JPH01168815A - Manufacture of non-oriented magnetic steel sheet - Google Patents

Abstract

PURPOSE:To obtain the title non-oriented magnetic steel sheet having low iron loss and excellent magnetic flux density by hot-rolling, annealing, cold-rolling, and then again annealing a steel having specified contents of C, Si, Mn, P, S, Al, N, and Fe under specified conditions. CONSTITUTION:A steel contg., by weight, 0.005-0.010% C, <=1.5% Si, 0.1-1.0% Mn, <=0.15% P, <=0.01% S, <=0.3% Al, <=0.007% N, the balance Fe, and inevitable impurity elements is refined into a slab. The slab is heated, hot-rolled, and then further hot-rolled in the temp. range from the median of the Ar3 and Ar1 to 750 deg.C. The obtained hot-rolled band steel is briefly annealed for <=5 min in the temp. range from Ar1 to (Ar3+50 deg.C), pickled, and then cold-rolled to a finishing thickness. The cold-rolled steel sheet is briefly decarburizing- annealed for 10sec to 5min in the temp. range below Ar3 to reduce the C content to <0.005%. By this method, a non-oriented magnetic steel sheet having low iron loss and excellent magnetic flux density is easily obtained.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for producing a non-oriented electrical steel sheet that has low core loss and excellent magnetic flux density and is suitable as core material for small transformers, motors, etc. It is something.

<Background Art> Due to the recent demand for energy conservation, there has been a strong desire for electrical equipment to be smaller and more efficient. Therefore, even higher magnetic flux density and lower iron loss are required for omnidirectional voltage detection MIm Fi, which is widely used as iron core material for small transformers, motors, and the like.

In conventional non-oriented electrical steel sheets, a method of increasing the content of Si or M, etc. is used for -a from the viewpoint of reducing eddy current loss due to increased specific resistance, as a means to lower iron loss. However, there was a problem that the magnetic flux density decreased.

In order to solve such problems, Japanese Patent Application Laid-Open No. 62-1771
No. 23 contains Cj 0.04 to 0.10%, Si: 1.
5% or less, B: 0.008% or less, N:
A hot rolled conditioned plate containing 0.007% or less and a BZN ratio of 0.5 or more is decarburized and annealed at 700 to 780°C to reduce C to 0.0.
A method for obtaining excellent magnetism by reducing the amount to 0.5% or less is disclosed.

However, in this method, hot-rolled steel containing as much as 0.04 to 0.10% of C is decarburized and annealed to reduce the C content to 0.04 to 0.10%.
This method is characterized by the fact that it is less than 0.005%, but since this annealing is an open coil decarburization annealing, it requires a long time of annealing that takes several days, which has poor production efficiency and is disadvantageous in terms of cost. there were.

In addition, a method is generally adopted in which the finishing temperature of the hot rolled steel strip is set above the A3 transformation point and then the hot rolled steel strip is annealed for a short time below the A3 transformation point, but the grain size of the hot rolled steel strip after annealing becomes too coarse. Therefore, after the final cold rolling, the surface of the steel sheet becomes uneven which is visible to the naked eye and spoils the appearance.In addition, when trying to select the optimum conditions to avoid such unevenness, it is necessary to ensure uniformity over the entire width of the coil. Could not obtain magnetism.

<Problems to be Solved by the Invention> The present invention is directed to the production of non-oriented electrical steel sheets that are superior to conventional ones in terms of iron loss and magnetic flux density, using a simpler method that does not have the above-mentioned manufacturing problems. The present invention provides a method.

Means for Solving Problems〉 This invention has C: 0.005 to 0.010 in weight%
%.

Si: 1.5% or less, Mn: 0.1=1.0%+
P:Q, 15% or less, s:o, o1% or lesst A1:0
．． 3% or less, N: 0.007% or less, and the remainder substantially consists of Fe and unavoidable impurity elements,
Subsequently, the slab is made into a hot rolled steel strip by heating and hot rolling.The hot rolling end temperature is set to the median value of Ars and Arl and a temperature range of 750°C, and then this steel strip is heated from ^r+ to ^r. -S
This is a method for producing a non-oriented electrical steel sheet, characterized by carrying out short-time decarburization annealing for 10 seconds or more and 5 minutes or less in a temperature range of 2 or less to reduce the C content to less than 0.005%.

Effects> The present inventors have diligently researched a manufacturing method that has magnetic properties, particularly high magnetic flux density, as a full-process product.

As a result, it was found that a combination of lowering the amount of C and Si, the hot finishing temperature, the subsequent annealing conditions for the hot rolled steel strip, and the final finishing annealing is effective for improving magnetism.

Furthermore, even in applications such as semi-processed products, properties superior to those of conventional products can be obtained.

The steel components and processing conditions of the present invention will be explained below.

C is a harmful component that increases iron loss and causes magnetic deterioration due to aging. In addition, when C becomes high, it takes a long time to decarburize and annealing, so it is set to 0.010% (wt% or less) or less. On the other hand, if it is less than 0.005%, grain growth during annealing of the hot rolled sheet will be suppressed and the magnetic properties will deteriorate, so it is necessary to have more than 0.005%.

As is well known, Si is added for the purpose of improving core loss, but it also lowers magnetic flux density. In recent years, particularly in order to downsize iron core materials, a particularly high magnetic flux density is required. Further, in order to improve the crystal structure and texture by utilizing the transformation point and further improve the magnetic flux density, Si is limited to 1.5% or less where the transformation point occurs.

Mn slightly improves iron loss. In addition, the hardness increases slightly and the punching property is improved, but if it exceeds 1.0%, the cost will increase.
On the other hand, if it is less than 0.1%, surface flaws will occur during hot rolling, so it is limited to 0.1 to 1.0%.

P is added to increase hardness and improve punchability, but
If it exceeds 0.15%, embrittlement occurs, so it is limited to 0.15% or less.

Since S generates MnS, which is a non-metallic inclusion that is harmful to improving magnetism, it is preferable to have a low content and is limited to 0.005% or less.

M is a component necessary for deoxidation. Further, like Si, it has the effect of lowering iron loss, but if it exceeds 0.3%, the magnetic flux density decreases, so it is limited to 0.3% or less.

Since N generates AZN which is harmful to magnetism and inhibits grain growth, it is necessary to limit it to 0.007% or less in order to improve properties.

After the steel whose composition has been adjusted in this way is made into a slab, it is hot rolled to an intermediate thickness.The finishing temperature of the hot rolling is Ar3.
A median value of and Ar and a temperature of 750°C are required.
If Ar is 3 or more, the crystal grains become too coarse during subsequent annealing of the hot rolled steel strip, resulting in insufficient appearance and hardness. On the other hand, at a finishing temperature higher than the median value of Ar3 and Arl,
During the subsequent continuous annealing of the hot-rolled steel strip, coarse grains are formed locally, leaving unevenness in the final product and resulting in non-uniform magnetic properties. On the other hand, at temperatures below 750° C., magnetic properties, particularly magnetic flux density, do not improve.

The reason why the properties improve between the median values of Arl and Ars at temperatures above 750°C is that ferrite below Ar+ and austenite above Arj coexist and crystal grains containing easy magnetization axes such as (110) (100) are hot-rolled. It is thought that this is due to the transformation of the inside.

Next, the hot-rolled steel strip hot-rolled as described above changes from Ar+ to A
Short-time annealing of 5 minutes or less in the temperature range r3 + 50°C is required. In order to control the hot rolling finishing temperature within the above range and obtain desirable magnetism in the final product, the temperature must be higher than Ar + temperature, ^r
Temperatures below s+50°C are optimal.

At temperatures below Ar3, the iron loss deteriorates, and at temperatures above Ari+50°C, both the iron loss and the magnetic flux density deteriorate. Furthermore, if the annealing time is too long, a problem of scale on the surface layer will occur, and descaling performance will be poor in the subsequent surface oxidation layer removal process such as pickling process, which is not economical and causes deterioration of magnetic flux density. This temperature range is preferably controlled during hot rolling (10
This is thought to be because the crystal grains with the 0) and (110) orientations become proper crystal grains that do not cause unevenness in the final product through short-time annealing of the hot-rolled steel strip.

Next, after descaling by pickling, it is cold rolled to the final thickness. Generally, the processing rate at this time is 6 in terms of rolling reduction.
About 0 to 80% is preferable.

Next, after degreasing the rolling oil as necessary after cold rolling,
Decarburization annealing is performed for a short time of 10 seconds or more and 5 minutes or less at a temperature below the r3 transformation temperature. If it is less than 10 seconds, there will be no decarburization effect, and if it is more than 5 minutes, an oxide film will form and the punching performance will deteriorate.

If the Ar temperature is exceeded, the magnetism deteriorates extremely, so Ar
Limited to 3 or less.

The pure atmosphere for decarburization sintering only needs to be a so-called decarburization atmosphere.
The purpose is to decarburize the C content to less than 0.005%, and there is no restriction as long as the purpose can be achieved.The C content after decarburization is 0. .0
0.05% or more, the magnetic improvement effect is insufficient, and 0.00% or more
Limited to less than 5%.

<Example> The steel shown in Table 1 was manufactured under the processing conditions shown in Table 2, and sheared into an Epstein sample, and the magnetic properties were measured. The measurement results are also shown in Table 2.

For comparison, it is seen that the present invention, which also includes those made with extremely low C through vacuum degassing during steel manufacturing, makes it possible to manufacture non-oriented electromagnetic copper sheets with extremely high magnetic flux density and low iron loss.

In addition, in order to understand the effect of applying the present invention to semi-processing, the above sample was sheared into a nib fin specimen, and then heated at 750°C
Strain relief annealing was performed for 2 hours and magnetic properties were measured. The measurement results are also shown in Table 2. It can be seen that the present invention makes it possible to manufacture non-oriented electromagnetic copper plates, which have extremely low iron loss and high magnetic flux density even as semi-processed materials.

<Effects of the Invention> According to the present invention, a non-oriented electrical steel sheet with low core loss and excellent magnetic flux density can be obtained, which is sufficient to meet the needs for downsizing and increasing efficiency of small transformers, motors, etc. In addition, stable and efficient production is possible, and its industrial effects are large.

Patent applicant: Kawasaki Steel Corporation

Claims (1)

[Claims] In weight%, C: 0.005 to 0.010%, Si: 1.
5% or less, Mn: 0.1 to 1.0%, P: 0.15% or less, S: 0.01% or less, Al: 0.3% or less, N: 0
．． 0.007% or less, with the remainder substantially consisting of Fe and unavoidable impurity elements, and then made into a slab,
When making a hot rolled steel strip by hot rolling after heating, the hot rolling end temperature is set to the median value of Ar_3 and Ar_1 and a temperature range of 750°C, and then this steel strip is rolled from Ar_1 to Ar_3+5.
Short-time annealing for 5 minutes or less in a temperature range of 0°C, pickling, and cold rolling to the final thickness, followed by short-time decarburization annealing for 10 seconds or more and 5 minutes or less in a temperature range of Ar_3 or less. C
A method for producing a non-oriented electrical steel sheet, characterized in that the content is less than 0.005%.