U.S. patent application number 09/790639 was filed with the patent office on 2001-10-11 for continuous casting method for steel.
Invention is credited to Hara, Masashi, Ikeda, Masahiro, Kawamoto, Masayuki, Kikuchi, Hirohisa, Murakami, Toshihiko, Oka, Masahiko.
Application Number | 20010027854 09/790639 |
Document ID | / |
Family ID | 18083338 |
Filed Date | 2001-10-11 |
United States Patent
Application |
20010027854 |
Kind Code |
A1 |
Kikuchi, Hirohisa ; et
al. |
October 11, 2001 |
Continuous casting method for steel
Abstract
Steel is continuously cast in a mold at a casting speed of 2.5
to 10 m/min while the mold is oscillated so as to satisfy the
relationship 450.ltoreq.(S.times.f/Vc).ltoreq.1000, wherein S is
the stroke of mold oscillation in mm, f is the frequency of mold
oscillation in cycles per minute, and Vc is the casting speed in
m/min.
Inventors: |
Kikuchi, Hirohisa;
(Amagasaki-shi, JP) ; Kawamoto, Masayuki;
(Kashima-shi, JP) ; Hara, Masashi; (Katori-gun,
JP) ; Murakami, Toshihiko; (Kashima-shi, JP) ;
Oka, Masahiko; (Takarazuka-shi, JP) ; Ikeda,
Masahiro; (Niihama-shi, JP) |
Correspondence
Address: |
BURNS DOANE SWECKER & MATHIS L L P
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Family ID: |
18083338 |
Appl. No.: |
09/790639 |
Filed: |
February 23, 2001 |
Current U.S.
Class: |
164/478 |
Current CPC
Class: |
B22D 11/053
20130101 |
Class at
Publication: |
164/478 |
International
Class: |
B22D 011/04 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 11, 1999 |
JP |
317003/1999 |
Claims
What is claimed is:
1. A continuous casting method comprising continuously casting
steel in a mold at a casting speed of at least 2.5 m/min and at
most 10 m/min to form a slab while oscillating the mold so as to
satisfy the relationship 450.ltoreq.(S.times.f/Vc).ltoreq.1000
wherein S is the stroke of mold oscillation in mm (4
mm.ltoreq.S.ltoreq.15 mm), f is the frequency of mold oscillation
in cycles per minute, and Vc is the casting speed in m/min.
2. A method as claimed in claim 1 wherein the mold has a cavity
with a thickness of 50-120 mm.
3. A method as claimed in claim 1 wherein the mold has a cavity
with a thickness of 70-110 mm.
4. A method as claimed in claim 1 including hot rolling the slab
after casting to form thin steel sheet without allowing the slab to
cool to below its Ac.sub.3 point between casting and hot
rolling.
5. A method as claimed in claim 4 wherein the casting speed Vc is
less than 8.0 m/min.
6. A method as claimed in claim 1 wherein the following
relationship is satisfied. 500.ltoreq.(S.times.Vc).ltoreq.900
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a continuous casting method for
steel. In particular, it relates to a high speed continuous casting
method which is capable of forming thin cast slabs having a good
surface quality without the occurrence of operational problems such
as sticking breakout.
[0003] This invention also relates to a method of manufacturing
thin steel sheet from a thin or medium thickness cast slab formed
by continuous casting.
[0004] 2. Description of the Related Art
[0005] In a typical method for manufacturing thin steel sheets, a
cast slab formed by continuous casting is cooled to room
temperature at the completion of casting and is then subjected to
hot rolling to obtain a desired sheet thickness. Due to the need to
reheat the cast slab from room temperature before hot rolling can
take place, this method is inefficient from the standpoint of
energy consumption.
[0006] Recently, a method has been developed in which cast slabs
produced by continuous casting are subjected to hot rolling without
first being cooled to room temperature. In this method, if the cast
slab which emerges from a casting machine is sufficiently thin, the
load of rough rolling of the slab can be reduced, further
increasing the efficiency of the method.
[0007] When performing continuous casting of thin or medium
thickness slabs, the thickness of the mold cavity (the internal
dimensions of the mold cavity in the thickness direction of a
casting formed by the mold) of a mold using for casting is a small
value of 50-120 mm, compared to a thickness of 200-300 mm for a
mold cavity for casting of ordinary slabs, Due to the small
thickness of the mold cavity, a continuous casting line for thin
cast slabs must operate at a higher casting speed than a continuous
casting line for thicker slabs in order to produce the same output
per unit length of time.
[0008] When operating at a high casting speed, it is necessary to
prevent sticking breakout, which refers to a phenomenon in which
the solidified shell of a slab sticks to the interior surface wall
of the mold due to a rupture of the film of the lubricant (which is
typically a powder prior to melting) present between the interior
surface of the mold and the solidified shell. The sticking
solidified shell breaks, and molten steel inside it leaks out from
the partially solid cast slab. This phenomenon can cause serious
problems. Methods of preventing sticking breakout include varying
the material properties of the lubricant powder (such as lowering
its solidification temperature or viscosity) and varying the
oscillation conditions of the mold.
[0009] However, if the solidification temperature of a lubricant
powder is lowered in order to prevent sticking breakout, uneven
solidification of the cast slab occurs, because the amount of heat
removal, through the walls of the mold increases. As a result, it
becomes easy for surface defects referred to as longitudinal cracks
to occur in the cast slab. In addition, if the viscosity of the
lubricant powder is decreased, the lubricant powder tends to flow
into the mold unevenly in the widthwise direction, and it again
becomes easy for longitudinal flaws to occur. Therefore, there is a
limit of the extent to which the material properties of lubricant
powder can be varied in order to prevent sticking breakout.
[0010] There have been many proposals of ways of varying mold
oscillating conditions during continuous casting, such as in
Japanese Published Unexamined Patent Applications Hei
2-197359/1990, Hei 4-231 159/1992, Hei 6-15425/1994, Hei
7-16718/1995, and Hei 9-234549/1997, However, in the casting
methods described in those publications in which oscillation is
applied to a mold, the casting speed is at most 2.2 m/min, so those
methods are not applicable to high speed casting or casting of thin
or medium thickness slabs.
[0011] Japanese Published Unexamined Patent Application Hei
8-187562/1996 discloses a method in which a mold oscillating
frequency f can be set to an optimal value in the range of 96-204
cycles per minute up to a casting speed (Vc) of 5.0 m/min, and the
mold oscillating stroke a (mm) is varied so as to satisfy the
relationship a=(1.9-2.5).times.Vc.
[0012] However, at a low frequency of 96-204 cycles per minute at
which oscillation is performed in that method, there is a tendency
for a cast slab to be easily stuck, the pitch of oscillation marks
(the distance in the lengthwise direction of a cast slab between
oscillation marks) formed on the cast slab becomes very long, and
there is a tendency for longitudinal cracks which are weak against
contraction in the widthwise direction due to solidification to be
easily generated.
[0013] Furthermore, in the above-mentioned publications, the stroke
of mold oscillation is varied as the casting speed increases, so a
conventional cam-type oscillating mechanism can not be employed,
making it difficult to apply those methods to existing casting
equipment. Thus, the methods in those publications are not very
practical.
[0014] Moreover, in the above-mentioned publications, there is no
mention of mold dimensions, and in particular, there is no mention
of the manufacture of thin cast slabs. There is also no disclosure
concerning a method for casting of thin or medium thickness cast
slabs immediately followed by hot rolling,
SUMMARY OF THE INVENTION
[0015] The present invention provides a high speed continuous
casting method in which sticking breakout does not occur, in which
surface defects such as longitudinal flaws do not occur, and which
is capable of manufacturing thin or medium thickness slabs suitable
for forming thin steel sheets.
[0016] The present invention also provides a method for
manufacturing thin steel sheet in which thin or medium thickness
cast slabs can be continuously cast at a high speed and immediately
thereafter subjected to hot rolling.
[0017] The present inventors realized that in order to perform
stable casting at a high casting speed of at least 2.5 m/min, the
oscillating conditions of a mold are important. As a result of
various experiments involving varying of mold oscillating
conditions, it was found that if mold oscillation is performed so
as to satisfy the relationship 450.ltoreq.S.times.f/Vc.ltoreq.1000,
wherein S is the stroke of mold oscillation in mm (4
mm.ltoreq.S.ltoreq.15 mm), f is the frequency of oscillation in
cycles per minute, and Vc is the casting speed in m/min, continuous
casting can be performed in a stable manner without the occurrence
of sticking breakout and without the formation of surface defects
such as longitudinal cracks.
[0018] The present inventors also found that at a casting speed of
2.5-10 m/min, manufacture of a thin or medium thickness cast slab
can be effectively performed with a mold cavity thickness of 50-120
mm, and that thin or medium thickness cast slabs which could not be
readily obtained by conventional technology can be economically
manufactured.
[0019] Thus, in one form of the present invention, a continuous
casting method comprises continuously casting steel at a casting
speed of at least 2.5 m/min and at most 10 m/min while oscillating
a mold so as to satisfy the relationship
450.ltoreq.S.times.f/Vc.ltoreq.1000
[0020] wherein S is the stroke of mold oscillation in mm (S=4 to 15
mm), f is the frequency of mold oscillation in cycles per minute,
and Vc is the casting speed in m/min.
[0021] A slab formed by a casting method according to the present
invention may be subjected to hot rolling after casting to form
steel sheet or other product having a desired thickness. Preferably
hot rolling is performed without letting the cast slab cool to room
temperature between casting and rolling, and more preferably
without letting the cast slab cool to below its Ac.sub.3 point.
When the cast slab is to be hot rolled into sheet, the mold
preferably has a mold cavity with a thickness of 50-120 mm.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a graph showing the relationship between the
frictional force between a mold and a cast slab and casting
speed.
[0023] FIG. 2 is a graph showing the relationship between the pitch
of oscillation marks on a cast slab and (S.times.f/Vc).
[0024] FIG. 3 schematically illustrates a continuous casting
machine which can be used in the present invention.
[0025] FIG. 4 illustrates the relationship between casting speed
and (S.times.f/Vc).
DESCRIPTION OF PREFERRED EMBODIMENTS
[0026] A continuous casting method according to the present
invention can be carried out on any continuous casting machine
suitable for continuous casting at a speed of at least 2.5 m/min.
The casting machine is not restricted to any particular shape. For
example, it may have a curved shape, a vertical shape, or other
shape.
[0027] The dimensions of the cavity of the casting mold of the
continuous casting machine can be selected in accordance with the
size of the cast slab which is to be formed. For example, when used
to form usual slabs, the mold cavity may have a thickness of 120 mm
or above. When used to form thin or medium thickness cast slabs,
the mold cavity will typically have a thickness of 50-120 mm and
preferably 70-110 mm.
[0028] The mold can be equipped with any type of oscillating
mechanism capable of oscillating the mold in the lengthwise
direction of a cast slab with the desired stroke and frequency.
Examples of suitable mechanisms include conventional oscillating
mechanisms with hydraulic actuators, conventional cam-operated
oscillating mechanisms, and conventional oscillating mechanisms
employing levers and cranks. The velocity profile of the mold
during each cycle of oscillation is not restricted. A sinusoidal
velocity profile (in which the displacement of the mold from a
reference position varies sinusoidally with respect to time) is
generally easy to implement, but other profiles can be
employed.
[0029] FIG. 1 shows the relationship between the frictional force
acting between the interior surface of a mold and a cast slab and
the casting speed when only the stroke of oscillation of a mold was
varied.
[0030] From this figure, it can be seen that the frictional force
between a mold and a cast slab increases as the stroke of
oscillation of the mold decreases, and that the frictional force
abruptly increases when the stroke of oscillation is less than 4
mm. This increase in frictional force is caused by the inflow of
lubricant powder between the mold surface and the cast slab being
suppressed when the stroke of is oscillation is small. On the other
hand, when the stroke exceeds 15 mm, the frictional force between
the mold and the cast slab abruptly decreases, leading to an
increase in the number of longitudinal cracks, which are thought to
be caused by excess inflow of lubricant powder between the mold and
the cast slab. Therefore, during high speed casting according to
the present invention at a casting speed of at least 2.5 m/min, the
optimal stroke of mold oscillation is 4 mm.
[0031] The reasons why the stroke S (mm) of mold oscillation, the
oscillation frequency f (cycles per minute), and the casting speed
Vc (m/min) are expressed by 450.ltoreq.S.times.f/Vc.ltoreq.1000 in
the present invention are as follows.
[0032] FIG. 2 shows the relationship between the value of
(S.times.f/Vc) and the pitch (mm) of oscillation marks observed in
a series of continuous casting experiments in which the stroke of
mold oscillation S (mm), the oscillation frequency f (cycles per
minute), and the casting speed Vc (m/min) were varied. S was varied
from 4 to 10 mm.
[0033] As can be seen from FIG. 2, the pitch of oscillation marks
decreased as the value of (S.times.f/Vc) increased. This tendency
became more marked as the stroke of oscillation increased. When the
stroke of mold oscillation was 15 mm and (S.times.f/Vc) was less
than 450, the pitch of oscillation marks was an extremely large
value of at least 33.3 mm. As a result, due to shrinkage of the
slab within the mold in the widthwise direction of the mold
resulting from solidification of the slab, a large number of
longitudinal flaws formed between oscillation marks. When
(S.times.f/Vc) exceeded 1000, the pitch of oscillation marks became
a small value of less than 15 mm, the number of oscillation marks
per unit length of a cast slab increased, resulting in an increase
in lubricant powder-related defects in the surface of a cast slab,
and the quality of a coil formed from the slab decreased. This is
partly due to an increase in the range of fluctuation of the
meniscus in the mold cased by an increase in the stroke and
frequency of mold oscillation, and partly due to an increase in the
amount of inclusions of lubricant powder caused by collapse of the
tip of the shell formed near the meniscus during casting. The
inclusion of lubricant powder increases in proportion to an
increase in the number of oscillation marks.
[0034] When the stroke of oscillation is small, the pitch between
oscillation marks becomes extremely small, so longitudinal cracks
are no longer generated. However, the frictional force between the
mold and the cast slab increases due to a decrease in the inflow of
lubricant powder between the mold and the slab, In addition, if
S.times.f/Vc is less than 450, the number of oscillation marks
contacting the surface of molten lubricant powder in the mold
decreases, so the amount of molten lubricant powder which is
carried into the mold decreases, and the danger of sticking
breakout increases. For this reason, when the stroke of oscillation
is 4 mm, it is difficult to perform stable operation unless
S.times.f/Vc is at least 450.
[0035] When the stroke has a small value of 4 mm, if S.times.f/Vc
exceeds 1000, the increase of the mold oscillation frequency
proceeds more than when the stroke is 15 mm. For this reason, large
fluctuations of the meniscus in the mold take place, and there is a
tendency for lubricant powder-related defects to increase.
[0036] Accordingly, when performing high speed continuous casting
at a casting speed of at least 2.5 m/min, in order to carry out
optimal operation in which there is no danger of sticking breakout
and the quality of the cast slab and coils formed from the slab is
maintained, the mold is oscillated with a stroke in the range of
4-15 mm while satisfying the relationship
450.ltoreq.S.times.f/Vc.ltoreq.1000. Preferably, (S.times.f/Vc) is
500-900.
[0037] The frequency of oscillation f is usually 80-2500 cycles per
minute. This range of frequencies can also be employed in the
method of the present invention. More preferably, the frequency f
is 100-500 cycles per minute.
[0038] When the method of the present invention is used to perform
continuous casting of thin or medium thickness cast slabs, casting
is preferably performed at a casting speed of 2.5 to 10 m/min and
preferably 2.5 to 8 m/min using a mold with a mold cavity having a
thickness of 50-120 mm. When manufacturing a thin or medium cast
slab, a casting speed of at least 2.5 m/min and preferably less
than 8 m/min is desirable in order to achieve economical operation.
There is no strict upper limit on the casting speed, but it is
difficult to perform stable operation if the casting speed exceeds
10 m/min, so preferably the casting speed is at most 10 m/min.
[0039] If the thickness of the mold cavity exceeds 120 mm, it is
not possible to omit rough rolling of the resulting slab, while if
the thickness is less than 50 mm, it is difficult to perform
continuous casting. Therefore, in cases in which it is desired to
omit rough rolling of the cast slab, the thickness of the mold
cavity is 50-120 mm, and preferably 70-110 mm.
[0040] After a thin or medium thickness cast slab is formed by a
continuous casting method according to the present invention, the
slab will typically be subjected to hot rolling to form steel sheet
or other rolled product having a desired thickness. Preferably, the
hot rolling is performed without the slab being allowed to cool to
room temperature, and more preferably without it being allowed to
cool below its Ac.sub.3 point between the completion of casting and
the start of hot rolling. In this case, the casting speed during
continuous casting is preferably less than 8 m/min so that hot
rolling can be efficiently performed immediately after continuous
casting. An upper limit on the casting speed can be determined
based on the capacity of the rolling equipment to which the cast
slab is supplied and is preferably sufficiently high that the cast
slab is not cooled to room temperature and preferably is not cooled
to below the AC.sub.3 point between the completion of casting and
the completion of rolling. If desired, a heating furnace may be
disposed in the manufacturing line to maintain the cast slab at a
suitable temperature for hot rolling.
[0041] Next, the effects of the present invention will be described
in more detail by the following examples.
EXAMPLES
[0042] Continuous casting of steel slabs was performed using a
continuous casting machine like the one schematically illustrated
in FIG. 3. The casting machine had an overall length of 15 meters
and included a vertical portion with a length of 1 meter. Molten
steel 1 in the form of low carbon aluminum-killed steel with a
carbon content of 0.05 percent was poured into a mold 2, and
continuous casting was performed at a casting speed in the range of
2.5-10 m/min. During casting, the mold 2 was oscillated by an
unillustrated oscillating mechanism in the direction of casting. A
cast slab which was pulled from the mold 2 was supported by guide
rolls 3 in the vertical and curved portions of the casting machine.
The slab was gradually cooled from the surface thereof, and
solidification of the molten steel was completed at solidification
point 5. After solidification, the slab was pulled out of the
continuous casting machine by pinch rolls 4 and was cut by an
unillustrated cutting apparatus. The slab was then transported to
an unillustrated hot rolling line without being cooled to below
room temperature and preferably without being cooled to below its
Ac.sub.3 point, using a heating furnace if necessary.
[0043] The mold 2 had a cavity with a width of 1500 mm and a
thickness of 120 mm. During continuous casting, the stroke of
oscillation of the mold 2 and the value of (S.times.f/Vc) were
varied.
[0044] The mold 2 was equipped with a plurality of thermocouples
for sensing the temperature of the mold wall. The outputs of the
thermocouples were monitored, and variations among the outputs were
analyzed using a known algorithm to determine the occurrence of
sticking breakout within the mold 2. An alarm was generated when
breakout was detected. The stability of operation during high speed
casting was evaluated based on the number of breakout alarms
generated per charge, with zero alarms per charge being an
acceptable value. The surface condition of each cast slab was
evaluated based on the number of sticking marks per 1 meter length
of the slab (number per charge). Zero marks was considered an
acceptable value.
[0045] The quality of each cast slab was evaluated by a
longitudinal crack length index equal to the length of longitudinal
cracks per meter of a cast slab (m/m). In addition, the surface of
each cast slab was machined to a depth of 1 mm, i.e., the top 1 mm
of the surface was removed, and the machined surface was observed
with a microscope to count the number of subsurface inclusions
having a size of at least 50 micrometers per 10 cm.sup.2 of area.
Furthermore, a coil defect index was determined by the following
formula:
[0046] Coil defect index=(weight in tons of coils having defects in
one charge)/(total weight of coils in one charge).
[0047] The results are shown in Table 1. Examples 1-6 are examples
of the present invention, while Examples 7-28 are comparative
examples outside the range of the present invention. In the columns
for Operational Stability and Quality, 0 indicates good, x
indicates poor, and xx indicates very poor.
[0048] In Examples 1-6 according to the present invention, there
were no breakout alarms and no sticking marks. The longitudinal
crack length index was 0-0.01 m/m, the number of subsurface
inclusions in the cast slabs was at most 3 inclusions per 10
cm.sup.2, and the coil defect index was at most 0.02, so these
examples had good values with respect to stability of operation and
quality.
[0049] In Examples 7-13, which were comparative examples, when the
stroke of mold oscillation was 3 mm, breakout alarms and sticking
marks occurred, and these examples were evaluated as having poor or
very poor operational stability.
[0050] Similarly, in Examples 22-28, when the stroke of oscillation
was 16 mm, although there were no breakout alarms or sticking
marks, there were many longitudinal cracks, the longitudinal crack
length index was at least 0.1 m/m, and the coil defect index was at
least 0.2, so these examples were evaluated as having poor or very
poor quality.
[0051] In Examples 14 and 15, when the stroke of oscillation was 4
mm and (S.times.f/Vc) was less than 450, there were no longitudinal
cracks, the number of subsurface inclusions in the cast slab was
small, and the coil defect index and the evaluation with respect to
quality were good. However, both breakout alarms and sticking marks
occurred, so these examples were evaluated as poor with respect to
operational stability.
[0052] In Examples 16 and 17, when the stroke of oscillation was 4
mm and (S.times.f/Vc) was greater than 1000, there were no breakout
alarms or sticking marks, but the number of subsurface inclusions
in the cast slab increased, and the coil defect index was 0.1-0.2,
so these examples were evaluated as being poor with respect to
quality.
[0053] In Examples 18 and 19, when the stroke of oscillation was 15
mm and (S.times.f/Vc) was less than 450, there were no breakout
alarms or sticking marks, but longitudinal cracks occurred, the
longitudinal crack length index was at least 0.1, and the coil
quality index was 0.1-0.2, so these examples were evaluated as
being poor with respect to quality.
[0054] In Examples 20 and 21, when the stroke of oscillation was 15
mm and (S.times.f/Vc) was greater than 1000, there were no breakout
alarms or sticking marks, but the number of subsurface inclusions
in the cast slab increased to 20-30 per cm.sup.2, and the coil
defect index was at least 0.1, so these examples were evaluated as
having poor quality.
[0055] FIG. 4 illustrates the significance of(S.times.f/Vc) based
on the above results. In the figure, the cross-hatched region
indicates the region in which the desired effects of the present
invention are exhibited.
[0056] Next, thin cast slabs obtained by Examples 1-6 were
subjected to hot rolling after high speed continuous casting
without being cooled to below the Ac.sub.3 point. Not rolling was
performed without rough rolling to obtain hot rolled steel sheet
with a thickness of 4 mm.
[0057] The resulting steel sheet did not have surface defects such
as ground burs, and hot rolled steel sheet having an excellent
surface condition was efficiently manufactured.
1 TABLE 1 Oscillation Breakout Sticking Longitudinal Subsurface
Coil Example Stroke mark pitch alarms marks per crack length
inclusions defect Operational No. (mm) Sf/Vc (mm) per charge charge
index (mm) per 10 sq cm index stabilty Quality THIS 1 4 450 2.9 0 0
0 1 0.01 0 0 INVENTION 2 4 600 6.7 0 0 0 2 0.01 0 0 3 4 1000 4.0 0
0 0 1 0.01 0 0 4 15 450 33.3 0 0 0.01 3 0.02 0 0 5 15 600 25.0 0 0
0.01 3 0.02 0 0 6 15 1000 15.0 0 0 0.01 3 0.02 0 0 COMPARATIVE 7 3
450 6.7 8 4 0 2 0.02 xx 0 EXAMPLES 8 3 500 6.0 7 3 0 2 0.01 xx 0 9
3 600 5.0 6 3 0 1 0.01 x 0 10 3 700 4.3 6 2 0 2 0.01 x 0 11 3 800
3.8 5 2 0 3 0.01 x 0 12 3 1000 3.0 5 2 0 20 0.10 x x 13 3 1050 2.9
4 2 0 30 0.15 x x 14 4 350 11.4 5 2 0 2 0.01 x 0 15 4 400 10.0 3 1
0 1 0.01 x 0 16 4 1050 3.8 0 0 0 7 0.08 0 x 17 4 1100 3.6 0 0 0 20
0.12 0 x 18 15 350 42.9 0 0 0.2 2 0.2 0 x 19 15 400 37.5 0 0 0.1 2
0.1 0 x 20 15 1050 14.3 0 0 0.01 20 0.1 0 x 21 15 1100 13.6 0 0
0.01 30 0.13 0 x 22 16 450 35.6 0 0 0.5 0 0.3 0 xx 23 16 500 32.0 0
0 0.4 0 0.2 0 x 24 16 600 26.7 0 0 0.35 0 0.2 0 x 25 16 700 22.9 0
0 0.2 0 0.22 0 x 26 16 800 20.0 0 0 0.2 1 0.25 0 x 27 16 1000 16.0
0 0 0.15 25 0.3 0 xx 28 16 1050 15.2 0 0 0.12 35 0.3 0 xx
* * * * *