Title:
Method and device for fixing an insert to a mold stool
United States Patent 3918624
Abstract:
Method and device for fixing an insert of a refractory material to a stool of an ingot mold, in which a weight having a metal flow way or path is placed on top of an insert fitted within the hollow of the stool, and a molten joint metal of cast iron or steel is poured into a gap between the insert and the hollow of the stool to form the joint using the metal flow way or path, and the joint metal is solidified. The weight prevents the insert from floating up, and the metal flow way distributes the molten metal uniformly to the top opening of the gap. A close contact of the insert and stool is thus obtained and it enhances the advantages of using an insert of carbon-bonded-silicon carbide-graphite material having a high strength and enough thermal conductivity to prevent internal defects of the ingot metal, because of its less interruption of the heat flow across the joint.
Application Number:
05/477046
Publication Date:
11/11/1975
Filing Date:
06/06/1974
View Patent Images:
Export Citation:
Assignee:
Nippon Rutsubo Kabushiki Kaisha (Tokyo, JA)
Primary Class:
Other Classes:
249/204, 164/332, 164/112, 228/212, 164/6
International Classes:
B22D7/06; B23K28/00; B22D7/00; B23K31/02
Field of Search:
249/204 164/92,112,332,412,6 29/473.1 228/112,212
Primary Examiner:
Husar, Francis S.
Assistant Examiner:
Roethel, John E.
Attorney, Agent or Firm:
Biebel, French & Bugg
Claims:
What is claimed is
1. A method of fixing an insert of refractory material to a stool of the top pouring type mold for casting steel ingots, comprising steps of:
2. fitting the insert within a hollow provided on a surface substantially at the center of the stool so as to form a gap between walls of the hollow and the insert,
3. placing a weight on a top surface of the insert, the weight is provided with a metal flow
4. The method of claim 1 in which said weight is sufficient to prevent the floating up of said insert during the pouring of said joint.
5. Apparatus useful in the manufacture of a completed mold stool comprising a refractory insert, means in the bottom of a stool base defining a clearance space between said bottom and said insert, molten metal joint distributing means consisting of a weight resting on an upper surface of said insert, means defining distribution passageways leading to said space for the guiding of molten metal poured onto an upper surface of said weight to form a joint in said space between said insert and said stool, said weight being sufficient to prevent the floating up of said insert during pouring of said joint.
6. The apparatus of claim 3 in which said weight is of plate form made of ferrous material and provided with radial grooves on its upper surface defining said passageways.
7. The apparatus of claim 3 in which said weight comprises separate segments, each segment being formed so as to provide radial grooves defining said passageways when placed on the top surface of the insert.
1. A method of fixing an insert of refractory material to a stool of the top pouring type mold for casting steel ingots, comprising steps of:
2. fitting the insert within a hollow provided on a surface substantially at the center of the stool so as to form a gap between walls of the hollow and the insert,
3. placing a weight on a top surface of the insert, the weight is provided with a metal flow
4. The method of claim 1 in which said weight is sufficient to prevent the floating up of said insert during the pouring of said joint.
5. Apparatus useful in the manufacture of a completed mold stool comprising a refractory insert, means in the bottom of a stool base defining a clearance space between said bottom and said insert, molten metal joint distributing means consisting of a weight resting on an upper surface of said insert, means defining distribution passageways leading to said space for the guiding of molten metal poured onto an upper surface of said weight to form a joint in said space between said insert and said stool, said weight being sufficient to prevent the floating up of said insert during pouring of said joint.
6. The apparatus of claim 3 in which said weight is of plate form made of ferrous material and provided with radial grooves on its upper surface defining said passageways.
7. The apparatus of claim 3 in which said weight comprises separate segments, each segment being formed so as to provide radial grooves defining said passageways when placed on the top surface of the insert.
Description:
BACKGROUND OF THE INVENTION
The present invention relates to molds for casting steel ingots, and more particularly to a method and device for fixing an insert to the mold stool.
In the art, an ingot mold of the top pouring type is generally used, in which a cast iron ingot case is placed on a flat cast iron plate, a so-called "stool" with its bottom open end down, and molten metal is cast into the mold through a top opening of the ingot case.
Accordingly, the unprotected surface of the stool, especially around the center, is eroded and severely pitted due to the vigorous pounding action of the flowing molten metal. The pitted rough surface thus produced results in sticking of ingot metal to the stool, so that severe and costly operations are required to separate them. Moreover, the life of the stools may be decreased by such severe separating operations.
Further, the bottom surface of the ingot which has been cast from such a defective stool becomes so irregular that the greater part of the bottom must be removed before being subjected to the subsequent operations. As a result, the cost of the products may be raised unduly by these defects.
As one of the methods of protecting stools from such defects, use of an insert of refractory material which is fixed within a hollow provided on a surface substantially at the center of the stool has been proposed. Fire-clay brick, silica brick or the like ceramic bonded refractory material have been widely used for the insert.
In this type of protection for stools, however, the insert is generally joined to the stool with a clay or the like ceramic material so that it necessitates the labor of ramming such joint material in a muddy state into a gap between walls of the hollow and insert. It also requires a long drying time. Insufficient drying may cause dangerous explosions when molten metal is poured into the mold. In addition, as the strength of the refractory joint material is not sufficient enough, the insert comes off from the hollow very often during casting operations.
Particularly, when an insert made of carbon-bonded-silicon carbide-graphite refractory material having a thermal conductivity within the range of from 20 to 30 Kcal/mhr°C which is shown in my previous patent application (U.S. Ser. No. 325,417, now U.S. Pat. No. 3,807,684) is used, the refractory joint material may interrupt the heat flow from insert to stool because of its low heat conductivity and decrease the advantages of using such an insert material of high mechanical strength and enough thermal conductivity for preventing defects within the ingot metal.
SUMMARY OF THE INVENTION
Accordingly, a main object of the present invention is to provide a joint material which has a high enough strength and heat conductivity, and can be applied by a very simple operation.
Another object of this invention is to provide a suitable method and devices for fixing the insert to the stool easily.
I have found that the foregoing and related objects may be readily attained in using a cast iron or steel as the joint material. Such metallic joint material has high strength and heat conductivity, and is able to fix the insert by a very simple method. Drying time is no longer required.
My fixing method includes the following steps:
1. Fitting the insert within the hollow of the stool so as to form a gap between walls of the hollow and the insert.
2. Placing a weight on a top surface of the insert, the weight being provided with metal flow way means such as radial grooves.
3. Pouring a molten joint metal of cast iron or steel into the gap through the metal flow way and allowing it to solidify within the gap.
The weight prevents floating up of the insert during the pouring opeation, and the metal flow way distributes the molten metal uniformly to a top opening of the gap.
These and other objects and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view of ingot mold embodying the present invention;
FIG. 2 is a schematic sectional view showing one embodiment of the present invention;
FIG. 3 is a sectional view showing another embodiment of the present invention;
FIG. 4 is an enlarged perspective view of the weight; and,
FIG. 5 is a perspective view of another form of the weight.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring now to the drawing, the top pouring type ingot mold 1 includes a cast iron case 2 placed on a cast iron stool 3 as is best shown in FIG. 1.
A recess or hollow 4 is formed about the center part of the surface of stool 3, and an insert 5 of plate form is fitted therein and firmly secured with joint metal 6 of cast iron or steel.
Annular or helical grooves 7 and 8 are provided on the opposed vertical walls of hollow 4 and insert 5 respectively. The joint metal 6 fills the grooves 7 and 8 and locks the insert 5 in the stool 3.
As is best shown in FIG. 2, insert 5 is of smaller dimension than the hollow and is fitted within hollow 4 so as to form a circumferential gap 9 between walls of the stool 3 at the hollow 4 and insert 5.
A weight 10 of plate or block form is placed upon a top surface of insert 5. The weight is made of ferrous material such as cast iron or thick steel plate, and provided with distribution means in the form of upwardly facing radial grooves 11 on its upper surface as shown in FIG. 4. A pair of grooves 11 are arranged diametrically and cruciform-like and have lower surfaced which are properly sloped downwards from center toward the periphery of the block. The grooves 11 are coated with graphite powder. The grooves may be curved for instance toward the tangential direction at about the periphery of the block 10.
Molten joint metal 6 is then poured on the center part of grooves 11 at the region of inspection from a ladle 12. The poured molten metal is distributed uniformly to the top opening of gap 9 by passing through the radial grooves 11, and is cast into gap 9 and solidified. The weight 10 also prevents the floating up of insert 5 during the pouring operation. The weight 10 is then removed from the top of insert 5 and the fixing operation is completed.
Thus the insert is fixed firmly to the stool with the joint metal of high strength and high thermal conductivity by a very simple fixing operation, without the necessity of drying after fixing, without the interruption of heat flow while casting steel ingot which otherwise may cause defects within the ingot metal.
I prefer that the space 9 be continued as at 9' in FIG. 3 between the interface of the bottom of the insert 5 and the bottom of the hollow 4. To accomplish this I use spacer blocks 13 between bottom surfaces of hollow 4 and insert 5, as shown in FIG. 3, so as to form the gap 9'. A more perfect thermal contact may be thus obtained between insert and stool by means of a joint metal filled within the bottom gap 9'.
Four quadrants 10' of block or plate material as shown in FIG. 5 may also be used as the weights in lieu of the single block 10. Each piece 10' is formed so as to provide and define radial grooves 11' therebetween when placed on the top surface of the insert.
The insert may be made of fire bricks, silica bricks or the like ceramic bonded refractory material, or more preferably the aforementioned carbon-bonded-silicon carbide-graphite refractory material as described and claimed in U.S. Pat. No. 3,807,684 having a thermal conductivity within the range of from 20 to 30 Kcal/mhr°C may be used for the insert.
The latter is composed principally of natural graphite, silicon carbide and silica, bonded together with an organic binder such as tar, and comprises 30-50% by weight of carbon and graphite, 30-50% by weight of silicon carbide and 5-20% by weight of silicon oxide.
While the method herein described, and the forms of apparatus for carrying this method into effect, constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise methods and forms of apparatus, and that changes may be made in either without departing from the scope of the invention.
The present invention relates to molds for casting steel ingots, and more particularly to a method and device for fixing an insert to the mold stool.
In the art, an ingot mold of the top pouring type is generally used, in which a cast iron ingot case is placed on a flat cast iron plate, a so-called "stool" with its bottom open end down, and molten metal is cast into the mold through a top opening of the ingot case.
Accordingly, the unprotected surface of the stool, especially around the center, is eroded and severely pitted due to the vigorous pounding action of the flowing molten metal. The pitted rough surface thus produced results in sticking of ingot metal to the stool, so that severe and costly operations are required to separate them. Moreover, the life of the stools may be decreased by such severe separating operations.
Further, the bottom surface of the ingot which has been cast from such a defective stool becomes so irregular that the greater part of the bottom must be removed before being subjected to the subsequent operations. As a result, the cost of the products may be raised unduly by these defects.
As one of the methods of protecting stools from such defects, use of an insert of refractory material which is fixed within a hollow provided on a surface substantially at the center of the stool has been proposed. Fire-clay brick, silica brick or the like ceramic bonded refractory material have been widely used for the insert.
In this type of protection for stools, however, the insert is generally joined to the stool with a clay or the like ceramic material so that it necessitates the labor of ramming such joint material in a muddy state into a gap between walls of the hollow and insert. It also requires a long drying time. Insufficient drying may cause dangerous explosions when molten metal is poured into the mold. In addition, as the strength of the refractory joint material is not sufficient enough, the insert comes off from the hollow very often during casting operations.
Particularly, when an insert made of carbon-bonded-silicon carbide-graphite refractory material having a thermal conductivity within the range of from 20 to 30 Kcal/mhr°C which is shown in my previous patent application (U.S. Ser. No. 325,417, now U.S. Pat. No. 3,807,684) is used, the refractory joint material may interrupt the heat flow from insert to stool because of its low heat conductivity and decrease the advantages of using such an insert material of high mechanical strength and enough thermal conductivity for preventing defects within the ingot metal.
SUMMARY OF THE INVENTION
Accordingly, a main object of the present invention is to provide a joint material which has a high enough strength and heat conductivity, and can be applied by a very simple operation.
Another object of this invention is to provide a suitable method and devices for fixing the insert to the stool easily.
I have found that the foregoing and related objects may be readily attained in using a cast iron or steel as the joint material. Such metallic joint material has high strength and heat conductivity, and is able to fix the insert by a very simple method. Drying time is no longer required.
My fixing method includes the following steps:
1. Fitting the insert within the hollow of the stool so as to form a gap between walls of the hollow and the insert.
2. Placing a weight on a top surface of the insert, the weight being provided with metal flow way means such as radial grooves.
3. Pouring a molten joint metal of cast iron or steel into the gap through the metal flow way and allowing it to solidify within the gap.
The weight prevents floating up of the insert during the pouring opeation, and the metal flow way distributes the molten metal uniformly to a top opening of the gap.
These and other objects and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view of ingot mold embodying the present invention;
FIG. 2 is a schematic sectional view showing one embodiment of the present invention;
FIG. 3 is a sectional view showing another embodiment of the present invention;
FIG. 4 is an enlarged perspective view of the weight; and,
FIG. 5 is a perspective view of another form of the weight.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring now to the drawing, the top pouring type ingot mold 1 includes a cast iron case 2 placed on a cast iron stool 3 as is best shown in FIG. 1.
A recess or hollow 4 is formed about the center part of the surface of stool 3, and an insert 5 of plate form is fitted therein and firmly secured with joint metal 6 of cast iron or steel.
Annular or helical grooves 7 and 8 are provided on the opposed vertical walls of hollow 4 and insert 5 respectively. The joint metal 6 fills the grooves 7 and 8 and locks the insert 5 in the stool 3.
As is best shown in FIG. 2, insert 5 is of smaller dimension than the hollow and is fitted within hollow 4 so as to form a circumferential gap 9 between walls of the stool 3 at the hollow 4 and insert 5.
A weight 10 of plate or block form is placed upon a top surface of insert 5. The weight is made of ferrous material such as cast iron or thick steel plate, and provided with distribution means in the form of upwardly facing radial grooves 11 on its upper surface as shown in FIG. 4. A pair of grooves 11 are arranged diametrically and cruciform-like and have lower surfaced which are properly sloped downwards from center toward the periphery of the block. The grooves 11 are coated with graphite powder. The grooves may be curved for instance toward the tangential direction at about the periphery of the block 10.
Molten joint metal 6 is then poured on the center part of grooves 11 at the region of inspection from a ladle 12. The poured molten metal is distributed uniformly to the top opening of gap 9 by passing through the radial grooves 11, and is cast into gap 9 and solidified. The weight 10 also prevents the floating up of insert 5 during the pouring operation. The weight 10 is then removed from the top of insert 5 and the fixing operation is completed.
Thus the insert is fixed firmly to the stool with the joint metal of high strength and high thermal conductivity by a very simple fixing operation, without the necessity of drying after fixing, without the interruption of heat flow while casting steel ingot which otherwise may cause defects within the ingot metal.
I prefer that the space 9 be continued as at 9' in FIG. 3 between the interface of the bottom of the insert 5 and the bottom of the hollow 4. To accomplish this I use spacer blocks 13 between bottom surfaces of hollow 4 and insert 5, as shown in FIG. 3, so as to form the gap 9'. A more perfect thermal contact may be thus obtained between insert and stool by means of a joint metal filled within the bottom gap 9'.
Four quadrants 10' of block or plate material as shown in FIG. 5 may also be used as the weights in lieu of the single block 10. Each piece 10' is formed so as to provide and define radial grooves 11' therebetween when placed on the top surface of the insert.
The insert may be made of fire bricks, silica bricks or the like ceramic bonded refractory material, or more preferably the aforementioned carbon-bonded-silicon carbide-graphite refractory material as described and claimed in U.S. Pat. No. 3,807,684 having a thermal conductivity within the range of from 20 to 30 Kcal/mhr°C may be used for the insert.
The latter is composed principally of natural graphite, silicon carbide and silica, bonded together with an organic binder such as tar, and comprises 30-50% by weight of carbon and graphite, 30-50% by weight of silicon carbide and 5-20% by weight of silicon oxide.
While the method herein described, and the forms of apparatus for carrying this method into effect, constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise methods and forms of apparatus, and that changes may be made in either without departing from the scope of the invention.