Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C24/00—Coating starting from inorganic powder
  • C23C24/08—Coating starting from inorganic powder by application of heat or pressure and heat
  • C23C24/082—Coating starting from inorganic powder by application of heat or pressure and heat without intermediate formation of a liquid in the layer
  • C23C24/085—Coating with metallic material, i.e. metals or metal alloys, optionally comprising hard particles, e.g. oxides, carbides or nitrides
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C24/00—Coating starting from inorganic powder
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C8/80—After-treatment
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
  • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
  • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
  • H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
  • H01F1/14—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys
  • H01F1/16—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of sheets
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
  • C21D8/1244—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the heat treatment(s) being of interest
  • C21D8/1255—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the heat treatment(s) being of interest with diffusion of elements, e.g. decarburising, nitriding
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
  • C21D8/1244—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the heat treatment(s) being of interest
  • C21D8/1272—Final recrystallisation annealing

Definitions

• This invention relates to a method for improving the brittleness of an oriented cold-rolled silicon steel sheet and at the same time forming an electrical insulating film having an excellent electric insulation, adhesion, bendability, space factor and heat resistance on the surface of the oriented cold-rolled silicon steel sheet.
• the term oriented cold-rolled silicon steel sheet used in the present invention means a cold-rolled silicon steel sheet consisting of 2 to 3.5% by weight Si, the rest being Fe and unavoidable impurities, and having a highly oriented crystal grain structure after being finally annealed. Further, it contains in addition one or more of the materials Al (0.1 to 0.09% by weight sol.
• the expression oriented means that a great part of crystal grains have (H0) [001] crystal orientation, which is called cube on edge" or (100) [001] crystal orientation, which is called cube on face.
• Oriented cold-rolled silicon steel sheet is used for laminated iron cores or wound iron cores. Such individual silicon steel sheets are coated with electrical insulating films so as to be electrically insulated from each other.
• Such electrical insulting film is required to be so tightly adhered to the sheet that it will not be peeled off during working and to have a high space factor and excellent resistance to heat. On the other hand, such insulating film should have no bad influence on the magnetic property of the steel sheet.
• the silicon steel sheet is generally subjected to a final annealing in which it is treated at a high temperature of about 1200 C. for a long time.
• Such final annealing is carried out on steel sheets which are laminated or wound in coils. in such case, in order to prevent the steel plates from sticking to each other due to heat, an annealing separator is used.
• annealing separator there is utilized a substance which acts to prevent sticking of the steel sheet and at the same time forms a glassy electrical insulating film by reacting with an oxide on the surface of the steel sheet at the annealing temperature.
• MgO used as the substance to act as a separator and as a glassy film forming agent.
• water When it is to be applied to a steel sheet, it is generally mixed with water so that it is in the form of a liquid suspension or slurry.
• MgO acts with water to become Mg(Ol-l) which discharges water of hydration while being heated and oxidizes and embn'ttles the steel sheet.
• An object of the present invention is to provide an insulating film forming process for stably forming a film having an excellent electric insulation property and heat resistance and which is strongly adherent and at the same time reducing the brittleness of the oriented cold-rolled silicon steel sheet itself.
• SiO adhesive insulating film
• a silicious base for the latter formation of a glassy film.
• Such a base is formed generally at the time of decarburizing annealing.
• the base composition is so sensitive to the temperature, time, atmosphere and dew point of the atmosphere that it is difficult to obtain a high quality glassy film in a stable manner with known substances capable of serving both as a separator to prevent sticking and as a glassy film forming agent with the result that a film which is poorly adherent is often produced.
• the water contained in the above-mentoned substance will be discharged in the final annealing, which will improperly oxidize the steel sheet and prevent the formation of a high quality glassy film at a temperature particularly above 1000 C.
• the present invention comprises heat-treating for a short time an oriented silicon steel sheet cold-rolled to any desired dimensions, for example in an atmosphere containing wet hydrogen gas so that a surface layer containing SiO, from the selective oxidation of Si in the steel sheet will be selectively formed on the surface of the steel sheet, then coating it with a substance which consists of a mixture of an oxide or hydroxide of Mg such as MgO or MG(OH), or an oxide or hydroxide such as TiO,, O -H O, TiO-(Ol-U or Ti(OH) and further heat-treating it in an atmosphere containing hydrogen so that a glassy insulating film will be formed.
• a substance which consists of a mixture of an oxide or hydroxide of Mg such as MgO or MG(OH)
• an oxide or hydroxide such as TiO,, O -H O, TiO-(Ol-U or Ti(OH)
• a uniform glassy film which is strongly adherent is stably obtained without being influenced by the heat-treating conditions of the atmosphere and the like. Further, the brittleness of the steel sheet itself is greatly reduced.
• the present invention is to be applied to oriented cold-rolled silicon steel sheets.
• Such an oriented cold-rolled silicon steel sheet is annealed continuously for a short time under a condition, for example, in a wet reducing atmosphere which prevents the oxidization of iron as much as possible but allows the oxidation of silicon in the steel so that SiO, will be formed on the surface of the steel sheet.
• the heat-treatment for the formation of the above-mentioned SiO is carried out under a condition which will prevent the oxidization of iron.
• a slight oxidization of iron is not always detrimental. But excess oxidization will reduce the quality of the glassy film and therefore must be avoided.
• a reducing atmosphere of hydrogen only or dissociated ammonia is generally used, the dew point of which is 55 to 70 C. and the temperature of which is 700 to 900 C.
• the holding time at the above-mentioned temperature is at least one minute or more than one minute.
• the dew point is preferably below 55 C.
• the decarburlzation of the oriented cold-rolled silicon steel sheet can be simultaneously carried out.
• the Mg cold-rolled silicon steel sheet surface on which a layer containing SiO, has been formed is further coated with a substance having as main components one or more mg. compounds such as MgO and Mg(OI-i) and one or more such Ti compounds such as p0,, O -H 0, TiO-(OH), or Ti(OH),,. It is most economical to use this substance as a glassy film-forming agent and also as a material which prevents sticking of the steel sheets during the final annealing.
• the above-mentioned substance is formed by mixing 0.5 to 40 parts by weight of a Ti compound with 100 parts by weight of an Mg compound.
• the amount of the Ti compound is larger than 40 parts, the substance after being dried will be likely to peel off the sheet, during handling the formation of the insulating film will be difficult. A surface having a metallic luster will be exposed and no uniform glassy film will be produced and, even if a phosphate-treatment is thereafter used, no highly adherent film will be obtained.
• the Ti compound in the substance has an excellent effect in that it reduces the brittleness of the steel sheet.
• the effect of reducing the brittleness of the steel sheet will appear.
• the amount is above the upper limit, there will be no substantial brittleness reducing effect. it is only when 5 to 20 parts of the Ti compound are used that the brittleness will be most reduced.
• MgO which is one of the components of the substance to be used in the present invention may be either a high-temperature baked product or a low-temperature baked product.
• the low-temperature baked MgO is more effective for attaining the object of the present invention.
• lts granularity can be as fine as about 325 meshes to obtain a favorable result.
• TiO can be either the rutile type or the anatase type or can be obtained by either low-temperature-dehydrating or hightemperature-baking of metatitanic acid.
• lts granularity can be fine as about 325 meshes the same as the above-mentioned MgO to obtain a favorable result.
• the film agent substance of the above-mentioned composition is preferably mixed with water so as to form a slurry and the slurry is applied to the surface of an oriented cold-roiled silicon steel on which a layer of SiO, has been formed by selective oxidization.
• the amount applied is preferably such that the amount of the substance which remains after being dried will be 2 to gJm. When the amount is 4 to 8 g./m the best result will be obtained.
• the sheet is dried and is then heated at a high temperature in a reducing atmosphere so that a glassy insulating film will be formed. It is most economical to carry out this glassy insulating film forming treatment at the time of the final annealing of the oriented cold-rolled silicon steel sheet.
• the oriented cold-rolled silicon steel sheet coated with the above-mentioned substance and then dried is wound up in the form of a coil or sheets cut to proper dimensions are attacked and final-annealed during which it is held at a high temperature above 1 C., such as, for example, 1200 C. for more than 5 hours in an annealing furnace in a reducing atmosphere such as, for example, of pure hydrogen.
• SiO present on the surface of the oriented cold-rolled silicon steel will react with the substance to form a blackish lustrous, compact and rustproof, acidproof highquality glassy insulating film having a composition in the SiO -MgO-TiO system.
• the substance applied to the surface of the oriented cold-rolled silicon steel sheet is also an annealing separator in the final annealing. That is to say, only a part of the applied substance reacts with SiO formed on the surface of the steel sheet so as to form a glassy film and the greater part of it remains as an annealing separator on the glassy film formed on the steel sheet surface. Therefore, in order to make the steel sheet into a product, it is necessary to remove the powder by such means as brushing or pickling.
• a high-quality insulating film is formed on the surface of an oriented cold-rolled silicon steel sheet and, at the same time, as another feature of the effect of the present invention, the brittleness of the oriented cold-rolled silicon steel sheet itself is reduced.
• the mixture of MgO-TiO, produced during the treatment reacts with SiO, on the surface of the oriented coldrolled silicon steel sheet to form a compact high quality glassy film, and therefore the oriented cold-rolled silicon steel sheet is not influenced by the annealing atmosphere and the Ti compound acts to directly purify the impurities in the oriented cold-rolled silicon steel sheet.
• the Mn compound is considered to act to suppress the influence of the M 0 formed on the steel sheet surface. That is to say, when heated, the Mn compound will become MnO, will be further reduced by the atmosphere and will enter the steel. The reaction in such case is considered to effectively act on the formation of a film. Further, the oxygen produced by the decomposition of the Mn compound in the reducing atmosphere below 1000 C. is also considered to effectively act. MnO, is excellent in that it is a compound which discharges oxygen and is readily available. lts granularity should be about 325 meshes to obtain favorable results.
• the substance effective for application to the above-mentioned Al-containing oriented cold-rolled silicon steel sheet is formed by mixing 0.5 to 80 parts, preferably 2 to 40 parts of a Ti compound and 0.5 to 50 parts, preferably 2 to 25 parts, of a Mn compound with 100 parts of a Mg compound.
• the Mn compound when the Mn compound is below the above-mentioned range, it will not be effective. On the other hand, when it is used in excess of 50 parts, the amount of oxygen discharged during the heat-treatment will be so large that the atmosphere will become oxidative and will have a bad influence on the formation of the glassy insulating film.
• the substance of the above composition is not only effective for application particularly to an Al-containing oriented coldrolled silicon steel sheet but also can be applied to such oriented silicon steel sheet containing no Al as is described above.
• EXAMPLE 1 An oriented cold-rolled steel sheet having 3.25 percent Si and reduced to a final thickness of 0.35 mm. was annealed for a short time of 5 minutes at a temperature of 800 C. in a wet dissociated ammonia atmosphere having a dew point of 61 C. so that SiO was selectively formed on the steel sheet surface, coated with a substance at each of the mixing rates in table 1 so that the amount coated on the sheet was 6 g./m. and was final-annealed for 20 hours at a temperature of 1200 C. in a dry hydrogen atmosphere.
• Table 2 The characteristics of the thus formed glassy insulating films are shown in table 2.
• table 3 there are shown the results of bending tests by the ASTM method to show the effects of reducing the brittleness of the steel sheets after the formation of glassy films. It is clear that the brittleness is greatly reduced in the films made by the method of the present invention.
• EXAMPLE 3 a An oriented cold-rolled silicon steel having 0.03 percent y total A1 and 2.85% Si was rolled to a sheet 0.l5 mm. thick, 7 1 was continuously annealed for a short time of 4 minutes at a temperature of 850 C. in a wet decomposed atmosphere having a dew point of 65 C. so that SiO was selectively formed on the surface, was coated on the surface with a substance at each of the below-mentioned mixing rates so that the amount of the substance after drying would be 6 g./m.”, was dried and was then final-annealed for 20 hours at a temperature of 1200" C. in a dry hydrogen atmosphere so that a glassy film was formed. As a result, excellent electrical insulating films as described below were obtained.
• a method for producing an electrical insulation film on an oriented silicon steel sheet containing 0.01 to 0.09 wt. percent sol. al. comprising the steps of subjecting the silicon steel sheet to a heat-treatment at a temperature of 700 to 900 C. to form SiO, on the surface of the steel sheet, applying to the said surface of the steel sheet a slurry by mixing l) 0.5 to 80 parts by weight of at least one compound selected from the group consisting of an oxide of Ti and a hydroxide of Ti, (2) 0.5 to 50 parts by weight of at least one compound selected from the group consisting of an oxide of Mn and a hydroxide of Mn, and (3) 100 parts of by weight of a compound selected from the groups consisting of an oxide of mg. and a hydroxide only.
• the slurry is prepared by mixing l 2 to 40 parts by weight of a compound selected from the group consisting of an oxide of Ti and a hydroxide of Ti, (2) 2 to 25 parts by weight of a compound selected from the group consisting of an oxide of Mn and a hydroxide of Mn and (3) parts by weight of a compound selected from the group consisting of an oxide of Mg and a hydroxide of Mg.

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Citations (5)

• 1967
  • 1967-12-12 JP JP42079243A patent/JPS5112451B1/ja active Pending
• 1968
  • 1968-12-06 US US781963A patent/US3627594A/en not_active Expired - Lifetime
  • 1968-12-09 GB GB1251827D patent/GB1251827A/en not_active Expired
  • 1968-12-11 BE BE725245D patent/BE725245A/xx not_active IP Right Cessation
  • 1968-12-12 SE SE17001/68A patent/SE347298B/xx unknown
  • 1968-12-12 FR FR1594432D patent/FR1594432A/fr not_active Expired

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