JP4837536B2 - Hot metal desulfurization refining agent and desulfurization method - Google Patents

Description

The present invention relates to a technique for effectively carrying out hot metal desulfurization refining without using CaF ₂ .

In the steel industry, when desulfurizing hot metal by a powder blowing method or a mechanical stirring method (KR method), CaO ₂ disclosed in Patent Document 1 The desulfurization treatment was carried out under strongly reducing conditions using a refining agent to which a substance having a large effect of melting CaO such as Al ₂ O ₃ described in Patent Document 2 and soda-lime glass presented in Patent Document 3 was added. ing. In particular, CaF _{2, which} is inexpensive and has a large CaO melting effect, has been widely added to CaO-based desulfurizing agents in various hot metal desulfurization methods. On the other hand, from the viewpoint of global environmental protection and effective utilization of industrial waste, the use of fluorite as a CaF ₂ source, which has been generally used so far, is limited, and the use of refining agents is wide as a desulfurization method. A mechanical stirring method (KR method) is being used.

  However, in the mechanical stirring method, high desulfurization efficiency cannot be realized even if a refining agent having a high desulfurization ability is simply used as described above. In other words, in the mechanical agitation method, the requirements for the refining agent are to maintain high desulfurization ability and to easily entrain the refining agent in the molten iron by mechanical agitation. From this viewpoint, a technique (for example, Patent Document 5) relating to the setting of the relative position relationship between the shape of the rotating blade (for example, Patent Document 4) and the rotating blade and the hot metal surface, which are advantageous for entrainment of the desulfurizing agent, is disclosed.

  However, these techniques merely disclose a technique for making desulfurization slag entrainment advantageous, and the inventors of the present invention that the entrainment situation of slag varies greatly depending on the composition of slag or the properties of slag. In view of the actual situation obtained, these technologies alone are not technologies that give sufficient conditions for obtaining high desulfurization ability.

  The present inventors investigated the properties and composition of the slag after the treatment in which the slag was efficiently involved and sufficient desulfurization reaction was achieved, and the slag after the treatment had a sphere equivalent diameter of 3 mmφ or more and 20 mmφ or less. In order to satisfy these conditions, the slag has a liquid phase ratio of 5% to 30% at the treatment temperature. A technique for adjusting the composition is disclosed (Patent Document 6). This disclosed technology makes use of the fact that slag is granulated (rolling granulation) while entraining molten iron in the middle of processing by using a slag composition having an appropriate liquid phase ratio, and it is easy to use molten iron in mechanical stirring. This technology is based on the creation of slag grains that are caught in the slag, but on the contrary, a certain amount of time is required until granulation, and during that time, slag is less likely to be entrained, so the desulfurization reaction is suppressed. It had the disadvantage that.

  Furthermore, the present inventors have disclosed a technique of adding a FeO source to CaO as a desulfurization agent for ensuring the appropriate liquid phase ratio (Patent Document 7). With regard to the disclosed technology, FeO, which has conventionally been considered to be necessary to contain as little as possible in the desulfurization material in order to increase the oxygen partial pressure, is inexpensive enough to secure a slag composition suitable for the above slag entrainment in an appropriate addition amount. Has been found to be a good additive. However, this technique is also based on the technique of forming slag grains suitable for slag entrainment during processing by controlling only the slag composition, and the disadvantage that a certain time is required until granulation Share with technology.

Japanese Patent Publication No. 55-51402 Japanese Patent Publication No. 61-24491 JP-A-8-209212 JP 2000-247910 A JP 2001-247910 A JP 2003-213313 A JP 2003-253315 A

  The present invention solves the above-mentioned problems of the prior art, and produces a desulfurization reaction from the initial stage of the mechanical stirring type desulfurization process without using fluorite, thereby realizing higher desulfurization efficiency in the hot metal desulfurization process. However, the present invention presents a technology that can effectively use steelmaking slag magnetic powder selection with little reuse.

That is, the gist of the present invention is as follows.
(1) A desulfurization refining agent used in the mechanical stirring desulfurization treatment of hot metal, wherein the amount of granular iron in the desulfurization refining agent is 1.5 to 5.0 mass%, and the FeO concentration is 2.0 to 7.0 mass. %, And a CaO concentration of 80% by mass or more.
Here, the FeO concentration is calculated on the assumption that all of the iron oxide contained in the desulfurization refining agent is FeO.
(2) The hot metal desulfurization refining agent according to (1) above, wherein quick lime or a mixture of quick lime and steelmaking slag is used as a main raw material, and steelmaking slag magnetic powder is further added.
(3) The hot metal desulfurization refining agent as described in (1) above, wherein the concentration of Al ₂ O ₃ in the desulfurization refining agent is 1.0 to 5.0% by mass or less.
(4) The hot metal desulfurization refining agent as described in (3) above, wherein quick lime or a mixture of quick lime and steelmaking slag is used as a main raw material, and further steelmaking slag magnetic powder and an Al ₂ O ₃ source are added. .
(5) The desulfurization refining agent for hot metal as described in (2) or (4) above, wherein a part or all of the steelmaking slag magnetic powder separation is a secondary refining magnetic powder powder.
(6) A hot metal desulfurization method comprising performing a mechanical stirring type desulfurization treatment using the desulfurization refining agent according to any one of (1) to (5) above.

By the method of the present invention, hot metal desulfurization treatment harmonized with the environment can be performed with high efficiency without using fluorite (CaF ₂ ), and steelmaking slag magnetic powder separation with extremely low utility value can be utilized. It was also possible to recover the iron source present in large quantities in the magnetic powder.

  The desulfurization refining agent of the present invention used for the mechanical stirring type desulfurization treatment of hot metal has a granular iron content of 1.5 to 5.0% by mass, a FeO concentration of 2.0 to 7.0% by mass, and CaO. The concentration is 80% by mass or more. Here, the FeO concentration is calculated on the assumption that all of the iron oxide contained in the desulfurization refining agent is FeO. The same applies hereinafter.

  By making the CaO concentration in the desulfurization refining agent of the present invention 80% by mass or more, the desulfurization ability by CaO can be sufficiently exhibited. Moreover, the FeO density | concentration in a desulfurization refining agent shall be 2.0-7.0 mass%, the hatching effect of CaO by FeO can be exhibited, and slag entrainment can be accelerated | stimulated in a mechanical stirring type desulfurization process.

  The greatest feature of the present invention is that the amount of granular iron in the desulfurization refining agent is 1.5 to 5.0% by mass. Since the density of granular iron is high, the density of the desulfurization refining agent containing granular iron can be increased, and since it is involved in the desulfurization reaction by being involved in the hot metal from the beginning of the mechanical stirring desulfurization treatment, the desulfurization rate is markedly Can be increased. Therefore, a high desulfurization rate similar to that when fluorite is contained can be realized without containing fluorite in the desulfurization refining agent. On the other hand, in the conventional case where granular iron is not included in the desulfurization refining agent, the desulfurization refining agent is not involved in the hot metal until a while after the mechanical stirring type desulfurization treatment is started, and a sufficiently high desulfurization rate is realized I can't.

  In the present invention, granular iron means granular metallic iron. It is detected as metallic iron when the desulfurization refining agent is chemically analyzed.

  In the desulfurization refining agent of the present invention, it is preferable to use quick lime or quick lime blended with steelmaking slag as a main raw material and further add steelmaking slag magnetic powder.

Steelmaking slag magnetic powder separation is a product in which the slag discharged in the steelmaking process is cooled, then slag is pulverized to approximately 5.0 mm or less, sorted with a magnet, and further pulverized to 2.0 mm or less. It is a slag powder containing fine grained iron. Table 1 shows the chemical composition of typical converter powder, and Table 2 shows the chemical composition of a typical converter powder before separating the magnetic powder. The example of Table 1 is magnetically selected using an electromagnet (magnetization area 0.3 m ² ) having a magnetic force of approximately 2000 gauss. Note that the iron oxide in the magnetically segregated powder contains FeO and Fe ₂ O _3, but the concentration of FeO in Table 1 is a T.C. obtained as a result of chemical analysis of slag. It is a value obtained by converting all Fe concentrations in iron oxide obtained by subtracting metal Fe (mass%) obtained from the same chemical analysis from Fe (mass%) into Fe mass% as FeO. All of the “FeO concentration” described in the present specification is as defined above.

  Steelmaking slag magnetic powder generated in the steelmaking process contains a large amount of granular iron as shown in Table 1, so that it has been difficult to use as a steelmaking refining agent in the past, and it is recycled as an iron source in a refining furnace such as a converter. It was about to do. The present inventors use quick lime widely used as a desulfurization refining agent or a mixture of quick lime and steelmaking slag as a main raw material, and by mixing an appropriate amount of steelmaking slag magnetically segregated powder, It was found that the desulfurization refining agent of the present invention having an amount of 1.5 to 5.0 mass%, an FeO concentration of 2.0 to 7.0 mass%, and a CaO concentration of 80 mass% or more can be obtained. As a result, higher desulfurization ability can be obtained as compared with the case where mechanical stirring desulfurization treatment is performed using a desulfurizing agent in which only FeO source not containing granular iron is mixed with CaO to obtain the same amount of FeO concentration. it can.

  Here, when steelmaking slag is blended with quick lime as the main raw material of the desulfurization refining agent, it is preferable to use steelmaking slag as a CaO source effective for desulfurization as the steelmaking slag. Steelmaking slag as an effective source of CaO for desulfurization means that converters (decarburization), hot metal pretreatment, secondary refining, etc. have a relatively high CaO concentration and are used when mixed with quicklime. This refers to steelmaking slag that retains or improves the desulfurization ability of CaO compared to a single-use desulfurization treatment. Specifically, any steelmaking slag may be used as long as it is a substitute for quick lime as a CaO component in the desulfurization refining agent and can maintain the CaO content in the desulfurization refining agent at 80% by mass or more.

As can be seen from Table 1, the converter magnetic powder selection contains a large amount of CaO that contributes to the desulfurization reaction itself, and in addition to the content of FeO that promotes the hatching of CaO, there is also a considerable amount of granular iron. include. Among these, the FeO content generates a CaO-FeO _x (X = 1.0-1.5) phase with a very low melting point, resulting in early hatching of CaO, which is necessary for rolling granulation in the KR mechanical stirring method. It is considered effective for securing a high liquid phase ratio. In addition, when the desulfurization refining agent contains a converter magnetic selection powder containing granular iron, the desulfurization rate is higher than when a FeO source not containing granular iron is used. Since the granular iron was integrated with the CaO and slag liquid components added from the beginning of the mechanical stirring process, and formed high-density slag grains and was involved in the hot metal from the very initial stage of the process, contributing to the desulfurization reaction. Is considered to be significantly higher. On the other hand, when using a FeO source that does not contain granular iron, hot metal is taken into the granulated slag grains, and the slag grains are not caught in the hot metal until the density is increased. It is considered that the desulfurization reaction was delayed and the desulfurization ability was inferior to that when a desulfurization agent containing granular iron was used. Therefore, in order to obtain such a remarkably high desulfurization ability in the hot metal desulfurization process by the mechanical stirring method, it is necessary that the CaO-based desulfurization agent contains an appropriate amount of FeO and granular iron. It becomes.

Here, as components having a hatching effect of CaO, Al ₂ O ₃ and SiO ₂ can be considered in addition to FeO, but as can be seen from the phase diagrams of CaO—Al ₂ O ₃ and CaO—SiO ₂ systems, These components alone do not generate a liquid at the temperature of the hot metal treatment (1300 ° C. to 1450 ° C.), and the liquid generation ability is inferior to that of FeO. The object of the present invention is to improve the reaction rate of the hot metal desulfurization treatment by mechanical stirring. Therefore, in the present invention, the presence of FeO having a high CaO dissolving ability is essential as a CaO hatching accelerator in the desulfurization agent. .

  In refining processes such as decarburization blowing and secondary refining, it is usual to apply a large stirring force to promote the refining reaction. Accordingly, granular iron is inevitably mixed in the slag generated by the refining process. Therefore, naturally, a large amount of granular iron is present in the magnetically separated powder generated by the magnetic separation process performed for the purpose of removing the granular iron. Further, in the cooling, crushing, and magnetic separation processes of slag, a part of the granular iron is oxidized, and FeO is generated in the magnetic separation powder. Further, in oxidation refining such as converter blowing, FeO is also present in the slag immediately after refining, and it remains as a FeO content in magnetically selected powder obtained by magnetically selecting the slag. Therefore, the magnetically segregated powder of the steelmaking slag contains a large amount of granular iron and FeO at the same time, and is a compound having the conditions necessary for achieving the present invention.

  In the present invention, there are suitable ranges for the amount of granular iron and the FeO concentration in the desulfurization refining agent. That is, the preferred range for the amount of granular iron is 1.5% by mass to 5.0% by mass, and the FeO concentration is 2.0% by mass to 7.0% by mass. Here, the reason for limiting the amount of granular iron in the desulfurizing agent is that when the amount of granular iron is less than 1.5% by mass, the density in the slag is low as described above, and the initial entrainment of the desulfurization treatment is suppressed. This is because the effects of the present invention cannot be exhibited, and when the amount of granular iron is more than 5.0% by mass, the refining agent granulated on the rotary blade used for mechanical stirring is fused. This is because the desulfurization function of the refining agent is reduced and the progress of the desulfurization reaction is hindered, so that the desired high desulfurization ability cannot be obtained. As for the FeO concentration, when the FeO concentration is lower than 2.0% by mass, the above-described CaO hatching effect by FeO cannot be sufficiently obtained. Conversely, when the FeO concentration is higher than 7.0% by mass, the slag desulfurization ability is obtained. This is because the desired high desulfurization ability cannot be obtained.

In the desulfurizing and refining agent of the present invention, it is necessary to ensure the CaO concentration in the desulfurizing and refining agent by 80% by mass or more. The findings of the present inventors, in the case of desulfurization treatment the hot metal in KR mechanical stirring method, basicity of the slag after the treatment ((% CaO) / (% SiO 2) ratio) necessary to control more than 3.5 There is. Usually, when hot metal is charged into a vessel for desulfurization treatment, low basicity slag based on blast furnace slag is inevitably mixed. The reason why the CaO concentration in the desulfurization refining agent is limited to 80% or more by mass% is that only under this condition, even when the desulfurization refining agent is mixed with the low basicity slag, the slag basicity after the treatment is 3.5. This is because it can be as described above.

The present inventors have found that in addition to the present invention containing granular iron and FeO, a higher desulfurization ability can be obtained by including Al ₂ O ₃ in the desulfurization refining agent. The reason is that in addition to the CaO hatching effect of FeO, the hatching effect of Al ₂ O ₃ is added, but in the case of Al ₂ O ₃ , unlike the case of increasing FeO, the slag oxygen potential is not increased. Therefore, the desulfurization inhibition by that hardly occurs, and it seems that the effect of improving the desulfurization rate by the magnetically segregated powder blend was promoted. This effect is exhibited when the content of Al ₂ O ₃ in the desulfurizing agent is 2.0% by mass or more. However, if too much Al ₂ O ₃ is blended, the desulfurization ability of the slag is inhibited, so the blending amount is limited so that the Al ₂ O ₃ content in the desulfurizing agent is 5.0% or less.

Any raw material can be used as the Al ₂ O ₃ source for containing Al ₂ O ₃ in the desulfurization refining agent. In particular, a part of or all of the steelmaking slag magnetic powder blended in the desulfurization refining agent is made into a secondary refining magnetic separation powder containing an appropriate amount of Al ₂ O ₃ , thereby providing an Al ₂ O ₃ source of the desulfurization refining agent. It can be. Secondary refined magnetic separation is obtained by magnetic separation of high basicity slag composed of slag produced by RH treatment, deoxidation treatment and desulfurization treatment, and decarburized soot inevitably flowing out of the converter. Table 3 shows the typical chemical composition of magnetically selected powder. A characteristic of the composition of the secondary refined magnetically segregated powder is that, in addition to containing granular iron and FeO, Al ₂ O ₃ is contained at a relatively high concentration. By using secondary refined magnetic separation, a higher desulfurization rate can be obtained than in the case of using other steelmaking slag magnetic separation, and the reason is as described above. In addition to a suitable amount of FeO and granular iron, a particularly high desulfurization rate obtained by adding a suitable amount of Al ₂ O ₃ to the desulfurization refining agent is steelmaking containing only a small amount of Al ₂ O _3. A combination of Al ₂ O ₃ sources other than slag magnetic powder separation and secondary refining slag magnetic powder separation is also obtained in the same manner.

  In the hot metal desulfurization method of the present invention, by performing the mechanical stirring type desulfurization treatment using the desulfurization refining agent of the present invention, the desulfurization refining agent has a remarkably high desulfurization rate even though it does not contain fluorite. It is possible to perform desulfurization refining.

[S] Hot metal desulfurization treatment was performed in a mechanical stirring desulfurization facility (KR desulfurization facility) using 250 ton of hot metal having a concentration of 0.033 to 0.040 mass% and a temperature in the range of 1330 ° C to 1360 ° C. The conditions of the hot metal desulfurization treatment were: refining agent input: 6.0 to 7.0 kg / ton, particle size of each raw material: 2.0 mm or less, rotating blade rotation speed: 100 to 120 rpm, rotating blade number: 4 sheets, rotation Blade outer diameter: 1.3-1.5 m, rotary blade immersion depth: 0.7-0.8 m, treatment time: 10-13 min, (CaO / SiO ₂ ) value after refining is 3.5 or more is there. Residual blast furnace slag was excluded so that its thickness was within 15 mm.

Table 4 shows examples using the desulfurization refining agent of the present invention together with comparative examples. Table 4 shows the composition ratio of raw materials constituting various desulfurization refining agents used in this test in mass%. The raw material uses quick lime, converter slag as steelmaking slag, converter slag magnetic separation as steelmaking slag magnetic powder, and in some cases, aiming to independently adjust FeO concentration and Al ₂ O ₃ concentration, Iron ore, Al ₂ O ₃ brick scrap and secondary refined magnetically selected powder are used respectively. Table 4 shows the component composition of the desulfurization refining agent composed of these raw materials together with the desulfurization rate obtained in the test. Among the component compositions, numerical values outside the scope of the present invention are underlined. The same applies to Table 6 below. The converter rod was used in a unified manner from the same lot that had previously been chemically analyzed and the chemical composition was known. The same applies to converter magnetic separation and secondary refining magnetic separation used in the examples. Al ₂ O ₃ brick scraps having an Al ₂ O ₃ concentration of 99% by mass were used. Table 5 shows the chemical compositions of the converter soot, the converter magnetizing powder, and the secondary refined magnetizing powder used here. Note that the desulfurization rate: η _S (%) shown in Table 4 is a value indicating the degree of desulfurization obtained from the test result given by the equation (1).
η _S (%) = (S _I −S _F ) / S _I (1)
Here, S _I is molten pig iron in S concentration (mass%) of the pretreatment, the S _F is hot metal in S concentration after treatment (mass%).

  Comparative Example 1 is a case where fluorite is added to quicklime, and when fluorite is used, a relatively high desulfurization rate is obtained. On the other hand, in addition to quicklime, the desulfurization rate when using a desulfurization refining agent to which a converter soot containing a relatively large amount of FeO is used is shown in Comparative Examples 3 to 5, and when fluorite and a converter soot are added simultaneously The desulfurization rate was shown in Comparative Example 2. In the case of adding only the converter soot, desulfurization ability comparable to the case of adding fluorite is obtained by setting the FeO concentration in an appropriate range. This is the technology disclosed in Patent Document 7 Is reproduced. However, the addition of the converter soot alone cannot further improve the desulfurization rate of the addition of fluorite. On the other hand, in Comparative Example 2 in which a converter slag was added in addition to fluorite, a higher desulfurization rate was obtained than in the case of adding fluorite alone (Comparative Example 2). This is considered to be due to the fact that, in addition to fluorite, the FeO content in the converter slag accelerated CaO hatching. In the present invention, the goal is to obtain a desulfurization refining agent that can obtain a desulfurization rate much higher than the addition of fluorite alone under the constraint condition of no addition of fluorite. Specifically, the desulfurization rate is Comparative Example 2 (desulfurization rate). = 85%) A desulfurization refining agent that is greater than or equal to 85%) was included in the scope of the invention.

  On the other hand, Test Nos. 6 to 12 show desulfurization test results in the case of using a desulfurization refining agent obtained by adding converter magnetic powder containing a large amount of granular iron and FeO to quick lime. As shown in Examples 7 to 10, FeO and granular iron are supplied from the converter magnetic separation powder, the FeO concentration in the desulfurization refining agent is 2.0% to 7.0%, and the concentration of granular iron is 1. When it was within the range of 5% to 5.0%, a remarkably high desulfurization ability of 85% or more was obtained. Furthermore, in Examples 7-10, the high desulfurization rate which was not obtained in the example (comparative example 3 and 4) of the converter iron single addition which contains the same degree FeO in a refining agent is obtained, These examples are The “effect of containing a suitable amount of granular iron”, which is a feature of the present invention, is simply shown. In addition, Comparative Example 6 is an example in which the target desulfurization rate was not obtained because the concentration of granular iron in the desulfurization refining agent was low, and Comparative Example 11 was FeO because the addition amount of the converter magnetic separation powder was too large. In addition, Comparative Example 12 is an example in which the granular iron is in a suitable range, but the FeO concentration exceeds the upper limit of the suitable range. It is. In any of the examples, the intended remarkably high desulfurization rate is not obtained.

No13-20 is an example at the time of adding a secondary refined magnetic selection powder to quicklime. In Test No18～20, it is added by adding Al ₂ O ₃ brick chips in order to increase the Al ₂ O ₃ concentration in the desulfurizing refining agent alone. As shown in Examples 14-16 and Examples 18 and 19, from the Al ₂ O ₃ brick scrap as a secondary refining slag magnetic separator powder or some Al ₂ O ₃ source, FeO, is granulated metallic iron and Al ₂ O ₃ The FeO concentration in the desulfurizing and refining agent is 2.0% to 7.0%, the concentration of granular iron is 1.5% to 5.0%, and the Al ₂ O ₃ concentration is 1.5%. When it is in the range of ˜5.0%, a remarkably high desulfurization ability is obtained. In addition, Comparative Example 13 is an example in which the amount of secondary refining magnetic separation powder is too small, and the Al ₂ O ₃ concentration is lower than a suitable concentration, and Comparative Example 17 has a suitable amount of granular iron. Example in which the amount is higher than the amount and Comparative Example 20 shows an example in which the Al ₂ O ₃ concentration is higher than a suitable concentration. In each case, the desulfurization rate of 85% or more targeted by the technology of the present invention Not reached. Moreover, test No21 is an Example of the invention shown in Claim 2 when using steelmaking slag magnetic powder containing only a small amount of Al ₂ O ₃ and brick scrap as an Al ₂ O ₃ source. Further, as the Al ₂ O ₃ source, secondary smelting iron containing a relatively large amount of Al ₂ O ₃ may be used. In Example 22, basicity is 2.9, FeO concentration = 14.1% by mass, granular iron An example in which a desulfurization refining agent is configured by blending a secondary smelting powder and an amount of Al ₂ O ₃ concentration of 20.2% by mass and a decarburized magnetically segregated powder into quicklime is shown.

  Table 6 shows examples and comparative examples according to the present invention in which a portion of quicklime is replaced with steelmaking slag to form a CaO source. The test conditions of the desulfurization test shown in Table 6 are the same as those in Example 1. However, the steelmaking slag and the steelmaking slag magnetically segregated powder were not extracted from those having a known chemical composition, and were extracted from any part of the storage location. The chemical composition was determined by analysis after blending the desulfurization refining agent.

  Test Nos. 23 to 25 are results when a desulfurization refining agent in which part of quick lime is replaced with a converter slag and further mixed with a converter magnetic separation powder is used. As shown in the examples of No. 23 and No. 24, even if a portion of quicklime is replaced with a converter slag, as long as a suitable CaO concentration, FeO concentration and amount of granular iron can be secured, the present invention shown in claim 1 can be used. The effect was obtained. When a portion of quicklime is replaced with steelmaking slag, the CaO concentration in the desulfurization and refining agent inevitably decreases. Therefore, if excessive replacement of quicklime with steelmaking slag is performed, the CaO concentration in the desulfurization and refining agent will be 80% by mass. The effect of the present invention is not obtained (Comparative Example 25).

  On the other hand, even if steelmaking slag other than decarburized slag is used as steelmaking slag to replace quicklime, the same effect can be obtained as long as a suitable CaO concentration, FeO concentration, and amount of granular iron are ensured. For example, test No. 26 is an implementation of the present invention when using slag after converter-type hot metal dephosphorization treatment with a basicity of 2.9, FeO concentration = 23 mass%, and iron content = 4 mass% as steelmaking slag to replace quicklime. An example is shown.

Furthermore, even in the present invention in which Al ₂ O ₃ is contained in the desulfurization refining agent, as shown in Example 27, a particularly high desulfurization rate is obtained even when quick lime is partially replaced with decarburized soot.

Claims (6)

A desulfurization refining agent used in the mechanical stirring desulfurization treatment of hot metal,
The amount of granular iron in the desulfurization refining agent is 1.5 to 5.0 mass%, the FeO concentration is 2.0 to 7.0 mass%, and the CaO concentration is 80 mass% or more. Refining agent.
Here, the FeO concentration is calculated on the assumption that all of the iron oxide contained in the desulfurization refining agent is FeO.   The hot metal desulfurization refining agent according to claim 1, wherein the main raw material is quick lime or a mixture of quick lime and steelmaking slag, and further steelmaking slag magnetic powder is added. Further desulfurizing refining agent of molten iron according to claim 1, Al ₂ O ₃ concentration in the desulfurizing refining agent is equal to or less than 1.0 to 5.0 wt%. A material obtained by blending a steelmaking slag lime or quicklime as a main raw material, desulfurizing refining agent molten iron according to claim 3, characterized in that the addition of further steel slag magnetic separating powder and Al ₂ O ₃ source. 5. The hot metal desulfurization refining agent according to claim 2, wherein a part or all of the steelmaking slag magnetic separation powder and the Al ₂ O ₃ source are secondary refining magnetic separation powder.   A method for desulfurizing hot metal, comprising performing a mechanical stirring type desulfurization treatment using the desulfurization refining agent according to any one of claims 1 to 5.