US3867134A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for producing stainless steel in a basic oxygen furnace
Assignee: Allegheny Ludlum Corp
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Filing: 1973-09-21
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Granted: 1975-02-18
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Expires: 1993-09-21
Abstract
Abstract Method for producing stainless steels in a top-blown vessel, characterized in that a mixture of cold chromium-containing material having a total carbon content of at least 3.5 percent is charged into the vessel, followed by top blowing with pure oxygen until in excess of about 50 percent, and preferably 70-80 percent of the total oxygen requirement is blown. The cold chromiumcontaining material constitutes at least 10 percent by weight of the total charge. Thereafter, a mixture of oxygen and a nonoxidizing gas is blown onto the surface of the melt preferably in two steps, the first of which is carried out with the lance at the normal blowing level above the surface of the molten metal and the second of which is carried out with the lance lowered or the gas impact pressure increased. This enables the attainment of less than 0.03 percent carbon in the blown heat.
Inventors
- 👤 Richard B Shaw
- 👤 Richard F Carlson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 19:34
CPC Classifications
C; C21; C21C; C21C5/00; C21C5/005
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
133 words
IN THE MANUFACTURE OF STAINLESS STEEL HAVING A CARBON CONTENT OF UNDER 0.03 PERCENT, THE STEPS OF: CHARGING INTO A VESSEL MOLTEN FERROUS METAL AND COLD CHROMIUM-CONTAINING MATERIALS WITH THE COLD MATERIAL CONSTITUTING AT LEAST 10 PERCENT BY WEIGHT OF CARBON, CHARGE AND THE MIXTURE OF MOLTEN AND COLD MATERIALS CONTAINING AT LEAST 3.5 PERCENT BY WEIGHT OF CARBON, TOP BLOWING ESSENTIALLY PURE OXYGEN ONTO THE SURFACE OF THE MOLTEN FERROUS MEATL THROUGH A NOZZLE POSITIONED ABOVE SAID SURFACE UNTIL AT LEAST 50 PERCENT OF THE TOTAL OXYGEN REQUIRED FOR REFINING HAS BEEN BLOWN ONTO THE SURFACE OF THE BATH, AND THEREAFTER BLOWING A MIXTURE OF OXYGEN AND A NON-OXIDIZING GAS ONTO THE SURFACE OF THE MOLTEN METAL THROUGH SAID NOZZLE UNTIL THE CARBON CONTENT THEREOF HAS BEEN REDUCED TO BELOW 0.03 PERCENT.
Claim 2
Dependent Claim
133 words
IN THE MANUFACTURE OF STAINLESS STEEL HAVING A CARBON CONTENT OF UNDER 0.03 PERCENT, THE STEPS OF: CHARGING INTO A VESSEL MOLTEN FERROUS METAL AND COLD CHROMIUM-CONTAINING MATERIALS WITH THE COLD MATERIAL CONSTITUTING AT LEAST 10 PERCENT BY WEIGHT OF CARBON, CHARGE AND THE MIXTURE OF MOLTEN AND COLD MATERIALS CONTAINING AT LEAST 3.5 PERCENT BY WEIGHT OF CARBON, TOP BLOWING ESSENTIALLY PURE OXYGEN ONTO THE SURFACE OF THE MOLTEN FERROUS MEATL THROUGH A NOZZLE POSITIONED ABOVE SAID SURFACE UNTIL AT LEAST 50 PERCENT OF THE TOTAL OXYGEN REQUIRED FOR REFINING HAS BEEN BLOWN ONTO THE SURFACE OF THE BATH, AND THEREAFTER BLOWING A MIXTURE OF OXYGEN AND A NON-OXIDIZING GAS ONTO THE SURFACE OF THE MOLTEN METAL THROUGH SAID NOZZLE UNTIL THE CARBON CONTENT THEREOF HAS BEEN REDUCED TO BELOW 0.03 PERCENT.
Claim 3
Dependent Claim
35 words
The method of claim 1 wherein 70-80 percent of the total oxygen required for refining has been blown onto the surface of the bath before said mixture of oxygen and a non-oxidizing gas is blown.
Claim 4
Dependent Claim
13 words
The method of claim 1 wherein said non-oxidizing gas comprises an inert gas.
Claim 5
Dependent Claim
22 words
The method of claim 1 wherein said mixture of oxygen and non-oxidizing gas contains 5 parts non-oxidizing gas to 2 parts oxygen.
Claim 6
Dependent Claim
43 words
The method of claim 1 wherein the mixture of oxygen and a non-oxidizing gas is initially blown onto said surface with the ratio of oxygen to non-oxidizing gas being greater than one and the ratio then decreased until it is less than one.
Claim 7
Dependent Claim
39 words
The method of claim 5 wherein the ratio of oxygen to non-oxidizing gas is initially 6 to 1 and is then reduced until at the end of a blow it is 6 parts non-oxidizing gas to 1 part oxygen.
Claim 8
Dependent Claim
80 words
The method of claim 1 wherein said nozzle is at a predetermined height above the surface of said bath while pure oxygen is being blown thereon, the nozzle remaining at said predetermined height when the mixture of oxygen and non-oxidizing gas is initially blown onto the surface of the bath, and thereafter lowering said nozzle relative to the surface of the bath after a predetermined amount of said mixture of oxygen and non-oxidizing gas has been blown onto the surface.
Claim 9
Dependent Claim
32 words
The method of claim 7 wherein said nozzle is lowered from about 40 inches above the surface of the bath to a distance of 35 inches above the surface of the bath.
Claim 10
Dependent Claim
26 words
The method of claim 1 wherein the temperature of the melt at the end of the blow is maintained at a temperature no greater than 3,450*F.
Claim 11
Dependent Claim
46 words
The method of claim 9 wherein said molten ferrous metal and chromium-containing materials are charged into said vessel in the ratio of about 10 percent to 40 percent by weight of cold chromium-containing materials to 50 percent to 90 percent by weight of molten ferrous metal.
Claim 12
Dependent Claim
45 words
The method of claim 1 including the step of increasing the gas flow through said nozzle after a predetermined amount of said mixture of oxygen and non-oxidizing gas has been blown onto the surface to increase the gas input pressure on the molten metal bath.
References Cited (Backward Citations)
US3046107A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-02-17 | 1978-08-19 | 1979-02-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-02-17 | 1982-08-19 | 1983-02-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-02-17 | 1986-08-19 | 1987-02-18 | $7700.00 | Window Closed / Lapsed |