JPH03138323A - Manufacture of mg-containing ni-cu base alloy ingot - Google Patents

Abstract

PURPOSE:To transfer and incorporate Mg into the ingot at high yield by adding MgO to slag constituted of CaF2, CaO and Al2O3 as a fundamental compsn. and subjecting it to electroslag remelting. CONSTITUTION:By weight, 0.5 to 1.5% MgO is added to slag constituted of 40 to 65% CaF2, 20 to 35% CaO and 15 to 25% Al2O3 as a fundamental compsn., which is subjected to electroslag remelting and is refined into an ingot. In this way, the yield of Mg transferred and incorporated into the ingot comes to nearly 100%, and the surface of the obtd. ingot is made excellent as well. Furthermore, the forgeability of the ingot is made satisfactory.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a Ni--Cu based alloy ingot used at extremely low temperatures, such as a superconducting power generation material, by electroslag remelting (ESR).

[Prior art] Generally, ingots of Ni-Cu-based alloys are manufactured by ESR in order to improve the internal properties of the ingots, but this alloy has poor hot workability. Cracks occur, reducing material yield, and in extreme cases, it becomes impossible to obtain the desired shape, and there are even cases where the product is discarded.

As a countermeasure to this problem, Mg
Alternatively, a trace amount of Zr is often added to the present alloy.

Regarding Zr in both of these elements, since this alloy usually contains a large amount of At, almost all of the Z contained in the electrode migrates into the ingot during ESR. In particular, although this does not cause any problems, Mg is a highly active and at the same time highly volatile element, so it dissipates and decreases during ESR, adjusting the content in the alloy within the desired range. It is extremely difficult to do so.

[Problems to be Solved by the Invention] Even if ESR is performed with Mg contained in the electrode, the basic composition of the slag and the appropriate amount of Mg O to be added to this slag are not clarified. There was a problem in that it was impossible to precisely control the Mg content therein.

However, in the present invention, a desired amount of Mg is contained in the electrode during the secondary melting by VIM, VOD, etc., and in the ESR of the secondary melting, the Mg content in the electrode is directly converted into E.
The purpose is to incorporate it into the SR ingot.

[Means for Solving the Problems] The present invention is intended to solve the above-mentioned problems, and its specific means is to reduce the weight when melting a Ni-Cu base alloy ingot containing a trace amount of Mg. On a % basis, Ca F2
40-65%, CaO20-35%, A120.15-
0.5% MgO in slag mainly composed of 25%
~1.5% is added and electroslag remelting is performed to produce an ingot.

[Function] By changing the amount of MgO added to the slag whose basic composition is CaF2-CaO-A1203, C (15 to 20%, TiO, 1 to 1.0%) on a weight percent basis.
, AIo, 5-7.0%, C095% or less, ZrO, 1
% or less, Mg 0.1% or less, and the balance is Ni, by measuring the Mg content in the obtained ingot using ESRL, and the relationship shown in Figure 1. I got it. In Figure 1, slag A has high CaO and low A1□
01 composition system, and the yield of Mg is rapidly improved only by adding a small amount of Mg 2 O. This slag has a low melting point, and the skin of the ingot obtained using this slag is good, but even if the amount of MgO added to the slag is slightly changed, the Mg yield fluctuates greatly. Furthermore, it is difficult to control the Mg yield.

Slag C has a medium CaO, low AlgOs composition system,
Unless a large amount of MgO is added, a high yield of Mg in the ingot cannot be obtained.This slag also has a low melting point, but Mg
If a large amount of Mg 2 O is added in order to obtain a high yield of g, there is a drawback that the ingot surface deteriorates.

In addition, slag D has a low Ca Ll and high A12 Os composition system, and even if a large amount of Mg O is added, a high yield of Mg cannot be obtained, and the melting point of the slag also becomes high. It has the disadvantage that the skin deteriorates significantly.

For these slags A, C, and D, 1. , slag B is C
a F240-65%, CaO20-35%, A1□0
, 15-25% as the basic composition, and 0.5-1.5% as the basic composition.
If %MgO is added, the Mg yield will be approximately 10%.
0%, and since the melting point of slag B is relatively low,
The skin of the ingot is also good.

Next, CaF2, CaOl and Al2 in the slag
The reason for limiting the composition range of O3 will be described.

First, if the content of CaF2 is less than 40%, the fluidity of the slag will deteriorate, and if it exceeds 65%, the content of A1203 must be reduced, which will reduce heat generation and cause the ingot skin to deteriorate. Since this would result in defects, the amount of Ca Fz in the slag was limited to a range of 240 to 60%.

If CaO is less than 20%, the Mg yield will be poor, and if it exceeds 35%, the Mg yield will be too good and it will be difficult to control the Mg yield. It was limited to a range of 35%.

When the amount of Alz O3 blended is less than 15%, the heat generation decreases to J
,=, 4;
The blending amount of lz 03 was limited within the range of 15 to 25%.

[Example] An electrode for ESR was produced by primary melting of a Ni-Cu-based alloy containing a trace amount of Mg.

This electrode, 50% Ca F, -30% Ca O-2
Using slag with 1% MgO added to the basic composition of 0% A1203, E of 260 mmφ and 600 mn + $
The SR ingot was melted.

Table 1 shows the Mg content of the electrodes used and the ESR ingots produced. In either case, the yield of Mg transferred from the electrode to the ingot was close to 100%, and the skin of the obtained ingot was also extremely good, and there were no problems in the subsequent forging process. [Effect] As described above, according to the present invention, it is possible to incorporate a small amount of Mg added into the ESR ingot at a high yield in order to improve the hot workability of the Ni-Cu alloy. Therefore, the forgeability of the obtained ingot is also extremely good.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the yield of Mg in an ESR ingot when Mg O is added to Ca Fz -Ca O-Ab 03 system slag. List of symbols in the diagram A: Slag A B: Slag B C: Slag C D: Slag D

Claims (1)

[Claims] When melting an ingot of Ni-Cu-based alloy containing a small amount of Mg, CaF_240 to 65% on a weight percent basis,
M is characterized by adding 0.5 to 1.5% of MgO to slag whose basic composition is 20 to 35% of CaO and 315 to 25% of Al_2O_3, and redissolving the electroslag.
A method for producing a g-containing Ni-Cu-based alloy ingot.