JPS5950118A - Production of unidirectional silicon steel plate having excellent magnetic characteristic - Google Patents

Abstract

PURPOSE:To obtain a titled unidirectional silicon steel plate by cooling a hot- rolled steel strip of a continuously cast slab of a blank steel for continuous casting of a silicon steel contg. C, Si, Mn, S or/and Se at a prescribed cooling rate after it leaves the final finishing stand then coiling the steel strip and allowing the same to cool. CONSTITUTION:A continuously cast slab of the silicon steel contg., by weight, 0.020-0.080% C, 2.5-4.0% Si, 0.02-0.10% Mn, 0.008-0.050% S or/and Se and contg. <=0.1% Sb according to need is hot-rolled as follows: After said hot- rolled steel strip leaves the final stand, the steel strip is cooled down to the range of the temp. calculated from the equations I , II at 7-40 deg.C/sec cooling rate, whereafter it is coiled and is allowed to cool. If the cooling rate and coiling temp. after the hot rolling are adequately controlled, the uniform crystalline structure is effectively obtained after intermediate annealing by subjecting the hot-rolled strip to cold rolling and annealing even if it has coarse stretched grains. As a result, the perfect secondary crystal structure is formed and the uniform and excellent magnetic characteristics are obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a unidirectional silicon steel sheet with excellent magnetic properties, and particularly to a method of manufacturing it from a continuously cast slab.

Unidirectional silicon steel sheets are mainly used as iron core materials for transformers and other electrical equipment, and are basically important because they have excellent magnetic properties such as iron strength value and magnetic flux density.

Essential elements in the manufacturing process of unidirectional silicon steel sheets e,
j1, +1 from the primary recrystallized grains in the so-called final high-temperature annealing
．． , + (l l < 001:) oriented crystal grains. For this purpose, a dispersed phase called an inhibitor is required to suppress the growth of normal grains of -order 1g crystal grains. Representative examples of this inhibitor are listed in Japanese Patent Publication No. 33-9255.
'! 1 Kosho 36 17154 ”5 K l S
e, 'f'j Kimiaki, l D-15644 AzN, special public show 5'] -11469 issue sh
The methods of , S and Se are known.

The inhibitory effect of these 71 inhibitors is due to the final high temperature annealing A
This is achieved by uniformly and appropriately sized dispersing the inhibitor at iI*. For this reason, in the case of 1μ-shaped slabs, the slab is heated to a high temperature before hot rolling to sufficiently dissolve the inhibitory elements, and after the hot rolling process, secondary internal crystals 1);
The precipitated dispersion pattern ku is controlled during the initial process.

In the conventional 1<1j force method for manufacturing unidirectional silicon steel sheets,
A slab with a thickness of 130 to 25 (l mh) was made from the steel ingot by blooming rolling, and the slab was heated at 1250°C or higher to dissolve the inhibitor in solid solution, and then it was made into a hot rolled sheet. The best practice is to cold-roll once or twice to obtain the final plate thickness, perform decarburization annealing, and then perform final high-temperature annealing for the purpose of secondary recrystallization and purification.

Incidentally, in recent years, in the manufacturing process of steel, the ingot forming method is being replaced by a continuous casting method (hereinafter abbreviated as continuous casting). When this method is applied to the production of unidirectional tI' silicon steel sheets, the cast structure is destroyed by blooming, and the crystal structure is destroyed by recrystallization. The assembling process is omitted/Columnar crystal grains due to rapid solidification peculiar to the method 1 tend to grow abnormally when heating the slab as described in 111-2, and remain as coarse drawn grains after hot rolling.

These coarse grains do not recrystallize even after cold rolling and annealing, and even if the suppressing effect of the inhibitor is sufficient, the secondary recrystallization of the Goss orientation is incomplete in the final high temperature annealing, so-called It has the disadvantage that it mainly has a band-like fine grain structure, which leads to deterioration of magnetic properties.

71 yen and a normal coil width of about 10 D Omm to 50 mm or 100 mm [degrees] When the slab is made into a rolled iron core material, the band-shaped fine grains occupy the entire slit width.
Transformer manufacturers are taking extreme caution because the 1-coupling becomes extremely high and the magnetic properties of the iron core are significantly deteriorated.

As a measure to prevent this band-like fine grain,
No. 0 is used in the production of unidirectional silicon steel sheets, and in addition, No. 1 is a high magnetic flux density unidirectional silicon steel sheet that is continuously cast to create hot-rolled sheets from slabs that are continuously cast twice. This technology is a technology that produces hot-rolled sheets through two hot-rolling processes, that is, a preliminary hot-rolling process that corresponds to the blooming process in the steel ingot process. , it cannot be considered a rational manufacturing method from the original purpose of Renkin 11 Law.

Regarding hot rolling method of unidirectional silicon steel, Special Publication No. 38-14
(1 (1 (No. 1 fruit ti Ii 9 [according to c<o, o
5. qI,~II]S, 0.1! 'i%;, S+
: Silicon steel containing 2.75 to 359 g is hot-rolled at 925°C or higher, and the temperature is 4 (2.75~359g or higher),
It is quenched at 65F/sec and wound up at a temperature below 1.54 (') °C, and then aged for a certain period of time within the range of 480 to 31 () °C to remove lens-shaped precipitates. The purpose is to
This method is related to a method for improving magnetism using 1l-L steel ingots, and the abnormal growth of crystal grains that occurs when slab heating of continuously cast slabs as described above does not occur, and band-like fine grains do not occur in the finished product. . However, this method was applied to continuously cast slabs. There were also cases where the effect of preventing band-like fine particles was insufficient for one knot. Furthermore, when we experimented with this method, we found that after coiling, 7.1M leaves the finishing mill and then winds it on the winder (
Because the cooling rate between = t < 4 is too high, waving becomes large, and the tip may be bent or 1
Accidents where the winding could not be unrolled frequently occurred due to jamming in the gap between the general feed rollers7, which caused problems in operability and economy.

Furthermore, according to JP-A No. 56-33431, in the process of hot rolling silicon steel, the coiling temperature is set at 7 (10 to 1 (j (l f
A method of controlling within the range of 1°C, and 700~1F'
He proposes a method of wrapping the copper strip at 1F and 10℃ and wrapping it in a water tank or the like. These drawing methods are aimed at improving the precipitation and dispersion state of AtN 2 and stabilizing secondary recrystallization.

1-1 of the present invention is to solve the above-mentioned problems of the prior art and to provide a method for manufacturing a unidirectional silicon steel sheet with excellent magnetic properties from continuous casting.

The above objects of the present invention can be achieved by the following two inventions.

The gist of the first invention is as follows. That is, in the tun III ratio, C: 0. (12fl~0080
%, Si: 2.5-4.0X, Mn: 0.
02 to 0.10%, S, % = any one of 1 or 2 fi 1) total force (1,008 to 0.05 ()% included, depending on the history S b: 0°], +1% or less In method No. 5 of manufacturing a unidirectional TI raw steel plate, which comprises the step of hot rolling a continuously cast slab of silicon steel containing
I) The Jl H14 hot-rolled belt was cooled at a cooling rate of 7 to 40°C/sheet after leaving the final stand in the temperature range calculated from equations (1) and (2) above. This is a patented method for manufacturing a unidirectional silicon steel sheet, which is characterized in that it includes a step of post-rolling and cooling, P-.

[35×! ．． 01,o■+515]℃・・・・・・(1)
[445x7o9,. V-57n] r.
``' (2) However, V: Cooling rate of the hot-rolled steel strip in the winding 11X/second after leaving the final finishing stand ('C/sec) The gist of the second invention is the same as the first invention. In the hot rolling of continuously cast slabs, the hot rolled steel strip is
After cooling the final stand to a temperature calculated from the following formula (3) at a cooling rate of 7 to 3oC/sec, it is coiled, and the coiled steel strip is further cooled with water. Features: 1. Unidirectional silicon steel sheet with excellent thermal properties.

[20×tOf,o■+555]℃・・・・・・(3)
The inventors of the present invention have conducted intensive research on a hot rolling method for producing uniformly L7 products with excellent magnetic 'Pf properties without band-like fine grains from a single continuously cast unidirectional silicon slab material. It was found that there is a significant relationship between the cooling rate during the winding η warp size after passing one roll on the final stand and the winding thickness 1 degree.

Next, while explaining the experimental data, we conducted a follow-up investigation into the cause of the generation of band-like fine grains, and found that it was largely influenced by the crystal structure of the hot-rolled sheet. The crystal structure of a hot-rolled sheet produced from a continuously cast slab through slab heating and hot rolling is shown in FIG. 1, and coarse drawn grains are present in the center of the sheet.

These coarsely stretched grains are coarse columnar crystals formed during continuous casting that grow abnormally during slab heating and are elongated during hot rolling.
l o O l < (1 1 1 > map ζ is (21
11<' (l I l >e'j. Even after the subsequent cold rolling, furnace, and blunting, it remains extremely stable and does not recrystallize (Fig. 2 φ), and Fig. 3 <A) Even after intermediate annealing and decarburization annealing, unrecrystallized grains remain. As a result, the finished product is shown in Figure 4 (A). Band-like fine grains appear, and the crystal orientation of this part is {1101<0(1
1> It is difficult to obtain uniform and excellent magnetic properties unless the direction is far off.

As a countermeasure to this problem, various methods for improving the crystal structure of hot-rolled sheets were investigated.It was found that the cooling rate after hot-rolling and the coiling temperature are the causes of the formation of band-like fine grains.

In other words, if the cooling rate and coiling temperature after hot rolling are appropriately controlled, even if there are coarse drawn grains in the hot rolled sheet, it will pass through cold rolling and annealing, and after intermediate annealing it will be as shown in Figure 2 (1). As shown in FIG. 3 (03) after heat and decarburization annealing, a uniform crystal structure can be effectively obtained. As a result, it was found that the final high-temperature annealing resulted in a complete secondary recrystallized structure as shown in FIG. 4 (13), resulting in uniform and excellent magnetic properties.

Next, the reason for limiting the components of the present invention will be explained.

C: C is an element necessary to refine the crystal structure of the hot rolled sheet. Next, an experiment to investigate the effect of C content on the crystal structure will be explained.

C: 0.009-0.056%, Si: 2.95-29
8%, Mn: 0.068 to 0.073%
, S:0. (A sheet bar with a thickness of 30 mm was made from nine continuously cast slabs with a composition of 118-0 (120%, The hot-rolled sheets were immediately cooled at 300° C. at a cooling rate of 24° C./sec. After pickling these %lE sheets, they were cold-rolled twice with so-called intermediate annealing to reduce the %lE to 0.3. (The product was made of a unidirectional silicon steel plate with a thickness of 1 mm, and the relationship between the C content and the area ratio of band-shaped fine grains was investigated for this product and is shown in Figure 5.

As is clear from Fig. 5, the content of C has a great relationship with the generation of band-shaped fine particles; if it is less than 0.02%, the generation rate of band-shaped fine particles is extremely large and there is no prevention effect; The area ratio of band-like fine grains is decreasing.

For this reason, the lower limit of the C content is set at 0.02%, but 0.02% is the lower limit.
If it exceeds 8%, decarburization before final high-temperature annealing becomes difficult and magnetic properties deteriorate, so C was limited to a range of 0.02 to 0.008%.

SI: When SI is less than 25%, α-γ transformation exists, which inhibits secondary recrystallization in the final high-temperature annealing. On the other hand, if it exceeds 40%, cracks tend to occur during cold rolling, so it is limited to a range of 2.5 to 40%.

Mn: Mn is an element that forms MnS or 4nSe and has an inhibitor effect, but (1,020%
If it is less than 0.0, the formation is insufficient. lo pσ
When it exceeds ire, the solid solution temperature of the inhibitor before hot rolling is ire,
＜, which makes it difficult to heat the slab (,),
(8 S, Se limited to the range of 120~0゛10%: S and Se each have the effect of an inhibitor, but if each alone or the combination of the two is less than o, oos%, complete secondary regeneration occurs. Since no crystals are obtained, 0.(l 08%
The above is necessary. On the other hand, if it exceeds 0.050% alone or in total of V and 2, the solid solution temperature before hot rolling will be high, and desulfurization or selenium removal in the final high-temperature annealing will be insufficient, so the upper limit should be set. 0. (It was set as 150%.

Sb: sb segregates at grain boundaries and suppresses the growth of primary recrystallized grains,
, Se can coexist with one or two types and improve the magnetic properties, but if it exceeds 0.10%, the effect will be saturated, so it was limited to 0.10% or less.

In the present invention, the inhibitor and [7teS, 8c
and Sb as well as other known inhibitors such as 13, B! , A ss P l) b, etc. may be added without adding one or two types.

Next, a method for manufacturing a grain-oriented silicon steel sheet from a continuously cast slab having the above-mentioned limited components will be described. First, we studied the relationship between the occurrence of band-shaped fine grains and the cooling rate, coiling temperature, and cooling method after hot-rolling, and obtained a method for manufacturing unidirectional silicon steel sheets with excellent magnetic properties without band-shaped fine grains. .

That is, C: O, (132%, Si: 3.01%, M
A sheet bar with a thickness of 30 fins was made from a continuously cast slab having a composition of n: 0.072% and S: 0.020%, and a portion of the sheet bar was cut out into 116 small pieces of the sheet bar. This sheet bar was heated at 320°C, hot-rolled into a 25-shrinkage hot-rolled plate, and hot-rolled at 850°C. This hot-rolled sheet is immediately cooled by various cooling methods, and when it reaches a temperature corresponding to the coiling temperature, it is immersed in a water bath to be rapidly cooled, and the sheet is pre-rolled in a furnace that can be cooled according to the copper strip cooling conditions. The material was adjusted to the desired temperature, charged into the furnace, and cooled in the furnace. After pickling, this hot-rolled sheet was cold-rolled twice with so-called intermediate annealing (a unidirectional silicon steel sheet having a thickness of 1.35 mm was obtained, and the generation of band-shaped TIL+ grains was investigated for this product.

FIGS. 6 and 7 show the relationship between the cooling rate after hot rolling, the coiling temperature, and the area ratio of band-like fine grains in the finished product. Note that FIG. 6 shows the case where the winding diameter is air-cooled, and FIG. 7 shows the case where the winding diameter is water-cooled.

The following can be seen from Figure 6. Cooling speed after hot rolling is slow 4
℃/sec, even if the winding temperature is lowered, the generation of band-like fine particles cannot be prevented. Cooling rate 7~b℃ or less, [445Xtof
', oV-57 (VJ℃ or higher, then winding and cooling the winding diameter to prevent the formation of band-like fine particles.The cooling rate is even faster, and by winding at 70~b), the band-like fine particles can be prevented. prevent the occurrence of

However, under these conditions, waving becomes large after the tip of the hot rolled steel strip leaves the rolling mill until it is wound, causing the tip to bend or get caught in the gap between the conveying rollers and unwound. In many cases, there is no such thing, making it less practical in terms of operability and economy.

From FIG. 7, the following can be seen in the case of water-cooled winding diameter.

When the cooling rate after hot rolling is slow at 4° C./sec, generation of band-like fine grains cannot be prevented even if the winding diameter is water-cooled. Cooling rate 7~:(
In the case of θ℃/sec, the winding temperature is [20×tnf, n V
-1-555: ] If the winding diameter is cooled to below ℃ and the winding diameter is water-cooled, narrow strips M1\'l can be effectively prevented. 40-b, where the cooling rate is four times faster. Even if water cooling is performed from the preheating temperature, generation of band-like fine particles cannot be prevented.

Example 1 C: O (138%, Si: 3.02%, M n :
(thickness 200% including 1,075%, S: 0.02%)
After heating 5 continuously cast slabs of silicon steel with a thickness of 1,300 mm, they were heated to 1,370°C, and then processed into a 25 mm thick hot-rolled steel strip using a rough rolling mill. After the hot-rolled steel strip is finished and leaves the rolls of the rolling mill, the cooling rate at the winding machine is adjusted to the first level by adjusting the cooling water h1.
Cooling was performed according to the cooling conditions shown in the table. These hot-rolled copper strips were pickled by a known method and then cold-rolled (185 tram intermediate plate j
Then, it was annealed at 950°C for 3 minutes, and then cold-rolled (with a final thickness of 1.35 corners and annealed at 840°C for 5 minutes).
! i+! After decarburizing and drying in water, MrO was applied, and a final high-temperature annealing was performed in hydrogen at 1170°C for 10 hours to obtain a unidirectional 1-element fM (i)-1 strip-like product. I investigated the attractiveness and magnetic properties of f1'1, and the results are shown in Chapter 1 (also in Part 1).

From the first person (on the shaft side A and E, band-like fine grains are generated)
Compared to this study example 1: (, C and D materials have excellent magnetic properties without 4'j-shaped fine grains in the finished product.) I understand.

Example 2 C: (1,4135%, S + : 2.98%, M
n:0. f”+6796,S:(1,(1(17%,S
e: (All five slabs of silicone Nakatsu guts with a thickness of 200 layers containing 1,013% were heated at 1350°C and the same as in Example 1 (~η
A P8 rolled steel strip with a thickness of 22 gates was made using the H method of ;rc 2
Which four hot-rolled strips were cooled in the W cooling dispute?
Acid using R11 JJ method, cool before and after! After being tempered for 2 minutes at 17.950°C with an intermediate thickness of 0.72 mm by Australia, it was P+ and cold rolled to a final thickness of 0.30 mm at 820°C.
After decarburizing annealing in wet hydrogen for 5 minutes, M Y □ was applied and I
The final height was 10 hours at 70°C in hydrogen, and the product was made into a unidirectional ('l: TI: elemental σ1'1 band product, and its output:
The presence or absence of fine grains and magnetic properties were investigated and are also shown in Table 2.

From Table 2, Comparative Example 1 = ", the J material has one band-like particle I, ll, and is inferior in temperature resistance, but the invention example Cl, H, and I materials have no band-like fine particles and have excellent magnetic properties. It can be seen that the same effect is obtained even when the inhibitor is 8.Se.

Real time column 3 C: (1,n 4 n,”s SI: 2.95
A, λ4n: 0.070%, S: 0.005. . 6.S
c: O, O], 55% sb: Five continuous slabs of silicon steel containing 0.025% were heated at 1370° C. 1, and a hot rolled steel strip with a thickness of 2.7 was prepared in the same manner as in Example J. Toshi 2,
Cool it under the cooling conditions shown in Table 3. These hot-rolled steel strips were pickled and cold-rolled to an intermediate thickness of 0.78mm by a known method, annealed at 950°C for 2 minutes to /nji l-, and then cold-rolled again to an IQ finish of 0.30mm. The plate thickness was set to 7.850°C for 5 minutes in wet hydrogen, and after decarburization <+'6, M f O was applied. These steel strips were held at R70 tl'' for 20,874 hours, heated to 1180°C, and then subjected to final high-temperature annealing in hydrogen for 10 hours to produce a unidirectional silicon steel strip. The presence or absence of magnetic properties and magnetic properties were investigated, and the results are also shown in Table 3.

Table 3 shows that Comparative Material No. 10 has band-like fine grains and is inferior in magnetic properties, while the present invention examples, M and N, have no band-like fine grains and have extremely excellent magnetic properties. It can be seen that there is a synergistic effect of the inhibitors S%Se and Sb.

As is clear from the above embodiments, the present invention has been achieved by limiting the components and by limiting the cooling conditions during and after winding the hot rolled copper strip from the finishing stand in the hot rolling process from the continuous cast slab. It is possible to produce unidirectional silicon steel sheets with no grains and excellent magnetic properties.

[Brief explanation of drawings]

Figure 1 is a cross-sectional micrograph of unidirectional silicon steel from a continuous cast slab after hot rolling, and Figure 2 (A) is a cross-sectional micrograph of unidirectional silicon steel from a continuous cast slab after intermediate annealing. Figure 2 (A) is a photograph taken by the conventional method, Figure 2 (03) is a photograph taken by the method of the present invention, and Figure 3 (A), σ3) is a photograph taken by the method of the present invention. The cross-sectional gIR micro-otoscope photograph after charcoal annealing was taken using the conventional method (Figure 3 (B)).
4(A) is a macrostructure photograph of a unidirectional silicon steel product, FIG. 4(5) is a photograph obtained by the conventional method, and FIG. 4(03) is a photograph obtained by the method of the present invention. Figure 5 is a diagram showing the relationship between the carbon meter and the area ratio of band-shaped fine grains, Figure 6 is the cooling rate after hot rolling in the case of late cooling after coiling.
A diagram showing the relationship between the winding speed and the area ratio of band-like fine grains in the finished product. Figure 7 shows the relationship between the winding diameter and the cooling rate after hot rolling in the case of water cooling, the coiling temperature, and the occurrence of band-like fine grains in the finished product. FIG. 3 is a diagram showing the relationship with area ratio. Agent Takeo Nakaji Fig. 1 Fig. 2 (A) CB) Fig. 3 (A) (B) Fig. 4 crn Fig. 5 Chariot amount (%) Fig. 6 Determination (・07 seconds) ) Figure 7 0 Inventor Shigeki Yamada 108 Kawasaki Steel Co., Ltd. Technical Research Laboratory, 1 Kawasakicho, Chiba City

Claims (2)

[Claims] (1) By weight ratio, C: 0.020-0.080%, S
r: 2.5-4.0%, Mn: 0.02-0.
10%, the total of any one or both of S and Se is 0
008-0050%, and if necessary, Sl): 0.
In a method for producing a grain-oriented silicon steel sheet comprising the step of hot rolling a continuously cast slab of silicon steel containing 10% or less, after the hot-rolled copper strip is finished and leaves the final stand, the following (1) ), (2) to a temperature range calculated from equation (2). [ 3 5 X tof,. V+51.5)'C...
...(1) C445×iof,. V-570]℃...
(2) However ■: Cooling rate of the hot-rolled steel strip at the coiler after leaving the final stand (°C/sec) (2) C: o. o2o~0. (1 8
0%, S i :2. 5-4. 0%, Mn
: 0. ('l2~O.10%, the total of any one or two of S and Se is 0008~005
81): In a method for producing a grain-oriented silicon steel sheet comprising the step of hot rolling a continuous cast slab of silicon steel containing 0.10% or less, the hot-rolled copper Unidirectional silicon with excellent magnetic properties characterized by including a step of water cooling the wound bts+strip to a temperature below the temperature calculated from the following formula (3) after finishing the strip and leaving the final stand. steel plate. [20X7or, oV+555] °C...-(3) However, ■: Cooling rate IO' of hot-rolled steel strip from leaving the final finishing stand until winding up (°C/sec)