[0001] The present invention relates to a pure titanium building material resistant to secular
discoloration for constructing external walls of buildings, and reinforcing members,
and a method of manufacturing such a pure titanium material.
[0002] A titanium material has a surface coated with an oxide film, which is perfectly resistant
to rusting, is excellent in corrosion resistance and has desirable mechanical properties.
Titanium building materials have been watched with keen interest for their excellent
properties.
[0003] Recent development of the waterfront and the recent progressively deteriorating environmental
conditions around buildings due to acid rain brought about various problems. Recent,
severe environmental conditions to which titanium building materials are exposed discolor
the titanium building materials from silver white into brownish color by aging.
[0004] The discolored titanium materials do not glitter in beautiful metallic colors any
longer and spoil the aesthetic design of buildings. Although it is possible to renew
the original beautiful appearance of titanium materials discolored by aging by maintenance
work including wiping or polishing, such maintenance work is very expensive, and some
parts of buildings reject maintenance work. Accordingly, studies have been made to
develop titanium materials resistant to secular discoloration.
[0005] A titanium or a titanium alloy material disclosed in JP-A 10-8234 has a surface finished
in a surface roughness Ra = 3 µm or below and coated with an oxide film of 20 Å or
above in thickness to suppress secular discoloration. Titanium and titanium alloy
materials disclosed in Jpn. Pat. No. 3255610 have an oxide film of 100 Å or below
and a surface layer having a specified C content.
[0006] A technique intended to solve problems resulting from secular discoloration by specifying
the C content of a surface layer is disclosed also in JP-A 2001-348634. A titanium
sheet manufacturing process according to this technique anneals a cold-rolled titanium
sheet at 750 to 800°C for 3 to 5 min to make a layer having a high C content, which
is considered to cause secular discoloration, vanish.
[0007] Requirements for suppressing the secular discoloration of titanium building materials
have progressively become severe in recent years, and the development of titanium
materials further resistant to secular discoloration has been earnestly desired. Test
data mentioned in the foregoing three reference documents are qualitative and not
quantitative. Titanium materials must be evaluated by a more precise evaluation system
to develop titanium materials meeting the recent severe requirements.
[0008] Although various pure titanium building materials resistant to secular discoloration
have been placed on the market, pure titanium building materials having further improved
secular-discoloration resistance are demanded because the severity of design of buildings
have been progressively increasing and maintenance cost has been progressively increasing
in recent years.
[0009] Accordingly, it is an object of the present invention to provide a pure titanium
material more resistant to secular discoloration than conventional titanium materials.
[0010] Inventors of the present invention studied various titanium materials to solve the
foregoing problems, and repeated sever evaluation of secular-discoloration resistance
of the titanium materials and found that specific impurities contained in the titanium
materials dominate the secular-discoloration resistance of the titanium materials.
[0011] Pure titanium and titanium alloys are used for forming pure titanium building materials.
Most pure titanium building materials are formed of industrial pure titanium of Grade
1 JIS containing impurities in a small quantity and excellent in formability. Even
if titanium building materials are formed of a material not containing titanium scraps
and containing only industrial titanium Grade 1, JIS, i.e., sponge titanium, the titanium
building materials inevitably contain various impurities in small contents. Chemical
requirements for industrial titanium Grade 1, JIS specify impurity contents including
oxygen content and iron content in terms of formability. Any attention has not been
paid to such impurity contents at all in improving secular-discoloration resistance.
[0012] The inventors of the present invention found that pure building materials formed
of pure titanium having specific impurity contents below predetermined levels are
scarcely subject to secular discoloration and have made the present invention.
[0013] According to the present invention, a pure titanium building material is formed of
pure titanium having an Fe content of 0.08% by mass or below, a Nb content of 0.02%
by mass or below, and a Co content of 0.02% by mass or below.
[0014] Preferably, the pure titanium building material has a surface oxide film of 170 Å
or below in thickness. Although a pure titanium building material having a thicker
surface oxide film has lower secular-discoloration resistance, the pure titanium building
material has a beautiful silver white color, and the growth of the surface oxide film
can be effectively suppressed when the pure titanium building material has the composition
defined as above and the surface oxide film is 170 Å or below. Therefore, the pure
titanium building material having a surface oxide film of 170 Å or below in thickness
is not subject to secular discoloration to an extent that spoils aesthetic design
and maintains silver white appearance.
[0015] A pure titanium building material manufacturing method according to the present invention
includes the steps of: forming a pure titanium building material of pure titanium
having an Fe content of 0.08% by mass or below, a Nb content of 0.02% by mass or below
and a Co content of 0.02% by mass or below, pickling the pure titanium building material;
and heating the pickled pure titanium building material at a temperature X (°C) in
the range of 130 to 280°C for a heating time T (min) so as to meet a condition expressed
by: T ≥ 239408 × X
-2.3237.
[0016] The heating step forms a surface oxide film of a proper thickness effective in suppressing
detrimental coloring and reduces impurities that cause discoloration as well. Thus,
the pure titanium building material manufactured by the pure titanium building material
manufacturing method is highly resistant to secular discoloration.
[0017] Having very high secular-discoloration resistance far higher than that of conventional
titanium or titanium alloy building materials, the pure titanium building material
of the present invention is very useful as a building material for constructing buildings
to which high aesthetic design is essential, those exposed to sea wind and acid rain,
those requiring high maintenance cost and those difficult to maintain. Thus, the pure
titanium building material of the present invention is very industrially useful.
[0018] The above and other objects, features and advantages of the present invention will
become more apparent from the following description taken in connection with the accompanying
drawings, in which:
Fig. 1 is a graph of assistance in explaining an AES method of measuring the thickness
of an oxide film; and
Fig. 2 is a graph showing the relation between heating time and heating temperature
effective in improving secular-discoloration resistance.
[0019] It is the most characteristic feature of a pure titanium building material according
to the present invention that the secular discoloration of the pure titanium building
material develops very slowly even when the pure titanium building material is used
for constructing a building exposed to a severe environment.
[0020] Although titanium or titanium alloy building materials resistant to secular discoloration
are available on the market, their secular-discoloration resistance is insufficient.
Even a conventional corrosion-resistant pure titanium building material discolors
with time. The inventors of the present invention found that specific impurities contained
in the titanium material of the pure titanium building material develops the secular
discoloration of the pure titanium building material and that a pure titanium building
material formed of a pure titanium containing impurities in controlled impurity contents
are highly resistant to secular discoloration even under severe environmental conditions,
and have made the present invention.
[0021] A pure titanium building material in a preferred embodiment according to the present
invention is formed of pure titanium having an Fe content of 0.08% by mass or below,
a Nb content of 0.02% by mass or below, and a Co content of 0.02% by mass or below.
Fe, Nb and Co contained in a pure titanium forming a pure titanium building material
cause the development of secular discoloration of the pure titanium building material.
This fact was discovered by the inventors. The development of the secular discoloration
of the pure titanium building material can be remarkably retarded by controlling the
Fe, Nb and Co contents of the pure titanium below the foregoing specified Fe, Nb and
Co contents. In specifying an impurity content, "X% by mass or below" signifies that
pure titanium does not contain the impurity at all or contains the impurity in an
ignorable amount. The content is expressed in "percent by mass", which will be simply
expressed by "percent" hereinafter. Preferably, Fe content is 0.06% or below (more
preferably, 0.05% or below), Nb content is 0.015% or below (more preferably, 0.01%
or below) and Co content is 0.015% or below (more preferably, 0.01% or below).
[0022] To obtain pure titanium having Fe, Nb and Co contents not exceeding the foregoing
specified Fe, Nb and Co contents, the Fe, Nb and Co contents of a raw titanium material
are adjusted. More concretely, the impurity contents of sponge titanium, i.e., a raw
titanium material, are measured, and the sponge titanium is used if the sponge titanium
has Fe, Nb and Co contents not exceeding the foregoing specified Fe, Nb and Co contents.
[0023] The term "pure titanium" used herein signifies a substance containing Fe, Nb and
Co in contents not exceeding the specified Fe, Nb and Co contents, inevitable impurities,
and Ti as the remainder.
[0024] Preferably, the thickness of the surface oxide film of the pure titanium building
material as manufactured is 170 Å or below. The pure titanium building material having
the surface oxide film of 170 Å or below in thickness and having a composition specified
by the present invention has a beautiful silver white color characteristic of titanium.
The pure titanium building material of the present invention effectively suppresses
the growth of the surface oxide film that causes discoloration and hence the pure
titanium building material is excellent as a building material.
[0025] The thickness of the surface oxide film can be adjusted by adjusting conditions for
growing a surface oxide film during the manufacture of the pure titanium building
material. The surface oxide film grows when the pure titanium building material is
exposed to oxygen contained in the atmosphere during an annealing process and is removed
by pickling. Therefore, the thickness of the surface oxide film can be adjusted by
adjusting vacuum for vacuum annealing, the temperature of the workpiece at the start
of exposure of the vacuum annealed workpiece to the atmosphere or the degree of rinsing
after a pickling process. More concretely, the thickness of a sample surface oxide
film and conditions for forming a surface oxide film are adjusted repeatedly to determined
desirable conditions.
[0026] Although there are not any particular restrictions on a method of measuring the thickness
of the surface oxide film, the thickness can be measured by, for example, Auger electron
spectroscopy. As shown in Fig. 1, the thickness of the surface oxide film can be determined
by multiplying sputtering time required for oxygen concentration to decrease to a
middle oxygen concentration between a maximum oxygen concentration and a base oxygen
concentration by sputtering rate, i.e., (Thickness of surface oxide film) = (Sputtering
time t) × (Sputtering rate). The sputtering rate may be estimated from a sputtering
rate at which a SiO
2 film is deposited by sputtering conforming to measuring sputtering conditions.
[0027] Generally, a pure titanium building material manufacturing method of the present
invention includes, at least an ingot manufacturing process, a hot-rolling process,
a cold-rolling process and a finishing process. Conditions for those processes may
be the same as those for generally known processes. The finishing process subsequent
to the cold-rolling process must be carefully designed because the finishing process
has significant influence on the surface property of the titanium material.
[0028] For example, the finishing process for finishing the titanium material is a vacuum
annealing process (VA process) or an atmospheric annealing and pickling process (AP
finishing process). It is understood that the surface oxide film of a titanium material
finished by the VA process contains a large amount of C which causes secular discoloration.
Therefore a pickling process is preferably employed in finishing the titanium material.
The pure titanium building material manufacturing method may include an additional
process, provided that the additional process does not spoil the effect of pickling.
For example, a workpiece processed by pickling may be finished by light rolling (skin
pass) using dulling rolls in a dull surface to improve the design (sharpness) of the
workpiece.
[0029] When the surface of the workpiece is treated by pickling in the finishing process,
a titanium material having high secular discoloration resistance can be obtained by
subjecting the pickled workpiece to a heat treatment process that heats the pickled
workpiece at a temperature X (°C) in the range of 130 to 280°C for a heating time
T (min) so as to meet a condition expressed by: T ≥ 239408 × X
-2.3237. Heating the workpiece at temperatures in the range of 130 to 280°C does not cause
detrimental discoloration that spoils the design, and the heat treatment process meeting
the condition expressed by the expression has further improved secular discoloration
resistance. Although the reason why the heat treatment process improves the secular
discoloration resistance is not clearly known, it is considered that the heat treatment
process changes the construction of the oxide film.
[0030] Sometimes, detrimental discoloration occurs when the workpiece is heated at a high
temperature not lower than 250°C (250 to 280°C) for a long time in the atmosphere.
Therefore it is desirable to heat the workpiece for a heating time not longer than
30 min, more preferably 10 min or below, when the workpiece is to be heated at such
a high temperature. Even if discoloration occurs, the workpiece is colored at the
initial stage of discoloration in a very light golden color, which improves the design
instead of spoiling the same. In some cases, the heating may be stopped at such an
initial stage to provide a pure titanium building material discolored in a very light
golden color.
[0031] The heat treatment process heats the workpiece in either a vacuum atmosphere or an
atmospheric atmosphere. Any upper limit heating time is specified for the heat treatment
process that heats the workpiece in a vacuum atmosphere because there is no possibility
that the workpiece is discolored when the workpiece is heated in a vacuum atmosphere.
[0032] The pure titanium building material of the present invention thus fabricated has
very high secular discoloration resistance as compared with conventional titanium
or titanium alloy building materials.
[0033] Examples of the present invention will be described.
Example 1
Specimens
[0034] Specimens Nos. 1 to 21 of high-purity titanium (5N, Purity: 99.999% or higher) containing
impurity elements in predetermined impurity element contents and respectively having
different chemical compositions were produced to examine the effect of impurity contents
on secular discoloration.
[0035] Titanium raw materials respectively having chemical compositions shown in Table 1
were melted in a vacuum button melting furnace and ingots of a weight in the range
of 100 to 200 g were produced. The ingots were heated by a first heating process at
1000°C for 1 hr, and then the ingots were hot-rolled by a first hot-rolling process
to obtain 6 mm thick plates. The 6 mm thick plates were heated by a second heating
process at 1000°C for 10 min and by a third heating process at 850°C for 1 hr, and
the thus heated 6 mm thick plates were hot-rolled by a second hot-rolling process
to obtain 3 mm thick sheets. The thus hot-rolled sheets were annealed by an annealing
process at 800°C for 10 min, and the annealed 3 mm thick sheets were air-cooled. Oxide
scale formed on one surface of each of the annealed 3 mm thick sheets was removed
by surface grinding in a depth of 0.5 mm. Then, the 3 mm thick sheets were cold-rolled
by a cold-rolling process to obtain about 1 mm thick pure titanium sheets. The about
1 mm thick pure titanium sheets were subjected to a final finishing process that annealed
the about 1 mm thick pure titanium sheets under the following annealing conditions.
Temperature: 650°C
Time for heating up to 650°C: 5 hr
Soaking time: 3 hr
Vacuum: 10-6 torr
Cooling: Exposed to the atmosphere at 200°C or below.
Test (Secular Discoloration Resistance Test)
[0036] The effect to Fe, Nb and Co as impurities on secular discoloration was tested by
immersing the pure titanium sheets in the specimens Nos. 1 to 21 in a sulfuric acid
solution of pH4 heated at 60°C for three days to simulate a situation where building
materials are exposed to acid rain and sea wind, the specimens Nos. 1 to 21 were rinsed
to remove the sulfuric acid solution remaining on the specimens Nos. 1 to 21 completely
so that the sulfuric acid solution may not promote discoloration, and then the specimens
Nos. 1 to 21 were dried. Then, the color difference (ΔE*) of the specimens were measured
using color-difference meter.
[0037] In determining color difference, a three-dimensional color space is assumed, the
color of the specimen is decomposed into three axial components, i.e., a component
on one lightness axis (white/black), and two hue axes (red/green and yellow/blue),
and the color is represented by three-dimensional coordinates. Color difference is
the difference in color between the specimens represented by the distance between
points specified by the coordinates representing the colors. A smaller color difference
corresponds to smaller degree of discoloration. When ΔE* is less than 5, it is judged
that secular discoloration is sufficiently suppressed. Measured data is shown in Table
1, in which underlined values are those outside ranges specified by the present invention.
[0038] As obvious from Table 1, the specimens Nos. 13 to 15 having Fe contents outside the
Fe content range specified by the present invention are conspicuously discolored,
i.e., color differences are large. Similarly, the specimens Nos. 16 and 17 having
Nb contents and Co contents outside a Nb content range and a Co content range specifiedby
the present invention, the specimen Nos. 19 and 21 having Nb contents outside the
specified Nb content range, and the specimens Nos. 18 and 20 having Co contents outside
the specified Co content range are discolored excessively and have color differences
ΔE* exceeding 5, even though those specimens have Fe contents within the specified
Fe content range.
[0039] On the other hand the specimens Nos. 1 to 12 having Fe, Nb and Co contents within
the specified Fe, Nb and Co content ranges have color differences ΔE* below 5, and
high secular discoloration resistance.
Example 2
Specimens
[0040] Pure titanium sheets of about 1 mm in thickness in specimens Nos. 22 to 45 having
chemical compositions shown in Table 2 were produced by the same process as that by
which the specimens Nos. 1 to 21 in Example 1 were produced.
[0041] The specimens Nos. 22 and 23 were subjected to pickling instead of vacuum annealing
in the last process; that is, the specimens Nos. 22 and 23 were treated by atmospheric
annealing at 700°C for 20 s after cold rolling, salt immersion at 550°C for 15 s,
and pickling of 40 µm in thickness using a mixture heated at 40°C and containing 15%
by mass nitric acid and 1.5% by mass hydrofluoric acid.
Test
[0042] The thickness of the surface oxide film of each of the specimens was measured before
immersing the specimens in a sulfuric acid solution for a secular discoloration resistance
test. More concretely, the specimens were subjected to ultrasonic cleaning in acetone,
the specimens were dried and oxygen concentration was measured under the following
conditions.
Apparatus: Scanning Auger Spectroscope, PH1650 (Parkin Elmer Co.)
Primary electrons: Energy 5 keV, Current: 300 nA, Incident angle: 30° to the normal
to the specimen
Analyzed area: about 10 µm × about 10 µm
Ion sputtering: Energy: 3 keV, Current: 25 mA, Incident angle: about 58° to the normal
to the specimen, Sputtering rate about 1.9 nm/min (SiO2 equivalent)
[0043] The thickness of the surface oxide film was calculated using measured data. The thickness
was determined by multiplying sputtering time (measured time) required for oxygen
concentration to decrease to a middle oxygen concentration between a maximum oxygen
concentration and a base oxygen concentration by sputtering rate of about 1.9 nm/min.
[0044] The color differences ΔE* of the specimens were measured similarly after the measurement
of the thickness of the surface oxide film. Measured data is shown in Table 2.
[0045] As obvious from Table 2, the pure titanium materials having Fe, Nb and Co contents
within the specified Fe, Nb and Co content ranges have color differences ΔE* below
5 and have high secular discoloration resistance.
[0046] The color differences ΔE* of the specimens finished by vacuum annealing are greater
than those of the specimens finished by pickling. Thus, it is preferable to finish
pure titanium building materials by pickling.
[0047] It was found that the specimens having the surface oxide films of a thickness not
greater than 170 Å have desirably small color differences ΔE* and sufficient secular
discoloration resistance.
Example 3
Specimens
[0048] Pure titanium sheets in specimens Nos. 46 to 83 were produced by using a pickling
process similar to that employed in Example 2. The specimens Nos. 46 to 83 had an
Fe content of 0.06 or 0.03% by mass, an Nb content of 0.001% by mass and a Co content
of 0.001% by mass. The specimens were finished by heat treatment processes under conditions
shown in Table 3. Values of 239408 × X
-2.3237 were calculated.
Test
[0049] The color differences of the specimens Nos. 46 to 83 were measured similarly to those
of the specimens in Example 1. Measured data is shown in Table 4.
[0050] The measured data shown in Table 4 proves that finishing pure titanium building materials
by a finishing process including pickling and subsequent heating treatment improves
the secular discoloration resistance remarkably.
[0051] Heating times for the heat treatment processes P, Q and R were shorter than the minimum
heating time expressed by 239408 × X
-2.3237 and hence the effect of the heat treatment processes P, Q and R is somewhat low.
Thus, it was known that the heating time T must meet an expression: T ≥ 239408 × X
-2.3237 for the further improvement of the secular discoloration resistance. Fig. 2 shows
the relation between heating time and heating temperature.
[0052] Although the specimen processed by the heat treatment process S has a small color
difference ΔE*, the specimen was colored in a golden color due to heating in the atmosphere
at a high temperature of 280°C for a long time of 150 min. Although pure titanium
building materials colored in such a golden color are unsuitable when noncolored pure
titanium building materials are desired, pure titanium building materials colored
in such a golden color have uses.
[0053] Although the color difference ΔE* of the specimen processed by the heat treatment
process L specifying a heating temperature of 280°C and a heating time of 120 min
is greater than that of the specimen processed by the heat treatment process S, the
color difference ΔE* is satisfactorily small. The specimen processed by the heat treatment
process L was colored less than that processed by the heat treatment process S, and
was colored in a golden color.
[0054] Heating time must be 30 min or shorter, more preferably, 10 min or shorter to prevent
coloring due to high-temperature heating in the atmosphere.
Table 1
Specimen No. |
Fe content (% by mass) |
Nb content (% by mass) |
Co content (% by mass) |
ΔE* |
1 |
0.08 |
0.02 |
0.02 |
4.5 |
2 |
0.08 |
0.01 |
0.01 |
4.0 |
3 |
0.08 |
0.005 |
0.005 |
3.3 |
4 |
0.08 |
0.001 |
0.001 |
2.9 |
5 |
0.06 |
0.02 |
0.02 |
2.5 |
6 |
0.06 |
0.01 |
0.01 |
2.4 |
7 |
0.06 |
0.005 |
0.005 |
2.1 |
8 |
0.06 |
0.001 |
0.001 |
1.9 |
9 |
0.03 |
0.02 |
0.02 |
2.2 |
10 |
0.03 |
0.01 |
0.01 |
2.1 |
11 |
0.03 |
0.005 |
0.005 |
1.8 |
12 |
0.03 |
0.001 |
0.001 |
1.3 |
13 |
0.10 |
0.001 |
0.001 |
9.1 |
14 |
0.15 |
0.001 |
0.001 |
14.7 |
15 |
0.20 |
0.001 |
0.001 |
18.2 |
16 |
0.08 |
0.03 |
0.03 |
8.9 |
17 |
0.03 |
0.03 |
0.03 |
6.9 |
18 |
0.08 |
0.005 |
0.03 |
6.6 |
19 |
0.08 |
0.03 |
0.005 |
6.3 |
20 |
0.03 |
0.005 |
0.03 |
5.4 |
21 |
0.03 |
0.03 |
0.005 |
5.7 |
Table 2
Specimen No. |
Fe content (% by mass) |
Nb content (% by mass) |
Co content (% by mass) |
Finishing process |
Thickness of oxide film (Å) |
ΔE* |
22 |
0.08 |
0.02 |
0.02 |
Pickling |
140 |
2.8 |
23 |
0.08 |
0.01 |
0.01 |
Pickling |
120 |
1.6 |
24 |
0.08 |
0.005 |
0.005 |
Pickling |
110 |
1.2 |
25 |
0.08 |
0.001 |
0.001 |
Pickling |
120 |
0.8 |
26 |
0.06 |
0.02 |
0.02 |
Pickling |
100 |
2.1 |
27 |
0.06 |
0.01 |
0.01 |
Pickling |
130 |
1.3 |
28 |
0.06 |
0.005 |
0.005 |
Pickling |
160 |
1.0 |
29 |
0.06 |
0.001 |
0.001 |
Pickling |
150 |
0.7 |
30 |
0.03 |
0.02 |
0.02 |
Pickling |
160 |
1.8 |
31 |
0.03 |
0.01 |
0.01 |
Pickling |
170 |
1.1 |
32 |
0.03 |
0.005 |
0.005 |
Pickling |
170 |
0.8 |
33 |
0.03 |
0.001 |
0.001 |
Pickling |
110 |
0.6 |
34 |
0.08 |
0.02 |
0.02 |
Vacuum annealing |
130 |
4.5 |
35 |
0.08 |
0.01 |
0.01 |
Vacuum annealing |
140 |
4.0 |
36 |
0.08 |
0.005 |
0.005 |
Vacuum annealing |
130 |
3.3 |
37 |
0.08 |
0.001 |
0.001 |
Vacuum annealing |
150 |
2.9 |
38 |
0.06 |
0.02 |
0.02 |
Vacuum annealing |
150 |
2.5 |
39 |
0.06 |
0.01 |
0.01 |
Vacuum annealing |
160 |
2.4 |
40 |
0.06 |
0.005 |
0.005 |
Vacuum annealing |
170 |
2.1 |
41 |
0.06 |
0.001 |
0.001 |
Vacuum annealing |
110 |
1.9 |
42 |
0.03 |
0.02 |
0.02 |
Vacuum annealing |
90 |
2.2 |
43 |
0.03 |
0.01 |
0.01 |
Vacuum annealing |
80 |
2.1 |
44 |
0.03 |
0.005 |
0.005 |
Vacuum annealing |
160 |
1.8 |
45 |
0.03 |
0.001 |
0.001 |
Vacuum annealing |
120 |
1.3 |
Table 3
Heating process |
|
Heating conditions |
|
239408 × X- 23237 |
|
Heating temperature (°C) |
Soaking time (min) |
|
|
(A) |
130 |
3 |
Atmospheric |
2.93 |
(B) |
130 |
20 |
Atmospheric |
2.93 |
(C) |
130 |
60 |
Atmospheric |
2.93 |
(D) |
130 |
120 |
Atmospheric |
2.93 |
(E) |
200 |
1.1 |
Atmospheric |
1.08 |
(F) |
200 |
20 |
Atmospheric |
1.08 |
(G) |
200 |
60 |
Atmospheric |
1.08 |
(H) |
200 |
120 |
Atmospheric |
1.08 |
(l) |
280 |
0.5 |
Atmospheric |
0.49 |
(J) |
280 |
20 |
Atmospheric |
0.49 |
(K) |
280 |
60 |
Atmospheric |
0.49 |
(L) |
280 |
120 |
Atmospheric |
0.49 |
(M) |
130 |
120 |
Vacuum |
2.93 |
(N) |
200 |
120 |
Vacuum |
1.08 |
(O) |
280 |
120 |
Vacuum |
0.49 |
(P) |
130 |
2 |
Atmospheric |
2.93 |
(Q) |
200 |
0.5 |
Atmospheric |
1.08 |
(R) |
280 |
0.2 |
Atmospheric |
0.49 |
(S) |
280 |
150 |
Atmospheric |
0.49 |
Table 4
Specimen No. |
Fe content (% by mass) |
Nb content (% by mass) |
Co content (% by mass) |
Finishing process |
Heat treatment process |
ΔE* |
46 |
0.06 |
0.001 |
0.001 |
Pickling |
(A) |
0.4 |
47 |
0.06 |
0.001 |
0.001 |
Pickling |
(B) |
0.4 |
48 |
0.06 |
0.001 |
0.001 |
Pickling |
(C) |
0.3 |
49 |
0.06 |
0.001 |
0.001 |
Pickling |
(D) |
0.3 |
50 |
0.06 |
0.001 |
0.001 |
Pickling |
(E) |
0.4 |
51 |
0.06 |
0.001 |
0.001 |
Pickling |
(F) |
0.3 |
52 |
0.06 |
0.001 |
0.001 |
Pickling |
(G) |
0.3 |
53 |
0.06 |
0.001 |
0.001 |
Pickling |
(H) |
0.2 |
54 |
0.06 |
0.001 |
0.001 |
Pickling |
(l) |
0.3 |
55 |
0.06 |
0.001 |
0.001 |
Pickling |
(J) |
0.3 |
56 |
0.06 |
0.001 |
0.001 |
Pickling |
(K) |
0.2 |
57 |
0.06 |
0.001 |
0.001 |
Pickling |
(L) |
0.2 |
58 |
0.06 |
0.001 |
0.001 |
Pickling |
(M) |
0.4 |
59 |
0.06 |
0.001 |
0.001 |
Pickling |
(N) |
0.3 |
60 |
0.06 |
0.001 |
0.001 |
Pickling |
(O) |
0.3 |
61 |
0.03 |
0.001 |
0.001 |
Pickling |
(A) |
0.3 |
62 |
0.03 |
0.001 |
0.001 |
Pickling |
(B) |
0.2 |
63 |
0.03 |
0.001 |
0.001 |
Pickling |
(C) |
0.2 |
64 |
0.03 |
0.001 |
0.001 |
Pickling |
(D) |
0.2 |
65 |
0.03 |
0.001 |
0.001 |
Pickling |
(E) |
0.2 |
66 |
0.03 |
0.001 |
0.001 |
Pickling |
(F) |
0.2 |
67 |
0.03 |
0.001 |
0.001 |
Pickling |
(G) |
0.2 |
68 |
0.03 |
0.001 |
0.001 |
Pickling |
(H) |
0.1 |
69 |
0.03 |
0.001 |
0.001 |
Pickling |
(l) |
0.2 |
70 |
0.03 |
0.001 |
0.001 |
Pickling |
(J) |
0.1 |
71 |
0.03 |
0.001 |
0.001 |
Pickling |
(K) |
0.1 |
72 |
0.03 |
0.001 |
0.001 |
Pickling |
(L) |
0.1 |
73 |
0.03 |
0.001 |
0.001 |
Pickling |
(M) |
0.2 |
74 |
0.03 |
0.001 |
0.001 |
Pickling |
(N) |
0.2 |
75 |
0.03 |
0.001 |
0.001 |
Pickling |
(O) |
0.2 |
76 |
0.06 |
0.001 |
0.001 |
Pickling |
(P) |
0.7 |
77 |
0.06 |
0.001 |
0.001 |
Pickling |
(Q) |
0.7 |
78 |
0.06 |
0.001 |
0.001 |
Pickling |
(R) |
0.7 |
79 |
0.06 |
0.001 |
0.001 |
Pickling |
(S) |
0.1 |
80 |
0.03 |
0.001 |
0.001 |
Pickling |
(P) |
0.6 |
81 |
0.03 |
0.001 |
0.001 |
Pickling |
(Q) |
0.6 |
82 |
0.03 |
0.001 |
0.001 |
Pickling |
(R) |
0.6 |
83 |
0.03 |
0.001 |
0.001 |
Pickling |
(S) |
0 |