JP5036213B2 - Consumable electrode - Google Patents

Description

  The present invention relates to a consumable electrode used for producing a high melting point active alloy.

  In general, ingots of high melting point active metals such as titanium and zirconium for industrial use and alloys thereof are obtained by a vacuum arc melting method or an electron beam melting method using a consumable electrode. As shown in FIG. 1, a plurality of compacts composed of a high melting point active metal 1 and an alloy component 2 are formed and welded. Taking the titanium alloy as an example of the compact form, a component other than titanium (hereinafter also referred to as an alloy component) is arranged at the center, and the periphery thereof is covered with titanium as a high melting point active metal (for example, sponge titanium). The form is general (for example, refer to Patent Document 1), and other than that, the form in which the alloy component is wound around the high melting point active metal, or the alloy component is dispersed and arranged in a layer or a lump in the compact. Some forms exist.

  Examples of the alloy component include elements such as Fe and Cr. These elements have the advantage of increasing the hardness of the ingot, but on the other hand, they may macrosegregate in the ingot and cause components to be biased. Ingots with uneven components may have variations in mechanical properties such as strength, and the yield may be significantly reduced. In particular, Ti-17 alloy (Ti-5Al-2Sn-2Zr-4Mo-4Cr), which is frequently used as an aircraft material, is demanded to have an alloy with high quality and sufficient reliability. Less ingots are required.

  In view of the above circumstances, Patent Document 2 focuses on the difference in melting point between the alloy component and the high melting point active metal, and the alloy component (such as tin) having a melting point lower than that of the high melting point active metal (titanium) is plate-like or The ingot which suppressed the local bias | inclination of the component is obtained by carrying out dispersion | distribution arrangement | positioning in the compact with a lump form. However, in order to produce an alloy containing several elements having different melting points (for example, the above-described Ti-17 alloy or Ti-6Al-2Sn-4Zr-6Mo alloy), the arrangement state is devised for each element. It is necessary and the manufacturing process becomes complicated. Further, the method of Patent Document 2 cannot cope with macro segregation that occurs in the entire ingot.

When manufacturing a high melting point active alloy using a vacuum arc melting method, etc., if the consumable electrode is melted at a constant current (steady current) and then the supply of current is stopped rapidly, the resulting ingot It is known that component segregation occurs at the top (macro segregation). Therefore, in Patent Document 3, when double melting is performed by a vacuum arc melting method using a consumable electrode, the concentration of “elements with significant segregation” is adjusted in the portion corresponding to the top portion of the finally obtained ingot. The method of suppressing the component segregation which arises in the top part of the ingot finally obtained by using the consumable electrode which was made is disclosed.
Japanese Examined Patent Publication No. 46-17413 JP 2004-263217 A JP-A-61-67724

  In the high melting point active alloy manufacturing method using the normal vacuum arc melting method, as shown in FIG. 2, after obtaining the ingot (primary ingot), the ingot obtained by inverting the top and bottom is consumed. The process of using an electrode (secondary inversion consumable electrode) to obtain a new ingot (secondary ingot) is repeated.

  The present inventors welded 12 compacts having a uniform composition among the compacts to produce a titanium alloy consumable electrode as shown in FIG. 1, and after obtaining a primary ingot using the consumable electrode, The center of the primary and secondary ingots obtained by using the production method of FIG. 2 for producing a secondary ingot by using the obtained inversion of the primary ingot as a secondary inversion consumable electrode The behavior of component segregation of Cr (an element that segregates positively with respect to Ti) on the axis was simulated. As a result, as shown in FIG. 3, component segregation of Cr occurred in the top portion (α1) in the primary ingot (the left graph in FIG. 3). Furthermore, in the secondary ingot (the right graph in FIG. 3), it was found that the component segregation of Cr occurred in the bottom part (α2) as well as the top part (β2) (FIG. 3).

  Since the manufacturing method described in Patent Document 3 is intended to suppress component segregation at the top portion (β2) of the finally obtained ingot (secondary ingot), the bottom portion as described above. The large component segregation produced in (α2) could not be dealt with.

  An object of the present invention is to provide a consumable electrode for obtaining a high melting point active alloy with little component segregation by suppressing component segregation occurring at the bottom portion (α2) of the secondary ingot.

  The present inventors have found that a high melting point active alloy with less component segregation can be produced by using a consumable electrode in which the concentration of the “segregating element” is changed at the top.

Further, when melting is performed using a vacuum arc melting method or the like, the depth of the molten metal pool increases corresponding to the melting current, and the “segregating element” (hereinafter “ The concentration is high at the top of the resulting ingot (especially the final solidified portion), and the concentration of “segregating elements” (negative segregating elements) with an equilibrium distribution coefficient of more than 1 is low. Focused on disappearance. Taking these into account, let the overall length of the consumable electrode be L, the first 0 / 12L to 1 / 12L from the top end, and the first 1 / 12L to 2 / 12L from the top. 2 Top part, 2 / 12L to 10 / 12L part in the center, 10/12 to 11 / 12L part in the second bottom part, 11 / 12L to 12 / 12L part in the first part When the average mass concentration at the central portion of the element segregating positively with respect to the refractory active metal is X and the average mass concentration at the central portion of the negative segregating element is Y, the following 2 The above problem could be solved by providing a variety of consumable electrodes.
(1) In the case of a consumable electrode containing an element that segregates positively with respect to the high melting point active metal, the average mass concentration of the element that segregates positively in the first top portion is 0.6X to 0.95X, and the second top portion The element is characterized in that the average mass concentration of the positive segregating element is 0.6X to 1X. At that time, the average mass concentration of the positive segregating element in the first bottom portion is 0.6X to 0.95X, and the average mass concentration of the positive segregating element in the second bottom portion is 0.6X to 1X. By doing, the component segregation in the top part of a secondary ingot can also be suppressed. Further, when titanium is used as the high melting point active metal, Cr and / or Fe can be cited as a positive segregation element to be controlled within the above concentration range.
(2) In the case of a consumable electrode containing an element that is negatively segregated with respect to the high melting point active metal, the average mass concentration of the negatively segregating element in the first top portion is 1.05Y to 1.4Y, and the second top portion The element is characterized in that the average mass concentration of the negative segregating element is 1Y to 1.4Y. At that time, the average mass concentration of the negative segregating element in the first bottom portion is 1.05Y to 1.4Y, and the average mass concentration of the negative segregating element in the second bottom portion is 1Y to 1.4Y. By doing, the component segregation in the top part of a secondary ingot can also be suppressed. Further, when titanium is used as the refractory active metal, examples of negative segregation elements to be controlled in the concentration range include Mo, Al, and O.

In addition, in the consumable electrode containing the positive segregating element and the negative segregating element,
The positive segregating element satisfies the requirement (1) above,
It is preferable that the negative segregating element satisfies the requirement (2).

Moreover, after forming an ingot by the vacuum arc melting method using the consumable electrode,
By using at least one step of forming a new ingot by vacuum arc melting using an inverted ingot of the obtained ingot as a consumable electrode, a high melting point active alloy with little component segregation can be obtained. it can.

  By using the consumable electrode of the present invention, a high melting point active alloy with little component segregation can be obtained.

  The consumable electrode of the present invention utilizes an equilibrium distribution coefficient of an alloy component with respect to a high melting point active metal, and is an arc melting method or a plasma arc melting method in a vacuum or an atmosphere of an inert gas (for example, Ar or He). It can be suitably used when producing a high melting point active alloy using a high frequency melting method, an electron beam melting method or the like.

  Examples of the refractory active metal include Ti, Zr, Hf, V, Nb, Ta, Mo, W, etc. Among them, Ti, Zr, and Ti are preferable.

  The alloy components included in the high melting point active alloy together with the high melting point active metal include Cr, Fe, Mo, Al, O, Zr, Hf, V, Mo, Nb, Ta, Mn, Co, Ni, Cu, and Ru. , Rh, Pd, Ir, Pt, Ag, Au, Si, Ge, Sn, B, P, S, C, N, H, etc., the kind of the refractory active metal and desired characteristics (for example, corrosion resistance) One type or a plurality of types may be selected according to the intensity and the like. The alloy components can be classified into “elements that segregate positively” in which the value of the equilibrium distribution coefficient for the high melting point active metal is less than 1 and “elements that segregate negatively” in which the above value exceeds 1.

For the equilibrium distribution coefficient (K _O), equilibrium diagram of FIG. 5 (horizontal axis: Alloy component concentration of the refractory active in metal, vertical axis: temperature) will be described with reference to, and the partition coefficient (K ₀₎ Is a method of cooling a high melting point active metal containing an alloy component from a liquid state ( _L ), and a ratio between a liquid phase side alloy component concentration (C _L ) and a solid phase side alloy component concentration (C _S ) at the start of solidification. (K _O = C _S / C _L ).

  Specifically, when Ti or Zr is taken as an example of the high melting point active metal, examples of elements that positively segregate include Cr, Fe, Ni, Sn, etc. Among them, Cr and Fe are particularly easily segregated. Examples of negative segregation elements include Mo, Al, and O.

  The concentration of the alloy component contained in the high melting point active alloy varies depending on the type of the high melting point active alloy and required characteristics, but is usually about 0.1 to 20% by mass. Moreover, when an alloy component consists of 2 or more types of elements, what is necessary is just to contain the said ratio so that it may become in said range about each element.

  As described above, segregating elements such as positive segregating elements and negative segregating elements with respect to high melting point active metals tend to segregate at the top and bottom of the ingot. In a primary ingot obtained using a normal consumable electrode, large component segregation often occurs particularly at the top portion (α1 in FIG. 2). As a result, in the consumable electrode (secondary reverse consumable electrode) obtained by inverting the upper and lower sides of the primary ingot as shown in FIG. 2, the above elements are segregated at the bottom portion (α1). Therefore, in the secondary ingot obtained using the secondary inversion consumable electrode, component segregation remains at the bottom portion (α2).

  On the other hand, in the consumable electrode of the present invention, the concentration of the segregating element is adjusted in the top portion (α) (the concentration is decreased for the element that is positively segregated and the concentration is increased for the element that is negatively segregated). Component segregation of the above elements at the top portion (α1) of the obtained primary ingot and the bottom portion (α1) of the secondary inversion consumable electrode is suppressed. Therefore, in the secondary ingot obtained using the secondary inversion consumable electrode, component segregation at the bottom portion (α2) is suppressed.

  In the consumable electrode of the present invention, when the portion whose concentration is adjusted extends to the vicinity of the center of the consumable electrode, the concentration of the element is biased near the center of the obtained ingot (primary / secondary ingot). . Therefore, it is necessary to provide a portion (center portion) where the concentration of the element is relatively uniform near the center of the consumable electrode. Therefore, the concentration of the segregating element and the concentration of the element at the bottom portion of the consumable electrode and the top portion described below may be determined according to the value of the equilibrium distribution coefficient for the refractory active metal of the alloy component. Specifically, for elements whose equilibrium partition coefficient is far from “1”, the concentration is changed more greatly than the central portion, the concentration is adjusted over a wider portion, or a combination thereof. To decide.

  Specifically, when the total length of the consumable electrode is L and the top end is the starting point, at least a length of 0 to 1 is required to suppress component segregation of the above-described elements that occurs at the bottom of the secondary ingot. The concentration of the above element may be adjusted at a portion of / 12L (hereinafter referred to as the first top portion).

  More specifically, the average mass concentration (X) of positive segregating elements in the portion of length 2 / 12L to 10 / 12L (hereinafter referred to as the central portion), or the average mass concentration of negative segregating elements in the central portion. Based on (Y), one (or both) of the positive segregation element and the negative segregation element is adjusted at the first top portion. That is, when the concentration of the positive segregation element is adjusted at the first top portion, the concentration of the positive segregation element at the first top portion is 0.6X or more (preferably 0.65X or more, more preferably 0.7X or more). 0.95X or less (preferably 0.9X or less, more preferably 0.85X or less). When adjusting the concentration of the negative segregation element in the first top portion, the concentration of the negative segregation element in the first top portion is 1.05Y or more (preferably 1.075Y or more, more preferably 1.1Y or more). , 1.4Y or less (preferably 1.35Y or less, more preferably 1.3Y or less). Further, if necessary, in an adjacent portion having a length of 1/12 to 2 / 12L (hereinafter referred to as a second top portion), “positive segregation element” is 0.6 × or more (preferably 0.65 × or more, More preferably 0.7X or more) and 1X or less (preferably 0.95X or less, more preferably 0.9X or less), and “negative segregation element” is 1Y or more (preferably 1.025Y or more, more preferably 1.05Y or more) and 1.4Y or less (preferably 1.35Y or less, more preferably 1.3Y or less).

  Further, when a secondary ingot is obtained using the secondary reversible consumable electrode, component segregation also occurs at the top portion (β2) of the secondary ingot. Therefore, from the viewpoint of suppressing component segregation occurring at the top portion (β2) of the secondary ingot, the top portion (β1) of the secondary inversion consumable electrode, that is, the bottom portion (β1) of the primary ingot, Similarly, it is preferable to adjust the concentration of the segregating element. In that case, since the component segregation is less likely to occur in the bottom portion of the ingot than in the top portion, segregation occurs at least in the portion of the consumable electrode having a length of 11/12 to 12 / 12L (hereinafter referred to as the first bottom portion: β). By adjusting the concentration of the element (either the positive segregation element or the negative segregation element (preferably both)), the concentration of the element at the bottom portion (β1) of the primary ingot can also be adjusted.

  Specifically, either the positive segregation element or the negative segregation element in the first bottom part based on the average mass concentration (X, Y) of the central part (parts of length 2 / 12L to 10 / 12L) ( Or both). That is, when adjusting the concentration of the positive segregation element at the first bottom portion, the concentration of the positive segregation element at the first bottom portion is 0.6X or more (preferably 0.65X or more, more preferably 0.7X or more). , 0.95X or less (preferably 0.9X or less, more preferably 0.85X or less). When the concentration of the element that negatively segregates in the first bottom portion is adjusted, the concentration of the negative segregation element in the first bottom portion is 1.05Y or more (preferably 1.075Y or more, more preferably 1.1Y or more. ), 1.4Y or less (preferably 1.35Y or less, more preferably 1.3Y or less). Further, if necessary, in an adjacent portion having a length of 10/12 to 11 / 12L (hereinafter referred to as a second bottom portion), “element segregating positively” is 0.6 × or more (preferably 0.65 × or more, More preferably 0.7X or more) and 1X or less (preferably 0.95X or less, more preferably 0.9X or less), and “negative segregation element” is 1Y or more (preferably 1.025Y or more, more preferably 1.05Y or more) and 1.4Y or less (preferably 1.35Y or less, more preferably 1.3Y or less).

  When selecting Ti as the high melting point active metal and Cr (element segregating positively with respect to Ti) as the segregation suppression target element, a consumable electrode is used to suppress Cr segregation at the bottom of the secondary ingot. Most preferably, the concentration at the first top portion is adjusted to 0.67 to 0.88X, or the concentration at the first and second top portions is adjusted to 0.8 to 0.88X. Furthermore, in order to suppress the segregation of Cr at the top portion of the secondary ingot, the concentration at the first bottom portion of the consumable electrode is 0.67 to 0.88X, or the concentration at the first and second bottom portions. Is most preferably adjusted to 0.75 to 0.88X. In addition, when Mo (an element that segregates negatively with respect to Ti) is selected as the segregation suppression target element, in order to suppress the segregation of Mo at the bottom portion of the secondary ingot, the first top portion of the consumable electrode The density may be adjusted to 1.12 to 1.25Y, or the density at the first and second tops may be adjusted to 1.12 to 1.06Y. Furthermore, in order to suppress the segregation of Mo at the top portion of the secondary ingot, the concentration at the first bottom portion of the consumable electrode is 1.12 to 1.25Y, or the concentration at the first and second bottom portions. May be adjusted to 1.12 to 1.06Y.

The concentration of the element in the first top portion, the second top portion, the first bottom portion, the second bottom portion, and the central portion indicates an average mass concentration in each portion. Therefore, the concentration may be constant in the portion, or may change continuously, stepwise, or randomly in the portion toward the end or from the end toward the center. In addition, when suppressing segregation of O (oxygen), N (nitrogen), etc. as an alloy component, they are in the form of oxides (for example, TiO ₂ ) and nitrides (for example, TiN) of high melting point active metals, The amount of oxide or nitride may be adjusted, or may be adjusted by controlling the amount of O or N contained in the high melting point active metal.

  Further, when the alloy component is a combination of two or more elements (including a combination of positive segregating elements and negative segregating elements), the concentration and the portion for adjusting the concentration may be determined for each element.

  For example, the consumable electrode is manufactured by separately producing a compact that becomes a central portion and a portion that becomes a top portion (first and second top portions), a portion that becomes a bottom portion (first and second bottom portions), and welds them. Can be manufactured. The compact configuration may be a structure in which, for example, as shown in FIG. 1, the alloy component 2 is arranged inside, and the refractory active metal 1 is arranged so as to surround the alloy component. In that case, the alloy component may be in a columnar form as shown in FIG. 1, or may be arranged in a rod-like or plate-like form. Further, the high melting point active metal may be surrounded by an alloy component. A known method can be applied to manufacture the compact. For example, after the alloy component is formed into a columnar shape or a plate shape, a high melting point active metal made of sponge or powder metal is disposed so as to surround the alloy component, and the alloy component may be manufactured by a method such as compression molding.

  As conditions such as a vacuum arc melting method, a plasma arc melting method, a high-frequency melting method, and an electron beam melting method, known methods can be applied according to the high melting point active metal, alloy components, and the like.

  The bottom portion of the consumable electrode is a portion that is melted mainly in the initial stage of melting. In an ingot obtained by solidifying the melt, the bottom portion is mainly a component of the bottom portion. Conversely, the top portion of the consumable electrode is a portion that is melted mainly in the later stage of melting, and the top portion mainly becomes a component of the top portion of the ingot after melting and solidification.

  The concentration of the element and the portion where the concentration is changed are determined by actually manufacturing a consumable electrode and investigating the behavior of component segregation of the element in the obtained primary or secondary ingot. May be. In addition, the concentration and the portion where the concentration is changed can be determined by simulating the behavior of component segregation by the method described below.

  The simulation can be performed according to the following procedure.

  (Procedure 1) The equilibrium distribution coefficient for the high melting point active metal of the alloy component contained in the high melting point active metal is determined.

  (Procedure 2) Based on the data obtained in (Procedure 1), a model of a consumable electrode is produced, and heat transfer / solidification analysis is performed on the model consumable electrode.

  (Procedure 3) The component segregation of the primary ingot is predicted from the result of melting and redistributing the consumable electrode based on the data of (Procedure 2).

  (Procedure 4) The behavior of component segregation in the secondary ingot is predicted, and the configuration of the consumable electrode is determined using the data obtained in (Procedure 2) and (Procedure 3).

  Each procedure will be described in more detail.

(Procedure 1) The equilibrium partition coefficient may be calculated using thermodynamic database software (for example, a database such as “Thermo-Calc” or “FactSage”). Specifically, the liquidus temperature and the solidus temperature are calculated in a multicomponent system, and the alloy component concentration (C _L ) on the liquid phase side at the start of solidification of the high melting point active metal containing a predetermined concentration of the alloy component and the solid phase The ratio of the alloy component concentration (C _S ) on the side is calculated, and the equilibrium distribution coefficient (K _O = C _S / C _L ) is obtained by taking the ratio.

  (Procedure 2) For heat transfer and solidification analysis of a consumable electrode produced as a model, for example, using a finite element method analysis code (“CASTEM”, etc.) manufactured by Kobe Steel, Ltd., vacuum arc melting (VAR) ) Calculate the molten pool shape (temperature distribution) during operation and the moving speed of the solidification interface.

(Procedure 3) The prediction of the result of the primary ingot obtained by melting and redistributing the consumable electrode produced as a model of (Procedure 2) is the effective distribution coefficient using the Burton equation of the following equation (1) (K _e ) can be obtained and calculated using this effective distribution coefficient (K _e ). The material balance of the alloy element can be calculated using the following formula (2).
K _e = K _o / {K _o + (1−K _o ) _e ^{(−R · d / D)} } (1)
K _e : Effective distribution coefficient, K _O : Equilibrium distribution coefficient, R: Solidification rate (m / sec), d: Diffusion layer thickness (m) of each element on the liquid phase side, D: Diffusion coefficient (m ² / sec) )
In the present invention, a literature value is adopted as “d / D” (d / D = 10000 seconds / m; William G. Pfann, Zone Melting second edition, 1966, John Wiley & Sons, Inc.).
C _S = (1−fs.crit) · C _l + fs.crit · K _e · C _l (2)
C _S : concentration of alloy component on the solid phase side at the start of solidification, fs.crit: cleaning limit solid fraction, C _l : concentration of alloy component in molten metal obtained from each compact, K _e : effective distribution coefficient In the invention, a literature value was adopted as “fs.crit” (fs.crit = 0.3; Tadayoshi Takahashi et al., Iron and Steel, Vol. 76, No. 5 (1990), p. 86).

  (Procedure 4) The composition distribution of the secondary consumable electrode is determined by inverting the composition data obtained in (Procedure 3) (that is, the value of the data obtained on the top portion side of the primary casting is The value on the bottom side of the secondary consumable electrode is used, and the data value obtained on the bottom side of the primary ingot is the value on the top side of the secondary consumable electrode). Using the data of the composition distribution of the secondary consumable electrode determined above, the same operation as described in the above (Procedure 2) and (Procedure 3) is repeated, and the behavior of component segregation in the secondary ingot To investigate the.

  In general, since ingots are considered to have large concentration fluctuations on the central axis, it is preferable that the central axis of the ingot be analyzed.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

Examples 1-14 and Comparative Examples 1-6
(Procedure 1) Calculation of equilibrium partition coefficient of element contained in high melting point active metal with respect to high melting point active metal In this example and the comparative example, Ti-17 (Ti-5Al-2Sn-2Zr-4Mo) was used as the high melting activation alloy. -4Cr) was used to simulate component segregation. That is, in this Ti-17, equilibrium distribution of Al, Sn, Zr, Mo and Cr to Ti according to the thermodynamic database “Thermo-Calc” (B. Sundman et al .: Calpad, Vol. 9 (1985), page 153). The coefficient (K _O = C _S / C _L ) was calculated. And in the secondary ingot, the distribution of Cr, which has the lowest equilibrium distribution coefficient and is considered to have a significant degree of positive segregation, and the Mo, which has the highest equilibrium distribution coefficient and has a significant degree of negative segregation. The situation was simulated.

The equilibrium partition coefficient values (K _O ) for Ti were 1.39 for Mo and 0.65 for Cr.

(Procedure 2-4)
Assuming the actual manufacturing process, the consumable electrode is primarily melted in the melting furnace to produce an ingot (primary ingot), and then the obtained primary ingot is used as a consumable electrode (secondary reversible consumable electrode) When a new ingot (secondary ingot) was obtained, a simulation was performed assuming that the primary ingot was inverted as the secondary inversion consumable electrode as shown in FIG. That is, as the data of the secondary inversion consumable electrode, data obtained by reversing the data of the composition of the primary ingot is turned upside down.

As the melting method, a vacuum arc melting method was assumed, and the site where the distribution of components was measured was on the central axis of the ingot, which is considered to have the greatest fluctuation. Primary melting and secondary melting were set to the following conditions.
Primary melting conditions Current used for melting: 16 kA steady current Secondary melting conditions Current used for melting: 12 kA steady current

The sizes of the consumable electrode, the primary melt, and the secondary melt were as follows.
Consumable electrode The consumable electrode used in the present example and the comparative example was assumed to have a length of 5090 mm and a diameter of 370 mm, and was manufactured by welding 12 compacts (A to L) as shown in FIG. The density | concentration of the alloy component 2 (Cr, Mo) in each compact was set as Tables 1-2. The sizes of the obtained primary ingot and secondary ingot were assumed as follows.
・ Primary ingot Ingot diameter: φ570
Ingot height: 2145mm
・ Secondary ingot Ingot diameter: φ700
Ingot height: 1420mm

  Further, the target concentrations of Cr and Mo in the primary and secondary melts to be measured were both 4% by mass.

  Using solidification analysis software “CASTEM” (manufactured by Kobe Steel, Ltd.), the solidification rate of each element under the above melting conditions was determined. And the behavior of component segregation of each element was investigated by applying the concept of solidification transition layer of Takahashi et al. (Tadayoshi Takahashi et al .: Iron and Steel, Vol. 76, No. 5 (1990), p. 86). The element redistribution was calculated using the Burton equation of the above equation (1). And the material balance of the alloy element was calculated using the said Formula (2).

  The results are shown in Tables 1 and 2.

Table 1 shows the simulation results of Cr distribution in the secondary ingot obtained using various consumable electrodes for Cr (k _O : 0.65), which is considered to have a significant degree of positive segregation. is there.

  The evaluation of Cr component segregation (“Cr segregation prevention ratio” in Table 1) is 4 ± 0.086% by mass with the Cr concentration at the center of the consumable electrode as the target concentration (4% by mass). It calculated | required from the ratio which exists in the range.

  The “top portion” in the table means the upper end side of the consumable electrode used when obtaining the primary ingot, and the “bottom portion” means the opposite.

  First, FIG. 3 shows the Cr concentration (mm: vertical axis) with respect to the ingot height (mm: vertical axis) of the primary and secondary ingots obtained by using a consumable electrode with a constant Cr mass% concentration shown in Comparative Example 1. The change in mass% (horizontal axis) is shown in a graph. As a result of the above, the segregation of Cr was observed on the top side in the primary ingot (left graph in FIG. 3), and Cr was observed on the top and bottom sides in the secondary ingot (right graph in FIG. 3). Segregation was observed. For this reason, only about 70% of the total component segregation was obtained (see the result of Comparative Example 1 in Table 1). On the other hand, in the secondary ingot (Example 1) obtained by using the consumable electrode in which the concentration of Cr is reduced at the first and second top portions (compact A, B), the portion with less component segregation Could be increased to 83% (see Table 1). Further, in the secondary ingot (Examples 2 to 8) obtained by using the consumable electrode in which the concentration of Cr is reduced at both the top portion and the bottom portion of the consumable electrode, the portion with less component segregation is further increased. I was able to. FIG. 4 is a graph showing the change in Cr concentration (mass%: horizontal axis) with respect to the ingot height (mm: vertical axis) of the primary and secondary ingots obtained using the consumable electrode shown in Example 5. It is a thing. As a result, even in the primary ingot of the high melting point active alloy obtained by using the consumable electrode in which the Cr concentration is reduced at the top part and the bottom part (the left graph in FIG. 4), Although component segregation was observed, the ratio was smaller than that of the primary ingot obtained using the consumable electrode of Comparative Example 1 shown in FIG. 3 (4.5 in the most consumable electrode of Example 5). (In contrast to the mass% of the consumable electrode of Comparative Example 1, it is 4.8 mass% or more). Moreover, in the secondary ingot of Example 5 (the graph on the right in FIG. 4), unlike Comparative Example 1 (FIG. 3), segregation of Cr components at the bottom is suppressed, and further, at the top. The component segregation was also suppressed more than that of the secondary ingot of Comparative Example 1 (the secondary ingot of Example 5 was about 4.2% by mass in the most part, whereas that of Comparative Example 1 (In the secondary ingot, it is about 4.3% by mass).

  However, in both the first top portion (compact A) and the first bottom portion (compact L) of the consumable electrode, the Cr concentration is 0.5X (concentration (X) at the center portion) outside the range defined in the present invention. In the secondary ingot obtained using the consumable electrode (= 4.0% by mass) (Comparative Example 2), the portion with less component segregation was reduced (61%). Further, the secondary ingot obtained by using the consumable electrode changed to the outside of the range defined by the present invention (compact A, B, C, J, K and L) (Comparative Example 3). However, the portion with less component segregation was rather reduced (65%).

Table 2 shows the simulation results of the distribution of Mo in the secondary ingot obtained using various consumable electrodes for Mo (k 2 _O : 1.39), which is considered to have a significant degree of negative segregation. is there.

  The evaluation of Mo component segregation (“Mo segregation prevention ratio” in Table 2) is 4 ± 0.1 mass% with the Mo concentration at the center of the consumable electrode as the target concentration (4 mass%). It calculated | required from the ratio which exists in the range.

  As shown in Table 2, in the secondary ingots (Examples 9 to 10) obtained using the consumable electrode in which the Mo concentration was increased in the top portion (compacts A and B), each compact had Mo. Compared with the secondary ingot obtained by using a consumable electrode having a constant concentration (Comparative Example 4), the portion with less component segregation could be increased to about 83 to 87%. Moreover, in the secondary ingot (Examples 11-14) obtained using the consumable electrode which increased the density | concentration of Mo in both the top part and the bottom part, the part with little component segregation increased further ( 89-91%).

  However, in both the first top portion (compact A) and the first bottom portion (compact L) of the consumable electrode, the Mo concentration is 1.50Y (concentration (Y) in the center portion) outside the range defined in the present invention. In the secondary ingot obtained using the consumable electrode (= 4.0% by mass) (Comparative Example 5), the portion with less component segregation was reduced (50%). In addition, the secondary ingot obtained by using the consumable electrode that was changed to outside the range defined by the present invention (compact A, B, C, J, K, and L) (Comparative Example 6). However, the portion with less component segregation was rather reduced (53%).

  In addition, although the simulation result was shown in the said Example, even if it actually conducts experiment, the same result is obtained.

FIG. 1 is a schematic view for explaining the configuration of a consumable electrode according to the present invention. FIG. 2 is a schematic view for explaining a process of obtaining primary and secondary ingots using the consumable electrode of the present invention. FIG. 3 is a graph showing the distribution of Cr in the primary and secondary ingots obtained by the method of FIG. 2 using the consumable electrode described in Comparative Example 1. FIG. 4 is a graph showing the distribution of Cr in the primary and secondary ingots obtained by the method of FIG. 2 using the consumable electrode described in Example 5. FIG. 5 is a graph for explaining positive segregation and negative segregation.

Explanation of symbols

1. 1. High melting point active metal Alloy component α. Top part of the consumable electrode α1. A top portion of the primary ingot and a bottom portion α2 of the secondary inversion consumable electrode; Bottom portion of secondary ingot β. Bottom portion of consumable electrode β1. The bottom part of the primary ingot and the top part β2 of the secondary inversion consumable electrode. Top of secondary ingot

Claims (4)

A consumable electrode for producing an alloy containing a high melting point active metal,
The length of the consumable electrode is L, the portion from 0 / 12L to 1 / 12L from the end on the top side is the first top portion, the portion from 1 / 12L to 2 / 12L is the second top portion, length 2 / 12L to 10 / 12L are referred to as the central part, 10/12 to 11 / 12L as the second bottom part, and 11 / 12L to 12 / 12L as the first bottom part. When the average mass concentration at the center of the element that segregates positively with respect to the melting point active metal is X,
The average mass density of the positive segregation to elements in the first top part is 0.6X～0.95X, average mass concentration of the element for the positive segregation in the second top part is Ri 0.6X~1X der ,
The average mass concentration of the positive segregating element in the first bottom portion is 0.6X to 0.95X, and the average mass concentration of the positive segregating element in the second bottom portion is 0.6X to 1X.
The refractory active metal is titanium, consumable electrode elements the positive segregation average mass density is controlled in the range wherein the Cr and / or Fe der Rukoto. A consumable electrode for producing an alloy containing a high melting point active metal,
The length of the consumable electrode is L, the portion from 0 / 12L to 1 / 12L from the end on the top side is the first top portion, the portion from 1 / 12L to 2 / 12L is the second top portion, length 2 / 12L to 10 / 12L are referred to as the central part, 10/12 to 11 / 12L as the second bottom part, and 11 / 12L to 12 / 12L as the first bottom part. When the average mass concentration at the center of the element that is negatively segregated with respect to the melting point active metal is Y,
Wherein the first top portion average mass density of the negative segregation elemental are 1.05Y～1.4Y, average mass concentration of the element to the negative segregation at the second top part is Ri 1Y~1.4Y der ,
The average mass concentration of the negative segregating element in the first bottom portion is 1.05Y to 1.4Y, and the average mass concentration of the negative segregating element in the second bottom portion is 1Y to 1.4Y,
The refractory active metal is titanium, consumable electrode to which the negative segregation elemental average mass density is controlled in the range, wherein at least one Tanedea Rukoto selected from among Mo, Al and O . A consumable electrode for producing an alloy containing at least a high melting point active metal and an element that segregates positively and negatively segregates with respect to the high melting point active metal,
The positive segregating element satisfies the requirements of claim 1 ,
A consumable electrode, wherein the negative segregating element satisfies the requirements of claim 2 . After forming an ingot by the vacuum arc melting method using the consumable electrode according to any one of claims 1 to 3 ,
A high melting point active alloy obtained by performing at least one step of forming a new ingot by a vacuum arc melting method using an inverted ingot obtained as an expendable electrode.

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