Process for dephosphorization of molten metal during a refining process

Patent metadata

Field	Value
Publication number	US-10822668-B2
Application number	US-201615541789-A
Country	US
Kind code	B2
Filing date	Jan 8, 2016
Priority date	Jan 9, 2015
Publication date	Nov 3, 2020
Grant date	Nov 3, 2020

Abstract

Process for dephosphorization of molten metal during a refining process using a lime composition in the form of compacted particles having a Shatter Test Index of less than 20%, leading to a refined metal reduced in phosphorus components to the extent that the refined metal reduced in phosphorus is showing a phosphorus content lower than 0.02 w % based on the total weight of the refined metal reduced in phosphorus.

First claim

The invention claimed is:

1. Process for dephosphorization of molten metal during a refining process comprising the steps of
charging a vessel with hot metal and optionally scrap
charging said vessel with a first lime composition
blowing oxygen into said vessel
forming slag with said first lime composition charged into said vessel
dephosphorization of hot metal to form a refined metal reduced in phosphorus components, and
discharging said refined metal reduced in phosphorus components characterized in that said first lime composition comprises at least one first calcium-magnesium compound fitting the formula
aCaCO 3 ·bMgCO 3 ·xCaO·yMgO·uI,

wherein I represents impurities, a, b and u each being mass fractions ≥0 and ≤50%, x and y each being mass fractions ≥0 and ≤100%, with x+y≥50% by weight, based on the total weight of said at least one calcium-magnesium compound, said at least one calcium-magnesium compound being in the form of particles, said first lime composition having a cumulative calcium and magnesium content in the form of oxides greater than or equal to 20% by weight based on the total weight of the first lime composition, and being in the form of compacts, each compact being formed with compacted and shaped particles of calcium-magnesium compounds which are shaped and compacted under compacting pressures between 200 and 700 MPa, said compacts having a Shatter Test Index of less than 20%, and in that said dephosphorization step of molten metal with said compacts increases contact duration between the lime composition and the slat, which action leads to a refined metal reduced in phosphorus component to the extent that the refined metal reduced in phosphorus is showing a phosphorus content lower than 0.02 w % based on the total weight of the refined metal reduced in phosphorus.

2. Process for dephosphorization of molten metal during a refining process according to claim 1 , wherein said first lime composition comprises one second compound selected from the group consisting of B 2 O 3 , TIO 2 , calcium aluminate, calcium ferrite, Ca 2 Fe 2 O 5 , CaFe 2 O 4 , metallic iron, C, and one of several oxides based on aluminum, iron, or manganese and mixture thereof.

3. Process for dephosphorization of molten metal during a refining process according to claim 1 , wherein said charging step of said vessel with first lime composition is performed simultaneously or separately with a charging step of said vessel with a second lime composition.

4. Process for dephosphorization of molten metal during a refining process according to claim 3 , wherein said second lime composition comprises at least one compound selected from the group consisting of compound i), compound ii) and/or compound iii):
i) calcium-magnesium compound under the form of pebble lime having a cumulative calcium and magnesium content in the form of oxides greater than or equal to 70% by weight based on the total weight of said calcium-magnesium compound,
ii) calcium-magnesium compound fitting the formula
aCaCO 3 ·bMgCO 3 ·xCaO·yMgO·uI,

wherein I represents impurities, a, b and u each being mass fractions ≥0 and ≤50%, x and y each being mass fractions ≥0 and ≤100%, with x+y≥50% by weight, based on the total weight of said at least one calcium-magnesium compound, said at least one calcium-magnesium compound being in the form of particles, said second lime composition having a cumulative calcium and magnesium content in the form of oxides greater than or equal to 20% by weight based on the total weight of the second lime composition, and being in the form of compacts, each compact being formed with compacted and shaped particles of calcium-magnesium compounds, said compacts having a Shatter Test Index of less than 10%, and
iii) a first calcium-magnesium compound fitting the formula
aCaCO 3 ·bMgCO 3 ·xCaO·yMgO·uI,

wherein I represents impurities, a, b and u each being mass fractions ≥0 and ≤50%, x and y each being mass fractions ≥0 and 100%, with x+y≥50% by weight, based on the total weight of said at least one calcium-magnesium compound, said at least one calcium-magnesium compound being in the form of particles, and one second compound chosen in the group consisting of B 2 O 3 , TiO 2 , calcium aluminate, calcium ferrite, Ca 2 Fe 2 O 5 , Ca 2 Fe 2 O 4 , metallic iron, C, and one or more oxides based on aluminum, iron, or manganese and mixtures thereof, said second lime composition having an cumulative calcium and magnesium content in the form of oxides greater than or equal to 20% by weight based on the total weight of the second lime composition, and being in the form of compacts, each compact being formed with compacted and shaped particles of calcium-magnesium compounds, said compacts having a Shatter Test Index of less than 20%.

5. Process for dephosphorization of molten metal during a refining process according to claim 1 , wherein said refined metal reduced in phosphorus is showing a phosphorus content lower than 0.015 w% based on the total weight of the refined metal reduced in phosphorus.

6. Process for dephosphorization of molten metal during a refining process according to claim 1 , wherein said compacts of said first lime composition under the form of compacts have a Shatter Test Index of less than 8%.

7. Process for dephosphorizaion of molten metal during a refining process according to claim 1 , wherein said compacts of said first lime composition under the form of compacts presents a Shatter Test Index of less than 20% after an Accelerated Ageing Test of Level 1 at 30° C. under 75% of relative humidity for 2 h.

8. Process for dephosphorization of molten metal during a refining process according to claim 1 , wherein said compacts of said first lime composition under the form of compacts presents a Shatter Test Index of less than 20% after an Accelerated Ageing Test of Level 2 at 40° C. under 50% of relative humidity for 2 h.

9. Process for dephosphorization of molten metal during a refining process according to claim 1 , wherein said compacts of said first lime composition under the form of compacts presents a Shatter Test Index of less than 20% after an Accelerated Ageing Test of Level 3 at 40° C under 60% of relative humidity for 2 h.

10. Process for dephosphorization of molten metal during a refining process according to claim 1 , wherein said compacts of said first lime composition under the form of compacts presents a Shatter Test Index of less than 20% after an Accelerated Ageing Test of Level 4 at 40° C under 70% of relative humidity for 2 h.

11. Process for dephosphorization of molten metal during a refining process according to claim 1 , wherein said particles have a size of less than or equal to 7 mm, observable by optical microscopy or by scanning electron microscopy and before compaction having a size of particles d 100 of less than or equal to 7 mm.

12. Process tor dephosphorization of molten metal during a refining process according to claim 1 , wherein said particles of said at least one calcium-magnesium compound before compaction have a d 90 of less than or equal to 3 mm.

13. Process for dephosphorization of molten metal during a refining process according to claim 1 , wherein said particles of said at least one calcium-magnesium compound before compaction have a d 50 of less than or equal to 1 mm.

14. Process for dephosphorization of molten metal during a refining process according to claim 1 , wherein said compacts are of a regular and homogeneous shape such shapes being selected from the group consisting of lozenges, tablets, compressed tablets, briquettes, platelets and balls and have a size comprised between 10 and 100 mm.

Assignees

• Lhoist Rech Et Developpement Sa

Inventors

• Nispel Michael
• Criniere Guillaume
• Perrin Eric
• Chopin Thierry
• Noldin Jose

Classifications

• C21C7/0645 Primary

  Agents used for dephosphorising or desulfurising · CPC title

• C21C1/025 Primary

  Agents used for dephosphorising or desulfurising · CPC title

• C21C7/064

  Dephosphorising; Desulfurising · CPC title

• C21C1/02

  Dephosphorising or desulfurising · CPC title

• Y02P10/20

  Recycling · CPC title