WO2011006649A1 - Casting mould powder - Google Patents
Casting mould powder Download PDFInfo
- Publication number
- WO2011006649A1 WO2011006649A1 PCT/EP2010/004292 EP2010004292W WO2011006649A1 WO 2011006649 A1 WO2011006649 A1 WO 2011006649A1 EP 2010004292 W EP2010004292 W EP 2010004292W WO 2011006649 A1 WO2011006649 A1 WO 2011006649A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- powder
- mould
- exothermic
- amount
- casting
- Prior art date
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/10—Supplying or treating molten metal
- B22D11/11—Treating the molten metal
- B22D11/111—Treating the molten metal by using protecting powders
Definitions
- the invention relates to a method for the continuous casting of steel, wherein molten steel is introduced in a pool of molten steel in a mould of a continuous casting apparatus to cast a strand of steel, and wherein on top of the pool of molten steel or meniscus a casting mould powder is applied, which casting mould powder melts on the meniscus to form a slag and the slag lubricates the steel during solidification in the mould.
- the melting of the casting mould powder extracts a certain amount of heat from the meniscus of the molten steel in the mould, since casting mould powders used for continuous casting need energy to melt.
- the flow pattern in the mould is determined by the Submerged Entry Nozzle through which the molten steel is introduced in the mould, and by an electromagnetic flow control device if this has been installed.
- At least one of these objects is achieved with a method for the continuous casting of steel, wherein molten steel is introduced in a pool of molten steel in a mould of a continuous casting apparatus to cast a strand of steel, and wherein on top of the pool of molten steel or meniscus a casting mould powder is applied, which casting mould powder melts on the meniscus to form a slag and the slag lubricates the steel during solidification in the mould, wherein the casting mould powder comprises an endothermic mould powder mixed with an amount of exothermic powder components.
- This invention has the big advantage that due to the use of exothermic powder components mixed with the usual endothermic mould powder, less energy or even no energy is needed to heat the mould powder so as to melt and form the slag. Since less or no energy is needed, less or no flow of molten steel to the meniscus is needed. Thus a more quiet flow in the mould can be achieved, resulting in an improved surface quality of the cast product.
- Exothermic powder components are known as part of so-called front powder or starter powder, which are used to start up the casting in a continuous casting device.
- This front powder or starter powder is purely exothermic and is not used for the continuous casting of molten steel.
- the exothermic powder components are usually FeSi or CaSi or a combination or these, creating heat upon oxidation.
- a neutralising amount of exothermic powder components is mixed with the endothermic mould powder such that the casting mould powder is neither exothermic nor endothermic or an amount of exothermic powder components is used that is between 75% less and 75% more of the neutralising amount of exothermic powder components.
- the neutralising amount of exothermic powder components provides that the casting mould powder is neither exothermic nor endothermic so under theoretical circumstances no additional energy from the molten steel is needed. In practical circumstances, for instance depending on the type of continuous casting device, it may be useful to use more or less of the exothermic powder components.
- the amount of exothermic powder components that is used is between 50% less and 50% more of the neutralising amount of exothermic powder components, preferably between 30% less and 30% more of the neutralising amount of exothermic powder components.
- one and the same casting mould powder can be used in varying process conditions, while the flow of the molten steel at the meniscus can always be such that the no slag is entrained into the steel.
- the molten steel is introduced in the mould using a Submerged Entry Nozzle (SEN) which is formed such that the molten steel flows out of the SEN in a downward direction between a vertical direction and a 45° angle thereof, such that a minimal level of velocity and turbulence at the meniscus is achieved.
- This SEN is thus formed such that less of the molten metal leaving the SEN flows to the meniscus of the molten steel, or virtually all molten steel leaving the SEN is directed downwards in the mould.
- Electromagnetic flow control devices are known in the art.
- a casting mould powder for use in the method elucidated above, wherein the casting mould powder comprises an endothermic mould powder mixed with an amount of exothermic powder components. This is the casting powder as described above for the method according to the first aspect of the invention.
- a neutralising amount of exothermic powder components is mixed with the endothermic mould powder such that the casting mould powder is neither exothermic nor endothermic or an amount of exothermic powder components is used that is between 75% less and 75% more of the neutralising amount of exothermic powder components.
- the amount of exothermic powder components that is used is between 50% less and 50% more of the neutralising amount of exothermic powder components, preferably between 30% less and 30% more of the neutralising amount of exothermic powder components. The reason for this is elucidated above.
- the inventors have calculated that with the information about the various reactions during heating of mould powder in the mould of a continuous casting apparatus together with the calculated heat capacity of the components of the continuous casting apparatus, the total enthalpy can be predicted when heating the powders and powder mixtures to 1600° C. Thus, the exact ration of both powders needed in a mould powder mixture can be determined, without the risk of an overreaction of the powder mixture, while a minimum amount of heat is drawn from the liquid steel bath for heating and melting the mould powder mixture.
- the ratio of the mould powder and the front powder has been calculated.
- This calculation resulted in the proposition to use 70 weight% mould powder 450/SD and 30 weight% front powder E8411.
- This mixture should give a zero-balanced heat consumption/production in air.
- This proposition is safe when considering the risk of a runaway reaction wherein an exothermic melting of the mixed mould powder could take place, because in practice less air will be present in the powder layer resulting in less heat production. This, in practice the mixed mould powder layer in the mould on the liquid steel will absorb some heat from the liquid steel bath.
- the mixed mould powder of 70 weight% mould powder 450/SD and 30 weight% front powder E8411 has been used in a casting test for one load, during approximately 45 minutes. This test worked out well, the mixed casting mould powder layer behaved normal and the mould lubrication by the slag resulted in stable mould forces.
- the slab produced by using the mixed mould powder had not yet been analysed regarding appearance and inclusions. From the test performed, it can be expected that the quality of the slab produced in accordance with the invention will be at least as good as the slabs produced using standard mould powder.
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Continuous Casting (AREA)
Abstract
The invention relates to a method for the continuous casting of steel, wherein molten steel is introduced in a pool of molten steel in a mould of a continuous casting apparatus to cast a strand of steel, and wherein on top of the pool of molten steel or meniscus a casting mould powder is applied, which casting mould powder melts on the meniscus to form a slag and the slag lubricates the steel during solidification in the mould. According to the invention the casting mould powder comprises an endothermic mould powder mixed with an amount of exothermic powder components. The invention also relates to a casting mould powder for use in the method.
Description
CASTING MOULD POWDER
The invention relates to a method for the continuous casting of steel, wherein molten steel is introduced in a pool of molten steel in a mould of a continuous casting apparatus to cast a strand of steel, and wherein on top of the pool of molten steel or meniscus a casting mould powder is applied, which casting mould powder melts on the meniscus to form a slag and the slag lubricates the steel during solidification in the mould.
The melting of the casting mould powder extracts a certain amount of heat from the meniscus of the molten steel in the mould, since casting mould powders used for continuous casting need energy to melt. To limit the cooling of the meniscus to acceptable values, it is general practice to engineer the flow pattern of the liquid steel in the mould in such a manner that a certain flow velocity at the meniscus is attained. This flow of molten steel should ensure that an acceptable degree of convective heat transfer to the meniscus is achieved. The flow pattern in the mould is determined by the Submerged Entry Nozzle through which the molten steel is introduced in the mould, and by an electromagnetic flow control device if this has been installed.
However, if the flow at the meniscus is too strong and/or the flow is turbulent, the surface quality of the cast product is deteriorated because slag is entrained into the steel. This means that a metallurgical Optimal flow velocity' has to lie between a minimum flow velocity to limit the cooling of the meniscus and a maximum flow velocity so as to limit the entrainment of slag. Varying process conditions however make it difficult to achieve a flow velocity that always meets the criteria of the minimum flow velocity at one time and the maximum flow velocity at another time.
It is an object of the invention to optimise the process conditions such that the surface quality of the cast product is improved.
It is a further object of the invention to provide a casting mould powder that is suitable for continuous casting of steel having an improved surface quality.
It is another object of the invention to provide a Submerged Entry Nozzle for an optimal flow condition to achieve an improved surface quality.
According to a first aspect of the invention, at least one of these objects is achieved with a method for the continuous casting of steel, wherein molten steel is introduced in a pool of molten steel in a mould of a continuous casting apparatus to cast
a strand of steel, and wherein on top of the pool of molten steel or meniscus a casting mould powder is applied, which casting mould powder melts on the meniscus to form a slag and the slag lubricates the steel during solidification in the mould, wherein the casting mould powder comprises an endothermic mould powder mixed with an amount of exothermic powder components.
This invention has the big advantage that due to the use of exothermic powder components mixed with the usual endothermic mould powder, less energy or even no energy is needed to heat the mould powder so as to melt and form the slag. Since less or no energy is needed, less or no flow of molten steel to the meniscus is needed. Thus a more quiet flow in the mould can be achieved, resulting in an improved surface quality of the cast product.
Exothermic powder components are known as part of so-called front powder or starter powder, which are used to start up the casting in a continuous casting device. This front powder or starter powder is purely exothermic and is not used for the continuous casting of molten steel. The exothermic powder components are usually FeSi or CaSi or a combination or these, creating heat upon oxidation.
Preferably a neutralising amount of exothermic powder components is mixed with the endothermic mould powder such that the casting mould powder is neither exothermic nor endothermic or an amount of exothermic powder components is used that is between 75% less and 75% more of the neutralising amount of exothermic powder components. The neutralising amount of exothermic powder components provides that the casting mould powder is neither exothermic nor endothermic so under theoretical circumstances no additional energy from the molten steel is needed. In practical circumstances, for instance depending on the type of continuous casting device, it may be useful to use more or less of the exothermic powder components.
Preferably, the amount of exothermic powder components that is used is between 50% less and 50% more of the neutralising amount of exothermic powder components, preferably between 30% less and 30% more of the neutralising amount of exothermic powder components. In the preferred embodiment one and the same casting mould powder can be used in varying process conditions, while the flow of the molten steel at the meniscus can always be such that the no slag is entrained into the steel.
According to a preferred embodiment the molten steel is introduced in the mould using a Submerged Entry Nozzle (SEN) which is formed such that the molten steel flows out of the SEN in a downward direction between a vertical direction and a 45° angle thereof, such that a minimal level of velocity and turbulence at the meniscus is achieved. This SEN is thus formed such that less of the molten metal leaving the SEN flows to the meniscus of the molten steel, or virtually all molten steel leaving the SEN is directed downwards in the mould.
Apart from the SEN discussed above, it is possible to use an electromagnetic flow control device to assist in the achieving of a minimal level of velocity and turbulence at the meniscus. Electromagnetic flow control devices are known in the art.
According to a second aspect of the invention there is provided a casting mould powder for use in the method elucidated above, wherein the casting mould powder comprises an endothermic mould powder mixed with an amount of exothermic powder components. This is the casting powder as described above for the method according to the first aspect of the invention.
Preferably in the casting mould powder a neutralising amount of exothermic powder components is mixed with the endothermic mould powder such that the casting mould powder is neither exothermic nor endothermic or an amount of exothermic powder components is used that is between 75% less and 75% more of the neutralising amount of exothermic powder components. Preferably, the amount of exothermic powder components that is used is between 50% less and 50% more of the neutralising amount of exothermic powder components, preferably between 30% less and 30% more of the neutralising amount of exothermic powder components. The reason for this is elucidated above.
The invention will be elucidated with the example given below.
The inventors have calculated that with the information about the various reactions during heating of mould powder in the mould of a continuous casting apparatus together with the calculated heat capacity of the components of the continuous casting apparatus, the total enthalpy can be predicted when heating the powders and powder mixtures to 1600° C. Thus, the exact ration of both powders needed in a mould powder mixture can be determined, without the risk of an
overreaction of the powder mixture, while a minimum amount of heat is drawn from the liquid steel bath for heating and melting the mould powder mixture.
In the example use is made of standard mould powder Scorialite SPH SL 450 SD (for short: 450/SD) and front powder or exothermic powder Scorialite E8411. The mineralogical composition of these powders can be analysed with standard analytical methods. The mould powders are supplied by the firm Metallurgica.
The endothermic and exothermic heat effects of both the mould powder 450/SD and the front powder E8411 have been measured in an air atmosphere and in a pure CO2 atmosphere, since in the mould the surface of the mould powder layer reacts with air while the powder in contact with the liquid steel is exposed to a gas atmosphere where all oxygen is consumed.
With these measured results, the ratio of the mould powder and the front powder has been calculated. This calculation resulted in the proposition to use 70 weight% mould powder 450/SD and 30 weight% front powder E8411. This mixture should give a zero-balanced heat consumption/production in air. This proposition is safe when considering the risk of a runaway reaction wherein an exothermic melting of the mixed mould powder could take place, because in practice less air will be present in the powder layer resulting in less heat production. This, in practice the mixed mould powder layer in the mould on the liquid steel will absorb some heat from the liquid steel bath.
The mixed mould powder of 70 weight% mould powder 450/SD and 30 weight% front powder E8411 has been used in a casting test for one load, during approximately 45 minutes. This test worked out well, the mixed casting mould powder layer behaved normal and the mould lubrication by the slag resulted in stable mould forces.
At the filing date of the patent application the slab produced by using the mixed mould powder had not yet been analysed regarding appearance and inclusions. From the test performed, it can be expected that the quality of the slab produced in accordance with the invention will be at least as good as the slabs produced using standard mould powder.
It will be clear to the person skilled in the art that apart from the mixed mould powder as used in the example, other mixed mould powders can be used in accordance with the following claims.
Claims
1. Method for the continuous casting of steel, wherein molten steel is introduced in a pool of molten steel in a mould of a continuous casting apparatus to cast a strand of steel, and wherein on top of the pool of molten steel or meniscus a casting mould powder is applied, which casting mould powder melts on the meniscus to form a slag and the slag lubricates the steel during solidification in the mould, characterised in that the casting mould powder comprises an endothermic mould powder mixed with an amount of exothermic powder components.
2. Method according to claim 1 , wherein a neutralising amount of exothermic powder components is mixed with the endothermic mould powder such that the casting mould powder is neither exothermic nor endothermic or such that an amount of exothermic powder components is used that is between 75% less and
75% more of the neutralising amount of exothermic powder components.
3. Method according to claim 2, wherein the amount of exothermic powder components that is used is between 50% less and 50% more of the neutralising amount of exothermic powder components, preferably between 30% less and 30% more of the neutralising amount of exothermic powder components.
4. Method according to any one of the preceding claims, wherein the molten steel is introduced in the mould using a Submerged Entry Nozzle (SEN) which is formed such that the molten steel flows out of the SEN in a downward direction between a vertical direction and a 45° angle thereof, such that a minimal level of velocity and turbulence at the meniscus is achieved.
5. Method according to claim 4, wherein an electromagnetic flow control device is used to assist in the achieving of a minimal level of velocity and turbulence at the meniscus.
6. Casting mould powder for use in the method according to any one of the preceding claims, characterised in that the casting mould powder comprises an endothermic mould powder mixed with an amount of exothermic powder components.
7. Casting mould powder according to claim 6, wherein a neutralising amount of exothermic powder components is mixed with the endothermic mould powder such that the casting mould powder is neither exothermic nor endothermic or such that an amount of exothermic powder components is used that is between 75% less and 75% more of the neutralising amount of exothermic powder components.
8. Casting mould powder according to claim 7, wherein the amount of exothermic powder components that is used is between 50% less and 50% more of the neutralising amount of exothermic powder components, preferably between 30% less and 30% more of the neutralising amount of exothermic powder components.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP09009150.5 | 2009-07-14 | ||
| EP09009150 | 2009-07-14 | ||
| EP09013339 | 2009-10-22 | ||
| EP09013339.8 | 2009-10-22 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO2011006649A1 true WO2011006649A1 (en) | 2011-01-20 |
Family
ID=43086027
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/EP2010/004292 WO2011006649A1 (en) | 2009-07-14 | 2010-07-14 | Casting mould powder |
Country Status (1)
| Country | Link |
|---|---|
| WO (1) | WO2011006649A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103447489A (en) * | 2013-09-12 | 2013-12-18 | 武汉钢铁(集团)公司 | Method for preparing high-iron-content continuous casting mold flux for laboratory |
| CN104331629A (en) * | 2014-11-17 | 2015-02-04 | 大连理工大学 | Uneven distributed calculating method of liquid, solid powder film and air gap thickness of continuous casting crystallizer casting powder |
Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1584146A (en) * | 1968-08-13 | 1969-12-12 | ||
| US3708314A (en) * | 1970-08-12 | 1973-01-02 | Sumitomo Metal Ind | Agent for adding to a mould in which molten ferritic stainless steel is cast by a continuous casting process |
| JPS4897735A (en) * | 1972-03-28 | 1973-12-12 | ||
| JPS5370039A (en) * | 1976-12-02 | 1978-06-22 | Kobe Steel Ltd | Exothermic flux for continuous casting |
| JPS58154445A (en) * | 1982-03-10 | 1983-09-13 | Daido Steel Co Ltd | Continuous casting method |
| JPS6127150A (en) * | 1984-07-17 | 1986-02-06 | Nippon Steel Corp | Continuous casting method of steel |
| JPS6466056A (en) * | 1987-09-04 | 1989-03-13 | Nippon Thermo Chem Kk | Mold powder for continuous casting |
| GB2211178A (en) * | 1987-10-19 | 1989-06-28 | Shinagawa Refractories Co | Calcium silicate mold additive |
| EP0513357A1 (en) * | 1990-11-30 | 1992-11-19 | Shinagawa Refractories Co., Ltd. | Exothermic mold powder for continuous casting |
-
2010
- 2010-07-14 WO PCT/EP2010/004292 patent/WO2011006649A1/en active Application Filing
Patent Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1584146A (en) * | 1968-08-13 | 1969-12-12 | ||
| US3708314A (en) * | 1970-08-12 | 1973-01-02 | Sumitomo Metal Ind | Agent for adding to a mould in which molten ferritic stainless steel is cast by a continuous casting process |
| JPS4897735A (en) * | 1972-03-28 | 1973-12-12 | ||
| JPS5370039A (en) * | 1976-12-02 | 1978-06-22 | Kobe Steel Ltd | Exothermic flux for continuous casting |
| JPS58154445A (en) * | 1982-03-10 | 1983-09-13 | Daido Steel Co Ltd | Continuous casting method |
| JPS6127150A (en) * | 1984-07-17 | 1986-02-06 | Nippon Steel Corp | Continuous casting method of steel |
| JPS6466056A (en) * | 1987-09-04 | 1989-03-13 | Nippon Thermo Chem Kk | Mold powder for continuous casting |
| GB2211178A (en) * | 1987-10-19 | 1989-06-28 | Shinagawa Refractories Co | Calcium silicate mold additive |
| EP0513357A1 (en) * | 1990-11-30 | 1992-11-19 | Shinagawa Refractories Co., Ltd. | Exothermic mold powder for continuous casting |
Non-Patent Citations (2)
| Title |
|---|
| DATABASE WPI Week 197426, Derwent World Patents Index; AN 1974-47724V, XP002581901 * |
| DATABASE WPI Week 197830, Derwent World Patents Index; AN 1978-54458A, XP002581902 * |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103447489A (en) * | 2013-09-12 | 2013-12-18 | 武汉钢铁(集团)公司 | Method for preparing high-iron-content continuous casting mold flux for laboratory |
| CN104331629A (en) * | 2014-11-17 | 2015-02-04 | 大连理工大学 | Uneven distributed calculating method of liquid, solid powder film and air gap thickness of continuous casting crystallizer casting powder |
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