Method for hot working of high-temperature alloy

Abstract

The invention relates to a high-temperature alloy hot working method which comprises the following steps that (1) a hard sheath outer ring and a workpiece to be machined are assembled according to interference fit, the workpiece with the hard sheath outer ring is obtained, and the diameter of the workpiece to be machined is 0.4-0.8 mm larger than the inner diameter of the hard sheath outer ring; (2) heating and forging the workpiece with the hard sheath outer ring; and (3) the forged hard sheath outer ring is removed through machining, and a machined workpiece is obtained. The to-be-machined workpiece is subjected to hard wrapping through interference fit, and prestress is formed, so that the surface tensile stress of the workpiece can be effectively reduced in the hot working process; in addition, the hard sheath outer ring plays a role in heat preservation, the hot working temperature of the to-be-machined workpiece can be guaranteed, and therefore the problem that the high-temperature alloy difficult to deform cracks in the hot working process is solved.

Description

Technical Field

[0001] The invention relates to the technical field of thermal processing, and in particular to a method for thermal processing of a high-temperature alloy. Background Art

[0002] Difficult-to-deform high-temperature alloys are an important material for engine components. This alloy improves the temperature bearing capacity and performance level by increasing the alloying level of ordinary deformable high-temperature alloys, which is mainly achieved by increasing the γ' phase forming elements such as Al and Ti. While high alloying brings excellent performance, it also causes a sharp deterioration in the hot processing performance of the material. It is generally believed that a difficult-to-deform high-temperature alloy has a Al+Ti content of more than 6% and a γ' phase content of more than 40%. Difficult-to-deform high-temperature alloys have high resistance to hot processing, poor hot processing plasticity, and a great risk of deformation cracking.

[0003] In order to solve the cracking problem, it is necessary to ensure that the temperature of the workpiece during forging is within the hot working window. Generally, the workpiece is wrapped in a jacket for heat preservation. There are two common wrapping methods, one is hard wrapping and the other is soft wrapping.

[0004] The soft-packing method mainly involves heating the workpiece to the required temperature and keeping it warm for a period of time, and then wrapping the outer surface of the workpiece with insulation cotton using a high-temperature adhesive. This method can ensure the workpiece temperature to a certain extent, but the insulation cotton is easy to fall off during the forging process, and the insulation effect drops sharply. The general hard-packing method uses a clearance fit method to connect the workpiece to the outer ring of the hard-packing at room temperature, and finally heats and forges the whole. The general hard-packing method solves the problem of the soft-packing insulation cotton falling off to a certain extent, but there is still a risk of forging cracking due to the lack of prestress.

[0005] CN116787088A discloses a method for extruding and encapsulating a hard-to-deform high-temperature alloy ingot, the method comprising the following steps: step one: manufacturing an extrusion encapsulation encapsulation, the encapsulation consisting of a front pad, a rear pad and an outer cylinder, the front pad and the rear pad being placed at both ends of the outer cylinder, and forming a cavity with the outer cylinder for placing the ingot; step two: ingot processing, cutting the hard-to-deform alloy integral blank into a cylindrical blank ingot matching the outer cylinder by a cutting device; step three: heating the outer cylinder to 300-400°C and keeping it warm for 2-4h; step four: pressing the ingot into the inner cavity of the outer cylinder, with both ends of the ingot extending 15mm beyond the end of the outer cylinder; step five: welding the front pad to the upper part of the outer cylinder and the rear pad to the lower part of the outer cylinder by a special stainless steel welding rod. It optimizes the jacket structure to reduce the temperature drop rate, thereby solving the problems of surface cracking of the extruded rod and increased deformation resistance during the extrusion process, so that the extrusion and blanking of the difficult-to-deform high-temperature alloy ingot can be completed smoothly. However, it only presses the ingot into the inner cavity of the outer cylinder, and the two are not tightly connected, so there is a risk of ingot displacement, which causes the ingot to still be at risk of cracking.

[0006] In summary, it is necessary to develop a method for hot processing of high-temperature alloys to effectively solve the cracking problem of difficult-to-deform high-temperature alloys. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides a method for hot processing of high-temperature alloys, in which the outer ring of the hard casing is interference fit with the workpiece to be processed, which can reduce the tensile stress on the surface of the workpiece during the hot processing. The outer ring of the hard casing used in the present invention has a simple structure and can effectively solve the problem of cracking during hot processing of difficult-to-deform high-temperature alloys.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] The present invention provides a method for hot working of a high temperature alloy, the method comprising the following steps:

[0010] (1) Assembling the hard casing outer ring and the workpiece to be processed according to an interference fit to obtain a workpiece with the hard casing outer ring, wherein the diameter of the workpiece to be processed is 0.4-0.8 mm larger than the inner diameter of the hard casing outer ring;

[0011] (2) heating and forging the workpiece with the hard jacket outer ring;

[0012] (3) The outer ring of the hard casing after forging is removed by machining to obtain a machined workpiece.

[0013] The diameter of the workpiece to be processed needs to be 0.4-0.8 mm larger than the inner diameter of the outer ring of the hard casing, for example, it can be 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm or 0.8 mm, but it is not limited to the listed values. Other values ​​not listed in the above range are also applicable.

[0014] The present invention first designs and manufactures a hard-packed outer ring, controls the diameter of a workpiece to be processed to be 0.4-0.8mm larger than the inner diameter of the hard-packed outer ring, and then assembles the hard-packed outer ring and the workpiece to be processed according to an interference fit to obtain a workpiece with a hard-packed outer ring, and then heats and forges the workpiece with the hard-packed outer ring. Prestress can be formed by hard-packing the workpiece to be processed through interference fit, so that the tensile stress on the surface of the workpiece during hot processing is effectively reduced. At the same time, the hard-packed outer ring has a heat-insulating effect, which can ensure the temperature of the hot processing of the workpiece, thereby solving the problem of hot processing cracking of difficult-to-deform high-temperature alloys. Then, the hard-packed outer ring after the hot processing is removed by machining to obtain a processed workpiece without cracks.

[0015] High-temperature alloy refers to a type of metal material based on iron, nickel and cobalt, which can work for a long time at high temperatures above 600°C and under certain stresses. It has excellent high-temperature strength, good oxidation resistance and thermal corrosion resistance, good fatigue performance, fracture toughness and other comprehensive properties.

[0016] The large number of alloying elements in high-temperature alloys leads to poor thermal conductivity. When heated, uneven temperature will occur, which will not only affect the crystal structure inside the high-temperature alloy, but may also cause cracks inside the high-temperature alloy. At the same time, during the heating and forging process of the high-temperature alloy, if the clearance fit between the high-temperature alloy and other components is too large, the workpiece may become loose or inaccurately positioned after assembly, which will not only affect the overall performance and precision of the product, but may also cause safety hazards. If the clearance fit between the high-temperature alloy and other components is too small, the workpiece may be difficult to insert or fit too tightly during assembly, which will not only increase the difficulty and cost of assembly, but may also damage the workpiece or cause the performance of the workpiece after assembly to deteriorate. Furthermore, the high-temperature alloy will undergo thermal expansion during the heating process. If the clearance fit design is unreasonable, the assembled high-temperature alloy will fail or its performance will deteriorate due to thermal expansion.

[0017] As a preferred technical solution of the present invention, the assembly in step (1) comprises the following steps:

[0018] (a) preheating the outer ring of the hard casing;

[0019] (b) connecting the workpiece to be processed with the outer ring of the hard casing to obtain a connection assembly;

[0020] (c) cooling the connection assembly.

[0021] The present invention can increase the inner hole size of the hard casing outer ring by preheating the hard casing outer ring, and then connect the workpiece to be processed with the hard casing outer ring by a press to obtain a connection assembly, cool the connection assembly, and the cooled hard casing outer ring is tightly connected to the workpiece to be processed by interference fit.

[0022] As a preferred technical solution of the present invention, the preheating temperature in step (a) is 450-550°C, and the preheating holding time is 90-120min. The preheating temperature can be 450°C, 470°C, 490°C, 510°C, 530°C or 550°C, and the preheating holding time can be 90min, 95min, 100min, 105min, 110min, 115min or 120min, but are not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0023] As a preferred technical solution of the present invention, the cooling process in step (c) includes air cooling.

[0024] Preferably, the target temperature of the cooling is 20-25°C, for example, it can be 20°C, 21°C, 22°C, 23°C, 24°C or 25°C, but is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0025] As a preferred technical solution of the present invention, the material of the workpiece to be processed in step (1) includes GH4079 and / or GH4698.

[0026] GH4079 and GH4698 are both highly alloyed high-temperature alloys with high hardness. They are difficult to deform during processing. At the same time, they have poor plasticity during hot working and are prone to cracking, which increases the difficulty of processing. The applicable temperature range for hot working of the alloy is very narrow, and the hot working parameters (such as temperature, deformation, etc.) will directly affect the organization and properties of the alloy. Therefore, the hot working parameters need to be strictly controlled during the hot working process.

[0027] The material of the outer ring of the hard casing in the present invention includes any one of 45# steel, 65# steel or 75# steel or a combination of at least two of them, wherein typical but non-limiting combinations include: a combination of 45# steel and 65# steel, a combination of 45# steel and 75# steel, a combination of 65# steel and 75# steel, and a combination of 45# steel, 65# steel and 75# steel.

[0028] The material of the hard casing outer ring selected by the present invention can ensure the quality of the hard casing outer ring during heat processing. At the same time, the material of the hard casing outer ring used in the present invention is generally acceptable, simple to process, and low in cost. If a hard casing outer ring made of other materials is used, the processing cost will increase.

[0029] As a preferred technical solution of the present invention, the heating temperature in step (2) is 1100-1140°C, and the holding time is (0.8-1.2)×D min, where D is the effective thickness of the workpiece with the hard jacket outer ring, and the unit of D is mm.

[0030] Among them, when the material of the workpiece to be processed is GH4698, the heating temperature in step (2) is 1100-1140°C, and the holding time is (0.8-1.2)×D min. The heating temperature can be 1100°C, 1110°C, 1120°C, 1130°C or 1140°C, and the holding time can be 0.8×D min, 0.9×D min, 1.0×Dmin, 1.1×D min or 1.2×Dmin, but are not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0031] When the material of the workpiece to be processed is GH4079, the heating temperature in step (2) is 1120-1140°C, and the holding time is (0.8-1.2)×D min. The heating temperature can be 1120°C, 1125°C, 1130°C, 1135°C or 1140°C, and the holding time can be 0.8×D min, 0.9×D min, 1.0×D min, 1.1×D min or 1.2×D min, but are not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0032] The present invention limits the holding time in the heating treatment process to (0.8-1.2)×D min, which can ensure that the workpiece with the hard casing outer ring is fully heated and has a uniform temperature distribution. If the holding time is less than 0.8×D min, the holding time is too short, the workpiece with the hard casing outer ring will not be fully heated and the temperature distribution will be uneven. The temperature difference between the inside and outside of the workpiece with the hard casing outer ring is large, which may cause the difficult-to-deform high-temperature alloy workpiece to crack in the subsequent processing process. If the holding time is greater than 1.2×D min, the holding time is too long, the grains of the difficult-to-deform high-temperature alloy workpiece will be coarse, increasing the risk of cracking of the difficult-to-deform high-temperature alloy workpiece.

[0033] As a preferred technical solution of the present invention, the wall thickness of the outer ring of the hard casing is 30-50 mm, for example, it can be 30 mm, 35 mm, 40 mm, 45 mm or 50 mm, but it is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0034] The present invention limits the wall thickness of the hard sleeve outer ring to 30-50mm, which can ensure the quality of the hard sleeve outer ring during hot working. If the wall thickness of the hard sleeve outer ring is less than 30mm, the hard sleeve outer ring is at risk of breaking during forging. If the wall thickness of the hard sleeve outer ring is greater than 50mm, the size of the workpiece with the hard sleeve outer ring after assembly is larger, which will increase the impact force of the equipment on the workpiece with the hard sleeve outer ring during forging, and there is a risk that the workpiece with the hard sleeve outer ring cannot be deformed during the forging process.

[0035] Preferably, the outer ring of the hard casing is equal to the height of the workpiece to be processed.

[0036] The present invention limits the height of the hard cover outer ring to be equal to that of the workpiece to be processed, rather than the hard cover outer ring being higher than the workpiece to be processed, so that the hard cover outer ring and the workpiece to be processed can be deformed synchronously, making the deformation process more stable and controllable.

[0037] As a preferred technical solution of the present invention, the forging process in step (2) includes upsetting or die forging.

[0038] As a preferred technical solution of the present invention, the deformation amount of the forging process is 25%-40%, for example, it can be 25%, 30%, 35% or 40%, but it is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0039] The present invention performs upsetting or die forging on a workpiece with a hard-packed outer ring. Since a hard-packed outer ring is arranged outside the workpiece to be processed, the hard-packed outer ring generates prestress on the periphery of the workpiece during the forging process, thereby offsetting the tensile stress on the outer peripheral surface of the workpiece. At the same time, the hard-packed outer ring has a heat-insulating effect, which can ensure the temperature of the workpiece during the forging process, thereby solving the problem of hot working cracking of difficult-to-deform high-temperature alloys.

[0040] Preferably, the single deformation amount in the forging process is 5-10%, for example, it can be 5%, 6%, 7%, 8%, 9% or 10%, but it is not limited to the listed values, and other values ​​not listed in the above numerical range are also applicable. The single deformation amount in the present invention refers to the deformation amount of a single upsetting or a single die forging, and at least 2 upsetting or die forging can be performed.

[0041] The present invention preferably controls the single deformation amount within the above range. When the single deformation amount is too high, the difficult-to-deform high-temperature alloy workpiece is at risk of cracking. When the single deformation amount is too small, the deformation amount cannot make the microstructure and performance of the difficult-to-deform high-temperature alloy workpiece meet the design requirements, that is, the microstructure and performance of the prepared workpiece after processing cannot meet the design requirements, which increases the risk of cracking of the difficult-to-deform high-temperature alloy workpiece.

[0042] The machining in step (3) of the present invention includes turning and / or milling.

[0043] As a preferred technical solution of the present invention, the method comprises the following steps:

[0044] (1) Preheating a hard-packed outer ring with a wall thickness of 30-50 mm at 450-550° C. and keeping the temperature for 90-120 min, then connecting a workpiece to be processed made of GH4079 and / or GH4698 with the hard-packed outer ring by interference fit to obtain a connection assembly, and cooling the connection assembly to 20-25° C. to obtain a workpiece with a hard-packed outer ring, wherein the diameter of the workpiece to be processed is 0.4-0.8 mm larger than the inner diameter of the hard-packed outer ring; and the hard-packed outer ring is equal to the height of the workpiece to be processed;

[0045] (2) When the material of the workpiece to be processed is GH4698, the workpiece with the hard-encapsulated outer ring is heated at 1100-1140°C and kept warm for (0.8-1.2)×D min, where D is the effective thickness of the workpiece with the hard-encapsulated outer ring, and the unit of D is mm; or, when the material of the workpiece to be processed is GH4079, the workpiece with the hard-encapsulated outer ring is heated at 1120-1140°C and kept warm for (0.8-1.2)×D min;

[0046] Then, the heated workpiece with the hard jacket outer ring is forged, wherein the deformation amount of the forging process is 25%-40%; and the single deformation amount in the forging process is 5-10%;

[0047] (3) The outer ring of the hard casing after forging is removed by machining to obtain a machined workpiece.

[0048] Compared with the prior art, the present invention has at least the following beneficial effects:

[0049] The present invention assembles the workpiece to be processed and the hard casing outer ring through interference fit. The hard casing outer ring generates prestress on the periphery of the workpiece, which can effectively reduce the tensile stress on the surface of the workpiece during hot working. In addition, the hard casing outer ring plays a heat-insulating role, which can ensure the hot working temperature of the workpiece to be processed. The hard casing outer ring used in the present invention has a simple structure and can effectively solve the problem of hot working cracking of difficult-to-deform high-temperature alloys. The defect rate of the prepared processed workpiece is less than 5%. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is a schematic structural diagram of a workpiece with a hard-encased outer ring provided by the present invention.

[0051] Figure 2 It is a schematic diagram of the structure of the hard casing outer ring provided by the present invention.

[0052] Figure 3 It is a structural schematic diagram of a workpiece provided by the present invention.

[0053] Among them, 1-hard package outer ring; 2-workpiece to be processed. DETAILED DESCRIPTION

[0054] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and through specific implementation methods. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0055] The structural schematic diagrams of the workpiece to be processed (high temperature alloy) and the outer ring of the hard casing provided in the following embodiments and comparative examples are as follows: Figure 1-Figure 3As shown, D1 is the inner diameter of the outer ring of the hard casing; D2 is the diameter of the workpiece to be processed; B is the wall thickness of the outer ring of the hard casing; H1 is the height of the outer ring of the hard casing; H2 is the workpiece to be processed, which is described in detail below.

[0056] Example 1

[0057] This embodiment provides a method for hot working of a high temperature alloy, the method comprising the following steps:

[0058] (1) The outer ring of the hard casing made of 45# steel and 40 mm in thickness B was preheated at 500°C for 100 minutes, and then the workpiece to be processed made of GH4079 was connected to the outer ring of the hard casing by interference fit to obtain a connection assembly, and the connection assembly was cooled to 22°C to obtain a workpiece with a hard casing outer ring, wherein the diameter D2 (180 mm) of the workpiece to be processed is 0.6 mm larger than the inner diameter D1 of the hard casing outer ring; the height H1 of the hard casing outer ring is equal to the height H2 (200 mm) of the workpiece to be processed; and the effective thickness D of the workpiece with the hard casing outer ring is 200 mm;

[0059] (2) heating the workpiece with the hard jacket outer ring at 1130° C. and keeping the temperature for 1.0×Dmin=200min;

[0060] Then, the heated workpiece with the hard casing outer ring is subjected to an upsetting forging process, wherein the total deformation amount of the forging process is 30%, and the deformation amount of a single upsetting forging process is 6%;

[0061] (3) The outer ring of the hard casing after forging is removed by machining to obtain a machined workpiece.

[0062] Example 2

[0063] This embodiment provides a method for hot working of a high temperature alloy, the method comprising the following steps:

[0064] (1) The outer ring of the hard casing made of 45# steel and 30 mm in wall thickness B is preheated at 450°C for 90 minutes, and then the workpiece to be processed made of GH4698 is connected to the outer ring of the hard casing by interference fit to obtain a connection assembly, and the connection assembly is cooled by 25°C to obtain a workpiece with a hard casing outer ring, wherein the diameter D2 (200 mm) of the workpiece to be processed is 0.8 mm larger than the inner diameter D1 of the hard casing outer ring; the height H1 of the hard casing outer ring is equal to the height H2 (250 mm) of the workpiece to be processed; and the effective thickness D of the workpiece with the hard casing outer ring is 250 mm;

[0065] (2) heating the workpiece with the hard jacket outer ring at 1120° C. and keeping the temperature for 0.8×Dmin=200min;

[0066] Then, the heated workpiece with the hard casing outer ring is subjected to die forging, wherein the total deformation of the forging is 25%, and the deformation of a single die forging is 5%;

[0067] (3) The outer ring of the hard casing after forging is removed by machining to obtain a machined workpiece.

[0068] Example 3

[0069] This embodiment provides a method for hot working of a high temperature alloy, the method comprising the following steps:

[0070] (1) The outer ring of the hard casing made of 45# steel and 50 mm in wall thickness B was preheated at 550°C for 120 min, and then the workpiece to be processed made of GH4079 was connected to the outer ring of the hard casing by interference fit to obtain a connection assembly, and the connection assembly was cooled to 20°C to obtain a workpiece with a hard casing outer ring, wherein the diameter D2 (160 mm) of the workpiece to be processed is 0.4 mm larger than the inner diameter D1 of the hard casing outer ring; the height H1 of the hard casing outer ring is equal to the height H2 (180 mm) of the workpiece to be processed; and the effective thickness D of the workpiece with the hard casing outer ring is 180 mm;

[0071] (2) heating the workpiece with the hard jacket outer ring at 1140° C. and keeping the temperature for 1.2×Dmin=216min;

[0072] Then, the heated workpiece with the hard casing outer ring is subjected to an upsetting forging process, wherein the total deformation amount of the forging process is 40%, and the deformation amount of a single upsetting forging process is 10%;

[0073] (3) The outer ring of the hard casing after forging is removed by machining to obtain a machined workpiece.

[0074] Example 4

[0075] This embodiment provides a method for hot working of a high temperature alloy, which is different from the first embodiment only in that, except for the holding time in step (2) being adjusted to 0.6×D min=120 min, the rest is the same as the first embodiment.

[0076] Example 5

[0077] This embodiment provides a method for hot working of a high temperature alloy, which is different from the first embodiment only in that, except for the holding time in step (2) being adjusted to 1.4×D min=280 min, the rest is the same as the first embodiment.

[0078] Example 6

[0079] This embodiment provides a method for hot processing of a high-temperature alloy, which is the same as that of Embodiment 1 except that the wall thickness of the outer ring of the hard casing is adjusted to 10 mm.

[0080] Example 7

[0081] This embodiment provides a method for hot working of a high temperature alloy, which is different from the embodiment 1 only in that the wall thickness of the hard casing outer ring is adjusted to 70 mm, and the rest is the same as the embodiment 1. The forging process cannot cause the workpiece with the hard casing outer ring to deform.

[0082] Example 8

[0083] This embodiment provides a method for hot working of a high temperature alloy, which is the same as that of the embodiment 1 except that the single deformation amount in the forging process is 2%.

[0084] Example 9

[0085] This embodiment provides a method for hot working of a high temperature alloy, which is the same as that of the first embodiment except that the single deformation amount in the forging process is 20%.

[0086] Comparative Example 1

[0087] This comparative example provides a method for hot processing of a high-temperature alloy, which differs from Example 1 only in that the hard coating treatment in step (1) is not performed, and the workpiece to be processed is directly heated. The rest is the same as Example 1.

[0088] Comparative Example 2

[0089] This comparative example provides a method for hot processing of a high-temperature alloy, which is different from Example 1 only in that, except that the inner diameter of the outer ring of the hard casing is 180.2 mm, so that the diameter of the workpiece to be processed is 0.2 mm smaller than the inner diameter of the outer ring of the hard casing, and the workpiece to be processed and the outer ring of the hard casing are assembled according to the clearance fit, the rest are the same as Example 1.

[0090] Comparative Example 3

[0091] This comparative example provides a method for hot processing of a high-temperature alloy, which is different from Example 1 only in that, except that the inner diameter of the outer ring of the hard casing is 180 mm so that the diameter of the workpiece to be processed is the same as the inner diameter of the outer ring of the hard casing, and the workpiece to be processed and the outer ring of the hard casing are assembled according to the clearance fit, the rest are the same as Example 1.

[0092] Comparative Example 4

[0093] This comparative example provides a method for hot processing of a high-temperature alloy, which is different from Example 1 only in that, except that the inner diameter of the outer ring of the hard casing is 180.1 mm so that the diameter of the workpiece to be processed is 0.1 mm smaller than the inner diameter of the outer ring of the hard casing, and the workpiece to be processed and the outer ring of the hard casing are assembled according to a transition fit, the rest are the same as Example 1.

[0094] Comparative Example 5

[0095] This comparative example provides a method for hot processing of a high-temperature alloy, which is the same as Example 1 except that the inner diameter of the outer ring of the hard casing is 179.8 mm so that the diameter of the workpiece to be processed is 0.2 mm larger than the inner diameter of the outer ring of the hard casing.

[0096] Comparative Example 6

[0097] This comparative example provides a method for hot processing of a high-temperature alloy, which is the same as Example 1 except that the inner diameter of the outer ring of the hard casing is 179 mm so that the diameter of the workpiece to be processed is 1.0 mm larger than the inner diameter of the outer ring of the hard casing.

[0098] Test method: Use ultrasonic testing equipment to test the processed workpiece. The crack length is the range of the minimum and maximum lengths of the cracks in the test workpiece. The defect rate = the number of cracked workpieces / the total number of test workpieces, where the total number of test workpieces is 40.

[0099] According to the ultrasonic testing data, the crack position, crack length and defect rate of the workpiece after processing are obtained. The results are shown in Table 1.

[0100] Table 1

[0101]

[0102]

[0103] The test results show that:

[0104] (1) It can be seen from Examples 1-3 that the method for hot working of high-temperature alloys provided by the present invention can solve the problem of hot working cracking of hard-to-deform high-temperature alloys, and the defect rate of the processed workpieces prepared therefrom is less than 5%.

[0105] (2) It can be seen from Example 1 and Examples 4-5 that the holding time of step (2) in Example 1 is 200 min, the crack length of the workpiece after processing in Example 1 is 0-3 mm, and the defect rate is 2.5%; while the holding time in Example 4 is 120 min, the workpiece after processing in Example 4 cracks internally, the crack length is 16-88 mm, and the defect rate increases to 65%; the holding time in Example 5 is 280 min, the workpiece after processing in Example 5 cracks internally, the crack length is 12 -36mm, the defect rate increases to 30%, which shows that the present invention controls the holding time to make the workpiece with the hard-packed outer ring fully heated and the temperature distribution uniform, so as to reduce the risk of cracking of the workpiece after processing. If the holding time is too short, the workpiece with the hard-packed outer ring will not be fully heated and the temperature distribution will be uneven. The temperature difference between the inside and outside of the workpiece with the hard-packed outer ring is large, which will increase the risk of cracking of the workpiece after processing. If the holding time is too long, the grains of the difficult-to-deform high-temperature alloy workpiece will be coarse, which will also increase the risk of cracking of the workpiece after processing.

[0106] (3) It can be seen from Example 1 and Example 6 that the wall thickness of the outer ring of the hard casing in Example 1 is 40 mm, the crack length of the workpiece after processing in Example 1 is 0-3 mm, and the defect rate is 2.5%; while the wall thickness of the outer ring of the hard casing in Example 6 is 10 mm, and the workpiece after processing in Example 6 cracks on the outer peripheral surface, the crack length is 20-102 mm, and the defect rate increases to 75%. This shows that the present invention can ensure the quality of the outer ring of the hard casing during hot working by limiting the wall thickness of the outer ring of the hard casing. If the wall thickness of the outer ring of the hard casing is too small, the outer ring of the hard casing has the risk of breaking during forging, which increases the risk of cracking of the workpiece after processing.

[0107] (4) Combining Example 1 and Examples 8-9, it can be seen that the deformation of the workpiece with a hard can outer ring in Example 1 after a single forging treatment is 6%, the crack length of the workpiece after processing in Example 1 is 0-3mm, and the defect rate is 2.5%; while the deformation of the workpiece with a hard can outer ring in Example 8 after a single forging treatment is 2%, the workpiece cracks inside after processing in Example 8, the crack length is 30-50mm, and the defect rate increases to 37.5%; the deformation of the workpiece with a hard can outer ring in Example 9 after a single forging treatment is 20%, the workpiece cracks inside after processing in Example 9, the crack length is 24-97mm, and the defect rate increases to 72.5%. This shows that when the single deformation is too small, the deformation cannot make the microstructure and properties of the difficult-to-deform high-temperature alloy workpiece meet the design requirements, which will increase the risk of cracking. At the same time, when the single deformation is too high, the risk of cracking of the difficult-to-deform high-temperature alloy workpiece is further increased.

[0108] (4) It can be seen from the combination of Example 1 and Comparative Example 1 that in Comparative Example 1, the workpiece to be processed was not hard-packed before the hot working treatment. After the processing, the workpiece cracked on the outer peripheral surface of the workpiece, and the crack length was 30-120 mm. The defect rate increased to 85%. This shows that the present invention hard packs the workpiece to be processed through interference fit to form prestress, which can effectively reduce the tensile stress on the workpiece surface during the hot working process; at the same time, the outer ring of the hard pack can play a role of heat preservation, which can ensure the hot working temperature of the workpiece to be processed, thereby solving the problem of cracking of the hard-deformed high-temperature alloy during hot working.

[0109] (5) It can be seen from Example 1 and Comparative Examples 2-4 that Comparative Examples 2-4 use clearance fit or transition fit to assemble the workpiece to be processed with the outer ring of the hard casing, and the workpieces after processing all crack on the outer peripheral surface of the workpiece. This shows that the present invention uses interference fit to hard casing the workpiece to be processed to form prestress, which can effectively reduce the tensile stress on the workpiece surface during hot working, thereby solving the problem of hot working cracking of difficult-to-deform high-temperature alloys.

[0110] (6) Combining Example 1 and Comparative Examples 5-6, it can be seen that the inner diameter of the outer ring of the hard cover in Example 1 is 179.4 mm, the crack length after processing in Example 1 is 0-3 mm, and the defect rate is 2.5%; while the inner diameter of the outer ring of the hard cover in Comparative Example 5 is 179.8 mm, and the workpiece cracks on the outer peripheral surface of the workpiece after processing in Comparative Example 5, and the crack length is 10-35 mm, and the defect rate increases to 27.5%. The inner diameter of the outer ring of the hard cover in Comparative Example 6 is 179 mm, and the inner diameter of the outer ring of the hard cover in Comparative Example 6 is 179 mm. After processing in Ratio 6, cracks occur on the outer peripheral surface of the workpiece, the crack length is 28-50mm, and the defect rate increases to 40%. This shows that the present invention can solve the problem of cracking during hot working of difficult-to-deform high-temperature alloys by controlling the diameter of the workpiece to be processed to be 0.4-0.8mm larger than the inner diameter of the hard casing outer ring, and then assembling the hard casing outer ring and the workpiece to be processed according to an interference fit to obtain a workpiece with a hard casing outer ring, and then heating and forging the workpiece with the hard casing outer ring.

[0111] In summary, the present invention designs and manufactures the outer ring of the hard casing, controls the diameter of the workpiece to be processed to be 0.4-0.8mm larger than the inner diameter of the outer ring of the hard casing, and then assembles the outer ring of the hard casing with the workpiece to be processed according to the interference fit to obtain the workpiece with the outer ring of the hard casing, and then performs heat treatment on the workpiece with the outer ring of the hard casing, and then removes the outer ring of the hard casing after the heat treatment by machining to obtain a processed workpiece without cracks. The outer ring of the hard casing used in the present invention has a simple structure and can effectively solve the problem of cracking caused by hot working of difficult-to-deform high-temperature alloys.

[0112] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for hot working of a high temperature alloy, characterized in that: The method comprises the following steps: (1) Assembling the hard casing outer ring and the workpiece to be processed according to an interference fit to obtain a workpiece with the hard casing outer ring, wherein the diameter of the workpiece to be processed is 0.4-0.8 mm larger than the inner diameter of the hard casing outer ring; (2) heating and forging the workpiece with the hard jacket outer ring; (3) The outer ring of the hard casing after forging is removed by machining to obtain a machined workpiece.

2. The method for hot working of a high temperature alloy according to claim 1, characterized in that: The assembly in step (1) comprises the following steps: (a) preheating the outer ring of the hard casing; (b) connecting the workpiece to be processed with the outer ring of the hard casing to obtain a connection assembly; (c) cooling the connection assembly.

3. The method for hot working of a high temperature alloy according to claim 2, characterized in that: The preheating temperature in step (a) is 450-550° C., and the preheating holding time is 90-120 min.

4. The method for hot working of a high temperature alloy according to claim 2, characterized in that: The cooling process in step (c) comprises air cooling; Preferably, the cooling target temperature is 20-25°C.

5. The method for hot working of a high temperature alloy according to any one of claims 1 to 4, characterized in that: The material of the workpiece to be processed in step (1) includes GH4079 and / or GH4698.

6. The method for hot working of a high temperature alloy according to any one of claims 1 to 5, characterized in that: The heating temperature in step (2) is 1100-1140° C., and the holding time is (0.8-1.2)×D min, where D is the effective thickness of the workpiece with the hard-encapsulated outer ring, and the unit of D is mm.

7. The method for hot working of a high temperature alloy according to any one of claims 1 to 6, characterized in that: The wall thickness of the outer ring of the hard casing is 30-50 mm; Preferably, the outer ring of the hard casing is equal to the height of the workpiece to be processed.

8. The method for hot working of a high temperature alloy according to any one of claims 1 to 7, characterized in that: The forging process in step (2) includes upsetting or die forging.

9. The method for hot working of a high temperature alloy according to any one of claims 1 to 8, characterized in that: The deformation amount of the forging process is 25%-40%; Preferably, the single deformation amount in the forging process is 5-10%.

10. The method for hot working of a high temperature alloy according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: (1) Preheating a hard-packed outer ring with a wall thickness of 30-50 mm at 450-550° C. and keeping the temperature for 90-120 min, then connecting a workpiece to be processed made of GH4079 and / or GH4698 with the hard-packed outer ring by interference fit to obtain a connection assembly, and cooling the connection assembly to 20-25° C. to obtain a workpiece with a hard-packed outer ring, wherein the diameter of the workpiece to be processed is 0.4-0.8 mm larger than the inner diameter of the hard-packed outer ring; and the hard-packed outer ring is equal to the height of the workpiece to be processed; (2) When the material of the workpiece to be processed is GH4698, the workpiece with the hard-encapsulated outer ring is heated at 1100-1140°C and kept warm for (0.8-1.2)×D min, where D is the effective thickness of the workpiece with the hard-encapsulated outer ring, and the unit of D is mm; or, when the material of the workpiece to be processed is GH4079, the workpiece with the hard-encapsulated outer ring is heated at 1120-1140°C and kept warm for (0.8-1.2)×D min; Then, the heated workpiece with the hard jacket outer ring is forged, wherein the deformation amount of the forging process is 25%-40%; and the single deformation amount in the forging process is 5-10%; (3) The outer ring of the hard casing after forging is removed by machining to obtain a machined workpiece.

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