EP0037679A1

EP0037679A1 - Coolant conduits incorporated in castings

Info

Publication number: EP0037679A1
Application number: EP81301262A
Authority: EP
Inventors: Thomas Westley
Original assignee: WESTLEY BROTHERS Ltd
Current assignee: WESTLEY BROTHERS Ltd
Priority date: 1980-03-28
Filing date: 1981-03-24
Publication date: 1981-10-14
Also published as: NO811033L; JPS56151161A

Abstract

For a copper casting forming an electrode clamp a coolant conduit assembly is made up of cast copper bend members 23 and 24 including U-shaped passages 25,26 and 28,29, 30 which are interconnected by copper tubes 13A, 13B, and 13C. Tighter bends can be formed than by bending copper pe and thus the coolant conduits can be placed in the best position for efficient cooling and the dimensions of the casting reduced. Welding or shrink fitting can be used to intercon- nectthetubes and the bend members.

Description

The present invention relates to coolant conduits incorporated in castings.
When a cast article is to be used in conditions where it requires cooling it is known to form coolant passages in the article either in the process of casting or by subsequent machirrlnp. It is also known, where the material of the casting is unsuitable for confining the coolant, or may become so during use, to pre-form the required coolant conduits and then cast the article around the preformed conduits so that they are incorporated in the finished casting.
Thus, for example, in casting blocks of copper to act as electrode holders in arc furnaces it is known to form a coolant duct by bending copper pipe and then to cast the body of the electrode holder around it.
The electrode holder carries current to the electrode and is exposed to severe heating when in use in the furnace and in particular may undergo severe local heating as a result of arcing between the electrode and the holder. As a result fine cracking can occur in the body of the casting which would allow cooling water to leak away if the coolant duct was formed directly in the casting. The integrity of the copper pipe incorporated in the casting is maintained for a much longer period and thus leakage of coolant is prevented.
There are, however, severe limitations on this manufacturing technique. It is difficult to bend copper piping while maintaining the necessary flow cross-section and in particular bends of small radius are impossible. This means that the form of the coolant duct is designed primarily to ensure the minimum of bends and the largest possible radius of curvature for each of those bends and consideration of which parts of the casting require the greatest cooling have to be treated as secondary.
In accordance with the present invention therefore a cast article incorporates coolant conduits which have been prefabricated from at least two bend members having generally U-shaped passages therein and a plurality of tubes joined at their ends to the bend members to connect the said U-shaped passages.
With such. a construction the tubes can be substantially straight, though curves and bends of large radius are possible to fit the shape of the cast article, and can be placed as required in the cast article for effecting the required cooling. In particular they can be more closely spaced than is possible with bent pipe because the formation of bends of small radius in the bend members, for example by casting the bend members, is relatively simple.
By way of example, the application of the.invention to the manufacture of an electrode clamp for use in an electric arc furnace will now be described in more detail. Reference is made first to British Patent Specification No. 1,404,661 in the name of British Steel Corporation which describes a form of electrode clamp for holding a coated graphite electrode in an electric arc furnace. That clamp has a copper body portion with a concave generally-cylindrical face carrying two graphite pads for engagement with the cylindrical surface of the electrode. A steel band embraces the electrode and clamps it against the graphite pads of the copper body. The body portion is provided with a U-shaped conduit for cooling water, the two limbs of the U being aligned with the two graphite pads.
Reference is now made to the accompanying drawings which show, for an electrode clamp similar to that described in specification No. 1,404,661, a cast body portion incorporating a cooling system and constructed in accordance with the present invention.
In the drawings:-

Fig. 1 is a side view of the body portion of a clamp,
Fig. 2 is an end view in the direction of the arrow A of Fig. 1,
Fig. 3 is a section on the line III-III of Fig. 2,
Fig. 4 is an end elevation of the coolant conduit assembly for the casting of Figs. 1 to 3,
Fig. 5 is a side elevation of the assembly of Fig. 4, and
Fig. 6 is a top view of the assembly of Fig. 4.

The body portion shown in Figs. 1, 2 and 3 is a copper casting. As seen in Fig. 3 the casting 10 has a concave face 11 provided with grooves 12 to receive graphite pads which engage a cylindrical coated graphite electrode.. Copper tubes 13 embedded in the casing 10 serve to convey cooling water through the casting at positions close to the grooves 12.
It will be seen that the casting is' economical in use of material because it follows the outline of the ccoling pipes and its back face has rectangular recesses bounded by side walls 14 and 15, a central fin 16 and top and bottom walls 17 and 18. Formed as an integral part of the casting is an upstanding bracket 19 with side plates 20 and 21 and a rearwardly extending connecting plate 22.
Turning now to Figs. 4 to 6 the coolant conduit assembly comprises the tubes 13, now identified as outer tubes 13A and 13B and four intermediate tubes 13C, and two castings 23 and 24. The upper casting 23 comprises two generally U-shaped pipe bend sections 25 and 26 joined by a web 27. The tubes 13C are welded to the bend sections 25 and 26 which connect the tubes in pairs. The lower casting 24 to which the tubes 13A, 13B and 13C are welded has three generally U-shaped pipe bend sections 28, 29 and 30 joined by webs 31 and 32. The bend section 29 connects the inner pair of intermediate tubes 13C while the bend sections 28 and 30 join the outer tubes 13A and 13B, respectively, to the adjacent intermediate tubes 13C. As can be seen in Figs. 5 and 6 the castings 23 and 24 are shaped to follow the curvature of the face 11 of the clamp body (Fig.3) and the upper ends of the outer tubes 13A and 13B are cranked back to emerge from the rear part of the top face of the body 10 as seen at 33 in Fig.l.
It will be seen that fabrication of the coolant conduit assembly involves producing the two castings 23 and 24 and welding lengths of copper tube to them. Only the tubes 13A and 13B require bending and this is only through relatively small angles. After fabrication of this assembly the body 10 is cast around it. The tubes 13 czn be accurately placed in the best positions to effect the cooling and the casting can be designed to fit closely around the assembly with a minimum of excess material.
While the example described relates to an electrode holder for a coated electrode it will be apparent that the invention may also be applied to other electrode holders and also to the cooling of other castings, for example for bearings. In the example described the cooling conduit assembly is of the same material as the casting but in other applications of the invention the materials may be different, for example steel tubes in a copper casting, and the invention is not limited to copper castings.
Instead of welding the cast pipe bend sections to the tubes they may be shrink fitted, using tubes of larger diameter than the openings in the pipe bend sections and expanding the latter by heating before assembly. This may give latter sealing against leakage of coolant.

Claims

1. A cast article incorporating a prefabricated coolant conduit assembly wherein the coolant conduit assembly comprises at least two bend members having generally U-shaped passages therein and a plurality of tubes joined at their ends to the bend members to connect the said U-shaped passages.

2. A cast article as claimed in claim 1 in which the bend members are castings.

3. A cast article as claimed in claim 1 or 2 in which the body of the article is of copper.

4. A cast article as claimed in claim 3 in which the coolant conduit assembly is also composed of copper.

5. An electrode clamp comprising a copper casting incorporating a prefabricated coolant conduit assembly, the assembly comprising at least two end castings having generally U-shaped passages therein and a plurality of copper tubes joined at their ends to the bend members to connect the said U-shaped passages.

6. A method of forming a cast article incorporating coolant conduits by prefabricating a coolant conduit assembly and casting the body of the article around the said assembly wherein the assembly is produced by forming at least two bend members having generally U-shaped passages therein and joining the ends of a plurality of tubes to the end members to connect the U-shaped passages.

7. A method as claimed in claim 6 in which the end members are formed as castings.

8. A method as claimed in claim 7 in which the castings are joined to the tubes by shrink fitting.

9. A method as claimed in any of claims 6 to 8 in which the coolant conduit assembly and the body of the article are all formed of copper.