A method for improving anisotropy of GH4079 alloy bar by forging

Abstract

This invention belongs to the field of high-temperature alloy hot working technology, specifically disclosing a forging method for improving the anisotropy of GH4079 alloy bars. The process is as follows: 1) Forging the ingot at 1150℃~1170℃, and performing at least two cycles of axial upsetting and drawing, with a deformation of 10%~30%, to obtain an intermediate billet with an octagonal cross-section; 2) Upsetting the billet axially at 1130℃~1150℃, with a height-to-diameter ratio of 0.4~0.8; then rolling the billet and drawing it radially, followed by radial upsetting and axial drawing to return it to its original size; 3) Repeating step 2) 1~3 times; 4) axially drawing the billet 2~3 times at 1100℃~1130℃, controlling the deformation to be 20%~40%, then performing one rounding and chamfering, and air cooling to room temperature to obtain the finished bar. This invention can significantly shorten the time difference between the transverse and longitudinal creep properties of bars, and significantly improve the anisotropy of GH4079 alloy bars.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature alloy hot working technology, specifically relating to a forging method for improving the anisotropy of GH4079 alloy bars. Background Technology

[0002] High-temperature alloys, also known as heat-resistant alloys or superalloys, are a class of metallic materials based on iron, nickel, and cobalt that can operate for extended periods at temperatures above 600°C and under certain stress. They possess high high-temperature strength, good oxidation and corrosion resistance, and excellent fatigue performance and fracture toughness. They are primarily used in the aerospace and energy sectors, such as in the manufacture of jet engines and the hottest components of various industrial gas turbines.

[0003] In recent years, with the rapid development of my country's aviation technology, high-temperature alloys are increasingly used in the aviation field, and the requirements for the mechanical properties and microstructure of high-temperature alloy forgings are becoming increasingly stringent. GH4079, as a highly alloyed Ni-Cr-Co based precipitation-strengthened wrought high-temperature alloy, has higher Al, Ti, and Nb contents compared to GH4742 alloy. It forms more age-hardening phases and also adds W and V for strengthening, resulting in a good balance between strength and plasticity, making it better suited for the fabrication of rotating components in aero-engines. Although GH4079 alloy has excellent comprehensive properties, its application is not widespread. This is because, on the one hand, it is difficult to process, leading to severe billet cracking during production; on the other hand, the creep rupture properties of the bars exhibit significant anisotropy, especially with a large difference between transverse and longitudinal creep rupture properties, seriously affecting the yield rate of subsequent bar performance. Therefore, it is necessary to improve the anisotropy of GH4079 alloy bars.

[0004] In view of this, this invention is hereby proposed. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a forging method for improving the anisotropy of GH4079 alloy bars, mainly used to reduce the time difference between the transverse and longitudinal creep properties of GH4079 alloy bars to within 20%.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] This invention provides a forging method for improving the anisotropy of GH4079 alloy bars, comprising the following steps:

[0008] Step 1: First, forge the GH4079 alloy ingot at a set temperature, and use at least two cycles of axial upsetting during the forging process to control the amount of deformation and obtain an intermediate billet with an octagonal cross section.

[0009] Step 2: Then, under a set temperature, the intermediate billet obtained in Step 1 is axially upset to control the height-to-diameter ratio; then, after rounding, the circular cross-section billet is radially elongated, then radially upset, then axially elongated, returning to the octagonal dimensions of Step 1.

[0010] Step 3: Repeat the actions in Step 2 1 to 3 times;

[0011] Step 4: Finally, at the set temperature, the billet obtained in Step 3 is subjected to axial elongation 2 to 3 times to control the amount of deformation, and then subjected to chamfering and rounding once. After air cooling to room temperature, the GH4079 alloy finished bar is obtained.

[0012] Furthermore, in step one, the GH4079 alloy ingot is obtained by a two-stage melting process of vacuum induction melting and vacuum consumable melting, or by a three-stage melting process of vacuum induction melting, electroslag remelting, and vacuum consumable melting.

[0013] Further, in step one, the chemical composition of the GH4079 alloy ingot by mass percentage is as follows: carbon 0.04%–0.08%, cobalt 12.5%–16.0%, chromium 10.0%–12.0%, molybdenum 4.0%–5.0%, aluminum 2.8%–3.3%, titanium 2.4%–3.0%, niobium 2.5%–3.0%, tungsten 2.0%–3.0%, vanadium 0.4%–0.8%, boron ≤0.01%, iron ≤1.0%, manganese ≤0.4%, silicon ≤0.3%, sulfur ≤0.01%, phosphorus ≤0.015%, with the remainder being nickel.

[0014] Furthermore, in step one, each forging process requires asbestos to be coated on the surface of the GH4079 alloy ingot.

[0015] Furthermore, in step one, the GH4079 alloy ingot is forged at 1150℃~1170℃, and the deformation is controlled to be 10%~30%.

[0016] Furthermore, in step two, the intermediate billet obtained in step one is axially upset at 1130℃~1150℃, and the height-to-diameter ratio is controlled to be 0.4~0.8.

[0017] Furthermore, in step four, the billet obtained in step three is subjected to axial elongation 2 to 3 times at 1100℃ to 1130℃, and the deformation is controlled to be 20% to 40%.

[0018] Furthermore, the forging method is used to improve the anisotropy of GH4079 alloy bars with a specification of Φ160mm~Φ250mm.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] This invention provides a forging method for improving the anisotropy of GH4079 alloy bars. Compared with existing technologies, it has two main advantages: First, because GH4079 alloy has a high carbon content (0.04%–0.08%), its microstructure contains a large number of carbides. Conventional ingot axial drawing or axial upsetting processes result in bars with a distinct banded distribution of carbides in the longitudinal microstructure, while the transverse microstructure shows a random distribution of carbides. This anisotropy of carbides leads to significant anisotropy in properties. This invention, however, uses a combined axial and radial upsetting process, which can improve the axial banded distribution of carbides to a certain extent, making their distribution more dispersed, thereby improving the anisotropy of properties. Second, the heat treatment process for GH4079 alloy before performance testing involves over-solution treatment. To reduce the tendency to crack during processing, conventional processing temperatures are typically set in the high-temperature single-phase region, resulting in a coarse-grained forged microstructure. After solution treatment, grain growth is minimal, and the characteristics of forging flow lines are preserved. However, this invention combines high-temperature and low-temperature forging, and by controlling parameters such as deformation amount and aspect ratio, effectively increases the recrystallization volume fraction of the GH4079 alloy grains. This results in a fine-grained forged microstructure, with significant grain growth after solution treatment, eliminating forging flow lines and further improving the anisotropy of its properties. Attached Figure Description

[0021] The accompanying drawings are incorporated in and form part of this specification, and together with the description serve to explain the principles of the invention.

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a flowchart of the improved anisotropic forging method for GH4079 alloy bars according to the present invention. Detailed Implementation

[0024] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples consistent with some aspects of the invention as detailed in the appended claims.

[0025] 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.

[0026] like Figure 1 As shown, the present invention provides a forging method for improving the anisotropy of GH4079 alloy bars, which specifically includes the following steps:

[0027] Step 1: Forge the GH4079 alloy ingot at 1150℃~1170℃, and use at least two cycles of axial upsetting during the forging process, with a deformation of 10%~30%, to obtain an intermediate billet with an octagonal cross section.

[0028] Specifically, the GH4079 alloy ingot used in this invention is obtained through a two-stage melting process of vacuum induction melting and vacuum arc remelting, or through a three-stage melting process of vacuum induction melting, electroslag remelting, and vacuum arc remelting. The chemical composition of the GH4079 alloy ingot, by mass percentage, is as follows: carbon 0.04%–0.08%, cobalt 12.5%–16.0%, chromium 10.0%–12.0%, molybdenum 4.0%–5.0%, aluminum 2.8%–3.3%, titanium 2.4%–3.0%, niobium 2.5%–3.0%, tungsten 2.0%–3.0%, vanadium 0.4%–0.8%, boron ≤0.01%, iron ≤1.0%, manganese ≤0.4%, silicon ≤0.3%, sulfur ≤0.01%, phosphorus ≤0.015%, with the remainder being nickel.

[0029] Preferably, asbestos needs to be wrapped on the surface of the GH4079 alloy ingot during each forging process to eliminate the stress caused by thermal expansion and contraction inside the casting and prevent cracking during forging.

[0030] Step 2: Axially upset the intermediate billet obtained in Step 1 at 1130℃~1150℃, controlling the height-to-diameter ratio to be 0.4~0.8; then roll it into a round shape and elongate it radially, then radially upset it, then axially elongate it to return to the original size (i.e. the size of the octagonal cross-section intermediate billet in Step 1).

[0031] Step 3: Repeat the actions in Step 2 1 to 3 times;

[0032] Step 4: Finally, the billet obtained in Step 3 is subjected to axial elongation 2 to 3 times at 1100℃~1130℃, with the deformation amount controlled at 20%~40%. Then, it is subjected to chamfering and rounding once, and air-cooled to room temperature to obtain GH4079 alloy finished bar.

[0033] To further verify the effectiveness of the preparation method of the present invention, the inventors conducted the following experiments:

[0034] Example 1 (Preparation of GH4079 alloy rods with a diameter of Φ160mm)

[0035] This invention provides a forging method for improving the anisotropy of GH4079 alloy bars (Φ160mm), specifically implemented according to the following steps:

[0036] 1) The GH4079 alloy ingot was forged at 1150℃ using a two-stage melting process of vacuum induction melting and vacuum arc remelting. The ingot had a diameter of Φ406mm and a chemical composition by mass percentage of: carbon 0.06%, cobalt 14.0%, chromium 11.0%, molybdenum 4.5%, aluminum 3.1%, titanium 2.7%, niobium 2.8%, tungsten 2.5%, vanadium 0.6%, boron ≤0.01%, iron ≤1.0%, manganese ≤0.4%, silicon ≤0.3%, sulfur ≤0.01%, phosphorus ≤0.015%, with the remainder being nickel. The GH4079 alloy ingot was then subjected to two cycles of axial upsetting with a deformation of 10%, yielding an intermediate billet with an octagonal cross-section and a diameter of 400mm.

[0037] 2) Then, the intermediate billet obtained in step 1) is axially upset at 1130℃, and the height-to-diameter ratio is controlled to be 0.6. The specification after rounding is Φ406mm. Then, the circular cross-section billet is radially elongated, radially upset, and axially elongated to return to the original size, that is, an octagon with a specification of 400mm.

[0038] 3) Repeat step 2) twice in total;

[0039] 4) The billet obtained in step 3) is subjected to axial drawing three times at 1120℃, with a deformation of 40%, followed by chamfering and rounding once. Then, it is air-cooled in the factory to obtain GH4079 alloy finished bars with a specification of Φ160mm.

[0040] Example 2 (Preparation of GH4079 alloy rods with a diameter of Φ200mm)

[0041] This invention provides a forging method for improving the anisotropy of GH4079 alloy bars (Φ200mm), which is implemented according to the following steps:

[0042] 1) The GH4079 alloy ingot was forged at 1160℃ using a triple melting process of vacuum induction melting, electroslag remelting, and vacuum arc remelting. The ingot had a diameter of Φ508mm and a chemical composition by mass percentage: carbon 0.04%, cobalt 16.0%, chromium 10.0%, molybdenum 5.0%, aluminum 2.8%, titanium 3.0%, niobium 2.5%, tungsten 3.0%, vanadium 0.4%, boron ≤0.01%, iron ≤1.0%, manganese ≤0.4%, silicon ≤0.3%, sulfur ≤0.01%, phosphorus ≤0.015%, with the remainder being nickel. The GH4079 alloy ingot was then subjected to three cycles of axial upsetting with a deformation of 20%, yielding an intermediate billet with an octagonal cross-section of 450mm.

[0043] 2) Then, the intermediate billet obtained in step 1) is axially upset at 1140℃, and the height-to-diameter ratio is controlled to be 0.7. The specification after rounding is Φ540mm. Then, the circular cross-section billet is radially elongated, radially upset, and axially elongated to return to the original size, that is, an octagon with a specification of 450mm.

[0044] 3) Repeat step 2) a total of 3 times;

[0045] 4) The billet obtained in step 3) is subjected to axial drawing three times at 1130℃, with a deformation of 30%, followed by chamfering and rounding once. Then, it is air-cooled in the factory to obtain GH4079 alloy finished bars with a specification of Φ200mm.

[0046] Example 3 (Preparation of GH4079 alloy rods with a diameter of Φ250mm)

[0047] This invention provides a forging method for improving the anisotropy of GH4079 alloy bars (Φ250mm), which is implemented according to the following steps:

[0048] 1) The GH4079 alloy ingot was forged at 1170℃ using a two-stage melting process of vacuum induction melting and vacuum arc remelting. The ingot's dimensions were Φ406mm, and its chemical composition (by mass percentage) was: carbon 0.08%, cobalt 12.5%, chromium 12.0%, molybdenum 4.0%, aluminum 3.3%, titanium 2.4%, niobium 3.0%, tungsten 2.0%, vanadium 0.8%, boron ≤0.01%, iron ≤1.0%, manganese ≤0.4%, silicon ≤0.3%, sulfur ≤0.01%, phosphorus ≤0.015%, with the remainder being nickel. The GH4079 alloy ingot was then subjected to two cycles of axial upsetting with a deformation of 30%, yielding an intermediate billet with an octagonal cross-section and a dimensions of 400mm.

[0049] 2) Then, the intermediate billet obtained in step 1) is axially upset at 1130℃, and the height-to-diameter ratio is controlled to be 0.8. The specification after rounding is Φ490mm. Then, the circular cross-section billet is radially elongated, radially upset, and axially elongated to return to the original size, that is, an octagon with a specification of 400mm.

[0050] 3) Repeat step 2) twice in total;

[0051] 4) The billet obtained in step 3) is subjected to axial drawing three times at 1100℃, with a deformation of 20%, followed by chamfering and rounding once. Then, it is air-cooled in the factory to obtain GH4079 alloy finished bar with a specification of Φ250mm.

[0052] After standard heat treatment, the properties of the three types of GH4079 alloy bars prepared by Examples 1-3 of the forging method of the present invention and the GH4079 alloy bars prepared by the conventional forging method after undergoing the same heat treatment regime are detailed in Table 1. Experimental results show that the difference in transverse and longitudinal creep properties of the GH4079 alloy bars treated by the process of the present invention is significantly improved.

[0053] Table 1 Comparison of transverse and longitudinal creep performance between the embodiments and the traditional hot forging process.

[0054]

[0055] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention.

[0056] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A forging method for improving the anisotropy of GH4079 alloy bars, characterized in that, Includes the following steps: Step 1: First, forge the GH4079 alloy ingot at a set temperature, and use at least two cycles of axial upsetting during the forging process to control the amount of deformation and obtain an intermediate billet with an octagonal cross section. Step 2: Then, under a set temperature, the intermediate billet obtained in Step 1 is axially upset to control the height-to-diameter ratio; then, after rounding, the circular cross-section billet is radially elongated, then radially upset, then axially elongated, returning to the octagonal dimensions of Step 1. Step 3: Repeat the actions in Step 2 1 to 3 times; Step 4: Finally, at the set temperature, the billet obtained in Step 3 is subjected to axial elongation 2 to 3 times to control the amount of deformation, and then subjected to chamfering and rounding once. After air cooling to room temperature, the GH4079 alloy finished bar is obtained. In step one, the GH4079 alloy ingot is specifically forged at 1150℃~1170℃, and the deformation is controlled to be 10%~30%. In step two, the intermediate billet obtained in step one is axially upset at 1130℃~1150℃, and the height-to-diameter ratio is controlled to be 0.4~0.

8. In step four, the billet obtained in step three is subjected to axial elongation 2 to 3 times at 1100℃ to 1130℃, and the deformation is controlled to be 20% to 40%.

2. The forging method for improving the anisotropy of GH4079 alloy bars according to claim 1, characterized in that, In step one, the GH4079 alloy ingot is obtained by a two-stage melting process of vacuum induction melting and vacuum consumable melting, or by a three-stage melting process of vacuum induction melting, electroslag remelting, and vacuum consumable melting.

3. The forging method for improving the anisotropy of GH4079 alloy bars according to claim 1, characterized in that, In step one, the chemical composition of the GH4079 alloy ingot by mass percentage is as follows: carbon 0.04%–0.08%, cobalt 12.5%–16.0%, chromium 10.0%–12.0%, molybdenum 4.0%–5.0%, aluminum 2.8%–3.3%, titanium 2.4%–3.0%, niobium 2.5%–3.0%, tungsten 2.0%–3.0%, vanadium 0.4%–0.8%, boron ≤0.01%, iron ≤1.0%, manganese ≤0.4%, silicon ≤0.3%, sulfur ≤0.01%, phosphorus ≤0.015%, and the remainder is nickel.

4. The forging method for improving the anisotropy of GH4079 alloy bars according to claim 1, characterized in that, In step one, asbestos needs to be wrapped around the surface of the GH4079 alloy ingot during each forging process.

5. The forging method for improving the anisotropy of GH4079 alloy bars according to any one of claims 1 to 4, characterized in that, The forging method is used to improve the anisotropy of GH4079 alloy bars with a diameter of Φ160mm to Φ250mm.

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