CA1143132A - Feeding of casting powder - Google Patents
Feeding of casting powderInfo
- Publication number
- CA1143132A CA1143132A CA000324640A CA324640A CA1143132A CA 1143132 A CA1143132 A CA 1143132A CA 000324640 A CA000324640 A CA 000324640A CA 324640 A CA324640 A CA 324640A CA 1143132 A CA1143132 A CA 1143132A
- Authority
- CA
- Canada
- Prior art keywords
- powder
- gas
- casting
- fluidized
- bed
- 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
-
- 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
- B22D11/108—Feeding additives, powders, or the like
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Continuous Casting (AREA)
- Manufacture Of Metal Powder And Suspensions Thereof (AREA)
- Cosmetics (AREA)
Abstract
Abstract of the Disclosure Powder is converted into the fluidized state by means of a pressurized, reacting or nonreacting gas, causing the fluidized powder to flow into a mold. The gas flow is adjusted to avoid, or at least impede, the development of a dust cloud.
Description
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The present invention relates to a method for f~eding casting additives such as casting powdcr to the surface of or into a bath of molten metal such as it exists in molds.
It is common practice in casting engineering to provide additives to the surface of the molten metal in the mold. Conventionally, operating personnel manually performed the feeding in one form or another.
Alternatively, pneumatic devices are used, being possibly of a variety which is combined with other types of mechanical and conveying devices.
Also, a high degree of automation has been introduced in this field. Manual feeding is rather primitive and not very accurate. Moreover, participating personnel are bothered to a considerable extent by the dust as it develops during the application of the casting powder. Another drawback is the lack of uniformity in the application which results in rather poor surface texture of the casting, particularly in the case of continuous casting.
The German printed patent applications Nos. 2,653,306 and
The present invention relates to a method for f~eding casting additives such as casting powdcr to the surface of or into a bath of molten metal such as it exists in molds.
It is common practice in casting engineering to provide additives to the surface of the molten metal in the mold. Conventionally, operating personnel manually performed the feeding in one form or another.
Alternatively, pneumatic devices are used, being possibly of a variety which is combined with other types of mechanical and conveying devices.
Also, a high degree of automation has been introduced in this field. Manual feeding is rather primitive and not very accurate. Moreover, participating personnel are bothered to a considerable extent by the dust as it develops during the application of the casting powder. Another drawback is the lack of uniformity in the application which results in rather poor surface texture of the casting, particularly in the case of continuous casting.
The German printed patent applications Nos. 2,653,306 and
2,651,266 describe pneumatic and pneumatic-mechanical feeders for casting powder. These devices are of a rather complicated construction and produce a considerable amount of flying dust. The dust development can be reducedp for example, in a device as shown in the German application No. 2,653,306 by placing a container or the like as a shield between the pneumatic and the mechanical sections. Such a shield, however, does not completely eliminate the development of flying dust. It should be noted further that pneumatic transport of casting powder inherently involves the production of flying dust and, as an unfortunate side effect, the components and constituents of the powder begin to physically separate so that the powder is in a rather non-homogeneous state. Another factor to be considered is the required separation of the conveyor gas from the casting powder. The separation ~ .
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equipment is quite extensive, and the entire application and feeding equipment experiences a considerable thermal load and temperature dif-ferential which enhances wear. Still another drawback of the known auto-mated methods and devices is that ~he casting powder is applied in a point-like manner via jets emerging from nozzles. This, again, is a factor which contributes to the lack of uniformity in the application resulting in non-uniform slag layers on top of the molten metal bath.
It is an object of the present invention to pro~ide a method which permits the controlled application of casting additi~es onto the surface of or into a bath of molten me~al and in a manner which ensures a substantially uniform distribution across the surface.
According to the present invention, there is provided method of feeding casting powder to molten metal in a mold, comprising the steps of providing a supply of powder; causing a mass of the powder to be disposed in a fluidized state by means of a pressurized gas; and causing and permitting the fluidized powder mass to flow into the mold, the gas pressure being insufficient to form a powder dust cloud.
Thus, in accordance with the present invention, the casting powder is fluidized, i.e., a fluidized bed of casting powder is established under conditions which permit the fluidized powder to flow out of the bed and ontoJ or into, the bath of molten metal to which such powder is to be applied. The fluidized state is established by providing a bed of cas~ing powder which is then subjected to a flow of gas in such a manner that the powder becomes fluidized and flows out of the bed. Application of the fluidizing agent is limited to such an extent that, with certainty, a powder cloud is not produced. It is found to be of particular advantage to meter the application of fluidized casting powder to the bath of molten ~43~
metal by causing fluidization of a bed of powder in an intermittent fashion preferably on Q periodic basis.
The primary function of the application of a gas is to convert a heaped quantity of po~der into a fluid, of course, without melting it. An inert gas may be used in order to avoid any unwanted side reactions because the casting powder is usually a blend of different components. In such cases, however, the casting powder may be subjected to a specific chemical reac*ion just prior to its application and; it is therefore, of advantage to employ a fluidization gas which will, in fact, produce and/or enhance such a chemical reaction.
The method in accordance with the present invention avoids the disadvantages and the drawbacks of known casting powder applications outlined above. It is emphasized that the state in which the powder is applied differs on one hand from a mere powder heap, i.e.S a firm bed of powder, and on the other hand from a flying dust cloud uhich is the result of pneumatic con-veyance. The decisive aspect is that gas is applied a~ such a rate that the powder behaves like a liquid. Hence, the application of fluidizing gas must be limited to such an extent that a cloud of dust is not produced.
While the specification concludes with claims particularly point-ing out and distinctly claiming the subject matter uhich is regarded as theinvention, it is believed that the invention, and its objects and features will be better understood from the follouing description of at present pre-ferred embodiments and described in connection with the accompanying drawings in which:
Figure 1 shows several gTaphical representations for explaining the method and function of the present invention;
Figure 2 is a perspective vieu of a casting powder applicator by means of which the inventive method can be practiced ~, ' ' . ' :~3~$~
Figure 3 is a top view of a portion of a machine for continuous casting in which two applicators of the type shown in Figure 2 are attached to a tundish; and Figure 4 is a side view of the device shown in Pigure 3.
Proceeding now to the detailed description of the drawings, we turn first to the diagrams of Figure 1. The diagram of Figure lA shows particularly the pressure loss ~P of a gas over the height H of a bed of fluidizable powder, plotted against the velocity Vg of such a gas. For rea-sons of scaling, the diagram is drawn on a log-log scale. The diagram reveals three ranges denoted respectively F, FL, and FLW.
The range F represents a range of low gas speeds in which the powder bed remains unfluidized. In other words, the height of the bed is so large or, for reasons of the powder consistency, the pressure drop is so low that for a given velocity, the flowing gas cannot lift the powder against gravity. The log-log relationship is a proportional one, the direct function of the relation being that of a parabola accordingly.
Upon reaching a critical velocity VgU, fluldization begins (range FL). This phenomenon is represented by the fact that the ratio ~P over H
remains almost constant with increasing gas speed. Specificially, as th0 speed of flow of the gas through the powder increases, and the bed becomes fluidized, the height of the bed increases as the particles ar0 being lifted by the upflow of gas; but that increase is proportional to the increase in pressure drop so that the ratio P/H remains, ind~ed, constant.
This state o fluidization i5 maintained until a second critical velocity Vg bas been reached. Figure 1 reveals that in the range FLW, established by gas velocities higher than Vg , the characteristic merges into a parabola being representative of the fact that the relationship between gas velocity and pressure drop now follows the Bernoulli equation, Moreover, , : :
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equipment is quite extensive, and the entire application and feeding equipment experiences a considerable thermal load and temperature dif-ferential which enhances wear. Still another drawback of the known auto-mated methods and devices is that ~he casting powder is applied in a point-like manner via jets emerging from nozzles. This, again, is a factor which contributes to the lack of uniformity in the application resulting in non-uniform slag layers on top of the molten metal bath.
It is an object of the present invention to pro~ide a method which permits the controlled application of casting additi~es onto the surface of or into a bath of molten me~al and in a manner which ensures a substantially uniform distribution across the surface.
According to the present invention, there is provided method of feeding casting powder to molten metal in a mold, comprising the steps of providing a supply of powder; causing a mass of the powder to be disposed in a fluidized state by means of a pressurized gas; and causing and permitting the fluidized powder mass to flow into the mold, the gas pressure being insufficient to form a powder dust cloud.
Thus, in accordance with the present invention, the casting powder is fluidized, i.e., a fluidized bed of casting powder is established under conditions which permit the fluidized powder to flow out of the bed and ontoJ or into, the bath of molten metal to which such powder is to be applied. The fluidized state is established by providing a bed of cas~ing powder which is then subjected to a flow of gas in such a manner that the powder becomes fluidized and flows out of the bed. Application of the fluidizing agent is limited to such an extent that, with certainty, a powder cloud is not produced. It is found to be of particular advantage to meter the application of fluidized casting powder to the bath of molten ~43~
metal by causing fluidization of a bed of powder in an intermittent fashion preferably on Q periodic basis.
The primary function of the application of a gas is to convert a heaped quantity of po~der into a fluid, of course, without melting it. An inert gas may be used in order to avoid any unwanted side reactions because the casting powder is usually a blend of different components. In such cases, however, the casting powder may be subjected to a specific chemical reac*ion just prior to its application and; it is therefore, of advantage to employ a fluidization gas which will, in fact, produce and/or enhance such a chemical reaction.
The method in accordance with the present invention avoids the disadvantages and the drawbacks of known casting powder applications outlined above. It is emphasized that the state in which the powder is applied differs on one hand from a mere powder heap, i.e.S a firm bed of powder, and on the other hand from a flying dust cloud uhich is the result of pneumatic con-veyance. The decisive aspect is that gas is applied a~ such a rate that the powder behaves like a liquid. Hence, the application of fluidizing gas must be limited to such an extent that a cloud of dust is not produced.
While the specification concludes with claims particularly point-ing out and distinctly claiming the subject matter uhich is regarded as theinvention, it is believed that the invention, and its objects and features will be better understood from the follouing description of at present pre-ferred embodiments and described in connection with the accompanying drawings in which:
Figure 1 shows several gTaphical representations for explaining the method and function of the present invention;
Figure 2 is a perspective vieu of a casting powder applicator by means of which the inventive method can be practiced ~, ' ' . ' :~3~$~
Figure 3 is a top view of a portion of a machine for continuous casting in which two applicators of the type shown in Figure 2 are attached to a tundish; and Figure 4 is a side view of the device shown in Pigure 3.
Proceeding now to the detailed description of the drawings, we turn first to the diagrams of Figure 1. The diagram of Figure lA shows particularly the pressure loss ~P of a gas over the height H of a bed of fluidizable powder, plotted against the velocity Vg of such a gas. For rea-sons of scaling, the diagram is drawn on a log-log scale. The diagram reveals three ranges denoted respectively F, FL, and FLW.
The range F represents a range of low gas speeds in which the powder bed remains unfluidized. In other words, the height of the bed is so large or, for reasons of the powder consistency, the pressure drop is so low that for a given velocity, the flowing gas cannot lift the powder against gravity. The log-log relationship is a proportional one, the direct function of the relation being that of a parabola accordingly.
Upon reaching a critical velocity VgU, fluldization begins (range FL). This phenomenon is represented by the fact that the ratio ~P over H
remains almost constant with increasing gas speed. Specificially, as th0 speed of flow of the gas through the powder increases, and the bed becomes fluidized, the height of the bed increases as the particles ar0 being lifted by the upflow of gas; but that increase is proportional to the increase in pressure drop so that the ratio P/H remains, ind~ed, constant.
This state o fluidization i5 maintained until a second critical velocity Vg bas been reached. Figure 1 reveals that in the range FLW, established by gas velocities higher than Vg , the characteristic merges into a parabola being representative of the fact that the relationship between gas velocity and pressure drop now follows the Bernoulli equation, Moreover, , : :
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the gas flow at these high speeds converts the powder into a flying dust cloud.
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-g~~ Figure lB shows a curve-P~ illustrating the corresponding distribu-tion of density in relation to gas speed. The two diagrams of Figures lA and lB are drawn in ali~nmentJ with corresponding velocity scale values, to permit the same identification of the speed ranges ~, FL, and PLW. A bed of un~
fluidized powder being flown through by gas at a velocity below vgU changes the overall apparent density very little. ~owever, once that lower and criti-cal velocity has been exceeded, the density drops with increasing speed. This decrease in density isJ of course, the equivalent to an increase in the height of the bed.
The figure lB shows also a curve dJ representing the density of some dust that develops during the 1uidization, above the fluid bed. The density of the powder drops with speed and the density of the dust increases.
When the two curves P and d merge, the fluid bed is converted into a flying dust cloud, where density decreases with speed.
The curve in Figure lC is drawn solely for the purpose of illus-trating an in~eresting thermodynamic analogy. The ordinate shows the density of a material which remains solid at temperatures below melting point Ts.
The density M of the material declines at higher temperature, whileJ in a 20 closed system, vapor or steam develops uhose density (s) increases with tem-perature. At the critical temperature Tg J those twv curves merge and only steam remains whose density continues to drop with temperature above Tg.
In accordance with the method of the present invention, a quan-tity of powder is to be con~erted into a fluidized bedO Suitable equipment is used ~or permitting powder to be fluidized and to be applied in the fluidized state, i.e., to flow towards the top or surface of a bath of molten metal. Figure 2 illustrates such a device. The device includes a bin 1, containing a supply o casting pouder and being open at the top to permit the ' ~ ' ~ " ' ' ' , ', ' 43~3;2 contents to be replenished. A duct 3 with a front opening extends laterally from bin 1, there being a transition zone 13 established between the generally vertically oriented main portion of the bin, and the duc~ 3 proper. This assembly is as far as a powder is concerned closed by a gas permeable parti~ion
the gas flow at these high speeds converts the powder into a flying dust cloud.
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-g~~ Figure lB shows a curve-P~ illustrating the corresponding distribu-tion of density in relation to gas speed. The two diagrams of Figures lA and lB are drawn in ali~nmentJ with corresponding velocity scale values, to permit the same identification of the speed ranges ~, FL, and PLW. A bed of un~
fluidized powder being flown through by gas at a velocity below vgU changes the overall apparent density very little. ~owever, once that lower and criti-cal velocity has been exceeded, the density drops with increasing speed. This decrease in density isJ of course, the equivalent to an increase in the height of the bed.
The figure lB shows also a curve dJ representing the density of some dust that develops during the 1uidization, above the fluid bed. The density of the powder drops with speed and the density of the dust increases.
When the two curves P and d merge, the fluid bed is converted into a flying dust cloud, where density decreases with speed.
The curve in Figure lC is drawn solely for the purpose of illus-trating an in~eresting thermodynamic analogy. The ordinate shows the density of a material which remains solid at temperatures below melting point Ts.
The density M of the material declines at higher temperature, whileJ in a 20 closed system, vapor or steam develops uhose density (s) increases with tem-perature. At the critical temperature Tg J those twv curves merge and only steam remains whose density continues to drop with temperature above Tg.
In accordance with the method of the present invention, a quan-tity of powder is to be con~erted into a fluidized bedO Suitable equipment is used ~or permitting powder to be fluidized and to be applied in the fluidized state, i.e., to flow towards the top or surface of a bath of molten metal. Figure 2 illustrates such a device. The device includes a bin 1, containing a supply o casting pouder and being open at the top to permit the ' ~ ' ~ " ' ' ' , ', ' 43~3;2 contents to be replenished. A duct 3 with a front opening extends laterally from bin 1, there being a transition zone 13 established between the generally vertically oriented main portion of the bin, and the duc~ 3 proper. This assembly is as far as a powder is concerned closed by a gas permeable parti~ion
4, underneath of which is provided a plenum chamber 6 which is closed except for the permeability of the partition 4J constituting the top of that plenum chamber, further excepting an inlet 5 for pressurized gas. This particular applicator is disposed so that the front opening of the duct 3 is positioned above the open top of a mold cavity 7, being for example the cavity of a mold for continuous casting.
The bin 1 is filled with powder which will pour into the transi-tion zone 13 as well as into the duct 3. As pressurized gas is applied to plenum 6, one establishes basically three beds. The first bed encompasses that portion of the powder in the bin 1 directly underneath the top opening thereof.
Next to that portion is the transition zone, followed by a zone for a bed of low height in duct 3.
As pressurized gas is applied to the plenum chamber 6, that gas penetrates little into the rather high bed in bin 1 and its state as an un-fluidized powder bed is not altered. Looking at Figure 1, it can be seen that the gas will have a low speed into the bed underneath the bin opening. The height is large and the flow resistance substantial, resulting in a rapid pres-sure drop. In fact, little gas flows into that portion of the powder and fluidization will not occur. On the other hand, the gas pressure as applied 17~m b er~
~_~ to the plenum 4~xuy~ is chosen so that the height of duct 3 is sufficiently low for establishing a fluidized bed in duct 3. The transition zone 13, there-fore, is that portion in which powder is moved from the solid type bed into the fluidization zone. The parameters, moreover, are chosen so that fluidized powder rather than a fLying dust cloud emerges from the froDt opening of duct 3.
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The pressure drop responsihle for fluidization is, of course, measured in the vertical. ~owever, a lateral pressure drop is suparimposed because the gas will follow the path of least resistance and will flow upward to a small extent only; the dominant gas flow is into and through duct 3, out of the opening thereof. As a consequence/a lateral pressure drop develops, causing the fluidized powder to flow into and through duct 3. Powder will pour out of the bin and into the transition zone to become fluidized therein.
The height of the bed in duct 3 is given by the height of the duct and the pressure drop is basically given by the di~ferential between ambient and plenum pressure. The latter is adjusted so that the resulting gas speed remains below V .
The gas pressure in plsnum 6 may be regulated in the feeder path for the gas to, thereby vary the amount of poNder flowing out. The front opening of duct 3 may be a variable one for the same reason. The rather wide ranges for speeds causing and maintaining ~luidization permit the rate of powder application to be controlled through speed and gas pres-sure control. In some cases, it may be desired to introduce intermittent control for the gas flow for metering the powder application in an ON OFF
fashion. The temperature of the slag layer on top o the bath in the mold may be a control parameter. Decisive in all these instances is that the powder, when flowing out of duct 3, will flow in the fluidized state, well below the critical speed of dust cloud development.
If the gas used to fluidize the powder is an inert gas, for ex-ample argon, no reaction will occur between any reactive component o~ the casting powder and the gas. Due to the reduced density of the fluidized bed in duct 3 as compared with the density of the powder in bin 1, one has, in fact, established a condition in which the casting powder is being _ 7 _ ~3~
applied under conditions o$ a reduced thermRl conduc~ivity. Frequently, carbon has been added to a casting powder primarily for purposes of loosen-ing up the powder as it i5 applied in the conyentional manner and for pur-poses of enhancing thermal isolation. The fluidization, as envisioned here, permits a reduction or even an elimination of the carbon con~ent in the casting powder because the fluidized powder has already a significantly reduc-ed conductivity.
For similar reasons, one may now use a casting powder which is either free from gas-releasing constituents such as borax, or has only a reduced content thereof. The fluidization by means o a gas and particular-ly by means of argon makes it unnecessary to provide the casting powder with such an inherent thermal insulation.
Applying the casting powder in the fluidized state ensures a very uniform coverage of the bath of molten metal with the powder. This, in turn, improves the surface texture and its overall uniformity and quality as far as the casting emerging through the bottom of cavity 7 is concerned. The inventive method, however, permits in addition that a supplemental use can be made of the fluidizing gas. This is particularly so when a reaction is needed between a casting add7tive in general and another medium just prior to application, or if the molten metal is to be protected from the uncontrolled entrance of oxygen.
For example, the gas to be used for fluidization may be an oxidizing gas, such as air enriched with oxygen. Oxygen will react with the casting powder particles, or with particular constituents thereof, such as carbon. The quantity of gas so applied can be controlled because a rather wide range of speeds and velocities is available for the fluidization so that sufficient quantities of the fluidization agent can be provided to react in a particular manner with the casting po~der, or a portion thereof.
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For e~ample, an organic gas may be used to react with a por~ion of the casting powder for the purpose of releasing carbon to the casting powder if such a supplemental carbon is needed for any reason.
Figures 3 and 4 illustrate how two such fluidization devices and casting powder applicators can be used in conjunction with a mold for continuous casting; the two applicators are attached to a tundish 8 by means of holders 2 and to both sides of an outlet pipe 9. Molten metal such as molten steel is fed through pipe 9 into the interior of the cavity of mold 7 for the discharge of the molten steel underneath the surface of the bath. A slag layer on top of the molten bath is replenished by the two powder applicators, causing powder to flow in liquid-like fashion onto slag 10. The liquid slag, in turn, runs along the mold wall cavity during con-tinuous casting.
The applicators 1 may be adjustable in their position in that they can be shifted along the three transverse a~es of a coordinate system, and they may well be mounted for pivoting in the hozizontal as well as above a vertical axis.
If the method is practiced in regular mold casting, the desir-able quantity of casting powder may be provided in a container in which a fluidized state of the powder is maintained through the application of gas 2~ under pressure. This container is placed into the mold and will be destroy-ed by the hot metal upon filling so that the fluidized casting powder is directly applied into the interiOr of such a mold and the additives will be flushed, or otherwise move up, to the surface of the bath upon filling of the mold. The period of time between charging such a container and introducing it into the molten metal should not exceed three minutes.
The invention is not limited to the embodiments described above, but all changes and modifîcations thereof not constituting depar~ures from the spirit and scope of the invention are intended to be included.
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The bin 1 is filled with powder which will pour into the transi-tion zone 13 as well as into the duct 3. As pressurized gas is applied to plenum 6, one establishes basically three beds. The first bed encompasses that portion of the powder in the bin 1 directly underneath the top opening thereof.
Next to that portion is the transition zone, followed by a zone for a bed of low height in duct 3.
As pressurized gas is applied to the plenum chamber 6, that gas penetrates little into the rather high bed in bin 1 and its state as an un-fluidized powder bed is not altered. Looking at Figure 1, it can be seen that the gas will have a low speed into the bed underneath the bin opening. The height is large and the flow resistance substantial, resulting in a rapid pres-sure drop. In fact, little gas flows into that portion of the powder and fluidization will not occur. On the other hand, the gas pressure as applied 17~m b er~
~_~ to the plenum 4~xuy~ is chosen so that the height of duct 3 is sufficiently low for establishing a fluidized bed in duct 3. The transition zone 13, there-fore, is that portion in which powder is moved from the solid type bed into the fluidization zone. The parameters, moreover, are chosen so that fluidized powder rather than a fLying dust cloud emerges from the froDt opening of duct 3.
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The pressure drop responsihle for fluidization is, of course, measured in the vertical. ~owever, a lateral pressure drop is suparimposed because the gas will follow the path of least resistance and will flow upward to a small extent only; the dominant gas flow is into and through duct 3, out of the opening thereof. As a consequence/a lateral pressure drop develops, causing the fluidized powder to flow into and through duct 3. Powder will pour out of the bin and into the transition zone to become fluidized therein.
The height of the bed in duct 3 is given by the height of the duct and the pressure drop is basically given by the di~ferential between ambient and plenum pressure. The latter is adjusted so that the resulting gas speed remains below V .
The gas pressure in plsnum 6 may be regulated in the feeder path for the gas to, thereby vary the amount of poNder flowing out. The front opening of duct 3 may be a variable one for the same reason. The rather wide ranges for speeds causing and maintaining ~luidization permit the rate of powder application to be controlled through speed and gas pres-sure control. In some cases, it may be desired to introduce intermittent control for the gas flow for metering the powder application in an ON OFF
fashion. The temperature of the slag layer on top o the bath in the mold may be a control parameter. Decisive in all these instances is that the powder, when flowing out of duct 3, will flow in the fluidized state, well below the critical speed of dust cloud development.
If the gas used to fluidize the powder is an inert gas, for ex-ample argon, no reaction will occur between any reactive component o~ the casting powder and the gas. Due to the reduced density of the fluidized bed in duct 3 as compared with the density of the powder in bin 1, one has, in fact, established a condition in which the casting powder is being _ 7 _ ~3~
applied under conditions o$ a reduced thermRl conduc~ivity. Frequently, carbon has been added to a casting powder primarily for purposes of loosen-ing up the powder as it i5 applied in the conyentional manner and for pur-poses of enhancing thermal isolation. The fluidization, as envisioned here, permits a reduction or even an elimination of the carbon con~ent in the casting powder because the fluidized powder has already a significantly reduc-ed conductivity.
For similar reasons, one may now use a casting powder which is either free from gas-releasing constituents such as borax, or has only a reduced content thereof. The fluidization by means o a gas and particular-ly by means of argon makes it unnecessary to provide the casting powder with such an inherent thermal insulation.
Applying the casting powder in the fluidized state ensures a very uniform coverage of the bath of molten metal with the powder. This, in turn, improves the surface texture and its overall uniformity and quality as far as the casting emerging through the bottom of cavity 7 is concerned. The inventive method, however, permits in addition that a supplemental use can be made of the fluidizing gas. This is particularly so when a reaction is needed between a casting add7tive in general and another medium just prior to application, or if the molten metal is to be protected from the uncontrolled entrance of oxygen.
For example, the gas to be used for fluidization may be an oxidizing gas, such as air enriched with oxygen. Oxygen will react with the casting powder particles, or with particular constituents thereof, such as carbon. The quantity of gas so applied can be controlled because a rather wide range of speeds and velocities is available for the fluidization so that sufficient quantities of the fluidization agent can be provided to react in a particular manner with the casting po~der, or a portion thereof.
' ~ ' .
~3~
For e~ample, an organic gas may be used to react with a por~ion of the casting powder for the purpose of releasing carbon to the casting powder if such a supplemental carbon is needed for any reason.
Figures 3 and 4 illustrate how two such fluidization devices and casting powder applicators can be used in conjunction with a mold for continuous casting; the two applicators are attached to a tundish 8 by means of holders 2 and to both sides of an outlet pipe 9. Molten metal such as molten steel is fed through pipe 9 into the interior of the cavity of mold 7 for the discharge of the molten steel underneath the surface of the bath. A slag layer on top of the molten bath is replenished by the two powder applicators, causing powder to flow in liquid-like fashion onto slag 10. The liquid slag, in turn, runs along the mold wall cavity during con-tinuous casting.
The applicators 1 may be adjustable in their position in that they can be shifted along the three transverse a~es of a coordinate system, and they may well be mounted for pivoting in the hozizontal as well as above a vertical axis.
If the method is practiced in regular mold casting, the desir-able quantity of casting powder may be provided in a container in which a fluidized state of the powder is maintained through the application of gas 2~ under pressure. This container is placed into the mold and will be destroy-ed by the hot metal upon filling so that the fluidized casting powder is directly applied into the interiOr of such a mold and the additives will be flushed, or otherwise move up, to the surface of the bath upon filling of the mold. The period of time between charging such a container and introducing it into the molten metal should not exceed three minutes.
The invention is not limited to the embodiments described above, but all changes and modifîcations thereof not constituting depar~ures from the spirit and scope of the invention are intended to be included.
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Claims (5)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Method of feeding casting powder to molten metal in a mold, comprising the steps of providing a supply of powder; causing a mass of the powder to be disposed in a fluidized state by means of a pressurized gas, and causing and permitting the fluidized powder mass to flow into the mold, the gas pressure being insufficient to form a powder dust cloud.
2. Method as in Claim 1 further comprising controlling the gas pressure in order to control the rate of flow of the fluidized casting powder.
3. Method as in Claim 1 or Claim 2 and including the step of intermittently causing said fluidized state.
4. Method as in Claim 1 and including using an inert gas for obtaining the fluidized state.
5. Method as in Claim 1 and including using a gas for obtaining the fluidized state which gas reacts with the casting powder or component thereof.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP2814492.5-24 | 1978-03-31 | ||
| DE19782814492 DE2814492A1 (en) | 1978-03-31 | 1978-03-31 | METHOD AND DEVICE FOR THE DOSED APPLICATION OF CASTING AIDS TO THE BATHROOM SURFACE OF METAL MELT |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1143132A true CA1143132A (en) | 1983-03-22 |
Family
ID=6036125
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000324640A Expired CA1143132A (en) | 1978-03-31 | 1979-04-02 | Feeding of casting powder |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS54133435A (en) |
| CA (1) | CA1143132A (en) |
| DE (1) | DE2814492A1 (en) |
| FR (1) | FR2421015A1 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE9304946U1 (en) * | 1993-04-01 | 1994-08-04 | Intocast GmbH Feuerfestprodukte und Gießhilfsmittel, 4030 Ratingen | Device for the continuous addition of powdered casting aids to the bath level of a melt in a continuous casting mold |
| FR2769526B1 (en) * | 1997-10-15 | 1999-12-03 | Soc Et Et De Realisations Tech | DEVICE FOR DISPENSING DAIRY POWDER AND CONTINUOUS CASTING INSTALLATION INCLUDING SUCH A DEVICE |
| JP4617756B2 (en) * | 2004-07-28 | 2011-01-26 | Ｊｆｅスチール株式会社 | Method of charging molten powder |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS4915532A (en) * | 1972-06-05 | 1974-02-12 | ||
| CH595161A5 (en) * | 1975-11-27 | 1978-01-31 | Concast Ag |
-
1978
- 1978-03-31 DE DE19782814492 patent/DE2814492A1/en not_active Ceased
-
1979
- 1979-02-27 FR FR7905029A patent/FR2421015A1/en active Granted
- 1979-03-28 JP JP3681179A patent/JPS54133435A/en active Pending
- 1979-04-02 CA CA000324640A patent/CA1143132A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DE2814492A1 (en) | 1979-10-04 |
| FR2421015A1 (en) | 1979-10-26 |
| JPS54133435A (en) | 1979-10-17 |
| FR2421015B1 (en) | 1982-04-16 |
| DE2814492B2 (en) | 1980-11-06 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |