JP2619064B2 - Method for producing grain-oriented silicon steel sheet with good punchability - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a grain-oriented silicon steel sheet having good magnetic properties, and more particularly to providing a grain-oriented silicon steel sheet most suitable for punching. It is.

(Prior art) Unidirectional silicon steel sheet is obtained by developing secondary recrystallized grains of (110) [001] orientation. It is performed in a high temperature range of 800 to 1200 ° C. after primary recrystallization annealing also serving as charcoal. During this annealing, the surface of the silicon steel sheet reacts with MgO, which is an annealing separator, and a surface oxide mainly composed of SiO ₂ generated during the primary recrystallization annealing to form a 2-5 μm-thick pore. A stellite coating (hereinafter referred to as forsterite coating) is formed, and impurities in the steel are removed to improve iron loss.
Deterioration due to aging is prevented. Usually, in order to further provide insulation, a phosphate-based coating is applied to the product.

By the way, since this forsterite film is extremely hard, a punching tool is easily worn when a steel plate is punched. Therefore, it is preferable that there be no forsterite film when performing punching.

Although it is possible to mechanically remove this forsterite film by grinding, the adhesion of the film requires strong and strong grinding, and as a result the magnetic properties are significantly degraded. Not used in the process.

Therefore, various techniques have been proposed for silicon steel sheets to be subjected to punching. For example, JP-A-53-22113 discloses a technique in which Al ₂ O ₃ and a hydrous silicate mineral are applied as an annealing separator to prevent formation of a forsterite film. Furthermore, in Japanese Patent Publication No. 58-44152,
In order to improve the removal of residual oxides in steel, in addition to Al ₂ O ₃ and hydrous silicate minerals, compounds containing Sr or Ba
The use of a separating agent containing CaO or Ca (OH) ₂ is disclosed. JP-A-59-96278 discloses that Al ₂ O _{2 is} used as a separating agent for further improving the removability of oxides in steel.
₃ Disclosed are those containing 15 to 70 parts by weight of inert MgO and S with respect to 100 parts by weight.

(Problems to be Solved by the Invention) However, when a coil is produced by actually using these annealing separators, the removal of impurities from the center to the inner winding of the coil becomes insufficient.

That is, no matter which annealing separator is used, the removal of impurities is incomplete, and the magnetic properties are partially or entirely deteriorated.

Further, the above prior art is characterized by minimizing the generation of oxide (forsterite film) generated on the surface of the steel sheet, but has the following disadvantages.
That is, the grain-oriented silicon steel sheet is cooled after the secondary recrystallization annealing, and during that period, impurity components such as nitrogen are diffused back into the steel from the surface layer to form precipitates such as nitrides. These deposits significantly impair the mechanical properties of the product, especially the venting properties.

An object of the present invention is to propose a method for manufacturing a grain-oriented silicon steel sheet which is excellent in magnetic properties and bend properties and is suitable for punching without a forsterite film.

(Means for Solving the Problems) In the grain-oriented silicon steel sheet, the forsterite film, which is the base film, is a main cause of deteriorating the punchability, but plays an important role in the production process of the grain-oriented silicon steel sheet. ing.

That is, first, it is performed at a high temperature of 800 to 1200 ° C.
It acts as a sink for impurities during the next recrystallization annealing and plays an active role in decomposing or removing impurities in the steel sheet.
Secondly, it prevents the impurity gas from diffusing back into the steel after cooling.

Therefore, in order to sufficiently remove impurities and to prevent back diffusion of gas components during cooling, it is advantageous to perform secondary recrystallization under conditions for forming a forsterite film, and then remove the forsterite film. It is.

However, when mechanical grinding is performed with a grinding roll or the like to remove the forsterite film, the amount of ground iron removed increases and composition distortion occurs during processing, so that the magnetism of the steel sheet is fatally deteriorated. Even if pickling is used, the adhesion of the forsterite film must be strong and strong pickling must be performed.
Therefore, the amount of dissolved base iron increases, and it is difficult to use it industrially.

Therefore, the present inventors have conducted various studies on a method of removing this forsterite film without giving significant distortion to the ground iron, and as a result, the polishing surface becomes an elastic material. It has been found that the above object can be achieved by polishing using abrasive grains or an elastic abrasive containing abrasive grains.

That is, the present invention is to provide a steel sheet containing slab which is heated and then hot-rolled, and then cold-rolled once or twice with intermediate annealing to a final thickness, and then subjected to primary recrystallization annealing combined with decarburization. After applying an annealing separator containing MgO as a main component on the surface of the steel sheet, and then subjecting the steel sheet subjected to finish annealing to removal of only the forsterite film generated on the surface layer, a short time is applied to the steel sheet. After pickling, the surface of the steel sheet is subjected to a polishing treatment using an elastic abrasive and an elastic abrasive containing free abrasive grains or abrasive grains. It is a manufacturing method.

In the method for manufacturing a grain-oriented silicon steel sheet according to the present invention, first, a starting material is formed into a slab of a molten steel component to which various inhibitor components such as conventionally known MnS, MnSe, AlN, Sb, and B are added, and then hot-rolled. As long as the final thickness is obtained by appropriately combining cold rolling and annealing, any process may be performed.

For example, the starting material is a conventionally known unidirectional silicon steel material component, for example, C: 0.01 to 0.050%, Si: 2.50 to 4.5%, Mn: 0.01 to 0.2%,
Mo: 0.003 to 0.1%, Sb: 0.005 to 0.2%, one or two types of S or Se, and a composition containing 0.005 to 0.05%, C: 0.01 to 0.08%, Si: 2.0 to 4.0%, S: 0.005-0.05%, A
l: 0.005 ~ 0.06%, N: 0.001 ~ 0.01%, Sn: 0.01 ~ 0.5%, Cu:
Composition containing 0.01 to 0.3%, Mn: 0.01 to 0.2% C: 0.011 to 0.06%, S: 2.0 to 4.0%, S: 0.005 to 0.05%,
B: 0.0003-0.0040%, N: 0.001-0.01%, Mn: 0.01-0.2%
It is applicable in compositions such as

Next, a hot-rolled sheet is subjected to homogenizing annealing at 800 to 1100 ° C, and then subjected to a single cold-rolling method to obtain a final sheet thickness by one cold rolling, or usually 850 ° C.
Cold rolling with intermediate annealing at 1050 ℃
In the latter case, the initial draft is 50% to 80%.
The final rolling reduction is about 50% to 85% and 0.15mm to 0.1%.
The final cold rolled sheet thickness is 35 mm.

(Operation) In the present invention, the cold rolled sheet described above is used for decarburization.
After the next recrystallization annealing, an annealing separator containing MgO as a main component is applied. The reason for applying the annealing separator containing MgO as the main component is that MgO and S which occur on the steel sheet surface during the decarburization primary recrystallization annealing
This is because a forsterite (2MgO.SiO ₂ ) undercoat is formed by reacting with an oxide containing iO ₂ as a main component. If a forsterite-based undercoat film is formed, the removal of the impurity components progressing during the secondary recrystallization annealing from the steel sheet is improved.

The annealing separator also affects the secondary recrystallization annealing, and in order to align the secondary recrystallized grains of the steel sheet to the (011) [100] orientation,
An annealing separator based on MgO is advantageous.

Further, when an annealing separator containing MgO as a main component is used, excellent mechanical properties can be secured. The mechanical properties are particularly required to be excellent in bend properties, and the bend properties are evaluated based on the presence or absence of breakage when the steel sheet is bent at 90 °.
Table 1 shows the incidence of defective products having a bending number of 3 or less.

The table shows that when MgO is used as the annealing separator, a steel sheet having excellent bend characteristics can be obtained as compared with the annealing separator used in the production of conventional silicon steel sheets for punching.

Next, since MgO was used as an annealing separator, the forsterite film formed on the steel sheet surface had to be removed.
In order to remove the forsterite film, a short-time pickling is first performed. The pickling may be hydrochloric acid or sulfuric acid.
For example, pickling is performed at about 80 ° C. for about 30 seconds using sulfuric acid having a concentration of about 10%. Without this pickling, the forsterite film cannot be removed by subsequent polishing.
Further, in order to remove the forsterite film only by pickling, it is necessary to perform pickling for a long time, which causes a decrease in yield and a deterioration in magnetic properties of the product.

It is considered that this short-time pickling causes cracks in the surface of the forsterite film, and the subsequent polishing easily breaks and peels the film.

The polishing treatment performed after the short-time pickling uses an elastic abrasive and abrasive grains. Preferably, the elastic abrasive is used in the form of a polishing roll or a polishing brush.

The polishing roll has a polished surface formed of an elastic material having a preferable Shore hardness of about A30 to A70, such as a nonwoven fabric or polyurethane.If the elastic material is too soft, the work efficiency is reduced, and if the elastic material is too hard, distortion is caused by ground iron. Introduced inside, the magnetism deteriorates.

On the other hand, the polishing brush is obtained by planting a brush thread made of nylon or the like on the peripheral surface of the roll, and it is desirable that the brush thread has sufficiently soft elasticity. Specifically, it is preferable that the load required to push down the brush thread by 1 cm on the fulcrum at an interval of 4 cm is 10 g or less.

It is preferable that the abrasive grains interposed between the steel plate and the elastic abrasive be free abrasive grains, or the abrasive grains are contained in a polished surface or a brush thread.

The loose abrasive is used by mixing the abrasive in a polishing liquid without fixing the abrasive to a polishing roll or brush. The abrasive used here is desirably a fine powder of # 240 or more in JIS R6001. This is because the coarser the grain, the greater the deterioration of the magnetism.

Further, abrasive grains may be used by being fixed to the polishing surface of a polishing roll or a brush thread of a polishing brush. In this case, it is desirable to use fine powder of # 240 or more in JIS R6001.

As described above, secondary recrystallization annealing was performed using an annealing separator containing MgO as a main component, and then a short-time pickling, and an elastic abrasive and abrasive grains contained or released therein were used. By the polishing treatment, it is possible to produce a grain-oriented coarse steel sheet having excellent magnetic properties and vent properties and good punching properties.

(Example) Example 1 C: 0.025%, Si: 3.10%, Mn: 0.08%, Al: 0.022%, Se: 0.01
A hot rolled sheet containing 8% and S: 0.01% was subjected to quenching treatment after homogenizing annealing at 1150 ° C. for 3 minutes, and then to a 300 ° C. warm rolling to obtain a final cold rolled sheet of 0.20 mm thickness. .

Then, after decarburizing annealing in 830 ° C wet hydrogen, apply an annealing separator mainly composed of MgO on the surface in the form of a slurry, and then raise the temperature from 800 ° C to 1200 ° C at 12 ° C / hr for secondary recrystallization. After
Purification annealing was performed at 1200 ° C. for 5 hours in dry hydrogen.

After removing the annealing separator from the steel sheet surface, the steel sheet was pickled at 70 ° C. in a 10% sulfuric acid aqueous solution for 40 seconds.

Next, a polishing roll (300 mmφ) made of nonwoven fabric and # 600
The forsterite film on the surface of the steel sheet was removed using the free abrasive grains. The polishing roll is rotated at 1000 RPM.
With the processing of the path. Thereafter, a phosphate-based coating was applied to the surface of the steel sheet to obtain a product.

As a comparison, an annealing separator containing Al ₂ O ₃ as a main component was applied, annealed at 1200 ° C. for 5 hours, and a phosphate coating was similarly applied to the steel sheet surface to obtain a product.

Table 2 shows the results of examining the punching properties and bend characteristics of the obtained products.

It can be seen from the table that the product obtained according to the present invention is excellent in both punching properties and bend characteristics.

Example 2 C: 0.03%, Si: 3.01%, Mn: 0.065%, Sb: 0.018%, Se: 0.02
The hot-rolled sheet containing 0% is subjected to a homogenizing annealing at 1150 ° C. for 3 minutes, followed by a quenching treatment, followed by a warm rolling at 300 ° C. for 0.2 minute.
The final cold-rolled sheet was 0 mm thick.

Then, after decarburizing annealing in 830 ° C wet hydrogen, apply an annealing separator mainly composed of MgO on the surface in the form of slurry, and then raise the temperature from 800 ° C to 1200 ° C at 15 ° C / hr for secondary recrystallization. After
Purification annealing was performed at 1200 ° C. for 5 hours in dry hydrogen.

Thereafter, the steel sheet surface was removed from the annealing separator, and then pickled at 80 ° C. in a 10% hydrochloric acid solution for 30 seconds.

Next, a polishing brush (300 mmφ) containing # 600 abrasive grains contained in the brush yarn was rotated at 1200 RPM to remove the forsterite film on the surface layer of the steel sheet. Thereafter, a phosphate-based coating was applied to the surface of the steel sheet to obtain a product.

As a comparison, an annealing separator containing Al ₂ O ₃ as a main component was applied, annealed at 1200 ° C. for 5 hours, and a phosphate coating was similarly applied to the steel sheet surface to obtain a product.

Table 3 shows the results of examining the punching properties and bend characteristics of the obtained products.

It can be seen from the table that the product obtained according to the present invention is excellent in both punching properties and bend characteristics.

(Effects of the Invention) According to the present invention, secondary recrystallization annealing is performed using an annealing separator containing MgO as a main component, and then pickling and subsequent polishing are performed, thereby producing a steel sheet surface. The forsterite film can be removed without deteriorating the magnetic properties and while ensuring excellent bend properties, and a grain-oriented silicon steel sheet having excellent punching properties can be manufactured.

Continuation of the front page (56) References JP-A-64-36727 (JP, A) JP-A-62-294131 (JP, A) JP-A-62-69501 (JP, A) JP-A-61-201732 (JP, A) , A)

Claims (1)

(57) [Claims] 1. A silicon-containing steel slab is heated and then hot-rolled, and then cold-rolled once or twice with intermediate annealing to a final sheet thickness, and then subjected to primary recrystallization annealing also serving as decarburization. After applying, an annealing separator containing MgO as a main component is applied to the surface of the steel sheet, and then the steel sheet subjected to finish annealing is applied.
In order to remove only the forsterite film formed on the surface layer, the steel sheet is subjected to a short-time pickling, and then the surface of the steel sheet is subjected to a polishing treatment using an elastic abrasive and free abrasive grains or an elastic abrasive containing abrasive grains. A method for producing a grain-oriented silicon steel sheet having good punching characteristics, wherein