US3193272A - Converter for steel plants - Google Patents

Description

3 Sheets-Sheet 1 /NVENTOE ATTRNE'YS July 6, 1965 H. KRAMER ETAL CONVERTER Foa STEEL PLANTS Filed Jan. 14, 1963 July 6, 1965 H. KRAMER r-:rAL 3,193,272

` CONVERTER FOR STEEL PLANTS Filed Jan. 14. 1963 3 Sheets-Sheet 2 /NVENTORS HELM ur KEMER WoLpBA/JE 25:55

July 6 1965 H. KRAMER TAL 3,193,272

CONVERTER FOR STEEL PLANTS Filed Jan. 14, 1963 3 Sheets-Sheet 3 ag L www HTTORNEH United States Patent O r 1s claims. (in. 26a-36) This invention relates generally to metal smelting equipment and to converters for the production of steel, and more particularly to a converter suitable for the oxygen blast method of steel production.

In general there are two types of converters known: converters with a loose supporting ring and converters with a fixed supporting ring welded around the vessel shell.

Ln the type of converters which have a loose supporting ring, the vessels are supported by means of radial straps on their supporting rings in such a way that the converter can expand freely with rising temperature and therefore have difficulty in withstanding thermal stresses. On the other hand, it was found that such converter vessels frequently are subjected to such high tensile stresses and temperatures that the elastic or ilow limit of the vessel material is exceeded and permanent deformations appear. The vessel then begins slowly to grow and can increase to such an extent after a number of years that in some cases converter vessels have completely grown into the oriffinal loose supporting ring, sometimes even bulging far over the supporting ring above and below the latter. Furthermore, due to these stresses and resulting expansion, cracks may appear in the converter shell, and in riveted converters the rivets may even shear oil.

The reason for these diiiiculties is the considerable pressure exerted by the refractory brickwork lining which is substantially hottter on the average than the converter shell and which therefore tends to expand to a greater extent with approximately the same coeicient of thermal expansion. The resulting state of tensile strs in the converter shell thus resembles that of a high-pressure tank. In addition, the strength of the vessel decreases with increasing temperature. The temperature in the vessel shell rises, however, with increasing wear of the refractory brickwork lining, because the insulating brick layer becomes thinner. At the same time, the pressure exerted by the brickwork diminishes also, but the remaining brickwork or permanent lining can still effect a relatively high internal pressure by sintering, compression, etc.

These disadvantages become increasingly noticeable with increasing size of converter, because the thickness of the converter shell cannot be increased indefinitely; otherwise unfavorable conditions would result in the welded joints in the case of Welded construction, and muitidirectional states of stress, etc., would occur, and these could represent additional sources of damage.

In the other general type of converter vessels, namely those with the supporting ring Welded on, the growth of the vessel is forcibly prevented in the center portion of the converter if the supporting ring is suiiiciently strong. However, above and below the supporting ring, in some cases inside the latter, considerable tensile stresses can still occur, namely when the brickwork is still new and thus can exert a considerable thermal expansion pressure. In this type of construction, when the brickwork is considerably burnt out, the temperature differences between the outer colder part of the supporting ring and the hot vessel shell can become so great that the vessel shell may come under high compressive stress even in the region where the supporting ring is secured, particuice larly when the brickwork is burnt out to such an extent that it can no longer exert a corresponding counter-pressure. These compressive stresses are particularly dangerous, because they can lead the formation of corrugations and wrinkles in the sheet forming the shell as soon as the critical buckling stress is exceeded, which may be much lower than the admissible tensile and compressive stresses. Local overstressing of the material in the wrinkles formed may again cause cracking in the vessel shell. In addition, the welded-on supporting ring partly relieves the converter vessel of the tensile stress in a new brick lining, but is always under tensile stress in its outer part, whether the brickwork is new or nearly burnt out. In particular, the great temperature differences existing between the sheet metal of the vessel shell and the outer strap of the supporting ring when the brickwork is nearly burnt-out, tensile stresses can occur which attain a value many times the stresses caused by the prevailing static forces and moments. The supporting ring is thus constantly stressed beyond the loads corresponding to its intended function proper, which is to support the vessel during the blasting and tipping operation. Consequently, converters with welded-on supporting rings will operate satisfactorily only if the converter supporting ring is carefully constructed and considerably over-dirnensioned.

lt is the object of the invention to eliminate these disadvantages of the known converters.

Another object of the invention is to provide a converter in which the radial heat expansion and reduction in strength `of the converter shell remains less than in the prior are converters.

A further `object of the invention is to provide a converter shell of simpler, less expensive and lighter weight construction than those of the prior art, but which will nevertheless withstand the thermal land mechanical stresses of operation even with partially burnt out refractory lining.

To these ends, and in accordance with one feature of the invention, the converter shell is provided, at least in its central portion, with several strong steel rings, secured to the vessel shell, extending radially from the shell and peripherially spaced from each other. These radial rings are preferably distributed approximately evenly, either over only its center portion or over the entire converter shell, depending upon the size of the converter. The radial rings, thus arranged on the shell, are advantageous in four respects. First, they relieve the vessel shell at all points from the particularly dangerous tangential stresses caused by the pressure of the briclswork. Secondly, due to the relatively small intervals between the radial rings, the buckling lengths or spans of the shell plate are reduced, and the critical buckling stresses are thus increased to such an extent that they can no longer be attained under the prevailing conditions. Thirdly, by conducting heat from the vessel shell over the radial ring, the temperature of the vessel shell is substantially reduced, and thus a reduction of its strength properties to a great extent prevented. At the same time the ternperature differences are reduced and the resulting thermal stresses diminished. Fourthly, :due to the action of the radial rings distributed over the vessel shell, the supporting ring is able to properly fulfill its intended main function, namely, the support `of the converter in all tipping positions, without the need Vfor being dimensioned larger than necessary. The above described advantages are particularly effective in large converter vessels, as they are used more and more in the production of steel according tothe oxygen blast method.

The radial rings can have different, but predominantly flat profiles; a reinforcement of the material toward the outer edge of the ring may be of advantage to absorb the 3 Q increased tensile stress. t is important that the radial rings be relatively thick-walled, or if the thickness of the material cannot be increased, that the rings be provided in correspondingly large numbers. Both measures have the same effect; i.e. they provide a Vgood reinforcement as well as a good flow of Vheat to the outside. In these radial rings the temperature differences and thermalV stresses are therefore very low. However, in certain cases the use yof straps lying ii'at against the sheet plate instead of radial rings projecting at some points from the shell of the converter vessel will suffice to solve the problem underlying the invention.

According to a further feature of the invention, hat but strong radial rings are provided, secured with their narrow side against the converter shell. Along the outer edges of these rings' are welded steel straps or sheet metal strips which either extend only about one ring, or which are so arranged that they form closed box-shaped ducts through which a coolant can be passed.

Strong steel straps, having their respective outer edges welded over the central region of the converter vessel,

, take over to advantage, at least to a substantial part,

the `function of the supporting ring.

According to another feature of the invention, 'the converter trunnions are secured in holding members of cast steel which are -inserted into the radial rings located on the center portion of the converter, the ends of the radial rings adjoining the holding members being welded with the tongue-shaped lugs of the holding members in alignment with the rings. The holding members are preferably hub-shaped in their centers to receive the converter trunnions, and terminate on the inside in a substantial-.ly rectangular shield which is curved with the same radius of :the converter shell and welded to .the latter. The holding members terminate on the outs-ide in a substantially rectangular shield, likewise welded on with the steel straps extending over the radial central rings. In this, the supporting ring is so included in the radial ring system that the eifectivenessof the radial rings is not impaired by the interruption of the rings. The supporting ring elements thus merely form an additional reinforcement because of the straps provided over the radial rings and the hub piecesinserted at those points where it is necessary to introduce and absorb the forces moments which arise during the supporting and tipping of the converter.

In those cases where the arrangement of radial rings distributed over the converter shell is not of itself sucient to reduce the stresses in the vessel shell to such an extent that vessel growth and cracks'are positively prevented, according to another feature of the invention, longitudinal straps can be arranged extending along the surface of the shell under the radial rings. These straps are correspondingly recessed on their inner edges. The longitudinal straps form an additional axial reinforcement which is of advantage when, in addition to the tangential stresses controllable by the arrangement of radial rings according to the invention, the stresses in Vaxial direction assume dangerous values.

In order to improve the conducting away of heat the radial rings are perforated according to the invention, the perforations being so arranged that a current of cooling air can flow around the converter shell from the lower to the upper end of the converter. Such a cooling air current is formed naturally due to convection during the operation of the converter, since the air at the shell plate and the radial rings is heated as well as on the longitudinal straps etc. when these are present, whilel cold air follows and is drawn in from below.

In certain stages of operation, cooling by the abovementioned natural cooling air current may perhaps not be sufiicient, particularly in the last portion of a converter campaign or run when the brickwork'eis burnt out to a `great extent and the remaining relatively thin lining ciers very little resistance to the flow Iof heat into the vessel shell. According to still another feature of the invention, a closed-circuit pipe line or conduit is therefore provided on the bottom part of the converter shell. This conduit is formed preferably by closing off two of the low-ermost radial rings by means of a thin outer plate covering the intervening space to form box-shaped ducts. The closed circuit conduit is provided with vupwardly directed blow-out openings and has at least'one laterally projecting air inlet scoop. Stationary compressed air nozzles are arranged at a sufficient distance ahead of the air inlet scoop sodas to permit unhindered tipping of the converter. These nozzles .are Idirected towar-d 'the air inlet scoops when the converter is in its blowing position. During the converter blowingV operation, i.e. when the greatest amount =of heat is to be eliminated, such an additional cooling current from the air nozzles can be superimposed on the naturally formed cooling air cur- Y rent. The supply of compressed air to the nozzles can be regulated by throttling in accordance with the respective'requirements.

In order to permit a particularly economical and yet safe cooling to take place, temperature sensing devices are arranged on the converter shell and, in cases where they occur, on the outer steel straps surrounding the radial rings. rIhe temperature sensing devices are preferably connected with temperature indicators, recorders, alarm systems, etc., of known type which permit checking of the temperature distribution on the converter, so that the supplemental cooling by compressed air can be added, as required. Of particular advantage is automatic control by 'a therm-ostatic control device actuated by the temperature sensors, which opens a valve to turn on the compressed air supply when the predetermined temperatures are exceeded.

Additional features and advantages of the invention will become apparent from the following description of preferred embodiments of the converter according to the invention by way of example only and with reference to the attached drawings, wherein:

FIG. l is a fragmentary sectional view of the Wall of a known type of converter with the supporting ring welded Yon;

FIG. 2 is a partial longitudinal sectional view taken along line II--II of FIG. 5 through the wall of a converter on Whose shell are arranged radial rings and longitudinal strap-s according to the invention;

FIG. 3 is a partial horizontal sectional detail view taken along the line III-III of FIG. 2;

FIG. 4 is a partial horizontal sectional View along the line IV-IV of FIG. 2;

FIG. 5 is a side elevational view of the converter according to an illustrative embodiment of the invention;

FIG. 6 shows a top plan view of the converter of FIGS. 2 and 5; Y 1

FIG. 7 shows a side elevational view of another converter according to a different embodiment of the invention;

FIG. 8 is a longitudinal sectional view taken along the line VIII-VIII of FIG. 7;

FIG. 9 is a partial horizontal sectional view taken along the line IX-IX of FIG. 7; l

FIG. l() is a sectional detail view taken along the plane of line X-X of FIG. 9; Y I

FIG. l1 is a partial horizontal sectional View along the plane of line XI-XI of FIG. 8;

FIGS. 12A, 12B, 12C shows three different modifican tions of the radial rings in cross section; and

FIG. l3is a schematic diagram of the automatic control device for switching on the forced air circulation.

For a better understanding of the invention, prior art supporting rings Vwill first be described. In FIG. 1a Vlsupporting ring of the prior art, consisting of a supporting ring strap 2 and of two radial ring plates 3 welded on the upper and lower edge of the .strap 2, is welded onto the cylindrical central portion of the shell of the converter bores 8.

,mouth or against other contamination.

vessel l. The Ibroken lines 4 and d indicate respectively the thickness of the refractory lining at the start and at the end of a converter campaign or run. ln this known type converter, the high tensile stresses in the vessel shell during operation are prevented by the supporting ring only locally at the fastening points between the shell and the supporting ring plates 3. The supporting ring 2, 3 is itself, however, subject to considerably higher stresses than those resulting from merely the forces and moments transmitted during the holding and tipping operation of the converter vessel l.

In the embodiment of the invention according to FlGS. 2 to 6, radial rings 5 are arranged over and welded to the entire shell 6 of the converter vessel at regular intervals to relieve the vessel shell of tangential stresses. The refractory brickwork lining at the start and at the end of a converter run is again indicated by broken lines 4 and 4. Apart from the radial rings 5, longitudinal straps 7 are provided along the outer surface of the vessel to absorb axial stresses. As shown in FIG. 3, these longitudinal straps 7 merely bear flat against the converter shell plate 6 but are not welded onto the shell plate. The longitudinal straps 7 extend along under their intersection locations with the radial rings 5, which are provided with Vrecesses or bores 8 well-rounded at the ends and are secured by welded joints 9 to the straps '7 at the edges of the Due to this type of fastening, longitudinal welded joints are avoided on the shell plate, since such joints would weaken its resistance to tangential stresses. The upper ends of the longitudinal straps 7 are Welded as shown in FlGS. 5 and 6, onto the tongue-shaped lugs l of a cap or junction co-ne "il disposed on the converter shell close to its mouth. The lower ends of straps 7 are secured in the same manner onto a junction cone ll at the lower end of the converter. The junction cones 1l, ll at the same time forni respective reinforcements of the mouth and of the bottom region of the converter. This reinforcing eect is particularly advantageous, because the mouth of the converter shell is subject to particularly high edge stresses created by the brickwork lining Wedging conically during its expansion, and by the particularly high temperature which occur at the mouth, While the converter bottom is stressed not only by the pressure of the brickwork but also in the vertical direction of the converter by the full weight of the charge.

In the central region of the converter, steel bands 12, extending parallel to the converter shell 6, are welded onto the outer edges of the radial rings 5, these bands closing the space between two radial rings to form a box or rectangular duct. rthese steel straps l2 must also take over the function of the supporting ring of FlG. 1 and are connected with diametrically opposed holding members which carry the trunnions 37 of the converter, as described more fully below. Longitudinal webs 13 (FIG. 3), which are welded onto the longitudinal straps 7, are provided to stiifen the arrangement, so that welded joints are again avoided on the shell plate, since such joints could reduce the resistance of the shell to tangential stresses. The above described arrangement may already be suicient to eliminate the diliculties appearing in the known converters according to the problem underlying the invention.

Beyond the foregoing, as a further feature of the invention, the intervals between the radial rings are closed in the lower converter portion, as shown in FIGS. 2 to 6, by means of thin sheet metal strips lo welded onto the outer edges of rings 5 to form a box or rectangular duct. ln the upper part of the converter, thin sheet metal strips or shielding plates l5 are welded onto the edges of the radial rings 5 in a similar manner. These shielding plates l5 are arranged at an angle to the converter shell in such a way that they shield the open intervals between the radial rings 5 and serve as a protecting roof against slag foaming out from the converter All of the radial rings 5 are provided at intervals with respective holes lo which are staggered relative to each other in the superposed rings. This has the effect that the entire converter shell is surrounded by cooling chambers or ducts which can be traversed by cooling air passing through openings lo from the bottom to the top of the converter, so that heat can be withdrawn from the converter shell o and from the radial rings 5. Due to the staggered arrangement of the holes lo in the superposed radial rings, the cooling air current receives lateral llow cornponents, so that the flow through the various cooling chambers and the scavenging of the hot air is thus improved. Between the projecting edges of the shielding plates l5 and the underlying radial rings 5, there is a suliicient open free cross section to permit the issuance or exit of a partial current of cooling air without any major ilow resistance, while the remaining part of the cooling air liows through the overlying cooling chambers or ducts. As long as the refractory lining of the converter vessel is still strong enough, the cooling air formed by natural convection suiices to keep the temperatures in the converter shell plate and in the radial rings within a range whichV ensures a suicient strength of the shell plate and keeps the thermal stresses within tolerable limits. With increasing wear of the converter lining, artificial cooling can then be started.

For this purpose, a closed-circuit pipe line or conduit 17, formed by closing of the interval between the two lowermost radial rings 5, 5', is provided with two oppositely arranged air inlet scoops or tunnels 18. These air inlet formels l have a suiciently large cross section and are so designed aerodynamically that they impair the natural convection cooling current only to a negligible extent. The wellaoundcd inlet 19 of the air tunnel (FIG. 4) is connected through an intermediate portion 2t), having a constant cross section as shown in FlG. 4, with a double dilfusor 2l in the form of a Y pipe opening tangentially at both sides into the closed-circuit conduit line TJ?. The double diusor 2l is formed on its outer side by the correspondingly bent ends of the sheet metal strap ldand on its side facing the converter shell by a baille or deiiecting plate 22 welded into the closed-circuit conduit; line l?. Along the bottom edge of the baille Y plate 22 is left a gap 23, between this bottom edge and the lowerrnost radial ring 5', through which the entering air can ilow to the part of the converter shell plate which is covered by the barile plate 22, so that this part of the shell is sufficiently cooled, but not impinged upon directly by the full jet of cooling air entering through air inlet scoops lo, which could possibly cool this point excessively. The air entering behind baille 22 through gap 23 flows through an aperture lo' in the penultimate radial ring 5 (FlG. 2) which forms the upper closure surface of the closed-circuit conduit line l as well as of the didusor 2l. The air iiows upward from the space behind the diiiusor and forms an air current along the upper portion of the converter shell to cool it in the same manner as the cooling takes place over the rest of the shell.

Additional cooling air can be blown into the closedcircuit conduit line l? through nozzles 24, located opposite the air inlet funnel 18, to increase the natural cooling current along the converter shell. As shown in FGS. 5 and 6, the nozzles 2d are connected to blowers 25 through pipe lines 25. Throttle valves 27, provided in the pipe lines Z5, permit regulation of the amount of additional cooling air supplied from the respective blowers. The distance between the nozzles 24 and the air inlet scoops 13 is so dimensioned that the converter vessel can be freely tipped without hindrance. At the same time, this spacing has the result that the natural air flow can pass into the funnel l unhindered, while the blast `air from nozzle 2d is not yet turned on.

In order to control the amount of additional cooling, temperature feelers sensors or thermocouples 2S are provided according to the invention at various points around the converter shell, to determine the shell temperature during its operation at such points. Another temperature sensor 28' checks the temperature of the steel bands 12, so that the temperature between the latter and the shell is also determined. Signals from the sensors 28, 2S are transmitted in the usual mannerto instruments so that the measured temperature values can be either read directly on indicators or recorded by means of temperature'recorders. The switching-on of the cooling air blower and the regulation of the cooling air current can then be effected manually on the basis of these values. Preferably, however, an automatic control device, which is known in itself, can be provided, as shown schematically in FIG. 13. The control device receives its control impulses from the temperature feelers 2S and switches on the cooling blower 26 at certain predetermined temperatures or moves throttle valve 27 to effect the regulation within a certain temperature range.

As shown in FlG. 13, the temperature feelers 23, 28' may be in the form of temperature responsive devices such as thermocouples, which at pre-set temperatures generate sufficient elcctromotive force to actuate a micro switch S, through an amplifier A if necessary, thus energizing a circuit from battery Bto magnet coil lvl. When energized, the magnet M opens the valve V, which corresponds to the valve 27 of the blower 26 in FIG. 5.

The cooling system according to the invention is extremely economical. First of all, suflicient cooling of the converter shell is achieved over a considerable part of the operation of the converter, even without the forced circulation 'from the blower nozzles 24, simply by the natural convection cooling current formed in the described structure. Secondly, the additional cooling provided from the blower is itself particularly economical, because the elimination of heat from the shell, with the converter lining burnt out to a considerable extent, requires large amounts of air. However, the pressure of the forced air current can be very low, since frictional pressure losses in the cooling circulation system can be kept at a minimum by corresponding suitable dimensioning of the flow cross section.

The arrangement according to the invention avoids the necessity for large and expensive blowers having large volume delivery capacity. The blowers 26 connected tothe nozzles 24 may have higher pressure capacity but with reduced rate of delivery volume. Such blowers are substantially smaller in size and cheaper than those rated for high volume delivery. In such smaller blowers the pressure of the blast air is converted into velocity (a total pressure of 150 mm. WC yields an air velocity of about 50 m./sec.), and the air jet issuing at a relatively high velocity inducts and entrains a considerable amount of air from the atmosphere into the air inlet scoops 18 so that the large amount of air necessary is achieved and utilized for cooling. The intermediate portion of the air inlet scoop acts at this point as a mixing tube in which a velocity equalization takes place between the blast air and the entrained atmospheric air carried along. Inrthis manner, a mixture of blast air and atmospheric air is delivered intoV the cooling system, whose combined amount and pressure corresponds to the cooling requirements in all operating stages of the converter.

Compared to the known cooling systems, for example in Bessemer converters where the blast air for refining the charge is first passed around the shell, the cooling Y system according to the invention has the advantage that natural cooling air is constantly utilized. VFurthermore, there is no conduction of the supply of cooling air through the converter trunnions, so that the need for cooling air connections with stuffing boxes is eliminated. Moreover, the cooling air flows substantially in the natural convection direction of flow from the bottom to the top of the converter,.so that relatively little cooling air Volume is required. n

FIGS. 7Y and 8 show a converter where no supplementary forced cooling is provided. Since different methods of operation are used for converters in steel plants, and the lining of the converter in one plant may be less burnt out than in another, e.g. from 1000 mm. to-250 mm. instead of 100 to 150 mm. residual lining, natural air cooling may sufce for the entire operating range under certain circumstancesrif the residual brick- Work or permanent lining are suiciently thick.

The shell 29 of the converter according to FIGS. 7 and 8 is surrounded with spaced radial rings Sti, similar to rings 5 in the above described embodiment. Under the rings 30 extend longitudinal straps 31 bearing tightly against the shell plate. The ends of the longitudinal straps 31 are weldedonto tongue-shapedV lugs 32 of plate rings 33 welded from the top and bottom onto the converterV shell plate, similar to the above described embodiment of FIGS. 2-6. As can be seen from FIGS. 9 and l0, for fastening the straps 31 at their intersection points made with radial rings 30, a ywedge-shaped fitting piece 34 is drivenin between the upper side of the longitudinal strap and the edge of the recess of the radial ring 30 and then is welded to the radial ring. By means of this arrangement, a particularly equalized pressure of the longitudinal straps can be achieved at all locationsof the vessel surface, and thus equal support of the load by all of the longitudinal straps. Repairs are easily carried out after burning loose the litting pieces 34 of the radial rings 30. As long as the fitting pieces 34 are not fixedly wedged in, the longitudinal straps are still-movable in this embodiment, and it is easily possible in this condition to attach several individual parts to a single longitudinal strap. Finally,

Y the fastening by means of wedge tting pieces oiers the further advantage that the longitudinal straps are not vweakened by transverse welding seams at their intersection points made with the radial rings.

At both sides of and close to the fastening locations Vof the longitudinal straps or wedge-shaped fitting pieces v34, rounded apertures 35 are provided, Which are advantageous for achieving a good distribution of the lines `of force acting through the plate and avoiding concentration of stresses. Furthermore, cool air can stream by through the openings at both sides of the longitudinal straps 31, so that as aV result of the large number of openings,va substantially normal convection cooling current can be formed from the bottom to the top along the converter shell. This cooling current acts along the vessel shell in such manner that the air located between 4the radial rings 30 is also placed into a rotating motion, and as a result an increase is also achieved in the 4an' circulation at the edges of the radial rings.

The intervals between the radial rings 30 are proportionately narrow over the cylindrical portion of the converter` shell. The cool outer surface is thereby enlarged, and ,the heat stress on the individual rings is less great, so that during the tilting of the converter, the static and dynamic forces which arise can be taken over by the rings to an increased extent.

For increasing the load-bearing capacity against the increased stresses which occur during tilting, steel bands 36 are welded on .along the outer edges of the radial rings 30" approximately at the lower and upper ends of the cylindrical central portion of the vessel. The

radial rings which lie between these bands 36 are suitably reinforced only in the zone of the converter trunnions by correspondingly shaped trunnion holders.

The trunnions 37 .are shrunk in a known manner into holding members SSof cast steel and also iixedly welded in by the weld seams 39, 39. The holding members 38 are hub-shaped in their respective centers for the insertion therein of the'converter trunnions 37 and pass overat their radial inner and radial outer ends into approximately rectangular shields 40 and 41. The inner shieldV 4t) is curved according to the radius of the converter shell and forms a part of the latter. The rectangular shape otters the advantage that the shield 40 can be welded simply between two plate sections of the shell, so as to avoid unfavorable shrinkage stresses which can appear when differently shaped, for example round, parts are inserted with so-called wrap-around or window-weld joints.

This fastening means for the converter trunnions can also be used with advantage in the converter according to FIGS. 2 to 6. In FIGS. 8 and l1, connection pieces 42, 42 are shown arranged on the lateral edges of the outer shield 41. The ends of pieces 42, 42 are welded to the ends of the steel bands 36 which encircle the radial rings 30". In the converter according to FIGS. 2 to 6, the edges of the shield 41 would correspondingly be welded to the adjoining ends of all steel bands 12 covering the radial rings S in the central portion of the converter vessel.

On the hub-shaped body portions of the holding members 38 are arranged tongue-shaped lugs 38 and 38 (FIG. 7). Lugs 38 are aligned with the radial rings 36 which are interrupted by the holding members, and lugs 3S are aligned with the longitudinal straps 31 which extend above and below the holding members 38. The respective ends of the radial rings 39 and of the longitudinal straps 3i' are butt-welded with these lugs 33', 3S". In this manner, a satisfactory and strong coupling is achieved between the converter trunnions 37, and with all the individual elements which are intended to absorb and transmit the forces and moments caused by the supporting and tipping of the converter vessel.

As can be seen from FIG. ll, the trunnion 37 does not extend through the holding member 3S to the converter shell, and thus a free cavity or air chamber 43 remains at the end of the trunnion which is ventilated through apertures d4. Cool air ilows to the apertures 44 from the cooling current formed along the converter shell, for example, through cooling air openings d5 in the two radial rings Sil (see FIG. 8). The cooling air chamber 43 is closed by a curved plate d6 on the side facing the lining of the converter to prevent the lining from being subjected in the region of the trunnions to cooling conditions other than those under the shell plate on the rest of the vessel wall. In this manner, local stresses are avoided at this point in the lining. The plate 46 is relatively thin and flexible, so that no cracks can occur in its fastening joints due to thermal stresses.

The converter trunnion 37 shown in FIGS. 8 and ll is a hollow, water-cooled type, known in itself and which can also be used with advantage in converters according to the invention. The trunnion 37 has an axial bore extending over its entire length which is traversed by cooling water introduced through a pipe 37". On the side facing the converter the cooling water current from pipe 37" is closed olf from the cooling air chamber 43 by a relatively thin and flexible plate 47, similar to the plate 46.

Due to the substantially openj that isg uncovered design of the converter in FIGS. 7 and 8, the heat radiation from the vessel shell and the surrounding straps and radial rings is hindered as little as possible, so that the above described cooling by the natural air current formed along the converter surface is further enhanced. It is advisable to attach, only in the upper vessel region plate strips 48 and 49 which project from the outer edge of a radial ring or on the converter shell itself, welded on so `as to project in the manner of a roof, thus shielding the converter shell and the rings protruding therefrom radially outward against splashes of overowing slag, etc.

FIG. l2 shows in cross section three different shapes 50, S0', 56" of radial rings which may be of advantage for reasons of strength, particularly because the tensile stresses of the radial rings attain their maximum values at their outer walls as soon as the temperature diierences exceed a certain value. The radial ring Si) comprises a rolled section which increases in thickness on one side and whose reinforcement at that side thus forms the outer edge of the ring. The radial rings 50' and Sti have a substantially nat rectangular cross section along whose outer edge are welded rods with respectively round and square cross sections.

As in the covered converter embodiment, the temperature can be checked in the uncovered converter of FIGS. 7-l2 by temperature feelcrs distributed over the vessel shell. Here the combination with artificial supplemental cooling may 'oe ot advantage under certain circumstances. To this end either a bottom closed circuit conduit line similar to line 17 could be provided in the same manner as described above relative to FIGS. 2 to 6. Or, the bottom radial ring 3i) could have mounted thereon a conduit for the supply of blast air, with outlet oriices or nozles pointing upward, directed toward the cooling air apertures 35 in the superposed ring. Basically, the various structural features shown in the two disclosed embodiments of converters can be combined, depending on the requirements in the specilic case. Likewise, details known from the art of converters can beemployed in the converters according to the invention. For example, in addition to the water-cooled converter trunnion 37 shown in FIGS. 8 and ll, there is illustrated in FIG. 8 a discharge connection 5l for removing the molten steel charge through a side opening 52 (FIG. 8). The ends of the radial ring interrupted by the discharge connection Sl are welded on at both sides of the connection. The use of a replaceable mouth ring 53 and of a replaceable bottom 5f:- is also possible.

A latitude of modification, change and substitution is intended in 'the foregoing disclosure, and in some instances some features of the invention will be employed without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the spirit and scope of the invention herein.

We claim:

1. A converter for the production of steel comprising a converter vessel having a shell and having a refractory lining within said shell, said shell having a converter mouth end and a lower end and a center portion between said two ends, and means attached to said shell for cooling said shell to reduce stresses on said shell induced by temperature differentials while relieving tangential stresses on said shell from pressure from said lining, said means comprising a plurality of radial rings at least partly welded to said shell and xedly secured in spaced relationship about at least the center portion of said shell, cap pieces secured to said vessel close to said mouth end and lower end thereof, said cap pieces having a plurality of lugs, and a plurality of straps lying against said shell and secured to said lugs, said rings having recesses at their inner edges, said straps extending longitudinally relative to said shell ends and through said recesses and being welded to said rings.

2. A converter according to claim 1, including wedgeshaped fitting pieces secured to said rings and being disposed in said recesses for urging said straps against said shell.

3. A converter according to claim 1, including longitudinal Webs having edges welded to said straps and secured to adjacent ones of said rings for reinforcing said rings.

4. A converter for the production of steel comprising a converter vessel having a shell and having a refractory lining within said shell, said shell having a converter mouth end and a lower end and a center portion between said two ends, and means attached to said shell for cooling said shell to reduce stresses on said shell induced by temperature diiercntials while relieving tangential stresses on said shell from pressure from said lining, said means comprising a plurality of radial rings at least partly welded to said shell and iixedly secured in spaced relationship about at least the center portion of said shell,

cap pieces secured to said vessel close to said mouth end and lower thereof, said cap pieces having a plurality of lugs, a plurality of longitudinally extending straps lying against said shell and secured to-said lugs, said rings having recesses at their inner edges, said straps extending through said recesses and being welded to said rings, and a plurality of bands secured to adjacent ones of said rings along the outer edges thereof to form closed box-shaped ducts for conductinga coolant, said rings having bores therethrough for permitting flow of coolant from the bottom to the top of said converter shell.

5. A converter for the production of steel comprising a converter vessel having a Vshell and having a refractory lining within said shell, said shell having a converter mouth end and a lower end and a center portion between said two ends, and means attached to said shell for cooling said shell to reduce stresses on said shell induced by temperature differentials while relieving tangential stresses on said shell from pressure from said lining, said means comprising a plurality of radial rings at least partly welded to said shell and iixedly secured in spaced relationship about at least the center portion of said shell, cap pieces secured to said vessel close to said mouth end and lower end thereof, said cap pieces having a plurality of lugs, a plurality of longitudinally extending straps lying against said shell and secured to said lugs, said rings having recesses at their inner edges, said straps extending through said recesses and being welded to said rings, and a plurality of bands secured to adjacent ones of said rings along the outer edges thereof to form ducts for conducting a coolant, said recesses in said rings being widely rounded about said straps at both sides to Vform passageways for coolant.

6. A converter for the production of steel comprising a converter vessel having a shell and having a refractory lining within said shell, said shell having a converter mouth end and a lower end and a center portion between said two ends, and means attached to said shell for cooling said shell to reduce stresses on said shell induced by temperature differentials while relieving tangential stresses on saidshell'frorn pressure from said lining, said means comprising a plurality of radial rings at least partly welded to said shell and xedly secured in spaced relationship about the center portion of said shell, cap pieces secured toV said vessel close to said mouth end and lower ends of said vessel, said cap pieces having a plurality of lugs, a plurality of longitudinally extending straps lying against said'shell and secured to said lugs, said rings hav jing recesses at their inner edges, said straps extending through said recesses and being welded to said rings, and a plurality of bands secured to adjacent ones of said rings along the outer edges thereof to form closed box-shaped ducts for conducting a coolant, said rings having bores therethrough for permitting ilow of coolant from the bottom to the top of said converter shell, and nozzle means spaced from said converter vvessel for permitting tipping of the latter for blowing a coolant toward said converter, and air scoop means connected to said rings for receiving aV coolant from said nozzle means.

7. A converter -according to claim 6 wherein said air scoops means is in the form of a Y-shaped pipe.

rneans comprising a plurality of radial rings at least partly welded to said shell and ixedly secured in spaced relationship about the center portion ofV said shell, said rings having flat surfaces extending radially from said shell and`centered around the longitudinal axis of said shell, said rings having inner edges welded fat least at peripherally spaced locations to said shell. Y

11. A converter according to claim 1t), said rings having respective radially outwardedges, and reinforcing means secured to the respective outer edges of adjacent ones of said rings and extending between said rings for reinforcing the latter. Y

12. A converter for the production of steel comprising a converter vessel having a shell and having a refractory lining within said shell, means attached to said shell for cooling said shell to reduce stresses on said shell in- 8. A converter according to claim 6 including temvperature sensitive means distributed over said shell for activating said nozzle means to supply a coolant.

9. A converter in accordance with claim including supply means for compressed air connected to said nozzle means for delivering compressed air as a coolant. A

10. A converter for the production of steel comprising a converter vessel having a shell and having a refractory `lining within said shell, said shell having a converter opening end and a lower end and a center portion between said ends, and means attached to said shell for cooling said' shell to reduce stresses on said shell induced byv` temperature differentials while relieving tangential stresses on'said shell from pressure from said lining, said duced by-temperature differentials while relieving tangential stresses on said shellrfrom pressure from said lin` ing, said means comprising a plurality of radial rings tixedly secured in spaced relationship about at least the center portion of said shell, said rings being at least partially welded along their narrow sides to said shell, said rings having a hat substantially rectangular profile welded along the narrow sides thereof to said shell, and a plurality of steel bands welded to the outer edges of adjacent ones of said rings.

13. A converter according to claim 12 wherein said bands are welded to the outer edges of adjacent rings and extendtherebetween forming closed box-shaped ducts for conducting a coolant.

14. A converter for theproduction of steel comprising a converter vessel having a shell and having a refractory lining within said shell, said shell having a converter opening end and a lower end and a center portion between said ends, and means attached to said shell for cooling said shell to reduce stresses on said shell induced by temperature diierentials while relieving tangential stresses on said shell from pressures from said lining, said means comprising a plurality of radial rings having narrow sides at least partly welded to said shell so as to tixedly'secure said rings in spaced relationship about said shell, a plurality of steel'bands welded to the outer edges of adjacent ones of said rings, some of said steel bands being welded to respective ones of said rings so as to extend outwardly of the ring below to form a roof.

15. A converter according to claim 10 including trunnions for supporting said vessel, said trunnions being inset into said rings, holding members extending across and fastened to said radial rings and to said shell, said trunnions having ends inserted into and fastened to said holding members. Y

16. A converter according to claim 15, wherein said holding members are hub-shaped for receiving said converter trunnions.

17. A converter for the production of steel comprising a converter vessel having a shell and having a refractory lining within said shell, said shell having a converter VVopening end and a lower end and a center portion between said ends, and means attached to said shell for cooling saidl shell to reduce stresses on said shell induced by temperature differentials while relieving tangential stresses'on said shell from pressure from said lining, said means comprising a plurality of radial ringsV at least partly welded to said shell and iixedly secured in spaced relationship about at least the center portion of said shell, andV a plurality of longitudinally extending straps lying against said shell, said rings having recess atrtheir innerv edges, said straps extending through said recesses.

18. A converter for the production of steel comprising a converter vessel having a shell and having a refractory liningV within said shell, said shell having a converter mouth end and a lower end and a center portion between said two ends, and Vmeans attached to said shell for cooling said shell to reduce stresses on said shell induced by temperature differentials while relieving tangential stresses on said shell from pressure from said lining, said means comprising a plurality of radial rings at least partly welded to said shell and xedly secured in spaced relationship about the center portion of said shell, cap pieces secured to said vessel close to said mouth end and said lower end thereof, said cap pieces having a plurality of lugs, and a plurality of longitudinally extending straps lying against said shell and secured to said lugs.

References Cited by the Examiner UNITED STATES PATENTS 2,143,557 l/39 Howat 266-39 5 MORRIS O. WOLK, Primary Examiner.

JAMES H. TAYMAN, JR., Examiner.

Claims (1)

1. A CONVERTER FOR THE PRODUCTION OF STEEL COMPRISING A CONVERTER VESSEL HAVING A SHELL AND HAVING A REFRACTORY LINING WITHIN SAID SHELL, SAID SHELL HAVING A CONVERTER MOUTH END AND A LOWER END AND A CENTER PORTION BETWEEN SAID TWO ENDS, AND MEANS ATTACHED TO SAID SHELL FOR COOLING SAID SHELL TO REDUCE STRESSES ON SAID SHELL INDUCED BY TEMPERATURE DIFFERENTIALS WHILE RELIEVING TANGENTIAL STRESSES ON SAID SHELL FROM PRESSURE FROM SAID LINING, SAID MEANS COMPRISING A PLURALITY OF RADIAL RINGS AT LEAST PARTLY WELDED TO SAID SHELL AND FIXEDLY SECURED IN SPACED RELATIONSHIP ABOUT AT LEAST THE CENTER PORTION OF SAID SHELL, CAP PIECES SECURED TO SAID VESSEL CLOSE TO SAID MOUTH END AND LOWER END THEREOF, SAID CAP PIECES HAVING A PLURALITY OF LUGS, AND A PLURALITY OF STRAPS LYING AGAINST SAID SHELL AND SECURED TO SAID LUGS, SAID RINGS HAVING RECESSES AT THEIR INNER EDGES, SAID STRAPS EXTENDING LONGITUDINALLY RELATIVE TO SAID SHELL ENDS AND THROUGH SAID RECESSES AND BEING WELDED TO SAID RINGS.

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