CA1216430A - Vacuum treating steels - Google Patents
Vacuum treating steelsInfo
- Publication number
- CA1216430A CA1216430A CA000445735A CA445735A CA1216430A CA 1216430 A CA1216430 A CA 1216430A CA 000445735 A CA000445735 A CA 000445735A CA 445735 A CA445735 A CA 445735A CA 1216430 A CA1216430 A CA 1216430A
- Authority
- CA
- Canada
- Prior art keywords
- tube
- vacuum
- rod
- bath
- molten
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/10—Handling in a vacuum
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
- C22B9/04—Refining by applying a vacuum
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Mechanical Engineering (AREA)
- Treatment Of Steel In Its Molten State (AREA)
- Manufacture And Refinement Of Metals (AREA)
- Superconductors And Manufacturing Methods Therefor (AREA)
- Coating With Molten Metal (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Molten steel or other electroconductive metal is treated with vacuum to remove dissolved gases therefrom. A rod of molten steel is drawn from a bath by applying vacuum to a vertical tube dipping into the molten bath. An electrical coil surrounding the tube applies an intense magnetic field to the steel rod by the passage of high frequency alternating current through the coil. The rod is compressed radially inwardly by the magnetic field exposing the whole of the external surface of the rod to vacuum. At the same time, the induced eddy currents superheat the steel rod. The large surface area of application of vacuum combined with the narrow dimension through which the gas must travel ensure rapid and efficient removal of the gases. The procedure is repeated until all the steel in the bath has been treated. Lack of contact of the steel rod with the tube surface eliminates loss of heat by convection and the superheating of the steel rod by the eddy currents ensures that the overall heat losses are minimal during processing of the molten metal bath.
Molten steel or other electroconductive metal is treated with vacuum to remove dissolved gases therefrom. A rod of molten steel is drawn from a bath by applying vacuum to a vertical tube dipping into the molten bath. An electrical coil surrounding the tube applies an intense magnetic field to the steel rod by the passage of high frequency alternating current through the coil. The rod is compressed radially inwardly by the magnetic field exposing the whole of the external surface of the rod to vacuum. At the same time, the induced eddy currents superheat the steel rod. The large surface area of application of vacuum combined with the narrow dimension through which the gas must travel ensure rapid and efficient removal of the gases. The procedure is repeated until all the steel in the bath has been treated. Lack of contact of the steel rod with the tube surface eliminates loss of heat by convection and the superheating of the steel rod by the eddy currents ensures that the overall heat losses are minimal during processing of the molten metal bath.
Description
~21~
TITLE OF INV~NTION
VACUUM TREATIIIG STEELS
FIELD OF INVENTION
The present invention relates to the processing of steels~
BACKGROUND TO THE INVENTION
The presence of dissolved gases, including hydrogen, oxygen and nitrogen, in metals, for example, steels can cause seve~al undesirable effects, such as, internal ruptures or flaking, embrittlement, void formation and inclusions. It i5 desirable, therefore, to remove the dissolved gases prior to solidification of the metal and vacuum often is employed for such purpose. The molten metal is housed in a large chamber and is agitated to facilitate removal of the gasss by vacuum applied to the chamber. This prior art operation, however, is somewhat unsatisfactory, in that a molten metal to be treated must be tapped from a furnace with sufficient temperature to withstand heat losses during treatment, and efficient removal of the gas is not achieved.
Lu~r OF I~V YIIC~
In accordance wlth the present invention, a novel method of degassing metals is provided. The invention is particularly applicable to the treatment of molten steel and ~ill be described mainly with ref2rence thereto, but the invention is also applicable to any other electroconductive metal. In the present invention, molten steel is drawn from a bath into a vertical column by the vacuum, d high frequency coil surrounds the vertical column and a high frequency alternating electrical curren-t is passed through the coil to provide an electrical field which compresses and contracts the vertical steel rod away from its confining walls. In this way the whole of the outer surface of the rod is exposed to vacuum and gas is drawn from the considerable surface area of the thin i,
TITLE OF INV~NTION
VACUUM TREATIIIG STEELS
FIELD OF INVENTION
The present invention relates to the processing of steels~
BACKGROUND TO THE INVENTION
The presence of dissolved gases, including hydrogen, oxygen and nitrogen, in metals, for example, steels can cause seve~al undesirable effects, such as, internal ruptures or flaking, embrittlement, void formation and inclusions. It i5 desirable, therefore, to remove the dissolved gases prior to solidification of the metal and vacuum often is employed for such purpose. The molten metal is housed in a large chamber and is agitated to facilitate removal of the gasss by vacuum applied to the chamber. This prior art operation, however, is somewhat unsatisfactory, in that a molten metal to be treated must be tapped from a furnace with sufficient temperature to withstand heat losses during treatment, and efficient removal of the gas is not achieved.
Lu~r OF I~V YIIC~
In accordance wlth the present invention, a novel method of degassing metals is provided. The invention is particularly applicable to the treatment of molten steel and ~ill be described mainly with ref2rence thereto, but the invention is also applicable to any other electroconductive metal. In the present invention, molten steel is drawn from a bath into a vertical column by the vacuum, d high frequency coil surrounds the vertical column and a high frequency alternating electrical curren-t is passed through the coil to provide an electrical field which compresses and contracts the vertical steel rod away from its confining walls. In this way the whole of the outer surface of the rod is exposed to vacuum and gas is drawn from the considerable surface area of the thin i,
2 ~ 3~
steel rod exposed to the vacuum. The vacuum then is shut off, permitting the rod of degassed steel to return to thP bath. The process then is repeated until all the gases have been removed. While being subjected to vacuum, the molten steel column is al50 inductively superheated by the eddy currents induced in the molten steel.
In addition to effecting efficient removal of dissolve~ gases from the molten steel, heat losses from the molten steel are minimized, since no conductive losses occur through contact with the confining walls and heat is added to the steel rod through the induced eddy currents.
As a result of the minimization o:E heat losses during treatment, the temperature at which the molten metal needs to be tapped from the furnace can be lower than in the prior art, typically about 1600C for the present invention in comparison with about 1650C for the pr~or art.
Although only a portion of the molten steel is treated at one time, the high efficiency of gas removal from the large surface area of the thin steel rod enables the dissolved gas content of the steel to be depleted to a ~Tery low level in a manageable number of passes. Depen~ing upon the volume of molten steel to be vacuum treated, a single treatment unit may be employed or a plurality of such treatment units may be used.
BRIEF DESCRIPTION OF DRAWINGS
Figure 1 of the drawings is a sectional view illustrating one embodiment of an apparatus for effecting vacuum treating of steel in accordance with one embodiment of the invention; and Figure ~ is a close-up view of a portion of the apparatus of Figure 1.
DESCRIPTION OF PREFERRED EMBODIMENT
.
Referring to the drawings, a steel-treating apparatus 10 comprises a pot 12 containing a bath 14 of molten steel to be treated. The bath may be stirred by
steel rod exposed to the vacuum. The vacuum then is shut off, permitting the rod of degassed steel to return to thP bath. The process then is repeated until all the gases have been removed. While being subjected to vacuum, the molten steel column is al50 inductively superheated by the eddy currents induced in the molten steel.
In addition to effecting efficient removal of dissolve~ gases from the molten steel, heat losses from the molten steel are minimized, since no conductive losses occur through contact with the confining walls and heat is added to the steel rod through the induced eddy currents.
As a result of the minimization o:E heat losses during treatment, the temperature at which the molten metal needs to be tapped from the furnace can be lower than in the prior art, typically about 1600C for the present invention in comparison with about 1650C for the pr~or art.
Although only a portion of the molten steel is treated at one time, the high efficiency of gas removal from the large surface area of the thin steel rod enables the dissolved gas content of the steel to be depleted to a ~Tery low level in a manageable number of passes. Depen~ing upon the volume of molten steel to be vacuum treated, a single treatment unit may be employed or a plurality of such treatment units may be used.
BRIEF DESCRIPTION OF DRAWINGS
Figure 1 of the drawings is a sectional view illustrating one embodiment of an apparatus for effecting vacuum treating of steel in accordance with one embodiment of the invention; and Figure ~ is a close-up view of a portion of the apparatus of Figure 1.
DESCRIPTION OF PREFERRED EMBODIMENT
.
Referring to the drawings, a steel-treating apparatus 10 comprises a pot 12 containing a bath 14 of molten steel to be treated. The bath may be stirred by
3 ~
any convenient procedure, for example, argon gas stirrin~ or electromagnetic stirring.
A vacuum app!ication unit 16 is used to effect treatment of the steel. The unit comprises a support member 18 which overlies the top of the pot 12 to enclose the molten steel bath 14. A hollow tube 22 extends through the support member 18 and dips into the bath 14. The tube 22 may be constructed of any convenient non-electrically-conducting and non-magnetir material, such as heat resistant refractory material.
The hollow tube at its upper end communicates with a vacuum line 24 wh~reby vacuum may be applied to the interior of the tube 22. An electrical coil 26 is wound around the exterior of the tube 22 and is connected to a source of high frequency alternating current (not shown).
While a single vacuum application unit 16 is illustrated for treatment of the molten steel bath 14, a plurality of such units 16 may be employed, the number depending on the volume of molten steel to be treated.
OPERATION
In operation, vacuum is applied to the interior of the tube 22 by vacuum line 24, causing ~ rod of molten steel 2~ to be drawn up into the hollow tube 22. A
high frequency alternating current, preferably at a frequency of about 25 to about 50 kHz, is passed through the coil 26. The resulting magnetic field establishes eddy currents in the molten steel rod 28 which adds superheat and counteracts heat losses. The eddy currents also result in a repellant magnetic field which causes the molten steel rod 28 to contract radially inwardly and to become detached from the inner wall of the tube 22, as shown in the detailed close up of Figure 2.
Since the molten steel rod 28 is detached from the inside wall of the tube 22, the whole of the exterior surface of the steel rod 28 over the length of the coil 26 is exposed to the vacuum applied by the vacuum tube .
24~ The narrow diameter of the rod 28 and the large surface area of the rod which is exposed to the vacuum permit dissolved gases to be readily and substantially completely removed from the steel rod 28.
Once the vacuum treatment of the molten steel rod 28 is complete, the vacuum is shut off, permitting the vacuum treated rod 28 to return to the bath 14. When a plurality of vacuum application units 16 is used, the vacuum may be applied and released simultaneously to all or a selected number of the tubes 22 or may be applied and released sequentially to the tubes 22.
The procedure described above then is repeated a sufficient number of times to treat all the molten steel in the bath 14. In the vacuum treatment process, hydrogen, oxygen and nitrogen are removed, while carbon also is removed as a reaction product of carbon and oxygen.
The vacuum may have any desired value to achieve the drawing of the steel rod 28 into the tube 2~ and to withdraw the dissolved gases from the molten steel rod.
Usually, a vacuum of about 10 to about 300 torrs is used.
The nu~ber of cycles necessary to effect complete treatment depends on the ovarall volume of the molten metal, the diameter of the tube 2~ and the value of the vacuum~ Usually about 30 to 50 cycles is sufficient, with each cycle being about 30 to 60 seconds in duration.
The procedure of the invention enables dissolved gases to b~ removed from molten steel or other electroconductive metals efficiently and rapidly in an energy efficient manner. The present invention thereby overcomes the problems of prior art procedures fQr vacuum treating of such metals.
SUMMARY OF DISCLOSURE
_, In summary of this disclosure, the present invention provides a novel method and apparatus for vacuum treating of steel or other electroconductive metal to remove dissolved gases therefrom, which 5 ~.2~L~43~3 involves exposure of a large surface area o narrow thickness of the molten metal to the action of vacuum while simultaneously heati~g the metalO Modifications are possible within the scope of this invention.
2~ .
3~
any convenient procedure, for example, argon gas stirrin~ or electromagnetic stirring.
A vacuum app!ication unit 16 is used to effect treatment of the steel. The unit comprises a support member 18 which overlies the top of the pot 12 to enclose the molten steel bath 14. A hollow tube 22 extends through the support member 18 and dips into the bath 14. The tube 22 may be constructed of any convenient non-electrically-conducting and non-magnetir material, such as heat resistant refractory material.
The hollow tube at its upper end communicates with a vacuum line 24 wh~reby vacuum may be applied to the interior of the tube 22. An electrical coil 26 is wound around the exterior of the tube 22 and is connected to a source of high frequency alternating current (not shown).
While a single vacuum application unit 16 is illustrated for treatment of the molten steel bath 14, a plurality of such units 16 may be employed, the number depending on the volume of molten steel to be treated.
OPERATION
In operation, vacuum is applied to the interior of the tube 22 by vacuum line 24, causing ~ rod of molten steel 2~ to be drawn up into the hollow tube 22. A
high frequency alternating current, preferably at a frequency of about 25 to about 50 kHz, is passed through the coil 26. The resulting magnetic field establishes eddy currents in the molten steel rod 28 which adds superheat and counteracts heat losses. The eddy currents also result in a repellant magnetic field which causes the molten steel rod 28 to contract radially inwardly and to become detached from the inner wall of the tube 22, as shown in the detailed close up of Figure 2.
Since the molten steel rod 28 is detached from the inside wall of the tube 22, the whole of the exterior surface of the steel rod 28 over the length of the coil 26 is exposed to the vacuum applied by the vacuum tube .
24~ The narrow diameter of the rod 28 and the large surface area of the rod which is exposed to the vacuum permit dissolved gases to be readily and substantially completely removed from the steel rod 28.
Once the vacuum treatment of the molten steel rod 28 is complete, the vacuum is shut off, permitting the vacuum treated rod 28 to return to the bath 14. When a plurality of vacuum application units 16 is used, the vacuum may be applied and released simultaneously to all or a selected number of the tubes 22 or may be applied and released sequentially to the tubes 22.
The procedure described above then is repeated a sufficient number of times to treat all the molten steel in the bath 14. In the vacuum treatment process, hydrogen, oxygen and nitrogen are removed, while carbon also is removed as a reaction product of carbon and oxygen.
The vacuum may have any desired value to achieve the drawing of the steel rod 28 into the tube 2~ and to withdraw the dissolved gases from the molten steel rod.
Usually, a vacuum of about 10 to about 300 torrs is used.
The nu~ber of cycles necessary to effect complete treatment depends on the ovarall volume of the molten metal, the diameter of the tube 2~ and the value of the vacuum~ Usually about 30 to 50 cycles is sufficient, with each cycle being about 30 to 60 seconds in duration.
The procedure of the invention enables dissolved gases to b~ removed from molten steel or other electroconductive metals efficiently and rapidly in an energy efficient manner. The present invention thereby overcomes the problems of prior art procedures fQr vacuum treating of such metals.
SUMMARY OF DISCLOSURE
_, In summary of this disclosure, the present invention provides a novel method and apparatus for vacuum treating of steel or other electroconductive metal to remove dissolved gases therefrom, which 5 ~.2~L~43~3 involves exposure of a large surface area o narrow thickness of the molten metal to the action of vacuum while simultaneously heati~g the metalO Modifications are possible within the scope of this invention.
2~ .
3~
Claims (14)
1. A method for the vacuum treating of molten metals, which comprises:
applying vacuum to a tube dipping into a molten bath of an electroconductive metal to draw said molten metal into said tube and to form an elongate rod of said molten metal within said tube, and electromagnetically radially-inwardly compressing the elongate rod, so as to detach said elongate rod from the internal wall of said tube and to expose the external surface of the electromagnetically-compressed rod to said vacuum, thereby to withdraw dissolved gases from said molten metal rod.
applying vacuum to a tube dipping into a molten bath of an electroconductive metal to draw said molten metal into said tube and to form an elongate rod of said molten metal within said tube, and electromagnetically radially-inwardly compressing the elongate rod, so as to detach said elongate rod from the internal wall of said tube and to expose the external surface of the electromagnetically-compressed rod to said vacuum, thereby to withdraw dissolved gases from said molten metal rod.
2. The method of claim 1, wherein said electromagnetic compression is effected by forming an electric coil about the external surface of said tube and passing a high frequency alternating current through said coil.
3. The method of claim 2 wherein said frequency is about 25 to about 50 kHz.
4. The method of claim 1, including, prior to said vacuum application step, providing said molten bath of steel in a container, and inserting said tube into said molten metal bath so as to dip into said molten metal bath and to extend substantially vertically upwardly therefrom.
5. The method of claim 4 including, following said electromagnetic compression of said molten metal rod and when said exposure of the external surface of the electromagnetically-compressed rod to said vacuum has been effected for a desired period of time, releasing said vacuum from said tube to permit the resulting vacuum-treated rod to fall back into the molten bath.
6. The method of claim 5 carried out repetitively for a desired number of cycles to permit substantially complete withdrawal of dissolved gases from all the metal in said molten bath.
7. The method of claim 6, including stirring said molten bath during the repetitive operations.
8. The method of claim 1 wherein said tube is formed of heat-resistant refractory material.
9. The method of claim 1 wherein said electroconductive metal is steel.
10. The method of claim 1, wherein a plurality of tubes are dipped into said molten bath to each of which vacuum is applied and the elongate rod in each tube is electromagnetically-compressed.
11. An apparatus for the vacuum treating of an electroconductive metal, comprising:
an elongate tube of heat-resistant non-electrically-conducting and non-magnetic material, having an internal bore and having one end adapted to be dipped into a molten bath of electroconductive metal to be treated and the other end adapted for the attachment of a vacuum line thereto for application of vacuum to said bore;
a support member through which said tube projects a distance sufficient to dip into the bath of molten metal when said support member engages a pot containing said bath of molten metal and located adjacent one end of said tube; and an electrical coil wound about the external surface of said tube in the region of the length of the tube between said support member and the other end of said tube.
an elongate tube of heat-resistant non-electrically-conducting and non-magnetic material, having an internal bore and having one end adapted to be dipped into a molten bath of electroconductive metal to be treated and the other end adapted for the attachment of a vacuum line thereto for application of vacuum to said bore;
a support member through which said tube projects a distance sufficient to dip into the bath of molten metal when said support member engages a pot containing said bath of molten metal and located adjacent one end of said tube; and an electrical coil wound about the external surface of said tube in the region of the length of the tube between said support member and the other end of said tube.
12. The apparatus of claim 11 including means for applying vacuum to said bore at said other end of said tube.
13. The apparatus of claim 11 including means for passing high frequency alternating current through said electrical coil.
14. The apparatus of claim 11 wherein said tube is constructed of heat-resistant refractory material.
Priority Applications (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000445735A CA1216430A (en) | 1984-01-20 | 1984-01-20 | Vacuum treating steels |
| AT84308261T ATE39948T1 (en) | 1984-01-20 | 1984-11-28 | METHOD OF VACUUM TREATMENT OF STEEL. |
| DE8484308261T DE3476086D1 (en) | 1984-01-20 | 1984-11-28 | Vacuum treating steels |
| EP84308261A EP0151872B1 (en) | 1984-01-20 | 1984-11-28 | Vacuum treating steels |
| JP60005115A JPS60159110A (en) | 1984-01-20 | 1985-01-17 | Metal vacuum treatment and device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000445735A CA1216430A (en) | 1984-01-20 | 1984-01-20 | Vacuum treating steels |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1216430A true CA1216430A (en) | 1987-01-13 |
Family
ID=4126993
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000445735A Expired CA1216430A (en) | 1984-01-20 | 1984-01-20 | Vacuum treating steels |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0151872B1 (en) |
| JP (1) | JPS60159110A (en) |
| AT (1) | ATE39948T1 (en) |
| CA (1) | CA1216430A (en) |
| DE (1) | DE3476086D1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU2046149C1 (en) * | 1994-01-19 | 1995-10-20 | Акционерное общество "Нижнетагильский металлургический комбинат" | Method of vacuum refining of metal and apparatus for performing the same |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AT138020B (en) * | 1933-07-19 | 1934-06-25 | Berndorfer Metallwarenfabrik | Method and device for degassing metal baths. |
| DE1147714B (en) * | 1957-08-01 | 1963-04-25 | Vacuumschmelze Ag | Device and method for holding and transporting electrically conductive, free-floating substances |
| DE1268790B (en) * | 1961-08-09 | 1968-05-22 | Erik Allan Olsson | Process for the continuous degassing of metal melts |
| US3347538A (en) * | 1965-04-28 | 1967-10-17 | Mc Graw Edison Co | Apparatus for the vacuum degassing of molten metal |
| DE1508214A1 (en) * | 1966-09-14 | 1970-03-05 | Kloeckner Werke Ag | Method and device for degassing molten metal, especially molten steel, under reduced pressure |
| US4298376A (en) * | 1980-04-14 | 1981-11-03 | Kobe Steel, Ltd. | Method for treating molten steel and apparatus therefor |
-
1984
- 1984-01-20 CA CA000445735A patent/CA1216430A/en not_active Expired
- 1984-11-28 EP EP84308261A patent/EP0151872B1/en not_active Expired
- 1984-11-28 DE DE8484308261T patent/DE3476086D1/en not_active Expired
- 1984-11-28 AT AT84308261T patent/ATE39948T1/en not_active IP Right Cessation
-
1985
- 1985-01-17 JP JP60005115A patent/JPS60159110A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| EP0151872A3 (en) | 1986-06-25 |
| JPH0142324B2 (en) | 1989-09-12 |
| JPS60159110A (en) | 1985-08-20 |
| EP0151872A2 (en) | 1985-08-21 |
| ATE39948T1 (en) | 1989-01-15 |
| DE3476086D1 (en) | 1989-02-16 |
| EP0151872B1 (en) | 1989-01-11 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |