JPH0435541B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is applicable to Fe-based and Co-based materials with extremely low sulfur content.
The present invention relates to a method for producing Ni-based alloys. [Prior Art] Many Fe-based, Co-based, and Ni-based alloys have excellent properties such as mechanical properties, heat resistance, and corrosion resistance. However, if the residual oxygen and sulfur are large, the processability will deteriorate, so it is necessary to sufficiently reduce the residual oxygen and sulfur. Regarding deoxidation and desulfurization during refining under vacuum or argon gas atmosphere, Special Publication No. 54-849, Special Publication No.
54-24688 and JP-A No. 52-58010, respectively.
It is characterized by adding aluminum (Al) or its alloy to the molten metal in a vacuum or argon gas atmosphere using a melting furnace or ladle backed by a basic refractory with a high CaO (calcium oxide) content. Deoxidation and desulfurization methods have been proposed. This principle reduces CaO in the refractory by adding Al,
Sulfur (S) and oxygen (O) in the molten metal are removed using calcium (Ca), which is a reduction product. Furthermore, JP-A No. 57-200513 describes that when the furnace wall is used repeatedly, the surface of the furnace wall gradually accumulates and becomes contaminated with oxysulfides, so a solvent is added in combination to prevent the furnace wall from contaminating. [Problems to be Solved by the Invention] The conventional methods described above are capable of deoxidizing and desulfurizing to a certain degree, but in the field of alloy refining, higher deoxidizing and desulfurizing abilities are required. It is hoped that new refining technology will emerge. [Means for Solving the Problems] The present invention has been made to obtain much superior desulfurization and deoxidizing effects, especially desulfurization effects, as compared to the above-mentioned conventional methods. Fe-based, Co _- based or Ni-based alloys in a melting furnace or vessel supported by a magnesia refractory containing 15% by weight or more of CaO and 1% by weight or less of SiO 2 By making Al exist in the molten metal in vacuum or in a non-oxidizing atmosphere, Mg can be added to 0.03 to 0.0001% by weight.
Ca 0.02 to 0.0001% by weight, sulfur 0.0015% or less, oxygen 0.002% or less, nitrogen 0.003% by weight
The gist of the present invention is a method for producing a high-purity ultra-low sulfur alloy, characterized by obtaining an alloy containing the following: In addition, % weight % is expressed below. The configuration of the present invention will be explained in detail below. In the method of the present invention, MgO is contained in an amount of 15 to 55%, CaO is contained in an amount of 15% or more, and the _SiO2 content is 1%.
Al is made to exist in a molten Fe-based, Co-based, or Ni-based alloy in a vacuum or non-oxidizing atmosphere in a container such as a melting furnace or ladle backed with the following magnesia refractory: A part of Al in the molten metal directly combines with oxygen in the molten metal to perform deoxidation, but the other part of Al reacts with MgO and CaO on the surface of the refractory to form 2Al + 3MgO → Al ₂ O ₃ + 3Mg. 2Al + 3CaO → Al ₂ O ₃ + 3Ca, producing Mg, Ca and Al ₂ O ₃ . This Mg,
Ca undergoes deoxidation and desulfurization reactions, resulting in MgO, CaO, MgS,
Becomes CaS. On the other hand, Al ₂ O ₃ forms calcium aluminate mainly composed of 3CaO・Al ₂ O ₃ (hereinafter sometimes referred to as C ₃ A) through the reaction Al ₂ O ₃ + 3CaO → 3CaO・Al ₂ O ₃ . . This C ₃ A has a high ability to desulfurize molten metal,
Desulfurization also proceeds with C ₃ A. In this way, deoxidation is performed by Al, and deoxidation and desulfurization are performed by active Mg, Ca, and C ₃ A generated by the reducing action of Al. This reaction proceeds very rapidly, e.g. Al
After being present in the molten metal, desulfurization and deoxidation are almost completed in about a few minutes. Further, as time passes, the amount of N in the molten metal gradually decreases. This is because N also leaves the molten metal as Ca and the like evaporate (boil). This denitrification rate improves significantly under an argon or vacuum atmosphere as deoxidation and desulfurization progress. In the present invention, the backing material of the melting furnace or container is
The reason why it is made of a refractory having a composition containing 15 to 75% MgO and 15% or more CaO will be explained. It is generally known that CaO refractories are stable even at high temperatures and are used for melting various highly reactive molten alloys. It is also known that when Al and/or Al alloy is added to the molten metal in a container lined with this CaO-based refractory, CaO is reduced by Al and Ca is generated, and deoxidation and desulfurization reactions proceed. be. However, the inventors conducted further studies and found that, as shown in the reaction equation above, in the furnace wall where MgO and CaO coexist, when Al and/or Al alloy is added, Mg is also produced in addition to Ca. It was found that even stronger deoxidation and desulfurization can be performed. The reason for adding 5% or less of a solvent such as an alkali metal or alkaline earth metal oxide, carbonate, halide, carbide, or alumina as necessary is exactly the same as in JP-A-57-200513. This is to prevent accumulated contamination by using a solvent, since oxysulfides adhere to the surface of the furnace wall and cause accumulated contamination when used repeatedly. Note that Figures 1 and 2 show the measurement results of desulfurization characteristics when the MgO content in the CaO-MgO-based backing refractory material was changed (Al content in the molten metal was 0.5%). It is clearly seen that when MgO is contained in an amount of 15 to 55%, especially 20 to 50%, an extremely strong desulfurization reaction takes place. Furthermore, Figure 2 also shows the analytical values for residual Al, and it was observed that the amount of Al decreased with the passage of reaction time.
Progress of the aforementioned reaction between MgO and Al is confirmed. The remainder other than MgO must be CaO. CaO is itself reduced by Al,
It generates Ca and promotes the reduction reaction of MgO by coexisting with MgO. The CaO content is preferably 15% or more of the entire furnace material, particularly preferably 40 or more. When the CaO content is less than 15%, particularly less than 40%, CaO in the refractory is strongly bonded to other oxides, so the activity of CaO is low and it is difficult to be reduced by aluminum. On the other hand, CaO in refractories containing 15% or more, especially 40% or more of CaO has high activity and can be reduced well by aluminum. In addition, refractories containing 15% or more CaO, especially 40% or more, easily react with oxides such as Al ₂ O ₃ and SiO ₂ .
Therefore, it absorbs oxides in the molten metal and significantly reduces the amount of oxides present. Furthermore, refractories containing CaO of 15% or more, especially 40% or more, have high stability against C, Ti, Zr, etc., and therefore can be melted at high temperatures. Note that this refractory preferably has a SiO ₂ content of 1% or less, especially less than 0.5%. in refractories
If SiO ₂ is excessively large, the added Al reacts with SiO ₂ in the refractory and is wasted, and the molten metal becomes an oxidizing atmosphere, making it difficult for the desulfurization reaction to proceed. Such refractory materials include, for example, CaO or
Dolomite refractory material enriched with MgO is preferably used. In the present invention, in addition to Al, at least one selected from the group consisting of B and alkali metals, or in addition to these, Ca may be allowed to coexist in the molten metal. Alkali metals include Na, K, and Li.
can be mentioned. Ca, B, Na, K, and Li present in the molten metal are
CaO, B ₂ O ₃ , Na ₂ O, K ₂ O, Li ₂ O, and Al ₂ O ₃ −CaO−B ₂ O ₃ Al ₂ O ₃ −CaO−B ₂ O ₃ −Na ₂ O in the refractory wall. It forms a low melting point composition such as Al ₂ O ₃ -CaO-B ₂ O ₃ -K ₂ O and increases the rate of deoxidation and desulfurization. That is, oxides such as Ca, B, Na, K, and Li lower the melting point of calcium aluminate compositions such as C ₃ A formed on the surface of the furnace wall, and lower the melting point of calcium aluminate compositions such as C 3 A formed on the surface of the furnace wall. ^2-, etc.) and accelerates deoxidation and desulfurization reactions. CaO, B ₂ O ₃ and alkali metal oxides, especially B ₂ O ₃ and alkali metal oxides, when incorporated into the slag, also lower the melting point of the slag and lower its viscosity. This increases the diffusion coefficient of ions such as S ^2- and other atoms and compounds into the slag, and greatly improves the desulfurization rate and desulfurization ability. Al, B and alkali metals are Fe,
The residual amount in Co and Ni-based alloys is: Al: 0.01 to 20% B, alkali metals and alkaline earth metals other than Mg and Ca: 0.001 in total
It is preferable that it be present in the molten metal in an amount of ~10%. In the present invention, the amount of Al remaining in the alloy is 0.01 to 20
The reason why it is preferable to use a range of
This is because desulfurization and deoxidation by Ca are hardly performed, and the amount of residual calcium in the finished alloy, which is a condition for sufficient desulfurization and deoxidation by Ca, does not exceed 0.0001%. On the other hand, the upper limit is 20% for aluminum.
This is because alloys exceeding the above range are of poor practical use. If the amount of B remaining is less than 0.001%, the amount is too small and the effect of the presence of B is small, and if it is more than 10.0%, the alloy becomes brittle. A particularly preferable residual amount of B is 0.005 to 3%. When adding Al, B, alkali metals, and alkaline earth metals other than Mg and Ca to the molten metal, they may be added in the form of an alloy or separately. There are no restrictions. Al,B
Although it is possible to add these separately, alkali metals and alkaline earth metals are highly reactive and have problems in handling.
Preferably, it is added in the form of an alloy. Whether alone or in an alloy, it can be added in various forms such as a linear body, a rod-shaped body, a block, or a powder. Mg and Ca of the alloy obtained by the method of the present invention
The residual amount of Mg is 300 to 1 ppm, preferably 30 to 5 ppm, and the residual amount of Ca is 200 to 1 ppm, preferably 100 to 5 ppm. If the residual amount of Mg or Ca is too small, deoxidation, desulfurization, and denitrification effects will be low, and if it is too large, the alloy will become brittle. In the present invention, a rare earth element may be further added to the molten metal so that the rare earth element remains in the resulting alloy in a range of 200 ppm or less. The alloy obtained by such a method of the present invention contains 15 ppm or less of sulfur, especially 10 ppm or less, 20 ppm or less of oxygen, especially 15 ppm or less, and 30 ppm or less of nitrogen, especially
It is an extremely clean alloy with less than 20ppm. The alloys targeted by the method of the present invention are Fe-based, Co-based, or Ni-based alloys. Fe-based alloys include common elements C, Si, Mn,
Carbon steel containing P, S and 2% or less of C, and in addition to the above ordinary elements to give special properties.
In addition to special elements such as Ni, Cr, Co, W, Mo, Al, etc., even those belonging to ordinary elements are added to them for the purpose of adding special properties beyond the content range of ordinary elements. It is. Among alloy steels, low-alloy steels include high-strength low-alloy steel, high-temperature, high-pressure low-alloy steel, and low-alloy steel for the petroleum industry; medium-alloy steels include chrome steel and nickel steel; There are high chromium stainless steel, high chromium-nickel stainless steel, etc. Examples of nickel-based alloys include heat-resistant and corrosion-resistant alloys and magnetic alloys that contain nickel as a main component, and alloys that belong to these include Ni-Cu alloy (monel metal), Ni-Cr-
Fe alloy (Inconel), Ni-Mo alloy (Hastelloy A, B), Ni-Mo-Cr-W alloy (Hastelloy C), Ni-Si alloy (Hastelloy D), Ni
-There are Ta-based alloys, etc. Co-based alloys include heat-resistant alloys, corrosion-resistant alloys, ultra-high alloys, and
Magnetic alloys, etc. Alloys belonging to this include Co
-Cr-W-C alloy (stellite), Co-Fe alloy (ductile cobalt), Co-Cr-Ni-Mo
(Eligiloy alloy), Co-Cr-Ni-W (Hayness),
Examples include Co alloys for magnetic materials such as Vicalloy, Renendur, and Permendur, and Co-based superalloys that utilize Ni ₃ Ti precipitation. In addition, in the manufacturing method of the present invention, being in a non-oxidizing atmosphere means that the molten metal is treated by blowing a non-oxidizing gas such as argon gas, nitrogen gas, or He gas into the molten metal in an open furnace or a closed furnace. , refers to the atmosphere when the molten metal is processed by forming such a gas atmosphere on the surface of the molten metal in a closed furnace. [Function] In the present invention, the molten alloy is subjected to strong deoxidation and desulfurization in the presence of Al in a melting furnace or container supported by a MgO--CaO refractory material. In particular, since Mg is generated in the molten metal, this Mg
acts on desulfurization together with Ca, and its desulfurization ability is extremely high. [Example] Examples and comparative examples will be described below. Comparative Example 1 In a CaO crucible with the composition shown in Table 1, 500 g of electrolytic iron with the composition shown in Table 2 and FeS added in advance to a sulfur content of about 0.03% was melted in a 50 KHz high-frequency melting furnace. , 0.4% Al alloy was added under an argon atmosphere. Oxygen content, sulfur content of the molten alloy in the crucible,
Changes in nitrogen content over time were measured. The results are shown in FIG. The CaO crucible used was a first-class reagent.
CaO was used as a raw material, which was crushed into 20 meshes, put into a crucible mold, and compacted well, and the solidified crucible was calcined in an electric resistance furnace at approximately 900°C for 24 hours.

【table】

[Table] Example 1 An MgO-CaO crucible with the composition shown in Table 3 was prepared using first-class reagents MgO and CaO as raw materials, and the experiment was conducted in the same manner as in Comparative Example 1, except that the crucible was used. I did this. The results are shown in FIG.

[Table] From FIG. 3, it is recognized that according to the method of the present invention, a molten metal with low contents of oxygen, sulfur, and nitrogen can be quickly obtained, and the desulfurization effect is particularly large. Example 2 and Comparative Example 2 Example 1 and Comparative Example 1 except that the amount of Al added was 0.5% and the MgO:CaO ratio of the furnace material was variously changed.
Refining was carried out in the same manner. The measurement results of the desulfurization properties and the residual amount of Al are shown in Figures 1 and 2. From these figures 1 and 2, as mentioned above,
It is recognized that a remarkable desulfurization effect can be obtained in the range of 15 to 55% MgO. [Effects] As described above, according to the present invention, extremely strong deoxidation, desulfurization, and denitrification of Fe-based, Co-based, or Ni-based superalloys can be performed, and the content of O, N, and S is extremely low. It is possible to produce alloys with outstanding properties such as creep strength, heat resistance, toughness, weldability, and forgeability. Also, there are almost no intervening oxides.

[Brief explanation of drawings]

Figures 1 and 2 are graphs showing the relationship between MgO content and desulfurization ability, and Figure 3 is the change over time in the oxygen, sulfur, and nitrogen contents in the molten metal obtained in Example 1 and Comparative Example 1. This is a graph showing.

Claims (1)

[Claims] 1. A melting furnace supported by a magnesia refractory containing 15 to 55% by weight of MgO, 15% by weight or more of CaO, and 1% or less of SiO ₂ by weight. Or, by making Al exist in a Fe-based, Co-based, or Ni-based alloy molten metal in a container in a vacuum or non-oxidizing atmosphere, Mg can be added to 0.03 to 0.0001% by weight.
Ca 0.02 to 0.0001% by weight, sulfur 0.0015% or less, oxygen 0.002% or less, nitrogen 0.003% by weight
A method for producing a high-purity ultra-low sulfur alloy, characterized by obtaining an alloy containing the following: 2. The method for producing a high-purity ultra-low sulfur alloy according to claim 1, characterized in that the solvent is used in an amount of 5% by weight or less. 3 The resulting alloy contains 0.01 to 20% by weight of Al, B,
The method for producing a high-purity ultra-low sulfur alloy according to claim 1, which contains a total of 0.001 to 10% by weight of alkali metals and alkaline earth metals other than Ca and Mg.