JP2006152336A - Conveying device in continuous heat treatment furnace for metal strip - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conveying device in a furnace for metal strip, wherein even in a continuous annealing furnace having such severe operational conditions as high temperature and high oxidizing atmosphere, a general-used hearth-roll can be used and the continuous using is allowed for long time. <P>SOLUTION: A heat-insulating material 5 is set in the range that comes in no contact with hearth roll and the metal strip, around the hearth rolls 3 for continuously conveying the metal strip 2, and cooling pipes 4 are set in a space between the heat-insulating material and the hearth roll. Furthermore, a thermometer 6 is arranged in the gap between the hearth roll 3 and the heat-insulating material 5, and an instrument for adjusting the quantity of cooling medium passed through a cooling pipe 4 so that an indicated temperature in the thermometer 6 becomes the pre-set temperature, is included. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a furnace equipment for continuously heat-treating a metal strip, for example, an in-furnace transfer apparatus such as a steel plate annealing furnace. Specifically, it is possible to improve the build-up resistance of the hearth roll placed in the furnace, extend the roll life, maintain a long-term stable operation, and prevent the decrease in thermal efficiency accompanying roll overcooling. The present invention relates to an in-furnace transfer device.

  Since the hearth roll disposed in the continuous annealing furnace conveys the metal strip in a harsh environment of an oxidizing or reducing atmosphere at 600 to 1300 ° C., the roll surface wears due to prolonged use, Alternatively, the deposited metal oxide or metal powder of the metal strip builds up on the surface of the roll, and causes the metal strip to be subsequently conveyed to be brazed and deteriorated in quality. In particular, in a high temperature range exceeding 1000 ° C., bending or cracking of the hearth roll is likely to occur, and a shape defect such as bending of the metal strip occurs.

  Usually, the hearth roll is replaced or polished before the above situation occurs, but it is necessary to stop the operation during this time, and the cost is also high, so the structure of the hearth roll that can be used continuously for a long time There have been various studies.

  In particular, as a main configuration of the hearth roll used in a high-temperature annealing furnace, there are one that water-cools the roll shaft portion and one that uses a high heat-resistant material on the roll surface. As an example of the former, Patent Document 1 discloses that in a roll in which cooling water is circulated through a roll shaft portion, a gap is provided between the cooling water distribution pipe and the roll body to prevent overcooling of the roll surface. Has been.

  Patent Document 2 discloses a means for filling a heat insulating material between a roll shaft body having an internal water cooling structure and a ceramic-coated high heat resistant sleeve so that the roll surface is not cooled by shaft cooling. .

  Further, as an example of using a high heat resistant material on the roll surface, Patent Document 3 discloses a means for preventing meandering due to roll fluctuation of the roll by covering the roll surface in contact with the metal strip with a heat insulating material such as zirconia. Is disclosed.

Patent Document 4 discloses means for achieving both high temperature resistance and prevention of meandering of the metal strip by using a roll outermost layer made of ceramic and a heat insulating layer therebelow.
JP 56-134616 A Japanese Patent Laid-Open No. 1-147017 JP-A-63-86821 JP 11-293334 A

  In the hearth roll of the water-cooled roll shaft part, roll bending can be prevented, but cooling may reach the roll surface and surface supercooling may occur, causing temperature deviations in the metal strip or metal strip oxide. Are likely to adhere and accumulate on the roll. The means described in Patent Document 1 and Patent Document 2 are for preventing overcooling, but the structure of the roll is complicated, and the roll surface layer is made of a material that can withstand the operating conditions of the continuous annealing furnace as it is. It was necessary to select, and the cost was high.

  In addition, the hearth rolls disclosed in Patent Document 3 and Patent Document 4 that do not use forced cooling for the roll shaft portion still require special surface processing, so that they are expensive and expensive, and are coated with thermal shock. There were practical problems such as peeling of the resin and deterioration at high temperature and high dew point.

  The present invention has been made in view of the problems as described above, and provides an in-furnace transport apparatus that can use the hearth roll for a long time with a relatively simple configuration using a general-purpose hearth roll. It is aimed.

The present invention comprises the following gist.
(1) A heat insulating material is installed around a hearth roll that continuously conveys the metal strip so as not to contact the hearth roll and the metal strip, and a cooling pipe is formed in a space between the heat insulating material and the hearth roll. An in-furnace transfer device for a continuous heat treatment furnace for a metal strip, characterized in that
(2) A thermometer was provided between the hearth roll and the heat insulating material, and a device for adjusting the amount of refrigerant passed through the cooling pipe so that the indicated temperature of the thermometer reached a preset temperature was provided. (1) The in-furnace conveying apparatus of the continuous heat treatment furnace of the metal strip characterized by the above-mentioned.

  By using the present invention, general-purpose hearth rolls can be used even in continuous annealing furnaces under severe operating conditions such as high temperatures and highly oxidizing atmospheres, and continuous use for a long time is possible. And can also be effective in improving productivity.

  The present invention is described in detail below. A feature of the present invention is that a heat insulating material is installed around the hearth roll so as not to contact both the metal strip and the hearth roll that are heated objects, and a space between the heat insulating material and the hearth roll is provided. In addition, a cooling pipe through which a coolant such as cooling water or a cooling gas flows is provided so that only the hearth roll surface can be cooled. Thereby, the hearth roll can be maintained at an appropriate temperature without affecting the entire annealing furnace or the metal strip by the temperature.

  In addition, a thermometer is installed in the space between the hearth roll and the heat insulating material of the apparatus, and the roll surface is adjusted to the optimum temperature by adjusting the amount of cooling water or cooling gas based on the indicated temperature of the thermometer. It becomes possible to control.

  An example of an embodiment of the present invention will be described with reference to cross-sectional views of a horizontal continuous heat treatment furnace shown in FIGS. In the figure, 7 and 8 indicate the ceiling and floor of the furnace body, and 1 indicates a heat source such as a burner or a radiant tube. In this, two metal strips are conveyed on three hearth rolls. The hearth roll 3 is rotatably supported at both ends in the longitudinal direction by appropriate bearing members disposed on the left and right sides outside the furnace body.

  The feature of the present invention is that the heat insulating material 5 is installed around the hearth roll 3 so as not to contact the hearth roll 3 and the metal strip 2, and the cooling pipe 4 is installed between the hearth roll 3 and the heat insulating material 5. It is in. The cooling pipe 4 is a steel cylinder whose longitudinal direction is aligned in parallel with the rotation axis direction of the hearth roll 3, and the refrigerant flows along the longitudinal direction inside the cooling pipe 4.

  And only the hearth roll surface can be cooled by this, and high temperature operation can be performed with a general purpose roll, without giving expensive coating to the roll surface. In addition, the structure of the present invention is simpler than the shaft cooling rolls as disclosed in Patent Documents 1 and 2, and is therefore effective in terms of equipment cost.

  Here, FIG. 1 shows a form in which the heat insulating material 5 is supported by left and right furnace walls (not shown), and FIG. 2 shows a form in which it is placed on the floor 8 of the furnace body. The heat insulating material 5 is preferably installed in the roll longitudinal direction in a range wider than at least the entire width of the metal strip 2 to be treated, and more preferably reaches the left and right furnace walls to cover the entire hearth roll.

  Moreover, it is necessary to keep the space | interval of the heat insulating material 5 and the cooling pipe 4, and the hearth roll 3 more than a certain amount. When these and the roll 3 are in contact with each other, there is a risk of wrinkles on the surface as the roll 3 rotates, and if the gap is not sufficiently wide, pieces such as the roll 3, the metal strip 2, and the furnace wall are caught. This is because there is a risk of wrinkles on the roll surface. Although the space | interval of the heat insulating material 5 and the roll 3 is determined in consideration of a roll diameter, the magnitude | size of the piece to produce | generate normally, the cooling capacity of a cooling pipe, etc., it is good to make it into the range of 1-100 mm normally.

  The number and size of the cooling pipes 4 and the type of refrigerant can be determined by the required cooling capacity based on the furnace temperature and the heat resistance temperature of the roll surface. For example, room temperature water or air can be used. It is. The amount of the refrigerant passed through the cooling pipe 4 may be fixed to an appropriate amount, but the flow rate may be adjusted so that the roll surface has an appropriate temperature. For this purpose, a thermometer 6 is installed between the heat insulating material 5 and the hearth roll 3, and a device for adjusting the flow rate so that the indicated temperature becomes a predetermined temperature, specifically an automatic flow control valve, This can be achieved by installing a controller.

  In the case where a plurality of cooling pipes 4 are arranged as in the illustrated example, the flow direction of the refrigerant may not flow in one direction for all the cooling pipes 4 but may flow in the opposite direction as appropriate. . For example, the direction in which the refrigerant flows may be reversed between adjacent cooling pipes 4. And if it does in this way, the cooling nonuniformity of the longitudinal direction (rotating-axis direction) of the hearth roll 3 can be prevented effectively.

  As the hearth roll 3, a carbon roll, a heat resistant metal roll, a ceramic roll, an asbestos roll or the like may be freely selected according to the metal strip material and heat treatment conditions. Although the upper surface part of the hearth roll 3 is always heated, since it immediately faces the cooling pipe 4 as it rotates, the heat is removed and the temperature rise is suppressed. The reached temperature of the hearth roll 3 is approximately the intermediate temperature between the temperature of the gap between the heat insulating material 5 and the hearth roll 3 and the furnace temperature, and is monitored by the thermocouple 6 to control the flow rate of the refrigerant introduced into the cooling pipe 4. It can be adjusted to a temperature range suitable for the hearth roll material.

  Ten continuous hearth rolls 3 were installed in the following five types in a continuous heat treatment furnace for treating various types of steel sheets 2 under conditions of a furnace temperature of 750 to 1150 ° C. and an atmospheric dew point of 0 to 75 ° C. It was used for about 1000 hours, and the quality status and energy consumption of the steel plate 2 during that time were investigated, and the status of the roll surface was investigated after use. The results are shown in Table 1.

  In Examples 1 and 2, four cooling pipes 4 are arranged at a lower portion of a carbon hearth roll 3 having an outer diameter of 150 mm, and a gap of 5 mm is provided from the hearth roll 3 at a predetermined interval in the circumferential direction of the roll 3. Then, a heat insulating material 5 made of fiber having a thickness of 150 mm was installed. In Example 1, the amount of cooling pipe water was adjusted so that the temperature indicated by the thermocouple 6 installed in the gap between the hearth roll 3 and the heat insulating material 5 was 800 ° C. In Example 2, cooling water with a substantially constant amount of water was circulated. The temperature indicated by the thermocouple 6 at that time was in the range of about 600 to 900 ° C.

In Comparative Example 1, the same carbon hearth roll 3 as that in Example 1 was installed without using the cooling pipe 4 and the heat insulating material 5 as in the past.
In Comparative Example 2, the outermost layer (14 mass% Y ₂ O ₃ partially stabilized ZrO ₂ ) was applied to the surface of the roll base material by plasma spraying at a thickness of 500 μm via a 100 μm bonding metal layer (NiCr). The laminated hearth rolls 3 were installed as usual without the cooling pipes 4 and the heat insulating material 5.
In Comparative Example 3, a hollow portion elongated in the axial direction is formed in the iron roll body, and a cooling water guiding pipe penetrating the hollow portion in the axial direction is spaced between the outer peripheral surface and the inner peripheral surface of the hollow portion. A water-cooled hearth roll 3 was used which was arranged so as to be open and configured so that the temperature difference between the center portion and the surface layer portion was not so large.

  In Examples 1 and 2 according to the method of the present invention, the state of the metal strip 2 in operation and the amount of energy loss were good, and the state of the roll surface after 1000 hours was also good.

Table 1

It is a figure which shows an example of the hearth roll structure of this invention. It is a figure which shows another example of the hearth roll structure of this invention.

Explanation of symbols

1 Heat source such as burner or radiant tube 2 Metal strip, steel plate 3 Hearth roll 4 Cooling tube 5 Heat insulation material 6 Thermocouple 7 Top part of furnace body 8 Floor part of furnace body

Claims (2)

  Around the hearth roll that continuously conveys the metal strip, a heat insulating material was installed in a range not in contact with the hearth roll and the metal strip, and a cooling pipe was installed in a space between the heat insulating material and the hearth roll. An in-furnace transfer apparatus for a continuous heat treatment furnace for a metal strip.   A thermometer is provided between the hearth roll and the heat insulating material, and a device is provided that adjusts the amount of refrigerant passed through the cooling pipe so that the indicated temperature of the thermometer becomes a preset temperature. The in-furnace conveyance apparatus of the continuous heat treatment furnace of the metal strip of Claim 1 to do.