EP0347351B1 - Procédé de traitement des aciers liquides par injection de gaz à travers le fond de poche - Google Patents

Procédé de traitement des aciers liquides par injection de gaz à travers le fond de poche Download PDF

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Publication number
EP0347351B1
EP0347351B1 EP89420220A EP89420220A EP0347351B1 EP 0347351 B1 EP0347351 B1 EP 0347351B1 EP 89420220 A EP89420220 A EP 89420220A EP 89420220 A EP89420220 A EP 89420220A EP 0347351 B1 EP0347351 B1 EP 0347351B1
Authority
EP
European Patent Office
Prior art keywords
ladle
injection
gas
process according
steel
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP89420220A
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German (de)
English (en)
French (fr)
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EP0347351A1 (fr
Inventor
Christian Naturel
Philippe Barthélémy
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Savoie Refractaires SA
Vallourec SA
Original Assignee
Savoie Refractaires SA
Vallourec SA
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Publication date
Application filed by Savoie Refractaires SA, Vallourec SA filed Critical Savoie Refractaires SA
Priority to AT89420220T priority Critical patent/ATE78876T1/de
Publication of EP0347351A1 publication Critical patent/EP0347351A1/fr
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Publication of EP0347351B1 publication Critical patent/EP0347351B1/fr
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    • 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
    • C22B9/05—Refining by treating with gases, e.g. gas flushing also refining by means of a material generating gas in situ
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D1/00—Treatment of fused masses in the ladle or the supply runners before casting
    • 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
    • C21C7/072—Treatment with gases

Definitions

  • the method and the device which are the subject of the invention relate to the treatment of the liquid steel in the ladle by means of gas injected from particular insufflation elements judiciously placed in the bottom of the ladle to ensure in particular dehydrogenation, decarburization, renitriding of steels, in particular stainless steels and decantation of the soaking inclusions.
  • the pocket treatment of liquid steels by injection of gas through the pocket bottom or by means of submerged lances has been used industrially for about twenty years with the aim of homogenizing the temperature of the metal, of desulfurizing it on contact slag and rid it of soothing inclusions.
  • the utility certificate FR 2223467 discloses a process for putting into circulation, no longer in a vacuum device but in a pocket, the whole of a cast iron bath pneumatically.
  • the aim of this process is to introduce desulphurizing agents, such as calcium carbide or inoculating graphitizing agents, into the melt itself.
  • desulphurizing agents such as calcium carbide or inoculating graphitizing agents
  • These agents having a density 2 to 3 times lower than that of cast iron impose on the current of central cast iron directed from top to bottom a speed higher than that of the rise of said agents, which imposes a porous ring whose width can reach a quarter of the inside diameter of the pocket, ie three-quarters of the surface of the bottom of the pocket.
  • the object of the present invention is quite different from that sought in FR 2223467 since it is sought in the present invention to multiply the metal gas exchange surfaces while keeping the individuality of each of the small bubbles emitted and their low rate of rise and that one also seeks to concentrate the slag in the center of the upper free surface of the liquid metal so that this slag cannot be entrained within the liquid steel itself.
  • This requires mixing surfaces much smaller than the surfaces indicated above, very specific gas flow rates, precise positioning of the mixing elements and a suitable porosity.
  • the process for treating a liquid steel according to the invention applies to a steel which has been in a first phase produced in the liquid state and then transferred to a ladle.
  • This steel is then treated in this pocket with a very large number of fine bubbles of gas or gas mixture which is injected through the bottom of the pocket from injection elements located at a distance from the center of the latter. at least equal to its half-radius and distant from the wall corresponding to the edge of the bottom of the pocket by a distance at least equal to one tenth of said radius.
  • this gas can consist of a rare gas from the air (most commonly argon) or nitrogen or carbon dioxide or a mixture of the above gases.
  • the injection elements have a surface of between S / 10 and S / 30, S being the surface of the bottom of the bag and the gas injection pressure is adjusted so that the average unit flow rate by cm2 of injection element surface is between 0.1 and 0.8 liters / minute in the case of dehydrogenation treatments, settling of inclusions and nitriding of stainless steels with high nitrogen content.
  • the calorie intake resulting from the combustion of the gas mixture such as argon oxygen or nitrogen oxygen cannot be greater than that resulting from the combustion of 0.1 to 0.6 liters d pure oxygen per minute and per cm2 of surface area of injection elements.
  • the proportion of argon or nitrogen, which varies during the operation, is a function of the carbon content and the temperature and will be adjusted in such a way that the partial pressure PCO obtained makes it possible to have the dissolved oxygen content in equilibrium with slag containing iron oxide in the case of carbon steels or with slag containing chromium oxide in the case of steels with high chromium content.
  • the injection of gas by the injection elements is carried out either through oriented channels or pores whose cross section perpendicular to the gas flow is not more than 0.8 mm2, the total surface of these channels being between 15 and 40 mm2 per dm2 of surface injection elements either through straight or non-rectilinear slits of thickness less than or equal to 0.4 mm separated from each other by a distance preferably between 1 and 3 cm, the total surface of the slits being between 45 and 105 mm2 per dm2 of injection element surface.
  • the injection pressures used corresponding to the above values will be for the channels or pores of the order of at most 4 bars above the ferrostatic pressure at the bottom of the pocket and for the slots of around 1 bar or even 0.5 bar above the ferrostatic pressure at the bottom of the pocket.
  • the injection sites can be distributed generally in an annular or pseudo-annular zone, whether continuous or not.
  • the greatest angular distance which separates these locations seen from the center of the pocket is not more than 30 °.
  • the permeable injection elements are refractory and can be of any shape: cylindrical, conical, pyramidal, parallelipiped or other.
  • they are coated on all their surfaces with the exception of that in contact with the liquid steel with a steel sheet which is connected to the gas inlet tube on the side which, after being placed in the bottom of pocket, look out of it.
  • These permeable elements can be arranged in a removable or fixed manner. Once mounted, they are part of the pocket bottom.
  • the distribution of the treatment gas to all the injection elements can be done for example from a central inlet which may or may not be linked to one of the injection elements.
  • the treatment operations will be carried out in a pocket under a cover allowing the capture of the fumes and the protection of the atmospheric environment and reducing the heat losses.
  • the liquid steel and the slag in the ladle can be reheated during the injection of at least one gas, for example by one or more electric arcs crossing the layer of the liquid slag formed inside the ring d intumescence.
  • the process according to the invention applies in particular to the dehydrogenation of steels thanks to the multiplication of bubble-liquid metal contact surfaces allowing the partial pressures to be balanced between the hydrogen contained in the liquid steel and that admitted in the bubbles.
  • the method according to the invention also allows an acceleration of the agglomeration of solid inclusions, in the case of steels whose deoxidation or denitriding products are solid (alumina or titanium nitride for example), which are very quickly entrained in the slag layer. It is thus possible to lower in a record time the total oxygen content on semi-finished product to around 1.5 times the dissolved oxygen content of the corresponding liquid steel by the sole injection of neutral gas from the bottom.
  • the process according to the invention also applies to the decarburization of steels with very low carbon content, microalloyed or not and in particular those containing less than 0.05% carbon. It also applies to the decarburization of steels with a high content of martensitic chromium or not or austenitic or austenoferritic chromium nickel.
  • the process according to the invention also applies to the nitriding of stainless steels with a high nitrogen content (for example 0.2 to 0.4% by mass) in which the decarburization under low partial pressure of CO is obtained by a mixture oxygen nitrogen and the final content of nitrogen is adjusted after calming and desulfurization of the metal by injection of pure nitrogen.
  • a high nitrogen content for example 0.2 to 0.4% by mass
  • the invention also relates to a pocket allowing the treatment of a liquid steel according to the method of the invention equipped with a pocket bottom comprising injection elements connected to gas supply means whose surface total is between S / 10 and S / 30, S being the surface of the bottom of the pocket, these injection elements being located at a distance from the center of the pocket bottom at least equal to the half-radius and distant from the wall internal pocket of a distance at least equal to a tenth of said radius, these injection elements comprising either pores or channels whose unit cross section is less than 0.8 mm2, the total surface being between 15 and 40 mm2 per dm2 of injection element, ie slots whose thickness is less than 0.4 mm, the total surface being between 45 and 105 mm2 per dm2 of injection elements.
  • FIG. 1 shows a pocket 1 according to the invention which allows the treatment by the method also according to the invention of a volume of liquid steel 2.
  • the bottom 3 of this pocket is provided, as shown in FIGS. 2 and 3, with 4 porous refractory pieces 4, 5, 6, 7 of frustoconical pyramidal shape.
  • the side walls of these parts, such as 8, 9 are coated with a sheet of steel which is connected in leaktight manner at the level of the large base to the gas inlet tube such as 10.
  • These refractory parts are crossed by oriented pores or channels, such as 11 which bring the surface of the large base into communication with that of the small base 12.
  • the small base 12 is at the level of the upper face 13 of the bottom of pocket.
  • the oriented pores 11 have an average diameter of 0.8 mm.
  • Each of the porous refractory pieces is crossed by 500 pores distributed over the surface of the small base which is in the case of the figure 1050 cm2 (100 cm long and 10.5 cm wide).
  • the total surface "SP" of the small bases of the 4 porous parts is therefore 4200 cm2 for a total number "of nt” of pores equal to 2000.
  • the surface "S” of the pocket bottom is 4.9 m2 which corresponds to a radius (R1) of 1.25 m.
  • the SP / S ratio is equal to 0.085 value which lies within the preferential range.
  • the surface of the pores per dm2 is 24 mm2 value also located within the preferential range.
  • the porous refractory pieces are entirely outside the circle of radius R2 corresponding to half of R1, that is 0.625 m and distant by more than R / 10, that is 0.125 meter from the edges of the bottom of the pocket.
  • the largest angular width of an area devoid of pores, seen from the center of the pocket bottom corresponds to the angle " ⁇ " which is equal to 25 °.
  • This angle “ ⁇ ” is less than the maximum angular width of 30 ° of an area devoid of pores of the device according to the invention.
  • the height “H” of liquid steel at rest in the pocket is approximately 2.5 m for a mass of steel "t” of 80 tonnes.
  • annular bulge 14 of height "h" above the level of the steel at rest, which contains the slag 15 in the axial zone and creates a permanent exchange zone of large surface and of great activity with this milkman.
  • the arrows F2 show the movement of the cooler liquid steel with return to the pocket bottom in the axial zone.
  • the low unit flow rate of the pores associated with the large surface area they cover on the bottom of the pocket and their geometric arrangement on said pocket bottom thus makes it possible to obtain a whole set of interesting results for the treatment in the pocket of the steel.
  • the device according to the invention also makes it possible to reheat the liquid steel and the slag by means, for example, of one or more arc heating electrodes, not shown, placed above the liquid steel in the zone close to the 'axis.
  • arc heating electrodes not shown
  • efficient heating is obtained without risk of overheating of the upper zones of the refractory walls of the pocket due to the protection due to the annular bulge 14.
  • the steel is poured through tap hole 17.
  • the ladle thus described can be used in particular for the treatment, by the process according to the invention, of a steel with 13% chromium.
  • a mother steel of the type containing 13% chromium is conventionally produced from scrap, fuel ferro-chromium and the usual additions.
  • This steel is decarburized in the oven to 0.4% carbon then it is poured into a pocket with sufficient guard height, avoiding as much as possible the presence of slag from the oven.
  • the composition of this pocket steel is then:
  • This mother steel is covered with grain lime and a little spar.
  • a significant intumescence is formed on the surface of the steel, permitted by the chosen guard height.
  • the percentage of oxygen by volume is gradually reduced from 80% to approximately 52%, which makes it possible to lower the carbon content to 0.08% without scorification of the chromium thanks to a reduced oxygen activity in the metal. without exceeding the temperature of 1680 ° C.
  • the additional treatments of deoxidation and calming of nuance and settling of the inclusions are then carried out by continuing the injection of argon alone with a flow rate of 10 liters / Ton / min for about 35 minutes.
  • the volume of oxygen injected by the permeable elements is close to 140 m3.
  • the steel is then poured.
  • the chromium yield is 98%.
  • the pocket decarburization at this temperature would not have been possible by a flow of pure oxygen without significant scorification of the chromium which it would have been difficult and costly to reduce during the final deoxidation; moreover, the temperatures obtained would have been higher and would have led to a rapid and dangerous deterioration of the insufflation bricks.
  • the low flow rate of oxygen injected per cm2 of surface of the porous parts, associated with the cooling due to the dilution by argon and the sweeping of the surface of the injection elements by the coolest liquid steel makes it possible to limit and d '' gradually dissipate the heat resulting from the combustion of oxygen on the surface of the insufflation elements.
  • a 60T casting is produced in an electric furnace with an eccentric tap hole of a 100 C 100 type steel with 1.1% carbon and 1.5% chromium from scrap. Poured into a pocket fitted with the injection system according to the invention, this steel with the usual additions and 300 kg of fresh and very dry lime and 30 kg of fluorspar are added.
  • the temperature is 1600 ° C.
  • the bag is transported to a bag processing installation with heating by 3 graphite electrodes so as to obtain a final temperature of 1630 °.
  • the pocket is under cover so that the atmosphere above the liquid steel is free of oxygen and hydrogen coming from the atmosphere.
  • the steel is stirred by a stream of pure argon at a flow rate of 1 Nm3 / min for 1 hour diffused by 4000 cm2 of permeable elements comprising 60 channels of unit cross section 0.5 mm2 per dm2 of surface permeable elements.
  • the analysis of the steel is as follows: the oxygen activity measured is 4 ppm.
  • the steel is then poured into an ingot mold entirely sheltered from the air to avoid any parasitic rehydrogenation and reoxidation reaction.
  • Analysis of the semi-finished product shows a total oxygen content of 6 ppm and a hydrogen content of 3 ppm.
  • the method and the ladle can be applied to the ladle treatment of a very wide variety of steels of all types and all compositions.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Treatment Of Steel In Its Molten State (AREA)
  • Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
  • Physical Or Chemical Processes And Apparatus (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
EP89420220A 1988-06-17 1989-06-15 Procédé de traitement des aciers liquides par injection de gaz à travers le fond de poche Expired - Lifetime EP0347351B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT89420220T ATE78876T1 (de) 1988-06-17 1989-06-15 Verfahren zur behandlung von fluessigen staehlen durch einblasen von gas durch den pfannenboden.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8808479A FR2632971B1 (fr) 1988-06-17 1988-06-17 Procede de traitement des aciers liquides par injection de gaz a travers le fond de poche
FR8808479 1988-06-17

Publications (2)

Publication Number Publication Date
EP0347351A1 EP0347351A1 (fr) 1989-12-20
EP0347351B1 true EP0347351B1 (fr) 1992-07-29

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ID=9367654

Family Applications (1)

Application Number Title Priority Date Filing Date
EP89420220A Expired - Lifetime EP0347351B1 (fr) 1988-06-17 1989-06-15 Procédé de traitement des aciers liquides par injection de gaz à travers le fond de poche

Country Status (7)

Country Link
US (1) US4957542A (https=)
EP (1) EP0347351B1 (https=)
JP (1) JPH0285315A (https=)
AT (1) ATE78876T1 (https=)
DE (1) DE68902283T2 (https=)
ES (1) ES2034727T3 (https=)
FR (1) FR2632971B1 (https=)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT398632B (de) * 1991-07-08 1995-01-25 Veitsch Radex Ag Metallurgisches gefäss
DE19604413C1 (de) * 1996-02-07 1997-05-28 Veitsch Radex Ag Gasspüleinrichtung für metallurgische Gefäße
JP5453751B2 (ja) * 2008-09-19 2014-03-26 Ｊｆｅスチール株式会社 溶鋼精錬用取鍋及び溶鋼の精錬方法
JP7118599B2 (ja) * 2017-04-28 2022-08-16 日本製鉄株式会社 溶鋼の取鍋精錬方法
JP6822304B2 (ja) * 2017-04-28 2021-01-27 日本製鉄株式会社 溶鋼の取鍋精錬方法
EP3537317B1 (en) * 2018-03-09 2022-11-16 Tata Consultancy Services Limited System and method for determination of air entrapment in ladles
CN110523966A (zh) * 2019-09-25 2019-12-03 张家港广大特材股份有限公司 一种钢包双透气芯

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE555593A (https=) *
US2826494A (en) * 1955-12-27 1958-03-11 Ohio Commw Eng Co Process for making alloys
BE735159A (https=) * 1969-06-25 1969-12-29
FR2223467A1 (en) * 1973-03-29 1974-10-25 Beatrice Foods Co Molten metal bath stirring appts - using gas introduced at the bottom of the vessel
FR2473064A1 (fr) * 1980-01-02 1981-07-10 Siderurgie Fse Inst Rech Procede de brassage pneumatique d'un bain de metal en fusion
LU82069A1 (fr) * 1980-01-09 1981-09-10 Arbed Procede d'affinage d'un bain de metal
DE3426736A1 (de) * 1984-07-20 1986-01-30 Klöckner CRA Technologie GmbH, 4100 Duisburg Verfahren zur spuelgasbehandlung von metallschmelzen
GB2169316B (en) * 1984-12-28 1988-05-11 United Engineering Steels Ltd Improvements in or relating to the treatment of molten metal

Also Published As

Publication number Publication date
JPH0420965B2 (https=) 1992-04-07
EP0347351A1 (fr) 1989-12-20
DE68902283T2 (de) 1993-03-11
US4957542A (en) 1990-09-18
FR2632971A1 (fr) 1989-12-22
JPH0285315A (ja) 1990-03-26
ES2034727T3 (es) 1993-04-01
ATE78876T1 (de) 1992-08-15
FR2632971B1 (fr) 1993-09-03
DE68902283D1 (de) 1992-09-03

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