EP1444372B1 - Method for the production of electrical sheet with non-oriented grains - Google Patents

Abstract

The invention relates to a method for the production of cold-rolled magnetic sheet or strip, with non-oriented granularity and a final thickness of </= 0.75 mm, comprising the following working steps: smelting a steel with (in wt. %) C: </= 0.01 %, Mn: </= 1.5 %, Si: 0.1 - 4.5 %, Al: 0.001 - 2.0 %, P: </= 0.1 %, Sn: </= 0.15 %, Sb: </= 0.15 %, the remainder iron and unavoidable impurities, casting the steel to give thin slabs, a heat treatment of the cast thin slab or strip following on continuously after the casting, hot-rolling of the thin slab or strip following continuously after the heat treatment to give a hot strip with a final thickness of </= 1.8 mm, winding the hot strip, cold-rolling the hot strip to give a cold strip with a final thickness of </= 0.75 mm and a final heat treatment of the cold strip. Said invention combines the effects of the application of a continuous casting and rolling unit (in-line casting and rolling) with the effects of the reduction in complexity on cold-rolling by application of continuously cast hot-rolled strip made from FeSi steels with a thickness of </= 1.8 mm, preferably </= 1.2 mm.

Description

The invention relates to a method for producing non-grain oriented electrical sheet or strip.

Under the term "non-grain oriented electrical sheet" is in this context a steel sheet or a Steel band understood, which is independent of his Texture below those mentioned in DIN 46 400 part 1 or 4 Sheet metal falls and its loss anisotropy in DIN 46 400 part 1 limits. The terms "tin" and "band" are synonymous here used.

• Erschmelzen des Stahls,
• Vergießen des Stahls zu Brammen oder Dünnbrammen,
• soweit erforderlich, Wiedererwärmen der Brammen oder Dünnbrammen,
• Einsetzen der Brammen oder Dünnbrammen in einer Warmwalzstraße,
• Vorwalzen der Brammen oder Dünnbrammen,
• Fertigwarmwalzen der Brammen oder Dünnbrammen zu einem Warmband, dessen Enddicke typischerweise zwischen 2 mm und 3 mm liegt,
• soweit erforderlich Glühen und Beizen des Warmbands, wobei diese Warmbandbehandlungen als kombiniertes Glühbeizen ausgeführt werden können,
• ein- oder mehrstufig mit zwischengeschalteter Glühung erfolgendes Kaltwalzen des Warmbands zu einem Kaltband, und
• Schlußglühen solcher Kaltbänder, die mit einem betragenden Gesamtumformgrad > 65 % kaltgewalzt worden sind, oder
• Glühen und Nachwalzen solcher Kaltbänder, die mit einem höchstens 20 % betragenden Gesamtumformgrad kalt nachgewalzt worden sind.

Conventionally, the production of non-oriented electric sheet (NO electric sheet) includes the steps of

• Melting the steel,
• Casting the steel into slabs or thin slabs,
• if necessary, reheating the slabs or thin slabs,
• Inserting the slabs or thin slabs in a hot rolling mill,
• Rough rolling of slabs or thin slabs,
• Finish hot rolling the slabs or thin slabs into a hot strip whose final thickness is typically between 2 mm and 3 mm,
• if necessary annealing and pickling of the hot strip, whereby these hot strip treatments can be carried out as a combined annealing pickling;
• one or more stages with intermittent annealing cold rolling of the hot strip to a cold strip, and
• Final annealing of such cold-rolled strips which have been cold-rolled to a total degree of deformation> 65%, or
• Annealing and temper rolling of such cold strips, which have been cold rolled with a Gesamtumformgrad totaling no more than 20%.

The variety of such conventional approach To be performed steps leads to high equipment and cost expenses. Therefore, since More recently, work has been done to increase the shedding of the steel and the subsequent rolling processes at the Hot strip production coordinated so that a continuous sequence of casting and rolling saving on reheating and pre-rolling is possible.

For this purpose, so-called "casting-rolling plants" been built. In these also "CSP plants" mentioned Devices, the steel becomes a continuous cast off strand, from the "in-line" Thin slabs are separated, which then also "in-line" to hot rolled to hot strip. The operation of Casting-rolling plants gained experience and advantages of "in-line" casting rolling for example in W. Bald et al. "Innovative technology for banding ", Stahl and Eisen 119 (1999) Nr. 3, Pages 77-85, or C. Hendricks et al. "Installation and first results of the casting rolling mill of Thyssen Krupp Stahl AG ", Stahl und Eisen 120 (2000) Nr. 2, p. 61 - 68, has been documented. The usual hot strip thicknesses lie in the range ≥ 1.8 mm.

The invention had the object of providing a method for cost-effective production of non-grain-oriented To create electrical sheet or strip.

• Erschmelzen eines Stahls mit (in Gew.-%) C: ≤ 0,01 %, Mn: ≤ 1, 5 %, Si: 0,1 - 4,5 %, Al: 0,001 - 2, 0 %, P: ≤ 0,1 %, Sn: ≤ 0,15 %, Sb: ≤ 0,15 %, Rest Eisen und unvermeidbare Verunreinigungen,
• Vergießen des Stahls zu Dünnbrammen oder gegossenem Band,
• kontinuierlich auf das Vergießen folgendes Wärmebehandeln der gegossenen Dünnbrammen oder des gegossenen Bandes,
• kontinuierlich auf das Wärmebehandeln folgendes Warmwalzen der Dünnbrammen oder des gegossenen Bandes zu einem Warmband mit einer Enddicke von ≤ 1,8 mm,
• Haspeln des Warmbands,
• Kaltwalzen des Warmbands zu einem Kaltband mit einer Enddicke von ≤ 0,75 mm, wobei der während des Kaltwalzens erzielte Gesamtumformgrad höchstens 65% beträgt, und
• Schlußwärmebehandeln des Kaltbands.

This object is achieved on the basis of the above-described prior art by a method for producing cold-rolled non-grain-oriented electrical steel or strip having a final thickness of ≤ 0.75 mm, which comprises the following steps:

• Melting a steel with (in wt%) C: ≤ 0.01%, Mn: ≤ 1, 5%, Si: 0.1-4.5%, Al: 0.001-2.0%, P: ≤ 0.1%, Sn: ≤ 0.15%, Sb: ≤ 0.15%, balance iron and unavoidable impurities,
• Casting the steel into thin slabs or cast strip,
• continuously heat-treating the cast thin slabs or the cast strip following casting
• continuously hot-rolling the thin slabs or the cast strip into a hot strip having a final thickness of ≤ 1.8 mm,
• Coiling the hot strip,
• Cold-rolling the hot strip to a cold-rolled strip with a final thickness of ≤ 0.75 mm, the total degree of deformation achieved during cold-rolling being no more than 65%, and
• Final heat treatment of the cold strip.

Depending on the respective production conditions and / or the required quality of the obtained Cold strip, the hot strip before cold rolling a Subjected to pickling treatment and / or before cold rolling be annealed.

The invention couples the through the use of a Casting rolling mill (in-line casting and rolling) achievable Effects with effects of reducing the workload Cold rolling by using hot-rolled strip made of FeSi steels in a thickness ≤ 1.8 mm, advantageously ≤ 1.2 mm.

Due to its nature, hot strip according to the invention can be processed with respect to the prior art significantly reduced effort to cold-rolled NO electrical steel whose final thickness typically 0.35 mm to 0.75 mm, in particular 0.2 mm, 0.35 mm, 0.50 mm or 0.65 mm. It has surprisingly been found that inventively produced NO electric sheet has despite the saving of conventional process always necessary process steps properties that are at least equal to the properties of conventionally produced NO electric sheets. Thus, according to the invention produced electrical sheets based on a FeSi alloy with 1.3% Si share re-magnetization losses P _1.5 of less than 5.3 W / kg. ("P _1.5 " is understood to mean the loss of magnetization at a polarization of 1.5 T and a frequency of 50 Hz.) The grades of the same alloy conventionally produced on the basis of conventional hot strip give values for P _1.5 of> 5.3 W / kg.

The the known casting rolls own continuous Sequence of potting steel to thin slabs and hot rolling the thin slabs to hot strip also allowed in the production of inventive hot strips the Saving of work steps, such as reheating slabs and roughing. In addition, it turns out that the saving of the relevant work steps Effects on the material condition in the different production phases. This is different in some cases significantly from the condition that occurs in the conventional production of hot strip is achieved at the one with a reheating of the cooled slabs is started. In particular, it is the macro segregations as well as the solution and excretion state, the According to the invention produced hot strips of conventional differentiates. In addition, in-line casting rolls the forming process during hot rolling at favorable thermal conditions. So can the Walzstiche applied with higher degrees of deformation and the Forming conditions targeted for the control of Structure development can be used.

According to an advantageous embodiment of the invention, when due to the respective processed steel composition, the transition temperature from the mixing zone to the ferrite A _r1 ≥ 900 ° C ± 20 ° C and in particular when the thickness of the finished hot-rolled hot strip is not more than 1.2 mm , during hot rolling, achieves at least 30% of the thickness decrease in the ferrite area. In such cases, when the transition temperature from the mixture region to the ferrite region A _r1 ≤ 900 ° C ± 20 ° C and the thickness of the finished hot-rolled hot strip is not more than 1.2 mm in particular, it is favorable if at least 35% of the thickness decrease during hot rolling in the two-phase region γ / α.

By being so targeted in the individual Phase state areas made rolls can be especially in the processing of transforming Alloys produce hot strips, which in relation to the NO-electric sheets optimized requirements Own properties. It has, for example shown that by a suitable combination of Phase sequence during hot rolling in conjunction with certain finish rolling and reel temperatures decisive increase of the magnetic polarization reach.

If a rolling is performed in the mixed area, can it also be appropriate to have at least one stitch in the perform pure ferrite. At this Embodiment of the method according to the invention are the By rolling in the mixing area achieved advantages combined with the positive effects of rolling in the Ferrite area brings with it. It is the Thickness decrease during rolling in the ferrite region preferably at least 10% and not more than 33%, so that the Emphasis of reshaping despite the final Rolling in the ferrite area unchanged in the mixed area Austenite / ferrite lies.

Preferably, if at least the last Strokes of hot rolling are carried out in ferrite during hot rolling at least one of the last Forming stitches rolled with lubrication. By hot rolling with lubrication occur on the one hand lower Shear deformations, so that the rolled strip in Result a more homogeneous structure across the cross section receives. On the other hand, by the lubrication the Walzkräfte reduced so that above the respective Walzstich a higher thickness decrease is possible. Therefore It can, depending on the desired properties of the too generating electric sheet, be advantageous if all occurring in the ferrite Umformstiche with a rolling lubrication be performed.

The reel temperature should be chosen so that it at least 300 ° C lower than that Hot rolling end temperature or higher than that by 150 ° C reduced hot rolling temperature. In compliance with the high Reel temperature can usually be at an additional Hot strip annealing entirely or at least substantially be waived. So rewinding at high supports Temperatures the further softening of the hot strip already in the coil, taking its properties determining Characteristics, such as grain size, texture and excretions, be additionally positively influenced.

The low reel temperatures are especially useful higher siliconized electrical sheet grades good Results of work, since in this case, in the course of the Coiling sets a microstructure state when subsequent cold rolling to the expression of a view favorable to the properties of NO electrical sheets Grain structure leads.

Especially if a reel at low Temperatures is carried out, it is in support the further softening of the invention produced Warmbands favorable to perform a hot strip annealing. So can annealed hot strips with particularly good magnetic and technological properties produce.

For the best possible surface finish To ensure the obtained NO-Elektroblechs and Malfunctions during cold strip processing too In addition, it may be useful to do that Hot strip to undergo a surface treatment. This surface treatment usually includes a Pickling of the hot strip, which sticking to the hot strip Tinder is removed. In addition or alternatively, the Surface treatment electrolytic, chemical and / or physically mechanical. The result will be here get a scale-free, as level as possible surface, which ensures a trouble-free cold rolling and the Production of a high-quality cold rolling product supported.

The procedure according to the invention in the production of intended for the production of electrical sheets Hot-rolled strips in particular have an advantageous effect when the thickness of the hot strip when leaving the Hot strip mill is not more than 1.2 mm. So thin According to the invention produced hot strip can be due to its small thickness in a particularly simple Process into a cold-rolled electrical sheet, its final thickness typically 0.35 mm to 0.75 mm, in particular 0.2 mm, 0.35 mm, 0.50 mm or 0.65 mm, is.

In addition, according to the invention on a casting-rolling plant produced hot strip of this thickness already in hot rolled condition at least partially solidified Having microstructure, so that high Gesamtumformgrade and accordingly high forming forces at his Cold forming can be avoided. Instead, it is it is characterized in that the hot strip according to the invention as thin as possibly generated, in particular to thicknesses below 1.2 mm is hot rolled, in the inventive approach regularly enough, the cold rolling with a 20% up 65% total deformation to perform the to achieve the end thicknesses required by the user.

The cold rolling can be multi-stage in a known manner respectively. If necessary, it can be done in the same way known manner between at least one of the stages of Kaltwalzens an intermediate annealing of the cold-rolled strip be performed. This intermediate annealing can be done in one decarburizing atmosphere to be carried out as possible low carbon contents of the resulting NO sheet adjust.

After completion of the cold rolling, the cold strip obtained in a conventional manner a final heat treatment be subjected to in the cold-rolled strip an optimal magnetic texture and grain distribution and size too achieve. In this case, the final heat treatment in a decarburizing atmosphere to be performed the lowest possible and accordingly the magnetic aging preventive carbon content of the finished NO-Elektroblechs set.

To achieve an optimal surface finish can ensure following the Final heat treatment an electrolytic, chemical and / or physical surface treatment of the Cold strip be performed.

Alternatively or additionally, it may improve the Dimensional accuracy and the deformability of the finished NO electric sheet be advantageous, the cold strip after the Nachrollzen final heat treatment, the Gesamtumformgrad <20%.

The invention will be explained below with reference to exemplary embodiments. In the diagram, the magnetic polarization J2500 is plotted against the magnetic reversal loss P _1.5 for various non-grain-oriented electrical sheets. Table 1, which is also attached, shows the properties and processing parameters for non-grain oriented electrical steel sheets produced under hot conditions W1 to W16 under laboratory conditions and Table 2 shows the properties and processing parameters for non grain oriented electrical steel sheets produced under hot conditions W17 to W22.

To determine the properties of the invention produced non-grain oriented electrical sheets is a FeSil.3 alloy with (in wt%) 0.0017% C, 0.195% Mn, 1.286% Si, 0.039% P and 0.128% Al, balance iron and unavoidable impurities have been melted.

The resulting molten steel is in a casting-rolling plant first shed to a strand, from which then in a continuous process Thin slabs were divided, which subsequently as well "in-line" in several passes to hot-rolled strips W1-W22 hot rolled and then reeled. The respective Final thickness WBd of hot strips W1-W22 is shown in Tables 1 and 2 specified. The hot strip thickness WBd of the invention produced hot strips W1-W9 and W17 to W20 was included each below 1.8 mm. For the hot tapes W3, W6, W9 and W17 were even less than 1.2 mm.

The hot tapes W10-W16 and W21 and W22 are in contrast, conventional, not inventive Means have been made by cutting the steel into slabs was poured, which was then first cooled to slabs, then reheated and then rolled, before getting to a final thickness in the hot rolling mill 2 mm hot rolled.

The hot strips W1, W2, W3 and the hot strip W10 are after rewinding into cold tapes 0.35 mm thick, the hot strips W4, W5, W6 and the hot strips W11, W12, W13 as well as the hot tapes W17 to W22 to cold tapes with a Thickness of 0.5 mm and the hot strips W7, W8, W9 and the Hot tapes W14, W15 and W16 to cold tapes with a thickness cold rolled from 0.65 mm. The achieved Forming degrees are in the column UG in the attached Tables entered.

Likewise, the electromagnetic characteristics P _1.0 , P _1.5 , P _1.7 , J ₈₀₀ , J ₁₀₀₀ , J ₂₅₀₀ , J ₅₀₀₀ and J ₁₀₀₀₀ are given in Tables 1.2. Under "P _1.0 ", "P _1.5 " or "P _1.7 " is the loss of magnetization at a polarization of 1.0 T, 1.5 T or 1.7 T and a respective frequency of 50 Hz understood. "J ₈₀₀ ", "J ₁₀₀₀ ", "J ₂₅₀₀ ", "J ₅₀₀₀ " and "J ₁₀₀₀₀ " respectively denote the magnetic polarization at a magnetic field intensity of 800 A / m, 1000 A / m, 2500 A / m, 5000 A / m or 10000 A / m.

It turns out that non-grain-oriented electrical sheets can be produced in the inventive procedure despite or even because of the savings made possible by the use of a casting-rolling plant in hot processing and low deformation in the cold strip production, their properties at least equal to those of conventionally produced sheets or even superior to that, as the diagram shows.

Claims (19)

1. Method for producing cold-rolled non-grain oriented electrical sheet or strip with an end thickness of ≤ 0.75 mm comprising the following working steps:

   melting a steel with (in % by weight) C ≤ 0.01% Mn ≤ 1.5% Si 0.1 - 4.5% Al 0.001 - 2.0% P ≤ 0.1% Sn ≤ 0.15% Sb ≤ 0.15% the remainder iron and unavoidable impurities,

   casting the steel to form thin slabs or cast strip,

   heat treatment of the cast thin slabs or the cast strip continuously following the casting,

   hot-rolling of the thin strips or the cast strip continuously following the heat treatment to form a hot strip with an end thickness of ≤ 1.8 mm,

   coiling the hot strip,

   cold-rolling the hot strip to form a cold strip with an end thickness of ≤ 0.75 mm, wherein the degree of total deformation achieved during the cold-rolling is at most 65%, and

   final heat treatment of the cold strip.
2. Method according to any one of the preceding claims, characterised in that the thickness of the hot strip is at most 1.2 mm and cold-rolling takes place with a degree of total deformation of 20% to 65%.
3. Method according to any one of the preceding claims, characterised in that the hot strip is subjected to a surface treatment.
4. Method according to Claim 3, characterised in that the surface treatment solely comprises pickling the hot strip.
5. Method according to one of Claims 3 or 4, characterised in that the surface treatment consists of a combination of a physical, in particular a mechanical treatment with a chemical treatment, such as pickling.
6. Method according to any one of the preceding claims, characterised in that at least 30% of the reduction in thickness is achieved during hot-rolling in the ferritic area, when the transition temperature from the mixed area to the ferritic area is A_r1 ≥ 900°C ± 20°C.
7. Method according to any one of Claims 1 to 5, characterised in that at least 35% of the reduction in thickness is achieved during hot-rolling in the two-phase area γ/α, when the transition temperature from the mixed area to the ferritic area is A_r1 ≤ 900°C ± 20°C.
8. Method according to Claim 6 or 7, characterised in that at least one pass is carried out in the pure ferritic area and in that the reduction in thickness during rolling in the ferritic area is at least 10% and at most 33%.
9. Method according to any one of the preceding claims, characterised in that at least one pass is carried out with lubrication during hot-rolling in the ferritic area.
10. Method according to any one of Claims 6 to 9, characterised in that for the coil temperature:

    coil temperature > hot rolling end temperature - 150°C applies.
11. Method according to any one of Claims 6 to 9, characterised in that for the coil temperature:

    coil temperature < hot rolling end temperature - 300°C applies.
12. Method according to any one of the preceding claims, characterised in that the hot strip is subjected to a hot strip annealing.
13. Method according to any one of the preceding claims, characterised in that the cold-rolling is carried out in a multi-stage manner.
14. Method according to Claim 13, characterised in that an intermediate annealing of the cold-rolled strip is carried out between at least one of the stages of the cold-rolling.
15. Method according to Claim 14, characterised in that the intermediate annealing is carried out in a decarbonising atmosphere.
16. Method according to any one of the preceding claims, characterised in that the final heat treatment is carried out in a decarbonising atmosphere.
17. Method according to any one of Claims 1 to 15, characterised in that the final heat treatment is carried out in a non-decarbonising atmosphere.
18. Method according to any one of the preceding claims, characterised in that an electrolytic, chemical and/or physical surface treatment of the cold strip is carried out following the final heat treatment.
19. Method according to any one of the preceding claims, characterised in that the cold strip is after-rolled after the final heat treatment with a degree of total deformation of < 15%.

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