US3885957A
Expired / Lapsed
US
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Method for the desulfurization of a steel melt
Assignee: Thyssen AG
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Filing: 1973-02-20
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Granted: 1975-05-27
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Expires: 1993-02-20
Abstract
Abstract A steel melt is desulfurized in a ladle lined with dolomite magnesite or other refractory lining have an aluminum oxide content in excess of 70 percent (wt), by injecting at least 2,000 mm below the melt surface, finely divided calcium-containing compound after a basic-slag layer is applied to the surface of the deoxidized steel melt. The melt is held at a temperature of at least 1,530*C during desulfurization.
Inventors
- 👤 Helmut Richter
- 👤 Eckehard Forster
- 👤 Edgar Spetzler
- 👤 Jochen Wendorff
- 👤 Heinrich Wilhelm Rommerswinkel
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 19:21
CPC Classifications
C; C21; C21C; C21C7/00; C21C7/04; C21C7/064
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
132 words
A METHOD OF DESULFURIZING A DEOXIDIZED STEEL MELT COMPRISING THE STEPS OF: COVERING THE DEOXIDIZED STEEL MELT WITH A BASIC-SLAG LAYER CONTAINING AT MOST 4 PERCENT BY WEIGHT FEO INTRODUCING AT A LOCATION AT LEAST 2,000 MM BELOW THE SURFACE OF THE DEOXIDIZED STEEL MELT COVERED WITH SAID BASIC SLAG LAYER A STREAM OF A CALCIUM-CONTAINING SUBSTANCE IN FINELY DIVIDED FORM IN A NUETRAL CARRIER GAS; MAINTAINING THE TEMPERATURE OF SAID MELT DURING THE INTRODUCTION OF SAID CALCIUM-CONTAINING SUBSTANCE THERETO AT AT LEAST 1,530*C, MAINTAINING SAID MOLTEN STEEL IN CONTACT WITH A LINING CONTAINING AT LEAST 70 PERCENT BY WEIGHT ALUMINIUM OXIDE DURING INTRODUCTION OF THE CALCIUM-CONTAINING SUBSTANCE THERETO; AND THE INTRODUCTION OF SAID CALCIUM-CONTAINING SUBSTANCE IS CARRIED OUT SO THAT SAID STEEL MELT CONTAINS AT LEAST 0.015 PERCENT BY WEIGHT ALUMINIUM.
Claim 2
Independent Claim
132 words
A METHOD OF DESULFURIZING A DEOXIDIZED STEEL MELT COMPRISING THE STEPS OF: COVERING THE DEOXIDIZED STEEL MELT WITH A BASIC-SLAG LAYER CONTAINING AT MOST 4 PERCENT BY WEIGHT FEO INTRODUCING AT A LOCATION AT LEAST 2,000 MM BELOW THE SURFACE OF THE DEOXIDIZED STEEL MELT COVERED WITH SAID BASIC SLAG LAYER A STREAM OF A CALCIUM-CONTAINING SUBSTANCE IN FINELY DIVIDED FORM IN A NUETRAL CARRIER GAS; MAINTAINING THE TEMPERATURE OF SAID MELT DURING THE INTRODUCTION OF SAID CALCIUM-CONTAINING SUBSTANCE THERETO AT AT LEAST 1,530*C, MAINTAINING SAID MOLTEN STEEL IN CONTACT WITH A LINING CONTAINING AT LEAST 70 PERCENT BY WEIGHT ALUMINIUM OXIDE DURING INTRODUCTION OF THE CALCIUM-CONTAINING SUBSTANCE THERETO; AND THE INTRODUCTION OF SAID CALCIUM-CONTAINING SUBSTANCE IS CARRIED OUT SO THAT SAID STEEL MELT CONTAINS AT LEAST 0.015 PERCENT BY WEIGHT ALUMINIUM.
Claim 3
Dependent Claim
45 words
The method defined in claim 1 wherein said basic-slag layer has an FeO content in excess of 2 percent, further comprising controlling the introduction of the calcium-containing substance to reduce the FeO content of the basic slag layer to less than 2 percent by weight.
Claim 4
Dependent Claim
11 words
The method defined in claim 1 wherein said gas is argon.
Claim 5
Dependent Claim
23 words
The method defined in claim 3 wherein said calcium-containing substance is introduced into said melt by a lance extending downwardly through the melt.
Claim 6
Dependent Claim
70 words
The method defined in claim 1 wherein said basic slag layer has essentially the following composition: 45 to 75 percent by weight calcium oxide, 0 to 25 percent by weight calcium fluoride, 0 to 20 percent by weight aluminum oxide, 0 to 30 percent by weight silicon oxide, 0.1 to 4 percent by weight FeO, and 0 to 10 percent by weight manganese oxide and/or phosphorus pentoxide and/or magnesium oxide.
Claim 7
Dependent Claim
53 words
The method defined in claim 5 wherein said slag has approximately the following composition: 50 percent by weight calcium oxide, 20 percent by weight calcium fluoride, 12 percent by weight aluminum oxide, 10 percent by weight silicon oxide, 0.5 percent by weight FeO, the balance being manganese oxide, phosphorus pentoxide and magnesium oxide.
Claim 8
Dependent Claim
32 words
The method defined in claim 5 wherein said calcium-containing substance is added to said melt in an amount corresponding to substantially 1.2 to 1.5 kg of calcium per ton of molten steel.
Claim 9
Dependent Claim
29 words
The method defined in claim 7 wherein said calcium-containing substance is selected from the group which consists of elemental calcium, a calcium-silicon, intermetallic compound or alloy, and calcium carbide.
Claim 10
Dependent Claim
55 words
The method defined in claim 8 wherein said calcium-containing substance is a calcium ferrosilicon containing substantially 30 percent by weight calcium, 60 percent by weight silicone and 10 percent by weight iron, the calcium ferro silicone being introduced into said melt in an amount of substantially 4 to 5 kgs per ton of molten steel.
Claim 11
Dependent Claim
24 words
The method defined in claim 8 wherein said molten steel contains at least 0.015 percent by weight of the deoxidizing agent for said melt.
Claim 12
Dependent Claim
26 words
The method defined in claim 1 wherein said slag layer is present in an amount of substantially 1 to 15 kgs per ton of molten steel.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-05-26 | 1978-11-25 | 1979-05-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-05-26 | 1982-11-25 | 1983-05-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-05-26 | 1986-11-25 | 1987-05-27 | $7700.00 | Window Closed / Lapsed |