JPH0564701B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a grain-oriented electrical steel sheet whose main orientation is {110}<001> and a method for manufacturing the same. [Prior art] Grain-oriented electrical steel sheet is an electromagnetic material mainly used for the iron core of transformers and generators, and is generally made of around 3% (weight %, the same applies hereinafter), which has excellent excitation characteristics and iron loss characteristics in the rolling direction. A material containing Si is used. In manufacturing such grain-oriented electrical steel sheets,
After hot rolling, special heat treatment steps are required, such as hot-rolled plate annealing, continuous decarburization annealing after cold rolling, and final annealing at a high temperature of 1000°C or higher. For this reason,
General grain-oriented electrical steel sheets are expensive. In order to solve this cost problem, various research and development efforts have been carried out in the past, including the
As shown in No. 207114, a method was proposed in which ultra-low carbon steel was used as the material and decarburization annealing was omitted during the process. Basically, a predetermined amount of Al and N are added to the raw material steel, and then the material is heated before finishing annealing.
By precipitating AlN and using this as an inhibitor to prevent grain coarsening before secondary recrystallization, secondary recrystallization occurs in the final annealing process. [Problems to be Solved by the Invention] However, since this method uses ultra-low carbon steel, if the amount of Si is 1.5% or more, α-γ transformation disappears and ridging tends to occur. For this reason, annealing of the hot rolled sheet is essential. In addition, the final finish annealing requires high-temperature annealing of 1000°C or higher, as in the general case. In other words, although decarburization annealing can be omitted, other heat treatments have no economic merit and cannot be effective measures for cost reduction. In addition, this method was unable to sufficiently produce the inhibitory effect of AlN and was unable to achieve stable secondary recrystallization, and in this respect, it was difficult to say that it was practically sufficient. . On the other hand, the present inventors have recently developed and proposed a method effective for cost reduction that is an extension of the above method (Japanese Patent Application Laid-open Nos. 61-91329 and 62-83421).
issue). These make it possible to generate secondary recrystallization during low-temperature annealing in the α region by minimizing the amount of Al in ultra-low carbon steel and optimizing the precipitation form of AlN as an inhibitor. That is what it is. Therefore, in addition to omitting the decarburization annealing described above, this method has the advantage that the temperature of the final annealing can be lowered, and can greatly contribute to cost reduction. However, Si1.5%
In the above method, it is no different from the previous method that hot rolled sheet annealing is essential to prevent ridging. Furthermore, when the Si content exceeds 0.5%, secondary recrystallization tends to be unstable, and it cannot be denied that this is a step forward in practical terms. Therefore, the present invention further develops the technology of this method, and in addition to omitting the decarburization annealing and lowering the finish annealing temperature, it also makes it possible to omit hot-rolled sheet annealing, thereby promoting cost reduction, and making it possible to reduce the cost by finishing the finish annealing. The purpose of this study is to improve the stability of secondary recrystallization and enable stable production of grain-oriented electrical steel sheets with excellent magnetic properties. [Means for Solving the Problems] The present inventors, by applying the technique disclosed in JP-A No. 62-83421, have succeeded in preventing the occurrence of ridging without using hot-rolled sheet annealing, and also stably and reliably As a result of conducting various experiments and research in order to find a means to achieve secondary recrystallization, the following findings were obtained. Generally, in ultra-low carbon steel (C≦0.01%), α-γ transformation disappears when the Si content becomes 1.5% or more.
However, when the amount of Mn in steel is increased to 1.0 to 2.0%, α-γ transformation occurs even in extremely low carbon high Si steel. Such an increase in Mn will prevent ridging from occurring during the cold rolling process. In addition, in the final annealing process, it contributes to improving the stability of secondary recrystallization, making it possible to ensure stability of secondary recrystallization even for steels containing Si of 0.5% or more, which is a problem. The present invention is based on the above knowledge, and its gist is the following grain-oriented electrical steel sheet and method for manufacturing the same. C0.01% or less, Si0.5~2.5%, Mn1.0~2.0%,
S0.010% or less, Sol.Al0.003~0.015%, N0.0010
A grain-oriented electrical steel sheet characterized by comprising ~0.0100%, the remainder consisting of Fe and unavoidable impurities. A hot-rolled steel sheet with the same composition as shown in
The final plate thickness is obtained by performing one cold rolling or two or more cold rollings with intermediate annealing in between, and then 600~
A method for producing a grain-oriented electrical steel sheet, which comprises performing continuous annealing at 950°C and then final annealing at 800 to 950°C. The present invention will be explained in detail below. Γ First, the reasons for limiting each component in the grain-oriented electrical steel sheet of the present invention will be described. C: When the amount of C in steel exceeds 0.01%, undesirable phenomena in terms of magnetic properties, such as worsening of iron loss and deterioration of magnetic aging, become noticeable. So C is 0.01%
The following was made. Note that since it is more advantageous to have less C in terms of magnetic properties, a lower limit is not particularly defined. Si: Si is an element that has a dominant effect on magnetic properties. Generally, as the amount of Si increases, iron loss tends to improve, while saturation magnetic flux density tends to deteriorate. One feature of the present invention is that a large amount of Mn is added to stabilize secondary recrystallization during final annealing, but if the Si content exceeds 2.5%,
The amount of Mn required to cause stable secondary recrystallization exceeds 2%, leading to deterioration of cold rollability. For this reason, the upper limit of Si was limited to 2.5%. Regarding the lower limit regulation of Si amount, Si0.5
If it is less than %, secondary recrystallization is automatically stabilized, so there is no need to take any measures, and this range is excluded from the scope of the present invention. The content of Si is actually determined within the above range of 0.5 to 2.5% so as to obtain the balance of magnetic properties (iron loss, magnetic flux density) required depending on the purpose of use. The performance as an electrical steel sheet is basically determined by the selection of this Si content. Incidentally, in conventional general grain-oriented electrical steel sheets, the amount of Si is fixed at around 3%, and there is no range in the balance of characteristics between iron loss and magnetic flux density, and the performance may exceed the intended use. There were inconveniences such as shortages. Mn: An element that characterizes the present invention. As mentioned above, in the present invention, Mn is used to prevent ridging from occurring during cold rolling and to ensure stability in secondary recrystallization. FIG. 1 shows the results of investigating the magnetic properties (magnetic flux density) by varying the amount of Mn. The sample material is C0.002~0.003%, Si0.90~1.10%, S0.003
%, Sol.Al0.006~0.008%, N0.0030~0.0040
% (within the range of the present invention), a 2.2 mm thick hot rolled sheet with such a composition was cold rolled to 0.35 mm, and then rolled at 750°C.
Continuous annealing for 20 seconds and final annealing at 880℃ for 10 hours (decomposed ammonia gas atmosphere for the initial 4 hours of heating and soaking, then switched to hydrogen)
This is the result of investigating the magnetic flux density in the rolling direction for the finished fired material obtained. While there is a large variation in magnetic flux density in the range where the Mn addition amount is less than 1.0%,
In the Mn 1.0 to 2.0% region, the magnetic flux density is stable at a high level. This is {110}<001>
This is because secondary recrystallization with the main orientation occurred stably. The reason for this stabilization of secondary recrystallization is still not fully understood, but Mn in steel acts as an inhibitor of primary recrystallization.
This is thought to be because it uniformizes the dispersion state of AlN and promotes stable formation of secondary recrystallization. In addition, in the figure, the magnetic flux density is low in the Mn2.0% region, but
This is because the α-γ transformation point was lowered at 880℃.
This is probably because the final annealing was performed in the γ region. Since the α-γ transformation point increases as the amount of Si increases, depending on the amount of Si, even if Mn is 2%, the above 880°C may be within the α range.
In this case, it is thought that a good magnetic flux density can be obtained. However, if the Mn content exceeds 2%, the Si content will be 2.5%.
%, the brittleness during cold rolling increases, which is unfavorable in terms of manufacturing. From the above, Mn is 1.0 to 2.0%
limited to. Regarding the influence of Mn on iron loss,
Mn has the effect of increasing the resistivity of steel sheets and reducing iron loss. However, the purpose of adding Mn in the present invention is to make the dispersion state of AlN, which is the inhibitor described above, uniform and to prevent ridging, which will be described later. Since secondary recrystallization occurs stably with an amount of Mn within the range of the present invention, iron loss is significantly reduced. In addition, the effect of preventing ridging can be improved by adding Mn even in the case of high Si steel with Si of 1.5% or more.
This is due to the occurrence of γ transformation,
In the case of the amount of Si within the range of the present invention, the above range of 1.0 to 2.0% is a range that effectively contributes to prevention of ridging. S: In the present invention, AlN is used as an inhibitor that suppresses grain growth of primary recrystallized grains until secondary recrystallization occurs. MnS is usually used as an inhibitor, but since MnS is not used, there is no need to add a large amount of S. In addition, in normal grain-oriented electrical steel sheets, in the latter half of finish annealing after secondary recrystallization is completed,
Inhibitor (MnS) that is no longer needed,
Removal is performed by purification annealing at a high temperature of 1100-1200°C. However, one aim of the present invention is to perform finish annealing at a low temperature in order to reduce costs, and the above-mentioned purifying annealing is not suitable for this purpose. If the purification treatment is not performed, MnS will remain, and if there is a large amount of MnS, good magnetic properties cannot be expected. For this reason, it is necessary to reduce S to a sufficiently low level at the steel manufacturing stage, and therefore it is set to a range of 0.010% or less. Sol.Al: An element necessary to form AlN that suppresses the grain growth of primary crystal grains, and the regulation of its addition amount has an extremely important meaning in the present invention. The reason why the Al content was set as 0.003 to 0.015% in terms of Sol.Al is that if it is less than the lower limit, the absolute amount of AlN as an inhibitor will be insufficient and a sufficient effect cannot be expected, whereas if it exceeds the upper limit This is because as the amount of the inhibitor becomes too large, the shape of the distribution becomes inappropriate, making it impossible to obtain stable secondary recrystallization in low-temperature finish annealing. N: An element essential for the formation of AlN as an inhibitor, and from that point of view, at least
0.0010% or more is required. However, 0.0100
Even if the content exceeds %, there is no meaning in terms of the inhibitor effect. Therefore, N is 0.0010~
It was set at 0.0100%. ΓNext, the manufacturing method of the present invention will be described. The method of the present invention basically uses a hot-rolled sheet having the above-mentioned composition, and after cold rolling, it undergoes primary recrystallization annealing (annealing after cold rolling) and secondary recrystallization annealing (finishing annealing). Apply the process. Each step will be explained as follows. Hot-rolled sheet manufacturing First, materials that match the product composition described above are used. Conventional grain-oriented electrical steel sheets have a carbon content of approximately 0.03 to 0.06% at the raw material (hot rolled sheet) stage.
This is usually reduced by decarburization annealing in the process after cold rolling, resulting in product C.
It is said to be the amount. This is based on the idea that the inclusion of C up to the middle of the process is useful for improving the magnetism of the final product, but the present invention provides excellent magnetic properties even without such C inclusion, and it is possible to improve the magnetic properties of the material steel. It is not necessary to include C in the. Rather, in order to reduce costs and omit the economically disadvantageous decarburization annealing, it is necessary to decarburize the steel at the steelmaking stage and keep the C content to an extremely low level of 0.01% or less. The hot rolled sheet manufacturing process is not particularly limited. Although it is a conventional method to go through the process of converter melting, continuous casting, and hot rolling, the same process can be used in the case of the present invention. Cold rolling Cold rolling is performed once or twice or more. 2
When round rolling is performed, an intermediate annealing process for softening is inserted between cold rolling. The conditions for intermediate annealing are generally 700 to 950°C. Annealing after cold rolling In order to generate stable secondary recrystallization, proper conditions (distribution and morphology) of AlN, which acts as an inhibitor, and primary recrystallization texture are required. This is achieved by annealing after cold rolling. Annealing after cold rolling requires rapid heating, and continuous annealing is suitable for this. The annealing conditions include a heating rate of 5°C/S.
It is desirable that the above is achieved. The annealing temperature is
Below 650℃, the annealing effect cannot be obtained, and
When the temperature exceeds 950°C, problems occur in terms of AlN distribution and primary recrystallization grain size. Yotsute 650
The temperature range was limited to ~950℃. Final annealing In the present invention, stable secondary recrystallization is caused by low-temperature final annealing by optimizing the ingredients, and high-temperature purifying annealing that decomposes MnS and removes S is not performed in final annealing. . This leads to cost reduction. If the final annealing temperature is lower than 800°C, sufficient secondary recrystallization will not occur and good magnetic properties cannot be expected. Furthermore, annealing at temperatures exceeding 950°C is not only unnecessary, but also increases costs. In addition, in high Mn steel such as the steel of the present invention, α
Some things are out of scope and have no meaning. For this reason, the annealing temperature was set at 800 to 950°C. [Example] Hot-rolled sheets of various component systems shown in Table 1 were subjected to cold rolling under the conditions shown in the table → continuous annealing → finish annealing (during the initial 4 hours of heating and soaking, decomposed ammonia gas atmosphere,
Then, the iron loss and magnetic flux density in the rolling direction were measured. The measurement was performed by taking 16 to 28 Epstein specimens with a width of 30 mm and a length of 280 mm from the rolling direction according to JIS C2550, and strain relief annealing at 750°C for 2 hours. The results are shown in the right column of the same table. In addition, the table also shows the occurrence of ridging during the manufacturing process.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, in the production of grain-oriented electrical steel sheets with 0.5 to 2.5% Si, hot rolled sheet annealing to prevent ridging and decarburization annealing in the middle of the process are omitted, and By adopting low-temperature annealing for final annealing, it is possible to realize a large cost reduction, and moreover, it is possible to stably obtain a high-performance grain-oriented electrical steel sheet with excellent magnetic properties and no occurrence of ridging. Therefore, the present invention can be said to be an industrially extremely useful invention.

[Brief explanation of the drawing]

FIG. 1 is a plot diagram showing the results of investigating the influence of Mn on magnetic flux density.

Claims (1)

[Claims] 1% by weight, C0.01% or less, Si0.5-2.5%,
Mn1.0~2.0%, S0.010% or less, Sol.Al0.003~
A grain-oriented electrical steel sheet characterized by comprising 0.015% of N, 0.0010 to 0.0100% of N, and the balance consisting of Fe and inevitable impurities. 2 Weight%: C0.01% or less, Si0.5-2.5%,
Mn1.0~2.0%, S0.010% or less, Sol.Al0.003~
A hot-rolled steel plate consisting of 0.015% N, 0.0010 to 0.0100%, the balance being Fe and unavoidable impurities, is subjected to one cold rolling or two or more cold rollings with intermediate annealing to obtain the final plate thickness, A method for producing a grain-oriented electrical steel sheet, which comprises then performing continuous annealing at 650 to 950°C, and then performing final annealing at 800 to 950°C.