JPS5996227A - Continuous annealing installation for silicon steel plate - Google Patents

Abstract

PURPOSE:To prevent the decrease in the iron loss characteristic owing to over- tension during annealing by providing isolatedly a drying furnace and an annealing furnace and providing a device for applying a difference in tension and a heat insulating device between both furnaces. CONSTITUTION:A drying furnace 5 and an annealing furnace 14 are installed isolatedly from each other and are respectively independently heated and controlled. A device 15 for applying a difference in tension for the purpose of eliminating the influence of the tension in a steel strip 2 on the furnace 5 side and the tension in a steel strip 2 on the furnace 14 side by providing a difference between both tensions, for example, a bridle roll is provided. A space necessary for inserting a threading bar used to lead the strip 2 is maintained between the device 15 and a heating zone 6 in the annealing furnace, and an openable and closable heat insulating device 18 for insulating the heat of the strip 2 passing in said space is provided therein.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to continuous annealing equipment for drying and strain relief annealing after application of a final insulating coating during the production of grain-oriented silicon steel sheets.

As is well known, silicon steel sheets are usually used in layers as the iron core of transformers, etc. In that case, it is necessary to provide interlayer insulation, so in the final stage of the silicon steel sheet manufacturing process, the surface Usually, an insulating film is formed on the surface. By the way, silicon copper plates are generally manufactured as coiled continuous belts.
When used in transformers, etc., it is cut into dimensions according to the intended use, but it is usually annealed at 800 to 900°C in a heavy base gas to eliminate the distortion caused by cutting. When producing a coiled 31-continuous silicon steel strip, it is necessary to form an insulating coating with high heat resistance that will not deteriorate due to the high temperatures during annealing.

On the other hand, in order to prevent noise from being generated due to magnetostriction when a silicon n-plate is used in a transformer, it is effective to form a wave film that is vitrified at high temperature. Recently, in order to form a highly heat-resistant 3-edge test film that is vitrified at high temperatures, an insulating coating liquid is applied to the circumferential surface and dried by heating, and then the coating is applied at the same time as strain relief annealing. A vitrification process has been developed.

Conventionally, as shown in FIG. 1, the equipment for applying the insulating coating liquid, dry bombing, and annealing is as shown in FIG.
After applying the insulating coating liquid to the surface of the copper strip in the coating device 4, the insulating coating liquid is dried and baked in the drying oven 5, and then annealed in the annealing furnace heating zone 6 and the homogenizing zone 7, Furthermore, equipment is known in which the coil is wound up by a coil winding device 10 after passing through a cooling zone 8 and an eye zone storage device 9. Furthermore, FIG. 2 shows an enlarged view of the drying furnace 5 and the annealing furnace heating zone 6 in the above-mentioned conventional equipment.

A steel strip 2 coated with an insulating coating liquid on both sides by a coating device 4
It is necessary to avoid any objects coming into contact with the surface until the insulating coating is completely burned out.
Therefore, as shown in FIG. 2, from the cloth bag [4] to the support row 511 near the outlet of the drying oven 5, it is not supported by rollers or the like, and travels in a sagging state due to its own weight. That is, the drying process 'P5 is a so-called catenary furnace.

Further, in FIG. 2, the fuel is subjected to non-oxidative combustion (air ratio 0.9 to 1.0) in the annealing furnace heating zone 6, and the exhaust gas that has been incompletely combusted in the annealing furnace heating zone 6 is pressure-adjusted by the damper 12. The air sent to the drying furnace 5 and blown out from the air supply port 13 in the drying furnace 5 and given a swirling motion reacts with the exhaust gas from the annealing furnace heating zone 6 and burns.

In the conventional equipment as described above, the tension due to the hanging part of the steel strip 2 in the drying furnace 5 (hereinafter referred to as the catenary part) - (7) dead weight is applied to the annealing furnace heating zone 6.
The tension is also added to the steel strip in the soaking process 7, and therefore the tension becomes too high for strain relief annealing, leading to deterioration of product properties. In other words, the appropriate tension for strain relief annealing of silicon steel is 0.3 to 0.7 k (approximately 1/r, preferably 0.5 kg/- or less, and if the tension is greater than this, the steel of the product will be damaged). Although the loss value becomes large, in a furnace with a catenary, the unit tension usually reaches about 1 to 2 kg/-, and it is extremely difficult to operate at less than about 0.5 kg/i, so the above-mentioned equipment was used. In some cases, deterioration of iron loss characteristics during strain relief annealing was avoided (in reality, this was not possible).

Additionally, the insulating coating that is generally applied, dried, and baked on silicon steel is extremely thin, with a thickness of about 2 to 5 tones at most.
Furthermore, since the insulating coating has not yet vitrified in the annealing furnace heating zone 6, if the atmosphere in the furnace at that stage is oxidizing, there is a risk that nitric elements in the atmosphere will diffuse into the coating and make the base steel profitable. be. However, oxygen is present during the annealing process of the fuel in the annealing furnace heating zone 6, and a large amount of moisture generated by combustion is present in the exhaust gas (dew point: 40 to 60°C), and the insulating coating liquid evaporates from the drying furnace. As a result, in the annealing furnace heating zone 6, the presence of oxygen and moisture causes the base iron on the surface of the steel strip to become molar, causing coloration due to oxides, which significantly impairs the appearance of the product, and also causes bending due to grain boundary oxidation. There is a problem of being vulnerable to Then, the exhaust gas sent from the annealing furnace heating zone 6 to the drying furnace 5 has a temperature of 1000~
As the temperature reaches as high as 1200°C, the rise in temperature of the copper strip in the drying oven 5 becomes unstable, making it impossible to maintain the board temperature below 600°C, which is required to prevent oxidation during heating in the air, and drying Oxidation of the base iron also occurs in the furnace 5, which may cause discoloration and embrittlement.

This invention was made in view of the above circumstances, and it is possible to independently control the steel strip tension during insulation technology, drying and baking of one liquid, and the wrapping tension during strain relief annealing. The basic purpose and purpose of this is to prevent the iron loss characteristics from deteriorating due to excessive tension during annealing.In addition, it is intended to effectively utilize the heat from the hatch, and to reduce the The purpose is to prevent this as much as possible.

In other words, this invention uses silicon 5! In continuous annealing equipment for applying an insulating film to the surface of the I-plate and annealing it, the drying furnace and annealing furnace are installed separately, and a drying furnace is installed between the drying furnace and the annealing furnace. It is characterized by being equipped with a tension difference applying device for applying a tension difference between the steel strip on the blast furnace side and the ζ] strip on the annealing furnace side, and an insulation opening for keeping the E3 zone warm. It is.

An example of the continuous annealing equipment of the present invention will be described in detail below with reference to FIG. 3. In FIG. 3, the same elements as those shown in FIG. 1 are denoted by the same reference numerals, and the explanation thereof will be omitted.

In Fig. 3, there is J3 (next to the coating device 4 for applying the insulating coating liquid to the j band 2, there is a drying process as in the case of Fig. M1).
iP5 is provided. However, this drying furnace 5 is separate from the annealing furnace 14, which consists of a heating zone 6, a soaking zone 7, and a cooling zone 8. That is, the drying furnace 5 and the annealing furnace 14 are
are installed at a distance from each other, and are configured to be heated independently of each other. Between the drying furnace 5 and the annealing furnace heating zone 6, a difference is created between the tension of the copper strip on the drying furnace side and the tension of the copper strip on the annealing furnace side to block the influence of both tensions. A tension difference applying device 15, for example a priddle roll, is provided, and the tension on the drying oven side is adjusted by a tension setting device 16 provided before the coating device 4, and the tension on the drying oven 14 side is adjusted after the cooling zone 8. They are each configured to be independently controlled by a tension setting device 17 provided therein.

Furthermore, between the tension difference imparting device 15 and the annealing furnace heating zone 6,
A necessary interval is maintained for inserting a threading bar to lead the steel strip into the annealing furnace 14, and a heat insulating device that can be opened and closed is installed at this interval to keep the copper strip passing through that section warm. 18 have been installed.

In the above practical example, the tension difference applying device 15 is provided between the drying furnace 5 and the annealing furnace 14 as described above.
The gate tension on the drying furnace 5 side and the 21st tension on the annealing furnace 14 side can be controlled independently. That is, the tension of the steel strip in the example of the annealing furnace 14 can be set to an appropriate level without being influenced by the tension of a part of the catenary in the drying furnace 5. Here, the present inventors have determined that the material grade G8 has a plate thickness of 0 and 3.
When the relationship between the tension during strain relief annealing and the iron loss value of the product ~'1' 17/50 was investigated for a silicon steel strip of .omm, the results shown in FIG. 4 were obtained. From Figure 4, the iron loss value ＼V17150 suddenly increases when the tension during annealing exceeds 0.51 (g/r4J). Therefore, in order to obtain a product with low iron loss, it is necessary to It is clear that it is preferable to suppress the belt tension to 0.5!+/- or less.In the case of the conventional equipment shown in FIGS. The weight of the part also affects the annealing furnace side, and the tension is 1 on the annealing furnace side as well.
~2 ko/rha, but in the case of this invention, the tension on the annealing furnace side is set to 0.5, regardless of the tension on the drying furnace 5 side that has a part of the catenary! It has actually become possible to suppress the value to a small value of II/- or less, and as a result, it has become possible to improve the characteristics of the product, especially the iron loss characteristics.

Further, the distance between the tension difference applying device 15 and the annealing furnace 14 is as follows:
As mentioned above, the threading bar is held only at a distance sufficient to insert the threading bar, but since a heat retaining device 18 that can be opened and closed is provided at this interval, the Bty1 sensible heat obtained in the drying oven 5 is is not wasted and is effectively used in the next annealing furnace heating zone 6, making it possible to achieve zero energy in the annealing furnace. That is, the appropriate drying temperature for the insulation coating on a silicon steel plate is 400 to 600'C, and the temperature for vitrification and strain relief annealing of the coating is 80°C.
A temperature of 0 to 850°C is considered appropriate, and in this case, assuming that 50% of the sensible heat obtained in the drying furnace is used in the annealing furnace without being dissipated, the annealing furnace will save about 20% of energy. It will be possible to achieve this.

The drying oven 5 is a conventional installation 5 shown in FIGS. 1 and 2.
Because the exhaust gas from the annealing furnace heating zone is not used as in the case of
In addition, 4) a source is required. The heating method in this drying furnace 5 can be any method such as gas combustion heating, electric n1 radiant tube heating, etc., but in any case, it is much more effective than the case where exhaust gas from the annealing furnace heating zone is used. It is possible to maintain a stable board temperature for up to 9q. Here, the present inventors, in the same way as above,
When we investigated the relationship between the board temperature and the appearance of the end piece during the drying and baking of the coating bag of the insulating coating liquid for 0-30 mm silicon 8 strips, the results shown in Table 1 were obtained.

From Table 1, it is clear that dry Ω baking causes poor appearance when the plate thickness reaches 800°C, and that a good outer a can be maintained by keeping the thickness below about 600°C. In the conventional equipment, the annealing furnace exhaust gas was introduced into the drying furnace by eight people, which caused the plate temperature to become unstable and cause poor appearance, but in the case of this invention, the plate temperature during drying It is now possible to stably suppress the thickness to about 600°C or less and reliably prevent appearance defects.

On the other hand, as for the heating method in the annealing furnace heating zone 6, since there is no need to send combustion exhaust gas to the drying furnace 5 unlike in conventional equipment, a radiant duplex is used to reduce oxygen and moisture in the atmosphere as much as possible. It is preferable to use vacuum heating or electric heating.

By using these heating methods, it is possible to prevent the presence of oxygen and moisture in the atmosphere in the furnace, and to prevent oxidation of the base iron. Further, since the drying furnace 5 is provided to be separated from the annealing furnace heating zone 6, moisture caused by evaporation of the insulating coating liquid in the drying furnace 5 is effectively prevented from entering the annealing furnace heating zone 6. Here, the inventors
The results of investigating the influence of the annealing atmosphere on the repeated bending resistance and appearance of the product for Type 1 G8 silicon steel strip are shown in the second section.
Shown in the table. However, the annealing conditions were 800°C for 20 seconds.

Table 2: At a dew point of 40°C, which is lower than about 50'C in the exhaust gas generated by the combustion of dark 'lHj, or at a dew point of 11%, the resistance to bending and appearance deteriorate, and the dew point decreases. Good repeated bending resistance and appearance are obtained only when the temperature is 20° C. and the oxygen content is 20%, both of which are low. Such conditions can only be achieved by radiant tube heating or electric heating, which does not burn fuel directly in the furnace.

In addition, in the above-mentioned example, the tension difference applying device 15 and the maintenance device 18 between the drying furnace 5 and the annealing furnace 14 are connected to the drying furnace 5.
Although the tension difference applying device 15 is arranged on the side of You can arrange it as follows.

As is clear from the above description, the annealing equipment of the present invention includes a drying furnace for drying and baking the insulating coating liquid;
The annealing furnace for vitrifying the insulating coating and strain relief annealing is provided one space apart from the annealing furnace, and a tension difference applying device is provided between them, so that the tension of the steel strip on the annealing side is adjusted to The catenary can be set to an appropriately small value without being affected by the tension caused by part of the suspension, which effectively prevents the steel strip tension during annealing from becoming excessive and deteriorating the properties of the product. In addition, since a heat retention device is provided between the drying furnace and the annealing furnace in addition to the tension difference applying device, the n-band sensible heat given during drying can be effectively used in the annealing furnace without being wasted. Therefore, the effect of reducing thermal energy consumption can also be obtained. Furthermore, according to the annealing equipment of the present invention, since the annealing furnace and the drying furnace are provided separately, the t3 evaporated in the drying furnace
There is no risk of moisture in the final coating liquid entering the annealing furnace, and there is no need to send the exhaust gas from the annealing furnace to the drying furnace. Since the presence of 00 elements and moisture in the annealing furnace atmosphere can be prevented by using this method, it is also possible to prevent the oxidation of the copper strip base iron in the annealing furnace heating zone and prevent deterioration of product appearance and repulsion resistance due to nization. Furthermore, since there are no 8 people on the same ladder to transfer the exhaust gas from the annealing furnace to the drying furnace, it is possible to keep the plate temperature stable in the drying furnace and reduce the m It is also possible to prevent
：It becomes Hi.

[Brief explanation of the drawing]

Figure 1 is an illustration showing an example of a 5-inch continuous annealing installation for a 5-inch annealing board for a Jouryo board, Figure 2 is an enlarged view of the main part of the equipment shown in Figure 1, and Figure 3
0 shows an example of the continuous annealing step failure of this invention, and FIG.
It is a graph showing the influence on /50. 2... Steel strip, 4... Gu'l' (i device, 5...
・Dry; 1″: Furnace, 6... Annealing furnace heating zone, 14...
- Annealing furnace, 15... tension difference imparting device, 18...
Heat retention device. Applicant Kawasaki Steel Co., Ltd. Agent Patent attorney Takehisa Wada (and 1 other person)

Claims (1)

[Scope of Claims] Continuous annealing equipment for coating the surface of a silicon steel plate with an insulating coating, drying it, and then baking it, comprising: a drying furnace and an annealing furnace provided separately; and a space between the drying furnace and the annealing furnace. A silicon steel plate characterized in that an external tension applying device for applying a tension difference between the copper strip on the drying furnace side and the copper strip on the annealing furnace side, and a heat retention device for keeping the copper strip warm are arranged. continuous annealing equipment.