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US3287183A - Process for producing single-oriented silicon steel sheets having a high magnetic induction - Google Patents

Process for producing single-oriented silicon steel sheets having a high magnetic induction Download PDF

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US3287183A
US3287183A US376627A US37662764A US3287183A US 3287183 A US3287183 A US 3287183A US 376627 A US376627 A US 376627A US 37662764 A US37662764 A US 37662764A US 3287183 A US3287183 A US 3287183A
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rolling
cold
annealing
sheet
silicon steel
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Taguchi Satoru
Sakakura Akira
Takashima Hironori
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Yawata Iron and Steel Co Ltd
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Yawata Iron and Steel Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon

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  • PROCESS F OR PRODUCING SINGLE-ORIENTED SILICON ISSIfEL SHEETS HAVING A HIGH MAGNETIC INDUCTION 7 Sheets-Sheet 6 Filed June 22,
  • FIGS (3) Rolling direcfion 5 m w w m Saforu Taguchi Akira Sakakura H i ronori Takashima BYW W M PM 1966 SATORU TAGUCHI ETAL 3,
  • This invention relates to processes for producing silicon steel sheets and more particularly to a process for producing single-oriented silicon steel sheets having a high magnetic induction.
  • Single-oriented silicon steel sheets are to be used mostly as iron cores for transformers and other electric devices.
  • excitation characteristics the relation between the intensity of the magnetic field and the magnetic induction
  • core loss characteristics the relation between the magnetic induction and the core loss value
  • the excitation characteristics are determined depending on the magnitude of the magnetic induction induced in the iron core by the given intensity of the magnetic field.
  • the core loss is an energy loss lost from the iron core in case a prescribed alternating current magnetic induction is given to the iron core. Therefore, the core loss should be as small as possible.
  • the core loss in the case of 50 cycles and an alternating current magnetic induction of 15,000 gausses is represented with W /50.
  • the iron core in order to reduce the weight of the iron core of an electric device, the iron core must be used in a place where the magnetic induction is high.
  • a large exciting electric power will be required therefor, thus the exciting electric power will become larger than the advantage obtained by the reduction of the weight of the iron core and the problem caused thereby will be larger.
  • the core loss value will quickly increase and the increase of the core loss caused by using the iron core in the place where the magnetic induction is high will be larger than the decrease of the core loss by the reduction of the weight of the core. Therefore, today, unless an iron core material excellent in excitation characteristics (high in the value of B can be produced, the weight reduction and therefore the material cost reduction of an electric device will not be able to be expected. Consequently, the supply of single-oriented silicon steel sheets high in B is strongly desired by electric manufacturers.
  • An object of the present invention is to provide a product far superior in magnetic characteristics to any conventional single-oriented silicon steel sheet.
  • Another object of the present invention is to provide a process for producing single-oriented silicon steel sheets of a high magnetic induction showing B of at least 18,000 gausses and 19,100 gausses at the maximum.
  • FIGURE 1 is a diagram showing excitation effective volt-ampere curves of a typical product A of 'the present invention and a typical product B of a conventional single-oriented silicon steel sheet;
  • FIGURE 2 is a diagram showing a relation between the content of acid-soluble Al and S in an ingot and the magnetic induction B in the rolling direction of the product;
  • FIGURE 3 is a diagram showing a relation between the combination of cold-rolling reduction in thickness and the magnetic induction B in the rolling direction of the product;
  • FIGURE 4 shows (110) pole FIGURES 1 and 2 and a pole FIGURE 3 showing the crystal orientation after each annealing step in case a product is obtained in the typical treating step of the present invention
  • FIGURE 5 shows pole FIGURES 1 and 2 and a 100) pole FIGURE 3 showing the crystal orientation after 'each annealing step in case a product is obtained in a conventional typical treating step for producing singleoriented silicon steel sheets;
  • FIGURE 6 is a diagram showing a relation between the temperature of annealing carried out just before the final cold-rolling step and the magnetic induction B in the rolling direction of the product.
  • a silicon steel material of specified contents of such elements as C, S and acid-soluble Al is hot-rolled to be a hot-rolled sheet, which is further subjected to special cold-rolling and annealing different from conventional ones to be a product. That is to say, in the process, the thickness of the final product is obtained by at least more than one annealing step and at least one or more cold-rolling steps. Especially there is a feature that the reduction in thickness in the final coldrolling is so high as to be in the range of 81 to 95% and that the reduction in thickness in other cold-rolling steps than the final cold-rolling step is kept to be in the range of 5 to 40%.
  • the two annealing steps to be carried out after the final cold-rolling that is, the annealing at such low temperature as 750 to 850 C. to give a primary recrystallization texture to a steel sheet and to decarburize it and the annealing at such high temperature as above 1000 C. for a long time to produce expected secondary recrystallization grains of the (110) [001] orientation may be carried out in the same manner as in the generally known art.
  • the annealing condition before the final cold-rolling (the final intermediate annealing condition). That is to say, before this annealing is carried out, the steel sheet must contain 0.020 to 0.080% C.
  • AlN must be 3 formed in the steel sheet, and the content of AlN must be such that N as AlN (N bound in the form of AlN) is more than 0.0020%.
  • the product A obtained by the present invention is superior in the excitation characteristics specifically at a magnetic induction above 15,000 gausses to the conventional singleoriented silicon steel sheet B.
  • the silicon steel material which is a starting material in the present invention means an ingot made by solidifying by any casting method a molten steelmade by such a steel making method which is an already known art' as, for example, by an open-hearth furnace, electric furnace or converter or melted by such a known melting method as, for example, by a high frequency electric furnace or vacuum melting furnace.
  • a slabby ingot obtained by a continuous casting method, which recently came into wide use, can be also used as a material in the present invention.
  • the atmosphere in the case of casting is usually of air but may be vacuum or of an inert gas as well.
  • the material in the present invention may be made by any steel making, melting and casting methods. But the composition of the material must satisfy the following conditions, irrespective of the method for producing the same.
  • the material (which shall be known as the ingot hereinafter) must contain 0.025 to 0.085% C, 2.5 to 4.0% Si, 0.010 to 0.065% acid-soluble Al and 0.005 to 0.050% S, the rest being iron and mixed impurities.
  • the acid-soluble Al so called here designates Al soluble in a dilute sulphuric acid solution of 1 part of sulphuric acid to 9 parts of water and is, to be concrete, a total of Al in a solid-solution in the silicon steel and such nitride of Al as AlN.
  • the acid-insoluble Al means such Al oxide as A1 It is needless to say that the sum total of acid-soluble Al and acid-insoluble Al is total Al.
  • the present invention is characterized by the steps of hot-rolling a silicon steel ingot of specified contents of C, Si, acid-soluble Al and S so as to be a hot-rolled sheet, cold-rolling the above mentioned hot-rolled sheet at a reduction in thickness of 5 to 40%,
  • the three conditions of the composition, the annealing carried out just before the final cold-rolling and the final cold-rolling are closely related with one another.
  • the treating steps having such three conditions there can be obtained a product far superior in magnetic characteristics to any conventional single-oriented silicon steel sheet.
  • a silicon steel ingot which contained about 3% Si and 0.040% C and in which the contents, of acid-soluble Al and S varied as shown in FIGURE 2 was rolled while hot to be a hot-rolled sheet 3 mm. thick.
  • the content of: C in the hot-rolled sheet was 0.040%
  • the sheet was first cold-rolled at a reduction in thickness of 30%, was then annealed at 1100 C. for 5 minutes, was finally cold-rolled at a reduction in thickness of 85.7% to be of a final gauge of 0.3 mm., was then decarburized at 800 C. and was finally box-annealed at 1200" C.
  • the relation between the magnetic induction B of the thus obtained product and the acid-solubleAl and S in the ingot is shown in FIGURE 2.
  • the magnetic induction B of the final product obtained by the producing steps according to the present invention is greatly different depending on the contents of S and acid-soluble Al.
  • the object product of the present "invention in which the magnetic induction B in the rolling direction is higher than 18,000 gausses will be obtained when the acid-soluble Al is 0.010 to 0.065% and S is 0.005 to 0.050%.
  • the addition eflect of S and acid-solubleAl is determined by the following formula of the addition ratio of both components:
  • the composition of the silicon steel ingot to be used in the present invention should be so specified that S be in the range of 0.005 to 0.050%, acid-soluble Al in the range of 0.010 to 0.050% and moreover in the addis(%) acid-soluble Al( +0;
  • a be in the range of 0.025 to 0.015.
  • Si is specified to be in the range of 2.5 to 4%. In case it is less than 2.5%, there will be a disadvantage that the electric resistance will be so low and the eddy current loss will be so high that the core loss value will be high. On the contrary, in case Si is more than 4%, breaks due to brittleness will be caused in cold-rolling. Therefore, in the present invention, the content of silicon in the silicon steel ingot is defined to. be 2.5 to 4%,
  • the magnetic induction B of the final product will not exceed 18,000 gausses in some case.
  • a further condition of composition must be specified. It is the content of aluminium nitride or AlN. This AlN must be precipitated in the steel sheet before the final cold-rolling but need not always be precipitated in the ingot, because, if the ingot contains Al, the Al will react with N in the steel in the heat-treatment and Will be precipitated as AlN in the steel.
  • FIGURE 2 shows also a specification of such content of AlN in the steel sheet be fore the final cold-rolling as is required in the present invention.
  • the numeral attached to each point in the diagram represents the content of AlN in the steel sheet before the final cold-rolling in N as AlN in percent by weight 10
  • N as AlN is less than 0.0020%, even if the main elements Si, acid-soluble Al and S in the above mentioned ingot are in the specified ranges, the magnetic induction B in the rolling direction of the final product will not exceed 18,000 gausses and the object of the present invention will not be able to be attained.
  • the content of AlN in the steel sheet before the final cold-rolling in the present invention must be such that N as AlN is more than 0.0020%.
  • AlN having such a size as being able to produce secondary recrystallization grains of the (110)[001] orientation should be present in the steel sheet before the final cold-rolling, and that such AlN should be precipitated in the annealing step just before the final cold-rolling.
  • the precipitation of such AlN can be attained by adjusting the content of C in the steel sheet before the annealing so as to be at least 0.020 to 0.080% and annealing the steel sheet at 950 to 1200 C. for 30 seconds to 30 minutes.
  • the silicon steel ingot in order to adjust the content of C in the steel sheet before the annealing so as to be in the range of 0.020 to 0.080%, it is necessary that the silicon steel ingot should contain at least 0.025 to 0.085% C, because slight decarburization (of about 0.005%) will occur in the hot-rolling of ingot and subsequent annealing of the ingot.
  • the contents of the four elements in the silicon steel ingot should be so defined as to be 0.025 to 0.085% C, 2.5 to 4.0% Si, 0.010 to 0.065% acid-soluble Al and 0.005 to 0.050% S and that the C content in the steel before the annealing step immediately antecedent to the final cold-rolling should be adjusted to be in the range of 0.020 to 0.080% in order that AlN having such a size as will produce secondary recrystallization grains of the (110) [001] orientation may be precipitated in an amount of at least 0.0020% of N as AlN in said annealing step. Only when such specifications of the composition and the final cold-rolling step at such a high reduction in thickness as is described in the following are closely combined together, it will be possible to produce a single-oriented silicon steel sheet of a high magnetic induction.
  • the concrete steps of one embodiment of the method according to the present invention are carried out in the following sequence.
  • the hot-rolled silicon steel sheet is pickled, it is subjected to a cold-rolling, the coldrolled sheet is annealed and the annealed sheet is again subjected to a cold-rolling by the conventional two annealing steps, that is, the annealing for decarburization and that for producing recrystallization grains to obtain a desired final product.
  • the first cold-rolling will be designated as the first cold-rolling step
  • the sequent annealing as the intermediate annealing step
  • the following cold-rolling as the final cold-rolling step
  • the annealing for producing recrystallization grains as the final annealing.
  • each cold-rolling step may comprise several rolling passes.
  • the cold-rolling step prior to the final cold-rolling step is not limited to only one. It may be repeated even several times, combined with the sequent annealing step according to conditions.
  • even the first cold-rolling step may be omitted. In such a case the cold-rolling will be carried out only in one step (that is, the final cold-rolling step as designated here) after the antecedent annealing step.
  • the features of the present invention reside in the reduction in thickness in the coldrolling steps, particularly in the final cold-rolling step and the annealing conditions in the intermediate annealing step immediately prior to the final cold-rolling step.
  • Silicon steel ingots made by melting in an electric furnace and casting and containing 0.040% C, 3.02% Si, 0.031% acid soluble Al and 0.030% S were bloomed, hot-rolled and finished to be hot-rolled sheets 7.0, 5.0, 3.4, 3.0, 2.6 and 1.8 mm. thick.
  • the content of C in each hot-rolled sheet was about 0.040%.
  • the first cold-rolling step was carried out at a reduction in thickness of 0 to as shown in the lower part in FIGURE 3. (In this case, 0 was not subjected to the first cold-rolling step and was therefore subjected to only one final cold-rolling'step.)
  • the sheet was then annealed at 1100 C.
  • the reduction in thickness in the final cold-rolling step required for the magnetic induction B in the rolling direction of the product to exceed 18,000 gausses should be at least 81%, but not exceed and is most preferably in the range of 83 to 92% and that the reduction in thickness in the first cold-rolling step should be kept less than 40%.
  • the first coldrolling step is carried out at a reduction in thickness not exceeding 5%, the effect On the improvement of the magnetic characteristics of the product will not be more remarkable than in the later described case of making the final product thickness in only one cold-rolling step, that is, in the case of omitting the first cold-rolling step.
  • it will be meaningless to carry out the cold-rolling in two steps which means that the reduction in thickness in the first cold-rolling step should be in the range of 5 to 40%.
  • the cold-rolling may be carried out only in one step or in two steps or even in several steps.
  • the reduction in thickness should be 81 to 95%.
  • the final coldrolling step should be carried out at a reduction in thickness of 81 to 95% and any cold-rolling step prior to the final cold-rolling step at a reduction in thickness of 5 to 40%.
  • the cold-rolling treatments at such specific reduction in thickness have never been seen in any already disclosed process for producing single-oriented silicon steel sheets. Only in the case of using a silicon steel ingot of the above specified composition contents, such cold-rolling treatments will be significant.
  • the silicon steel sheet to be used as an iron core for electric devices is mostly about 0.3 mm. thick.
  • the thickness of the hot-rolled sheet is 2.6 to 3.4 mm.
  • the cold-rolling at a reduction in thickness of to 40% and the annealing are repeated several times, followed by the final intermediate annealing and the final cold-rolling to obtain a product of a high magnetic induction comparable to that of the former.
  • a product high in magnetic induction may be obtained.
  • the thickness of the hot-rolled sheet is more than 7 mm., it is difficult to wind the sheet to be in the form of a coil or to strip and cold-roll it. Further, it is difficult in the hot rolling technique to make a hot-rolled sheet less than 1.5 mm. thick. Therefore, for factory conditions, it is defined that in case two or more cold-rolling steps are included the sheet thickness should be 1.5 to 7 mm.
  • FIGURES 4 and 5 show with (110) and (100) pole figures the crystal orientations obtained after carrying out the respective annealing in the products corresponding to A (of B of 19,100 gausses) and B (of B of 17,600 gausses) in FIGURE 3, respectively.
  • FIGURES 4 1 and 5 1 are (110) pole figures after the respective intermediate annealings (at 1100 C. for 5 minutes in the former and at 1100 C. for 5 minutes in the latter).
  • FIGURES 4 2 and 5 2 are (110) pole figures after the decarburizing annealings (at 850 C. for 5 minutes in both).
  • FIGURES 4 3 and 5 3 are (100) pole figures after the final annealings (at 1200 C. for 20 hours in both).
  • the numerals in FIG. 4 1 and 2, and FIG. 5 1 and 2 designate the strength of crystal orientation as compared with that of random crystal orientation in the X-ray diffraction as the standard value, taking the latter as 1.0 and those in FIG. 4 3 and FIG. 5 3 the grain numbers of the secondary recrystallization grains.
  • the decarburizing annealing is carried out to remove C detrimental to the development of secondary recrystallization grains of the (110) [001] orientation in the final annealing and at the same time to make the cold-rolled structure a primary recrystallization structure.
  • the primary recrystallization orientation (FIGURE 5 2) after the decarburizing annealing in the case of carrying out the conventional cold-rolling treatment is a main orientation rotated by about degrees around the 110 rotation axis parallel with the rolling direction with the (100) [001] orientation as a center.
  • the crystal orientation (FIGURE 4 2) after the decarburizing annealing in the case of carrying out the cold-rolling treatment according to the present invention has a feature that the 110 rotation axis is deviated by about 20 to 25 degrees to right and left from the rolling direction.
  • the parallelisms between the 100 axis of the secondary recrystallization grains of the (100) [001] orientation produced when both of them were finally annealed and the rolling direction are as respectively shown by (100) pole figures in FIGURES 4 3 and 5 3.
  • the former is remarkably superior in the 3 and thereafter subject the thus obtained sheet to known annealings for decarburization and secondary recrystallization.
  • the thickness of the hotrolled sheet must be 1.5 to 5 mm.
  • the annealing step shall now be described. First of all, the conditions of the intermediate annealing step iIII'. mediately prior to the final cold-rolling step, which make one of the most important features in the present invention, shall be described.
  • a silicon steel ingot prepared by melting in an electric furnace and casting and containing 0.038% C, 3.0% Si, 0.030% acid-soluble Al and 0.028% S was bloomed and hot-rolled to be a hotrolled sheet having a thickness of 3.0 mm. The content of C in the hot-rolled sheet was 0.037%
  • the sheet was coldrolled by 30%, was then annealed in H at temperatures of 800, 900, 950, 1000, 1050, 1100, 1150, 1200 and 1300 C.
  • the annealing tempera- I ture to obtain a product of a magnetic induction B of 18,000 gausses in the rolling direction as desired in the present invention must be in the range of 950 to 1200 C. and that the most preferable temperature range is 1050 to 1150 C.
  • the annealing time in this temperature minutes.
  • the atmosphere for the annealing has nothing to do with the precipitation of AlN in the steel sheet before the final cold-rolling step.
  • the ingot as it is will contain more than 0.0040% N which will further increase in the hot-rolling.
  • AlN having the desirable size will be able to be precipitated as more than 0.0020% N as AlN'by subjecting the steel sheet to the intermediate annealing immediately prior to the final cold-rolling step, even if nitrogen is not specifically added in this annealing, provided that the content of C in the steel sheet is being kept in the range of 0.020 to 0.080% as already specified.
  • any of reductive and neutral atmospheres such as, for example, of H Ar and N gases or mixtures of them may be used for the atmospherefor the annealing.
  • N in the ingot will be so little that, unless nitrogen is added in the annealing before the final cold-rolling, it will be impossible to precipitate more than 0.0020% N as AlN.
  • the method of adding nitrogen. is not specified.
  • the steel sheet finally cold-rolled to be of a product sheet thickness is then subjected to the carburizing annealing.
  • This annealing is to make the cold-rolled structure a primary recrystallization structure and at the same time to remove C detrimental to the development of secondary recrystallization grains of the (110)[001] orientation in the final annealing.
  • the decarburizing method may be used any known method. For example, there can be enumerated a method of annealing in wet hydrogen at a temperature of 750 to 850 C. for a short time.
  • the final annealing should be carried out at such temperature and for such time that secondary recrystallization grains of the 110) [001] orientation can Well develop.
  • the steel sheet In order that the secondary recrystallization grains may perfectly develop, the steel sheet must be annealed at a temperature higher than 1000 C. for at least hours. Even if the atmosphere for the final annealing is a neutral or reductive atmosphere or such Weakly oxidative atmosphere as will not remarkably oxidize the steel sheet, the object product of the present invention in which the magnetic induction B in the rolling direction is more than 18,000 gausses Will be obtained. However, in order to reduce the core loss value, it is usually recommended to finally anneal the steel sheet in H2.
  • Example I A silicon steel ingot containing 0.037% C, 3.00% Si, 0.028% acid-soluble Al and 0.031% S was prepared in an electric furnace, was bloomed and was hot-rolled to be a hot-rolled sheet 3 mm. thick. The content of C in the hot-rolled sheet was 0.036%. The sheet was first cold-rolled by 30% and Was then annealed in H at 1100 C. for 5 minutes.
  • the content of AlN in the steel sheet after the annealing was 0.0049% N as AlN.
  • the sheet was then coldrolled by 85.7% to be of a product sheet thickness of 0.3 mm., was decarburized in wet hydrogen at 800 C. for 5 minutes, was pickled and was finally annealed in hydrogen at 1200 C. for 20 hours.
  • W 17/50 core loss value at 17,000 gausses at 50 cycles 1.30 watts/kg.
  • Example 2 A silicon steel ingot containing 0.035% C, 3.00% Si, 0.037% acid-soluble Al and 0.036% S was prepared in an electric furnace, was bloomed and was hot-rolled to be a hot-rolled sheet 5 mm. thick. The sheet was coldrolled by 30%, was annealed at 900 C. for 2 minutes so as to be recrystallized and was then again cold-rolled by 30%. At this time, the content of C in the steel sheet was 0.031%. The sheet was then annealed in H at 1100 C. for 5 minutes. The content of AlN in the steel sheet after the annealing was 0.0046% N as AlN.
  • the sheet was then cold-rolled by 87.8% to be of a product sheet thickness of 0.3 mm., was decarburized in wet hydrogen at 800 C. for 5 minutes and was finally annealed in H at 1200" C. for 20 hours.
  • the magnetic characteristics in the rolling direction of the product were as follows:
  • Example 3 A silicon steel ingot containing 0.040% C, 3.02% Si, 0.030% acid-soluble Al and 0.030% S was prepared in an electric furnace, was bloomed and was hot-rolled to be a hot-rolled sheet 3 mm. thick. The content of C in the hot-rolled sheet was 0.040%. It was annealed in H at 1050 C. for 5 minutes.
  • the content of AlN in the steel sheet after the annealing was 0.0055 N as AlN.
  • the sheet was then cold-rolled at a reduction in thickness of 89% to be of a product sheet thickness of 0.33 mm., was decarburized in wet hydrogen at 800 C. for 5 minutes and was finally annealed in hydrogen at 1200 C. for 20 hours.
  • a process for producing single-oriented silicon steel sheet of (110) [001] orientation in which a silicon steel ingot composed of 0.025 to 0.085 wt. percent C, 2.5 to 4.0 wt. percent Si, 0.010 to 0.050 wt. percent acid-soluble Al and 0.005 to 0.050 wt.

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Description

N Z 19 SATORU TAGUCHI ETAL I 3,
PROCESS FOR PRODUCING SINGLE-ORIENTED SILICON H STEEL SHEETS HAVING A HIGH MAGNETIC INDUCTION rlled June 22, 1964 7 Sheets-Sheetl FIG. I
Magnetic fluxdensity (Kilogauss) I 5 lllllll i fiLllllllI |1| O] 0.2 030.405 2 3 45 I0 20 304050 I00 Exciting effective VA( VOHAmperes/ kg) INVEN TORS.
Saforu Taguchi Akira Sakakura H i fan or/ Takashirpa WWW F MM 3,287,183 ORIENTED SILICON 7 Sheets-Sheet 2 N 1 SATORU TAGUCHI ETAL PROCESS FOR PRQDUCING SINGLE STEEL SHEETS HAVING A HIGH MAGNETIC INDUCTION Flled June 22, 1964 Taguchi Sakakura IN VENTORS.
Saforu A kira Hironor/ Takashima Acid soluble AL N 19 SATORU TAGUCHI ETAL 3,
PROCESS FOR PRODUCING SINGLE'ORIENTED SILICON STEEL SHEETS HAVING A HIGH MAGNETIC INDUCTION Filed June 22, 1964 7 Sheets-Sheet B (guuss) INVENTORS.
Saforu Taguchi Akira Sakakura Hi ronori Takashi/pa gym/44 Nov. 22, 1966 SATORU TAGUCHI ETAL 3,287,183 PROCESS FOR PRODUCING SINGLE-ORIENTED SILICON STEEL SHEETS HAVING A HIGH MAGNETIC INDUCTION Filed June 22, 1964 7 Sheets-Sheet 4 F|G.4 (I) Rolling direction FIG.5 (I) m m E V W Rolling direction Taguch/ Saforu Akira Sakakura Hironori Takashi ma Lav W 1966 SATORU TAGUCHI ETAL 3, 3
PROCESS FOR PRODUCING SINGLE-ORIENTED SILICON STEEL SHEETS HAVING A HIGH MAGNETIC INDUCTION Filed June 22, 1964 7 Sheets-$heet 5 .FIG.4 (2) Rolling direclion FIG.5 (2) Rolling direcrion NVEN TORS.
Saforu Taguchi Akira Sakakura Hironol i Takashima BY Wm M 1966 SATORU TAGUCHI ETYAL 3,287,183
PROCESS F OR PRODUCING SINGLE-ORIENTED SILICON ISSIfEL SHEETS HAVING A HIGH MAGNETIC INDUCTION 7 Sheets-Sheet 6 Filed June 22,
Rolling direcfion FIGS (3) Rolling direcfion 5 m w w m Saforu Taguchi Akira Sakakura H i ronori Takashima BYW W M PM 1966 SATORU TAGUCHI ETAL 3,
PROCESS FOR PRODUCING SINGLE-ORIENTED SILICON STEEL SHEETS HAVING A HIGH MAGNETIC INDUCTION Filed June 22, 1964 7 Sheets-Sheet 7 (gcuss) [9000 IBOOO f ITOOO Annealing temperature (C) before final cold-rolling IN VE N TORS.
Saforu Taguchi Akfra Sakakura Hironori Takashima BYWMJL, M
United States Patent PROCESS FOR PRODUCING SINGLE-ORIENTED SILICON STEEL SHEETS HAVING A HIGH MAG- ,NETIC INDUCTION Satoru Taguchi, Akira Sakakura, and Hironori Takashima, Kitakyushu, Fukuoka, Japan, assignors to Yawata Iron & Steel Co., Ltd., Tokyo, Japan, a corporation of Ja an P Filed June 22, 1964, Ser. No. 376,627
4 Claims. (Cl. 148-111) This invention relates to processes for producing silicon steel sheets and more particularly to a process for producing single-oriented silicon steel sheets having a high magnetic induction.
Single-oriented silicon steel sheets are to be used mostly as iron cores for transformers and other electric devices. For their magnetic characteristics, excitation characteristics (the relation between the intensity of the magnetic field and the magnetic induction) and core loss characteristics (the relation between the magnetic induction and the core loss value) must be favorable. The excitation characteristics are determined depending on the magnitude of the magnetic induction induced in the iron core by the given intensity of the magnetic field. For example, the magnetic induction generated in the iron core by the intensity H= (0e) of the magnetic field is represented as B With the iron core high in B a small ampere turn will do to generate the same magnetic induction and therefore the electric device can be made small.
The core loss is an energy loss lost from the iron core in case a prescribed alternating current magnetic induction is given to the iron core. Therefore, the core loss should be as small as possible. In the case of singleoriented silicon steel sheets, the core loss in the case of 50 cycles and an alternating current magnetic induction of 15,000 gausses is represented with W /50.
More than about 70% of the cost of production of a transformer is said to be the material cost. It is therefore advisable to reduce the material cost by making the transformer as small as possible. I
Generally, in order to reduce the weight of the iron core of an electric device, the iron core must be used in a place where the magnetic induction is high. However, a large exciting electric power will be required therefor, thus the exciting electric power will become larger than the advantage obtained by the reduction of the weight of the iron core and the problem caused thereby will be larger.
Further, if the iron core is used in a place where the magnetic induction is high, the core loss value will quickly increase and the increase of the core loss caused by using the iron core in the place where the magnetic induction is high will be larger than the decrease of the core loss by the reduction of the weight of the core. Therefore, today, unless an iron core material excellent in excitation characteristics (high in the value of B can be produced, the weight reduction and therefore the material cost reduction of an electric device will not be able to be expected. Consequently, the supply of single-oriented silicon steel sheets high in B is strongly desired by electric manufacturers.
Now, in order to improve the magnetic property of a single-oriented silicon steel sheet, it is necessary first to highly arrange in the rolling direction the l00 axis of the crystal grains forming the steel sheet and second to reduce the impurities in the final product to be as little as possible.
Since a process for producing single-oriented silicon steel sheets by two-step rolling was invented by N. P. Goss, numerous improvements and suggestions have been made and the magnetic induction and core loss value have ice been improved year after year. In recent years, due to the development of steel making, surface treating and annealing techniques, the core loss value has become considerably lower. However, the improvement of the magnetic induction B may be said to be in a saturated state. Even the so far reported highest value is, as shown in US. Patent No. 2,867,557, B =18,690 gausses at the maximum, ranging from 17,610 to 18,690 gausses and averaging 18,090 gausses.
An object of the present invention is to provide a product far superior in magnetic characteristics to any conventional single-oriented silicon steel sheet.
Another object of the present invention is to provide a process for producing single-oriented silicon steel sheets of a high magnetic induction showing B of at least 18,000 gausses and 19,100 gausses at the maximum.
Other objects of the present invention and the substance of the invention will be able to be more completely understood with reference to the following specification and claims together with the accompanying drawings in which:
FIGURE 1 is a diagram showing excitation effective volt-ampere curves of a typical product A of 'the present invention and a typical product B of a conventional single-oriented silicon steel sheet;
FIGURE 2 is a diagram showing a relation between the content of acid-soluble Al and S in an ingot and the magnetic induction B in the rolling direction of the product;
FIGURE 3 is a diagram showing a relation between the combination of cold-rolling reduction in thickness and the magnetic induction B in the rolling direction of the product;
FIGURE 4 shows (110) pole FIGURES 1 and 2 and a pole FIGURE 3 showing the crystal orientation after each annealing step in case a product is obtained in the typical treating step of the present invention;
FIGURE 5 shows pole FIGURES 1 and 2 and a 100) pole FIGURE 3 showing the crystal orientation after 'each annealing step in case a product is obtained in a conventional typical treating step for producing singleoriented silicon steel sheets;
FIGURE 6 is a diagram showing a relation between the temperature of annealing carried out just before the final cold-rolling step and the magnetic induction B in the rolling direction of the product.
According to the present invention, a silicon steel material of specified contents of such elements as C, S and acid-soluble Al is hot-rolled to be a hot-rolled sheet, which is further subjected to special cold-rolling and annealing different from conventional ones to be a product. That is to say, in the process, the thickness of the final product is obtained by at least more than one annealing step and at least one or more cold-rolling steps. Especially there is a feature that the reduction in thickness in the final coldrolling is so high as to be in the range of 81 to 95% and that the reduction in thickness in other cold-rolling steps than the final cold-rolling step is kept to be in the range of 5 to 40%. The two annealing steps to be carried out after the final cold-rolling, that is, the annealing at such low temperature as 750 to 850 C. to give a primary recrystallization texture to a steel sheet and to decarburize it and the annealing at such high temperature as above 1000 C. for a long time to produce expected secondary recrystallization grains of the (110) [001] orientation may be carried out in the same manner as in the generally known art. To be specified in the annealing step in the present invention is the annealing condition before the final cold-rolling (the final intermediate annealing condition). That is to say, before this annealing is carried out, the steel sheet must contain 0.020 to 0.080% C. and the annealing should be carried out at such high temperature as 950 to 1200 C. After this annealing, AlN must be 3 formed in the steel sheet, and the content of AlN must be such that N as AlN (N bound in the form of AlN) is more than 0.0020%.
By treating the hot-rolled sheet of such composition as has been described above by cold-rolling and annealing conditions quite different from conventional ones, there can be produced a single-oriented silicon steel sheet in which the parallelism between the rolling direction and the [001] direction of the crystallization grains is very favorable and in which therefore the magnetic induction is very high. As shown in FIGURE 1, the product A obtained by the present invention is superior in the excitation characteristics specifically at a magnetic induction above 15,000 gausses to the conventional singleoriented silicon steel sheet B.
The present invention shall now be explained in detail in the following.
The silicon steel material which is a starting material in the present invention means an ingot made by solidifying by any casting method a molten steelmade by such a steel making method which is an already known art' as, for example, by an open-hearth furnace, electric furnace or converter or melted by such a known melting method as, for example, by a high frequency electric furnace or vacuum melting furnace. A slabby ingot obtained by a continuous casting method, which recently came into wide use, can be also used as a material in the present invention. The atmosphere in the case of casting is usually of air but may be vacuum or of an inert gas as well.
As described above, the material in the present invention may be made by any steel making, melting and casting methods. But the composition of the material must satisfy the following conditions, irrespective of the method for producing the same. The material (which shall be known as the ingot hereinafter) must contain 0.025 to 0.085% C, 2.5 to 4.0% Si, 0.010 to 0.065% acid-soluble Al and 0.005 to 0.050% S, the rest being iron and mixed impurities. The acid-soluble Al so called here designates Al soluble in a dilute sulphuric acid solution of 1 part of sulphuric acid to 9 parts of water and is, to be concrete, a total of Al in a solid-solution in the silicon steel and such nitride of Al as AlN. The acid-insoluble Al means such Al oxide as A1 It is needless to say that the sum total of acid-soluble Al and acid-insoluble Al is total Al.
As described above, the present invention is characterized by the steps of hot-rolling a silicon steel ingot of specified contents of C, Si, acid-soluble Al and S so as to be a hot-rolled sheet, cold-rolling the above mentioned hot-rolled sheet at a reduction in thickness of 5 to 40%,
thereafter annealing the cold-rolled sheet at such high temperature as 950 to 1200 C. so that AlN having such a size as will markedly facilitate the production of secondary recrystallization grains of the (110) [001] orientation may be precipitated, cold-rolling the annealed .sheet at a reduction in thickness of 81 to 95% and subjecting the thus obtained sheet -to known annealings for decarburization and secondary recrystallization.
That is to say, if the contents of C, Si, acid-soluble Al and S in the silicon steel ingot are specified as in the present invention and the annealing before the final cold-rolling is carried out at such high temperature as 950 to 1200- C. for 30 seconds to 30 minutes, AlN having such a size as can produce secondary recrystallization grains of' the (110) [001] orientation in which the parallelism between the l00 axis and the rolling direction is very excellent will be able to be precipitated as more than 0.0020% N as AlN. Only in case such a steel sheet is finally coldrolled at such a high reduction in thickness as is specified in the present invention, the object of the present invention will be able to be attained. In case any one of the elements of the composition deviates from the specified range or in case the temperature and time of the final annealing do not conform to the specified conditions, it will be impossible to precipitate the specified amount of V 4 AlN having such a size as will produce secondary recrystallization grains of the (110) [001] orientation in the steel sheet before the final cold-rolling, whereby the object product will not be obtained.
As in the above, in the present invention, the three conditions of the composition, the annealing carried out just before the final cold-rolling and the final cold-rolling are closely related with one another. By the treating steps having such three conditions, there can be obtained a product far superior in magnetic characteristics to any conventional single-oriented silicon steel sheet.
The reasons for specifying the composition of the ingot in the present invention shall be explained in the followmg.
A silicon steel ingot which contained about 3% Si and 0.040% C and in which the contents, of acid-soluble Al and S varied as shown in FIGURE 2 was rolled while hot to be a hot-rolled sheet 3 mm. thick. The content of: C in the hot-rolled sheet was 0.040% The sheet was first cold-rolled at a reduction in thickness of 30%, was then annealed at 1100 C. for 5 minutes, was finally cold-rolled at a reduction in thickness of 85.7% to be of a final gauge of 0.3 mm., was then decarburized at 800 C. and was finally box-annealed at 1200" C. The relation between the magnetic induction B of the thus obtained product and the acid-solubleAl and S in the ingot is shown in FIGURE 2. That is to say, the magnetic induction B of the final product obtained by the producing steps according to the present invention is greatly different depending on the contents of S and acid-soluble Al. As evident from this diagram, the object product of the present "invention in which the magnetic induction B in the rolling direction is higher than 18,000 gausses will be obtained when the acid-soluble Al is 0.010 to 0.065% and S is 0.005 to 0.050%. I As shown by the curve of the magnetic induction B in FIG. 2 the addition eflect of S and acid-solubleAl is determined by the following formula of the addition ratio of both components:
In this formula as is to be made the value ranging from 0.025 (straight line A in FIG. 2) to 0.015 (straight line B in FIG. 2). It is most preferableto contain S and acid-soluble A1 in such a ratio that a may be about 0.010
(straight line C in FIG. 2) in the above formula, when t and acid-soluble Al is less than 0.010% or more than 0.050%, the production of secondary recrystallization grains of the [001] orientation in the final annealing will become remarkably low and the magnetic induction B in the rolling direction of .the final product will not exceed 18,000 gauses, even if-the addition ratio of S and acid-soluble Al would be limited in the range as mentioned in the above formula. For the above described reasons, the composition of the silicon steel ingot to be used in the present invention should be so specified that S be in the range of 0.005 to 0.050%, acid-soluble Al in the range of 0.010 to 0.050% and moreover in the addis(%) acid-soluble Al( +0;
a be in the range of 0.025 to 0.015.
Si is specified to be in the range of 2.5 to 4%. In case it is less than 2.5%, there will be a disadvantage that the electric resistance will be so low and the eddy current loss will be so high that the core loss value will be high. On the contrary, in case Si is more than 4%, breaks due to brittleness will be caused in cold-rolling. Therefore, in the present invention, the content of silicon in the silicon steel ingot is defined to. be 2.5 to 4%,
It was shown that in this case the magnetic,
However, as seen in FIGURE 2, even if a silicon steel ingot in which Si, acid-soluble Al and S are in the above mentioned specified ranges is treated, the magnetic induction B of the final product will not exceed 18,000 gausses in some case. Taking such a case into consideration, a further condition of composition must be specified. It is the content of aluminium nitride or AlN. This AlN must be precipitated in the steel sheet before the final cold-rolling but need not always be precipitated in the ingot, because, if the ingot contains Al, the Al will react with N in the steel in the heat-treatment and Will be precipitated as AlN in the steel. FIGURE 2 shows also a specification of such content of AlN in the steel sheet be fore the final cold-rolling as is required in the present invention. The numeral attached to each point in the diagram represents the content of AlN in the steel sheet before the final cold-rolling in N as AlN in percent by weight 10 As seen from this, in case N as AlN is less than 0.0020%, even if the main elements Si, acid-soluble Al and S in the above mentioned ingot are in the specified ranges, the magnetic induction B in the rolling direction of the final product will not exceed 18,000 gausses and the object of the present invention will not be able to be attained.
For the above reasons, the content of AlN in the steel sheet before the final cold-rolling in the present invention must be such that N as AlN is more than 0.0020%.
Now, it has been found to be requisite that AlN having such a size as being able to produce secondary recrystallization grains of the (110)[001] orientation should be present in the steel sheet before the final cold-rolling, and that such AlN should be precipitated in the annealing step just before the final cold-rolling. The precipitation of such AlN can be attained by adjusting the content of C in the steel sheet before the annealing so as to be at least 0.020 to 0.080% and annealing the steel sheet at 950 to 1200 C. for 30 seconds to 30 minutes. It has been confirmed that, in case the content of C in the steel sheet before the annealing is less than 0.020% or exceeds 0.080%, even if the content of AlN is such that N as AlN is more than 0.0020%, the precipitate size will not be proper and, as a result, secondary recrystallization grains of the (110) [001] orientation will not be produced in the final annealing. Therefore, in the present invention, in order to adjust the content of C in the steel sheet before the annealing so as to be in the range of 0.020 to 0.080%, it is necessary that the silicon steel ingot should contain at least 0.025 to 0.085% C, because slight decarburization (of about 0.005%) will occur in the hot-rolling of ingot and subsequent annealing of the ingot.
As described above, it has been confirmed that in the present invention, the contents of the four elements in the silicon steel ingot should be so defined as to be 0.025 to 0.085% C, 2.5 to 4.0% Si, 0.010 to 0.065% acid-soluble Al and 0.005 to 0.050% S and that the C content in the steel before the annealing step immediately antecedent to the final cold-rolling should be adjusted to be in the range of 0.020 to 0.080% in order that AlN having such a size as will produce secondary recrystallization grains of the (110) [001] orientation may be precipitated in an amount of at least 0.0020% of N as AlN in said annealing step. Only when such specifications of the composition and the final cold-rolling step at such a high reduction in thickness as is described in the following are closely combined together, it will be possible to produce a single-oriented silicon steel sheet of a high magnetic induction.
The concrete steps of one embodiment of the method according to the present invention are carried out in the following sequence. After the hot-rolled silicon steel sheet is pickled, it is subjected to a cold-rolling, the coldrolled sheet is annealed and the annealed sheet is again subjected to a cold-rolling by the conventional two annealing steps, that is, the annealing for decarburization and that for producing recrystallization grains to obtain a desired final product. Hereinafter the first cold-rolling will be designated as the first cold-rolling step, the sequent annealing as the intermediate annealing step, the following cold-rolling as the final cold-rolling step and the annealing for producing recrystallization grains as the final annealing. Of course, each cold-rolling step may comprise several rolling passes. However, in the present invention the cold-rolling step prior to the final cold-rolling step is not limited to only one. It may be repeated even several times, combined with the sequent annealing step according to conditions. Further, in another embodiment even the first cold-rolling step may be omitted. In such a case the cold-rolling will be carried out only in one step (that is, the final cold-rolling step as designated here) after the antecedent annealing step. The features of the present invention reside in the reduction in thickness in the coldrolling steps, particularly in the final cold-rolling step and the annealing conditions in the intermediate annealing step immediately prior to the final cold-rolling step.
First of all, the cold-rolling condition will be explained.
Silicon steel ingots made by melting in an electric furnace and casting and containing 0.040% C, 3.02% Si, 0.031% acid soluble Al and 0.030% S were bloomed, hot-rolled and finished to be hot-rolled sheets 7.0, 5.0, 3.4, 3.0, 2.6 and 1.8 mm. thick. The content of C in each hot-rolled sheet was about 0.040%. By using each sheet as a starting material, the first cold-rolling step was carried out at a reduction in thickness of 0 to as shown in the lower part in FIGURE 3. (In this case, 0 was not subjected to the first cold-rolling step and was therefore subjected to only one final cold-rolling'step.) The sheet was then annealed at 1100 C. for 5 minutes, was then subjected to the second cold-rolling step (final cold-rolling step) at the reduction in thickness also shown in the lower part of the diagram so as to be of a final thickness of 0.3 mm., was decarburized in wet hydrogen at 800 C. for 5 minutes and was finally box-annealed at 1200 C. for 20 hours. The relation between the magnetic induction B of the thus obtained product and the reduction in thickness is shown in FIGURE 3. The facts evident from this diagram are the following two points. It has been found that the reduction in thickness in the final cold-rolling step required for the magnetic induction B in the rolling direction of the product to exceed 18,000 gausses should be at least 81%, but not exceed and is most preferably in the range of 83 to 92% and that the reduction in thickness in the first cold-rolling step should be kept less than 40%. However, in case the first coldrolling step is carried out at a reduction in thickness not exceeding 5%, the effect On the improvement of the magnetic characteristics of the product will not be more remarkable than in the later described case of making the final product thickness in only one cold-rolling step, that is, in the case of omitting the first cold-rolling step. Thus, in such a case it will be meaningless to carry out the cold-rolling in two steps, which means that the reduction in thickness in the first cold-rolling step should be in the range of 5 to 40%.
To sum up, the cold-rolling may be carried out only in one step or in two steps or even in several steps. In case the cold-rolling is carried out only in one step, the reduction in thickness should be 81 to 95%. But, in case it is carried out in two or more steps, the following conditions must be absolutely fulfilled: that is, the final coldrolling step should be carried out at a reduction in thickness of 81 to 95% and any cold-rolling step prior to the final cold-rolling step at a reduction in thickness of 5 to 40%. The cold-rolling treatments at such specific reduction in thickness have never been seen in any already disclosed process for producing single-oriented silicon steel sheets. Only in the case of using a silicon steel ingot of the above specified composition contents, such cold-rolling treatments will be significant.
The silicon steel sheet to be used as an iron core for electric devices is mostly about 0.3 mm. thick. When such a final sheet thickness is to be obtained with two cold-rolling steps and one annealing step, it will be most preferable that the thickness of the hot-rolled sheet is 2.6 to 3.4 mm. However, in case the thickness of the hot-rolled sheet is 7 mm. a product high in magnetic induction will be hardly obtained with two cold-rolling steps only. In such a case, the cold-rolling at a reduction in thickness of to 40% and the annealing are repeated several times, followed by the final intermediate annealing and the final cold-rolling to obtain a product of a high magnetic induction comparable to that of the former.
In the present invention, irrespective of the sheet thickness of the final product, a product high in magnetic induction may be obtained. However, usually, if the thickness of the hot-rolled sheet is more than 7 mm., it is difficult to wind the sheet to be in the form of a coil or to strip and cold-roll it. Further, it is difficult in the hot rolling technique to make a hot-rolled sheet less than 1.5 mm. thick. Therefore, for factory conditions, it is defined that in case two or more cold-rolling steps are included the sheet thickness should be 1.5 to 7 mm.
Though the theoretical ground of the cold-rolling treatment in the present invention is not apparent, a clear difference from any conventional cold-rolling treatment can be perceived from the observation of the crystal orientation. FIGURES 4 and 5 show with (110) and (100) pole figures the crystal orientations obtained after carrying out the respective annealing in the products corresponding to A (of B of 19,100 gausses) and B (of B of 17,600 gausses) in FIGURE 3, respectively.
From the above figures it is evident that the crystal orientation shown after carrying out the decarburization annealing is quite different between the case of carrying out the cold-rolling treatments (at reduction in thickness of in the first cold-rolling step and 87.5% in the final cold-rolling step) according to the present invention and the case of carrying out the conventional cold-rolling treatments (at reduction in thickness of 70% in the first cold-rolling step and 66.7% in the final cold-rolling step).
FIGURES 4 1 and 5 1 are (110) pole figures after the respective intermediate annealings (at 1100 C. for 5 minutes in the former and at 1100 C. for 5 minutes in the latter). FIGURES 4 2 and 5 2 are (110) pole figures after the decarburizing annealings (at 850 C. for 5 minutes in both). FIGURES 4 3 and 5 3 are (100) pole figures after the final annealings (at 1200 C. for 20 hours in both). The numerals in FIG. 4 1 and 2, and FIG. 5 1 and 2 designate the strength of crystal orientation as compared with that of random crystal orientation in the X-ray diffraction as the standard value, taking the latter as 1.0 and those in FIG. 4 3 and FIG. 5 3 the grain numbers of the secondary recrystallization grains.
As described later, the decarburizing annealing is carried out to remove C detrimental to the development of secondary recrystallization grains of the (110) [001] orientation in the final annealing and at the same time to make the cold-rolled structure a primary recrystallization structure. The primary recrystallization orientation (FIGURE 5 2) after the decarburizing annealing in the case of carrying out the conventional cold-rolling treatment is a main orientation rotated by about degrees around the 110 rotation axis parallel with the rolling direction with the (100) [001] orientation as a center. On theother hand, the crystal orientation (FIGURE 4 2) after the decarburizing annealing in the case of carrying out the cold-rolling treatment according to the present invention has a feature that the 110 rotation axis is deviated by about 20 to 25 degrees to right and left from the rolling direction. The parallelisms between the 100 axis of the secondary recrystallization grains of the (100) [001] orientation produced when both of them were finally annealed and the rolling direction are as respectively shown by (100) pole figures in FIGURES 4 3 and 5 3. The former is remarkably superior in the 3 and thereafter subject the thus obtained sheet to known annealings for decarburization and secondary recrystallization. However, in this case the thickness of the hotrolled sheet must be 1.5 to 5 mm.
The annealing step shall now be described. First of all, the conditions of the intermediate annealing step iIII'. mediately prior to the final cold-rolling step, which make one of the most important features in the present invention, shall be described. A silicon steel ingot prepared by melting in an electric furnace and casting and containing 0.038% C, 3.0% Si, 0.030% acid-soluble Al and 0.028% S was bloomed and hot-rolled to be a hotrolled sheet having a thickness of 3.0 mm. The content of C in the hot-rolled sheet was 0.037% The sheet was coldrolled by 30%, was then annealed in H at temperatures of 800, 900, 950, 1000, 1050, 1100, 1150, 1200 and 1300 C. for 5 minutes each, Was then finally cold-rolled at a reduction in thickness of 85.7% to be of a product thickness, was annealed to be decarburized at 800 C. for 5 minutes and was then finally annealed in H at 1200 C. for 20 hours. The relation between the magnetic induction B in the rolling direction of the product and the annealing condition before the final cold-rolling is shown in FIGURE 6.
It is understood from this that the annealing tempera- I ture to obtain a product of a magnetic induction B of 18,000 gausses in the rolling direction as desired in the present invention must be in the range of 950 to 1200 C. and that the most preferable temperature range is 1050 to 1150 C. The annealing time in this temperature minutes.
the time exceeds 30 minutes, the crystal grains will grow,
after the recrystallization has been completed, resulting in an incomplete development of the secondary recrystallization grains of the [001] orientation in the final annealing in both cases. As already described, the atmosphere for the annealing has nothing to do with the precipitation of AlN in the steel sheet before the final cold-rolling step. Usually, in case the silicon steel ingot is made in an open-hearth furnace or the like, the ingot as it is will contain more than 0.0040% N which will further increase in the hot-rolling. Therefore, AlN having the desirable size will be able to be precipitated as more than 0.0020% N as AlN'by subjecting the steel sheet to the intermediate annealing immediately prior to the final cold-rolling step, even if nitrogen is not specifically added in this annealing, provided that the content of C in the steel sheet is being kept in the range of 0.020 to 0.080% as already specified. Hence, any of reductive and neutral atmospheres such as, for example, of H Ar and N gases or mixtures of them may be used for the atmospherefor the annealing. 'However, in case the silicon steel ingot is made by melting in a vacuum melting furnace or the like or by casting by a vacuum casting method or the like, N in the ingot will be so little that, unless nitrogen is added in the annealing before the final cold-rolling, it will be impossible to precipitate more than 0.0020% N as AlN. The method of adding nitrogen. is not specified. But, in the present invention, it is recommended to carry out the annealing in a neutral or reductive gas containing at least 10% by volume N The reason Why the annealing immediately prior to the final cold-rolling step in the present invention is carried out at a temperature higher than in the annealing in any conventional process for producing singleoriented silicon steel sheets is presumed to be that, on account of C contained in the steel sheet before being subjected to the annealing the my transformation will oc-cur in this range of annealing temperature and the precipitation of AlN having such a size as will facilitate the production of secondary recrystallization grains of the (110) [001] orientation will be accelerated thereby. It is considered that such AlN together with the subsequent final cold-rolling treatment at a high reduction in thickness and annealing treatment will make it possible to produce nuclear crystal grains of the (110)[ 001] orientation very excellent in; the parallelism between the 100 axis and the rolling direction. In case the intermediate annealing is to be repeated between several coldrolling steps before the final intermediate annealing, it may be carried out at such temperature and for such time as are sufficient to make the cold-rolled structure (obtained by cold-rolling) a primary recrystallization structure.
The steel sheet finally cold-rolled to be of a product sheet thickness is then subjected to the carburizing annealing. This annealing is to make the cold-rolled structure a primary recrystallization structure and at the same time to remove C detrimental to the development of secondary recrystallization grains of the (110)[001] orientation in the final annealing. For the decarburizing method may be used any known method. For example, there can be enumerated a method of annealing in wet hydrogen at a temperature of 750 to 850 C. for a short time.
The final annealing should be carried out at such temperature and for such time that secondary recrystallization grains of the 110) [001] orientation can Well develop. In order that the secondary recrystallization grains may perfectly develop, the steel sheet must be annealed at a temperature higher than 1000 C. for at least hours. Even if the atmosphere for the final annealing is a neutral or reductive atmosphere or such Weakly oxidative atmosphere as will not remarkably oxidize the steel sheet, the object product of the present invention in which the magnetic induction B in the rolling direction is more than 18,000 gausses Will be obtained. However, in order to reduce the core loss value, it is usually recommended to finally anneal the steel sheet in H2.
Example I A silicon steel ingot containing 0.037% C, 3.00% Si, 0.028% acid-soluble Al and 0.031% S was prepared in an electric furnace, was bloomed and was hot-rolled to be a hot-rolled sheet 3 mm. thick. The content of C in the hot-rolled sheet was 0.036%. The sheet was first cold-rolled by 30% and Was then annealed in H at 1100 C. for 5 minutes.
The content of AlN in the steel sheet after the annealing was 0.0049% N as AlN. The sheet was then coldrolled by 85.7% to be of a product sheet thickness of 0.3 mm., was decarburized in wet hydrogen at 800 C. for 5 minutes, was pickled and was finally annealed in hydrogen at 1200 C. for 20 hours.
The magnetic characteristics in the rolling direction of the product were as follows:
B =19,070 gausses W /50 (core loss value at 15,000 gausses at 50 cycles) =0.99 watts/kg.
W 17/50 (core loss value at 17,000 gausses at 50 cycles) 1.30 watts/kg.
Thus a very excellent single-oriented silicon steel sheet Was obtained.
Example 2 A silicon steel ingot containing 0.035% C, 3.00% Si, 0.037% acid-soluble Al and 0.036% S was prepared in an electric furnace, was bloomed and was hot-rolled to be a hot-rolled sheet 5 mm. thick. The sheet was coldrolled by 30%, was annealed at 900 C. for 2 minutes so as to be recrystallized and was then again cold-rolled by 30%. At this time, the content of C in the steel sheet was 0.031%. The sheet was then annealed in H at 1100 C. for 5 minutes. The content of AlN in the steel sheet after the annealing was 0.0046% N as AlN.
The sheet was then cold-rolled by 87.8% to be of a product sheet thickness of 0.3 mm., was decarburized in wet hydrogen at 800 C. for 5 minutes and was finally annealed in H at 1200" C. for 20 hours. The magnetic characteristics in the rolling direction of the product were as follows:
B 19,000 gausses W 15/5-0=1.01 watts/kg. W 17/50=1.31 watts/kg.
Example 3 A silicon steel ingot containing 0.040% C, 3.02% Si, 0.030% acid-soluble Al and 0.030% S was prepared in an electric furnace, was bloomed and was hot-rolled to be a hot-rolled sheet 3 mm. thick. The content of C in the hot-rolled sheet was 0.040%. It was annealed in H at 1050 C. for 5 minutes.
The content of AlN in the steel sheet after the annealing was 0.0055 N as AlN. The sheet was then cold-rolled at a reduction in thickness of 89% to be of a product sheet thickness of 0.33 mm., was decarburized in wet hydrogen at 800 C. for 5 minutes and was finally annealed in hydrogen at 1200 C. for 20 hours.
The magnetic characteristics in the rolling direction of the product were as follows:
B =l8,800 gausses W 15/50 (core loss value at 15,000 gausses at 50 cycles)=1.05 watts/kg.
W 17/50 (core loss value at 17,000 gausses at 50 cycles)=l.35 Watts/kg.
What is claimed is: 1. A process for producing single-oriented silicon steel sheet of (110) [001] orientation, in which a silicon steel ingot composed of 0.025 to 0.085 wt. percent C, 2.5 to 4.0 wt. percent Si, 0.010 to 0.050 wt. percent acid-soluble Al and 0.005 to 0.050 wt. percent S and the rest being iron is hot-rolled to produce a hot-rolled steel sheet, said hotrolled steel sheet is subjected to an annealing and coldrolling to obtain a steel sheet of final thickness, said steel sheet of final thickness is thereafter subjected to an annealing for decarburization and further for secondary recrystallization, comprising the steps of hot-rolling a material, in which the ratio of S and acid-solution Al is made to be S( acid-soluble A1(%)+0.025 to 0.015
to make the thickness of said material to 1.5 mm. to 7 mm., cold-rolling the thus hot-rolled steel sheet at a reduction in thickness of 5 to 40%, annealing the coldrolled sheet at a temperature ranging from 950 to 1200 C. for 30 seconds to 30 minutes and then finally cold-rolling the thus annealed steel sheet at a reduction in thickness of 81 to 2. A process for producing single-oriented silicon steel sheet claimed in claim 1, in which a material, in which the ratio of S and acid-soluble Al is made to be acid-soluble Al( +0.010 is subjected to a hot-rolling.
3. A process for producing single-oriented silicon steel sheet claimed in claim 1, in Which a cold-rolled steel sheet containing 0.020 to 0.080 wt. percent C is annealed at a temperature ranging from 950 to 1200 C. for 30 seconds to 30 minutes and thereafter the thus annealed steel sheet is finally cold-rolled.
4. A process for producing single-oriented silicon steel sheet claimed in claim 1, in which a material is hot-rolled to make the thickness of said material to 1.5 to 7 mm., the thus obtained steel sheet is then annealed at a temperature ranging from 950 to 1200" C. for 30 seconds to 30 minutes and the thus annealed steel sheet is cold-rolled at a reduction in thickness of 83 to 96%.
No references cited.
DAVID L. RECK, Primary Examiner.
N. F. MARKVA, Assistant Examiner.

Claims (1)

1. A PROCESS FOR PRODUCING SINGLE-ORIENTED SILICON STEEL SHEET OF (110) 001! ORIENTATION, IN WHICH A SILICON STEEL INGOT COMPOSED OF 0.025 TO 0.085 WT. PERCENT C, 2.5 TO 4.0 WT. PERCENT SI, 0.010 TO 0.050 WT. PERCENT ACID-SOLUBLE AL AND 0.005 TO 0.050 WT. PERCENT S AND THE REST BEING IRON IS HOT-ROLLED TO PRODUCE A HOT-ROLLED STEEL SHEET, SAID HOTROLLED STEEL SHEET IS SUBJECTED TO AN ANNEALING AND COLDROLLING TO OBTAIN A STEEL SHEET OF FINAL THICKNESS, SAID STEEL SHEET OF FINAL THICKNESS IS THEREAFTER SUBJECTED TO AN ANNEALING FOR DECARBURIZATION AND FURTHER FOR SECONDARY RECRYSTALLIZATION, COMPRISING THE STEPS OF HOT-ROLLING A MATERIAL, IN WHICH THE RATIO OF S AND ACID-SOLUTION AL IS MADE TO BE
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US3632456A (en) * 1968-04-27 1972-01-04 Nippon Steel Corp Method for producing an electromagnetic steel sheet of a thin sheet thickness having a high-magnetic induction
US3636579A (en) * 1968-04-24 1972-01-25 Nippon Steel Corp Process for heat-treating electromagnetic steel sheets having a high magnetic induction
DE2348249A1 (en) * 1972-09-28 1974-04-04 Allegheny Ludlum Ind Inc GRAIN ORIENTED SILICONE STEEL AND THE METHOD FOR MANUFACTURING IT
US3853641A (en) * 1968-04-02 1974-12-10 Nippon Steel Corp Method for producing single-oriented silicon steel sheets having high magnetic induction
DE2435413A1 (en) * 1973-07-23 1975-02-13 Centro Speriment Metallurg PROCESS FOR PRODUCING GRAIN ORIENTED PLATE FOR MAGNETIC PURPOSES AND GRAIN ORIENTED SHEET METAL
US3933024A (en) * 1973-06-18 1976-01-20 Nippon Steel Corporation Method for cold rolling of a high magnetic flux density grain-oriented electrical steel sheet or strip having excellent properties
US3990924A (en) * 1972-08-01 1976-11-09 Nippon Steel Corporation Method for producing high magnetic flux density grain-oriented electrical steel sheet and strips having excellent characteristics
US4006044A (en) * 1971-05-20 1977-02-01 Nippon Steel Corporation Steel slab containing silicon for use in electrical sheet and strip manufactured by continuous casting and method for manufacturing thereof
US4066479A (en) * 1972-07-08 1978-01-03 Nippon Steel Corporation Process for producing non-directional electric steel sheets free from ridging
US4318758A (en) * 1977-04-18 1982-03-09 Nippon Steel Corporation Method for producing a grain-oriented magnetic steel sheet having good magnetic properties
DE3232518A1 (en) * 1981-12-11 1983-06-30 Nippon Steel Corp., Tokyo METHOD FOR PRODUCING GRAIN-ORIENTED ELECTRO-STEEL SHEET
US4416707A (en) * 1981-09-14 1983-11-22 Westinghouse Electric Corp. Secondary recrystallized oriented low-alloy iron
DE3218821A1 (en) * 1982-05-06 1983-11-24 Armco Inc., 45043 Middletown, Ohio Stable slurry of inactive magnesium oxide, and process for the preparation thereof
US4623407A (en) * 1982-09-24 1986-11-18 Nippon Steel Corporation Method for producing a grain-oriented electrical steel sheet having a high magnetic flux density
US4623406A (en) * 1982-09-24 1986-11-18 Nippon Steel Corporation Method for producing a grain-oriented electrical steel sheet having a high magnetic flux density
DK151899B (en) * 1973-10-31 1988-01-11 Kawasaki Steel Co PROCEDURE FOR MANUFACTURING BANDS OF ELECTRIC CONDUCTIVE STEEL ORIENTED IN A DIRECTION AND WITH A HIGH MAGNETIC INDUCTION
US4797167A (en) * 1986-07-03 1989-01-10 Nippon Steel Corporation Method for the production of oriented silicon steel sheet having excellent magnetic properties
EP0326912A2 (en) * 1988-02-03 1989-08-09 Nippon Steel Corporation Process for production of grain oriented electrical steel sheet having high flux density
EP0378131A2 (en) * 1989-01-07 1990-07-18 Nippon Steel Corporation A method of manufacturing a grain-oriented electrical steel strip
EP0400549A2 (en) * 1989-05-29 1990-12-05 Nippon Steel Corporation Process for producing grainoriented electrical steel sheet having superior magnetic and surface film characteristics
EP0648847A1 (en) * 1993-10-19 1995-04-19 Nippon Steel Corporation Production method of grain oriented electrical steel sheet having excellent magnetic characteristics
US5415703A (en) * 1988-12-22 1995-05-16 Nippon Steel Corporation Very thin electrical steel strip having low core loss and high magnetic flux density and a process for producing the same
US5453136A (en) * 1991-12-26 1995-09-26 Pohang Iron & Steel Co., Ltd. Process for manufacturing high magnetic flux density grain oriented electrical steel sheet having superior magnetic properties
DE19745445C1 (en) * 1997-10-15 1999-07-08 Thyssenkrupp Stahl Ag Process for the production of grain-oriented electrical sheet with low magnetic loss and high polarization
WO1999053106A1 (en) * 1998-04-09 1999-10-21 Koenigbauer Georg Method for producing grain-oriented anisotropic electrotechnical steel sheets
WO2003023074A1 (en) * 2001-09-13 2003-03-20 Ak Properties, Inc. Method of continuously casting electrical steel strip with controlled spray cooling
WO2007135877A1 (en) 2006-05-24 2007-11-29 Nippon Steel Corporation Unidirectionally grain oriented electromagnetic steel sheet having excellent iron loss properties
WO2011114178A1 (en) 2010-03-19 2011-09-22 Arcelormittal Investigación Y Desarrollo Sl Process for the production of grain oriented electrical steel
US20120000262A1 (en) * 2008-12-31 2012-01-05 Baoshan Iron & Steel Co., Ltd. Method for manufacturing grain-oriented silicon steel with single cold rolling
EP2933350A1 (en) 2014-04-14 2015-10-21 Mikhail Borisovich Tsyrlin Production method for high-permeability grain-oriented electrical steel

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US3853641A (en) * 1968-04-02 1974-12-10 Nippon Steel Corp Method for producing single-oriented silicon steel sheets having high magnetic induction
US3636579A (en) * 1968-04-24 1972-01-25 Nippon Steel Corp Process for heat-treating electromagnetic steel sheets having a high magnetic induction
US3632456A (en) * 1968-04-27 1972-01-04 Nippon Steel Corp Method for producing an electromagnetic steel sheet of a thin sheet thickness having a high-magnetic induction
US4006044A (en) * 1971-05-20 1977-02-01 Nippon Steel Corporation Steel slab containing silicon for use in electrical sheet and strip manufactured by continuous casting and method for manufacturing thereof
US4066479A (en) * 1972-07-08 1978-01-03 Nippon Steel Corporation Process for producing non-directional electric steel sheets free from ridging
US3990924A (en) * 1972-08-01 1976-11-09 Nippon Steel Corporation Method for producing high magnetic flux density grain-oriented electrical steel sheet and strips having excellent characteristics
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US3855018A (en) * 1972-09-28 1974-12-17 Allegheny Ludlum Ind Inc Method for producing grain oriented silicon steel comprising copper
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US4318758A (en) * 1977-04-18 1982-03-09 Nippon Steel Corporation Method for producing a grain-oriented magnetic steel sheet having good magnetic properties
US4416707A (en) * 1981-09-14 1983-11-22 Westinghouse Electric Corp. Secondary recrystallized oriented low-alloy iron
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DE3218821A1 (en) * 1982-05-06 1983-11-24 Armco Inc., 45043 Middletown, Ohio Stable slurry of inactive magnesium oxide, and process for the preparation thereof
US4623407A (en) * 1982-09-24 1986-11-18 Nippon Steel Corporation Method for producing a grain-oriented electrical steel sheet having a high magnetic flux density
US4623406A (en) * 1982-09-24 1986-11-18 Nippon Steel Corporation Method for producing a grain-oriented electrical steel sheet having a high magnetic flux density
US4797167A (en) * 1986-07-03 1989-01-10 Nippon Steel Corporation Method for the production of oriented silicon steel sheet having excellent magnetic properties
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US5453136A (en) * 1991-12-26 1995-09-26 Pohang Iron & Steel Co., Ltd. Process for manufacturing high magnetic flux density grain oriented electrical steel sheet having superior magnetic properties
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US20030062147A1 (en) * 2001-09-13 2003-04-03 Ak Properties, Inc. Method of continuously casting electrical steel strip with controlled spray cooling
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US20090173413A1 (en) * 2006-05-24 2009-07-09 Yoshiyuki Ushigami Grain-Oriented Electrical Steel Sheet Superior in Core Loss Characteristic
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