GB2202317A

GB2202317A - Lance for metallurgical use

Info

Publication number: GB2202317A
Application number: GB08803656A
Authority: GB
Inventors: James Forbes Corsar
Original assignee: STEIN REFRACTORIES; Gr Stein Refractories Ltd
Current assignee: STEIN REFRACTORIES; Gr Stein Refractories Ltd
Priority date: 1987-03-21
Filing date: 1988-02-17
Publication date: 1988-09-21
Also published as: GB8803656D0; GB8706763D0

Abstract

A lance 1 for metallurgical use, and adapted to be hand or machine-held, comprises a length of stainless steel tubing 2; a metallic mesh 5 surrounding the external periphery 4 of the tubing 2 along at least a portion of its length; and a coating 8 of monolithic refractory material applied externally to the mesh 5 so as to encase the tubing 2 in refractory material. The lance may be joined to another lance by an internally screw-threaded connector 12. In an alternative lance (1A, Fig. 3) a socket (7) of one lance receives the spigot (6) of the next succeeding lance. <IMAGE>

Description

LANCE FOR METALLURGICAL USE This invention relates to a lance for metallurgical use and adapted to be hand or machine-held.

Several types of hand-held lances are currently in use, for the purpose of injecting gases and/or suspended solids into molten metal in electric arc furnaces. A widely used type basically consists of a mild steel tube, and whilst this is cheap, it is consumed at several feet per minute and consequently requires large stocks and several lance changes per blow. Another type consists of a calorized mild steel tube, which although approximately five times the price of the plain mild steel tube, does not give five times the performance but does present savings in the form of lower stocks and fewer lance changes. It is also known to provide the calorized type of mild steel tube with a refractory "wash" coating, the coating adding of course to the cost but providing savings in the form of lower stocks and fewer lance changes.Yet another version of lance consists of a calorized or plain steel tube protected by externally applied refractory sleeves, which are usually assembled on site.

Again these are more expensive than the other types but give longer lance life. On the other hand, substantial stocks of refractory sleeves are required, while additional costs are involved in the assembly of this type of lance and a further drawback is the considerable weight increase, which is not insignificant with a hand-held lance, compared with plain or calorized mild steel tubes.

According to a first aspect of the present invention, there is provided a lance, for metallurgical use, and adapted to be hand or machine-held, the lance comprising: a length of stainless steel tubing; a metallic mesh surrounding the external periphery of the tubing along at least a portion of its length; and a coating of monolithic refractory material applied externally to the mesh so as to encase the tubing in refractory material.

The lance in accordance with the invention has a greatly reduced rate of consumption compared with prior art proposals, for most hand-held lances are used for oxygen injection, and stainless steel does not readily oxidise.

Thus, even compared with a refractory sleeved lance, the lance in accordance with the invention is consumed at a fraction of the rate of consumption of the refractory sleeved lance.

Furthermore, if the lance is intended to be hand-held the lance weight is of primary importance, and the weight of the lance in accordance with the invention is approximately onequarter the weight of plain steel tubing, and, depending on size, approximately one-tenth of the weight of a refractory sleeved lance.Although the lance in accordance with the invention is more expensive to produce than even the refractory sleeved lance of comparable length, substantial savings can be enjoyed in terms of stock space and capital outlay, as firstly the diameter of lances in accordance with the invention can be slightly less (approximately 1%) than mild steel or calorized lances, they are only a fraction of the diameter of sleeved lances, and with regard to costs, the lances in accordance with the invention giving many times the performance compared with conventional lances, are more cost effective and less capital is tied up in stock.

The length of the lance over which the refractory coating and mesh is applied depends on particular operating circumstances and/or customer requirements. Thus, the lance could be refractory coated over the whole of its length, or a substantial portion thereof, or alternatively could be coated over only a minor proportion e.g., 3%, of its length.

In detail, the stainless steel tubing may be of relatively light gauge, e.g. .6 to l.lmm, wall thickness.

The mesh is preferably also of stainless steel and may be of the general kind currently produced for air etc. filters. The tubing may have any desired length, up to 6 metres, with the refractory coating stopping short of each end of the tubing e.g. by approximately 50mum, for a jointing device e.g. a B.S.P. screwed coupling or thread, to be applied, although any method of joining, such as welding, bell and crimp joints, spigot and socket joints, collet chucks etc., can be employed.

Lances in accordance with the invention may be produced by any convenient means. Thus, in accordance with another aspect of the invention stainless steel tubing, of desired length is selected, stainless steel "stocking" mesh slipped over the tube and the refractory coating applied e.g., by an extrusion process. The refractory coating material is prepared to a suitable consistency and is preferably made from high alumina materials, but any satisfactory refractory material can be employed. The refractory material penetrates the interstices of the mesh, the latter being not only embedded within the refractory material, but spaced from the external periphery of the stainless steel tubing.

The invention will now be described in greater detail, by way of examples, with reference to the accompanying drawings in which: Figure 1 is a side elevation of a first embodiment of lance in accordance with the invention; Figure 2 is a section through the lance of Figure 1; Figure 3 is a side elevation of a second embodiment of lance in accordance with the invention; and Figure 4 is a section through the lance of Figure 3.

In both embodiments, like components are accorded like reference numerals.

A lance 1 comprises a length of stainless steel tubing 2 of relatively light gauge e.g., .6 to l.lmm wall thickness, with the interior 3 of the tubing length 2 being adapted, in use, for the conveyance of gases and/or suspended solids for the injection thereof into molten metal, and with the external periphery 4 of the tubing length 2 being provided with a stainless steel "stocking" mesh illustrated in dotted line at 5, and stopping short of the respective ends 6, 7 of the tubing length 2.To the mesh 5 is applied e.g., by an extrusion process, a coating 8 of monolithic refractory material, preferably a high alumina material, some of which refractory material penetrates the interstices of the mesh 5 so that the mesh is not only embedded within the thickness e.g., 2-3 mm, of the coating 8 but is also spaced from the external periphery 4 of the tubing length 2.

In the embodiment of Figures 1 and 2 a collar 9 is secured by weld metal 1B to each end 6, 7 of the tubing length 2, each collar 9 being provided with an externally screw threaded portion 11, onto which may be screwed an internally threaded B. S. P. coupling 12, whereby a leading end of one lance 1 may be attached to a trailing end of a preceding lance 1 for progressive use as the preceding lance is consumed by the molten metal.

In the embodiment illustrated in Figures 3 and 4, is shown a lance 1A, in which the metallic mesh 5 and the refractory coating 8 are continued over the lance end 7, but as before stop short of the lance end 6, the lance end 7 being expanded to form a socket, for a spigot and socket connection with the next succeeding lance 1

Claims

1. A lance, for metallurgical use, and adapted to be hand or machine-held, the lance comprising: a length of stainless steel tubing; a metallic mesh surrounding the external periphery of the tubing along at least a portion of its length; and a coating of monolithic refractory material applied externally to the mesh so as to encase the tubing in refractory material.

2. A lance as claimed in Claim 1, wherein the coating of refractory material extends over the whole length of the lance.

3. A lance as claimed in Claim 1, wherein the coating of refractory material extends over a major portion of the lengh of the lance.

4. A lance as claimed in Claim 1, wherein the coating of refractory material extends over a minor portion of the length of the lance.

5. A lance as claimed in any preceding Claim, wherein the stainless steel tubing is of light gauge, being .lmm to l.lmm wall thickness.

6. A lance as claimed in any preceding Claim, wherein the mesh is also of stainless steel.

7. A lance as claimed in any preceding Claim, wherein the refractory coating stops short of each end of the stainless steel tubing for a jointing device to be applied.

8. A lance as claimed in Claim 7, wherein the jointing device is a B.S.P. screwed coupling or thread.

9. A lance as claimed in Claim 7, wherein the jointing device is a weld.

18. A lance as claimed in Claim 7, wherein the jointing device is a bell joint.

11. A lance as claimed in Claim 7, wherein the jointing device is a crimp joint.

12. A lance as claimed in Claim 7, wherein the jointing device is a spigot and socket joint.

13. A lance as claimed in Claim 7, wherein the jointing device is a collet chuck.

14. A lance as claimed in any preceding Claim, wherein the refractory material is a high alumina material.

15. A lance substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.

16. A lance substantially as hereinbefore described with reference to Figures 3 and 4 of the accompanying drawings.

17. 17. A method of making a lance as defined in any preceding Claim, comprising selecting stainless steel tubing of desired length, slipping stainless steel "stocking" mesh over the tube and applying the refractory coating.

18. A method as claimed in Claim 17, wherein the refractory coating is applied by an extrusion process.

19. A method of making a lance, substantially as hereinbefore described with reference to the accompanying drawings.