JPS5980725A - Manufacture of thin nondirectional silicon steel strip having superior magnetic characteristic - Google Patents

Abstract

PURPOSE:To manufacture stably a nondirectional silicon steel sheet having superior magnetic characteristics by solidifying a molter high Si steel by rapid cooling, regulating the average surface roughness of the resulting rapidly cooled thin strip to a specified value or below, and annealing the strip. CONSTITUTION:A molten steel contg. 2.0-8.0wt% Si is continuously fed onto a cooling body whose cooling surface is moved at high speed, and it is solidified by rapid cooling. The average surface roughness of the resulting rapidly cooled thin strip is regulated to <=0.4mum by pickling or chemical polishing, and the strip is annealed at 1,050-1,300 deg.C to manufacture a thin silicon steel strip. By this method a thin nondirectional silicon steel strip having superior magnetic characteristics, especially iron loss characteristics can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a non-oriented silicon steel ribbon with excellent magnetic properties, and in particular, to develop tertiary recrystallization during annealing by adjusting the surface roughness of the silicon steel ribbon. Te (100)
By increasing the degree of integration of crystal grains whose surfaces are parallel to the plate surface, it is intended to advantageously improve iron loss characteristics among magnetic properties.

Silicon steel sheets containing about 8% by weight of 8i are widely used as core materials for electrical equipment such as transformers, motors, and generators. Such silicon steel sheets are usually manufactured through hot and cold rolling and annealing, but especially for high quality ones, the rolling process is far more complex and requires a more precise annealing process. Therefore, its production cost was significantly higher than other steel types.

Recently, metal ribbons have been manufactured by continuously supplying a molten metal from a circular hole-shaped or slit-shaped nozzle to the surface of a cooling body, such as a roller, whose cooling surface is updated and moved at high speed, and rapidly solidifying it. A method was developed.

By using this quenched ribbon manufacturing method, it was previously impossible to make thin sheets by conventional rolling treatment due to their high brittleness, and therefore it was considered impossible to manufacture them on an industrial scale.
High-silicon steel containing about 5% by weight or more of Sl (hereinafter simply expressed as %) can now be easily made into a ribbon. Furthermore, this manufacturing method has the advantage of significantly reducing manufacturing costs, since all complicated rolling processes can be omitted.

However, the ribbon obtained by the above manufacturing method is
In the rapidly cooled state, the strain is large and the texture is not in good condition, so the magnetic properties are generally inferior to silicon steel sheets obtained by conventional methods.

In this regard, the inventors have completely explained in Japanese Patent Application Laid-Open No. 56-87627 that a thin film of 1 x 10 to 5 x 10
1050~1300℃ in a vacuum of about -7 Torr,
We have proposed a method for producing a non-oriented silicon steel sheet whose magnetic properties can be advantageously improved by annealing for 3 minutes or more.

Although this manufacturing method increased the degree of integration of (100) planes parallel to the plate surface and considerably improved magnetic properties,
It is difficult to say that its characteristics are sufficient, and moreover, it is difficult to say that its characteristics are sufficient (1
00) orientation remained in that the texture could not be stably obtained.

This invention relates to an improvement in the manufacturing method for non-oriented silicon steel sheets disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 56-87627, and is a method that enables stable manufacturing of non-oriented silicon steel sheets with even better magnetic properties. The purpose is to propose.

The inventors aimed to achieve the above objective (as a result of intensive research, they newly discovered that the magnetic properties are closely related to the surface roughness of the rapidly solidified ribbon before annealing, and based on this new knowledge, He completed this invention.

That is, in this invention, molten steel containing 2.0 to 8.0% Si is continuously supplied onto a cooling body whose cooling surface is updated and moved at high speed, and is rapidly solidified into a thin ribbon. When producing a silicon steel ribbon by annealing the quenched ribbon at a temperature range of 1050 to 1300°C, the average roughness of the surface of the quenched ribbon is adjusted to 0.4 μm or less prior to the annealing. , is a solution to the above problem.

In this invention, pickling and chemical polishing treatments are particularly advantageous for adjusting the surface roughness of the quenched ribbon.

This invention will be specifically explained below.

It is generally known that when a silicon steel ribbon is annealed at a high temperature of 1050 to 1300°C, crystal grains with (100) surfaces grow abnormally, and this phenomenon is called tertiary recrystallization. . This tertiary recrystallization occurs because under conditions such as vacuum, the surface energy of the (100) plane becomes lower than the surface energy of other oriented planes. It is thought that this phenomenon occurs due to the erosion of crystal grains in other orientation planes using the driving force.

Therefore, in order to cause such eighth-order recrystallization, it is necessary to keep the surface of the ribbon clean, and in this regard, the above-mentioned Japanese Patent Application Laid-open No. 5
The method described in Japanese Patent No. 6-87627 also proposes to perform pickling, cleaning, electrolytic degreasing, or ultrasonic cleaning before annealing to remove deposits on the surface.

However, even when the above-mentioned cleaning treatment was performed, the desired magnetic properties were often not obtained.

Therefore, the inventors conducted numerous experiments and studies to solve the above problem, and found that making the surface texture of the quenched ribbon as smooth as possible is extremely effective in stably obtaining excellent magnetic properties. Through trial and error, he discovered that this was the case, and came up with this invention.

In the method described in the above-mentioned Japanese Patent Application Laid-Open No. 56-87627, the relationship between the surface condition of the quenched ribbon and the magnetic properties is also considered. That is, the relationship between the average roughness of the surface of the ribbon and the magnetic properties, which is not just a simple removal of surface deposits, is a new fact discovered for the first time in this invention.

FIG. 1 shows the relationship between the surface average roughness Ra of the rapidly solidified ribbon before annealing and the area ratio of tertiary recrystallized grains in the ribbon surface after annealing, that is, the tertiary recrystallization rate.

As is clear from the figure, the average roughness Ra of the surface of the quenched ribbon
When the crystal grains were less than 0.4 μm, 8th order recrystallization occurred stably, that is, a (100) in-plane non-directional texture was obtained in which crystal grains with the (100) [OKe] orientation were highly concentrated. .

For reference, when we investigated the surface roughness of ribbons cleaned according to the method described in JP-A-56-87627, we found that the average roughness Ra varied widely in the range of 0.4 to 1.0 μm. Therefore, in the above method, (1
00) It is considered that it was not possible to stably obtain an in-plane non-directional structure.

Next, embodiments of the invention will be described.

Molten steel containing 6.5% Si and the remainder essentially having a composition of Fe is rapidly cooled by a twin roll method to a thickness of 150 μm.
A thin ribbon of m was made. Next, this ribbon was heated to 10% at 80°C.
By immersing T(, So, aqueous solution, and a solution of phosphoric acid and 30% H2O2 aqueous solution in a ratio of 1=2 for 5 to 60 seconds, the diameter of the brush wire was 0.45 m.
The deposits on the surface of the ribbon were removed and the surface roughness was adjusted by grinding with a brush roll containing an alumina grindstone using Nibrad material. Average roughness Ra of each ribbon surface
was in the range of 0.18 to 1.80 μm as shown in Table 1. These ribbons were then coated with a release agent to form a coil, and then annealed at 1200°C for 3 hours in a vacuum of I x 10''-8 Torr.

The tertiary recrystallization rate and 1.25 T of each obtained ribbon.

Table 1 also shows the results of investigating the iron loss w12°515o at 50Hz.

Table 1 As is clear from Table 1, in all cases where the average surface roughness is 0.4 μm or less according to the present invention, the 8th recrystallization rate is 90% or more, and the iron loss is significantly reduced compared to the comparative example. are doing.

Examples 4 to 5 8i: Molten steel containing 6.5% and the remainder substantially Fe was rapidly cooled by a twin roll method to a thickness of 130 μm.
A thin ribbon of m was made. Next, this ribbon was heated to 10% at 80°C.
It was immersed in H2So and aqueous solutions for 5 seconds, 10 seconds, and 30 seconds to remove deposits, adsorbates, and oxides on the surface, and to adjust the surface roughness. The surface average roughness Ra of each ribbon is
As shown in Table 2, it was in the range of 0.13 to 0.99 μm. Each of these ribbons was then coated with a release agent to form a coil, and then annealed at 1180'C for 5 hours in a vacuum of 5 x 10''-8 Torr.

Tertiary recrystallization rate and iron loss W12・%0 of each obtained ribbon
The results of the investigation are also shown in Table 2.

Table 2 As is clear from the table, the average surface roughness is 0.4μm
The following ribbons are W12. It exhibits excellent iron loss characteristics unparalleled in the past, with l/, as low as about 0.5'W/kg.

As described above, the present invention enables stable production of non-oriented silicon steel ribbon with excellent magnetic properties by adjusting the surface roughness of the rapidly cooled ribbon before annealing to 0.4 μm or less. It is possible and advantageous.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the surface average roughness Ra of the ribbon and the 8th order recrystallization rate.

Claims (1)

[Claims] Molten steel containing LSi: 2.0 to 8.0% by weight is continuously supplied onto a cooling body whose cooling surface is updated and moved at high speed, and is rapidly solidified into a thin ribbon. 10 on the obi
When producing a silicon steel ribbon by annealing at a temperature range of 50 to 1300°C, the average roughness of the surface of the quenched ribbon is adjusted to 0.4 μm or less prior to the annealing. A method for manufacturing non-oriented silicon steel sheet with excellent magnetic properties.