US3985550A
Expired / Lapsed
US
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Method of producing low sulfur steel
Assignee: United States Steel Corp
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Filing: 1975-01-23
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Granted: 1976-10-12
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Expires: 1995-01-23
Abstract
Abstract A method of producing steel by the bottom blown basic oxygen process in which the residual sulfur content is reduced to an exceptionally low level. The process comprehends a standard bottom blown basic oxygen steelmaking process incorporating the injection of a gas carrying particulate desulfurizing agent to desulfurize the steel while maintaining reducing conditions in the bath.
Inventors
- 👤 Ethem T. Turkdogan
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 18:35
CPC Classifications
C; C21; C21C; C21C7/00; C21C7/04; C21C7/068; C21C7/064
Claims Analysis
Total Claims: 37
Claim 1
Independent Claim
80 words
In the process for refining a molten iron base metal containing sulfur, silicon and carbon as impurities to be removed by refinement wherein at least one oxygen stream, surrounded by a protective jacket fluid, are blown into the bath to oxidize impurities therefrom, the improvement comprising including in said process a distinct and separate desulfurizing blow wherein an inert carrier gas is blown into the bath having a particulate desulfurizing agent suspended therein while maintaining reducing conditions within said bath.
Claim 2
Dependent Claim
80 words
In the process for refining a molten iron base metal containing sulfur, silicon and carbon as impurities to be removed by refinement wherein at least one oxygen stream, surrounded by a protective jacket fluid, are blown into the bath to oxidize impurities therefrom, the improvement comprising including in said process a distinct and separate desulfurizing blow wherein an inert carrier gas is blown into the bath having a particulate desulfurizing agent suspended therein while maintaining reducing conditions within said bath.
Claim 3
Dependent Claim
32 words
A process according to claim 1 in which oxygen is admixed with said inert carrier gas and a protective jacket fluid is simultaneously injected surrounding the admixed oxygen and inert carrier gas.
Claim 4
Dependent Claim
31 words
A process according to claim 1 in which reducing conditions within said bath are maintained by performing the desulfurizing blow before the bath carbon and silicon contents have been appreciably reduced.
Claim 5
Dependent Claim
29 words
A process according to claim 1 in which reducing conditions within said bath are maintained by injecting a strong deoxidizing agent into the bath simultaneously with said desulfurizing agent.
Claim 6
Dependent Claim
24 words
A process according to claim 1 in which said desulfurizing agent is selected from the group consisting of lime, calcium carbide and mixtures thereof.
Claim 7
Dependent Claim
27 words
A process according to claim 4 in which said deoxidizing agent is selected from the group consisting of aluminum, titanium, zirconium, rare earth elements and mixtures thereof.
Claim 8
Dependent Claim
22 words
A process according to claim 1 in which said desulfurizing blow is effected for a period of from 1 to 2 minutes.
Claim 9
Independent Claim
187 words
A method of refining a molten iron base metal bath containing sulfur, silicon and carbon as impurities to be removed by refinement, comprising: a. blowing the bath with at least one stream of a desulfurizing treatment material injected through an injection zone extending under the surface of the bath, said treatment material comprising a solid particulate desulfurizing agent suspended in a carrier fluid selected from the group consisting of an inert gas, and mixtures of oxygen and an inert gas, the carrier fluid composition being so proportioned and the treatment material being injected at a rate and for a time sufficient to remove at least a major portion of the sulfur impurity from the molten bath while maintaining the silicon and carbon contents of the bath sufficiently high to provide a reducing condition in the bath; b. surrounding with a protective fluid each oxygen-containing stream injected into the bath during desulfurization; and c. thereafter injecting into the bath through said zone at least one protected stream of oxygen in an amount and for a time sufficient to remove the silicon and carbon impurities to desired final levels.
Claim 10
Independent Claim
187 words
A method of refining a molten iron base metal bath containing sulfur, silicon and carbon as impurities to be removed by refinement, comprising: a. blowing the bath with at least one stream of a desulfurizing treatment material injected through an injection zone extending under the surface of the bath, said treatment material comprising a solid particulate desulfurizing agent suspended in a carrier fluid selected from the group consisting of an inert gas, and mixtures of oxygen and an inert gas, the carrier fluid composition being so proportioned and the treatment material being injected at a rate and for a time sufficient to remove at least a major portion of the sulfur impurity from the molten bath while maintaining the silicon and carbon contents of the bath sufficiently high to provide a reducing condition in the bath; b. surrounding with a protective fluid each oxygen-containing stream injected into the bath during desulfurization; and c. thereafter injecting into the bath through said zone at least one protected stream of oxygen in an amount and for a time sufficient to remove the silicon and carbon impurities to desired final levels.
Claim 11
Dependent Claim
13 words
A method in accordance with claim 8 wherein the desulfurizing agent is lime.
Claim 12
Dependent Claim
25 words
A method in accordance with claim 9 wherein at least about 0.1 percent Si is maintained in the bath until completion of the desulfurization treatment.
Claim 13
Dependent Claim
40 words
A method in accordance with claim 10, wherein desulfurization is carried out substantially to the equilibrium sulfur level in the bath in accordance with the reaction 2CaO + S + 178 Si = CaS + 1/2Ca 2 SiO 4 .
Claim 14
Dependent Claim
18 words
A method in accordance with claim 11 wherein the bath is de-slagged after completion of the desulfurization treatment.
Claim 15
Dependent Claim
23 words
A method in accordance with claim 8 wherein the inert gas is selected from the group consisting of nitrogen, argon and mixtures thereof.
Claim 16
Dependent Claim
13 words
A method in accordance with claim 9 wherein the carrier fluid is nitrogen.
Claim 17
Dependent Claim
55 words
A method in accordance with claim 8, wherein, after removal of carbon to a desired final level in the bath, the bath is further desulfurized by blowing into the bath through the injection zone a solid particulate desulfurizing agent and a solid particulate deoxidizing agent suspended in a carrier fluid non-reactive with the deoxidizing agent.
Claim 18
Dependent Claim
15 words
A method in accordance with claim 15 wherein the carrier fluid is an inert gas.
Claim 19
Dependent Claim
13 words
A method in accordance with claim 16 wherein the inert gas is argon.
Claim 20
Dependent Claim
28 words
A method in accordance with claim 17 wherein the desulfurizing agent is selected from the group consisting of lime, calcium carbide and mixtures of lime and calcium carbide.
Claim 21
Dependent Claim
27 words
A method in accordance with claim 18 wherein the deoxidizing agent is selected from the group consisting of aluminum, titanium, zirconium, rare earth elements and mixtures thereof.
Claim 22
Dependent Claim
19 words
A method in accordance with claim 17 wherein the desulfurizing agent is lime and the deoxidizing agent is aluminum.
Claim 23
Dependent Claim
55 words
A method in accordance with claim 20 wherein the further desulfurization treatment is carried out at a rate and for a time sufficient to reduce the sulfur content of the bath substantially to the equilibrium sulfur level in accordance with the reaction 4CaO + 2Al + 3S = 3CaS + CaAl 2 O 4 .
Claim 24
Dependent Claim
50 words
A method of producing a killed, low sulfur steel comprising the method of claim 17 wherein aluminum is provided in sufficient quantity to reduce the oxygen content of the bath substantially to the equilibrium oxygen level in accordance with the reaction 2Al + 30 = Al 2 O 3 .
Claim 25
Independent Claim
182 words
A method of producing a rimming, low sulfur steel by refining a molten iron base metal bath containing sulfur, silicon and carbon impurities, comprising: a. injecting through an injection zone extending under the surface of the bath at least one stream of oxygen surrounded by a protective fluid, and at a rate and for a time sufficient substantially to remove the silicon impurity and to reduce the carbon impurity content of the bath; b. substituting for the oxygen an inert carrier fluid and purging the injection zone of oxygen while maintaining therein a fluid pressure sufficient to prevent entry therein of molten metal; c. injecting into the bath through the purged injection zone and suspended in the carrier fluid a particulate solid treating material comprising a deoxidizing agent and a desulfurizing agent at a rate and for a time sufficient substantially to deoxidize and desulfurize the bath; and d. thereafter resuming the treatment of the bath in accordance with step (a) at a rate and for a time sufficient to reduce the carbon content of the bath to a desired final level.
Claim 26
Independent Claim
182 words
A method of producing a rimming, low sulfur steel by refining a molten iron base metal bath containing sulfur, silicon and carbon impurities, comprising: a. injecting through an injection zone extending under the surface of the bath at least one stream of oxygen surrounded by a protective fluid, and at a rate and for a time sufficient substantially to remove the silicon impurity and to reduce the carbon impurity content of the bath; b. substituting for the oxygen an inert carrier fluid and purging the injection zone of oxygen while maintaining therein a fluid pressure sufficient to prevent entry therein of molten metal; c. injecting into the bath through the purged injection zone and suspended in the carrier fluid a particulate solid treating material comprising a deoxidizing agent and a desulfurizing agent at a rate and for a time sufficient substantially to deoxidize and desulfurize the bath; and d. thereafter resuming the treatment of the bath in accordance with step (a) at a rate and for a time sufficient to reduce the carbon content of the bath to a desired final level.
Claim 27
Dependent Claim
25 words
A method in accordance with claim 23 wherein the bath is deslagged after it is deoxidized and desulfurized but before the resuming treatment of (d).
Claim 28
Dependent Claim
59 words
A method in accordance with claim 23, wherein the carrier fluid is selected from the group consisting of nitrogen and argon, the deoxidizing agent is selected from the group consisting of aluminum, titanium, zirconium, rare earth elements and mixtures thereof, and the desulfurizing agent is selected from the group consisting of lime and mixtures of lime and calcium carbide.
Claim 29
Dependent Claim
29 words
A method in accordance with claim 25, wherein the carrier fluid is nitrogen and the desulfurization treatment is terminated while the bath contains upwardly of about 0.1 percent carbon.
Claim 30
Dependent Claim
44 words
A method in accordance with claim 26 wherein the deoxidizing agent is aluminum and the desulfurizing agent comprises lime and calcium carbide in proportions, by parts by weight of lime to calcium carbide, of from about 3 to 1 to about 1 to 1.
Claim 31
Dependent Claim
13 words
A method in accordance with claim 27 wherein the desulfurizing agent is lime.
Claim 32
Independent Claim
152 words
A method of producing a substantially killed, low sulfur steel by refining a molten iron base metal bath containing sulfur, silicon and carbon impurities, comprising: a. injecting through an injection zone extending under the surface of the bath at least one stream of oxygen, surrounded by a protective fluid, and at a rate and for a time sufficient to reduce the silicon and carbon impurities in the bath substantially to desired final levels; b. substituting for the oxygen an inert carrier fluid and purging the injection zone of oxygen while maintaining therein a fluid pressure sufficient to prevent entry therein of molten metal; c. injecting into the bath through the purged injection zone and suspended in the carrier fluid a particulate solid treating material comprising a deoxidizing agent and a desulfurizing agent each such agent being injected at a rate and for a time sufficient substantially to deoxidize and desulfurize the bath.
Claim 33
Independent Claim
152 words
A method of producing a substantially killed, low sulfur steel by refining a molten iron base metal bath containing sulfur, silicon and carbon impurities, comprising: a. injecting through an injection zone extending under the surface of the bath at least one stream of oxygen, surrounded by a protective fluid, and at a rate and for a time sufficient to reduce the silicon and carbon impurities in the bath substantially to desired final levels; b. substituting for the oxygen an inert carrier fluid and purging the injection zone of oxygen while maintaining therein a fluid pressure sufficient to prevent entry therein of molten metal; c. injecting into the bath through the purged injection zone and suspended in the carrier fluid a particulate solid treating material comprising a deoxidizing agent and a desulfurizing agent each such agent being injected at a rate and for a time sufficient substantially to deoxidize and desulfurize the bath.
Claim 34
Dependent Claim
51 words
A method in accordance with claim 29 wherein the carrier fluid is argon, the deoxidizing agent is selected from the group consisting of aluminum, titanium, zirconium, rare earth elements and mixtures thereof, and the desulfurizing agent is selected from the group consisting of lime and mixtures of lime and calcium carbide.
Claim 35
Dependent Claim
44 words
A method in accordance with claim 30 wherein the deoxidizing agent is provided in sufficient quantity to reduce the oxygen content of the bath substantially to the equilibrium oxygen level in accordance with the reaction 2Al + 30 = Al 2 O 3 .
Claim 36
Dependent Claim
43 words
A method in accordance with claim 31, wherein the deoxidizing agent is aluminum and the desulfurizing agent comprises lime and calcium carbide proportions, by parts by weight of lime to calcium carbide, of from about 3 to 1 to about 1 to 1.
Claim 37
Dependent Claim
13 words
A method in accordance with claim 32, wherein the desulfurizing agent is lime.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-10-12 | 1980-04-12 | 1980-10-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-10-12 | 1984-04-12 | 1984-10-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-10-12 | 1988-04-12 | 1988-10-12 | $7700.00 | Window Closed / Lapsed |