Technical Field
[0001]
The present invention relates to a titanium cast product for hot rolling and a
10 method of manufacturing the same, and relates particularly to a titanium cast product
for hot rolling that can keep surface properties after hot rolling satisfactory even
when a slabing step and a finishing step are omitted, and a method of manufacturing
the same.
15 Background Art
[0002]
A titanium material is generally manufactured by making an ingot obtained
through a melting step into a shape of a slab or a billet, mending the surface,
performing hot rolling, and then subjecting the resultant to annealing or cold working.
20 The melting step includes, in addition to a vacuum arc remelting (VAR) method
which is being used widely, an electron beam remelting (EBR) method or a plasma
arc melting method involving performing melting at a place other than a mold and
pouring the resultant into the mold. Since the shape of the mold is limited to a
cylindrical shape in the former, a slabing step or a forging step is required for
25 manufacturing a sheet material. The latter has high flexibility regarding the shape
of the mold, hence can use a square-shaped mold in addition to the cylindrical mold.
Accordingly, using the electron beam remelting method or the plasma arc melting
method, the square-shaped ingot or the cylindrical ingot can be cast directly.
Therefore, in the case of manufacturing a sheet material from a square-shaped ingot
30 or in the case of manufacturing a wire material or a bar material from a cylindrical
ingot, the slabing step can be omitted from the viewpoint of the shape of the ingot.
PCT/JP2014/076087
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In this case, since the cost and time spent for the slabing step can be reduced,
remarkable improvements in production efficiency can be expected.
[0003]
However, an as-cast structure of a large-sized ingot that is industrially used
5 has coarse grains each having a grain size of several tens of millimeters. In the case
where such an ingot is directly subjected to hot rolling without undergoing the
slabing step, concavities and convexities are formed on the surface by the influence
of deformation anisotropy in grains and between crystal grains due to coarse crystal
grains and become surface defects. Accordingly, in the case where the square-
10 shaped ingot or the cylindrical ingot is directly manufactured by the electron beam
remelting method or the plasma arc melting method and the slabing step is omitted,
surface defects occur in the hot rolling which is performed thereafter. In order to
remove the surface defects occurred in the hot rolling, it is necessary that the amount
of the surface of the hot-rolled sheet to be molten off in a pickling step be increased,
15 and there arise problems that the cost is increased and the yield is reduced. That is,
it is necessary that a finishing step for removing the surface defects be newly
introduced. Therefore, there is a concern that the expected improvements in
production efficiency owing to the omission of the slabing step may be cancelled due
to the newly introduced fmishing step. In regard to such a concern, there are
20 proposed a method of manufacturing a material for hot rolling and a method of
reducing the surface defects by performing fashioning or heat treatment after the
manufacturing.
[0004]
Patent Literature I proposes a method including, in the case where an ingot
25 of a titanium material is not subjected to a slabing step and is directly subjected to a
hot rolling process, in order to make crystal grains near an surface layer fine,
providing a strain to the surface layer, and then performing heating to higher than or
equal to recrystallization temperature and performing recrystallization on the surface
to a depth of more than or equal to 2 mm. As means to provide a strain, there are
30 given forging, roll reduction, shot blasting, and the like.
[0005]
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Patent Literature 2 proposes a method of reducing waviness or creases on
the surface formed during rolling due to deformation anisotropy of coarse grains and
reducing surface defects, by heating an ingot of a titanium material to higher than or
equal to T~+50°C, then cooling the ingot to lower than or equal to T~-50°C, and then
5 performing hot rolling.
[0006]
Patent Literature 3 proposes, as a method of reducing surface defects of a
rolled product in the case where the titanium material undergoes a slabing step, a
method involving setting temperature at the end of a slabing step to a temperature in
10 the a phase or perfmming heating before hot rolling in the temperature in the a
phase, thereby rendering a portion more than or equal to 60 J.Lm from the surface
equiaxed crystals. In this way, Patent Literature 3 mentions that forming of a partly
deep oxygen-rich layer can be avoided, the oxygen-rich layer can be removed in a
descaling step, and hence, ununiform part in regard to hardness and ductility is
15 eliminated, so the surface properties after cold working is improved.
[0007]
Patent Literature 4 proposes a method in which, in the case where an ingot
of a titanium material is not subjected to a hot working step and is directly subjected
to hot rolling, an surface layer serving as a rolling surface of the ingot is molten and
20 resolidified by high-frequency induction heating, arc heating, plasma heating,
electron beam heating, laser heating, and the like, to thereby be turned into fine
grains to a depth of more than or equal to 1 mrn from the surface layer, and an
surface layer structure after the hot rolling is improved. In the above, the surface
layer portion is subjected to quench solidification to form a solidified structure
25 having a fine structure with random orientations, and thus, the occurrence of the
surface defects is prevented. Examples of methods for melting the surface layer
structure of titanium slab include high-frequency induction heating, arc heating,
plasma heating, electron beam heating, and laser heating.
30 Citation List
Patent Literature
5
10
[0008]
Patent Literature I:
Patent Literature 2:
Patent Literature 3:
Patent Literature 4:
Technical Problem
[0009]
4/25
JP HOI-156456A
JP HOS-060317 A
JP H07-102351A
JP 2007-332420A
Smnmary of Invention
PCT/JP2014/076087
However, although the method of Patent Literature 1 gives the shot blasting
as means to provide a strain, the depth of the strain provided by general shot blasting
is approximately 300 to 500 IJ1l1, which is not sufficient for forming the recrystallized
layer having a depth of more than or equal to 2 mm that is necessary for improving
the quality. Accordingly, it is practically necessary that the strain be provided to a
15 deeper position by the forging or the roll reduction, but a large plant is required for
20
performing the forging or the roll reduction on a large-sized ingot for hot rolling,
therefore, the cost is not reduced compared to the case of performing an ordinary
slabing step.
[0010]
Further, the method of Patent Literature 2 has an effect that coarse crystal
grains recrystallize and are made fine by heating to a temperature in the ~ phase.
However, in the case where the slabing step is omitted, there are few recrystallized
nuclei since no work strain is applied and the sizes of the crystal grains become large
since the whole ingot is heated so the cooling rate after the heating is reduced.
25 Therefore, effects obtained by fine-making owing to recrystallization are limitative,
and the reduction of the deformation anisotropy is not sufficient. It is also a factor
of not being able to eliminate the deformation anisotropy that crystal orientations of
the original coarse grains have influence over the recrystallized grains. On the
contrary, moderate fine-making increases grain boundaries which cause concavities
30 and convexities of the surface, and the occurrence of the surface defects is increased.
[0011]
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Still further, the method of Patent Literature 3 is performed from the
assumption that the cast structure is broken to be turned into fine and equiaxed grains
by undergoing the slabing step, and makes no sense in the case where the slabing
step is omitted. If the slabing step is omitted and only heat treatment is performed
5 to form equiaxed grains to a depth of more than or equal to 60 f.ll1l from the surface,
it is a simple recrystallization, and the crystal orientation of the recrystallization is
influenced by the original crystal orientation. Accordingly, the method is
insufficient for preventing concavities and convexities due to deformation anisotropy
of coarse grains of the as-cast structure, and it is apparent that problems caused by
10 the surface defects occur.
[0012]
Moreover, in the method of Patent Literature 4, modification is performed
on the structure of the ingot outer layer portion, and this has an effect of improving
the surface properties after hot rolling.
15 [0013]
20
Accordingly, the present invention aims to provide a titanium alloy cast
product that can keep surface properties after hot rolling satisfactory even when a
slabing step and a finishing step are omitted, and a method of manufacturing the
same.
Solution to Problem
[0014]
In order to attain the above object, the inventors of the present invention
have conducted intensive studies and have found the following. In manufacturing a
25 titanium product from an ingot by performing hot rolling and omitting a slabing step
and a finishing step, an a stabilizer element or a neutral element is caused to be
contained in a slab surface layer by placing or scattering a material (powder, chips, a
wire, a thin film, and the like) containing the a stabilizer element or the neutral
element on a rolling surface layer of an as-cast titanium material and remelting the
30 slab surface layer together with the material as the previous step of hot rolling, hence,
a structure of the slab surface layer portion can be kept fine even during hot rolling
L
5
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heating, and as a result, surface defects due to an influence of deformation anisotropy
of an original coarse solidified structure are reduced, and the same surface properties
as the case of undergoing the slabing step and the finishing step can be obtained.
[0015]
The gist of the present invention is as follows.
(1)
A titanium cast product for hot rolling made of a titanium alloy, the titanium
cast product including:
a layer in a range of more than or equal to 1 mm in depth on a surface
10 serving as a rolling surface, the layer containing one or more elements out of any one
of or both of at least one a stabilizer element and at least one neutral element,
wherein a total concentration of the at least one a stabilizer element and the
at least one neutral element in the range of more than or equal to 1 mm in depth is
higher than a total concentration of the at least one a stabilizer element and the at
15 least one neutral element in a base metal by, in mass%, more than or equal to 0.1%
and less than 2.0%.
(2)
The titanium cast product according to (1 ),
wherein the at least one a stabilizer element and the at least one neutral
20 element each include AI, Sn, and Zr.
(3)
The titanium cast product according to (1 ),
wherein the layer containing one or more elements out of any one of or both
of the at least one a stabilizer element and the at least one neutral element further
25 contains, in mass%, less than or equal to 1.5% of one or more ~ stabilizer elements.
(4)
(5)
A method of manufacturing a titanium cast product, the method including:
melting a surface serving as a rolling surface of the titanium cast product
30 together with a material containing one or more elements out of any one of or both of
at least one a stabilizer element and at least one neutral element, and then solidifYing
PCT/JP2014/076087
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the surface,
wherein a total concentration of the at least one a stabilizer element and the
at least one neutral element in the range of more than or equal to 1 mm in depth is
made higher than a total concentration of the at least one a stabilizer element and the
5 at least one neutral element in a base metal by, in mass%, more than or equal to 0.1%
and less than 2.0%.
(6)
The method of manufacturing a titanium cast product according to (5),
wherein the material containing one or more elements out of any one of or
10 both of the at least one a stabilizer element and the at least one neutral element
includes one or more of powder, chips, a wire, a thin film, and swarf.
(7)
The method of manufacturing a titanium cast product according to (5),
wherein the surface of the titanium cast product is molten by using one or
15 more of electron beam heating, arc heating, laser heating, plasma heating, and
induction heating.
(8)
The method of manufacturing a titanium cast product according to (5),
wherein the surface of the titanium cast product is molten in a vacuum
20 atmosphere or an inert gas atmosphere.
Advantageous Effects of Invention
[0016]
The titanium cast product for hot rolling and the method of manufacturing
25 the same according to the present invention make it possible to manufacture a
titanium material having surface properties that are higher than or equal to the case
of undergoing a slabing step and a finishing step, even when, in manufacturing a
titanium material, a hot working step such as slabing and forging and a fmishing step
to be performed thereafter, which have been necessary in the past, are omitted.
30 Since improvements in the yield can be achieved by reduction in heating time owing
to omission of a hot working step, reduction in cutting mending owing to slab surface
5
10
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smoothing, reduction in an amount of pickling owing to improvements in surface
quality, and the like, great effects can be expected not only on reduction of
manufacturing cost but also on improvements in energy efficiency, and industrial
effects are immeasurable.
Brief Description of Drawings
[0017]
[FIG. I] FIG. I shows a schematic view of change in concentrations of a moltenresolidified
layer.
Description of Embodiments
[0018]
Hereinafter, the present invention will be described in detail.
15 [0019]
[Thickness of molten-resolidified layer]
In the present invention, a titanium material made of a titanium alloy has, on
a surface serving as a rolling surface, a molten-resolidified layer of more than or
equal to 1 mm. As described above, the occurrence of surface defects after hot
20 rolling is caused by concavities and convexities of the surface of the titanium
material, which occur due to a structure having coarse crystal grains. Accordingly,
the crystal grain size only in an ingot surface layer portion may be made as small as
possible. In order to suppress crystal grain growth during hot rolling heating by
adding an a stabilizer element and/or a neutral element to be mentioned below and to
25 thereby suppress the occurrence of surface defects, it is necessary that the thickness
of the molten-resolidified layer containing the a stabilizer element and/or the neutral
element be 1 mm. In the case where the thickness of the molten-resolidified layer is
· less than 1 mm, surface defects occur by being influenced by a cast structure of a
lower structure, and the surface properties are not improved. Note that the
30 maximum depth is not particularly defmed, but if the melting depth is too large, there
is a risk that a layer containing an alloying element may remain even after a shot
5
PCT/JP2014/076087
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pickling step which is performed after hot rolling, therefore, the melting depth is
desirably up to approximately 5 mm. Note that, examples of the titanium materials
to be subjected to hot rolling include an ingot, a slab, and a billet.
[0020]
The molten-resolidified layer is formed by melting a surface of a titanium
cast product, and then quenching and resolidifying the surface. Viewing a crosssection
in a direction perpendicular to a scanning direction of a molten bead, the
shape of the molten-resolidified layer tends to be the deepest at the center of the
molten bead in remelting of the titanium cast product surface layer. When the
10 molten beads are overlapped, a portion midway between adjacent molten beads is the
shallowest, and the deepest part and the shallowest part are periodically repeated.
In this case, if the difference between the deepest part and the shallowest part is large,
this difference causes a difference in deformation resistances in hot rolling, which
may cause defects. Accordingly, the difference is desirably less than 2 mm. Note
15 that the depth of the molten-resolidified layer according to the present invention is
set to more than or equal to 1 mm, and the depth indicates the depth of the shallowest
part as viewed in a cross-section in a direction perpendicular to a scanning direction
of a molten bead.
20
[0021]
Here, a titanium alloy is usually molded into a sheet material by hot rolling
and/or cold rolling, and is also produced as products in the forms of a wire material,
a bar material, and the like. Here, as the titanium alloy, an a titanium alloy, an a+~
titanium alloy, or a ~ titanium alloy may be used. Thus, in the present invention,
the composition of the titanium alloy is not particularly limited.
25 [0022]
[Content of a stabilizer element or neutral element]
In the present invention, the molten-resolidified layer of the titanium
material contains one or more elements out of a stabilizer elements or neutral
elements, the content of the one or more elements being higher than the content in
30 the base metal portion by more than or equal to a certain content. In the present
invention, as will be described later, in order to concentrate one or more elements out
PCT/JP20 14/076087
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of u stabilizer elements or neutral elements, a technique is used that the ingot surface
layer portion is molten together with a material made of one or more elements out of
those elements. When melting and resolidification treatment is performed without
adding those elements, since the composition of the molten portion is kept uniform,
5 the crystal grains can be made fine to some extent on their own in accordance with
the alloy composition. On the other hand, when the surface layer is molten together
with a material containing the u stabilizer element(s) and/or the neutral element(s),
since the melting time is short and ununiformity of components remains, the
structure is rendered ununiform. However, since the melting is only performed to
10 the extent that the molten layer can be removed by a pickling step to be performed
thereafter, no influence is exerted on the fmal product. The ununiformity remains,
hence, the u stabilizer element(s) and/or the neutral element(s) is/are concentrated at
the part at which the ununiformity remains, and a fmer structure is formed. Further,
when the structure is made fine by the melting and resolidification treatment, a
15 colony in which crystal grains having crystal orientations identical to each other are
gathered may be formed. The number of such colonies may be more than the
number of single crystal grains, therefore, when colonies occur, there are cases where
the colonies may trigger hot rolling defects. However, owing to the ununiformity,
the finer structures are formed at some parts as described above, and this can
20 suppress the occurrence of colonies and the growth of colonies during hot rolling
heating to be performed after that and can perform hot rolling on the fine crystal
grains as they are, therefore, the surface defects during hot rolling can be further
suppressed. Moreover, when the u stabilizer element(s) and/or the neutral
element(s) is/are added, the ~ transformation temperature hardly changes, or the ~
25 transformation temperature increases, therefore, when the hot rolling heating
temperature is immediately below the ~ transformation temperature, a situation in
which only the surface layer portion experiences ~ transformation can be suppressed.
Only by adding the u stabilizer element(s) or neutral element(s) in a manner that the
average concentration of the u stabilizer element(s) or neutral element(s) in the
30 molten-resolidified layer is higher by more than or equal to 0.1% in total compared
to the base metal portion, the above effects can be exhibited, therefore, the lower
PCT/JP2014/076087
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limit is set to 0.1 %. On the other hand, when the average concentration in the
molten portion is higher by more than or equal to 2.0% than the concentration in the
base metal portion, there are risks that a difference of hot workability may occur
between the surface layer portion containing the . alloying element and the interior,
5 and that the quality of the material of the product may be deteriorated since the
addition amount is large even when the elements are concentrated in the surface layer
portion and a large amount of alloying element contained in the surface layer portion
is diffused into the interior during heat treatment such as hot rolling heating,
therefore, the upper limit is set to 2.0%. Two or more of the a stabilizer element(s)
10 and/or the neutral element(s) may be added in combination, and the concentration of
the a stabilizer element(s) and the neutral element(s) in that case is the total
concentration of the concentrations of the respective elements.
[0023]
[Types of a stabilizer element and neutral element]
15 In the present invention, as the a stabilizer element(s) and the neutral
element(s), there may be used Al, Sn, and Zr. Those elements are each dissolved as
a solid solution in the a phase, and suppress crystal grain growth in the heating
temperature range during hot rolling.
[0024]
20 [~ stabilizer element]
In the present invention, a ~ stabilizer element may be contained together
with the a stabilizer element(s) and/or the neutral element(s). When the~ stabilizer
element is contained, not only the above-mentioned crystal grain growth, but also
further structure-fine-making can be expected, since the ~ phase, which is the second
25 phase in the heating temperature range during hot rolling, is easily generated, so that
the crystal grain growth is further suppressed. In addition, by using titanium alloy
scrap containing those alloying elements as an addition material, cost reduction can
be expected.
[0025]
30 [Method of measuring thickness of molten-resolidified layer]
The present invention defines that the molten-resolidified layer in which the
PCT/JP2014/076087
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content of alloying element(s) of the a stabilizer element(s) or the neutral element(s)
is/are concentrated has a depth of more than or equal to 1 mm. The method of
measuring the thickness of the molten-resolidified layer will be described. An
embedded polishing sample of the cross-section of the concentrated layer can be
5 easily detennined by scanning electron microscopy (SEM)/electron probe
microanalyser (EPMA). FIG. 1 shows a measurement example of change in
concentrations of the molten-resolidified layer. Owing to the addition of the a
stabilizer element(s) and/or the neutral element(s), the molten-resolidified layer has
higher concentration of the a stabilizer element(s) 'and/or the neutral element(s) in
10 comparison to the base metal portion, and the thickness of the portion in which the
concentration of the a stabilizer element(s) and/or the neutral element(s) is higher is
set to the thickness of the molten-resolidified layer. Note that, in the case where the
molten-resolidified layer is larger than the measurement range of SEMIEPMA, the
measurements are performed several times in the thickness direction, and the results
15 are combined to measure the thickness of the molten-resolidified layer.
[0026]
[Ununiformity in molten-resolidified layer]
In the present invention, there is ununiformity in the molten-resolidified
layer, and this can also be easily confirmed by the above-mentioned SEMIEBSP.
20 As shown in FIG. 1, when melting and resolidification treatment is performed by
adding additive elements, the concentration is high in total in the molten-resolidified
portion, but at that part, the concentration is not uniform and fluctuates, which is
different from the base metal portion, and it can be confirmed that the ununiformity
occurs.
25 [0027]
[Method of measuring element concentrations in molten portion and base metal
portion]
The concentrations in the molten-resolidified layer and the base metal
portion are determined by cutting out test pieces for analytical use from a part at
30 which the concentration is increased and a central part of the material and performing
ICP emission spectroscopic analysis on the test pieces. Regarding measurement of
PCT/JP2014/076087
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the concentrations, analysis samples may be collected from within 1 mm of the
surface layer of any multiple sites (for example, 10 sites) of the rolling surface of a
titanium cast product, ICP emission spectroscopic analysis may be performed on the
analysis samples, and the average value thereof may be set as the concentration in the
5 molten-resolidified layer. Further, by way of comparison, analysis samples may be
collected from within 20 mm of the surface layer of any multiple sites (for example,
3 sites) of the rolling surface of the titanium cast product before remelting the surface
layer of the titanium cast product, the ICP emission spectroscopic analysis may be
performed in the same manner, and the average value thereof may be set as the
10 concentration in the base metal portion.
[0028]
[Addition method]
In the present invention, in order to concentrate one or more elements out of
a stabilizer elements or neutral elements in the surface layer portion of the ingot, a
15 technique is used that the ingot surface layer portion is molten together with a
material made of one or more elements out of those elements. In this way, the
concentration of those elements in the surface layer portion of the ingot can be
increased. Further, a titanium alloy containing those elements may be used. In
this way, a ~ stabilizer element may also be contained easily together with those
20 elements. As a material, powder, chips, a wire, a thin film, and swarf can be used
individually or in combination.
[0029]
[Method of melting surface layer]
The present invention is characterized in that the titanium material surface
25 layer portion is heated together with a material made of one or more elements out of
a stabilizer elements or neutral elements, and is molten and resolidified. As the
methods of heating the surface layer portion, there may be used electron beam
heating, induction heating, arc heating, plasma. heating, and laser heating may
individually or in combination. In the case where the above methods are used in
30 combination, for example, the surface layer may be preheated by induction heating,
and then may be molten by laser heating. The method to be employed may be
PCT/JP20 14/07608 7
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selected by taking into account conditions such as cost, the size of the titanium
material, and treatment time. In the present invention, the titanium material surface
layer portion is preferably heated in a vacuum or an inert gas atmosphere. Since
titanium is an extremely active metal, a large amount of oxygen and nitrogen is
5 mixed in the molten-resolidified portion if the treatment is performed in the
atmosphere, resulting in change in the quality. Therefore, when the treatment is
performed in a container under a vacuum or an inert atmosphere, a satisfactory result
can be obtained. Note that inert gases according to the present invention represent
argon and helium, and do not include nitrogen which reacts with titanium. The
10 degree of vacuum in the case where the treatment is performed in a vacuum container,
the degree ofvacuun1 is desirably approximately higher than or equal to 5xJ0"5 Torr.
[0030]
The present invention provides a titanium material for hot rolling including
a molten-resolidified layer in which one or more elements out of a stabilizer
15 elements or neutral elements are concentrated in the above-mentioned range on an
surface layer in a range of more than or equal to 1 mm in depth, and the other portion
of the material is an as-cast structure or a structure obtained by performing casting,
then performing heating to higher than or equal to the f:l transformation temperature,
and thereafter performing quenching. Using this material, even when a slabing step
20 is omitted, a titanium material having the same surface quality as the case of
undergoing an ordinary slabing step can be obtained.
[Examples]
[0031]
Hereinafter, the present invention will be described in detail by way of
25 examples. Nos. 1 to 24 shown in Table 1 are each an example in which a sheet
material is used, and Nos. 25 to 31 are each an example in which a wire material is
used.
[0032]
[Table 1]
J u 11 H 1 1 1 1 l l 1 1 1 1 1 l l 1 1 1 1 1 1 1 1 u H 11 1 l 1 l
' l ~ ~ l l l l l l l l l '' l l l l l l l l l l l l l ! ! l l l l l l!f II l!f "i ! ' . ... ; i ! ! ! ! ! ! ! ! ! i i ! ! l ' . I ! •• ' ! i '. i. i !• !lt H ' ' ' ' ~ li u '' '' l ! m I I I ~ ' i I l l l l l l l l I I I I I I I I I I I I I ! I !
il I ~ ' ' '• ~ • ' ' ~ ' ' ' ~ ' ' ' ' ' ' ' ' ' ' I ~ ' ' ' '• '
HI " II I I I I I I I I I I I I I ' I I I I ' I I I " II " I I I I
l l. I I I I I I I I I I I I I I I I I I I I I I I I I
Ji p I ' ' ' ' I
!} ll l. H1 I . ' - ' ' ' ' ' ' ' ' ' ' ' ! ! ! ' ' ' ~ ~ ' I 0 ' - ' ' ' ; .
H !" I I I I I I I I I I I , ' , ·I : I I I I I I I I I I I I I I I I
1 H
I ilj ! "- I : ' ' ' ' ' ' ' - - ' ' - ' ! ! ~ ' ' 0 ~ ! ' H I ' ' ' ' ' '
fl ·jj, I I I I I I I I I I I : " ' ' I I I I I I I I I I I I I I I I
}
! ill I ' ' ' ' ' : : ' ' : : : ' ' : ' ' ' ' ' ' ' - I l !!l ' ' ' ' ' '
lf I I ' ' ' ' ' ' ' ! j l '' 'I I' ' ' ' ' ' ' ' ' ' I I ' ' ' ' '
l I ' dl ' ' ' : ' , ' : ,
' ' : : ' : : ' ' ' ' ' I ' '' ' ' ' :
Hi I I I I I I ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' I I I I I ' '
i ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' I ' ' ' ' ' '
l H ll ll I lll ll ! l llll ll ! l !l !I l j lj
"l " ! l!l !l !l !Ill !l ! l !j I J 1] 11 I J I J lj I J
~ ~ ! ~ ~ ~ ' ' ~ ~ ' ~ ~ ~ ! i ! ~ ~ ' ~ ! I l l l ' ! ~ ~ j '' ! ~ ~ ~ ~ ~ ~' ~ ' • • ' ' ' ' ' ' ' ' ' ' ' ' ' • ~ ' ~ ' ! ' ' ' ' ' ' ' ' ; " 0 - . - 0 - . 0 ' ' ' ' ' ' ' ' ' ' ' ' ' " ' ' ' ' ' ' ' '
I
PCT/JP2014/076087
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[0033]
In each of Reference Example, Examples, and Comparative Examples
shown in Nos. 1 to 21 of Table 1, a titanium cast product was manufactured by the
electron beam remelting method, and was casted using a square-shaped mold. On
5 the other hand, in each of Examples shown in Nos. 22 to 24 of Table I, a titanium
cast product was manufactured by a plasma arc melting method, and was casted
using a square-shaped mold. After casting, in the case where cutting mending of a
casting surface was performed, the cutting mending of an surface layer of the
titanium cast product was performed, and in the cai;e where the cutting mending is
10 not performed, the melting of the surface layer was performed without performing
the cutting mending of the surface layer. Next, an ingot having a thickness of 250
mm, a width of 1000 mm, and a length of 4500 mm was hot rolled using a hot rolling
plant for a steel material, and was manufactured into a belt-shaped coil having a
thickness of 4 mm. Note that an evaluation of surface defects was performed by
15 visually observing a sheet surface layer after being subjected to pickling.
[0034]
In each of Reference Example, Examples, and Comparative Examples of
Nos. 7 to 24, after an ingot was manufactured, a casting surface of the ingot (cast
product) was cut and removed. On the other hand, in each of Examples of Nos. 6 to
20 31, after an ingot was manufactured, a casting surface was subjected to melting and
resolidification treatment.
[0035]
In "melting method" shown in Table 1, "EB" represents performing melting
and resolidification of the surface layer by an electron beam, "TIG" represents
25 performing melting and resolidification of the surface layer by TIG welding, and
"laser" represents performing melting and resolidification of the surface layer by
laser welding. For the melting of the surface layer using the electron beam, an
electron beam welding apparatus having a standard output of 30 kW was used. The
melting of the surface layer performed by the TIG welding was performed at 200 A
30 without using a filler material. For the melting of the surface layer performed by
the laser welding, a C02 laser was used.
PCT/JP2014/076087
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[0036]
Reference Example of No. 1 describes a case where manufacturing was
performed by using Ti-5Al-Fe titanium alloy and following a conventional slabing
step. Since the slabing step is performed, surface defects of the manufactured sheet
5 material were minor.
[0037]
In Comparative Example of No. 2, the ingot was subjected to cutting
mending, and then was subjected to surface layer melting treatment using EB without
adding an a stabilizer element or a neutral element. · Therefore, the thickness of the
10 molten-resolidified layer was as deep as more than or equal to 1 mm, and although
the surface defects were minor, the surface defects that are not minor occurred in
some parts and were deteriorating.
[0038]
In Comparative Example of No. 3, the ingot was subjected to the cutting
15 mending, and then the surface of the ingot was subjected to the surface layer melting
treatment using EB together with Al powder. Although the content of Al in the
molten-resolidified portion was high, which was higher by more than or equal to
0.1% compared to the base metal portion, the thickness was as small as 0.5 mm, and
hence, slightly coarse surface defects were observed in some parts.
20 [0039]
In Example of No.4, the ingot was subjected to the cutting mending, after
that, the surface of the ingot was subjected to the surface layer melting treatment
using EB together with Al chips, the content of Al in the molten-resolidified layer
was high, which was higher by more than or equal to 0.1% compared to the base
25 metal portion, and the thickness was as deep as more than or equal to 1 mm, and
hence, the surface defects were minor, which was the same level as the case of
undergoing the slabing step.
[0040]
In Example of No. 5, the ingot was subjected to the cutting mending, after
30 that, the surface of the ingot was subjected to the surface layer melting treatment
using laser together with Al foil, the content of Al in the molten-resolidified layer
PCT/JP2014/076087
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was high, which was higher by more than or equal to 0.1% compared to the base
metal portion, and the thickness of the Al-concentrated layer was as deep as more
than or equal to 1 mm, and hence, the surface defects were minor, which was the
same level as the case of undergoing the slabing step.
5 [0041]
Iri Example of No. 6, the ingot was subjected to the cutting mending, after
that, the surface of the ingot was subjected to the surface layer melting treatment
using TIG together with AI foil, the content of AI in the molten-resolidified layer was
high, which was higher by more than or equal to 0."1% compared to the base metal
10 portion, and the thickness was as deep as more than or equal to 1 mm, and hence, the
surface defects were minor, which was the same level as the case of undergoing the
slabing step.
[0042]
In Example of No. 7, the ingot was not subjected to cutting, the surface of
15 the ingot was subjected to the surface layer melting treatment using EB together with
AI powder, the content of AI in the molten-resolidified layer was high, which was
higher by more than or equal to 0.1% compared to the base metal portion, and the
thickness was as deep as more than or equal to 1 mm, and hence, the surface defects
were minor, which was the same level as the case of undergoing the slabing step.
20 [0043]
In Example of No. 8, the ingot was not subjected to cutting, the surface of
the ingot was subjected to the surface layer melting treatment using EB together with
Sn powder, the content of Sn in the molten-resolidified layer was high, which was
higher by more than or equal to 0.1% compared to the base metal portion, and the
25 thickness was as deep as more than or equal to 1 mm, and hence, the surface defects
were minor, which was the same level as the case of undergoing the slabing step.
[0044]
In Example of No. 9, the ingot was not subjected to cutting, the surface of
the ingot was subjected to the surface layer melting treatment using EB together with
30 Zr swarf, the content of Zr in the molten-resolidified layer was high, which was
higher by more than or equal to 0.1% compared to the base metal portion, and the
----=---·==---'-··- --
PCT/JP20 14/076087
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thickness was as deep as more than or equal to 1 mm, and hence, the surface defects
were minor, which was the same level as the case of undergoing the slabing step.
[0045]
In Example of No. 10, the ingot was not subjected to cutting, the surface of
5 the ingot was subjected to the surface layer melting treatment using TI G together
with powder of Al and Zr, the total content of Al and Zr in the molten-resolidified
layer was high, which was higher by more than or equal to 0.1% compared to the
base metal portion, and the thickness was as deep as more than or equal to 1 mm, and
hence, the surface defects were minor, which was' the same level as the case of
10 undergoing the slabing step.
[0046]
In Example of No. 11, the ingot was not subjected to cutting, the surface of
the ingot was subjected to the surface layer melting treatment using TIG together
with swarf of a titanium alloy containing AI and Sn, the total content of AI and Sn in
15 the molten-resolidified layer was high, which was higher by more than or equal to
0.1% compared to the base metal portion, and the thickness was as deep as more than
or equal to 1 mm, and hence, the surface defects were minor, which was the same
level as the case of undergoing the slabing step.
20
[0047]
In each of Examples of No. 12 to 15, the ingot was not subjected to cutting,
the surface of the· ingot was subjected to the surface layer melting treatment using
TIG together with swarf of a titanium alloy containing AI and a ~ stabilizer element,
the content of Al in the molten-resolidified layer was high, which was higher by
more than or equal to 0.1% compared to the base metal portion, and the content of
25 the ~ stabilizer element was as low as less than or equal to 1.5%. Further, the
thickness was as deep as more than or equal to 1 mm, and hence, the surface defects
were minor, which was the same level as the case of undergoing the slabing step.
[0048]
Each of Examples of Nos. 16 to 24 is a result of an ingot made of a titanium
30 alloy. No. 16 is Ti-0.06Pd titanium alloy, No. 17 is Ti-0.5Ni-0.05Ru titanium alloy,
No. 18 is Ti-lFe-0.350 titanium alloy, No. 19 is Ti-5AI-1Fe-0.25Si titanium alloy,
I_
PCT/JP2014/076087
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No. 20 is Ti-3Al-2.5V titanium alloy, No. 21 is Ti-4.5Al-2Fe-2Mo-3V titanium alloy,
No. 22 is Ti-l Cu titanium alloy, No. 23 is Ti-l Cu-0.5Nb titanium alloy, and No. 24 is
Ti-1Cu-1Sn-0.3Si-0.2Nb titanium alloy. In each of the above, the ingot was not
subjected to cutting, the surface of the ingot was subjected to the surface layer
5 melting treatment using EB together with Al powder, the content of AI in the moltenresolidified
layer was high, which was higher by more than or equal to 0.1%
compared to the base metal portion, and the thickness was as deep as more than or
equal to 1 mm, and hence, the surface defects were minor, which was the same level
as the case of undergoing the slabing step.
10 [0049]
In each of Reference Example, Comparative Examples, and Examples
shown in Nos. 25 to 31 of Table 1, Ti-3Al-2.5V titanium alloy was used, and a
titanium ingot was manufactured by the vacuum arc remelting method or the electron
beam remelting method. An ingot having a diameter of 170 mm and a length of 12
15 m was hot rolled, and was manufactured into a wire material having a diameter of 13
mm. Note that an evaluation of surface defects was performed by visually
observing a sheet surface layer after being subjected to pickling.
[0050]
In each of Reference Example, Comparative Examples, and Examples of
20 Nos. 25 to 29, after an ingot was manufactured, a casting surface of the ingot was cut
and removed. On the other hand, in each of Examples of Nos. 30 and 31, after an
ingot was manufactured, a casting surface was subjected to melting and
resolidification treatment.
25
[0051]
Reference Example of No. 25 describes a case where manufacturing was
performed by following a conventional slabing step.
[0052]
In Comparative Example of No. 26, the ingot was subjected to cutting
mending, and then was subjected to surface layer melting treatment using EB without
30 adding an a stabilizer element or a neutral element. Therefore, the thickness of the
molten-resolidified portion was as deep as more than or equal to 1 mm, and although
PCT/JP2014/076087
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the surface defects were minor, they occurred in some parts and were deteriorating.
[0053]
In Comparative Example of No. 27, the ingot was subjected to the cutting
mending, and then the surface of the ingot was subjected to the surface layer melting
5 treatment using EB together with AI foil. Although the content of AI in the moltenresolidified
portion was high, which was higher by more than or equal to 0.1%
compared to the base metal portion, the thickness was as small as 0.5 mm, and hence,
slightly coarse surface defects were observed in some parts.
10
[0054]
In Example of No. 28, the ingot was subjected to the cutting mending, after
that, the surface of the ingot was subjected to the surface layer melting treatment
using EB together with AI foil, the content of AI in the molten-resolidified layer was
high, which was higher by more than or equal to 0.1% compared to the base metal
portion, and the thickness was as deep as more than or equal to 1 mm, and hence, the
15 surface defects were minor, which was the same level as the case of undergoing the
slabing step.
[0055]
In Example of No. 29, the ingot was subjected to the cutting mending, after
that, the surface of the ingot was subjected to the surface layer melting treatment
20 using TIG together with AI foil, the content of AI in the molten-resolidified layer was
high, which was higher by more than or equal to 0.1 %, and the thickness was as deep
as more than or equal to 1 mm, and hence, the surface defects were minor, which
was the same level as the case of undergoing the slabing step.
25
[0056]
In Example of No. 30, the ingot was subjected to the cutting mending, after
that, the surface of the ingot was subjected to the surface layer melting treatment
using laser together with Sn powder, the content of Sn in the molten-resolidified
layer was high, which was higher by more than or equal to 0.1% compared to the
base metal portion, and the thickness of the Al-concentrated layer was as deep as
30 more than or equal to 1 mm, and hence, the surface defects were minor, which was
the same level as the case of undergoing the slabing step.
PCT/JP2014/076087
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[0057]
In Example of No. 31, the ingot was subjected to the cutting mending, after
that, the surface of the ingot was subjected to the surface layer melting treatment
using EB together with AI foil, the content of AI in the molten-resolidified layer was
5 high, which was higher by more than or equal to 0.1% compared to the base metal
portion, arid the thickness of the Al-concentrated layer was as deep as more than or
equal to 1 mrn, and hence, the surface defects were minor, which was the same level
as the case of undergoing the slabing step.

CLAIMS
Claim I (Amended)
A titanium cast product made of a titanium alloy, the titanium cast product
comprising:
5 a layer in a range of more than or equal to 1 mm in depth on a surface
serving as a rolling surface, the layer containing one or more elements out of any one
of or both of at least one a stabilizer element and at least one neutral element,
wherein a total concentration of at least one a stabilizer element and at least
one neutral element in the range of more than or equal to 1 mm in depth is higher
10 than a total concentration of at least one a stabilizer element and at least one neutral
element in a base metal by, in mass%, more than or equal to 0.1% and less than
2.0%.
15
20
Claim 2 (Amended)
The titanium cast product according to claim 1,
wherein the at least one a stabilizer element and the at least one neutral
element each include AI, Sn, and Zr.
Claim 3 (Amended)
The titanium cast product according to claim 1,
wherein the layer containing one or more elements out of any one of or both
of at least one a stabilizer element and at least one neutral element further contains,
in mass%, less than or equal to 1.5% of one or more ~ stabilizer elements.
25 Claim 4 (Amended)
A method of manufacturing a titanium cast product, the method comprising:
melting a surface serving as a rolling surface of the titanium cast product
together with a material containing one or more elements out of any one of or both of
at least one a stabilizer element and at least one neutral element, and then solidifying
30 the surface,
wherein a total concentration of at least one a stabilizer element and at least
5
PCT/JP2014/076087
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one neutral element in the range of more than or equal to 1 mm in depth is made
higher than a total concentration of at least one a stabilizer element and at least one
neutral element in a base metal by, in mass%, more than or equal to 0.1% and less
than2.0%.
Claim 5 (Amended)
The method of manufacturing a titanium cast product according to claim 4,
wherein the material containing one or more elements out of any one of or
both of at least one a stabilizer element and at least one neutral element includes one
10 or more of powder, chips, a wire, a thin fihn, and swarf.
Claim 6 (Amended)
The method of manufacturing a titanium cast product according to claim 4,
wherein the surface of the titanium cast product is molten by using one or
15 more of electron beam heating, arc heating, laser heating, plasma heating, and
induction heating.
20
25
Claim 7 (Amended)
The method of manufacturing a titanium cast product according to claim 4,
wherein the surface of the titanium cast product is molten in a vacuum
atmosphere or an lneti gas atmosphere.