ISO/TR 14745:2015

Welding — Post-weld heat treatment parameters for steels

ISO/TR 14745:2015 provides recommendations for post-weld heat treatment (PWHT) of steels with recommendations for holding temperatures and holding times for different materials and material thicknesses. These recommendations are limited to stress relieving for non-alloy steels (groups 1, 2, 3, 4, and 11) and to tempering for Cr-Mo-(Ni) steels (groups 5 and 6) and martensitic stainless steels (group 7.2), and are independent of type of product or location. The recommendations do not supersede any guidance given in material supplier specifications, e. g. thermo-mechanically treated fine-grain steels. It does not specify when PWHT is required. Such requirements are given in product standards, material specifications, or material data sheets.

Soudage — Paramètres de traitement thermique après soudage des aciers

General Information

• Status: Withdrawn
• Publication Date: 06-Jan-2015
• ICS: 25.160.01 - Welding, brazing and soldering in general
• Technical Committee: ISO/TC 44/SC 10 - Quality management in the field of welding
• Drafting Committee: ISO/TC 44/SC 10 - Quality management in the field of welding
• Current Stage: 9599 - Withdrawal of International Standard
• Completion Date: 25-May-2022

Standards Content (Sample)

TECHNICAL ISO/TR
REPORT 14745
First edition
2015-01-15
Welding — Post-weld heat treatment
parameters for steels
Soudage — Paramètres de traitement thermique après soudage des
aciers
Reference number
ISO/TR 14745:2015(E)
©
ISO 2015

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ISO/TR 14745:2015(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2015
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
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ii © ISO 2015 – All rights reserved

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ISO/TR 14745:2015(E)

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 2
4.1 Symbols . 2
4.2 Abbreviated terms . 2
5 General information . 2
6 Heat treatment conditions . 2
7 Application of PWHT . 4
7.1 General . 4
7.2 Heating and cooling . 4
7.3 Heating in a furnace . 7
8 Post-weld heat treatment of dissimilar ferritic joints . 8
8.1 General . 8
8.2 Holding temperature . 8
Annex A (informative) Additional information about PWHT . 9
Bibliography .11
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ISO/TR 14745:2015(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
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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
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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).
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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 44, Welding and allied processes, Subcommittee
SC 10, Unification requirements in the field of metal welding.
Requests for official interpretations of any aspect of this Technical Report should be directed to the
Secretariat of ISO/TC 44/SC 10 via your national standards body. A complete listing of these bodies can
be found at www.iso.org.
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TECHNICAL REPORT ISO/TR 14745:2015(E)
Welding — Post-weld heat treatment parameters for steels
1 Scope
This Technical Report provides recommendations for post-weld heat treatment (PWHT) of steels with
recommendations for holding temperatures and holding times for different materials and material
thicknesses. These recommendations are limited to stress relieving for non-alloy steels (groups 1, 2, 3, 4,
and 11) and to tempering for Cr-Mo-(Ni) steels (groups 5 and 6) and martensitic stainless steels (group
7.2), and are independent of type of product or location. The recommendations do not supersede any
guidance given in material supplier specifications, e. g. thermo-mechanically treated fine-grain steels.
This Technical Report does not specify when PWHT is required. Such requirements are given in product
standards, material specifications, or material data sheets.
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.
EN 10052, Vocabulary of heat treatment terms for ferrous products
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 10052 and the following apply.
3.1
cooling rate
variation in temperature as a function of time during cooling cycle
[SOURCE: ISO 4885:1996, 3.37]
3.2
heating rate
variation in temperature as a function of time during heating cycle
[SOURCE: ISO 4885:1996, 3.78]
3.3
holding temperature
temperature at which the product or component is kept in order to achieve specified properties
Note 1 to entry: The holding temperature depends on the type of heat treatment, type of material, and
material thickness.
Note 2 to entry: Normally the holding temperature is expressed as a temperature range.
[SOURCE: ISO 17663:2009, 3.3]
3.4
holding time
time the product or component is kept at the holding temperature
Note 1 to entry: The holding time starts when the temperature in all measuring points has reached the minimum value
of the range of the holding temperature and stops when one of the measuring points falls below that temperature.
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ISO/TR 14745:2015(E)

Note 2 to entry: The holding time depends on the type of heat treatment, material, and material thickness.
[SOURCE: ISO 17663:2009, 3.4]
3.5
post-weld heat treatment
PWHT
heat treatment carried out after welding in order to decrease residual welding stress, and/or to adjust
to desired properties and/or the microstructure
4 Symbols and abbreviated terms
4.1 Symbols
P Hollomon–Jaffe parameter
t material thickness, in mm
NOTE Symbols other than those specified here are used in other International Standards.
4.2 Abbreviated terms
NT normalized and tempered
PWHT post-weld heat treatment
QT quenched and tempered
5 General information
PWHT should be performed in accordance with a written procedure which describes the parameters
critical to the PWHT process.
Equipment used for the PWHT should be suitable according to ISO 17663. It should permit the
temperature control of the component with adequate accuracy and uniformity. The PWHT of products
or components should be recorded by the manufacturer indicating the holding temperature, holding
time, and the heating- and cooling-rate.
6 Heat treatment conditions
PWHT, with the exception of those materials mentioned in Clause 8, should be applied to steels in
accordance with Table 1 upon completion of welding. If PWHT of materials, not listed in Table 1, is
considered necessary, the PWHT holding time and holding temperature should take into account
recommendations of the application standard, as well as the recommendations of the material and
welding consumable manufacturer to achieve the required material properties.
Where welded joints are connecting parts with different thicknesses, the thickness to be used in applying
the requirements for PWHT should be as follows:
a) for butt welds (excluding in T joints), the thickest part of the weld of the two parts (see Figure 1);
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ISO/TR 14745:2015(E)

Key
s weld thickness
Figure 1 — Example of thickest part of the weld
b) for butt welds in T joints, the thickness of the weld;
c) for fillet welds, the throat thickness of the weld;
d) for butt-welded set-on nozzles, the thickness of the nozzle;
e) for set-through nozzles, the thickness of the plate or shell;
f) for set-in nozzles, the thickness of the weld.
PWHT may be carried out on steels of thickness lower than those specified by Table 1. Such instances
may include products subject to stress corrosion cracking or at risk of brittle fracture.
When additional welds or weld repairs have been made after PWHT, a further heat treatment is normally
carried out. The thickness to be used in defining the holding time required at temperature should be the
thickness of the weld applied after the PWHT.
In Table 1, a P value is introduced. This parameter, a critical Hollomon–Jaffe value, should not be
crit
exceeded without proving the mechanical properties.
PWHT as per Table 1, particularly in the upper range of holding temperature and/or holding time, may
unduly impair the physical properties, e. g. yield strength, tensile strength, and toughness of the material.
A higher PWHT temperature than tempering temperature for NT- and QT-materials could impair the
mechanical properties of the material.
The whole PWHT cycle consisting of heating rate, holding temperature, holding time, and cooling rate
can have an essential influence on the mechanical properties. The data for heating and cooling can be
taken out of the relevant product standards. If required by application standards or specifications, the
PWHT cycle should be qualified by a procedure test including parent metal. This belongs especially for
multi-PWHT cycles.
The additional effect of multiple heating cycles should be considered. This effect is explained by the
[4]
Hollomon-Jaffe parameter, P, as given in
−3
PT=+20 lgt ×10 (1)
()
s h
where
T is the holding temperature, in Kelvin;
s
t is the holding time, in hours.
h
NOTE The Hollomon-Jaffe parameter describes the effect of tempering for a certain time, t, at a certain
temperature, T, and a parameter, C, that is unique to the material used. This mathematical relationship has proved
to be of particular value in highly complex welding procedure qualifications where considerable costs can arise
by application of multiple-stage PWHT in the production process. The Hollomon-Jaffe parameter may be used in
the calculation and application of more cost effective single-cycle PWHT.
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ISO/TR 14745:2015(E)

7 Application of PWHT
7.1 General
PWHT can be applied with a furnace or with local heating (e.g. induction or resistance). Reference should
be made to ISO 17663 for the methods of application.
The PWHT temperatures and times should be in accordance with Table 1.
7.2 Heating and cooling
During the heating and cooling periods, for temperatures up to 500 °C, variation in temperature
throughout the product or component should not exceed 150 °C within 4 500 mm and the temperature
gradient should be gradual. Above 500 °C, this variation should not exceed 100 °C.
When the product or component has attained a uni
...