Recrystallization in the metal of welding joints of steam trucks
The recrystallization process in the structure of welded joints of steam pipelines from heat-resistant pearlitic steels, operated for a long time under creep conditions (Te = 545…585 °С, Рe = 20…25 MPa), reduces their performance. Studying the peculiarities of the recrystallization process will allo...
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
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irk-123456789-1952132023-12-03T17:30:04Z Recrystallization in the metal of welding joints of steam trucks Dmytryk, V.V. Glushko, A.V. Tsar, A.K. Physics of radiation damages and effects in solids The recrystallization process in the structure of welded joints of steam pipelines from heat-resistant pearlitic steels, operated for a long time under creep conditions (Te = 545…585 °С, Рe = 20…25 MPa), reduces their performance. Studying the peculiarities of the recrystallization process will allow slowing down its passage, which is important for increasing the service life of welded joints of steam pipelines, which are characterized by the presence of a certain structural heterogeneity. Процес рекристалізації в структурі зварних з'єднань паропроводів із теплостійких перлітних сталей, які тривалий час працюють в умовах повзучості (Те = 545…585 °С, Ре = 20…25 МПа), сприяє зниженню їх експлуатаційних характеристик. Вивчення особливостей процесу рекристалізації дозволить уповільнити їх проходження, що актуально для збільшення ресурсу зварних з'єднань паропроводів, що характеризуються наявністю певної структурної неоднорідності. Процесс рекристаллизации в структуре сварных соединений паропроводов из теплоустойчивых перлитных сталей, длительно работающих в условиях ползучести (Тэ = 545…585 °С, Рэ = 20…25 МПа), способствует снижению их эксплуатационных характеристик. Изучение особенностей процесса рекристаллизации позволит замедлить его прохождение, что актуально для увеличения ресурса сварных соединений паропроводов, характеризующихся наличием определенной структурной неоднородности. 2019 Article Recrystallization in the metal of welding joints of steam trucks / V.V. Dmytryk, A.V. Glushko, A.K. Tsar // Problems of atomic science and technology. — 2019. — № 5. — С. 49-52. — Бібліогр.: 5 назв. — англ. 1562-6016 http://dspace.nbuv.gov.ua/handle/123456789/195213 669.017+620.186.4 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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English |
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Physics of radiation damages and effects in solids Physics of radiation damages and effects in solids |
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Physics of radiation damages and effects in solids Physics of radiation damages and effects in solids Dmytryk, V.V. Glushko, A.V. Tsar, A.K. Recrystallization in the metal of welding joints of steam trucks Вопросы атомной науки и техники |
| description |
The recrystallization process in the structure of welded joints of steam pipelines from heat-resistant pearlitic steels, operated for a long time under creep conditions (Te = 545…585 °С, Рe = 20…25 MPa), reduces their performance. Studying the peculiarities of the recrystallization process will allow slowing down its passage, which is important for increasing the service life of welded joints of steam pipelines, which are characterized by the presence of a certain structural heterogeneity. |
| format |
Article |
| author |
Dmytryk, V.V. Glushko, A.V. Tsar, A.K. |
| author_facet |
Dmytryk, V.V. Glushko, A.V. Tsar, A.K. |
| author_sort |
Dmytryk, V.V. |
| title |
Recrystallization in the metal of welding joints of steam trucks |
| title_short |
Recrystallization in the metal of welding joints of steam trucks |
| title_full |
Recrystallization in the metal of welding joints of steam trucks |
| title_fullStr |
Recrystallization in the metal of welding joints of steam trucks |
| title_full_unstemmed |
Recrystallization in the metal of welding joints of steam trucks |
| title_sort |
recrystallization in the metal of welding joints of steam trucks |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2019 |
| topic_facet |
Physics of radiation damages and effects in solids |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/195213 |
| citation_txt |
Recrystallization in the metal of welding joints of steam trucks / V.V. Dmytryk, A.V. Glushko, A.K. Tsar // Problems of atomic science and technology. — 2019. — № 5. — С. 49-52. — Бібліогр.: 5 назв. — англ. |
| series |
Вопросы атомной науки и техники |
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| first_indexed |
2025-07-16T23:04:38Z |
| last_indexed |
2025-07-16T23:04:38Z |
| _version_ |
1837846578335842304 |
| fulltext |
ISSN 1562-6016. PASТ. 2019. №5(123), p. 49-52.
UDC 669.017+620.186.4
RECRYSTALLIZATION IN THE METAL OF WELDING JOINTS
OF STEAM TRUCKS
V.V. Dmytryk, A.V. Glushko, A.K. Tsaryk
National Technical University “Kharkiv Polytechnic Institute”,
E.O. Paton Electric Welding Institute
Kharkiv, Ukraine
E-mail: alyonaglushko@gmail.com, tel. +38-066-312-51-99
The recrystallization process in the structure of welded joints of steam pipelines from heat-resistant pearlitic
steels, operated for a long time under creep conditions (Te = 545…585 °С, Рe = 20…25 MPa), reduces their
performance. Studying the peculiarities of the recrystallization process will allow slowing down its passage, which
is important for increasing the service life of welded joints of steam pipelines, which are characterized by the
presence of a certain structural heterogeneity.
INTRODUCTION
Recrystallization in welded joints are considered as a
process of gradual elimination of separate fragments of
grain boundaries and further elimination of the grain
boundaries themselves, which leads to the formation of
large grains.
The goal of this work is a theoretical justification of
the recrystallization process as applied to the structure
of welded joints of steam pipelines, which are used for a
long time under creep conditions.
The mechanism of recrystallization in metal of
welded joints of steam pipelines that work for a long
time under creep conditions has distinctive features
from recrystallization during annealing of cold-
deformed metal: recrystallization during annealing has
an incubation period and occurs as the effect of grain
growth by eliminating grain boundaries, as well as the
formation and growth of stress-free germs.
Recrystallization in the metal of welded joints does not
have an incubation period, is characterized by the
absence of nucleation and begins approximately after
their production time of more than 270000 h, and also
proceeds relatively slowly in the future.
Recrystallization in the metal of welded joints of steam
pipelines is the most pronounced in areas of incomplete
recrystallization, overheating, and fusion of the heat-
affected zone (HAZ).
Recrystallization are considered as a component of
the effect of degradation of the structure, resulting in a
decrease by about 15…20% of the strength properties of
the metal of welded joints, as well as by 15…20% of
toughness [1–3].
MATERIALS AND EXPERIMENTAL
TECHNIQUES
In this work, steels 12Kh1M1F and 15Kh1M1F
were used. Accordingly, the operating temperature
should not exceed 570…580 °C.
Сhemical composition of heat-resistant pearlitic
steel 12X1MF, %: C – 0.10…0.15; Si – 0.17…0.37;
Mn – 0.40…0.70; Cr – 0.90…1.20; Mo – 0.25…0.35;
V – 0.15…0.30; Ni no more than 0.25; Cu no more than
0.20; S no more than 0.025; P no more than 0.025.
Сhemical composition of heat-resistant pearlitic steel
15Kh1M1F, %: C – 0.10…0.16; Si – 0.15…0.37; Mn –
0.40…0.70; Cr – 1.10…1.40; Mo – 0.90…1.10; V –
0.20…0.35; Ni no more than 0.25; Cu no more than
0.20; S no more than 0.025; P no more than 0.025.
The experimental technique included the use of
optical and electron microscopy. The study of
dislocations in α-phase grains (matrix ferrite and bainite
tempering) was performed using the thin foil method.
By using a scanning electron microscope JSM-820 with
an X-ray microanalyzer system LINK AN101856, the
chemical composition of the phase grains, carbides, and
non-metallic inclusions was determined.
RESULTS AND DISCUSSIONS
Recrystallization occurs while simultaneously
reducing the level of the lattice distortion by diffusion
of the alloying elements from the central regions of the
crystal to their border regions, which contributes to the
subsequent increase in its deformation. The recrys-
tallization process begins to manifest itself when the
metal is deformed from approximately 2…3%, which is
typical for areas of incomplete recrystallization,
overheating, and fusion of the HAZ. The base metal, as
well as the weld metal and the metal of other HAZ sites,
when welded joints reach more than 270000 h, usually
deforms less than 1%, and there is no noticeable
manifestation of recrystallization in their structure.
During long-term operation in the metal of welded
joints, self-diffusion ensures the formation in the border
zones of α-phase grains of segregations from chromium,
molybdenum, silicon and manganese elements [1, 2],
which leads to a decrease in the level of crystal
distortion, and at the same time increases its
deformation capacity. In the process of long-term
development under creep conditions, the original
structure of welded joints is transformed into a ferrite-
carbide mixture. In the process of crystal deformation,
elimination and partial displacement of high-angle grain
boundaries occurs. Recrystallization is preceded by a
return, which includes the rearrangement of
dislocations, their nucleation, recombination, and
annihilation. Under creep conditions, “static”
recrystallization takes place, leading to the elimination
of grain boundaries, which is ensured by the desire to
possess less free energy. The growth of individual
grains occurs due to the elimination of grain boundaries
(Fig. 1). There is a restructuring of the structural state of
mailto:alyonaglushko@gmail.com
the grains in the presence of plastic deformation. The
deformation of the metal of the HAZ sections, as well as
the weld metal and the base metal of welded joints,
when operating for 250000…280000 h, is different and
consists of: overheating section 1…3%, incomplete
recrystallization 3…7%, base metal 0.3…0.5%, weld
metal 0.4…0.6% [2, 3].
The recrystallization process in the structure of
welded joints is facilitated by carbide reactions М3С →
М7С3 → М23С6, the separation of grain boundaries
from carbides, dislocation displacements and their
interaction [1–4]. Together, these factors lead first to a
local one (see Fig. 1), and then to the complete
elimination of individual grain boundaries (Fig. 2).
Fig. 1. Structure of the HAZ overheating section.
The elimination of fragments of grain boundaries is
indicated by arrows. Welded joint from steel 12Х1MF.
Working hours 280000 h, х300
Fig. 2. Structure of the HAZ overheating section.
The intergranular boundaries that have been eliminated
are indicated by arrows.
Welded joint from steel 15Х1M1F, 286000 h
The presence in the crystal of the α-phase of the
substitutional elements (chromium, molybdenum,
vanadium), as well as “sedentary” dislocations, ensures
its uneven deformation. Different density of dislocations
on the body of grains and on their boundaries, incl. near
the discharge of the second phases [4], provides a
different level of strain accumulation, which seems to
be an integral part of the energy factor of their
movement.
Recrystallization in the metal of welded joints has
no separation into primary, collective, secondary. The
recrystallization process under consideration is
characterized by an increase in the grain size. Their
increase occurs at different rates in the presence of a
characteristic structure, respectively, for each HAZ site,
as well as the weld metal and the base metal. Grain
growth occurs by eliminating grain boundaries (see
Figs. 1 and 2). In the process of their merging, the shape
of the grains acquires a gradual change. The rate of
elimination of grain boundaries is the highest in the area
of incomplete recrystallization of HAZ, where new
austenite decomposition products represent globulized
perlite (Fig. 3).
Fig. 3. Structure of the site of incomplete
recrystallization of HAZ. New austenite decomposition
products represent globularized perlite (indicated by
arrows). Welded joint from steel 15Kh1M1F, x360
The work of eliminating, under creep conditions,
grain boundaries can be considered as the applied
energy and the Gibbs energy difference G of two
contacting grains per unit volume of the grain boundary
(J/μm
3
).
The reduction of the energy level of the system state
(grain boundary) depends on its structure, and is also
ensured by the joint manifestation of work, both
external and internal forces. When studying the features
of eliminating intergranular boundaries, a reference
system was adopted, i.e. its initial position (Fig. 4).
It was assumed that the E fragment in the S1
reference system provides for the elimination of the
intergranular boundary with the progressive velocity V
relative to the S2 reference system. We write:
21
' '
2
E E mV P , (1)
where ' 'P mV is the momentum of the fragment in
the system 'S ; m is the mass of the fragment of the
intergranular boundary.
It was taken into account that when eliminating
grain boundaries, the Gibbs energy decreases,
respectively. Imagine:
1 2 3( )dG P P dAdx P d
, (2)
where d is the changed volume of the grain with the
elimination of a fragment of the grain boundary; A is the
element of the fragment.
а
b
c
Fig. 4. Schematic representation of the successive
elimination of grain boundaries: a – the initial state of
the structure; b – fragment of elimination of the
intergranular boundary; c – complete elimination of the
grain boundary; S1-S2 – the reference system
The driving force, under creep conditions, is the
local manifestation of free energy per unit volume
1P
and energy
2P
, as an effect of the operating voltage
1 2 .
dG
d
P P
In the process of recrystallization, the acting force
ensuring the elimination of grain boundaries is the
accumulated energy of the existing “sedentary” as well
as the resulting dislocations. At the initial stage of
recrystallization, the driving force is the energy of the
grain boundaries. It was established that the dislocation
density at the boundary areas of the contacting grains is
10
12
, and 10
10
m
-2
along their body.
To determine the volume fraction of the
recrystallized structure f(t) during time t, an expression
was proposed:
1 2( ) 1
kVV t
f t e
, (3)
where is the correction factor; V1 is the rate of
formation of fragments of elimination of grain
boundaries; V2 – fragment growth rate; 2 < k < 4.
The proposed relationship provides a curve (Fig. 5),
which corresponds to the operating time of the welded
joint of the steam line, in creep conditions, of 280000 h.
Fig. 5. Dependence of metal recrystallization of the
HAZ overheating area on time t.
Welded joint from steel 15X1M1F
The elimination of grain boundaries occurs
simultaneously with the formation of segregations (from
replacement elements), the separation of the second
phases Mo2C and VC, coagulation of M7C3 and M23C6.
The diffusion movement of chromium and molybdenum
from the central regions of the grains to their border
areas also contributes to the elimination of grain
boundaries. It was established that in the process of
eliminating grain boundaries, their fragments are
eliminated first, and then the boundaries themselves (see
Figs. 1, 2). In the recrystallization process, the
intergranular boundaries are initially eliminated, which
are exposed to the applied relative to the highest
operating voltage, which depends on their shape,
location, type of structure and level of deformation of
the contacting grains.
The local elimination of fragments of grain
boundaries (operating time over 270000 h) is not
accompanied by a simultaneous change in the different
structural orientations of both grains to the same.
Accelerations of up to 600…650 °C (emergency
steam discharge) contribute to the acceleration (by
about 10…15%) of the recrystallization process, which
allows the process to be considered as thermally
activated. The passage of the process in time, which is
confirmed by the data (see Fig. 5), is:
Q
RTt A e ,
where A is a constant; Q is the activation energy of the
recrystallization process; T is the temperature; R is the
gas constant.
The magnitude of the activation energy of
recrystallization depends on the structural state of
welded joints, as well as on the conditions of their
operation. Allowed overheating leads to a certain
acceleration of the recrystallization process. It is
important to establish the dependence of the onset of
recrystallization on the level of deformation of the metal
of welded joints and the presence of segregations, which
manifests itself on the internal surfaces of grain
separation (subgrain boundaries), as well as in the
border zones of the grains [1–4]. Mostly, the presence
of segregation is typical for HAZ sites: incomplete
recrystallization (where new austenite decomposition
products represent globulized perlite (see Fig. 3)) and
overheating (where the austenitic grain is less than 4th,
GOST 5639-82). The formation of segregations occurs
with simultaneous creeping of dislocations, which leads
to the local elimination of grain boundaries. It makes
sense to establish the onset of recrystallization with the
presence of segregations.
Most intensively, in welded joints of steam
pipelines, recrystallization occurs in the structure of the
section of incomplete recrystallization of HAZ, where
fine-grained globulized perlite is present (see Fig. 3),
grouped as discontinuous chains in a ferrite-bainite,
ferrite-sorbitol, or ferrite-reed structure. Average grain
size – 9. With a slightly lower activity (about
20…30%), the recrystallization process takes place in
the overheating area, where the structure is
characterized by the presence of grains of various sizes
(Fig. 6). Average grain size – 3. Grains in the
overheating area belong to the same structural type,
which ensures a reduction in the level of
recrystallization.
Fig. 6. The structure of the HAZ overheating section.
Welded joint from steel 15X1M1F.
Working hours 280000 h, х400
The study of the recrystallization mechanism made it
possible to reveal its manifestation in the metal of long-
term operated welded joints of steam pipelines. The
revealed features of the mechanism of the
recrystallization process can be represented in a grouped
form:
– elimination of grain boundaries occurs depending
on the applied voltage and their location;
– the rate of elimination of grain boundaries depends
on their structural state;
– elimination of grain boundaries is accelerated in
the presence of overheating (temperature is higher than
the recommended regulatory documentation);
– the merging of the grains leads to the subsequent
formation of the same structural orientation of the
merged, by coaliscence, grains.
We believe that the mechanism of the process of
recrystallization of metal of welded joints of steam
pipelines, under creep conditions, should be
supplemented by invoking the provisions of the theory
of dislocations and the theory of grain boundaries.
CONCLUSION
1. Theoretically substantiated the peculiarities of the
recrystallization process in the metal structure of welded
joints of steam pipelines, which are operated for a long
time under creep conditions.
2. Developed a model of the recrystallization
process, taking into account the dependence of its
passage on the structural state and on the level of
deformation of the metal of welded joints, which work
for a long time under creep conditions.
3. The dependence of the recrystallization rate on the
structural state of welded joints and the conditions of
their operation was established.
REFERENCES
1. В.В. Дмитрик, В.Н. Баумер. Металлофиз. но-
вейшие технологии. 2007, v. 29, №7, p. 937.
2. В.В. Дмитрик, С.Н. Барташ. Металлофиз.
новейшие технологии. 2010, v. 32, №12, р. 1657.
3. В.В. Дмитрик, А.В. Глушко, Т.А. Сыренко,
С.Г. Григоренко. Автоматическая сварка. 2018,
№5, р. 9.
4. A. Glushko // Eastern-European Journal of
Enterprise Technologies, 2016, v. 6, N 1(84), p. 14;
DOI: 10.15587/1729-4061.2016.85852.
5. А.В. Глушко, В.В. Дмитрик, Т.А. Сыренко.
Металлофиз. новейшие технологии. 2018, v. 40, №5,
p. 683.
Article received 19.08.2019
РЕКРИСТАЛЛИЗАЦИЯ В МЕТАЛЛЕ СВАРНЫХ СОЕДИНЕНИЙ ПАРОПРОВОДОВ
В.В. Дмитрик, А.В. Глушко, А.К. Царюк
Процесс рекристаллизации в структуре сварных соединений паропроводов из теплоустойчивых
перлитных сталей, длительно работающих в условиях ползучести (Тэ = 545…585 °С, Рэ = 20…25 МПа),
способствует снижению их эксплуатационных характеристик. Изучение особенностей процесса
рекристаллизации позволит замедлить его прохождение, что актуально для увеличения ресурса сварных
соединений паропроводов, характеризующихся наличием определенной структурной неоднородности.
РЕКРИСТАЛІЗАЦІЯ В МЕТАЛІ ЗВАРНИХ З'ЄДНАНЬ ПАРОПРОВОДІВ
В.В. Дмитрик, А.В. Глушко, А.К. Царюк
Процес рекристалізації в структурі зварних з'єднань паропроводів із теплостійких перлітних сталей, які
тривалий час працюють в умовах повзучості (Те = 545…585 °С, Ре = 20…25 МПа), сприяє зниженню їх
експлуатаційних характеристик. Вивчення особливостей процесу рекристалізації дозволить уповільнити їх
проходження, що актуально для збільшення ресурсу зварних з'єднань паропроводів, що характеризуються
наявністю певної структурної неоднорідності.
http://dx.doi.org/10.15587/1729-4061.2016.85852
|