JPS61231120A - Manufacture of nonoriented electrical steel sheet having superior magnetic characteristic - Google Patents

Abstract

PURPOSE:To manufacture a nonoriented electrical steel sheet having small magnetic anisotropy by carrying out soaking, CONSTITUTION:A slab for a nonoriented electrical steel sheet contg. <0.05wt% C, 2.5-4wt% Si and <1.5wt% Al is hot rolled,.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for manufacturing a non-oriented electrical steel sheet with excellent magnetic properties, and is the highest grade non-oriented electrical steel sheet specified by the JIS standard. S9 [Iron loss W1 5AO is 2.
90 w/9 or less (0.50m plate thickness), same <
The present invention relates to a method for manufacturing a high-grade non-oriented electrical steel sheet having a grade equivalent to 7'CSB or higher, which is even better than 2.40 w/9 or less (0.35-plate thickness)].

High-grade non-oriented electromagnetic steel sheets are generally widely used as core materials for Daisei rotary machines, and the above-mentioned S'9 grade is currently in use. However, recently, in order to reduce costs and increase efficiency of Daisei rotary machines, there has been a strong demand for the development of high-grade non-oriented electrical steel sheets as core materials that have even lower core loss than S9 grade. .

(Prior art) Generally, the final annealing process for non-oriented electrical steel sheets is to recrystallize (normal grains) after cold rolling, promote grain growth, and improve crystal orientation. This is a process that plays an important role in reducing iron loss. For this reason, conventionally, when manufacturing high-grade non-oriented AT magnetic steel sheets,
Several improvements have been made to finish annealing. For example, according to the method described in Japanese Patent Publication No. 59-15966, finish annealing is carried out in two stages: a low-temperature soaking in the temperature range of 850°C to 1000°C in the first stage and a high-temperature soaking in the temperature range of 1000°C to 1100°C in the latter stage. By stage annealing, (normal grain) after cold rolling
The recrystallized grains are completely sized to improve magnetic properties.

(Problems to be Solved by the Invention) The magnetic properties of a non-oriented electrical steel sheet are the rolling direction (hereinafter referred to as the backward direction) and the direction perpendicular to the rolling direction within the plate surface (hereinafter referred to as the C direction). Generally, the magnetism in the C direction is inferior to that in the L direction. In order to manufacture the highest grade of non-oriented electrical steel sheet, we focus on the difference in magnetic properties between the L direction and the C direction, that is, the magnetic anisotropy, and by improving this magnetic anisotropy, we can improve υ and magnetic properties. There is no technology to improve it.

Therefore, the present inventors accumulated many experimental results and completed the present invention from the viewpoint that reducing the magnetic anisotropy, that is, to less than 100 nm, would lead to lower core loss of the steel sheet as a whole.

(Problem 5I--Rounding Means to Solve) That is, in the present invention, C: 0.005% or less, Si: 2.
5-4.04, ht: A non-oriented electrical steel sheet slab containing 5% or less of L is hot-rolled and then annealed, and cold-rolled once and fc twice with intermediate annealing in between. In the method for producing a non-oriented electrical steel sheet in which the final plate thickness is obtained by cold rolling and final annealing is performed as described above, the final annealing is performed at 950°C in the first stage.
This is a patented manufacturing method characterized by soaking in a temperature range of 1100°C for 5 seconds to 1 minute, then holding in a temperature range of 800°C to 950°C for 10 seconds to 2 minutes, and then cooling.

Further, the present invention includes a case where medical evaluation is further performed for 10 seconds to 2 minutes at a temperature range of 800° C. to 950° C. before the preliminary soaking in the final annealing. In addition, the present invention provides a method in which after soaking in the first stage, 7
This also includes cases where slow cooling is performed where the cooling rate to 00°C is 100°C/min or less.

Furthermore, the present invention provides C: 0.005% or less, Si: 2.
5-4.0%, AL: 1. Including sections 5 and below, S, N
, O containing sludge of 0.0020% or less, respectively.

The present invention will be explained in detail based on FIG.

Figure 1 shows C2 0.0027%, Si: 3.02%,
AL2 0.94'vague; , S: 0.0
009 9-1, N: 0.0012
Jiwarm; .

A slab for a non-oriented electrical steel sheet containing 0:0.0016% was heated and hot-rolled to form a 1.8 m thick hot-rolled plate, and then hot-rolled plate annealed at 980°C for 2 minutes to obtain a 0. The iron loss value W when the product is cold rolled to a product thickness of .35 and subjected to each of the final annealing conditions A1 to A4, and the ratio of the iron loss value in the L direction V50 and the iron loss value in the C direction (hereinafter referred to as L, C ratio) (describe). In other words, as is clear from Figure 1, by performing low temperature holding (corresponding to A3) or slow cooling (corresponding to A4) after the normal soaking annealing in the final annealing, the iron loss value can be significantly reduced. L, C ratio is improved,
We discovered that it is possible to achieve low iron loss. This is caused by low temperature retention or slow cooling in the subsequent stage, and recrystallization. This is thought to be due to the fact that the inside of the crystal grains is cleaned after grain growth, and the cooling strain introduced at about 800° C. or higher and carried over to room temperature is reduced. This effect is.

This is further promoted by using high-purity steel with low S, N, and O'4 impurity elements in the steel sheet.

Next, reasons for limiting the constituent elements of the present invention will be described.

First, in the chemical composition of the slab, C is an element that deteriorates magnetic aft, and if it exceeds Q,005%, magnetic aging will occur and the magnetic properties will deteriorate significantly, so the content should be 0.005% or less.

Si is an element that increases the specific resistance of steel and improves iron loss, and if it is less than 2.596, it has little effect. However, when it exceeds 4.0, the steel becomes brittle and cold rollability deteriorates.

Like St, AL is an element added to increase the specific resistance of steel and improve iron loss, as well as to deoxidize the steel, but at 1.5%? Exceeding this will cause the steel to become brittle.

Furthermore, since S, N, and O are elements that generate impurities and deteriorate magnetic properties when their contents are increased, it is preferable that the content of each of S, N, and O be 20 ppm or less.

(Function) Next, a slab for a non-oriented electrical steel sheet having a chemical composition of M, which is a feature of the present invention, is bathed in a converter and manufactured by continuous casting or ingot-blurring rolling.

The steel slab is heated and hot rolled in a known manner.

After hot rolling, after hot-rolled plate annealing, the final plate thickness is achieved by cold rolling - times, or by cold rolling two or more times with annealing in between. .

In the final annealing, after soaking in the temperature range of 950°C to 1100°C in the first stage, the temperature is maintained in the temperature range of 800°C to 950°C in the second stage. If the soaking temperature in the first stage is less than 950℃.

The crystal grains after recrystallization are small and iron loss deteriorates. Also, 11
If the temperature exceeds 00°C, an oxide film is formed on the surface of the steel sheet, and the magnetic properties are significantly deteriorated.

Furthermore, if the pre-soaking time is less than 5 seconds, grain growth after recrystallization will be poor and iron loss will deteriorate. Also.

Even if you hold it for more than 1 minute, it will have almost no effect.

Post-retention 7: IE above 950°C and below 800°C.

There is no formula for improving iron loss value or C ratio.

Further, when the post-stage retention time is less than 10 seconds or more than 2 minutes, the effect is small.

The effect of the above-mentioned second-stage retention is that the cooling after the first-stage soaking is 700%
It can be replaced by slow cooling in which the cooling rate to °C is less than 100 °C/min. If the cooling rate to 700°C exceeds 100°C/min, the effect will be small. Also, 700℃
Cooling rate below will not affect the effect.

(9) If holding is further carried out in the temperature range of 8000 to 950° C. before the first-stage soaking, uniform recrystallization will occur, the crystal grains after final annealing will become regular, and iron loss will be improved. 8oo
If the temperature is less than 0.degree. C., uniform recrystallization is difficult to occur and iron loss is not improved. Moreover, at temperatures exceeding 950° C., the crystal grain size and texture change and the magnetism deteriorates.

Furthermore, if the holding time before the first stage soaking is less than 10 seconds, uniform recrystallization is difficult to occur and iron loss is not improved. Also, 2
Even if it is retained for more than a minute, there is little effect.

As described above, by carrying out the present invention, the iron loss value and the C ratio are significantly improved, and a reduction in iron loss can be achieved.
It is possible to manufacture unprecedented high-grade non-oriented electrical steel sheets that correspond to grades equivalent to 86° or higher, especially grades equivalent to 86°S5.

(Example) Next, examples of the present invention will be described.

Example I C: 0.0028LII, St: 3.00%, A
t: 1.00%, S: 0.00061. N:0.00
1 (1,0:0.001496t) A non-oriented electrical steel sheet slab was heated and hot-rolled to form a hot-rolled plate with a thickness of 1.8fi, and then the hot-rolled plate was annealed at 9500 for 2 minutes. .3
It was cold rolled to a product thickness of 5 m. Thereafter, final annealing was performed under the conditions shown in Table 1, and the results of all magnetic measurements were also shown in Table 1.

A1 to &4 are comparative materials, and compared to the present invention, there are cases where there is no post-stage retention in finish annealing, cases where there is retention before pre-soaking but no post-stage retention, cases where the post-stage retention temperature is low, and cases where the pre-stage soaking temperature is low. This corresponds to each case. A5 and 6 are materials of the present invention. The comparison material is equivalent to S6 (W ≦1.8 w
lk & )! It is clear that with the material of the present invention, a product equivalent to S6 can be obtained.

Example 2 C: 0.0025cm, Si: 3.24cm, ht: o, 6
69b.

S: 0.0007 section, N: 0.0012 section, O: 0.0
A slab for a non-oriented electrical steel sheet containing O15 was heated and hot-rolled to form a hot-rolled sheet with a thickness of 1.8 m.
The hot-rolled sheet was annealed for 1 minute and cold-rolled to a product thickness of 0.50 m. After that, finish annealing is performed under the conditions shown in Table 2.
Magnetism measurements were performed. The results are also shown in Table 2.

A1 to Ya4 are comparative materials, and compared to the present invention, there are cases where the after-stage taste is not fixed in finish annealing, where there is retention before the first-stage soaking but no second-stage taste setting, where the second-stage holding temperature is low, and when the first-stage equalization is not done. This corresponds to each case when the thermal temperature is high. A5 to A7 are materials of the present invention. Comparison material is equivalent to S5 (W ≦z, tOw/
It is difficult to obtain V50 in 9), but with the material of the present invention, a product equivalent to S5 can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between final annealing conditions, iron loss value W, iron V50 loss value, and C ratio. Amendment to the 4-ton article I-bee procedure on the ground (voluntary) July 8, 1985 Mr. Uga Michibu, Commissioner of the Patent Office■, Indication of the case 1985 Patent Application No. 073303 2, Name of the invention Magnetic Manufacturing method for non-oriented electrical steel sheets with excellent properties 3, relationship with the amended case Patent applicant: 2-6-3 Otemachi, Chiyoda-ku, Tokyo (665) Nippon Steel Corporation Representative Takeshi 1 ) Yutaka 4, Agent 〒100 6, Subject of amendment

Claims (4)

[Claims] (1) C: 0.005% or less, Si: 2.5-4.0%
, a slab for non-oriented electrical steel sheets containing Al: 1.5% or less is hot-rolled, then hot-rolled and annealed, and then cold-rolled once or twice or more with annealing in between. In a method for producing a non-oriented electrical steel sheet in which the final plate thickness is obtained by rolling and final annealing is performed, the final annealing is performed at a temperature range of 950°C to 1100°C in the first stage for 5 seconds to 1 minute, and then in the second stage at 800°C to 90°C.
A method for manufacturing a non-oriented electrical steel sheet with excellent magnetic properties, characterized by reducing magnetic anisotropy by maintaining the temperature in a temperature range of 50° C. for 10 seconds to 2 minutes and then cooling. (2) Before the pre-soaking in the final annealing, 800
The method for manufacturing a non-oriented electrical steel sheet with excellent magnetic properties according to claim 1, wherein holding is carried out for 10 seconds to 2 minutes in a temperature range of .degree. C. to 950.degree. (3) The magnetism according to claim 1 or 2, characterized in that after the pre-soaking in final annealing, cooling is performed from the soaking temperature to 700°C at a cooling rate of 100°C/min or less. A method for manufacturing non-oriented electrical steel sheets with excellent properties. (4) C: 0.005% or less, Si: 2.5-4.0%
, Al: 1.5% or less, and the S, N, and O contents are each 0.0020% or less. A method for producing a non-oriented electrical steel sheet with excellent magnetic properties as described in the above.