ISO/TR 17671-3:2002

TECHNICAL ISO/TR
REPORT 17671-3
First edition
2002-02-01
Welding — Recommendations for welding
of metallic materials —
Part 3:
Arc welding of stainless steels
Soudage — Recommandations pour le soudage des matériaux
métalliques —
Partie 3: Soudage à l'arc des aciers inoxydables

Reference number
©
ISO 2002
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©  ISO 2002
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ii © ISO 2002 – All rights reserved

Contents Page
Foreword.iv
Introduction.v
1 Scope .1
2 References .1
3 Terms and definitions .2
4 Parent metal .2
5 Storage and handling.2
6 Welding consumables.3
7 Fabrication .3
8 Quality requirements of welds .4
9 Distortion.5
10 Post-weld cleaning .5
Annex A Welding of austenitic stainless steels .7
Annex B Welding of ferritic stainless steels.12
Annex C Welding of austenitic-ferritic stainless steels.15
Annex D Welding of martensitic and martensitic-austenitic stainless steels.19

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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.
The main task of technical committees is to prepare International Standards. Draft International Standards adopted
by the technical committees are circulated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting a vote.
In exceptional circumstances, when a technical committee has collected data of a different kind from that which is
normally published as an International Standard (“state of the art”, for example), it may decide by a simple majority
vote of its participating members to publish a Technical Report. A Technical Report is entirely informative in nature
and does not have to be reviewed until the data it provides are considered to be no longer valid or useful.
Attention is drawn to the possibility that some of the elements of this part of ISO/TR 17671 may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO/TR 17671-3 was prepared by Technical Committee ISO/TC 44, Welding and allied processes, Subcommittee
SC 10, Unification of requirements in the field of metal welding.
ISO/TR 17671 consists of the following parts, under the general title Welding — Recommendations for welding of
metallic materials:
 Part 1: General guidance for arc welding
 Part 2: Arc welding of ferritic steels
 Part 3: Arc welding of stainless steels
 Part 4: Arc welding of aluminium and aluminium alloys
iv © ISO 2002 – All rights reserved

Introduction
This part of ISO/TR 17671 is being issued with several annexes in order that it may be extended to cover the
different types of steel which will be produced to all the International steel standards for stainless steels.
When this part of ISO/TR 17671 is referenced for contractual purposes, the ordering authority should state the
need for compliance with the document and such other annexes as are appropriate.
This part of ISO/TR 17671 gives general guidance for the satisfactory production and control of welding and details
the possible detrimental phenomena that may occur with advice on methods by which they may be avoided. It is
generally applicable to all stainless steels and is appropriate regardless of the type of fabrication involved, although
the application standard may have additional requirements. Permissible design stresses in welds, methods of
testing and acceptance levels are not included because they depend on the service conditions of fabrication. These
details should be obtained from the design specification.
This part of ISO/TR 17671 contains additional details for fusion welding of stainless steels and should be read in
conjunction with the general recommendations in ISO/TR 17671-1.
TECHNICAL REPORT ISO/TR 17671-3:2002(E)

Welding — Recommendations for welding of metallic materials —
Part 3:
Arc welding of stainless steels
1 Scope
This part of ISO/TR 17671 gives general recommendations for the fusion welding of stainless steels. Specific details
relevant to austenitic, austenitic-ferritic, ferritic and martensitic stainless steels are given in annexes A to D.
2 References
ISO 3581, Welding consumables — Covered electrodes for manual metal arc welding of stainless and heat-
resisting steels — Classification
ISO 5817, Welding — Fusion-welded joints in steel, nickel, titanium and their alloys (beam welding excluded) —
Quality levels for imperfections
ISO 8249, Welding — Determination of Ferrite Number (FN) in austenic and duplex ferritic-austenitic Cr-Ni
stainless steel weld metals
ISO 9692-1, Welding and allied processes — Recommendations for joint preparation — Part 1: Manual metal-arc
welding, gas-shielded metal-arc welding and gas welding of steels
ISO 9956-2, Specification and approval of welding procedures for metallic materials — Part 2: Welding procedure
specification for arc welding
ISO 14175, Welding consumables — Shielding gases for arc welding and cutting
ISO 14343, Welding consumables — Wire electrodes, wires and rods for arc welding of stainless and heat resisting
steels — Classification
ISO/TR 15608:2000, Welding — Guidelines for a metallic materials grouping system
ISO/TR 17671-1, Welding — Recommendations for welding of metallic materials — Part 1: General guidance for
arc welding
EN 10088-1:1995, Stainless steels — Part 1: List of stainless steels
EN 12073, Welding consumables — Tubular cored electrodes for metal arc welding with or without a gas shield of
stainless and heat resisting steels — Classification
3 Terms and definitions
For the purposes of this part of ISO/TR 17671, the following terms and definitions apply.
3.1
passive layer
thin, transparent and tightly adherent film on the surface of stainless steels, which protects them from corrosive attack
3.2
stabilized steels
steels containing additions of strong carbide/nitride-forming elements (usually titanium or niobium), which limit the
formation of chromium carbides/nitrides, allowing the stainless steel to retain its corrosion resistance, particularly
around grain boundaries
3.3
non-stabilized steels
steels without the addition of strong carbide/nitride-forming elements (see 3.2)
3.4
ferrite number
FN
a number indicating magnetic attraction, relative to a series of reference samples and therefore, proportional to the
ferro-magnetic phase content, approximately equal to ferrite (delta ferrite) content over the range 0 % to 10 % but more
readily measured
[ISO 8249]
3.5
consumable insert
length of filler metal that is manufactured to conform to the shape and dimensions of the weld preparation and is melted
to become an integral part of the joint during welding
3.6
proof strength
R
p0,2
tensile load which produces a plastic extension of 0,2 % of the original gauge length of the test specimen
4 Parent metal
This part of ISO/TR 17671 applies to stainless steels of the austenitic, ferritic, martensitic and austenitic/ferritic types, in
accordance with groups 7 to 10 of ISO/TR 15608:2000.
5 Storage and handling
When storing, handling or fabricating stainless steel, the environment should be controlled to avoid permanent
breakdown of the passive layer, which gives stainless steel its good corrosion resistance. Stainless steels should be
protected from contamination and surface damage during all stages of storage, fabrication and transportation.
Contact between stainless steels and other materials, e.g. carbon steels, copper, paints, dyes and tapes, which cause
a breakdown of the passive layer or other detrimental effects should be avoided. When contact is not avoidable, care
should be taken that all residues are removed.
Racking for stainless steels should be strongly built and lined in a secure manner with materials that will not
contaminate stainless steel, e.g. dry wood or stainless steel. Unlined or painted carbon steel racking should not be
used. Lifting grabs should be made from or lined with a non-contaminating material.
2 © ISO 2002 – All rights reserved

Welding fixtures, earth clamps or manipulators should be either manufactured from or lined with non-contaminating
materials.
6 Welding consumables
Filler materials should be selected with regard to the parent metals and the particular application and should comply
with the relevant standards.
Where consumable inserts are used they should correspond with the relevant filler metal composition.
7 Fabrication
7.1 General
Facilities for fabrication of stainless steels should be segregated from other works and kept free of all possible
contaminating materials such as lead, zinc, copper, copper alloys or carbon steels, etc.
Forming tools should be cleaned thoroughly before use to avoid cross contamination. All lubricants used in the forming
operations should be removed from the workpiece.
Only tools dedicated to stainless steel should be employed. This particularly applies to grinding wheels and wire
brushes.
Welding heats up the parent metal and this causes formation of oxide films both on the weld metal and on the
surrounding areas of the weld. These oxides as well as slags produced by covered electrodes, flux cored wires and
submerged arc welding, should be removed if the weld is to be exposed to a corrosive medium or for other reasons
(see clause 10).
When preparing fusion faces, oxidation, hardening and general contamination from thermal cutting processes should
be eliminated by mechanically machining to a sufficient depth from the cut face. During shearing, cracking can occur.
Thise may also require to be removed prior to welding.
Where cut edges do not form fusion faces, care should be taken to ensure that the shearing or thermal cutting does not
adversely affect the performance of the fabrication.
Hard stamping should be avoided, but when it has to be used attention is drawn to the danger of it being applied in
highly stressed or corrosive areas and the purchaser should give guidance as to the location of such marks.
Indentations used for marking in radiographic examination should be subject to similar precautions.
Welds which are to be inspected and approved should not be painted or otherwise treated until they have been
accepted.
7.2 Weld details
Welding details should be described in an appropriate Welding Procedure Specification (WPS) in accordance with
ISO 9956-2.
Further details of weldability aspects are given in annexes A to D.
Acceptance criteria for misalignment of joints are given in ISO 5817. For certain applications (e.g. the welding of
pipework) and welding processes, closer tolerances may be necessary.
Where run-on/run-off pieces are used these should be manufactured from a grade of stainless steel compatible with
that used for the fabrication and should have a thickness and edge preparation similar to that used for the joint.
The removal of run-on/run-off pieces should be performed by a method that does not adversely affect the properties of
the parent metal and weld deposit. Inspection should be carried out to demonstrate that both the parent material and
weld deposit are free from unacceptable imperfections.
Where the weld has to be made from one side only, it may be necessary to protect the root side from atmospheric
contamination in order to maintain the corrosion resistance of the joint. The root run of such welds is generally made
using the TIG or plasma welding process.
NOTE Pulse MIG/MAG-technique is also used.
7.3 Weld backing
Permanent backing should consist of a compatible grade of stainless steel and should not be used where there is a risk
of crevice corrosion.
When it is not appropriate to use part of the structure as backing material, the material to be used should be as
required by the design specification.
When using copper as a temporary backing material, a groove should be machined into the backing material in the
fusion area. Care should be taken when welding as there is a risk of copper pick-up. This can be reduced by nickel or
chromium plating of the copper backing material. When using high heat input, the copper backing may be water-
cooled.
Backing material shall be free from contamination such as grease, moisture, oxide, etc.
Where temporary or permanent backing is used, the joint should be arranged in such a way as to ensure that complete
fusion of the parts to be joined is readily obtained.
When it is necessary to prevent oxidation on the reverse side of a weld, purging using a suitable gas supply should be
carried out. This is where a high purity gas or gas mixture, in accordance with ISO 14175, compatible with the parent
and weld metal, is passed over the weld root. The purpose is to prevent contamination by the atmosphere, principally
oxygen, which can lead to unacceptable imperfections in the weld and/or a reduction of corrosion resistance.
Where purging of the root area is to be carried out, the duration of purging prior to welding should be sufficient to
ensure that the level of root oxidation is as required by the design specification. The prepurge time will depend
principally on gas flow rate, volume to be purged and, to a lesser extent, purging gas density and injection point.
Where maximum permissible oxygen levels are specified in the contract, it will be necessary to use an oxygen analyser
of suitable sensitivity to measure the oxygen content of the exit gas. As a guideline, it is suggested that ten volume
changes be made before commencing welding.
Gas purging should be maintained for sufficient duration to ensure that the finished weld underside surface oxidation
level is contractually acceptable.
8 Quality requirements of welds
Welded joints should be free from imperfections that would impair the service performance of the construction.
Acceptance levels should be in accordance with the application standard where it exists. If no application standard
exists, acceptance levels should be based on ISO 5817.
Special quality requirements for stainless steels may be taken into account, such as appearance and corrosion
resistance, and shall be specified in the contract.
4 © ISO 2002 – All rights reserved

9 Distortion
Distortion in a weldment results from non-uniform expansion and contraction of weld metal and adjacent parent metal
during welding. In austenitic stainless steel, this phenomenon is much more pronounced than in unalloyed steel due to
a larger expansion coefficient and a lower thermal conductivity.
There are various practical ways of minimizing distortion such as:
 minimizing the weld metal volume;
 balanced (double sided) joint welding;
 reduced heat input;
 reduced numbers of weld layers;
 backstep welding;
 preset of the parts to be welded;
 jigs and mechanical restraints;
 tack welding;
 heat sinks.
Care should be taken that the methods chosen do not have a deleterious effect on the properties of the welds and the
overall structure.
10 Post-weld cleaning
10.1 General
The corrosion resistance of stainless steel weldments is significantly affected by their surface condition. The degree of
post-weld cleaning necessary depends upon the weld quality requirements and should be as required by the design
specification.
Post-weld cleaning can be carried out by several processes, either separately or in combination. See 10.2 to 10.6.
10.2 Brushing
Dedicated wire brushes made with stainless steel bristles or other compatible material should be used. This
technique cannot be used, in general, to remove adherent contaminants. Care should be taken when using
mechanical rotary brushing as this may deform the surface giving microcrevices which will reduce corrosion
resistance. It may be necessary to follow brushing with a pickling operation (see 10.5).
10.3 Shot blasting
This technique is used for the removal of adherant contaminants and also to give residual compressive stresses in
the surface. Recommended blasting media include glass and stainless steel shot. These should be free from iron
or carbon steel contamination. It is also known as peening.
10.4 Grinding
Dedicated iron free grinding discs, belts or wheels should be used. Excessive grinding should be avoided to
prevent damage to the surface and thinning of the parent metal. The technique is used to remove heavy surface
contaminants and to blend the weld smoothly into the parent metal.
10.5 Pickling
Pickling removes surface oxides or surface layers of the steel by chemical reaction. An acid medium is used whose
composition is dependent on the type of steel, pickling temperature and time. Careful removal of all pickling
products needs to be carried out.
10.6 Electro-polishing
This is used, generally, on non-stabilized stainless steels in order to give a smooth surface for optimum corrosion
resistance.
For optimum corrosion resistance, the most effective cleaning processes are pickling and electro-polishing, followed by
a natural or induced passivation treatment.

6 © ISO 2002 – All rights reserved

Annex A
Welding of austenitic stainless steels
A.1 General
A.1.1 Chemical composition
The chemical compositions of typical austenitic stainless steels are listed in EN 10088-1. These steels generally
contain a minimum of 16,5 % chromium, with sufficient nickel and/or manganese, carbon and nitrogen to produce an
austenitic microstructure. They may also contain additions of other elements such as molybdenum, nitrogen, titanium,
niobium, copper, silicon or sulfur to improve specific properties such as corrosion resistance, oxidation resistance, or
machinability, etc.
A.1.2 Microstructure
The microstructures of austenitic stainless steels are governed by the balance of ferrite- and austenite-stabilizing
elements. The principal ferrite-stabilizing elements are chromium, molybdenum and silicon, while the principal austenite
stabilizing elements are nickel, manganese, carbon and nitrogen. The structure which will form in the weld metal may
be predicted from the balance of ferrite- and austenite-stabilizing elements, using e.g. a Schaeffler, DeLong, W.R.C. or
Espy diagram.
Austenitic stainless steels consist of an austenite matrix which, in certain grades, may contain small quantities of delta
ferrite, the amount of ferrite increasing during welding without the addition of a filler metal. Other grades are fully
austenitic and contain no ferrite, even after welding.
Austenitic stainless steels are usually supplied in the solution annealed condition, which involves heating to
approximately 1 050°C, or higher, followed by rapid cooling to room temperature. Annealing results in softening of the
steel and minimizes the delta ferrite content, so that even steels which form delta ferrite during welding will generally
contain virtually no ferrite in the annealed condition.
A.1.3 Types of austenitic stainless steel
A.1.3.1 Standard austenitic stainless steels
Most of the standard austenitic stainless steels are not fully austenitic but may form a small amount of delta ferrite after
welding without the addition of a filler metal. The standard stainless steels in this category are still referred to as
austenitic stainless steels, even when a small amount of ferrite is present, e.g. grades 1.4301, 1.4401 and 1.4436 of
EN 10088-1:1995.
The carbon content of the standard austenitic stainless steels is normally less than 0,06 %.
In order to minimize the formation of chromium carbides during welding, low carbon (< 0,03 %) versions of many
standard grades are produced, resulting in improved corrosion resistance in certain environments, e.g. grades 1.4307,
1.4404 and 1.4432 of EN 10088-1:1995.
Similar improvements in the corrosion resistance of standard grades may be obtained through the additions of either
titanium, or niobium/tantalum, which combine with carbon, preventing the formation of chromium carbides during
welding. These grades are referred to as 'stabilized' austenitic stainless steel, e.g. grades 1.4541 and 1.4550 of
EN 10088-1:1995.
A.1.3.2 Fully austenitic stainless steels
The compositional balance of these steels is adjusted to obtain specific properties such as low magnetic permeability
(non magnetic), increased corrosion resistance or high temperature creep/oxidation resistance, resulting in a fully
austenitic structure at all times, e.g. grade 1.4335 of EN 10088-1:1995. Due to their high toughness at low
temperatures, fully austenitic steels may also be used for cryogenic applications.
The risk of solidification cracking during welding is increased in these steels.
Superaustenitic and enhanced corrosion resistant grades belong to the fully austenitic family. These steels contain
increased chromium contents and additions of other elements, including molybdenum and nitrogen for increased
resistance to pitting and crevice corrosion, and copper for enhanced acid corrosion resistance. An increased nickel
content is added to stabilize a fully austenitic structure. These steels possess extremely high corrosion resistance and
require particular care during welding in order to maintain the high corrosion resistance of the parent metal, e.g. grades
1.4539 and 1.4547 of EN 10088-1:1995.
A.1.3.3 Other variations with improved properties
Other austenitic stainless steels exist in which the chemical composition has been adjusted to improve specific
properties. Depending on the actual chemical composition, each of these grades belongs in one of the above
mentioned categories (A.1.3.1 and A.1.3.2) and should be welded with similar precautions.
a) Nitrogen alloyed austenitic steels with high proof strength. These steels contain small additions of
nitrogen (up to 0,45 %), resulting in an increase in R . The nitrogen may be added to both normal and low
p0,2
carbon grades of stainless steel. Nitrogen is an austenite-stabilizing element and may result in a reduction in
delta ferrite content during welding.
b) Heat resistant austenitic steels. Steels for use at high temperatures may contain increased chromium and/or
silicon contents in order to provide enhanced oxidation resistance. Additions of molybdenum, nitrogen,
aluminium, carbon, rare earth elements, titanium and/or niobium may also be made to increase high
temperature properties.
c) Austenitic steels with improved machinability. Improved machining grades contain increased sulfur
contents (up to 0,35 %) and/or additions of other elements such as calcium or selenium and consequently
generally exhibit reduced weldability and corrosion resistance.
A.2 Welding aspects
A.2.1 Welding details
All of the common welding processes listed in ISO/TR 17671-1 are suitable for welding austenitic stainless steels.
Heat input should be low in order to reduce the risk of distortion, hot cracking and sensitization or intermetallic
precipitation.
Preheat should be avoided when welding austenitic stainless steels as the additional heat input will increase the risk of
distortion, hot cracking, sensitization and intermetallic precipitation.
Joint preparations for welding are similar to those used for carbon steels, although different angles and root gaps may
be used, e.g. nitrogen alloyed steels may require wider joint preparations.
When welding thin sheet and plate, a weld may be possible by fusing the joint edges together, without filler metal.
8 © ISO 2002 – All rights reserved

A.2.2 Welding consumables
All consumables should be selected in accordance with the manufacturer's/supplier's recommendations.
Where required, filler metals/rods should be selected in accordance with ISO 3581, ISO 14343 or EN 12073.
Consumables for standard austenitic stainless steels are generally designed to result in a ferrite content of between
3 FN and 15 FN in the as-deposited fusion zone, for enhanced resistance to hot cracking.
Schaeffler, De Long, W.R.C. or Espy diagrams may be used to determine if the consumable will provide the correct
ferrite content, taking dilution effects into account.
Fully austenitic stainless steels are non magnetic. The presence of delta ferrite in the austenite results in a small
degree of magnetism and this characteristic is used to measure the proportion of ferrite in the weld metal, after welding.
The chemical composition of the welding consumable is usually slightly over-alloyed with respect to the parent metal, to
optimize corrosion resistance by compensating for alloy losses, segregation effects, inclusions and surface
imperfections inherent in the weld metal.
Fully austenitic stainless steels require the use of approximately similar or slightly over-alloyed consumables and are
susceptible to hot cracking. The precautions indicated in A.3.1 should, therefore, be followed. The consumables may
contain increased manganese contents, to minimize the risk of hot cracking.
Nickel-based consumables are gene
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