ISO 14788:2017
(Main)Steel sheet, zinc-5 % aluminium alloy-coated by the continuous hot-dip process, of commercial, drawing and structural qualities
Steel sheet, zinc-5 % aluminium alloy-coated by the continuous hot-dip process, of commercial, drawing and structural qualities
ISO 14788:2017 is applicable to the minimum requirements for steel sheet, in coils and cut lengths, metallic-coated by the continuous hot-dip process, with zinc-5 % aluminium alloy coating. The product is intended for applications requiring corrosion resistance, formability and paintability. The steel sheet is produced in a number of quality designations and grades, coating type, coating mass, surface treatments and coating finish conditions designed to be compatible with differing application requirements.
Tôles en acier revêtues à chaud en continu d'alliage zinc-aluminium 5 %
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Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 14788
Fourth edition
2017-11
Steel sheet, zinc-5 % aluminium alloy-
coated by the continuous hot-dip
process, of commercial, drawing and
structural qualities
Tôles en acier revêtues à chaud en continu d'alliage zinc-
aluminium 5 %
Reference number
ISO 14788:2017(E)
©
ISO 2017
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ISO 14788:2017(E)
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© ISO 2017, Published in Switzerland
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ISO 14788:2017(E)
Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Dimensions . 3
5 Conditions of manufacture . 3
5.1 Steelmaking . 3
5.2 Chemical composition . 3
5.3 Chemical analysis . 3
5.3.1 Heat analysis . . 3
5.3.2 Product analysis . 4
5.4 Mechanical properties . 5
5.4.1 Commercial and drawing quality . 5
5.4.2 Structural quality . . 6
5.5 Coating . 7
5.5.1 Coating mass. 7
5.5.2 Coating adherence . 7
5.6 Weldability . 9
5.7 Painting . 9
5.8 Coating finish condition . 9
5.9 Surface treatment . 9
5.9.1 Mill passivation . 9
5.9.2 Oiling .10
5.10 Coated coil joining .10
5.11 Dimensional and shape tolerances .10
6 Sampling .10
6.1 Tensile test .10
6.2 Coating tests .10
6.2.1 Coating mass.10
6.2.2 Triple-spot test .10
6.2.3 Single-spot test .10
6.2.4 Coating adherence .11
7 Test methods .11
7.1 Tensile tests .11
7.2 Coating properties .11
7.2.1 Coating mass.11
7.2.2 Coating adherence .11
8 Designation system .11
8.1 General .11
8.2 Coating designation .11
8.3 Coating mass .12
8.4 Coating finish condition .12
8.5 Surface treatment .12
8.6 Base-metal quality .12
8.7 Examples .13
9 Retests .13
9.1 Machining and flaws.13
9.2 Elongation .14
9.3 Additional tests .14
10 Resubmission .14
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ISO 14788:2017(E)
11 Workmanship .14
12 Inspection and acceptance .14
13 Coil size .14
14 Marking .15
15 Information to be supplied by the purchaser.15
Annex A (normative) Orders requiring base-metal thickness .17
Bibliography .19
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ISO 14788:2017(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 17, Steel, Subcommittee SC 12, Continuous
mill flat rolled products.
This fourth edition cancels and replaces the third edition (ISO 14788:2011), which has been technically
revised.
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INTERNATIONAL STANDARD ISO 14788:2017(E)
Steel sheet, zinc-5 % aluminium alloy-coated by the
continuous hot-dip process, of commercial, drawing and
structural qualities
1 Scope
This document is applicable to the minimum requirements for steel sheet, in coils and cut lengths,
metallic-coated by the continuous hot-dip process, with zinc-5 % aluminium alloy coating.
The product is intended for applications requiring corrosion resistance, formability and paintability.
The steel sheet is produced in a number of quality designations and grades, coating type, coating mass,
surface treatments and coating finish conditions designed to be compatible with differing application
requirements.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 1460, Metallic coatings — Hot dip galvanized coatings on ferrous materials — Gravimetric
determination of the mass per unit area
ISO 2178, Non-magnetic coatings on magnetic substrates — Measurement of coating thickness —
Magnetic method
ISO 3497, Metallic coatings — Measurement of coating thickness — X-ray spectrometric methods
ISO 6892-1, Metallic materials — Tensile testing — Part 1: Method of test at room temperature
ISO 7438, Metallic materials — Bend test
ISO 16163, Continuously hot-dipped coated steel sheet products — Dimensional and shape tolerances
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at https://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp
3.1
commercial
base-metal quality intended for general fabricating purposes where sheet is used in the flat condition,
or for bending or moderate forming
3.2
drawing
base-metal quality intended for parts where drawing or severe forming may be involved
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ISO 14788:2017(E)
3.3
deep drawing
base-metal quality intended for parts where severe forming or severe drawing (3.2) may be involved
3.4
deep drawing aluminium killed
base-metal quality intended for fabricating parts where particularly severe drawing (3.2) or forming
may be involved or essential freedom from ageing (3.13) is required
3.5
extra-deep drawing stabilized
base-metal quality intended for applications requiring interstitial-free steel (IF steel) (3.6) which is non-
ageing and has maximum formability
3.6
interstitial-free steel
IF steel
extra-low-carbon steel in which all interstitial elements are combined with titanium and/or equivalent
elements
Note 1 to entry: Interstitial-free steel is sometimes referred to as “stabilized steel”.
3.7
breakage allowance
agreed upon level of acceptable die breakage not subject to claim
3.8
continuous hot-dip zinc-5 % aluminium-coated steel sheet
steel sheet product in coils or cut lengths manufactured on a continuous coating line with a hot-dip
zinc-5 % aluminium coating on base metal of cold-reduced or hot-rolled descaled steel
3.9
differential coating
coating deliberately produced to have a different coating mass on each surface
3.10
normal spangle
coating formed as a result of the unrestricted growth of zinc-5 % aluminium alloy crystals during
normal solidification
3.11
smooth finish
smoothness produced by skin passing (3.12) the coated material in order to achieve an improved surface
condition as compared with the normal as-coated product
3.12
skin pass
light cold rolling of the coated steel sheet
Note 1 to entry: The purpose of the skin passing is one or more of the following: to minimize the appearance of
coil breaks, stretcher strains and fluting; to control the shape; to obtain the required surface finish.
Note 2 to entry: Some increase in hardness and some loss in ductility will result from skin passing.
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ISO 14788:2017(E)
3.13
ageing
change in steel properties with the passage of time
Note 1 to entry: Ageing may result in a change in yield strength and a corresponding decrease in ductility
during storage. Ageing always has a negative effect on formability. The redevelopment of a definite yield point
phenomenon as a result of ageing can result in a renewed susceptibility to surface imperfections, such as
stretcher strain marks (Lüder’s lines) and fluting when the steel is formed. To avoid these adverse outcomes, it
is essential that the period between final processing at the producing mill and fabrication be kept to a minimum.
Rotation of stock, by using the oldest material first, is important. Effective roller levelling immediately prior to
fabrication can achieve reasonable freedom from stretcher strain marks.
3.14
lot
up to a specified quantity of steel sheet of the same designation rolled to the same thickness and coating
condition
3.15
coating mass
total amount of coating on both sides of the sheet
Note 1 to entry: Expressed in grams per square metre.
4 Dimensions
4.1 Zinc-5 % aluminium alloy-coated steel sheet is produced in thicknesses from 0,25 mm to 5 mm
inclusive after coating, and in widths of 600 mm and over in coils and cut lengths. Zinc-5 % aluminium
alloy-coated steel sheet less than 600 mm wide may be slit from wide sheet and will be considered as sheet.
4.2 The thickness of zinc-5 % aluminium alloy-coated sheet steel may be specified as a combination
of the base metal and metallic coating, or as the base metal alone. The purchaser shall indicate on the
order which method of specifying thickness is required. In the event that the purchaser does not indicate
any preference, the thickness as a combination of the base metal and coating shall be provided. Annex A
describes the requirements for specifying the thickness of the base metal alone.
5 Conditions of manufacture
5.1 Steelmaking
Unless otherwise agreed by the interested parties, the processes used in making the steel and in
manufacturing zinc-5 % aluminium alloy-coated sheet are left to the discretion of the manufacturer. On
request, the purchaser shall be informed of the steelmaking process being used.
5.2 Chemical composition
The chemical composition (heat analysis) shall conform to the requirements given in Tables 1 and 2.
5.3 Chemical analysis
5.3.1 Heat analysis
An analysis of each heat shall be made by the manufacturer in order to determine compliance with the
requirements given in Tables 1 and 2. On request, a report of the heat analysis shall be made available
to the purchaser or the purchaser’s representative. Each of the elements listed in Tables 1 and 2
shall be included in the report of the heat analysis. When the amount of copper, nickel, chromium or
molybdenum present is less than 0,02 %, the analysis may be reported as “< 0,02%”.
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ISO 14788:2017(E)
5.3.2 Product analysis
A product analysis may be made by the purchaser in order to verify the specified analysis of the product
and shall take into consideration any normal heterogeneity. The product analysis shall be in accordance
with Tables 2 and 3.
Table 1 — Chemical composition (heat analysis)
Mass fractions in percent
Base-metal quality C Mn P S Ti
Designation Name max. max. max. max. max.
01 Commercial 0,15 0,60 0,05 0,035 —
02 Drawing 0,10 0,50 0,04 0,035 —
a
03 Deep drawing 0,08 0,45 0,03 0,03 —
a
04 Deep drawing aluminium killed 0,06 0,45 0,03 0,03 —
a
05 Extra-deep drawing stabilized 0,02 0,25 0,02 0,02 0,15
b
220 to 550 Structural 0,25 1,70 0,035 0,035 —
a
Interstitial-free steel may be applied (see 5.4.1.3).
b
Grades 250 and 280: phosphorus – 0,10 % max. Grade 350: phosphorus – 0,20 % max.
Table 2 — Limits on additional chemical elements
Mass fractions in percent
a a a,b a,b c c,d d
Element Cu Ni Cr Mo Nb V Ti
max. max. max. max. max. max. max.
Heat analysis 0,20 0,20 0,15 0,06 0,008 0,008 0,008
Product analysis 0,23 0,23 0,19 0,07 0,018 0,018 0,018
a
The sum of copper, nickel, chromium and molybdenum shall not exceed 0,50 % on heat analysis. When one or more of
these elements are specified, the sum does not apply, in which case, only the individual limits on the remaining elements apply.
b
The sum of chromium and molybdenum shall not exceed 0,16 % on heat analysis. When one or more of these elements
are specified, the sum does not apply, in which case, only the individual limits on the remaining elements apply.
c
For interstitial-free steels only, the value of 0,15 % maximum for titanium, and 0,10 % maximum for niobium and
vanadium are acceptable to ensure that the carbon and nitrogen are fully stabilized.
d
Heat analysis greater than 0,008 % may be supplied after agreement between the manufacturer and the purchaser.
Table 3 — Product analysis tolerances for Table 1
Mass fractions in percent
Tolerance over maximum
Element Maximum of specified element
specified
0,02 0,01
C 0,15 0,03
0,25 0,04
0,60 0,03
Mn
1,70 0,05
P 0,20 0,01
S 0,035 0,01
Ti 0,15 0,01
NOTE The above maximum tolerance is the allowable excess over the requirement of heat analysis shown in Table 1.
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ISO 14788:2017(E)
5.4 Mechanical properties
5.4.1 Commercial and drawing quality
5.4.1.1 Ordering conditions
Zinc-5 % aluminium alloy-coated steel sheet of designations 01, 02, 03, 04 and 05 is supplied under the
following two ordering conditions.
a) Ordering condition A: steel when ordered to mechanical properties shall, at the time the steel
is made available for shipment, satisfy the applicable requirements of Table 4, when they are
determined on test pieces obtained in accordance with the requirements in Clause 7. The values
specified in Table 4 are applicable for the periods indicated in Table 5 from the time that the steel is
available for shipment.
b) Ordering condition B: steel when ordered to make an identified part shall be supplied with a
commitment to satisfactory manufacturing performance within a properly established breakage
allowance, which shall be previously agreed upon between the interested parties. In these cases,
the part name, the details of fabrication, and special requirements (such as freedom from stretcher
strain or fluting) shall be specified.
In the case of ordering condition B, mechanical properties of the steel sheet may also be agreed upon
by the interested parties and such properties may not necessarily satisfy the requirements of Table 4.
5.4.1.2 Fabrication qualities
Zinc-5 % aluminium alloy-coated steel sheet is available in several fabrication qualities as given in
3.1 to 3.5.
5.4.1.3 Interstitial-free steel
Stabilized interstitial-free (IF) steel is applicable to orders for designations 03, 04 and 05, provided that
the purchaser is informed of the substitution and that related shipping documents reflect the actual
material shipped.
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ISO 14788:2017(E)
Table 4 — Mechanical properties of commercial and drawing quality grades
A
c
Base-metal quality R R min. r n
eL m
a b d,e,f d,e,f
max. max. % min. min.
Designation Name MPa MPa L = 80 mm L = 50 mm
0 0
01 Commercial — — — — — —
02 Drawing 340 430 30 31 — —
03 Deep drawing 300 410 34 35 — —
Deep drawing
04 270 410 36 37 — —
aluminium killed
Extra deep
05 250 380 38 38 1,4 0,17
drawing stabilized
R = lower yield strength
eL
R = tensile strength
m
A = percentage elongation after fracture
L = gauge length of original test piece
o
r = index of drawability of the product
n = index of the stretchability of the product
2
1 MPa = 1 N/mm
For products produced according to performance criteria (ordering condition B), the typical mechanical properties
presented here are non-mandatory. For products specified according to mechanical properties (ordering condition A),
the purchaser may negotiate with the manufacturer if a specific range, or a more restrictive range, is required for the
application. When agreed to, such values may be specified.
NOTE With the exception of footnote c and d, these typical mechanical properties apply to the full range of steel sheet
thicknesses. The yield strength tends to increase and some of the formability tends to decrease as the sheet thickness
decreases.
a
The values apply to 0,2 % proof strength when a definite yield phenomenon is not present, otherwise to the lower yield
strength, R .
eL
b
The minimum tensile strength for qualities 02, 03 and 04 would normally be expected to be 270 MPa. For design
purposes, the lower limit for R may be assumed to be 140 MPa for grades 01, 02, 03, and 04 and 120 MPa for grade 05. All
eL
tensile strength values are determined to the nearest 10 MPa.
c
For materials of thickness up to and including 0,6 mm, the elongation percentages in this table shall be reduced by 2.
d
r and n values are only applicable to thickness ≥ 0,5 mm. For thickness > 2,0 mm, the r value is reduced by 0,2.
e
r can also be written as r-bar and n can also be written as n-bar.
f
r and n values may be modified or excluded from this specification, by agreement between the manufacturer and the
purchaser.
Table 5 — Applicable period for values specified in Table 4
Designation Period
01 Not applicable
02 8 d
03 30 d
04 6 months
05 6 months
5.4.2 Structural quality
The mechanical properties, at the time the steel is made available for shipment, shall satisfy the
requirements listed in Table 6.
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ISO 14788:2017(E)
Table 6 — Mechanical properties of structural-quality grades
A
a
min.
Grade R R %
eL m
designation min. min. L = 80 mm L = 50 mm
0 0
MPa MPa
220 220 310 18 20
250 250 360 16 18
280 280 380 14 16
320 320 430 12 14
350 350 450 10 12
380 380 540 10 12
b
550 550 570 — —
R = lower yield strength
eL
R = tensile strength
m
A = percentage elongation after fracture
L = gauge length of original test piece
o
e = thickness of steel sheet in mm
a = thickness of bend test piece in mm
2
1 MPa = 1 N/mm
NOTE 1 R is measured by 0,5 % total elongation proof strength (proof strength under load) or by 0,2 % offset when a
eL
definite yield phenomenon is not present.
NOTE 2 In determining the base-metal mechanical properties, the base-metal thickness is measured after stripping the
coating from the end of the specimen contacting the grips of the tension-testing machine before testing.
a
The elongation v
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