US1932307A - Silicon steel and method of making the same - Google Patents

Description

Oct. 24, 1933. E, M -FREELAND SILICON STEEL AND METHOD OF MAKING THE SAME Filed Sep. 15. 1932 5 Sheets-Sheet l QN MM. WN

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SILICON STEEL AND METHOD OF MAKING THE SAME I Filed sept. 13, 1952 :s [email protected],etA 3 Oct. 24, 1933.

Patented Oct. 24, 1933 PATENT OFFICE SILICON STEEL AND METHOD F MAKING THE SAME Edward M. Freeland, Youngstown, Ohio Application September 13, 1932 Serial No. 632,917

14 Claims.

The present invention relates broadly to the art of metal working, -and more particularly to that branch of the art having to do with the subjecting of a predetermined composition or alloy to a treatment of such nature that the electrical properties thereof are materially modified, thereby enabling the production of an improved article having such properties as to better adapt it to electrical uses.

It is customary in order to improve the efciency of different types of electrical apparatus, such as motors, dynamos, transformers and the like, to utilize a ferrous material, usually in the form of a. series of sheets or laminae characterized by a high electrical efficiency from the standpoint of watt loss, magnetic permeability, low magnetic hysteresis and the like. In this connection, it is known that sheets of iron-silicon, or iron-silicon-aluminum alloys constitute a superior material. The present invention contemplates not only a variation in the silicon content for the purpose of obtaining certain desirable results, but also a special mechanical and heat treatment whereby the material with a given silicon content willhalve its electrical lprop- 25' erties improved.

It is customary in the art to divide so-called electrical steels into a number of diTerentGgradeS, generally with reference to the particular use to which the steels are to be put. It is to be understood, therefore, that' the term electrical steels or its equivalent, as hereinafter utilized, unless specifically restricted to a specified grade by way of example, is to be considered as a generic term including all the various grades without regard to the specic properties or uses contemplated.

For purposes of a better understanding of the invention, it will hereinafter be illustrated and described as applicable to a ferrous material containing silicon, having a low watt loss and produced initially from a hot rolled strip, the term strip being used herein in its commonly accepted sense in the steel industry.

Among other things, I have found that the eiciency of electrical steels, regardless of their grade, or silicon content, when intended for use as laminae in apparatus of the character described, is materially improved where the steel is produced by a method which includes an operation which will impart the smooth surface generally characteristic of a cold rolling operation, oi" an operation generally equivalent thereto. Such a smooth surface enables the individual -sheets to be assembled in more compact relationship, thereby providing a greater metal cross section, and consequently, a greater magnetic flux path, per unit of area. In this connection, however, it is desirable that Where steels have such a surface characteristic, the treatment include as one of the steps thereof a heat-treating operation under such conditions as to insure a film of oxidized metal on the surface of the steels. Such a film, where closely adhering and of relatively minute thickness, provided an insulating layer between adjacent laminae in such manner that the disadvantages, such as objectionable heating, which usually characterize lamin free of any insulation, or a solid core, are obviated.

As a general observation, it may be stated that the electrical properties, particularly with Vrespect, to watt loss, are improved as the silicon content is increased. I have likewise found that regardless of the silicon content, provided it lies within a certain range, the electrical properties may be improved by certain characteristic treatment steps preferably in a certain order. There are thus afforded two Variables which must be taken into consideration in the production of any given grade of material, it being possible with a relatively lower silicon content to obtain the desired results by a more elaborate mechanical and/or heat treating operation, or with a relatively higher silicon content to obtain the desired results utilizing a relatively simpler and usually fewer number of mechanical and heat treating steps. As to certain grades, however,wherein best guaran- 85 tees, particularly with respect to watt loss, must be met, it is necessary to resort not only to the advantages incident to a relatively higher silicon content, but also to the most advantageous series and sequence of heat treating and mechanical treatment steps. i

I have also found that the electrical properties of a steel of the character herein contemplated are improved materially when the steel is produced by a rolling operation characterized vthroughout by rolling in the direction only in which the original ingot was reducedv in the blooming mill, provided the user of the material takes advantage of the direction of rolling and so cuts and assembles the lamina: that in the 10o completed structure the direction of the magnetic ux will be parallel or substantially parallel to the direction of rolling. My invention therefore contemplates, among other things, a material which, regardless of its silicon content and the different treatment steps to which it may have been subjected, will be characterized by having been subjected to rolling in one direction only.

Reference has heretofore been made to the fact that the invention preferably contemplates the production of electrical steels from material which at least at some time during the treatment to which it is subjected has been in the form of a hot rolled strip. Heretofore, the only known method of reducing a hot rolled strip to certain of the gauges required for electrical steels, has been by cold rolling, and it has been a commonly accepted belief that the excessive strain incident to the cold rolling operation would preclude the use of such a material from the electrical field. My invention not only provides a method of treatment wherein the objections incident to such excessive strain may be completely obviated, but whereby the material when delivered in the form of a one-piece strip wound in successive convolutions to provide a coil to facilitate handling and transportation thereof, may be substantially free from coil set. Elimination of coil set, from a coiled strip of electrical steel which, in itself, constitutes a new article of manufacture, enables lamin to be cut from the metal of the coil and assembled without introducing strain in the lamin by the attening operation usually incident to the assembly of the laminas.,

The production of the hot rolled strip which is used in the present invention may be effected by suitable hot rolling in a succession of passes to a desired gauge while always rolling the metal in the direction only in which the ingot was rolled. Such a succession of passes may obviously be obtained by repeatedly subjecting. the metal to rolling operations in the same mill, or to repeated rolling operations in a succession of mill stands such as afforded by a continuous or tandem mill. While the last mentioned procedure is desirable from the standpoint of production and the comparatively few handling operations involved, it will be apparent to those skilled in the art that my invention is not limited to the constructional or operating characteristics of the mills, or the number of stands utilized in perfecting the production of the hot rolled strip. It is desirable, in accordance with my invention, that the last hot rolling operation be accomplished at a temperature which bears a definite and predetermined relationship to the recalescence point of the particular material undergoing treatment. If the material, during the last hot rolling pass, is at a temperature higher than the recalescence temperature, the finished material, with a given silicon content, will be characterized by an absence of re-crystallization and by certain electrical properties. If the last rolling operation in the hot mill is accomplished atsubstantially the recalescence temperature, the material while characterized likewise by the absence of recrystallization will have-generally superior electrical properties to the product before referred to. In like manner, final rolling at a temperature slightly below the recalescence temperature will further improve the electrical properties. While such material may be characterized by grain growth, I have found that at least insofar as it has been possible to make any definite measurements, the grain growth is not a determining factor in the electrical characteristics. If the-last hot rolling step is -accomplished at a temperature suilclently below the recalescence point to cause re-crystallization upon subsequent heat treatment, the resulting product will have electrical properties which are generally inferior to-the corresponding properties characteristic of material wherein the last hot rolling was at a temperature above, equal toor but slightly below the recalescence point. By properly varying the silicon content, however, a material rolled with the last pass appreciably below the recalescence point may have electrical `properties superior to metal of a lower silicon content rolled at slightly below or above the recalescence point.

In most cases, it has been proposed in the art to subject silicon steel in sheet form to an annealing operation. While such an annealing operation may 'be utilized in accordance with my invention, I have found that the properties desirable from an electrical standpoint are improved if normalizing is practiced on the material instead of annealing, and that these properties may be further improved by an operation including both normalizing and annealing, generally regardless of the order in which these two heat treating steps are performed. I am therefore of the belief that the electrical properties for some reason unknown to me vary in proportion to the temperature to which the'material, regardless of how produced, is subjected.

From the foregoing it will be apparent that apart from 'the rolling in one direction only, and special treatment steps which will be hereinafter described, there are three variables which must be taken into account in the production of elec- 4trical steel to meet the guarantees for a required grade, these variables being, respectively, and probably in the order of importance, the silicon content, the temperature at which the last hot rolling pass is accomplished, and the temperature at which the heat treating following the hot rolling is carried out.

In the accompanying drawings, I have shown, largely diagrammatically, for purposes of illustration only, certain practices in accordance with which my invention may be carried out. In the drawings, Figures l to l5, inclusive, are diagrammatic views illustrating different characteristic operations both as to sequence and type, each operation, however, being characterized by a rolling of the material throughout in the direction only in which the material is reduced from the ingot in the blooming mill. In all of the figures, I have used descriptive legends for the purpose of facilitating a reading and understanding of the operations diagrammatically illustrated.

In accordance with the form of my invention illustrated in Figure 1, a suitable silicon steel ingot having the desired silicon content is subjected to the usual back and forth roughy rolling in the blooming mill 2 for reducing it to a billet 3. This billet in turn may be subjected to suitable hot rolling in a succession of passes in a hot mill herein illustrated as comprising four roll stands l effective for producing a hot rolled strip 5. This hot rolled strip may be subjected to a suitable pickling operation in a pickling bath 6, effective for producing a pickled hot rolled strip 7. This hot rolled strip may then be heated in any suitable furnace 8 up to a temperature bearing a predetermined relationship to the recalescence temperature of the metal and previously determined upon by reason of the silicon content and the grade of steel to be produced. Having been raised to this temperature, it mayA be lgiven -a nal pass in a hot roll stand 9 veiective for producing a hot rolled strip 10.' This strip may then be coiled in 2 suitable coiler 11 and box annealed in a suitable box annealing. chamber 12. If desired, the box annealing may be replaced by normalizing. In the case of a box anneal, the product may be sold directly, or it may be reheated and allowed to cool in the at to remove coil set. In the case of normalizing, the product may be' immediately coiled, or it may .be allowed to cool in the flat before coiling, in

order to preclude any coil set. This'latter procedure will be more clearly pointed out in connection with Figure 5. Also it will be apparent. that the box anneal or normalized product so produced may be subjected to a suitable leveling operation, as by a roller leveller, then sheared and either box annealed or normalized.

In the showing of Figure 1, the roll stands 4 may be considered as only effective for rolling to an intermediate gauge, and the stand 9 effective for' producing the finished gauge.

In Figure 1, I have indicated the heating furnace 8, the-hot roll stand 9 and the hot vrolled strip 41() as included within a frame bearing the designation May omit under specified conditions. Thus, if the rolling operation in the hot mill including the stands of rolls 4, is so carried out that the last hot rolling operatori is at the desired predetermined temperature with relationship to the Yrecaleseence temperature, it is unnecessary to effect subsequent heating of this material to such a temperature followed by rolling. In most cases, however, an accurate temperature control without heating is difficult, so that a heating furnace in advance of the last rolling pass may usually be considered as desirable. To this end, I may, if desired, locate the' heating furnace 8 in the dotted line position 1 8 of Figure 1 wherein it will be effective for insuring the last hot rolling pass at the desired temperature, and then eliminate the hot roll stand 9.

In Figure 2 there is illustrated a slightly modified embodiment of the invention wherein parts corresponding to the parts shown in Figure 1 are designated by the same reference characters having the suffix a added thereto. In accordance with this embodiment, the pickled hot rolled strip 7a is sheared by a suitable shear 14 to provide a plurality of pieces of sheared hot roll strip 15. These individual pieces 15 may then be raised to the predetermined temperature in the heating furnace 8a, hot rolled at that temperature in the roll stand 9a to provide sheets 16, which are then box annealed or normalized in a suitable furnace or box 17. If desired, there may be both an anneal and normalizing. With this form of the invention, assuming that the furnace 18a has been utilized, the parts 8a, 9a and 16 enclosed within the border may be omitted for vreasons pointed out in connection with Figure l. It will also be apparent that the shear 14 can be placed after the furnace on box 17, and then followed by a normalizing or annealing treatment.

,In Figure 3, parts corresponding to the parts illustrated in Figure 2 are designated by the same base numberwith the suffix b added thereto. ,In accordance with this form of my invention, sheets after having been box annealed or normalized in theifurnace or box 17h, are subjected to a cold rolling operation in a rollstand 21, preferably so adjusted as to introduce a strain in the sheets corresponding to that represented by an elongation of somewhere in the range of from approximately 1 to 5%. AWhile an elongation of 1% will introduce sufficient strain for the purposes intended, I have found that the introduction of additional strain up to the limit indicated is not objectionable and constitutes a safety factor in insuring that at least the desired minimum will be introduced. The strained sheets 22 -having this desirable strain component therein are then subjected to an annealing or normalizing operation, preferably in a suitable furnace or box 23. I have found that such a strain introduction a strain introduced and subsequently removed therefrom. V

In Figure 4, there is illustrated another embodiment of my invention in which parts corresponding to the parts illustrated in Figure l are designated by the same reference characters having the suflix c added thereto. In accordance with this embodiment of the invention, the coiled strip after having been subjected to a box annealing or normalizing 12o is given a cold rolling treatment in one or more cold rolling stands 21o, corresponding in function to the stand 21 of Figure 3, but effective for producing a strip 24 having va desirable strain component of the character indicated therein. This strip may then be coiled in a suitable coiler 25 after which it may be placed in an annealing box 26 and subjected to an annealing temperature of the order indicated for effecting substantially complete strain removal, or may be normalized for this purpose. In either case, coil set may be eliminated as referred to in connection with Figure l.

In Figure 5, I have shown another embodiment of my invention which is generally similar to that illustrated in Figure 1, and wherein parts corresponding to the parts of Figure 1 are designated by the same reference characters having the suflix d added thereto. In accordance with this embodiment, the hot rolled strip after having been coiled in the coiler 11d is subjected to a normalizing treatment in a normalizing furnace 27, after which it may be again coiled in a suitable coiler 28. By the normalizing operation, the

material is subjected to a higher temperature than that which is generally considered possible of attainment by annealing and more particularly box annealing, and the electrical properties are correspondingly improved. This modification' has been `referred to -in connection with Figure l, as well also as the possibility of placing a shear after the furnace 28, followed by further heattreatment, if desired. By spacing the coiler 28 from the furnace 27, the material may be cooled in the flat before coiling and coil set obviated.

Figure 6 shows an embodiment generally similar to Figure 5 with the parts desfgnated by the same refere e characters as those used in Figure 1, but with the suix e added thereto. In accordance with this form, a strip coiled in the coiler 11e is passed through either a normalizing or an annealing furnace. 29 and either normalized or annealed, and thereafter passed through an annealing or normaliz'ng furnace 30, wherein the operation which was not performed in the furnace 29 is carried out. Thereafter, the material in strip form which has been subjected to both an annealing and normalizing operation is coiled in a suitable coiler 28e.` Suitable shearing and heat treating may follow the unit 20, or the treatment may be as before described, to remove or prevent coil set.

Attention has already been called to the fact that the step of strain introduction followed by a proper heat treating operation improves the electrical properties. In Figure 7, there is shown a lay-out generally similar tol that of Figure 5,

serves to anneal, the annealed coil may be relili? heated and then cooled in the flat before coiling.

The lay-out of Figure 8 is similar to that of Figure 7, and the same system of reference numerals has been followed with the suffix changed. In accordance with this embodiment, the material after having been subjected to strain introduction in the cold rolling stand 21g and either before or after having been coiled in a suitable coiler 31g is subjected to normalizing in a furnace 30g. Upon leaving the furnace it is carried an appreciable distance in fiat form, and permitted to cool in this form so as to remove coil set, after which it is coiled in a suitable coiler 32g. In this manner, there is obtained a material which, when unwound from the coil, willlie perfectly at with the result that the laminze cut or punched therefrom will also lie flat and thus permit of assembly without the introduction of a ilattening strain. In this manner, a superior product is insured.

With the forms of my invention heretofore described and particularly those illustrated in Figures 3, 4, '7 and 8, the strain introduction involves only a very small reduction in thickness, and while relied upon to give some reduction, is yprimarily for the purpose of introducing a desirable strain component of the order referred to. In many cases, however, the hot rolling operat'on and particularly where carried out in a continuous mill is customarily relied upon for producing a hot rolled strip substantially free from any cold Working strains, having a thickness of approximately .0625 inch, corresponding to 16 gauge, and having any desired width. Electrical sheets customarily have a thickness lying within and including 22to 30 gauge (United States standard). This material in strip form can most effectively be reduced by cold rolling in a continuous mill, but such a continuous mill has heretofore been considered impracticable for the production of electrical steels by reason of the excessive strain introducedinto the metal thereby, the cold rolling effecting a very appreciable reduction. If this reduction is from .0625 inch to 024 inch, there is a ,reduction of .0385 inch, equal to approximately 61%. These figures are representative of thicknesses frequently produced in the cold rolling of steel for purposes other than the production of electrical steels. While such a cold rolling operation is effective for reducing the hot rolled strip to the desired nished gauge, the strain introduced by reason of the reduction effected is far in excess of the strain heretofore though permissible in the production of electrical steels. In accordance With one embodiment of my invention, however, I take advantage of the strain introduct'on thus effected, and consider the strain as including both a desirable component of the order previously mentioned and an undesirable component, which is that in excess of the desirable component. In Figure 9, I have shown an embodiment of the invention-operating according to the immediately preceding description.

In this form of the invention, material, for example, after having been normalized or annealed at 27h and after being coiled in a suitable coiler 28h, is passed to a continuous cold mill 33 comprising a plurality of 4stands in tandem effective for giving the desired reduction in thickness. As an incident to this reduction, the excessive strain referred to is introduced. This material may then be coiled in a coiler 34 and subjected to a partial annealing in a suitable furnace 35 after which it may or may not be coiled in a suitable coiler 36 and then subjected to a normalizing operation in a furnace 37, after which it may be coiled for shipment in a suitable coiler 38. On the other hand, after leaving the coiler 34, it may be partially normalized in the furnace 35 and then, after coiling in the coiler.

36, be annealed in the furnace 37, or without such coiling or with it as preferred, be normalized in thisifurnace. If normalized it may again be coiled in the coiler 38.

In my copending application Ser. No. 593,783, filed February 18, 1932, I have described and claimed the general two-stage heat treating operation including a partial anneal or a partial normalizing followed either by a complete anneal or a complete normalizing, the partial anneal or partial normalizing being carried out to the extent required to remove the undesirable strain component and` leave only the desirable strain component in the material, so that the final anneal or 'normalize will be effective on material which only has such a desirable strain component therein.

With any given silicon content, the undesirable strain component wiil vary with changes in the reduction effected lby the cold rolling operation, the strain increasing with increased reductions, and decreasing with smaller reductions. While the actual strain introduced under varyes'I ing reductions is not a straight line function,

it is a function which is readily determinable.`

In like manner, the undesirable strain component increases in amount as the silicon content of the material undergoing treatment increases, with any given percentage of reduction by the cold mill. 4

In practicing my invention I have successfully employed a continuous heating furnace as indicated at 35 in Figure 9. The furnace had a length of approximately 30 feet and was maintained at a temperature of approximately 1900 F. Silicon steel strip` containing approximately 1% of silicon, which steel had been subjected to a 61% reduction by cold rolling, and having a nal thickness of .024",Y was passed through the furnace at the rate of 15 feet per minute, giving a total time in the furnace of two minutes. I have estimated that in the furnace employed the heat penetrated'with sufficient rapidity to bring the strip up to the desired minimum temperature in approximately 30 seconds, thus leaving 90 seconds of additional heating time available for continued heating. Under the above conditions the heat treatment eliminated the undesirable strain component and left the desirable strain component therein.

It is generally assumed that the rate of heat penetration varies directly with the thickness of the material and hence if the strip being treated were only half as thick, that is to say, .0125 inches, then only 15 seconds would be required to bring it up to the desired minimum temperature. Adding to this the continued heating time of 90 seconds, the total time for heating such strip in the furnace in question would be 105 seconds.

It may thus be ascertained that the total timetemperature treatment for effecting removal of the undesirable strain component varies directly as the thickness of the material undergoing treatment, assuming a predetermined silicon content and a predetermined reduction. This treatment may be considered as involving the two factors of time and temperature. If it is desired to decrease the time of treatment, it is necessary to increase the temperature, while if it is desired to increase the time, there should be a corresponding reduction in temperature.

Since the undesirable strain component increases with higher silicon and decreases with lower silicon, and likewise increases with the percentage of reduction and vice versa, it is necessary to make a corresponding change in the time-temperature characteristic to accommodate vthe treatment to either the siliconcontent or the percentage of reduction. By taking these factors into consideration, the furnace 35, whether an annealing or a normalizing furnace, may be used for partial strain removal only, with definite assurance that a desirable strain will be retained in the material.

Figure 10 illustrates an operation generally similar to that of Figure 9, but differing in that the material coiled in the'coiler 381 is heated in a suitable furnace 39 and then cooled in the flat to remove coil set before being subsequently coiled in the coiler 321.

In Figure 11, the material after having been cold rolled in the continuous mill 331 and after having been coiled in the collar 34j may be either annealed or normalized in a furnace 40. Thereafter it may be coiled in a coiler 41, passed through a cold rolling stand 21j effective for introducing a desirable strain component only, thereafterrecoiled in a coiler 42 with subsequent annealing or normalizing in a furnace 375 followed by coiling in a collar 383. With this form of the invention, it will be apparent that the heat treating furnace 40 is effective for completely removing all of the strain introduced by cold rolling, and that thereafter, only a desirable strain component is introduced.

Figure 12 shows a lay-out generally similar to that of Figure 9, but differing principally in that the material,.usually after having been coiled in a coiler 36k, is passed through anormalizing furnace 43 and thereafter cooled in the fiat to remove coil set and then coiled in a suitable coiler 32k.

In Figure 13, the operations correspond generally to those carried out in accordance with Figure 11, up to the point of coiling in the coiler 421, After this operation, the material is normalized in a furnace 431, cooled in the fiat to remove coil set and coiled in the coiler 321.

The next two figures of the drawings differ from each other in that one relates to excessive strain introduction and the other to normal strain introduction only. The procedure in accordance with Figure 14 is generally similar to that of Figure '7, up to the coiler 31m. From .this coiler, the

material may pass through a roller leveler 44 to a suitable shear 14m effective for producing sheets 45 which may thereafter be box annealed in an annealing box 19m.

In Figure 15, the operation of Figure 9 is followed up to the coiling in the coiler 341 after which the material may pass through a roller leveler 44 to a shear 14n eiective for forming sheets 45n which may be partially annealed in a box 46 to remove only the undesirable strain component and thereafter again anneal in a suitable box anneal 47 to complete the strain removal.

If in any case, the finishing temperature on the hot mill, where rolling to an intermediate gauge, is not satisfactorily controlled, an annealing or normalizing step may be introduced following the hot rolling to intermediate gauge and prior to any subsequent rolling.

The pickling step illustrated may be varied as to its time of performance, as desired, its function being only to eiect removal of scale or oxide.

Also, the shearing step may be practiced without roller leveling, if desired, although I have found the leveling operation to be generally more satisfactory.

Wherever the material is annealed in coils, -it may be reheated and cooled in the fiat to remove coil set, and wherever it is normalized in strip form, it may be cooled in the flat before being recoiled, in order that coil set may be eliminated.

From the foregoing description, it will be apparent that all forms of my invention contemplate starting with a hot rolled strip followed by certain after operations, including in some cases limited cold rolling and in other cases material reduction by cold rolling. In all cases, any rolling is in the direction of the original rolling operation in the roughing millor, to be more specific, the material at no time is subjected to a cross rolling operation. This constitutes one of the features of my invention.

Another feature of my invention relates to the accomplishing of the last hot rolling pass in definite predetermined relationship to the recalescence point ofthe metal for reasons pointed out in detail.

My invention further contemplates taking advantage of the variable factors hereinbefore referred to and using them either individually or combined to produce superior electrical properties. By properly utilizing these variables, it is possible to meet guarantees as shown below in the table containing seven different grades of electrical steels, each with an identifying title, together with' the Watt loss per pound at frequencies of both 50 and 60 cycles at the assumed specific gravities indicated, the maximum watt losses in the case of some of the grades being shown for a plurality of different gauges, these ranges covering the gauges ordinarily manufactured. In all cases, the Wattloss is figured at a ux density of 10,000-B and determined in Laccordance with the specification A-34-28 of the American Society for Testing Materials.`

There is indicated one permissible range of k silicon variation for each grade.

Regular transformer (Assumed sp. gr. 7.50)

Silicon 3% plus-U S. standard gauges 30G. 29o. 28o. 27o. 26o 25o. 24a. 23o. 22a.

Watts per 1b.-60 cycles 76 76 80 .85 .89 .93 .98 Watts per kg.60 cycles l. 67 1. 67 1. 76 1.87 l. 96 2.05 2. 16 Watts per lb.-50 cycles. 62 62 64 .-68 7l 75 78 Watts per kg.-50 cycles 1. 375 1. 375 1.41 l. 50 1. 56 1. 65 1. 72 i Lecc Special transformer (Assumed sp. gr. 7.50)

Silicon'8% plus `30o. 29o. 284e 27o zoo 25o. 24o. 23o. 22o

Watts per lbf-60 cycles Watts per lig-60 cycles Watts per lb.-50 cycles. Watts per kg.50 cycles Extra special transformer (Assumed sp. gr. 7.60)

Silicon 3% plus Watts per lb.-60 cycles 64 Watts per kg.-60 cycles. 1. 42 Watts per lb.-50 cycles. 52 90 Watts per kg.-50 cycles 1.15 4

Armature (Assumed sp. gr. 7.70) Silicon .8-.7 (U. S. standard gauges) Watts per 1b.-60 cycles 1. 35 l. 40 1. 46 1.53 l. 65 l. 85 2.15 2. 50 2. 80 Watts per kg.-G0 cycles 2. 97 3. 08 3. 20 3. 57 3. 63 4.07 4. 73 5. 50 6.16 Watts per 1b.50 cycles-- l. 12 1.17 1. 20 l. 30 l. 42 1. 53 1. 75 2.00 2. 30 Watts per kg.-50 cycles 2. 46 2.57 2. 64 Y 2.86 3. 12 3. 57 3. 85 4. 40 5. 06

Electrical (Assumed sp. gr. 7.70) Silicon .75-1.5 (U. S. standard gauges) Watts per lb.--60 cycles- 1. l5 1.20 1. 28 1. 35 1.40 1.55 1. 80 2.10 2. 30 Watts per kg.-60 Cycles. 2. 53 2. 64 2. 82 2. 97 3.08 3. 41 3. 96 4. 62 5.06 Watts per lb.-50 cyCleS .95 1.00 1.07 1. 14 1. 18 1. 30 1. 50 l. 70 1.85 Watts per kg.-50 cyc1es 2. 09 2. 20 2. 35 2. 5l 2. 60 2.86 3. 30 3. 74 4. 07 105 Special motor (Assumed sp. gr. 7.50) Silicon 2.0-3.0 (U. S. standard gauges) Watts per lb.60 cycles 1. 00 1.03 l. 08 1.15 1. 20 l. 25 1. 30 1l() Watts per kg.-60 cycles 2. 20 2. 27 2. 38 63 2. 64 2. 75 2. 86 Watts per 1b.-50 cycles. 84 86 90 94 97 l. 00 l. 05 Watts per kar-50 cycles 1.85 1. 89 l. 98 2. 07 2.13 2. 20 2.31

Special dynamo (Assumed sp. gr. 7.50) Silicon 275-35 L'. S'. standard gauges) MM5 Watts per IIL-60 cycles. 86 90 95 1. 00 l. 05 Watts per kg -60 cycles.-. 1.87 1.89 1. 98 2.09 2. 20 2. 3l Watts per 1b.-50 cycles, 68 70 73 77 82 86 Watts per ktn-50 cycles 1. 50 1. 55 1. 61 1. 70 1.81 1. 89

My invention further contemplates the production of superior electrical steel in either sheet or coil form, and in the case of coil strip either with or without the coil set removed therefrom.

Other advantages of the invention will be readily apparent to those skilled in the art from the foregoing descriptions and illustrations, it being understood that changes in the construction and relationship of the parts may be made without departing either from the spirit of my invention or the scope ofthe broader claims, the figures of the drawings being illustrative only and not exclusive of various changes, such, for example, as generally referred to herein.

claim:

l. In the method of making silicon steel in sheet-like form, the steps consisting in casting a steel ingot of the desired silicon content andhot rolling the ingot to reduce it, all the hot rolling passes in which any substantial reduction is effected being in the direction in which the ingot was rolled, thereby to improve the electrical properties ofthe material.

2. -In the method of making silicon steel in sheet-like form, the steps consisting in casting a steel ingot of the desired silicon content and hot rolling the ingot to reduce it, all the hot rolling passes in which any substantial reduction is effected being in the direction in which the meot was rolled, thereby to improve the electrical properties of the material, and further controlling the electrical properties of the steel by varying the temperature at whichthe last hot rolling is effected.

3'. In the method of making silicon steel in sheet-like form, the steps consisting in casting a steel ingot of the desired silicon content, hot roll-= ing the ingot to reduce it, all the hot rolling passes in which a y substantial reduction is effected loeq ing in the ecton in which the ingot was rolled, thereby to improve the electrical properties of the material, and then raising the temperature of the material suilciently to eiect substantial elimination of the strains therein.

4. In the method of making silicon steel in sheet-like form, the steps consisting in casting a steel ingot of the desired silicon content, hot rolling the ingot to reduce it, all the hot rolling passes in which any substantial reduction is ef- MG fected being in the direction in which the ingot was rolled, thereby to improve the electrical properties of the material, raising the temperature of the material sumciently to eect elimination of part but not all of the strains therein, allowing the material to cool, and then annealing it.

5. In the method of making silicon steel in sheet-like form, the steps consisting in 'casting a. steel ingot of the desired silicon content, hot roll- 150 ing the ingot to reduce it, all the hot rolling passes in which any substantial reduction is eiected being in the direction in which the ingot was rolled, thereby t'o improve the electrical properties of the material, then raising the temperature of the material sufliciently to effect substantial elimination of the strains therein, then so working the material as to introduce strain therein, and then annealing it to remove such strain.

6. In the method of making silicon steel in sheet-like form, the steps consisting in castinga steel ingot of the desired silicon content, hot rolling the ingot to reduce it, all the hot rolling passes in which any substantial reduction is effected being in the direction in which the ingot was rolled, thereby to improve the electrical properties of the material, then raising the temperature of the material sufficiently to effect substantial elimination of the strains therein, cold rolling the material, and then annealing it.

7. As a new article of manufacture, electrical steel in sheet-like form containing .1 to 6% silicon and having the electrical properties characteristic of those obtained when a steel of substantially the same silicon content within such range is subjected to reduction by hot rolling with all substantial reductions effected by .rolling in the same the same direction, followed by heating to a temperature sufficient to remove the strain.

9. As a new article of manufacture, electrical steel in sheet-like form containing .1 to 6% silicon and having the electrical properties characteristic'of those obtained when a steel of substantially the same silicon content within such range is subjected to reduction by -hot rolling with all substantial reductions effected by rolling stantially the same silicon content within such range' is subjected to reduction by hot rolling with all substantial reductions effected by rolling in the same direction, followed by cold rolling to elect a substantial reduction in thickness, heating to a suilcient temperature and for such limited time as to remove part but not all of the strain in the material, cooling and then annealing 11. In the method of making silicon steel in sheet-like form, the steps consisting in casting a steel ingot of lthe desired silicon content and reducing the ingot to sheet-like form by hot rolling passes and subsequent cold rolling passes, all of the rolling passes in `which any substantial reduction' is effected being in the direction in which the ingot was rolled, thereby to improve the electrical properties of the material.

12. As a new article of manufacture, electrical steel in sheet-like form containing .1 to 6% silicon and having the electrical properties characteristic of those obtained when a steel of substantially the same silicon content, within such range, is subjected to reduction by hot rolling` passes followed by cold rolling passes, with all substantial reduction effected by rolling in the same direction.

, 13. As a new article of manufacture, electrical steel in sheet-like; form containing .1 to 6% silicon and having the electrical properties charall substantial reductions which are made being effected by rolling in the same direction.

14. As a new article of manufacture, electrical steel in sheet-like fo'rm containing .l to 6% silicon and having electrical properties characteristic Ao1 those obtained when a steel of substantially the same silicon-content, within such range, is subjected to reduction by hot rolling followed by cold rolling to effect a substantial reductiony in thickness', heating to. a suillcientv temperature and for such limited time as to remove part but not all of the strain in the material, cooling, and then annealing it, all substantial reductions which are made being effected by rolling in the same direction.

. EDWARD M. FREELAND.

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