JPH0257635A - Manufacture of extra thin foil of grain-oriented silicon steel with low core loss - Google Patents

Abstract

PURPOSE:To manufacture an extra thin foil of grain-oriented silicon steel with low core loss by successively applying respective treatments of purification annealing, cold rolling, and high-temp. heat treatment to a stock of non-oriented silicon steel strip under respectively specified conditions. CONSTITUTION:A stock of non-oriented silicon steel strip (1.5-8wt.% silicon content, <=0.005wt.% Al content) is held in hydrogen at 1000-1200 deg.C for >=3hr to undergo purification annealing, by which Al compounds are removed by decomposition. Subsequently, The above stock is subjected to cold rolling at >=10% draft per pass and >=70% total draft so as to be formed into an intermediate extra thin toil of <=150mu thick. Further, the above foil is heated to 950-1100 deg.C in a nonoxidizing or reduced-pressure atmosphere at >=0.5 deg.C/sec temp.-rise rate and the temp. is retained for 1-3hr, by which an extra thin foil consisting of a texture of secondary-recrystallized grains having (110) [001] orientations is formed. By this method, the extra thin foil of grain-oriented silicon steel with low core loss having <=150mu thickness can be obtained inexpensively.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for producing a so-called grain-oriented silicon steel strip having an axis of easy magnetization (001) in the rolling direction of the steel strip. The present invention relates to a method for producing a grain-oriented silicon steel strip with high magnetic flux density and low iron loss.

[Conventional technology]

A grain-oriented silicon steel strip material containing 2 to 8% by weight of silicon is cold-rolled under conditions of a plate thickness of 150 μm or less and a rolling reduction of 5096 or more to produce an ultra-thin strip with a (11x)[”112] orientation, and then In a heat treatment process in an oxidizing atmosphere or a reduced pressure atmosphere, magnetic properties can be improved by heating from room temperature at a temperature increase rate of 1.5'cA!p or more, holding at about 1000 to 1400°C for more than 3 hours, and then cooling. Excellent, extremely large average grain size of 5u or more, (001
) A highly oriented silicon steel strip having an average axis deviation angle of λ5° or less can be obtained. Its characteristics include low iron loss as shown in FIG. 1, and sharp -H loop characteristics as shown in FIG. 2. This results in a grain-oriented silicon steel strip that is thinner than so-called grain-oriented silicon steel strips, has high magnetic flux density in terms of magnetic properties, has low coercive force, has low core loss, and is highly oriented. be able to.

[Problem to be solved by the invention]

However, this method uses a grain-oriented silicon steel strip as the starting material, so the material cost is high and the temperature rises rapidly (1
, 5° C./ec or higher).

An object of the present invention is to solve the problems of the prior art as described above, to use an inexpensive non-oriented silicon steel strip as a starting material, and to realize temperature increase at a lower rate.

(Means for solving the 1m! problem) In order to achieve the above-mentioned object, the present invention uses a non-oriented silicon steel strip which has a simple manufacturing process and is inexpensive, and after removing the surface breakage, hydrogen Among them, a first step of performing high-temperature purification annealing at, for example, 1200° C. for 5 hours, a second step of cold rolling the material to obtain an intermediate ultra-thin strip, and after the second step, the intermediate ultra-thin strip is, for example, By performing high-temperature heat treatment at, for example, 1000°C for about 2 hours under reduced pressure or in a non-oxidizing atmosphere, a low-loss orientation consisting of a secondary recrystallized texture with highly integrated (No) [ool] orientations is produced. and a third step of obtaining an ultra-thin silicon steel strip.

[Embodiments of the invention]

The silicon steel strip used in the present invention does not undergo high-temperature annealing for secondary recrystallization during the manufacturing process, and is manufactured through a process of hot rolling, cold rolling, and annealing, for example, and silicon It is preferable to use a content of 1.5 to 8% by weight.

A silicon steel strip containing about 1.5% by weight or more of silicon is r
There is no transformation, and the crystal grains can be enlarged by high-temperature annealing.
Although it is possible to cause secondary recrystallization to form a preferable texture, the above-mentioned characteristics are not exhibited when the silicon content is less than t,S weight percent. On the other hand, if the silicon content exceeds 8% by weight, the saturation magnetic flux density will be about 1.7 T or less, which is not only unsuitable as a magnetic material but also makes it mechanically extremely fragile, which is not preferable.

Particularly, those having a silicon content of 2.5 to 4.0% by weight are suitable for excellent mechanical properties such as rolling and high saturation magnetic flux density.

Additionally, 0.1 to 1.0% by weight of M is added to the non-oriented silicon steel strip in order to remove impurities and make the steel clean, as well as increase electrical resistance and improve magnetic properties. However, AI combines with the 0 present in the steel, forming AlzOs
layer precipitates on the surface, which acts to prevent recrystallization using surface energy.

Furthermore, AJ combines with N and acts as AjN to inhibit the growth of primary recrystallization, and also affects the growth of secondary recrystallization grains. Therefore, it is necessary that tAl, which performs these functions, be 0.003% by weight or less.

Furthermore, since Mn acts as an inhibitor in the form of MnS, the content of Mn needs to be 0.04% by weight or less.

Next, as an unavoidable mixed element, for example, N! ICtL@M0
It may also contain small amounts of 1W, Cr, etc. moreover,
The content of unavoidable impurities such as 0C and N must be limited depending on the quality of the final target ribbon.

As the non-oriented silicon steel material used in the present invention, a commercially available non-oriented silicon steel strip as shown in FIG. 10, for example, can be used.

Some commercially available non-oriented silicon steel strips have a thickness of α35m, as shown in FIG. These silicon steel strips are used as raw materials, and after the surface coating is removed with acid, an annealing separation agent such as MIO is applied. After that, Al
Tos, AI compounds such as AIN, or cylindrical compounds such as MJ precipitate on the surface and block surface energy to prevent recrystallization, or decompose substances that act as inhibitors into forms such as S and N. In order to remove it from the steel by dissipating it into the gas phase or by concentrating it in a state such as AlzCh 1Mn5 into a 7 orsterite coating (MgzSiO<), the holding time was 3 at 1000-1200°C in hydrogen.
It takes more than an hour.

Next, using the material purified in this way, it is cold rolled to a size of 150 □ or less. It is sufficient for this rolling reduction rate to be at least 10% per roll and at least 70% in total.
The original purpose of cold rolling is to obtain an extremely thin crystalline body with crystal distortion. Further, in the present invention, it is thought that when the thickness exceeds 150 μm, the surface energy becomes a driving force and the thickness is too thick for the (110) plane with the lowest surface energy to grow.

In the heat treatment after cold rolling, (100) [OAt
) In order to suppress the formation of tissues, inert gas and 10% or more hydrogen gas or 100% hydrogen gas or 2
The vacuum may be approximately 10-' to 2 X IQ-"l'Orr.

The heating furnace for heat treatment may be of a patch type or a continuous type. Heat treatment holding temperature is 950-1100℃
A holding time of 1 to 3 hours is required. According to this method, the heat treatment temperature increase rate is α5! 1.5 seconds or more is sufficient, compared to the conventional 1.5 seconds.
The temperature rise is much slower than that during φ seconds.

After heat treatment, the preferable texture obtained at high temperature can be maintained by cooling in a non-oxidizing atmosphere to avoid deterioration of mechanical properties and magnetic properties. Next, a specific example of the processing method according to the present invention will be explained.

A non-oriented silicon steel strip (So 9 ) was used as the material. The properties of this non-oriented silicon steel strip are as follows.

Width: 30 cm Length: 300 m Density? , 65 El/di iron loss (Was
/sa) 140 W/+? Magnetic flux density (Bso
) 1.62T This silicon steel strip was immersed in a mixed solution of concentrated sulfuric acid and hydrofluoric acid (3 sulfuric acid: 1 part hydrofluoric acid) for 40 minutes, then washed with water, further pickled with a 10% aqueous nitric acid solution, and then washed with water. The insulation film and oxide film formed on the surface of the steel strip are removed.

Next, MgO, which is an annealing separator, is applied, followed by purification annealing, which is heated to a temperature of 1200° C. in hydrogen gas and held for 5 hours. Thereafter, it was rolled to 70 μm (1 to 7 times) using a 4-roll mill with a diameter of 20 m, and then cut into pieces with a width of 1 ON and a length of 100 m, excluding each end, to prepare a sample. As mentioned above, the sample was made by rolling a sheet of 350 mm thick to a thickness of 70 μm, so the rolling reduction ratio of this sample was 80 μm.

This sample was then placed in a quartz tube, 5 x 10'''T
Temperature increase rate is 30'' using a heating furnace under high vacuum of orr.
Heat treatment was performed under cA+ conditions. The crystal grains after heat treatment were observed using an X-ray Laue photograph, an X-ray pole observation, and an optical microscope, and the magnetic properties were measured using a B-H loop tracer.

Figure 3 shows the heat treatment holding temperature and magnetic properties. As shown in this figure, the B8 value shows a low value below 700°C, but gradually increases from around 700°C, and at 950°C, the B8 value shows a low value.
s reaches 1.93T. At this time again (11o) [001
) The appearance of texture was confirmed by X-ray Laue photography.

As is clear from this experiment, strain removal, recovery, and primary recrystallization begin at 600°C, and growth of primary recrystallized grains occurs at 700°C. Then, secondary recrystallization occurs at SOO℃, and 95
When the temperature is maintained at 0°C or higher, it is covered with secondary recrystallized grains with a grain size of 5 to 10 m. Therefore, it can be seen that the coercive force rapidly decreases at temperatures above SOO° C. where the growth of secondary recrystallization begins.

The degree of vacuum at this time was 5.times.10-"l'Orr, and next, an experiment was conducted to investigate the influence of the degree of vacuum.

Below IQ""pOff or in argon gas (110
) [001) Texture is limited and does not develop, (100
) [OAZ) tissue partially develops. In addition, by adding 10% or more hydrogen to argon gas, Bs
= 1.93T was able to be satisfied. As a result, it was found that the heat treatment atmosphere may be a vacuum degree of x□-4Toff or more or a non-oxidizing atmosphere containing 10% or more of hydrogen.

Next, we will discuss the rolling reduction ratio. FIG. 4 shows the relationship between rolling reduction and coercive force. The coercive force is high when the reduction rate is 70% or less, and the results of X-ray Laue photograph observation after heat treatment also show that (110)
Crystals with other orientations also appear in [001),
It is thought that a rolling reduction of 70 inches or more is required. Moreover, since small holes appear in the rolled ribbon at a rolling reduction of more than 90%, a range of rolling reduction of 70 to 90% is preferable. Further, it is considered that the thickness after rolling needs to be 150 pm or less in consideration of the state of surface energy.

Based on the results found in previous experiments, the coercive force of each sample was measured by rolling at a reduction rate of 80%, under a vacuum degree of 5 x 10'' pOrr, and by changing the holding time at a holding temperature of 1000°C. The results are shown in Figure 5.As is clear from this figure, if the holding time is less than 1 hour, the secondary recrystallized grains will not be fully developed and the coercive force will not be sufficiently reduced. For hours or more (110) [00
A tertiary recrystallized structure other than 1) occurs, and the coercive force tends to increase. Therefore, the optimum condition is a holding time of 1 to 3 hours.

Next, the influence of Al content among additives was investigated. In FIG. 6, the horizontal axis shows the AJli amount of the AJ compound contained as AIN, etc., and the vertical axis shows the coercive force.

These various Al-containing materials were subjected to rolling heat treatment under optimal conditions and the coercive force was measured.
At weights above -, AI acts as a harmful substance and the third
This impedes secondary re-agglomeration growth in the process, causing a rapid increase in coercive force. Therefore, in the first step, high-temperature purification annealing in hydrogen was performed for purification, and the Al content of the starting material was reduced to 0.0.
05 weight - or less.

Similarly, a similar experiment was conducted regarding the 4 content, and it was confirmed that the 4 content should be 0.04% or less.

The magnetic properties of ultrathin silicon steel strips processed under the various optimal conditions described above are shown. Figure 7(a) shows after cold rolling at a reduction rate of 80 inches,
B-H loop characteristics after heat treatment at 1000℃ x 2 hours,
Because the secondary recrystallized grains are sufficiently developed, Fig. 7(b)
It can be seen that the B-H loop characteristic of the non-oriented silicon steel strip shown in FIG.

Figure 8 shows the total iron loss at each magnetic flux density for the material in Figure 7 (a), where curve B is the curve for the as-heat-treated material, and curve A is for the steel strip coated with a magnesium salt-based film forming agent on the surface. This is an iron loss value curve when the steel strip is heated to approximately SOO° C. and a tension of approximately 1 to 4 cm is applied to the steel strip. It can be seen that even after the heat treatment, Ws s / s o =0.32 WAg, which is significantly improved compared to the so-called grain-oriented silicon steel sheet (Hi-V). In addition, by applying tension with the coating, Ws s/s o =0.27 W/kf and 2
Six improvements have been made.

〔Effect of the invention〕

FIG. 10 is a diagram showing the magnetic properties of a oriented silicon ultra-thin steel strip with low loss and high orientation obtained by the manufacturing method according to the present invention and a conventional product. As shown in this figure, the same level of orientation as conventional high magnetic flux density silicon steel strips has been achieved at less than 150 μm, and the price of the starting raw material is % of that of the highly oriented silicon steel strips mentioned in the conventional example. Because the temperature is low, the heat treatment holding time is short, and the temperature increase rate is less than 1% of the conventional rate, purification annealing is
The energy cost during heat treatment is 2
It is possible to reduce manufacturing costs. Therefore, 150 yen is cheap.
It is possible to obtain a low-loss oriented silicon steel ribbon of less than μ.

Note that the low-loss oriented ultrathin silicon steel strip has high orientation, with an average deviation angle of the (001) axis relative to the rolling direction being within 27 degrees.

[Brief explanation of the drawing]

Figure 1 is an iron loss vs. magnetic flux density characteristic diagram of the conventional example, Figure 2 is a B-H characteristic diagram of the conventional example, Figure 3 is a magnetic flux density (Bs) vs. heat treatment temperature characteristic diagram, and Figure 4 is a coercive force vs. A characteristic diagram of rolling reduction ratio, Figure 5, shows the characteristics of coercive force and holding time of B after treatment according to the present invention.
-H characteristic diagram, FIG. 8 is an iron loss and magnetic flux density characteristic diagram according to the present invention, FIG. 9 is a characteristic diagram showing an example of non-oriented silicon steel, and FIG.
The θ diagram is a comparison diagram of the magnetic properties of materials obtained by the method of the present invention, the conventional method, the ultra-quenching method, etc. Figure 1, 2nd page o, al B (KG), 10,000,000,000,000,000,000,000,000,000,000 (T), 3rd ward, 4, 1, 5, 1, 3, 3, 4, 1 Yo, 5, 3 (T), 7th page, ζC, f3 (KG Noi ÷ = Bi Fig. 5 J Toyo L gate (min.) Fig. 6 Fig. 7 (b) B (KG) ', 1 -20 [ Fig. 8 Magnetic flux/g false (T) Fig. 10

Claims (11)

[Claims] (1) Non-oriented silicon steel strip material at 1000-1200℃
The first step is to perform purification annealing in hydrogen to decompose and remove Al compounds remaining in the steel, and after that first step, cold rolling is performed to form an intermediate material with a thickness of 150 μm or less. A second step of producing an ultra-thin strip, and further, after the second step, the intermediate ultra-thin strip is subjected to high-temperature heat treatment in a non-oxidizing atmosphere or a reduced pressure atmosphere, thereby producing secondary recrystallization having a (110)[001] orientation. A method for producing an ultra-thin strip of low-loss grain-oriented silicon steel, the method comprising: a third step of producing an ultra-thin strip having a texture of grains. (2) In claim (1), the silicon content in the non-oriented silicon steel strip material is 1.5 to 8% by weight, and the Al content after the first step is 0.005% by weight. % or less. (3) In claim (1) and claim (2),
[ with respect to the rolling direction of the low loss oriented silicon steel ultra-thin strip
001] A method for producing a low-loss oriented silicon steel ultrathin strip having high orientation with an average axis deviation angle of 2.7 degrees or less. (4) In claim (1) and claim (2),
A method for producing a low-loss grain-oriented silicon steel ultrathin strip, characterized in that the non-oxidizing atmosphere is an inert gas atmosphere, a hydrogen gas atmosphere, or a mixed atmosphere of hydrogen gas and inert gas. (5) A method for producing a low-loss grain-oriented silicon steel ultrathin strip according to claim (4), characterized in that the non-oxidizing atmosphere of the gas is under reduced pressure. (6) The method for producing a low-loss grain-oriented silicon steel ultrathin strip according to claim (1), characterized in that the heat treatment holding time in the first step is regulated to 3 hours or more. (7) In claim (1), the low-loss grain-oriented silicon steel ultrathin strip is characterized in that the rolling reduction rate in the second step is 10% or more in one round and a total rolling reduction rate of 70% or more. Production method. (8) In claim (1) and claim (2),
The heat treatment holding temperature in the third step is 950 to 1100°C
A method for producing a low-loss grain-oriented silicon steel ultrathin strip, characterized in that the heat treatment holding time is regulated to 1 to 3 hours. (9) In claim (1) and claim (2),
A method for producing a low-loss grain-oriented silicon steel ultrathin strip, characterized in that the heat treatment temperature increase rate in the third step is 0.5° C./sec or more. (10) In claim (1), in the temperature raising process for obtaining a heat treatment holding temperature of 950 to 1100 °C in the third step, the temperature is preheated to 500 °C and the subsequent temperature increase rate is approximately 0 °C.
．． A method for producing a low-loss grain-oriented silicon steel ultrathin strip, characterized in that the temperature is 5° C./sec or more. (11) In claims (1) and (2), the ultra-thin steel strip is cooled after the third step, and then a film forming agent is applied to the surface of the ultra-thin steel strip and heated. 1. A method for producing a low-loss grain-oriented silicon steel ultrathin strip, the method comprising forming a film by: