JP5592874B2 - Non-oriented electrical steel sheet - Google Patents

Description

The present invention relates to a non-oriented electrical steel sheet widely used as a core material of the rotating device, in particular, it relates to and the magnetic flux density low core loss is high non-oriented electrical steel sheet.

Non-oriented electrical steel sheet is an important part necessary for the conversion of electrical energy into mechanical energy in rotating machinery. For energy saving, it has its magnetic properties, ie low iron loss and high magnetic flux density. This is very important. Here, iron loss is energy that disappears in the process of energy conversion and disappears, so the lower it is, the more efficient it is. The magnetic flux density is the force that generates power. is there.

In recent years, as part of measures to efficiently use energy and reduce CO _2, technology has been rapidly developed to convert the driving of automobiles from gasoline or diesel engine systems to some (hybrid) or all electric. ing.

The motor used in this technology is required to have the following two characteristics. One is excellent acceleration performance at the time of departure, and the other is high fuel efficiency while driving (low power consumption). If the characteristics required of the motor are replaced with the magnetic characteristics of the non-oriented electrical steel sheet, the former has a high saturation magnetic flux density (Bs), and the latter has a high-frequency iron loss (W10 / 400, W5 / 1000). ) Is less. If this is replaced with manufacturing conditions, the former is better when the amount of alloying elements such as Si is reduced to lower the specific resistance, while the latter is increased by increasing the amount of alloying elements such as Si to increase the specific resistance. The more you do it, the more you will get better.

Currently, high-grade non-oriented electrical steel sheets that are used as drive motors for electric vehicles are 35A300 to 35A230 (JIS standard). However, since these products contain a large amount of addition of alloy elements such as Si, Interworkability is poor and productivity is poor. In addition, thinning is required to improve high-frequency iron loss corresponding to heat loss during high-speed rotation, but the products currently in use are poor in workability and cannot be thinned easily. Productivity is inferior. In order to improve such problems, that is, iron loss and productivity reduction in the high frequency region, the content of the component Al having a specific resistance equivalent to that of Si is increased, the content of Si is reduced, or compared with Si. Thus, a method has been proposed in which {100} texture is strengthened by adding Mn having about half the specific resistance. Such conventional techniques are dealt with in Japanese Patent Application Laid-Open Nos. 2002-146490, 2001-59145, and 2003-293099, but due to complex problems such as crystal grain growth, hardness, and magnetism. It has not yet reached mass production. Therefore, there is a need for a design for optimum compositional components for producing a non-oriented electrical steel sheet having good crystal grain growth, low hardness, and excellent magnetism.

DISCLOSURE OF THE INVENTION Technical Problem The present invention is to solve the above-mentioned problems of the prior art, and its purpose is to optimize the additive components of Al, Si, Mn, and P to improve the grain growth property. Thus, an object is to provide a non-oriented electrical steel sheet having low hardness and excellent magnetism.

Technical Solution In order to solve the above technical problem, the present invention has a chemical composition in weight%, Al: 1.3 to 2.5%, Si: 0.8 to 2.0%, Mn: 0.6 % or more and less than 1.0 %, P: 0.05 to 0.2%, C: 0.004% or less, S: 0.004% or less, N: 0.002% or less, the balance being Fe and It consists of other inevitable impurities, and Al + Si + Mn + P = 3.9 to 4.45%, Al + Si = 2.5 to 3.8%, Al / Si = 0.65 to 3.1, Mn / P = 4 to 16 Non-oriented electrical steel sheet characterized by satisfying the equation, maintaining a specific resistance of 50 to 60 μΩ · cm, having a Vickers hardness (Hv) of a cross section of 185 or less and a crystal grain size of 70 to 130 μm I will provide a.

Advantages of the Invention By optimizing the additive components of Al, Si, Mn, and P, the present invention exhibits low hardness, excellent magnetic properties in a high frequency range, and easy production processability. The production cost is low and the effect of improving productivity can be expected.

The figure which shows the optimal range of the addition amount of Mn and P of this invention. The figure which shows the optimal range of the addition amount of Al of this invention, and Si.

  In order to solve the above-described problems, the present invention provides not only Al, Si, and Mn as alloy elements to be added to steel, but also the addition amount of P and the ratio of Al / Si and Mn / P are different. By confirming the hardness value, crystal orientation, and grain growth of each composition component system, we tried to find a range that showed excellent magnetic properties and markedly improved steel plate productivity.

  Next, the reason for selecting each additive element and the reason for limiting the addition ratio will be described.

In order to maintain the saturation magnetic flux density (Bs) equivalent to the currently used Fe-Si non-oriented electrical steel sheets 35A300 to 35A230 (JIS standard), the same specific resistance (ρ) is 50 to 60μΩ · cm. The following empirical formula was used for the relationship between the component system (%) and the specific resistance (ρ) on the assumption that the range.
ρ = 13.25 + 11.3 (Al + Si + P + Mn / 2)

In the present invention, the specific resistance value of high-grade steel is higher than that of normal steel, specifically, it is necessary to set the value to 50 μΩ · cm or more. In order to use it in high-grade steel, the specific resistance value must be high. However, if the specific resistance is low, the loss of eddy current increases, making it difficult to use it in high-grade non-oriented electrical steel sheets. It is. Specific composition components for giving such a specific resistance include Si, P and the like, and these elements have the effect of increasing the specific resistance and reducing the loss of eddy current. When the Si content is high to some extent, the magnetic flux density is lowered and the workability is deteriorated.

  Therefore, in order to reduce the loss of eddy current and obtain good workability, the specific resistance range must be adjusted within the range of 50 to 60 μΩ · cm.

The present invention tried to confirm these effects by selecting four components of Al, Si, Mn, and P as alloy elements. As shown in Table 1, the current Fe-Si system is represented by S0, the Fe-Al system is represented by S1, the Fe-Al-Si system is represented by S2, and the Fe-Al-Si-Mn-P system is represented by S3. Furthermore, the specific resistance was fixed to 56 μΩ · cm, and comparison was made for four components. In the manufacturing process of the non-oriented electrical steel sheet, first, hot-rolled sheet annealing was performed, then one-stage cold rolling was performed, and finally final annealing was performed at 1050 ° C. for 38 seconds. The results thus obtained are shown in Table 1.

  In the case of S0, the hardness (Hv) was as high as 200 and the brittleness was strong, so the productivity was poor. In the case of S1 and S2, crystal grain growth was inferior to that of S0, and as a result, it was inferior in terms of iron loss. On the other hand, in the case of S3 in which Mn and P were increased, the crystal grain growth was good, and the values of crystal orientation and iron loss were close to S0. Therefore, it can be seen that an optimal combination of Mn and P for improving the crystal grain growth is necessary.

  Next, the reason for selecting the optimum range of Mn and P will be described.

In order to investigate the optimum range of Mn and P, Al and Si of S3 were fixed to 2.5% and 0.8%, respectively, and the addition amount of Mn and P was changed. , S3-2, S3-3, represented by S3- 4, and the results are shown in Table 2.

  The remaining examples of the present invention excluding Comparative Example S3-1 had low iron loss and good crystal grain growth. Therefore, the optimum ranges of Mn and P are Mn: 0.6 to 1.2% and P: 0.05 to 0.2%, and the ratio of Mn / P is Mn / P = 4 to 16, In FIG. 1, the inside of the thick line corresponds to this. That is, the crystal grain growth property is the best within this range, but if this is exceeded, the hardness becomes too high and the brittleness increases.

  Next, the reason for selecting the optimum range of Al and Si will be described.

  In order to investigate the optimum values of Al and Si, the values of Mn and P indicating crystal grain growth were fixed to Mn = 0.8% and P = 0.08%, and Al was within the range of specific resistance 56 μΩ · cm. / Si was changed. Examples with Al / Si of 1.5, 1.0, and 0.65 are indicated by T1, T2, and T3, respectively. Table 3 also shows S0 as a comparative example.

  As can be seen from Table 3, the examples of the present invention have lower hardness and better magnetism than S0 as a comparative example. Therefore, it can be seen that the optimum Al / Si ratio is 0.65 to 3.1. Considering Mn and P, the composition ratio satisfying the specific resistance of 50 to 60 μΩ · cm is Al + Si = 2.5 to 3. 8%, Al = 1.3 to 2.5%, and Si = 0.8 to 2.0%. When such a condition is shown in FIG. 2, the optimum range is inside a thick line.

  Next, the reason for the optimum range combination of Al, Si, Mn, and P will be described.

  In the optimum combination of Al, Si, Mn, and P satisfying the specific resistance of 50 to 60 μΩ · cm, when Al + Si is 3.8%, the values of Mn and P for satisfying the specific resistance of 60 μΩ · cm are minimized. Therefore, the minimum content of each component is 0.6% and 0.05%, respectively. Conversely, when Al + Si is 2.5%, the values of Mn and P for satisfying the specific resistance of 50 μΩ · cm must be maximized, so the maximum content of each component is 1.2%, 0.2%. Therefore, the range of Al + Si + Mn + P is 3.9 to 4.45%.

  Next, the reason for limiting the impurity elements will be described.

Since C causes magnetic aging, it should be 0.004% or less, preferably 0.003% or less. S and N are combined with Mn and Al to form MnS and AlN, thereby hindering crystal grain growth. Therefore, it is good that it is 0.004% or less, preferably 0.002% or less. Ti promotes the growth of an undesirable crystal orientation [111] in the non-oriented electrical steel sheet, so it is 0.004% or less, preferably 0.002% or less.

  Next, the reasons for limiting the crystal grain size and magnetism will be described.

  As shown in Table 1, there is a strong correlation between iron loss and crystal grain size, but in order to manufacture high-grade steel with a specific resistance of 50-60 μΩ · cm, the iron loss must be good and the average The crystal grain size must be 100 μm or more. On the other hand, within the range of the composition component of the present invention, the average crystal grain size at a steel sheet thickness of 0.35 mm is 100 μm or more. In consideration of the correlation with the frequency, the crystal grain size at commercial frequencies of 50 and 60 Hz is preferably as large as 100 to 200 μm, and the crystal grain size in the high frequency region of 400 Hz or higher is preferably as small as 70 to 100 μm. Therefore, it is preferable to limit the crystal grain size within the range of the composition component of the present invention to the range of 70 to 130 μm when the thickness of the steel sheet is 0.30 to 0.15 mm.

  Hereinafter, the present invention will be described in more detail with reference to examples.

The Fe-Si system of S0 and Comparative Examples were carried out in Fe-Al-Si-Mn- P system S3, T1, T2, T3, T 4. The results are shown in Table 4.

  After manufacturing the steel ingot which satisfy | fills the composition component mentioned above, the steel ingot was heated at 1150 degreeC and hot rolled at 850 degreeC, and the hot rolled sheet with a steel plate thickness of 2.0 mm was manufactured. Next, the hot-rolled sheet is annealed at 950 ° C. for 4 minutes, pickled, then cold-rolled to a thickness of 0.35 to 0.15 mm, and then finally annealed at 1050 ° C. for 38 seconds. went. The results thus obtained are shown in Table 5.

Since the hardness shows a strong relationship with the Si content, the Fe—Al-based S0 as a comparative example had a very high hardness (Hv) of 204, but the Fe—Al—Si— according to the example of the present invention. Mn-P based S3, T1, T2, T3, T 4 has the hardness (Hv) is 183 or less and very low cold workability was also good.

  The magnetic flux density (B50) decreases as the steel plate thickness decreases. However, when comparing the magnetic flux density of S0 as a comparative example and the embodiment of the present invention, the magnetic flux density of the present invention is S0 even if the thickness is reduced. Although it does not decrease as much, this is because the present invention is less affected by the cold rolling reduction. Such a phenomenon leads to an advantage that the selection range of the thickness of the hot-rolled sheet can be widened.

  The high-frequency iron loss (W10 / 400, W5 / 1000) has a clear relationship with the steel plate thickness, and the high-frequency iron loss improves as the thickness decreases. In the case of W10 / 400, based on the iron loss at 0.35 mm, it is about 88% at 0.30 mm, 75% at 0.25 mm, about 65% at 0.20 mm, and about 60% at 0.15 mm. In the case of W5 / 1000, the iron loss at 0.15 mm is reduced to about 50% compared to the iron loss at 0.35 mm. Therefore, it can be seen that the most effective method for improving the high-frequency iron loss is to reduce the thickness of the steel sheet.

Claims (2)

In weight percent, Al: 1.3-2.5%, Si: 0.8-2.0%, Mn: 0.6 % or more and less than 1.0 %, P: 0.05-0.2%, C: 0.004% or less, S: 0.004% or less, N: 0.002% or less, the balance is made of Fe and other inevitable impurities, Al + Si + Mn + P = 3.9 to 4.45%, Al + Si = 2. It satisfies the composition formula of 5 to 3.8%, Al / Si = 0.65 to 3.1, Mn / P = 4 to 16, maintains the specific resistance at 50 to 60 μΩ · cm, and has a Vickers hardness of the cross section. A non-oriented electrical steel sheet having a thickness (Hv) of 185 or less and a crystal grain size of 70 to 130 μm.   The non-oriented electrical steel sheet has a magnetic flux density (B50) of 1.60 to 1.70 T, an iron loss of 11.0 to 25.0 W / Kg at W10 / 400, and 11.0 to W5 / 1000. The non-oriented electrical steel sheet according to claim 1, wherein the non-oriented electrical steel sheet is 27.0 W / Kg.