US3905843A

US3905843A - Method of producing silicon-iron sheet material with boron addition and product

Info

Publication number: US3905843A
Application number: US506546A
Authority: US
Inventors: Howard C Fiedler
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1974-01-02
Filing date: 1974-09-16
Publication date: 1975-09-16
Anticipated expiration: 1992-09-16

Abstract

High-permeability silicon-iron sheet is produced by providing a melt containing about 10 parts per million boron, 45 parts per million nitrogen and about 0.030 per cent of manganese and sulfur, hot rolling from about 2250*F, and finishing with a final cold reduction of 80 per cent.

Description

United States Patent 1191 Fiedler Sept. 16, 1975 METHOD OF PRODUCING SILICON-IRON [56] References Cited SHEET MATERIAL WITH BORON UNITED STATES PATENTS ADDITION AND PRODUCT 3.575.739 4/1971 Fiedler 148/1 1 1 [75] Inventor: Howard C. Fiedler, Schenectady, 7 5 10/1972 Tanaka et 4 I43/ I l 3,725,143 4/1973 Alworth etal. 75 123 B [73] Assignee: General Electric Company, FOREIGN PATENTS 0R APPLICATIONS Schenectady, N.Y. -7663 4/1965 Japan 148 11 1 22 F] d: S t. 16, 1974 1 le ep Primary Examiner-Walter R. Satterfield [2 l Appl. No.: 506,546 Attorney, Agent, or Firm-Charles T. Watts; Joseph T.

Related US. Application Data Cohen; Jerome Squmaro [6U] Continuation-impart of Ser, No. 429,791, Jan. 2,

I974, abandoned, which is a continuation-in-part of [57] ABSTRACT SBr. N0. Z n- I973, flbandflned- High-permeability silicon-iron sheet is produced by providing a melt containing about 10 parts per million 148/111; 75/123 B; 75/123 L; boron, parts per million nitrogen and about 0.030 148/3155; 148/] per cent of manganese and sulfur, hot rolling from [S 1] Int. Cl. H0" 1/04 about 225mg and fi i hi with a fma| m reduction 1581 Field of Search 148/111, 110, 112, 31.55; f 80 percent,

/123 B, I23 L l3 Claims, N0 Drawings I METHOD OF PRODUCING SILICON-IRON SHEET MATERIAL WITH BORON ADDITION AND PRODUCT This is a continuation-in-part of my copcnding patent application Ser. No. 429.7%, now abandoned. filed Jan. 2. I974. which is a continuation-in-part of my patent application Ser. No. 320.669. filed Jan. 2. W73 (now abandoned). both assigned to the assignee hereof.

The present invention relates generally to the art of making polycrystalline. magnetically soft. rolled silicon-iron products. and is more particularly concerned with a novel method of producing highpcrmeability. singly oriented siliconiron sheet including as essential features the use of boron in small but critical amount. nitrogen in the metal in critical ratio to the boron. the presence of manganese and sulfur in a ratio less than 2.1. a cold rolling schedule including an intermediate annealing step and a final heavy cold rolling reduction. This invention additionally concerns a new hot-rolled silicon-iron band product.

CROSS REFERENCES This invention is related to the invention disclosed and claimed in patent application Ser. No. 43l.l28 now abandoned. filed Jan. 7. I974 as a COI'IIIIIUZIIIOI'PIII- part of patent application Ser. No. 326.852 (now abandoned). filed .Ian. 27. 1973. entitled Method of Producing Oriented Silicon-lron Sheet Material With Boron Addition in the name of Herbert E. Grenoble and assigned to the assignee hereof. which pertain to the concept of using small but critical amounts of boron to enable the production of singly-oriented silicon-iron sheet.

The invention disclosed and claimed herein also relatcs to that disclosed and claimed in patent application Ser. No. 429.800. now abandoned. filed .Ian. 2. I974. as a ctmtinuation-in-part of patent application Ser. No. 32ll.hb8 (now abandoned). filed Jan. 2. I973. entitled Method of Producing Oriented Silicon-Iron Sheet Material With Boron Addition" in my name and assigned to the assigncc hereof. which pertain to the novel concept ofcold rolling hot-rolled silicon-iron sheet directly to final thickness without an intermediate heat treatment through the use of small but critical amounts of boron and by maintaining the ratio of manganese to sulfur in the metal at less than [.5.

BACKGROUND OF THE INVENTION The sheet materials to which the invention is directed are usually referred to in the art as electric-til silicon steels or. more properly. silicon-irons and are ordinarily composed principally ofiron alloyed with about 2.2 to 4.5 per cent silicon and relatively minor amounts of various impurities and very small amounts of carbon. These products are of the cube-on-edgc" type. more than about 70 percent of their crystal structure being oriented in the 1 HUIHUI texture. as described in Miller Indices terms.

Such grain-oriented silicon-iron sheet products are currently made commercially by the sequence of hot rolling. heat treating. cold rolling. heat treating. again cold rolling and then final heat treating to dccarhurizc. dcsulfurize and recrystallize. lngots are conventionally hot-worked into a strip or sheet-like configuration less than H.150 inch in thickness. referred to as hot rolled band." The hot rolled band is then cold rolled with appropriate intermediate annealing treatment to the finished sheet or strip thickness usually involving at least a 50 per cent reduction in thickness. and given a final or texture-producing annealing treatment.

From time to time. there have been reports in the literature of methods by which unusually high permeability silicon-iron sheet materials can be consistently produced through departures from conventional practice in respect to melt chemistry. rolling schedules and heat-treating conditions. To the best of my knowledge. however. none of these methods has proven to be entirely satisfactory. In some cases the cost is too high, while in others residues of processing additives defy removal efforts and penalize product magnetic properties.

SUMMARY OF THE INVENTION I have discovered that unusually high permeability silicon-iron sheet material can be consistently produced by a novel process. the economics of which compare favorably with those of present commercial operations. Thus. I have found that these results can be obtained by making new departures from the present general practice which do not require modification ofconventional silicon-iron mill production or processing equipment and do not significantly increase either labor or material costs.

In the practice of this invention. a silicon-iron melt containing at least (H)! per cent manganese and being otherwise of ordinary chemistry can be used. a small but critical amount of boron being added to establish a nitrogen to boron ratio in the metal in the range of one to fifteen parts of nitrogen per part of boron and the ratio of manganese to sulfur being adjusted to less than 2.l. Further. I have found that finished products of substantially improved magnetic properties can be obtained by cold rolling to an intermediate thickness and then heat treating the cold-worked sheet. and thereafter subjecting the silicon-iron sheet to a final heavy cold reduction.

l contemplate in addition the use ofselenium in place of part of or all the sulfur required in accordance with this invention. As in the case of sulfur. the selenium requirement of this new process can be met in various Ways. my preference being to add the requisite amount to the ladle in elemental form or as ferroselcnium.

DETAILED DESCRIPTION OF THE INVENTION Generally described. my present invention comprises the steps of providing a silicon-iron melt containing 2.2 to 4.5 per cent silicon. manganese and sulfur in amounts in a ratio of manganese to sulfur of less than 2. 1. between about three and 35 parts per million boron and between 30 and 60 parts per million nitrogen in the ratio to boron of l to l 5 parts per part of boron. casting the melt to form an ingot. hot rolling the ingot. then cold rolling the resulting hot-rolled band to intermediate thickness. heat treating the cold-worked sheet. and then subjecting the silicon-iron sheet to a final heavy cold reduction. Thereafter. the cold-rolled sheet is subjected to a final heat treatment to decarburizc it and to develop cube-on-edge secondary recrystallization texture in it.

Preferably. the boron content of the metal at the outset of the final heat treatment is from 5 to 25 parts per million. such amount of boron in suitable form being added at the melt stage. It is contemplated. however. that the boron will be in amount from about three to about 35 parts per million as l have found that addition of less than three ppm of boron to silicon-iron melts is not sufficient to consistently produce the new results of this invention. and amounts of boron greater than 35 ppm require the presence of nitrogen in amounts in ex' cess of those normally obtained in conventional melting practice.

The boron content of the metal at the melt stage can differ significantly from that at the hot-rolled band stage. particularly when the melt addition of the boron source is made early or when the ingot is soaked at unusually high temperature or for a prolonged period of time. Boron loss. however. has been found to be negligible when the boron source is added to the ladle and hot rolling is begun as the ingot reaches hot rolling te mperature as subsequently described. Thus. it is possible in carrying out this invention process to produce a hotrolled band and a cold-rolled sheet of final gauge thickness which have apparently the same bulk contents of boron. nitrogen. manganese and sulfur as the melt in the ladle from which they were derived. By the same token. it is possible to produce such band and sheet materials of substantially different chemistry. The important consideration. however. is the composition of the band or sheet. particularly in terms of the foregoing four elements and their critical ratios during the cold rolling and intermediate and final annealing stages of this process.

lt will be understood from the foregoing that this invention has both article and method aspects. the new product being a hot-rolled band containing 2.2 to 4.5 per cent silicon. manganese and sulfur in the ratio of manganese to sulfur less than 2. l between about 3 and 35 parts per million boron. and between 30 and 60 parts per million nitrogen in the ratio to boron of l to 15 parts per part of boron.

The boron content of ordinary silicon-iron is negligible. proving on wet analysis to be less than one part per million. Accordingly. for practical purposes in this specification and the appended claims. the terms boron content" and boron addition in their various forms have the same essential meaning.

Permeabilities in the rolling direction of typical prod ucts of the present invention l l-mil strip materials) are of the order of [850 to I920 gauss as measured in a l-oerstcd magnetic field. The watt losses of these materials likewise are in a highly favorable range. being of the order of 0.52 to 0.60 watt per pound (wpp) at l5.000 gauss and 0.67 to 0.77 wpp at 17.000 gauss (60 hertz According to the present invention as I prefer to practice it. silicon steels containing about 0.03 per cent of each manganese and sulfur. and about 0.03 per cent of carbon. and usual amounts of incidental impurities are produced in the form of strips or sheets for use in electrical equipment including transformers and mo tors by providing a melt of the required chemistry and adding to it a source of boron equivalent to to parts per million of boron to establish a nitrogen to boron ratio of one to fifteen parts per part of boron. Ingots cast from the melt are heated preferably to about 2200 to 2300F and hot rolled in a series of passes until the thickness of the resulting sheets is about l00 mils. After pickling and annealing. the sheets are cold rolled to intermediate thickness of about 60 mils and reheated and then cold rolled again to final thickness of about l mils. Thereafter. the cold-worked sheet is given a dccarburizing heat treatment and a recrystallizing (texturizingj anneal during which boron is largely. if not entirely. eliminated from the sheet or strip product.

ln a commercial-scale operation designed to test the capabilities of this new process in a production'type operation. a -ton melt was prepared using BOF silicon-iron. Five parts per million of boron in the form of i'erroboron were added to the melt in the ladle. which then had the following composition:

Silicon 1 l5 percent (oppcr 0 24 hromium 0.033 Aluminum 0.005 Manganese 0.035 Sulfur 0.03l Carbon 0.030 Boron 0.0006 Nilruge'll 0.01150 lron Remainder Eight ingots were cast from this melt and four of these were heated to 2350 for hot rolling, while the other four were heated to 2250". Hot rolling was carried out in accordance with standard production prac tice in a six-strand tandem hot strip mill to provide hotrolled bands from to l 30 mils thick. Samples of the hot-rolled hand from the butt and hot top end of each hot-rolled coil were pickled in the conventional acid solution and then heat treated in hydrogen for approximately 3 minutes at 900C. Some of these sample ieces were cold rolled without tension directly to a thickness of approximately l l mils. while others were cold rolled without tension to 60 mils thickness and then heat treated in hydrogen for 3 minutes at 900C before rolling to l l mils.

Epstein-size strips of all the resulting coldrolled sheet materials were decarburized at 800C in hydrogen (room temperature dewpoint) by heating for 3 min utes. The strips comprising the Epstein pack were lightly dusted with alumina powder and stacked and then heat treated. being loaded at 800C and heated at 50C per hour to 10S0C in nitrogen and then to ll50"C in hydrogen where they were held for two hours. Magnetic properties of the Epstein packs are set forth in Tables I and ll.

As shown by the data in Tables I and II. both ends of a coil more consistently develop high permeabilities and low losses if a heat treatment step at 60 mils is included in the cold-rolling schedule. Furthermore. it is apparent from these data that very good magnetic properties are more consistently obtained in these materials when hot rolling is begun at 2250F than when the temperature of the ingot at the outset of hot rolling is [00F higher.

TABLE l Magnetic Properties ol Stun Hol Rol|ed From 2350? TABLE l-Continued Magnetic Properties ol Strip Hot-Rolled From 2350 F The manganese and sulfur analyses and the boron added in each instance are set out in Table I]! together with the rolling and heat-treating conditions and the re- (iage Losses. Inwpp salts of permeability and watt loss measurements made (ml Location MIls ISUkB lhjkli I'HlkB alllH 5 on each individual finished prfiduct Two Staged Rolled (6U Mil Intermediate (iagc) I Butt H2 524 Mu n77 luo} A I Hot H 3 Ml ma) Ham Slices l.75 Inch thIck were cut trom SU-pound ingots j r cast from each melt of this series and heated either to ot o I. y s. 5 Bun p H2 5W M7 (7U I 175C or l2(l(l( for hot roll ng. as noted In Table Ill. 5 Hot lop IL: 53! 62*) as! Isun The ingot portions were hot rolled to 90 mils thickness in six passes without reheating. Each resulting hot- TABl E rolled band was pickled and then cold rolled to intermediate thickness either of 60 mils or of 28 mils. then heat treated for three minutes at 900 in h 'dro en d Magnetic Properties of Strip HobRolled Front IISUI" q g age [40mgv mwpp finally cold rolled to l lm1l thickness. (Nominal l l-nnl (oil Location Mils Isokn 16,3I-4B 17am NIH strip ranged in these runs from 11.0 to ll.3 mils in Direct Cold Rolled thlckncss' 1 Butt Ill (33 7uo was Ins :3 I a Epstein strips of each of these cold-rolled sheet Prodi L i 7 Hot lop II. 1 5% 7m 7:44 lsftn ucts were decarburized by sub ecting them for 3 mm- 8 Butt utes to a temperature of 800C in hydrogen at room s Hot l'op H1 594 7I2 79o II 27 3 M )d Th f h l l'uo Staged Rolled [o Mil intermediate (iagc) L'WljolnL or t 8 1nd dnned Wat (I Bun ll 2 l NIX I loss strips (3 cm X 30.5 cm) were lightly dusted wIth 6 Hot lop ll 1 54) 644 703 lXUU t 7 mm U 538 62 77 W25 alumina powder and stacked. Patks of l 1 mil strlops 7 Hot lop I I} 55a 05a 7w Imn were loaded at 800C. heated at 50 per hour to 1050 C H i f in nitrogen and then to l l5UC in hydrogen, where they it Hot lop ll I 3! (13h (U3 lX lI were held for 2 hours.

TABLE III Magnctic Properties of l-pstcin Packs of l l Mil Thick Strips Processed With An Intermediate Hcat lrcatment Heat 'lrcatcd at h!) Mils Heat 'l'reated at 28 Mils ppm B l osscsi mupp. til) Hert/ Losscs mwpp (it! Hert/ Run \tltl'.ti I Mn "l s Mn/S Isak-Ii Inna; ,ultlH IS an; I7.nkn Ian I 5 ma .Ull 2.7 Ion: I475 Hlltl 15824 3 l5 am now 3,3 777 lntl4 n45 s 17m 1 o n34 vIII7 2n s78 i i543 n3l 9H2 I72! 4 5 .Im .Ulh 2.I n27 l727 Shl 7113 1x3? 5 on on 2,0 524 704 I 7n 537 7:4 Ix-u (I n H33 .035 I 1 10m I444 on x4 i779 7 5 H36 n 1.4 54x 70v Iss3 54s 74! Is4s s In n34 n21 Is 543 7I7 Iss6 555 740 I855 a 2o (:34 .Im 1.5 SR7 (ms was SSI 723 Ixnn In 3o on .023 l 54s 7a: was 5x5 776 Iss0 ll an o2: L4 n33 Ht) III S75 83H I756 I2 [I In: .033 In I054 I47s SQI s4I I772 I). 5 at: am an 555 m7 IvIm 500 725 I86!" 14 In M3} on In 555 7II min 575 7m 1x33 I5 In an am as 567 73a liq-to This invention has been further explored in a series of l5 experiments designed to test the composition and processing parameters, particularly the boron content. the manganese and sulfur content and ratio and the extent of thickness reduction during the final or second cold rolling phase of a two-stage cold-rolling process. In carrying out these experiments each of the heats was melted in an air induction furnace in an argon atmosphere using electrolytic iron ot98 per cent i'crrosilicon to provide a melt of the following composition:

Silicon i l percent (.Irhnn II oj upper (I l ('hronlnnn (Ltl Nllrngcn (Ill-i5 Iron Remainder Preparation of these and subsequent heats resulted in nitrogen contents from 30 to 60 parts per million with above-indicated average content.

As indicated by the data reported in Table Ill, the magnetic properties of the products were substantially improved by the addition of boron when the ratio of manganese to sulfur in the silicon-iron was less than 2.1. Further. high permeabilities were obtained through the addition of five to 30 parts per million of boron, but the addition of 40 parts per million of boron resulted in incomplete secondary recrystallization and consequent substantially diminished permeability. Fi nally permeability was improved by heavier final cold reductions. which is surprising in view of general experiencc in conventional practice to the contrary.

Four additional experiments were run as a series to test the two-stage cold reduction process against the single stage or direct cold reduction method. Permca bility and watt loss measurements made on finished l l mil silicon-iron strip materials resulted in the data set out in Table IV. which also indicates in each instance the rolling procedure and lists the amounts of boron added and the manganese and sulfur content of each individual melt of this series.

TABLE I\" TABLE VI nntpp (iugc lSkB lhulkli l7kll p10" A ll )lll I5]: I! H! H Slll 594 040 lull ltL J F5: -H (\Hi lUUZ t) 10.) in? has 734 1x7;

Comparison of Properties Obtained By Direct (old Rolling to l l Mils With Heat l rcatment at Intermediate (iagc of (i0 Mils Rolling ppm B Run Procedure Added '1 Mn S lillkli l 0H1 ultlll In" Direct 5 0m: 00% ins 75s 1x49 I7 00 mil [(5 55 ol7 lJlh IX Direct l0 00-11 0.03: 574 745 lNSS l 0 mil K; 530 MR 1908 Hill rolled liom ll'i'it' others hot rolled from lllltl t proves the magnetic properties of the final product. as contrasted to cold rolling direct to final gauge from the hot rolled bandv In addition. in view of the foregoing experimental results. it will be understood that the final cold reduction carried out in the two-stage cold-rolling operation of this invention is preferably of the order of at least (10 per cent and most desirably upwards of 70 or 80 per cent. Acceptable or satisfactory results may. however. m

be obtained at reductions of the order of 50 per cent and even less. other factors influencing the develop ment of secondary recrystallization texture and good magnetic properties being the same and within the crit ical limits defined above.

In laboratory experiments illustrating the utility of selenium in this process. four heats were melted in an air induction furnace under an argon cover using electrolytic iron and 98 per cent ferrosilicon. Five parts per million of boron were added to each heat and (1.025 per cent of selenium was added to two heats [B and C) and 0.045 per cent selenium was added to another (heat D). 'l he chemical analyses of these heats were as follows:

in one instance in the course of carrying out this experiment. 0.020 per cent of selenium was added to the melt which had the following analyzed composition:

' \ln '1 S (J03! (LOU-l tl,l)l5 1.] ill 0.0} .03

As in the other heats of this series. five parts per million of boron were added to the molten metal and processing for one sample (X) was as described above, while in the case of a second sample (Y). the interme diate heat treatment was carried out at l000(. instead of 900C. The measured magnetic characteristics of these final products were:

It is apparent that selenium is more effective than sulfur when compared on an atomic weight basis at lcast Slices 1.75 inches thick from the resulting SU-pound ingots were heated to 1200C and rolled without reheating in six passes to a thickness of 90 to Hit) mils. After pickling, samples of the hot rolled band were heated in hydrogen for 3 minutes, cold rolled to 60 mils. heated again for 3 minutes at 900C in hydrogen and cold rolled to the final thickness of l l mils. Epstein strips were decarburized by heating for 3 minutes at 800C in wet hydrogen. after which they were separated with alumina powdcr and given the final anneal. The final anneal consisted of heating at C per hour from 800C to 10S0C in nitrogen. then in hydrogen to l l75( and holding 3 hours. The magnetic properties of Epstein packs of these materials were measured with the following results:

.026 atomic per cent sulfur being required with 0030 per cent manganese but only 0.0[7 atomic per cent of selenium being necessary.

As used herein and in the appended claims. the term ingot'- means and refers to a body made by solidifying b any casting method a molten steel made by any suit able stcelmaking method. and this includes a slab-like ingot obtained by a continuous casting method.

\Vhenever in this specification and in the appended claims reference is made to amounts. ratios, percent ages or proportions. the weight basis is meant and in tended unless otherwise expressly stated.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. The method of producing grain-oriented siliconiron sheet which comprises the steps of providing a silicon-iron melt containing 2.2 to 4.5 per cent silicon. manganese and sulfur in amounts in a ratio of manganese to sulfur less than 2.l. between about three and about 35 parts per million boron. and between and 60 parts per million nitrogen in the ratio to boron of one to fifteen parts per part of boron. casting the melt to form an ingot. hot rolling the ingot. then cold rolling to intermediate thickness. then heat treating the resulting cold-worked sheet. then cold rolling and reducing the sheet to final thickness. and finally subjecting the cold-rolled sheet to heat treatment to decarburize it and to develop I [0)[001 secondary recrystallization texture in it.

2. The method ofclaim 1 in which the hot rolling step is begun with the ingot at temperature in the range from 2100F to 2400F.

3. The method of claim I in which the hot rolling step is begun with the ingot at temperature between 2200F and 2300F.

4. The method of claim 1 in which the sheet is reduced in thickness to about 60 mils in the first coldrolling operation, and in which the second cold rolling operation results in about 80 per cent reduction in thickness of the sheet.

5. The method of claim I in which the final cold rolling step results in reduction of thickness of the siliconiron sheet of about 60 per cent.

6. The method of claim I in which the amount of manganese is from about 0.0l to 0.10 per cent and the amount of sulfur is from about 0.005 to 0.05 per cent.

7. The method of claim I in which the melt contains about 50 parts per million nitrogen. about five parts per million boron are added to the melt. and in which the manganese content of the melt is about 0.035 per cent and the sulfur content of the melt is about 0.030 per cent. and the ingot is at 2250F at the outset of hot rolling. and the sheet thickness is reduced to 60 mils in the first cold rolling stage and the sheet is then normalized in hydrogen for 3 minutes at 900C and thereafter cold rolled to final thickness of about l l mils.

8. The method of claim 1 in which the manganese content of the silicon-iron melt is at least 0.0l per cent.

9. The method of producing grain-oriented siliconiron sheet which comprises the steps of providing a sili con-iron melt containing 2.2 to 4.5 per cent silicon. additionally containing sulfur or selenium or sulfur and selenium in amount from 0.005 to 0.05 per cent. and additionally containing from 0.0l to 0. [0 per cent manganese in an amount in the ratio to sulfur or selenium or sulfur plus selenium of less than 2.1. and containing between 30 and parts per million nitrogen. and finally containing incidental impurities and the balance consisting of iron. adding from about three to about 35 parts per million of boron to the melt and thereby establishing a nitrogen to boron ratio to the melt of l to l5 parts of nitrogen per part of boron. casting the melt to form an ingot hot rolling the ingot. then cold rolling to intermediate thickness. then heat treating the resulting cold-worked sheet. then cold rolling and reducing the sheet to final thickness, and finally subjecting the cold-rolled sheet to heat treatment to decarburize it and to develop l l())[()()] secondary recrystallization texture in it.

[0. The method of claim 9 in which the metal melt contains about 0.0l9 per cent selenium. about 0.004 per cent sulfur and about 0.033 per cent manganesev II. The method of claim 9 in which the metal melt contains from 0.0[5 to 0.037 per cent selenium. about 0.004 per cent sulfur and about 0.03 per cent manganese.

l2. The method of producing grain-oriented SlllCUlP iron sheet which comprises the steps of providing a hotrollcd band containing 2.2 to 4.5 per cent silicon. be tween three 35 parts per million boron. between 30 and 60 parts per million nitrogen in the ratio of l to l5 parts per part of boron. and amounts of manganese and sultur in the ratio of manganese to sulfur less than ll. cold rolling the hot-rolled band to intermediate thickness. then heating the resulting cold-worked sheet, then cold rolling and reducing the sheet to final gauge thickness. and finally subjecting the cold-rolled sheet to heat treatment to develop( 1 l0)| 001 secondary recrystallization texture in it.

[3. A silicomiron hot-rolled band containing 2.3 to 4.5 per cent silicon. manganese and sulfur in amounts in a ratio of manganese to sulfur less than 3. l between about three and 35 parts per million boron. and between 30 and 60 parts per million nitrogen in the ratio to boron of l to l5 parts per part of boron.

Claims

1. THE METHOD OF PRODUCING GRAIN-ORIENTED SILICON-IRON SHEET WHICH COMPRISES THE STEPS OF PROVIDING A SILICON-IRON MELT CONTAINING 2.2 TO 4.5 PER CENT SILICON, MANGANESE AND SULFUR IN AMOUNTS IN A RATIO OF MANGANESE TO SULFUR LESS THAN 2.1, BETWEEN ABOUT THREE AND ABOUT 35 PARTS PER MILLION BORON, AND BETWEEN 30 AND 60 PARTS PER MILLION NITROGEN IN THE RATIO TO BORON OF ONE TO FIFTEEN PARTS OF BORON, CASTING THE MELT TO FORM AN INGOT, HOT ROLLING THE INGOT, THEN COLD ROOLING TO INTERMEDIATE THICKNESS, THEN HEAT TREATING THE RESULTING COLD-WORK SHEET, THEN COLD ROLLING AND REDUCING THE SHEET TO FINAL THICKNESS, AND FINALLY SUBJECTING THE COLD-ROLLED SHEET TO HEAT TREATMENT TO DECARBURIZE IT AND TO DEVELOP (110)(001) SECONDARY RECYSTALLIZATION TEXTURE IN IT.

2. The method of claim 1 in which the hot rolling step is begun with the ingot at temperature in the range from 2100*F to 2400*F.

3. The method of claim 1 in which thE hot rolling step is begun with the ingot at temperature between 2200*F and 2300*F.

4. The method of claim 1 in which the sheet is reduced in thickness to about 60 mils in the first cold-rolling operation, and in which the second cold rolling operation results in about 80 per cent reduction in thickness of the sheet.

5. The method of claim 1 in which the final cold-rolling step results in reduction of thickness of the silicon-iron sheet of about 60 per cent.

6. The method of claim 1 in which the amount of manganese is from about 0.01 to 0.10 per cent and the amount of sulfur is from about 0.005 to 0.05 per cent.

7. The method of claim 1 in which the melt contains about 50 parts per million nitrogen, about five parts per million boron are added to the melt, and in which the manganese content of the melt is about 0.035 per cent and the sulfur content of the melt is about 0.030 per cent, and the ingot is at 2250*F at the outset of hot rolling, and the sheet thickness is reduced to 60 mils in the first cold rolling stage and the sheet is then normalized in hydrogen for 3 minutes at 900*C and thereafter cold rolled to final thickness of about 11 mils.

8. The method of claim 1 in which the manganese content of the silicon-iron melt is at least 0.01 per cent.

9. The method of producing grain-oriented silicon-iron sheet which comprises the steps of providing a silicon-iron melt containing 2.2 to 4.5 per cent silicon, additionally containing sulfur or selenium or sulfur and selenium in amount from 0.005 to 0.05 per cent, and additionally containing from 0.01 to 0.10 per cent manganese in an amount in the ratio to sulfur or selenium or sulfur plus selenium of less than 2.1, and containing between 30 and 60 parts per million nitrogen, and finally containing incidental impurities and the balance consisting of iron, adding from about three to about 35 parts per million of boron to the melt and thereby establishing a nitrogen to boron ratio to the melt of 1 to 15 parts of nitrogen per part of boron, casting the melt to form an ingot, hot rolling the ingot, then cold rolling to intermediate thickness, then heat treating the resulting cold-worked sheet, then cold rolling and reducing the sheet to final thickness, and finally subjecting the cold-rolled sheet to heat treatment to decarburize it and to develop (110)(001) secondary recrystallization texture in it.

10. The method of claim 9 in which the metal melt contains about 0.019 per cent selenium, about 0.004 per cent sulfur and about 0.033 per cent manganese.

11. The method of claim 9 in which the metal melt contains from 0.015 to 0.037 per cent selenium, about 0.004 per cent sulfur and about 0.03 per cent manganese.

12. The method of producing grain-oriented silicon-iron sheet which comprises the steps of providing a hot-rolled band containing 2.2 to 4.5 per cent silicon, between three 35 parts per million boron, between 30 and 60 parts per million nitrogen in the ratio of 1 to 15 parts per part of boron, and amounts of manganese and sulfur in the ratio of manganese to sulfur less than 2.1, cold rolling the hot-rolled band to intermediate thickness, then heating the resulting cold-worked sheet, then cold rolling and reducing the sheet to final gauge thickness, and finally subjecting the cold-rolled sheet to heat treatment to develop (110)(001) secondary recrystallization texture in it.

13. A silicon-iron hot-rolled band containing 2.2 to 4.5 per cent silicon, manganese and sulfur in amounts in a ratio of manganese to sulfur less than 2.1, between about three and 35 parts per million boron, and between 30 and 60 parts per million nitrogen in the ratio to borOn of 1 to 15 parts per part of boron.