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
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
• • 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/12—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
• • 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
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of silicon
• • 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
  • C21D2211/00—Microstructure comprising significant phases
  • C21D2211/005—Ferrite
• • 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
  • C21D6/00—Heat treatment of ferrous alloys
  • C21D6/002—Heat treatment of ferrous alloys containing Cr
• • 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
  • C21D6/00—Heat treatment of ferrous alloys
  • C21D6/008—Heat treatment of ferrous alloys containing Si
• • 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/06—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires

Definitions

• Ferritic stainless steel suitable for ferromagnetic parts.
• the present invention relates to a ferritic stainless steel usable for ferromagnetic parts.
• Ferritic stainless steels are characterized by a determined composition, the ferritic structure being in particular ensured, after rolling and cooling of the composition, by an annealing heat treatment giving them said structure.
• ferritic stainless steels which can contain up to 0.17% carbon. These steels, after the cooling which follows their development, have a two-phase austeno-ferritic structure. They can however be transformed into ferritic stainless steels after annealing despite a relatively high carbon content. ferritic stainless steels with a chromium content of around 11 or 12%. They are quite close to martensitic steels containing 12% chromium, but different in their carbon content which is relatively low. When hot rolling, the steel structure can be two-phase, ferritic and austenitic.
• the final structure is ferritic and martensitic. If it is slower, the austenite partially decomposes into ferrite and carbides, but with a content of carbide richer than the surrounding matrix, the austenite having hot dissolved more carbon than ferrite.
• tempering or annealing must therefore be carried out on hot rolled and cooled steels to generate a totally ferritic structure.
• the tempering can take place at a temperature of approximately 820 ° C. lower than the transition temperature alpha - »gamma, which generates a precipitation of carbides.
• the ferritic structure is obtained by limiting the quantity of carbides, this is why stainless steels Ferritics, developed in this area, have a carbon content of less than 0.02%.
• Steels which are usable for their magnetic properties are known, for example in document US Pat. No. 5,769,974 which describes a process for manufacturing a ferritic steel which is resistant to corrosion and which can reduce the value of the coercive field of said steel.
• the steel used in the process is a steel of the re-sulfurized type. Sulfur reduces the cold deformation properties.
• the steel contains a high silicon content to increase the resistivity of the material and reduce the eddy currents.
• the object of the present invention is to present a stainless steel of ferritic structure which can be used for magnetic parts having high magnetic properties and having good processing properties in terms of cold stamping and good machinability properties.
• the subject of the invention is a ferritic stainless steel which can be used for ferromagnetic parts, which is characterized in that it comprises in its weight composition:
• the weight composition also includes calcium and oxygen so that: Ca> 3010- 4 %
• the steel contains inclusions of silico-aluminale of lime of the anorthite and / or pseudo-wollastonite and / or gehlenite type.
• steel comprises in its weight composition:
• the invention also relates to a process for producing a ferritic steel, characterized in that the weight composition is subjected, after hot rolling and cooling, to an annealing heat treatment and then to a section modification of the wire drawing or drawing type.
• the drawn or drawn steel can be subsequently subjected to an additional recrystallization annealing in order to perfect the magnetic properties of the part.
• the single figure presents a ternary diagram giving the general composition of the inclusions of aluminosilicates of lime.
• the invention relates to a steel of the following general composition:
• the composition of a steel favors the appearance of the ferritic phase of centered cubic structure.
• These elements are called alpha-genes. Among these are in particular chromium and molybdenum.
• Other elements known as gamma-genes favor the appearance of the gamma-austenitic phase of cubic structure with centered faces.
• nickel, carbon and nitrogen are examples of these elements. It is therefore necessary to reduce the content of these elements and it is for these reasons that the steel according to the invention comprises in its composition less than 0.030% of carbon, less than 0.5% of nickel, less than 0.030% nitrogen.
• Carbon is bad for impact, corrosion and machinability.
• the precipitates In general, in the field of magnetic properties, the precipitates must be reduced because they constitute obstacles to the movements of the walls of blocks.
• Titanium and / or niobium form compounds including titanium and / or niobium carbide, which prevents the formation of carbides and nitrides of chromium. They therefore promote corrosion resistance and in particular the corrosion resistance of welds.
• the sulfur is limited so as to optimize the behavior of steel in the field of cold stamping and to optimize the magnetic properties. Silicon is necessary to increase the resistivity of the steel in order to reduce the eddy currents, and is favorable for the resistance to corrosion.
• the steels according to the invention may also contain from 0.2% to 3% of molybdenum, an element improving the resistance to corrosion and promoting the formation of ferrite.
• molybdenum an element improving the resistance to corrosion and promoting the formation of ferrite.
• ferritic stainless steels pose machinability problems.
• ferritic steels a big drawback of ferritic steels is the poor conformation of the chip. They produce long, tangled chips, which are very difficult to fragment. This drawback can become very detrimental in machining modes where the chip is confined, such as for example in deep drilling, cutting.
• a solution provided to overcome the machining problems of ferritic steels is to introduce sulfur into their composition or elements of the lead, tellurium, selenium type which harm either the mechanical properties of cold deformation of corrosion resistance, or magnetic properties.
• Said ferritic steels usually contain hard inclusions of the chromite (Cr Mn, Al Ti) 0, alumina (AIMg) O, silicate (SiMn) O, abrasive type for cutting tools.
• ferritic stainless steel may further contain in its composition by weight more than 30 10-4% calcium and more than 70 10 "4% oxygen.
• the malleable oxides are liable to deform in the rolling direction, while the hard oxides which they replace remain in the form of grains.
• the inclusions chosen according to the invention significantly reduce the breakage rate of the drawn wire.
• the ferritic steel, according to the invention comprising malleable inclusions, can be polished with much more ease in order to obtain an improved polished surface condition.
• the steel is produced by electric fusion and then poured continuously to form blooms.
• the blooms are then subjected to hot rolling for forming, for example wire rod or bars. Annealing is necessary to ensure the cold processing operations of the product, for example drawing and drawing.
• the steel is subjected to an additional recrystallization annealing in order to restore and perfect the magnetic properties.
• the steels according to the invention have better magnetic characteristics than the reference steels, as presented in the following table 2.
• Steel 2 performs very well in the area of machining by bar turning, despite a limited sulfur content. This is explained by the presence of calcium and oxygen.
• Steel 1 has a very good ability to cold stamping, due to its low sulfur content. On parts previously struck, the machining by screw cutting is carried out correctly, without any particular problem.
• Steels 1 and 2 behave very well in the corrosion field, despite their low chromium content, as can be seen in the following table 3. This is due to steel 1 with a low sulfur content and for steel 2 with a limited sulfur content associated with a low manganese content.
• the steel according to the invention can be used particularly for the manufacture of ferromagnetic parts such as, for example, parts of solenoid valves, of injector for direct gasoline injection system, of centralized door closings in the field of automotive or any application requiring parts of the magnetic core or inductor type.
• ferromagnetic parts such as, for example, parts of solenoid valves, of injector for direct gasoline injection system, of centralized door closings in the field of automotive or any application requiring parts of the magnetic core or inductor type.
• sheet form it can be used in current transformers or magnetic shields.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Manufacturing & Machinery (AREA)
• Electromagnetism (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Soft Magnetic Materials (AREA)
• Heat Treatment Of Steel (AREA)
• Hard Magnetic Materials (AREA)
• Heat Treatment Of Strip Materials And Filament Materials (AREA)
• Compounds Of Iron (AREA)

Applications Claiming Priority (3)

Publications (2)

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• 2000
  • 2000-07-12 FR FR0009152A patent/FR2811683B1/fr not_active Expired - Fee Related
• 2001
  • 2001-07-10 BR BR0106950-0A patent/BR0106950A/pt not_active Application Discontinuation
  • 2001-07-10 AU AU72635/01A patent/AU7263501A/en not_active Abandoned
  • 2001-07-10 EP EP01951783A patent/EP1299569B1/de not_active Expired - Lifetime
  • 2001-07-10 CA CA002384754A patent/CA2384754A1/fr not_active Abandoned
  • 2001-07-10 CN CNB018020100A patent/CN1202275C/zh not_active Expired - Lifetime
  • 2001-07-10 JP JP2002509542A patent/JP2004502867A/ja not_active Withdrawn
  • 2001-07-10 DE DE60103899T patent/DE60103899T2/de not_active Expired - Lifetime
  • 2001-07-10 KR KR1020027003223A patent/KR20020029408A/ko not_active Withdrawn
  • 2001-07-10 AT AT01951783T patent/ATE269426T1/de not_active IP Right Cessation
  • 2001-07-10 WO PCT/FR2001/002214 patent/WO2002004689A1/fr not_active Ceased
  • 2001-07-10 MX MXPA02002629A patent/MXPA02002629A/es active IP Right Grant
• 2002
  • 2002-03-07 ZA ZA200201897A patent/ZA200201897B/en unknown
  • 2002-03-08 US US10/092,448 patent/US6821358B2/en not_active Expired - Fee Related
• 2004
  • 2004-10-20 US US10/968,192 patent/US20050279425A1/en not_active Abandoned

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