JP2548805B2 - Manufacturing method of non-oriented electrical steel sheet excellent in magnetic properties, weldability and space factor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a full-process non-oriented electrical steel sheet which is excellent in magnetic properties and also in space factor and weldability during lamination. .

<Prior Art> Non-oriented electrical steel sheets used as iron core materials for motors and transformers have been developed with low iron loss and high magnetic permeability in response to recent demands for energy saving and miniaturization. Further, such electromagnetic steel sheets are punched into a predetermined shape, and after laminating them, they are assembled by side surface TIG welding or automatic caulking. Therefore, the electromagnetic steel sheet is required to be excellent not only in magnetic properties but also in punchability and weldability.

Conventionally, such improvements in punchability and weldability have been carried out exclusively by modifying the insulating coating formed on the surface of the steel sheet, and various coatings have been developed so far.

For example, it has been found that punchability is remarkably improved by using an organic resin, and recently, a mixed coating film containing a dichromate and an organic resin as main components has been frequently used. However, when an iron core plate is laminated after punching and the side surface is TIG welded, an organic resin-containing insulating film thermally decomposes organic matter to generate gas, and due to this generated gas, blows to the bead part. There was a problem where holes were created.

Therefore, Japanese Patent Publication No. Sho 49-6744 proposes an electrical steel sheet in which the surface of the steel sheet is provided with an appropriate roughness to form an escape passage for gas generated during welding, thereby preventing blowhole formation. However, this method has a drawback that although the weldability is improved, the magnetic properties are deteriorated due to the surface roughness of the steel sheet.

Further, in JP-B-49-19078, by adding organic particles having a particle diameter of 2 μm or more to an insulating coating treatment liquid,
A method has been proposed in which the insulating coating is provided with a surface roughness of 2 μH _MAX or more to facilitate the escape of gas generated in the weldability and improve the weldability. However, this method has a problem in that the dispersibility of the organic particles in the treatment liquid and the adhesion to the steel sheet are not sufficient.

Although a method of treating an uncured coating film with a roll having roughness has been proposed, this method has a drawback in that the coating film is easily peeled off when the roughness is imparted and dusting occurs.

Therefore, as a result of various studies on weldability, magnetic properties, coating adhesion, etc., in order to solve the above problems, the inventors can control the uneven pattern on the steel plate base iron surface.
We have found that it is extremely effective in improving these characteristics, and have already filed as Japanese Patent Application No. 63-123882.

That is, the present invention is that a hot-rolled sheet having a composition containing C: 0.010 wt% or less (hereinafter simply represented by%) and Si: 2.5% or less is cold-rolled and then annealed, and then a dichromate-organic In manufacturing a non-oriented electrical steel sheet by a series of steps for forming a resin-based insulating coating, in the final pass of the cold rolling step, as a rolling roll, the roll surface has a circle equivalent diameter of 500 μm or less and The difference between the convex part and the most concave part is 3
A roll in which the craters having a shape of -40 μm are arranged in the number of 1 to 400 per unit area 1 cm ² and without overlapping with each other is used.

However, this invention is because of the unevenness imparted to the steel plate surface,
The deterioration of the space factor is unavoidable.

<Problems to be Solved by the Invention> The present invention has been developed in view of the above-mentioned current situation, excellent weldability is obtained when TIG welding is performed after lamination, and magnetic characteristics are not deteriorated, and further It is an object to propose an advantageous manufacturing method of a non-oriented electrical steel sheet having an excellent space factor.

<Means for Solving the Problem> The present invention, C: 0.010 wt% or less, Si: hot rolled sheet having a composition containing 2.5 wt% or less, after cold rolling, then annealed,
In producing a non-oriented electrical steel sheet by a series of steps for forming an insulating film, in the preceding stage of the final pass of the cold rolling step, as a rolling roll, the roll surface has a circle equivalent diameter of 500 μm or less and the most convex portion. Is 3 to 4
Cold rolling is performed by using rolls in which the number of craters having a shape of 0 μm is 1 to 400 per unit area 1 cm ² and they are arranged without overlapping each other, and as a rolling roll in the final pass. , A method for producing a non-oriented electrical steel sheet with excellent magnetic properties, space factor and weldability, which is characterized by performing cold rolling under a light reduction using a bright roll. 5.0% is desirable, and as the insulating coating, an organic resin coating or a mixed coating of one or two chromate-based or phosphate-based and organic resin can be advantageously used.

<Operation> First, the experimental results which are the basis of the present invention will be described.

The inventors formed various concave-convex patterns on the surface of a steel sheet metal by rolling the final pass during cold rolling using a roll processed by a laser beam, a plasma flame or photo-etching, and the concave-convex patterns are welded. The effect on magnetic properties and magnetic properties was investigated.

FIG. 1 schematically shows the concavo-convex shape of the roll surface used for the final pass during cold rolling and the concavo-convex shape of the surface of the base metal transferred to the steel plate, and the circle-converted diameter of the concavo-convex formed on the roll surface is D (Μm) and the difference between the most concave and the most convex is h (μ
m), the number of irregularities per unit area 1 cm ² is N
It shall be represented by (pieces).

FIG. 2 shows the results of examining the relationship between B ₅₀ (magnetic flux density at a magnetizing force of 5000 A / m) and N of a steel sheet when D is 90 to 120 μm and h is 5 to 7 μm. The material is 0.5
% Si steel sheet.

As is clear from the figure, a good B ₅₀ was obtained in the case of N400 pieces, but the B ₅₀ deteriorated sharply in the case of N> 400 pieces. It should be noted that N is limited to the range of 1 to 400 because there is no weldability improving effect unless one or more exists.

Next, in Fig. 3, the number of craters N is kept constant at 300,
The results of examining the B ₅₀ of the steel sheet when the diameter D of the crater in terms of circle and the difference h between the most convex portion and the most concave portion are variously changed are summarized.

As is clear from the figure, D500 μm and h = 3
Particularly good B ₅₀ is obtained in the range of ˜40 μm. It was also confirmed that the weldability was good in this range.

Therefore, in the present invention, the crater to be formed on the surface of the roll for skin pass rolling has D500 μm, H = 3 to
The range is 40 μm, N = 1 to 400. In actual crater formation, it is very difficult to make D less than 20 μm, so it is practical to make D 20 μm or more.

A suitable example of the crater sequence is schematically shown in FIGS. It is preferable that the crater shapes are almost the same and the periodicity of the arrangement is constant in the circumferential and axial intervals of the roll, but the periodicity is somewhat disturbed (h in the figure), and the sizes are uneven. (I in the figure).

By the way, when this material is punched and laminated, the space factor becomes smaller than expected. This is because the protrusions formed by the final pass during cold rolling are not uniform, so if the highest protrusions hit each other during stacking, the space factor will drop significantly, and the tips of the protrusions will be chevron-shaped. Therefore, it is considered that the space factor is disadvantageous.

Therefore, in the present invention, regarding the most convex portion formed,
It has been found that when the space factor is improved by flattening the tip of the mountain portion of the convex portion, that is, by making the convex portion uniform, more excellent magnetic properties and weldability can be obtained.

 The method of the present invention will be described in more detail below.

First, the reason why the main component of the raw material is limited to the above range in the present invention will be described.

C: 0.010% or less C is an element that deteriorates both iron loss and magnetic permeability, so it is preferable to reduce it as much as possible, but it is allowable within the range of 0.010% or less.

Si: 2.5% or less Si is a useful element that increases the specific resistance and reduces the eddy current loss. However, if it exceeds 2.5%, not only the magnetic permeability decreases but also the cold workability deteriorates. It was supposed to be added within the range.

Although the main components have been described above, other surface oxynitriding inhibitors such as Sb and Sn and specific resistance improving elements such as Mn, Al, Cu and Ni may be added to the present invention.

The hot-rolled steel sheet adjusted to have the above preferable composition is annealed as it is or at a temperature of 750 ° C. or higher and 1000 ° C. or lower for about 15 seconds or more, and then cold-rolled to a final thickness.
At this time, the preceding stage of the cold-rolling final pass is performed by using a roll which has been subjected to unevenness processing of a pattern as shown in FIG. 4 by laser beam, plasma flame or photoetching to give an uneven pattern on the surface of the steel sheet. .

After that, a bright roll is further used as a rolling roll and cold rolling is performed under light reduction to reduce the most convex portion, that is, to make the convex portion uniform.

When the rolling reduction at this time is less than 0.3%, it does not contribute much to the reduction of the most convex portion. On the other hand, if it exceeds 5.0%, all the convex portions are deformed and sufficient weldability cannot be obtained. Therefore, the rolling reduction is preferably 0.3 to 5.0%.

Then, final annealing is performed. Annealing conditions are 700-1000 ℃, 0.1
About 3 minutes is preferable. After that, it is to form an insulating coating on the surface of the steel sheet, but in forming such an insulating coating, the treatment liquid to be described later is uniformly applied to the surface of the electromagnetic steel sheet by a roll coater or a spray, A desired good insulating film can be obtained by baking at a temperature of about 300 to 700 ° C for a short time.

As the insulating coating, a chromate-based or phosphate-based one or two types and a mixed coating of an organic resin or an organic resin coating is preferable. Chromate refers to Ca, Mg, Zn, etc.
It is a chromate containing one or more kinds selected from valent metals or a mixture of this with a small amount of chromic anhydride.

The organic resin to be added to improve the punching property includes acrylic, vinyl acetate, styrene and copolymer emulsions thereof, and water-soluble resins such as polyvinyl alcohol and polyacrylic cellulose. Momo can be used, and the compounding amount thereof is preferably about 5 to 120 parts by weight in terms of resin solid content with respect to 100 parts by weight of CrO ₃ . This is because if the resin solid content is less than 5 parts by weight, the punchability is poor, and if it is more than 120 parts by weight, the resulting coating becomes soft.

Furthermore, as a chromium organic reducing agent that makes the coating insoluble,
Polyhydric alcohols such as glycerin, ethylene glycol and sucrose can also be added. The compounding amount is Cr
O _3: preferably about 10 to 60 parts by weight per 100 parts by weight. This is because if it is less than 10 parts by weight, the water resistance is poor, and if it exceeds 60 parts by weight, the reduction reaction proceeds too quickly during the treatment, and the treatment liquid becomes unstable.

In addition, boric acid can sometimes be added as a heat resistance improving component of the coating.

On the other hand, phosphate may be used instead of chromate, and a mixed system may be used. The phosphate used at this time is a phosphate of magnesium, calcium, zinc, aluminum or the like. On the other hand, as the organic resin coating,
One or more of acrylic resins and copolymers thereof, vinyl acetate resins and copolymers thereof, alkyd resins, melamine resins, phenol resins, polyester resins, epoxy resins or modified products thereof are used.

 This organic resin coating may be used alone.

 Examples will be described below.

<Example> In cold rolling a hot rolled sheet having the composition shown in FIG.
The surface concavo-convex pattern of the front-stage work roll of the final cold rolling stand was variously changed and cold-rolled to a thickness of 0.50 mm. Then, cold rolling was further performed under a light reduction of 1.0%. Next, this was continuously annealed at a soaking temperature of 770 ° C., and then the treatment liquid shown in Table 2 was applied by a rubber roll and baked at 450 ° C. for 70 seconds to form a film. The surface roughness of the work roll of the last stage of the final cold rolling stand at this time is D (μm), h (μm), N (pieces)
Table 3 shows the relationship between the three-dimensional roughness SRa (μm), the maximum welding speed, and the magnetic properties.

Here, the maximum welding speed is the maximum welding speed at which blowholes do not occur in the welded portion when steel plates are laminated to a thickness of about 30 mm and the end surface is TIG welded with a welding current of 120A.

The magnetic properties were measured by cutting out eight Epstein test pieces (30 width × 280 length mm) from the rolling direction of the product sheet and the direction perpendicular to the rolling direction. W _15/50 and (W / kg) is, 50H _z
Is the iron loss when magnetized to 1.5T at the frequency of
B ₅₀ (T) is the magnetic flux density of the sample when magnetized with a magnetizing force of 5000 A / m.

As is clear from Table 3, all of the electrical steel sheets obtained according to the present invention have excellent weldability, space factor and magnetic characteristics.

<Effect of the Invention> Thus, according to the present invention, it is possible to easily obtain a non-oriented electrical steel sheet having excellent weldability, space factor, and magnetic properties.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a cross-sectional shape of craters formed on the roll surface and the surface of the base metal, and FIG. 2 is a diagram showing the relationship between the number N of craters and the magnetic flux density B _50. FIG. 3 is a graph showing the influence of the circle-converted diameter D of the crater and the difference h between the most convex portion and the most concave portion on the magnetic properties, and FIG. 4 is a to i that are suitable craters. It is the figure which showed arrangement.

Claims (3)

(57) [Claims] 1. A hot-rolled sheet having a composition containing C: 0.010 wt% or less and Si: 2.5 wt% or less is cold-rolled and then annealed,
In producing a non-oriented electrical steel sheet by a series of steps for forming an insulating film, in the preceding stage of the final pass of the cold rolling step, as a rolling roll, the roll surface has a circle equivalent diameter of 500 μm or less and the most convex portion. Is 3 to 4
Cold rolling is performed using rolls in which the number of craters having a shape of 0 μm is 1 to 400 per unit area 1 cm ² and they are arranged without overlapping each other, and as a rolling roll in the final pass. , A method for producing a non-oriented electrical steel sheet having excellent magnetic properties, space factor and weldability, which is characterized by performing cold rolling under light reduction using a bright roll. 2. The production of a non-oriented electrical steel sheet excellent in magnetic properties, space factor and weldability according to claim 1, characterized in that the reduction ratio of cold rolling under light reduction is 0.3 to 5.0%. Method. 3. The magnetic characteristics and the occupancy ratio according to claim 1 or 2, wherein the insulating coating is an organic resin coating or a mixed coating of one or two of chromate type and chlorine phosphate and an organic resin. A method for manufacturing a non-oriented electrical steel sheet excellent in product ratio and weldability.