A gh625 forged bar and method of making the same

Abstract

The application discloses a GH625 forging bar and a preparation method thereof, and belongs to the technical field of metallurgy. The preparation method of the GH625 forging bar comprises the following steps: subjecting a consumable ingot to homogenization treatment; and subjecting the consumable ingot subjected to the homogenization treatment to forging. The homogenization treatment comprises the following steps: 1100 DEG C.-1150 DEG C. heat preservation for 10h-30h and 1150 DEG C.-1220 DEG C. heat preservation for 10h-80h. The preparation method of the GH625 forging bar can efficiently reduce segregation and shrinkage holes formed in the preparation process of the super-large-size GH625 forging bar by combining the homogenization treatment and the forging deformation process, and improves the product yield and the qualified rate.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, specifically to a GH625 forged bar and its preparation method. Background Technology

[0002] GH625 alloy is a solid solution strengthened nickel-based wrought superalloy with molybdenum and niobium as the main strengthening elements. It possesses excellent corrosion resistance and oxidation resistance, and exhibits good tensile and fatigue properties from low temperatures to 980℃. Furthermore, GH625 nickel-based superalloy is one of the main materials for manufacturing the hot-end rotating components of aero-engines, with turbine blades being a crucial component. Due to its superior mechanical properties and microstructural stability, this superalloy can operate stably for extended periods under extreme conditions, making it a preferred material for next-generation turbine blade superalloys.

[0003] However, as aero-engines continue to develop towards higher thrust-to-weight ratios, turbine blades must withstand higher temperatures and stresses, and operate in increasingly harsher environments. This places more stringent demands on the high-temperature alloy forgings used to manufacture turbine blades, namely, the need to achieve large-scale production of materials for turbine blade manufacturing. For example, the weight of forgings used to manufacture the integral casing of a certain aero-engine reaches 1.2 tons, the weight of a single forging for a shipborne gas turbine reaches 1.5 tons, and the weight of a single billet for a ground-based gas turbine exceeds 6 tons. However, in the aerospace field, GH625 high-temperature alloy forgings typically weigh less than 1 ton and have dimensions less than or equal to ≤Φ250mm.

[0004] Furthermore, the large-scale production of GH625 high-temperature alloy forgings also places higher demands on the forgings' yield strength, grain size, carbides, and low-temperature performance, presenting significant technical challenges. To address the drawbacks of large-scale GH625 high-temperature alloy forgings for turbine blades, appropriate forging processes and heat treatment methods are needed to ensure that the forgings' carbides and grain size meet the requirements, thereby improving the alloy's strength and low-temperature plasticity.

[0005] Therefore, the development of an ultra-large size nickel-based high-temperature alloy GH625 forging bar and its preparation method is of great theoretical and engineering guiding significance for improving the economy and reliability of the preparation process of ultra-large size GH625 high-temperature alloy forging bars, and even improving the quality of high-temperature alloy components. Summary of the Invention

[0006] The purpose of this invention is to provide a GH625 forged bar and its preparation method, which solves the technical problems of difficulty in producing large-size GH625 forged bar alloys and the poor strength and low-temperature plasticity of the prepared large-size GH625 forged bar alloys in the prior art.

[0007] To achieve the above objectives, one embodiment of the present invention provides a method for preparing a GH625 forged bar, comprising the following steps:

[0008] The consumable ingots are homogenized.

[0009] The homogenized consumable ingot is forged.

[0010] The homogenization treatment includes: holding at 1100℃-1150℃ for 10h-30h and holding at 1150℃-1220℃ for 10h-80h.

[0011] In one preferred embodiment of the present invention, the forging process includes a first-fire forging, in which the homogenized consumable ingot is upset and then held at 1150℃-1190℃ for 2h-6h.

[0012] In one preferred embodiment of the present invention, the forging process further includes a second forging process, in which the steel ingot after the first forging process is upset and drawn, and then held at 1150℃-1190℃ for 2h-6h after drawing.

[0013] In one preferred embodiment of the present invention, the forging process also includes a third forging process, in which the steel ingot after the second forging process is upset and drawn, and then held at 1150℃-1190℃ for 15h-25h after drawing.

[0014] In one preferred embodiment of the present invention, the forging process also includes a fourth forging process, in which the steel ingot after the third forging process is upset and then held at 1100℃-1190℃ for 2h-6h.

[0015] In one preferred embodiment of the present invention, the forging process also includes a fifth forging process, in which the steel ingot after the fourth forging process is drawn out and then held at 1150℃-1190℃ for 2h-6h.

[0016] In one preferred embodiment of the present invention, the forging process further includes a sixth forging process, in which the steel ingot after the fifth forging process is upset, and then held at 1100℃-1190℃ for 2h-6h. After the holding is completed, the steel ingot is sheathed, and then held at 1100℃-1190℃ for another 2h-6h.

[0017] In one preferred embodiment of the present invention, the forging process further includes a seventh forging process, in which the steel ingot after the sixth forging process is drawn out, and then held at 1100℃-1190℃ for 2h-6h. After the holding is completed, the steel ingot is sheathed, and then held at 1100℃-1190℃ for another 2h-6h.

[0018] In one preferred embodiment of the present invention, the forging process also includes an eighth forging process, in which the steel ingot after the seventh forging process is drawn out and then air-cooled.

[0019] The present invention also discloses a GH625 forged bar, which is prepared by the above-described method for preparing a GH625 forged bar.

[0020] In summary, the beneficial effects of the present invention are as follows:

[0021] 1. The preparation method of GH625 forged bars of the present invention, through the combination of homogenization treatment and forging deformation process, can effectively reduce segregation and shrinkage cavities formed during the preparation of ultra-large GH625 forged bars, and improve the product yield and qualification rate.

[0022] 2. GH625 alloy is a nickel-based alloy containing 9.0% Mo and 3.7% Nb. When the ingot diameter increases from the conventional Φ450mm and Φ550mm to Φ810mm, the higher Mo and Nb content leads to a significant increase in segregation during solidification. Segregation deteriorates the alloy's hot working properties and is extremely detrimental to the performance of the final product. This invention employs an appropriate homogenization process to minimize carbide segregation in the ingot and reduce the aggregation of the second phase within the forged bar, resulting in a uniform distribution of precipitated phases.

[0023] 3. GH625 is a fine-grained strengthening alloy. In order to make the yield strength of GH625 body reach 410 MPa or above, the grain size must be controlled to be equal to or finer than grade 6. To this end, the present invention adopts the method of "multiple upsetting and drawing + step-by-step cooling + soft sleeve + high temperature homogenization of intermediate billet" to obtain forging bar with a grain size finer than grade 6 and a yield strength ≥ 410 MPa.

[0024] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention will be apparent from the effects described in the description and the accompanying drawings. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the head grains of the GH625 forged bar prepared in Example 1 of the present invention;

[0026] Figure 2 This is a schematic diagram of the tail grains of the GH625 forged bar prepared in Example 1 of the present invention;

[0027] Figure 3 This is a schematic diagram of the head grains of the GH625 forged bar prepared in Example 2 of the present invention;

[0028] Figure 4 This is a schematic diagram of the tail grains of the GH625 forged bar prepared in Example 2 of the present invention;

[0029] Figure 5This is a schematic diagram of the head grains of the GH625 forged bar prepared in the comparative example of this invention;

[0030] Figure 6 This is a schematic diagram of the tail grains of the GH625 forged bar prepared in the comparative example of this invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0033] This invention provides a method for preparing GH625 forged bars, comprising the following steps:

[0034] Step (1): Homogenize the consumable ingot; specifically, homogenize the Φ810mm consumable ingot obtained from smelting, ignite and heat it to 1100℃-1150℃ for 10h-30h, then heat it to 1150℃-1220℃ and hold it for 10h-80h; the original microstructure and precipitate distribution diagram of the consumable ingot are shown in Figure 1, and the microstructure and precipitate distribution diagram of the homogenized consumable ingot are shown in Figure 2. Figure 2 As shown;

[0035] Step (2): Forging the homogenized consumable ingot; specifically, forging is carried out using the method of "four upsetting and four drawing + gradual cooling + soft sleeve + intermediate heating and long-term homogenization", including the following steps:

[0036] Step (201): First forging: After the homogenized consumable ingot is taken out of the heating furnace, it is upset to Φ800mm*2100mm, chamfered to octagonal, and then held at 1150℃-1190℃ for 2h-6h;

[0037] Step (202): Second forging: Take the steel ingot after the first forging process out of the heating furnace, upset it to Φ940mm*1700mm, then immediately draw it to Φ830mm*2150mm, chamfer it, and continue to hold it at 1150℃-1190℃ for 2h-6h or more.

[0038] Step (203): Third forging: Take the steel ingot after the second forging process out of the heating furnace, upset it to Φ1150mm*1200mm, then immediately draw it to Φ830mm*2150mm, chamfer it, and continue to hold it at 1150℃-1190℃ for 15h-25h.

[0039] Step (204): Fourth forging: Take the steel ingot after the third forging process out of the heating furnace, upset it to 1200mm*Φ1150mm, chamfer it, and continue to hold it at 1100℃-1190℃ for 2h-6h or more.

[0040] Step (205): Fifth forging: Take the steel ingot after the fourth forging process out of the heating furnace, draw it to Φ830mm*2150mm, and continue to hold it at 1150℃-1190℃ for 2h-6h or more.

[0041] Step (206): Sixth forging: Take the steel ingot after the fifth forging process out of the heating furnace, upset it to H=1200mm, chamfer it, and continue to hold it at 1100℃-1190℃ for more than 2h-6h. Then, perform a sheathing process on the steel ingot and hold it for more than 2h-6h.

[0042] Step (207): Seventh forging: Take the steel ingot after the sixth forging process out of the heating furnace, draw it to Φ750mm*2320mm, make a clamp at the tail, continue to keep it at 1100℃-1190℃ for 2h-6h or more, then perform a sheathing process on the steel ingot, and keep it at 2h-6h or more.

[0043] Step (208): Eighth forging: Take the steel ingot after the seventh forging process out of the heating furnace, draw it to Φ550mm*4000mm, and finally air cool it to room temperature.

[0044] The present invention also discloses a GH625 forged bar, which is prepared by the above-mentioned method for preparing a GH625 forged bar. The specifications of the prepared GH625 forged bar include: a diameter of Φ440mm-Φ550mm and a length of 4000mm-6000mm.

[0045] The GH625 forged bar requires a grain size grade of not less than 3, with a grain size difference of no more than 3 grades within the same field of view. After heat treatment, the measured grain size of the forged bar is 7.0, which is qualified.

[0046] Example 1

[0047] A method for preparing a GH625 forged bar includes the following steps:

[0048] a. Homogenization process: The Φ810mm consumable ingot is placed in a chamber furnace for homogenization treatment. The furnace is ignited and heated. After 12 hours, the furnace temperature is raised from room temperature to 1135℃ and held for 25 hours. After 5 hours, the temperature is raised to 1165℃ and held for 25 hours. After 6 hours, the temperature is raised to 1220℃ and held for 80 hours. The furnace is then cooled to 190℃ and removed from the furnace to cool to room temperature.

[0049] b. Forging process:

[0050] First heat: Heat the consumable ingot to 1170℃ and hold for 12 hours. After taking it out of the heating furnace, upset it to H=2100mm, bevel it into an octagon, and then hold it at 1170℃ for 6 hours.

[0051] Second heat (one upsetting and one drawing): The steel ingot after the first heat treatment is taken out of the heating furnace, upset to H=1700mm, and then immediately drawn to Φ820mm, chamfered, and held at 1170℃ for 6 hours.

[0052] Third heat (two upsetting and two drawing): The steel ingot after the second heat treatment is taken out of the heating furnace, upset to H=1200mm, and then immediately drawn to Φ820mm, chamfered, and held at 1190℃ for 20h.

[0053] Fourth heat (third upsetting): The steel ingot after the third heat treatment is taken out of the heating furnace, upset to H=1100mm, chamfered, and then held at 1170℃ for 6 hours.

[0054] Fifth heat (third drawing): The steel ingot after the fourth heat treatment is taken out of the heating furnace, drawn to Φ820mm, chamfered, and kept at 1150℃ for 6 hours.

[0055] The sixth heat (four upsettings + soft sheathing): The steel ingot after the fifth heat treatment is taken out of the heating furnace, upset to H=1100mm, chamfered, and held at 1100℃ for 6 hours. Then the steel ingot is sheathed and held for another 4 hours.

[0056] Seventh heat (fourth drawing + soft sleeve): Take the steel ingot after the sixth heat treatment out of the heating furnace, draw it to Φ750mm, make a clamp at the tail, continue to keep it at 1100℃ for 6 hours, then make the steel ingot sleeve treatment, and keep it at 4 hours or more.

[0057] Eighth heat (drawing to length): The steel ingot treated in the seventh heat is taken out of the heating furnace, drawn to Φ550mm*4000mm, and finally air-cooled to room temperature.

[0058] Using the preparation process described in Example 1 above, a Φ550mm ultra-large nickel-based superalloy GH625 forged bar was finally obtained; the grain size at the head of the Φ550mm forged bar is as follows: Figure 1 As shown, the grain size at the tail of the Φ550mm forged bar Figure 2 As shown in Table 1, the mechanical properties of the Φ550mm forged bar are as follows.

[0059] Table 1: Mechanical properties of the GH625 forged bar prepared in Example 1

[0060]

[0061] As can be seen from Table 1, the GH625 forged bar prepared in Example 1 has excellent mechanical properties.

[0062] Example 2

[0063] a. Homogenization process: The Φ810mm consumable ingot is placed in a chamber furnace for homogenization treatment. The furnace is ignited and heated. After 12 hours, the furnace temperature is raised from room temperature to 1140℃ and held for 24 hours. After 6 hours, the temperature is raised to 1160℃ and held for 24 hours. After 6 hours, the temperature is raised to 1220℃ and held for 80 hours. The furnace is then cooled to 220℃ and removed from the furnace to cool to room temperature.

[0064] b. Forging process:

[0065] First heat: Heat the consumable ingot to 1170℃ and hold for 12 hours. After taking it out of the chamber furnace, upset it to H=2000mm, bevel it to an octagon, and then hold it at 1170℃ for 6 hours.

[0066] Second heat (one upsetting and one drawing): The steel ingot after the first heat treatment is taken out of the heating furnace, upset to H=1600mm, and then immediately drawn to Φ830mm, chamfered, and held at 1170℃ for 6 hours.

[0067] Third heat (two upsetting and two drawing): The steel ingot after the second heat treatment is taken out of the heating furnace, upset to H=1100mm, and then immediately drawn to Φ830mm, chamfered, and held at 1190℃ for 20h.

[0068] Fourth heat (third upsetting): The steel ingot after the third heat treatment is taken out of the heating furnace, upset to H=1100mm, chamfered, and then held at 1170℃ for 6 hours.

[0069] Fifth heat (third drawing): The steel ingot after the fourth heat treatment is taken out of the heating furnace, drawn to Φ830mm, chamfered, and held at 1150℃ for 6 hours.

[0070] The sixth heat (four upsettings + soft sheathing): The steel ingot after the fifth heat treatment is taken out of the heating furnace, upset to H=1100mm, chamfered, and held at 1100℃ for 6 hours. Then the steel ingot is sheathed and held for another 4 hours.

[0071] The seventh heat (fourth drawing + soft sleeve): The steel ingot after the sixth heat treatment is taken out of the heating furnace, drawn to Φ830mm, chamfered into an octagon, and held at 1100℃ for 6 hours. Then the steel ingot is sleeved and held for another 4 hours.

[0072] Eighth heat: Take the steel ingot treated in the seventh heat out of the heating furnace, draw it to 600mm octagon, make a clamp at the tail, and then put it back in the furnace to be held at 1100℃ for 6 hours. Take it out and wrap it, and then hold it for another 4 hours.

[0073] Ninth heat: The steel ingots treated in the eighth heat are taken out of the heating furnace, drawn into an octagonal shape of 450mm, rolled into a round shape of Φ440mm, and air-cooled to room temperature after forging.

[0074] Using the preparation process described in Example 2 above, a Φ440mm ultra-large nickel-based superalloy GH625 forged bar was finally obtained; the grain size at the head of the Φ440mm forged bar is as follows: Figure 3 As shown, the grain size at the tail of the Φ440mm forged bar is as follows: Figure 4 As shown in Table 2, the mechanical properties of the Φ440mm forged bar are as follows.

[0075] Table 2: Mechanical properties of the GH625 forged bar prepared in Example 2

[0076]

[0077] As can be seen from Table 3, the GH625 forged bar prepared in Example 2 has excellent mechanical properties.

[0078] Comparative Example

[0079] Unlike Examples 1 and 2, in the comparative example, the homogenization process did not involve a long-term holding at 1220°C, the forging process did not involve a long-term holding at 1190°C after the third heat (two upsetting and two drawing), and the fourth upsetting and fourth drawing were not performed. The preparation of the forged bar included the following steps:

[0080] a. Homogenization process: The Φ810mm consumable ingot is placed in a chamber furnace for homogenization treatment. The furnace is ignited and heated. After 12 hours, the furnace temperature is raised from room temperature to 1135℃ and held for 25 hours. After 5 hours, the temperature is raised to 1165℃ and held for 25 hours. After 6 hours, the temperature is raised to 1180℃ and held for 72 hours. The furnace is then cooled to 190℃ and removed from the furnace to cool to room temperature.

[0081] b. Forging process:

[0082] First heat: Heat the consumable ingot to 1170℃ and hold for 12 hours. After taking it out of the chamber furnace, upset it to H=2100mm, bevel it to an octagon, and then hold it at 1170℃ for 6 hours.

[0083] Second heat (one upsetting and one drawing): The steel ingot after the first heat treatment is taken out of the heating furnace, upset to H=1700mm, and then immediately drawn to Φ820mm, chamfered, and held at 1170℃ for 6 hours.

[0084] Third heat (two upsetting and two drawing): The steel ingot after the second heat treatment is taken out of the heating furnace, upset to H=1100mm, and then immediately drawn to Φ820mm, chamfered, and held at 1170℃ for 6 hours.

[0085] Fourth heat (third upsetting): The steel ingot after the third heat treatment is taken out of the heating furnace, upset to H=1100mm, and then held at 1170℃ for 6 hours;

[0086] Fifth heat (third drawing): The steel ingot after the fourth heat treatment is taken out of the heating furnace, drawn to Φ750mm, clamped at the tail, and then held at 1100℃ for 6 hours before being wrapped.

[0087] The sixth heat: The steel ingot after the fifth heat treatment is taken out of the heating furnace, drawn into an octagonal shape of 560mm, rolled into a round shape of Φ550mm, and then air-cooled to room temperature after forging.

[0088] Using the above comparative preparation process, a Φ550mm ultra-large nickel-based superalloy GH625 forged bar was finally obtained; the grain size at the head of the Φ550mm forged bar is as follows: Figure 5 As shown, the grain size at the tail of the Φ550mm forged bar Figure 6 As shown in Table 3, the mechanical properties of the Φ550mm forged bar are as follows.

[0089] Table 3: Mechanical properties of GH625 forged bars prepared in the comparative example

[0090]

[0091] As can be seen from Table 3, the room temperature reduction of area, high temperature elongation after fracture, and reduction of area of ​​the GH625 forged bar prepared in the comparative example are not up to standard.

[0092] In summary, the preparation method of GH625 forged bars of the present invention, through the combination of homogenization treatment and forging deformation process, can effectively reduce segregation and shrinkage cavities formed during the preparation of ultra-large GH625 forged bars, thereby improving the product yield and pass rate.

[0093] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a GH625 forged bar, characterized in that, Includes the following steps: The consumable ingots are homogenized. The homogenized consumable ingot is forged. The homogenization treatment includes: holding at 1100℃-1150℃ for 10h-30h and holding at 1150℃-1220℃ for 10h-80h; The forging process includes a first-fire forging, in which the homogenized consumable ingot is upset and then held at 1150℃-1190℃ for 2-6 hours. The forging process also includes a second forging process, in which the forging billet after the first forging process is upsetting and drawing, and then held at 1150℃-1190℃ for 2h-6h after drawing. The forging process also includes a third forging process, in which the forging billet after the second forging process is upset and drawn, and then held at 1150℃-1190℃ for 15h-25h after drawing. The forging process also includes a fourth forging process, in which the forging billet after the third forging process is upset and then held at 1100℃-1190℃ for 2h-6h. The forging process also includes a fifth forging process, in which the forging billet after the fourth forging process is drawn out and then held at 1150℃-1190℃ for 2h-6h. The forging process also includes a sixth forging process, in which the forging billet after the fifth forging process is upset, and then held at 1100℃-1190℃ for 2h-6h. After the holding is completed, the forging billet is wrapped, and then held at 1100℃-1190℃ for another 2h-6h. The forging process also includes a seventh forging process, in which the forging billet after the sixth forging process is drawn out, and then held at 1100℃-1190℃ for 2h-6h. After the holding is completed, the forging billet is wrapped, and then held at 1100℃-1190℃ for another 2h-6h. Forging also includes the eighth forging process, which involves drawing the forged billet after the seventh forging process and then air cooling it.

2. A GH625 forged bar, characterized in that: The GH625 forged bar was prepared using the method described in claim 1.

3. The GH625 forged bar as described in claim 2, characterized in that: The specifications of the GH625 forged bar include: diameter of Φ440mm-Φ550mm and length of 4000mm-6000mm.

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