JPS62222025A - Manufacture of nonoriented electrical sheet superior in brittleness resistance and magnetic characteristic after stress relief annealing - Google Patents

Abstract

PURPOSE:To manufacture electrical sheet free from embrittlement and superior in magnetic characteristic after stress relief annealing, by hot rolling low C steel contg. specified quantities of Mn, Al B under a specified condition, then applying cold rolling contg. skin pass rolling, next punching and stress relief annealing the sheet. CONSTITUTION:Slab composed of, by weight <=0.020%C, <=0.1% Si, 0.75-1.50% Mn, >0.10-<=0.60% Al, 0.0003-0.0100% B and the balance Fe with inevitable impurity is prepd. The slab is hot rolled at >=900 deg.C finish rolling temp. and >=800 deg.C winding up temp., and wound up, annealed by the heat held thereby. Next, cold rolling at one time of >=2 times contg. skin pass rolling interposing intermediate annealing. The sheet is punched, successively stress relief annealed as it is or after finish annealing. In this way, productivity of nonoriented electrical sheet can be improved with a shortened process.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to the production of semi-processed non-oriented electrical steel sheets, and a method for producing non-oriented electrical steel sheets with excellent brittle resistance and magnetic properties after stress relief annealing. Regarding.

(Prior Art) Non-oriented electrical steel sheets are used for cores of motors and transformers, and are divided into full process materials and semi-process materials depending on the manufacturing method. For fully processed materials, the steel sheet manufacturer
It has been cold rolled and annealed more than once, up to so-called final finish annealing.

10,000 semi-processed materials are cold-rolled and annealed one or more times by the steel plate manufacturer 11111, and the steel plate manufacturer side 1
1, after punching and shearing into a predetermined shape, strain relief annealing is performed to develop predetermined magnetic properties.

The punching and cutting process of this semi-processed material is
Since it is removed by Tamatori annealing and the growth of crystal grains occurs during this annealing, the iron loss is generally lower than that of full process materials.

Various proposals have been made regarding the production of semi-processed non-oriented electrical steel sheets. For example, JP-A-51-215]1
In Publication No. 3, in order to produce a product with low core loss and excellent magnetic flux density, the final cold rolling reduction is increased to 65 to 70% and strain relief annealing is performed.

In Japanese Patent Application Laid-Open No. 56-98420, 5nr0.03~
Silicon steel containing 0.40% is hot rolled, this hot rolled steel plate is annealed at 709 to 1000°C, cooled to 700 to 400°C at a cooling rate of 5°C/min or less, and then cold rolled,
Annealing is used to reduce iron loss and improve magnetic permeability.

Furthermore, in Japanese Patent Application Laid-Open No. 57-203718, Cf O,
Ultra-low coal with OO of 5% or less and S content of 0.010 or less.1. U2O, silicon steel containing 15% or more, or containing the above-mentioned C, S, M O, OO5-0.1%, 13
i 0.0 OI O~O, Silicon mk containing 50% OO is hot rolled, this hot rolled steel plate is annealed at 800℃ or higher, and after cold rolling, it is heated at a temperature of s o O”C or higher for less than 2 minutes. High-temperature, short-time annealing is performed to prevent internal oxidation.
In addition, the crystal grains are made larger, reducing iron loss and 1. We are trying to improve the f1 density.

As a result of these proposals, the magnetic properties of semi-processed non-oriented electrical steel sheets have been improved, and good ones are now available.

However, electric devices such as motors and transformers are required to be energy-saving types or to have higher performance. For this reason, it is necessary to continuously study how to improve the magnetic properties of semi-processed non-oriented electrical steel sheets, which are used as core materials for these electrical devices.

(Problems to be solved by the invention) By the way, the iron core of transformers, etc. is made of non-oriented electrical steel sheet.
It is punched into a predetermined shape and subjected to foot annealing.

This strain relief annealing is carried out in a decarburizing atmosphere in order to completely improve the magnetic properties, but it is a failure.

By annealing in such an atmosphere, carbon content is further reduced, crystal grain growth is also promoted, and magnetic properties are improved. However, the iron core (non-oriented electrical steel sheet) after strain relief annealing becomes brittle, and cracks are sometimes observed when the iron core is assembled into a transformer, for example.

In addition, it is necessary to reduce the manufacturing cost of such non-oriented electrical steel sheets, and it is also important to omit at least one manufacturing process to increase productivity.

(Means for Solving the Problems) The present invention does not become brittle after strain relief annealing, can be assembled and molded into the core of a desired electrical device, such as a transformer, without causing troubles such as cracks, and has excellent magnetic properties. The purpose is to obtain non-oriented electrical steel sheets at low cost and with high productivity.

The gist of the present invention is 1 in terms of weight, C: 0.020% or less, S
i: 1.0% or less, Mn: 0.75% or more 1.50
% or less, M: O, lO% or less, a o % or less, B:
A slab consisting of O,0O03% or more and 0.0100% or less, the balance being iron and unavoidable impurities, is hot rolled at a finish rolling exit temperature of 900°C or higher and a coiling temperature of SOO°C or higher, after 1 coiling. The material is annealed with its retained heat, cold rolled once or twice or more including skin pass rolling with an intermediate annealing in between, and then subjected to strain relief annealing either as is or after annealing and punching. .

Next, the present invention will be described in detail.

The inventors of the present invention have conducted studies to produce a powerless isostatic electrical steel sheet that has excellent magnetic properties, does not become brittle after strain relief annealing, and is inexpensive and highly productive. As a result, silicon steel with a C content of 0.020 mm or less was made to contain a large amount of Mnf from 0.75 to 150%, M from more than 0.10% to 0.60%, and B.
When O, OOO3 to O, OI O0% is contained, the magnetic properties are excellent, and even if the atmosphere for strain relief annealing is decarburizing or oxidizing, internal oxidation does not occur and the brittle resistance is excellent. It was discovered that no cracks were formed in the iron core during assembly and molding.

In addition, in hot rolling, the finish rolling temperature is set to 9
If the coiling temperature is set at 00'C or higher and the coiling temperature is 800C or higher and annealing is performed using the retained heat after winding, manufacturing costs can be reduced and productivity can be improved.

Next, the constituent elements of the present invention will be explained.

In order to improve the magnetic properties, it is preferable to have a small amount of C, and since it causes magnetic aging, the content should be 0.020% or less.

Sl is included to increase specific resistance and improve core loss, but since the present invention is aimed at semi-processed non-oriented electrical steel sheets, it is included to improve workability. The content shall be 1.0% or less.

Mn has the effect of improving magnetic properties, and for this purpose it is necessary to contain it in an amount of 0.75% or more. - If this content increases, ferrite-austenite transformation is likely to occur during annealing after hot rolling or during intermediate annealing, leading to deterioration of magnetic properties, so 1.5o
% or less.

AEi/j has the effect of increasing specific resistance and lowering iron loss, and for this purpose O,l is set to exceed O%. On the other hand, if the content is too large, the magnetic properties will deteriorate, so the content should be 0.60 or less.

B has the effect of preventing internal oxidation of the steel plate and preventing embrittlement during strain relief annealing, and for this purpose, it must be contained in an amount of 0.0003 or more. On the other hand, if this content is large, cracks may occur in the slab before hot rolling, so 0.01
00% or less.

It is preferable that components unavoidably included as impurities such as S, P, Ti, and Zr be as small as possible.

A slab consisting of the above components is heated at a known heating temperature, e.g.
It is heated to 00 to 1400°C and hot rolled. In this hot rolling, the finish rolling exit temperature is set at 900°C or higher, and the coiling temperature is set at 800°C or higher. If the exit temperature of the finish rolling is low, the magnetic properties will deteriorate and the morphology of the crystal grains in the hot rolled sheet will deteriorate. In order to prevent this, the outlet temperature is set to 900° C. or higher.

Regarding the coiling temperature, in order to omit the subsequent separate hot-rolled sheet annealing and save process steps, we also improved the magnetic properties.
Wind it into a coil at a temperature of 800°C or higher.

When a hot-rolled sheet of the above components is wound up to form a coil at a temperature of SOO° C. or higher, the heat retained therein achieves rectification and growth of crystal grains. Further, if necessary, a heating device may be used to supplement the retained heat to perform self-annealing.

Then, after one cold rolling or intermediate annealing, 2
The desired thickness is obtained by cold rolling more than once. This cold rolling includes skin pass rolling performed at a rolling reduction of 2 to 12 inches. In the case of skin pass rolling, if the rolling reduction rate is small, the growth of crystal grains will be small in subsequent annealing such as strain relief annealing, and the magnetic properties will not be good, so it is set to 2- or more.

On the other hand, if the rolling reduction rate becomes too high, the growth of crystal grains becomes weak, so it is set to 12 inches or less. After that, as cold rolled,
Or an iron core that is annealed and shaped into a predetermined shape, such as EI.
Cocoa is stamped.

After punching, strain relief annealing is performed at, for example, 700 to 900° C. in order to remove strain and improve magnetic properties. In this strain relief annealing, the growth of crystal grains or C in the steel
The process is carried out in a decarburizing atmosphere in order to reduce f and remove impurities, but in the present invention, since B2 is contained as described above, internal oxidation, especially grain boundary oxidation, does not occur and the steel does not become brittle. Furthermore, since no internal oxidation occurs, there is no deterioration in magnetic properties, and the magnetic properties are excellent due to the effects of strain relief annealing, such as crystal grain growth and carbon removal.

Furthermore, since the present invention contains a large amount of both Mn + ktf as described above, the magnetic properties are excellent from this point as well.

(Example) Test steels having the steel compositions shown in Table 1 were processed under the conditions shown in Table 2 to produce non-oriented magnetic steel sheets. The magnetic properties and workability of the obtained non-oriented electrical steel sheets were investigated, and the results are summarized in Table 2.

As is clear from the results shown in Table 2, the characteristics of the electrical steel sheet obtained by the method according to the present invention are, for example, Mn,
It is clear that this is much better than the conventional example in which components such as AM and B, hot rolling conditions, etc. were not fully controlled.

Furthermore, the material according to the present invention has excellent repeated bending properties and moldability in EI cocoa molding.

From Photo 1.2, it can be seen that by adding B, the oxidation near the surface layer is the same as in the conventional example, but the degree of oxidation at the grain boundaries is much smaller than in the conventional example.

(Effects of the Invention) According to the present invention, as described above, the steel plate after strain relief annealing is free from embrittlement and can be formed into a desired electric imager such as EI cocoa without any problem. It has excellent magnetic properties and is further annealed using its own heat after hot rolling and winding, so a separate annealing process is omitted, shortening the manufacturing process and improving productivity.

Thermal energy required for manufacturing is reduced.

[Brief explanation of drawings]

Fig. 1 is a microscopic microstructure photograph of the surface layer of a steel plate of sample code 1 (manufactured through a skin pass rolling process) according to an example of the present invention, and Fig. 2 is a photograph of the surface layer of a steel plate of sample code 7 according to a comparative example. A microscopic tissue photograph is shown.

Claims (1)

[Claims] 1. In weight%, C: 0.020% or less, Si: 1.0%
Below, Mn: 0.75% or more and 1.50% or less, Al: 0
．． Over 10% but not more than 0.60%, B: 0.0003% or more 0
．． A slab consisting of 0.0100% or less, the balance consisting of iron and unavoidable impurities is hot rolled at a finish rolling temperature of 900°C or higher and a coiling temperature of 800°C or higher, and after coiling, it is annealed using the retained heat. , cold rolling is performed once or twice or more including skin pass rolling with intermediate annealing in between, and strain relief annealing is performed either directly or after annealing and punching. and a method for manufacturing non-oriented electrical steel sheets with excellent magnetic properties. 2. The method for producing a non-oriented electrical steel sheet according to claim 1, wherein the rolling reduction ratio of the skin pass rolling is 2 to 12%.