Title of Invention

METHOD FOR THE PRODUCTION OF NON-GRAIN ORIENTED ELECTRICAL SHEET

Abstract

This invention relates to a 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 reminder 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, cooling 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. The invention couples the effects which can be achieved by the use of a casting and rolling plant (in-line casting and rolling) with the effects of the reduction in outlay in cold-rolling by the use of cast and rolled hot strip made of FeSi steels in a thickness ≤, 1.8 mm, advantageously ≤ 1.2 mm.

Full Text

METHOD FOR THE PRODUCTION OF NON-GRAIN ORIENTED ELECTRICAL SHEET The invention relates to a method for the production of non-grain oriented electrical sheet or strip. In this context, the term "non-grain- oriented electrical sheet" is taken to mean a steel sheet or steel strip which regardless of its texture comes under the sheets mentioned in DIN 46 400 Part 1 or 4 and the loss anisotropy of which does not exceed the maximum values established in DIN 4 6 400 Part 1. The terms "sheet" and "strip" are used' synonymously here. Conventionally, the production of non-grain oriented i electrical sheet (NO electrical sheet) comprises the steps: melting the steel, casting the steel to form slabs' or thin slabs, if necessary, reheating the slabs or thin slabs,. using the slabs or thin slabs in a hot-rolling line, prerolling the slabs or thin slabs, finishing hot-rolling of the slabs or thin slabs to form a hot strip, of which the end thickness is typically between 2 mm and 3 mm, if necessary, annealing and pickling of the hot strip, wherein these hot strip treatments can be carried out as combined annealing pickling, single-stage or mul^i-stage cold-ro'lling of the hot strip taking place with interposed annealing to form a cold strip, and final annealing of cold strips of this type which have been cold-rolled wi;h' a degree of total deformation > 65%, or annealing and after-rolling of cold strips of this type which have been cold aftier-rolled with a degree of total deformation of at most 2 0%. The large number of working steps to be carried, out , in a conventional procedure o:: this type leads to high outlay in terms of apparatus and costs. Therefore 'recently increased efforts have been made to match the casting of the steel and subsequent rolling 'processes in the hot strip production to one another such that a continuous sequence of the casting and rolling' process is made possible dispensing with the reheating and the prerolling. For this purpose, so-called "casting/rolTing plants" have been set up. In these devices also called "CSP plants'", the steel is cast to form a continuously drawn strand, from which thin slabs are then separated off "in-lin,e", are then hot-rolled to form hot st.rip, also "in-line". The experiences obtained during the operation of casting and rolling plants and the advantages of the "in-line" casting/rolling have been documented, for example, irf W. Bald et al. "Innovative Technologic zur Banderzeugung", Stahl und Eisen, 119 (1999) No. 3, pages 77 to 85, or C, Hendricks et al. "Inbetriebnahme und erste Ergebnisse der Gieftwalzanlage der Thyssen Krupp Stahl AG", Stahl und Eisen (Steel and iron), 120 (2000) No. 2, pages 61 to 68. The conventional hot strip thicknesses are here in the ranqe > 1.8 mm. The invention was based on the object of providing a method for economical production of non-grain oriented electrical sheet or strip. This object is achieved, starting from the above-described prior art, by a 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 witi (in % by weight) C: = 0.01%, Mn: ¦ = 1.5%, Si: 0.1 - 4.5%, Al: 0.001 - 2.0%, P: = 0.1%, 1 i , ' ' i ' ¦ i Sn: = 0.15%, Sb: = 0.15%, the remainder iron and unavoidable impurities, casting the steel to form thin slabs or cast stifip, 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, and final heat treatment, of the cold strip. Depending, on the respect Lve .production conditions and/or the required composition of the cold strip obtained, the hot strip can be subjected to a pickling treatment prior to the cold-rolling and/qr can be annealed prior to the cold- rolling. The invention couples the effects which can be achieved by the use of a casting and rolling plant (in-line casting and rolling) with effects of reduction in the outlay durdlng cold-rolling by the use of cast and rolled hot strip made of FeSi steels in a thickness = 1.8 mm, .preferably = 1.2 mm. Owing to its composition, a hot strip according to the invention can be processed to form cold-*rolled NO electrical sheet with isignificantly reduced outlay compared 'to the prior art, the; end thickness of the ;N0 elect^iqdl! sheet typically being 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 shown that NO electrica L sheet produced according to the invention, despite dispensing with process steps which are constantly necessary in the case of conventional procedures, has properties which are at 'least equal to the properties of conventionally produced NO electrical sheets. Electrical sheets produced, according to t;he invention on the basis of an FeSi alloy with 1.3% Si content thus have magnetic losses Pi.5 of less than 5.3 W/kg. ("Pi.5" is taken to mean the magnetic less at a polarisation of 1.5 T and a frequency of 50 Hz) . ,The grades of1 the s^me alloy pitotijuced conventionally on the bas:.s of conventional hot strip in each case produce values ror PL5 of > 5.3 W/kg. The continuous sequence particular to known continuous casting and rolling, of casting the steel to form thin slabs and hot-rolling the thin slabs to form hot strip, also allo'ws working steps to be dispense^ with in the production of hot strips according to the invention, as for example the reheating of r.he slabs and pJrerolling. Moreover, it has been 'shown that dispensing with the corresponding working,' steos influences the 'material I stlatfe in the various production phases. This sometimes differs considerably from the state achieved in the conventional production of hot strip in which at the beginning the cooled slab is reheated. In particular, it is the macroliquations and the solution and precipitation state which differentiates hot strips produced according to the invention from those produced conventionally. In addition, the forming process during, the hot,-rollin_g takes place in favourable thermal conditions in in-line casting and rolling. Thus the rolling passes can be 'applied with higher degrees of deformation! and the deformation conditions can be used in a targeted,' marner to control the1 structure development. According to an advantageous configuration of the invention, at least 30% of the reduction in thickness in the ferritic area is achieved during the hot-rolling, if owing to the respectively processed steel composition, the transition temperature of the mixed area to the ferritic area is Arl > 900°C ± 20°C and in particular, when the thickness of the finished hot-rolled hot strip is not more than 1.2 mm. In such cases when the transition temperature i ¦; from the mixed area to the ferritin area is Ari = 900°C + 20°C and the thickness of the finished hot-rolled hot strip is, i.n particular, not mors than 1.2 mm,' it is favourable in contrast if at least 35% of the reduction in thickness during the hot-rolling 'is achieved in the two phase ^rea y/cx. Owing to the rolling carried out in a targeted manner of this type in the individual .phase state areas, in particular during the processing of converting alloys, hot strips can be produced, which have optimised properties with respect to the requirements made of'NO electrical sheets. It has been shown, for example, that owing to .a1 t suitable combination of the phase sequence during hot- ' rolling, in conjunction with specific end.rolling and coil temperatures, a decisive increase in the magnetic polarisation can be achieved. If a rolling is carried out in the mixed area, it may equally be expedient, to carry out at least one pass in the pure ferr.itic area. In this configuration of the method according to the invention, the advantages achieved by rolling in the mixed area are combined with the positive effects entailed by rqlling in the ferritic area. In the process, the reduction in thickness during , rolling in .the ferritic area is advantageously at least 10% and at most 33%, so that the emphasis of the deformation, despite the final rolling in the ferritic area lies unchanged in the austenitic/ferritic mixed area. If at least the last passes of the hot-rolling are carried out in the ferritic area, rolling is advantageously carried out with lubrication, at least in one of the last deformation passes during the hot-rolling. Owing to the hot-rolling with lubrication, on the one hand smaller shearing strains occur, so the rolled strip therefore receives a more uniform structure over the cross-section. On the other hand, the rolling forces are reduced owing to the lubrication, so a higher reduction in thickness is possible over the respective rolling pass. It may therefore be advantageous, depending on the desired properties of the electrical sheet to be produced, if all ,the deformation passes taking place in the ferritic area are carried out with a rolling lubrication. . The coil temperature should be selected ,such that it is at least 300°C lower than, the hot-rolling end temperature or is higher than the hot-rclling temperature .reduced by 150°C. In maintaining the high coil temperature an additional hot strip annealing can generally be completely or at least substantially dispensed with. Thus, the coiling at high temperatures assists the further softening of* the hot strip already in the coil, the features determining its properties, such as grain size, texture ,and precipitations also being positively influenced. The low coil temperatures produce good working results, in particular with highly siLiconised grades of electrical sheet, as in this case, in the course of coiling, a structural state is adjusted whichi during the s-ubsecjueprtf cold-rolling leads to the development of a grain structure which is favourable in ?:_ew of the properties of NO electrical sheets. In particular, when coiling is carried Out at low temperatures, it. is favourable for assisting further softening1 of the hot strip, produced according to the invention, to carry out a hot strip annealing. Annealed hot strips can thus be produced with particularly good magnetic and technological properties. To ensure a surface composition of the NO electrical sheet obtained which is as perfect as possible and to avoid operating disturbances during the cold strip treatment, it may moreover be sensible to subject the hot strip to a surface treatment. This surface treatment generally comprises pickling the hot strip, during which scales adhering to the hot strip are removed. In addition1or alternatively, the surface.treatment cantbe carried out electrolytically, chemically and/or physically mechanically. As a result, a scale-free 'surface which is as flat as possible is obtained and which ensures disruption- free cold-rolling and assists the production of a highl- grade cold-rolled product. The procedure according to the invention in the production of hot strips intended for the production of electrical sheets is particularly advantageous when the thickness of the hot strip on leaving the hot strip line is at most 1.2 mm. A thin strip of this type produced according to the invention can be processed'in a particularly simple manner owing to its small thickness to form a cold-rolled electrical sheet, the end thickness of which is typically 0.35 mm to 0.75 mm, in particular 0.2 mm), 0.35 mm, 0.50 mm or 0.65 mm. In addition, a hot strip of this thickness produced according to the invention on a casting and rolling plant in the hot-roll€id state already has an at least parti'ally softened structure, so high degrees of total deformation and correspondingly high deformation forces can be avoided during its cold deformation. Instead, because the hot strip is produced as thin as passible according to the invention, in particular is hot-rolled to thicknesses below 1.2 mm, in the procedure according to the invention it is regularly i sufficient to carry out the cold-rollingjwith a degree of toral deformation of 20? to 65% to'1 achieve -the 'end thicknesses required by the user. The cold-rolling can ta'-ce place in a multi-stage manner as is known. If required, as is also known, an intermediate annealing of the cold-rolled strip can be carried out between at least one of the stages of cold rolling. This intermediate annealing can be carried out in a , decarbonising atmosphere in-order to adjust carbon contents of the NO electrical sheet obtained which are as low as possible. On completion of the bold-rolling,' the cdld strip obtaiiirited can be subjected in a conventional manner to a final heat treatment in order to achieve an optimum magnetic texture and grain distribution and size in the cold ship. In the process, the final heat treatment can also be carried out in a decarbonising atmosphere in order to adjust a carbon content of the finished NO electrical sheet which is as small as possible and accordingly prevents the magnetic ageing. In order to ensure an optimum surface composition, following the final heat treatment, an electrolytic, 1 ' ' ' I 'i chemical and/or physical surface treatment of the cold strip can be carried out As an alternative or additionally, to improve the dimensional stability anc deformability of the finished NO electrical sheet, it may be advantageous to after-roll the cold strip after the final heat treatment, the degree of total deformation being = 20%. The invention will be described hereinafter with the aid of embodiments. The magnetic polarisation J2500 is plotted in the graph over the magnetic loss Px 5 for'various non-girain oriented electrical sheets. The properties and processing parameters for non-grain oriented electr-ical sheets produced from hot strips Wl to W16 under laboratory conditions are given in the also attached Table 1 and, the properties and processing parameters for non-grain oriented electrical sheets produceo from hot strips W17 to W22 under operating conditions are given in Table 2. An FeSil.3 alloy with (in % by weight) 0*0017% C, 0.195% Mn, 1.286% Si, 0.039% P and 0.128% Al, the remainder iron i and unavoidable impurities were melted t=j> determine the properties of non-grain oriented electrical sheets produced according to the invention. The steel melt obtained is firstly cast to form a strdland in a casting and rolling plant, from which strand thin slabs are then separated off in a continuous operation, the thin slabs then being hot-rolled also "in-line" in a plurality of passes, to form hot strips Wl to W22 and are then coiled. The respective end thickness WBd of the hot strips Wl to W22 is given in Table 1 and 2. The hot s^trip thickness WBd of the hot strips Wl t,o W9 and W17 to W20 prqduced according to the invention was, jj.ni each case, below i L-.Q-'-mm here. In the hot strips W3, W6, W9 and W17 it was even less than 1.2 mm. The hot strips W10 to W16 and W21 and W22 were in cprftrast produced in a conventional manner not according to the invention, in that the st.eel was cast to form slabs which were then firstly cooled to form slabs, then pre-heated and then pre-rolled before they .were hot-rolled in thehot- rolling stands to an end thickness of 2 mm. i The hot strips Wl, W2,, W3 and the hot strip W,10 were co^d- rolled after coiling to form cold strips wj,th a- thickness of 0.35 mm, the hot strips W4, W5, W6 and the hot stri'p^, Wll, W12, W13 and the hot: strips W17 to W22 were cold- rolled to form cold strips with a thickness of 0.5 mm and the hot strips W7, W8, W9 and the hot strips W14, W.l^ and W16 were cold-rolled to form cold strips with a thickness of 0.65 mm. The degrees of deformation thus achieved are entered in the column UG in the attached tables. The electromagnetic properties Pi.o, Pi.5, Pi.7, Jboo? J1000/ J2500, J5000 and J10000 are given in Tables 1, 2. "P1.0", "Pi.5" and "Pi.7" are here takjen to mean the maqnetiq loss at a. polarisation of 1 .0 TV, l.b T and'l1. 7 T and la re'specttiv|4,'"i' frequency of 50 Hz. "J800'\ "Jiooo", "J2500", "J5000" and -/ "J10000" designate the magnetic polarisation at a magnetic field intensity of 800 A/m, 1000 A/m, 2500 A/m, 5000 A/m and 10000 A/m. It has been shown that in the procedure 'according to the invention, despite or precisely because of dispensing with working s'teps owing to'the, use of .a casting and rolling plant in the heat processing and the small degrees of deformation in the cold strip production^ non-grain oriented electrical sheets can be produced, the properties of which are at least' equal to those of sheets produced ! conventionally or are even superior to them, as the graph shows. We Claim: 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%, AI:0.001-2.0%, P:=0.1%, Sn:=0.15%, Sb:=0.15%,the remainder being 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 from a hot strip with an end thickness of = 1.8mm, - cooling the hot strip, - cold-roiling the hot strip to form a cold strip with an end thickness of =0.75mm, 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 as claimed in any one of the preceding claims, wherein 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 as claimed in any one of the preceding claims wherein the hot strip is subjected to a surface treatment. 4. Method as claimed in claim 3, wherein the surface treatment solely comprises pickling the hot strip. 5. Method as claimed in one of claims 30or 4, wherein the surface treatment consists of a combination of a physical, in particular a mechanical treatment with a chemical treatment, such as pickling. 6. Method as claimed in one of the preceding claims, wherein at least 30% of the reduction in thickness is achieved during hot during hot-rolling in the ferritic area, when the transition temperature from the mixed area to the ferritic area is Arl>900°C ±20°C. 7. Method as claimed in claim any one of claims 1 to 5, wherein at least 35% of the reduction in thickness is achieved during hot-rolling in the two phase area Yd, when the transition temperature from the mixed area to the ferritic area is Ari=900°C±20°C. 8. Method as claimed in claim 6 or 7, wherein 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 as claimed in any one of the preceding claims, wherein at least one pass is carried out with lubrication during hot-rolling in the ferritic area. 10. Method as claimed in any one of claims 6 to 9, wherein the coil temperature is higher than the hot rolling end temperature reduced by 150°C. 11. Method as claimed in any one of claims 6 to 9, wherein the coil temperature is at least 300°C lower than the hot-nlling end temperature. 12. Method as claimed in any one of the preceding claims, wherein the hot strip is subjected to a hot strip annealing. 13. Method as claimed in any one of the preceding claims, wherein the cold- rolling is carried out in a multi-stage manner. 14. Method as claimed in any claim 13, wherein an intermediate annealing of the cold-rolled strip is carried out between at least one of the stages of the cold- rolling. 15. Method as claimed in any claim 14, wherein an intermediate annealing is carried out in a decarbonising atmosphere. 16. Method as claimed in any one of the preceding claims, wherein the final heat treatment is carried out in a decarbonising atmosphere. 17. Method as claimed in any one of claims 1 to 15, wherein the final heat treatment is carried out in a non-decarbonising atmosphere. 18. Method as claimed in one of tha preceding claims, wherein an electrolytic, chemical and/or physical surface treatment of the cold-strip is carried out following the final heat treatment. 19. Method as claimed in one of the preceding claims, wherein the cold strip is after-rolled after the final heat treatment with a degree of total deformation being less than 15%. This invention relates to a 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 reminder 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, cooling 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. The invention couples the effects which can be achieved by the use of a casting and rolling plant (in-line casting and rolling) with the effects of the reduction in outlay in cold-rolling by the use of cast and rolled hot strip made of FeSi steels in a thickness ≤, 1.8 mm, advantageously ≤ 1.2 mm.

Documents:

626-kolnp-2004-abstract.pdf

626-kolnp-2004-assignment.pdf

626-KOLNP-2004-CLAIMS 1.1.pdf

626-kolnp-2004-claims.pdf

626-kolnp-2004-correspondence.pdf

626-kolnp-2004-description (complete).pdf

626-kolnp-2004-drawings.pdf

626-kolnp-2004-examination report.pdf

626-kolnp-2004-form 1.pdf

626-kolnp-2004-form 18.pdf

626-kolnp-2004-form 2.pdf

626-kolnp-2004-form 26.pdf

626-kolnp-2004-form 3.pdf

626-kolnp-2004-form 5.pdf

626-kolnp-2004-form 6.pdf

626-kolnp-2004-granted-abstract.pdf

626-kolnp-2004-granted-assignment.pdf

626-kolnp-2004-granted-claims.pdf

626-kolnp-2004-granted-correspondence.pdf

626-kolnp-2004-granted-description (complete).pdf

626-kolnp-2004-granted-drawings.pdf

626-kolnp-2004-granted-examination report.pdf

626-kolnp-2004-granted-form 1.pdf

626-kolnp-2004-granted-form 18.pdf

626-kolnp-2004-granted-form 2.pdf

626-kolnp-2004-granted-form 26.pdf

626-kolnp-2004-granted-form 3.pdf

626-kolnp-2004-granted-form 5.pdf

626-kolnp-2004-granted-form 6.pdf

626-kolnp-2004-granted-reply to examination report.pdf

626-kolnp-2004-granted-specification.pdf

626-kolnp-2004-granted-translated copy of priority document.pdf

626-kolnp-2004-others.pdf

626-kolnp-2004-reply to examination report.pdf

626-kolnp-2004-specification.pdf

626-kolnp-2004-translated copy of priority document.pdf