JPH0575818B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing extremely pure ferrosilicon, and more particularly ferrosilicon with extremely low titanium content and low content of other trace elements. Ferrosilicon with a low titanium content is primarily used to produce transformer steel, ie steel as material for transformers. During the process of producing grain-oriented silicon steel sheets, ie silicon-containing grain-oriented transformer steels, their silicon content is adjusted by adding ferrosilicon.
In order to produce a grain-oriented silicon steel sheet, ie, silicon-containing grain-oriented transformer steel, which has a low power loss, it is important to keep the titanium content of the steel sheet as low as possible. The main source of titanium in transformer steels is titanium contained in ferrosilicon, which is added to the steels to adjust the silicon content. Ferrosilicon produced by carbothermal reduction in an electric melting furnace usually has a titanium content in the range 0.05-0.25% by weight. Although titanium in ferrosilicon is difficult to remove, titanium can be removed to very low concentrations by refining molten ferrosilicon. Therefore, for the production of ferrosilicon with a low titanium content, it is necessary to select raw materials with a low titanium content. By careful selection of raw materials, it is currently possible to produce ferrosilicon with titanium content down to as low as 100 ppm. Currently, the standard specifications for low titanium ferrosilicon are:
In 66% FeSi, the titanium content is 0.02% by weight, and in 75% FeSi, the titanium content is 0.03% by weight. However, the price of raw materials with low titanium content is always on the rise, and therefore the cost of producing ferrosilicon with low titanium content is expected to rise rapidly in the future. The object of the present invention is to provide a method for producing ferrosilicon with a titanium content down to 5 ppm and a low content of other trace elements. The invention therefore relates to a process for producing ferrosilicon with a low titanium content and a low content of other trace elements, in which the silicon content is higher than 50% by weight, i.e. between 50 and 50% by weight.
A melt of ferrosilicon with a silicon content of 98% by weight and a calcium content of 1 to 10% by weight is produced, after which the melt is solidified and crushed, and then the crushed ferrosilicon is silicon _FeCl3
and/or leaching in an aqueous solution of (FeCl ₃ +HCl),
thereby dissolving the CaSi ₂ phase in the ferrosilicon and liberating the titanium-containing phase contained in the CaSi ₂ phase, and then washing the liberated titanium-containing phase from the ferrosilicon. Remove by. The obtained ferrosilicon is optionally alloyed with iron to adjust the Fe content to a preset value. Silicon content higher than 50% by weight i.e. 50~
During the solidification of molten ferrosilicon with a silicon content of 98% by weight, the following phases are formed: elemental silicon, FeSi ₂ , Ti(Zr)FeSi ₂ , CaSi ₂ and Cu(Al)
Phases of CaSi ₂ are formed. Of these phases,
Elemental silicon and FeSi ₂ phases do not dissolve in aqueous solutions of FeCl ₃ or (FeCl ₃ + HCl), but
The _CaSi2 and Cu(Al) _CaSi2 phases are easily dissolved. During the solidification of the calcium-containing ferrosilicon, the CaSi _two phases precipitate on the grain boundaries of the ferrosilicon, and the FeCl ₃ aqueous solution and (FeCl ₃
+HCl) during leaching with an aqueous solution, _{the two} CaSi phases are dissolved and eluted, causing disintegration of ferrosilicon along the grain boundaries. The Ti(Zr)FeSi _two -phase described above does not dissolve in the FeCl ₃ aqueous solution or (FeCl ₃ +HCl) aqueous solution, but when ferrosilicon is alloyed with calcium,
It was unexpectedly found that the titanium-containing phase mentioned above precipitates within the CaSi ₂ phase. The above CaSi ₂ phase is
It easily dissolves in FeCl ₃ aqueous solution or (FeCl ₃ + HCl) aqueous solution and causes pulverization of ferrosilicon along the grain boundaries, so calcium-containing ferrosilicon is
During leaching with FeCl ₃ or (FeCl ₃ +HCl), the titanium-containing phase is liberated as fines. Once leaching is completed, the fine powder is removed from the leached ferrosilicon by washing with water. The fine powder contains a titanium-rich phase, which is liberated during dissolution of the CaSi ₂ phase. Silicon content higher than 50% by weight i.e. 50~
In ferrosilicon with a silicon content of 98% by weight, most of the titanium is the aforementioned Ti(Zr).
It was found that it exists in the FeSi ₂ phase. For the above reasons, the method of the present invention allows the removal of most of the titanium from ferrosilicon. As mentioned above, the FeSi _two phase itself is FeCl ₃ /HCl
Does not dissolve in solution. Therefore, only the iron present in the Ti(Zr)FeSi ₂ phase is removed from the ferrosilicon during leaching. The iron content in the ferrosilicon is therefore substantially unaffected by the method described above. According to another embodiment of the invention, the titanium content is increased in a second step in which the ferrosilicon is treated with an aqueous HF solution.
It is further reduced in the leaching process. During this second leaching step, the FeSi ₂ phase in ferrosilicon dissolves and
And another titanium-rich phase that may exist on the grain boundaries of the FeSi ₂ phase is liberated. After washing with water, a silicon metal (ie ferrosilicon) with a very low titanium content and a very low content of other trace elements is obtained. The silicon metal is then alloyed with iron having a low titanium content, such as transformer steel, in order to adjust the iron content to a predetermined level. Another embodiment of the above is because the FeSi ₂ phase is removed.
Particular preference is given when using ferrosilicon with a silicon content of 90 to 98% by weight. If ferrosilicon with an even lower silicon content is used, the process is not economically viable because large amounts of iron are removed during leaching with HF solution. However, according to a second embodiment of the invention, 75% ferrosilicon can be produced with titanium content down to 5 ppm. During HF leaching it is preferred to use an aqueous solution containing 0.5-5% HF. According to the method of the present invention, the content of a number of trace elements in ferrosilicon is substantially reduced, among which the trace elements Zr, Ni, V and Mn are present in calcium-containing ferrosilicon. is present in the titanium-containing phase and copper-containing phase. Example 1 Standard 75% with the composition shown in table
FeSi was melted in a graphite crucible placed in a 5KW induction furnace. After melting the ferrosilicon, CaO was added to the melt, and then the melt was cast into a mold made of graphite. The chemical composition of the obtained Ca-containing ferrosilicon is shown in Table 1. After that, the molded ferro silicone is
It was crushed to a particle size of 30 mm and leached in FeCl ₃ /HCl (10% aqueous solution) for 24 h at 20 °C and then dissolved in FeCl ₃ /HCl (10% aqueous solution) for 24 h.
Leaching with HCl (10% aqueous solution) at 90°C for 3 hours. The leached Ferrosilicon was washed with water. The chemical composition of the thus obtained cleaned ferrosilicon is shown in Table 1.

[Table] *Standard ferrosilicon contains copper as an impurity.
As shown in Table 1, the titanium content ranges from 0.082% by weight (820ppm) to
Reduced to 0.020% by weight (200ppm). Furthermore, the results in the table show that for ferrosilicon, Al, Cu, and Ni
This shows that a significant reduction in 300～
By using raw material ferrosilicon with an even lower titanium content of 400ppm,
It is clear that ferrosilicon can be obtained with titanium contents even lower than 100 ppm. Example 2 Ca content 92% having the chemical composition shown in the table
Ferrosilicon was dissolved in FeCl ₃ /HCl solution at 105°C for 6 hours.
Time leached. Thereby, cleaned ferrosilicon having the chemical composition shown in Table 1 was obtained. The above leached ferrosilicon has the following chemical composition (wt%): Fe96.6, Al0.0025, Ca0.0016, Ti0.0045,
It was melted together with transformer steel having Si3.18 and P0.074. The amount of iron added was adjusted to obtain ferrosilicon with an iron content of 20.4%. The chemical composition of the produced low titanium content ferrosilicon is shown in Table 1.

【table】

[Table] As shown in the table, 0.0051% by weight
Ferrosilicon with extremely low titanium content (51 ppm) was obtained. Example 3 The ferrosilicon obtained from the FeCl ₃ /HCl leaching in Example 2 was subjected to a separate leaching step in an aqueous HF solution containing 1.2% HF. Thereby, 0.1%Fe, 0.002%Ti, 0.08%Al, 0.03%Ca,
0.001% Cu, 0.002% Ni, 0.001% or less Cr, 0.006
% P and less than 0.001% Mn was obtained. The alloy that underwent the above-described separate leaching process was alloyed with a transformer steel having the same chemical composition as the transformer steel used in Example 2.
The amount of iron was finally adjusted so that ferrosilicon contained 20.9% iron. The chemical composition (wt%) of the produced low titanium content ferrosilicon was as follows. Fe20.9, Ti0.0027, Al0.03, Ca0.002,
Cu0.007, Mn0.007, Ni0.006, Cr0.014 and
P0.024. In the method of this example, ferrosilicon was thereby obtained with a titanium content of 27 ppm and a low content of other trace elements. The above examples show that the method of the invention allows the production of ferrosilicon with extremely low titanium content. By using an iron source with a lower titanium content to alloy the purified ferrosilicon, ferrosilicon with titanium content down to 5 ppm can be produced. In addition, the above examples include phosphorus, chromium, magnesium,
It shows that the content of trace elements such as nickel and copper is substantially reduced. Example 4 A 66% FeSi (ferrosilicon) melt containing 30% by weight of Fe, 3.48% by weight of Ca and 120 ppm of Ti was produced, solidified, then crushed and treated at 80% by weight in an aqueous HCl solution (10%). Leached for 17 hours at °C. After that,
The leached ferrosilicon was washed with water. The purified ferrosilicon obtained was analyzed. The chemical composition (% by weight) of the purified ferrosilicon was as follows. Fe36.8%, Ca0.090%, Ti5ppm

Claims (1)

[Claims] 1. Silicon content of 50-98% by weight and 1-10% by weight
producing a ferrosilicon melt having a calcium content of , solidifying and then crushing the melt;
Thereafter, the crushed ferrosilicon is treated with an aqueous solution of FeCl ₃ and/or (FeCl ₃ +HCl) to dissolve the CaSi ₂ phase in the ferrosilicon, thereby dissolving the CaSi 2 phase contained in the CaSi ₂ phase. A ferro having a low titanium content and a low content of other trace elements, characterized in that a titanium-containing phase is liberated and the liberated titanium-containing phase is removed by washing from the ferrosilicon. Silicon manufacturing method. 2. Silicon content of 50-98% by weight and 1-10% by weight
producing a ferrosilicon melt having a calcium content of , solidifying and then crushing the melt;
Thereafter, the crushed ferrosilicon is treated with an aqueous solution of FeCl ₃ and/or (FeCl ₃ +HCl) to dissolve the CaSi ₂ phase in the ferrosilicon, thereby dissolving the CaSi 2 phase contained in the CaSi ₂ phase. The obtained ferrosilicon is then released in order to liberate the titanium-containing phase, remove the liberated titanium-containing phase by washing it from the ferrosilicon, and then adjust the iron content to a preset level. A process for producing ferrosilicon with a low titanium content and a low content of other trace elements, characterized in that silicon is alloyed with an iron source.