Method for producing grain-oriented electrical steel sheet

Abstract

The purpose of the present invention is to provide a method for producing a grain-oriented electrical steel sheet with which it is possible to stably produce a grain-oriented electrical steel sheet having further improved iron loss characteristics. According to one aspect of the present invention, provided is a method for producing a grain-oriented electrical steel sheet, said method being characterized by comprising a reheating step, a hot rolling step, a hot-rolled sheet annealing step, a cold rolling step, a decarburization annealing step, and a finished product annealing step, the decarburization annealing step includes: a heating step in which the cold-rolled sheet is heated from an entry-side temperature T0 DEG C to a soaking temperature T2 DEG C; and a soaking step for maintaining the temperature of the cold-rolled sheet at a soaking temperature T2 DEG C. In the heating step of the decarburization annealing step, the heating rate HR1 of the temperature of the cold-rolled sheet from the inlet-side temperature T0 DEG C to the arrival temperature T1 DEG C is set to 40 DEG C / sec or more. The heating rate (HR2) of the temperature of the cold-rolled sheet from the reaching temperature (T1 DEG C) to the reaching soaking temperature (T2 DEG C) is set to be more than 15 DEG C / sec and not more than 30 DEG C / sec.

Description

technical field [0001] The present invention relates to a method for producing a grain-oriented electrical steel sheet. Background technique [0002] A grain-oriented electrical steel sheet is a steel sheet in which grains accumulated in {110}<001> orientation (such grains are also called Goss-oriented grains) are highly aligned and contain approximately 7% by mass or less of Si. The control of the crystal orientation in the production of such a grain-oriented electrical steel sheet is achieved by utilizing a catastrophic grain growth phenomenon called secondary recrystallization. [0003] As a method of controlling this secondary recrystallization, the following method is industrially implemented: After the inhibitor is completely dissolved in the steel slab before hot rolling, it is used in the hot rolling and the subsequent hot rolled sheet annealing process. It precipitates finely. In this method, it is necessary to heat the steel slab at 1350 to 1400° C. in orde...

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Problems solved by technology

However, this heating temperature is about 200°C higher than the heating temperature for producing ordinary steel, so there is a problem that a heating furnace dedicated to the production of grain-oriented electrical steel sheets is required.

However, in this technique, the inhibitor may not be sufficiently formed during decarburization annealing

In this case, according to Patent Document 3, the coefficient of variation of the grain size distribution of the primary recrystallized grain texture becomes larger than 0.6, so the primary recrystallized grain texture becomes non-uniform

As a result, there is a problem that the secondary recrystallized grain structure becomes non-uniform and unstable.

Therefore, when it is desired to heat the steel plate to a temperature higher than this temperature, an induction heating device cannot be used, and another heating device must be used in combination.

[0011] However, when other heating devices are used in combination, various problems arise

For example, since the electric heating device and the like come into contact with the steel plate, there are not only problems such as damage to the steel plate, but also the advantage of the induction heating device in terms of equipment is lost.

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