JPS619521A - Manufacture of grain oriented silicon steel sheet superior in surface property and having high magnetic flux density, low iron loss - Google Patents

Abstract

PURPOSE:To obtain extremely stably the titled grain oriented silicon steel by condensing Mo (compound) to a silicon steel slab surface layer having a specified component compsn., then heating, hot rolling, cold rolling, next applying primary recrystallization treatment and final finishing annealing to said material. CONSTITUTION:A silicon steel slab contg. by weight 0.01-0.06% C, 3.2-4.5% Si, 0.050-0.2% Mn, 0.008-0.1% Se, 0.003-0.1% Mo and 0.005-0.1% Sb is manufactured. Next, inorganic compound (e.g. CuMoO3, H2MoO3, etc.) contg. Mo is coated uniformly on the surface of the slab, said body is heated, then hot rolled to obtain the hot rolled plate having usually about 2-5mm. thickness. Next the hot rolled plate is homogenizing annealed then cold rolled >=2 times interposing intermediate annealing at 850-1,000 deg.C to the final product thickness (usually 0.3mm. thickness), then subjected to primary recrystallization annealing applied also as decarbonization, further subjected to the final finishing annealing. As the result, the grain oriented silicon steel sheet in which secondary recrystallized grain having {110}<001> orientation is developed is obtained.

Description

[Detailed Description of the Invention] (Technical Field) The technical contents described in this specification related to the production of unidirectional silicon steel sheets with high magnetic flux density and low core loss are related to the improvement of surface properties in addition to the above performance. The aim is to propose development results.

(Technical background) Unidirectional silicon steel sheets are mainly used as iron cores in transformers and other electrical equipment, and have excellent magnetization characteristics, that is, low iron loss (represented by W1?/so). That is required.

For this purpose, firstly, the secondary recrystallized grains in the steel sheet must be
＞It is necessary to highly align the oriented grains in the rolling direction,
Secondly, it is necessary to reduce as much as possible the impurities and precipitates present in the final steel product.

Unidirectional silicon steel sheets manufactured under careful consideration of these points have been improved over the years through many improvement efforts, and recently products with a thickness of 0-80+si have achieved W" Products with a low core loss value of /so of about 1.05 Vkg are manufactured.

However, after the energy crisis a few years ago, the trend for electrical equipment with less power loss became even stronger, and there was a demand for the production of unidirectional silicon steel sheets with even lower iron loss as the iron core material for these devices. It has become.

(Prior art and its problems) By the way, in order to reduce the core loss of unidirectional silicon steel sheets, there are several ways to: - Increase the Si content. - Reduce the thickness of the product. - Make secondary recrystallization finer. - Contain impurities. Mainly metallurgical methods are generally known, such as reducing the amount and aligning the secondary recrystallized grains in the (110}<001> orientation to a higher degree, but these methods are not compatible with current production methods. The iron loss has reached its limit value, and it is extremely difficult to improve it any further, and even if some improvement is recognized, the situation has reached such a point that the effective improvement in iron loss will be small compared to the efforts made.

Apart from these methods, as disclosed in Japanese Patent Publication No. 54-28647, it has been proposed to make secondary recrystallized grains finer by forming a secondary crystal blocking region on the surface of a steel sheet. There is. However, this technique cannot be said to be practical because control of the secondary recrystallized grain size is not stable.

On the other hand, Japanese Patent Publication No. 58-5968 discloses a technique for reducing iron loss by introducing micro-strain into the surface of a steel plate after secondary recrystallization using ballpoint pen-shaped balls to reduce iron loss. 52-2252, the iron loss is reduced by irradiating the surface of the final product sheet with a laser beam at slight intervals almost perpendicular to the rolling direction to introduce high dislocation density regions on the steel sheet surface to refine the width of the magnetic domain. Techniques to reduce this have also been subsequently proposed. And also Japanese Patent Publication No. 57-18881
No. 0 proposes a similar technique in which minute strain is introduced into the surface of a steel plate by electrical discharge machining to refine the magnetic domain width and reduce iron loss.

All of these eight methods aim to reduce iron loss by refining the magnetic domain width by introducing minute plastic strain to the surface of the base steel of the steel sheet after secondary recrystallization, and are uniformly practical. However, the effect of introducing plastic strain is reduced by heat treatment such as strain relief annealing after punching, shearing, and winding of steel sheets, and baking of other coatings. With drawbacks. In addition, when introducing minute plastic strain after the coating process, the insulating coating must be repainted to maintain insulation properties, which significantly increases the number of processes such as the strain applying process and the repainting process, resulting in an increase in costs. .

As outlined above, there are no practical problems with the series of development trends of general and recent low core loss unidirectional silicon steel sheets.

In particular, recently, from the perspective of energy saving, in addition to products with a normal product board thickness of 0.80.
, 2Qsm thick products are increasingly being used, but under these circumstances, development research to more effectively manufacture low iron loss unidirectional silicon steel sheets is required.
It has become necessary to fundamentally reexamine all processes, from material composition to the final coating treatment process.

In order to manufacture a grain-oriented silicon steel sheet with low core loss, the inventors have long been working on the current 8. A method is adopted in which the amount of Si in Owt% (hereinafter simply expressed as %) is further increased to increase electrical resistance and lower iron loss. However, usually S
When the i content is 8.2% or more, hot embrittlement becomes noticeable and hot cracking occurs during slab heating or hot rolling, and this surface cracking occurs during the two cold rollings after hot rolling. A study was conducted on the serious problem of N, which remains even after four annealing treatments and significantly deteriorates the surface properties of the product (Iro, Ito: Bulletin of the Japan Institute of Metals, Vozz 8. (19s4), p. 276). advanced.

In order to solve this problem, the inventors first developed a special
In the specification of No. 8-90040, 0.005 to 0.1% Mo is added to 8.1 to 4.5% high silicon steel,
Furthermore, this silicon steel slab was charged into a heating furnace at 800°C.
We proposed a method for manufacturing unidirectional silicon steel sheets with excellent surface properties and magnetic properties by increasing the temperature to the above temperature. Although the surface quality of high-silicon steel has been significantly improved by adopting this method, the surface quality of the product still deteriorates when the slab heating temperature is high or when the Se or sb content in silicon steel is high. occurs frequently and remains a major problem.

(Motivation for the invention) Under these circumstances, the inventors conducted numerous trials to find out how to stably create a situation in which the surface quality of the product is good in high-silicon steel of 8.2% or more. When the experiment was conducted, the results were 00.01-0.06%,
st 8.2-4.5%, li[n 0.050% and Se 0.008-0.1%, Moo, 008
By enriching Mo or Mo compounds in the surface layer of silicon steel slab containing ~0.1% and Sb0.005~0.1%, it has good surface quality, high magnetic flux density and low core loss. The inventors have discovered that it is possible to produce a unidirectional silicon steel sheet having the following properties, and have completed this invention.

(Structure of the invention) This invention is 00.01 to 0.06%.

si 8.2-4.5%.

Contains In 0.050-0.2% and Se 0.050-0.2%.
008-0.1%.

A silicon steel slab containing Moo, 008-0.1% and Sb 0.005-0.1% is heated and then hot-rolled to obtain a hot-rolled sheet, and then this hot-rolled sheet is subjected to homogenization annealing. Cold rolling is performed two or more times with intermediate annealing in between to obtain a cold rolled sheet with the final product thickness.After that, primary recrystallization annealing is performed which also serves as decarburization, and final finish annealing is performed (110}<001 A method for producing a unidirectional Si5till plate that develops secondary recrystallized grains in the > orientation, characterized by enriching Mo or a Mo compound in the surface layer of the slab, with high magnetic flux density and excellent surface properties; This is a method for producing a low iron loss unidirectional silicon steel sheet.

Hereinafter, this invention will be specifically explained based on the experimental results that led to its origin.

C0,041%, Si8.00%, Mn 0.065
%, steel ingot (A) containing 0.018% Be and 0.025% Sb.

co, o4o%1sj-8,00%+ In o, o
6 B%, Se0.018%, No o, Oi
Steel ingot (B) containing a% and 0.025% of 3b.

00.048%, si, 8.42%, Mn0.072%
Steel ingot (0) containing 0.019% of Se and 0.028% of Sb, and 0.044% of C, 8.48% of Si and 0.0
19%.

Four types of steel ingots (D) containing Moo, 014% and SbQ, 02a% (all 100 to 9wi ingots) were made into slabs with a thickness of 50 mm. After polishing the surface of the slab and removing all the scale (3aMo0.17), dilute aqueous solution (0-1mo
l/l) was applied to both sides of the slab in a ratio of 59/+2. For comparison, uncoated slabs were also prepared. These slabs were heated in Ar gas at 1850° C. for 1 hour and then hot rolled to a thickness of 2.7 mm.

Then, after equalization annealing at 900°C for 3 minutes, 950°C
Cold rolling was performed twice with intermediate annealing for 8 minutes in between to obtain a final cold rolled sheet with a thickness of Q, 30 tm.

After decarburization and primary recrystallization annealing at 820°C for 5 minutes in wet hydrogen, an annealing separator containing MgO as a main component was applied to the surface of the steel sheet, and then annealing at 850°C in Ar gas for 50 minutes. A secondary recrystallization annealing for 1 hour and a blunting annealing at 1180° C. for 5 hours in dry H2 were performed.

The magnetic properties and surface properties of the products at that time are summarized in Table 1.

From Table 1, the magnetic properties B10 of the test slabs (A) and (B) with normal Si content are 1.92 to 1.98T, and the iron loss W
1? /li O is 1.10~1.14 W/Ic9
However, the test slab (B) with a small amount of Mo added to the steel is B10yW1? /6゜ both were slightly better.On the other hand, the surface quality of the product was slightly worse in the sample (A) without surface coating, but in the sample (B) in which a small amount of Mo was added to the steel, the surface quality of the product was good regardless of whether or not surface coating was applied. was good.

On the other hand, when the amount of Si is increased as shown in test slabs (0) and (D) in Table 1, the magnetic properties of the products become B1. is 1.92-1.98T, which is comparable to that of sample (A) or (B), but the value of W17150 is 0.98-1,0
It is noted that at 2 W/9 it is better than both samples (A) or (B).

In addition, in the comparison of samples (0) and (D), the W17/I of sample (D) with a small amount of Mot added to the steel, 0 is better.0 Furthermore, the surface texture of the product is significantly different from the experimental conditions. This is noteworthy. In other words, the surface quality of the product in sample (0) is slightly improved when Mo compound is applied to the surface, but
If it is not coated, the surface quality is poor.

On the other hand, when a small amount of Mo is added to the steel of the slab (D), the surface quality of the product is extremely good when a Mo compound is applied to the surface, but the surface quality is slightly poor when no Mo compound is applied.

Figures 1 (a) and (b) show the surface of the slab of sample (D) in Table 1 after applying a dilute aqueous solution of caM OO4.
Electrons on the surface when heated at 5°C for 1 hour
Fe, In by probe microanalyzer
.

5irot S, se, sb, P tMo, ca
Typical results of line analysis of each element of Mg
Give an example.

As can be seen from Fig. 1(a) and (b), it is noteworthy that P, s, Be, and sb are high at the position where Mo is detected, and conversely, OtFe*Si, Oa is low. .

The results of line analysis using this electron probe* microanalyzer show that when the slab is heated after coating the M0 compound on the slab surface, Mo becomes a hot embrittling element.
Since S, 38, and sb have the effect of concentrating and strengthening the grain boundaries near the surface, it is possible to effectively prevent grain boundary cracking during slab heating or hot rolling. It was confirmed that it is possible to improve the surface properties of products even by increasing the amount of Si in the raw steel.

As a result, the inventors previously reported in Japanese Patent Publication No. 5B-82215 that a unidirectional silicon steel containing low In of 0.05% or less using fine MnS or 5o1utes as an inhibitor can be used for slab surfaces or hot rolled sheets. A method of enriching Mo content on a surface has already been disclosed.

This manufacturing method uses fine MnS or 5
The aim is to create products with high magnetic flux density by finely dispersing oluteS into steel to strengthen the inhibitor. ), but a small amount of Mo can prevent surface defects by preferentially precipitating fine precipitates of sulfurized No (probably <Mo, 88) compounds on or near the surface of the steel sheet. That's what I was aiming for.

On the other hand, in this invention, Si is used to reduce iron loss.
In the case of increasing amounts, with a typical In content of 0.051-0.2% and Be 0.0% as an inhibitor.
M
The surface quality was improved by applying an o compound.

Therefore, when this invention is compared with Japanese Patent Publication No. 58-32215, the magnetic properties of the product are as follows: BIG is 1.98 T.
Although the degree is the same, Wlv/6o is 0.10 to 0.
It is noteworthy that the present invention has an extreme improvement of about 1.5 grades at 12W/9.

As a means to manufacture such high-quality products with low iron loss, this invention succeeded in simultaneously improving the surface properties by coating the surface of the slab with Mo compounds, and achieved the level of magnetic properties at the time. Judging from this, it was unexpected that it would be possible to manufacture high-grade products with such low core loss.

Next, the reason for limiting the composition of silicon steel in this invention will be explained.

If C is less than 0.01%, it is difficult to refine coarse grains during hot rolling, and if it exceeds 0.06%, decarburization takes time in the decarburization process and is not economical. 0.0
It needs to be within the range of 6%.

In this invention, the Si content must be 8.2% or more in order to obtain a product with low iron loss. On the other hand, if it exceeds 4.5%, brittle cracking is likely to occur during cold rolling, so Si
．． It is an important element for finely dispersing the inhibitor of O Kn &'1MnSe, which needs to be in the range of 2 to 4.5%.
FeS causes surface defects when n is less than o or oso%.
Since the amount of e or 5olute S increases, it cannot be stably used industrially. Also, when In exceeds 0.2%,
Mn is 0.0 because high-temperature slab heating is required to dissociate and dissolve MnSe precipitates, making it uneconomical.
It is necessary to keep it within 5-0.2%.

If Se is less than 0.008%, the effect of suppressing the inhibitor of MnSe is weak, while if it is more than 0.1%, hot and cold workability will be significantly deteriorated, so Se is o, o o s~
It is necessary to keep it within the range of 0.1%.

If Mo is less than o or o o a%, the effect of suppressing the growth of primary recrystallized grains is not obvious, while if it is more than 0.1%, hot and cold workability will be reduced, and the decarburization process will be delayed. Since charcoal takes time and is not economical, Mo is o, ooa% ~
It is necessary to keep it within the range of 0.1%.

If sb is less than o, o o s%, the inhibitor suppressing effect will be weak, and if it is more than 0,1%, hot and cold workability will be significantly deteriorated, so sb is 0.006 to 0.1%.
Must be within the range.

According to this invention, c, 81, Mn, Se, No, and S, which are limited to silicon steel as described above, are
It is necessary to control b, but in addition, any one of the known inhibitors AI and B, which are usually added to silicon steel.
Even if one or more species are added in a total amount of 0.08% or less, the effects of the present invention will not be impaired.

Others generally include Or, Ti, V, Zr,
Nb, Ta.

Ou # NIT Sn * P s AS and even S
There is no hindrance to the inclusion of trace amounts of unavoidable elements such as.

Next, a series of manufacturing steps according to the present invention will be explained.

Of course, the material of this invention can be melted using an LD converter, an electric furnace, an open hearth, or other known steelmaking methods.
Vacuum treatment and vacuum melting can be used together. Further, as for the ingot-forming means, in addition to the usual means of pouring into a mold, continuous casting can also be suitably performed.

Next, an inorganic compound containing Mo (for example, OuMo0.l Woo8. H8Mo08, etc.) may be uniformly applied to the surface of the slab before heating.

Also, the concentration of the Mo compound aqueous solution applied to the slab surface is 0.005m0/! Above, the coating amount is 0.5 to 269
/fax, and any conventionally known method may be used for this coating method. After such surface coating, the slab is heated at 1250° C. or higher to dissociate and dissolve MnSe in the steel, and then hot rolled, and is usually formed into a hot rolled sheet having a thickness of about 2 to 5 mm.

The hot rolled sheet is then uniformly annealed and then cold rolled. Cold rolling is 850
Cold rolling is performed twice with intermediate annealing at ~1000° C. to obtain a final cold-rolled sheet with a thickness of 0.18 to 35111111, but the thickness is usually 0.8 mm.

After the final cold rolling, the steel plate that has reached the product thickness is subjected to the next decarburization annealing. The purpose of this annealing is to improve the primary recrystallization of the cold-rolled structure and at the same time to remove harmful C when developing secondary recrystallized grains with the (i 1 o}<o o 1> orientation in the final annealing. For example, from 750°C to 850°C for 8 minutes to 1
Any known method can be used, such as annealing in wet hydrogen for about 5 minutes.

Final annealing is performed to sufficiently develop secondary recrystallized grains with (110}<001> orientation, and is usually performed by immediately raising the temperature to 1000°C or higher by box annealing and maintaining it at that temperature. This final annealing is usually performed by applying an annealing separator such as magnesia and box annealing, but in this invention, in order to develop secondary recrystallized grains that are extremely aligned in the (110}<001> orientation, is 820°
It is more advantageous to perform retention annealing at a low temperature of 900° C., but alternatively, it may be annealed at a temperature of 0.5 to 900° C.

Next, the present invention will be described with reference to embodiments.

Example 1 Or
Mo0. 2 g of an aqueous solution (0,005 mol/l) of
/, 2 was uniformly coated, heated at 1880°C for 1 hour, and then hot rolled to obtain a hot rolled sheet with a thickness of 2.4.

Then homogenized annealing at 900"C for 8 minutes and 950"C for 8 minutes.
The thickness is 0.8011111 with intermediate annealing for 0.8 min.
Each final cold-rolled sheet had a thickness of 28 mm.

After that, after decarburization and primary crystal annealing in wet hydrogen at 820°C for 8 minutes, an annealing separator containing MgO as a main component was applied to the steel sheet surface, followed by secondary recrystallization annealing and drying at 850°C for 50 hours. Annealing was performed in hydrogen at 1200°C for 5 hours.

The magnetic properties and surface properties of the product at that time were as follows.

Q, 3 Q tpun thick product'Blo = 1.9
ijl T s W17/6゜: 0.97 W/right, good surface quality, o, p, sv, m thickness products: B = 1-90 T
, W□7/l5o=0.85 W/N9, surface quality is good, Example 2 00.046%, sia, eo%, In 0.076
597 m of an aqueous solution of MoO2 (0.01 mat/i) was deposited on the surface of a continuous casting slab containing 380.019% of Sb, 0.018% of No. and 0.028% of Sb.
``After being uniformly coated, it was heated at 1850°C for 2 hours, and then hot-rolled to obtain a hot-rolled sheet with a thickness of 2.0 mm.

Then, after homogenization annealing at 900°C for 8 minutes, 950″C
After intermediate annealing for 8 minutes, a final cold-rolled sheet with a thickness of 0-28 was obtained.

Then, after decarburization annealing at 800°C for 5 minutes in wet hydrogen, an annealing separator containing MgO as a main component was applied to the surface of the steel plate, and then secondary recrystallization annealing at 850°C for 50 hours.
1.90T, W = o, a4W/&9 This product 1
0 17/! The surface quality of +0 was good.

Example 8 Contains 0.051%, si+, 2o%, Mn0.082% and se0.025%, Moo, 040% and s
b 0.06.

H, MoOB on the surface of continuous cast steel slab containing %
An aqueous solution (o, o 5 mot/l") of 89/vn
After applying uniform GCIk cloth, it was heated at 1880°C for 90 minutes, and then hot rolled to obtain a hot rolled sheet with a thickness of 2.0. After that, it was uniformly annealed at 950°C for 8 minutes, and then heated at 960°C. A final cold-rolled sheet with a thickness of Q, 9 Q was obtained by intermediate annealing for 8 minutes at 100° C. After decarburization annealing at 820°C for 5 minutes in wet hydrogen, MgO was the main component on the surface of the steel sheet. After applying the annealing separator, secondary recrystallization annealing was performed at 850°C for 50 hours and blunting annealing at 1200°C for 6 hours in dry hydrogen.The magnetic properties and surface properties of the product were as follows. There was O B = 1.89 T W, y150 = 0.7
6 W/9, the surface quality of this product was good with no defects such as scratches and lines.

(Effects of the Invention) As described above, according to the present invention, Blo is a high magnetic flux density of 1.90 T or more, and the iron loss is Q, 3Qm and 1. OOW/ 9 or less,
Q, 23 van thickness 0-90W/9 or less and Oe
A unidirectional silicon steel sheet with a thickness of 20 tan, a low core loss of 9 or less, and excellent surface quality can be produced in an extremely stable manner.

[Brief Description of the Drawings] Figure 1 shows Fe near the surface of a silicon steel slab using an electron probe microanalyzer. Mn, Si, O, S, Se, Sb,
FIG. 3 is a diagram showing line analysis of P, No, Oa and Mg elements. Figure 1(a)

Claims (1)

[Scope of Claims] 1. Contains 0.01 to 0.06 wt% of C, 3.2 to 4.5 wt% of Si, 0.050 to 0.2 wt% of Mn, and Se0.
A silicon steel slab containing 0.008 to 0.1 wt%, Mo0.003 to 0.1 wt%, and Sb0.005 to 0.1 wt% is heated and then hot rolled to form a hot rolled sheet. The hot-rolled sheet is cold-rolled two or more times, including uniform annealing and intermediate annealing, to produce a cold-rolled sheet with the final product thickness.Then, the hot-rolled sheet is subjected to primary recrystallization annealing that also serves as decarburization, and then final finish annealing. A method for manufacturing a grain-oriented silicon steel sheet in which secondary recrystallized grains with {110}<001> orientation are developed by applying a surface texture to the surface layer of the slab, comprising enriching Mo or a Mo compound in the surface layer of the slab. A method for manufacturing unidirectional silicon steel sheets with excellent high magnetic flux density and low iron loss.