JPH10287922A - Stable production of nonoriented silicon steel sheet with high magnetic flux density - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of stable production of a nonoriented silicon steel sheet having high magnetic flux density and used for an iron core material for electrical equipment. SOLUTION: A slab, having a composition consisting of, by weight, 0.10-4.00% Si, 0.10-1.50% Mn, <=0.0050% C, <=0.0050% N, <=0.0050% S, and the balance Fe with inevitable impurities, is hot-rolled, and the resultant hot rolled plate is cold-rolled once or is cold-rolled two or more times while process annealed between cold rolling stages, followed by finish annealing. In this case, the volume fraction of the lubricating oil mixed into roll cooling water used for a finish hot rolling mill in the hot rolling stage is regulated to <=1.0% at the first stand and to 1.0-10% at least one stand among the stands from the second stand on, and the kinematic viscosity of the lubricating oil is regulated to 100 to 800 cSt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a non-oriented electrical steel sheet having excellent magnetic properties with high magnetic flux density and low iron loss, which is used as an iron core material of electric equipment.

[0002]

2. Description of the Related Art In recent years, in the fields of electric machines, especially rotating machines and medium-sized and small-sized transformers in which non-oriented electrical steel sheets are used as iron core materials, worldwide electric power and energy savings, as well as chlorofluorocarbon gas regulations. Among the movements for global environmental conservation, such as the above, the movement for higher efficiency is rapidly spreading. Therefore, there is an increasing demand for non-oriented electrical steel sheets to have improved properties, that is, high magnetic flux density and low iron loss.

By the way, in non-oriented electrical steel sheets,
Conventionally, as a means of reducing iron loss, a method of increasing the content of Si, Al, or the like has been generally adopted from the viewpoint of reducing eddy current loss due to an increase in electric resistance. However, this method has a problem that the magnetic flux density cannot be reduced. In order to overcome such problems, a method of improving both the magnetic flux density and the iron loss by increasing the crystal grain size of the hot-rolled sheet has been performed. As this method, conventionally, in a non-transformed non-oriented electrical steel sheet having a high Si content, after the finish hot-rolling, hot-rolled sheet annealing by box annealing or continuous annealing is performed to increase the crystal structure. Has been done.
However, it has not been possible to solve the problem of a decrease in magnetic flux density due to the increase in Si.

[0004] In the hot rolling of low-Si non-oriented electrical steel sheets, the end temperature of the hot rolling is increased to the upper limit of the α range to achieve recrystallization and grain growth in a short time after finishing the hot rolling. Although the magnetic flux density has been improved, it has not been sufficient to meet the demand for the improvement of the magnetic flux density.

In order to solve this problem, the present inventors disclosed in Japanese Patent Application Laid-Open No. Sho 62-284016 a non-oriented electrical steel sheet having an αγ transformation with a Si content of 1% or less, and an Ar ₃ point of 500 ° C. or less. Cumulative rolling reduction 3 in the above temperature range
It discloses a method for improving magnetic properties by performing rolling at a low friction rate of 0% or more.

Japanese Patent Application Laid-Open No. 1-306524 discloses a method of improving magnetic properties by lubricating hot rolling in which the rolling reaction force is reduced by 3% or more in a process for producing a non-oriented electrical steel sheet in which hot rolling sheet annealing is performed. It has been disclosed. This publication discloses, as a method of performing lubricating rolling, a method of directly applying lubricating oil to a roll, a method of mixing lubricating oil in roll cooling water, and spraying the lubricating oil onto a work roll.

[0007]

However, when performing the finishing hot rolling with a low friction coefficient such as the lubricating hot rolling by the conventional method described above, the frictional force is insufficient and the leading end of the sheet bar is engaged with the finishing hot rolling machine. In some cases, it was not possible to reduce the total rolling reduction of the finish rolling ratio by reducing the thickness of the sheet bar. As a result, the temperature at the rear end of the thin-finished sheet bar is reduced during the finish rolling, and as a result, there remains a problem that it is difficult to control the hot rolling temperature during the finish.

The present invention is intended to improve the magnetic properties of a non-oriented electrical steel sheet and improve the hot rolling operation of a non-oriented electrical steel sheet by determining the lubricating oil concentration and viscosity of a finishing hot rolling mill, which were conventionally determined from the viewpoints of work roll life and rolling reaction force control. By studying both aspects of stability, controlling the roll cooling water concentration for each stand and determining the lubricating oil viscosity, the non-directionality that improves the magnetic flux density while ensuring the operational stability of the hot-rolled finish An object of the present invention is to provide a method for manufacturing an electromagnetic steel sheet.

[0009]

The gist of the present invention is as follows. (1) 0.10% ≦ Si ≦ 4.00%, 0.10% ≦ Mn ≦ 1.50%, C ≦ 0.0050%, N ≦ 0.0050%, S ≦ 0.0050% by weight %, With the balance being Fe and unavoidable impurities, hot-rolled to form a hot-rolled sheet, then subjected to one or two or more cold-rollings with intermediate annealing, followed by finish annealing In the method for producing a non-oriented electrical steel sheet, the volume fraction of the lubricating oil mixed into the roll cooling water used in the finishing hot rolling mill in the hot rolling step is 1.0% or less in the first stand,
In addition, at least one of the second and subsequent stands has a kinetic viscosity of 1.0% or more and 10% or less, and the kinematic viscosity of the lubricating oil is 100 cSt or more and 800 cSt. Stable manufacturing method.

(2) By weight%, 0.10% ≦ Si ≦ 4.00%, 0.10% ≦ Mn ≦ 1.50%, C ≦ 0.0050%, N ≦ 0.0050%, S ≦ The magnetic flux density according to (1), wherein the slab contains 0.0050%, further contains 0.10% ≦ Al ≦ 1.00%, and the balance is Fe and unavoidable impurities. Method for stable production of non-oriented electrical steel sheets.

(3) The kinematic viscosity of the lubricating oil mixed in the roll cooling water used in each stand of the finishing hot rolling machine is 200 cSt or more and 800 cSt or less, wherein (1) or (2). A stable method for producing a non-oriented electrical steel sheet having a high magnetic flux density as described above.

(4) The leading end of the sheet bar obtained by roughly rolling the slab is joined to the trailing end of the preceding sheet bar to integrate a plurality of sheet bars. The method for stably producing a non-oriented electrical steel sheet having a high magnetic flux density according to the above (1), (2) or (3), wherein the non-oriented electrical steel sheet is continuously subjected to finish hot rolling.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION In the case of general finishing hot rolling, in order to extend the life of a work roll, lubricating oil having a volume fraction of several × 10 ^-1 % is mixed into roll cooling water to form a work roll. Inject. The present inventors have repeatedly studied the lubricating oil concentration and viscosity of the finishing hot rolling mill, which were conventionally determined from the viewpoint of reducing the work roll life and reducing the rolling reaction force. It has been found that the magnetic flux density of a steel sheet can be improved.

However, when the lubricating oil concentration and the viscosity are increased, when the sheet bar of the finishing hot-rolling machine is caught, it is easy to stop rolling due to poor biting, so that the lubricating oil concentration in the roll cooling water is increased. There was a limit naturally.

The inventors of the present invention have made intensive studies to solve this problem, and as a result, by actively controlling the lubricating oil concentration in the roll cooling water used in the continuous finishing hot rolling mill for each rolling stand. It has been found that it is possible to improve the magnetic flux density of the non-oriented electrical steel sheet while solving the problem of poor biting at the leading stand.

That is, while the volume fraction of the lubricating oil in the roll cooling water at the first stand in the finishing hot rolling step is suppressed to 1.0% or less, at least one volume after the second stand is reduced.
In one stand, the volume fraction of the lubricating oil in the roll cooling water is 1.0% or more and 10% or less, and the kinematic viscosity of the lubricating oil mixed in the roll cooling water is 100 cSt or more and 80% or less.
It has been found that by controlling the temperature to 0 cSt or less, both stable operation of the finish hot rolling under high lubrication and improvement of the magnetic properties of the non-oriented electrical steel sheet by high lubrication rolling can be achieved.

Hereinafter, the present invention will be described in detail. First,
Describing the components, Si is added to increase the specific resistance of the steel sheet, reduce the eddy current loss, and improve the iron loss value. If the Si content is less than 0.10%, the specific resistance required for the low iron loss non-oriented electrical steel sheet aimed at by the present invention cannot be sufficiently obtained, so it is necessary to add 0.10% or more. On the other hand, if the Si content exceeds 4.00%, edge cracks at the time of rolling increase remarkably, and rolling becomes difficult.
% Or less.

Al is relatively expensive compared to Si,
Like Si, it has the effect of increasing the specific resistance of the steel sheet and reducing eddy current loss, and is added as necessary. A
In order to obtain a low iron loss and high magnetic flux density non-oriented electrical steel sheet intended by the present invention by adding l, Al may be added in an amount of 0.10% or more. On the other hand, if the Al content exceeds 1.00%, the magnetic flux density decreases and the cost increases.
00% or less.

Mn, like Al and Si, has the effect of increasing the specific resistance of a steel sheet and reducing eddy current loss. For this purpose, the Mn content needs to be 0.10% or more. On the other hand, if the Mn content exceeds 1.50%, the deformation resistance during hot rolling increases, and hot rolling becomes difficult, and the crystal structure after hot rolling tends to become finer, which deteriorates the magnetic properties of the product. The Mn content needs to be 1.50% or less.

Further, the amount of Mn addition is extremely important from the viewpoint of securing the strength of the high temperature sheet bar joint before the hot rolling. This is because the addition of Mn can prevent hot embrittlement of the sheet bar joint due to the presence of a low-melting sulfide at the crystal grain boundary. For this purpose, it is necessary to set the value of Mn / S, which is the ratio of the weight concentrations of Mn and S, to 20 or more. In the component range defined in the present invention, since the Mn content is 0.10% or more and the S content is 0.0050% or less, the value of Mn / S is kept at 20 or more.

In order to improve the mechanical properties, magnetic properties and rust resistance of the product or for other purposes, P,
Even if one or more of B, Ni, Cr, Sb, Sn, and Cu are contained in steel, the effect of the present invention is not impaired.

When the C content exceeds 0.0050%, iron loss is deteriorated due to magnetic aging during use and energy loss during use is increased. Therefore, the C content is 0.0050% or less, more preferably 0.0020% or less. It is necessary to control the following.

S and N partially re-dissolve during slab heating in the hot rolling process, and sulfides such as MnS and A
A nitride such as 1N is formed. The presence of these prevents the grain growth of the hot-rolled structure and the crystal grain growth during the finish annealing, and deteriorates the iron loss.
Or less, more preferably 0.0020% or less, and N is 0.1% or less.
0050% or less, more preferably 0.0020%.

Next, the process conditions of the present invention will be described. The steel slab composed of the above components is produced by melting in a converter and being manufactured by continuous casting or ingot-bulking rolling. The steel slab is heated by a known method and subjected to a hot rolling step. The hot rolling step of the present invention includes a rough rolling step and a finish hot rolling step. The steel slab is formed into a sheet bar by rough rolling and then into a hot rolled sheet by finish hot rolling.

First, in the present invention, the volume fraction of the lubricating oil mixed in the roll cooling water used in the finishing hot rolling mill in the hot rolling step is 1.0% or less at the first stand and at least 1% after the second stand. 1.0% or more and 10% for one stand
The following is assumed.

Here, the reason why the volume fraction of the lubricating oil is set to 1.0% or less at the first stand is that the volume fraction of the lubricating oil is more than 1.0% at the first stand of the finishing hot rolling mill. This is because poor biting at the time of biting the sheet bar tends to occur.

As for the volume fraction of the lubricating oil after the second stand, it is necessary that the volume fraction of the lubricating oil in at least one of the stands is 1% or more from the viewpoint of improving the magnetic flux density. On the other hand, if the volume fraction of the lubricating oil in the roll cooling water exceeds 10%, the effect is saturated and uneconomical. For the above reasons, the volume fraction of the lubricating oil is 1.0% or more in at least one stand after the second stand.
% Or less.

By adjusting the concentration of the lubricating oil in the roll cooling water used in the finishing hot-rolling machine so as to satisfy the above conditions, it is possible to prevent biting failure when the sheet bar bites in the first stand, Finish hot rolling with high density improving effect can be performed.

Hereinafter, the kinematic viscosity of the lubricating oil used in the present invention will be described. The kinematic viscosity of the lubricating oil specified in the present invention refers to the kinematic viscosity of the lubricating oil at the time when the lubricating oil is actually sprayed on the roll at a temperature in a state of being mixed with the roll cooling water. Here, the kinematic viscosity of the lubricating oil decreases exponentially with increasing temperature. Therefore, in order to keep the kinematic viscosity of the lubricating oil within the range specified in the present invention, it is necessary to appropriately control not only the temperature of the lubricating oil itself but also the temperature of the roll cooling water.

With respect to the kinematic viscosity of the lubricating oil used for the hot-rolling finishing in the present invention, the kinematic viscosity is 100 c at the temperature mixed in the roll cooling water actually injected into the work roll.
St (centistokes) or more is required. If the kinematic viscosity of the lubricating oil is less than 100 cSt, the effect of improving the magnetic flux density cannot be sufficiently obtained. More preferably, the kinematic viscosity of the lubricating oil is 200 cSt or more.

If the kinematic viscosity of the lubricating oil exceeds 800 cSt, the effect is saturated, the clogging is liable to occur in the piping system for conveying the high-viscosity lubricating oil, and the cooled lubricating oil adheres to the stands and rolls. Since the operation must be frequently stopped for the removal, the kinematic viscosity of the lubricating oil is set to 800 cSt or less.

Further, in order to prevent clogging of a piping system for conveying lubricating oil having a high viscosity, the lubricating oil temperature is set high in the conveying system, and the lubricating oil is conveyed in a low-viscosity state. By mixing, the temperature of the lubricating oil may be reduced, and the kinematic viscosity in a state where the roll cooling water and the lubricating oil are mixed may be controlled so as to fall within the range of the present invention.

The following experiment was conducted to investigate the relationship between the lubricating oil concentration in the roll cooling water of each stand during finishing hot rolling and the stability at the time of sheet bar biting. A slab for non-oriented electrical steel having the components shown in Table 1 was heated by a usual method, and was converted into a sheet bar having a thickness of 40 mm by a rough rolling mill, and then a hot-rolled sheet having a thickness of 2.5 mm was formed by a finishing hot rolling mill. did.

[0034]

[Table 1]

Here, the concentration of the lubricating oil mixed in the cooling water of the roll of the finishing hot rolling machine is as shown in Table 2. The kinematic viscosity of the lubricating oil is controlled by controlling the roll cooling water temperature to 52 ° C.
330 cSt. The lubricating oil was piped to a position just before the work roll with a pipe of a different system from the roll cooling water, and the injection amount was adjusted by modifying the shape of each nozzle to change the volume fraction with respect to the cooling water.

[0036]

[Table 2]

As a comparative example, finish hot rolling was performed under the same conditions except that the lubricating oil concentration in the roll cooling water was all set to 3.0%. The hot rolling finish temperature was 865 ° C. The experiment was performed 50 times for each of the present invention and the comparative example, and the occurrence rate of sheet bar biting failure was determined. . Table 3 shows the rates of occurrence of biting defects in the head stand that occurred during hot rolling in the finishes of the present invention and comparative examples.

[0038]

[Table 3]

From Table 3, it can be seen that according to the present invention, it is possible to prevent the sheet bar from being bitten by the finishing hot rolling machine.

Next, an experiment was conducted on the effect of the kinematic viscosity of the lubricating oil mixed in the roll cooling water for the finish rolling on the magnetic properties. The slab for non-oriented electromagnetic steel having the components shown in Table 4 was heated by a usual method, finished to a sheet bar having a thickness of 40 mm by a rough rolling mill, and then finished to 2.5 mm by a hot rolling mill. Table 5 shows the concentration of the lubricating oil mixed in the roll cooling water of the finishing hot rolling mill. The kinematic viscosity of the lubricating oil was changed by changing the roll cooling water temperature. The lubricating oil was piped to a position just before the work roll with a pipe of a different system from the roll cooling water, the injection amount was adjusted by devising the shape of each nozzle, and the volume fraction relative to the roll cooling water was changed.

[0041]

[Table 4]

[0042]

[Table 5]

The hot-rolling finishing temperature was set at 865 ° C. for steel A, cooled with water and wound at 650 ° C. Hot rolling finish temperature of steel B is 90
The temperature was adjusted to 0 ° C, immediately cooled with water, and wound at 550 ° C. Steel B
Was subjected to hot rolled sheet annealing at 900 ° C. for 45 seconds in a continuous annealing furnace.

The hot-rolled sheet was pickled, finished to 0.50 mm by one cold rolling, and 950 steel A was obtained by a continuous annealing furnace.
The steel B was subjected to finish annealing at 980 ° C. for 30 seconds and 980 ° C. for 30 seconds to obtain a product. An Epstein sample was cut out from the obtained product coil, and its magnetic properties were measured. The result is shown in FIG.

As shown in FIG. 1, when the kinematic viscosity of the lubricating oil in the roll cooling water is 100 cSt or more, the product magnetic flux density is improved. Further, when the kinematic viscosity of the lubricating oil in the roll cooling water is set to 200 cSt or more, the product magnetic flux density is further improved. According to the experimental results, the kinematic viscosity of the lubricating oil in the roll cooling water used at the time of finishing hot rolling is 100 cSt or more, and more preferably 200 cSt.
At least t.

Here, the lubricating oil used in the present invention will be described. The lubricating oil used in the finishing hot rolling is usually composed of components such as a base oil, an extreme pressure additive, an adhesion improver, and an oil agent as main components. Refined mineral oil is usually used as the base oil.

The oleaginous agent comprises a non-polar hydrocarbon group and a polar group, and the hydrocarbon group has an affinity for a base oil molecule which is a main component of the lubricating oil. On the other hand, since the polar group of the oil agent has an affinity for the metal or water molecule as the material to be rolled, the oil agent adsorbs on the metal or water and forms an adsorption film on the metal surface.
This adsorbing film suppresses friction and wear between the steel plate and the work roll when the load is low. As the oil agent, various fats and oils represented by long-chain fatty acids such as oleic acid, various synthetic oils, and the like are used.

Extreme pressure additives act when the load increases. When the load increases, a part of the metal breaks through the adsorbing film and comes into direct contact with the roll, and the heat generated by the frictional heat causes the roll temperature to rise, causing further destruction of the adsorbing film and causing seizure and scuffing. Extreme pressure additives are added for the purpose of preventing the wear of the metal surface in such a lubricated state and enabling lubrication, and include phosphate ester polymers, metal dithiophosphate salts, and organic sulfur compounds. , Organic halogen compounds and the like are used.

The adhesion improver is added for the purpose of improving the adhesion of the lubricating oil to the surface of the work roll or the surface of the hot-rolled steel slab. Usually, a hydrocarbon polymer or the like is used.

Recently, in order to increase the viscosity of the lubricating oil and improve the roll life, a lubricating oil composed of a component system in which the viscosity of the extreme pressure additive is increased and the oil agent is omitted has been used.

Examples of the lubricating oils whose component systems have been described above include Cudol 5149, Cudol 0B068,
Q-doll 4B313 (all are trade names of Kyodo Yushi Co., Ltd.).

However, in the present invention, by appropriately controlling the kinematic viscosity of the lubricating oil used in each stand of the finishing hot rolling mill and the concentration of the lubricating oil in the roll cooling water, the magnetic flux density of the product of the non-oriented electrical steel sheet is controlled. And finish hot rolling is performed stably. Therefore, the lubricating oil used in practicing the present invention is not limited to those constituted by the above-mentioned component systems.

When a high-viscosity lubricating oil is mixed in the cooling water for the roll of the finish hot-rolling as in the present invention, the method of performing the finish rolling more stably is as follows: It is also effective to reduce it. As a method of reducing the number of bites of the sheet bar, a plurality of sheet bars are integrally formed by joining a front end portion of the sheet bar obtained by roughly rolling the slab with a rear end portion of the preceding sheet bar, and integrating the sheet bar. It is particularly effective to continuously provide a plurality of sheet bars thus obtained to hot rolling for finishing.

Here, as a method of joining the preceding sheet bar and the following sheet bar, a method of joining the rear end of the preceding sheet bar and the tip of the following sheet bar and welding the butted portion, or a method of joining the butted portion is used. Pressing by applying pressing force,
There is a method of welding the butt portion and then pressing the butt portion. Also,
The welding may be performed while applying a pressing force to the butted portion. In addition, as a method of welding the butt portion, for example, a laser welding method, a method by induction heating, and the like can be mentioned.

The hot-rolled sheet obtained as described above is subjected to cold rolling once or twice or more with intermediate annealing to obtain a product by finish annealing. Further, a skin pass rolling step may be added to obtain a product. Skin pass rolling rate is 2%
If it is less than 20%, the effect cannot be obtained, and if it is more than 20%, the magnetic properties are deteriorated.

Further, in order to further improve the properties, hot-rolled sheet annealing using a continuous annealing furnace or a box annealing furnace may be performed before cold rolling. Further, in order to improve magnetic properties at low cost, the hot-rolled coil may be wound at a high temperature of 750 ° C. or more and 1000 ° C. or less, and self-annealing may be performed using the heat retained by the coil itself. Alternatively, finishing hot rolling may be terminated at a high temperature of 950 ° C. or higher, and after a certain period of time without water injection, cooling and winding may be performed.

Further, the hot-rolled sheet may be finished thinly and made into a product without being subjected to cold rolling as it is, or a film may be applied after pickling to form a final product as it is.

[0058]

Next, an embodiment of the present invention will be described. [Example 1] In a full-process material by a single cold rolling method with no hot-rolled sheet annealing, the concentration of lubricating oil at each stand during finishing hot rolling has a sheet bar biting defect rate during finishing hot rolling, and a product magnetic property. The following experiments were conducted to investigate the effect on the odor. Here, the full-process material refers to a product obtained by a manufacturing method that is subjected to one or two or more cold-rolling operations including intermediate annealing and then annealed to obtain a final product.

The slab for non-oriented electrical steel having the components shown in Table 6 was heated by a conventional method, finished to a sheet bar having a thickness of 40 mm by a rough rolling mill, and then to a thickness of 1.8 mm by a finishing hot rolling mill. Finished. Table 7 shows the concentration of the lubricating oil mixed in the cooling water of the roll of the finishing hot rolling machine. The kinematic viscosity of the lubricating oil was 340 cSt by controlling the roll cooling water temperature to 52 ° C. The lubricating oil was piped to a position just before the work roll with a pipe of a different system from the roll cooling water, and the volume fraction with respect to the roll cooling water was changed by deliberately injecting the shape of each nozzle and jetting.

[0060]

[Table 6]

[0061]

[Table 7]

As a comparative example, finish hot rolling was carried out using the same lubricating oil under the same condition with all the lubricating oil concentrations in the roll cooling water set to 0.4% and 3.0%. Hot rolling finish temperature is 8
65 ° C.

The experiment was carried out 50 times for each of the present invention and the comparative example, and the occurrence rate of the sheet bar biting failure was obtained. The magnetic properties were obtained by using a hot rolled sheet having no biting failure. The average value of the product properties was used. Thereafter, the obtained hot rolled sheet was subjected to pickling, and was finished to a thickness of 0.50 mm by cold rolling. This is 950 in a continuous annealing furnace.
Annealed at 30 ° C. for 30 seconds. From this product, an Epstein sample was cut out and its magnetic properties were measured. Table 8 shows the occurrence ratio of the occurrence of jamming in the finishing head stand of the present invention and the comparative example, and Table 9 shows the measurement results of the magnetic properties.

[0064]

[Table 8]

[0065]

[Table 9]

From Table 8, it can be seen that in the present invention and Comparative Example 1, it is possible to prevent the sheet bar from biting into the finishing hot rolling machine. Table 9 shows that it is possible to manufacture a non-oriented electrical steel sheet having a high magnetic flux density in the present invention and Comparative Example 2.

From the above results, as a method for stably producing a non-oriented electrical steel sheet having a high magnetic flux density, the lubricating oil concentration in the roll cooling water for finishing hot rolling is set to 1.
It can be seen that while suppressing the lubricating oil concentration to 0% or less, the lubricating oil concentration in the roll cooling water injected to the work rolls after the second stand is preferably 1% or more and 10% or less in at least one pass. This manufacturing method enables stable operation of hot-rolled finish under high lubrication and stable production of non-oriented electrical steel sheets with high magnetic flux density and excellent magnetic properties. Became possible.

Example 2 The concentration of the lubricating oil in each stand at the time of finishing hot rolling in the full-process material by the single cold rolling method with the omission of hot-rolled sheet annealing, the sheet bar biting failure rate at the time of finishing hot rolling, and The following experiment was conducted to investigate the effect on the magnetic properties of the product.

A slab for non-oriented electromagnetic steel having the components shown in Table 10 was heated by a usual method, finished into a 35 mm-thick sheet bar by a rough rolling mill, and then 2.7 mm thick by a finishing hot rolling mill. Finished. Table 11 shows the concentration of the lubricating oil mixed in the roll cooling water of the finishing hot rolling mill. The kinematic viscosity of the lubricating oil was 350 cSt by controlling the temperature of the roll cooling water to 50 ° C. The lubricating oil was piped to a position just before the work roll with a pipe of a different system from the roll cooling water, and the volume fraction with respect to the roll cooling water was changed by devising the shape of each nozzle.

[0070]

[Table 10]

[0071]

[Table 11]

As a comparative example, finishing hot rolling was performed using the same lubricating oil while keeping the lubricating oil concentration in the roll cooling water constant at 1.0% or less and 3.5%. The hot rolling finishing temperature was 865 ° C. The experiment was performed for both the present invention and the comparative example.
Each time, the occurrence rate of sheet bar biting failure was determined, and as a magnetic property, an average value of the properties of the obtained product was used using a hot rolled sheet in which no biting failure occurred. Thereafter, the obtained hot rolled sheet was subjected to pickling, and was finished to a thickness of 0.50 mm by cold rolling. This is a continuous annealing furnace 7
Annealed at 50 ° C. for 30 seconds. From this product, an Epstein sample was cut out and its magnetic properties were measured. Table 12 shows the incidence rates of the occurrence of bite defects in the finishing head of the present invention and the comparative example,
Table 13 shows the results of the magnetic measurement.

[0073]

[Table 12]

[0074]

[Table 13]

From Table 12, it can be seen that in the present invention and Comparative Example 3, it is possible to prevent the sheet bar from biting into the finishing hot rolling machine. Table 13 shows that it is possible to manufacture a non-oriented electrical steel sheet having a high magnetic flux density in the present invention and Comparative Example 4.

From the above results, as a method for stably producing a non-oriented electrical steel sheet having a high magnetic flux density, the lubricating oil concentration in the roll cooling water for finishing hot rolling is set to 1.
It can be seen that while suppressing the lubricating oil concentration to 0% or less, the lubricating oil concentration in the roll cooling water injected to the work rolls after the second stand is preferably 1% or more and 10% or less in at least one pass. This manufacturing method enables stable operation of hot-rolled finish under high lubrication and stable production of non-oriented electrical steel sheets with high magnetic flux density and excellent magnetic properties. Became possible.

Example 3 The following experiment was conducted to investigate the effect of the viscosity of the lubricating oil on the magnetic properties of the finished product in the hot rolling process in the full process material by hot rolling. A slab for non-oriented electromagnetic steel having the components shown in Table 14 was heated by a usual method, finished to a sheet bar having a thickness of 40 mm by a rough rolling mill, and then finished to a thickness of 1.7 mm by a finishing hot rolling mill. . Finish hot rolling end temperature is 900 ℃
Immediately after completion of hot rolling, the resultant was cooled with water and the hot rolled sheet was wound at 550 ° C. Table 15 shows the concentration of the lubricating oil mixed in the roll cooling water of the finishing hot rolling mill. The kinematic viscosity of the lubricating oil was controlled by changing the temperature of the roll cooling water. The lubricating oil was piped to a position just before the work roll with a pipe of a different system from the roll cooling water, and the volume fraction with respect to the roll cooling water was changed by devising the shape of each nozzle.

[0078]

[Table 14]

[0079]

[Table 15]

In the present invention, the finish hot rolling is performed by using a high-viscosity lubricating oil. Therefore, it is possible to avoid the possibility that the individual sheet bars are liable to be jammed and to perform the finish hot rolling stably. Laser welding was performed while the rolled sheet bar was pressed against the preceding sheet bar, and finish hot rolling was continuously performed. The obtained hot rolled sheet was subjected to hot rolled sheet annealing at 950 ° C. for 30 seconds in a continuous annealing furnace. Thereafter, it was pickled and cold rolled to a thickness of 0.50 mm. This is 95 in a continuous annealing furnace.
Annealed at 0 ° C. for 30 seconds. From this product, an Epstein sample was cut out and its magnetic properties were measured. Table 16 shows the results of the magnetic measurement.

[0081]

[Table 16]

As shown in Table 16, the kinematic viscosity of the lubricating oil at the time of hot rolling was 100 cSt or more, and moreover 200 cSt.
From the above, it can be seen that the product magnetic flux density further increases. [Example 4] In order to investigate the influence of the viscosity of the lubricating oil upon the finished hot rolling on the magnetic properties of the finished product in the semi-processed material by the single cold rolling method, the following experiment was conducted. Was. Here, the semi-processed material is a product in a manufacturing method that is a final product in a state in which the steel sheet is subjected to one or two or more cold rollings including an intermediate annealing, then annealed, and then subjected to a skin pass to obtain a final plate thickness. Point out and say. After ordinary processing of this product by punching or the like in a consumer and forming, the product is subjected to annealing called magnetic annealing or strain relief annealing to improve iron loss characteristics and be used for actual use.

A slab for non-oriented electromagnetic steel having the components shown in Table 17 was heated by a usual method, finished into a 50 mm-thick sheet bar by a rough rolling mill, and then 2.7 mm thick by a finishing hot rolling mill. Finished. Finish hot rolling end temperature is 860 ° C
After completion of hot rolling, the resultant was cooled with water and the hot rolled sheet was wound at 650 ° C.

Table 18 shows the concentration of the lubricating oil mixed in the cooling water of the roll of the finishing hot rolling mill. The kinematic viscosity of the lubricating oil was controlled by changing the temperature of the roll cooling water. The lubricating oil was piped up to just before the work roll in a separate system from the roll cooling water, and the volume fraction relative to the roll cooling water was changed by devising the shape of each nozzle.

[0085]

[Table 17]

[0086]

[Table 18]

In the present invention, the finish hot rolling is performed using a high-viscosity lubricating oil. Therefore, it is possible to avoid the possibility that individual sheet bars are liable to be jammed, and to perform the finish hot rolling stably. The rolled sheet bar was welded by laser while applying a pressing force to the preceding sheet bar, and finish hot rolling was continuously performed.

At this time, the sheet bar after the rough rolling is wound into a coil and stored in a plurality of coil boxes installed to prevent a temperature drop, so that the finish rolling can be performed without interruption. The sheet bar after the rough rolling was sequentially unwound and welded to finish hot rolling.

Thereafter, the obtained hot-rolled sheet was pickled and cold-rolled to a thickness of 0.55 mm. This was annealed at 720 ° C. for 30 seconds in a continuous annealing furnace. Then, change this to 9
A 0.50 mm thickness was finished by skin pass rolling at%, and an Epstein sample was cut out from this product, and then subjected to magnetic annealing at 750 ° C. for 2 hours, which is usually performed in a consumer. Table 19 shows the magnetic measurement results of this sample.

[0090]

[Table 19]

As shown in Table 19, the kinematic viscosity of the lubricating oil at the time of hot rolling was 100 cSt or more, and moreover 200 cSt.
From the above, it can be seen that the product magnetic flux density further increases.

Example 5 Self-annealing process Influence of the viscosity of the lubricating oil on the magnetic properties of finished products during the hot rolling of a full-process and semi-process non-oriented electrical steel sheet manufactured by a single cold rolling process. To do this, the following experiment was conducted. A slab for non-oriented electrical steel having the components shown in Table 20 was heated by a usual method, finished to a sheet bar having a thickness of 60 mm by a rough rolling mill, and then finished to a thickness of 2.7 mm by a finishing hot rolling mill. . The finishing hot rolling end temperature was 1000 ° C., and after the hot rolling was completed, water was cooled and the hot rolled sheet was wound at 840 ° C., and the coil was immediately charged into the heat retaining cover.
Self-annealing was performed at 30 ° C. for 1 hour. Table 21 shows the concentration of lubricating oil mixed in the roll cooling water for each stand of the finishing hot rolling mill. The kinematic viscosity of the lubricating oil was controlled by changing the temperature of the roll cooling water. The lubricating oil was piped to a position just before the work roll in a separate line from the roll cooling water, and the volume fraction of the roll cooling water was changed by devising the shape of each nozzle.

[0093]

[Table 20]

[0094]

[Table 21]

In the present invention, the finish hot rolling is performed by using a high-viscosity lubricating oil. Therefore, it is possible to avoid the possibility that individual sheet bars are liable to be jammed and to perform the finish hot rolling stably. The rolled sheet bar was welded to the preceding sheet bar, and finish hot rolling was continuously performed.

Thereafter, the characteristics of the steel C in the full process and the semi-process were investigated. As a full process step of steel C, 0.50 mm
This was annealed at 850 ° C. for 30 seconds in a continuous annealing furnace. In the semi-process of steel C, the obtained hot-rolled sheet was pickled and cold-rolled to a thickness of 0.55 mm. This was annealed at 800 ° C. for 30 seconds in a continuous annealing furnace. Thereafter, this was subjected to 9% skin pass rolling to form a 0.1% skin pass.
Finished to a thickness of 50 mm, from this product an Epstein sample is cut out, and is then usually performed at the consumer.
The sample was subjected to magnetic annealing at 0 ° C. for 2 hours to obtain a sample for measuring magnetic properties. Steel D was pickled and then cold-rolled once to a thickness of 0.50 mm. This was annealed at 980 ° C. for 30 seconds in a continuous annealing furnace.

An Epstein sample was cut out from a full process product of steel C and steel D and used as a sample for measuring magnetic properties. The magnetic properties of these samples were measured. Table 22 shows the magnetic measurement results.

[0098]

[Table 22]

As shown in Table 22, the kinematic viscosity of the lubricating oil at the time of hot rolling for finishing was 100 cSt or more, and moreover 200 cSt.
From the above, it can be seen that the product magnetic flux density further increases in both the full process material and the semi-process material.

[Example 6] In a method for producing a non-oriented electrical steel sheet, in which a cold rolling step is omitted after finishing hot rolling to obtain a final product,
The following experiment was conducted to investigate the effect of lubricating oil concentration at each stand on the magnetic properties of the finished product during hot rolling. A slab for non-oriented electrical steel having the components shown in Table 23 was heated by a usual method, and was subjected to a roughing mill to a thickness of 6 mm.
The sheet was finished to a sheet bar of 0 mm, and then to a thickness of 0.80 mm by a finishing hot rolling machine. Table 24 shows the concentration of the lubricating oil mixed in the roll cooling water of the finishing hot rolling mill. The kinematic viscosity of the lubricating oil was 330 cSt by controlling the roll cooling water temperature to 51 ° C. The lubricating oil was piped to a position just before the work roll in a separate line from the roll cooling water, and the volume fraction of the roll cooling water was changed by devising the shape of each nozzle. As a comparative example, finish hot rolling was performed using the same lubricating oil under the same conditions with all the lubricating oil concentrations in the roll cooling water set to 0.4% and 4.0%.

[0101]

[Table 23]

[0102]

[Table 24]

The hot rolling finish temperature was 86 for both the present invention and the comparative example.
The temperature was adjusted to 5 ° C, cooled with water, and wound at 650 ° C. The experiment was performed 50 times in each of the present invention and the comparative example, and the occurrence rate of sheet bar biting failure was determined. The average of was used. From this product, an Epstein sample was cut out and its magnetic properties were measured. Table 25 shows the incidence rate of bite defects in the finishing head of the present invention and the comparative example,
Table 26 shows the magnetic measurement results.

[0104]

[Table 25]

[0105]

[Table 26]

From Table 25, it can be seen that in the present invention and Comparative Example 5, it is possible to prevent the sheet bar from biting into the finishing hot rolling machine. Table 26 shows that it is possible to manufacture a non-oriented electrical steel sheet having a high magnetic flux density in the present invention and Comparative Example 6.

From the above results, as a method for stably producing a non-oriented electrical steel sheet having a high magnetic flux density, the lubricating oil concentration in the roll cooling water of the finish hot rolling is set to 1.
It can be seen that while suppressing the lubricating oil concentration to 0% or less, the lubricating oil concentration in the roll cooling water injected to the work rolls after the second stand is preferably 1% or more and less than 10% in at least one pass. By this manufacturing method, it is possible to stably operate the finish hot rolling under high lubrication, and it is possible to stably manufacture non-oriented electrical steel sheets with high magnetic flux density and excellent magnetic properties. It has become possible.

[0108]

As described above, according to the present invention, it is possible to manufacture a non-oriented electrical steel sheet having high magnetic flux density and excellent magnetic properties by stable hot rolling.

[Brief description of the drawings]

FIG. 1 is a chart showing a relationship between kinematic viscosity and magnetic flux density of lubricating oil in roll cooling water at the time of finish hot rolling.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01F 1/16 H01F 1/16 A

Claims (4)

[Claims] 1.% by weight: 0.10% ≦ Si ≦ 4.00%, 0.10% ≦ Mn ≦ 1.50%, C ≦ 0.0050%, N ≦ 0.0050%, S ≦ 0 A slab containing 0.0050% with the balance being Fe and unavoidable impurities is hot-rolled to form a hot-rolled sheet, and then subjected to one or two or more cold rolling operations including intermediate annealing, and then to finish annealing. In the method for producing a non-oriented electrical steel sheet, the volume fraction of lubricating oil mixed in the roll cooling water used in the finishing hot rolling mill in the hot rolling step is 1.0% or less in the first stand,
In addition, at least one of the second and subsequent stands has a kinetic viscosity of 1.0% or more and 10% or less, and the kinematic viscosity of the lubricating oil is 100 cSt or more and 800 cSt. Stable manufacturing method. 2. In% by weight, 0.10% ≦ Si ≦ 4.00%, 0.10% ≦ Mn ≦ 1.50%, C ≦ 0.0050%, N ≦ 0.0050%, S ≦ 0 2. The slab according to claim 1, wherein the slab contains 0.150% ≦ Al ≦ 1.00%, and the balance is Fe and unavoidable impurities. A stable production method for non-oriented electrical steel sheets. 3. The kinematic viscosity of lubricating oil mixed in roll cooling water used in each stand of a finishing hot rolling machine is 20 or less.
The method for producing a non-oriented electrical steel sheet having a high magnetic flux density according to claim 1, wherein the magnetic flux density is 0 cSt or more and 800 cSt. 4. A front end of a sheet bar obtained by roughly rolling a slab is joined to a rear end of a preceding sheet bar to integrate a plurality of sheet bars, and the integrated plurality of sheet bars are continuously connected. 4. The method for producing a non-oriented electrical steel sheet having a high magnetic flux density according to claim 1, wherein the non-oriented electrical steel sheet has a high magnetic flux density.