Title of Invention

INJECTION LANCE FOR REFINING, INJECTION LANCE EQUIPEMENT FOR REFINING, HOT-METAL DESILICONIZATION PROCESS, AND HOT-METAL PRETREATMENT PROCESS

Abstract

An injection lance 1 for blowing an oxygen gas into molten metal is provided. The injection lance 1 has a double-tube structure composed of an inner tube 2 and an outer tube 3. An oxygen gas is blown from the inner tube, and a hydrocarbon-based gas is blown from a space between the inner tube and the outer tube. The outer surface of at least a tip part of the outer tube is coated with a refractory coating layer formed of an Al2O3-MgO-based refractory concrete containing 5% to 30% by mass of MgO. The injection lance has high durability and a longer life time of use than before, thus contributing to the reduction in manufacturing costs. A hot-metal desiliconization process using the injection lance is also provided.

Full Text

DESCRIPTION INJECTION LANCE FOR REFINING, INJECTION LANCE EQUIPMENT FOR REFINING, HOT-METAL DESILICONIZATION PROCESS, AND HOT-METAL PRETREATMENT PROCESS Technical Field The present invention relates to an injection lance and lance equipment for injecting an oxygen gas into molten metal to refine the molten metal. The present invention also relates to a process for pretreating hot metal contained in a transfer container, in particular, a hot-metal desiliconization process, using the injection lance or the lance equipment. The lance may be used to inject a refining agent together with an oxygen gas. The pretreatment process does not exclude temporarily injecting a carrier gas other than the oxygen gas from the lance. Background Art Hot metal produced by reduction of iron ore in a blast furnace contains impurities, such as silicon, sulfur, and phosphorus. In recent years, as steel has been upgraded, to reduce the phosphorus content or streamline the steelmaking process, a hot-metal dephosphorization process has widely been performed in a converter or a transfer container, such as a ladle or a torpedo car. Furthermore, to perform the dephosphorization process efficiently, a desiliconization process for removing silicon in hot metal is also performed before the dephosphorization process. The desiliconization process and the dephosphorization process are generally referred to as a hot-metal pretreatment process. Phosphorus and silicon in hot metal are removed by oxidation. Thus, in the dephosphorization process and the desiliconization process, an oxygen source, such as an oxygen gas or iron oxide, is supplied to hot metal to remove phosphorus or silicon in the hot metal by oxidation. A flux, such as lime (lime powder), is also added to hot metal to improve the reaction efficiency or control the composition of the resulting slag. A reaction in which silicon in hot metal is removed by oxidation is referred to as desiliconization. A reaction in which phosphorus in hot metal is removed by oxidation is referred to as dephosphorization. Althdugh oxygen can be supplied to hot metal by charging iron oxide (solid oxygen source) into the hot metal, the solid oxygen source has a tendency to decrease the temperature of the hot metal by the fusion and decomposition of the solid oxygen source. The reduction in temperature of hot metal may reduce the scrap ratio or result in an insufficient heat capacity in decarburization refining in a converter in the next process. Thus, in one known method, an oxygen gas is supplied to hot metal to prevent the reduction in temperature of hot metal. In the hot-metal dephosphorization process and the hot- metal desiliconization process, an oxygen gas is supplied to hot metal generally by two methods. In one method, an oxygen gas is blown on the surface of a hot metal, for example, using a top-blowing lance that is not in contact with the hot metal (hereinafter referred to as "oxygen top blowing") (see, for example, Japanese Unexamined Patent Application Publication No. 53-78913). In the other method, an oxygen gas is directly injected into hot metal with an injection lance immersed in the hot metal or a tuyere disposed, for example, at the bottom of a reaction vessel (hereinafter referred to as "injection of oxygen gas") (see, for example, Japanese Unexamined Patent Application Publication No. 61-42763). These two methods have their advantages. The injection of oxygen gas can efficiently supply the oxygen gas and improve the agitation force. However, a heat load on the immersed portion of the injection lance is large (for example, the immersed portion wears quickly even compared with a tuyere that is under a unidirectional heat load) , and the life time of use of the injection lance is limited. By contrast, in the oxygen top blowing, the top-blowing lance is under a reduced heat load and can be used for an extended period of time. However, the oxygen top blowing cannot supply the oxygen gas efficiently and lacks agitation force. Thus, the oxygen top blowing or the injection of oxygen gas is selected in consideration of these advantages and disadvantages. For example, in a torpedo car, the oxygen top blowing has a low reaction efficiency because of the shape of the processing container; therefore, the injection of oxygen gas must be selected. More specifically, the shape of a torpedo car is not suitable for agitation and mixing. Furthermore, the opening area of a torpedo car is small in relation to the volume of hot metal. The oxygen top blowing cannot therefore achieve a desired reaction efficiency. As described above, since an immersed portion of an injection lance for use in the injection of oxygen gas wears quickly, various methods have been proposed to solve this problem. For example, Japanese Unexamined Utility Model Registration Application Publication No. 6-6447 discloses a technique for preventing the erosion of a tip part of an injection lance, wherein the injection lance is composed of the tip part, which is to be immersed in molten metal, and a holder for holding the tip part, and the tip part has an entirely calorized single-tube structure and is coated with a refractory. Furthermore, Japanese Unexamined Patent Application Publication No. 58-221210 discloses a technique for preventing the erosion of a tip part of an injection lance, wherein the injection lance has a double-tube structure coated with a refractory, a refining agent and an oxygen gas are blown from the inner tube, and a hydrocarbon- based gas is blown from the outer tube. In the technique according to Japanese Unexamined Patent Application Publication No. 58-221210, the hydrocarbon-based gas decomposes when heated, and the endothermic decomposition heat of the hydrocarbon-based gas is used to cool the tip part of the injection lance. Furthermore, paying attention to an external force exerted on a lance, Japanese Unexamined Patent Application Publication No. 54-23019 discloses a technique for increasing the life time of an injection lance, wherein a tip part of the injection lance is provided with a horizontal portion to reduce the reaction force of blowing, thus reducing vibrations of an immersed portion or the stress acting on the immersed portion. Furthermore, Japanese Unexamined Patent Application Publication No. 60- 234908 discloses a technique for reducing vibrations caused by blowing, wherein an injection lance is provided with an upper fixing apparatus comprising rollers arranged in the direction surrounding the lance and a pinchable sandwich- type lower fixing apparatus. Disclosure of the Invention Problems to be Solved by the Invention However, the existing techniques described above have the following problems. In a container, such as a torpedo car, that is not suitable for agitation and mixing and has a small opening area in relation to the volume of hot metal, it is desirable to blow a large amount of oxygen into the hot metal in the desiliconization process and other processes. However, as in Japanese Unexamined Utility Model Registration Application Publication No. 6-6447, in a technique in which an immersed portion is a calorized pipe coated with a refractory, an oxygen source is mainly iron oxide, and the oxygen gas ratio, that is, the ratio of the oxygen gas supply to the total oxygen gas supply (iron oxide (in terms of oxygen gas) + oxygen gas) is in the range of 20% to 30% at most. At an oxygen gas ratio of more than these values (that is, if the oxygen gas flow rate is increased, or if only an oxygen gas is blown), the oxidation reaction is too exothermic for the single-tube structure to withstand. The oxygen gas ratio is preferably 100% to effectively utilize heat generated by the oxidation reaction. However, in this technique, the injection lance does not have sufficient durability to withstand the blowing of an oxygen gas alone. In the technique disclosed in Japanese Unexamined Patent Application Publication No. 58-221210, the tip part of the injection lance is cooled by endothermic decomposition of a based gas. However, the endothermic effect of the hydrocarbon-based gas is mainly achieved at the tip (or at the very end), that is, a nozzle, and does not contribute to the cooling of the refractory that coats the injection lance. Thus, the refractory itself must secure durability in a different way. However, Japanese Unexamined Patent Application Publication No. 58- 221210 does not disclose specific composition of the refractory. Furthermore, Japanese Unexamined Utility Model Registration Application Publication No. 6-6447 and Japanese Unexamined Patent Application Publication No. 58-221210 take no measure against physical cracks or detachment (spalling) of the refractory caused by vibrations of the injection lance by a blowing process. Concerning vibrations of the injection lance, Japanese Unexamined Patent Application Publication No. 54-23019 discloses a technique of providing the tip of the injection lance with a horizontal portion to reduce the reaction force of blowing, thus reducing the stress acting on the immersed portion. However, blowing of a large amount of oxygen gas generates strong vibrations of the whole injection lance equipment, as well as vibrations of the immersed portion. Thus, the technique cannot solve the problem thoroughly. In Japanese Unexamined Patent Application Publication No. 60-234908, the upper fixing apparatus of a circumferential roller disposed around the injection lance and the sandwich-type lower fixing apparatus are provided to restrain vibrations. These apparatuses are effective in a vertical injection lance. However, it is difficult to adapt the sandwich-type fixing apparatus to an inclined injection lance. In this case, vibrations cannot be restrained. Furthermore, iron ore or slag deposited on the injection lance makes the maintenance of the roller and the sandwich portion difficult. Furthermore, the pretreatment process itself has the following problems. An oxygen gas blown on the surface of a hot metal and a carbon monoxide (CO) gas generated by decarbonization of hot metal produce post combustion, which can provide thermal compensation effectively. However, in the technique according to Japanese Unexamined Patent Application Publication No. 53-78913, in which an oxygen gas is blown only to the surface of a hot metal, because the CO gas is generated in small quantities, the post combustion heat cannot be produced in large quantities. The thermal compensation cannot therefore be achieved effectively. Furthermore, in the technique according to Japanese Unexamined Patent Application Publication No. 61-42763, in which an oxygen gas is supplied below the surface of a hot metal, the transition from the desiliconization stage to the dephosphorization stage is accompanied by vigorous decarbonization, thus disadvantageously suppressing dephosphorization. In view of the situations described above, it is an object of the present invention to provide at least one of the following: (A) an oxygen injection lance for blowing an oxygen gas into molten metal, such as hot metal, wherein the oxygen injection lance has high durability and a longer life time of use than before, and contributes to reduction in manufacturing costs; (B) a hot-metal desiliconization process using the injection lance; (C) injection lance equipment for blowing an oxygen gas or an oxygen gas together with a refining agent into molten metal, such as hot metal, wherein the injection lance equipment has a longer life time of use than before even when only the oxygen gas is blown in large quantities, and contributes to reduction in manufacturing costs; (D) a hot-metal desiliconization process using the injection lance equipment; and (E) a hot-metal pretreatment process in which thermal compensation is effectively provided in a desiliconization stage to solve the problems, such as reduction in scrap ratio or an insufficient heat capacity, in decarburization refining in a converter in the next process. Means for Solving the Problems (1) An injection lance for blowing at least an oxygen gas into molten metal, wherein the injection lance has a double-tube structure composed of an inner tube and an outer tube, the oxygen gas is blown from the inner tube, a hydrocarbon-based gas is blown from a space between the inner tube and the outer tube, and the outer surface of the outer tube is coated with an Al2O3-MgO-based refractory concrete containing 5% to 30% by mass of MgO. (2) The injection lance according to (1), wherein the outer surface of the outer tube at a tip part of the lance is coated with the Al2O3-MgO-based refractory concrete, and the outer surface of the outer tube at an body part adjacent to the tip part of the lance is coated with an Al2O3-SiO2- based refractory concrete containing 10% to 40% by mass of SiO2. Preferably, an interface between the refractory concrete at the tip part and the refractory concrete at the body part is located below the hot metal surface. (3) The injection lance according to (1) or (2), wherein the injection lance is immersed in a molten metal at an angle with respect to the molten metal surface, and the injection lance is provided at the tip thereof with a horizontal portion having a length 0.5 to 2.0 times the outer diameter of the injection lance. (4) A hot-metal desiliconization process, including the steps of: immersing the injection lance according to any one of (1) to (3) in hot metal; and blowing an oxygen gas from the inner tube of the injection lance into the hot metal and blowing a hydrocarbon-based gas from the space between the inner tube and the outer tube into the hot metal to remove silicon in the hot metal by oxidation. (5) Injection lance equipment for blowing at least an oxygen gas into molten metal, including: the injection lance according to any one of (1) to (3); a holder for holding the injection lance; and a lifting and lowering apparatus for lifting and lowering the holder, wherein the injection lance equipment further includes a slat and a slat support as a mechanism for restraining vibrations of the injection lance. The slat holds an upper end of the injection lance. The slat support is disposed on the lifting and lowering apparatus and clamps the slat. Preferably, the angle between the plane of the slat and the molten metal surface is the same as the inclination angle of the injection lance with respect to the molten metal surface. (6) A hot-metal desiliconization process, including the steps of: using the injection lance equipment according to (5) to immerse an injection lance in hot metal; and blowing an oxygen gas from the inner tube of the injection lance into the hot metal and blowing a hydrocarbon-based gas from the space between the inner tube and the outer tube into the hot metal to remove silicon in the hot metal by oxidation. (7) A hot-metal pretreatment process for pretreating hot metal contained in a container by desiliconization and dephosphorization, including the steps of: during a desiliconization state, supplying a solid oxygen source into the hot metal; blowing an oxygen gas on the surface of a hot metal; and blowing an oxygen gas from the injection lance according to (1) or (2) into the hot metal. Preferably, during a dephosphorization stage, a solid oxygen source is supplied to the hot metal, and an oxygen gas is blown on the surface of a hot metal. Preferably, the total oxygen supply rate of the solid oxygen source and the oxygen gas supplied into the hot metal is less than 0.23 Nm3/t/min during the desiliconization stage. Brief Description of Drawings Fig. 1 is a schematic cross-sectional view of an oxygen injection lance according to the present invention. Fig. 2 is a schematic view illustrating desiliconization of hot metal contained in a torpedo car using an oxygen injection lance according to the present invention. Fig. 3 is a schematic cross-sectional view of another oxygen injection lance according to the present invention. Fig. 4 is a schematic view illustrating desiliconization of hot metal contained in a torpedo car using injection lance equipment for refining according to the present invention. Fig. 5 is a schematic cross-sectional view taken along line X-X' in Fig. 4. Fig. 6 is a schematic view taken along line Y-Y' in Fig. 5. Fig. 7 is a schematic cross-sectional view of still another oxygen injection lance for use in the present invention. Fig. 8 is a schematic view of the structure of a hot- metal pretreatment process according to the present invention. Fig. 9 is a schematic view illustrating procedures of a hot-metal pretreatment process according to the present invention. Fig. 10 is a graph illustrating the relationship between the oxygen supply rate (the total supply rate of solid oxygen and an oxygen gas blown into hot metal) and the incidence of slopping during a desiliconization stage according to the present invention. Fig. 11 is a graph illustrating changes in concentration of components of hot metal in a hot-metal pretreatment process according to the present invention. Fig. 12 is a schematic cross-sectional view of still another oxygen injection lance according to the present invention. Reference Numerals 1 oxygen injection lance 1A tip part of lance 1B horizontal portion at tip of lance 1C center of lance 2 inner tube 3 outer tube 4 refractory coating layer 4A refractory of tip part 4B refractory of body part 5 torpedo car 6 hot metal 6A hot metal surface 7 bend part 11 injection lance equipment for refining 12 lifting and lowering apparatus 13 holder 13A upper portion of holder 19 equipment for restraining the lance vibration 20 iron slat 20A slat reinforcing member 21 iron slat support 21A, 21B slat support member 22 guide roller 2 6 top-blowing lance Best Modes for Carrying Out the Invention The present invention will be further described below. The present inventors have investigated the extension of life time of an oxygen injection lance in a hot-metal desiliconization process, in which the injection lance is immersed in hot metal contained in a torpedo car, and an oxygen gas is blown from the injection lance into the hot metal. The present inventors found that an oxygen injection lance having a metallic outer surface cannot resist erosion due to hot metal. It was also found that, calorizing treatment of the outer surface, as in Japanese Unexamined Utility Model Registration Application Publication No. 6- 6447, has a little effect when oxygen is blown in large quantities, that is, the lance seriously wears. Thus, it was found that at least the outer surface of an immersed portion of an oxygen injection lance in hot metal must be coated with a refractory layer to improve the durability of the oxygen injection lance. It was also found that, even coated with a refractory, an immersed portion having a single-tube structure has low durability. Thus, an oxygen injection lance preferably have at least a double-tube structure and, a cooling hydrocarbon- based gas flows through a space between an inner tube and an outer tube of the double-tube structure. This is because an endothermic decomposition of the hydrocarbon-based gas was found to reduce the temperature of at least the tip part of the oxygen injection lance, thus preventing erosion of the tip part. However, these measures could not achieve intended durability. Thus, a used injection lance was examined to identify impediments to the extension of life time. The investigation showed that wear to an immersed portion of the injection lance was divided into two types: erosion due to hot metal and slag, and physical damage, that is, spalling. Further investigation showed that the cooling effect of a hydrocarbon-based gas on the erosion of the tip part of the lance was negligible except for the tip, and that the most damaged portion in the refractory coating the injection lance is not the tip but a portion that is disposed slightly apart from the tip and that does not benefit from the cooling effect of a hydrocarbon-based gas. These findings indicate that the erosion rate of a refractory coating an oxygen injection lance must be reduced to improve the durability of the oxygen injection lance. In other words, the refractory must be erosion resistant to hot metal. Accordingly, a test was performed to optimize the material of the refractory. The test was performed with an oxygen injection lance used in desiliconization of hot metal contained in a torpedo car. Figs. 1 and 3 are schematic cross-sectional views of the oxygen injection lances used in the test. Fig. 2 illustrates desiliconization of hot metal contained in a torpedo car. In Figs. 1 and 3, reference numeral 1 denotes an oxygen injection lance, reference numeral 2 denotes an inner tube, reference numeral 3 denotes an outer tube, and reference numeral 4 denotes a refractory coating layer formed of a refractory concrete (cementitious refractory that is formable into a target shape; for example, a castable refractory). In Fig. 1, the refractory coating layer 4 includes a refractory of tip part 4A and a refractory of body part 4B, each formed of different refractories. An oxygen gas flows through the inner tube 2. A hydrocarbon- based gas flows through a space between the inner tube 2 and the outer tube 3. The oxygen gas and the hydrocarbon-based gas are blown from the tip part 1A of the oxygen injection lance 1 into hot metal. Reference numeral 1C denotes the center of the lance. Reference numeral 7 denotes a bend part (defined by an intersection point of the center lines of the lance in front of and to the rear of the bend). In Fig. 2, reference numeral 5 denotes a torpedo car. Reference numeral 6 denotes hot metal. The tip 1A of the oxygen injection lance 1 illustrated in Fig. 1 or 3 is immersed in the hot metal 6 contained in the torpedo car 5. To perform desiliconization of the hot metal 6, an oxygen gas (if necessary, together with a refining agent) is blown from the inner tube 2, and a hydrocarbon-based gas is blown from the space between the inner tube 2 and the outer tube 3'. In this hot-metal desiliconization process, the composition of the refractory coating layer 4 (or the refractory of tip part 4A and the refractory of body part 4B) was changed to examine the durability of the oxygen injection lance 1. In the test, to perform the desiliconization process, an oxygen gas was blown at a flow rate of 30 Nm3/min from the inner tube 2 into about 300 tons of hot metal 6 contained in the torpedo car 5, and a propane gas was blown at a flow rate in the range of 2 to 5 Nm3/min from the space between the inner tube 2 and the outer tube 3 into the hot metal 6. The unit Nm3 means the volume expressed in m3 under standard condition. The inner tube 2 and the outer tube 3 were stainless steel pipes. Table 1 shows the test conditions in the desiliconization process. The test was performed using an Al2O3-SiO2-based castable refractory (Al2O3-20% by mass of SiO2) and an A12O3- MgO-based castable refractory as the refractory coating layer 4 of the lance illustrated in Fig. 3. In the Al2O3- MgO-based castable refractory, the MgO content was set to be 3%, 5%, 10%, 20%, 30%, 40%, 50%, or 70% by mass to examine the effect of the MgO content on the wear rate of the refractory coating layer 4. In the lance illustrated in Fig. 1, an Al2O3-7% by mass of MgO castable refractory was used as the refractory of tip part 4A, and an Al2O3-20% by mass of SiO2 castable refractory was used as the refractory of body part 4B. An interface between the tip part and the body part was located at the hot metal surface, the position of the bend part, or the midpoint (center) therebetween. The hot metal surface is not the surface of slag, but the surface of hot metal itself. Table 2 shows the test results. As shown in Table 2, the Al2O3-20% by mass of SiO2 castable refractory had a wear rate of.200 mm per charge (hereinafter referred to as "mm/ch"). However, the Al2O3- MgO-based castable refractories containing 5% to 30% by mass of MgO had a wear rate of 15 mm/ch or less. However, the Al2O3-MgO-based castable refractory containing less than 5% by mass of MgO had a large wear rate, and the effect of MgO was small. On the other hand, the Al2O3-MgO-based castable refractories containing more than 30% by mass of MgO had noticeable cracks in the refractory coating layer 4 because of high Young's moduli of the refractories. An improvement in durability could not be expected owing to the cracks caused by spalling. These results show that the Al2O3-MgO-based refractory concretes containing 5% to 30% by mass of MgO are optimum refractories for the refractory coating layer 4. Use of these refractory concretes can improve the durability of the oxygen injection lance 1. Furthermore, use of an Al2O3-MgO refractory concrete at the tip part and an Al2O3-SiO2-based refractory concrete at the body part yielded the best result, and had a wear rate lower than those of the oxygen injection lances 1 coated only with the Al2O3-MgO refractory concretes. The reason for that is considered as described below. Al2O3-SiO2-based refractory concretes basically have spalling resistance higher than that of the Al2O3-MgO-based refractory concretes having an appropriate composition described above. In particular, the Al2O3-SiO2-based refractory concretes are resistant to thermal shock generated just above the hot metal surface. An Al2O3-SiO2-based refractory concrete at the body part therefore further improves the durability of the lance. Furthermore, the present inventors also tested Al2O3- Cr2O3-based, Al2O3-ZrO2-based, and SiO2-ZrO2-based refractories, alone or in combination. However, these refractories are not as effective as the refractories according to present invention. The present invention is based on these test results. As illustrated in Figs. 1 and 3, an oxygen injection lance 1 for refining according to invention has a double-tube structure composed of an inner tube 2 and an outer tube 3. An oxygen gas (if necessary, together with a refining agent) is blown from the inner tube 2, and a hydrocarbon-based gas is blown from a space between the inner tube 2 and the outer tube 3. As illustrated in Fig. 3, the outer surface of the outer tube 3 is coated entirely with an Al2O3-MgO-based refractory concrete containing 5% to 30% by mass of MgO. Alternatively, as illustrated in Fig. 1, the tip part is coated with an Al2O3-MgO-based refractory concrete, and the remaining body part is coated with an Al2O3-SiO2-based refractory concrete. Also in the oxygen injection lance 1 illustrated in Fig. 1, the Al2O3-MgO-based refractory concrete at the tip part contains 5% to 30% by mass of MgO. The Al2O3-SiO2-based refractory concrete is effective when it contains 10% to 40% by mass of SiO2. In terms of spalling resistance, the refractory of body part 4B preferably coats an outer surface area of the lance 1 at least extending to the hot metal surface. Preferably, the refractory of tip part 4A coats a sufficient area to resist erosion. For example, in the lance illustrated in Fig. 1, the refractory of tip part 4A coats an outer surface area of the lance 1 at least extending to a bend part 7. In other words, in the lance illustrated in Fig. 1, an interface between the refractory of tip part 4A and the refractory of body part 4B is preferably located between the bend part and the hot metal surface. Preferably, the refractory of tip part 4A and the refractory of body part 4B are continuously formed at the interface. This is easily achieved by forming a mold around the outer tube 3 and pouring a refractory concrete into the mold to coat the lance while changing the type of refractory. An Al2O3-MgO-based refractory concrete and an Al2O3-SiO2- based refractory concrete for use in the present invention- may contain about 7% or less of impurities without causing any problem. In both of the lances illustrated in Figs. 1 and 3, in terms of spalling resistance, the MgO content in the Al2O3-MgO-based refractory concrete is most preferably in the range of 5% to 10% by mass. Preferably, the refractory layer has a thickness of at least about 25 mm. An oxygen injection lance 1 for refining according to the present invention may be applied to any refining in which an oxygen gas or an oxygen gas together with a refining agent is supplied to molten metal. The oxygen injection lance 1 is most suitably used as an oxygen gas- supply means in a hot-metal desiliconization process. This is because an Al2O3-MgO-based refractory concrete containing 5% to 30% by mass of MgO used in the refractory coating layer 4 or the refractory of tip part 4A in the present invention has high erosion resistance to SiO2-based slag, which is produced in the hot-metal desiliconization process. The refining agent, as used herein, refers to iron oxide or flux, such as lime (lime powder) or limestone, serving as an oxygen source. Furthermore, a lance according to the present invention is suitable for applications in which a large amount of oxygen (for example, at least 10 Nm3/min, preferably at least 15 Nm3/min) is blown to perform a process, such as a desiliconization process in a torpedo car. When an oxygen injection lance 1 for refining according to the present invention is used to perform desiliconization of the hot metal 6, the desiliconization is performed in the same way as in the test described above, that is, an oxygen gas is blown from the inner tube 2, and a hydrocarbon-based gas is blown from the space between the inner tube 2 and the outer tube 3. In this case, the oxygen injection lance 1 may be used in combination with another oxygen gas-supply means, such as oxygen-gas supply with a nonimmersed-type top-blowing lance. Furthermore, in the oxygen injection lance 1 for refining illustrated in Fig. 1 or 3, while the inner tube 2 and the outer tube 3 are unbranched to the tip part 1A, the inner tube 2 and the outer tube 3 may be branched in the vicinity of the tip such as T-shaped or Y-shaped. Fig. 12 illustrates a T-shaped lance according to another embodiment of the present invention. The reference numerals are the same as in Fig. 1. The usage of the T-shaped lance is also the same as the lance illustrated in Fig. 1 except that the T-shaped lance is vertically immersed in hot metal. In the lance illustrated in Fig. 12, to reduce erosion sufficiently, the refractory of tip part 4A coats the lance from the tip to at least a position located at a distance twice the distance d between the center 1C of the opening of the lance and the tip of the lance. That is, the interface between the refractory of tip part 4A and the refractory of body part 4B is preferably located between the hot metal surface and the position located at a distance of 2d from the tip of the lance. This also applies to a Y-shaped lance. The inner tube 2 and the outer tube 3 are not necessarily a stainless steel pipe, and may be a carbon steel pipe. Furthermore, to reduce the flow rate of the oxygen gas blown from the inner tube 2, the oxygen gas may be combined with an inert gas, such as a nitrogen gas or an Ar gas. Alternatively, an oxygen-containing gas, such as oxygen-rich air, may be used if necessary. The oxygen content may be determined appropriately by the required amount of oxygen. In association with variations in flow rate of the oxygen gas blown from the inner tube 2, the hydrocarbon-based gas blown from the outer tube 3 may be combined with an inert gas, such as a nitrogen gas or an Ar gas, to reduce the flow rate of the hydrocarbon-based gas. As a standard, the amount of hydrocarbon gas is preferably in the range of about 5% to 20% by volume of oxygen supplied from the inner tube 2. Examples of the hydrocarbon gas include propane (C3H8) , methane (CH4) , ethane (C2H6) , and butane (C4H10) . Since these gases decompose at relatively low temperatures and have a large endothermic heat of decomposition, they are conveniently used in steelmaking processes. The present inventors then investigated the improvement in the shape of a lance immersed in molten metal, at an angle with respect to the molten metal surface. More specifically, in a container, such as a torpedo car, that has a small opening area in relation to the volume of hot metal, it is advantageous to immerse a lance in hot metal at an angle with respect to the hot metal surface in terms of pervasive agitation. However, adverse effects of vibrations are greater than a vertically immersed lance. Thus, to prevent spalling of an immersed portion of an injection lance, a horizontal portion was formed at a tip of the injection lance, and the length of the horizontal portion was altered experimentally. In the experiment using the lance illustrated in Fig. 1 or 3, as illustrated in Fig. 7, the length (L) of a horizontal portion 1B was altered within the range of zero to three times the outer diameter (D) of the oxygen injection lance 1. The length (L) of the horizontal portion 1B is defined by the length of an axis of the inner tube 2. In Fig. 7, reference numeral 20 denotes an iron slat (described below). In the test, to perform desiliconization, an oxygen gas was blown at a flow rate of 30 Nm3/min from the inner tube 2 into about 300 tons of hot metal contained in a torpedo car, and a propane gas was blown at a flow rate in the range of 2 to 5 Nm3/min from the space between the inner tube 2 and the outer tube 3 into the hot metal. The inner tube 2 and the outer tube 3 were stainless steel pipes. A refractory coating layer 4 was the same as No. 10 in Table 2, that is, a combination of an Al2O3-5% by mass of MgO castable refractory and an Al2O3-20% by mass of SiO2 castable refractory. The refractory coating layer 4 has a thickness of 35 mm. The inclination angle (angle between the lance (body part) and the hot metal surface) of the oxygen injection lance 1 immersed in the hot metal surface was 65°. The angle between the horizontal portion 1B and the hot metal surface was about 0°. The test conditions of the desiliconization process was the same as in Table 1. Table 3 shows the damage of the immersed portion at different lengths (L) of the horizontal portion IB. As shown in Table 3, the wear rate was 8 mm/ch or less at a length (L) of the horizontal portion 1B 0.5 to 2.0 times the outer diameter (D) of the oxygen injection lance 1, indicating further improvement over the results shown in Table 2. The length of the horizontal portion 1B in the experiment shown in Table 2 was 0.4 times the outer diameter D. By contrast, when no horizontal portion 1B was provided or when the length (L) of the horizontal portion 1B was 0.3 times the outer diameter (D) of the oxygen injection lance 1, the wear rate was in the range of 9 to 10 mm/ch at the maximum. In these cases, the horizontal portion 1B had no vibration restraining effect (the lance was easily affected by a force from the hot metal), and the life time before spalling occurs was not improved significantly. When the length (L) of the horizontal portion 1B was at least 2.5 times the outer diameter (D) of the oxygen injection lance 1, the wear rate was in the range of 10 to 12 mm/ch at the maximum. In this case, a crack in a nonimmersed portion of the oxygen injection lance 1 was a bottleneck. These results show that the optimum length (L) of the horizontal portion 1B is 0.5 to 2.0 times the outer diameter (D) of the oxygen injection lance 1, and the durability of the oxygen injection lance 1 is improved in this range. Thus, the length (L) of the horizontal portion 1B can be adjusted to an appropriate value to restrain vibrations due to the blowing of an oxygen gas. This can prevents spalling of the immersed portion of the oxygen injection lance 1 and the generation of cracks in the nonimmersed portion of the oxygen injection lance 1, thus allowing stable blowing of an oxygen gas. A present invention is based on these test results. An injection lance 1 for refining according to the present invention has a refractory concrete coating layer 4 (or 4A and 4B) at the outer surface, and is immersed in a molten metal at an angle with respect to the molten metal surface. The injection lance 1 has a horizontal portion 1B in the tip part thereof. The horizontal portion 1B has a length 0.5 to 2.0 times the outer diameter of the injection lance 1. The inclination angle of the lance is preferably in the range of 45° to 85° and more preferably in the range of 60° to 85°. Furthermore, the horizontal portion forms an angle in the range of -20° to +20°, preferably 0°, with the hot metal surface (horizontal plane). vibration)> As described above, it is preferable to optimize the refractory or the shape of an injection lance to increase the life time of the injection lance. Furthermore, it is also effective to restrain vibrations of the lance efficiently and at low cost to increase the life time of the injection lance. More specifically, an increase in oxygen gas supply, for example, use of only an oxygen gas as an oxygen source in desiliconization, increases vibrations of an injection lance and wear due to spalling. Vibrations of an injection lance may cause cracks in or falling off of a refractory coating layer at a nonimmersed portion, as well as at an immersed portion, of the injection lance. Furthermore, vibrations of an injection lance may cause cracks in an apparatus for lifting and lowering the lance. The injection lance may reach the end of its life time due to these defects. These defects may also lead to destruction of the equipment. On the basis of these findings, to improve the durability of an injection lance, it is effective and desired to restrain vibrations of not only the injection lance, but also the whole injection lance equipment, including a holder for holding the injection lance and a lifting and lowering apparatus for lifting and lowering the holder. Thus, a measure for restraining the lance vibration was investigated to restrain vibrations of the whole injection lance equipment for refining. As a result of trial manufacture and investigations, it was found that an equipment for restraining the lance vibration can be installed at an upper end of an injection lance to restrain vibrations in the vertical direction. Injection lance equipment having an equipment for restraining the lance vibration according to an embodiment of the present invention will be described below with reference to the accompanying drawings. Fig. 4 is a schematic view illustrating desiliconization of hot metal contained in a torpedo car using injection lance equipment for refining according to the present invention. Fig. 5 is a schematic cross-sectional view taken along line X-X' in Fig. 4. Fig. 6 is a schematic view taken along line Y-Y' in Fig. 5. As illustrated in Fig. 4, injection lance equipment 11 for refining according to the present invention includes an oxygen injection lance 1 to be immersed in hot metal 6 at an angle with respect to the hot metal surface, a holder 13 for holding the oxygen injection lance 1, and a lifting and lowering apparatus 12 for lifting and lowering the holder 13. More specifically, the holder 13 is fixed to the lifting and lowering apparatus 12 via an upper portion 13A of the holder 13. The lifting and lowering apparatus 12 operates to immerse the oxygen injection lance 1 in the hot metal 6 contained in the torpedo car 5. The oxygen injection lance 1 has a horizontally oriented horizontal portion 1B in a tip part thereof, and is coated with a refractory coating layer 4 formed of a refractory concrete. A refractory coating layer may preferably have a combination structure as illustrated in Fig. 1. An equipment for restraining the lance vibration 19, which is attached to the lifting and lowering apparatus 12, is disposed directly below a joint between the holder 13 and the oxygen injection lance 1 when the oxygen injection lance 1 is immersed at a predetermined position. The equipment for restraining the lance vibration 19 supports a portion of the oxygen injection lance 1 not coated with the refractory coating layer 4. Reference numeral 22 denotes a guide roller. The guide roller 22 is optional. A single guide roller 22 or a plurality of guide rollers 22 configured to guide the oxygen injection lance 1 is effective to improve the workability of replacing the oxygen injection lance 1. The equipment for restraining the lance vibration 19 will be described below with reference to Figs. 5 and 6. The oxygen injection lance 1 is provided with an iron slat 20 on the undersurface thereof. While the slat is preferably formed of iron in view of following aspect, the slat may be formed of a nonferrous material that has the required strength and that is of reasonable material and processing costs. Because of the location of the equipment for restraining the lance vibration, the equipment for restraining the lance vibration is susceptible to damage due to the deposition of slag or iron ore. Therefore, it is important that the equipment for restraining the lance vibration should be replaceable at low cost. The iron slat 20 can hold the oxygen injection lance 1 by any means. For example, the slat 20 is fixed to the oxygen injection lance 1 by welding or as such. Alternatively, the iron slat 20 may be provided with reinforcing members 20A. More specifically, the oxygen injection lance 1 is fixed in a recessed portion defined by the two slat reinforcing members 20A and the iron slat 20 so as not to vibrate. In this case, the lance may be joined to the iron slat 20, or may be placed without joining to simplify the installation. When the oxygen injection lance 1 is not joined to the iron slat 20, the equipment for restraining the lance vibration illustrated in Fig. 5 cannot prevent vibrations of the lance in the upward direction in the drawing. Because vibration force in the upward direction in the drawing is relatively small, the oxygen injection lance 1 does not need to be joined to the iron slat 20. However, holding-down means may be provided to restrain vibrations of the lance in the upward direction in the drawing. For example, as the holding-down means, a gate hinged on a reinforcing member 20A may be closed after the lance is installed. Iron slat supports 21 are disposed to the left and the right of the iron slat 20. Each of the iron slat supports 21 is composed of a member 21A disposed in the vertical direction and a pair of members 21B attached to the member 21A. The opposed pair of members 21B have a gap therebetween. The iron slat 20 is inserted into the gap. Thus, the iron slat supports 21 clamp and guide the iron slat 20 from both sides. In this case, preferably, the plane of the iron slat 20 is parallel to the direction of immersion of the oxygen injection lance 1. Furthermore, preferably, the angle between the plane of the iron slat 20 and the molten metal surface is the same as the inclination angle of the oxygen injection lance 1 with respect to the molten metal surface. If the slat is not fixed to the lance, a jig may be provided to prevent the slat from falling before the installation of the lance. For example, as the jig for preventing the slat from falling, a stopper is installed at the lower end of the slat supp'ort members 21B illustrated in Fig. 6. While the slat support is not necessarily formed of iron, the slat support is preferably formed of iron for the same reason as the slat. Thus, the iron slat 20 is guided by the iron slat supports 21 to restrain vibrations of the oxygen injection lance 1 in the vertical direction. The equipment for restraining the lance vibration 19 is characterized by the iron slat 20 and the iron slat supports 21, and other details (for example, the structure, the design of "looseness" between the slat and the slat supports, etc.) may be determined appropriately. The injection lance equipment 11 having such a structure can restrain vibrations of the oxygen injection lance 1 in the vertical direction caused by the reaction force of blowing. This prevented the generation of cracks in and falling off of the refractory coating layer 4 at a nonimmersed portion of the injection lance 1 and the generation of cracks in the lifting and lowering apparatus 12. For example, in a test using the equipment illustrated in Figs. 5 and 6 under the conditions of No. 25 in Table 3, the wear rate was 7 mm/ch or less, indicating further improvement over the results shown in Table 3. Thus, the installation of the equipment for restraining the lance vibration 19 can restrain vibrations due to the blowing of an oxygen gas. This can further prevents spalling of the immersed portion of the oxygen injection lance 1 and the generation of cracks in the nonimmersed portion of the oxygen injection lance 1 and the lifting and lowering apparatus 12, thus allowing further stable blowing of an oxygen gas. A present invention is based on these test results. The features are; the injection lance equipment 11 for blowing an oxygen gas or an oxygen gas together with a refining agent into molten metal according to an embodiment of the present invention includes: the oxygen injection lance 1 that has a refractory concrete coating layer 4 at the outer surface and is immersed in molten metal at an angle with respect to the molten metal surface; the holder 13 for holding the oxygen injection lance 1; and the lifting and lowering apparatus 12 for lifting and lowering the holder 13. Also the features are; the injection lance equipment 11 further includes the (iron) slat 20 and the (iron) slat supports 21 as a mechanism for restraining vibrations of the injection lance, the (iron) slat 20 holds an upper end of the oxygen injection lance 1, and the (iron) slat supports 21 are disposed on the lifting and lowering apparatus 12 and clamp the (iron) slat 20. Preferably, the plane of the slat 20 is parallel to the direction of immersion of the oxygen injection lance 1. Furthermore, preferably, the angle between the plane of the slat 20 and the molten metal surface is the same as the inclination angle of the oxygen injection lance 1 with respect to the molten metal surface. Preferably, the slat 20 is guided by the slat supports 21 to restrain vibrations of the oxygen injection lance 1 particularly in the vertical direction. Injection lance equipment 11 for refining according to the present invention may be applied to any refining in which an oxygen gas or an oxygen gas together with a refining agent is supplied to molten metal. The injection lance equipment 11 is most suitably used as an oxygen gas- supply means in a hot-metal desiliconization process. This is because the present invention can be applied to a desiliconization process to generate a heat capacity, which can be utilized to melt scrap iron. The -refining agent, as used herein, refers to iron oxide or flux, such as calcium oxide, which serves as an oxygen source. Points to note in desiliconization of the hot metal 6 using the injection lance equipment 11 for refining according to the present invention are the same as those in the case of using injection lance according to the present invention. A hot-metal pretreatment process according to the present invention will be described below with reference to drawings. Fig. 8 illustrates a pretreatment facility according to an embodiment of the present invention. Reference numeral 5 denotes a torpedo car that contains hot metal 6 tapped from a blast furnace (not shown). A top-blowing lance 26 and injection lance equipment 11 are installed in the torpedo car 5 and can move horizontally and vertically. The top-blowing lance 26 blows an oxygen gas on the surface 6A of the hot metal 6 in the torpedo car 5. The oxygen gas supplied by the top-blowing lance 26 is hereinafter referred to as a top-blown oxygen gas. The injection lance equipment 11 blows an oxygen gas into the hot metal 6 and supplies solid oxygen, such as iron oxide, into the hot metal 6. The oxygen gas supplied by the injection lance equipment 11 is hereinafter referred to as an injection oxygen gas. After pretreatment of the hot metal 6, the torpedo car 5 moves to a converter (not shown) and charges the hot metal 6 into the converter. A hot-metal pretreatment process according to the present embodiment will be described below with reference to Figs. 9 and 10. As illustrated in Fig. 9, in a desiliconization stage of an early stage of the pretreatment process, the injection lance equipment 11 supplies solid oxygen and an injection oxygen gas, and the top-blowing lance 26 supplies a top- blown oxygen gas. Furthermore, in a dephosphorization stage after the desiliconization stage, the injection oxygen gas is stopped, and the solid oxygen and the top-blown oxygen gas are supplied continuously. An increase in the oxygen supply rate of solid oxygen and injection oxygen gas (hereinafter referred to as the total oxygen supply rate) supplied to the torpedo car 5 in the desiliconization stage may result in an abrupt reaction of carbon in the hot metal 6, causing splashes and the gushing of splashes from a tap hole of the torpedo car 5, that is, slopping. Thus, the present inventors investigated the total oxygen supply rate of the solid oxygen and the injection oxygen gas. The present inventors examined the relationship between the incidence of slopping in the desiliconization stage and the total oxygen supply rate using the hot metal 6 having a composition shown in Table 4. Fig. 10 shows the relationship. No slopping occurred at a total oxygen supply rate of less than 0.23 Nm3/t/min. However, the incidence of slopping increased at a total oxygen supply rate of 0.23 Nm3/t/min or more. The total oxygen supply rate in the desiliconization stage was therefore set to be less than 0.23 Nm3/t/min. The function and effect of a hot-metal pretreatment process according to the present embodiment will be described below with reference to Figs. 8 to 11. Fig. 11 shows changes in concentration of carbon (C), silicon (Si), and phosphorus (P) in the hot metal 6 in the desiliconization stage and the dephosphorization stage. As shown in Fig. 11, in the desiliconization stage, the concentration of silicon in the hot metal 6 decreases greatly. The solid oxygen and the injection oxygen gas supplied from the injection lance equipment 11 into the hot metal 6 produce a sufficient amount of CO gas by decarbonization of the hot metal 6. The sufficient amount of CO gas generated from the hot metal 6 reacts with the top-blown oxygen gas supplied from the top-blowing lance 26 on the surface 6A of the hot metal 6, generating a large amount of post combustion heat. Thus, in the desiliconization stage, the large amount of post combustion heat can provide thermal compensation effectively. Furthermore, as described above, since the total oxygen supply rate in the desiliconization stage is set to be less than 0.23 Nm3/t/min, the gushing of splashes from a tap hole of the torpedo car 5, that is, slopping can be prevented. On the other hand, in the present embodiment, in the dephosphorization stage after the desiliconization stage, the injection oxygen gas is stopped, and the solid oxygen and the top-blown oxygen gas are supplied continuously. In the present embodiment, the solid oxygen blown into the hot metal 6 reacts preferentially with [P] in the hot metal rather than [C] , thus reducing decarbonization. Accordingly, as shown by line C in Fig. 11, the carbon concentration decreases relatively slowly. By contrast, in a conventional method in which an injection oxygen gas is supplied into hot metal 6 from the early period of the dephosphorization stage, the oxygen gas reacts preferentially with [C] in the hot metal rather than [P] . Accordingly, as shown by line C in Fig. 11, the carbon concentration decreases relatively rapidly. This results in an insufficient heat capacity in the subsequent decarbonization process. Thus, in the dephosphorization stage according to the present embodiment, dephosphorization occurs relatively faster than decarbonization, thereby ensure reduction of the phosphorus concentration, as shown by line P in Fig. 11. By contrast, in a conventional method in which an injection oxygen gas is supplied into hot metal 6 from the early period of the dephosphorization stage, decarbonization occurs relatively faster than dephosphorization. Accordingly, as shown by line P' in Fig. 11, the phosphorus concentration in the hot metal 6 does not decrease rapidly. Thus, in the desiliconization stage according to the present embodiment, the solid oxygen and the injection oxygen gas are supplied into the hot metal 6, and the top- blown oxygen gas is blown on the surface 6A of the hot metal 6. Furthermore, in the dephosphorization stage, the injection oxygen gas is stopped, and the solid oxygen and the top-blown oxygen gas are supplied. Thus, thermal compensation can be provided effectively, and impurities can be removed efficiently. The desiliconization stage and the dephosphorization stage -can be distinguished by measurement of the exhaust gas temperature with a dust collection system of the torpedo car 5 or by sampling. For example, a sudden rise in exhaust gas temperature indicates the completion of the desiliconization stage. EXAMPLES EXAMPLE 1 The injection lance equipment for refining illustrated in Fig. 4 and the injection lance illustrated in Figs. 1 and 7 were used in the hot-metal desiliconization process in a torpedo car (see Table 5). The equipment for restraining the lance vibration illustrated in Figs. 5 and 6 was used in some examples (inventive examples 3, 5, and 6), but was not used in the other examples (inventive examples 1, 2, and 4). The inclination angle of the lance was 70° In inventive example 7, a T-shaped lance illustrated in Fig. 12 was immersed vertically in hot metal. A refractory coating layer of the oxygen injection lance was formed of an Al2O3-10% by mass of MgO castable refractory (inventive example 1) , or an Al2O3-7% by mass of MgO castable refractory from the tip to the hot metal level and an Al2O3-20% by mass of SiO2 castable refractory above the hot metal level (inventive examples 2 to 7). In the desiliconization process, a propane gas was blown from a space between an inner tube and an outer tube, while an oxygen gas was blown from the inner tube. Desiliconization of 36 to 51 charges was performed. A horizontal portion at the tip of the injection lance had a length (L) 0.3 to 1.0 time the outer diameter (D). For purposes of comparison, desiliconization was performed using different refractory coating layers or blown gases (see Table 6) . In some comparative examples, instead of oxygen gas, iron oxide (iron ore) in a nitrogen carrier gas was blown as an oxygen source from the inner tube (comparative examples 5 and 6). The oxygen content in iron oxide was 0.15 Nm3 of oxygen gas per kilogram of iron oxide as determined by chemical analysis. The oxygen flow rate was maintained constant. Conditions for inventive examples and comparative examples were identical, except for the conditions described in Tables 5 and 6. In the inventive examples and the comparative examples, the life time of an oxygen injection lance and the temperature of hot metal were evaluated. Tables 5 and 6 show the test conditions and the test results. - 49 - In the inventive examples, when oxygen was blown at 30 Nm3/min with an inclined lance, the life time of a lance was in the range of 6.5 to 8.5 charges per lance (hereinafter referred to as "ch/lance") on an average, (inventive examples 1 to 5), and good results were also obtained under other conditions. Furthermore, when an oxygen gas was used as an oxygen source in desiliconization, removal of 0.01% by mass of silicon in hot metal by oxidation increased the temperature of hot metal by about 3°C. Furthermore, use of a composite coating layers increases the life time of a lance (inventive example 1 vs. inventive example 2). The life time of a lance is also improved at a length of front horizontal portion 0.5 to 2.0 times the outer diameter (inventive example 2 vs. inventive example 4). Use of an equipment for restraining the lance vibration further improves the life time of a lance (inventive example 4 vs. inventive example 5). On the other hand, when an oxygen injection lance was coated with a refractory coating layer of an Al2O3-20% by mass of SiO2 castable refractory, and the other desiliconization conditions were the same as in the inventive example 5 (comparative example 1), the erosion was large, and the life time of a lance was 1.0 ch. Also in a vertical immersion lance, use of an Al2O3-20% by mass of SiO2 castable refractory for the refractory layer greatly reduces the life time of a lance (inventive example 7 vs. comparative example 7). Furthermore, following was confirmed. When an Al2O3-20% by mass of SiO2 castable refractory was used as a refractory layer, when, instead of an oxygen gas, iron oxide (iron ore) in a nitrogen carrier gas was blown as an oxygen source from the inner tube, and when a nitrogen gas was blown from the space between the inner tube and the outer tube, although the life time of a lance was acceptable, heat was absorbed as sensible heat of the iron oxide, and the temperature of hot metal was reduced (this increases energy to compensate the insufficient heat capacity in a downstream process) (comparative examples 5 and 6). When an Al2O3-MgO-based castable refractory containing more than 30% by mass of MgO was used, alone or in combination, as a refractory layer, the life time of a lance was much shorter than that in the present invention because of spalling (comparative examples 2 and 3). Even if an Al2O3-MgO-based castable refractory according to the present invention is used, when a hydrocarbon gas is not supplied from the space between the inner tube and the outer tube, the life time of a lance is reduced greatly (comparative example 4) . EXAMPLE 2 In Table 7, a desiliconization stage of a hot-metal pretreatment process according to the present invention is compared with comparative processes different from the process according to the present invention (hereinafter referred to as comparative examples). The pretreatment facility used was that illustrated in Fig. 8. The lance equipment used was the same one as in the inventive example 5 in Example 1 (Table 5). In the desiliconization stage according to the present invention, solid oxygen and an injection oxygen gas are supplied into hot metal 6, and a top-blown oxygen gas is blown on the surface 6A of the hot metal 6. In comparative example A, solid oxygen and an injection oxygen gas are supplied in the desiliconization stage. In comparative example B, solid oxygen and a top- blown oxygen gas are supplied in the desiliconization stage. A heat capacity shown in Table 7 is calculated from the carbon concentration and the temperature of hot metal before and after the desiliconization stage. A higher heat capacity is indicative of more effective thermal compensation. In comparative example A, the solid oxygen and the injection oxygen gas yield a sufficient amount of CO gas by decarbonization of hot metal. However, in the absence of a top-blown oxygen gas, the post combustion occurs in lesser quantities. Thus, comparative example A has a heat capacity smaller than those of comparative example B and the present invention. In comparative example B, the amount of CO gas generated from the hot metal is small in the presence of the solid oxygen alone. Thus, the post combustion between the CO gas and the top-blown oxygen gas cannot generate sufficient heat. The heat capacity of comparative example B is therefore smaller than that of the present invention. By contrast, in the present invention, the solid oxygen and the injection oxygen gas yield a sufficient amount of CO gas by decarbonization of hot metal. The post combustion between the CO gas and the top-blown oxygen gas generates sufficient heat at the hot metal surface. The heat is deposited in the hot metal, thus increasing the heat capacity. Table 8 shows comparisons between a process according to the present invention and processes different from the process conducted according to the present invention (hereinafter referred to as comparative examples) in a dephosphorization process after the desiliconization stage in the hot-metal pretreatment process. In the dephosphorization stage according to the present invention, solid oxygen is supplied into hot metal 6, and a top-blown oxygen gas is blown on the surface 6A of the hot metal 6. In comparative example C, solid oxygen and an injection oxygen gas are supplied to hot metal in the dephosphorization stage. In comparative example D, in the dephosphorization stage, solid oxygen and an injection oxygen gas are supplied to hot metal, and a top-blown oxygen gas is blown on the surface 6A of the hot metal 6. A heat capacity shown in Table 8 is calculated from the carbon concentration and the temperature of hot metal before and after the dephosphorization stage. As in Table 7, a higher heat capacity is indicative of more effective thermal compensation. In a process according to the present invention, since the injection oxygen gas is stopped, and the solid oxygen and the top-blown oxygen gas are supplied to hot metal, dephosphorization exceeds decarbonization, and the heat capacity increases. Industrial Applicability A gas-injection lance for refining according to the present invention can greatly reduce the rate of wear in an oxygen injection lance compared to conventional art. Thus, a single injection lance can be used to supply an oxygen gas in a refining reaction efficiently and with increased agitation force for a long period of time, without using a tuyere of a bottom-blown converter or the like. Furthermore, an oxygen gas can be blown to create a heat capacity. The heat capacity can be used to melt scrap iron, thus contributing to the reduction in CO2 emission in the production of steel materials. The extension of life time of an oxygen injection lance can reduce the frequency of replacing the lance, and increase the immersion depth of the lance. In particular, an oxygen injection lance according to the present invention can be used in a hot-metal desiliconization process to effectively utilize heat generated by desiliconization. Gas-injection lance equipment for refining according to the present invention can restrain vibrations of an injection lance while an oxygen gas is blown. This can reduce stress acting on the injection lance due to the vibrations, and prevent spalling at an immersed portion and the generation of cracks in a nonimmersed portion of the injection lance. Thus, the injection lance can have much higher durability than before. This can further improve the effects described above. In a hot-metal pretreatment process according to the present invention, solid oxygen supplied into hot metal and an oxygen gas blown into the hot metal in a desiliconization stage can yield a sufficient amount of CO gas by decarbonization of the hot metal. The sufficient amount of CO gas and an oxygen gas blown on the surface of the hot metal actively produce post combustion at the surface, thus generating a large amount of post combustion heat, which is deposited in the hot metal. This can effectively provide thermal compensation of the hot metal, and solve the problems, such as reduction in scrap ratio or an insufficient heat capacity, in decarburization refining in a converter in the next process. WE CLAIM: 1. An injection lance for blowing at least an oxygen gas into molten metal, wherein the injection lance (1) has a double-tube structure composed of an inner tube (2) and an outer tube (3), the oxygen gas is blown from the inner tube (2), a hydrocarbon-based gas is blown from a space between the inner tube (2) and the outer tube (3), characterized in: the outer surface of the outer rube (3) at a tip part of the lance is coated with an Al2O3-MgO-based refractory (4A) concrete containing 5% to 30% by mass of MgO, and the outer surface of the outer tube (3) at a body part adjacent to the tip part of the lance is coated with an Al2O3-SiO2-based refractory (4B) concrete containing 10% to 40% by mass of SiO2. 2. The injection lance as claimed in Claim 1, wherein the injection lance (1) is immersed in a molten metal (6) at an angle with respect to the molten metal surface, and the injection lance(1) is provided at the tip thereof with a horizontal portion (13) having a length 0.5 to 2.0 times the outer diameter of the injection lance (1). 3. Injection lance equipment (11) for blowing at least an oxygen gas into molten metal (6), comprising: the injection lance(l) as claimed in any one of Claims 1 to 3; a holder (13) for holding the injection lance(l); and a lifting and lowering apparatus(12) for lifting and lowering the holder(13), wherein the injection lance equipment(11) further comprises a slat (20) and a slat support (21) as a mechanism for restraining vibrations of the injection lance(1), the slat (20) holding an upper end of the injection lance (1), the slat support(21) being disposed on the lifting and lowering apparatus(12) and clamping the slat (20). 4. A hot-metal desiliconization process, comprising the steps of: immersing the injection lance as claimed in any one of Claims 1 to 3 in hot metal; and blowing an oxygen gas from the inner tube of the injection lance into the hot metal and blowing a hydrocarbon-based gas from the space between the inner tube and the outer tube into the hot metal to remove silicon in the hot metal by oxidation. 5. A hot-metal desiliconization process, comprising the steps of: using the injection lance equipment as claimed in Claim 3 to immerse an injection lance in hot metal; and blowing an oxygen gas from the inner tube of the injection lance into the hot metal and blowing a hydrocarbon-based gas from the space between the inner tube and the outer tube into the hot metal to remove silicon in the hot metal by oxidation. 6. A hot-metal pretreatment process for pretreating hot metal contained in a transfer container by desiliconization and dephosphorization, comprising the steps of: during the desiliconization, supplying a solid oxygen source into the hot metal; blowing an oxygen gas on the surface of a hot metal; and blowing an oxygen gas from the injection lance as claimed in Claim 1 or 2 into the hot metal. 7. The hot-metal pretreatment process as claimed in Claim 6, further comprising the steps of: during the dephosphorization, supplying a solid oxygen source into the hot metal; and blowing an oxygen gas on the surface of a hot metal (6). 8. The hot-metal pretreatment process as claimed in Claim 6 or 7, wherein the total oxygen supply rate of the solid oxygen source and the oxygen gas supplied into the hot metal is less than 0.23 Nm3/t/min during the desiliconization. Title: INJECTION LANCE FOR REFINING, INJECTION LANCE EQUIPEMENT FOR REFINING, HOT-METAL DESILICONIZATION PROCESS, AND HOT-METAL PRETREATMENT PROCESS ABSTRACT An injection lance 1 for blowing an oxygen gas into molten metal is provided. The injection lance 1 has a double-tube structure composed of an inner tube 2 and an outer tube 3. An oxygen gas is blown from the inner tube, and a hydrocarbon-based gas is blown from a space between the inner tube and the outer tube. The outer surface of at least a tip part of the outer tube is coated with a refractory coating layer formed of an Al2O3-MgO-based refractory concrete containing 5% to 30% by mass of MgO. The injection lance has high durability and a longer life time of use than before, thus contributing to the reduction in manufacturing costs. A hot-metal desiliconization process using the injection lance is also provided.

Documents:

3501-KOLNP-2008-(06-01-2012)-CORRESPONDENCE.pdf

3501-KOLNP-2008-(06-01-2012)-DRAWINGS.pdf

3501-KOLNP-2008-(06-01-2012)-ENGLISH TRANSLATION.pdf

3501-KOLNP-2008-(28-06-2012)-PETITION UNDER RULE 137.pdf

3501-KOLNP-2008-(30-11-2011)-ABSTRACT.pdf

3501-KOLNP-2008-(30-11-2011)-CLAIMS.pdf

3501-KOLNP-2008-(30-11-2011)-CORRESPONDENCE.pdf

3501-KOLNP-2008-(30-11-2011)-DESCRIPTION (COMPLETE).pdf

3501-KOLNP-2008-(30-11-2011)-FORM-1.pdf

3501-KOLNP-2008-(30-11-2011)-FORM-2.pdf

3501-KOLNP-2008-(30-11-2011)-FORM-3.pdf

3501-KOLNP-2008-(30-11-2011)-OTHERS.pdf

3501-kolnp-2008-abstract.pdf

3501-kolnp-2008-claims.pdf

3501-KOLNP-2008-CORRESPONDENCE 1.1.pdf

3501-KOLNP-2008-CORRESPONDENCE 1.2.pdf

3501-kolnp-2008-correspondence.pdf

3501-kolnp-2008-description (complete).pdf

3501-kolnp-2008-drawings.pdf

3501-KOLNP-2008-EXAMINATION REPORT.pdf

3501-kolnp-2008-form 1.pdf

3501-KOLNP-2008-FORM 18.pdf

3501-kolnp-2008-form 2.pdf

3501-KOLNP-2008-FORM 26.pdf

3501-kolnp-2008-form 3.pdf

3501-kolnp-2008-form 5.pdf

3501-KOLNP-2008-GRANTED-ABSTRACT.pdf

3501-KOLNP-2008-GRANTED-CLAIMS.pdf

3501-KOLNP-2008-GRANTED-DESCRIPTION (COMPLETE).pdf

3501-KOLNP-2008-GRANTED-DRAWINGS.pdf

3501-KOLNP-2008-GRANTED-FORM 1.pdf

3501-KOLNP-2008-GRANTED-FORM 2.pdf

3501-KOLNP-2008-GRANTED-FORM 3.pdf

3501-KOLNP-2008-GRANTED-FORM 5.pdf

3501-KOLNP-2008-GRANTED-SPECIFICATION-COMPLETE.pdf

3501-kolnp-2008-international publication.pdf

3501-kolnp-2008-others pct form.pdf

3501-KOLNP-2008-OTHERS.pdf

3501-kolnp-2008-pct priority document notification.pdf

3501-kolnp-2008-pct request form.pdf

3501-KOLNP-2008-PETITION UNDER RULE 137.pdf

3501-KOLNP-2008-POWER OF ATTORNEY.PDF

3501-KOLNP-2008-REPLY TO EXAMINATION REPORT.pdf

3501-kolnp-2008-specification.pdf

3501-KOLNP-2008-TRANSLATED COPY OF PRIORITY DOCUMENT.pdf

abstract-3501-kolnp-2008.jpg