DE102005004037B3 - Preparation of steel band or sheet having low magnetic losses combined with good magnetizability useful in electromagnetic applications by dipping a starting substrate in hypereutetice (Si,Al) melt in non-oxidizing atmosphere - Google Patents

Abstract

Preparation of steel band or sheet having low magnetic losses conbined with good magnetizability by dipping a starting substrate in hypereutetice (Si,Al) melt at less than 950[deg]C in non-oxidizing atmosphere to give (Si,Al) coating and enrichment of (Si,Al) in surface region of band or sheet, with partial or complete stripping off of excess melt after dipping with cold rolls at less than 400[deg]C to the end thickness and final glow treatment at more than 700[deg]C in the non-oxidizing atmosphere.

Description

The The invention relates to a method for producing FeSi tape or Boards with higher Held on silicon, homogeneously distributed or as gradient material, in the range of 0.10 to 1 mm thickness for electromagnetic applications.

Usually be for the production of non-grain oriented electrical steel FeSi steels used their Si contents are at most 3.5 wt .-%. Such limited Si contents having FeSi steel alloys allow trouble-free production on the usual melt metallurgical production route. In particular, is through a restriction of the Si content to contents ≤ 3.2 Weight% ensured that in conventional procedure the obtained sheet is free of cracks after cold rolling.

in the In the course of conventional manufacturing, after the melting of the Steel alloy the melt to a slab or thin slab shed. This raw material is then in direct use without reheating or after a cool down and a reheating in a hot rolling process consisting of a descaling, a rough rolling and a finished hot rolling carried out in a generally multi-stand hot rolling mill rolled to a hot strip. The hot strip is then one usually carried out as a pickling surface treatment subjected to a glow (Hot strip annealing) combined can be. A hot strip annealing before the hot strip is cold rolled to cold strip, can also after take the cold rolling. After all the ribbon is finally annealed or a glow with following Subjected to post-deformation.

Nice at Si contents of more than 3.2 wt .-%, first difficulties during cold rolling in the form of high rolling forces and increasing Susceptibility to cracking. Thus, cold rolling of FeSi alloys with FeSi contents occurs more as 3.5 wt .-% produced hot strips (conventional metallurgical manufacturing route) regularly cracks on that the production of a high quality electric sheet product with thicknesses ≤ 0.75 mm above exclude the conventional manufacturing process.

The Difficulty in the production is opposite, that the increase of Si content to an increase of electrical resistance and thus to a lowering of the magnetic losses in use leads. For a range of applications, especially for used in audio, video, data processing and medical technology Small and very small machines also for Drives and for Magnetic cores in electromagnetic applications with higher frequencies work, are therefore ribbons or sheets of FeSi alloys having Si contents in the range of 3.0% to 7.0% by weight of particular interest. Here, the higher Si content over both the entire cross section of the tape or the panel as well as advantageous only one Area near the surface of the band or the panel (gradient material) be pronounced.

FeSi materials with an Si content of approximately 6.5% by weight are on available on the market. The production of these products takes place by way of a chemical Deposition of a highly-silica FeSi layer on a conventional electrical steel strip and a subsequent diffusion annealing. On Although this can be done in conventional production difficulties encountered by high silicon content sheets avoid. However, additional work steps are required which complicate the production and make it more expensive.

In the scientific literature there are numerous papers in which the forming behavior of FeSi alloys with Si contents of more than 3.2 wt .-% investigated and the possibilities of producing such a steel have been considered in the usual metallurgical way. Such is from the German patent specification DE 102 20282 C1 a method is known, which allows, with suitably chosen technology of hot rolling and the subsequent cold rolling process steels of the type discussed above on a melt metallurgical way without the occurrence of cracks. According to DE 102 20 282 C1 For the manufacture of a cold-rolled steel strip or sheet for electromagnetic applications in thicknesses ≤ 0.70 mm, a steel containing (in% by weight) C: <0.01%, Si: 3.2-7%, Al <2%, Mn: ≤ 1%, remainder containing iron and common impurities, potted after melting into a raw material such as a slab, a thin slab or a thin strip. Then the material at a temperature T _R> is heated to 1000 ° C and finished hot rolled at a final hot T _F of> 800 ° C into a hot strip. This hot strip is then cooled starting from a temperature of at least 750 ° C, but less than 850 ° C T _{C of} the hot strip with a at least 400 ° C / min cooling rate .DELTA.T / .DELTA.t to a temperature less than 300 ° C, after Cooling one Surface treatment such as a mechanical descaling and / or pickling, cold rolled after this surface treatment at a maximum of 500 ° C temperature T _cR and finally final annealed.

The above summarized, in the DE 102 20 282 C1 described Herstellungsweg is characterized in that a complex technological procedure before cold rolling is required. This approach places extremely high demands on the realization of this special type of hot rolling to ensure high output with high quality.

• – Ros-Yänez T., Y. Houbaert and M. De Wulf: "Evolution of magnetic properties and microstructure of high-silicon steel during hot dipping and diffusion annealing", IEEE Transactions on Magnetics, Vol. 38, No. 5, September 2002, pp. 3201-3203, ISI/IF:0.720,
• – Ros-Yänez T., Y. Houbaert and V.Gomez Rodriguez: "High-silicon steel produced by hot dipping and diffusion annealing", Journal of Applied Physics, vol. 91 no. 10 (2002),
• – Y. Houbaert. T. Ros-Yänez and M. Prado, Materials Science Forum vols 373-376 (2001), pp 733-736,
• – Houbaert, Y, Colas R, Barros J, Ruiz D, Vandenberghe R, De Wulf M, Ros-Yänez T: "Advances on the characterization of high-silicon steel for electrical applications produced by thermomechanical and dippingannealing treatment", MATERIALS SCIENCE FORUM 426-4 (2003) pp. 1145-1150,
• – Ros-Yänez T., D. Ruiz, J. Barros and Y. Houbaert: "Advances in the production of high-silicon electrical steel by thermomechanical processing and by immersion and diffusion annealing", Journal of Materials and Compounds Vol 369/1-2 (2004) pp 125 – 130,
• – EP 1 260 598 A1
• – WO 04029318 A1
• – WO 04044252 A1
• – Ros-Yänez T., M. De Wulf and Y. Houbaert: "Influence of the Si and Al gradient on the magnetic properties of high-Si electrical steel produced by hot dipping and diffusion annealing", JMMM (2004),

beschrieben.As an alternative route to the production of higher-silica FeSi strips or sheets, the process path can be considered by applying a (Si, Al) layer to a substrate made of conventionally produced electrical steel sheet and subsequent diffusion annealing. Corresponding procedures are each in

• Ros-Yänez T., Y. Houbaert and M. De Wulf: "Evolution of magnetic properties and microstructure of high-silicon steel during hot dipping and diffusion annealing", IEEE Transactions on Magnetics, Vol. 5, September 2002, pp. 3201-3203, ISI / IF: 0.720,
• - Ros-Yänez T., Y. Houbaert and V. Gomez Rodriguez: "High-silicon steel produced by hot dipping and diffusion annealing", Journal of Applied Physics, vol. 91 no. 10 (2002),
• - Y. Houbaert. T. Ros-Yänez and M. Prado, Materials Science Forum vols 373-376 (2001), pp 733-736,
• - Houbaert, Y, Colas R, Barros J, Ruiz D, Vandenberghe R, De Wulf M, Ros-Yänez T: "Advances in the characterization of high-silicon steel for electrical applications produced by thermomechanical and dipping annealing treatment", MATERIALS SCIENCE FORUM 426-4 (2003) pp. 1145-1150,
• - Ros-Yänez T., D. Ruiz, J. Barros and Y. Houbaert: "Advances in the production of high-silicon electrical steel by thermo-mechanical processing and by diffusion and diffusion annealing", Journal of Materials and Compounds Vol 369/1 -2 (2004) pp 125-130,
• - EP 1 260 598 A1
• - WO 04029318 A1
• - WO 04044252 A1
• - Ros-Yänez T., M. De Wulf and Y. Houbaert: "Influence of the Si and Al gradient on the magnetic properties of high-Si electrical steel produced by hot dipping and diffusion annealing", JMMM (2004),

described.

disadvantage the ways outlined in these references are in addition to one huge procedural effort in particular the poor surface finish and the high roughness of the bands or panels, which is especially in the case of electrical sheet as a substrate in thicknesses ≤ 0.35 mm whose usability in electromagnetic devices severely impaired. Furthermore, the tapes or sheets produced in this way are difficult to machine compared to conventional electrical steel and process, which in its use a significant cost factor represents.

• – Wahl eines geeigneten Substratmaterials bestehend aus einer FeSi-Legierung in Bandform oder als Tafel mit einer Dicke von > 0,1 mm als Substratmaterial,
• – Tauchen des Bandes bzw. der Tafeln, gefertigt auf konventionellem, schmelzmetallurgischen Weg mit einer gegebenen Dicke d, in einer hypereutektischen (Si,Al)-Schmelze) bei Temperaturen kleiner als 950 °C und beim Vorhandensein einer nichtoxidierenden Atmosphäre,
• – Herausnehmen des Bandes bzw. der Tafel nach einer Reaktionszeit von ≤ 30 sec. aus der Schmelze und Entfernen der Schmelze vom Band durch ein geeignetes Verfahren, wie zum Beispiel Abstreifen,
• – Abkühlen des Bandes auf Raumtemperatur, wobei die Abkühlung vorteilhaft extrem rasch mit einer Abkühlrate ΔT/Δt > 400 °C/min erfolgt, auf Temperaturen unterhalb von T ≤ 400 °C,
• – Kaltwalzen des Substrates bei Temperaturen T ≤ 400 °C auf Enddicken des Bandes bzw. der Tafeln im Bereich von 0,10 bis 0,75 mm,
• – Stanzen von Formteilen oder Segmenten des kaltgewalzten Materials,
• – Glühbehandeln der gestanzten Teile oder des kaltgewalzten Materials bei Temperaturen oberhalb 700 °C in einer nichtoxidierenden Atmosphäre.

Based on the above explained prior art, the object of the invention to provide a simplified feasible method for producing intended for electromagnetic applications, easy to process, made of FeSi alloys tapes and sheets, the thicknesses of 0.10 mm to 1.00 mm and over their entire cross section or only in the region of their surface have an increased (Si, Al) content, the obtained steel product over the prior art have technological advantages in its production, an improved surface finish, especially a low roughness, have and no or only minor problems with respect to the processing and processing should occur. In order to achieve the above-mentioned objects, the invention proposes a method for the production of magnetic tape or sheets for electromagnetic applications in which the following steps are carried out:

• Choice of a suitable substrate material consisting of a FeSi alloy in strip form or as a board with a thickness of> 0.1 mm as the substrate material,
• Dipping the strip or plates made by a conventional melt metallurgical route of a given thickness d, in a hypereutectic (Si, Al) melt) at temperatures lower than 950 ° C and in the presence of a non-oxidizing atmosphere,
• Removing the strip or slab from the melt after a reaction time of ≦ 30 seconds and removing the melt from the strip by a suitable method, such as stripping,
• Cooling the strip to room temperature, the cooling taking place advantageously extremely rapidly with a cooling rate ΔT / Δt> 400 ° C./min, to temperatures below T≤400 ° C.,
• Cold rolling of the substrate at temperatures T ≦ 400 ° C. to final thicknesses of the strip or sheets in the range from 0.10 to 0.75 mm,
• Punching of molded parts or segments of the cold-rolled material,
• Annealing the stamped parts or the cold rolled material at temperatures above 700 ° C in a non-oxidizing atmosphere.

The Type of removal of the tape or the slab from the melt can depending on the type of realization by pulling out - in the case a diving - or by determining the residence time in the bath with continuous movement of the tape done by the bath.

Of the The invention is based on the idea of the method step "application a highly silicated layer "in the known production of non-oriented final annealed electrical steel to integrate.

technological Advantages occur through the omission of the additional process step "diffusion annealing" after application the layer on an already final annealed electrical strip as a substrate one.

On the material side was an improvement in surface roughness as well as the magnetic Properties by cold rolling after application of Si-rich Layer reached.

Further A way was found, the punching of moldings or segments to realize before the diffusion of silicon into the material, for this höhersiliziertes Base material naturally causes problems the processing and processing occur.

• i) Si: 1,8 – 3,5 Gew.-%, Al: < 1,5 Gew.-%; oder
• ii) Si: 0 – 1,8 Gew.-%, Al: < 1,7 Gew.-%

verwendet werden.In this case, a steel with contents of Si and Al of the type:

• i) Si: 1.8-3.5 wt%, Al: <1.5 wt%; or
• ii) Si: 0-1.8% by weight, Al: <1.7% by weight

be used.

• i) ein schlussgeglühtes, in der Fachsprache auch als "fully finished" bezeichnetes Elektroband,
• ii) ein nicht schlussgeglühtes, in der Fachsprache auch als "semi finished" bezeichnetes Elektroband,
• iii) warmgewalztes Band oder warmgewalzte Tafeln, vorteilhaft mit Dicken ≤ 1,5 mm; oder
• iv) kaltgewalztes Warmband

handeln.The strip used as the substrate material with the above composition and produced by the conventional molten metallurgical route or in the likewise obtained boards used as the substrate material may be

• i) a final annealed, in technical language also referred to as "fully finished" electrical steel,
• (ii) a non-final annealed electrical steel, also referred to in technical language as semi-finished;
• iii) hot rolled strip or hot rolled sheets, advantageously with thicknesses ≤ 1.5 mm; or
• iv) cold rolled hot strip

act.

• i) eine Gesamtabnahme ε von < 2 %,
• ii) eine Gesamtabnahme von 2 % < ε ≤ 20 % oder
• iii) eine Gesamtabnahme von 30 % < ε ≤ 82

erreicht wird.The chosen total decrease during cold rolling can be chosen according to the desired final thickness and with a suitable choice of the thickness of the substrate so that

• i) an overall decrease ε of <2%,
• ii) an overall decrease of 2% <ε ≤ 20% or
• iii) an overall decrease of 30% <ε ≤ 82

is reached.

Surprised it has been shown that cold rolling of the in the (Si, Al) melt submerged tape or panels possible is and at the same time a good surface finish or low Roughness of the strip or sheets with a homogeneous distribution of the Si over the cross section, as in the case of an inhomogeneous distribution of the Si over the cross-section (gradient material), after the final annealing treatment can be achieved.

On the other hand is the band or plates after diving and immediately after annealing at the bottom the resulting high Si content in the material not or only very difficult cold rolling.

In addition, as described above, moldings or segments after the application of a Make layer on the substrate and then cold rolling finished (eg by cutting, punching, etc.), which are then subjected to a final annealing to the expression of the final properties. This can reduce the problems of processing and the resulting disadvantages especially for steels with very high Si contents.

On the other hand is a conventional processing, such as punching, on the on the well-produced, highly silicided, the fully processed Material not or only under extreme conditions that are not economical Allow production, possible.

short Times of ≤ 25 sec for immersion in the hypereutectic (Si, Al) melt is sufficient, to apply a silicon-rich layer of 30 to 100 microns on the tape.

Advantageous is the melt with a gas veil of a non-oxidizing Gas or gas mixture covered.

The Temperature of the substrate before immersion in the melt should be at the most be equal to the temperature of the melt, but preferably smaller.

The process step "Immersion in a (Si, Al) -rich melt" can advantageously be designed so that the formation of a DO ₃ layer of appreciable thickness directly on the substrate is avoided. The reason is that this layer is difficult to form. Conveniently, this proves a rapid cooling after dipping in the melt by short dipping times of ≤ 0.25 sec and subsequent cooling after removal with ΔT / Δt ≥ 400 ° C / min to temperatures of ≤ 400 ° C.

In the outer layer with a (Si, Al) content up to 12.6 wt .-% is also the possible occurrence of Si precipitates with "larger diameter" by appropriate Choice of process parameters, such as the immersion time in to avoid the melt.

The Cold rolling can also be done as hot cold rolling with temperatures T ≤ 400 ° C.

following The invention will be explained in more detail with reference to embodiments.

It shows 1 schematically a variant of the method, in which a steel strip A is unwound as a starting substrate of a coil C and passed at a conveying speed v through a formed by a Si / Al melt hot dip T in a continuous process. The strip coated in this way is pulled out of the hot-dip bath T at a time dependent on the conveying speed v and the immersion distance traveled in the bath T and fed to further processing not shown here.

2 on the other hand, also schematically shows a discontinuous process in which sheets are separated by transverse cutting by means of a pair of scissors Q from the respective steel strip A. The panels L are then immersed for a certain immersion time in the hot dip T, which in turn is formed by a Si / Al melt. In Table 1, the compositions of steels "FeSi1,3", "FeSi2,4" and "FeSi3,2" are indicated, from which the steel strips A have been made according to one of the methods described in U.S. Pat 1 or 2 have been treated.

Tabelle 1

Table 1

Examples of treated tapes produced according to the production routes described can be found in Tables 2 and 3 reproduced below. The magnetic characteristics given there relate to measurements on strips (longitudinal samples). These values are therefore not mixed values. With B ₂₅ the value of the magnetic induction B at H = 2500 A / m, with B ₁₀ the value of the magnetic induction B at H = 1000 A / m and with P _1.0 the value of the magnetic losses P at B = 0.1 T and 50 Hz.

Tabelle 2 Homogene Si-Verteilung für unterschiedliche Ausgangssubstrate

Table 2 Homogeneous Si distribution for different starting substrates

Tabelle 3 Inhomogene Si-Verteilung für unterschiedliche Ausgangssubstrate

Table 3 Inhomogeneous Si distribution for different starting substrates

The Difference in terms of a classification of the end products in electrical steel with homogeneous and inhomogeneous distribution (gradient material) of silicon diagrams Diag. 1 to Diag. 3, of which the diag. 1 the element distribution E in the starting substrate FeSi1,3, the diag. 2 a homogeneous element distribution E corresponding to the sample FeSi1,3 according to table 2 and Diag. 3 an inhomogeneous element distribution E corresponding to Sample FeSi1,3 according to table 3 each applied over the referred sheet thickness Bd shows. The value "0.0" of related sheet thickness Bd corresponds to the top of the respective Substrate (steel strip A or derived from panel L), during the Value "1.0" for the bottom the respective substrate is.

Claims (20)

Method of making tape or sheets with low magnetic losses and good magnetizability by dipping a starting substrate of thickness d in a hypereutectic (Si, Al) melt at temperatures lower than 950 ° C and in the presence of a non-oxidizing atmosphere for coating with (Si, Al) and enrichment of (Si, Al) in the near-surface Band or panel area, complete or partial stripping the excess melt after dipping the tape or the board by a suitable Followed by cold rolling at temperatures below 400 ° C on the final thickness and a final annealing treatment at temperatures above 700 ° C in a non-oxidizing atmosphere. Method according to 1, characterized in that the Tape or panels have a thickness of 0.10 mm to 1 mm. Method according to one of the preceding claims, characterized marked that in addition from the strip or the panels molded parts by a suitable shaping, such as As stamping, after the cold rolling and before the final annealing be made. Method according to one of claims 1 to 3, characterized in that a formation of a DO ₃ layer between the substrate and the (Si, Al) -rich FeSiAl layer by a short immersion time in the dipping bath of t ≤ 0.25 sec and a rapid Cooling after removal from the dipping bath with ΔT / Δt ≥ 400 ° C / min to a temperature ≤ 400 ° C is almost avoided. Method according to one of Claims 1 to 4, characterized that after the annealing treatment gives a gradient material, characterized in that the (Si, Al) -rich layer on the top and bottom of the tape or the panel a thickness <d / 2 has. Method according to claim 5, characterized in that that the (Si, Al) -rich Layer on the top and bottom of the tape or board a thickness ≤ d / 4 has. Method according to one of claims 1 to 6, characterized that the roughness of the annealed sheet or the board is ≤ 5 μm. Method according to claim 7, characterized in that that the roughness of the annealed Sheet or table below ≤ 1.5 μm. Method according to one of claims 1 to 8, characterized, that to improve the magnetic losses as a starting substrate a steel with contents (in% by weight) Si:> 1.8 - 3.5 Al: <1.5 used becomes. Method according to one of claims 1 to 8, characterized, that For a good combination of magnetic loss and magnetizability as starting substrate a steel, with contents of (in% by weight) Si: ≤ 1.8 Al: <1.7 used becomes. Method according to one of claims 1 to 10, characterized in that the dipping of the starting substrate takes place in a (Si, Al) melt with additives. Method according to claim 11, characterized in that that the additions the group of elements "Sn, Sb "come from. Method according to one of claims 1 to 12, characterized that one already finally annealed Electric tape (fully finished electrical steel) in the thickness range of 0.35 mm to 1 mm is used as a substrate. Method according to one of claims 1 to 13, characterized that a not finally annealed Electrical steel (semi-finished electrical steel) in the thickness range of 0.35 mm to 1 mm is used as a substrate. Method according to one of claims 1 to 14, characterized that a hot strip with thicknesses ≤ 1.5 mm is used. Method according to one of claims 1 to 15, characterized that a cold-rolled hot strip in the thickness range of greater than 0.10 mm is used as a substrate. Method according to one of claims 1 to 16, characterized that the cold rolling after immersing the starting substrate in a silicon-rich (Si, Al) melt used to smooth the surface becomes. Method according to claim 17, characterized in that that the cold rolling does not exceed a total decrease ε of 2%. Method according to one of claims 1 to 16, characterized that the cold rolling after immersing the starting substrate in a silicon-rich (Si, Al) melt with an overall decrease ε of 2% ≤ ε ≤ 20%. Method according to one of claims 1 to 16, characterized that the cold rolling after immersing the starting substrate in a silicon-rich (Si / Al) melt with an overall decrease ε of 30% <ε ≤ 82% occurs.