Method for avoiding crystal mixing of Inconel 625 forge piece and product thereof

Abstract

The invention relates to a method for avoiding crystal mixing of an Inconel 625 forge piece and a product of the Inconel 625 forge piece. The method comprises the steps that rolling is conducted, specifically, a forge piece is heated to the temperature T DEG C for a preset time, then multi-heating-number rolling is conducted on the forge piece, the deformation amount of each heating number is controlled not to exceed D, and when T ranges from 1080 DEG C to 1150 DEG C, D ranges from 30% to 45%; and when T is less than 1080 DEG C, D = (-0.34 T + 370) * 100%, and if the calculated D is less than 15%, the value of D is 15%.

Description

Technical Field

[0001] This application relates to the field of alloy processing, and more specifically to a method for avoiding mixed crystal formation in Inconel 625 forgings and the product thereof. Background Technology

[0002] Inconel 625 is a Ni-Cr-Mo based solid solution strengthened superalloy, primarily enhanced by the addition of elements such as chromium, molybdenum, and niobium to improve its corrosion resistance and high-temperature strength. The core mechanism of this material is the formation of a solid solution of Mo and Nb atoms within the Ni-Cr matrix, which hinders dislocation movement and improves the material's strength, maintaining excellent mechanical properties, especially at high temperatures. Furthermore, the material also enhances its oxidation and corrosion resistance through the formation of a dense oxide film by Cr and other elements. Inconel 625 has a face-centered cubic (FCC) structure, exhibiting high lattice stability at high temperatures. Combined with the solid solution strengthening mechanism, it effectively suppresses grain coarsening and creep deformation. This material maintains excellent mechanical properties and oxidation resistance even at high temperatures ranging from 600°C to 900°C, making it widely used in fields such as aero-engines. It is suitable for manufacturing complex structural components (e.g., for engine hot-end components such as combustion chamber bushings and nozzles, turbine blades and sealing rings, fasteners and connectors), and is a typical high-performance engineering material.

[0003] However, in the existing technology, some forgings are prone to mixed crystal phenomena in local areas, which affects mechanical properties. This is especially true when manufacturing forgings with complex geometric features such as significant differences in wall thickness and irregular cross-sections, which significantly increases the difficulty of microstructure control during hot working. Summary of the Invention

[0004] Studies have found that the grain size of forgings with different geometric characteristics is significantly affected by variations in temperature, time, deformation amount, and number of forging passes. Grains with significant wall thickness differences and irregular cross-sections are particularly sensitive, affecting the final grain structure uniformity and mechanical properties. Sufficient heating of the ingot before forging promotes uniform grain growth and reduces grain size variations caused by localized temperature differences. During forging, it is crucial to avoid localized deformation falling into the critical range of 5–15%, as insufficient recrystallization driving force in this range easily leads to coarse grain formation. Multiple forging passes and segmented pressure application ensure sufficient plastic deformation in each region, promoting dynamic recrystallization.

[0005] Based on this, the present invention proposes a method to avoid mixed crystal formation in Inconel 625 forgings, comprising rolling, wherein the rolling includes heating the forging to a temperature T degrees Celsius for a predetermined time, and then performing multi-pass rolling, wherein the deformation amount in each pass is controlled not to exceed D, wherein when T is between 1080°C and 1150°C, D is 30% to 45%, and when T is less than 1080°C, D = (-0.34T + 370) × 100%, and if the calculated D is less than 15%, then D is taken as 15%. For example, if the forging temperature T = 1000°C, the maximum deformation amount D is 30%.

[0006] In one embodiment, the forging is a ring forging.

[0007] In one embodiment, the predetermined time is 0.5 to 1.2 minutes multiplied by the maximum effective thickness (mm) of the forging cross-section. In the embodiments of this application, "maximum effective thickness" refers to the thickness of the part of the forging with the longest heat conduction path and the most difficult heat penetration, a definition known to those skilled in the art.

[0008] In one embodiment, the forging is heated to 900°C to 1100°C and held for 0.5 to 2 hours, and then the forging is subjected to multiple rolling processes, with the deformation amount controlled at 15% to 45% per process.

[0009] In one embodiment, the forging is heated to 950°C to 1100°C.

[0010] In one embodiment, prior to rolling, the Inconel 625 billet is heated to 1000°C to 1100°C for 0.5 to 2 hours, and then upset and punched.

[0011] In one embodiment, after rolling, the forging is further subjected to heating to 800°C to 910°C for 0.5 to 2 hours, followed by single-fire ring expansion to control the amount of plastic deformation to below 5%; and annealing heat treatment at 870°C to 920°C for 1 to 3 hours, followed by air cooling to room temperature.

[0012] In one embodiment, after rolling, the forging is further subjected to heating to 800°C to 910°C for 0.5 to 2 hours, followed by single-fire ring expansion to control the amount of plastic deformation to below 3%; and annealing heat treatment at 870°C to 920°C for 1 to 2 hours, followed by air cooling to room temperature.

[0013] The present invention also proposes an Inconel 625 product prepared according to the above method.

[0014] Existing technologies do not consider the relationship between deformation and forging temperature. This application solves the problem of microscopic mixed grains in the alloy ring forging by matching the forging temperature and deformation. Detailed Implementation

[0015] In embodiments of the present invention, conventional instruments and equipment can be used to perform various processing operations. In embodiments of the present invention, various known standards can be used to perform performance tests. In embodiments of the present invention, the method may include additional steps or omit certain steps as needed.

[0016] In one implementation, room temperature tensile properties are tested according to ASTM E8. The test uses standard-prepared bar specimens, subjected to tension on a universal testing machine, with strain measured using a high-precision extensometer to ensure the accuracy of parameters such as yield strength, tensile strength, and elongation. The test method requires continuous loading at a specified stress or strain rate until the specimen fractures, and recording a complete load-displacement curve.

[0017] In one implementation, the Brinell hardness test is performed according to ASTM E10. The test method involves pressing a tungsten carbide ball indenter, typically 10 mm in diameter, into the sample surface at room temperature under a specified test force for a given time. The indenter diameter is then measured, and the hardness value HB is calculated. The equipment used is a Brinell hardness tester with an optical microscopic measuring device capable of accurately recording the indentation size.

[0018] In one implementation, grain size assessment is performed according to ASTM E112 standard. The testing method involves preparing metallographic specimens of the alloy at room temperature, followed by polishing and etching. The microstructure is then observed under a metallographic microscope and compared with a standard grain size comparison chart to assess the average grain size. The equipment primarily includes a metallographic microscope and sample preparation equipment. These methods allow for accurate assessment of the grain size and uniformity of nickel-based alloys, thereby determining their microstructure control level and the stability of their mechanical properties.

[0019] Example 1

[0020] S1. Cutting: Select the bar size and cutting weight according to the final product size.

[0021] S2. Punching: The billet is heated to 1000℃ in a high-temperature gas furnace for 0.5 hours. Then the billet is taken out of the high-temperature gas furnace and transported to the press for upsetting and punching.

[0022] S3. Ring rolling: The punched ring forging is heated to 900°C in a high-temperature gas furnace for 0.5 hours. Then the forging is taken out of the high-temperature gas furnace and transferred to the ring rolling mill for multi-pass rolling. The deformation is controlled between 15% and 45%.

[0023] S4. Ring expansion: After heating the forging to 800℃ and holding for 0.5 hours, the ring is expanded in a single heat using a ring expander to control the amount of plastic deformation to below 5%.

[0024] S5. Heat treatment: Anneal at 870℃ for 1 hour, then air cool to room temperature.

[0025] S6. Tissue performance test: Perform room temperature tensile testing, hardness testing, and grain size distribution analysis.

[0026] Example 2

[0027] S1. Cutting: Select the bar size and cutting weight according to the final product size.

[0028] S2. Punching: The billet is heated to 1050℃ in a high-temperature gas furnace for 1.25 hours. Then the billet is taken out of the high-temperature gas furnace and transported to the press for upsetting and punching.

[0029] S3. Ring rolling: The punched ring forgings are heated to 1000°C in a high-temperature gas furnace for 1.25 hours. The forgings are then removed from the high-temperature gas furnace and transferred to a ring rolling mill for multi-pass rolling. The deformation is controlled between 15% and 45%.

[0030] S4. Ring expansion: After heating the forging to 850℃ for 1.25 hours, the ring is expanded in a single heat using a ring expander to control the amount of plastic deformation to below 3%.

[0031] S5. Heat treatment: Anneal at 890℃ for 2 hours, then air-cool to room temperature.

[0032] S6. Tissue performance test: Perform room temperature tensile testing, hardness testing, and grain size distribution analysis.

[0033] Example 3

[0034] S1. Cutting: Select the bar size and cutting weight according to the final product size.

[0035] S2. Punching: The billet is heated to 1100℃ in a high-temperature gas furnace for 2 hours. Then the billet is taken out of the high-temperature gas furnace and transported to the press for upsetting and punching.

[0036] S3. Ring rolling: The punched ring forgings are heated to 1100°C in a high-temperature gas furnace for 2 hours. The forgings are then removed from the high-temperature gas furnace and transferred to a ring rolling mill for multi-pass rolling. The deformation is controlled between 15% and 45%.

[0037] S4. Ring expansion: After heating the forging to 910℃ for 2 hours, the ring is expanded in a single heat using a ring expander to control the amount of plastic deformation to below 3%.

[0038] S5. Heat treatment: Anneal at 920℃ for 3 hours, then air-cool to room temperature.

[0039] S6. Tissue performance test: Perform room temperature tensile testing, hardness testing, and grain size distribution analysis.

[0040] result

[0041] Performance tests in Examples 1-3 show that, compared to products prepared using conventional methods, the products obtained using the method of this invention have a more uniform overall grain distribution, with no abnormally large grains or irregular structures. The grain size is above level 5, and there are no mixed crystals.

[0042] Various embodiments of the invention have been described to achieve its various objectives. It should be understood that these embodiments merely illustrate the principles of the invention. Many variations thereof will be apparent to those skilled in the art without departing from the spirit and scope of the invention.

Claims

1. A method for avoiding mixed grain formation in Inconel 625 forgings, characterized in that, Includes rolling, wherein the rolling process includes: The Inconel 625 forging is heated to temperature T and held for a predetermined time, then subjected to multiple rolling passes, with the deformation in each pass not exceeding D, wherein: When T is between 1080℃ and 1150℃, D is 30% to 45%; and When T is less than 1080℃, D = (-0.34T + 370)×100%, and if the calculated D is less than 15%, then D is taken as 15%.

2. The method according to claim 1, characterized in that, The forging is a ring forging.

3. The method according to claim 1, characterized in that, The predetermined time is the maximum effective thickness of the forging in millimeters multiplied by 0.5 minutes to 1.2 minutes.

4. The method according to claim 1, characterized in that, The forging is heated to 900°C to 1100°C and held for 0.5 to 2 hours. Then the forging is subjected to multiple rolling processes, with the deformation amount controlled at 15% to 45% per process.

5. The method according to claim 4, characterized in that, The forging is heated to 950°C to 1100°C.

6. The method according to claim 1, characterized in that, The process includes, prior to the rolling, the following: The Inconel 625 billet is heated to 1000°C to 1100°C and held for 0.5 to 2 hours, and then the Inconel 625 billet is upset and punched.

7. The method according to claim 1, characterized in that, The process following the rolling process also includes: The forging is heated to 800°C to 910°C and held at that temperature for 0.5 to 2 hours, followed by a single-stage ring expansion process to control the plastic deformation to below 5%; and Annealing heat treatment is carried out at 870℃ to 920℃ for 1 to 3 hours, followed by air cooling to room temperature.

8. The method according to claim 1, characterized in that, The process following the rolling process also includes: The forging is heated to 800°C to 910°C and held at that temperature for 0.5 to 2 hours, followed by a single-fire ring expansion process to control the plastic deformation to below 3%; and Annealing heat treatment is carried out at 870℃ to 920℃ for 1 to 2 hours, followed by air cooling to room temperature.

9. An Inconel 625 product prepared by the method according to any one of claims 1 to 8.