KR20080063521A - Highly strong, non-oriented electrical steel sheet and method for manufacture thereof - Google Patents

Abstract

Disclosed is a non-oriented electrical steel sheet having a high strength, excellent magnetic properties and excellent productivity. The steel sheet comprises 0.010% by mass or less of C and 0.010% by mass or less of N, provided that C + N <= 0.010% by mass, and also comprises 1.5 to 5.0% by mass of Si and 0.8% by mass or less of Ti or a mixture of Ti and V, provided that (Ti + V)/(C + N) >= 16. The steel sheet may also have a content of a non-recrystallized recovery structure of 50% or more.

Description

High strength non-oriented electrical steel sheet and its manufacturing method {HIGHLY STRONG, NON-ORIENTED ELECTRICAL STEEL SHEET AND METHOD FOR MANUFACTURE THEREOF}

The present invention relates to a high-strength non-oriented electrical steel sheet and a method of manufacturing the same. The steel sheet of the present invention is particularly suitable for use in electronic components subjected to a large stress, which is typical of the rotor of a high speed rotor. Here, as a high speed rotor, a turbine generator, the drive motor of an electric vehicle and a hybrid vehicle, the servo motor of a robot or a machine tool, etc. are mentioned, for example.

In recent years, the development of a motor drive system has made it possible to control the frequency of a drive power supply. Therefore, motors that perform variable speed operation and motors that perform high-speed rotation above commercial frequencies have increased. In a motor involving such a high speed rotation, the centrifugal force acting on the rotor increases in proportion to the rotation radius and in proportion to the power of the rotation speed. For this reason, high strength (especially high tensile strength) is needed for the rotor material of a medium and large high speed motor.

Moreover, in recent years, an embedded controlled brushless DC motor, which has been increasingly employed in drive motors, compressor motors, and the like in hybrid vehicles, forms magnets by forming slits in the rotor. For this reason, stress is concentrated in the narrow bridge | bridging part between slit at the time of motor rotation, and high mechanical strength is needed for the core material used for a rotor. Moreover, since the stress state changes with acceleration / deceleration operation and vibration of the motor, it is preferable that the core (iron core) material used for the rotor has a high fatigue strength.

On the other hand, in order to use electromagnetic phenomena, a rotary device such as a motor or a generator has a high electromagnetic property in the core material (that is, low iron loss, and preferably magnetic fluss). high density) is also required.

In particular, in high-speed rotary motors, it is important that the high frequency iron loss is low (that is, excellent in the high frequency iron loss characteristic) because the eddy current generated by the high frequency magnetic flux causes the reduction of the motor efficiency.

Usually, the core for a rotor is used by laminating a non-oriented electrical steel sheet press-punched. However, in a high speed rotary motor, when the raw material of a rotor cannot satisfy the above-mentioned mechanical strength, a higher strength cast steel ( Iii) Rotors, etc. must be used. However, since the casting rotor is not a laminate but an integrated body, there is a problem that the eddy current loss is significantly higher than that of the rotor on which the electronic steel sheet is laminated.

Therefore, an electrical steel sheet which is excellent in magnetic properties and high in strength is desired as a raw material for the rotor.

Solid steel hardening, precipitation hardening, fine-grain hardening, and complex-phase hardening are known as steel sheet hardening methods, but all of these hardening methods are known. In order to deteriorate the magnetic properties, it is generally very difficult to achieve both strength and magnetic properties.

Under these circumstances, several proposals have been made regarding non-oriented electrical steel sheets having high strength.

For example, Japanese Laid-Open Patent Publication No. 60-238421 has a Si content of 3.5 to 7.0% (mass% or less, the same), and further increases Ti, W, Mo, Mn, Ni, and Co for solid solution strengthening. A method of increasing the strength by adding elements such as and Al has been proposed. In addition, Japanese Patent Laid-Open No. 62-112723 proposes a method of improving the magnetic properties by setting the crystal grain size to 0.01 to 5.0 mm by controlling the final annealing conditions in addition to the above strengthening method. .

However, when these methods are applied to factory production, troubles, such as plate breakage, tend to occur in the rolling line after hot rolling, and there is a problem such that yield decrease and line stoppage cannot be avoided. In addition, about plate breaking, it is reduced by making cold rolling into warm rolling of several hundred degreeC of plate temperature. However, the load on process management increases, such as the necessity of correspondence with facilities for warm rolling, and the increase in production constraints.

In addition, Japanese Patent Laid-Open No. Hei 2-22442 proposes a method for achieving solid solution strengthening with Mn and Ni in a steel with a Si content of 2.0 to 3.5%. In addition, Japanese Patent Laid-Open No. 6-330255 discloses a technique using precipitation strengthening and fine grain hardening by carbonitrides of Nb, Zr, Ti, and V in steels having a Si content of 2.0 or more and less than 4.0%, and Japanese Unexamined Patent Application Publication No. 2-8346 proposes a technique of adding solid solution strengthening by adding Mn and Ni to this, and achieving both high strength and magnetic properties.

However, when the method described in JP-A 2-22442 does not provide sufficient strength, and in the methods of JP-A 6-330255 and JP-A 2-8346, high strength is obtained. However, the technical problem remains that the deterioration of magnetic properties is large.

Moreover, when the fatigue property was evaluated about the steel plate produced by the said method, it turned out that the fatigue property suitable for expectation was not acquired even if high strength is obtained. In other words, even if the yield strength or the tensile strength of the steel is simply increased, the fatigue properties are often not improved, and the material design method considering the fatigue properties has not been established.

As a high-strength electrical steel sheet that pays attention to fatigue characteristics, Japanese Unexamined Patent Application Publication No. 2001-234303 achieves a fatigue limit of 350 MPa or more by controlling the crystal grain size according to the steel composition of an electrical steel sheet having a Si content of 3.3% or less. Techniques are disclosed. However, with this method, the attainment level of the fatigue limit itself was low (actually up to about 430 MPa) and did not satisfy the currently desired level, for example, the fatigue limit: 500 MPa or more.

In addition, as a manufacturing method of a high strength electrical steel sheet, in Japan Unexamined-Japanese-Patent No. 2005-113185, it is aimed at high strength by remaining a work hardening structure in steel inside about 0.2-3.5% of steel containing Si. Techniques have been proposed. As a specific method, even if it does not heat-process after cold rolling, even if it does, it does not reach to the grade equivalent to 30 second or more holding | maintenance at 750 degreeC or more, Preferably it is 700 degrees C or less, More preferably, it is 650 degrees C or less, 600 degrees C or less, Means to be 550 ° C. or less and 500 ° C. or less are disclosed. In addition, 5% of the processed texture rate at annealing at 750 ° C.-30 seconds, 20% at 700 ° C.-30 seconds, and 50% at 600% -30 seconds are illustrated as the results.

In this case, since annealing temperature is low temperature, there exists a problem that shape correction of sufficient rolling strip is not performed. And when a steel plate shape is bad, problems, such as the fall of the lamination factor after laminating | stacking a motor core etc., and the nonuniform stress distribution at the time of high speed rotation as a rotor generate | occur | produce.

In general, finish annealing of the non-oriented electrical steel sheet is carried out using a continuous annealing furnace, and the furnace is conventionally adjusted to an atmosphere containing several percent or more hydrogen gas in order to suppress oxidation of the steel sheet surface. In such continuous annealing facilities, in order to perform low temperature annealing below 700 ° C, not only does it require time for switching the furnace setting, but also requires a large number of operational conditions such as the need for replacement of the atmosphere in the furnace to avoid hydrogen explosion. Constraints will arise.

In addition, when the technique is applied after the high temperature finish annealing, coating coating-baking treatment, or the like, for example, by introducing the processing structure by re-rolling, the manufacturing process is added, resulting in an increase in cost and equipment limitations. . In addition, there arises a problem that the insulating coating on the surface of the coated and baked steel sheet after finishing annealing is destroyed by subsequent processing, thereby lowering the insulation.

In JP-A-4-337050, recrystallization of the crystal structure is 95% or less by heat-treating the steel sheet after cold rolling in a composition of Si: 4.0 to 7.0% at a specific temperature defined in relation to the Si content. The technique which aims at reinforcement by making a remainder substantially rolled structure is disclosed. In this formula, for example, when heat treatment at 700 ° C., about 5.9% or more of Si is required. In this technique, a practical soft magnetic material having a high tensile strength of 80 kgf / mm 2 or more, some elongation, and excellent magnetic properties is obtained.

In Japanese Laid-Open Patent Publication No. 2005-264315, in an electronic steel sheet containing 0.2: 4.0% of Si and having a ferrite phase as a main phase, Ti, Nb, Ni, and the like are added to the inside of the steel to have a diameter of 0.050 µm or less. Disclosed is a method of producing a liver compound to promote fortification. In this technique, a non-oriented electrical steel sheet having a tensile strength and wear resistance of 60 kgf / mm 2 or more and excellent in magnetic flux density and iron loss can be produced without impairing cold rolling property.

Disclosure of the Invention

Problems to be Solved by the Invention

As described above, some proposals have been made regarding high strength non-oriented electrical steel sheets, but industrially stable manufacturing using conventional electronic steel sheet manufacturing equipment while achieving required strength, good magnetic properties and steel sheet shape is achieved. What cannot be done is the present situation.

Accordingly, an object of the present invention is to provide a non-oriented electrical steel sheet having high strength and excellent plate shape and magnetic properties, and a method of manufacturing the same, without substantially adding steel sheet manufacturing constraints or a new process to the production of a conventional non-oriented electrical steel sheet. It is to provide.

It is another object of the present invention to propose a non-oriented electrical steel sheet having high strength, excellent magnetic properties and fatigue properties, and also excellent in manufacturability, with its advantageous manufacturing method.

Means to solve the problem

The gist of the present invention is as follows.

(1) In mass%, C and N are suppressed to C: 0.010% or less and N: 0.010% or less, and C + N ≦ 0.010%, Si: 1.5% or more and 5.0% or less, Mn: 3.0% or less, Al: 3.0% or less, P: 0.2% or less, S: 0.01% or less, and further contain Ti in a range of 0.05% or more and 0.8% or less, and satisfying Ti / (C + N) ≧ 16, A high strength non-oriented electrical steel sheet having a component composition which is a residual Fe and an unavoidable impurity, and wherein the ratio of the non-recrystallized recovery structure in the steel sheet is 50% or more by area ratio.

Here, the recrystallization and the recrystallization recovery organization will be described. First, recrystallization is a phenomenon in which crystal grains with low defect density and thermodynamically stable crystals are newly formed and grow while encroaching on a matrix having a high surrounding defect density. In recrystallization, the defect density decreases drastically as the grain boundary moves.

On the other hand, recovery is a phenomenon in which the deformation energy decreases as a result of the defect itself moving thermally toward the sink and reducing the dislocation density, regardless of passage of grain boundaries. In the short time continuous annealing which is normally applied to a non-oriented electrical steel sheet, recovery is apparent when it is processed on the annealing temperature of 500 degreeC or more. Recovery and recrystallization can be mixed, but recrystallization predominates with annealing at high temperatures. Recrystallization advances rapidly at 600-650 degreeC or more in the electrical steel plate of a normal composition, and most of it becomes a recrystallization structure at 700 degreeC or more.

In the steel annealed at 500 ° C. or higher, the recrystallized structure and the unrecrystallized recovery structure can be easily distinguished by observing the structure (microstructure: microstructure) by an optical microscope. Here, the structure observation is made possible by grinding the plate thickness direction cross section which is usually carried out, and then etching with nital (nitric alcohol solution).

Moreover, in invention of said (1), it is preferable that they are Si: 1.5% or more and 4.0% or less by mass%. In the invention of (1) above, in terms of mass%, Ni: 0.1 to 5.0%, Sb: 0.002 to 0.1%, Sn: 0.002 to 0.1%, B: 0.001 to 0.01%, Ca: 0.001 to 0.01%, Rem It is preferable to further contain at least 1 sort (s) chosen from the group which consists of: 0.001-0.01% and Co: 0.2-5.0%. These preferable conditions may be combined freely.

 (2) In mass%, C and N are suppressed to C: 0.010% or less and N: 0.010% or less, and C + N ≦ 0.010%, Si: 1.5% or more and 5.0% or less, Mn: 3.0% or less, Al: 3.0% or less, P: 0.2% by mass or less, S: 0.01% by mass or less, further in a range of 0.05% by mass or more and 0.8% by mass or less, and satisfying Ti / (C + N) ≧ 16 When the steel slab having the component composition to be contained is hot rolled, and then cold rolled or cold rolled to a cold rolled coil having a final sheet thickness, when finish annealing, the finish annealing is performed at an annealing temperature of 700 ° C. or higher and 850 ° C. or lower. Strip unit tension in furnace The manufacturing method of the high strength non-oriented electrical steel sheet characterized by carrying out in 2.5 Mpa or more and 20 Mpa or less.

Here, the in-vehicle tension is the tension per unit cross-sectional area of the steel strip in the furnace section (mostly after the heating section or in the soaking section) where the steel sheet becomes the highest temperature in the annealing furnace.

In addition, in the invention of the above (2), it is preferable that the balance of Fe and inevitable impurities in the component composition of the steel slab is the same as the invention of the above (1).

Also in the invention of (2), in the same manner as in the invention of the above (1), Si: 1.5% or more and 4.0% or less, and / or Ni: 0.1 to 5.0%, Sb: 0.002 to 0.1 %, Sn: 0.002% to 0.1%, B: 0.001% to 0.01%, Ca: 0.001% to 0.01%, Rem: 0.001% to 0.01%, and Co: 0.2% to 5.0%, further containing at least one selected from the group consisting of It is preferable.

The invention of the above (2) is particularly preferably used in order to obtain a steel sheet of the invention of the above (1), that is, a steel sheet having a proportion of 50% or more in terms of area ratio.

Moreover, in order to solve the said subject, the inventors earnestly examined about the influence of the various reinforcement methods on the manufacturability, mechanical property, fatigue property, and magnetic property of a non-oriented electrical steel sheet. And, in order to strengthen the solid solution, the alloying component on the manufacturability (specifically, bending property and cold rolling property of the hot rolled sheet and hot rolled annealing plate) of the high alloy steel sheet which increased the amount of solid solution strengthening elements such as Si The impact was examined in detail.

As a result, the following was found regarding the carbonitride-forming element.

(a) By reducing the solid solution C and N as much as possible, the rolling property can be significantly improved also for high alloy steel containing more than 3.5 mass% of Si.

(b) For this purpose, while reducing the amount of C and N, it is effective to add carbon nitride forming elements such as Ti, V, Nb and Zr in an excessively sufficient amount to C and N in an atomic ratio.

From the above point of view, it is possible to achieve high productivity by greatly reducing troubles in the process such as plate breaking during the manufacture of the high alloy steel sheet.

Next, the influence which these carbonitride forming elements have on the mechanical property, fatigue property, and magnetic property of an electronic steel plate was investigated, and the following was found.

 (c) While carbonitrides of Ti, V, Nb, and Zr are effective for high tensile strength by the precipitation strengthening action, abundant amounts of them lead to deterioration of fatigue characteristics and magnetic properties (iron loss and magnetic flux density).

 (d) On the other hand, Ti, V, Nb, and Zr added excessively to C and N have a solid solution strengthening effect, greatly increase the tensile strength, improve the fatigue characteristics, and also precipitate the deterioration of magnetic properties. It is greatly reduced in comparison with the case of reinforcement.

In addition, as a result of investigating the influence on the mechanical properties, fatigue properties, and magnetic properties of major solid solution elements, the following findings were found.

 (e) Of the main elements added to the non-oriented electrical steel sheet, solid solution strengthening using Si is most effective in terms of both mechanical and magnetic properties. However, when the amount of Si added is excessive, the tensile strength (tensile strength) increases, but the fatigue characteristics are greatly deteriorated. That is, in order to be balanced and to improve mechanical properties, fatigue properties and magnetic properties, there is an optimum range in the amount of Si added.

The present invention has also been developed on the basis of the above novel aspects, and the gist structure is as follows.

 (3)

 (3-1) In mass%, C and N are set to C: 0.010% or less and N: 0.010% or less, and C + N ≦ 0.010%, Si: more than 3.5% and 5.0% or less, Mn: 3.0% or less , Al: 3.0% or less, P: 0.2% or less and S: 0.01% or less,

Or further Ni: not more than 5.0%,

Furthermore, any 1 type or 2 types of Ti and V are included in the range which sums: 0.01% or more and 0.8% or less and satisfy | fills (Ti + V) / (C + N) ≥16, and remainder is Fe and an unavoidable thing. A high strength non-oriented electrical steel sheet excellent in manufacturability and excellent in fatigue characteristics and magnetic characteristics, characterized by being an impurity composition.

 (3-2) In mass%, C and N are set to C: 0.010% or less and N: 0.010% or less, and C + N ≦ 0.010%, Si: more than 3.5% and 5.0% or less, Mn: 3.0% or less , Al: 3.0% or less, P: 0.2% or less and S: 0.01% or less,

Or further Ni: not more than 5.0%,

In addition, any one or two of Nb and Zr is contained in a range in which the total: 0.01% or more and 0.5% or less and (Nb + Zr) / (C + N) ≥ 10 is satisfied, and the balance is Fe and inevitable. A high strength non-oriented electrical steel sheet excellent in manufacturability and excellent in fatigue characteristics and magnetic characteristics, characterized by being an impurity composition.

 (3-3) In mass%, C and N are set to C: 0.010% or less and N: 0.010% or less, and C + N ≦ 0.010%, Si: more than 3.5% and 5.0% or less, Mn: 3.0% or less , Al: 3.0% or less, P: 0.2% or less and S: 0.01% or less,

Or further Ni: not more than 5.0%,

Further, at least one of Ti and V and at least one of Nb and Zr are 0.01% ≦ (Ti + V + Nb + Zr) ≦ 0.5%, and (Ti + V + Nb + Zr) / (C + N A high strength non-oriented electrical steel sheet having excellent manufacturability and excellent fatigue and magnetic properties, wherein the content is in a range satisfying? 16, and the balance comprises Fe and inevitable impurities.

 (3-4) In the invention according to any one of the above (3-1) to (3-3), Sb: 0.002 to 0.1%, Sn: 0.002 to 0.1%, B: 0.001 to 0.01%, It is excellent in manufacturability characterized by the composition which further contains 1 type (s) or 2 or more types chosen from the group which consists of Ca: 0.001-0.01%, Rem: 0.001-0.01%, and Co: 0.2-5.0%. High strength non-oriented electrical steel sheet with excellent fatigue and magnetic properties.

 (4) After hot rolling the steel slab which is the composition shown in any one of said (3-1)-(3-4), after performing hot-rolled sheet annealing as needed, one cold rolling or warm rolling or It is excellent in manufacturability, it is made into the final plate | board thickness by two or more cold rolling or warm rolling which sandwiched the intermediate annealing, and then finish-annealing on conditions of annealing temperature: 700 degreeC or more and 1050 degrees C or less. In addition, a method for producing a high strength non-oriented electrical steel sheet excellent in fatigue properties and magnetic properties.

Here, it is preferable to make the said final board thickness into 0.15 mm or more.

According to the present invention, and in particular, the inventions of (1) and (2), by controlling the composition and structure of the components, non-directional electrons having high strength and excellent plate shape and magnetic properties without adding steel sheet manufacturing constraints or new processes. Steel sheet can be provided.

Moreover, according to this invention, especially the invention of (3) ((3-1)-(3-4)) and (4), it goes without saying that it is high strength and has the outstanding magnetic characteristic, and it is excellent in a fatigue characteristic, Furthermore, the non-oriented electrical steel sheet excellent in manufacturability can be obtained stably.

1: is a figure which shows the relationship between Ti amount (horizontal axis: unit = mass%), annealing temperature (vertical axis: unit = degreeC), and recrystallization rate (number in a circle: unit = area%).

FIG. 2 is a graph showing the effect of the amount of (C + N) in the steel (horizontal axis: unit = mass%) on the flowability (number of bendings) (vertical axis: unit = number) in the production line.

3 is a graph showing the effect of the amount of (C + N) in the steel (horizontal axis: unit = mass%) on cold rolling property (edge crack depth of the rolled plate cross section) (vertical axis: unit = mm).

Fig. 4 shows the effect of Ti amount in steel (horizontal axis: unit = mass%) on the sheeting property (number of bending) (vertical axis: unit = number) in the production line; The graph shown for.

FIG. 5 shows the effect of the Ti / (C + N) ratio (horizontal axis) on the sheeting ability (the number of bendings) (vertical axis: unit = number of times) in the production line for the amount of steel (C + N) at four levels. The graph shown.

6 shows the effect of the amount of Ti in the steel (horizontal axis: unit = mass%) on the cold rolling property (edge crack depth of the rolled plate cross section) (vertical axis: unit = mm); ) Is a graph showing the quantity.

Fig. 7 shows the effect of Ti / (C + N) ratio (horizontal axis) on the cold rolling property (edge crack depth of the rolled plate cross section) (vertical axis: unit = mm). This is the graph shown for.

8 is a graph showing the effect of the Ti amount (horizontal axis: unit = mass%) in steel on the tensile strength TS (horizontal axis: unit = MPa) with respect to the amount of steel (C + N) in four levels.

9 is a graph showing the effect of Ti amount in steel (horizontal axis: unit = mass%) on fatigue limit FS (horizontal axis: unit = MPa) with respect to four levels of steel (C + N) amount. .

10 is a high-frequency iron loss (W _10/1000) (vertical axis: unit = W / ㎏) the amount of Ti in steel on the (horizontal axis: unit =% by weight) the amount of the impact of, (C + N) of the four-level steel This is the graph shown for.

In addition, in FIG.4-10, ◆ C + N: 0.0038-0.0048 mass%, ■ silver C + N: 0.0074-0.0092 mass%, ▲ silver C + N: 0.0175-0.0196 mass%, x is C + N : 0.0353-0.0391 mass% are shown.

Implement the invention  Best form for

Hereinafter, the "%" display regarding a component shall mean the mass% unless there is particular notice.

[Invention principle]

First, the principle of invention of said (1) and (2) is demonstrated.

The inventors earnestly examined the means for manufacturing the non-oriented electrical steel sheet which makes high strength and magnetic property compatible with one of the subjects mentioned above industrially stable, and also in favorable steel plate shape. Specifically, the high strength required here is a tensile strength of 600 MPa or more, preferably 700 MPa or more, and more preferably 800 MPa or more. In addition, the magnetic properties, in particular high-frequency low iron loss properties required, for example in the non-oriented electrical steel sheet having a thickness of 0.35㎜ W _10/400 value of 50W / ㎏ or less, preferably 40W / ㎏ or less, more preferably Is the level which becomes 30 W / kg or less.

As a result of the above examination, in particular, in a high strength material having a tensile strength exceeding 700 MPa, it has been found that it is effective to suppress the recrystallization of the steel sheet structure in finish annealing and fix it as a recovery structure. However, in order to obtain a recovery structure using the non-oriented electromagnetic steel material of the conventional steel composition, the finish annealing temperature should be carried out at a low temperature of 600 ° C or lower. In order to manufacture industrially stably using such low-temperature annealing, it is necessary to solve the problem of the steel plate shape deteriorating, the time-consuming work load which takes a long time to replace an annealing atmosphere, or change a furnace condition.

Therefore, various studies on the steel component have been conducted. By making the steel composition in which Ti is excessively added to C and N, the strength is increased even at a finish annealing temperature of 700 ° C. or higher, which is equivalent to the annealing of a conventional non-oriented electrical steel sheet. It was found that effective recovery tissue is obtained stably.

(Experiment 1)

That is, the result of having examined the influence of Ti addition amount and finishing annealing temperature (cracking time 20s) on recrystallization behavior of 2.8% Si-0.35% Al steel reduced to C + N <= 0.01% is shown in FIG. Here, the horizontal axis of the graph is Ti amount (mass%) and the vertical axis is annealing temperature (° C), and the numbers in each circle represent the recrystallization ratio (area%) under the conditions. Moreover, the recrystallization rate is also computed from the optical structure observation result of a plate thickness direction cross section, and the ratio (area%) of unrecrystallized recovery structure is 100-recrystallization rate (area%).

Usually, in the non-oriented electrical steel sheet, Ti is a harmful element that deteriorates the magnetic properties, and it is generally controlled to 0.005% by mass or less, but at this Ti-containing level, since recrystallization proceeds rapidly at 650 ° C or higher, it is stable. In order to obtain a recovery structure, it is necessary to perform finish annealing at a low temperature below 600 ° C.

On the other hand, when 0.05 mass% or more of Ti was added, recrystallization start temperature rose 100 degreeC or more, and also it discovered that the recovery structure was obtained stably also in the annealing temperature 700 degreeC or more conventionally performed industrially. Then, by setting the finishing annealing temperature of 700 ° C. or more and 850 ° C. or less and the furnace tension of 2.5 MPa or more and 20 MPa or less, it was found that the recovery structure was stably obtained and that the shape of the steel sheet was also controlled well. The high strength non-oriented electrical steel sheet excellent in shape and productivity, and its manufacturing method were completed.

Next, the principle of invention of said (3) and (4) is demonstrated.

Hereinafter, the experimental result which became the basis of this invention is demonstrated.

(Experiment 2)

First, in order to investigate the effect of steel composition on the manufacturability of high alloy steels with a Si content of more than 3.5%, a cold crucible induction melting furnace, which can produce ultra-high purity steel, is used. While controlling the amount of Si in the range of 4.1 to 4.3%, the test ingot which changed the amount of C and N in various ways was melted. Subsequently, the obtained steel ingot was hot rolled to a sheet thickness of 2 mm, and then subjected to annealing (hot rolled sheet annealing) at 900 ° C., followed by cold rolling to a plate thickness of 0.35 mm.

At that time, the hot-rolled annealing plate was cut out to a width of 30 mm, a repeated bending test with a bending radius of 15 mm and a bending angle of 90 ° was carried out at a temperature of 30 ° C. to simulate the sheet-flow characteristics in the production line. In addition, it is known that the breaking frequency in the production line increases when the material is less than ten times of the repeated bending. Moreover, as an evaluation of cold rolling property, the edge crack length of the cross section of the said hot rolled annealing plate was measured.

2 and 3 show the results. Here, the horizontal axis of the graph is the (C + N) amount in the steel (mass%), and the vertical axis is the sheet-passability (the number of bendings) and the cold rolling property (edge crack depth of the rolled plate cross section) (mm) in the production line, respectively. to be.

As shown to FIG. 2 and FIG. 3, it became clear that the sheet | seat property (bending characteristic of a hot rolled sheet) and cold rolling property (edge crack depth), ie, manufacturability, in a manufacturing line strongly depend on the total amount of C and N. FIG. In other words, if C + N is reduced to 0.0015% or less in total, sufficient manufacturability is exhibited even in high alloy steel of 4.2% Si class, but if the amount of C + N is increased, the manufacturability deteriorates rapidly.

However, with the current technology using general equipment such as converter refining and degassing secondary refining, it is very difficult to make the C + N amount normally 0.0015% or less.

(Experiment 3)

Therefore, in consideration that the solid solution C and N present in the steel may be the main cause of the deterioration of the manufacturability evaluated this time, an attempt was made to precipitate-fix C and N by adding a tantalum generating element.

That is, the amount of Si is controlled in the range of 4.1 to 4.3% using an electric furnace, and the total amount of C + N is (1) 0.0038 to 0.0048%, (2) 0.0074 to 0.0092%, and (3) 0.0175. The steel ingot which controlled to 4 levels of the range of-0.0196% and (4) 0.0353-0.0391%, and changed the amount of Ti addition variously was produced. Subsequently, it hot-rolled to plate | board thickness: 2 mm, performed hot-rolled sheet annealing at 900 degreeC, cold rolled to plate | board thickness: 0.35 mm, and finish annealing was performed at 950 degreeC.

About the sample obtained in this way, it carried out similarly to the above, and the result which investigated the sheet | seat property (bending characteristic of a hot rolled sheet) and cold rolling property (edge crack depth) in a manufacturing line is shown to FIGS. 4-7. Represent each. Here, the horizontal axis of FIGS. 4 and 6 is Ti amount (mass%) in steel, and the horizontal axis of FIGS. 5 and 7 is C + N amount (sum of C amount in steel and N amount in steel: mass%). It is ratio of Ti amount (mass%) in steel, ie, Ti / (C + N). In addition, the vertical axis | shaft of FIG. 4 and FIG. 5 is the board | substrate property (number of bending times) in a manufacturing line, and the vertical axis | shaft of FIG. 6 and FIG. 7 is cold rolling property (edge crack depth of the rolling plate cross section) (mm). In addition, in the figure, black rhombus ◆ C + N said level (1), black square ■ is the same level (2), black triangle ▲ is the same level (3), bracing × is the same level (4) Respectively.

From these results, by adding excess Ti at an atomic ratio of about 4 times or more (16 times or more by mass% ratio) to the amount of C + N, the bending properties and cold rolling properties of the hot rolled sheet are remarkably improved, resulting in industrial mass production. It was proved that even if the amount of C + N of the purity level which can be achieved can manufacture a high alloy steel stably.

However, when the amount of C + N is too large, the effect of improving the manufacturability by adding Ti is small, and both the number of bending of the hot rolled sheet and the depth of the edge cracking of the cold rolled steel are at levels that are a problem in industrial production (number of bending: less than 10 times, edge cracking depth: More than 3 mm).

Further, even at the C + N amount level where the manufacturability is sufficiently improved by Ti addition, it was found that the manufacturability deteriorated when the Ti addition amount exceeded 0.8%. In addition, in the composition with a large amount of C + N and a small amount of Ti and an excessive amount of Ti, the edge crack at the time of cold rolling reached 10 mm or more, and plate breakage was also generated.

(Experiment 4)

Next, the mechanical property and the fatigue property were investigated using the test piece cut out from the obtained steel plate parallel with a rolling direction. Here, the mechanical property was evaluated by the tensile strength in a tensile test using JIS5 tensile test piece (parallel part length 25mm). In addition, the fatigue characteristics were examined by a partial tensile (tensile-tension) fatigue test with a stress ratio of 0.1 and a frequency of 20 Hz, using a fatigue test piece having a parallel part length of 15 mm, and the plate fracture after 10 million (107) cycles. The maximum stress which does not arise was calculated | required as a fatigue limit.

The obtained result is shown to FIG. 8 and FIG. Here, the horizontal axis of the graph is Ti amount (mass%) in steel, the longitudinal axis of FIG. 8 is the tensile force (TS) (MPa), and the vertical axis of FIG. 9 is the fatigue limit (MPa). In addition, the relationship between the level of the plotted symbol and the amount of C + N is the same as in Figs.

As shown in Fig. 8, the tensile strength TS increased with the amount of Ti added, and the effect was remarkable as the amount of C + N increased. This reason can be considered that the higher the amount of C + N steel, the higher the strength due to the precipitation strengthening caused by the precipitation of carbonitride of Ti. On the other hand, in steel with a small amount of C + N and steel in which the Ti addition amount is excessively large relative to the amount of C + N, it is presumed that the strength of solid solution Ti is mainly increased.

Moreover, as shown in FIG. 9, compared with the result of tensile strength, the fatigue limit showed the higher fatigue characteristic in the group with less C + N amount as compared with the result of a pull force. This is presumably because in the group having a large amount of C + N, the precipitated carbonitride size tends to be large and its abundance is large, and thus, the starting point of fatigue fracture is large.

In addition, the result of having evaluated the magnetic characteristic by the Epstein method using the test piece for magnetic measurements cut out from the rolling direction and the rolling perpendicular direction in the same number is shown in FIG. Here, the horizontal axis of the graph is Ti amount (mass%) in steel, the vertical axis is high frequency iron loss (W _10/1000 ) (W / kg), and the symbol of C + N level is the same as that of FIGS.

As shown in the figure, in the group with a large amount of C + N, the iron loss characteristics deteriorated rapidly due to the addition of a small amount of Ti, whereas in the group in which the amount of C + N was suppressed, the deterioration of iron loss due to the addition of Ti was slight.

From the above results, in order to obtain a non-oriented electrical steel sheet which satisfies the contrary demands of industrially sufficient manufacturability, high strength considering the fatigue strength, and excellent magnetic properties in a high dimension, the amount of C + N can be industrially possible. It has been found that it is important to utilize Ti as an element that precipitates and fixes solid solution C and N and as a solid solution strengthening element in the high alloy steel which has been reduced as much as possible.

Based on the above points, the amount of C + N is reduced to an industrially possible level, and Si, Mn, and Si are based on steel to which an appropriate amount of carbonitride-forming elements (V, Nb, Zr) including Ti is added. Systematic evaluation was performed on the effect of the addition of alloying elements such as Al, Ni, and P, and the optimum steel composition conditions were clarified.

[Steel composition]

EMBODIMENT OF THE INVENTION Hereinafter, the reason for limitation of the component composition range of this invention which was determined based on said viewpoint is demonstrated.

C: 0.010% or less and N: 0.010% or less, and C + N ≦ 0.010%

In the present invention, C and N are harmful elements that significantly reduce the manufacturability of steel when present in a solid solution state, but are carbons such as Ti or Nb, V, Zr (in the invention (3) and (4)) described later. By adding an appropriate amount of a cargo forming element, it is possible to reduce the adverse effect on the manufacturability to a level without difficulty in producing on an industrial scale. Nevertheless, the production of carbonitride also causes deterioration of magnetic properties and fatigue properties, and therefore it is desirable to reduce C and N as much as possible. Therefore, C: 0.010% or less, N: 0.010% or less, and C + N?

Preferably it is C: 0.005% or less and N: 0.005% or less, More preferably, it is C: 0.003% or less, and N: 0.003%. Although it is not necessary to contain C and N, the minimum which can be industrially reduced is about 0.0001%, respectively.

Si: 1.5% or more and 5.0% or less:

Si is a main element constituting the non-oriented electrical steel sheet, which is generally used as a deoxidizer and has an effect of increasing the electrical resistance of steel to reduce iron loss. It also has high employment reinforcement. That is, compared with other solid solution strengthening elements, such as Mn, Al, and Ni, which are added to a non-oriented electrical steel sheet, since it is an element which can balance the high tension tension, high fatigue strength, and low iron loss in the most balanced manner, this invention In (1) and (2), it adds at 1.5% or more. More preferably, it is 2.0% or more. In the present invention (3) and (4), more than 3.5% is added more aggressively, and the high characterization by increasing the tensile strength and fatigue limit strength and reducing iron loss obtained with the increase in the amount of Si is utilized.

On the other hand, when the amount of Si exceeds 5.0%, the tensile strength increases, but the fatigue limit strength decreases drastically, and as the cracks occur during cold rolling, the manufacturability decreases. This reason is considered to be because a regular phase is produced with high Si. Moreover, when Si amount exceeds 3. toughness will begin to fall, and when it exceeds 4.0%, toughness deterioration will show up clearly. In addition, when it exceeds 5.0%, toughness deterioration becomes remarkable, high control is required at the time of sheet metal and rolling, and productivity also falls. Therefore, the upper limit of the amount of Si was 5.0%. Preferably it is 4.0% or less. In the case of focusing on toughness in the inventions (1) and (2), the content is more preferably 3.5% or less.

Ti: 0.05% or more and 0.8% or less, and Ti / (C + N) ≥16 (Invention (1) and (2))

Any one of the following conditions (Invention (3) and (4))

(3-1) Ti + V: 0.01% or more and 0.8% or less, and (Ti + V) / (C + N) ≥ 16,

(3-2) Nb + Zr: 0.01% or more and 0.5% or less, and (Nb + Zr) / (C + N) ≧ 10,

Or (3-3) 0.01% ≦ (Ti + V + Nb + Zr) ≦ 0.5%,

Also (Ti + V + Nb + Zr) / (C + N) ≥16

Ti is an important element in this invention. That is, Ti has the effect of raising the recrystallization temperature of steel, and has the effect of being able to remain unrecrystallized structure enough in this invention (1) (2) even if it raises the finishing annealing temperature of steel plate to 750 degreeC or more. . In addition, Ti also acts as a solid solution strengthening element, contributing to high tension tension. To stably exhibit these effects, Ti: 0.05% or more and Ti / (C + N) ≧ 16 is required. On the other hand, when Ti exceeds 0.8%, a defect called a peeling defect tends to occur, and the upper limit is made 0.8% because manufacturability and yield decrease.

In addition, Ti has an effect of forming carbonitride and precipitating and solidifying solid solution C and N present in the steel to improve the manufacturability of the high alloy steel. It also acts as a solid solution strengthening element, effectively contributing to the increase in high tensile strength and fatigue fatigue. Especially in this invention (3) * (4) which adds more than 3.5% of Si, and utilizes solid solution strengthening as much as possible, these effects are utilized. That is, it is assumed to be 0.01% or more and 0.8% or less, and (Ti + V) / (C + N) ≧ 16 in combination with V, which is the same carbonitride-forming element and the solid solution strengthening element. In order to stably fix and fix C and N during the manufacturing process, it is necessary to contain 0.01% of Ti and V in total Ti + V at least, and to add C and N in excess. It is contained in the range which satisfy | fills (Ti + V) / (C + N) ≥16 by mass% ratio. Preferably it is 0.05% or more by Ti + V. On the other hand, when Ti + V exceeds 0.8%, since manufacturability falls, the upper limit of Ti + V is set to 0.8%.

Nb and Zr also have the effect of forming carbonitrides and depositing and solidifying solid solution C and N present in the steel in the same way as Ti and V described above to improve the manufacturability of the high alloy steel. It also acts as a solid solution strengthening element and contributes effectively to high tension tension and fatigue fatigue. For this reason, in this invention (3) * (4), you may use these elements instead of Ti or V. FIG. In order to stably fix and fix C and N during the manufacturing process, it is necessary to contain 0.01% of Nb + Zr in total at the minimum of Nb and Zr, and to add C and N in excess. It was made to contain in the range which satisfy | fills (Nb + Zr) / (C + N) ≥10 by mass% ratio. On the other hand, when Nb + Zr exceeds 0.5%, since manufacturability falls, the upper limit of Nb + Zr is set to 0.5%.

As mentioned above, since Ti, V, Nb, and Zr all have the same effect as a carbonitride forming element and as a solid solution strengthening element, these 4 types can also be compounded and contained. In this case, in order to stably fix and fix C and N during the manufacturing process, 0.01% of Ti, V, Nb, and Zr are required to contain 0.01% of the total Ti + V + Nb + Zr. Since it is necessary to add in excess excessively with respect to N, it is necessary to satisfy (Ti + V + Nb + Zr) / (C + N) ≥16 by mass% ratio. However, when Ti + V + Nb + Zr exceeds 0.5%, the manufacturability decreases, so the upper limit of Ti + V + Nb + Zr is 0.5%.

In addition, since Ti is remarkably superior to Nb, V, and Zr in securing an unrecrystallized recovery structure and achieving both high strength and magnetic properties, Ti is essential for the present invention (1) and (2).

ㆍ Mn: 3.0% or less

Mn is an element effective for improving hot brittleness in addition to being an element effective for improving strength by solid solution strengthening, and preferably added at 0.03% or more. However, since excessive addition results in deterioration of iron loss, the amount of addition is limited to 3.0% or less.

ㆍ Al: 3.0% or less

Al has the effect | action which raises the electrical resistance of steel and reduces iron loss in addition to the effect which acts as a strong deoxidizer. Moreover, it is effective for strength improvement by strengthening solid solution. However, since excessive addition leads to the deterioration of rolling property, the upper limit is made into 3.0%. More preferably, it is 2.0% or less. In this invention (1) * (2) which mainly uses reinforcement by a non-recrystallized structure, it is preferable to make Si + Al <= 4.0%.

In addition, this Al does not necessarily need to be contained. For example, you may suppress addition of Al to 0.005% or less. That is, for example, deoxidation with Si can reduce Al, while deposits such as AlN can be reduced to reduce iron loss. However, the lower limit of the amount of Al in the steel that can be industrially reduced is about 0.0001%.

ㆍ P: 0.2% or less

P is very effective for high strength, and is preferably added at 0.005% or more because a large solid solution strengthening ability can be obtained even with a relatively small amount of addition. However, since excessive addition causes grain boundary cracking and rolling property deterioration by embrittlement by segregation, the addition amount is limited to 0.2% or less, preferably 0.20% or less. However, the lower limit of the amount of P in steel that can be industrially reduced is about 0.001%.

ㆍ S: 0.01% or less

S, when present in excess, forms sulfides such as MnS and degrades magnetic properties. MnS may also be a starting point for fatigue failure. For this reason, although it is preferable to reduce the amount of S in steel as much as possible, since it can accept as much as 0.01% of content, the addition amount was made into 0.01% or less. However, the lower limit of the amount of S in the steel that can be industrially reduced is about 0.0003%.

ㆍ Other

The basic composition of the non-oriented electrical steel sheet according to the present invention is as described above, but in addition to the above components, Ni, Sb, Sn, B, Ca, rare earth elements (Rem) and Co, which are known as elements for improving magnetic properties, may be used alone or in combination. Can be added. However, these addition amounts should be such that they do not impair the object of the present invention. Specifically, the range is as follows. Sb: 0.002 to 0.1%, Sn: 0.002 to 0.1%, B: 0.001 to 0.01%, Ca: 0.001 to 0.01%, Rem: 0.001 to 0.01%, Co: 0.2 to 5.0% and Ni: 5.0% or less, preferably Is 0.1 to 5.0%.

In particular, addition of Ni is preferable. That is, while many elements contributing to solid solution strengthening and high-electrode resistance result in the decrease of the saturation magnetic flux density by addition, Ni does not lower the saturation magnetic flux density but improves strength and solid-state resistance by solid-solution strengthening. It is a very effective element that can reduce iron loss. However, since Ni is an expensive element and excessive addition leads to an increase in cost, it is preferable to contain it at 5.0% or less.

In addition, the remainder composition of steel is Fe and an unavoidable impurity. Examples of unavoidable impurities include Cu (which may be mixed when using scrap steel in the raw material) in addition to the above-mentioned elements (when inevitably contained for reasons of cost).

[Strong organization]

Next, the reason for limitation of the steel plate structure in this invention (1) * (2) is described.

In order to achieve both high strength and magnetic properties which are objects of the present invention, the steel sheet structure is preferably a recovery structure. In the processed structure in the rolled state, the magnetic properties are remarkably inferior. On the other hand, when recrystallization advances by finish-annealing, magnetic property will become favorable, but the fall of intensity will increase. In contrast, the recovery tissue is formed by annealing at approximately 500 ° C. or higher, which has a high strength and can obtain relatively good magnetic properties. In the present inventions (1) and (2), it is important to effectively use this recovery structure, and in order to make both the strength and the magnetic properties compatible, the recovery structure of the non-recrystallized material is determined by the area ratio in the thickness section observation of the steel sheet. It is necessary to have more than 50%.

In addition, in the present invention (3) and (4), since the employment reinforcement is the main reinforcing mechanism, it is not necessary to secure an unrecrystallized recovery structure. Therefore, as long as the strength can be ensured, the recrystallized structure may be 100% to ensure more stable industrial productivity. However, it does not exclude using together the use of reinforcement by a non-recrystallization recovery organization.

[Production method]

Finally, the manufacturing method which concerns on this invention is demonstrated, and the reason for limitation is described.

In this invention, the manufacturing process from a steel solvent to cold rolling can be performed according to the method normally employ | adopted by the general non-oriented electrical steel sheet. In particular, the present invention relates to a high alloy steel having a Si content of more than 3.5%, which is generally a problem in the sheeting and cold rolling properties of the hot rolled coil by controlling the appropriate amount of C and N and the addition of carbonitride-forming elements. Also, since the manufacturability has been greatly improved, a conventional non-oriented electrical steel sheet production process can be applied.

Examples of typical production methods are given below.

First, molten steel which has been melted with a predetermined component in a converter, secondary refining, or an electric furnace is made into a steel slab by the continuous casting method or the ingot-disintegration method.

Next, although hot rolling is performed to steel slab, the finishing temperature and winding temperature in the said hot rolling do not need to be specifically defined, General conditions, for example, finish rolling temperature: 700 degreeC-900 degreeC, and winding temperature : 400-800 degreeC is good.

Next, if necessary, hot rolled sheet annealing can be performed at a temperature of about 600 to 1100 ° C for the purpose of softening the steel sheet or improving the magnetic properties of the final product.

After hot-rolled sheet annealing (after winding up if hot-rolled sheet annealing is not performed), cold rolling or warm rolling is performed, and it is set as predetermined product sheet thickness (final board thickness). In addition, it is good also as a final board thickness by one cold rolling or a warm rolling, and you may make it the final board thickness by performing two or more cold rolling or warm rolling which interposed the intermediate annealing. In addition, warm rolling is normally performed at 100-300 degreeC of plate temperature.

Moreover, it is preferable to make final board thickness into 0.15 mm or more.

In other words, the plate thickness has a large influence on the magnetic properties of the product, particularly the iron loss characteristics in the high frequency range of several hundred Hz or more, which is important when used as a rotor material of a high speed rotary motor, and in this respect, the thinner the plate thickness is, the more advantageous. On the other hand, as a result of examining the effects of the product plate thickness on the mechanical properties, fatigue properties and magnetic properties, the mechanical properties in the tensile test are hardly affected by the plate thickness, whereas the fatigue properties are abrupt when thinner than 0.15 mm. It was degraded. In addition, excessive thinning becomes disadvantageous in terms of productivity due to an increase in the number of press punching operations and an increase in the number of laminations in the motor manufacturing process. Therefore, especially when fatigue strength is important, it is preferable that the minimum of plate | board thickness shall be 0.15 mm. Moreover, about the upper limit of plate | board thickness, although it can determine suitably according to the level of the magnetic property required, what is generally used as an electrical steel sheet is 0.65 mm or less. Further, in the present invention, deterioration of the magnetic properties accompanying high strength is suppressed compared to conventionally known high strength electrical steel sheets, and when the equivalent strength level and the plate thickness are used, magnetic properties superior to conventional steels can be obtained.

Subsequently, finish annealing is performed in a continuous annealing furnace, and the annealing conditions are separately defined as the inventions (1) and (2) and the inventions (3) and (4).

In the inventions (1) and (2), the furnace tension per unit cross-sectional area of the steel strip (the direction perpendicular to the plate, the cross-sectional area of the so-called TD direction cross section) is maintained at 2.5 MPa or more and 20 MPa or less, and is 700 ° C. or more and 850 ° C. or less. It is important to carry out in the temperature range. By finish-annealing the rolled coil made of the steel composition of the present invention under the above conditions, the restoring structure of the unrecrystallized crystal remains in the steel sheet, thereby achieving both magnetic properties and high strength, and exhibiting sufficient coil shape correction effects. have.

That is, when annealing temperature is less than 700 degreeC or less than 2.5 Mpa of tension, shape correction is not enough. On the other hand, when it exceeds 850 degreeC, since recrystallization advances, a fall of intensity | strength is caused. In addition, when the furnace tension exceeds 20 MPa, local deformation may occur in the coil and the shape may deteriorate or break in the furnace. Therefore, the upper limit is 20 MPa. From a viewpoint of improvement of a steel plate shape, a more preferable operating range is finishing annealing temperature of 750 degreeC or more and 850 degrees C or less, and furnace pressure of 5 Mpa or more and 15 Mpa or less.

In addition, it is preferable to control annealing conditions, such as finishing annealing temperature, so that 50% or more of unrecrystallized recovery structure may be ensured by area ratio. The annealing conditions substantially satisfy the requirements, but when the amount of Ti in the steel is less than 0.3%, the finish annealing temperature T (° C.) is estimated in FIG.

T≤850-160 (0.3-x) (where x = Ti content in steel: mass%)

It is preferable from the viewpoint of ensuring more than 50% of the unrecrystallized recovery tissue more reliably.

In addition, in this invention (3) * (4), finish annealing is performed in the range of annealing temperature: 700 degreeC or more and 1050 degrees C or less. If the finishing annealing temperature is less than 700 ° C, recrystallization does not proceed sufficiently and unrefined grains are unnecessarily increased, so shape correction becomes insufficient. In addition, the magnetic properties also become stable at 700 ° C or higher. Iron loss characteristics improve with an increase in annealing temperature, but mechanical properties (bearing strength, tensile strength) and fatigue characteristics tend to decrease, so the annealing temperature can be appropriately determined according to the required magnetic property level and strength level. . It is 900-1050 degreeC, More preferably, it is 925-1025 degreeC from a viewpoint of iron loss characteristics in high frequency ranges, such as a commercial frequency (50-60 Hz)-several kilohertz. However, if the finish annealing temperature exceeds 1050 ° C., not only the improvement of the magnetic properties will be seen, but also the mechanical properties will be lowered and the energy will be disadvantageous. Therefore, the upper limit is limited to 1050 ° C.

Following the finishing annealing, an insulating coating is applied to the steel sheet by application of a processing liquid and baking to obtain a final product. The kind, film thickness, provision conditions, etc. of an insulation film should just be a normal range. For example, a phosphate coating etc. are used preferably.

(Example 1: Invention (1) and (2))

After hot-rolling the steel slab of the component composition shown in Table 1 to 2.5 mm of sheet thicknesses, after performing hot-rolled sheet annealing hold | maintained at 900 degreeC for 60 s, acid wash and cold rolling to 0.35 mm of sheet thickness were implemented. Here, in the steel G whose Ti amount exceeds the range of the present invention, since a peeling defect occurred after cold rolling, subsequent processing was not performed. In addition, steel N with a high Si content of 4.3% and almost no Ti, and steel P with an Si content exceeding the present invention range were not broken because the plate was broken during cold rolling. Next, finish annealing with a crack time of 20 s was performed under the conditions shown in Table 2. In addition, the in-house tension was measured with an in-house tension meter of a tension meter roll system in which the load cell was mounted on the lower part of the bearing.

The mechanical properties of the steel sheet thus obtained were evaluated using a JIS No. 5 tensile test piece cut parallel to the rolling direction, and an equivalent amount of Epstein test pieces were taken from the rolling direction and the rolling right direction for magnetic properties. It was.

Moreover, the steel plate was cut along the rolling direction, the thickness section was polished, and the structure was observed to determine the area ratio of the recrystallized structure. For structures with a finish annealing temperature of 500 ° C. or more, the area excluding the recrystallized portion was regarded as the recovery structure ratio.

In addition, in accordance with JIS C 2550, the flatness of the steel sheet before and after annealing was also measured.

The above measurement or evaluation result is written together in Table 2.

Note) Steel G: Not processed after delamination bundles during cold rolling

    Steel N, P: Not broken after cold rolling

In Table 2, No. 1, which is a rolled state made of steel A of the conventional composition, and No. 2 annealed at 400 ° C., in which the finish annealing temperature did not reach the recovery temperature of the steel, are made of 100% processed structure, and the tensile strength is Although not high, iron loss is significantly reduced. In addition, No. 3 and No. 4, which were annealed at 600 ° C to 650 ° C and retained the recovery structure, had high strength and tended to improve iron loss, but the flatness was hardly improved before and after annealing, and was insufficient in the form of steel sheet. . On the other hand, in No. 5 and 15b in which the area ratio of the unrecrystallized grains is less than 50%, and the recrystallized grains are mainly, the decrease in strength is remarkable. Moreover, sufficient strength cannot be obtained in No. 33 and No. 41 in which Ti amount in steel does not reach 16 times C + N, and iron loss is high in No. 34 in which C + N exceeds 0.010%.

On the other hand, Nos. 6 to 15, 17 to 19, 32, 35 to 38 and 40, which are invention examples using steel made of the steel composition of the present invention, exhibit high strength and low iron loss and are also excellent in the point of steel plate shape. .

In addition, No.37 with Si amount exceeding 4.0% and No.38 with Si + Al amount exceeding 4.0% have the bending characteristics after hot-rolled sheet annealing 27 times and 23 times, respectively. On the other hand, all other invention examples are 40 or more times, and are more excellent in manufacturability. Here, the bending characteristic is evaluated by the number of times until a crack generate | occur | produces by performing the repeated bending test of a bending radius of 15 mm and a bending angle of 90 degrees at the temperature of 30 degreeC.

(Example 2: Invention (1) and (2))

After hot-rolling the slabs of the steels A and D of Table 1 to a sheet thickness of 2 mm, the hot-rolled sheet annealing was maintained at 800 ° C. for 60 s, followed by acid cleaning and cold rolling to a plate thickness of 0.35 mm, to prepare a coil. . The obtained coil was subjected to finish annealing by a continuous annealing furnace under the conditions shown in Table 3, and the same evaluation as in Example 1 was performed.

The results are written together in Table 3. As can be seen from Table 3, both steels A and D have a small degree of improvement in the shape of the steel sheet even if the furnace tension is increased at 650 ° C. with low annealing temperature. On the other hand, the steel plate shape of the coil which raised to the annealing temperature of 800 degreeC and controlled the furnace tension in the range of this invention is remarkably improved. While this finish annealing increases the strength drop in conventional steel A and is insufficient for use as a high strength material, in steel D according to the present invention, both high strength and excellent steel sheet shape can be achieved.

In addition, when the tension in the furnace exceeds 20 MPa of the upper limit of the appropriate range, iron loss is increased and the steel sheet shape is also deteriorated.

(Example 3: Invention (1) and (2))

The steel slab of the component composition shown in Table 4 was cold-rolled to the final plate | board thickness on the conditions of any one of the following ac.

a: After hot-rolling to 2.0 mm of plate | board thickness, hot rolling is performed without hot-rolled sheet annealing to the final plate | board thickness of 0.35 mm (plate temperature 250 degreeC)

b: After hot-rolling to 3.8 mm of plate | board thickness, it cold-rolled to 1.5 mm without performing hot-rolled sheet annealing, and after carrying out the intermediate annealing which hold | maintained 1000 degreeC-30s after that, it cold-rolled to the final plate thickness of 0.35 mm.

c: After hot-rolling to 2.5 mm of plate | board thickness, after performing the hot-rolled sheet annealing hold | maintained at 1050 degreeC-30 s, cold rolling to 1.0 mm, and carrying out the intermediate annealing which hold | maintained 1000 degreeC-30 s after that, to final plate thickness 0.20 mm Warm rolling (pan temperature 200 ℃)

Subsequently, the finish annealing of crack time 10s was performed on the conditions shown in Table 5, evaluation similar to Example 1 was performed, and the result was written together in Table 5. Each inventive steel achieves excellent strength and magnetic properties.

(Example 4: Invention (3) and (4))

After hot-rolling the steel slab which becomes the component composition shown in Table 6 to hot plate thickness: 2 mm, after performing hot-rolled sheet annealing hold | maintained at 900 degreeC for 60 s, it acid-washed and then cold-rolled to plate thickness: 0.35 mm, The finish annealing which hold | maintained 30s at 950 degreeC was implemented.

At that time, the hot-rolled annealing plate was cut out to a width of 30 mm, and a repetition bending test of a bending radius of 15 mm and a bending angle of 90 ° was performed at a temperature of 30 ° C. to simulate the flowability in the production line. It was. Moreover, the edge crack depth of the rolling plate cross section was measured as evaluation of cold rolling property.

In this way the mechanical properties (tensile strength (TS)), the fatigue properties of the resulting steel sheet (fatigue limit strength (FS)) and magnetic properties (magnetic flux density B _50, high-frequency iron loss W _10/1000) Table 7 shows the results of the investigation.

In addition, the evaluation method of each characteristic is as follows.

Mechanical characteristics were performed using the JIS No. 5 tensile test piece cut out parallel to a rolling direction.

Fatigue characteristics were cut out in parallel with the rolling direction, and the cross section was polished with 800 edges, and then subjected to partial tension (tensile-tensile) with a stress ratio of 0.1 and a frequency of 20 Hz. It evaluated by the maximum stress (fatigue limit intensity | strength (FS)) which plate fracture does not generate | occur | produce after a cycle progress.

Magnetic properties were evaluated by taking an equivalent amount of Epstein test pieces from the rolling direction and the rolling right angle direction.

As shown in Table 7, according to the present invention, the invention examples in which Si is more than 3.5%, the amount of C and N are controlled, and an appropriate amount of Ti are added are all excellent in manufacturability and have high tensile strength and fatigue limit. It turns out that it has a good magnetic characteristic.

(Example 5: Invention (3) and (4))

After hot-rolling the steel slab which becomes the component composition shown in Table 8 to plate | board thickness: 2 mm, after performing hot-rolled sheet annealing hold | maintained at 900 degreeC for 60 s, it acid-cleansed and then cold-rolled to plate | board thickness: 0.25 mm, The finish annealing which hold | maintained 30s at 950 degreeC was implemented.

At that time, the hot rolled annealing plate was cut out to a width of 30 mm, a repeated bending test with a bending radius of 15 mm and a bending angle of 90 ° was performed at a temperature of 30 ° C. to simulate evaluation of the sheet flow in the production line. Moreover, the edge crack depth of the rolling plate cross section was measured as evaluation of cold rolling property.

In this way the mechanical properties (tensile strength (TS)) fatigue properties of the obtained silicon steel sheet (the fatigue limit strength (FS)) and magnetic properties (magnetic flux density B _50, high-frequency iron loss W _10/1000) The result of having investigated about is shown in Table 9.

*) Ti + V> 0.8%

As shown in Table 9, the invention examples in which the steel sheet component is controlled to the amount of C and N satisfying the present invention, and in which an appropriate amount of Ti and V are added, are all excellent in manufacturability, have high tensile strength and fatigue limit, and It can be seen that good magnetic properties are obtained.

On the other hand, when the addition amount of Si exceeds 5%, the deterioration of the bendability and cold rolling property of the hot rolled sheet is increased, and the fatigue limit strength tends to decrease even though the tensile strength is high.

(Example 6: Invention (3) and (4))

After hot-rolling the steel slab which becomes the component composition shown in Table 10 to plate | board thickness: 2.2 mm, performing the hot-rolled sheet annealing hold | maintained at 800 degreeC for 90 s, acid-cleaning, and then cold-rolling to plate | board thickness: 0.30 mm, The finish annealing which hold | maintained 30s at 1000 degreeC was implemented. No.67 only omits hot rolled sheet annealing, hot rolled sheet thickness 3.0mm → no hot rolled sheet annealing → warm rolling to sheet thickness 1.5mm (pan temperature 280 ℃) → 900 ℃ -30s intermediate annealing → cold rolled sheet thickness 0.30mm The rolling process called was adopted.

Further, the hot rolled annealing plate (No. 67 is a hot rolled plate) was cut out to a width of 30 mm, a repeated bending test of a bending radius of 15 mm and a bending angle of 90 ° was carried out at a temperature of 30 ° C., and the sheetability in the production line was obtained. Was simulated. Moreover, the edge crack depth of the rolling plate cross section was measured as evaluation of cold rolling property.

In this way the mechanical properties (tensile strength (TS)) fatigue properties of the obtained silicon steel sheet (the fatigue limit strength (FS)) and magnetic properties (magnetic flux density B _50, high-frequency iron loss W _10/1000) The result of having investigated about is shown in Table 11.

*) Nb + Zr> 0.5%

**) (Ti + V + Nb + Zr) / (C + N)

＊) Hot rolled to 3.0mm thickness → No hot-rolled sheet annealing → Warm rolling to 1.5mm thickness (plate temperature 280 ℃) → 900 ℃ -30s Intermediate annealing → Cold rolled to final thickness 0.30mm

As shown in Table 11, the invention examples in which the steel sheet component was controlled to the amount of C and N satisfying the present invention, and the optimum Nb, Zr, or additionally, Ti and V were all excellent in manufacturability and high tensile strength. It has an excessive fatigue limit and also has good magnetic properties.

(Example 7: Invention (3) and (4))

Composition 3.9% Si, 0.14% Mn, 0.33% Al, 2.67% Ni, 0.02% P, 0.002% S, 0.0009% C, 0.0018% N, 0.28% Ti and 0.055% Sn composition (Ti) /(C+N)=103.7) steel slab after hot rolling to plate thickness: 2 mm, after performing hot-rolled sheet annealing maintained at 1000 ° C. for 60 s, followed by acid cleaning and then cold rolling to various plate thicknesses And finish annealing maintained at 950 ° C for 30 seconds to investigate the effect of plate thickness on each characteristic.

The obtained results are shown in Table 12.

As shown in Table 12, the high frequency iron loss characteristics are greatly improved by reducing the plate thickness. In addition, the tensile strength is almost the same in any plate thickness.

However, fatigue limit strength improves more remarkably that plate | board thickness is 0.15 mm or more.

According to the present invention, non-directional electrons having high strength or excellent fatigue characteristics, and also excellent plate shape and magnetic properties, without restricting the composition or additional structure, without adding constraints on steel sheet production or new processes. Steel sheet can be obtained stably.

Claims (10)

In mass%, C and N, C: 0.010% or less and N: 0.010% or less, Furthermore, C + N ≤ 0.010%, Si: 1.5% or more and 5.0% or less, Mn: 3.0% or less, Al: 3.0% or less, P: 0.2% or less, S: contains 0.01% or less, and further Ti is contained in the range of 0.05% or more and 0.8% or less, and satisfying Ti / (C + N) ≥ 16, and has a component composition that is balance Fe and an unavoidable impurity, Furthermore, the high strength non-oriented electrical steel sheet whose ratio of unrecrystallized recovery structure in a steel plate is 50% or more by area ratio. The method of claim 1, A high strength non-oriented electrical steel sheet having a mass% of Si: 1.5% or more and 4.0% or less. The method according to claim 1 or 2, In mass%, Ni: 0.1-5.0%, Sb: 0.002-0.1%, Sn: 0.002-0.1%, B: 0.001-0.01%, Ca: 0.001-0.01%, Rem: 0.001-0.01%, and Co: 0.2-1.0 High strength non-oriented electrical steel sheet further containing at least 1 sort (s) chosen from the group which consists of 5.0%. In mass%, C and N, C: 0.010% or less and N: 0.010% or less, Further, C + N ≤ 0.010%, Si: over 3.5% and 5.0% or less, Mn: 3.0% or less, Al: 3.0% or less, P: 0.2% or less S: 0.01% or less, or further Ni: 5.0% or less, Furthermore, any 1 type or 2 types of Ti, V, Total: 0.01% or more and 0.8% or less, and contained in a range satisfying (Ti + V) / (C + N) ≥ 16, The balance is a high strength non-oriented electrical steel sheet which is composed of Fe and unavoidable impurities. In mass%, C and N, C: 0.010% or less and N: 0.010% or less, Further, C + N ≤ 0.010%, Si: over 3.5% and 5.0% or less, Mn: 3.0% or less, Al: 3.0% or less, P: 0.2% or less S: 0.01% or less, or further Ni: 5.0% or less, Further, any one or two of Nb and Zr, Total: 0.01% or more and 0.5% or less, and contained in a range satisfying (Nb + Zr) / (C + N) ≥ 10, The balance is a high strength non-oriented electrical steel sheet which is composed of Fe and unavoidable impurities. In mass%, C and N, C: 0.010% or less and N: 0.010% or less, Further, C + N ≤ 0.010%, Si: over 3.5% and 5.0% or less, Mn: 3.0% or less, Al: 3.0% or less, P: 0.2% or less S: 0.01% or less, and further Ni: 5.0% or less, Further, at least one of Ti and V and at least one of Nb and Zr, 0.01% ≤ (Ti + V + Nb + Zr) ≤ 0.5%, also (Ti + V + Nb + Zr) / (C + N) ≥ 16 Contained in a range satisfying The balance is a high strength non-oriented electrical steel sheet which is composed of Fe and unavoidable impurities. The method according to any one of claims 4 to 6, By mass%, Sb: 0.002 to 0.1%, Sn: 0.002 to 0.1%, B: 0.001 to 0.01%, Ca: 0.001 to 0.01%, Rem: 0.001 to 0.01% and Co: 0.2 to 5.0% High strength non-oriented electrical steel sheet further containing one or two or more. In mass%, C and N, C: 0.010% or less and N: 0.010% or less, Furthermore, C + N ≤ 0.010%, Si: 1.5% or more and 5.0% or less, Mn: 3.0% or less Al: 3.0% or less, P: 0.2 mass% or less S: 0.01 mass% or less, and further Hot-rolled steel slabs having a component composition containing Ti in a range of 0.05% by mass or more and 0.8% by mass or less and satisfying Ti / (C + N) ≧ 16, Subsequently, after cold or warm rolling into a cold rolled coil of final sheet thickness, The method of manufacturing a high strength non-oriented electrical steel sheet, in which the finish annealing is performed at annealing temperature of 700 ° C. or higher, 850 ° C. or lower, and an in-house tension of 2.5 MPa or more and 20 MPa or less. Steel slab which becomes the composition shown in any one of Claims 4-7, After hot rolling, after performing hot-rolled sheet annealing as needed, The final sheet thickness is obtained by one or more cold rolling or warm rolling with one cold rolling or warm rolling or intermediate annealing, Subsequently, annealing temperature: The manufacturing method of the high strength non-oriented electrical steel sheet which carries out finish annealing on the conditions of 700 degreeC or more and 1050 degrees C or less. The method of claim 9, A method for producing a high strength non-oriented electrical steel sheet, wherein the final sheet thickness is 0.15 mm or more.

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