CN102329920B - Method for smelting high-aluminum low-silicon ultra pure ferritic stainless steel - Google Patents
Method for smelting high-aluminum low-silicon ultra pure ferritic stainless steel Download PDFInfo
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- 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
- C21C7/06—Deoxidising, e.g. killing
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- 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
- C21C7/068—Decarburising
- C21C7/0685—Decarburising of stainless steel
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- 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
- C21C7/10—Handling in a vacuum
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Abstract
The invention provides a method for smelting high-aluminum low-silicon ultra pure ferritic stainless steel. The method comprises the following steps of: performing vacuum oxygen decarburization and free decarburization treatment on molten ferritic stainless steel in a vacuum oxygen decarburization (VOD) furnace, improving the reduction process of a VOD vacuum treatment process, performing preliminary deoxidation, final deoxidation and vacuum breaking, adding high-density aluminum iron, controlling the alkalinity of slag, performing wire feeding treatment, performing continuous casting by adopting the measures of protective casting and the like, and thus obtaining the high-aluminum low-silicon ultra pure ferritic stainless steel based on VOD to continuous casting treatment. By the method, the acid washing performance of the ultra pure ferritic stainless steel is improved, the purity of the molten steel and the casting performance of the continuous casting process are further improved, formation of magnesia alumina spinel serving as a harmful inclusion is effectively inhibited, Al2O3 inclusion is effectively removed, oxidation of the titanium in the titanium-containing steel is inhibited, and tundish water gap blockage of the continuous casting process is avoided.
Description
Technical field
The present invention relates to the stainless steel smelting field, particularly, relate to a kind of smelting process of ferritic stainless steel, more specifically, relate to a kind of smelting process of high-aluminum low-silicon super-purity ferrite stainless steel.
Background technology
Super-purity ferrite stainless steel is the elaboration of ferritic stainless steel, general requirement carbon nitrogen total content is less than 150ppm, total oxygen content is lower than 40ppm, and the quantity of inclusion, size and type are effectively controlled, and super-purity ferrite stainless steel can partly substitute austenitic stainless steel, because it does not require and contains nickel element, has played the effect of saving nickel resources.
The smelting process of super-purity ferrite stainless steel generally will be passed through vacuum-oxygen decarbonizing stove (being called for short the VOD stove) and be carried out the dark decarburization of oxygen blast, denitrogenation processing under the ultravacuum condition, and the routine operation of described VOD stove is as follows:
One, the molten steel of handling through AOD enters VOD with the ladle transportation and processes station, measures temperature and composition, enters vacuum processing chamber after qualified, stirs with ugly vacuum and the end first; Two, the beginning oxygen decarburization is processed under the vacuum condition, and top blowing oxygen decarburization under the end agitation condition determines whether the termination 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 Treatment 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 at last casting.
Yet in the oxygen decarburization treating processes of above-mentioned second step, oxygen blast can not be used for decarburization fully, has quite a few oxygen will enter the molten bath and exists with the form of chromic oxide or dissolved oxygen, so after the 3rd free decarburization, also will carry out deoxidation treatment.
Wherein, silicon, aluminium are the deoxidant elements of commonly using.Each Iron And Steel Company's original adoption of Europe be the pure silicon deoxy technology, reason is to adopt the aluminium deoxidation can a large amount of Al that form
2O
3Is mingled with, and then most steel grades are produced detrimentally affects, yet the entire oxygen content in the steel content of silicon deoxidation is very high, in the strand total oxygen more than 60ppm, thereby affect the performance of the finished product.
Along with the requirement to super-purity ferrite stainless steel is more and more higher, it is extremely low-level to need its total oxygen content also to be in, and people begin to attempt adopting sial complex deoxidization technique, with further reduction oxygen content in steel, for sial complex deoxidization technique, mainly exist at present following patent to ask down:
Day the present invention JP2002030324 (A) has provided the sial complex deoxidization and has smelted the method that prevents strip flaw (also claiming watt rib shape defective) ferritic stainless steel, deoxidation process adds first ferrosilicon, the target silicone content is controlled at 0.20～3.0wt%, basicity of slag (CaO and SiO in the slag
2Mass ratio) be controlled at 1.2～2.4, use at last aluminium deoxidation, require the ratio of molten steel Al content and Ti content before casting between 0.01～0.10, this method can improve molten steel and (wherein form the percentage that equiax crystal accounts for whole crystallizations after being crystalline solidification at the equiaxial crystal ratio of casting process.Be exactly center equiax crystal district diameter and strand diameter per-cent such as strand center equiaxial crystal ratio.) reach 60%, and control well composition of inclusions, preventing the casting cycle clogging of tundish nozzle were, final molten steel total oxygen content also remains on lower level.Yet it is still very high that this patent basicity of slag is controlled at the oxygen activity that means slag between 1.2～2.4, is difficult to the molten steel oxygen level is reduced to extremely low-level.
Chinese patent CN101058837, patent name: in the smelting process of a kind of super-purity ferrite stainless steel decarburization, denitrogenation, provided a kind of smelting process of super-purity ferrite stainless steel, after the molten steel vacuum-treat decarburization, under vacuum condition (vacuum tightness≤5mbar), add first the ferrosilicon deoxidation, add again the aluminium deep deoxidation, deaeration time 5～10 minutes, and then finely tune with alloy, this method of deoxidation treatment time is short, and deoxidation effect is pretty good, is widely used.
Yet JP2002030324 (A) and CN101058837 do not provide the method for concrete interpolation aluminium in the molten steel, because aluminium block or aluminum shot density are significantly less than molten steel density, directly adding directly contacts with slag and reacts also in a large number heat releases floating over molten steel top under the VOD vacuum condition, be difficult to effectively to enter the molten steel molten bath and carry out bulk deoxidation, this just causes directly adding aluminium and is difficult to the aluminium content of control steel after processing finishes, thereby can't guarantee the bulk deoxidation effect.
Simultaneously, the final content of silicon, aluminium element that adopts the sial complex deoxidization to relate to is processed by the deoxidation effect of steel, rear operation and the structure property of steel also has certain impact, be mainly manifested in: one) if aluminium content is low in the steel, deoxidation effect is then not obvious, be that oxygen level is higher in the molten steel, process if will feed subsequently titanium, then can form a large amount of titanium oxide and be mingled with, a large amount of titanium oxide is mingled with may stop up middle water containing opening; Two), current research shows that the ferritic stainless steel of high silicon content (it is generally acknowledged that content is higher than 0.3%) is large in rear operation pickling difficulty, has affected the stainless steel product surface smoothness.So, in order further to improve the quality of products and to guarantee to produce smoothly, for a lot of super-purity ferrite stainless steel kinds, the control of deoxidant element content is towards low silicon, high alumina future development, be specially the silicone content requirement less than 0.3% or lower, other require to determine lower limit according to steel grade, and aluminium content is controlled in 0.01～0.1% the scope, total oxygen content can be effectively reduced, and the subsequently oxidation of Ti Alloying process titanium can be prevented.
Smelting for low silicon, high alumina super-purity ferrite stainless steel, the front is also mentioned, Patents and ordinary method can not improve in the steel aluminium content effectively to the target content scope in the VOD treating processes, simultaneously, if improved aluminium content, in case basicity of slag control is improper, silicone content also is difficult to be controlled in the OK range in the steel.If copy the aluminium deoxidation method of carbon steel smelting process, namely improve aluminium content in the steel by feeding aluminium wire, because it is too large to feed the silk difficulty under the vacuum condition, can only could feed aluminium wire by the non-vacuum condition behind vacuum-treat end and vacuum breaker so, this can improve aluminium content in the steel really, yet, can not stir greatly again the Al of generation to the stainless steel molten steel behind hello the aluminium wire
2O
3Be mingled with and be difficult to grow up rapidly and to get rid of, and feed the risk that aluminium wire can increase absorption of nitrogen by steel under the non-vacuum condition, and prolong the treatment time, so hello aluminium wire is not scientific approach under the non-vacuum condition.If under vacuum condition, jet aluminium powder, can realize improving aluminium content in the steel, but the vacuum blowing device is complicated, and the control difficulty is very large.
Therefore, prior art and routine operation can conscientiously not solve and improve aluminium content and effective technical problem of controlling silicone content in the steel under vacuum condition.
Summary of the invention
For solving the problem of above-mentioned existence; the object of the present invention is to provide a kind of smelting process of high-aluminum low-silicon super-purity ferrite stainless steel; by the reduction process of VOD vacuum-treat process is improved; add highdensity ferro-aluminum; the control basicity of slag; feed subsequently that silk is processed and adopt the measure such as protective casting at casting process; realization smelts the high-aluminum low-silicon super-purity ferrite stainless steel from VOD to the continuous casting treating processes; improve the pickling performance of super-purity ferrite stainless steel; and further improve the purity of molten steel and the castability energy of casting process; Al is effectively removed in the formation of the harmful inclusion magnesium-aluminium spinel of establishment simultaneously
2O
3Inclusion, and in Ti-containing steel, suppressed the oxidation of titanium, avoided the clogging of tundish nozzle were of casting process.
For achieving the above object, the present invention takes following technical scheme:
The invention provides a kind of smelting process of high-aluminum low-silicon super-purity ferrite stainless steel, it is characterized in that, comprise the steps:
(1), the ferritic stainless steel molten steel is carried out vacuum-oxygen decarbonizing and free carbonization treatment in the VOD stove, the ferritic stainless steel molten steel main component that obtains after the processing requires: chromium quality percentage composition 10～23%, carbonaceous amount percentage composition is less than 0.01%, and nitrogen quality percentage composition is less than 0.01%;
(2), pre-deoxidation: in the ferritic stainless steel molten steel that after step (1) is processed, obtains, add ferrosilicon and/or aluminium block and carry out the pre-deoxidation processing, and add lime and fluorite carries out slag making, and then under high vacuum strong mixing condition, treatment time 5～10min;
(3), final deoxygenation: in the ferritic stainless steel molten steel that after step (2) is processed, obtains, add ferro-aluminum and carry out the final deoxygenation processing, the quality percentage composition of aluminium is 20～60% in the described ferro-aluminum, and add lime and fluorite carries out slag making, then under vacuum condition, middle intensity stirs 2～5min, then under high vacuum strong mixing condition, processes 12～18min;
(4), vacuum breaker;
(5), under condition of normal pressure, with the soft stirring 8～10min of described ferritic stainless steel molten steel, then under condition of normal pressure, feed the calcium silk to described ferritic stainless steel molten steel, feed after the calcium silk finishes soft stirring 5～10min;
(6), continue soft stirring 15～30min, afterwards the ferritic stainless steel molten steel is carried out continuous casting in protective atmosphere, finally obtain the high-aluminum low-silicon super-purity ferrite stainless steel.
Smelting process according to a kind of high-aluminum low-silicon super-purity ferrite stainless steel provided by the invention, what adopt is, in the step (2), the total add-on of described ferrosilicon and/or aluminium block is 4～9kg/t, the quality percentage composition of described Silicon in Ferrosilicon is 70～80%, and described lime adding quality value is the higher value in following two scopes: ferrosilicon adds 4～6 times or 2～3 times of aluminium block adding quality of quality; It is 0.05～0.3 times that lime adds quality that described fluorite adds quality, and after step (2) was processed, the mass content of silicon required the mass content of oxygen greater than 0.01% less than 0.1%, greater than 0 in the described ferritic stainless steel molten steel.
Smelting process according to a kind of high-aluminum low-silicon super-purity ferrite stainless steel provided by the invention, what adopt is, in the step (3), the add-on of fine aluminium is 2～6kg/t in the described ferro-aluminum, the add-on of described lime is 2～3 times of fine aluminium add-on in the ferro-aluminum, the fluorite add-on is 0.05～0.3 times that lime adds quality, after step (3) is processed, the mass content of silicon is less than 0.3%, greater than 0 in the described ferritic stainless steel molten steel, the mass content of aluminium is 0.01～0.1%, and the mass content of oxygen is less than 0.003%.
Smelting process according to a kind of high-aluminum low-silicon super-purity ferrite stainless steel provided by the invention, what adopt is, in step (5), the described calcium silk of feeding is to feed pure calcium silk in the ferritic stainless steel molten steel, described pure calcium silk feed quantity is 0.1～0.3kg/t, after step (5) was processed, the mass content of calcium was 15～30ppm in the described ferritic stainless steel molten steel.
According to the smelting process of a kind of high-aluminum low-silicon super-purity ferrite stainless steel provided by the invention, employing be, in step (5), fed calcium silk and soft stirring after, feeding titanium silk in the ferritic stainless steel molten steel, the pure titanium amount in the described titanium silk is 1～3kg/t.
According to the smelting process of a kind of high-aluminum low-silicon super-purity ferrite stainless steel provided by the invention, employing be, in final prepared high-aluminum low-silicon super-purity ferrite stainless steel, siliceous amount percentage composition is less than 0.3%, aluminium quality percentage composition is 0.01～0.1%.
According to the smelting process of a kind of high-aluminum low-silicon super-purity ferrite stainless steel provided by the invention, employing be, in the step (2),
When the higher limit of siliceous amount content in the high-aluminum low-silicon super-purity ferrite stainless steel that requires finally to make is 0.3%, all add ferrosilicon;
When the higher limit of siliceous amount content in the high-aluminum low-silicon super-purity ferrite stainless steel that requires finally to make is lower than or equals 0.2%, all add aluminium block;
When the higher limit of siliceous amount content in the high-aluminum low-silicon super-purity ferrite stainless steel that requires finally to make is between 0.2～0.3%, add ferrosilicon and aluminium block, the additional proportion of described ferrosilicon and aluminium block=(higher limit-0.2% of siliceous amount content in the high-aluminum low-silicon super-purity ferrite stainless steel that finally makes)/(higher limit of siliceous amount content in the high-aluminum low-silicon super-purity ferrite stainless steel that 0.3%-finally makes).
According to the smelting process of a kind of high-aluminum low-silicon super-purity ferrite stainless steel provided by the invention, employing be, in the step (3), described ferro-aluminum is shaped as block or spherical, density is 4.5～6.5g/cm
3, diameter 3～6cm; After step (3) is processed, CaO and SiO in the slag
2Mass ratio be higher than 2.8, CaO and Al in the slag
2O
3Mass ratio be higher than 1.
According to the smelting process of a kind of high-aluminum low-silicon super-purity ferrite stainless steel provided by the invention, employing be,
The condition of described high vacuum strong mixing is: vacuum pressure is controlled at below the 800Pa, and VOD furnace bottom argon blowing rate is controlled between 4～8L/ (mint);
The condition that described middle intensity stirs is: vacuum pressure is controlled at below the 2000Pa, and VOD furnace bottom argon blowing rate is controlled between 1～4L/ (mint);
The condition of described soft stirring is: under condition of normal pressure, between VOD furnace bottom argon blowing rate control 1～5L/ (mint).
The smelting process beneficial effect of a kind of high-aluminum low-silicon super-purity ferrite stainless steel provided by the present invention is:
1, can in the VOD smelting process, effectively improve aluminum precipitation deoxidation efficient, effectively improve aluminium content in the steel, and prevent that element silicon turns back in the molten steel in the slag, and be in lower level with the control silicone content, realized the smelting of high-aluminum low-silicon content super-purity ferrite stainless steel;
2, casting process adopts the protective casting measure, can prevent the secondary oxidation of high aluminium content molten steel, processes in conjunction with calcium, can avoid the obstruction of middle water containing opening; Moreover, owing to just realized aluminium deoxidation effect and the target control of aluminium content, the Al of generation in the VOD process
2O
3Being mixed in the large whipping process of VOD can fully grow up, and can effectively float behind the vacuum breaker, and then improve the purity of molten steel;
3, because the aluminium that institute adds the high-density ferro-aluminum can fully enter molten steel, greatly reduced its with slag in the probability of MgO direct reaction generation magnesium-aluminium spinel, establishment is harmful to the formation of inclusion magnesium-aluminium spinel, Al
2O
3The formation of the effective removal that is mingled with and inhibition magnesium-aluminium spinel can be avoided the obstruction of middle water containing opening equally;
4, because the lifting of aluminium content needs Ti Alloying such as steel grade, then in feeding the titanium process, can greatly suppress the oxidation of titanium, can improve yield of Titanium, the present invention has active effect to preventing owing to the nozzle clogging that titanium oxide causes;
5, the method safety of the present invention's design is reliable, and operating performance is strong, can greatly improve stability and the quality product of smelting.
Embodiment
Technological principle of the present invention is as follows:
One, the present invention requires to smelt target silicon, the aluminium content of super-purity ferrite stainless steel and is: siliceous amount percentage composition is less than 0.3%, and the purpose of aluminium quality percentage composition between 0.01～0.1% is:
The silicone content requirement mainly is in order to improve this stainless pickling performance less than 0.3%, if silicone content is higher than 0.3%, then the pickling difficulty of steel becomes large, has affected the smooth finish of steel, and in addition, the silicon of this content range can be guaranteed the toughness of steel, improves its processing characteristics; The aluminium specification of quality is between 0.01～0.1%, mainly consider from deoxidation effect, through calculation of thermodynamics, under 1550 ℃ of conditions, for the ferrite stainless molten steel of different Cr content, Al content is that the dissolved oxygen scope of 0.01% correspondence is 0.002～0.0025% (namely 20～25ppm), owing to also include inclusion in the total oxygen, so under the condition of total oxygen requirement less than 30ppm in the strand, the aluminium content requirement that this patent relates to is higher than 0.01%; Simultaneously, the aluminium upper content limit is 0.1%, mainly considers for some Ti-containing steels, need to guarantee aluminium-titanium content than greater than 0.15, the aluminium upper content limit is 0.1% can guarantee that titanium content can design and be limited to 0.7%, certainly, if aluminium content surpasses 0.1%, it is large that smelting cost becomes, and there is no need.
Two, pre-deoxidation and final deoxygenation:
For the as above smelting of the ferritic stainless steel of sial content range, the present invention adopts and carries out pre-deoxidation with ferrosilicon and aluminium block first, adds ferro-aluminum again and carries out final deoxygenation, shown in step (2) and (3).The present invention also requires to adopt the mode that ferrosilicon, aluminium block and ferro-aluminum carry out deoxidation that adds, and reason is, if whole deoxidation process only adds ferro-aluminum, because the ferro-aluminum cost is high than ferrosilicon, then whole smelting cost can promote, and causes easily carburetting serious; If only add ferrosilicon and aluminium block, because aluminium block is light, can not effectively enter molten steel, then can not finish the purpose that improves aluminium content in the steel; And if ferrosilicon, aluminium block and ferro-aluminum add the realization final deoxygenation together, because the binding ability of aluminium and oxygen is much larger than the bonding force of silicon and oxygen, Cr in slag
2O
3In the situation of substantially being reduced, aluminium meeting and SiO
2Kickback occuring, cause that silicone content raises fast in the steel, probably can not satisfy the terminal point silicone content less than 0.3% requirement.So, the present invention adopts and to add first the mode that ferrosilicon and part aluminium block carry out pre-deoxidation, in the pre-deoxidation process, oxygen content in steel can not drop to very low, Thermodynamics Formulas according to silicon, oxygen balance, pre-deoxidation process element silicon can react with oxygen in large quantities, thereby has guaranteed that silicone content is in the lower value scope in the treating processes steel.After pre-deoxidation is processed, add ferro-aluminum and carry out final deoxygenation, because it is a lot of that the density of ferro-aluminum will be higher than the fine aluminium piece, major part can sink in the molten steel after then ferro-aluminum can guarantee to enter the molten steel molten bath, and the aluminium that discharges after the fusing then can be introduced into molten steel, realizes effective bulk deoxidation, and effectively improve aluminium content in the steel, certainly, also have aluminium behind the partial melting and can directly enter in the slag and react, but this does not hinder the fast lifting of aluminium content in the steel.
1), pre-deoxidation
Step of the present invention (2) pre-deoxidation, adding the silicone content mass percent and be 70～80% ferrosilicon and/or aluminium block carries out pre-deoxidation and processes, the total add-on of ferrosilicon and/or aluminium block is 4～9kg/t, and add lime and fluorite carries out slag making, it is that ferrosilicon adds the higher value in 4～6 times of quality with the aluminium block add-on 2～3 times that lime adds quality, it is 0.05～0.3 times that lime adds quality that fluorite adds quality, high vacuum strong mixing 5～10min of lower treatment time of condition, processing requires siliceous amount content less than 0.1% after finishing, and the oxygen mass content is greater than 0.01%.
Before this step, molten steel has just passed through the processing of oxygen decarburization, a large amount of dissolved oxygens and chromic oxide are arranged in the molten bath, adding the purpose that ferrosilicon and aluminium block carry out pre-deoxidation is to utilize ferrosilicon or aluminium block that the chromium in the chromic oxide is restored, and do not reduce oxygen level in the steel as far as possible, aluminium block has very strong reducing power, can be directly and Cr in the slag
2O
3Reaction, the reducing power of influences silicon here, the Si reduction reactional equation is as follows:
1.5[Si]+(Cr
2O
3)＝2[Cr]+1.5(SiO
2)
Through calculation of thermodynamics, suppose oxide compound (Cr
2O
3) and (SiO
2) the thermodynamic activity take pure substance as standard be 1, calculate in chromium content is 18% stainless steel, silicone content need to just can impel reaction forward to carry out greater than 0.6%, this density that just means ferrosilicon can not be too large, guarantee to float on the ferrosilicon molten steel top directly and (the Cr in the slag
2O
3) react, the molten steel local silicon content that guarantees to contact with slag is greater than 0.6%, and thus, this patent is selected ferrosilicon commonly used, and its silicone content is 70～80%, can satisfy the not too high requirement of ferrosilicon density, and certainly, along with the fusing of lime, slag is middle SiO mutually
2Activity reduces, and has also accelerated silicon and has carried out pre-deoxidation.Why the present invention also selects aluminium to carry out pre-deoxidation, mainly is that Wen Houyou further discusses for some lower steel grades of target silicone content requirement.Since the ferrosilicon that contains 75% silicon with etc. the aluminium block deoxidation amount of weight close to 1, so for ferrosilicon and aluminium block add-on scope, also low situation of the low simultaneously initial carbon content of chromium content in steel, it is fewer needing ferrosilicon and aluminium block to add total amount, on the contrary, the high simultaneously initial carbon content of chromium content is also high in the steel, and it is many needing ferrosilicon and aluminium block total amount, below with two kinds of extreme cases that may occur aborning as the example of analyzing, determine that with this ferrosilicon and aluminium block add the scope of total amount.Through calculating, for the ferrite stainless smelting steel of low chromium content, be 11.6% steel grade such as chromium content, molten steel enters that initial carbon is under 0.3% condition before the VOD, the about 7Nm of ton steel blowing oxygen quantity
3/ t can remove carbon under vacuum condition, according to previous experiences, 30～40% oxygen meeting chromic oxide formation Cr is arranged approximately
2O
3The pure silicon or the 3.5～4.6kg fine aluminium that then need about 2.6～3.45kg, consider the content of Silicon in Ferrosilicon, the lower value that the present invention sets demand ferrosilicon and aluminium block total amount is 4kg/t, and for the smelting of high chromium steel, be 22.6% steel grade such as chromium content, enter initial carbon before the VOD and be in 0.6% the situation, the about 13Nm of ton steel blowing oxygen quantity
3/ t can remove carbon under vacuum condition, according to previous experiences, 35～45% oxygen meeting chromic oxide formation Cr is arranged approximately
2O
3, then need the pure silicon of about 5.6～7.24kg or the fine aluminium of 7.5～9.7kg, consider the content of Silicon in Ferrosilicon, the higher limit that the present invention sets demand ferrosilicon and the total add-on of aluminium block is 9kg/t.The add-on of lime is according to the SiO that generates
2Amount come to be determined, satisfy the scope that basicity requires, and the present invention determines that it is that ferrosilicon adds the higher value in 4～6 times of quality with the aluminium block add-on 2～3 times that lime adds quality, can satisfy basicity of slag and be controlled at scope more than 2.8, CaO and Al in the slag
2O
3Mass ratio be higher than 1.For the adding of fluorite, main purpose is to accelerate dissolving and the fusing of lime, and its add-on will be determined according to the complexity of lime fusing itself, according to knowhow, determines that it is 0.05～0.3 times that lime adds quality that fluorite adds quality.Because the ferrosilicon and the aluminium block that add in the step (2) do not reduce dissolved oxygen content in the steel significantly, and require oxygen level greater than 0.01%, can guarantee reaction later in the steel silicone content less than 0.1%.Although this step has been stipulated the scope of ferrosilicon and the total add-on of aluminium block, in practical implementation, also will be according to the carbon rejection process institute oxygen blast gas of smelting process in decarburization, secondary combustion, loss, the concrete allocation proportion that enters the molten bath is determined the oxygen amount that ferrosilicon and aluminium block need be sloughed, because decarburized amount is known, post-combustion rate can analyze according to composition of fumes, loss amount also can return out according to historical data, then the oxygen ratio that enters the molten bath can calculate, can calculate thus the occurrence of ferrosilicon and the total add-on of aluminium block, this value is in the scope that the present invention determines.
The present invention is for step (2), also requires to determine the ferrosilicon that relates to and/or the additional proportion of aluminium block:
If when being limited to 0.3% on the siliceous amount content (being the target silicone content) in the high-aluminum low-silicon super-purity ferrite stainless steel that a requires finally to make, all add ferrosilicon;
If siliceous amount upper content limit requirement is lower in the high-aluminum low-silicon super-purity ferrite stainless steel that b requires finally to make, namely when higher limit is lower than 0.2% (comprising 0.2%), require all to add aluminium blocks;
C, when siliceous amount upper content limit in the high-aluminum low-silicon super-purity ferrite stainless steel that requires finally to make between 0.2～0.3% the time, the additional proportion of ferrosilicon and aluminium block=(higher limit-0.2% of siliceous amount content in the high-aluminum low-silicon super-purity ferrite stainless steel that finally makes)/(higher limit of siliceous amount content in the high-aluminum low-silicon super-purity ferrite stainless steel that 0.3%-finally makes).
Wherein, the higher limit of siliceous amount content represents the value that silicone content can not surpass in the described high-aluminum low-silicon super-purity ferrite stainless steel that finally makes.
Why the present invention also selects aluminium to carry out pre-deoxidation, mainly be for some lower steel grades of target silicone content requirement, when the target silicone content only requires less than 0.3% the time, all add ferrosilicon herein and the control of the basicity by thereafter can be realized this goal, yet, if the target silicone content requires less than 0.2%, consider that the final deoxygenation process also can form certain silicon amount that increases, greatly about about 0.1～0.2%, if then adding ferrosilicon herein forms and to increase silicon and just can not satisfy final silicone content less than 0.2% requirement, so, this situation requires all to add aluminium, and between 0.2～0.3%, the present invention designs ferrosilicon and aluminium block is mixed for the siliceous amount upper content limit of target value, concrete ratio requires to determine according to target silicone content higher limit, can meet the demands.
2), final deoxygenation
Step of the present invention (3) final deoxygenation process, add ferro-aluminum and carry out the final deoxygenation processing, ferro-aluminum contains aluminium quality percentage composition 20～60%, carbonaceous amount content is less than 0.1%, all the other are iron and some micro impurity elements, add-on 2～the 6kg/t of fine aluminium in the ferro-aluminum, and add lime and fluorite, the lime additional amount is 2～3 times of fine aluminium amount in the ferro-aluminum, it is 0.05～0.3 times that lime adds quality that fluorite adds quality, stir 2～5min in the lower intensity of vacuum condition first after material adds, then process 12～18min under the high vacuum strong mixing condition, processing can guarantee that siliceous amount content is less than 0.3% after finishing, aluminium mass content 0.01～0.1%, the oxygen mass content is less than 0.003%.
Selection is with the reductor of the relatively high ferro-aluminum of density as final deoxygenation, discuss as the front, after ferro-aluminum adds, its aluminium that comprises can enter the molten steel molten bath, and do not resemble add the fine aluminium after in large quantities with slag in oxide compound reaction and substantially do not enter the molten steel molten bath, this point that production practice are verified, aluminium quality percentage composition 20～60% is except satisfying the density requirements scope in the selection ferro-aluminum, be lower than 20% if also considered aluminium content, then iron content is excessive, because the present invention has requirement to the add-on of fine aluminium, then can cause the add-on of ferro-aluminum own excessive, not only can cause carbon increasing amount to increase, and can cause the molten bath temperature drop excessive, 1kg aluminium is participated in energy that reaction discharges and can be satisfied about 4kg iron and be heated to current 1700 ℃ of molten steel from room temperature as calculated, thus, determine that the whole aluminium content of ferro-aluminum should be higher than 20%, aluminium content is lower than 60% and mainly requires to consider from density control in the ferro-aluminum, and ferro-aluminum requires density to be higher than 4.5g/cm
3, corresponding aluminium content is 60%.Carbon content is less than 0.01% in the requirement ferro-aluminum, mainly be to consider from the aspect of control carburetting, because smelting steel grade is ultra low-carbon steel, carburetting is the smaller the better after should controlling ferro-aluminum and adding, and is 0.1% situation for the ferro-aluminum carbon containing, and a ton steel adds in the situation of ferro-aluminum amount 10kg, the molten steel carbon increasing amount is 10ppm, this basic or acceptable, so require that carbon content should be less than 0.1% in the ferro-aluminum, this also is that ferro-aluminum is produced attainable carbon content scope.The add-on of ferro-aluminum is by wherein fine aluminium, and the present invention requires the fine aluminium add-on at 2～6kg/t, and aluminium adds the dissolved oxygen that not only will slough in the steel, Cr in the slag that the pre-deoxidation process ferrosilicon that also will further reduce fails to remove
2O
3, consume approximately fine aluminium 0.5～2.4kg/t, and might with SiO in the slag
2Further reaction, the silicon amount 0.1%～0.2% of returning that causes, consume approximately fine aluminium 1.4～2.6kg/t, also satisfy in addition the target 0.01～0.1% of final aluminium content, consume approximately fine aluminium 0.1～1kg/t, to draw the scope 2～6kg/t of fine aluminium add-on such as upper lower limit value addition and higher limit addition, the ferro-aluminum add-on is that the fine aluminium add-on is divided by its aluminum content.The purpose of adding lime is to continue to guarantee CaO and Al in the slag
2O
3Mass ratio.After requiring this step material to add, the present invention stirs 2～5min in the lower intensity of vacuum condition first, its objective is the stirring that requires molten steel is had on the one hand some strength, impel aluminium to enter molten steel, on the other hand, if stirring intensity is excessive, can be sprayed onto ferro-aluminum on the top of the slag, cause aluminium not enter in the molten steel, so, take middle intensity to stir here.This step requires high vacuum strong mixing treatment time 12～18min will guarantee that mainly the sufficient time allows Al
2O
3Be mingled with and grow up, could the soft whipping process under atmospheric condition thereafter fully float and removed.In addition, it is to be noted, because the aluminium in the ferro-aluminum can fully enter molten steel, when deoxidation is arrived to a certain degree, avoided aluminium directly to enter the MgO that goes in the slag in the reducing slag, thereby greatly restricted the formation of magnesium-aluminium spinel, for stainless steel, magnesium-aluminium spinel is the inclusion that is harmful to very much, can cause product defects.Just because of adopt ferro-aluminum to realize the control of control of aluminum and silicon, processing can guarantee siliceous amount content less than 0.3% after finishing, aluminium mass content 0.01～0.1%, and the oxygen mass content is less than 0.003%.
This patent has been done requirement to shape and density that step (3) adds ferro-aluminum, and for the ferro-aluminum that step (3) relates to, it is block or spherical to require it to be shaped as, real density 4.5～6.5g/cm
3, diameter 3～6cm.
Be shaped as and block or spherically make and convenient the adding for convenient, and if diameter less than 3cm, may cause ferro-aluminum to enter the molten steel molten bath from feed bin after, its impact depth is inadequate, and size needs less than 6cm, considers that mainly size is inconvenient to feed in raw material after too large.Require 4.5～6.5g/cm for density range
3, mainly be to want 2/3 part to be immersed in the molten steel in order to satisfy after it adds, molten steel density 6.9～7.2g/cm
3About, so require density to be greater than 4.5g/cm
3, consider that simultaneously aluminium content can not be lower than 20%, then upper density limit is 6.5g/cm
3
This patent is for smelting step (3), require final deoxygenation after, basicity of slag is CaO and SiO in the slag
2Mass ratio control be higher than 2.8, CaO and Al in the slag
2O
3Mass ratio be higher than 1.
Requiring basicity of slag to be higher than 2.8 behind the final deoxygenation mainly is from control SiO
2Consider on the activity, according to CaO-SiO
2-Al
2O
3Ternary activity figure, under this basicity value condition take pure substance as standard state SiO
2Activity quotient be approximately 0.028, through calculation of thermodynamics, be example for the super-purity ferrite stainless steel of smelting 22.6%Cr content, balance SiO in the slag that 0.01% aluminium content and 0.3% silicone content are corresponding in the steel
2Activity is 0.009, and under this basicity condition, further inverse goes out SiO
2Molar fraction 0.32 in slag, because basicity set and has been higher than 2.8, and SiO then
2Percentage composition inevitable less than 26%, this scope substantially can draw its molar fraction and generally can be controlled in 0.32, can find out thus, this basicity scope can guarantee that Al under the as above sial content condition no longer removes the SiO in the reducing slag
2For the steel grade of other chromium content, if chromium content less than 22.6%, owing to chromium is to reduce the element that silicon activity improves aluminium activity, according to smelting thermodynamic principles, silicon activity becomes large and aluminium activity reduces in the steel, the Al element further can not remove the SiO in the reducing slag
2Otherwise the Al element agree to remove SiO in the reducing slag
2Consider that it is not a lot of that chromium content is higher than 22.6% steel grade, and can be by regulating SiO in the slag
2The mode of content stops SiO in the further reducing slag of Al
2, and the too high meeting of basicity lower limit set causes the quantity of slag to increase, so the present invention determines that finally basicity of slag should be higher than 2.8, this also is the minimum requirements to the basicity of slag value.For basicity of slag, there is not upper limit requirement, mainly consider if the aluminium content requirement is higher Al in the slag
2O
3Increase, basicity of slag may raise, even final slag becomes SiO
2The low-down aluminium calcium slag of content, namely slag is with CaO-Al
2O
3Be the slag of main component, this allows in the present invention.The present invention requires CaO and Al in the slag
2O
3Mass ratio be higher than 1, mainly be for SiO in the slag
2Content is lower, develops into the situation of aluminium calcium slag, CaO and Al in the requirement
2O
3Mass ratio be higher than 1, can guarantee well that slag has and absorb well Al
2O
3Ability, for aluminium calcium slag, CaO and Al
2O
3Mass ratio in the 1.1-1.4 situation, slag has the ability of good absorption inclusion, and has good flowability.The present invention is to CaO and Al
2O
3The also not restriction of the ratio upper limit, mainly also be the situation for non-aluminium calcium slag series, allow Al
2O
3In the low levels scope.For the control of CaO content in the slag, in the setting of step (2) and (3) lime adding amount, control.
Three, for step (5)
1), soft stirring
Feed soft stirring before the pure calcium silk and allow the inclusion Al that under vacuum condition, has grown up
2O
3Inclusion floating enters the slag phase, feeds soft stirring behind the pure calcium silk and promotes to feed the low melting point calcium aluminate that generates behind the calcium and be mingled with further come-up and enter the slag phase.
2), feed silk
A), feed calcium silk (being the calcium treatment process)
The calcium treatment process, namely under normal pressure, feed pure calcium silk with wire feeder to molten steel, pure calcium feed quantity is 0.1～0.3kg/t, after having fed the calcium silk, under condition of normal pressure, the bottom Argon is carried out soft stirring to molten steel, and soft churning time 5～10min requires after processing finishes that the mass content of calcium is controlled at 15～30ppm in the steel.
Because what the present invention smelted is high-aluminum steel, the add-on of deoxidation process aluminium is relatively very large, although by the Al of various measures to generating
2O
3Be mingled with and carried out from molten steel, discharging, and prevent secondary oxidation, yet, in production practice, still there is Al
2O
3Stop up the risk of middle water containing opening, reason is in the high situation of aluminium content, and the MgO of aluminium in still might reducing slag, the magnesium-aluminium spinel of formation are mingled with and are difficult to get rid of, thereby may form the origin of obstruction, adds and does not get rid of clean Al
2O
3Be mingled with, thereby have the risk of nozzle clogging.This case has dropped to this risk by various measures very low, yet, in order to ensure high-aluminum steel produce highly stable, the present invention has still adopted the calcium treatment technology, with the risk of avoiding nozzle clogging to form.It mainly is with Al that calcium is processed
2O
3Be mingled with and change into 12CaO7Al
2O
3Low melting point be mingled with, it is generally acknowledged Al in the steel
2O
3Content is 0.01% to the maximum, with the Al of this amount
2O
3Become 12CaO7Al
2O
3The calcium contents that needs is 67ppm, the dissolving content general requirement of the rear calcium constituent self of simultaneously calcium processing end is 0.09 times to 0.15 times of aluminium content, if aluminium content 0.03%, then solubilize calcium content requires 30ppm approximately, the pure calcium amount that need to enter like this molten steel is 0.01% for 100ppm then, consider that the recovery rate for high-aluminum steel hello calcium process calcium is higher than 30%, final definite pure calcium feed quantity is 0.1～0.3kg/t, and finally determine calcium contents span of control 15～30ppm, can satisfy the calcium of aluminium content range of the present invention processes, realize effective sex change of inclusion, if final ca content is higher than 30ppm, the risk that corrodes middle water containing opening is arranged.
B), feed the titanium silk
For the steel grade that requires to smelt titaniferous, can in the ferritic stainless steel molten steel, feed the titanium silk again, pure titanium amount is 1～3kg/t in the described titanium silk, realizes Ti Alloying.Wherein, pure titanium amount is that titanium silk feed quantity multiply by titanium content in the titanium silk.
Four, for step (6)
1), soft stirring 15～30min
This soft churning time fully guarantees the further come-up of inclusion, has further improved the purity of molten steel.
2), require molten steel is carried out continuous casting under protective atmosphere
Carry out argon shield and the argon shield of middle water containing opening and the argon shield of tundish top that continuous casting has comprised large water-coating port under the protective atmosphere; purpose is the secondary oxidation that prevents molten steel; smelt for high-aluminum steel; these protections also need; these are attainable ripe continuous casting technology, exceed description herein.
Five, for described middle intensity stirring, high vacuum strong mixing and soft stirring
The condition that described middle intensity stirs is: vacuum pressure is controlled at below the 2000Pa, and VOD furnace bottom argon blowing rate is controlled between 1～4L/ (mint);
The condition of described high vacuum strong mixing is: vacuum pressure is controlled at below the 800Pa, and VOD furnace bottom argon blowing rate is controlled between 4～8L/ (mint);
The condition of described soft stirring is: under condition of normal pressure, between VOD furnace bottom argon blowing rate control 1～5L/ (mint).
Wherein, the setting of correlation parameter is determined according to production practice, the lower intensity of vacuum condition stirs will guarantee not fierce seething of the top of the slag, high vacuum strong mixing condition will guarantee that the molten steel splash does not affect production, and soft stirring will guarantee that the top of the slag is not blown open, under these conditions, grope according to production, finally determined relevant bottom blowing flow range.
Need to prove, symbol in the unit that the present invention relates to " t " expression ton molten steel, " L " be for rising, " min " expression minute, the kilogram amount that " kg/t " expression adds in the molten steel per ton, " L/ (mint) " expression in steel per ton, the argon gas amount that is blown into of per minute.
Embodiment
Describe the inventive method in detail in the embodiment of producing low silicon high-aluminum ferritic stainless steel and the effect that obtains below in conjunction with embodiment, be illustrated as an example of the super-purity ferrite stainless steel of producing 409,443 and 445 these 3 trade mark steel grades example respectively.
Embodiment 1
Present embodiment is to the requirement of refining unit VOD stove: equipment can be processed molten steel 120t, and final vacuum is less than 300Pa, and Argon always air blowing ability in bottom is higher than 60Nm
3/ h, ladle lining are magnesia-calcium brick.Steel grade is 409, molten steel amount 116000kg, i.e. and 116t, the molten steel Initial Composition was before VOD smelted:
C:0.3%, Si:0.25%, Cr:11.6%, S:0.010%, N:0.025%, Mn:0.56%, P:0.015%, full O:0.02%, Ti:0.01%, Al:0.001%, all the other are Fe and micro impurity element.
1580 ℃ of molten steel initial temperatures.
Present embodiment silicone content target is less than 0.26%, aluminium content about 0.03%, and concrete steps are as follows:
1) molten steel is after oxygen decarburization and free carbonization treatment, and the oxygen depletion amount is 885Nm
3, free decarburization time 15min, after processing finishes, 1630 ℃ of molten steel temperatures, composition is as follows:
C:0.003%, Si:0.01%, Cr:11.1%, S:0.008%, N:0.007%, Mn:0.14%, P:0.015%, full O:0.04%, Ti:0.01%, Al:0.001%, all the other are Fe and micro impurity element.
2) pre-deoxidation, be 0.27% according to siliceous amount content requirement higher limit in the high-aluminum low-silicon super-purity ferrite stainless steel that finally makes, adding siliceous 77% ferrosilicon 400kg (is 3.45kg/t, conversion method: 400kg ÷ molten steel amount 116t, in embodiment 1 scope, except the quality of delime and fluorite, under the conversion method with) and aluminium block 200kg (being 1.71kg/t) total 600kg (being 5.16kg/t) carry out pre-deoxidation, and adding lime 1.6t, fluorite 200kg carries out slag making, material adds the final vacuum pressure-controlling below 800Pa, and argon bottom-blowing stirring intensity 600L/min (be 5.17L/ (mint), conversion method: 600L/min ÷ molten steel amount 116t, in embodiment 1 scope, same under the conversion method), treatment time 8min guarantees that lime tentatively melts.Silicone content 0.08% after processing finishes, oxygen level 0.015%.
3) final deoxygenation adds the ferro-aluminum 650kg that contains aluminium 40%, ferro-aluminum diameter 5cm, density 5.4g/cm
3Carbon containing 0.008%,, contain fine aluminium 260kg (being 2.24kg/t), and add lime 600kg, fluorite 50kg carries out final deoxygenation, adjusts the end after material adds and stirs argon blowing rate to 150L/min, middle intensity stirs 3min, carry out subsequently high strength and stir argon bottom-blowing flow 800L/min (being 6.90L/ (mint)), treatment time 15min.After processing finishes, silicone content 0.19%, aluminium content 0.054%, oxygen level 7.8ppm.The slag main component is: CaO 60%, SiO
212%, Al
2O
317%, MgO 3%, satisfies basicity of slag requirement and CaO and Al
2O
3Ratio is greater than 1.Temperature was 1570 ℃ after processing finished.
4) vacuum breaker.
5) soft stirring 10min, argon bottom-blowing stirring intensity 200L/min (being 1.72L/ (mint)).Calcium is processed, and adds pure calcium silk 20kg (being 0.17kg/t) by wire feeder, feeds silk and finishes rear soft stirring 10min, argon bottom-blowing stirring intensity 200L/min (being 1.72L/ (mint)).This steel grade need to feed the titanium silk and carry out Ti Alloying, and the pure titanium amount in the titanium silk is 150kg (being 1.38kg/t), terminal point titanium 0.1%.
6) continue soft stirring 20min, argon bottom-blowing stirring intensity 180L/min (being 1.55L/ (mint)).Continuous casting in the protective atmosphere, large water-coating port, middle water containing opening all have blowing argon.
The middle water containing opening opening degree is highly stable in the casting cycle, and violent fluctuation does not occur, and total fluctuation range shows that mouth of a river knot does not occur to be filled in, and the mouth of a river does not occur yet corrode in 3%.
Final molten steel is cast into base, and composition is as follows:
C:0.006%, Si:0.20%, Cr:11.7%, S:0.001%, N:0.008%, Mn:0.23%, P:0.015%, full O:0.0020%, Ti:0.09%, Al:0.044%, all the other are Fe and micro impurity element.
Wherein silicone content slightly rises behind vacuum breaker, may be SiO in the slag
2On a small quantity by the result of aluminium reducing; And aluminium content slightly descends, reason is along with the passing of the reduction of temperature and time and possible secondary oxidation, has impelled contacting of aluminium and oxygen, causes its composition slightly to descend; Deoxidation process causes carbon content relatively before the processing to a certain degree rising to be arranged because the ferro-aluminum that adds contains a certain amount of carbon, but still in ultrapure scope.
The relative old process of magnesium-aluminium spinel the amount of inclusions greatly reduces in the strand, and mainly to be size be mingled with and spherical plasticity CaO-Al below the 10 μ m at the TiN below the 5 μ m or Ti (CN) inclusion
2O
3-SiO
2Be mingled with (part contain a small amount of MgO), to the performance of steel especially surface property without harmful effect.
Embodiment 2
Present embodiment is to the requirement of refining unit VOD: equipment can be processed molten steel 120t, and final vacuum is less than 300Pa, and Argon always air blowing ability in bottom is higher than 60Nm
3/ h, ladle lining are magnesia-calcium brick.Steel grade is 443, molten steel amount 108400kg, i.e. and 108.4t, the molten steel Initial Composition was before VOD smelted:
C:0.36%, Si:0.018%, Cr:20.8%, S:0.005%, N:0.015%, Mn:0.3%, P:0.010%, full O:0.02%, Ti:0.01%, Al:0.001%, all the other are Fe and micro impurity element.
1600 ℃ of molten steel initial temperatures.
Present embodiment silicone content target is less than 0.2%, aluminium content about 0.02%, and concrete steps are as follows:
1) molten steel is after oxygen decarburization and free carbonization treatment, and the oxygen depletion amount is 1266Nm
3, free decarburization time 20min, after processing finishes, 1670 ℃ of molten steel temperatures, composition is as follows:
C:0.005%, Si:0.01%, Cr:19.7%, S:0.004%, N:0.004%, Mn:0.14%, P:0.015%, full O:0.05%, Ti:0.01%, Al:0.001%, all the other are Fe and micro impurity element.
2) pre-deoxidation, be 0.2% according to siliceous amount content requirement higher limit in the high-aluminum low-silicon super-purity ferrite stainless steel that finally makes, all add aluminium block under this requirement condition, and do not add ferrosilicon, avoid increasing silicon, adding aluminium block 780kg (is 7.20kg/t, conversion method: 780kg ÷ molten steel amount 108.4t, in embodiment 2 scopes, except the quality of delime and fluorite, under the conversion method with) carry out pre-deoxidation, and add lime 1.6t, and fluorite 100kg carries out slag making, and material adds the final vacuum pressure-controlling below 800Pa, argon bottom-blowing stirring intensity 700L/min (is 6.46L/ (mint), conversion method: 700L/min ÷ molten steel amount 108.4t, in embodiment 2 scopes, same under the conversion method), treatment time 6min guarantees that lime tentatively melts.Silicone content 0.04% after processing finishes, oxygen level 0.02%.
3) final deoxygenation adds the ferro-aluminum 500kg (being 4.61kg/t) that contains aluminium 40%, ferro-aluminum diameter 5cm, density 5.4g/cm
3Carbon containing 0.01%, contain fine aluminium 200kg (being 1.85kg/t), and add lime 400kg, fluorite 50kg, carry out final deoxygenation, adjust the end after material adds and stir argon blowing rate to 200L/min (being 1.85L/ (mint)), middle intensity stirs 4min, carries out subsequently high strength and stirs, argon bottom-blowing flow 800L/min (being 7.38L/ (mint)), treatment time 18min.After processing finishes, silicone content 0.20%, aluminium content 0.018%, oxygen level 10ppm.The slag main component is: CaO55%, SiO
22%, Al
2O
337%, MgO 5%, satisfies basicity of slag requirement and CaO and Al
2O
3Ratio is greater than 1.Temperature was 1605 ℃ after processing finished.
4) vacuum breaker.
5) soft stirring 9min, argon bottom-blowing stirring intensity 200L/min (being 1.85L/ (mint)).Calcium is processed, and adds pure calcium silk 12.8kg (being 0.12kg/t) by wire feeder, feeds silk and finishes rear soft stirring 10min, argon bottom-blowing stirring intensity 200L/min (being 1.85L/ (mint)).This steel grade need to feed the titanium silk and carry out Ti Alloying, and pure titanium amount is 300kg (being 2.77kg/t) in the described titanium silk, terminal point titanium 0.2%.
6) continue soft stirring 25min, argon bottom-blowing stirring intensity 160L/min (being 1.48L/ (mint)).Continuous casting in the protective atmosphere, large water-coating port, middle water containing opening all have blowing argon.
The middle water containing opening opening degree is highly stable in the casting cycle, and violent fluctuation does not occur, and total fluctuation range shows that mouth of a river knot does not occur to be filled in, and the mouth of a river does not occur yet corrode in 3%.
Final molten steel is cast into base, and composition is as follows:
C:0.008%, Si:0.20%, Cr:20.8%, S:0.001%, N:0.006%, Mn:0.21%, P:0.015%, full O:0.0018%, Ti:0.15%, Al:0.019%, all the other are Fe and micro impurity element.
Wherein aluminium content slightly rises, and this is the reason that further reduces molten steel oxygen gesture owing to hello titanium; And silicone content remains unchanged, and reason is SiO in the slag
2Content is extremely low, has avoided silicon deoxidation process in the further reducing slag of aluminium or titanium; Because the ferro-aluminum that adds contains a certain amount of carbon, cause carbon content relatively before the processing to a certain degree rising to be arranged, but still in ultrapure scope.
The relative old process of magnesium-aluminium spinel the amount of inclusions greatly reduces in the strand, and mainly to be size be mingled with and spherical plasticity CaO-Al below the 10 μ m at the TiN below the 5 μ m or Ti (CN) inclusion
2O
3-SiO
2Be mingled with (part contain a small amount of MgO), to the performance of steel especially surface property without harmful effect.
Embodiment 3
Present embodiment is to the requirement of refining unit VOD: equipment can be processed molten steel 120t, and final vacuum is less than 300Pa, and Argon always air blowing ability in bottom is higher than 60Nm3/h, and ladle lining is magnesia-calcium brick.Steel grade is 444, molten steel amount 110000kg, i.e. and 110t, the molten steel Initial Composition was before VOD smelted:
C:0.40%, Si:0.06%, Cr:18.8%, S:0.005%, N:0.012%, Mn:0.3%, P:0.010%, full O:0.02%, Ti:0.01%, Al:0.001%, all the other are Fe and micro impurity element.
1620 ℃ of molten steel initial temperatures.
Present embodiment silicone content target is less than 0.3%, aluminium content about 0.04%, and concrete steps are as follows:
1) molten steel is after oxygen decarburization and free carbonization treatment, and the oxygen depletion amount is 1440Nm
3, free decarburization time 20min, after processing finishes, 1700 ℃ of molten steel temperatures, composition is as follows:
C:0.006%, Si:0.20%, Cr:17.4%, S:0.005%, N:0.005%, Mn:0.14%, P:0.015%, full O:0.05%, Ti:0.01%, Al:0.001%, all the other are Fe and micro impurity element.
2) pre-deoxidation, be 0.3% according to siliceous amount content requirement higher limit in the high-aluminum low-silicon super-purity ferrite stainless steel that finally makes, the full ferrosilicon that adds under this requirement condition, and do not add aluminium block, adding the ferrosilicon 900kg that contains 77% silicon (is 8.12kg/t, conversion method: 900kg ÷ molten steel amount 110t, in embodiment 3 scopes, except the quality of delime and fluorite, same under the conversion method), do not add the aluminium block pre-deoxidation, and add lime 3.6t, and fluorite 200kg carries out slag making, and material adds the final vacuum pressure-controlling below 400Pa, argon bottom-blowing stirring intensity 800L/min (is 7.27L/ (mint), conversion method: 800L/min ÷ molten steel amount 110t, in embodiment 3 scopes, same under the conversion method), treatment time 10min guarantees that lime tentatively melts.Silicone content 0.1% after processing finishes, oxygen level 0.013%.
3) final deoxygenation adds the ferro-aluminum 750kg (being 6.82kg/t) that contains aluminium 47%, ferro-aluminum diameter 5cm, density 5.1g/cm
3Carbon containing 0.007%, contain fine aluminium 350kg (being 3.18kg/t), and add lime 700kg, fluorite 200kg, carry out final deoxygenation, adjust the end after material adds and stir argon blowing rate to 200L/min (being 1.82L/ (mint)), middle intensity stirs 5min, carries out subsequently high strength and stirs, argon bottom-blowing flow 750L/min (being 6.82L/ (mint)), treatment time 18min.After processing finishes, silicone content 0.27%, aluminium content 0.035%, oxygen level 10ppm.The slag main component is: CaO65%, SiO
218%, Al
2O
310%, MgO5% satisfies basicity of slag requirement and CaO and Al
2O
3Ratio is greater than 1.Temperature was 1642 ℃ after processing finished.
4) vacuum breaker.
5) soft stirring 10min, argon bottom-blowing stirring intensity 200L/min (being 1.82L/ (mint)).Calcium is processed, and adds pure calcium silk 25kg (being 0.23kg/t) by wire feeder, feeds silk and finishes rear soft stirring 10min, argon bottom-blowing stirring intensity 180L/min (being 1.64L/ (mint)).This steel grade need not Ti Alloying, so need not to feed the titanium silk.
6) continue soft stirring 15min, argon bottom-blowing stirring intensity 180L/min (being 1.64L/ (mint)).Continuous casting in the protective atmosphere, large water-coating port, middle water containing opening all have blowing argon.
The middle water containing opening opening degree is highly stable in the casting cycle, and violent fluctuation does not occur, and total fluctuation range shows that mouth of a river knot does not occur to be filled in, and the mouth of a river does not occur yet corrode in 5%.
Final molten steel is cast into base, and composition is as follows:
C:0.01%, Si:0.29%, Cr:18.6%, S:0.001%, N:0.007%, Mn:0.21%, P:0.015%, full O:0.0017%, Ti:＜0.01%, Al:0.030%, all the other are Fe and micro impurity element.
And aluminium content slightly descends, and silicone content keeps slightly rising, and reason is SiO in the slag
2Content is higher, has caused silicon in the further reducing slag of aluminium, and deoxidation process causes carbon content relatively before the processing to a certain degree rising to be arranged because the ferro-aluminum that adds contains a certain amount of carbon, but still in ultrapure scope.
The relative old process of magnesium-aluminium spinel the amount of inclusions greatly reduces in the strand, and inclusion mainly is the spherical plasticity CaO-Al of size below 10 μ m
2O
3-SiO
2Be mingled with (part contain a small amount of MgO), to the performance of steel especially surface property without harmful effect.
The smelting process of a kind of high-aluminum low-silicon super-purity ferrite stainless steel provided by the present invention, but smelting Si content is less than 0.3%, the low silicon high alumina super clean ferritic stainless steel of aluminium content 0.01～0.1%, the steel billet total oxygen content is less than 30ppm, improved the pickling performance of product, but present method is the formation of the harmful inclusion magnesium-aluminium spinel of establishment also, effectively removes Al
2O
3Inclusion, and in Ti-containing steel, suppressed the oxidation of titanium, avoided the clogging of tundish nozzle were of casting process.
Claims (8)
1. the smelting process of a high-aluminum low-silicon super-purity ferrite stainless steel is characterized in that, comprises the steps:
(1), the ferritic stainless steel molten steel is carried out vacuum-oxygen decarbonizing and free carbonization treatment in the VOD stove, the ferritic stainless steel molten steel main component that obtains after the processing requires: chromium quality percentage composition 10 ~ 23%, carbonaceous amount percentage composition is less than 0.01%, and nitrogen quality percentage composition is less than 0.01%;
(2), pre-deoxidation: in the ferritic stainless steel molten steel that after step (1) is processed, obtains, add ferrosilicon and/or aluminium block and carry out the pre-deoxidation processing, and add lime and fluorite carries out slag making, the total add-on of described ferrosilicon and/or aluminium block is 4 ~ 9kg/t, the quality percentage composition of described Silicon in Ferrosilicon is 70 ~ 80%, and described lime adding quality value is the higher value in following two scopes: ferrosilicon adds 4 ~ 6 times or 2 ~ 3 times of aluminium block adding quality of quality; It is 0.05 ~ 0.3 times that lime adds quality that described fluorite adds quality, then under high vacuum strong mixing condition, and treatment time 5 ~ 10min;
(3), final deoxygenation: in the ferritic stainless steel molten steel that after step (2) is processed, obtains, add ferro-aluminum and carry out the final deoxygenation processing, the quality percentage composition of aluminium is 20 ~ 60% in the described ferro-aluminum, and add lime and fluorite carries out slag making, the add-on of fine aluminium is 2 ~ 6kg/t in the described ferro-aluminum, the add-on of described lime is 2 ~ 3 times of fine aluminium add-on in the ferro-aluminum, the fluorite add-on is 0.05 ~ 0.3 times that lime adds quality, then under vacuum condition, middle intensity stirs 2 ~ 5min, then under high vacuum strong mixing condition, process 12 ~ 18min;
(4), vacuum breaker;
(5), under condition of normal pressure, with the soft stirring 8 ~ 10min of described ferritic stainless steel molten steel, then under condition of normal pressure, feed the calcium silk to described ferritic stainless steel molten steel, feed after the calcium silk finishes soft stirring 5 ~ 10min;
(6), continue soft stirring 15 ~ 30min, afterwards the ferritic stainless steel molten steel is carried out continuous casting in protective atmosphere, finally obtain the high-aluminum low-silicon super-purity ferrite stainless steel, its siliceous amount percentage composition is less than 0.3%, aluminium quality percentage composition is 0.01 ~ 0.1%.
2. the smelting process of a kind of high-aluminum low-silicon super-purity ferrite stainless steel according to claim 1, it is characterized in that, in the step (2), after step (2) is processed, the mass content of silicon requires the mass content of oxygen greater than 0.01% less than 0.1%, greater than 0 in the described ferritic stainless steel molten steel.
3. the smelting process of a kind of high-aluminum low-silicon super-purity ferrite stainless steel according to claim 1, it is characterized in that, in the step (3), after step (3) is processed, the mass content of silicon is less than 0.3%, greater than 0 in the described ferritic stainless steel molten steel, the mass content of aluminium is 0.01 ~ 0.1%, and the mass content of oxygen is less than 0.003%.
4. the smelting process of a kind of high-aluminum low-silicon super-purity ferrite stainless steel according to claim 1, it is characterized in that, in step (5), the described calcium silk of feeding is to feed pure calcium silk in the ferritic stainless steel molten steel, described pure calcium silk feed quantity is 0.1 ~ 0.3kg/t, after step (5) was processed, the mass content of calcium was 15 ~ 30ppm in the described ferritic stainless steel molten steel.
5. the smelting process of a kind of high-aluminum low-silicon super-purity ferrite stainless steel according to claim 1, it is characterized in that, in step (5), fed calcium silk and soft stirring after, feed the titanium silk in the ferritic stainless steel molten steel, the pure titanium amount in the described titanium silk is 1 ~ 3kg/t.
6. the smelting process of a kind of high-aluminum low-silicon super-purity ferrite stainless steel according to claim 1 and 2 is characterized in that, in the step (2),
When the higher limit of siliceous amount content in the high-aluminum low-silicon super-purity ferrite stainless steel that requires finally to make is 0.3%, all add ferrosilicon;
When the higher limit of siliceous amount content in the high-aluminum low-silicon super-purity ferrite stainless steel that requires finally to make is lower than or equals 0.2%, all add aluminium block;
When the higher limit of siliceous amount content in the high-aluminum low-silicon super-purity ferrite stainless steel that requires finally to make is between 0.2 ~ 0.3%, add ferrosilicon and aluminium block, the additional proportion of described ferrosilicon and aluminium block=(the higher limit ﹣ 0.2% of siliceous amount content in the high-aluminum low-silicon super-purity ferrite stainless steel that finally makes)/(higher limit of siliceous amount content in the high-aluminum low-silicon super-purity ferrite stainless steel that 0.3% ﹣ finally makes).
7. according to claim 1 or the smelting process of 3 described a kind of high-aluminum low-silicon super-purity ferrite stainless steels, it is characterized in that in the step (3), described ferro-aluminum is shaped as block or spherical, density is 4.5 ~ 6.5g/cm
3, diameter 3 ~ 6cm; After step (3) is processed, CaO and SiO in the slag
2Mass ratio be higher than 2.8, CaO and Al in the slag
2O
3Mass ratio be higher than 1.
8. the smelting process of a kind of high-aluminum low-silicon super-purity ferrite stainless steel according to claim 1 is characterized in that,
The condition of described high vacuum strong mixing is: vacuum pressure is controlled at below the 800Pa, and VOD furnace bottom argon blowing rate is controlled between 4 ~ 8L/ (mint);
The condition that described middle intensity stirs is: vacuum pressure is controlled at below the 2000Pa, and VOD furnace bottom argon blowing rate is controlled between 1 ~ 4L/ (mint);
The condition of described soft stirring is: under condition of normal pressure, between VOD furnace bottom argon blowing rate control 1 ~ 5L/ (mint).
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| CN 201110327941 CN102329920B (en) | 2011-10-25 | 2011-10-25 | Method for smelting high-aluminum low-silicon ultra pure ferritic stainless steel |
| KR1020147003789A KR101787179B1 (en) | 2011-10-25 | 2012-01-06 | Method for smelting high-aluminum-low-silicon ultrapure ferritic stainless steel |
| PCT/CN2012/070096 WO2013060101A1 (en) | 2011-10-25 | 2012-01-06 | Method for smelting high-aluminum-low-silicon ultrapure ferritic stainless steel |
| IN1547CHN2014 IN2014CN01547A (en) | 2011-10-25 | 2012-01-06 | |
| EP12843727.4A EP2772554B1 (en) | 2011-10-25 | 2012-01-06 | Method for smelting high-aluminum-low-silicon ultrapure ferritic stainless steel |
| JP2014537454A JP5833767B2 (en) | 2011-10-25 | 2012-01-06 | Smelting method of high aluminum low silicon ultra pure ferritic stainless steel |
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| CN103225034B (en) * | 2013-04-25 | 2015-05-06 | 山西太钢不锈钢股份有限公司 | Method for improving yielding rate of ultra pure ferrite stainless steel titanium |
| CN103397141B (en) * | 2013-07-30 | 2014-12-24 | 山西太钢不锈钢股份有限公司 | Smelting method of high-aluminum stainless steel |
| CN103388052A (en) * | 2013-08-08 | 2013-11-13 | 山西太钢不锈钢股份有限公司 | Production method of deoxidizing low-silicon steel by adding silicon-containing alloy |
| CN104946855B (en) * | 2015-07-15 | 2017-03-08 | 武汉钢铁(集团)公司 | A kind of vacuum processing method of high alumina ultra-low-carbon steel |
| CN105648148B (en) * | 2016-01-06 | 2017-08-15 | 山西太钢不锈钢股份有限公司 | A kind of super-purity ferrite stainless steel deoxidation and the method for Control and Inclusion Removal |
| CN109423536B (en) * | 2017-08-25 | 2021-04-13 | 宝山钢铁股份有限公司 | Smelting method of ultra-low carbon 13Cr stainless steel |
| CN107876211B (en) * | 2017-11-28 | 2023-08-29 | 嘉峪关天源新材料有限责任公司 | Composite magnetic focusing medium rod with high magnetic field strength and preparation method thereof |
| CN108167301A (en) * | 2018-02-26 | 2018-06-15 | 嘉兴市劼力机械科技有限公司 | A kind of fastener and its production technology |
| CN112063801B (en) * | 2020-09-17 | 2022-08-23 | 浦项(张家港)不锈钢股份有限公司 | Stainless steel and preparation method thereof |
| CN112475255B (en) * | 2020-11-18 | 2022-04-01 | 山西太钢不锈钢股份有限公司 | Continuous casting production method of high-aluminum ferrite stainless steel |
| CN113151637B (en) * | 2021-03-31 | 2022-10-14 | 北京科技大学 | Method for controlling pit defect of chromium-containing steel surface polishing inclusion |
| CN113560509B (en) * | 2021-07-27 | 2023-02-24 | 上海电气上重铸锻有限公司 | Method for manufacturing low-silicon boron-controlled steel large steel ingot |
| CN113737081B (en) * | 2021-08-31 | 2022-04-01 | 中国科学院上海应用物理研究所 | Stainless steel smelting method, stainless steel modification method and stainless steel |
| CN115287403A (en) * | 2022-08-15 | 2022-11-04 | 广东韶钢松山股份有限公司 | Low-carbon low-silicon cold heading steel deoxidation method |
| CN115369207A (en) * | 2022-09-06 | 2022-11-22 | 重庆钢铁股份有限公司 | Method for controlling nitrogen content of non-vacuum smelting plate blank |
| CN115522124B (en) * | 2022-09-20 | 2023-03-14 | 中天钢铁集团有限公司 | Method for improving continuous casting castability and sulfide form of medium-carbon S-containing Al-containing steel |
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| JPH101710A (en) * | 1996-06-13 | 1998-01-06 | Daido Steel Co Ltd | Manufacture of chromium-aluminum-(low n)-silicon steel |
| JPH1180826A (en) * | 1997-09-01 | 1999-03-26 | Nippon Steel Corp | Low silicon steel and production thereof |
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| CN102199688B (en) * | 2010-03-25 | 2013-02-06 | 宝山钢铁股份有限公司 | Method for efficiently refining ultra-pure ferritic stainless steel |
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