CN116904776A - Control method for cracking defect of high-alloying nickel-based deformation superalloy phi 508mm cast ingot - Google Patents
Control method for cracking defect of high-alloying nickel-based deformation superalloy phi 508mm cast ingot Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 57
- 238000005336 cracking Methods 0.000 title claims abstract description 29
- 229910000601 superalloy Inorganic materials 0.000 title claims abstract description 24
- 230000007547 defect Effects 0.000 title claims abstract description 18
- 238000005275 alloying Methods 0.000 title abstract description 13
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 title description 9
- 229910052759 nickel Inorganic materials 0.000 title description 5
- 238000003723 Smelting Methods 0.000 claims abstract description 96
- 239000000956 alloy Substances 0.000 claims abstract description 50
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 49
- 238000007711 solidification Methods 0.000 claims abstract description 35
- 230000008023 solidification Effects 0.000 claims abstract description 35
- 239000002893 slag Substances 0.000 claims abstract description 33
- 238000002844 melting Methods 0.000 claims description 23
- 230000008018 melting Effects 0.000 claims description 23
- 238000001816 cooling Methods 0.000 claims description 19
- 239000000112 cooling gas Substances 0.000 claims description 19
- 238000005266 casting Methods 0.000 claims description 16
- 238000000137 annealing Methods 0.000 claims description 15
- 230000006698 induction Effects 0.000 claims description 14
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 10
- 239000001307 helium Substances 0.000 claims description 8
- 229910052734 helium Inorganic materials 0.000 claims description 8
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims description 8
- 229910004261 CaF 2 Inorganic materials 0.000 claims description 5
- 229910010413 TiO 2 Inorganic materials 0.000 claims description 5
- 239000000498 cooling water Substances 0.000 claims description 5
- 239000002994 raw material Substances 0.000 claims description 5
- 239000007790 solid phase Substances 0.000 claims description 4
- 238000007599 discharging Methods 0.000 claims description 3
- 239000000463 material Substances 0.000 claims description 3
- 238000010438 heat treatment Methods 0.000 claims description 2
- 230000035882 stress Effects 0.000 abstract description 14
- 230000008646 thermal stress Effects 0.000 abstract description 6
- 230000000694 effects Effects 0.000 abstract description 3
- 239000007769 metal material Substances 0.000 abstract description 2
- 230000000052 comparative effect Effects 0.000 description 11
- 239000007789 gas Substances 0.000 description 11
- 238000010586 diagram Methods 0.000 description 6
- 239000002245 particle Substances 0.000 description 6
- 239000002184 metal Substances 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
- 239000000203 mixture Substances 0.000 description 3
- 238000001556 precipitation Methods 0.000 description 3
- 238000004321 preservation Methods 0.000 description 3
- 238000005728 strengthening Methods 0.000 description 3
- 238000009825 accumulation Methods 0.000 description 2
- 238000007600 charging Methods 0.000 description 2
- 238000004737 colorimetric analysis Methods 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 238000005457 optimization Methods 0.000 description 2
- 238000005498 polishing Methods 0.000 description 2
- 238000007670 refining Methods 0.000 description 2
- 238000005204 segregation Methods 0.000 description 2
- 238000003466 welding Methods 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000005496 eutectics Effects 0.000 description 1
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- C22C1/00—Making non-ferrous alloys
- C22C1/02—Making non-ferrous alloys by melting
- C22C1/023—Alloys based on nickel
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
- C22B9/16—Remelting metals
- C22B9/18—Electroslag remelting
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
- C22B9/16—Remelting metals
- C22B9/20—Arc remelting
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Abstract
The application belongs to the technical field of metal materials, and particularly relates to a control method for cracking defects of a high-alloy nickel-base deformed superalloy phi 508mm cast ingot, which reduces thermal stress and tissue stress generated in a smelting process by a method of adding a wedge riser and optimizing solidification conditions of the cast ingot, optimizing ESR slag system and combining low-power method feeding and VAR four-stage feeding through VIM, so as to achieve the effect of improving the cracking defects of the high-alloy superalloy cast ingot. The high-alloying superalloy cast ingot prepared by the method has good surface quality, no cracking defect is found in the triple smelting process, and the effect of remarkably reducing the cracking tendency of the high-alloying superalloy cast ingot can be achieved.
Description
Technical Field
The application belongs to the technical field of metal materials, and particularly relates to a control method for cracking defects of a high-alloy nickel-base deformed superalloy phi 508mm cast ingot.
Background
With the rapid development of the aerospace industry, the thrust-weight ratio of the aircraft is increased, the working temperature of engine parts is continuously increased, and the development and application of the deformed superalloy for the turbine disc are promoted. In order to improve the service performance of the alloy and meet the requirement of high-temperature strength, a large amount of precipitation strengthening elements (Al, ti and Nb) are added into the deformed superalloy for the high-performance turbine disk, and the alloy is also called as a high-alloying deformed superalloy. Because the strengthening elements in the high-alloying deformation high-temperature alloy are very high, component segregation and interdendritic eutectic precipitation phases are inevitably generated in the alloy, so that the alloy has high cracking tendency.
The causes of cracking of the high-alloyed superalloy ingots mainly comprise: (1) exogenous factors: in the alloy cooling process, the temperature difference between the center and the surface of the ingot causes uneven volume expansion and shrinkage to generate larger thermal stress; (2) internal cause: the high-alloying high-temperature alloy has higher content of precipitation strengthening elements, and the microscopic segregation of the alloy elements is serious, so that larger tissue stress exists in the cast ingot. In order to improve the cracking defect of the high-temperature alloy ingot, the thermal stress and the structural stress generated in the alloy cooling process should be reduced as much as possible. The prior art mainly optimizes the process from the aspects of forging and heat treatment of high-temperature alloy materials to prevent the alloy from cracking, and in the field of alloy smelting, no effective method for controlling the cracking defect of the high-alloy high-temperature alloy cast ingot has been researched yet.
Disclosure of Invention
The application aims to provide a control method for cracking defects of a high-alloy nickel-base deformed superalloy phi 508mm specification ingot, which comprises the steps of smelting by a vacuum induction smelting (VIM) +electroslag remelting (ESR) +vacuum consumable remelting (VAR) triple process, adding a wedge riser in the VIM smelting and optimizing the solidification condition of the ingot, adopting an optimized premelting combined power reduction method for feeding in the ESR smelting, adopting a four-stage feeding process in the VAR smelting, and reducing the cracking tendency of the ingot in each smelting step by combining the processes in each smelting period, so that the final high-alloy superalloy ingot does not crack.
In order to achieve the above purpose, the technical scheme provided by the application is a control method for cracking defects of a high-alloy nickel-base deformed superalloy phi 508mm specification ingot, comprising the following steps:
(1) Vacuum induction melting: vacuum induction smelting is carried out on high-temperature alloy raw materials, a wedge-shaped heat-preserving riser is additionally arranged at the head of an ingot mould before casting, the temperature of the ingot mould is controlled to be 1420-1500 ℃, the cooling time is determined according to the solidification time of the ingot after casting is finished, demoulding is carried out after cooling, and thermal annealing is carried out after measuring the surface temperature of the ingot after demoulding is proper;
(2) Electroslag remelting: electroslag smelting is carried out on the cast ingot prepared in the step (1), and feeding is carried out by combining stage reduction power with timing power off in the later smelting period;
(3) Vacuum arc consumable remelting: and (3) carrying out vacuum arc consumable smelting on the cast ingot prepared in the step (2), wherein the steady-state smelting stage adopts smelting speed and droplet control, the feeding stage adopts current reduction and droplet control improvement, and the cooling gas adopts linear flow reduction control.
Preferably, the high-alloy nickel-base wrought superalloy comprises the following components in percentage by mass: al 2.55-3.90%, ti 2.65-5.20%, nb 0-3.40%, C0.038-0.07% and Ni in balance.
Preferably, in the step (1), before casting, the ingot mould is preheated to 400-600 ℃, and the ingot mould is filled into an ingot mould chamber and is pumped out until the casting time is 30-90 min; wherein the ingot mould has taper, the bottom inner diameter is phi 360 plus or minus 20mm, and the top inner diameter is phi 340 plus or minus 20mm; the length of the wedge-shaped heat-preserving riser is 300-450 mm, the thickness is 20-40 mm, the inclination angle is 2-7 degrees, and the riser solidification time/ingot casting solidification time=1.15-1.35; the solidification time of the cast ingot is the time when the solid phase volume fraction reaches more than or equal to 92%; the cooling time is the solidification time of the cast ingot plus or minus 10 minutes; annealing at 600-800 deg.c.
Preferably, in the step (1), the crucible is powered off in the early stage of casting, and the crucible power is increased to 20-50 kW after the crucible tilting angle is more than 60 °.
Preferably, the steady-state smelting setting power is 180-250 kW, and the slag resistance is 4-10MΩ; the feeding is divided into 7 stages, the feeding time is more than or equal to 70 minutes, and the power P and the time t of the feeding stage are calculated according to the following formula:
P n ＝P 0 *e (-a·t)
wherein P is 0 For steady state smelting power, P n The smelting power in the nth stage is e, a is a natural constant, and the range of each stage a is 0.001-0.002, 0.002-0.004, 0.004-0.007, 0.0070-0.010, 0.010-0.013, 0.013-0.016 and 0.016-0.02;
immediately powering off after the power of the final stage is reduced to a set value, and cooling for 50+/-20 min, wherein the cooling water temperature is set to be 25-30 ℃ during furnace cooling; and (5) performing thermal annealing after discharging.
Preferably, in the step (2), the primary component of the premelting slag is Al in percentage by weight 2 O 3 24.5±3.0％、TiO 2 5.0±0.5％、CaO 23.0±3.0％、MgO 3.5±0.5％、CaF 2 44.0+ -3.0%; pre-slag characteristic parameters: the water content is less than or equal to 0.04 percent, and the water content after baking is less than or equal to 0.02 percent; the grain size is 0-10 mm, and the weight of slag materials with the size less than 1mm is not more than 10%; conductivity at 1700 ℃ is more than or equal to 3.5 omega -1 The viscosity is 0.010 to 0.020 Pa.s.
Preferably, the step (3) specifically includes: a steady-state smelting stage: the melting speed is set to be 2.5-3.5 kg/min, and the melting drop is set to be 3.00-8.50 s -1 The flow rate of the cooling gas is 0.1-0.2L/min; the feeding stage is divided into four stages, and the current sum is reduced in stagesThe molten drop is improved, the flow of cooling gas is linearly reduced to be below 0.02L/min, and the feeding time of each stage is 10-30 min.
Preferably, the process parameters of the four stages of feeding in step (3) are as follows:
the first stage: the current is reduced to 75-85% of the stable smelting current, the molten drops are increased to 130-150% of the stable smelting molten drops, and the flow of cooling gas is reduced to 90-95% of the stable smelting flow;
and a second stage: the current is reduced to 60% -75% of the stable smelting current, the molten drops are increased to 150% -160% of the stable smelting molten drops, and the flow of cooling gas is reduced to 70% -90% of the stable smelting flow;
and a third stage: the current is reduced to 30-60% of the stable smelting current, the molten drop is increased to 160-165% of the stable smelting molten drop, and the flow of cooling gas is reduced to 30-70% of the stable smelting flow;
fourth stage: the current is reduced to 20-30% of the stable smelting current, the molten drop is increased to 165-170% of the stable smelting molten drop, and the flow of cooling gas is reduced to 15-30% of the stable smelting flow.
Preferably, in step (3), the cooling gas is helium.
Preferably, in the step (2), the inner diameter of the electroslag crystallizer is phi 440+/-10 mm.
Compared with the prior art, the application has the beneficial effects that:
in VIM smelting, through adding a wedge-shaped heat-preserving riser, strictly controlling the pouring temperature and the ingot mould preheating temperature, the riser solidification time and the ingot solidification time are in a fixed ratio, the solidification process of molten metal in the ingot mould is optimized, the shrinkage cavity in the center of the ingot mould is reduced, and cracking caused by larger solidification rate difference is avoided.
In ESR smelting, customized premelting slag is adopted, so that the premelting slag has lower water content and smaller particle size, ensures that the premelting slag can be uniformly distributed in an electroslag furnace, ensures that a molten pool is uniformly heated, and avoids macrosegregation of alloy caused by uneven temperature distribution. The higher conductivity can improve the thermal efficiency of ESR, improve the temperature of a molten pool, ensure the stability of an electroslag remelting process, reduce parameter fluctuation and reduce the occurrence probability of metallurgical defects. The moderate viscosity can ensure that the premelting slag has good fluidity, effectively adsorb the inclusions in the alloy, and reduce the accumulation of crack sources in the alloy.
The size of the shrinkage cavity area at the head of the VAR ingot can be obviously reduced by adopting a four-stage feeding process, the stress of the head area is reduced, and the cracking risk of the VAR ingot is reduced.
The thermal stress and the tissue stress generated in the smelting process are reduced by a method of VIM (vertical gravity modeling) additional installation of a wedge riser, optimization of the solidification condition of the ingot and optimization of ESR slag system combined with power reduction method feeding and VAR four-stage feeding, so that the cracking defect of the high-alloy high-temperature alloy ingot is improved.
The high-alloying superalloy cast ingot prepared by the method has good surface quality, no cracking defect is found in the triple smelting process, and the effect of remarkably reducing the cracking tendency of the high-alloying superalloy cast ingot can be achieved.
Drawings
FIG. 1 is a comparative view of a VIM ingot according to example 1 of the present application and a VIM ingot according to comparative example 1; wherein FIG. c is a physical diagram of example 1, and FIGS. a and b are physical diagrams of comparative example 1.
FIG. 2 is a graphical representation of the ESR ingot of example 1 of the present application versus the ESR ingot of comparative example 2; in this example, FIG. e is a physical diagram of example 1, and FIG. d is a physical diagram of comparative example 2.
FIG. 3 is a comparative view of the VAR ingot of example 1 of the present application and the VAR ingot of comparative example 3; FIG. h is a physical diagram of example 1, and FIGS. f and g are physical diagrams of comparative example 3.
Detailed Description
The present application will be described in further detail below with reference to the accompanying drawings and examples, and the following detailed description of the embodiments of the present application will be given, but the present application is not limited to these embodiments, and any substantial modifications or substitutions in the present examples are still within the scope of the present application as claimed.
The specific description is: the following examples, in which specific conditions are not specified, are conducted under conventional conditions or conditions recommended by the manufacturer, and the raw materials used in the following examples are commercially available from ordinary sources unless otherwise specified.
The nickel-based superalloy comprises the following components in percentage by mass: al 2.55-3.90%, ti 2.65-5.20%, nb 0-3.40%, C0.038-0.07% and Ni in balance.
The application relates to a control method for cracking defects of a high-alloy nickel-base deformation superalloy phi 508mm cast ingot, which comprises the following steps:
(1) Vacuum induction melting:
smelting high-temperature alloy raw materials in a vacuum induction furnace, wherein the vacuum induction smelting comprises charging, melting, refining, alloying and pouring. The alloy pouring temperature is 1420-1500 ℃, the crucible is powered off in the early stage of pouring, the crucible power is increased to 20-50 kW after the crucible tilting angle is more than 60 ℃, an ingot mould which is preheated to 400-600 ℃ and is provided with a wedge-shaped (upper narrow and lower wide) heat-preserving riser is adopted for pouring, and the ingot mould is put into an ingot mould chamber of a vacuum induction melting furnace and is pumped out until the pouring time is 30-90 min; wherein the ingot mould has taper, the bottom inner diameter is phi 360 plus or minus 20mm, and the top inner diameter is phi 340 plus or minus 20mm; the length of the wedge-shaped heat-preserving riser is 300-450 mm, the thickness is 20-40 mm, the inclination angle is 2-7 degrees, the size of the wedge-shaped heat-preserving riser is adjusted within the size range according to the size of the ingot mould and the alloy solidification characteristics, and finally the riser solidification time/the ingot solidification time=1.15-1.35, and the ingot solidification time is the time when the solid phase volume fraction reaches more than or equal to 92%. Vacuum cooling in the ingot mould chamber to reach the solidification time of the ingot within +/-10 min, demoulding, measuring the surface temperature of the ingot by adopting a colorimetry infrared thermometer after demoulding, and putting the ingot into a resistance annealing furnace for annealing when the temperature is 600-800 ℃.
In the step (1), the wedge-shaped heat-preserving riser is arranged at the head of the ingot mould, so that the shrinkage cavity depth of the center of the VIM ingot can be reduced, the stress in the ingot is reduced, and the crack sensitive area is reduced. The size and shape of the wedge-shaped heat-preserving riser can obviously influence the solidification time of the riser of the ingot, if the solidification time of the riser is too short, molten metal at the riser cannot be fed well, the shrinkage cavity depth at the center of the ingot is deeper, and the overall stress of the ingot is increased; if the riser solidification time is too long, excessive molten metal remains at the riser, so that shrinkage holes at the riser are larger, and the stress at the upper part of the ingot is increased. Therefore, the size and the shape of the heat-preserving riser are reasonably designed, so that the solidification time of the riser is moderate, and the molten metal at the riser can be normally fed, thereby reducing the stress in the cast ingot. According to domestic and foreign literature records and actual production experience, the length, thickness and inclination angle of the heat-preserving riser are restrained, and the length, thickness and inclination angle of the heat-preserving riser are properly adjusted within the restraining range, so that the riser solidification time/ingot solidification time=1.15-1.35, and a high-alloy high-temperature alloy VIM ingot with smaller stress can be prepared under the condition.
The preheating treatment of the ingot mould can obviously reduce the thermal stress generated when the molten liquid enters the cold ingot mould. Proper demolding time and demolding temperature are selected, so that thermal stress in the ingot is reduced, the ingot mold is supercooled due to the fact that the demolding time is too long, and larger stress is generated in the ingot; too short demolding time can lead to higher temperature of the cast ingot after demolding, and the surface temperature is rapidly reduced after the cast ingot contacts cold air, so that larger stress is generated on the surface of the cast ingot.
(2) Electroslag remelting:
and (3) carrying out surface polishing treatment on the annealed VIM ingot, welding an auxiliary electrode, and carrying out electroslag remelting smelting. The electroslag remelting comprises a slag melting stage, a stable smelting stage and a feeding stage. The inner diameter of the electroslag crystallizer is phi 440+/-10 mm, and before the slag melting stage begins, the ESR pre-slag which is uniformly mixed is added into the electroslag furnace. The premelting slag component is Al in percentage by mass 2 O 3 24.5±3.0％、TiO 2 5.0±0.5％、CaO 23.0±3.0％、MgO 3.5±0.5％、CaF 2 44.0.+ -. 3.0%. The optimized premelting slag parameters meet the following requirements: (1) the water content is less than or equal to 0.04 percent, and the mixture is dried to less than or equal to 0.02 percent before being put into a furnace; (2) the particle size is less than or equal to 4mm; (3) conductivity at 1700 ℃ is more than or equal to 3.5 omega -1 /cm; (4) the viscosity is 0.010 to 0.020 Pa.s. The steady-state smelting setting power is 180-250 kW, and the slag resistance is 4-10MΩ. Feeding technology of reducing power in seven stages and combining timed power-off is adopted in the later smelting stage, the total feeding time is more than or equal to 70 minutes, and each stage is fedThe power (P) and time (t) settings for the segment are calculated as follows:
P n ＝P 0 *e (-a·t)
wherein P is 0 For steady state smelting power, P n The smelting power in the nth stage is e, t is a natural constant, a is a feeding time, and a is a coefficient, and the ranges of each stage a are 0.001-0.002, 0.002-0.004, 0.004-0.007, 0.0070-0.010, 0.010-0.013, 0.013-0.016 and 0.016-0.02 respectively.
And in the final stage, the power is immediately cut off after the power is reduced to a set value, the furnace is cooled for 50+/-20 minutes, the cooling water temperature is set to be 25-30 ℃ during furnace cooling, and the thermal annealing is carried out after the furnace is discharged.
In the step (2), ESR pre-melted slag has lower water content and smaller particle size, so that the pre-melted slag can be uniformly distributed in the electroslag furnace, a molten pool is uniformly heated, and macrosegregation of the alloy due to uneven temperature distribution is avoided. The higher conductivity can improve the thermal efficiency of ESR, improve the temperature of a molten pool, ensure the stability of an electroslag remelting process, reduce parameter fluctuation and reduce the occurrence probability of metallurgical defects. The moderate viscosity can ensure that the premelting slag has good fluidity, effectively adsorb the inclusions in the alloy, and reduce the accumulation of crack sources in the alloy.
(3) Vacuum arc consumable remelting:
and (3) carrying out vacuum consumable smelting on the cast ingot prepared in the step (2), wherein the smelting speed and the molten drop are adopted in the steady-state smelting stage, the flow control is adopted for cooling gas (helium), and the four-stage feeding method is adopted for feeding.
Wherein, the steady state smelting stage: the melting speed is set to be 2.5-3.5 kg/min, and the melting drop is set to be 3.00-8.50 s -1 The flow rate of the cooling gas is 0.1-0.2L/min;
the feeding stage adopts current and molten drop control, and linearly reduces the helium flow to below 0.02L/min, the feeding time of each stage is 10-30 min, and the technological parameters of each stage are as follows:
the first stage: the current is reduced to 75-85% of the stable smelting current, the molten drop is increased to 130-150% of the stable smelting molten drop, and the helium flow is reduced to 90-95% of the stable smelting flow;
and a second stage: the current is reduced to 60% -75% of the stable smelting current, the molten drop is increased to 150% -160% of the stable smelting molten drop, and the helium flow is reduced to 70% -90% of the stable smelting flow;
and a third stage: the current is reduced to 30-60% of the stable smelting current, the molten drop is increased to 160-165% of the stable smelting molten drop, and the helium flow is reduced to 30-70% of the stable smelting flow;
fourth stage: the current is reduced to 20% -30% of the stable smelting current, the molten drop is increased to 165% -170% of the stable smelting molten drop, and the helium flow is reduced to 15% -30% of the stable smelting flow.
The area of the shrinkage cavity of the VAR head is the area where the ingot stress is most concentrated and is the sensitive area of alloy cracking. The four-stage feeding process can obviously reduce the size of the shrinkage cavity area at the head of the VAR ingot, reduce the stress at the head area and reduce the cracking risk of the VAR ingot.
The preferred embodiments are described below in detail.
Example 1
(1) Smelting high-temperature alloy raw materials in an 8-ton vacuum induction furnace, wherein the vacuum induction smelting comprises charging, melting, refining, alloying and pouring. The alloy comprises the following chemical components in percentage by weight: 0.07% of C, 18.00% of Cr, 15.00% of Co, 1.50% of W, 3.20% of Mo, 3.10% of Al, 4.20% of Ti, 2.10% of Nb, 0.020% of B, 0.045% of Zr and the balance of Ni. The alloy pouring temperature is 1480 ℃, the crucible is powered off in the early stage of pouring, the crucible power is increased to 40kW after the crucible tilting angle is more than 60 ℃, an ingot mould which is preheated to 600 ℃ and is provided with a wedge-shaped (upper narrow lower wide) heat-preserving riser is adopted for pouring, and the ingot mould is filled into an ingot mould chamber of a vacuum induction melting furnace and is pumped out until the pouring time is 50min; wherein the ingot mould has taper, the bottom inner diameter is phi 360mm, and the top inner diameter is phi 340mm; the length of the heat preservation riser is 320mm, the thickness of the heat preservation riser is 30mm, the inclination angle is 5 degrees, the size of the heat preservation riser can be adjusted within the size range according to the size of an ingot mould and the solidification characteristics of alloy, and finally the riser solidification time/the ingot solidification time=1.20 can be achieved. The solidification time of the ingot is the time required when the solid phase volume fraction is more than or equal to 92%, demoulding is carried out after the vacuum cooling in the ingot mould chamber reaches the solidification time of the ingot plus or minus 10min, the surface temperature of the ingot is measured by adopting a colorimetry infrared thermometer after demoulding, and the ingot is put into a resistance annealing furnace for annealing when the temperature is about 700 ℃;
(2) And carrying out surface polishing treatment on the annealed VIM ingot, welding an auxiliary electrode, and carrying out electroslag remelting smelting, wherein the electroslag remelting comprises a slag melting stage, a stable smelting stage and a feeding stage. The size of the electroslag crystallizer is phi 450mm, and the inner diameter is phi 440mm. Before the beginning of the slag melting stage, adding ESR pre-melted slag which is uniformly mixed into an electroslag furnace, optimizing an ESR slag system, wherein the optimized slag system comprises the following components in percentage by weight 2 O 3 22.5％、TiO 2 5.0％、CaO 24.0％、MgO 4.0％、CaF 2 44.5%. The customized premelting slag has lower water content, smaller particle size, proper conductivity and viscosity, and the optimized premelting slag parameters meet the following requirements: (1) the water content is 0.035%, and the mixture is dried to 0.02% before being put into a furnace; (2) the particle size is 0-3 mm; (3) conductivity at 1700℃3.8. Omega -1 /cm; (4) the viscosity was 0.014 Pa.s. The steady-state smelting setting power is 200kW, and slag resistance is 5MΩ. And a feeding process of reducing power in seven stages and timing power off is adopted in the later smelting stage, the total feeding time is about 70 minutes, and the power (P) and time (t) set values in the feeding stage are calculated according to the following formula:
P n ＝P 0 *e (-a·t)
wherein P is 0 For steady state smelting power, P n The smelting power of the nth stage is a coefficient, and the ranges of the stages a are 0.001-0.002, 0.002-0.004, 0.004-0.007, 0.0070-0.010, 0.010-0.013, 0.013-0.016 and 0.016-0.02 respectively.
The power of each feeding stage is 185kW, 160kW, 140kW, 110kW, 90kW, 70kW and 55kW respectively. And in the final stage, the power is immediately cut off after the power is reduced to a set value, the furnace is cooled for 50min, the cooling water temperature is set to 25 ℃ during furnace cooling, and the thermal annealing is carried out after the furnace is taken out.
(3) And carrying out vacuum consumable melting by taking the ESR cast ingot as a VAR electrode, wherein the vacuum consumable melting comprises an arcing stage, a stable melting stage and a feeding stage. The size of the crystallizer is phi 508mm, the smelting speed and the molten drop control are adopted in steady-state smelting, and the flow control is adopted for cooling gas (He gas). Feeding the VAR ingot in four stages, gradually reducing the current, increasing the molten drop, reducing the He gas flow, feeding for 25min in each stage, and annealing after discharging. The process parameters of each feeding stage are as follows:
stable smelting stage: the melting speed is 2.8kg/min, the current is 5.5kA, the molten drops are 6.5/s, and the He gas flow rate is 0.015L/min.
The first stage: the current was 4.5kA, the droplet was 9.0 pieces/s, and the He gas flow was 0.014L/min.
And a second stage: the current is 3.6kA, the molten drop is 10.0/s, and the He gas flow rate is 0.012L/min.
And a third stage: the current is 2.2kA, the molten drop is 10.5/s, and the He gas flow rate is 0.005L/min.
Fourth stage: the current is 1.2kA, the molten drop is 11.0/s, and the He gas flow rate is 0.003L/min.
The high-alloy high-temperature alloy cast ingot prepared by the method has no cracking in the triple smelting process, namely no cracking defect is found in the VIM cast ingot, the ESR cast ingot and the VAR cast ingot.
Comparative example 1
The VIM ingot shown in fig. 1 was compared with the VIM ingot of example 1 in real object, and was performed according to the method of example 1, except that in the vacuum induction melting casting step operation: the casting adopts an ingot mould which is preheated to 300 ℃ and is provided with a straight cylindrical heat-preserving riser, the ingot mould is put into an ingot mould chamber of a vacuum induction smelting furnace, and the time for casting is 50min; the inner diameter of the ingot mould is phi 350mm; the length of the insulated riser was 480mm and the thickness was 45mm, and the riser solidification time/ingot solidification time=1.67 was calculated. And (5) vacuum cooling for 120min in a casting chamber, demolding, and cooling to room temperature after demolding. The high-alloying superalloy VIM cast ingot prepared by the method has transverse cracking and larger shrinkage cavity in the center of the cast ingot.
Comparative example 2
As shown in FIG. 2, the ESR ingot was compared with the ESR ingot of example 1 in a manner as in example 1, except that the electroslag system composition was Al 2 O 3 30.0％、TiO 2 3.0％、CaO 28.0％、MgO 2.5％、CaF 2 36.5%. The premelting parameters are as follows: (1) the water content is 0.06%, and the materials are put into a furnace without drying treatment; (2) the particle size is 0.1-10 mm; (3) conductivity 3.0. Omega. At 1700 DEG C -1 /cm; (4) the viscosity was 0.03 Pa.s. The steady-state smelting setting power is 200kW, and slag resistance is 3.5MΩ. And a feeding process of reducing power in three stages and timing power off is adopted in the later smelting stage, the total feeding time is about 60 minutes, and the power in each feeding stage is 140kW, 90kW and 50kW respectively. And in the final stage, the power is immediately cut off after the power is reduced to a set value, the furnace is cooled for 40min, the set value of the cooling water temperature is 25 ℃ during furnace cooling, and the thermal annealing is carried out after the furnace is taken out. The high-alloying superalloy ESR cast ingot prepared by the method is longitudinally cracked.
Comparative example 3
The VAR ingot shown in fig. 3 was compared with the VAR ingot of example 1 in real terms, and was performed according to the method of example 1, except that the VAR ingot was fed in two stages, the current was gradually decreased, the droplet was increased, the He gas flow was decreased, the feeding time in each stage was 50min, and annealing was performed after tapping. The process parameters of each feeding stage are as follows:
stable smelting stage: the melting speed is 2.8kg/min, the current is 5.5kA, the molten drops are 6.5/s, and the He gas flow rate is 0.015L/min.
The first stage: the current is 4.8kA, the molten drop is 10.5/s, and the He gas flow rate is 0.012L/min.
And a second stage: the current is 2.6kA, the molten drop is 11.5/s, and the He gas flow rate is 0.006L/min.
The head shrinkage cavity of the high-alloy high-temperature alloy VAR cast ingot prepared by the method is larger, and longitudinal cracking occurs.
Claims (10)
1. The control method for the cracking defect of the ingot casting with the specification of phi 508mm of the high-alloy nickel-base deformation superalloy is characterized by comprising the following steps:
(1) Vacuum induction melting: vacuum induction smelting is carried out on high-temperature alloy raw materials, a wedge-shaped heat-preserving riser is additionally arranged at the head of an ingot mould before casting, the temperature of the ingot mould is controlled to be 1420-1500 ℃, the cooling time is determined according to the solidification time of the ingot after casting is finished, demoulding is carried out after cooling, and thermal annealing is carried out after measuring the surface temperature of the ingot after demoulding is proper;
(2) Electroslag remelting: electroslag remelting is carried out on the cast ingot prepared in the step (1), a slag system is optimized, and feeding is carried out by adopting a method of combining stage reduction power with timing power off in the later smelting stage;
(3) Vacuum arc consumable remelting: and (3) carrying out vacuum arc consumable remelting on the cast ingot prepared in the step (2), wherein a steady-state smelting stage adopts a smelting speed and molten drop control, a feeding stage adopts a method for reducing current and improving molten drop control, and a cooling gas adopts a method for linearly reducing flow control.
2. The method for controlling cracking defects of a high-alloy nickel-base wrought superalloy phi 508mm specification ingot according to claim 1, wherein the high-alloy nickel-base wrought superalloy comprises the following components in percentage by mass: 2.55 to 3.90 percent of Al, 2.65 to 5.20 percent of Ti, 0 to 3.40 percent of Nb, 0.038 to 0.07 percent of C and the balance of Ni.
3. The control method according to claim 1, wherein in the step (1), before casting, the ingot mould is preheated to 400-600 ℃, and the time from filling the ingot mould into the ingot mould chamber to casting is 30-90 min; wherein the ingot mould has taper, the bottom inner diameter is phi 360 plus or minus 20mm, and the top inner diameter is phi 340 plus or minus 20mm; the length of the wedge-shaped heat-preserving riser is 300-450 mm, the thickness is 20-40 mm, the inclination angle is 2-7 degrees, and the riser solidification time/ingot casting solidification time=1.15-1.35; the solidification time of the cast ingot is the time when the solid phase volume fraction is more than or equal to 92%; the cooling time is the solidification time of the cast ingot plus or minus 10 minutes; annealing at 600-800 deg.c.
4. A control method according to claim 3, wherein in the step (1), the power is turned off in the early stage of pouring, and the heating power is increased to 20 to 50kW after the crucible tilting angle is more than 60 °.
5. The control method according to claim 1, wherein the steady-state smelting setting power is 180-250 kW, and slag resistance is 4-10mΩ; the feeding is divided into 7 stages, the feeding time is more than or equal to 70 minutes, and the power P and the time t of the feeding stage are calculated according to the following formula:
P n ＝P 0 *e (-a·t)
wherein P is 0 For steady state smelting power, P n The smelting power in the nth stage is e, t is a natural constant, a is a feeding time, and the range of each stage a is 0.001-0.002, 0.002-0.004, 0.004-0.007, 0.0070-0.010, 0.010-0.013, 0.013-0.016 and 0.016-0.02 respectively;
immediately powering off after the power of the final stage is reduced to a set value, and cooling for 50+/-20 min, wherein the cooling water temperature is set to be 25-30 ℃ during furnace cooling; and (5) performing thermal annealing after discharging.
6. The control method according to claim 1, wherein the primary component of the premelted slag in weight percent is Al in the step (2) 2 O 3 24.5±3.0％、TiO 2 5.0±0.5％、CaO 23.0±3.0％、MgO 3.5±0.5％、CaF 2 44.0+ -3.0%; pre-slag characteristic parameters: the water content is less than or equal to 0.04 percent, and the water content after baking is less than or equal to 0.02 percent; the grain size is 0-10 mm, and the weight of slag materials with the size less than 1mm is not more than 10%; conductivity at 1700 ℃ is more than or equal to 3.5 omega -1 The viscosity is 0.010 to 0.020 Pa.s.
7. The control method according to claim 1, wherein the step (3) specifically includes: a steady-state smelting stage: the melting speed is set to be 2.5-3.5 kg/min, and the melting drop is set to be 3.00-8.50 s -1 The flow rate of the cooling gas is 0.1-0.2L/min; the feeding stage is divided into four stages, the current is reduced and the molten drops are increased in stages, the flow of cooling gas is linearly reduced to be below 0.02L/min, and the feeding time of each stage is 10-30 min.
8. The control method according to claim 7, wherein the process parameters of the four stages of feeding in step (3) are as follows:
the first stage: the current is reduced to 75-85% of the stable smelting current, the molten drops are increased to 130-150% of the stable smelting molten drops, and the flow of cooling gas is reduced to 90-95% of the stable smelting flow;
and a second stage: the current is reduced to 60% -75% of the stable smelting current, the molten drops are increased to 150% -160% of the stable smelting molten drops, and the flow of cooling gas is reduced to 70% -90% of the stable smelting flow;
and a third stage: the current is reduced to 30-60% of the stable smelting current, the molten drop is increased to 160-165% of the stable smelting molten drop, and the flow of cooling gas is reduced to 30-70% of the stable smelting flow;
fourth stage: the current is reduced to 20-30% of the stable smelting current, the molten drop is increased to 165-170% of the stable smelting molten drop, and the flow of cooling gas is reduced to 15-30% of the stable smelting flow.
9. The control method according to claim 1, wherein in step (3), the cooling gas is helium.
10. The control method according to claim 1, wherein in the step (2), the inner diameter of the electroslag crystallizer is Φ440±10mm.
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