WO2007063581A1

WO2007063581A1 - Nonoriented electromagnetic steel sheet and process for producing the same

Info

Publication number: WO2007063581A1
Application number: PCT/JP2005/021960
Authority: WO
Inventors: Hiroshi Fujimura; Hiroyoshi Yashiki; Satoshi Okamura
Original assignee: Sumitomo Metal Industries, Ltd.
Priority date: 2005-11-30
Filing date: 2005-11-30
Publication date: 2007-06-07
Also published as: CN101321883B; CN101321883A

Abstract

A nonoriented electromagnetic steel sheet that exhibits high strength, being low in high-frequency iron loss; and a process for producing the same. There is provided a nonoriented electromagnetic steel sheet characterized by being composed of, by mass percentage, 0.02% or less C, 1 to 4% Si, 1% or less Mn, 0.2% or less P, 0.03% or less S, 0.1 to 3% Al, more than 1 to 4% Cu and 0.02 to 0.3% the sum of at least either Ti or Nb, optionally together with 0 to 0.3% V, 0 to 0.3% Zr, 0 to 2% Ni and 0 to 0.010% B, and the balance Fe and impurities.

Description

Specification

Non-oriented electrical steel sheet and manufacturing method thereof

Technical field

The present invention relates to a rotor (rotor) of a rotating machine such as an electric motor (motor) or a generator rotating at high speed.

) It relates to a non-oriented electrical steel sheet suitable as a material for an iron core. In particular, the present invention is capable of withstanding stress during rotation or stress fluctuation during acceleration / deceleration, and requires excellent strength and magnetic characteristics, such as an embedded magnet motor (IPM motor) and salient pole type surface magnet motor (saliency pole). Technology related to non-oriented electrical steel sheets suitable as a material for rotor cores of type SRM motors)

[0002] In order to reduce global warming gas, it is necessary to develop new products that consume less energy in the fields of automobiles and home appliances. For example, in the automotive field, there are two types of fuel vehicles: a gasoline engine and motor hybrid drive vehicle (HEV) or a motor drive electric vehicle. In the field of home appliances, there are high-efficiency air conditioners and refrigerators with low annual electricity consumption. These common technologies are motors, and it is important to improve motor efficiency. In the process of motor efficiency, the motor drive system has become more sophisticated and various rotational drive controls are possible. In other words, the number of motors that enable variable speed operation and high-speed operation above the commercial frequency has been increased by controlling the frequency of the drive power supply.

In order to realize such a high-speed rotating machine, it is necessary to develop a rotor that can withstand high-speed rotation. In general, the centrifugal force acting on the rotor is proportional to the radius of rotation and proportional to the square of the rotational speed. For this reason, when operating at high speed, the force acting on the rotor may exceed 500 MPa, for example. Therefore, a material with high yield strength is required for the rotor. In addition, during high-speed rotation of the rotor, repeated stresses such as external vibration and frequent acceleration / deceleration may occur, so the rotor material has not only high yield strength! High fatigue strength is also required. As the means to increase the fatigue strength, it is most effective to increase the tensile strength. It can be said that high yield strength and high tensile strength are necessary!

[0004] Normally, laminated non-oriented electrical steel sheets are used for the motor rotor, but there are cases where the required strength cannot be satisfied by the motor rotating at high speed as described above. In that case, high strength steel is used as the rotor material. However, since the motor rotor uses magnetic properties at the time of rotation, the material is required to have excellent mechanical properties as well as mechanical properties as described above. In other words, a monolithic steel rotor has a problem that the eddy current loss becomes very large and the efficiency of the motor decreases. In addition, in the case of an IPM motor, there is a problem that the magnet characteristics deteriorate due to heat generated by the loss in the rotor.

[0005] As described above, the rotor core material of the motor that rotates at high speed as described above must have high mechanical strength and magnetically have high frequency and low iron loss. Generally, in the field of cold rolled steel sheets, methods such as solid solution strengthening, precipitation strengthening, fine grain strengthening, and transformation strengthening are used as means for increasing the strength of steel sheets. In general, the magnetic properties are in conflict with each other, and it has been extremely difficult to satisfy them simultaneously.

[0006] In order to solve such problems, several proposals have recently been made on non-oriented electrical steel sheets having high tensile strength. For example, Patent Document 1 proposes a method of increasing the tensile strength by increasing the Si content to 3.5 to 7.0% and adding an element having a large solid solution hardening thereto. In Patent Document 2, ordinary non-oriented electrical steel sheet contains 2.0% or more and less than 4.0% Si, and at the same time, one or two of Nb and Zr, or 1 of Ti and V. By using seeds or two types of carbonitrides and controlling hot rolling conditions and finish annealing conditions, non-oriented electrical steel sheets with high yield strength that have both mechanical and magnetic properties are manufactured. A method has been proposed. Furthermore, Patent Document 3 proposes a method for increasing the tensile strength by including a metal phase made of Cu having a diameter of 1.0 m or less in the steel material.

[0007] Patent Document 1: JP-A-60-238421

Patent Document 2: JP-A-6-330255

Patent Document 3: Japanese Patent Application Laid-Open No. 2004-84053 Disclosure of the invention

Problems to be solved by the invention

[0008] However, the steel sheet obtained by the invention described in Patent Document 1 is very brittle. Therefore, there is a problem that the steel sheet is easily broken during cold rolling and the yield is very low.

The invention described in Patent Document 2 has a problem that because the finish annealing temperature is low, the crystal grain size of the steel sheet is very small and the iron loss is very large.

Further, in the invention described in Patent Document 3, there is room for further improving the strength because the finish annealing conditions are not optimized. Furthermore, since the hot rolled steel sheet is not annealed or annealed at a high temperature of 980 ° C, Cu is finely dispersed inside the hot rolled steel sheet, and the hot rolled steel sheet becomes very hard. Therefore, the subsequent cold rolling becomes difficult and there is a problem of poor productivity.

[0009] The present invention has been made in view of the above problems, and has as its main object to provide a low-strength non-oriented electrical steel sheet having high strength and high iron loss at high frequencies, and a method for producing the same.

Means for solving the problem

[0010] As a result of intensive research from the viewpoint of increasing the strength by precipitation strengthening by aging heat treatment and not being able to produce a steel sheet having excellent magnetic properties, the present inventors have obtained both magnetic properties and strength properties. Based on advantageous Si and A1-containing steel, Cu is used as precipitation strengthening element, and also carbide of Ti, Nb, V, Zr is used, and non-directional with both strength and magnetic properties. The present invention was completed by finding that a magnetic steel sheet could be obtained. In the present invention, “carbide” includes carbonitride.

[0011] That is, the present invention, in mass%, C: 0.02% or less, Si: 1% or more and 4% or less, Mn: 1% or less, P: 0.2% or less, S: 0.03% A1: 0.1% or more and 3% or less, Cu: more than 1% and 4% or less, and a total of at least one of Ti and Nb is 0.02% or more and 0.3% or less In addition, V: 0% to 0.3%, Zr: 0% to 0.3%, Ni: 0% to 2%,: 0% to 0.001% as optional elements And providing a non-oriented electrical steel sheet characterized in that the balance consists of Fe and impurities.

According to the present invention, by setting the steel composition of the non-oriented electrical steel sheet to the above-described configuration, the magnetic properties and strength properties can be improved. [0012] The non-oriented electrical steel sheet of the present invention contains at least one element of V and Zr in mass%, V: 0.01% or more and 0.3% or less, Zr: 0.01% or more It is preferably contained at 3% or less. This is because V and Zr generate carbides and are effective in increasing the strength.

[0013] The non-oriented electrical steel sheet of the present invention preferably contains Ni: 0.05% or more and 2% or less by mass. By containing Ni, the strength of the steel sheet can be further increased.

[0014] Further, the non-oriented electrical steel sheet of the present invention preferably contains B: 0.0003% or more and 0.0010% or less in mass%. This is because inclusion of B improves the toughness of the steel sheet and can suppress breakage during cold rolling.

[0015] Furthermore, the non-oriented electrical steel sheet of the present invention preferably has a yield strength of 500 MPa or more. By setting the yield strength within the above range, when the non-oriented electrical steel sheet of the present invention is applied to a rotating machine such as an electric motor or a generator using, for example, a rotor, deformation or breakage occurs during operation. This is because it can be used stably without any problems.

[0016] The present invention also provides a finish annealing step in which a cold-rolled steel plate having the above-described steel composition is subjected to a finish annealing at a finish annealing temperature of 900 ° C or higher and 1150 ° C or lower, and a steel plate after the finish annealing step. And a cooling process in which the average cooling rate is l ° CZs or higher in a temperature range of 900 ° C or lower and 600 ° C or higher. .

[0017] According to the present invention, by properly controlling the steel composition of the cold-rolled steel sheet, the finish annealing temperature in the finish annealing step, and the average cooling rate in the cooling step, the magnetic properties are good. A non-oriented electrical steel sheet can be manufactured. In addition, the strength characteristics can be improved by subjecting the non-oriented electrical steel sheet obtained by the finish annealing process to the cooling process to an aging heat treatment.

[0018] In the above invention, the hot-rolled steel sheet is held at 600 ° C or higher and 900 ° C or lower for 2 hours or longer on the hot-rolled steel plate that is the material of the cold-rolled steel plate before the finish annealing step. You may perform the hot rolled sheet annealing process which anneals, and the cold rolling process which cold-rolls the said hot-rolled steel plate in which the hot-rolled sheet annealing was performed. This is because by performing hot-rolled sheet annealing under predetermined conditions, the ductility of the steel sheet is improved, and breakage in the cold rolling process can be suppressed. [0019] Further, in the present invention, the steel sheet after the above-described finish annealing step and cooling step has an aging heat treatment temperature of 400 ° C to 700 ° C, and a heat treatment parameter P represented by the following formula (1) is 1 3000 or more. An aging heat treatment step may be performed in which an aging heat treatment is performed so as to be 18000 or less.

P = (T + 273) X (20 + log (t))… (1)

(Here, T is the aging heat treatment temperature (° C) and t is the aging heat treatment time (h).) Strength characteristics are effectively improved by appropriately controlling the aging heat treatment temperature and the heat treatment parameters. You can

[0020] Furthermore, the present invention provides a rotor core characterized by laminating the non-oriented electrical steel sheets described above. Since the rotor core of the present invention is formed by laminating the above-mentioned non-oriented electrical steel sheets, for example, when applied to an electric motor, it can improve the motor efficiency and can be used stably. . In addition, when applied to a generator, high-speed rotation is possible, leading to improved power generation efficiency.

The present invention also provides a rotating machine using the above rotor core. In the present invention, since the above-described rotor core is used, for example, as an electric motor, it is possible to improve motor efficiency and achieve long-term use stability. As a generator, the power generation efficiency can be improved.

The invention's effect

[0022] In the present invention, it is possible to obtain a non-oriented electrical steel sheet having high strength by aging heat treatment in addition to low iron loss at high frequencies. If a rotor core manufactured using such a non-oriented electrical steel sheet is incorporated into a motor rotor that rotates at high speed, the motor efficiency will not only increase, but it will not be deformed or destroyed during operation for a long period of time. It can be used stably. These energy saving effects can contribute to the creation of a future society with less impact on the global environment.

Brief Description of Drawings

[0023] FIG. 1 is a graph showing the relationship between the aging heat treatment temperature and the yield strength of a steel sheet.

FIG. 2 is a graph showing the relationship between the aging heat treatment temperature and the iron loss W of the steel sheet.

10/400

FIG. 3 is a graph showing the relationship between the heat treatment parameter P and the yield strength of the steel sheet. BEST MODE FOR CARRYING OUT THE INVENTION

[0024] In order to obtain a non-oriented electrical steel sheet having high strength and excellent magnetic properties, the present inventors have made the non-oriented electrical steel sheet high in strength by precipitation strengthening using aging heat treatment. The effects of steel components on the strength and magnetic properties of steel sheets after aging heat treatment were investigated. As a result, based on Si and A1 containing steel, which is advantageous for both magnetic properties and strength properties, Cu is used as a precipitation strengthening element, and Ti, Nb, V, and Zr carbides are also used. It was found that a non-oriented electrical steel sheet having both properties and magnetic properties can be obtained. Hereinafter, the knowledge that has led to the present invention and the experimental results that lead to it will be described.

[0025] In a vacuum melting furnace, the main components are mass%, Si: 2%, Mn: 0.2%, P: 0.09%, S: 0.003%, A1: 0.7%, N : 0. 002%, Cu: 2.0%, C and Nb content strength different pieces A and B were prepared, heated at 1100 ° C, and then hot rolled at a finishing temperature of 850 ° C. A hot-rolled steel sheet having a thickness of 2.5 mm was produced. The hot-rolled steel sheet was ground to a thickness of 2.1 mm, subjected to hot-rolled sheet annealing at 750 ° C for 10 hours, and then cold-rolled to a thickness of 0.35 mm. The cold-rolled steel sheet obtained by this cold rolling was subjected to finish annealing at 1000 ° C and then cooled to room temperature at an average cooling rate of 20 ° C Zs to produce a single-sheet test piece having a width of 55 mm and a length of 55 mm. . After this single plate test piece was subjected to aging heat treatment at 550 ° C. for 2 hours, iron loss W and strength were measured.

10/400

[0026] The following table shows the evaluation results of the strength (yield strength YS, tensile strength TS) and iron loss W of the steel sheet after aging heat treatment. As is clear from this result, it contains almost no C or Nb.

10/400

When steel plate A and steel plate B containing C and Nb were compared, steel plate B was found to have the same strength and higher iron loss.

[0027] [Table 1]

[0028] Next, in a vacuum melting furnace, the main components are mass%, C: 0.005%, Si: 2%, Mn: 0.2 %, P: 0.09%, S: 0.001%, A1: 0.7%, N: 0.002%, Cu: 2.5%, Ti content is 0.002% or 0 A 04% piece was produced, heated at 1100 ° C, and then hot rolled at a finishing temperature of 850 ° C to produce a 2.6 mm thick hot rolled steel sheet. This hot-rolled steel sheet was ground to a thickness of 2. Omm and then cold-rolled to a thickness of 0.35 mm. The cold-rolled steel sheet obtained by this cold rolling was subjected to a final annealing at 950 ° C for 20 seconds, then cooled to room temperature at an average cooling rate of 20 ° CZs, and a single sheet with a width of 55 mm and a length of 55 mm A test piece was prepared. The single plate specimen was subjected to aging heat treatment at 350 to 800 ° C. for 10 minutes, and the yield strength and iron loss W were measured.

10/400

[0029] Fig. 1 shows the relationship between aging heat treatment temperature and yield strength, and Fig. 2 shows aging heat treatment temperature and iron loss W.

The relationship with 10/400 is shown. As is clear from Figs. 1 and 2, under the above experimental conditions, it is clear that the yield strength is 500 MPa or more in the aging heat treatment from 400 ° C to 650 ° C, and the iron loss is hardly deteriorated by the aging. became. Furthermore, it was found that a steel sheet containing 0.04% Ti has a slightly deteriorated magnetic property, but its yield strength is higher than that of a steel sheet containing 0.002% Ti.

In Fig. 1, the increase in yield strength is observed when the aging heat treatment temperature is 800 ° C. This is because Cu precipitates during the cooling process after the aging heat treatment after Cu re-dissolves. Conceivable.

[0030] Further, aging heat treatment was performed with various combinations of temperature and time conditions, and the relationship between the heat treatment parameter P represented by the following formula (1) and the yield strength was determined. The results are shown in Figure 3.

[0031] P = (T + 273) X (20 + log (t)) (1)

(Here, T is the aging heat treatment temperature (° C), and t is the aging heat treatment time (h).)

[0032] As shown in FIG. 3, it became apparent that a yield strength of 500 MPa or more was obtained when the heat treatment parameter P was in the range of 13000 or more and 18000 or less.

[0033] Conventionally, the precipitation phase has been considered to have an adverse effect on the magnetic properties. This is also the force that was thought to degrade the magnetic properties because the precipitated phase creates new magnetic domains to reduce the magnetostatic energy around it, and hinders domain wall movement. However, from the above experimental results, it became clear that the fine Cu phase produced by aging heat treatment does not degrade the magnetic properties. Although its mechanism is not clear, The present inventors presume as follows. In other words, the particle size (10 to 40 nm) at which Cu precipitation hardening is most prominent is less than or equal to the thickness of the domain wall, so it is estimated that no new magnetic domain is generated and it does not hinder the domain wall movement. The In addition, when the Nb and Ti contents are high, the yield strength increases because of precipitation strengthening of Nb and Ti carbides.

Hereinafter, the non-oriented electrical steel sheet and the manufacturing method thereof, the rotor core, and the electric motor according to the present invention will be described in detail.

[0034] A. Non-oriented electrical steel sheet

The non-oriented electrical steel sheet of the present invention is, in mass%, C: 0.02% or less, Si: 1% or more and 4% or less, Mn: 1% or less, P: 0.2% or less, S: 0. 03% or less, A1: 0.1% or more and 3% or less, Cu: more than 1% and 4% or less, and a total of at least one of Ti and Nb is 0.02% or more and 0.3% or less In addition, V: 0% to 0.3%, Zr: 0% to 0.3%, Ni: 0% to 2%, B: 0% to 0.001% And the balance is Fe and impurity power.

“%” Indicating the content of each element means “mass%” unless otherwise specified. Further, in the present invention, “the balance consists of Fe and impurities” means that it contains a case where other elements are contained within a range that does not impair the effects of the present invention.

[0035] As described above, according to the present invention, excellent strength characteristics can be obtained by subjecting a steel sheet having the above steel composition to an aging heat treatment. Therefore, in the present invention, the non-oriented electrical steel sheet having the above steel composition includes a steel sheet that is subjected to an aging heat treatment using only the steel sheet after the aging heat treatment.

Hereinafter, the steel components of the non-oriented electrical steel sheet according to the present invention will be described.

[0036] 1. Steel composition

(D C

C is an element effective for increasing the strength of the steel sheet. However, when the C content exceeds 0.02%, carbides such as cementite and ε-carbide precipitate, and the magnetic property deterioration may become remarkable. Therefore, the C content is 0.02% or less. In order to further improve the magnetic properties, particularly the iron loss, it is preferable to set the upper limit of the C content to 0.010%. Good. On the other hand, in order to actively promote precipitation strengthening by carbides such as Ti, Nb, V, and Zr, it is preferable to control the C content from 0.005% to 0.02%.

[0037] (2) Si

Si increases the specific resistance of steel and is effective in reducing iron loss. Si is also effective in increasing the strength of steel sheets by solid solution strengthening. The Si content may be determined according to the required iron loss characteristics and strength characteristics. However, if the Si content is less than 1%, the required strength and iron loss may not be obtained. On the other hand, when the Si content force is exceeded, the dispersion state of Cu precipitates becomes non-uniform and the strength improvement effect tends to be saturated. Also, in cold rolling, there is a case where the production cost is significantly increased due to breaking and breaking. Therefore, the Si content is 1% or more and 4% or less. Furthermore, in order to suppress the yield reduction due to fracture during cold rolling, the Si content is preferably 1.5% or more and 3% or less.

[0038] Further, it is preferable that an appropriate Si content for obtaining a steel sheet having a yield strength of 500 MPa or more by aging heat treatment is determined by the Cu content. Specifically, when the Si and Cu contents (mass%) are [Si] and [Cu], respectively, it is preferable that the following formula is satisfied.

. [Si]> 0 4 [ Cu] 2 - 2 [Cu] +4

[0039] (3) Mn

Mn is an unavoidable impurity and does not need to be added. However, Mn increases the specific resistance of steel and is effective in reducing iron loss. In order to acquire the effect, it is preferable to contain 0.1% or more. On the other hand, if the Mn content exceeds 1%, the raw material cost may increase. Therefore, the Mn content is limited to 1% or less.

[0040] (4) P

P is an unavoidable impurity and need not be added. However, P is an element effective for increasing the strength of the steel sheet by solid solution strengthening. To obtain the effect, P is preferably contained in an amount of 0.05% or more. On the other hand, if the P content exceeds 0.2%, the toughness of the steel deteriorates and there is a risk of fracture during cold rolling. Therefore, the P content is limited to 0.2% or less.

[0041] (5) S

S is an inevitable impurity and does not need to be added. If the S content exceeds 0.03%, coarse Mn and Cu-containing sulfides are formed, which deteriorates the toughness of the steel and breaks during cold rolling. There is a risk. Therefore, the S content is limited to 0.03% or less.

[0042] (6) A1

A1, like Si, increases the specific resistance of steel and is effective in reducing iron loss. In addition, it is an element effective for deoxidation, and can reduce non-metallic inclusions. However, if the A1 content exceeds 3%, the saturation magnetic flux density is significantly reduced, and the core performance may be degraded. On the other hand, in order to efficiently deoxidize molten steel, it is necessary to contain 0.1% or more of A1. Therefore, the A1 content is limited to 0.1% to 3%. In order to improve the magnetic flux density by improving the texture, the A1 content is preferably 0.6% or more.

[0043] (7) Cu

Cu is an essential element in the present invention. As described above, when the Cu precipitate is very fine, there is an effect of improving the strength characteristics without substantially degrading the magnetic characteristics. However, if the Cu content is less than 1%, the strength increase due to Cu precipitation may not be obtained sufficiently. On the other hand, as the Cu content increases, the age hardening amount increases, but if it exceeds 4%, Cu precipitates disperse unevenly during finish annealing, reducing the strength after aging heat treatment, and reducing the magnetic flux density of the steel sheet. There is a case. Therefore, the Cu content is limited to more than 1% and 4% or less. In addition, the Cu content is preferably 1.5% or more and 3% or less from the viewpoint that precipitation strengthening becomes most prominent.

[0044] (8) Ti and Nb

Ti and Nb form carbides and are effective for increasing the strength. At least one of Ti and Nb is an essential element in the present invention. In order to improve the strength characteristics, it is necessary to contain at least one of Ti and Nb in a total of 0.02% or more. In addition, if at least one element of Ti and Nb exceeds 0.3% in total, carbides may be coarsely dispersed and the magnetic properties may be significantly deteriorated. Therefore, the total content of Ti and Nb should be 0.02% or more and 0.3% or less. In order to further improve the magnetic properties, the total content is preferably 0.02% or more and 0.1% or less.

In order to ensure precipitation strengthening due to the formation of carbides, it is preferable that the content of either element of Ti or Nb is independently 0.02% or more, more preferably 0.03% or more. [0045] (9) V and Zr

V and Zr are optional added elements and are not essential elements in the present invention. However, V and Zr, like Ti and Nb above, form carbides and are effective in increasing strength. In order to further improve the strength characteristics, it is preferable to contain at least one element of V and Zr at V: 0.01% or more and Zr: 0.01% or more. Also, if the V content or Zr content exceeds 0.3%, carbides may be coarsely dispersed and the magnetic properties may be significantly deteriorated. Therefore, the V content is preferably 0.01% or more and 0.3% or less, and the Zr content is preferably 0.01% or more and 0.3% or less. In order to further improve the magnetic properties, the V content is preferably 0.01% or more and 0.1% or less, and the Zr content is preferably 0.01% or more and 0.1% or less.

In order to ensure precipitation strengthening due to the formation of carbides, it is preferable that the V content is 0.02% or more and the Zr content is 0.02% or more.

[0046] (10) Ni

Ni is an unavoidable impurity and need not be added. However, Ni is an element effective for increasing the strength of the steel sheet by solid solution strengthening. To obtain the effect, Ni is preferably contained in an amount of 0.05% or more. On the other hand, if the Ni content exceeds 2%, the raw material cost increases. Therefore, the Ni content is limited to 2% or less.

[0047] (11) B

B is an optional additive element and is not an essential element in the present invention. However, when B is contained in an amount of 0.0003% or more, the toughness of the hot-rolled steel sheet is improved, and breakage occurs during cold rolling. On the other hand, if the B content exceeds 0.001%, a coarse B compound is produced, which may break during cold rolling. Therefore, the B content is 0.0010% or less. Further, from the viewpoint of steel plate manufacturability, the B content is more preferably 0.0003% or more and 0.0040% or less.

[0048] (12) Other inevitable impurities

Cr and Mo exist as impurities that may be mixed in steel in the steelmaking process and may be mixed by 0.01% or more. If the contents of both Cr and Mo are reduced to 1% or less, the effects of the present invention are not impaired. Other than the above ingredients As long as the content of any impurity component is reduced to 0.05% or less, the effect of the present invention is not affected.

[0049] 2. Yield strength

The yield strength of the non-oriented electrical steel sheet of the present invention is preferably 500 MPa or more, more preferably 600 MPa or more. By making the yield strength in the above range, when the non-oriented electrical steel sheet of the present invention is used, for example, as a motor rotor, the force that can be used stably without causing deformation or breakage during operation is also obtained. It is.

The upper limit of the yield strength is not particularly limited, but is usually less than lOOOMPa

[0050] The yield strength can be measured by the method specified in JIS-Z-2241.

[0051] B. Method for producing non-oriented electrical steel sheet

Next, the manufacturing method of the non-oriented electrical steel sheet of this invention is demonstrated.

The method for producing a non-oriented electrical steel sheet according to the present invention includes a finish annealing step of subjecting a cold rolled steel sheet having the above-described steel composition to a finish annealing at a finish annealing temperature of 900 ° C. or higher and 1150 ° C. or lower, and the finish described above. And a cooling step of cooling the steel sheet after the annealing step in a temperature range of 900 ° C or lower and 600 ° C or higher so that the average cooling rate is 1 ° CZs or higher.

[0052] In the present invention, before the finish annealing step, usually, a hot rolling step in which hot rolling is performed on the steel ingot or steel slab having the steel composition described above, and the hot rolling step are used. And a cold rolling process in which cold rolling is performed on the hot rolled steel sheet. Moreover, you may perform the hot-rolled sheet annealing process which performs hot-rolled sheet annealing to a hot-rolled steel plate after a hot rolling process. Furthermore, after the above-described finish annealing step, an aging heat treatment step of performing aging heat treatment on the steel plate may be performed. Each step in the method for producing a non-oriented electrical steel sheet of the present invention will be described below.

[0053] 1. Finish annealing process

The finish annealing step in the present invention is a step of subjecting the cold rolled steel sheet having the above-described steel composition to finish annealing at a finish annealing temperature of 900 ° C. or more and 1150 ° C. or less. [0054] The control of the finish annealing temperature in this step is very important for improving the strength characteristics of the steel sheet before the aging heat treatment and the strength characteristics and magnetic properties after the aging heat treatment. If the finish annealing temperature is less than 900 ° C, the recrystallized grain growth is insufficient and the magnetic properties may be significantly deteriorated. On the other hand, if the temperature exceeds 1150 ° C, the flatness of the steel sheet will deteriorate significantly, and the punchability may deteriorate. Therefore, the finish annealing temperature is limited to 900 ° C or higher and 1150 ° C or lower. In order to further reduce the iron loss, the higher the finish annealing temperature, the better. The temperature is preferably 950 ° C or higher.

[0055] The steel components of the cold-rolled steel sheet are the same as those described in the above-mentioned section "A. Non-oriented electrical steel sheet", and thus description thereof is omitted here.

[0056] 2. Cooling process

The cooling step in the present invention is a step of cooling the steel plate after the finish annealing step so that the average cooling rate becomes l ° CZs or higher in a temperature range of 900 ° C. or lower and 600 ° C. or higher.

[0057] In the present invention, controlling the cooling rate means that Cu is brought into a supersaturated solid solution state in the cooling step, and then an aging heat treatment step is performed to promote Cu precipitation and to obtain the desired yield strength. Is important to. For this reason, when cooling the temperature range of 900 ° C or lower and 600 ° C or higher where Cu precipitation is active, it is necessary to cool at an average cooling rate of 1 ° CZs or higher. 900 ° C or less When the average cooling rate in the temperature range of 600 ° C or more is less than l ° CZs, Cu precipitation proceeds excessively during the cooling process, so the Cu supersaturation before performing the aging heat treatment process This is because a solid solution state cannot be realized, and the target yield strength may not be obtained even if aging heat treatment is performed thereafter. In addition, the upper limit of the average cooling rate is not particularly limited as long as the supersaturated solid solution state can be realized before the aging heat treatment step, but when the average cooling rate is excessive, the flatness deteriorates and the iron core is manufactured (punched lamination). ) Is difficult, the average cooling rate is preferably 100 ° CZs or less.

[0058] In the cooling step, the steel sheet may be cooled to room temperature, or may be cooled to an aging heat treatment temperature described later. When the steel sheet is cooled to the aging heat treatment temperature, it is not necessary to raise the temperature of the steel sheet again to the aging heat treatment temperature in the aging heat treatment process described later, so that the manufacturing process is simplified and the cooling process and the aging heat treatment process are performed. Can be done continuously [0059] 3. Hot rolling process

In the present invention, before the finish annealing step, a hot rolling step is generally performed in which hot rolling is performed on a steel ingot or steel slab (hereinafter sometimes referred to as a slab) having the above steel composition.

A general method can be used as hot rolling. Conditions such as the slab temperature, the finishing temperature in hot rolling, and the cutting temperature should be appropriately selected depending on the steel composition of the slab, the thickness of the target steel sheet, and the like.

A hot-rolled steel sheet is usually subjected to cold rolling after removing the scale formed on the surface of the steel sheet during hot rolling by pickling. When hot-rolled sheet annealing described below is performed on a hot-rolled steel sheet, it may be pickled before / after hot-rolled sheet annealing or after hot-rolled sheet annealing!

[0060] 4. Hot-rolled sheet annealing process

In this invention, you may perform the hot-rolled sheet annealing process which performs hot-rolled sheet annealing to a hot-rolled steel plate after the said hot-rolling process. In this step, it is preferable to subject the hot-rolled steel sheet to hot-rolled sheet annealing at 600 ° C or higher and 900 ° C or lower for 2 hours or longer. This hot-rolled steel sheet is a material for the cold-rolled steel sheet used in the finish annealing process. Although the hot-rolled sheet annealing process is not necessarily an essential process, it is a useful process for increasing the efficiency of the subsequent cold rolling.

[0061] The annealing temperature in hot-rolled sheet annealing is preferably 600 ° C or higher and 900 ° C or lower. On the other hand, if the annealing temperature is lower than the above range, the strength of the steel sheet becomes too high, and cold rolling may be difficult. On the other hand, even if the annealing temperature exceeds the above range, Cu solute / reprecipitation occurs, which increases the strength of the steel sheet and may make cold rolling difficult. A more preferable annealing temperature is 650 ° C or higher and 850 ° C or lower.

The holding time at the annealing temperature is preferably 2 hours or more. If the holding time is less than 2 hours, the Cu precipitates become finer, the strength of the steel sheet increases, and cold rolling may become difficult. The holding time is more preferably 8 hours or longer. On the other hand, the upper limit of the holding time is not particularly limited, but it is preferable that the economic viewpoint power is 48 hours or less.

[0062] 5. Cold rolling process

In the present invention, before the finish annealing step, usually, a hot-rolled steel plate or hot-rolled steel is used. A cold rolling process is performed in which cold rolling is performed on the hot-rolled steel sheet that has been subjected to plate annealing. As the cold rolling, a general method can be used. Conditions such as temperature and rolling reduction during cold rolling are appropriately selected depending on the steel composition of the material to be rolled, the thickness of the target steel sheet, and the like.

[0063] In this step, the hot-rolled steel sheet may be cold-rolled twice or more with intermediate annealing. Although the intermediate annealing is not necessarily essential, the intermediate annealing has the advantage that the ductility of the steel sheet is improved and the fracture during cold rolling is reduced.

The conditions such as the annealing temperature in the intermediate annealing are preferably the same as those in the hot-rolled sheet annealing.

[0064] 6. Aging heat treatment process

In the present invention, an aging heat treatment step in which aging heat treatment is performed on the steel sheet may be performed after the finish annealing step. In this process, the steel sheet after the cooling process is aged so that the heat treatment parameter P represented by the following formula (1) is 13 000 or more and 18000 or less at an aging heat treatment temperature of 400 ° C or higher and 700 ° C or lower. It is preferable to apply heat treatment.

P = (T + 273) X (20 + log (t))… (1)

[0065] Aging heat treatment is effective in increasing the strength of the non-oriented electrical steel sheet. In order to obtain the effect of strengthening aging, the aging heat treatment temperature is preferably 400 ° C or higher. Aging heat When the treatment temperature is less than 400 ° C, the aging heat treatment time is long, and this may be inferior in productivity. On the other hand, if the aging heat treatment temperature exceeds 700 ° C, it will be over-aged, and the Cu precipitate particles will be coarsened and the desired yield strength will not be obtained, and the magnetic properties may deteriorate. Therefore, it is preferable that the aging heat treatment temperature is 400 ° C or more and 700 ° C or less! /.

[0066] Further, it is preferable to satisfy the condition that the heat treatment parameter P force is 13000 or more and 18000 or less represented by the above formula (1) by the aging heat treatment temperature T (° C) and the aging heat treatment time t (h). When heat treatment parameter P is less than 13000, aging precipitation is insufficient, and when heat treatment parameter P exceeds 18000, overaging occurs, and the desired yield strength cannot be obtained. .

[0067] Further, the non-oriented electrical steel sheet produced according to the present invention may be subjected to aging heat treatment after the rotor core is processed. Manufactured from non-oriented electrical steel sheets with aging heat treatment If a rotor core that has been aged or heat-treated after processing is incorporated into a motor rotor that rotates at high speed, the motor efficiency will not only increase, but it will be stable over a long period of time without being deformed or broken during operation. Can be used.

[0068] 7. Other processes

In the present invention, after the finish annealing step, it is preferable to perform a coating step of applying an insulating film consisting of only an organic component, only an inorganic component, or an organic-inorganic composite cover to the steel sheet surface according to a general method. . From the viewpoint of reducing the environmental burden, an insulating film not containing chromium may be applied. Further, the coating process may be a process of applying an insulating coating that exhibits adhesive ability by heating and pressurizing. As the coating material exhibiting the adhesive ability, acrylic resin, phenol resin, epoxy resin or melamine resin can be used.

[0069] C. Rotor core

Next, the rotor core of the present invention will be described. The rotor core of the present invention is formed by laminating the non-oriented electrical steel sheets described above. Usually, the rotor core is formed by punching and stacking the non-oriented electrical steel sheets.

Since the non-oriented electrical steel sheet constituting the rotor core is excellent in magnetic characteristics and strength characteristics as described above, when the rotor core of the present invention is applied to a rotor of an electric motor, for example, a motor Efficiency can be improved, and it can be used stably over a long period of time without deformation or destruction during operation. In addition, when applied to a generator rotor, deformation or destruction does not occur during operation, so high-speed rotation is possible, leading to improved power generation efficiency.

[0070] D. Rotating machine

Next, the rotating machine of the present invention will be described. The rotating machine of the present invention has the above-described rotor. Examples of the rotating machine include an electric motor and a generator. A rotating machine that receives electric power and generates mechanical power is an electric motor, and a rotating machine that receives mechanical power and generates electric power is a generator. Since the structure of both is basically the same, the following explanation will be given for an example of an electric motor.

[0071] An electric motor (motor) is, for example, a stator (stator) formed by winding a stator winding. And a rotor (rotor) that rotates by excitation by energization of the stator winding at the center of the stator. The rotor has the above-described rotor iron core and a permanent magnet provided on the rotor iron core. The stator is obtained by winding a stator winding around a stator iron core having a slot. The stator core is configured by punching and stacking non-oriented electrical steel sheets in the same manner as the rotor core.

The non-oriented electrical steel sheets used for the rotor core are those described in the section “A. Non-oriented electrical steel sheets” above. Further, the non-oriented electrical steel sheet used for the stator core is not particularly limited.

[0072] According to the present invention, since the rotor core formed by laminating non-oriented electrical steel sheets having excellent magnetic properties and strength properties is used, the motor is improved in motor efficiency and used for a long period of time. be able to. In addition, the generator can improve power generation efficiency.

Note that the present invention is not limited to the above-described embodiment. The above embodiment is an exemplification, and any device that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits the same operational effects can be used. It is included in the technical scope.

Example

Hereinafter, the present invention will be specifically described with reference to examples.

[Example 1]

230 tons of molten steel decarburized and desulfurized in a converter were put into the ladle and the ladle was moved to the RH vacuum degassing equipment. After decarburization under reduced pressure with RH vacuum degassing equipment, the C content in the steel is reduced to 0.015% or less, then Si, Mn, P, S, Al, Cu, B, Ni, Ti, Nb, V And the Zr content was adjusted, and the slab was made with a continuous forging machine.

The slab was heated to 1150 ° C in a heating furnace and hot-rolled at a finishing temperature of 800-850 ° C and a winding temperature of 500 ° C to obtain a hot-rolled steel sheet with a thickness of 2. Omm. Next, pickling and descaling, annealing at 750 ° C for 10 hours, cold-rolling to a thickness of 0.35 mm, finish annealing at a maximum reached temperature of 1000-1050 ° C, and insulating coating on the steel plate surface Was applied.

Table 2 below shows the component analysis values of the product, and Table 3 shows the finish annealing conditions. [0075] A 28 cm Epstein specimen was collected from the steel sheet thus obtained and subjected to aging heat treatment at 550 ° C for 2 hours. The iron loss W of the steel sheet after aging heat treatment was measured by the method defined in JIS-C-2550. Furthermore, JIS-Z-2 for steel plates after aging heat treatment

10/400

The tensile test specified in 241 was conducted, and the yield strength YS and tensile strength TS were measured. Table 3 below shows the magnetic and strength data.

[0076] [Table 2]

s3¾007

The underlined portion indicates that it is outside the scope of the present invention.

Finish annealing Cooling rate YS TS Wl 0/400

Steel mark

Temperature (° c) (° C / s) (MPa) (MPa) (W / kg)

A1 1000 20 361 461 21.5

A2 1000 20 464 558 22.0

A3 1000 20 467 589 26.4

A4 1050 20 714 836 30.0

A5 1050 20 714 836 26.5

A6 1050 20 718 840 23.0

A7 1050 20 730 852 22.9

A8 1050 20 740 862 12.1

A9 1050 20 737 868 22.1

A10 1050 20 712 843 22.3

A1 1 1000 20 765 891 21.6

A12 1000 20 760 891 22.0

[0078] A steel sheet having a steel composition within the range of the present invention has a yield strength YS of 500 MPa or more, a tensile strength of TS force of OOMPa or more, and an iron loss W of 25 WZkg or less.

10/400

It was. On the other hand, the steel compositions (A1 to A3) whose steel composition was outside the scope of the present invention had a yield strength YS of less than 500 MPa, which was clearly inferior to the examples of the present invention. The steel sheets (A4, A5) had the same strength characteristics as the examples of the present invention, but the iron loss was clearly inferior to the present invention.

[0079] [Example 2]

Using the cold-rolled steel sheets of steel marks A7 and A12 manufactured in Example 1, the final annealing temperature was changed from 850 ° C to 1150 ° C and the average cooling rate was changed from 0.8 ° CZs to 30 ° CZs. Finish annealing was performed, and an insulating film was applied to the steel sheet surface. Table 4 below shows the finish annealing conditions.

[0080] A 28 cm Epstein specimen was collected from the steel sheet thus obtained and subjected to aging heat treatment at 500 ° C for 0.5 hour. The iron loss W of the steel sheet after the aging heat treatment was measured by the method defined in JIS-C-2550. Furthermore, JIS-Z for steel sheets after aging heat treatment

10/400

— The tensile test specified in 2241 was performed, and the yield strength YS was measured. Table 4 below shows the magnetic and strength data.

In Table 4, flatness refers to the steel strip force of 3 m in the longitudinal direction after finish annealing, put it on a horizontal surface plate, and set the side wave height (h) and wavelength (L). The hZL value obtained by measurement is used as a reference, and the flatness lOOhZL value is 0.4 or less. “◯” mark, flatness lOOhZL value greater than 0.4 and less than 0.8 mark “△” mark, flatness exceeding lOOhZL value SO.8 mark “X” mark.

[Table 4]

[0082] The steel sheet produced according to the finish annealing conditions specified in the present invention had a yield strength YS of 600 MPa or more and an iron loss W of 25 WZkg or less, and required characteristics were obtained. on the other hand,

10/400

The steel sheet manufactured under conditions other than the provisions of the present invention was clearly inferior to the examples of the present invention, because the yield strength YS was less than 600 MPa, or the iron loss W 10/400 exceeded 25 WZkg.

[0083] [Example 3]

Thickness of steel mark A10 produced in Example 1 2. After performing various hot-rolled sheet annealing using a hot-rolled steel sheet of Omm, the thickness is 0. The operability was evaluated by the number of cold rolling passes up to 35 mm. The results are shown in Table 5 below.

[0084] [Table 5]

If the annealing temperature in hot-rolled sheet annealing is 600 ° C or higher and 900 ° C or lower, 9 passes for cold pressure If the annealing temperature is less than 600 ° C or more than 900 ° C, the annealed steel sheet is very hard and can be rolled to 0.35 mm in 9 passes. It turned out that the operability was inferior.

[0086] [Example 4]

Using the cold-rolled steel plates with steel marks A7 and A10 manufactured in Example 1, finish annealing is performed at 1050 ° C and average cooling rate is 20 ° CZs, and an insulating film is applied to the steel plate surface. did. Next, aging heat treatment was performed under various conditions, and the iron loss W was measured by the method of JIS-C-2550. In addition, JIS—

10/400

A specified tensile test was conducted on Z-2241 and the yield strength YS was measured. Table 6 below shows data on aging heat treatment conditions, magnetic properties and strength properties.

[0087] [Table 6]

[0088] By applying an aging heat treatment so that the heat treatment parameter P is 13000 or more and 18000 or less, the yield strength YS is 500 MPa or more and the iron loss W is 25 WZkg or less.

10/400

The characteristics were obtained. Steel sheet A10 had a YS of 500 MPa or more despite the heat treatment parameter P of less than 13000. Compared with steel plate A7, steel plate A10 has the desired strength in the state of finish annealing because it contains more Cu, Al, C and the like. In any case, it was proved that a steel plate with excellent strength and magnetic properties can be obtained by appropriate aging heat treatment.

Claims

The scope of the claims

[1] By mass%, C: 0.02% or less, Si: 1% or more, 4% or less, Mn: l% or less, P: 0.2% or less, S: 0.03% or less, A1: 0. 1% or more, 3% or less, Cu: more than 1%, 4% or less, and at least one element of Ti and Nb in total of 0.02% or more and 0.3% or less, and more optional V: 0% or more and 0.3% or less, Zr: 0% or more and 0.3% or less, Ni: 0% or more and 2% or less,: 0% or more and 0.010% or less, with the balance being Fe And a non-oriented electrical steel sheet characterized by having an impurity power.

[2] It is characterized by containing at least one element of V and Zr in a mass% of V: 0.01% or more and 0.3% or less, Zr: 0.01% or more and 0.3% or less. The non-oriented electrical steel sheet according to claim 1 or 2.

[3] The non-oriented electrical steel sheet according to claim 1 or 2, characterized by containing Ni: 0.05% to 2% by mass.

[4] The non-oriented electrical steel sheet according to any one of claims 1 to 3, wherein the content of B is 0.003% or more and 0.0010% or less in terms of mass%. .

[5] The yield strength is 500 MPa or more. The non-oriented electrical steel sheet according to any of the above.

[6] Finish annealing in which a cold-rolled steel sheet having the steel composition described in any one of claims 1 to 4 is subjected to finish annealing at a finish annealing temperature of 900 ° C or higher and 1150 ° C or lower. And a cooling step of cooling the steel sheet after the finish annealing step in a temperature range of 900 ° C or lower and 600 ° C or higher so that the average cooling rate is 1 ° CZs or higher. Method for producing an electrical steel sheet.

[7] A hot-rolled sheet annealing step for subjecting the hot-rolled steel sheet, which is a material of the cold-rolled steel sheet, to hot-rolled sheet annealing at 600 ° C or higher and 900 ° C or lower for 2 hours or more before the finish annealing step; A method for producing a non-oriented electrical steel sheet according to claim 6, further comprising: a cold rolling process in which cold rolling is performed on the hot rolled steel sheet subjected to hot-rolled sheet annealing.

[8] The steel plate after the cooling step is subjected to the following formula at an aging heat treatment temperature of 400 ° C or higher and 700 ° C or lower.

The claim 6 or 7 has an aging heat treatment step of performing an aging heat treatment so that the heat treatment parameter P shown in (1) is 13000 or more and 18000 or less. The manufacturing method of the non-oriented electrical steel sheet of description.

P = (T + 273) X (20 + log (t))… (1)

[9] Claim 1st term force A rotor core comprising the non-oriented electrical steel sheets according to any one of claims 5 to 5 laminated.

[10] A rotating machine using the rotor core according to claim 9.