Classifications

• • 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

Definitions

• the present invention relates to nonoriented electrial steel sheets used for the core materials of the electrical machinery and equipment such as various motors, generators, small size transformer, ballast core and the like, and methods for manufacturing thereof, and more specifically, to nonoriented electrial steel sheets with low iron loss and high magnetic flux density and permeability, and methods for manufacturing thereof.
• the product of nonoriented electrial steel sheets in general, can be classified according to Si content.
• Such product is graded a low-class product where Si content is less than 1 %, a middle-class product where it has 1-2 % Si, and a high-class product where it exceeds 2 % Si.
• the aforesaid grading is based on the fact that iron loss becomes low as long as Si content is more added. However, magnetic flux density or permeability decreases as long as Si content becomes higher.
• the superior magnetic properties mean that iron loss is low, and that magnetic flux density and permeability are high.
• Iron loss of nonoriented electrial steel sheets can be largely divided into hysteresis loss and eddy current loss.
• Eddy current loss is decided by chemical composition of the product, thickness, frequency, etc. In the vicinity of a frequency for normal uses, 60 Hz , hystresis loss becomes more than 50 % . However , eddy current loss can be bigger than hysteresis loss where it is used for special uses with high frequency.
• the element with high resistivity among chemical composition, such as Si and Al can be more added or thickness of the final product can be thinned.
• the methods for manufacturing the aforesaid nonoriented electrial steel sheets are deivided into fully-process and semi-process.
• Steel slab is heated, hot rolled, and hot rolled sheet can be pickled after annealing.
• hot rolled sheet is pickled, is cold rolled, and is annealed.
• the following process is processing by consumers, so to speak, the electric apparatus manufacturers.
• semi-process hot rolled sheet is pickled, is cold rolled, intermediate annealing is conducted, and then skin pass rolling or temper rolling is conducted.
• the following processes are processing by consumers, so to speak, the electric apparatus manufacturers and annealing with stress relieving.
• nonoriented electrial steel sheets manufactured by semi-process is the skin pass rolled or temper rolled product
• consumers, so to speak the electric apparatus manufacturers must carry out annealing with stress relieving after processing.
• This annealing with stress relieving has a purpose of grain growth but stress occurring during processing is relieved.
• the nonoriented electrial steel sheets manufactured by fully- process more or less stresses can occur during processing by consumers, so to speak, the electric apparatus manufacturers and residual stresses during high temperature annealing can be relieved.
• magnetic properties during annealing with stress relieving by consumers, so to speak the electric apparatus manufacturers can be improved.
• 63-317627 teaches the steel manufactured by semi-process, containing one kind or more than two kinds among Sn or Sb, Ni and Cu, and adding Mn of 1.0-1.5 %, with methods for manufacturing thereof. In this method, excessive addition of Mn causes cost increase. Also, as Mn is an element easily forming austenite phase, it becomes austenite phase up to low temperature, and thus it has the drawbacks which magnetic properties are poor and especially, magnetic flux density is low, by carrying out hot rolling under austenite phase.
• the present invention provides for nonoriented electrial steel sheets with superior magnetic properties, manufactured by semi-process or fully-process by properly selecting component system of nonoriented electrial steel sheets.
• the present invention is that the basic component system is the component system simultaneously adding one kind or two kinds of Sn and Sb, beside addition of Cu and Ni to the steel containing maximum 3.5% of Si, maximum 0.7 % of Al and less than 1 % of Mn among component system manufactured under such steel preparation process.
• C, P, Ca or rare earth element(REM) can be added.
• other impurity such as O, S and N is little if possible, it is advantageous to magnetic properties but such impurity can be inevitably added to the certain extent. If a lot of C are added, decarburizing annealing is necessary.
• these elements adding only one element or two elements do not represent the property of the present invention.
• it contains Ni and Cu as well as one kind or two kinds of Sn and Sb should be necessarily added at the same time, it represents the characteristic of the present invention.
• These elements develop textures advantageous to magnetic properties, such as (110) plane and (200) plane, and especially, enable to grow grain well.
• the steel slab constructed mentioned above is manufactured with melted steel under converter, electric furnace, etc., is manufactured with continuous casting or rough blooming, and then is charged into heating furnace under the hot state or cooled state.
• the steel slab heated from heating furnace is hot rolled, coiled, and then cold rolled after pickling under the state of annealed or non-annealed hot-rolled sheet.
• Cold rolled sheet can be manufactured by fully-process or semi-process.
• Fully-process is the process which pickling of hot rolled sheet is carried out, cold rolling with one cold rolling method or double cold rolling method is conducted, and then final high-temperature annealing is carried out.
• Semi-process is the process which a first cold rolling of hot rolled sheet is carried out, the skin pass rolling or temper rolling is done after intermediate annealing, and annealing with stress relieving must be carried out after processing by consumers, so to speak, the electric apparatus manufacturers.
• Each manufacturing condition mentioned above can vary according to component system of steel. Also, even though the steel contains the same content of it, variation of the aforesaid condition of manufacturing process can vary the subsequent condition of manufacturing process.
• continuous annealing of hot rolled sheet can be carried out or annealing process of hot rolled sheet can be omitted, by controlling steel component and hot rolling condition so that hot finish rolling can be carried out under ferrite phase. Even though it is manufactured by such method, nonoriented electrical steel sheets which iron loss is low, and magnetic flux density and permeability are high, among magnetic properties, is manufactured.
• box annealing of hot rolled sheet can improve magnetic properties , but the extent for improvement of magnetic properties do not reach that for added cost.
• the inventor of the present invention carried out the following experiment to look over how finish rolling temperature affects magnetic properties.
• a hot compression test was conducted after steel slab comprising, in the unit of weight percentage, C: 0.003 %, Si:0.61 %, Mn:0.25 %, P:0.05 %, S:0.008 %, N:0.004 %, 0:0.002 %, Al:0.27 %, Ni:0.09 % , Cu:0.075 %, Sn:0.09 %, residual Fe and other inevitable impurity, was hot rolled, and processing with cylinder having 13 mm height and 8 mm diameter was conducted. Temperatures during hot compression test were 840°C under ferrite phase and 930°C under austenite phase.
• the steel slab comprising the aforesaid component was heated at 1230°C, was rolled with the percentage reduction in thickness of 19 % respectively at 840°C and 930°C during hot finish rolling, was cooled by 15°C per hour at 800°C, and then was cold rolled with the thickness of 0.5 mm after pickling.
• High temperature annealing of cold rolled sheets was conducted in the mixed atmosphere of nitrogen and hydrogen for 2 minutes at 960°C.
• the nonoriented electrical steel sheets manufactured according to the present invention is characterized that iron loss is low even with relatively low Si content and that magnetic flux density and permeability are high even with relatively high Si content.
• nonoriented electrical steel sheets improvement of magnetic properties is caused by the facts that Sn, Sb, etc., are segregated to grain boundary, interstitial element intruding into inside of steel during manufacturing process of steel is prevented from diffusing, grain forming and texture are controlled.
• Cu forms large sulphurous precipitates with S and Mn.
• corrosion resistance in high temperature is improved, and surface oxidization layer is inhibited from deepening.
• grain grows and texture of the (110) plane and (200) plane advantageous to magnetic properties is formed quite better due to combined operation of addition element. This enables to manufacture the nonoriented electrical steel sheets with superior magnetic properties.
• the formulaf 1) indicates the texture coefficient of (hkl) plane selected at random from measured steel sheet
• the formula(2) indicates texture parameter as the ratio of texture coefficient between the planes (200), (100) and (310) of crystal plane advantageous to magnetic properties, and the planes (211), (222) and (321) of crystal plane disadvantageous to magnetic properties.
• I hkl means texture intensity of measurement test piece
• I R.hkl means random intensity of standard test piece
• N hkl means multiplicity factor.
• Magnetic properties are improved as texture intensity of the planes (200), (110), and (310) becomes larger, and texture intensity of the planes (211), (222) and (321) becomes smaller. Also, magnetic properties are improved as texture parameter becomes larger, and the steel according to the present invention indicates the texture parameter of more that 0.2 at least.
• the present invention relates to nonoriented electrical steel sheets with superior magnetic properties comprising, in the unit of weight percentage, C:less than 0.02 %, Si:1.0-3.5 %, Mniless than 1.0 %, P:less than 0.10 %, S:less than 0.01 %, N: less than 0.008 %, Al:less than 0.7 %, Ni:0.05-1.0 %, Cu:0.02-0.5 %, sum of one kind or two kinds of Sn and Sb:0.02-0.2 % , residual Fe and other inevitable impurity.
• the present invention relates to nonoriented electrical steel sheets with superior magnetic properties, comprising the component and component range mentioned above, in which grain has the size of more than 30 ⁇ m, desirably has the size of 30-200 ⁇ m, more desirably has the size of 60-150 ⁇ m, and texture parameter calculated by Horta formula is more than 0.2, desirably is more than 0.5.
• the present invention relates to nonoriented electrical steel sheets with superior magnetic properties, comprising, in the unit of weigh percentage, C:less than 0.02 %, Si: less than 1.0 %, Mn : less than 0.5 %, P: less than 0.15 %, S: less than 0.01 %, N:less than 0.008 %, 0: less than 0.005 %, Al : less than 0.7 %, Ni:0.05-1.0 %, Cu:0.02-0.5 %, sum of one kind or two kinds of Sn and Sb:0.02-0.2%, residual Fe and other inevitably containing impurity.
• the present invention relates to nonoriented electrical steel sheetss with superior magnetic properties comprising the component and component rage mentioned above, in which grain has the size of more than 20 ⁇ m, desirably has the size of 20-250 ⁇ m, more desirably has the size of 40-200 ⁇ m, and texture parameter calculated by Horta formula is more than 0.2, desirably is more than 0.5.
• the present invention relates to nonoriented electrical steel sheetss with superior magnetic properties comprising, in the unit of weight percentage, C:less than 0.02 %, Si:less than 3.5 %, Mn:less than 0.5 %, P:less than 0.15 %, S:less than 0.01 %, N:less than 0.008 % , Airless than 0.7 %, Ni:0.02-1.0 %, Cu:0.02-0.5 % , sum of one kind or two kinds of Sn and Sb: 0.02-0.2 %, Ca:0.001-0.02 % and/or rare earth element ( REM) : 0.003-0.03 %, residual Fe, and other inevitably containing impurity.
• the present invention relates to nonoriented electrical steel sheetss with superior magnetic properties comprising the component and component range mentioned above , in which grain has the size of more than 30 ⁇ m , desirably has the size of 30-250 ⁇ m, more desirably has the size of 50-200 ⁇ m, and texture parameter calculated by Horta formula is more than 0.2, desirably is more than 0.5.
• the present invention relates to nonoriented electrical steel sheets with superior magnetic properties comprising, in the unit of weight percentage, C:0.02-0.06%, Si:less than 3.5 %, Mn:less than 0.5 %, P:less than 0.15 %, S:less than 0.01 %, N:less than 0.008 %, Ai:less than 0.7 %, 0: less than 0.005 %, Ni:0.02-1.0 %, Cu:0.02-0.5 % , sum of one kind or two kinds of Sn and Sb:0.02-0.2%, residual Fe and other inevitably containing impurity.
• the present invention relates to nonoriented electrical steel sheetss with superior magnetic properties comprising the component and component range mentioned above, in which grain has the size of more than 20 ⁇ m, desirably has the size of 20-250 ⁇ m, more desirably has the size of 40-180 ⁇ m, and texture parameter calculated by Horta formula is more than 0.3, desirably is more than 0.5.
• the aforementioned C which is the compound enabling to form texture advantageous to magnetic properties, can be added up to maximum 0.06 % considering the decarburization efficiency. However, in order to lower the residual C further, less than 0.02 % is desirable. In case that C is more than 0.008 % in the slab, decarburization annealing is possible. To inhibit magnetic aging by the residual C, restriction to less than 0.003 % is desirable.
• the aforementioned Si is the basic element indicating the product properties of nonoriented electrical steel sheets well, and lowers iron loss by increasing resistivity.
• adding up to less than 3.5 % is desirable as the aforesaid Si makes worse of the workability of cold rolling.
• Si is less than 1.0 %, cold rollability is improved as well as magnetic flux density and permeability can be improved.
• the aforesaid Mn has effects of lowering iron loss by increasing resistivity, but as it is precipitated with fine MnS by combining with S, and thus makes worse of magnetic properties, there is a problem that S should be managed low to inhibit this. Also, as more fine precipitates under Mn content more than 1.0% can be formed if reheating temperature becomes higher than 1200oC, restricting Mn content to less than 1.0 % is desirable, and restriction of Mn up to less than 0.5 % is more desirable.
• P lowers eddy current loss in iron loss by increasing resistivity, and it improves magnetic properties by developing texture of the planes (200) and (110) advantageous to magnetic property, it can be added up to maximum 0.15 %. But, as the P heightens basically strength of raw material, P can be added up to 0.1 % in order to improve the workability of cold rolling.
• the aforesaid S is an inevitable impurity and thus not to add it if possible is advantageous to magnetic properties. But it can be contained up to 0.01 % in the present invention. And in the present invention, even if S is contained up to 0.015 %, it does not affect magnetic properties largely in case that Mn is less than 0.5 %.
• Mn(Cu)S which is large precipitates is formed in stead of forming fine precipitates, and thus grain is grown as well as texture advantageous to magnetic properties is formed.
• N which is an impurity, forms fine precipitates and makes worse of magnetic properties, it is advantageous to contain little if possible and is allowable to contain up to maximum 0.008 %.
• the aforesaid O which is an impurity, is deoxidized by Al, etc., but increase of O among final compound during steel manufacturing means increase of fine precipitates or nonmetallic inclusions. As the result, it is desirable to contain little if possible, for improvement of steel purification and for advantageous growth of grain. As the (111) plane, etc, detrimental to magnetic properties among textures can be reduced by containing O little, it is desirable to restrict the contents up to 0.005 %.
• Ni has a little effects on the independent addition, grows grain by adding in combination with the element including Cu, P, etc, forms texture advantageous to magnetic properties, and thus lowers iron loss by increasing resistivity. But Ni costs high, and it is desirable to add up to maximum 1.0 % considering improvement degree of magnetic properties subject to addition volume. Also, it improves corrosion resistance during high-temperature annealing and corrosion resistance of P addition steel, and it is desirable to add up to minimum 0.02 % considering improvement degree of magnetic properties. More desirable content of the aforesaid Ni is 0.05-1.0 %.
• Sn or Sb combined addition of one kind or two kinds is possible. These elements are added to control grain form as segregation elements, to inhibit the (111) plane detrimental to magnetic properties from growing, and to develop textures advantageous to magnetic properties. If addition volume of these elements is less than 0.02 %, the addition effects are little, and if it is more than 0.2 %, cold rolling of hot rolled sheets is difficult. Accordingly, it is desirable to restrict sum of one kind or two kinds of Sn or Sb to be 0.02-0.2 % . However, if Cu is added up to less than 0.4 %, Sn or Sb can be added up to maximum 0.3 % independently or in combination.
• the aforesaid Cu has an effect on increasing corrosion resistance, lowering iron loss by increasing resistivity, forming large posphurous precipitates, growing grain largely, developing well texture advantageous to magnetic properties, and increasing rapidly oxidizing resistance of P addition steel. And, as Cu is added at the same time in comparison with Ni independent addition steel, oxidization especially on high temperature can be inhibited. To keep better surface without cracks of hot-rolled sheets for the steels adding simultaneously with segregation element of grain boundary including Sn, etc., Cu is added up to maximum 0.5 % and magnetic properties can be improved by adding more than 0.02 % at least. Accordingly, it is desirable to restrict the Cu content to 0.02-0.5 %. However, in the steel to which Sn or Sb was added up to more than 0.2 % independently or in combination, surface form of hot rolled sheet can be satisfied with adding Cu up to 0 . 4 % .
• the aforesaid Ca or REM can be added independently or in combination, and it functions to grow grain by roughing the precipitates including fine MnS , etc, whereby magnetic properties of product can be improved.
• the present invention relates to a method for manufacturing nonoriented electrical steel sheets with superior magnetic properties, by fully-process in which a steel slab comprising, in the unit of weight percentage, C:less than 0.02 %, Si:1.0-3.5 %, Mn:less than 1.0 %, Prless than 0.10 %, S:less than 0.01 %, N: less than 0.008%, Al:less than 0.7 %, Ni:0.05-1.0 %, Cu:0.02-0.5 %, sum of one kind or two kinds of Sn and Sb:0.02-0.2 %, residual Fe and other inevitable impurity, is hot rolled, annealing of hot rolled sheet is conducted, is pickled, a first-order cold rolled or a second-order cold rolled with a cold rolling method, high-temperature annealing of cold rolled plane is conducted, and annealing with stress relieving is conducted.
• a steel slab comprising the aforesaid compound range is charged into hot rolling heating furnace, is heated and is hot rolled, it
• Hot rolled sheet which was hot rolled as mentioned above is annealed, and with respect of annealing method of the aforesaid hot rolled sheet, continuous annealing method which annealing is conducted at 700-1100°C during 10 seconds-20 minutes, or box annealing method which annealing is conducted at 600-1000oC during 30 minutes-10 hours.
• continuous annealing method which annealing is conducted at 700-1100°C during 10 seconds-20 minutes
• annealing time by continuous annealing method is less than 10 seconds, magnetic properties deteriorate.
• restriction of facility is accompanied.
• Hot rolled sheet which was annealed by continuous annealing method or box annealing method is pickled by a normal method, one stage cold rolled or a first-order cold rolled, intermediate annealing is conducted, a second- order cold rolled by double cold rolling method, and high temperature annealing is conducted.
• the aforesaid high temperature annealing is conducted by continuous annealing within the temperature range of 700-1100°C during less than 10 minutes, and it is desirable to carry out the annealing in the atmosphere of 100 % nitrogen gas or mixed gas of nitrogen and hydrogen, and others.
• C content of the aforesaid cold rolled sheet is more than 0.008 %
• decarburization can be conducted in the mixed atmosphere of nitrogen and hydrogen during less than 10 minutes with the dew point of 20-70°C before high temperature annealing.
• heat treatment can be conducted by cosumers, so to speak, the electric apparatus manufacturers with decarburization atmosphere during annealing with stress relieving. Insulation coating can be done after high temperature annealing of the aforesaid coled rolled sheet, and cosumers, so to speak, the electric apparatus manufacturers can carry out bluing heat treatment for non-coated product.
• grain of the nonoriented electrial steel sheets according to the present invention manufactured as mentioned above has the size of 30 ⁇ m, desirably the size of 30-200 ⁇ m and more desirably the size of 60-150 ⁇ m, and texture parameter calculated by Horta formula is more than 0.2 and desirably more than 0.5.
• the present invention relates to a method for manufacturing nonoriented electrial steel sheets with superior magnetic properties, by semi-process in which a steel slab comprising, in the unit of weigh percentage, C:less than 0.02 %, Si:less than 1.0 %, Mn:less than 0.5%, P:less than 0.15 %, S:less than 0.01 %, N:less than 0.008 %, O:less than 0.005 %, Al:less than 0.7 %, Ni:0.05-1.0%, Cu: 0.02-0.5%, sum of one kind or two kinds of Sn and Sb: 0.02-0.2 %, residual Fe and other inevitable impurity is hot rolled, annealing of hot rolled sheet is conducted, is pickled, is cold rolled, intermediate annealing is conducted, is skin pass rolled and annealed, and by fully-process in which the steel slab comprising the aforesaid compound is hot rolled, annealing of hot rolled sheet is conducted, is pickled, cold rolled, and is annea
• the aforesaid hot rolling is conducted whereby final temperature of finish rolling is more than 750°C under ferrite phase of less than Ar 1 point. At this time, magnetic flux density and permeability of product are poor when final temperature of finish rolling is more than Ar1 point, and rolling load during compression rolling becomes excessive when the temperature is less than 750°C.
• the sheet which was hot rolled as mentioned above can be annealed by continuous annealing method or box annealing method. If hot rolled sheet is annealed by continuous annealing, it is desirable to carry out the annealing at 700-1000°C during 10 seconds-20 minutes. If it is annealed by box annealing, it is desirable to carry out the annealing at 600-950°C during 30 minutes-10 hours.
• Grain does not grow sufficiently if annealing time by the aforesaid continuous annealing is less than 10 seconds or the annealing temperature is less than 750°C, magnetic properties deteriorate if the annealing temperature is more than 1000°C, and productivity deteriorates if the annealing time is more than 20 minutes. As the result, it is desirable to restrict annealing temperature by continuous annealing up to 700-1000°C and the annealing time up to 10 seconds-20 minutes.
• annealing temperature by the aforesaid box annealing is less than 600°C and the annealing temperature is less than 30 minutes, grain does not grow sufficiently and thus effects of box annealing are little. If the annealing temperature is more than 950°C, magnetic properties deteriorate. Also, if the annealing time more than 10 hours, it is not economical. As the result, it is desirable to restrict the annealing temperature up to 600- 950°C and the annealing time up to 30 minutes-10 hours.
• Annealing atmosphere can be non-oxidizing atmosphere during continuous annealing or box annealing. Hot rolled sheet which was annealed as mentioned above is put in acid solution such as HCl, is pickled and is cold rolled.
• cold rolled plane is high-temperature annealed at 700-1050°C during less than 10 minutes.
• the electric apparatus manufacturers can carry out annealing with stress relieving after processing where necessary, and decarburization annealing can be conducted before high-temperature annealing if C is high.
• This decarburization annealing can be conducted in the mixed atmosphere of hydrogen and nitrogen by normal method.
• intermediate annealing is conducted at 650-950°C for less than 5 minutes
• skin pass rolling is conducted with the percentage reduction in thickness of 2.0-15.0 %
• annealing with stress relieving for relieving stress and for grain growth is conducted after processing by cosumers, so to speak, the electric apparatus manufacturers. If intermediate annealing sheet is rolled with less than 2.0 %, grain is not sufficiently grown, and if the sheet is rolled with the percentage reduction in thickness of more than 15.0 %, grain becomes smaller and thus magnetic properties deteriorate. As the result, it is desirable to restrict the percentage reduction in thickness during rolling up to 2.0-15.0 %.
• Insulation coating can be done as for each product (steel sheet) manufactured by the aforesaid fully- process and semi-process before forwarding to cosumers, so to speak, the electric apparatus manufacturers.
• Bluing treatment can be conducted as for non-coated product during heat treatment by cosumers, so to speak, the electric apparatus manufacturers.
• grain of the steel has the size of more than 20 ⁇ m, desirably has the size of 20-150 ⁇ m, more desirably has the size of 40-120 ⁇ m, and texture parameter calculated by Horta formula is more than 0.2, desirably is more than 0.5.
• the present invention relates to a method for manufacturing nonoriented electrical steel sheets with superior magnetic properties, in which a steel slab comprising, in the unit of weight percentage, C:less than 0.02 %, Si:less than 3.5 %, Mn: less than 0.5 %, P:less than 0.15 %, S:less than 0.015 %, Al : less than 0.7 %, O:less than 0.005 %, N:less than 0.008 %, sum of one kind or two kinds of Sn and Sb:0.02-0.3 %, Ni:0.02-1.0 %, Cu:0.02-0.4 %, residual Fe and other inevitably containing impurity is heated, is hot rolled whereby finish rolling is conducted under ferrite phase of more than 800°C with the percentage reduction in thickness of more than 7 %, hot rolled sheet is coiled at more than 600°C, is cooled in the air, is pickled, is cold rolled with one stage cold rolling method or double cold rolling method, and is high-temperature annealed within the range
• hot rolling is conducted. Reheating of slab is possible up to 1300°C but the temperature of less than 1250°C is more desirable. This is because that AlN, MsS and sulphurous precipitates containing Cu are likely to grow roughly at up to 1250°C, but if more than 1300°C, precipitates are resolved and thus fine precipitates detrimental to magnetic properties can be formed.
• Finish rolling temperature during hot rolling is important, and especially in order to manufacture nonoriented electrical steel sheets which iron loss is low, magnetic flux density and permeability are high, and thus magnetic properties are superior, finish rolling should be conducted under ferrite phase having the finish rolling temperature of more than 800°C. Also, it is desirable for the percentage reduction in thickness to be more than 7 %. This is because that grain under ferrite phase is easily grown with finish rolling reduction ratio more than 7 %.
• finish hot rolling is conducted with the percentage reduction in thickness of at least more than 7 % at more than 800°C under ferrite phase of less than Ar 1 point temperature, that is, at higher temperature under ferrite phase, and high-temperature annealing is conducted.
• maximum limit of finish rolling temperature can be decided by reheating temperature. If hot rolling is conducted with the percentage reduction in thickness of less than 7 % or at the finish rolling temperature of less than 800°C, magnetic properties deteriorate as grain does not grow sufficiently.
• this finish rolling magnetic properties are improved even with the percentage reduction in thickness of 50 %, maximum limit of final percentage reduction in thickness is not restricted, and the percentage reduction in thickness of not more than 50 % is desirable considering deformation resistance.
• the sheet which was hot rolled as mentioned above is coiled at more than 600°C, and final grain product is grown largely by cooling in the air with a normal method during coiling. If coiling temperature is not more than 600°C, final grain is not grown sufficiently and thus magnetic properties deteriorate.
• the maximum limit of the aforesaid coiling temperature is not specially restricted, and coiling is possibly conducted at not more than finish rolling temperature after finish rolling under ferrite phase.
• the sheet which was hot rolled as mentioned above is coiled, it is desirable to coil at more than 600°C and then to conduct a slow cooling with the cooling speed of not more than 30°C per hour on the basis of middle part of hot coil after coiling. By having such slow cooling, annealing of hot rolled sheet can be omitted.
• Final sheet which was cold rolled as mentioned above is high-temperature annealed after degreasing a normal rolling lubrication with alkaline solution.
• High-temperature annealing is subjected to Si content but it is desirable to conduct high-temperature annealing with the range of 700-1100°C during 10 seconds-10 minutes. This is because that grain does not grow sufficiently during annealing if annealing temperature is not more than 700° C or annealing time is less than 10 seconds, and that magnetic properties deteriorate due to excessive oxidization during annealing if annealing temperature is more than 1100°C or annealing time exceeds 10 minutes.
• grain of the steel sheet has the size of more than 25 ⁇ m, desirably has the size of 25-200 ⁇ m and more desirably has the size of 30-150 ⁇ m, and texture parameter is more than 0.2 and more desirably is more than 0.5.
• the present invention relates to a method for manufacturing nonoriented electrical steel sheets with superior magnetic properties, by fully-process in which a steel slab comprising, in the unit of weight percentage, C:less than 0.02 %, Si:less than 3.5 %, Mn:less than 0.5 %, P:less than 0.15 %, S: less than 0.01 %, N:less than 0.008 %, Al: less than 0.7 %, Ni:0.02-1.0 %, Cu:0.02-0.5%, sum of one kind or two kinds of Sn and Sb:0.02-0.2 %, Ca:0.001-0.02 % and/or REM: 0.003-0.3 %, residual Fe and other inevitably containing impurity is hot rolled, is coiled, is pickled as hot rolled sheet is or after hot rolled sheet is annealed, is cold rolled with one stage cold rolling method or double cold rolling method, and is high-temperature annealed, or by semi-process in which the steel slab comprising the aforesaid composition is hot
• each element is inputted before continuous casting, slab solidified with crude metal or steel ingot is made.
• Ca can be inputted before or during degasification.
• REM element is inputted during degasification or continuous casting operation, actual yield ratio becomes high.
• Other addition element can be inputted at any process from starting point to degasification process.
• the steel slab manufactured as mentioned above is charged into heating furnace in order to conduct hot rolling and the hot rolling is conducted after heating and heat-keeping operation.
• hot rolling there are no problems if final temperature is higher than 750°C.
• the sheet which was hot rolled as mentioned above is cold rolled with final thickness after pickling.
• hot rolled sheet can be annealed with continuous annealing or box annealing. By such annealing, magnetic properties are improved further. It is desirable to conduct such annealing at higher than 700°C.
• the aforesaid hot rolled sheet can be a first-order cold rolled, intermediate annealing can be conducted within the range of 700-1000°C, and then a second-order cold rolling can be conducted.
• a second-order cold rolling can be conducted with less than 15 %, it can be forwarded to cosumers, so to speak, the electric apparatus manufacturers without high-temperature annealing, and annealing with stress relieving can be conducted after processing by cosumers, so to speak, the electric apparatus manufacturers.
• Final product can be forwarded to cosumers, so to speak, the electric apparatus manufacturers after insulation coating.
• grain of the steel sheet has the size of more than 30 ⁇ m, desirably has the size of 30-200 ⁇ m, more desirably has the size of 50-150 ⁇ m, and texture coefficient calculated by Horta formula becomes more than 0.2 and desirably becomes more than 0.5.
• the present invention relates to a method for manufacturing nonoriented electrical steel sheets with superior magnetic properties, by fully-process in which a steel slab comprising, in the unit of weight percentage, C:0.02-0.06 %, Si: less than 3.5 %, Mn: less than 0.5 %, P: less than 0.15 %, S:less than 0.01 %, N:less than 0.008 %, Al:less than 0.7 %, Orless than 0.005 %, sum of one kind or two kinds of Sn and Sb:0.02-0.2 %m Ni:0.02-1.0 %, Cu:0.02-0.05 %, residual Fe and other inevitably adding impurity is hot rolled, is pickled, is cold rolled with one stage cold rolling method or double cold rolling method, decarburization annealing of coled rolled sheet is conducted at the temperature range of 750-900°C in the mixed atmosphere of 60-90 % nitrogen and 40-10 % hydrogen with the dew point of 30-60°C, and final high-temperature annealing is conducted
• texture is improved and thus, especially, permeability is improved by conducting decarburization annealing with respect to C which is known as the element deteriorating magnetic properties by making small grain size of the final sheet.
• the sheet which was hot rolled as mentioned above can be cold rolled after pickling without annealing process. Also, it can be cold rolled after annealing and pickling.
• the hot rolled sheet can be annealed with continuous annealing method or box annealing method, and it is desirable to conduct annealing at the temperature range of 700-1100°C during 10 seconds-20 minutes in case of the continuous annealing, and at the temperature range of 600- 1000° C during 30 minutes-10 hours in case of the box annealing. Meanwhile, the box annealing prevent oxidation of the sheet surface caused by long hours' annealing as this annealing can be conducted in the non-oxidizing atmosphere including nitrogen or others.
• one stage cold rolling or a first-order cold rolling is conducted, intermediate annealing is conducted normally at the temperature range of 700-1000°C, double cold rolling for a second-order cold rolling is conducted, and the coled rolled sheet is high-temperature annealed after decarburization annealing.
• decarburization annealing is conducted, decarburization is to be insufficient if content of nitrogen and hydrogen in the atmosphere is too much or less, and residual C after decarburization becomes much if the dew point is too high or low.
• a first-order cold rolling is conducted, intermediate annealing is conducted at 650-950°C during less than 10 minutes, and it is processed by cosumers, so to speak, the electric apparatus manufacturers after skin pass rolling with 2-15 % is conducted.
• decarburization annealing can be conducted.
• decarburization annealing can be conducted during annealing with stress relieving by cosumers, so to speak, the electric apparatus manufacturers. In this case, it is desirable to conduct the decarburization annealing during annealing with stress relieving at 750-850°C in the atmosphere of 60-90 % nitrogen and 40-10 % hydrogen with the dew point of 30-60°C.
• the slab constructed under steel manufacturing process comprising the composition listed in the following Table 1 is heated at 1220°C, is hot rolled as listed in the following Table 2 to make the thickness of 2.3 mm, is coiled, annealing of hot rolled sheet is conducted, and is cold rolled with the thickness of 0.5 mm.
• the coled rolled sheet was annealed in the atmosphere of 20 % hydrogen and 80 % nitrogen for 3 minutes. After annealing with stress relieving was conducted at 790°C in the atmosphere of 100 % nitrogen for 2 hours with respect to coled rolled and annealed sheets, magnetic properties were measured respectively and the measured results are indicated in the following Table 2.
• a steel slab comprising, in the unit of weight percentage, C:0.006 %, Si:2.95 %, Mn:0.35 % , P:0.03 %, S:0.005 %, Al.0.28 %, N:0.003 % , Sn:0.11 %, Ni:0.25 % and Cu:0.16 % was heated at 1200°C, was hot rolled with the thickness of 2 mm and the final temperature of finish rolling of 900°C under ferrite phase, was coiled at 700°C, annealing of hot rolled sheet was conducted under the condition listed in Table 5, was pickled, a first-order cold rolling was conducted with the thickness of 1.0 mm, intermediate annealing was conducted at 900°C for 2 minutes, a second-order cold rolling was conducted to be the thickness of 0.5 mm with the percentage reduction in thickness of 50 %, and cold rolling with double cold rolling method was conducted.
• the present invention has effects on maximizing efficiency of electrical product and energy conservation by providing nonoriented electrical steel sheets having low iron loss and high magnetic flux density and permeability.
• test piece was manufactured by semi-process in which a steel slab comprising the composition listed in the following Table 6 was heated at 1210°C, was hot rolled under the condition listed in the following Table 7, was coiled, annealing of hot rolled sheet was conducted, was cold rolled, intermediate annealing and skin pass rolling were conducted, and heat treatment by cosumers, so to speak, the electric apparatus manufacturers was conducted. Final thickness of the test piece was 0.47 mm and annealing was conducted in the nitrogen atmosphere. With respect to the test piece manufactured as mentioned above, magnetic properties were measured and the measured results were indicated as the average value of rolling direction and opposite direction of rolling.
• the invention product(1) according to the present invention has superior magnetic properties in comparison with the comparative product(1-4) which was made, of comparative steel (a) without content of Cu, comparative steel(b) with 0.8 % Mn, comparative steel(c) with 1.1 % Si, 0.55 % Mn, and 0.002 % O, and comparative steel (d) with 1.25 % Mn.
• Example 5 Compare steel (a) without content of Cu, comparative steel(b) with 0.8 % Mn, comparative steel(c) with 1.1 % Si, 0.55 % Mn, and 0.002 % O, and comparative steel (d) with 1.25 % Mn.
• a slab comprising the composition listed in the following Table 8 was heated at 1200°C and was hot rolled as listed in the following Table 9, was coiled, and was pickled, was cold rolled and annealing of coled rolled sheet was conducted.
• the atmosphere during annealing of coled rolled sheet was 20 % H 2 and 80 % N 2 .
• the magnetic properties indicated in the following Table 9 were measured under the condition listed in Table 7 of Example 4.
• the slab of invention steel(c) presented in Table 8 of the above Example 5 was heated at 1200°C, was hot rolled as listed in the following Table 10, was coiled, was pickled, was cold rolled, and annealing of coled rolled sheet was conducted in the atmosphere of hydrogen and nitrogen.
• the coled rolled sheet was annealed and cut, and then was annealed at 790°C in the atmosphere of 20 % H 2 and 80 % N 2 during 2 hours. After that, magnetic properties were measured and the measured results were indicated in the following Table 10.
• the magnetic properties presented in the following Table 10 was measured under the same condition as that listed in Table 7 of the Example 4.
• the invention product(7-10) made of the invention steel(c) having the composition range of the present invention with the fixed hot rolling finish rolling temperature(oC), coiling temperature (°C) and annealing condition of coled rolled sheet, as well as with variation of hot rolled sheet annealing condition within the range of the present invention has superior magnetic properties.
• Example 7 A steel slab comprising, in the unit of weight percentage, C:0.003 %, Si:0.52 %, Mn:0.45.%, P:0.06 % , S:0.004 %, Al:0.30 %, N:0.002 %, 0:0.003 %, Ni:0.35 % , Cu:0.21 %, Sn:0.11 % and residual Fe was reheated and manufactured by semi-process as shown on the following Table 11. Intermediate annealing of coled rolled sheet was conducted in the mixed atmosphere of hydrogen and nitrogen, skin pass rolling was conducted and heat treatment was conducted at 790°C in the nitrogen atmosphere during 2 hours by cosumers, so to speak, the electric apparatus manufacturers. With respect to each test piece manufactured as mentioned above, magnetic properties were measured and the measured results were indicated in the following Table 11. The magnetic properties presented in the following Table 11 was measured under the same condition as that presented in Table 7 of the above Example 4.
• the invention product(1-5) manufactured by semi-process which accords to the present invention has superior magnetic properties in comparison with the comparative product(1) which final hot rolling was conducted under austenite phase.
• a steel slab comprising, in the unit of weight percentage, C:0.005 %, Si:0.85 %, Mn:0.25 %, P:0.06 %, S:0.005 % , Al:0.35 %, N:0.002 %, Ni:0.25 %, Cu:0.17 %, Sn:0.21 % and residual Fe was reheated at 1230°C, and hot rolled sheet was manufactured under the condition of finish rolling and coiling presented in the following Table 12.
• Ar 1 temperature, maximum temperature under ferrite phase was 910°C
• thickness of hot rolled sheet was 2.0 mm.
• the hot rolled sheet which, finish rolling was conducted as listed in the following Table 12, was coiled in the air and pickled in HCl solution.
• the present invention product(1-4) has the grain size of 85-98 ⁇ m and superior magnetic properties, whereas comparative product(1) was hot rolled under ferrite phase, but finish rolling temperature and coiling temperature were low and final percentage reduction in thickness was low, whereby magnetic properties deteriorate, and comparative product(2) has low finishing percentage reduction in thickness but is hot rolled at the higher temperature than Ar1, a boundary point of 100 % ferrite phase, and thus grain is grown little and magnetic properties deteriorate.
• a steel slab comprising, in the unit of weight percentage, C:0.003 %, Si:1.1 %, Mn:0.20 %, P:0.06 %, S:0.03 %, Al.0.35 %, N.0.002 %, Sn.0.11 %, Sb:0.05 %, Ni:0.09 %, Cu:0.21 % and residual Fe was reheated at 1150° C and manufactured by fully-process as indicated in the following Table 13.
• a boundary temperature of ferrite phase was 940°C and hot rolling with the finishing percentage reduction in thickness of 30 % was conducted to make the thickness of 2.3 mm after hot rolling.
• the hot rolled sheet which finish rolling was conducted at the temperature presented in the following Table 13 was coiled and cooled, and was pickled in acid solution.
• the invention product(5) and invention product(6) of the following Table 13, on which concurrent heating cover was put, were coiled and cooled in the nitrogen atmosphere.
• the cooling speed was 10-15°C per hour, and comparative product(3) was coiled and cooled in the air.
• a first-order cold rolling was conducted with 1.0 mm and intermediate annealing was conducted at 900°C in the mixed atmosphere of hydrogen and nitrogen for 2 minutes.
• intermediate annealing aheet a second-order cold rolling was conducted with 0.47 mm and high-temperature annealing was conducted with the annealing condition presented in the following Table 13. The high-temperature annealing was conducted at the drying atmosphere of 40 % hydrogen and 60 % nitrogen.
• High-temperature annealing sheet was cut after insulation coating and annealing with stress relieving was conducted at 820°C in the drying atmosphere of 100 % nitrogen during 90 minutes. After that, magnetic properties and size of grain were measured and the measured results were indicated in the following Table 13.
• a steel slab comprising the composition presented in the following Table 14 was manufactured with the steel which Ca or REM was added to melted steel outputted from steel manufacturing process, and with the steel which Ca or REM was not added thereto.
• REM of invention steel(b) in the following Table 14 is Nd
• REM of invention steel(d) is Ce.
• the steel slab constructed as mentioned above was heated a 1210°C, was hot rolled with the finish rolling temperature of 870°C and the thickness of 2.0 mm, and was coiled at 720°C, annealing of hot rolled sheet was conducted at 900°C during 5 minutes, was pickled, and was cold rolled with the thickness of 0.47 mm.
• Example 11 A steel slab comprising, in the unit of weight percentage, C:0.003 %, Si:2.2 %, Mn:0.35 %, P:0.04 %, S:0.002 %, Al:0.3 %, N:0.002 %, Sn:0.15 % , Ni;0.25 %, Cu:0.13 % and Ca:0.009 % was reheated at 1140°C, was hot rolled with the finish rolling final temperature of 850°C and the thickness of 2 mm, and was coiled at 720°C.
• box annealing was conducted at 900°C during 2 hours, pickling was conducted, a first-stage cold rolling was conducted to make the thickness of 1.0 mm, intermediate annealing was conducted at 900°C for 3 minutes, a second-order cold rolling was conducted to make the thickness of 0.50 mm, and then final coled rolled sheet was made by double cold rolling method.
• nonoriented electrical steel sheets manufactured according to the present in-vention has low iron loss and high magnetic flux density and permeability.
• the steel slab comprising the composition presented in the following Table 17, manufactured under the steel manufacturing process was heated at 1200°C, hot rolling was conducted with the final temperature of 850°C during hot finish rolling to make the thickness of 2.0 mm, and then was coiled at 600°C.
• Hot rolled sheet was pickled under the condition presented in the following Table 18 with or without annealing, and then cold rolling was conducted with the thickness of 0.5 mm. Where box annealing was conducted as for hot rolled sheet, surface oxide was inhibited by 100 % nitrogen atmosphere. Continuous annealing was conducted with the atmospheric atmosphere.
• decarburization annealing was conducted in the mixed gas atmosphere of 30 % hydrogen and 70 % nitrogen with the dew point of 40°C during 3 minutes as described in the following Table 18, and high-temperature annealing was conducted.
• High-temperature annealing was conducted in the atmosphere of 20 % hydrogen and 80 % nitrogen during 3 minutes. After cutting the annealing sheet which high- temperature was conducted as mentioned above, permeability was measure and the measured results were indicated in the following Table 18.
• a steel comprising the composition system presented in the following Table 19 was reheated at 1230°C, hot finish rolling was conducted at 850°C, and the steel coil was coiled at 750°C.
• Comparative product(1-2) and invention product(1-3) presented in the following Table 20 were manufactured by fully-process.
• decarburization annealing of coled rolled sheet was conducted at respective temperature in the mixed atmosphere of 20 % hydrogen and 80 % nitrogen with the dew point of 45°C for 4 minutes, and high-temperature annealing was conducted at respective temperature in the atmosphere of 30 % hydrogen and 70 % nitrogen for 3 minutes.
• decarburization annealing was conducted in the furnace atmosphere of 50 % hydrogen and 50 % nitrogen with the dew point of 80°C.
• Comparative product(3-4) and invention product(4-6) were manufactured by semi-process.
• decarburization annealing was conducted at respective temperature in the mixed atmosphere of 70 % nitrogen and 30 % hydrogen with the dew point of 40°C for 2 hours during annealing with stress relieving after intermediate annealing, and furnace cooling was conducted.
• decarburization annealing was conducted in the mixed atmosphere of 40 % nitrogen and 60 % hydrogen with the dew point of 10°C for 2 hours.
• decarburization annealing was conducted in the atmosphere of 20 % nitrogen and 80 % hydrogen with the dew point of 45 % during intermediate annealing.
• decarburization annealing can be conducted at the time of intermediate annealing process and of annealing with stress relieving.
• grain size was 80 ⁇ m and 75 ⁇ m, respectively and texture parameter was 0.40 and 0.25, respectively.
• texture parameter was 0.40 and 0.25, respectively.
• grain size was 120 ⁇ m and texture parameter was 0.68.
• product (1) manufactured by fully-process grain size was 75 ⁇ m and texture parameter was 0.5.

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• 1992
  • 1992-10-22 RU RU9293043462A patent/RU2092605C1/ru not_active IP Right Cessation
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