JP3083653B2 - Manufacturing method of retaining ring material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a retaining ring material for a turbine generator made of a nonmagnetic iron-based alloy.

[0002]

2. Description of the Related Art Retaining ring materials for turbine generators made of a non-magnetic iron-based alloy are often electroslag remelted (hereinafter referred to as ESR) for the purpose of improving the internal properties.
Manufactured from ESR ingots. The ESR method melts the electrode with Joule heat generated by energization from the solid electrode to the molten slag, drops it under the slag, and directs and solidifies the molten metal pool in the mold to obtain good skin and internal properties. It is a method of obtaining an ingot having. In order to obtain such a high quality ingot, it is necessary to control the molten metal pool while maintaining an appropriate slag temperature, electrode feeding speed, voltage, current, slag bath depth, slag composition, fill Factors such as ratio (electrode diameter / mold diameter) must be appropriately controlled.

[0003]

The retaining ring material to which the present invention is directed is ASTM A28.
9 Although it is a known material standardized as Class B and C, it contains a large amount of Mn and Cr.
Applying the method, and even controlling the above factors, freckle-like or streak-like macro-segregation is likely to appear in the ingot,
In many cases, a product having good performance cannot be obtained. The present invention has been made in order to solve the above-mentioned problems, and provides a manufacturing method capable of reducing segregation of an ESR ingot to obtain a retaining ring material having excellent performance.

[0004]

Means for Solving the Problems To solve the above-mentioned problems, the present invention relates to a method for producing a composition comprising: C: 0.4 to 0.6% by weight;
n: 16 to 20%, Si: 0.8% or less, Cr: 3.5
-6%, N: 0.2% or less, the balance being Fe and unavoidable impurities, the manufacturing method of the retaining ring material, the hollow electrode having a hole formed along the axial direction in the electrode core. It is characterized in that the electroslag is redissolved by using it. In the second invention, C: 0.13% by weight%
Hereinafter, Mn: 17.5 to 20%, Si: 0.8% or less,
In a method of manufacturing a retaining ring material containing Cr: 17.5 to 20% and N: 0.45 to 1%, the balance being Fe and unavoidable impurities, a hole is formed in the electrode core along the axial direction. The electroslag is redissolved by using the formed hollow electrode.

According to a third aspect of the present invention, the cross-sectional area of the hollow portion of the electrode is 0.04 to 0.5 to the total cross-sectional area of the electrode including the hollow portion.
It consists of 9 ratios. According to a fourth aspect of the present invention, in the hollow electrode having a cylindrical shape, the inner diameter of the electrode is 0.2 to 0.1 mm with respect to the outer diameter.
95, and the outer diameter of the electrode is 0.4 to 0.95 with respect to the inner diameter of the mold.

[0006]

In order to produce an ESR ingot with good internal properties without macro-segregation, it is essential to make the molten metal pool shallow and dish-like, and when it becomes deeper, the densification of the solidification structure is hindered. The structure is likely to be coarse, and macro segregation such as reverse V segregation is likely to occur. However, when the ingot becomes larger than the limit size, it is difficult to make the pool into a shallow pool that does not generate macro-segregation while maintaining good skin.

For example, considering the influence of the shape of the ESR electrode, when the fill ratio is small, a large amount of heat is generated in the central portion of the molten slag, a large amount of current flows in the solidified ingot, and a large amount of Joule heat is generated. Pools tend to be deep. On the other hand, if the fill ratio is large, heat is generated in the entire molten slag, and the ratio of current flowing to the mold increases, so that the pool tends to be shallow. However, even with the latter method of increasing the fill ratio, it is not easy to make the pool shallow enough to prevent segregation.

[0008] Based on such knowledge, the present invention provides 18Mn-5Cr or 18Mn-18 having a large segregation tendency.
In the production of the ESR ingot of the retaining ring material of Cr, the current flowing in the ingot from immediately below the center of the electrode is reduced by adopting the hollow electrode, and the depth of the molten pool in the center becomes shallower and the whole becomes As a result, the pool shape is flattened and an ESR ingot with good internal properties without macro segregation is obtained. Further, in the vicinity of the mold, the amount of electricity increases and the temperature of the slag increases, resulting in a good ingot surface.

The method for producing the electrode of the present invention is not particularly limited. For example, melting, refining,
Ingots made from ingots, hollow ingots, drilled solid ingots, ingots processed into plates and bent and welded, and hollow electrode split materials assembled and welded, etc. A hollow electrode can be obtained. The outer shape of the electrode manufactured in this way can be not only a circular shape but also a square shape or another irregular shape. The hole formed in the electrode is usually located at the center of the electrode, but is not limited to the one completely located at the center, as long as it is formed at the core which is almost at the center. Good.

Although the shape of the hole is not particularly limited, it is usually formed in a sectional shape similar to the outer wall of the electrode. For example, a circular hole is formed in a columnar electrode, and a square hole is formed in a prismatic electrode. This hole is usually penetrated at both ends of the electrode, but is not necessarily limited to this.
At the beginning or end of the ESR operation, the hole may be closed at one or both ends of the electrode so as to melt the solid part. In addition, the hole is usually formed in a straight hole shape having the same cross-sectional shape along the axial direction, but may have a modified cross-section depending on the axial position, for example, the inner surface shape of the hole in the axial direction. It is also conceivable to have a tapered shape along. Also, although one hole is usually formed in the core of the electrode, a plurality of holes may be formed.

Next, the reason why the relationship between the electrode hole diameter, electrode outer diameter, mold inner diameter and the like is limited will be described. Hollow section cross section / (total electrode cross section including hollow section) or pore diameter / electrode outer diameter ratio When the above ratio is less than the lower limit, the influence on the shape change of the molten metal pool is small, and the molten pool is sufficiently flat. No effect of conversion is observed. On the other hand, if the upper limit is exceeded, the electrode length for obtaining the required ingot weight increases, and it becomes difficult to apply the electrode to actual operation. Therefore, the cross-sectional area ratio is 0.04 to 0.9 and the diameter ratio is 0. The range of 0.2 to 0.95 was made desirable.

Ratio of electrode outer diameter / mould inner diameter If the above ratio is less than 0.4, the electrode length for obtaining the required ingot weight increases, and application to actual operation becomes difficult. When the ratio exceeds 0.95, the distance between the mold and the electrode becomes narrow, and the mold and the electrode may come into contact with each other when the mold or the electrode is moved up and down, which may make application to actual operation difficult. The ratio is preferably in the range of 0.4 to 0.95.

In addition to using the electrode of the present invention as a single electrode, for example, when producing a hollow ESR ingot, a plurality of hollow electrodes can be arranged on the circumference to perform ESR. Also, the effect unique to the hollow electrode can be obtained.

[0014]

(Example 1) A retaining ring material according to the present invention shown in Table 1 was melted by an ordinary method, and a cylindrical electrode having a round hole at the center was cast using a core. In addition, as shown in Table 2, four kinds of electrodes having different inner diameter / outer diameter ratios of the electrodes were defined as invention electrodes A to D. Solid electrodes cast by a conventional method without using a core were prepared as reference electrodes E and F.
These electrodes had approximately the same electrode cross-sectional area (excluding holes), and ESR conditions were set so that the same dissolution rate was obtained.

By using these ESR electrodes, 1000
ESR was performed using slag in a mold having a diameter of mm.
After the obtained ESR ingot was disc-shaped, macro segregation was evaluated by macro corrosion and the ingot surface was evaluated. The results are shown in Table 3. As shown in Table 3, when the conventional solid electrode was used, the ingot surface was defective or slightly defective, and macrosegregation was generated in any of the internal properties. In contrast, in the case of using a hollow electrode, the ingot surface,
The internal properties were significantly improved, and a good quality ESR ingot was obtained.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

[Table 3]

(Example 2) Inventive electrode A used in Example 1
Examples 1 and 2 using Comparative Examples E and F and Comparative Electrodes E and F
The dissolution rate of the electrode was measured under the same mold and slag conditions as in Example 1 while changing the ESR current. As a result, the inventive electrode obtained a higher dissolution rate at the same ESR current than the comparative electrode. Therefore, it was confirmed that the use of the hollow electrode of the present invention significantly increased the dissolution rate and reduced the ESR power cost. This seems to be due to the increase in the contact area between the electrode and the slag.

(Embodiment 3) In Embodiments 1 and 2 described above, a case where a circular hole was formed in a columnar electrode was described. However, the shapes of the electrode and the hole are not limited to this. For example, FIG. As shown, a prism electrode 1, a segmented electrode 2, an electrode 3, an electrode 4, and the like can be exemplified.

[0021]

As described above, according to the present invention,
In applying the ESR method to the 18Mn-5Cr or 18Mn-18Cr-based retaining ring material, the shape of the molten pool becomes shallow and flattened by adopting a hollow electrode, and the generation of segregation is suppressed. It is possible to manufacture ESR ingots with various internal properties and ingot skin,
A retaining ring material with excellent performance can be obtained.

[Brief description of the drawings]

FIG. 1 is an electrode cross-sectional view showing a modified example of the electrode shape of the present invention.

[Explanation of symbols]

 1 prism electrode 2 segment electrode 3 segment electrode 4 segment electrode

Continuation of the front page (51) Int.Cl. ⁷ Identification code FI F01D 25/00 C22C 38/38 // C22C 38/00 302 C22B 9/18 A 38/38 (56) References JP-A-60-124442 ( JP, A) JP-A-52-149224 (JP, A) JP-A-5-285632 (JP, A) JP-A-57-107804 (JP, U) JP-A-55-83505 (JP, U) (58) ) Surveyed field (Int.Cl. ⁷ , DB name) B22D 23/10 531 B22D 23/10 522 C22B 9/18 C22B 9/187 F01D 11/00 F01D 25/00 C22C 38/00 302 C22C 38/38

Claims (4)

(57) [Claims] C. 0.4 to 0.6% by weight, Mn
: 16 to 20%, Si: 0.8% or less, Cr: 3.5
-6%, N: 0.2% or less, the balance being Fe and unavoidable impurities, a method of manufacturing a retaining ring material, wherein a hollow electrode having a hole formed in an electrode core portion along an axial direction. For producing a retaining ring material by performing electroslag remelting using the method 2. In% by weight, C: 0.13% or less, Mn:
17.5-20%, Si: 0.8% or less, Cr: 17.
5-20%, N: 0.45-1%, the balance being Fe
And a method for producing a retaining ring material comprising unavoidable impurities, wherein the electroslag is redissolved by using a hollow electrode having a hole formed in the electrode core along the axial direction. Production method 3. The method for producing a retaining ring material according to claim 1, wherein the cross-sectional area of the hollow portion of the electrode is in a ratio of 0.04 to 0.9 with respect to the total cross-sectional area of the electrode including the hollow portion. 4. A cylindrical hollow electrode, wherein the inner diameter of the electrode is 0.2 to 0.95 relative to the outer diameter, and the outer diameter of the electrode is 0.4 to the inner diameter of the mold. ~
3. The method for producing a retaining ring material according to claim 1, wherein the ratio is 0.95.