JPH03193820A - Production of nonoriented silicon steel sheet excellent in magnetic property - Google Patents

Abstract

PURPOSE:To produce a nonoriented silicon steel sheet excellent in magnetic properties by subjecting a slab of a steel having a specific composition consisting of C, Si, Mn, P, S, Al, B, N, and Fe to hot rolling at specific temp., to cold rolling, and to finish annealing. CONSTITUTION:A slab of a steel having a composition consisting of, by weight, <=0.010% C, 0.1-1.2% Si, <=1.0% Mn, <=0.15% P, <=0.005% S, >0.1-0.8% Al, 0.0003.0.0060% B, <=0.0050% N, and the balance Fe with inevitable impurities is hot-rolled. At this time, finishing temp. and coiling temp. are regulated to (Ar1-50 deg.C)-(Ar1+50 deg.C) and >=650 deg.C, respectively. Subsequently, the resulting hot rolled plate is cold-rolled and finish-annealed. If necessary, the resulting cold rolled sheet is further subjected to skin pass rolling at 2-15% rolling reduction. By this method, the low-Si nonoriented silicon steel sheet in which grains are sufficiently grown in the surface layer at the time of stress relief annealing and which has low iron loss and high magnetic flux density can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a low-Sl non-oriented electrical steel sheet with low core loss and high magnetic flux density.

(Prior Art) Non-oriented electrical steel sheets are used as core materials for electrical equipment such as motors and small and medium-sized transformers.

Nowadays, for example, compressors, refrigerators, automobiles, etc. in which motors are incorporated are required to have higher performance, to be energy-saving, and to be lower in cost. The non-oriented electrical steel sheets used for these are required to have lower iron loss and higher magnetic flux density than conventional ones, and it is also important that they be inexpensive.

As a non-oriented electrical steel sheet that meets such requirements, for example, as disclosed in Japanese Patent Application Laid-open No. 57-203718, 81 is 0.3 to 2.0 with ultra-low carbon of 0.005% or less.
After hot rolling electromagnetic steel containing %
A non-oriented electrical steel sheet is processed as described above, and the annealing after cold rolling is performed at a high temperature of 800°C or higher for a short period of time within 2 minutes to grow crystal grains, prevent internal oxidation, and improve iron loss and magnetic flux density. A manufacturing method has been proposed.

Furthermore, in Japanese Patent Application Laid-Open No. 62-267421, the Sl content is 0.6% or less, Mn is 0.1 to 1.0%, A, 7
7 in an amount of 0.15 to 0.60%, and unavoidable impurities C,
S, N.

Non-directional electromagnetic material with low core loss can be produced by reducing O and by increasing the winding temperature during hot rolling to 700°C or higher, or by annealing the hot rolled sheet at 700°C or higher after hot rolling to grow crystal grains. A method of manufacturing steel plate has been proposed.

(Problem to be solved by the invention) Although these methods have corresponding effects and are effective, it is possible to further improve the performance and efficiency of electrical equipment such as the motors and small and medium-sized transformers at low cost. In order to achieve this goal, it is necessary to further improve both the core loss and magnetic flux density of the non-oriented electrical steel sheet. In addition, such non-oriented electrical steel sheets are punched into a shape suitable for electrical equipment, or after being skin-pass rolled, punched into a predetermined shape and strain-relief annealed. It may not be as good as the middle part in the thickness direction, which hinders improvement in magnetic properties.

The purpose of the present invention is to obtain a non-oriented electrical steel sheet in which sufficient grain growth occurs even in the surface layer of the steel sheet during strain relief annealing, excellent iron loss characteristics, and sufficient improvement in magnetic flux density peculiar to low S1. .

(Means for Solving the Problems) In order to achieve the above object, the gist of the present invention is as follows: C・o, oto% or less in weight% Si: 0.1 to 1.2% Mn: 1.0% or less P ・0.15% or less S ・0.005% or less AN; more than 0.1% and 0.8% or less B ・0.0003 to 0.0060% N ・Contains 0.0050% or less, the balance being iron and unavoidable impurities, the finishing temperature is Ar, -50℃ or higher, Ar, +50℃
The following is a patented manufacturing method characterized by hot rolling at a winding temperature of 650° C. or higher, cold rolling, and final annealing.

Further, if necessary, a skin pass with a reduction ratio of 2 to 15% is performed after the annealing.

The present invention will be described in detail below.

Experiments and experiments were conducted to improve the magnetic properties of low-Si non-oriented electrical steel sheets.
As a result of our investigation, we found that adding a small amount of B to ultra-low carbon electrical steel containing 0.1 to 1.0% Sl solved the problem of poor grain growth during strain relief annealing, which was observed in the surface layer of the steel sheet. Ru. In addition, in hot rolling, core loss and magnetic flux density are reduced by preventing grain refinement due to passing through a transformation point after hot rolling and increasing the growth of crystal grains in hot rolled sheets through a combination of hot rolling conditions and steel components. We found that both were excellent.

The present invention is based on this knowledge, and will first be described from the reasons for limiting the steel components.

A large content of C increases core loss and causes magnetic aging, so the content should be 0.0100% or less.

Sl is a component contained in order to lower iron loss, and 0.1% or more is required to exhibit this effect.

However, if the content increases, the magnetic flux density will deteriorate and the steel will become brittle, which is unfavorable in terms of workability and cost.
1.2% or less.

Mn is contained in a range of 1.0% or less in order to increase specific resistance and reduce iron loss, and to prevent embrittlement cracking during hot rolling.

P has the effect of increasing punching properties, but if its content increases, the steel becomes brittle and workability deteriorates, so it is reduced to 0.15%.
The following shall apply.

S forms sulfides and impairs the growth of crystal grains, so 0.0
It is necessary to keep it below 0.05%.

A, 17 is a necessary component for deoxidation and has the effect of reducing iron loss, and in order to obtain these effects, 0.1
% super gold content. On the other hand, if the content increases, the cost will increase and the magnetic flux density will deteriorate, so the content should be 0.8% or less.

It is known that B is included in the production of non-oriented electrical steel sheets (see, for example, Japanese Patent Application Laid-Open No. 183720/1983), but the known B has an Al1 content of 0.0000 to reduce cost. When lowered to 1%, fine nitrides A, 9N
is precipitated, so it is contained to prevent this from occurring. For this reason, conventionally B is included when the Afi content is low, but it is not included when the Afi content is high, exceeding 0.1%.

Incidentally, in the present invention, B is contained in order to enhance grain growth in the surface layer of the steel sheet during strain relief annealing among annealing, but B is required to be present in an amount of o, oooa% or more in order to produce this effect. On the other hand, when its content increases, the magnetic flux density deteriorates, so 0.00
60% or less.

Since N deteriorates the magnetic properties, it should be kept at 0.0050% or less.

The steel component composition is as described above, and the steel slab, the remainder of which is iron and unavoidable impurities, is manufactured by continuous casting or ingot-blending and blooming rolling.

After the steel slab is heated to the desired temperature, it is hot rolled.

In hot rolling, grains are prevented from becoming finer by passing through a transformation point from γ phase to α phase after hot rolling. For this reason, the finishing temperature is set to Ar, -50°C or higher, and Ar, +5Q°C or lower. Ar, -50℃ or higher means finishing temperature is Ar
, below, grain refinement due to transformation does not occur after hot rolling is completed, but if the temperature is too low, the processed structure will remain in the hot rolled sheet and the magnetic properties will not improve, so the lower limit of Ar is set at 50°C. On the other hand, when the finishing temperature becomes higher than Ar, +5Q℃,
After hot rolling, the ratio of crystal grains that pass through the transformation point increases, causing grain refinement in the hot rolled sheet and deteriorating the magnetic properties.

During hot rolling, N is precipitated as relatively coarse AfIN that does not inhibit grain growth, and in order to prevent the precipitation of fine AJN during annealing after cold rolling, the temperature is 650°C or higher. Wind it up.

Thereafter, it is cold rolled and finish annealed.

After annealing, skin pass rolling is performed at a reduction rate of 2 to 15% as required. The reason why the rolling reduction ratio is set to 2% or more is to cause grain growth to occur during strain relief annealing. However, as the rolling reduction rate increases, grain growth deteriorates, so the upper limit is set at 15%.

Next, examples will be shown.

Non-oriented electrical steel sheets were manufactured using samples having the steel components listed in Table 1 as test materials under the conditions shown in the table. Some of the test materials were subjected to skin pass rolling.

For the obtained steel plate (0.50 mm t), iron loss,
The magnetic flux density was measured and the results are shown in Table 2.

As is clear from Table 2 above, the iron loss value of the present invention is extremely superior to that of the comparative materials. Also, a product with high magnetic flux density was obtained.

(Effects of the Invention) According to the present invention, a non-oriented electrical steel sheet with low iron loss and high magnetic flux density can be obtained.

Claims (2)

[Claims] (1) C in weight%; 0.010% or less Si; 0.1-1.2% Mn; 1.0% or less P; 0.15% or less S; 0.005% or less Al; 0.1% A steel slab containing more than 0.8% or less B; 0.0003 to 0.0060% N; 0.0050% or less, with the balance consisting of iron and unavoidable impurities, at a finishing temperature of Ar_1-50℃ to Ar_1+50℃
A method for producing a non-oriented electrical steel sheet with excellent magnetic properties, comprising hot rolling at a winding temperature of 650° C. or higher, cold rolling, and final annealing. (2) C in weight%; 0.010% or less Si; 0.1-1.2% Mn; 1.0% or less P; 0.15% or less S; 0.005% or less Al; 0.1% A steel slab containing ultra-0.8% or less B; 0.0003 to 0.0060% N; 0.0050% or less, with the balance consisting of iron and unavoidable impurities, at a finishing temperature of Ar_1-50°C or higher, Ar_1+5
Hot rolling at a temperature of 0°C or lower and a winding temperature of 650°C or higher,
A method for producing a non-oriented electrical steel sheet with excellent magnetic properties, which comprises cold rolling, final annealing, and then skin pass rolling at a rolling reduction of 2 to 15%.