JPH0551640A - Method for highly densifying crystalline grain in goss direction of silic0n steel sheet - Google Patents

Abstract

PURPOSE:To relatively easily and remarkably improve the magnetic properties of the conventional grain-oriented silicon steel sheet or the preceding invented steel sheet without severe manufacturing management and selection or the remarkable rise of manufacturing cost. CONSTITUTION:At first, a hot rolled steel strip contg. about silicon is subjected to cold rolling for one or two times while it is subjected to process annealing, and decarburization annealing is executed at 750 to 850 deg.C. After that, by induction or conduction in the subject invention, this steel sheet is heated to 860 to 980 deg.C at >=20 deg.C/min heating rate while tensile strain of <=10% is applied thereto, and it is held for <=60sec and is thereafter cooled at the rate of >=10 deg.C/min. After that, in usual final annealing, secondary recrystallized grains in the Goss direction of high density are formed to obtain a high magnetic flux density grain-oriented silicon steel sheet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for preferentially generating goss-oriented secondary recrystallized grains during final annealing by rapid heating for a short time following decarburizing annealing during the production of grain-oriented silicon steel sheet. ..

[0002]

2. Description of the Related Art Oriented silicon steel sheets have a long history of research and development since the invention of the manufacturing method by Goth. Usually, this steel sheet is cold-rolled 1 to 2 times while hot-rolling the hot-rolled steel sheet, and after continuous decarburization annealing, a suspension containing MgO as a main component is applied, and at a high temperature of 1150 to 1200 ° C. Annealed and manufactured. In the final high temperature annealing, referred to as secondary recrystallization, crystal grains having a Goss orientation grow at a remarkably high rate. Therefore, the magnetic properties of the steel sheet in the rolling direction are remarkably excellent. When such a silicon steel sheet is used in a transformer, the efficiency of the iron core is improved, and the power loss is significantly reduced. Therefore, research and development of a silicon steel sheet having a high-density Goss-oriented crystal grain is extremely important and many inventions have been made. Many of the inventions relate to special second-phase grains for effectively inducing Goss-oriented secondary recrystallized grains in final high temperature annealing. For example, Japanese Patent Publication No. 53-28375 shows A
1N, Patent Publication Sho 51-13469 is MnSe, US
PatNo. In 4096001, addition of B is attempted to achieve high density of the Goss-direction secondary recrystallized grains. It is a fact that the performance of the grain-oriented silicon steel sheet was significantly improved by these techniques. However, its performance is far from the theoretically possible limit, and there is plenty of room for improvement. Despite a great deal of effort, the development of this technology has been extremely small in recent years. Originally, the technology is not easy to implement. Therefore, extremely strict manufacturing control is required, and a significant increase in manufacturing cost cannot be avoided, and it is mainly limited to the production of the highest quality grain oriented silicon steel sheet with a small demand.

[0003]

DISCLOSURE OF THE INVENTION The present invention can improve the magnetic properties of the conventional grain-oriented silicon steel sheet or the prior invention steel sheet remarkably easily without strict production control, selection, or significant increase in production cost. The purpose is to do.

[0004]

The present invention will be described below with reference to the drawings. FIG. 1 schematically shows a manufacturing process of a grain-oriented silicon steel sheet according to the present invention. A feature of the present invention is the introduction of a heating device for the silicon steel sheet by induction or conduction after decarburization annealing as shown in step 6. The other steps are the same as the conventional method or the prior invention method. The new furnace introduced by the present invention is referred to as a rapid flash heating furnace (hereinafter abbreviated as a rapid heating furnace). Next, the metallurgical effect of the rapid heating furnace will be described. Table 1 shows the chemical composition of the silicon steel sheet used in the present invention. First, a 0.18 mm cold rolled steel sheet was recrystallized and decarburized and annealed at 800 ° C. for 6 minutes. After that, the steel plate is heated to 800 ° C./in a rapid heating furnace of the present invention.
It was heated to various temperatures at a temperature rising rate of min, held for 5 seconds, and then cooled to room temperature at a rate of 400 ° C./min. Thereafter, the silicon steel sheet was held in a final annealing furnace in a pure hydrogen atmosphere for 7 hours. The magnetic properties of the silicon steel sheet subjected to such heat treatment were investigated.

[0005]

[Table 1]

FIG. 2 shows the relationship between the magnetic orientation percentage of the steel sheet after the final annealing and the temperature in the rapid heating furnace. The magnetic orientation of the final annealed steel with decarburization annealing is low, but that of the steel subjected to the rapid heat treatment increases remarkably as the temperature increases. This is because of the large number of primary recrystallized grains after decarburization annealing, the Goss-oriented crystal grains were remarkably activated as the growth nuclei of the secondary recrystallized grains by the rapid heating furnace treatment. This activation should theoretically become more pronounced at higher temperatures, but in practice 9
Rapid heating to 10 ° C. maximizes the magnetic properties, and heating to higher temperatures causes deterioration of the magnetic properties. Rapid heating to extremely high temperatures is detrimental. This is because the second phase particles such as MnS are coarsened as the temperature of the rapid heating furnace increases.
In addition, since the number decreases, the force for suppressing the growth of normal grains necessary for secondary recrystallization in the final high temperature annealing decreases, and the driving force for generating Goss-oriented secondary recrystallized grains disappears. .. Curves 1 and 2 in FIG. 2 show the relationship between the magnetic orientation after the final annealing and the rapid heating temperature when 5% and 10% tensile work was introduced into the steel sheet during rapid heating, respectively. The magnetic characteristics in this case also increase as the rapid heating temperature rises. The temperature range in which the effect exists is expanded as compared with the case where no processing is performed.

[0007]

In Table 2, the magnetic properties of the final product obtained by decarburizing and annealing the silicon steel shown in Table 1 and subjecting it to rapid heating at 910 ° C. for 10 seconds as compared with those of the conventional method steel are shown in Table 2. Show.

[0008]

[Table 2]

It can be seen that the magnetic properties of the silicon steel sheet according to the invented method are remarkably superior to those of the conventional method steel. In conclusion, the application of rapid flash heating immediately after decarburization annealing according to the invention significantly improves the magnetic properties of silicon steel products. The present invention specifies that the decarburization annealing temperature is set higher than usual. Pat. May be confused with 1521680. The invention showed that a slight improvement in magnetic characteristics was obtained by increasing the decarburization annealing temperature.
It can only be applied to the production of moderate quality silicon steel sheets. Moreover, it is a well-known fact that this method is not generally used as a surely effective method. This is because even if the temperature is raised before the decarburization is completed, the growth of normal crystal grains is generally promoted, and the specific Goss-oriented crystal grains are not activated. It is essential that decarburization be completed without fail, and then rapidly heated and maintained within the temperature range of the present invention. Further, in the present invention, the decarburization annealing temperature is UK. Pat. Contrary to 1521680, it is specified as low. This suppresses an increase in the average crystal grain size after decarburization. This is because the smaller the average crystal grain is, the more marked the activation of the Goss-oriented crystal grain due to rapid heating becomes.

[0010]

INDUSTRIAL APPLICABILITY The present invention facilitates preferential growth of Goss-oriented secondary recrystallized grains in the final high temperature annealing regardless of the grain size of the grain-oriented silicon steel sheet produced by the conventional method or the prior invention method, and its magnetic properties. Is remarkably improved. Further, the effect of the method of the present invention is more remarkable with respect to silicon steel, which inherently has low magnetic properties. Therefore, it greatly contributes to the reduction of magnetic property variation in the product, that is, the stabilization of quality and the facilitation of quality control. The rapid instantaneous heating furnace which is the equipment of the present invention is inexpensive as seen in the tin-plated steel sheet reflow furnace, and can be easily added to existing equipment.

[Brief description of drawings]

FIG. 1 schematically shows an installation position of a rapid instantaneous heating furnace of the present invention. Step 1 is homogenization annealing of hot rolled silicon steel strip, Step 2
Indicates primary cold rolling, step 3 indicates intermediate annealing, step 4 indicates secondary cold rolling, step 5 indicates decarburizing annealing, step 6 indicates rapid instantaneous heating of the present invention, and step 7 indicates final high temperature annealing.

FIG. 2 shows the metallurgical effect of rapid flash heating of the present invention.
Curves 1, 2 and 3 show the relationship between the magnetic orientation of a silicon steel sheet having tensile strains of 0%, 5%, and 10% added during heating and the rapid instantaneous heating temperature for 5 seconds. Shows the grain size number (as-is) of the secondary recrystallized grains of silicon steel added with 0% tensile strain shown in curve 1 as a function of the temperature of the rapid flash heating furnace.

Claims (1)

[Claims] 1. In producing a grain-oriented silicon steel sheet containing about 3% of silicon, after cold rolling once or twice, 7
Following decarburization annealing at 50 to 850 ° C, induction or energization gives 860 to 9 while applying a tensile strain of 10% or less to the steel sheet at a heating rate of 20 ° C / min or more.
After heating to 80 ° C and holding for 60 seconds, 10 ° C / min
A method for producing a high-flux-density grain-oriented silicon steel sheet by producing high-density Goss-oriented secondary recrystallized grains in the subsequent final high-temperature annealing by cooling at the above rate.