JPH0450380B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention particularly relates to a non-oriented electrical steel sheet that is excellent in both iron loss and magnetic flux density. [Prior Art] Non-oriented electrical steel sheets are mainly used as iron core materials for small motors, small transformers, etc., and their magnetic properties are required to have low core loss and high magnetic flux density. By the way, iron loss and magnetic flux density are generally considered to be contradictory, and for this reason, it is considered extremely difficult to achieve excellent properties of both at the same time, partly due to economic considerations. There is. [Problems to be solved by the invention] Various methods have been disclosed for improving the properties of non-oriented electrical steel sheets, but none are effective in terms of achieving both iron loss and magnetic flux density. When it comes to countermeasures, the reality is that there are not enough. In general, it has been revealed that adding alloying elements such as Si and Al, coarsening crystal grains, etc. are effective in reducing iron loss. Iron loss is mainly divided into eddy current loss and hysteresis loss. The above method reduces eddy current loss, and hysteresis loss. In this method, the specific electrical resistance of steel is increased by adding Si, Al, etc., but adding large amounts of these alloying elements not only reduces the magnetic flux density but also increases costs. Become. A well-known method is to increase the amount of Al added to agglomerate and coarsen AlN precipitates that inhibit grain growth. However, even with this method, the amount of precipitates increases, resulting in a decrease in magnetic flux density, which is also unfavorable in terms of cost. In addition, in terms of manufacturing processes, we have adopted the double cold rolling method and the double cold rolling method.
It is said that the use of the re-annealing method is effective in improving magnetic properties by coarsening crystal grains and controlling texture. However, these methods have problems in that the manufacturing process becomes complicated and costs increase significantly, and high magnetic flux density cannot be expected. On the other hand, the effectiveness of Zr has recently been confirmed,
Various methods have been proposed to utilize this to produce non-oriented electrical steel sheets with good magnetic properties.
No. 58-19726, Japanese Patent Publication No. 58-25426, No. 59-83723
issue). Fine precipitates such as AlN and MnS act as inhibitors to grain growth and are harmful.
Zr has the effect of preventing the formation of these harmful fine precipitates. However, it takes
The method utilizing the effect of Zr has not yet been satisfactory from the standpoint of obtaining excellent properties in both iron loss and magnetic flux density at low cost industrially. An object of the present invention is to provide a non-oriented electrical steel sheet that has low iron loss, high magnetic flux density, and low cost. [Means for Solving the Problems] The present inventors paid particular attention to the effectiveness of Zr, and conducted comprehensive experiments and research from the composition aspect. The present invention has been completed by discovering an effective component composition for simultaneously achieving good properties. That is, the gist of the present invention is the following non-oriented electrical steel sheet. In weight%, C less than 0.004%, Si less than 3.5%, Mn 1.0
% or less, P0.15% or less, Al0.01~0.10%, Zr0.01~
0.10%, further containing 0.0001 to 0.0015% B as necessary, the balance consisting of Fe and unavoidable impurities,
S, N, and O as unavoidable impurities are S≦0.01
%, N≦0.005%, O≦0.005%, and Zr
A non-oriented electrical steel sheet with good magnetic properties, characterized in that the value of (%)/6.5×N (%) is 1 to 3. [Function] The gist of the present invention is to control the Al content to below a predetermined level and then add an appropriate amount of Zr or B to enable the precipitation of fine AlN that inhibits grain growth. Furthermore, by limiting S, N, and O as impurities to below a certain level, the total amount of precipitates can be reduced, thereby reducing iron loss and high magnetic flux density. This makes it possible to achieve both at the same level. The reasons for limiting the steel components in the present invention will be described in detail below. C: Affects magnetic properties, especially iron loss, and from the viewpoint of lower iron loss, the smaller the amount, the better. In particular, if it exceeds 0.004, the increase in iron loss due to magnetic aging becomes large, so it was set to less than 0.004%. Note that the lower limit is not particularly limited because as mentioned above, the smaller the number of C, the better. Si: The most important element in electrical steel sheets and has a dominant effect on magnetic properties. As the amount of Si increases, the iron loss decreases, but the magnetic flux density also tends to decrease. The amount of Si added is actually selected in consideration of this tendency and according to the magnetic properties required for the application. Up to 3.5% Si, the higher the amount, the better the iron loss can be obtained, but 3.5%
If it exceeds this, the effect will be saturated and the deterioration of cold workability will become noticeable. Therefore, it was set at 3.5% or less. Note that the lower limit value of Si is not particularly specified because the appropriate amount changes depending on the required level of magnetic properties and cannot be determined unconditionally. Mn: Necessary for preventing embrittlement cracking caused by S during hot rolling and for improving mechanical properties such as hardness. However, if it exceeds 1.0%,
Degrades magnetic properties. Therefore, Mn was set to 1.0% or less. Regarding the lower limit of Mn, it is generally required to be 0.05% or more from the viewpoint of preventing hot embrittlement, but in the present invention, since Zr also has an S fixing effect, it may be lower than that and is not particularly limited. P: An effective element for increasing the hardness of steel sheets and improving workability during core punching, but if it exceeds 0.15%, workability deteriorates. Therefore, it was limited to 0.15% or less. Note that the lower limit is not stipulated because even the amount of unavoidable impurities does not cause any particular problem. Al: Added as a deoxidizing agent. Al has a very strong affinity with N. For this reason, the level normally used for non-oriented electrical steel sheets (about 0.1 to 0.5%)
When AlN is contained, it combines with N in the steel and precipitates a large amount of fine AlN, which hinders grain growth. As a result, iron loss in particular increases. In order to eliminate this tendency and achieve good magnetic properties, it is necessary to reduce Al as much as possible. However, if the Al amount is too low,
Due to insufficient fixation of O in the steel, O of added Zr
As a result, N is not sufficiently fixed by Zr, resulting in deterioration of magnetic properties. FIG. 1 shows the results of an experimental investigation into the relationship between Al content and magnetic properties. This is 0.003%
C-5.0%Si-0.5%Mn-0.02%P-0.03%Zr-
It is a 0.003% S-0.002% N-0.002% O system, and the influence on magnetic properties was shown by changing the Al content within a range of 0.02% or less.The test material was manufactured using the manufacturing process shown in the example below. This is a cold-rolled annealed sheet with a thickness of 0.5 mm. The characteristics shown in the figure are both iron loss and magnetic flux density measured using a single-plate magnetometer. According to the figure, both iron loss and magnetic flux density have excellent values when the Al content is in the range of 0.01 to 0.10%. Al content is less than 0.01% or 0.10%
It is observed that there is a tendency for both iron loss and magnetic flux density to deteriorate rapidly above . For this reason, in the present invention, Al0.01~
Limited to 0.10%. Zr: A strong nitride-forming element that effectively contributes to improving magnetic properties through improving grain growth by fixing N in steel and preventing the precipitation of fine AlN. If it is less than 0.01%, the effect of N fixation will not be sufficient and the magnetic properties will not be effectively improved. On the other hand, when it exceeds 0.10%, precipitates increase and the magnetic flux density deteriorates. Therefore, Zr is 0.01 ~
Limited to 0.10%. Regarding the amount of Zr, it is also important to consider the balance with the amount of N in the steel, and in order to obtain good magnetic properties, Zr must be added so as to satisfy a certain relationship with the amount of N. Zr for N
The appropriate amount of addition can be defined by the ratio of Zr (%)/6.5×N (%) (hereinafter referred to as X value), and is expressed as a range in which the value of this ratio is 1 to 3. FIG. 2 shows the relationship between the X value and magnetic properties. This data is 0.003%C-1.5%Si-0.25%Mn-
In the 0.04%P-0.05%Al-0.003%S-0.002%O system, the Zr amount is 0.01 to 0.10 for the N amount of 0.005% or less.
This is the result of investigating the magnetic properties by changing the magnetic properties in the range of
It is a cold rolled annealed plate with a thickness of 0.5mm. The value of magnetic properties is
This is a measurement value using a single-plate magnetometer. According to the figure, in the region where the X value is less than 1 or more than 3, there is a tendency for both iron loss and magnetic flux density to deteriorate, and only in the region where the X value is 1 to 3, the iron loss and magnetic flux density are excellent. It is understood that For this reason, in the present invention, an X value is introduced and its range is defined as 1 to 3. B: Like Zr, this element contributes to improving iron loss and magnetic flux density by fixing N, and is added as necessary.
If it is less than 0.0001%, the effect of N fixation will not be exhibited.
No improvement in magnetic properties can be expected. On the other hand, 0.0015%
If it exceeds this, the amount of precipitates will increase and the magnetic properties will deteriorate. Therefore, B was set at 0.0001 to 0.0015%. N: Generally, it is an element that combines with Al to produce fine AlN and deteriorates magnetic properties, and the smaller the amount, the better. In the case of the present invention, Zr or even B is combined to precipitate as ZrN or BN, but if the amount is large, the magnetic properties will be impaired. For this reason, it was limited to 0.05% or less. S: generally produces sulfide-based inclusions and deteriorates magnetic properties, so the smaller the amount, the better. Especially in the case of the present invention, when the amount of S is large, the added Zr
Zr, which is consumed as ZrS and is effective for fixing N, decreases. For this reason, it was limited to 0.01% or less. O: generally generates oxide inclusions and deteriorates magnetic properties, so the smaller the content, the better.
In the present invention, especially if the amount of O is large, Zr will be consumed, so it is limited to 0.005% or less. The reasons for limiting the components of the electromagnetic steel sheet of the present invention are as described above, and such electromagnetic steel sheets are usually produced industrially by a single cold rolling method. In other words, in a typical manufacturing method, molten steel whose composition has been adjusted in a converter is continuously cast into steel slabs with a thickness of about 200 mm. Regarding the adjustment of C, a vacuum refining method is often used, but carbon may be removed in a subsequent process such as an annealing process. There is also a method in which the steel is cast into a large steel ingot and then bloomed, but it is rarely used these days from the viewpoint of economy and increased segregation. The cast steel billet is then hot rolled into a coil with a thickness of about 2 to 3 mm. The heating temperature is approximately 1,100 to 1,300°C, and after sufficient soaking, the material is rolled in a tandem rolling mill. Finishing temperature of rolling is 800~900
℃, and the coil winding temperature is normally 500 to 700℃. After being wound into a coil, it is left to cool to room temperature. Next, the oxide scale on the steel surface is removed by pickling. If necessary, the hot rolled sheet may be annealed before or after pickling. This is aimed at recrystallizing the crystal structure of the hot rolled sheet, and is effective in improving cold rolling properties and magnetic properties. After pickling, the plate is cold rolled to a predetermined thickness of 0.35 to 0.5 mm.
Final annealing is usually carried out at a temperature in the range of 600-1100°C. It is necessary to sufficiently recrystallize and further adjust the crystal grain size, and the annealing temperature also differs depending on the component system. The annealing method is sometimes carried out by batch-type box annealing, but in recent years, continuous annealing is often used. At this stage, the electrical steel sheet is shipped to the customer. Full-processed materials are assembled into cores directly after punching. Semi-processed materials are subjected to strain relief annealing after punching and before or after being assembled into an iron core. The steel of the present invention may be applied to either. In the examples, a fully processed material will be explained, but in a semi-processed material, the magnetic properties are further improved by releasing punching strain and growing crystal grains. [Example] Next, an example of the present invention will be described. The three Si amounts shown in Table 1 are 0.5%, 1.5%, and 2.5%.
Steels of various compositions with different levels are melted using a 50Kg high-frequency vacuum melting furnace, cast into molds to make slabs, hot forged to a thickness of 30mm, and then heated to 1250℃. Reheat to a finishing temperature of 850℃
Hot rolling was performed to a thickness of 2.3 mm, and immediately after rolling, the material was cooled to 550°C with water spray, and then charged into a furnace at 550°C and cooled. The hot-rolled sheet obtained in this way was finished to a thickness of 0.5 mm by cold rolling after pickling, and then in a nitrogen atmosphere.
0.5%Si type: 700℃×1min, 1.5%Si type: 800℃×
1 min, 2.5% Si system: Final annealing was performed using a continuous annealing pattern of 900°C x 1 min. The magnetic properties (core loss value, magnetic flux density) of the obtained final annealed material were measured using a single plate magnetometer. The results are shown in the right column of Table 1.

【table】

〔Effect of the invention〕

As is clear from the above explanation, the present invention can simultaneously and effectively achieve reduction in iron loss and improvement in magnetic flux density in non-oriented electrical steel sheets, and there is no need to take any special measures in terms of manufacturing. So,
There is no increase in man-hours, and it is advantageous in terms of cost.
Its practical value is extremely large.

[Brief explanation of the drawing]

FIG. 1 shows the experimental results showing the relationship between Al content and magnetic properties, and FIG. 2 shows the experimental results showing the relationship between the X value (Zr (%)/6.5×N (%)) and magnetic properties.

Claims (1)

[Claims] 1% by weight, C less than 0.004%, Si 3.5% or less,
Mn 1.0% or less, P 0.15% or less, Al 0.01~0.10%,
Contains 0.01 to 0.10% Zr, the balance consists of Fe and unavoidable impurities, S, N as unavoidable impurities,
O is S≦0.01%, N≦0.005%, O≦0.005%, and the value of Zr (%) / 6.5 × N (%) is 1 to 3.
A non-oriented electrical steel sheet with good magnetic properties. 2 Weight%: C less than 0.004%, Si less than 3.5%,
Mn 1.0% or less, P 0.15% or less, Al 0.01~0.10%,
Contains Zr0.01~0.10%, further contains B0.0001~0.0015%, and the balance consists of Fe and unavoidable impurities, S, N, O as unavoidable impurities are S≦0.01
%, N≦0.005%, O≦0.005%, and Zr
A non-oriented electrical steel sheet with good magnetic properties, characterized in that the value of (%)/6.5×N (%) is 1 to 3.