U.S. patent application number 11/786841 was filed with the patent office on 2007-08-23 for process for producing ingot.
This patent application is currently assigned to Daido Tokushuko Kabushiki Kaisha. Invention is credited to Makoto Chujoya, Teppei Okumura, Kazumi Yamamoto.
Application Number | 20070193710 11/786841 |
Document ID | / |
Family ID | 37498225 |
Filed Date | 2007-08-23 |
United States Patent
Application |
20070193710 |
Kind Code |
A1 |
Chujoya; Makoto ; et
al. |
August 23, 2007 |
Process for producing ingot
Abstract
A large and uniform ingot is produced by casting smaller ingots
from a melt of a metallic material which may include a
high-melting-point active metal such as Ti or a Ti alloy obtained
by a cold crucible induction melting method, forming a consumable
electrode by using these smaller ingots, re-melting this consumable
electrode by a vacuum arc re-melting method, and casting a larger
ingot by using the obtained melt.
Inventors: |
Chujoya; Makoto; (Nagoya,
JP) ; Yamamoto; Kazumi; (Nagoya, JP) ;
Okumura; Teppei; (Nagoya, JP) |
Correspondence
Address: |
BEYER WEAVER LLP
P.O. BOX 70250
OAKLAND
CA
94612-0250
US
|
Assignee: |
Daido Tokushuko Kabushiki
Kaisha
|
Family ID: |
37498225 |
Appl. No.: |
11/786841 |
Filed: |
April 12, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP06/05099 |
Mar 15, 2006 |
|
|
|
11786841 |
Apr 12, 2007 |
|
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Current U.S.
Class: |
164/61 ; 164/470;
164/495 |
Current CPC
Class: |
C22B 9/20 20130101; B22D
7/00 20130101; C22B 34/1295 20130101; B22D 7/08 20130101; B22D
7/005 20130101 |
Class at
Publication: |
164/061 ;
164/470; 164/495 |
International
Class: |
B22D 27/15 20060101
B22D027/15; B22D 27/02 20060101 B22D027/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 9, 2005 |
JP |
2005-169319 |
Claims
1. A process for producing an ingot, said process comprising the
steps of: casting smaller ingots from a melt obtained by a cold
crucible induction melting method; forming a consumable electrode
by using said smaller ingots; re-melting said consumable electrode
by a vacuum arc re-melting method to obtain another melt; and
casting a larger ingot larger than said smaller ingots by using
said another melt.
2. The process of claim 1 comprising Step A, Step B and Step C
wherein said Step A comprises melting a metallic material by a cold
crucible induction melting method to obtain said melt and pouring
said melt into a smaller mold to obtain smaller ingots by casting;
wherein said Step B comprises joining a plurality of the smaller
cast ingots after carrying out said Step A once or more times; and
wherein said Step C comprises using the joined smaller ingots
obtained in said Step B as said consumable electrode for re-melting
to obtain said another melt and obtaining said larger ingot by a
casting method by pouring said another melt into a larger mold
larger than said smaller mold.
3. The process of claim 1 comprising Step a, Step b and Step c
wherein said Step a comprises melting a metallic material by a cold
crucible induction melting method to obtain said melt and pouring
said melt into a portion of a larger mold to obtain a smaller ingot
by casting, said smaller ingot being smaller than the space inside
said larger mold; wherein said Step b comprises joining a plurality
of the smaller cast ingots inside said larger mold after carrying
out said Step a once or more times; and wherein said Step c
comprises using the joined smaller ingots obtained in said Step b
as said consumable electrode for re-melting to obtain said another
melt and obtaining said larger ingot by a casting method by pouring
said another melt into said larger mold.
4. The process of claim 2 wherein said Step B comprises joining
said plurality of the smaller cast ingots over surfaces extending
along the axis of the consumable electrode used in said Step C.
5. The process of claim 3 wherein said Step b comprises joining
said plurality of smaller cast ingots sequentially over surfaces
extending along the axis of the consumable electrode used in said
Step c.
6. The process of claim 2 wherein said Step B comprises joining
said plurality of the smaller cast ingots over surfaces extending
perpendicularly to the axis of the consumable electrode used in
said Step C.
7. The process of claim 3 wherein said Step b comprises joining
said plurality of smaller cast ingots sequentially over surfaces
extending perpendicularly to the axis of the consumable electrode
used in said Step c.
8. The process of claim 2 wherein said metallic material is a
high-melting-point active metal or an alloy thereof.
9. The process of claim 3 wherein said metallic material is a
high-melting-point active metal or an alloy thereof.
10. The process of claim 2 wherein said metallic material is Ti or
an alloy thereof.
11. The process of claim 3 wherein said metallic material is Ti or
an alloy thereof.
Description
[0001] This application is a continuation of International
Application No. PCT/JP2006/305099, filed Mar. 15, 2006 which claims
priority on Japanese Patent Application 2005-169319 filed Jun. 9,
2005.
BACKGROUND OF THE INVENTION
[0002] This invention relates to a process for producing an ingot
and more particularly to a process for economically producing a
large and uniform ingot.
[0003] For mass-producing wrought products of Ti or Ti alloys, for
example, large and uniform ingots are necessary on the order of
several tons. This invention relates to a process for producing
large and uniform ingots even in the case of an active metal having
a high melting point such as Ti.
[0004] As an example of process for producing an ingot containing
an active metal having a high melting point such as Ti, Japanese
Patent Publication Tokkai 2001-131651 has disclosed a process of
melting a metallic material by a cold crucible induction melting
method and obtaining an ingot by pouring its melt into a mold.
Japanese Patent Publication Tokkai 9-31558 has disclosed another
process of obtaining an ingot by re-melting a consumable electrode
made of a metallic material by a vacuum arc re-melting method and
pouring its melt into a mold.
[0005] The prior art process of melting a metallic material by a
cold crucible induction melting method is advantageous in that the
melts become uniform as a whole since they are mixed together
collectively. As a result, the overall composition of the melt can
be grasped by sampling and analyzing only a portion of it and it
can be adjusted, if it is different from its target value, by
adding a necessary material thereto.
[0006] This process is disadvantageous, however, in that a large
crucible with a power-supply equipment is necessary because a
high-frequency current must be passed through the coils provided on
its outer periphery. Such a crucible with a large capacity is
difficult to construct, and since it would be a heavy financial
burden to construct and operate an apparatus with a large crucible,
an apparatus equipped with a significantly smaller crucible is
usually constructed and operated, obtaining relatively smaller
ingots. Smaller ingots are disadvantageous from the point of view
of yield and productivity as they are used in a production process.
In order to serve as wrought products, ingots of at least one ton
are considered to be necessary.
[0007] The prior art process of producing an ingot by re-melting a
consumable electrode made of a metallic material by a vacuum arc
re-melting method is capable of producing large ingots of several
tons. Since the consumable electrodes that are used by this method
are produced by forming layers of a metallic material in the
direction of its axis, its components in the direction of the axis
become non-uniform and hence the ingot produced by using such a
consumable electrode also becomes non-uniform.
[0008] It is therefore an object of this invention to provide a
process for economically producing a large and uniform ingot even
if the ingot contains an active metal with a high melting point
such as Ti.
SUMMARY OF THE INVENTION
[0009] The present invention relates, in view of the object
described above, to a process for producing an ingot comprising the
steps of casting smaller ingots from a melt obtained by a cold
crucible induction melting method, forming a consumable electrode
by using these smaller ingots, re-melting this consumable electrode
by a vacuum arc re-melting method to obtain another melt, and
casting a larger ingot by using the latter melt.
[0010] By such a method, the composition of the (smaller) ingots
cast by the cold crucible induction melting method can be adjusted
within a target range and these ingots can be produced evenly.
Thus, the distribution of components of the consumable electrode
can also be made uniform in its axial direction, and a larger ingot
which is uniform throughout can be produced if such a consumable
electrode is re-melted by a vacuum arc re-melting method.
[0011] Cold crucible induction melting method and vacuum arc
re-melting method of known types may be used according to this
invention but a process (according to a first embodiment of the
invention) by Steps A, B and C as described below is preferable,
Step A comprising the step of melting a metallic material by a cold
crucible induction melting method to obtain a melt and pouring this
melt into a smaller mold to obtain a smaller ingot by casting, Step
B comprising the step of joining a plurality of the smaller cast
ingots after carrying out Step A once or more times, and Step C
comprising the step of using the joined smaller ingots obtained in
Step B as the consumable electrode for re-melting in a vacuum arc
re-melting method to obtain the latter melt and obtaining the
larger ingot by a casting method by pouring this latter melt into a
larger mold larger than the aforementioned smaller mold.
[0012] According to a second embodiment of the invention, the cold
crucible induction melting and vacuum arc re-melting methods are
carried out by Steps a, b and c, Step a comprising the step of
melting a metallic material by a cold crucible induction melting
method to obtain a melt and pouring the melt into a portion of a
larger mold to obtain a smaller ingot by casting, the smaller ingot
being smaller than the space inside the larger mold, Step b
comprising the step of joining a plurality of the smaller cast
ingots inside the larger mold after carrying out Step a once or
more times, and Step c comprising the step of using the joined
smaller ingots obtained in Step b as a consumable electrode for
re-melting by a vacuum arc re-melting method to obtain another melt
and obtaining a larger ingot by a casting method by pouring the
latter melt into the larger mold.
[0013] In the above, the smaller ingots mean smaller than the ingot
obtained in Step C or c, and there is no particular limitation on
their mass but their mass is usually intended to be on the order of
several hundred kilograms to a ton. This is because the equipment
to be used for the cold crucible induction melting method for
obtaining ingots of this size is convenient from the operational
and economical points of view. What is herein referred to as the
larger ingot is usually of a mass on the order of several tons.
[0014] There is no particular limitation on the manner in which the
smaller ingots are to be joined but a common method is to weld them
together where they contact each other.
[0015] Neither is there any particular limitation on the shape of
the smaller ingots to be sequentially formed and joined in a method
according to the second embodiment of the invention. They may be
sequentially formed or dummy partitions may be used and
sequentially removed. In all cases, those ingots that are earlier
hardened are integrated into those becoming hardened later.
[0016] Methods of joining the smaller ingots over surfaces
extending along planes extending along the axis of the consumable
electrode used in Step C or c are advantageous because the
compositions of the ingots obtained in Steps A and a become uniform
in the axial direction. Since a consumable electrode that is
uniform in the axial direction can be obtained by joining them, a
uniformly formed larger ingot can be easily produced by melting
such a consumable electrode.
[0017] By these method, furthermore, the compositions of the ingots
cast in Steps A and a may be different somewhat because the
consumable electrode obtained by joining them together in Step B or
b is melted again. Thus, it is sufficient if the composition of the
mixed melts of these component ingots is within the allowable range
of the target large ingot. If the first smaller ingot obtained
contains too much of a certain element, for example, the content of
that element may be reduced when the next smaller ingot is
produced.
[0018] Methods of joining the smaller ingots over surfaces
extending along planes perpendicular to the axis of the consumable
electrode used in Step C or c in Step B or adding them sequentially
along this axis in Step b are advantageous because a larger ingot
with a uniform composition in the axial direction can be obtained
without using a mold of any particular shape. When these methods
are used to produce a large ingot, it is generally necessary to
analyze samples of the melt in Step A or a and to use in Step B or
b only those smaller ingots with components adjusted to be uniform.
This method can be used in the cold crucible induction melting
method because components can be grasped and adjusted.
[0019] This invention does not impose any limitation on the kind
and composition of the metallic material to be used in Step A or a.
This invention is particularly useful when a high-melting-point
active metal such as Ti, Nb, W, Zr and Ta and their alloy is used,
and more particularly when it is Ti or a Ti alloy. It is preferable
in carrying out Steps A and a to sample a portion of the melt and
to analyze it when the metallic material is melted and to readjust
the composition of the melt based on the result of such
analysis.
[0020] The present invention has the merit wherein a large and
uniform ingot can be obtained economically even if a
high-melting-point active metal such as Ti is contained.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a diagonal view of a consumable electrode used in
a method of this invention.
[0022] FIG. 2 is a diagonal view of another consumable electrode
used in a method of this invention.
[0023] FIG. 3 is a diagonal view of still another consumable
electrode used in a method of this invention.
[0024] FIG. 4 is a diagonal view of an example of the step of
pouring a melt according to this invention.
[0025] FIG. 5 is a sectional view of an example of the step
according to this invention subsequent to the step shown in FIG.
4.
[0026] FIG. 6 is a sectional view of an example of the step
according to this invention subsequent to the step shown in FIG.
5.
[0027] FIG. 7 is a sectional view of an example of the step
according to this invention subsequent to the step shown in FIG.
6.
[0028] FIG. 8 is a sectional view of an example of the step
according to this invention subsequent to the step shown in FIG.
7.
[0029] FIG. 9 is a sectional view of an example of the step
according to this invention subsequent to the step shown in FIG.
8.
[0030] FIG. 10 is a sectional view of an example of the step
according to this invention subsequent to the step shown in FIG.
9.
[0031] FIG. 11 is a sectional view of an example of the step
according to this invention subsequent to the step shown in FIG.
10.
[0032] FIG. 12 is a sectional view of an example of the step
according to this invention subsequent to the step shown in FIG.
11.
[0033] FIG. 13 is a sectional view of an example of the step
according to this invention subsequent to the step shown in FIG.
12.
DETAILED DESCRIPTION OF THE INVENTION
[0034] FIG. 1 is a diagonal view of a consumable electrode used in
one of the methods (the first method) of this invention. As shown,
it is constructed by assembling four smaller ingots 1a, 1b, 1c and
1d obtained by cutting a cylinder with a pair of mutually
perpendicular planes crossing each other along its axis and
soldering them together so as to form a single consumable electrode
1.
[0035] FIG. 2 is a diagonal view of another consumable electrode
used in the first method of this invention, being constructed by
assembling four smaller ingots obtained by assembling four smaller
ingots 2a, 2b, 2c and 2d by cutting a cylinder with three mutually
parallel planes extending parallel to its axis and soldering them
together so as to form another single consumable electrode 2.
[0036] FIG. 3 is a diagonal view of still another consumable
electrode used in the first method of this invention, being
constructed by assembling four smaller ingots obtained by
assembling four smaller ingots 3a, 3b, 3c and 3d by cutting a
cylinder with three mutually parallel planes extending radially and
soldering them together so as to form still another single
consumable electrode 3.
[0037] FIGS. 4-13 are drawings (FIG. 4 being a diagonal view and
FIGS. 5-13 being transverse sectional views) for showing the
casting routines in Step a and Step b of another method (the second
method) of this invention. As shown in FIGS. 4 and 5, four frames
4a, 4b, 4c and 4d of the same shape are inserted slidingly into a
larger mold 4 having a cylindrical inner space so as to be
intimately in contact with one another. Next, one of these four
frames (4a) is removed, as shown in FIGS. 6 and 7, and a melt is
poured into this empty space, which is left there by the removal of
this frame 4a, by the cold crucible induction melting method such
that a smaller ingot 5a is produced.
[0038] Next, as shown in FIGS. 8 and 9, another frame 4b is removed
and a melt is poured into the empty space left there in the shape
of the frame 4b by its removal such that not only another smaller
ingot 5b is produced by the cold crucible induction melting method
but also that it will be joined to the earlier produced ingot 5a to
form a single integrated ingot.
[0039] Next, as shown in FIGS. 10 and 11, still another frame 4c is
removed and a melt is poured into the empty space left there in the
shape of the frame 4c by its removal such that not only still
another smaller ingot 5c is produced by the cold crucible induction
melting method but also that it will be joined to the earlier
produced ingots 5a and 5b to form a single integrated ingot.
[0040] Finally, thereafter, as shown in FIGS. 12 and 13, the fourth
frame 4d is removed and a melt is poured into the empty space left
there in the shape of the frame 4d by its removal such that not
only still another smaller ingot 5d is produced by the cold
crucible induction melting method but also that it will be joined
to the earlier produced ingots 5a, 5b and 5c to form a single
integrated larger ingot. This finally obtained larger ingot is used
as a consumable electrode in a vacuum arc re-melting method which
is herein referred to as Step c.
[0041] Although a method by using dummy frames has been described
above with reference to FIGS. 5-13 as the second method, the second
method according to this invention may be carried out alternatively
by sequentially forming layers inside a mold by adding a melt. Such
a method may be carried out by sequentially adding a melt in the
axial direction inside a melt or by keeping the mold sideways in a
laid-down position and adding a melt from above sequentially.
TEST EXAMPLE 1
[0042] Steps a and b were carried out as explained above with
reference to FIGS. 4-13 by using a Ti alloy (6Al-4V-Ti) as metallic
material and carrying out a cold crucible induction melting method
under the following conditions: TABLE-US-00001 Inputted power: 3000
kW; Frequency: 2500 Hz; Inner diameter of crucible: 700 mm; Amount
melted per cycle: 450 kg; Mass of each ingot: 400 kg.
[0043] Next, the larger joined ingot 5 obtained in Steps a and b
was used as a consumable electrode to carry out a vacuum arc
re-melting method by Step c under the following conditions:
TABLE-US-00002 Current intensity: 15 kA; Voltage: 3 5V; Degree of
vacuum: 1 Pa; Ratio of crucible inner diameter to outer diameter of
consumable 1/0.85; electrode: Mass of larger cast ingot: 1.6 t.
Sample pieces were scraped off from a top part, a middle part and a
bottom part of the larger cast ingot and the contents (mass %) of
Al and V were analyzed five times. The averaged values of these
analyses are shown in Table 1 below.
COMPARISON EXAMPLE 1
[0044] Another consumable electrode was produced by press-molding a
metallic material of the same Ti alloy as in Test Example 1 and
used in a primary vacuum arc melting process under the same
conditions as in Test Example 1 and the resultant melt was used to
obtain a consumable electrode of the same size as in Test Example 1
for re-melting. The latter electrode was used to carry out a
secondary vacuum arm melting (vacuum arc re-melting) under the same
conditions as in Test Example 1 and an ingot of the same size as in
Test Example 1 was cast from the melt thus obtained. Similar
analyses were carried out on the ingot thus obtained and the
obtained average values are also shown in Table 1 below.
TABLE-US-00003 TABLE 1 Element Al (mass %) V (mass %) Position Top
Middle Bottom Top Middle Bottom Standard 5.5-6.75 3.5-4.5 Aimed
value 6.0 4.0 Test Example 1 6.05 6.01 6.03 4.02 4.03 3.99
Comparison 6.17 6.18 6.03 4.22 4.17 4.09 Example 1
[0045] Table 1 makes it clear that large and uniform ingots can be
economically obtained by a method of this invention even if an
active metal with high melting point such as Ti is contained.
Although results of experiments using the latter of the two methods
described are shown above, similar results were also obtained by
experiments using the former method.
* * * * *