JP5605337B2 - Hot metal desulfurization agent and desulfurization method - Google Patents

Description

  The present invention relates to a desulfurization agent and a desulfurization method used when performing desulfurization treatment of hot metal.

It is generally known that the hot metal desulfurization treatment uses a desulfurization agent in which CaO is a main component and CaF ₂ disclosed in Patent Document 1 is mixed. This is because CaO alone has a high melting point of about 2500 ° C. and poor reactivity with hot metal, so CaF ₂ is added to lower the melting point and improve the reactivity with hot metal.

However, in recent years, the use of CaF ₂ that has been used so far has been restricted in order to suppress refractory material melting and protect the global environment. In the future, to address the tendency of demand for low sulfur concentration of the steel is increased, the desulfurization agent obtained by reducing the CaF _2, or, there is a need to develop a desulfurization agent that does not contain CaF _2.

As a means for solving such a problem, Patent Document 2 discloses that the hot metal desulfurization treatment targets 0.02 to 0.05 parts by weight of Na ₂ O and 1 part by weight of Al ₂ O ₃ with respect to 1 part by weight of CaO. A hot metal desulfurization agent characterized by using glass cullet or sodium metasilicate as the Na ₂ O content is disclosed.

In Patent Document 3, CaO = 30 to 60% by mass, MgO = 3 to 10% by mass, Al ₂ O ₃ = 25 to 50% by mass, and SiO ₂ = 2 to 15% by mass for molten steel desulfurization treatment. A calcium aluminate-based desulfurization agent characterized by having a melting point of 1300 ° C. to 1600 ° C. and good fluidity is disclosed.

Japanese Patent Publication No. 55-51402 Japanese Patent No. 4414562 JP 2002-60832 A

  The desulfurization agent disclosed in the above patent document has the following problems.

  For sea construction materials and UO line pipes, countermeasures for low sulfidation in the refining process are extremely important, as well as countermeasures for reducing center segregation, in order to cope with increasing thickness, strength, and toughness. Such ultra-low sulfur steel is required to stably reduce S to 50 ppm or less by hot metal desulfurization treatment.

However, when the desulfurizing agent described in Patent Document 2 was added to the hot metal in a gas stirring type desulfurization apparatus and desulfurized, it could not be stably reduced to 50 ppm or less. This is because the desulfurization agent described in Patent Document 2 is a desulfurization agent premised on mechanical stirring treatment that impairs the desulfurization ability when the liquid phase ratio is too high, and the desulfurization behavior is different from the gas stirring method. Conceivable. Furthermore, since the refractory material was significantly melted by Na ₂ O, stable production of extremely low sulfur steel was difficult.

  Moreover, when the desulfurizing agent described in Patent Document 3 was added to the hot metal in a gas stirring type desulfurization apparatus and desulfurized, it could not be stably reduced to 50 ppm or less. When slag observation after desulfurization treatment was performed using SEM / EDS (scanning electron microscope / energy dispersive X-ray analyzer), in the molten metal desulfurization experiment at 1350 to 1400 ° C., undehydrated CaO was found in the slag. One of the causes is considered to be that the desulfurization agent could not be sufficiently hatched.

  Moreover, since only a small amount of S was fixed at about 0.1 to 2% in the low melting point slag, it was considered that one of the causes was that the desulfurization ability of the low melting point slag was low. Furthermore, in the hot metal desulfurization experiment at 1400 to 1450 ° C., only a small amount of S was fixed at about 0.1 to 2% in the low melting point slag, so the desulfurization ability of the low melting point slag was low. it is conceivable that.

  Accordingly, an object of the present invention is to provide a desulfurization material that contributes to the stable production of ultra-low sulfur steel and has a small effect on the refractory melting loss, and a desulfurization method for hot metal using the desulfurization material. To do.

In order to establish a technique for stably producing extremely low sulfur steel, the present inventors have obtained a high desulfurization efficiency without using CaF ₂ and have a small influence on the refractory melt damage. We studied earnestly. As a result, when the present inventors mixed and used CaO, Al ₂ O ₃ , Na ₂ O, SiO ₂ , and MgO in an appropriate composition range, the refractory was prevented from being melted and high desulfurization capability. I found out that

  The present invention is based on the above findings, and the gist thereof is as follows.

(1) By mass ratio, with respect to CaO1, Al ₂ O ₃ min is 0.30 to 0.80, Na ₂ O min is 0.04 to 0.35, SiO ₂ min is 0.05 to 0.30, The MgO content is 0.05 to 0.44, and the Na ₂ O content is 0.50 to 3.00 and the mass% is CaO, Al ₂ O ₃ , Na ₂ O, SiO2 with respect to MgO1. ₂ and a total amount of MgO of 90% or more, the balance being inevitable impurities, a hot metal desulfurization agent.

(2) By mass ratio, with respect to CaO1, Al ₂ O ₃ min is 0.30 to 0.80, Na ₂ O min is 0.04 to 0.35, SiO ₂ min is 0.05 to 0.30, in MgO content from 0.35 to 0.44, further, to MgO1, with Na ₂ O content from 0.50 to 3.00, and, by _{mass%, CaO, Al 2 O 3} , Na 2 O, SiO ₂ and a total amount of MgO of 90% or more, the balance being inevitable impurities, a hot metal desulfurization agent.

  (3) A hot metal desulfurization agent comprising 1 to 15% by mass of metal Mg in terms of Mg added to the hot metal desulfurization agent according to (1) or (2).

  (4) A hot metal desulfurization agent comprising 1 to 10% by mass of metal Al added to the hot metal desulfurization agent according to any one of (1) to (3).

  (5) As said MgO content, 1 type (s) or 2 or more types of a calcined dolomite, a calcined brucite, and a MgO type | system | group refractory material are used, The said (1)-(4) characterized by the above-mentioned. Hot metal desulfurization agent.

(6) The hot metal desulfurization agent according to any one of (1) to (5), wherein one or two types of soda lime glass and sodium silicate are used as the Na ₂ O content.

  (7) A hot metal desulfurization method, wherein the hot metal desulfurization agent according to (1) or (2) is used for desulfurization treatment.

(8) A hot metal desulfurization method, wherein the hot metal desulfurization agent according to any one of (3) to (6) is used.

  According to the present invention, the melting loss of the refractory is suppressed, and a high desulfurization ability is obtained. Therefore, it is possible to stably manufacture an extremely low sulfur steel.

The hot metal desulfurization agent of the present invention (hereinafter sometimes referred to as “the present desulfurization agent”) is 0.30 to 0.80 in terms of mass ratio of Al ₂ O ₃ to CaO 1 and Na ₂ O content. 0.04 to 0.35, SiO ₂ content is 0.05 to 0.30, MgO content is 0.05 to 0.44 (in the case of further reducing refractory melt damage, 0.44), furthermore, with respect MgO1, with Na ₂ O content from 0.50 to 3.00, and, by _{mass%, CaO, Al 2 O 3} , Na 2 O, SiO 2 and,, MgO The total is 90% or more, and the balance is inevitable impurities.

  The desulfurization agent of the present invention has a small influence on the refractory melting loss, and when used for desulfurization of hot metal, S ≦ 50 ppm can be stably achieved.

  The present invention is described in detail below.

  Since S in steel has high affinity with Ca, it is preferable to use a desulfurizing agent mainly composed of CaO when low cost and high efficiency desulfurization is intended. However, since the reaction of solid CaO and S causes a slow mass transfer within the solid of S, a high desulfurization ability cannot be expected for a desulfurization agent mainly composed of solid CaO at the treatment temperature.

  In order to improve the desulfurization ability, it is important to melt CaO at a hot metal desulfurization treatment temperature of 1300 to 1500 ° C. to generate slag excellent in S absorption ability. That is, it is preferable to produce a low melting point slag having a high CaO activity.

The present inventors have, for the following _{reasons, CaO, Al 2 O 3,} Na 2 O, SiO 2, and focuses on the desulfurizing agent using MgO, the use of a mixture of these components in the proper composition range It was found that refractory melts were suppressed and high desulfurization ability was obtained.

Usually, a desulfurization agent using CaO, Al ₂ O ₃ , and SiO ₂ in combination is used in the hot metal desulfurization treatment under the condition where CaF ₂ is not used. This desulfurization agent has a lower desulfurization ability than a desulfurization agent using both CaO and CaF _2, and cannot stably produce low-sulfur steel.

However, when Na ₂ O and MgO are added in combination, high desulfurization efficiency can be expected. This is because when Na ₂ O and MgO are added in combination with CaO, Al ₂ O ₃ and SiO ₂ , the melting point is further lowered as compared with the case where Na ₂ O and MgO are added individually. Because.

Furthermore, Na ₂ O is an alkali metal oxide and is ion-dissociated in the slag by the following formula (1).
(Na ₂ O) → 2 (Na ²⁺ ) + (O ²⁻ ) (1)

When ion dissociation advances and the (O ²⁻ ) concentration increases, desulfurization is promoted by the following formula (2) indicating an ion exchange reaction between slag and metal.
[S] + (O ²⁻ ) → (S ²⁻ ) + [O] (2)

Further, Na ₂ O is known to greatly reduce the viscosity of slag, and it is expected that high desulfurization ability can be obtained by promoting slag hatching and mass transfer of S in the slag.

MgO is an oxide of an alkaline earth metal and is ion-dissociated in the slag by the reaction of the following formula (3).
(MgO) → (Mg ²⁺ ) + (O ²⁻ ) (3)

When ion dissociation proceeds and the (O ²⁻ ) concentration increases, desulfurization is promoted by the above equation (2) indicating the ion exchange reaction between slag and metal. Furthermore, since MgO reduces the viscosity of slag, it can be expected that the hatching of slag and the mass transfer of S in the slag are promoted and a high desulfurization ability is obtained.

In addition, when Na ₂ O is added alone in the desulfurizing agent, the refractory is melted, but when MgO is present in a certain amount or more in the desulfurizing agent, the refractory is prevented from being melted. Here, the refractory is a refractory generally used in the steel making process, which contains MgO as a main component (80% by mass or more).

However, when the MgO concentration is excessively increased with respect to Na ₂ O, solid MgO is generated, so that the desulfurization ability is lowered. In order to maintain high desulfurization capability and suppression of refractory melt damage, it is necessary to control MgO and Na ₂ O to appropriate concentrations.

  Next, the reason for limitation of the component, mass ratio, and mass% of the desulfurizing agent of the present invention will be described.

Al ₂ O ₃ :
Al ₂ O ₃ contributes to lowering the melting point of slag. In order to stably form a low melting point phase at the hot metal desulfurization temperature and form a low melting point phase in the CaO saturated region, it is necessary that the mass ratio of Al ₂ O ₃ is 0.30 or more with respect to CaO1. There is. Preferably it is 0.40 or more.

On the other hand, if the Al ₂ O ₃ content is too high and exceeds 0.80, the desulfurization ability decreases, so the Al ₂ O ₃ content for CaO 1 is set to 0.80 or less. Preferably it is 0.70 or less.

Na ₂ O:
Na ₂ O contributes to lowering the melting point of slag, and further contributes to the release of O ^{2− in} the slag and lowering the viscosity of the slag, thereby improving the desulfurization ability. The effect of addition is expressed by mass ratio when the Na ₂ O content relative to CaO1 is 0.04 or more, so the lower limit is 0.04. Preferably it is 0.08 or more.

On the other hand, if the Na ₂ O content is too high, vaporization loss occurs and the refining efficiency decreases, so the Na ₂ O content relative to CaO 1 is set to 0.35 or less. Preferably it is 0.30 or less.

Moreover, since Na ₂ O affects the solubility of MgO, it is important to use it together with MgO in order to improve the desulfurization ability and protect the refractory. In order to dissolve the added MgO stably, the Na ₂ O content needs to be 0.50 or more with respect to MgO 1 in terms of mass ratio. Preferably it is 0.70 or more.

On the other hand, if the Na ₂ O content is too high, the refractory is melted, vaporization loss occurs, and the refining efficiency decreases, so the Na ₂ O content relative to MgO 1 is set to 3.00 or less. Preferably it is 2.50 or less.

SiO ₂ :
SiO ₂ contributes to lowering the melting point of slag. In the desulfurization treatment temperature hot metal stably to form a low-melting phase, to form a low melting point phase in the CaO saturation region, the mass ratio, it is necessary to make the SiO ₂ minutes and 0.05 or more to CaO1 . Preferably it is 0.10 or more.

On the other hand, if the SiO ₂ content is too high and exceeds 0.30, the desulfurization ability decreases, so the SiO ₂ content for CaO1 is set to 0.30 or less. Preferably it is 0.26 or less.

MgO:
MgO contributes to lowering the melting point of slag, and further contributes to the release of O ²⁻ into the slag and lowering the viscosity of the slag, thereby improving the desulfurization ability. In order to stably form a low melting point phase at the hot metal desulfurization temperature and form a low melting point phase in the CaO saturated region, it is necessary to make the MgO content 0.05 or more with respect to CaO1 by mass ratio. Preferably it is 0.07 or more.

  Further, the addition of MgO is effective in terms of protecting the refractory, and when it is desired to suppress refractory melting, the MgO content is preferably 0.35 or more with respect to CaO1 in terms of mass ratio.

On the other hand, if the MgO content is too high and exceeds 0.44, the desulfurization ability decreases, so the MgO content with respect to CaO1 is set to 0.44 or less. Preferably it is 0.40 or less. The relationship with Na ₂ O is as described above.

CaO:
CaO is a basic oxide and is indispensable as a basic oxide that enhances the desulfurization ability of slag. In order to form a low melting point phase in the CaO saturated region at the hot metal desulfurization temperature, it is necessary to control the composition of Al ₂ O ₃ , Na ₂ O, SiO ₂ and MgO with respect to CaO. In the desulfurization agent of the present invention, the mass ratio of Al ₂ O ₃ , Na ₂ O, SiO ₂ , and MgO to CaO is defined as described above.

  The inevitable impurities in the desulfurizing agent are preferably a trace amount from the viewpoint of promoting desulfurization.

When the total of CaO, Al ₂ O ₃ , Na ₂ O, SiO ₂ and MgO is 90% or more by mass%, the effect of the present invention is exhibited. When the total is 95% or more, the effects of the present invention are remarkably exhibited.

  In the desulfurization agent of the present invention, calcined dolomite, calcined brucite, MgO-based refractory, etc. can be used as the MgO content. The calcined dolomite is obtained by calcining dolomite, and its composition is such that the Ca content is 55 to 80% by mass in terms of CaO, the Mg content is 25 to 45% by mass in terms of MgO, and the balance is inevitable impurities.

  The calcined brucite is obtained by calcining brucite, and its composition is such that the Mg content is 75 to 95% by mass in terms of MgO, and the balance is inevitable impurities. Dolomite and brucite are preferably fired in a temperature range that maintains a fine state because MgO grains become coarse when fired at a high temperature for a long time. MgO-based refractories contain 80% by mass or more of Mg in terms of MgO.

In the desulfurizing agent of the present invention, soda lime glass, sodium silicate, soda ash and the like can be used as the Na ₂ O content. Soda lime glass contains 65 to 90% by mass of Si in terms of SiO ₂ and 10 to 45% by mass of Na in terms of Na ₂ O, with the balance being CaO and inevitable impurities. Sodium silicate contains 35 to 75% by mass of Si in terms of SiO ₂ and 25 to 65% by mass of Na in terms of Na ₂ O, with the remainder being inevitable impurities.

When SiO ₂ and Na ₂ O coexist, the activity of Na ₂ O is greatly reduced, so that it is stable in the hot metal, is less economically evaporated by Na gas, and is economical. Therefore, the desulfurization agent is preferably adjusted as much as possible with soda lime glass or sodium silicate, and the insufficient Na ₂ O content is preferably adjusted using soda ash or the like.

Any desulfurizing agent that becomes CaO, Al ₂ O ₃ , SiO ₂ , MgO, and Na ₂ O is preferably used after pulverizing the particle size to 1 mm or less in consideration of reactivity. Further, a CaO component, Al ₂ O _{3 component} , SiO _{2 component} , MgO component, Na ₂ O component mixed and premelted in a heating furnace may be used as a desulfurizing agent.

Higher desulfurization efficiency can be obtained by using metal Mg or metal Al in combination. Metal Mg has a Mg quality of 95% by mass or more, and promotes desulfurization in the hot metal by the reaction of the following formula (4).
Mg (g) + [S] → MgS (s) (4)

  In the desulfurization agent of the present invention, when 1% by mass or more of metal Mg was added in terms of Mg, the desulfurization ability was improved, but even when added in excess of 15% by mass in terms of Mg, there was a difference in desulfurization ability. I couldn't. Metal Mg is expensive. When metal Mg is added, 1 to 15% by mass in terms of Mg is preferable from the viewpoint of cost reduction.

  Metal Al contains 30 mass% or more of Al grade, and may be Al dross generated during Al refining, aluminum can chip, or the like.

When metal Al is added, a reaction of the following formula (5) occurs in the hot metal, and desulfurization is promoted from the formula (2).
2Al (s) +3 [O] → Al ₂ O ₃ (s) (5)

In the desulfurization agent of the present invention, when 1% by mass or more of metal Al is added in terms of Al, the desulfurization ability is improved. It was. This is considered to be caused by the increase in the Al ₂ O ₃ concentration and the decrease in the CaO activity. When adding metal Al, addition of 1 to 10% by mass in terms of Al is preferable.

  By using together with metal Mg, it can be expected that high desulfurization efficiency can be obtained at low cost by preventing oxidation loss of metal Mg, reducing the amount of expensive metal Mg used, and promoting equation (4).

  Although the desulfurizing agent has been described above, it is apparent that the same effect can be obtained even if the desulfurization treatment is performed under the slag having the same component composition as the desulfurizing agent.

That is, in terms of mass ratio, with respect to CaO1, Al ₂ O ₃ is 0.30 to 0.80, Na ₂ O is 0.04 to 0.35, SiO ₂ is 0.05 to 0.30, in MgO content from 0.05 to 0.44, further, with respect to MgO1, with Na ₂ O content from 0.50 to 3.00, and, by _{mass%, CaO, Al 2 O 3} , Na 2 O, When the total of SiO ₂ and MgO is 90% or more and the remainder is desulfurized under slag of inevitable impurities, the same effect as that obtained by using the desulfurizing agent of the present invention can be obtained.

  Furthermore, when metal Mg and / or metal Al is added to the slag having the above composition before or during the treatment, the desulfurization ability of the slag is improved. Moreover, as a method of adding the desulfurizing agent to the molten iron according to the present invention, a desulfurizing effect can be obtained more reliably by a method of placing the desulfurizing agent in a pan or a TPC (kneading vehicle) and / or a method of injection. Can do.

  Next, examples of the present invention will be described. The conditions in the examples are one example of conditions used for confirming the feasibility and effects of the present invention, and the present invention is based on this one example of conditions. It is not limited. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

Example 1
Using a melting furnace, 100 kg of hot metal having [C] = 4.5% by mass, [Si] = 0.5% by mass, and [S] = 0.03% by mass is manufactured, and the temperature of the hot metal is set to 1350 to 1450 ° C. I held it. Thereafter, 1 kg of a desulfurizing agent shown in Table 1 was added upward to the hot metal, and Ar gas was blown from the furnace bottom at 0.6 L / min and stirred for 5 minutes.

As a raw material of the desulfurizing agent, the desulfurizing agent No. No. 4 uses soda-lime glass as a part of the Na ₂ O source. 5 used sodium silicate. As the MgO source, desulfurization agent No. No. 1 uses calcined brucite and has a desulfurizing agent no. No. 9 uses calcined dolomite and has a desulfurizing agent No. 9. No. 10 used an MgO-based refractory containing 80% by mass or more of MgO. Other raw materials were mixed with reagents.

  The refractory that comes into contact with the hot metal in the melting furnace is a refractory that is generally used in a steel making process containing MgO as a main component (about 80% by mass).

Table 2 shows the values of Al ₂ O ₃ , Na ₂ O, SiO ₂ , MgO, and CaF ₂ with respect to CaO 1 and the value of Na ₂ O with respect to MgO 1 in terms of mass ratio.

  In Table 3, the desulfurization agents used in the examples and comparative examples in the desulfurization experiment when the hot metal temperature is 1350 to 1400 ° C., S (ppm) before treatment, S (ppm) after treatment, desulfurization rate (%), and Indicates the degree of refractory erosion.

Here, the desulfurization rate was calculated | required from the following formula.
Desulfurization rate = (pre-treatment S-post-treatment S) × 100 / (pre-treatment S)

  For the evaluation of refractory erosion, the thickness of the refractory at the place where the slag and the refractory were in contact with each other was measured before and after the test, and the amount of decrease at the largest decrease was investigated as the amount of refractory erosion. . Further, the desulfurizing agent No. Calculate the refractory erosion amount for each test when the refractory erosion amount of 11 (comparative example) is 1, and when it exceeds 0.0 and is 0.3 or less, it is “small” and exceeds 0.3 When the ratio was 0.7 or less, “medium” was set, and when it exceeded 0.7 and 1.0 or less, “large” was set.

  Desulfurization agent No. 1 to 6 (invention examples) are the desulfurization agent Nos. Disclosed in Patent Documents 1 to 3. 11 to 13 (comparative examples) all show a high desulfurization rate and a low post-treatment S (mass%), and it is understood that S ≦ 50 ppm, which is a condition of extremely low sulfur steel, is stably achieved. .

  Also, desulfurizing agent No. 2 and desulfurizing agent No. No. 6, and a desulfurization agent No. 1 containing metal Al and / or metal Mg added. 7 to 10 (invention examples), the desulfurization rate is further improved than the desulfurization agent before addition, and the S after treatment shows a low value. By using metal Al and / or metal Mg in combination, the desulfurization ability is further increased. You can see that

Desulfurization agent No. No. 2 based on the desulfurization agent No. 2 with CaO, Al ₂ O ₃ , Na ₂ O, SiO ₂ and MgO added. Since 14-19 (comparative example) was outside the range of the present invention and desulfurization ability fell, all after processing S could not achieve 50 ppm or less.

  Observing the treated slag of the inventive example using SEM / EDS, the desulfurization agent Nos. It was not possible to confirm unhatched CaO present in the slag after the treatment of 11 to 13 (comparative example).

In addition, about 1 to 8% of S is fixed in the CaO—Al ₂ O ₃ —Na ₂ O—SiO ₂ —MgO-based low melting point slag. In 11-13 (comparative example), the slag containing high concentration S could not be confirmed.

  That is, it is considered that the desulfurization agent of the present invention has a high desulfurization ability because the low melting point slag having excellent hatchability and excellent desulfurization ability was produced.

  Further, when the amount of refractory melt was measured, desulfurization agent No. Nos. 1 to 10 (Invention Examples) are all desulfurization agents No. 1 disclosed in Patent Documents 1 to 3. It is equivalent to 11-13 (comparative examples), and it can be seen that the desulfurization agent of the present invention is superior to the prior art in terms of protecting the refractory.

  Among them, the desulfurizing agent No. 6 and no. 10 (Invention Example) is a desulfurizing agent No. 1-No. Among 10 (invention examples), the amount of refractory melted was the smallest, and good results were obtained in both refractory protection and desulfurization ability.

  In Table 4, the flux used in the examples and comparative examples in the desulfurization experiment when the hot metal temperature is 1400 to 1450 ° C., S (ppm) before treatment, S (ppm) after treatment, desulfurization rate (%), And shows the refractory erosion relationship. The definitions of desulfurization rate and refractory erosion are as described above.

  Desulfurization agent No. 1 to 10 (invention example) improved the desulfurization rate with respect to the desulfurization experiment in which the hot metal temperature was 1350 to 1400 ° C., and S after treatment was able to achieve 50 ppm or less. Also, desulfurizing agent No. Although 11-19 (comparative example) improved a desulfurization rate with respect to the desulfurization experiment whose hot metal temperature was 1350-1400 degreeC, none was able to achieve 50 ppm or less.

  The refractory melting loss is equivalent to the desulfurization experiment at 1350 to 1400 ° C. in all tests, and the desulfurization agent of the present invention enables stable production of extremely low sulfur steel with S ≦ 50 ppm even at the hot metal temperature of 1400 to 1450 ° C. Confirmed that it was possible.

  As described above, according to the present invention, refractory melting is suppressed and a high desulfurization ability is obtained, so that it is possible to stably manufacture an extremely low sulfur steel. Therefore, the present invention has high applicability in steelmaking technology in the steel industry.

Claims (8)

In terms of mass ratio, with respect to CaO1, Al ₂ O ₃ is 0.30 to 0.80, Na ₂ O is 0.04 to 0.35, SiO ₂ is 0.05 to 0.30, and MgO is 0.05 to 0.44, and further MgO1 has a Na ₂ O content of 0.50 to 3.00 and, in mass%, CaO, Al ₂ O ₃ , Na ₂ O, SiO ₂ , and And the total content of MgO is 90% or more, the balance being inevitable impurities, hot metal desulfurization agent In terms of mass ratio, with respect to CaO1, Al ₂ O ₃ is 0.30 to 0.80, Na ₂ O is 0.04 to 0.35, SiO ₂ is 0.05 to 0.30, and MgO is in 0.35 to 0.44, further, to MgO1, with Na ₂ O content from 0.50 to 3.00, and, by _{mass%, CaO, Al 2 O 3} , Na 2 O, SiO 2 and, A hot metal desulfurization agent characterized in that the total amount of MgO is 90% or more and the balance is inevitable impurities.   The hot metal desulfurization agent according to claim 1, further comprising 1 to 15% by mass of metal Mg in terms of Mg.   The hot metal desulfurization agent according to any one of claims 1 to 3, further comprising 1 to 10% by mass of metal Al in terms of Al added to the hot metal desulfurization agent.   The hot metal desulfurization agent according to any one of claims 1 to 4, wherein one or more of calcined dolomite, calcined brucite, and MgO-based refractory are used as the MgO content. . The hot metal desulfurization agent according to any one of claims 1 to 5, wherein one or two types of soda-lime glass and sodium silicate are used as the Na ₂ O content.   A method for desulfurizing hot metal, comprising performing desulfurization treatment using the desulfurizing agent for hot metal according to claim 1 or 2. A hot metal desulfurization method, wherein the hot metal desulfurization agent according to any one of claims 3 to 6 is used for desulfurization treatment.