EP0163784B1 - Zweistufiges Desoxidationsverfahren bei der Stahlherstellung - Google Patents

Zweistufiges Desoxidationsverfahren bei der Stahlherstellung Download PDF

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Publication number
EP0163784B1
EP0163784B1 EP84303555A EP84303555A EP0163784B1 EP 0163784 B1 EP0163784 B1 EP 0163784B1 EP 84303555 A EP84303555 A EP 84303555A EP 84303555 A EP84303555 A EP 84303555A EP 0163784 B1 EP0163784 B1 EP 0163784B1
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EP
European Patent Office
Prior art keywords
molten steel
steel
deoxidizing
silicon
added
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP84303555A
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English (en)
French (fr)
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EP0163784A1 (de
Inventor
Maw-Cheng Shieh
Seng-Jung Chen
Li-Jung Hu
Jin-Luh Su
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
China Steel Corp
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China Steel Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by China Steel Corp filed Critical China Steel Corp
Priority to DE8484303555T priority Critical patent/DE3480350D1/de
Priority to EP84303555A priority patent/EP0163784B1/de
Priority to AT84303555T priority patent/ATE47727T1/de
Priority to ZA852015A priority patent/ZA852015B/xx
Priority to AU40220/85A priority patent/AU567212B2/en
Publication of EP0163784A1 publication Critical patent/EP0163784A1/de
Application granted granted Critical
Publication of EP0163784B1 publication Critical patent/EP0163784B1/de
Expired legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0056—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 using cored wires
    • 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

Definitions

  • This invention relates to deoxidation practice in steelmaking.
  • An object of the present invention is to provide an improved deoxidation process whereby steel products of improved cold heading formability may be obtained.
  • the use of very minor amounts of deoxidizer results in a high free oxygen content in the molten rimmed steel, which results in a solid skin layer around the ingot surface of good surface quality and soft characteristics but the inner portion of the rimmed steel ingot is not suitable for high grade applications because of contamination by impurities.
  • rimmed steel with a high free oxygen content cannot be cast in a continuous casting process.
  • An object of the invention is to overcome or alleviate the defects stated above to provide lower cost and higher quality steel products.
  • AI and/or Ti are the major deoxidizers used in the continuous casting process.
  • Killed steel for cold working or forming applications could be classified into AI-killed and Ti-killed steel according to the deoxidizer adopted.
  • Si-containing ferroalloy cannot be added to molten steel during the steelmaking process-only Al is used as the deoxidizer.
  • alumina clusters AI 2 0 31 form in the molten steel and remain in the solid steel as inclusions. These inclusions cannot be elongated during deformation, and thus interfere with the cold heading or working formability.
  • An object of the invention is to overcome the above shortcoming of deoxidation practice, that is to reduce the work hardening effect.
  • US 2,705,196 discloses a method for the deoxidation of molten steel produced in a furnace by a steelmaking process, comprising a predeoxidizing step in which a silicon-containing ferroalloy is added to the molten steel, and a subsequent deoxidizing step in which a deoxidizing metal is added to the pre-deoxidized molten steel.
  • the method of the invention starting from this known method provides that said silicon-containing ferroalloy is added in a controlled amount sufficient to reduce the free oxygen content of the melt to a level below 340 ppm but insufficient to result in substantial retention of elemental silicon in the melt; after the pre-deoxidizing step the molten steel is stirred, by gas-bubbling to separate silicon dioxide from the molten steel, and said deoxidizing metal is added in finely divided form by a continuous feeder arrangement so as substantially to prevent retention of silicon in the steel.
  • the process of the invention increases the recovery rate of deoxidizing metal, decreases the amount of deoxidizer and ferroalloy consumption and saves on production cost. Because of the reduced deoxidizing metal and alloy addition, deoxidized formations can be reduced, resulting in a remarkable improvement in the internal cleanliness of the steel products.
  • Optional features of the invention are set out in Claims 2 to 8 below. After treating by AI and/or Ti with the above process, good shrouding systems should be adopted during continuous casting or ingot teeming processes to protect the molten steel from reoxidizing by the atmosphere. Consequently, cleaner steel could be acquired by this new predeoxidation process, which is referred to below as a WPD (weak predeoxidation) process.
  • WPD weak predeoxidation
  • Figure 2 indicates that with appropriate amount of Si containing ferroalloy addition the free oxygen content in the liquid steel before AI deoxidation can evidently be lowered.
  • the recovery of deoxidizer can be improved and the oxides retained in the liquid steel after deoxidation can be reduced as well, thus the quality of bloom, slab and ingot can be improved.
  • Figure 3(a) and 3(b) compare the Si content in the liquid steel between WPD Process and non-WPD Process.
  • Figure 3(a) shows the distribution of Si contents in the final molten steel treated by weak pre-deoxidizing with Si contained ferroalloy.
  • Figure 3(b) shows the distribution of Si contents in the final molten steel without WPD treatment.
  • Figure 3(a) and 3(b) indicates the percent of the number of melts which contain Si less than 0.02% in the liquid steel by using WPD Process is 96.8%, while that of non-WPD Process is 95.8%.
  • the data obviously shows that the proportion of Si content below 0.02% in the liquid steel of WPD Process is even a little bit higher than that of non-WPD Process.
  • the Si content analyzed by spectro-scope is total Si content (including silica), thus confirms that Si contained ferroalloy will not cause Si to be retained in the liquid steel. (It can also be confirmed by microscope). While Si contained ferroalloy is added into liquid steel, Si will react with free oxygen first and forms silicon dioxide (Si0 2 ) particles, which distribute in the whole liquid steel.
  • Figure 4 shows the comparison of the rate of A) recovery between AI-killed steel produced by Weak Pre-Deoxidation Process and conventional deoxidation process.
  • the rate of AI recovery was evidently increased by this invention as indicated in Figure 4, that is due to the content of free oxygen in molten steel as remarkably decreased. Because of higher recovery rate of Al, caused less AI addition, deoxidation formations could be effectively reduced. Consequently, the internal cleanliness and surface quality of the steel product was remarkably improved by this new process.
  • Table 1 shows the comparison of free oxygen content between WPD Process and conventional deoxidation process before aluminum and/or titanium addition, when the content of free oxygen according to the invention is 1.
  • a feature of this invention is to reduce the free oxygen content of molten steel as much as possible before the addition of deoxidizers (aluminum and/or titanium) but without retention of Si in the melt.
  • deoxidizers aluminum and/or titanium
  • the data listed in the table obviously show that after WPD Process treatment the free oxygen content can be greatly decreased before the addition of deoxidizers.
  • the amount of free oxygen content lowered can be controlled directly by adjusting the amount of Si-containing ferroalloy addition. Owing to the decrease of free oxygen content, recovery of aluminum can be improved, cost can be lowered, and the quality of steel products can be improved remarkably.
  • Table 2 shows the comparison of typical chemical compositions between the general cold working AI-killed steel grade and the steel designed according to this invention for the same end use.
  • typical chemical composition designed according to this invention has lower aluminum content than that of conventional AI-killed steel grade.
  • the reason for this composition design is to decrease the inclusion formation of deoxidation to get cleaner molten steel. Because of more deoxidizers are added, more chances to form consistins would result and the cost is also higher. Therefore, the principle of chemical composition design by this invention is to lower the addition of deoxidizers such as aluminum and/or titanium under the condition of no poor deoxidation and good formabilty. And with the aid of WPD Process, the amount of deoxidizers added can be decreased, cleaner steel and lower production cost will be resulted.
  • This deoxidation method is also suitable for af other kind of AI-killed steel grade.
  • Table 3 shows the comparison of estimated index of inclusions between different deoxidation processes.
  • the main purpose of WPD Process is to improve the internal cleanliness, and improve the quality of casted steel.
  • the table obviously shows that under this new process, the estimated index of inclusions is much better than that of conventional process. It can also be sured that the WPD Process has much improvement on internal quality of casted steel.
  • Table 4 (page 4) shows the comparison of grinding speed of billets between different deoxidation processes. In respect of quality, the WPD process improves not only the internal cleanliness of the casted steel, but also its surface quality. Data listed in the table represent pieces of billets to be ground within unit time (per hour).
  • the WPD Process can make much improvement on surfacial quality of casted steel, and save much surface conditioning cost.
  • the invention is applicable both to Basic Oxygen and Electric Arc Furnace Steel making processes.
  • Si-containing ferroalloy is added to the molten steel as weak predeoxidation agent.
  • the free oxygen content of molten steel can be lowered efficiently whilst ensuring that silcon will not remain in molten steel.
  • This method not only increases the recovery of aluminum and/or titanium, saves much production cost, improves surfacial and internal quality of steel which is good for formability, but also keeps steelmaking operation in good stability.
  • the weak pre-deoxidation step is suitably executed after blowing end and before the addition of aluminum and/or titanium deoxidizer.
  • Remark Estimated index value 0-4, 0 is the best.
  • Depth of defects to be ground are more than 1.2 mm

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Treatment Of Steel In Its Molten State (AREA)

Claims (8)

1. Verfahren zur Desoxidation einer in einem Stahlerzeugungsverfahren in einem Ofen erzeugten Stahlschmelze mit einem Vordesoxidationsschritt, in dem der Stahlschmelze eine siliciumhaltige Ferrolegierung zugegeben wird, und einem darauffolgenden Desoxidationsschritt, in dem der vordesoxidierten Stahlschmelze ein desoxidierend wirkendes Metall zugesetzt wird, dadurch gekennzeichnet, daß die Zugabe der siliciumhaltigen Ferrolegierung derart dosiert wird, daß der freie Gehalt der Schmelze an freiem Sauerstoff unter 340 ppm herabgesetzt wird, elementares Silicium aber nicht in beträchtlicher Menge in der Schmelze verbleibt; daß nach dem Vordesoxideren die Stahlschmelze durch Eileiten von Gas derart bewegt wird, daß sich Siliciumdioxid von dem schmelzflüssigen Stahl abscheidet, und daß das desoxidierend wirkende Metall mittels einer kontinuierliche betriebenen Aufgabevorrichtung in feinverteilter Form derart zugegeben wird, daß ein Verbleib von Silicium in dem Stahl im wesentlichen verhindert wird.
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß der Vordesoxidationsschritt und der Desoxidationsschritt in verscheidenen Stationen durchgeführt werden.
3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß das desoxidierend wirkende Metall in Form von Draht oder Schrot in die Stahlschmelze eingebracht wird.
4. Verfahren nach einem jer vorhergehenden Ansprüche, dadurch gekennzeichnet, daß das desoxidierend wirkende Metall Aluminium oder Titan ist.
5. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die Stahlschmelze vor dem Vordesoxidationsschritt im weseentlichen frei ist von gelöstem Silicium und daß die Zugabe der siliciumhaltigen Ferrolegierung derart dosiert wird, daß nach dem Desoxidationsschritt der Gesamtsiliciumgehalt der Stahlschmelze unter 0,02% beträgt.
6. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß der Stahl zusätzlich Mangan enthält.
7. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die Stahlschmelze in einerm Sauerstoffaufblaskonverter oder in einem Lichtbogen-Elektroofen erzeugt wird.
8. Verfahren zum Erzeugen von Gußstahlprodukten, in dem eine Stahlschmelze erzeugt und nach einem Verfahren nach einem der vorhergehenden Ansprüche, desoxidiert wird und die so erhaltene desoxidierte Stahlschmelze zum Erzeugen der Gußstahlprodukte stranggegossen wird.
EP84303555A 1984-05-25 1984-05-25 Zweistufiges Desoxidationsverfahren bei der Stahlherstellung Expired EP0163784B1 (de)

Priority Applications (5)

Application Number Priority Date Filing Date Title
DE8484303555T DE3480350D1 (en) 1984-05-25 1984-05-25 Two stage deoxidation process in steel-making
EP84303555A EP0163784B1 (de) 1984-05-25 1984-05-25 Zweistufiges Desoxidationsverfahren bei der Stahlherstellung
AT84303555T ATE47727T1 (de) 1984-05-25 1984-05-25 Zweistufiges desoxidationsverfahren bei der stahlherstellung.
ZA852015A ZA852015B (en) 1984-05-25 1985-03-18 Si contained ferro-alloy addition as a weak pre-deoxidation process in steelmaking
AU40220/85A AU567212B2 (en) 1984-05-25 1985-03-21 Pre-deoxidation process in steelmaking

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP84303555A EP0163784B1 (de) 1984-05-25 1984-05-25 Zweistufiges Desoxidationsverfahren bei der Stahlherstellung
AU40220/85A AU567212B2 (en) 1984-05-25 1985-03-21 Pre-deoxidation process in steelmaking

Publications (2)

Publication Number Publication Date
EP0163784A1 EP0163784A1 (de) 1985-12-11
EP0163784B1 true EP0163784B1 (de) 1989-11-02

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ID=36838654

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EP84303555A Expired EP0163784B1 (de) 1984-05-25 1984-05-25 Zweistufiges Desoxidationsverfahren bei der Stahlherstellung

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EP (1) EP0163784B1 (de)
AT (1) ATE47727T1 (de)
AU (1) AU567212B2 (de)
DE (1) DE3480350D1 (de)
ZA (1) ZA852015B (de)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2406580B (en) * 2000-06-05 2005-09-07 Sanyo Special Steel Co Ltd High-cleanliness steel and process for producing the same
GB2410503B (en) * 2000-06-05 2005-09-07 Sanyo Special Steel Co Ltd High-cleanliness steel and process for producing the same
GB2381537B (en) * 2000-06-05 2005-09-14 Sanyo Special Steel Co Ltd High-cleanliness steel and process for producing the same

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE957665C (de) * 1957-01-17 Max-Planck-Institut iur Eisenforschung e V, Dussel dorf Verfahren und Einrichtung zum Behandeln von Eisen- und Stahlbadern
US2705196A (en) * 1952-02-20 1955-03-29 Manufacturers Chemical Corp Process for de-oxidizing a molten metal
DE969295C (de) * 1954-01-27 1958-05-22 Hoesch Westfalenhuette Ag Verwendung von Stahl- oder Spiegeleisen zur Vordesoxydation von Stahl
FR2387292A1 (fr) * 1977-04-14 1978-11-10 Siderurgie Fse Inst Rech Nouveau procede de desoxydation d'un bain d'acier
US4170468A (en) * 1977-12-22 1979-10-09 United States Steel Corporation Deoxidation of steel

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
"Die physikalische Chemie der Eisen- und Stahlerzeugung", 1964, p. 221 *

Also Published As

Publication number Publication date
DE3480350D1 (en) 1989-12-07
AU567212B2 (en) 1987-11-12
ATE47727T1 (de) 1989-11-15
EP0163784A1 (de) 1985-12-11
AU4022085A (en) 1986-09-25
ZA852015B (en) 1985-09-19

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