JPH0361329A - Method for continuously annealing nonoriented magnetic steel plate - Google Patents

Abstract

PURPOSE:To ensure a fine sheet shape and satisfactory magnetic characteristics for a steel plate by using a horizontal continuous furnace and regulating the cooling rate of the steel plate after annealing to a prescribed range in accordance with the temp. of the steel plate at the time of cooling. CONSTITUTION:When a nonoriented magnetic steel plate is continuously annealed with a horizontal continuous furnace, the annealed steel plate is cooled to 400 deg.C at a cooling rate R ( deg.C/sec) regulated in accordance with the difference A (=t-T) between the temp. (t) of the steel plate at the time of cooling and the soaking temp. T. The cooling rate R is <=4 deg.C/sec in case of -100<=A<=0 deg.C, <=6 deg.C/sec in the case of -200<=A<=-100 deg.C, <=9 deg.C/sec in the case of -300<=A<=-200 deg.C and <=11 deg.C/sec in the case of A<=-300 deg.C and t>=400 deg.C. A non-oriented magnetic steel plate ensuring a fine sheet shape and satisfactory magnetic characteristics is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a continuous annealing method for non-oriented electrical steel sheets using a horizontal continuous furnace.

[Conventional technology and issues to be solved]

Generally, a vertical continuous annealing furnace is used for annealing low-grade electrical steel sheets. Since the shape of electromagnetic steel sheets has a large effect on the magnetic properties of the product, it is necessary to obtain a good shape without warping. In continuous annealing of electrical steel sheets, annealing #lt
Warpage is likely to occur due to uneven shrinkage of the plate due to cooling after 1. For this reason, with regard to annealing in a vertical continuous furnace, from the viewpoint of preventing such sheet warpage, a proposal has been made to cool the area from 900°C to 400°C at a cooling rate of 25°C/see or less. being done.

However, in the vertical continuous furnace, there is a problem in that the plate is distorted by being wrapped around rolls at high temperatures, and its magnetic properties, especially low magnetic field properties, are likely to deteriorate. When the cooling rate is reduced as described above, the hot yield stress of the plate decreases, and the amount of strain introduced into the plate due to the roll damage increases, resulting in deterioration of the low magnetic field characteristics.

In view of these problems, an object of the present invention is to provide a continuous annealing method capable of obtaining a non-oriented electrical steel sheet having good shape and O magnetic properties.

[Means to solve the problem]

For this reason, the present invention uses a horizontal continuous furnace in which the plate does not wrap around rolls while hot, and by setting the cooling rate under specific conditions, it is possible to ensure a good plate shape and magnetic properties. It is something.

That is, the present invention is characterized in that when a non-oriented electrical steel sheet is continuously annealed in a horizontal continuous furnace, the steel sheet is cooled after sintering at a cooling rate R (° C./sec) that satisfies the following conditions.

1) At -100℃<A≦0℃, R≦4℃/5ee II) At -200℃<A≦-100℃, R≦6℃
/see river) -300℃<A≦-200℃, R≦9℃/5
ee 1v) R at A≦-300℃ and t≧400℃
≦11°C/sec However, A-(plate temperature during cooling t-soaking temperature T) Below, the present invention will be described in detail.

The present invention uses a horizontal continuous annealing furnace in which the plate does not wrap around rolls while hot. In the case of a horizontal continuous furnace, only the catenary portion of the sheet is wound around the rolls during hot heating. For this reason,
Compared to a vertical continuous furnace, the strain introduced into the plate is practically not a problem, and as shown in the example in FIG. 1, its superiority in low magnetic field characteristics is clear.

Next, considering the issue of plate shape, generally a steel plate immediately after soaking is held at a high temperature under constant tension for a certain period of time, and the shape distortion caused by cold rolling is corrected. therefore,
If the plate in such a state is cooled uniformly over the front, back, and width directions by ultra-slow cooling, it is possible to maintain a good shape up to room temperature.

Based on such a viewpoint, the present inventors investigated a cooling rate that can maintain a good plate shape. Figure 2 shows the results. Depending on the temperature of the cooling process, there is an upper limit to the cooling rate at which a good plate shape can be obtained, and cooling up to 400°C is performed at a cooling rate outside the diagonal lines in the figure. It was found that this resulted in improper plate shape, leading to problems during punching and deterioration of magnetic properties. In other words, the cooling rate R (°C/sec) up to 400°C needs to be defined in the following range according to the difference A (-t-T) between the plate temperature t of the cooling temperature and the soaking temperature T. be.

J) R≦4℃/5ee at -100℃<A≦O℃ 11) R≦6℃ at -200℃<A≦-100℃
/5ee jij) -36g℃<A≦R≦9 at -200℃
℃/5ee IV) At A<-300℃ and t>400℃
≦11° C./sec Note that such cooling rate control can be easily performed, for example, by controlling the blower rotation speed in the sinter 6 furnace cooling zone.

〔Example〕

After heating the slag having the composition shown in Table 1 to 1150°C,
After hot rolling to 2.0 mm t and then cold rolling to 0.50 mm t, it was annealed in an Fi4 type continuous annealing furnace under the conditions shown in Table 2. Table 3 shows the shape and magnetic properties of the non-oriented electrical steel sheet thus obtained.

Table 1 Table 3 * is a comparative example. The numerical values are h/1° in Fig. 3. [Effects of the Invention] According to the present invention described above, a horizontal continuous furnace is used, and the cooling rate after annealing is By setting the temperature within a predetermined range depending on the sheet temperature during cooling, a non-oriented electrical steel sheet with good sheet shape and magnetic properties can be obtained.

[Brief explanation of drawings]

FIG. 1 shows the B3 value in the sheet width direction of an electrical steel sheet manufactured in a horizontal continuous furnace and an electrical steel sheet manufactured in a vertical continuous furnace. FIG. 2 shows the influence of the cooling rate on the plate shape during annealing in a horizontal continuous furnace. FIG. 3 is a diagram showing the definitions of the numerical values of ear wave and mid-length elongation listed in Table 3 of Examples. Figure 1 Figure 2 A shows the plate during cooling; and t - equalization temperature T)

Claims (1)

[Claims] When continuously annealing a non-oriented electrical steel sheet in a horizontal continuous furnace, the cooling rate R (°C/sec.
) A continuous annealing method for a non-oriented electrical steel sheet, which is characterized by cooling the steel sheet. i) R≦4℃/sec at -100℃<A≦0℃ ii) R≦6℃/sec at -200℃<A≦-100℃
sec iii) R≦9℃ at -300℃<A≦-200℃
/sec iv) At A≦-300℃ and t≧400℃, R≦
11℃/sec However, A = (plate temperature t during cooling - soaking temperature T)