Method of manufacturing NGO electrical steel

Abstract

The invention relates to method according to claim 1 of producing Si alloyed NGO electrical steel with a low amount of CaS based non-metallic inclusions.

Description

[0001] METHOD OF MANUFACTURING NGO ELECTRICAL STEEL

[0002] FIELD OF THE INVENTION

[0003] The invention relates to method of producing Si alloyed NGO electrical steel with a low amount of CaS based non-metallic inclusions.

[0004] BACKGROUND TO THE INVENTION

[0005] Materials for electrical steels consist mostly of an iron-silicon alloy or iron-silicon-aluminium alloy, wherein a distinction is made between grain-oriented (GO) and non-grain-oriented (NGO) electrical steels and these are used for different applications. In particular, aluminium and silicon are added in order to obtain an increase in strength and reduction in density and in particular an increase in the electrical resistance to reduce eddy current losses with the magnetic saturation polarization remaining unchanged as far as possible.

[0006] For applications in electrical engineering in which the magnetic flux is not fixed to a specific direction and therefore equally good magnetic properties are required in all directions, an electrical strip having the most isotropic properties possible is typically produced and is referred to as a non-grain-oriented (NGO) electrical steel strip or sheet. This is used predominantly in generators, electric motors, switches, relays and small transformers.

[0007] The magnetic properties in the electrical strip or sheet are determined substantially by a high degree of purity, the content of silicon and aluminium and targeted addition of other alloy elements, such as e.g. manganese, as well as by hot-rolling, cold-rolling and annealing processes. The established NGO electrical steel strip or sheet thicknesses are in the range of considerably less than 1.0 mm, e.g. about 0.15 mm or about 0.35 mm.

[0008] The production of NGO electrical steel strip or sheet comprises the steps of: in a steelmaking process producing a steel melt having a defined alloy composition; manufacturing rolling slabs by casting the steel in a horizontal or vertical continuous casting process thick slab or thin slab casting process; re-heating the slabs to about 1050°C to 1250°C; and then hot-rolling the slabs to form a hot-rolled strip; coiling the hot-rolled strip at a coiling temperature, typically between 850°C and room temperature; optionally annealing the hot-rolled strip or sheet at a temperature in a range of about 800°C to 1100°C. Next, the hot-rolled strip or sheet is pickled and / or mechanically brushed and / or shot blasted to remove scale from the surface, and next cold-rolled to a predetermined thickness. The reduction rate is differently applied depending on the hot-rolled sheet or strip thickness, but cold rolling may be performed by applying a reduction rate of about 70% to 97% so that the final thickness is typically between about 0.1 and 1 mm, more typically between about 0.1 and 0.65 mm. In order to reach the desired reduction rate, cold rolling two times or more with an intermediate annealing interposed therebetween may be performed. The sheet after final cold rolling is final annealed at a temperature between about 800°C to 1100°C. Thereafter, an organic or inorganic insulation layer may be applied as is well known in the art of non-grain-oriented electrical steel sheet.

[0009] The steelmaking process includes primary steelmaking process in the form of a converter to produce molten steel and a secondary metallurgy treatment for decarbonization of the molten steel and to arrive at the required steel composition by the addition of alloying elements (e.g. Si, Al, and Mn). After this, the molten steel is transferred from a ladle to a tundish, and continuously cast to form cast steel in the form of slabs. In this steelmaking process non-metallic inclusions can be formed. It has been found that in the production of silicon alloyed NGO electrical steel notably CaS based non-metallic inclusions may be formed. Accumulation of CaS in the casting nozzle or submerged entry nozzle (SEN) used in the transfer of the molten steel from a tundish to the casting mould may result in clogging, thus in a process instability. CaS based non-metallic inclusions may break free of the casting nozzle or SEN and end up in the cast product forming detrimental surface defects in the final rolled product. The surface quality of NGO electrical steel sheet is important because it affects the performance of the motor. For example it may lead to increased eddy current losses causing reduced efficiency and increased heat generation in the motor. In addition, surface defects may lead to irregularities or non-flatness of the applied insulation layer such that these do not stack properly, which amongst others can results in gaps between the laminations causing the magnetic flux to leak out of the core, resulting in reduced efficiency and increased noise and vibration in the electric motor.

[0010] Patent document EP4053302-A1 discloses a non-oriented electrical steel sheet containing, in wt.%, C: 0.0100 wt.% or less, P: 0.100 wt.% or less, Si: 2.00-5.00 wt.%, Mn: 5.00 wt.% or less, Al: 3.00 wt.% or less, S: 0.0100 wt.% or less, N: 0.0050 wt.% or less, Zn: 0.0005-0.0030 wt.%, Mo: 0.001-0.100 wt.%, Cu: 0.2 wt.% or less, Nb: 0.010 wt.% or less, and O: 0.0050 wt.% or less, with the balance being Fe and inevitable impurities; and a microstructure in which a ratio of non-recrystallized microstructure is 5-70%, and the number of inclusion having a diameter of 5 micrometres or more is not more than 5 counts / mm2. It is disclosed that by appropriately controlling the amount of Zn and Mo added to a non-oriented electrical steel sheet having a non-recrystallized microstructure and reducing inclusions in the steel, it is possible to make magnetic flux density B5o and high-frequency iron loss properties excellent, and fatigue strength and tensile strength high, and reduce the variation in tensile strength. Patent document EP3404124-A1 discloses a non-oriented electrical steel sheet and a method of its manufacture, the steel having a chemical composition containing C: not more than 0.0050 wt.%, Si: 0.1-5.0 wt.%, Mn: 0.02-3.0 wt.%, sol. Al: not more than 0.0050 wt.%, P: not more than 0.2 wt.%, S: not more than 0.0050 wt.%, N: not more than 0.0040 wt.%, and the remainder being Fe and inevitable impurities, and wherein the total Ca concentration (T.Ca) in steel is 0.0010-0.0080 wt.%, and a total oxygen concentration (T.O) is not more than 0.0100 wt.%, and a concentration ratio (T.Ca / T.O) of a total Ca to a total oxygen is in a range of 0.50 to 2.0. It is disclosed that it is effective to increase a grain growth property in hot band annealing or finish annealing in order to increase the magnetic flux density and decrease the iron loss in the non-oriented electrical steel sheet, and to this end, it is important to control a concentration ratio of the total Ca to the total oxygen (T.Ca / T.O) in steel by decarburizing the C concentration in a raw steel material to an extremely low carbon region, adding Si, decreasing the Al content as much as possible and then adding Ca alloy.

[0011] Patent document US2021 / 0332463-A1 discloses a non-oriented electrical steel sheet and a method of its manufacture, the steel having a chemical composition containing C: 0.0050 wt.% or less, Si: 1.5-5.0 wt.%, Mn: 0.2-3.0 wt.%, soLAI: 0.0030 wt.% or less, P: 0.2 wt.% or less, S: 0.0050 wt.% or less, N: 0.0040 wt.% or less, T.Ca: 0.0010-0.0080 wt.%, T.O: 0.0100 wt.% or less, REM: 0.0001-0.0050 wt.%, and a balance of Fe and inevitable impurities, wherein a value of a mass-related fractional expression ((T.Ca+REM) / (T.O+S)), which is a relational expression for masses of four constituents including T.Ca, REM, T.O, and S, is 0.4 or more. In the disclosed method the Si is added to deoxidize the steel during the vacuum degassing followed by the addition of REM-containing alloys to limit the formation of sulfide-based inclusions in the steel.

[0012] There is a demand for a steelmaking process suppressing or limiting the formation of CaS based non-metallic inclusions, in particular in the production of Si alloyed NGO electrical steel.

[0013] DESCRIPTION OF THE INVENTION

[0014] It is another object to provide a method of producing Si alloyed non-grain-oriented (NGO) electrical steel with a low amount of CaS based non-metallic inclusions.

[0015] This and other objects and further advantages are met or exceeded by the present invention providing a process according to independent claim 1 and with preferred embodiments in the dependent claims and the description. In order to achieve these objects, the present invention proposes, in a first aspect, a method of producing Si-alloyed non-grain-oriented (NGO) electrical steel having at least (in wt.%): up to 0.08% of C, 0.5 to 10% of Si, 0.2 to 4% of Al, up to 5% of Mn, the method comprising the consecutive process steps of:

[0016] providing molten steel obtained via a primary steelmaking process, preferably obtained via a BOF or EAF steelmaking process;

[0017] performing a decarbonization treatment in a vacuum degassing apparatus, preferably in a RH or RH-OB station, and reducing the oxygen content in the molten steel to a range of 30 to 150 ppm;

[0018] alloying the molten steel with Si in a ladle furnace (LF) to a range of 0.5 to 10 wt.%, and thereafter alloying the molten steel with aluminium in a range of 0.2 to 4 wt.%;

[0019] and thereafter transferring the treated molten steel from the ladle furnace (LF) into a tundish for the continuous casting of slabs in a casting machine.

[0020] Regarding the production process, the inventors learned that adding considerable amounts of Si, notably in the form of FeSi, as alloying element to fully killed molten steel is highly undesirable at it leads to the release of calcium (Ca) from the slag floating on top of the molten steel in a LF. As there is very limited or no oxygen available in the molten fully killed steel to form CaO that may rise to the slag, substantial amounts of detrimental CaS based non-metallic inclusions are formed in the steel. Now, by having still a substantial amount of oxygen present in the molten steel following the treatment in the vacuum degassing apparatus and adding the silicon in the LF prior to adding the aluminium, the calcium originating from the slag reacts with the oxygen available to form CaO particles rising back into the slag. Thereby the formation of detrimental CaS based non-metallic inclusions is significantly reduced or even avoided and consequently the negative effects associated with the CaS inclusions, e.g. resulting from the clogging of the immersion nozzle or SEN in a continuous casting process, the surface defects in NGO electrical steel sheet and the effects on the performance of an electrical motor, are prevented. After the addition of the Si as alloying element the oxygen content of the molten steel can be further reduced by adding deoxidizing agents to the molten steel in the LF. The time delay between adding the last Si as alloying element and the addition of the deoxidizing agents is preferably at least 5 minutes. The addition of Si as alloying element to the molten steel after adding the aluminium in the LF is to be avoided. Thus the sequence of the various method steps is paramount in solving the problem posed.

[0021] The first step in the method according to the invention molten steel is to provide molten steel obtained via a primary steelmaking process. In an embodiment the molten steel is obtained via a converter process. Basic oxygen steelmaking (commonly abbreviated as BOS, BOP, or BOF), also known as Linz-Donawitz steelmaking or the oxygen converter process, is a method of primary steelmaking in which carbon-rich molten pig iron is converted into steel. Blowing oxygen through a lance over the molten pig iron inside the converter lowers the carbon content of the molten iron and changes it into low-carbon steel.

[0022] In an embodiment the molten steel is obtained via an electric arc furnace (EAF) steelmaking process. An electric arc furnace is a furnace that heats the material by means of an electric arc, which can be supplemented with the chemical energy provided by reaction between the oxygen and the fuel. The use of the electric arc furnaces allows producing molten steel starting from a raw material composed of up to 100% metal scraps, which allows to reduce the energy required for the production of steel compared to the production of steel from ferrous minerals. The electric arc furnace is capable of melting different charge mixes, e.g. it can be charged with a combination of a direct reduced iron (DRI) product and ferrous scrap, the combination having 90 wt.% to 10 wt.% ferrous scrap and 10 wt.% to 90 wt.% of DRI product, based on the combined amount of DRI and ferrous scrap charged. An electric arc furnace operates under oxidizing conditions.

[0023] It is an important feature of the method that the molten steel from the primary steelmaking process is tapped from the primary steelmaking furnace into a ladle or other metallurgical vessel where it is subjected next to a decarbonization treatment in a vacuum degassing apparatus to achieve degassing and decarbonization of the molten steel. The carbon content is reduced further to a level of 0.08 wt.% maximum, preferably not exceeding 0.03 wt.%, and more preferably not exceeding 0.010 wt.%. Most importantly, the oxygen content in the molten steel is reduced to a range of 30 to 150 ppm. In industrial practice this means that the molten steel is not fully killed by reducing the oxygen content to a level wherein all entrapped oxygen is eliminated from the molten steel. A certain lower or minimum threshold level of oxygen should remain in the molten steel for the secondary metallurgy treatment whereby Si is added to the molten steel as alloying element to arrive at the Si content required for the steel. Reducing the oxygen content in the molten steel is achieved amongst others by adding deoxidizing agents, e.g. aluminium. In an embodiment the lower-limit for the oxygen after the Al killing content is 50 ppm, and preferably 60 ppm. In an embodiment the upper-limit for the oxygen content is 100 ppm.

[0024] The vacuum treatment can be done using a vacuum tank degasser (VD or VTD). In a preferred embodiment, the vacuum degassing apparatus is a Rheinstahl-Hereus (RH) vacuum degassing apparatus as is well known in the art to the skilled person. The metal refining in the RH vacuum degassing apparatus include decarburization under vacuum to achieve low carbon contents and degassing of the metal by removing hydrogen, nitrogen, etc. Increasing the circulation rate is effective for accelerating the decarburization speed in vacuum decarburization or the degassing speed. Alternatively, a variant of an RH, i.e. an RH-OB vacuum degassing apparatus may be used.

[0025] In a next process step, the vacuum treated molten steel having the defined oxygen content is treated in a ladle furnace to increase the Si content to a level of at least 0.5 wt.%, preferably of at least 1 wt.%, and more preferably of at least 2 wt.%, to create a Si-alloyed NGO electrical steel. Also other alloying elements like Mn can be added to the molten steel. In addition, the molten steel can be subjected to a desulphurisation treatment. The silicon as alloying element can be added using pure Si or Si based alloys. Industrially, the silicon requirement of the molten steel is met preferably with ferrosilicon (FeSi) instead of high-purity silicon addition. FeSi, a silicon-rich alloy, contains at least 65 wt.%, and preferably at least about 70 wt.% of silicon, and more preferably in a range of about 70 to 85 wt.%, and limited amounts of iron, aluminium, carbon, and minor impurities typically inherited from its manufacturing stage.

[0026] It is another important feature of the invention that only after adding all the required Si to the molten steel in the ladle furnace, that further aluminium is added in the ladle furnace to kill the molten steel and to arrive at an Al level as alloying element required for the Si-alloyed NGO electrical steel. The added aluminium has the effect to fully kill the steel. The minimum amount of Al in the molten steel should be 0.2 wt.%, and is preferably at least 0.4 wt.%, and in a more preferred embodiment is at least 0.5 wt.%. At the end of the LF treatment the steel slag is skimmed to prevent sulphur and calcium reversion at the LF.

[0027] Following the secondary metallurgy treatment the treated molten steel of final composition is transferred to a tundish for continuous casting into a thick slab in a horizontal or vertical continuous casting process or thin slab in a thin slab casting process. In an embodiment the method further comprises the steps of hot rolling the slab, cold rolling, preferably cold rolling to a thickness in a range of 0.1 to 0.65 mm, and final annealing at a temperature in a range of about 800°C to 1100°C, to provide a non-grain-oriented (NGO) electrical steel sheet.

[0028] In an preferred embodiment, the method according to this invention has proven to be suitable in particular for the production of non-grain-oriented electrical steel sheet comprising, in wt.%,

[0029] up to 0.03% of C, preferably up to 0.010%;

[0030]

[0031] 0.4 to 2% of Al, preferably 0.4 to 1.50%;

[0032] 0.1 to 2.5% of Mn, preferably 0.1 to 2.0%;

[0033] and the remainder of Fe and inevitable impurities, viz. residual and tramp impurities from the ironmaking and steelmaking process.

[0034] In another embodiment, the non-grain-oriented electrical steel sheet comprising of, and preferably consisting of, in wt.%,

[0035] up to 0.08% of C, preferably up to 0.03%, more preferably up to 0.010%;

[0036] 0.5% to 10% of Si, preferably 1% to 6%, more preferably of 2% to 4.5%;

[0037] 0.2% to 4% of Al, preferably 0.4% to 2%, more preferably 0.4% to 1.50%;

[0038] up to 5% of Mn, preferably 0.1% to 2.5%, more preferably 0.1% to 2.0%;

[0039] up to 2% of Cr, preferably up to 0.5%, more preferably up to 0.10%;

[0040] up to 0.1% of Ti, preferably up to 0.050%; more preferably up to 0.020%;

[0041] up to 0.1% of Cu;

[0042] up to 0.1% of Sn;

[0043] up to 0.1% of B, preferably up to 0.050%;

[0044] up to 0.1% of N, preferably up to 0.050%, and more preferably up to 0.020%;

[0045] up to 0.1% of S, preferably up to 0.050%;

[0046] up to 0.05% of P, preferably up to 0.030%;

[0047] up to 0.010% of Ca, preferably up to 0.005%, and more preferably up to 0.0010%; and the remainder of Fe and inevitable impurities, viz. residual and tramp impurities from the ironmaking and steelmaking process.

[0048] The content of carbon should be kept as low as possible in order to prevent, in the finished NGO electrical steel strip, magnetic ageing which is caused by carbide precipitations. Low carbon contents result in an improvement in the magnetic properties because fewer flaws caused e.g. by the carbon atoms and carbides occur in the material. Maximum carbon contents of about 0.08 wt.% have been shown to be favourable, and is preferably not to exceed about 0.03 wt.%, and more preferably not to exceed 0.010 wt.%.

[0049] An addition of Si effects a high strength while lowering iron loss by increasing the electrical resistance of the material. In accordance with the invention, in order to achieve an effect, a minimum content of 0.5 wt. % is required. For contents of more than 10 wt.% Si, the cold-rollability is reduced too much because the material becomes increasingly more brittle with increasing Si content and edge cracks become increasingly visible on the steel strip. Therefore, contents of 0.5 to 5 wt.% and preferably of 1 to 6 wt. %, and more preferably of 2 to 4.5 wt.%, are advantageously set. The addition of Si and Al in the selected alloy element contents represents an optimal combination of an increase in electrical resistance and a decrease in magnetic saturation polarization.

[0050] Aluminium serves to increase resistivity of a material to lower core loss and also to secure high strength. When too little Al is added, it is not effective for reducing high-frequency iron loss and for securing high strength. Also fine nitrides are formed, which may reduce magnetism. In contrast, when too much of Al is added, the physical properties of a casting powder are changed in a process such as steelmaking and continuous casting, thereby greatly deteriorating productivity. Therefore, Al may be added in the range of 0.2 to 4 wt.%. More specifically, Al may be included in a range of 0.4 to 2 wt.%, and preferably of 0.4 to 1.5 wt.%.

[0051] The NGO electrical steel manufactured in accordance with the invention contains manganese in an amount of not more than 5 wt.%. Manganese increases the specific volume resistance and increases mechanical strength. In order to produce a corresponding effect, preferably the steel should contain at least 0.1 wt.% manganese. In order to ensure problem-free further processing by hot-rolling and cold-rolling, the manganese content should not be above 5 wt.%, preferably not above about 2.5 wt.%, and more preferably not above 2.0 wt.%, owing to the formation of brittle phases. A negative effect of Mn on rollability depends in a complex manner upon the total of the elements Al, Si and Mn.

[0052] According to a further aspect, the invention is directed to the use of the NGO electrical steel sheet obtained by the method according to this invention and as described herein in the manufacture of a stator or rotor of an electric machine. For example, the NGO electrical steel sheet according to an embodiment may be cut into suitable parts, for example by stamping. The parts may be stacked, wherein for example about 200 to 3000, preferably about 500 to 1000 steel parts are stacked together. Preferably, the NGO electrical steel sheets are stacked in the axial direction of the electric machine to build the hub of a stator or rotor.

[0053] In an embodiment, the invention is further directed to a stator or rotor of an electric machine comprising the NGO electrical steel sheet obtained by the method according to this invention, in particular a stack of multiple NGO electrical steel sheet parts. The electric machine may be an electric motor or an electric generator or an electric machine which is able to act both ways, and which is preferably used in electric vehicles, in order to allow both electric propulsion and reuse of braking energy. The invention will now be illustrated with reference to non-limiting comparative and examples according to the invention.

[0054] EXAMPLE

[0055] At the Direct Sheet Plant of Tata Steel in IJmuiden, NL, high alloyed NGO electrical steel have been cast and hot-rolled to strip having a thickness in a range of 1.8-2.5 mm. The high alloyed NGO electrical steel had as it main constituents (target values): 0.003 wt.% C, 3.2 wt.% Si, 1 wt.% Al, 0.2 wt.% Mn, balance Fe and inevitable impurities.

[0056] In the “Old Practice” steel from the BOF steelmaking plant is treated in a RH vacuum degassing apparatus and also fully killed by adding substantial amounts of aluminium to achieve an oxygen level of about 1 ppm, next in a ladle furnace Si in the form of FeSi alloy is added to achieve to required Si level and also a small amount of Al is added to arrive at the required Al content in the steel. The molten steel is transferred to a tundish and continuous cast into slabs having a thickness of 72 mm and directly hot rolled to a thickness of 1.8-2.5 mm and coiled.

[0057] In the “New Practice” according to the invention steel from the BOF steelmaking plant is treated in a RH vacuum degassing apparatus but not fully killed by limited amounts of aluminium to achieve an oxygen level in a range of 30-150 ppm, and typically to about 60-80 ppm, next in a ladle furnace Si in the form of FeSi alloy is added to achieve to required Si level and thereafter also Al is added is added to arrive at the required Al content of about 1 wt.% in the steel.

[0058] Each hot-rolled coil has a length of about 800 meters. The surface of the hot-rolled coil is inspected at pre-selected positions of the hot-rolled coil, in total covering about 24 meters of the rolling surface. In particular an assessment is made for so-called “canoe” shaped surface defects having a length of more than 40 cm and a width of about 1-3 cm; these typical surface defects are caused by non-metallic inclusions at and just under-neath the rolling surface of the strip and which become elongated as a result of the hot-rolling process. An example is shown in Fig.1. having a length of about 50 cm. Such long surface defects adversely affect the surface quality of the final cold rolled NGO electrical steel sheet and subsequently affect the performance of a stator or rotor of an electric machine. Earlier investigations have learned that these “canoe” shaped surface defects can be attributed predominantly to non-metallic CaS particles mostly originating from clogging of the SEN.

[0059] Fig. 2 shows the average of “canoe” shaped defects larger than 40 cm per 100 meter of hot-rolled coil for both the “Old Practice” (average over 552 coils) and “New Practice” (average over 470 coils). From this Fig. 2 it can be seen that the practice according to the invention results in a very significant reduction of said surface defects when producing NGO electrical steel strip.

Claims

CLAIMS1. A method of producing Si-alloyed low-carbon steel having at least (in wt.%): up to 0.08% of C, 0.5 to 10% of Si, 0.2 to 4% of Al, up to 5% of Mn, the method comprising the steps of:providing molten steel obtained via a primary steelmaking process; performing a decarbonization treatment in a vacuum degassing apparatus and reducing the oxygen content in the molten steel to a range of 30 to 150 ppm; alloying the molten steel with Si in a ladle furnace and thereafter alloying the molten steel with aluminium; andtransferring the treated molten steel from the ladle furnace into a tundish and casting of the molten steel into slabs in a casting machine.

2. Method according to claim 1, wherein the oxygen content in the molten steel is reduced to a range of 50 to 100 ppm during the decarbonization treatment in the vacuum degassing apparatus.

3. Method according to claim 1 or 2, wherein the vacuum degassing apparatus is an RH or RH-OB vacuum degassing apparatus.

4. Method according to any one of claims 1 to 3, wherein the Si is added to the ladle furnace in the form of ferrosilicon (FeSi) alloy, preferably the FeSi alloy having a Si content of at least 65 wt.%, and preferably at least 70 wt.%.

5. Method according to any one of claims 1 to 4, wherein the oxygen content of the molten steel in the vacuum degassing apparatus is controlled by adding aluminium.

6. Method according to any one of claims 1 to 5, wherein the primary steelmaking process is a basic oxygen furnace (BOF) convertor process.

7. Method according to any one of claims 1 to 5, wherein the primary steelmaking process is a electric arc furnace (EAF) steelmaking process.

8. Method according to any one of claims 1 to 7, further comprising the step of continuously casting the molten steel to form a slab.

9. Method according to claim 8, further comprising the steps of hot rolling the slab, cold rolling, preferably cold rolling to a thickness in a range of 0.1 to 0.65 mm, and final annealing at a temperature in a range of 800 °C to 1100°C.

10. Method according to any one of claims 1 to 9, wherein the method is to produce Si alloyed non-grain-oriented (NGO) electrical steel, said steel comprising, in wt.%, up to 0.03% of C, preferably up to 0.010%;1 to 6% of Si, preferably of 2 to 4.5%;0.4 to 2% of Al, preferably 0.4 to 1.50%;0.1 to 2.5% of Mn, preferably 0.1 to 2.0%;and the remainder of Fe and inevitable impurities.

11. Method according to any one of claims 1 to 9, wherein the method is to produce Si alloyed non-grain-oriented (NGO) electrical steel, said steel comprising of, in wt.%, up to 0.08% of C;0.5% to 10% of Si;0.2% to 4% of Al;up to 5% of Mn;up to 2% of Cr;up to 0.1% of Ti;up to 0.1% of Cu;up to 0.1% of Sn;up to 0.1% of B;up to 0.1% of N;up to 0.1% of S;up to 0.05% of P;up to 0.010% of Ca;and the remainder of Fe and inevitable impurities.

12. Method according to any one of claims 1 to 9, wherein the method is to produce Si alloyed non-grain-oriented (NGO) electrical steel, said steel comprising of, in wt.%, up to 0.03% of C, preferably up to 0.010%;1% to 6% of Si, preferably of 2 to 4.5%;0.4% to 2% of Al, preferably 0.4 to 1.50%;0.1% to 2.5% of Mn, preferably of 0.1 to 2.0%;up to 0.5% of Cr, preferably up to 0.10%;up to 0.1% of Ti;up to 0.1% of Cu;up to 0.1% of Sn;up to 0.1% of B;up to 0.1% of N;up to 0.1% of S;up to 0.05% of P;up to 0.010% of Ca;and the remainder of Fe and inevitable impurities.

13. Use of a non-grain-oriented electrical steel sheet obtained by the method according to any one of claims 9 to 12 in the manufacturing of a stator or rotor of an electric machine.

14. A stator or rotor of an electric machine comprising cold rolled and annealed non-grain- oriented electrical steel sheets having a thickness in a range of 0.1 to 0.65 mm manufactured by the method according to any one of claims 1 to 12.

Images