ISO 4991:2024
(Main)Steel castings for pressure purposes
Steel castings for pressure purposes
This document covers steel castings for pressure containing parts. It includes materials which are used for the manufacture of components subject to pressure vessel codes and components not subject to codes. This document relates to castings manufactured from unalloyed and alloyed steel grades (characterized by their chemical composition given in Table 1, and mechanical properties in Tables 2, 3, 4 and 5). NOTE Annex D gives information on ISO grade designation and available UNS numbers which are similar to the ISO grade designation.
Pièces moulées en acier pour service sous pression
General Information
Relations
Standards Content (Sample)
International
Standard
ISO 4991
Fourth edition
Steel castings for pressure purposes
2024-11
Pièces moulées en acier pour service sous pression
Reference number
© ISO 2024
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Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Information to be supplied by the purchaser . 1
5 Heat treatment . 2
6 Welding . 2
7 Requirements . 2
7.1 Chemical composition .2
7.2 Mechanical properties .2
8 Inspection and testing . 3
8.1 General .3
8.2 Sampling .3
8.3 Formation of test lots . .3
8.4 Non-destructive testing .3
8.5 Marking .3
9 Supplementary requirements . 3
Annex A (normative) Supplementary requirements .11
Annex B (informative) Welding conditions .13
Annex C (informative) Creep properties .15
Annex D (informative) UNS cast grades similar to ISO cast grades .18
Bibliography .20
iii
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
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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 document 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).
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rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
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www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
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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 www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 17, Steel, Subcommittee SC 11, Steel castings.
This fourth edition cancels and replaces the third edition (ISO 4991:2015), which has been technically
revised.
The main changes are as follows:
— grade names and numbers have been corrected;
— a cast steel grade for higher temperature applications (550 °C to 700 °C) has been added;
— two austenitic-ferritic stainless steel (duplex) grades have been added for pressure parts up to 250 °C;
— the application temperature range of some special steels has been extended;
— qualification requirements for welders have been added.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
International Standard ISO 4991:2024(en)
Steel castings for pressure purposes
1 Scope
This document covers steel castings for pressure containing parts.
It includes materials which are used for the manufacture of components subject to pressure vessel codes
and components not subject to codes.
This document relates to castings manufactured from unalloyed and alloyed steel grades (characterized by
their chemical composition given in Table 1, and mechanical properties in Tables 2, 3, 4 and 5).
NOTE Annex D gives information on ISO grade designation and available UNS numbers which are similar to the
ISO grade designation.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content are
requirements for 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 148-1, Metallic materials — Charpy pendulum impact test — Part 1: Test method
ISO 4885, Ferrous materials — Heat treatments — Vocabulary
ISO/TS 4949, Steel names based on letter symbols
ISO 4990, Steel castings — General technical delivery requirements
ISO 6892-1, Metallic materials — Tensile testing — Part 1: Method of test at room temperature
ISO 6892-2, Metallic materials — Tensile testing — Part 2: Method of test at elevated temperature
ISO 9606-1, Qualification testing of welders — Fusion welding — Part 1: Steels
ISO 11970, Specification and qualification of welding procedures for production welding of steel castings
ISO 13520, Determination of ferrite content in austenitic stainless steel castings
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 4885, ISO/TS 4949 and ISO 4990 apply.
ISO and IEC maintain terminological databases for use in the standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .ort/ obp.
— IEC Electropedia: available at https:// www .electropedia .org/
4 Information to be supplied by the purchaser
Materials specified in this document shall conform to the applicable requirements of ISO 4990, including the
supplementary requirements listed in Annex A that are specified in the enquiry and purchase order.
5 Heat treatment
The type of heat treatment shall conform with Table 6 for the specified grades. The temperatures given are
for information only.
When a grade may be delivered at different strength levels depending on the type of heat treatment (see
Table 2), the purchaser shall state at the time of enquiry and order the type of heat treatment required.
The symbols for the type of heat treatment are as follows:
— +N normalized
— +QT quenched and tempered
— +AT solution treated
NOTE For definitions, see ISO 4885.
6 Welding
Welding is permitted, unless otherwise agreed. All the welds shall conform to the same criteria for non-
destructive testing as the relevant part of the casting. Welding shall be carried out in accordance with
ISO 11970, and the welding personnel for permanent joining of components shall be qualified according to
ISO 9606-1.
The welding conditions are given in Annex B.
7 Requirements
7.1 Chemical composition
An analysis of each heat shall be made by the manufacturer to determine the contents of the specified
elements.
The chemical composition shall comply with the values given in Table 1.
Permissible deviations for the product analysis are specified in ISO 4990.
7.2 Mechanical properties
The mechanical properties shall comply with the values given in Tables 2, 3, 4 and 5.
Mechanical properties shall be measured on test pieces taken from test blocks (according to ISO 4990).
The tensile tests at room temperature shall be carried out in accordance with ISO 6892-1 and, if specified,
impact tests in accordance with ISO 148-1.
If required by agreement at the time of enquiry and order, impact energy properties at low temperature
shall conform with Table 3.
If required by agreement at the time of enquiry and order, impact energy values at room temperature shall
conform with Table 4.
If required by agreement at the time of enquiry and order, verification of the elevated temperature proof
stress values shall be carried out at elevated temperatures in accordance with ISO 6892-2. In such a case, the
values shall conform with Table 5.
Creep resistance mean values are given for information, for some grades in Annex C.
8 Inspection and testing
8.1 General
For all products ordered to the requirements of this document, specific inspection and testing is required.
8.2 Sampling
Test blocks shall be heat treated in production furnaces to the same procedure as the castings they represent.
Test pieces shall not be cut from the test block until the latter has been heat treated.
8.3 Formation of test lots
The formation of test lots shall be carried out in accordance with ISO 4990.
8.4 Non-destructive testing
The following information shall be given at the time of enquiry and order in accordance with ISO 4990:
— non-destructive testing required,
— area to be tested,
— acceptance criteria.
8.5 Marking
Castings shall be marked for material identification.
a) Heat numbers or serial numbers that are traceable to heat numbers, shall be marked on all castings.
b) For small castings, it may be agreed at the time of the enquiry and order that they may be batched and
that their identification is marked on a label attached to each batch.
c) Castings shall be marked with the manufacturer's identification or symbol except where other
provisions have been made between the manufacturer and purchaser.
d) When more than one heat treatment type is available, the heat treatment applied shall be marked with a
suffix added to the grade designation (see Table 2).
9 Supplementary req
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