CA1128307A - Slide gate and method for its manufacture - Google Patents
Slide gate and method for its manufactureInfo
- Publication number
- CA1128307A CA1128307A CA313,504A CA313504A CA1128307A CA 1128307 A CA1128307 A CA 1128307A CA 313504 A CA313504 A CA 313504A CA 1128307 A CA1128307 A CA 1128307A
- Authority
- CA
- Canada
- Prior art keywords
- refractory
- container
- slide gate
- metal
- gate portion
- 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
- B22D41/00—Casting melt-holding vessels, e.g. ladles, tundishes, cups or the like
- B22D41/14—Closures
- B22D41/22—Closures sliding-gate type, i.e. having a fixed plate and a movable plate in sliding contact with each other for selective registry of their openings
- B22D41/28—Plates therefor
- B22D41/30—Manufacturing or repairing thereof
- B22D41/32—Manufacturing or repairing thereof characterised by the materials used therefor
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- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Mechanical Engineering (AREA)
- Casting Support Devices, Ladles, And Melt Control Thereby (AREA)
- Valve Housings (AREA)
- Compositions Of Oxide Ceramics (AREA)
Abstract
Abstract of the Disclosure A refractory slide gate for a container dispensing molten material is comprised of a metal-supporting can filled with a low-fired coherent bonded refractory. The refractory is formed into a coherent refractory body within the metal supporting can and is directly affixed thereto, without the use of refractory mortar. An orifice through the refractory forms the means of controlling the flow of molten material.
Description
sackground of the Invention ;; The present invention relates to a sliding gate mechanism for a bottom pouring vessel used for the storage, transport and dispensiny of molten materials such as liquid metals.
In such devices, such as casting ladles or tundish pouring systems, the flow of molten metal from the vessel is `, controlled by a sliding gate mechanism. Such mechanisms i typically consist of a series of shutter plates having orifices or holes therethrough. The plates are attached under the vessel such that the plates may be displaced with respect to each other thereby aligning or misaligning the , orifices. This allows the liquid metal to flow from the vessel at a rate dependent upon the degree of coaxial alignment of the orifices.
Sliding gate valve systems have been successfully used to control molten metal flow from containing vessels for several years. E~amples of typical sliding gate valve systems can be found in U.S. Pa-tents 3,918,613 to Shapland and 3,581,948 to Detalle.
There are numerous advantages associated with using a sliding gate mechanism for pouring molten metals as compared to other flow-controlling mechanisms such as those using a stopper and an associated stopper rod. The absence o~ the stopper rod mechanism leading out of the container makes the slide gate pouring system particularly useful in vacuum or continuous casting. The sliding gate system, being outside the containing vessel, is less susceptible to the damaging effects of metal temperatures, chemical attack from molten slag and metal erosion. In addition, the sliding ~2~33~7 gate syste~ more effectively controls molten metal flow by controlling the degree of coa~i,al alignment of the urifices in the sliding plates.
Conventionally, sliding gate mechanisms include a prefired refractory plate which is assembled into a metal-supporting can after firing. The refractory/metal assembly is securely attached to the bottom of the vessel containing molten metal. Another refractory/metal assembly is matched to the first such that the degree of coaxial alignment of the orifices in the refractory plates will control the rate f molten metal flow from the vessel, through the sliding gate mechanism and into the appropriate mold. In order to insure an effecti~e seal between the refractory plates in the sliding gate mechanism, the mating surfaces of the prefired refractory plates are precision ground before they are attached to the containing vessel. This grinding operation normally occurs after the refractory is assembled into the supporting can, but the grinding operation may also be carried out prior to the assembly of the refractory into the metal ~
can.
The actual manufacture and assembly of the precision ground refractory is critical to the successful operation of the sliding gate system. A key element in this operation is the assembly of the prefired refractory plate and its supporting metal can. The bond between the refractory and the metal can is crucial. Weak bonds between the refractory and the metal can cause the refractory plate to wobble or shift within the metal can. This shifting hampers efforts to obtain a precision ground surface on the matching faces of the refractories necessar~ to form an effective seal. If an ~3~
3~7 effective seal canno~ be forrned, the entire assembly rnust be scrapped. In addition, if weak bonds are not discovered during assembly or during the grinding operation and the assembly is used to control the molten metal flow in a containing vessel, the refractory plate may shift when the sliding gate mechanism is used. The shifting may hamper the closing of the valve, causing leaks and, in general, may create a dangerous situation for operating personnel.
Currently, refractory/metal assemblies of the prior art are produced by pressing a prefired refractory plate into a preformed metal can using a refractory mortar as the bonding medium. In order to accomplish -this operation, the refractory mortar must be fluid enough to flow around the refractory plate during pressing such that the space (usually 1/8-1/4 inch) between the plate and the metal can is filled with mortar. A mortar with sufficient fluidity to fill this space undergoes considerable shrinkage upon firing.
Assemblies made in this manner exhibit significant amounts of separation between the metal can and the refractory plate where the mortar has shrunk from the metal can. This type of bonding is dependent on the mechanical locking associated with flaws or irregularities in the metal can. This means of locking the refractory plate to the metal can is unsatisfactor~
and refractory plates have been known to separate totally from the metal can and fall out of the assembly.
Another disadvantage of the prior art method of assembling the refractory in the metal can is the pressing operation. The pressing of prefired refractory plates that are slightly warped, flawed or dimensionally inaccurate can cause damage to the part which, in turn, causes the assembly 3f~7 to be scrapped. Even if the refractory plate is dimensionally ; correct, ir it is pressed in a me-tal can containing too thick or too stiff a mortar, or if there is an improper distribution of this stiff mortar in the metal can, the refractory plate or the metal can will be damaged by the ~pressing operation.
Still another disadvantage of this prior art assembly method is that uneven distribution of mortar between refractory plate and metal can can develop uneven stress ',distributions in the assembly. During the grinding operation, ithis may cause cracking of the refractory plate.
Yet another disadvantage of this operation is that the layer of mortar between refractory plate and metal can is necessarily thin. This precludes the use of mechanical ~locks between metal can and mortar such as metal pins, which could extend from the metal can into the mortar layer. A
system using mechanical interlocking means would require a relatively thick mortar layer. lhis would only aggravate shrinkage and mortar distribution problems Still another disadvantage of the prior art method ~of assembling the refractory in the metal can is the result of using prefired refractory plates. These plates are relatively difficult to manufacture and their manufacture entails a considerable cost in energy resources and manpower.
Refractory shapes which are off-size, warped, chipped, or ;cracked must be scrapped, which significantly adds to the cost of the finished product. The finished refractory plates are themselves brittle and easily damaged during shipping, handling and the assembly operation. Damage to the correctly manufactured refractory plates adds still more to their final cost.
3~7 ; Yet another disadvantage o~ the prior art products is the expense of the manufacturin~ method. The prefirecl refractory plates that are bonded to the me-tal cans are made of refractory mixes which are pressed, low fired and then high fired. These prefired refractory plates are then pressed into the metal can with refractory mortar and then refired at low temperature, usually about 600F. The elimination of the second pressing operation and the associated lo~ firing step, as well as the elimination of the high firing step, would considerably reduce the consumption of energy and the ultimate cost of the product.
The present invention is more economical to manufacture but produces a better product. It also results in safer I operation of the vessels dispensing molten metal with slide sate valves.
Additional advantages will be set forth in part in j the description which follows, and in part will be obvious , rom the description, or may be learned by practice of the ;~invention. The advantages of the invention may be reali~ed and attained by means of the combinations particularly pointed out in the appended claims.
Summary of the Invention . . , In accordance with the purposes of the invention, as embodied and broadly described herein, the present invention comprises a portion of a slide gate valve for controlling the flow of molten material, such as metal. The slide gate portion of the valve is comprised of a metal container, having an unfired coherent refractory directly affixed within it. The refractory is formed in the container from a particulate ceramic mixture that includes a binder~
1.
ll 83~7 Preferably, -the binder honds the particulate ceramic mixture into a coherent refractory by forming a chemical hond at a temperature below that of conventional ~'firing temperatures, as for example, at a temperature less ithan 700F. A particularly preferred binder for the present invention comprises a source of phosphorus pentoxide. It is also preferred that the source of phosphorus pentoxide forming the binder comprise phosphoric acid.
It is further preferred that the refractory be comprised of alumina or magnesia. The slide gate portion of the valve may also include means for fixing the refraciory ~! to its inner sur~ace, such as projections from the inner surface of the container.
The preferred method of forming a slide gate j~portion of the valve includes providing a container for ,containing the refractory and then placing a particulate mixture of ceramic material and a binder into the container.
The mixture is then shaped within the container by applying pressure. The mixture is then heated within the container to form a chemical bond between the ceramic particles, ~forming a coherent refractory and also fixing the refractory ~to the container.
It is preferred that where the mixture contains a source of phosphorus pentoxide to form the chemical bond, that the heating step subject the mixture to a temperature in the range of from ~00 to 600F.
;Brief Description of the Drawin~
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one embodiment of the invention and, together with the t~e~cription, serve to explain the principles of the invention.
~2fl3~7 ; Of the Drawings:
Fig. 1 is a cross-sectlonal view of a portion of a slide valve for a tundish.
I Fig. 2 is a detailed view of a portion of the ;embodiment of Fig. 1.
Fig. 3 is a cross-sectional view of a mold assembly for forming the embodiment depicted according to the method of the present invention.
Description of the Preferred Embodiments In order to effectively disclose the preferred ~embodiments of the present invention, the means of forming prior art struct~res is discussed.
soth the prior art and the present invention are directed to the production of a refractory slide gate component having the following general specifications:
Table 1 ApparentBulk Density Cold MOR Hot (2700F) MOR
Porosity (Modulus of Rupture) 14-18%2.89-3.05 gms/cc 2000+ psi 500 psi.
Prefired refractory plates for use in sliding gate systems of the prior art are generally manufactured of three general ceramic oxide classes: 85~ A12O3, 9090 A12O3 and 96% MgO. Within each class, blends of particulate ceramic materials are mixed with suitable binders and pressing agents. These particulate mixtures are fed to hydraulic, mechanical or impact presses for forming into suitable shapes. The pressed shapes are then dried at elevated temperatures, usually between 250 and 400F. The dried shapes are then fired at hi~h temperature to effect a ceramic bond between the particles. The temperature of the firing depends on the composition of the ceramic. Normal firing 1 , .i 8~7 temperatures are, however, usually in the range of from 2200F to 3200F. It should be evident that the elimination of such a firing step has a very significant effect on the economics of manufacturing such products due to the high energy cost associated with heating materials to such temperatures.
Table II illustrates the properties typically associated with prefired refractory plates of various compositions used in conventional slide gate systems.
Table II
Hot (2700~F) Ceramic Class Apparent Porosity Bulk Density Cold MOR MOR
85% Alumina 17% 2.82 gms/cc 3000 psi 1000 psi 90% Alumina 15% 2.90 gms/cc 2000 psi 2100 psi 96% MgO 16% 2.87 gms/cc 2300 psi 1900 psi The prefired plates that are within specification and have survived the various handling processes associated with their manufacture conventionally are then pressed into the supporting me-tal container using refractory mortar to bond the refractory plate to the metal container. The surface of the refractory plate may be ground to the appropriate finish and shaped prior to, or after, assembly into the metal container.
This method of manufacture has numerous shortcomings that have been set out above. In order to eliminate such shortcomings, the present invention was developed.
The present invention comprises a slide gate portion of a valve for controlling the flow of molten metal and a method for its manufacture.
~, .
~L~.21~3~7 In accordance with the invention, the slide yate portion of the valve includes a metal container. As herein embodied and most clearly illustrated in Fiy. 1, the slide gate portion 10 has a shaped metal con-tainer 12 surrounding the refractory 14. The metal container has several functions.
In the present invention, as opposed to prior art devices, the container forms a portion of the mold that shapes the particulate ceramic formed into the refractory 14.
The fact the container shapes the ceramic formed into the ;refractory and is in direct contact therewith, is a si~nificant departure from previously disclosed prior art devices. The shape of the container is dependent upon the mechanism used to actuate the slide gate portion of the valve. The shape of the container depicted in Fig. 1 is merely illustrative of one used typically in a slide valve for a tundish. With the exception of one specific feature, to be hereinafter disclosed, the shape of the container 12 is conventional.
The refractory 14 of the device of the present invention is not bonded to the container 12 with a refractory ;mortar. The refractory 14 abutts and bonds directly to the container 12. The direct bonding of the refractory to the container through the use of low fired refractories is another significant departure from the conventional devices of the prior art. The direct contact of the refractory to the container allows the present invention to include mechanical means for ~affixing the refractory 14 to the inner surface of the metal I ;
container.
As herein embodied and depicted in detail in Fig. 2, the container 12 of the present invention may include projections on the inner surface of the container 12. The ~10-~.2~3~7 projection ~8, shown in Fig. 2, is the edge of the container 12 that is bent or formed in a manner to project inwardly.
This embodiment is merely illustrative of a projection or projections that could be used to accomplish the same function.
The function of the projection(s) is to interlock with the refractory within the container to enhance and strengthen the attachment o~ the refractory to the container. Separation of the refractory from the container can cause catastrophic release of the molten metal being controlled by the valve.
Such an occurren~e is a very severe hazard to those using the equipment in addition to being wasteful and destructive o the equipment itself.
In accordance with the invention, the slide gate portion of the valve includes an unfired coherent refractory within the container. As herein embodied and depicted in Fig. 1, the slide gate portion 10 includes the coherent refractory 14. The refractory 14 is formed from particulate ;ceramic materials that can be rendered coherent by pressing followed by heating to a temperature below conventional firing temperatures. The refractory should also remain dimensionally stable when subjected to the temperatures of operation of the slide gate valve.
The refractory used in the present invention will depend on the type of molten materials being controlled with the slide gate valve. Basic refractories such as dead- ¦
burned magnesite or synthetic periclase may be used. The refractory can be modified by the addition of such materials as refractory grade chrome ore. Acid or neutral refractories such as alumina, aluminum silicate, mullite, zirconium oxide or zirconium silicate may be used where the situation ~dictates.
. I
he selection of the characteristics of the ceramic component of the refractory is wi-thin the s~.ill of those in ~! this technology and no exhaustive disclosure of operable refractories or their ceramic components is necessary.
,I The criteria determining whether a ceramic material lwill be operable with the present inventlon are its ability ' to form an unfired coherent refractory with a low temperature ;.bond and to remain dimensionally stable when exposed to the temperature of operation of the slide gate valve.
The chemical bonding of the ceramic materials can i'be effe~ted by the addition of a binder known to bond the 'ceramic materials and to render them coherent at relatively ,low temperatures. Typically, the following inorganic materials lare known to form chemical bonds with ceramic materials:
,silicates, sulphates, nitrates, chlorides and phosphates.
Particular success has been experienced with the use of phosphate bonding for the practice of the present invention. Additions of phosphorus pentoxide (P2O5) to `.certain refractory compositions have been known to provide excellent low temperature chemical bonds that form the ,particulate ceramic to a coherent refractory. These bonds are well developed at temperatures in the ~00-600F range, .which is compatible with the temperatures necessary to prevent the warpage or melting of the metal container surrounding the refractory. ~he strength of the refractor~
mixture formed by the development of phosphate bonds, as measured by -the modulus of rupture, is adequate to allow handling of the bonded structure as well as the grlnding operation forming the sealing face 16 of the slide valve portion. E~:posure of the device to higher temperatures in ~!2~3~
operation does not normally alter the dimensions of the preformed refractory and the additional heating further strengthens the bonding between the particulate ceramic materials forming the refractory. The bonding of the ceramic particles to form the coherent refractory also results in the ceramic material being bonded directly to the container, thus eliminating the need for other materials, such as refractory cements or mortar, being ir1troduced to bond the refractory to the container.
In addition to the inorganic binders disclosed, the invention may also utilize organic binder systems such as lignosulfate ~r pitch-bonded refractories.
In any case, the binder should form the particulate ceramic into a coherent refractory by chemically bonding the component particles at temperatures below conventional firing temperatures. Preferably, the binder will render the particulate ceramic coherent at a temperature less than about 700F.
One embodiment of the invention is disclosed in the following example:
A refractory mix of approximately 85% alumina was ~prepared in a standard dry pan mixer using phosphoric acid ~as a source of phosphorus pentoxide~ The composition of the mix was as follows: ¦
MaterialWeight Percent -14 mesh Calcined Bauxite 35 -150 mesh Calcined Bauxite S5 -325 mesh Calcined Alumina 5 Plastic Kaolin 5 ~13-, ' .
8;~7 To that mi~ture, approximately 5~- b~ weight of 75~ concer.tra-ted ,phosphoric acid was added and the moisture content adjusted to approximately 5 to 7 weiyht percent. The composition of the mixture and particle size of the components were intended to achieve a pressed product having a press ~density of 2.99 gms/cc.
Tooling for a hydraulic im?act press, normally used to produce prefired refractory slide gate plates, was ;modified to accept the larger metal-supporting can as generally depicted in Fig. 3. The metal-supporting can was inserted into the press which included tooling contoured to provide full support for the metal-supporting can. A pre-weighed portion of the above described refractory mix was then charged into the metal-supporting can. The mix charged into the metal-supporting can was preweighed in order to achieve size and density control, but volume charging of the mix would also be possible.
The ceramic mix and metal support were then compressed according to standard operating procedures for this type of press. The action of the present hydraulic impact press allo~7s maximum density to be attained at moderate pressing pressures. However, the use of screw impact, hydraulic or mechanical presses would also achieve satisfactory refractory shape and density. After pressing, the ceramic/metal assembly was removed from the press and the surrounding tooling as an integral metal can/refractory plate assembly.
Inspection and testing of the as-presse~ metal can/refractory plate assembly indicated that the presence of the metal-supporting can did not interfere with the achievement of the desired press density which was measured at 2.98 gms/cc.
!
~3.~:~3~7 Visual inspection oE the assembly revealed clean, sharp ' edges, especially around the bore area. The refractory rnix as pressed solidly within the metal can. Contact between Ithe metal can and the ceramic was intimate and the assembly 'could be easily handled without damage to the assembly or llthe refractory separating and falling from the metal can.
1, The assembly was then placed directly into an ! index drier where the assembly was exposed to a temperature ' from 180F to 500F over a twelve hour cycle. The low fired assembly was again inspected and tested. Visual inspection revealed a hard, sharply defined refractory shape in intimate contact with the metal supporting can. The low fired refractory did not shrink away from the supporting metal can nor did the drying temperature cause excessive expansion of the metal can that could cause rupture of the bond between the `refractory and the metal can. I
The results of testing the low fired assembly (as set out in Table III below) indicate the assembly meets the ,~desired properties for such assemblies as set out previously ¦lin Table I.
,I Table III
., .
'Refractory Apparent Bulk Density Cold rlOR Hot (2700F) MOR i Component Porosity 85% Alumina 17% 2.84 gms/cc 2400 psi 1000 psi Class As the above example illustrates, the present invention is capable of providing a component of a slide gate valve having the necessary properties for such components with siynificant advantages while being produced at significant savlngs.
3~7 The present invention in both its article and 1.
method embodiments is disclosed herein both generally and by exampl~- It will be apparent to those skilled in the art that modifiCatiOnS and variations of the disclosed invention can be made. Such modifications and variations of the disclosed invention are intended to be within the scope of the invention as defined by the appended claims~ ¦
.' , ~ .
In such devices, such as casting ladles or tundish pouring systems, the flow of molten metal from the vessel is `, controlled by a sliding gate mechanism. Such mechanisms i typically consist of a series of shutter plates having orifices or holes therethrough. The plates are attached under the vessel such that the plates may be displaced with respect to each other thereby aligning or misaligning the , orifices. This allows the liquid metal to flow from the vessel at a rate dependent upon the degree of coaxial alignment of the orifices.
Sliding gate valve systems have been successfully used to control molten metal flow from containing vessels for several years. E~amples of typical sliding gate valve systems can be found in U.S. Pa-tents 3,918,613 to Shapland and 3,581,948 to Detalle.
There are numerous advantages associated with using a sliding gate mechanism for pouring molten metals as compared to other flow-controlling mechanisms such as those using a stopper and an associated stopper rod. The absence o~ the stopper rod mechanism leading out of the container makes the slide gate pouring system particularly useful in vacuum or continuous casting. The sliding gate system, being outside the containing vessel, is less susceptible to the damaging effects of metal temperatures, chemical attack from molten slag and metal erosion. In addition, the sliding ~2~33~7 gate syste~ more effectively controls molten metal flow by controlling the degree of coa~i,al alignment of the urifices in the sliding plates.
Conventionally, sliding gate mechanisms include a prefired refractory plate which is assembled into a metal-supporting can after firing. The refractory/metal assembly is securely attached to the bottom of the vessel containing molten metal. Another refractory/metal assembly is matched to the first such that the degree of coaxial alignment of the orifices in the refractory plates will control the rate f molten metal flow from the vessel, through the sliding gate mechanism and into the appropriate mold. In order to insure an effecti~e seal between the refractory plates in the sliding gate mechanism, the mating surfaces of the prefired refractory plates are precision ground before they are attached to the containing vessel. This grinding operation normally occurs after the refractory is assembled into the supporting can, but the grinding operation may also be carried out prior to the assembly of the refractory into the metal ~
can.
The actual manufacture and assembly of the precision ground refractory is critical to the successful operation of the sliding gate system. A key element in this operation is the assembly of the prefired refractory plate and its supporting metal can. The bond between the refractory and the metal can is crucial. Weak bonds between the refractory and the metal can cause the refractory plate to wobble or shift within the metal can. This shifting hampers efforts to obtain a precision ground surface on the matching faces of the refractories necessar~ to form an effective seal. If an ~3~
3~7 effective seal canno~ be forrned, the entire assembly rnust be scrapped. In addition, if weak bonds are not discovered during assembly or during the grinding operation and the assembly is used to control the molten metal flow in a containing vessel, the refractory plate may shift when the sliding gate mechanism is used. The shifting may hamper the closing of the valve, causing leaks and, in general, may create a dangerous situation for operating personnel.
Currently, refractory/metal assemblies of the prior art are produced by pressing a prefired refractory plate into a preformed metal can using a refractory mortar as the bonding medium. In order to accomplish -this operation, the refractory mortar must be fluid enough to flow around the refractory plate during pressing such that the space (usually 1/8-1/4 inch) between the plate and the metal can is filled with mortar. A mortar with sufficient fluidity to fill this space undergoes considerable shrinkage upon firing.
Assemblies made in this manner exhibit significant amounts of separation between the metal can and the refractory plate where the mortar has shrunk from the metal can. This type of bonding is dependent on the mechanical locking associated with flaws or irregularities in the metal can. This means of locking the refractory plate to the metal can is unsatisfactor~
and refractory plates have been known to separate totally from the metal can and fall out of the assembly.
Another disadvantage of the prior art method of assembling the refractory in the metal can is the pressing operation. The pressing of prefired refractory plates that are slightly warped, flawed or dimensionally inaccurate can cause damage to the part which, in turn, causes the assembly 3f~7 to be scrapped. Even if the refractory plate is dimensionally ; correct, ir it is pressed in a me-tal can containing too thick or too stiff a mortar, or if there is an improper distribution of this stiff mortar in the metal can, the refractory plate or the metal can will be damaged by the ~pressing operation.
Still another disadvantage of this prior art assembly method is that uneven distribution of mortar between refractory plate and metal can can develop uneven stress ',distributions in the assembly. During the grinding operation, ithis may cause cracking of the refractory plate.
Yet another disadvantage of this operation is that the layer of mortar between refractory plate and metal can is necessarily thin. This precludes the use of mechanical ~locks between metal can and mortar such as metal pins, which could extend from the metal can into the mortar layer. A
system using mechanical interlocking means would require a relatively thick mortar layer. lhis would only aggravate shrinkage and mortar distribution problems Still another disadvantage of the prior art method ~of assembling the refractory in the metal can is the result of using prefired refractory plates. These plates are relatively difficult to manufacture and their manufacture entails a considerable cost in energy resources and manpower.
Refractory shapes which are off-size, warped, chipped, or ;cracked must be scrapped, which significantly adds to the cost of the finished product. The finished refractory plates are themselves brittle and easily damaged during shipping, handling and the assembly operation. Damage to the correctly manufactured refractory plates adds still more to their final cost.
3~7 ; Yet another disadvantage o~ the prior art products is the expense of the manufacturin~ method. The prefirecl refractory plates that are bonded to the me-tal cans are made of refractory mixes which are pressed, low fired and then high fired. These prefired refractory plates are then pressed into the metal can with refractory mortar and then refired at low temperature, usually about 600F. The elimination of the second pressing operation and the associated lo~ firing step, as well as the elimination of the high firing step, would considerably reduce the consumption of energy and the ultimate cost of the product.
The present invention is more economical to manufacture but produces a better product. It also results in safer I operation of the vessels dispensing molten metal with slide sate valves.
Additional advantages will be set forth in part in j the description which follows, and in part will be obvious , rom the description, or may be learned by practice of the ;~invention. The advantages of the invention may be reali~ed and attained by means of the combinations particularly pointed out in the appended claims.
Summary of the Invention . . , In accordance with the purposes of the invention, as embodied and broadly described herein, the present invention comprises a portion of a slide gate valve for controlling the flow of molten material, such as metal. The slide gate portion of the valve is comprised of a metal container, having an unfired coherent refractory directly affixed within it. The refractory is formed in the container from a particulate ceramic mixture that includes a binder~
1.
ll 83~7 Preferably, -the binder honds the particulate ceramic mixture into a coherent refractory by forming a chemical hond at a temperature below that of conventional ~'firing temperatures, as for example, at a temperature less ithan 700F. A particularly preferred binder for the present invention comprises a source of phosphorus pentoxide. It is also preferred that the source of phosphorus pentoxide forming the binder comprise phosphoric acid.
It is further preferred that the refractory be comprised of alumina or magnesia. The slide gate portion of the valve may also include means for fixing the refraciory ~! to its inner sur~ace, such as projections from the inner surface of the container.
The preferred method of forming a slide gate j~portion of the valve includes providing a container for ,containing the refractory and then placing a particulate mixture of ceramic material and a binder into the container.
The mixture is then shaped within the container by applying pressure. The mixture is then heated within the container to form a chemical bond between the ceramic particles, ~forming a coherent refractory and also fixing the refractory ~to the container.
It is preferred that where the mixture contains a source of phosphorus pentoxide to form the chemical bond, that the heating step subject the mixture to a temperature in the range of from ~00 to 600F.
;Brief Description of the Drawin~
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one embodiment of the invention and, together with the t~e~cription, serve to explain the principles of the invention.
~2fl3~7 ; Of the Drawings:
Fig. 1 is a cross-sectlonal view of a portion of a slide valve for a tundish.
I Fig. 2 is a detailed view of a portion of the ;embodiment of Fig. 1.
Fig. 3 is a cross-sectional view of a mold assembly for forming the embodiment depicted according to the method of the present invention.
Description of the Preferred Embodiments In order to effectively disclose the preferred ~embodiments of the present invention, the means of forming prior art struct~res is discussed.
soth the prior art and the present invention are directed to the production of a refractory slide gate component having the following general specifications:
Table 1 ApparentBulk Density Cold MOR Hot (2700F) MOR
Porosity (Modulus of Rupture) 14-18%2.89-3.05 gms/cc 2000+ psi 500 psi.
Prefired refractory plates for use in sliding gate systems of the prior art are generally manufactured of three general ceramic oxide classes: 85~ A12O3, 9090 A12O3 and 96% MgO. Within each class, blends of particulate ceramic materials are mixed with suitable binders and pressing agents. These particulate mixtures are fed to hydraulic, mechanical or impact presses for forming into suitable shapes. The pressed shapes are then dried at elevated temperatures, usually between 250 and 400F. The dried shapes are then fired at hi~h temperature to effect a ceramic bond between the particles. The temperature of the firing depends on the composition of the ceramic. Normal firing 1 , .i 8~7 temperatures are, however, usually in the range of from 2200F to 3200F. It should be evident that the elimination of such a firing step has a very significant effect on the economics of manufacturing such products due to the high energy cost associated with heating materials to such temperatures.
Table II illustrates the properties typically associated with prefired refractory plates of various compositions used in conventional slide gate systems.
Table II
Hot (2700~F) Ceramic Class Apparent Porosity Bulk Density Cold MOR MOR
85% Alumina 17% 2.82 gms/cc 3000 psi 1000 psi 90% Alumina 15% 2.90 gms/cc 2000 psi 2100 psi 96% MgO 16% 2.87 gms/cc 2300 psi 1900 psi The prefired plates that are within specification and have survived the various handling processes associated with their manufacture conventionally are then pressed into the supporting me-tal container using refractory mortar to bond the refractory plate to the metal container. The surface of the refractory plate may be ground to the appropriate finish and shaped prior to, or after, assembly into the metal container.
This method of manufacture has numerous shortcomings that have been set out above. In order to eliminate such shortcomings, the present invention was developed.
The present invention comprises a slide gate portion of a valve for controlling the flow of molten metal and a method for its manufacture.
~, .
~L~.21~3~7 In accordance with the invention, the slide yate portion of the valve includes a metal container. As herein embodied and most clearly illustrated in Fiy. 1, the slide gate portion 10 has a shaped metal con-tainer 12 surrounding the refractory 14. The metal container has several functions.
In the present invention, as opposed to prior art devices, the container forms a portion of the mold that shapes the particulate ceramic formed into the refractory 14.
The fact the container shapes the ceramic formed into the ;refractory and is in direct contact therewith, is a si~nificant departure from previously disclosed prior art devices. The shape of the container is dependent upon the mechanism used to actuate the slide gate portion of the valve. The shape of the container depicted in Fig. 1 is merely illustrative of one used typically in a slide valve for a tundish. With the exception of one specific feature, to be hereinafter disclosed, the shape of the container 12 is conventional.
The refractory 14 of the device of the present invention is not bonded to the container 12 with a refractory ;mortar. The refractory 14 abutts and bonds directly to the container 12. The direct bonding of the refractory to the container through the use of low fired refractories is another significant departure from the conventional devices of the prior art. The direct contact of the refractory to the container allows the present invention to include mechanical means for ~affixing the refractory 14 to the inner surface of the metal I ;
container.
As herein embodied and depicted in detail in Fig. 2, the container 12 of the present invention may include projections on the inner surface of the container 12. The ~10-~.2~3~7 projection ~8, shown in Fig. 2, is the edge of the container 12 that is bent or formed in a manner to project inwardly.
This embodiment is merely illustrative of a projection or projections that could be used to accomplish the same function.
The function of the projection(s) is to interlock with the refractory within the container to enhance and strengthen the attachment o~ the refractory to the container. Separation of the refractory from the container can cause catastrophic release of the molten metal being controlled by the valve.
Such an occurren~e is a very severe hazard to those using the equipment in addition to being wasteful and destructive o the equipment itself.
In accordance with the invention, the slide gate portion of the valve includes an unfired coherent refractory within the container. As herein embodied and depicted in Fig. 1, the slide gate portion 10 includes the coherent refractory 14. The refractory 14 is formed from particulate ;ceramic materials that can be rendered coherent by pressing followed by heating to a temperature below conventional firing temperatures. The refractory should also remain dimensionally stable when subjected to the temperatures of operation of the slide gate valve.
The refractory used in the present invention will depend on the type of molten materials being controlled with the slide gate valve. Basic refractories such as dead- ¦
burned magnesite or synthetic periclase may be used. The refractory can be modified by the addition of such materials as refractory grade chrome ore. Acid or neutral refractories such as alumina, aluminum silicate, mullite, zirconium oxide or zirconium silicate may be used where the situation ~dictates.
. I
he selection of the characteristics of the ceramic component of the refractory is wi-thin the s~.ill of those in ~! this technology and no exhaustive disclosure of operable refractories or their ceramic components is necessary.
,I The criteria determining whether a ceramic material lwill be operable with the present inventlon are its ability ' to form an unfired coherent refractory with a low temperature ;.bond and to remain dimensionally stable when exposed to the temperature of operation of the slide gate valve.
The chemical bonding of the ceramic materials can i'be effe~ted by the addition of a binder known to bond the 'ceramic materials and to render them coherent at relatively ,low temperatures. Typically, the following inorganic materials lare known to form chemical bonds with ceramic materials:
,silicates, sulphates, nitrates, chlorides and phosphates.
Particular success has been experienced with the use of phosphate bonding for the practice of the present invention. Additions of phosphorus pentoxide (P2O5) to `.certain refractory compositions have been known to provide excellent low temperature chemical bonds that form the ,particulate ceramic to a coherent refractory. These bonds are well developed at temperatures in the ~00-600F range, .which is compatible with the temperatures necessary to prevent the warpage or melting of the metal container surrounding the refractory. ~he strength of the refractor~
mixture formed by the development of phosphate bonds, as measured by -the modulus of rupture, is adequate to allow handling of the bonded structure as well as the grlnding operation forming the sealing face 16 of the slide valve portion. E~:posure of the device to higher temperatures in ~!2~3~
operation does not normally alter the dimensions of the preformed refractory and the additional heating further strengthens the bonding between the particulate ceramic materials forming the refractory. The bonding of the ceramic particles to form the coherent refractory also results in the ceramic material being bonded directly to the container, thus eliminating the need for other materials, such as refractory cements or mortar, being ir1troduced to bond the refractory to the container.
In addition to the inorganic binders disclosed, the invention may also utilize organic binder systems such as lignosulfate ~r pitch-bonded refractories.
In any case, the binder should form the particulate ceramic into a coherent refractory by chemically bonding the component particles at temperatures below conventional firing temperatures. Preferably, the binder will render the particulate ceramic coherent at a temperature less than about 700F.
One embodiment of the invention is disclosed in the following example:
A refractory mix of approximately 85% alumina was ~prepared in a standard dry pan mixer using phosphoric acid ~as a source of phosphorus pentoxide~ The composition of the mix was as follows: ¦
MaterialWeight Percent -14 mesh Calcined Bauxite 35 -150 mesh Calcined Bauxite S5 -325 mesh Calcined Alumina 5 Plastic Kaolin 5 ~13-, ' .
8;~7 To that mi~ture, approximately 5~- b~ weight of 75~ concer.tra-ted ,phosphoric acid was added and the moisture content adjusted to approximately 5 to 7 weiyht percent. The composition of the mixture and particle size of the components were intended to achieve a pressed product having a press ~density of 2.99 gms/cc.
Tooling for a hydraulic im?act press, normally used to produce prefired refractory slide gate plates, was ;modified to accept the larger metal-supporting can as generally depicted in Fig. 3. The metal-supporting can was inserted into the press which included tooling contoured to provide full support for the metal-supporting can. A pre-weighed portion of the above described refractory mix was then charged into the metal-supporting can. The mix charged into the metal-supporting can was preweighed in order to achieve size and density control, but volume charging of the mix would also be possible.
The ceramic mix and metal support were then compressed according to standard operating procedures for this type of press. The action of the present hydraulic impact press allo~7s maximum density to be attained at moderate pressing pressures. However, the use of screw impact, hydraulic or mechanical presses would also achieve satisfactory refractory shape and density. After pressing, the ceramic/metal assembly was removed from the press and the surrounding tooling as an integral metal can/refractory plate assembly.
Inspection and testing of the as-presse~ metal can/refractory plate assembly indicated that the presence of the metal-supporting can did not interfere with the achievement of the desired press density which was measured at 2.98 gms/cc.
!
~3.~:~3~7 Visual inspection oE the assembly revealed clean, sharp ' edges, especially around the bore area. The refractory rnix as pressed solidly within the metal can. Contact between Ithe metal can and the ceramic was intimate and the assembly 'could be easily handled without damage to the assembly or llthe refractory separating and falling from the metal can.
1, The assembly was then placed directly into an ! index drier where the assembly was exposed to a temperature ' from 180F to 500F over a twelve hour cycle. The low fired assembly was again inspected and tested. Visual inspection revealed a hard, sharply defined refractory shape in intimate contact with the metal supporting can. The low fired refractory did not shrink away from the supporting metal can nor did the drying temperature cause excessive expansion of the metal can that could cause rupture of the bond between the `refractory and the metal can. I
The results of testing the low fired assembly (as set out in Table III below) indicate the assembly meets the ,~desired properties for such assemblies as set out previously ¦lin Table I.
,I Table III
., .
'Refractory Apparent Bulk Density Cold rlOR Hot (2700F) MOR i Component Porosity 85% Alumina 17% 2.84 gms/cc 2400 psi 1000 psi Class As the above example illustrates, the present invention is capable of providing a component of a slide gate valve having the necessary properties for such components with siynificant advantages while being produced at significant savlngs.
3~7 The present invention in both its article and 1.
method embodiments is disclosed herein both generally and by exampl~- It will be apparent to those skilled in the art that modifiCatiOnS and variations of the disclosed invention can be made. Such modifications and variations of the disclosed invention are intended to be within the scope of the invention as defined by the appended claims~ ¦
.' , ~ .
Claims (11)
1. A slide gate portion of a valve for controlling the flow of molten material, said portion comprising:
a metal container; and a coherent refractory within said container, said refractory being affixed in direct contact with said container, said refractory being formed in said container from a particulate ceramic mixture with a binder, said binder being capable of forming a chemical bond with said ceramic at a temperature of less than 700 F.
a metal container; and a coherent refractory within said container, said refractory being affixed in direct contact with said container, said refractory being formed in said container from a particulate ceramic mixture with a binder, said binder being capable of forming a chemical bond with said ceramic at a temperature of less than 700 F.
2. The slide gate portion of claim 1 wherein said binder bonds said particulate ceramic mixture into a coherent refractory by forming a chemical bond at a temperature below conventional high firing temperatures.
3. The slide gate portion of claim 1 wherein said binder forms a chemical bond at a temperature less than about 700°F.
4. The slide gate portion of claim 2 wherein said binder comprises a source of phosphorus pentoxide.
5. The slide gate portion of claim 4 wherein said source of phosphorus pentoxide is phosphoric acid.
6. The slide gate portion of claim 2 wherein said refractory is comprised of alumina or magnesia.
7. The slide gate portion of claim 2 wherein said metal container includes means for mechanically affixing said refractory to its inner surface.
8. The slide gate portion of claim 7 wherein said affixing means are projections on the inner surface of said container.
9. A method of forming a slide gate portion of a valve for controlling the flow of molten material, said method comprising the steps of:
a) providing a container for containing a refractory therein;
b) placing a particulate mixture of ceramic material and a binder into said container;
c) shaping said mixture in said container by applying pressure thereto; and d) heating said mixture in said container for forming a chemical bond between the ceramic particles forming a coherent unfired refractory and also for affix-ing said refractory directly to said container.
a) providing a container for containing a refractory therein;
b) placing a particulate mixture of ceramic material and a binder into said container;
c) shaping said mixture in said container by applying pressure thereto; and d) heating said mixture in said container for forming a chemical bond between the ceramic particles forming a coherent unfired refractory and also for affix-ing said refractory directly to said container.
10. The method of claim 9 wherein said mixture contains a source of phosphorus pentoxide to form said chemical bond and said heating step includes subjecting said mixture to a temperature in the range of 400 to 600°F.
11. The method of claim 9 wherein said refractory is alumina or magnesia.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US84311277A | 1977-10-17 | 1977-10-17 | |
| US843,112 | 1977-10-17 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1128307A true CA1128307A (en) | 1982-07-27 |
Family
ID=25289106
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA313,504A Expired CA1128307A (en) | 1977-10-17 | 1978-10-16 | Slide gate and method for its manufacture |
Country Status (14)
| Country | Link |
|---|---|
| JP (1) | JPS5465714A (en) |
| AR (1) | AR219952A1 (en) |
| AT (1) | ATA743878A (en) |
| BE (1) | BE871321A (en) |
| BR (1) | BR7806822A (en) |
| CA (1) | CA1128307A (en) |
| DE (1) | DE2844951C2 (en) |
| ES (1) | ES474096A1 (en) |
| FR (1) | FR2406138A1 (en) |
| GB (1) | GB2006411B (en) |
| IT (1) | IT1099954B (en) |
| MX (1) | MX150597A (en) |
| SE (1) | SE435244B (en) |
| ZA (1) | ZA785505B (en) |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0043160B2 (en) * | 1980-06-27 | 1989-07-05 | Cockerill Sambre | Casting equipment for fused masses |
| JPS5939508A (en) * | 1982-08-30 | 1984-03-03 | 日本鋼管株式会社 | Manufacture of sliding nozzle brick of molten-metal discharger |
| US4474362A (en) * | 1983-03-24 | 1984-10-02 | Flo-Con Systems, Inc. | Valve and method and components thereof |
| JPS59153055U (en) * | 1983-04-01 | 1984-10-13 | 品川白煉瓦株式会社 | Refractory housing structure for slide valves |
| GB8507277D0 (en) * | 1985-03-20 | 1985-04-24 | British Steel Corp | Refractory component |
| DE3512796C1 (en) * | 1985-04-10 | 1986-02-06 | Stopinc Ag, Baar | Slide unit in a slide lock |
| DE3526083A1 (en) * | 1985-07-20 | 1987-02-12 | Alfred Klein Blechverformung K | Sheet-metal casing for a sliding plate with a nozzle, for a casting ladle or the like, and method for its manufacture |
| JPS6284866A (en) * | 1985-10-11 | 1987-04-18 | Kawasaki Refract Co Ltd | Nozzle plate brick and its production |
| DE3700895A1 (en) * | 1987-01-14 | 1988-07-28 | Intracon Handel | Closure for bottom tapping holes, and closing material suitable for this purpose |
| FR2830473B1 (en) * | 2001-10-10 | 2005-01-14 | Andre Daussan | PROCESS FOR MAKING A CASTING TUBE |
| FR2830472A1 (en) * | 2001-10-10 | 2003-04-11 | Andre Daussan | Manufacture of pouring tube for molten metal involves pouring a refractive sintering compound is into an annular space between an external metallic ferrule and an internal refractive forming tube |
| CN107253262B (en) * | 2017-07-12 | 2019-10-18 | 济南新峨嵋实业有限公司 | A kind of sliding plate brick brick compacting mold |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB678637A (en) * | 1950-04-26 | 1952-09-03 | Cleveland Magnesite & Refracto | Improvements in or relating to reinforced bricks for basic furnace lining |
| US3522063A (en) * | 1967-07-26 | 1970-07-28 | Gen Refractories Co | Phosphate-bonded basic refractory composition |
| SE407023B (en) * | 1973-12-21 | 1979-03-12 | Zimmermann & Jansen Gmbh | SLIDING DEVICE DEVICE FOR CAST COVER FOR LIQUID METALS |
| AT344218B (en) * | 1975-06-02 | 1978-07-10 | Didier Werke Ag | WEAR PARTS, IN PARTICULAR FOR VALVE LATCHES ON CONTAINERS CONTAINING METAL MELT |
| AT342223B (en) * | 1975-07-16 | 1978-03-28 | Oesterr Amerikan Magnesit | SLIDER CLOSURE MADE OF FIRE-RESISTANT BASIC MATERIAL |
| GB1575601A (en) * | 1976-01-22 | 1980-09-24 | Didier Werke Ag | Refractory structures for outlet valves for metallurgical vessels |
| GB1593371A (en) * | 1976-06-25 | 1981-07-15 | Didier Werke Ag | Refractory structures |
-
1978
- 1978-05-18 AT AT0743878A patent/ATA743878A/en not_active Application Discontinuation
- 1978-09-28 ZA ZA00785505A patent/ZA785505B/en unknown
- 1978-10-04 AR AR273956A patent/AR219952A1/en active
- 1978-10-06 JP JP12274978A patent/JPS5465714A/en active Pending
- 1978-10-10 ES ES474096A patent/ES474096A1/en not_active Expired
- 1978-10-13 GB GB7840533A patent/GB2006411B/en not_active Expired
- 1978-10-16 FR FR7829427A patent/FR2406138A1/en active Pending
- 1978-10-16 BR BR7806822A patent/BR7806822A/en unknown
- 1978-10-16 SE SE7810782A patent/SE435244B/en not_active IP Right Cessation
- 1978-10-16 CA CA313,504A patent/CA1128307A/en not_active Expired
- 1978-10-16 DE DE2844951A patent/DE2844951C2/en not_active Expired
- 1978-10-16 MX MX175241A patent/MX150597A/en unknown
- 1978-10-17 IT IT28840/78A patent/IT1099954B/en active
- 1978-10-17 BE BE191167A patent/BE871321A/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| ZA785505B (en) | 1979-10-31 |
| MX150597A (en) | 1984-06-06 |
| IT7828840A0 (en) | 1978-10-17 |
| DE2844951A1 (en) | 1979-04-19 |
| BR7806822A (en) | 1979-05-08 |
| GB2006411A (en) | 1979-05-02 |
| BE871321A (en) | 1979-02-15 |
| GB2006411B (en) | 1982-02-03 |
| SE435244B (en) | 1984-09-17 |
| FR2406138A1 (en) | 1979-05-11 |
| IT1099954B (en) | 1985-09-28 |
| SE7810782L (en) | 1979-04-18 |
| AR219952A1 (en) | 1980-09-30 |
| ES474096A1 (en) | 1980-01-01 |
| JPS5465714A (en) | 1979-05-26 |
| ATA743878A (en) | 1987-06-15 |
| DE2844951C2 (en) | 1985-03-21 |
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