A variable cross-section In718 alloy bar and its rapid forging deformation method

Abstract

This invention relates to the field of turbine shaft forging technology, specifically disclosing a variable cross-section In718 alloy bar and its rapid forging deformation method. This invention utilizes In718 alloy material with a high return ratio for smelting, resulting in a more uniform Nb element distribution; it directly forges steel ingots into the required variable cross-section bar specifications, reducing the requirements for forging equipment and significantly lowering production costs. During the variable cross-section forging process, an intermediate deformation section is set between the large and small round bars, and this intermediate deformation section deforms in each forging pass, solving the problem of misalignment of the variable cross-section In718 alloy bars in rapid forging mill production, while also avoiding the problem of dry burning between the large and small round bars; the uniform deformation of both the large and small round bars in each forging pass ensures the uniformity of their deformation; furthermore, the deformation amount of the small round bars in each pass is greater than that of the large round bars, ensuring the forging quality of both the large and small round bars.

Description

Technical Field

[0001] This invention relates to the field of turbine shaft forging technology, specifically disclosing a variable cross-section In718 alloy bar and its rapid forging deformation method. Background Technology

[0002] In718 alloy is a Ni-Cr-Fe based precipitation-hardening wrought superalloy. It exhibits excellent comprehensive properties within a temperature range of -253 to 700℃, with the highest yield strength among wrought superalloys below 650℃. It also possesses good fatigue resistance, radiation resistance, oxidation resistance, and corrosion resistance, as well as good machinability, weldability, and long-term structural stability. It has found widespread application in the aerospace, nuclear energy, and petroleum industries. Variable cross-section In718 alloy bars are used as raw materials for turbine shafts, a critical rotating component in engines. This critical component places strict requirements on the composition, microstructure uniformity, and mechanical properties of the raw material bars.

[0003] Currently, In718 alloy variable cross-section bars for turbine shafts are mostly smelted from virgin materials, forged into large-diameter bars using a high-speed forging mill, and then machined to the required variable cross-section bar specifications (see...). Figure 1 ); or it can be forged directly into the required variable cross-section bar specifications by using a fast forging machine and a radial forging machine. The existing forging methods for variable cross-section In718 alloy bars have the following defects: (1) The In718 alloy has a high Nb content. When pure Nb is added during the smelting process, Nb has a high melting point and is not easy to melt. If the stirring is not proper or the refining time is short, metallurgical defects such as segregation are very easy to occur. In addition, the cost of smelting new materials is high. (2) In the variable cross-section In718 alloy bars for turbine shafts, the size and length of large round bars and small round bars are very different. Therefore, the technical solution of fast forging into large-specification bars and then machining them to the variable cross-section bar specifications is extremely costly and inefficient. Furthermore, since the small round bars are machined from the large round bars, the performance of the small round bars (actually the performance of the large round bars) is significantly different from that of the directly forged small round bars. (3) The technical solution of using a fast forging machine for billet opening and a radial forging machine for forming to directly forge In718 alloy bars with variable cross-section has high equipment requirements. It requires two different forging machines to work together, resulting in a large production investment. At the same time, the forming characteristics of the radial forging machine lead to a large difference in the microstructure between the edge and the radius and the core of the bar. Often, the grain size is fine at the edge and coarse at the radius and core. In addition, during the precision forging process, the forging characteristics of the precision forging machine cause the insulation cotton on the surface of the bar to fall off easily and cannot be repaired at any time, resulting in local low temperature of the bar and defects such as elongated grain incompatibility. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a variable cross-section In718 alloy bar and its rapid forging deformation method, which not only improves the microstructure uniformity of the variable cross-section In718 alloy bar, but also reduces production costs and the requirements for forging equipment.

[0005] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0006] A rapid forging deformation method for In718 alloy bars with variable cross-section includes the following steps:

[0007] S1, add 70% to 80% of the total mass of In718 alloy recycled material to the molten steel, and carry out triple smelting to obtain steel ingots;

[0008] S2, the head of the steel ingot is pressed with clamps and forged 2 to 3 times, with each forging completing one upsetting and drawing to obtain a forging billet;

[0009] S3, the forging billet is drawn 1 to 2 times, the tail is pressed with a clamp, and the middle is cut to obtain a bar.

[0010] S4, the bar is forged with a variable cross-section to obtain a variable cross-section In718 alloy bar;

[0011] The variable cross-section forging includes 3 to 4 drawing cycles; an intermediate deformation section is provided between the large and small round bars of the variable cross-section forged bar, and the large round bar, the small round bar, and the intermediate deformation section are deformed in each drawing cycle, with the deformation of the small round bar in each drawing cycle increasing by 5% to 15% compared to the large round bar; the reheating temperature of the forging billet, the bar, and the variable cross-section bar decreases sequentially.

[0012] Compared to existing technologies, the rapid forging deformation method for variable cross-section In718 alloy bars provided by this invention utilizes In718 alloy material with a high return ratio for smelting, which is equivalent to a secondary melting and purification of the In718 alloy, resulting in a more uniform distribution of Nb elements and thus reducing the risk of Nb segregation. This invention directly forges steel ingots into the required variable cross-section bar specifications, reducing the requirements for forging equipment and significantly lowering production costs compared to the rapid forging machine billet preparation combined with radial forging machine forming technology. In this invention, the reheating temperature of the billet, bar, and variable cross-section bar decreases sequentially (i.e., a stepped cooling heating method), ensuring the final forging temperature of the variable cross-section In718 alloy bar and improving the uniformity of the bar's microstructure. In step S2, the forging process employs 2-3 upsetting and drawing operations to increase the total deformation. In step S4, during the variable cross-section forging process, an intermediate deformation section is set between the large and small round bars, and this intermediate deformation section deforms in each forging pass, solving the problem of variable cross-section In718 alloy bars being prone to uneven forging in rapid forging machine production. The concentricity issue is addressed, while avoiding the problem of dry burning between the large and small round bars. In step S4, during each round of variable cross-section forging, both the large and small round bars are forged, ensuring the uniformity of deformation between them. This avoids the problem of mixed crystals in the core of the bar caused by the low final forging temperature due to forging one end first and then the other, further improving the uniformity of the microstructure of the variable cross-section bar. In addition, the deformation of the small round bar per round is greater than that of the large round bar, which can ensure the forging quality of both the large and small round bars.

[0013] Preferably, in step S1, the triple smelting process includes vacuum induction melting, electroslag remelting, and vacuum arc furnace remelting.

[0014] More preferably, in step S1, the conditions for vacuum induction melting include: the temperature of the molten steel is 1250 to 1750°C; and the vacuum degree of the melting chamber under working conditions is below 0.1 Pa, more preferably 0.05 to 0.1 Pa.

[0015] For example, the specifications of the casting vacuum electrode rod for vacuum induction melting are φ250mm.

[0016] More preferably, in step S1, the conditions for electroslag remelting include a melting rate of 3.5 to 4.8 kg / min.

[0017] For example, the electrode rod for electroslag remelting has a specification of φ250mm, and the surface must be polished, flat-headed, and free from black skin, heavy skin, burrs, and phenomena such as turning blue due to heat. Shrinkage cavities must be cleaned thoroughly. The specification of the crystallizer is φ420mm.

[0018] More preferably, in step S1, the conditions for remelting in the vacuum electric arc furnace include: a melting rate of 3.3 to 3.8 kg / min; helium cooling to increase the solidification rate; and a helium pressure of 300 to 720 Pa.

[0019] For example, the electrode surface remelted in the vacuum arc furnace is not allowed to have transverse cracks, and impurities such as slag and rust must be removed, and the surface must be dry and free from oxidation; the bottom of the electrode must be flat and dry, and there must be no liquid or slag inclusions in the shrinkage cavities; the welding of the dummy electrode and the electrode must be firm; the crystallizer specification is φ508mm.

[0020] For example, after the vacuum arc furnace remelting is completed, diffusion annealing is also included to obtain a homogenized steel ingot; the steel ingot is heated (the heating temperature is 1080-1120°C) and then subjected to subsequent forging.

[0021] Preferably, in step S2, the deformation amount per forging pass is 55% to 60%.

[0022] Preferably, in step S2, one upsetting and drawing process includes 3 to 4 consecutive upsetting operations and 1 drawing operation, with a resting time of 8 to 12 seconds between two adjacent upsetting operations.

[0023] By setting the upsetting conditions, this invention can further prevent excessive heating of the core of the forging billet, which could lead to mixed crystals.

[0024] Preferably, in step S3, the deformation amount per drawing cycle is 35% to 40%.

[0025] It should be noted that after cutting in step S3, two bars for variable cross-section forging can be obtained.

[0026] Preferably, in step S2, the remelting temperature of the forging billet is 1060-1100℃; in step S3, the remelting temperature of the bar is 1040-1080℃; and in step S4, the remelting temperature of the variable cross-section bar is 980-1050℃.

[0027] Preferably, in step S4, in the two adjacent drawing operations of the variable cross-section forging, the intermediate deformed section and small round bar of the variable cross-section bar in the previous drawing operation are drawn into the small round bar of the variable cross-section bar in the next drawing operation, and the large round bar of the variable cross-section bar in the previous drawing operation is drawn into the large round bar and intermediate deformed section of the variable cross-section bar in the next drawing operation.

[0028] Preferably, in step S4, the deformation amount per firing of the large round bar is 30% to 50%, the deformation amount per firing of the small round bar is 40% to 60%, and the deformation amount per firing of the intermediate deformation section is 30% to 55%.

[0029] By limiting the deformation amount of large round bars, small round bars, and intermediate deformation sections per firing, this invention can ensure sufficient deformation of the bar cross-section during forging, thereby further guaranteeing the forging quality of variable cross-section forging.

[0030] Preferably, in step S4, the pressing rate per heat treatment of the large round bar is 100%, the pressing rate per heat treatment of the small round bar is 65% to 70%, and the pressing rate per heat treatment of the intermediate deformation section is 65% to 70%.

[0031] In this invention, for the same number of forging passes, the deformation of small round bars is greater than that of large round bars. To prevent excessive heating of the bar core during forging, which could lead to mixed grains, different reduction rates are used to prevent uneven microstructure caused by heating of the small round bar core. Through extensive trial forging experiments, the inventors discovered that the grain size microstructure of both large and small round bars is relatively better when deformed at the aforementioned reduction rates.

[0032] Preferably, in steps S2 to S4, after the rod and the variable cross-section rod are taken out of the furnace, both ends are wrapped with ceramic fibers for heat preservation.

[0033] This invention, by wrapping ceramic fibers at both ends of the bar stock and the variable cross-section bar stock, facilitates timely remediation during the forging process and further ensures the final forging temperature of the bar stock.

[0034] Preferably, in steps S2 to S4, octagonal deformation forging is used.

[0035] Octagonal deformation can further ensure the uniformity of microstructure in each cross section of the bar and variable cross section bar.

[0036] For example, after the variable cross-section forging is completed, it is also necessary to perform machining to remove the oxide black scale on the surface of the bar; and cutting to remove the excess length at both ends of the variable cross-section In718 alloy bar.

[0037] The present invention also provides a variable cross-section In718 alloy bar obtained by the above-mentioned rapid forging deformation method of variable cross-section In718 alloy bar.

[0038] The variable cross-section In718 alloy bars provided by this invention have no mixed crystal problem in the core, resulting in a uniform microstructure and high purity. The large and small round bars are not eccentric and exhibit uniform deformation. Example results show that the Nb element distribution in the variable cross-section In718 alloy bars is more uniform; the grain size of both the large and small round bars meets the standard and exhibits better uniformity, with the grain size difference within the same cross-section controlled to within level 2; and the yield of steel ingots is increased from 38% to 57%.

[0039] Preferably, the diameter of the large round bar of the variable cross-section In718 alloy bar is 240-270 mm and the length is 300-500 mm; the diameter of the small round bar of the variable cross-section In718 alloy bar is 130-170 mm and the length is 1300-1700 mm; and the diameter of the transition section bar of the variable cross-section In718 alloy bar is 140-180 mm and the length is 80-120 mm. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the existing technology of first forging large-diameter bars and then machining them to the required cross-section bars.

[0041] Figure 2 This is a diagram showing the carbide microstructure at the midpoint of the cross-sectional radius of the large round In718 alloy bar with variable cross-section in Embodiment 1 of the present invention;

[0042] Figure 3 This is a diagram showing the carbide microstructure at the midpoint of the cross-sectional radius of the large round bar of the variable cross-section In718 alloy bar in Comparative Example 1 of the present invention;

[0043] Figure 4 This is a metallographic diagram of the edge of the cross-section of the large round In718 alloy bar with variable cross-section in Embodiment 1 of the present invention;

[0044] Figure 5 This is a metallographic diagram of the midpoint of the cross-sectional radius of the large round In718 alloy bar with variable cross-section in Embodiment 1 of the present invention.

[0045] Figure 6 This is a metallographic diagram of the center of the cross-section of the large round In718 alloy bar with variable cross-section in Embodiment 1 of the present invention;

[0046] Figure 7 This is a metallographic diagram of the edge of the cross-section of the small round bar of the variable cross-section In718 alloy bar in Embodiment 1 of the present invention;

[0047] Figure 8 This is a metallographic diagram of the midpoint of the cross-sectional radius of the small round bar of the variable cross-section In718 alloy bar in Embodiment 1 of the present invention;

[0048] Figure 9 This is a metallographic diagram of the center of the cross-section of the small round bar of the variable cross-section In718 alloy bar in Embodiment 1 of the present invention. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0050] In this invention, the three-stage smelting process employs a vacuum induction furnace, a protective atmosphere electroslag furnace, and a vacuum consumable ingot furnace. The vacuum electrode rods used in vacuum induction melting are φ250mm in diameter, and full elemental analysis is performed on the molten steel. The electrode rods used in electroslag remelting are also φ250mm in diameter, requiring a polished surface, flat ends, and freedom from black scale, heavy scale, burrs, and blue discoloration caused by grinding. Shrinkage cavities must be thoroughly cleaned. The crystallizer is φ420mm in diameter; samples are taken from both ends for C, S, Al, and Ti analysis. The electrode surface used in vacuum arc furnace remelting is free from transverse cracks, and impurities such as slag inclusions and rust must be removed. The surface must be dry and free from oxidation. The bottom of the electrode must be flat and dry, and no liquid or slag inclusions are allowed in shrinkage cavities. The welding between the dummy electrode and the electrode must be secure. The crystallizer is φ508mm in diameter; samples are taken from both ends of the consumable ingot for C, Al, and Ti analysis.

[0051] In steps S2 to S4 of this invention, forging is performed on a 60MN high-speed forging machine.

[0052] To better illustrate the present invention, further examples are provided below.

[0053] Example 1

[0054] This embodiment provides a rapid forging deformation method for In718 alloy bars with variable cross-section, including the following steps:

[0055] S1, add 75% of the total mass of In718 alloy recycled material to the molten steel, carry out triple smelting, diffusion annealing, and obtain steel ingots.

[0056] The three-stage smelting process includes vacuum induction melting, electroslag remelting, and vacuum arc furnace remelting. The conditions for vacuum induction melting include: a steel temperature of 1550℃; and a vacuum level of 0.07 Pa in the melting chamber. The melting rate for electroslag remelting is 4.0 kg / min. The conditions for vacuum arc furnace remelting include: a melting rate of 3.5 kg / min; helium cooling at a pressure of 500 Pa.

[0057] S2, heat the above steel ingot to 1100℃, take it out of the furnace, press the head with clamps (first heating), and return it to the furnace at 1080℃;

[0058] After being taken out of the furnace, it undergoes a second octagonal deformation forging, completing one upsetting and drawing (one upsetting and drawing includes three consecutive upsetting and one drawing, with a 10-second resting time between two adjacent upsetting), with a deformation of 57%, and a furnace return temperature of 1080℃.

[0059] After being taken out of the furnace, it undergoes a third octagonal deformation forging process, completing one upsetting and drawing (one upsetting and drawing includes three consecutive upsettings and one drawing, with a 10-second resting time between two adjacent upsettings), with a deformation amount of 58%, and a furnace return temperature of 1080℃.

[0060] After being taken out of the furnace, a forged blank is obtained.

[0061] S3, after the above forging billet is taken out of the furnace, both ends are wrapped with ceramic fiber, and it is subjected to the fourth octagonal deformation and elongation with a deformation amount of 37%. The tail is pressed with clamps, the middle is cut, and the furnace temperature is 1060℃.

[0062] After baking, you get 2 bars.

[0063] S4, after the above-mentioned bars are taken out of the furnace, both ends are wrapped with ceramic fibers, and they are subjected to a fifth octagonal deformation elongation and variable cross-section forging (the large round bar part is not forged); an intermediate deformation section is set between the large round bar and the small round bar of the variable cross-section forged bar, the deformation amount of the intermediate deformation section is 47%, and the reduction rate is 65%; the deformation amount of the small round bar is 51%, and the reduction rate is 65%; the remelting temperature is 1000℃;

[0064] After being removed from the furnace, both ends are wrapped with ceramic fiber. The material undergoes a sixth firing process involving octagonal deformation and elongation. The middle deformation section and small round bar from the fifth firing process are elongated into the small round bar of the sixth firing process, with a deformation amount of 46% and a reduction rate of 65%. The large round bar from the fifth firing process is elongated into the large round bar and middle deformation section of the sixth firing process, with a deformation amount of 37.5% and a reduction rate of 100% for the large round bar and a deformation amount of 44% and a reduction rate of 65% for the middle deformation section. The reflow temperature is 1000℃.

[0065] After being removed from the furnace, both ends are wrapped with ceramic fibers. The seventh firing process involves octagonal deformation and elongation. The middle deformation section and small round bar of the variable cross-section bar from the sixth firing process are elongated into the small round bar of the variable cross-section bar of the seventh firing process, with a deformation amount of 47% and a reduction rate of 68%. The large round bar of the variable cross-section bar from the sixth firing process is elongated into the large round bar and transition section (middle deformation section) of the variable cross-section bar of the seventh firing process, with a deformation amount of 37% and a reduction rate of 100%. The deformation amount of the middle deformation section is 44% and the reduction rate is 68%. The bar is then machined and cut to obtain a variable cross-section In718 alloy bar.

[0066] For specific forging processes, please refer to Table 1. The resulting variable cross-section In718 alloy bars are shown in [reference needed]. Figure 2 The large round bar has a diameter of 250mm and a length of 450mm; the small round bar has a diameter of 145mm and a length of 1600mm; and the transition section bar has a diameter of 160mm and a length of 100mm.

[0067] Table 1. Forging process of variable cross-section In718 alloy bar in Example 1 (rapid forging deformation)

[0068]

[0069]

[0070]

[0071] Example 2

[0072] This embodiment provides a rapid forging deformation method for In718 alloy bars with variable cross-section, including the following steps:

[0073] S1, add 70% of the total mass of In718 alloy recycled material to the molten steel, carry out triple smelting, diffusion annealing, and obtain steel ingots.

[0074] The three-stage smelting process includes vacuum induction melting, electroslag remelting, and vacuum arc furnace remelting. The conditions for vacuum induction melting include: a steel temperature of 1300℃; and a vacuum level of 0.05 Pa in the melting chamber. The melting rate for electroslag remelting is 3.5 kg / min. The conditions for vacuum arc furnace remelting include: a melting rate of 3.3 kg / min; and helium cooling at a pressure of 700 Pa.

[0075] S2, heat the above steel ingot to 1080℃, remove it from the furnace, press the head with clamps, and perform 3 rounds of octagonal deformation forging. The furnace temperature is 1060℃ for each round of forging. Each round of forging completes one upsetting and drawing (one upsetting and drawing includes three consecutive upsetting and one drawing, with a 12s resting time between two adjacent upsettings). The deformation amount of each round is 55%, resulting in a forged billet.

[0076] S3, the above forging billet is subjected to one octagonal deformation and elongation in one furnace. After exiting the furnace, both ends are wrapped with ceramic fiber. The deformation amount is 40%. The tail is clamped and cut in the middle. The furnace temperature is 1040-1080℃ to obtain two bars.

[0077] S4. The above-mentioned bars are subjected to variable cross-section forging (4 heats of octagonal deformation and elongation). After exiting the furnace, both ends are wrapped with ceramic fiber, and the reheating temperature is 980℃. An intermediate deformation section is set between the large and small round bars of the variable cross-section forged bars. In the two adjacent heats of elongation of the variable cross-section forging, the intermediate deformation section and small round bar of the variable cross-section bar of the previous heat are elongated to become the small round bar of the variable cross-section bar of the next heat. The large round bar of the variable cross-section bar of the previous heat is elongated to become the large round bar and intermediate deformation section of the variable cross-section bar of the next heat. The bars are then machined and cut to obtain variable cross-section In718 alloy bars.

[0078] The deformation per heat treatment of large round bars is 30%, that of small round bars is 40%, and that of the intermediate deformation section is 30%. The reduction rate per heat treatment of large round bars is 100%, that of small round bars is 65%, and that of the intermediate deformation section is 65%.

[0079] Of the obtained variable cross-section In718 alloy bars, the large round bar has a diameter of 240 mm and a length of 300 mm; the small round bar has a diameter of 130 mm and a length of 1300 mm; and the transition section bar has a diameter of 140 mm and a length of 80 mm.

[0080] Example 3

[0081] This embodiment provides a rapid forging deformation method for In718 alloy bars with variable cross-section, including the following steps:

[0082] S1, add 80% of the total mass of In718 alloy recycled material to the molten steel, carry out triple smelting, diffusion annealing, and obtain steel ingots.

[0083] The three-stage smelting process includes vacuum induction melting, electroslag remelting, and vacuum arc furnace remelting. The conditions for vacuum induction melting include: a steel temperature of 1700℃; and a vacuum level of 0.1 Pa in the melting chamber. The melting rate for electroslag remelting is 4.6 kg / min. The conditions for vacuum arc furnace remelting include: a melting rate of 3.8 kg / min; and helium cooling at a pressure of 400 Pa.

[0084] S2, heat the above steel ingot to 1120℃, remove it from the furnace, press the head with clamps, and perform two rounds of octagonal deformation forging. The furnace temperature is 1100℃ for both rounds. Each round of forging completes one upsetting and drawing (one upsetting and drawing includes four consecutive upsettings and one drawing, with an 8-second resting time between two adjacent upsettings). The deformation amount per round is 60%, resulting in a forged billet.

[0085] S3, the above forging billet is subjected to two octagonal deformation and elongation in two firings. After exiting the furnace, both ends are wrapped with ceramic fiber. The deformation amount in each firing is 35%. The tail is pressed with clamps, cut in the middle, and returned to the furnace at a temperature of 1080℃ to obtain two bars.

[0086] S4. The above-mentioned bars are subjected to variable cross-section forging (3-pass octagonal deformation elongation). After exiting the furnace, both ends are wrapped with ceramic fiber, and the reheat temperature is 1050℃. An intermediate deformation section is set between the large and small round bars of the variable cross-section forged bars. In the two adjacent elongation passes of the variable cross-section forging, the intermediate deformation section and small round bar of the variable cross-section bar of the previous pass are elongated to become the small round bar of the variable cross-section bar of the next pass. The large round bar of the variable cross-section bar of the previous pass is elongated to become the large round bar and intermediate deformation section of the variable cross-section bar of the next pass. The bars are then machined and cut to obtain variable cross-section In718 alloy bars.

[0087] The deformation per heat treatment of large round bars is 50%, that of small round bars is 60%, and that of the intermediate deformation section is 55%. The reduction rate per heat treatment of large round bars is 100%, that of small round bars is 70%, and that of the intermediate deformation section is 70%.

[0088] Of the obtained variable cross-section In718 alloy bars, the large round bar has a diameter of 270 mm and a length of 500 mm; the small round bar has a diameter of 170 mm and a length of 1700 mm; and the transition section bar has a diameter of 180 mm and a length of 120 mm.

[0089] Comparative Example 1

[0090] This comparative example provides a rapid forging deformation method for In718 alloy bars with variable cross-sections, including the following steps:

[0091] S1 uses 100% new metal raw materials by mass of molten steel for triple smelting, followed by diffusion annealing to obtain steel ingots.

[0092] The triple smelting process includes vacuum induction melting, electroslag remelting, and vacuum arc furnace remelting. The triple smelting process is the same as in Example 1 and will not be described again. Using entirely new metallic raw materials to smelt In718 alloy steel ingots is a standard practice in the field and will not be elaborated upon here.

[0093] S2 to S4 are the same as in Example 1, and will not be described again.

[0094] Comparative Example 2

[0095] This comparative example provides a method for preparing a variable cross-section In718 alloy bar, comprising the following steps:

[0096] S1 is the same as in Example 1, and will not be described again;

[0097] S2, heat the above steel ingot to 1100°C, remove it from the furnace, press the head with clamps (first heat), return it to the furnace at 1100°C, and press down at 100% speed.

[0098] After being taken out of the furnace, the billet undergoes a second octagonal deformation forging process, completing one upsetting and drawing (one upsetting and drawing includes three consecutive upsettings and one drawing, with a 10-second resting time between two adjacent upsettings), with a deformation amount of 55% and a reduction rate of 70%, resulting in a Φ530 steel billet. The remelting temperature is 1080℃.

[0099] After being taken out of the furnace, it undergoes a third octagonal deformation forging process, completing one upsetting and drawing (one upsetting and drawing includes three consecutive upsettings and one drawing, with a 10-second resting time between two adjacent upsettings), with a deformation amount of 52% and a reduction rate of 70%, resulting in a Φ580 forging billet, which is then returned to the furnace at a temperature of 1050℃.

[0100] S3, after the above forging billet is taken out of the furnace, both ends are wrapped with ceramic fiber, and it is subjected to the fourth octagonal deformation elongation with a deformation amount of 31.5% and a reduction rate of 70%, to obtain a Φ480 bar. The return temperature is 1050℃.

[0101] After being removed from the furnace, both ends are wrapped with ceramic fiber. The fifth octagonal deformation elongation is carried out with a deformation amount of 30.6% and a reduction rate of 70%, resulting in a Φ400 bar. The remelting temperature is 1020℃.

[0102] After being taken out of the furnace, both ends are wrapped with ceramic fiber. The sixth furnace is then subjected to octagonal deformation and elongation with a deformation amount of 32% and a reduction rate of 70%, resulting in a Φ340 bar. The re-furnace temperature is 1020℃.

[0103] After being removed from the furnace, both ends are wrapped with ceramic fibers. The material undergoes a seventh octagonal deformation elongation process with a deformation amount of 31.6% and a pressing rate of 100%, resulting in a Φ270 bar.

[0104] S4. The above-mentioned bar is machined and cut to obtain a variable cross-section In718 alloy bar (same specifications as in Example 1).

[0105] Comparative Example 3

[0106] This comparative example provides a method for preparing a variable cross-section In718 alloy bar, comprising the following steps:

[0107] S1 to S2 are the same as Comparative Example 2, and will not be repeated here;

[0108] S3, after the above forging billet is taken out of the furnace, both ends are wrapped with ceramic fiber, and it is subjected to the fourth octagonal deformation elongation with a deformation amount of 37% and a reduction rate of 70%, to obtain a Φ460 bar. The return temperature is 1050℃.

[0109] After being taken out of the furnace, both ends are wrapped with ceramic fiber. The fifth octagonal deformation elongation is carried out with a deformation amount of 30% and a reduction rate of 70%, resulting in a Φ385 bar. The furnace temperature is 1020℃.

[0110] After being removed from the furnace, both ends are wrapped with ceramic fibers. The material undergoes a sixth octagonal deformation elongation with a deformation amount of 31% and a reduction rate of 70%, resulting in a Φ320 bar. The bar is then returned to the furnace at a temperature of 1020℃.

[0111] S4. After the above-mentioned bar is taken out of the furnace, it is forged on a diameter forging machine; then machined and cut to obtain a variable cross-section In718 alloy bar (same specifications as in Example 1).

[0112] Composition and high-magnification testing

[0113] Carbide distribution was analyzed in the variable cross-section In718 alloy bars of Example 1 and Comparative Example 1. The microstructure images are shown below. Figure 2 and Figure 3 As can be seen from the figure, the carbide distribution in variable cross-section In718 alloy bars produced using virgin metal raw materials and recycled materials accounting for 70% to 80% of the total mass of molten steel is similar, and the purity levels of the two are comparable.

[0114] The distribution of Nb in the variable cross-section In718 alloy bars of Examples 1-3 and Comparative Example 1 was tested. Cross-sections of 10 large round bars with uniform distribution were taken, and two edges (1 cm) were randomly selected from each cross-section. 2 ), at the center of the two radii (1cm) 2 ) and the center (1cm) 2 The Nb mass content was measured, and the average value of all data for each part was taken as the Nb mass content of that part. The test results are shown in Table 2. As can be seen from Table 2, compared with virgin metal raw materials, the Nb distribution in the variable cross-section In718 alloy bars produced using recycled material accounting for 70% to 80% of the total mass of molten steel is more uniform, reducing the risk of segregation.

[0115] Table 2 shows the mass content of Nb in the large round bars of Examples 1-3 and Comparative Example 1 (unit: %).

[0116]

[0117] The grain size and ingot yield of the large and small round bars in Examples 1-3 and Comparative Examples 2-3 were tested. The test results are shown in Table 3. The metallographic diagram of Example 1 is shown in Table 3. Figures 4-9 From Table 3 and Figures 4-9 As can be seen from the above, compared with comparative examples 2-3, the present invention, through the control of the forging process, ensures that the grain size of both the large and small round bars in the forged variable cross-section In718 alloy bars meets the standard requirements and has good uniformity, with the grain size difference of the same cross-section being below level 2; the yield of steel ingots is also greatly improved.

[0118] Table 3 shows the grain size grades of the large and small round bars from Examples 1-3 and Comparative Examples 2-3.

[0119]

[0120] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A rapid forging deformation method for In718 alloy bars with variable cross-section, characterized in that, Includes the following steps: S1, add 70% to 80% of the total mass of In718 alloy recycled material to the molten steel, and carry out triple smelting to obtain steel ingots; S2, the head of the steel ingot is pressed with clamps and forged 2 to 3 times, with each forging completing one upsetting and drawing to obtain a forging billet; S3, the forging billet is drawn 1 to 2 times, the tail is pressed with a clamp, and the middle is cut to obtain a bar. S4, the bar is forged with a variable cross-section to obtain a variable cross-section In718 alloy bar; The variable cross-section forging includes 3 to 4 drawing cycles; an intermediate deformation section is provided between the large and small round bars of the variable cross-section forged bar, and the large round bar, the small round bar, and the intermediate deformation section are deformed in each drawing cycle, with the deformation of the small round bar in each drawing cycle increasing by 5% to 15% compared to the large round bar; the reheating temperature of the forging billet, the bar, and the variable cross-section bar decreases sequentially.

2. The rapid forging deformation method for variable cross-section In718 alloy bars as described in claim 1, characterized in that, In step S4, during the two adjacent drawing operations of the variable cross-section forging, the intermediate deformed section and small round bar of the variable cross-section bar in the previous drawing operation are drawn into the small round bar of the variable cross-section bar in the next drawing operation, and the large round bar of the variable cross-section bar in the previous drawing operation is drawn into the large round bar and intermediate deformed section of the variable cross-section bar in the next drawing operation.

3. The rapid forging deformation method for variable cross-section In718 alloy bars as described in claim 1 or 2, characterized in that, In step S4, the deformation amount per firing of the large round bar is 30% to 50%, the deformation amount per firing of the small round bar is 40% to 60%, and the deformation amount per firing of the intermediate deformation section is 30% to 55%.

4. The rapid forging deformation method for variable cross-section In718 alloy bars as described in claim 1 or 2, characterized in that, In step S4, the pressing rate per heat treatment of the large round bar is 100%, the pressing rate per heat treatment of the small round bar is 65% to 70%, and the pressing rate per heat treatment of the intermediate deformation section is 65% to 70%.

5. The rapid forging deformation method for variable cross-section In718 alloy bars as described in claim 1, characterized in that, In step S2, the deformation per forging pass is 55% to 60%; and / or In step S2, one upsetting and drawing cycle includes 3-4 consecutive upsetting passes and 1 drawing pass, with a resting period of 8-12 seconds between adjacent upsetting passes; and / or In step S3, the deformation amount per drawing cycle is 35% to 40%.

6. The rapid forging deformation method for variable cross-section In718 alloy bars as described in claim 1, characterized in that, In step S2, the remelting temperature of the forging billet is 1060-1100℃; in step S3, the remelting temperature of the bar is 1040-1080℃; in step S4, the remelting temperature of the variable cross-section bar is 980-1050℃.

7. The rapid forging deformation method for variable cross-section In718 alloy bars as described in claim 1, characterized in that, In steps S2 to S4, after the bar and the variable cross-section bar are taken out of the furnace, both ends are wrapped with ceramic fiber for heat preservation; and / or In steps S2 to S4, octagonal deformation forging is used.

8. The rapid forging deformation method for variable cross-section In718 alloy bars as described in claim 1, characterized in that, In step S1, the three-stage smelting process includes vacuum induction melting, electroslag remelting, and vacuum arc furnace remelting. The conditions for vacuum induction melting include: a steel temperature of 1250–1750°C; a vacuum level of less than 0.1 Pa in the melting chamber during operation; and / or The conditions for electroslag remelting include: a melting rate of 3.5–4.8 kg / min; and / or The conditions for remelting in the vacuum electric arc furnace include: a melting rate of 3.3 to 3.8 kg / min; helium cooling to increase the solidification rate; and a helium pressure of 300 to 720 Pa.

9. A variable cross-section In718 alloy bar, characterized in that, It is prepared by the rapid forging deformation method of the variable cross-section In718 alloy bar as described in any one of claims 1 to 8.

10. The variable cross-section In718 alloy bar as described in claim 9, characterized in that, The diameter of the large round bar of the variable cross-section In718 alloy bar is 240-270 mm, and the length is 300-500 mm; the diameter of the small round bar of the variable cross-section In718 alloy bar is 130-170 mm, and the length is 1300-1700 mm; the diameter of the transition section bar of the variable cross-section In718 alloy bar is 140-180 mm, and the length is 80-120 mm.

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