EP2675927A1

EP2675927A1 - Method for producing a grain-oriented flat steel product

Info

Publication number: EP2675927A1
Application number: EP11761066.7A
Authority: EP
Inventors: Eyup DUMAN; Christof Holzapfel; Thorsten KRENKE; Ludger Lahn; Régis Lemaitre; Chaoyong Wang; Thierry BELGRAND
Original assignee: ThyssenKrupp Electrical Steel GmbH
Current assignee: ThyssenKrupp Electrical Steel GmbH
Priority date: 2011-02-14
Filing date: 2011-09-22
Publication date: 2013-12-25
Anticipated expiration: 2031-09-22
Also published as: JP2014512453A; MX367050B; CN103429767A; KR101581878B1; PL2675927T3; US20140034193A1; BR112013019877A2; KR20130114246A; JP5822243B2; CN103429767B; MX2013009016A; ES2759823T3; EP2675927B1; DE102011000712A1; RU2013138224A; BR112013019877B1; RU2547377C2; WO2012110111A1

Abstract

The invention relates to a method for producing a grain-oriented flat steel product that is intended for the manufacture of parts for electrotechnical applications and has minimized magnetic loss values and optimized magneto-restrictive properties, said method comprising the work steps of a) providing a flat steel product, and b) laser-treating the flat steel product, wherein, in the course of the laser treatment, linear deformations, which are arranged with a spacing a, are molded into the surface of the flat steel product by means of a laser beam emitted by a laser radiation source with a power P. The method according to the invention for producing flat steel products is optimally suitable for the manufacture of parts for transformers. This is achieved in that the apparent power S1.7/50 of the flat steel product before and after the laser treatment (operation b)), determined at a frequency of 50 Hertz and a polarization of 1.7 Tesla, is measured, and in that the parameters of the laser treatment are varied in such a way that the difference between the apparent power S1.7/50 measured before and after the laser treatment is less than 40%.

Description

Method for producing a grain-oriented

Flat steel product

The invention relates to a method for producing a grain-oriented flat steel product with minimized magnetic loss values and optimized

magnetostrictive properties.

In the case of the grain-oriented ones in question here

Flat steel products, also referred to in technical language as "HGO material", are steel strips, in technical language simply also "electrical tapes", or

Steel sheets, in technical language also simple

Called "electrical sheets". From such flat steel products parts are manufactured for electrical engineering applications.

Grain-oriented electrical steel or sheet is particularly suitable for applications in which a particularly low loss of magnetization is in the foreground and high demands are placed on the permeability or polarization. Such requirements exist

especially parts for power transformers, distribution transformers and higher quality

Small formators.

As explained in detail, for example, in EP 1 025 268 B1, is generally in the course of the production of

SI / cs 100859WO September 2011 Steel flat products, first of all a steel containing (in% by weight) typically 2.5 to 4.0% Si, 0.010 to 0.100% C, up to 0.150% Mn, up to 0.065% Al and up to 0.0150% N, and each optionally 0.010 to 0.3% Cu, to 0.060% S, to 0.100% P, to 0.2% each of As, Sn, Sb, Te, and Bi, balance iron and unavoidable impurities, to a starting material, such as a Slab, thin slab or a cast strip, potted. The starting material is then subjected, if necessary, to an annealing treatment to be subsequently hot rolled into a hot strip.

After reeling and an optional addition

performed annealing as well as one as optional

Completed Ent zunderungs- or pickling treatment is then rolled out of the hot strip in one or more steps, a cold strip, between the cold rolling steps, if necessary, an intermediate annealing can be performed. In the subsequently performed

Decarburization annealing is usually significantly reduced to avoid magnetic aging of the carbon content of the cold strip.

After decarburization annealing, an annealing separator, which is typically MgO, is applied to the strip surfaces. The annealing separator prevents the turns of a coil wound from the cold strip during the subsequent high-temperature annealing

stick together. During the high-temperature annealing, which is typically carried out in a hood furnace under protective gas, the texture is created in the cold strip by selective grain growth. Further, forms on the

Band surfaces a Forsteritschicht, the so-called

SI / cs 100859WO September 2011 "Glass Film", off. In addition, the steel material is cleaned by diffusion processes occurring during the high-temperature annealing.

Following the high-temperature annealing, the steel flat product thus obtained is coated with an insulating layer, thermally directed and in one

final "final annealing" low-stress annealed.

This final annealing can be done before or after

Assembling of the steel flat product produced in the manner described above to those for the

Further processing required blanks take place, which can be reduced by a final annealing after Äbteilen the blanks incurred during the Abteilvorgangs additional stresses. So generated

Flat steel products generally have a thickness of 0.15 mm to 0.5 mm.

The metallurgical properties of the material that set in the production of flat steel products

Forming degrees of the cold rolling processes and the parameters of the heat treatment steps are each coordinated so that targeted recrystallization processes occur. These recrystallization processes lead to the typical for the material "Goss texture", in which the direction of the easiest magnetization in

Rolling direction of the finished strips lies. grain-oriented

Accordingly, flat steel products have a strongly anisotropic magnetic behavior.

There are various ways of improving the core losses of a grain-oriented flat steel product

SI / cs 100859WO September 21, 2011 Methods. For example, the orientational sharpness of the Goss texture of the flat steel product can be improved.

Further loss reductions can be achieved by reducing the spacings of the 180 ° domain walls. High tensile stresses in the rolling direction, which are transferred to the steel surface via insulating coatings, also contribute to the reduction of the domain distances and concomitantly to the reduction of the

Magnetic losses at. However, the required tension values are only for technical reasons

restricted feasible.

A example in DE 18 04 208 Bl or the

EP 0 409 389 A2 proposed further possibility of loss improvement is that on the surface of the flat steel product partial plastic deformations are generated. This can be done for example by a

mechanical scoring or piercing of the surfaces of the respective flat steel product. The significant improvements achieved in this way

magnetic properties has the disadvantage that the mechanical treatment of the surface, the applied insulating layer of the flat steel product is damaged. This can, for example, in the case of the production of transformer plates from such

Steel flat product cause short circuits in the stacked core of the transformer as well as localized corrosion.

Attempts to take advantage of mechanical scoring or piercing without destroying the insulation have relied on the use of laser sources

concentrated (EP 0 008 385 B1, EP 0 100 638 B1,

SI / cs 100859WO September 21, 2011 EP 1 607 487 A1). The common use of laser-based methods is that a laser beam focuses on the surface of the flat steel product to be treated, where it undergoes thermal stress in the material

Basic material is generated. This leads to the formation of dislocations, involving components of the magnetic

River from the surface of the flat steel product

escape. As a result, the magnetic stray field energy is locally raised, to compensate for the formation of so-called "termination domains" takes place in the

Technical terminology can also be referred to as "secondary structures". At the same time, there is a reduction of

Main domain spacing.

Since the abnormal core loss depends on the distance of the main domains, the losses are minimized by a suitable laser treatment. By the

In laser treatment, the loss of magnetization of a grain-oriented flat steel product with a typical nominal thickness of 0.23 mm for these products can be improved by more than 10% compared to the untreated state. The loss enhancements depend both on the properties of the base material, such as the grain size and texture sharpness, and on the laser parameters, to which the distance L of the lines along which the

Laser beams are guided to the respective _flat steel _{product, the} contact time t _dW eii and the specific

Energy density U _s belong. The tuning of these parameters has a decisive influence on the respectively achieved reduction of the re-magnetization losses.

SI / cs 100859WO September 2011 In addition to the Ummagnetisierungsverlusten plays

Transformers also the noise a role. This is based on a known as magnetostriction physical effect.

Magnetostriction is the change in length of a

ferromagnetic material in the direction of his

Magnetization. By operating a ferromagnetic component, such as a transformer, in an alternating magnetic field, the 180 °

Main domains shifted, which alone, however, does not contribute to the magnetostriction. However, there are transitions between the 180 ° main domains to the 90 °

Termination domains magnetostrictive tension in the

Material. These form during operation in the magnetic

Alternating field a sound source and are the cause of the transformer noise.

The introduction of additional 90 ° termination domains, ie of secondary structures, by laser treatment generally leads to an increase in the magnetostriction and thus the noise emissions, in particular during operation of a transformer.

The demands made on minimizing noise in the operation of transformers are constantly increasing. On the one hand, this is due to continuously tightened legal requirements and standards. On the other hand, consumers today generally no longer accept electrical appliances that cause an audible "transformer drone". So today depends the acceptance of large transformers in the vicinity

SI / cs 100859WO September 2011 of residential development is crucially dependent on the noise emissions resulting from the operation of such transformers.

There are a number of laser treatment processes

have been proposed, which can be achieved by selecting suitable process parameters both loss improvements and better magnetostrictive properties (DE 601 12 357 T2 / EP 1 154 025 Bl, DE 698 35 923 T2 /

EP 0 897 016 B1, EP 2 006 397 A1, EP 1 607 487 A1). However, the optimization of the parameters of the laser treatment has in each case been undertaken only with a view to improving the re-magnetization losses.

Against the background of the prior art discussed above, the object of the invention was to provide a method for producing flat steel products, which are optimally suitable for the production of parts for transformers.

This object has been achieved according to the invention, that in the production of a flat steel product, the operations specified in claim 1 are performed.

Advantageous embodiments of the invention are specified in the dependent claims and are explained below as the general inventive concept in detail.

In accordance with the prior art discussed above, a method of the invention for producing a grain-oriented flat steel product having minimized magnetic loss values and optimized magnetostrictive properties comprises the operations

SI / cs 100859WO September 2011 a) providing a flat steel product,

and

b) laser treatment of the flat steel product, wherein in the course of the laser treatment in the surface of the

Flat steel product by means of a laser beam emitted with a power P from a laser beam line deformations are formed, which are arranged at a distance L.

Special requirements for the way the

Production of the flat steel product provided according to step a) does not exist. Thus, the provided for the inventive method

Flat steel product using those skilled in the art

Well-known, initially summarized measures and are made on the basis of suitable steel alloys, which are known from the prior art

also already well known. Of course, this also includes such manufacturing processes and alloys that are not yet known.

According to the invention, the parameters of

Laser treatment {step b)) adjusted so that a steel flat product produced according to the invention not only has minimized Ummagnetisierungsverluste, but also given his after laser treatment

Apparent power Si _{> 7/50} AFTER is optimized.

For this purpose, the invention in a

Frequency of 50 hertz and a polarization of 1.7 Tesla apparent power Si, ₇ so that with the laser beam to

SI / cs 100859WO September 21, 2011 treated steel flat product before and after the

Laser treatment (step b)) recorded.

Depending on the difference between the apparent power Si, _{7 5} o VOR detected before the laser treatment and the apparent power detected after the laser treatment

Si, 7 / 5o NACH then the parameters of the laser treatment are varied so that the difference between the respectively detected before and after the laser treatment apparent power Si, ₇ is less than 40%.

The parameters of the laser treatment are thus

According to the invention adjusted so that an increasing in the course of the laser treatment increase in

Apparent power Si _/ 7/50 of a processed according to the invention flat steel product by adjusting the parameters of the laser treatment is limited so that after the

Laser treatment detected apparent power Si, so NACH meets the following condition:

Sl, 7/50 AFTER <1.4 X Sl ₍ 7/50 VOR

Accordingly, the increase in apparent power caused by the laser treatment is so limited in the present invention that the apparent power after the laser is not more than 40% as compared with its value at the same time

Workpiece is increased before lasing.

The invention thus takes into account that in the design transformers usually not the

Correction losses of each processed

Steel flat products in the foreground, but the apparent power. Therefore, according to the invention, the parameters

SI / cs 100859WO September 2011 the laser treatment not only in terms of

Core losses but also on the

Apparent performances optimized for the same polarization.

The subject of the method according to the invention is thus an optimization of the laser parameters with regard to

Minimization of the magnetization loss Pi, _{7 /} so and the apparent power Si _{i7 / 5} o. It turned out that minimizing the apparent power minimizes the noise increase. This means that the laser treatment, although superficially causes the refinement of the main domains, which leads to the desired loss reduction, but so that by the inventive

Optimization of the laser treatment with regard to the lowest possible apparent power is accompanied by a comparatively small increase in the volume ranges with secondary magnetic structures.

In principle, it is conceivable to start the laser treatment

Make electrical sheets or sheet metal blanks.

However, it proves to be particularly practical when a flat steel product present as strip material

is processed, the laser treatment in the

passes through continuous passage.

In the case that the respective apparent power Si, _7/50 before and after the laser treatment during operation is recorded online and the parameters of the laser treatment as a function of the difference of the detected

Apparent performances Si _{/ 7} can be varied online, so it is possible to react to changes in the result of the laser treatment in a particularly timely manner.

SI / cs 100859WO September 2011 However, it is also possible to perform the detection of the apparent power before and after the laser treatment as well as the calibration of the laser parameters decoupled in time. This can be done at certain intervals

Samples of the flat steel product to be taken, be determined according to the laser treatment and the parameters of the laser treatment, depending be varied from the result of this detection to these samples, the respective apparent power Si _(7/5 o before and. This configuration allows the inventive method having a comparable

Execute process and measurement technology.

As parameters that can be varied with regard to the optimization of the results of the laser treatment, for example, the distance L of the linear deformations, the exposure time t _dwe ii of the laser beam, the specific energy density U _s , the laser power P, the focus size As or the scan speed come v _so in question.

Practical experiments have shown that it is for

Achieving optimum apparent power Si ₎ may be appropriate, the distance L of the line-shaped deformations in the range of 2 - 10 mm, in particular 4-7 mm, too

vary .

Likewise, a minimization of the change in the apparent power Si _7/50 that occurs via the laser treatment can be achieved in that the exposure time t _dw ii of the

Laser beam is varied in the range of 1 x IGT ⁵ s to 2 x KT ⁴ s.

SI / cs 100859 O September 2011 In the case that a fiber laser is used as the laser source, the laser power P in today available fiber lasers in order to minimize the onset of the laser treatment change in the

Apparent power Si _{/ _7/5} ° in the range of 200 - 3000 W can be varied. Fiber lasers have the particular advantage here of allowing close focusing of the laser beam. Thus, track widths of less than 20 μm can be achieved with a fiber laser.

However, it is also possible to carry out the method according to the invention as a laser source

C02 ~ laser to use. Due to the fact that with such a laser the laser beam can not be so strongly focused, here at the today's available

standing C0 ₂ lasers, a variation of the laser power P in the range of 1000 - 5000 W in order to minimize the on the laser treatment entering change in the

Apparent power Si, ₇ / so displayed.

Of course, the invention can be

Process preferred on such flat steel products

perform at least one isolation layer. In addition, between the

Insulation layer and the steel substrate of the

Flat steel product, for example, a glass or

Forsteritschicht be present.

To demonstrate the effect of the invention are the following

Examples of a procedure according to the invention

been examined. Show it:

SI / cs 100859WO September 2011 Fig. 1 is a diagram in which the loss improvement

ΔΡι, 7 5ο and apparent power change AeSi are _7/50 plotted against the distance L between the laser tracks;

Fig. 2 is a diagram in which from the measured

Length change calculated noise N as a function of polarization J are shown.

As part of systematic investigations, various parameters of the operational laser device were varied with a 1 kW multimode fiber laser. The parameters to be optimized were the distance L of the laser lines, the

Laser power P, the focus size As and the

Scan speed v _scan

The empirical evaluation of a test matrix showed that variations of the above parameters at

Significant improvements in the Ummagnetisierungsverluste simultaneously can cause drastic changes in apparent power.

As an example, Fig. 1 loss improvement ΔΡι _{) 7/5} ο

(symbolized by filled squares) and

Apparent power change ASi _7/50 (by empty circles

symbolized) as a function of the distance L of

On laser tracks. As a reference are the changes respectively ΔΡι, _7/5 ₀ of the power loss Pi, _{7 /} so and

Change ASi _{(7 50 of} the apparent power Si, _7/50 compared to the un-lasered state, ie the state before the

Laser treatment (step b)) specified.

SI / cs 100859WO September 2011 By varying the focus size As and the

_Scanning speed v _scanr, ie the speed at which the laser is moved, different _times exposure _times t _dwe ii of the laser beam were generated on the surface of the present as strip material _{flat steel product} . The relationship between t _dwe iir As and v _scan can be described as follows: tdwell ^~ As / v _scan

Of 1 x 1CT ⁵ seconds to 2 x 10 ^{~ 4} seconds reaching range of exposure times result in a certain range with equally large improvements in the

Correction losses Pi, ₇ / so in different apparent power changes ASi, _7/50 . It was found that with minimized apparent power changes ASi _<7 / 5o an optimal noise behavior of each treated

Flat steel product.

The following examples show the influence of the reaction time td eii on the loss of magnetization Pi, 7 / so and

Apparent power Si _(7/5 ₀ :

0.23 mm thick steel strips were laser-treated. The _contact time t _dwe ii was varied on the basis of the above-explained relationships.

After measuring the magnetic characteristics, the results summarized in Table 1 below

Changes AP _{1 (7/50} , ASi, _7/5 o of the magnetization losses Pi, 7 / 5o and the apparent power Si, _7/5 o:

SI / cs 100859WO September 21, 2011 Sample P As tdwell ΔΡΐ, 7/50 ASi, 7/50

[W] [mm] [s] [%] [%]

1 900 5 9, 9 * 10- 5 -12 + 70

2 900 5 6, 6 * 10- 5 -13 + 46

3 900 5 3, 3 * 10- 5 -13 + 18

Table 1

The samples were below in terms of their

investigated magnetostrictive properties and calculates the expected noise during operation. A method was used to calculate the noise from the magnetostriction measurements, as described in the IEC Technical Report IEC 62581 TR and in the publication of

E. Reiplinger, "Assessment of grain-oriented transformer sheets with respect to transformer noise", Journal of Magnetism and Magnetic Materials 21 (1980), 257-261.

Fig. 2 shows that from the measured change in length

calculated noise N as a function of polarization J.

The solid curve represents in Fig. 2 the

Reference state before the laser treatment ("without

Laser treatment "), where the measured values that form the basis of this curve, by circles filled with black

are symbolized.

The dashed line whose measured values are characterized by unfilled squares is shown in FIG

Noise development in a laser treatment again, which has led to a change in the apparent power Si, 7 _/ so by + 70%.

SI / cs 100859WO September 2011 - -

The narrower dashed line, whose measured values are characterized by unfilled triangles, reproduces the noise development in a laser treatment in FIG. 2, which leads to a change in the apparent power Si ₍ 7/5 o um

+ 46%.

The dotted line whose measured values are indicated by unfilled circles is shown in FIG

Noise development in a laser treatment again, in which the parameters of the laser treatment have been chosen according to the invention so that the change in the apparent power Si _(7/50 has remained limited to + 18%.

The change ΔΡι achieved with the laser treatment _{| 7/50} of the power loss Pi, _{7 /} as was in each case - 13% compared to the initial state before the laser treatment.

The calculated noise with the invention

achieved, optimized apparent power changes of

AS = + 18% are therefore always smaller than

Starting condition.

If, on the other hand, no attention is paid to the apparent power, a noise increase of 1.1 to 1.5 dB is observed for comparable loss improvements.

From Fig. 2 shows while it is clear that at high

Controllers of the transformer until, for example

1.7 Tesla, the differences in noise emission between a flat steel product treated according to the invention and a conventionally treated flat steel product are only slight. However, they are still there

SI / cs 100859WO September 2011 given systematically. In addition, these differences show up very clearly at a lower level of control

Transformers, so at smaller magnetic

Polarizations.

By optimizing the laser parameters in accordance with the invention such that the difference between the apparent power Si, ₇ measured before and after the laser treatment is less than 40%, it is thus possible on the one hand to obtain a

effective minimization of power losses Pi, ₇ so

On the other hand, but also minimize the noise emission during operation. It is irrelevant whether the inventively carried out comparison of measured before and after the laser treatment values of the apparent power Si, 7 / 5o online churning or in the context of temporally decoupled held calibrations

is carried out.

SI / cs 100859WO September 2011

Claims

PATENT APPLICATIONS

1. A method for producing a grain oriented flat steel product intended for the manufacture of parts for electrical applications with minimized magnetic loss values and optimized

magnetostrictive properties, comprising the

steps

a) providing a flat steel product,

b) laser treating the flat steel product, wherein in the course of the laser treatment in the surface of the flat steel product by means of a with a power P from a laser beam source

emitted laser beam linear

Deformations are formed, which are arranged at a distance a,

characterized,

d a s s determined at a frequency of 50 Hertz and a polarization of 1.7 Tesla

Apparent power Si, _{7/50 of} the _flat steel _product before and after the laser treatment (step b)) is detected and

Thus, the parameters of the laser treatment are so

be varied that the difference between the before

SI / cs 100859WO September 21, 2011 - 2 - and recorded after the laser treatment

Apparent power Si, ₇ is less than 40%.

2. The method of claim 1, d a d u r c h

e n c ia n, the s

Laser treatment in continuous flow

is carried out.

3. The method according to any one of the preceding claims, characterized in that the respective apparent power Si _7/5 o is recorded online before and after the laser treatment during operation and the parameters of the laser treatment in

Dependence on the difference of the detected

Apparent performances Si _/ 7/50 can be varied online.

4. The method according to any one of claims 1 or 2,

d a d u r c h e s e s t e s t e s, s at certain intervals Samples of the

Flat steel product are taken on these samples, the respective apparent power Si, ₇ / 5o is determined before and after the laser treatment and the parameters of the laser treatment are varied depending on the result of this detection.

5. The method according to any one of the preceding claims, characterized in that as parameters of the laser treatment, the distance a of the linear deformations, the _contact time t _dwe ii

SI / cs 100859WO September 2011 - 3 - of the laser beam, the specific energy density U _s , the laser power P, the focus size As or the

Scan speed v _{scan can be} varied.

6. The method of claim 5, d a d u r c h

e g e s e n e, e s the distance a of the line-shaped deformations in the range of

2 - 10 mm is varied.

7. The method of claim 6, d a d u r c h

4 - 7 mm is varied.

8. The method according to any one of claims 5 to 7,

characterized in that the contact time t _d w _e ii of the laser beam in the range of 1 x 10 ^"5 s to 2 x 10 ^{~ 4} s is varied.

9. The method according to any one of claims 5 to 8,

The laser source used is a fiber laser, and the power P is varied in the range of 200-3000 W. In FIG.

10. The method according to any one of claims 5 to 8,

characterized in that a C0 ₂ laser is used as the laser source and the

SI / cs 100859WO September 21, 2011 - 4 -

Power P is varied in the range of 1000 - 5000 W.

Method according to one of the preceding claims, characterized in that the flat steel product is covered with an insulating layer.

SI / cs 100859WO September 21, 2011