JPS6333518A - Non-oriented electrical steel sheet having low iron loss and excellent magnetic flux density and its production - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a non-oriented electrical steel sheet with low core loss and excellent magnetic flux density, and a method for manufacturing the same.

Non-oriented electrical steel sheets are used for the cores of motors, transformers, etc., and recently there has been a strong demand for these electrical devices to be energy-saving types.

In particular, for small and medium-sized electrical equipment that has conventionally mainly used relatively inexpensive non-oriented electrical steel sheets, it is possible to improve There is a strong demand for the development of materials with low iron loss.

To accommodate this, the iron loss is W,%/,. at 4.5W/
kg or less and has a magnetic flux density of B. at 1.71 Te
There is a need to manufacture non-oriented electrical steel sheets with an excellent sla or better.

As is well known, the magnetic properties of non-oriented electrical steel sheets include iron loss and magnetic flux density, and depending on the values of iron loss and magnetic flux density, 360
It is graded up to 439 grade.

By the way, in order to manufacture high-grade grades with low iron loss, it is common practice to increase the Si content. For example, the Si content of 860 grade is close to zero, but the Si content of 323 grade is about 1.
It is rumored that 5%, 318th grade is about 2.0%, and 39th grade is about 3.0%. On the other hand, as the Si content increases, the magnetic flux density decreases, so the relationship between the iron loss value and the magnetic flux density value of conventional non-oriented electrical steel sheets is as shown by curve 1.1' in Figure 1, that is, As the loss becomes lower, the magnetic flux density decreases.

Further, in this figure, 2 is a straight line connecting the limit values of 309 to S23 in JIS standard C2552.

Conventionally, in order to improve the magnetic properties, it is not only necessary to simply increase the Si content, but also to take component measures such as adding Al, reducing C, reducing S, and adding B, and increasing the annealing temperature. , efforts have been made to increase the cold reduction rate before final annealing.

For example, the present inventors also determined that B is the N content in steel and the weight ratio B/
JP-A-54-163720 describes the economical production of non-oriented electrical steel sheets with low iron loss by incorporating N in a manner that promotes the growth of crystal grains during annealing.
It was proposed in the publication. According to this, a product with low iron loss is manufactured, but the relationship between iron loss value and magnetic flux density is still within the range of curve 1.1' in FIG.

Furthermore, manufacturing a non-oriented electrical steel sheet with low iron loss by incorporating Sn has been proposed, for example, in Japanese Patent Laid-Open No. 102520/1983. The inclusion of Sn lowers the core loss, but in order to achieve the effect of SffSn inclusion, it is necessary to slow down the cooling rate during hot-rolled sheet annealing and slow down the heating rate during final annealing. subject to restrictions. Furthermore, although the iron loss is reduced by the inclusion of Sn, the magnetic flux density is not reduced by much, and the curve 1 in FIG.
, 1', and cannot meet the demand for producing a non-oriented electrical steel sheet with low iron loss and excellent magnetic flux density.

In view of this fact, the present invention has an iron loss of WIS/S. So 4.5
Low iron loss of less than w/kg and magnetic moxibustion density of B.

The object is to provide a non-directional electromagnetic wJ plate that is greater than or equal to 1.71 Tesla, ie at least equal to line 3 in FIG.

Another object of the present invention is to provide a method for producing a non-oriented electrical steel sheet having the defined core loss and magnetic flux density as described above.

The present inventors made silicon steel contain Sn and Mn.
After hot rolling a steel containing B with a higher B content and a predetermined relationship between the N content in the steel and the weight ratio B/N, hot rolled sheet annealing or hot rolling is performed. It has been found that when rolled and self-annealed in a high temperature range of 700° C. or higher after rolling, an electromagnetic steel with low core loss and high magnetic flux density can be obtained, and the above object can be achieved.

In addition, it has been found that continuous short-time annealing can be applied to the hot-rolled sheet annealing, and continuous short-time annealing can also be applied to finish annealing after cold rolling. That is, the non-oriented electrical steel sheet of the present invention can be manufactured in a relatively short manufacturing period and in a process with low processing cost.

The present invention was made based on the above-mentioned findings,
The gist of this is, in weight percent, C: 0.015% or less, St: 0.3 to 2.0%, Mn: more than 1.0% and 1.5% or less, Sn: 0.02 to 1.5%. 0.20%, acid soluble Aji! : 0.005-0.1%, N: 0
．． 007% or less, B: 0.005% or less, and B/N:
A non-oriented electrical steel sheet having a relationship of 0.5 to 1.5, with the balance being Fe and unavoidable impurities, and having low iron loss and excellent magnetic flux density, and in weight percent, C: 0.015% or less, Si: 0, 3-2.0%, Mn: over 1.0% 1
．． 5% or less, Sn: 0.02-0.20%, acid-soluble Al: 0.005-0.1%, N: 0.
0.007% or less, B: 0.005% or less and B/N
': o,s ~ 1.5, and the remainder consists of Fe and unavoidable impurities. After hot rolling, the steel
Either coiling and self-annealing in a temperature range of 750°C or higher, or hot rolling and then annealing in a temperature range of 750°C or higher, followed by cold rolling once or twice or more with an intermediate annealing process. The present invention provides a method for producing a non-oriented electrical steel sheet with low core loss and excellent magnetic flux density, which comprises rolling and then continuous annealing at a temperature of 750° C. or higher. Yet another point is that after the continuous annealing of the cold-rolled sheet, the reduction rate is 2.
The point is to perform skin pass rolling at ~10%.

The present invention will be explained in detail below.

First, let's talk about the ingredients of steel.

C is a harmful component that increases core loss and causes magnetic aging, so it should be kept at 0.015% or less. The preferable C content is 0.00, which reduces iron loss and increases magnetic flux density by containing Mn, Sn, and acid-soluble A1 or B for purposes other than deoxidizing.
It is less than 5%.

As is well known, St is a component that has the effect of reducing iron loss, and in order to exhibit this effect, it is contained in an amount of 0.3% or more. On the other hand, if the content increases, the magnetic flux density decreases as described above, rolling workability deteriorates, and costs increase, so it is set to 2.0% or less.

Al is a necessary component for deoxidation, and for this action, 0
．． It is desirable to contain 0.005% or more.

Conventionally, Mn was not used to improve the magnetic properties of non-oriented electrical steel sheets because it easily generates nonmetallic inclusions such as oxides and sulfides, but with the development of high-purity steel manufacturing technology, its use is now possible. Became. According to the inventor's findings, Mn
develops (100) and (110) textures that are desirable for magnetic properties and (11) that are undesirable for magnetic properties.
1) It has the effect of suppressing aggregated Mn weave. In order to bring about this effect, the content of Mn needs to exceed 0.75% as proposed in Japanese Patent Application No. 56-213368. .0
It is desirable that the amount exceeds %. Mn lowers the ferrite-austenite transformation temperature, so if the Mn content exceeds 1.5%, ferrite-austenite transformation occurs during annealing of the hot-rolled sheet.
Austenite transformation occurs, and the texture-improving effect and magnetism-improving effect of Mn disappears. Therefore, the Mn content is set to more than 1.0% and less than 1.5%.

Since N is a component harmful to magnetic properties, in the present invention it is set to 0.007% or less.

B is an important component in the present invention, and includes Sn and M, which will be described later.
The combined action with n has the effect of reducing iron loss and increasing magnetic flux density. On this day, N is contained based on the relationship of the weight ratio B/N with the N content in the steel. And B/N is 0.
If it is less than 5, it is difficult to eliminate the harmful effects of N, so the lower limit is set to 0.5. On the other hand, as B/N increases, solute B increases and it becomes difficult to maintain good core loss and magnetic flux density.
．． 5 or less. Further, the absolute content of B is set to 0.005% or less in order to prevent the occurrence of cracks in the steel billet.

Sn has the effect of reducing iron loss and increasing magnetic flux density due to its composite content with Mn and B, but in order to exhibit this effect, it is necessary to have an amount of 0.02% or more. On the other hand, even if this content increases, its effect will be saturated and the cost will increase, so it is set to 0.20% or less.

Components other than those mentioned above are Fe and unavoidable impurities.

Next, the combined effect that is a feature of the present invention will be explained.

Sn mainly segregates to the grain boundaries and is initiated at the grain boundaries (1
11) Suppresses recrystallization of orientation and promotes recrystallization within grains. Moreover, Mn is (110) and (1
00) It has the effect of developing texture. Furthermore, since B fixes N as BN, it prevents the precipitation of AIN, which is harmful to magnetism, and also prevents this BN from precipitating between crystal grains.
(110) and (100) desirable for magnetic properties
It acts as a recrystallization nucleus that promotes the formation of texture.

Desired magnetic properties can only be obtained when these effects of Sn, Mn and B are realized simultaneously.

As understood from the above, in the non-oriented electrical steel sheet of the present invention, a high Mn content plays an important role in improving magnetic properties. The dependence of magnetic properties on this Mn content is shown in FIG.

The non-oriented electrical steel sheet shown in this drawing is made by hot rolling steel having the composition shown in Table 1 to 2.3 llI, rolling it at 750°C, annealing it at 900°C for 2 minutes, and forming it into a 0.53m copper strip. cold rolled for 1 minute, finish annealed at 850°C for 1 minute, skin pass rolled at a rolling reduction of 6%, and annealed for 1 hour in a 100% N2 atmosphere.
It was manufactured by performing stress relief annealing at 90°C.

As can be seen from Table 1 and Figure 2, when the Mn content exceeds 1%, the non-directional electromagnetic material contains Sn and B in a weight ratio such that 0.5≦B/N≦1.5. The iron loss and magnetic flux density of the steel are improved compared to those without Sn.

The manufacturing method according to the present invention will be explained in detail below.

Steel made of the above-mentioned components is melted in a converter or electric furnace, and is made into a slab by continuous casting or ingot-forming and then blooming rolling.

Next, it is heated to a predetermined temperature and hot rolled. In this hot rolling, after hot rolling, it is rolled up at a temperature of 700° C. or higher, and self-annealed using the heat possessed by the hot coil. During this self-annealing, it is convenient to cover the hot coil with a heat retaining cover to prevent heat dissipation. By the way, the reason why the steel is rolled up at 700° C. or higher is that if the temperature is lower than this temperature, fine precipitates are formed during subsequent annealing, which suppresses the growth of crystal grains. Moreover, below this temperature, even if Sn, Mn, and B are contained in combination, the core loss cannot be reduced and the magnetic flux density cannot be increased.

Further, instead of rolling the sheet to a temperature of 700° C. or higher and self-annealing it during hot rolling, the hot-rolled sheet is annealed at a temperature of 750° C. or higher after hot rolling. Although this also makes it possible to lower the core loss and increase the magnetic flux density, it is necessary to perform annealing at a temperature of 750° C. or higher in order to achieve this effect.

In this hot-rolled sheet annealing, it is better to have both a faster heating rate and a faster cooling rate, and continuous annealing can be applied.

Then, with one cold rolling and intermediate annealing in between,
A predetermined plate thickness is obtained by cold rolling two or more times.

In final annealing, continuous annealing is performed because rapid heating rather than a low heating rate has the effect of reducing core loss and increasing magnetic flux density. The annealing temperature at this time is 750° C. or higher and can be changed depending on the desired magnetic properties.

In the present invention, the fact that continuous annealing is preferable is advantageous not only from the viewpoint of improving magnetic properties but also from the viewpoint of increasing productivity, and is an effect of the composite plate of Sn, Mn, and B.

With the above steps, a non-oriented electrical steel sheet is manufactured. Next, stress relief annealing is performed or a skin bath is applied for 2 to 10 minutes.
%, and a so-called semi-process type non-oriented electrical steel sheet may be manufactured in which strain relief annealing is performed after punching into a predetermined shape.

The reason why the skin pass rate is set to 2 to 10% is because if it is less than 2%, the magnetic properties will not be excellent during strain relief annealing, and the reason why the upper limit is set to 10% is because if it exceeds this, the magnetic properties will deteriorate. .

Next, examples will be shown.

Example 1 Steels having the components shown in Table 2 were produced under the treatment conditions shown in Table 2, and their magnetic properties were measured. The measurement results are also shown in the same table.

The magnetic properties of a non-oriented electrical steel sheet having the composition of steel plate 11 are shown in FIG. 1 below.

Example 2 After pickling the hot-rolled steel plate used in Example 1, the
cold rolled and continuously annealed at 750°C for 60 seconds,
Next, skin pass rolling was performed at a reduction rate of 4%.

Then, cut into Epstein samples and heat at 790°C x lhr.
The magnetic properties were measured after strain relief annealing.

The results are shown in Table 3.

Table 3 This magnetic property is shown as m1ls in FIG.

As described above, according to the present invention, a non-oriented electrical steel sheet with low iron loss and excellent magnetic flux density can be provided.

[Brief explanation of the drawing]

FIG. 1 shows a conventional non-oriented electrical steel sheet and an iron loss W87 targeted by the present invention. . and magnetic flux density B,. A diagram showing the relationship between
Figure 2 shows Mn content and iron loss WIs/s. and magnetic flux density B,
. FIG.

Claims (1)

[Claims] 1) In weight%, C: 0.015% or less, Si: 0.3 to
2.0%, Mn: more than 1.0% and less than 1.5%, Sn:
0.02-0.20%, acid-soluble Al: 0.005-0.
1%, N: 0.007% or less, B: 0.005% or less, and has a relationship of B/N: 0.5 to 1.5, and the iron loss is low and the balance is Fe and unavoidable impurities. Non-oriented electrical steel sheet with excellent magnetic flux density. 2) In weight%, C: 0.015% or less, Si: 0.3~
2.0%, Mn: more than 1.0% and less than 1.5%, Sn:
0.02-0.20%, acid-soluble Al: 0.005-0.
1%, N: 0.007% or less, B: 0.005% or less, and has a relationship of B/N: 0.5 to 1.5, with the balance consisting of Fe and unavoidable impurities. After rolling, 7
Either coiling and self-annealing in a temperature range of 00°C or higher, or hot rolling annealing in a temperature range of 750°C or higher, then 1
It is characterized by low iron loss and magnetic flux density, which is characterized by cold rolling performed twice or more with an intermediate annealing process, and then continuous annealing in a temperature range of 750°C or higher. An excellent manufacturing method for non-oriented electrical steel sheets.