Forging method for improving structure consistency of difficult-to-deform nickel-based superalloy

Abstract

The invention provides a forging method for improving the structure consistency of a difficult-to-deform nickel-based superalloy, which comprises the following steps: 1) carrying out cogging forging, at least four heating numbers of axial upsetting and octagonal drawing on a difficult-to-deform nickel-based superalloy cast ingot after heat preservation and thorough heating at the temperature of 1120-1170 DEG C, and obtaining an intermediate blank with an octagonal section by 15-35% of deformation per heating number; returning the forged hot material to the furnace; and (2) after heat preservation and thorough heating are conducted at the temperature of 1080-1120 DEG C, one-heating-number square drawing-out is conducted on the octagonal-section middle blank, the deformation amount is 30%-45%, a square middle blank is obtained, and then the edges of the square middle blank are slightly chamfered. Returning the forged hot material to the furnace; (3) after heat preservation and thorough heating are conducted at the temperature of 1040-1080 DEG C, one-heating-number six-rotation one-step diagonal drawing is conducted on the square middle blank, and every six rotation one cycle is conducted; according to the difficult-to-deform nickel-based high-temperature alloy bar forged through the method, the structure uniformity of the core part, the edge part, the first-forged end and the later-forged end is remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of high-temperature alloy hot processing, in particular to a forging method for improving the structural consistency of a difficult-to-deform nickel-based high-temperature alloy. Background Art

[0002] Difficult-to-deform nickel-based high-temperature alloys usually contain a large amount of γ' strengthening phase, which is strengthened with carbides such as MC, M6C and M23C6, so that the alloy has good strength-toughness matching characteristics. It is mainly used in the preparation of rotating parts of aircraft engines and gas turbines. Difficult-to-deform nickel-based high-temperature alloys have high deformation resistance, and the structure is extremely sensitive to hot working temperature and deformation uniformity. In the actual production process, there are often problems such as large grain size difference between the core and edge of the bar, and insufficient grain size consistency between the first forging end and the later forging end. The uneven structure has a genetic effect during the subsequent hot working of the forging, resulting in inconsistent grain sizes in different parts of the prepared forgings and large differences in grain sizes of forgings prepared from bars at different positions, which seriously reduces the quality stability of the product. Therefore, it is necessary to improve the consistency of the structure of difficult-to-deform nickel-based high-temperature alloy bars. Summary of the invention

[0003] The object of the present invention is to provide a forging method for improving the consistency of the structure of a difficult-to-deform nickel-based high-temperature alloy. In order to improve the consistency of the structure between the core and the edge, and between the first forging end and the later forging end of the difficult-to-deform nickel-based high-temperature alloy, the object of the present invention is to provide a forging method for improving the consistency of the structure of a difficult-to-deform nickel-based high-temperature alloy, so as to reduce the grain size difference between the core and the edge of the difficult-to-deform nickel-based high-temperature alloy rod to within 2.5 levels, and reduce the grain size difference at the same position between the first forging end and the later forging end to within 1 level.

[0004] To achieve the above object, the present invention provides the following technical solution: a forging method for improving the microstructure consistency of a difficult-to-deform nickel-based high-temperature alloy, comprising the following steps:

[0005] 1) After being heated through at 1120°C to 1170°C, the hard-to-deform nickel-based high-temperature alloy ingot is forged, axially upsetting and elongated in at least four times, with a deformation of 15% to 35% in each time, to obtain an intermediate billet with an octagonal cross section; the hot material is returned to the furnace after forging;

[0006] 2) After being heated thoroughly at 1080℃~1120℃, the octagonal cross-section intermediate billet is subjected to a first-time four-way drawing, with a deformation amount of 30%~45%, to obtain a four-way intermediate billet, and then the edges of the four-way intermediate billet are slightly chamfered; the hot material after forging is returned to the furnace;

[0007] 3) After being heated thoroughly at 1040℃~1080℃, the square intermediate billet is subjected to one-time six-turn diagonal stretching, with one cycle for every six turns. The schematic diagram of the pressing sequence is as follows: Figure 1As shown; the specific operation method is: press edge 1, 5 → (rotate 90° clockwise) press edge 3, 7 → (rotate 90° clockwise) press edge 1, 5 for the second time → (rotate 90° clockwise) press edge 3, 7 for the second time → (rotate 45° clockwise) press plane 4, 8 → (rotate 90° clockwise) press plane 2, 6 → (rotate 45° counterclockwise) feed; get the intermediate billet with octagonal cross section, the deformation amount is 25% to 35%; after forging, the hot material is returned to the furnace;

[0008] 4) After being heated thoroughly at 1000°C to 1040°C, the intermediate billet with an octagonal cross section is subjected to a first rounding and chamfering of the same specification, and then air-cooled in the factory to obtain a finished rod of a difficult-to-deform nickel-based high-temperature alloy.

[0009] Preferably, the Al+Ti element content of the hard-to-deform nickel-based high-temperature alloy in step 1 is 4.0% to 5.5%.

[0010] Preferably, the hard-to-deform nickel-based high-temperature alloy ingot in step 1 is obtained by a triple melting process of vacuum induction melting, electroslag remelting and vacuum consumable melting.

[0011] Preferably, the hammer anvil used in the six-turn one-step diagonal stretching process in step 3 is a 650mm wide flat anvil with a R=130mm rounded corner transition.

[0012] Preferably, each forging process in S1 requires that the material surface be coated with thermal insulation asbestos before deformation, and the specification of the finished rod is Φ180mm~Φ300mm.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] When using upper and lower flat anvils to draw the difficult-to-deform nickel-based high-temperature alloy in the forming fire, due to the presence of a temperature drop quenching zone and a friction deformation dead zone between the material surface and the hammer anvil contact surface, the temperature and equivalent strain of the edge area of ​​the billet during the drawing deformation are both lower than those of the core area of ​​the material, making it more difficult to recrystallize the edge. Usually, in order to achieve complete recrystallization of the edge and obtain a uniform structure, the drawing deformation amount used in the forming fire is usually 40% to 55%. At this time, the edge can obtain a fine-grained structure that has just completed recrystallization, while the core area will have a significant coarsening of the structure due to the drastic deformation temperature rise, which is not conducive to the control of the grain size difference between the core and the edge. At the same time, the existing drawing method is to feed one side in turn and draw one side in turn. In the later stages of drawing, the material length is longer, and the time required for one drawing is longer. At this time, there is no thermal insulation asbestos on the surface, and the deformation temperature difference between the first forging end and the last forging end is large, which is not conducive to the control of the grain size consistency between the first forging end and the last forging end.

[0015] The square billet edges are deformed by contact with the hammer anvil, and the deformation method is six turns and one step. While reducing the temperature drop and deformation dead zone caused by the contact between the material and the hammer anvil, all six pressing deformations in the area are completed in a short time, and the temperature drop of the edge of the material is small. At this time, the deformation required for complete recrystallization of the edge area can be greatly reduced to 25% to 35%, so that the deformation temperature rise of the core can also be greatly reduced, and finally the grain size difference between the core and the edge is greatly reduced. At the same time, because the undeformed area is always wrapped with thermal insulation asbestos during drawing, there is almost no temperature drop on the surface, and the deformation temperature difference between the first forging end and the last forging end is small, and finally the grain size difference between the first forging end and the last forging end is greatly reduced. This forging method has a very obvious effect on improving the consistency of the structure of difficult-to-deform nickel-based high-temperature alloys. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the sequence of six-turn one-step diagonal pulling and pressing down.

[0017] Figure 2 The core structure of the forged end of Φ300mm bar is prepared by conventional forging method.

[0018] Figure 3 The forging end and edge structure of Φ300mm bar is prepared by conventional forging method.

[0019] Figure 4 The core structure of the forged end of a Φ300mm bar prepared by conventional forging method.

[0020] Figure 5 The microstructure of the end edge of a Φ300mm bar prepared by conventional forging method.

[0021] Figure 6 The core structure of the forged end of a Φ300mm bar is prepared by the forging method of the present invention.

[0022] Figure 7 The forging method of the present invention is used to prepare the forging end edge structure of a Φ300mm bar.

[0023] Figure 8 The core structure of the forged end of a Φ300mm bar prepared by the forging method of the present invention.

[0024] Fig. 9 The forging method of the present invention is used to prepare the end edge structure of a Φ300mm bar after forging. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] See also Figure 1-4 The present invention provides a technical solution: The present invention relates to a forging method for improving the consistency of the structure of a difficult-to-deform nickel-based high-temperature alloy, which specifically includes the following steps:

[0027] Step 1, heat-insulate and heat-thaw the hard-to-deform nickel-based high-temperature alloy ingot at 1120℃~1170℃, forge it, axially upset it and stretch it in eight directions for at least four times, with a deformation of 15%~35% in each time, to obtain an intermediate billet with an eight-direction cross section. After forging, the hot material is returned to the furnace;

[0028] Step 2, after being heated through at 1080℃~1120℃, the octagonal cross-section intermediate billet is subjected to a first-time quadrangular elongation with a deformation amount of 30%~45% to obtain a quadrangular intermediate billet, and then the edges of the quadrangular intermediate billet are slightly chamfered. The hot material after forging is returned to the furnace;

[0029] Step 3, after being heated thoroughly at 1040℃~1080℃, the square intermediate billet is subjected to one-time six-turn one-step diagonal stretching, with one cycle of six turns. The schematic diagram of the pressing sequence is as follows: Figure 1 As shown. The specific operation method is: press edge 1, 5 → (rotate 90° clockwise) press edge 3, 7 → (rotate 90° clockwise) press edge 1, 5 for the second time → (rotate 90° clockwise) press edge 3, 7 for the second time → (rotate 45° clockwise) press plane 4, 8 → (rotate 90° clockwise) press plane 2, 6 → (rotate 45° counterclockwise) feed. Get the intermediate billet with octagonal cross section, with a deformation of 25% to 35%. After forging, the hot material is returned to the furnace;

[0030] Step 4, after being heated through at 1000°C to 1040°C, the intermediate billet with an octagonal cross section is subjected to a first-time chamfering and rounding with the same specifications, and then air-cooled in the factory to obtain a finished rod of a difficult-to-deform nickel-based high-temperature alloy.

[0031] Example 1

[0032] A forging method for improving the microstructure consistency of a difficult-to-deform nickel-based high-temperature alloy comprises the following steps:

[0033] Step 1: After keeping the temperature at 1170℃ for 5 hours, the hard-to-deform nickel-based high-temperature alloy ingot is forged, and after five times of axial upsetting and eight-way stretching, the deformation amount of each time is 22%, and an intermediate billet of 470mm in eight directions is obtained. After forging, the hot material is returned to the furnace;

[0034] Step 2, after keeping at 1120℃ for 3h, the 470mm square intermediate billet is stretched once, with a deformation of 39%, to obtain a 335mm square intermediate billet, and then the edges of the square intermediate billet are slightly chamfered to 450mm. The hot material after forging is returned to the furnace;

[0035] Step 3, after keeping at 1080℃ for 2.5h, the square 335mm intermediate billet is subjected to one-time six-turn diagonal stretching, one cycle for every six turns. The schematic diagram of the pressing sequence is as follows: Figure 1 As shown. The specific operation method is: press edge 1, 5 to 350mm → (rotate 90° clockwise) press edge 3, 7 to 370mm → (rotate 90° clockwise) press edge 1, 5 to 280mm → (rotate 90° clockwise) press edge 3, 7 to 290mm → (rotate 45° clockwise) press plane 4, 8 to 290mm → (rotate 90° clockwise) press plane 2, 6 to 300mm → (rotate 45° counterclockwise) feed 280mm. Press down successively to complete one-pass stretching deformation, and obtain an intermediate blank with a cross section of 300mm on all sides, with a deformation amount of 33%.

[0036] After forging, the hot material is returned to the furnace;

[0037] Step 4, after keeping at 1050°C for 2.5h, the 300mm intermediate billet is subjected to a rounding process with the same specifications, and then air-cooled in the factory to obtain Φ300mm difficult-to-deform nickel-based high-temperature alloy finished bars.

[0038] The core and edge structures of the forged end of the Φ300mm bar are as follows: Figure 6 and Figure 7 As shown in the figure, the core and edge structures of the rear forging end are as follows: Figure 8 and Fig. 9 As shown. It can be seen that in the existing forging process, the grain size difference between the center and edge of the first forging end is 3.5 levels, the grain size difference between the center and edge of the rear forging end is 4.5 levels, the maximum grain size difference between the first forging end and the rear forging end at the same position is 2 levels, and the overall grain size uniformity of the material is poor. However, in the forging process of the present invention, the grain size difference between the center and edge of the first forging end is 2.0 levels, the grain size difference between the center and edge of the rear forging end is 2.0 levels, the maximum grain size difference between the first forging end and the rear forging end at the same position is 0.5 levels, and the overall grain size uniformity of the material is significantly improved. The grain size rating results of different positions of Φ300mm bars prepared by different processes are shown in Table 1.

[0039] Table 1 Grain size rating results at different positions of Φ300mm bars prepared by different processes

[0040]

[0041]

[0042] Example 2

[0043] A forging method for improving the microstructure consistency of a difficult-to-deform nickel-based high-temperature alloy comprises the following steps:

[0044] Step 1: After keeping the temperature at 1160℃ for 5 hours, the hard-to-deform nickel-based high-temperature alloy ingot is forged, and after four rounds of axial upsetting and eight-way stretching, the deformation amount of each round is 25%, and an intermediate billet of 410 mm in length is obtained. After forging, the hot material is returned to the furnace;

[0045] Step 2, after keeping at 1110℃ for 3h, the 410mm square intermediate billet is stretched once, with a deformation of 40%, to obtain a 290mm square intermediate billet, and then the edges of the square intermediate billet are slightly chamfered to 390mm. The hot material after forging is returned to the furnace;

[0046] Step 3, after keeping at 1070℃ for 2.5h, the square 290mm intermediate billet is subjected to one-time six-turn diagonal stretching, one cycle for every six turns. The schematic diagram of the pressing sequence is as follows: Figure 1 As shown. The specific operation method is: press edge 1, 5 to 300mm → (rotate 90° clockwise) press edge 3, 7 to 320mm → (rotate 90° clockwise) second press edge 1, 5 to 240mm → (rotate 90° clockwise) second press edge 3, 7 to 250mm → (rotate 45° clockwise) press plane 4, 8 to 250mm → (rotate 90° clockwise) press plane 2, 6 to 260mm → (rotate 45° counterclockwise) feed 250mm. Press down successively to complete one-pass stretching deformation, and obtain an intermediate blank with a cross section of 260mm on all sides, with a deformation amount of 33%.

[0047] After forging, the hot material is returned to the furnace;

[0048] Step 4, after keeping at 1040℃ for 2h, the 260mm intermediate billet is subjected to a rounding process with the same specifications, and then air-cooled in the factory to obtain a Φ260mm difficult-to-deform nickel-based high-temperature alloy finished bar.

[0049] Example 3

[0050] A forging method for improving the microstructure consistency of a difficult-to-deform nickel-based high-temperature alloy comprises the following steps:

[0051] Step 1: After keeping the temperature at 1150℃ for 5 hours, the hard-to-deform nickel-based high-temperature alloy ingot is forged, and after four rounds of axial upsetting and eight-way stretching, the deformation amount of each round is 28%, and an intermediate billet of 370mm in eight directions is obtained. After forging, the hot material is returned to the furnace;

[0052] Step 2, after keeping at 1100℃ for 2.5h, the 370mm square intermediate billet is stretched once, with a deformation of 43%, to obtain a 255mm square intermediate billet, and then the edges of the square intermediate billet are slightly chamfered to 340mm. The hot material after forging is returned to the furnace;

[0053] Step 3, after keeping at 1060℃ for 2.0h, the square 255mm intermediate billet is subjected to one-time six-turn diagonal stretching, one cycle for every six turns. The schematic diagram of the pressing sequence is as follows: Figure 1 As shown. The specific operation method is: press edge 1, 5 to 270mm → (rotate 90° clockwise) press edge 3, 7 to 290mm → (rotate 90° clockwise) press edge 1, 5 to 210mm → (rotate 90° clockwise) press edge 3, 7 to 220mm → (rotate 45° clockwise) press plane 4, 8 to 220mm → (rotate 90° clockwise) press plane 2, 6 to 230mm → (rotate 45° counterclockwise) feed 230mm. Press down successively to complete one-pass stretching deformation, and obtain an intermediate blank with a cross section of 230mm on all sides, with a deformation amount of 32%.

[0054] After forging, the hot material is returned to the furnace;

[0055] Step 4, after keeping at 1030°C for 1.5h, the 230mm intermediate billet is subjected to a first tempering and chamfering and rounding of the same specification, and then air-cooled in the factory to obtain a Φ230mm difficult-to-deform nickel-based high-temperature alloy finished bar.

[0056] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A forging method for improving the microstructure consistency of a difficult-to-deform nickel-based high-temperature alloy, characterized in that: The following steps are involved: 1) After being heated through at 1120°C to 1170°C, the hard-to-deform nickel-based high-temperature alloy ingot is forged, axially upsetting and octagonally drawing are performed for at least four times, with a deformation amount of 15% to 35% in each time, to obtain an intermediate billet with an octagonal cross section, and the hot material is returned to the furnace after forging; 2) After being heated through at 1080℃~1120℃, the octagonal cross-section intermediate billet is subjected to a first-time four-way elongation with a deformation of 30%~45% to obtain a four-way intermediate billet, and then the edges of the four-way intermediate billet are slightly chamfered, and the hot material is returned to the furnace after forging; 3) After being heated thoroughly at 1040℃~1080℃, the square intermediate billet is subjected to one-time six-turn one-step diagonal elongation, and each six-turn cycle is a cycle. The pressing sequence is: pressing edge 1, 5 → pressing edge 3, 7 → second pressing edge 1, 5 → second pressing edge 3, 7 → pressing plane 4, 8 → pressing plane 2, 6 → feeding, and an octagonal cross-section intermediate billet is obtained, with a deformation of 25%~35%, and the hot material is returned to the furnace after forging; 4) After being heated thoroughly at 1000°C to 1040°C, the intermediate billet with an octagonal cross section is subjected to a first rounding and chamfering of the same specification, and then air-cooled in the factory to obtain a finished rod of a difficult-to-deform nickel-based high-temperature alloy.

2. A forging method for improving the microstructure consistency of a difficult-to-deform nickel-based high-temperature alloy according to claim 1, characterized in that: In the step 1, the Al+Ti element content of the hard-to-deform nickel-based high-temperature alloy is 4.0% to 5.5%.

3. A forging method for improving the microstructure consistency of a difficult-to-deform nickel-based high-temperature alloy according to claim 1, characterized in that: In step 1, the hard-to-deform nickel-based high-temperature alloy ingot is obtained by a triple melting process of vacuum induction melting, electroslag remelting and vacuum consumable melting.

4. A forging method for improving the microstructure consistency of a difficult-to-deform nickel-based high-temperature alloy according to claim 1, characterized in that: The hammer anvil used in the six-turn one-step diagonal stretching process in step 3 is a 650mm wide flat anvil with a R=130mm rounded corner transition.

5. A forging method for improving the microstructure consistency of a difficult-to-deform nickel-based high-temperature alloy according to claim 1, characterized in that: In the forging process of S1, each fire needs to be coated with thermal insulation asbestos on the surface of the material before deformation, and the specification of the finished rod is Φ180mm~Φ300mm.

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