Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
  • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
  • C21C5/28—Manufacture of steel in the converter
  • C21C5/42—Constructional features of converters
  • C21C5/46—Details or accessories
  • C21C5/4606—Lances or injectors
  • C21C5/4613—Refractory coated lances; Immersion lances
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
  • F27D3/00—Charging; Discharging; Manipulation of charge
  • F27D3/16—Introducing a fluid jet or current into the charge
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
  • F27D3/00—Charging; Discharging; Manipulation of charge
  • F27D3/18—Charging particulate material using a fluid carrier
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
  • F27B3/00—Hearth-type furnaces, e.g. of reverberatory type; Tank furnaces
  • F27B3/10—Details, accessories, or equipment peculiar to hearth-type furnaces
  • F27B3/22—Arrangements of air or gas supply devices
  • F27B3/225—Oxygen blowing
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
  • F27D3/00—Charging; Discharging; Manipulation of charge
  • F27D3/16—Introducing a fluid jet or current into the charge
  • F27D2003/168—Introducing a fluid jet or current into the charge through a lance
  • F27D2003/169—Construction of the lance, e.g. lances for injecting particles

Definitions

• the present invention relates generally to lances used for treating molten metal baths.
• lances are used that may be generally named injection lances and that in their basic design consist of a hollow bar having an internal channel for introducing the substances. Due to the high temperatures, such lances are traditionally provided with a refractory coating that shall protect the hollow bar against the high temperatures.
• the coating consists of a ceramic material and serves excellently as a heat shield as long as it is intact.
• such a conventional lance is formed of a very thick hollow bar in order to minimize deflection of the lance, which may have a length of for instance about 4 meters.
• deflection of the lance exposes the ceramic material to very great stress, leading to cracks and fracture of the material.
• the invention eliminates the above discussed problems in an efficient and appropriate way.
• a general object of the invention is to provide a solution to the problem of the comparatively short useful life of lances that at their outer jacket are provided with a layer of refractory material serving as a heat shield.
• a basic object of the invention is to find a simple and appropriate way of providing a lance that on the one hand has sufficient flexural rigidity not to cause any harmful deflection during normal operation, and that on the other hand minimizes the problems of different thermal expansion of the constituent materials of the lance.
• the invention is based on the knowledge that the risk of cracking of the refractory material may be eliminated by simultaneously optimizing the flexural rigidity of the lance and minimizing the difference in thermal expansion between the different parts of the lance. According to the invention, this is accomplished by arranging a spacing means between an outer jacket pipe and an inner inlet pipe.
• the spacing means is in the form of at least one generally tubular member making only point contact with the jacket pipe and being firmly connected thereto in at least some of the contact points.
• the lance comprises two or more spacing members between jacket pipe and inlet pipe and the spacing members make mutual point contact with each other, whereby stiffening or strengthening may be increased and heat transfer may be reduced.
• the spacing members or an inner spacing member also make/makes point contact with the inner inlet pipe, whereby heat transfer is further reduced.
• the spacing member is firmly connected also to the inner inlet pipe, at least in some of the contact points.
• the spacing member is moreover connected to the jacket pipe and possibly also to the inlet pipe by spot welds in the contact points.
• the outer contact points are arranged in groups along the length of the lance; the contact points of the groups are arranged uniformly distributed around the circumference; and/or the outer contact points of the respective groups are provided in different numbers or displaced relative to each other around the circumference. All of these embodiments contribute to accomplishing an advantageous distribution of the heat transfer as well as a uniform strengthening or stiffening of the lance.
• the inner contact points are arranged in groups along the length of the lance; these inner contact points of the groups are arranged to be uniformly distributed around the circumference; and/or the inner contact points of the respective groups are likewise provided in different numbers or displaced relative each other around the circumference. All of these embodiments contribute further to accomplishing the advantageous distribution of the heat transfer as well as the uniform stiffening of the lance.
• the outer and the inner contact points, respectively consist of depressed areas or indentations in the jacket pipe and the spacing member, respectively.
• Another object of the invention is to provide an appropriate method of producing a lance according to the invention.
• an inlet pipe is inserted into a tubular spacing member, which is then deformed in points into contact with the inlet pipe, that the spacing member with inserted inlet pipe is then inserted into an outer jacket pipe or alternatively into a further spacing member and then into a jacket pipe that is in turn brought into point contact with the spacing member or the outer spacing member.
• the jacket pipe and the spacing member or the outer spacing member are connected by spot welding in the deformed areas.
• the spacing members are mutually connected by spot welding in the deformed areas
• a lance according to the invention is used as an oxygen injection lance by steelmaking.
• the present invention offers the following advantages: • A long useful life due to a substantially reduced risk of cracking in a surrounding refractory material; • Elongation through heating may in principle be avoided;
• a structure with flexural strength may be achieved with a comparatively very thin inlet pipe, i.e. having a small heat absorbing mass;
• Cooling medium that is conducted in the channels may be given an advantageous course of flow by mutual displacement of the contact points in the different groups.
• Fig. 1 is a partial perspective view, partly in section, of a first embodiment of a lance according to the invention
• Fig. 2 is another partial perspective view of the lance according to fig. 1, cut open to more clearly illustrate the outer jacket and the spacing pipe of the lance,
• Fig. 3 is a sectional view through the inlet pipe and the spacing pipe of the lance according to fig. 1,
• Fig. 4 is a sectional view through the lance according to fig. 1,
• Fig. 5 is a partial perspective view, partly in section, of a second embodiment of a lance according to the invention
• Fig. 6 is a sectional view through the inlet pipe and the spacing pipe in the lance according to fig. 5
• Fig. 7 is a sectional view through the lance according to fig. 5,
• Fig. 8 is a sectional view through an inlet pipe and a spacing pipe in a further embodiment of the invention.
• Fig. 9 is a sectional view through a lance corresponding to the embodiment illustrated in fig. 8, and
• Fig. 10 is a sectional view through a lance according to yet another embodiment of the invention.
• Figs. 1 and 2 illustrate a short portion of a lance 1 according to the invention, which in practice typically has a length of about 4 meters. Furthermore, in the figures the lance 1 is partly cut up in two different ways in order to illustrate the constituent elements and parts thereof.
• the lance 1 is built up of an inner inlet pipe 2 that is employed to introduce treatment substances in a melt (i.e. a molten bath), not illustrated, for instance in a converter.
• the inlet pipe 2 is inserted into a spacing member 3 that is likewise generally tubular. Accordingly, the spacing member substantially concentrically surrounds the inlet pipe 2.
• the spacing member 3 is in turn surrounded by an outer jacket 4 that at is outer surface supports a heat shield in the form of a layer of cast refractory material 8, preferably ceramic material, of which only a short portion is illustrated in fig. 1.
• the spacing member 3 is formed by a pipe having an inner diameter being essentially larger than the outer diameter of the inlet pipe 2.
• Contact between the inlet pipe 2 and the spacing member 3 is established by forming indented or depressed areas 6 in the circumferential surface of the spacing member 3.
• These indented or depressed areas 6 form inner contact points 10, i.e. there is essentially point contact present between the inlet pipe 2 and the spacing member 3.
• the inlet pipe 2 may also be connected to the spacing member 3 in some or all of the contact points 10, preferably by spot welds, as will be described further below.
• fig. 1 and particularly fig. 4 show that in the illustrated embodiment the jacket pipe 4 is formed by a pipe having an inner diameter that is essentially larger than the outer diameter of the spacing member 3.
• Contact between the jacket pipe 4 and the spacing member 3 is likewise established through indented areas 7 that are formed in the circumferential surface of the jacket pipe 4.
• These indented areas 7 form outer contact points 11, i.e. there is essentially point contact present also between the jacket pipe 4 and the spacing member 3.
• the jacket pipe 4 is firmly connected to the spacing member 3, primarily for the purpose of preventing too substantial elongation of the jacket pipe in relation to the refractory heat shield 8.
• This connection preferably consists of spot welds applied in at least some of the outer contact points 11. Depending upon the field of application spot welds are in some cases applied to all outer contact points 11.
• the outer as well as the inner contact points 10 and 11, respectively, i.e. the corresponding indented or depressed areas 6 and 7, respectively, are each arranged in groups separated from each other along the length of the lance 1.
• Each such group consists of a number of, in the illustrated example three, contact points 10 and 11, respectively, arranged to be uniformly distributed around the circumference of the spacing member 3 and the jacket pipe 4, respectively.
• the groups of inner contact points 10 are axially, with regard to the center axis C of the lance 1, separated from the groups of outer contact points 11.
• the inner contact points 10 and the outer contact points 11 are also in their groups rotated half a pitch in relation to each other.
• all inner contact points 10 are displaced in the circumferential direction in relation to the outer contact points 11, and at the same time all groups of contact points 10, 11 are separated along the length of the lance 1.
• this arrangement is also illustrated in fig.
• the different constituent pipes 2, 3, 4 of the lance 1 may be relatively thin- walled without reducing the flexural rigidity of the lance 1. This, as well as the pure point contact provided between the pipes results in a much reduced heat transfer when compared to conventional designs. All in all, this results in a substantial reduction of the stress on the refractory heat shield 8 that is otherwise caused by thermal expansion of the parts of the lance 1 that are positioned inside the shield 8.
• an inlet pipe 2 is inserted into a spacing member 3.
• the spacing member 3 is inserted into a chuck that in fig. 3 is only illustrated by its indicated jaws 5, three in number.
• the chuck is activated to form the depressed areas 6. Thereby, all of these areas 6 of the group are formed with such a depth that they, i.e. the spacing member 3, engage the inlet pipe 2.
• the used chuck does in itself not constitute any part of the invention and is not illustrated and described further herein.
• each suitable chuck or corresponding tool may be used that in this manner is capable of applying uniform pressure to a number of points at the circumference of a tubular workpiece.
• the spacing member 3 is inserted in steps into the chuck, with activation thereof after each displacement, for forming the rest of the groups of depressed areas 6.
• the spacing member 3 is then connected to the inlet pipe 2 in some or all of the contact points 10, preferably by spot welding.
• the unit formed by the spacing member 3 and the inlet pipe 2 is then inserted into a jacket pipe 4.
• the jacket pipe is inserted into the chuck in a corresponding manner, up to the position of the first group of outer contact points 11.
• outer depressed areas 7 are formed down into contact with the spacing pipe 3.
• the difference in diameter between the jacket pipe and the spacing member is less than mat between the spacing member and the inlet pipe, whereby in this case the outer depressed areas 7 will be both shallower and smaller.
• all of the outer depressed areas 7 are then formed by alternating stepwise insertion of the jacket pipe into the chuck and activation of the latter.
• the jacket pipe 4 is rotated and inserted into the chuck so that the groups of outer depressed areas 7 or contact points 11 are positioned between the groups of inner depressed areas 6 and displaced around the center axis C of the lance in relation thereto.
• the spacing member 3 is then connected to the jacket pipe 4, preferably in all contact points 11, likewise by spot welding.
• Figs. 5-7 illustrate a second embodiment of a lance 100 according to the invention.
• this lance 100 corresponds completely to the lance 1 according to the first embodiment and differs therefrom only by the positioning of the groups of inner and outer depressed areas 6 and 7, respectively. More specifically, the inner contact points 10 of successive groups are displaced in relation to each other around the circumference of the lance
• the outer and inner depressed areas 6 and 7, respectively, of successive groups are displaced by a half pitch in relation to each other around the circumference of the lance 100, which is most clearly visible in the sectional views of figs. 6 and 7, but also in fig. 5.
• the inner and outer areas of the respective first groups have thereby been denoted by 6 and 7, respectively, while the inner and outer areas of the respective second groups have been denoted by 6' and T , respectively.
• hidden areas have in fig. 5 been denoted by the addition of D.
• the invention also comprises designs where adjacent groups are alternatively displaced in larger or smaller steps than by half a pitch.
• This second embodiment of the lance 100 is likewise produced basically in the same way as the first embodiment according to figs. 1-4. The difference is that when the groups of depressed areas 6, 7 are being formed, the spacing pipe 103 and the jacket pipe 104, respectively, are here rotated in one and the same or alternating directions in the chuck, in the example by half a pitch between the depressed areas of the group, after the forming of each group.
• this lance consists of an inlet pipe 2 that is inserted into a spacing member 203.
• the spacing member 203 is also here formed with depressed areas 206 forming inner contact points 210 with the inlet pipe and possibly being connected thereto.
• the depressed areas 206 are formed in a corresponding chuck having jaws 5, but in this case the spacing member 203 is allowed to bulge outwardly between the depressed areas 206, forming bulging or convex areas 207. Such bulging of the areas between the jaws 5 occurs automatically if these areas are not restrained during activation of the chuck.
• the bulging areas 207 protrude past the original circumference of the spacing member 203.
• this unit which is formed by the inlet pipe and the spacing member, is inserted into the jacket pipe 204, these bulging areas 207 form the outer contact points 211 with the jacket pipe, without requiring any deformation thereof. Consequently, the jacket pipe 204 may be directly connected to the spacing member 203, preferably likewise by spot welding.
• the jacket pipe 204 is suitably selected having an inner diameter that basically corresponds to, but is slightly larger than an imaginary circumferential line being tangential to the bulging areas 207 of the spacing member.
• the groups of depressed and bulging areas may be formed and distributed in the manners described above, as well as with the modifications and variations described below.
• fig. 10 is illustrated an embodiment of the invention that starts from the embodiment according to figs. 8 and 9 but that may likewise be applied to the designs according to figs. 1-7.
• the lance 300 according to this design consists of an inlet pipe 2 that is inserted into an inner spacing member 303 A.
• the lance 300 consists of an inlet pipe 2 that is inserted into an inner spacing member 303 A.
• this inner spacing member 303 A is formed with depressed and bulging areas 306 A, 307A, respectively, the former thereby forming inner contact points 319 with the inlet pipe 2 and possibly being connected thereto.
• the formed unit 2, 303A is not inserted into a jacket pipe but into an outer spacing member 303B having a larger diameter.
• the outer spacing member 303B is likewise formed with depressed and bulging areas 306B and 307B, respectively, the former thereby forming intermediate contact points 315 with the bulging areas 307 A of the inner spacing member 303 A, and possibly being connected thereto by spot welding.
• the unit formed by the inlet pipe 2 and the inner and outer spacing members 303 A, 303B is inserted into a jacket pipe 304, which is dimensioned in relation to the outer spacing member 303B in accordance with the principle described in connection to fig. 8 and 9.
• the bulging areas 307B of the outer spacing member 303B form outer contact points 311 with the jacket pipe 304 and are connected thereto in these points.
• fig. 10 describes the use of two spacing members 303A and 303B, it shall be apparent that the invention also comprises building up the lance 300 using any other number of spacing members that is suitable for a specific application.
• the invention also comprises the possibility of arranging different numbers of depressed and bulging areas, respectively, in the different groups, both in groups having the same and different types of contact points. These variations may possibly also be combined with the displacement around the circumference.
• the number of depressed areas in each group may preferably be between 1-6, whereby, in the case with one area per group, the areas may be arranged in a helical shape around the circumference. However, in most cases a number of 3-4 areas per group are suitable, and where spot welding is employed, it has turned out that the best result is obtained with 4 areas per group.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Furnace Charging Or Discharging (AREA)
• Feeding, Discharge, Calcimining, Fusing, And Gas-Generation Devices (AREA)

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Publications (1)

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Cited By (3)

Citations (5)

• 2000
  • 2000-06-29 SE SE0002458A patent/SE516609C2/sv not_active IP Right Cessation
• 2001
  • 2001-06-27 WO PCT/SE2001/001467 patent/WO2002002827A1/en active Application Filing
  • 2001-06-27 AU AU2001266517A patent/AU2001266517A1/en not_active Abandoned

Patent Citations (5)

Non-Patent Citations (1)

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