EP2252722B1 - Method for producing a grain-oriented magnetic strip - Google Patents

Abstract

A method for producing a grain-oriented magnetic strip, covered with a phosphate layer, comprising applying a phosphate solution, which contains a colloid component and at least one colloid stabilizer as an additive to the magnetic strip.

Description

The invention relates to a method for producing a grain-oriented electrical tape which is coated with a phosphate layer. A phosphate-coated, grain-oriented electrical steel which can be produced by the process of the present invention can be used as a core material in a transformer.

Electrical steel is a well-known material of the steel industry with special magnetic properties. The material usually has a thickness of 0.2 mm to 0.5 mm and is produced by a complex manufacturing process, consisting of cold rolling and heat treatment processes. The metallurgical properties of the material, the degree of deformation of the cold rolling processes and the parameters of the heat treatment steps are 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 the rolling direction of the finished strips.

Base material for electrical steel is a silicon steel sheet. A distinction is made between grain-oriented electrical steel and non-grain-oriented electrical steel. In non-grain oriented electrical steel, the magnetic flux is set to no particular direction, so that it is the same in all directions form good magnetic properties (isotropic magnetization).

Anisotropic electrical steel, on the other hand, exhibits strongly anisotropic magnetic behavior. This is due to a uniform orientation of the crystallites (crystallographic texture). In the case of grain-oriented electrical steel, efficient production of grain growth is carried out by the complex production. Its grains show a nearly ideal texture with a slight misorientation in the final annealed material - the "Goss texture" named after its inventor. The surfaces of electrical steel are usually coated with oxide layers and inorganic phosphate layers. These should act essentially electrically insulating.

Grain-oriented electrical steel is particularly suitable for applications in which it depends on a particularly low loss of magnetization loss and particularly high demands on permeability or polarization are made, as in power transformers, distribution transformers and higher quality small transformers. The main application is grain-oriented electrical steel as a core material in transformers. The cores of the transformers consist of stacked electrical steel panels (lamellas). The electric strip boards are stacked so that the rolling direction with the easiest magnetization is always aligned in the direction of the effective coil magnetic field. As a result, the energy loss in Ummagnetisierungsprozessen in the alternating field is minimal. Due to this connection, the total energy loss of a transformer depends, among other things, on the quality of the electrical tape used in the core. In addition to energy losses, noise generation also plays a role in transformers. This is based on a known as magnetostriction physical effect and is among other things influenced by the properties of the electrical steel core material used.

In order to meet these requirements, on the surface of grain oriented electrical steel is usually provided a two-ply layer system with a ceramic-like layer disposed on the electrical tape (commonly referred to as a glass film) and a phosphate film disposed on the glass film. This layer system is intended to ensure the required for the application in the stack electrical insulation of the slats. In addition to this insulating property, the layer system can also influence the magnetic properties of the core material. By a tensile stress transmitted from the layer system to the base material, the magnetic reversal losses can be lowered again. In addition, the magnetostriction and thus the transformer noise are minimized by the tensile stress. In order to exploit these influences, the layer system usually consists of a glass film and an overlying phosphate layer. Both layers should exert permanent tensile stresses on the metallic core material.

To generate a permanent tensile stress, the phosphate solution of the prior art may contain a colloidal component. The tensile stress is generated by the colloid component, the phosphate itself acts as a binder. Such systems of phosphate solutions / colloids are governed by laws commonly referred to as sol / gel transformation and known in various coating technologies. In the present case, it is advantageous if the sol / gel transition takes place after application of the phosphate solution to the strip surface, ie during the drying process. To ensure this, the combination of a phosphate with a colloid component is not enough. In fact, the sol / gel transition is sensitive to the pH of the solution, to contaminants with foreign substances, especially foreign ions, and to the temperature of use. Especially for large-scale industrial applications, pure phosphate / colloid mixtures are too sensitive in terms of their stability.

In order to provide a method which can be used in a stable manner in practice, the phosphate / colloid mixtures according to the prior art are additionally admixed with an addition of hexavalent chromium, which is usually brought into the solution as chromium trioxide or chromic acid. In the DE 22 47 269 For example, a process based on monoaluminum phosphate and silica sol (colloidal SiO ₂ ) is protected, with 0.2% to 4.5% chromium trioxide or chromate added to find practical application. In the EP 0 406 833 mentions a mixture of several phosphates and different colloids, in turn combined with chromium trioxide. The EP 0 201 228 describes a mixture of magnesium and aluminum phosphate with finely divided SiO ₂ powder. This mixture is also enriched with Cr (VI).

In the prior art, chromium, in particular hexavalent chromium, is used in the phosphatization of electrical steel special importance. In particular, when applying phosphate coatings in large-scale processes and in phosphations which contain a colloid component to optimize the tensile stress, chromium is considered to play an important role. The use of chromium is highlighted in the prior art in particular because hexavalent chromium improves the applicability of the phosphate solution on the strip surface and thus enables the creation of a homogeneous finished strip insulation layer. Furthermore, hexavalent chromium prevents the formation of sticky finished film layers and modifies the interaction of the phosphate solution with the strip material such that no iron goes into solution. This can prevent harmful contamination of the phosphate solution with iron ions. Finally, hexavalent chromium influences the polymerization of the colloidal solution component such that it does not take place until the layer is dried at higher temperatures. This prevents uncontrolled polymerization or gel formation during the application of the phosphate solution to the strip surface-which would inevitably lead to time-consuming production stoppages.

The effect of hexavalent chromium in phosphate / colloid mixtures is essentially due to the fact that the transition from sol to gel is controlled so that it does not take place until the layer is dried during baking.

However, an enormous drawback of the use of chromium-containing solution systems, which is increasingly coming to the fore in the course of time, is the fact that especially hexavalent chromium is very toxic, harmful to the environment and water. There are worldwide efforts, six-valued To eliminate chromium compounds from manufacturing processes. If it is not possible to substitute chromium, then enormous expenses must be incurred in the processing of occupational safety and environmental protection. In addition to technical safety, special protective equipment for personal protection, protection devices to prevent unintentional release, measures for disposal and accident plans must be integrated into the process. But despite all protective measures, there is a considerable risk for humans and the environment that can not be ignored. Attempts to simply omit hexavalent chromium from the phosphate solution have not yet reached beyond a laboratory scale.

JP 2000 178760 A describes a method for producing a grain-oriented electrical tape coated with a phosphate layer, wherein a phosphate solution containing a colloid component and an organic acid is applied to the electrical steel strip. Out JP 2000 178760 A shows that the solution is chromium-free, the colloid stabilizer is used in an amount of 0.1 to 5 wt.% Based on the total weight of aluminum, magnesium and / or calcium phosphate, colloidal silica is used as a colloid component, the pH implicit <3 and the electrical tape provided with the phosphate solution is fired at a temperature of more than 800 ° C.

US Pat. No. 3,562,011 describes a process for preparing a grain-oriented electrical tape coated with a phosphate layer wherein a phosphate solution containing colloidal silica and 0.5% by weight of sodium oxide as a colloid stabilizer is applied to the electrical steel strip. In addition, it is described that the tape can be used as a core material in a transformer.

JP 2007 023329 A describes a method for producing a grain-oriented electrical tape coated with a phosphate layer, wherein a chromium-free phosphate solution (magnesium phosphate) containing colloidal silica and ferric oxide is applied to the electrical steel strip. In addition, it is described that the electric tape provided with the phosphate solution is fired at a temperature of more than 800 ° C.

COLLOIDS AND SURFACES. A, PHYSICOCHEMICAL AND ENGINEERING ASPECTS, ELSEVIER, AMSTERDAM, NL, Vol. 294, No. 1-3, 2 February 2007, pages 212-220 , describes the suspension stability of nanoparticulate (50 nm) barium titanate with various nonaqueous solvents and phosphate esters.

The object of the present invention is to provide a method for producing a phosphate layer on grain-oriented electrical steel, which makes it possible to dispense with the use of hexavalent chromium, without the above-mentioned disadvantages in the production to be accepted. In particular, a homogeneous application of the phosphate solution and thus homogeneous finished layer qualities should be achieved.

This object is achieved by a method for producing a coated with a phosphate layer grain-oriented electrical tape in which on the electrical tape, a phosphate solution is applied, which contains a colloid component and at least one phosphoric acid ester as a colloid stabilizer (A) as an additive, and that the Phosphod solution has a content of hexavalent chromium of less than 0.2% by weight.

By the term "the phosphate solution contains a colloidal component" is understood according to the invention that a proportion the phosphate solution consists of solid particles or supramolecular aggregates with sizes of a few nanometers to a few micrometers. Preferably, the size of the colloid component in the phosphate solution is in the range of 5 nm to 1 μm, preferably in the range of 5 nm to 100 nm, and more preferably in the range of 10 nm to 100 nm.

The proportion of the colloid component in the phosphate solution may vary. Preferably, the proportion of the colloid component in the phosphate solution is in the range of 5 wt% and 50 wt%, more preferably 5 wt% and 30 wt%. As a colloid component, the most diverse substances can be used. Conveniently, these substances should not be phosphoric acid-soluble.

Good results are achieved especially with oxides, preferably with Cr ₂ O ₃ , ZrO, SnO ₂ , V ₂ O ₃ , Al ₂ O ₃ , SiO ₂ , preferably as aqueous suspensions. Particularly suitable is SiO ₂ . A colloid component which is particularly suitable according to the invention is thus silica sol. Excellent results are obtained with silica sol having a content of SiO ₂ in water of from 10 to 50% by weight, preferably from 20 to 40% by weight. SiO ₂ particularly useful particle sizes are 5 to 30 nm, preferably 10 to 20 nm.

The inventive method is characterized in that the phosphate solution contains a phosphoric acid ester as a colloid stabilizer (A) as an additive. This procedure can ensure that the transition from sol to gel takes place only during the drying of the phosphate layer. In addition, the use of colloid stabilizers allows homogeneous application of the phosphate solution resulting in homogeneous

Ready-made layer qualities can be achieved. The use of phosphoric acid ester as colloidal stabilizer (A) thus makes it possible to dispense with the use of hexavalent chromium in the phosphate solution in the phosphating of electrical sheet, which largely avoids the problems that usually occur in chromium-free production using colloid-containing phosphate solutions can be.

Colloid stabilizers according to the invention are additives which stabilize colloids and prevent an uncontrolled sol / gel transition or coagulation of the solid. Advantageously, colloid stabilizers furthermore ensure a temperature insensitivity in the range of application before application of the phosphate solution and make the system insensitive to foreign substances, in particular foreign ions.

According to the invention, a wide variety of phosphoric acid esters can be used as colloid stabilizer, provided that they are stable in acidic solutions. Furthermore, it is advantageous if the phosphoric acid esters do not disturb the stability of the colloidal solution and do not adversely affect the quality of the applied phosphate layer. It is also advantageous if the phosphoric acid esters have the lowest possible toxicity as colloid stabilizers. Furthermore, the phosphoric acid ester used should not interfere with the other, optionally present in the phosphate solution additives in a way that the additives are hindered in their individual effect.

According to the invention, a phosphoric acid ester is used as the colloid stabilizer. The term "phosphoric acid ester" according to the invention organic esters of phosphoric acid with the formula OP (OR) ₃ understood, which act as colloid stabilizers. According to the invention, the term "phosphonic acid ester" refers to organic esters of phosphonic acid with the formula R (O) P (OR) ₂ , which act as colloid stabilizers. The radicals R can hereby independently of one another be hydrogen, an aromatic or an aliphatic group, it not being possible for all the radicals R to be hydrogen at the same time. The term aliphatic group includes alkyl, alkenyl and alkynyl groups.

Alkyl groups include saturated aliphatic hydrocarbon groups having 1 to 8 carbon atoms. An alkyl group may be straight or branched. Particularly suitable alkyl groups according to the invention are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, n-pentyl, n-heptyl. An alkyl group may be further substituted with one or more substituents. Suitable substituents are in particular aliphatic radicals. Further suitable substituents are alkoxy groups, nitro groups, sulfoxy groups, mercapto groups, sulfonyl groups, sulfinyl groups, halogen, sulfamide groups, carbonylamino groups, alkoxycarbonyl groups, alkoxyalkyl groups, aminocarbonyl groups, aminosulfonyl groups, aminoalkyl groups, cyanoalkyl groups, Alkylsulfonyl groups, sulfonylamino groups and hydroxyl groups.

The term alkenyl refers to an aliphatic carbon group having 2 to 10 carbon atoms and at least one double bond. An alkenyl group may be straight-chain or branched. Particularly preferred alkenyl groups according to the invention are allyl, 2-butenyl and 2-hexynyl. An alkenyl group may optionally be substituted with one or more substituents. Suitable substituents are those already mentioned above as alkyl substituents.

The term alkynyl refers to an aliphatic carbon group having 2 to 8 carbon atoms and at least one triple bond. An alkynyl group may be straight-chain or branched. Also, an alkynyl group may be substituted with one or more substituents. Suitable substituents are those already mentioned above as alkyl substituents.

Further suitable substituents for the aliphatic groups are aryl groups, aralkyl groups or cycloaliphatic groups. Aryl refers to monocyclic groups such as phenyl, bicyclic groups such as indenyl, naphthalenyl, tricyclic groups such as fluorenyl or a benzo-linked group having three rings. Aryl may also be substituted by one or more substituents. Suitable substituents are those already mentioned above for alkyl substituents.

Aralkyl refers to an alkyl group substituted with an aryl group. The term "cycloaliphatic" refers to a saturated or partially unsaturated monocyclic, bicyclic or tricyclic hydrocarbon ring bonded to a single bond to the rest of the molecule. Cycloaliphatic rings are 3 to 8-membered monocyclic rings and 8 to 12-membered bicyclic rings. A cycloaliphatic group includes a cycloalkyl group and cycloalkenyl groups. Aralkyl may also be substituted by one or more substituents. Suitable substituents are those already mentioned above as alkyl substituents.

Further suitable substituents for the aliphatic groups are the abovementioned substituents in which one or more carbon atoms are substituted by heteroatoms.

Particularly suitable according to the invention is the use of ethyl phosphates, in particular monoethyl phosphate and / or diethyl phosphate as phosphoric acid ester. Particularly suitable is the product ADACID VP 1225/1 from Kebo Chemie.

The inventive method thus allows the use of a chromium-free phosphate solution. Of course, the phosphate solution may still contain chromium. According to the invention, the phosphate solution contains a chromium content of less than 0.2% by weight, preferably less than 0.1% by weight and in particular less than 0.01% by weight.

According to a preferred embodiment of the invention, the phosphate solution further contains at least one additive selected from the group consisting of pickling inhibitors (B) and wetting agents (C). Through the use of pickle inhibitors (B) and / or wetting agents (C), the properties of the grain-oriented electrical tape produced by the method according to the invention can be further improved. Accordingly, the use of a phosphate solution containing in addition to the colloid stabilizer (A) at least one pickling inhibitor (B) and at least one wetting agent (C) is particularly preferred according to the invention.

Additives belonging to Group B are pickle inhibitors. According to the invention, the term "pickling inhibitors" refers to additives which influence the chemical interaction of the phosphate solution with the strip surface in such a way that no or only small amounts of iron go into solution. The use of pickling inhibitors thus prevents contamination of the phosphate solution with iron ions and the phosphate solution has constant properties over a long time. This procedure is advantageous because an enrichment of the phosphate solution with iron reduces the chemical resistance of the phosphate layer on the electrical steel strip. Particularly advantageous is the use of pickle inhibitors in a colloidal system, as it is used according to the invention, since the sol / gel transition strongly depends on foreign ions. Consequently, by adding pickling inhibitors, the stability of the colloidal system can be considerably improved.

According to the invention can be used as Beizinhibitor (B) a variety of additives, provided that they are stable in acidic solutions. It is also advantageous if the pickle inhibitor the quality of the applied phosphate layer not adversely affected. It is further advantageous if the pickle inhibitor has the lowest possible toxicity. In principle, the pickling inhibitors used should be adapted to the phosphate solution used. Furthermore, the pickling inhibitors used should not adversely affect the stability of the colloid constituents. In addition, the Beizinhibitor used should not interact with the other additives in the phosphate solution so that the additives are hindered in their individual effect.

Practical experiments have shown that thiourea derivatives, C _2-10 -alkynols, triazine derivatives, thioglycolic acid, C _1-4 -alkylamines, hydroxy-C _2-8 -thiocarboxylic acid and / or fatty alcohol polyglycol ethers are particularly effective pickling inhibitors.

By pickling inhibitors in the form of thiourea derivatives, pickling inhibitors according to the invention are understood which have the thiourea structure as the basic skeleton. From 1 to 4 hydrogen atoms of the thiourea may be replaced by suitable substituents. Particularly suitable substituents according to the invention are aliphatic groups as already defined above.

Other suitable substituents on the nitrogen atoms of the thiourea backbone are aryl groups, aralkyl groups or cycloaliphatic groups as defined above.

A particularly suitable thiourea derivative according to the invention is C _1-6 -dialkylthiourea, preferably C _1-4 -dialkylthiourea. Preferably, the alkyl substituents are unsubstituted. Most notably preferred is the use of diethylthiourea, in particular 1,3-diethyl-2-thiourea. Especially suitable is the product Ferropas7578 Alufinish.

Pickling inhibitors which are likewise particularly suitable according to the invention are C _2-10 -alkenols, in particular C _2-6 -alkanols, where alkyne has the abovementioned meaning. In accordance with the invention particularly suitable C _2-6 -Alkindiole the alkyne substituents are unsubstituted and have a double bond. Even more preferred according to the invention is butyne-1,4-diol, in particular but-2-yne-1,4-diol and prop-2-yn-1-ol.

Also very suitable according to the invention pickling inhibitors are triazine derivatives. A pickling inhibitor in the form of a triazine derivative is understood according to the invention as a pickling inhibitor which contains the triazine skeleton. In the triazine derivatives which are suitable according to the invention, one or more hydrogen atoms of the triazine skeleton may be substituted by suitable substituents. Suitable substituents are those already mentioned above for alkyl substituents.

Other particularly suitable pickling inhibitors according to the invention are fatty alcohol polyglycol ethers. Fatty alcohol polyglycol ethers according to the invention are understood to mean the reaction product of fatty alcohols with an excess of ethylene oxide. Fatty alcohols particularly suitable according to the invention have from 6 to 30, preferably from 8 to 15, carbon atoms. The proportion of ethylene oxide groups in the polyglycol ether is preferably high enough to render the fatty alcohol polyglycol ether water-soluble. Accordingly, preferably at least as many -O-CH ₂ -CH ₂ groups should be present in the molecule as carbon atoms in Alcohol. Alternatively, the water solubility can also be achieved by suitable substitution such as, for example, esterification with sulfuric acid and conversion of the ester into the sodium salt. In principle, the hydrogen atoms in the fatty alcohol polyglycol ethers may also be substituted with suitable substituents. Suitable substituents are the substituents already mentioned above for alkyl groups.

Also suitable are thioglycolic acid and hexamethylenetetramine for use as a pickling inhibitor.

Additives of group C are wetting agents. In the method according to the invention, a wide variety of wetting agents can be used, as long as they are stable in acidic solutions. Furthermore, it is advantageous if the wetting agents do not adversely affect the quality of the applied phosphate layer. It is further advantageous if the wetting agents have the lowest possible toxicity. In addition, the wetting agents used should not adversely affect the stability of the colloid constituents. Furthermore, the wetting agent used should not interact with the other additives present in the phosphate solution in such a way that the additives are hindered in their individual action.

The use of wetting agents in the process according to the invention results in that the application of the phosphate solution to the strip surface is improved. In addition, the homogeneity of the phosphate layer increases. Practical experiments have shown that fluorosurfactants are outstandingly suitable as wetting agents. An advantage of fluorosurfactants is that they are stably applicable in a variety of phosphate solutions, even in Cr (VI) -containing phosphate solutions. For the process according to the invention, the most varied fluorosurfactants are suitable as an additive. The term fluorosurfactant is understood according to the invention to mean a surfactant which has a perfluoroalkyl radical as the hydrophobic group, where alkyl has the meaning defined above. Fluorosurfactants are distinguished from non-fluorinated surfactants in that they cause a significant reduction in the surface tension of the water even in extremely low concentrations. In addition, fluorosurfactants have high chemical and thermal stability. Suitable surfactant components of the fluorosurfactant preferably used according to the invention are the most varied surfactants in question, provided they are stable in acidic solutions. Furthermore, it is advantageous if the fluorosurfactants do not disturb the stability of the colloid solution and do not adversely affect the quality of the applied phosphate layer. It is further advantageous if the fluorosurfactants have the lowest possible toxicity.

Practical experiments have shown that C _1-9 -Tetraalkylammoniumperfluor-C _5-10 alkyl sulfonates according to the invention are particularly suitable fluorosurfactants. A particularly suitable wetting agent is the NC 709 product from Schwenk, which contains tetraethylammonium perfluorooctane sulfonate.

The amounts in which the various additives A to C are contained in the phosphate solution can be varied in a wide range. Practical experiments have shown that particularly good results are achieved when the colloid stabilizer (A) in an amount of 0.001 to 20 wt.%, Preferably in an amount of 0.01 to 10 wt.% and in particular in an amount of 0, 1 to 2 wt.% Is used. The pickling inhibitor (B) is suitably used in an amount of 0.001 to 10% by weight, preferably in an amount of 0.005 to 1% by weight, and more preferably in an amount of 0.01 to 0.08% by weight. The wetting agent (C) is suitably used in an amount of 0.0001 to 5% by weight, preferably in an amount of 0.001 to 1% by weight, and more preferably in an amount of 0.01 to 0.1% by weight, respectively based on the total weight of the phosphate solution.

The phosphate solution according to the invention may contain a wide variety of phosphates. For example, the phosphate solution may contain calcium, magnesium, manganese phosphate and / or mixtures thereof. Due to their good water solubility, primary phosphates (monophosphates) are particularly preferred according to the invention. Particularly good results are achieved with a phosphate solution containing aluminum and / or magnesium phosphate. Very particular preference is given to phosphate solutions which contain Al (H ₂ PO ₄ ) ₃ , in particular in an amount of from 40 to 60% by weight.

• 0,5 < Al(H₂PO₄)₃: SiO₂ < 20, vorzugsweise
• 0,7 < Al (H₂PO₉) ₃: SiO₂ < 5 und insbesondere
• Al (H₂PO₄) ₃: SiO₂ = 1,36.

If a phosphate solution containing Al (H ₂ PO ₄ ) ₃ as the phosphate and SiO ₂ (silica sol) as the colloid component is used, the following quantitative ratio has proven particularly suitable:

• 0.5 <Al (H ₂ PO ₄ ) ₃ : SiO ₂ <20, preferably
• 0.7 <Al (H ₂ PO ₉ ) ₃ : SiO ₂ <5 and in particular
• Al (H ₂ PO ₄ ) ₃ : SiO ₂ = 1.36.

Basis for the phosphate solution is preferably water; however, other solvents may of course be used used, provided they have a similar reactivity and polarity as water.

According to the invention, the concentration of the phosphate in the phosphate solution is preferably 5 to 90% by weight, preferably 20 to 80% by weight, more preferably 30 to 70% by weight and in particular 40 to 60% by weight.

In practice, baking phosgenation within the scope of flash annealing has proven to be particularly suitable for forming the phosphate layer on the electrical steel strip. In the baking phosphating, the phosphate solution is first applied to the strip and then baked at temperatures of more than 700 ° C., preferably more than 800 ° C., in particular about 850 ° C. Burning in a continuous furnace has proven particularly useful.

As already explained above, the phosphate solution contains a colloid component. This embodiment is advantageous because with the colloid component during the drying of the phosphate layer, a tensile stress can be transferred to the electrical steel. The tensile stress leads to a significant reduction in the re-magnetization losses when using the electrical tape. In addition, the magnetostriction and thus the occurrence of noise when used in transformers can be minimized.

A particularly suitable colloid component according to the invention is colloidal silica. In view of the stability of the colloidal system, besides the use of a colloidal stabilizer, the pH of the phosphate solution is important. To increase the stability of the phosphate solution before drying increase pH values of <3, preferably from 0.5 to 1, have proven particularly useful.

A further increase in the tensile stress on the electrical steel can be achieved by applying a glass film between the phosphate layer and the electrical steel strip. Under glass film is understood according to the invention a ceramic-like layer, which preferably contains predominantly Mg ₂ SiO ₄ and embedded sulfides. The glass film is preferably formed in a manner known per se during the high-temperature annealing of magnesium oxide and silicon oxide.

A grain-oriented electrical steel coated with a phosphate layer, which has been produced by the method according to the invention, is characterized in that the content of chromium in the phosphate layer is less than 0.2 wt.%, Preferably less than 0.1 wt.% ,

According to a preferred embodiment of the invention, a glass film is arranged between the phosphate layer and the electrical strip.

The phosphate layer and the optional glass film can be arranged on the top and / or bottom of the electrical tape. Preferably, phosphate layer and glass film are arranged on top and bottom of the electrical tape.

The grain-oriented electrical steel obtained is suitable for a wide variety of applications. A particularly noteworthy use of the obtained grain-oriented electrical tape is the use as a core material in a transformer.

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

• Wechselwirkung der Phosphatlösung mit einer Bandoberfläche
• kolloidstabilisierende Wirkung
• Benutzungseigenschaft der Phosphatlösung.

In the following, various additives are investigated with respect to the following effects:

• Interaction of the phosphate solution with a ribbon surface
• colloid stabilizing effect
• Use property of the phosphate solution.

The following methods were used:

Method 1: Evaluation of the interaction of the phosphate solution with an electrical strip surface

The phosphate solution or the phosphate / colloid mixture is placed in a beaker. Subsequently, the additive to be evaluated is added with stirring. A weighed electric tape specimen with a bright metallic surface is dipped in the solution and weighed after various immersion times. The weight loss (pickling loss) is calculated from the measurements. The method is partly carried out at different temperatures.

Method 2: Evaluation of the colloid stabilizing effect

The phosphate solution or the phosphate / colloid mixture is placed in a beaker. Subsequently, the additive to be evaluated is added with stirring. A weighed electric tape sample with a metallic bright surface is immersed in the solution. After various aging times, the turbidity of the solution is evaluated and checked for gelation. The test is carried out at different temperatures.

Method 3: Evaluation of the colloid stabilizing effect

The sol / gel transformation can, as exemplified in FIG. 1 shown viscometrically very well.

Method 4: Assessment of wetting property

Equal volumes of the solutions to be evaluated are placed on a glass plate with underlying graph paper. After a lapse of 10 minutes, the areas to which the liquids have spread are determined. For this, the areas are approximated by circular areas and the diameters of the circles are given as area equivalent.

• Monoaluminiumphosphat (kurz MAL); eine wässrige Al (H₂PO₄)₃-Lösung mit 50 M% Al (H₂PO₄)₃.
• VE-Wasser : Vollentsalztes Wasser; Leitfähigkeit < 15 µS/cm.
• Monomagnesiumphosphat kurz (MMG); 15 g MgO gelöst in 100 g 75 M% H₃PO₄ und 76 g VE-Wasser.
• Kieselsol ; wässriges Kolloid, bestehend aus 30 M% SiO₂ mit einer mittleren Partikelgröße von 15 nm und einem pH-Wert con 9.

In the embodiments, the following basic chemicals were used:

• Monoaluminum phosphate (MAL for short); an aqueous Al (H ₂ PO ₄ ) ₃ solution with 50 M% Al (H ₂ PO ₄ ) ₃ .
• Demineralised water : demineralized water; Conductivity <15 μS / cm.
• Monomagnesium Phosphate Short (MMG); 15 g of MgO dissolved in 100 g of 75 M% H ₃ PO ₄ and 76 g of deionized water.
• Silica sol ; aqueous colloid, consisting of 30 M% SiO ₂ with an average particle size of 15 nm and a pH con 9.

EMBODIMENT 1 Effect of Pickling Inhibitors on Phosphate Solutions Without a Colloid Component

MAL =

Monoaluminiumphosphatlösungen 50%

MMG =

Monomagnesiumphosphat Mg (H₂PO₄)₂ 2 = 100 g 75%ige H₃PO₄ + 15 g MgO + 76 g VE-Wasser

H15 =

Ferropas7578, Alufinish, Wirksubstanz: Diethylthioharnstoff

H31 =

Adacid HV 27 N, Kebo Chemie, Wirksubstanz: But-2-in-1,4-diol

H32 =

Adacid 328, Kebo Chemie, Wirksubstanzen: Hexamethylentetramin, Prop-2-in-1-ol

H33 =

Adacid VP 1112, Kebo Chemie, But-2-in-1,4-diol

H36 =

Antischaum 48, Alufinish, Wirksubstanz: Fettalkoholethoxylat

Diethylthiourea (H15), but-2-yn-1,4-diol (H31), hexamethylenetetramine and prop-2-yn-1-ol (H32), but-2-yn-1,4-diol (H33) and fatty alcohol ethoxylate (H36) based pickling inhibitors were used in 50% monoaluminum phosphate (MAL) solutions and 50% monomagnesium phosphate (MMG) solutions. Table 1 solution component 1 2 3 4 5 6 7 8th TIMES G 150 150 150 150 150 150 MMG G 150 150 VE water G 50 50 50 50 50 50 50 50 H15 G 1 1 H31 G 1 H32 G 1 H33 ml 1 H36 ml 1

MAL =

Monoaluminum phosphate solutions 50%

MMG =

Monomagnesium phosphate Mg (H ₂ PO ₄ ) ₂ 2 = 100 g 75% H ₃ PO ₄ + 15 g MgO + 76 g DI water

H15 =

Ferropas 7578, Alufinish, active ingredient: diethylthiourea

H31 =

Adacid HV 27 N, Kebo chemistry, active ingredient: but-2-yne-1,4-diol

H32 =

Adacid 328, Kebo chemistry, active ingredients: hexamethylenetetramine, prop-2-yn-1-ol

H33 =

Adacid VP 1112, Kebo chemistry, but-2-yne-1,4-diol

H36 =

Antifoam 48, Alufinish, active ingredient: fatty alcohol ethoxylate

The solutions were evaluated according to method 1 and the results for a contact time of 20 hours are in the Figures 1 and 2 shown. It turns out that all pickling inhibitors used have an excellent effectiveness in the sample solution. The best effect, however, shows additive H15.

Exemplary Embodiment 2 Effect of Pickling Inhibitors in Phosphate / Colloid Mixtures

H27 =

LITHSOLVENT HVS N, Kebo Chemie, Wirksubstanz: But-2-in-1,4-diol, ethoxyliert

H29 =

ADACID RKT 1, Kebo Chemie, Wirksubstanz: Thioglykolsäure

The following phosphate solutions were prepared: Table 2 solution component basic solution Monoaluminum phosphate 50% G 90 90 90 90 Silica sol 30% G 110 110 110 110 CrO ₃ G 7 H27 G 2 H29 G 2

H27 =

LITHSOLVENT HVS N, Kebo Chemistry, active ingredient: but-2-yn-1,4-diol, ethoxylated

H29 =

ADACID RKT 1, Kebo chemistry, active substance: thioglycolic acid

The solutions were evaluated according to method 1. The results of the evaluation are in FIG. 3 shown. Result: The basic solution interacts strongly with the steel sample. The weight loss of the steel sample is very large, which suggests a strong accumulation of the phosphate solution with iron ions. CrO ₃ has a strong inhibiting effect on the solution and thus suppresses the contamination of the phosphate solution with iron ions. The effect is clearly visible on the sample surfaces. The surface of the sample from the base solution is dull to black. The sample surface of the solution mixed with CrO ₃ is unchanged bright metallic. We out FIG. 3 shows, the additives H27 and H29 act as pickling inhibitors. However, they have lower activity-inhibiting effects than CrO ₃ .

Exemplary Embodiment 3 Effect of Pickling Inhibitors on Phosphate / Colloid Mixtures

H15 =

Ferropas7578, Alufinish, Wirksubstanz: Diethylthioharnstoff

The following phosphate solutions were prepared: Table 3 solution component basic solution Monoaluminum phosphate 50% G 90 90 Silica sol 30% G 110 110 H15 G 3

H15 =

Ferropas 7578, Alufinish, active ingredient: diethylthiourea

The solutions were evaluated according to method 1. The results of the evaluation are in FIG. 4 shown.

Result: Additive H15 shows a similar effect to CrO ₃ . The interaction between the phosphate solution and the Steel sample is strongly inhibited. The surface of the sample from the solution with additive H15 remains unchanged for a long time, while the sample from the base solution has a strong pickling attack.

Exemplary Embodiment 4: Effect of Pickling Inhibitors in Phosphate / Colloid Mixtures

H25 =

ADACID 337, Kebo Chemie

H26 =

KEBOSOL FB, Kebo Chemie

H27 =

LITHSOLVENT HVS N, Kebo Chemie, Wirksubstanz: But-2-in-1,4-diol, ethoxyliert

H29 =

ADACID RKT 1, Kebo Chemie, Thioglykolsäure

The following phosphate solutions were prepared: Table 4 solution component basic solution Monoaluminum phosphate 50% G 90 90 90 90 90 Silica sol 30% G 110 110 110 110 110 H25 G 3 H26 G 3 H27 3 H29 3

H25 =

ADACID 337, Kebo Chemistry

H26 =

KEBOSOL FB, Kebo Chemistry

H27 =

LITHSOLVENT HVS N, Kebo Chemistry, active ingredient: but-2-yn-1,4-diol, ethoxylated

H29 =

ADACID RKT 1, Kebo chemistry, thioglycolic acid

The solutions were evaluated according to method 1. The results of the evaluation are in FIG. 5 shown. Result: All additives act as pickling inhibitors. The effect is below that of chromium trioxide and additive 15. Crucial observation in the attempt is that additives can catalyze the sol / gel transformation. This means that an additive effective as a pickling inhibitor can, on the other hand, accelerate the sol-gel transformation. Such additives are not applicable in colloidal mixtures.

Embodiment 5: Effect of colloid stabilizers in Phosphate / colloid mixtures

H15 =

Ferropas7578, Alufinish, Wirksubstanz: Diethylthioharnstoff

H28 =

ADACID VP 1225/1, Kebo Chemie, Wirksubstanz: Triethylphosphat

The following phosphate solutions were prepared: Table 5 solution component basic solution Monoaluminum phosphate 50% G 90 90 90 90 90 Silica sol 30% G 110 110 110 110 110 H15 G 3 3 3 3 H28 G 2 4 6

H15 =

Ferropas 7578, Alufinish, active ingredient: diethylthiourea

H28 =

ADACID VP 1225/1, Kebo chemistry, active substance: triethyl phosphate

The solutions were evaluated according to Method 2 at a temperature of 50 ° C.

Result: Additive H15 leads to an inhibition of the pickling reaction in the phosphate / silica sol mixture, as already documented above. Additive H15, however, does not contribute to the stabilization of the colloid. Additive H28, on the other hand, acts on the colloidal system, in which it apparently retards the polymerization. An addition of 3 M% leads to the fact that after 8 hours of aging at 50 ° C, despite the presence of steel in the solution, the degree of turbidity has increased little. The colloid is therefore still far removed from the sol / gel transformation.

Embodiment 6: Effect of Combination Pickling Inhibitor and Colloid Stabilizer in Phosphate / Colloid Mixtures

H15 =

Ferropas7578, Alufinish/Hr. Ritter, Wirksubstanz: Diethylthioharnstoff

H28 =

ADACID VP 1225/1, Kebo Chemie, Wirksubstanz: Triethylphosphat

The following phosphate solutions were prepared: Table 6 solution component basic solution Monoaluminum phosphate 50% G 90 90 90 90 Silica sol 30% G 110 110 110 110 H15 G 3 3 H28 G 6 6

H15 =

Ferropas7578, Alufinish / Hr. Ritter, active substance: diethylthiourea

H28 =

ADACID VP 1225/1, Kebo chemistry, active substance: triethyl phosphate

The solutions were evaluated according to Methods 1 and 2 at a temperature of 22 ° C. The results of the reviews are in FIG. 6 shown.

Result: It can be seen that no foam formation occurs when the electrical tape sample is added to the phosphate solutions containing the additive 15. This can be taken as an indicator that additive 15 clearly acts as a pickling inhibitor. The foaming is namely a consequence of the hydrogen generation from the pickling reaction.

The colloid stabilizer Additive H28 has no effect on the chemical interaction of the solution with the steel surface, as indicated by the strong pickling loss in FIG. 6 and foaming on the solution surface. However, the additive acts on the sol / gel transformation to delay the transition to the gel. This can be seen in the turbidity of the solutions. The solutions in the beakers doped with additive H28 show a significantly lower degree of turbidity than the solutions in the beakers without the additive H28.

This demonstrates that a pickle inhibitor with its specific action can be used in combination with a colloid stabilizer and its specific action in a phosphate / colloid mixture without the two components interacting and the effects or disturbing the colloidal system.

Thus, two effects of a chemical compound, namely the CrO ₃ or hexavalent Cr compounds are represented by two separate additives.

Exemplary Embodiment 7: Effect of a Colloid Stabilizer in Phosphate / Colloid Mixtures

H28 =

ADACID VP 1225/1, Kebo Chemie, Wirksubstanz: Triethylphosphat

The following phosphate solutions were prepared: solution component basic solution Monoaluminum phosphate 50% G 158 158 158 Silica sol 30% G 193 193 193 Dest.Wasser G 6 H28 G 6 Table 7

H28 =

ADACID VP 1225/1, Kebo chemistry, active substance: triethyl phosphate

The solutions were evaluated according to Method 3 at a temperature of 50 ° C. The results of the reviews are in FIG. 7 shown.

Result: Increasing the temperature and contamination of the solutions with iron ions under the conditions critical for the sol / gel transition, the phosphate solution mixed with additive H28 is considerably more stable. While the sol / gel transformation in the phosphate / colloid mixture already after 3 Hours, the transition can be pushed to about 6 hours using the additive H28.

Exemplary embodiment 8: Improvement of the wettability by addition of wetting agents

• H15 = Beizinhibitor Ferropas7578, Alufinish, Wirksubstanz: Diethylthioharnstoff
• H5 = Netzmittel NC 709, Schwenk, Wirksubstanz: Tetraethylammoniumperfluoroktansulfonat

The following phosphate solutions were prepared: Table 8 solution component 1 2 3 4 5 6 Monoaluminum phosphate 50% G 90 90 90 90 90 90 Silica sol 30% 9 110 110 110 110 110 110 CrO ₃ G 7 7 H15 G 2 2 H5 G 0.5 0.5 0.5

• H15 = stain inhibitor Ferropas 7578, alufinish, active substance: diethylthiourea
• H5 = wetting agent NC 709, swivel, active ingredient: tetraethylammonium perfluorooctane sulfonate

These solutions were evaluated according to method 4. Table 9 solution component 1 2 3 4 5 6 area equivalent 16 19 18 22 28 27

It can be seen that the solutions 4 and 5 added with the pickling inhibitor H15 markedly improve the wettability of the millimeter paper provided with them. Their effect even exceeds that of CrO ₃ .

Exemplary embodiment 9: Application of the method according to the invention in operational production

H15 =

Beizinhibitor Ferropas7578, Alufinish, Wirksubstanz: Diethylthioharnstoff

H28 =

Kolloidstabilisator ADACID VP 1225/1, Kebo Chemie, Wirksubstanz: Triethylphosphat

H5 =

Netzmittel NC 709, Schwenk, Wirksubstanz: Tetraethylammoniumperfluoroktansulfonat

The following phosphate solution was used under operational conditions: Table 10 solution component Monoaluminum phosphate 50% kg 450 Silica sol 30% kg 550 H15 kg 7.5 H28 kg 30 H5 kg 0.4 the. water kg 80

H15 =

Pickling inhibitor Ferropas 7578, Alufinish, active ingredient: diethylthiourea

H28 =

Colloid stabilizer ADACID VP 1225/1, Kebo chemistry, active substance: triethyl phosphate

H5 =

Wetting agent NC 709, swivel, active ingredient: tetraethylammonium perfluorooctane sulfonate

About 850 t of PowerCore H 0.30 mm (high permeability grain oriented electrical steel) electrical steel were treated with this phosphate solution. As qualitative characteristics, the mean value of the magnetic reversal losses P _1.7 in W / kg and the average of the volume resistivities were determined and compared with the data of a reference quantity of about 20,000 t, which was treated with Cr (VI) -containing insulation (cf. Figure 8 ). Table 11 hysteresis loss Contact resistance attempt 1.028 W / kg ± 0.035 82 Ωcm ² reference 1.014 W / kg ± 0.030 31 Ωcm ²

Claims (14)

1. Method for producing a grain-oriented magnetic strip covered with a phosphate layer, characterised in that a phosphate solution, which comprises a colloidal component and at least one phosphoric acid ester as a colloid stabiliser (A) as an additive, is applied onto the magnetic strip, and in that the phosphate solution has a hexavalent chromium content of less than 0.2% by weight.
2. Method according to Claim 1, characterised in that a phosphate solution, which contains at least one additive selected from the group consisting of pickling inhibitors (B) and wetting agents (C), is applied onto the magnetic strip.
3. Method according to Claim 1 or 2, characterised in that a phosphate solution having a hexavalent chromium content of less than 0.1% by weight is used.
4. Method according to one of the preceding claims, characterised in that a monoethyl phosphate and/or diethyl phosphate is used as the colloid stabiliser (A).
5. Method according to one of Claims 2 to 4, characterised in that a thiourea derivative, a C_2-10 alkynol, a triazine derivative, thioglycolic acid, a C_1-4 alkyl amine, a hydroxy-C_2-8-thiocarboxylic acid and/or a fatty alcohol polyglycol ether is used as pickling inhibitor (B).
6. Method according to one of Claims 2 to 5, characterised in that diethyl thiourea, prop-2-yn-1-ol, butyn-1,4-diol, thioglycolic acid and/or hexamethylenetetramine is used as the pickling inhibitor (B).
7. Method according to one of Claims 2 to 6, characterised in that a fluorosurfactant, preferably tetraethylammonium perfluorooctane sulfonate, is used as the wetting agent (C).
8. Method according to one of Claims 2 to 7, characterised in that a phosphate solution comprising at least one pickling inhibitor (B) and at least one wetting agent (C) is used.
9. Method according to one of Claims 2 to 8, characterised in that the colloid stabiliser (A) is used in an amount of from 0.001 to 20% by weight, the pickling inhibitor (B) is used in an amount of from 0.001 to 10% by weight and/or the wetting agent (C) is used in an amount of from 0.0001 to 5% by weight, respectively expressed in terms of the total weight of the phosphate solution.
10. Method according to one of the preceding claims, characterised in that a phosphate solution comprising aluminium phosphate and/or magnesium phosphate is applied onto the magnetic strip.
11. Method according to Claim 10, characterised in that colloidal silicon dioxide is used as the colloidal component.
12. Method according to one of the preceding claims, characterised in that a phosphate solution having a pH < 3, preferably between 1 and 2, is applied onto the magnetic strip.
13. Method according to one of the preceding claims, characterised in that a glass film is applied between the phosphate layer and the magnetic strip.
14. Method according to one of the preceding claims, characterised in that the magnetic strip provided with the phosphate solution is fired at a temperature of more than 800°C.

Images