0001]The present invention and sulfur additive material to be added to molten steel in order to perform component adjustment of the molten steel, a manufacturing method for manufacturing sulfur-containing steel with sulfur additive.
BACKGROUND
[0002]Sulfur (S) is because it is an element to improve the machinability of the steel, the molten steel of the machine structural steel that is machined to particularly complex shapes, is often added required amount in the steelmaking process. At this time, as a sulfur additive, pure sulfur which is highly purified, industrially produced iron sulfide or pyrite obtained by various beneficiation process, marcasite and pyrrhotite is used.
[0003]
　These sulfur additive material, because it is produced through the industrial process, price is inevitably really high. On the other hand, in recent years, as a less expensive sulfur additive, the pyrite, which is taken from the mine, has been out is adopted to be used as it is.
[0004]
　Incidentally, the molten steel was refined in a converter or vacuum treatment vessel contains a large amount of oxygen, this large amount of oxygen, the Al deoxidation element affinity is strong and oxygen about 0.015 to 0.100 wt% was added to deoxidation is a common approach.
[0005]
　However, Al by Al deoxidation 2 O 3 inclusions is generated, which collectively coagulation, coarse alumina clusters are generated. The alumina clusters, the molten steel, adhered to the inner wall of the continuous casting nozzles used to inject the tundish into the mold (injection amount adjusting nozzle such sliding nozzle, including immersion nozzle), these nozzles clogging during continuous casting phenomenon (hereinafter referred to as "nozzle clogging") to generate.
[0006]
　In particular, the iron sulfide, as it is when used as a sulfur additive in the molten steel, impurities (such as oxides and carbonates) sulfide in iron becomes the oxygen source, the alumina clusters produce more, nozzle clogging is more generated It tends to be.
[0007]
　Such respect oxygen source contamination problems from additive or additive alloy to molten steel, Patent Document 1, decarburization of the molten steel by a vacuum degassing apparatus, deoxidation and addition of alloying elements to the molten steel in secondary refining method of molten steel performed performed during decarburization of the molten steel to the addition of alloy elements, then, it has been proposed to carry out the deoxidization treatment.
[0008]
　However, when adding sulfur additive material to the molten steel, since the desulfurization proceeds by reaction with the molten steel ladle slag, early, the addition of sulfur additive material to the molten steel, the yield of sulfur in the molten steel is not stable , it is difficult to stably ensure the composition of the sulfur of the resulting sulfur-containing steel.
CITATION
Patent Document
[0009]
Patent Document 1: JP 2000-087128 JP
Summary of the Invention
Problems that the Invention is to Solve
[0010]
　In view of the current problems of the prior art, upon addition of sulfur additive material to the molten steel, to stabilize the yield of sulfur in the molten steel, and prevention of the continuous casting, the occurrence of nozzle clogging due to impurities it is an object to, to solve the problem, inexpensive, and to provide an impurity a small amount of sulfur additive, and to provide a method of producing a sulfur-containing steel with sulfur additive for the purpose.
Means for Solving the Problems
[0011]
　The present inventors have intensively studied a technique for solving the above problems, as a result, the use of pyrite having a specific particle size which is sized by crushing a sulfur additive, the yield of sulfur in the molten steel stably It turned into, and found that at the time of continuous casting, the occurrence of nozzle clogging can be prevented.
[0012]
　The present invention has been made based on the above findings, its gist the following.
[0013]
　(1) Sulfur respect to the total mass% of the additive, the sulfur additive material for use in molten steel, which comprises the pyrite particles having a particle diameter of 5.0 ~ 37.5 mm or more 85 wt%.
[0014]
　(2) sulfur additive to molten steel according to (1) wherein the particle size is characterized in that it is a 9.5 ~ 31.5 mm.
[0015]
　Al deoxidized by said molten steel comprises a sulfur addition step of adding a sulfur additive material according to (1) or (2),
in
mass%, C: 0.07 ~
1.20%, Si: 0 than, 1.00% or
less, Mn: 0, more than 2.50% or
less, N: 0 than 0.02% or less
S:
0.012 ~ 0.100%, Al: 0.015 ~
0.100, P: It is limited to 0.10% or less, the production method of the sulfur-containing steel, which comprises melting a sulfur-containing steel balance of iron and unavoidable impurities.
[0016]
　(4) the sulfur-containing steel is further, by
mass%, Cu: 2.00% or
less, Ni: 2.00% or
less, Cr: 2.00% or
less, Mo: 2.00% or
less, Nb: 0 .25% or
less, V: 0.25% or
less, Ti: 0.30% or
less, B: 0.005% or less,
one or more elements selected from
characterized by containing the ( method for producing a sulfur-containing steel according to 3).
Effect of the invention
[0017]
　According to the present invention, inexpensive, and can provide the amount of impurities less sulfur additive, also upon addition of sulfur added feedstocks molten steel to stabilize the yield of sulfur in the molten steel, and , during continuous casting, thereby preventing the occurrence of nozzle clogging, it is possible to provide a manufacturing process for producing sulfur-containing steel.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018]
[1] brand A of pyrite used as a sulfur additive, B, and C, the particle size (mm) of each pyrite particle, a diagram showing a relationship between the oxygen concentration in each pyrite particle (%) is there.
DESCRIPTION OF THE INVENTION
[0019]
　Sulfur additive material of the present invention using the molten steel (hereinafter sometimes referred to as "the present invention additives".) Is, with respect to the total mass% of sulfur additive, 85 mass pyrite particle size 5.0 ~ 37.5 mm %, characterized in that it comprises more.
[0020]
　The method of producing sulfur-containing steel of the present invention (. The following sometimes referred to as "production method of the present invention") is, using the present invention additives, Al: 0.015 ~ 0.100 wt%, and, S: 0. characterized by melting the Al deoxidized sulfur-added steel containing from 012 to 0.100 mass%.
[0021]
　In the present invention production process, the present invention additives, at RH degassing process, it is preferably added after adjusting the components other than sulfur.
[0022]
　Hereinafter, the elapsed up to the present invention from the idea, the present invention will be described additives and the manufacturing method of the present invention.
[0023]
　The present inventors, in order to use an inexpensive pyrite as a sulfur additive, was investigated in detail with the composition and properties of the sulphide ore.
[0024]
　First, to investigate the composition of the iron sulfide by chemical analysis and X-ray diffraction method. As a result, the main component of iron sulphide is pyrite, the iron sulfide, otherwise, dolomite, often contain carbonates and oxides such as quartz was found. These impurities (dolomite, carbonates and oxides such as quartz, hereinafter, simply referred to as "impurities".) Is, in terms of oxygen concentration, it contains about 3 to 20 mass% in the iron sulfide It was found.
[0025]
　Next, to investigate the existence form of these impurities. Pyrite were cut and the cross section thereof, an optical microscope or a scanning electron microscope (SEM) results of observation by using a, impurities, (a) the sulfide in iron, the particle size of several millimeters or less fine particles be present as aggregates, and was found to have uniformly absent, unevenly distributed in (b) iron sulfide. Further, a result of observing a plurality of pyrite having different particle sizes Similarly, between (c) pyrite particles, it was found that there is a difference in distribution of the impurity.
[0026]
　The present inventors, based on this result, conceived as a "by the particle size of the pyrite, the amount of impurities may differ contained", under this concept, sieved pyrite particles, iron sulfide the amount of impurities in each particle size (by mass in terms of oxygen concentration) was measured in such conventional chemical analysis and X-ray diffraction method.
[0027]
　1, as an example, production area is different, three practical issues A, B, milled sulfide ore and C, the particle size (mm) of pyrite after sieving in multiple stages, each It shows the relationship between the oxygen concentration of sulfide in iron per particle (mass%). The oxygen concentration of the pyrite is inert gas fusion is a kind of chemical analysis - was measured by the infrared absorption method. As can be seen from Figure 1, even origin are different, the relationship between the particle size and the oxygen concentration showed almost the same behavior, a range of particle size 5.0 ~ 37.5 mm, and more preferably the particle size is 9. in the range of 5 ~ 31.5mm, oxygen concentration becomes low.
　Further, from FIG. 1, the particle size of the iron sulfide in the range of 5.0 ~ 37.5 mm, less concentration in oxygen content (10% by mass or less in oxygen concentration), The particle size is 9.5 to 31 oxygen concentration even less in the range of .5mm (oxygen concentration of 9 mass% or less) it is seen. In this respect, three types of stocks A, B, and C together similar results were obtained. From this result, even if the same analysis to blend each security, in the case as well as a range of particle size 5.0 ~ 37.5 mm single name, and more preferably a particle size of 9.5 to 31 and will wrap around. in the range of 5 mm, expected oxygen concentration becomes low.
[0028]
　Reason why such results were obtained are considered as follows.
[0029]
　The pyrite to yield from the mine, carbonates, although impurities such as oxides are inevitably contained, the particle size is less than a small few millimeters. Then, the pyrite is the main component of iron sulfide, the hardness of these impurities are very different. Usually, iron sulfide, as easy to handle, but used by crushing ore crusher or the like, crushing the different pyrite hardnesses - believed to occur by starting from the interface of impurities.
[0030]
　Furthermore, during crushing, fine impurities particles are finely dispersed, relatively coarse (5.0 ~ 37.5 mm) of hardly remaining impurities in pyrite particles, whereas, less than 5.0mm of flour during pyrite particles considered impurities is relatively large residual. Note that the coarse (37.5 mm greater) of pyrite, impurity particles is considered to be remaining intact without being crushed.
[0031]
　Based on the above findings, pyrite particles having a particle diameter is 5.0 ~ 37.5 mm, preferably, the pyrite particles of a particle size of 9.5 ~ 31.5 mm, as the sulfur additive material to be added to the molten steel it was decided to use.
[0032]
　Usually, by crushing the pyrite ore, grain size of the pyrite of 5.0 ~ 37.5 mm used sieved, but not crushed, particle size of 5.0 ~ 37.5 mm range pyrite in the is, as it is to use. Particles results particle size sieving exceeds 37.5mm is crushed again, the particle size may also be made in the range of 5.0 ~ 37.5mm. Particle size of the same when using the pyrite particles 9.5 ~ 31.5 mm.
[0033]
　Sulfur additive material to be added to the molten steel, pyrite particles having a particle diameter is 5.0 ~ 37.5 mm, preferably, the pyrite particles having a particle diameter is 9.5 ~ 31.5 mm, in mass%, 85% by weight It used those containing more.
[0034]
　When pyrite particles having a particle size of 5.0 ~ 37.5 mm sulfur additive in is less than 85 mass%, it becomes difficult to adjust accurately the amount of sulfur in the molten steel to the required range, for sulfur additives the total amount, the amount of pyrite particles having a particle diameter is 5.0 ~ 37.5 mm is set to 85 mass% or more. Preferably at least 90 mass%.
[0035]
　The particle size of the pyrite particles of iron sulfide is measured by sieving the method prescribed in JIS Z 8815 (ISO2591-1). Passing through the JIS Z 8801-1 sieve screen test of nominal opening 37.5mm specified in (ISO3310-1), and the particle the pyrite remaining on the sieve screen test of nominal opening 5.0mm diameter 5.0 and pyrite particles of ~ 37.5mm.
[0036]
　The present inventors, in order to confirm the effect of the present invention additives, was added pyrite particles in the molten steel was investigated the variation of oxygen concentration in the molten steel. It is increased in oxygen concentration after the addition of pyrite was observed, the amount of change is smaller with the addition of pyrite particles in the range of particle size 5.0 ~ 37.5 mm, further, the particle size from 9.5 to 31 it was possible to confirm that smaller with the addition of pyrite particles in the range of .5mm.
[0037]
　Next, a method for manufacturing the sulfur-containing steel of the present invention.
[0038]
　BOF and electric furnace or the like to adjust the component composition of the primary refining the molten steel. If necessary, RH type degassing apparatus, the ladle-heating type refining apparatus, a simple formula molten steel processing equipment or the like, and secondary refining. After the primary refining, or, in the middle secondary refining, performing deoxidation by Al. When performing deoxidation after the primary refining, when the ladle tapping, may be added to the Al source. When performing deoxidation in the secondary refining middle idea except ladle slag position for addition of Al source, yield of Al is stable.
[0039]
　Incidentally, Al source, and added to the molten steel as early as possible after the primary refining, then stirred molten steel, Al 2 O 3 is preferred to flotation inclusions.
[0040]
　In the production method of the present invention, the present invention is added after Al deoxidation step of adding Al to the molten steel performs deoxidation, a secondary refining end finishing the adjustment of the molten steel chemical composition, the molten steel is Al deoxidized adding wood (particle size 5.0 to pyrite 85 mass% or more 37.5 mm). Incidentally, the secondary refining before or secondary refining early, if the present invention additive material is added, the desulfurization proceeds reacts with ladle slag, the sulfur concentration of the resulting sulfur-containing steel that can not be controlled in the required range afraid there is.
[0041]
　Thus, the secondary refining end, when added to molten steel of the present invention additives are Al deoxidized, Al are generated from oxygen present in impurities pyrite particles 2 O 3 proceeds and flotation of inclusions hard, at the time of continuous casting, the occurrence of nozzle clogging can be suppressed. In addition, a stable yield of sulfur in the molten steel.
[0042]
　The thus prepared molten steel, the cast slab by continuous casting according to conventional methods. During continuous casting, oxygen source is prevented from contaminating the molten steel. When oxygen source to the molten steel is mixed, Al 2 O 3 since inclusions are generated, Al 2 O 3 is to prevent the formation of inclusions.
[0043]
　Incidentally, the immersion nozzle used in continuous casting can be of inexpensive alumina graphite material, but it is also possible to use hard-to-adhere nozzle containing CaO.
[0044]
　Production method of the present invention, S: is suitable for melting sulfur containing steel containing from 0.012 to 0.100 wt%. Sulfur-containing steel obtained by the present invention production process, after Al deoxidation, Al: including from 0.015 to 0.100 wt%.
[0045]
　The following describes reasons for limiting the chemical composition of the sulfur-containing steel that is melted in a manufacturing method of the present invention (hereinafter sometimes referred to as "added steel according to the present invention".). Hereinafter,% means mass%.
[0046]
　S: 0.012 ~ 0.100%
　S is an element necessary for securing the cutting of the steel, also affects the elements in the occurrence of nozzle clogging during continuous casting. When S content is less than 0.012%, requires less amount of sulfur additive, nozzle clogging does not occur, can not be ensured the required machinability, S amount is 0.012% or more . Preferably 0.015% or more.
[0047]
　On the other hand, when the S content exceeds 0.100%, CaS sulfur in Ca and the molten steel in the ladle slag reacts generates, during continuous casting, the nozzle clogging occurs, the amount of S is 0.100 % or less to be. Preferably not more than 0.075%.
[0048]
　Al: 0.015 ~
　0.100% Al reacts with O in the molten steel Al 2 O 3 to generate an element used to deoxidizing the molten steel. If Al content is less than 0.015%, since the deoxidizing effect is not exhibited sufficiently, the Al content is 0.015% or more. Preferably 0.025% or more. On the other hand, when the Al amount exceeds 0.100%, Al 2 O 3 inclusions are produced in large quantities, during continuous casting, the nozzle clogging occurs frequently, Al content is set to 0.100% or less. Preferably is less than or equal to 0.070%.
[0049]
　Added steel according to the present invention is basically, S: 0.012 contained to 0.100%, further, Al: it is sufficient to contain 0.015 to 0.100% of the other elements While the composition is not particularly limited, in order to more effectively express the effect of improving the machinability by sulfur addition, C: 0.07 ~ 1.20%, Si: 0 a greater, 1.00% or less, Mn: 0 a greater, 2.50% or less, P: 0 a greater, more than 0.10%, N: 0 a greater, controlled to 0.02% or less. It will be described below.
[0050]
　C: 0.07 ~ 1.20%,
　C is an element necessary for securing the hardenability of the strength and the weld of the steel. When C content is less than 0.07%, it becomes difficult to ensure the strength necessary for mechanical structural steel, the C content is 0.07% or more. More preferably 0.10% or more. On the other hand, when the C content exceeds 1.20%, the toughness is reduced, the C content is less than 1.20%. More preferably not more than 1.00%.
[0051]
　Si: 0, more than 1.00% or less
　Si is a solution hardening element which contributes to the improvement of the strength of the steel. When Si amount exceeds 1.00%, since the toughness is lowered, the amount of Si is 1.00% or less. More preferably 0.70%. The lower limit is not particularly limited, in order to obtain a sufficient effect of adding Si, preferably at least 0.01%. More preferably 0.10% or more.
[0052]
　Mn: 0, more than 2.50% or less
　Mn enhances the hardenability of steel, which is an element contributing to the improvement of strength. When Mn content exceeds 2.50%, the weldability of the steel is lowered, Mn is less than 2.50%. More preferably not more than 2.00%. The lower limit is not particularly limited, in order to obtain a sufficient effect of adding Mn, preferably at least 0.30%. More preferably 0.50% or more.
[0053]
　P: 0, more than 0.10%
　P is segregated, it is an element that inhibits toughness. When the P content exceeds 0.10%, the toughness is significantly decreased, the P content is 0.10% or less. More preferably 0.05% or less. The lower limit is not particularly limited, when reducing the P content to less than 0.001%, because the manufacturing cost is significantly increased, practically steel, 0.001%, which is substantially the lower. In terms of manufacturing cost, more preferably 0.010% or more.
[0054]
　N: 0 than 0.02% or less
　N is a solid solution strengthening, an element which contributes to the improvement of the strength of the steel. When N content exceeds 0.02%, the amount of solid solution N increases, the strength is increased, so the toughness is lowered, the amount of N is 0.02% or less. More preferably 0.015% or less. The lower limit is not particularly limited, when reducing the N to less than 0.001%, the production cost is greatly increased, practically steel, 0.001%, which is substantially the lower. In terms of manufacturing cost, more preferably 0.002% or more.
[0055]
　Added steel according to the present invention, further improve characteristics, (a) Cu: 2.00 or less, and / or, Ni: 2.00% or less, (b) Cr: 2.00% or less, and / or, Mo: 2.00% or less, (c) Nb: 0.25% or less, and / or, V: 0.25% or less, and, (d) Ti: 0.30% or less, and / or, B: it may contain 0.005% or less of the element group one or more than one.
[0056]
　(a) group elements
　　Cu: 2.00 or less
　　Ni: 2.00% or less
　Cu and Ni are both an element which contributes to the improvement of the strength of the steel. When Cu content exceeds 2.00%, excessively increased strength, since the toughness decreases, the Cu content is preferably 2.00% or less. More preferably not more than 1.60%. The lower limit is not particularly limited, in order to obtain a sufficient effect of adding Cu, preferably at least 0.10%. More preferably 0.20% or more.
[0057]
　When Ni exceeds 2.00%, as with Cu, too increase strength, since the toughness is decreased, Ni content is preferably 2.00% or less. More preferably not more than 1.60%. The lower limit is not particularly limited, in order to obtain a sufficient effect of adding Ni, preferably at least 0.10%. More preferably 0.30% or more.
[0058]
　(b) group elements
　　Cr: 2.00% or less
　　Mo: 2.00% or less
　Cr and Mo are each an element contributing to the improvement of the strength of the steel. When Cr content exceeds 2.00%, the strength is excessively increased, so the toughness is lowered, the amount of Cr is preferably equal to or less than 2.00%. More preferably not more than 1.60%. The lower limit is not particularly limited, in order to obtain a sufficient effect of adding Cr, preferably at least 0.15%. More preferably 0.25% or more.
[0059]
　When Mo content exceeds 2.00%, as with Cr, too increase strength, since the toughness is lowered, Mo content is preferably 2.00% or less. More preferably not more than 1.60%. The lower limit is not particularly limited, in order to obtain a sufficient effect of adding Mo, preferably at least 0.02%. More preferably 0.10% or more.
[0060]
　(c) element of the group
　　Nb: 0.25% or less
　　V: 0.25% or less
　Nb and V are both formed carbonitride, the pinning effect of carbonitrides, contributes to the improvement of strength and toughness it is an element. When Nb content exceeds 0.25%, carbonitrides become coarse, so the toughness is lowered, Nb content is preferably 0.25% or less. More preferably not more than 0.20%. The lower limit is not particularly limited, in order to obtain a sufficient effect of adding Nb, preferably 0.01% or more. More preferably 0.02% or more.
[0061]
　When V is more than 0.25%, as with Nb, carbonitride are coarsened, since the HAZ (Heat-Affected-Zone) toughness decreases, V content is preferably 0.25% or less. More preferably not more than 0.20%. The lower limit is not particularly limited, in order to obtain a sufficient effect of adding the V content is preferably 0.01% or more. More preferably 0.10% or more.
[0062]
　group (d) element
　　Ti: 0.30% or less
　　B: 0.005% or less
　Ti is to form a nitride fine crystal grains by combining with N, an element which contributes to the improvement of toughness. When Ti content exceeds 0.30%, the cutting resistance is reduced, the Ti content is preferably 0.30% or less. More preferably not more than 0.25%. The lower limit is not particularly limited, in order to obtain a sufficient effect of adding Ti, preferably 0.01% or more. More preferably 0.02% or more.
[0063]
　B is to suppress the formation of grain boundary ferrite, an element which contributes to the improvement of toughness. When the amount of B exceeds 0.005%, BN is precipitated in the austenite grain boundaries, since the toughness decreases, B content is preferably 0.005% or less. More preferably not more than 0.003%. The lower limit is not particularly limited, in order to obtain the effect of adding B sufficiently, preferably at least 0.0005%. More preferably 0.0010% or more.
Example
[0064]
　Next, a description will be given of an embodiment of the present invention, the conditions in the examples, is one of the example of conditions adopted for confirming the workability and effects of the present invention, the present invention is the one condition example the present invention is not limited to. The present invention does not depart from the gist of the present invention, as long as they achieve the object of the present invention, it is capable of adopting various conditions.
[0065]
　(Example 1)
　when tapping the molten steel which is primary refining in a converter furnace capacity 300 tons in a ladle, was performed Al deoxidation by adding metal Al. In Example 1, using the pyrite particles stocks A shown in FIG. 1 as a sulfur additive.
[0066]
　Table 1 shows the invention Examples and in the continuous casting of sulfur-containing steel of the comparative example, the composition of the molten steel after the addition of the sulfur additive material.
[0067]
[Table 1]

　Note: "T.Al" represents the total amount of Al.
[0068]
　After Al deoxidation, adjusting the temperature in ladle heating refining device, then degassed with RH type degassing unit, thereby implementing the component adjustment, to remove inclusions stirring molten steel. Degassing, after component adjustment, the sulfur additive material containing different particle sizes pyrite, was added to the molten steel. After the addition of sulfur additives, to remove inclusions followed by stirring for more uniform mixing times.
[0069]
　Thus the melted and sulfur steels were continuously cast. Continuous casting was carried out in the cross-sectional size 220 mm × 220 mm Broome 6 strands caster.
[0070]
　Molten steel superheat in the tundish during continuous casting (the temperature of the molten steel, the value obtained by subtracting the liquidus temperature of the steel of the chemical composition) was 10 ~ 60 ° C.. (Casting molten steel per unit time) throughput of the molten steel was 0.3 ~ 0.6 t / min. Throughput was adjusted by the sliding nozzle opening.
[0071]
　Table 2, weight percent pyrite particle size 5.0 ~ 37.5 mm, weight% of pyrite particle size of less than 5.0 mm, the weight percent of pyrite to a particle diameter exceeding 37.5 mm, nozzle clogging index, and, a nozzle clogging results, respectively. Here, in Table 2 of "No." corresponds to the "No." in Table 1.
[0072]
[Table 2]

[0073]
　Nozzle clogging index is obtained by indexation of sliding nozzle opening is defined exponential as follows. The actual degree of opening of the sliding nozzle and index the ratio of the sliding theoretical degree of opening of the nozzle in the absence of nozzle clogging calculated from molten steel throughput and the molten steel head (= actual opening / theoretical degree) it is intended.
　Here, the "theoretical opening", in a state submerged nozzle and / or the sliding nozzle is not closed or closed erosion is that the opening of the sliding nozzle required to produce a given throughput. Further, the "actual opening" opening the injection system of the gauge actually shown during casting and. Submerged nozzle and / or alumina cluster or the like is attached to the sliding nozzle, to achieve the same flow rate when the occlusion progresses, the opening degree of the sliding nozzle is increased. Therefore, the larger the nozzle clogging index, which means that nozzle clogging occurs frequently, the goal is 1 or less.
　Moreover, the situation of nozzle clogging was evaluated in changes to the nozzle opening of the stationary casting phase.
　In Table 2 the symbol item "nozzle change of opening" and "+", an increase of the nozzle opening, i.e., indicates a nozzle clogging tendency, "-" means a reduction in the nozzle opening, i.e., nozzle clogging decline or nozzle opening degree indicates that the stable.
[0074]
　Nozzle clogging performance is the result of the evaluation of the nozzle clogging index in three stages, the nozzle clogging index less than 1 ◎ (good), 1 more than 3 following the △ (not good), was greater than 3 and × (bad) .
[0075]
　Invention Example 1 In continuous casting of ~ 50, both the percentage of pyrite particles having a particle diameter of 5.0 ~ 37.5 mm in sulfur additive is at least 85 wt%, nozzle clogging index is 1 or less, the nozzles occlusion without generating, it was possible to carry out continuous casting.
[0076]
　In the continuous casting of Comparative Examples 51-65, the ratio of the pyrite particles having a particle diameter of 5.0 ~ 37.5 mm in sulfur additive is less than 85 wt%, during continuous casting, nozzle clogging occurred frequently.
[0077]
　(Example 2)
　In Example 2, as a sulfur additive, brand B shown in FIG. 1, except for using the pyrite particles stocks C, subjected to continuous casting of sulfur-containing steel in the same manner as in Example 1 It was.
[0078]
　　Table 3 shows inventive examples and in the continuous casting of sulfur-containing steel of the comparative example, the composition of the molten steel after the addition of the sulfur additive material.
[0079]
[Table 3]

　Note: "T.Al" represents the total amount of Al.
[0080]
　Table 4 wt% of pyrite particle size 5.0 ~ 37.5 mm, weight% of pyrite particle size of less than 5.0 mm, the weight percent of pyrite to a particle diameter exceeding 37.5 mm, nozzle clogging index, and, a nozzle clogging results, respectively. Here, in Table 4, "No." corresponds to the "No." in Table 3.
[0081]
[Table 4]

[0082]
　Table As can be seen from 4, brand B, even iron sulfide and C, at the rate of pyrite particles having a particle diameter of 5.0 ~ 37.5 mm in sulfur additive is 85 wt% or more, nozzle clogging index 1 or less, without nozzle clogging occurs, it was possible to perform continuous casting. In contrast, the percentage of pyrite particles having a particle diameter of 5.0 ~ 37.5 mm in sulfur additive is less than 85 mass%, during continuous casting, nozzle clogging occurred frequently.
Industrial Applicability
[0083]
　As described above, according to the manufacturing method of the present invention, to stabilize the yield of the sulfur in the molten steel, and, during continuous casting, thereby preventing the occurrence of nozzle clogging, less expensive, and less sulfur addition amount of impurities it is possible to provide the wood. Accordingly, the present invention has high applicability in the steel industry.

WE CLAIM

Sulfur with respect to the total mass% of the additive, the sulfur additive material for use in molten steel, which comprises the pyrite particles having a particle diameter of 5.0 ~ 37.5 mm 85 mass% or more.
[Requested item 2]
　Sulfur additive material to the molten steel according to claim 1, wherein the particle size is 9.5 ~ 31.5 mm.
[Requested item 3]
　Wherein sulfur addition step of adding a sulfur additive material according to claim 1 or 2 in Al deoxidized by molten steel,
by
mass%, C: 0.07 ~
1.20%, Si: 0, greater than 1.00 % or
less, Mn: 0, more than 2.50% or
less, N: 0 than 0.02% or less
S:
0.012 ~ 0.100%, Al: containing 0.015 ~
0.100, P: It is limited to 0.10% or less, the production method of the sulfur-containing steel, which comprises melting a sulfur-containing steel balance of iron and unavoidable impurities.
[Requested item 4]
　It said sulfur-containing steel is further, by
mass%, Cu: 2.00% or
less, Ni: 2.00% or
less, Cr: 2.00% or
less, Mo: 2.00% or
less, Nb: 0.25%
hereinafter, V: 0.25% or
less, Ti: 0.30% or
less, B: 0.005% or less,
one or more elements selected from
claim 3, characterized in that it contains the method of manufacturing sulfur-added steel.