CN113877982B

CN113877982B - Hardly-deformable GH4720Li high-temperature alloy small-size bar, preparation method and blade forging

Info

Publication number: CN113877982B
Application number: CN202110985803.7A
Authority: CN
Inventors: 曲敬龙; 杜金辉; 史玉亭; 安腾; 孟令胜; 谷雨; 段方震; 王民庆; 王成宇
Original assignee: Central Iron and Steel Research Institute; Gaona Aero Material Co Ltd
Current assignee: Central Iron and Steel Research Institute; Gaona Aero Material Co Ltd
Priority date: 2021-08-26
Filing date: 2021-08-26
Publication date: 2022-07-19
Anticipated expiration: 2041-08-26
Also published as: CN113877982A

Abstract

The application relates to the field of nickel-based superalloy hot working, and particularly discloses a GH4720Li superalloy small-size bar difficult to deform, a preparation method and a blade forging. The preparation method of the difficult-to-deform GH4720Li high-temperature alloy small-size bar comprises the following steps of S1: preparing an alloy ingot by adopting a duplex or a triplex smelting process; s2: rapid forging, comprising elongation of at least 2 shots and/or upsetting of at least 1 shot; s3: radial forging, wherein unidirectional drawing of at least 1 fire time is carried out along the axial direction; s4: rolling for at least 1 heating number along the axial direction, sheathing the product by using heat-insulating cotton in the preparation process, wherein the alloy bar has good high-temperature strength and hot-working plasticity and high yield, the tensile strength at 750 ℃ reaches more than 1135MPa, the elongation reaches more than 12 percent after heat treatment, the small-specification bar has uniform and controllable structure, and the grain size can reach ASTM grade 8 and above.

Description

Hardly-deformable GH4720Li high-temperature alloy small-size bar, preparation method and blade forging

Technical Field

The application relates to the technical field of nickel-based superalloy hot working, in particular to a GH4720Li superalloy small-size bar difficult to deform, a preparation method thereof and a blade forging.

Background

The GH4720Li high-temperature alloy is used as a novel nickel-based high-temperature alloy difficult to deform, the long-term service temperature of the alloy can reach 700-750 ℃, and the alloy has good high-temperature strength, good fatigue and creep properties, excellent corrosion resistance and oxidation resistance and long-term high-temperature structure stability. When the sum of the Al element content and the Ti element content reaches 7.5 wt% or more, the gamma' strengthening phase mass fraction of the GH4720Li high-temperature alloy reaches 42-45%, but the GH4720Li high-temperature alloy has increased deformation resistance, reduced hot working plasticity, increased cracking tendency in the bar forging and rolling process, and high sensitivity of grain recrystallization to deformation parameters, so that the difficulty in the bar forging and rolling thermal deformation process and the structure control is increased.

Currently, in related researches, when preparing GH4720Li high-temperature alloy forgings, alloy ingots with the diameter of phi 508mm or phi 406mm are directly prepared into rods with the diameter of phi 100 and phi 250mm through a forging process. However, when a blade forging with a smaller volume is prepared, an ingot with the diameter of phi 508mm or phi 406mm needs to be prepared into a small-size bar with the diameter of phi 15-50mm, but when the small-size bar with the diameter of phi 15-50mm is prepared by the existing forging process, the bar of the GH4720Li high-temperature alloy has the problems of large cracking tendency, low yield and poor performance.

Disclosure of Invention

In order to provide small-size bars with good performance and high yield, the application provides the GH4720Li high-temperature alloy small-size bars difficult to deform, a preparation method and a blade forging.

In a first aspect, the application provides a preparation method of a small-size bar of a GH4720Li high-temperature alloy difficult to deform, which adopts the following technical scheme:

a preparation method of a hardly deformable GH4720Li high-temperature alloy small-size bar comprises the following steps:

s1: preparation of alloy ingot

Carrying out Vacuum Induction Melting (VIM), vacuum consumable melting (VAR) and homogenizing annealing on alloy raw materials to obtain an alloy ingot;

s2: quick forging

Performing unidirectional drawing on the alloy cast ingot for more than 2 times of fire, wherein the finish forging temperature of each fire is not lower than 950 ℃, and obtaining an alloy bar blank;

s3: radial forging

Carrying out unidirectional drawing on the alloy bar blank for more than 1 fire time along the axial direction, wherein the finish forging temperature of each fire time is not lower than 950 ℃, and obtaining an intermediate blank;

s4: rolling of

And (3) rolling the intermediate blank for more than 1 fire time along the axial direction, wherein the finish forging temperature of each fire time is not lower than 950 ℃, and obtaining the small-specification bar.

By adopting the technical scheme, the alloy ingot consists of the following chemical elements in percentage by weight: c (0.006-0.012)%; cr (16.0-17.0)%; ti (4.95-5.20)%; al (2.45-2.65)%; b (0.01-0.02)%; co (14.00-15.00)%; fe is less than or equal to 0.50 percent; w (1.10-1.40)%; mo (2.75-3.25)%; zr (0.025-0.05)%; ni is the rest. Then the alloy ingot with the diameter of phi 406mm is prepared by a Vacuum Induction Melting (VIM), a vacuum consumable melting (VAR) and a homogenizing annealing, namely a duplex smelting process.

The Vacuum Induction Melting (VIM) comprises three stages of a melting period, a refining period and a pouring period, wherein the total melting temperature in the melting period is 1470-1520 ℃, the refining temperature in the refining period is 1520-1550 ℃, and the pouring temperature in the pouring period is 1445-1465 ℃; in the stage of vacuum consumable melting (VAR), the vacuum degree is controlled to be 0.2-0.55Pa in the vacuum consumable melting period, helium is filled after a molten pool is formed, and the melting speed of the induction electrode bar is 2.5-3.5 kg/min. Finally, carrying out homogenization annealing treatment on the alloy ingot, wherein the annealing temperature is 1150-1200 ℃, and the heat preservation time is 60-90 h.

And (3) heating the alloy ingot after the homogenizing annealing again, placing the alloy ingot in a heating furnace for heating at the temperature of 1120-1150 ℃, and then performing unidirectional drawing on the alloy ingot on a quick forging machine for more than 2 times to obtain an alloy bar blank, wherein the deformation of the single time is not more than 50%, and when the deformation is more than 50%, the alloy bar blank has a large cracking tendency and irreparable cracks, so that the bar is scrapped. And heating the alloy bar blank to 1100-1130 ℃ in a heating furnace, and performing unidirectional drawing on the alloy bar blank on a radial forging machine for more than 1 fire number, wherein the deformation is not more than 50 percent, so as to obtain an intermediate blank. Heating the intermediate billet to 1080-1130 ℃ in a heating furnace, and rolling the intermediate billet for more than 1 fire time on a hot rolling mill along the axial direction of the intermediate billet to finally obtain the GH4720Li high-temperature alloy small-specification bar with the diameter of phi 15-50 mm. In the processes of quick forging, radial forging and rolling, the blank is integrally wrapped by heat-insulating cotton, so that the cooling of the blank is delayed, the working time is increased, and the heating times of the bar are reduced.

Quick forging: the rapid forging is an effective method for preparing bars from cast ingots by deforming the high-temperature alloy, and the GH4720Li high-temperature alloy is forged by unidirectional drawing or upsetting, so that the structure in the cast ingots can be effectively broken at a heating temperature to obtain fine and uniform grain structures. Meanwhile, the shape and the size of the cast ingot are finished according to the requirement of the bar, and meanwhile, the excellent plasticity of the fine grain structure is matched, so that the preparation is made for the subsequent hot processing.

Radial forging: the rapid forging process is more sufficient for the deformation of the center and the R/2 position of the bar, but the deformation of the surface of the bar is smaller, and the surface structure of the bar is relatively thicker only through the rapid forging treatment. The diameter forging process mainly improves the surface structure of the bar and can obtain fine and uniform grain structure. Because the fast forged bar is large in size and poor in surface quality, the shape and size of the bar can be finished to meet the bar requirement through the radial forging process.

Quick forging and radial forging: therefore, by adopting the forging mode combining the quick forging and the radial forging, the grain structure in the intermediate blank is uniform and fine from the center to the edge, so that the intermediate blank has better hot working plasticity and is ready for preparing small-specification bars in the subsequent rolling process, and meanwhile, the size of the intermediate blank obtained by the alloy ingot casting is matched with the size of rolling equipment after the alloy ingot casting is subjected to the quick forging and the radial forging.

Rolling: the rolling process in the application is mainly a hot rolling process, the grain structure is further refined through large deformation and temperature matching, and meanwhile, a small-specification bar for preparing the blade forging is obtained through rolling, and the diameter of the small-specification bar is phi 15-50 mm.

Preferably, the alloy ingot preparation step further comprises electroslag remelting (ESR) which is performed after Vacuum Induction Melting (VIM) and before vacuum consumable melting (VAR).

By adopting the technical scheme, after Vacuum Induction Melting (VIM) and before vacuum consumable melting (VAR), electroslag remelting (ESR) is carried out, so that the content of non-metallic inclusions in the alloy ingot can be effectively reduced, and the structure in the alloy ingot is more uniform. Alloy ingots with the diameter of phi 508mm are prepared by utilizing Vacuum Induction Melting (VIM), electroslag remelting (ESR), vacuum consumable melting (VAR) and homogenizing annealing, namely a triple smelting process. In the electroslag remelting (ESR) stage, the slag system selected is CaF₂/CaO/Al₂O₃/TiO₂MgO, slag CaF₂：CaO：Al₂O₃：TiO₂: the weight ratio of MgO is 55: 20: 15: 5: 5.

preferably, the step S2 of fast forging may further include upsetting more than 1 heating, the upsetting forging is suitable for the aspect ratio not greater than 3, and the upsetting is performed before the unidirectional drawing.

By adopting the technical scheme, for example, the size of the alloy ingot with the diameter of phi 406mm is about 406mm multiplied by 1500mm, the height-diameter ratio is 3.7mm, the size of the alloy ingot with the diameter of phi 508mm is 508mm multiplied by 1400mm, and the height-diameter ratio is 2.76 mm.

When the height-diameter ratio of the alloy cast ingot reaches more than 3, the length direction dimension of the alloy cast ingot is longer, the diameter direction dimension of the alloy cast ingot is shorter, the alloy cast ingot is inclined and folded due to instability in the upsetting process due to the equipment centering problem, the alloy cast ingot structure is not subjected to deformation refinement with more fire times, the plasticity is extremely poor, cracks which cannot be closed are easily generated at the folded position, and even the alloy bar blank prepared from the alloy cast ingot can be scrapped.

And the alloy ingot with the height-diameter ratio of less than 3 is not easy to be unstable in the upsetting process, and the upsetting process with at least 1 heating number is more favorable for refining grains along the axial direction of the alloy ingot, so that the axial and radial uniformity of the equiaxial crystal structure of the alloy bar blank prepared from the alloy ingot can be ensured.

Preferably, the alloy ingot is subjected to unidirectional drawing for 5 times.

Preferably, the alloy bar billet is subjected to unidirectional drawing for 2 times.

By adopting the technical scheme, generally, in the quick forging process, the unidirectional drawing times are more than 3-6 times, and more than 6 times or even more times are possible according to the requirements of products. According to the method, the unidirectional drawing of 3 fire times or 4 fire times or 5 fire times is carried out on a quick forging machine, and the deformation of the alloy cast ingot is accumulated. In the radial forging process, unidirectional drawing of 1 or 2 or 3 fire passes is generally performed, when the number of unidirectional drawing fire passes is small, the risk of cracking exists, and when the number of unidirectional drawing fire passes is large, the risk of cracking can be minimized, but resources are wasted.

Preferably, the intermediate billet is rolled by 10 passes in the axial direction.

By adopting the technical scheme, the intermediate blank is rolled by 1 fire, then is changed into a small-specification bar with the diameter of phi 15-50mm, if the intermediate blank is rolled by 2 fire, 3 fire and above, the deformation of each fire is controlled, and when the rolling frequency reaches 10 fire, the cracking possibility of the intermediate blank is lower, and the yield is higher.

Preferably, the step S2 of rapid forging further includes 2 times of upsetting.

By adopting the technical scheme, the step S2 of quick forging also comprises 2 times of heating or 3 times of heating and more than upsetting, when 2 times of heating or 3 times of heating are adopted, the upsetting is firstly carried out for 1 time of heating, then the unidirectional lengthening is carried out for 1 time of heating, then the upsetting is carried out for 1 time of heating, and finally the unidirectional lengthening is carried out for 1 time of heating or more than one time of heating.

In a second aspect, the application provides a small-size bar made of a GH4720Li high-temperature alloy difficult to deform, and the following technical scheme is adopted:

a hardly deformable GH4720Li high-temperature alloy small-size bar is prepared by the preparation method.

Preferably, the size of the small-size bar is phi 15-50 mm.

By adopting the technical scheme, a plurality of specifications of high-temperature alloy ingots are internationally used at present, a phi 340mm alloy ingot prepared by a single-link (VIM) smelting process, a phi 406mm alloy ingot prepared by a double-link smelting process and a phi 508mm alloy ingot prepared by a triple-link smelting process are utilized, alloy ingots with the diameter of phi 660mm can be prepared to the maximum extent by utilizing a triple-link smelting process, and the process and the size of each specification are matched with each other. The single-connection smelting process has serious shrinkage cavity and is not suitable for most high-temperature alloys. According to actual production and demand conditions, the GH4720Li high-temperature alloy is most suitable for duplex or triple, the smelting process and the size of a crystallizer are matched, two general specifications of phi 406mm prepared by duplex smelting and phi 508mm prepared by triple smelting are mainly adopted, and the technology of the phi 660mm specification for the difficultly-deformed high-temperature alloy is not mature.

The small-size bar is prepared from GH4720Li high-temperature alloy cast ingots with the diameter of phi 508mm or phi 406mm by the preparation method, and the diameter of the small-size bar is phi 15-50 mm. Generally, the GH4720Li high-temperature alloy is prepared into bars with the specification of phi 100 and 250mm by adopting smelting and quick forging or smelting, quick forging and radial forging methods, and is mainly used for preparing engine disc parts. The bar with the diameter of 15-50mm and smaller specification is difficult to prepare by using the same process, the cracking in the preparation process is serious, the forging of the blade by adopting the bar with the diameter of 100-250mm is more material-wasting, and the performance is poorer.

In a third aspect, the application provides a GH4720Li superalloy blade forging, which adopts the following technical scheme: a GH4720Li high-temperature alloy blade forging is prepared from a small-specification GH4720Li high-temperature alloy bar which is difficult to deform.

By adopting the technical scheme, the forged blade is widely applied to an aircraft engine compressor, particularly as a last-stage blade of a novel high-pressure compressor, and the red line temperature of the forged blade reaches 730 ℃. The widely applied high-temperature alloy is GH4169 alloy at present, and GH4169 high-temperature alloy blade forging material is mainly used below 650 ℃, and cannot meet the requirement of high-temperature long-term service temperature of the last-stage blade of the high-pressure compressor. The GH4720Li high-temperature alloy is used as a novel nickel-based high-temperature alloy difficult to deform, the long-term service temperature of the GH4720Li high-temperature alloy can reach 700-750 ℃, and the GH4720Li high-temperature alloy has good high-temperature strength, good fatigue and creep properties, excellent corrosion resistance and oxidation resistance and long-term high-temperature tissue stability. GH4720Li high-temperature alloy cast ingots with the diameter of phi 508mm or phi 406mm are prepared through a smelting process, small-specification bars with the diameter of phi 15-50mm are prepared through a quick forging, radial forging and rolling method, and then the small-specification bars are used for producing blade forgings.

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

1. according to the application, the GH4720Li high-temperature alloy is adopted to prepare the small-specification bar, wherein the sum of the Al element content and the Ti element content is 7.4-7.85 wt%, the mass fraction of the gamma' strengthening phase is as high as 42-45%, and the bar has good high-temperature strength, good fatigue and creep properties and long-term high-temperature structure stability;

2. the application adopts the preparation method of fast forging, radial forging and rolling, so that the small-sized bar has good high-temperature strength and hot working plasticity and high yield, and after heat treatment, the tensile property at 400 ℃, 650 ℃ and 750 ℃ reaches the service requirement; the tensile strength at 400 ℃ can reach more than 1560MPa, and the elongation can reach more than 27%; the tensile strength at 650 ℃ can reach more than 1410MPa, and the elongation can reach 23% and more; the tensile strength at 750 ℃ can reach more than 1135MPa, and the elongation can reach more than 12%.

3. The preparation method of rapid forging, radial forging and rolling is adopted, so that the small-size bar has uniform and controllable structure and no coarse crystal or strip structure. After the bar is subjected to heat treatment, the grain size can reach ASTM grade 8 or above;

4. by adopting the preparation method of quick forging, radial forging and rolling, the small-size bar has good forging plasticity, can be used for preparing the compressor blade forging and provides material support for the development of an aeroengine.

Drawings

FIG. 1 is a 100 times grain photograph of the GH4720Li superalloy of example 1;

FIG. 2 is a 100 times grain photograph of the GH4720Li superalloy of example 2;

FIG. 3 is a 100 times grain photograph of the GH4720Li superalloy of example 3;

FIG. 4 is a 100 times grain photograph of the GH4720Li superalloy of example 4;

FIG. 5 is a 100 Xgrain photograph of the GH4720Li superalloy of example 5;

FIG. 6 is a 100 times grain photograph of the GH4720Li superalloy of example 6;

FIG. 7 is a 100 times grain photograph of the GH4720Li superalloy of comparative example 1;

FIG. 8 is a 100 Xgrain photograph of GH4720Li superalloy of comparative example 2;

FIG. 9 is a 100 times grain photograph of the GH4720Li superalloy of comparative example 3;

FIG. 10 is a 100 times grain photograph of the GH4720Li superalloy of comparative example 4;

FIG. 11 is a 100 times grain photograph of the GH4720Li superalloy of comparative example 5;

FIG. 12 is a 100 Xgrain photograph of GH4720Li superalloy of comparative example 6.

Detailed Description

The present application will be described in further detail with reference to the drawings and examples.

The small-size bar is prepared from GH4720Li high-temperature alloy ingots with the diameter of phi 508mm or phi 406mm, raw materials are prepared into the small-size bar with the diameter of phi 15-50mm through smelting, quick forging, radial forging and rolling, and the small-size bar can be used for preparing compressor blade forgings.

Examples of the present application include the following preparation processes.

Vacuum Induction Melting (VIM)

1. Preparing raw materials, namely C (0.006-0.012%) by using the following chemical elements in percentage by weight; cr (16.0-17.0)%; ti (4.95-5.20)%; al (2.45-2.65)%; b (0.01-0.02)%; co (14.00-15.00)%; fe is less than or equal to 0.50 percent; w (1.10-1.40)%; mo (2.75-3.25)%; zr (0.025-0.05)%; the balance being Ni.

2. Charging and vacuumizing, namely putting the raw materials into a vacuum induction furnace and vacuumizing;

3. fully melting the raw materials, adding the raw materials containing W, Mo, Co and Ni elements in the melting period, wherein the full melting temperature is 1485 +/-5 ℃; raw materials containing Cr, Ti and Al elements are added in the refining period, and electromagnetic stirring is carried out; the refining temperature is 1525 +/-5 ℃;

4. sampling and detecting, namely after the element content reaches a specified range, adding Ni-Mg rare earth, and discharging;

5. pouring, before pouring, argon is filled into an ingot mold (the diameter is phi 100-150mm), and the alloy liquid is poured when the temperature is controlled at 1460 +/-5 ℃;

6. and (5) cooling and solidifying, namely continuously cooling the alloy liquid to room temperature in the ingot mould, and solidifying to obtain the induction electrode bar.

(II) electroslag remelting (ESR)

The surface is polished, a riser is cut, and then the electrode head is welded.

Carrying out electroslag remelting smelting on the induction electrode bar, introducing argon in the whole smelting process, wherein the adopted slag system is CaF₂/CaO/Al₂O₃/TiO₂The proportion of MgO is 55 wt% -20 wt% -15 wt% -5 wt%, and the electroslag remelting electrode rod is obtained through the stages of slagging → arcing → remelting → feeding → cooling → demoulding and the like.

(III) vacuum consumable melting (VAR)

And (3) performing polishing treatment on the surface of the remelted electrode rod, removing surface oxide skin, processing until the head end surface and the tail end surface are parallel, and then welding the head part of the electrode.

Vacuum consumable melting, controlling the vacuum degree to be 0.3Pa, filling helium gas after a molten pool is formed, controlling the pressure of the helium gas to be 500Pa, controlling the melting speed of the induction electrode bar to be 3.0kg/min, solidifying the molten alloy in a steel ingot mould (the diameter is phi 508mm or phi 406mm), and demoulding to obtain an alloy ingot;

homogenizing annealing of (IV) alloy ingot

And (3) placing the alloy ingot into a heat treatment furnace for homogenization annealing, wherein the heat treatment furnace is a gas heat treatment furnace generally, the annealing temperature is 1170 +/-5 ℃, and the heat preservation time is 68 +/-0.5 h.

(V) quick forging

And (3) reheating the alloy ingot after the homogenizing annealing, wherein the heating temperature is 1120-1150 ℃, upsetting for at least 1 fire time and unidirectional drawing for at least 2 fire times are carried out on the alloy ingot on a quick forging machine along the axial direction, the finish forging temperature of each fire time is not lower than 950 ℃, the ratio of the upset lower pressure to the diameter is not more than 3, the deformation of each fire time is not more than 50%, an alloy bar blank is obtained, and heat insulation cotton is adopted to sheath the alloy ingot in the forging process.

(VI) radial forging

Heating the alloy bar blank to 1100-1130 ℃ in a heating furnace, carrying out unidirectional drawing of the alloy bar blank on a radial forging machine for at least 1 fire time along the axial direction, wherein the finish forging temperature of each fire time is not lower than 950 ℃, the deformation of each fire time is not more than 50 percent, obtaining an intermediate blank, and sheathing the alloy bar blank by using heat insulation cotton in the radial forging process;

(seventh) Rolling

Heating the intermediate billet to 1080-1130 ℃ in a heating furnace, and rolling the intermediate billet for at least 1 fire time on a hot rolling mill along the axial direction of the intermediate billet to obtain the GH4720Li high-temperature alloy small-specification bar with the diameter of phi 15-50 mm.

Examples

The parameters in examples 1-6 in this application are shown in table 1.

TABLE 1 parameters in examples 1-6

Table 1 double refers to: vacuum Induction Melting (VIM), vacuum consumable melting (VAR) and homogenizing annealing; triple refers to: vacuum Induction Melting (VIM), electroslag remelting (ESR), vacuum consumable melting (VAR) and homogenizing annealing; in Table 1, "-" indicates that no upsetting treatment was performed in examples 1 and 2.

Comparative example

The differences between comparative examples 1 to 6 and examples 1 to 6 are shown in Table 2.

Table 2 parameters in comparative examples

Table 2 double refers to: vacuum Induction Melting (VIM), vacuum consumable melting (VAR) and homogenizing annealing; triplet refers to: vacuum Induction Melting (VIM), electroslag remelting (ESR), vacuum consumable melting (VAR) and homogenizing annealing; in Table 2, "-" indicates that no upsetting treatment was performed in comparative example 1 and comparative example 2.

Performance test

Firstly, measuring components

Elements and contents within the small scale are determined by wet chemical or spectrochemical methods, according to the ASTM E354 standard. Because the embodiment 1 and the comparative example 1 adopt a duplex smelting process and belong to the same batch production, and the embodiments 2-6 and the comparative examples 2-6 are prepared by the duplex smelting process and belong to the same batch production, only the elements and the contents of the embodiments 1 and 2 need to be measured, and the specific results are shown in table 3.

Table 3 ingredient test table (wt%)

Element(s)	C	Cr	Ti	Al	B	Co	W	Mo
									Example 1	0.008	16.35	5.05	2.46	0.013	14.78	1.3	3.18
Example 2	0.009	16.34	5.07	2.54	0.013	14.7	1.28	3.07
									Element(s)	Zr	Fe	Si	P	S	O	N	Ni
Example 1	0.033	0.093	0.017	＜0.005	0.0004	0.0005	0.0012	Balance of
									Example 2	0.033	0.096	0.014	＜0.005	＜0.0004	0.0004	0.001	Balance of

Second, observation of metallographic structure

1. Sampling: the sample should be taken in a square shape with a size of 30X 50mm, which ensures that the observation surface of the sample does not change the structure.

2. Preparing a metallographic sample: rough grinding → fine grinding → polishing → corrosion, the structure observation is carried out under the metallographic microscope.

Thirdly, detecting the mechanical property and the yield

The alloy ingot is subjected to rapid forging, radial forging and rolling to obtain a small-size bar with the diameter of 15-50mm, the small-size bar needs to be subjected to heat treatment, the heat treatment process comprises solution heat treatment and two-step aging heat treatment, and specific parameters can be referred to book of China handbook, China quality control Press, China Standard Press, first edition of 7 months 2012. The high temperature tensile properties were measured according to ASTM E21 and tested on small gauge bars at 400 deg.C, 650 deg.C and 750 deg.C.

The yield is a certain ratio relation determined by production enterprises according to the conditions of qualified finished products produced by the products and the total input amount of approved product materials in the process of producing the products, the input products in the application refer to alloy ingots obtained after smelting, and the qualified products refer to flawless small-size bars obtained after fast forging, radial forging and rolling of the alloy ingots.

The specific results are shown below:

TABLE 4 mechanical property test results at 400 deg.C

Categories	Tensile strength/MPa	Yield strength/MPa	Elongation rate/%)
				Example 1	1560	1134	27
Example 2	1568	1140	28
				Example 3	1570	1142	28
Example 4	1572	1142	27.5
				Example 5	1572	1145	28.5
Example 6	1575	1151	28.5
				Comparative example 1	1510	1085	18
Comparative example 2	1512	1087	18.5
				Comparative example 3	1512	1090	19
Comparative example 4	1515	1090	20
				Comparative example 5	1532	1113	23.5
Comparative example 6	1505	1075	15

TABLE 5 mechanical Property test results at 650 deg.C

TABLE 6 mechanical property test results at 750 deg.C

Categories	Tensile strength/MPa	Yield strength/MPa	Elongation rate/%)
				Example 1	1135	870	12.5
Example 2	1143	875	12.5
				Example 3	1143	876	12
Example 4	1145	878	12.5
				Example 5	1147	878	13
Example 6	1148	880	13
				Comparative example 1	1115	855	10
Comparative example 2	1115	850	10.5
				Comparative example 3	1118	852	10
Comparative example 4	1120	850	9.5
				Comparative example 5	1126	860	11
Comparative example 6	1107	848	9

TABLE 7 yield (%)

As can be seen by combining examples 1-6 and comparative examples 1-6 with tables 4, 5, 6, and 7, the tensile strength, yield strength, elongation, and yield rate were higher in examples 1-6 than in comparative examples 1-6 at 450 deg.C, 600 deg.C, and 700 deg.C.

Combining example 1 and comparative example 1, example 2 and comparative example 2, and combining tables 4, 5 and 6, it can be seen that the finish forging temperature of comparative example 1 and comparative example 2 is below 950 ℃, which directly affects the tensile strength, yield strength and elongation at different temperatures.

When the number of fire cycles of the unidirectional elongation in comparative example 5 is 1, the tensile strength, yield strength and elongation are reduced in different temperature ranges, which directly affects the yield, and the yield is low, thereby increasing the production cost, as can be seen by combining example 5 with comparative example 5 and tables 4, 5, 6 and 7.

As can be seen from the combination of examples 1-6 and FIGS. 1-6, the metallographic photograph of the bar prepared by the duplex ingot in example 1 and the metallographic photograph of the bar prepared by the triplet ingot in examples 2-6 show that the average grain size of the bars prepared by the duplex ingot in examples 2-6 can reach ASTM grade 8 or even be finer, and the grains are uniformly distributed without mixed grains. Examples 2 to 6 did not show precipitation of harmful TCP phases, and no aggregation of foreign substances.

As can be seen by combining examples 1-6 and comparative examples 1-6 with FIGS. 1-12, the metallographic pictures of examples 1-6 are superior to comparative examples 1-6 in terms of grain structure uniformity, average grain size and mixed grains.

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 preparation method of a hardly deformable GH4720Li high-temperature alloy small-size bar is characterized by comprising the following steps of,

s1: preparation of alloy ingot

Performing Vacuum Induction Melting (VIM), electroslag remelting (ESR), vacuum consumable melting (VAR) and homogenizing annealing on alloy raw materials to obtain an alloy ingot with the size of phi 508mm or phi 406 mm;

s2: quick forging

Performing unidirectional drawing on the alloy ingot for more than 2 times, wherein the heating temperature of the alloy ingot is 1120-1150 ℃, the deformation of the alloy ingot for one time is not more than 50%, and the finish forging temperature of each time is not lower than 950 ℃ to obtain an alloy bar blank;

s3: radial forging

Performing unidirectional drawing on the alloy bar blank for more than 1 fire time along the axial direction, wherein the heating temperature of the alloy bar blank is 1100-1130 ℃, the deformation is not more than 50%, and the finish forging temperature of each fire time is not lower than 950 ℃, so as to obtain an intermediate blank;

s4: rolling of

Rolling the intermediate blank for more than 1 fire time along the axial direction, heating the intermediate blank to 1080-1130 ℃ in a heating furnace, wherein the final rolling temperature of each fire time is not lower than 950 ℃, and obtaining a small-specification bar material, wherein the size of the small-specification bar material is phi 15-45 mm;

the tensile strength of the small-size bar at 750 ℃ can reach more than 1143MPa, and the elongation can reach more than 12%.

2. The method for preparing the difficult-to-deform GH4720Li high-temperature alloy small-size bar according to claim 1, wherein the method comprises the following steps: the step S2 of quick forging also comprises upsetting more than 1 firing time, wherein the diameter-diameter ratio under upsetting is not more than 3, and the upsetting is operated before unidirectional drawing.

3. The preparation method of the difficult-to-deform GH4720Li high-temperature alloy small-size bar according to claim 1, wherein the method comprises the following steps: and (3) carrying out unidirectional drawing of the alloy ingot for 5 times.

4. The preparation method of the difficult-to-deform GH4720Li high-temperature alloy small-size bar according to claim 1, wherein the method comprises the following steps: and (3) carrying out unidirectional drawing on the alloy bar blank for 2 times.

5. The preparation method of the difficult-to-deform GH4720Li high-temperature alloy small-size bar according to claim 1, wherein the method comprises the following steps: and rolling the intermediate blank for 10 times in the axial direction.

6. The method for preparing the difficult-to-deform GH4720Li high-temperature alloy small-size bar according to claim 2, wherein the method comprises the following steps: the step S2 of rapid forging also includes 2 times of upset forging.

7. A hardly deformable GH4720Li high temperature alloy small-sized bar, characterized in that the small-sized bar is prepared by the preparation method of any one of claims 1 to 6.

8. The GH4720Li superalloy blade forging, its characterized in that: prepared from a hard-to-deform GH4720Li superalloy small gauge bar of claim 7.