Pure vanadium and titanium for low activation alloys
The refining processes of vanadium and titanium from metal and gas impurities by physical methods in vacuum are considered. The effectiveness of using electron-beam melting, zone recrystallization and electrotransport for purification of these metals is shown. Vanadium and titanium in a purity of...
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nasplib_isofts_kiev_ua-123456789-1154042025-02-09T17:46:34Z Pure vanadium and titanium for low activation alloys Чистые ванадий и титан для малоактивируемых сплавов Чисті ванадій і титан для малоактивованих сплавів Pylypenko, M.M. Lavrinenko, S.D. Материалы реакторов на тепловых и быстрых нейтронах The refining processes of vanadium and titanium from metal and gas impurities by physical methods in vacuum are considered. The effectiveness of using electron-beam melting, zone recrystallization and electrotransport for purification of these metals is shown. Vanadium and titanium in a purity of more than 99.99% have been produced. Рассмотрены процессы рафинирования ванадия и титана от металлических и газовых примесей физическими методами в вакууме. Показана эффективность использования электронно-лучевой плавки, зонной рекристаллизации и электропереноса для очистки этих металлов. Получены образцы титана и ванадия чистотой более 99,99 мас.%. Розглянуто процеси рафінування ванадію і титану від металевих і газових домішок фізичними методами у вакуумі. Показана ефективність використання електронно-променевої плавки, зонної рекристалізації і електропереносу для очищення цих металів. Отримано зразки титану і ванадію чистотою понад 99,99 мас.%. 2016 Article Pure vanadium and titanium for low activation alloys / M.M. Pylypenko, S.D. Lavrinenko // Вопросы атомной науки и техники. — 2016. — № 4. — С. 49-53. — Бібліогр.: 11 назв. — англ. 1562-6016 https://nasplib.isofts.kiev.ua/handle/123456789/115404 669.054; 669.292; 669.295 en Вопросы атомной науки и техники application/pdf Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Материалы реакторов на тепловых и быстрых нейтронах Материалы реакторов на тепловых и быстрых нейтронах |
| spellingShingle |
Материалы реакторов на тепловых и быстрых нейтронах Материалы реакторов на тепловых и быстрых нейтронах Pylypenko, M.M. Lavrinenko, S.D. Pure vanadium and titanium for low activation alloys Вопросы атомной науки и техники |
| description |
The refining processes of vanadium and titanium from metal and gas impurities by physical methods in vacuum
are considered. The effectiveness of using electron-beam melting, zone recrystallization and electrotransport for
purification of these metals is shown. Vanadium and titanium in a purity of more than 99.99% have been produced. |
| format |
Article |
| author |
Pylypenko, M.M. Lavrinenko, S.D. |
| author_facet |
Pylypenko, M.M. Lavrinenko, S.D. |
| author_sort |
Pylypenko, M.M. |
| title |
Pure vanadium and titanium for low activation alloys |
| title_short |
Pure vanadium and titanium for low activation alloys |
| title_full |
Pure vanadium and titanium for low activation alloys |
| title_fullStr |
Pure vanadium and titanium for low activation alloys |
| title_full_unstemmed |
Pure vanadium and titanium for low activation alloys |
| title_sort |
pure vanadium and titanium for low activation alloys |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2016 |
| topic_facet |
Материалы реакторов на тепловых и быстрых нейтронах |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/115404 |
| citation_txt |
Pure vanadium and titanium for low activation alloys / M.M. Pylypenko, S.D. Lavrinenko
// Вопросы атомной науки и техники. — 2016. — № 4. — С. 49-53. — Бібліогр.: 11 назв. — англ. |
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ISSN 1562-6016. ВАНТ. 2016. №4(104) 49
UDC 669.054; 669.292; 669.295
PURE VANADIUM AND TITANIUM FOR LOW ACTIVATION ALLOYS
M.M. Pylypenko
1
, S.D. Lavrinenko
1,2
1
National Science Center “Kharkov Institute of Physics and Technology”,
Kharkov, Ukraine
E-mail: mpylypenko@kipt.kharkov.ua;
2
V.N. Karazin
Kharkov National University, Kharkov, Ukraine
The refining processes of vanadium and titanium from metal and gas impurities by physical methods in vacuum
are considered. The effectiveness of using electron-beam melting, zone recrystallization and electrotransport for
purification of these metals is shown. Vanadium and titanium in a purity of more than 99.99% have been produced.
INTRODUCTION
Modern tendencies of development of reactor
technologies are aimed to further increase reliable and
safe operation of power units and to provide efficiency
and competitiveness of nuclear power. This requires an
increase in power density, power of units, increasing the
duration of campaigns, more efficient fuel burning,
including by improving the quality of construction
materials [1-4].
The progress achieved in the field of nuclear
physics, reactor physics and reactor materials in recent
years, led to the development of a number of advanced
nuclear energy systems [1]. These projects have
advantages in economy, security, reliability and non-
proliferation of nuclear materials.
New structural materials must be pure. We know
that high levels of impurities and gases in steels and
alloys significantly worsen their mechanical, corrosion
and radiation properties and, therefore, limit their use in
operating and designing reactors. Use of high-purity
metals as initial components of new structural materials
will provide desired properties in the resulting products
[5, 6]. Vanadium, titanium and chromium are metallic
elements which are necessary components to produce
low-activity alloys for nuclear energy of present and
future.
Vanadium alloys are considered as a promising
candidate structural material for fusion and fast-fission
reactors applications because of their attractive
properties such as superior high temperature thermal
and physical properties, good resistance against neutron
irradiation and low neutron activation level. It is well
known that increased level of interstitial impurities such
as C, N, O would result in loss of workability,
weldability and irradiation resistance [78]. On the
other hand, increased level of undesirable elements such
as Co, Nb, Ag, Mo, Al, Na, Ni, Cu, Fe etc. would
dominate the activation level of vanadium alloys which
would substantially influence not only the recycling
aspects of used reactor materials but also the waste
management aspects of them. The required impurity
levels for hands-on recycling of the low-activity
vanadium alloys are around the magnitude
concentrations of 0.01, 0.1, 0.01, 10, 0.5 and 30 wppm,
respectively, for the elements Co, Nb, Ag, Mo, Cu, Ni
and Al based on the neutron irradiation fluence of
15 (MW∙year)/m
2
[7].
Impurities increase the strength of titanium, also
greatly reduces it ductility, but interstitial impurities
such as H, O, N, and C have the strongest negative
action on properties of titanium. Titanium entirely loses
its ability to plastic deformation and becomes brittle if it
contains 0.003, 0.02, and 0.7 wt.% hydrogen, nitrogen
and oxygen, respectively. Under neutron irradiation the
embrittlement of titanium alloys increases with
increasing contents of oxygen, nitrogen and hydrogen in
the alloy.
The activation level of vanadium alloys will be
depending on impurity contents in alloys. So obtaining
of high-purity components (vanadium and titanium) for
low-activity alloys is relevant today.
1. METHODS AND TECHNOLOGIES
FOR REFINING OF METALS
To obtain pure metals at different stages of refining,
the various chemical and physico-chemical methods are
used, but usually the refining process comprises of
physical methods – distillation, zone recrystallization,
electrotransport and various combinations thereof.
These methods are mainly physical processes:
evaporation and condensation, crystallization, diffusion
and electromigration, etc. The advantages of these
methods over the others are the ability to yield high
purity material, and the final product is obtained in a
compact form including single crystals with a perfect
crystal structure.
Electron beam melting (EBM) of metals is
performed on an ultra-high vacuum installation. To
pump installation, the two hetero-ion pumps were used
with a pumping speed of 5000 l/s each, and the titanium
sublimation pump was applied also. Application of such
a system of vacuum pumping allows to get an ultimate
vacuum in the installation 1.7∙10
-6
Pa [9]. In the
spectrum of the residual gas in installation were absent
heavy hydrocarbons. Refining of metals was carried out
in vacuum (1…5)·10
-5
Pa. Refining was conducted in
the regime: heating ⇒ melting ⇒ excerpt of metal in
molten state ⇒ crystallization ⇒ pulling ingot. Zone
recrystallization with an electron-beam heating is
carried out, as a rule, in installations with combined
pumping systems [9]. Diffusion pumps are equipped
with sorption and condensation traps; sorption,
cryogenic and ion-sorption pumps are used to give “oil-
free” ultrahigh vacuum. Electron-beam zone
recrystallization was carried out in vacuum
mailto:mpylypenko@kipt.kharkov.ua
50 ISSN 1562-6016. ВАНТ. 2016. №4(104)
1·10
-6
…1·10
-5
Pa. Choice of pumping system for
different methods of refining was determined mainly by
degree of interaction of metals with residual gases of the
vacuum environment under refining conditions.
2. RESULTS AND DISCUSSION
Results of physical methods of refining of vanadium
and titanium which are important components for the
production of low-activity alloys for nuclear power are
given below. The metals differing by initial degree of
purity and method of preparation were used to research
the purification processes.
2.1. Vanadium
The initial materials used for research: rods of
technical vanadium, electrolytic vanadium VEL-1 and
vanadium, which was received by iodide refining (IV).
Studies have shown that carrying out EBM of
electrolytic vanadium reduces the metallic impurities,
for example, chromium concentration was reduced by
two orders of magnitude, as well as potassium
concentration was reduced by about 75 times; but no
reduction of silicon concentration. Carrying out electron
beam melting of vanadium in vacuum 5·10
-4
Pa allowed
to increase the purity of metal up to 99.95 wt.%. The
impurity concentrations of that vanadium are given in
Table 1.
Carrying out zone melting can effectively remove
impurities of aluminum, iron, nickel, copper and
chromium. Silicon is slightly removed while impurities
of refractory metals (tungsten, molybdenum, tantalum
and niobium) accumulated during long recrystallization
of vanadium [10]. Table 2 compares the effectiveness of
purification of technical vanadium rods by EBM
methods and zone melting (ZM). ZM of vanadium is
carried out at a speed of 4 cm/hour. The data in Table 2
show that ZM is more effective method for purification
of vanadium samples than EBM. Silicon content in a
technical metal is high, and it is the limiting impurity
for ZM process.
Table 1
The impurity contents of vanadium, ppm
Metal Al Fe Si Cu Cr Na K Mn Ni Cl P O
Initial 120 70 17 100 850 3 130 1.5 8 42 70 590…800
After EBM 11 10 17 18 7 0.4 1.7 0.11 5 4 0.5 160…200
Table 2
The content of impurities in the technical vanadium after EBM and ZM
Type of metal
Content of impurities, ppm
Fe Cr Cu Mo Si Mg Al
Initial 1000 30 5 60 1500 16 200
After EBM in vacuum 5·10
-4
Pа 200 < 30 2.4 40 1500 5 20
After ZM in vacuum 2·10
-5
Pа 17 < 30 < 1.4 20 1300 < 0.5 < 10
For the study of ZM process IV was also used. The
content of impurities in the IV after one pass of ZM is
given in Table 3. The distribution of the relative residual
resistivity (RRR = R (300 K)/R (4.2 K)) and
microhardness of vanadium along the sample are shown
in Fig. 1.
High efficiency of this method with respect to
reduce concentration of gas-forming impurities was
proved by study of thermal desorption of the initial
samples and after refining. The dependence of total
pressure on heating of vanadium samples in the
temperature range 25…800 °C is given in Fig. 2. The
degassing intensity for the sample after refining is five
times less than for initial metal. The mass-spectra of
gases released from vanadium sample during the
thermal desorption are correspond to H2O, CO, N2, CO2
etc. The highest intensity of degassing took place in the
temperature range 300…600 °C, peaking at about
500 °C [11].
Fig. 1. Distribution of RRR (1) and microhardness (2)
along the length of the sample of IV after one pass
of molteng zone
ISSN 1562-6016. ВАНТ. 2016. №4(104) 51
Table 3
The content of impurities in the IV after ZM
Type of metal
Content of impurities, ppm
Fe Cu Mo Mn Si Mg Al
Initial 920 9 13 6 40 1.5 80
After ZM
initial end of sample 150 4.8 16 1 40 <1 <10
last end of sample 600 11 12 2 37 <1 <10
Fig. 2. The dependence of total pressure of vapors on heating of vanadium before (1) and after refining (2)
in temperature range 25…800 °C
The results of metallographic measurements of
vanadium samples before and after EBM under vacuum
are given in Fig. 3. The initial samples of compacted
powders were in tablets form. Refined sample has a
relatively large grain with size of about 380 m, which
can be observed visually (see Fig. 3,b). The grains are
equiaxial, the grain boundaries are clean. The
microhardness of the initial vanadium is
Hμ = 1090 MPa, after electron-beam melting
Hμ = 1440 MPa. Increasing the microhardness of
vanadium after EBM can be explained by the fact that
the initial samples of compacted powders were
produced from flakes of electrolytic vanadium.
Consequently, these samples have a higher porosity and,
correspondingly, less microhardness value.
a b
Fig. 3. Obtained samples of vanadium (a) and their microstructure (b)
The most pure vanadium was obtained using method
of electrotransport or electromigration on wire samples
produced from metal after double EBM of electrolytic
powder vanadium. Solid state electrotransport is another
technique useful particularly in the removal of
interstitial impurities such as H, O, N, and C from
refractory metals and has met with unprecedented
success. Studies have shown that interstitial impurities
are migrated to the cathode side of the vanadium sample
when passing a constant electric current of high density,
52 ISSN 1562-6016. ВАНТ. 2016. №4(104)
i.e. effective charge of these impurities is positive. From
the numerical solution of the equation for
electrotransport follows that at 1650 °C for 200 hours at
a current density of approximately 5·10
3
А/cm
2
the
electrotransport will result in a significant reduction of
oxygen, nitrogen and carbon. It is experimentally shown
that under the above conditions the RRR of vanadium
samples after purification by electrotransport increases
from 50 up to 1600. The chemical composition of high-
purity vanadium with RRR = 1200 and purity more than
99.99% wt.%, which was obtained by electrotransport,
is as follows (mass spectral method, at.%):
Na < 1.0·10
-5
; K – 1.0·10
-5
; Ca – 4.0·10
-5
; Cu – 5.0·10
-5
;
Mg < 1.0·10
-5
; Zn < 9.0·10
-5
; Al – 9.0·10
-5
;
Si – 2.0·10
-3
; Ti – 4.0·10
-5
; P – 1.0·10
-4
; As – 3.0·10
-5
;
S < 4.0·10
-5
; Mn < 1.0·10
-5
; Fe – 2.0·10
-5
; Cl – 7.0·10
-5
;
Nb – 4.0·10
-5
; Cr – 1.0·10
-3
; F – 1.0·10
-3
; Ni – 3.0·10
-5
;
Ga – 3.0·10
-5
; Zr – < 5.0·10
-5
; Mo – 2.0·10
-5
;
C < 1.0·10
-2
; N2 < 1.0·10
-2
; O2 < 9.0·10
-3
.
Analysis results indicates that for a higher degree of
purification of vanadium it is necessary to use
combination of different refining methods which would
allow remove impurities such as silicon, refractory
metals, carbon, nitrogen, oxygen from vanadium.
Vacuum distillation of vanadium, which can reduce
silicon content in the metal more than ten times as well
as impurities of refractory metals, is worth exploring.
2.2. Titanium
Titanium sponge TG-90 and titanium produced by
iodide refining (ITi) were used as starting materials for
purification by electron-beam melting.
EBM of titanium sponge was carried out in two
stages. In the first step the pieces of titanium sponge
were heated to a high temperature and melted. Gaseous
impurities intensively removed from the metal during
heating and melting. During a second stage the obtained
ingots were melted by drip melt method. Titanium
ingots with diameter of 150 mm and 99.99 wt.% purity
were produced by EBM method. The content of
impurities in titanium after EBM is given in Table 4.
Analysis of the results of experimental melting of
titanium sponge TG-90 showed that the hydrogen
content of titanium after EBM decreased by 4.5 times
compared to the initial concentration and the
concentration of O and N was significantly decreased.
The impurity content in the produced titanium ingots
decreased much more than required by the standards for
titanium.
Table 4
The content of impurities in titanium, ppm
Type of metal Al V Fe Si Ni O N H
Initial sponge TG-90 100 3 500 100 400 400 200 72
After EBM 7 1.5 400 5 50 70 15 16
More pure titanium was obtained after EBM of the
initial iodide titanium. Impurity contents in the ITi after
two electron-beam remelting are as follows:
Al – 8.0·10
-1
; P – 1.0; S – 8.0; K – 6.0·10
-1
; Ca – 2.0;
V – 3.0; Cr – 3.0; Mn < 9.0·10
-1
; Fe – 15; Ni – 50;
Cu – 3.0; Zn – 2.0; As – 8.0; Sn < 8.0 ppm.
It should be noted that EBМ of titanium favorably
affects to the vacuum conditions of the installation due
to the good getter abilities of titanium layers deposited
on the chamber walls owing to evaporation at EBM [2].
CONCLUSIONS
Regularities refining of vanadium and titanium were
investigated; it has allowed reaching a higher level of
purity metals by applying methods of electron-beam
melting, zone recrystallization and electrotransport in
vacuum. These methods had demonstrated high
efficiency of purification of vanadium and titanium
from interstitial impurities and majority of metallic
impurities. Vanadium and titanium in a purity of more
than 99.99 % have been produced. Suggested methods
for obtaining high-purity metals have created the
necessary prerequisites for their use in improving
existing and producing new structural materials.
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p. 19-24.
3. V.N. Voyevodin. Actual problems of scientific
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4. V.N. Voyevodin, I.M. Neklyudov. Evolution of
the Structure Phase State and Radiation Resistance of
Structural Materials. Kiev: “Naukova dumka”, 2006,
375 p.
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penko. Pure and super pure metals in atomic energy //
PAST. Series “Vacuum, Pure Materials,
Superconductors”. 2007, N 4, p. 3-12.
6. M.M. Pylypenko. The role of high-purity metals
in the creation of new materials for structural elements
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Superconductors”. 2008, N 1, p. 10-17.
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8. I.M. Neklyudov, V.M. Azhazha, G.P. Kovtun,
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30 June 6, 2008, Varna, Bulgaria). Dnepropetrovsk,
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10. V.M. Azhazha, P.N. Vyugov, S.D. Lavrynenko,
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Статья поступила в редакцию 01.06.2016 г.
ЧИСТЫЕ ВАНАДИЙ И ТИТАН ДЛЯ МАЛОАКТИВИРУЕМЫХ СПЛАВОВ
Н.Н. Пилипенко, С.Д. Лавриненко
Рассмотрены процессы рафинирования ванадия и титана от металлических и газовых примесей
физическими методами в вакууме. Показана эффективность использования электронно-лучевой плавки,
зонной рекристаллизации и электропереноса для очистки этих металлов. Получены образцы титана и
ванадия чистотой более 99,99 мас.%.
ЧИСТІ ВАНАДІЙ І ТИТАН ДЛЯ МАЛОАКТИВОВАНИХ СПЛАВІВ
М.М. Пилипенко, С.Д. Лавриненко
Розглянуто процеси рафінування ванадію і титану від металевих і газових домішок фізичними методами
у вакуумі. Показана ефективність використання електронно-променевої плавки, зонної рекристалізації і
електропереносу для очищення цих металів. Отримано зразки титану і ванадію чистотою понад 99,99 мас.%.
|