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Publication numberUS3892605 A
Publication typeGrant
Publication dateJul 1, 1975
Filing dateJul 17, 1974
Priority dateFeb 22, 1972
Publication numberUS 3892605 A, US 3892605A, US-A-3892605, US3892605 A, US3892605A
InventorsThornburg Donald R
Original AssigneeWestinghouse Electric Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Method of producing primary recrystallized textured iron alloy member having an open gamma loop
US 3892605 A
Abstract
An iron base alloy is described which contains low amounts of alloying elements and is suitable for use as a transformer core material. The alloy is characterized by a (110) [001] texture, and a primary recrystallized and normal grain growth microstructure. The process for obtaining the oriented structure is either a two stage or a three stage process in which the final cold reduction effects only a moderate reduction in cross-sectional area to finish gauge. In all cases the alloy is subjected to a final anneal at a temperature below the Ac1 temperture of the alloy.
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United States Patent Thornburg METHOD OF PRODUCING PRIMARY RECRYSTALLIZED TEXTURED IRON ALLOY MEMBER HAVING AN OPEN GAMMA LOOP Donald R. Thornburg, Pittsburgh, Pa.

1972, abandoned, and a division of Ser. No. 312,681, Dec. 11, 1972, Pat. No. 3,849,212.

Inventor:

U.S. Cl 148/120; 75/123 K; 148/121;

148/122; l48/3l.55 Int. Cl. H01f 1/00 Field of Search 148/120, 121, 122, 31.55,

[111 3,892,605 [451 July 1, 1975 Primary Examiner-Walter R. Satterfield Attorney, Agent, or FirmR. T. Randic 5 7] ABSTRACT An iron base alloy is described which contains low amounts of alloying elements and is suitable for use as a transformer core material. The alloy is characterized by a (110) [001] texture, and a primary recrystallized and normal grain growth microstructure. The process for obtaining the oriented structure is either a two stage or a three stage process in which the final cold reduction effects only a moderate reduction in crosssectional area to finish gauge. In all cases the alloy is subjected to a final anneal at a temperature below the Ac temperture of the alloy.

15 Claims, 12 Drawing Figures SHEET 1 ROLLING DIRECTION 1.0 2 2.0 o 3 3.0 4 4.0 o 5 5.0 32 s 6.0 LL IO 7 6.2

I I I I l I I I r I I l I I I l I 9 75 so 30 l5 0 PATENTEUJUD 915 3. 892,606

SHEET 2 ROLLING DIRECTION O0 Z DIGIT CONTOUR 2 I LO 0 2 2.0 g 20- 3 3.0 w 4 4.0 5 4.7

O I I I I I I r I I I I I I I I ALPHA FIG. 2A

SHEET 3 ROLLING DIRECTION FIG. 3

DIGIT CONTOUR 4O 1 1.0 2

2 .5 9 so 3 2.0 B

T3 I' YI'IJULI I975 3,892,605

SHEET 4 ROLL NG DIRECTION DIGIT CONTOUR 40 I |.0 z 2 |.s 9 so 3 2.0 5 4 3.0 12 20 5 a: 6

4.0 LL WW FI I O I I I I I I l l l l I I I l l I I I 90 75 6O 45 30 l5 0 ALPHA SHEET 5 ROLLING DIRECTION DIGIT CONTOUR 4O 1 2.0 2 r 2 3.0 o 3 4.0 5 4 5.0 5 6.0 E F e 6.| IO

ll'fllllllllllil 9o 75 6O 45 30 I5 '0 ALPHA FIG. 5A

SHEET ROLLING DIRECTION DIGIT CONTOUR ALPHA FIG. 6A

METHOD OF PRODUCING PRIMARY RECRYSTALLIZED TEXTURED IRON ALLOY MEMBER HAVING AN OPEN GAMMA LOOP CROSS REFERENCES TO RELATED APPLICATIONS Status Serial No. Filing Date Copcnding 228,07] Feb. 22, 1972 Now Pat. No 3,843,424 Copending 228.319 Feb. 22. 1972 Now abandoned 228,070 Feb.22. 1972 Now abandoned 228,320 Feb. 22, 1972 BACKGROUND OF THE INVENTION 1. Field of the Invention:

The present invention relates to an iron base alloy which contains low amounts of alloying components and which, when processed in accordance with either one of the two methods set forth hereinafter, will produce an oriented grain structure in the finished product which is characterized by a cube-on-edge orientation or as described in Miller Indices as (ll)[00l] grain orientation, and Comprising a primary recrystallized and normal grain growth microstructure. Such magnetic materials are useful, for example, as core materials in power and distribution transformers.

2. Description of the Prior Art:

The operating inductions of a large proportion of today's transformers are limited by the saturation value of the magnetic sheet material which forms the core. In extensive use today is an iron base alloy containing nominally 3.25% silicon which is processed in order to obtain a cube-on-edge or l l0)[00l] grain orientation in the final product. An example of this well known steel depending upon the final magnetic characteristics is called type M-5 and has the final grain orientation developed by means of a secondary recrystallized microstructure. This microstructure is attained during final box annealing in which preferentially oriented grains grow at the expense of nonpreferentially oriented grains with the result that the alloy usually has an extremely large grain size such that the diameter usually greatly exceeds the thickness of the sheet material. However, in order to obtain such large grains in a secondarily recrystallized microstructure it requires a long time, high temperature heat treatment for the development of the orientation. This anneal is also required for the removal of residual sulfur content. Sulfur contents in excess of about 100 ppm in the finished product adversely affects the magnetic characteristics exhibited by the silicon-iron alloy.

In addition to the long time, high temperature box anneal, which is quite costly, the addition of 3.25 percent silicon to pure iron, while effective and generally desirable for greatly improving the volume resistivity, nonetheless lowers the saturation value so that in most commercially produced iron-3.25 percent silicon containing alloys, the saturation value of such. alloys usually does not exceed 20,300 gauss. Thus, there is the obvious tradeoff of improved volume resistivity which relates to the core losses of the material for lower saturation value, since the saturation value of commercially pure iron is about 21,500 gauss. It will be recognized further that such saturation values are only obtained where the material possesses a high degree of l l0)[00l] orientation in the final product. Moreover, since commercial iron will have substantially higher watt losses and substantially higher coercive force values than silicon steel it was prudent to balance the overall observed magnetic characteristics and the best balance heretofore obtained was that of the iron 3.25 percent silicon alloy which exhibited the cube-on-edge orientation.

The alloy of the present invention also employs a trade-off of the various magnetic characteristics. The observed magnetic characteristics especially those where the material is used as in transformer core approach those of the commercially produced 3.25 silicon steel materials employed today. The present low alloy composition is radically altered from the 3.25 percent silicon containing iron, but the same orientation is attained by means of the processes set forth hereinafter so that the microstructure is primarily recrystallized with normal grain growth. Thus the alloy of the present invention produced comparable magnetic characteris tics without employing the costly secondarily recrystallized microstructure, yet obtains the same orientation in a composition which is quite diverse from that of the commercially used materials- BRIEF DESCRIPTIONQFTHE DRAWINGS FIG. 1 is a 1 l0) Pole Figure and FIG. 1A is a Histogram for Heat No. 1482;

FIG. 2 is a (200) Pole Figure and FIG. 2A is a Histogram for the same material of FIG. 1;

FIG. 3 is a (110) Pole Figure and FIG. 3A is a Histogram for a commercial size heat identified as Heat No.

FIG. 4 is a (200) Pole Figure and FIG. 4A is a Histogram for the material of FIG. 3;

FIG. 5 is a l 10) Pole Figure and FIG. 5A is a Histogram for another commercial size heat identified as Heat No. 3523; and

FIG. 6 is a (200) Pole Figure and FIG. 6A is a Histogram of the material of FIG. 5.

SUMMARY OF \THE INVENTION ,1

The present invention relates to an iron base alloy containing up to about 0.03% carbon, up to l% manganese, from about 0.3% to about 4% of at least one of the volume resistivity improving elements selected from the group consisting of up to about 2% silicon, up to 2% chromium, and up to about 3% cobalt, and the balance essentially iron with incidental impurities. This alloy is processed by hot working and cold working in either a two or a three stage operation, the final stage of working effecting only a moderate reduction in the cross-sectional area of the material being processed, said last reduction in cross-sectional area lying generally within the range between about 50% and about The finish gauge material is thereafter subjected to a final anneal at a temperature which is in the range between about 750C and the Ac, temperature exhibited by the alloy. As thus produced, the alloy exhibits a cube-on-edge or a l l)l00l I texture as the predominant texture, a primarily recrystallized and normal grain growth microstructure. The magnetic characteristic exhibited by the-alloy approached those of commercially produced 3.25% silicon steels in use today.

DESCRIPTION OF THE PREFERRED EMBODIMENT The alloy of the present invention has a composition which includes up to about 0.03% carbon, up to about l% manganese, at least 0.3% up to about 4% of at least one of the volume resistivity improving elements selected from the group consisting of up to 2% silicon, up to about 2% chromium. and up to about 3% cobalt, and the balance being essentially iron with incidental impurities. The carbon in the final product which is maintained as low as possible is usually included with the composition initially for dcoxidation purposes in the normal melting of the components. While it is desirable to maintain the carbon content in the melt as low as possible. up to about 0.03% can be employed without adversely affecting the magnetic characteristics of the alloy as melted. With about 0.03% carbon, it is possible to decarburize the finished alloy and remove the carbon content to the desired low level.

The alloy also contemplates the use of manganese in amounts up to 1% usually for the purpose of deoxidizing the material. It will be noted hereinafter however that the addition of manganese also improves the volume resistivity of the alloy but not to the same extent as silicon. Good results have been obtained where the manganese content of the alloy is about 0.5%.

In order to improve the volume resistivity of the alloy, at least 0.3% and up to 4% of at least oneelement of the group consisting of silicon, chromium and cobalt is necessary in the alloy of the present invention. Where silicon is employed, amounts of up to 2% can be utilized in order to improve the volume resistivity. Good results have been obtained where the silicon content is maintained within the range between about 0.5% to l.5%. The silicon content is preferably limited to the foregoing range in order that the alloy will exhibit an open gamma loop to enable one to utilize a primary recrystallization technique for developing the desired grain texture within the alloy. Where chromium is used the volume resistivity improving element, a minimum of about 0.3% chromium should be employed and amounts in excess of about 2% chromium should be avoided. Since cobalt also improves the saturation value of the alloy. up to about 3% is contemplated within the composition for improving the volume resistivity as well as the saturation value of the alloy. Combinations of any two or all three of these resistivity improving components are particularly effective. Sulfur should be as low as practicable since the element will not be removed during subsequent processing.

In this respect sulfur should not exceed about 0.012% and preferably it should be below about 0.010%. It has been noted that sulfur appears to adversely affect the coercive force and hence the core loss properties of the alloys. In contrast to presently available commercial oriented silicon-iron wherein sulfur unites with manganese to form a particle which is effective in developing a high degree of texture in the final product, such mechanism is not believed to be involvedin developing the texture observed in the alloy of the present invention. Moreover, when it is considered that in the commercially available material the final heat treatment temperature is in excess of about 1000C which is effective for dissacating the manganese sulfide, the sulfur is removed from the alloy after it has served its purpose. However, this can only occur at temperatures in excess of about l000C. In contrast thereto, once the open gamma loop alloy of the present invention is finished hot working, it is never heated above its Ac, temperature. Consequently, any sulfur which is present will not be significantly reduced during such subsequent operations. Accordingly, it is necessary to control the sulfur content and outstanding results have been obtained where the sulfur content is maintained at about 0.005 maximum. The balance consists essentially of iron with the usual incidental impurities that are found in the manufacture of magnetic alloys on a commercial scale.

The alloy having the composition set forth hereinbefore is melted and is cast into ingots in the regular commercial manner. The metal may be continuously cast into slabs or bars. The cast ingots are thereafter hot worked usually at a temperature within the range about l000C and 1000C to a desired intermediate gauge. Where the alloy is to be processed by employing two-stage cold working operation it is preferred to hot work the metal to a thickness of about 0.10 0.025 inch. On the other hand where the alloy is to be processed by employing a three-stage cold working operation, the preferred finished hot work gauge is about 0.180 0.030 inch. While it is not absolutely essential to protect the steel during such hot working operation, an argon or other non-oxidizing atmosphere may be used in order to prevent excessive scaling of the alloy during such hot working. It is preferred to hot work the alloy at a temperature of about l050C to the desired final hot work gauge depending upon the cold working operation to which the alloy will be subjected. Following such hot working to the desired gauge, the alloy is descaled, usually by pickling in order to remove any scale which may have formed on the surface thereof during such hot working operation.

Following hot working the alloy is thereafter cold worked in two or more operations or stages to finish gauge. Where cold rolling is employed it may be usually necessary to pass the alloy strands a number of times through said cold working rolls in order to attain the desired reduction in area. Regardless of the number of passes employed the several cold working operations require an intervening intermediate anneal at a temperature within the range between about 750C and the Ac temperature of the alloy being processed. Thus in a two-stage cold working of the alloy to finish gauge, the initial hot worked material of about 0.l0 inch in thickness is first cold worked to about 0.025 inch and then annealed for one hour at a temperature of about 850C in an atmosphere preferably of hydrogen having a dew point of less than about 40C. Thereafter the alloy sheet or strip is given the second stage cold working to the finish gauge usually within a thickness of between about 0.010 inch and about 0.014 inch.

Thus, in a typical exemplary two-stage cold working operation an approximately reduction in crosssectional area is effected on the alloy in the initial cold working operation and, following intermediate annealing, a reduction in cross-sectional area of about 50% to finish gauge is produced in the second stage operation. The first stage of cold rolling may effect high reductions of up to 90% or more. It is imperative that only moderate amounts of cold work be employed in the final cold working operation such that the reduction in cross-sectional area will range between about and 75% reduction in cross-sectional area from the thickness or the cross-sectional area of the material of intermediate gauge resulting from the initial cold working operation. Excellent results have been achieved where the final cold reduction effects a reduction in crosssectional area of between about and about to finish gauge.

Where thinner final gauge material is desired, advantageously a three-stage cold working operation may be performed with each cold working stage being followed by an intervening intermediate anneal at a temperature within the range between about 750C and about the Ac temperature of the alloy. In this three stage process. in each of the cold working operations only modcrate amounts of cold work are effected, usually within the range between about 50% and about reduction in cross sectional area from the preceding gauge material.

Thus, a typical three-stage cold working operation would start with a hot work gauge of about 0.18 inch strand thickness, which strand is thereafter descaled, usually by pickling and annealing for about five hours at a temperature of between 850C and 900C. The annealed alloy strand is then first cold worked to a thickness of about 0.080 inch in thickness, i.e., 55% reduction, annealed for about five hours at a temperature within the range between about 800 and 900C, cold worked to a thickness of about 0.020 inch in thickness, (Le. a 75% reduction) annealed for about 1 hour at a temperature within the range between about 800C and 900C and thereafter cold worked to a finish thickness usually within the range between about 0.005 and about 0.007 inch in thickness, a reduction of about 75% to 65% In both the two-stage and the three-stage cold working process. part of the cold working operation except the last one may be performed at an elevated temperature between room temperature and about 300C. The working at elevated temperatures is referred to as hotcold working. Such hot-cold working can take place at any temperature above room temperature and below the recrystallization temperature of the alloy being processed. Where such hot-cold working is employed in any of the cold working operations except the last, it is preferred to employ an argon atmosphere in order to reduce any tendency towards appreciable oxidation of the surface of the alloy strand being processed. Moreover. at each of the intermediate annealing heat treatments which are interposed between the cold working operations, a protective atmosphere and preferably a hydrogen atmosphere having a dew point of less than about -40C is employed. 40

Moreover. it will be appreciated that one or more of the intermediate anneals can be accomplished by means ofa strip anneal versus a box anneal. Thus a single strand from a coil of the alloy may be continuous fed into a strip annealing furnace where the material is heated to a temperature typically of about 900C wherein each increment of the strip is maintained at this temperature for a time period of typically 3 minutes. A hydrogen atmosphere having a dew point of 40C may be advantageously employed.

Following cold working to finish gauge the alloy sheet or strip is subjected to a final anneal, usually a box anneal, at a temperature within the range between about 750C and the Ac, temperature of the alloy such box annealing usually being carried out in an atmosphere of hydrogen having a dew point of less than about 40C. The alloy is maintained at a temperature which is always below the alphato gamma transformation temperature in order to obtain a primary recrystallized microstructure with normal grain growth. It has been found that the alloy so processed and subjected to the final annealing attains the desired degree of orientation usually within a time period within the range between the 24 hours and 48 hours while at the box annealing temperature. Upon cooling to room temperature following such box annealing, the alloy will possess a grain structure having a preponderance of the grains aligned in the cube-on-edge or l l0)[00l] orientation. It has been found that the grains which attain the preferred orientation have cube edges which are aligned within ten degrees of the rolling direction.

In order to more clearly demonstrate the alloys and the processes of the present invention, below are examples of a number of heats melted and processed in accordance with the teachings of the present invention and such alloy products demonstrate the desired (1l0)[00l] texture with a primary recrystallized and normal grain growth microstructure. Reference is directed to Table l which illustrates the chemical composition of a number of alloys which were made and tested in comparison with a commercially available 3.2571 silicon containing alloy which was processed to produce a cube-on-edgc orientation by a secondary recrystallization and preferred grain growth.

TABLE I HEAT /rMn '/1Cr /(Si 71C* p (p. fl-em) 1480 1 l48l 0. l5 0.03 l 1.4 M82 0.]5 (L6 0.03 14.5 l483 0. l5 0.6 V9.2 I484 0.15 1.2 20.3 M-5 0.10 3.2 0.03 44.0

" Excess for deoxidation Table 1 also lists the resistivity (p) which was measured for the various alloys. These alloys were made and processed in accordance with the following outlined procedures.

PROCESS NUMBER 1 PROCESS NUMBER 2 Hot roll at 1050C in argon to 0. l inch in thickness pickle and anneal live hours at a temperature within the range between 850C and 900C employing dry hydrogen. Warm roll at 260C. employing argon, to 0.080 inch. Anneal five hours at the intermediate annealing temperature of about 850C in dry hydrogen. Warm 'roll at 260C, employingar gon to 0.040 inch in thick- Process 2 produced some general improvement in the peak torquevalues and slightly higher peak ratios in comparison with the commercial 3.20% silicon steel. However, once again the preponderating texture which was developed was that characterized as (110)1001]. In particular heat 1482 with 0.6% chromium has a B value identical to the commercially produced 13- 4% silicon steel and a B value. higher than that of the commercial material. The silicon containing alloys namely alloy 1483 and 1484 had slightly lower B ibut higher B values. As would be expected from the peak torque values exhibited, neither heat 1480 nor l48l d eveloped good texture using either process. 8

TABLE 2 1 Y Reference is now directed to Table 3 which summa- Tlxllonllinal T Peak P k H B B 15 rizes the 60 hertz AC properties of the alloys 1482,

IC "CS5 orque ea 9' HEAT Process (mils) (erg/cm) Ratio (Oe) (k8) (k 03 1483 and 1484 a y efnploymgprpcless NO The AC data definitely indicate that the highly textured :23? l g-Zf; 12-2 :88 alloys had properties approaching that of type M-5 1482 1 5 1641200, -1 3- /4% silicon steel. The alloys with silicon additions had 1 1 12 3. 9. 0.19 191 sli m1 better losses but oorer excitin characteristics 1484 1 12 135.700 0.50 0.13 17.3 19.9 l h h. h g H 1480 2 6 106.100053 0.23 16.9 19.7 l e C i mfi m a 14x1 2 -0 85.900 0.55. 0.26 16.9 19.6 1482 2 177.700 0.49 0.20 18.3 20.7 T apove results Show? hlg.h degree of i 1O)[00.l.] 1483 2 6 144.100'061 0.17 17.9 20.5 onmatilon has beenobtamed 10W a l "9" y P"- l48 2' 6 5 (1-16 mary recrystallization and normal grain growth. These M-5 11 167.000 0.34 0.10 18.3 19.8 1 1 useful textures have been obtained with alloys contami v l s ing small amounts of chromiumand silicon. Since both TABLE 3 Nominal Thickness ris m; P417 1117 P PPM: 3 HEAT (mils) (W411i) (VA/lb) (W/lb) .(VA/lb) (W/lb) (VA/lb) From the data set forth in Table 11, it may be seen that require only moderate final cold reductions with the the alloys which were processed using the Process 1 4O final cold reduction playing a major role in the texture show that a relatively good 1 10)[O0l] orientation was obtained in the alloys containing chromium and silicon. This is evident by the peak ratios which lie within the range between 0.42 and 0.50. Commercial 3.2% silicon steel with a peak ratio 0.34 has an excellent degree of l l0)[001] orientation. However, the peak ratios measured for heats 1482, 1483 and 1484 establishes that a preponderance of the grains have the (l l0)[001] texture developed therein. Note that'while'the'B values are lower the saturation values B eitherarecomparable or exceed the type M.-5 values. The coercive force is also quite good. An examination of the microstructures of samples 1481', 1482, 1483 and 1484 indicated that all had'a primary 'recrystallized microstructure characterized by normal grain growth.-

development, a highly useful and inexpensive magnetic composition has been developed; The resulting alloys have B values equivalent to type M-5 commercial silicon steel and B values higher than commercially available silicon steel. The -Hz AC properties of the 6 mil material approach thosevalues found for the commercially available silicon ste 'el. 1

" In order to more clearly demonstrate-the present invention, two commercial size heats were made each having a composition within the limits set forth hereinbefore. Forcomparativepurposes, parallel'data were also obtained from Heat No. 1482 which was processed in accordance with Process Number 2 set forth hereinbefore. The chemical analysis and the electrical resistivity are set forth hereinafter in 'Table'lV.

TABLE 4 Chemical Analyses and Electrical Resistivity %C HEAT lngot- After NO. 715i 7zCr 7Mn 7:5 720 VIN; Added Ladle Final Box (p(l-cm) Anneal 'Nominal Y i I "-"Hot Band All analyses weredonc on the ingot (or air melt ladle) samples except when indicated otherwise.

9 Heats 3524 and 3523 were both air induction melted heats having a weight of approximately 5000 lbs. for each heat. The 5000 lb. heat was cast into an ingot which was thereafter vacuum arc remelted, forged and Reference is now directed to Table V which lists the DC magnetic properties as well as the torque data on the material as processed as set forth hereinbefore.

separated into two billets for hot working. One of the 5 TABLE 5 billets was hot rolled in air to 0.160 inches and thereafter part of the hot band material was processed as fol Torque values and DC Magnetic properties lows:

For heat 3524 the hot rolled band had a thickness of HEAT $215 Peak BM BM Hr Br 0.160 inch. The hot rolled band was thereafter de- 1 NO. (erg/cm) Ratio (to) (kG) (k0) (kG) scaled, cold rolled to 0.08 inch, annealed for 1 hour at 850C in dry hydrogen followed by cold rolling to 0.02 3 ggjggg 8:23 {3:2 3?; gig 13:: inch in thickness. The 0.02 inch thick material was then 3523 204,100 0.41 19.3 21.3 0.29 17.4 subjected to a strip anneal at 900C in an atmosphere of dry hydrogen. The material was maintained at the 15 temperature of 900C time Period of 3 minu tes- From an examination of the Peak Torque data as well After annealing, the materlal was cold rolled to ath1ckas the Peak Ratio it will appear that these data indicate neSS of 0.006 inCh which was the desired finished a i degree f lOllOOl] type orientation while a gauge. Thereafter the finished gauge material was subperfect Single crystal of 3% Sllieomlron having a jected to a final annealing for a time period of 48 hours l lollooll Orientation will exhibit peak Ratio of at a temperature of 900C While employing a hydrogen about 0.35 and a Peak Torque of about 215,000 ergs atmosphere having a due Point of less than 4000 The per cubic centimeter, these data indicate that a high samples were placed in the furnace cold and program preponderance of the grains exhibit o oo heated at the rate of 50C per hour to 900C and after type Orientation holding at C for 48 hours, y were Program One interesting feature ofthe DC magnetic data indi- Cooled at P hour until a temperature of 300C cate that the saturation value nominally the B value, was attained. From the foregoing, it will be apparent is approximately 21,300 kllogauss Comparing the Bl0 that the Processing of Heat 3524 involved a three data with the saturation data, it is seen that these alloys p cold rolling sequence and closely approaches are so highly textured that they all exhibited in excess C655 2 as Set forth hereinbefreof 85% of the saturation value at a magnetizing force In contrast thereto, one of the billets from Heat No. of lo Oersted, thereby Confirming the highv degree of 3523 was also hot rolled in air to the same hot rolled texture within the alloys band thickness of 0.160 inch. It was thereafter cleared Reference is now directed to Table vl Whleh summa by descaling F by an anneal for 1 hour at a rizes the AC magnetic characteristics of the same heats perature of 850 C 1n dry hydrogen. The first cold rollas Table TABLE VI 60 Hz AC Magnetic Properties 0 HEAT Gage Pr (W/lb) -1 vA/1h) NO. (mils) ISkG l7kG l8kG 19kG 20kG l5kG l7kG l8kG l9kG 20kG ing involved a hot-cold rolling at a temperature of 260C wherein the material was reduced from 0.160 inch in thickness to 0.050 inch. This latter material was subjected to an anneal at a temperature of 850C for a time period of 1 hour while employing a dry hydrogen atmosphere following which the material was hotcold" rolled at 260C to a thickness of 0.016 inch. Once again, the material was annealed for 1 hour at a temperature of 850C and employing dry hydrogen following which the material was cold rolled to finish gauge of 0.006 inch in thickness. The finished gauge material was subjected to a final box anneal for a time period of 48 hours at a temperature of 850C while employing a hydrogen atmosphere having a dew point of less than C. In contrast, to the processing for Heat No. 3524, the samples of Heat No. 3523 were placed into the furnace at temperature and following the annealing they were program cooled at a rate of 50 centigrade degree per hour until a temperature of 300C was achieved.

In order to substantiate the grain texture or orientation developed in these alloys, both and (200) X-ray reflection pole figures and their corresponding histograms were taken on each sample and are graphically depicted in FIGS. 1 through 6 and 1A through 6A, inclusive. An examination of the various pole figures tend to confirm the torque data, the magnetic properties and the domain analysis as is set forth hereinafter.

As graphically illustrated in FIGS. 1 through 6, each contour shows multiples of iron random intensity, the

digit and contour relationship being set forth in each Figure.

In order to further verify the strong texture developed in these alloys, a quantitative domain analysis was performed on each of the samples to determine the volume percent of the (1 10) plane within 12 of the sample surface. Commensurate with this same analysis, the volume percent of the 100) plane which was found to be within 12 of they sample surface was also deter mined together with the percentage of the grains in which the [001] direction was within various angles in degrees of the rolling direction. These results are set forth hereinafter in Table VII.

TABLE VII The histogram data from the pole figures set forth in Table VIII and compared with the data set forth by the domain analysis in Table VII shows reasonably good agreement between the two. Thus, in comparison with the torque data especially the Peak Ratio, the presence of the (100) within 10 of the sheet surface together with the alignment of the cube edges with the [001] or rolling direction would account for the higher values of the peak ratio as well as the peak torque set forth hereinbefore for Table IV.

From the foregoing, it is clear that alloys having the composition set forth within the limits enunciated hereinbefore and processed in accordance with the manner Quantative Domain Analyses HEAT Vol. 71 of 1 10) Vol. of(10()) 71 of Grains with 72 of Grains with Average Deviation of NO. within 12 of within 12 of [001] within 10 [001] within 15 [001] from Sheet Surface Sheet Surface of RD f RD" RD 'RD Rolling Direction From the test results set forth in Table VII, it is seen that each of the samples have in excess of 50% of the volume of the grains having the 1 l0) plane within 12 of the sheet surface. It is interesting to note that there is a component of the (100) plane within 12 of the sheet surface and in each instance this volume turns out to be between 15 and 25%. Since both the (110) and the (100) textures are present and the cube edges are strongly aligned in the [001 direction, these data tend to confirm the magnetic data especially the torque analysis set forth hereinbefore.

These quantitative domain analysis were performed on three Epstein samples which were scanned over a distance of 0.5 centimeters. The alignment of the easy direction of magnetization, that-is, the [001] with the rolling direction ofthe samples was determined by measuring 50 grainseither the (110) or the (100) in the samples using a special optical goniometer attachment to a metallograph. In all cases, the volume percent of the sample with the (1 10) planes within 12 of the sheet surface far exceeds 50%. Moreover, with the minor- (100) planar component being aligned in the same manner as the (110) plane the improved magnetic characteristics are noted. Thus, there is also reasonable agreement between the average angular deviation of the [001] direction from the rolling direction in Table VI and these results tend to confirm the B values listed hereinbefore in Table IV.

In order to complete the analysis from the X-ray pole figures, the histogram results are set forth hereinafter in Table VIII.

TABLE VIII Histogram Results 71 (110) Within 10 '7: (100) Within 10 "'Sce Histograms FIGS. 1 and 2. See Histograms FIGS. 3 and 4. "See Histograms FIGS. and 6. Corrected for (1 multiplicity.

set forth hereinbefore produce outstanding magnetic characteristics which are developed in these alloys through a major portion of the grains having been oriented into the cube-on-edge or 1 10)[001 orientation. This texture is achieved in which the final product is characterized by a primarily recrystallized and normal grain growth structure which contributes significantly to the observed magnetic characteristics as set forth hereinbefore.

In contrast to the production of commercial 3% silicon steel, the alloy of the present invention does not require a separate decarburization anneal prior to the final box anneal. It has been found that employing either Process No. l, or Process No. 2, neither of which employs a wet hydrogen decarburization anneal, the alloy often final box annealing will exhibit a carbon content of nominally less than about 0.003%. Actual carbon analysis from both the ingot condition and after final box anneal are set forth hereinbefore in Table IV. Where desired, however, a decarburizing anneal may be employed in order to obtain extremely low carbon contents without adversely affecting the magnetic characteristic exhibited by the alloy.

Comparable results will be obtained by adding cobalt to the alloys. Thus an alloy with 0.6% chromium, 0.5% cobalt or an alloy comprising 0.4 chromium, 1% silicon and 0.3% cobalt when processed by either the twostage or three-stage process will give a sheet with a high proportion of (l10)[001] grains, and good magnetic properties.

What is claimed is:

1. In the process for producing 1 l0)[001 texture in iron base alloys which are suitable for use as transformer core materials, the steps comprising melting a composition including up to 0.03% carbon, up to 1% manganese, from 0.3% to 4% of at least one of the volume resistivity improving elements selected from the group consisting of up to 2% silicon, up to 2% chromium, up to 3% cobalt the balance essentially iron with incidental impurities, casting the melt, hot working the casting at a temperature within the range between about lOOC and 1 100C, cold working the hot worked material in two or more operations to finish gauge, the last cold working operation effecting a reduction in cross-area of between about 50% and about 75%, with an intermediate anneal interposed between each of said cold working operations, said intermediate anneal being at a temperature within the range between about 750C and the Ac, temperature of the composition, and final annealing the finish gauge material at a temperature within the range between about 800C and the Ac temperature of the composition, the material exhibiting a preponderance of the grains having a (1 l0)[OOl] orientation and primarily recrystallized and normal grain growth microstructure.

2. The process of claim 1 in which part of the cold working in all but the last cold working step takes place at a temperature in the range between room tempera ture and 300C.

3. The process of claim 1 in which the final annealing is a box anneal for a time period of between 24 hours and 48 hours in a hydrogen atmosphere having a dew point of less than about 40C.

4. The process of claim 1 in which the final cold working operation to finish gauge effects a reduction in cross-sectional area within the range between 60% and 70%.

5.111 the process for producing l l0)[OOl] texture in iron base alloys which are suitable for use as transformer core materials, the steps comprising making a melt having a composition including up to 0.03% carbon, up to 1% manganese, 0.3% to 4% of at least one of the volume resistivity improving elements selected from the group consisting of up to 2% silicon, up to 3% cobalt, up to 2% chromium, and the balance iron with incidental impurities, casting the melt, hot working the casting at a temperature within the range between l0OOC and 1 100C, pickling the hot worked material, cold working the pickled hot worked material in two operations to finish gauge with an intermediate anneal interposed therebetween, each of said cold working operations affecting a reduction in cross-sectional area of between about 50% and about 75%, said intermediate anneal being conducted at a temperature within the range between about 800C and the Ac temperature of the material and finally annealing the finish gauge material at a temperature within the range between about 800C and the Ac temperature, said finally annealed material exhibiting a preponderance of the grains having a (l l0)[OOl] texture, a primary recrystallized and normal grain growth microstructure.

6. The process of claim 5 in which a portion of the initial cold working takes place at a temperature within the range between room temperature and 300C.

7. The process of claim 5 in which the final anneal is a box anneal for a time period of between 24 and 48 hours and during said box annealing the material is subjected to an atmosphere of hydrogen having a dew point of less than about 40C.

8. The process of claim 5 in which the material has a finish gauge thickness of between about 10 mil and 14 mil.

9. The process of claim 5 in which the casting is hot rolled to a thickness of 0.10 i 0.025 inch, initially cold rolled to a thickness of 0.025 :t 0.010 inch and finally cold rolled to finish gauge of between 0.012 t 0.002 inch.

10. The process of claim 5 in which the final cold rolling to finish gauge effects a reduction in crosssec tional area of between 60 and 11. In the process for producing (llO)[00l] texture in iron base alloys suitable for use as transformer core materials, the steps comprising, making a melt having a composition including up to 0.03% carbon, up to 1% manganese, from 0.3% to about 4% of at least one of the volume resistivity improving elements selected from the group consisting of up to 2% silicon, up to 2% chromium, up to 3% cobalt, and the balance iron with incidental pickling impurities, casting the melt, hot working the casting at a temperature within the range between about 1000C and ll00C, cold working the hot worked material in three operations to finish gauge with an intermediate anneal interposed between each of the cold working operations, at least the last of said cold working operations effecting a reduction in crosssectional area of between 50 and about the intermediate annealing taking place at a temperature within the range between about 800C and the Ac temperature of the composition and finally annealing the finish gauge materials at a temperature within the range between about 800C and the Ac temperature of the composition, the material exhibiting a preponderance of the grains having a (l10)[001] orientation, a primary recrystallized and normal grain growth microstructure.

12. The process of claim 11 in which the final anneal is a box anneal for a time period of between 24 hours and 48 hours and during said box annealing the material is subjected to a hydrogen atmosphere having a dew point of less than about 40C.

13. The process of claim 11 in which the material has a finish gauge thickness of between about 5 mil and about 7 mil.

14. The process of claim 11 in which the melt is hot rolled to a thickness of 0.180 i 0.030 inch, initially cold rolled to 0.080 i 0.030 inch, cold rolled to 0.020 i 0.010 inch and finally cold rolled to finish gauge of 0.006 1 0.001 inch.

15. The process of claim 11 in which the final cold reduction to finish gauge effects a reduction in cross sectional area of between 60 and 70%.

Patent Citations
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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4251294 *Aug 22, 1978Feb 17, 1981National Steel CorporationMethod for producing fully-processed low-carbon electrical steel
US4251295 *May 11, 1979Feb 17, 1981Westinghouse Electric Corp.Annealing to remove sulfer
US4251296 *May 11, 1979Feb 17, 1981Westinghouse Electric Corp.Method of preparing an oriented-low-alloy iron from an ingot of controlled sulfur, manganese and oxygen contents
US4255215 *May 11, 1979Mar 10, 1981Westinghouse Electric Corp.Oriented low-alloy iron containing critical amounts of silicon and chromium
US4265683 *Feb 7, 1979May 5, 1981Westinghouse Electric Corp.Development of grain-oriented iron sheet for electrical apparatus
US4269634 *Dec 4, 1979May 26, 1981Westinghouse Electric Corp.Loss reduction in oriented iron-base alloys containing sulfur
US4282046 *Jul 16, 1979Aug 4, 1981General Electric CompanyMethod of making permanent magnets and product
US5073211 *Mar 14, 1990Dec 17, 1991Nkk CorporationMethod for manufacturing steel article having high magnetic permeability and low coercive force
US5779819 *Feb 20, 1997Jul 14, 1998Armco Inc.Grain oriented electrical steel having high volume resistivity
US6007642 *Dec 8, 1997Dec 28, 1999National Steel CorporationHot rolling, (no hot band annealing), cold rolling, first batch annealing, second cold rolling, second batch annealing and temper rolling: steel (iron, carbon, silicon, aluminum, manganese and antimony) remains ferritic
US6416592Feb 8, 2001Jul 9, 2002Kawasaki Steel CorporationElectromagnetic steel sheet having excellent magnetic properties and production method thereof
EP0897993A2 *Aug 14, 1998Feb 24, 1999Kawasaki Steel CorporationElectromagnetic steel sheet having excellent magnetic properties and production method thereof
Classifications
U.S. Classification148/120, 148/308, 148/121, 148/311, 148/122
International ClassificationC22C38/08, H01F1/16, C22C38/02, C22C38/18, H01F1/12, C21D8/12
Cooperative ClassificationC21D8/1261, C21D8/1222, C22C38/18, H01F1/16, C21D8/1227, C22C38/02, C21D8/12, C22C38/08
European ClassificationC21D8/12, H01F1/16, C22C38/08, C22C38/02, C22C38/18
Legal Events
DateCodeEventDescription
Jun 7, 1990ASAssignment
Owner name: ABB POWER T&D COMPANY, INC., A DE CORP., PENNSYLV
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:WESTINGHOUSE ELECTRIC CORPORATION, A CORP. OF PA.;REEL/FRAME:005368/0692
Effective date: 19891229