Forging method for improving recrystallization degree of nickel-based superalloy

Abstract

The invention belongs to the technical field of high-temperature alloy hot working, and relates to a forging method for improving the recrystallization degree of nickel-based high-temperature alloy. The nickel-based alloy cast ingot is sequentially subjected to first-stage cogging forging and second-stage cogging forging within the single-phase region temperature, a cogging material is formed, then the cogging material is sequentially subjected to intermediate billet forging and finished bar forging, and a finished bar is obtained; wherein the first-stage cogging forging mode is that axial drawing-out is carried out after upsetting, and the second-stage cogging forging mode is that radial drawing-out is carried out after upsetting.

Description

Technical Field

[0001] The present invention belongs to the technical field of hot working of superalloys, and relates to a forging method for improving the recrystallization degree of nickel-based superalloys. Background Art

[0002] Nickel-based superalloys belong to precipitation-strengthened nickel-based wrought superalloys, with a γ′ phase content ≥ 40%. The service temperature range of this type of alloy is 760°C to 870°C, and it is widely used in many fields such as aviation, aerospace, petroleum, chemical industry, and power generation. Nickel-based superalloys are suitable for manufacturing a variety of key parts, such as turbine disks, working blades, high-temperature fasteners, rocket launchers, shafts, turbine casings, etc. Among them, forged bars are one of the main product forms.

[0003] However, the forging penetration of nickel-based superalloys is poor. After the forging of bars is completed, regions with incomplete recrystallization are very likely to appear (as shown in Figure 2 ), which will lead to a decline in the alloy's performance and even problems such as unqualified products. Therefore, improving the recrystallization degree of difficult-to-deform nickel-based superalloys and making the structures of all parts of the forged bars fine and uniform is an urgent problem to be solved. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art and propose a forging method for improving the recrystallization degree of nickel-based superalloys.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A forging method for improving the recrystallization degree of nickel-based superalloys, in which a nickel-based alloy ingot is successively subjected to first-stage cogging forging and second-stage cogging forging within the single-phase region temperature to form a cogged material, and then the cogged material is successively subjected to intermediate billet forging and finished bar forging to obtain a finished bar; wherein, the first-stage cogging forging method is upsetting followed by axial drawing, and the second-stage cogging forging method is upsetting followed by radial drawing.

[0007] Specifically, a difficult-to-deform superalloy ingot with a γ′ phase content greater than or equal to 40% is selected, and then during the cogging forging process, by adding one or two single-phase region upsetting + radial drawing, the structure of the difficult-to-deform superalloy ingot is fully broken within the single-phase region, thereby improving the recrystallization degree of the finished bars of the difficult-to-deform superalloy. This nickel-based superalloy ingot can be a GH4065A alloy ingot, a GH4720Li alloy ingot, or a GH4151 alloy ingot.

[0008] Furthermore, as shown in Figure 1 , it specifically includes the following steps:

[0009] Step 1: Subject the nickel-based alloy ingot to first-stage cogging forging and second-stage cogging forging in sequence to obtain cogged material; the temperatures of both the first-stage cogging forging and the second-stage cogging forging are within the single-phase region temperature of the nickel-based alloy. The method of the first-stage cogging forging is upsetting followed by axial drawing, and the method of the second-stage cogging forging is upsetting and radial drawing to obtain the cogged material;

[0010] Step 2: Subject the cogged material to intermediate billet forging. The forging method is upsetting followed by axial drawing to obtain intermediate billet material. The temperature of the intermediate billet forging is within the two-phase region temperature of the nickel-based alloy;

[0011] Step 3: Subject the intermediate billet material to finished bar forging. The forging method is axial drawing followed by rounding to obtain the finished bar.

[0012] Specifically, the above forging process requires asbestos coating throughout, and the cooling method of the bar after forging is air cooling.

[0013] Further, the number of heats for the first-stage cogging forging is 3 to 7 heats, and the heating temperature is 1150°C to 1170°C.

[0014] Specifically, after heating for each heat, upsetting + axial drawing is performed, repeated 3 to 7 times. The number of heats for the first-stage cogging forging can be 3 heats, 4 heats, 5 heats, 6 heats, 7 heats, and the heating temperature can be 1150°C, 1155°C, 1160°C, 1165°C, 1170°C, which can be specifically selected according to actual requirements.

[0015] Further, the heating temperature of the second-stage cogging forging is 1150°C to 1170°C.

[0016] Specifically, the heating temperature of the second-stage cogging forging can be 1150°C, 1155°C, 1160°C, 1165°C, 1170°C, which can be specifically selected according to actual requirements.

[0017] Further, the number of heats for the second-stage cogging forging is 1 to 2 heats.

[0018] Further, the deformation amounts of both the axial drawing and the radial drawing are 20% to 40%.

[0019] Specifically, the deformation amount of the second-stage radial drawing can be 20% to 40%. If it is 1 heat, then one upsetting + radial drawing is performed, and the deformation amount of the radial drawing is 30% to 40%. If it is two upsetting + radial drawing, then the deformation amount of each radial drawing is 20% to 30%.

[0020] Further, the number of heats for the intermediate billet forging is 6 to 12 heats.

[0021] Specifically, after each heating, upsetting + axial drawing is performed, and this is repeated 6 to 12 times to obtain an intermediate billet material.

[0022] Furthermore, the number of heating times for forging the finished bar is 3 to 7 times.

[0023] Specifically, after each heating, axial drawing + rounding is performed, and this is repeated 3 to 7 times to obtain the finished bar.

[0024] Furthermore, the specifications of the finished bar are Φ150mm to Φ400mm.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention provides a forging method for improving the recrystallization degree of nickel-based superalloys. By adding two-stage bloom forging, one or two upsetting + radial drawing in the single-phase region are obtained, so that the ingot structure of the nickel-based alloy is fully broken in the single-phase region. After the subsequent forging of the finished bar is completed, the recrystallization degree can be significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings here are incorporated into the specification and form a part of this specification, and are used together with the specification to explain the principles of the present invention.

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative efforts.

[0029] Figure 1 It is a schematic flow chart of the forging method of the present invention;

[0030] Figure 2 It is the incomplete recrystallization structure that is likely to appear in the difficult-to-deform superalloy bar;

[0031] Figure 3 It is the complete recrystallization structure of the difficult-to-deform superalloy bar in the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] Here, the exemplary embodiments will be described in detail. The implementation manners described in the following exemplary embodiments do not represent all implementation manners consistent with the present invention. On the contrary, they are only examples consistent with some aspects of the present invention detailed in the appended claims.

[0033] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0034] Example 1

[0035] The present invention provides a forging method for improving the recrystallization degree of nickel-based superalloys, which is characterized in that the method specifically comprises the following steps:

[0036] Step 1: Subject the nickel-based alloy ingot to first-stage cogging forging and second-stage cogging forging in sequence to obtain cogged materials; the temperatures of both the first-stage cogging forging and the second-stage cogging forging are within the single-phase region temperature of the nickel-based alloy, the method of the first-stage cogging forging is upsetting and axial drawing, and the method of the second-stage cogging forging is upsetting and radial drawing to obtain cogged materials;

[0037] Among them: the number of heats of the first-stage cogging forging is 3 heats, the heating temperature is 1150 °C, and the deformation amount of axial drawing is 20%;

[0038] The number of heats of the second-stage cogging forging is 1 heat, the heating temperature is 1170 °C, and the deformation amount of radial drawing is 20%;

[0039] Step 2: Subject the cogged materials to intermediate billet forging, and the forging method is upsetting followed by axial drawing to obtain intermediate billet materials, and the temperature of the intermediate billet forging is within the two-phase region temperature of the nickel-based alloy;

[0040] Among them: the number of heats of the intermediate billet forging is 6 heats, and the forging method is upsetting and axial drawing;

[0041] Step 3: Subject the intermediate billet materials to finished bar forging, and the forging method is axial drawing followed by rounding to obtain finished bars, and the bar specification is Φ400 mm; among them: the number of heats of the finished bar forging is 3 heats;

[0042] During the whole forging process, asbestos needs to be coated, and the cooling method of the bars after forging is air cooling.

[0043] As Figure 3 shown, it is the fully recrystallized structure of the difficult-to-deform superalloy bars in this embodiment. It can be seen that the recrystallization degree of this fully recrystallized structure is significantly higher than that of the recrystallized structure in the traditional forging method in Figure 2 the prior art.

[0044] Example 2

[0045] The present invention provides a forging method for improving the recrystallization degree of nickel-based superalloys, which is characterized in that the method specifically comprises the following steps:

[0046] Step 1: Subject the nickel-based alloy ingot to first-stage cogging forging and second-stage cogging forging in sequence to obtain cogged material; the temperatures of both the first-stage cogging forging and the second-stage cogging forging are within the single-phase region temperature of the nickel-based alloy. The method of the first-stage cogging forging is upsetting and axial drawing, and the method of the second-stage cogging forging is upsetting and radial drawing to obtain the cogged material;

[0047] Among them: the number of heats for the first-stage cogging forging is 5 heats, the heating temperature is 1160 °C, and the deformation amount of axial drawing is 30%;

[0048] The number of heats for the second-stage cogging forging is 2 heats, the heating temperature is 1150 °C, and the deformation amount of radial drawing is 30%;

[0049] Step 2: Subject the cogged material to intermediate billet forging. The forging method is upsetting followed by axial drawing to obtain intermediate billet material. The temperature of the intermediate billet forging is within the two-phase region temperature of the nickel-based alloy;

[0050] Among them: the number of heats for the intermediate billet forging is 9 heats, and the forging method is upsetting and axial drawing;

[0051] Step 3: Subject the intermediate billet material to finished bar forging. The forging method is axial drawing followed by rounding to obtain the finished bar, and the bar specification is Φ270 mm; among them: the number of heats for the finished bar forging is 5 heats;

[0052] During the whole forging process, it is necessary to wrap with asbestos, and the cooling method of the bar after forging is air cooling.

[0053] Example 3

[0054] The present invention provides a forging method for improving the recrystallization degree of nickel-based superalloys, which is characterized in that it specifically includes the following steps:

[0055] Step 1: Subject the nickel-based alloy ingot to first-stage cogging forging and second-stage cogging forging in sequence to obtain cogged material; the temperatures of both the first-stage cogging forging and the second-stage cogging forging are within the single-phase region temperature of the nickel-based alloy. The method of the first-stage cogging forging is upsetting and axial drawing, and the method of the second-stage cogging forging is upsetting and radial drawing to obtain the cogged material;

[0056] Among them: the number of heats for the first-stage cogging forging is 7 heats, the heating temperature is 1170 °C, and the deformation amount of axial drawing is 40%;

[0057] The number of heats for the second-stage cogging forging is 2 heats, the heating temperature is 1160 °C, and the deformation amount of radial drawing is 40%;

[0058] Step 2: Forge the bloom material into an intermediate billet. The forging method is upsetting followed by axial drawing to obtain the intermediate billet material. The temperature of the intermediate billet forging is within the two-phase region temperature of the nickel-based alloy;

[0059] Among them: The number of heats for the intermediate billet forging is 12 heats, and the forging methods are upsetting and axial drawing;

[0060] Step 3: Forge the intermediate billet material into finished bars. The forging method is axial drawing followed by rounding to obtain the finished bars. The bar specification is Φ150mm. Among them: The number of heats for the finished bar forging is 7 heats;

[0061] The whole forging process needs to be covered with asbestos, and the cooling method of the bars after forging is air cooling.

[0062] The above are only the specific embodiments of the present invention, which enable those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0063] It should be understood that the present invention is not limited to the above-described content and can be modified and changed without departing from its scope. The scope of the present invention is only limited by the appended claims.

Claims

1. A forging method for improving the recrystallization degree of a nickel-based high-temperature alloy, characterized in that: The nickel-based alloy ingot is subjected to one-stage blank forging and two-stage blank forging in a single-phase temperature range to form blank material, and then the blank material is subjected to intermediate blank forging and finished bar forging to obtain finished bar; wherein the one-stage blank forging is performed by axial drawing after upsetting, and the two-stage blank forging is performed by radial drawing after upsetting.

2. A forging method for improving the recrystallization degree of a nickel-based high-temperature alloy according to claim 1, characterized in that: The specific steps include: Step 1: subjecting the nickel-based alloy ingot to first-stage blank forging and second-stage blank forging in sequence to obtain blank material; the heating temperatures of the first-stage blank forging and the second-stage blank forging are both in the single-phase region temperature of the nickel-based alloy, the first-stage blank forging is performed by upsetting and axial drawing, and the second-stage blank forging is performed by upsetting and radial drawing to obtain blank material; Step 2: forging the blank material into an intermediate blank by upsetting and axial stretching to obtain an intermediate blank material, wherein the forging temperature of the intermediate blank is in the two-phase region temperature of the nickel-based alloy; Step 3: Forging the intermediate billet material into finished bars by axially stretching and then rounding to obtain finished bars.

3. A forging method for improving the recrystallization degree of a nickel-based high-temperature alloy according to claim 1, characterized in that: The first stage blank forging has 3 to 7 fires and a heating temperature of 1150°C to 1170°C.

4. A forging method for improving the recrystallization degree of a nickel-based high-temperature alloy according to claim 1, characterized in that: The heating temperature of the second-stage blank forging is 1150°C to 1170°C.

5. A forging method for improving the recrystallization degree of a nickel-based high-temperature alloy according to claim 1, characterized in that: The two-stage blank forging has 1 to 2 fires.

6. A forging method for improving the recrystallization degree of a nickel-based high-temperature alloy according to claim 1, characterized in that: The deformation of axial stretching and radial stretching is 20% to 40%.

7. A forging method for improving the degree of recrystallization of a nickel-based high-temperature alloy according to claim 1, characterized in that: The intermediate billet is forged for 6 to 12 times.

8. A forging method for improving the degree of recrystallization of a nickel-based high-temperature alloy according to claim 1, characterized in that: The finished bar is forged with 3 to 7 fires.

9. A forging method for improving the degree of recrystallization of a nickel-based high-temperature alloy as described in claim 1, characterized in that: The finished bar specifications are Φ150mm to Φ400mm.

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