JP2009079257A - Method for producing molten steel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To produce molten steel by effectively utilizing Mn-containing dust generated in a production process of ferro-manganese as Mn source in an alloy component for steel. <P>SOLUTION: The production method for molten steel in this invention is performed as the followings, that a formed material containing Mn-containing dust, aluminum dross generated in the production process for ferro-manganese and binder for agglomerating these materials, is charged in a ladle during tapping off of the molten steel from a refining furnace into a ladle, and manganese oxide in the Mn-containing dust is reduced with the metallic Al in the aluminum dross to recover the Mn-content in the Mn-containing dust into the molten steel. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing molten steel while effectively utilizing manganese-containing dust recovered during ferromanganese production as a Mn source of steel alloy components in a steelmaking process.

  Ferromanganese (Fe—Mn alloy) is widely used in the steel refining process for adjusting the component of Mn, which is a typical alloy component of steel. This ferromanganese is obtained by adding coke as a reducing agent to manganese ore, heating them with electric energy or the combustion heat of coke, and reducing and smelting manganese ore with carbon in coke or CO generated from this carbon. It is manufactured.

In this ferromanganese manufacturing process, dust recovered from exhaust gas during smelting (hereinafter referred to as “Mn-containing dust”) contains 30% by mass or more of Mn, and is sufficiently used as a Mn source in the steelmaking process. Is possible. Mn in the Mn-containing dust is mainly Mn in the oxide form, but Mn in the metal state is also present. In particular, in a ferromanganese manufacturing process using a sealed electric furnace or a sealed shaft furnace, the atmosphere is kept reducible, so that metallic Mn is also recovered. When Mn-containing dust is used as a Mn source in a steelmaking process, Mn in a metal state is preferable because it does not require a reduction step. However, whether in oxide form or metal form, it is sufficiently useful as a Mn source in the steelmaking process. Mn in the oxide form is MnO, Mn ₃ O ₄ , Mn ₂ O ₃ or the like.

  Usually, ferromanganese is put into a ladle when molten steel produced in a converter or an electric furnace is discharged from these refining furnaces into a ladle. During the steel output, the ferromanganese charged into the ladle is strongly stirred by the steel output flow and quickly dissolves in the molten steel. However, when Mn-containing dust is thrown into the steel output, the Mn-containing dust is a fine powder, so it is rolled up by hot air of molten steel and scattered or collected in a dust collector, and the yield is extremely low. The effect as a substitute for manganese cannot be expected. In addition, even after adding steel, the surface of the molten steel in the ladle is covered with slag, the powdered Mn-containing dust has a small apparent specific gravity, and Mn-containing dust cannot be immersed in the molten steel. Similarly, the effect as a substitute for ferromanganese cannot be expected. Furthermore, when placed in the ladle in advance, when the steel is put out, it adheres to the bottom in a state covered with the molten steel, which floats after the steel is pulled out, reacts rapidly with the molten steel, and the molten steel comes from the ladle. Trouble that erupts.

  Thus, since it is difficult to use the Mn-containing dust generated in the ferromanganese manufacturing process as it is, conventionally, as a method of using the Mn-containing dust, Patent Document 1 discloses a dry dust collector. 20 to 65 parts of the recovered Mn-containing dust is mixed with 80 to 35 parts of Mn-containing dust obtained by wet processing of the Mn-containing dust recovered by the wet dust collector or the Mn-containing dust recovered by the dry dust collector. A method has been proposed in which pellets are made into pellets, dried at 100 to 230 ° C., and reused as a raw material for producing ferromanganese. Patent Document 2 proposes a blocky slag foaming depressant formed by adding water to Mn-containing dust and adding a binder such as bentonite, molasses, starch, etc., if necessary, and then molding the mixture.

In addition, although it is not a technique using Mn-containing dust, as a similar technique, Patent Document 3 includes an iron alloy powder such as ferromanganese, a fibrous reinforcing material whose water content is adjusted to 16% by mass or less, slaked lime, An alloy iron powder molding composition for a converter having a particle size of 10 to 80 mm and an apparent specific gravity of 4.5 or more, composed of a mixture of molasses, has been proposed.
JP-A 49-84915 JP 2006-274430 A JP-A-8-260020

  However, the above prior art has the following problems.

  That is, in Patent Document 1, Mn-containing dust is recycled and used in the ferromanganese manufacturing process, that is, it is reformed to ferromanganese through reductive smelting again, and is effectively used as a Mn source in the steelmaking process. This is a technique different from the object of the present invention. In particular, the metal Mn contained in the Mn-containing dust is subjected to unnecessary smelting, which is not an effective method in terms of energy.

  In Patent Document 2, a molded body made of Mn-containing dust or the like is basically used for suppressing slag forming, and Mn-containing dust is mixed with the slag, and the Mn source is not recovered. Even when Mn is recovered in the hot metal when used as a forming inhibitor, the hot metal is then subjected to dephosphorization refining and decarburization refining, and Mn is oxidized and removed by these refining. It is hard to say that the valuable Mn source is used effectively.

  In Patent Document 3, considering the fact that the molded body is put into the furnace from a hopper provided on the converter furnace, in order to increase the crushing strength of the molded body, the addition of fiber reinforcement, slaked lime, and molasses Therefore, the manufacturing process of the molded body is complicated, and the cost of the molded body is increased. Moreover, although oxide is contained in Mn containing dust, in patent document 3, only the alloy iron powder is made into object as a metal raw material which comprises a molded object, and it is a technique fundamentally different from the utilization method of Mn containing dust. . In other words, manganese oxide is contained in the case of Mn-containing dust, and measures for reducing this oxide are necessary. However, Patent Document 3 contains a substance that should be a reducing agent for Mn. Absent.

  The present invention has been made in view of the above circumstances, and the object of the present invention is to effectively utilize Mn-containing dust recovered in the ferromanganese manufacturing process as a Mn source of alloy components of steel in the steelmaking process. It is possible to provide a method for producing molten steel.

  The method for producing molten steel according to the first invention for solving the above-mentioned problem is to refine a molded body containing Mn-containing dust, aluminum dross generated in the production process of ferromanganese, and a binder for agglomerating them. The steel is put into the ladle from the furnace to the ladle, and manganese oxide in the Mn-containing dust is reduced with the metal Al in the aluminum dross, and the Mn content in the Mn-containing dust is recovered in the molten steel. It is characterized by this.

  The method for producing molten steel according to the second invention is characterized in that, in the first invention, a binder containing no water is used as the binder.

  According to the present invention, Mn-containing dust and aluminum dross generated in the production process of ferromanganese are kneaded, and a molded body formed by molding these with a binder is added to the steel discharged from the smelting furnace to the ladle. It can be added to molten steel without scattering the contained dust. Aluminum dross contains metallic Al, and the manganese oxide in the Mn-containing dust is easily reduced by the thermite reaction between the metallic Al and the manganese oxide in the Mn-containing dust. Migrate in. Although the reduction reaction of manganese oxide is an endothermic reaction, thermite reaction heat is generated by the reduction using the thermite reaction, and the addition of Mn-containing dust while the temperature of the molten steel is raised is achieved. It is also possible to reduce the steel output temperature. Furthermore, when molding is performed using an anhydrous binder, generation of ammonia due to the reaction between aluminum nitride and water in aluminum dross is prevented, and Mn-containing dust and aluminum dross are molded without generating ammonia. can do.

  The present invention will be specifically described below.

  First, the background to the present invention will be described. The present inventors tested and examined a method for effectively using Mn-containing dust generated in the production process of ferromanganese as a Mn source in the steelmaking process. As a result, in order to use Mn-containing dust more effectively as a Mn source, it was concluded that it was optimal to add it during the steel output from the converter or electric furnace to the ladle. The problem of adding to the inside was examined.

  As a result, one problem is that even if powdered Mn-containing dust having a maximum particle size of 3 mm or less and an average particle size of 0.5 mm or less is added to the ladle during the steel output, It was rolled up and hardly entered the ladle, and for that purpose, it was found that it was necessary to mold and agglomerate. The second problem is that Mn-containing dust is mainly composed of manganese oxide, and even if this Mn-containing dust is added, strong deoxidizing elements (Al, Si, etc.) having a stronger affinity for oxygen than Mn. Unless it is reduced in (), it is not a yield as a Mn source in molten steel. In this case, when an expensive metal Al or Fe—Si alloy is used as the reducing agent, the cost becomes higher than the case where Mn-containing dust is recycled in the ferromanganese manufacturing process as described in Patent Document 1 described above. It is not true.

  As a result of studying to solve these two problems, the use of aluminum dross (also referred to as “Al 滓” or “Al ash”) as an inexpensive reducing agent can prevent an increase in cost due to the reducing agent. Since the dross is in the form of powder, it can be confirmed that it can be easily kneaded with the Mn-containing dust as it is without being subjected to special pulverization, and can be molded by adding a binder.

  Here, aluminum dross refers to aluminum used for various beverages, aluminum sashes, gates, fences, ladders, and other building materials, or aluminum wheels used for automobiles, etc. It is produced by reacting with oxygen in it, and is mainly composed of aluminum oxide, but contains 10 to 50% by mass of metal Al, and also contains aluminum nitride produced by reacting with nitrogen in the air. Is.

  The present invention has been made on the basis of the above examination results, and took a molded body containing Mn-containing dust, aluminum dross generated in the manufacturing process of ferromanganese, and a binder for agglomerating these from a refining furnace. It is put into the ladle during the steel out to the pan, the manganese oxide in the Mn-containing dust is reduced with the metal Al in the aluminum dross, and the Mn content in the Mn-containing dust is recovered in the molten steel It is said.

  Ferromanganese is usually manufactured by smelting manganese ore using a carbonaceous material such as coke as a reducing agent in a closed electric furnace, an open electric furnace, or a closed blast furnace type shaft furnace. As long as it is dust collection dust generated in these smelting processes, any form of dust can be used as Mn-containing dust. However, since it is added to the molten steel in the ladle and used, the impurities in the Mn-containing dust become slag. From the viewpoint of reducing the generated slag, the higher the Mn concentration in the dust, the more preferable the Mn pure content. Is preferably 30% by mass or more of dust.

  The Mn-containing dust and the above aluminum dross are mixed, and further, a binder is added and kneaded. The kneaded product is formed into a molded body using a compression molding method or an extrusion molding method. The compression molding method is a method in which a kneaded product is strongly compressed and molded in a fixed container, and includes a briquette manufacturing machine. The extrusion molding method is a method in which a kneaded product is extruded and molded from a porous die or a wire mesh with a strong extrusion force.

  When producing a molded object, it is preferable that the mixture ratio of Mn containing dust shall be 30-70 mass%, and the mixture ratio of aluminum dross shall be 70-30 mass%. When the blending ratio of the Mn-containing dust is less than 30% by mass, the amount of Mn is small and a large amount of a molded body must be added, and the amount of slag in the ladle increases, and there is a risk of slag jetting due to slag forming, When the mixing ratio of the Mn-containing dust exceeds 70% by mass, the mixing ratio of the aluminum dross is lowered correspondingly, the metal Al as the reducing agent is decreased, and the reduction of the manganese oxide may be delayed.

  As the binder to be used, bentonite, polyvinyl alcohol, etc. can be used, but these contain water, and when water is added, ammonia is generated by the reaction between aluminum nitride in the aluminum dross and water, giving off a strange odor. It is preferable to use a binder that does not contain water. As the binder not containing water, wax, molasses and the like can be used. When wax is used, it is preferable to heat up the Mn-containing dust and aluminum dross to a temperature at which the wax melts. This is because molding is facilitated by melting the wax. The blending ratio of the binder may be set according to the binder to be used because the addition amount that can be agglomerated varies depending on the type of the binder.

  The size of the molded body is not particularly specified, but the major axis may be 10 to 50 mm. It only needs to have a size that does not allow the compact to be rolled up by hot air of molten steel when it is put into the ladle. This condition is satisfied if the major axis is 10 mm or more. When the molded body is added to the ladle, it will be heated to cause a thermite reaction spontaneously.In this case, if the molded body is too large, the thermite reaction will be violent and the molten steel may be scattered. It is preferable to be 50 mm or less. Here, the major axis refers to the largest part among the diameter, width and length of the molded body.

  When the molten steel is formed into the ladle from the converter or the electric furnace, the formed body thus formed is added into the ladle along with the outgoing steel flow. The formed body is heated by the heat of the molten steel, and the thermite reaction of the metal Al in the aluminum dross and the manganese oxide in the Mn-containing dust proceeds. An example of the thermite reaction formula in this case is shown in the following formula (1).

8Al + 3Mn ₃ O ₄ → 9Mn + 4Al ₂ O ₃ ΔH = -61.2kcal / mol (1)
In the formula (1), ΔH is reaction heat (enthalpy), and means that there is an exotherm of 61.2 kcal per mole of Mn ₃ O ₄ . The molten steel is heated by this reaction heat.

Manganese oxide in the Mn-containing dust is reduced by the above thermite reaction and migrates into the molten steel. On the other hand, the produced Al ₂ O ₃ becomes slag on the molten steel. In addition, among the metal Al in aluminum dross, metal Al that is equal to or more than the manganese oxide in the Mn-containing dust functions as a deoxidizer for molten steel, reducing the amount of separately added Al-based deoxidizer. Contribute.

  As described above, according to the present invention, a molded body is produced with Mn-containing dust and aluminum dross generated in the production process of ferromanganese, and this molded body is added to the steel discharged from the refining furnace to the ladle. Therefore, the Mn-containing dust can be added to the molten steel with a high yield without scattering. In addition, aluminum dross contains metal Al, and manganese oxide in Mn-containing dust is easily reduced by the thermite reaction between this metal Al and manganese oxide in Mn-containing dust. Mn can be transferred into the molten steel.

  When manufacturing high carbon ferromanganese by reducing and smelting manganese ore using coke as a heat source and reducing agent in a closed shaft furnace, the present invention is implemented using Mn-containing dust recovered from exhaust gas from the shaft furnace. did.

  First, the Mn-containing dust and aluminum dross were mixed, and wax was added as a binder to prepare a spindle briquette having a major axis of about 30 mm. In preparation of the molded body, the mixing ratio of Mn-containing dust was 53 mass%, the mixing ratio of aluminum dross was 35 mass%, and the mixing ratio of wax was 12 mass%. Table 1 shows the component composition of Mn-containing dust, aluminum dross, and molded body. In addition, although C exists in the component of a molded object, this is brought from the binder wax.

  The compact shown in Table 1 was added to the ladle during the steel output from the converter to the ladle. FIG. 1 is a diagram showing the investigation results of the Mn recovery rate at that time. As shown in FIG. 1, the Mn recovery rate in the three test operations was 97.4% on average, and it was confirmed that Mn in the Mn-containing dust could be recovered in the molten steel with a very high yield. Here, the Mn recovery rate is a percentage obtained by dividing the Mn increase by the amount of Mn added.

  Moreover, it was possible to reduce the metal Al for molten steel deoxidation by about 0.1 kg per ton of molten steel. Furthermore, no pick-up of the carbon concentration of the molten steel was observed, and it was confirmed that the influence of the wax in the formed body on the steel component was negligible.

  The calorific value due to the thermite reaction is calculated to increase the temperature by about 2 ° C. by adding 1 kg of the compact per ton of molten steel, but the number of tests was small and the temperature increase could not be determined. However, it was visually observed that the thermite reaction occurred, and it was confirmed that it contributed to the temperature rise.

It is a figure which shows the investigation result of the Mn collection | recovery rate when the molded object containing Mn containing dust is added.

Claims (2)

  A molded body containing Mn-containing dust, aluminum dross generated in the ferromanganese manufacturing process, and a binder for agglomerating them is put into the ladle during steel removal from the refining furnace to the ladle, and the aluminum A method for producing molten steel, characterized by reducing manganese oxide in Mn-containing dust with metal Al in dross and recovering Mn content in Mn-containing dust in molten steel.   The method for producing molten steel according to claim 1, wherein a binder containing no water is used as the binder.

Images