CN102199684A - Production method of ultralow-oxygen titanium-containing ferrite stainless steel - Google Patents
Production method of ultralow-oxygen titanium-containing ferrite stainless steel Download PDFInfo
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Abstract
The invention discloses a production method of ultralow-oxygen titanium-containing ferrite stainless steel, which comprises the following steps: 1) preparing molten ferrite stainless steel under a vacuum condition in a vacuum oxygen blowing decarburization furnace, wherein the carbon mass percentage content and nitrogen mass percentage content in the molten ferrite stainless steel are both less than 0.01 percent; 2) performing deoxidization, namely adding 6 to 12 kilograms of aluminum block or grains into each ton of steel and adding 10 to 28 kilograms of active lime into each ton of steel; 3) alloying silicon and aluminum, namely adding 2 to 9 kilograms of silicoferrite which contains 70 to 80 percent of silicon into each ton of steel and adding 0 to 1 kilogram of aluminum blocks or grains into each ton of steel, wherein the aluminum content is 0.02 to 0.1 percent; 4) performing desulphurization; (5) breaking vacuum; 6) softly stirring; 7) feeding titanium wires; 8) feeding silicon and calcium wires, wherein the calcium content is 5 to 30ppm; 9) softly stirring; and 10) continuously casting. The method can be used for producing ultralow-oxygen titanium-containing ferrite stainless steel, prevent or inhibit forming magnesia alumina spinel which are harmful impurities in a production process, improve product quality, prevent the water gap of tundish from being blocked in a continuous casting process and guarantee smooth production.
Description
Technical field
The present invention relates to the stainless steel smelting field, particularly a kind of production method of ultralow oxygen titaniferous ferritic stainless steel.
Background technology
Current, the little ferritic stainless steel of nickel resources dependency more and more is subjected to social attention, the interstitial element carbon in the ferritic stainless steel, nitrogen have a strong impact on its performance, mainly are the ductility of room temperature fragility, solidity to corrosion and weld.For ferritic stainless steel, the molten steel purity affects the use properties of steel equally, high purity can prolong stainless work-ing life, improve product surface quality, the purity of molten steel mainly characterizes with total oxygen, sulphur content, and total oxygen content is represented the content summation of oxygen in molten steel in the dissolved oxygen content and inclusion in the steel.Simultaneously, titanium can improve the stability of interstitial element C, N, Ti and C reaction generate the generation that TiC suppresses crystal boundary CrC, prevent the dilution of crystal boundary Cr, Ti and N reaction generate TiN as the forming core core, improve equiaxial crystal ratio, and titanium elements can also improve anti-oxidant, the thermal fatigue resistance of ferritic stainless steel, so ferritic stainless steel generally needs titanium alloyization.
From present technology, stainless desulfurization is out of question, and the vacuum desulfurization is handled back molten steel final sulfur content and can be reduced to below the 20ppm.The core missions of ferrite stainless smelting steel are decarburization, denitrogenation and deoxidation, and the formation of the harmful inclusion of control, prevent to be smelt that the middle water containing opening at continuous casting working procedure stops up in the molten steel casting process.
At present, generally be to adopt the vacuum-oxygen decarbonizing stove to cooperate strong mixing to reduce carbon nitrogen content in the steel, good can be controlled at carbon nitrogen total content below the 150ppm.For stainless deoxidation process, each Iron And Steel Company's original adoption of Europe be the silicon deoxy technology, reason is to adopt the aluminium deoxidation can a large amount of Al of formation
2O
3Be mingled with and can produce detrimentally affect to most steel grades, yet the entire oxygen content in the steel content of silicon deoxidation is very high, the strand total oxygen affects the performance of the finished product more than 60ppm; In Japan, some Iron And Steel Company begins to use in a large number aluminium to carry out deoxy technology, and the molten steel total oxygen content is reduced greatly, yet, adopt aluminium deoxidation can form Al in a large number
2O
3Especially surface property is influential to be mingled with not only performance to most steel grades, and can cause middle water containing opening and stop up, and has hindered carrying out continuously of casting; The calcium treatment technology can be so that Al
2O
3Be mingled with and become that low melting point is yielding to be mingled with.Yet, because the most of steel grades of ferritic stainless steel need titanium alloyization, as SiO in the pomace
2Content is high, and titanium enters behind the molten steel easily SiO in the reducing slag
2Generate TiO
2(or Ti
2O
3), then form uhligite (CaOTiO in the calcium treating processes easily
2) be mingled with, uhligite is mingled with and also belongs to the high-melting-point material, and the easier middle water containing opening that causes stops up.For Control and Inclusion Removal, the most deleterious inclusion is a magnesium-aluminium spinel in the stainless steel, also can continued growth TiN on the magnesium-aluminium spinel matrix in the titaniferous stainless steel, the spinels that might form size bigger (more than the 8 μ m) is mingled with, generally be the formation that prevents or suppress magnesium-aluminium spinel by MgO content in the control slag, because traditional VOD smelting process generally adds the fluorite slag that quality is an amount of lime 1/3, the inevitable serious furnace lining (main component MgO) that corrodes, cause that MgO content uprises in the slag, the difficulty that the control magnesium-aluminium spinel generates is very big.
Along with society is more and more higher to the requirement of ferrite stainless steel quality, not only require its carbon, nitrogen content extremely low, purity requirement to oxygen level and steel is also more and more higher, and we generally call ultrapure clean ferritic stainless steel to the extremely low ferritic stainless steel of carbon, nitrogen and oxygen level.Generally be to adopt three-step approach (EAF (electric arc furnace)+AOD (the multiple blown converter of argon oxygen)+VOD (vacuum-oxygen decarbonizing stove)) to smelt super purified ferritic stainless steel, and stainless deoxidation is mainly in the reduction phase of vacuum-oxygen decarbonizing stove smelting and the atmospheric treatment stage behind the vacuum breaker.
Day the present invention JP2002030324 (A) has provided the method that the sial complex deoxidization is smelted the titaniferous ferritic stainless steel, titaniferous is handled at 0.05-0.30wt% stainless steel molten steel elder generation vacuum decarburization, then, molten steel adds ferrosilicon, utilize slag-metal reaction to realize deoxidation, 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 aluminium deoxidation at last, the ratio that requires molten steel Al content and Ti content before casting is between 0.01～0.10, this method can improve molten steel and reach 60% at the equiaxial crystal ratio of casting process, and control composition of inclusions well, prevent that the casting cycle middle water containing opening from stopping up, 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, the molten steel oxygen level can not be reduced to extremely low-level, simultaneously molten steel Ti will with SiO in the slag
2Reaction, TiO
2(or Ti
2O
3) a large amount of risks that have middle water containing opening to stop up that generate.
Chinese patent CN101058837 has 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 the ferrosilicon deoxidation earlier, add the aluminium deep deoxidation again, deaeration time 5～10 minutes, and then alloy fine setting, this method of deoxidation treatment time is short, and deoxidation effect is pretty good, is widely used.Yet, too high as the control of terminal point aluminium content, be easy to generate in a large number Al
2O
3Be mingled with, easily cause middle water containing opening to stop up, Just because of this, this method needs the low terminal point aluminium content of strict control, can not drop to total oxygen of molten steel and dissolved oxygen extremely low-level.
Korean Patent KR20040059785 (A) has provided two-step approach EAF+AOD and has smelted the method for deoxidation of chromium content at the ferritic stainless steel of 11-19wt.%, equiaxial crystal ratio with strand after the continuous casting processing that improves ferritic stainless steel, concrete grammar is, in the AOD stove, add earlier the silicon deoxidation, processing finishes the back tapping, molten steel enters ladle, to molten steel ladle winding-up aluminum shot and calcium alloy, aluminium content is controlled at 0.01-0.06%, calcium contents is controlled at 4-15ppm, and adds titanium alloy, guarantees that titanium content is carbon nitrogen total content 6-12 times, then by the big stir process of steel ladle bottom argon blowing, this method can effectively be controlled the total amount of terminal point molten steel inclusion, and has taked the method for calcium processing to promote the generation of low melting point inclusion, and improves the equiaxial crystal ratio of continuously cast bloom, because its aluminium content is higher relatively, the terminal point oxygen level is in low relatively level.Yet this patent does not consider how to prevent TiO
2(or Ti
2O
3) a large amount of generations and the generation of uhligite, explain the front, these inclusiones can impel middle water containing opening to stop up, simultaneously, this patent adopts the method for winding-up to add aluminium and calcium, can make the molten steel secondary oxidation unavoidably, in addition, blowing process equipment complexity, influential to environment.
In a word, high-quality ferritic stainless steel requirement molten steel should have high purity, harmful inclusion is few and oxygen level is in extremely low-level, require the fusing point of inclusion low simultaneously, to avoid casting cycle to stop up middle water containing opening, this just requires need carry out calcium and handles in the strong deoxidation with aluminium, make Al
2O
3Become low-melting calcium-aluminate inclusion.Because present most of super-purity ferrite stainless steels all will carry out the titanium alloy processing, so will prevent in the calcium treating processes that forming dystectic uhligite is mingled with.As above Jian Suo patent does not all take into full account above-mentioned requirements.Patent of the present invention will be from preventing TiO
2(or Ti
2O
3) angle that generates, take a kind of new method of deoxidation, smelt high-quality ultralow oxygen titaniferous ferritic stainless steel.
Summary of the invention
Purpose of the present invention provides a kind of production method of ultralow oxygen titaniferous ferritic stainless steel, guaranteeing that molten steel casting cycle middle water containing opening does not stop up under the prerequisite, the ferritic stainless steel total oxygen content is controlled at extremely low-level, purity with further reduction interstitial element total content and raising molten steel, prevent or suppress the formation of harmful inclusion magnesium-aluminium spinel simultaneously, finally improve the quality of ferritic stainless steel.
For achieving the above object, technical scheme of the present invention is,
In the atmospheric treatment stage after VOD stove (vacuum-oxygen decarbonizing stove) is smelted stainless reduction phase of ferrite and vacuum breaker, by being main reductor with aluminium, deoxidation process and alloying process separate, SiO in Al content and the slag in the strict control steel
2Content carries out calcium and handles behind hello the titanium silk, can guarantee that final molten steel has extremely low oxygen level, prevent or suppress the formation of harmful inclusion magnesium-aluminium spinel simultaneously, and molten steel middle water containing opening in casting process does not stop up.The inventive method need not equipment is transformed, and is simple to operate, safe and reliable.
Particularly, the production method of the ultralow oxygen titaniferous of the present invention ferritic stainless steel, its step is as follows:
1) after molten steel process vacuum-oxygen decarbonizing and the free decarburization, main component requires: molten steel chromium content weight percent is between 10%-25%, and the carbon content weight percent is less than 0.01%, and the nitrogen content weight percent is less than 0.01%;
2) deoxidation treatment, add aluminium block or aluminum shot 6-12kg/ (t steel), add quickened lime 10-28kg/ (t steel) simultaneously, material adds moderate strength stirring under the final vacuum condition, vacuum pressure is controlled at below the 400Pa, the argon bottom-blowing stirring intensity between 2L/ (mint)-4L/ (mint), treatment time 4-6min;
3) siluminization, add siliceous amount percentage composition simultaneously at the ferrosilicon 2-9kg/ of 70-80% (t steel), add a small amount of aluminium block or aluminum shot 0-1kg/ (t steel), molten steel is carried out alloying, require silicone content to meet its steel grade requirement, aluminium quality percentage composition is between 0.02-0.1%, and in this scope, aluminium content further is controlled to be 0.1-0.3 times of target titanium content mass ratio;
4) treatment time 8-12min is handled in desulfurization;
5) vacuum breaker;
6) soft stirring;
Behind the vacuum breaker, under condition of normal pressure, the bottom Argon is carried out soft stirring to molten steel, between flow control 1L/ (mint)-5L/ (mint), and treatment time 8-10min;
7) feed the titanium silk, realize titanium alloyization
Feed the titanium silk with wire feeder to molten steel under normal pressure, require the molten steel titanium content to meet the steel grade requirement after the end, the titanium content weight percent is between 0.1%～0.4%;
8) feed the calcium silk
Under normal pressure with wire feeder to molten steel feeding silico-calcium silk, pure calcium feed quantity is 0.1-0.5kg/ (a t steel), feeds to require after silk finishes that the mass content of calcium is controlled at 5-30ppm in the steel;
9) soft stirring
After having fed the calcium silk, under condition of normal pressure, the bottom Argon is carried out soft stirring to molten steel, between flow control 1L/ (mint)-5L/ (mint), and treatment time 5-10min;
10) continuous casting
Ladle enters the continuous casting station, casts, because steel inclusion has been carried out denaturing treatment, can guarantee that middle water containing opening does not stop up.
Further, for step (2), the aluminium add-on needs also after aluminium adds, to need to guarantee that aluminium quality percentage composition is lower than 0.01% in the steel by according to the decision of molten bath peroxidation degree that the dissolved oxygen mass content is at 50ppm-100ppm.
Again, in deoxidation treatment and silumin process, promptly step (2) and step (3) also require SiO in the final VOD slag
2The quality percentage composition between 10%-15%, Al
2O
3The quality percentage composition between 20-40%, basicity of slag (CaO and SiO in the slag
2Mass ratio) be controlled between the 3-4.
In addition, for step (4), under the ultravacuum condition, vacuum pressure is lower than 400Pa, improves argon blowing rate between 4L/ (mint)-8L/ (mint), carries out desulfurization and handles treatment time 8-12min.
The present invention adds aluminium block or aluminum shot 6-12kg/ (t steel) in deoxidation treatment, add lime 10-28kg/ (t steel) quickened lime simultaneously.Material adds that moderate strength stirs under the final vacuum condition, and vacuum pressure is controlled at below the 400Pa, the argon bottom-blowing stirring intensity between 2L/ (mint)-4L/ (mint), treatment time 4-6min.
Method of deoxidation of the present invention is main reductor with aluminium, and different and routine is main reductor with silicon.With aluminium is the aluminium calcium slag that main reductor can be produced good flowing properties, and aluminium calcium slag has low-down oxygen gesture, be to smelt the stainless essential condition of ultralow oxygen, and for controlling SiO in the slag subsequently
2Content and raising basicity have been created good condition.Al
2O
3Has good change slag effect, i.e. Al
2O
3Can make the very fast fusing of solid-state lime, be that main reductor can improve Al in the slag greatly with aluminium
2O
3Content, can no longer need to add the fluorite slag, in the slag not fluoride ion also can further alleviate the furnace lining erosion of (mainly containing MgO), can reduce MgO content in the slag thus, prevent the generation of magnesium-aluminium spinel in the molten steel, magnesium-aluminium spinel is the indeformable inclusion of high-melting-point, and is very big to the performance impact of steel.Material adopts medium stirring intensity after adding, and has both guaranteed the quick fusing of lime, can prevent from again to form big splash too strongly owing to stirring.
Simultaneously, the inventive method requires in deoxidation process, and the aluminium add-on needs also after aluminium adds, to need to guarantee that aluminium content is lower than 0.01% in the steel by according to the decision of molten bath peroxidation degree that dissolved oxygen is at 50ppm～100ppm.If molten steel by deep deoxidation, can cause in the lime melting process to molten steel carburetting, for this reason, guarantee that the certain oxygen gesture (oxygen activity) of molten steel can prevent lime carburetting.
The siluminization of the inventive method (step 3), add silicone content simultaneously at ferrosilicon 2～9kg/ (t steel) of 70～80%, add a small amount of aluminium block or aluminum shot 0～1kg/ (t steel), molten steel is carried out alloying, require silicone content to meet its steel grade requirement, aluminium content is between 0.02～0.1%, and in this scope, aluminium content further is controlled to be 0.1-0.3 times of target titanium content mass ratio.
The inventive method is divided deoxidation (previous step) and silumin and is driven row into, is different from traditional deoxidation and siluminization and handles simultaneously, and processing can improve the recovery rate of silicon at alloying process like this, reduces the oxidation of silicon, this means SiO in the slag
2It is very low that content can be controlled.For the titanium alloy process of back operation, titanium be only time with the active element of aluminium, very strong with oxygen combining power, add that the back is very easy to and slag in SiO
2Reaction generates TiO
2(or Ti
2O
3).Because can be with SiO in the method that this step adopts
2It is very low that content can be controlled, SiO in the slag
2Activity also very low, can avoid after titanium adds so in large quantities with slag in SiO
2React, thereby restricted TiO
2(or Ti
2O
3) generation, for the calcium treating processes avoids forming a large amount of uhligite (CaOTiO
2) created condition.Aluminium content is at 0.02-0.1%, simultaneously in order to control the competitive oxidation of aluminium in the molten steel, titanium better, also requires 0.1-0.3 that aluminium content further is controlled to be target titanium content mass ratio doubly.
Competitive oxidation between aluminium, titanium is calculated, as shown in Figure 1, the activity implication is the product of element quality percentage composition and activity quotient among the figure, the activity quotient of aluminium and titanium is similar in the stainless steel molten steel, between 1-3, then aluminium content further is controlled to be 0.1～0.3 times of target titanium content mass ratio, can satisfy well that oxygen is preferential in the steel reacts with Al, and does not react with Ti.TiO in the steel
2(or Ti
2O
3) be mingled with very for a short time, very difficult come-up is gone in the slag, and Al
2O
3Be mingled with and very easily grow up and float, to suppress TiO in the molten steel
2(or Ti
2O
3) generation and allow Al
2O
3Fully generation can guarantee that inclusion fully floats in the slag, thereby reduces total oxygen content.
In a word, owing to take above-mentioned measure, comprise that terminal point aluminium content improves, controlled competitive oxidation between Al, the Ti well, add SiO in the slag
2It is very low that content is controlled, and can suppress or prevent TiO
2(or Ti
2O
3) generation, and the oxygen gesture (oxygen activity) that has guaranteed molten steel and slag is all very low, allow deoxidation type inclusion fully float in the slag simultaneously, can smelt excess of export hypoxemia ferritic stainless steel, these measures can also guarantee that its recovery rate of titanium alloy process has also obtained improving greatly.
In deoxidation treatment and silumin process, promptly step (2) and step (3) are also stipulated SiO in the final VOD slag
2Content between 10%-15%, Al
2O
3Content is between 20-40%, and basicity of slag is controlled between the 3-4.
Require such slag system except effect described above, promptly control the oxidation of titanium alloy process titanium and, also have following effect: can guarantee SiO between the basicity control 3-4 for the ultralow oxygen ferritic stainless steel of smelting creates conditions
2Activity at slag further reduces, and the slag ingredient as above scope of being controlled at can guarantee that slag has the ability that good flowability and absorbing oxide are mingled with.
The inventive method feed the calcium silk (step 7), under normal pressure with wire feeder to molten steel feeding calcium silk, the calcium feed quantity is 0.1～0.5kg/ (a t steel), feeds to require after silk finishes that the content of calcium is controlled at 5-30ppm in the steel.
The purpose of feeding the calcium silk is dystectic Al
2O
3Inclusion becomes low-melting 12CaO.7Al
2O
3Or other low-melting aluminium calcium acid, simultaneously because the step of front has been controlled TiO
2(or Ti
2O
3) generate high-melting-point uhligite (CaOTiO
2) be difficult to a large amount of the generation, guaranteed carrying out smoothly of casting.
The inventive method requires all molten steel to be carried out soft stir process behind vacuum breaker and before the casting, and purpose is to allow inclusion fully float, and further reduces entire oxygen content in the steel.Wherein, the Al2O3 that molten steel mainly exists behind the vacuum breaker is mingled with to assemble and grows up, abundant come-up, and before cast, and the inclusion fusing point after handling through calcium is low, and slag also has and well goes up i its high adsorption capacity.
The present invention is main deoxidation dosage with aluminium mainly, require aluminium add-on 6-12kg/ (t steel), and ordinary method is main reductor with silicon mainly, and the aluminium add-on is in 5kg/ (t steel); The ferrosilicon of the inventive method adds the alloying process that is mainly used to realize silicon, promptly satisfies the final silicone content of steel grade.This purpose is aluminium-deoxidized resultant Al
2O
3Replace the rapid slag of fluorite (fast instantizing lime), guarantee SiO in the slag simultaneously
2Content is in lower level.Do not add fluorite and can reduce MgO content in the slag, to preventing that the formation of magnesium-aluminium spinel is useful in the molten steel.
The present invention separates deoxidation process and alloying process.In the alloying with silicon process, because steel liquid deoxidation is finished substantially, silicon oxidized amount in alloying process significantly reduces, and has guaranteed SiO in the slag equally like this
2Content is in lower level.
The inventive method is by controlling the oxidation after suitable aluminium content suppresses the titanium adding, and the 0.1-0.3 that aluminium content further is controlled to be target titanium content mass ratio can guarantee that doubly aluminium has precedence over titanium and combines with oxygen.
On the oxidized measure basis of strictness control Ti, the present invention has adopted calcium treating method, allows inclusion modification, can guarantee that the casting process middle water containing opening does not stop up, the inclusion of finally staying simultaneously steel grade is because size is little, and deformability is good, and is very little to the performance impact of steel.
More than 4 integrate exactly in order to prevent the oxidation of titanium, implement the calcium treatment technology well, come deep deoxidation so that control higher aluminium content, because the oxide inclusion of aluminium is compared the oxide inclusion of titanium more to remove, finally reached the purpose of smelting into ultralow oxygen titaniferous ferritic stainless steel, steel inclusion has also obtained good control.
Beneficial effect of the present invention
According to the inventive method, the inventive method is produced the titaniferous ferritic stainless steel and can not formed at continuous casting middle water containing opening place and stop up, and can realize the strand total oxygen content between 10-20ppm, and main in the strand that exist is harmless substantially CaO-Al about 1 μ m
2O
3Duplex impurity and TiN are mingled with, uhligite (CaO.TiO
2) be mingled with considerably lessly, do not contain deleterious magnesium-aluminium spinel in the strand substantially and be mingled with.Taking cost into account, the inventive method VOD process is not by adding fluorite and improving the titanium recovery rate and saved cost.
In a word, the inventive method reduces the total oxygen content of titaniferous ferrite stainless product made from steel greatly on the basis that guarantees the production direct motion, improved the purity of steel, and prevented from the generation of harmful inclusion to have improved quality product greatly, and smelting cost also decreases.
Description of drawings
Fig. 1 is an aluminium activity under the differing temps (a[Al]) and the ratio of titanium activity (a[Ti]).
Fig. 2 is the process flow sheet of the inventive method.
Embodiment
Describe the inventive method in detail in the embodiment of producing ultralow oxygen titaniferous ferrite ferritic stainless steel and the effect that obtains below in conjunction with embodiment, respectively with produce 430L, 439 and the super-purity ferrite stainless steel of these 3 trade mark steel grades of 409L be that example is illustrated.
Embodiment 1
Present embodiment is to the requirement of refining unit VOD: equipment can be handled molten steel 120t, and final vacuum is less than 100Pa, and Argon air blowing ability always in bottom is higher than 60Nm
3/ h, ladle lining are magnesia-calcium brick.Steel grade is 430L, molten steel amount 104000kg, and the initial composition of molten steel was before VOD smelted:
C:0.4%, Si:0.17%, Cr:16.4%, S:0.005%, N:0.017%, 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.
Initial temperature: 1600 ℃.
Present embodiment implementation step following (referring to Fig. 2):
(1) molten steel is through vacuum-oxygen decarbonizing and free carbonization treatment, and total blowing oxygen quantity is 1350Nm
3, processing finishes back molten steel main component and is:
C:0.009%, Si:0.01%, Cr:15.4%, S:0.002%, N:0.009%, 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) deoxidation treatment adds aluminium block 700kg, adds lime 2150kg, and material adds the final vacuum pressure-controlling below 400Pa, argon bottom-blowing stirring intensity 300L/ (min), and treatment time 5min guarantees that lime tentatively melts;
(3) siluminization adds siliceous amount content simultaneously at 77% ferrosilicon 300kg, adds aluminium 50kg, and molten steel is carried out alloying;
(4) treatment time 10min is handled in desulfurization;
(5) vacuum breaker;
(6) soft stir process 8min;
(7) feed titanium silk (containing Ti 75%wt) 500m, pure titanium amount 125kg;
(8) feed silico-calcium silk (containing Ca 40%wt) 80m, contain pure calcium 20kg;
(9) soft stir process 8min;
After the soft stir process, the situation of molten steel and slag is measured.
Decide the oxygen result and be 3.6ppm, molten steel component is:
C:0.009%, Si:0.2%, Cr:16.4%, S:0.001%, N:0.01%, Mn:0.7%, P:0.015%, full O:0.003%, Ti:0.119%, Al:0.05%, all the other are Fe and micro impurity element.
Soft stirring is got slag specimen and is measured its composition and be:
SiO
2: 14%, CaO:51%, Al
2O
3: 30%, MgO:3%, TiO
2(Ti
2O
3): 0.02%, all the other are Cr
2O
3, Mn and FeO isoreactivity oxide compound group member and oxide impurity.About basicity 3.6.The temperature of fusion of slag is between 1350-1390 ℃.
From slag composition TiO the slag as can be seen
2(Ti
2O
3) extremely low, it is oxidized to show that Ti does not have substantially.
(10) continuous casting
In the casting cycle, middle water containing opening maximum opening degree 64%, this opening degree can not form middle water containing opening and stop up, and guarantee to cast to carry out smoothly.
It is as follows to measure the strand composition at last:
C:0.01%, Si:0.2%, Cr:16.4%, S:0.001%, N:0.011%, Mn:0.71%, P:0.015%, full O:0.001%, Ti:0.115%, Al:0.03%, Ca:0.0011%, all the other are Fe and micro impurity element.
From the strand composition, total oxygen content has only 10ppm, is lower than the 20-30ppm of common process, and C, N content meet the steel grade requirement, and calcium contents is 11ppm, and the recovery rate of Ti reaches 95.6% simultaneously, far above the 80%-90% of common process.
Get the analysis of metallographic sample on strand, use scanning electron microscope observation, what exist in the strand is that TiN is mingled with, Al
2O
3-CaO duplex impurity, also has a spot of Al
2O
3Be mingled with, TiO
2(Ti
2O
3) be mingled with, Al
2O
3-Cr
2O
3Duplex impurity, size all between 0.5-2 μ m, do not observe deleterious magnesium-aluminium spinel.
Embodiment 2
Present embodiment is to the requirement of refining unit VOD: equipment can be handled molten steel 120t, and final vacuum is less than 100Pa, and Argon air blowing ability always in bottom is higher than 60Nm
3/ h, ladle lining are magnesia-calcium brick.Steel grade is 439, molten steel amount 110000kg, and the initial composition of molten steel was before VOD smelted:
C:0.35%, Si:0.04%, Cr:17.6%, S:0.005%, N:0.011%, Mn:0.22%, P:0.013%, full O:0.02%, Ti:0.01%, Al:0.001%, all the other are Fe and micro impurity element.
Initial temperature: 1600 ℃.
The present embodiment implementation step is as follows:
(1) molten steel is through vacuum-oxygen decarbonizing and free carbonization treatment, and total blowing oxygen quantity is 1094Nm
3, processing finishes back molten steel main component and is:
C:0.005%, Si:0.01%, Cr:16.7%, S:0.002%, N:0.005%, Mn:0.20%, P:0.013%, full O:0.04%, Ti:0.01%, Al:0.001%, all the other are Fe and micro impurity element.
(2) deoxidation treatment adds aluminium block 800kg, adds lime 1400kg, and material adds the final vacuum pressure-controlling below 400Pa, argon bottom-blowing stirring intensity 300L/ (min), and treatment time 4min guarantees that lime tentatively melts.
(3) siluminization adds siliceous amount content simultaneously at 77% ferrosilicon 820kg, adds aluminium 50kg, and molten steel is carried out alloying;
(4) treatment time 12min is handled in desulfurization;
(5) vacuum breaker;
(6) soft stir process 9min;
(7) feed titanium silk (containing Ti 75%wt) 1500m, pure titanium amount 375kg;
(8) feed silico-calcium silk (containing Ca 40%wt) 100m, contain pure calcium 25kg;
(9) soft stir process 8min;
After the soft stir process, the situation of molten steel and slag is measured.
Decide the oxygen result and be 3.0ppm, molten steel component is:
C:0.005%, Si:0.51%, Cr:17.9%, S:0.001%, N:0.005%, Mn:0.23%, P:0.013%, full O:0.0028%, Ti:0.35%, Al:0.07%, all the other are Fe and micro impurity element.
Soft stirring is got slag specimen and is measured its composition and be:
SiO
2: 13.5%, CaO:47%, Al
2O
3: 34%, MgO:4%, TiO
2(Ti
2O
3): 0.035% all the other be Cr
2O
3, Mn and FeO isoreactivity oxide compound group member and oxide impurity.The temperature of fusion of slag is between 1300～1340 ℃.
From slag composition TiO the slag as can be seen
2(Ti
2O
3) extremely low, it is oxidized to show that Ti does not have substantially.
(10) continuous casting
In the casting cycle, middle water containing opening maximum opening degree 60%, this opening degree can not form middle water containing opening and stop up, and guarantee to cast to carry out smoothly.
It is as follows to measure the strand composition at last:
C:0.007%, Si:0.53%, Cr:17.8%, S:0.001%, N:0.006%, Mn:0.23%, P:0.012%, full O:0.0013%, Ti:0.33%, Al:0.04%, Ca:0.0015%, all the other are Fe and micro impurity element.
From the strand composition, total oxygen content has only 13ppm, is lower than the 20-30ppm of common process, and C, N content meet the steel grade requirement, and calcium contents is 15ppm, and the recovery rate of Ti reaches 96.8% simultaneously, far above the 80%-90% of common process.
Get the analysis of metallographic sample on strand, use scanning electron microscope observation, what exist in the strand is that TiN is mingled with, Al
2O
3-CaO duplex impurity, also has a spot of Al
2O
3Be mingled with, TiO
2(Ti
2O
3) be mingled with, Al
2O
3-Cr
2O
3Duplex impurity, minute quantity Ti
2O
3-CaO is mingled with, and size all between 1-2 μ m, does not observe deleterious magnesium-aluminium spinel.
Need to prove that this steel grade titanium content requires high relatively, the target titanium content has surpassed 10 times of C+N total content.
Embodiment 3
Present embodiment is to the requirement of refining unit VOD: equipment can be handled molten steel 120t, and final vacuum is less than 100Pa, and Argon air blowing ability always in bottom is higher than 60Nm
3/ h, ladle lining are magnesia carbon brick.Steel grade is 409L, molten steel amount 107000kg, and the initial composition of molten steel was before VOD smelted:
C:0.26%, Si:0.15%, Cr:11.5%, S:0.004%, N:0.013%, Mn:0.3%, P:0.013%, full O:0.025%, Ti:0.02%, Al:0.001%, all the other are Fe and micro impurity element.
Initial temperature: 1620 ℃.
The present embodiment implementation step is as follows:
(1) molten steel is through vacuum-oxygen decarbonizing and free carbonization treatment, and total blowing oxygen quantity is 938Nm
3, processing finishes back molten steel main component and is:
C:0.006%, Si:0.01%, Cr:10.8%, S:0.002%, N:0.007%, Mn:0.10%, P:0.013%, full O:0.04%, Ti:0.01%, Al:0.001%, all the other are Fe and micro impurity element;
(2) deoxidation treatment adds aluminium block 700kg, adds lime 1100kg, and material adds the final vacuum pressure-controlling below 400Pa, argon bottom-blowing stirring intensity 300L/ (min), and treatment time 4min guarantees that lime tentatively melts;
(3) siluminization adds siliceous amount content simultaneously at 77% ferrosilicon 490kg, adds aluminium 50kg, and molten steel is carried out alloying;
(4) treatment time 10min is handled in desulfurization;
(5) vacuum breaker;
(6) soft stir process 8min;
(7) feed titanium silk (containing Ti 75%wt) 500m, pure titanium amount 125kg;
(8) feed silico-calcium silk (containing Ca 40%wt) 80m, contain pure calcium 20kg;
(9) soft stir process 8min;
After the soft stir process, the situation of molten steel and slag is measured.
Decide the oxygen result and be 3.8ppm, molten steel component is:
C:0.007%, Si:0.45%, Cr:11.6%, S:0.001%, N:0.007%, Mn:0.3%, P:0.013%, full O:0.0032%, Ti:0.12%, Al:0.05%, all the other are Fe and micro impurity element.
Soft stirring is got slag specimen and is measured its composition and be:
SiO
2: 12.5%, CaO:45%, Al
2O
3: 38%, MgO:3%, TiO
2(Ti
2O
3): 0.02% all the other be Cr
2O
3, Mn and FeO isoreactivity oxide compound group member and oxide impurity.Basicity of slag 3.6.The temperature of fusion of slag is between 1280-1320 ℃.
From slag composition TiO the slag as can be seen
2(Ti
2O
3) extremely low, it is oxidized to show that Ti does not have substantially.
(10) continuous casting
In the casting cycle, middle water containing opening maximum opening degree 58%, this opening degree can not form middle water containing opening and stop up, and guarantee to cast to carry out smoothly.
It is as follows to measure the strand composition at last:
C:0.009%, Si:0.47%, Cr:11.6%, S:0.001%, N:0.008%, Mn:0.3%, P:0.013%, full O:0.0010%, Ti:0.11%, Al:0.03%, Ca:0.0013%, all the other are Fe and micro impurity element.
From the strand composition, total oxygen content has only 13ppm, is lower than the 20-30ppm of common process, and C, N content meet the steel grade requirement, and calcium contents is 15ppm, and the recovery rate of Ti reaches 94.1% simultaneously, far above the 80%-90% of common process.
Get the analysis of metallographic sample on strand, use scanning electron microscope observation, what exist in the strand is that TiN is mingled with, Al
2O
3-CaO duplex impurity, also has a spot of Al
2O
3Be mingled with, TiO
2(Ti
2O
3) be mingled with, Al
2O
3-Cr
2O
3Duplex impurity, size all between 0.5-2 μ m, do not observe deleterious magnesium-aluminium spinel.
Claims (5)
1. the production method of ultralow oxygen titaniferous ferritic stainless steel, its step is as follows:
1) after molten steel process vacuum-oxygen decarbonizing and the free decarburization, main component requires: chromium content quality weight percent is between 10%～25% in the molten steel, and the carbon content mass percent is less than 0.01%, and the nitrogen content mass percent is less than 0.01%;
2) deoxidation treatment, add aluminium block or aluminum shot 6～12kg/ (t steel), add quickened lime 10～28kg/ (t steel) simultaneously, stir under the material adding final vacuum condition, vacuum pressure is controlled at below the 400Pa, the argon bottom-blowing stirring intensity between 2L/ (mint)～4L/ (mint), treatment time 4～6min;
3) siluminization, add the silicone content mass percent simultaneously at ferrosilicon 2～9kg/ (t steel) of 70～80%, add a small amount of aluminium block or aluminum shot 0～1kg/ (t steel), molten steel is carried out alloying, require silicone content to meet its steel grade requirement, aluminium quality percentage composition is between 0.02～0.1%, and in this scope, aluminium content further is controlled to be 0.1～0.3 times of target titanium content mass ratio;
4) treatment time 8～12min is handled in desulfurization;
5) vacuum breaker
6) soft stirring
Behind the vacuum breaker, under condition of normal pressure, the bottom Argon is carried out soft stirring to molten steel, between flow control 1L/ (mint)-5L/ (mint), and treatment time 8-10min;
7) feed the titanium silk, realize titanium alloyization
Feed the titanium silk with wire feeder to molten steel under normal pressure, require the molten steel titanium content to meet the steel grade requirement after the end, the titanium content weight percent is between 0.1%～0.4%;
8) feed the calcium silk
Under normal pressure with wire feeder to molten steel feeding silico-calcium silk, pure calcium feed quantity is 0.1～0.5kg/ (a t steel), feeds to require after silk finishes that the mass content of calcium is controlled at 5～30ppm in the steel;
9) soft stirring
After having fed the calcium silk, under condition of normal pressure, the bottom Argon is carried out soft stirring to molten steel, between flow control 1L/ (mint)～5L/ (mint), and treatment time 5～10min;
10) continuous casting
Ladle enters the continuous casting station, casts, because steel inclusion has been carried out denaturing treatment, can guarantee that middle water containing opening does not stop up.
2. the production method of ultralow oxygen titaniferous ferritic stainless steel as claimed in claim 1, it is characterized in that, for step (2), the aluminium add-on also needs by determining according to molten bath peroxidation degree, after aluminium adds, need to guarantee that aluminium quality percentage composition is lower than 0.01% in the steel, the dissolved oxygen mass content is at 50ppm～100ppm.
3. the production method of ultralow oxygen titaniferous ferritic stainless steel as claimed in claim 1 is characterized in that, in deoxidation treatment and silumin process, promptly step (2) and step (3) also require SiO in the final VOD slag
2The quality percentage composition between 10%～15%, Al
2O
3The quality percentage composition between 20～40%, basicity of slag (CaO and SiO in the slag
2Mass ratio) be controlled between 3～4.
4. the production method of ultralow oxygen titaniferous ferritic stainless steel as claimed in claim 1 is characterized in that, for step (4), under the ultravacuum condition, vacuum pressure is lower than 400Pa, improves argon blowing rate between 4L/ (mint)～8L/ (mint), carry out desulfurization and handle treatment time 8～12min.
5. the production method of ultralow oxygen titaniferous ferritic stainless steel as claimed in claim 1 is characterized in that, in deoxidation treatment, adds aluminium block or aluminum shot 6～12kg/ (t steel), adds lime 10～28kg/ (t steel) quickened lime simultaneously; Material adds under the final vacuum condition and stirs, and vacuum pressure is controlled at below the 400Pa, the argon bottom-blowing stirring intensity between 2L/ (mint)～4L/ (mint), treatment time 4～6min.
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