WO2017166960A1

WO2017166960A1 - Vacuum melting process for nickel-based superalloy

Info

Publication number: WO2017166960A1
Application number: PCT/CN2017/074558
Authority: WO
Inventors: 李道乾; 王雷; 刘玉庭; 马中钢; 孙红波
Original assignee: 山东瑞泰新材料科技有限公司
Priority date: 2016-03-30
Filing date: 2017-02-23
Publication date: 2017-10-05
Also published as: CN105734314A; CN105734314B

Abstract

Disclosed is a vacuum melting process for a nickel-based superalloy, comprising: adding graphite accounting for 50% of a total carbon-containing mass of a superalloy into a crucible of a vacuum furnace and placing the graphite at the bottommost portion of the crucible, and adding all elements, except for aluminum, titanium, boron, zirconium, and nickel, in the superalloy into the crucible of the vacuum furnace to be molten; raising the temperature, adding the remaining graphite into the crucible, and carrying out refining and then cooling; adding aluminum and titanium into the crucible, and raising the temperature until the aluminum and the titanium are completely molten; holding the temperature to range from 1410°C to 1430°C, adding a nickel-boron alloy and zirconium into the crucible, and raising the temperature until the nickel-boron alloy and the zirconium are completely molten, thereby obtaining molten metal; and carrying out cooling to freeze the molten metal, raising the temperature, and carrying out tapping and pouring. The process is able to improve the endurance property and the room-temperature tensile property of a superalloy, and a high-quality superalloy can be obtained from purified molten metal.

Description

Vacuum smelting process of nickel base superalloy

Technical field

The invention relates to an alloy smelting process, in particular to a vacuum smelting process of a nickel-based superalloy.

Background technique

The technical difficulty in vacuum smelting of aerospace and civil superalloys is that the gas content (oxygen, nitrogen, hydrogen) in the alloy is strictly controlled. At present, according to the enterprise standard, the oxygen and nitrogen contents of many alloys are generally around 20 ppm. Only by reducing the content of harmful impurities in the alloy, reducing the segregation of alloying elements, and improving the purity of the alloy melt can improve the performance and life of the alloy. However, the vacuum smelting process is a very complicated thermal processing process, and the design of any one process step will have an important influence on the gas content of the alloy, the impurity content and the properties of the alloy.

O, N, S in the alloy will form non-metallic inclusions in the alloy solution, such as (Al ₂ O ₃ ), (Ti, Ta) C / N, the number of non-metallic inclusions in the (Ti, Ta)S alloy Both the form and the form have a major impact on the overall performance of the alloy. In addition, the purity of the alloy melt is an important indicator for measuring the quality and manufacturing level of the master alloy ingot. In vacuum smelting, carbon is the main deoxidizing element. Due to the decomposition reaction of carbon, the oxygen of the metal solution is removed, thereby reducing the gas content in the alloy, purifying the metal solution, and improving the quality of the alloy. As the carbon deoxygenation reaction progresses, the carbon monoxide gas overflows, and the hydrogen and nitrogen harmful gases in the alloy are carried out. The lower the oxygen content, the more easily the metal melt evaporates, and the low melting point harmful impurity elements in the alloy are also easily eliminated. Therefore, deoxidation is a key step in the vacuum smelting process. The deoxidation effect directly determines the content of harmful impurities in the alloy, which determines whether the alloy performance and life can be improved.

In alloys used in aviation, the components generally include several low melting point elements such as aluminum, titanium, boron, and zirconium. When these low-melting-point elements are added for alloying treatment, if the timing, temperature, and degree of vacuum are not strictly controlled, large burning and volatilization occur, and the chemical composition of the alloy is difficult to control, resulting in waste. Specifically, when aluminum, titanium, boron, and zirconium are added, the degree of vacuum is too low or the equipment leak rate is large, and a large amount of aluminum, titanium, boron, and zirconium elements are oxidized and burned, and the composition is difficult to control. When aluminum and titanium are added, the temperature of the molten metal is too high, and a large amount of aluminum and titanium are burnt and volatilized due to the exothermic release. When aluminum or titanium is added to the molten metal, a severe exothermic reaction occurs, and especially when the amount of addition is large, the exothermic reaction of the molten metal is large. Even if the temperature of the molten metal is suitable when aluminum and titanium are added, the chemical composition of the alloy is hard to control because the amount of the primary addition is too large, and the burning and vacuum volatilization are also caused.

In addition, since aluminum, titanium, boron, and zirconium are lighter in themselves and have a small density, after being added to the molten metal, floating on the surface of the molten metal is liable to cause segregation, which seriously affects the overall performance of the alloy. In particular, the addition time of boron is also very important. It is too early to be burned, and it is easy to burn. It is too late to be distributed, so it is very important to master the time of boron addition.

In view of the current state of the art, it is urgent to develop a vacuum smelting process of a nickel-base superalloy having uniform chemical composition, low melting point element burning and low volatilization, long-lasting properties of the alloy and strong tensile properties at room temperature.

Summary of the invention

SUMMARY OF THE INVENTION The object of the present invention is to provide a vacuum smelting process for a nickel-base superalloy having uniform chemical composition, low-melting-point element burning loss and low volatilization, long-lasting properties of the alloy and strong tensile properties at room temperature.

The vacuum smelting process of the nickel-based superalloy according to the present invention comprises the following steps:

(1) First step carbon deoxidation:

Adding 50% of the total carbon content of the superalloy to the vacuum furnace, placing it at the bottom of the crucible, adding all the elements in the superalloy except aluminum, titanium, boron, zirconium and nickel into the vacuum furnace. Smelting;

(2) The second step of carbon deoxidation:

The temperature is raised to 1570 ~ 1590 ° C, the remaining graphite is added to the crucible, refined, and then cooled;

(3) cooling to 1370 ~ 1390 ° C, adding aluminum, titanium, and heating until aluminum and titanium are all melted;

(4) maintaining a temperature of 1410 ~ 1430 ° C, adding nickel boron alloy, zirconium, heating to nickel boron alloy, zirconium all melted to obtain a molten metal;

(5) Cool down, freeze the molten metal, wait until the temperature drops to 1360 ~ 1380 ° C, and then heat up to 1450 ~ 1470 ° C, for tapping.

among them:

Step (1) Graphite is a particle in which the spectral graphite electrode is broken up to 2 to 5 mm.

Step (1) The smelting temperature is 1560 to 1580 ° C, and the smelting time is 20 to 30 min.

Step (2) The temperature of the molten metal is raised to 1570 to 1590 ° C, and the remaining graphite is added to the crucible, and refined at a power of 80 KW for 20 to 30 minutes.

Step (3) is heated until aluminum and titanium are all melted, and then stirred for 3 to 5 minutes.

Step (4) is heated until the nickel-boron alloy and zirconium are all melted, and then stirred for 3 to 5 minutes.

The degree of vacuum when adding aluminum, titanium, nickel boron alloy, or zirconium is ≤ 0.1 Pa. Boron should be added in the late stage of smelting before tapping. When aluminum and titanium are added in a large amount, they should be added in two or more batches. When aluminum is about 3 wt.%, and titanium is about 3 wt.%, it can be added twice. If more aluminum and titanium content should be considered, more times should be added.

Step (5) Cooling the molten metal melt can be in the form of natural cooling after power failure, and other cooling forms can also be used. The invention preferably takes the form of a natural cooling of power outages.

The beneficial effects of the present invention are as follows:

The invention adopts a secondary carbon deep deoxidation process to add one-half of the total carbon content of the alloy before the start of the high-temperature alloy smelting, and the graphite is added to the bottom of the crucible. After the metal is completely melted, it is raised to a certain temperature, and subjected to a secondary carbon addition operation to further perform deep deoxidation. At the same time, by controlling the timing and temperature of the addition of aluminum, titanium, boron, and zirconium, the chemical composition of the alloy is more uniform, and the low melting point element is burned. And less volatile; the frozen metal melt dissolves in the process of cooling and solidifying the molten metal The harmful gas in the molten metal floats up, and the harmful gas is further removed by the negative pressure difference generated by the vacuum furnace smelting. The invention can improve the long-term performance and the room temperature tensile property of the high-temperature alloy, further purify the molten metal, thereby obtaining a high-quality high-temperature alloy, and also ensuring the maximum reduction of the O, N, H harmful gas content and the low melting point in the high-temperature alloy. The content of harmful impurities reaches the pure alloy melt, reduces the segregation of alloying elements, and ensures the performance of the alloy. The comprehensive mechanical properties of the alloy and the quality of the alloy have reached the level of high-quality alloys at home and abroad.

detailed description

The invention will be further described below in conjunction with the embodiments.

Example 1

According to the standard of B1914 alloy, the vacuum smelting process of the present invention is used for production, and the chemical composition and performance parameters thereof are shown in Table 1.

Taking a 200 Kg vacuum furnace as an example, the vacuum smelting process of the present invention is as follows:

(1) First step carbon deoxidation:

Adding 50% of the total carbon content of the superalloy to the vacuum furnace, placing it at the bottom of the crucible, adding all the elements in the superalloy except aluminum, titanium, boron, zirconium and nickel into the vacuum furnace. Smelting; graphite is a graphite electrode crushed to 2 ~ 5mm particles; smelting temperature 1570 ± 10 ° C, smelting time 25min;

(2) The second step of carbon deoxidation:

The temperature was raised to 1580±10 ° C, and the remaining graphite was added into the crucible, and refined at a power of 80 KW for 25 min, and then cooled;

(3) cooling to 1380 ± 10 ° C, adding aluminum, titanium, heating to aluminum, titanium all melted, and then stirred for 5 min;

(4) maintaining a temperature of 1420 ± 10 ° C, adding nickel-boron alloy, zirconium, heating to nickel-boron alloy, zirconium all melted, and then stirred for 3min, to obtain a molten metal;

(5) Cooling the molten metal, and the temperature is lowered to 1370±10 °C, and then the temperature is raised to 1460±10 °C, and the tapping is performed.

The degree of vacuum when adding aluminum, titanium, nickel boron alloy, or zirconium is ≤ 0.1 Pa.

Table 1 Example 1 alloy composition performance parameter table

It was measured by a German imported ON900 type oxygen nitrogen analyzer: oxygen (O) 7.6 ppm nitrogen (N) 8.06 ppm.

Example 2

According to the standard of B1914 alloy, the vacuum smelting process of the present invention is used for production, and the chemical composition and performance parameters thereof are shown in Table 2.

(1) First step carbon deoxidation:

Adding 50% of the total carbon content of the superalloy to the vacuum furnace, placing it at the bottom of the crucible, adding all the elements in the superalloy except aluminum, titanium, boron, zirconium and nickel into the vacuum furnace. Smelting; graphite is broken by spectral graphite electrode to 2 ~ 5mm particles; smelting temperature is 1580 ± 10 ° C, smelting time 20min;

(2) The second step of carbon deoxidation:

The temperature was raised to 1590±10 ° C, and the remaining graphite was added into the crucible, and refined at a power of 80 KW for 20 min, and then cooled;

(3) cooling to 1390 ± 10 ° C, adding aluminum, titanium, heating to aluminum, titanium all melted, and then stirred for 3 min;

(4) maintaining a temperature of 1410 ± 10 ° C, adding nickel boron alloy, zirconium, heating to nickel boron alloy, zirconium all melted, and then stirred for 5 min, to obtain a molten metal;

(5) Cooling the molten metal melt, and the temperature is lowered to 1380±10 °C, and then the temperature is raised to 1470±10 °C, and the tapping is performed.

The degree of vacuum when adding aluminum, titanium, nickel boron alloy, or zirconium is ≤ 0.1 Pa. The rest is as in Example 1.

Table 2 Example 2 alloy composition performance parameter table

It was measured by a German imported ON900 type oxygen nitrogen analyzer: oxygen (O) 8.2 ppm nitrogen (N) 8.07 ppm.

Example 3

(1) First step carbon deoxidation:

Adding 50% of the total carbon content of the superalloy to the vacuum furnace, placing it at the bottom of the crucible, adding all the elements in the superalloy except aluminum, titanium, boron, zirconium and nickel into the vacuum furnace. Smelting; graphite is broken by spectral graphite electrode to 2 ~ 5mm particles; smelting temperature is 1560 ± 10 ° C, smelting time 30min;

(2) The second step of carbon deoxidation:

The temperature was raised to 1570±10°C, and the remaining graphite was added into the crucible, and refined at a power of 80 KW for 30 min, and then cooled.

(3) cooling to 1370 ± 10 ° C, adding aluminum, titanium, heating to aluminum, titanium all melted, and then stirred for 4 min;

(4) maintaining a temperature of 1430 ± 10 ° C, adding nickel boron alloy, zirconium, heating to nickel boron alloy, zirconium all melted, and then stirred for 4 min, to obtain a molten metal;

(5) Cooling the molten metal, and the temperature is lowered to 1360±10 °C, and then the temperature is raised to 1450±10 °C, and the tapping is performed.

Table 3 Example 3 alloy composition performance parameter table

It was measured by a German imported ON900 type oxygen nitrogen analyzer: oxygen (O) 7.9 ppm nitrogen (N) 8.05 ppm.

It can be seen from Table 1-3 that the content of oxygen and nitrogen in the B1914 alloy is very low. Due to the secondary carbon deep deoxidation process, the alloying process and the frozen metal melt process, the content of other harmful impurities in the alloy is significantly reduced. The most prominent is that the alloy's room temperature tensile properties and long-lasting properties are greatly improved.

Claims

A vacuum smelting process for a nickel-based superalloy characterized by the following steps:

(1) First step carbon deoxidation:

Adding 50% of the total carbon content of the superalloy to the vacuum furnace, placing it at the bottom of the crucible, adding all the elements in the superalloy except aluminum, titanium, boron, zirconium and nickel into the vacuum furnace. Smelting;

(2) The second step of carbon deoxidation:

The temperature is raised to 1570 ~ 1590 ° C, the remaining graphite is added to the crucible, refined, and then cooled;

(3) cooling to 1370 ~ 1390 ° C, adding aluminum, titanium, and heating until aluminum and titanium are all melted;

(4) maintaining a temperature of 1410 ~ 1430 ° C, adding nickel boron alloy, zirconium, heating to nickel boron alloy, zirconium all melted to obtain a molten metal;

(5) Cool down, freeze the molten metal, wait until the temperature drops to 1360 ~ 1380 ° C, and then heat up to 1450 ~ 1470 ° C, for tapping.
The vacuum smelting process for a nickel-based superalloy according to claim 1, wherein the graphite in the step (1) is a particle of a graphite electrode crushed to 2 to 5 mm.
The vacuum smelting process of the nickel-base superalloy according to claim 1, characterized in that the step (1) smelting temperature is 1560 to 1580 ° C, and the smelting time is 20 to 30 min.
The vacuum smelting process of the nickel-base superalloy according to claim 1, wherein the temperature of the molten metal in the step (2) is raised to 1570 to 1590 ° C, and the remaining graphite is added into the crucible, and refined at a power of 80 KW. 30min.
The vacuum smelting process of the nickel-base superalloy according to claim 1, wherein the step (3) is heated until the aluminum and the titanium are all melted, and then stirred for 3 to 5 minutes.
The vacuum smelting process of the nickel-based superalloy according to claim 1, wherein the step (4) is heated until the nickel-boron alloy and the zirconium are all melted, and then stirred for 3 to 5 minutes.
The vacuum smelting process for a nickel-based superalloy according to any one of claims 1 to 6, characterized in that the degree of vacuum when aluminum, titanium, nickel boron alloy and zirconium are added is ≤ 0.1 Pa.