Method for improving forging cracking of GH4079 alloy and application thereof

Abstract

The invention belongs to the technical field of high-temperature alloy hot working, and particularly relates to a method for improving forging cracking of a GH4079 alloy and application of the method. According to the method, the structure evolution control in the forging process is realized by regulating and controlling parameters such as temperature and deformation in the hot working process, so that the hot working cracking tendency is reduced; through specific heating, heat preservation, forging deformation and cooling modes, the problem of cracking of the GH4079 alloy in the hot working process is remarkably solved. According to the method for improving the forging cracking of the GH4079 alloy, the alloy performance can meet the standard requirement, the defects that due to the fact that a large number of strengthening elements are added, the hot working performance is sharply reduced, and the forging cracking tendency is serious are overcome, the problems that the yield of the GH4079 alloy is low and the production cost is high are solved, and application of the GH4079 alloy is promoted.

Description

Technical Field

[0001] The present invention belongs to the technical field of hot working of superalloys, and particularly relates to a method for improving forging cracking of GH4079 alloy and its application. Background Art

[0002] GH4079 alloy is developed on the basis of GH742 alloy. Compared with GH742 alloy, the contents of Al, Ti, Nb and W in GH4079 alloy are increased on the original basis, so its performance has been greatly improved. It should be noted that with the addition of a large number of strengthening elements, on the one hand, the temperature-bearing capacity of GH4079 alloy is greatly improved, and the highest service temperature can reach 850°C; on the other hand, a large number of refractory elements also make the hot working performance of the alloy decrease sharply, resulting in a serious cracking tendency during forging, and finally resulting in disadvantages such as low finished product rate and high production cost, which severely limit the application of GH4079 alloy.

[0003] Therefore, there is an urgent need for a method to improve forging cracking of GH4079 alloy to significantly reduce the cracking problem of GH4079 alloy during hot working, and the alloy performance can meet the standard requirements. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above-mentioned disadvantages of the prior art and provide a method for improving forging cracking of GH4079 alloy and its application.

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

[0006] On the one hand, the present invention provides a method for improving forging cracking of GH4079 alloy, which specifically includes the following steps:

[0007] Step 1: First, hold the to-be-treated GH4079 alloy ingot at 1150°C to 1180°C for 120 min to 240 min, then perform cogging forging, and use multiple cycles of axial upsetting and drawing with a deformation amount of 10% to 30% to obtain a billet A with an octagonal cross-section;

[0008] Step 2: First, air-cool the billet A to 980°C to 1050°C and hold it for 60 min to 240 min, then heat it up to 1120°C to 1150°C and hold it for 60 min to 240 min, and then use multiple cycles of axial upsetting and drawing with a height-diameter ratio of 2.0 to 2.2 and a deformation amount of 20% to 40% to obtain a billet B with an octagonal cross-section;

[0009] Step 3: First, perform 2 to 3 passes of axial drawing on the billet B at 1100°C to 1130°C with a deformation amount of 20% to 40%, and then perform 1 pass of chamfering to obtain a billet C;

[0010] Step 4: Perform one-pass cogging of the blank C at 1090°C to 1120°C with a deformation amount of 20% to 40%, and then air-cool to obtain the GH4079 alloy with improved cracking resistance.

[0011] Specifically, during the forging process, asbestos needs to be coated on the surface of the material for each pass to keep warm and reduce the temperature drop on the surface layer of the material.

[0012] Specifically, the chemical composition of the GH4079 alloy ingot selected in Step 1, by mass percentage, includes: carbon: 0.04% to 0.08%, cobalt: 12.5% to 16.0%, chromium: 10.0% to 12.0%, molybdenum: 4.0% to 5.0%, aluminum: 2.8% to 3.3%, titanium: 2.4% to 3.0%, niobium: 2.5% to 3.0%, tungsten: 2.0% to 3.0%, vanadium: 0.4% to 0.8%, boron: ≤0.01%, iron: ≤1.0%, manganese: ≤0.4%, silicon: ≤0.3%, sulfur: ≤0.01%, phosphorus: ≤0.015%, and the balance is nickel and inevitable impurity elements.

[0013] Specifically, the GH4079 alloy ingot selected in Step 1 is prepared by a two-stage melting process of (vacuum induction melting + vacuum consumable melting) (the two-stage melting process is selected when the quality requirements for the ingot are low), or a three-stage melting process of (vacuum induction melting + electroslag remelting + vacuum consumable melting) (the three-stage melting process is selected when the quality requirements for the ingot are high).

[0014] Specifically, the finished bar obtained after improving the forging cracking of the GH4079 alloy ingot has a specification of Φ180mm to Φ220mm.

[0015] On the other hand, the present invention provides an application of a method for improving the forging cracking of the GH4079 alloy, which is applied to improving the forging cracking of the GH4079 alloy.

[0016] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0017] 1. By regulating parameters such as temperature and deformation amount during the hot working process, the present invention realizes the control of microstructure evolution during the forging process, thereby reducing the tendency of hot working cracking; through specific heating, heat preservation, forging deformation and cooling methods, the problem of cracking of the GH4079 alloy during the hot working process is significantly reduced.

[0018] 2. Meeting the performance standard requirements: The method for improving the forging cracking of the GH4079 alloy according to the present invention enables the alloy performance to meet the standard requirements, overcomes the disadvantages such as the sharp reduction of hot working performance and the serious tendency of forging cracking caused by the addition of a large number of strengthening elements, solves the problems of low finished product rate and high production cost of the GH4079 alloy, and helps to promote the application of the GH4079 alloy. DETAILED DESCRIPTION

[0019] Here, exemplary embodiments will be described in detail. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Instead, they are only examples consistent with some aspects of the present invention as detailed in the appended claims.

[0020] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with embodiments.

[0021] The GH4079 alloy ingot to be processed in the embodiment of the present invention is prepared using the chemical composition shown in Table 1.

[0022] Table 1

[0023]

[0024] Example 1 (Preparation of GH4079 alloy bars with a specification of Φ180 mm)

[0025] This embodiment provides a method for improving forging cracking of GH4079 alloy, which specifically includes the following steps:

[0026] Step 1, firstly heat-insulate the GH4079 alloy ingot to be treated at 1150° C. for 120 min, then forge the blank, and perform four cycles of axial upsetting with a deformation amount of 14% to obtain a blank A with an octagonal cross section;

[0027] It should be noted that the GH4079 alloy ingot to be processed is prepared by a two-step melting process (vacuum induction melting + vacuum consumable melting);

[0028] Step 2, first cooling the blank A to 1045° C. and keeping the temperature for 90 min, then heating it to 1130° C. and keeping the temperature for 180 min, and then performing two cycles of axial upsetting, with the aspect ratio controlled at 2.0 and the deformation amount at 38%, to obtain blank B;

[0029] Step 3, firstly subjecting the blank B to axial drawing forging at 1110° C. for 3 times with a deformation of 23%, and then subjecting it to chamfering for 1 time to obtain the blank C;

[0030] Step 4: First, the billet C is axially stretched once at 1095° C., a U-shaped anvil is used, and the deformation amount is 30%, and then air-cooled in the factory to obtain a GH4079 alloy bar X with a specification of Φ180 mm.

[0031] Example 2 (Preparation of GH4079 alloy bars with a diameter of Φ200 mm)

[0032] This embodiment provides a method for improving the forging cracking of GH4079 alloy, which includes the following steps:

[0033] Step 1: First, keep the GH4079 alloy ingot to be processed at 1160 °C for 180 min, then perform cogging forging, carry out three cycles of axial upsetting and drawing, with a deformation amount of 21%, to obtain a blank A with an octagonal cross-section;

[0034] It should be noted that the GH4079 alloy ingot to be processed is prepared by a triple melting process of (vacuum induction melting + electroslag remelting + vacuum consumable melting);

[0035] Step 2: First, cool the blank A to 1015 °C and keep it for 120 min, then heat it up to 1130 °C and keep it for 120 min, and then carry out three cycles of axial upsetting and drawing, with the height-diameter ratio controlled at 2.2 and a deformation amount of 32%, to obtain a blank B;

[0036] Step 3: First, perform two passes of axial drawing forging on the blank B at 1120 °C, with a deformation amount of 30%, and then perform one pass of chamfering to obtain a blank C;

[0037] Step 4: First, perform one pass of axial drawing on the blank C at 1110 °C, with a V-shaped anvil for the hammer and anvil, with a deformation amount of 30%, and then air-cool it in the workshop to obtain a GH4079 alloy bar Y with a specification of Φ200 mm.

[0038] Example 3 (preparing a GH4079 alloy bar with a specification of Φ220 mm)

[0039] This embodiment provides a method for improving the forging cracking of GH4079 alloy, which includes the following steps:

[0040] Step 1: First, keep the GH4079 alloy ingot to be processed at 1170 °C for 240 min, then perform cogging forging, carry out two cycles of axial upsetting and drawing, with a deformation amount of 29%, to obtain a blank A with an octagonal cross-section;

[0041] It should be noted that the GH4079 alloy ingot to be processed is prepared by a double melting process of (vacuum induction melting + vacuum consumable melting);

[0042] Step 2: First, cool the blank A to 980 °C and keep it for 180 min, then heat it up to 1140 °C and keep it for 90 min, and then carry out four cycles of axial upsetting and drawing, with the height-diameter ratio controlled at 2.2 and a deformation amount of 22%, to obtain a blank B;

[0043] Step 3: First, perform two passes of axial drawing forging on the blank B at 1130 °C, with a deformation amount of 37%, and then perform one pass of chamfering to obtain a blank C;

[0044] Step 4: First, perform one-pass axial drawing on the blank C at 1120°C. Use a U-shaped anvil for the hammer and anvil, with a deformation amount of 25%. Then, perform air cooling in the workshop to obtain a GH4079 alloy bar Z with a specification of Φ220mm.

[0045] It should be noted that in the above embodiments, asbestos needs to be coated on the surface of the material for each pass in the forging process to reduce the temperature drop on the surface layer, ensure the temperature of the material during forging, and prevent excessive temperature drop from generating stress.

[0046] For the three GH4079 alloy bars prepared in Embodiments 1-3 of the present invention and the GH4079 alloy bars prepared by the traditional forging method, the statistical details of the grinding loss are shown in Table 1.

[0047] Table 1

[0048] Process Input quantity / kg Output quantity of black-skin bars / kg Grinding loss / % Current process 2152 921 57.2 Example 1 (Bar X) 2203 1201 45.5 Example 2 (Bar Y) 2152 1322 38.6 Example 3 (Bar Z) 2232 1356 39.2

[0049] As can be seen from Table 1, during the forging process of the GH4079 alloy bar processed by the process of the present invention, the output of the black-skin bar is significantly increased. By controlling parameters such as temperature and deformation amount in the hot working process, the morphology and distribution of the carbide strengthening phase in the alloy during the forging process are controlled, and the stress distribution state of the material is improved. Therefore, by using the method of the present invention, the forging cracking of the GH4079 alloy bar can be significantly improved.

[0050] The above are only specific embodiments of the present invention, enabling 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. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0051] 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 only limited by the appended claims.

Claims

1. A method for improving the forging cracking of GH4079 alloy, characterized in that, Specifically, it includes the following steps: Step 1: First, perform the first heat preservation on the GH4079 alloy ingot to be processed, then carry out cogging forging. After the first upsetting and drawing, blank A is obtained; Step 2: First, cool down the blank A and perform the second heat preservation, then heat up and perform the third heat preservation, and then carry out the second upsetting and drawing to obtain blank B; Step 3: First, perform multi-pass drawing of the blank B at the first temperature, and then perform chamfering in 1 pass to obtain blank C; Step 4: Perform 1-pass anvil drawing of the blank C at the second temperature to obtain the GH4079 alloy that can improve cracking.

2. The method for improving the forging cracking of GH4079 alloy according to claim 1, characterized in that, In Step 1, for the GH4079 alloy ingot to be processed, by mass percentage, its chemical composition is: 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 balance is nickel and inevitable impurity elements.

3. The method for improving the forging cracking of GH4079 alloy according to claim 1, characterized in that, In Step 1, the temperature of the first heat preservation is 1150°C - 1180°C, and the time is 120 min - 240 min.

4. The method for improving the forging cracking of GH4079 alloy according to claim 1, characterized in that, In Step 1, the first upsetting and drawing adopts multiple cycles of axial upsetting and drawing, and the deformation amount is 10% - 30%.

5. The method for improving the forging cracking of GH4079 alloy according to claim 1, characterized in that, In Step 2, the temperature of the second heat preservation is 980°C - 1050°C, and the time is 60 min - 240 min; the temperature of the third heat preservation is 1120°C - 1150°C, and the time is 60 min - 240 min.

6. The method for improving the forging cracking of GH4079 alloy according to claim 1, wherein In Step 2, the second upsetting and drawing adopts multiple cycles of axial upsetting and drawing, and the deformation amount is 20% - 40%.

7. The method for improving the forging cracking of GH4079 alloy according to claim 1, characterized in that, In Step 3, the first temperature is 1100°C - 1130°C.

8. The method for improving the forging cracking of GH4079 alloy according to claim 1, characterized in that, In Step 3, perform 2 - 3 passes of axial drawing at the first temperature, and the deformation amount is 20% - 40%.

9. The method for improving the forging cracking of GH4079 alloy according to claim 1, characterized in that, In Step 4, the second temperature is 1090°C - 1120°C; the deformation amount of the anvil drawing is 20% - 40%.

10. Use of the method for improving forging cracking of GH4079 alloy according to any one of claims 1 to 9, characterized in that, It is applied to improve the forging cracking of the GH4079 alloy.

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