GB2327259A

GB2327259A - Steel making lances

Info

Publication number: GB2327259A
Application number: GB9714802A
Authority: GB
Inventors: Christopher John Treadgold; Ronald Cockbain
Original assignee: British Steel PLC
Current assignee: British Steel PLC
Priority date: 1997-07-15
Filing date: 1997-07-15
Publication date: 1999-01-20
Anticipated expiration: 2017-07-15
Also published as: GB9714802D0; GB2327259B

Abstract

A lance for conveying oxygen under pressure to a steel making converter has an elongate body through which cooling fluid is conveyed and a tip through which oxygen leaves the lance through one or more ports (5) and within which cooling fluid is circulated. Cooling fluid enters the lance tip through an opening of a baffle plate (8) which is positioned to direct the cooling fluid into contact with a crown (10) of the tip. A hub with fins is positioned within or adjacent to the baffle hole for dividing the cooling water entering the tip into a plurality of discrete flows to inhibit rotation thereof.

Description

STEEL MAKING LANCES This invention relates to lances for use in the production of steel.

In the basic oxygen steel making process, oxygen is blown onto the surface of a bath of molten iron within a converter vessel through a lance positioned with its tip immediately above the surface of the molten metal.

A layer of fluxes and/or slag is normally present on this surface. During the steel making process the temperature of the molten metal rises to 14000C and above. To withstand such temperatures the body and tip of the oxygen delivery lance are cooled by a flow of water which is pumped through the lance body to and from the lance tip. Conventional lances are used typically for 240 to 275 heats before they need to be replaced.

A conventional steel making lance is illustrated in Figures 1 to 3 of the accompanying drawings. In these drawings Figure 1 is side view partly in section of a conventional steel making lance, the section being taken along line I-I of Figure 2; Figure 2 is a section taken along line ll-ll of Figure 1; and Figure 3 illustrates the flow path of water passing through the tip of the lance illustrated in Figures 1 and 2.

The elongate body of the lance shown in Figure 1 comprises three open-ended generally coaxial steel tubes 1, 2, 3 whose open ends are linked by a lance tip 4. In use, oxygen is delivered from a source to the surface of a bath of molten metal within a converter vessel, oxygen being supplied from a source to the lance tip 4 through the innermost tube 1. The oxygen flows from the tube 1 and enters a series of outwardly inclined ports 5 from which it is discharged continuously onto the surface of the liquid metal. Six oxygen discharge ports are illustrated in Figures 2 and 3. Greater or lesser numbers of discharge ports may be provided.

As mentioned previously, to facilitate operation of the lance within the high temperature environment of the converter vessel both the body and tip of the lance are cooled. Conventionally, cooling is effected by pumping water under pressure to the lance tip 4 through an annular passageway 6 defined between the two innermost tubes 1 and 2. This water then passes over the upper surface 7 of a baffle plate 8 which forms part of the lance tip 4, and enters a cooiant flow passageway 9 defined between a crown 10 of the lance tip and the undersurface 11 of the baffle plate 8. On entering the passageway 9, cooling water passes through a central baffle hole 12.

Cooling water flows from the passageway 9 into a return flow passageway 14 defined between the two outermost tubes 2,3. The oxygen ports 5 pass through the baffle plate 8 and the passageway 9. Less conventionally, water is passed to the tip through the passageways 14 and returns through the passageways 6.

The baffle plate 8 acts to direct water passing from the passageway 6 through the passageway 9 and into the passageways 14. The intended purpose of the baffle plate is to ensure effective cooling of the internal surface of the lance tip crown 10.

Typically a lance tip is produced from high conductivity copper or copper alloy and may be manufactured as a single piece casting or as a multi-piece fabrication.

Successful operation of a lance of a basic oxygen steel making converter depends to a large extent on its ability to withstand the elevated temperature environment within the converter vessel. Effective cooling of the tip and in particular the lance tip crown is therefore essential. When used in a conventional operational set-up as shown in Figures 1 and 2, cooling water passing from the passageways 6, flows over the upper surface 7 of the baffle 8, through the central baffle hole 12 and onto the internal surface of the crown 10 before being returned via the underside 11 of the baffle to the outermost passageways 14.

In water flow simulation studies conducted by the applicants using a lance tip as shown in Figures 1 and 2, water was found to pass through the baffle hole 1 2 in a rotational flow pattern as illustrated in Figure 3. This flow pattern is indicated by lines 1 5. As a consequence, regions of the internal crown surface were found to be inefficiently cooled. These regions are indicated by lines 13. When the results of these studies were compared to regions on the internal crown surface which were known from experience to suffer from the degradation during operation, these conventionally degraded regions were found to match the crown areas found to be inefficiently cooled because of the rotational flow pattern discussed above.

One object of the present invention is to eradicate these regions of inefficient cooling and to provide a steel making lance having enhanced cooling efficiency and longevity.

According to the present invention in one aspect there is provided a lance for conveying oxygen under pressure to a steel making converter, the lance having an elongate body through which cooling fluid is conveyed and a tip through which oxygen leaves the lance through one or more ports and within which cooling fluid is circulated, cooling fluid entering the lance tip through an opening of a baffle plate positioned to direct the cooling fluid into contact with a crown of the tip to cool the same, and means positioned within or adjacent to the baffle hole for dividing the cooling water entering the tip into a plurality of discrete flows to inhibit rotation thereof.

Preferably, the baffle hole is positioned generally centrally within the baffle.

The flow dividing means may comprise a hub positioned generally centrally within or with respect to the baffle hole and includes a plurality of outwardly extending fins which act to direct cooling fluid into and through the baffle hole. The number of fins may be the same as the number of oxygen ports. The fins may be positioned between neighbouring ports or may be aligned with these ports. The fins may be aligned generally radially with respect to the centre line of the lance.

The cooling fluid is preferably water.

The edge of each oxygen port may be tapered to a point adjacent the edge of the baffle hole.

The invention will now be described by way of example only with reference to the accompanying diagrammatic drawings in which: Figure 4 is a section taken through a lance tip in accordance with the invention, the section being taken along line iV-IV of Figure 5; Figure 5 is a section taken along line V-V of Figure 4; and Figure 6 illustrates the flow path of water passing through the lance tip illustrated in Figure 4.

Like integers to those illustrated in Figures 1 to 3 have been given the same reference numerals.

In order to alleviate or reduce significantly flow rotation of water passing through the baffle hole 12, a plurality of fins 1 6 are positioned within or adjacent to the baffle hole, the fins extending substantially radially outwardly from a central hub 17 which forms part of the tip structure. As will be apparent from Figure 5, the fins effectively create a number of individual discrete channels for water entering the passageway 9. Trials conducted by the applicants have established that the presence of these fins effectively prevent rotation of the cooling water thereby significantly increasing cooling of the crown 10. This effect is illustrated in Figure 6, the direction of flow of the water being indicated by arrows 18.

As shown the fins 16 are orientated to match the number of oxygen ports 5, one fin being located generally centrally between neighbouring pairs of ports 5. Other designs may however be adopted, these including the presence of more or less fins than the number of oxygen ports and the fins being orientated to lie opposite rather than between the oxygen ports. Thus, any fin assembly which has the effect of eliminating or reducing rotation of cooling water entering the crown region of the lance tip may be adopted.

The fins may be incorporated into the lance tip as part of a casting or alternatively may form part of a fabricated tip.

As will be seen from Figures 5 and 6, each oxygen port 5 has a tapered profile 19 which extends to the edge of the baffle hole 12 thereby further inhibiting the onset of rotational movement of the cooling water.

In trials carried out by the applicants that lances in accordance with the invention have a life expectancy in excess of 350 melts. Indeed, one lance was used for 545 melts before it required replacement.

It will be appreciated that the foregoing is merely exemplary of steel making lances in accordance with the invention and that modifications can readily be made thereto without departing from the true scope of the invention.

Claims

1. A lance for conveying oxygen under pressure to a steel making converter, the lance having an elongate body through which cooling fluid is conveyed and a tip through which oxygen leaves the lance through one or more ports and within which cooling fluid is circulated, cooling fluid entering the lance tip through an opening of a baffle plate positioned to direct the cooling fluid into contact with a crown of the tip to cool the same, and means positioned within or adjacent to the baffle hole for dividing the cooling water entering the tip into a plurality of discrete flows to inhibit rotation thereof.

2. A lance as claimed in claim 1 wherein the baffle hole is positioned generally centrally within the baffle.

3. A lance as claimed in claim 1 or claim 2 wherein the flow dividing means comprises a hub positioned generally centrally within or with respect to the baffle hole and including a plurality of outwardly extending fins which act to direct cooling fluid into and through the baffle hole.

4. A lance as claimed in claim 3 wherein the number of fins is the same as the number of oxygen ports.

5. A lance as claimed in claim 3 or claim 4 wherein the fins are positioned between neighbouring ports.

6. A lance as claimed in claim 3 or claim 4 wherein the fins are aligned with the ports.

7. A lance as claimed in any one of claims 3 to 6 wherein the fins are aligned generally radially with respect to the centre line of the lance.

8. A lance as claimed in any preceding claim wherein the cooling fluid is water.

9. A lance as claimed in any one of the preceding claims wherein the edge of each oxygen port is tapered to a point adjacent the edge of the baffle hole.

1 0. A lance substantially as herein described and as described with reference to the accompanying diagrammatic drawings.