CN111187929A

CN111187929A - Method for denitrifying nickel-based superalloy

Info

Publication number: CN111187929A
Application number: CN202010094540.6A
Authority: CN
Inventors: 王吉孝; 王黎; 马李; 莫才颂; 李柏茹; 黄敏; 王君; 金国
Original assignee: Guangdong University of Petrochemical Technology
Current assignee: Guangdong University of Petrochemical Technology
Priority date: 2020-02-16
Filing date: 2020-02-16
Publication date: 2020-05-22

Abstract

The invention discloses a method for denitrifying nickel-based superalloy, which comprises the steps of selecting smelting raw materials, smelting an Inconel690 alloy ingot by adopting a ZG-0.025 type vacuum induction smelting furnace, and carrying out the following process parameters: vacuumizing to 0.01Pa, and 10-15 kW: 10-20 min; 20-25 kW until melting; refining for 10min under the condition that the vacuum degree is less than or equal to 0.05Pa, and electromagnetically stirring; vacuum lowering, low-power freezing and air releasing, heating again, and repeating for 2-3 times; introducing high-purity argon into the high vacuum, adjusting the temperature, adding deoxidizing elements of silicon, aluminum and volatile element of manganese, electromagnetically stirring, adding microalloying elements of niobium, titanium and molybdenum, and electromagnetically stirring; reducing power, pouring, cooling, taking out the cast ingot, and cutting off a dead head. The process flow of the invention is easy to realize, safe, stable and reliable, and the nitrogen content of the obtained ingot is less than or equal to 10 ppm.

Description

Method for denitrifying nickel-based superalloy

Technical Field

The invention relates to the technical field of nickel-based superalloy denitrification, in particular to a denitrification method of high-vacuum induction melting, a prefabricated calcium oxide crucible and high-purity metal chromium.

Background

The nickel-based alloy has excellent corrosion resistance and high-temperature oxidation resistance, and is often used for equipment with harsh use conditions and high safety requirements. With the continuous and high-speed development of the economy of China, equipment manufacturing has already become the pillar industry of the economy of China, and the outstanding characteristics of the development of the equipment manufacturing industry are as follows: the parameters of the single machine equipment are higher and higher, the use conditions are more and more rigorous, and the requirements on the safety are higher and higher. Welding is a key manufacturing process in modern industry, and the quality of a welded joint is key to ensuring the safety of industrial equipment. In order to meet the increasing performance requirements of large-scale industrial equipment, the domestic demand for nickel-based welding materials is rapidly increased, and at present, the demand for the nickel-based welding materials is increased from 300-400 tons/year ten years ago to 3000-4000 tons/year, and the demand is increased by ten times.

The high sensitivity of welding cracks, the great influence of trace elements on the performance of joints and the high sensitivity of welding pores are important characteristics of nickel-based welding materials and are also technical keys for material development. The main means for solving the technical problems is to strictly control the gas content and the component fluctuation of the welding material and strictly limit the content of impurity elements, namely to develop a high-purity welding material, and technically, vacuum smelting and refining processes (such as AOD, VOD, ESR and the like) are usually adopted. Due to the demand, domestic top-level steel enterprises have the technical capability of producing nickel-based welding materials, do not care about the development of the nickel-based welding materials, and do not have related products; and although a few small-sized enterprises pay attention to the market of the nickel-based welding material, the qualified special nickel-based welding material is difficult to develop due to limited technical strength, so that the existing nickel-based welding material basically depends on import.

Another characteristic of the nickel-based welding material is that the joint quality and the stability of the welding process are closely related, and the technical development trend is that the ratio of automatic welding is higher and higher, which not only requires that the welding material (such as a welding wire) meets the corresponding component requirements, but also requires that the welding wire has excellent process properties, such as the stability of the surface state, the geometric dimension and the physical properties of the welding wire. These requirements place higher demands on the manufacturing process of the welding wire, and new demands on the aspects of the surface roughness control, the surface coating of the welding wire, the wire drawing process and the like are placed. The technology is mastered by a few large international companies, so that products can smoothly enter the Chinese market; there is no related production experience in China, and in order to realize the localization of the nickel-based welding material, the key technology needs to be mastered through development and development.

The harm of nitrogen in the nickel-based alloy is mainly reflected by that: the dissolved nitrogen is precipitated in a gaseous state during the cooling of the molten steel and exists in the steel in a bubble or loose form, thereby destroying the compactness of the steel and causing the macroscopic defect. Nitrogen can form various nitrides in solid steel, such as chromium nitride, aluminum nitride, titanium nitride, and zirconium nitride, as well as the corresponding cyanides, and the like. The presence of these nitrides reduces the plasticity of the alloy, making it brittle. Thereby reducing the processing plasticity and mechanical property of the metal. These nitrides are hard and brittle inclusions, and they do not deform when the metal matrix deforms. Therefore, cracks are easily generated around the nitride, and these cracks develop to cause the metal to break. Nitrogen can reduce the amount of strengthening phases formed in the alloy, thereby reducing the room or high temperature strength of the metal. Especially, the main strengthening phase in the nickel-base high-temperature alloy containing aluminum and titanium is Ni₃Al or Ni₃Ti, the nitrogen in the alloy will cause a portion of the aluminum and titanium to form aluminum nitride and titanium nitride, thereby reducing the amount of strengthening phases and increasing the amount of inclusions, ultimately resulting in a reduction in the thermal strength of the metal. Therefore, the control and reduction of the content of nitrogen elements are the key points of the related technology of vacuum smelting, which is the nickel-based welding material technology, and the method is carried out aiming at the technical problem.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a method for denitrifying nickel-based superalloy, which is used for obtaining a compact alloy ingot with ultra-low nitrogen content.

The invention is realized by the following technical scheme: a method of denitrogenation of a nickel-base superalloy, the method comprising:

(1) selecting smelting raw materials including pure iron, aurora nickel, high-purity metal chromium, metal molybdenum, silicon, electrolytic manganese, metal aluminum, metal niobium and titanium, pickling and derusting the surface of the pure iron, drying the raw materials, and drying the ingot mold, the heat preservation cap and the pouring cup at high temperature;

(2) an Inconel690 alloy ingot is smelted by adopting a ZG-0.025 type vacuum induction smelting furnace, and the process parameters are as follows: vacuumizing to 0.01Pa, and 10-15 kW: 10-20 min; 20-25 kW until melting; refining for 10min under the condition that the vacuum degree is less than or equal to 0.05Pa, and electromagnetically stirring; reducing the vacuum power to 5kW, freezing, deflating, heating again, and repeating for 2-3 times; introducing high-purity argon into the high vacuum, adjusting the temperature, adding deoxidizing elements of silicon, aluminum and volatile element of manganese, electromagnetically stirring, adding microalloying elements of niobium, titanium and molybdenum, and electromagnetically stirring; reducing power, pouring, cooling, taking out the cast ingot, and cutting off a dead head.

The nickel-based superalloy comprises the following chemical component requirements in wt%: c is less than or equal to 0.03, Si is less than or equal to 0.50, Mn is less than or equal to 1.0, P is less than or equal to 0.005, S is less than or equal to 0.005, Cr: 28.0-31.5, Fe: 8.0-12.0, Mo is less than or equal to 0.5, Co is less than or equal to 0.10, Cu is less than or equal to 0.10, Ti is less than or equal to 1.0, Al is less than or equal to 1.1, Nb: 0.5-1.0, others are less than or equal to 0.5, Ni: a base body which is provided with a plurality of grooves,

the high-purity metallic chromium contains nitrogen element which is less than or equal to 0.0015 percent in mass fraction.

The method adopts a prefabricated calcium oxide crucible in the smelting process, high-purity metal chromium (less than or equal to 0.0015 percent by mass) can be subjected to nitrogen reduction greatly, refining is carried out under high vacuum, and further sufficient nitrogen removal is carried out by utilizing the electromagnetic stirring effect and a freezing mode, wherein the nitrogen removal is mainly carried out on the upper surface of the alloy liquid.

The invention has the advantages that:

(1) the special smelting process and the prefabricated calcium oxide crucible are adopted, high-purity metal chromium is used, refining, electromagnetic stirring and freezing treatment are carried out under high vacuum, so that the nitrogen can be greatly removed, and the method plays an important role in obtaining the Inconel690 ultralow-content nitrogen.

(2) The Inconel690 with ultra-low content of nitrogen reduces the amount of nitride inclusions in the ingot and greatly improves the mechanical properties of the nickel-based alloy.

(3) The Inconel690 nickel-based welding material with ultralow nitrogen content can be applied to important fields such as nuclear power and the like, plays a role in promoting domestic welding materials,

(4) the Inconel690 nickel-based alloy denitrification method is relatively low in cost and relatively easy to realize in process, and further plays a reference role in obtaining the ultralow nitrogen content for other nickel-based alloys.

Detailed Description

Example (b):

selecting smelting raw materials comprising pure iron, aurora nickel, high-purity metal chromium, metal molybdenum, silicon, electrolytic manganese, metal aluminum, metal niobium and titanium, pickling and derusting the surface of the pure iron, drying the raw materials and adding the raw materials into a crucible, drying a steel ingot mould, a heat preservation cap and a pouring cup at high temperature and putting the raw materials into a hearth, wherein the nitrogen element contained in the high-purity metal chromium is 0.0012 percent by mass fraction. An Inconel690 alloy ingot is smelted by adopting a ZG-0.025 type vacuum induction smelting furnace, and the process parameters are as follows: vacuumizing to 0.01Pa, 12 kW: 15 min; 22kW until melting; refining at the vacuum degree of 0.05Pa for 10min, and electromagnetically stirring; pre-deoxidizing by using carbon in the raw material; reducing the vacuum power to 5kW, freezing, deflating, heating again, and repeating for 3 times; introducing high-purity argon into the high vacuum, adjusting the temperature, adding deoxidizing elements of silicon, aluminum and volatile element of manganese, electromagnetically stirring, adding microalloying elements of niobium, titanium and molybdenum, and electromagnetically stirring; reducing power, pouring, cooling, taking out the cast ingot, and cutting off a dead head. And removing oxide skin on the surface of the cast ingot by a mechanical processing vehicle to obtain a smooth surface cast ingot, analyzing chemical elements, and finally forging, rolling and drawing the smooth surface cast ingot into a welding wire with a certain specification.

The nitrogen element analysis adopts a thermal conductivity method (national standard GB/T223.82-2007), and the analysis precision is 0.0001% (mass fraction).

The chemical composition of the nickel-base superalloy ingot obtained in this example in wt% (mass fraction) is as follows: n: 0.0008, O: 0.0015, H: 0.0002, C: 0.011, Si: 0.10, Mn: 0.75, P: 0.0016, S: 0.0012, Cr: 29.55, Fe: 9.75, Mo: 0.32, Co: 0.012, Cu: 0.008, Ti: 0.83, Al:0.75, Nb: 0.77, Ni: a substrate.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims.

Claims

1. a method for denitrification of nickel-based superalloys, characterized in that the method comprises:

(1) Selected smelting raw materials, including pure iron, Jinchuan nickel, high-purity metal chromium, metal molybdenum, silicon, electrolytic manganese, metal aluminum, metal niobium and titanium, pure iron surface pickling and rust removal, raw material drying, steel ingot mold And heat preservation and pouring cup high temperature drying;

(2) Use ZG-0.025 vacuum induction melting furnace to smelt Inconel690 alloy ingot, the process parameters are: vacuum to 0.01Pa, 10-15kW: 10-20min; 20-25kW until melting; vacuum degree ≤0.05Pa, refining 10min, electromagnetic stirring; reduce the power to 5kW under vacuum, freeze and deflate, then heat up, repeat 2-3 times; fill high vacuum with high-purity argon, adjust the temperature, add deoxidized elements silicon, aluminum and volatile element manganese, electromagnetic stirring After adding microalloying elements niobium, titanium and molybdenum, electromagnetic stirring; reducing the power, pouring, cooling to take out the ingot, and cutting the riser.

2. The method for denitrification of a nickel-based superalloy as claimed in claim 1, wherein the chemical composition requirements of the nickel-based superalloy in wt% are as follows: C≤0.03, Si≤0.50, Mn≤1.0 , P≤0.005, S≤0.005, Cr: 28.0-31.5, Fe: 8.0-12.0, Mo≤0.5, Co≤0.10, Cu≤0.10, Ti≤1.0, Al≤1.1, Nb: 0.5-1.0, others≤0.5 , Ni: matrix.

3 . The method for denitrification of a nickel-based superalloy according to claim 1 , wherein the nitrogen element contained in the high-purity metal chromium is ≤0.0015% by mass fraction. 4 .