Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
  • C21C1/00—Refining of pig-iron; Cast iron
  • C21C1/02—Dephosphorising or desulfurising
  • C21C1/025—Agents used for dephosphorising or desulfurising
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
  • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
  • C21C7/04—Removing impurities by adding a treating agent
  • C21C7/064—Dephosphorising; Desulfurising
  • C21C7/0645—Agents used for dephosphorising or desulfurising

Definitions

• the present invention relates to a new product for the desulfurization of refining and molding irons, and of steels, and for the nodulization of molding irons, a product which is particularly well suited for direct injection, with a lance, in a stream of carrier gas in cast iron or liquid steel, and consisting of magnesium-based shot associated with slag granules.
• magnesium is absorbed on a porous support such as coke (French patent n ° 1 417 474 of American Cast Iron Pipe Company) or a porous ceramic (French patent n ° 1 357 511 of Foseco Trading AG), or on an iron sponge (French patent No. 1,568,576 to Jamforadling).
• a porous support such as coke (French patent n ° 1 417 474 of American Cast Iron Pipe Company) or a porous ceramic (French patent n ° 1 357 511 of Foseco Trading AG), or on an iron sponge (French patent No. 1,568,576 to Jamforadling).
• magnesium is mixed with a diluent, which can also play a role in the desulfurization process, such as lime (French patents n ° 1,125,154, 1,168,646, 1,168,750 from the Institut de Research in the steel industry).
• the magnesium is coated with an inert substance, (metal oxides, halogen salts).
• the present invention satisfactorily solves the problem of injecting magnesium into a bath of cast iron or liquid steel, and ensures both personnel safety, regularity of operation, obtaining '' a minimum sulfur content and simplifies handling.
• It relates to a product for the desulfurization of cast irons and steels in the liquid state, by injection with a lance in a stream of carrier gas, characterized in that it comprises, in combination, from 10 to 90% of shot based magnesium and 90 to 10% of granulated slag, and preferably 20 to 80% of magnesium-based shot and 80 to 20% of granulated slag, these percentages being expressed by weight.
• Granulated slag can be obtained by granulating slag from ingredients particular sition, either by pouring the molten slag into water, optionally followed by drying, then sieving, or by granulation in a gas or steam jet, or by any other known process such as pelletization or "pelletizing "on plate or pelletizing cylinder, which provides grains with rounded contours.
• the granulation also gives the slag granules very good physical and chemical inertness during storage.
• the granules do not disintegrate and are not hygroscopic. Conservation is a breeze compared to mixtures containing lime.
• the granules also have a good solidity which guarantees their particle size stability until the moment of their use
• the granules whose individual mass is much greater than that of the particles of fine powder additives, such as lime, make it possible to increase the amount of movement - therefore the kinetic energy of the product injected and thus to increase the penetration jet in the cast iron or steel bath.
• dairy products of basic character are particularly well suited, with a basicity index greater than 1 and, preferably, greater than 2, which may contain, in addition to lime, alumina, silica and magnesia, one or more additional constituent (s) such as calcium fluorides or sodium fluorides, alkali metal oxides, alkali metal and alkali metal borates - earthy which allow to adjust the melting point or viscosity or any other physico-chemical characteristic.
• Basicity can be identified by the weight index (MgO + CaO + Na 2 O) / (SiO 2 + Al 2 O 3 ).
• the magnesium shot can be obtained by any known means making it possible to give the particles a shape with rounded contours, free of sharp edges, which is essential for ensuring the product, object of the invention, good flow characteristics in the pipes and in the injection lance.
• any known means making it possible to obtain these forms mention may be made of the grinding of shavings or of turning, or of any other product of the removal of material, the spraying or atomization of liquid metal by projection or centrifugation.
• the particle size can be chosen within relatively wide limits. In practice, a particle size between 0.1 and 3 mm, and preferably between 0.3 and 2 mm, gives the best results in the use of the desulphurizing or inoculating product.
• the shot consists of unalloyed magnesium, containing the usual impurities; but it is also possible, depending on the results sought, either to facilitate the shaping of magnesium in the shot state, or to give cast iron or steel special properties, use shot which may contain, in addition magnesium, at least one additional element chosen from aluminum, up to 25% by weight, calcium up to 25% by weight, silicon up to 10% by weight, and one or more metals from the group of rare earths or their mixture called mischmetall, from 0.1 to 10% by weight.
• the desulphurizing or nodulating product which is the subject of the invention comprises variable proportions of granules and slag, depending on the applications. If one refers, for example, to the desulfurization of a "hematite" refining pig, it is known that the operation, for various reasons, should not last more than 6 to 8 minutes. Taking into account the initial content and the final sulfur content targeted and the magnesium yield and the flow rate of the injection lance, it is easy to calculate the theoretical amount of magnesium required, and to adjust the mixture accordingly. It is thus possible, by adjusting the magnesium / milk ratio, to regulate the flow rate, the duration and the efficiency of the desulfurizing injection.
• composition intervals ranging from 10 to 90% (by weight) of magnesium shot, and from 90 to 10% of granulated slag make it possible to resolve all the cases which. occur, the preferred compositions being in the range from 20 to 80% magnesium shot and 80 to 20% granulated slag.
• the magnesium used was obtained by the same Magn ⁇ therm process with a magnesium titer greater than 99.5% and a particle size of 0.3 to 1.6mm.
• the desulphurizing or inoculating product which is the subject of the invention, there may be mentioned: - the total elimination of any risk of ignition of the product during storage even in the event of projection of cast iron or incandescent adier. ease of handling, the absence of any polluting effect, any release of smoke or harmful gases. - the very good reliability of the injection, the elimination of the risk of clogging of the lances; the very good reproducibility of operations thanks to the control and mastery of the injection time and of the mixing of the metal, by adjusting the relative proportions of magnesium shot and slag granules; the dramatic increase in the lifespan of injection lances. - excellent metallurgical performance: obtaining very low desulphurization rates while retaining very good yields of introduced magnesium, thus guaranteeing the most economical treatment as a function of the initial sulfur content and the sulfur content in the metal treated .

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
• Treatment Of Steel In Its Molten State (AREA)

Applications Claiming Priority (2)

Publications (2)

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Family Applications (1)

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Family Cites Families (17)

• 1979
  • 1979-05-15 FR FR7913279A patent/FR2456779A1/fr active Granted
• 1980
  • 1980-04-24 IN IN475/CAL/80A patent/IN152626B/en unknown
  • 1980-05-08 IT IT21891/80A patent/IT1140849B/it active
  • 1980-05-12 BR BR8008679A patent/BR8008679A/pt not_active IP Right Cessation
  • 1980-05-12 WO PCT/FR1980/000073 patent/WO1980002565A1/fr active IP Right Grant
  • 1980-05-12 DE DE8080900923T patent/DE3065758D1/de not_active Expired
  • 1980-05-12 JP JP55501086A patent/JPS5942725B2/ja not_active Expired
  • 1980-05-12 US US06/224,535 patent/US4364771A/en not_active Expired - Fee Related
  • 1980-05-12 RO RO102896A patent/RO81381B/ro unknown
  • 1980-05-12 AU AU59824/80A patent/AU532686B2/en not_active Ceased
  • 1980-05-13 ZA ZA00802844A patent/ZA802844B/xx unknown
  • 1980-05-13 MX MX182303A patent/MX153816A/es unknown
  • 1980-05-14 BE BE0/200613A patent/BE883297A/fr not_active IP Right Cessation
  • 1980-05-14 CA CA000351885A patent/CA1150058A/fr not_active Expired
  • 1980-05-15 AR AR281068A patent/AR219255A1/es active
  • 1980-12-01 EP EP80900923A patent/EP0029038B1/de not_active Expired

Non-Patent Citations (1)

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