Forging process for improving grain size of GH4145 high-temperature alloy

Abstract

The invention relates to the technical field of high-temperature alloy forging, in particular to a forging process for improving the grain size of GH4145 high-temperature alloy, which comprises the following steps: S1, free forging: after heating and heat preservation are finished, upsetting, punching, hole expanding, rounding and end face flattening are sequentially carried out on a blank; s2, after heating and heat preservation are finished, the blank is subjected to ring rolling; s3, heat treatment; stepped heating is adopted before free forging is started, so that the storage time of a forged piece at high temperature is shortened, generation and growth of overlarge grains are reduced, meanwhile, the process steps of a high-temperature alloy before forging are reduced, and ring piece forming is achieved by controlling the stage heating temperature, the deformation amount and the forging heating number, the grain size is larger than or equal to 6 grades, the tensile strength is larger than or equal to 1268 MPa, and the yield is larger than or equal to 90%. The reduction of area is greater than or equal to 44, energy consumption is reduced, and resource waste is reduced; and during ring rolling, ring piece forming is controlled to be completed within two times of fire, the forge piece production efficiency is improved, and the production cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of high-temperature alloys, and in particular to a forging process for improving the grain size of a GH4145 high-temperature alloy. Background Art

[0002] GH4145 is a nickel-based high-temperature alloy strengthened by aging with γ′[Ni3(Al, Ti, Nb)] phase. It has good corrosion resistance and oxidation resistance below 980℃, high strength below 800℃, and good relaxation resistance at 540℃. It is suitable for corrosion-resistant ring parts, structural parts, bolts and other parts of aircraft engines that work below 800℃ and require high strength.

[0003] GH4145 material has complex composition and is usually forged under high temperature conditions. However, forging will cause grain coarsening due to grain growth, which will lead to degradation of the microstructure and performance of the high-temperature alloy.

[0004] In order to solve the above problems, the present invention decides to reasonably formulate the forging process to solve the problems. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a forging process for improving the grain size of GH4145 high temperature alloy.

[0006] A forging process for improving the grain size of GH4145 high temperature alloy comprises the following steps:

[0007] S1. Free forging:

[0008] The blank is first heated to 840-860°C and kept warm, and then heated to 1090-1110°C and kept warm;

[0009] After the heat preservation is completed, the blank is subjected to a free forging process, wherein the steps of the free forging sequentially include upsetting, punching, hole expansion, rounding, and flat end surface to obtain a forging;

[0010] S2, Ring rolling:

[0011] The forging obtained in step S1 is heated to 1050-1070° C. in a furnace and kept warm;

[0012] After the heat preservation is completed, the forging is subjected to a ring rolling process, wherein the total deformation amount of the ring rolling is 38.5-39.5%, and a ring is obtained;

[0013] S3. Heat treatment:

[0014] The ring obtained in step S2 is first subjected to a stepwise solution treatment and then to a stepwise precipitation hardening to obtain a forged GH4145 high-temperature alloy.

[0015] Furthermore, in steps S1 and S2, the shortest insulation time is calculated as 0.7-0.9 min / mm, and the longest insulation time is calculated as the shortest insulation time + 40 min, wherein the mm in min / mm refers to the maximum of the diameter and length of the billet or forging.

[0016] Note: The insulation regulation with furnace temperature rise allows the billet to be heated evenly. For larger billets, the insulation time is calculated based on the larger of the billet diameter and length, which ensures that the entire billet reaches a uniform temperature before forging or rolling, avoiding problems such as uneven deformation and inconsistent structural stress caused by uneven temperature, which is beneficial to improving product quality and performance stability.

[0017] Furthermore, in steps S1 and S2, during the free forging or ring rolling process, when the temperature of the billet or forging is lower than the holding temperature, the billet or forging is returned to the furnace, heated to the holding temperature and held again, and the shortest holding time for the second holding is calculated as 0.4 to 0.6 min / mm, and the longest holding time is the shortest holding time + 40 min, where the mm in min / mm refers to the maximum of the diameter and length of the billet or forging.

[0018] Note: The insulation regulations for reheating ensure that the billet can be heated evenly. For larger billets, the insulation time is calculated based on the larger of the billet diameter and length, which can ensure that the entire billet reaches a uniform temperature before forging or rolling, avoiding problems such as uneven deformation and inconsistent structural stress caused by uneven temperature, which is conducive to improving product quality and performance stability.

[0019] Furthermore, in steps S1 and S2, after the heat preservation is completed, the surface of the blank and the forging is wrapped with heat-insulating cotton having a thickness of 4.5 to 5.5 mm until entering the next step.

[0020] Description: The thermal insulation cotton has good thermal insulation performance, which can effectively reduce heat loss, keep the billet at a high temperature during the transfer process, prevent new stress concentration and cracks caused by too rapid cooling, and ensure the organizational properties and mechanical properties of the billet; the thermal insulation cotton can isolate the air and reduce the contact between the billet and oxygen, thereby reducing the degree of oxidation and improving the surface quality of the forging.

[0021] Furthermore, the initial ratio A of the outer diameter to the inner diameter of the forging obtained in step S1 is 2 to 2.2, and the diameter ratio r of the driving roller to the core roller is 1.5 to 2. In the ring rolling process of step S2, the driving roller rotation speed and the core roller feed speed are adjusted according to the ratio m of the ratio a of the outer diameter to the inner diameter of the ring to the initial ratio A, that is, m=a / A. The adjustment method is as follows:

[0022] When m < m1, the rotational speed V1 of the driving roller is 15 - 20 r / min, and the feeding speed v1 of the core roller is 0.4 - 0.7 m / s;

[0023] When m1 < m < m2, the rotational speed V2 of the driving roller is a × m × V1, and the feeding speed v2 of the core roller is a × m × v1 / r;

[0024] When m > m2, the rotational speed V3 of the driving roller is 1.2 - 1.5 × m × V2, and the feeding speed v3 of the core roller is 1.2 - 1.5 × m × v2 / r;

[0025] Among them, m1 = 30 - 40%, m2 = 50 - 55%.

[0026] Note: During the ring rolling process, as the rolling progresses, the outer diameter and inner diameter of the ring blank will gradually change. In the initial stage of ring rolling, relatively low rotational speeds of the driving roller and feeding speeds of the core roller are adopted, which can enable the ring blank to gradually and smoothly enter the rolling state, avoiding defects such as cracks in the blank caused by too fast deformation speed. As the rolling progresses, when reaching a certain range, gradually increasing the rotational speed of the driving roller and the feeding speed of the core roller can accelerate the deformation speed of the ring, improve the rolling efficiency, shorten the production cycle of a single ring, thereby improving the production efficiency on the premise of ensuring product quality. Reasonable adjustment of the rotational speed of the driving roller and the feeding speed of the core roller can make the deformation of the ring more uniform during the rolling process, and the metal streamline more smooth, thereby reducing the generation of internal stress concentration and microstructural defects, which helps to improve the mechanical properties of the ring, such as increasing strength, toughness, and fatigue life, etc.

[0027] Further, in step S3, the stepped solution treatment is as follows: The blank is first kept at 880 - 890 °C for 1.5 - 2.5 h, then heated in the furnace to 980 - 985 °C, and water - cooled after being kept at this temperature for 75 - 85 min.

[0028] Note: The stepped solution treatment can improve the strength and hardness of the material and maintain its good plasticity and toughness.

[0029] Further, in step S3, the stepped precipitation hardening is as follows: The blank is first kept at 730 - 735 °C for 7.5 - 8.5 h, then cooled in the furnace to 620 - 625 °C, and air - cooled after being kept at this temperature for 7.5 - 8.5 h.

[0030] Note: The stepped precipitation hardening can also improve the corrosion resistance and high - temperature stability of the alloy material.

[0031] Furthermore, during the period of furnace cooling from 730-735°C to 620-625°C, the ring is subjected to a first stage of water mist mixed cooling, and the blank is simultaneously subjected to electric pulse assisted treatment, with a current of 150-250A and a frequency of 60-80Hz; during the period of furnace cooling from 620-625°C to room temperature, the ring is subjected to a second stage of water mist mixed cooling, with the current adjusted to 300-400A and the frequency adjusted to 90-120Hz.

[0032] Description: The ring is cooled with the assistance of electric pulse and water mist, which makes the metal atoms distribute and diffuse more evenly during the cooling process, inhibits the growth of grains, refines the grain structure, and improves the strength and toughness of the material. The water mist mixed cooling can achieve rapid and uniform cooling, so that the precipitation phase can nucleate and grow evenly in a wider area during formation, further improving the comprehensive mechanical properties of the material.

[0033] Furthermore, the cooling medium of the one-stage water mist hybrid cooling is a water mist mixed gas sprayed by mixing 15-18KPa compressed air with 24-26L / h of water, and the temperature of the cooling medium is 50-60°C; the cooling medium of the two-stage water mist hybrid cooling is a water mist mixed gas sprayed by mixing 10-12KPa compressed air with 28-30L / h of water, and the temperature of the cooling medium is 15-25°C.

[0034] Description: Water mist mixed cooling achieves uniform heat exchange through full contact between atomized water particles and the material surface, avoids local overheating or overcooling, and reduces the concentration of thermal stress inside the material.

[0035] Compared with the existing high temperature alloy forging process, the beneficial effects of the present invention are:

[0036] (1) Before the free forging of the GH4145 high-temperature alloy begins, the present invention adopts a step-by-step heating method, and the temperature is selected as the phase precipitation temperature of 850°C, which can achieve the purpose of uniform grains, reduce the storage time of the forgings at high temperatures, reduce the generation and growth of excessively large grains, and reduce the process steps of the high-temperature alloy before forging. Then, by controlling the stage heating temperature, deformation amount and forging times, the grain size of the ring is ≥6 levels, the tensile strength is ≥1268MPa, and the cross-sectional shrinkage rate is ≥44, so that the ring can be formed within two times, thereby reducing energy consumption, reducing resource waste, improving forging production efficiency, and reducing production costs.

[0037] (2) The present invention adopts a relatively low driving roller speed and core roller feed speed at the initial stage of ring rolling, so that the ring blank can gradually and smoothly enter the rolling state, avoiding defects such as cracks in the blank caused by excessive deformation speed. As the rolling progresses, when a certain range is reached, the driving roller speed and core roller feed speed are gradually increased, which can accelerate the deformation speed of the ring, improve the rolling efficiency, and shorten the production cycle of a single ring, thereby improving production efficiency while ensuring product quality. Reasonable adjustment of the driving roller speed and core roller feed speed can make the deformation of the ring more uniform during the rolling process and the metal flow line smoother, thereby reducing internal stress concentration and the generation of microstructure defects, which helps to improve the mechanical properties of the ring, such as improving strength, toughness and fatigue life.

[0038] (3) In the present invention, during the cooling process of step-type precipitation hardening, the ring is cooled with the assistance of electric pulses and water mist, so that the metal atoms are more evenly distributed and diffused during the cooling process, the growth of grains is inhibited, and the grain structure is refined, and the strength and toughness of the material are improved. The water mist mixed cooling can achieve rapid and uniform cooling, so that the precipitated phase can nucleate and grow evenly in a wider area during formation, thereby further improving the comprehensive mechanical properties of the ring. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a metallographic image of the GH4145 high-temperature alloy of Example 1 of the present invention under a 100X optical microscope. DETAILED DESCRIPTION

[0040] In order to further illustrate the method adopted by the present invention and the effect achieved, the technical solution of the present invention will be clearly and completely described in combination with experiments below.

[0041] Embodiment 1: A forging process for improving the grain size of GH4145 high temperature alloy, comprising the following steps:

[0042] S1. Free forging:

[0043] The Ø130×212mm billet is first heated to 850℃ and kept warm, and then heated to 1100℃ and kept warm;

[0044] After the heat preservation is completed, the blank is subjected to a free forging process, wherein the steps of the free forging sequentially include upsetting, punching, hole expansion, rounding, and flat end surface, to obtain a forging of 287×130×49 mm in diameter.

[0045] S2, Ring rolling:

[0046] The forging obtained in step S1 is heated to 1060° C. in a furnace and kept warm;

[0047] After the heat preservation is completed, the forging is subjected to a ring rolling, wherein the total deformation of the ring rolling is 38.9%, and a ring of Φ388×Φ292×49 mm is obtained;

[0048] In steps S1 and S2, after the heat preservation is completed, the surface of the blank and the forging is wrapped with heat preservation cotton with a thickness of 5 mm until entering the next step;

[0049] S3. Heat treatment:

[0050] Firstly, the ring obtained in step S2 is subjected to a step-by-step solution treatment, and then to a step-by-step precipitation hardening to obtain a forged GH4145 high-temperature alloy;

[0051] The step-by-step solution treatment is as follows: the blank is first kept at 885°C for 2 hours, then heated to 982°C in the furnace, kept for 80 minutes, and then water-cooled; the step-by-step precipitation hardening is as follows: the blank is first kept at 72°C for 8 hours, then cooled to 623°C in the furnace, kept for 8 hours, and then air-cooled;

[0052] In steps S1 and S2, the shortest holding time of the insulation is calculated as 0.8min / mm, and the longest holding time is calculated as the shortest holding time + 40min, where mm in min / mm refers to the maximum of the diameter and length of the billet or forging; that is, the holding time of step S1 is

[0053] In steps S1 and S2, during the free forging or ring rolling process, when the temperature of the billet or forging is lower than the holding temperature, the billet or forging is returned to the furnace, heated to the holding temperature and held again, and the shortest holding time for the second holding is calculated as 0.5 min / mm, and the longest holding time is the shortest holding time + 40 min, where the mm in min / mm refers to the maximum of the diameter and length of the billet or forging.

[0054] Example 2: This example is different from Example 1 in that the blank is first heated to 840°C and kept warm in the furnace, and then heated to 1110°C and kept warm in the furnace.

[0055] Example 3: This example is different from Example 1 in that the blank is first heated to 860°C and kept warm, and then heated to 1090°C and kept warm.

[0056] Example 4: This example is different from Example 1 in that the deformation amount of free forging and the total deformation amount of ring rolling are 38.5%.

[0057] Example 5: This example is different from Example 1 in that the deformation amount of free forging and the total deformation amount of ring rolling are 39.5%.

[0058] Example 6: The difference between this example and Example 1 is that the forging obtained in step S1 is heated in the furnace to 1050 °C and held for heat preservation.

[0059] Example 7: The difference between this example and Example 1 is that the forging obtained in step S1 is heated in the furnace to 1070 °C and held for heat preservation.

[0060] Example 8: The difference between this example and Example 1 is that in steps S1 and S2, the shortest heat preservation time for heat preservation is calculated at 0.7 min / mm, and the shortest heat preservation time for re-heat preservation is calculated at 0.4 min / mm.

[0061] Example 9: The difference between this example and Example 1 is that in steps S1 and S2, the shortest heat preservation time for heat preservation is calculated at 0.9 min / mm, and the shortest heat preservation time for re-heat preservation is calculated at 0.6 min / mm.

[0062] Example 10: The difference between this example and Example 1 is that the stepped solution treatment is as follows: the blank is first held at 880 °C for 1.5 h, then heated in the furnace to 985 °C, held for 85 min and then water-cooled.

[0063] Example 11: The difference between this example and Example 1 is that the stepped solution treatment is as follows: the blank is first held at 890 °C for 2.5 h, then heated in the furnace to 980 °C, held for 75 min and then water-cooled.

[0064] Example 12: The difference between this example and Example 1 is that the stepped precipitation hardening is as follows: the blank is first held at 730 °C for 7.5 h, then cooled in the furnace to 625 °C, held for 8.5 h and then air-cooled.

[0065] Example 13: The difference between this example and Example 1 is that the stepped precipitation hardening is as follows: the blank is first held at 735 °C for 8.5 h, then cooled in the furnace to 620 °C, held for 7.5 h and then air-cooled.

[0066] Example 14: The difference between this example and Example 1 is that the initial ratio A of the outer diameter to the inner diameter of the forging obtained in step S1 is 2.1, and the diameter ratio r of the driving roll to the core roll is 1.8. During the ring rolling process in step S2, according to the ratio m of the outer diameter to the inner diameter a of the ring part to the initial ratio A, that is, m = a / A, the rotational speed of the driving roll and the feeding speed of the core roll are adjusted. The adjustment method is as follows:

[0067] When m < m1, the rotational speed V1 of the driving roll is 18 r / min, and the feeding speed v1 of the core roll is 0.6 m / s;

[0068] When m1 < m < m2, the rotational speed V2 of the driving roller is a × m × V1, and the feeding speed v2 of the core roller is a × m × v1 / r;

[0069] When m > m2, the rotational speed V3 of the driving roller is 1.4 × m × V2, and the feeding speed v3 of the core roller is 1.4 × m × v2 / r;

[0070] Among them, m1 = 35% and m2 = 52%.

[0071] Example 15: The difference between this example and Example 14 is that the initial ratio A of the outer diameter to the inner diameter of the forging is 2, and the diameter ratio r of the driving roller to the core roller is 1.5.

[0072] Example 16: The difference between this example and Example 14 is that the initial ratio A of the outer diameter to the inner diameter of the forging is 2.2, and the diameter ratio r of the driving roller to the core roller is 2.

[0073] Example 17: The difference between this example and Example 14 is that when m1 = 30%, the rotational speed V1 of the driving roller is 15 r / min, and the feeding speed v1 of the core roller is 0.4 m / s.

[0074] Example 18: The difference between this example and Example 14 is that when m1 = 40%, the rotational speed V1 of the driving roller is 20 r / min, and the feeding speed v1 of the core roller is 0.7 m / s.

[0075] Example 19: The difference between this example and Example 14 is that m1 = 30% and m2 = 55%.

[0076] Example 20: The difference between this example and Example 14 is that m1 = 40% and m2 = 50%.

[0077] Example 21: The difference between this example and Example 14 is that when m2 = 50%, the rotational speed V3 of the driving roller is 1.2 × m × V2, and the feeding speed v3 of the core roller is 1.2 × m × v2 / r.

[0078] Example 22: The difference between this example and Example 14 is that when m2 = 55%, the rotational speed V3 of the driving roller is 1.5 × m × V2, and the feeding speed v3 of the core roller is 1.5 × m × v2 / r.

[0079] Example 23: The difference between this example and Example 1 is that, during the period of furnace cooling from 732°C to 623°C, the ring is subjected to a first stage of water mist mixed cooling, and the blank is simultaneously subjected to electric pulse assisted treatment, with a current of 200A and a frequency of 70Hz; during the period of furnace cooling from 623°C to room temperature, the ring is subjected to a second stage of water mist mixed cooling, with the current adjusted to 350A and the frequency adjusted to 105Hz; the cooling medium of the first stage of water mist mixed cooling is a water mist mixed gas sprayed by mixing 16.5KPa of compressed air with 25L / h of water, and the temperature of the cooling medium is 55°C; the cooling medium of the second stage of water mist mixed cooling is a water mist mixed gas sprayed by mixing 11KPa of compressed air with 29L / h of water, and the temperature of the cooling medium is 20°C.

[0080] Example 24: The difference between this example and Example 23 is that, in the one-stage water mist mixing cooling, the cooling medium is a water mist mixture sprayed by mixing 15KPa of compressed air with 24L / h of water, and the temperature of the cooling medium is 50°C; the cooling medium of the two-stage water mist mixing cooling is a water mist mixture sprayed by mixing 10KPa of compressed air with 28L / h of water, and the temperature of the cooling medium is 15°C.

[0081] Example 25: The difference between this example and Example 23 is that the cooling medium of the one-stage water mist mixing cooling is a water mist mixture sprayed by mixing 18KPa of compressed air with 26L / h of water, and the temperature of the cooling medium is 20°C; the cooling medium of the two-stage water mist mixing cooling is a water mist mixture sprayed by mixing 12KPa of compressed air with 30L / h of water, and the temperature of the cooling medium is 25°C.

[0082] Example 26: The difference between this example and Example 23 is that, during the period of furnace cooling from 732°C to 623°C, the ring is subjected to a first stage of water mist mixed cooling, and the blank is simultaneously subjected to electric pulse assisted treatment, with a current of 150A and a frequency of 60Hz; during the period of furnace cooling from 623°C to room temperature, the ring is subjected to a second stage of water mist mixed cooling, with the current adjusted to 400A and the frequency adjusted to 120Hz.

[0083] Example 27: The difference between this example and Example 23 is that, during the period of furnace cooling from 732°C to 623°C, the ring is subjected to a first stage of water mist mixed cooling, and the blank is simultaneously subjected to electric pulse assisted treatment, with a current of 250A and a frequency of 80Hz; during the period of furnace cooling from 623°C to room temperature, the ring is subjected to a second stage of water mist mixed cooling, with the current adjusted to 300A and the frequency adjusted to 90Hz.

[0084] Experimental Example: The description of this experimental example is based on the scheme described in Example 1, and is intended to illustrate the practical application effect of the present invention.

[0085] The grain size and tensile strength of the GH4145 forged in each example were tested. Each example was tested three times, and the average data of the three times was taken as the final experimental result.

[0086] 1. Investigate the effects of various parameters of free forging, ring rolling and heat treatment on the grain size and tensile strength of GH4145.

[0087] Table 1 Grain size and tensile strength of Examples 1 to 13 and Comparative Examples 1 to 3

[0088]

[0089] The difference between the comparative example 1 and the embodiment 1 is that in step S1, the blank is directly heated to 1100°C without stepwise heating to 850°C;

[0090] The difference between Comparative Example 2 and Example 1 is that in step S3, the temperature is raised to 982°C in one step during the solution treatment;

[0091] The difference between Comparative Example 3 and Example 1 is that in step S3, the precipitation hardening treatment is heated to 623°C in one step;

[0092] From the results in Table 1, it can be seen that the control example 1 lacks the step-wise heating before forging, the control example 2 lacks the step-wise heating of the solution treatment, and the control example 3 lacks the step-wise heating of the precipitation hardening treatment. Compared with the GH4145 of Examples 1 to 13, the grain size and tensile strength of the GH4145 are significantly reduced. Therefore, the step-wise treatment plays a certain role in improving the grain size and tensile strength of GH4145.

[0093] By comparing Examples 1 to 13, it can be seen that if the parameter difference of the step-by-step heating is too small or too large, the deformation of free forging and ring rolling is too small or too large, the temperature of the furnace heating before ring rolling is too small or too large, the calculation of the shortest holding time is too small or too large, the temperature difference of the step-by-step solution treatment is too small or too large, and the temperature difference of the step-by-step precipitation hardening treatment is too small or too large, the grain size or tensile strength of GH4145 will be reduced. Therefore, in comprehensive comparison, the parameter effect of Example 1 is relatively better, and Figure 1 As shown, the grain distribution of Example 1 is uniform and the grain size is high.

[0094] 2. To explore the effect of the parameters of adjusting the driving roller speed and core roller feed speed according to the ratio of the outer diameter and inner diameter of the ring rolling on the grain size and tensile strength of GH4145.

[0095] Table 2 Grain size and tensile strength of Examples 14 to 22

[0096]

[0097]

[0098] From the results in Table 2, it can be seen that the driving roller speed and the core roller feed speed are adjusted according to the ratio of the outer diameter to the inner diameter of the ring rolling. Compared with Examples 1 to 13, the average degree of grain size is significantly improved, and the tensile strength is also significantly improved. Therefore, the adjustment method significantly enhances the performance of GH4145;

[0099] And by comparing Examples 14 to 22, it can be seen that if the initial ratio and diameter ratio are too small or too large, and m and the corresponding driving roller speed are too small or too large, the grain size and tensile strength of GH4145 will be reduced. Therefore, in comprehensive comparison, the parameter effect of Example 14 is relatively better.

[0100] 3. Investigate the influence of the parameters of electric pulse and water mist mixed assisted cooling on the grain size and tensile strength of GH4145 during step precipitation hardening.

[0101] Table 3 Grain size and tensile strength of Examples 23 to 27 and Comparative Examples 4 to 5

[0102]

[0103] The difference between Control Example 4 and Example 23 is that the parameters of the electric pulse remain unchanged;

[0104] The difference between Comparative Example 5 and Example 23 is that the cooling parameters remain unchanged when the two stages of water mist are mixed;

[0105] It can be seen from the results in Table 3 that Example 23 further improves the average data of grain size and tensile strength on the basis of Example 14. Comparative Example 4 lacks the two-stage change of electric pulse and Comparative Example 5 lacks the two-stage change of water mist mixed cooling, and the tensile strength of Examples 23 to 27 is reduced. Therefore, the parameter changes of electric pulse and water mist mixed cooling according to the cooling temperature have a certain effect on improving the grain size and tensile strength of GH4145.

[0106] By comparing Examples 23 to 27, it can be seen that if the difference between the parameters of the two-stage electric pulse assisted treatment is too small or too large, and if the difference between the parameters of the two-stage water mist mixed cooling is too small or too large, the grain size and tensile strength of GH4145 will be reduced. Therefore, in comprehensive comparison, the parameter effect of Example 27 is relatively better.

[0107] From the above investigations 1 to 3, it can be seen that the grain size of GH4145 forged by the present invention is ≥ grade 6, and the tensile strength is ≥ 1268 MPa.

Claims

1. A forging process for improving the grain size of GH4145 high temperature alloy, characterized in that: It includes the following steps: S1. Open-die forging: First, heat the blank in the furnace to 840 - 860 °C and hold for heat preservation, then heat it in the furnace to 1090 - 1110 °C and hold for heat preservation; After the heat preservation ends, conduct one-pass open-die forging on the blank. The total deformation amount of the open-die forging is 68.4%. The steps of the open-die forging sequentially include upsetting, punching, hole expanding, rolling into a circle, and flattening the end face to obtain a forging; S2. Ring rolling: Heat the forging obtained in step S1 in the furnace to 1050 - 1070 °C and hold for heat preservation; After the heat preservation ends, conduct one-pass ring rolling on the forging. The total deformation amount of the ring rolling is 38.5 - 39.5% to obtain a ring; S3. Heat treatment: First, conduct step-by-step solution treatment on the ring obtained in step S2, and then conduct step-by-step precipitation hardening to obtain the forged GH4145 superalloy.

2. A forging process for improving the grain size of GH4145 high temperature alloy as claimed in claim 1, characterized in that: In steps S1 and S2, the shortest heat preservation time for the heat preservation is calculated as 0.7 - 0.9 min / mm, and the longest heat preservation time = the shortest heat preservation time + 40 min, where the mm in min / mm refers to the maximum value of the two data of the diameter and length of the blank or forging.

3. A forging process for improving the grain size of GH4145 high temperature alloy as claimed in claim 1, characterized in that: In steps S1 and S2, during the open-die forging or ring rolling process, when the temperature of the blank or forging is lower than the heat preservation temperature, return the blank or forging to the furnace to heat it to the heat preservation temperature and hold for heat preservation again. The shortest heat preservation time for the re-heat preservation is calculated as 0.4 - 0.6 min / mm, and the longest heat preservation time = the shortest heat preservation time + 40 min, where the mm in min / mm refers to the maximum value of the two data of the diameter and length of the blank or forging.

4. A forging process for improving the grain size of GH4145 high temperature alloy as claimed in claim 1, characterized in that: In steps S1 and S2, after the heat preservation ends, wrap the surfaces of the blank and forging with heat-insulating cotton with a thickness of 4.5 - 5.5 mm until entering the next step.

5. A forging process for improving the grain size of GH4145 high temperature alloy as claimed in claim 1, characterized in that: The initial ratio A of the outer diameter to the inner diameter of the forging obtained in step S1 is 2 - 2.2, and the diameter ratio r of the driving roll to the core roll is 1.5 - 2. During the ring rolling process in step S2, according to the ratio m of the outer diameter to the inner diameter a of the ring to the initial ratio A, that is, m = a / A, adjust the driving roll rotation speed and the core roll feeding speed. The adjustment method is as follows: When m < m1, the driving roll rotation speed V1 is 15 - 20 r / min, and the core roll feeding speed v1 is 0.4 - 0.7 m / s; When m1 < m < m2, the driving roll rotation speed V2 is a × m × V1, and the core roll feeding speed v2 is a × m × v1 / r; When m > m2, the driving roll rotation speed V3 is 1.2 - 1.5 × m × V2, and the core roll feeding speed v3 is 1.2 - 1.5 × m × v2 / r; Among them, m1 = 30 - 40%, m2 = 50 - 55%.

6. A forging process for improving the grain size of GH4145 high temperature alloy as claimed in claim 1, characterized in that: In step S3, the step-by-step solution treatment is as follows: First, hold the blank at 880 - 890 °C for 1.5 - 2.5 h, then heat it in the furnace to 980 - 985 °C, and cool it in water after holding for 75 - 85 min.

7. A forging process for improving the grain size of GH4145 high temperature alloy as claimed in claim 1, characterized in that: In step S3, the step-by-step precipitation hardening is as follows: First, hold the blank at 730 - 735 °C for 7.5 - 8.5 h, then cool it in the furnace to 620 - 625 °C, and air-cool it to room temperature after holding for 7.5 - 8.5 h.

8. A forging process for improving the grain size of GH4145 high temperature alloy as claimed in claim 7, characterized in that: During the period of furnace cooling from 730-735°C to 620-625°C, the ring is subjected to a first stage of water mist mixed cooling, and the blank is simultaneously subjected to electric pulse assisted treatment, with a current of 150-250A and a frequency of 60-80Hz; during the period of furnace cooling from 620-625°C to room temperature, the ring is subjected to a second stage of water mist mixed cooling, with the current adjusted to 300-400A and the frequency adjusted to 90-120Hz.

9. A forging process for improving the grain size of GH4145 high temperature alloy as claimed in claim 8, characterized in that: The cooling medium of the one-stage water mist mixing cooling is a water mist mixture sprayed by mixing 15-18KPa compressed air with 24-26L / h of water, and the temperature of the cooling medium is 50-60°C; the cooling medium of the two-stage water mist mixing cooling is a water mist mixture sprayed by mixing 10-12KPa compressed air with 28-30L / h of water, and the temperature of the cooling medium is 15-25°C.

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