JPS6012408B2 - Method for dephosphorizing metals or alloys - Google Patents

Description

Detailed Description of the Invention The present invention provides Fe, Cr, Mn, Si, Mo, Zr, V, T
The present invention relates to a method for removing impurities such as S, 0, Sb, etc. from a metal or alloy made of one or more of a, Nb, W, and Ni, and at the same time, removing P to a trace amount.

In recent years, due to the depletion of high-grade resources, the use of low-grade resources that contain high amounts of harmful impurities such as P and S is being avoided.
The content of P and S in metals or alloys manufactured by using such low-grade resources inevitably tends to increase. On the other hand, as the negative effects of impurity elements such as P, S, and Sb on various properties of steel materials have been revealed, there is a strong demand for reducing the content of impurities, especially in alloy steels such as stainless steel, superalloy steel, and heat-resistant steel. It has become so. Therefore, in order to obtain a metal or alloy with a low content of these impurities, it is necessary to remove the impurities during the process of manufacturing the raw material alloy or the process of manufacturing the final product. In order to remove P from metals or alloys, oxidative refining is usually carried out using slag high in Fe○. On the other hand, since the removal of S is usually accomplished by reduction refining, it is currently necessary to go through at least two or more refining steps in order to obtain a low phosphorus and low sulfur metal or alloy. Furthermore, in alloys containing easily oxidized alloy elements such as Cr, Si, Mn, etc., it is difficult to remove P without reducing the yield of Cr, Si, Mn, etc. The present inventors have previously invented a method for simultaneously removing impurities such as P, S, and Sb to minute amounts from metals or alloys in a single refining process without reducing the rate of oxidizable elements (particularly Sardine Sho 50-2943 Hakama Shou Sho 50-99143).

This method involves contacting a molten metal or alloy whose carbon content is less than the saturated carbon dissolved concentration with a slag consisting of calcium carbide and alkali metal fluorides in a non-oxidizing atmosphere to convert CaC2→Ca+2 [ C] Metallic calcium is produced in the slag phase by the reaction, and P and S in the molten metal phase are removed by the produced metallic calcium.

However, with this method, it is not possible to dephosphorize the molten metal, which has a saturated dissolved carbon concentration, and ■ the carbon concentration of the molten metal increases due to the decomposition of CaC2. It is necessary to increase the CaC2 concentration in the slag phase, which increases the carbon concentration in the molten metal.■The dephosphorization reaction progresses after the decomposition reaction of CaC2, so the dephosphorization reaction is somewhat slow. There is a problem. In order to solve these problems, the present inventors
As a result of further studies and research, we succeeded in developing an effective method for removing impurities from steel, alloys, and raw material alloys. That is, the present invention is carried out in a non-oxidizing atmosphere and (
An atmosphere in which the sum of the volume percentages of one or more oxidizing gases such as oxygen gas and water vapor is less than 8%, non-nitriding atmosphere (an atmosphere in which the volume percentage of nitrogen gas in the atmosphere is less than 20%) In an atmosphere of This is a method for simultaneous dephosphorization and desulfurization of metals or alloys, which is characterized by bringing the metal or alloy into contact with a slag prepared by adding one or more types of metal calcium alloys.

The details of the configuration of the present invention will be explained below.

The basis of the technical idea of the present invention is the relationship between CaC2 and Ca in the molten slag and [C] in the molten metal phase.Slag phase Slag phase Metal phase CaC2 Ca+[C]...
The point is that Ca is present in the slag according to the formula {1}, and impurities such as P and S in the molten metal phase are simultaneously removed to a certain extent. In a molten metal with a saturated carbon concentration, no matter how much CaC2 is added, the m-type reaction will not proceed to the right, and since Ca is not present in the molten slag, dephosphorization and desulfurization of the molten metal will not occur.

However, by adding metallic calcium or a calcium alloy to the slag, calcium is absorbed into the slag phase, and other metal components are dissolved into the molten metal phase. This Ca can remove P and S in the molten metal phase. In order to achieve effective dephosphorization and desulfurization, 3% or more of Ca is required based on the amount of slag. In removing P and S, the higher the concentration of Ca present in the slag phase, the more advantageous it is, but if it is too high, evaporation of Ca will be rapid and Ca cannot be used effectively. Furthermore, it reacts with C in the molten metal phase to produce CaC2, and does not participate in dephosphorization and desulfurization. Therefore, in order to effectively utilize Ca and perform effective dephosphorization and desulfurization, the upper limit of the Ca concentration added to the slag is 50% (weight percentage). On the other hand, even if metallic calcium or calcium alloy is simply added, CaC2
Without this, the reaction in equation [1] proceeds to the left, Ca reacts with C in the molten metal phase to form CaC2, and Ca decreases.
Effective use of Ca cannot be achieved, and dephosphorization and desulfurization cannot be performed.
Therefore, in order to effectively utilize Ca, it is necessary to
It is necessary to contain C2 in the slag in advance, and the content must be at least 30%. On the other hand, in order to strongly dephosphorize molten metal whose concentration is less than the saturated carbon concentration, it is necessary to increase the concentration of CaC2 in the slag in order to increase the concentration of Ca in the slag.
The reaction in the equation proceeds to the right and the [C]% of the molten metal increases. In order to suppress the increase in [C]% in this molten metal phase to a certain limit, or to suppress the increase in [C]% at all and perform strong dephosphorization, it is necessary to increase the slag concentration without changing the CaC2 concentration. This objective can be achieved by increasing only the concentration of Ca as required. For this purpose, metallic calcium or a calcium-containing alloy may be added to the slag. Even in this case, in order to carry out effective dephosphorization and desulfurization and to prevent the [C]% of the molten metal from increasing, the slag must contain Ca in an amount of 3% or more.

If CaC2 is not present in the slag, the reaction of equation 1 will proceed to the left and the added Ca will not be used effectively, so the C
It is necessary to include aC2 in the slag in an amount of 3% or more. Ca
The slag base used as necessary with C2, metallic calcium, and calcium-containing alloys is chemically stable at the temperature at which it comes into contact with the molten metal phase, and coexists with Ca and CaC2, stably adding Ca to the slag phase. It needs to be something to keep.

Furthermore, the reaction product between Ca and P and S in the molten metal phase must be stably transferred to the slag phase. After examining various slag base materials that meet these requirements, it was found that alkali metal halides are most suitable. Among them, from the viewpoint of chemical stability at high temperatures, price, etc.
CaF2 is the best. This slag base must be contained in an amount of 10% or more for the above reasons. On the other hand, it is preferable that the amount of oxidizing oxides such as silicon oxide, aluminum oxide, iron oxide, and manganese oxide be as small as possible. It should be kept to 20% or less, including the portion unavoidably mixed in from the slag raw material. When these oxidizing oxides are present in large amounts in the slag, CaC2 and Ca in the slag react with these oxides and are lost, causing the slag to lose its dephosphorizing ability. However, although calcium oxide may be added as necessary to adjust the melting point and fluidity of the slag, the amount added should be limited to 50% so as not to inhibit the dephosphorizing ability of the slag. When dephosphorizing an alloy or an alloy using the slag of the present invention, the influence of the atmosphere during the treatment is significant.

In an atmosphere of an oxidizing gas such as oxygen gas or water vapor, or nitrogen gas, the added CaC2 and Ca* are oxidized and lost, or nitrided and lost, and are not effectively utilized for dephosphorizing the above-mentioned metals. Therefore, the atmosphere during refining must be controlled to contain 8% or less oxidizing gas and 20% or less nitrogen gas. When dephosphorizing metals or alloys using the slag of the present invention, the already known Hazusa method may be used in order to increase the reaction rate and reaction efficiency.

For example, mechanical slag and rope injection that inject all of the slag or one or more of the constituent components of slag are effective. Example 1 The slag 5k9 of the present invention was added to a molten alloy having the following components and having a carbon saturation dissolved concentration of about 100k9, which was melted in a refining vessel of an induction melting furnace.
The results shown in Table 1 were obtained by refining in an argon atmosphere.

Table 1: Units are weight unit) ○a as Si: OA in the blended slag when calcium silicon alloy is blended The raw material of the phosphorus slag is granular C
aC2 (purity 85%, the rest is mostly Ca○),
They are powdered CaF2 (purity %), granular metallic calcium (purity 99.9%), granular Ca○ (purity %), and granular calcium silicon (40%Ca-55%Sj).

Example 2 5 kg of the slag of the present invention was added to a molten alloy of the following components having a carbon saturation dissolved concentration of less than about 100k9, which was melted in a refining container of an induction melting furnace, and was refined in an argon atmosphere.
The results shown in the table were obtained.

In experiment a, de-IJ and desulfurization can be carried out, but the carbon concentration in the molten alloy increases, but in experiments b and c using the slag of the present invention, the carbon concentration in the molten alloy does not increase. , dephosphorization and desulfurization can be performed.

The raw materials for slag are granular CaC2 (purity 85%, the remainder is mostly Ca○), powdered CaF2 (purity 98%), granular metallic calcium (99.9% purity), granular calcium silicon (40% Ca-55). %Si). 2nd
Table unit is weight (grandchild)

Claims (1)

[Claims] 1 In a non-oxidizing, non-nitriding atmosphere, the metal or alloy to be dephosphorized is mainly composed of calcium carbide and alkaline earth metal halides, and calcium-containing metals such as metallic calcium, calcium silicon, calcium silicon manganese, etc. When dephosphorizing the slag by contacting it with the slag to which one or more of the following are added, it is recommended to use a slag to which the calcium concentration of the calcium-containing metal added is 3 to 50% of the slag. Characteristic method for dephosphorizing metals or alloys.