Ingenieria

Materials and Design 30 (2009) 581–589

Contents lists available at ScienceDirect

Materials and Design
journal homepage: www.elsevier.com/locate/matdes

Parameter optimisation for automatic pipeline girth welding using a new
friction welding method
Koen Faes a,*, Alfred Dhooge a, Patrick De Baets b, Eric Van Der Donckt c, Wim De Waele b
a

Belgian Welding Institute,St.-Pietersnieuwstraat 41, 9000 Ghent, Belgium
Laboratory Soete, Ghent University, St.-Pietersnieuwstraat 41, 9000 Ghent, Belgium
c
Denys NV, Wondelgem, Industrieweg 124, 9032 Wondelgem, Ghent, Belgium
b

article

info

Article history:
Received 24 July 2007
Accepted 23 May 2008
Available online 11 June 2008
Keywords:
Friction welding
Pipeline

abstract
A new welding method for fully automaticwelding of pipelines has been developed. The proposed welding procedure, called Friex, is a new variant of the well-known friction welding process. An intermediate
ring is rotated in between the pipes to be welded to generate the heat necessary to realise the weld. In the
first part of this paper, the working principles of the Friex welding process are briefly described. Following, the influence ofthe rotation speed on the weld properties is discussed for welding 3 in. pipes in the
pipeline steel API-5L X52. Two normalised fine-grained steels were used for the welding ring. The optimisation of the thickness of the welding ring is discussed.
Ó 2008 Elsevier Ltd. All rights reserved.

1. Introduction

2. Friex welding process

Pipe joining is one of the most critical, expensive, butinefficient
processes in the construction industry. Some factors that contribute significantly to the high cost of welding originate from the
complexity of the welding processes and the stringent requirements. In industrial practice, the quality of the welds is highly
dependant on the welder skills. Due to the fact that standards
are getting more stringent, it is difficult for the welder to complywith these requirements. There tends to be a high degree of variability in the weld quality, which results in a frequent need for rework. In shielded-metal arc welding the need to shield the weld arc
from impurities in the atmosphere is a source of major concern and
extra expense if rework is required.
Successful implementation of advanced joining techniques for
pipes could yield insignificant reductions in the processing time
and the need for skilled labour, in a decrease of costs associated
with the welding process and in improvements in the joint quality.
Several advanced welding technologies have the potential to improve the current pipe-joining practice. Magnetically impelled
arc butt welding (MIAB), homopolar, induction and friction stir
welding have been investigated aimingat achieving their eventual
implementation for pipeline welding [1–7]. Currently, a new variant of the well-known friction welding method, called Friex, has
been investigated for use for automatic pipeline welding.

2.1. Working principles

* Corresponding author. Tel.: +32 9 264 4228; fax: +32 9 223 7326.
E-mail addresses: Koen.Faes@Soete.Ugent.be (K. Faes), Patrick.DeBaets@UGent.
be (P.De Baets), Eric.VanDerDonckt@Denys.Com (E. Van Der Donckt), Wim.
DeWaele@UGent.be (W. De Waele).
0261-3069/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.matdes.2008.05.073

Conventional friction welding is a forge welding process in
which the heat required to realise the weld is generated as a result
of the friction between two surfaces rubbing against eachother under controlled axial pressure. The relative motion or rubbing of the
parts is continued until sufficient heat has been generated. At that
moment the relative motion is stopped and the two pieces are
forged [8]. Most applications involve welding of bars or cylindrical
parts, because friction can simply be generated by relative rotation
[9].
The disadvantage of rotational friction...