Ferronickel alloy and its manufacturing method

Abstract

To provide a ferronickel alloy which has a good shape when being used as a raw material of a stainless steel and a special steel, has high purity, especially, effectively utilizes a very small amount of a sulfur content.SOLUTION: A ferronickel alloy contains, by mass%, 10-40% Ni, 1% or less C, 0.1-2% S, 0.04% or less P, 2% or less Co, 0.15-2% Cr, and the balance Fe with inevitable impurities, and has a particle size of 0.05 mm to 50 mm, wherein the particles are composed of an Fe-Ni phase and an Fe-Ni-S phase, the Fe-Ni phase contains 10-50% Ni, the Fe-Ni-S phase contains 10-80% Fe, 5-50% Ni and 10-40% S, in the ferronickel alloy particles, the Fe-Ni-S phase is distributed between the Fe-Ni phases, or the Fe-Ni phases are dispersed in the Fe-Ni-S phase.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a ferronickel alloy used as a Ni source in the steelmaking process for stainless steel, special steel, etc., and in particular to a ferronickel alloy that can be handled as a raw material in an optimal form in the steelmaking process by improving its chemical composition and particle size. [Background technology]

[0002] Ferronickel alloys are widely used as a nickel source for nickel-containing austenitic stainless steels, duplex stainless steels, alloy steels, etc. Conventionally, ferronickel alloys are produced by reducing nickel oxide and iron oxide contained in nickel oxide ore.

[0003] Methods for producing ferronickel alloys include a method of drying and reducing using a rotary kiln as disclosed in Patent Document 1, a method of drying and reducing using a combination of a rotary dryer and an electric furnace as disclosed in Patent Document 2, and a method of reducing using an electrically powered reducing furnace as disclosed in Patent Document 3.

[0004] The ferronickel alloy smelting method disclosed in Patent Document 1 uses a rotary kiln to semi-molten nickel ore and reduce it with coal. In this process, the ferronickel alloy is effectively agglomerated to produce clinker, which is a mixture of slag and ferronickel alloy particles. The key here is that if the ferronickel alloy particles are not grown sufficiently, there is a technical problem that it is difficult to recover the ferronickel alloy particles through the subsequent clinker crushing, flotation in water, and magnetic separation. In other words, there is a problem that there is a disadvantage in terms of nickel yield.

[0005] On the other hand, Patent Documents 2 and 3 are the most widely used methods for producing ferronickel alloys. In this method, nickel ore and coal are mixed, pre-dried and pre-reduced in a rotary kiln, and then charged into an electric furnace to completely melt the ferronickel alloy and slag. In other words, since the molten slag is separated on the molten ferronickel alloy and the ferronickel alloy is recovered, this is advantageous in terms of Ni yield. However, this method requires discharge arc melting equipment equipped with three-phase graphite electrodes and consumes a large amount of electricity, which is disadvantageous in terms of cost. In addition, there is a problem that a large amount of equipment must be invested in initially.

[0006] In addition, the method of smelting using a rotary kiln has a problem that slag rings are formed on the inner wall of the rotary kiln, significantly impairing productivity, as described in Patent Document 4. Furthermore, as described in Patent Document 5, there is also a problem that appropriate operation cannot be carried out unless the combination of nickel ores is carefully selected.

[0007] As for the above-mentioned technology related to nickel yield, as shown in Patent Document 6, in the technology disclosed in Patent Documents 1, 4, and 5 using a rotary kiln, the clinker discharged from the rotary kiln at 1300°C and cooled with water is mainly composed of slag and ferronickel particles, and the surface of this ferronickel alloy particle is covered with a sulfide phase of Fe and Ni. However, there is no disclosure about the function of the sulfide. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 3-10026 [Patent Document 2] JP 2016-211032 A [Patent Document 3] JP 2016-35085 A [Patent Document 4] JP 2011-047020 A [Patent Document 5] JP 2006-336028 A [Patent Document 6] Japanese Patent Application Publication No. 05-295469 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention provides a high-purity ferronickel alloy that has a good shape suitable for use in stainless steel and special steel. In particular, the present invention aims to provide a ferronickel alloy that effectively utilizes a small amount of sulfur. [Means for solving the problem]

[0010] The inventors have conducted extensive research to provide a new ferro-nickel alloy. Experiments were conducted using a rotary kiln with a diameter of 3.6 m and a length of 72 m. The raw materials were heated using a pulverized coal burner from the front side of the kiln, that is, the side where the clinker is discharged. The raw materials were made by mixing crushed nickel ore, coal as a reducing agent and heat source, and limestone as a slag melting material, adjusting the moisture content to about 20%, and molding them into briquettes. Anthracite was mainly used as the coal, and its basic unit was 150 kg / ore ton (mixture amount per ton of Ni ore). The limestone was in the form of unburned calcium carbonate, and was 60 kg / ore ton. The briquettes were charged from the back side of the furnace and heated by the burner, while air was introduced into the furnace from the front side by an exhaust fan installed in the exhaust gas system, and the maximum temperature was controlled to 1400°C and 1300°C at the discharge position.

[0011] An experiment was conducted on reducing nickel ore with coal. As a result, by including 0.1 to 2% sulfur in the ferronickel alloy, the ferronickel alloy particles grew, and it was successful in obtaining a ferronickel alloy that could be fully recovered even after the clinker, which is a mixture with slag, was subjected to crushing flotation and magnetic separation. The ferronickel alloy is characterized by its high purity, with low C concentration, low phosphorus concentration, and low Cr concentration, and the details of the invention are shown below.

[0012] That is, the ferro-nickel alloy of the present invention contains, in mass %, Ni: 10 to 40 %, C: 1% or less, S: 0.1~2%, P: 0.04% or less, Co: 2% or less, Cr: 0.15~2% The grain size is 0.05 mm to 50 mm, and the grains are characterized by being composed of an Fe-Ni phase and an Fe-Ni-S phase.

[0013] Furthermore, the ferro-nickel alloy particles are further characterized in that the Fe-Ni phase is composed of Ni: 10-50%, and the Fe-Ni-S phase is composed of Fe: 10-80%, Ni: 5-50%, and S: 10-40%.

[0014] In addition, the structure of the ferro-nickel alloy particles is such that the Fe-Ni-S phase is distributed between the Fe-Ni phases, and the Fe-Ni phase is dispersed in the Fe-Ni-S phase. Further features include .

[0015] Furthermore, the present invention also provides a method for producing the above ferro-nickel alloy. 2 : 36-52%, Al 2 O 3 :0.2 ~3%, Fe:6~20%, MgO:17~30%, Ni:1.5~3%, Co:0.5% or less, Cr 2 O 3 Nickel oxide ore containing unavoidable impurities, Fixed-C: 70-80%, SiO 2 , Al 2 O 3 100-180 kg / ore ton of carbonaceous material with 10-15% CaO ash, 0.3-1.0% S, and 10-15% Ig-loss, and 10-100 kg / ore ton of slag melting agent are crushed and mixed, the moisture content is adjusted to 8-30%, and the briquettes are made into briquettes. The briquettes are charged into a rotary kiln, and while air is introduced into the furnace to heat the clinker discharge side, the briquettes are rolled and semi-melted and reduced to clinker. The temperature inside the furnace is controlled at 1200 to 1300°C at the discharge position.The discharged clinker is cooled, crushed, and dressed in a process for producing a ferro-nickel alloy. [Brief description of the drawings]

[0016] [Figure 1] FIG. 2 is a schematic cross-sectional view showing a ferronickel alloy particle of an example of the present invention. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing a ferronickel alloy particle of an example of the present invention. [Diagram 3] FIG. 2 is a schematic cross-sectional view showing a ferronickel alloy particle of a comparative example. [Figure 4] FIG. 2 is a schematic cross-sectional view showing a ferronickel alloy particle of a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The chemical components of the ferro-nickel alloy of the present invention will now be described. Ni:10~ 40 % The concentration obtained from ore alone is over 10%. 40 %, in the steelmaking process of stainless steel, for example, Fe-18%Cr-8%Ni alloy represented by SUS304, the Ni concentration becomes too high, and it becomes necessary to mix not only ferronickel alloy but also expensive low phosphorus iron scrap to replenish Fe, which increases the manufacturing cost. 40 %, preferably 20 to 40%.

[0018] C: 1% or less In the smelting process of ferronickel alloys, raw materials are reduced using anthracite, and this element inevitably gets mixed into the ferronickel alloy. When added to stainless steel, if the C content is too high, it increases the load during the decarburization process of stainless steel refining. For this reason, it is specified to be 1% or less. Preferably, it is 0.1% or less.

[0019] S: 0.1-2% Sulfur is an extremely important component in the present invention. If S is less than 0.1%, the Fe-Ni-S phase cannot be formed in the ferronickel alloy. If S exceeds 2%, the Fe-Ni-S phase becomes too much, and the ferronickel alloy becomes molten in the kiln and adheres to the furnace wall, does not reach the discharge side, and the ferronickel alloy cannot be obtained. In addition, when manufacturing stainless steel and special steel using ferronickel alloy as a raw material, S inhibits the weldability of the alloy and reduces hot workability, so it is necessary to reduce it. However, desulfurization is possible with recent refining technology using AOD and VOD, but the load of the process is increased. Therefore, it is specified to be 0.1 to 2%. It is preferably 0.2 to 1%.

[0020] P:0.04% or less When manufacturing stainless steel or special steel using ferronickel alloy as a raw material, P inhibits the weldability of the alloy and impairs hot workability, so it is necessary to reduce it. Therefore, it is specified to be 0.04% or less. Preferably, it is 0.03% or less.

[0021] Co: 2% or less When manufacturing stainless steel or special steel using ferronickel alloy as a raw material, Co has the effect of improving the corrosion resistance of the alloy. On the other hand, it is also an element that is regulated in nuclear power applications. Therefore, the content should be kept to 2% or less. Preferably, it is 1% or less.

[0022] Cr: 0.15~2% When stainless steel or special steel is manufactured from ferro-nickel alloy, Cr has the effect of improving the corrosion resistance of the alloy. On the other hand, when manufacturing Fe-Ni alloys such as Fe-36%Ni low thermal expansion alloy, a Cr removal process is required. Therefore, the content should be kept to 2% or less. Preferably, it is 1% or less. The above chemical composition is the average composition of the ferro-nickel alloy as a whole, not limited to local Fe-Ni phase or Fe-Ni-S phase.

[0023] Ferro-nickel alloy grain size: 0.05mm~50mm The size of the ferronickel alloy that can be recovered through crushing clinker, flotation, and magnetic separation is 0.05 mm or more. If it exceeds 50 mm, it will separate in the kiln and cannot be discharged, which will actually reduce the Ni yield. Therefore, it is set to 0.05 mm to 50 mm. Preferably, it is 0.1 to 10 mm.

[0024] The particles are ferro-nickel alloys consisting of Fe-Ni and Fe-Ni-S phases. Sulfur inhibits weldability when manufacturing stainless steel and special steel, but when it reacts with Fe-Ni to form the Fe-Ni-S phase, which contains a high concentration of sulfur, it lowers the melting point and helps the ferro-nickel alloy melt in the temperature range inside the kiln furnace, causing the particles to coalesce and grow, which is effective in growing to the size of 0.05 mm or more mentioned above. Therefore, it was decided that the alloy should be composed of an Fe-Ni phase and an Fe-Ni-S phase.

[0025] The Fe-Ni phase in the ferro-nickel alloy particles is Ni: 10-50%, and the Fe-Ni-S phase is Fe: 10-80%, Ni: 5-50%, S: 10-40%. If the Fe-Ni phase does not contain 10% or more Ni, the Ni content of 10% or more as described in claim 1 cannot be achieved. If the Ni content exceeds 50%, the melting point of the Fe-Ni phase decreases, making it difficult for grains to grow by fusion via the Fe-Ni-S phase. For this reason, the Fe-Ni phase is set to Ni: 10-50%. If the Fe-Ni-S phase is not composed of Fe: 10-80%, Ni: 5-50%, and S: 10-40%, the meltability of the ferronickel alloy cannot be ensured, so this range is specified. Note that this phase may contain 2% or less Cr. This is because the properties related to melting do not change.

[0026] The Fe-Ni-S phase in the ferro-nickel alloy particles is distributed between the Fe-Ni phases. The Fe-Ni phase is dispersed in the Fe-Ni-S phase in the ferro-nickel alloy particles. Since the Fe-Ni-S phase generates a liquid phase in the furnace temperature range and promotes the aggregation and coalescence of the Fe-Ni phase to grow the ferronickel alloy particles, the structure of the ferronickel alloy particles is preferably such that the Fe-Ni-S phase is distributed between adjacent Fe-Ni phases in any one particle as shown in Figure 1. It is also possible to have a form in which the content of the Fe-Ni-S phase is higher than this, and the Fe-Ni phase, which is relatively smaller than that in Figure 1, is dispersed in the Fe-Ni-S phase as shown in Figure 2. on the other hand As shown in Fig. 3, a single Fe-Ni phase exists and is surrounded by an Fe-Ni-S phase. and However, a structure consisting only of an Fe-Ni phase and not including an Fe-Ni-S phase, as shown in FIG. 4, is outside the scope of the present invention.

[0027] A preferred manufacturing method for satisfying the above chemical composition is also described. In particular, the size of the rotary kiln is not limited, but a rotary kiln with a diameter of 3.6 m, a length of 72 m, and an inclination angle of 2 degrees is used for operation. The rotation speed is 45 to 60 rph. The raw materials are heated using a pulverized coal burner from the front side of the kiln, that is, the side from which the clinker is discharged. The raw materials are a mixture of crushed nickel ore, coal as a reducing agent and heat source, and limestone as a slag melting material, and the moisture is adjusted to 8 to 30% and molded into briquettes. About 15% is preferable. Anthracite is mainly used as the coal, and its basic unit is 100 to 180 kg / ore ton. The limestone is in the form of uncalcined calcium carbonate, and is 10 to 100 kg / ore ton. The briquettes were charged from the back of the furnace at a feed rate of 10 to 25 ore tons / hr and heated by the burner. At the same time, air was introduced into the furnace from the front of the furnace by an exhaust fan installed in the exhaust gas system, and the maximum temperature was controlled to 1300 to 1500°C and 1200 to 1300°C at the discharge position. Approximately 1400°C and approximately 1300°C are preferable, respectively.

[0028] In the present invention, the nickel oxide ore used in the reduction treatment has a chemical composition of SiO 2 : 36-52%, Al 2 O 3:0.2~3%, Fe:6~20%, MgO:17~30%, Ni:1.5~3%, Co:0.5% or less, Cr 2 O 3 Anthracite is preferably used with a content of Fixed-C: 70-80%, SiO 2 , Al 2 O 3 , CaO ash content: 10~15%, S: 0.3~1.0%, Ig-loss: 10~15% are recommended.

[0029] First, the coal and the air supplied into the furnace are heated by the burner and react, resulting in the following reaction: C (coal)+1 / 2O 2 (air) = CO(gas)…(1)

[0030] As the raw materials gradually move toward the front of the furnace, the temperature of the raw materials rises. In the high temperature region, this CO gas reduces the nickel oxide and iron oxide in the raw materials, forming micron-sized fine ferro-nickel alloy particles mainly in the olivine minerals in the raw materials. In a reducing atmosphere, the sulfur content, which is mainly supplied from coal, forms CaS from limestone through the reactions of the following reaction formulas (2) to (4) with CaO produced by the thermal decomposition of limestone. CaCO 3 (limestone)=CaO(solid phase)+CO 2 (Gas)…(2) CO 2 + C(coal) = 2CO(gas)…(3) CaO(solid phase) + S(gas) + CO = CaS(solid phase) + CO 2 (Gas)…(4)

[0031] Furthermore, when the raw material temperature increases, the SiO 2 , CaO, Al 2 O 3 , the MgO begins to fuse and form a molten slag. SiO 2 (ore) + CaO(ore) + Al 2 O 3 (ore) + MgO(ore) =CaO-MgO-SiO2 -Al 2 O 3 (Molten slag)…(5)

[0032] The amount of molten slag (liquid phase) formed by formula (5) is very small, but CaS melts into this liquid phase. In this way, S becomes distributed in the liquid phase of the slag, causing the following reaction. Fe-Ni (ferro-nickel alloy) + S (molten slag) = Fe-Ni-S (sulfide)…(6)

[0033] This Fe-Ni-S phase plays a very important role. In other words, the Fe-Ni-based ferro-nickel alloy alone, whose structure is shown in Figure 4, does not melt at the maximum kiln temperature of 1400°C, even when referring to the phase diagram, whereas the Fe-Ni-S phase has a melting point of about 1000°C, so it melts in the temperature range of the rotary kiln. This molten Fe-Ni-S phase envelops the Fe-Ni phase, moves through the liquid phase in the slag, and when it comes into contact with another identical particle, it combines with it. The rotation of the kiln promotes this process, causing it to grow logarithmically in size. Furthermore, trace amounts of P oxides and Cr oxides contained in the ore are also reduced by CO gas and move into the ferro-nickel alloy. P 2 O 5 (Ore) + 5CO(Gas) = ​​2P(Ferronickel Alloy) + 5CO 2 (Gas)…(7) Cr 2 O 3 (ore) + 3CO(gas) = ​​2Cr(ferronickel alloy) + 3CO 2 (Gas)…(8)

[0034] By this type of coalescence growth, the grain size of the ferronickel alloy can grow to 0.05 mm to 50 mm, and the Fe-Ni-S phase in the ferronickel alloy particle is distributed between the Fe-Ni phases.

[0035] Furthermore, as the clinker moves to the discharge side, the proportion of the air introduced by the exhaust fan that remains unreacted increases, and the oxygen partial pressure increases. As a result, the iron in the ferro-nickel alloy oxidizes, producing FeO in the liquid phase of the slag according to the following formula: Fe (ferro-nickel alloy) + 1 / 2O 2 (gas) = ​​FeO (solid phase)…(9) CaO-MgO-SiO 2 -Al 2 O 3 (Molten slag) + FeO (solid phase) =CaO-MgO-SiO 2 -Al 2 O 3 -FeO (molten slag)…(10)

[0036] This FeO reacts with Cr and P contained in the ferronickel alloy and migrates into the slag according to the following formula, thereby making it possible to control the content within the range of the present invention. 2P (ferro-nickel alloy) + 5FeO (molten slag) =5Fe (ferro-nickel alloy) + P 2 O 5 (Molten slag)…(11) 2Cr (ferro-nickel alloy) + 3FeO (molten slag) =3Fe (ferro-nickel alloy) + Cr 2 O 3 (Molten slag)…(12)

[0037] The inserted coal is almost completely consumed by reduction and as a heat source before reaching the discharge side, so that the C in the ferro-nickel alloy is oxidized as CO gas, thereby making it possible to control the C concentration within the range of the present invention.

[0038] The coal consumption rate is the rate at which this oxygen partial pressure is appropriately controlled, and is 100 to 180 kg / ton of ore. Furthermore, by controlling the rotation speed of the rotary kiln, which determines the speed at which the charged raw materials are moved, to 45 to 60 rph, the composition ratio of the molten part of the slag, i.e., the liquid phase part, can be controlled to 20 to 50 volume %, and the chemical composition, structure, and particle size of the ferronickel alloy of the present invention can be satisfied. EXAMPLES

[0039] The following examples are presented to clarify the effects of the present invention. A rotary kiln with a diameter of 3.6 m, a length of 72 m, and an inclination angle of 2 degrees was used for the operation. The rotation speed of the rotary kiln was 55 rph. The raw materials were heated using a pulverized coal burner from the front side of the kiln, that is, the side from which the clinker is discharged. The raw materials were a mixture of crushed nickel oxide ore, coal as a reducing agent and heat source, and limestone as a slag melting material, and the moisture was adjusted to about 20% and molded into briquettes. Anthracite was used as the coal, and its basic unit was 100 to 180 kg / ore ton. The limestone was in the form of uncalcined calcium carbonate, and was 10 to 100 kg / ore ton.

[0040] These briquettes were fed into the furnace from the rear at a feed rate of 20 ore tons / hr and heated by the burner. At the same time, air was introduced into the furnace from the front by an exhaust fan installed in the exhaust gas system, and the maximum temperature was controlled to about 1400°C, and about 1300°C at the discharge position. The operation was carried out continuously for one month to clarify the results.

[0041] The nickel oxide ore mentioned above is often changed in type during the operation period, and the range of the chemical composition that changes as a result is SiO 2 : 36-52%, Al 2 O 3 :0.2 ~3%, Fe:6~20%, MgO:17~30%, Ni:1.5~3%, Co:0.5% or less, Cr 2 O 3 Anthracite was also often changed during the operation period, and the fluctuation range was Fixed-C: 70-80%, SiO 2 , Al 2 O 3 The CaO ash content was 10-15%, S: 0.3-1.0%, and Ig-loss: 10-15%. The results are shown in Table 1. The measurement and evaluation methods for each item were as follows.

[0042] 1) Chemical composition 1 kg of ferronickel alloy was melted in a high-frequency induction furnace while flowing nitrogen gas, and then poured into a φ35 mm mold. The resulting steel ingot was cut at a position 15 mm from the bottom to obtain a sample for measuring the average composition. The cut surface of the steel ingot was polished with a belt grinder and measured by fluorescent X-ray analysis. C and S were analyzed by the combustion method using cuttings made from the steel ingot with a drill.

[0043] 2) Particle size The ferronickel alloy was sieved and measured.

[0044] 3) Chemical composition of the Fe-Ni and Fe-Ni-S phases of ferronickel alloys Approximately 1000 ferro-nickel alloy particles were embedded in resin and polished, after which each phase was analyzed while observing the constituent phases by SEM-EDS. Note that more than 100 particles were measured, and the average composition of each phase is shown in Table 1.

[0045] 4) Distribution of Fe-Ni-S phase During the SEM observation, the morphology of the Fe-Ni-S phase relative to the Fe-Ni phase was determined, and the type of morphology was recorded as A, B, C, or D shown in Figures 1 to 4.

[0046] 5) Issues when used in downstream stainless steel melting processes This shows the situation when the ferro-nickel alloy particles of the present application were mixed in an electric furnace when actually smelting stainless steel. In other words, this was left as a record when there were issues with using the ferro-nickel alloy of the present application in addition to raw materials such as stainless steel scrap, ferrochrome, and iron scrap when forming the SUS304 composition. In addition, refining was performed after that by AOD, decarburization, Cr reduction, and desulfurization were performed.

[0047] 6) Overall rating The evaluation was as follows: ◎: Chemical composition and grain size of ferronickel alloy, chemical composition of Fe-Ni phase and Fe-Ni-S phase, Figure 1 Grain structure of or Figure 2 When the particle structure of ○: Chemical composition and grain size of ferronickel alloy, chemical composition of Fe-Ni phase and Fe-Ni-S phase, Figure 2 When the particle structure of △: Chemical composition and particle size of ferronickel alloy, Figure 3 When the particle structure of ×: Problems occur when used in the downstream process of stainless steel melting

[0048] 7) Notes The remarks indicate the reasons why the comparative examples deviated from the present invention examples.

[0049] [Table 1]

[0050] Each example of the invention will be explained below. Note that values ​​in parentheses are outside the scope of claim 1. Nos. 1 to 6 were rated as ⊚ because they satisfied all the ranges. Nos. 7 to 9 were rated as ◯ because some of the chemical components of the Fe-Ni-S phase in the ferro-nickel alloy were off, and were selected as reference examples. Nos. 10 and 11 were rated as △ because some of the chemical components of the Fe-Ni-S phase in the ferro-nickel alloy were off, and at the same time, the distribution form of the Fe-Ni-S phase was off, and were selected as reference examples.

[0051] A comparative example will be described. In No. 12, the coal consumption rate was 200 kg / ton of ore, which resulted in high C, S, and P concentrations exceeding the upper limit range, and many particles of 50 mm or larger were generated, resulting in poor Ni yield. As a result, decarburization and desulfurization were required during the production of SUS304, which hindered productivity.

[0052] At No. 13, the coal consumption rate was 80 kg / ton, which resulted in the S concentration falling below the lower limit, and the grain size of 0.05 mm or less, which had a negative effect on the growth of the ferro-nickel alloy. In addition, the Ni concentration exceeded the upper limit, which forced the use of scrap iron when manufacturing SUS304.

[0053] At No.14, the Ni content of the ore was low, and the operation was carried out with a coal consumption rate of 210 kg / ton of ore, which resulted in a low Ni concentration, high C concentration, low S concentration, high P concentration, and high Cr concentration. The grain size of the ferronickel alloy also became fine, with some grains being 0.05 mm or less. When manufacturing SUS304, the Ni concentration was low and the P content was high, so it was necessary to use it in small amounts. In addition, decarburization strengthening was also carried out, which hindered productivity.

[0054] No.15 was operated with a coal consumption rate of 50kg / ore ton, so the Ni concentration exceeded the upper limit range and the S concentration was low and outside the range. As a result, the Fe-Ni-S phase was not formed in the ferronickel alloy, and the grain size of the ferronickel alloy was significantly higher than 0.05mm, making it unusable for SUS304 production. The Ni concentration also exceeded the upper limit range.

[0055] No.16 was operated with a coal consumption rate of 190 kg / ton of ore, so both the C and P concentrations exceeded the upper limit range. As a result, when manufacturing SUS304, decarburization was strengthened, but the P concentration became high, so it could only be used in small amounts, which hindered productivity.

[0056] No.17 was a ferro-nickel alloy with a low Ni concentration because the Ni content of the ore was extremely low. Therefore, when manufacturing SUS304, other Ni sources were added to deal with the problem, which significantly increased the manufacturing cost.

[0057] No.18 was operated with a coal consumption rate of 190kg / ton of ore, which resulted in high S concentration and grain sizes exceeding 50mm, which led to poor Ni yield. When producing SUS304, enhanced desulfurization was required, which hindered productivity. [Industrial Applicability]

[0058] According to the present invention, a ferronickel alloy of excellent purity can be provided at low cost, and stainless steel can be produced at low cost.

Claims

1. A ferro-nickel alloy comprising, in mass %, Ni: 10-40%, C: 1% or less, S: 0.1-2%, P: 0.04% or less, Co: 2% or less, Cr: 0.15-2%, the balance being Fe and unavoidable impurities, the particle size being 0.05 mm to 50 mm, the particles being composed of an Fe-Ni phase and an Fe-Ni-S phase, the Fe-Ni phase being Ni: 10-50%, the Fe-Ni-S phase being Fe: 10-80%, Ni: 5-50%, and S: 10-40%, and in the particles, the Fe-Ni-S phase being distributed between the Fe-Ni phases, or the Fe-Ni phase being dispersed in the Fe-Ni-S phase.

2. A method for producing the ferro-nickel alloy according to claim 1, comprising the steps of: The following is in mass%: SiO ２ :36-52%, Al ２ O ３ :0.2 to 3%, Fe: 6 to 20%, MgO: 17 to 30%, Ni: 1.5 to 3%, Co: 0.5% or less, Cr ２ O ３ Nickel oxide ore containing unavoidable impurities, Fixed-C: 70-80%, SiO ２ , Al ２ O ３ 100 to 180 kg / ore ton of carbonaceous material having an ash content of 10 to 15% CaO, 0.3 to 1.0% S, and 10 to 15% Ig-loss is crushed and mixed with 10 to 100 kg / ore ton of slag melting agent, and the moisture content is adjusted to 8 to 30%, and the mixture is made into briquettes. The briquettes are charged into a rotary kiln, Air is introduced into the furnace to heat the clinker discharge side, The briquettes are semi-melted and reduced while rolling to form clinker. The temperature inside the furnace is controlled to 1200-1300°C at the discharge position. The method for producing a ferro-nickel alloy is characterized by cooling, crushing and dressing the discharged clinker.

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