JP2647323B2 - Manufacturing method of grain-oriented electrical steel sheet with low iron loss - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing 2.5-7.0% S
It is an object of the present invention to provide a method for producing a grain-oriented electrical steel sheet having excellent cold-rolling productivity and low iron loss.

[0002]

2. Description of the Related Art Generally, the magnetic properties of a grain-oriented electrical steel sheet are evaluated based on both iron loss properties and excitation properties. Increasing the excitation characteristics is effective in reducing the size of equipment that increases the design magnetic flux density. On the other hand, reducing the iron loss characteristics is effective in that when it is used as an electric device, heat loss is reduced and power consumption can be saved. But,
The grain-oriented electrical steel sheet contains 2.5 to 7.0% of Si,
Not only is it brittle and fragile than ordinary steel materials, it is also extremely high in deformation resistance. Therefore, during cold rolling, a roll mill is generally used, such as a Sendzimir mill having a small roll diameter of about 100 mmφ, and a rolling speed of about 500 mpm. It had to be rolled at a very low speed. Therefore, the productivity was extremely low as compared with a multi-stand tandem mill that performs high-speed rolling in one direction.

As a method for producing a grain-oriented electrical steel sheet using a tandem mill, there is a method in which the reduction ratio distribution at the final stand is restricted, as disclosed in Japanese Patent Application Laid-Open No. 2-173210. However, this method seeks to reduce the surface roughness of the steel sheet, and it has been found that sufficient magnetic properties cannot be obtained.

[0004]

SUMMARY OF THE INVENTION Recently, productivity improvement,
From the viewpoint of improving quality and yield and saving labor, it has been aimed to produce hard-to-roll materials such as grain-oriented electrical steel sheets with a high-efficiency tandem mill. However, the conventional method of manufacturing a grain-oriented electrical steel sheet alone has a problem that the magnetic properties of the high-grade electrical steel sheet are very unstable and unstable. The present invention provides a manufacturing method for solving the problem.

[0005]

SUMMARY OF THE INVENTION The present invention provides a C:
0.10% or less, Si: 2.5 to 7.0%, containing a usual inhibitor component, the balance being a unidirectional electromagnetic steel hot-rolled steel sheet consisting of Fe and unavoidable impurities, subjected to hot-rolled sheet annealing, In a method for producing a grain-oriented electrical steel sheet by performing cold rolling at a rate of 50% or more, decarburizing annealing, and then performing final finishing annealing, the cold rolling is performed by a tandem mill having a plurality of stands, and By heating the strip rolled to the product thickness to a temperature of 700 ° C or more at a heating rate of 80 ° C / sec or more before decarburizing annealing, a unidirectional electromagnetic coil with excellent productivity and low iron loss is obtained. It has been found that a method for manufacturing a steel sheet can be obtained.

Hereinafter, the present invention will be described in detail. The grain-oriented electrical steel sheet can be manufactured by sufficiently causing secondary recrystallization during the final annealing in the manufacturing process to obtain a so-called Goss texture. In order to obtain this Goss texture, coarsening of primary recrystallized grains is suppressed, and only recrystallized grains of the (110) <001> orientation are selectively grown in a certain temperature range.
In other words, it is necessary to make a base material for secondary recrystallization. To do so, the material must be MnS, AlN,
Fine inclusions such as Cu ₂ S must be uniformly dispersed as an inhibitor of the growth of primary recrystallized grains. Furthermore, in the stage of primary recrystallization, it is necessary to increase the (110) plane recrystallized grains as much as possible.

However, in the unidirectional rolling by the tandem mill, it has been found that the (110) plane recrystallized grains after the primary recrystallization are not so many as compared with the conventional reverse rolling. Was. Therefore, as a result of repeated studies on the improvement of the primary recrystallization structure on the assumption of a tandem mill, the strip rolled to the final product thickness was heated at a heating rate of at least 80 ° C./sec to 700 ° C. or more immediately before decarburizing annealing. It was ascertained that a heat-treated steel sheet having a good magnetic property can be obtained by performing a heat treatment at a temperature of.

[0008]

Next, the reason why the steel composition and the manufacturing conditions are limited as described above in the present invention will be described in detail. The reasons for limiting the steel components are as follows. The upper limit of 0.10% for C is limited because if it is more than this, the time required for decarburization becomes longer and it is economically disadvantageous. The lower limit of Si is set to 2.5% in order to improve iron loss, but if it is too large, it is likely to break during cold rolling and processing becomes difficult, so the upper limit is set to 7.0%.

Further, in order to produce a grain-oriented electrical steel sheet, it is preferable to add the following component elements as ordinary inhibitor components. When MnS is used as an inhibitor, Mn and S are added. Mn is desirably 0.02 to 0.15% in order to obtain an appropriate dispersion state of MnS. S is an element necessary for forming MnS and (Mn · Fe) S.
~ 0.05% is desirable. Further, when AlN is used as an inhibitor, acid-soluble Al and N are added. In order to obtain an appropriate dispersion state of acid-soluble Al and AlN, 0.01 to 0.04% is desirable. N is also preferably 0.003 to 0.02% in order to obtain a proper dispersion state of AlN. In addition, at least one of Cu, Sn, Sb, Cr and Bi may be added at 1.0% or less for the purpose of strengthening the inhibitor.

Next, the above-mentioned molten steel is subjected to a usual ingot casting method or a continuous casting method, and hot-rolled to obtain a strip having an intermediate thickness. At this time, the strip casting method can also be applied to the present invention. Further, when a nitride is required as an inhibitor, 950 to 120 is required for precipitation of AlN or the like.
It is desirable to perform intermediate annealing at 0 ° C. for 30 seconds to 30 minutes.

Next, a strip having a final product thickness is obtained by one rolling. The rolling reduction at this time is desirably 50% or more in order to obtain a product having a high Goss integration degree. Lower limit 5
If the value is less than 0%, a necessary Goss nucleus cannot be obtained. As a cold rolling method at this time, a tandem mill having a plurality of stands is used to improve productivity. The roll diameter at this time is preferably 600 mmφ or less, if possible, in order to impart stability to the rolling of the brittle material.

As described above, the strip rolled to the final product thickness is subjected to a heat treatment. First, the strip is rapidly heated to a temperature of 700 ° C. or more at a heating rate of 80 ° C./sec or more. The lower limit of the heating rate at this time, 80 ° C./sec, is below (110) <00 after primary recrystallization, which is the nucleus of secondary recrystallization.
1) The orientation grain size was reduced, and fine secondary recrystallized grains could not be obtained. The lower limit of 700 ° C. was limited because recrystallization does not start below this temperature. FIG. 1 shows the (110) plane strength after primary recrystallization in each manufacturing method.

[0013] This is 0.27 mm from a 2.2 mm hot rolled sheet.
When a thick strip is cold rolled, a conventional reverse rolling (Senzimir mill) method and a tandem rolling method will be described. When tandem rolling is performed to improve productivity, the (110) plane strength is reduced. Therefore, the strip rolled to the final thickness is 85 ° C. at a heating rate of 90 ° C./sec.
Rapid heating to 0 ° C. increases the (110) plane strength.
Note that it is desirable to perform this rapid heating treatment in a reducing atmosphere or a non-oxidizing atmosphere as much as possible in view of problems such as film formation.

The above-mentioned rapid heating treatment can be incorporated into the decarburizing annealing step as a heating step of the decarburizing annealing even if it is performed before the next decarburizing annealing. After this,
Decarburization annealing is performed in a wet hydrogen atmosphere. At this time, carbon must be reduced to 0.005% or less so as not to deteriorate magnetic properties of the product. Here, when the slab heating temperature in hot rolling is low and only AlN is used as an inhibitor, nitriding treatment may be added in an ammonia atmosphere. Further, an annealing separator such as MgO is applied and finish annealing at 1100 ° C. or higher is performed for secondary recrystallization and purification, whereby a grain-oriented electrical steel sheet having low iron loss characteristics is manufactured. In order to further improve the iron loss of the obtained product, it is possible to subject the above-mentioned grain-oriented electrical steel sheet to a treatment for subdividing magnetic domains.

[0015]

【Example】

(Example 1) A hot rolled sheet containing the chemical components shown in Table 1 and hot-rolled to a thickness of 2.3 mm was annealed at 1100 ° C for 1 minute. Thereafter, it was rolled to a final sheet thickness of 0.27 mm by two types of cold rolling methods: reverse rolling by a Sendzimir mill and unidirectional rolling by a tandem mill.

Further, when the obtained strip is decarburized and annealed, it is heated at 10 ° C./sec, 85 ° C./sec, 150 ° C./sec.
After heating under three conditions of 2 seconds, decarburizing annealing in wet hydrogen and applying MgO powder, high-temperature annealing was performed at 1200 ° C. for 10 hours in a hydrogen gas atmosphere. Table 2 shows the productivity and magnetic properties of the obtained product. According to the present invention, a grain-oriented electrical steel sheet having good productivity and excellent magnetic properties has been obtained.

[0017]

[Table 1]

[0018]

[Table 2]

Example 2 A molten steel containing the composition shown in Table 3 was cast, heated to a slab, and then hot-rolled to 2.3 mm.
Was obtained. This was annealed at 1100 ° C. for 5 minutes, pickled, and then tandem cold rolled in 6 stands to a thickness of 0.22 mm. The rolled steel sheet is heated at a heating rate of 290 ° C./sec.
Heated to 45 ° C. Thereafter, decarburization annealing was performed in wet hydrogen at the same uniform temperature of 845 ° C. Next, after applying MgO powder, high-temperature annealing was performed at 1200 ° C. for 10 hours in a hydrogen gas atmosphere. The magnetic properties of the resulting product are:
A unidirectional electrical steel sheet having an extremely low iron loss of B ₈ = 1.94 T and W _17/50 = 0.83 (W / kg) was obtained.

[0020]

[Table 3]

[0021]

According to the present invention, it is possible to produce a grain-oriented electrical steel sheet having excellent productivity and good iron loss characteristics.

[Brief description of the drawings]

FIG. 1 is a chart showing a change in texture by a cold rolling method.

Claims (2)

(57) [Claims] 1. C: 0.10% or less by weight, Si: 2.
5 to 7.0% as well as the usual inhibitor components,
The remainder is subjected to hot-rolled sheet annealing of a unidirectional electromagnetic steel hot-rolled sheet composed of Fe and unavoidable impurities, cold-rolled at a reduction ratio of 50% or more, decarburized annealing, and then subjected to final finish annealing. In the method for producing a grain-oriented electrical steel sheet, the cold rolling is performed by a tandem mill having a plurality of stands, and the strip rolled to a final product thickness is heated at a heating rate of 80 ° C./sec or more before decarburizing annealing. A method for producing a grain-oriented electrical steel sheet having a low iron loss, wherein the method is heat-treated to a temperature of 700 ° C. or more. 2. The method according to claim 1, wherein the rapid heating treatment is performed as a heating stage of the decarburizing annealing.