Heating – Work feeding – agitating – discharging or conveying... – Having closure or seal for work feeder's entrance passage
Reexamination Certificate
1999-10-07
2002-01-29
Lu, Jiping (Department: 3749)
Heating
Work feeding, agitating, discharging or conveying...
Having closure or seal for work feeder's entrance passage
C432S008000, C432S059000, C034S242000, C277S413000
Reexamination Certificate
active
06341955
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a seal roll apparatus for preventing atmospheric gases from leaking out of the heat treatment zone in a continuous heat-treatment furnace for continuously heat-treating a workpiece strip, such as a steel strip or an aluminum strip, and to a sealing method.
2. Description of Related Art
A continuous heat-treatment furnace basically includes a heating zone in which a workpiece strip is heated to a predetermined temperature for annealing treatment and a cooling zone in which the annealed workpiece is cooled down to room temperature.
FIG. 3
is a diagram showing a typical example of a continuous heat-treatment furnace for a cold-rolled steel strip. The following elements are disposed in the continuous heat-treatment furnace in the following order: a pre-heating section
15
for pre-heating a steel strip S by recovering and heat-exchanging usable heat of exhaust gases from a heating section
14
, the heating section
14
for heating the steel strip S to a predetermined temperature, a soaking section
16
for soaking the steel strip S which has been heated to the predetermined temperature, a slow-cooling section
17
for slow-cooling the soaked steel strip S, a rapid-cooling section
18
for rapid-cooling the slow-cooled steel strip S, an over-aging section
19
for over-aging treatment, and a final cooling section
20
for finally cooling the steel strip S down to room temperature. The pre-heating section
15
, the heating section
14
, and the soaking section
16
constitute a heating zone, and the slow-cooling section
17
through the final cooling section
20
constitute a cooling zone.
The cold-rolled steel strip S which has been subjected to work hardening is passed through the individual treatment sections by a hearth roll
21
mounted in the furnace. When a workpiece that does not require over-aging treatment is subjected to heat treatment, the over-aging section may be used as a slow-cooling section.
The product quality is damaged if the surfaces of steel strips are oxidized during annealing treatment. Therefore, in a continuous heat-treatment furnace, the furnace is generally filled with a non-oxidizing atmospheric gas by providing gas feed channels
22
a
to
22
f
and gas discharge channels
23
a
to
23
g
in the individual treatment sections. A mixed gas (HN gas) of hydrogen gas and nitrogen gas has been used generally as the atmospheric gas in the continuous annealing furnace.
In the continuous heat-treatment furnace, different atmospheric gases may be used in adjacent treatment sections in the heating zone or in the cooling zone when heat treatment is performed.
For example, with an aim of improving the aging of low carbon steels, a method is disclosed in Japanese Examined Patent Publication No. 55-1969 or Japanese Unexamined Patent Publication No. 6-346156 in which, in order to increase the cooling rate in the rapid-cooling section before over-aging treatment, the heat-transfer coefficient is improved by increasing the hydrogen content in a cooling gas that is cyclically used in the rapid-cooling section.
In accordance with the processes disclosed in the above patent publications, if an atmospheric gas having a high hydrogen content in the rapid-cooling section leaks into the adjacent slow-cooling section or into the over-aging section, a large amount of hydrogen gas must be fed so that the high hydrogen content in the rapid-cooling section is maintained. Therefore, there is a need for a sealing apparatus which avoids mixture of atmospheric gases having different compositions between the rapid-cooling section and the slow-cooling section and between the rapid-cooling section and the over-aging section.
FIG. 4
is a schematic diagram showing an example of a seal roll apparatus which has been conventionally used for shutting off atmospheric gases in a continuous heat-treatment furnace. As shown in
FIG. 4
, seal rolls
24
a
and
24
b
are disposed so as to be opposed to each other with a steel strip S therebetween, and a partition
25
is disposed in the vicinity of the seal rolls in order to improve the sealing properties. The steel strip S passes through a space (hereinafter referred to as “a roll gap”) between the seal rolls
24
a
and
24
b
. The roll gap is adjusted to be as small as possible to improve the sealing properties, and each seal roll rotates (driven by motors M) so that scratches do not occur on the surfaces of the steel strips even when the travelling steel strip and the rolls are in contact with each other.
As a means for sealing atmospheric gases, an alternative to the seal roll apparatus described above, for example, a bulkhead structure is disclosed in Japanese Unexamined Patent Publication No. 5-125451. The bulkhead structure is disposed at the boundaries between atmospheric gases having different compositions and also functions as a plurality of treatment rooms enabling the feeding and discharging of atmospheric gases having different compositions. A seal roll apparatus is disclosed in Japanese Examined Utility Model Publication No. 63-19316 in which sealing members are disposed so as to be in contact with both surfaces of a steel strip. In Japanese Unexamined Patent Publication No. 59-133330, an apparatus is disclosed in which seal rolls, blowing nozzles, and seal dampers are combined.
However, there are problems in the conventional sealing apparatus as follows.
Although the contact-type sealing apparatus have excellent sealing properties, scratches may occur on the surfaces of the metal strips.
With respect to the gas sealing apparatus, although scratches do not occur on the surfaces of the metal strips because of the non-contact sealing structure, since the sealing gas must always be fed at a certain rate, the consumption of gas is increased. Additionally, in order to maintain sealing properties, the gas feeding must be controlled with high precision, resulting in a high cost of equipment.
In seal roll apparatus in which a steel strip is brought into contact with rotating seal rolls, such drawbacks associated with the above apparatus are not observed. Therefore, such seal roll apparatus are advantageous for practical use. However, since thermal expansion of seal rolls is unavoidable due to radiation heat from the steel strips or furnace walls or due to convective heat transfer through the atmospheric gases, there is a limit to narrowing the roll gap between the seal rolls, and thus atmospheric gases are not sufficiently shut off.
FIGS. 5A through 5C
schematically show a seal roll apparatus in which a steel strip S is brought into contact with rotating seal rolls. When seal rolls
24
a
and
24
b
are subjected to radiation heat from the high-temperature steel strip S undergoing annealing and from the furnace wall, thermal expansion having a non-uniform temperature profile (hereinafter referred to as “a thermal crown”) is caused in the roll barrel direction of the seal rolls
24
a
and
24
b
. Thus, it is difficult to maintain a minimum gap between the seal rolls
24
a
and
24
b
in the roll barrel direction.
In order to eliminate the effect of the thermal crown, a certain distance must be maintained between the seal rolls and a partition
25
for separating the individual reaction sections.
Moreover, when the roll gap between seal rolls is narrowed, the seal rolls are operated in an attempt to prevent scratches from occurring even if a steel strip and the seal rolls are brought into contact with each other. However, unless the peripheral velocity of the seal rolls and the conveying velocity of the steel strip coincide with each other, scratches unavoidably occur on the surfaces of the steel strip.
The probability of scratches increases as the roll gap between seal rolls is decreased and the opportunity for contact between the seal rolls and the steel strip increases.
Normally, the peripheral velocity of the seal rolls is set to be equal to the value obtained by multiplying a measured rotational frequency of a conveyor roll by a circumference calculated fr
Iida Sachihiro
Samejima Ichiro
Ueno Naoto
Kawasaki Steel Corporation
Lu Jiping
Oliff & Berridg,e PLC
LandOfFree
Sealing apparatus in continuous heat-treatment furnace and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Sealing apparatus in continuous heat-treatment furnace and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Sealing apparatus in continuous heat-treatment furnace and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2824714