1. A production method of high-temperature alloy is characterized by adopting VIM-VAR-VAR production process, and specifically comprises the following steps:

the method comprises the following steps: pouring an electrode by adopting a conventional vacuum induction melting VIM procedure to obtain an electrode E1;

step two: the first vacuum arc remelting VAR process is carried out, wherein an electrode E1 is dried after being polished or shot-blasted by a grinding wheel, and is welded with an auxiliary electrode after being dried, the first vacuum arc remelting VAR process is started, and in the vacuum arc remelting VAR process: the large filling ratio is adopted, namely the diameter of the electrode E1/the diameter of the crystallizer is 0.8-0.85; setting the melting speed (kg/min) = 1.5-2 times of the diameter (dm) of the crystallizer; the arc length is controlled to be 10-15mm by selecting the droplet short-circuit level to be 6-10 and setting the droplet short-circuit parameter to be 1.5-2.5ms or 3-6 Hz; the electrode E2 is obtained without a hot top sealing process;

step three: and a second vacuum arc remelting VAR step of turning the electrode E2 on a lathe and welding the electrode E2 to an auxiliary electrode, wherein: the diameter of the electrode E2/the diameter of the crystallizer is 0.7-0.75; setting the melting speed (kg/min) = 0.6-0.72 of the diameter (dm) of the crystallizer; the arc length is controlled to be 6-8mm by selecting the droplet short-circuit level from 0-3 and setting the droplet short-circuit parameter to be 0.2-0.5ms or 12-15 Hz; and carrying out a hot top sealing process to obtain the final target product.

2. The method for producing a superalloy according to claim 1, wherein the electrode E2 obtained in step two is cooled in the mold under vacuum for more than 3 hours before being demolded.

3. The method for producing a superalloy as in claim 1, wherein in the second step, the electrode E1 and the auxiliary electrode are welded outside the furnace, and the shrinkage cavity of the electrode E1 faces downward during welding.

4. The method for producing the high-temperature alloy according to claim 1, wherein the electrode E2 and the auxiliary electrode are welded outside the furnace in the third step, the shrinkage cavity of the electrode E2 faces upwards during welding, and a gap with the welding length of 5-10% is left at the welding position of the electrode E2 and the auxiliary electrode.

5. The method for producing a superalloy as in claim 1, wherein the electrode in step three, E2, is required to have a single side finishing thickness of 8-12 mm.

6. A high-temperature alloy production method as claimed in claim 1 or 4, characterized in that in the third step, stirring coils are arranged at the bottom and the top of the crystallizer, the height of the stirring coil is the same as the diameter of the crystallizer, and the stirring coils are used for additional stirring when the depth of a molten pool is less than half of the diameter of the crystallizer in the processes of arc starting and hot topping, and the stirring process parameters are as follows: the magnetic field intensity is 50 gauss, the current is 20-40A, and clockwise and anticlockwise alternate every 5 min.

Background

The high-quality high-performance high-temperature alloy is mainly used in the fields of aerospace, nuclear power, energy and chemical engineering and the like, with the continuous increase of the use temperature, the alloy elements such as Ti, Al, Nb and the like in the high-temperature alloy are continuously increased, the high-quality high-temperature alloy at present adopts Vacuum Induction Melting (VIM) -electroslag remelting (ESR) -Vacuum Arc Remelting (VAR), namely a commonly-known triple process, wherein the last VAR is a key process for determining the metallurgical quality of a high-temperature alloy ingot, and due to the inherent characteristic of the VAR, an ingot crown is generated at the top end of a consumable ingot due to the splashing of metal liquid drops. The ingot crown is composed of volatile matters, splashed metal particles and the like, and the height is 50-100 mm or even higher along with the difference of the arc length and the electrode gas release degree. There was also more spatter on the side of the molten end of the VAR electrode, and there was also a protrusion (Torus) at the very bottom of the side, the length of the protrusion being about 10mm and the height being about 5 mm. In the actual vacuum consumable smelting process, due to reasons of smelting splashing, unstable electric arc, branch-crystal spacing, uneven melting of dendrite stems and the like, abnormal melts such as splashed objects, dendrites, ingot crowns, bulges, shelves and the like can fall into a molten pool. These drops may fall into the bath and the surface may adhere to volatiles on the walls of the crystallizer, or oxides or other inclusions on the surface of the bath. Because the falling object has a lower temperature and a density higher than that of the liquid state of the molten pool, the falling object gradually falls to the bottom of the molten pool. Since the molten pool has a certain degree of superheat after the drop falls into the molten pool, it appears that the thinner portion and the peripheral portion of the drop melt first, and then the Nb-rich interdendritic low-melting phase (Laves phase) melts preferentially. If the degree of superheat is low, the drop will not melt sufficiently completely, leaving a higher melting point fraction with a slightly lower overall Nb content. The Nb content is slightly low, so that the quantity of delta phase is small, the dissolution temperature is low, the crystal grain growth cannot be effectively inhibited in the hot working process, the crystal grain size is large, and the crystal grain presents bright white in the macroscopic corrosion process.

With the development of the domestic and foreign aviation industry, the requirements for white spot inspection are becoming stricter and stricter from the viewpoint of aviation flight safety. Particularly, the dirty and white spot defect is easy to become a fatigue crack source in the using process of the engine. Therefore, innovative methods are required to reduce the probability of white spots generation and even to completely solve the white spot problem.

From the current retrieval information, the analysis of the formation mechanism of the dirty white spot and the detection thereof are mainly concerned, such as documents of cause research on white spot defects in the vacuum arc remelting process of the high-temperature alloy, ultrasonic inspection on black spots and white spot segregation in GH169 alloy parts, research and development on several important problems in the production process of deformed high-temperature alloys, and the like.

Based on the mechanism analysis of the generation of the white spots, the current triple process has the following defects:

(1) in order to improve the compactness and promote the VAR stability of the VIM vacuum-treated electrode, ESR is added in the middle, and the ESR can cause the increase of N, O content in a high-temperature alloy ingot, subcutaneous inclusions/slag inclusions and the like, so that the stability of a subsequent VAR arc can be influenced, and the white spot occurrence probability is increased.

(2) In the last VAR process, in order to solve the black spot and white spot defects, a large filling ratio (referring to the diameter ratio of the electrode to the crystallizer), a low melting speed, a shallow molten pool and the like are needed, which causes that splashes and condensed shells which are knocked off by the electric arc cannot be melted in time after falling into the molten pool, and the situation of considering the defects is often caused.

Disclosure of Invention

In order to effectively solve the problem of white spots and dirt of high-quality high-performance high-temperature alloy, the invention adopts the following technical scheme:

the whole process flow is adjusted from the traditional VIM-ESR-VAR to VIM-VAR-VAR, the high-temperature alloy is always smelted or remelted in a vacuum environment in the whole ingot manufacturing stage, and the content of N, O in the whole process flow is ensured to be stably reduced. The specific technical scheme is as follows:

a production method of high-quality high-temperature alloy adopts a VIM-VAR-VAR production process, and specifically comprises the following steps:

the method comprises the following steps: pouring an electrode by adopting a conventional vacuum induction melting VIM procedure to obtain an electrode E1;

step two: in the first vacuum arc remelting VAR process, an electrode E1 is ground by a grinding wheel or dried after shot blasting, and is welded with an auxiliary electrode (also called a false electrode) after being dried, and in the process, a large filling ratio is adopted, and the diameter of the electrode E1/the diameter of a crystallizer is 0.8-0.85; setting the melting speed (kg/min) = 1.5-2 times of the diameter (dm) of the crystallizer; the arc length is controlled to be 10-15mm by selecting the droplet short-circuit level to be 6-10 and setting the droplet short-circuit parameter to be 1.5-2.5ms or 3-6Hz, and conventional heat sealing is not needed in the working procedure, so that the electrode E2 is obtained. After the smelting is finished, the electrode E2 needs to be cooled in a crystallizer for more than 3 hours under the vacuum condition, and the mold can be demolded in a breaking way. In this step, there is no fear of black spot defects under high melting speed conditions, because this problem can be solved in the next second vacuum arc remelting VAR step, in which inclusions/inclusions in the electrode are discharged to the edge skull, gas is effectively removed by conditions such as high-temperature arc, vacuum environment, deep molten pool, etc., and the inclusions/inclusions remaining in the vacuum induction melting VIM step are discharged to the edge of the electrode (ingot) obtained in the first vacuum arc remelting VAR step by the flow of the molten pool from the center to the edge. The process does not need heat capping, because the process is one of the whole production processes, the obtained electrode E2 is an unfinished product, even if the electrode E2 has a shrinkage defect, the problem can be overcome by the next second vacuum arc remelting, and the process does not need heat capping, so that the power consumption can be reduced, the production cost and time can be saved, and the production efficiency can be improved.

Step three: the second vacuum arc remelting VAR process is to obtain good solidification quality, avoid the generation of black spots and point deviation and enable a solidified shell which falls off occasionally to be dissolved in a molten pool, and the process adopts the following technical means: firstly, peeling the surface of an electrode E2, wherein the thickness of a unilateral vehicle is 8-12mm, so as to remove inclusions/slag inclusions discharged at the position during first vacuum arc remelting, no flat head is needed at the end part of the electrode E2, then the electrode E2 is welded with an auxiliary electrode, the shrinkage cavity of the electrode E2 faces upwards during welding, and a gap with the welding length equal to 5-10% is left at the welding position of the electrode E2 and the auxiliary electrode for discharging gas in the shrinkage cavity; the filling ratio in this step is required to be 0.7 to 0.75 for the diameter of the electrode E2/the diameter of the mold; setting the melting speed (kg/min) to be 0.6-0.72 of the diameter (dm) of the crystallizer; the arc length is controlled to be 6-8mm by selecting the droplet short-circuit level from 0-3 and setting the droplet short-circuit parameter to be 0.2-0.5ms or 12-15 Hz; and the heat capping process refers to a conventional process flow to obtain a final target product. In the process, stirring coils are arranged at the bottom and the top of the crystallizer, the height of each stirring coil is the same as the diameter of the crystallizer, and the stirring coils are used for extra stirring when the depth of a molten pool is less than half of the diameter of the crystallizer in the processes of arc starting and hot top sealing so as to promote splashing or skull melting falling into the molten pool, and stirring parameters are as follows: the magnetic field intensity is 50 gauss, the current is 20-40A, and clockwise and anticlockwise alternate every 5 min.

In the second step, the electrode E1 and the auxiliary electrode are welded outside the furnace, and the shrinkage cavity of the electrode E1 faces downwards during welding.

In the third step, the electrode E2 and the auxiliary electrode are welded outside the furnace, the shrinkage cavity of the electrode E2 faces upwards during welding, and a gap with the welding length of 5-10% is required to be reserved at the welding position of the electrode E2 and the auxiliary electrode.

In the third step, stirring coils are arranged at the bottom and the top of the crystallizer, the height of each stirring coil is the same as the diameter of the crystallizer, the stirring coils are used for additional stirring in the arc striking period and the hot top sealing process when the depth of a molten pool is less than half of the diameter of the crystallizer, and the stirring parameters are as follows: the magnetic field intensity is 50 gauss, the current is 20-40A, and clockwise and anticlockwise alternate every 5 min.

The technical principle of the invention is as follows: based on the formation mechanism of dirty and white spots, the existing non-vacuum smelting process flow of the intermediate process is replaced by three vacuum smelting of the whole special metallurgy flow, two vacuum arc remelting VAR processes are creatively adopted after the traditional vacuum induction smelting, the first vacuum arc remelting VAR process and the second vacuum arc remelting VAR process are matched with each other, the filling ratio is set based on different stages, the arc length, the smelting speed and the like are controlled, specifically, the first vacuum arc remelting VAR process adopts a large filling ratio, a high melting speed and a longer arc length to discharge impurities/slag inclusions in electrodes to the edge skull, gas is effectively removed, the impurities/slag inclusions remained in the VIM are discharged to the edge of an ingot obtained by the process through the flow of a molten pool from the center to the edge, and the black spot defect under the high melting speed condition is not needed to worry in the process, because the problem can be solved in the next second vacuum arc remelting VAR procedure, the second vacuum arc remelting VAR procedure adopts a small filling ratio, a low melting speed and a shorter arc length to overcome the black spot defect caused by the first vacuum arc remelting VAR procedure and ensure the production quality of the procedure. The whole production process is carried out under the vacuum condition, thereby avoiding the oxidation and pollution in the traditional triple process.

The beneficial technical effects of the invention are as follows: the method reduces the burning loss and oxidation of endogenic inclusions of the electrode and elements such as aluminum, titanium and the like in the intermediate process, further improves the purity of a high-temperature alloy molten pool, reduces the probability of a skull being hit by an electric arc and falling into the molten pool, and realizes the effective control of metallurgical defects such as black spots, white spots and the like of the high-quality high-temperature alloy.

Detailed Description

Example 1

Production of high-temperature alloy GH738 high-quality ingot for aircraft engine turbine disc

Firstly, casting VIM electrode according to conventional VIM procedure to obtain electrode E1, E1 with diameter phi 310 mm.

And secondly, a VAR process is carried out in a first vacuum arc remelting process, an electrode E1 is polished by a grinding wheel and then dried, an electrode E1 and an auxiliary electrode are welded outside the furnace, the shrinkage cavity of the electrode E1 faces downwards during welding, the size of a crystallizer is phi 375mm, the melting speed is 7.5kg/min, the level of molten drop short circuit is 8, the parameter of molten drop short circuit is set to be 2.5ms, the vacuum degree is less than 0.1Pa, the gas leakage rate is less than 0.5Pa/min, direct electrification and arc striking are carried out, heat sealing top is not carried out, power is cut off when 30-50kg of the electrode E1 remains, and the electrode E2 is obtained after 4 hours of breaking.

And thirdly, performing a second vacuum arc remelting VAR process, polishing the electrode E2 to the normal temperature by using a lathe, polishing the single side by 10mm, then welding the electrode E2 by using a shrinkage cavity facing upwards (namely the shrinkage cavity of the electrode E2 is in butt joint with an auxiliary electrode), reserving a gap in a welding seam by 20mm, ensuring the diameter of the electrode E2 to be 350mm, ensuring the specification phi of the crystallizer to be 500mm, and assembling a stirring coil with the height of 500mm at the upper part and the lower part of the crystallizer. The melting speed is 3.2kg/min, the molten drop short circuit level is 2, the molten drop short circuit parameter is set to be 0.3ms, the vacuum degree is less than 0.1Pa, the air leakage rate is less than 0.5Pa/min, the arc is started when the power is on, the molten pool depth is less than half of the diameter of the crystallizer after the weight (namely the weight of a finished product ingot) of the electrode E2 which is molten reaches 80kg, and the stirring coil is started, and the stirring parameter is as follows: the magnetic field intensity is 50 gauss, the current is 20A, clockwise and anticlockwise alternate every 5min, and the stirring is stopped after entering a steady-state melting speed control stage. The hot topping process was performed when 150kg remained for electrode E2, and the stirring control was turned on again, with stirring parameters: the magnetic field intensity is 50 gauss, the current is 20A, clockwise and anticlockwise alternate every 5min, the power is cut off when 40kg of the electrode E2 is remained, and the final product is obtained after the air is broken and the mold is removed after 1 h. And forging and polishing, and adopting low-power inspection and water immersion flaw detection to find out that the finished product ingot has no white spot or black spot metallurgical defects.

Example 2

Large-size turbine disk high-temperature alloy GH4169 high-quality ingot production for large gas turbine

In the first step, VIM electrode E1 was cast according to the conventional VIM procedure, electrode E1 diameter was phi 450 mm.

And secondly, performing a VAR (vacuum arc remelting) process for the first time, performing shot blasting on an electrode E1, drying, welding an electrode E1 and an auxiliary electrode outside the furnace, setting the shrinkage cavity of the electrode E1 to be downward during welding, setting the specification of a crystallizer to be phi 530mm, the melting speed to be 9kg/min, the level of molten drop short circuit to be 10, setting the molten drop short circuit parameter to be 2ms, setting the vacuum degree to be less than 0.1Pa, setting the gas leakage rate to be less than 0.5Pa/min, directly electrifying for arcing, not performing heat seal capping, cutting off power when 50-80kg of the electrode E1 remains, and breaking the electrode E2 after 4 hours.

And thirdly, performing a second vacuum arc remelting VAR process, wherein the specification of the crystallizer is 700mm, the diameter of an electrode E2 is 500mm, after the electrode E2 is cooled to the normal temperature, turning by a lathe is adopted, the thickness of a single-side turning is 12mm, then welding is performed by adopting a mode that a shrinkage cavity faces upwards (namely the shrinkage cavity of the electrode 2 is butted with an auxiliary electrode), a gap is reserved in a welding seam by 40mm, and a stirring coil with the height of 700mm is assembled at the upper part and the lower part of the crystallizer. The melting speed is 4kg/min, the molten drop short circuit level is 0, the molten drop short circuit parameter is set to be 0.1ms, the vacuum degree is less than 0.1Pa, the air leakage rate is less than 0.5Pa/min, the molten pool depth is less than half of the diameter of the crystallizer after the weight (namely the weight of a finished product ingot) of the electrified arcing electrode E2 which is melted reaches 150kg, a stirring coil is started, and the stirring parameter is as follows: the magnetic field intensity is 50 gauss, the current is 20A, clockwise and anticlockwise alternate every 5min, and the stirring is stopped after entering a steady-state melting speed control stage. The top heat sealing process was performed when 300kg remained on electrode E2, and the stirring control was turned on again, with the stirring parameters: the magnetic field intensity is 50 gauss, the current is 20A, clockwise and anticlockwise alternate every 5min, the power is cut off when 80kg of the electrode E2 is remained, and the final product is obtained after the air is broken and the mold is removed after 1 h. And forging and polishing, and adopting low-power inspection and water immersion flaw detection to find out that the finished product ingot has no white spot or black spot metallurgical defects.