Classifications

• • 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
  • C21D8/1216—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the working step(s) being of interest
  • C21D8/1222—Hot rolling
• • 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
  • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
• • 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
  • C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
• • 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
  • C22C38/008—Ferrous alloys, e.g. steel alloys containing tin
• • 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
• • 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
  • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
• • 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
  • H01F1/147—Alloys characterised by their composition
  • H01F1/14766—Fe-Si based alloys
  • H01F1/14775—Fe-Si based 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
  • C21D8/1216—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the working step(s) being of interest
  • C21D8/1233—Cold rolling
• • 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
• • 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
  • C21D8/1277—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties involving a particular surface treatment
  • C21D8/1283—Application of a separating or insulating coating

Definitions

• the present invention relates to a new composition of non-oriented grain magnetic steel having improved magnetic, mechanical and thermal properties.
• This type of steel is used in particular for the manufacture of parts for electrical engineering, the role of which is to couple different electrical circuits to allow the transfer of electromagnetic energy from one to the other.
• the first consists of highly alloyed steels, the level of magnetic losses of which essentially depends on the chemical composition. These steels contain from 1.4 to 3.3% by weight of silicon as well as from aluminum up to 0.1 to 1.0% by weight. They have the drawback of having a low thermal conductivity and an excessively high hardness which leads to excessive wear of the tools for cutting the parts. Their high alloy content also makes them expensive.
• the second family of non-oriented grain magnetic steels consists of low-alloy steels which generally contain only silicon at contents of the order of 0.5% by weight. These steels are said to have improved magnetic permeability, and allow reach high induction levels for applied fields of the order of 5000 A / m while maintaining average loss levels. They also have good thermal conductivity, but have poor mechanical properties, with in particular a yield strength and low hardness. This is why, in practice, this family of steels can only be used for static or dynamic machines at low speeds. Furthermore, the production of parts in these grades also poses a problem, since frequent deformations are observed during their cutting, which results in losses of material and of productivity.
• the present invention therefore aims to provide such a material whose range of applications may be more extensive than that of materials of the prior art, and which will in particular allow to increase the specific power without risk of overheating important electrical insulators present.
• a first object of the invention consists of a magnetic steel, the composition of which comprises, expressed in% by weight:
• the present inventors have in fact discovered that the combination of the claimed aluminum, tin and phosphorus contents surprisingly and significantly improves the magnetic, mechanical and thermal conductivity properties of the steel grade.
• the tin content of the composition according to the invention must be between 0.09 and 0.12% by weight. In fact, if it is less than this range, there is not enough reduction in magnetic losses observed. On the other hand, if the tin content exceeds 0.1 2% by weight, the steel has too low a ductility.
• the carbon content of the composition according to the invention must be less than 0.005% by weight because any excess of this value leads to an unacceptable tendency to magnetic aging since it seriously limits the duration of use of the parts.
• the silicon content of the composition according to the invention must be between 1.2 and 1.4% by weight. The more the silicon content is increased, the more the thermal conductivity of the steel decreases, but, at the same time the more the magnetic losses decrease, hence the choice of the claimed range.
• the aluminum content of the composition according to the invention must be between 0.18 and 0.22% by weight. Aluminum improves the magnetic properties of steel but must not be present too much because it is harmful to the ductility of the steel and it decreases its thermal conductivity. Its content is also limited to avoid the precipitation of too fine aluminum nitrides which would block the movements of the magnetic domains.
• the nitrogen content of the composition must be less than 0.01% by weight to also limit the precipitation of aluminum nitrides.
• the manganese content of the composition according to the invention must be between 0.25 and 0.35% by weight. Manganese improves the mechanical properties of steel by preventing it from breaking during hot rolling. Below 0.25% by weight, it does not improve these mechanical properties sufficiently, while above 0.35% by weight, it deteriorates the magnetic properties of the grade and it decreases the thermal conductivity of the steel.
• the phosphorus is present in the steel according to the invention in a content of 0.10 to 0.14% by weight. It allows the hardening of steel while significantly increasing its yield strength. Its content is limited to 0.14% by weight because it reduces the thermal conductivity of the steel. It increases the resistivity of the alloy which reduces losses due to eddy currents. In a preferred embodiment, its content is between 0.1 1 and 0.13% by weight.
• the sulfur content is less than 0.015% by weight, since this element is detrimental to the characteristics of the steel, but it is also greater than 0.005% by weight, since a lower content would require an additional desulphurization step which is not not justified in the context of the present invention.
• composition according to the invention can be produced in a conventional manner and by any suitable process comprising a decarburization step, the carbon level to be reached being very low.
• the steel can be cast in the form of a slab which is heated to a temperature above about 1150 ° C. to hot roll it until it reaches a thickness of 1 'order of
• the hot rolled sheet is then pickled and cold rolled, preferably to the desired final thickness, to undergo a final heat treatment which is preferably annealing in a non-oxidizing atmosphere. If the carbon content of the sheet is still too high at this stage, decarburization is carried out during annealing.
• the present inventors have however discovered that by applying special conditions during the hot rolling and winding operation, it was possible to considerably improve the induction of the sheet obtained while removing a step from the conventional process.
• a second subject of the invention therefore consists of a process for manufacturing a sheet of composition in accordance with the invention, comprising:
• the temperature at the end of rolling is such that it ends in the ferritic domain. This characteristic combined with the control of a relatively high winding temperature allows the recrystallization and the enlargement of the grains of the hot sheet by a self-annealing phenomenon.
• the significant improvement in induction is probably due to the formation of Goss texture components, as can be found in oriented grain steels, but also of planar texture.
• the unfavorable component ⁇ 1 1 1 ⁇ is also reduced during the process thanks to the presence of tin which, by segregating at the grain boundaries, prevents the germination and growth of grains of texture ⁇ 1 1 1 ⁇ during recrystallization, thus promoting the growth of the grains in the final annealing after cold rolling.
• the self-annealing which takes place during this process makes it possible to do away with the conventional annealing step of the coiled sheet which is no longer applicable.
• the winding temperature is greater than 700 ° C, in particular greater than 720 ° C, which allows to further improve the magnetic performance of materials.
• a heat treatment is thus carried out taking the form of an annealing carried out at a temperature above 900 ° C., and in another preferred embodiment, it is carried out continuously in an oven in which the sheet has a residence time less than or equal to 50 s.
• a third object of the invention is constituted by sheets of magnetic steel with non-oriented grains of composition in accordance with the present invention and by sheets obtained by implementing the method according to the invention in its different variants.
• the sheets obtained by the method according to the invention have the particular advantage of not having to be subjected to an additional heat treatment, after cutting the parts, to allow the magnetic properties to be expressed fully. Such treatment would indeed not only be costly but also harmful for the subsequent mechanical behavior of the parts.
• the sheets obtained according to the invention are therefore directly ready for use and it is also possible to cover them with an insulating coating on each side if the application requires it.
• These sheets may in particular be used to manufacture parts for rotating machines, motors, transformers, but could also be used in the field of household appliances and electrical engineering in general.
• flows 2 and 4 are in accordance with the present invention while flows 1 and 3 are used for comparison.
• the sheets subjected to the various tests have a thickness of 0.50 mm in order to be able to compare the results obtained, since the magnetic losses are a function of this thickness.
• Two sheets are made from casting 1 and from casting 2 according to the invention, by hot rolling the corresponding slabs without following the process according to the invention.
• the winding is carried out at a temperature of approximately 645 ° C.
• the sheets are then pickled and then cold rolled.
• the final annealing is carried out continuously at 950 ° C., in an oven in which the sheets remain for 25 s.
• Example 2 Influence of the hot rolling / winding process
• Two sheets are made in the same casting 2 according to the invention, in a manner analogous to that used in Example 1, but by winding at a temperature of 640 ° C for one of the sheets and at a temperature of 730 ° C for the other.
• the total magnetic losses W1, 5T and the induction B5000 are then measured and the following results are obtained:
• Two sheets are made in casting 2 according to the invention and in casting 3 in a similar manner to that used in Example 1, but by winding at a temperature of 720 ° C.
• a series of slabs is made in the casting 4 according to the invention which is hot rolled using the process according to the invention.
• the sheets are then cold rolled until a thickness of 0.50 mm is obtained and these sheets are annealed continuously in an oven by varying the annealing temperature and the residence time of the sheets in this oven.
• the results are collated in the following table:
• Sheet metal sheets according to the invention are subjected to a number of conductivity measurements and it is found that values greater than or equal to 35 W / m.K are obtained.
• a highly alloyed steel of the prior art comprising 2.9% of silicon has a conductivity of 20 W / m.K.
• a highly alloyed grade of the prior art comprising 1.4% of silicon has an elastic limit of 250 MPa and a hardness of 140 Hv5.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Metallurgy (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Manufacturing & Machinery (AREA)
• Crystallography & Structural Chemistry (AREA)
• Thermal Sciences (AREA)
• Dispersion Chemistry (AREA)
• Power Engineering (AREA)
• Manufacturing Of Steel Electrode Plates (AREA)
• Soft Magnetic Materials (AREA)

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Citations (7)

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• 2000
  • 2000-12-27 FR FR0017084A patent/FR2818664B1/fr not_active Expired - Lifetime
• 2001
  • 2001-12-20 CZ CZ20031798A patent/CZ303205B6/cs not_active IP Right Cessation
  • 2001-12-20 DE DE60103933T patent/DE60103933T2/de not_active Expired - Lifetime
  • 2001-12-20 ES ES01994925T patent/ES2223961T3/es not_active Expired - Lifetime
  • 2001-12-20 TR TR2004/01448T patent/TR200401448T4/xx unknown
  • 2001-12-20 EP EP01994925A patent/EP1346069B1/fr not_active Expired - Lifetime
  • 2001-12-20 AT AT01994925T patent/ATE269421T1/de active
  • 2001-12-20 WO PCT/FR2001/004093 patent/WO2002052048A1/fr not_active Application Discontinuation
  • 2001-12-20 EA EA200300729A patent/EA004912B1/ru not_active IP Right Cessation

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