JP5001611B2 - Method for producing high magnetic flux density grain-oriented silicon steel sheet - Google Patents

Description

  The present invention relates to a method for producing a directional silicon steel sheet excellent in magnetism, particularly in magnetic flux density, used for iron core materials for power transformers, iron core materials for rotating equipment, and the like.

  The technology for producing grain-oriented silicon steel sheets was announced as a two-stage cold rolling method of NPGoss (Patent Document 1), and the principle of its production is JEMay & D. as a secondary recrystallization phenomenon in the presence of fine precipitates MnS. Revealed in 1958 by Turnbull (Non-Patent Document 1). Apart from this, the present inventors invented the Al-containing one-stage strong cold rolling method and announced the effectiveness of fine precipitates AlN (Patent Document 2). On the other hand, unlike the precipitates, trace elements such as Sb, Nb, Se, S, Mo, Cu, and Sn, which are solid-dissolved, have a strong primary recrystallized grain growth inhibiting action, which promotes secondary recrystallization. Tatsuo Saito announced for the first time (Non-patent Document 2). In this way, the secondary recrystallization phenomenon used in the actual manufacturing technology requires the presence of precipitates or dissolved solid elements, but as a secondary recrystallization phenomenon in the absence of precipitates, The secondary recrystallization phenomenon in the presence of a texture (Texture Inhibition) composed of a stable crystal structure solidified in a certain crystal orientation was basically clarified by CGDunn (Non-patent Document 3).

Furthermore, the production principle of the high magnetic flux density directional silicon steel sheet is clear by the effect of the present inventors on the secondary recrystallization of AlN (Non-patent Document 4). That is, regarding the effect of AlN on the cold rolling / recrystallization phenomenon of the (110) [001] -Goss orientation single crystal, when the starting single crystal contains a small amount of very fine AlN of 5 nm or less, {111} <110> When it becomes a primary recrystallization growth structure of -C orientation and contains a very large amount of fine AlN of about 10 nm, the first orientation (110) [001] is reproduced by secondary recrystallization, and a relatively large AlN of about 1 μm In the case where a large amount of is included, two of the three types of orientations {120} <001> -A orientation, {362} <012> -B orientation, and {111} <110> -C orientation 2 are similarly obtained by secondary recrystallization. Next recrystallized grains appear. This completely agrees with the research result of the 3% Si silicon steel single crystal containing no impurities by CGDunn described above. From these research results, it can be seen that it is critically important to secure AlN of about 10 nm in the state of hot-rolled sheet for the production of high magnetic flux density directional silicon steel sheet.
Secondary recrystallization does not occur with very fine AlN of 5 nm or less and should be avoided. In addition, coarse AlN of about 1 μm is meaningless.

  Conventionally, in order to secure AlN of around 10 nm, which is indispensable for the production of high magnetic flux density grain-oriented silicon steel sheets, in the state of hot-rolled sheets, a slab (thickness approximately) obtained by split rolling or continuous casting. 200 mm or more) is reheated to a high temperature of 1300 ° C. or more (fired heating) to completely dissolve AlN once, and then a 20 mm to 70 mm thickness bar is formed using a continuous hot rolling machine. Furthermore, it was rolled by a continuous hot finish rolling mill to obtain a final plate thickness and wound at about 500 ° C., but the steel was rapidly cooled during finish rolling. However, for thick slabs around 200 mm thick, when the flame is heated at a high temperature of 1350 ° C. or higher, the temperature difference between the slab surface and the bottom surface is large, and in order to achieve the desired effect, the surface temperature must be extremely increased. For this reason, abnormal growth of slab crystal grains and work problems caused by the scale of the silicon steel surface being melted and deposited in the furnace have also occurred.

  Although it is very difficult to solve this problem, it is oxidized by adopting a low-temperature slab heating method (Non-patent Document 5) as one manufacturing method or induction heating at the final stage after flame heating. There exists a method (for example, patent document 3) etc. which prevent melt | dissolution of a scale. Furthermore, in order to secure preferable AlN of about 10 nm with the same thickness as the hot-rolled sheet, a concept of adopting a thin continuous casting method (for example, Patent Document 4) with a thickness of several millimeters has been announced. The method of reheating the cold slab after once cooling the CC slab has problems in productivity and workability, and improvement is desired.

Further, Patent Document 5 discloses a method of manufacturing a grain-oriented electrical steel sheet by manufacturing a thin slab having a thickness of 20 to 80 mm by continuous casting and employing hot rolling with a rolling start temperature of 1100 to 1200 ° C. Yes. However, in this method, AlN having a large grain size is formed during hot rolling, and sufficient magnetic properties cannot be obtained in a normal processing step. Therefore, nitriding after decarburization annealing is required.
: US Patent 1,965,559 : JP-B 33-4710, U.D. S. P. 3,159,511 (1962) : JP-A-05-117751 : JP-A-02-258922 : Special table 200-500568 : Trans. AIME, 212 (1958), 769 : Tatsuo Saito Journal of the Japan Institute of Metals, 27 (1963), 191 : Acta Metallurgica, 1 (1953), 163 : Akira Sakakura, Ferum, Vol. 9, no. 2 (2004), 52 : N. Takahashi, J. Harase, Mater. Sci. Forum, 204/206, No. Pt1 (1996), 143

As described above, conventionally, the effect of dispersion and precipitation of fine AlN necessary for the production of a high magnetic flux density grain-oriented silicon steel sheet is that AlN is once dissolved in silicon steel by a high-temperature reheating operation using a hot slab of a thick slab. After that, it was achieved again by the rapid cooling effect by hot rolling, but there was a problem due to the high temperature heating scale melting of thick slabs, and the problem of crystal orientation and brittleness of the cast structure in the thin continuous casting method of several mm thickness This is a major problem that hinders practical application.
Furthermore, in the method of starting hot rolling of a continuous cast slab of medium thickness at a temperature of 1200 ° C. or less, AlN is precipitated and coarsened before hot rolling, and has not reached a state that is sufficiently effective for improving magnetism.

  The present invention produces a medium-thick slab by a continuous casting method, maintains the slab at a temperature that is at least a minimum that can be hot-rolled, and performs continuous hot rolling of AlN that has already been dissolved in a molten steel state. Is kept in the steel without precipitation, and after the thick CC slab is cooled once by fine precipitation by the rapid cooling effect during continuous hot rolling, the slab is heated to a high temperature of 1350 ° C or higher. The present invention provides a method for producing a high-flux-density directional silicon steel sheet that can solve the problems in the conventional method, can greatly improve work efficiency and energy efficiency, and has a more uniform and superior crystal directionality and iron loss than conventional ones. For the purpose.

In order to achieve the above object, the configuration of the present invention is as follows. That is,
(1) By mass C: 0.010 to 0.075%, Si: 2.95 to 4.0%, acid-soluble Al: 0.010 to 0.040%, N: 0.0010 to 0.0150% , S or Se alone or both in an amount of 0.005 to 0.1%, continuously casting a molten steel composed of the remaining Fe and inevitable impurities to produce a medium-thickness bar having a thickness of 20 to 70 mm, After the bar is cast or extracted from the heating furnace (including the in-furnace time of the heating furnace) at a temperature exceeding 1200 ° C. (preferably less than 1350 ° C.) and within 500 seconds, enter the hot finish rolling mill at the inlet. The hot rolling is started to reach 1.5 mm to 5 mm thickness by hot rolling, and the cooling time until reaching 600 ° C. after the hot rolling is 150 seconds or less, High magnetic flux density directionality for normal cold rolling, intermediate annealing, decarburization annealing, finish annealing, etc. A method for producing a silicon steel sheet.
(2) In the molten steel, further segregation at grain boundaries to suppress crystal growth, Sb: 0.005 to 0.2%, Nb: 0.005 to 0.2%, Mo: 0.003 to 0 0.1, Cu: 0.02 to 0.2%, Sn: at least one selected from the group of 0.02 to 0.3%, the high magnetic flux according to (1) above A method for producing a density-oriented silicon steel sheet.
(3) Hot finish rolling within 500 seconds at the longest when the medium-thickness bar maintains a temperature of 1250 ° C or higher, and within 150 seconds when the temperature of 1200 ° C or higher is maintained. The method for producing a high magnetic flux density directional silicon steel sheet according to (1), wherein the method reaches the entrance of the machine.
(4) When the required time to reach the entrance of the hot finishing mill after the medium thickness bar manufactured by continuous casting exceeds 200 seconds or when the temperature of the bar is 1000 ° C. When the temperature is low as in the above, the high magnetic flux density directional silicon steel sheet according to the above (1), which is passed through a heating furnace for maintaining these bars at a temperature of 1300 to 1350 ° C. Method.

  As in the present invention, AlN obtained by rapid cooling in a hot rolling finish rolling mill (tandem mill) from a state in which it is completely dissolved in a solid cast piece produced by continuous casting is uniformly and finely dispersed. It is sufficient to generate primary recrystallized nuclei with excellent crystal orientation, and at the same time, it has a sufficient effect of suppressing crystal growth, and the crystal structure obtained by casting is destroyed by hot rolling. Therefore, there is no adverse effect of the abnormally grown grains of the slab by conventional high-temperature heating, and uniform and complete secondary recrystallized grains are formed by final annealing, and the magnetic flux density direction has excellent characteristics of magnetic flux density B10 ≧ 1.90T. -Resistant silicon steel sheet can be obtained. Moreover, the high-temperature reheating operation of 1350 ° C. in the conventional slab heating furnace is completely unnecessary, and the retained heat of the steel slab is fully utilized, which leads to a significant improvement in energy efficiency. It can also solve the major work problems caused by high-temperature heating of slabs.

The present invention is described in detail below.
First, the reason for limitation of each component contained in the molten steel of the present invention will be described.
C is an element necessary for causing a certain γ transformation during hot rolling depending on the amount of Si, and if it is less than 0.010%, secondary recrystallization cannot be stably generated. On the other hand, if it exceeds 0.075%, the decarburization annealing time becomes longer, which is not preferable for production, so the content is made 0.010 to 0.075%.
If Si is less than 2.95%, an excellent iron loss value cannot be obtained as a high-grade high magnetic flux density directional silicon steel sheet. Further, if added over 4%, it is not preferable because cracks and the like occur during cold rolling due to brittleness, and its content is set to 2.95 to 4.0%.
Oxidation-soluble Al and N are elements necessary for producing AlN suitable as an inhibitor, and the sufficient amount thereof is in the range of 0.010 to 0.040% and 0.0010 to 0.0150%. .
S and Se form Mn, MnS, and MnSe, and act as a precipitated dispersed phase for secondary recrystallization. Therefore, these are contained individually or in an amount of 0.005% to 0.015%. In addition, Sb: 0.005 to 0.2%, Nb: 0.005 to 0.2%, Mo: 0.003 to 0.1, Cu: 0.02 to strengthen the inhibitor as necessary. At least one selected from the group of 0.2% and Sn: 0.02 to 0.3% can be contained.

  In order to produce the high magnetic flux density directional silicon steel sheet of the present invention, it is essential that AlN having a thickness of about 10 nm (5 to 50 nm) be present in the state of a hot-rolled sheet. If the bar temperature is 1200 ° C or higher while manufacturing a medium-thickness bar of ~ 70mm and maintaining the solid solution state of AlN by the heating means to prevent the heat retention of this bar or the temperature drop of heat insulation furnace etc. Within 150 seconds at the maximum after extraction from the heat-retaining furnace, when the temperature is 1250 ° C. or higher, the transition to the hot rolling mill entrance is performed within 500 seconds at the maximum, and hot rolled steel sheet having a thickness of 1.5 mm to 5 mm by hot rolling, By setting the cooling time until reaching 600 ° C. after the hot rolling to 150 seconds or less, fine AlN in the vicinity of 10 nm (5 to 500 nm) is deposited.

  In the present invention, the bar is limited to a medium thickness of 20 to 70 mm. If it is less than 20 mm, a large facility for heat retention is required. If it exceeds 70 mm, a hot rolled sheet cannot be obtained only by a finishing mill. This is because a roughing mill is required and economic production is not achieved.

  The means for producing and rolling a 20 to 70 mm thick bar is not particularly limited. An example of a known continuous casting-hot rolling continuous equipment is schematically shown in FIGS. FIG. 1 shows that a thin slab 2 extracted from a mold 1 is continuously cast, and the cut slab 3 is inserted into a heat-retaining furnace 4 in order to maintain a constant temperature, and then immediately rolled by a continuous finishing hot rolling machine 5 to make it thin. Hot-rolled steel strip is wound up. In FIG. 2, after the continuous slab 2 is continuously cast, it is wound to form a coil 7, and the coil is inserted into the coil box 8 to equalize the temperature, and then rolled by the continuous finishing hot rolling machine 5. A device for winding and winding.

Next, the processing conditions for the medium thickness bar will be described with reference to FIGS. 3 and 4.
Roll a silicon steel ingot containing 0.045% C, 3.20% Si, 0.025% Al, and other impurities in mass% to start a 40mm-thick bar, and divide this into 4 parts. I tried the experiment. These were kept in a bar heating furnace at 1300 ° C for 3 hours, and AlN was completely dissolved in the ground iron and then allowed to cool. These four bars had temperatures of 1250 ° C, 1210 ° C, 1100 ° C and 1000 ° C. Were immediately placed in furnaces maintained at temperatures of 1250 ° C., 1210 ° C., 1100 ° C., and 1000 ° C., respectively, at 1250 ° C. for 480 seconds (total of 500 seconds after bar heating furnace extraction), and at 1210 ° C. After holding for 120 seconds (same total 150 seconds), 1100 ° C. for 50 seconds (same total 100 seconds), and 1000 ° C. for 20 seconds (same total 50 seconds), hot rolling was performed, and after rolling, it was allowed to cool to the atmosphere. FIG. 4 shows the overall heat history. In this figure, the curve (A) is a cooling curve when rolling is performed immediately after extraction from the bar heating furnace, and the cooling curves of (B), (C), (D, (E) are as described above.
This hot-rolled sheet is cold-rolled, decarburized, finish-annealed to obtain the final product, and the magnetic properties (B10) of the product are measured. FIG. 3 shows the relationship with the total time required to reach the finishing mill entrance including the furnace time.
As is apparent from FIG. 3, when the hot rolling shown by the cooling curve in FIG. 4 (A) is performed, the retention time is 0, so that the magnetic characteristics are the best as shown by the black circle 1 in FIG. 4B, the magnetic properties when hot rolling is performed after holding at 1000 ° C. for 20 seconds in FIG. 4 (B) are shown in FIG. The characteristics show considerable deterioration, and if the time exceeds 100 seconds, the secondary recrystallization itself becomes unstable.
Further, the magnetic characteristics when hot rolling is performed after holding at 1100 ° C. for 50 seconds as shown in FIG. 4 (C) are slightly improved because the holding time is long but the temperature is high as shown by the half-black circle 3 in FIG. Has been. Furthermore, as shown in the black circle 4 in FIG. 3, the magnetic characteristics when the film is hot rolled after being held at 1200 ° C. for 120 seconds in FIG. 4 (D) can be obtained by increasing the temperature even if the holding time is long. A value close to the best value is shown.
Finally, as shown in FIG. 4 (E), when the magnetic rolling is performed after holding at 1250 ° C. for 480 seconds and then performing hot rolling, the small black circle 5 in FIG. 3 shows a very long holding time. Compared to the best value, the value is slightly inferior.
In this way, the decrease in the bar temperature is fatal to the B10 characteristics, but it is possible to give a grace period to the holding time if a high temperature exceeding 1200 ° C. is secured, and it is found that excellent characteristics can be obtained. It was.

  When the hot rolling shown in the cooling curves of FIGS. 4B and 4C is performed, as is apparent from FIG. 3, the holding temperature before rolling is not sufficient. It has been shown that precipitation of AlN proceeds and causes magnetic deterioration. In the case of the cooling curve in FIG. 4C, it is possible to ensure a certain degree of magnetism if it can reach the hot rolling machine inlet in an extremely short time. It is clear that the production work cannot be performed unless the thermal history is along the cooling curve of 4 (D) or FIG. 4 (E).

  In the case of 3.0 to 4.0% Si in which the iron loss value is regarded as important as a high magnetic flux density grain-oriented silicon steel sheet, it is described in the above [0015] section as compared with the case where the Si content is less than 3%. As described above, the processing conditions are quite severe, and the time allowed for production work is relatively short. The reason is that in the case of low Si, precipitation is prevented because the solid solubility of AlN is increased by the γ transformation. Therefore, in the case of a high Si content, temperature can only be used as a means for preventing precipitation. The meaning is that the higher the temperature of AlN precipitation, the more rapidly it delays. Therefore, if it takes time to reach the inlet of the finishing hot rolling machine, the holding temperature should be increased. That is, as described in claim 4, when the required time to reach the inlet of the hot finishing mill after the medium thickness bar manufactured by continuous casting exceeds 200 seconds is required. , A method of passing through a heating furnace for maintaining the bar at a temperature of 1250 to 1350 ° C., and further maintaining the bar at a temperature of 1250 to 1350 ° C. even when the temperature of the bar is as low as 1000 ° C. Precipitation of AlN can be prevented by such means as passing through a heating furnace.

FIG. 5 shows that a 0.046% C, 3.10% Si, 0.029% Al silicon steel ingot is rolled into a 40 mm thick bar, heated at 1350 ° C. for 30 minutes, and then immediately rolled to approximately 1000 ° C. at 3 ° C. When finished into a 5-thick hot-rolled sheet and water-cooled from the cooling process immediately after the end of hot-rolling to create 5 types of hot-rolled sheets, cold-rolled, decarburized, and finished annealed to obtain the final product 2 shows the relationship between the magnetic characteristics and the thermal history. The thick line in the figure indicates the starting point of cooling (water cooling) after hot rolling, and the thin line indicates the magnetic properties (B10).
From this result, the material after completion of hot rolling should be subjected to rapid cooling treatment from the earliest possible timing, that is, by slow cooling (cooling in the air) as in a range not exceeding 150 seconds after completion of hot rolling. Without. b. c. d. In order to obtain magnetic characteristics, it is necessary to perform cooling at a speed as fast as possible from a high temperature as in e. For example, in the case of e, a high value of B10 = 1.95T is obtained. The temperature for cooling in a range not exceeding 150 seconds is at least 600 ° C. Usually, a hot-rolled steel sheet is wound up when it is 600 ° C. or lower, and is cooled slowly, so that AlN does not precipitate.

FIG. 6 shows the relationship between the hot rolling cooling cycle and the AlN precipitation amount. For reference, the precipitation curve in the case of low Si (1.12% Si, 2.17% Si) is also shown. As can be seen from the comparison with this, it is 1250 ° C. when the Si amount is 3.10%. Precipitation of AlN begins and progresses rapidly at 1200 ° C. or less, whereas in the case of 1.1% Si, AlN deposition hardly progresses to 1000 ° C., and begins to precipitate at 1000 ° C. or less.
This is because the α-γ transformation region of the material increases or decreases depending on the amount of contained C and Si, and the precipitation behavior of AlN is closely related to the amount of γ transformation.

In summary, the hot rolling conditions for producing an excellent high magnetic flux density grain-oriented silicon steel sheet by utilizing the effect of suppressing crystal growth by AlN are as follows.
(1) When hot rolling a medium thickness bar in which AlN is completely dissolved in a silicon steel material containing 2.95 to 4% Si, the bar is heated to the holding temperature after casting or extraction from a heating furnace. Accordingly, when the temperature is 1250 ° C. or higher, the hot rolling is started by reaching the inlet of the hot finishing mill within 500 seconds at the longest, and preferably when the temperature is higher than 1200 ° C. within 150 seconds.
(2) The cooling after the end of the hot rolling is that the time to 600 ° C. does not exceed 150 seconds at the maximum. AlN is precipitated by cooling from a high temperature. At this time, if it is gradually cooled over time, the AlN coarsens with the passage of time and becomes about 1 μm in an extreme case, and has no meaning for the purpose of the present invention. It becomes a form. When AlN in a completely solid solution is cooled to 600 ° C. for a time not exceeding 150 seconds, the precipitation size becomes approximately 10 nm, which is a preferable state for the present invention.

The present invention will be described below based on examples.
[Example 1]
Containing 0.045% C, 3.05% Si, 0.032% Al, the balance being Fe and unavoidable impurities (the remainder is omitted in the following examples as well), and silicon steel molten steel is continuously used. The bar was 60 mm thick with a casting machine (hereinafter referred to as “CC machine”) and immediately finished and hot rolled to a thickness of 3.0 mm. The finishing hot rolling inlet temperature was 1210 ° C. at the bar head and 1205 ° C. at the bottom. The amount of C in the hot-rolled sheet is 0.041%, and decarburization is slightly occurring. This was first cold-rolled at a reduction rate of 30% to a thickness of 2.1 mm, then annealed at 1100 ° C. for 2 minutes in nitrogen, and then cooled by blowing a jet stream. The cooling rate was about 18 seconds from 1100 ° C. to 850 ° C. and about 27 seconds from 850 ° C. to 400 ° C. The annealed AlN was analyzed to be 0.0055% (NasAlN). Next, this was cold rolled at a rolling rate of 83.3% to a thickness of 0.35 mm, decarburized at 800 ° C. for 3 minutes in hydrogen, and then annealed at 1200 ° C. for 20 hours. The B10 characteristic in the rolling direction of the product was 1.93 T, and W17 / 50 was 1.15 W / kg.
[Comparative Example] A bar having the same components as in Example 1 was allowed to stand for about 40 seconds in front of the finishing hot rolling machine inlet, and then finishing hot rolling was started. The finishing rolling start temperature of the bar at that time was 1150 ° C. at the bar head and 1120 ° C. at the bottom. Thereafter, the treatment was carried out in the same manner as in Example 1, and the secondary recrystallization rate occurrence rate of the most repaired product was examined.

[Example 2]
Containing 0.048% C, 3.13% Si, 0.10% Mn, 0.029% Al, 0.029% S, and the balance Fe and unavoidable impurities (the balance is defined as follows) The description of the examples is also omitted. The silicon steel molten steel was made into a bar having a thickness of 50 mm by the CC machine, and immediately finished and hot rolled to a thickness of 2.8 mm. The finishing hot rolling inlet temperature was 1210 ° C. at the bar head and 1200 ° C. at the bottom, and after 10 seconds and 50 seconds, the hot rolling was finished, and the temperatures at that time were 1010 ° C. and 1000 ° C. The winding was completed after about 75 seconds. C after hot rolling was analyzed to be 0.040%, and AlN was analyzed to be 0.0040% (NasAlN). This hot-rolled sheet is pickled and cold-rolled at a rolling rate of 87.5% to obtain a final gauge of 0.35 mm thickness, decarburized in wet hydrogen at 850 ° C. for 3 minutes, and then annealed in hydrogen at 1200 ° C. for 15 hours. did. The B10 characteristics in the rolling direction of the product were 1.92 T and W17 / 50 was 1.05 W / kg, respectively.

[Example 3]
A silicon steel molten steel containing 0.050% C, 3.18% Si, 0.075% Mn, 0.021% Al, 0.035% S in mass% is made into a 40 mm thick bar with the CC machine, Immediately, it was hot rolled to a thickness of 3.0 mm. The finishing hot rolling inlet temperature was 1210 ° C. at the bar head and 1205 ° C. at the bottom, and the hot rolling was finished after 12 seconds and 53 seconds, respectively. The temperatures at that time were 1020 ° C. and 990 ° C., respectively. The winding was completed after about 80 seconds.
This was continuously annealed at 1100 ° C. for 1 minute in a nitrogen atmosphere, then forcedly cooled to 930 ° C. by a nitrogen gas blowing device at the outlet of the furnace, and further rapidly cooled to 200 ° C. by a laminar flow device. At this time, C was analyzed as 0.045%, and AlN was analyzed as 0.0040% (NasAlN). This was pickled and cold rolled at a rolling rate of 88.3% to obtain a final gauge having a thickness of 0.35 mm, decarburized in wet hydrogen at 850 ° C. for 3 minutes, and then annealed in hydrogen at 1200 ° C. for 15 hours. The magnetic properties in the rolling direction of the product were 1.92 T for B10 and 1.05 W / kg for W17 / 50.
[Comparative Example] A bar having the same components as in Example 3 was allowed to stand for about 150 seconds in front of the finishing hot rolling machine inlet, and then finishing hot rolling was started. The finishing rolling start temperature of the bar at that time was 950 ° C. at the bar head and 930 ° C. at the bottom. Thereafter, the final product was processed under the same conditions as in Example 3 and as a result, the secondary recrystallization rate occurrence rate was examined. As a result, it was 20%, and it was not a product.

[Example 4]
Silicon steel molten steel containing 0.050% C, 3.12% Si, 0.041% Al, 0.030% S, 0.050% Se, 0.030% Te in mass% is 60 mm with the CC machine. A thick bar was formed and immediately finished and hot rolled to a thickness of 3.0 mm. The finishing hot rolling inlet temperature was 1230 ° C. at the bar head and 1210 ° C. at the bottom, and the hot rolling was finished after 15 seconds and 60 seconds, respectively. The temperatures at that time were 1050 ° C. and 1020 ° C., respectively. The winding was completed after about 90 seconds.
This was continuously annealed at 1100 ° C. for 2 minutes in a nitrogen atmosphere, then cold-rolled by 50%, then annealed for 1 minute for primary recrystallization, and further reduced to 0.23 mm at a rolling rate of 84.7%. . After decarburization annealing, this was subjected to finish annealing at 1200 ° C. for 20 hours with removal of Se, removal of Te, and removal of S. The magnetic properties of the product were 1.93 T for B10 and 1.05 W / kg for W17 / 50.

[Example 5]
A silicon steel molten steel containing 0.046% C, 3.20% Si, 0.031% Al, 0.025% S in mass% is made into a 50 mm-thick bar with the CC machine, and immediately finished hot rolled. The thickness was 2.5 mm. The finish hot rolling entrance temperature was 1220 ° C. at the bar head and 1205 ° C. at the bottom, and the hot rolling was finished after 12 seconds and 50 seconds, respectively. The temperatures at that time were 1005 ° C. and 990 ° C., respectively. The winding was completed after about 85 seconds.
This was continuously annealed at 1130 ° C. for 2 minutes, then pickled, cold-rolled to a final thickness of 0.23 mm, and then decarburized and annealed in wet hydrogen at 850 ° C. for 2 minutes. The steel sheet is mixed with TiO ₂ : 10 and MnO ₂ : 5 by weight with respect to MgO: 100, and further, an annealing separator containing 0.1 to 3% boric acid and an annealing separator not containing boric acid are separated. After separately coating, it was annealed in hydrogen at 1200 ° C. for 20 hours.
As shown in the table below, the addition of boric acid to MgO improves the B10 characteristics and at the same time reduces the iron loss value, and also reduces each variation, and the glass film, which is very important as a grain-oriented silicon steel sheet, has good properties. became.
Boric acid-added magnetic flux density, B10 (T) Iron loss value, W17 / 50 (W / kg) Remarks,
Addition,% Minimum Maximum Average Difference Minimum Maximum Average Difference TiO ₂ , MnO ₂ added
0 1.88 1.92 1.905 0.04 1.15 1.32 1.235 0.17 None
0.1 1.89 1.94 1.915 0.05 0.99 1.12 1.055 0.13
0.5 1.90 1.93 1.915 0.03 0.96 1.08 1.020 0.12 Yes
1.0 1.91 1.93 1.920 0.02 0.94 0.98 0.960 0.04
3.0 1.88 1.91 1.895 0.03 1.02 1.17 1.095 0.15

[Example 6]
A silicon steel molten steel containing 0.04% C, 3.30% Si and 0.029% Al in mass% was made into a bar having a thickness of 60 mm by the CC machine, and immediately finished by hot rolling to a thickness of 2.3 mm. The finishing hot rolling inlet temperature was 1230 ° C. at the bar head and 1205 ° C. at the bottom, and the hot rolling was finished after 12 seconds and 45 seconds, respectively. The temperatures at that time were 1010 ° C. and 995 ° C., respectively. The winding was completed after about 85 seconds.
This hot-rolled sheet was continuously annealed at 1150 ° C. for 2 minutes, then rapidly cooled and pickled, cold-rolled to a final sheet thickness of 0.27 mm, decarburized and annealed in hydrogen at 850 ° C., and finally annealed at 1200 ° C. did. When performing cold rolling, the same pass schedule (6 passes of 1.6mm, 1.2mm, 1.0mm, 0.8mm, 0.6mm, 0.45mm), with aging treatment at 5 different temperatures ). That is, the relationship between the conditions and the magnetic characteristics is as shown in the table below.
This shows that aging between passes at around 200 ° C. is effective.
(1). Heat treatment at 50 ℃ for 5 minutes for each cold rolling pass ・ ・ B10 = 1.920 (T), W17 / 50 = 1.024 (W / kg)
(2). Heat treatment at 150 ℃ for 5 minutes for each cold rolling pass ・ ・ B10 = 1.944 (T), W17 / 50 = 1.001 (W / kg)
(3). Heat treatment at 200 ℃ for 5 minutes for each cold rolling pass ・ ・ B10 = 1.951 (T), W17 / 50 = 0.998 (W / kg)
(4). Heat treatment at 350 ℃ for 5 minutes for each cold rolling pass ・ ・ B10 = 1.925 (T), W17 / 50 = 1.012 (W / kg)
(5). Heat treatment at 500 ℃ for 5 minutes for each cold rolling pass ・ ・ B10 = 1.880 (T), W17 / 50 = 1.195 (W / kg)

[Example 7]
In mass%, 0.085% C, 3.20% Si, 0.073% Mn, 0.025% S, 0.025% acid-soluble Al, 0.0085% N, 0.08% Sn, 0.005%. Silicon steel molten steel containing 07% Cu was made into a 60 mm thick bar by the CC machine, and immediately finished hot rolled to 2.0 mm. The finishing hot rolling entrance temperature was 1220 ° C. at the bar head and 1201 ° C. at the bottom, and the hot rolling was finished after 15 seconds and 55 seconds, respectively. The temperatures at that time were 990 ° C. and 985 ° C., respectively. The winding was completed after about 90 seconds.
This hot-rolled sheet was continuously annealed at 1130 ° C. for 2 minutes, then rapidly cooled in hot water at 100 ° C., subjected to precipitation heat treatment, pickled, and then subjected to final aging treatment at 250 ° C. for 5 minutes. The sheet was cold-rolled to a thickness of 0.22 mm. Next, decarburization annealing was performed in an atmosphere of dew point of 62 ° C. in Craced-NH ₃ for 2 minutes at 850 ° C., and an annealing separator mixed with MgO and TiO ₂ was applied and final annealing was performed at 1200 ° C. A tension coating was applied after the final annealing.
The magnetic properties and grain size of the product are B10 = 1.92 (T), W17 / 50 = 0.88 W / kg, ASTM No. It was 5. When Sn and Cu are not added, B10 = 1.92 (T), W17 / 50 = 0.95 W / kg, ASTM No. 3.

[Example 8] A silicon steel molten steel containing 0.05% C, 3.05% Si, 0.07% Mn, 0.03% S, and 0.026% acid-soluble Al in mass% is obtained as the CC. Machined as a 40mm thick bar. After casting, it was cut into a single bar and the bar temperature at that time was 1255 ° C. While maintaining the temperature by the heating device so as not to lower the temperature to 1250 ° C. or less, the temperature reached the inlet of the finishing hot rolling machine at about 300 seconds, and immediately started hot rolling to a thickness of 30 mm. The finish hot rolling inlet temperature was 1220-1230 ° C., and the hot rolling was completed after 15 seconds and 60 seconds at the front and rear ends of the hot rolled sheet, respectively. The temperatures at that time were 1030 ° C. and 1020 ° C., respectively, and the winding was completed after about 70 seconds.
This hot-rolled sheet was continuously annealed at 1130 ° C. for 3 minutes, then forced-cooled to immerse the bath containing boiling water at the outlet of the furnace, pickled, cold-rolled at a rolling reduction of 90%, and 0.3 mm Thickness. This was decarburized and annealed at 1200 ° C. for about 20 hours in H ₂ .
The magnetic properties of the product in the rolling direction were B10 = 1.93 (T) and W17 / 50 = 1.01 W / kg.
[Comparative example] After the bar having the same composition as in Example 8 was cast and conveyed to the finishing hot rolling machine inlet without holding the temperature by the heating device, the temperature dropped to 1100 ° C. The finished hot-rolled sheet was processed to the final product under the same conditions as in Example 3 and the secondary recrystallized grain ratio occurrence rate was examined. The coil was 30% or less, and it could be a finished product. There wasn't.

[Example 9] A silicon steel molten steel containing 0.055% C, 3.20% Si, 0.025% S, and 0.30% acid-soluble Al in mass% is bar-shaped 30 mm thick with the CC machine. As cast. After casting, it was cut into a single bar and the bar temperature at that time was 1150 ° C. This bar was immediately inserted into a heating furnace heated to 1330 ° C. to dissolve the side AlN, and then extracted from the furnace, reached the inlet of the finishing hot rolling machine for about 120 seconds, immediately started hot rolling, and had a thickness of 25 mm. Say it. The finish hot rolling inlet temperature was 1210 to 1220 ° C., and the hot rolling was completed after 16 seconds and 50 seconds at the front end and the rear end of the hot rolled plate, respectively. The temperatures at that time were 1010 ° C. and 998 ° C., respectively, and the winding was completed after about 70 seconds.
After this hot-rolled sheet was continuously annealed at 1130 ° C. for 2 minutes, it was forcibly cooled with a sprayer at the outlet of the furnace, pickled, and cold-rolled to a thickness of 0.3 mm. Decarburization annealing was performed in wet hydrogen at 835 ° C. for 3 minutes. This steel sheet was coated with MgO containing 800 ppm of B as a slurry, wound around a coil, and annealed in hydrogen at 1200 ° C. for 20 hours.
The magnetic properties of the product in the rolling direction were B10 = 1.92 (T), W17 / 50 = 0.89 W / kg.
[Comparative Example] After the bar having the same composition as in Example 8 was cast and immediately conveyed to the finishing hot rolling machine inlet, the temperature further decreased to 1080 ° C. The hot-rolled sheet that was immediately finished and hot-rolled was processed to the final product under the same conditions as in Example 3, and the secondary recrystallization rate occurrence rate was examined. As a result, only 20% was generated and it could be a finished product. There wasn't.

The schematic diagram which shows an example of continuous casting-hot rolling continuous equipment. The schematic diagram which shows the other example of continuous casting-hot rolling continuous equipment. The figure which shows the influence (3.20% Si) which the holding temperature and time after an AlN solid solution process have on magnetic characteristics. The figure which shows the typical thermal history curve (3.10% Si) in the hot rolling after an AlN solid solution process. The figure which shows the relationship (3.10% Si) of the rapid cooling (tandem rolling) start temperature and magnetic characteristic in the hot rolling after an AlN solid solution process. The figure which shows the influence of the amount of Si on the cooling curve after AlN solid solution processing, and precipitation of AlN.

Claims (4)

By mass C: 0.010 to 0.075%,
Si: 2.95 to 4.0%,
Acid-soluble Al: 0.010 to 0.040%,
N: 0.0010 to 0.0150%
0.005 to 0.1% of S or Se alone or both
A molten steel consisting of the remaining Fe and unavoidable impurities is continuously cast to produce a medium-thickness bar having a thickness of 20 to 70 mm. After the bar is cast or extracted from a heating furnace (in-furnace of the heating furnace) (Including the time) The hot finish rolling is started by reaching the inlet of the hot finishing mill within a temperature of over 1200 ° C. and within 500 seconds, and the hot rolling with a thickness of 1.5 mm to 5 mm is performed. A high magnetic flux density directional silicon which is made into a plate and has a cooling time of 150 seconds or less after completion of hot rolling until it reaches 600 ° C., and which performs normal cold rolling, intermediate annealing, decarburization annealing, finish annealing, etc. A method of manufacturing a steel sheet. In the molten steel, further segregation at grain boundaries to suppress crystal growth, Sb: 0.005 to 0.2%, Nb: 0.005 to 0.2%, Mo: 0.003 to 0.1, The high magnetic flux density directional silicon according to claim 1, comprising at least one selected from the group consisting of Cu: 0.02 to 0.2% and Sn: 0.02 to 0.3%. A method of manufacturing a steel sheet. When the intermediate thickness bar holds a temperature of 1250 ° C. or higher, the hot finish rolling mill entrance is within 500 seconds at the longest, and when it maintains a temperature of 1200 ° C. or higher, within 150 seconds. The method for producing a high magnetic flux density directional silicon steel sheet according to claim 1, wherein: When it takes more than 200 seconds to reach the entrance of the hot finishing mill after the medium thickness bar manufactured by continuous casting exceeds 200 seconds, or the temperature of the bar is 1000 ° C. 2. The method for producing a high magnetic flux density grain-oriented silicon steel sheet according to claim 1, wherein when the temperature is low, the bar is passed through a heating furnace for maintaining the bar at a temperature of 1300 to 1350 ° C. 3.

Images