KR20140086716A

KR20140086716A - Oriented electrical steel sheet and method for manufacturing the same

Info

Publication number: KR20140086716A
Application number: KR1020120157550A
Authority: KR
Inventors: 나광덕; 전근하; 함영택
Original assignee: 주식회사 포스코
Priority date: 2012-12-28
Filing date: 2012-12-28
Publication date: 2014-07-08

Abstract

The present invention relates to a grain-oriented electrical steel sheet and a manufacturing method therefor which heats steel slab, and then successively performs hot rolling, cold rolling, decarbonizing, nitride annealing, and final high temperature annealing. Disclosed is the grain-oriented electrical steel sheet and the manufacturing method therefor, wherein the method maintains furnace sulfide within a normal operation level by controlling the opening degree of burn off for each section or the opening degree of a seal roll on an entrance or exit side when the ratio of hydrogen of a decarbonizing and nitride annealing furnace is changed ±2.5% or greater than that of the decarbonizing and nitride annealing furnace in a normal operation state.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a directional electric steel sheet,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0002] The present invention relates to a directional electrical steel sheet and a method of manufacturing the same. More particularly, the present invention relates to a directional electrical steel sheet that senses fluctuation of fluctuation and responds to magnetic variation.

The directional electric steel sheet is a steel sheet having excellent magnetic properties in the rolling direction. In order to have such characteristics, the following process steps are generally required.

After the cold rolling is completed, primary recrystallization of an appropriate size is caused in the decarburization and annealing process. Secondary recrystallization occurs in the high temperature annealing process, which requires a long time of about 5 days. The magnetic properties of the oriented electrical steel sheet are as follows: how well {110} <001> texture is formed in the secondary recrystallization It depends. The magnetic quality is excellent when the {110} plane and the <001> direction in the rolling direction are arranged in a direction exactly parallel to the rolling surface, and this error is 7 ° or less in the normal directional electric steel sheet. 3 [deg.].

In order to form a good secondary recrystallization, the size of the primary recrystallized grains, which is the driving force of the secondary recrystallization in the decarburization and nitriding annealing process, must be appropriately controlled. That is, if the size of the primary recrystallized grain is large, the formation of the secondary recrystallization becomes insufficient due to the weakening of the driving force of the secondary recrystallization. If the size of the primary recrystallized grain becomes too small, Recrystallization occurs and it becomes impossible to produce an electric steel sheet having excellent magnetic properties.

In order to increase the size of the primary recrystallization to a desired range without any variation, the annealing temperature must be controlled constantly in the decarburization and nitriding annealing process, and the steepness must occur at a certain point of time.

Although the decarburization and nitriding annealing temperatures have the greatest influence on the size of the primary recrystallization, they are easy to manage and change, and the steepness fluctuates with the decarburization and the annealing of the nitriding anneal, .

To solve the above problems, in order to obtain a primary recrystallized grain size in a desired range stably in the decarburization and nitriding annealing process, To provide a method for manufacturing an electric steel sheet.

In one or more embodiments of the present invention, there is provided a method of manufacturing a grain-oriented electrical steel sheet in which a steel slab is subjected to hot rolling, cold rolling, decarburization and nitriding followed by final high-temperature annealing, When the temperature of the annealing furnace fluctuates by more than +/- 2.5% of the consumption of water during normal operation, the burn-off is maintained at the normal operating state by controlling the opening of the burn-off or the opening of the inlet- A method of manufacturing a directional electric steel sheet can be provided.

And the water consumption increases as the opening degree of the burn-off and the opening degree of the input-output side silo increase.

The opening degree of the burn-off is characterized by controlling water consumption in each section of the heating stand, the crack stand, and the cooling stand.

And the opening degree of the inlet-outlet-side silole regulates the consumption of water in the entirety of the furnace.

The burn-off and the opening degree of the silole are controlled so that when the water consumption in the decarburization and nitriding annealing is as high as + 2.5% or more than the water consumption in the normal operation, the opening rate is lowered, And when it is smaller than 2.5%, the opening ratio is increased.

In addition, the consumption of water during the normal operation is characterized by being water consumption which enables the primary recrystallization to be stably grown.

According to the embodiment of the present invention, the deviation of the primary grain size is reduced by controlling the burn-off opening and the opening degree of the seal roll on the inlet and outlet sides based on the consumption of water, Deviations from the magnetic quality of the product can be reduced and magnetic scrap can be reduced.

FIG. 1 is a graph showing changes in water consumption due to general fluctuation of fluctuation.
2 is a graph showing the relationship between the primary recrystallization size and the magnetic quality.
3 is a schematic view of a structure in an annealing furnace according to an embodiment of the present invention.

Advantages and features of the present invention and methods of achieving them will become apparent with reference to the embodiments described in detail below. However, it is to be understood that the present invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. It is intended that the disclosure of the present invention be limited only by the terms of the appended claims.

The embodiment according to the present invention relates to a method for detecting and responding to fluctuation of fluctuation in order to stably maintain the infiltration point, wherein the fluctuation of fluctuation is quantified by sensing the consumption of water in the furnace, And controlling the openings of the seal rolls and the burn-off on the input / output side to reduce the magnetic deviation.

First, FIG. 1 is a graph showing the change in water consumption from the front end of the heating zone to the rear end of the crack zone in accordance with the fluctuation of the sulfur. That is, it is a graph showing a change in water consumption in the section "A" in Fig. Referring to FIG. 1, the portion indicated by the solid black line B indicates the consumption of water during the normal operation, and the portion indicated by the blue dotted line A is low at the inlet side, that is, at the front end of the heating stand, (C) in the area near the back of the crack was higher than that in the normal operation, while the consumption in the area indicated by the red dotted line (C) was higher at the inlet side of the furnace, It shows the situation. In the embodiment according to the present invention, consumption of water during normal operation is water consumption which enables stable growth of primary recrystallization. This is a hydrogen ratio during normal operation.

As the sulfur is basically designed to flow in the annealing furnace from the outlet to the inlet side, if the consumption is high or low at the inlet side of the annealing furnace, the opposite phenomenon occurs at the outlet side of the annealing furnace.

3 is a schematic view of the structure in the annealing furnace according to the embodiment of the present invention, in which the inlet side seal roll 10 is formed at the inlet side of the annealing furnace, the outlet side oil roll 30 is formed at the outlet side of the annealing furnace, A plurality of burn-offs (20) are formed in the section between the cracking zone and the cooling zone. 3 shows the annealing furnace from the front end of the heating zone to the rear end of the crack.

Decontamination and nitriding annealing can change the consumption of water in the inlet and outlet depending on the fluctuation of phosphorus sulfur. It is possible to check whether the point of sinking is slower or slower than the normal operation, Predictability is possible. For example, when the burn off 20 located in the heating zone and the crack zone is adjusted, the sulfur moves to the more open side, so the water consumption in the open side increases.

That is, the portion indicated by the red dotted line in FIG. 1 means that the time of immersion is faster than that during normal operation, and the portion indicated by blue dotted line means that the immersion time is slower than that during normal operation.

FIG. 2 is a graph showing the relationship between the primary grain size and the magnetic flux density, wherein A, B, and C in FIG. 1 correspond to?,?, And? In FIG.

1 and 2, the primary crystal grains grow to an appropriate size at a set annealing temperature when the roots are normal ((B in FIG. 1, (1) in FIG. 2) In the case of C in FIG. 1 and in the case of (2) in FIG. 2, the primary grain size becomes small. In other words, it can be seen that iron loss phenomenon occurs when the sinking point moves to the inlet side.

On the other hand, when the sulfur is accelerated to the exit side by annealing rather than during normal operation, that is, in case of A in FIG. 1 and in (3) of FIG. 2, This causes magnetic scrap.

As shown in FIG. 1, the prediction of the time of soaking can be confirmed by changing the consumption of water due to the fluctuation of the flow rate, and the consumption of water in the normal and abnormal conditions can be managed and quantified.

In the embodiment according to the present invention, when the water consumption is abnormally changed, the operation of recovering to the normal state is controlled by adjusting the burn-off (20) opening degree located in each section of the heating stand, the crack stand and the cooling stand. The burn off 20 serves as a gas discharge passage in an annealing furnace to burn hydrogen gas as an atmospheric gas and discharge it into the atmosphere. As shown in FIG. 3, a plurality of burnout openings 20 are formed in each section.

The adjustment of the opening of the burn-off for each section to decarburization and annealing of the nitriding influences the direction of the flow of sulfur in the center portion. Therefore, by adjusting the burnoff 20 so as to be opposite to the fluctuation direction of the rhodium sulfur, it is possible to prevent the rhodium sulfur from being varied due to a specific cause.

Examples of such specific causes include equipment replacement, replacement, and repair, such as repair, roll replacement, etc., after a line stop. In this case, it is important to note that since the influence of the self-capacity and surrounding structures varies depending on the burn-off, the priorities and the like should be evaluated through experiments and these factors should be reflected in the measures.

In the embodiment according to the present invention, the water consumption can be adjusted not only by the control by the burn-off 20 but also by adjusting the opening of the inlet-side silo rolls 10, 30 of the annealing furnace. The input / output side silos (10, 30) can properly align the slag by controlling the opening degree when the consumption consumption movement occurs in the entire annealing furnace. That is, the inlet / outlet side rolls 10 and 30 are affected more by the entire annealing furnace and are more influential than the burn off 20.

When the water consumption is higher than the water consumption at the normal operation by + 2.5% or more, the opening ratio and the opening degree control at the inlet / outlet side silo are lowered, and the water consumption at the inlet / In this case, the opening rate is increased.

However, the above-mentioned values of ± 2.5% are only examples according to the present invention, and thus are not limited to the above numerical ranges.

While the present invention has been described in connection with certain exemplary embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined by the appended claims.

It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be interpreted as being included in the scope of the present invention .

Claims

A method for producing a grain-oriented electrical steel sheet in which a steel slab is heated, followed by hot rolling, cold rolling and decarburization annealing and nitriding annealing followed by final high temperature annealing,
When the temperature of the decarburization and nitriding annealing is changed to ± 2.5% or more of the consumption of water during normal operation, the burnoff is controlled to be maintained at the normal operating state by adjusting the opening of the burn-off or the opening of the inlet- Wherein said method comprises the steps of:

The method according to claim 1,
And water consumption is increased as the opening degree of the burn-off and the opening degree of the inlet-side silvol are increased.

3. The method of claim 2,
Wherein the opening degree of the burn-off controls the consumption of water in each section of the heating zone, the crack zone, and the cooling zone.

3. The method of claim 2,
Wherein the opening degree of the inlet / outlet silo regulates the consumption of water in the entire annealing furnace.

The method according to claim 1,
The burn-off and the opening degree of the silole may be adjusted,
When the water consumption in the decarburization and nitriding annealing is higher than + 2.5% of water consumption during normal operation, the opening rate is lowered. When the water consumption is lower than -2.5% in normal operation, the opening rate is increased Wherein said method comprises the steps of:

6. The method according to any one of claims 1 to 5,
Wherein the consumption of water at the time of normal operation is water consumption so as to stably grow the primary recrystallization.

A directional electrical steel sheet produced by any one of claims 1 to 6.