Preparation method of low residual stress, creep resistant, coarse-grained superalloy rings against temperature gradient

Abstract

This invention belongs to the field of high-temperature alloy ring forging and processing, specifically relating to a method for preparing low residual stress, creep-resistant, coarse-grained high-temperature alloy rings against a reverse temperature gradient. The technical solution is as follows: including the following steps: Step 1, determining the critical temperature T for grain growth through a fire-starting test. C and critical time t C Step 2: Determine the critical deformation for obtaining uniform fine and coarse grains in high-temperature alloy materials through near-isothermal compression tests on double-cone specimens; Step 3: Upset and punch the high-temperature alloy bars; Step 4: Low-temperature large deformation pre-rolling; Step 5: High-temperature small deformation final rolling; Step 6: Bulging: The bulging heating temperature is T. C -30℃~T C At -80℃, the bulging deformation is 1%~4%. This invention constructs a multi-scale structure of "coarse-grained, low residual stress, creep-resistant matrix + high-density dislocation reinforcement band" through reverse temperature gradient process design, providing sufficient creep resistance and low residual stress while ensuring strength and stiffness.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature alloy ring forging and processing, and specifically relates to a method for preparing low residual stress, creep-resistant, coarse-grained high-temperature alloy rings against the temperature gradient. Background Technology

[0002] The casing is a major load-bearing component of an aero-engine, with a complex external structure. During operation, it primarily bears gas loads and inertial forces, as well as thermal loads, acoustic loads, and assembly stresses. Therefore, in addition to ensuring strength and rigidity, sufficient creep resistance and low residual stress are required, necessitating the preparation of a uniform coarse-grained microstructure for high-temperature alloy casing rings. With rising raw material prices and increasing demand for high-temperature alloy rings, improving material utilization through irregularly shaped ring forming is the preferred path to reduce the manufacturing costs of rings and aero-engines. However, irregularly shaped rings have complex cross-sections. While methods that gradually decrease the temperature and increase the deformation with each heat treatment can achieve a relatively uniform microstructure distribution, they typically result in significant grain refinement, accompanied by high residual stress and low creep resistance, making it difficult to meet the performance requirements of low residual stress and creep resistance for aero-engine rings. Existing high-temperature alloy ring forming processes employ a gradient temperature method with step-by-step cooling during upsetting, punching, pre-rolling, and final rolling, and a method for forming large deformation amounts. While this results in forgings with fine grains, it also presents problems such as high residual stress, large machining allowance, and low creep performance. Summary of the Invention

[0003] This invention provides a method for preparing low residual stress, creep-resistant coarse-grained superalloy ring components using a reverse temperature gradient. By designing a reverse temperature gradient process, a multi-scale structure of "coarse-grained, low residual stress, creep-resistant matrix + high-density dislocation reinforcement band" is constructed. While ensuring strength and stiffness, this method provides sufficient creep resistance and low residual stress, thereby ensuring the low-cost and high-performance preparation of aero-engine casing ring components.

[0004] The technical solution of the present invention is as follows:

[0005] A method for preparing low residual stress, creep-resistant, coarse-grained superalloy rings against a reverse temperature gradient includes the following steps:

[0006] Step 1: Through fire-out tests and metallographic analysis, establish the relationship between the grain size grade of high-temperature alloy materials and the heating temperature and time of the fire-out test, and determine the critical temperature T for grain growth. C and critical time t C ;

[0007] Step 2: Through near-isothermal compression tests on double-cone specimens, determine the critical equivalent strain ε for high-temperature alloy materials to achieve uniform fine grains under different temperature conditions. FCand the critical equivalent strain ε for obtaining uniform coarse grains CC ;

[0008] Step 3: The high-temperature alloy bar is upsetting and punching. The heating temperature for both upsetting and punching is T. C +30℃~T C At +50℃, the equivalent strain is ≥ε FC ; Obtain the billet;

[0009] Step 4, Low-temperature large deformation pre-rolling: The billet is pre-rolled twice, with the heating temperature for both pre-rolling stages being T. C -10℃~T C -40℃, pre-rolled equivalent strain ≥0.5×(ε) FC +ε CC ); to obtain pre-rolled parts;

[0010] Step 5, High-Temperature Small Deformation Final Rolling: The pre-rolled part is subjected to final rolling at a heating temperature of T. C +5℃~T C +30℃, heating time ≥t C The final rolling equivalent becomes (0.6~0.9)×ε CC ; to obtain the final rolled product;

[0011] Step 6, Bulging: The final rolled part is bulged, and the bulging heating temperature is T. C -30℃~T C At -80℃, the bulging deformation is 1%~4%.

[0012] Furthermore, in the method for preparing low residual stress, creep-resistant, coarse-grained high-temperature alloy rings against the reverse temperature gradient, in step 1, the temperature interval of the air-firing test heating temperature is 10℃, and the heating time is 30min~240min.

[0013] The beneficial effects of this invention are as follows: This invention achieves small-margin forming of high-temperature alloy rings by using a reverse temperature gradient process design, low-temperature large deformation pre-rolling + high-temperature small deformation final rolling, and constructs a multi-scale structure of "coarse-grained low residual stress creep-resistant matrix + high-density dislocation strengthening band". While ensuring strength and stiffness, it provides sufficient creep resistance and low residual stress, thereby ensuring low-cost and high-performance preparation of aero-engine casing rings. Attached Figure Description

[0014] Figure 1 Flowchart of a method for preparing low residual stress, creep-resistant, coarse-grained superalloy rings against the reverse temperature gradient;

[0015] Figure 2 Comparison of metallographic structures before and after application of the reverse temperature gradient preparation method for GH4169 alloy irregular cross-section rings; where (a) is before application and (b) is after application.

[0016] Figure 3 Comparison of metallographic structures before and after application of the reverse temperature gradient preparation method for GH4738 alloy irregular cross-section rings; where (a) is before application and (b) is after application. Detailed Implementation

[0017] Example 1

[0018] like Figure 1 As shown, the method for preparing a GH4169 alloy irregular cross-section ring with an inverse temperature gradient includes the following steps:

[0019] Step 1: Through fire-off tests and metallographic analysis, the relationship between the grain size grade of GH4169 alloy and the fire-off test heating temperature and heating time was established. The fire-off test heating temperature was 960℃~1040℃, the temperature interval was 10℃, and the heating time was 30min~240min. The grain size grade was evaluated according to GB / T 6394-2017, and the evaluation results are shown in Table 1. The critical temperature T for grain growth was obtained. C For 1000℃ and critical time t C For 40 minutes;

[0020] Table 1: Grain Size Grades of GH4169 Alloy under Heating

[0021]

[0022] Step 2: Through near-isothermal compression tests on double-cone specimens, determine the critical equivalent strain ε for GH4169 alloy to achieve uniform fine grains under different temperature conditions. FC and the critical equivalent strain ε for obtaining uniform coarse grains CC The data is shown in Table 2:

[0023] Table 2: Critical Deformation of GH4169 Alloy Rings

[0024]

[0025] Step 3: The GH4169 alloy bar is upset and punched. The heating temperature for both upset and punching is T. C +40℃ = 1040℃, the equivalent effect becomes 1.8 ≥ ε FC =1.5; Improves the uniformity of grain structure to obtain billet;

[0026] Step 4, Low-temperature large deformation pre-rolling: The billet is pre-rolled twice, with the first pre-rolling heating temperature being T. C -20℃ = 980℃, the pre-rolling equivalent becomes 1.3 ≥ 0.5 × (ε) FC +ε CC=0.5×(1.8+0.43)=1.115; the second pre-rolling heating temperature is T. C -20℃ = 980℃, the pre-rolling equivalent becomes 1.2 ≥ 0.5 × (ε) FC +ε CC =0.5×(1.8+0.43)=1.115; A fine-grained or non-uniform structure is obtained, yielding the pre-rolled part;

[0027] Step 5, High-Temperature Small Deformation Final Rolling: The pre-rolled part is subjected to final rolling at a heating temperature of T. C +20℃ = 1020℃, heating time 60min ≥ t C =40min, the final rolling equivalent effect becomes 0.9×ε CC =0.9×0.38=0.342; A uniform coarse-grained structure is obtained, and the final rolled part is obtained;

[0028] Step 6, Bulging: The final rolled part is bulged, and the bulging heating temperature is T. C -40℃ = 960℃, the bulging deformation is 2.5%; high-temperature bulging reduces residual stress.

[0029] The GH4169 alloy irregular-shaped ring parts produced show a significant reduction in forging allowance; for example... Figure 2 As shown, the grain size coarsened after the application of the reverse temperature gradient preparation method; the tensile properties were comparable, but the residual stress and creep deformation were significantly reduced. The residual stress was detected using the blind hole method at 45° intervals along the circumference of the ring, and the average value was taken for comparison. The data are shown in Tables 3, 4, and 5.

[0030] Table 3: Comparison of tensile properties of GH4169 alloy rings before and after application

[0031]

[0032] Table 4: Comparison of creep performance of GH4169 alloy rings before and after application

[0033]

[0034] Table 5: Residual stress at 8 locations along the circumference of GH4169 alloy ring before and after application (unit: MPa)

[0035]

[0036] The data in Table 5 show that the average residual stress at the eight locations before application was -447.5 MPa, and the average residual stress at the eight locations after application was -261.5 MPa, indicating a significant reduction in residual stress.

[0037] Example 2

[0038] The method for preparing GH4738 alloy irregular cross-section rings with inverse temperature gradient includes the following steps:

[0039] Step 1: Through fire-in-the-place tests and metallographic analysis, the relationship between the grain size grade of GH4738 alloy and the fire-in-the-place test heating temperature and heating time was established. The fire-in-the-place test heating temperature was 1000℃~1100℃, the temperature interval was 10℃, and the heating time was 30min~240min. The grain size grade was evaluated according to GB / T 6394-2017, and the evaluation results are shown in Table 6. The critical temperature T for grain growth was obtained. C For 1050℃ and critical time t C For 50 minutes;

[0040] Table 6: Heating Grain Size Grades of GH4738 Alloy

[0041]

[0042] Step 2: Through near-isothermal compression tests on double-cone specimens, determine the critical equivalent strain ε for GH4738 alloy to achieve uniform fine grains under different temperature conditions. FC and the critical equivalent strain ε for obtaining uniform coarse grains CC The data is shown in Table 7:

[0043] Table 7: Critical Deformation of GH4738 Alloy Rings

[0044]

[0045] Step 3: The GH4738 alloy bar is upset and punched. The heating temperature for both upset and punching is T. C +50℃ = 1100℃, the equivalent effect becomes 1.8 ≥ ε FC =1.71; Improves the uniformity of grain structure to obtain billet;

[0046] Step 4, Low-temperature large deformation pre-rolling: The billet is subjected to two pre-rolling processes. The heating temperature of the first pre-rolling is T. C -10℃ = 1040℃, the equivalent effect becomes 1.4 ≥ 0.5 × (ε) FC +ε CC =0.5×(1.82+0.41)=1.115; the second pre-rolling heating temperature is T. C -10℃ = 1040℃, the equivalent effect becomes 1.5 ≥ 0.5 × (ε) FC +ε CC =0.5×(1.82+0.41)=1.115; A fine-grained or non-uniform structure is obtained, resulting in a pre-rolled part;

[0047] Step 5, High-Temperature Small Deformation Final Rolling: The pre-rolled part is subjected to final rolling at a heating temperature of T. C +10℃=1060℃, heating time 60min≥t C =50min, the final rolling equivalent effect becomes 0.67×ε CC =0.67×0.42 =0.28; A uniform coarse-grained structure is obtained, yielding the final rolled part;

[0048] Step 6, Bulging: The final rolled part is bulged, and the bulging heating temperature is T. C -40℃ = 1010℃, the bulging deformation is 3%; high-temperature bulging reduces residual stress.

[0049] The GH4738 alloy irregular-shaped ring parts produced show a significant reduction in forging allowance; for example... Figure 3 As shown, the grain size coarsened after the application of the reverse temperature gradient preparation method; the tensile properties were comparable, but the residual stress and creep deformation were significantly reduced. The residual stress was detected using the blind hole method at 45° intervals along the circumference of the ring, and the average value was taken for comparison. The data are shown in Tables 8, 9, and 10.

[0050] Table 8: Comparison of tensile properties of GH4738 alloy rings before and after application

[0051]

[0052] Table 9: Comparison of creep performance of GH4738 alloy rings before and after application

[0053]

[0054] Table 10: Residual stress at 8 locations along the circumference of GH4738 alloy ring before and after application (unit: MPa)

[0055]

[0056] The data in Table 10 show that the average residual stress at the eight locations before application was -570.75 MPa, and the average residual stress at the eight locations after application was -251.9 MPa, indicating a significant reduction in residual stress.

Claims

1. A method for preparing a low residual stress, creep resistant, coarse-grained, high-temperature alloy ring under a reverse temperature gradient, characterized in that, The method comprises the following steps: Step 1, establish the relationship between the grain size grade of high-temperature alloy material and the heating temperature and heating time of the air burning test through the air burning test and metallographic analysis, the grain size grade is evaluated according to GB / T 6394-2017, and the critical temperature T C and the critical time t C of grain growth are determined Step 2, determine the critical equivalent strain ε of the superalloy material to obtain uniform fine grains at different temperature conditions by double-cone sample near-isothermal compression test FC and the critical equivalent strain ε to obtain uniform coarse grains CC ; Step 3, the high-temperature alloy rod is upset and punched, and the heating temperature of the upsetting and punching is T C +30℃~T C +50℃, and the equivalent strain is ≥ε FC to obtain a blank Step 4, low temperature large deformation pre-rolling: the blank is pre-rolled twice, and the heating temperature of the two pre-rolling is T C -10℃~T C -40℃, pre-rolling equivalent strain ≥ 0.5×(ε FC +ε CC ); a pre-rolled piece is obtained; Step 5: high-temperature small-deformation finish rolling: finish rolling the pre-rolled piece, the finish rolling heating temperature is T C + 5℃ ~ T C + 30℃, heating time ≥ t C , the finish rolling equivalent strain is (0.6~0.9) × ε CC ; obtaining a finish-rolled piece; Step 6, bulging: the finish-rolled piece is subjected to bulging, the bulging heating temperature being T C -30°C ~ T C -80°C, the bulging deformation amount being 1% ~ 4%.

2. The inverse temperature gradient production of a low residual stress, creep resistant, coarse-grained, high-temperature alloy ring as recited in claim 1, wherein, In the step 1, the temperature interval of the heating temperature of the empty burning test is 10℃, and the heating time is 30min~240min.

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