ISO 14590:2016

INTERNATIONAL ISO
STANDARD 14590
Third edition
2016-08-15
Cold-reduced steel sheet of high
tensile strength and low yield point
with improved formability
Tôles en acier laminées à froid à haute résistance à la traction et
faible limite d’élasticité, et aptitude au formage accrue
Reference number
©
ISO 2016
© ISO 2016, Published in Switzerland
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ii © ISO 2016 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Dimensions . 2
5 Conditions of manufacture . 3
5.1 Steelmaking . 3
5.2 Chemical composition . 3
5.3 Chemical analysis . 4
5.3.1 Heat analysis . . 4
5.3.2 Product analysis . 4
5.4 Mechanical properties . 4
5.5 Application . 6
5.6 Weldability . 6
5.7 Surface condition . 6
5.8 Surface finish . 7
5.9 Oiling . 7
5.10 Dimensional and shape tolerances . 7
6 Sampling — Tensile test . 7
7 Test methods — Tensile test . 7
8 Retests . 7
8.1 Machining and flaws. 7
8.2 Elongation . 7
8.3 Additional tests . 7
9 Resubmission . 8
10 Workmanship . 8
11 Inspection and acceptance . 8
12 Coil size . 8
13 Marking . 8
14 Information to be supplied by the purchaser. 9
Annex A (normative) Bake hardening test method.10
Bibliography .12
Foreword
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bodies (ISO member bodies). The work of preparing International Standards is normally carried out
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electrotechnical standardization.
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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
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The committee responsible for this document is ISO/TC 17, Steel, Subcommittee SC 12, Continuous mill
flat rolled products.
This third edition cancels and replaces the second edition (ISO 14590:2005), which has been technically
revised.
iv © ISO 2016 – All rights reserved

INTERNATIONAL STANDARD ISO 14590:2016(E)
Cold-reduced steel sheet of high tensile strength and low
yield point with improved formability
1 Scope
This International Standard applies to cold-reduced steel sheet of two types that are commercially
available in the world. Type 1 represents steels that are produced to mechanical properties only and
Type 2 represents steels that are produced to both chemical and mechanical properties. Bake hardening
steels are included in both types.
This International Standard does not cover steels designated as commercial quality or drawing qualities
(covered in ISO 3574), steels of structural quality (covered in ISO 4997) or steels of higher strength
with improved formability (covered in ISO 13887).
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 6892-1, Metallic materials — Tensile testing — Part 1: Method of test at room temperature
ISO 16162, Cold-rolled steel sheet products — Dimensional and shape tolerances
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
bake hardenable steel
highly formable steel that, subsequent to cold working, has been subjected to a low-temperature heat
treatment, such as that used for paint baking (170 °C to 200 °C), in order to effect a significant increase
in its yield strength, primarily due to carbon ageing
3.2
cold-reduced steel sheet
product obtained from hot-rolled descaled steel sheet by cold-reducing to the required sheet thickness
followed by annealing to recrystallize the grain structure
3.3
dual-phase steel
steel whose thermal processing has resulted in a multi-phase structure that includes one or more low-
temperature transformation products, thus providing for improved formability at higher strength levels
3.4
skin pass
light cold-rolling of the product
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; and to obtain the required surface finish.
Note 2 to entry: Some increase in hardness and some decrease of ductility will result from skin passing.
3.5
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.
3.6
lot
up to a specified quantity of steel sheet of the same designation rolled to the same thickness and grade
3.7
Type 1
cold-reduced steel sheet (3.2) specified to mechanical properties only
3.8
Type 2
cold-reduced steel sheet (3.2) specified to both mechanical properties and chemical composition
3.9
preliminary strain load
F
WH
load (kgf or N) of work hardening reached when the preliminary strain elongation specified in the
tensile test is reached
Note 1 to entry: Preliminary strain elongation herein shall be 2 %.
Note 2 to entry: to entry: Refer to Figure A.2.
3.10
strain ageing yield load
F
SA
load (kgf or N) at yielding measured during the tensile testing of the specimen after it has been strained
and heat-treated at 170 °C for 20 min
Note 1 to entry: Refer to Figure A.1.
3.11
BH amount
O
BH
2 2
value (kgf/mm or N/mm ) obtained by dividing the value (kgf or N) derived by subtracting the
preliminary strain load, F , from the strain ageing yield load, F , of the test piece parallel portion
WH SA
original area (mm ) before the preliminary strain
4 Dimensions
Cold-reduced steel sheet of high tensile strength and low yield point with improved formability is
produced in thicknesses from 0,25 mm to 3,2 mm and in widths of 600 mm and over in coils and cut
lengths. Product less than 600 mm wide, slit from wide sheet, will be considered as sheet.
2 © ISO 2016 – All rights reserved

5 Conditions of manufacture
5.1 Steelmaking
Unless otherwise agreed upon by the interested parties, the processes used in making the steel and in
manufacturing cold-reduced steel 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.
Table 1 — Chemical composition for Type 2 (heat analysis)
Mass fractions in percent
C Si Mn P S
a
Grade
max. max. max. max. max.
SS220 0,10 0,50 1,00 0,100 0,030
SS260 0,10 0,50 1,50 0,120 0,030
SS300 0,15 0,50 1,50 0,140 0,030
DP250 0,10 0,70 2,00 0,030 0,030
DP280 0,12 0,70 2,50 0,030 0,030
DP300 0,14 1,40 2,00 0,080 0,030
DP350 0,14 1,40 2,50 0,100 0,030
DP400 0,18 1,40 2,50 0,030 0,030
DP600 0,20 1,40 3,00 0,030 0,030
BH180 0,04 0,50 0,70 0,060 0,030
BH220 0,08 0,50 0,70 0,080 0,030
BH260 0,08 0,5
...