US3615354A - Method of removing contaminants from steel melts - Google Patents
Method of removing contaminants from steel melts Download PDFInfo
- Publication number
- US3615354A US3615354A US725510A US3615354DA US3615354A US 3615354 A US3615354 A US 3615354A US 725510 A US725510 A US 725510A US 3615354D A US3615354D A US 3615354DA US 3615354 A US3615354 A US 3615354A
- Authority
- US
- United States
- Prior art keywords
- metal
- mixture
- halide
- calcium
- steel
- 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 - Lifetime
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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
- C21C7/04—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
- C21C7/06—Deoxidising, e.g. killing
Definitions
- ABSTRACT Described herein is a method of removing con- [56] References cued taminants such as oxygen and sulfur from steel which includes UNITED STATES PATENTS the step of adding to a molten steel melt a mixture of a reac- 771,645 10/1904 Kugelgen 1,335,370 3/1920 Ellis 1,922,037 8/1933 Hardy tive alkali or alkaline earth metal and a halide of the metal adjusted so that the proportion of metal does not exceed its solubility in the halide.
- This invention relates to an improved process for removing contaminants such as oxygen from steel.
- one of the aims is to obtain molten metal that is substantially free of contaminating ingredients.
- oxygen although other impurities such as sulfur may also be present. It is very desirable to reduce these impurities to a level which is acceptable for the grade of steel being manufactured.
- nonfree-machining grades of steel for example, it is conventional practice to maintain the maximum sulfur content as about 0.03% and it is considered highly desirable to limit the oxygen content of all stainless steel grades at less than about 0.01%.
- impurities such as oxygen and sulfur are removed from a molten bath by adding materials to the furnace which form a slag that floats to the surface of the molten metal.
- a slag typically contains lime (calcium oxide) which serves to remove the sulfur by reacting with iron sulfide or other metallic sulfides to form calcium sulfide.
- Oxygen is generally removed from the bath by the oxidation of various metallic materials such as manganese, aluminum, or silicon, or by combining with carbon to be removed as carbon monoxide gas.
- Such conventional methods take considerable time and frequently result in entrained inclusions as a result of small amounts of calcium oxide, calcium sulfide, silicon oxides and other similar compounds being trapped within the molten metal. If such compounds do not rise to the surface to be removed with the slag, they will remain in the metal and'solidi fy upon teeming to form undesirable nonmetallic inclusions.
- halides of calcium such as calcium chloride and calcium fluoride
- the halides do not react with oxygen or sulfur within the melt and, therefore, do not contribute to their removal.
- Alkali and alkaline earth metals in elemental form are highly reactive and would effectively combine with both sulfur and oxygen if they could be supplied to the molten steel in sufficiently pure form.
- these metals in elemental form are so'violently reactive in molten steel that they volatize or oxidize explosively before they could possibly be brought into intimate contact with the steel to react with the contaminants.
- the present invention provides a method whereby alkali and alkaline earth metals, i. e., metals in Groups I and II of the Periodic Table, may be supplied to molten steel in such a manner that it will not oxidize or volatilize prior to entering the molten steel bath.
- alkali and alkaline earth metals i. e., metals in Groups I and II of the Periodic Table
- such elements may be used to combine with contaminants, e.g., oxygen and sulfur, in the bath to effectively reduce the quantities of such impurities and put them in a form that may be removed by fiuxing. It has been found that alkali and alkaline earth metals may be added to molten steel as a mixture of the metal and its halide salt without the difiiculties previously described.
- the proportions of the reactive metal and halide in the mixture must be carefully controlled, however, to accomplish reaction with contaminants without danger of explosion. This can be achieved if the proportions of reactive metal and halide salt are such that the concentration of metal does not exceed its solubility in the respective halide and the reaction products, e.g., deoxidation products, do not exceed their solubility in the halide flux. If one or both of these conditions are not met then either the reaction will be violent or the deoxidation products will not be completely fluxed from the bath.
- EXAMPLE I- A l00-pound induction furnace heat of Type 302 was melted and treated in the ingot mold with a molten mixture of calcium dissolved in calcium chloride.
- the molten calciumcalcium chloride mixture was made by premelting 2770 grams CaCl, in an iron crucible under an inert atmosphere and adding36 grams of calcium metal chips to the molten CaCl,. Themelt was stirred with an iron rod to aid the dissolution of the calcium metal.
- the molten Ca-CaCl mixture was poured into the mold. The heat was immediately tapped on top of the molten mixture.
- a sample taken from the teemed stream showed an oxygen content of 0.028%.
- the average oxygen content of the ingot was 0.0 l7%. This is a decrease in oxygen of 39%.
- EXAMPLE III A mixture of calcium dissolved in calcium-chloride was prepared by melting 453 grams of CaCl in an iron crucible under an inert atmosphere at 820 C. and adding 59 grams of calcium in the form of metal chips to the crucible when the chloride was molten. The mixture was stirred with an iron rod to aid the dissolution of calcium in the chloride when the calcium metal dissolved. This material was poured onto a chill plate, cooled, crushed and charged into a moisture free Airco Batch fluidizer. This mixture was then blown into the teemed stream of a l20-pound induction heat of Type 302. Analysis showed that an untreated sample has an oxygen content of 0.029% oxygen. The average oxygen content from the ingot was 0.0 l 35% oxygen, which is at 54% decrease.
- EXAMPLE IV A 120-pound heat of Type A-286 was melted in an induction furnace. One-half of this heat (60 pounds) was cast as a standard ingot. The other half of this heat was treated in the furnace with a molten mixture of 40 grams of calcium dissolved in 230 grams of CaCl prepared in accordance with the procedure of Example 1. The average oxygen content of the standard ingot was 0.0063% oxygen, and the average oxygen content of the treated ingot was 0.005l% oxygen. This corresponds to a 19% decrease in oxygen content.
- EXAMPLE V A 23-ton arc furnace heat of Type 304 was melted and tapped into a 25-ton ladle. This ladle teemed 27 ingots. The 24th ingot of this teem was treated in the stream with a molten mixture of 1.3 pounds calcium, 1.07 pounds Caland 8.6 pounds CaCI This mixture was prepared as follows. The CaCl and Cal ⁇ were melted together in an iron crucible under an argon atmosphere. When this mixture was molten, the calcium in the form of chips was added to the chlorides, and argon was blown into the mixture to aid the dissolution of calcium in the molten halide salts.
- the material When the entire mixture was molten, the material was poured into a launder so as to combine with the first portion of steel being teemed into the tundish of a 12 inches X 12 inches square ingot mold.
- the average oxygen content of a standard ingot from this heat was 0.0069% oxygen.
- the average oxygen content of the treated ingot was 0.0043% oxygen. This corresponds to a 38.8% decrease in oxygen.
- Solubility Vapor Pressure Theoretically there is no lower solubility limit of the metal in its halide, and mixtures having very little reactive metal would have a beneficial result which corresponds to the amount of reactive metal used. It has been observed, for example, that concentrations of as little as 1% of the metal have been dissolved satisfactorily in its halide to form a mixture which has been useful in deoxidizing molten steel. However, for practical purposes a lower limit of a 1%-solution of the metal in its halide is generally regarded as a preferred minimum.
- the amount and specific material used to accomplish removal of contaminants in a give metal heat is dependent entirely upon the purity of the bath and the raw materials used as well as the desired final level of impurities.
- a method for removing oxygen and sulfur from steel which comprises:
- a mixture consisting essentially of (1 metal selected from the group consisting of alkali and alkaline earth metals and (2) at least one halide of the same metal. the proportion of metal to halide in said mixture being such that the amount of metal in said mixture does not exceed its solubility in the halide in said mixture, said metal being present in solution in said halide in said mixture;
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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)
Abstract
Description
Claims (6)
- 2. A method according to claim 1 wherein said reactive metal and halide mixture contains at least 1% metal.
- 3. A method according to claim 1 wherein said reactive metal is calcium.
- 4. A method according to claim 3 wherein said halide is calcium chloride.
- 5. A method according to claim 1 wherein the oxygen content of said steel melt is lowered to less than about 0.01%
- 6. A method according to claim 1 wherein said other contaminants include sulfur and wherein the sulfur content of said steel melt is lowered to a maximum of about 0.03%.
- 7. A method according to claim 1 wherein said mixture of reactive metal and halide is added in solid form to melt and then mixed into said steel melt.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US72551068A | 1968-04-30 | 1968-04-30 |
Publications (1)
Publication Number | Publication Date |
---|---|
US3615354A true US3615354A (en) | 1971-10-26 |
Family
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Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US725510A Expired - Lifetime US3615354A (en) | 1968-04-30 | 1968-04-30 | Method of removing contaminants from steel melts |
Country Status (1)
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US (1) | US3615354A (en) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3716352A (en) * | 1969-10-24 | 1973-02-13 | Kawasaki Steel Co | Sintered desulfurizer for off-furnace use |
US3850618A (en) * | 1973-03-19 | 1974-11-26 | K Naguro | Demolybdenum refining method of molybdenum containing alloy steel material |
FR2522686A1 (en) * | 1982-03-03 | 1983-09-09 | Sumitomo Metal Ind | PROCESS FOR DEPHOSPHORIZING AND DESULFURIZING A FUSION IRON ALLOY CONTAINING CHROME |
US20120000317A1 (en) * | 2009-03-19 | 2012-01-05 | Flemings Merton C | Method Of Refining The Grain Structure Of Alloys |
-
1968
- 1968-04-30 US US725510A patent/US3615354A/en not_active Expired - Lifetime
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3716352A (en) * | 1969-10-24 | 1973-02-13 | Kawasaki Steel Co | Sintered desulfurizer for off-furnace use |
US3850618A (en) * | 1973-03-19 | 1974-11-26 | K Naguro | Demolybdenum refining method of molybdenum containing alloy steel material |
FR2522686A1 (en) * | 1982-03-03 | 1983-09-09 | Sumitomo Metal Ind | PROCESS FOR DEPHOSPHORIZING AND DESULFURIZING A FUSION IRON ALLOY CONTAINING CHROME |
US20120000317A1 (en) * | 2009-03-19 | 2012-01-05 | Flemings Merton C | Method Of Refining The Grain Structure Of Alloys |
US8597398B2 (en) * | 2009-03-19 | 2013-12-03 | Massachusetts Institute Of Technology | Method of refining the grain structure of alloys |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: ALLEGHENY LUDLUM CORPORATION Free format text: CHANGE OF NAME;ASSIGNOR:ALLEGHENY LUDLUM STEEL CORPORATION;REEL/FRAME:004779/0642 Effective date: 19860805 |
|
AS | Assignment |
Owner name: PITTSBURGH NATIONAL BANK Free format text: SECURITY INTEREST;ASSIGNOR:ALLEGHENY LUDLUM CORPORATION;REEL/FRAME:004855/0400 Effective date: 19861226 |
|
AS | Assignment |
Owner name: PITTSBURGH NATIONAL BANK Free format text: ASSIGNMENT OF ASSIGNORS INTEREST. RECORDED ON REEL 4855 FRAME 0400;ASSIGNOR:PITTSBURGH NATIONAL BANK;REEL/FRAME:005018/0050 Effective date: 19881129 |