Patent Application
20210371963
The invention relates to a method for the manufacture of a nickel-base alloy.
EP 1 377 690 B1 discloses a method for the manufacture of a nickel-base superalloy, which is substantially free of positive and negative segregation, wherein the method comprises the following:
The nickel-base alloy preferably relates to alloy 718 or alloy 706.
It is generally known that heat treatments in the higher temperature range (e.g. 500-1250° C.) may be used in order to homogenize increases and to relieve stresses in the material.
The task of the invention is to provide an alternative, more inexpensive method for the manufacture of a nickel-base alloy, by means of which an improvement of the microstructure as well as a reduction of the defects introduced into the material during the last remelting step is possible, in order to do justice to future customer requirements. Compared with the method disclosed in EP 1 377 690 B1, costs incurred by complex process control between the first and the second remelting are to be avoided. And the quality is to be significantly improved by avoiding defects induced by melting and remelting.
This task is accomplished by a method for the manufacture of a nickel-base alloy in which
Advantageous further developments of the method according to the invention (e.g. further steps of remelting by VAR) can be inferred from the dependent claims.
Compared with the prior art, the heat-treatment step following remelting by ESR is eliminated and the remelting rate is specified more precisely. Thus the heat treatment takes place exclusively on the basic electrode and not, as described in the prior art, on the ESR ingot. The material generated in this way has a much lower content of remelting-induced defects.
Due to the selective heat treatment of the VIM ingot, internal stresses are relieved and segregation defects are eliminated. This acts positively on the subsequent remelting steps of ESR and VAR.
This task is preferably also accomplished by a method for the manufacture of a nickel-base alloy in which
It may be of advantage if the electrode is subjected prior to its first remelting to a machining of the surface (e.g. by brushing, grinding, pickling, cutting, scalping, etc.). In the process, defects may be removed that are not eliminated by the further remelting and that may cause impairment for subsequent applications.
According to a further idea of the invention, the ESR ingot is subjected prior to its VAR remelting to a further machining of the surface (e.g. by brushing, grinding, pickling, cutting, scalping, etc.), wherein it is also possible in the process to remove defects that cannot be eliminated by the further remelting.
According to a further idea of the invention, a remelting by VAR is performed directly instead of the remelting by ESR.
This method can be applied to any Ni alloy and in particular to alloys according to Table 1.
In the following, an alloy composition is presented that may be produced by means of the process parameters according to the invention. All values are in wt %:
and manufacturing-related impurities.
As well as, optionally (values in wt %):
Advantageously, the following elements may be adjusted as shown below (values in wt %):
In the following, an example of an alloy on the basis of alloy 718 is presented (values in wt %):
Alternatively, this alloy may also have higher Ni contents.
As well as, optionally (values in wt %):
Further restrictions are conceivable such as below (values in wt %):
As well as, optionally if necessary (values in wt %):
Mo 8-10
In the following, an example of an alloy on the basis of alloy 780 is presented (values in wt %):
Material manufactured by this fabrication process usually has significantly fewer defects (50%) having comparison defect size of 0.8 mm in an ultrasonic inspection.
The method according to the invention is intended to be usable preferably for the following alloys:
As examples, Table 1 shows ranges of analysis of the aforementioned alloys.
Ingot formats >400 mm (round and polygonal) are achieved.
The VIM, ESR and VAR ingots may also be forged to electrode dimension, in order to create better homogeneity, as may be necessary depending on alloy and ingot diameter.
The hot forming to the required product shape and dimension may be carried out by the usual methods (forging, rolling, etc.).
The ingots and bars fabricated according to this method may be further fabricated further to semi finished product forms (bars, sheets, strips, foils, wires, etc.) with conventional methods.
By way of example, the method according to the invention is explained as follows:
Several heats, e.g. S3 and S4, were fabricated with the method according to the invention.
All heats (both those according to the invention and the comparison heats) were fabricated according to the analysis reports of alloy 718 (see Table 1).
The deviations from the chosen remelting rates that occurred during fabrication are shown in FIGS. 1 to 4.
Deviations of the remelting rate occurred up to the following levels.
VIM Vacuum Induction Melting
VOD Vacuum Oxygen Decarburization
VLF Vacuum Ladle Furnace
ESR Electroslag Remelting
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2017 128 663.2 | Dec 2017 | DE | national |
| 10 2018 009 375.2 | Nov 2018 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/DE2018/100980 | 12/3/2018 | WO | 00 |
