CN114226610A

CN114226610A - Cogging method of large-size high-temperature alloy ingot and prepared bar

Info

Publication number: CN114226610A
Application number: CN202111382654.1A
Authority: CN
Inventors: 秦鹤勇; 张建英; 田强; 田沛玉; 张文云; 伏浩; 于萍; 王旻石; 李振团; 段然; 张晓敏; 郝永洲
Original assignee: Central Iron and Steel Research Institute; Gaona Aero Material Co Ltd; Baowu Special Metallurgy Co Ltd
Current assignee: Central Iron and Steel Research Institute; Gaona Aero Material Co Ltd; Baowu Special Metallurgy Co Ltd
Priority date: 2021-11-22
Filing date: 2021-11-22
Publication date: 2022-03-25
Anticipated expiration: 2041-11-22
Also published as: CN114226610B

Abstract

The application relates to the technical field of high-temperature alloys, and particularly discloses a cogging method of a large-size high-temperature alloy ingot, which is characterized by comprising the following steps: s1, heating and preserving heat of the high-temperature alloy cast ingot subjected to the multi-stage homogenization treatment by gradually raising the temperature; s2, performing multi-fire repeated upsetting treatment on the heat-insulated cast ingot in an alloy single-phase region, and gradually reducing the heating temperature during the multi-fire repeated upsetting treatment; and S3, reducing the heating temperature to a double-phase region for multi-fire upsetting treatment, wherein the heating temperature is gradually reduced during multi-fire upsetting. The application also discloses a bar prepared by the method. The method has the characteristics of improving the hot working plasticity of the alloy, realizing ingot casting cogging of high-alloying large-size high-temperature alloy and obtaining a homogeneous bar under the condition of preventing cracking.

Description

Cogging method of large-size high-temperature alloy ingot and prepared bar

Technical Field

The application relates to the technical field of high-temperature alloys, in particular to a cogging method of a large-size high-temperature alloy ingot and a prepared bar.

Background

With the iterative updating of aero-engines and gas turbines, the development of nickel-based precipitation strengthening type superalloy disc forgings which occupy important positions in materials used by the aero-engines and the gas turbines presents the trend of high alloying and large specification, and the hot processing performance of cast ingots is deteriorated.

At present, a plurality of problems exist in the cogging process of high-alloying large-size high-temperature alloy cast ingots at home and abroad, such as surface cracking of bars, coarse structure, large grain grade difference and the like. And because the hot working process from the bar to the disc forging piece shows the tissue inheritance, the adoption of which method to cogging the ingot directly influences the tissue performance of the bar and finally influences the tissue performance of the disc forging piece. The break-through of the cogging method needs to improve the hot working plasticity of the alloy by establishing a reasonable homogenization annealing system and a proper heading process, and a homogeneous bar is obtained under the condition of preventing cracking.

Disclosure of Invention

In order to improve the hot working plasticity of the alloy, realize the cogging of a cast ingot of a high-alloying large-size high-temperature alloy and obtain a homogeneous bar under the condition of preventing cracking, the application provides a cogging method of a large-size high-temperature alloy cast ingot and a prepared bar.

In a first aspect, the cogging method for the large-size high-temperature alloy ingot adopts the following technical scheme:

a cogging method of a large-size high-temperature alloy ingot comprises the following steps:

s1, heating and preserving heat of the high-temperature alloy cast ingot subjected to the multi-stage homogenization treatment by gradually raising the temperature;

s2, performing multi-fire repeated upsetting treatment on the heat-insulated cast ingot in an alloy single-phase region, and gradually reducing the temperature of the melting furnace during the multi-fire repeated upsetting;

and S3, reducing the heating temperature to a double-phase region for multi-fire pier drawing treatment, and gradually reducing the remelting temperature during multi-fire pier drawing.

By adopting the technical scheme, the consumable ingot is subjected to multi-section type uniform treatment, the consumable ingot is subjected to low-temperature pretreatment at first, a low-melting-point phase appearing at a crystal boundary is dissolved, then high-temperature diffusion is carried out, under the condition that the crystal boundary does not melt or have holes, the component segregation and the structure segregation of the obtained large-size consumable ingot are obviously improved, the obtained ingot is uniform in structure, carbides are granular, the thermoplasticity of the ingot is improved, then the cogging forging process is carried out, the interaction of alloy gamma' strengthening phases and the carbides with dynamic recrystallization is utilized during cogging forging, the hot working plasticity of the ingot is gradually improved in the upsetting process by adopting a method of cooling in a single-phase region and a double-phase region, and the interaction of reducing deformation temperature and improving the structure is achieved. Finally, the large-size bar with uniform structure is obtained, and the obtained bar can meet the HB/Z34-1998 AA-level requirement (the single defect does not exceed the equivalent flat-bottom hole with the diameter of 1.2 mm), and the cast structure is completely eliminated.

Optionally, the specific operation of reducing the heating temperature to the two-phase region in step S3 is: cooling to Ts +/-10 ℃ in a furnace, slowly cooling to (Ts-50) - (Ts-150) DEG C, preserving heat for 1.5-2.5h, and then heating to (Ts-30) -Ts ℃ for multiple times of pier drawing;

wherein Ts is the gamma' phase full melting temperature of the wrought superalloy.

By adopting the technical scheme, when the temperature of the single-phase region is reduced to the double-phase region, slow cooling is firstly carried out, so that the alloy is subjected to coarse gamma 'strengthening phase and fan-shaped structure separation, the grain boundary is bent, the hot working plasticity of the alloy is improved, the rheological stress peak value of the alloy during deformation is reduced, and then the temperature is increased to the double-phase region for upsetting, so that the alloy can obtain uniform structure under the cross action of the middle gamma' strengthening phase and dynamic recrystallization.

Optionally, in step S2, the heat treatment temperature for the first hot upsetting and elongation is (Ts + 30) - (Ts + 50) ° c, and then the temperature is reduced to the heat treatment temperature of (Ts + 10) - (Ts + 20) ° c to perform the second hot upsetting and elongation;

the specific operation of step S3 is: and (3) furnace-cooling the alloy processed in the step S2 to Ts +/-10 ℃, then slowly cooling to (Ts-50) - (Ts-150) DEG C, preserving heat for 1.5-2.5h, then heating to (Ts-30) -Ts ℃ to carry out third fire upsetting and stretching, then cooling at (20-30) ° C/fire and then carrying out subsequent multi-fire upsetting and stretching.

By adopting the technical scheme, the step-by-step cooling control can further improve the hot working plasticity of the alloy, reduce the thermal deformation rheological stress of the alloy and improve the crack expansion resistance of the alloy, thereby enlarging the hot working window of the alloy. And after the gradual cooling and upsetting of the two-phase region, the sector structure is changed into a fine-grained structure, so that the structural uniformity of the alloy is improved.

Optionally, the cooling rate of slowly cooling to (Ts-50) - (Ts-150) ° C in step S3 is (5-120) ° C/h.

Optionally, the multi-segment homogenization processing in step S1 includes the following steps:

preserving the temperature of the consumable ingot obtained by smelting at the temperature of 830-; then heating to 1120 +/-10 ℃, and preserving heat for 10-14 h; heating to 1135 +/-10 ℃, and preserving heat for 22-26 h; heating to 1180 +/-20 ℃, preserving the temperature for 62-66h, and cooling to obtain a high-temperature alloy ingot.

Optionally, in step S1, the temperature rising rate of the temperature rising to 1120 ± 10 ℃ is (45-60) ° c/h;

the heating rate of heating to 1135 +/-10 ℃ is (4-10) DEG C/h;

the heating rate is (3-6) DEG C/h when the temperature is increased to 1180 +/-20 ℃.

By adopting the technical scheme, the temperature is firstly raised to 1120 +/-10 ℃ and then is preserved, so that the low-melting-point phase sigma of the high-temperature alloy which is difficult to deform is dissolved back in a solid solution mode, then the temperature is raised to 1135 +/-10 ℃ at the temperature raising rate of (4-10) DEG C and is preserved, the low-melting-point phase eta and boride are continuously dissolved back, and the too large internal and external temperature difference caused by the too fast temperature raising and the too slow temperature raising can be prevented from causing the too long time consumption of the process and the increase of the fuel cost by adopting the temperature raising rate of (4-10) DEG C/h. And finally, heating to 1180 +/-20 ℃ at the heating rate of (3-6) DEG C/h, accelerating the diffusion of elements, reducing microsegregation, and finally adopting the multi-section homogenization system in the application to obviously reduce the component segregation and the structure segregation of the consumable ingot, thereby obtaining the ingot with a uniform structure and improving the plasticity of the ingot.

Optionally, in step S1, the specific operation of cooling after heat preservation at 1180 ± 20 ℃ for 62-66h is as follows: cooling to 1020-1050 ℃, preserving the heat for 1.5-2.5h, and then cooling.

By adopting the technical scheme, when the high-temperature alloy homogenization treatment process is adopted, the high-temperature alloy is cooled to 1020-1050 ℃ and then cooled, the high-temperature alloy is in a gamma + gamma' double-phase region, a special sector structure form is obtained, the crystal boundary state is improved, the thermoplasticity of the high-temperature alloy is further improved, the alloy is further prevented from cracking during cogging, and cogging and forging of large-size difficultly-deformed high-temperature alloy are realized.

Optionally, in step S2, the upsetting deformation parameter is: firstly, performing primary deformation by using the deformation amount of 20-25%, standing for 3-5s, and performing secondary deformation by using the deformation amount of 15-20%; the elongation deformation parameters are as follows: elongation deformation amount is 30-35%;

in step S3, the upsetting deformation amount is 35 + -5%, the elongation deformation amount is 30 + -5%, and the elongation deformation amount in the last fire is 40 + -5%.

Optionally, the consumable ingot in step S1 is a consumable ingot obtained by triple process melting of vacuum induction melting, protective atmosphere electroslag remelting, and vacuum consumable remelting.

By adopting the technical scheme, the consumable ingot prepared by the triple smelting process is in a large specification of phi 660mm, the large consumable ingot is subjected to multi-stage homogenization treatment and a multi-fire repeated upsetting process of 'single-phase region and double-phase region cooling', the obtained bar is high in yield and not easy to crack, and the obtained bar has no as-cast structure and is uniform in structure.

In a second aspect, the present application provides a bar, which adopts the following technical scheme:

a bar produced by the above-described cogging method.

By adopting the technical scheme, through the multi-section homogenization system, under the condition of avoiding no fusion or holes at the crystal boundary, the composition segregation and the structure segregation of the cast ingot are obviously improved, the carbide is granular, the thermoplasticity of the cast ingot is obviously improved, the homogenization treatment of the phi 660mm nickel-based high-temperature alloy consumable ingot difficult to deform can be realized, a foundation is laid for preparing large-size bars, then 2-3 times of high-temperature single-phase region pier-drawing crushing cast-state structures are formulated on the basis to improve the hot processing performance of the cast ingot, finally the heating temperature is reduced to a double-phase region pier-drawing process for 1-2 times of fire, the interaction of an alloy gamma' strengthening phase and the carbide with dynamic recrystallization is utilized, and the homogeneous bar of the difficult-to deform high-temperature alloy with the diameter of more than 400mm and the maximum size of low-power crystal grains of 2.8mm is finally obtained.

In summary, the present application has the following beneficial effects:

1. according to the method, the thermoplasticity of the ingot is improved through the improvement of a high-temperature multi-section homogenization system, the hot working plasticity of the ingot is gradually improved in the process of upsetting by adopting a method of 'single-phase region and gradual cooling of double-phase region' in cogging, the interaction of deformation temperature reduction and tissue improvement is achieved, and finally the difficultly-deformed high-temperature alloy homogeneous bar with the diameter larger than 400mm and the macroscopic grain maximum size of 2.8mm is obtained;

2. in the application, when the cogging is carried out by cooling a single-phase region to a two-phase region, slow cooling is firstly carried out to separate out a coarse gamma 'strengthening phase and a fan-shaped structure from the alloy, a crystal boundary is bent, the hot working plasticity of the alloy is improved, the rheological stress peak value of the alloy during deformation is reduced, and then the temperature is raised to the two-phase region for upsetting, so that the interaction between the gamma' strengthening phase and dynamic recrystallization of the alloy is realized, and a uniform structure can be obtained;

3. according to the method, a multi-section homogenization system is adopted, under the condition that no melting or hole is generated at a crystal boundary, the composition segregation and the structure segregation of the cast ingot are obviously improved, the carbide is granular, the thermoplasticity of the cast ingot is obviously improved, the homogenization treatment of the phi 660mm hard-deformation nickel-based high-temperature alloy consumable ingot can be realized, and a foundation is laid for preparing large-size bars;

4. in the application, cogging is carried out, 2-3 times of heating are adopted to carry out upsetting crushing on the as-cast structure in a high-temperature single-phase region, the hot processing performance of the cast ingot is improved, finally, 1-2 times of heating are carried out, the heating temperature is reduced to a double-phase region upsetting process, and the interaction of an alloy gamma' strengthening phase and carbide and dynamic recrystallization is utilized to finally obtain the difficult-to-deform high-temperature alloy homogeneous bar with the diameter of more than 400mm and the maximum size of 2.8mm of macroscopic grains.

Drawings

FIG. 1 is an external view of a finished bar product produced by the method of the present application;

FIG. 2 is a macrostructure diagram of a bar produced by the process of the present application;

FIG. 3 is a metallographic microstructure of a bar made by the method of the present application;

FIG. 4 is a C-scan of an ultrasonic water immersion flaw detection of bars made by the method of the present application;

FIG. 5 is a macrostructure diagram of a bar obtained by the single-temperature upsetting method in comparative example 3;

FIG. 6 is a metallographic microstructure of a bar obtained by the single-temperature upsetting method in comparative example 3;

FIG. 7 is a graph of the sector tissue OM produced by the homogenization of the cast tissue and subsequent cooling of the homogenized cast tissue in step S1;

FIG. 8 is an SEM image of a fan-shaped structure formed after homogenization and cooling of the as-cast structure in step S1 of the present application;

FIG. 9 is a view of a γ' phase sector structure OM generated after the forged structure is gradually cooled in step S3 of the present application;

FIG. 10 is an SEM image of a gamma' -phase sector structure formed after the forged structure is gradually cooled in step S3;

FIG. 11 is an SEM photograph of the forged structure of the present application after slow cooling in step S3, showing coarse γ' phase;

FIG. 12 is an OM diagram after 1150 ℃ upsetting in step S2 of the present application;

FIG. 13 is a graph of OM after 1080 ℃ upsetting in step S3 of the present application;

fig. 14 is an OM diagram after 1050 ℃ upsetting in step S3 of the present application.

Detailed Description

The present application will now be described in further detail with reference to the following figures and examples, in which: the following examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer, and the starting materials used in the following examples are available from ordinary commercial sources unless otherwise specified.

GH4742 is Ni-based precipitation hardening type deformation high-temperature alloy, has higher endurance and creep strength and good comprehensive capability within the range of 650-800 ℃, has better structural stability and corrosion resistance, and is widely applied to manufacturing high-temperature bearing parts of aviation and aerospace engines and ship gas engines, such as turbine discs and the like.

However, the GH4742 alloy is a typical hard-to-deform nickel-base superalloy with the primary age-strengthening elements Al, Ti, and Nb adding up to approximately 8.0wt.%, with the gamma prime phase mass fraction exceeding 40% (above the level of some cast superalloys), and with a total of approximately 30wt.% of solid solution strengthening elements such as Cr, Co, and Mo. Such a high alloying degree leads to serious dendrite segregation and a high cracking tendency in the alloy smelting process, and particularly leads to more serious dendrite segregation and a higher cracking risk for large-specification ingot types.

Therefore, in the related technologies at home and abroad, for the refractory alloy GH4742, the diameter of an unburnt ingot is only 508mm, and the structure of a bar subjected to cogging is not uniform, so that the requirement of HB/Z34-1998A grade can be met only (the single defect does not exceed a flat bottom hole with the equivalent of phi 2.0 mm), and the performance is poor due to casting with as-cast condition residues. Later, with the gradual application of triple smelting processes (vacuum induction smelting, protective atmosphere electroslag remelting and vacuum consumable remelting), cogging ingots with the diameter of 660mm can be obtained, but the cogging of the large-size ingots is still easy to crack due to poor thermoplasticity.

On the basis, the applicant obtains the dissolution and melting rules of the alloy low-melting-point phase by evaluating GH4742 alloy cast ingots and calculating thermodynamic and kinetic properties in the non-equilibrium solidification process, obtains the principle of dissolving the low-melting-point phase at a low temperature section and accelerating element diffusion at a high temperature section, comprehensively considers time and energy consumption cost according to the influence rule of temperature and time on element diffusion, improves the existing single-section homogenization system, formulates a specific multi-section homogenization system, and further eliminates dendrite segregation by dissolving the low-melting-point phase at a crystal boundary under the condition of avoiding no melting or holes at the crystal boundary, and then diffusing at high temperature, thereby improving the thermoplasticity of cast ingots and laying a good foundation for preparing large-size bars;

on the basis, the influence rule of factors such as deformation mode, deformation amount and the like in the cogging process on the cracking of the large-size GH4742 high-temperature alloy ingot in the cogging process is explored through high-temperature hot pressing and hot stretching, the hot working performance of the ingot is improved by finally setting the high-temperature single-phase region pier-drawing broken as-cast structure for 2-3 times of fire, and finally the heating temperature is reduced to the two-phase region pier-drawing process for 1-2 times of fire.

The cogging test of the following examples is illustrated by taking GH4742 alloy as an example, and the total melting temperature of the gamma' phase of the GH4742 alloy is about 1100-1120 ℃ through thermodynamic calculation and structure observation.

Example 1

s1, preparing a consumable ingot with phi 660mm by using a triple smelting process of vacuum induction, electroslag remelting and vacuum consumable tapping, and performing multi-section homogenization heat treatment to obtain a surface polished section, wherein the specific operation of the multi-section homogenization heat treatment is as follows:

charging a GH4742 alloy consumable ingot with the diameter of 660mm obtained by triple smelting at a charging temperature of 580 ℃, then heating to 600 ℃ along with the furnace, preserving heat for 2h, then heating to 1000 ℃ within 10h, and preserving heat for 3 h; then heating to 1120 ℃ at the heating rate of 50 ℃/h, and preserving heat for 12 h; heating to 1135 ℃ at the heating rate of 7 ℃/h, and keeping the temperature for 24 h; heating to 1180 ℃ at the heating rate of 5 ℃/h, preserving heat for 64h, and then cooling, wherein the cooling specifically comprises the following steps:

firstly, furnace cooling is carried out to 1030 ℃, heat preservation is carried out for 2 hours at the temperature, furnace cooling is carried out continuously to 600 ℃, then discharging and air cooling are carried out to room temperature, a phi 660 nickel-based high-temperature alloy ingot which is difficult to deform is obtained, and surface polishing is carried out;

heating the cast ingot with the polished surface to 1150 ℃ along with the furnace, preserving heat for 3h, taking the cast ingot out of the furnace, covering the cast ingot by adopting a hot covering technology, and returning the cast ingot to the furnace for preserving heat for 3h after covering;

s2, and then carrying out first hot upsetting with the upsetting strain rate of 0.3S^-1Firstly, performing primary deformation by 25% of deformation, standing for 4s, performing secondary deformation by 15% of deformation, then returning to the furnace, heating to 1150 ℃ along with the furnace, preserving heat for 3h, taking out of the furnace, covering by adopting a hot covering technology, and returning to the furnace and preserving heat for 3h after covering;

second fire elongation is carried out with a strain rate of 0.3s^-1The elongation deformation is 35%, the temperature is raised to 1150 ℃ after the furnace is returned, the temperature is kept for 3h, the furnace is taken out and sheathed by adopting a hot sheathing technology, and the furnace is returned to keep the temperature for 3h after the sheathing is finished;

performing third hot upsetting with strain rate of 0.3s^-1First, the first time is carried out with a deformation of 25%Deforming, standing for 4s, performing secondary deformation by 15% deformation, then returning to the furnace, heating to 1130 ℃ along with the furnace, preserving heat for 3h, taking out from the furnace, covering by adopting a hot covering technology, and returning to the furnace and preserving heat for 3h after covering is completed;

carrying out the fourth fire drawing with the strain rate of 0.3s^-1The elongation deformation is 35 percent, the temperature is raised in a furnace, the temperature is raised to 1130 ℃ along with the furnace, and the temperature is preserved for 3 hours;

s3, cooling the furnace to 1100 ℃ (Ts =1100 ℃), then slowly cooling the furnace to 1000 ℃ (Ts-100 =1000 ℃) at a cooling rate of 100 ℃/h, keeping the temperature for 2h, then heating the furnace to 1080 ℃ (Ts-20 =1080 ℃) at 100 ℃/h, and keeping the temperature for 3 h;

performing fifth hot upsetting with strain rate of 0.3s^-1Then deforming by 35% of deformation, returning to the furnace for heating, heating to 1080 ℃ along with the furnace, preserving heat for 3 hours, taking out of the furnace, sheathing by adopting a hot sheathing technology, and returning to the furnace for preserving heat for 3 hours after sheathing is finished;

carrying out sixth fire elongation with the strain rate of 0.3s^-1Drawing out deformation of 30%, returning to the furnace, heating to 1050 ℃ along with the furnace, keeping the temperature for 3h, taking out of the furnace, sheathing by adopting a hot sheathing technology, and returning to the furnace and keeping the temperature for 3h after sheathing is finished;

performing seventh hot upsetting with the strain rate of 0.3s^-1Then deforming by 35% of deformation, returning to the furnace for heating, heating to 1050 ℃ along with the furnace, preserving heat for 3 hours, taking out of the furnace and covering by adopting a hot covering technology, and returning to the furnace for preserving heat for 3 hours after covering is finished;

carrying out the eighth fire elongation with the strain rate of 0.3s^-1Drawing out deformation of 30%, returning to the furnace, heating to 1050 ℃ along with the furnace, keeping the temperature for 3h, taking out of the furnace, sheathing by adopting a hot sheathing technology, and returning to the furnace and keeping the temperature for 3h after sheathing is finished;

carrying out the ninth fire elongation with the strain rate of 0.3s^-1Drawing out deformation of 40%, returning to the furnace, heating to 1050 ℃ along with the furnace, keeping the temperature for 3h, taking out of the furnace, sheathing by adopting a hot sheathing technology, and returning to the furnace and keeping the temperature for 3h after sheathing is finished;

the tenth fire 1 is thrown and formed, and the strain rate is 0.3s^-1And the deformation is 50%, so that the GH4742 alloy bar is obtained.

Example 2

charging a GH4742 alloy consumable ingot with the diameter of 660mm obtained by triple smelting at a charging temperature of 580 ℃, then heating to 590 ℃ along with the furnace, preserving heat for 3h, then heating to 900 ℃ within 9h, and preserving heat for 4 h; then heating to 1110 ℃ at the heating rate of 45 ℃/h, and keeping the temperature for 14 h; heating to 1125 ℃ at the heating rate of 4 ℃/h, and keeping the temperature for 26 h; heating to 1160 ℃ at a heating rate of 3 ℃/h, preserving heat for 66h, and then cooling, wherein the specific cooling operation is as follows:

firstly, furnace cooling is carried out to 1020 ℃, heat preservation is carried out for 2.5 hours at the temperature, furnace cooling is carried out continuously to 600 ℃, then discharging and air cooling are carried out to room temperature, thus obtaining phi 660 nickel-based high-temperature alloy cast ingots which are difficult to deform, and surface polishing is carried out;

heating the cast ingot with the polished surface to 1140 ℃ along with the furnace, preserving heat for 4h, taking the cast ingot out of the furnace, covering the cast ingot by adopting a hot covering technology, and returning the cast ingot to the furnace for preserving heat for 4h after covering;

s2, and then carrying out first hot upsetting with the upsetting strain rate of 0.1S^-1Firstly, performing primary deformation by using 20% of deformation, standing for 3s, performing secondary deformation by using 20% of deformation, then returning to the furnace, heating to 1140 ℃ along with the furnace, preserving heat for 4h, taking out of the furnace, covering by using a hot covering technology, and returning to the furnace for preserving heat for 4h after covering is completed;

second fire elongation is carried out with a strain rate of 0.1s^-1The elongation deformation is 30%, the temperature is raised to 1140 ℃ after the furnace is returned, the temperature is kept for 4h, the steel plate is taken out of the furnace and sheathed by adopting a hot sheathing technology, and the furnace is returned to keep the temperature for 4h after the sheathing is finished;

performing third hot upsetting with strain rate of 0.1s^-1Firstly, performing primary deformation by using 20% of deformation, standing for 3s, performing secondary deformation by using 20% of deformation, then returning to the furnace, heating to 1120 ℃ along with the furnace, preserving heat for 4h, taking out of the furnace, covering by using a hot covering technology, and returning to the furnace and preserving heat for 4h after covering;

carrying out the fourth fire drawing with the strain rate of 0.1s^-1Elongation deformation of 30%, returning to furnace and heatingHeating the furnace to 1120 ℃, and preserving heat for 4 hours;

s3, cooling the furnace to 1050 ℃ (Ts-50 ℃), preserving heat for 1.5h at the temperature, then raising the temperature to 1070 ℃ (Ts-30 ℃) at 80 ℃/h, and preserving heat for 4 h;

performing fifth hot upsetting with strain rate of 0.1s^-1Then deforming by 35% of deformation, returning to the furnace for heating, heating to 1070 ℃ along with the furnace, preserving heat for 4 hours, taking out of the furnace for sheathing by adopting a hot sheathing technology, and returning to the furnace for preserving heat for 4 hours after sheathing is finished;

carrying out sixth fire elongation with the strain rate of 0.1s^-1Drawing out deformation of 30%, returning to the furnace, heating to 1040 ℃ along with the furnace, keeping the temperature for 44h, taking out from the furnace, sheathing by adopting a hot sheathing technology, and returning to the furnace and keeping the temperature for 4h after sheathing is finished;

performing seventh hot upsetting with the strain rate of 0.1s^-1Then deforming by 35% of deformation, returning to the furnace for heating, heating to 1040 ℃ along with the furnace, preserving heat for 4 hours, taking out of the furnace, sheathing by adopting a hot sheathing technology, and returning to the furnace for preserving heat for 4 hours after sheathing is finished;

carrying out the eighth fire elongation with the strain rate of 0.1s^-1Drawing out deformation of 30%, returning to the furnace, heating to 1040 ℃ along with the furnace, keeping the temperature for 4h, taking out of the furnace, sheathing by adopting a hot sheathing technology, and returning to the furnace and keeping the temperature for 4h after sheathing is finished;

carrying out the ninth fire drawing with the strain rate of 0.1s^-1Drawing out deformation of 40%, returning to the furnace, heating to 1040 ℃ along with the furnace, keeping the temperature for 4h, taking out of the furnace, sheathing by adopting a hot sheathing technology, and returning to the furnace and keeping the temperature for 4h after sheathing is finished;

the tenth fire 1 is thrown and formed, and the strain rate is 0.1s^-1And the deformation is 40%, so that the GH4742 alloy bar is obtained.

Example 3

charging a GH4742 alloy consumable ingot with the diameter of 660mm obtained by triple smelting at a charging temperature of 580 ℃, then heating to 610 ℃ along with the furnace, preserving heat for 2h, then heating to 1010 ℃ within 11h, and preserving heat for 2 h; then heating to 1130 ℃ at the heating rate of 60 ℃/h, and preserving heat for 10 h; heating to 1145 ℃ at the heating rate of 10 ℃/h, and keeping the temperature for 22 h; heating to 1200 ℃ at the heating rate of 6 ℃/h, preserving heat for 62h, and then cooling, wherein the specific cooling operation is as follows:

firstly, furnace cooling is carried out to 1050 ℃, heat preservation is carried out for 2.5 hours at the temperature, furnace cooling is carried out continuously to 600 ℃, then discharging and air cooling are carried out to room temperature, thus obtaining phi 660 nickel-based high-temperature alloy cast ingots which are difficult to deform, and surface polishing is carried out;

heating the cast ingot with the polished surface to 1160 ℃ along with the furnace, preserving heat for 3h, taking the cast ingot out of the furnace, covering the cast ingot by adopting a hot covering technology, and returning the cast ingot to the furnace for preserving heat for 3h after covering;

s2, and then carrying out first hot upsetting with the upsetting strain rate of 0.5S^-1Firstly, performing primary deformation by 25% of deformation, standing for 5s, performing secondary deformation by 15% of deformation, then returning to the furnace, heating to 1160 ℃ along with the furnace, preserving heat for 3h, taking out of the furnace, covering by adopting a hot covering technology, and returning to the furnace and preserving heat for 3h after covering;

second fire elongation is carried out with a strain rate of 0.5s^-1The elongation deformation is 35%, the temperature is raised to 1160 ℃ after the furnace is returned, the temperature is kept for 3h, the steel plate is taken out of the furnace and sheathed by adopting a hot sheathing technology, and the furnace is returned to keep the temperature for 3h after the sheathing is finished;

performing third hot upsetting with strain rate of 0.5s^-1Firstly, performing primary deformation by 25% of deformation, standing for 5s, performing secondary deformation by 15% of deformation, then returning to the furnace, heating to 1140 ℃ along with the furnace, preserving heat for 3h, taking out of the furnace, covering by adopting a hot covering technology, and returning to the furnace for preserving heat for 3h after covering;

carrying out the fourth fire elongation with the strain rate of 0.5s^-1The elongation deformation is 35 percent, the temperature is raised in a furnace, the temperature is raised to 1140 ℃ along with the furnace, and the temperature is kept for 3 hours;

s3, cooling the furnace to 950 ℃ (Ts-150 ℃), preserving heat for 2.5h at the temperature, then heating to 1100 ℃ (Ts ℃) at 120 ℃/h, and preserving heat for 2-4 h;

performing fifth hot upsetting with strain rate of 0.5s^-1Then deforming by 35% of deformation, returning to the furnace and heating up, heating up to 1090 ℃ along with the furnace, preserving heat for 3h, and discharging from the furnace by adopting a hot-covering technologySleeving, returning to the furnace and preserving heat for 3 hours after the sheathing is finished;

carrying out sixth fire elongation with the strain rate of 0.5s^-1Drawing out deformation of 30%, heating in a furnace again, heating to 1060 ℃ along with the furnace, keeping the temperature for 3h, taking out of the furnace, sheathing by adopting a hot sheathing technology, and keeping the temperature for 3h after sheathing is finished;

performing seventh hot upsetting with the strain rate of 0.5s^-1Then deforming by 35% of deformation, returning to the furnace for heating, heating to 1060 ℃ along with the furnace, preserving heat for 3 hours, taking out of the furnace and sheathing by adopting a hot sheathing technology, and returning to the furnace for preserving heat for 3 hours after sheathing is finished;

carrying out the eighth fire elongation with the strain rate of 0.5s^-1Drawing out deformation of 30%, heating in a furnace again, heating to 1060 ℃ along with the furnace, keeping the temperature for 3h, taking out of the furnace, sheathing by adopting a hot sheathing technology, and keeping the temperature for 3h after sheathing is finished;

carrying out the ninth fire elongation with the strain rate of 0.5s^-1Drawing out deformation of 40%, heating in a furnace again, heating to 1060 ℃ along with the furnace, keeping the temperature for 3h, taking out the steel tube from the furnace, sheathing by adopting a hot sheathing technology, and keeping the temperature for 3h after sheathing is finished;

the tenth fire 1 is thrown and formed, and the strain rate is 0.5s^-1And the deformation is 60 percent, and the GH4742 alloy bar is obtained.

The method in the embodiment 1-3 is adopted to finally obtain the large-size bar with the diameter of more than 400mm, the yield is up to more than 70%, the average grain size of the obtained bar is 6-8 grades, the structure is uniform, and the average grain size of the bar in the embodiment 1 is 8 grades.

Example 4

The cogging method of the large-size high-temperature alloy ingot is carried out according to the method in the embodiment 1, and the difference is that in the step S1, the temperature is raised to 1180 ℃, the temperature is kept for 64 hours, then the ingot is directly cooled to 600 ℃, and then the ingot is discharged from the furnace and cooled to the room temperature in air. In the embodiment, furnace cooling is directly performed after homogenization, the yield is 55-60%, and compared with the embodiment 1, the embodiment 1 has higher yield, and the slow cooling heat preservation measure in the embodiment 1 can improve the thermoplasticity of the high-temperature alloy and further prevent the high-temperature alloy from cracking during cogging.

Example 5

The cogging method of the large-size high-temperature alloy ingot is carried out according to the method in the embodiment 1, and the difference is that in the step S1, the temperature is raised to 1180 ℃, the temperature is kept for 64 hours, then the furnace is cooled to 1100 ℃, then the furnace is directly cooled to 600 ℃, and then the ingot is discharged from the furnace and air-cooled to the room temperature.

Example 6

A cogging method of large-size high-temperature alloy ingots is carried out according to the method in the embodiment 1, except that in the step S1, the temperature is raised to 1135 ℃, and then the temperature is kept for 24 hours for cooling.

Example 7

A method for cogging a large-size superalloy ingot, the method of example 1 being followed, except that in step S2, a fourth hot-drawing operation is performed, in which: strain rate of 0.3s^-1The elongation deformation is 35 percent, the temperature is raised in a furnace, the temperature is raised to 1130 ℃ along with the furnace, and the temperature is preserved for 3 hours;

then directly heating to 1080 ℃ and preserving heat for 3 h. In the embodiment, the steel bar is directly cooled during cogging, slow cooling, heat preservation and temperature rise measures are omitted, the yield is about 60 percent, and the average grain size of the obtained bar is 5-6 grades.

Comparative example 1

The cogging method of the large-size high-temperature alloy ingot is carried out according to the method in the embodiment 1, and the difference is that in the step S1, the consumable GH4742 alloy ingot with the diameter of 660mm obtained by triple smelting is charged at the charging temperature of 580 ℃, then the temperature is raised to 600 ℃ along with the furnace, the temperature is kept for 2 hours, then the temperature is raised to 1180 ℃ within 9 hours, and the temperature is kept for 64 hours and then cooled.

Comparative example 2

A cogging method of a large-size high-temperature alloy ingot is carried out according to the method in the embodiment 1, and the difference is that in the step S2, before first hot heading, the ingot is slowly cooled to 1000 ℃ at a cooling rate of 100 ℃/h, then the ingot is heated to 1150 ℃ at a cooling rate of 100 ℃/h, and heat preservation is carried out for 3 h; then carrying out first hot upsetting;

the fourth fire-drawing operation is as follows: strain rate of 0.3s^-1The elongation deformation is 35 percent, the temperature is raised in a furnace, the temperature is raised to 1130 ℃ along with the furnace, and the temperature is preserved for 3 hours; taking out the furnace and covering by adopting a hot covering technology, and returning the furnace and preserving heat for 3 hours after covering is finished; then, fifth hot upsetting is performed. In this comparative example, the alloy is subjected to upsetting treatment before upsetting, and is used for the hard-to-deform superalloy of the present application, and the yield is30-40%, and the average grain size of the obtained bar is 2-4 grade, and the uniformity of the structure is poor.

Comparative example 3

A method of cogging a superalloy ingot as in example 1, except that:

step S1, heating the cast ingot with the polished surface to 1170 ℃ along with the furnace, preserving heat for 3h, taking the cast ingot out of the furnace, sheathing by adopting a hot sheathing technology, and returning the cast ingot to the furnace for preserving heat for 3h after sheathing;

then multi-fire repeated mound drawing is carried out, the remelting temperature in the multi-fire repeated mound drawing process is 1170 ℃, the heat preservation time is 3 hours, and step-by-step temperature reduction treatment is not carried out. The comparative example is cogging, a single-temperature upsetting process is adopted, the obtained bar material has the specification of phi 360mm, the average grain size of the obtained bar material is about 2-4 grades, and the structural uniformity is poor.

Comparative example 4

A method for cogging a superalloy ingot, which was performed as in example 1, except that the operation in step S2 was: and (3) upsetting and drawing the ingot after the remelting and heat preservation twice, remelting the bar, reducing the temperature to 1080 ℃, preserving the heat for 3 hours, slowly cooling to 1000 ℃ at a cooling rate of 100 ℃/h, preserving the heat for 1 hour at the temperature, then heating to 1080 ℃ at 100 ℃/h, preserving the heat for 3 hours, and then performing subsequent upsetting treatment to obtain the GH4742 alloy bar with the diameter of 412 mm. The average grain size of the alloy bar is 1-4 grades, and the structure uniformity is poor.

Performance detection

First, in order to consider the influence of the multistage homogenization and cooling treatment on the alloy ingot in step S1, the segregation coefficients of Nb elements were measured for the ingots obtained by the triple smelting in step S1 and the homogenization and cooling treatment in step S1 in examples 1 and 4 to 6 and comparative example 1, and the measurement results are shown in table 1 below.

Table 1:

detecting items	Example 1	Example 4	Example 5	Example 6	Comparative example 1
						Segregation coefficient of Nb	0.028	0.035	0.033	0.045	0.074

As can be seen from table 1 above, the segregation coefficient of the ingot obtained by the multi-stage homogenization and cooling treatment in the present application is lower. Cogging is performed after the multi-section homogenization system provided by the application is adopted for treatment.

Forging and cogging are carried out according to the methods in the above embodiments and comparative examples, firstly, it can be seen that in the present application, a GH4742 alloy consumable ingot with the specification of phi 660mm is obtained through triple smelting, and a large-sized bar with the specification exceeding phi 400mm is obtained through cogging, a finished product of the phi 412mm bar obtained in example 1 is shown in fig. 1, compared with the existing bar with the specification of phi 360mm, the cogging method provided by the present application realizes the cogging method of the large-sized bar, and the observation of the low-multiple structure is carried out on the bar obtained in example 1 as shown in fig. 2, and the metallographic microstructure diagram of the bar obtained in example 1 is shown in fig. 3, so that it can be seen that the bar obtained by the cogging method in the present application embodiment has a uniform structure, completely eliminates the as-cast structure, and has no metallurgical defects such as shrinkage cavity, crack, bubble, loose center, white spot and black spot segregation, and the maximum size of the macroscopic crystal grains is less than or equal to 2.8mm, thereby meeting the requirements of technical indexes.

Referring to a C-scan drawing of ultrasonic water immersion flaw detection of GH4721 phi 412mm large-size bars in embodiment 1 of the application in FIG. 4, the ultrasonic water immersion flaw detection is performed according to phi 1.2mm flat bottom hole flaw detection, and through C-scan ultrasonic detection, no standard exceeding defect is found in the detected workpiece, so that GB/T4162 AA level is met.

The macrostructure of the bar and the metallographic microstructure of the bar are respectively shown in fig. 5 and 6 after the bar is subjected to single-temperature upsetting in comparative example 3, and it can be seen that the bar obtained by the step-by-step cooling cogging method in the present application has residual as-cast structure, and the obtained specification is only phi 360 mm. Therefore, the large-size bar obtained in the scheme of the application has uniform structure and no residual cast structure.

The OM obtained by performing metallographic microscopy on the ingot obtained by cooling the ingot in step S1 to 1030 ℃ and keeping the temperature for 2 hours in example 1 and the SEM obtained by scanning electron microscopy are shown in fig. 7 and 8, respectively, and it can be seen that a special sector structure form can be generated after the slow cooling operation in the cooling step during homogenization in the present application.

In addition, the OM photograph and SEM photograph of the γ 'phase fan-shaped structure produced after the temperature is raised to 1080 ℃ after the slow cooling operation in step S2 of example 1 and the SEM photograph of the coarse γ' phase generated by the slow cooling are respectively shown in fig. 9, fig. 10 and fig. 11, the OM photograph obtained by performing the metallographic scanning on the ingot after the upsetting at 1150 ℃ in example 1 is shown in fig. 12, the metallographic scanning on the ingot after the upsetting at 1080 ℃ and the ingot after the upsetting at 1050 ℃ in example 1 is shown in fig. 13 and fig. 14, respectively, it can be seen that when the temperature of the single phase region is reduced to the two-phase region in the cogging process, the coarse γ 'phase and the special γ' phase fan-shaped structure are generated in the ingot after the slow cooling step, and the fan-shaped structure is converted into the fine crystal structure after the multiple times of the stepwise temperature reduction in the two-phase region, the structure uniformity of the alloy is improved, and the low power crystal grain size of the bar finally obtained is not more than 2.8mm, the average grain size reaches 6-8 grades, and the technical index is met.

The alloy in example 1, which was furnace-cooled to 600 ℃ after the slow cooling and holding at the time of the homogenization operation in step S1, was subjected to the 1100 ℃ hot tensile test, and the alloy in example 4, which was furnace-cooled directly to 600 ℃ at the time of the homogenization operation and was not subjected to the slow cooling step, was also subjected to the 1100 ℃ hot tensile test, and the test results are shown in table 2 below:

table 2:

step S1	Specifying the Plastic elongation Strength (Rp)_0.2)MPa	Elongation after break (A)%	Reduction of area (Z)%
				Homogenization	45	90	92
Homogenization and slow cooling	35	112	95

The hot compression test was performed on the alloy which was furnace-cooled to 600 ℃ after the slow cooling and the heat preservation in the homogenization operation in example 1, and the hot compression test was also performed on the alloy which was furnace-cooled to 600 ℃ directly in the homogenization operation in example 4 without the slow cooling step, and the hot compression test conditions were as follows: 30% deformation, 0.1s^-1The strain rates of (A) were respectively heated to 1150 deg.C, 1130 deg.C and 1110 deg.C to obtain the rheological stresses, and the results are shown in Table 3 below.

Table 3: 30% deformation, 0.1s^-1Strain rate thermo-compressive rheological stress peak data

Step S1	1150℃	1130℃	1110℃
				Homogenization	180MPa	182MPa	232MPa
Homogenization and slow cooling	169MPa	179MPa	199MPa

As can be known from the table 2 and the table 3, the alloy is cooled uniformly and then cooled again, so that the thermoplasticity of the high-temperature alloy difficult to deform can be further improved, the alloy is further prevented from cracking during cogging, and the cogging forging of the large-size high-temperature alloy difficult to deform is more favorably realized.

Further, the slow cooling bar obtained by performing slow cooling to 1000 ℃ and warming to 1080 ℃ after the fourth fire elongation in example 1 was subjected to the 1100 ℃ hot tensile property, and the forged bar obtained by performing the direct slow cooling after the fourth fire elongation in example 7 was also subjected to the 1100 ℃ hot tensile test, and the test results are shown in table 4 below.

Table 4:

s2 pier pulling process	Tensile strength (R) MPa	Specifying Plastic elongation Strength (Rp0.2) MPa	Elongation after break (A)%	Reduction of area (Z)%
					Slow cooling state	52	20	154	98
In the forged state	91	18	64	97

Similarly, the thermal compression test is performed on the slow-cooling bar material which is slowly cooled to 1000 ℃ after the fourth fire is drawn out and is kept warm and is heated to 1080 ℃ in the example 1, and the thermal compression test is also performed on the forged bar material which is directly slowly cooled after the fourth fire is drawn out in the example 7, wherein the thermal compression test conditions are as follows: 30% deformation, 0.1s^-1The strain rate of (A) was adjusted to 1100 deg.C, 1080 deg.C, 1050 deg.C to obtain the rheological stress, and the results are shown in Table 5 below.

Table 5: 30% deformation, 0.1 s^-1Strain rate thermo-compressive rheological stress peak data

Step S2 pier drawing	1100℃	1080℃	1050℃
				Slow cooling state	180MPa	252MPa	320MPa
In the forged state	200MPa	272MPa	410MPa

As can be seen from the above tables 4 and 5, when the single-phase region and the double-phase region are adopted for gradual cooling, the alloy rheological stress is reduced and the alloy plasticity is remarkably improved through the slow cooling and heat preservation steps.

The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.

Claims

1. A cogging method of a large-size high-temperature alloy ingot is characterized by comprising the following steps:

s2, performing multi-fire repeated upsetting treatment on the heat-insulated cast ingot in an alloy single-phase region, and gradually reducing the heating temperature during the multi-fire repeated upsetting treatment;

and S3, reducing the heating temperature to a double-phase region for multi-fire upsetting treatment, wherein the heating temperature is gradually reduced during multi-fire upsetting.

2. The method of claim 1, wherein the method comprises the following steps: the specific operation of reducing the heating temperature to the two-phase region in the step S3 is as follows: cooling to Ts +/-10 ℃ in a furnace, slowly cooling to (Ts-50) - (Ts-150) DEG C, preserving heat for 1.5-2.5h, and then heating to (Ts-30) -Ts ℃ for multiple times of pier drawing;

3. The method of claim 1, wherein the method comprises the following steps: in the step S2, the heat treatment temperature of the first hot upsetting and drawing is (Ts + 30) - (Ts + 50) DEG C, and then the temperature is reduced to the heat treatment temperature of (Ts + 10) - (Ts + 20) DEG C for second hot upsetting and drawing;

4. The method of claim 2, wherein the method comprises the following steps: in step S3, the cooling rate is gradually decreased to (Ts-50) - (Ts-150) DEG C, which is 5-120℃/h.

5. The method of claim 1, wherein the method comprises the following steps: the multi-segment homogenization processing in step S1 includes the following steps:

6. The method of claim 5, wherein the method comprises the following steps: in step S1, the heating rate of the temperature rising to 1120 +/-10 ℃ is (45-60) DEG C/h;

the heating rate of heating to 1135 +/-10 ℃ is (4-10) DEG C/h;

7. The method of claim 5, wherein the method comprises the following steps: in step S1, the specific operation of cooling after heat preservation at 1180 +/-20 ℃ for 62-66h is as follows: cooling to 1020-1050 ℃, preserving the heat for 1.5-2.5h, and then cooling.

8. The method of claim 1, wherein the method comprises the following steps: in step S2, the upsetting deformation parameter is: firstly, performing primary deformation by using the deformation amount of 20-25%, standing for 3-5s, and performing secondary deformation by using the deformation amount of 15-20%; the elongation deformation parameters are as follows: elongation deformation amount is 30-35%;

9. The method of claim 1, wherein the method comprises the following steps: the consumable ingot in the step S1 is obtained by smelting through a triple process of vacuum induction smelting, protective atmosphere electroslag remelting and vacuum consumable remelting.

10. A bar produced by the cogging method of any one of claims 1 to 9.