CN102199688A - Method for efficiently refining ultra-pure ferritic stainless steel - Google Patents
Method for efficiently refining ultra-pure ferritic stainless steel Download PDFInfo
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Abstract
The invention comprises a method for efficiently refining ultra-pure ferritic stainless steel, which comprises the following steps of: (1) conveying a steel ladle to a vacuum oxygen decarbonizing (VOD) furnace; (2) vacuumizing, and carrying out top oxygen decarbonizing and bottom argon stirring simultaneously, wherein the oxygen blowing flow is 290L/(min.t)-310L/(min.t); (3) carrying out ultrahigh vacuum decarbonizing and top-bottom composite argon stirring, wherein the top gun height, i.e., the gun position is 1.4-1.6m, the flow is 200L/(min.t)-260L/(min.t) and the treatment time is 8-12min; (4) adding ferrosilicon and an aluminum block to carry out composite decarbonizing, and adding lime and fluorite to carry out slagging, wherein the treatment time is 15-20min; and (5) breaking an vacuum, softly stirring, feeding yarns, then softly stirring again, conveying the steel ladle into a continuous casting station and casting. According to the method disclosed by the invention, the oxygen consumption and reducing agent consumption can be reduced, the vacuum treatment time is shortened, and the total content of carbon and nitrogen at the end can be stably controlled below 150ppm because the decarbonizing effect is high.
Description
Technical field
The invention belongs to the stainless steel smelting field, relate to the method for utilizing VOD stove (vacuum-oxygen decarbonizing stove) refining super-purity ferrite stainless steel.
Background technology
Studies show that, the reduction of ferritic stainless steel intermediate gap Elements C, N content helps to improve the ferritic stainless steel performance, these performances comprise: the ductility of room temperature fragility, solidity to corrosion and weld usually is called super-purity ferrite stainless steel with the C+N total content less than the ferritic stainless steel of 150ppm.In the industrial production, walk three-step approach usually and produce such steel grade, three-step approach is: EAF (electric arc furnace)+AOD (the multiple blown converter of argon oxygen)+VOD (vacuum-oxygen decarbonizing stove), the refining of VOD stove is control end point carbon, the most key operation of nitrogen content.
The VOD routine operation is as follows: one, the molten steel of handling through AOD enters VOD with the ladle transportation and handles station, measures temperature and composition, enters vacuum processing chamber after qualified, and stir at the first forvacuum and the end; Two, begin oxygen decarburization under the vacuum condition and handle, top blowing oxygen decarburization under the end agitation condition judges whether to stop oxygen blast according to composition of fumes, CO+CO in furnace gas
2When content is lower than certain value, stop oxygen blast; Three, free carbonization treatment under the ultravacuum condition adopts greatly and stirs; Four, reduction process adds the alloying that ferrosilicon, aluminium, lime and fluorite carry out deoxidation and silicon; Five, vacuum breaker; Six, feed silk and soft stirring under the atmospheric condition, send casting at last.
Routine operation for carbon nitrogen content in the steel is dropped to utmost point low value, is taked big blowing oxygen quantity operation usually when smelting super-purity ferrite stainless steel, wish to take off carbon content very low by many oxygen blast, and 110t VOD stove blowing oxygen quantity is at 800-1400Nm
3Between, the disadvantageous effect that high blowing oxygen quantity brings is that oxygen utilization rate (be used for the oxygen of decarburization and the ratio of total blowing oxygen quantity) reduces, high blowing oxygen quantity can cause the molten bath overheated serious simultaneously, the molten bath top temperature is all more than 1720 ℃ when stopping oxygen, high blowing oxygen quantity directly causes vacuum processing time elongated, and in addition, high blowing oxygen quantity also can cause reductor (being also referred to as reductive agent) add-on to increase, corresponding smelting cost increases, and also is unfavorable for the control of inclusion.
The free carbon rejection process decarbonization rate of routine operation is on the low side, no doubt there is carbon content in the steel to be in the reason that lower level causes the decarburization difficulty to increase, yet analyze from decarburization thermodynamics, influenced by ferrostatic pressure, free decarburization can only occur in the upper strata and the exposed molten steel surface in molten steel molten bath, analyze from decarburization kinetics, it is very big that molten steel molten bath inner carbon oxygen spontaneous reaction forms decarburization bubble difficulty, the reaction area that provides for decarburization mainly concentrates on the molten steel exposed surface and BOTTOM ARGON BLOWING rises to the air pocket that inner upper strata, molten steel molten bath forms, at identical conversion zone, the reaction area that the reaction area that air pocket provides will provide much smaller than the disperse small bubbles is so the reaction area of free carbon rejection process has been subjected to great restriction.
According to above analysis as can be known, the routine operation blowing oxygen quantity is big, and oxygen blow duration is long partially, and the decarburization nitric efficiency of free carbon rejection process is on the low side, causes vacuum processing time long, and blowing oxygen quantity is big, and reductive agent consumption is big.At these problems, following patent has proposed corresponding novel method.
Japanese patent application publication No. JP8209226 (A) has proposed a kind of spray gun of using to oxygenants such as molten steel surface winding-up iron ore, manganese ores in the vacuum refinement process, can promote denitrification reaction at high-carbon regions, strengthen the method for decarburizing reaction in the low-carbon (LC) district, this method is also referred to as the VOD-PB method, this method advantage is that nitric efficiency is very high, yet the equipment complexity that this method requires, the breeze of jetting simultaneously may cause the molten steel phosphorization and increase sulphur.
Thereby Japanese patent application publication No. JP11106823 is by increasing the bottom blown gas flow improves the VOD treating processes to the big stirring method of molten steel decarburization and nitric efficiency, the inventive method has obtained in the whole world using widely, yet, excessive end stirring intensity can cause big splash, and so-called strong mixing method is subjected to severely restricts in fact.
Korean Patent Publication No. KR20030003846 has proposed that winding-up lime improves decarbonization rate and prevents that lime is to molten steel carburetting in the free carbon rejection process of high vacuum after stopping oxygen, yet the lime of pre-spirt is difficult to fusing, can form hard solid slag, influence flowing of molten bath on the contrary.
Chinese patent publication number CN101058837A has proposed the method that VOD smelts super-purity ferrite stainless steel, is actually conventional VOD operation steps, and this patent is too short in the molten steel deep deoxidation aftertreatment time, and this is disadvantageous to liquid steel desulphurization.
By the oxygen balance of VOD smelting process is analyzed as can be known, the oxygen of ordinary method winding-up only 30%-40% is used for decarburization, and residue oxygen major part (mainly is Cr with dissolved oxygen and oxide compound
2O
3) mode stay in the molten steel molten bath, the oxygen amount in the molten bath is enough taken off utmost point low value with molten steel carbon, if can improve the decarburization nitric efficiency of free carbon rejection process, then can reduce the time of oxygen decarburization and reduce blowing oxygen quantity, has shortened vacuum processing time.Patent of the present invention has been developed the method for the new ultrapure clean ferritic stainless steel of high efficiency production based on this.
Summary of the invention
Purpose of the present invention provides a kind of method of efficiency refining high super-purity ferrite stainless steel, can improve the decarburization nitric efficiency of VOD smelting process, shortens vacuum processing time to enhance productivity, and reduces oxygen consumption and reductive agent consumption.
For achieving the above object, technical scheme of the present invention is:
VOD stove (vacuum-oxygen decarbonizing stove) is smelted the stainless oxygen decarburization stage of ferrite and is adopted few oxygen blast operation, adopt the compound Argon in the end, top to strengthen the decarburization denitrogenation in the free decarburization stage, by as above technological improvement, can improve the decarburization nitric efficiency of VOD smelting process, shorten vacuum processing time to enhance productivity, reduce oxygen consumption and reductive agent consumption, and further reduce the end point carbon nitrogen content.
Particularly, the method for efficiency refining high super-purity ferrite stainless steel, its step is as follows:
1) ladle enters vacuum-oxygen decarbonizing stove VOD, and the vacuum tank internal pressure satisfies less than 100Pa, and the initial chromium content of molten steel mass percent is between 10%～25%, and the carbon content mass percent is between 0.25%～0.60%, and the molten steel initial temperature is higher than 1620 ℃;
2) vacuumize also top blowing oxygen decarburization, the while bottom is blown into argon gas molten steel is stirred, and top blowing oxygen flow 270L/ (mint)～310L/ (mint) takes few oxygen blast operation, and the initial carbon mass content is 0.25% o'clock total blowing oxygen quantity (Nm
3) be controlled to be 6.3-6.8Nm
3/ t, the initial carbon mass content exceeds 0.1% than 0.25%, and then total blowing oxygen quantity need increase 1.6-1.8Nm
3/ t;
3) the free carbonization treatment of ultravacuum, vacuum pressure requires less than 1000Pa, the compound Argon in the end, top, during Argon the rifle head of top rifle apart from the molten steel identity distance from (rifle position) 1.4-1.6m, flow is at 200L/ (mint)～260L/ (mint), the BOTTOM ARGON BLOWING total flux is at 2L/ (mint)-6L/ (mint), treatment time 8-12min;
4) add ferrosilicon (siliceous amount content is 70～80%) 2.8-10kg/t, aluminium block 1.0-6.0kg/t and carry out deoxidation, and add lime 10-30kg/t and fluorite 2-8kg/t slag making, desulfurization simultaneously, treatment time 15～20min;
5) vacuum breaker, silk (titanium silk or calcium silk or niobium alloy) is fed in soft stirring, Alloying Treatment or inclusion modification, soft again stirring, ladle enters the continuous casting station and casts; It does not repeat them here for existing routine techniques.
Preferably, when step 3) begins, add aluminium block 0-2kg/t and be used to the molten steel temperature that raises, add in the aluminium process argon bottom-blowing total flux between 2L/ (mint)-4L/ (mint).
Further, in whole smelting process, ferrosilicon (siliceous amount content is at the 70-80%) add-on that participates in oxidation is higher than 2.8kg/t, and total ferrosilicon add-on comprises the ferrosilicon amount that participates in oxidation and be used for the ferrosilicon amount of molten steel alloying that total fine aluminium add-on is higher than 2.3kg/t.
The inventive method can shorten vacuum processing time, reduces oxygen depletion and reductive agent consumption, and end point carbon adds that the nitrogen total content is stable to be controlled at below the 150ppm simultaneously.
The relative ordinary method of the inventive method adopts few oxygen blast operation, reduces oxygen consumption and reductive agent consumption, and shortens vacuum processing time.
The inventive method step 2) smelt thermally equilibrated angle from VOD and control total blowing oxygen quantity, and difference is controlled total blowing oxygen quantity with conventional from consideration decarburization angle.Reason is, institute's oxygen blast has only 30-40% to be used for decarburization, and other oxygen also major part are stayed in the molten bath, and anoxic source not in fact for decarburization if the speed of free decarburization (not oxygen blast) is raised under the high vacuum, then need not to be blown into a large amount of oxygen and guarantees decarburization.To set forth from the energy balance angle below and consider total blowing oxygen quantity, meet the requirements to satisfy needed comparatively high temps of VOD decarburization and terminal temperature.
The top blowing oxygen of VOD is except direct reinforcement decarburization, another very important effect is to provide chemical energy to the molten bath, with the whole vacuum treated thermosteresis of compensation VOD, can be furnished with the electric arc heating plant because the VOD stove can't resemble the common ladle refining furnace, then the energy that discharges of the chemical energy that produces of oxygen blast and alloying with silicon has become only energy supply.Through heat calculation, smelting process for the VOD stove, under the situation about vacuum processing time 65min, the thermosteresis that thermal radiation and ladle heat absorption form is about can reduce about 140 ℃ of molten steel temperatures, in order to remedy this part power loss, guarantee that the VOD terminal temperature meets the requirements, except requiring molten steel initial temperature height, the energy that relies on chemical energy that oxygen blast brings and alloying with silicon to discharge exactly remedies the energy of this loss.
Molten steel molten bath with whole VOD smelting process is a research object, because oxidized chromium finally goes out by silicon or aluminium reducing, then the energy income mainly from oxygen blown decarburizing reaction comprise the energy that the reaction of the reaction of energy, oxygen and silicon that secondary combustion is emitted and oxygen and aluminium is emitted.As calculated, sloughing energy that 0.1% carbon emits in the steel under the condition of post-combustion rate 60% can make molten steel temperature raise to be about 12 ℃; The energy that the pasc reaction of 75% in oxygen and the ton 1kg ferrosilicon that steel added discharges can make molten steel temperature raise 24 ℃, but because the SiO of generation
2Entering needs in the slag to fix and the fluorite slag with CaO in the lime, basicity of slag (CaO and SiO in the slag
2Mass ratio) be controlled under 2.5 conditions, the fluorite add-on is under lime adding amount 1/4 condition, lime of Jia Ruing and fluorite can reduce about 11 ℃ of respective steel liquid temps in the heat absorption of intensification and melting process for this reason, in general, the energy that produces of oxygen and the reaction of ton a 1kg ferrosilicon that steel added is deducted corresponding lime and the fluorite fusing energy requirement that heats up and can be made molten steel temperature raise about 13 ℃; The energy that ton 1kg aluminium that steel added and oxygen reaction discharge can make molten steel temperature raise 32 ℃; Silicon is strong heat release element, and ton steel 1kg ferrosilicon (siliceous 75%) also can make molten steel temperature raise 4.1 ℃ in alloying process.Calculate from oxygen consumption aspect, the amount of oxygen that silicon oxidation needs in the 1kg ferrosilicon (siliceous 75%) is 0.60Nm
3, the amount of oxygen that 1kg aluminium needs is 0.62Nm
3, the ton steel is sloughed 0.1% carbon, and to need clean amount of oxygen approximately be 1.4Nm
3
According to above-mentioned analysis, when the molten steel initial temperature is higher than 1620 ℃, energy as chemical energy and alloying with silicon release can remedy the energy that the molten steel temperature loss adds 20 ℃ of correspondences that embody into insurance, then terminal temperature meets the requirements substantially, according to such thinking the inventive method blowing oxygen quantity is designed.In order to guarantee that the energy supply reduces blowing oxygen quantity simultaneously, should add aluminium deoxidation and add silicon less, reason is the calorific value height of aluminium, and need adding lime, the oxide compound that forms behind the silicon oxidation controls basicity, considering needs to guarantee that certain quantity of slag is so that higher desulfuration, the inventive method requires for one ton of molten steel, and the ferrosilicon amount (siliceous 75%) that is used for oxidizing reaction is no less than 2.8kg.And in order to guarantee molten steel energy supply oxygen blast less simultaneously, total aluminium add-on is no less than 2.3kg/ (t steel).
Specifically, for the smelting process of super-purity ferrite stainless steel molten steel, be 2.3kg/ (t steel) as total aluminium add-on, when initial carbon was 0.25%, the ferrosilicon 2.72kg/ (t steel) that is used for oxidation can satisfy energy compensating, corresponding total oxygen consumption 6.56Nm
3/ (t steel); Initial carbon is 0.35% o'clock, and vacuum processing time will prolong, and under the constant situation of aluminium amount, the ferrosilicon 3.45kg/ (t steel) that is used for oxidation can satisfy energy compensating, and total oxygen consumption is 8.39Nm
3/ (t steel); When initial carbon was 0.45%, total oxygen consumption was 10.16Nm
3/ (t steel); When initial carbon was 0.6%, total oxygen consumption was 12.81Nm
3/ (t steel).Can draw thus, when initial carbon exceeds 0.1 percentage point of 0.25% carbon content, then the oxygen consumption needs to improve 1.8Nm
3/ t.Certainly, if the aluminium add-on increases, the oxygen consumption can also reduce slightly.The ordinary method initial carbon is 0.25% o'clock, and for the molten steel of 110t, oxygen consumes at 800-900Nm
3Between, the inventive method only needs 720Nm
3Oxygen consumption.
Take all factors into consideration, it is 0.25% o'clock total blowing oxygen quantity (Nm that the inventive method proposes initial carbon
3) be controlled to be 6.3-6.8Nm
3/ t, initial carbon exceeds 0.25% carbon content 0.1%, and then total blowing oxygen quantity need increase 1.6-1.8Nm
3/ t.Requirement simultaneously uses the ferrosilicon add-on with oxidation to be higher than 2.8kg/t, and total aluminium add-on is higher than 2.3kg/t.
Reduce blowing oxygen quantity and can shorten oxygen blow duration, thereby reduce whole vacuum processing time, but the reduction dosage of conserve oxygen consumption simultaneously and saving reduction period consumes.
In addition, the present invention has increased the operation of top blast argon at the free carbon rejection process of ultravacuum, has improved decarburization denitrogenation speed greatly, and the free carbonization treatment time also decreases.
The inventive method step 3) requires in the free carbon rejection process of ultravacuum, the compound Argon in the end, top, during Argon the rifle head of top rifle apart from the molten steel identity distance from (rifle position) 1.4-1.6m, flow is at 200L/ (mint)～260L/ (mint), the BOTTOM ARGON BLOWING total flux is at 2L/ (mint)-6L/ (mint), treatment time 8-12min.When beginning, step 3) can preferably adopt to add aluminium rising molten steel temperature, to improve decarburization denitrogenation speed.
For the free decarburization operation of VOD of routine, generally take BOTTOM ARGON BLOWING violent stirring operation under the high vacuum condition, according to the introduction of front to the routine operation method, the decarburization nitric efficiency of this method has been subjected to the limited restriction of reaction area.Traditional view thinks that the mixing effect that bottom blowing is stirred is better than top blast greatly and stirs.Process is to the free decarburization denitrification process of VOD analysis of dynamics, discovery is except vacuum and stirring intensity, decarburization denitrification reaction area is the central factor that influences its speed of reaction, if be a lot of small bubbles of quantity so the few air pocket of the subsurface quantity of molten steel can be broken, then decarburization denitrification reaction area will increase greatly.The top Argon has such function, result according to water model observation, top blast can be the decarburization denitrogenation enough micro-bubble sources is provided, the decarburization denitrogenation need not spontaneous nucleation, can directly react on these Argon Bubble surfaces, the top blast argon is to the vibrations of molten steel surface impacts simultaneously, and the subsurface air pocket of molten steel also can be broken, in addition, these argon gas that are blown into molten steel inside can further reduce the CO dividing potential drop and the N of bubble inside
2Dividing potential drop is improved the thermodynamic condition of decarburization denitrification reaction.As can be seen, though VOD top Argon is limited to the castering action of the stirring intensity of molten bath integral body, it can improve the speed of reaction of decarburization and denitrogenation greatly.
The inventive method is uncomplicated for production operation, top blow oxygen lance can be directly used in the Argon operation, the argon gas stream of jetting in order to guarantee simultaneously has enough surging forces, its flow set is suitable with the oxygen blast flow, because argon gas standard state lower density is higher than oxygen, its flow set should be slightly less than the oxygen blast flow, and the rifle position when the rifle position is than oxygen blast simultaneously is lower slightly.
General VOD oxygen rifle is the supersonic speed rifle, is with three shower nozzles, and about throat diameter 16mm, Mach 2 ship 3 imposes a condition down above-mentioned, and top blast argon flow is at 1300-1700Nm
3/ h, as calculated, during the 1.4-1.6m of rifle position, between 20cm-30cm, major part can enter molten steel inside to the top blast argon in the argon gas stream to the degree of depth of molten steel zap pit, form micro-bubble, the bubble that enters molten steel inside will be diffused into other zones of molten steel face below, because the intensively stirred effect of bottom blowing laterally with the molten steel motion, these micro-bubbles quite a few be involved in depths, molten steel molten bath, will prolong their residence time in molten steel inside.Because top rifle Argon has been brought top, molten bath strong reaction, then traditional relatively 6L/ (the mint)-10L/ (mint) of BOTTOM ARGON BLOWING flow reduces slightly, is controlled at 2L/ (mint)-6L/ (mint).
Because the relative ordinary method of the inventive method blowing oxygen quantity decreases, molten steel temperature when molten steel temperature may be lower than ordinary method and stops oxygen when stopping oxygen, in order to guarantee that free carbon rejection process molten steel temperature subsequently maintains high value, before free decarburization begins, can add the aluminium molten steel temperature that raises, the aluminium that is added mainly be with bath in Cr
2O
3Reaction, as calculated, the ton steel whenever adds 1kg aluminium, and to participate in the temperature that energy that this reaction discharges can make molten steel raise be 10 ℃.If molten steel its temperature when stopping oxygen has surpassed 1700 ℃, then can not add the aluminium elevated temperature, if its temperature is lower than 1700 ℃ when stopping oxygen, adds aluminium molten steel temperature is elevated to 1700 ℃, adding aluminium amount 0-2kg/t can meet the demands.
Need to prove that because the inventive method decarburization nitric efficiency height, molten steel end point carbon, nitrogen content have also obtained effective control, its total content can be stablized and is controlled at below the 150ppm.
Beneficial effect of the present invention:
According to the inventive method, the end point carbon of VOD refining super-purity ferrite stainless steel, nitrogen total content can be stablized and be controlled at below the 150ppm, and the VOD vacuum processing time shortens 5-10min than ordinary method on this basis, and oxygen consumption and reductive agent consumption are necessarily reduced.In a word, the inventive method has improved the ferritic stainless steel quality product, has shortened the treatment time, has reduced consumption.
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Embodiment
Describe the inventive method in detail in the embodiment of refining super-purity ferrite stainless steel and the effect that obtains below in conjunction with embodiment, respectively with VOD refining 409L, 439 and the super-purity ferrite stainless steel of these 3 trade mark steel grades of 430L be that example is illustrated.
Embodiment 1
The present embodiment equipment requirements: 120t VOD handles stove, and final vacuum is less than 100Pa, three Argon air ports, bottom, and air blowing ability always reaches 60Nm
3/ h, changeable connection oxygen of top blast rifle and argon gas.1620 ℃ of initial steel liquid temps, molten steel weight 110t smelts steel grade 409L, and main component was as follows before it was handled:
C:0.3%, Si:0.03%, Cr:11.7%, S:0.005%, N:0.018%, Mn:0.22%, P:0.015%, all the other are Fe and micro impurity element.
In conjunction with VOD routine operation and the inventive method, the present embodiment implementation step is as follows:
(1) enters vacuum processing chamber after molten steel is skimmed.
(2) carry out oxygen decarburization after the forvacuum and handle, vacuum pressure is between 12000Pa-2000Pa, and pressure is higher during beginning, oxygen blast flow 1800Nm
3/ h, BOTTOM ARGON BLOWING total flux 45Nm
3/ h is when blowing oxygen quantity is 820Nm
3The time stop oxygen blast, this stage processing time is 30min.
(3) add aluminium block 100kg aluminium and be used to the bath temperature that raises, add in the aluminium process argon bottom-blowing flow at 15Nm
3/ h.
(4) free carbonization treatment under the high vacuum condition, vacuum pressure are at 400Pa～200Pa, and the top blast rifle is from molten steel face height (being the rifle position) 1.5m, its argon flow amount 1400Nm
3/ h, the argon bottom-blowing flow is at 30Nm
3/ h, treatment time 9min.
(5) stop high vacuum, vacuum pressure returns to 12000Pa, adds ferrosilicon (silicon content 75%) 880kg, and wherein 340kg is used for participating in oxidizing reaction, aluminium block 150kg, lime 1.5t, fluorite 300kg.
(6) deoxidation under the high vacuum condition, change slag and desulfurization, basicity of slag is 2.5, and vacuum pressure is at 200Pa～100Pa, and the argon bottom-blowing flow is at 45Nm
3/ h, treatment time 16min.
(7) vacuum breaker, the titanium silk is fed in soft stirring, soft again stirring, ladle enters the continuous casting station and casts.
Above vacuum refinement processing finishes 1627 ℃ of back molten steel temperatures, vacuum processing time 57min (more than the ordinary method vacuum processing time 62min), and the molten steel ultimate constituent is as follows:
C:0.0040%, Si:0.4%, Cr:11.6%, S:0.001%, Ti:0.12%, N:0.0060%, Mn:0.24%, P:0.014%, Al:0.015%, all the other are Fe and micro impurity element.
Open jar and decide the total oxygen of oxygen: 6.2ppm: 0.003%
Above molten steel temperature and composition all meet technical requirements, can directly go up the continuous casting platform and pour into a mould.
Embodiment 2
The present embodiment equipment requirements: 120t VOD handles stove, and final vacuum is less than 100Pa, three Argon air ports, bottom, and air blowing ability always reaches 60Nm
3/ h, changeable connection oxygen of top blast rifle and argon gas.1625 ℃ of initial steel liquid temps, molten steel weight 109t smelts steel grade 439, and main component was as follows before it was handled:
C:0.4%, Si:0.05%, Cr:17.5%, S:0.005%, N:0.015%, Mn:0.1%, P:0.013%, all the other are Fe and micro impurity element.
In conjunction with VOD routine operation and the inventive method, implementation step is as follows:
(1) enters vacuum processing chamber after molten steel is skimmed.
(2) carry out oxygen decarburization after the forvacuum and handle, vacuum pressure is between 12000Pa-2000Pa, and pressure is higher during beginning, oxygen blast flow 1850Nm
3/ h, BOTTOM ARGON BLOWING total flux 45Nm
3/ h is when blowing oxygen quantity is 1020Nm
3The time stop oxygen blast, this stage processing time is 37min.
(3) add aluminium block 60kg aluminium and be used to the bath temperature that raises, add in the aluminium process argon bottom-blowing flow at 10Nm
3/ h.
(4) free carbonization treatment under the high vacuum condition, vacuum pressure are at 400Pa～200Pa, and the top blast rifle is from molten steel face height (being the rifle position) 1.4m, its flow 1350Nm
3/ h, the argon bottom-blowing flow is at 30Nm
3/ h, treatment time 10min.
(5) stop high vacuum, vacuum pressure returns to 12000Pa, adds ferrosilicon (silicon content 75%) 1000kg, and wherein 420kg is used for participating in oxidizing reaction, aluminium block 200kg, lime 1.8t, fluorite 500kg.
(6) deoxidation under the high vacuum condition, change slag are handled and desulfurization, and basicity of slag is 2.5, and vacuum pressure is at 200Pa～100Pa, and the argon bottom-blowing flow is at 45Nm
3/ h, treatment time 15min.
(7) vacuum breaker, the titanium silk is fed in soft stirring, soft again stirring, ladle enters the continuous casting station and casts.
Above vacuum refinement processing finishes 1640 ℃ of back molten steel temperatures, vacuum processing time 64min (more than the ordinary method vacuum processing time 70min), and the molten steel ultimate constituent is as follows:
C:0.0060%, Si:0.45%, Cr:17.4%, S:0.001%, Ti:0.22%, N:0.0070%, Mn:0.1%, P:0.013%, Al:0.019%, all the other are Fe and micro impurity element.
Open jar and decide the total oxygen of oxygen: 5.4ppm: 0.0035%.
Above molten steel temperature and composition all meet technical requirements, can directly go up the continuous casting platform and pour into a mould.
Embodiment 3
The present embodiment equipment requirements: 120t VOD handles stove, and final vacuum is less than 100Pa, three Argon air ports, bottom, and air blowing ability always reaches 60Nm
3/ h, changeable connection oxygen of top blast rifle and argon gas.1620 ℃ of initial steel liquid temps, molten steel weight 109t smelts steel grade 430L, and main component was as follows before it was handled:
C:0.4%, Si:0.17%, Cr:16.3%, S:0.005%, N:0.017%, Mn:0.7%, P:0.013%, all the other are Fe and micro impurity element.
In conjunction with VOD routine operation and the inventive method, implementation step is as follows:
(1) enters vacuum processing chamber after molten steel is skimmed.
(2) carry out oxygen decarburization after the forvacuum and handle, vacuum pressure is between 12000Pa-2000Pa, and pressure is higher during beginning, oxygen blast flow 1900Nm
3/ h, BOTTOM ARGON BLOWING total flux 45Nm
3/ h is when blowing oxygen quantity is 1100Nm
3The time stop oxygen blast, this stage processing time is 36min.
(3) add aluminium block 150kg aluminium and be used to the bath temperature that raises, add argon bottom-blowing total flux 10Nm in the aluminium process
3/ h.
(4) free carbonization treatment under the high vacuum condition, vacuum pressure are at 400Pa～200Pa, and the top blast rifle is from molten steel face height (being the rifle position) 1.6m, argon flow amount 1500Nm
3/ h, the argon bottom-blowing flow is at 30Nm
3/ h, treatment time 10min.
(5) stop high vacuum, vacuum pressure returns to 12000Pa, adds ferrosilicon (silicon content 75%) 464kg, and wherein 420kg is used for participating in oxidizing reaction, aluminium block 150kg, lime 2t, fluorite 500kg.
(6) deoxidation under the high vacuum condition, change slag are handled and desulfurization, and basicity of slag is 2.5, and vacuum pressure is at 200Pa～100Pa, and the argon bottom-blowing flow is at 45Nm
3/ h, treatment time 16min.
(7) vacuum breaker, the titanium silk is fed in soft stirring, soft again stirring, ladle enters the continuous casting station and casts.
The vacuum refinement processing finishes 1620 ℃ of back molten steel temperatures, vacuum processing time 64min (more than the ordinary method vacuum processing time 70min), and the molten steel ultimate constituent is as follows:
C:0.0054%, Si:0.2%, Cr:16.4%, S:0.002%, Ti:0.105%, N:0.0084%, Mn:0.66%, P:0.013%, Al:0.03%, all the other are Fe and micro impurity element.
Open jar and decide the total oxygen of oxygen: 3.6ppm: 0.0025%.
Above molten steel temperature and composition all meet technical requirements, can directly go up the continuous casting platform and pour into a mould.
Claims (3)
1. the method for an efficiency refining high super-purity ferrite stainless steel, its step is as follows:
1) ladle enters vacuum-oxygen decarbonizing stove VOD, and the vacuum tank internal pressure satisfies less than 100Pa, and the initial chromium content of molten steel mass percent is between 10%～25%, and the carbon content mass percent is between 0.25%～0.60%, and the molten steel initial temperature is higher than 1620 ℃;
2) vacuumize, and the top blowing oxygen decarburization, the while bottom is blown into argon gas molten steel is stirred, and top blowing oxygen flow 270L/ (min (t steel))～310L/ (min (t steel)) takes few oxygen blast operation, and the initial carbon mass content is 0.25% o'clock total blowing oxygen quantity (Nm
3) be controlled to be 6.3～6.8Nm
3/ (t steel), the initial carbon mass content exceeds 0.1% than 0.25%, and then total blowing oxygen quantity need increase by 1.6～1.8Nm
3/ (t steel);
3) the free carbonization treatment of ultravacuum, vacuum pressure requires less than 1000Pa, the compound Argon in the end, top, during Argon the rifle head of top rifle apart from the molten steel identity distance from (rifle position) 1.4～1.6m, flow is at 200L/ (min (t steel))～260L/ (min (t steel)), the BOTTOM ARGON BLOWING total flux is at 2L/ (min (t steel))～6L/ (min (t steel)), treatment time 8～12min;
4) add ferrosilicon (siliceous amount content is 70～80%) 2.8-10kg/ (t steel), aluminium block 1.0-6.0kg/ (t steel) and carry out deoxidation, and add lime 10-30kg/ (t steel) and fluorite 2-8kg/ (t steel) slag making, desulfurization simultaneously, treatment time 15～20min;
5) vacuum breaker, silk is fed in soft stirring, soft again stirring, ladle enters the continuous casting station and casts.
2. the method for efficiency refining high super-purity ferrite stainless steel as claimed in claim 1, it is characterized in that, when step (3) begins, add aluminium block 0～2kg/ (t steel) and be used to the molten steel temperature that raises, add in the aluminium process argon bottom-blowing total flux between 2L/ (min (t steel))～4L/ (min (t steel)).
3. the method for efficiency refining high super-purity ferrite stainless steel as claimed in claim 1, it is characterized in that, in whole smelting process, ferrosilicon (siliceous amount content is 70～80%) add-on that participates in oxidation is higher than 2.8kg/ (t steel), total ferrosilicon add-on comprises the ferrosilicon amount that participates in oxidation and is used for the ferrosilicon amount of molten steel alloying that total fine aluminium add-on is higher than 2.3kg/ (t steel).
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