JPS6159386B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention can achieve high yields of Ti and Al by controlling the reaction equilibrium between slag and metal.
This paper relates to an electroslag remelting method for Ni-based and Co-based superalloys containing Ti and Al. Vacuum arc remelting (VAR) and electroslag remelting (ESR) may be applied as methods for melting superalloys containing active metals such as Ti and Al. ―
It is said that it is difficult to understand the equilibrium of metal reactions,
Even if an inert gas such as Ar is used, the oxidation-reduction reaction of Ti, Al, etc. due to the slag progresses, resulting in inconsistent yields and many problems in quality control during production. Therefore, when implementing the ESR method,
The optimal one for each type of steel or brand of superalloy.
It is said that it is common to find ESR conditions, and the reality is that the optimum composition, especially for flux composition, is found by groping. Therefore, it is unavoidable
We often relied on VAR, but
Considering the literature, ESR is superior in terms of ingot quality such as mechanical properties, and according to experiments by the present inventors, it is also superior in terms of solidification structure (on the other hand, solidification).
It has been confirmed that ESR is better. Therefore, there is a strong desire to establish a method that can produce Ti, Al, etc. at a high yield and at a suitable medium rate by highly controlling the slag-metal reaction in ESR. The present invention was made with attention to such circumstances, and in particular, a flux composition suitable for melting Ni-based and Co-based superalloys containing Ti and Al in a certain ratio by ESR, The present invention aims to provide a method for manufacturing Ni-based and Co-based superalloys while maintaining a high yield of Ti and Al by using the flux found based on the Ti and Al content in the electrode. That is. Therefore, the ESR according to the present invention includes Ti: 0.2% by weight or more (hereinafter simply referred to as %), Al: 0.2% or more, and satisfies log([%Ti] ³ /[%Al] ⁴ )≦2. This is an electroslag remelting method _{for Ni} -based and Co-based superalloys, in which the content of _each component is
CaO: 20 to ₆₅ parts by weight, _Al2O3 : 28 to 65 parts by weight,
Contains _TiO2 : 16 parts by weight or less, and 0.85log ([%Ti] ³ /[%Al] ⁴ )≦-0.68292
+0.0745 (X-40) +0.0177 (Y-40) +0.3471
(Z-5)-(0.00103(X-40) ² +0.00346(Y-
40) ² -0.0277(Z-5) ² +0.00001(X-40) ³ -
0.00003(Y-40) ³ +0.00175(Z-5) ³ ≦
1.15log ([%Ti] ³ / [%Al] ⁴ ) ...(1) [In the formula, [%Ti] and [%Al] are the respective weight percentages of Ti and Al contained in the electrode (hereinafter simply referred to as percentages) , X, Y, and Z represent the parts by weight of each component of CaO, Al ₂ O ₃ , and TiO ₂ when the total of the three components is 100 parts _by weight. ₃ - The main point is to select a TiO ₂ -based flux or a flux made by adding CaF ₂ as a solvent to it and perform ESR in an inert atmosphere. The slag-metal reaction of Ti and Al is expressed by the equilibrium equation shown below. 4 [Al] + 3 (TiO ₂ )
3[Ti]+2(Al ₂ O ₃ )...(2) Therefore, log([%Ti] ³ /[%Al] ⁴ ) is calculated by the following formula
As shown in (3), it can be expressed as a function of log [(%Al ₂ O ₃ ) ² /(%TiO ₂ ) ³ ] (where K is the equilibrium constant of the reaction and f is the activity coefficient). log([%Ti] ³ / [%Al] ⁴ ) = logK−log [(%Al ₂ O ₃ ) ² / (%TiO ₂ ) ³ ] −log[f _Al2O3 2/f _TiO2 3] −log[f _Ti 3/f _Al 4]...(3) On the other hand, ESR fluxes for Ni-based and Co-based superalloys are generally CaF ₂ -CaO system, CaF ₂
-CaO-Al ₂ O ₃ system, CaF ₂ -Al ₂ O ₃ system, etc. are used, and some literature considers CaF ₂ to be the diluent. Therefore, we have created a flux whose main composition is CaO--Al ₂ O ₃ ---TiO ₂ system, and by adding CaF ₂ as a solvent if necessary, the physical properties such as the melting point and electrical conductivity of the entire flux are adjusted. ESR in an inert gas (Ar) atmosphere using various Ni-based superalloy electrodes with varying Ti and Al contents.
〓〓〓〓
I did this. log calculated from the slag composition at the final stage of dissolution, when the reaction in equation (2) is considered to have almost reached equilibrium.
[(%Ti) ³ / (%Al) ⁴ ] at that time [CaO-Al ₂ O ₃
―TiO ₂ ] Plot it on the ternary graph and calculate the log
Figure 1 shows the [(%Ti) ³ /(%Al) ⁴ ] line drawn. In this way, regardless of alloy type or operating conditions,
The fact that the log [(%Ti) ³ / (%Al) ⁴ ] curve can be drawn means that the first and third terms on the right side of equation (3)
This means that the term and the fourth term can be treated as almost constants. Therefore, when we found quadratic and cubic function equations that satisfied each curve in Fig. 1, we found that the former was log([%Ti] ³ /[%Al] ⁴ ) = -0.98434+
0.08332 (X-40) + 0.0301 (Y-40) + 0.40012
(Z-5)-0.00052(X-40) ² +0.00278(Y-
40) ² −0.01443(Z−5) ² …(4) Also, for the latter, log([%Ti] ³ /[%Al] ⁴ ) = −0.68292+
0.0745 (X-40) + 0.0177 (Y-40) + 0.3471 (Z
-5) -0.00103 (X-40) ² +0.00346 (Y-40) ² -
0.0277(Z-5) ² +0.00001(X-40) ³ -
0.00003(Y-40) ³ +0.00175(Z-5) ³ ...(5) (However, the meanings of [%Ti], [%Al], X, Y, and Z are the same as before). Ta. In other words, once [%Ti] and [%Al] of the electrode are determined, according to equation (4) or (5) (if necessary, a multidimensional equation with a quartic function or higher may be used). CaO of flux, Al ₂ O ₃
When the flux prepared based on this _{determination} was used, it was found that the yield of Ti and Al was at an extremely high level of 90% or more. If formulas (4) and (5) are not used, the flux is determined from the points on the curve in Figure 1, but log([%Ti] ³ /[%Al]
⁴ ) When the value corresponds to between the curves shown in Figure 1, such as 1.9, 1.8, 1.45, etc., draw a corresponding curve proportionally based on the degree of curvature of each curve, and It is also possible to determine the flux composition from the points. However, from an accuracy standpoint, it is better to use a functional formula rather than a graph, and it goes without saying that even for the same functional formula, cubic formula (5) is better than quadratic formula (4). Nor. Therefore, the present inventors conducted ESR in an inert gas atmosphere using various electrodes and various fluxes based on the above cubic equation, and investigated the yield of Ti and Al in the ingot. The results shown in Table 1 were obtained. Table 1 also shows the results of ESR conducted under atmospheric conditions.

[Table] 〓〓〓〓

[Table] As seen in Table 1, the log according to the electrode material
([%Ti] ³ /[%Al] ⁴ ) and the composition of the flux used, log([%
Ti] ³ / [%Al] ⁴ ) (hereinafter, the log of each electrode
([%Ti] ³ / [%Al] ⁴ ), log of flux used
(abbreviated as [%Ti] ³ / [%Al] ⁴ ) When the values are almost equal, the yield is extremely high, but when both values are significantly different, the yield is uncertain, especially
It was found that the yield balance of Ti and Al was greatly out of balance. Therefore, the log of the electrode and flux used is
([%Ti] ³ / [%Al] ⁴ ) When considering the extent to which the value discrepancy is allowed from the perspective of each yield, it was found that it is practically satisfactory if it is within ±15%. Knowing that a yield and a precision value can be obtained, the above-mentioned formula (1) was used as the condition of the present invention. In addition, when ESR is performed in the atmosphere, Ti
The yield of Al decreases and the variation increases. Therefore, it is an essential condition of the present invention to perform ESR under an inert atmosphere. Next, the basis for limiting each numerical condition in the present invention will be explained. First, the lower limit of Ti and Al in Ni-based and Co-based superalloys was set at 0.2% each because in many Ni-based and Co-based superalloys, Ti and Al are each about 0.2% or more. However, those with lower values were excluded from this study. Also, log([%Ti] ³ /[%Al]
The upper limit of ⁴ ) was set at 2 because many Ni and Co groups have a log([%Ti] ³ /[%Al] ⁴ ) of 2 or less, so those exceeding that value were excluded from this study. . Alloying elements other than Ti and Al in Ni-based superalloys include Cr, Mo, Nb, Co, W, Cu,
B, V, Fe, C, Si, Mn or other unavoidable impurities are shown, but any new or known impurities that do not depart from the scope of Ni-based and Co-based superalloys are included in the present invention. Next, regarding flux, CaO, Al ₂ O ₃ ,
When the total amount of TiO ₂ is 100 parts by weight, the content of each component is determined to be: CaO: 20 to 65 parts by weight, Al ₂ O ₃ : 28 to 65 parts by weight, TiO ₂ : 16 parts by weight or less. The reason for limiting CaO and Al ₂ O ₃ is as follows. Hydrogen pick-up occurs due to moisture absorption.
- Holes are generated (CaO excess). Quality reproducibility is poor, especially the yield of Ti and Al fluctuates (too much and too little CaO, Al ₂ O ₃ ). Poor operational stability (same as above) Melting point of slag becomes too high (same as above). In addition, when considering desulfurization and deoxidation,
It is desirable that the CaO/Al ₂ O ₃ ratio is 1 or more.
The reason for setting the upper limit of TiO ₂ to 16 parts by weight is because of the metal
This is because the value of log([%Ti] ³ /[%Al] ⁴ was set to be 2 or less, and as seen in Figure 1, TiO ₂ is 16
Exceeding parts by weight is log([%Ti] ³ /[%Al]
⁴ ) exceeds 2, which is outside the scope of the present invention. As a component of the flux, some CaO is
Good results were obtained even after changing to MgO. As mentioned above, CaF ₂ etc. may be added to the flux in order to adjust the melting point and electrical conductivity, but the content ratios of CaO, Al ₂ O ₃ , TiO ₂ , MgO etc. are the same except for CaF _2. On the other hand, for CaF ₂ etc., it can be considered as a ratio to the total amount of flux. At this time, CaF ₂
The content should be 70% or less; if it exceeds 70%, the electrical conductivity will increase significantly and the operability of melting will deteriorate, so it was limited. Since the present invention is configured as described above, if an electrode with log([%Ti] ³ /[%Al] ⁴ )=1 is used, the above equations (4) and (5) may be followed. However, if we follow Figure 1 as a simplified method, (1.0) in the figure
It is sufficient to take any one point on the curve shown by, for example, if CaO = 50%, Al ₂ O ₃ = 41%, TiO ₂ = 9
%, and if CaO = 60%, Al ₂ O ₃ = 33%,
TiO ₂ = 7%, and the flux composition shown from each point can be prepared and used for ESR, but if half (50%) of the flux is composed of CaF ₂ , the above ratio should be maintained. A flux having a composition of 50CaF ₂ −25CaO−20.5Al ₂ O ₃ −4.5TiO ₂ or 50CaF ₂ −30CaO−16.5Al ₂ O ₃ −3.5TiO ₂ may be used. In the present invention, the optimum flux composition is determined as described above, but since it is desired that the ESR atmosphere be as inert as possible, it is recommended that the ESR be carried out in an inert atmosphere such as Ar or He. , to the ground
The yield of Ti and Al was improved in a well-balanced manner, and the accuracy rate was also increased. Therefore, it has become possible to easily produce Ni-based and Co-based superalloys containing Ti and Al by ESR, and it has also become possible to obtain better ingots than when using VAR or the like. Next, examples of the present invention will be described. Example 1 ESR was conducted in an Ar atmosphere using electrode materials having the compositions shown in Table 2 and fluxes having the compositions shown in Table 3. The yields of Ti and Al in the obtained ingots are shown in Table 4.

[Table] 〓〓〓〓〓

【table】

[Table] As shown in Table 4, the deviation from equation (5) is ±15
When the yield was within ±30%, the yield of Ti and Al was 90%, but when the yield was within ±30%, an abnormal decrease in the yield of either Ti or Al was observed. Example 2 Electrode material with the composition shown in Table 5 and the log of the electrode material
A flux (Table 6) showing almost the same value as ([%Ti] ³ /[%Al] ⁴ ) was prepared and ESR was performed in an Ar atmosphere. Ti in the obtained ingot
The yields of Al and Al were as shown in Table 7, and all yields were extremely high.

【table】

[Table] 〓〓〓〓〓

【table】

【table】

【table】 [Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between log([%Ti] ³ /[%Al] ⁴ ) and flux composition. 〓〓〓〓〓

Claims (1)

[Claims] 1 Ni-based and Co-based superalloys containing Ti: 0.2% by weight or more, Al: 0.2% by weight or more, and satisfying log([%Ti] ³ /([%Al] ⁴ )≦2 In this _electroslag remelting _method , the content of _each component is CaO:
20-65 parts _by weight, _Al2O3 : 28-65 parts by weight, _TiO2 : 16
Each is essential so that it is not more than part by weight, and 0.85log ([%Ti] ³ / ([%Al] ⁴ ) ≦-
0.68292+0.0745(X-40)+0.0177(Y-40)+
0.3471 (Z-5) - 0.00103 (X-40) ² +0.00346
(Y-40) ² -0.0277(Z-5) ² +0.00001(X-
40) ³ -0.00003 (Y-40) ³ +0.00175 (Z-5) ³
≦1.15log ([%Ti] ³ / ([%Al] ⁴ ) Y and Z represent the parts by weight of each component of CaO, Al ₂ O ₃ , and TiO ₂ when the sum of the three components is 100 parts by weight.] CaO--Al ₂ O ₃ ---TiO An electroslag remelting method for Ni-based and Co-based superalloys, which is characterized by performing electroslag remelting in an inert atmosphere using _{a 2-} based flux or a flux obtained by adding CaF ₂ as a solvent. 2 An electroslag remelting method using a flux in which the content of CaF ₂ is 70% by weight or less based on the total weight of the flux, as set forth in claim 1. 3 Ti: 0.2% by weight or more, Al: 0.2% by weight % or more and satisfies log([%Ti] ³ /([%Al] ⁴ )≦2, the method is an electroslag remelting method for Ni-based and Co-based superalloys containing CaO, MgO, Al ₂ O ₃ , _TiO2
The content of each component when the total sum is 100 parts by weight is
CaO + MgO: 20 to 65 parts by weight, Al ₂ O ₃ : 28 to 65 parts by weight, and TiO ₂ : ¹⁶ parts by weight or less. Al] ⁴ )≦−
0.68292+0.0745(X-40)+0.0177(Y-40)+
0.3471 (Z-5) - 0.00103 (X-40) ² +0.00346
(Y-40) ² -0.0277(Z-5) ² +0.00001(X-
40) ³ -0.00003 (Y-40) ³ +0.00175 (Z-5) ³
≦1.15log ([%Ti] ³ / ([%Al] ⁴ ) Y, Z are CaO + MgO, Al ₂ O ₃ when the total of the above four components is 100 parts by weight,
The content of each component of TiO ₂ is expressed in parts by weight.] CaO + MgO - Al ₂ O ₃ - TiO ₂ flux with a composition that satisfies the following, or CaF ₂ is added as a solvent to this.
The method is characterized in that electroslag remelting is carried out under an inert atmosphere using a flux obtained from
Electroslag remelting method of Ni-based and Co-based superalloys. 4. The electroslag remelting method according to claim 3, using a flux in which the content of CaF ₂ is 70% by weight or less based on the total weight of the flux.