JPH0324250A - Nonoriented silicon steel sheet reduced in in-plane anisotropy - Google Patents

Abstract

PURPOSE:To inexpensively obtain a nonoriented silicon steel sheet reduced in in-plane anisotropy and having low iron loss by specifying a composition consisting of C, Si, Mn, P, S, Al, N, B, and Fe. CONSTITUTION:This steel sheet is a high or medium grade nonoriented silicon steel sheet consisting of, by weight, <=0.005% C, >1.0-<4.0% Si, >0.1-<1.5% Mn, <=0.1% P, <=0.002% S, >0.10-<1.0% Al, <=0.004% N, >0.0003-<0.0015% B, and the balance Fe with inevitable impurities, extremely reduced in the anisotropy of electromagnetic properties in a sheet surface, and also reduced in iron loss. In the above silicon steel sheet, reduction in anisotropy is attained by using, in combination, relatively large amounts of Al and small amounts of B, and this silicon steel sheet is suitable for iron core material for motor and transformer.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a so-called medium to high-grade non-oriented electrical steel sheet with a Si content of 1.0 to 4.0%, and particularly to magnetic properties in the plane of the rolled sheet. This relates to non-oriented electrical steel sheets with small anisotropy. (Prior art) Non-directional tMis plates are mainly used as core materials for motors and transformers, and comply with the JIS standard (C-255
2 revision), they are divided into types based on plate thickness and iron loss value. The iron loss is
It represents the heat loss that occurs when iron is magnetized.Of course, the smaller the value, the better, but the grade is selected according to the purpose based on economic efficiency and the size of the equipment. Generally, as equipment becomes larger, the amount of heat generated by iron loss increases in proportion to its volume, while the amount of heat dissipated is only proportional to its surface area, making it difficult to cool the equipment. For this reason, the larger the equipment, the more materials with low iron loss are required. Iron loss is dominated by two factors: eddy current loss and hysteresis loss. Eddy current loss is a loss due to eddy currents induced by magnetization, and depends on the plate thickness and the electrical resistance of the steel. The thinner the plate, the better, but if it is too thin, problems such as the time-consuming work of laminating the iron core will occur, so the JIS standard is 0.65.
Three types are specified: , 0.50, and 0.35 opening. The higher the electrical resistance of steel, the better, and Si is often used as an alloying element because it has a large electrical resistance increase rate per unit addition amount and is inexpensive. This is why electrical steel sheets are also called silicon steel sheets; the higher the St content, the higher the iron loss. For the same purpose, Al and Mn are also added as necessary. On the other hand, hysteresis loss decreases as there are fewer fine precipitates and grain boundaries that impede domain wall movement during the magnetization process. Therefore, it is important to use steel of as high purity as possible and to make the crystal grains a certain length.Ti, Nb, V, etc. produce fine carbonitrides, and their precipitates form crystal grains. Because it interferes with Kaicho, the magnetic properties are significantly deteriorated. For this reason, the addition of these carbonitride-forming elements to tM1 steel sheets is strictly limited. Affi also produces fine ^lN and has a similar negative effect, so it is generally not added to low-grade ill steel sheets. In medium to high-grade electrical steel sheets, ^l is added to increase the electrical resistance, but in this case it is usually 0.
By adding a large amount of 1% or more to coarsen the precipitates, adverse effects on hysteresis loss are avoided. In other words, it is common knowledge that it is better not to add Affi at all or, conversely, to add it in large amounts.On the other hand, when boron (B) is added, the Al content is 0.1%. It has been reported that good magnetic properties can be obtained even if the
20731 Publication). The reason for this is not clear, but it is believed that it is necessary to balance it in a certain relationship with the amount of nitrogen (N) in the steel. That is, the B/N ratio is 0.5 to 2.
．． Considering that the range of 5 is considered appropriate, it is presumed that there is a close relationship with the precipitation of BN. In this case, A
It is said that if the ffi content exceeds 0.1%, it will only lead to an increase in price and the effect of B addition will not be sufficiently obtained. In this way, although B is a nitride-type element, it is thought to have relatively little negative effect on magnetic properties, but its actions and effects have not been fully clarified. So-called medium to high-grade non-directional with low iron loss! Magnetic steel sheets are particularly required to have small anisotropy within the mask of magnetic properties. In other words, in the iron core of a motor or transformer, lines of magnetic force flow in various directions within the mask, so if the magnetic properties in a certain direction are bad, it will affect the performance of the entire device. Evaluation of the magnetic properties of non-directional iM1 sea bream plate is usually done by
This is done using the average values of the rolling direction (L direction) and the direction perpendicular to it (T direction), but when it comes to medium to high-grade electrical steel sheets, it is dangerous to design equipment using only the average values. Even if the average value of iron selection is within the control range of the grade, if the difference between the L direction and the T direction is large, the performance of the equipment will be affected by the characteristics in the bad direction. In comparison, the magnetic properties in the T direction are usually poor. In the case of low-grade non-oriented electrical steel sheets, the level of iron loss is high, so some anisotropy is not a problem, but for medium to high-grade non-oriented tIlt1 steel sheets with low iron loss, even a slight anisotropy makes a difference. It's getting bigger and bigger! 1! ! It becomes. Non-oriented electrical steel sheets are originally used on the premise that they have no anisotropy. On the other hand, in the case of grain-oriented T-magnetic steel sheets, the magnetic properties in the L direction are maximized by aligning the crystal grains in a specific direction and maximizing the anisotropy using secondary recrystallization. It has been improved to. Devices using grain-oriented electrical steel sheets are designed to utilize only the characteristics in the L direction.

In other words, the uses of grain-oriented electrical steel and non-oriented titanium steel are generally different. In order to reduce the iron loss of the non-oriented iM1 steel sheet, as mentioned above,
Adding alloying elements such as Si to reduce eddy current loss,
Efforts have been made to reduce hysteresis loss by increasing the purity of the steel. However, medium to high grade non-directional electricity 1
When it comes to 61 steel sheets, it is difficult to obtain the desired low iron loss using these methods alone, and various methods have been investigated to control the texture (crystal grain orientation) by adding special alloying elements and modifying manufacturing conditions. There is. In the case of non-oriented electrical steel sheet, directionality a
! Although it is not possible to create a strong texture like that of FI steel sheets, it is possible to create a texture with a certain degree of easy magnetization (100} orientation.However, conventional methods cannot improve the average value of magnetic properties. Although it is possible to
This often has the fatal drawback of increasing anisotropy within the mask. That is, in conventional texture control, the overall properties are improved by improving the properties in the L direction, but the properties in the T direction often remain almost unchanged or even slightly deteriorate. In this way, medium to high-grade non-oriented electrical steel sheets with low iron loss,
Although it is desired to reduce the anisotropy within the mask, there is currently no effective means to achieve this. (Problems to be Solved by the Invention) In view of the above circumstances, an object of the present invention is to provide a medium to high-grade non-oriented electrical steel sheet with small anisotropy in the mask and low core loss. ．． (Means for Solving the Problem!) The present inventor conducted a detailed study on the effects of various alloying elements that affect electrical steel sheets. As a result, it was found that the above objective could be achieved by keeping the content of each of the precepts, including Si and An, within appropriate ranges, and then adding B within a certain content range. The gist of the present invention resides in the following non-oriented electrical steel sheet. weight%
C: 0.005% or less, Si: more than 1.0% and less than 4.0%, Mn: more than 0.1% and less than 1.5%, P: 0.1% or less, S: 0. 002% or less, ^1: More than 0.10% and less than 1.0%, N: 0.00
4% or less, B: more than 0.0003% and less than 0.0015%, and the remainder consists of Fe and unavoidable impurities. Conventionally, it has been thought that B exerts its effects through BN precipitation, and emphasis has been placed on its relationship with N content. That is, it is necessary to add B in an amount sufficient to fix N to some extent (preferably, to completely fix it) in chemical equivalent terms. Therefore, in this case B is basically Aj! The same camphor has the function of fixing N, but the precipitated BN is AI! Af has less negative impact on magnetic properties than H, so it is only used for electrical steel sheets.
Although the details of the precipitates when fi and B are added in combination are not fully clarified, it is thought that AffiN precipitates with BN as the core, resulting in steel with a relatively low ^2 content. However, it is understood that the precipitation of fine AlN is suppressed and the magnetic properties are improved. In response, the present inventors focused on the effect of B addition on anisotropy and investigated medium to high-grade electrical steel sheets with high Si and A1 contents. As a result, the Al content was 0.10
They found that when a small amount of B is added to high Affi steel exceeding 10%, the anisotropy of the magnetic properties is significantly reduced. In this case, N is almost completely fixed by ^l, and solute N is practically close to zero, so the effect of B is due to the effect of B in solid solution.
This is thought to be due to Although the detailed mechanism is still unclear, it is probably due to the segregation of solid t9B at grain boundaries, etc.
It is presumed that the process of cold rolling and subsequent recrystallization annealing contributes to the formation of a texture with small anisotropy. (Function) The effects of the alloying elements in the im steel sheet of the present invention will be explained below along with the reason for limiting the content. C: C is an element that produces carbides and deteriorates all magnetic properties, so it is desirable to keep its content as low as possible. In particular, to prevent magnetic aging, o. It is necessary to keep it below oos%, and furthermore, 0. It is desirable to keep it below 0.003%. Si: The Si content is set to exceed 1.0% in order to obtain the core loss necessary for a medium to high-grade non-oriented electrical steel sheet.
% or less, the eddy current loss will be large and the iron loss will not be as low as the target. On the other hand, if Si is contained in an amount of 4.0% or more, cold rolling properties are significantly deteriorated.

Mn = Mn is contained in an amount exceeding 0.1% to prevent hot embrittlement caused by S. Mn is also effective in increasing electrical resistance and reducing eddy current loss. However, the Mn content is 1
．． If it exceeds 5%, the steel will become brittle and grain growth will deteriorate, so it should be less than this. P: P may be contained up to 0.1% for the purpose of adjusting strength and increasing electrical resistance, but if it exceeds this, cold rollability deteriorates. S: S produces sulfide-based precipitates and deteriorates magnetic properties, so it is best to suppress it to 0.002% or less. Ai: Medium to high-grade non-oriented electrical steel sheets generally contain 0.1% or more for the purpose of increasing electrical resistance and coarsening AlN, but in the present invention, in addition to these effects, N is completely eliminated. 0.0 to fully exhibit the action and effect of B. 1
Contain more than 0%. On the other hand, if the content exceeds 1.0%, the effect will be saturated and the price will only increase, so the content should be less than this. N N prevents nitrides and impairs magnetic properties, so 0.00
The content should be 4% or less, preferably 0.002% or less. B: B is contained in an amount exceeding 0.0003% in order to reduce the anisotropy of magnetic properties. If it is less than 0.0003%, it becomes solid RB.
If the amount of is insufficient, the anisotropy will increase. On the other hand, 0.001
Even if the content exceeds 5%, not only the effect of reducing anisotropy is saturated, but also the overall magnetic properties tend to deteriorate due to an increase in precipitates.

The effect of adding a small amount of B on reducing the anisotropy of magnetic properties is only effective when the Al content is high. That is, it is essential to add a sufficient amount of Al as described above and also to add a small amount of B. Usually B is 0.00
It is suitable that the content is in the range of 0.08 to 0.0012%.

The electric wire mm+i of the present invention having the above-described structural strength can be manufactured by the following method. The slab heating temperature in the hot rolling process should be in the range of 1l00 to 1250°C.It is better to heat the slab at a low temperature to prevent deterioration of magnetic properties due to fine precipitation of MnS, but in order to ensure the hot rolling finishing temperature, It cannot be heated to low temperatures. A temperature of about 1150 to 1200°C is suitable. The hot rolling finishing temperature should be higher.
The temperature should be 800°C or higher, preferably 850°C or higher. It is better to wind it at a high temperature, but in consideration of pickling properties, 550
A suitable winding temperature is ~650°C.

After hot rolling, in order to recrystallize the processed structure of hot rolling, 7
The hot rolled sheet is annealed at 50°C or higher, preferably 850°C or higher. However, if this temperature becomes too high, the crystal grains become coarse and cracks are likely to occur during the next cold rolling, so it is better to keep it below 1050°C. Usually 90
Continuous annealing is performed at 0 to 1000°C for less than 5 minutes, but 800°C
Box annealing at ~900°C may also be used. The reduction ratio of cold rolling is in the range of 60 to 90%. From the viewpoint of magnetic properties, it is appropriate to perform a one-time cold rolling process with a reduction of about 75 to 85%.
If reducing iron loss is important, cold rolling may be performed two or more times including intermediate annealing. Final annealing is 85
It is preferable to perform continuous annealing at 0'C or higher for less than 3 minutes. (Example) The steel shown in Table 1 was melted in a laboratory and made into a thin plate with a thickness of 0.5 mm in the next manufacturing process. That is, the heating temperature for hot rolling was 1150°C, the finishing temperature for rolling was 850°C, and after rolling, the material was air cooled to 600°C, and then placed in a furnace maintained at 600°C for furnace cooling. This is a heat treatment equivalent to winding a hot-rolled coil. The thickness of the hot rolled plate is 2.3m
- After pickling, heat treatment was further performed at 950''C for 3 minutes.
This is done to recrystallize the structure of the hot rolled sheet. Sea bream, which has a high Si content, tends to leave processing &lI weave in hot-rolled sheets, and the surface shape deteriorates during cold rolling, which is why hot-rolled sheets are heat-treated in this way. Thereafter, it was cold rolled to a thickness of 0.5 at a rolling reduction of 78%. 95 to this cold-rolled plate
After recrystallization annealing for 0"CXI, specimens were taken by punching from the L direction and the T direction, and the magnetic properties were measured. The results of the measurements are shown in Table 2. , 2, and g), the difference between the L direction and the T direction is small, and it is clear that the average properties are also excellent.On the other hand, even steel with a high Al content contains B. In steels with no Al content (ku, ho, chi) and 'w4 (c, ri) with low Al content even if B is added, the anisotropy is large, and the purpose of the present invention is not achieved. If the amount of steel is too large, the magnetic anisotropy will be slightly larger and the average value will also be worse. It is extremely small and can be manufactured at low cost.The electrical steel sheet of the present invention greatly contributes to improving the performance of motors and transformers as core materials.

Claims (1)

[Claims] In weight%, C: 0.005% or less, Si: more than 1.0% and less than 4.0%, Mn: more than 0.1% and less than 1.5%,
P: 0.1% or less, S: 0.002% or less, Al: 0.
More than 10% and less than 1.0%, N: 0.004% or less, B
: A non-oriented electrical steel sheet with small in-plane anisotropy, characterized by containing more than 0.0003% and less than 0.0015%, with the remainder consisting of Fe and unavoidable impurities.