The present invention relates to a pressure pipe for cooling high temperature metal rod or bar running in the direction of its length.

It is known in the manufacture of metal rod to cool the rod by passing water around the rod in a confined pipe, known as the pressure pipe. The effectiveness of the cooling can, in theory, be increased with increase in water pressure around the rod. The successful application of this principle would have significant technical and economic advantages.

According to the invention, there is provided a pressure pipe for cooling high temperature metal rod or bar moving in the direction of its length comprising a structure defining a first passage section followed by a second passage section through which the rod can pass, the first section having a bore which is less than that of the second section, means for introducing cooling water under pressure into the first section to apply dynamic pressure to rod passing therethrough, part of said dynamic pressure being replaced by an increase in static pressure in the second section and tubular guide means for guiding the rod as it passes through at least part of the length of the second section.

By providing an internal pipe to guide the

rod within the second high static water pressure section of the pressure pipe, the risk of a cobble occurring is reduced.

Preferably, the guide means include a guide pipe at the entrance to the second section and that guide pipe has perforations to allow the water to escape from the first section into the second section of the pressure pipe. This allows the rod to be guided into the second high pressure section while the water is allowed to expand and, reducing in velocity, increase in static pressure.

A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:-

Figure la is a sectional side view of an entry end of the pressure pipe installation;

Figure lb is a sectional side view exit end of the pressure pipe installation of Figure la;

Figure 2 is a cross-section taken along line A-A of Figure la; and

Figure 3 is a section taken along line B-B of Figure la.

Referring to Figures la and lb of the drawings, a pressure pipe installation generally comprises an entrance and water input section 1, an intermediate nozzle section 3, a main pipe section 2, and an exit section 4. The entrance and water input section 1 has a chamber 5 into which projects an

entrance guide 6. The guide 6 has a tapered entrance bore 8 joining a cylindrical bore 9 and an outer tapered end portion 10 which projects into the chamber 5 within the entrance section 1. The intermediate nozzle section 3 has a tapered entrance bore 11 joined to a cylindrical bore 12 which, in turn, joins to an outwardly tapering bore 13 which, in turn, is joined to a larger diameter cylindrical bore 14. The tapered bore 11 of the intermediate nozzle section 3 projects into the chamber 5 in the entrance section 1 to be situated about and close to the tapered end portion 10 of the entrance guide 6. An annular gap G is provided between the outer surface of the tapered end portion 10 of the entrance guide 6 and the tapered internal bore 11 of the intermediate nozzle 3. The internal bores of the entrance guide 6 and intermediate nozzle portion 3 are axially aligned. Within the nozzle 3, a perforated sleeve or tube 15 is positioned with one end fitted into an enlarged part of the narrow cylindrical bore 12 and the other end in the larger diameter cylindrical bore 14. The perforated cylinder 15 has elongate slots 16 and is supported by ribs 17 (see Figure 2) within the cylindrical bore 14.

The main pipe section 2 has an outer tube 20 and an inner tube 21 supported within the outer tube 20 by means of angularly spaced apart ribs 22 (see Figure 3). The bore of the tube 21 is substantially the same as that of the bore 12. The inner tube 21 has a

tapered entrance bore 23 followed by a main cylindrical bore 24. The main pipe 2 is bolted by means of bolts 25 to the intermediate nozzle section 3 to be axially aligned with the perforated tube 15. The tube 21 is spaced from the perforated tube 15 and the latter may easily be replaced, for example, with a different diameter tube for guiding different size products by disconnecting the main pipe 2 and withdrawing the tube 15. At distances along its length, the main pipe section 2 is supported by supporting members, as indicated at 40 in Figure lb.

The exit section 4 has a tapered internal bore 30 spaced from the end of the inner pipe 21 of the main cylindrical section 2, and the tapered bore 30 is followed by a cylindrical bore 31 of substantially the same bore as the bore 12. The exit section 4 is bolted to the main cylindrical section by means of bolts 32.

In use, hot rod is guided into the entrance section 1 through the guide 6 by the tapered bore 8. Once the rod is in the cylindrical bore 9 it is closely guided. Water is provided in the chamber 5 under high pressure (e.g., up to 15 bar) and passes through the annular gap G between the end 10 of entrance guide 6 and the tapered entrance 11 to the intermediate nozzle section 3 and passes about the rod as the rod enters the intermediate section 3. The water flow in this first passage section will be at high velocity. The rod is guided into the intermediate section 3 by tapered bore

11 and is guided in cylindrical section 12 and then in the perforated tube 15. The water can pass through the slots in the perforated tube 15 and into the larger diameter cylindrical bore 14. Thus, the velocity of the water in this second passage section will decrease and static pressure of water will increase from the cylindrical bore 12 to the larger cylindrical bore 14. The rod continues to be guided by the perforated cylinder 15 and then enters the inner cylinder 21 of the main pipe section 2 through the tapered entrance 23 to the inner tube 21 and is guided within the bore 25 of the inner tube 21. Eventually the rod exits through the exit section 4.

The high static pressure within the larger diameter cylindrical bore 14 of the intermediate nozzle section 3 is maintained in both the outer and inner tubes of the main pipe section 2. The narrowing exit section 4 guides the rod out of the main pipe and creates a back pressure to supplement the high pressure in the main pipe section 2.

After rod has passed through the pressure pipe, the pipe may be purged with high pressure air via valve 50.

Variations to the embodiment shown are envisaged, for example, the conical annular gap G could be replaced with radial holes, or provision made to adjust the size of the annular gap G. It would be possible to flood the entrance guide 6 by suitable

provision of water supply to enhance the cooling of the rods and reduce the amount of air drawn into the pressure pipe. The water for cooling may be externally degassed and/or cooled, etc., to improve cooling.

The pressure pipe of the invention could be used in the following applications: a) between rolling mill stands; b) before entry to the finishing block; c) incorporated with the rolling mill guides between stands in the finishing block; d) after the finishing block to achieve required laying head temperatures of metallurgical qualities; and e) prior to, or incorporated with, the rod laying head.