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Abstract:
This paper describes the latest implementation status
of the narrow gap welding process by the high speed
rotating arc method developed by JFE Engineering in
1980s. In case of the engine crankcases, adaptive con-
trol function of the welding speed corresponding to the
variation of the groove width has been newly developed.
Tandem welding system by one operator without watch-
ing the two equipment has been also employed, shorten-
ing the welding lead-time to less than half that of the
conventional method. Furthermore, for innovation of the
narrow gap welding, another oscillation pattern of the
welding torch by the circular weaving has been added to
the conventional equipment. In case of the turbine mem-
bers, application range has been expanded to be able to
apply to the inclined narrow gap joints, and it was con-
rmed that the groove width could be decreased from
the conventional 13 mm to about 8 mm.
1. Introduction
In welding of extra-heavy gauge plates with thick-
nesses exceeding 50 to 100 mm, use of an I-shaped nar-
row gap groove is effective, as this groove shape greatly
reduces the cross-sectional area of the groove. Begin-
ning in the 1980s, various narrow gap welding methods
were developed and applied into practical uses. I-shaped
narrow gap grooves are widely used in various types of
large-scale structures because this groove shape not only
significantly reducing the welding deposition volume,
thereby shortening the welding time as the plate thick-
ness increases, but also realizes low strain due to the
reduced heat input and a fracture toughness improve-
ment effect as a result of reheating. NKK (now JFE
Engineering) also independently developed the “high
speed rotating arc narrow gap welding method,” which
it applied to its own products and sold to customers
beginning the 1980s. Subsequently, with the aims of
achieving higher efficiency and a higher level of auto-
mation, JFE Engineering also developed an adaptive
control function of welding speed by use of an arc sen-
sor, and promoted expanded application by adding new
oscillation patterns.
This paper presents an outline of the high speed
rotating arc narrow gap welding process and the recent
condition of practical application, and also reports on
the status of efforts to improve the penetration shape by
addition of a circular weaving function, improve
response to variations in groove width, expand applica-
tion to inclined welded joints, etc., and to realize a nar-
rower welding gap.
2. HighSpeedRotatingArc
NarrowGapWeldingMethod
2.1 HistoryandTypesofNarrowGapWelding
Narrow gap welding process was first developed in
1963 by Battelle Memorial Institute in the United States.
Much research and development on this technology has
been carried out in countries around the world, but
where practical application is concerned, Japan was the
most enthusiastic. It is generally said that there was a
feeling that a variety of narrow gap welding methods
flowered all at once in Japan in the 1980s. Various inter-
pretations have also been given to the definition of nar-
JFETECHNICALREPORT
No.20(Mar.2015)
Narrow Gap Gas Metal Arc (GMA) Welding
Technologies
†
MURAYAMA Masatoshi
*1
OAZAMOTO Daisuke
*2
OOE Kensuke
*3
†
Originally published in JFE GIHO No. 34 (Aug. 2014), p. 98–103
*2
Project Planning Sec.,
Tsu Works,
Steel Structure Engineering Sector,
JFE Engineering
*1
Principle (Welding),
Machinery Center,
Industrial Machinery Sector,
JFE Engineering
*3
Planning Sec.,
Machinery Center,
Industrial Machinery Sector,
JFE Engineering