CN101351565A - Method for manufacturing ferritic stainless steel slabs with equiaxed grain structures and the ferritic stainless steel manufactured by it - Google Patents
Method for manufacturing ferritic stainless steel slabs with equiaxed grain structures and the ferritic stainless steel manufactured by it Download PDFInfo
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- CN101351565A CN101351565A CNA2006800497022A CN200680049702A CN101351565A CN 101351565 A CN101351565 A CN 101351565A CN A2006800497022 A CNA2006800497022 A CN A2006800497022A CN 200680049702 A CN200680049702 A CN 200680049702A CN 101351565 A CN101351565 A CN 101351565A
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- 238000000034 method Methods 0.000 title claims abstract description 65
- 229910001220 stainless steel Inorganic materials 0.000 title claims abstract description 47
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 5
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 97
- 239000010959 steel Substances 0.000 claims abstract description 97
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 41
- 239000001301 oxygen Substances 0.000 claims abstract description 41
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 33
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 29
- 239000013078 crystal Substances 0.000 claims abstract description 19
- 238000005275 alloying Methods 0.000 claims abstract description 14
- 238000005261 decarburization Methods 0.000 claims abstract description 14
- 229910052751 metal Inorganic materials 0.000 claims abstract description 7
- 239000002184 metal Substances 0.000 claims abstract description 7
- 238000003756 stirring Methods 0.000 claims abstract description 7
- 239000011261 inert gas Substances 0.000 claims abstract description 5
- ODINCKMPIJJUCX-UHFFFAOYSA-N Calcium oxide Chemical compound [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 claims description 37
- 239000010935 stainless steel Substances 0.000 claims description 35
- 150000004645 aluminates Chemical class 0.000 claims description 27
- 235000012255 calcium oxide Nutrition 0.000 claims description 18
- 239000000292 calcium oxide Substances 0.000 claims description 18
- 229910052782 aluminium Inorganic materials 0.000 claims description 14
- 238000009749 continuous casting Methods 0.000 claims description 13
- 238000005516 engineering process Methods 0.000 claims description 10
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 claims description 10
- 238000007670 refining Methods 0.000 claims description 10
- 239000002893 slag Substances 0.000 claims description 9
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 7
- 239000000203 mixture Substances 0.000 claims description 7
- 229910010413 TiO 2 Inorganic materials 0.000 claims description 6
- 238000002347 injection Methods 0.000 claims description 3
- 239000007924 injection Substances 0.000 claims description 3
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 abstract description 30
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 abstract description 7
- 230000000694 effects Effects 0.000 abstract description 7
- 238000005266 casting Methods 0.000 abstract description 4
- QDOXWKRWXJOMAK-UHFFFAOYSA-N dichromium trioxide Chemical compound O=[Cr]O[Cr]=O QDOXWKRWXJOMAK-UHFFFAOYSA-N 0.000 abstract 4
- 238000007664 blowing Methods 0.000 abstract 1
- 239000002131 composite material Substances 0.000 abstract 1
- 230000006911 nucleation Effects 0.000 description 15
- 238000010899 nucleation Methods 0.000 description 15
- 150000001875 compounds Chemical class 0.000 description 6
- 230000002950 deficient Effects 0.000 description 6
- 238000007711 solidification Methods 0.000 description 6
- 230000008023 solidification Effects 0.000 description 6
- 238000004458 analytical method Methods 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 229910020068 MgAl Inorganic materials 0.000 description 3
- -1 TiN oxide compound Chemical class 0.000 description 3
- 230000006866 deterioration Effects 0.000 description 3
- 229910000640 Fe alloy Inorganic materials 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 229910052596 spinel Inorganic materials 0.000 description 2
- 239000011029 spinel Substances 0.000 description 2
- 229910001887 tin oxide Inorganic materials 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 1
- 239000004411 aluminium Substances 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 125000004429 atom Chemical group 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 125000004433 nitrogen atom Chemical group N* 0.000 description 1
- 239000003507 refrigerant Substances 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 238000010079 rubber tapping Methods 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/52—Manufacture of steel in electric furnaces
-
- 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
-
- 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
-
- 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
- C21C7/0006—Adding metallic additives
-
- 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
-
- 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
-
- 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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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Treatment Of Steel In Its Molten State (AREA)
- Continuous Casting (AREA)
Abstract
Disclosed is a method for manufacturing ferritic stainless steel slabs with equiaxed grain structures and the ferritic stainless steel manufactured by it, which control concentration of alumina inclusions in molten steel to maximize an available TiN generation effect serving as a non-uniform nucleating site of ferrite when solidifying it, thereby improving equiaxed crystal ratio, the method comprising the steps of: performing oxygen decarburization reaction by blowing oxygen from the upper part of the molten steel in a vacuum oxygen decarburization ladle; injecting Al in the molten steel to which the oxygen decarburization reaction is made for Cr2O3 reduction; making composite deoxidation by injecting deoxidizer in the molten steel into which the Al is injected for the Cr2O3 reduction; making alloying process by injecting alloying metal in the molten steel; first judging for judging whether Al concentration is in the range of a setting value by analyzing the Al concentration in the molten steel; if the Al concentration satisfies the setting value, stirring it using inert gas and second judging for judging whether alumina inclusion concentration in the final molten steel corresponds to a target value; and if the alumina inclusion concentration satisfies the target value, continuously casting the molten steel.
Description
Technical field
The present invention relates to a kind of be used to the make method of ferrite stainless steel base and the ferritic stainless steel of making by this method with equiaxed grain structures, more particularly, the present invention relates to a kind of like this be used to the make method of ferrite stainless steel base and the ferritic stainless steel of making by this method with equiaxed grain structures, this method is controlled the concentration of the aluminate in the molten steel, with generation maximum effect with useful TiN, thereby raising equiaxial crystal ratio, wherein, TiN is used as ferritic heterogeneous nucleation position when making molten steel solidification.
Background technology
Usually, there is such situation, that is, in Cr concentration is 10%～30% ferritic stainless steel, adds 0.2%～0.5% Ti, to improve the corrosion stability of this ferritic stainless steel.In this case, the reaction formula below passing through the process from process for making to continuous casting process forms TiN, wherein, when the size of TiN with distribute when suitable, in making the process of molten steel solidification, TiN is as ferritic heterogeneous nucleation position, thus the acquisition equiaxed grain structures.
[reaction formula 1]
Ti+N＝TiN
In order to make equiaxed grain structures, reported following technology by the aforesaid technology that control TiN generates the process from process for making to continuous casting process.
No. 5868875 United States Patent (USP) described to having 8%～25% Cr, 0.1%～1.5% Mn, 1.5% or less than 1.5% Si, 0.05% or less than 0.05% N, 0.08% or less than 0.08% C and 0.01% or carry out in the process of Ti deoxidation less than the molten steel of 0.01% Al, the concentration of Ti satisfies (%Ti/48)/[%C/120+ (%N/14)]＞1.5.
In addition, No. 924313 European patent described when the concentration of Ti, Al and N satisfies [%Ti] * [%N] 〉=0.14 * [%Al], can guarantee that equiaxial crystal ratio in the slab is 50% or greater than 50%.
Yet, as in above-mentioned patent, stainless steel water is being carried out in the process of Ti deoxidation, if the oxygen concn height in the molten steel, the major part of the Ti of Zhu Ruing can be oxidized with the form of Ti oxide compound so.This can become the factor that TiN generates according to above-mentioned reaction formula 1 that hinders.
In addition, because the generation meeting of excessive TiN oxide compound causes the dross of submerged nozzle (submerged entry nozzle) and cause the defective of steel-making ability in steel slab surface to have limitation so use the Ti deoxidation simply in the continuous casting process process.
No. 1491646 European patent described and can have been made the slab with equiaxed grain structures by the Mg that adds 2ppm～50ppm in the molten steel of forming to the Ti by 10%～20% Cr, 0.001%～0.01% C, 0.01%～0.3% Si, 0.01%～0.3% Mn, 0.001%～0.02% N and 0.05%～0.3%.
In other words, if proposed the composition and the distribution of inclusion are controlled, to satisfy 17.4 (Al
2O
3)+3.9 (MgO)+0.3 (MgAl
2O
4)+18.7 (CaO)≤500 and (Al
2O
3)+(MgO)+(MgAl
2O
4)+(CaO) 〉=95 (every kind of component is all based on molar percentage), these inclusiones will be used as ferritic heterogeneous nucleation position when making molten steel solidification so.
Yet, in this case, in the time can not controlling the concentration of each oxide compound simultaneously, that is, even work as specific components (such as Al
2O
3) dense or MgAl
2O
4Concentration when very low, also can satisfy above-mentioned formula, yet, can not easily obtain equiaxed grain structures.This is because if Al in the inclusion
2O
3Excessive concentration, Al so
2O
3/ TiN or Al
2O
3It is very big that the difference of the lattice mismatch the between/ferrite becomes, that is, it is big that interfacial energy becomes, and makes these inclusiones be difficult to when making molten steel solidification as ferritic heterogeneous nucleation position.
The 2002-030324 Japanese Patent has been described and has been passed through CaO-SiO
2The basicity of base slag is controlled at 1.2～2.4, and in molten steel control [%Al]/[%Ti]=0.01～0.1, promptly, [%Ti]/[%Al]=10～100, can in slab, obtain 70% or greater than 70% equiaxial crystal ratio, wherein, described slag keeps chemical equilibrium with the molten steel of the Ti with 10%～30% Cr, 0.2%～3.0% Si and 0.05%～0.3%.
Yet, when the composition of the Ti of the high density in employing is in described concentration range and the Al of lower concentration is operated, have the risk that generates a large amount of Ti oxide compounds.This can become the factor of the defective of the dross that causes the mouth of a river in foundry technology process or steel slab surface.
The 2000-1602999 Japanese Patent has been described when carrying out the vacuum-oxygen decarbonizing refining, by injecting CaO and Al so that CaO-Al
2O
3The basicity of base slag in 0.7～2.5 scope and to molten steel stirred 5 minutes or the longer time and add Ti so that only the TiN nitride have 0.01% or greater than 0.01% area than (area ratio), thereby can in slab, obtain 60% or greater than 60% equiaxial crystal ratio.
Yet it is very difficult not being subjected to the influence of oxide inclusion in the stainless steel water and suitably forming TiN, and wherein, inclusion is distributed in the whole stainless steel water with the form of oxide compound.This makes oxide inclusion be used as the heterogeneous nucleation position when forming TiN, and meet a large amount of facts that distribute of oxide compound-TiN complex inclusion, wherein, when observation had the inside of slab of equiaxial substantially crystalline-granular texture, TiN utilized oxidation-inclusion to come crystallization as nucleus.
The 2004-043838 Japanese Patent has been described when refining has the molten steel of 9%～30% Cr, by making the scope that [%Ti] in the molten steel * [%N] equals 0.007～0.004, and in molten steel, injecting suitable reductor so that utilize the oxygen activity of the molten steel that oxygen sensor records to be log a
0After=-5～-3 molten steel is cast, can be improved equiaxial crystal ratio.
Yet, can conclude, no matter when stainless steel water is carried out refining, time utilization oxygen sensor more than all need spending is relatively measured the oxygen activity in the molten steel, its accuracy reduces slightly, and do not describe the particular type of reductor in detail, thereby make and become that some is indeterminate reductor being used for actual operating process reductor.
Summary of the invention
Therefore, the present invention is proposed to solve aforesaid the problems of the prior art.The object of the present invention is to provide a kind of be used to the make method of ferrite stainless steel base and the ferritic stainless steel of making by this method with equiaxed grain structures, this method utilizes the complex deoxidization of Si/Mn/Al/Ti that the concentration of the aluminate in the molten steel is controlled in vacuum-oxygen decarbonizing refinery practice process, with generation maximum effect with useful TiN, have high equiaxial crystal ratio and good plasticity (promptly thereby make, low wrinkling defective) ferrite stainless steel base, wherein, TiN is used as ferritic heterogeneous nucleation position when making molten steel solidification.
Beneficial effect
With of the prior art based on comparing such as the method that is used to make plate slab of technology such as casting temp control and the control of electromagnetism combined power with equiaxed grain structures, aforesaidly be used to make the method for ferrite stainless steel base and accurately controlled the component (such as Si and Mn etc.) of molten steel and the concentration of aluminate by the ferritic stainless steel of this method manufacturing with equiaxed grain structures according to of the present invention, to generate useful TiN effectively, make this method to make to have equiaxed grain structures and high equiaxial crystal ratio the ferrite stainless steel base and improve operational stability simultaneously, the ferrite stainless steel base with equiaxed grain structures of obtain to have excellent moldability thereby (that is, low wrinkling defective).
Description of drawings
Fig. 1 shows the schema of the method that is used to make the ferrite stainless steel base with equiaxed grain structures according to the preferred embodiment of the invention;
Fig. 2 shows equiaxial crystal ratio in the slab according to the figure to the variation of the control of alumina inclusion concentration;
Fig. 3 is the figure that the result of Fig. 2 is depicted as distributed data;
Fig. 4 shows the method for comparing by being used to make the ferrite stainless steel base with equiaxed grain structures according to the preferred embodiment of the invention with conventional example and reduces Al
2O
3And TiO
xThe graphic representation of inclusion;
Fig. 5 shows the electromicroscopic photograph of comparing the form of the oxide compound-TiN complex inclusion that distributes in the slab inside with equiaxed grain structures by the method that is used to make the ferrite stainless steel base with equiaxed grain structures according to the preferred embodiment of the invention with conventional example.
Embodiment
In order to realize purpose of the present invention, a kind of method that is used to make the ferrite stainless steel base with equiaxed grain structures is provided, said method comprising the steps of: in the vacuum-oxygen decarbonizing ladle,, thereby carry out oxygen decarburization reaction from the top oxygen blast of molten steel; In order to reduce Cr
2O
3, in the molten steel that has carried out oxygen decarburization reaction, inject Al; By in order to reduce Cr
2O
3Carry out complex deoxidization and inject reductor to its molten steel that injects Al; Carry out alloying technology by in molten steel, injecting metal of alloying; Judge that for the first time wherein, judgement for the first time is used for judging by the concentration of analyzing molten steel Al whether the concentration of Al is in the scope of set(ting)value; If the concentration of Al satisfies set(ting)value, utilize the stirring of inert gas molten steel so, and carry out the second time and judge, wherein, whether the concentration of judging the aluminate that is used for judging final molten steel for the second time is corresponding to target value; If the concentration of aluminate satisfies target value, so molten steel is carried out continuous casting.
Here, in the complex deoxidization step, reductor can be Si and Mn, and in the alloying step, metal of alloying can be 0.2%～0.4% Ti for mass percent.
In addition, in the continuous casting step, the concentration of the aluminate in the molten steel satisfies following conditions.
[Al]
Aluminum oxide＜70ppm
Wherein, [Al]
Aluminum oxide=[Al]
Always-[Al]
Molten
In the continuous casting step, preferably, the component of molten steel satisfies following conditions.
[Si]+[Mn]＝0.5％～1.0％
Wherein, the per-cent here is mass percent.
In addition, preferably, the final composition of the slag after the refining in the vacuum-oxygen decarbonizing refining ladle satisfies following conditions.
1.1≤(％CaO)/(％Al
2O
3)≤1.4
4≤(％TiO
2)/(％SiO
2)≤6
Wherein, the per-cent here is mass percent.
In addition, molten steel is 80 tons～85 tons.
Preferably, the set(ting)value of the Al concentration in the step of judging for the first time is a mass percent 0.05%～0.12%, wherein, if the concentration of Al is lower than mass percent 0.05%, so described method also comprises for 80 tons～85 tons molten steel injects the step of the Al of 30Kg～40Kg in addition, if the concentration of Al is mass percent 0.12% or greater than mass percent 0.12%, so described method also comprises for 80 tons～85 tons molten steel injects the step of the unslaked lime of 250Kg～300Kg in addition.
In addition, the target value of the concentration of the aluminate in judging for the second time is 70ppm or less than 70ppm.
The method that is used to make the ferrite stainless steel base with equiaxed grain structures according to the present invention is made the ferrite stainless steel base with equiaxed grain structures of the present invention, the concentration that it is characterized in that aluminate is 70ppm or less than 70ppm, and the equiaxial crystal ratio in the slab is 40% or greater than 40%.
Hereinafter, in more detailed mode the preferred embodiments of the present invention are described with reference to the accompanying drawings.
Fig. 1 shows the schema of the method that is used to make the ferrite stainless steel base with equiaxed grain structures according to the preferred embodiment of the invention.
The method that is used for making the ferrite stainless steel base with equiaxed grain structures according to the preferred embodiment of the invention may further comprise the steps: at the vacuum-oxygen decarbonizing ladle, from the top oxygen blast of molten steel, thereby carry out oxygen decarburization reaction (S10); In order to reduce Cr
2O
3, in the molten steel that has carried out oxygen decarburization reaction, inject Al (S20); By in order to reduce Cr
2O
3Carry out complex deoxidization (S30) and inject reductor to its molten steel that injects Al; Carry out alloying technology (S40) by in molten steel, injecting metal of alloying; Judge for the first time (S50) that wherein, judgement for the first time is used for judging by the Al concentration of analyzing molten steel whether the concentration of Al is in the scope of set(ting)value; If the concentration of Al satisfies set(ting)value, utilize stirring of inert gas molten steel (S60) so, and carry out judging the second time (S70), wherein, whether the concentration of judging the aluminate that is used for judging final molten steel for the second time is corresponding to target value; If the concentration of aluminate satisfies target value, so molten steel is carried out continuous casting (S80).
Here, the set(ting)value of the Al concentration in the step of judging for the first time (S50) is mass percent 0.05%～0.12% (S51), wherein, preferably, if the concentration of Al is less than mass percent 0.05% (S52), so also comprise the step (S54) of injecting Al,, inject unslaked lime (S56) so if the concentration of Al is mass percent 0.12% or greater than mass percent 0.12%.
In addition, in the step (S30) of complex deoxidization, reductor is Si and Mn, and in the step (S40) of alloying, metal of alloying is Ti.
Fig. 2 shows equiaxial crystal ratio in the slab according to the figure to the variation of the control of alumina inclusion concentration, and Fig. 3 is the figure that the result of Fig. 2 is depicted as distributed data.
With reference to Fig. 2 and Fig. 3, can think that along with the reduction of alumina inclusion concentration in the molten steel, the equiaxial crystal ratio in the slab increases.Here, the concentration of suitable aluminate can be set at less than 70ppm.When satisfying this condition, can obtain equiaxial crystal ratio and be 40%～100% slab.At this moment, if the concentration of aluminate surpasses 70ppm, suppressed the generation of useful TiN so, thereby can not guarantee the target equiaxial crystal ratio.
In order to control the component of molten steel as above, by finishing oxygen decarburization reaction and injecting Al subsequently and reduce the Cr that slag is generated by oxygenant
2O
3, wherein, finish oxygen decarburization reaction by top oxygen blast in vacuum-oxygen decarbonizing (VOD) ladle from 80 tons～85 tons molten steel.
Reduce Cr by injecting Al
2O
3Step by injecting Si and Mn and inject Ti subsequently and carry out complex deoxidization, thereby come controlled target to form.
Carrying out the concentration of Al being carried out initial analysis after Ti injects about 5 minutes.If initial Al concentration is too low, the Al that reinjects so, if initial Al concentration is too high, unslaked lime so reinjects.Next, utilize rare gas element to stir, make the concentration of the aluminate in the final molten steel be controlled as and meet target zone, thereby carry out continuous casting in the bottom of ladle.
In vacuum-oxygen decarbonizing technology, after carrying out oxygen blast for oxygen decarburization, in molten steel, exist as below reaction formula 2 with [Cr]/(Cr
2O
3) oxygen of concentration of balance correspondence.
[reaction formula 2]
2[Cr]+3[O]＝(Cr
2O
3)
According to the document of previously known, known at 1650 ℃ of down [Cr] and Cr of about 20%
2O
3Oxygen concn in the equilibrated molten steel is in 0.06%～0.07% level.As a result, be used for the Al of effective deoxidant element of deoxidation by in molten steel, adding conduct, thereby cause reaction such as following reaction formula 3 and 4, and the Cr in the reduced blast furnace
2O
3
[reaction formula 3]
2[Al]+3[O]＝(Al
2O
3)
[reaction formula 4]
(Cr
2O
3)+2[Al]＝(Al
2O
3)+2[Cr]
Yet, carry out in molten steel, having numerous Al under the situation of deoxidation at basis reaction formula 3 and 4 as above
2O
3Inclusion.At this moment, the aluminate that forms is reunited and is also grown up, and make aluminate float or be removed, yet, have at aluminate under the situation of fine size of a few μ m orders of magnitude, aluminate will be retained in molten steel inside until casting.
In addition, by [%Al] with prior art
Aluminum oxide[%Si]+[%Mn] and [Al] of the present invention
Aluminum oxide[%Si]+[%Mn] compares, the existence that equiaxial crystal ratio and defective be shown in the table 1 below with do not exist.
Table 1
As shown in table 1, compare with the example of prior art, the present invention can obtain 40% or greater than 40% higher equiaxial crystal ratio.
Simultaneously, form TiN in the molten steel by being reflected at of reaction formula 1; Yet the time point of formation TiN changes according to the composition and the temperature of molten steel.If before making molten steel solidification, in ladle or tundish, form TiN, can generate TiN by homogeneous nucleation and growth by the reaction of Ti atom and N atom so, yet, according to thermodynamics at the 3rd interface (for example, at the interface of oxidation-inclusions/molten etc.) to carry out nucleation be favourable.At this moment, the oxidation-inclusion as the heterogeneous nucleation position that TiN is provided has Al in some cases
2O
3, MgO, TiO
x, MgO-Al
2O
3, CaO-TiO
x, MgO-Al
2O
3-TiO
xDeng.As representing that TiN is easy to carry out the indirect index of heterogeneous nucleation on the surface of these inclusiones, exist as following equation 5 defined lattice mismatches.
[equation 5]
Wherein, I
Oxide compoundAnd I
TiNRepresent oxidation-inclusion crystal and TiN crystalline lattice parameter respectively.This shows when the δ between two kinds of materials becomes big, is difficult to as the heterogeneous nucleation position.
For example, the Al of hexagonal structure
2O
3And the δ between the TiN of face-centered cubic (FCC) structure
Al2O3-TiNBe approximately 0.1, and be all face-centred cubic MgO or Mg Al
2O
3δ between spinel and the TiN
MgO (or Spinel)-TiNBe approximately 0.0002.As a result, can expect that MgO base inclusion will be easy to as the heterogeneous nucleation position, rather than Al
2O
3The base inclusion.
Therefore, exist in molten steel under the situation of a large amount of aluminates, TiN nucleation deterioration makes that this can become the factor that causes ferritic heterogeneous nucleation deterioration when solidifying.
Therefore, in order to make slab, must reduce the aluminate in the molten steel with equiaxed grain structures.Simultaneously, in order to reduce TiO
xThe base inclusion must obtain the complex deoxidization effect by injecting Si/Mn.
Fig. 4 shows the method for comparing by being used to make the ferrite stainless steel base with equiaxed grain structures according to the preferred embodiment of the invention with conventional example and reduces Al
2O
3And TiO
xThe graphic representation of inclusion.
With reference to Fig. 4,, just do not form Ti when [Si] in existing molten steel+[Mn] is that 0.1%～0.4% level and [Al] are constant 0.03% the time
3O
5Critical [Ti] of inclusion is approximately 0.45%, is 0.6%～0.94% and [Al] when being 0.03% and work as [Si]+[Mn], can think that reaching about 0.5% until [Ti] can suppress Ti
3O
5Generation.In addition, when the concentration of [Si]+[Mn] low and [Ti] constant 0.4% the time, just do not form Ti
3O
5Critical [Al] of inclusion is approximately 0.027% level, and works as the concentration of [Si]+[Mn] high and [Ti] when being 0.4%, can think that the level until [Al]=0.024% can not form Ti
3O
5Inclusion.
As mentioned above, in order in molten steel, to inject [Si]+[Mn] to meet the scope of aimed concn (%), specifically, for the concentration with aluminate is controlled at 70ppm or less than 70ppm, about 5 minutes time point carries out initial analysis to [Al] concentration of molten steel in the past after injection.
If [Al] concentration that analysis obtains is not carried out sufficient Cr so less than 0.05%
2O
3Reduction, if analyze [Al] concentration obtain and be 0.12% or greater than 0.12%, the concentration of so final aluminate surpasses 70ppm, if [Al] concentration that analysis obtains is less than 0.05%, the Al of 30Kg～40Kg then reinjects, if analyze [Al] concentration obtain and be 0.12% or, the unslaked lime of the 250Kg～300Kg that reinjects so greater than 0.12%.Next, utilize the stirring of inert gas molten steel, make the concentration of the aluminate in the final molten steel be controlled as 70ppm or, carry out continuous casting, thereby help the generation of useful TiN less than 70ppm in the bottom of ladle.
Here, when Al concentration less than 0.05% the time, if inject the aluminium that is less than 30Kg, its additive effect is inapparent for 80 tons～85 tons molten steel so, thereby can not reduce Cr effectively
2O
3If, inject the Al that surpasses 40Kg, Al concentration can surpass 0.12% so.Therefore, preferably, the amount of the Al of interpolation is 30Kg～40Kg.
In addition, when the concentration of Al is 0.12% or greater than 0.12% the time, if inject the unslaked lime that is less than 250Kg, can cause surface imperfection so in the finished product, if inject the unslaked lime that surpasses 300Kg, the concentration of so final Al inclusion can surpass 70ppm.Therefore, preferably, the amount of the unslaked lime of interpolation is 250Kg～300Kg.
Preferably, the slag after the refining in the vacuum-oxygen decarbonizing ladle finally consists of 1.1≤(%CaO)/(%Al
2O
3)≤1.4 and 4≤(%TiO
2)/(%SiO
2)≤6.
As (%CaO)/(%Al
2O
3) less than 1.1 o'clock, alumina inclusion concentration can surpass 70ppm, as (%CaO)/(%Al
2O
3) surpass at 1.4 o'clock, can in final product, cause surface imperfection etc.Therefore, preferably, 1.1≤(%CaO)/(%Al
2O
3)≤1.4.
In addition, as (%TiO
2)/(%SiO
2) less than 4 o'clock, the effect of generation that suppresses excessive Ti oxide compound was not remarkable, as (%TiO
2)/(%SiO
2) surpass at 6 o'clock because excessive TiN oxide compound, thus can deterioration when solidifying as the generation of the TiN at ferritic heterogeneous nucleation position.Therefore, preferably, 4≤(%TiO
2)/(%SiO
2)≤6.
By this way, be that equiaxial crystal ratio in the slab of 200mm～220mm is 40% or greater than 40% by guaranteeing thickness, can make slab, and reduce the wrinkling defective that in the process that forms final cold-rolled products, produces with equiaxed grain structures.
[example]
Now example of the present invention will be described.
In order to have the composition of Fe-17%Cr, fusing scrap iron and iron alloy carry out oxygen decarburization process to it then in the AOD refining furnace in electric furnace, 1780 ℃ of tappings down, enter into ladle.In ladle, there are molten steel and slag.In order to improve the efficient of vacuum-oxygen decarbonizing, mechanically remove slag.At this moment, the temperature of molten steel is about 1600 ℃.Ladle is moved on on the vacuum-oxygen decarbonizing refining support, wherein, vacuum cover is placed on the ladle, utilize spray gun on the molten steel top then to the ladle supply oxygen.Utilize this technology, after finishing oxygen decarburization reaction, the temperature of molten steel is increased to about 1670 ℃, analyzes the composition of molten steel, as following table 2.
Table 2
| Component | C | Si | Mn | S | Cr | Ti | Al | N |
| Concentration (weight percent) | 0.005 | 0.0 | 0.3 | 0.008 | 17 | 0.0 | 0.01 |
After finishing oxygen blast, the Al that injects about 320Kg is with reduction Cr
2O
3And under vacuum atmosphere to deoxidation of molten steel.At this moment, by injecting Si and Mn and Al, suppressed the generation of Ti oxide compound.By injecting the Ti of form of sponge, [Ti] in the molten steel is in 0.3% level.
The time point in past 5 minutes after injecting iron alloy is because [Al] in the molten steel is in 0.04% level, so the Al of the 30Kg that reinjects as mentioned above supplies Ar to stir molten steel about 20 minutes from the bottom of ladle then.Finish refinery practice under vacuum after, the temperature of molten steel is about 1600 ℃.For casting temp being controlled to 1550 ℃, under this atmosphere, inject refrigerant etc.
After ladle process, ladle is sent to continuous casting process.Analyze the component of the molten steel in the final tundish, as following table 3.
Table 3
| Component | C | Si | Mn | S | Cr | Ti | Al Aluminum oxide | Al Aluminum oxide | N |
| Concentration (weight percent) | 0.004 | 0.3 | 0.4 | 0.003 | 18 | 0.30 | 0.02 | 0.004 | 0.011 |
In the component of the molten steel of table 3, [the Al that exists as aluminum oxide
Aluminum oxide] concentration is 40ppm.Can think that this concentration within the scope of the invention.
At this moment, the N concentration in the molten steel is about 110ppm, and with 0.30% [Ti] reaction to help to generate useful TiN, as shown in Figure 5, thereby obtain slab with equiaxed grain structures.
Though illustrated and described some embodiments of the present invention, but those skilled in the art should understand that, without departing from the principles and spirit of the present invention, can modify this embodiment, scope of the present invention is limited in claim and the equivalent thereof.
Claims (15)
1, a kind of method that is used to make the ferrite stainless steel base with equiaxed grain structures said method comprising the steps of:
In the vacuum-oxygen decarbonizing ladle, carry out oxygen decarburization reaction by top oxygen blast from molten steel;
In order to reduce Cr
2O
3, in the molten steel that has carried out oxygen decarburization reaction, inject Al;
By in order to reduce Cr
2O
3Carry out complex deoxidization and inject reductor to its molten steel that injects Al;
Carry out alloying technology by in molten steel, injecting metal of alloying;
Judge that for the first time wherein, judgement for the first time is used for judging by the concentration of analyzing molten steel Al whether the concentration of Al is in the scope of set(ting)value;
If the concentration of Al satisfies set(ting)value, utilize the stirring of inert gas molten steel so, and carry out the second time and judge, wherein, whether the concentration of judging the aluminate that is used for judging final molten steel for the second time is corresponding to target value;
If the concentration of aluminate satisfies target value, so molten steel is carried out continuous casting.
2, the method that is used to make the ferrite stainless steel base with equiaxed grain structures as claimed in claim 1, wherein, in the complex deoxidization step, reductor is Si and Mn.
3, the method that is used to make the ferrite stainless steel base with equiaxed grain structures as claimed in claim 1, wherein, in the alloying step, metal of alloying is Ti.
4, the method that is used to make the ferrite stainless steel base with equiaxed grain structures as claimed in claim 3, wherein, the mass percent of Ti is 0.2%～0.4%.
5, the method that is used to make ferrite stainless steel base as claimed in claim 1 with equiaxed grain structures, wherein, in the continuous casting step, the concentration of the aluminate in the molten steel satisfies following conditions:
[Al]
Aluminum oxide＜70ppm
Wherein, [Al]
Aluminum oxide=[Al]
Always-[Al]
Molten
6, the method that is used to make ferrite stainless steel base as claimed in claim 1 with equiaxed grain structures, wherein, in the continuous casting step, the component of molten steel satisfies following conditions:
[Si]+[Mn]＝0.5％～1.0％，
Wherein, the per-cent here is mass percent.
7, the method that is used to make ferrite stainless steel base as claimed in claim 1 with equiaxed grain structures, wherein, the final composition of the slag after the refining in the vacuum-oxygen decarbonizing refining ladle satisfies following conditions:
1.2≤(％CaO)/(％Al
2O
3)≤1.4
4≤(％TiO
2)/(％SiO
2)≤6
Wherein, the per-cent here is mass percent.
8, the method that is used to make the ferrite stainless steel base with equiaxed grain structures as claimed in claim 1, wherein, molten steel is 80 tons～85 tons.
9, the method that is used to make the ferrite stainless steel base with equiaxed grain structures as claimed in claim 1, wherein, the set(ting)value of the Al concentration in the step of judging for the first time is a mass percent 0.05%～0.12%.
10, the method that is used to make the ferrite stainless steel base with equiaxed grain structures as claimed in claim 9, wherein, if the concentration of Al is lower than mass percent 0.05%, so described method also comprises the step of other injection Al.
11, the method that is used to make the ferrite stainless steel base with equiaxed grain structures as claimed in claim 10 wherein, is injected the Al of 30Kg～40Kg for 80 tons～85 tons molten steel.
12, the method that is used to make ferrite stainless steel base as claimed in claim 9 with equiaxed grain structures, wherein, if the concentration of Al is mass percent 0.12% or greater than mass percent 0.12%, so described method also comprises the step of other injection unslaked lime.
13, the method that is used to make the ferrite stainless steel base with equiaxed grain structures as claimed in claim 12 wherein, is injected the unslaked lime of 250Kg～300Kg for 80 tons～85 tons molten steel.
14, the method that is used to make the ferrite stainless steel base with equiaxed grain structures as claimed in claim 1, wherein, the target value of the concentration of the aluminate in the step of judging for the second time is 70ppm or less than 70ppm.
15, a kind of according to the ferritic stainless steel with equiaxed grain structures of claim 1 to the described method manufacturing of claim 14, wherein, the concentration of aluminate is 70ppm or less than 70ppm, and equiaxial crystal ratio is 40% or greater than 40%.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| KR1020050131297A KR100729934B1 (en) | 2005-12-28 | 2005-12-28 | Method for manufacturing ferritic stainless steel slabs with equiaxed grain structures and the ferritic stainless steel manufactured by it |
| KR1020050131297 | 2005-12-28 | ||
| PCT/KR2006/004673 WO2007074970A1 (en) | 2005-12-28 | 2006-11-09 | Method for manufacturing ferritic stainless steel slabs with equiaxed grain structures and the ferritic stainless steel manufactured by it |
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| Publication Number | Publication Date |
|---|---|
| CN101351565A true CN101351565A (en) | 2009-01-21 |
| CN101351565B CN101351565B (en) | 2011-02-02 |
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Country Status (6)
| Country | Link |
|---|---|
| US (1) | US20090223603A1 (en) |
| EP (1) | EP1974063A4 (en) |
| JP (1) | JP5221379B2 (en) |
| KR (1) | KR100729934B1 (en) |
| CN (1) | CN101351565B (en) |
| WO (1) | WO2007074970A1 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| TWI412597B (en) * | 2010-05-28 | 2013-10-21 | China Steel Corp | Bearing steel refining method for improving fatigue life |
| CN107574385A (en) * | 2017-08-28 | 2018-01-12 | 北京科技大学 | A kind of process for improving bistable ferrite stainless steel continuous casting billet equiaxial crystal ratio |
| CN107709536A (en) * | 2015-04-17 | 2018-02-16 | 密苏里大学管理者 | Crystal grain refinement in iron-based material |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2047926A1 (en) * | 2007-10-10 | 2009-04-15 | Ugine & Alz France | Method of manufacturing stainless steels comprising fine carbonitrides, and product obtained from this method |
| KR100922059B1 (en) * | 2007-12-20 | 2009-10-16 | 주식회사 포스코 | Method for manufacturing high chrome stainless steel including titannium |
| 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 |
| CA2819997C (en) | 2010-11-05 | 2019-06-25 | Kyushu University | Preventive or therapeutic agent for pain associated with herpes zoster in acute phase |
| KR101198589B1 (en) | 2010-12-27 | 2012-11-06 | 주식회사 포스코 | Method of refining of high Cr ferrite stainless steel and refining apparatus thereby |
| JP5687590B2 (en) * | 2011-09-27 | 2015-03-18 | 日本冶金工業株式会社 | Method for producing boron-containing stainless steel |
| JP6306353B2 (en) * | 2014-01-21 | 2018-04-04 | Ｊｆｅスチール株式会社 | Method for producing slab for ferritic stainless steel cold rolled steel sheet and method for producing ferritic stainless steel cold rolled steel sheet |
| KR101898165B1 (en) * | 2016-12-06 | 2018-09-13 | 주식회사 포스코 | Method for manufacturing ferritic stainless steel having fine cast structure |
| KR101896340B1 (en) * | 2017-06-01 | 2018-09-07 | 주식회사 포스코 | Molten steel manufacturing method |
| CN113502376A (en) * | 2021-06-18 | 2021-10-15 | 鞍钢联众(广州)不锈钢有限公司 | Method for improving secondary skin inclusion of titanium-containing stainless steel billet |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0949010A (en) * | 1995-08-09 | 1997-02-18 | Nisshin Steel Co Ltd | Production of continuous casting ferritic stainless steel slab having high equi-axial crystal ratio |
| JP3288626B2 (en) * | 1997-03-21 | 2002-06-04 | 新日本製鐵株式会社 | High workability ferritic stainless steel sheet excellent in ridging characteristics and method for producing the same |
| TW496903B (en) * | 1997-12-19 | 2002-08-01 | Armco Inc | Non-ridging ferritic chromium alloyed steel |
| JP2000073146A (en) * | 1998-08-27 | 2000-03-07 | Nisshin Steel Co Ltd | Ferritic stainless steel excellent in ridging resistance |
| JP2000160230A (en) * | 1998-11-20 | 2000-06-13 | Nisshin Steel Co Ltd | Production of ferritic stainless steel excellent in ridging resistance |
| WO2000061322A1 (en) * | 1999-04-08 | 2000-10-19 | Nippon Steel Corporation | Cast steel piece and steel product excellent in forming characteristics and method for treatment of molted steel therefor and method for production thereof |
| JP2001049322A (en) * | 1999-08-05 | 2001-02-20 | Nisshin Steel Co Ltd | Production of ferritic stainless steel excellent in ridging resistance |
| JP3668087B2 (en) * | 2000-02-03 | 2005-07-06 | 日本冶金工業株式会社 | High-cleaning refining method for stainless steel |
| KR100355369B1 (en) * | 2000-06-07 | 2002-10-11 | 고려용접봉 주식회사 | Flux cored wire for arc-welding of austenitic stainless steel |
| JP3624804B2 (en) * | 2000-07-14 | 2005-03-02 | 住友金属工業株式会社 | Method for producing ridging resistant ferritic stainless steel |
| JP3733098B2 (en) * | 2002-10-23 | 2006-01-11 | 新日本製鐵株式会社 | Method of melting steel sheet for ultra-low carbon or low-carbon sheet with excellent surface quality and continuous cast slab |
| DK1637785T3 (en) * | 2004-09-15 | 2010-08-16 | Sumitomo Metal Ind | Steel pipes with excellent exfoliation resistance to peel on the inner surface |
-
2005
- 2005-12-28 KR KR1020050131297A patent/KR100729934B1/en active IP Right Grant
-
2006
- 2006-11-09 EP EP06812508A patent/EP1974063A4/en not_active Withdrawn
- 2006-11-09 CN CN2006800497022A patent/CN101351565B/en not_active Expired - Fee Related
- 2006-11-09 WO PCT/KR2006/004673 patent/WO2007074970A1/en active Application Filing
- 2006-11-09 JP JP2008548373A patent/JP5221379B2/en not_active Expired - Fee Related
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| TWI412597B (en) * | 2010-05-28 | 2013-10-21 | China Steel Corp | Bearing steel refining method for improving fatigue life |
| CN107709536A (en) * | 2015-04-17 | 2018-02-16 | 密苏里大学管理者 | Crystal grain refinement in iron-based material |
| CN107709536B (en) * | 2015-04-17 | 2021-08-27 | 密苏里大学管理者 | Grain refinement in iron-based materials |
| CN107574385A (en) * | 2017-08-28 | 2018-01-12 | 北京科技大学 | A kind of process for improving bistable ferrite stainless steel continuous casting billet equiaxial crystal ratio |
Also Published As
| Publication number | Publication date |
|---|---|
| KR100729934B1 (en) | 2007-06-18 |
| JP2009521599A (en) | 2009-06-04 |
| EP1974063A4 (en) | 2010-07-21 |
| EP1974063A1 (en) | 2008-10-01 |
| US20090223603A1 (en) | 2009-09-10 |
| JP5221379B2 (en) | 2013-06-26 |
| WO2007074970A1 (en) | 2007-07-05 |
| CN101351565B (en) | 2011-02-02 |
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