TECHNICAL FIELD
[0001] This disclosure relates to a high-Mn steel suitable for a structure used in cryogenic
environments, such as a tank for liquefied gas storage, and a method for manufacturing
the same.
BACKGROUND
[0002] A structure for liquefied gas storage is used at cryogenic temperatures. Therefore,
a steel sheet used for this type of structure is required to have not only high strength
but also excellent toughness at cryogenic temperatures. For example, when a hot rolled
steel sheet is used for liquefied natural gas storage, it is necessary to ensure excellent
toughness at a temperature of -164 °C, which is the boiling point of the liquefied
natural gas, or lower. If the low-temperature toughness of the steel material is inferior,
the safety as a structure for cryogenic storage may not be maintained. Therefore,
there is a strong demand for improving the low-temperature toughness of the applied
steel material.
[0003] In response to this demand, austenitic stainless steel, 9 % Ni steel, and 5000 series
aluminum alloy, where austenite, which does not exhibit brittleness at cryogenic temperatures,
is the main structure of the steel sheet, have conventionally been used. However,
because of the high alloy cost and manufacturing cost, there has been a desire for
a steel material that is inexpensive yet has excellent low-temperature toughness.
[0004] JP 2016-84529 A (PTL 1) and
JP 2016-196703 A (PTL 2) propose using a high-Mn steel containing a large amount of Mn, which is a
relatively inexpensive austenite-stabilizing element, as a structural steel in cryogenic
environments, as a new steel material to replace conventional cryogenic steels.
[0005] That is, PTL 1 proposes controlling the carbide coverage of austenite crystal grain
boundaries, and PTL 2 proposes controlling the austenite crystal grain size by a carbide
coating as well as addition of Mg, Ca, and REM.
CITATION LIST
Patent Literature
SUMMARY
(Technical Problem)
[0007] However, in applications such as tanks for liquefied gas storage, it is required
to have excellent fracture resistance under severe fracture conditions in which an
initial crack becomes sharper, specifically, excellent CTOD property at low temperatures
from the viewpoint of ensuring the safety of the tanks. Although PTL 1 and PTL 2 described
above evaluate the low-temperature toughness by a Charpy impact test, they do not
guarantee excellent CTOD property.
[0008] It could thus be helpful to provide a high-Mn steel which not only has high strength
and excellent low-temperature toughness but also has excellent CTOD property at low
temperatures. As used herein, the "high strength" means that the yield strength is
400 MPa or more, the "excellent low-temperature toughness" means that the absorbed
energy vE-196 of a Charpy impact test at -196 °C is 100 J or more, and the "excellent
CTOD property at low temperatures" means that the CTOD value at -165 °C is 0.25 mm
or more.
(Solution to Problem)
[0009] We have conducted extensive research on methods for solving the problem with respect
to high-Mn steels. As a result, we found the following a to b.
- a. High-Mn steels do not develop brittle fractures even at cryogenic temperatures,
and, if a fracture occurs, it is generated from crystal grain boundaries. Therefore,
in order to improve the fracture resistance of high-Mn steels, it is effective to
regulate the size of crystal grains in anticipation of reducing the area of crystal
grain boundaries that are the starting point of fractures.
- b. In addition, realizing homogenization in conjunction with the above regulation
of crystal grain size is more effective in improving the fracture resistance of high-Mn
steels.
- c. As means for achieving the above a and b, it is appropriate to perform hot rolling
and cooling under appropriate manufacturing conditions.
[0010] The present disclosure is based on the aforementioned findings and further studies.
We thus provide the following.
- 1. A high-Mn steel comprising
a chemical composition containing (consisting of), in mass%,
C: 0.10 % or more and 0.70 % or less,
Si: 0.05 % or more and 0.50 % or less,
Mn: 20 % or more and 30 % or less,
P: 0.030 % or less,
S: 0.0070 % or less,
Al: 0.01 % or more and 0.07 % or less,
Cr: 0.5 % or more and 7.0 % or less,
Ni: 0.01 % or more and less than 0.1 %,
Ca: 0.0005 % or more and 0.0050 % or less,
N: 0.0050 % or more and 0.0500 % or less,
O: 0.0050 % or less,
Ti: less than 0.0050 %, and
Nb: less than 0.0050 %,
the balance consisting of Fe and inevitable impurities, and
a microstructure having austenite as a base phase, where the austenite has a grain
size of 1 µm or more and a standard deviation of 9 µm or less.
- 2. The high-Mn steel according to the above 1., wherein the chemical composition further
contains, in mass%, at least one selected from the group consisting of
Cu: 1.0 % or less,
Mo: 2.0 % or less,
V: 2.0 % or less,
W: 2.0 % or less,
Mg: 0.0005 % or more and 0.0050 % or less, and
REM: 0.0010 % or more and 0.0200 % or less.
- 3. A method of manufacturing a high-Mn steel, comprising heating a steel material
having the chemical composition according to the above 1. or 2. to a temperature range
of 1100 °C or higher and 1300 °C or lower, then subjecting the steel material to hot
rolling where a rolling finish temperature is 750 °C or higher and lower than 950
°C and an average rolling reduction for one pass is 9 % or more, and then subjecting
the hot rolled material to cooling where an average cooling rate from a temperature
of (rolling finish temperature - 100 °C) or higher to a temperature range of 300 °C
or higher and 650 °C or lower is 1.0 °C/s or more.
(Advantageous Effect)
[0011] According to the present disclosure, it is possible to provide a high-Mn steel having
excellent CTOD property and low-temperature toughness especially at cryogenic temperatures.
Therefore, by using the high-Mn steel of the present disclosure, it is possible to
realize an improvement in safety and product life of a steel structure used in cryogenic
environments, such as a tank for liquefied gas storage, which exhibits remarkable
industrial effects.
DETAILED DESCRIPTION
[0012] The following describes the high-Mn steel of the present disclosure in detail.
[Chemical composition]
[0013] First, the chemical composition of the high-Mn steel of the present disclosure and
reasons for limitation will be described. Note that the unit "%" of each component
is "mass%" unless otherwise specified.
C: 0.10 % or more and 0.70 % or less
[0014] C is an inexpensive austenite-stabilizing element and is an important element in
obtaining austenite. To obtain this effect, the C content needs to be 0.10 % or more.
On the other hand, when the C content exceeds 0.70 %, Cr carbides are excessively
formed, and the low-temperature toughness is deteriorated. Therefore, the C content
is 0.10 % or more and 0.70 % or less. The C content is preferably 0.20 % or more.
The C content is preferably 0.60 % or less.
Si: 0.05 % or more and 0.50 % or less
[0015] Si is an element that acts as a deoxidizing material. It not only is necessary for
steelmaking but also dissolves in steel to increase the strength of a steel sheet
by solid solution strengthening. To obtain these effects, the Si content needs to
be 0.05 % or more. On the other hand, when the Si content exceeds 0.50 %, the weldability
is deteriorated and the low-temperature toughness, especially the toughness at cryogenic
temperatures is lowered. Therefore, the Si content is 0.05 % or more and 0.50 % or
less. The Si content is preferably 0.07 % or more and 0.50 % or less.
Mn: 20 % or more and 30 % or less
[0016] Mn is a relatively inexpensive austenite-stabilizing element. Mn is an important
element for the present disclosure to achieve both the strength and the toughness
at cryogenic temperatures. To obtain this effect, the Mn content needs to be 20 %
or more. On the other hand, when the content exceeds 30 %, the effect of improving
low-temperature toughness saturates, leading to an increase in alloy cost. In addition,
the weldability and the cuttability deteriorate. Further, it promotes segregation
and promotes the occurrence of stress corrosion cracking. Therefore, the Mn content
is 20 % or more and 30 % or less. The Mn content is preferably 23 % or more. The Mn
content is preferably 28 % or less.
P: 0.030 % or less
[0017] When P is contained in excess of 0.030 %, it segregates at grain boundaries and becomes
a starting point of stress corrosion cracking. Therefore, the upper limit is set to
0.030 %, and the P content is desirably as low as possible. Thus, the P content is
0.030 % or less. Note that the P content is desirably 0.002 % or more, because excessive
reduction of P content increases refining cost and is economically disadvantageous.
The P content is preferably 0.005 % or more. The P content is preferably 0.028 % or
less. The P content is more preferably 0.024 % or less.
S: 0.0070 % or less
[0018] S is an element that deteriorates low-temperature toughness and base metal ductility.
Therefore, the upper limit is set to 0.0070 %, and the S content is desirably as low
as possible. Thus, the S content is 0.0070 % or less. Note that the S content is desirably
0.001 % or more, because excessive reduction of S content increases refining cost
and is economically disadvantageous. The S content is preferably 0.0020 % or more.
The S content is preferably 0.0060 % or less.
Al: 0.01 % or more and 0.07 % or less
[0019] Al acts as a deoxidizer and is most commonly used in a molten steel deoxidation process
of a steel sheet. To obtain this effect, the Al content needs to be 0.01 % or more.
On the other hand, when the Al content exceeds 0.07 %, Al is mixed into a weld metal
part during welding and deteriorates the toughness of the weld metal. Therefore, the
Al content is 0.07 % or less. Thus, the Al content is 0.01 % or more and 0.07 % or
less. The Al content is preferably 0.02 % or more. The Al content is preferably 0.06
% or less.
Cr: 0.5 % or more and 7.0 % or less
[0020] Cr is an element that stabilizes austenite when added in an appropriate amount and
is an element effective in improving low-temperature toughness and base metal strength.
To obtain these effects, the Cr content needs to be 0.5 % or more. On the other hand,
when the content exceeds 7.0 %, the low-temperature toughness and the stress corrosion
cracking resistance are deteriorated due to formation of Cr carbides. Therefore, the
Cr content is 0.5 % or more and 7.0 % or less. The Cr content is preferably 1.0 %
or more. The Cr content is preferably 6.7 % or less. The Cr content is more preferably
1.2 % or more. The Cr content is more preferably 6.5 % or less. In order to further
improve the stress corrosion cracking resistance, the content is still more preferably
2.0 % or more and 6.0 % or less.
Ni: 0.01 % or more and less than 0.1 %
[0021] Ni has the effect of improving low-temperature toughness. However, minimizing the
necessary alloy cost is an important viewpoint in designing the composition of the
present disclosure, and from this viewpoint, the Ni content is 0.01 % or more and
less than 0.1 %. Examples of austenitic steels having excellent low-temperature toughness
include stainless steels such as SUS304 and SUS316. However, a large amount of Ni
is added in these steels to optimize the Ni equivalent and the Cr equivalent as an
alloy design for obtaining an austenitic structure. Compared with these steels, the
present disclosure is an austenitic material whose price is lowered by minimizing
necessary Ni. Note that the minimization of necessary Ni is realized by optimizing
the addition amount of Mn. The Ni content is preferably 0.03 % or more. The Ni content
is preferably 0.07 % or less.
Ca: 0.0005 % or more and 0.0050 % or less
[0022] Ca improves ductility, toughness and sulfide stress corrosion cracking resistance
by controlling the morphology of inclusions described below. In addition, Ca suppresses
the deterioration of hot ductility and is effective in reducing the occurrence of
cracks in cast steel. To obtain these effects, the Ca content needs to be 0.0005 %
or more. On the other hand, when the Ca content exceeds 0.0050 %, the ductility, toughness,
and sulfide stress corrosion cracking resistance may be rather deteriorated, and the
effect of suppressing the deterioration of hot ductility may saturate. Therefore,
the Ca content is 0.0005 % or more and 0.0050 % or less. The Ca content is preferably
0.0010 % or more. The Ca content is preferably 0.0045 % or less.
N: 0.0050 % or more and 0.0500 % or less
[0023] N is an austenite-stabilizing element and is an element effective in improving low-temperature
toughness. To obtain these effects, the N content needs to be 0.0050 % or more. On
the other hand, when the content exceeds 0.0500 %, nitrides or carbonitrides are coarsened
and the toughness is deteriorated. Therefore, the N content is 0.0050 % or more and
0.0500 % or less. The N content is preferably 0.0060 % or more. The N content is preferably
0.0400 % or less.
O: 0.0050 % or less
[0024] O deteriorates low-temperature toughness due to formation of oxides. Therefore, the
O content is in the range of 0.0050 % or less. The O content is preferably 0.0045
% or less. Note that the O content is desirably 0.0003 % or more, because excessive
reduction of O content increases refining cost and is economically disadvantageous.
Ti and Nb contents each suppressed to less than 0.005 %
[0025] Ti and Nb form high-melting carbonitrides in steel and suppress the coarsening of
crystal grains, and as a result, they become a starting point of fractures and propagation
path of cracks. In particular, they hinder the microstructure control for enhancing
the low-temperature toughness and improving the ductility in the high-Mn steel. Therefore,
the contents of Ti and Nb must be suppressed intentionally. That is, Ti and Nb are
components inevitably mixed from raw materials and the like, and they are generally
mixed in the ranges of Ti: 0.005 % to 0.010 % and Nb: 0.005 % to 0.010 %. Therefore,
it is necessary to avoid the inevitable mixing of Ti and Nb and to suppress the content
of each of Ti and Nb to less than 0.005 % according to a method described below. By
suppressing the content of each of Ti and Nb to less than 0.005 %, it is possible
to eliminate the above-mentioned adverse effects of carbonitrides and to ensure excellent
low-temperature toughness and ductility. The contents of Ti and Nb are preferably
0.003 % or less.
[0026] The balance other than the above essential components is iron and inevitable impurities.
Examples of the inevitable impurities here include H, and a total of 0.01 % or less
is acceptable.
[0027] In order to further improve strength and low-temperature toughness, the following
elements can be contained as necessary in addition to the above essential components
in the present disclosure.
At least one of Cu: 1.0 % or less, Mo: 2.0 % or less, V: 2.0 % or less, W: 2.0 % or
less, Mg: 0.0005 % to 0.0050 %, or REM: 0.0010 % to 0.0200 % Cu: 1.0 % or less, Mo,
V, W: each 2.0 % or less
[0028] Cu, Mo, V and W contribute to the stabilization of austenite and to the improvement
of base metal strength. To obtain these effects, the contents of Cu, Mo, V and W are
preferably 0.001 % or more. On the other hand, when the Cu content exceeds 1.0 % and
the contents of Mo, V and W each exceed 2.0 %, coarse carbonitrides are formed, which
may be a starting point of fractures, and the manufacturing cost also increases. Therefore,
when these alloying elements are contained, the contents are 1.0 % or less for Cu
and 2.0 % or less for Mo, V and W. The contents are preferably 0.003 % or more. Further,
the contents of Mo, V and W are preferably 1.7 % or less. The contents of Mo, V and
W are more preferably 1.5 % or less.
Mg: 0.0005 % to 0.0050 %, and REM: 0.0010 % to 0.0200 %
[0029] Mg and REM are useful elements for controlling the morphology of inclusions and can
be contained as necessary. Controlling the morphology of inclusions means making expanded
sulfide-based inclusions into granular inclusions. By controlling the morphology of
inclusions, the ductility, toughness and sulfide stress corrosion cracking resistance
are improved. To obtain these effects, the Ca and Mg contents are preferably 0.0005
% or more, and the REM content is preferably 0.0010 % or more. On the other hand,
when any of these elements is contained in a large amount, the amount of nonmetallic
inclusions increases, and the ductility, toughness, and sulfide stress corrosion cracking
resistance may rather be deteriorated. In addition, it may be economically disadvantageous.
Therefore, when Mg is contained, the content is 0.0005 % to 0.0050 %, and when REM
is contained, the content is 0.0010 % to 0.0200 %. The Mg content is preferably 0.0010
% or more. The Mg content is preferably 0.0040 % or less. The REM content is preferably
0.0020 % or more. The REM content is preferably 0.0150 % or less.
[Microstructure]
Microstructure having austenite as a base phase
[0030] When the crystal structure of a steel material is a body-centered cubic structure
(bcc), the steel material is not suitable for use in low-temperature environments
because it may cause brittle fractures in low-temperature environments. In consideration
of the use in low-temperature environments, the base phase of the steel material should
be an austenitic structure where the crystal structure is a face-centered cubic structure
(fcc). As used here, "austenite as a base phase" means that the austenite phase has
an area ratio of 90 % or more. The remainder other than the austenite phase is a ferrite
phase or a martensite phase. Of course, the austenite phase may be 100 %.
Austenite grain size: 1 µm or more
[0031] Because the high-Mn steel has a microstructure having austenite as a base phase,
brittle fractures do not occur even at cryogenic temperatures, and, if a fracture
occurs, it is generated from crystal grain boundaries. It is advantageous to reduce
the area of crystal grain boundaries, which are the starting point of fractures, to
improve the fracture resistance of the high-Mn steel. Therefore, it is important that
the austenite grain size be 1 µm or more. This is because, when the grain size is
less than 1 µm, the increasing amount of grain boundary area increases, which increases
the number of locations where fractures occur. It is preferably 2 µm or more.
Standard deviation of austenite: 9 µm or less
[0032] Realizing homogenization in conjunction with the regulation of crystal grain size
is effective in further improving the fracture resistance of the high-Mn steel. That
is, in a mixed-grain-size microstructure, a wide grain size distribution from coarse
crystal grains to fine crystal grains results in containing of crystal grains of less
than 1 µm, and especially when the standard deviation exceeds 9 µm, the tendency is
remarkable. Therefore, it is necessary to avoid a mixed-grain-size microstructure
having a standard deviation of more than 9 µm.
[Manufacturing method]
[0033] During the manufacture of the high-Mn steel of the present disclosure, first, the
steel material may be a molten steel having the above-described chemical composition
obtained with a known smelting method such as a converter or an electric furnace.
In addition, secondary refinement may be performed in a vacuum degassing furnace.
At that time, in order to limit Ti and Nb, which hinder the control of a preferable
microstructure, to the above-described ranges, it is necessary to avoid inevitable
mixing from raw materials and the like and take measures to reduce the contents thereof.
For example, by lowering the basicity of slag in the refining stage, these alloys
are concentrated and discharged into the slag, which reduces the concentration of
Ti and Nb in a final slab product. Alternatively, a method of blowing oxygen to oxidize
the Ti and Nb and floating and separating the alloy of Ti and Nb in reflux may also
be used. Subsequently, it is preferable to obtain a steel material such as a slab
having a predetermined size with a known casting method such as a continuous casting
method or an ingot casting method. It is also acceptable to subject the slab after
continuous casting to blooming to obtain a steel material.
[0034] The following specifies the manufacturing conditions for making the above steel material
into a steel material having excellent low-temperature toughness.
Steel material heating temperature: 1100 °C or higher and 1300 °C or lower
[0035] The heating temperature before hot rolling is 1100 °C or higher to increase the crystal
grain size of the microstructure of the steel material. However, when the temperature
exceeds 1300 °C, partial melting may start. Therefore, the upper limit of the heating
temperature is set to 1300 °C. The temperature control here is based on the surface
temperature of the steel material.
Rolling finish temperature: 750 °C or higher and lower than 950 °C
[0036] The steel material (steel ingot or slab) is subjected to hot rolling after the heating.
In order to obtain coarse crystal grains, it is preferable to increase the cumulative
rolling reduction at high temperatures. That is, performing hot rolling at a low temperature
makes the microstructure fine and causes excessive working strain. As a result, the
low-temperature toughness is deteriorated. Therefore, the lower limit of the rolling
finish temperature is set to 750 °C. On the other hand, when the finish temperature
is in the range of 950 °C or higher, the crystal grain size becomes excessively coarse,
and a desired yield strength cannot be obtained. Therefore, it is necessary to perform
the final finish rolling of one or more passes at a temperature of lower than 950
°C. It is preferably 900 °C or lower.
Average rolling reduction for one pass: 9 % or more
[0037] During the hot rolling, in order to realize the homogenization of austenite grain
size and control the crystal grain size to 1 µm or more, it is effective to promote
the recrystallization of austenite, and it is important to have an average rolling
reduction for one pass of 9 % or more during the hot rolling. It is preferably 11
% or more.
Average cooling rate from a temperature of (rolling finish temperature - 100 °C) or
higher to a temperature range of 300 °C or higher and 650 °C or lower: 1.0 °C/s or
more
[0038] Cooling is immediately performed after the hot rolling. If the steel sheet after
hot rolling is cooled slowly, formation of precipitates is promoted and the low-temperature
toughness is deteriorated. The formation of these precipitates can be suppressed by
cooling the steel sheet at a cooling rate of 1.0 °C/s or more. Excessive cooling distorts
the steel sheet and lowers the productivity. Therefore, the upper limit of the cooling
start temperature is set to 900 °C. For the above reasons, in the cooling after the
hot rolling, the average cooling rate at the steel sheet surface from a temperature
of (rolling finish temperature - 100 °C) or higher to a temperature range of 300 °C
or higher and 650 °C or lower is 1.0 °C/s or more. On the other hand, from the viewpoint
of industrial production, the average cooling rate is preferably 200 °C/s or less.
EXAMPLES
[0039] The following provides a more detailed explanation of the present disclosure through
examples. However, the present disclosure is not limited to the following examples.
[0040] Steel slabs having the chemical composition listed in Table 1 were prepared by a
process for refining with converter and ladle and continuous casting. Next, the steel
slabs thus obtained were subjected to blooming and hot rolling under the conditions
listed in Table 2 to obtain steel sheets having a thickness of 10 mm to 30 mm. The
steel sheets thus obtained were subjected to tensile property, toughness and microstructure
evaluation as described below.
(1) Tensile test property
[0041] A JIS No. 5 tensile test piece was collected from each steel sheet thus obtained,
and the tensile test piece was subjected to a tensile test according to the provisions
of JIS Z2241 (1998) to investigate the tensile test property. In the present disclosure,
a yield strength of 400 MPa or more and a tensile strength of 800 MPa or more were
determined to be excellent in tensile properties. Further, elongation of 40 % or more
was determined to be excellent in ductility.
(2) Low-temperature toughness
[0042] A Charpy V-notch test piece was collected from a direction parallel to the rolling
direction at a position at a depth of one-fourth of the sheet thickness from the surface
of each steel sheet having a thickness of more than 20 mm (hereinafter referred to
as "position of sheet thickness × 1/4"), or a position at a depth of half of the sheet
thickness of each steel sheet having a thickness of 20 mm or less (hereinafter referred
to as "position of sheet thickness × 1/2") according to the provisions of JIS Z2202
(1998). Three Charpy impact tests were performed on each steel sheet according to
the provisions of JIS Z2242 (1998) to determine the absorbed energy at -196 °C, thereby
evaluating the base metal toughness. In the present disclosure, when the average of
three absorbed energy (vE-196) values was 100 J or more, it was determined to be excellent
in base metal toughness.
(3) CTOD value evaluation
[0043] A CTOD test piece was collected from a direction parallel to the rolling direction
at the position of sheet thickness × 1/2 of the steel sheet, and two or three tests
were conducted at -165 °C to evaluate the average value. In the present disclosure,
a CTOD value of 0.25 mm or more was determined to be excellent in fracture resistance.
(4) Microstructure
[0044] Electron backscatter diffraction (EBSD) analysis was performed on a L cross section
at the position of sheet thickness × 1/4 of the steel sheet. Two or three visual fields
of 200 µm × 200 µm were selected arbitrarily and observed, and the minimum value of
austenite crystal grain size in each visual field was measured. In addition, the standard
deviation of the austenite grain size was evaluated from the distribution of the area
ratio of each crystal grain size using the results of the EBSP analysis. All the crystal
grain sizes thus obtained were taken as a population, a variance that is a sum of
squares of the difference between each individual value and the average value was
obtained, and a square root of the variance was obtained to determine the standard
deviation.
[0045] The evaluation results thus obtained are listed in Table 3.
[0046] It has been confirmed that the high-Mn steel of the present disclosure satisfies
the above-mentioned desired performance (the yield strength of base metal is 400 MPa
or more, the average value of absorbed energy (vE-196) is 100 J or more with respect
to the low-temperature toughness, and the average value of CTOD value is 0.25 mm or
more). On the other hand, Comparative Examples, which are outside the scope of the
present disclosure, do not satisfy at least one of the above-mentioned desired performance
of yield strength, low-temperature toughness, and CTOD value.
Table 2
Sample No. |
Steel No. |
Plate thickness (mm) |
Hot rolling method |
Remarks |
Slab heating temperature (°C) |
Rolling finish temperature (°C) |
Average rolling reduction for one pass (%) |
Cooling start temperature (°C) |
Cooling rate until the range of 300 °C or higher and 650 °C or lower (°C/s) |
1 |
A |
31 |
1180 |
857 |
11 |
830 |
9 |
Example |
2 |
B |
25 |
1150 |
830 |
12 |
800 |
10 |
Example |
3 |
C |
11 |
1160 |
785 |
14 |
730 |
12 |
Example |
4 |
D |
20 |
1100 |
796 |
12 |
764 |
10 |
Example |
5 |
E |
25 |
1130 |
855 |
12 |
825 |
10 |
Example |
6 |
F |
14 |
1130 |
842 |
14 |
787 |
11 |
Example |
7 |
G |
9 |
1250 |
883 |
15 |
819 |
16 |
Example |
8 |
H |
10 |
1220 |
766 |
14 |
707 |
13 |
Example |
9 |
I |
15 |
1150 |
826 |
13 |
770 |
3 |
Example |
10 |
J |
30 |
1150 |
848 |
10 |
821 |
2 |
Example |
11 |
C |
10 |
1100 |
758 |
14 |
708 |
12 |
Example |
12 |
J |
12 |
1150 |
775 |
13 |
723 |
11 |
Example |
12 |
L |
20 |
1250 |
779 |
10 |
747 |
9 |
Comparative Example |
13 |
M |
30 |
1250 |
890 |
11 |
863 |
8 |
Comparative Example |
14 |
N |
14 |
1120 |
825 |
13 |
770 |
12 |
Comparative Example |
15 |
O |
25 |
1120 |
858 |
11 |
828 |
10 |
Comparative Example |
16 |
P |
20 |
1180 |
807 |
11 |
764 |
5 |
Comparative Example |
17 |
Q |
10 |
1180 |
773 |
12 |
714 |
11 |
Comparative Example |
18 |
R |
20 |
1150 |
801 |
11 |
764 |
9 |
Comparative Example |
19 |
S |
15 |
1150 |
810 |
12 |
754 |
10 |
Comparative Example |
20 |
T |
30 |
1130 |
845 |
9 |
821 |
2 |
Comparative Example |
21 |
C |
12 |
1180 |
673 |
10 |
618 |
11 |
Comparative Example |
22 |
D |
19 |
1200 |
804 |
11 |
772 |
0.4 |
Comparative Example |
23 |
A |
31 |
1200 |
759 |
7 |
732 |
9 |
Comparative Example |
24 |
E |
25 |
1030 |
848 |
12 |
818 |
10 |
Comparative Example |
25 |
D |
10 |
1100 |
763 |
6 |
716 |
11 |
Comparative Example |
26 |
B |
25 |
1130 |
993 |
10 |
955 |
10 |
Comparative Example |
Table 3
Sample No. |
Steel No. |
Minimum value of γ grain size (µm) |
Standard deviation of γ grain size (µm) |
Yield strength (MPa) |
Tensile strength (MPa) |
Total elongation (%) |
Absorbed energy at -196 °C (vE-196°C) (J) |
CTOD value (mm) |
Remarks |
1 |
A |
5.2 |
7.6 |
418 |
850 |
69 |
133 |
0.41 |
Example |
2 |
B |
3.4 |
7.4 |
554 |
941 |
58 |
118 |
0.39 |
Example |
3 |
C |
2.6 |
5.7 |
566 |
969 |
62 |
123 |
0.36 |
Example |
4 |
D |
2.9 |
7.1 |
559 |
952 |
55 |
115 |
0.36 |
Example |
5 |
E |
5.5 |
7.3 |
489 |
886 |
64 |
138 |
0.42 |
Example |
6 |
F |
6.1 |
6.2 |
453 |
854 |
67 |
139 |
0.44 |
Example |
7 |
G |
5.9 |
4.9 |
418 |
936 |
62 |
126 |
0.44 |
Example |
8 |
H |
3.1 |
5.5 |
512 |
968 |
61 |
104 |
0.37 |
Example |
9 |
I |
5.7 |
6.6 |
447 |
849 |
66 |
131 |
0.43 |
Example |
10 |
J |
4.8 |
7.8 |
407 |
847 |
69 |
136 |
0.40 |
Example |
11 |
C |
1.9 |
5.4 |
575 |
978 |
58 |
115 |
0.36 |
Example |
12 |
J |
2.8 |
5.8 |
557 |
952 |
63 |
124 |
0.37 |
Example |
12 |
L |
2.3 |
7.9 |
622 |
970 |
51 |
58 |
0.21 |
Comparative Example |
13 |
M |
4.9 |
7.4 |
363 |
818 |
70 |
127 |
0.40 |
Comparative Example |
14 |
N |
5.5 |
6.8 |
443 |
868 |
68 |
36 |
0.17 |
Comparative Example |
15 |
O |
4.7 |
7.3 |
447 |
878 |
64 |
72 |
0.33 |
Comparative Example |
16 |
P |
4.8 |
7.5 |
529 |
940 |
59 |
79 |
0.36 |
Comparative Example |
17 |
Q |
2.9 |
6.1 |
502 |
957 |
61 |
89 |
0.37 |
Comparative Example |
18 |
R |
4.5 |
7.3 |
518 |
935 |
60 |
48 |
0.34 |
Comparative Example |
19 |
S |
5.2 |
6.8 |
455 |
850 |
67 |
83 |
0.40 |
Comparative Example |
20 |
T |
4.3 |
7.9 |
417 |
853 |
68 |
75 |
0.40 |
Comparative Example |
21 |
C |
1.7 |
6.5 |
667 |
1057 |
49 |
42 |
0.29 |
Comparative Example |
22 |
D |
2.5 |
7.3 |
547 |
943 |
56 |
67 |
0.34 |
Comparative Example |
23 |
A |
0.7 |
9.8 |
534 |
964 |
59 |
103 |
0.15 |
Comparative Example |
24 |
E |
3.5 |
7.4 |
476 |
875 |
63 |
69 |
0.36 |
Comparative Example |
25 |
D |
0.4 |
10.5 |
569 |
970 |
60 |
119 |
0.12 |
Comparative Example |
26 |
B |
4.9 |
7.5 |
375 |
795 |
70 |
112 |
0.37 |
Comparative Example |