JP3959747B2 - Method for producing high silicon steel strip - Google Patents

Description

[0001]
[Industrial application fields]
TECHNICAL FIELD The present invention relates to a method for producing a high silicon steel strip having a good surface property free of pressing in a high silicon steel strip production or heat treatment line having a high-temperature continuous furnace having an in-furnace hearth roll.
[0002]
[Prior art]
In a continuous processing furnace that manufactures or heat-treats high silicon steel strips, deposits are generated and deposited on the surface of the hearth roll in the furnace due to various causes, which cause crushing on the steel strip and deteriorate the surface properties of the steel strip. There is a problem. For example, in the magnetic annealing and decarburization annealing of the high silicon steel strip performed in a continuous annealing furnace, the oxide scale on the bottom surface of the steel strip is the surface of the hearth roll in the furnace. In the production of high silicon steel strip by gas silicidation treatment performed in a continuous siliconization furnace, trace oxygen and moisture in the furnace react with silicon tetrachloride and the like. It is thought that the main cause is that silica (SiO ₂ ) produced by reacting with gas adheres to and deposits on the surface of the hearth roll in the furnace. In addition, the refractory in the furnace that has fallen off and scattered also adheres and accumulates on the surface of the hearth roll in the furnace.
Conventionally, in order to remove such deposits on the hearth roll in the furnace, the furnace is cooled down and the furnace is opened to clean the hearth roll in the furnace or the high silicon steel strip is stopped and the furnace is stopped. A method of scraping off the deposits by rotating the hearth roll and slipping the hearth roll with respect to the high silicon steel strip is employed.
[0003]
[Problems to be solved by the invention]
However, in the former method, it is necessary to stop the operation for a long time in order to open the furnace and start up the furnace after that, and also in the latter method, in order to effectively scrape off the deposits, Since it is necessary to lower the temperature, there is a problem that substantial operation cannot be performed during that time.
Thus, conventionally, when trying to produce a high silicon steel strip without push rods in a continuous processing furnace having an in-furnace hearth roll, the deposits on the in-furnace hearth roll must be periodically removed by the above method. Therefore, it was difficult to continuously produce a high silicon steel strip having a good surface property with no lashes for a long time.
Accordingly, an object of the present invention is to continuously produce a high silicon steel strip having a good surface property without a crush for a long time in a production or heat treatment line of a high silicon steel strip such as a continuous annealing furnace or a continuous siliconization furnace. It is to provide a method that can be manufactured.
[0004]
[Means for Solving the Problems]
In order to achieve such an object, the present invention provides a furnace hearth peripheral speed with respect to the sheet passing speed of the steel strip within a range in which there is an effect of scraping off deposits and the steel strip does not undergo elongational deformation due to creep. By slowing down and slipping the steel strip and the hearth roll surface, the deposits on the hearth roll surface in the furnace are constantly scraped off by contact with the steel strip, and thus the deposits on the surface of the hearth roll in the furnace are removed. The accumulation is prevented.
That is, the present invention relates to the in-furnace hearth roll peripheral speed relative to the steel strip passage speed when the steel band is passed through a high-temperature continuous furnace having a hearth roll in the furnace in the production of a high silicon steel strip or a heat treatment line. Is slowed down to satisfy the following formula, and the steel strip is passed through so that the in-furnace hearth roll always slips relative to the steel strip.
0.3 ≦ [1− (hearth speed in furnace / steel strip speed)] × 100 ≦ 5.0
[0005]
[Action]
FIG. 1 shows one configuration example of a horizontal continuous annealing furnace to which the method of the present invention is applied, where 1 is a heating zone, 2 is a soaking zone, and 3 is a cooling zone. FIG. 2 shows an example of the configuration of a horizontal continuous siliconizing furnace to which the method of the present invention is applied. 4 is a heating zone, and 5 is a siliconizing furnace to which a reaction gas for siliconizing treatment is supplied. A treatment zone, 6 is a soaking zone for diffusing Si permeating into the steel strip surface layer in the thickness direction by heat treatment, and 7 is a cooling zone. In these horizontal continuous processing furnaces, the steel strip S is supported by the in-furnace hearth roll 8 and passes through.
[0006]
In such a continuous processing furnace that manufactures or heat-treats high silicon steel strips, there are various causes for the deposits that generate push rods on the steel strip surface to be generated and deposited on the hearth roll in the furnace. In the magnetic annealing and decarburization annealing performed in the continuous annealing furnace as shown in FIG. 1, the main cause is that the oxide scale generated on the lower surface of the steel strip S adheres to and accumulates on the surface of the hearth roll 8 in the furnace, In addition, in the gas silicidation treatment performed in a continuous siliconization treatment furnace as shown in FIG. 2, silica (SiO ₂ ) produced by reaction of trace amounts of oxygen and moisture in the furnace with a reaction gas (such as silicon tetrachloride) is produced. The main cause is adhesion and deposition on the surface of the hearth roll 8 in the furnace.
[0007]
The amount of deposits deposited on the in-furnace hearth roll 8 increases with time, and as a result, the generation of push rods in the steel strip S becomes significant. However, the steel in the furnace hearth roll 8 always slips against the steel strip S. If the strip S is made to pass through, the adhering matter adhering to the roll surface during one rotation of the furnace hearth roll 8 will always be scraped off at the contact surface with the steel strip S. Accumulation of deposits that may occur is prevented, and scraping of the deposits itself is easy. For this reason, in this invention, the peripheral speed of the hearth roll 8 in a furnace is made small with respect to the plate | board speed of the steel strip S, and the scraping action of the above deposits is acquired.
[0008]
In the present invention, the speed difference between the sheet feeding speed of the steel strip S and the peripheral speed of the in-furnace hearth roll 8 is an important condition. That is, if this speed difference is too small, the effect of scraping off the deposits is small. On the other hand, if the speed difference is too large, the steel strip S undergoes plate deformation due to creep elongation. As a result of the experiment, the peripheral speed of the hearth roll 8 in the furnace is decelerated within a range corresponding to 0.3 to 5.0% with respect to the plate feed speed of the steel strip S, that is, the reduction ratio = [1− (furnace Inner hearth roll peripheral speed / steel strip through speed)] × 100 is defined as 0.3 to 5.0, so that the inner hearth roll surface can be attached without causing plate deformation due to creep elongation. It has been found that the kimono can be scraped off effectively, thereby preventing the deposition of deposits that would cause push folds.
[0009]
Accumulation of deposits on the surface of the hearth roll in the furnace is likely to occur mainly in the soaking zone 2 in the continuous annealing furnace as shown in FIG. 1 and mainly in the silicified zone 5 in the continuous siliconizing furnace as shown in FIG. Therefore, it is preferable to apply the method of the present invention to at least these treatment zones. However, the peripheral speed of the in-furnace hearth roll 8 in the upstream processing zone (the heating zone 1 in FIG. 1 and the heating zone 4 in FIG. 2) is higher than the peripheral speed of the in-furnace hearth roll 8 in these processing zones. In such a case, the steel strip S may be slackened in the longitudinal direction. Therefore, in the continuous annealing furnace as shown in FIG. 1, at least the heating zone 1 and the soaking zone 2 and the continuous siliconization treatment as shown in FIG. In the furnace, the method of the present invention is preferably applied to at least the heating zone 4 and the siliconization zone 5. Needless to say, the method of the present invention can be applied to other processing zones.
In addition, from the viewpoint of scraping off the adherence of the hearth roll in the furnace, a method of reducing the steel strip passing speed with respect to the peripheral speed of the hearth roll in the furnace is also conceivable. Since the slackening occurs, the plate-passability of the steel strip is significantly impaired.
[0010]
【Example】
[Example 1]
In the horizontal type continuous annealing furnace shown in FIG. 1, the steel strips of the following (1) to (3) are subjected to magnetic annealing under conditions of 1200 ° C. × 3 minutes, and at that time, The creep ratio of the steel strip on the furnace exit side was measured by changing the reduction ratio of the inner hearth roll peripheral speed.
(1) 6.5% Si steel plate (plate thickness: 0.1 mm × plate width: 900 mm)
(2) 3.0% Si steel plate (plate thickness: 0.1 mm x plate width: 900 mm)
(3) 1.0% Si steel plate (plate thickness: 0.1 mm × plate width: 900 mm)
[0011]
FIG. 3 shows the relationship between the reduction ratio of the hearth roll peripheral speed in the furnace with respect to the steel strip passing speed and the creep elongation of the steel strip on the furnace exit side for each steel strip. Decreasing the hearth speed in the furnace relative to the plate speed of the steel strip generates a frictional force between the steel strip and the surface of the hearth roll. Will occur. And when this elongation becomes too large, a wave-like deformation occurs in the sheet width direction, and at the same time, the magnetic properties of the Si steel sheet are significantly deteriorated. In order to suppress the deterioration of the magnetic characteristics, the creep elongation needs to be about 0.3% or less. According to FIG. 3, the extent of creep elongation due to the reduction of the hearth roll speed in the furnace relative to the steel plate passing speed is the highest in the 6.5% Si steel strip, which is a high silicon steel strip, and this 6.5% Si steel. It can be seen that the reduction ratio needs to be 5.0% or less in order to suppress the creep elongation of the belt to 0.3% or less.
[0012]
[Example 2]
In the continuous silicidation furnace shown in Fig. 2, the siliconization process is performed by changing the reduction ratio of the peripheral speed of the hearth roll in the furnace to the steel plate passage speed, and the steel strip surface is inspected on the furnace exit side. Thus, the speed of occurrence of pressing sticks (the number of pressing sticks generated per unit time, 0 means no occurrence of pressing sticks). FIG. 4 shows the result. When the speed reduction ratio is 0.3% or more, the speed of occurrence of pushing stick becomes almost zero, and pushing stick is not generated. That is, by setting the reduction ratio of the hearth roll peripheral speed in the furnace to the steel strip passing speed to be 0.3% or more, it is possible to appropriately remove deposits such as silica (SiO ₂ ) attached to the furnace hearth roll. understood.
[0013]
【The invention's effect】
According to the above-described method of the present invention, in a continuous annealing furnace for high silicon steel strips or a continuous siliconization treatment furnace using a gas immersion method, the surface of the hearth roll in the furnace without causing plate deformation or deterioration of magnetic properties of the steel strip. Adhesive deposits can be removed appropriately and quickly, thereby preventing deposits from accumulating on the surface of the hearth roll in the furnace, and high silicon steel strips with good surface properties without crushing can be continuously applied for a long time. It can be manufactured.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing a continuous annealing furnace for a silicon steel strip. FIG. 2 is an explanatory view showing a continuous siliconizing furnace using a gas immersion method. FIG. 3 is a steel strip through plate in a continuous annealing furnace for a silicon steel strip. Fig. 4 is a graph showing the relationship between the reduction ratio of the hearth roll peripheral speed in the furnace to the speed and the creep elongation of the steel strip. [Fig. 4] In the continuous siliconization furnace using the gas siliconization method, Graph showing the relationship between the speed reduction ratio and the speed at which the pushing rod is generated [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Heating zone, 2 ... Soaking zone, 3 ... Cooling zone, 4 ... Heating zone, 5 ... Soaking zone, 6 ... Soaking zone, 7 ... Cooling zone, 8 ... Hearth roll in furnace, S ... Steel zone

Claims (1)

When passing a steel strip in a high-temperature continuous furnace with a hearth roll in the furnace in the production of a high silicon steel strip or in a heat treatment line, the peripheral speed of the hearth roll in the furnace satisfies the following equation The method of manufacturing a high silicon steel strip, characterized by causing the steel strip to pass through so that the hearth roll in the furnace always slips relative to the steel strip.
0.3 ≦ [1− (hearth speed in furnace / steel strip speed)] × 100 ≦ 5.0

Images