JP-7856920-B2 - Non-oriented electrical steel sheet and method for manufacturing the same

Inventors

• 屋鋪 裕義
• 名取 義顕
• 竹田 和年
• 田中 一郎
• 堀 弘樹

Assignees

• 日本製鉄株式会社

Dates

Publication Date

20260512

Application Date

20230315

Priority Date

20220315

Claims (3)

1. The chemical composition of the base material is, in mass percent, C: 0.0050% or less, Si: more than 3.70% and less than 4.60%, Mn: more than 0.20% and less than 0.50%, Al: 0.23-0.75%, P: 0.030% or less, S: 0.0018% or less, N: 0.0040% or less, Ti: Less than 0.0050%, Nb: Less than 0.0050% Zr: Less than 0.0050%, V: Less than 0.0050%, Cu: Less than 0.200% Ni: Less than 0.500%, Sn: 0.005-0.040%, Sb: 0 to 0.040%, The remainder consists of Fe and impurities. The following equation (i) is satisfied, The N content [N]s from the surface of the base material to a depth of 20 μm is 0.0060% or less. The average grain size of the base material is 50 to 120 μm. The saturation magnetic flux density is 1.945 T or higher. The tensile strength is 600 MPa or more. The plate thickness is 0.10 to 0.30 mm. Non-oriented electrical steel sheet. 4.2≦Si+Al+0.5×Mn≦4.9...(i) However, the element symbols in the above formula represent the content (mass %) of each element.
2. The surface of the base material has an insulating coating, The non-oriented electrical steel sheet according to claim 1.
3. A method for manufacturing a non-oriented electrical steel sheet according to claim 1 or claim 2, In mass percent, C: 0.0050% or less, Si: more than 3.70% and less than 4.60%, Mn: more than 0.20% and less than 0.50%, Al: 0.23-0.75%, P: 0.030% or less, S: 0.0018% or less, N: 0.0040% or less, Ti: Less than 0.0050%, Nb: Less than 0.0050% Zr: Less than 0.0050%, V: Less than 0.0050%, Cu: Less than 0.200% Ni: Less than 0.500%, Sn: 0.005-0.040%, Sb: 0 to 0.040%, The remainder consists of Fe and impurities. For a steel ingot having a chemical composition satisfying the following equation (i), The process involves, in order, a hot rolling process, a pickling process, a batch-type hot-rolled sheet annealing process at a soaking temperature of 650 to 780°C for 8 to 36 hours, a cold rolling process to reduce the sheet thickness to 0.10 to 0.30 mm, and a finish annealing process at a soaking temperature of 880 to 1020°C for 1 second to 10 minutes. A method for manufacturing non-oriented electrical steel sheets. 4.2≦Si+Al+0.5×Mn≦4.9...(i) However, the element symbols in the above formula represent the content (mass %) of each element.

Description

This invention relates to non-oriented electrical steel sheets and a method for manufacturing the same. In recent years, global environmental issues have attracted increasing attention, and the demand for energy conservation efforts has grown significantly. In particular, there is a strong demand for increased efficiency in electrical equipment. Therefore, the need for improved magnetic properties in non-oriented electrical steel sheets, which are widely used as core materials for motors and generators, is becoming even stronger. This trend is particularly pronounced in drive motors for electric and hybrid vehicles, as well as in motors for air conditioner compressors. The motor cores of the various motors described above consist of a stator, which is the stationary part, and a rotor, which is the rotor. The characteristics required of the stator and rotor that make up the motor core are different from each other. The stator requires excellent magnetic properties (low iron loss and high magnetic flux density), especially low iron loss and high saturation magnetic flux density, while the rotor requires excellent mechanical properties (high strength). Because the required characteristics differ between the stator and the rotor, the desired characteristics can be achieved by manufacturing separate non-oriented electrical steel sheets for the stator and the rotor. However, preparing two types of non-oriented electrical steel sheets leads to a decrease in yield. Therefore, in order to achieve the high strength required for the rotor while achieving the low iron loss and high saturation magnetic flux density required for the stator, non-oriented electrical steel sheets that are superior in both strength and magnetic properties have been considered for a long time. For example, Patent Documents 1 to 4 describe attempts to achieve excellent magnetic properties and high strength. International Publication No. 2019/017426International Publication No. 2020/091039International Publication No. 2020/091043Japanese Patent Publication No. 2010-90474 As a result of diligent research conducted by the inventors to solve the above problems, we have obtained the following findings. To achieve high strength, low iron loss, and high saturation magnetic flux density while ensuring toughness during cold rolling, it is necessary to optimize the content of the main alloying elements: Si, Mn, and Al. Specifically, the mixture contains Si in a concentration of over 3.70% to 4.60%, as Si has the highest solid solution strengthening ability and contributes most to the increase in electrical resistance. In addition, to obtain good grain growth properties, it contains 0.23% or more Al. On the other hand, to suppress the deterioration of the saturation magnetic flux density, the Al content is kept to 0.75% or less. Furthermore, although Mn has the lowest solid solution strengthening ability among the three elements, it contains more than 0.20% Mn, which contributes to the increase in electrical resistance with minimal toughness deterioration. Through repeated investigations, the inventors found that nitriding of the surface layer of the steel sheet degrades iron loss. Although the mechanism is not yet clear, they discovered that Mn influences the nitriding of the surface layer of the steel sheet. To suppress the degradation of iron loss due to nitriding of the surface layer of the steel sheet, the Mn content is set to 0.50% or less. Furthermore, it was found that Sn also has the effect of suppressing nitriding of the surface layer of the steel sheet. Therefore, Sn is included at a concentration of 0.005 to 0.040%. In typical continuous hot-rolled sheet annealing, scale-covered hot-rolled sheets are inserted into the annealing furnace, resulting in the formation of scale that is difficult to remove during pickling after annealing. Therefore, mechanical descaling, such as shot blasting, is necessary before pickling. However, with high-alloy steels as mentioned above, shot blasting causes twinning deformation on the sheet surface, and this twinning deformation can easily lead to problems such as sheet fracture and edge cracking during cold rolling. In this invention, the hot-rolled sheet is pickled before annealing, and then annealed in a batch furnace. Since the scale on the hot-rolled sheet can be easily removed by pickling, shot blasting is unnecessary, and twinning deformation does not occur. Therefore, good toughness can be ensured even with high-alloy steel, and problems such as sheet fracture and edge cracking during cold rolling can be suppressed. This invention is based on the above findings. The requirements of this invention will be described in detail below. 1. Overall Configuration The non-oriented electrical steel sheet according to one embodiment of the present invention has high strength and excellent magnetic properties, making it suitable for both stators and rotors. Furthermore, the non-oriented electrical steel sheet accord