US3802937A

US3802937A - Production of cube-on-edge oriented siliconiron

Info

Publication number: US3802937A
Application number: US00583459A
Authority: US
Inventors: D Kohler; M Littmann
Original assignee: Armco Inc
Current assignee: Armco Inc
Priority date: 1966-09-30
Filing date: 1966-09-30
Publication date: 1974-04-09
Anticipated expiration: 1991-04-09
Also published as: DE1583326A1; CS194651B2; BE704464A; BG17635A3; SE350281B; GB1197800A

Abstract

An improvement in the production of cube-on-edge silicon-iron comprising the step of heating the silicon-iron having an oxygen content no greater than 0.0045 percent to a temperature of from 2,100*F. to not more than 2,400*F. immediately prior to hot rolling.

Description

United States Patent Kohler et al.

[111 3,802,937 1 1 Apr. 9, 1974 PRODUCTION OF CUBE-ON-EDGE ORIENTED SILICON-IRON [75] Inventors: Dale M. Kohler; Martin F.

Littmann, both of Middletown, Ohio [73] Assignee: Armco Steel Corporation,

Middletown, Ohio [22] Filed: Sept. 30, 1966 [21] Appl. No.: 583,459

[52] U.S. Cl 148/111, 148/3155, 148/110, 148/112 [51] Int. Cl. ..H01f1/04 [58] Field of Search 148/31.55, 110,l11,112

[56] References Cited UNITED STATES PATENTS 2,599,340 6/1952 Littmann 148/111 2,826,520 3/1958 Rickett 148/111 2,867,557 1/1959 Crede 148/111 3,105,782 10/1963 Walter 148/111 X 3,305,354 2/1967 Boni et al. 148/3155 3,333,991 8/1967 Kohler 148/111 3,333,992 8/1967 Kohler 148/111 3,345,219 10/1967 Detert 148/111 Primary Examine -L. Dewayne Rutledge Assistant Examiner-W. R. Satterfield Attorney, Agent, or Firm-Me1ville, Strasser, Foster & Hoffman 5 7 ABSTRACT An improvement in the production of cube-on-edge silicon-iron comprising the step of heating the siliconiron having an oxygen content no greater than 0.0045 percent to a temperature of from 2,100F. to not more than 2,400F. immediately prior to hot rolling.

8 Claims, No Drawings PRODUCTION OF CUBE-ON-EDGE ORIENTED SILICON-IRON This invention relates to a method of producing grain-oriented silicon-iron sheet or strip for magnetic purposes. The grain orientation to which this invention refers is that wherein the body-centered cubes making up the grains or crystals are oriented in the cube-onedge position, designated (110) [001] in accordance with the Miller lndices. More specifically, this invention relates to an improved and economical method of producing grain-oriented silicon-iron, whereby the temperature range to which the silicon-iron is heated prior to hot rolling is lowered by maintaining the oxygen content of the silicon-iron below a critical lower limit.

As is well known, silicon-irons having the (1 [001] orientation are characterized by a relatively high permeability in the rolling direction and a relatively low permeability in a direction at a right angle thereto. A commercial product of this nature has been used successfully for many years for the manufacture of laminations or cores in transformers, generators and the like, because of its low coreloss and high permeability in the rolling direction.

The greater part of the cube-on-edge'oriented silicon-iron sheet stock is currently made from the raw materials by a number of steps which include melting, refining, casting and hot rolling ingots or slabs of a suitable composition to hot bands usually less than 0.1 inch thick. Following annealing and pickling steps, the material is cold rolled in one or more stages with intermediate anneals, subjected to a decarburizing step, and finally annealed at a temperature high enough to cause secondary recrystallization. The secondary recrystallization has been of the grain boundary energy type.

As indicated above, current practice begins the hot rolling step either with a slab or directly with an ingot. In the first instance an ingot is cast. The ingot is soaked at a high temperature of about 2,200 F. to 2,300 F. for several hours in order to equalize the ingot temperature to obviate problems caused by differential cooling in the ingot. The ingot is then rolled into a slab, generally about 6 inches thick, and allowed to cool slowly.

Prior to the hot rolling step, the slab is reheated to about 2,500 to 2,550 F.

When direct hot rolling from an ingot is practiced, it is'usual to cast an ingot and soak it at about 2,45.0 F. prior to the hot rolling step.

The temperature to which a slab is reheated or an ingot is heated prior to the hot rolling step has been the subject of much study among prior art workers. It was taught by Goss in US. Pat. No. 2,084,337, issued June sally by the industry. Such extremely high temperaposal of slag which forms on the slabs or ingots when they are heated above about 2,400 F. This slag comprises liquid oxide formed by the oxidation of the surface of the slab. Accumulation of this slag eventually interferes with the operation of the slab or ingot heating furnace and it becomes necessary to take the furnace out of operation in order to remove the slag. Because of the dependence of the hot rolling mill on a steady supply of slabs or ingots, the output of the hot mill is severely curtailed each time a furnace is down for repairs. In fact, the production of the entire steel making facility is affected. In addition to costly shutdowns because of slag accumulation, such high temperatures incur higher heating costs, and require more expensive heating equipment. The high temperatures and corrosive effect of the slag greatly reduce furnace refractory life. Nevertheless, all of these disadvantages 22, 1937, that the ingot should be heated to about 2,000 F. or above, and the reduced slab should be heated to about 2,000 F. Although silicon-iron may be rolled at a temperature as low as 2,000 E, the final product does not exhibit good magnetic qualities.

Littmann and Heck in US. Pat. No. 2,559,340, issued June 3, 1952, taught that superior permeabilities could be obtained in silicon-iron by hot rolling from a high initial temperature. They discovered that the magnetic properties of nominal 3 percent silicon-iron would be much improved if the ingot or reheated slab were taken to a temperature above about 2,300 F. and up to about 2,5 F. (or the highest temperature possible without burning) prior to the hot rolling step. As indicated above, this teaching has been adopted univerhave been considered unavoidable and the expense entailed thereby has been considered necessary in order to produce silicon-iron of the highest quality.

It was taught by Rickett in US. Pat. No. 2,826,520 issued Mar. ll, 1958, that the slag problem could be eliminated by heating the slabs within the limited temperature range of 2,225 F to 2,275 F. for a minimum of 8 hours. However, this method has not been adopted commercially and the productproduced thereby is not characterized by high magnetic qualities While all of the work represented by the aforementioned. patents concerned so-called critical ranges within the broad general range of slab heatingtemperatures, for commercially produced silicon-iron alloys containing the standard elements, none was dependent upon nor related to the oxygen content which normally exceeded 0.005 percent, and often was as high as 0.010 percent.

, It may be seen from the foregoing discussion of the prior art that there are different and sometimes conflicting teachings as to the most desirable temperatures for the ingot and slab heating steps in the production of grain oriented silicon-iron. It is therefore a primary object of the present invention to provide a method of producing cube-on-edge oriented silicon-iron whereby the slab or ingot temperature prior to the hot rolling step has been rendered nugatory in relation to the quality of the final product.

It is also a primary objectof the present invention to provide a more economical method for the manufac, ture of cube-on-edge silicon-iron whereby savings are realized both in the processing of the 'materialand in the less severe conditions affecting the apparatus or equipment used .in its manufacture.

It is an object'of the present invention to providesuch a method without sacrificing the high standards allow its metallurgical structure to be controlled at each step of the process.

These and other objects of the invention which will be set forth hereinafter or will be apparent to one skilled in the art upon reading these specifications are inhibitor of normal grain growth must be provided in order to promote secondary growth of the decarburized, primary recrystallized structure during the final I high temperature anneal. While a number of inhibitors such as manganese selenide may be used, for purposes of an exemplary showing the process of the present application will bedescribed in terms of manganese sulfide as the inhibitor. I

. It is known that when the manganese sulfide, in the I amount formed by having the manganese and sulfur contents in the ranges given below, is well dispersed as submicroscopic precipitates in the silicon-iron, these precipitates will inhibit primary grain growth following recrystallization after cold rolling. Thus, during the final anneal of the material, the secondary grains which start to grow at about 1,700 F. can engulf the primary grains to produce the desired cube-on-edge orientation.

I It has been discovered that when the oxygen content of the silicon-iron is kept within the limits given below,

. a better performance from the manganese sulfide inhibitor is obtainable, and high slab'or ingot temperatures are not required. In fact, slab or ingot tempera-' tures may be used which are below what would normally be thought to be the temperature at which the majority of the manganese sulfide would go into solution. The reason for this is not fully understoodnwhile not intending to be bound by theory, it is believed that the silicon-iron of the present invention, having the low oxygen content givenbelow, may naturally give a finer dispersion of the sulfide phase because of the absence of oxide nucleation sites. I v

In the practice of the present invention, the composition of the silicon-iron is critical. The amount of oxygen should not exceed 0.0045 percent and'preferably' should not exceed 0.0030 percent. The vmanganese content; should be from about 0.03 percent to about. 0.08 percent, and preferably from about 0.045 percent to about 0.065 percent. The lower limit is determined by the amount of manganese necessary to form a sufficient quantity of manganese sulfide to act as a grain growth inhibitor; The upper limit is determined by the solubility of the manganese sulfide prior to hot rolling, the higher manganese causing the sulfide tobe less soluble. Also, higher manganese contents render sulfur additions to the silicon-iron at later stages of the processingless effective. Initial sulfur should be presentin about 0.025 percent. Selenium may be substituted for tial carbon content should be from about 0.015 percent to about 0.035 percent, and preferably from about 0.020 percent to about 0.030 percent. The silicon con tent may be from about 1.8 to '4 percent or higher, the lower limit being the minimum silicon which will avoid a phase change to gamma iron upon heating, while the upper limitisdependent upon the ability of the material to be cold rolled without breakage. The nitrogen content should not exceed about 0.007 percent and preferaly should not exceed about 0.004 percent. No more than about 0.008 percent total aluminum should be present. It is preferred to have thatv portion of the aluminum present in the acid-soluble form constitute less than 0.002 percent.

To obtain the critical oxygen content of the present invention, any low oxygen refining process may be used, including vacuum techniques. One process, which has the advantage of being amenable to the use of existing apparatus such as the open hearth or electric furnace, is disclosed by Boni and Heck, U.S. Pat. No. 3,305,354. The re-ladling process of their invention is capable of removing oxygen to a level of about ten parts per million or 0.001 percent. v

The silicon-iron having the melt composition given above may be conventionally cast into ingots or it may be continuously. cast into slab-ingots. Hereinafter the use of the terms slabs and ingots is intended to in- I clude silicon-iron which has been continuously cast.

Prior to the step of rolling to hot bands, the siliconiron will be heated whether it be in ingot form (where direct rolling to strip is usedlor slab form (where a reheating step is practiced). In accordance with the presentinvention, the slabs or ingots are heated to within a temperature range between the lowest temperature at which the ingots or slabs are workable and the highest temperature at which no appreciable amount of slag will be formed. Conventionally the slabs will be held at temperature for a period of less than one hour, while ingots are generally soaked for several hours.

While slabs or' ingots are workable in .the laboratory at temperatures as low as 1,800" F.', it has been found that the lowest practical temperature under plant processing conditions is about 2,l00 F.

The highest temperature at which no appreciable amount of slag will be formed is dependent upon a number of factors. These factors include time at temperature, atmosphere,- type of flame and the like. Nevertheless, it has been determined thatlthe above depractice of the present invention, the temperature at which the hot rolling is completed is not considered to be critical in and of itself. It is preferred that the finish-' ing temperature be above 1,650 P. Similarly, the coiling temperature has not been found to be extremely critical. A temperature of about 1,200 F. is normal. The steps of the process following hot rolling are conventional. The hot band may be annealed before it is cold rolled in order to improve the structure. If an initial anneal is used, the temperature may vary from about 1,650 F. to about 2,000 F., and preferably is about l,800 F., for a time of up to about four minutes at temperature.

Oriented silicon-iron having a final thickness of ent invention, the teachings herein are particularly ap-- plicable to the production of oriented silicon-iron having a final thickness of about 0.014 inch or less.

The silicon-iron will be decarburized to a value of 0.003 percent or less during one or more of the anneals. This may be done in an atmosphere such as wet hydrogen.

After decarburization, the strip is generally coated with an annealing separator and box annealed for at least 8 hours at a minimum temperature of 2,000 F. Higher temperatures and longer times at temperature are used when it is necessary to remove sulfur or other undesirable impurities. The sulfur content will be reduced to less than 0.002 percent during the final anneal.

Various modifications may be made in the processing steps following the hot rolling withoutdestroying the beneficial effects imparted by the particular composition of the silicon-iron and especially its oxygen content. Therefore, it will be understood that the processing of the material beyond the hot rolling stage has been described as exemplary and does not constitute a limitation upon the invention.

When the oxygen content of the silicon-iron, which may be from a trace to 0.0045 percent is in the upper portion of this range, and particularly when it is above about 0.0030 percent, it may be found desirable to heat the ingots or slabs to a temperature within the upper portion of the above given range, i.e. to a temperature from about 2,300 F. to about 2,400 F.

It is a feature of the present invention that the siliconiron sheet stock may be treated at final gauge, and immediately prior to or during the primary grain growth portion of the final anneal, with sulfur, selenium or their compounds from an external source. The use of sulfur is preferred'for economic reasons. The sulfur- 6 to hot rolling, will yield a product having excellent magnetic properties. For example, when the oxygen content of the silicon-iron is within the upper part of the above given range, the addition of sulfur from an external source will insure an excellent product even at a slab or ingot heating temperature of 2,l00 F.

As a non-limiting example silicon-iron of the above outlined composition in the form of slabs or ingots may be heated within the range of 2, 100 F. to 2,400 F. and rapidly rolled to the desired hot band thickness. If an initial anneal is used the temperature may vary from about l,650 F. to about 2,000 F. for a time of up to about four minutes at temperature. When a final product about 0.012 inch'thick is desired, the silicon-iron will be cold rolled in a first stage to an intermediate gauge of about 0.030 inch. This will be followed by an intermediate anneal at about 1,700 F., and a second stage of cold rolling to final gauge. The material may then be decarburized as described above. Sulfur from an external source may be added in any of the ways and in an amount as taught in .the above mentioned Kohler patents, and the material will be subjected to a final box anneal at a minimum temperature of 2,000 F. for at least 8 hours. Again, with respect to the final anneal, higher temperatures and'longer times atv temperatures will be used if it is necessary to remove sulfur or other undesirable impurities. I

The addition of sulfur from an external source in the process of the present inventionwill also serve to insure a product of excellent magneticqualities when a single stage cold rolling step is used. The process will be substantially the same as that just described except that the desired final gauge is achieved by a single cold rolling may be added in the ways taught by Kohler in US. Pat.

Nos. 3,333,991 and.3,333,992. As taught in these patents the sulfur addition maybe made in several ways. For example, sulfur or sulfur-bearing compounds may be added to the annealing separator in the finalanneal. Similarly, the annealing atmosphere of the final anneal may be charged with a gaseous sulfur compound providing the atmosphere is in contact with the surfaces of the silicon-iron. In yet another variant, sulfur or sulfurbearing compounds may be made available at the surfaces of the sheet material during a decarburizing anneal prior to the final anneal.

The practice of the present invention requires accurate melting and accurate chemical analysis. While the degree of accuracy both in melting and in chemical analysis in plant processing is increasing rapidly, it is often not possible to achieve the degree of accuracy in plant processing that is obtainable in the laboratory. It has been found that in some instances the addition of sulfur from an external source will serve as insurance that the silicon-iron of the present invention, when heated within the above given temperature rangeprior stage.

Three slabs (hereinafter designated A, B and C) about 6 inches thick were selected from a heat of silicon-ironwhich had been melted in an open hearth using the previously mentioned method of Boni and last reduction. The ceiling temperature for all three slabs, which was regulated by the amount of water sprayed on the strip, was about l,200 F. and the hot band thickness was about 0.080 inch. The hot rolled bands were annealed at l,800 F. j

The hot rolled bands were then cold rolled to 0.030

inch, strip annealed at 1,700 F., cold rolled to 0.012

TABLE I Slab Slab Core Losses Number mp r Permeability Pl;60 w/lb. Pl7;60 w/lb.

A 2550 F. 183i .575 .803 a 2400 F. 1833 .566 .793 c 2100" F. 1823 .553 .785

It may be seeiifi rn 5155560315150 015i iii; narrate properties of the material which had been hot rolled from widely different temperatures are surprisingly comparable.- Whereas the permeability of the 2,100 F. material is substantially the same, the corresponding core losses are slightly better than those for material rolled from the higher temperatures. It may be said that the provision of a silicon-iron of an initial composition within the above described limits, and particularly with a very low oxygen content, has made the slab temperature nugatory in relation to the quality of the product- Of course, it is usually better from a cost consideration to use the lowest temperature consistent with mill practices. For instance, when silicon-iron slabs are being heated with slabs of carbon steel or stainless steel, it

- would be more practical to heat the silicon-iron slabs The permeability values show that the low oxygen content of the hot rolled band is strongly associated with high permeability. These values also indicate that,

as the oxygen content increases, the permeability decreases more rapidly when the-initial annealing temper- .......5XMPPE11 Two slabs about six inches thick representing two ingots were selected at random from each of two heats having ladle analyses as follows;

Heat Number %Mn 708 %Si %N %O 7 %Al (total) %C A .026 .066 .023 3.21, .0052 .0070 .0053 B .053 .023 3. l 3 f .0057 .0023 .006l

to the temperature range dictated by the other materials. 3

EXAMPLE n about three minutes in air. All of the samples were then processed to a final thickness of 0.012 in two stages of cold reduction. I

The samples were annealed at 1,675 F. in hydrogen for about 1 minute at their intermediate thickness of 0.026 inch. After the second coldrolling, they were decarburized at 1,500 F. for about three minutes in wet hydrogen and given a final box anneal at 2,200 F. in

hydrogen for 24 hours.

Table II shows the initial compositions and final per meability values for the materials given the two initial annealing temperatures. r

ck. Essentially no liquid slag was formed. The temperature immediately after hot rolling was about l,800 F. and .the strip was coiled at about 1,200 F. The hot bands were strip annealed at 1,675 F. for about one minute, pickled and cold rolled to 0.024 inch. After an intermediate anneal at 1,700? P. the coils were cold rolled to about 0.0105 inch, strip decarburized, coated with magnesia, and annealed at 2,200 F. for 24-hours in a'hydrogen'atmosphere. The magnetic properties are shown in Table III and illustrate the value of low oxygen in attaining excellenrmagnetic quality. Table III is divided into two parts, each relating to one of the heats. Within each part the first three values in each column refer to samples from the front, middle and back of the coil from the first slab of the respective heat. Similarly the next three values represent samples from the front, middle and back of the coil from the second slab of the same heat. The last valueis an average of the values. of all six samples.

TABLE ll 1675 F. l800 F. initial Anneal Initial Anneal Permeability Permeability Slab %C %Mn 705 %O %N H =10 H.= H)

A .022 V .059 .022 .00l5 .0057 i771 l79l B .023 .060 .024 .0019 .0057 l73 l I797 C ,0l6 .062 (H8 .0030 .0030 N376 1761 D .0l9 .062 .(ll) .0050 .0054 164i I747 E .023 .043 .016 .0076 .0074 1596 i706 TABLE 111 HEAT A (.0070% O) EXAMPLE v One slab six inches thick from each of four different heats was reheated to a temperature of 2,l F. and

Thickhot rolled into coils 0.076 inch thick. Samples were 3? Perm taken from the centers of these coils and processed in M11. Pl5;60 w/lb. Pl7;60 w/lb. 1-1=10. the laboratory. The samples were annealed at l,800 F. 11.0 .500 .725 l825 for about 3 minutes, cold rolled directly to 0.012 inch 8% g; 3%? :23? 1 without an intervening anneal, decarburized in a strip 105 I555 1900 1740 anneal in wet hydrogen at l,500 F., coated with'mag- 88 228 {3 nesia with and without sulfur, and box annealed in hydrogen at 2,200 F. for 30 hours. The permeability val- 10.5 .552 .863 172 A e g ues obtained are shown below in Table V together with the analyses of thehot rolledsamples.

TABLE V NO Sulfur 4% Sulfur Added to MgO Added to MgO Slab %c %Mn %s 7.0 %N Perm.H 10 Perm H= 10 A .022 .059 .022 .0015 .0057 I 1605 e 1770 B .022 i .060 .023 .0018 .0057 1625 1745 c .024 .048 .017 .0065 .0076 1552 1665 D .021 .069 .020 .0090 .0050 1590 1632 HEAT B .0023% 0) 7 These data showthat a sulfur addition to the magne- Thicb sia is rendered more effective when the oxygen content ness is maintained within the critical range of the invention. The test results for the materials to which sulfur has M115 P15;60 w/lb. P17;60 w/lb. 1-1 =10.

been added represent excellent magnetic quality, when 10.6 .520 .760 18l5 it is considered that only a single cold reduction was 10.4 .500 .740 1820 d 11.0 .515 .760 1805 use 10.5 .490 .730 1330 It Wlll be seen from the above examples that it 1s poslgg ag 22 :3; sible to attain excellent magnetic properties in the product without heating the slabs or ingots to a temper- 10.5 .503 .74s 1819 Average ature range wherein liquid slag is formed.

Modifications may' be made in the inventionwithout EXAMPLE lV Two slabs about 6 inches thick representing two ingots were selected at random from each of six heats with varying amounts of oxygen. These slabs were heated to a temperature of 2,385 F. or just below the slagging temperature and hot rolled rapidly 'to hot bands 0.076 inch thick. Samples representing the center of the coils were processed in the laboratory. The hot rolled pieces were annealed at l,800 F. for about departing from the spirit of it.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In' a method for-producing cube-on-edge siliconiron having a silicon contentof from about 1.8 percent to about 4 percent andprocesse'dby steps including hot rolling to intermediate gauge, cold rolling to final I 2,100-"F. to not more than 2400E .irnmediatel 3 prior to said hot r olling step.

. 2. In a method for producing cube-on-edge silicon- I TABLE [V Pl7; Perm. Heat %C %Mn 705 %Si I %N 700 W/lb. H=l0.

A .023 I .070 .025 3.23 .0060 .0012 I .639 l837 B .0 l 3 .06l .024 3.05 .0067 .00! 3 .657 1825 C .022 .047 .023 3.16 .006l .0044 .666 l82l D .020 .052 .020 3.24 .0056 .0064 .730 I760 E .022 .069 .021 3.2l .0052 .0070 .90 1695 F .024 .044 .0 l 7 3.13 .0070 .0077 .90 l675 These data clearly show the verystrong effect of oxyiron having a silicon content of from about 1.8 percent gen content on the texture and magnetic properties obtainable. The core loss values attained for the samples lower than those hitherto obtainable.

with oxygen below 0.0020 percent are excellent and' to about 4.percent and processed by steps including hot rolling to intermediate gauge, cold rolling to final gauge, decarburizing and annealing whereby to effect secondary recrystallization favoring growth of cube onment comprising in combination therewith the step of heating said silicon-iron having an oxygen content no greater than 0.0030 percent to a temperature of from 2,100? F. to not more than 2,400 F. immediately prior to said hot rolling step.

3. In a method for producing cube-on-edge siliconiron having a silicon content of from about 1.8 percent to about 4 percent and processed by steps including hot rolling to intermediate gauge, cold rolling to final gauge, decarburizing and annealing whereby to effect secondary recrystallization favoring growth of cube-onedge nuclei by grain boundary energy, the improvement comprising in combination therewith. the step of heating said silicon-iron having an oxygen content no greater than 0.0045 percent to a temperature of from 2,300 F. to not more than 2,400 F. immediately prior to said hot rolling step.

'4. The process claimed in claim 1 wherein said silicon-iron has an initial composition including from about 0.015 percent to about 0.035 percent carbon, from about 0.03 percent to about 0.08 percent manganese, from about 0.015 percent to about 0.030percent sulfur, 0.007 percent maximum nitrogen, 0.008 per- .cent maximum total aluminum and the balance subcon-iron has an initial composition including from 7 about 0.020 percent to about 0.030 percent carbon,

. 12 from about 0.045 percent to about 0.065 percent manganese, from about .020% to about 0.025% sulfur, 0.004 percent maximum nitrogen, .002% maximum acid-soluble aluminum, and the balance substantially iron.

6. The process claimed in claim 2 including the step of reacting said silicon-iron with sulfur from an external source after said cold rolling and prior to said secondary recrystallization whereby to inhibit primary grain growth.

7. In a method for producing cube-on-edge siliconiron having a silicon content of from about l.8 percent to about 4 percent and processed by steps including hot rolling to intermediate gauge, cold rolling to final gauge, decarburizing and annealing whereby to effect secondary recrystallization favoring growth of cube-onedge nuclei by grain boundary energy, the improvement comprising in combination therewith the steps of heating said silicon-iron havingan oxygen content no greater than 0.0045 percent to a temperature of from 2,100 F. to not more than 2,400 F. immediately prior to said hot rolling step, and reacting said silicon-iron with sulfur from an external source after said cold rolling and prior to said secondary recrystallization whereby to inhibit primary grain growth.

8. The process claimed in claim 7 wherein said cold rolling step is a single stage reduction to gauge.

Claims

2. In a method for producing cube-on-edge silicon-iron having a silicon content of from about 1.8 percent to about 4 percent and processed by steps including hot rolling to intermediate gauge, cold rolling to final gauge, decarburizing and annealing whereby to effect secondary recrystallization favoring growth of cube-on-edge nuclei by grain boundary energy, the improvement comprising in combination therewith the step of heating said silicon-iron having an oxygen content no greater than 0.0030 percent to a temperature of from 2,100* F. to not more than 2,400* F. immediately prior to said hot rolling step.
3. In a method for producing cube-on-edge silicon-iron having a silicon content of from about 1.8 percent to about 4 percent and processed by steps including hot rolling to intermediate gauge, cold rolling to final gauge, decarburizing and annealing whereby to effect secondary recrystallization favoring growth of cube-on-edge nuclei by grain boundary energy, the improvement comprising in combination therewith the step of heating said silicon-iron having an oxygen content no greater than 0.0045 percent to a temperature of from 2,300* F. to not more than 2,400* F. immediately prior to said hot rolling step.
4. The process claimed in claim 1 wherein said silicon-iron has an initial composition including from about 0.015 percent to about 0.035 percent carbon, from about 0.03 percent to about 0.08 percent manganese, from about 0.015 percent to about 0.030 percent sulfur, 0.007 percent maximum nitrogen, 0.008 percent maximum total aluminum and the balance substantially iron.
5. The process claimed in claim 2, wherein said silicon-iron has an initial composition including from about 0.020 percent to about 0.030 percent carbon, from about 0.045 percent to about 0.065 percent manganese, from about .020% to about 0.025% sulfur, 0.004 percent maximum nitrogen, .002% maximum acid-soluble aluminum, and the balance substantially iron.
6. The process claimed in claim 2 including the step of reacting said silicon-iron with sulfur from an external source after said cold rolling and prior to said secondary recrystallization whereby to inhibit primary grain growth.
7. In a method for producing cube-on-edge silicon-iron having a silicon content of from about 1.8 percent to about 4 percent and processed by steps including hot rolling to intermediate gauge, cold rolling to final gauge, decarburizing and annealing whereby to effect secondary recrystallization favoring growth of cube-on-edge nuclei by grain boundary energy, the improvement comprising in combination therewith the steps of heating said silicon-iron having an oxygen content no greater than 0.0045 percent to a temperature of from 2,100* F. to not more than 2,400* F. immediately prior to said hot rolling step, and reacting said silicon-iron with sulfur from an external source after said cold rolling and prior to said secondary recrystallization whereby to inhibiT primary grain growth.
8. The process claimed in claim 7 wherein said cold rolling step is a single stage reduction to gauge.