ISO 4955:2016

INTERNATIONAL ISO
STANDARD 4955
Fourth edition
2016-05-01
Heat-resistant steels
Aciers réfractaires
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 . 2
4 Designation . 2
5 Information to be supplied by the purchaser. 2
6 Classification of grades . 3
7 Requirements . 3
7.1 Manufacturing process. 3
7.2 Delivery condition . 3
7.3 Chemical composition . 4
7.4 Mechanical properties . 4
7.4.1 Mechanical properties at room temperature . 4
7.4.2 Mechanical properties at elevated temperatures . 4
7.5 Surface quality . 4
7.6 Internal soundness . 5
7.7 Dimensions and tolerances on dimensions and shape . 5
8 Inspection, testing and conformance of products. 5
8.1 General . 5
8.2 Inspection procedures and types of inspection documents . 6
8.3 Specific inspection and testing . 6
8.3.1 Extent of testing . 6
8.3.2 Selection and preparation of samples and test pieces . 6
8.4 Test methods . 6
8.5 Retest . 7
9 Marking . 7
Annex A (informative) Technical information on heat- and creep-resistant steels .21
Annex B (informative) Data for creep strength to 1 % plastic strain and creep rupture strength .28
Annex C (informative) Designations of the steels given in Table 2 and of comparable grades
covered in various designation systems .33
Annex D (informative) Applicable dimensional International Standards.36
Bibliography .37
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 meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical
Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 17, Steel, Subcommittee SC 4, Heat treatable and
alloy steels.
This fourth edition cancels and replaces the third edition (ISO 4955:2005), which has been technically
revised.
iv © ISO 2016 – All rights reserved

INTERNATIONAL STANDARD ISO 4955:2016(E)
Heat-resistant steels
1 Scope
This International Standard specifies requirements for the grades listed in Table 2, which are
usually employed for products for which the resistance to the effects of hot gases and the products of
combustion at temperatures in the region above 550°C and/or to long-term mechanical stress is the
main requirement.
NOTE 1 Grades mentioned in this International Standard may also be used for corrosion and creep resistant
purposes.
This International Standard is applicable to the following:
— flat products;
— bars, sections, rod, semi-finished products and forgings.
NOTE 2 Hammer-forged semi-finished products (blooms, billets, slabs, etc.), seamless rolled rings and
hammer-forged bars are in the following, covered under semi-finished products or bars and not under the term
“forgings”.
NOTE 3 Not all of the grades included in this International Standard are necessarily available in all
product forms.
NOTE 4 In Table 2, two alloys are listed in addition to the steels since they belong to the heat resistant grades.
NOTE 5 Heat resistant wire in the cold worked condition is covered by ISO 16143-3.
NOTE 6 Corrosion resistant stainless steels for which resistance to corrosion is of primary importance are
covered by ISO 16143-1 and ISO 16143-2.
NOTE 7 Heat-resistant steels for valves are covered by ISO 683-15.
In addition to this International Standard, the general technical delivery requirements of ISO 404 are
applicable.
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 377, Steel and steel products — Location and preparation of samples and test pieces for mechanical testing
ISO 404, Steel and steel products — General technical delivery requirements
ISO 4885, Ferrous products — Heat treatments — Vocabulary
ISO/TS 4949, Steel names based on letter symbols
ISO 6506-1, Metallic materials — Brinell hardness test — Part 1: Test method
ISO 6892-1:2009, Metallic materials — Tensile testing — Part 1: Method of test at room temperature
ISO 6929, Steel products — Vocabulary
ISO 9443, Heat-treatable and alloy steels — Surface quality classes for hot-rolled round bars and wire
rods — Technical delivery conditions
ISO/TR 9769, Steel and iron — Review of available methods of analysis
ISO 10474, Steel and steel products — Inspection documents
ISO 14284, Steel and iron — Sampling and preparation of samples for the determination of chemical
composition
ISO 15510, Stainless steels — Chemical composition
ISO 20723, Structural steels — Surface condition of hot-rolled sections — Delivery requirements
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 377, ISO 404, ISO 4885,
ISO 6929, ISO 14284 and the following apply.
3.1
heat resistant steels
heat resistant steels of this International Standard are used at above 550°C (wustite point) due to their
excellent resistance to the effects of hot gases and products of combustion, as well as their resistance
to the influence of molten salts and molten metals but also showing good mechanical properties during
short and long-term stressing
3.2
creep resistant grades
steels, nickel- or cobalt-alloys with a minimum of 8 % chromium, which are characterised by good
mechanical behaviour at temperatures above 500 °C under long-range service conditions, i.e. primarily
by creep strength to 1 % plastic strain or creep rupture strength during long-time stressing
4 Designation
For the steel grades covered by this International Standard, the steel names as given in the tables are
allocated in accordance with ISO/TS 4949.
For the steel grades covered by this International Standard, the steel numbers as given in the tables are
allocated in accordance with ISO 15510.
5 Information to be supplied by the purchaser
It shall be the responsibility of the purchaser to specify all requirements that are necessary for products
under this specification. Such requirements to be considered include, in the order listed, but not limited
to, the following:
— the desired quantity;
— the product form;
— the number of the appropriate dimensional standard (see Annex A), the nominal dimensions, plus
any choice of requirements;
— the type of material (grade);
— the number of this International Standard (ISO 4955);
— the name or number of the steel grade;
2 © ISO 2016 – All rights reserved

— if, for the relevant steel in Tables 6 and 7 for the mechanical properties, more than one treatment
condition is covered, the symbol for the desired heat treatment;
— the desired process route, including surface finish (see 7.2, 7.5 and Table 4, footnote d);
— if a verification of internal soundness is required, the requirements have to be agreed at the time of
enquiry and order;
— any further optional test agreed between the manufacturer and purchaser at the time of enquiry
and order;
— the type of inspection document and its designation in accordance with ISO 10474 (see 8.2).
EXAMPLE 1 ton of plates according to ISO 9444-2 with a specified thickness of 5,0 mm, a specified width
of 1 200 mm, with trimmed edges (T) and a specified length of 2 500 mm made of a steel grade with the name
X8NiCrAlTi32–21 (4876–088–00-I) as specified in ISO 4955, in process route 1U and inspection certificate 3.1 as
specified in ISO 10474:
1 t plate ISO 9444-2 — 5,0 × 1200T × 2500
Steel ISO 4955 — X8NiCrAlTi32–21 + 1U
ISO 10474 — 3.1
or
1 t plate ISO 9444-2 — 5,0 × 1200T × 2500
Steel ISO 4955 — 4876-088-00-I + 1U
ISO 10474 — 3.1
6 Classification of grades
Heat-resistant steels covered in this International Standard are classified according to their structure
into the following:
— austenitic grades;
— ferritic grades;
— martensitic grades;
— precipitation hardening grades.
7 Requirements
7.1 Manufacturing process
Unless a special steelmaking process is agreed when ordering, the steelmaking process shall be at the
discretion of the manufacturer. When he so requests, the purchaser shall be informed what steelmaking
process is being used.
7.2 Delivery condition
The products shall be supplied in the delivery condition agreed in the order by reference to the process
route given in Tables 4 and 5 (see also Annex A) and where different alternatives exist to the treatment
conditions given in Tables 6 and 7.
7.3 Chemical composition
7.3.1 The chemical composition requirements given in Table 2 apply with respect to the chemical
composition of the cast analysis.
7.3.2 The product analysis may deviate from the limiting values for the cast analysis given in Table 2 by
values listed in Table 3.
7.4 Mechanical properties
7.4.1 Mechanical properties at room temperature
The mechanical properties at room temperature as specified in Tables 6 and 7 apply for the relevant
specified heat treatment condition. This does not apply to the process route 1U (hot rolled, not heat-
treated, not descaled). If, by agreement at the time of ordering, the products are to be supplied in a non-
heat-treated condition, the mechanical properties specified in Tables 6 and 7 shall be obtainable from
reference test pieces which have received the appropriate heat treatment (simulated heat treatment).
7.4.2 Mechanical properties at elevated temperatures
The mechanical properties at elevated temperature as specified in Table 8 apply for each specified
heat treatment condition. This does not apply to the process route 1U (hot rolled, not heat-treated, not
descaled) and to semi-finished products.
The tensile test at elevated temperature shall be carried out at temperature of interest only when
agreed at the time of enquiry and order.
If, by agreement at the time of ordering, the products are to be supplied in a non-heat-treated condition,
the mechanical properties specified in Table 8 shall be obtainable from reference test pieces which have
received the appropriate heat treatment (simulated heat treatment).
7.5 Surface quality
Availability, and the determination of the types of process route and surface finish (for flat products,
see Table 4 and for long products, see Table 5) most suited to a particular case, should be discussed
with the manufacturer.
The general surface appearance with respect to soundness and surface finish shall be consistent with
good production practice, for the grade and quality ordered, as determined by visual inspection.
When flat products are delivered in coil form, the degree and extent of imperfections may be expected
to be higher, due to the impracticability of removing short lengths of coil.
Flat products delivered with hot-rolled or cold-rolled finishes (see Table 4) shall, unless otherwise
agreed, be supplied with only one surface inspected to the required finish (the prime surface). In
such instances, the manufacturer should indicate the prime surface, by marking the material or the
packaging, or by some other agreed method. The default method is to mark the prime surface, and
to make this surface the top surface of plates, sheets and cut lengths, or the outside surface of coiled
products.
For long products, the available surface finishes are given in Table 5. Slight surface imperfections,
inherent to the production process, are permitted. Exact requirements concerning the maximum depth
of acceptable discontinuities for bars, rods and sections in the relevant conditions are given in Table 1.
4 © ISO 2016 – All rights reserved

Table 1 — Maximum depth of acceptable discontinuities for bars, rods and sections
a
Conditions Product forms Permissible depth of discontinuities Max. % of delivered weight in
excess of permissible depth of
discontinuities
1U, 1C, 1E, 1D Sections To be agreed upon at the time of enquiry and order on the basis of ISO 20723.
1U, 1C, 1E, 1D Rounds and rod Specified at the time of enquiry and order, otherwise ISO 9443 class 1 za2.
b
1X Rounds —  max. 0,2 mm for d ≤ 20 mm 1 %
—  max. 0,01 d for 20 < d ≤ 75 mm
—  max. 0,75 mm for d > 75 mm
Hexagons —  max. 0,3 mm for d ≤ 15 mm 2 %
—  max. 0,02 d for 15 < d ≤ 63 mm
Other bars —  max. 0,3 mm for d ≤ 15 mm 4 %
—  max. 0,02 d for 15 < d ≤ 63 mm
1G Rounds Technically defect free by manufacture. 0,2 %
a
Depth of discontinuities is understood as being the distance, measured normally to the surface, between the bottom of
the discontinuities and that surface.
b
At the time of enquiry and order, it may be agreed that the product shall be delivered with a surface that is technically
defect free by manufacture. In this case, also the maximum % of delivered weight in excess of permissible depth of
discontinuities shall be agreed.
7.6 Internal soundness
For the internal soundness, where appropriate, requirements together with the conditions for their
verification may be agreed at the time of enquiry and order, if possible, with reference to other
International Standards (e.g. ISO 17577 for flat products of thickness equal to or greater than 6 mm).
7.7 Dimensions and tolerances on dimensions and shape
7.7.1 The dimensions and the tolerances on dimensions and shape are to be agreed at the time of
enquiry and order, as far as possible with reference to the dimensional International Standards listed in
Annex D. The ordered dimensions shall, where applicable, include the minimum machining allowances.
7.7.2 If none of the International Standards listed in Annex D is applicable, then the dimensions
and tolerances should be agreed at the time of enquiry and order on the basis of regional or national
standards.
8 Inspection, testing and conformance of products
8.1 General
The manufacturer shall carry out appropriate process control, inspection and testing to ensure that the
delivery complies with the requirements of the order.
This includes the following:
— a suitable frequency of verification of the dimensions of the products;
— an adequate intensity of visual examination of the surface quality of the products;
— an appropriate frequency and type of test to ensure that the correct grade of steel is delivered.
The nature and frequency of these verifications, examinations and tests are determined by the
manufacturer, based on the degree of consistency that has been determined by the evidence of his
quality system. In view of this, verifications by specific tests for these requirements are not necessary
unless otherwise agreed upon.
8.2 Inspection procedures and types of inspection documents
8.2.1 Products complying with this International Standard shall be ordered and delivered with one of
the inspection documents as specified in ISO 10474. The type of document shall be agreed upon at the
time of enquiry and order. If the order does not contain any specification of this type, a test report 2.2
shall be issued.
8.2.2 If, in accordance with the agreements made at the time of enquiry and order, a test report is to be
provided, this shall cover the following:
a) a statement that the material complies with the requirements of the order;
b) the results of the cast analysis for all elements specified for the type of steel supplied.
8.2.3 If, in accordance with the agreements in the order, an inspection certificate 3.1 or 3.2 is to be
provided, the specific inspections and tests described in 8.3 shall be carried out and their results shall be
certified in the document.
In addition to the details in 8.2.2, the document shall cover the following:
a) the results of the mandatory tests marked in the second column of Tables 9 and 10 by an “m”;
b) the results of any optional test or inspection agreed when ordering.
8.3 Specific inspection and testing
8.3.1 Extent of testing
The tests to be carried out, either mandatorily (m) or by agreement (o) and the composition and size
of the test units, and the number of sample products, samples and test pieces to be taken are given in
Tables 9 and 10.
8.3.2 Selection and preparation of samples and test pieces
8.3.2.1 The general conditions for selection and preparation of samples and test pieces shall be in
accordance with ISO 377 and ISO 14284.
8.3.2.2 The samples for the tensile test shall be taken in accordance with Figures 1 to 3. Samples
from flat products shall be taken in such a way that they are located halfway between the centre and a
longitudinal edge.
The samples shall be taken from products in the delivery condition. If agreed, the samples may be taken
from flat products before flattening or from bars before straightening.
For samples to be given a simulated heat treatment, the conditions for annealing shall be agreed.
8.3.2.3 Samples for the hardness test, where requested, shall be taken from the same locations as those
for the tensile test.
8.4 Test methods
8.4.1 Unless otherwise agreed when ordering, the choice of a suitable physical or chemical method of
analysis to determine the product analysis is at the discretion of the manufacturer. In cases of dispute,
the analysis shall be carried out by a laboratory approved by the two parties. In these cases, the reference
method of analysis shall be agreed, where possible, with reference to ISO/TR 9769.
6 © ISO 2016 – All rights reserved

8.4.2 The tensile test at room temperature shall be carried out in accordance with ISO 6892-1, taking
into account for flat products the additional or deviating conditions specified in Figure 3, footnote a. It
shall be performed under controlled conditions in accordance with ISO 6892-1:2009, Clause 5.
Unless otherwise agreed, the tensile strength and elongation after fracture shall be determined and,
in addition, for ferritic, martensitic, precipitation-hardening, austenitic free-cutting and austenitic-
ferritic steels, the 0,2 % proof strength, and for austenitic steels, the 0,2 % and 1 % proof strength.
8.4.3 The Brinell hardness test shall be carried out in accordance with ISO 6506-1.
8.4.4 Dimensions and dimensional tolerances of the products shall be tested in accordance with the
requirements of the relevant dimensional International Standards given in Annex D.
8.5 Retest
See ISO 404.
9 Marking
9.1 The products shall be marked with the manufacturer’s trademark or symbol and the steel name
or number. The product shall also be marked with the cast number, thickness or dimension (and if an
inspection, certificate is requested) an identification number related to the inspection certificate.
9.2 Unless otherwise agreed, the method of marking and the material of marking shall be at the option
of the manufacturer. Its quality shall be such that it shall be durable for at least one year, can withstand
normal handling and can be stored in unheated storage under cover. The corrosion resistance of the
product shall not be impaired by the marking.
9.3 Each unit shall be marked:
— for flat products as an alternative, for items that are wrapped, bundled or boxed, or where the
surface is ground or polished, the marking may be applied to the packaging or to a tag securely
attached to it;
— for semi-finished products, bars, sections and forgings by means of labels attached to the bundle
or, by agreement at the time of enquiry and order, by inking, adhesive labels, electrolytic etching or
stamping;
— for rods, by means of a label attached to the coil.
Table 2 — Chemical composition (cast analysis)
a
Designation % (mass fraction)
Name ISO-number C Si Mn P S Cr Ni N Others
Austenitic steels for heat resistant applications
X6CrNiSiNCe19–10 4818–304– 0,04 to 1,00 to 1,00 0,045 0,015 18,0 to 9,0 to 0,12 to Ce: 0,03 to 0,08
15-E 0,08 2,00 20,0 11,0 0,20
X15CrNiSi20–12 4828–305– 0,20 1,50 to 2,00 0,045 0,030 19,0 to 11,0 to 0,10 —
09-I 2,50 21,0 13,0
X7CrNiSiNCe21–11 4835–308– 0,05 to 1,40 to 0,80 0,040 0,030 20,0 to 10,0 to 0,14 to Ce: 0,03 to 0,08
15-U 0,10 2,00 22,0 12,0 0,20
X18CrNi23–13 4833–309– 0,20 1,00 2,00 0,045 0,030 22,0 to 12,0 to 0,10 —
08-I 24,0 15,0
X8CrNi25–21 4845–310– 0,10 1,50 2,00 0,045 0,015 24,0 to 19,0 to 0,10 —
08-E 26,0 22,0
X15CrNiSi25–21 4841–314– 0,20 1,50 to 2,00 0,045 0,015 24,0 to 19,0 to 0,10 —
00-E 2,50 26,0 22,0
X8NiCrAlTi32–21 4876–088– 0,05 to 1,00 1,50 0,015 0,015 19,0 to 30,0 to — Al: 0,15 to 0,60
00-I 0,10 23,0 34,0 Ti: 0,15 to 0,60
Cu: 0,70
X6NiCrSiNCe35–25 4854–353– 0,04 to 1,20 to 2,00 0,040 0,015 24,0 to 34,0 to 0,12 to Ce: 0,03 to 0,08
15-E 0,08 2,00 26,0 36,0 0,20
Austenitic steels for creep resistant applications
Mo: 0,80 to 1,20
X10CrNiMoMnNbV 4982–215– 0,06 to 0,20 to 5,50 to 14,0 to 9,0 to V: 0,15 to 0,40
0,035 0,015 0,10
B15–10–1 00-E 0,15 1,00 7,0 16,0 11,0 Nb: 0,75 to 1,25
B: 0,003 to 0,009
X7CrNi18–9 4948–304– 0,04 to 1,00 2,00 0,045 0,030 17,0 to 8,0 to — —
09-I 0,10 19,0 11,0
X7CrNiTi18–10 4940–321– 0,04 to 1,00 2,00 0,045 0,030 17,0 to 9,0 to — Ti: 5 × C to 0,80
09-I 0,10 19,0 12,0
c
X7CrNiNb18–10 4912–347– 0,04 to 1,00 2,00 0,045 0,030 17,0 to 9,0 to — Nb: 10 × C to 1,20
09-I 0,10 19,0 12,0
4961–347– 0,04 to 0,30 to 15,0 to 12,0 to — Nb: 10 × C to 1,20
X8CrNiNb16–13 1,50 0,035 0,015
77-E 0,10 0,60 17,0 14,0
4918–316– 0,04 to 16,0 to 12,0 to 0,10 Mo: 2,00 to 2,50
X6CrNiMo17–13–2 0,75 2,00 0,035 0,015
09-E 0,08 18,0 14,0
X7NiCrWCuCoNbN 4990–310– 0,04 to 0,40 0,60 0,025 0,015 21,5 to 23,5 to 0,20 to Co: 1,0 to 2,0
B25–23–3-3–3-2 35-U 0,10 23,5 26,5 0,30 Cu: 2,5 to 3,5
Nb: 0,40 to 0,60
W: 3,0 to 4,0
B: 0,002 to 0,008
Ferritic steels for heat resistant applications
X10CrAlSi7 4713–503– 0,12 0,50 to 1,00 0,040 0,0150 6,0 to 8,0 — — Al: 0,50 to 1,00
72-E 1,00
X2CrTi12 4512–409– 0,03 1,00 1,00 0,040 0,015 10,5 to — — Ti: 6 × (C+N) to
d
10-I 12,5 0,65
X6Cr13 4000–410– 0,08 1,00 1,00 0,040 0,030 12,0 to 1,00 — —
08-I 14,0
X10CrAlSi13 4724–405– 0,12 0,70 to 1,00 0,040 0,015 12,0 to 1,00 — Al: 0,70 to 1,20
77-I 1,40 14,0
Elements not quoted in this table shall not be intentionally added to the steel without the agreement of the purchaser, except for finishing the cast. All
appropriate precautions shall be taken to avoid the addition of such elements from scrap or other materials used in production, which would impair
mechanical properties and the suitability of the steel.
a
Maximum values unless otherwise indicated.
b
The stabilization may be by use of titanium and/or niobium and/or zirconium. According to the atomic mass of these elements and the content of
carbon and nitrogen, the equivalence shall be the following: Nb (% by mass) = Zr (% by mass) = 7/4 Ti (% by mass).
c
Tantalum determined as niobium.
d
By agreement at the time of enquiry and order, this grade can also be delivered with Ti: 6 x C to 0,75.
e
Patented grades.
8 © ISO 2016 – All rights reserved

Table 2 (continued)
a
Designation % (mass fraction)
Name ISO-number C Si Mn P S Cr Ni N Others
X6Cr17 4016–430– 0,08 1,00 1,00 0,040 0,030 16,0 to 1,00 — —
00-I 18,0
X3CrTi17 4510–430– 0,05 1,00 1,00 0,040 0,015 16,0 to — — Ti:
35-I 18,0 [4 × (C+N) + 0,15]
b
to 0,80
X2CrTiNb18 4509–439– 0,03 1,00 1,00 0,040 0,015 17,5 to — — Ti: 0,10 to 0,60
40-X 18,5 Nb: (3 × C + 0,30)
c
to 1,00
Mo: 1,75 to 2,50
4521–444– 17,0 to
X2CrMoTi18–2 0,025 1,00 1,00 0,040 0,015 — 0,030 Ti: ≥4 × (C+N) +
00-I 20,0
b
0,15 to 0,80
X10CrAlSi18 4742–430– 0,12 0,70 to 1,00 0,040 0,015 17,0 to 1,00 — Al: 0,70 to 1,20
77-I 1,40 19,0
X10CrAlSi25 4762–445– 0,12 0,70 to 1,00 0,040 0,015 23,0 to 1,00 — Al: 1,20 to 1,70
72-I 1,40 26,0
X15CrN26 4749–446– 0,20 1,00 1,00 0,040 0,030 24,0 to 1,00 0,15 to —
00-I 28,0 0,25
Martensitic steels for creep resistant applications
0,05 to Mo: 0,30 to 0,90
4916–600– 0,15 to 0,50 to 10,0 to
X18CrMnMoNbVN12 0,50 0,040 0,030 0,60 0,10 Nb: 0,20 to 0,60
77-J 0,20 1,00 13,0
V: 0,10 to 0,40
4923–422– 0,18 to 0,40 to 11,0 to 0,30 to — Mo: 0,80 to 1,20
X22CrMoV12–1 0,50 0,025 0,015
77-E 0,24 0,90 12,5 0,80 V: 0,25 to 0,35
Precipitation hardening grades for creep resistant applications
Mo: 1,00 to 1,50
Ti: 1,90 to 2,35
X6NiCrTiMoVB2 4980–662– 13,5 to 24,0 to
0,08 1,00 2,00 0,040 0,030 — Al: 0,35
e e
5–15–2 86-X 16,0 27,0
V: 0,10 to 0,50
B: 0,001 to 0,010
NiCr19Fe19Nb5Mo3 4668–077– 0,020 to 0,35 0,35 0,015 0,015 17,0 to 50,0 to — Al: 0,30 to 0,70
18-I 0,08 21,0 55,0 Co: 1,00, Cu:0,30
Mo: 2,80 to 3,3
Nb + Ta: 4,7 to 5,5
Ti: 0,60 to 1,20
B: 0,002 to 0,006
NiCr20TiAl 4952–070– 0,04 to 1,00 1,00 0,020 0,015 18,0 to ≥65,0 — Al: 1,00 to 1,80
80-I 0,10 21,0 Co: 1,00, Cu:0,20
Fe: 1,50
Ti: 1,80 to 2,70
B: 0,008
Elements not quoted in this table shall not be intentionally added to the steel without the agreement of the purchaser, except for finishing the cast. All
appropriate precautions shall be taken to avoid the addition of such elements from scrap or other materials used in production, which would impair
mechanical properties and the suitability of the steel.
a
Maximum values unless otherwise indicated.
b
The stabilization may be by use of titanium and/or niobium and/or zirconium. According to the atomic mass of these elements and the content of
carbon and nitrogen, the equivalence shall be the following: Nb (% by mass) = Zr (% by mass) = 7/4 Ti (% by mass).
c
Tantalum determined as niobium.
d
By agreement at the time of enquiry and order, this grade can also be delivered with Ti: 6 x C to 0,75.
e
Patented grades.
Table 3 — Permissible deviations between the product analysis and the limiting values given in
Table 2 for the cast analysis
a
Element Specified limits, cast analysis Permissible deviation
% by mass % by mass
Carbon ≤0,030 +0,005
>0,030 ≤0,20 ±0,01
>0,20 ≤0,60 ±0,02
Silicon ≤1,00 ±0,05
>1,00 ≤3,00 ±0,10
Manganese ≤1,00 ±0,03
>1,00 ≤2,00 ±0,04
>2,00 ≤15,0 ±0,10
Phosphorus ≤0,045 +0,005
Sulfur ≤0,015 +0,003
>0,015 ≤0,030 ±0,005
Chromium ≤15,0 ±0,15
>15,0 ≤20,0 ±0,20
>20,0 ≤35,0 ±0,25
Nickel ≤1,00 ±0,03
>1,00 ≤5,0 ±0,07
>5,0 ≤10,0 ±0,10
>10,0 ≤20,0 ±0,15
>20,0 ≤38,0 ±0,20
>38,0 ±0,50
Nitrogen ≤0,10 + 0,01
≥0,10 ≤0,60 ±0,02
Aluminium ≤0,30 ±0,05
>0,30 ≤2,00 ±0,10
Boron ≤0,010 ±0,000 5
Cerium ≤0,08 ±0,01
Cobalt ≤2,00 ±0,10
Copper ≤1,00 +0,04
>1,00 ≤5,0 ±0,10
Molybdenum ≤ 0,60 ±0,03
>0,60 ≤1,75 ±0,05
>1,75 ≤3,50 ±0,10
Niobium ≤1,50 +0,05
Titanium ≤1,00 +0,05
>1,00 ≤3,0 ±0,07
Tungsten ≤4,0 ±0,07
Vanadium ≤0,85 ±0,03
a
± means that in one cast, the deviation may occur over the upper value or under the lower value of the specified range
in Table 2, but not both at the same time.
10 © ISO 2016 – All rights reserved

a
Table 4 — Type of process route and surface finish of heat-resistant flat steel products
Type of process Surface
b
Abbreviation Notes
route finish
Hot rolled, not
Covered with Suitable for products which are to be
Hot rolled 1U heat-treated, not
the rolling scale further worked, e.g. strip for rerolling.
descaled
Suitable for parts which will be
Hot rolled, heat- Covered with descaled or machined in subsequent
1C
treated, not descaled the rolling scale production or for certain heat-resistant
applications.
The type of mechanical descaling,
e.g. coarse grinding or shot blasting,
Hot rolled, heat-
depends on the steel grade and the
1E treated, mechanically Free of scale
product, and is left to the manufac-
descaled
turer’s discretion, unless otherwise
agreed upon.
Usually standard for most steel types
to ensure good corrosion resistance;
Hot rolled, heat- also common finish for further
1D Free of scale
treated, pickled processing. It is permissible for grind-
ing marks to be present. Not as smooth
as 2D or 2B.
Suitable for parts which will be
Cold rolled, Smooth with
descaled or machined in subsequent
Cold rolled 2C heat-treated, not scale from heat
production or for certain heat-resistant
descaled treatment
applications.
Cold rolled,
Usually applied to steels with scale that
heat-treated, Free of scale,
2E is very resistant to pickling solutions.
mechanically see footnote f.
May be followed by pickling.
descaled
Cold rolled, Finish for good ductility, but not as
2D Smooth
heat-treated, pickled smooth as 2B or 2R.
Most common finish for most steel
types to ensure good corrosion
Cold rolled,
Smoother than resistance, smoothness and flatness.
2B heat-treated, pickled,
2D Also common finish for further pro-
skin passed
cessing. Tension levelling may be used
as an alternative to skin passing.
Cold rolled,
Smoother and
heat-treated, Typical finish for ferritic grades when
2A more reflec-
bright-pickled, skin high reflectivity is desired.
tive than 2B
passed
Cold rolled, bright Smooth, bright, Smoother and brighter than 2B. Also
2R
c
annealed reflective common finish for further processing.
Grade of grit or surface roughness can
Special
d
1G or 2G Ground See footnote e. be specified. Undirectional texture, not
finishes
very reflective.
a
Not all process routes and surface finishes are available for all steels.
b
First digit, 1 = hot rolled, 2 = cold rolled.
c
May be skin passed.
d
One surface only, unless specifically agreed upon at the time of enquiry and order.
e
Within each finish description, the surface characteristics can vary, and more specific requirements may need to be
agreed upon between manufacturer and purchaser (e.g. grade of grit or surface roughness).
f
Different methods of mechanical descaling can be used. Shot blasting will result in a rough and dull surface while
brushing can result in a smooth surface.
a
Table 5 — Type of process route and surface finish of heat-resistant long steel products
Product form
Abbre- Type of
Condi- Surface
Bars,
via- process Notes
Semi- Forg-
tion finish
Rods sec-
b
tion route
finished ings
tions
Hot Covered Suitable for products to
formed, not with scale be further hot formed. For
1U heat-treat- (spot ground X X X — semi-finished products,
ed, not if necessary) ground on all sides can be
descaled specified
Hot formed, Covered Suitable for products to
heat-treat- with scale be further processed. For
c
1C ed, not (spot ground X X X X semi-finished products,
descaled if necessary) ground on all sides can be
specified
Hot formed, Largely free The type of mechanical
heat- of scale (but descaling, e.g. grinding,
c
treated, some black peeling or shot blasting, is
Hot
mechanical- spots may left to the manufacturer’s
formed 1E X X X X
ly descaled remain) discretion unless
otherwise agreed. Suitable
for products to be further
processed
d,e
Hot formed, Free of scale Tolerance ≥ IT 14
heat-
1D X X — X
c
treated,
pickled
d,e
Hot formed, Metallically Tolerance ≥ IT 12
heat- clean
c
1X treated, — X — X
rough ma-
chined
Centreless Uniform Surface roughness can be
ground finish. Type specified. Finish for close
and degree ISO-tolerances. Normally
1G — X — —
of grinding obtained from material in
to be agreed finishes 1E, 1D, 2H or 2B.
d,e
Tolerance ≤ IT 8
Special
Polished Smoother Surface roughness can be
finishing
and brighter specified. Finish for close
process
than finish ISO-tolerances.
1G or 2G. Normally obtained from
1P — X — —
Type and material in finishes 1E, 1D,
degree of 2B, 1G or 2H.
d,e
polishing to Tolerance ≤ IT 11
be agreed
a
Not all process routes and surface finishes are available for all steels.
b
First digit, 1 = hot formed, 2 = cold processed.
c
On ferritic and austenitic grades, the heat treatment may be omitted if the conditions for hot forming and subsequent
cooling are such that the requirements for the mechanical properties of the product are obtained.
d
For information: IT = international tolerance, as defined in ISO 286-1, and in other dimensional tolerance standards.
e
Specific tolerance within the ranges shall be agreed upon at the time of enquiry and order.
12 © ISO 2016 – All rights reserved

Table 6 — Mechanical properties for flat products in the usual delivery condition
a
Designation Thickness Heat Hard- Proof strength Tensile Elongation after
c,d e
treat- ness strength fracture
b
ment
Name ISO-number t HBW R R R A A
p0,2 p1,0 m 80
f f
flat products  MPa MPa 0,5 ≤ t < 3 3 ≤ t
mm % %
max. max. min. min. min.
(lg. + tr.) lg. tr.
Austenitic steels for heat resistant applications
X6CrNiSiNCe19–10 4818–304–15-E 0,5 ≤ t ≤ 75 +AT 210 290 330 600 to 800 30 40 40
X15CrNiSi20–12 4828–305–09-I 0,5 ≤ t ≤ 75 +AT 223 230 270 550 to 750 28 30 30
X7CrNiSiNCe21–11 4835–308–15-U 0,5 ≤ t ≤ 75 +AT 210 310 345 650 to 850 37 40 40
X18CrNi23–13 4833–309–08-I 0,5 ≤ t ≤ 75 +AT 192 210 250 500 to 700 33 35 35
X8CrNi25–21 4845–310–08-E 0,5 ≤ t ≤ 75 +AT 192 210 250 500 to 700 33 35 35
X15CrNiSi25–21 4841–314–00-E 0,5 ≤ t ≤ 75 +AT 223 230 270 550 to 750 28 30 30
X8NiCrAlTi32–21 4876–088–00-I 0,5 ≤ t ≤ 75 +AT 192 170 210 450 to 680 28 30 30
X6NiCrSiNCe35–25 4854–353–15-E 0,5 ≤ t ≤ 75 +AT 210 300 340 650 to 850 40 40 40
Austenitic steels for creep resistant applications
X10CrNiMoMnNbV
4982–215–00-E — — — — — — — — —
B15–10–1
X7CrNi18–9 4948–304–09-I 0,5 ≤ t ≤ 75 +AT 192 195 230 500 to 700 37 40 40
X7CrNiTi18–10 4940–321–09-I 0,5 ≤ t ≤ 75 +AT 215 190 230 500 to 720 40 40 40
X7CrNiNb18–10 4912–347–09-I 0,5 ≤ t ≤ 75 +AT 192 205 240 510 to 710 28 30 30
X8CrNiNb16–13 4961–347–77-E 0,5 ≤ t ≤ 75 +AT — 200 240 500 to 750 30 30 35
X6CrNiMo17–13–2 4918–316–09-E — — — — — — — — —
X7NiCrWCuCoNbN 4990–310–35-U
— — — — — — — — —
B25–23–3-3–3-2
Ferritic steels for heat resistant applications
X10CrAlSi7 4713–503–72-E 0,5 ≤ t ≤ 12 +A 192 220 — 420 to 620 — 20 15
X2CrTi12 4512–409–10-I 0,5 ≤ t ≤ 12 +A — 210 — 380 to 560 25 25 25
X6Cr13 4000–410–08-I 0,5 ≤ t ≤ 12 +A 197 230 — 400 to 630 18 20 18
X10CrAlSi13 4724–405–77-I 0,5 ≤ t ≤ 12 +A 192 250 — 450 to 650 13 15 15
X6Cr17 4016–430–00-I 0,5 ≤ t ≤ 12 +A 197 250 — 430 to 630 18 20 18
X3CrTi17 4510–430–35-I 0,5 ≤ t ≤ 12 +A — 230 — 420 to 600 23 23 23
X2CrTiNb18 4509–439–40-X 0,5 ≤ t ≤ 12 +A — 230 — 430 to 630 18 18 18
X2CrMoTi18–2 4521–444–00-I 0,5 ≤ t ≤ 12 +A — 280 300 420 to 620 20 20 20
X10CrAlSi18 4742–430–77-I 0,5 ≤ t ≤ 12 +A 212 270 — 500 to 700 13 15 15
X10CrAlSi25 4762–445–72-I 0,5 ≤ t ≤ 12 +A 223 280 — 520 to 720 13 15 15
X15CrN26 4749–446–00-I 0,5 ≤ t ≤ 12 +A 212 280 — 500 to 700 13 15 15
Martensitic steels for creep resistant applications
X18CrMnMoNbV 0,5 ≤ t ≤ 75 — — — — — — —
4916–600–77-J
N12
X22CrMoV12–1 4923–422–77-E 0,5 ≤ t ≤ 75 +QT — 600 — 800 to 950 — 14
Precipitation hardening grades for creep resistant applications
a
For other thicknesses, the mechanical properties shall be negotiated.
b
+A = annealed; +AT = solution annealed; +QT quenched and tempered; +P precipitation hardened (see also Table B.1).
c
For guidance only.
d
For thin materials, the HRB or HV hardness test may be used, by agreement between purchaser and manufacturer, where it is not practicable to use the
HBW test.
e
In the case of ferritic and austenitic steels, the values for flat products having a thickness t ≥ 3 mm are valid for a gauge length of L = 5,65 √S ; for flat
0 0
products of thickness with 0,5 ≤ t < 3 mm, the values are valid for both test pieces specified in ISO 6892-1.
f 2
1 MPa = 1 N/mm .
Table 6 (continued)
a
Designation Thickness Heat Hard- Proof strength Tensile Elongation after
c,d e
treat- ness strength fracture
b
ment
Name ISO-number t HBW R R R A A
p0,2 p1,0 m 80
f f
flat products  MPa MPa 0,5 ≤ t < 3 3 ≤ t
mm % %
max. max. min. min. min.
(lg. + tr.) lg. tr.
X6NiCrTiMoV
4980–662–86-X 0,5 ≤ t ≤ 75 +P — 590 — 900 to 1 150 — 15
B25–15–2
NiCr19Fe19Nb5 4668–077–18-I — 1 030 — ≥1 230 — 12
0,5 ≤ t ≤ 20 +P
Mo3
NiCr20TiAl 4952–070–80-I 0,5 ≤ t ≤ 20 +P — 600 — ≥1 000 — 18
a
For other thicknesses, the mechanical properties shall be negotiated.
b
+A = annealed; +AT = solution annealed; +QT quenched and tempered; +P precipitation hardened (see also Table B.1).
c
For guidance only.
d
For thin materials, the HRB or HV hardness test may be used, by agreement between purchaser and manufacturer, where it is not practicable to use the
HBW test.
e
In the case of ferritic and austenitic steels, the values for flat products having a thickness t ≥ 3 mm are valid for a gauge length of L = 5,65 √S ; for flat
0 0
products of thickness with 0,5 ≤ t < 3 mm, the values are valid for both test pieces specified in ISO 6892-1.
f 2
1 MPa = 1 N/mm .
14 © ISO 2016 – All rights reserved

Table 7 — Mechanical properties for long products in the usual delivery condition
a
Designation Thickness Heat Hard- Proof Tensile Elongation
f e
product form treat- ness- strength strength after
b c,d,e,f g
ment fracture
Name ISO- Bars Rods and forgings HBW R R A
...