JP3132936B2 - Method for producing grain-oriented silicon steel sheet with excellent magnetic properties - Google Patents

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 grain-oriented silicon steel sheet having excellent magnetic properties, which is mainly used as a core material for transformers and other electric equipment.

[0002]

2. Description of the Related Art As the iron core material of this kind of electric equipment,
Excellent magnetic properties, specifically 800A /
It is required that the magnetic flux density B ₈ (T) at m is high and the iron loss characteristic W _17/50 (W / kg) at an AC magnetic flux density of 1.7 T at 50 Hz is low. For this reason, oriented silicon steel sheets
The {110} <001> orientation, a so-called Goss orientation, is developed using secondary recrystallization. In order to obtain a material with excellent magnetic properties, the easy axis <001>
The axis must be highly aligned in the rolling direction, and it is important to stably develop the secondary recrystallized grains in the Goss orientation by various processes combining appropriate rolling and heat treatment.
In particular, it is important to uniformly and finely disperse precipitates such as AlN and MnS and MnSe, which are called inhibitors.

To achieve this, Japanese Patent Publication No. 50-21291
Japanese Patent Laid-Open Publication No. H10-15064 discloses a method in which the finish front temperature during hot rolling is set to 1150 ° C. or lower to precipitate an inhibitor during finish rolling. In this method, a steel sheet is cooled to a temperature lower than the precipitation temperature of an inhibitor such as AlN or the like, and strain such as rolling is introduced into the steel sheet to precipitate an inhibitor such as AlN. However, this method has a problem that the surface layer is cooled before finish rolling, so that inhibitors such as AlN on the surface layer of the sheet become coarse and precipitate, so that secondary recrystallization becomes unstable.

In Japanese Patent Publication No. 59-45730, AlN
This shows a method of controlling the precipitation of steel at a high temperature during hot rolling, but it is difficult to control the temperature uniformly in the longitudinal and width directions of the coil industrially, which is not practical. .

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to propose a manufacturing method capable of industrially stably obtaining a grain-oriented silicon steel sheet having excellent magnetic properties.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a method for producing S by weight%.
i: 2.0-4.5%, C: 0.01-0.12%, acid-soluble Al: 0.0
10 to 0.06%, N: 0.0030 to 0.0120%, Mn: 0.02 to 0.15
%, And one or two of S or Se.
After hot rolling a steel containing 0.005 to 0.060%, the steel sheet is subjected to one or more cold rolling steps including one or more intermediate annealing steps to obtain a final sheet thickness, followed by decarburizing annealing, followed by application of an annealing separator and final finishing annealing. In manufacturing a grain-oriented silicon steel sheet by a series of processes, the end temperature of rough rolling during hot rolling should be 1200 ° C or higher, the time from the end of rough rolling to the finish rolling exit side should be 150 seconds or less, and finish rolling The side temperature is 1000 ° C or less, and the steel sheet is annealed before final cold rolling to reduce the carbon content of the surface layer from 0.01 to 0.04.
%, Then remove the oxides by pickling in advance, reduce the oxides remaining on the plate surface after final cold rolling to 0.15 g / m ² or less in oxygen content, and further reduce the surface generated by decarburization. 0.9 to 1.8 g / m ² in terms of oxygen amount
This is a method for producing a grain-oriented silicon steel sheet having excellent magnetic properties.

[0007]

The present inventors have intensively studied an inhibitor control method in order to obtain an electromagnetic steel sheet having excellent electromagnetic characteristics. As a result, the inhibitor was refined during hot rolling, the texture was optimized, and the secondary refining was performed. It has been found that controlling the amount of carbon and controlling surface oxides in various steps before crystal annealing is very effective.

That is, it is desirable that the inhibitor be finely precipitated during the finish rolling as a means of making the inhibitor fine during the hot rolling. To this end, the finish temperature of the rough rolling is set to 1200 ° C. or higher, and the finish rolling is performed after the completion of the rough rolling. The time to the finish side should be within 150 seconds, and
It is necessary to keep the temperature below 00 ° C. Further, in order to make the texture proper, it is necessary to perform cold rolling by annealing the hot-rolled sheet to reduce the carbon in the surface layer by 0.02 to 0.03%.

At this time, in order to effectively use the inhibitor, the amount of the surface oxide generated by the final decarburization treatment must be reduced.
Unless the amount is 1.0 to 1.8 g / m ² , the secondary recrystallization is incomplete. If the oxide is out of this range, dissociation of the inhibitor into the annealing atmosphere cannot be prevented. Further, when controlling the amount of the oxide, it is necessary to remove as much as possible the scale generated during the decarburization annealing of the hot-rolled sheet. If the scale remains at this time, the secondary recrystallization will be incomplete even if the surface oxide during the final decarburization treatment is controlled as described above.

Here, the effect of oxides generated during the last decarburization treatment on secondary recrystallization will be described. The oxide generated during the decarburization annealing is mainly composed of silica, and is further composed of various oxides of iron and the like. These oxides react with the subsequently applied MgO as an annealing separator during the finish annealing to form an insulating glass film. Secondary recrystallization occurs during this finish annealing to produce a grain-oriented electrical steel sheet having good magnetic properties. At this time, depending on the nature of the oxide formed during the finish annealing,
It has been found that it is dissociated and discharged out of the plate before being useful for the next recrystallization, and the effect is lost.

The present invention is based on the finding that not only the quantity of the oxide before the secondary recrystallization annealing but also the quality of the oxide is important. The quality of the oxide can be controlled by the amount of the residual scale before the final decarburizing annealing, and even if the amount of the oxide is appropriate, even if the amount of the oxide is not within the range of the residual scale shown in the present invention. It became clear that stable secondary recrystallized grains could not be obtained.

Next, a preferred composition range of the electromagnetic steel sheet used in the present invention will be described. Si: 2.0-4.5% Si increases the specific resistance of the steel sheet and effectively contributes to the reduction of iron loss. However, when it exceeds 4.5%, the cold-rolling property is impaired, whereas when it is less than 2.0%, the specific resistance only decreases. Not secondary recrystallization
Since the crystal orientation is randomized by the α-γ transformation during the final high-temperature annealing performed for purification, and a sufficient iron loss improvement effect cannot be obtained, the Si content is preferably about 2.0 to 4.5%.

C: 0.01 to 0.12% C is an element useful not only for uniform micronization of the structure during hot rolling and cold rolling, but also for the development of the Goss orientation.
The content is preferably 0.01% or more. However, if the content exceeds 0.12%, the Goss orientation is rather disturbed. Therefore, the upper limit is preferably about 0.12%.

Mn: 0.02 to 0.15% Mn needs to be at least about 0.02% in order to prevent hot embrittlement, but if it is too much, the magnetic properties are deteriorated. Therefore, the upper limit should be set to about 0.12%. preferable. Inhibitors include the following AlN-based inhibitors,
There are nS and MnSe systems.

First, in the case of AlN system, acid-soluble Al: 0.01 to 0.06% N: 0.0030 to 0.0120% Al and N are effective elements as inhibitors for controlling secondary recrystallization of grain-oriented silicon steel sheets. From the viewpoint of securing the restraining force, at least 0.01% of Al and 0.0090% of N are required. However, if Al exceeds 0.060% and N exceeds 0.0120%, the effects are impaired. .
01% and N: 0.0030%, upper limit is Al: 0.06% and N: 0.01
20%.

In the case of MnS or MnSe, at least one selected from Se and S: 0.005 to 0.3.
The ranges of 060% Se and S are also set in the above ranges for the same reason as in the case of the AlN system described above. MnS described above
, MnSe-based and AlN-based are preferably used together in terms of electromagnetic characteristics.

As the inhibitor component, the above-mentioned S, S
e, Al, Cu, Ni, Sn, Cr, Ge, Sb, Mo, Zn, Te, Bi
And P etc. are also advantageously used, so that they can be contained together in small amounts. Here, the preferable addition ranges of the above components are Cu, Ni, Sn, Cr: 0.01 to 0.15%, Ge, S
b, Mo, Zn, Te, Bi: 0.005 to 0.1%, P: 0.01 to 0.2
%, And each of these inhibitor components can be used alone or in combination.

The silicon steel slab having the above-mentioned composition is heated at a high temperature and subjected to hot rough rolling and subsequently hot finish rolling. The end temperature of hot rough rolling must be 1200 ° C or higher. If the ratio is less than this, the inhibitor coarsely precipitates in the subsequent hot finish rolling to make the magnetic properties unstable. The finish temperature of hot finish rolling must be 1000 ° C or less. If it exceeds this, not only the inhibitor which is sufficiently refined cannot be obtained, but also the formed texture is insufficient, and the orientation after secondary recrystallization is lost. The time from the end of hot rough rolling to the end of hot finish rolling must be 150 seconds or less. Above this, the inhibitor precipitated during hot finish rolling becomes coarse, and secondary recrystallization becomes incomplete.

The hot-rolled sheet obtained by the hot-rolling method is cold-rolled by a known method, and the cold-rolling may be performed by a plurality of cold-rolling steps including recrystallization annealing in the middle even if performed once. May go. In the annealing before the final cold rolling, the surface layer needs to be decarburized. The amount of decarburization is 0 in the analysis including the entire thickness direction.
A reduction of 01 to 0.04% is necessary, and if it falls below this range, there is no decarburizing effect and a texture with good orientation cannot be obtained by secondary recrystallization.
On the other hand, if it exceeds, secondary recrystallization becomes insufficient.

Further, the oxide generated by the decarburization treatment is:
It contains silica as the main component, and is penetrated into the surface layer of the steel sheet. To completely remove the steel sheet, it is necessary to enhance pickling and to lightly grind the brush. After final cold rolling (before final decarburizing annealing)
If the amount of oxides remaining on the sheet surface exceeds 0.15 g / m ^{2 in the} amount of oxygen, secondary recrystallization becomes incomplete during final finish annealing.
This is presumed to be because, when the residual scale is large, a large amount of iron oxide is formed on the surface layer during the final decarburization annealing, and the inhibitor dissociates during the final finish annealing and escapes from the base steel. .

The steel sheet is subjected to final decarburization annealing after being cold-rolled to the final thickness. At this time, an oxide mainly composed of silica is also formed on the surface, but the amount is 0.9% in terms of oxygen.
1.81.8 g / m ² . Outside of this range, too much or too little secondary recrystallization will be incomplete or film quality will be poor, losing product value. However, even in the above range, if the amount of scale remaining on the sheet surface after the final cold rolling exceeds 0.15 g / m ² in the amount of oxygen, the secondary recrystallization is incomplete.

Further, a slurry of MgO, which is generally known as an annealing separator, is applied to the surface of the steel sheet. The coated steel sheet is usually wound into a coil and subjected to finish annealing. Finish annealing is annealing that combines secondary recrystallization and purification for removing impurities in steel, and is usually performed at a high temperature of about 1200 ° C. The coil after the finish annealing is coated with an insulating coating as necessary to obtain a product.

[0023]

【Example】

Example 1 C: 0.06%, Si: 3.05%, Mn: 0.075%, Se: 0.020
%, SolAl: 0.020% and N: 0.0085% are subjected to hot rolling, and the hot rough rolling end temperature is 1230.
° C and the hot finish rolling end temperature was 980 ° C. As comparative examples, the hot rough rolling end temperature was 1150 ° C, and the hot finish rolling end temperature was 920 ° C and 1000 ° C.

Also, the time required for finish rolling (rough pressure end-
Finish) was changed to 80 seconds, 100 seconds, 120 seconds, and 150 seconds. Further, by changing the amount of decarburization, the amount of residual scale, and the amount of surface oxygen after the final decarburizing annealing, the process up to the final finishing annealing was processed, an insulating film was formed, and the magnetic properties were measured. Table 1 shows the obtained magnetic properties B8.

[0025]

[Table 1]

Example 2 C: 0.06%, Si: 3.06%, Mn: 0.079%, S: 0.016
%, SolAl: 0.022% and N: 0.0090% are subjected to hot rolling, and the hot rough rolling end temperature is 1235.
° C and the hot finish rolling end temperature was 980 ° C. As a comparative example, the hot rough rolling end temperature was 1160 ° C., and the hot finish rolling end temperature was 1050 ° C.

The time required for finish rolling (rough pressure end-
Finish) was changed to 80 seconds and 150 seconds. Further, the amount of decarburization was set to 0.02%, the amount of residual scale and the amount of surface oxygen after final decarburization annealing were changed, the process up to final finish annealing was performed, an insulating coating was applied, and the magnetic properties were measured. Table 2 shows the obtained magnetic properties B8.

[0028]

[Table 2]

[0029]

According to the process of the present invention, a grain-oriented silicon steel sheet having good magnetism can be stably manufactured.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) C21D 8/12 C22C 38/00 303 C22C 38/60 H01F 1/16

Claims (1)

(57) [Claims] (1) Si: 2.0-4.5% by weight, C: 0.01-0.
12%, acid-soluble Al: 0.010-0.06%, N: 0.0030-0.01
After hot rolling a steel containing 20%, Mn: 0.02 to 0.15% and further containing 0.005 to 0.060% of one or two of S or Se, a plurality of cold rollings including one to intermediate annealing are performed. In order to produce a grain-oriented silicon steel sheet by a series of steps of applying an annealing separating agent following decarburizing annealing and applying a final finish annealing after decarburizing annealing, the end temperature of rough rolling during hot rolling is set to 1200. ℃ or more, the time from the end of rough rolling to the finish rolling exit side is within 150 seconds, and the finish rolling exit temperature is 10
100 ° C. or lower, and the steel sheet is annealed before final cold rolling to reduce the carbon content of the surface layer by 0.01 to 0.04%. The remaining oxide is reduced to 0.15 g / m ² or less in terms of oxygen, and the amount of oxide on the surface generated by the decarburization treatment is determined in terms of oxygen.
A method for producing a grain-oriented silicon steel sheet having excellent magnetic properties, characterized in that the thickness is 0.9 to 1.8 g / m ² .