JPS59193220A - Preparation of unidirectional silicon steel plate - Google Patents

Abstract

PURPOSE:To prepare a unidirectional silicon steel plate excellent in iron loss characteristics, by coating a steel plate containing a specific compositional amount of Si and a minute amount of S, Se and N with an annealing separating agent containing Nb-oxide before applying final annealing to the coated steel plate under a specific condition. CONSTITUTION:After a steel plate after final cold rolling containing 4.5wt% or less Si and a minute amount of at least one element among S, Se and N is subjected to decarburizing annealing, the treated steel plate is coated with an Nb-oxide-containing annealing separating agent and, succeedingly, final annealing is applied to the coated steel plate at a temp. ranging from 1,000-1,200 deg.C in a hydrogen atmosphere to completely remove precipitates such as nitride, sulfide or selenide after the completion of secondary recrystallization from steel as impurities. By this method, a unidirectional silicon steel plate excellent in iron loss characteristics is obtained. As the above mentioned annealing separating agent, it is pref. to use one containing Nb-oxide in an amount so as to bring Nb-adhesion amount per the single surface of the steel plate to be 0.02- 0.5g/m<2>.

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to an improved method for promoting the removal of trace impurities during final annealing, which is useful for manufacturing unidirectional silicon steel sheets, particularly for improving core loss.

(Problem) Unidirectional silicon steel sheets are mainly used as iron cores for electrical equipment such as transformers, and it is important that they have excellent excitation characteristics and iron loss characteristics. Due to the recent rise in energy costs, there has been a strong demand for unidirectional silicon steel sheets with particularly excellent iron loss characteristics.

Generally, in the production of grain-oriented silicon steel sheets, it is possible to develop a so-called Goss-oriented secondary recrystallized structure with (110)<100> orientation during the final annealing at high temperatures. This is important. For the development of the secondary recrystallized structure, precipitates such as nitrides, sulfides, and oxides are finely dispersed in the steel and the secondary recrystallized grains in the Goss orientation are sufficiently developed. It is essential to suppress the growth of primary recrystallized grains.

On the other hand, if the precipitates still remain in the steel at the product stage, they become an obstacle to domain wall movement during magnetization and deteriorate iron loss characteristics. must be removed from the steel.

Nitride, sulfide, selenide, etc. are usually used as the precipitates, and these precipitates such as nitrogen, sulfur, and selenium should be completely removed from the steel in the final high-temperature annealing as described above. , often remaining at the interface between the glass coating and the steel, or in the steel immediately below the glass coating, and the iron loss characteristics of products are currently not sufficiently excellent.

(Objective of the invention) To further improve the iron loss characteristics of the product by sufficiently removing impurities such as nitrogen, sulfur, and selenium in the vicinity of the glass coating from the steel and the glass coating, thereby providing a product that can meet the above requirements. The purpose is to make it possible to manufacture a unidirectional silicon steel sheet that has much better iron loss characteristics than conventional unidirectional silicon steel sheets.

(Structure of the Invention) As a result of studying a method for eliminating the above impurities, it was found that in the manufacturing process of unidirectional silicon steel sheets, S = +5% by weight (hereinafter simply referred to as "O") or less and S, Se, and N. After decarburizing and annealing the final cold-rolled steel sheet containing a trace amount of at least one of these, a Z annealing separator containing Nb oxide is applied, followed by final annealing in a temperature range of 1000 to 1200°C in a urea atmosphere. By annealing, we succeeded in obtaining a product with almost no impurities and excellent iron loss characteristics.

This Nb oxide has a content of 0.02 to 0.02 per side of the steel plate as Nb.
o. Apply the annealing separator mixed so as to satisfy the area weight range of 597 m1. In this way, the iron loss of the unidirectional silicon steel sheet product that underwent final annealing, W17150, was reduced to 0.
．． 02 to 0.05 WA9 can be improved.

The reason why the iron loss of the product is improved by including Nb oxide in the annealing separator is that it removes impurity elements such as S g Se and N from the steel during final annealing to the N on the surface of the copper plate.
This is because the adsorption of the b oxide produces a cleaning effect directly beneath the glass film or at the interface with the steel.

In addition, if elemental Nb is contained in the separating agent instead of Nb# compound, Nb will diffuse into the steel during final annealing, combine with the impurities, and remain as inclusions in the steel. , it actually has the opposite effect.

The reason why the coating conditions for the Nb oxide-containing separation agent are limited in this invention will be explained based on the following experimental results.

8.1 weight of Sl, 0.02 of S as an inhibitor
In addition to 154, an appropriate amount of O*Mn and N as an impurity were added.
Molten steel for unidirectional silicon steel containing 0.004 oz was made into a product with a thickness of -0.30113 by known casting methods, hot rolling methods, and cold rolling methods, and then heated at 840°C for 2 minutes in a wet hydrogen atmosphere. After decarburization annealing, a slurry containing 0.1 to 2.0% NbzOB in an annealing separator mainly composed of MgO is applied to the steel plate, and after drying, the cut plates are stacked and placed in a urea atmosphere. 1200"C5Hr annealed.

As shown in Table 1, the results showed that Nb was 0.0% per side of the steel plate.
02 (It was found that under the separation agent application conditions where the basis weight is 1/mZ or more, the product iron loss W17150 is improved by 0.02wAl or more.The upper limit of the Nb basis weight is regulated from the point of view of the product iron loss. Although it is not necessary from now on, when the Nb coating amount exceeds a certain amount, the effect is saturated and the cost only increases.
Therefore, the upper limit of Nb basis weight is Q, 597 mt (
Example 1) C: 0.085%, Si: 2.98
%, Mn: 0.07%.

S: 0.021% and N as an impurity! 0
．． After hot rolling a continuous cast silicon steel slab containing 004 to a thickness of 12.0 mm, it was cold rolled twice to give o and ao.
IIjIF! ! - Binding - Decarburized annealing at 820°C for 8 minutes in a wet hydrogen atmosphere.

Next, a gO slurry containing 1 g of Nbl○5 was applied so that the Nb basis weight per one side of the copper plate was 0.08 L;
Box annealing was performed at 00°C for 5 hours. At that time M
The coil coated with gO-only slurry was also annealed in the same way. Table 2 shows the analytical values for product magnetism and residual impurities for the glass-coated samples.

As shown in the table, when a separating agent containing Nb oxide is applied, impurities in the product are significantly reduced, iron loss is improved, and variations are also reduced.

(Example 2) C: 0.045%, sl: 3.29%XMn:
0.06%, Se: 0.025%, Sb: 0.
After hot-rolling a large number of continuously cast silicon steel slabs containing S and N as impurities in addition to 0.25% to a thickness of 3.0M, the finished product thickness was made to 0.85M by a known two-step cold rolling process. , 800
Decarburization annealed in a wet hydrogen atmosphere at °C. Then (1) Nb2O58%, TiO:' L, S %, S
Two slurries of MgO (2) containing 1% rSO41% and 1.5% Ti0g and MgO containing 5rS041% were prepared separately, and both were heated at 850°C, 80Hr, in a nitrogen atmosphere for +100°C, 10H.
After finishing annealing in a hydrogen atmosphere, the glass-coated samples were examined for product magnetism and residual impurities.

As a result, as shown in Table 3, when the Nb5Os-containing separating agent was applied, residual impurities were small and the iron loss of the product was significantly improved.

(Effects of the Invention) As described above, according to the present invention, it is possible to advantageously produce a grain-oriented silicon steel sheet in which the removal of inhibitors is appropriately promoted during final annealing, and the iron loss characteristics are significantly improved. We were able to.

Patent applicant: Kawasaki Steel Corporation

Claims (1)

[Claims] L Si: 4.53Ii1% or less and s, s
A final cold-rolled steel sheet containing trace amounts of at least one of e and N(7) was subjected to de-annealing and then coated with an annealing separator containing Nb oxide, and heated in a 4-hole hydrogen atmosphere at 1,000 mL. A method for producing a unidirectional silicon steel sheet, characterized in that final annealing is performed in a temperature range of C to 1200 C.
02~0.59/m! Contains Nb oxide. 1. The method according to 1.