ES2230591T3 - MANUFACTURING PROCEDURE OF MAGNETIC STEEL SHEET OF NON-ORIENTED GRAINS AND SHEET OBTAINED BY THE PROCEDURE. - Google Patents

Abstract

The manufacture of magnetic strip with non-orientated grains comprises: (a) the production of a steel under vacuum with a given composition; (b) production of a slab; (c) hot rolling the slab at a reheat temperature lower than 1300[deg]C and a finishing temperature lower than 950[deg]C; (d) coiling the hot rolled strip at a temperature greater than 550C; (e) submitting the coiled strip to static annealing at a temperature between 700 and 1050[deg]C for longer than 1 hour; (f) submitting the annealed strip to a shot blasting operation; (g) submitting the treated strip to a pickling operation; (h) cold rolling the pickled strip, with a reduction rate of between 25 and 90%, in a single cold rolling operation to a thickness of less than or equal to 1.5 mm; (i) submitting the cold rolled strip to a final annealing operation effected in defilement.

Description

Steel sheet manufacturing procedure magnetic of non-oriented grains and sheet obtained by the process.

The present invention relates to a Manufacturing process of magnetic grain steel sheet Not oriented

Magnetic plates called grain not oriented, that is, they have isotropic magnetic properties, they are particularly intended for the construction of devices electromagnetic in which the magnetic flux generated by the electric windings is not constant, as for example in rotating machines Some transformers used in the field of appliances use these types of plates for reasons economic.

These electromagnetic devices are constituted by trimmed and mounted plates. The plates have a effectiveness that is evaluated based on two parameters that are the induction, on the one hand, and specific losses, on the other part.

Induction is limited, on the one hand, by magnetization until plate saturation and this magnetization It is so much higher the richer in iron is steel. The adding alloy elements to steel implies an increase in the electrical resistance, which has the function of reducing Foucault current losses.

The vacuum processing of steel allows to improve, on the one hand, the property and purity of said steel and, on the other part, reduce hysteresis losses.

Therefore, it is necessary to find a compromise, from the point of view of the composition, between the magnetization and the losses.

It is known from EP 0 469 980 a procedure used in the field of sheet metal fabrication magnetic of non-oriented grains, comprising the procedure successively, after vacuum processing of a steel, a vacuum rolling operation followed by winding, annealing fast called in procession of hot rolled sheet, a optional graining operation, a pickling operation, a cold rolling operation in one or several stages followed by a annealing, the final annealing being performed under atmosphere controlled, decarburizing, if necessary.

The plates obtained by this procedure, for a final thickness of approximately 0.50 mm, they have losses specific below 6.5 W / Kg under an induction of 1.5 Tesla and a frequency of 50 Hz as well as a magnetization greater than 1.74 Tesla under an electric field of 5000 A / m.

For a sheet thickness of approximately 0.65 mm, total mass losses are less than 7.5 W / kg low an induction of 1.5 Tesla and a frequency of 50 Hz. magnetization is greater than 1.75 Tesla under a field of 5000 A.M.

The invention aims to improve the Magnetic characteristics of non-oriented grain plates made with a steel that only contains very little silicon, is say, reduce magnetic losses and increase magnetization under a certain electric field.

Its purpose is a manufacturing procedure of a magnetic sheet of non-oriented grains from the vacuum processing of a steel that has a composition with less 0.5% silicon, in particular:

carbon <0.01%,

silicon <0.5%,

manganese, from 0.05 to 0.5%,

aluminum <0.03%,

phosphorus <0.20%,

sulfur <0.015%,

nitrogen <0.01%,

oxygen <0.01%, iron and impurities inevitable,

said iron being subjected, put in the form of rough, successively to:

a hot rolled with a temperature of overheating of roughing less than 1300 ° C, a temperature of end of hot rolling below 950 ° C, the winding being wound hot rolled strip at a temperature above 550 ° C, a optional graining operation, a pickling operation, to then cold rolled in at least one rolling operation cold to a thickness less than or equal to 1.5 mm, being subjected the cold rolled strip to a final annealing.

The other features of the invention They are:

in a formation of the invention,

- cold rolling in one operation is performed under a reduction percentage between 25 and 90%

in another form of the invention,

- final annealing in process is performed at a temperature between 700 and 1050 ° C for a while less than 10 min.

In addition, after the final annealing, the sheet previously trimmed to an annealing elimination of tensions

- Stress removal annealing is performed at a temperature above 650 ° C, for a while more than 3 min.

The following description, which gives a series of Examples of embodiment will make the invention well understood.

The unique figure presents a curve of magnetization based on cold rolling percentages, cold rolling being performed in a single operation.

According to the present invention, it is evidenced that mass losses can be reduced to 1.5 Tesla and 50 Hz, to less than 5 W / Kg for a sheet thickness of approximately 0.35 mm, at less than 6 W / Kg for a sheet thickness of approximately 0.50 mm; at less than 8 W / Kg for a sheet thickness of approximately 0.65 mm, less than 11 W / kg for a sheet thickness of approximately 1 mm, and obtain a magnetization equal to or greater than 1.72 T under an electric field of 5000 A / m for a 0.35 mm sheet thick, a magnetization equal to or greater than 1.75 Tesla for 0.50 mm, 0.65 mm and 1 mm thick plates, subject according to method of the invention, to a steel having the composition given to:

- a hot rolling with a temperature of overheating of roughing less than 1300 ° C, a temperature of end of hot rolling below 950 ° C, the winding being wound hot rolled strip at a temperature above 550ºC, at cold rolled continuation with a percentage reduction greater than or equal to 25%, in a cold rolling operation up to a thickness less than or equal to 1.5 mm, the band being subjected cold rolled to final annealing.

In this procedure, an annealing is not performed Quick hot rolled sheet.

Examples 1 to 5 below illustrate the general characteristics of the present invention.

Example 1

A roughing of steel No. 1, whose composition Weight chemistry is given in Table 1, was reheated to 1200 ° C, He was then subjected to a first hot rolling with a 86% reduction percentage and a second hot rolling with a reduction percentage of 93%. The temperature of the end of hot rolled was 860 ° C, the laminated sheet web in 2.5 mm thick hot was wound at the temperature of 710 ° C.

TABLE 1 No. 1 steel

C Mn Yes S To the P 0.003% 0.308% 0.347% 0.010% 0.001% 0.160%

For comparative measurements, the band Sheet metal obtained in this way was divided into sections:

- a part of the sections experienced a 2.5 minutes fast annealing at 1050 ° C before cold rolling To serve as a reference.

- the other sections were cold rolled, according to the invention, without annealing before rolling in cold.

Sections underwent cold rolling in a single operation to obtain sections of final thickness of 0.35 mm, 0.50 mm, 0.65 mm and 1 mm, which corresponds to percentages cold reduction of 86%, 80%, 74% and 60%.

A final anneal was performed at a temperature of 880 ° C for 2 min. for 0.35 mm, 0.50 mm sheet sections and 1 mm thick. The final annealing was carried out at a temperature 920 ° C for 2.5 minutes (min) for the sheet metal sections of final thickness of 0.65 mm.

Table 2 presents the characteristics in Mass losses in W / Kg at 1.5 Tesla and 50 Hz and magnetization in Tesla under an electric field of 5000 A / m for sheet thickness about 0.35 mm, about 0.50 mm, of approximately 0.65 mm and approximately 1 mm.

TABLE 2

W 1.5 / 50 B5000 (W / kg) (Tesla) Lock 0.35 mm with annealing (reference) 3.95 1.78 Sheet metal 0.50 mm with annealing (reference) 4.70 1.78 Sheet metal 0.65 mm with annealing (reference) 5.90 1.78 1 sheet mm with annealing (reference) 11.16 1.79

W 1.5 / 50 B5000 (W / kg) (Tesla) Lock no annealing (invention) Sheet metal 0.35 mm thick 4.10 1.75 Lock 0.50 mm thickness 5.20 1.77 0.65 mm sheet of thickness 6.72 1.77 1 mm sheet of thickness 9.60 1.76

The ability to magnetize the sheet final thickness of 1 mm, 0.65 mm and 0.50 mm is equal to or greater than 1.75 Tesla under a field of 5000 A / m, while the thickness before Cold rolled ranges from 2mm to 3.3mm (as summarized in the Table 2a) in the case of winding the hot rolled sheet to the temperature above 650 ° C and in the absence of annealing before cold rolled. For the sheet of final thickness of 0.35 mm, the thickness before cold rolling should be less than 3.3 mm to obtain a magnetization equal to or greater than 1.75 Tesla.

TABLE 2 bis

one

Example 2

A roughing of No. 1 steel was rolled in hot in the same way as in example 1, but with a winding at the temperature of 610 ° C, being cold rolled a sheet metal section with a reduction percentage of 80%, the other section with a reduction percentage of 74%, without initial annealing, that is, without annealing before cold rolling.

After the same final annealing as in the example 1, the magnetic characteristics presented were obtained in Table 3.

TABLE 3

W 1.5 / 50 B5000 (W / kg) (Tesla) Lock no annealing (invention) Sheet metal 0.50 mm thick 5.95 1.74 Lock 0.65 mm thick 7.67 1.74

Example 3

A roughing of No. 1 steel was rolled in hot in the same way as in example 1, but with a temperature of the end of hot rolling of 910ºC, being cold rolled sheet with a reduction percentage of 80% without final annealing

After the same final annealing as in the example 1, the magnetic characteristics presented were obtained in Table 4.

TABLE 4

W 1.5 / 50 B5000 (W / kg) (Tesla) Lock no annealing (invention) Sheet metal 0.50 mm thick 5.25 1.72

The preceding comparative examples put in evidence, for the variation of the values obtained in losses and induction and with the composition of the present invention, the need to increase the winding temperature as well as limit the temperature of the end of hot rolling in absence of annealing treatment of the laminated web in hot.

Example 4

A roughing of steel No. 2, whose composition Weight given in Table 5, was treated under the same conditions that the roughing of steel No. 1 of example 1, being cold rolled the sheet without initial annealing.

TABLE 5 No. 2 Steel

C Mn Yes S To the P 0.003% 0.870% 0.342% 0.008% 0.001% 0.188%

The magnetic characteristics obtained are presented in Table 6.

TABLE 6

W 1.5 / 50 B5000 (W / kg) (Tesla) Lock no annealing 0.50 mm sheet thickness 5.32 1.71 0.65 mm sheet of thickness 6.32 1.72

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Example 5

A roughing of steel No. 3, whose composition Weight given in Table 7, was treated under the same conditions that the roughing No. 1 of example 1, the sheet being cold rolled No final annealing.

TABLE 7 No. 3 steel

C Mn Yes S To the P 0.003% 0.106% 0.326% 0.007% 0.001% 0.173%

The magnetic characteristics obtained are presented in Table 8.

TABLE 8

W 1.5 / 50 B5000 (W / kg) (Tesla) Lock no annealing (invention) Sheet metal 0.50 mm thick 5.80 1.77 Lock 0.65 mm thick 7.03 1.77

It is observed, comparing examples 4 and 5 and the tables of values 6 and 8 that the manganese content should be less than 0.5%, since a high manganese content generates a decrease in magnetization. However, a minimum of 0.05% manganese, since a decrease in Manganese content tends to generate an increase in losses.

From the point of view of the composition, the presence of silicon and manganese in solid solution in iron considerably increases the electrical resistance and, by consequently, it reduces the energy losses that accompany the variation of the magnetic induction flow. However, the magnetic polarization until saturation decreases depending on the content in silicon, in aluminum, in manganese. This results in a lower magnetic permeability of steel at the point of usual operation of the machines. Therefore it is necessary find the best compromise between content in elements of alloy and the expected magnetic yields. In consecuense, the steel according to the invention has a silicon mass content less than 0.5%, and a manganese content less than 0.5% for Get high permeability.

Thermal conductivity is a parameter. important in the construction of electric machines. Indeed, energy losses due to Joule effect in materials are evacuated to the outside by means of the magnetic circuit constituted by stacked trimmed sheets. The addition of silicon, of manganese and aluminum to iron translates by a decrease of thermal conductivity.

From this point of view, steel must be no Alloy or very low alloy, low silicon content, manganese and in aluminum the steel according to the invention allows to limit the engine warming that is detrimental to good behavior of the insulators that cover the conductors. The improved evacuation of calories can also allow a increase in mass power, through the increase in induction levels, without temperature rise.

In other words, the composition of the invention, by the thermal conductivity conferred on steel, ensures thermal conduction cooling of the devices electrical

According to the invention, it is shown that with a steel having a certain chemical composition can achieve the realization of magnetic sheet that has remarkable properties:

- without fast annealing of the sheet hot rolled, thanks to better temperature control of the end of hot rolling and winding and on condition of limit the manganese content included in the composition of the steel.

The sheet obtained by the procedure can be submitted, after cutting and mounting the magnetic circuits, to an annealing of elimination of tensions.

This annealing of stress elimination due to the cut causes a sensible reduction of losses without degradation of the aptitude for magnetization:

- in the absence of initial annealing and with only one cold rolled.

Claims (5)

1. Sheet metal fabrication procedure magnetic grain not oriented from vacuum processing of a steel that has a composition: carbon <0.01%, silicon <0.5%, manganese, from 0.05 to 0.5%, aluminum <0.03%, phosphorus <0.20%, sulfur <0.015%, nitrogen <0.01%, oxygen <0.01%, the rest being iron e inevitable impurities, said iron being subjected, put in the form of rough, successively to: a hot rolled with a temperature of overheating of roughing less than 1300 ° C, a temperature of end of hot rolling below 950 ° C, the winding being wound hot rolled strip at a temperature above 550 ° C, a optional graining operation, a pickling operation, to cold rolled continuation with a percentage reduction greater than or equal to 25%, in a cold rolling operation up to a thickness less than or equal to 1.5 mm, the band being subjected cold rolled to final annealing. 2. Method according to claim 1, characterized in that the cold rolling in an operation is carried out with a reduction percentage between 25 and 90%. 3. Method according to claims 1 to 2, characterized in that the final annealing in procession is carried out at a temperature between 700 and 1050 ° C for a time of less than 10 min. 4. Method according to claims 1 to 3, characterized in that, in addition, after the final annealing, the previously trimmed sheet is subjected to annealing of stress removal. 5. Method according to claim 4, characterized in that the annealing of the stresses is carried out at a temperature greater than 650 ° C for a time greater than 3 min.