the trim components are made; and super-purity

alloys for use when maximum specular reflectivity

is an advantage, such as would be required by light

units.

4.8 Rubber

The value of rubber lies in the fact that it can be

readily moulded or extruded to any desired shape,

and its elastic quality makes it capable of filling

unavoidable and irregular gaps and clearances. It is

an ideal material in door shuts and as the gasket for

window glass, and in both instances it provides the

means for excluding dust and water, although with

windscreens and back-lights additional use has generally

to be made of a sealing material. Rubber

specifications have been built on the basis of the

properties of material which has given satisfaction.

One major difficulty has been to ensure and measure

resistance to weathering; rubber is subject to oxidation

by ozone in the atmosphere, and this results in

cracking. In addition to natural rubber, a variety of

types of synthetic rubbers are used by the motor

industry; these vary in price and characteristics, and

all are more expensive than natural rubber. For complete

ozone resistance, it is necessary to use either

butyl or neoprene rubber; both satisfy atmospheric

and ozone ageing tests. Butyl rubber, however, is

‘dead’ to handle and contains no wax, and so whilst

neoprene is costly its use is essential for some parts.

142Repair of Vehicle Bodies

Sponge sealing rubbers can be provided with

built-in ozone resistance by giving them a live skin

of neoprene, and a further way of providing ozone

resistance is to coat the rubber components with

Hypalon; more recently, continuously extruded

neoprene sponge has been adopted. Apart from

weather resistance, the important requirement of

door and boot lid seals is that their compression

characteristics should ensure that they are capable

of accommodating wide variations in clearance,

without giving undue resistance to door closing.

Various types of foam rubber have been evolved

to suit the different parts of the car seating, and the

designer’s choice of material is governed by cost,

comfort, durability, the type of base, the type of

car, and whether it is a cushion or a squab, a rear or

front seat. When considering the foams available, it

is apparent that the number of permutations is

large. The types of foam available today fall into

seven broad categories. These are:

Moulded latex foam

Low-grade fabricated polyether

Fabricated polyether

Moulded polyether

Fabricated polyester

Polyvinyl chloride foam

Reconstituted polyether.

Latex foam today utilizes a mixture of natural and

synthetic latexes to obtain the best qualities of

both. After being stabilized with ammonia, natural

latex is shipped in liquid form to this country from

Malaysia, Indonesia and other rubber producing

countries. Synthetic latex, styrene butadiene rubber,

is made as a byproduct of the oil cracker plants.

Polyether foam can now be made in different grades,

and the physical properties of the best grades

approach those of latex foam. As a general guide,

service life and physical properties improve as

the density increases for any given hardness. As the

cost is proportional to weight, it follows that the

higher-performance foams are more costly.

Flexible polyurethane foam seats are replacing

heavy and complicated padded metal spring structures.

Moulded seats simplify assembly, reduce

weight and give good long-term performance.

A major innovation here has been the cold cure

systems. These produce foams of superb quality,

particularly in terms of strength, comfort and longterm

ageing. The systems are particularly suitable for

the newer seat technologies such as dual hardness,

where the wings are firm to give lateral support,

leaving the seat pad softer and more comfortable.

4.9 Sealers

The history of sealers is longer than that of the

motor car. Mastic, bitumen compounds and putties

of various kinds have been used since the invention

of the horseless carriage. It is likely that early

coach builders used putties of some kind – possibly

paint fillers – to bridge joints in various applications

on motor bodies, but it is generally conceded

that the first use of specialized sealers on a large

scale was in the early 1920s when, in America, the

pressed steel body became popular. In this country

it was 1927 before one of the first truly effective

sealers was introduced. It was known as Dum Dum

and is still in use. It was a modified roof sealer, and

proved to have many applications in body production.

It was not until the late 1930s, when all-steel

bodies and unitary construction became a common

feature of mass produced cars, that more thought

was given to the points that required the use of

sealing compounds, and to the nature of these

products. Amongst the first developed was interweld

sealing compound, primarily to prevent corrosion.

Since then, particularly in the post-war years, there

have been remarkable developments, probably

accelerated by criticisms from overseas markets

that British cars were susceptible to dust and water

entry. Companies specializing in the manufacture

of mastic compounds have developed a range of

materials which are now used not only for welding

and for general putty application but also for floor

pans, drip rails, body joints, exterior trim and many

other points, leading to well sealed car bodies

equal to any produced elsewhere in the world

(Figure 4.2, Table 4.10).

The term ‘sealer’ covers a wide variety of materials

used in the motor industry for sealing against

water and dust, from products which remain virtually

mastic throughout their life to others which

harden up but still retain some measure of elasticity.

They range from mixtures of inert fillers and semidrying

oils to heat curing plastisols which may be

applied in a thin paste form as an interweld sealer

or as extruded beads. Sealing compounds can be

categorized into the following general groups: oilbased

compositions, rubber-based compositions and

Metals and non-metals used in vehicle bodies 143

Figure 4.2Problem areas requiring body sealing