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
• • 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
  • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
  • C21D1/68—Temporary coatings or embedding materials applied before or during heat treatment
  • C21D1/70—Temporary coatings or embedding materials applied before or during heat treatment while heating or quenching
• • 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
• • 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
  • C23C10/00—Solid state diffusion of only metal elements or silicon into metallic material surfaces
  • C23C10/28—Solid state diffusion of only metal elements or silicon into metallic material surfaces using solids, e.g. powders, pastes

Definitions

• ABSTRACT OF THE DISCLOSURE A method of manufacturing steel sheets having a cube on edge grain texture and high magnetic properties in the rolling direction, which comprises the steps of using as a starting material a steel strip capable of receiving said cube on edge texture but not having same, by resorting to a suitable composition and to a suitable cold rolling of the steel sheet, followed by a decarburizing annealing step to reduce the carbon content to less than about 0.005%, wherein aluminum is deposited on said strip and subsequently hot diffused throughout the mass of the strip to be treated, in the solid phase, said aluminum diffusion taking place before performing the hot secondary recrystallization to produce the desired cube on edge grain texture.
• the present invention relates to the manufacture of steel sheets of a Goss texture, or cube on edge texture, as defined by the Millers indicia (110) [001], of the higher grade.
• This grade is now currently standardized under the symbol M4 and guaranteed for a maximum watt loss of .89 w./ kg. if the thickness is .011", under 1.5 Tesla and 50 Hertz.
• the solution adopted for achieving this object consists in increasing the metal resistivity. In this direction it is known that if an element such as aluminum or additional silicon is added to a steel already containing from 2.8% to 3.5% Si the resistivity of the metal will increase considerably.
• the aluminum must be added by diffusing same into the metal in the solid phase.
• the first object of the present invention consists in providing a method of producing steel sheets with grains oriented according to the so-called cube on edge [001] texture having high magnetic properties in the rolling direction, this method consisting in using as an initial material a steel strip capable of receiving the cube on edge grain texture (but not having same so far), by selecting a suitable steel composition and a suitable cold rolling operation followed by a decarburizing annealing step for reducing the carbon content to less than 0.005% this method being characterized in that aluminum is deposited on said strip and subsequently diffused in the hot state throughout the metal mass to be treated, in the solid phase, this aluminum diffusion being performed before carrying out in the hot state the secondary recrystallization to provide the desired cube on edge grain texture.
• the thickness of the aluminum strip is selected as a function of the desired average aluminum content in the metal after the diffusion step.
• the thickness of the aluminum strip is of the order of microns if it is desired to obtain about 1.1% of aluminum after diffusion in a sheet having a final thickness of 0.28 mm.
• the width of the aluminum strip is at least equal to that of the strip to be treated.
• the first heat treatment is performed at a temperature within the range of from 660 C. to 950 C., and preferably from 660 C. to 800 C.
• the second heat treatment takes place at a temperature within the range of from 950 C. to l,250 C.
• a feature characterizing this invention is that the time required for each heat treatment varies in the opposite direction to the treatment temperature.
• each one of the two successive heat treatments is characterized by the fact that the product is kept at a constant temperature or at a temperature varying slightly during a time period of at least one hour, and preferably of 6 to 48 hours.
• the whole or part of the aluminum can be replaced by silicon, germanium or cobalt.
• This invention is also concerned with steel sheets obtained by applying the method set forth hereinabove and having definitely reduced watt losses characteristics in the rolling direction, for example less than 0.80 w./kg., and even less than 0.75 w./kg., for a thickness of 0.28 mm. under a 1.5-Tesla induction and a SO-Hertz frequency.
• the metal resistivity is improved through commercially applicable means by depositing and diffusing aluminum in the solid phase (in contrast to the deposit and diffusion of silicon in solid phase which are extremely difiicult and costly to carry out in actual practice) while reducing the anisotropy constant K1, thus permitting of reducing the detrimental effects, from the magnetic point of view, of the slight uncertainties or confusions observed in all cases in the commercial manufacture of steel having a cube on edge grain texture.
• the aluminum liquefied at the beginning of the diffusion annealing step adheres to the metal to be treated without flowing, by simple capillarity, thus aifording a homogeneous distribution of said aluminum throughout the steel mass at the end of the diffusion step.
• this invention is advantageous in that the liquid aluminum reduces the silica and the oxides of metals less electro-positive than aluminum, which oxides always remain on the skin of the metal after the decarburizing treatments and develop alumina acting as an anti-adhesive layer between the successive turns of the coil during the secondary recrystallization annealing step.
• a very low carbon steel containing 0.030% carbon maximum is processed in a open hearth furnace.
• ferro-silicon is added to this molten steel in order to increase the silicon content to 3.25%, and the resulting metal is cast into 7-ton ingots, after adding to the melt metal at least one of the elements capable of subsequently promoting the development of the cube on edge texture.
• the pickled coil is then cold rolled a first time to a thickness of 0.58 mm., then shortly heat treated (during afew seconds) at 925 C. in a dry hydrogen atmosphere.
• the coil is then cold rolled again to a thickness of 0.28 mm. and subsequently annealed for decarburization in a wet hydrogen atmosphere at 815 C. during 2 minutes.
• the coil is uncoiled and recoiled in sandwich form with a strip of pure aluminum having a thickness of 10 microns.
• the coil thus obtained is box annealed at 725 C. during 24 hours in a dry hydrogen atmosphere, thus causing the aluminum to diffuse in the strip to be treated up to an Al content of 1.1%, whereafter a second box annealing step is performed at 1,180 C. during 24 hours, this second annealing step producing the secondary recrystallization giving the desired cube on edge grain texture.
• the resistivity of the metal thus obtained is 62 microohms/sq. cm./cm., the resistivity of a similar metal but without the aluminum diffusion being about 50 microohms/sq. cm./cm.
• the product thus obtained is characterized by a watt loss of 0.75 w./ kg. in the rolling direction under 1.5 Tesla and 50 Hertz.
• this invention is applicable to thin sheets of different thicknesses, preferably less than 0.40 mm.
• a method of manufacturing a steel sheet having a cube-on-edge grain texture and high magnetic properties in the rolling direction thereof which comprises casting steel containing 2.8-3.5% silicon, rolling the cast steel into a strip, removing oxides from the strip, cold-rolling the strip to a thickness of less than 0.40 mm., subjecting the cold-rolled strip to a decarburization and annealing to reduce the carbon content of the strip to less than 0.005%, coiling the decarburized strip in conjunction with an aluminum strip of a thickness sufficient to provide an aluminum content of at least 0.7% in the strip after diffusion of the aluminum into the strip, annealing the coiled strip having the aluminum deposited thereon at 660-950 C. for 6-48 hours in a dry hydrogen atmosphere to diffuse the aluminum into the strip, and annealing the resultant strip at 950-1250 C. for 6-48 hours to cause secondary recrystallization, thus providing the cube-on-edge grain texture.
• a method according to claim 1, wherein the first heat treatment for diffusing the aluminum in the metal to be treated is carried out at a temperature within the range of 660 C. to 800 C.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Physics & Mathematics (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Manufacturing Of Steel Electrode Plates (AREA)
• Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
• Heat Treatment Of Sheet Steel (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=9042500

Family Applications (1)

Country Status (8)

Cited By (4)

Family Cites Families (4)

• 0
  • BE BE756731D patent/BE756731A/xx not_active IP Right Cessation
• 1969
  • 1969-11-03 FR FR6937712A patent/FR2067409A5/fr not_active Expired
• 1970
  • 1970-09-28 DE DE2047671A patent/DE2047671C2/de not_active Expired
  • 1970-10-13 US US00080411A patent/US3756867A/en not_active Expired - Lifetime
  • 1970-10-27 GB GB5102770A patent/GB1310278A/en not_active Expired
  • 1970-11-02 SE SE14734/70A patent/SE363354B/xx unknown
  • 1970-11-03 SU SU1489090A patent/SU452108A3/ru active
  • 1970-11-04 JP JP45097502A patent/JPS496733B1/ja active Pending

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