JPS61296703A - Iron loss reduction method for single directional grain oriented silicon steel plate - Google Patents

Abstract

PURPOSE:To avoid loss of effect caused through high temperature hysteresis such as strain relief anneal by a method wherein a grain oriented silicon steel plate which is finished to have mirror surface is rolled into a loose coil in which the plate surfaces are separated from each other and subjected to a depressurized CVD process to form a very thin tension film on the steel plate surface. CONSTITUTION:A grain oriented silicon steel plate is rolled into a loose coil 9 and the coil 9 is inserted into a vacuum furnace 1 and the vacuum rate in the furnace is made to be 10<-2>-10<-4> Torr by the operation of a vacuum pump through a vacuum passage 8. After that, while H2 gas is being introduced through a gas introduction passage 4, in order to improve circulation of the gas in the furnace, the gas is extracted through a gas exhaust passage 10 and the inside of the furnace is always under the depressurized condition (normal operating pressure is 1-500 Torr) and the gas flow through the gaps between the steel plates of the loose coil 9 is kept smooth. Then, after a heater 3 is operated and the coil temperature reaches 600 deg.C-1,000 deg.C and kept at that, a mixture gas such as TiCl4 and N2, TiCl4 and CH4 or TiCl4 and CH4 and N2 is introduced through the gas introduction passage 4 and a very thin tension film is formed on the steel plate surface by a depressurized CVD method in 5min-100hr.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) Regarding the method for reducing iron loss in grain-oriented silicon steel sheets, this specification proposes the results of research and development on the advantageous application of reduced pressure CvD treatment.

Remarkable development efforts in recent years to meet the extreme demands of improving the electrical and magnetic properties of unidirectional silicon steel sheets and reducing core loss are gradually bearing fruit. A serious problem associated with this is that when using unidirectional silicon steel sheets, if so-called strain relief annealing is applied after processing and assembly (this inevitably causes deterioration of properties and limits the use of the sheets). Disadvantages are pointed out.

It is important to satisfy the above requirements regardless of whether or not the material undergoes a high temperature thermal history such as strain relief annealing.

As is well known, unidirectional silicon steel sheets have secondary recrystallized grains (110) (001), or Goss (
It is mainly used as the iron core of transformers and other electrical equipment, and its electrical and magnetic properties include high magnetic flux density (represented by the Boo value) and iron loss (WI7150). (represented by the value) is desirable.

This unidirectional silicon steel plate is manufactured through a wide variety of complicated processes, but numerous inventions and improvements have been made so far, and today a product with a thickness of 0.30 mm has magnetic properties of B+
o1.90T or more, W+, /S. The magnetic properties of a product with a weight of less than 1.05 kg/kg and a plate thickness of 0.23 mm are B. 1.
89T or more, Lt/s. Unidirectional silicon steel sheets with ultra-low core loss of 0.90 W/kg or less are being manufactured.

In particular, recently there has been a marked increase in demand for features that reduce power loss from the perspective of energy conservation, and in Europe and America, when creating a transformer with low loss, the reduction in iron loss is converted into a monetary amount and added to the transformer price. The "loss evaluation" (iron loss evaluation) system is becoming widespread.

(Prior art) Under these circumstances, recently, the surface of a unidirectional silicon steel plate after finish annealing is irradiated with a laser in a direction approximately perpendicular to the rolling direction to introduce local microstrain to subdivide the magnetic domains. It has been proposed to reduce iron loss (see Japanese Patent Application Laid-open No. 57-2252, Japanese Patent Publication No. 57-53419, Japanese Patent Publication No. 58-26405, and Japanese Patent Publication No. 58-26406).

This magnetic domain refining technology is effective for transformer materials that do not undergo strain relief annealing, but is difficult to introduce by laser irradiation for strain relief annealed materials, mainly wound core transformer materials. The disadvantage is that the laser irradiation effect is lost because the local microstrain is released by the annealing treatment and the magnetic domain width becomes wider.

(Problems to be Solved by the Invention) A more advantageous method that does not cause loss of effectiveness due to high-temperature thermal history, such as the crack annealing that is accompanied by low iron loss according to the conventional method. It is an object of the present invention to provide a method for reducing iron loss in a unidirectional silicon steel plate.

(Means for Solving the Problems) This invention involves winding a grain-oriented silicon steel plate, which has undergone finish annealing to remove oxides on the surface and make it mirror-like, into a loose coil with plate surfaces spaced apart from each other. This is a method for reducing iron loss of a unidirectional silicon steel sheet, which is characterized by forming an ultra-thin tension film on the surface of the steel sheet by performing a low-pressure CVD treatment.

First, in order to perform a CVD reaction, a spacer is inserted between steel plates to create a gap to form a loose coil, and then a low pressure CVD process is performed. A spacer for creating a gap between the coils is inserted into the upper or lower end of the coil, and this end is cut off by trimming after the CvD reaction.

This low pressure CVD treatment is performed using v, Nb, Ta, Cr, no, W
+ at least one nitride and/or carbide selected from the group consisting of Mn, Co, Ni +i, B and St, and at least one selected from the group consisting of ^1, Ni, Cu, Itl, St and Zn By forming an extremely thin tensile coating such as an oxide on the loose coil, the core loss of the unidirectional silicon steel plate can be significantly reduced.

FIG. 1 shows a cross section of an example of a CVD apparatus used for carrying out the present invention, in which 1 is a vacuum furnace, 2 is a soaking top cover, 3 is a heating heater, 4 is a gas introduction path, 5 is a valve, and 6 is a vacuum furnace. 1 is a motor, 7 is a forced fan, 8 is a vacuum path, 9 is a loose coil made of grain-oriented silicon steel plate subjected to a predetermined treatment, and 10 is an exhaust gas path.

The predetermined treatment here refers to finishing annealing performed on a grain-oriented silicon steel sheet through a series of steps to remove oxides on the surface and further make it mirror-like.

An extremely thin tension film is formed on the surface of the steel plate using this loose coil as follows.

That is, the coil 9 wound into a loose coil shape is inserted into the vacuum furnace 1, and then the inside of the furnace is moved from 10-2 to 10-') through the vacuum path 8 by operating the vacuum pump.
the vacuum level.

After that, at the same time as introducing H2 gas from the gas introduction path 4,
To ensure good gas flow in the furnace, gas is drawn through the exhaust gas path 10 to constantly reduce the pressure inside the vacuum furnace (the normal operating pressure is 1
~500 torr) to improve the flow of gas in the gap between the steel plates of the loose coil 9.

Next, the heating heater 3 is activated to heat and maintain the coil at a temperature of 600°C to 1000°C, and then, for example, TiC14, Nz + TlCl4, and C1 are introduced from the gas introduction path 4.
1 or a mixed gas of TiCl4, CH4, and N2 is introduced, and an ultra-thin tension film is formed on the surface of the steel plate by low pressure CVD for 5 minutes to 100 hours.

At this time, in order to uniformly heat the inside of the loose coil 9.

The heat cover 2 is used, and a forced fan 7 is operated by a motor 6 to improve the gas flow in the atmosphere between the layers of the coil.
This promotes uniform gas distribution.

In this way, preferably 0.1 to 1.
An ultra-thin tensile coating with a thickness of 0 μm can be formed, and by forming this coating, it is possible to reliably achieve ultra-low iron loss in a unidirectional silicon steel plate.

(Function) In this invention, the formation of an ultra-thin tension film by low-pressure CVD is applied to a loose coil whose mirror-finished plate surfaces are spaced apart from each other. This is to form a thin tensile film, and the mirror surface condition is suitable for the degree of surface roughness with a center line average roughness of 0.4 μm or less, which means that the finished steel plate surface with such surface roughness On the other hand, it becomes possible to form an ultra-thin tension coating with excellent adhesion to the steel plate.

TiN + Tic and Ti using TiCl4 gas
The (CN) film forming reaction is, for example, as follows.

2TiC1a +4H2+N2→2TiN + 811
ClTiCl 4+ Clf, →TiC+41 ((J!
2Tic e a + 2cH4, + N2 → 2T
i (CN) + 8HC1 Since the coatings formed on the surfaces of these steel plates, including those mentioned above, have a difference in thermal expansion from the base steel, the tension of the steel plates introduced by this can effectively reduce iron loss. In addition to contributing to
It is not affected by high temperature thermal history.

Unidirectional silicon steel plate with large stop annealing finish (plate thickness 0.2.3m5
) After removing oxides from the surface of the steel plate by pickling and making the steel plate surface mirror-like by electrolytic polishing,
．． After inserting a spacer of 5 fins φ to form a loose coil 9 and inserting it into the vacuum furnace 1 shown in FIG.
℃, 0.7 μm on the steel plate surface after treatment for 20 hr.
A thick TiN layer was formed.

After that, a coating treatment containing phosphate and colloidal silica as the main ingredients was applied. The magnetic properties of the product thus obtained are 8+o = 1.927, Jtzso = 0.7
It was 3'A/kg.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a CVD apparatus. 1...Vacuum furnace 2...Top lid for soaking 3...
・Heating heater 4... Gas introduction path 8... Vacuum path 9... Coil 10... Exhaust gas path

Claims (1)

[Claims] 1. A grain-oriented silicon steel plate that has been subjected to final annealing to remove oxides on the surface and has a mirror finish is wound into a loose coil with plate surfaces spaced apart from each other, and the coil is subjected to low pressure CVD treatment to be coated on the surface of the steel plate. A method for reducing iron loss in a unidirectional silicon steel sheet, characterized by forming an ultra-thin tensile film.