JPS62132761A - Refractories for refinement and method therefor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a calcia (Cao)-based refractory material for refining and a refining method using the same.

More specifically, in addition to deoxidation and desulfurization, dephosphorization is also performed at the same time.
) The present invention relates to the above-mentioned refractory material and refining method.

[Prior Art] In alloys, impurities, especially oxygen (0) and sulfur M (S
), or that its properties can be significantly improved by reducing phosphorus (P). and low-temperature toughness deteriorates. Also,
Hydrogen-induced cracking (HIC), which occurs in line pipes for transporting crude oil and natural gas containing H2S, originates from elongated inclusions such as MnS and hardened structures such as bainite (B) and martensite (M). grow along. Phosphorus in steel is significantly positively segregated in macro-segregation areas of steel ingots and continuous casting slag, promoting the formation of hardened structures in thick plates. Therefore, H
In order to prevent the occurrence of IC, it is necessary to reduce the phosphorus concentration below a critical value. Furthermore, stress corrosion cracking (SCC) of austenitic stainless steels is promoted by phosphorus.

Additionally, phosphorus generally deteriorates high-temperature ductility due to segregation at grain boundaries. Furthermore, it is well known that when the concentration of oxygen and sulfur in the molten alloy is high, various properties such as ductility and toughness deteriorate.

By the way, CaO-based refractories are thermodynamically stable even at high temperatures, and are known to exhibit oxide absorption, deoxidation, and desulfurization effects through the so-called furnace wall slag reaction.
A method of deoxidizing and desulfurizing molten steel using this has been developed (for example, Japanese Patent Publication No. 54-849).

In addition, a method of dephosphorization using a CaO crucible containing CaF2 is also known (Tohoku University Research Institute for Materials Research, Common Facilities Technology Laboratory Report No.

10, P, 49-50).

Conventionally, dephosphorization of molten iron has been carried out using slag, such as Na 70 Si 02 and Ca C.

Soda-based slag containing substances such as
9th Honda Memorial Lecture, April 1984, 111). Also, C
a0-CaF: + system (7) 7 lux or CaC2
A method using -CaF2-based flux (Japanese Patent Publication No. 11099) is also known.

[Problems to be Solved by the Invention] According to the refining method known in Japanese Patent Publication No. 54-849, etc., it is possible to perform strong deoxidation and desulfurization, but dephosphorization is not possible. It's almost never done.

In addition, the dephosphorization method using a CaO-CaF2 crucible dissolves iron whose surface has been oxidized in advance, and is applicable to a limited number of alloy types. It lacks versatility, such as being unable to do so.

On the other hand, in the method of phosphorizing using slag, the furnace wall may be damaged due to contact between the slag and the furnace wall.

There are problems such as entrainment of slag into the molten metal or ingot, and generation of fumes and odors. In addition, the conventional dephosphorization method using slag is carried out in an oxidizing atmosphere, but it is difficult to prevent the oxidation of the alloy, and if the process is performed using a vacuum melting furnace, the slag must be removed. There is a problem that slag removal processing is difficult.

[Means and effects for solving the problems] The refractory material for refining of the present invention is characterized in that it contains 50i [1% or less] of CaC2, and the remainder is mainly CaO.

Further, in the refining method of the present invention, the molten alloy is held in a non-oxidizing state in a container whose inner surface is made of the refractory material for refining, and if necessary, a deoxidizing material is included in the molten alloy. It is characterized by this.

According to the present invention, it is possible to perform deoxidation, desulfurization, and dephosphorization simultaneously without using slag.

The present invention will be explained in more detail below.

% (hereinafter abbreviated as %) and the remainder is mainly composed of CaO. The composition of the remainder may be composed essentially only of CaO, or may contain CaF2 in an amount of 10% or less of the n6J refractory, in addition to CaO.

In the refractory material for refining of the present invention, if the content of CaC2 exceeds 50%, the difficulty in handling increases and the corrosion resistance and fire resistance of the refractory material decrease. Also, CaC
If CaCt is less than 0.5%, the dephosphorization effect will decrease, so the blending range of CaCt should be 0.5 to 0.5%.
20%, especially 1-to% is preferred.

In addition, Ca C2 content r+ in the refractory material for refining of the present invention
means the content of C a C2 in the entire refractory material, and may locally exceed 50%. For example, as described below, when CaCp is produced by molding a CaO raw material and bringing it into contact with a carbon material, the contact surface with the carbon material may locally contain more than 50% CaC,
, may exist, but such uneven distribution of Ca C2 is permissible as long as it does not impair the properties as a refractory material.

In addition, if the refractory material for refining of the present invention contains CaF2, it can inhibit the phosphorus effect and is extremely advantageous; however, if too much CaF2 is present, the melting point of the refractory material will decrease, resulting in high temperatures. It becomes impractical because dissolution becomes impossible. Therefore, it is suitable that the blending range of CaF2 is 10% or less, preferably 8% or less of the refractory material.

In addition, the refractory material for refining of the present invention includes S i Op , AM 201 , MgO1Z r
O2, Fe, O:l, Bad, metal compounds such as MnO2, nofluorinated compounds such as MgF2, CaCl2
, M g CfL 2 etc. No 11! chemical compound or CaCN
One or more types of slag constituent materials of kJ may be contained. When the content of slag constituent materials becomes excessively high, the CaO content in the refractory material becomes relatively small.
Effective deoxidation and desulfurization effects become difficult to perform, and depending on the type of slag constituent material, the corrosion resistance and fire resistance of the refractory material may be reduced. For this reason, it is preferable that the slag constituent material contains 40% or less of the refractory material, i.e., lI+L.

The raw material for CaO, which is the t'J3m compound that makes up the refractory material, is
Various materials such as calcined Ca COJ, Ca (OH) 2, and fused calcia can be used. Note that fused calcia is preferable because it is dense. In addition, when the refractory material contains a slag constituent material, it is also possible to use larunite, melwinite, anorsite, dolomite, etc. as a raw material for the CaO source.

To produce the refractory material of the present invention, 1, for example, granules of CaO, Cac2 powder, and, if necessary, CaFz powder and slag component powder (or granules) are mixed in appropriate proportions. To make an amorphous refractory material such as a stamp material, a non-aqueous binder (for example, ethanol in which calcium chloride is dissolved, pitch, tar, etc.) is used. Moreover, in order to form a shaped refractory, it is sufficient to press-form with or without adding these non-aqueous binders, and sinter as necessary.

In addition, Cac2 is CaO when producing fused calcia.
It is relatively easily produced by arc heating melting in the presence of C. Also, the reaction between C and CaO is 1800
This occurs at temperatures as high as 7°C or higher, and CaC2 is easily obtained. For this reason, it is possible to produce fused calcia by arc melting CaO in the presence of C or by melting CaO in the presence of C.
By heating a mixture of
A CaO-based refractory material containing C:r can be obtained.

In addition, by firing a CaO-based molded body in contact with a carbon material, a CaO-based body containing CaC,
For example, if a CaO raw material is formed into a crucible shape, a carbon material is inserted into the crucible, and induction heating is performed, sintering and CaC2 generation can be performed simultaneously.

In the refining method of the present invention, a molten alloy is held in a container whose at least the inner surface is made of the refractory material for refining, and if necessary, a deoxidizing material is contained therein. In the case of a crucible, this container may be a refractory container to which a refining refractory material (either a regular refractory or a monolithic refractory) made of only the refining refractory material described below is attached. Only the inner surface is Ca
It may also be a C2-enriched CaO-based refractory composition.

In addition, in a CaO-based crucible or a refractory container lined with a CaO-based refractory material, Ca C2 is formed by heating in the presence of C by inserting a graphite rod into the inner surface of the crucible or refractory container, and forming Ca C2 on the inner surface. A structure in which a Ca C2-enriched layer is formed in the portion may also be suitably used.

To hold the molten alloy in this container, molten metal melted in another melting device may be poured into this container, or all or part of the alloy raw material may be charged into the container. , heating, or melting to form a molten metal.

In the present invention, the molten alloy 1 is held in the container in a non-oxidizing atmosphere. The non-oxidizing atmosphere is preferably a vacuum or an inert gas such as argon or nitrogen.

It is possible to perform deoxidation by adding it.

As deoxidizing materials, C, All Si, Ti, Zr, Hf
, alkaline earth metals, B, rare earth elements (lanthanoid elements), etc., or two or more types thereof can be used. Among these deoxidizing materials, An, Si, and Ti are particularly suitable. Note that these deoxidizing materials may be added as a pure metal or as an alloy.

In the refining method according to the present invention, it is preferable to add sufficient deoxidizing material to carry out the deoxidizing reaction, and
It is preferable to select the amount of metal remaining in the molten metal so that the residual amount does not deteriorate the properties of the obtained alloy.For example, when adding aluminum to the molten metal of carbon steel or alloy steel, Aluminum residual amount of 0.0
It is preferable to set it to about 0.05 to 20%. In this case, if the amount of residual aluminum is less than 0,000%, sufficient deoxidation and desulfurization will not be carried out, and if the amount of residual aluminum exceeds 20%, the resulting steel will have poor practicality.

In the present invention, the molten alloy undergoes the dephosphorization action because:
It is presumed that the reaction is based on the following reaction formula.

CaC2+Ca+2C 3Ca + 2 P + Ca :l P 2Cart
P2 +CaO+Cat P:! *CaO furthermore,
When a deoxidizing agent such as AM, Si, or Ti is added, for example, A
In the case of addition, deoxidation and desulfurization are performed by the following reactions, which complement the phosphorus reaction described above.

That is, the added An is 0 in the molten metal and CaO on the furnace wall.
and reacts with O generated by the reaction with S in the molten metal (Cao+s→CaS+O), resulting in 2A+30→A 1 203 and A 1 203 is produced. Further, AM in the molten metal reacts with CaO on the furnace wall to form 2AJl+3CaO+Au203+3Ca (g), which also produces Al203.

(In this case, the generated Ca is deoxidized, desulfurized, and
It has the effect of promoting dephosphorization. )Ca (g) +04
Ca.

Ca (g)+S-+Ca5 3Ca (g)+2P=Ca:+P2All 20
:l reacts with CaO on the furnace wall as shown in the following formula to form 3Ca
O” A l 203 or 12CaO-7A cross 203
An active layer is formed on the wall surface.

A L; L20 J + 3 Ca O43Ca Om
A l 20 ]7A1203 + l 2CaO = 12 Ca O・7 A l 2 03 (1)
l 2 Ca O・7 A l 203 and 3CaOe
Au20: +, especially 3 CaO@A l 20 ] 4
The sulfur capacity of the molten metal is high, and S removal progresses well.

In this way, the active 3CaO・Au 20:+ generated by O removal by Ai and the reducing action of AR,
l 2 Ca O117A l 2 0
S removal is performed by 3 and CaO.

In addition, N in the molten metal is caused by the reaction between AQ and CaO mentioned above (:
Due to evaporation (boiling) of Ca, etc. generated by the decomposition reaction of aC2, it is released from the molten metal, and the molten metal is removed. ! A 111 also,
CaO is an oxide and sulfide in the molten alloy.

Phosphides, nitrides, etc. are absorbed, and the refining reaction also progresses.

As described above, according to the present invention, in addition to the strong dephosphorization reaction, the de-O, S, and N reactions are performed, and the CaO furnace wall prevents contamination by impurities. O of
, S, P, and N content are significantly reduced. As a result, extremely clean alloys are produced.

The refining method of the present invention can be applied to Fe-based, CO-based, Ni-based,
Applicable to various alloys such as Cr-based, Mn-based, and Cu-based.In addition, although the means for heating the molten metal listed in -h are arbitrary and α, if an induction heating device is used, its unique stirring action can be utilized. It is possible and suitable.

[Examples] The present invention will be explained in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples without exceeding the gist thereof. .

"l/LthD-1 CaO-5%CaC2-3%CaF crucible was used, and this crucible contained O, S, and P [0O903%, 50% respectively]
．． 02%, Po, 05% Fe-30wt%Cr alloy was stored, and under Ar1, Oatm atmosphere, 15%
It was melted by high frequency induction heating at 50°C. Figure 1 shows the time-dependent changes in 0, S, and P in the 0 alloy molten metal to which 2 grains of AJJ were added at 0.5% to the molten metal immediately after melting. concentration begins to decrease,
It was observed that the concentration reached 1/1O of the initial concentration in about 10 minutes. At the same time, a rapid decrease in O and S was also observed due to the addition of hemi. Note that in the drawings, 0, S, and P are shown as the ratio of the concentration C to the initial concentration CO.

[Effects of the Invention] As is clear from the above description, according to the present invention, dephosphorization, deoxidation, desulfurization, and denitrification can be performed in one treatment step.
It is Tr11 and can perform strong dephosphorization. Furthermore, the furnace wall was damaged, slag was caught in the #4 lump,
Since there are no problems such as the generation of fumes or odors, the refining operation is easy.

[Brief explanation of drawings]

FIG. 1 is a graph showing the measurement results in Example 1.

Claims (4)

[Claims] (1) Contains 50% by weight or less of CaC_2, with the balance being CaO
A refractory material for refining, mainly consisting of (2) The refractory material for refining according to claim 1, wherein the remainder is mainly CaO and further contains CaF_2 in an amount of 10% by weight or less. (3) The molten alloy is held in a non-oxidizing atmosphere in a container whose inner surface is made of a refractory material for refining, with at least 50% by weight of CaC_2 and the remainder being mainly CaO. Characteristic alloy refining method. (4) Holding the molten alloy in a non-oxidizing atmosphere in a container in which at least the inner surface is made of a refining refractory material containing 50% by weight or less of CaC_2 and the remainder being mainly CaO, and A method for refining an alloy, characterized in that the molten metal contains a deoxidizing material.