JPH10219359A - Method for managing decarburization annealing of grain oriented silicon steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a grain oriented silicon steel sheet having stable film characteristics and magnetic characteristics by controlling the atmosphere of a heating zone for decarburization annealing by separating from a soaking zone atmosphere and evaluating the degree of oxidation of this atmosphere by measuring the oxidation layer of a decarburization plate with fluorescent X-rays. SOLUTION: At the time of producing the grain oriented silicon steel sheet, an atmosphere separating seal is inserted into the heating zone and the soaking zone in its decarburization annealing stage and two atmospheric gas control systems are arranged respectively in correspondence to the heating zone and the soaking zone. The degree of oxidation (PH2 O/PH2 ) of the heating zone in this constitution is estimated by the fluorescent X-ray intensity of Si and the degree of oxidation of the soaking zone is estimated by the fluorescent X-ray intensity of P. As a result, the oxidation layer of the decarburization plate is rapidly measured and evaluated by the fluorescent X-rays, by which the management of the degree of oxidation of the atmosphere is made possible. The grain oriented silicon steel sheet having the industrially stable film characteristic and magnetic characteristics is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a coating film by controlling decarburization annealing in the process of manufacturing a so-called ordinary grain-oriented electrical steel sheet in which crystal grains are accumulated in the {110} <001> direction with a Miller index. And a manufacturing method for stably producing magnetic characteristics.

[0002]

2. Description of the Related Art Grain-oriented electrical steel sheets are {110} <001.
> 0.8% of Si composed of crystal grains accumulated in the orientation
It is a steel sheet containing 〜4.8%. This steel sheet is required to have excitation characteristics and iron loss characteristics as magnetic characteristics. As an index indicating the excitation characteristic, a magnetic flux density: B8 at a magnetic field strength of 800 A / m is usually used. As an index representing iron loss characteristics, iron loss per kg of steel sheet when magnetized at a frequency of 50 Hz to 1.7 T: W17 / 50 is used. Magnetic flux density:
B8 is the largest controlling factor of iron loss characteristics, and the magnetic flux density: B
8 The higher the value, the better the iron loss characteristics. Magnetic flux density: B8
In order to increase the crystallinity, it is important to make the crystal orientation highly uniform. The control of the crystal orientation is achieved by utilizing a catastrophic grain growth phenomenon called secondary recrystallization.

In general, a forsterite (Mg ₂ SiO ₄ ) -based insulating film is formed on the surface of a grain-oriented electrical steel sheet. The magnetic properties are improved by providing. This forsterite film is formed by a solid phase reaction between the surface oxide layer (SiO ₂ ) formed in the decarburizing annealing step and MgO applied to the surface as an annealing separator during the finish annealing. The formation behavior of the forsterite film during finish annealing depends on Al, an influencing factor of secondary recrystallization.
It affects the change behavior of fine precipitates (inhibitors) such as N and MnS. Therefore, uniform formation of a film is important for stably performing secondary recrystallization.

In order to make the forsterite forming reaction uniform, it is important to control the decarburizing annealing conditions to control the type, amount, form, distribution, etc. of the oxide formed on the surface layer. . As a technique for controlling an oxide layer in decarburization annealing, there is a technique disclosed in, for example, Japanese Patent Publication No. 57-1575. Further, a method for managing the quality of the oxide layer with respect to the management of the oxide layer in JP-59-41480 example of decarburization annealed sheet (fayalite (Fe ₂ SiO ₄₎ and silica (the ratio of SiO ₂₎₎ In addition, JP-A-2-274817 proposes a method for controlling the amount of oxygen.

The present inventors have conducted research on the decarboxylation layer and found that the initial oxidation in the heating zone of decarburization annealing is particularly important for controlling the morphology of oxides. Is proposed in Japanese Patent Application Laid-Open No. Hei 2-305921 to control the temperature separately from the uniform tropical atmosphere.

[0006]

In the decarburization annealing step, it is important to separate and control the heating zone and the isotropy atmosphere gas in controlling the form and distribution of a plurality of oxides present in the oxide layer. It has an effect on the stabilization of the film properties and magnetic properties of the product. However, in the decarburization annealing process, the decarburization reaction occurs together with the oxidation reaction of the steel sheet. Poor characteristics may occur.

However, until now, there has been no method for independently estimating the degree of oxidation of the atmosphere gas immediately above the heating zone and the steel plate in the soaking zone after decarburization annealing, and no method for managing the on-site operation has been found.

According to the present invention, an oxide layer of a steel sheet is quickly analyzed after decarburization annealing for variations in the oxide layer caused by operational disturbances and the like, the atmosphere gas for decarburization annealing is controlled, and the film characteristics and magnetic properties are improved. An object of the present invention is to provide a method for manufacturing a grain-oriented electrical steel sheet having stable characteristics.

[0009]

Means for Solving the Problems In the production process of grain-oriented electrical steel sheets, the present inventors have developed a decarburized annealed sheet prepared by independently controlling the heating zone in the decarburization annealing step and the atmosphere gas in the soaking zone. As a result of examining the oxidized layer by various analysis methods, it was found that it is possible to separate and estimate the atmospheric oxidation degree of the heating zone and the isotropy atmospheric oxidation degree in the decarburization annealing process by a known X-ray fluorescence analysis method. . Separating and controlling the heating zone and the solitary atmosphere is achieved by inserting an atmosphere separation seal between the heating zone and the soaking zone, and arranging two systems for the atmosphere gas control system corresponding to each of the heating zone and the soaking zone. Was. The fluorescent X-ray analysis can be performed in the atmosphere as the measurement atmosphere, and since it is a non-contact and non-destructive analysis, it can also be performed on-line by a decarburization annealing facility.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, description will be made based on experimental results.
Si: 3.2% by weight, C: 0.05%, acid soluble A by weight
l: 0.027%, N: 0.08%, Mn: 0.1%,
P: A 0.23 mm thick cold rolled sheet containing 0.03 was heated to 830 ° C. at a heating rate of 25 ° C./sec.
Seconds decarburized annealing. Atmospheric gas _{N 2: 25% + H 2} : 7
At 5%, the heating zone and the isotropy oxidation degree (PH ₂ O / P H
₂ ): Changed independently in the range of 0.14 to 0.72. FIG. 1 shows the results of X-ray fluorescence analysis after decarburizing annealing.

From FIG. 1, the Si intensity of the fluorescent X-rays depends on the oxidation degree of the gas in the heating zone atmosphere and does not depend on the oxidation degree of the soaking atmosphere, so that the oxidation degree of the heating zone can be estimated from the X-ray fluorescence intensity of Si. I understand. Further, since the P intensity of the fluorescent X-rays depends on the gas oxidation degree of the soaking zone atmosphere and does not depend on the oxidation degree of the heating zone atmosphere, it can be seen that the oxidation degree of the soaking zone can be estimated from the fluorescent X-ray intensity of P. Since the X-ray fluorescence intensity of Fe does not depend on the degree of oxidation of the atmosphere gas in the heating zone or the soaking zone, and shows a substantially constant value, it is possible to normalize the intensity of each element by the intensity of Fe. It can also be seen that it is effective to reduce the measurement error.

From the above results, it can be seen that X-ray fluorescence analysis is an effective method for managing the heating zone of decarburizing annealing and the substantial oxidation degree of the atmospheric gas in the tropical zone. These fluorescent X
Other factors that determine the linear strength include, of course, the chemical composition of the steel sheet. When preparing a calibration curve for fluorescent X-rays, it is necessary to prepare each of steel types having different component systems of oxide-forming elements. Next, the surface condition immediately before the decarburizing annealing may affect. The oxidation behavior of the heating zone in particular changes due to the remaining scale before the cold rolling step, the remaining rolling oil in the cold rolling step, and other stains, and the fluorescent X-ray intensity of Si and P may fluctuate.

[0013]

【Example】

[Example 1] Si: 3.2%, C: 0.05%, acid-soluble Al: 0.03%, N: 0.007%, Mn: 0.1
%, S: 0.007%, Cr: 0.1%, Sn: 0.0
115% silicon steel slab containing 5%, P: 0.025%
It was heated to 0 ° C. and hot rolled to a thickness of 2.3 mm. This hot-rolled sheet was annealed at 1120 ° C., pickled, and then cold-rolled to a final sheet thickness of 0.23 mm. These samples were heated to 830 ° C. while changing the atmosphere oxidation degree in the heating zone at a heating rate of 25 ° C./sec, and were decarburized and annealed at 830 ° C. for 120 seconds with an oxidation degree of 0.44. Then, at 750 ° C. in an atmosphere containing ammonia,
Annealing was performed for 0 second to reduce the amount of nitrogen to 0.02%. Then, Mg
1200 ° C. after applying an annealing separator mainly containing O
For 20 hours. From Table 1, it can be seen that the oxidation degree of the heating zone corresponds to the fluorescent X-ray intensity of Si, and that the coating properties and magnetic properties are affected by the oxidation degree of the heating zone.

[0014]

[Table 1]

[Example 2] Si: 3.2%, C: 0.0
7%, acid-soluble Al: 0.027%, N: 0.007
%, Mn: 0.07%, S: 0.025%, Cu: 0.
A silicon steel slab containing 15%, Sn: 0.1%, and P: 0.01% was heated to 1350 ° C. and hot-rolled to a thickness of 2.3 mm. After annealing this hot-rolled plate at 1120 ° C and pickling,
Cold rolling was performed to a final thickness of 0.28 mm. These samples were heated at a heating rate of 25 ° C./sec.
4 to 830 ° C. and 0.4 seconds at 830 ° C. for 150 seconds
Decarburization annealing was performed at an oxidation degree of 4. Some samples are in the latter half of soaking
0 seconds was annealed with a degree of oxidation of 0.72. Next, after applying an annealing separator mainly composed of MgO,
Finish annealing was performed for 0 hours. From Table 2, it can be seen that when a part of the solitary zone has a high oxidation degree, the fluorescent X-ray intensity of P increases, and the film properties and magnetic properties are correspondingly deteriorated.

[0016]

[Table 2]

[0017]

According to the present invention, the heating zone atmosphere of the decarburizing annealing is controlled separately from the soaking zone atmosphere, and the oxidation degree of the atmosphere is quickly measured and evaluated by the fluorescent X-rays on the oxidized layer of the decarburized plate. In this way, variations in operation can be reduced, and a grain-oriented electrical steel sheet having industrially stable coating characteristics and magnetic characteristics can be manufactured.

[Brief description of the drawings]

FIG. 1 shows the X-ray fluorescence intensity (Si-
a, Pb, and Fec diagrams).

Claims (2)

[Claims] In the decarburizing annealing step of grain-oriented electrical steel sheets, the atmosphere gas in the heating zone is controlled separately from the soaking zone, and the oxide film after annealing is evaluated by a fluorescent X-ray apparatus, and the decarburizing annealing is performed. A method for controlling decarburization annealing in the production of grain-oriented electrical steel sheets, characterized by controlling atmosphere gases. 2. The atmosphere gas dew point of the heating zone is determined by the fluorescent X-ray S
2. The method for controlling decarburization annealing in the production of grain-oriented electrical steel sheets according to claim 1, wherein the i-strength and the dew point of the atmosphere gas in the soaking zone are controlled by the P intensity of the fluorescent X-ray.