WO2008068835A1 - 極低硫高清浄鋼の溶製方法 - Google Patents
極低硫高清浄鋼の溶製方法 Download PDFInfo
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- WO2008068835A1 WO2008068835A1 PCT/JP2006/324194 JP2006324194W WO2008068835A1 WO 2008068835 A1 WO2008068835 A1 WO 2008068835A1 JP 2006324194 W JP2006324194 W JP 2006324194W WO 2008068835 A1 WO2008068835 A1 WO 2008068835A1
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- ladle
- molten steel
- gas
- steel
- ultra
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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
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/0075—Treating in a ladle furnace, e.g. up-/reheating of molten steel within the ladle
-
- 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
- C21C7/064—Dephosphorising; Desulfurising
-
- 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
- C21C7/064—Dephosphorising; Desulfurising
- C21C7/0645—Agents used for dephosphorising or desulfurising
-
- 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
- C21C7/072—Treatment with gases
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
- C22B9/10—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals with refining or fluxing agents; Use of materials therefor, e.g. slagging or scorifying agents
Definitions
- the present invention relates to a method for melting ultra-low sulfur high clean steel.
- [0002] Extremely low-sulfur steel with an S concentration in molten steel (hereinafter referred to as [S]) of lOppm or less is produced by the following procedure.
- the molten iron with an [S] of about 300 ppm discharged from the blast furnace is desulfurized to about 20 ppm by the injection desulfurization method or the KR desulfurization method using mechanical stirring.
- this hot metal is directly decarburized and blown in a converter.
- the molten steel in the converter is taken out into the ladle.
- the molten steel in the ladle is desulfurized.
- the hot metal dephosphorization is usually performed before or after hot metal desulfurization.
- a laxative has been formulated and used.
- Patent Document 1 JP-A-10-212514
- An object of the present invention is that the necessary combing force using CaF does not increase the steel temperature of the converter.
- the present invention includes a step 1 of adding CaO-based flux to molten steel in a ladle under atmospheric pressure, a lance force immersed in the molten steel in a ladle under atmospheric pressure, and blowing a stirring gas into the ladle in the ladle and CaO.
- the steel flux is agitated and an acidic gas is supplied to the molten steel in the ladle, and the acidic product generated by the reaction between the acidic gas and the molten steel in the ladle is mixed with the CaO flux.
- the electrode is characterized in that the ratio (tZt) to the stirring time t after the gas supply is stopped is 0.6 or more.
- This is a method for producing low-sulfur high-clean steel.
- ultra-low sulfur high clean steel refers to, for example, steel having [S] of 10 ppm or less and T. [O] of 40 ppm or less.
- Step 4 it is desirable to further perform Step 4 after Step 3 to remove inclusions in the molten steel using an RH vacuum degassing apparatus.
- the acidic gas is oxygen gas or a mixed gas of oxygen gas and inert gas.
- the oxidizing gas is supplied by being sprayed onto the surface of the molten steel or slag through the top blowing lance, and the top blowing lance has a water-cooled structure. Desirable to have.
- step 2 and step 3 it is desirable to provide a cover on the top of the ladle and connect this cover to the dust device. That's right.
- an ultra-low sulfur highly clean steel having [S] of lOppm or less and T. [O] of 40ppm or less is used as a molten steel in a ladle.
- FIG. 1 is a graph showing the relationship between the ratio (tZt) and the desulfurization rate (%).
- FIG. 2 is a graph showing the relationship between the ratio (tZt) and T. [O] (ppm) after step 3 is completed.
- Fig. 3 shows the number N of inclusions with a size of 100 m or more, which was obtained by counting the molten steel samples that completed Step 3 with an optical microscope, and the melting during the RH reflux treatment in Step 4.
- NZN the number of inclusions
- Step 1 to Step 4 described below are performed in order. Therefore, these steps 1 to 4 will be described.
- step 1 CaO flux is added to the molten steel in the ladle under atmospheric pressure.
- step 1 the molten steel is blown to the molten steel in the steel being tapped from the converter to the ladle or on top of the molten steel in the ladle that has been tapped from the converter.
- CaO flux system has a high melting point, This is because the already added CaO-based flux is rapidly fed by the high-temperature region generated by the supply of the acidic gas in the subsequent step 2. Even if the CaO-based flux is added after the supply of the acidic gas is stopped, the high-temperature region does not exist after the supply of the acidic gas is stopped. It cannot be promoted by the high temperature region.
- the CaO flux includes quick lime or Al O, MgO, etc. mainly composed of quick lime.
- the composition of the molten steel in the ladle according to the present embodiment is C: 0.03% to 0.2% (in the present specification, “%” means “mass%” unless otherwise specified), Si : 0.001% or more 1. 0% or less, Mn: 0.05% or more and 2.5% or less, P: 0.005% or more and 0.05% or less, S: 15ppm or more and 60ppm or less, sol.A1: 0.005% or more and 2.0% or less, T. [O]: 50ppm or more and lOOppm or less, and the temperature is about 1600 ° C or more and 1700 ° C or less.
- CaO-based flux can be obtained by injecting powder into molten steel in the ladle via a lance, spraying powder onto the surface of the molten steel in the ladle, placing it on the molten steel in the ladle, In addition, it may be added by adding CaO-based flux into the ladle at the time of steelmaking.
- An arrow blade-type slag outflow prevention tool (hereinafter referred to as “dart” in the present specification) disclosed by Japanese Patent Application Laid-Open No. 2005-113192 is introduced and arranged to form a vortex at the top of the exit steel hole.
- (c) slag outflow of converter power is detected electrically, optically or mechanically, and the outflow of steel is stopped in accordance with the slag outflow timing. desirable.
- step 1 not only step 1 but also steps 2 to 4 described below are performed under atmospheric pressure. This is because when the processes 1 to 4 are performed under reduced pressure, both the equipment cost and the running cost increase. (Process 2)
- Step 2 the molten steel in the ladle and the CaO flux are stirred by blowing the immersed lance force stirring gas into the molten steel in the ladle at atmospheric pressure to which the CaO flux has been added after Step 1.
- Step 2 an acidic gas is supplied to the molten steel in the ladle, and the oxide produced by the reaction between the acidic gas and the molten steel in the ladle is mixed with the CaO-based flux.
- the reason for supplying the oxidizing gas to the molten steel in the ladle in step 2 is that the oxidation of the molten steel in the ladle is heated or the temperature is lowered by using the oxidation exothermic reaction caused by the reaction with the components of the molten steel in the ladle. This is to suppress it. Therefore, the supplied acidic gas is a gas that generates heat by reacting with the components of the molten steel in the ladle. For example, pure oxygen, carbon dioxide, and a mixed gas of these with an inert gas such as argon gas. Etc. can be used.
- the mixed gas may be premixed on the upstream side of the gas blowing nozzle, or may be mixed on the outlet side of the nozzle having a double tube structure.
- the CaO-based flux can be heated by the acidic gas by flowing an acidic gas through the inner tube and an inert gas through the outer tube. It is only necessary to protect the nozzle itself by just crawling.
- the acidic gas is injected into the molten steel in the ladle, or the acidic gas from the lance or nozzle force disposed above the molten steel in the ladle. It can be supplied by spraying.
- the heat generated by the reaction between the oxidative gas and the molten steel in the ladle is first transferred to the molten steel in the ladle and then indirectly transferred to the CaO flux.
- the oxidizing gas reacts with the molten steel in the ladle, the CaO-based flux existing on the molten steel in the ladle can easily pass through that point. is there.
- the CaO-based flats can be directly heated using the high-temperature region present at this fire point to promote wiping. Therefore, it is desirable to supply the acidic gas by spraying the lance or nozzle force molten steel placed above the molten steel in the ladle.
- step 2 when desulfurizing the molten steel by adding CaO-based flux to the molten steel in the ladle under atmospheric pressure, it is preferably placed above the molten steel in the ladle.
- the oxidant gas such as lance or nozzle, is sprayed on the molten steel in the ladle, and the oxidizing gas reacts with the molten steel in the ladle.
- the supply time t of the acidic gas in step 2 is about 3 minutes to 18 minutes.
- the supply rate of the acidic gas in step 2 is 75 NLZmin or more and 240 NLZmin or less per ton of molten steel in the ladle in terms of pure oxygen. If the supply rate of the oxidizing gas is less than 75 NLZmin, the acid delivery rate is too low, the heating of the CaO-based flux becomes insufficient, the desulfurization ability decreases, and the temperature rise time becomes long. May decrease. From the same point of view, the supply rate of the acidic gas is more than lOONLZmin.
- step 2 if the supply rate of the acidic gas in step 2 exceeds 240 NLZmin, the oxygen potential of the slag that can sufficiently heat the CaO-based flux becomes too high, and the subsequent step 3 There is a possibility that the desulfurization will be adversely affected and the life of the refractories in the lance and ladle may be reduced.
- Molten steel surface strength of the molten steel in the ladle The distance to the tip of the lance or nozzle is preferably about 0.1 lm or more and 5 m or less. If this distance is less than 0.1 lm, the spitting of the molten steel becomes intense and the life of the lance or nozzle is reduced. On the other hand, if the distance exceeds 5 m, the oxygen-containing gas jet does not reach the surface of the molten steel in the ladle, and the oxygen efficiency is significantly reduced. There is a risk.
- step 2 by supplying the acidic gas to the molten steel in the ladle in this way, the hatching of the CaO-based flux is promoted by utilizing the high temperature region existing at the fire point. Furthermore, in step 2, the stirring gas from the lancer immersed in the molten steel in the ladle is blown to stir the molten steel in the ladle and the CaO-based flux. The acid oxide produced by the reaction with the CaO-based flux is mixed.
- Acid oxides produced by the reaction between the acid gas and the molten steel in the ladle are Al 2 O, FeO, Mn
- FeO and MnO both increase the oxygen potential of the slag and are thermodynamically disadvantageous for desulfurization of molten steel.
- the flow rate of the stirring gas in Step 2 is desirably 3.5 NLZmin or more and 20 NLZmin or less per ton of molten steel in the ladle. If the stirring gas injection flow rate is less than 3.5 NL / min, the stirring force is insufficient, the oxygen potential of the slag increases at the end of step 2, and the oxygen potential of the slag in step 3 is insufficiently reduced. There is a risk of becoming. On the other hand, if the flow rate of the stirring gas exceeds 20 NLZmin, the occurrence of splash becomes extremely large, which may reduce productivity.
- step 3 the supply of the acidic gas from the top blowing lance force is stopped, and the stirring by blowing the stirring gas from the lance force immersed in the molten steel in the ladle under atmospheric pressure is continued. This will desulfurize the molten steel in the ladle and remove inclusions.
- the ratio (tZt) between the stirring time t by blowing the stirring gas after stopping the supply of the acidic gas and the acidic gas supply time t in the step 2 (tZt) is set to 0.6 or more, and the oxidation is performed. After stopping the supply of sex gas In addition, by continuously stirring the molten steel in the ladle, it is possible to produce ultra-low sulfur high clean steel. The reason for this will be explained.
- step 2 in order to prevent the oxygen potential of the slag from being increased during the supply of the acidic gas! It is conceivable to supply an acidic gas while blowing an extremely large amount of stirring gas into the ladle in the ladle under atmospheric pressure.
- the stirring of the molten steel in the ladle and the slag is carried out by an acidic solution. It is divided into the supply period of the oxidizing gas (process 2) and the subsequent non-supply period of the oxidizing gas (process 3). In other words, even after the supply of the acidic gas from the top blowing lance is stopped, the stirring gas is continuously blown from the lance power immersed in the molten steel in the ladle.
- step 2 by allowing the oxygen potential of the slag to be increased by the oxide generated by the reaction between the acidic gas and the molten steel in the ladle, the CaF
- step 2 it is possible to promote the CaO flux that needs to be added.
- the desulfurization efficiency in step 2 is reduced to some extent to allow an increase in the oxygen potential of the slag.
- the slag having an increased oxygen potential is agitated with the molten steel in the ladle even after the supply of the oxidizing gas is stopped in the step 3 performed after the step 2, the slag The desulfurization efficiency can be increased by lowering the oxygen potential. This makes it possible, for example, to desulfurize molten steel in the ladle to an extremely low sulfur region where [S] is 10 ppm or less.
- step 3 along with this desulfurization, the oxide inclusions generated by supplying the acidic gas in step 2 are simultaneously separated.
- the stirring time t in step 3 is determined so that Zt) is 0.6 or more.
- the ratio (tZt) is 0 If it is less than 6, the oxygen potential of the slag that has risen due to the supply of the acidic gas in step 2 cannot be sufficiently reduced in step 3, so that the desulfurization rate is sufficiently increased and the inclusion concentration index T It is impossible to suppress [O] sufficiently.
- FIG. 2 shows the results of the relationship between (tZt) and T. [0] (ppm) after Step 3.
- the ratio (tZt) is 0.8 or more.
- step 3 The reason why the gas agitation performed in step 3 is performed by introducing the agitation gas from the lancer immersed in the molten steel in the ladle is that the agitation gas is introduced from the porous plug cauldron installed at the bottom of the ladle. This is because a sufficient flow rate cannot be secured, and the reducing power of FeO and MnO in process 3 becomes insufficient, making it impossible to produce an extremely low sulfur steel.
- the flow rate of the stirring gas in Step 3 is preferably 3.5 NLZmin or more and 20 NL Zmin or less per ton of molten steel. 3. If it is less than 5 NLZmin, the stirring force is insufficient, and the reduction of slag oxygen potential in process 3 may be insufficient. On the other hand, if it exceeds 20 NLZmin, the occurrence of splash may become extremely large, resulting in a decrease in productivity.
- step 3 the longer the stirring time t by blowing the stirring gas after the supply of the acidic gas is stopped, the longer the desulfurization proceeds and the inclusion concentration decreases.
- Process 3 If the time is too short, the oxygen potential of the slag will not be sufficiently lowered and it will not be possible to desulfurize to the extremely low sulfur region, and it will also be difficult to remove the inclusions produced in step 2.
- the stirring time t depends on the supply time of the acidic gas, but it is desirable that the stirring time is, for example, about 1.8 minutes to 20 minutes.
- an ultra-low sulfur highly clean steel having [S] of lOppm or less and T. [O] of 40ppm or less, such as C: 0.3% 0.2% or less, Si: 0.001% or more, 0.05% or less, Mn: 0.05% or more, 2.5% or less, P: 0.005% or more, 0.0 5% or less, S: 10ppm
- an ultra-low sulfur high clean steel having a steel composition of sol. A1: 0.005% or more and 2.0% or less and T.
- 40 ppm or less can be produced.
- the temperature at the end of the process is about 1580 ° C to 1630 ° C.
- a cover is provided on the upper portion of the ladle and this cover is connected to the dust collector (hereinafter, the cover connected to the dust collector is referred to as "dust collector cover"). ⁇ ) is desirable.
- the CaO flux does not need to be added to the molten steel in the ladle.
- Step 4 is additionally performed following Step 3 in the case of producing an ultra-low sulfur high-purity steel having a higher purity than that obtained in Step 3.
- step 3 described above slag may be entangled in the molten steel during stirring of the molten slag steel, and slag inclusions may remain. Therefore, in order to reduce the residual amount of such slag inclusions and achieve higher cleaning, after step 3, the inclusions are suppressed while suppressing the slag entrainment by suppressing the stirring of the molten slag steel. It is desirable to provide a process for separating
- RH vacuum degasser immerses two dip tubes provided at the bottom of the lower tank in the molten steel in the ladle, and circulates the molten steel through these dip tubes. For this reason, since inclusions can be separated in a state in which the stirring of the slag is weak and the slag is not entrained, an even higher level of cleanliness can be achieved.
- Fig. 3 shows that the supply rate of acidified gas per ton of molten steel (pure oxygen conversion) X (NmVmin-in) is changed in the range of 0.15 to 0.3 and step 3 is completed.
- the number N of inclusions with a size of 100 m or more obtained by counting the molten steel samples with an optical microscope
- the number of inclusions (NZN) which is the ratio of the number N of inclusions with a size of 100 m or more, obtained by counting the molten steel samples during the RH recirculation treatment in step 4 with an optical microscope
- the RH reflux treatment time in Step 4 is preferably 8 minutes or more, more preferably 10 minutes or more, and further preferably 15 minutes or more. This RH recirculation treatment time can be appropriately determined according to the required inclusion level or hydrogen level!
- the hot metal which had been desulfurized and dephosphorized in advance as needed, was charged into a 250-ton scale top-bottom converter. Next, rough decarburization was blown until [C] reached 0.03% or more and 0.2% or less, and the end temperature was set to 1630 ° C or more and 1690 ° C or less to take out the crude decarburized molten steel into the ladle. did.
- step 1 of the present invention 10 kg of quick lime, which is a CaO-based flux, was added to molten steel in a ladle under atmospheric pressure per ton of molten steel in the ladle.
- step 2 of the present invention an immersion lance that can be raised and lowered is immersed in the molten steel in the ladle.
- the molten steel and quicklime were agitated by blowing Ar gas from the soaking lance at a flow rate of 8 NL / min per ton of molten steel in the ladle.
- pure oxygen gas, 150, 200 or Oxygen is generated by the reaction between pure oxygen gas and molten steel by blowing up at a supply speed of 300 NLZmin for a supply time t (8 minutes).
- This top blow lance was found to be short-lived due to melting damage in the non-water-cooled lance from the results of preliminary experiments conducted in advance, so a lance having a water-cooled structure was used.
- Sarako as step 3, the supply of pure oxygen gas is stopped, and the lance force immersed in the molten steel in the ladle is also used for stirring gas at a flow rate of 8 NLZmin per ton of molten steel for more than 1.2 minutes 20 Desulfurization and inclusion removal were performed by continuously blowing for less than a minute.
- the temperature of the molten steel at the end of Step 3 was 1580 ° C or higher and 1630 ° C or lower.
- Steps 1 to 3 in this example were performed without immersing the dip tube of the RH vacuum degassing apparatus in the molten steel in the ladle.
- Step 2 and Step 3 a dust collection cover was installed at the top of the ladle.
- CaF is not added to the ladle, and the ladle slag after the desulfurization treatment of the molten steel is completed.
- the CaF concentration was less than 0.1%.
- RH reflux treatment conditions were as follows: treatment time 14 minutes, dip tube diameter 0.66m, reflux gas flow 2000NL Zmin, ultimate vacuum is 133Pa.
- UST defect rate the defect rate (hereinafter referred to as "UST defect rate”) in an internal ultrasonic flaw test performed after rolling and subjected to continuous forging after RH reflux treatment was investigated. Then, (No. 12—2 to 12—8, 113 failure rate for RH reflux treatment) (! 3 ⁇ 41 Do you want to perform reflux treatment? ⁇ 0. 12—1 US T failure rate) UST failure rate It was calculated as an index and evaluated by this UST defect rate index.
Abstract
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Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
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CN200680056233A CN101535508A (zh) | 2006-12-05 | 2006-12-05 | 超低硫高清净钢的熔炼方法 |
KR1020097008338A KR101028914B1 (ko) | 2006-12-05 | 2006-12-05 | 극저황 고청정 강의 용제 방법 |
PCT/JP2006/324194 WO2008068835A1 (ja) | 2006-12-05 | 2006-12-05 | 極低硫高清浄鋼の溶製方法 |
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PCT/JP2006/324194 WO2008068835A1 (ja) | 2006-12-05 | 2006-12-05 | 極低硫高清浄鋼の溶製方法 |
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KR (1) | KR101028914B1 (ja) |
CN (1) | CN101535508A (ja) |
WO (1) | WO2008068835A1 (ja) |
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JP6981589B1 (ja) * | 2020-06-16 | 2021-12-15 | Jfeスチール株式会社 | 高清浄度鋼の製造方法 |
Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS61143510A (ja) * | 1984-12-13 | 1986-07-01 | Nippon Steel Corp | 取鍋内溶鋼の精錬法 |
JPS63266017A (ja) * | 1987-04-23 | 1988-11-02 | Sumitomo Metal Ind Ltd | 取鍋内溶鋼の昇熱精錬方法 |
JPS6465226A (en) * | 1987-09-04 | 1989-03-10 | Sumitomo Metal Ind | Ladle refining method |
JPH01100216A (ja) * | 1987-10-12 | 1989-04-18 | Nippon Steel Corp | 溶鋼の取鍋精錬法 |
JPH0873923A (ja) * | 1994-06-29 | 1996-03-19 | Sumitomo Metal Ind Ltd | 耐水素誘起割れ性に優れた清浄鋼の製造法 |
JPH0953109A (ja) * | 1995-08-21 | 1997-02-25 | Sumitomo Metal Ind Ltd | 溶鋼の昇熱精錬方法 |
-
2006
- 2006-12-05 CN CN200680056233A patent/CN101535508A/zh active Pending
- 2006-12-05 WO PCT/JP2006/324194 patent/WO2008068835A1/ja active Application Filing
- 2006-12-05 KR KR1020097008338A patent/KR101028914B1/ko active IP Right Grant
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS61143510A (ja) * | 1984-12-13 | 1986-07-01 | Nippon Steel Corp | 取鍋内溶鋼の精錬法 |
JPS63266017A (ja) * | 1987-04-23 | 1988-11-02 | Sumitomo Metal Ind Ltd | 取鍋内溶鋼の昇熱精錬方法 |
JPS6465226A (en) * | 1987-09-04 | 1989-03-10 | Sumitomo Metal Ind | Ladle refining method |
JPH01100216A (ja) * | 1987-10-12 | 1989-04-18 | Nippon Steel Corp | 溶鋼の取鍋精錬法 |
JPH0873923A (ja) * | 1994-06-29 | 1996-03-19 | Sumitomo Metal Ind Ltd | 耐水素誘起割れ性に優れた清浄鋼の製造法 |
JPH0953109A (ja) * | 1995-08-21 | 1997-02-25 | Sumitomo Metal Ind Ltd | 溶鋼の昇熱精錬方法 |
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CN101535508A (zh) | 2009-09-16 |
KR20090057459A (ko) | 2009-06-05 |
KR101028914B1 (ko) | 2011-04-12 |
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