JPS61243134A - Production of extra-low sulfur alloy - Google Patents

Abstract

PURPOSE:To deoxidize, desulfurize and denitrify an Al-contg. alloy by adding powder consisting essentially of MaO and CaO in a vacuum state into the molten alloy in a melting furnace lined internally with refractories contg. a specific ratio of CaO. CONSTITUTION:The powder consisting essentially of MgO and CaO is added in the vacuum or non-oxidizing atmosphere into the molten alloy contg. Al in the melting furnace or vessel lined internally with the refractories contg. >=40% CaO. The MgO-CaO powder contg. about 17-75%, more particularly about 20-60% MgO and about >=15%, more particularly about >=40% CaO is preferably and is so added that the produced alloy contains 0.03-0.0001% Mg and 0.002-0.001% Ca. The pure alloy contg. about <=15ppm S, about <=20ppm O and about <=30ppm N is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing an alloy with extremely low contents of oxygen, sulfur and nitrogen, and particularly to a method for producing an alloy with significantly reduced sulfur content.

[Conventional technology] Fe-based, Co-based, and Ni-based alloys have mechanical properties.

Many of them have excellent properties such as heat resistance and corrosion resistance, but if residual oxygen and sulfur are present in large amounts, processability will be reduced, so it is important to sufficiently reduce residual oxygen and sulfur.

Regarding deoxidation and desulfurization during refining under vacuum or argon gas atmosphere, Japanese Patent Publication No. 54-849, Japanese Patent Publication No. 54-24
68.8 and JP-A-52-58010, respectively.
It is characterized by adding aluminum (/11) 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 ab (lucium oxidizing ability) content. A deoxidizing and desulfurizing method has been proposed. This principle is based on the addition of An to reduce CaO in the refractory, and the reduction product calcium (C
Sulfur (S) and oxygen (0) in the molten metal are removed by a). .

Additionally, a method has been proposed in which a calcia composition and Al (or just the calcia composition is sufficient if the molten alloy contains AJI) are injected into the molten alloy using an inert gas such as Ar gas. There is (Sca
nd, J. Metallurgy4 (1975),
P42-48 etc.), as a method using flux injection, in addition to Ca0-An system, Cao-AJI
203, Cao-CaF2. Ca0-Al2O
2CaF2-based materials have also been proposed. Others, CaO
A method of simultaneously adding metal Mg and Mg is also known as the Lime-Mg method (published by P, J. Koros) [Problems to be solved by the invention] Showa 52
According to the method described in Publication No. 58010, it is possible to perform deoxidation and desulfurization to a certain extent, but the method using a melting furnace or ladle backed with a basic refractory requires advanced technology for the refractory backing. In addition, since the calcia composition on the inner wall surface of the melting furnace or ladle is utilized for desulfurization and deoxidation reactions, when the amount of molten metal becomes large, the interfacial area where the molten metal contacts the inner wall surface becomes relative to the amount of molten metal. There are problems in that the reaction rate decreases, a lot of time is required for cleaning the molten metal, and the reaction efficiency decreases as the number of times it is used increases.

However, when the reaction efficiency decreases as the number of times of use increases, various activation treatments such as adding flux and activating it by its desulfurization effect are required (Japanese Patent Laid-Open No. 57-200513 ), which was disadvantageous as it increased the number of processing steps.

On the other hand, the method of flux injection of a calcia composition and the Lime-Mg method have a problem in that the level of 0 and S (final equilibrium value) that can be reached by deoxidation and desulfurization is not so low.

[Means for Solving the Problems] The present invention provides powders containing MgO and CaO as main components, in order to obtain much superior desulfurization and deoxidizing effects, especially desulfurization effects, as compared to the above-mentioned conventional methods. By further adding An to the molten alloy, the reaction rate is increased, and
The final equilibrium value is reduced, and the main components are MgO and CaO in a molten alloy containing A-type in a melting furnace or container supported by a refractory with Ca040% or more in a vacuum or non-oxidizing atmosphere. A method for producing an ultra-low sulfur alloy, characterized by adding powder.

and Mg in a vacuum or non-oxidizing atmosphere in a molten alloy in a melting furnace or container backed by a refractory with Ca040% or more.
The gist of the present invention is a method for producing an ultra-low sulfur alloy characterized by adding powder containing O and CaO as main components and Al.

In this specification, % represents weight %.

The configuration of the present invention will be explained in detail below.

In the method of the present invention, powder containing MgO and CaO as main components (
(hereinafter referred to as MgO-CaO powder), or Ai is further added to this as necessary.

That is, A9. °
If the content is within the range of the preferred residual amount of Ai described later, it is sufficient to add only MgO-CaO powder, and if the combined amount of Al is less than the range of the preferred residual amount of Ai. , or in the case of alloys containing no Al, M
In addition to gO-CaO powder, AIL is further added.

The M g Q -C&O powder used in the present invention is M
It is a powder whose main component is CaO, such as gO-CaO-based flux, and in addition to MgO-CaO powder, MgO-
Ca O-Ca F2 powder, pd g Q-Ca
O-S i O2 powder, MgO-Ca0-AJ120a
-CaF2 powder etc. can also be suitably employed. These CaO-MgO powders have a large contact area with the molten alloy, and the following reactions are carried out extremely efficiently.
The composition of gO-CaO powder is Mg015-75%,
In particular, those containing 20 to 60% CaO, 15% or more, especially 40% or more are preferable.

In the present invention, by adding MgO-CaO powder and AM as necessary, a part of the An originally present in the molten metal or newly added is directly converted to oxygen in the molten metal. The other part of Ai reacts with MgO-CaO powder to form 2 A fL+ 3 M g O → AJL203 +3
Mg2 A l + 3 Ca O” A l 203
+3Ca, and Mg, Ca and Al203 are generated. These Mg and Ca undergo deoxidation and desulfurization reactions, and MgO and Ca
O1Mg5. It becomes CaS.

On the other hand, Al203 is Al203+ 3 Ca O+ 3 CIL Oa
3CaO*AJL2 by the reaction A jL 203
Forms calcium aluminate mainly composed of o3 (hereinafter sometimes referred to as C3A). This C3A has a high ability to desulfurize the molten metal, and desulfurization also progresses with this C3A.

In this way, deoxidation is performed by AIL, and deoxidation and desulfurization are performed by active Mg, Ca, and C3A generated by the reducing action of An.

This reaction progresses extremely rapidly, and desulfurization and deoxidation are almost completed within a few minutes after Al, for example, is present in the molten metal.

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 markedly in an argon or vacuum atmosphere as deoxidation and desulfurization progress.In the present invention, MgO to C
In addition to the aO powder and Ai, B and/or B 203 or metals such as Na, K and Li, and alkaline earth metals such as Ca may be added.

Ca, B, Na, and Li present in the molten metal are Cao
, B203, N&20, K20.

L i 20, and in the molten metal, A l 20 z -Ca O-B 203A i20
3 C&O-B 203- Na20A! L20
3-Cao B20a - is formed with a low melting point composition such as 20 to increase the deoxidation and desulfurization rate.

That is, oxides such as Ca, B, Na, Li, etc. lower the melting point of calcium aluminate compositions such as C3A formed in the molten metal, and lower the melting point of calcium aluminate compositions such as C3A formed in the molten metal. ) and accelerates deoxidation and desulfurization reactions.

C ao, B203, alkali metal oxides, especially B2O3, alkali metal oxides also lower the melting point of the slag and reduce its viscosity when incorporated into the slag. As a result, the diffusion coefficient of ions such as 82- and other atoms and compounds into the slag becomes large, and the desulfurization rate and desulfurization ability are greatly improved.

Furthermore, B2O3 can also exhibit deoxidizing and desulfurizing effects by absorbing inclusions such as A or 203.3io2.

In the present invention, the addition of MgO-CaO powder, Ca, B and/or B2O3, AJl, and alkali metals is determined by the residual amount in the manufactured alloy (MgO is the Mg equivalent value, CaO is the Ca equivalent value, and B2O3 is the B conversion value) are respectively Mg: 1 to 300 ppm, especially 5 to 30 PPmCa: 1 to
20ppm especially 5-20ppmB and alkali metal = 0
．． 001-10% Al: It is preferable to add it to the molten metal in an amount of 0.01 to 20%.

In the method of the present invention, the residual amount of Mg in one alloy is 1 to 30
The reason why it is preferable to keep it within the range of 0 ppm is as follows.
When the Mg content is less than 1 ppm, the effect of reducing oxygen, sulfur, and nitrogen in the alloy is small;
This is because if the content exceeds ppm, the resulting alloy becomes brittle.

The reason why it is preferable to keep the amount of Ca remaining in the alloy in the range of 1 to 20 ppm is because it is difficult to significantly reduce oxygen, sulfur, and nitrogen in the alloy when the Ca content is less than 1 ppm. This is because if the Ca content exceeds 20 ppm, the alloy may similarly become brittle.

If the residual amount of B and alkali metal is less than o,oot%, the amount present is too small and the effect of the presence of B and alkali metal is small, and if it is more than 10%, the alloy becomes brittle. Particularly preferable B and alkali metal residual amounts are 0.005 to 3
%.

The reason why the residual amount of An in the alloy is set in the range of 0.01 to 20% is that when the residual amount of aluminum is less than 0.01%, not only is sufficient deoxidation not performed, but also Mg and Ca are not generated. This is because desulfurization and deoxidation by Mg and Ca are hardly performed, and the amount of residual calcium in the finished alloy, which is a condition for sufficient desulfurization and deoxidation by Mg and Ca, does not exceed 0.0001%. Further, alloys containing more than 20% aluminum are impractical.

M g O-Ca O powder, B and/or B2O3, AQ
When adding , Ca, and alkali metals to the molten metal, they may be added simultaneously or separately, and there is no particular restriction on the method of addition.

Regarding AIB, it is possible to add these separately, but since Ca and alkali metals are highly reactive and have problems in handling, it is preferable to add them in the form of an alloy. In any case, it can be added in various forms such as a linear body, a rod-shaped body, a block, or a powder. Moreover, there is no particular limitation on the mode of addition, and in the case of powder, a blowing method may be adopted.

The method of the present invention is particularly effective when dealing with Fe-based, Co-based, or N1-based alloys.

As Fe-based alloys, common elements C, Si, Mn, P,
Carbon steel containing S and 2% or less of C, and in addition to the above ordinary elements, Ni, Cr, Co,
In addition to special elements such as W, Mo, and A1, even those belonging to ordinary elements are typically added to alloy steels that exceed the content range of ordinary elements and are added for the purpose of adding special properties.

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. 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 alloys (monel metal) and Nt-Cr-Fe alloys. Alloy (Inconel), Ni-Mo alloy (Hastelloy A, B), Ni
-Mo-Cr-W alloy (Hastelloy C), Ni-5i
There are alloys such as Hastelloy D, Ni-Ta alloys, etc.

Examples of CO-based alloys include heat-resistant alloys, corrosion-resistant alloys, ultra-high alloys, and magnetic alloys that contain CO as a main component. Alloys belonging to these include Co-Cr-W-C alloys ( stellite), Go-Fe alloys (ductile
c ob att) □, Co-Cr-Ni-
Mo (El i gi 1oy alloy), Co-Cr-
NEW-W (Hayness), Vicalloy, Re
nendur.

Co alloy for magnetic materials such as Permendur, or Ni
An example is a CO-based superalloy that utilizes the precipitation of 3Ti.

In the present invention, the addition of various powders to the molten alloy is
By carrying out the process in a container supported by gO-CaO-based refractories, especially MgO-CaO-based basic refractories containing 40% or more of Ca, these refractories are also involved in the refining reaction, resulting in deoxidation and deoxidation. Desulfurization and denitrification effects can be further improved.

The backing used is calcia refractory (Ca
b), Larnite refractory (stabilized 2CaO S E O
2) Melwinite refractory (3CaO*MgO
-2SiO2), anorsite refractory (Caoa Al
2O3" 2S i 02 ) and CaO-enriched dolomite refractories, both of which have CaO enriched with 4
It is a basic refractory containing 0% or more.

The reason why it is preferable to use a refractory with a CaO content of 40% or more is because in basic refractories containing less than 40% CaO, the CaO therein is strongly bonded to other oxides. are doing. Therefore, CaO has low activity and is not reduced by added aluminum, whereas CaO in basic refractories containing 40% or more of CaO has high activity and is well reduced by aluminum.

In addition, refractories containing 40% or more of CaO are AIL 2
It easily reacts with oxides such as 0 s and S i O2, and therefore absorbs oxides in the molten metal, greatly reducing the amount of oxides present. In addition, refractories containing 40% or more of CaO include C, Ti.
, Zr, etc., so high temperature melting is possible. Note that in the manufacturing method of the present invention, "in a non-oxidizing atmosphere" means that the molten metal is in an open furnace or a closed furnace with argon gas,
This refers to an atmosphere in which molten metal is treated by blowing nitrogen gas, helium gas, etc., or by forming such a gas atmosphere on the surface of molten metal in a closed furnace.

The alloy obtained by the method of the present invention has sulfur 1
It is an extremely clean alloy containing 5 ppm or less, 20 ppm or less of oxygen, and 30 ppm or less of nitrogen.

[Function] As mentioned above, An existing in the alloy or added Al2. , and M g O--Ca O powders perform effective deoxidation, desulfurization, and denitrification. Especially Mg in the molten metal
is generated, this Mg acts on desulfurization together with Ca, and the desulfurization ability becomes extremely high.

In the method of the present invention, since the MgO--CaO is added in the form of powder, the contact area between the molten metal and the MgO powder and CaO powder can be made extremely large. Therefore, the reaction adsorption, desulfurization, and
It is believed that the deoxidation reaction can be carried out extremely effectively and that it is possible to obtain an alloy with extremely high purity.

In addition, since the addition form of Mg is MgO, it is possible to avoid violent reactions when adding Mg and Mg alloys as in the conventional method of adding CaO powder and Mg.
There is no scattering of g, etc., and the workability is extremely good.

[Examples] The present invention will be explained in more detail by examples below.
The present invention is not limited to the following examples unless it exceeds the gist thereof.

Example 1 3 kg of electrolytic iron having the composition shown in Table 1 and FeS added in advance to a sulfur content of about 0.03% was heated at 50 KH.
M g O-Ca O powder (composition: M
g030%, Ca070%) and An powder, respectively, 2
%, 0.2% was added.

Changes over time in the oxygen content, sulfur content, and nitrogen content of the molten alloy in the crucible were measured.

The results are shown in FIG.

Table 1 (Electrolytic iron composition) (wt%) Example 2 Measurements were carried out in the same manner as in Example 1, except that the treatment was carried out in a CaO crucible having the composition shown in Table 2.

The results are shown in FIG.

The CaO crucible used was made from CaO, a -grade reagent, which was crushed into 20 meshes, put into a crucible mold and compacted well, and the solidified crucible was heated at approximately 900°C for 24
It was prepared by calcining in an electric resistance furnace for hours.

Table 2 Comparative Example I M g O-Ca Measurements were carried out in the same manner as in Example 1 except that CaO powder was added instead of adding O powder. The results are shown in FIG.

From FIG. 1, it is recognized that according to the method of the present invention, a molten metal with low oxygen, sulfur, and nitrogen contents can be obtained quickly, and that the desulfurization effect is particularly large.

[Effects] As described above, according to the present invention, it is possible to perform extremely strong deoxidation, desulfurization, and denitrification of an alloy, and the amount of oxygen, sulfur, and nitrogen is extremely low, and the creep strength is improved.

It is possible to produce alloys with outstanding properties such as heat resistance, toughness, weldability, and forgeability. Furthermore, there are almost no intervening oxides.

[Brief explanation of drawings]

FIG. 1 is a graph showing changes over time in the oxygen, sulfur, and nitrogen contents in the molten metal obtained in Example 1.2 and Comparative Example 1. Agent Patent Attorney Tsuyoshi Shigeno Figure 1 □ Time (min)

Claims (1)

[Scope of Claims] (1) Powder mainly composed of MgO and CaO is added in vacuum or in a non-oxidizing atmosphere to a molten alloy containing Al in a melting furnace or container supported by a refractory containing 40% CaO or more. A method for producing an ultra-low sulfur alloy, characterized by adding (2) The ultra-low sulfur alloy according to claim 1, wherein the resulting alloy contains Mg: 0.03 to 0.0001% by weight and Ca: 0.002 to 0.0001% by weight. Production method. (3) The resulting alloy contains Mg: 0.03 to 0.0001% by weight, Ca: 0.002 to 0.0001% by weight, and S: 0.0015% by weight.
Below, oxygen: 0.002% by weight or less, nitrogen: 0.003
A method for producing an ultra-low sulfur alloy according to claim 1, wherein the ultra-low sulfur alloy contains at most % by weight. (4) The resulting alloy contains Mg: 0.03 to 0.0001% by weight, Ca: 0.002 to 0.0001% by weight, and S: 0.0015% by weight.
Below, oxygen: 0.002% by weight or less, nitrogen: 0.003
% by weight or less, Al: 0.01 to 20 weight %, B and alkali metal: 0.001 to 10 weight %. (5) A powder mainly composed of MgO and CaO and Al are added in a vacuum or non-oxidizing atmosphere to a molten alloy in a melting furnace or container supported by a refractory containing 40% or more CaO. Method for producing ultra-low sulfur alloy. (6) The ultra-low sulfur alloy according to claim 5, wherein the resulting alloy contains Mg: 0.03 to 0.0001% by weight and Ca: 0.002 to 0.0001% by weight. Production method. (7) The resulting alloy contains Mg: 0.03 to 0.0001% by weight, Ca: 0.002 to 0.0001% by weight, and S: 0.0015% by weight.
Below, oxygen: 0.002% by weight or less, nitrogen: 0.003
% or less by weight of the ultra-low sulfur alloy according to claim 5. (8) The resulting alloy contains Mg: 0.03 to 0.0001% by weight, Ca: 0.002 to 0.0001% by weight, and S: 0.0015% by weight.
Below, oxygen: 0.002% by weight or less, nitrogen: 0.003
The method for producing an ultra-low sulfur alloy according to claim 5, which contains Al: 0.01 to 20 weight %, B and alkali metals: 0.001 to 10 weight %.