Electric Resistance Welding of Dissimilar Pipes

Abstract

Numerous studies have shown that corrosion of the casing outer side is one of the factors that has a negative impact on the accident rate of the casing string and is the reason of loss of tightness and various failures and complications in the well. The article describes a method of electric resistance welding of dissimilar steel bonding, which allows to increase the corrosion resistance of casing strings in elevator sections with an increased exterior aggressiveness. The developed technology solutions for welding conditions are presented. Metallographic studies of welded joints and recommendations for technological welding conditions are given.

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Electric Resistance Welding of Dissimilar Pipes
To cite this article: A D Davydov et al 2020 IOP Conf. Ser.: Mater. Sci. Eng. 986 012043
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III Quality Management and Reliability of Technical Systems
IOP Conf. Series: Materials Science and Engineering 986 (2020) 012043
IOP Publishing
doi:10.1088/1757-899X/986/1/012043
1
Electric Resistance Welding of Dissimilar Pipes
A D Davydov1, Ya I Evstratikova1, N O Shaposhnikov1 and G G Klimov2
1National Technology Initiative Center for Advanced Manufacturing Technologies based on the
Institute of Advanced Manufacturing Technologies of Peter the Great St. Petersburg Polytechnic
University Polytechnicheskaya, 29, St.Petersburg, 195251, Russia, goy95.95@mail.ru
2Gottfried Wilhelm Leibniz Universität Hannover
Abstract. Numerous studies have shown that corrosion of the casing outer side is one of the
factors that has a negative impact on the accident rate of the casing string and is the reason of
loss of tightness and various failures and complications in the well. The article describes a
method of electric resistance welding of dissimilar steel bonding, which allows to increase the
corrosion resistance of casing strings in elevator sections with an increased exterior
aggressiveness. The developed technology solutions for welding conditions are presented.
Metallographic studies of welded joints and recommendations for technological welding
conditions are given.
1. Introduction
Corrosion is a common cause of oil field equipment and flow string failures [6, 12]. Corrosion damage
to casing pipes often occurs due to loss of cement integrity under the influence of groundwater. Despite
many research works to improve the quality of casing cementing [9], damage cannot be avoided.
The choice of corrosion-resistant materials can reduce the possibility of corrosion damage, but it is not
always economically justified [18]. Since the corrosive media at different levels of the casing string is
different, it may technically and economically be feasible to setup the casing pipe from dissimilar
materials, that means to use low-alloyed and corrosion-resistant pipes in one string [3, 10].
One of the main requirements for pipe steel is a combination of strength and plastic properties, high rate
of impact elasticity, fatigue resistance and corrosion resistance. DSS provides a good combination of
mechanical properties along with high corrosion resistance of these steels (table 1) [4, 15, 17]. Among
austenite and ferrite corrosion-resistant steels, duplex steels (DSS) stand out for their higher strength,
toughness, corrosion resistance and heat conductivity. [1].
Joining pipes made of dissimilar materials by electric resistance welding is one of the advance research
directions, since it allows to stop using sophisticated thread connections. A proper connection is ensured
at high current densities, minimal heating time, while the development of a coarse-grained structure is
excluded and the decontamination and oxide phase and overheated metal disposal from the welding area
is provided [7, 19]. However the process of electric resistance welding has difficulties with a decrease
in the stress-strain properties of connections, especially plasticity [8], nonsymmetrical strain conditions,
which complicate the substitution of oxide films from the joint and the development of high-quality
connections [7], with the generation of hardening texture at a high rate cooling.
While crystallizing duplex steel weld pool there is a risk that the ferrite content will be about 65%,
which reduces the toughness and corrosion resistance of the weld. Consequently while predicting the

III Quality Management and Reliability of Technical Systems
IOP Conf. Series: Materials Science and Engineering 986 (2020) 012043
IOP Publishing
doi:10.1088/1757-899X/986/1/012043
2
behavior of a welded joint, it is necessary to know about the distribution of ferrite and austenite over the
entire section of the welded joint and in the heat-affected area. [14, 16].
Therefore, the object of the work is to study the possibility of building up a casing string from dissimilar
steels (low-alloy and duplex steel), connected by electric resistance welding. For this purpose the
structure of the material in the weld area as well as stress-strain properties and corrosion resistance were
investigated.
2. Methods and materials
To get a weld joint we used duplex 2205 corrosion resistant duplex steel and 09G2S low alloyed steel
(Table 1).
Table 1. S31803 (duplex 2205) [20] and 09G2S [11] steel chemical composition.
S31803(duplex 2205)
09G2S
C, %
0,03
C, %
0,12
Cr, %
21,0 - 23,0
Cr, %
0,3
Ni, %
4,5 - 6,5
Ni, %
0,3
Mn, %
2
Mn, %
1,3-1,7
Si, %
1
Si, %
0,5-0,8
Mo, %
2,50 - 3,50
Cu, %
0,3
N, %
0,08 - 0,20
N, %
0,008
P, %
0,03
P, %
0,035
S, %
0,02
S, %
0,04
FPREN
31 - 38
As, %
0,08
For the study electric resistance welding was considered for five samples of pipes of duplex and low-
alloy steel with different welding conditions (Table 2). In these welding conditions, the parts were
compressed, followed by the electric current transmission, which led to the heating of the metal. As a
result, interatomic bonds were set between the excited atoms located on the surfaces to be connected,
that means a welded joint was formed.
Table 2. Welding conditions.
№
I, A∙с
j,
А/mm2
tw, s
U, V
pос1, bar
pос2, bar
Δoc,
mm
IF, A∙с
1
1845
3,33
5,58
24,1
122,2
120,2
4,95
53,3
2
1733
3,13
5,28
26,1
131,6
123,8
3,58
50,7
3
1948
3,52
5,77
25,1
127,9
123
4,86
54,8
4
1467
2,65
4,48
25,6
129,9
122
2,7
44,5
5
1701
3,07
5,28
28,6
136,6
124,8
4,07
50,7
Where j – current density, tw – welding time, U – welding voltage, pос1- pос2 – welding pressure, Δoc –
welding value, IF – coil current [9].
The sample was a pipe with an external diameter of 48 mm, a wall thickness of 4 mm and a height of
90 to 100 mm (Figure 1). The distance from the current lead to the pipe joint was 50 mm.
After that a metallographic sample was cut in the longitudinal direction to study the heat-affected zone
and the welded joint. The studies were carried out using an optical microscope (×500). Hardness
measurements were performed by the Vickers method with a load of 180 g (HV0,18).

III Quality Management and Reliability of Technical Systems
IOP Conf. Series: Materials Science and Engineering 986 (2020) 012043
IOP Publishing
doi:10.1088/1757-899X/986/1/012043
3
а
b
Figure 1. Test item: а – general view, b – dimensions.
3. Research results
The microstructure in the welded joint is shown in Figure 2.
1) DSS microstructure
2) The welded joint
macrophotograph
3) 09G2S microstructure
Figure 2. The metal structure of the welded joint of the sample №3.
During the compression of the parts towards the inner and outer walls of the pipe, the non-liquid metal
spread out (Fig. 2). When the welded joint was formed, a line of separation of two metals with
discontinuities appeared (Fig. 3).
1
2
3
4
5
Figure 3. Discontinuities of different modes in the welded joint: 1-5, ×500.
DSS
09G2S
Welded joint
Heat affected zone

III Quality Management and Reliability of Technical Systems
IOP Conf. Series: Materials Science and Engineering 986 (2020) 012043
IOP Publishing
doi:10.1088/1757-899X/986/1/012043
4
For modes 2 and 4 discontinuities reach 20-25 microns, for mode 5 - 45 microns. Also, as we can see
on Figure 4, there are drops of duplex steel metal on the inner surface of the pipe, which is the result of
heating above the solidus during welding. Also some part of duplex steel flowed into low-alloyed steel,
which also confirms the heating which exceeds the duplex steel solidus temperature.
Figure 4. Dropping metal duplex steel side (mode 5).
Low alloyed steel pipe grain in the welded joint is a martensite (Fig. 5, area 1), average hardness by
mode was approximately 600 HV0,18. In the heat-affected area near the welded joint (Fig. 5, area 2),
we have the banding of the low-alloy steel grain in martensite strips form, which are characterized by
reduced hardness values), alternating with bainitic ones.
Figure 5. Panorama of the heat-affected zone of the welded joint low-
alloyed steel side (mode 5), ×25.
Then there is the area 3, which has a bainite grain (Figure 6, area 3), the average hardness of the area
by mode is about 390 HV0,18. The base metal grain is sorbite (Fig. 6, area 4).
1
2
3
4

III Quality Management and Reliability of Technical Systems
IOP Conf. Series: Materials Science and Engineering 986 (2020) 012043
IOP Publishing
doi:10.1088/1757-899X/986/1/012043
5
Area 3 grain
Area 4 grain
Figure 6. Low-alloyed steel grain in the welded joint, ×500.
The grain of a part of a duplex steel pipe in the welded joint area is a mixture of ferrite and austenite in
an approximate ratio of 50/50 banded morphology (Fig. 7, dark areas are austenite, light areas are
ferrite). Average hardness of area 3 (Fig. 7) for all welding conditions was ≈ 290 HV0,18. In the heat-
affected zone close to the welded joint (area 1), there is no banding of the grain, the average hardness
of the area for all welding conditions is about 320 HV0,18.
Microstructure close to welded joint
Base metal microstructure
Figure 7. Duplex steel grain close to welded joint, ×500.
To accurate determine the grain in different areas of welded joints, as well as to determine the
dimensions of the heat-affected area at the weld boundary, the hardness of the welded joints was
measured by metallographic study. The results of measuring the hardness of welded joints, carried out
after welding, including the heat-affected area and welded joint metal are shown in Fig. 8.

III Quality Management and Reliability of Technical Systems
IOP Conf. Series: Materials Science and Engineering 986 (2020) 012043
IOP Publishing
doi:10.1088/1757-899X/986/1/012043
6
Figure 8. Distribution of hardness over the pipe section in the joint area.
According to NACE MR0175 the maximum permitted hardness value for the welded area must be 250
HV. These hardness values are unacceptable for H2S media and the requirement is not met [20].
4. Discussion
Metallographic studies have shown that there are discontinuities in the joints, which affects the
mechanical properties of the construction. There are areas of increased hardness in the welded joint area,
which can also adversely affect the corrosion resistance of the pipe under voltage [20].
Hardening grains have also been found in the welded joint, which can adversely affect resistance to
corrosion cracking, especially in a hydrogen sulfide environment.
For this welding method, there are low specific pressures, which are responsible for plastic deformation,
which is the main activating factor in a welded joint development in the solid phase. Heating is also an
activating factor, but its main function is to reduce the resistance to deformation and, as a result, to
lighten plastic deformation. Although with a temperature increase, the concentration of vacancies
increases, which intensifies the diffusion, which is an accompanying process, but rather important in the
welded joint development in the solid phase. Due to relatively low specific pressures and increased
contact resistances in comparison with classical electric resistance welding, local melting and drops
splashing in the joint are observed (Figure 4) The use of heating to certain temperatures reduces the
deformation resistance of the metal and forces diffusion processes. According to this the temperature
increase contributes to all those processes that can provide a reliable welded joint, and the correct
technology will ensure that hardening grains and discontinuities are avoided [2, 5].
So the welding technology requires modification of the welding conditions. The optimal parameters for
the welding conditions are: higher welding current density and lower voltages [5, 13].
5. Conclusion
We have studied the result of electric resistance welding of dissimilar pipes - duplex and low-alloyed
steel. The investigated technology allows us to use corrosion-resistant casing pipes in the well lift in
those areas where their use is economically reasonable, but the technology has its own requirements and
limitations, therefore the welding conditions should be carefully selected. To improve the welding, a
higher welding current density, about 20-60 A / mm2, and lower voltages of 1.5-5 V are required.
In the material grain in the area of the welded joint on the low-alloyed steel side, hardening grains of
the martensite and tempered martensite type with high values of hardness were noted, which is
unacceptable in a hydrogen sulfide environment and can significantly reduce the corrosion resistance.

III Quality Management and Reliability of Technical Systems
IOP Conf. Series: Materials Science and Engineering 986 (2020) 012043
IOP Publishing
doi:10.1088/1757-899X/986/1/012043
7
This technology requires further study for choosing the optimal welding conditions.
References
[1] Kall`yari I, Breda M, Frigo M 2014 Izotermicheskoe starenie e`konomno legirovannoj dupleksnoj
nerzhaveyushhej stali Vestnik Magnitogorskogo gosudarstvennogo tekhnicheskogo universiteta
im. G. I. Nosova (№ 4) pp 44-53
[2] Karakozov E` S Soedinenie metallov v tverdoj faze
[3] Blinov P A, Dvoynikov M V, Sergeevich K M and Rustamovna A E 2017 Influence of mud
filtrate on the stress distribution in the row zone of the well International Journal of Applied
Engineering Research (12(15) ISSN 0973- 4562) pp 5214-5217
[4] Ermakov B S and Shaposhnikov N.O Effect of Production Factors on Main Oil Pipeline Pipe
Metal Property Formation Metallurgist (62(7-8) DOI: 10.1007/s11015-018-0718-7)
[5] Kuchuk-Yaczenko S I and Lebedev V K 1976 Kontaktnaya sty`kovaya svarka neprery`vny`m
oplavleniem (Kiev: Nauk. Dumka) p 216
[6] Blinov P A and Dvoynikov M V 2018 Rheological and filtration parameters of the polymer salt
drilling fluids based on xanthan gum Journal of Engineering and Applied Sciences (13(14) DOI:
10.36478/jeasci.2018.5661.5664) pp 5661-5664
[7] Kuchuk-Yaczenko S I, Nakonechny`j A A, Zyakhor I V, Chernobaj S V and Zavertanny`j M S
Tekhnologiya i oborudovanie dlya sty`kovoj svarki soprotivleniem detalej bol`shogo secheniya
iz raznorodny`j stalej (IE`S im. E.O. Patona)
[8] Kunshin A A, Dvoynikov M V and Blinov P A 2019 Topology and dynamic characteristics
advancements of liner casing attachments for horizontal wells completion Youth Technical
Sessions Proceedings: VI Youth Forum of the World Petroleum Council - Future Leaders Forum
(WPF 2019), June 23-28, 2019, Saint Petersburg, Russian Federation (ISBN 9780367346683)
pp 376-381
[9] Chudinova I V, Nikolaev N I and Petrov A A 2019 Design of domestic compositions of drilling
fluids for drilling wells in shales Youth Technical Sessions Proceedings: VI Youth Forum of the
World Petroleum Council - Future Leaders Forum (WPF 2019), June 23-28, 2019, Saint
Petersburg, Russian Federation (DOI: 10.1201/9780429327070) pp 371-375
[10] Davydov A, Alekseeva E and Gaev A Specificity to the choice of materials for wellhead
equipment Materials Today: Proceedings
[11] GOST 19281-2014
[12] Nutskova M V, Kupavykh K S, Sidorov D A and Lundaev V A 2019 Research of oil-based
drilling fluids to improve the quality of wells completion IOP Conference Series: Materials
Science and Engineering (Vol. 666, No. 1, 012065, DOI: 10.1088/1757-899X/666/1/012065)
[13] Krasulin Yu L and Nazarov G V 1976 Mikrosvarka davleniem Metallurgiya p 160
[14] Zubchenko A S and Fedorov A V Kompleksny`e issledovaniya svarivaemosti i korrozionnoj
stojkosti austenitnoferritnoj (dupleksnoj) stali saf 2507
[15] Alkhimenko A 2019 Corrosion testing of experimental steels for oilfield pipelines E3S Web of
Conferences (121, 01001, DOI: 10.1051/e3sconf/201912101001)
[16] Kovalev M, Alkhimenko A and Shakhmatov A 2020 Electrochemical studies of welded joints
corrosion resistance made from stainless steels Materials today: proceedings (DOI:
10.1016/j.matpr.2020.01.034)
[17] Andrey Lapechenkov, Aleksandr Fedorov, Ekaterina Alekseeva, Lyudmila Galata and Aleksey
Piskarev 2020 Comparative analisys of corrosion resistance of S31200 duplex stainless steel and
its analogue Materials today: proceedings February 2020 (DOI: 10.1016/j.matpr.2019.12.174)
[18] Laptev A and Bugay D 2010 Fighting against corrosion in oil and gas complex of Russia:
Problems and the ways of their solving European Corrosion Congress (EUROCORR 2010)
[19] Sakhaczkij G P 1963 Issledovanie kontaktnoj sty`kovoj svarki oplavleniem i soprotivleniem (№
10) pp 26–32
[20] NACE MR0175/ISO 15156-1