Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
  • C22B9/16—Remelting metals
  • C22B9/18—Electroslag remelting

Definitions

• ABSTRACT Slag recovered from a previous electroslag remelting of a metal or similar thereto is dried and ground into a fine powder and then mixed with a metal to be added to an electroslag melt, e.g., of steel, in order to alloy it or deoxidize it.
• the mixture is formed into granules having a density closer to that of the slag than to that of the metallic component from which the granules were formed. These granules can even be lighter than the slag in the melt, so that when added they float thereon.
• The'present invention relates to the electroslag melting of a metal and, more particularly, to an additive for an electroslag refining or alloying melt, e.g., to supply alloying ingredients or refining agents such as deoxidizers.
• the invention also relates to a method of making the additive and to a method of remelting metals using same.
• Heat being is withdrawn from the mold by cooling the pool of molten metal beneath the slag layer to subject the melt to a progressive oriented solidification.
• the process has been used heretofore simply for the remelting of solid metal, e.g., ingots, scrap, ingots and scrap together for the alloying of the melt with one or more alloying metals (e.g.,chromium, nickel, molybdenum, manganese, tungsten or vanadium in the case of steel), and/or for the refining or treatment of a melt (e.g., for the deoxidation of a steel bath by the addition of aluminum thereto).
• the slag consists generally of fluorides, oxides and mixtures thereof and is, in effect, a flux promoting heating andmelting-refining of the metal.
• the metal is usually just charged onto the melt continuously as a divided powder which, due to its density, sinks through the slag and enters into the melt.
• This powder has a composition different from that of the melt and from that of the electrodes in order to impart a particular composition to the body of molten metal.
• a great disadvantage of such a method is that the powder tends to agglomerate either on the cold walls of the ingot mold when it is carried as lumps into the bath when the level of the slag layer rises, or between the electrodes where it creates a short circuit (being more conductive than the slag).
• This latter disadvanta'ge is particularly great in cases where the refilling factor, i.e., the ratio of the cross-sectional area of the electrodes to the cross-sectional area of the crucible is large. In this case the free space between electrodes and between the electrodes and the wall of the vessel is meager.
• the finished ingots often exhibit marked segregation and inhomogeneity of the distribution of the added substance throughout their cross-section.
• Another object is the provision of an improved additive useful in the alloying of steel.
• -Yet another object is to provide an additive which can combine the functions of deoxidizing or otherwise react with slag with that of alloying.
• a further object is to provide an improved alloying additive which mixes well with and melts completely in the body of molten bath or slag.
• the very hot slag thereby melts away the nonmetal base and combines therewith, thereby liberating the heavy metal either to react with the slag or to pass through the slag in a fully melted condition and mix with the metal melt. Due to the relatively long time the metal will pass in the hotter slag layer it will be completely melted so that the finished ingot will be almost perfectly integrated.
• the granules have an overall density or specific gravity which is less than that of its metallic component or components. Generally such densities lie between 3.2 g/cm and 6.5 g/cm".
• Metallic components usable in the granules can be, for example, titanium, molybdenum, vanadium, tungsten, manganese, niobium, chromium, cobalt, nickel, or copper. These metals are usually used in the form of ferroalloys or base-metal alloys with several components.
• metals serving to restore the reducing power of the slag for the production of low-oxygen steel.
• Aluminum or reducing ferroalloys are used for instance.
• the reducing metals need be included in the granules along with, of course, the relatively light mineralic base component.
• the base is formed of a mixture or compound corresponding to that of the slag in the melt, even as far as 1 relative proportions of the components are concerned in order to avoid any disadvantage change in the melt after addition. Fluorides, oxides, or mixtures thereof have been found useful.
• the electrical conductivity, viscosity, fusion temperature, and basicity of the nonmetallic component of the additive granules should be calculated so as not to upset those characteristics of the existing slag.
• a binder chosen preferably amongst the hydrocarbons which are completely destroyed in the subsequent fusion of the granules.
• a nonmetallic base component which is hygroscopic or hydrous
• the water must be removed prior to use. This can be done by melting it for several minutes in an are or induction furnace, as is the case with remelting slags before use. It is therefore possible to employ a slag from a previous or different melt as mineral base for the granules, preferably a slag which was only used once.
• the dehumidified base is ground up to the desired mesh size and mixed fully with the also dried and finely divided metallic component.
• a binder is added if necessary and porous granules are formed by bricketting or pelletizing. Moisture must be eliminated or avoided at every step since it is difficult to eliminate hydrogen from the melt once the hydrogen has been absorbed.
• the additive according to the present invention is so light it rests for a relatively long time on or in the slag layer. This gives the metallic component sufficient time to either react with this slag or to fuse completely. The resultant tiny drops of metal in the slag have a relatively large surface area in comparison to their mass so that they heat up well.
• the composition of the slag is, of
• SPECIFIC EXAMPLE In order to make lightweight porous granules containing 40 percent by weight of chromium the necessary quantity of ferrochrome having a chromium content of 65 percent by weight was ground up to a granule size of 0.4 mm to 0.8 mm. Slag consisting of 60 percent by weight CaF 20 percent by weight of A1 0 and 20 percent by weight of CaO was also reduced to this mesh size. The ferrochrome and the ground-up slag were mixed completely and then compacted in a press into pellets which were then broken up into granules of an average diameter between 2 mm and 4 mm and an overall density of 3.50 g/cm.
• a method of smelting a metal comprising the steps of: I
• a slag-covered melt of a metal by electroslag heating; producing a granular additive by compacting a mixture of a finely divided metal with a finely divided nonmetallic composition to produce a body having a density substantially between 3.2 g/cm and 6.5 g/cm and less than that of the metal of said melt, and granulating said body to form said additive;
• nonmetallic composition consists essentially of fluorides, oxides, or mixtures thereof.
• An additive for treatment of a slag-covered metal melt comprising granules of a compacted mixture of finely divided metallic component and a nonmetallic component, said granules having an overall density substantially less than that of said metallic component between 3.2 g/cm and 6.5 g/cm and corresponding generally to that of the slag on said melt.
• a method of smelting a metal comprising the steps of:

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Manufacture And Refinement Of Metals (AREA)
• Manufacture Of Alloys Or Alloy Compounds (AREA)

Applications Claiming Priority (2)

Publications (1)

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Country Status (9)

Cited By (11)

Citations (9)

• 1971
  • 1971-07-06 GB GB3176571A patent/GB1361046A/en not_active Expired
  • 1971-07-07 BE BE769605A patent/BE769605A/xx unknown
  • 1971-07-08 FR FR7125052A patent/FR2100424A5/fr not_active Expired
  • 1971-07-08 DE DE19712133963 patent/DE2133963B2/de not_active Withdrawn
  • 1971-07-09 JP JP5095271A patent/JPS5422402B1/ja active Pending
  • 1971-07-09 SE SE7108912A patent/SE393124B/xx unknown
  • 1971-07-09 NL NL7109522A patent/NL7109522A/xx not_active Application Discontinuation
  • 1971-07-09 AT AT599471A patent/AT338851B/de not_active IP Right Cessation
  • 1971-07-12 US US00161957A patent/US3768996A/en not_active Expired - Lifetime

Patent Citations (9)

Non-Patent Citations (1)

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