GB2154839A - Direct resistance heating electrode - Google Patents

Direct resistance heating electrode Download PDF

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Publication number
GB2154839A
GB2154839A GB08404322A GB8404322A GB2154839A GB 2154839 A GB2154839 A GB 2154839A GB 08404322 A GB08404322 A GB 08404322A GB 8404322 A GB8404322 A GB 8404322A GB 2154839 A GB2154839 A GB 2154839A
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GB
United Kingdom
Prior art keywords
electrode
electrode according
thermal break
electrode body
replaceable
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.)
Granted
Application number
GB08404322A
Other versions
GB2154839B (en
GB8404322D0 (en
Inventor
Robert Stanley Ellis
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
IPW Ltd
Original Assignee
IPW Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by IPW Ltd filed Critical IPW Ltd
Priority to GB08404322A priority Critical patent/GB2154839B/en
Publication of GB8404322D0 publication Critical patent/GB8404322D0/en
Publication of GB2154839A publication Critical patent/GB2154839A/en
Application granted granted Critical
Publication of GB2154839B publication Critical patent/GB2154839B/en
Expired legal-status Critical Current

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Classifications

    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05BELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00Ohmic-resistance heating
    • H05B3/02Details
    • H05B3/03Electrodes

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  • Resistance Heating (AREA)

Abstract

The disclosed electrode is of the kind which is connected to one side of an electrical power source and contacts an article to be electrically heated, e.g. a titanium bar, connected to the other side of the power source. The electrode includes an electrode body 1 for connection to the power source, containing cooling passages 4. In order to avoid excessive cooling in the region of the bar that contacts the electrode, the electrode includes an electrically conductive member 3 providing a thermal break between the electrode body and the bar. The member 3 is preferably of lower thermal conductivity and higher electrical resistance than the electrode body, and may be a mesh with an open area of less than 50%. The electrode may include a replaceable wear-resistant contact plate 2 with the mesh in front of and/or behind the plate. <IMAGE>

Description

SPECIFICATION Direct resistance heating electrodes Direct resistance heating involves passing a high current through a metal article such as a bar, billet or tube, so that the inherent electrical resistance of the article causes it to heat up.
Electrical contact with the article is often made by means of a cooled electrode. This invariably results in heat loss from the article in the region of the electrode and in some instances this can cause considerable problems. An example of this is in the heating of titanium bars of various sections which are later to be rolled into a circle. Here, contact is made with the ends of the bars with the result that the ends are heated to a lower temperature than the remainder of the bar. Consequently, when the bars are rolled undesirable kinks are produced in the end regions.
Now, however, the present invention provides a direct resistance heating electrode comprising an electrode body for connection to one side of an electrical power source, the body being provided with cooling means, and an electrically conductive member that provides a thermal bream between the electrode body and the article to be heated which is connected to the other side of the power source.
It has been found that simply by incorporating such a thermal break the heat loss can be reduced to a level which is no longer significant.
The electrode is suitable for a range of direct resistance heating applications, including whole bar heating of the type referred to above, bar end heating in which only an end portion is heated, and tube heating.
The member providing the thermal break is preferably formed of a material having a lower thermal conductivity than the electrode body.
The material preferably has a higher electrical resistance than the electrode body so that when current flows through the electrode heat is actually generated in the thermal break.
Suitable materials include stainless steels, nickel based alloys and nickel heat resisting steels such as monel.
The member may be in the form of a solid block or blocks up to 25 mm thick. It may also be of laminated construction to give improved thermal barrier characteristics. However, in a preferred form the member is of a foraminous nature, preferably in the form of a woven mesh. The member thus contains numerous air spaces which greatly improve its efficiency as a thermal barrier.
The open area of the foraminous member, that is to say, the percentage of its area which is comprised of holes, is preferably less than 50%.
The electrode preferably includes a replaceable electrically conductive member in series with the foraminous member. The replaceable member is preferably of a hard, oxidation resistant material.
The invention will now be exemplified with reference to the accompanying drawings, in which: Figure 1 is a front view of an electrode in accordance with the invention, including an enlarged detail, and Figure 2 is a section ll-ll of Fig. 1.
The electrode comprises an electrode body 1 in the form of a solid copper block, and a plate 2 for contacting one end of an article to be heated such as a titanium bar (not shown).
The contact plate is formed of a hard, oxidation resistant, high electrical conductivity material such as a beryllium-copper alloy or one of the other resistance welding electrode materials. A stainless steel mesh 3 is sandwiched between the block 1 and the plate 2.
The block 1 contains three transverse passages 4 through which water or another cooling medium is pumped via copper pipes 5.
These pipes also serve to connect the electrode to one side of a high current, low voltage a.c. or d.c. power source (not shown), the other side of which is coupled to the bar either by a similar electrode located at the opposite end of the bar or, in the case of bar end heating, by an electrical contact which grips the bar at a suitable position along its length. The rear face of the block 1 contains two tapped drillings 6 for mounting the electrode. The front face contains eight tapped drillings 7 for use in securing the contact plate 2 to the block.
The contact plate 2 is of the same profile as the block 1 and contains eight untapped countersunk drillings 8 which correspond with the drillings 7. In Fig. 1 part of the plate 2 is shown cut away to reveal the mesh 3.
As can be seen in the enlarged detail of Fig.
1, the mesh 3 is of woven construction and is of the same profile as the plate 2 and block 1.
In this particular example the mesh is formed of 28 swg (0.3759 mm diameter) stainless steel wires 9 to give a 28 mesh material. The size of the apertures 10 is 0.532 mm and the open area of the mesh is 34%.
The contact plate 2 is clamped to the block 1 by countersunk screws 11 inserted through the drillings 8 and the mesh 3 and screwed into the tapped drillings 7.
In use the bar to be heated comes into contact with the front face of the plate 2 and a high current flows through the block 1, mesh 3, contact plate 2 and into the bar causing it to heat up to a high temperature.
The block 1 is kept relatively cool by the flow of cooling water through the passages 4.
Although the contact plate receives heat from the bar and so becomes very hot the mesh 3 acts as a thermal break preventing large-scale loss of heat from the end of the bar into the block 1. It has also been found that the inherent electrical resistance of stainless steel tends to cause heating of the mesh itself as the current flows through it, which further helps to reduce heat loss from the ends of the bar.
Instead of being located behind the contact plate 2, satisfactory results have also been achieved with the mesh 3 in front of the plate so that the mesh makes direct contact with the article being heated. This arrangement is particularly good where the article is, for example, a bar with an irregular end face since better electrical contact is made. Two sheets of mesh could be used, one in front of and one behind the plate 2.
When the plate 2 becomes worn it can be removed and replaced with a new one.
The electrode has also been used very successfully for heating tubes.

Claims (12)

1. A direct resistance heating electrode comprising an electrode body for connection to one side of an electrical power source, the body being provided with cooling means, and an electrically conductive member that provides a thermal break between the electrode body and the article to be heated which is connected to the other side of the power source.
2. An electrode according to Claim 1, in which the member providing the thermal break is formed of a material having a lower thermal conductivity than the electrode body.
3. An electrode according to Claim 1 or 2, in which the member providing the thermal break is formed of a material having a higher electrical resistance than the electrode body.
4. An electrode according to any preceding claim, in which the electrode body is of copper and the member providing the thermal break is of a stainless steel, a nickel based alloy or a nickel heat resisting steel.
5. An electrode according to any preceding claim, in which the member providing the thermal break is of a foraminous nature.
6. An electrode according to Claim 5, in which the foraminous member is in the form of a woven mesh.
7. An electrode according to Claim 5 or 6, in which the open area of the foraminous member is less than 50%.
8. An electrode according to any preceding claim, in which there is a replaceable electrically conductive member in series with the member providing the thermal break.
9. An electrode according to Claim 8, in which the replaceable member is of a hard, oxidation resistant material.
10. An electrode according to Claim 9, in which the replaceable member is of a beryllium-copper alloy or other resistance welding electrode material.
11. An electrode according to Claim 8, 9 or 10, in which the replaceable member is arranged to contact the article to be heated and the member providing the thermal break is sandwiched between the replaceable member and the electrode body.
12. An electrode according to Claim 11, in which screw fastening means are inserted through the replaceable member and the member providing the thermal break into the electrode body.
1 3. A direct resistance heating electrode which is substantially as described with reference to the drawings.
GB08404322A 1984-02-18 1984-02-18 Direct resistance heating electrode Expired GB2154839B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB08404322A GB2154839B (en) 1984-02-18 1984-02-18 Direct resistance heating electrode

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB08404322A GB2154839B (en) 1984-02-18 1984-02-18 Direct resistance heating electrode

Publications (3)

Publication Number Publication Date
GB8404322D0 GB8404322D0 (en) 1984-03-21
GB2154839A true GB2154839A (en) 1985-09-11
GB2154839B GB2154839B (en) 1987-04-01

Family

ID=10556821

Family Applications (1)

Application Number Title Priority Date Filing Date
GB08404322A Expired GB2154839B (en) 1984-02-18 1984-02-18 Direct resistance heating electrode

Country Status (1)

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GB (1) GB2154839B (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10005821A1 (en) * 2000-02-10 2001-08-23 Schott Glas Electrode used for heating a glass melt in the glass producing industry comprises an outer casing made of precious metal or precious metal alloy, a heat insulating layer directly

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112927956B (en) * 2021-01-22 2022-04-01 中国科学院金属研究所 Electric contact material and preparation method thereof

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB325552A (en) * 1928-10-18 1930-02-18 Frank William Thompson Improvements in and relating to electrodes for the electric heat treatment of metallic articles
GB823769A (en) * 1955-09-09 1959-11-18 Elemelt Ltd Improvements relating to electrodes for glass melting furnaces

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB325552A (en) * 1928-10-18 1930-02-18 Frank William Thompson Improvements in and relating to electrodes for the electric heat treatment of metallic articles
GB823769A (en) * 1955-09-09 1959-11-18 Elemelt Ltd Improvements relating to electrodes for glass melting furnaces

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10005821A1 (en) * 2000-02-10 2001-08-23 Schott Glas Electrode used for heating a glass melt in the glass producing industry comprises an outer casing made of precious metal or precious metal alloy, a heat insulating layer directly

Also Published As

Publication number Publication date
GB2154839B (en) 1987-04-01
GB8404322D0 (en) 1984-03-21

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PCNP Patent ceased through non-payment of renewal fee