CA1182853A - Electrode joints - Google Patents
Electrode jointsInfo
- Publication number
- CA1182853A CA1182853A CA000402023A CA402023A CA1182853A CA 1182853 A CA1182853 A CA 1182853A CA 000402023 A CA000402023 A CA 000402023A CA 402023 A CA402023 A CA 402023A CA 1182853 A CA1182853 A CA 1182853A
- Authority
- CA
- Canada
- Prior art keywords
- insert
- electrode
- electrodes
- gap
- section
- 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
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/25—Process efficiency
Landscapes
- Discharge Heating (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An improved method or joining sections of a segmented electrode is provided wherein a fusible, electrically-conductive, solid insert is positioned in a gap between faces of abutting electrode sections, so that, upon the passage of an electric current through the electrode, the insert melts and flows to fill the gap with electrically-conductive fluid medium. In this way, local overheating in the joint owing to non face-to-face contact is avoided.
An improved method or joining sections of a segmented electrode is provided wherein a fusible, electrically-conductive, solid insert is positioned in a gap between faces of abutting electrode sections, so that, upon the passage of an electric current through the electrode, the insert melts and flows to fill the gap with electrically-conductive fluid medium. In this way, local overheating in the joint owing to non face-to-face contact is avoided.
Description
32~3 ELECTRODE JOINTS
The present invention relates to an improved method of forming the joints between adjacent sections of pre-baked electrodes of the type which are employed in continuous electxic arc furnaces.
Continuous electric arc furnaces are widely used in the manufacture of, for example, elemental phosphorus, ferro alloys, elemental silicon and in steel melting. The invention provides a novel method for 10 effecting a joint between two electrode sections and electrodes which are adopted for use in that method.
The electrodes, which are formed of carbon or graphite or mixtures of the two, are consumed during the operation of the furnace. So that the furnace can be 15 operated on a continuous basis~ the electrodes are formed in sections, each end of which is provided with a threaded portion whereby it can be joined to another section. Thus, while the furnace is operational, further electrode sections can be jointed together and fed into 20 the furnace. The joint may take the form of a threaded nipple which engages thrPaded sockets in two adjacent electrode sections or a "male/female" joint wherein one end of the electrode is machined to form a threaded nipple as an integral part of its structure, that nipple 25 engaging the socket of an adjacent electrode section~
One serious problem which has been encountered, particularly in modern furnaces which are relatively large, is the tendency of the electrodes to break during use. Such breakages almost invariably occur in the 0 region of the joint. The breakages result from splits and cracks produced by stresses caused by the flexural strain and thermal gradients experienced by the joint when it is being fed into the furnace. Numerous proposals to vary the design of the joint have been suggested but none has been wholly effective in eliminating the problem of breakages. Even a small number of breakages is extremely damaging to the economic operation of large furnaces which must be closed down ,", ~
5,~3 whi.le the broken electrode section is removed and a new electrode section assembled in its place.
One problem, when designing an electrode joint of this type, is that of the thermal expansion which the joint undergoes as it enters the furnace and electric 5 current flows through i.t. This can be exacerbated by the fact that the electrodes may be formed from a different material, for example, semi-graphite carbonaceous material, from the nipple, which may be formed from graphite. Due to the radial temperature gradients, the 10 joint face becomes distorted as the electrode heats up.
For this reason, the ends of the electrode sections are normally made slightly concave so that their outer peripheries contac-t one another when two adjacent sections are joined and there is a clearance between them 15 so as to allow for their expansion~ It is important that the peripheries of the electrodes remain in contact at all times in order to maximize the flex~ral strength of the electrode column. However, such measures cannot be wholly effective in ma.intaining contact between the faces 20 of adjacent electrode sections because of the wide temperature range to which they are subjected in use and consequent change in the shape of the electrode face.
This, in turn, leads to local overheating in the areas of the faces which remain in contact since the majority of 25 the electric current will flow through these areas.
The present invention provides an improved method of forrning a segmented electrode which consists of a plurality of sections having two abutting faces in contact with the next preceding and next succeeding 30 section respectively, wherein at least one abutti.ng face betweell at least one part of successive electrode sections is concave whereby said successive electrode sections are in contact substantially around the periphery thereof and enclose a gapO The improvement 35 consists in arran~ing a fusible, electrically-conductive, solid insert within the gap whereby on passage of an electric current thxough electrodes, the insert melts, ~ ~3X~i3 .. 3 thereby providing electrically-conduc-tive fluid medium substantially filling the gap. The solid material i5 formed from a material selected from the group consisting of lead, tin, aluminiumt antimo.ny, bismuth, magnesium, æinc, cadmium and alloys thereof.
By locating this electrically-conductive fluid medium in the gap, face~to-face contact between abutting electrode faces is achieved and -the local overheating problems o:E the prior art are avoided.
The electrically-conducting medium used in this 10 invention need only be fluid at temperatures which are sufficient to develop thermal stresses in the joint.
Preferably, the novel method is carried out by mounting the solid material on the face of a cold elect.rode section, which solid material has a relatively low 15 melting point, usually less than about 700C and preferably less than about 300C, and thereby becomes molten and fills the gap between the electrode faces when a current is passed through two electrode sections. The material preferably remains in a molten state through as 20 large a range of temperature as possible, in order to remain effective for the longest period, although it may vaporize before the electrode joint reaches the electric arc where very high temperatures, for example, of the order of 2000C, may be encountered. Preferably, the 25 solid material has a boiling point above about 600C and preferably above ahout 1000C.
_,~
_ ,, 30 ..
_ --,~ --___._ `
The invention is described further, by way of illustration, with reference to the accompanying drawing, in which:
Figure 1 is a diagrammatic cross-sectional view of an electrode joint constructed in accordance with one embodiment of the invention.
Referring to the drawing, an electrode joint comprises an upper electrode section 1 and a lower electrode section 2 of generally cylindrical cross section mounted co-axially, one above the other~ The upper section 1 is provided with a cylindrical threaded socket 3 in its lower face 4 and the lower section 2 is provided with a threaded socket 5 in its upper face 6.
The sec~ions 1 and 2 are connected by means of a threaded lS nipple 7, which is engaged in both of the socke-ts 3 and 5. The adjacent faces 4 and 6 are shaped so as to contact .on~ another at their peripheries 8 and 9 but are spaced one from the other at their central portions 10 and 11. The lower face 4 is provided with an annular
The present invention relates to an improved method of forming the joints between adjacent sections of pre-baked electrodes of the type which are employed in continuous electxic arc furnaces.
Continuous electric arc furnaces are widely used in the manufacture of, for example, elemental phosphorus, ferro alloys, elemental silicon and in steel melting. The invention provides a novel method for 10 effecting a joint between two electrode sections and electrodes which are adopted for use in that method.
The electrodes, which are formed of carbon or graphite or mixtures of the two, are consumed during the operation of the furnace. So that the furnace can be 15 operated on a continuous basis~ the electrodes are formed in sections, each end of which is provided with a threaded portion whereby it can be joined to another section. Thus, while the furnace is operational, further electrode sections can be jointed together and fed into 20 the furnace. The joint may take the form of a threaded nipple which engages thrPaded sockets in two adjacent electrode sections or a "male/female" joint wherein one end of the electrode is machined to form a threaded nipple as an integral part of its structure, that nipple 25 engaging the socket of an adjacent electrode section~
One serious problem which has been encountered, particularly in modern furnaces which are relatively large, is the tendency of the electrodes to break during use. Such breakages almost invariably occur in the 0 region of the joint. The breakages result from splits and cracks produced by stresses caused by the flexural strain and thermal gradients experienced by the joint when it is being fed into the furnace. Numerous proposals to vary the design of the joint have been suggested but none has been wholly effective in eliminating the problem of breakages. Even a small number of breakages is extremely damaging to the economic operation of large furnaces which must be closed down ,", ~
5,~3 whi.le the broken electrode section is removed and a new electrode section assembled in its place.
One problem, when designing an electrode joint of this type, is that of the thermal expansion which the joint undergoes as it enters the furnace and electric 5 current flows through i.t. This can be exacerbated by the fact that the electrodes may be formed from a different material, for example, semi-graphite carbonaceous material, from the nipple, which may be formed from graphite. Due to the radial temperature gradients, the 10 joint face becomes distorted as the electrode heats up.
For this reason, the ends of the electrode sections are normally made slightly concave so that their outer peripheries contac-t one another when two adjacent sections are joined and there is a clearance between them 15 so as to allow for their expansion~ It is important that the peripheries of the electrodes remain in contact at all times in order to maximize the flex~ral strength of the electrode column. However, such measures cannot be wholly effective in ma.intaining contact between the faces 20 of adjacent electrode sections because of the wide temperature range to which they are subjected in use and consequent change in the shape of the electrode face.
This, in turn, leads to local overheating in the areas of the faces which remain in contact since the majority of 25 the electric current will flow through these areas.
The present invention provides an improved method of forrning a segmented electrode which consists of a plurality of sections having two abutting faces in contact with the next preceding and next succeeding 30 section respectively, wherein at least one abutti.ng face betweell at least one part of successive electrode sections is concave whereby said successive electrode sections are in contact substantially around the periphery thereof and enclose a gapO The improvement 35 consists in arran~ing a fusible, electrically-conductive, solid insert within the gap whereby on passage of an electric current thxough electrodes, the insert melts, ~ ~3X~i3 .. 3 thereby providing electrically-conduc-tive fluid medium substantially filling the gap. The solid material i5 formed from a material selected from the group consisting of lead, tin, aluminiumt antimo.ny, bismuth, magnesium, æinc, cadmium and alloys thereof.
By locating this electrically-conductive fluid medium in the gap, face~to-face contact between abutting electrode faces is achieved and -the local overheating problems o:E the prior art are avoided.
The electrically-conducting medium used in this 10 invention need only be fluid at temperatures which are sufficient to develop thermal stresses in the joint.
Preferably, the novel method is carried out by mounting the solid material on the face of a cold elect.rode section, which solid material has a relatively low 15 melting point, usually less than about 700C and preferably less than about 300C, and thereby becomes molten and fills the gap between the electrode faces when a current is passed through two electrode sections. The material preferably remains in a molten state through as 20 large a range of temperature as possible, in order to remain effective for the longest period, although it may vaporize before the electrode joint reaches the electric arc where very high temperatures, for example, of the order of 2000C, may be encountered. Preferably, the 25 solid material has a boiling point above about 600C and preferably above ahout 1000C.
_,~
_ ,, 30 ..
_ --,~ --___._ `
The invention is described further, by way of illustration, with reference to the accompanying drawing, in which:
Figure 1 is a diagrammatic cross-sectional view of an electrode joint constructed in accordance with one embodiment of the invention.
Referring to the drawing, an electrode joint comprises an upper electrode section 1 and a lower electrode section 2 of generally cylindrical cross section mounted co-axially, one above the other~ The upper section 1 is provided with a cylindrical threaded socket 3 in its lower face 4 and the lower section 2 is provided with a threaded socket 5 in its upper face 6.
The sec~ions 1 and 2 are connected by means of a threaded lS nipple 7, which is engaged in both of the socke-ts 3 and 5. The adjacent faces 4 and 6 are shaped so as to contact .on~ another at their peripheries 8 and 9 but are spaced one from the other at their central portions 10 and 11. The lower face 4 is provided with an annular
2~ recessed grove 12O An annular ring 13 of a 60:40 lead/tin alloy is mounted and retained in the groove 1~.
A backing ring 14 is mounted on the interior face of the ring 13 in the space 15 between the faces of the upper section 1 and the lower section 2 in the area of the nippl~ 7-In practice, the gap between the opposed faces4 and 6 of the upper and lower sections will be very much smaller, say 0.050 inches, than i.s emphasi2ed for illustrative purposes in Figure 1. It is preferable to 30 provide suf~icient of the electrically-conductive fluid medium as will effectively fill this gap upon melting of the annular ring 13 of lead/tin alloy.
This is conveniently achieved by arranging a relatively narrow deep annulus 12 containing appropriate 35 matexi.al 15 of low melting point in communication with the gap between faces 4 and 6, the depth of the annulus 12 being such that it provides sufficient pressure to enable the molten material to ~low across the face 6 of lower section 2 and thus fill the gap between the adjacent faces 4 and 6 of the two electrode sections 1 and 2~ The groove 12 is preferably cut into the lower face 4 of the upper section 1 so as to accommodate the upper part of the annulus 13 while the lower face of that 5 annulus lies 1ush with the upper face 6 o~ the lower section 2. The annulus 13 is conveniently situated close to the innermost portion of the electrode sections 1 and 2, since the electrode heats up from the centre and the annulus will be melted more quickly and hence will ensure 10 the maximum electrical~conductivity across the joint.
The backing ring 14 minimizes any tendency of the molten annulus of the electroconductive material to flow through the space 15 into the threaded sockets 3 and 5, thereby restraining the molten material in the gap 15 between the electrode faces. 5uch precautions minimize the quantity of conductive material which need be employed, which is valuable in minimizing expense and also any possible contamination of the products of the furnace with that material. It is preferable that the 20 ring 14 should not form a gas tight seal to the space 15 so as to allow the escape of any vapours which may form when the electrode is heated.
The electrically-conductive material which is used to provide the annular ring 13, in small quantities 5 in the products of the furnace will not lead to any deleterious effects. Alternatively, it may be made of a material which will form part of the furnace slag and thereby be removed. In practice, it is usually more important to select a material which melts readily and remains in a molten, electrically-conductive state over a wide range of temperatures. Any tendency o-f the material to oxidize or degrade, and hence lose its electrical conductivity, shouLd be avoided if possible. Among the materials which may be employed are metals, such asl lead, tin, aluminium, antimony, bismuth, magnesium, zinc and cadmium and alloys thereof, which alloys may contain other constituents, for example, copper. The preferred materials for present use are the alloys of the above metals havi.ng a melting point in the range about 200 to 350C, for example, the lead~tin alloys used as solder.
In summary of this disclosure, the present invention provides a novel method of assembly of S electrodes and novel electrodes formed thereby.
Modifications are possible within the scope of the invention.
,~
s ~ i .
A backing ring 14 is mounted on the interior face of the ring 13 in the space 15 between the faces of the upper section 1 and the lower section 2 in the area of the nippl~ 7-In practice, the gap between the opposed faces4 and 6 of the upper and lower sections will be very much smaller, say 0.050 inches, than i.s emphasi2ed for illustrative purposes in Figure 1. It is preferable to 30 provide suf~icient of the electrically-conductive fluid medium as will effectively fill this gap upon melting of the annular ring 13 of lead/tin alloy.
This is conveniently achieved by arranging a relatively narrow deep annulus 12 containing appropriate 35 matexi.al 15 of low melting point in communication with the gap between faces 4 and 6, the depth of the annulus 12 being such that it provides sufficient pressure to enable the molten material to ~low across the face 6 of lower section 2 and thus fill the gap between the adjacent faces 4 and 6 of the two electrode sections 1 and 2~ The groove 12 is preferably cut into the lower face 4 of the upper section 1 so as to accommodate the upper part of the annulus 13 while the lower face of that 5 annulus lies 1ush with the upper face 6 o~ the lower section 2. The annulus 13 is conveniently situated close to the innermost portion of the electrode sections 1 and 2, since the electrode heats up from the centre and the annulus will be melted more quickly and hence will ensure 10 the maximum electrical~conductivity across the joint.
The backing ring 14 minimizes any tendency of the molten annulus of the electroconductive material to flow through the space 15 into the threaded sockets 3 and 5, thereby restraining the molten material in the gap 15 between the electrode faces. 5uch precautions minimize the quantity of conductive material which need be employed, which is valuable in minimizing expense and also any possible contamination of the products of the furnace with that material. It is preferable that the 20 ring 14 should not form a gas tight seal to the space 15 so as to allow the escape of any vapours which may form when the electrode is heated.
The electrically-conductive material which is used to provide the annular ring 13, in small quantities 5 in the products of the furnace will not lead to any deleterious effects. Alternatively, it may be made of a material which will form part of the furnace slag and thereby be removed. In practice, it is usually more important to select a material which melts readily and remains in a molten, electrically-conductive state over a wide range of temperatures. Any tendency o-f the material to oxidize or degrade, and hence lose its electrical conductivity, shouLd be avoided if possible. Among the materials which may be employed are metals, such asl lead, tin, aluminium, antimony, bismuth, magnesium, zinc and cadmium and alloys thereof, which alloys may contain other constituents, for example, copper. The preferred materials for present use are the alloys of the above metals havi.ng a melting point in the range about 200 to 350C, for example, the lead~tin alloys used as solder.
In summary of this disclosure, the present invention provides a novel method of assembly of S electrodes and novel electrodes formed thereby.
Modifications are possible within the scope of the invention.
,~
s ~ i .
Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a method of forming a segmented electrode which consists of a plurality of sections having two abutting faces in contact with the next preceding and next succeeding section respectively, wherein at least one abutting face between at least one pair of successive electrode sections is concave whereby said successive electrode sections are in contact substantially around the periphery thereof and enclose a gap, the improvement which consists in arranging a fusible electrically-conductive solid insert within said gap, whereby, on passage of an electric current through electrodes, said insert melts, thereby providing an electrically-conductive fluid medium substantially filling said gap, said insert being formed from a material selected from the group consisting of lead, tin, aluminium, antimony, bismuth, magnesium, zinc, cadmium and alloys thereof.
2. The method of claim 1, wherein the insert is formed from a material having a melting point of less than 700°C.
3. The method of claim 2, wherein the insert is formed from a material having a melting point of less than 300°C.
4. The method of claim 1, wherein the insert is formed from a lead/tin alloy having a melting point in the range of about 200° to about 350°C.
5. The method of claim 1, 2 or 3, wherein the electrodes are of a generally cylindrical cross-section and the insert takes the form of an annular ring of solid material.
6. The method of claim 4, wherein the electrodes are of a generally cylindrical cross-section and the insert takes the form of an annular ring of solid material.
7. The method of claim 1, 2 or 4, wherein the electrodes are of a generally cylindrical cross section and the insert takes the form of an annular ring of solid material mounted in the proximity of the threaded nipple joining the two electrode sections.
8. The method of claim 1, 2 or 4, wherein the electrodes are of a generally cylindrical cross section, the insert takes the form of an annular ring of solid material, and the gap between the two electrode faces is closed at its interior and by the provision of a backing ring.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8115038 | 1981-05-15 | ||
| GB8115038 | 1981-05-15 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1182853A true CA1182853A (en) | 1985-02-19 |
Family
ID=10521852
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000402023A Expired CA1182853A (en) | 1981-05-15 | 1982-04-30 | Electrode joints |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1182853A (en) |
-
1982
- 1982-04-30 CA CA000402023A patent/CA1182853A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEC | Expiry (correction) | ||
| MKEX | Expiry |