ISO/TR 17671-6:2005

TECHNICAL ISO/TR
REPORT 17671-6
First edition
2005-02-15
Welding — Recommendations for
welding of metallic materials —
Part 6:
Laser beam welding
Soudage — Recommandations pour le soudage des matériaux
métalliques —
Partie 6: Soudage par faisceau laser

Reference number
©
ISO 2005
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.

©  ISO 2005
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2005 – All rights reserved

Contents Page
Foreword. v
Introduction . vi
1 Scope. 1
2 Normative references . 1
3 Terms and definitions. 3
4 Health and safety and protection of the environment. 3
5 Quality requirements . 3
6 Equipment. 4
6.1 General. 4
6.2 Provisions for acceptance testing . 4
6.3 Provisions for maintenance and calibration .4
7 Qualification of welding personnel . 4
8 Welding procedure specification . 5
9 Welding procedure test . 5
10 Consumables. 5
10.1 Filler metals . 5
10.2 Gases. 5
11 Design . 6
11.1 Overall design of structure or product . 6
11.2 Joint design . 6
11.3 Joint preparation. 6
12 Laser beam welding. 7
12.1 Characteristics . 7
12.2 Advantages and limitations . 9
12.3 Assembling and fixtures . 10
12.4 Process control . 10
12.5 Inspection and testing. 10
12.6 Imperfections. 10
Annex A (informative) Equipment. 11
A.1 Description of laser process. 11
A.2 Laser beam sources . 12
A.3 Guiding, shaping and focussing the beam . 14
A.4 Devices used to crate a relative movement between the laser beam and the work piece. 18
A.5 Fixtures used to hold the work piece. 18
A.6 Cooling system . 19
A.7 Control systems . 19
Annex B (informative) Laser beam properties. 20
Annex C (informative) Information about weldability of metallic materials . 22
C.1 General. 22
C.2 Steels and iron alloys . 22
C.3 Nickel alloys . 24
C.4 Aluminium and magnesium alloys. 24
C.5 Copper and its alloys. 24
C.6 Refractory and reactive materials . 24
C.7 Titanium and its alloys.25
C.8 Dissimilar metals.25
C.9 Non-metals .25
Annex D (informative) Information about causes of weld imperfections and their prevention.26
Annex E (informative) Beam control and monitoring.28
E.1 General .28
E.2 Focal point .28
E.3 Beam alignment and pilot beam coincidence .28
E.4 Beam power .29
E.5 Beam power distribution .29
E.6 Nozzle alignment .29
E.7 Pulsed beam power data .30
E.8 Manipulators, guides, etc. .30
Annex F (informative) Laser beam processing.31
F.1 Laser beam cutting.31
F.2 Laser beam drilling.33
F.3 Laser beam surface treatment .33
F.4 Laser beam cladding.34
F.5 Laser beam marking and engraving.35
Bibliography.36

iv © ISO 2005 – All rights reserved

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 2.
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 document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO/TR 17671-6 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
 Part 5: Welding of clad steels
 Part 6: Laser beam welding
 Part 7: Electron beam welding
Introduction
ISO/TR 17671 has been issued in several parts in order that it can be extended to cover the different types of
metallic material that are produced in accordance with all International Standards for weldable metallic
materials.
When ISO/TR 17671 is referenced for contractual purposes, the ordering authority or contracting parties
should state the need for compliance with the relevant parts of ISO/TR 17671 and such of the annexes as are
appropriate.
This part of ISO/TR 17671 gives general guidance for the satisfactory production and control of welding and
associated processes and details of some of the possible detrimental phenomena that can occur, with advice
on methods by which they can be avoided. It is generally applicable to laser beam processing of metallic
materials and also to some extent for non-metallic materials. It is appropriate regardless of the type of
fabrication involved, although the relevant product standard, structural code or design specification can have
additional requirements. Permissible design stresses, methods of testing and inspection levels are not
included because they depend on the service conditions of fabrication. These details should be obtained from
the relevant application standard or established by agreement between the contracting parties.
It has been assumed in the drafting of this part of ISO/TR 17671 that the execution of its provisions is
entrusted to appropriately qualified, experienced and trained personnel.
Requests for official interpretations of any aspect of this part of ISO/TR 17671 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.
vi © ISO 2005 – All rights reserved

TECHNICAL REPORT ISO/TR 17671-6:2005(E)

Welding — Recommendations for welding of metallic
materials —
Part 6:
Laser beam welding
1 Scope
This document gives general guidance for laser beam welding of metallic materials in all forms (e.g. cast,
wrought, extruded, forged), and associated processes.
NOTE Some guidance on laser beam cutting, drilling, surface treatment and cladding is given in Annex F.
2 Normative references
The following referenced documents are indispensable for the application of 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 286-2, ISO system of limits and fits — Part 2: Tables of standard tolerance grades and limit deviations for
holes and shafts
ISO 636, Welding consumables — Rods, wires and deposits for tungsten inert gas welding of non-alloy and
fine-grain steels — Classification
ISO 3834-2, Quality requirements for fusion welding of metallic materials — Part 2: Comprehensive quality
requirements
ISO 3834-5, Quality requirements for fusion welding of metallic materials — Part 5: Normative references for
the requirements of ISO 3834-2, ISO 3834-3 and ISO 3834-4
ISO 6520-1, Welding and allied processes — Classification of geometric imperfections in metallic materials —
Part 1: Fusion welding
ISO 9013, Thermal cutting — Classification of thermal cuts — Geometrical product specification and quality
tolerances
ISO 10218, Robots for industrial environments — Safety requirements
ISO 11145, Optics and optical instruments — Lasers and laser-related equipment — Vocabulary and symbols
ISO 11553-1, Safety of machinery — Laser processing machines — Part 1: General safety requirements
ISO 13919-1, Welding — Electron and laser-beam welded joints — Guidance on quality levels for
imperfections — Part 1: Steel
ISO 13919-2, Welding — Electron and laser-beam welded joints — Guidance on quality levels for
imperfections — Part 2: Aluminium and its weldable alloys
ISO 13920, Welding — General tolerances for welded constructions — Dimensions for lengths and angles —
Shape and position
ISO 14175, Welding consumables — Shielding gases for arc welding and cutting
ISO 14232, Thermal spraying — Powders — Composition and technical supply conditions
ISO 14341, Welding consumables — Wire electrodes and deposits for gas shielded metal arc welding of non
alloy and fine grain steels — Classification
ISO 14343, Welding consumables — Wire electrodes, wires and rods for arc welding of stainless and heat
resisting steels — Classification
ISO 14732, Welding personnel — Approval testing of welding operators for fusion welding and resistance
weld setters for fully mechanized and automatic welding of metallic materials
ISO 14919, Thermal spraying — Wires, rods and cords for flame and arc spraying — Classification —
Technical supply conditions
ISO 15609-4, Specification and qualification of welding procedures for metallic materials — Welding
procedure specification — Part 4: Laser beam welding
ISO 15613, Specification and qualification of welding procedures for metallic materials — Qualification based
on pre-production welding test
ISO 15614-7, Specification and qualification of welding procedures for metallic materials — Welding
procedure test — Part 7: Overlay welding
ISO 15614-11, Specification and qualification of welding procedures for metallic materials — Welding
procedure test — Part 11: Electron and laser beam welding
ISO 15616-1, Acceptance tests for CO -laser beam machines for high quality welding and cutting — Part 1:
General principles, acceptance conditions
ISO 15616-2, Acceptance tests for CO -laser beam machines for high quality welding and cutting — Part 2:
Measurement of static and dynamic accuracy
ISO 15616-3, Acceptance tests for CO -laser beam machines for high quality welding and cutting — Part 3:
Calibration of instruments for measurement of gas flow and pressure
ISO 16834, Welding consumables — Wire electrodes, wires, rods and deposits for gas shielded arc welding of
high strength steels — Classification
ISO 17632, Welding consumables — Tubular cored electrodes for gas shielded and non-gas shielded metal
arc welding of non-alloy and fine grain steels — Classification
ISO 17633, Welding consumables — Tubular cored electrodes and rods for gas shielded and non-gas
shielded metal arc welding of stainless and heat-resisting steels — Classification
ISO 17634, Welding consumables — Tubular cored electrodes for gas shielded metal arc welding of creep-
resisting steels — Classification
ISO 17662, Welding — Calibration, verification and validation of equipment used for welding, including
ancillary activities
ISO/TR 17671-1:2002, Welding — Recommendations for welding of metallic materials — Part 1: General
guidance for arc welding
2 © ISO 2005 – All rights reserved

ISO 18273, Welding consumables — Wire electrodes, wires and rods for welding of aluminium and aluminium
alloys — Classification
ISO 18274, Welding consumables — Wire and strip electrodes, wires and rods for arc welding of nickel and
nickel alloys — Classification
ISO 18276, Welding consumables — Tubular cored electrodes for gas-shielded and non-gas-shielded metal
arc welding of high-strength steels — Classification
ISO 22827-1, Acceptance tests for Nd:YAG laser beam welding machines — Machines with optical fibre
delivery — Part 1: Laser assembly
ISO 22827-2, Acceptance tests for Nd:YAG laser beam welding machines — Machines with optical fibre
delivery — Part 2: Moving mechanism
IEC 60825-1, Safety of laser products — Part 1: Equipment classification, requirements and user's guide
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 11145 apply.
4 Health and safety and protection of the environment
A general checklist on protection of the environment in welding and allied processes is in preparation by
CEN/TC 121. It covers laser applications.
Laser beam processing introduces additional hazards over and above those normally experienced in arc
welding. Specialist advice should be sought, see e.g. IEC 60825-1 and ISO 11553-1.
Guidance on safety aspects related to the application of industrial robots for manipulation of the focussing
devices and/or the components to be welded can be found in ISO 10218.
5 Quality requirements
Laser beam welding is a complex process needing detailed process control. All processing is performed under
numerical control, necessitating programming of each single operation. The application has to be controlled at
a level compatible with ISO 3834-2 and ISO 3834-5.
NOTE This does not entail a requirement for certification, but the process control should operate in accordance with
ISO 3834-2 and ISO 3834-5.
It is a condition for efficient process control that quality requirements for joint geometry and other relevant
requirements have been specified prior to start of fabrication. A number of International Standards specify joint
geometry and relevant quality criteria and can be used for reference, as appropriate (see Table 1).
Table 1 — Quality criteria
Requirements and tolerances Standard No.
Quality requirements for beam welded joints ISO 13919-1
ISO 13919-2
Quality requirements for cut surfaces ISO 9013
General tolerances ISO 13920
General requirements ISO 3834-2 and ISO 3834-5 specify provisions for information and items
to be agreed and specified prior to the start of fabrication.
ISO/TR 17671-1:2002, Annex A, can be used as guidance if ISO 3834-2
and ISO 3834-5 are not called for.

6 Equipment
6.1 General
Information about particular equipment for laser beam processing has to be found in information from the
supplier. A number of textbooks and a large number of articles provide background information. Annex A
provides some very general information on principles and techniques. Annex B provides general information
on the properties of laser beams.
6.2 Provisions for acceptance testing
Provisions for acceptance of laser beam equipment are found in the following standards (see Table 2).
Table 2 — Provisions for acceptance testing
Type of equipment Standard No.
CO laser beam equipment ISO 15616-1, ISO 15616-2 and/or ISO 15616-3
Nd:YAG laser equipment ISO 22827-1, ISO 22827-2

6.3 Provisions for maintenance and calibration
Provisions for maintenance are not standardized. The supplier's manuals have to be consulted. Principles for
calibration, verification and validation and minimum requirements are specified in ISO 17662.
7 Qualification of welding personnel
The requirements for the qualification of personnel for fully mechanized and automatic welding and allied
processes are laid down in ISO 14732. Among the different procedures specified in this standard, the
functional test is particularly suitable as a basis for qualification of personnel responsible for the operation and
set-up of laser beam processing. In a functional test, the operator or setter demonstrates his/her knowledge of
working with a procedure specification and of setting, supervising and checking the laser beam processing
machine.
4 © ISO 2005 – All rights reserved

8 Welding procedure specification
All details for the laser beam welding of components are to be recorded in a welding procedure specification
(WPS) in accordance with ISO 15609-4. Procedure specifications for cutting, drilling, surface treatment and
cladding are not standardized. ISO 15609-4 can, however, give some guidance.
9 Welding procedure test
Formal qualification of all procedures for laser processing is recommended for all applications and required for
many applications. Qualification of procedures for laser beam welding (when required) can be performed by
procedure testing (see ISO 15614-11). Qualification by pre-production testing can also be relevant, however
(see ISO 15613). Qualification by pre-production testing is common practice for cutting, drilling and surface
treatment. ISO 15613 can give some guidance.
Qualification of procedures for laser beam welding for cladding (when required) can be performed by
procedure testing (see ISO 15614-7). Qualification by pre-production testing can also be relevant, however
(see ISO 15613).
10 Consumables
10.1 Filler metals
Filler metals are used for laser beam cladding and sometimes for laser beam welding. The main problem as
regards filler metals for laser applications is that the market for such filler metals is rather small and that
dedicated standards for filler metals for laser applications do not exist. The usual form of delivery is solid
cylindrical wires but powders can also be used, in particular for cladding. What is commercially available is the
following:
 Wires marketed as consumables for gas shielded metal arc welding and tungsten inert gas welding.
However, it should be noted that metal cored tubular wires might also be suitable. Small-scale
(experimental) production of tubular wires can even be feasible for special applications. Relevant
standards are ISO 636, ISO 14341, ISO 14343, ISO 17633, ISO 18273, ISO 18274, ISO 17632,
ISO 17634, ISO 18276, ISO 16834.
 Wires marketed as consumables for thermal spraying. The usual form of delivery is solid cylindrical wires.
Such wires are standardized in ISO 14919.
 Powders for thermal spraying. Such powders are standardized in ISO 14232.
 Powders for powder metallurgy.
10.2 Gases
Gases are used for shielding and plasma suppressing in laser beam welding, as cutting assist gases in laser
beam cutting, and for shielding in laser beam cladding, drilling and marking. Further, CO lasers may need a
continuous supply of laser gas.
The only relevant standard is ISO 14175. This standard is, however, not adequate for all gases used for laser
beam processing. Careful specification of composition, tolerances, etc., is necessary for all non-standardized
gases when ordering.
11 Design
11.1 Overall design of structure or product
The main consideration is to ensure that all joints are accessible. It can be an advantage for the focussing
head to be some distance from the surface of the joint. However, when shielding gas or plasma suppression
jets are used, these nozzles have to be placed close to the surface. The use of sensors augments the
requirements for accessibility.
11.2 Joint design
Joint design is, of course, relevant to laser beam welding. The default joint is a normal square butt weld in a
butt joint. T-joints are welded similarly but full penetration may not be necessary. Overlap points are used for
spot welding.
Laser beam welding can ensure welding of components to tight tolerances. It is a condition, however, that
either the fixtures hold the parts very accurately or that the joints are “self-positioning”.
Laser beam welding with root backing can be employed if spatter and undercut are to be avoided.
For axial circular welds on components with narrow dimensional tolerances, a press fit like H7/r6 to H7/n6
(see ISO 286-2) is recommended. For circular welds with a clearance fit, tacking is essential.
11.3 Joint preparation
The quality of laser beam welding relies on the accuracy and cleanliness of joint preparation. Joints can be
prepared by machining or cutting. Attention should be paid to the resulting surface condition. Cleaning of weld
joint surfaces should be carried out if they are contaminated by oxides, oil, grease, coolant or paint.
The specific cleaning method used will be dependent on the material type, the component size and the quality
requirements as well as the operational circumstances. The following treatments can be used:
 manual degreasing with a solvent;
 cleaning in a closed solvent vapour unit or in an ultrasonic bath;
 pre-treatment by steam cleaning with a slightly alkaline additive, following by drying;
 acid pickling neutralization, washing in distilled water, drying, short-term storage;
 mechanical cleaning by grinding, brushing, etc.;
 primers and similar layers on steel plates can be burnt away by de-focussing the laser beam and moving
it along the joint prior to welding (very high speeds in excess of 100 mm/s can be used during this
treatment).
Where components have surface layers produced by carburizing, anodizing, cadmium plating, nitriding,
phosphating, galvanizing, etc., these layers usually have to be removed, preferentially by machining of the
surface in the weld joint region.
If the component cannot be machined in the weld start and finish regions to remove the end crater, run-on or
run-off plates should be used (see Figure 1). These run-on/run-off plates also suppress heat accumulation at
the work piece ends. The run-on/run-off plates should be attached to the work piece by clamping or welding to
achieve good thermal contact and are removed subsequently.
6 © ISO 2005 – All rights reserved

Key
1 run-on plate
2 work piece
3 run-off plate
4 start of weld
5 end of weld
Figure 1 — Work piece with run-on and run-off plate for separating the weld start and weld end
12 Laser beam welding
12.1 Characteristics
12.1.1 Modes
Laser beam welding is a fusion welding process and the joint is characterized by heat-affected zones in the
parts joined by weld metal.
Laser beam welding is often performed as keyhole mode welding. Keyhole mode welding requires a beam
with a high power density, able to vaporize the material at the point of interaction. The beam then is able to
create (by the vapour pressure) a deep cavity, roughly cylindrical in shape. The walls of the cavity are covered
by molten material. When the process is under control, the cavity is propagated with the beam along the joint.
Heat and material propagation is essentially two-dimensional. The material melts at the front of the cavity and
moves to the trailing edge, where it solidifies, creating the weld metal. A small proportion of the material
evaporates or is ejected as spatter and this part of the material is transported in the direction along the axis of
the beam. Keyhole mode welding is the usual mode for full and partial penetration butt welds in thick materials.
Another mode is conduction mode welding. In this mode, the intensity of the beam is insufficient to create a
keyhole and the heat distribution becomes similar to the heat distribution in arc welding. Conduction mode
welding occurs when the beam (of low intensity) is de-focussed or oscillated. Conduction mode welding can
result in a three-dimensional heat distribution and the weld cross-section is then approximately circular with a
width at the surface approximately two times the depth of penetration. However, the heat input can be spread
over a wider area, resulting in a weld with a width larger than two times the depth of penetration. A similar
technique is used for laser beam cladding where penetration usually is minimized.
In spot welding, the focussing head is kept stationary in relation to the parent material during welding. Welding
time for each spot can be measured in milliseconds. Pulsed lasers are commonly used for this purpose. The
resulting weld profile is usually intermediate between conduction and keyhole welds.
12.1.2 Energy transfer
The energy is transferred from the laser beam into the base material where it melts the material and creates
the keyhole (in the keyhole mode). Energy transfer is influenced primarily by two factors:
 reflection of (a part of) the beam energy from the surface of the base material and liquid weld material;
 creation of a plume of vaporized elements and/or of a plasma cloud (CO laser).
Laser beams are reflected from the surface of materials. The proportion of the energy reflected depends on
the surface condition (at the microscopic level), e.g. the surface roughness and also the surface temperature.
The proportion reflected can be very high, close to 90 % for polished materials and wavelengths above 1 µm,
at room temperature. The proportion is much lower below 50 % for shorter wavelength and less reflective
surfaces. However, if the beam has enough power to establish a keyhole, reflection becomes of minor
importance. Consideration of the reflectivity of the material has become less important with the general
availability of high power and high beam quality lasers. When reflectivity causes problems, this can result in
the process becoming unstable and the keyhole not being established locally where for some reason a higher
percentage of the beam energy is reflected.
Laser beam welding is usually accompanied by vaporization of part of the base material. This results in a
plume of vapour above the keyhole. High-power CO lasers induce such high temperatures that at least a part
of the plume is ionized and a cloud of plasma is created in and above the joint (the keyhole). The plasma
cloud can attenuate the beam and the usual precaution is to apply a jet of helium, blowing the plasma away.
Helium is the preferred gas for plasma suppression. However, other gases such as N or Ar have been used
on an experimental basis. The plasma cannot be entirely suppressed, but welding appears to be feasible none
the less.
Vaporization affects the various chemical constituents of the base material selectively. Components with a
high vapour pressure will vaporize more readily. The weld metal will consequently be depleted in such
components compared to the base material.
12.1.3 Pulsed beam welding
Pulsed beam welding can be used for spot welding. The high peak power in pulsed lasers can for certain
applications be used for establishment of keyhole mode welds in comparatively thick materials. However,
welding speed is less than for a powerful laser having a continuous output.
12.1.4 Beam oscillation
Oscillation of the beam can be used to establish a wider weld profile and can be beneficial where gaps have
to be bridged. The augmented welded cross-section is accompanied by diminished cooling rates.
12.1.5 Ramping
The numerical control of laser beam power sources usually permits ramping (slope-up and slope-down) which
— together with focus control — can be used to obtain satisfactory welds in the start and stop positions. This
is of course very important for welding of circumferential and planetary welds.
12.1.6 Beam focussing
The laser beam is usually focussed at or near the surface of the base material.
12.1.7 Gas shielding
Some gas shielding is needed for most applications. The weld pool, the hot part of the weld immediately
behind the weld pool and the underside (for full penetration welding) may have to be protected. Gas nozzles
of a suitable design should be used. The need for shielding and the type of shielding gas to be used depend
8 © ISO 2005 – All rights reserved

on the material welded. Sufficient shielding of all hot parts is of key importance, e.g. when welding stainless
steels in order to maintain good resistance to corrosion. Full penetration welds in mild steel can, however,
often be welded without any gas shielding at the weld root. High-speed welding of thin materials can also be
carried out without a gas shield.
12.1.8 Use of consumables
Consumables may be needed, e.g. when welding with a gap in order to avoid underfill. Consumables may
also be needed for metallurgical reasons. However, very accurate positioning of the wire is necessary. A
hybrid arc process can be a better solution.
12.1.9 Hybrid processes
Hybrid processes involve a combination of laser beam welding with an arc welding process, plasma arc
welding, TIG welding, MAG welding, etc. This can be a good solution when addition of a filler material is
needed. High welding speed and low heat input can still be achieved. Combined butt/fillet weld is another
option when a hybrid process is used. ISO/TR 17671-1 can be consulted as regards recommendations for arc
welding.
12.2 Advantages and limitations
Laser beam welding using the keyhole mode has a number of advantages compared to other fusion welding
processes:
 Joining is established by creation of a minimum of weld metal. This is associated with a minimum of heat
input, narrow heat affected zones and minimal shrinkage and distortion.
 High welding speeds are possible and most joints are established by one or at most two runs, one from
each side.
 Welds can be established in materials down to a few hundredths of a millimetre thick. The upper limit is
presently of the order of 25 mm for full penetration butt welds in steels, welded from one side only.
Compared to electron beam welding, laser beam welding has the advantages of being performed under
normal atmospheric conditions and there is no generation of X-rays.
The limitations are mainly:
 The high cooling rates necessary call for special attention with some materials in order to avoid
unacceptable material properties.
 Cracking and/or porosity can occur in certain materials.
 Materials with highly reflective surfaces can be difficult to weld because the beam energy is reflected and
not absorbed.
 Present laser beam sources are characterized by a low efficiency. The total energy consumption can be
of the order of 10 to 30 times the beam energy.
 Manual welding is not very practical. In practice, mechanized equipment has to be used and all
operations can be pre-programmed.
 The weld metal can be depleted in components with a high vapour pressure due to evaporation.
 The requirements for the quality of joint preparation and accurate positioning of the weld or seam tracking
are strict.
 Surface coatings can result in imperfections.
12.3 Assembling and fixtures
All conventional fixtures, manipulators, X-Y tables, etc., can be used for laser beam welding. Laser beam
welding does not, in principle, require fixtures different from those used for other welding processes. However,
if the full potential regarding the accuracy and close tolerances of the welded components is to be realized,
fixtures must have a compatible accuracy. ISO 15616-1 to ISO 15616-3 give some guidance.
12.4 Process control
Laser beam welding is performed under numerical control. Adjustments or feedback during welding is rarely
possible, except by the use of sensors, which dynamically adjust the trajectory of the beam in relation to the
work piece. Sensors monitoring the process by observation of e.g. the spectrum and intensity of the
secondary light from the weld area have, however, been installed on an experimental basis.
12.5 Inspection and testing
ISO 15614-11 provides references to standards for destructive testing. ISO standards for non-destructive
examination of laser beam welded joints have not yet been established. Standards for examination of arc
welded joints can be used with suitable modifications.
12.6 Imperfections
The terminology for imperfections is defined in ISO 6520-1. Quality levels suitable for process control are
specified in ISO 13919-1 and ISO 13919-2.
10 © ISO 2005 – All rights reserved

Annex A
(informative)
Equipment
A.1 Description of laser process
A.1.1 Principles
Laser is an acronym of Light Amplification by Stimulated Emission of Radiation. A laser is essentially a device
which generates a beam of light which is sufficiently narrow and powerful to be used for welding, cutting,
surface treatment and drilling purposes. A laser can, from one point of view, be considered a black box. The
mechanism generating the beam and the actual design of a particular laser is of interest only to the extent it is
of significance for the daily maintenance, calibration and those repair operations the user is able to perform.
The user's manual (repair manual) for the particular device should then be consulted. However, this point of
view is not realistic due to the fact that there exist a number of different types of laser and each has particular
characteristics, which limits its applications. A brief description of the various types is a necessity if for no
other reason than to provide the necessary terminology for this part of ISO 17671. However, several textbooks
and papers, and other information, are available on lasers, and users are referred to these sources for
detailed information.
All laser devices include a resonator where the light is generated and amplified. The resonator is comprised of
reflective and partially reflective mirrors, plus other forms of mirror used as barriers.
Inside the resonator is some medium able to generate light, continuously or pulsed. A proportion of the light
stored in the resonator is permitted to escape, forming the actual laser beam.
Energy is delivered from an outside source into the medium inside the resonator (energy for “pumping”). The
energy is not converted 100 % into the laser beam and the excess energy has to be removed by a cooling
mechanism.
A.1.2 Components
The laser beam source forms only a part of the entire installation. All laser processing involves mechanized,
automatic or robotic installations. The only exception is the hand-held application of low-power lasers for
special purposes (non-industrial).
A typical laser installation (workstation) includes the following categories of component:
 the laser beam source;
 devices for guiding, shaping and focussing the laser beam onto the work piece;
 devices used to create a relative movement between the laser beam and the work piece;
 fixtures used to hold the work piece;
 cooling systems;
 control systems.
A.2 Laser beam sources
A.2.1 CO lasers
Table A.1 — CO lasers
Key properties Characteristics
State of technology Carbon dioxide (CO ) lasers have been commercially available f
...