JP2011106027A - Piping structure of open fire furnace in continuous annealing furnace, open fire furnace, continuous annealing furnace, and method for manufacturing metal strip - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piping structure of an open-fire furnace in a continuous annealing furnace with which as the piping structure of the open-fire furnace in the continuous annealing furnace, the stickness of foreign matters to a heat-treating material can be restrained and also, a cost of facility investment can be reduced. <P>SOLUTION: As the piping structure of the open-fire furnace 20 in the continuous annealing furnace, filters 2 are set in the fuel gas piping for open-fire heating burner 15, and the up-stream side of the filter 2 is used with a general carbon steel pipe 1 and the down-stream side of the filter 2 is used with SUS (stainless steel) piping 3. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a piping structure of a heating zone (direct furnace) using a direct heating heating burner in a continuous annealing furnace, a direct heating furnace, a continuous annealing furnace, and a method for producing a metal strip.

  In recent years, a high quality level is required for cold-rolled steel sheets, in particular, cold-rolled steel sheets for automobiles, and in the continuous annealing process (continuous annealing furnace), it is necessary to produce such that defects are hardly generated.

  In general, a continuous annealing furnace for a metal strip (for example, a steel strip) is provided with a heating zone, a soaking zone, and a cooling zone, and the heating zone is a heating zone (direct furnace) using a direct fire heating burner. (For example, Patent Document 1).

  In a heating zone (direct furnace) using such a direct fire heating burner, a general carbon steel pipe (a pipe using a general carbon steel pipe) is usually used as a fuel gas pipe.

  However, in the case of general carbon steel piping, it may react and corrode with impurity components contained in the fuel gas to generate foreign matter, and the generated foreign matter may be burned black on the surface of the metal strip. In that case, there is a concern not only that the surface appearance of the metal strip is bad, but also that the mold is damaged during press molding of the metal strip.

  Therefore, the adhesion of foreign matter to such a metal strip is most strictly managed in the outer plate for automobiles. The foreign matter adhering portion in the metal band cannot be shipped as a product and is cut. Furthermore, depending on the position of the foreign matter, the vicinity of the foreign matter attachment portion may be scrapped due to insufficient single weight, resulting in a decrease in product yield.

  In order to prevent foreign matter from adhering to such metal strips, if SUS piping (piping using stainless steel pipe) is used instead of general carbon steel piping, the fuel gas piping will not corrode, and foreign matter will be generated and adhered. Is suppressed.

JP 2005-213624 A

  However, as shown above, the use of the SUS pipe as the fuel gas pipe of the direct furnace in the continuous annealing furnace has a problem that the capital investment is expensive compared to the general carbon steel pipe. .

  The present invention has been made in view of the circumstances as described above. As a piping structure of a direct-fired furnace in a continuous annealing furnace, it is possible to accurately prevent foreign matter from adhering to a heat treatment material (for example, a metal strip) and to install a facility. A direct-fired furnace piping structure in a continuous annealing furnace that can reduce investment costs. It is another object of the present invention to provide a direct furnace having the piping structure, a continuous annealing furnace having the direct furnace, and a method for producing a metal strip using the continuous annealing furnace.

  In order to solve the above problems, the present invention has the following features.

  [1] A piping structure of a direct-fired furnace in a continuous annealing furnace, wherein a filter is installed in the piping of the direct-fired heating burner.

  [2] The piping structure of the direct-fired furnace in the continuous annealing furnace according to [1], wherein the upstream side of the filter is a general carbon steel pipe and the downstream side of the filter is a SUS pipe.

  [3] The piping structure of the direct-fired furnace in the continuous annealing furnace according to [1] or [2], wherein the piping before and after the filter is bypassed.

  [4] A direct furnace in a continuous annealing furnace having the piping structure according to any one of [1] to [3].

  [5] A continuous annealing furnace having the direct-fired furnace according to [4].

  [6] A method for producing a metal strip, comprising producing the metal strip using the continuous annealing furnace according to [5].

  In the present invention, as a direct-fired furnace piping structure in a continuous annealing furnace, adhesion of foreign matters to the heat treatment material (metal strip) can be accurately suppressed, and the cost of capital investment can be reduced. Moreover, according to the metal strip manufacturing method of the present invention, it is possible to stably manufacture a steel plate for an automobile outer plate that requires high surface quality while maintaining excellent surface quality and at a high yield.

It is a figure which shows Embodiment 1 of this invention. It is a figure which shows Embodiment 2 of this invention. It is a figure which shows Embodiment 2 of this invention. It is a figure which shows the result of Example 1 of this invention.

  Embodiments of the present invention will be described with reference to the drawings.

[Embodiment 1]
As described above, conventionally, the fuel gas piping of a direct furnace of a continuous annealing furnace of a metal strip (for example, a steel strip) is a carbon steel piping, and impurity components (mainly sulfur) contained in the fuel gas and the carbon steel piping. Reacts and corrodes to generate foreign matter (mainly FeS), and the foreign matter accumulated over a long period of time reaches the burner (direct fire heating burner) and is sprayed onto the metal strip.

  On the other hand, in Embodiment 1 of this invention, the fuel gas piping of the direct-fired furnace of a continuous annealing furnace is as shown in FIG.

  That is, as shown in FIG. 1, in the direct-fired furnace 20 in the first embodiment, the in-furnace roll 13 is used by using the direct-fired heating burner 15 installed in each zone (the first zone 4 to the eighth zone 11). A filter (strainer) 2 is installed in the fuel gas piping of the direct-fired heating burner 15 when the metal strip 12 supported and conveyed by is heated. The upstream side of the filter 2 is a general carbon steel pipe 1, and the downstream side of the filter 2 is a SUS pipe 3.

  By adopting such a pipe structure, even if the general carbon steel pipe 1 on the upstream side of the filter 2 reacts and corrodes with the impurity component contained in the fuel gas, and foreign matter is generated, the filter 2 moves downstream. Is prevented from reaching the direct fire heating burner 15.

  In order to suppress the movement of foreign matter downstream, the filter 2 is preferably installed in the fuel gas pipe immediately before the direct fire heating burner 15 and within 10 m before the direct fire heating burner 15 (upstream of the direct fire heating burner). If the distance is within 5 m before the direct fire heating burner, more excellent effects can be obtained.

  Further, the SUS pipe 3 on the downstream side of the filter 2 does not corrode due to the reaction with the fuel gas and does not become a source of foreign matter. Therefore, the adhesion of foreign matter to the metal strip can be greatly reduced. As the general carbon steel pipe, for example, a carbon steel pipe for piping (SGP), a carbon steel pipe for pressure piping (STPG), a carbon steel pipe for high pressure piping (STS), a carbon steel pipe for high temperature piping (STPT), etc. are used. Is possible. Moreover, as the SUS pipe, SUS304, SUS309, or the like can be used.

  Here, the mesh of the filter 2 is preferably # 40 mesh (about 0.63 mm square) to # 120 (about 0.21 mm square). This is because if it exceeds # 120 mesh, clogging occurs and there is a concern that the line will stop due to a decrease in the fuel gas flow rate.

  As for the material of the filter 2, it is preferable to use stainless steel, for example, SUS304, SUS309, etc., in order to prevent corrosion due to reaction with the fuel gas.

  As described above, in the first embodiment, as a piping structure of the direct-fired furnace 20 in the continuous annealing furnace for the metal strip, it is possible to accurately prevent foreign matter from adhering to the metal strip and reduce the cost of capital investment. It has become.

  And it becomes possible to manufacture a metal strip having a good surface property by performing continuous annealing of the metal strip using a continuous annealing furnace having such a direct-fired furnace piping structure.

[Embodiment 2]
In the first embodiment, the filter 2 can be replaced only when the line is stopped.

  On the other hand, the finer the mesh of the filter 2 can reduce the adhesion of foreign matters to the metal band 12, but the period until clogging is shortened. When the occurrence of clogging is shorter than the periodic repair interval, it is necessary to stop the line for replacing the filter 2, and there is a concern that the line operation rate may be lowered.

  Therefore, in the second embodiment, in order to cope with the above-described case, as shown in FIG. 2, pipes before and after the filter 2 are bypassed.

  That is, as shown in FIG. 2, two filters 2 (filter 2a, filter 2b) are installed in parallel and can be switched by the switching valve 16, and the other filter 2b is not used while one filter 2a is in use. In operation, when the filter 2a in use is clogged, the filter 2a in use is not used by the switching valve 16, and the filter 2b that has not been used is used.

  This makes it possible to replace the clogged filter 2a with a good filter without stopping the line operation.

  Further, although not particularly illustrated, when replacing the clogged filter 2a, the replacement of the filter 2a can be performed safely by enabling air replacement in the piping before and after the filter 2a. .

  FIG. 3 shows a direct-fired furnace 21 configured by applying the bypassed piping structure in the second embodiment shown in FIG. 2 to the first embodiment shown in FIG. Incidentally, in FIG. 3, among the direct fire zones (first zone 4 to eighth zone 11) in FIG. 1, the third zone 6, the fourth zone 7, the seventh zone 10, and the eighth zone 11 are bypassed. Applicable piping structure is applied. Other configurations are the same as those in FIG.

  In this way, in the second embodiment, by using a bypassed piping structure, even when the filter 2 is clogged using a fine mesh filter 2, the line operation is stopped. Therefore, the clogged filter 2 can be replaced.

  The continuous annealing furnace is not particularly shown, but it is equipped with a direct-fired furnace, annealing furnace (soaking furnace), cooling furnace, overaging furnace, etc. from the upstream side of the line. This equipment is effective when applied in a short time, and it is possible to produce a metal strip having a good surface property by using a direct furnace having a piping structure in the present invention. The continuous annealing furnace is equipped with equipment that performs surface treatment (for example, hot dip galvanization, plating alloying treatment, etc.) on the surface of the heat treatment material (metal strip) in addition to the direct furnace, annealing furnace, and cooling furnace. May be applied to the present invention, and even in that case, it is possible to produce a metal strip having a good surface property.

  Example 1 of the present invention is shown below.

  As an example of the present invention, using a continuous annealing furnace provided with the direct-fired furnace 20 according to the first embodiment of the present invention shown in FIG. That is, in the present invention example, the filter 2 is installed in the fuel gas pipe immediately before the direct fire heating burner 15 (position 5 m before the direct fire heating burner), and the upstream side of the filter 2 is the general carbon steel pipe 1. The downstream side of the filter 2 is a SUS pipe 3.

  At this time, the case where the mesh of the filter 2 is # 40 mesh (approximately 0.63 mm square) is the present invention example 1, and the case where the mesh of the filter 2 is # 120 (approximately 0.21 mm square) is the present invention example. 2.

  On the other hand, as a conventional example, a continuous annealing furnace provided with a direct-fired furnace in which all fuel gas pipes are general carbon steel pipes was used for continuous annealing of steel sheets for automobile outer plates. Incidentally, in the conventional example, no filter is installed in the fuel gas pipe.

  FIG. 4 compares the foreign matter crash rate in the conventional example and the inventive examples 1 and 2 (the ratio of the steel plate for automobile outer plates that has been degraded due to adhesion of foreign matter in the direct-fired furnace of the continuous annealing furnace (scrap ratio)). Is.

  As shown in FIG. 4, compared to the conventional example, the foreign matter degradation rate is reduced to about ½ in the present invention example 1, and the foreign matter degradation rate is reduced to 1/10 or less in the present invention example 2. .

  This confirmed the effectiveness of the present invention.

  Example 2 of the present invention is shown below.

  As Invention Example 3, continuous annealing of a metal strip (steel plate for automobile outer plate) was performed using a continuous annealing furnace provided with the direct-fired furnace 21 of Embodiment 2 of the present invention shown in FIG.

  At this time, the meshes of the filters 2 (2a, 2b) in the third zone 6, the fourth zone 7, the seventh zone 10, and the eighth zone 11 that are bypassed are set to # 120 (about 0.21 mm square), and are bypassed. The meshes of the filter 2 in the first zone 4, the second zone 5, the fifth zone 8, and the sixth zone 9 that were not used were also set to # 120 (about 0.21 mm square).

  Then, in the third zone 6, the fourth zone 7, the seventh zone 10, and the eighth zone 11, when the bypassed filter 2 (using the filter 2a, not using the filter 2b) was operated, periodic repair (6 weeks) ) The filter 2a is clogged in a period shorter than the interval (2 weeks), so that the operation is not stopped by setting the filter 2a to the non-use state and the filter 2b to the use state by the switching valve 16. In addition to continuous annealing, the clogged filter 2a was replaced.

  As a result, in this invention example 3, the foreign matter crash rate is 0.12%, and the same effect as in the invention example 2 in the above-described embodiment 1 is obtained, and it is necessary to stop the line for replacing the filter. The decrease in line operation rate was suppressed.

  Thus, the effectiveness of the present invention was further confirmed.

1 Carbon steel piping 2 Filter (strainer)
2a, 2b filter (strainer)
3 SUS piping 4 Direct-fired furnace 1st zone 5 Direct-fired furnace 2nd zone 6 Direct-fired furnace 3rd zone 7 Direct-fired furnace 4th zone 8 Direct-fired furnace 5th zone 9 Direct-fired furnace 6th zone 10 Direct-fired furnace 7th zone 11 Direct-fired furnace 8th Zone 12 Metal strip 13 In-furnace roll 15 Direct-fired heating burner 16 Switching valve 20 Direct-fired furnace 21 Direct-fired furnace

Claims (6)

  A direct-fired furnace piping structure in a continuous annealing furnace, wherein a filter is installed in the piping of a direct-fired heating burner.   The piping structure of a direct-fired furnace in a continuous annealing furnace according to claim 1, wherein the upstream side of the filter is a general carbon steel pipe, and the downstream side of the filter is a SUS pipe.   The piping structure of the direct-fired furnace in the continuous annealing furnace according to claim 1 or 2, wherein piping before and after the filter is bypassed.   The direct-fired furnace in the continuous annealing furnace which has the piping structure in any one of Claims 1-3.   A continuous annealing furnace having the direct-fired furnace according to claim 4.   A metal strip production method using the continuous annealing furnace according to claim 5.

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