Welding of defects in cast cases of turbines with perlite electrodes without heating and thermal processing
The regularities of structural formation of the weld metal and HAZ during multilayer welding, made by the transverse humping method, with short sections of defects on cast steel 15Kh1M1FL with perlite electrodes without heating and heat treatment are considered. It has been established that the stru...
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
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irk-123456789-1944182023-11-24T15:12:15Z Welding of defects in cast cases of turbines with perlite electrodes without heating and thermal processing Efimenko, N.G. Artyomova, S.V. Physics of radiation and ion-plasma technologies The regularities of structural formation of the weld metal and HAZ during multilayer welding, made by the transverse humping method, with short sections of defects on cast steel 15Kh1M1FL with perlite electrodes without heating and heat treatment are considered. It has been established that the structure of all the studied zones of the welded joint is represented by upper granular bainite of varying degrees of dispersion. The difference in the hardness of the structures in the upper and middle parts of the welded joint is insignificant (3I4 and 296 HV, respectively). In the upper part, the formation of a hypereutectoid ferrite is found, which is located along the grain boundaries, which is also related with edge effect. The plastic properties of the weld metal are increased by more than 1.5 times, KCV – by more than 3 times in comparison with the base metal. Розглянуто закономірності структуроутворення металу шва і зони термічного впливу (ЗТВ) при багатошаровій заварці короткими ділянками дефектів на литій сталі 15Х1М1ФЛ перлітними електродами способом поперечної горки (СПГ) без підігріву і термічної обробки. Встановлено, що структура усіх досліджуваних зон зварного з’єднання представлена верхнім зернистим бейнітом різної міри дисперсності. Різниця в твердості структур у верхній і середній частинах зварного з’єднання незначна (314 і 296 HV відповідно). У верхній частині виявлено формування доевтектоїдного фериту, розташованого по межах зерен, що пов’язано, в тому числі, з крайовим ефектом. Пластичні властивості металу шва збільшені більш ніж у 1,5 рази, KCV – більш ніж у 3 рази в порівнянні з основним металом. Рассмотрены закономерности структурообразования металла шва и зоны термического влияния (ЗТВ) при многослойной заварке короткими участками дефектов на литой стали 15Х1М1ФЛ перлитными электродами способом поперечной горки (СПГ) без подогрева и термической обработки. Установлено, что структура всех исследуемых зон сварного соединения представлена верхним зернистым бейнитом различной степени дисперсности. Разница в твердости структур в верхней и средней частях сварного соединения незначительна (314 и 296 HV соответственно). В верхней части обнаружено формирование доэвтектоидного феррита, располагающегося по границам зерен, что связано, в том числе, с краевым эффектом. Пластические свойства металла шва увеличены более чем в 1,5 раза, KCV – более чем в 3 раза по сравнению с основным металлом. 2020 Article Welding of defects in cast cases of turbines with perlite electrodes without heating and thermal processing / N.G. Efimenko, S.V. Artyomova // Problems of atomic science and tecnology. — 2020. — № 4. — С. 84-88. — Бібліогр.: 15 назв. — англ. 1562-6016 PACS: 62.20.-x; 62.20.Mk; 68.35.Gy; 81.70.Bt http://dspace.nbuv.gov.ua/handle/123456789/194418 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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Physics of radiation and ion-plasma technologies Physics of radiation and ion-plasma technologies |
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Physics of radiation and ion-plasma technologies Physics of radiation and ion-plasma technologies Efimenko, N.G. Artyomova, S.V. Welding of defects in cast cases of turbines with perlite electrodes without heating and thermal processing Вопросы атомной науки и техники |
| description |
The regularities of structural formation of the weld metal and HAZ during multilayer welding, made by the transverse humping method, with short sections of defects on cast steel 15Kh1M1FL with perlite electrodes without heating and heat treatment are considered. It has been established that the structure of all the studied zones of the welded joint is represented by upper granular bainite of varying degrees of dispersion. The difference in the hardness of the structures in the upper and middle parts of the welded joint is insignificant (3I4 and 296 HV, respectively). In the upper part, the formation of a hypereutectoid ferrite is found, which is located along the grain boundaries, which is also related with edge effect. The plastic properties of the weld metal are increased by more than 1.5 times, KCV – by more than 3 times in comparison with the base metal. |
| format |
Article |
| author |
Efimenko, N.G. Artyomova, S.V. |
| author_facet |
Efimenko, N.G. Artyomova, S.V. |
| author_sort |
Efimenko, N.G. |
| title |
Welding of defects in cast cases of turbines with perlite electrodes without heating and thermal processing |
| title_short |
Welding of defects in cast cases of turbines with perlite electrodes without heating and thermal processing |
| title_full |
Welding of defects in cast cases of turbines with perlite electrodes without heating and thermal processing |
| title_fullStr |
Welding of defects in cast cases of turbines with perlite electrodes without heating and thermal processing |
| title_full_unstemmed |
Welding of defects in cast cases of turbines with perlite electrodes without heating and thermal processing |
| title_sort |
welding of defects in cast cases of turbines with perlite electrodes without heating and thermal processing |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2020 |
| topic_facet |
Physics of radiation and ion-plasma technologies |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/194418 |
| citation_txt |
Welding of defects in cast cases of turbines with perlite electrodes without heating and thermal processing / N.G. Efimenko, S.V. Artyomova // Problems of atomic science and tecnology. — 2020. — № 4. — С. 84-88. — Бібліогр.: 15 назв. — англ. |
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2025-07-16T21:41:50Z |
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ISSN 1562-6016. PASТ. 2020. №4(128), p. 84-88.
WELDING OF DEFECTS IN CAST CASES OF TURBINES WITH
PERLITE ELECTRODES WITHOUT HEATING
AND THERMAL PROCESSING
N.G. Efimenko
NTU KhPI, Kharkiv, Ukraine
tel. +38(098)798-02-70;
S.V. Artyomova
Turboatom JSC, Kharkiv, Ukraine
E-mail: artemova@turboatom.com.ua; tel. +38(057)349-26-72, +38(063)189-10-45
The regularities of structural formation of the weld metal and HAZ during multilayer welding, made by the
transverse humping method, with short sections of defects on cast steel 15Kh1M1FL with perlite electrodes without
heating and heat treatment are considered. It has been established that the structure of all the studied zones of the
welded joint is represented by upper granular bainite of varying degrees of dispersion. The difference in the
hardness of the structures in the upper and middle parts of the welded joint is insignificant (3I4 and 296 HV,
respectively). In the upper part, the formation of a hypereutectoid ferrite is found, which is located along the grain
boundaries, which is also related with edge effect. The plastic properties of the weld metal are increased by more
than 1.5 times, KCV – by more than 3 times in comparison with the base metal.
PACS: 62.20.-x; 62.20.Mk; 68.35.Gy; 81.70.Bt
The performance and durability of power equipment
is largely dependent on the quality of the hull parts of
power units made of heat-resistant steels by casting.
Practice has established that the vast majority of defects
detected at the manufacturing stage are casting ones [1]:
porosity, shrinkage shells, cracks associated with the
influence of shrinkage stresses. These defects, as a rule,
are most often characteristic of massive thick-walled
parts. Single selections of defective places for correction
(by welding) often reach 3–5 thousand cm³. The most
commonly used universal correction method is manual
arc welding. A feature of welding heat-resistant steels is
the high metal sensitivity of individual sections of the
heat-affected zone (HAZ) heated during welding to the
austenization temperature, to various cooling rates
below the decomposition temperature of austenite.
Upon cooling, solid and brittle structures in these areas
of the HAZ are formed. At a certain level of residual
welding and structural stresses formed, this leads to the
formation of cold cracks. The main way to prevent cold
cracking of the HAZ metal is pre-heating and
concurrent heating. Depending on the weight of the
construction and wall thickness, as well as on the
chemical composition of the metal, the heating
temperature ranges from 250 to 400 °C, followed by
high-temperature tempering of welded joints after
welding. Such a technology for correcting casting
defects causes production difficulties and is labor-
intensive, and in some cases impossible.
At one of the stages, when repairing damaged cast
parts, the technology of electric arc welding using
austenitic electrodes was used [2]. However, during
high-temperature operation at the boundary “weld metal
- base metal”, diffusion processes lead to the formation
of brittle martensitic layers, heterogeneity of mechanical
properties. To avoid this effect, according to [3], nickel-
based electrodes should be used for welding.
The accumulated long-term experience of domestic
and foreign researchers has established that a
technology with the use of welding materials of the
same chemical composition with the base metal as the
most promising for welding low-alloy heat-resistant
steels is more promising. This technology minimizes
undesirable diffusion processes, reduces the
microchemical heterogeneity and heterogeneity of
mechanical properties in welded joints. At the same
time, to reduce the creep rate during high-temperature
operation, the carbon content in both cast parts and weld
metal should be extremely low [4, 5]. An increase in
carbon content leads to depletion of the solid solution
by alloying elements (Cr, Mo), which leads to
accelerated creep. To reduce the intensity of diffusion
processes, the carbon content is limited. In Russia, VTI
scientists have developed and recommended for welding
heat-resistant chromium-molybdenum-vanadium steels
electrodes of the ТМL-4В, ТML-5 grades [1], which
provide a low carbon content in the weld metal
(~ 0.06%). This carbon content was obtained by using a
low-carbon wire (CB-04A) as a rod, as well as the
limited introduction of calcium carbonate CaCO3 into
the coating composition. However, a change in the
composition of the coating leads to a deterioration of
technological properties [1] and, as a result, adversely
affects the quality of the weld. An analysis of foreign
scientific and practical developments shows that, in
order to maintain heat resistance, a decrease in the
carbon content in heat-resistant steels and materials for
their welding is impractical. So in the USA, pearlitic
steels containing ~ 0.25% carbon (WCA, WC1, etc.),
but with high plastic properties, are used for the power
system [1]. High viscous plastic properties are achieved
by increasing the purity of the metal in sulfur (≤ 0.01%)
and phosphorus. To neutralize the negative effects of S
and P, rare-earth metals (REM) – cerium ligature are
introduced into carbon steel [6]. This increases the
plastic properties by 15…25% and impact strength. In
Japan, for the welding of chrome-molybdenum-
vanadium steel, GMB-95 grades are used [7], the
deposited metal of which is characterized by a high
level of ductility and a low hydrogen content. The
mailto:artemova@turboatom.com.ua
carbon content is not reduced and is in the range of
0.08…0.12%. High plastic properties of the metal are
also achieved due to microalloying additives of rare-
earth metals [6–8].
Thus, from the information presented it follows that
the most promising today is the use of weld metal with
high viscoplastic properties as a welding material that
provides a pearlite structure.
The purpose of the work is to study the structure and
mechanical properties of welded joints on steel
15Kh1M1FL, made by the transverse humping method
(THM) without heating and subsequent heat treatment
with perlite electrodes containing REM (Y)
microadditives.
RESEARCH MATERIALS AND METHODS
We studied welded joints made on massive plates of
steel 15Kh1M1FL with a size of 250×200×110 mm,
cast under production conditions. After casting, the
plates were subjected to heat treatment according to
standard technology. In the middle part of the plates
along the long side, the metal was mechanically
sampled with a length of 130 mm, a width and depth of
60 mm, simulating a remote defect. The sample was
filled by manual arc welding of THM. Welding was
performed with UNL-1 electrodes [9] with a diameter of
4 mm in the mode: Iw = 160…170 A, U∂ = 26…27 B. It
should be noted that THM provides layer-by-layer
formation of a seam with multiple auto-heating with
welding heating of each layer of deposited metal. The
chemical composition of the weld metal, %:
C = 0.1…0.12; Mn = 0.6…0.65; Si = 0.5…0.65;
Cr = 0.6…0.9; Mo = 0.5…0.7; S ≤ 0.012; P ≤ 0.019;
REM (Y) = 0.009; Mechanical properties: Ultimate
tensile strength (UTS) = 570…580 MPa; y =
400…440 MPa; = 25…26%; = 68…72%; KCV+20 =
96…100 J/cm
2
.
When filling in deep samples, the temperature
conditions of the HAZ metal are not the same. Under
the influence of thermocyclic influence during layer-by-
layer filling, the cooling rates of HAZ sections are also
different. Under the conditions of the pronounced
influence of the edge effect associated with the limited
size of the part, i.e. when barriers arise in the way of
heat fluxes, this leads to overheating of the surface local
sections of the HAZ metal, the formation of structures,
including quenching. Therefore, the HAZ sections were
examined at a depth of 10 mm and 35 mm from the
surface (Fig. 1). The scheme for cutting samples for
research is shown in Fig. 2. Toughness KCV was
determined on standard samples made from different
zones of the welded joint (see Figs. 2, 3). The
microstructure was investigated by optical microscopy.
Grain boundaries were revealed by etching thin sections
in a supersaturated aqueous solution of picric acid with
the addition of surfactants. The grain size and its
morphology were studied in all zones of the welded
joint. In the main and deposited metal (weld), the grain
size was estimated by the grid of the boundaries of the
ferrite component, and in the high-temperature zone of
the HAZ with a predominance of bainite, the grain was
determined by the etched grid of the boundaries of the
former austenite [10].
Fig. 1. Measurement scheme (a) and microhardness (b)
in various zones of a welded joint
Fig. 2. The scheme for cutting samples for testing
Fig. 3. Macrostructure of a welded joint on steel
15X1M1FL, made by THM
RESEARCH RESULTS
Evaluation of grain size according to the GOST
5639-82 scale and using quantitative metallography [15]
showed that when welding THM, the structure of all
areas of the HAZ and weld metal is fine-grained.
Especially fine grain in the weld metal – 9, 10 points. In
the HAZ, at a distance of up to 3 mm from the fusion
boundary, 8, 9 points; in the HAZ near the fusion
boundary – 7, 8 points; in the base metal – 6, 7 points.
It was established that the weld metal of the same
type and slightly different from the main chemical
composition has a higher hardness of 287…303 and
240…250 HV respectively (see Fig. 1). This is
explained by the modifying effect of REM
microadditives contained in the electrode material, as
well as by metallurgical processing of deposited metal
layers during repeated thermal exposure during layer-
by-layer filling of the groove. An increase in hardness
(314 HV) observed in the high-temperature region of
the HAZ indicates the formation of a nonequilibrium
structure. The width of the HAZ with increased
hardness reaches 0.5…0.7 mm. At a distance of
3.0…3.5 mm from the fusion zone, hardness decreases
and reaches the level of 240…250 HV (see Fig. 1).
Analysis of the phase composition of the HAZ at
different levels along the seam height showed that it is
not the same. The increased sensitivity of 15Kh1M1FL
steel to the cooling rate leads to the appearance in the
high-temperature heating zone of the HAZ in the upper
part of the weld, in addition to granular bainite,
structurally-free hypereutectoid ferrite, which is located
along the grain boundaries of the former austenite and
inside these grains (Fig. 3). It is acceptable that the
appearance of ferrite is due to a decrease in the cooling
rate and is associated with auto-heating directly from
the welding heating, which is provided during LNG
welding. According to the MIS classification [11],
intragranular ferrite I (PF) is idiomorphic, and the ferrite
precipitated along the grain boundaries is referred to as
prime ferrite PF (G) ferrite. The light discharge of a
rounded shape discovered during the study is separated
by grain boundaries and is clearly visible against the
background of a bainitic structure (Fig. 4). According to
[12], the presence of hypereutectoid ferrite in
combination with upper bainite provides Cr-Mo-V-
steels with an optimal combination of long-term
strength and stability, which is associated with the
precipitation of dispersed vanadium carbides in ferrite.
In addition, the presence of a small amount of ferrite in
steel (up to 20%) increases the plastic properties.
The formation of idiomorphic ferrite is apparently
associated with the intragranular structure of austenite,
when, under conditions of heating above critical points
with small plastic strains in austenite, dynamic in situ
processes of crystallization occur [13]. Moreover, in
austenitic grains, subgrain boundaries are formed at the
joints and along the boundaries of which nuclei I (PF)
appear upon cooling. The heating and cooling
conditions are such that these ferritic grains do not have
time to grow, and the bulk of austenite turns into a
granular bainite structure. It is possible that part of
ferrite I (PF) is formed on precipitated dispersed
inclusions of secondary phases (vanadium carbides) [13,
14]. It should also be noted that in the middle part of the
welded joint, a structure of granular bainite is formed,
which has increased etchability. In the HAZ, when
approaching the conditional fusion boundary
(overheating area), the amount of granular bainite
increases and a predominantly finely dispersed granular
structure is observed near the boundary (see Fig. 4).
These structural changes are provided by auto-heating
and thermal cycling during multilayer weld formation
and a multiple phase of recrystallization.
a
b
Fig. 4. Microstructure in the high-temperature region
of HAZ, 500:
a – in the upper part of the weld;
b – in the middle part of the weld
Fig. 5 shows the mechanical properties of the metal
of various zones of the welded joint. The metal is
characterized by high plastic properties. So ψ and δ
have values that are 1.8 and 1.5 times greater than the
identical values of the base metal, respectively.
Attention should also be paid to the fact that the most
dangerous part of the HAZ, characterized by increased
hardness (see Fig. 1), has sufficiently high plastic
properties (Fig. 5). The microalloying additive of rare-
earth metals in the welding material ensured high
toughness to the weld metal, which is more than 3 times
higher than that of the base metal.
A comparative analysis of the results of structural
changes, hardness and mechanical properties in the
near-surface and middle layers (in depth) of the welded
joint did not reveal significant differences. The structure
of the upper granular bainite containing up to 20% of
hypoeutectoid ferrite is formed in the HAZ. In the
middle layers, a highly dispersed structure with a
reduced hardness is formed (see Fig. 1).
Fig. 5. Mechanical properties of the zones of welded
joints on steel 15X1M1FL, made by THM electrodes
without heating and heat treatment
Thus, it has been established that the use of pearlite
class electrodes with high viscoplastic properties of the
deposited metal when welding casting defects on
15Kh1M1FL steels by the transverse slide method
allows to obtain high-quality compounds without
preliminary heating and heat treatment after welding.
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Article received 25.06.2020
ЗАВАРКА ДЕФЕКТОВ В ЛИТЫХ КОРПУСНЫХ ДЕТАЛЯХ ТУРБИН ПЕРЛИТНЫМИ
ЭЛЕКТРОДАМИ БЕЗ ПОДОГРЕВА И ТЕРМИЧЕСКОЙ ОБРАБОТКИ
Н.Г. Ефименко, С.В. Артемова
Рассмотрены закономерности структурообразования металла шва и зоны термического влияния (ЗТВ)
при многослойной заварке короткими участками дефектов на литой стали 15Х1М1ФЛ перлитными
электродами способом поперечной горки (СПГ) без подогрева и термической обработки. Установлено, что
структура всех исследуемых зон сварного соединения представлена верхним зернистым бейнитом
различной степени дисперсности. Разница в твердости структур в верхней и средней частях сварного
соединения незначительна (314 и 296 HV соответственно). В верхней части обнаружено формирование
доэвтектоидного феррита, располагающегося по границам зерен, что связано, в том числе, с краевым
эффектом. Пластические свойства металла шва увеличены более чем в 1,5 раза, KCV – более чем в 3 раза по
сравнению с основным металлом.
ЗАВАРКА ДЕФЕКТІВ У ЛИТИХ КОРПУСНИХ ДЕТАЛЯХ ТУРБІН ПЕРЛІТНИМИ
ЕЛЕКТРОДАМИ БЕЗ ПІДІГРІВУ ТА ТЕРМІЧНОЇ ОБРОБКИ
М.Г. Єфіменко, С.В. Артьомова
Розглянуто закономірності структуроутворення металу шва і зони термічного впливу (ЗТВ) при
багатошаровій заварці короткими ділянками дефектів на литій сталі 15Х1М1ФЛ перлітними електродами
способом поперечної горки (СПГ) без підігріву і термічної обробки. Встановлено, що структура усіх
досліджуваних зон зварного з'єднання представлена верхнім зернистим бейнітом різної міри дисперсності.
Різниця в твердості структур у верхній і середній частинах зварного з'єднання незначна (314 і 296 HV
відповідно). У верхній частині виявлено формування доевтектоїдного фериту, розташованого по межах
зерен, що пов'язано, в тому числі, з крайовим ефектом. Пластичні властивості металу шва збільшені більш
ніж у 1,5 рази, KCV – більш ніж у 3 рази в порівнянні з основним металом.
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