ES2276191T3 - MANUFACTURING PROCEDURE OF A 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

Manufacturing procedure of a sheet magnetic steel of non-oriented grains and sheet obtained by the process.

The present invention concerns a Manufacturing procedure of a magnetic steel sheet non-oriented grains

Magnetic sheets of non-oriented grains, that is to say that they have isotropic magnetic properties 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 household electrical appliances use that kind of badges for economic reasons.

Those electromagnetic devices are constituted of cut and assembled sheets. The plates have an efficiency 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 by magnetization to plate saturation and this magnetization is on the other hand more high if steel is rich in iron. The addition of elements of alloy in steel brings with it an increase in resistivity electric, which has the function of reducing losses by Foucault currents.

Vacuum steel processing allows improve on the one hand, the property and purity of said steel and on the other hand, reduce hysteresis losses.

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

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

The plates obtained by this procedure, for a final thickness of approximately 0.50 millimeters, they have specific losses of less than 6.5 W / kg under an induction of 1.5 Tesla and a frequency of 50 Hertz as well as a superior magnetization at 1.74 Tesla under an electric field of 5000 A / m.

For a sheet thickness of approximately 0.65 mm, the total mass losses are less than 7.5 W / Kg under an induction of 1.5 Tesla and a frequency of 50 Hertz. The 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 contains very little silicon, that is reduce magnetic losses and increase magnetization under a determined electric field.

It has as its object a procedure of manufacture of a magnetic sheet of non-oriented grains that It comprises the stages that consist of:

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make a steel under vacuum following composition:

carbon < 0.01%

silicon < 0.5%,

manganese 0.05 to 0.5%

aluminum < 0.03%,

match < 0.20%,

sulfur < 0.015%,

nitrogen < 0.01%,

oxygen < 0.01%,

the rest being iron and inevitable impurities,

-

put on steel in the form of ingot,

-

hot roll the ingot with a heating temperature below 1300 ° C, a temperature at hot rolling end lower than 950 ° C,

-

wind the hot rolled strip to a temperature higher than 550 ° C,

-

subject the coil band to an annealing static at a temperature between 700 and 1050 ° C for a time greater than 1 hour,

-

subject the annealed band to a optional shot blasting operation,

-

submit the annealed band and eventually shot blasting, to a pickling operation, and then

-

cold strip the stripped strip, with a reduction rate between 25 and 90%, in a single cold rolling operation at a thickness less than or equal to 1.5 mm, and then

-

subject the cold rolled strip to a final annealing performed in the parade

-

after final annealing, the sheet previously cut to an annealing elimination of tensions

The other features of the invention They are:

-

he final annealing in the parade is performed at a temperature between 700 and 1050 ° C for a time less than 10 mn.

Stress annealing it can be carried out at a temperature higher than 650ºC during a time exceeding 3 minutes.

The description that follows provides a series of embodiments will make you better understand the invention.

The unique figure has a magnetization curve Depending on cold rolling rates, cold rolling being performed in a single operation.

According to the invention, the process of manufacture of a steel from a magnetic grain plate not oriented includes vacuum processing of a steel following composition:

carbon < 0.01%

silicon < 0.5%,

manganese 0.05 to 0.5%

aluminum < 0.03%,

match < 0.20%,

sulfur < 0.015%,

nitrogen < 0.01%,

oxygen < 0.01%,

the rest being iron and impurities inevitable.

The presence of silicon and manganese in solid solution in iron greatly increases the electrical resistivity and therefore decreases losses of energy that accompany the variation of the induction flow magnetic. However, magnetic saturation polarization decreases depending on the content of silicon, aluminum, manganese. This results in a lower magnetic permeability of the steel at the usual operating point of the machines. Is by therefore necessary to find the best compromise between the content of alloy elements and the intended magnetic results. Consequently, the steel according to the invention has a content silicon mass less than 0.5%, and a manganese content less than 0.5% to obtain 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 cut sheets. The addition of silicon, manganese and from aluminum to iron translates into a decrease in Thermal conductivity.

From that point of view, steel should not be or should be very low alloy, the low silicon content of Manganese and aluminum steel according to the invention allows to limit engine warming that is detrimental to good conservation of the insulators that cover the conductors. The best calorie evacuation can thus authorize an increase in mass power, by increasing the levels of induction, without temperature rise.

In other words, the composition of the invention, by the thermal conductivity that it confers on steel, ensures thermal conduction cooling of the devices electric

After processing, the steel is cast in the form of ingots, and then the ingot is laminated in warm with a heating temperature below 1300 ° C, and a temperature at the end of hot rolling below 950 ° C.

The hot rolled sheet is wound to a temperature above 550 ° C, and then subjected to annealing static at a temperature between 700 and 1050 ° C for a Time greater than 1 hour.

After the static annealing stage, the band may undergo an optional blasting operation with shot, before being subjected to a pickling operation.

In short, the stripped strip is cold rolled, with a reduction rate between 25 and 90%, in a single cold rolling operation at a thickness less than or equal to 1.5 mm, and then undergoes a final annealing performed in the parade. He final annealing in the parade is preferably performed at a temperature between 700 and 1050 ° C, for a while less than 10 mn.

It is shown that losses can be reduced magnetic below 4.5 W / kg for a sheet thickness of 0.35 mm, below 5.30 W / Kg for a sheet thickness of 0.50 mm, per below 7 W / Kg for a sheet thickness of 0.65 mm, below 12.5 W / Kg for a sheet thickness of 1 mm and obtain a magnetization equal to or greater than 1.77 Tesla performing a static annealing of the hot rolled sheet strip, associated with cold rolled in a single operation followed by continuous annealing in the paraded

Examples 1 to 6 illustrate this characteristic.

Example 1

A No. 4 steel ingot whose composition Weight chemistry is given in Table 1 is heated to 1173 ° C and then  undergoes a first hot rolling with a reduction rate of 86% and a second hot rolling with a reduction rate of 93% The temperature at the end of hot rolling is 843 ° C, The hot rolled sheet web is temperature wound of 738 ° C. The sheet in the form of a coil is subjected to a static annealing at the temperature of 800 ° C for 10 hours under an atmosphere of hydrogen or hydrogen and nitrogen. The sheet is then cold rolled with an 80% reduction rate for obtain a sheet of thickness of 0.50 mm. The final annealing is carried out at a temperature of 880 ° C for 2 minutes under atmosphere of nitrogen and hydrogen.

TABLE 1 No. 4 steel

C Mn Yes S To the P 0.002% 0.343% 0.322% 0.006% 0.001% 0.159%

The magnetic characteristics obtained are presented in table 2.

TABLE 2

W 1.5 / 50 (W / Kg) B5000 (Tesla) Lock 0.50 mm thick according to the invention 4.9 1.80

Example 2

A # 4 steel ingot whose composition weight is given in table 1 is treated in the same way as the steel of example 1, ie with the same reduction rates in hot and cold.

The heating temperature of the ingot is 1185 ° C, the temperature at the end of hot rolling is 857 ° C. The hot rolled sheet strip is wound to the temperature of 636 ° C. A piece of the coil is subjected to a static annealing at the temperature of 800 ° C for 10 hours under an atmosphere of hydrogen or hydrogen and nitrogen. The sheet is then cold rolled to reach a 0.50 mm sheet of thickness. The final annealing is carried out at the temperature of 880 ° C for 2 minutes under nitrogen and hydrogen atmosphere.

The magnetic characteristics obtained are presented in table 3.

TABLE 3

W 1.5 / 50 (W / Kg) B5000 (Tesla) Lock 0.50 mm thick according to the invention 4.7 1.79

Example 3

A # 4 steel ingot whose composition weight is given in table 1 is treated in the same way as the steel of example 1, ie with the same reduction rates in hot and cold.

The heating temperature of the ingot is of 1221 ° C, the temperature at the end of hot rolling is 910 ° C. The hot rolled sheet strip is wound to the temperature of 785 ° C. The sheet in the form of a coil is subjected at a static annealing at the temperature of 800 ° C for 10 hours under an atmosphere of hydrogen or hydrogen and nitrogen. The sheet is then cold rolled to reach a sheet of 0.50 mm thick. The final annealing is carried out at the temperature 880 ° C for 2 minutes under nitrogen atmosphere and hydrogen.

The magnetic characteristics obtained are presented in table 4.

TABLE 4

W 1.5 / 50 (W / kg) B5000 (Tesla) Lock 0.50 mm thick according to the invention 4.62 1.82

Under the same treatment conditions, the steel # 2, whose composition is given in table 5, which comprises in its composition a manganese content of 0.87% leads to identical magnetic properties to those in table 4. The Manganese content must however be limited to less than 0.5% to improve thermal conductivity.

The lower the annealing temperature static, it is necessary to increase its duration.

TABLE 5 No. 2 steel

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

Example 4

A piece of the laminated sheet coil in hot obtained under the conditions described in example 2 is subjected to static annealing at a temperature of 710 ° C for 40 hours under an atmosphere of hydrogen or nitrogen and of hydrogen.

The magnetic characteristics obtained are presented in table 6.

TABLE 6

W 1.5 / 50 (W / kg) B5000 (Tesla) Lock 0.50 mm thick according to the invention 4.88 1.79

Example 5

A # 4 steel ingot whose composition weight is given in table 1 is treated in the same way as in example 1, that is with the same hot reduction rates and cold

Steel ingot No. 4 is heated to 1188 ° C, the temperature at the end of hot rolling is 816 ° C. The Hot rolled sheet metal strip is wound at the temperature of 702 ° C. A piece of sheet in the form of a coil is subjected to a static annealing at the temperature of 1000 ° C for 10 hours under an atmosphere of hydrogen or hydrogen and nitrogen. The sheet is then cold rolled to reach a 0.50 mm sheet of thickness. The final annealing is carried out at the temperature of 880 ° C for 2 minutes under nitrogen and hydrogen atmosphere.

The magnetic characteristics obtained are presented in table 7.

TABLE 7

W 1.5 / 50 (W / kg) B5000 (Tesla) Lock 0.50 mm thick according to the invention 4.59 1.80

Example 6

A piece of the laminated sheet coil in hot obtained under the conditions described in example 2 is subjected to static annealing at a temperature of 740 ° C for 40 hours under an atmosphere of hydrogen or nitrogen and of hydrogen. After annealing the piece is divided into four parts suffering cold rolling respectively with a rate of 60%, 74%, 80% and 86% reduction to obtain a 1 mm sheet of 0.65 mm, 0.50 mm, and 0.35 mm thick.

The 0.5 mm thick sheet and the 0.35 sheet mm thick undergo an annealing at a temperature of 880 ° C for 2 mn.

0.65 mm thick sheet undergoes annealing at a temperature of 880 ° C for 2 min 30 s.

The 1 mm thick sheet undergoes annealing to a temperature of 880 ° C for 3 min 40 s.

Final annealing is performed in an atmosphere of hydrogen and nitrogen. Magnetic characteristics obtained are presented in table 8.

TABLE 8

W 1.5 / 50 (W / kg) B5000 (Tesla) According the invention: 0.35 mm sheet thickness 3.76 1.78 0.50 mm sheet of thickness 4.70 1.79 0.65 sheet mm thick 6.36 1.80 1 sheet mm thick 11.80 1.80

The unique figure shows that the rolling rate cold must be less than 90% to obtain equal magnetization or greater than 1.77 Tesla when static annealing is performed after hot rolling.

In the case where the sheet is made with a static annealing after hot rolling, has been found that an annealing performed on magnetic nodes performed by cutting and stacking the sheet according to the invention, it generates a decrease of losses without degradation of magnetization, the Annealing being intended to eliminate internal stresses due to the cut. It is thus possible to make sheets that have a thickness  0.35 mm end, which after post cutting annealing have magnetic losses less than 4.0 W / Kg with equal magnetization or higher than 1.77 Tesla. It is possible to make plates that have a final thickness of 0.50 mm, which after post cutting annealing they have magnetic losses of less than 4.70 W / kg with magnetization  equal to or greater than 1.77 Tesla. Under certain conditions, it is possible make plates that have losses of less than 4 W / kg with a magnetization higher than 1.80 Tesla. These results are essentially due to the fact that in the process according to the invention the sheet is subjected to static annealing before rolling in cold.

The invention comprises the following steps: a static annealing before cold rolling, cold rolling in a single operation, a final annealing as presented in the Examples 1, 2, 3, 4, 5 and 6. After cutting the elements of circuit and stacking, annealing of stress elimination internal is carried out in said circuits.

Stress annealing internal generated by cutting allows to reduce significantly losses without any degradation of sheet metal magnetization according to the invention.

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Preferably, the sheet undergoes an annealing of removal of tensions at a temperature above 650ºC, for a time exceeding 3 minutes.

Example 7 illustrates that purpose.

Example 7

Epstein specimens that have a thickness of 0.35 mm, 0.50 mm, 0.65 mm and 1 mm, used to measure the magnetic characteristics of sheets presented in examples 1, 3, 4, and 5, have undergone an annealing of 750 ° C for 2 hours under an atmosphere of nitrogen and hydrogen.

0.50 mm thick sheet with annealing according to the invention:

Example 1 4.13 1.80 Example 3 3.80 1.82 Example 4 4.15 1.79 Example 5 3.62 1.80

Example 8

The Epstein test tubes used in example 6 to measure the magnetic characteristics are subjected to a Annealing at 750 ° C for two hours under nitrogen atmosphere and hydrogen.

The magnetic characteristics obtained are presented in table 9.

TABLE 9

W 1.5 / 50 B5000 (W / kg) (Tesla) Lock 0.35 mm thickness 3.37 1.78 0.5 mm sheet of thickness 3.94 1.79 0.65 sheet mm thick 5.36 1.80 1 sheet mm thick 10.62 1.80 according to invention.

In the case where the sheet according to the invention It is performed with static annealing after rolling in hot, you can thus obtain sheets that have a final thickness of 0.35 mm, 0.50 mm, 0.65 mm and 1 mm and that after annealing post cut have respectively mass losses of less than 4 W / Kg, 4.70 W / Kg, 6 W / Kg and 11.5 W / Kg as well as an equal magnetization or higher than 1.77 Tesla.

According to the invention, it is shown that one can arrive with a steel that has a certain chemical composition for the realization of magnetic sheet that has properties highlighted, performing a long-term static annealing of the hot rolled sheet followed by a single rolled in cold.

When the sheet according to the invention is laminated hot and subjected to long-term static annealing followed by a single cold rolling, it presents in thickness 0.50 mm and 0.65 mm, a noticeable reduction in mass losses and an improvement in the ability to magnetize.

For thickness 1 mm, static annealing before cold rolling increases magnetization ability with, in contrast, a degradation of losses.

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

That annealing of elimination of tensions due to cutting, causes a significant reduction in losses no degradation of the ability to magnetize, with static annealing of the hot rolled strip and then cold rolled in a single operation

Claims (3)

1. Sheet metal fabrication procedure magnetic non-oriented grains comprising the stages that its about:

-

make a steel of the following composition under vacuum:

carbon < 0.01%

silicon < 0.5%,

manganese 0.05 to 0.5%

aluminum < , 03%,

match < 0.20%,

sulfur < 0.015%,

nitrogen < 0.01%,

oxygen < 0.01%,

the rest being iron and inevitable impurities,

-

 put on steel in the form of ingot,

-

hot rolling the ingot with a heating temperature below 1300 ° C, a temperature at the end of hot rolling below 950 ° C,

-

wind the hot rolled strip at a temperature above 550 ° C,

-

subject the coil web to static annealing at a temperature between 700 and 1050 ° C for more than 1 time hour,

-

subject the annealed belt to an optional blasting operation with shot

-

subject the band annealed and eventually shot blasting, to a pickling operation, and then

-

cold strip the stripped strip, with a reduction rate between 25 and 90%, in a single rolling operation in cold to a thickness less than or equal to 1.5 mm,

-

subject the cold rolled strip to a final annealing performed in the parade, and then

-

cut the band to form plates, and subject said plates to a Stress removal annealing.

2. Method according to claim 1, characterized in that the final annealing in the parade is carried out at a temperature between 700 and 1050 ° C for a time less than 10 mn. 3. A method according to claim 1 or 2, characterized in that the annealing of stress elimination is carried out at a temperature greater than 650 ° C for a time greater than 3 mn.