JPH03202425A - Manufacture of nonoriented silicon steel sheet - Google Patents

Abstract

PURPOSE:To manufacture the nonoriented silicon steel sheet having low core loss and high magnetic flux density in a low magnetic field by subjecting a silicon steel slab to hot rolling, annealing the hot rolled sheet according to necessary, thereafter subjecting it to single cold rolling into a final sheet thickness and furthermore executing two stage finish annealing under specified conditions. CONSTITUTION:A slab of a silicon steel contg., by weight, <=0.01% C, <=3.5% Si, 0.1 to 1.0% Mn, <=0.1% P, <=0.01% S and 0.1 to 1.0% Al is hot rolled into a hot rolled sheet, is thereafter descaled and is annealed according to necessary. Next, the hot rolled sheet is subjected to single cold rolling to work into a final objective sheet thickness and is subjected to two stage finish annealing. Namely, the former annealing is executed in the temp. range of 500 to 700 deg.C for 30sec to 5min, and then, the latter one is executed in the temp. range higher than the annealing temp. of the former one, i.e., from 700 deg.C to the Ac1 transformation point. The nonoriented silicon steel sheet suitable as a core material for small size motors and small size transformers can be obtd.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is suitable as an iron core material for small motors, small power transformers, etc., and has low iron loss and non-directionality with excellent magnetic flux density characteristics in low magnetic fields. The present invention relates to a method for manufacturing electromagnetic steel sheets.

(Prior Art) In recent years, in the field of various electrical devices, competition to improve the efficiency of devices from the viewpoint of energy conservation has become even more intense. For example, in order to increase the efficiency of transformers for small motors and small power supplies, it is very effective to use electrical steel sheets with low iron loss and high saturation magnetic flux density to reduce iron loss and copper loss during load operation. It is. Furthermore, recently, there has been an increasing demand for improving the magnetic flux density characteristics in low magnetic fields for purposes such as reducing no-load current in small transformers.

In addition, the recent progress in OA and FA has been remarkable, and the demand for small control motors is increasing.
Since responsiveness is a problem in equipment A, the electromagnetic steel sheet used as the core material is required to have a sharp rise in the magnetization curve, that is, to have a high magnetic flux density in the low magnetic field region.

Conventionally, as a manufacturing method for non-oriented electrical steel sheets with excellent low magnetic field properties, as described in JP-A No. 61-264131, two-time cold rolling, two-time annealing method, secondary cold rolling, etc. When performing this, a method has been proposed in which rolling is performed at a rolling reduction rate of 1-15% and a rolling speed of 500 tm/win or more.

(Problems to be Solved by the Invention) However, in the two-time cold rolling and two-time annealing method, the steps are complicated, and an increase in cost due to the increase in the number of steps is unavoidable.

The present invention has been made in order to solve the problems of the prior art described above, and uses a simple method of 1-hour cold rolling annealing to achieve low iron loss and improve magnetic flux density characteristics in a low magnetic field region. The object of the present invention is to provide a method for manufacturing excellent electrical steel sheets.

(Means for Solving the Problems) As a result of intensive research to achieve the above object, the present inventors have determined that in the upper cold rolling single annealing method, finishing annealing is heated in two stages, and the heating temperature of the first stage is We have discovered that by setting the temperature to an appropriate temperature, the texture of the final product can be improved, and a non-oriented electrical steel sheet with low iron loss and excellent magnetic flux density characteristics in the low magnetic field region can be manufactured. This invention has been made.

That is, in the present invention, C20.01%, SiS2°5%
, 0.1%≦Mn≦1.0%, P≦0.1%, S≦0.
After hot rolling a steel slab containing 0.01% and 0.1%≦AI2≦1.0%, with the balance consisting of Fe and unavoidable impurities, the hot-rolled plate is annealed as necessary.

Then, when final annealing is performed after one cold rolling to obtain the final plate thickness, the first stage is soaked at a temperature range of 500 to 700°C for 30 seconds to 5 minutes, and the second stage is soaked at a temperature higher than the soaking temperature of the first stage. The gist of the present invention is to provide a method for manufacturing a non-oriented electrical steel sheet that is characterized by low core loss and excellent magnetic flux density characteristics in a low magnetic field.

The present invention will be explained in more detail below.

(Function) First, the results of basic experiments in which knowledge was obtained regarding two-stage heating during final annealing, which is the key point of the present invention, will be explained.

In this experiment, C: O, 004%, Si: 2.52%,
Mn: 0.25%, P: 0.014%, S: O, O
A steel slab containing 1% O and 0.30% Aff, with the remainder consisting of Fe and unavoidable impurities, was made into a hot-rolled sheet with a thickness of 2.4 mm using a normal method, and after descaling treatment, the recrystallized structure was removed. In order to obtain this, a hot rolled sheet was annealed at 750° C. for 5 hours. Subsequently, the final plate thickness was set to 0.5 am by cold rolling, and final annealing was performed by two-stage heating. During final annealing, the soaking temperature in the previous stage was varied between 500 and 800°C, and the soaking time at that time was 90 seconds. Soaking in the latter stage was performed at 1000'CX for 60 seconds.

Regarding the non-oriented electrical steel sheet manufactured by the above process,
Nib tine test pieces were cut out from the rolling direction and from the direction perpendicular to the rolling direction, respectively, and their magnetic properties were measured. The results are shown in FIG. Note that the point labeled "conventional method" on the horizontal axis represents the magnetic properties of the material produced by one-stage heating.

That is, it shows the magnetic properties of a material that was only annealed at 1000° C. for 60 seconds after cold rolling. In the figure, B2. B
, ,B, have magnetizing forces of 200A/ta and 30, respectively.
It represents the value of magnetic flux density at 0 A/+1.500 A/m.

As is clear from Fig. 1, the magnetic flux densities B2 and B in the low magnetic field
3. B5 has a higher value than the conventional method when the pre-heating temperature is 500 to 700° C., and the improvement effect is particularly large at lower magnetic flux densities such as B2 and B. In addition, regarding iron loss, in the case of two-stage heating, the iron loss is lower than in the case of one-stage heating, and especially in the range of 500 to 700°C, the iron loss is lower.

In order to investigate the reason for this, the texture of each material was investigated. The results are shown in FIG.

As is clear from Fig. 2, in the region where the pre-heating temperature is 500 to 700°C, where the magnetic flux density is high in a low magnetic field as described above, the effective (200) ) The strength of the surface is strong.

When the preheating temperature is 500℃, the (200) strength is
The strength of the (222) plane, which is disadvantageous in terms of magnetization characteristics, is lower than when the pre-heating temperature is above 700°C, which is outside the range of the present invention, although it is comparable to that when the temperature is above 700°C.

This is achieved by performing two stages of finishing annealing in the single cold rolling and single annealing method, and by regulating the soaking temperature of the first stage heating within an appropriate range, the (200) recrystallized grains, which are effective for magnetic properties, are produced more frequently. This is thought to be due to the fact that grains can be grown in the subsequent post-heating without changing the texture, which is effective in terms of magnetization properties, obtained in the pre-heating. It is thought that the magnetic flux density in a low magnetic field increases due to the texture improvement effect for the above reasons.

In addition, when the magnetic flux density in the low magnetic field increases, hysteresis
It is thought that the rise of the loop becomes sharper and the area of the hysteresis loop becomes smaller.

This means that hysteresis loss is reduced, resulting in a reduction in total iron loss.

As described above, by setting the soaking temperature in the previous stage to an appropriate temperature during final annealing in the single cold rolling single annealing method, non-directional properties with low iron loss and excellent magnetic flux density characteristics in low magnetic fields can be achieved. It was discovered that electromagnetic steel sheets could be produced, and the method of the present invention was developed.

Next, the reason for limiting the chemical composition of steel in the present invention will be explained.

C: C is an element that is harmful to magnetic properties, and the less it is, the lower the core loss is, and in order to prevent deterioration of magnetic properties due to aging,
The amount of C is regulated to 0.01% or less.

Si: Si is an element that increases the specific resistance of steel and reduces iron loss, but if added in excess of 3.5%, the steel becomes brittle and difficult to roll, so the amount of Si should be 3.5% or less. shall be.

Mn: Mn is an element that suppresses hot embrittlement, but if it is less than 0.1%, it has no effect, and if it is more than 1.0%, it causes deterioration of magnetic properties, which is not preferable.

Therefore, the amount of Mn is set in the range of 0.1 to 1.0%.

P: P is an element added to give good hardness to punching when the amount of Si is small, but if it is added in excess of 0.1%, the steel will become brittle and cold rollability will be impaired. The amount is 0.1
% or less.

S: If S is contained in a large amount, it will produce precipitates such as MnS that are harmful to magnetic properties, so the smaller the better, it is regulated to 0.01% or less.

AL: Fine AQN precipitation is harmful to magnetic properties, so AQN
In order to precipitate coarse AIN by adding a large amount of Q,
The amount of Al needs to be 0.1% or more. Although the reason is not clear, the effect of the two-stage heating mentioned above is that Afl is 0.
It has been confirmed that the expression does not occur unless it is contained at 1% or more.

On the other hand, if it is added in an amount exceeding 1.0%, it not only deteriorates the cold rollability but also increases the cost for the following reason: 0.1%≦Al≦1.0%.

Next, the reasons for limiting the manufacturing process in the present invention will be explained.

The steel having the above chemical composition is made into a slab by a conventional method, and further into a hot rolled steel strip by hot rolling. After hot rolling, after descaling treatment, hot-rolled plate annealing is performed as necessary, and the final plate thickness is obtained by subsequent cold rolling.

After cold rolling, finish annealing is performed. In this finish annealing, the first stage is soaked at a temperature in the range of 500 to 700°C, and the second stage is soaked at a higher temperature than the first stage soaking temperature to cause grain growth.

As mentioned above, the pre-stage soaking temperature is less than 500°C or 7°C.
If the temperature exceeds 00° C., a material with low iron loss and high magnetic flux density in a low magnetic field cannot be obtained. The soaking time in the first stage is limited to 30 seconds or more and 5 minutes or less, since the effect of improving the texture is small if it is less than 30 seconds, and the effect is saturated even if annealing is performed for more than 5 minutes.

The purpose of the subsequent soaking is to grow crystal grains so that a predetermined core loss can be obtained. Therefore, a temperature higher than the pre-soaking temperature is required.

Furthermore, it is preferable to change the soaking temperature depending on the amount of Si. That is, in the case of steel with a small amount of Si, when α → γ transformation occurs, it becomes a mixed grain structure, which has a negative effect on magnetic properties, so the temperature range of 700°C to Ac1 transformation point is appropriate for the subsequent soaking temperature. . On the other hand, in α single-phase steel with a large amount of Si,
In order to sufficiently enlarge the crystal grains, a subsequent soaking temperature of 800°C or higher is preferable, but if the temperature exceeds 1100°C, secondary recrystallization will occur, the texture will change, an oxide film will grow on the surface, and the magnetic properties will deteriorate. is deteriorated, so the subsequent soaking temperature is 80℃.
A temperature of 0°C or more and 1100°C or less is appropriate.

The soaking time at this time is 10 seconds or more and 3 minutes or less, and the crystal grains grow sufficiently.

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

A steel slab having the two types of chemical components shown in Table 1 was made into a hot-rolled plate with a thickness of 2.4 am using the usual method, and after descaling treatment, it was hot-rolled at 75 o'c for 5 hours. The plate was annealed and cold rolled to a product thickness of 0.50 mm. Subsequent final annealing was performed under the conditions listed in Table 1 to obtain a final product.

Epstein specimens were cut out from each material in the rolling direction and in a direction perpendicular to the rolling direction, and the magnetic properties were measured. The results are also shown in Table 1.

In Table 1, 8111 is the steel of the present invention, &2~&
5 is comparative steel. Comparative steel Na2 is an example without pre-soaking temperature, 3 is an example where the pre-soaking temperature is low, &4 is an example where the pre-soaking temperature is high, and 5 is an example with a low AQ amount.

As is clear from Table 1, only the steel of the present invention has low iron loss and high magnetic flux density in the low magnetic field region.

A steel slab having chemical compositions with three levels of Si shown in Table 2 was made into a hot-rolled plate with a thickness of 2.0 to 2.4 mm by the usual method, and after descaling treatment, A For steel and B steel, hot rolled sheet annealing was not performed, and for C steel, hot rolled sheet annealing was performed at 950° C. for 3 minutes and then cold rolled to a product thickness of 0.50 mm.

Subsequent final annealing was performed under the conditions shown in Table 3 to obtain a final product.

Epstein specimens were cut out from each material in the rolling direction and in a direction perpendicular to the rolling direction, and the magnetic properties were measured. The results are also shown in Table 3.

In Table 3, Mal, l! 15, Shame 9 is the invention steel, comparative steels Nα2, Na6, &10 are examples without pre-soaking temperature, Na3, Na7, N (111 are examples with low pre-soaking temperature, Nα4, Nα8, Nα12 are This is an example where the pre-stage soaking temperature is high.

As is clear from Table 3, only the steel of the present invention has low core loss and high magnetic flux density in the low magnetic field region.

[Blank below] (Effects of the invention) As detailed above, according to the present invention, in the one-time cold rolling one-time annealing method, the finishing annealing is performed as a two-stage annealing, and the soaking temperature in the first stage is adjusted to an appropriate temperature range. By regulating this, it is possible to manufacture non-oriented electrical steel sheets with low iron loss and excellent magnetic flux density characteristics in the low magnetic field region.

[Brief explanation of drawings]

The first diagram shows the relationship between the pre-stage soaking temperature, iron loss (W, /,.), and the magnetic flux density B, , B,, B, in the low magnetic field region. Figure 2 shows the relation between the pre-stage soaking temperature and (110), (200), (2
22) It is a diagram showing the relationship with the polar density ratio of each surface.

Claims (1)

[Claims] In weight% (the same applies hereinafter), C≦0.01%, Si≦3.
5%, 0.1%≦Mn≦1.0%, P≦0.1%, S≦
After hot rolling a steel slab containing 0.01% and 0.1%≦Al≦1.0%, with the remainder consisting of Fe and unavoidable impurities, the hot rolled plate is annealed as necessary, and then once. When performing final annealing after cold rolling to final plate thickness,
The first stage is soaked in a temperature range of 500 to 700°C for 30 seconds to 5 minutes, and the second stage is soaked at a higher temperature than the first stage.It has low iron loss and excellent magnetic flux density characteristics in a low magnetic field. A method for producing a non-oriented electrical steel sheet.