JPS5823408A - Manufacture of unidirectional electromagnetic steel plate having superior magnetism - Google Patents

Abstract

PURPOSE:To stably form with good yield a unidirectional electromagnetic steel plate having low iron loss and consisting of crystal grains having an azimuth represented as (110)[001]by Miller indices by a method wherein a specific amount of P is contained in a silicon steel material containing C: 0.020-0.080%, Si: 2.0-4.5%, Mn: 0.04-0.10%, S: 0.015-0.033%. CONSTITUTION:P of 0.013% or less is contained in a silicon steel material including C: 0.020-0.080%, Si: 2.0-4.5%, Mn: 0.04-0.10%, S: 0.015-0.033%, and a unidirectional electromagnetic steel plate having superior magnetism is formed by the secondary recrystallization phenomenon. The lower content of the above P makes better iron loss and a content of 0.013% or less remarkably improves the iron loss.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a so-called unidirectional electrical steel sheet, which is composed of crystal grains having an orientation expressed by Miller index (110) (001).

This stiff unidirectional electrical steel sheet is produced by appropriately repeating the annealing process and the cold rolling process, and by annealing the final finished product at a high temperature of 90%, primary recrystallized grains with (110)(001) orientation are selected. (by the so-called secondary recrystallization phenomenon). Unidirectional electrical steel sheets are mainly used in transformers and generator cores, and must have good magnetic properties such as magnetization and iron loss properties.The quality of magnetization is determined by the magnetic field induced in the core. magnetic flux density (B,.

(represented by) 00 is determined by the size. As for iron loss characteristics, it is desired that when a predetermined alternating current magnetic flux density is applied to the iron core, the energy loss (represented by W17150) that is lost as heat within the iron core is small. In order to reduce iron loss, it is necessary to reduce the impurities and residual stress remaining in the product, and to increase the specific resistance.

Although it is effective to reduce the size of crystal grains in the product, the influence of magnetization characteristics is even greater.

Recently, from the viewpoint of energy saving, there has been a strong demand for unidirectional electrical steel sheets with low iron loss.

However, in the ninth stage of manufacturing this low core loss unidirectional electrical steel sheet, the manufacturing process becomes complicated, and it becomes unstable as an industrial product, resulting in a decrease in yield and the energy required for manufacturing. This is contrary to the purpose of producing unidirectional electrical steel sheets for energy saving purposes.

From this point of view, the present invention provides a method for manufacturing unidirectional electrical steel sheets with low iron loss, which can be made more stable as an industrial product and improve yield without making the manufacturing process more complicated than before.

By the way, in order to obtain a unidirectional electrical steel sheet with improved magnetic flux density and excellent iron loss, complete secondary recrystallization is required in the final high temperature annealing process.
It is necessary to increase the degree of integration of directions. Therefore, Kti1
It is necessary to contain impurities to suppress the growth of secondary recrystallized grains until a high temperature is reached. Conventionally, Mn8, At
Precipitated dispersed phase of N, Mn8・, TiN, and further 8b
It is common practice to use elements that tend to segregate at grain boundaries, such as s Ass Pb B. For example, there is a method for producing high magnetic flux density unidirectional electrical steel sheets using AtN as the dispersed phase. This is proposed in Japanese Patent Publication No. 15644/1973. Further, Japanese Patent Publication No. 51-13469 discloses a method in which a silicon steel cable containing hs or S@ containing sb is used as a starting material and maintained at a high temperature finish annealing in the range of 800 to 920° C. for a long time. However, in the former case, it is necessary to strictly control the dispersion state of AtH, and there is a problem of lack of stability during industrial production. Regarding the latter, there are problems such as the use of expensive SB, and the long time required for final high-temperature annealing, which constantly increases the amount of energy used.

As mentioned above, various grain growth inhibitors are used to manufacture unidirectional electrical steel sheets with increased magnetic flux density and improved core loss, but all of them have problems with industrial stability or manufacturing. There are problems such as high costs.

By the way, even if 1Mn5Fi is not added, it has been used for a long time in the double cold rolling process because it is an effective grain growth inhibitor for secondary recrystallization in the range where it is normally contained in steel as an impurity. This method using MnS does not significantly increase the magnetic flux density, but it can be produced stably as an industrial product, and the process conditions are simple, so the manufacturing cost is low and the amount of energy used is low. Many attempts have been made to develop technology to improve magnetism in this process. This work! In order to obtain excellent magnetism, it is important to form FiMns uniformly and finely. Japanese Patent Application Laid-Open No. 48-69 as a method for controlling MnS
As shown in Japanese Patent Publication No. 72, the slab is sufficiently heated during heating and hot rolled at an appropriate cooling rate. A method is known in which silica-based nonmetallic inclusions are reduced by performing Aj deoxidation at 11 degrees, which leaves some acid-soluble At. Regarding the former, it is difficult to make the magnetism uniform because there is a difference in the cooling rate in the longitudinal and width directions of the coil, and regarding the latter, acid-soluble At remaining in the steel is
As shown in Japanese Patent No. 17619, this technique is not always satisfactory, as it has an adverse effect on magnetism and does not improve magnetism as much as expected.

In the present invention, when the P content in the silicon steel material is reduced, the Mn8 in the hot rolled sheet becomes extremely uniform and fine. It has been discovered that products with good magnetic properties can be stably manufactured using the two-step cold rolling process used.

Regarding P, techniques have been disclosed for improving magnetism by intentionally adding P, as typified by the method described in JP-A-50-72817.

In the present invention, we have discovered for the first time that magnetism can be improved by reducing the P content in silicon-containing steel as much as possible, which has not been known until now, based on the knowledge that the dispersion of Mns becomes uniform and fine. It is very practical to be able to improve magnetism simply by reducing the P content without adding expensive elements or adding complicated process conditions as in the present invention.

The effect of P content will be shown below based on experimental results.

CO,045--Sl 3.25*s Mn 0.
Molten steel containing 081G, SO, 026- is melted in a converter, and one is slaged twice during refining using the so-called double slug method, with a P of 0.0061 and the other once, which is normally carried out once. This molten steel, which had a P content of 0.020-0 with the waste slag, was made into slag by continuous casting, and after being heated at 1380° C. for 4 hours, it was continuously hot-rolled into a hot-rolled sheet with a thickness of 2.3 dew.

The results of electron microscopy of Mn9 at the center of the thickness of this hot-rolled sheet are
Po in Figure (a), Po in 006-1 Figure 1), 020
In the hot-rolled sheet with a low -P of 0.006-, there is almost no large Mn8, and the P is 0.0201! MnS is precipitated more uniformly compared to those with higher i. The above hot rolled sheet was cold rolled to 0.75mm, annealed at 870°C x 3win, 0
．． Cold rolled to 30cm, annealed at 850℃ x 3 min in wet hydrogen and heated to 1200℃ at a heating rate of 25℃/hr.
Annealed for hr. At this time, Po, 006- is B
= 1.87 (T), W17150-L 15 (
W/'kg) s p0 0.020- is B. -1,84(T),Wl
7150-1, 25 (W/kf).

The product with a low P content had excellent magnetic flux density and iron loss, corresponding to the uniform dispersion of Mn8 in the hot rolled sheet.

Next, the change in iron loss when the P content is changed will be explained. C
approx. 0.04816.81 approx. 3.2011, Mn approx. o, o
30 types of molten steel containing approximately 0.0251 ss and B
50 was melted in a converter. The P content at this time is 0.003
It was varied within the range of ~0.032-. The molten steel was continuously cast to form a cis slug, heated at 1380°C for 4 hours, and then continuously hot rolled to form a 2.3-〇 hot-rolled plate.

This hot-rolled sheet was annealed to 0.75 mm at 870°C x 3 m1n, cold rolled to 0.30 m, and 850°C x 3 m1 in wet hydrogen.
n annealing, heating to 1200°C at a heating rate of 20°C/hr and annealing for 2ohr. Figure 2 shows the iron loss at this time.

It can be seen that as the P content decreases, the iron loss improves, and the degree of improvement in the iron structure becomes particularly large at 0.013- or less.

Next, the constituent elements of the present invention will be explained.

In order to obtain the molten steel which is the starting material of the present invention, a known steel manufacturing method such as a converter can be used, but care must be taken in treating the slag to reduce the P content. Steel middle P
Oxygen is oxidized in the melting furnace by an oxidizing agent such as sulfur or iron ore and becomes phosphorus oxide, which is transferred into the slag and removed from the furnace as waste. Since there is a certain value between the molten steel P and the phosphorus oxide in the slag, which is determined by the slag temperature and basicity, the molten steel P cannot be reduced beyond that value. Therefore, in order to reduce the P content in the steel, an effective method is to remove the slag during melting and then re-create the molten slag to lower the P content and at the same time prevent the P from returning. Of course, it is effective to reduce the p content of hot metal, which is a raw material for molten steel, through preliminary treatment.

The composition range of this molten steel is C0,02~0,08-1
Si 2.0~4.5*s MnO, 04~0.
10% -80,020 to 0.033- is required. If C is higher than the upper limit, the decarburization annealing time in the subsequent step will be long, which is economically disadvantageous. On the other hand, if the lower limit is too low, secondary recrystallization will occur, causing fine grains to be generated in the final product and deteriorating the magnetism. .5- Closed. Also, if it is too small, the iron loss will deteriorate due to low specific resistance, so it was set to 2- or more. Mn and S amount #-1t This specifies the amount of MnS as an important grain growth inhibitor for secondary recrystallization grain growth, and below the lower limit of the above range, the absolute amount of MnS for secondary recrystallization is insufficient. Therefore, the development of secondary recrystallization becomes insufficient. On the other hand, M
When the n and S amounts are above the upper limit of the above range, Mn is
Since S is not sufficiently dissolved in the solid solution, MnS #'i precipitated during continuous hot rolling is non-uniformly dispersed, and secondary recrystallization is not sufficiently developed even if MnS is used. As can be seen from FIG. 2, the lower the P content, the better the iron loss, but it becomes significantly better at 0.013- or less. In particular, when the magnetic flux density is below o, oos-, the highest gray F of the current JISI standard for unidirectional electrical steel sheets, C9, and G8H, a high magnetic flux density unidirectional electrical steel sheet, are clearly expressed. The iron loss is almost the same.

Molten steel containing the above-mentioned components is solidified to form slag, which can be formed into a slab by continuous casting or by compressing the cast stubble into a mold. The slab is heated to a temperature at which MnS can be sufficiently dissolved in solid solution depending on the amount of Mn and S in the material. 6 If the amount of Mn e B of the present invention is used, a heating temperature of 1300 to 1400° C. is appropriate.

After heating, it is continuously hot-rolled to a 2.3mm front ridge. It is desirable to adopt a heating history such that the hot-rolled sheet stays in the temperature range of 1200 to 950°C for an appropriate period of time during which MnS precipitates during this hot-rolling process.This hot-rolled sheet is annealed as necessary. It is then cold rolled. The plate thickness at this time should be determined so that the rolling reduction during the second cold rolling is in the range of 45 to 70 inches. Cold rolled to final thickness. Furthermore, after decarburization annealing in wet hydrogen, Mg0%At20. An annealing separator such as the following is applied, and high-temperature annealing is performed at approximately 1200° C. for approximately 20 hours.

The heating rate at this time is 15"C, which does not reduce productivity.
A relatively high speed of 7'hr to 50'C/11r is desirable. Specific examples of the present invention will be described below.

Example 1 Molten steel whose P content was lowered by performing slag treatment during melting of 150 in a converter, and molten steel with relatively high P value tapped without slag treatment were formed into slabs by continuous casting. At this time, the component tl is C0,055.

ss3.35-lMn O,08Ls, SO,027
%”t”P content is 0.006-10.022 respectively
It was Chi.

After heating the slab at 1380℃ for 3 hours, it was continuously hot rolled 2
．． It was made into a hot-rolled sheet with a thickness of 3cm and cold-rolled to a thickness of 0.75cm.

Further, it was annealed at 950°C x 2ml and then cold rolled to a thickness of 0.30cm. This cold-rolled sheet was subjected to decarburization annealing at 850° C. x 3 ml in wet hydrogen, coated with MgO as an annealing separator, heated to 1200° C. at a heating rate of 30 N7 hr, and then heated to 1200° C.
Annealing was performed for hr. The magnetism at this time was as follows.

Po, 006% material B 10 ; L 89 T #
W1y15 o==l, 15 wAPo, 022%
Material B. = e1.85 pieces w Wl 715 o
-1.23 wA9 or higher, the low P material was superior in both magnetic flux density and iron loss.

[Brief explanation of drawings]

FIG. 1 is an electron micrograph showing the metal structure at the center of the thickness of a hot rolled sheet, and FIG. 2 is a diagram showing the relationship between the P content in the material and iron loss. Patent Applicant Nippon Steel Corporation Representative Kazu Ozeki Mistake 1 Diagram (al (b) Procedural Amendment (Spontaneous) October 26, 1980 Commissioner of the Japan Patent Office Shima 1) Hibiki Jumei 1, Incident Indication 1981 Patent Application No. 122729 2 Title of the invention Method for manufacturing unidirectional electrical steel sheet with excellent magnetism 3 Relationship to the case of the person making the amendment Patent applicant 2-6-3 Otemachi, Chiyoda-ku, Tokyo (665) Nippon Steel Corporation Representative Takeshi 1) Amount 4, Agent 2-4-1-5, Marunouchi 2-4-1, Chiyoda-ku, Tokyo 100, Date of amendment order: Showa, Month, Day 6,
Target of amendment (1) Amend the box spacing of the patent claims as shown in the attached sheet. (2) Specification page 9 lines 13-14 rs0.020-0.0
33 whisper" is corrected to r80.015~0-033%". Claims CO, 020-0.080%, 812.0-4.5
%. Mn 0.04-0.10%, 80.015-0.03
A silicon steel material containing 3% was hot-rolled, and this hot-rolled sheet was cold-rolled twice with annealing in between to obtain a cold-rolled sheet with the final product thickness, and then subjected to primary recrystallization annealing that also served as decarburization. In the method for manufacturing a unidirectional electrical steel sheet, which comprises a series of steps of performing final high-temperature annealing to develop secondary recrystallized grains with (110) (001) orientation, the P content in the silicon steel material is 0. 013
% or less.

Claims (1)

[Claims] C0,020~o, oso%, 812.0~4.511
°Mn 0.04~0.1096.80.020~0.
A silicon steel material containing 0.33% is hot-rolled, and the hot-rolled sheet is cold-rolled twice with annealing to obtain a cold-rolled sheet with the final product thickness, and then subjected to primary recrystallization annealing that also serves as decarburization. In the method for manufacturing a unidirectional electrical steel sheet, which comprises a series of steps of performing final high-temperature annealing to develop secondary recrystallized grains with (110) (001) orientation, the P content in the silicon steel material is 0.01
3. A method for producing a unidirectional electrical steel sheet with excellent magnetic properties.