JPH0559437A - Method for induction-heating slab for electrical steel sheet - Google Patents

Abstract

PURPOSE:To secure the necessary and suitable temp. to form the solid-solution to an inhibitor over the whole length of a slab for short time by providing an induction heating plate and a heat insulating material at the specific position in a furnace at the time of heating the slab having shorter than the prescribed length in a vertical type induction heating furnace. CONSTITUTION:At the time of manufacturing a grain oriented electrical steel sheet having the specific crystal orientation by using the slab 1 for electrical steel sheet incorporating >=2.0wt.% Si, the slab 1 having no prescribed length is heated in the vertical type induction heating furnace. At this time, e.g. the slab 1 in set while matching with the prescribed position of one side (B side) of the furnace having a side wall 5 and a coil 4, and the induction heating plate 2 for auxiliary heating is set while approaching to the A side end of the slab 1 and the heat insulating material 3 is set at this back race. By this method, insufficient heating at the end part of the slab can be eliminated and the deterioration of the magnetic characteristic at the end corresponding part of the slab in the finish-product is prevented and the yield can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the production of mill ends produced inevitably during the production of grain-oriented electrical steel sheet slabs. When heating, we propose a method to effectively prevent insufficient heating of the slab end that is caused by being shorter than a predetermined length.By doing so, deterioration of the electromagnetic characteristics of the slab end equivalent part in the final product can be prevented. It aims to prevent and improve the stake.

As is generally known, Si: 2.0 wt%
The excellent magnetic properties of the grain-oriented electrical steel sheet containing the above are:
It is obtained by selectively developing secondary recrystallized grains of (110) plane on the plate surface and <001> axis in the rolling direction by final annealing. Therefore, it is important to finely precipitate fine precipitates called inhibitors in the steel, for example, MnS, MnSe, AlN, etc.The control of the dispersion form of this inhibitor is controlled by slab heating prior to hot rolling. These precipitates are once solid-dissolved therein and then hot-rolled.

The slab heating performed for such a purpose is
In order to sufficiently dissolve the inhibitor in solid solution, it is usually carried out at a heating temperature of 1300 ° C or higher. Conversely, if this heating temperature becomes too high, a large amount of scale will be generated, which will not only hinder the operation of the heating furnace. Surface defects such as dents and the like are generated to impair the surface quality, and variations in the magnetic properties of the product also increase. Therefore, it is important to ensure the temperature required for the solid solution of the inhibitor in a short time and uniformly over the entire length of the slab without unnecessarily heating at a high temperature for a long time.

[0004]

2. Description of the Related Art Many means have been proposed so far for uniform heating over the entire length of a slab by induction heating.

For example, Japanese Patent Publication No. 52-47179 discloses that
An induction heating device is proposed and disclosed in which the end of the heated material is covered with a refractory heat insulating material. Although this is effective in preventing heat dissipation from the end of the heated material, induction of the end of the heated material is proposed. We can not cope with the shortage of heat generation due to the smaller current density,
Further, Japanese Utility Model Publication No. 52-50447 discloses an induction heating device which places an iron core outside the heating coil to focus the induced magnetic flux to heat the end of the material to be heated, and Japanese Utility Model Publication No. 61-39149. , An induction heating device, which disposes a heating element such as a resistance heating element or a radiant tube in the vicinity of the corner of the material to be heated, is proposed and disclosed, but these are end heating auxiliary devices, that is, Since the position of the iron core or heating element is fixed, if the slab length changes shortly with respect to the optimum length of each heating furnace (hereinafter simply referred to as the prescribed length), the temperature of the slab end should be It was not possible to secure a stable supply.

Therefore, the inventor of the present invention, as means for coping with changes in the length of the slab, arranges a conductive heat insulating plate which is movable in proximity to the end of the slab in Japanese Patent Laid-Open No. 3-31422. A method and furnace for heating slabs for grain-oriented silicon steel have been proposed and disclosed. By this means, although a considerable improvement can be seen, when the slab is shorter than the specified length, the amount of heat released from the back surface of the heat insulation plate to the furnace space increases, so the heating of the slab end also becomes insufficient and the final product There was a problem that the magnetic properties at that time were inferior at the slab end equivalent part.

Incidentally, in the production of the continuous cast slab, a method of cutting the slab according to a predetermined length is used, but the predetermined length is not always obtained at the rear part of the casting, A slab of mill ends that does not reach will inevitably occur. Then, although the slab that has not reached the above predetermined length is also commercialized for improving the yield, when heating this slab in an induction heating furnace, if insufficient heating occurs at the slab end as described above, this When the product is a final product, the magnetic properties deteriorate and the yield decreases.

[0008]

DISCLOSURE OF THE INVENTION The present invention is intended to solve the above-mentioned problems advantageously, and is necessary for the solid solution of an inhibitor in a short time in the induction heating of a slab that does not reach a predetermined length, and is preferable. The purpose of the present invention is to propose a method for heating a slab for electromagnetic steel sheets that can secure a constant temperature over the entire length of the slab, and in turn, to improve the yield.

[0009]

According to the present invention, when heating a slab for an electromagnetic steel sheet which has not reached a predetermined length in a rigid induction heating furnace, in order to perform sufficient heating over the entire length of the slab, an end portion is required. This is because it was found that it is effective to arrange a heat insulating material in addition to the arrangement of the induction heating plate for auxiliary heating.

That is, the gist of the present invention is that Si: 2.0 wt.
In producing a grain-oriented electrical steel sheet having a specific crystal orientation from a magnetic steel sheet slab containing at least 100% by weight,
When heating the slab mill ends for electromagnetic steel sheets that do not reach the prescribed length in a rigid induction heating furnace, the induction space for end auxiliary heating is provided in the furnace space created by the short slab length, close to the slab end face. This is an induction heating method for electromagnetic steel sheet slabs in which a heat generating plate is arranged, and a heat insulating material is arranged in the furnace space formed on the back surface of the induction heating plate in the vicinity of the induction heating plate.

Here, when the slab of this length is used, the predetermined length is preferably a distance between both end faces of the slab and the furnace side walls facing each other, and the slab end can be heated similarly to the central part (slab). It means a unique length determined by an induction heating furnace that allows uniform heating over the entire length.

[0012]

The present invention will be specifically described below. When a slab of a predetermined length is heated by a rigid induction heating furnace, the slab has a suitable distance between both end faces of the slab and the furnace side wall and the heating coil facing the slab, so that the slab is sufficiently heated over the entire length of the slab. Done.

However, when heating a slab that has not reached a predetermined length, the amount of heat released from the slab end face increases due to the expansion of the furnace space, and the slab end face and the induction heating coil facing the slab end face are increased. As a result of a longer distance, etc., insufficient heating occurs at the slab end. In order to compensate for insufficient heating of the end of the slab, even if an induction heating plate for auxiliary heating of the end is placed close to the end face of the slab, heat is radiated from the back surface of the induction heating plate to the space inside the furnace and the induction heating plate is assisted. In some cases, the heating effect is reduced and the heating of the slab edge is still insufficient.

Therefore, according to the present invention, when heating a slab that has not reached a predetermined length, an induction heating plate is disposed in the vicinity of the slab end face to perform auxiliary heating of the slab end portion, and a furnace behind the induction heating plate. By disposing a heat insulating material in the inner space close to the induction heating plate, the amount of heat radiated from the back surface of the induction heating plate is reduced. By doing so, sufficient heating can be achieved even at the end of the slab. become.

When the slab that has not reached the predetermined length is heated, the position of the slab in the furnace is the same as the position of the slab in the furnace at both ends (hereinafter referred to as the predetermined position) when the slab having the predetermined length is arranged. It may be within the range, but it is practical to place it close to one side of the predetermined position.

As the induction heating plate, one having a property of generating heat by the induced current from the induction heating coil is used.
As the material, an iron-based metal having both conductivity and heat resistance, or a ceramic containing a conductive substance is advantageously suitable, and the control of the calorific value is the same as that of the object to be heated under induction heating. It is carried out by selecting a material having a heating value.

Further, the heat insulating material is preferably made of a refractory and has the same property as that of the side wall of the heating furnace in order to make the heat radiation amount equal to that of the other member, and its thickness (in the slab length direction) is the same as that of the side wall of the heating furnace. It is preferable to be equal to or more than the same.

Next, the present invention will be described based on experimental examples. A slab was heated in a rigid induction heating furnace by the method shown in FIGS. 1, 2, and 3 below, and a product plate having a plate pressure of 0.23 mm was manufactured by the double cold rolling method. Here, FIGS. 1, 2 and 3 are transverse cross-sectional views showing a state in which the slab is arranged with one side (B side) of the rigid induction heating furnace aligned with a predetermined position, and these are respectively as follows. .. FIG. 1 shows a comparative example in which only the slab 1 is charged. FIG. 2 shows a conventional example in which the induction heating plate 2 is arranged close to the A end of the slab 1. Figure 3
Arranges the induction heating plate 2 close to the A end of the slab 1,
Furthermore, a case where the heat insulating material 3 is arranged on the back surface of the induction heating plate 2 will be shown as a conforming example of the present invention.

In these figures, 4 is an induction heating coil, 5 is a furnace side wall, and L is a predetermined length.

FIG. 4 shows the change in iron loss of the grain-oriented electrical steel sheet thus obtained, measured in the length direction from the portion corresponding to the A end of the slab. As is clear from FIG. 4, on the A end side, since the comparative example does not have an induction heating plate and a heat insulating material, in addition to insufficient heat generation at the end of the slab, insufficient heat generation due to a large amount of heat radiation occurs, which results in iron loss. However, even in the conventional example, since there is no heat insulating material, the amount of heat radiated from the back surface of the induction heating plate is large, resulting in insufficient heating at the end of the slab and deterioration of iron loss.

On the other hand, the iron loss of the conforming example is hardly deteriorated, and the effect of using the heat insulating material in addition to the induction heating plate is clearly shown.

Further, the procedure for inserting each member into the furnace when the induction heating of the electromagnetic steel sheet slab according to the present invention is performed will be described. FIG. 5 is an explanatory diagram showing a procedure for charging a slab, an induction heating plate, and a heat insulating material into a rigid induction heating furnace. One end of the slab is subjected to a predetermined heating in the furnace when the slab that has not reached a predetermined length is induction-heated. The case where the charging is performed at the same position will be described.

In FIG. 5, 1 is a slab and 2 is a slab 1.
Induction heating plate 3 arranged in the vicinity of the A end surface of 3 is an induction heating plate 2
Insulating material to be placed near the induction heating plate 2 in the furnace space generated on the back side of the furnace, 5 is a furnace side wall, 6 is a hearth, and 7 is an extractor for arranging the slab 1 and the heat insulating material 3 on the hearth. is there.

To insert each member into the furnace, first, the slab extracted from the gas heating type furnace is transferred to the front of the furnace by a roller table and placed on the extractor 7. At this time, the slab 1 has its B end aligned with a predetermined position on the extractor 7 in advance so as to match the predetermined position in the furnace when the slab 1 is loaded into the furnace. Next, from the heat insulating material storage area, select the heat insulating material 3 having a thickness suitable for the length of the slab 1 (longitudinal direction of the slab when loaded into the furnace), and transport the heat insulating material 3 by a transportation means such as a crane. The slab 1 is transported and placed on the A end side of the slab 1 on the extractor 7 so that the space between the slab and the slab is optimal with the induction heating plate 2 interposed therebetween.

Extract the slab 1 and the heat insulating material 3 into the extractor 7
After arranging it on the upper side, the extractor 7 is moved to be transferred onto the hearth 6 at the same time while keeping the positional relationship between the slab 1 and the heat insulating material 3 as it is.

On the other hand, in the induction heating furnace, an slab 1 is provided with an induction heating plate 2 attached to a movable supporting member (not shown).
Place it in a suitable position according to the length.

After this, by moving the hearth 6 upward, the slab 1, the induction heating plate 2 and the heat insulating material 3 are arranged at suitable positions in the induction heating furnace. Since the relationship between the end of the slab 1 arranged close to one side and the position inside the furnace depends on the alignment accuracy on the extractor 7, the close side, that is, FIG.
An induction heating plate 2'may be arranged on the B side to prevent temperature unevenness due to an error in alignment accuracy. Further, in this example, the slab 1 is arranged on one side, but the same effect can be obtained by arranging the slab 1 toward the center and disposing the induction heating plate and the heat insulating material at both ends thereof.

[0028]

[Example] C: 0.05 wt%, Si: 3.51 wt% melted in a converter
%, Mn: 0.08 wt%, Se: 0.030 wt% continuously cast slab for electromagnetic steel sheets (slab thickness: 215 mm) with a slab length of 8
It was cut into m pieces and charged into a rigid induction heating furnace having a predetermined length of 10 m together with an induction heating plate and a heat insulating material.

As shown in FIG. 3, these disposition positions are arranged so that one end of the slab B is aligned with the end of the slab B at a predetermined position in the furnace, and the end of the slab A is thick (slab length direction). )
The distance between the 200 mm steel induction heating plate and the slab is 80 mm,
In addition, on the back surface of the induction heating plate, a heat insulating material with a ceramic fiber surface coating on a high Al ₂ O ₃ brick with a thickness (in the slab length direction) of 1500 mm is arranged so that the space between the induction heating plate and the insulation heating plate is 50 mm. I placed it.

In this way, after heating in the rigid induction heating furnace, hot rolling was performed to obtain a hot rolled sheet having a sheet thickness of 2.5 mm. After that, the plate thickness was 0.7 mm in the first cold rolling, intermediate annealing was performed, and then the product plate thickness was 0.23 mm in the second cold rolling. Then, after decarburizing annealing, an annealing separator containing MgO as a main component was applied, and finish annealing was performed.

With respect to the product plate thus obtained, the electromagnetic characteristics of the portions corresponding to the positions of 0.1 m and 2.0 m from the end of the slab A were investigated. The results are shown in Table 1.

[0032]

As is clear from Table 1, it is understood that the slab edge also has excellent magnetic characteristics.

[0034]

INDUSTRIAL APPLICABILITY The present invention, when heating a slab for an electromagnetic steel sheet which does not reach a predetermined length, which is inevitably generated at the time of manufacturing the slab, in a rigid induction heating furnace, is used for end auxiliary heating near the slab end face. By disposing a heat insulating material close to the induction plate and the back surface of this induction heating plate, insufficient heating of the slab end is eliminated, and by doing so, deterioration of the magnetic properties of the slab end equivalent part in the final product. Can be prevented, which can greatly contribute to improving the yield.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a case where a slab that has not reached a predetermined length is loaded into one side of a rigid induction heating furnace by moving it to one side.

FIG. 2 is a transverse cross-sectional view of a case where a slab that has not reached a predetermined length has been loaded into a rigid induction heating furnace while being pushed to one side, and an induction heating plate is arranged near the end surface of the slab.

[Fig. 3] A slab that has not reached a predetermined length is loaded into a rigid induction heating furnace by pushing it to one side, and an induction heating plate is arranged close to the end face of the slab. It is a cross-sectional view when a heat insulating material is charged in close proximity.

FIG. 4 is a graph showing a change in iron loss measured from the end of the grain-oriented electrical steel sheet in the length direction.

FIG. 5 is an explanatory diagram showing a procedure for charging a slab, an induction heating plate, and a heat insulating material into a rigid induction heating furnace.

[Explanation of symbols]

 1 slab 2 induction heating plate 3 heat insulating material 4 induction heating coil 5 furnace side wall 6 hearth 7 extractor L prescribed length

Claims (1)

[Claims] 1. When manufacturing a grain-oriented electrical steel sheet having a specific crystal orientation from a slab for electrical steel sheet containing Si: 2.0 wt% or more, a slab end material for electrical steel sheet that does not reach a predetermined length. When heating the slab with a rigid induction heating furnace, an induction heating plate for auxiliary heating of the end portion is arranged in the furnace space caused by the short length of the slab, close to the end face of the slab, and the induction heating plate is further heated. An induction heating method for an electromagnetic steel sheet slab, characterized in that a heat insulating material is arranged in the furnace space formed on the back surface in the vicinity of the induction heating plate.