A method for radial forging of Ni30 type alloy super-long material

Abstract

This invention discloses a radial forging method for Ni30 alloy ultra-long products, relating to the field of metal forging technology. The radial forging steps are as follows: S1: First, heat the intermediate billet to a holding temperature. After holding for T1 time, remove the intermediate billet; S2: Cover both ends of the intermediate billet with insulating material, then place the intermediate billet back into the furnace for a second holding time (T2 time). After the second holding time, the insulating material forms an insulating layer at both ends of the intermediate billet. The thermal conductivity of the insulating layer is lower than that of the intermediate billet, thus obtaining the billet to be forged; S3: Clamp the insulating layer at both ends of the billet to be forged using the jaws of a radial forging machine, and then perform open forging to obtain the finished ultra-long billet. This invention, by using a soft-wrapping technology at both ends of the intermediate billet, avoids direct contact between the jaws of the radial forging machine and the intermediate billet, reducing the heat transfer rate and allowing the temperature at both ends of the billet to be maintained above 900℃ for a longer period, achieving continuous deformation without cracking.

Description

Technical Field

[0001] This invention relates to the field of metal forging technology, specifically to a radial forging method for Ni30 type alloy ultra-long materials. Background Technology

[0002] Ni30 alloy is a Fe-Ni based high-temperature alloy. Compared with traditional nickel-based high-temperature alloy valve materials GH80A and GH751, its internal Ni content is 50% and 40% lower, respectively. Therefore, Ni30 alloy is an ideal Ni-saving high-temperature alloy valve material. Moreover, its mechanical properties are comparable to GH80A and GH751, which can fully meet the requirements of automobile engine exhaust valves. From the perspective of resource conservation, it is an ideal material to replace nickel-based high-temperature alloy valves.

[0003] Ni30 alloy is an age-hardening alloy in which Al, Ti, and Ni elements form the γ' phase, which plays a role in age-hardening. During the forging process, as the temperature drops below 900℃, a large amount of γ' phase precipitates, resulting in significant strengthening. However, work hardening leads to difficulties in deformation and a high susceptibility to cracking. This is particularly true when forging ultra-long billets, where the forging time is long. Because the billet is held at both ends by the forging machine jaws, heat is transferred to the jaws via thermal conduction, causing the billet ends to cool down rapidly, leading to cracking, scrap, and reduced yield. Therefore, a radial forging method for ultra-long Ni30 alloy products is proposed. Summary of the Invention

[0004] The purpose of this invention is to provide a radial forging method for Ni30 type alloy ultra-long materials to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for radial forging of Ni30 type alloy ultra-long materials, wherein the radial forging steps are as follows:

[0006] S1: First, heat the intermediate billet to the holding temperature, hold it for T1 time, and then take out the intermediate billet;

[0007] S2: The intermediate billet is wrapped with insulation material at both ends, and then the intermediate billet is put into the furnace for secondary insulation. After the secondary insulation time T2, the insulation material forms an insulation layer at both ends of the intermediate billet. The thermal conductivity of the insulation layer is less than that of the intermediate billet, thus obtaining the billet to be forged.

[0008] S3: The insulation layer at both ends of the billet to be forged is held by the jaws of the forging machine, and then the billet is forged to obtain an extra-long finished billet.

[0009] In this preferred embodiment of the technical solution, the step of obtaining the intermediate billet in step S1 is as follows:

[0010] S11: First, heat the electroslag ingot to the holding temperature, hold it for T3 time, and then forge the electroslag ingot into a specified diameter to obtain a rough forging billet;

[0011] S12: Cut the rough forging billet into sections so that the rough forging billet has a specified length;

[0012] S13: After the rough forging billet cools, it becomes the intermediate billet.

[0013] In this preferred embodiment, the insulation temperature range is 1050℃ to 1150℃.

[0014] In this preferred embodiment, the length ratio of the insulation layer to the intermediate blank is 1:10 to 3:10, and the length direction is parallel to the axial direction of the intermediate blank.

[0015] In this preferred embodiment, the length-to-diameter ratio of the intermediate billet is 10 to 20, and the length-to-diameter ratio of the extra-long billet is 80 to 150.

[0016] In this preferred embodiment, the range of time T1 is 60 min to 180 min, and the range of time T2 is 120 min to 180 min.

[0017] In this preferred embodiment, the T3 time range is 120 min to 150 min.

[0018] In this preferred embodiment, the insulation material includes insulation cotton, and one side of the insulation cotton is coated with an adhesive.

[0019] In this preferred embodiment, the thickness of the insulation cotton is 15-20mm, and the thermal conductivity of the insulation cotton is less than 0.23W / (mK).

[0020] In the preferred embodiment of this technical solution, the step of covering both ends of the intermediate billet with thermal insulation material in step S2 is as follows:

[0021] S21: After the intermediate blank is removed, attach the adhesive side of the insulation cotton to the end surface of the intermediate blank;

[0022] S22: Use a tool to press the insulation cotton until the adhesive melts, so that the insulation cotton can be firmly bonded to the intermediate blank.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] The radial forging method for this Ni30 alloy ultra-long material uses a soft-sleeving technology at both ends of the intermediate billet to avoid direct contact between the forging machine jaws and the intermediate billet, thereby reducing the heat transfer rate and allowing the temperature at both ends of the billet to be maintained above 900℃ for a longer period of time. This achieves continuous deformation without cracking. Furthermore, the soft-sleeving technology means that the resulting insulation layer can deform with the metal without leaving any dents on the surface of the billet, thus not affecting its subsequent machinability. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the insulation layer formed at both ends of the intermediate blank proposed in this invention.

[0026] In the diagram: 1. Intermediate billet; 2. Insulation layer. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] It should be noted that in the description of this invention, the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0029] Furthermore, it should be understood that, for ease of description, the dimensions of the various components shown in the accompanying drawings are not drawn to actual scale; for example, the thickness or width of some layers may be exaggerated relative to other layers.

[0030] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined or described in one figure, it will not need to be discussed or described in detail in the description of the subsequent figures.

[0031] It is important to understand that in the metal radial forging process, extra-long products refer to forgings with an aspect ratio greater than 20. The production of forgings with a longer aspect ratio means that the forging time is also longer. For Ni30 alloys, both ends are in direct contact with the jaws of the radial forging machine. Therefore, as time goes by, the temperature at both ends drops rapidly. When the forging time is long, the temperature at both ends drops below 900°C, which can easily cause cracks at both ends. Radial forging of extra-long products is intended to reduce production time, improve production efficiency, and reduce energy consumption. Conventional radial forging requires cutting a billet produced from an electroslag ingot into four pieces, and then forging each billet into a finished billet 7 to 8 meters long. Forging four billets into finished billets requires four operations: unloading from the furnace, loading, radial forging, and unloading from the forging line. The unloading, loading, and unloading processes take twice as long as producing extra-long billets (one electroslag ingot produces two intermediate billets), resulting in longer heating time in the furnace, higher energy consumption, and lower production efficiency. Secondly, to improve yield, the ends of the finished billets need to be trimmed with irregular sections (commonly known as "flat ends"). Conventionally, one electroslag ingot forges four finished billets, requiring eight flat ends. However, when producing extra-long billets, one electroslag ingot can only produce two extra-long billets, requiring only four flat ends. Therefore, radial forging of extra-long products can improve production efficiency, increase yield, and reduce energy consumption.

[0032] Therefore, the present invention provides an embodiment: a method for radial forging of Ni30 type alloy ultra-long materials.

[0033] In this embodiment, the specific composition of the Ni30 alloy used is as follows: 0.5 wt% C, 0.2 wt% Mn, 0.01 wt% P, 0.003 wt% S, 0.25 wt% Si, 32 wt% Ni, 14.8 wt% Cr, 2.0 wt% Al, 2.7 wt% Ti, 0.7 wt% Mo, 0.7 wt% Nb, 0.004 wt% B, and the balance Fe.

[0034] Specifically, the radial forging steps are as follows:

[0035] S1: First, heat the intermediate billet 1 to the holding temperature for 300 minutes, and after holding for T1 time, take out the intermediate billet 1;

[0036] Specifically, the holding time T1 ranges from 60 min to 180 min. It can be any one of the following: 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, 120 min, 130 min, 140 min, 150 min, 160 min, 170 min, and 180 min, or any time between two adjacent times mentioned above. It's important to understand that this holding operation is to ensure the intermediate billet 1 is thoroughly fired before the coating operation in step S2. In practice, the T1 time can be set empirically or determined using the following calculation method:

[0037] T1 = D / 2, where D is the diameter of intermediate billet 1 in mm; T1 is in min.

[0038] In this embodiment, time T1 is selected as 120 minutes.

[0039] It is also important to understand that, due to the production of ultra-long materials, it is difficult to complete the material forming in a single forging process. Therefore, this invention employs a two-stage forging process for radial forging of the ultra-long material, that is, first forging an intermediate billet 1, and then forging the ultra-long billet. This results in more stable material forming. The specific forging method for the intermediate billet 1 is as follows:

[0040] S11: First, the electroslag ingot is heated to the holding temperature for 360 minutes and held at that temperature for T3 time. Then, the electroslag ingot is forged into a specified diameter to obtain a rough forging billet. It should be noted that in this technical solution, the holding temperature of the electroslag ingot and the intermediate billet 1 is the same, and their holding temperature range is 1050℃ to 1150℃, which can be 1050℃, 1060℃, 1070℃, 1080℃, 1090℃, 1100℃, 1110℃, 1120℃, etc. The temperature can be any one of 1130℃, 1140℃, and 1150℃, or any temperature between the above adjacent temperatures. In this embodiment, the heat preservation temperature is selected as 1110℃, and the heat preservation time T3 range is 120min to 150min, which can be 120min, 125min, 130min, 135min, 140min, 145min, and 150min, or any time between the above two adjacent times.

[0041] S12: Cut the rough forging billet into sections so that the rough forging billet has a specified length;

[0042] S13: After the rough forging billet cools, it becomes the intermediate billet 1. Specifically, the length-to-diameter ratio of the intermediate billet 1 is controlled to be between 10 and 20. It can be any one of 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 and 20, or any value between two adjacent values ​​mentioned above. In this embodiment, the size of the intermediate billet 1 is controlled to be φ260*3400mm.

[0043] S2: The intermediate billet 1 is wrapped with heat-insulating material at both ends, and then the intermediate billet 1 is put into the furnace for secondary heat preservation. After the secondary heat preservation time T2, the heat-insulating material forms heat-insulating layer 2 at both ends of the intermediate billet 1. The thermal conductivity of the heat-insulating layer 2 is less than that of the intermediate billet 1, thereby obtaining the billet to be forged.

[0044] Specifically, the range of the secondary heat preservation time T2 is 120 min to 180 min, which can be 120 min, 130 min, 140 min, 150 min, 160 min, 170 min and 180 min, or any time between two adjacent times mentioned above. The main purpose of the secondary heat preservation is to enable the heat preservation material to form a firm and dense heat preservation layer 2 at both ends of the intermediate billet 1, and to continue to burn through the intermediate billet 1.

[0045] As can be seen from step S2, the main method of the present invention is to reduce the cooling rate of the two ends of the intermediate billet 1 during the forging process by setting the heat insulation layer 2 at both ends of the intermediate billet 1, thereby allowing the temperature of the two ends of the intermediate billet 1 to be maintained above 900°C for a longer period of time, thereby reducing the scrap rate of the intermediate billet 1 during the forging process. Specifically, the heat insulation material in the present invention includes heat insulation cotton, one side of which is coated with an adhesive. The adhesive is used to make the heat insulation cotton adhere to the intermediate billet 1. The adhesive used in this embodiment is glass powder, which is a common existing technology in this field, so it will not be described in detail here. The advantage of using heat insulation cotton for wrapping is that the protective layer formed by the heat insulation cotton on the surface of the intermediate billet 1 can be easily removed with the deformation of the metal. Moreover, when the heat insulation cotton is used for heat insulation, it will not be pressed into the surface of the intermediate billet 1 during forging like ceramics or glass fibers, thus affecting the subsequent machinability of the billet.

[0046] In summary, in order to ensure that the subsequently formed insulation layer 2 has a good heat insulation effect, the insulation cotton selected in this invention should preferably have a thermal conductivity of less than 0.23 W / (mK), and its covering thickness should be 15 mm to 20 mm. It can be any thickness among 15 mm, 16 mm, 17 mm, 18 mm, 19 mm and 20 mm, or any thickness between two adjacent thicknesses. In this embodiment, the insulation cotton thickness is selected as 18 mm.

[0047] Meanwhile, when covering both ends of the intermediate blank 1, in order to further improve the thermal insulation effect, the insulation material needs to fully cover the circumferential surface of the intermediate blank 1 around the axial direction. In order to facilitate subsequent clamping and use, the insulation material also needs to have a certain length along the axial direction of the intermediate blank 1, so that the subsequently formed insulation layer 2 has a fixed length. Specifically, the length ratio of the subsequently formed single insulation layer 2 to the intermediate blank 1 is 1:10 to 3:10. In this embodiment, the length of a single insulation layer 2 is 600mm.

[0048] It is important to understand that the specific steps for covering both ends of the intermediate blank 1 with insulation material are as follows:

[0049] S21: After the intermediate blank 1 is taken out, quickly stick the side of the insulation cotton with adhesive to the end surface of the intermediate blank 1.

[0050] S22: Press the insulation cotton with a tool until the adhesive melts and the insulation cotton is firmly bonded to the intermediate blank 1. The tool can be a homemade fixture, a shovel, or a press, etc. During the operation, the insulation cotton must not be broken, so as to expose the intermediate blank 1.

[0051] S3: The insulation layer 2 at both ends of the billet to be forged is held by the jaws of the forging machine, and then the billet is forged to obtain the finished ultra-long billet. Theoretically, the method of this invention can be used to manufacture any forging material with an aspect ratio exceeding 20. However, in order to make more reasonable and economical use of the method of this invention, the aspect ratio of the ultra-long billet should be controlled between 80 and 150 when producing the ultra-long billet. It can be any value among 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, and 150, or any value between the above adjacent values. In this embodiment, the forging of the intermediate billet 1 and the ultra-long billet is carried out by a 16MN forging machine. The size of the ultra-long billet is φ120*15000mm.

[0052] To verify the effectiveness of the method of the present invention, a comparative example was also set up. In the comparative example, all the process parameters of the operation were the same as those of the above embodiment. The only difference was that in step S2, the insulation material was not wrapped around both ends of the intermediate billet 1. The process methods of the embodiment and the comparative example were used to make ultra-long billets with a size of φ120*15000mm, and the number of cracks that appeared at the ends during the forging process was counted. When cracks appeared at both ends of the ultra-long billet, the cut length of the end (i.e., flat end) of each ultra-long billet was longer than that of the ultra-long billet without cracks, generally 1000mm. When there were no cracks at the ends of the ultra-long billet, the cut length at the end was generally 200mm. Therefore, the end cut loss rate in the comparative example and the embodiment can be calculated by this method. End cut loss rate = total length of flat end cut / total length of ultra-long billet * 100%. After multiple experiments in the embodiment and the comparative example, the specific data are shown in Table 1.

[0053] Table 1

[0054] project Example Comparative Example Number of tests (roots) 116 24 Number of end cracks (roots) 0 24 Total length of extra-long billet (mm) 1740000 360000 Total length of the cut-off head (mm) 23200 24000 End-cut loss rate (%) 1.33 6.67

[0055] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for radial forging of Ni30 type alloy ultra-long materials, characterized in that, The radial forging steps are as follows: S1: First, heat the intermediate billet to the holding temperature and hold it for T1 time, then take out the intermediate billet; T1 = D / 2, where D is the diameter of the intermediate billet in mm, T1 is in min, and the length-to-diameter ratio of the intermediate billet is controlled to be 10 to 20. S2: The ends of the intermediate billet are covered with heat-insulating material, and then the intermediate billet is put into the furnace for secondary heat preservation. After the secondary heat preservation time T2, the heat-insulating material can form a firm and dense heat-insulating layer at both ends of the intermediate billet and continue to burn through the intermediate billet. The thermal conductivity of the heat-insulating layer is less than the thermal conductivity of the intermediate billet, thus obtaining the billet to be forged. S3: Use the jaws of a radial forging machine to hold the insulation layer at both ends of the billet to be forged, and then perform open forging of the billet to obtain an ultra-long finished billet with a length-to-diameter ratio of 80 to 150. The steps for obtaining the intermediate billet in step S1 are as follows: S11: First, heat the electroslag ingot to the holding temperature, hold it for T3 time, and then forge the electroslag ingot into a specified diameter to obtain a rough forging billet; S12: Cut the rough forging billet into sections so that the rough forging billet has a specified length; S13: After the rough forging billet cools, it becomes the intermediate billet; The holding time T1 ranges from 60 min to 180 min; the holding time T3 ranges from 120 min to 150 min; the second holding time T2 ranges from 120 min to 180 min; and the holding temperature ranges from 1050℃ to 1150℃. The insulation material is wrapped around the axial direction of the intermediate blank and completely covers the circumferential surface of the intermediate blank. The insulation material also has a length along the axial direction of the intermediate blank, thereby forming an insulation layer. The length ratio of the insulation layer to the intermediate blank is 1:10 to 3:10, and the length direction is parallel to the axial direction of the intermediate blank. The insulation material includes insulation cotton, one side of which is coated with an adhesive. The thermal conductivity of the insulation cotton is less than 0.23 W / (mK), and its covering thickness is 15 mm to 20 mm.

2. The radial forging method for Ni30 type alloy ultra-long materials according to claim 1, characterized in that, In step S2, the step of covering both ends of the intermediate billet with insulation material is as follows: S21: After the intermediate blank is removed, attach the adhesive side of the insulation cotton to the end surface of the intermediate blank; S22: Use a tool to press the insulation cotton until the adhesive melts, so that the insulation cotton can be firmly bonded to the intermediate blank.

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