JPS59205420A - Manufacture of unidirectional silicon steel sheet - Google Patents

Abstract

PURPOSE:To save energy and to reduce process period in manufacture by a method in which the stock of an unidirectional electromagnetic steel sheet containing specified amount of Si is made into the finished sheet by way of hot roll and cold roll and decarburization annealing and secondary recrystallization annealing are achieved in one process, while coating the finished sheet with an annealing separation reagent. CONSTITUTION:After the stock of an unidirectional silicon steel sheet containing 2-4wt% Si is hot-rolled and then is cold rolled, a finally finished sheet with specified thickness is obtained. This finally finished sheet is coated with an annealing separation reagent and decarburization and secondary recrystallization are successively carried out, while carrying out said decarburization annealing and secondary recrystallization annealing in one process. Thus, the unidirectional silicon steel sheet is obtained. As the annealing separation reagent, the material containing one or more kinds of carbonate or silicate family compounds of alkali metal or alkali earth metal by 1-50% and residual MgO, is used.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing grain-oriented silicon steel sheets, and relates to decarburization annealing, which is sometimes essential in the manufacturing process.

As is well known, unidirectional silicon steel sheets are used in transformers and various other electrical devices, and are required to have excellent electromagnetic properties. That is, as a magnetization characteristic, the magnetic flux density B10 value is high when the excitation current is 11000V, and as an iron loss characteristic, the iron loss value W1715° is low when the magnetic flux density is 1.7 T (Tesla) and the frequency is 50 Hz. is important. Recently, due to advances in manufacturing technology for unidirectional silicon steel sheets, the B value has increased to 1.89 T or more, Wl. Unidirectional silicon steel sheets with excellent properties having a value of 1.05W or less have been manufactured.

The conventional method for manufacturing such a unidirectional silicon steel sheet includes Si4H or less, C0.06% or less, and a small amount of inhibitor-forming elements such as S and Se.

Or As, sb, Te, as necessary
A unidirectional silicon steel sheet material with a known composition containing Bi etc. is hot rolled, normalized and annealed as necessary, and then cold rolled once or twice or more with intermediate annealing in between. A common method is to obtain a cold-rolled steel plate with the final finish thickness by cold rolling, then decarburize it, and then apply an annealing separator mainly composed of magnesia (MgO) to the steel plate surface for final finish annealing. It is.

By the way, in order to improve the magnetic properties of unidirectional silicon steel sheets, it is necessary to achieve a high degree of accumulation of the so-called Goss orientation (110) [001] orientation, and for this purpose, decarburization annealing as described above is generally performed. After final finish annealing (110
) The secondary recrystallization of the (001] orientation is sufficiently developed.In this way, the nucleation and development of the secondary recrystallization of the (110)[001] orientation is sufficiently promoted in the final finish annealing. In order to achieve this, it is necessary to add MnS or Mn to suppress the growth of primary recrystallized grains with inappropriate orientation.
The precipitated dispersed phase as an inhibitor of Se, etc. is appropriately dispersed, and a primary recrystallization texture suitable for nucleation of secondary recrystallization in the (110)(001':1 orientation) is formed. In order to form an appropriate primary recrystallization texture, decarburization annealing was conventionally performed on the final finished cold-rolled sheet as an independent process as described above. The metallurgical meaning is to remove carbon, which is an impurity that is unnecessary after final annealing and is harmful to secondary recrystallization, from the steel sheet, and to obtain an appropriate primary recrystallization texture as described above. There is a particular thing.

After performing decarburization annealing in this way, an annealing separator is applied and final finish annealing is performed again (110) [
A unidirectional silicon steel sheet with excellent magnetic properties was obtained by sufficiently developing secondary recrystallized grains in the 001] orientation.

However, the conventional method described above requires two steps of decarburization annealing and final finish annealing as heat treatment after cold rolling, which increases energy consumption and increases the cost of unidirectional silicon steel sheets. In addition, the process time after cold rolling was long, which was one of the causes of hindering productivity.

However, as mentioned above, decarburization annealing is (140) (001)
Since it is necessary to form a primary recrystallization texture that is optimal for the development of secondary recrystallization of orientation and to remove carbon harmful to secondary recrystallization, at least start secondary recrystallization. From this, it is considered that there is little need to perform decarburization annealing as a separate process prior to final finish annealing. Focusing on this point, the inventors conducted various experiments and studies, and found that in the final annealing process, sufficient decarburization is achieved at least in a lower temperature range than the temperature at which secondary recrystallization begins, and an appropriate It has been found that it is indeed possible to generate a secondary recrystallization texture and subsequently complete the secondary recrystallization. In other words, even if decarburization annealing is not performed as an independent step in a series of silicon treatment steps, one step of final annealing can
The generation and decarburization of the primary recrystallization texture necessary for the development of the secondary recrystallization of the (11,0) [001) orientation, and the subsequent growth of the secondary recrystallization are sufficiently completed, and the 1200
They discovered that it is possible to purify impurities by maintaining the temperature at a high temperature around 0.degree. C., leading to the creation of this invention.

Therefore, the method for manufacturing a unidirectional silicon steel sheet of the present invention is as follows:
A unidirectional silicon steel material containing 2 to 4% Si is hot-rolled and cold-rolled to form a final finished plate of a predetermined thickness, then an annealing separator is applied to the final finished plate, and then desorption is performed. It is characterized in that charcoal annealing and secondary recrystallization annealing are performed in one step, and decarburization and secondary recrystallization are performed continuously.

The method of the present invention will be explained in more detail below.

The steel material to be used in the method of the present invention may be obtained by using a known steel manufacturing method, such as a converter, an electric furnace, an open hearth, etc., to produce molten steel using a known continuous casting method or an ingot-blowing rolling method. Depending on the situation, you can use slabs and shiramono. Here, the steel material may contain 2 to 4 Si and a small amount of Mn, S, Se, etc. as an inhibitor-forming element. Specifically, C006% or more1
', contains 2-4% of Si, 0.01-0.1% of Mn, 70.005% or less of acid-soluble A,
and any one or more of SO, OO5 to 0.050, and if necessary, As 0.0
1~0.10%, sbo, oi~0.10 or Bi, Pb.

P, Sn, Zr, etc. (7) 0.005-0.10
It is desirable that the composition contains 14% or 2 or more kinds of Fe, and the balance is Fe.

The above-mentioned material slab is heated to a temperature of about 1400°C, preferably 1250°C or higher, and hot-rolled by a known method to form a hot-rolled plate, and as needed. Perform normalizing annealing. Then, by cold rolling two or more times with intermediate annealing in between, or by cold rolling once, the final finished plate thickness is about 0.35 to (115 trrm).The steel plate at this point (final finished cold rolled plate) The amount of carbon usually exists at least about 0.020 to 0.050%.

Such a final cold-rolled sheet is not subjected to independent decarburization annealing, but is directly coated with an annealing separator and then subjected to final annealing. During this final final annealing step, decarburization and formation of a suitable primary recrystallization texture, secondary recrystallization and final purification are performed. In other words, at a relatively low temperature during the heating process in final annealing, an oxidizing atmosphere is created between each layer of the steel sheet, and decarburization and primary recrystallization occur at around 800°C, followed by secondary recrystallization at a temperature of 850°C or higher. In order to achieve sufficient decarburization in a continuous process where recrystallized grains develop rapidly and eventually become sluggish at about 1200°C, it is necessary to use an annealing separator to be applied beforehand. MgO, which has been commonly used in the past, is insufficient, and MgO
Those containing gO as a main ingredient and containing one or more carbonates of alkali metals or alkaline earth metals, or the same (mainly containing MgO and containing one or two or more silicate compounds) It is desirable to use MgO as an annealing separator, with the combined addition of one or more alkali metal or alkaline earth metal carbonates and one or more silicate compounds. As mentioned above, the carbonate is an alkali metal or an alkaline earth metal, that is, Li.
, K, Na, Rb, Cs, Mg.

Carbonates such as Ca, Sr', and Ba can be used, specifically BaCO3, CaC0, K2CO2,
ti2co3°Rb2CO3, C3CO3, etc. are used. On the other hand, as the silicate compound, serpentine, talc, kaolin, bentonite, acid clay, activated clay, etc. can be used. Here, if the blending amount of the carbonate or silicate compound as mentioned above is less than 1%, the blending effect, that is, the decarburization promoting effect, is insufficient, and if it exceeds 50%, the blending effect will further improve. Not only is this not effective, but it is also uneconomical, so it is desirable that the total amount of these components be in the range of 1 to 50%, with the remainder being MgO.

The annealing separator mentioned above is usually hydrated and suspended in water and applied to the surface of a cold-rolled sheet that has been cold-rolled to the final thickness and subjected to final annealing. It is necessary to pay sufficient attention to the temperature increase rate or temperature increase time during final annealing as it affects decarburization. In Figure 1, as an extreme example, after being held for 24 hours at various temperatures in the low temperature range (beyond the secondary recrystallization temperature in order to perform decarburization), it was held at 1200°C for 5 hours for secondary recrystallization and purification. The relationship between the holding temperature in the low temperature range and the carbon content in the steel is shown for various annealing separators. It is clear from FIG. 1 that the amount of residual carbon in the steel tends to increase when the holding temperature is 750° C. or higher. For this reason, it is better to hold the water for a long period of time especially for decarburization, rather than holding it continuously for a long time from room temperature.
It can be seen that the amount of residual carbon in the steel decreases when the temperature is raised to about 200°C. According to detailed experiments conducted by the present inventors, it has been found that a temperature increase rate of 50° Vhr or less can sufficiently decarburize the steel during the temperature increase process in final finish annealing. However, if it is slower than 5°C/hr, the time required to raise the temperature becomes longer, resulting in an economic disadvantage, and if it is faster than 50'C/hr, decarburization may be insufficient. Therefore, it is desirable that the temperature increase rate in the temperature increase process of final annealing be within the range of 5 to 50' IC/hr.

Figure 2 shows that the amount of B a C03 (BaCO3t relative to the amount of MgO) blended as an alkaline earth metal carbonate in an annealing separator mainly composed of MgO is varied, and each annealing separator Cold rolled steel plate coated with 1180
The magnetic properties of the product (magnetic flux density B, and iron loss W1715° ) is shown. From Figure 2, M of B aCO5
It is clear that the magnetic properties are improved when the amount of gO is 1% or more (approximately the same as the amount of B a CO5 of 1 or more with respect to the total amount of annealing and separation). Further, FIG. 3 shows the magnetic properties of a product treated in the same manner as in FIG. 2 using an annealing separator containing 090% Mg and 10% qyIJ of various silicate compounds.

From FIG. 3, it is clear that even when an annealing separator containing a silicate-based compound mixed with MgO is used, the magnetic properties of the product are superior to those using MgO alone. Further, FIG. 4 shows the macrostructure of a product sheet obtained when the same final annealing as described above was performed using an annealing separator to which 0 to 50 g of K2CO3 (however, the ratio to the MgO deposit) was added.

From FIG. 4, it is clear that when 2CO3 is added to MgO in an amount of 1 or more, secondary red crystals are sufficiently completed.

As mentioned above, the details of why decarburization is promoted in the temperature rising process of annealing by using an annealing separator containing MgO mixed with an alkali metal or alkaline earth metal carbonate or silicate compound. Although it is not yet clear, it can be considered as follows. That is, the above-mentioned carbonate or silicate Li2Co3 is heated at 618°C, Cs C05
In both cases, the temperature is below 800°C, 610°C for serpentinite, and 500 to 700°C for serpentinite. Therefore, it decomposes before the start of secondary recrystallization in the heating process and creates an interlayer atmosphere in the interlayer part of the coil or plate. Make it oxidizing. As is well known, decarburization is achieved by the combination of carbon and oxygen in an oxidizing atmosphere on the surface of a steel sheet, and it is known that it is necessary to ensure an oxidizing atmosphere. Therefore, even when carbonate or silicate compounds such as those mentioned above are used, p-decarburization is thought to be promoted by the generation of an oxidizing atmosphere.

If the final cold-rolled finished plate thickness exceeds 0.35m, decarburization during the temperature raising process in final final annealing may be insufficient, so the final cold-rolled finished plate thickness should be 0.351m or less. is desirable. However, if it is too thin, iron loss will deteriorate, so
It is desirable that the plate thickness be at least 0.1rTcIn or more, and it is desirable that the final finished plate thickness be within the range of 0.1 to 0.35 mm.

This will be explained below based on examples.

Example I C0,034%, Si3.00%, Mn0.06%.

After hot rolling a unidirectional silicon steel sheet material containing 0.020% SeO, 0.030% Sb and the remainder substantially Fe to a thickness of 3.0 mm, and removing oxide scale by pickling. A cold-rolled steel plate having a thickness of 0.27 m was obtained by performing a first inter-mesh rolling, and after an intermediate annealing at 950° C. for 5 minutes, a second inter-mesh rolling was performed. On the surface of the cold-rolled side plate, B is added to MgO.
a Apply an annealing separator mixed with 0 to 30% CO3 (ratio to the amount of MgO) and heat at 18.20C/h.
Raise the temperature to 1180℃ at a heating rate of r, and further increase the temperature to 1180℃
A final finish annealing was performed by holding in hydrogen for 5 hours. The results of investigating the magnetic properties of the obtained unidirectional silicon steel sheet are shown in B.
a Table 1 shows the amount of C05 added.

Table 1 Example 2 CO, 030%, Si 2.90%, %n 0.07.

□ An ingot of a unidirectional silicon copper plate material containing 0.020% Se, 030% SbO, and the remainder being essentially Fe was hot rolled, and after the first inter-rolling, it was rolled at 980°C for 50 minutes. It was intermediately annealed for a minute and then cold rolled a second time to a thickness of 0.30 ran. On the surface of the cold-rolled plate, CaCO5 was added to MgO.
~30% (ratio to MgO content) A mixed annealing separator hydration solution is applied, the temperature is raised to 1200°C at a heating rate of 30'C/hr, and the final finish annealing is continued by holding at 1200°C for 51 days. was carried out in dry hydrogen at a dew point of -60'C. The magnetic properties of the obtained unidirectional silicon steel sheets are shown in Table 2 in correspondence with the amount of MgO in the annealing separator and the C a COs meter.

Table 2 Example 3 C0,035%, Si3.5%, Mn 0.060%
.

A unidirectional silicon steel sheet material containing 0.19% of SeU and 0.25% of SbO, with the remainder being substantially Fe, was hot-rolled into a hot-rolled sheet with a thickness of 2.71111 mm. Next, normalizing annealing was performed, followed by first intermetal rolling, resulting in a 950"
After performing intermediate annealing for 5 minutes at C, the final finished plate thickness was made 0.18 m by second cold rolling. On the surface of the cold-rolled plate, Mg
Mix O to 30% of serpentinite (ratio to MgOt) and apply an annealing separator, raise the temperature to 1200°C at a heating rate of 5'C/br, and then hold at 1200°C for 5 hours. Final annealing was performed. However, the atmosphere for final annealing was Ar up to 400°C, and in dry hydrogen above 400°C. Table 3 shows the relationship between the amount of serpentine and the amount of MgO.

Table 3 From each of the above examples, decarburization annealing is performed as an independent step by using an annealing separator that is a mixture of MgO with about 1% or more BaCO3*CaCO5 or serpentinite as an annealing separator. It is clear that excellent magnetic properties can be obtained even if the annealing is performed during the temperature raising process of final finish annealing. In addition, in each example, compared to the case where conventional decarburization annealing is performed as an independent process, the energy cost after the cold rolling process is reduced by about 20 to 30 inches, and the process required after the cold rolling process is reduced. It was confirmed that the time was reduced by about 10 to 30 hours.

As is clear from the above description, the method of the present invention eliminates the need for the decarburization process, which was conventionally performed as an independent process before applying an annealing separator after cold rolling.
Therefore, various effects can be obtained, such as the energy cost being significantly reduced compared to the conventional method, and the process time after the cold rolling process being significantly reduced compared to the conventional method, thereby improving productivity.

[Brief explanation of the drawing]

Figures 1 (A) and (B) are diagrams showing the relationship between the low-temperature holding temperature in the final finish annealing and the amount of residual carbon in the pot in the final product for various annealing separators in the case of maintaining an Ar atmosphere and maintaining an H2 atmosphere. , Figure 2■. (B) shows the magnetic properties of the product produced by the method of this invention when MgO is mixed with B a C05 as an annealing separator.
Figures 3 (4) and (B), which show the correlation between the amount of BaCO5 and the amount of gO, show that Mg090% is used as an annealing separator.
A diagram showing the magnetic property distribution of a product produced by the method of the present invention using a mixture of 1 and 10 silicate compounds, corresponding to each compound. It is a metal structure photograph showing the macrostructure of a product after final finish annealing by the method of the present invention when 0 to 50 g of 2C03 is added to MgO. Applicant Kawasaki Steel Co., Ltd. Agent Patent attorney Takehito Toyota (and one other person) Figure 2 BeLoQaf (KgOtt211sutiL
'A C Figure 3 (A) (Each IO% 10MyO'?O%) Procedure Amendment @ (Method) September 8, 1980 Commissioner of the Patent Office Kazuo Wakasugi 1, Indication of the case 1982 Patent Application No. 77885 2, Title of invention: Method for manufacturing unidirectional silicon steel sheet 3, Relationship with the amended case Patent applicant address: 1-1-28 Kitahonmachi-dori, Chuo-ku, Kobe, Hyogo Prefecture
@ Name (125) Kawasaki Steel Co., Ltd. 4, Agent address: 3-4-18-5, Mita, Minato-ku, Tokyo, Date of amendment order: August 30, 1980 (shipment date) 7. Contents of amendment (1) ) Written on the last line of page 17 of the specification cylinder [Figure 1 (A)
, (B)" should be corrected as "Fig. 1 is." (2) [Figures 4 (A) to (F)] written in Book M, page 18, line 10 is corrected to ``J'' in Figure 4. 11

Claims (2)

[Claims] (1) After hot rolling and cold rolling a unidirectional electrical steel sheet material containing 2 to 4 Ti (wt%, same hereinafter) of Si to a final finished plate of a predetermined thickness, the final finishing process is performed. A unidirectional silicon steel sheet characterized in that an annealing separator is applied to the sheet, and then decarburization annealing and secondary recrystallization annealing are performed in one step so that decarburization and secondary recrystallization are performed continuously. Production method. (2) The annealing separator contains 1 to 50 of one or more of carbonates of alkali metals or alkaline earth metals, or silicate compounds, and the balance is MgO.
2. A method for producing a grain-oriented silicon steel sheet according to claim 1, characterized in that a material comprising: