Claims
- 1. A method of dephosphorizing a molten alloy containing at least about 4% in total of elements more oxidizable than iron and having a carbon content lower than the solubility of carbon in the molten alloy comprising adding a flux composition comprising 3 to 90% by weight of calcium carbide and not less than 10% in total of at least one alkali earth metal halide under a non-oxidizing atmosphere satisfying the condition:
- P.sub.O.sbsb.2 +P.sub.CO.sbsb.2 +P.sub.H.sbsb.2.sub.O +P.sub.SO.sbsb.2 <60 mmHg.
- 2. A process for producing a low phosphorous stainless steel comprising a first step of smelting a high chrome ferrous metal containing at least about 4% in total of elements more oxidizable than iron and having a carbon content of 0.2 to 2.0%, a second step of refining the molten metal by addition of a flux composition comprising calcium carbide and at least one alkali earth metal fluoride in a non-oxidizing atmosphere, and a third step of performing finishing decarburization until the concentration of carbon in the resulting molten alloy reaches a predetermined level.
- 3. A method according to claim 1, wherein said flux composition further comprises one selected from the group consisting of metallic calcium and calcium alloys including Ca-Si, Ca-Si-Mn and Ca-Si-Fe in an amount of about 3 to 50% as calcium by weight based on the total weight of said flux composition.
- 4. A method according to claim 1, wherein said atmosphere contains nitrogen gas in a partial pressure of not more than about 400 mmHg.
- 5. A method according to claim 1, wherein after the oxygen content of said molten metal or alloy is adjusted to about 180 p.p.m. or less, said flux composition is added thereto.
- 6. A method according to claim 1, wherein the percentage of calcium carbide in said flux composition is determined by the following formula ##EQU6##
- 7. A process according to claim 2, wherein the first step includes reduction of oxides of iron and chromium by a carbonaceous reducing agent to make a molten metal in which Cr/Fe<1.0, and subsequently removes silicon from the molten metal.
- 8. A process according to claim 2, wherein in the third step the flux composition is added when the molten metal is transferred from the melting furnace to a molten metal receptacle of which the interior space is maintained in a non-oxidizing atmosphere, and only the dephosphorized molten metal is tapped out from the receptacle to effect the separation between the slag and the molten metal.
- 9. A process according to claim 2, wherein in the second step a tiltable reactor having a gas injection plug is used and is charged with the molten metal from the first step and then with the flux composition while stirring the molten metal charge by the bubbling with non-oxidizing gas blown through the gas injection plug to perform dephosphorization, and thereafter the layer of slag is oxidized by the blowing of an oxidizing gas as directed to the above of, or into the slag layer.
- 10. A process according to claim 2, wherein the second and third steps are performed in such a manner that, after the slag covering the molten metal charge from the first step is pushed by a removable slag-layer breaker to expose the molten metal surface to the atmosphere, the flux composition is added to the molten metal charge through the atmosphere-exposed surface to perform dephosphorization, and thereafter the slag layer breaker is removed to permit the mixing of the slag from the first step with the slag formed in the second step.
- 11. A method of treating a slag separated from dephosphorized molten metal or alloy by contact with a flux comprising calcium carbide and a halide of an alkali earth metal, which comprises making the slag react with another molten metal under an oxidizing atmosphere.
- 12. A method of treating a slag separated from dephosphorized molten metal or alloy by contact with a flux comprising calcium carbide and a halide of an alkali earth metal, which comprises oxidizing the slag under an oxidizing atmosphere.
- 13. A method of treating a slag separated from dephosphorized molten metal or alloy by contact with a flux comprising calcium carbide and a halide of an alkali earth metal, which comprises oxidizing the slag by an oxidizing frame of a burner.
- 14. A method of treating a slag separated from dephosphorized molten metal or alloy by contact with a flux comprising calcium carbide and a halide of an alkali earth metal, which comprises exposing the slag to an oxidizing atmosphere and then to an atmosphere containing 10% or more of CO.sub.2 at a temperature ranging from about 800.degree. to 300.degree. C.
- 15. The method according to claim 1 wherein said flux composition is to form a slag containing 5 to 50% of CaC.sub.2 with a CaC/alkali earth metal halide ratio of 0.05 to 1.0 in case of electro-slag refining.
- 16. The method according to claim 1 wherein said flux comprises 20 to 80 percent of CaC.sub.2 with a CaC/alkali earth metal halide ratio of 5 to 0.25 in case of refining in an oxide type refractory lining receptacle.
Parent Case Info
This is a continuation of application Ser. No. 700,193, filed on June 28, 1976 now abandoned.
US Referenced Citations (5)
Continuations (1)
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Number |
Date |
Country |
Parent |
700193 |
Jun 1976 |
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