SE1300554A1 - An apparatus for stirring in steel ingots in an ingot molding process - Google Patents
An apparatus for stirring in steel ingots in an ingot molding process Download PDFInfo
- Publication number
- SE1300554A1 SE1300554A1 SE1300554A SE1300554A SE1300554A1 SE 1300554 A1 SE1300554 A1 SE 1300554A1 SE 1300554 A SE1300554 A SE 1300554A SE 1300554 A SE1300554 A SE 1300554A SE 1300554 A1 SE1300554 A1 SE 1300554A1
- Authority
- SE
- Sweden
- Prior art keywords
- mold
- stirring
- unit
- ingot
- electromagnetic
- Prior art date
Links
- 238000003756 stirring Methods 0.000 title claims abstract description 29
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 24
- 239000010959 steel Substances 0.000 title claims abstract description 24
- 238000000034 method Methods 0.000 title 1
- 238000000465 moulding Methods 0.000 title 1
- 238000005266 casting Methods 0.000 claims abstract description 6
- 238000007711 solidification Methods 0.000 description 7
- 230000008023 solidification Effects 0.000 description 7
- 239000007788 liquid Substances 0.000 description 4
- 239000012071 phase Substances 0.000 description 4
- 210000001787 dendrite Anatomy 0.000 description 2
- 230000001627 detrimental effect Effects 0.000 description 2
- 230000004907 flux Effects 0.000 description 2
- 239000000155 melt Substances 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 238000005204 segregation Methods 0.000 description 2
- 229910001018 Cast iron Inorganic materials 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 230000005672 electromagnetic field Effects 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000013528 metallic particle Substances 0.000 description 1
- 238000009832 plasma treatment Methods 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 230000000750 progressive effect Effects 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 239000002893 slag Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
- F27D27/00—Stirring devices for molten material
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Continuous Casting (AREA)
Abstract
Föreliggande uppfinning avser en anordning (1) för omrörning av stålgöt i en kokill (2) i en götgjutningsprocess. Anordning (1) innefattar en elektromagnetisk omrörarenhet (12, 14) för elektromagnetisk omröring i stålgöt (24), en multi-fas AC-strömförsörjning (20) som är operativt ansluten till den elektromagnetiska omrörningsenheten (12, 14), och en styrenhet (30) operativt ansluten till strömmatningen (20) för att styra driften av den elektromagnetiska omrörningsenheten (12, 14), varvid den elektromagnetiska omrörningsenheten (12, 14) är positionerad intill den yttre ytan av kokillen (2).(Fig. 1a)The present invention relates to a device (1) for stirring steel ingots in a mold (2) in an ingot casting process. Device (1) comprises an electromagnetic stirring unit (12, 14) for electromagnetic stirring in steel ingot (24), a multi-phase AC power supply (20) operatively connected to the electromagnetic stirring unit (12, 14), and a control unit ( 30) operatively connected to the power supply (20) to control the operation of the electromagnetic stirring unit (12, 14), the electromagnetic stirring unit (12, 14) being positioned adjacent the outer surface of the mold (2). (Fig. 1a)
Description
15 20 25 30 flow in the liquid steel. The strongest flow speed appears along the mush- liquid interface where melt locally flows downwards with typical speeds of a few centimeters per second. Closer to the center of the ingot, the flow recirculates upward again. 15 20 25 30 flow in the liquid steel. The strongest flow speed appears along the mush- liquid interface where melt flows locally downwards with typical speeds of a few centimeters per second. Closer to the center of the ingot, the flow recirculates upward again.
An uncontrolled traditional progressive solidification typically results in a number of defects in the cast ingot, for example segregation due to the fact that some solute elements have a much lower solubility in a solid than in a liquid phase, cracks, inclusions and center porosity. This leads to un- desired low yields for high quality steels as defect areas or entire ingots must be re-melted and cast again. These metallurgical problems can all be related to low flow speeds and insufficient turnaround of the melt.An uncontrolled traditional progressive solidification typically results in a number of defects in the cast ingot, for example segregation due to the fact that some solute elements have a much lower solubility in a solid than in a liquid phase, cracks, inclusions and center porosity. This leads to un- desired low yields for high quality steels as defective areas or entire ingots must be re-melted and cast again. These metallurgical problems can all be related to low flow speeds and insufficient turnaround of the melt.
Plasma Treatment Casting, denoted as PTC is a technology for stirring ingots. PTC imposes an electric field over the height of the ingot by apply- ing a rotating DC electrode above the ingot and another electrode at the base of the mold. A plasma arc strikes the top surface of the ingot in a rotating manner, feeding a varying current density to the steel in the mold.Plasma Treatment Casting, denoted as PTC is a technology for stirring ingots. PTC imposes an electric field over the height of the ingot by applying- ing a rotating DC electrode above the ingot and another electrode at the base of the mold. A plasma arc strikes the top surface of the ingot in a rotating manner, feeding a varying current density to the steel in the mold.
The varying current density induces a varying magnetic flux density, and the current and the magnetic field together create a time varying stirring force on the ingot. Thus, stirring may increase yield by 10% for high grade steel ingots. However, when using PTC for stirring, the top surface of ingot steel may be exposed for oxidation when the rotating DC top electrode breaks the ambient gas protective slag layer on top of the molten steel.The varying current density induces a varying magnetic flux density, and the current and the magnetic field together create a time varying stirring force on the ingot. Thus, stirring may increase yield by 10% for high grade steel ingots. However, when using PTC for stirring, the top surface of ingot steel may be exposed to oxidation when the rotating DC top electrode breaks the ambient gas protective slag layer on top of the molten steel.
Furthermore, PTC requires replacing electrodes frequently.Furthermore, PTC requires replacing electrodes frequently.
OBJECTS AND SUMMARY OF THE INVENTION The object of the present invention is to provide an alternative solution for stirring ingots in a steel ingot casting process in order to achieve a strong and controllable convection in the part of the steel ingot that has not yet solidified. Thus, high production and quality of cast products are achieved. 10 15 20 25 30 This object is achieved by an apparatus defined in claim 1. The apparatus for stirring of steel ingot comprises an electromagnetic stirrer unit for elec- tromagnetically stirring steel ingot, wherein the electromagnetic stirrer unit is arranged adjacently to the outer surface of the mold, a multi-phase AC current supply operatively connected to the electromagnetic stirrer unit, and a control unit operatively connected to the current supply to control the operation of the electromagnetic stirrer unit.OBJECTS AND SUMMARY OF THE INVENTION The object of the present invention is to provide an alternative solution for stirring ingots in a steel ingot casting process in order to achieve a strong and controllable convection in the part of the steel ingot that has not yet solidified. Thus, high production and quality of cast products are achieved. 10 15 20 25 30 This object is achieved by an apparatus defined in claim 1. The apparatus for stirring of steel ingot comprises an electromagnetic stirrer unit for elec- tromagnetically stirring steel ingot, wherein the electromagnetic stirrer unit is arranged adjacently to the outer surface of the mold, a multi-phase AC current supply operatively connected to the electromagnetic stirrer unit, and a control unit operatively connected to the current supply to control the operation of the electromagnetic stirrer unit.
Due to the application of an electromagnetic stirrer, melt in the mold may flow with a speed about ten times higher than those of free convection. lt is easy to adapt the strength of the electromagnetic stirrer. Thus, a control of the different stages of solidificatíon in case that different amount of convection is needed is achieved. lt is advantageous to use electromagnetic stirring in an ingot casting pro- cess since it is a contactless technology that needs a minimum mainte- nance. Furthermore, electromagnetic fields can penetrate mold, covers and mold powder and thus the application of an electromagnetic stirring minimizes risk of oxidation of the top surface of the ingot steel in compari- son with PTC. Moreover, there is almost no wear on the electromagnetic stirrer, which has a very long lifetime.Due to the application of an electromagnetic stirrer, melt in the mold may flow with a speed about ten times higher than those of free convection. lt is easy to adapt the strength of the electromagnetic stirrer. Thus, a control of the different stages of solidification in case that different amount of convection is needed is achieved. lt is advantageous to use electromagnetic stirring in an ingot casting pro- cess since it is a contactless technology that needs a minimum maintenance. Furthermore, electromagnetic fields can penetrate mold, covers and mold powder and thus the application of an electromagnetic stirring minimizes risk of oxidation of the top surface of the ingot steel in comparison with PTC. Moreover, there is almost no wear on the electromagnetic stirrer, which has a very long lifetime.
The mold is conical shaped and its head is arranged at an end of the mold that has a larger diameter. ln one embodiment of the invention, the elec- tromagnetic stirrer unit is mounted on the outer surface of the head. Al- ternatively, the electromagnetic stirrer unit is mounted above of the head of the mold.The mold is conical shaped and its head is arranged at an end of the mold that has a larger diameter. In one embodiment of the invention, the electromagnetic stirrer unit is mounted on the outer surface of the head. Al- ternatively, the electromagnetic stirrer unit is mounted above the head of the mold.
BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be explained more closely by the description of dif- ferent embodiments of the invention and with reference to the appended figures. 10 15 20 25 30 Fig. 1a shows a schematic view of an apparatus according to one embod- iment of the invention, wherein an electromagnetic stir unit is mounted on the outer surface of the head of a mold.BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be explained more closely by the description of dif- ferent embodiments of the invention and with reference to the appended figures. 10 15 20 25 30 Fig. 1a shows a schematic view of an apparatus according to one embodiment of the invention, wherein an electromagnetic stir unit is mounted on the outer surface of the head of a mold.
Fig. 1b shows a schematic view of an apparatus according to another em- bodiment of the invention, wherein an electromagnetic stir unit is mounted above of the head of the mold.Fig. 1b shows a schematic view of an apparatus according to another em- bodiment of the invention, wherein an electromagnetic stir unit is mounted above of the head of the mold.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION Figure 1a shows a schematic view of an apparatus according to a first em- bodiment of the invention, wherein an electromagnetic stir unit is mounted on the outer surface of the head of a mold.DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION Figure 1a shows a schematic view of an apparatus according to a first em- bodiment of the invention, wherein an electromagnetic stir unit is mounted on the outer surface of the head of a mold.
Figure 1b shows a schematic view of an apparatus according to a second embodiment of the invention, wherein an electromagnetic stir unit is mounted above of the head of the mold.Figure 1b shows a schematic view of an apparatus according to a second embodiment of the invention, wherein an electromagnetic stir unit is mounted above the head of the mold.
With reference to Figure 1a and 1b, the apparatus 1 comprises an elec- tromagnetic stirrer unit 10 for electromagnetically stirring steel ingot in a mold 2, a multi-phase AC current supply 20 operatively connected to the electromagnetic stirrer unit 10, and a control unit 30 operatively connected to the multi-phase AC current supply 20 to control the operation of the electromagnetic stirrer unit. ln those examples, the control unit 30 and the multi-phase AC current supply 20 are separate units, but they may be also configured to operate the electromagnetic stirring unit 12 as a single unit.With reference to Figure 1a and 1b, the apparatus 1 comprises an electromagnetic stirrer unit 10 for electromagnetically stirring steel ingot in a mold 2, a multi-phase AC current supply 20 operatively connected to the electromagnetic stirrer unit 10, and a control unit 30 operatively connected to the multi-phase AC current supply 20 to control the operation of the electromagnetic stirrer unit. In those examples, the control unit 30 and the multi-phase AC current supply 20 are separate units, but they may also be configured to operate the electromagnetic stirring unit 12 as a single unit.
The mold 2 has a conical shape and is made of cast iron, wherein molten steel/melt 24 is filled. Its bottom/base has a smaller diameter, while its top/head has a larger diameter. The electromagnetic stirrer unit 10 may be arranged adjacently to the outer surface of the mold and arranged for stir- ring molten steel poured from a teeming ladle (not shown in the figures). 10 15 20 25 30 35 ln the first embodiment, the electromagnetic stir unit 10 comprises an electromagnetic stirrer 12 disposing circularly on the outer surface of the head 22 of the mold. With this arrangement, a circulating horizontal stir- ring is applied at the head of the mold, which creates a strong circulating flow covering the entire solidification front in a homogeneous fashion. This flow may have a velocity in the range 0.3-0.5 m/s and a vertical speed in the range 0-0.15 m/s. This arrangement may minimize segregation prob- lems since the flow speed homogenizes temperatures in the liquid and breaks off the dendrite tips of the solidification front to provide a homoge- neously equiaxed solidification with impurities distributed homogeneously. ln the second embodiment, a linear straight electromagnetic stirrer 14 is arranged on top of the head 22 of the mold 2. Thus the stirrer creates ver- tically circulating flow pattern induced in ingot, which may achieve a verti- cal speed in the range 0.3-0.5 m/s in the liquid transporting molten steel in a vertical circulation loop. This vertical speed enables a vertical transport of detrimental inclusions and thus an easier removal of the detrimental inclusions.The mold 2 has a conical shape and is made of cast iron, where molten steel / melt 24 is filled. Its bottom / base has a smaller diameter, while its top / head has a larger diameter. The electromagnetic stirrer unit 10 may be arranged adjacently to the outer surface of the mold and arranged for stir- ring molten steel poured from a teeming ladle (not shown in the figures). 10 15 20 25 30 35 ln the first embodiment, the electromagnetic stir unit 10 comprises an electromagnetic stirrer 12 disposing circularly on the outer surface of the head 22 of the mold. With this arrangement, a circulating horizontal stir- ring is applied at the head of the mold, which creates a strong circulating flow covering the entire solidification front in a homogeneous fashion. This flow may have a velocity in the range 0.3-0.5 m / s and a vertical speed in the range 0-0.15 m / s. This arrangement may minimize segregation prob- lems since the flow speed homogenizes temperatures in the liquid and breaks off the dendrite tips of the solidification front to provide a homoge- neously equiaxed solidification with impurities distributed homogeneously. ln the second embodiment, a linear straight electromagnetic stirrer 14 is arranged on top of the head 22 of the mold 2. Thus the stirrer creates ver- tically circulating flow pattern induced in ingot, which may achieve a verti- cal speed in the range 0.3 -0.5 m / s in the liquid transporting molten steel in a vertical circulation loop. This vertical speed enables a vertical transport of detrimental inclusions and thus an easier removal of the detrimental inclusions.
When multiphase AC currents are fed to the electromagnetic stirrer unit 11, 12 or 14 a travelling magnetic field is generated in the mold. For the first embodiment, the direction of this travelling magnetic flux density wave is along the circumference of the mold, while for the second embodiment along the stirrer length at the top of the mold. The harmonic magnetic field wave induces eddy currents in the electrically conducting ingot, combining with the magnetic field to produce a force distribution in the ingot. The main force direction is aligned with the travelling magnetic wave, thus cre- ating a stirring flow in the molten steel.When multiphase AC currents are fed to the electromagnetic stirrer unit 11, 12 or 14 a traveling magnetic field is generated in the mold. For the first embodiment, the direction of this traveling magnetic flux density wave is along the circumference of the mold, while for the second embodiment along the stirrer length at the top of the mold. The harmonic magnetic field wave induces eddy currents in the electrically conducting ingot, combining with the magnetic field to produce a force distribution in the ingot. The main force direction is aligned with the traveling magnetic wave, thus creating a stirring flow in the molten steel.
Due to the application of electromagnetic stirring to the ingot casting dur- ing solidification, the flow of the molten steel is drastically strengthened and controllable. The strong flow homogenizes temperatures in the melt and breaks off the dendrite tips. Therefore the equiaxed ratio of a solidi- fied product is increased. The flow circulation also washes non-metallic inclusions off the solidification front. Moreover, by the buoyancy effect due to the density difference between steel and non-metallic particles, the flow circulation enables inclusions to float up to the top of the mold where they can be extracted from the solidified clean steel. Thus, a final product of high quality is obtained.Due to the application of electromagnetic stirring to the ingot casting dur- ing solidification, the flow of the molten steel is drastically strengthened and controllable. The strong flow homogenizes temperatures in the melt and breaks off the dendrite tips. Therefore the equiaxed ratio of a solidi- fied product is increased. The flow circulation also washes non-metallic inclusions off the solidification front. Moreover, by the buoyancy effect due to the density difference between steel and non-metallic particles, the flow circulation enables inclusions to float up to the top of the mold where they can be extracted from the solidified clean steel. Thus, a final product of high quality is obtained.
Claims (3)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE1300554A SE1300554A1 (en) | 2013-08-20 | 2013-08-20 | An apparatus for stirring in steel ingots in an ingot molding process |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE1300554A SE1300554A1 (en) | 2013-08-20 | 2013-08-20 | An apparatus for stirring in steel ingots in an ingot molding process |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| SE1300554A1 true SE1300554A1 (en) | 2013-08-30 |
Family
ID=49182589
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| SE1300554A SE1300554A1 (en) | 2013-08-20 | 2013-08-20 | An apparatus for stirring in steel ingots in an ingot molding process |
Country Status (1)
| Country | Link |
|---|---|
| SE (1) | SE1300554A1 (en) |
-
2013
- 2013-08-20 SE SE1300554A patent/SE1300554A1/en not_active Application Discontinuation
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