CA1150057A - Method of making steel from solid ferrous metal charges - Google Patents
Method of making steel from solid ferrous metal chargesInfo
- Publication number
- CA1150057A CA1150057A CA000361173A CA361173A CA1150057A CA 1150057 A CA1150057 A CA 1150057A CA 000361173 A CA000361173 A CA 000361173A CA 361173 A CA361173 A CA 361173A CA 1150057 A CA1150057 A CA 1150057A
- Authority
- CA
- Canada
- Prior art keywords
- converter
- steel
- set forth
- slag
- adjusted
- 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
Links
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
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/56—Manufacture of steel by other methods
- C21C5/562—Manufacture of steel by other methods starting from scrap
-
- 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
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/28—Manufacture of steel in the converter
-
- 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
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/28—Manufacture of steel in the converter
- C21C5/30—Regulating or controlling the blowing
- C21C5/35—Blowing from above and through the bath
-
- 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
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/52—Manufacture of steel in electric furnaces
- C21C5/527—Charging of the electric furnace
- C21C2005/5276—Charging of the electric furnace with liquid or solid rest, e.g. pool, "sumpf"
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Carbon Steel Or Casting Steel Manufacturing (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
This invention relates to a method of making steel from solid ferrous metal charges in a converter which is provided both with means for blowing oxygen onto the top of the melt surface and with means for injecting carbonaceous fuels beneath the surface of the melt. The method consists in producing in the converter from between 10% - 30% more molten steel than is required for a desired quantity of steel which is to be tapped from the converter and then, following such tapping of the desired steel quantity, the surplus amount of molten steel which has been produced in the converter is drained into another, separate vessel which acts as an auxiliary or holding ladle.
This invention relates to a method of making steel from solid ferrous metal charges in a converter which is provided both with means for blowing oxygen onto the top of the melt surface and with means for injecting carbonaceous fuels beneath the surface of the melt. The method consists in producing in the converter from between 10% - 30% more molten steel than is required for a desired quantity of steel which is to be tapped from the converter and then, following such tapping of the desired steel quantity, the surplus amount of molten steel which has been produced in the converter is drained into another, separate vessel which acts as an auxiliary or holding ladle.
Description
This invention relates to a method of mal;in~ steel from solid ferrous metal charges~ particularly scrap iron, solid pig iron9 ferrous pellets, iron spon~e, or any mi~ture of these, in a through-blo~n converter which is provided with means for blowing o ygen at the top of the surface of the melt and with means for injectin~ carbonaceous fuels beneath the surface of tlle melt.
The production of steel from scrap metal ~ithout using molten pig iron is nowadays frequently carried out in electric arc ~urnaces but the economic viability of this method depends very largely on current electrical energy costs. By comparison ~ith an electric arc furnace~ the conventional converter method where o~ygen is blo~n on top of, or through the melt, is faster and cheaper. Mo~ever~
for making steel in a converter it has hitherto been necessary to use liquid pig iron to which iron scrap is added at an appropriate rate in relation l~rith its composition as a cooling agent in the course of the refining process. Normally the scrap proportion will amount up to 30,S of the steel ~eight.
~ :`
rrhere are however kno~n methods of producing steel in a converter which per~it the abo~e~mentioned scrap ercen-tage being increased. The requisite heat is applied to the melt by preheating the scrap and by injecting carbonaceous ~uels into the melt. The thermal efficiency of these fuels essentially determines the cost efficiency of th s ty~e of process.
German Patents 50S 966 and 537 7t31, respective dating back as far as tne years 1924 and 1929, already describe a method of smelting ore in a converter wherein coal dust and o~ygen? or o~ygcn-enriclled air, are introduced into the melt. ~videntl the introduction o~
the fuels and the transmission of the required a~ount of heat to the melt ~roved difficult because the patent of -~ 57 addition No. 537 781 suggests that the process according to Patent 508 966 be undertaken in an electrically heated converter.
U.S. Patent No. 41 95,985 relating to a method of applying heat in steel making in a converter describes a con-venient mode of working aimed at enabling the scrap percentage in the converter to be increased as may be desired so as ultimate-ly to produce a steel melt solely from a solid ferrous charge.
However, according to the method proposed in this patent applica-tion the scrap is introduced into the converter and preheated for approximately 10 minutes. During this preheating phase ; oxygen tuyeres in the converter bottom operate as burners. After preheating, molten pig may be added to the converter charge, or else the work may be continued without an addition of such pig iron. ~s soon as a melt has formed in the converter, ground carbonaceous fuel, mainly coke or coke dust, and oxygen are `injected through the tuyeres beneath the surface level of the -` melt, the injected jet of fuel being sheathed in a protective envelope of hydrocarbon gas medium. At the same time about the same amount of oxygen as that which is injected beneath the 2Q melt surface is blown in a downwardly directed stream through s ~
the free converter space on to the top of the melt surface.
In the practical application of this method it was found that i~f the molten pig iron percentage relative to steel weight is reduced substantially, even to the extent of using exclusively solid ferrous charges, the melting down time required for the solid charge tends to grow disproportionately longer. This entails a corresponding prolongation of charge-sequence time. Furthermore, energy consumption fluctuates in the melting phase and mean energy consumption is higher. Con-sequently it is evident that this known method cannot be applied as reliably and economically without liquid pig addition as with a minimum addition of molten pig to each charge. A longer charge cycle must be ex-pected and there are fluctuations in thermal efficiency of the fuels which are used in the scrap-melting phase.
It is the aim of the present invention to provide a steel-making method whereby steel can be reliably produced from solid ferrous charges without an addition of molten pig iron but with a high degree of energy economy, that is to say, at the same kind of energyconsumption rate as normal when using a mini-mum liquid pig iron charge addition, in relatively quick charge cycles and therefore in a more cost efficient way than hereto-fore possible.
Accordingly, the present invention provides a method for producing steel from solid, iron containing metallic pieces in a blown oxygen converter equipped with submerged injection devices for oxygen and pulverized fuel, said method comprising the steps of: introducing a charge of solid, iron containing metallic pieces into a said converter. preheating said charge;
contacting said preheated charge in said converter with a quan-tity of molten steel to produce a batch; smelting said batch for a sufficient period of time to fuse the entire batch and convert the same into a steel product; tapping a first portion of said steel product from the converter for further processing; tapping a second portion of said steel product from the converter and retaining the same separately from said converter; and subse-quently reintroducing said retained second portion of steel pro-duct into the converter and using the same as said quantity of molten steel during said contacting step, said second portion and therefore said quantity of molten steel being of sufficient size to substantially reduce the length of said smelting time period.
In one example of carrying out a method in accordance with the invention use may be made of a through-blown converter ~ _ ~,`.i,~
such as is described in U.S. Patent No. 4,195,985. This conver-ter has oxygen-injecting tuyeres disposed beneath the surface level of the melt through which oxygen-containing fining agents, preferably conventional oxygen, hydrocarbon-sheathed for tuyere protection, can be injected into the melt. At the same time the converter is provided with oxygen injection means above the sur-face level of the melt through which oxygen can be directed at the top surface of the melt. These oxygen injection means may be jet nozzles or tuyeres, or they may be water-cooled lances of conventional kind. Between 20~ and 80~ of the total amount of oxygen is supplied from above by one or more nozzles or tu-yeres which throughout a ,.
- 4a -5~7 substantial part of the fining process operate as iree jets blowing into a gas-containing space. lhe converter is further provided wi-th jet no~les for injectin~ carbon-containing fuels below the melt surface. Suitable fuels for this purpose are cole~ lignite coke, graphite, various quality coal and mi~tures of these.
The solid ferrous metal char~es, particularl~ scrap iron, solid pig iron, pellets, iron sponge or any mixture of these are initially preiheated in the above described converter. During this preheating phase, the tuyeres benea-th the melt surface are operated as burners, ~uelled by liquid and/or gaseous hydrocarbons, preferably natural ~as or oil.
Surprisin~ly it ~ras found that the melting do~m time and the thermal efficiency of the a~lied fuels ~`or melting the scrap remain approximately constant with an increase of the char~e amount of solid ferrous metals in a 30 tonne converter up to 30,~ of the melt~ in a 60 tonne converter up to approximately 20~' o~ thc melt and in a 200 tonne converter up to about 10,' of the melt.
Ilith lOOC~ solid charges (e g. scrap iron) ~elting do time, that is to say, the tim_ followin~ the ~reheatinO
phase until a melt is for~ed in the re~ion of the jets at the converter bottom, is prolon~ed more than had been e~pected and effective use of the energy of applied ~uels fluctuates rather widely during this phase, bein, on a~rerage lo~ter tllan in co~arative ~elts containin~ a liquid cllarge percenta2e. Probably an e-i~lanation of this e~tended meltin~ c'o~m phase and ttle artlr increased energ-~r consumption ~then wor.;ing ~itnout a liquid char e addition consists in that the transition fro~l prelleated scrap to a liquid sum? of ade~uate volurle ~;herein tile carbon-containin~ fue7s can be disscl;ed and burnt to ~a~e C0 and liber2te heat~ tends to ~-ary o~rin~r to the relatively ~; c'el~
fluctuatin~ operative condl-tiolls in tihis process ~llase.
~.~5~D~57 Varyin~ operative conditions ma~ be caused, for e~am~le, by different lcinds of scrap, the ?acl~ing in the converter~ the de~ree of o~idation achieved in the preheatin~ phase of the solid charge and the resultin~ modification in heat transmission. `~Ioreover~ fluctuations must be e~pected durin~ meltin~ down and in the initial formation of the melt in the converter, and its position relative to the tuyeres.
~ Io~Yever, according to the present invention, from lOp to 30~'~ more steel is produced in the specified ConVQrter than the desired tap~ing weight, i.e. the al~ount of steel desi~nated for further proccssing in the steelworl;s For e~ample, approcimately 120 tonnos of st~el are re~ined in a 100 tonne converter but only 100 tonnes of this melt are tapped off for further processin~.
~ fter the main melt has been tapped off~ the additionally ~roducccl ~uan1;ity of steel, amountin~ to 10',' - 30Co of the convorter contents~ i9 dra:ined into a holding vessel, e.~. a suitable ladle acting as a holcling or au~iliary ladle9 In this holding ladle the steel is held for a certain time and then added to tlle ne~.t rnelt after the ~reheating phase of tne ne~t soli~ c~arg~e.
It is important ~or the pra~tical application as ~rell as from the point of view of an econor~icall~ efficient modus operandl of the new process that the liquid steel wllich i9 intended to be used in the ne.:t char~e be drained from tlle converter and re-introduction aftcr the scra~p iron o~ tllc neJt charO~e ~as been char~ed and preheatecl in tile converterO
Leavin~ a resiclual amount of molten stesl inside the ccnverter would en-tail tlro vi-tal dra~rbaclcs: a re~aincler of liquid steel in the converter makes it ~mpossible to ~reheat the ne~s o]lo~rin~ sol:d scrap iron cha ~e b~r me-ans of the b-lrncrs in the con~erter bottom. ln t~at case ~t least vwice tlle amount OL liquid stoel wou~cl be needed as ~5~57 compared with what is recuired wnen operatlng with preheated scrap char~es. Furthermore, it is alwavs ha~arclous to adcl a scrap iron charge to a steel melt~ especiall~J ~hen therc is a lar~e quantity of thc latter, becaus~ normally the operation of introducin~ the solid scrap into the converter involves manipulations at the converter and also because additional reactions may then occur bet~een the scrap ancl the molten steel.
The molten steel remainder which is to be recycled in the converter, i.e. the additional lG~ of 30'o of steel ~lich were overproduced in the precedin~ charge cycle, mav be re-carbonised to achieve a carbon contcnt wllich is higher tllan l~ot preferably bet~een 2Co and 3~ hilst such carbllrisation ent~ils coolin~ of the steel in the holding ladle~ the lo~erin~ of free~ temperature for the hlgller carbon melt on the other hand reduces tihe risl; of the molten remainder in tlle holding ladle Pree~in~ partiall~,~
~hsn comin~ into contact with the solid scrap iron on bein~ re-char~ed into the convertor, In the final result the injection of o~:~gen~ with the consequent combus-tion o~
the carbon contained in the melt~ produces energ~ ~ich contributes to the desired fast heating up of the sump in the converter and increases the amount of li~uid melt in the converter.
ln order to achieve optimum thermal efficiency in the preheating of the solid ferrous metal charge in the converter it is desirable that no residual amount of s~eel should remain in the converter at tne end of a charge c~cle.
I-Io~ever, if thc steel is drained completel~,~ from the convarter a certain amount oi molten slag ~ill inevitabl~;
be carried alon~ with it. Therefore there is a rlsl; of uncontrolled rcactlons betueen this sla~ hich is rich in lron o~ides and the carburised stcel in tlle holding ladle.
For this reason, according to tlle present invent on, i7 deo;idising agents, e.g. silicon, in percentages rznging from 0.1 to 1.5,~ are preferably added to the residual melt and this largely suppresses such undesirable slag/steel reactions.
It is found particularly economical to acld carbon, either ~holly or partly, to the resiclual amount of molten steel while this i9 still in the converter and before it is tapped into the holding ladle. Recarburization is thus easily achievecl by the injection of carbon-containing fuels in finely ground form, e.g. coke, through the e.{isting bottom tuyeres.
.
Rccarburization of the residual melt in the eonverter has speeial advantagcs when the stcel is rcfined by application of the so-callod two-slag process. Accordin~
to this t~ro-slag process, the first slag is dra~n off as completely as possible after the main refining periocl.
This is the slag which contains the major part of those elements which are to be removed in the course of the refining process~ sucll as phosphorous and sulphur. During the after-blowing, or finishing phase a second slag is ~ormed in the converter with an iron-o~ide content which is nor~ally be-tween 1~-, and 20c,:,. If no~ carbon is inJected into the residual amount of steel which is to be recycled in the ne~t char~e of the converter~ this will at the same time reduce the iron oxide content of this secondary sla~
l~lich is still contained inside the converter. The sla~
becomes viscous and crumbl~ or friable, ancd can in this condltion be more easily held bacl inside tha converter ~;hen the remaincl0r o~ the steel is tap~ed off into the holdin~ ladle. This sla~ is le~t in the converter as a source ol lime for the ne t .mel-t. This method also cuts clo~n on lime consum~tion lJilil S t a~ the sama time improving thermal efficiency inasmuch as there is less lime to be lleated u~ a 4 the be.gillning of the crcle~ It was ~urther found that such partly crumbly slag consistency improves thermal efficiency of the system as a ~hole in the preheating phase by comparison with a molten slag.
Probably this is due to the fact that liquid slag tends to free~e more readily on coming into contact Wit;l the solid metallic charge, e.g. scra~ iron, and thus detracts ~rom a ready heat e~change. Besides~ as already mentioned, it is very difficult to drain the residual amount of steel completely from the converter ~.hile the sla~ has a thinly liquid consistency. On the other hand3 residual amounts of steel inside the converter clearly entail a deterioration in thermal efficiency of applied fuels during the proheat~n~
~hase as previously mentioned.
It is fully within the scope of this invention to adapt its essential characteristic aspects, namoly tho recyclin~
of a residual amount of suxplus molten steol in the ne~t charge~ to tlle speci~ic operative parameters of different steelworl;s. This eovers varlations within ver~ id~ limits in respect o~ the quan-tit~ of re-cyeled steel, time of addition and allo~ing percentages, partic~larly in regard to carbon and silicon, ~hilst maintaining the basic inventive principle of producing steel ~ithout tne aid of molten plg iron.
~ . . .
The production of steel from scrap metal ~ithout using molten pig iron is nowadays frequently carried out in electric arc ~urnaces but the economic viability of this method depends very largely on current electrical energy costs. By comparison ~ith an electric arc furnace~ the conventional converter method where o~ygen is blo~n on top of, or through the melt, is faster and cheaper. Mo~ever~
for making steel in a converter it has hitherto been necessary to use liquid pig iron to which iron scrap is added at an appropriate rate in relation l~rith its composition as a cooling agent in the course of the refining process. Normally the scrap proportion will amount up to 30,S of the steel ~eight.
~ :`
rrhere are however kno~n methods of producing steel in a converter which per~it the abo~e~mentioned scrap ercen-tage being increased. The requisite heat is applied to the melt by preheating the scrap and by injecting carbonaceous ~uels into the melt. The thermal efficiency of these fuels essentially determines the cost efficiency of th s ty~e of process.
German Patents 50S 966 and 537 7t31, respective dating back as far as tne years 1924 and 1929, already describe a method of smelting ore in a converter wherein coal dust and o~ygen? or o~ygcn-enriclled air, are introduced into the melt. ~videntl the introduction o~
the fuels and the transmission of the required a~ount of heat to the melt ~roved difficult because the patent of -~ 57 addition No. 537 781 suggests that the process according to Patent 508 966 be undertaken in an electrically heated converter.
U.S. Patent No. 41 95,985 relating to a method of applying heat in steel making in a converter describes a con-venient mode of working aimed at enabling the scrap percentage in the converter to be increased as may be desired so as ultimate-ly to produce a steel melt solely from a solid ferrous charge.
However, according to the method proposed in this patent applica-tion the scrap is introduced into the converter and preheated for approximately 10 minutes. During this preheating phase ; oxygen tuyeres in the converter bottom operate as burners. After preheating, molten pig may be added to the converter charge, or else the work may be continued without an addition of such pig iron. ~s soon as a melt has formed in the converter, ground carbonaceous fuel, mainly coke or coke dust, and oxygen are `injected through the tuyeres beneath the surface level of the -` melt, the injected jet of fuel being sheathed in a protective envelope of hydrocarbon gas medium. At the same time about the same amount of oxygen as that which is injected beneath the 2Q melt surface is blown in a downwardly directed stream through s ~
the free converter space on to the top of the melt surface.
In the practical application of this method it was found that i~f the molten pig iron percentage relative to steel weight is reduced substantially, even to the extent of using exclusively solid ferrous charges, the melting down time required for the solid charge tends to grow disproportionately longer. This entails a corresponding prolongation of charge-sequence time. Furthermore, energy consumption fluctuates in the melting phase and mean energy consumption is higher. Con-sequently it is evident that this known method cannot be applied as reliably and economically without liquid pig addition as with a minimum addition of molten pig to each charge. A longer charge cycle must be ex-pected and there are fluctuations in thermal efficiency of the fuels which are used in the scrap-melting phase.
It is the aim of the present invention to provide a steel-making method whereby steel can be reliably produced from solid ferrous charges without an addition of molten pig iron but with a high degree of energy economy, that is to say, at the same kind of energyconsumption rate as normal when using a mini-mum liquid pig iron charge addition, in relatively quick charge cycles and therefore in a more cost efficient way than hereto-fore possible.
Accordingly, the present invention provides a method for producing steel from solid, iron containing metallic pieces in a blown oxygen converter equipped with submerged injection devices for oxygen and pulverized fuel, said method comprising the steps of: introducing a charge of solid, iron containing metallic pieces into a said converter. preheating said charge;
contacting said preheated charge in said converter with a quan-tity of molten steel to produce a batch; smelting said batch for a sufficient period of time to fuse the entire batch and convert the same into a steel product; tapping a first portion of said steel product from the converter for further processing; tapping a second portion of said steel product from the converter and retaining the same separately from said converter; and subse-quently reintroducing said retained second portion of steel pro-duct into the converter and using the same as said quantity of molten steel during said contacting step, said second portion and therefore said quantity of molten steel being of sufficient size to substantially reduce the length of said smelting time period.
In one example of carrying out a method in accordance with the invention use may be made of a through-blown converter ~ _ ~,`.i,~
such as is described in U.S. Patent No. 4,195,985. This conver-ter has oxygen-injecting tuyeres disposed beneath the surface level of the melt through which oxygen-containing fining agents, preferably conventional oxygen, hydrocarbon-sheathed for tuyere protection, can be injected into the melt. At the same time the converter is provided with oxygen injection means above the sur-face level of the melt through which oxygen can be directed at the top surface of the melt. These oxygen injection means may be jet nozzles or tuyeres, or they may be water-cooled lances of conventional kind. Between 20~ and 80~ of the total amount of oxygen is supplied from above by one or more nozzles or tu-yeres which throughout a ,.
- 4a -5~7 substantial part of the fining process operate as iree jets blowing into a gas-containing space. lhe converter is further provided wi-th jet no~les for injectin~ carbon-containing fuels below the melt surface. Suitable fuels for this purpose are cole~ lignite coke, graphite, various quality coal and mi~tures of these.
The solid ferrous metal char~es, particularl~ scrap iron, solid pig iron, pellets, iron sponge or any mixture of these are initially preiheated in the above described converter. During this preheating phase, the tuyeres benea-th the melt surface are operated as burners, ~uelled by liquid and/or gaseous hydrocarbons, preferably natural ~as or oil.
Surprisin~ly it ~ras found that the melting do~m time and the thermal efficiency of the a~lied fuels ~`or melting the scrap remain approximately constant with an increase of the char~e amount of solid ferrous metals in a 30 tonne converter up to 30,~ of the melt~ in a 60 tonne converter up to approximately 20~' o~ thc melt and in a 200 tonne converter up to about 10,' of the melt.
Ilith lOOC~ solid charges (e g. scrap iron) ~elting do time, that is to say, the tim_ followin~ the ~reheatinO
phase until a melt is for~ed in the re~ion of the jets at the converter bottom, is prolon~ed more than had been e~pected and effective use of the energy of applied ~uels fluctuates rather widely during this phase, bein, on a~rerage lo~ter tllan in co~arative ~elts containin~ a liquid cllarge percenta2e. Probably an e-i~lanation of this e~tended meltin~ c'o~m phase and ttle artlr increased energ-~r consumption ~then wor.;ing ~itnout a liquid char e addition consists in that the transition fro~l prelleated scrap to a liquid sum? of ade~uate volurle ~;herein tile carbon-containin~ fue7s can be disscl;ed and burnt to ~a~e C0 and liber2te heat~ tends to ~-ary o~rin~r to the relatively ~; c'el~
fluctuatin~ operative condl-tiolls in tihis process ~llase.
~.~5~D~57 Varyin~ operative conditions ma~ be caused, for e~am~le, by different lcinds of scrap, the ?acl~ing in the converter~ the de~ree of o~idation achieved in the preheatin~ phase of the solid charge and the resultin~ modification in heat transmission. `~Ioreover~ fluctuations must be e~pected durin~ meltin~ down and in the initial formation of the melt in the converter, and its position relative to the tuyeres.
~ Io~Yever, according to the present invention, from lOp to 30~'~ more steel is produced in the specified ConVQrter than the desired tap~ing weight, i.e. the al~ount of steel desi~nated for further proccssing in the steelworl;s For e~ample, approcimately 120 tonnos of st~el are re~ined in a 100 tonne converter but only 100 tonnes of this melt are tapped off for further processin~.
~ fter the main melt has been tapped off~ the additionally ~roducccl ~uan1;ity of steel, amountin~ to 10',' - 30Co of the convorter contents~ i9 dra:ined into a holding vessel, e.~. a suitable ladle acting as a holcling or au~iliary ladle9 In this holding ladle the steel is held for a certain time and then added to tlle ne~.t rnelt after the ~reheating phase of tne ne~t soli~ c~arg~e.
It is important ~or the pra~tical application as ~rell as from the point of view of an econor~icall~ efficient modus operandl of the new process that the liquid steel wllich i9 intended to be used in the ne.:t char~e be drained from tlle converter and re-introduction aftcr the scra~p iron o~ tllc neJt charO~e ~as been char~ed and preheatecl in tile converterO
Leavin~ a resiclual amount of molten stesl inside the ccnverter would en-tail tlro vi-tal dra~rbaclcs: a re~aincler of liquid steel in the converter makes it ~mpossible to ~reheat the ne~s o]lo~rin~ sol:d scrap iron cha ~e b~r me-ans of the b-lrncrs in the con~erter bottom. ln t~at case ~t least vwice tlle amount OL liquid stoel wou~cl be needed as ~5~57 compared with what is recuired wnen operatlng with preheated scrap char~es. Furthermore, it is alwavs ha~arclous to adcl a scrap iron charge to a steel melt~ especiall~J ~hen therc is a lar~e quantity of thc latter, becaus~ normally the operation of introducin~ the solid scrap into the converter involves manipulations at the converter and also because additional reactions may then occur bet~een the scrap ancl the molten steel.
The molten steel remainder which is to be recycled in the converter, i.e. the additional lG~ of 30'o of steel ~lich were overproduced in the precedin~ charge cycle, mav be re-carbonised to achieve a carbon contcnt wllich is higher tllan l~ot preferably bet~een 2Co and 3~ hilst such carbllrisation ent~ils coolin~ of the steel in the holding ladle~ the lo~erin~ of free~ temperature for the hlgller carbon melt on the other hand reduces tihe risl; of the molten remainder in tlle holding ladle Pree~in~ partiall~,~
~hsn comin~ into contact with the solid scrap iron on bein~ re-char~ed into the convertor, In the final result the injection of o~:~gen~ with the consequent combus-tion o~
the carbon contained in the melt~ produces energ~ ~ich contributes to the desired fast heating up of the sump in the converter and increases the amount of li~uid melt in the converter.
ln order to achieve optimum thermal efficiency in the preheating of the solid ferrous metal charge in the converter it is desirable that no residual amount of s~eel should remain in the converter at tne end of a charge c~cle.
I-Io~ever, if thc steel is drained completel~,~ from the convarter a certain amount oi molten slag ~ill inevitabl~;
be carried alon~ with it. Therefore there is a rlsl; of uncontrolled rcactlons betueen this sla~ hich is rich in lron o~ides and the carburised stcel in tlle holding ladle.
For this reason, according to tlle present invent on, i7 deo;idising agents, e.g. silicon, in percentages rznging from 0.1 to 1.5,~ are preferably added to the residual melt and this largely suppresses such undesirable slag/steel reactions.
It is found particularly economical to acld carbon, either ~holly or partly, to the resiclual amount of molten steel while this i9 still in the converter and before it is tapped into the holding ladle. Recarburization is thus easily achievecl by the injection of carbon-containing fuels in finely ground form, e.g. coke, through the e.{isting bottom tuyeres.
.
Rccarburization of the residual melt in the eonverter has speeial advantagcs when the stcel is rcfined by application of the so-callod two-slag process. Accordin~
to this t~ro-slag process, the first slag is dra~n off as completely as possible after the main refining periocl.
This is the slag which contains the major part of those elements which are to be removed in the course of the refining process~ sucll as phosphorous and sulphur. During the after-blowing, or finishing phase a second slag is ~ormed in the converter with an iron-o~ide content which is nor~ally be-tween 1~-, and 20c,:,. If no~ carbon is inJected into the residual amount of steel which is to be recycled in the ne~t char~e of the converter~ this will at the same time reduce the iron oxide content of this secondary sla~
l~lich is still contained inside the converter. The sla~
becomes viscous and crumbl~ or friable, ancd can in this condltion be more easily held bacl inside tha converter ~;hen the remaincl0r o~ the steel is tap~ed off into the holdin~ ladle. This sla~ is le~t in the converter as a source ol lime for the ne t .mel-t. This method also cuts clo~n on lime consum~tion lJilil S t a~ the sama time improving thermal efficiency inasmuch as there is less lime to be lleated u~ a 4 the be.gillning of the crcle~ It was ~urther found that such partly crumbly slag consistency improves thermal efficiency of the system as a ~hole in the preheating phase by comparison with a molten slag.
Probably this is due to the fact that liquid slag tends to free~e more readily on coming into contact Wit;l the solid metallic charge, e.g. scra~ iron, and thus detracts ~rom a ready heat e~change. Besides~ as already mentioned, it is very difficult to drain the residual amount of steel completely from the converter ~.hile the sla~ has a thinly liquid consistency. On the other hand3 residual amounts of steel inside the converter clearly entail a deterioration in thermal efficiency of applied fuels during the proheat~n~
~hase as previously mentioned.
It is fully within the scope of this invention to adapt its essential characteristic aspects, namoly tho recyclin~
of a residual amount of suxplus molten steol in the ne~t charge~ to tlle speci~ic operative parameters of different steelworl;s. This eovers varlations within ver~ id~ limits in respect o~ the quan-tit~ of re-cyeled steel, time of addition and allo~ing percentages, partic~larly in regard to carbon and silicon, ~hilst maintaining the basic inventive principle of producing steel ~ithout tne aid of molten plg iron.
~ . . .
Claims (15)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for producing steel from solid, iron containing metallic pieces in a blown oxygen converter equip-ped with submerged injection devices for oxygen and pulverized fuel, said method comprising the steps of: introducing a charge of solid, iron containing metallic pieces into a said converter;
preheating said charge; contacting said preheated charge in said converter with a quantity of molten steel to produce a batch;
smelting said batch for a sufficient period of time to fuse the entire batch and convert the same into a steel product; tap-ping a first portion of said steel product from the converter for further processing; tapping a second portion of said steel product from the converter and retaining the same separately from said converter; and subsequently reintroducing said retain-ed second portion of steel product into the converter and using the same as said quantity of molten steel during said contacting step, said second portion and therefore said quantity of molten steel being of sufficient size to substantially reduce the length of said smelting time period.
preheating said charge; contacting said preheated charge in said converter with a quantity of molten steel to produce a batch;
smelting said batch for a sufficient period of time to fuse the entire batch and convert the same into a steel product; tap-ping a first portion of said steel product from the converter for further processing; tapping a second portion of said steel product from the converter and retaining the same separately from said converter; and subsequently reintroducing said retain-ed second portion of steel product into the converter and using the same as said quantity of molten steel during said contacting step, said second portion and therefore said quantity of molten steel being of sufficient size to substantially reduce the length of said smelting time period.
2. A method as set forth in claim 1, wherein the size of said second tapped portion of steel product is 10 to 30 of the size of said first tapped portion of steel product.
3. A method as set forth in claim 1, wherein said second portion of steel product is recarburized prior to the re-introduction thereof into the converter.
4. A method as set forth in claim 3, wherein said second portion is recarburized in the converter before the same has been tapped therefrom but after said first portion has been tapped for further processing.
5. A method as set forth in claim 1, wherein the bulk of the slag is removed from said converter prior to the tapping of said second portion.
6. A method as set forth in claim 3, wherein the bulk of the slag is removed from said converter prior to the tapping of said second portion.
7. A method as set forth in claim 4, wherein the bulk of the slag is removed from said converter prior to the tapping of said second portion.
8. A method as set forth in claim 3, wherein the de-oxidizer content of said second portion is adjusted sufficiently to suppress undesirable reactions between slag and recarburized steel.
9. A method as set forth in claim 4, wherein the de-oxidizer content of said second portion is adjusted sufficiently to suppress undesirable reaction between slag and recarburized steel.
10. A method as set forth in claim 6, wherein the de-oxidizer content of said second portion is adjusted sufficient-ly to suppress undesirable reaction between slag and recarburiz-ed steel.
11. A method as set forth in claim 7, wherein the de-oxidizer content of said second portion is adjusted sufficient-ly to suppress undesirable reaction between slag and recarbur-ized steel.
12. A method as set forth in claim 8, wherein said de-oxidizer is silicon and the content thereof is adjusted to be-tween 0.1 and 1.5% of said second portion.
13. A method as set forth in claim 9, wherein said de-oxidizer is silicon and the content thereof is adjusted to be-tween 0.1 and 1.5% of said second portion.
14. A method as set forth in claim 10, wherein said deoxidizer is silicon and the content thereof is adjusted to be-tween 0.1 and 1.5% of said second portion.
15. A method as set forth in claim 11, wherein said deoxidizer is silicon and the content thereof is adjusted to between 0.1 and 1.5% of said second portion.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE2939859A DE2939859C2 (en) | 1979-10-02 | 1979-10-02 | Steel making process |
| DEP2939859.2-24 | 1979-10-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1150057A true CA1150057A (en) | 1983-07-19 |
Family
ID=6082450
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000361173A Expired CA1150057A (en) | 1979-10-02 | 1980-09-29 | Method of making steel from solid ferrous metal charges |
Country Status (21)
| Country | Link |
|---|---|
| JP (1) | JPS6034605B2 (en) |
| AR (1) | AR222716A1 (en) |
| AT (1) | AT384241B (en) |
| AU (1) | AU535449B2 (en) |
| BE (1) | BE885490A (en) |
| BR (1) | BR8006314A (en) |
| CA (1) | CA1150057A (en) |
| CS (1) | CS270404B2 (en) |
| DE (1) | DE2939859C2 (en) |
| ES (1) | ES495340A0 (en) |
| FR (1) | FR2466509A1 (en) |
| GB (1) | GB2059997B (en) |
| HU (1) | HU178901B (en) |
| IT (1) | IT1132903B (en) |
| LU (1) | LU82813A1 (en) |
| MX (1) | MX155004A (en) |
| NL (1) | NL8004569A (en) |
| PL (1) | PL124716B1 (en) |
| SE (1) | SE448553B (en) |
| SU (1) | SU1009279A3 (en) |
| ZA (1) | ZA805219B (en) |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4433727A (en) * | 1981-06-19 | 1984-02-28 | Marathon Oil Company | Oil recovery process |
| DE3226590C1 (en) * | 1982-07-16 | 1983-11-24 | Klöckner-Werke AG, 4100 Duisburg | Process for the production of steel from solid, metallic iron supports |
| US4557758A (en) * | 1982-12-16 | 1985-12-10 | Mizin Vladimir G | Steelmaking process |
| DE3316367A1 (en) * | 1983-05-05 | 1984-11-08 | Mannesmann AG, 4000 Düsseldorf | METHOD AND DEVICE FOR PRODUCING STEEL |
| JPS60174812A (en) * | 1984-02-16 | 1985-09-09 | Kawasaki Steel Corp | Converter steel making method using large amount of ferrous cold charge |
| JPS6227514A (en) * | 1985-07-30 | 1987-02-05 | Nippon Steel Corp | Melt-reduction refining method for oxide |
| DE3607777A1 (en) * | 1986-03-08 | 1987-09-17 | Kloeckner Cra Tech | METHOD FOR PRODUCING STEEL FROM SCRAP |
| DE3743380A1 (en) * | 1987-12-21 | 1989-07-06 | N Proizv Ob Tulatschermet | METHOD FOR MELTING STEEL IN AN OXYGEN BLOW CONVERTER |
| DE4215858C2 (en) * | 1992-05-14 | 1995-09-14 | Metallgesellschaft Ag | Method and device for the production of molten steel |
| DE4343957C2 (en) * | 1993-12-22 | 1997-03-20 | Tech Resources Pty Ltd | Converter process for the production of iron |
| DE4434369C2 (en) * | 1994-09-15 | 1997-08-07 | Mannesmann Ag | Method and device for the metallurgical treatment of iron |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| BE794178A (en) * | 1972-02-02 | 1973-05-16 | Centre Rech Metallurgique | PROCESS FOR TREATMENT OF FERROUS MACHINERY |
| SE447911B (en) * | 1977-05-04 | 1986-12-22 | Maximilianshuette Eisenwerk | SET FOR MANUFACTURE OF STEEL IN CONVERTERS |
| DE2755165B2 (en) * | 1977-12-10 | 1980-09-18 | Eisenwerk-Gesellschaft Maximilianshuette Mbh, 8458 Sulzbach-Rosenberg | Method of increasing the scrap rate in steelmaking |
| US4195985A (en) * | 1977-12-10 | 1980-04-01 | Eisenwerk-Gesellschaft Maximilianshutte Mbh. | Method of improvement of the heat-balance in the refining of steel |
-
1979
- 1979-10-02 DE DE2939859A patent/DE2939859C2/en not_active Expired
-
1980
- 1980-08-05 AR AR28205080A patent/AR222716A1/en active
- 1980-08-12 NL NL8004569A patent/NL8004569A/en active Search and Examination
- 1980-08-25 ZA ZA00805219A patent/ZA805219B/en unknown
- 1980-09-16 GB GB8029841A patent/GB2059997B/en not_active Expired
- 1980-09-17 PL PL1980226790A patent/PL124716B1/en unknown
- 1980-09-24 CS CS806454A patent/CS270404B2/en unknown
- 1980-09-24 SU SU802984447A patent/SU1009279A3/en active
- 1980-09-25 ES ES495340A patent/ES495340A0/en active Granted
- 1980-09-29 CA CA000361173A patent/CA1150057A/en not_active Expired
- 1980-09-30 IT IT2502880A patent/IT1132903B/en active
- 1980-09-30 AU AU62805/80A patent/AU535449B2/en not_active Ceased
- 1980-09-30 AT AT488480A patent/AT384241B/en not_active IP Right Cessation
- 1980-09-30 LU LU82813A patent/LU82813A1/en unknown
- 1980-10-01 SE SE8006853A patent/SE448553B/en not_active IP Right Cessation
- 1980-10-01 HU HU239880A patent/HU178901B/en not_active IP Right Cessation
- 1980-10-01 MX MX8673A patent/MX155004A/en unknown
- 1980-10-01 BE BE0/202302A patent/BE885490A/en not_active IP Right Cessation
- 1980-10-01 BR BR8006314A patent/BR8006314A/en not_active IP Right Cessation
- 1980-10-01 FR FR8021072A patent/FR2466509A1/en active Granted
- 1980-10-02 JP JP55136812A patent/JPS6034605B2/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6034605B2 (en) | 1985-08-09 |
| FR2466509B1 (en) | 1983-10-14 |
| JPS5658916A (en) | 1981-05-22 |
| IT8025028A0 (en) | 1980-09-30 |
| CS645480A2 (en) | 1989-11-14 |
| DE2939859C2 (en) | 1983-06-23 |
| ZA805219B (en) | 1981-09-30 |
| BE885490A (en) | 1981-02-02 |
| PL124716B1 (en) | 1983-02-28 |
| AU6280580A (en) | 1981-04-09 |
| PL226790A1 (en) | 1981-08-21 |
| SE448553B (en) | 1987-03-02 |
| CS270404B2 (en) | 1990-06-13 |
| DE2939859A1 (en) | 1981-04-09 |
| ES8106018A1 (en) | 1981-06-16 |
| BR8006314A (en) | 1981-04-14 |
| AT384241B (en) | 1987-10-12 |
| AR222716A1 (en) | 1981-06-15 |
| ATA488480A (en) | 1987-03-15 |
| GB2059997A (en) | 1981-04-29 |
| IT1132903B (en) | 1986-07-09 |
| GB2059997B (en) | 1983-04-07 |
| MX155004A (en) | 1988-01-19 |
| SE8006853L (en) | 1981-04-03 |
| ES495340A0 (en) | 1981-06-16 |
| NL8004569A (en) | 1981-04-06 |
| SU1009279A3 (en) | 1983-03-30 |
| AU535449B2 (en) | 1984-03-22 |
| FR2466509A1 (en) | 1981-04-10 |
| HU178901B (en) | 1982-07-28 |
| LU82813A1 (en) | 1980-12-15 |
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