KR20020033021A - Method f0r producing a grain-oriented electrode steel sheet of sheet shaping having the high magnetic flux density - Google Patents

Abstract

PURPOSE: To provide a cold rolling method for obtaining a grain oriented silicon steel sheet using AlN as an inhibitor by which thinning can be combined with increase of magnetic flux density. CONSTITUTION: In the method for manufacturing the grain oriented silicon steel sheet: a slab having a composition containing 0.025-0.100% C, 2.5-4.5% Si and 0.007-0.040% Al is hot-rolled; the resultant plate is cold-rolled one or more times after hot rolled plate annealing or while process-annealed between the cold rolling stages; and the resultant sheet is subjected to primary recrystallization annealing and then to secondary recrystallization annealing. In the method of cold rolling for obtaining the grain oriented silicon steel sheet of < =0.23 mm product sheet thickness having high magnetic flux density, final cold rolling after the hot rolled plate annealing or the process annealing is performed using a reversing mill constituted of a housing splittable into the upper and the lower part in such a way that: at passes in the former stage of rolling, rolling is carried out using work rolls of 95-180 mmΦ diameter at least to < =0.40 mm intermediate sheet thickness; in the stage of sheet thickness midway through the rolling, the sheet is held at 100-350°C at least for >=1 min; and subsequent rolling to Tf (mm) product sheet thickness is performed by replacing the above work rolls by work rolls of < =(Tfx520) mm diameter.

Description

Manufacturing method of high magnetic flux density thin unidirectional electrical steel sheet {METHOD F0R PRODUCING A GRAIN-ORIENTED ELECTRODE STEEL SHEET OF SHEET SHAPING HAVING THE HIGH MAGNETIC FLUX DENSITY}

TECHNICAL FIELD This invention relates to the manufacturing method of the unidirectional electrical steel plate used for iron core materials of electrical appliances, such as a transformer and a generator.

The unidirectional electrical steel sheet should have good magnetization and iron loss characteristics in the rolling direction. The good and bad magnetization characteristics are determined by the high and low magnetic flux density which is induced in the iron core in a given magnetic field, and the high magnetic flux density can reduce the core size. Iron loss is the power loss consumed as thermal energy when a predetermined alternating magnetic field is applied to the iron core. The magnitude of magnetic flux density, sheet thickness, film tension, impurity amount, specific resistance, grain size, and magnetic domain width are affected by the good and bad. Crazy Among them, high magnetic flux density and thin plate thickness are important for reducing iron loss.

At present, according to the progress of manufacturing technology, for example, in a sheet thickness of 0.23 mm, the magnetic flux density B8 (value at the magnetization force 800 A / m) is 1.92T, the iron loss W17 / 50 (a maximum of 1.7T at 50 Hz). The value at the time of magnetization), such as 0.85 W / kg excellent product can be produced on an industrial scale. However, in recent years, as a countermeasure against global warming, there has been a demand for the development of a new high magnetic flux density thin plate type unidirectional electrical steel sheet having a plate thickness of 0.20 and 0.18 mm.

The unidirectional electrical steel sheet having such excellent magnetic properties is composed of a crystal structure in which [110] <001> orientation, which is an easy magnetization axis of iron, is formed precisely in the rolling direction of the steel sheet. It is formed through a phenomenon called secondary recrystallization which preferentially massively grows grains having a [110] <001> orientation called a Goss orientation.

As a basic requirement for sufficiently growing such goth bearing grains, in the second recrystallization process, the presence of an inhibitor that inhibits the growth of crystal grains having undesirable orientations other than the goose orientation, and It is well known that the formation of primary recrystallized tissues that are likely to develop preferentially is indispensable.

At this time, as an inhibitor, precipitates such as AlN, Mn (S, Se), Cu ₂ (S, Se) and the like are generally used, and components having a strong grain boundary segregation tendency such as Sn and Sb are used as auxiliary. In addition, it is important for the primary recrystallized structure to have a grain structure in which the grain size and its uniformity, azimuth grains having a corresponding relationship with the high-orientation grains and the high-orientation grains are formed in the rolling direction.

The method of obtaining the unidirectional electrical steel sheet with a high magnetic flux density is known from the past, For example, as disclosed in Unexamined-Japanese-Patent No. S46-23820, the method of using AlN as an inhibitor is widely known.

Such a method is to produce a unidirectional electrical steel sheet by solidifying the inhibitor component of AlN once by high temperature slab heating (≥1300 ° C) and finely depositing AlN during annealing before final cold rolling.

On the other hand, Japanese Unexamined Patent Publication No. S62-403l5 discloses a method in which an AlN inhibitor is formed by a nitriding treatment in a later step and introduced, followed by low temperature slab heating (≦ 1250 ° C.).

Such a method has been developed to solve equipment and operational problems for high temperature slab heating.

In the manufacturing method using such an AlN inhibitor, it is well known that a high magnetic flux density cannot be obtained unless an appropriate primary recrystallization structure is provided.

Formation of the primary recrystallized structure has a great influence on the cold rolling conditions, and in general, it is preferable that the reduction ratio of the final cold rolling is as high as 81% or more.

Regarding other cold rolling, l) Japanese Unexamined Patent Publication S54-13846 discloses a technique for aging treatment at 50 to 350 ° C. for at least 1 minute between passes of cold-rolled steel. 2) Japanese Unexamined Patent Publication S54-29182 The publication discloses a technique of holding at 300 to 600 ° C. for 1 to 30 seconds.

The technique of 1) is intended for reverse rolling, and the technique of 2) is intended for tandem rolling.

The high temperature rolling using a tandem rolling machine has technical difficulty in installation and operation, and at this time, high temperature rolling is performed using the processing heat of reverse rolling, and the aging effect after winding a reel in the middle of rolling is used.

In general, a reverse rolling mill arranges rolls, such as quadruple and hexagonal, in series. However, when the work roll diameter is reduced, roll deformation tends to occur, and a large diameter roll of 250 mm or more is generally used.

On the other hand, a Zendimere rolling mill and an NMS rolling mill in which rolls such as six, twelve, and twenty rolls are arranged in a cluster shape back up the work rolls in various ways, so that a small diameter work roll can be used.

Since a unidirectional electrical steel sheet contains a large amount of Si, the rolling reaction force is high, and the method of using a small diameter work roll in thinning a product plate thickness is advantageous. Therefore, a cluster type reverse rolling mill is often used for high temperature rolling of a unidirectional electrical steel plate.

On the other hand, with regard to the work roll diameter of a cold rolling machine, 3) Japanese Unexamined Patent Publication No. S50-37130, a technique performed with a small diameter roll of 300 mm or less in the whole pass or the rear pass of rolling, and 4) Japanese Unexamined Patent Publication S02-282422 The technique of carrying out the warm rolling of 150-230 degreeC with the small diameter roll of 30-100 mm (s) in a rear pass to a publication, and 5) Japanese Unexamined-Japanese-Patent H05-33056 by 150-350 degreeC with a small diameter roll of 50-150 mm (ø) in a shear pass. 6) Japanese Unexamined Patent Application Publication No. H09-287025 discloses a technique of raising the rolling temperature (100 to 350 ° C) with increasing diameter of the work roll (40 to 500 mm).

The cluster rolling machine used for the conventional electrical steel sheet has mainly used a small diameter work roll of 95 mm or less from the viewpoint of the mainstream and the rolled rolling mills represented by 21 and 22 types being mainstream.

For example, although the roll diameter was 50-150 mm in the technique of said 5), only the examples of 80 and 90 mm are described in the Example.

In addition, in the production of Al-containing unidirectional electrical steel sheet, as disclosed in the above 3), the cold rolled work roll is preferably a small diameter, and the cluster rolling machine, which is advantageous for thinning, meets such a request. In addition, as disclosed in the above-mentioned 4) to 6), even in the rolling on the premise of the aging treatment between the passes, a small diameter roll is considered to be advantageous from the viewpoint of the magnetic properties.

MEANS TO SOLVE THE PROBLEM The present inventors examined the influence of the work roll diameter on magnetic property in detail about manufacture of the Al containing unidirectional electrical steel plate which age-processes the pass using a cluster type reverse rolling mill. As a result, in the case of rolling with a conventional work roll diameter of 90 mm or less, the magnetic flux density was low, and rather, the magnetic flux density improving effect was found by rolling with a larger work roll with a diameter of 95 to 170 mm. (Japanese Patent Application No. H2000-002944).

However, in manufacture of a thin plate material, a large diameter work roll is disadvantageous from a rolling reaction force viewpoint. Then, it investigated whether the effect of increasing the work roll diameter is effective in the front pass or the back pass of the rolling. As a result, in the shear pass of rolling, it was found that carrying out a large diameter work roll rolling had a larger magnetic characteristic improvement effect.

This is in contrast to the description of 3) and 4) above.

Therefore, in order to manufacture a thin plate material by this invention, it is warm-rolled to the intermediate thickness in the cold rolling mill of the large diameter work roll of 95-170 mm (o), and then finishes in another cold rolling machine by the small diameter roll of 65 mm (or less), for example. As with the method of rolling to plate | board thickness, it rolls with two cold rolling machines.

However, according to such a method, there exists a fault that the fixed cost of cold rolling increases, and productivity is inferior.

This problem can be overcome if, for example, the diameter of the work roll can be changed in one cold rolling machine, but the Zendimere rolling mill represented by 21 and 22 types used in the conventional production of unidirectional electrical steel sheet is a single unit. Since the block-shaped housing is a basic configuration, it is difficult to change the work roll diameter in the middle of the rolling pass.

Therefore, the present inventors first applied a cluster rolling machine composed of a split housing to manufacture a unidirectional electrical steel sheet, rolled the shear pass of the roll to a work roll diameter of 95 mm or more, and deformed the trailing pass into a small diameter roll suitable for sheet rolling. It succeeded in rolling and established the technique which manufactures the thin unidirectional electrical steel plate with high magnetic flux density with one rolling mill with low fixed cost and high productivity. The present invention is an organic combination of metallurgical findings in which the large diameter work roll effect of a cluster rolling mill is considered to be effective at the front end of a rolling pass, and an efficient cold rolling technique of a split housing cluster rolling mill. Same as

(1) hot-rolled an electromagnetic steel slab containing C: 0.025 to 0.10%, Si: 2.5 to 4.5%, and A1: 0.007 to 0.040% by mass, followed by hot rolling annealing to perform one cold rolling, Or in the manufacturing method of the unidirectional electrical steel plate which performs 2 or more cold rolling containing intermediate annealing, and performs primary recrystallization annealing and secondary recrystallization annealing afterwards, Final cold rolling carries out the final cold rolling from 95-300 A method for producing a unidirectional electrical steel sheet having excellent magnetic properties, which is performed by a reverse mill of 180 mm.

(2) After hot-rolling an electromagnetic steel slab containing C: 0.025 to 0.10%, Si: 2.5 to 4.5%, and Al: 0.007 to 0.040% by mass, hot rolled sheet annealing to perform one cold rolling, Or in the manufacturing method of the unidirectional electrical steel plate which performs 2 or more cold rolling containing intermediate annealing, and performs primary recrystallization annealing and secondary recrystallization annealing after that, the final cold rolling is performed with the work roll diameter of 95-95. A method for producing a unidirectional electrical steel sheet having excellent magnetic properties, which is performed by a reverse mill of 180 mm ø and changes the work roll diameter in the sheet thickness step during rolling.

(3) hot-rolling a steel slab containing C: 0.025 to 0.10%, Si: 2.5 to 4.5%, and Al: 0.007 to 0.040% by mass, followed by hot rolling annealing to perform one cold rolling, or In the manufacturing method of the unidirectional electrical steel sheet which carries out 2 or more cold rolling containing an intermediate annealing, and performs a 1st recrystallization annealing and a 2nd recrystallization annealing, the final cold rolling is a work roll diameter of 95-180 mm ø It is carried out by a reverse rolling mill, and in the sheet thickness step during the rolling, the shear pass of the final cold rolling is cold rolled to a middle sheet thickness of at least 0.40 mm or less with a work roll having a diameter of 95 to 180 mm, and then from the intermediate sheet thickness to the final sheet thickness Tf. A method for producing a unidirectional electrical steel sheet having excellent magnetic properties, wherein the work roll diameter is cold rolled by a work roll having a diameter D (mm ø) in which rolling up to (mm) is D ≦ Tf × 520.

(4) In at least 1 time between the passes of the final cold rolling in said cold rolling, steel plate strip temperature is maintained in 100-350 degreeC for at least 1 minute, In (1)-(3) characterized by the above-mentioned. The manufacturing method of the unidirectional electrical steel sheet excellent in the magnetic property of any one of Claims.

(5) The method for producing a unidirectional electrical steel sheet having excellent magnetic properties according to any one of (1) to (4), wherein the electromagnetic steel slab further contains Mn: 0.03 to 0.45% by mass. .

(6) A method for producing a unidirectional electrical steel sheet having excellent magnetic properties according to any one of (1) to (5), wherein the product sheet thickness is 0.23 mm or less.

(7) In the cold rolling, the final cold rolling is performed with one rolling mill as the diameter is changed to work rolls having different diameters at the plate thickness stage during the multi-pass rolling, using a cluster-type inverse rolling mill composed of a housing that can be divided up and down. Rolling is carried out, The manufacturing method of the unidirectional electrical steel sheet excellent in the magnetic property in any one of (1)-(4) characterized by the above-mentioned.

1 is a view showing the relationship between the work roll diameter and the magnetic flux density,

2 is a view showing the relationship between the minimum sheet thickness and magnetic flux density of shear rolling;

3 is a diagram showing an analysis result regarding the primary recrystallized texture of the steel sheet when the work roll diameter is changed;

4 is a view showing the relationship between the work roll diameter and the minimum plate thickness rollable,

5 is a schematic diagram of a 20 stage cluster mill of a single block housing and a split housing.

First, the test result which became the basis of this invention is demonstrated.

[Experiment 1]

Electron steel slabs containing C: 0.005%, Si: 3.3%, Mn: 0.1%, S: 0.07%, Al: 0.0282%, N: 0.0070%, and Sn: 0.07% by mass% were prepared at 1150 ° C. After heating the low temperature slab, hot rolling was performed to form a 1.8 mm thick hot rolled coil.

After the hot rolled coil was annealed at 1100 ° C., a 20-inch Zendimere rolling mill was used to cold-roll at a rolling reduction of 90% to finish a sheet thickness of 0.18 mm. In this case, the work roll diameter of the rolling mill was changed to the range of 40-180 mm (ø), and the pass schedule and the number of passes (five times) were rolled on the same conditions until plate thickness 0.26 mm.

Moreover, the aging treatment for 5 minutes was performed at 200 degreeC in the plate | board thickness step in the middle of 2nd path | route, 3rd path | route, and 4th path | route. Thereafter, rolling from 0.26 mm to 0.18 mm was completed in one pass with a work roll diameter of 60 mm ø.

Subsequently, the cold rolled sheet was subjected to decarburization annealing by adjusting the temperature so that the primary recrystallized grain became 23 µm, followed by nitriding annealing so that [N] was 240 ppm, and then a magnesia slurry was applied. After finish-annealing such a coil by the usual method, "Al + phosphate colloidal silica insulation coating" was apply | coated, and it shape | molded by coating baking, and shape-forming annealing was carried out, and it commercialized. And the magnetic flux density B8 of this product was measured.

The relationship between the work roll diameter and B8 is shown in FIG. It was clear from Fig. 1 that the magnetic flux density B8 was improved in the range of the workpiece roll diameter of 95 to 180 mm.

[Experiment 2]

An electromagnetic steel slab of the same component as in Experiment 1 was heated with a 1150 ° C. low temperature slab and hot rolled to produce a 2.0 mm thick hot rolled coil. After annealing this hot rolled coil at 1100 degreeC, it cold-rolled at 90% of the reduction ratio using the 20-median Zendimere rolling machine, and finished it by 0.20 mm of sheet thickness.

At that time, the work roll diameter of the rolling mill was made into two levels of i) 100 mm ø and ii) 60 mm ø, and rolled to a plurality of intermediate plate thicknesses in the range of 0.60 mm to 0.20 mm.

At this time, the aging treatment for 5 minutes was performed at 200 degreeC in the plate | board thickness step between 2nd pass (1.00mm) and 3rd pass (0.80mm). Subsequently, 0.22 mm or more corresponds to the conditions of said i) and ii), i) was 60 mm (degree) and ii) was deformed into the diameter work roll of 100 mm (degree), respectively, and it rolled to 0.20 mm.

Thereafter, the cold rolled sheet was subjected to decarburization annealing by adjusting the temperature so that the primary recrystallized grain diameter was 23 µm, followed by nitriding annealing so that [N] was 220 ppm, and then magnesia was applied. The coil was subjected to finish annealing in a conventional manner, and coated with "insulation coating of Mg + colloidal silica phosphate", and then subjected to shape correction annealing serving as coating annealing to commercialize. And the magnetic flux density B8 of this product was measured.

The relationship between the minimum plate | board thickness (median plate | board thickness) of the shear rolling, and the magnetic flux density B8 at the time of rolling by changing the work roll diameter in the front end and the rear end pass is shown in FIG.

As a result, under the condition of i) in which the front pass of the rolling is made into a large diameter work roll, when a large diameter work roll is rolled to a plate thickness of at least 0.40 mm, a high B8 can be secured, but the rear end pass is rolled into a large diameter work roll. Ii) could not obtain B8 under any conditions.

As described above, the magnetic flux density of the unidirectional electrical steel sheet affects the inhibitor and the primary recrystallized structure. In [Experiment 1] and [Experiment 2], since [N] after nitriding annealing did not change the inhibitor under a certain condition, it is assumed that the rolling condition influenced the magnetic flux density through the primary recrystallization structure change.

Therefore, primary recrystallization samples corresponding to the work roll diameters of 50, 95, and 150 mm in [Experiment 1] were taken, and the primary recrystallized texture was examined. X-ray analysis was carried out by sampling around a sheet thickness of 1 / 5t, and analysis was performed by the SGH method (raw materials: Japanese Metal Society Bulletin No. 29, No. 7 P552).

Fig. 3 shows the intensity IN around the ND axis of the goth orientation and the intensity Ic 9 of the Σ9 corresponding orientation. Through FIG. 3, the larger the work roll diameter is, the higher the IN strength of the goth bearing (rotation angle is 0 ° C), the smaller the IN strength is about 25 ° away from the ND axis, and the sharper the distribution of IcΣ9 around the ND axis. Able to know. In obtaining a unidirectional electrical steel sheet with a high magnetic flux density, it is required to have many goth azimuths and a Σ9 corresponding orientation for growing the goth first as a condition that the primary recrystallized texture should be provided. By controlling the work roll diameter according to the present invention, a primary recrystallized grain structure suitable for increasing the goose density of secondary recrystallization is obtained.

The above is the result according to the low-temperature slab heating method using the AlN inhibitor, but the present inventors auxiliaryly add MnS, AlN + MnS (MnSe) inhibitor, Sn, Sb, Cu, etc. as shown in Example 1 The same investigation was performed also about the high temperature slab heating method.

As a result, the improvement of the magnetic flux density by the increase of the work roll diameter was confirmed in the whole material of the component system containing AlN as an inhibitor. On the other hand, in the component system which does not contain AlN, the effect could not be confirmed.

AlN is known to have stronger inhibitor strength and thermal stability than MnS (MnSe). When such an AlN inhibitor is used, it is estimated that the primary recrystallized texture obtained by this invention exhibits the effect of improving magnetic flux density effectively.

The mechanism of the relationship between work roll diameter control and primary recrystallized texture is not clear at present, but is hypothesized as follows. It is known that when the work roll diameter is small, the shear deformation component of the steel sheet surface portion increases during cooling rolling, and after the first recrystallization, the (110) plane increases and the (111) plane decreases (Kawano et al .: iron and steel). , 68 (1982), P. 58). At this time, with respect to the (110) plane, it is assumed that the orientation group rotated around the ND axis from the goth azimuth increases, which is an undesirably large aggregate structure that is undesirable for the unidirectional electrical steel sheet. Therefore, it is presumed that sharpening the texture by increasing the diameter of the work roll is effective for increasing the magnetic flux density. In addition, it is judged that the work roll diameter increase effect is effective in the shear pass of rolling because the engagement angle with respect to the material of the work roll is large and the shear deformation component of the steel plate surface portion is large in the case where the sheet thickness is thick.

Next, the reason for limitation to the component composition of the unidirectional electromagnetic steel concerning this invention, and a suitable component range are demonstrated. In addition, the unit of composition content is mass%.

C is an important element for forming austenite and is required at 0.025% or more. If the content is excessive, decarburization is difficult, so the upper limit is made 0.100%.

When Si is too small, electric resistance will become small and favorable iron loss property will be hard to obtain, whereas when the content is excessive, cold rolling will become difficult, so content is made into 2.5% or more and 4.5% or less.

Mn is an unavoidable component, and the lower limit is 0.03%. When the content is excessive, when high temperature slab heating is premised, it is difficult to solidify MnS and MnSe, so the upper limit is 0.45%.

S and Se are added in an appropriate amount depending on the kind of inhibitor used. These combine with the Mn to form MnS or MnSe, which acts as an inhibitor.

The component ranges of S and Se are in the range of 0.1% or more and 0.44% or less in any case, alone or in combination.

However, in order to deposit MnS and MnSe finely, high temperature slab heating is required. On the other hand, in the low-temperature slab heating method using the post-process nitriding method, since fine MnS and MnSe are unnecessary, 0.015% or less is preferable. Therefore, in particular, the range of S and Se is not limited.

In the present invention, as an inhibitor component, in particular, containing Al is indispensable in obtaining a high magnetic flux density, and it is necessary to add a certain content or more. However, when the content is excessive, the high temperature slab heating time for the solution becomes long and the productivity deteriorates, so the Al content is set to 0.007% or more and 0.040% or less.

Since N needs to form AlN in the annealing before final cold rolling, it is contained in 0.003% or more and 0.020% or less when it presupposes high temperature slab heating. On the other hand, in the low temperature slab heating method, since AlN is formed by nitriding after primary recrystallization, it is not necessary to necessarily contain N in a steelmaking step. Therefore, in particular, the range of N is not limited.

In addition to the matters described above, components such as Sn, Sb, Cu, Ni, Cr, P, V, B, Bi, Mo, Nb, and Ge may be appropriately added in a known range for improving the magnetic properties.

Next, the conditions according to the manufacturing process will be described.

In this invention, a well-known manufacturing method is applied to the manufacturing process of a steel material. The manufactured ingot or slab is processed as needed, sized, heated and hot rolled.

The slab heating temperature is in the range of 1100 ° C to 1450 ° C as necessary, and a normal gas heating furnace or an induction and energization heating furnace is used at the time of heating.

The steel strip after hot rolling is made into final board thickness by the 1st cold rolling method after hot-rolled sheet annealing, or the multiple cold rolling method containing intermediate annealing.

In addition, annealing is performed on well-known conditions before final cold rolling. In the case of premise of high temperature slab heating, annealing is essentially performed before final cold rolling, after securing sufficient fine precipitation of AlN in hot rolling.

On the other hand, in the case of low-temperature slab heating, annealing before final cold rolling for AlN precipitation control is not essential, but for the control technique of carbide or solid solution C, quenching after annealing, addition of processing strain during cooling, and precipitation of carbide Since the technique such as the above correction makes the aging treatment between the passes of the present invention more effective, the effect of the present invention is not lowered even if annealing before the final cold rolling is performed.

Thereafter, the steel sheet is subjected to final cold rolling by reverse rolling. At this time, in order to obtain a high magnetic flux density, it is preferable to use a reduction ratio of 81% or more as is known in the related art.

In the present invention, the aging treatment during cold rolling and the warm rolling are important for improving the magnetic properties.

In particular, when heating a high temperature slab, it is known that it is effective from the viewpoint of linear fine grain generation rather than a magnetic characteristic improvement effect. And in this invention, as shown in Example 3, it is important to hold | maintain for 1 minute or more in the temperature range of 100-350 degreeC in the plate | board thickness step during rolling.

Another feature of the present invention is to manufacture a unidirectional electrical steel sheet excellent in magnetic properties by increasing the work roll diameter of the cold rolling shear pass. As shown in Fig. 1, the magnetic flux density is remarkably lowered at a work roll diameter of 90 mm or less, improved at 95 mm or more, and tends to be substantially saturated at 120 mm or more.

Therefore, in the present invention, the diameter of the work roll is 95 mm or more, preferably l20 mm or more. On the other hand, when the work roll diameter is excessively large, not only the effect is saturated but also the scale of the cluster rolling mill increases and the equipment cost increases, so that the upper limit is 180 mm. Moreover, the range which applies the large diameter work roll of diameter 95-180 mm (o) is effective in the shear path | pass of the thick plate | board thickness, and it is necessary to carry out at least 0.40 mm or less of plate | board thickness, Preferably it is necessary to carry out to 0.26 mm or less. It can be seen from 2.

On the other hand, in the rolling of the trailing pass, as the thickness of the finished plate decreases, the rolling reaction force increases, so that rolling is difficult to be performed in a large diameter work roll having a diameter of 95 to 180 mm. Therefore, it is necessary to select the work roll diameter according to the product sheet thickness required.

Accordingly, the present inventors experimentally obtained the relationship between the work roll diameter and the minimum rollable sheet thickness using a work roll diameter variable rolling mill. As a result, when the work roll diameter was set to Dmm and the minimum plate thickness was set to Tfmm, the relationship of Tf = D / 520 was obtained. This relationship is somewhat higher than Stone's equation (μ = 0.1), but it is judged to be due to adverse effects such as thermal crown due to high temperature rolling.

In conclusion, as shown in Fig. 4, it is possible to show the relationship between the work roll diameter and the final sheet thickness of the rolling. Hereinafter, the rolling method of the present invention will be described by dividing into a rolling path path and a rear end path. The work roll diameter is set to 95 to 180 mm ø up to a plate thickness of at least 0.40 mm of the shear pass of rolling.

In this case, rolling assumes aging treatment between high temperature rolling and a pass.

Next, in the post pass pass rolling, when the finished sheet thickness is Tfm, the thin sheet material is stably obtained by rolling at a work roll diameter of (520 x Tf) mm or less.

For example, in the case of the work roll of 120 mm which is preferable for magnetic flux density improvement, since the sheet thickness of 0.23 mm is a rolling limit, the product sheet thickness of 0.23 mm or less is hard to finish by rolling. In the case where the product sheet thickness is 0.20 mm, it is possible to finish with a work roll of 95 mm, which is the lower limit of the shear pass of the present invention, but it is difficult to obtain a high magnetic flux density stably. And when the product plate thickness is 0.18 mm or less, since it is impossible to roll with a 95 mm ø work roll, when it rolls using the work roll of the same diameter over the whole path | pass, for example, it is a l20 mm ø work roll which is preferable for magnetic flux density improvement. In the case, since the plate thickness of 0.23 mm is the rolling limit, it was difficult to finish the product plate thickness of 0.23 mn or less.

Moreover, when the product plate | board thickness is 0.20 mm, although it could roll over the whole pass with the 95 mm square work roll which is the lower limit of the shear path of this invention, it was difficult to obtain a high magnetic flux density stably. And when the product plate | board thickness is 0.18 mm or less, since it cannot finish even with a 95 mm diameter work roll, it is necessary to roll with a small diameter roll of 60 mm diameter, for example, but it was difficult to obtain a high magnetic flux density. For the above reasons, in order to obtain a stable magnetic flux density improving effect, when the shear pass is rolled with a work roll of 95 mm or more, the product sheet thickness of 0.23 mm, which needs to be replaced by a small diameter work roll in the rear pass of the rolling, is the upper limit of the present invention. do.

The cold rolling mill is limited to a cluster type reverse rolling mill (such as a Zendimere rolling mill or an NMS rolling mill) such as six-, twelve, and twenty-two in consideration of the stability of high-temperature rolling and sheet rolling. In addition, it is a feature of claim 2 of the present invention to change the housing roll diameter to a suitable work roll diameter in the intermediate rolling step, and to perform the above-described rolling with one rolling mill. A conceptual diagram of a conventional single block housing in FIG. 5 (a) and a split housing in FIG. 5 (b) is shown. In (a), although the work roll diameter can be changed by changing the diameter of an intermediate roll, since the change range is small about 10 mm and a maintenance work load is large, it is unrealistic.

(b) makes it possible to change the work roll diameter by elevating the upper and lower housings and adjusting the distance between the bores. Moreover, since a cluster rolling machine does not have a choke in a work roll, a work roll can be changed quickly during the rolling of a coil, and there is no fall of productivity.

After the degreasing treatment is performed on the steel sheet after the final rolling, annealing which combines decarburization and primary recrystallization is performed. In the low temperature slab heating method having a slab heating temperature of 1250 ° C. or lower, it is effective to form an AlN inhibitor by performing nitriding treatment between the primary recrystallization and the secondary recrystallization. As a nitriding treatment method, the mixed gas of "hydrogen + nitrogen + ammonia" is carried out while running the strip disclosed in Japanese Patent Laid-Open Publication No. S60-l79885 and the strip disclosed in Japanese Laid-Open Patent Publication No. H1-82393. There is a method of annealing. In order to stably develop good secondary recrystallized grains, the amount of nitrogen is required to be 120 ppm or more, preferably 150 ppm or more. In addition, by using together the control of the primary recrystallized grain disclosed in Unexamined-Japanese-Patent No. S1-82939 etc., a magnetic characteristic can be improved further.

Next, after apply | coating the annealing separator which has a MgO slurry as a main component to a steel plate, it winds up in a coil shape and performs final finishing annealing. Thereafter, the insulating coating is carried out as necessary, and it is also effective to perform the self-fragmentation treatment by laser, plasma, mechanical methods, etching and other methods.

Example l

In the manufacturing process conditions shown in Table 2, the electromagnetic steel slab containing the component shown in Table 1, 1350-1400 degreeC high temperature slab heating a), b), and c), and 1150-1290 degreeC low temperature slab heating d) It was hot rolled by the method of (e) and (f), and the hot rolled steel strip was manufactured.

a), c) and f) were two cold rolling methods including intermediate annealing, and b), e) and d) were one cold rolling method after hot-rolled sheet annealing. All the final cold rolling used the reverse rolling mill, and the reduction ratio was 75 to 92%. Intermediate plate thickness and final plate thickness are as shown in the table. Cold rolling changed the work roll diameter as shown in Table 1, and rolled in 2 to 5 passes to 0.30 mm of sheet thickness. The intermediate | middle plate | board thickness of the minimum 2 pass in the middle of rolling was selected, and the aging process was performed at 200 degreeC for 5 minutes.

Subsequently, it rolled in one pass to 0.18 mm of plate | board thickness with the work roll diameter of 60 mm. The cold rolled steel strip is subjected to decarburization annealing in a conventional manner, among which d) and e) are subjected to decarburization annealing, followed by addition of nitriding annealing, so that the amount of nitriding shown in Table 1 (after nitriding before nitriding) is achieved. Reinforced inhibitor.

Then, the magnetic flux density (B8) of the product steel strip obtained by performing magnesia application | coating, finishing annealing, insulation coating, shape correction, and annealing annealing by the normal method was measured. Then, after performing magnetic domain control by a mechanical method, the iron loss (W17 / 50) of the obtained steel strip was measured. As shown in Table 1, when the work roll diameter of cold rolling is controlled in the component containing Al within the range prescribed | regulated by this invention, it turns out that the product excellent in magnetic properties can be obtained.

(* Unit is% by mass or ppm by mass) division ingredient C (%) Si (%) Mn (%) S (ppm) Se (ppm) Al (ppm) N (ppm) Cu (%) Sn (%) Sb (ppm) a) 0.063 3.4 0.07 50 200 261 79 0.05 - 230 b) 0.072 3.2 0.07 240 - 267 81 0.08 0.12 - c) 0.056 3.1 0.08 240 - 15 22 - - - d) 0.055 3.3 0.10 70 - 282 84 - 0.07 - e) 0.061 3.2 0.04 130 - 255 42 0.05 - f) 0.035 3.1 0.20 50 - 234 105 0.50 0.07 -

division Process conditions Magnetic flux density B8 (T) Magnetic flux density W17 / 50 (W / kg) Remarks Slab heating temperature (℃) Hot Rolled Sheet Thickness (mm) Intermediate plate thickness (mm) Final plate thickness (mm) Final rolling reduction (%) Work roll diameter (mm) Nitriding amount (ppm) a) 1370 2.3 1.6 0.18 88.8 60 - 1.892 0.824 Comparative example 100 1.924 0.673 Example 150 1.928 0.664 Example b) 1400 1.8 - 0.18 90.0 60 - 1.888 0.822 Comparative example 100 1.930 0.662 Example 130 1.931 0.651 Example c) 1350 2.2 0.7 0.18 74.3 60 - 1.855 0.901 Comparative example 100 1.862 0.900 Comparative example 150 1.863 0.898 Comparative example d) 1150 2.0 - 0.18 91.0 60 130 1.898 0.878 Comparative example 100 1.925 0.657 Example 150 1.927 0.647 Example e) 1270 1.8 - 0.18 90.0 60 110 1.899 0.792 Comparative example 100 1.929 0.651 Example 150 1.930 0.650 Example f) 1290 2.0 1.0 0.18 82.0 60 - 1.870 0.891 Comparative example 100 1.912 0.680 Example 150 1.922 0.677 Example

Example 2

As shown in Table 3, the annealing material having a thickness of 1.6 mm shown in a) of Table 1 and a) of Table 2, as shown in Table 3, was used to combine 10 work roll diameters by combining 120 mm ø and 60 mm ø. Cold rolled to plate thickness 0.20mm. Aging between passes was processed at 200 ° C. for 5 minutes in the plate thickness step shown in Table 2. About the cold rolled steel strip, the magnetic flux density (B8) of the product steel strip obtained by decarburizing annealing, magnesia application | coating, finishing annealing, insulation coating, shape correction, and annealing annealing by the usual method was measured. Then, after performing magnetic domain control by a mechanical method, the iron loss (W17 / 50) of the obtained steel strip was measured. As shown in Table 2, it can be seen that a product having excellent magnetic flux density can be obtained by applying a large diameter work roll of l20 mm ø to at least a sheet thickness of 0.4 mm or less in the shear pass of rolling.

Condition Cold Rolling Pass Schedule Magnetic flux density B8 (T) Iron loss W17 / 50 (W / kg) Remarks Plate thickness (mm) 1.3 1.0 0.7 0.4 0.3 0.2 One Work roll diameter (mm) 120 60 1.931 0.681 Example Aging treatment ○ ○ ○ ○ ○ - 2 Work roll diameter (mm) 120 60 1.929 0.693 Example Minutes ○ ○ ○ ○ - - 3 Work roll diameter (mm) 120 60 1.908 0.883 Comparative example Minutes ○ ○ ○ - - - 4 Work roll diameter (mm) 120 60 1.782 1.112 Comparative example Minutes ○ ○ - - - - 5 Work roll diameter (mm) 120 60 1.432 Not measurable (fine grain) Comparative example Minutes ○ - - - - - 6 Work roll diameter (mm) 60 1.421 Not measurable (fine grain) Comparative example Minutes - - - - - - 7 Work roll diameter (mm) 120 60 1.911 0.845 Comparative example Minutes ○ ○ ○ ○ ○ - 8 Work roll diameter (mm) 120 60 1.905 0.902 Comparative example Minutes ○ ○ ○ ○ ○ - 9 Work roll diameter (mm) 120 60 1.492 Not measurable (fine grain) Comparative example Aging treatment - - - - - - 10 Work roll diameter (mm) 120 60 1.926 0.705 Example Aging treatment - - ○ - - -

Example 3

The annealing material having a thickness of 1.6 mm shown in a) of Table 1 and a) of Table 2 was used for the 12 interpass holding temperatures and times shown in Table 4, using a reverse rolling mill having a work roll diameter of 165 mm. After rolling up to 0.30 mm under conditions, it cold-rolled to the final plate thickness of 0.15 mm with 50 mm ø of work roll diameter.

The cold rolled steel strip was subjected to decarburization annealing, magnesia coating, finish annealing, insulation coating, shape correction, and annealing annealing in a conventional manner, and the magnetic flux density (B8) of the obtained steel strip was measured. Then, after magnetic domain control was performed by etching, the iron loss (W17 / 50) of the obtained steel strip was measured. As shown in Table 4, the product excellent in magnetic properties was obtained by hold | maintaining for 1 minute or more in the temperature range of 100-350 degreeC in the plate | board thickness step during rolling.

Condition Cold Rolling Pass Schedule Magnetic flux density B8 (T) Iron loss W17 / 50 (W / kg) Remarks Plate thickness (mm) 1.2 0.9 0.6 0.3 0.15 One Temperature (℃) - - - - - 1.477 Not measurable (fine grain) Comparative example Minutes - - - - - 2 Temperature (℃) - - 80 - - 1.605 Not measurable (fine grain) Comparative example Minutes - - 5 - - 3 Temperature (℃) - - 100 - - 1.906 0.623 Example Minutes - - 5 - - 4 Temperature (℃) - - 200 - - 1.915 0.620 Example Minutes - - 5 - - 5 Temperature (℃) - - 300 - - 1.919 0.611 Example Minutes - - 5 - - 6 Temperature (℃) - - 400 - - 1.895 0.805 Comparative example Minutes - - 5 - - 7 Temperature (℃) - 200 - - - 1.484 Not measurable (fine grain) Comparative example Minutes 0.5 - - - 8 Temperature (℃) - - 300 - - 1.522 Not measurable (fine grain) Comparative example Minutes - - 0.5 - - 9 Temperature (℃) - - 200 - - 1.910 0.625 Example Minutes - - One - - 10 Temperature (℃) - - 200 - - 1.917 0.615 Example Minutes - - 5 - - 11 Temperature (℃) - 200 200 - - 1.925 0.598 Example Minutes - 5 5 - - 12 Temperature (℃) - 200 200 150 - 1.930 0.580 Example Minutes - 5 5 5 -

As described above, in the thin plate-oriented unidirectional electrical steel sheet containing Al and having a product plate thickness of 0.23 mm or less, the magnetic properties can be improved by improving the magnetic flux density. Therefore, the present invention can contribute to low iron loss and miniaturization of transformers and the like.

Claims (7)

After hot-rolling an electromagnetic steel slab containing C: 0.025 to 0.10%, Si: 2.5 to 4.5%, and Al: 0.007 to 0.040% by mass, hot rolled sheet annealing was performed to perform one cold rolling or intermediate annealing. In the method for producing a grain-oriented electrical steel sheet which is subjected to two or more cold rollings, and then subjected to primary recrystallization annealing, followed by secondary recrystallization annealing, the final cold rolling is performed with a work roll diameter of 95 A method for producing a unidirectional electrical steel sheet having excellent magnetic properties, characterized in that it is performed with a reverse mill of ˜180 mm ø. After hot rolling to an electromagnetic steel slab containing C: 0.025 to 0.10%, Si: 2.5 to 4.5%, and Al: 0.007 to 0.040% by mass, hot rolled sheet annealing was performed to perform one cold rolling or intermediate In the manufacturing method of the unidirectional electrical steel sheet which carries out 2 or more cold rolling containing annealing, and then performs primary recrystallization annealing and then secondary recrystallization annealing, the final cold rolling is a work roll diameter of 95-180 mm ø A method for producing a unidirectional electrical steel sheet excellent in magnetic properties, which is performed by a reverse rolling mill and changes the work roll diameter in the sheet thickness step during rolling. After hot rolling to an electromagnetic steel slab containing C: 0.025 to 0.10%, Si: 2.5 to 4.5%, and Al: 0.007 to 0.040% by mass, hot rolled sheet annealing was performed to perform one cold rolling or intermediate In the method for producing a unidirectional electrical steel sheet which is subjected to two or more cold rollings including annealing, and then subjected to primary recrystallization annealing and secondary recrystallization annealing, the final cold rolling is performed in a station having a work roll diameter of 95 to 180 mm. It is carried out by a rolling mill, and in the sheet thickness step during the rolling, the shear pass of the final cold rolling is cold rolled up to an intermediate sheet thickness of 0.40 mm or less with a work roll having a diameter of 95 to 180 mm, and then from the intermediate sheet thickness to the final sheet thickness Tf (mm A method for producing a unidirectional electrical steel sheet having excellent magnetic properties, characterized in that the work roll diameter is cold rolled by using a work roll having a diameter D (mmø) of rolling to D ≦ Tf × 520. The method according to any one of claims 1 to 3, The manufacturing method of the unidirectional electrical steel sheet excellent in the magnetic characteristic in one or more of the last cold rolling passes in the said cold rolling, The steel strip strip temperature is maintained for 100 minutes or more in 1 minute or more. The method according to any one of claims 1 to 4, A method for producing a unidirectional electrical steel sheet having excellent magnetic properties, characterized in that the electromagnetic steel slab contains Mn: 0.03 to 0.45% by mass. The method according to any one of claims 1 to 5, The product sheet thickness is 0.23mm or less, the manufacturing method of the unidirectional electrical steel sheet excellent in magnetic properties. The method according to any one of claims 1 to 4, In the above cold rolling, the final cold rolling is performed by one rolling mill by replacing the work rolls with different diameters in the plate thickness step during the multi-pass rolling using a cluster-type reverse rolling mill composed of a housing that can be divided up and down. A method for producing a unidirectional electrical steel sheet having excellent magnetic properties.