Method for producing wrought co-crm alloy bar

Abstract

The application discloses a preparation method of a deformed CoCrMo alloy rod, which comprises the following steps: preparing a cylindrical CoCrMo alloy ingot according to design requirements and performing homogenization treatment; transferring the cylindrical CoCrMo alloy ingot to a press to perform first forging to obtain a rod blank, and performing first annealing treatment on the rod blank; transferring the rod blank to the press to perform second forging to further obtain a rod blank, and performing second annealing treatment on the rod blank; transferring the rod blank to the press to perform third forging to further obtain a rod blank, and performing third annealing treatment on the rod blank; transferring the rod blank to a precision forging machine to perform radial forging to obtain a square blank, and performing fourth annealing treatment on the square blank; transferring the square blank to a hot rolling machine to perform hot rolling, and obtaining a deformed CoCrMo alloy rod. The deformed CoCrMo alloy rod obtained by adopting the preparation method has fine grains, uniform and stable structure, grain size reaches more than 11 levels, and has good mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of CoCrMo alloy material preparation technology, specifically relating to a method for preparing modified CoCrMo alloy rods. CoCrMo alloy rods prepared by this method are particularly suitable for the biomedical field. Background Technology

[0002] As is well known, CoCrMo alloys possess high strength, high hardness, good wear resistance, and corrosion resistance, and are currently widely used in the biomedical field. With the increasing aging of the global population, joint replacement surgery is becoming more and more common. In the past, the replacement materials used in joint replacement surgeries were often titanium alloys or stainless steel, but these materials have poor wear resistance. CoCrMo alloys, due to their better biocompatibility and superior wear resistance, have become one of the preferred materials for artificial joint replacement.

[0003] Early joints made from cast CoCrMo alloys suffered from wear and corrosion over long-term use, failing to meet long-term service requirements. Forged CoCrMo alloys, however, offer a more ideal service life. However, forged CoCrMo alloys have poor plastic deformation capacity, necessitating measures to prevent cracking during deformation, as well as the formation of banded grains and localized coarse grains. Furthermore, slight variations in deformation at different locations during press deformation can lead to uneven grain structure, and excessive trimming at the beginning and end results in a lower yield. Currently, no technology has been reported for manufacturing forged CoCrMo alloys that prevents cracking during production and achieves stable microstructure in the final bar. Therefore, a method for preparing deformed CoCrMo alloy bars needs to be developed to address the technical problems of existing CoCrMo alloy forging methods, such as easy cracking, poor microstructure uniformity, and low yield.

[0004] Chinese patent application CN111575539A discloses a method for preparing hot-workable cobalt-based alloy rods and wires, comprising the following steps: preparing cobalt-based alloy ingots that meet chemical composition requirements by vacuum induction melting and electroslag remelting; subjecting the cobalt-based alloy ingots to homogenization heat treatment at 1150-1270℃ for 4-24 hours; subjecting the homogenized heat-treated cobalt-based alloy ingots to rough forging at 1150-1230℃ for 3-8 hours, with a deformation of 20-40%, and a final forging temperature of 1100±20℃; and then... High-temperature forging is used to prepare cobalt-based alloy billets or wire blanks. The forging temperature is 1100-1230℃, and the holding time is 1-5 hours to forge billets or wire blanks with a diameter of 30mm or more. The deformation amount per forging is 20-30%, and the final forging temperature is 1050±20℃. High-temperature forging is continued at a forging temperature of 1050-1150℃ and a holding time of 1-3 hours to forge billets or wire blanks of various specifications. The deformation amount per forging is 10-30%, and the final forging temperature is 1000±20℃. The high-temperature forged billets or wire blanks are straightened, turned, or centerless ground to prepare finished bars or wires. The technical solution involves 2-3 forgings, but the number of forgings and the amount of deformation of the alloy ingot are not clearly defined in each forging process. The number of forgings can vary, and the amount of deformation can vary. Only the final deformation amount of each forging is limited. Due to the different number of forgings and the different amounts of deformation, the final forging billet will have different microstructure and properties, making it difficult to guarantee the uniformity of the final product in terms of mechanical properties and microstructure. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a method for preparing modified CoCrMo alloy rods, the preparation method comprising the following steps in sequence:

[0006] Step 1: Prepare cylindrical CoCrMo alloy ingots according to design requirements;

[0007] Step 2: Place the cylindrical CoCrMo alloy ingot into a heat treatment furnace for homogenization treatment;

[0008] Step 3: After the homogenization process is completed, the cylindrical CoCrMo alloy ingot is transferred to a press for the first forging to obtain a billet. The billet obtained from the first forging is then placed in a heat treatment furnace for the first annealing process.

[0009] Step 4: After the first annealing treatment is completed, the billet is transferred to the press for a second forging and further processed into a billet. The billet obtained from the second forging is then placed in a heat treatment furnace for a second annealing treatment.

[0010] Step 5: After the second annealing process is completed, the billet is transferred to the press for the third forging and further processed into a billet. The billet obtained from the third forging is then placed in a heat treatment furnace for the third annealing process.

[0011] Step 6: After the third annealing process is completed, the billet is transferred to the precision forging machine for radial forging to obtain a square billet. The square billet obtained by radial forging is then placed in the heat treatment chamber for the fourth annealing process.

[0012] Step 7: After the fourth annealing process, the billet is transferred to a hot rolling mill for hot rolling to obtain a bar. After the hot rolling is completed, the modified CoCrMo alloy bar can be obtained.

[0013] Preferably, in step one, the chemical composition of the cylindrical CoCrMo alloy ingot, by mass percentage, includes Cr 26.0-30.0 wt%, Mo 5.0-7.0 wt%, Ni ≤ 1.0 wt%, C ≤ 0.35 wt%, Fe ≤ 0.75 wt%, Si ≤ 1.0 wt%, Mn ≤ 1.0 wt%, N ≤ 0.35 wt%, with the balance being Co. The cylindrical CoCrMo alloy ingot is prepared by a dual-melting process, namely, vacuum induction melting and protective atmosphere electroslag remelting. The key parameters of the vacuum induction melting process are: the vacuum pressure during the cleaning stage does not exceed 30 Pa, the vacuum pressure during the refining stage does not exceed 10 Pa, and the pouring temperature is 1500-1550℃. The key parameters of the protective atmosphere electroslag remelting process are: the melting speed is not higher than 4.5 kg / min, the argon flow rate is not lower than 5 L / min, and the feeding weight is not lower than 85 kg.

[0014] In any of the above schemes, it is preferred that, in step two, the homogenization treatment process for the cylindrical CoCrMo alloy ingot is as follows: the cylindrical CoCrMo alloy ingot is placed in a heat treatment furnace, and the temperature is increased from room temperature to 500°C at a heating rate of 5-10°C / min, and held for 1-2 hours; the temperature is then increased from 500°C to 900°C at a heating rate of 5-10°C / min, and held for 1-2 hours; the temperature is then increased from 900°C to 1150-1250°C at a heating rate of 5-10°C / min, and held for 1-6 hours; no protective atmosphere is required during the homogenization treatment.

[0015] In any of the above schemes, preferably, in step three, after the homogenization treatment is completed, the cylindrical CoCrMo alloy ingot is taken out of the heat treatment furnace and transferred to the press within 3 minutes; the process of the first forging is as follows: the cylindrical CoCrMo alloy ingot is placed horizontally on the platform of the press, and the press head performs the first forging from one end of the ingot to the other end. After the first forging is completed, the ingot is rotated 60° axially, and the press head continues to perform the second forging from one end of the ingot to the other end. After the second forging is completed, the ingot is rotated 60° axially, and the press head continues to perform the third forging from one end of the ingot to the other end, and so on, until the total deformation reaches 8-20%, the first forging is completed and the billet is obtained. The deformation of the two adjacent forgings is 1-2%, and the temperature of the billet is not lower than 900℃ after the last forging.

[0016] In any of the above schemes, it is preferred that, in step three, the process of the first annealing treatment is as follows: annealing temperature 1150-1220℃, annealing time 1-3h, and no protective atmosphere is required during the first annealing treatment.

[0017] In any of the above schemes, preferably, in step four, after the first annealing treatment is completed, the billet is taken out from the heat treatment furnace and transferred to the press within 3 minutes; the process of the second forging is as follows: the billet is placed horizontally on the platform of the press, and the press head performs the first forging from one end of the billet to the other. After the first forging is completed, the billet is rotated 60° axially, and the press head continues to perform the second forging from one end of the billet to the other. After the second forging is completed, the billet is rotated 60° axially, and the press head continues to perform the third forging from one end of the billet to the other, and so on, until the total deformation reaches 25-45%, the second forging is completed and the billet is further obtained. The deformation of each of the two adjacent forgings is 2-4%. After the last forging is completed, the temperature of the billet is not lower than 900℃.

[0018] In any of the above schemes, it is preferred that, in step four, the process of the second annealing treatment is as follows: annealing temperature 1100-1180℃, annealing time 1-3h, and no protective atmosphere is required during the second annealing treatment.

[0019] In any of the above schemes, preferably, in step five, after the second annealing treatment is completed, the billet is taken out from the heat treatment furnace and transferred to the press within 3 minutes; the process of the third forging is as follows: the billet is placed horizontally on the platform of the press, and the press head performs the first forging from one end of the billet to the other end. After the first forging is completed, the billet is rotated 60° axially, and the press head continues to perform the second forging from one end of the billet to the other end. After the second forging is completed, the billet is rotated 60° axially, and the press head continues to perform the third forging from one end of the billet to the other end, and so on, until the total deformation reaches 10-30%, the third forging is completed and the billet is further obtained. The deformation of the two adjacent forgings is 2-4%, and the temperature of the billet is not lower than 900℃ after the last forging.

[0020] In any of the above schemes, it is preferred that, in step five, the process of the third annealing treatment is as follows: annealing temperature 1120-1200℃, annealing time 1-4h, and no protective atmosphere is required during the third annealing treatment.

[0021] In any of the above schemes, preferably, in step six, after the third annealing treatment is completed, the billet is taken out from the heat treatment furnace and transferred to the precision forging machine within 3 minutes; the radial forging process is as follows: the billet is installed on the precision forging machine, and the forging hammer performs a first radial forging from one end of the billet to the other to obtain an elliptical billet. After the first radial forging, the forging hammer performs a second radial forging from one end of the elliptical billet to the other to obtain a circular billet. After the second radial forging, the forging hammer performs a third radial forging from one end of the circular billet to the other to obtain an elliptical billet again. After the third radial forging, the forging hammer performs a fourth radial forging from one end of the elliptical billet to the other to obtain a circular billet again. After the fourth radial forging, the forging hammer performs a fifth radial forging from one end of the circular billet to the other to obtain a square billet. The deformation amount of each adjacent radial forging is 6-12%, and after the fifth radial forging, the temperature of the square billet is not lower than 930℃.

[0022] In any of the above schemes, it is preferred that, in step six, the process of the fourth annealing treatment is as follows: annealing temperature 1150-1220℃, annealing time 1-4h, and no protective atmosphere is required during the fourth annealing treatment.

[0023] In any of the above schemes, it is preferred that, in step seven, after the fourth annealing treatment is completed, the billet is taken out from the heat treatment furnace and transferred to the hot rolling mill within 3 minutes; the hot rolling process is that at least two hot rollings are performed, and the deformation amount of each of the two adjacent hot rollings is 10-30%.

[0024] In step two, the purpose of homogenizing the cylindrical CoCrMo alloy ingot is to reduce segregation and prevent grain growth, thereby improving subsequent forging plasticity. Because the as-cast CoCrMo alloy has poor plasticity, homogenization is necessary before billet preparation, but the time should not be too long; otherwise, grain growth will occur, and the plasticity will not reach its optimal state.

[0025] In steps three through five, the cylindrical CoCrMo alloy ingot is forged in three stages: first, second, and third forging. Each forging process involves several passes of forging, with very small deformation in each pass. This allows the transformation from the as-cast structure to the deformed structure to be achieved through small deformation, resulting in sufficient recrystallization, grain refinement, and a reduced chance of billet cracking. At the same time, it improves the plasticity of the alloy, reduces the need for crack repair and grinding, saves time, and increases the yield.

[0026] In steps six and seven, the billet obtained by the forging process is subjected to radial forging and hot rolling. During radial forging, the deformation is triaxial stress, resulting in finer grains, a more uniform and stable microstructure, and a higher yield.

[0027] The method for preparing the modified CoCrMo alloy rod of this invention employs a combined processing technology of double melting + multi-fire forging (each forging process includes several passes of small deformation forging) + radial forging + hot rolling. In every stage of the entire processing, the probability of ingot / billet cracking is very small or even nonexistent. The resulting modified CoCrMo alloy rod has fine grains, a uniform and stable microstructure, and a grain size of grade 11 or higher. It possesses excellent mechanical properties, with a tensile strength of 1376-1410 MPa, a yield strength of 980-1100 MPa, an elongation of section of not less than 44.5%, and a reduction of area of ​​not less than 39.5% in the processed state, meeting the requirements of the biomedical field for the microstructure and properties of CoCrMo alloys. Attached Figure Description

[0028] Figure 1 A flowchart of a preferred embodiment of the method for preparing modified CoCrMo alloy rods according to the present invention;

[0029] Figure 2 for Figure 1 The illustrated embodiment shows a photograph of the on-site operation of radial forging of the billet;

[0030] Figure 3 for Figure 1 A photograph of the modified CoCrMo alloy rod prepared in the illustrated embodiment;

[0031] Figure 4 for Figure 1 Micrograph of the modified CoCrMo alloy rod prepared in the illustrated embodiment. Detailed Implementation

[0032] To further understand the invention, the following detailed description of the invention will be provided in conjunction with specific embodiments.

[0033] Example 1:

[0034] like Figure 1 As shown, in a preferred embodiment of the method for preparing modified CoCrMo alloy rods according to the present invention, the preparation method includes the following steps in sequence:

[0035] Step 1: Prepare cylindrical CoCrMo alloy ingots according to design requirements;

[0036] Step 2: Place the cylindrical CoCrMo alloy ingot into a heat treatment furnace for homogenization treatment;

[0037] Step 3: After the homogenization process is completed, the cylindrical CoCrMo alloy ingot is transferred to a press for the first forging to obtain a billet. The billet obtained from the first forging is then placed in a heat treatment furnace for the first annealing process.

[0038] Step 4: After the first annealing treatment is completed, the billet is transferred to the press for a second forging and further processed into a billet. The billet obtained from the second forging is then placed in a heat treatment furnace for a second annealing treatment.

[0039] Step 5: After the second annealing process is completed, the billet is transferred to the press for the third forging and further processed into a billet. The billet obtained from the third forging is then placed in a heat treatment furnace for the third annealing process.

[0040] Step 6: After the third annealing process is completed, the billet is transferred to the precision forging machine for radial forging to obtain a square billet. The square billet obtained by radial forging is then placed in the heat treatment chamber for the fourth annealing process.

[0041] Step 7: After the fourth annealing process, the billet is transferred to a hot rolling mill for hot rolling to obtain a bar. After the hot rolling is completed, the modified CoCrMo alloy bar can be obtained.

[0042] In step one, the chemical composition of the cylindrical CoCrMo alloy ingot, by mass percentage, includes Cr 28.0wt%, Mo 6.0wt%, Ni 1.0wt%, C 0.35wt%, Fe 0.75wt%, Si 1.0wt%, Mn 1.0wt%, N 0.35wt%, with the balance being Co; the cylindrical CoCrMo alloy ingot has a length of 1.5m and a diameter of 480mm; the cylindrical CoCrMo alloy ingot is prepared by a dual-melting process, namely, vacuum induction melting and protective atmosphere electroslag remelting; the key parameters of the vacuum induction melting process are: a vacuum pressure of 30Pa for the purification stage, a vacuum pressure of 10Pa for the refining stage, and a pouring temperature of 1520℃; the key parameters of the protective atmosphere electroslag remelting process are: a melting speed of 4.5kg / min, an argon flow rate of 5L / min, and a feeding weight of 85kg.

[0043] In step two, the homogenization process for the cylindrical CoCrMo alloy ingot is as follows: the cylindrical CoCrMo alloy ingot is placed in a heat treatment furnace and heated from room temperature to 500°C at a rate of 8°C / min, and held at that temperature for 1.5 hours; then the temperature is further increased from 500°C to 900°C at a rate of 8°C / min, and held for 1.5 hours; then the temperature is further increased from 900°C to 1200°C at a rate of 8°C / min, and held for 4 hours; no protective atmosphere is required during the homogenization process.

[0044] In step three, after the homogenization treatment is completed, the cylindrical CoCrMo alloy ingot is removed from the heat treatment furnace and transferred to the press within 3 minutes. The process of the first forging is as follows: the cylindrical CoCrMo alloy ingot is placed horizontally on the platform of the press, and the press head performs the first forging from one end of the ingot to the other. After the first forging, the ingot is rotated 60° axially, and the press head continues to perform the second forging from one end of the ingot to the other. After the second forging, the ingot is rotated 60° axially, and the press head continues to perform the third forging from one end of the ingot to the other. This process is repeated until the total deformation reaches 12%, at which point the first forging is completed and a billet is obtained. The deformation of each adjacent forging is 1.5%. After the eighth forging, the temperature of the billet is 900℃.

[0045] The process for the first annealing treatment is as follows: annealing temperature 1180℃, annealing time 2h, and no protective atmosphere is required during the first annealing treatment.

[0046] In step four, after the first annealing treatment is completed, the billet is removed from the heat treatment furnace and transferred to the press within 3 minutes. The process for the second forging is as follows: the billet is placed horizontally on the platform of the press, and the press head performs the first forging from one end of the billet to the other. After the first forging, the billet is rotated 60° axially, and the press head continues to perform the second forging from one end of the billet to the other. After the second forging, the billet is rotated 60° axially, and the press head continues to perform the third forging from one end of the billet to the other. This process is repeated until the total deformation reaches 42%, at which point the second forging is completed and the billet is further produced. The deformation of each adjacent forging is 3%. After the twelfth forging, the temperature of the billet is 900℃.

[0047] The process for the second annealing is as follows: annealing temperature 1140℃, annealing time 2h, and no protective atmosphere is required during the second annealing process.

[0048] In step five, after the second annealing process is completed, the billet is removed from the heat treatment furnace and transferred to the press within 3 minutes. The process for the third forging is as follows: the billet is placed horizontally on the platform of the press, and the press head performs the first forging from one end of the billet to the other. After the first forging, the billet is rotated 60° axially, and the press head continues to perform the second forging from one end of the billet to the other. After the second forging, the billet is rotated 60° axially, and the press head continues to perform the third forging from one end of the billet to the other. This process is repeated until the total deformation reaches 19%, at which point the third forging is completed and the billet is further produced. The deformation of each of the two adjacent forging passes is 3%. After the sixth forging pass, the temperature of the billet is 900℃.

[0049] The process for the third annealing treatment is as follows: annealing temperature 1160℃, annealing time 2h, and no protective atmosphere is required during the third annealing treatment.

[0050] In step six, after the third annealing treatment is completed, the billet is removed from the heat treatment furnace and transferred to the precision forging machine within 3 minutes. The radial forging process is as follows: the billet is installed on the precision forging machine, and the forging hammer performs the first radial forging from one end of the billet to the other to obtain an elliptical billet. After the first radial forging, the forging hammer performs the second radial forging from one end of the elliptical billet to the other to obtain a circular billet. After the second radial forging, the forging hammer performs the third radial forging from one end of the circular billet to the other to obtain an elliptical billet again. After the third radial forging, the forging hammer performs the fourth radial forging from one end of the elliptical billet to the other to obtain a circular billet again. After the fourth radial forging, the forging hammer performs the fifth radial forging from one end of the circular billet to the other to obtain a square billet. The deformation amount of each adjacent radial forging is 9%. After the fifth radial forging, the temperature of the square billet is 930℃.

[0051] The process for the fourth annealing treatment is as follows: annealing temperature 1180℃, annealing time 2h, and no protective atmosphere is required during the fourth annealing treatment.

[0052] In step seven, after the fourth annealing process is completed, the billet is taken out of the heat treatment furnace and transferred to the hot rolling mill within 3 minutes; the hot rolling process is as follows: at least two hot rollings are performed, and the deformation amount of each of the two adjacent hot rollings is 10%.

[0053] In step two, the purpose of homogenizing the cylindrical CoCrMo alloy ingot is to reduce segregation and prevent grain growth, thereby improving subsequent forging plasticity. Because the as-cast CoCrMo alloy has poor plasticity, homogenization is necessary before billet preparation, but the time should not be too long, otherwise grain growth will occur, and the plasticity will not reach its optimal state. In steps three through five, the cylindrical CoCrMo alloy ingot undergoes a first, second, and third forging process sequentially. Each forging process involves several passes of forging, with very small deformation amounts in each pass. This allows the transformation from the as-cast structure to the deformed structure to a fully recrystallized structure, refining the grains and reducing the probability of billet cracking. Simultaneously, it improves the alloy's plasticity, reduces the need for crack repair grinding, saves time, and increases the yield. In steps six and seven, the billet obtained from the aforementioned forging is subjected to radial forging and hot rolling. During radial forging, the deformation is triaxial stress, resulting in finer grains, a more uniform and stable structure, and a higher yield.

[0054] In this embodiment, the on-site operation photos of the radial forging of the billet are as follows: Figure 2 As shown; a photograph of the final prepared modified CoCrMo alloy rod is shown below. Figure 3 As shown, the diameter of the alloy rod is 35 mm; the microstructure of the final prepared deformed CoCrMo alloy rod is shown in the image. Figure 4As shown in the figure, the alloy rod has a uniform and stable microstructure, with fine grains and a grain size of grade 11 or higher.

[0055] The method for preparing the modified CoCrMo alloy rod in this embodiment employs a combined processing technology of double melting + multi-fire forging (each forging process includes several passes of small deformation forging) + radial forging + hot rolling. In every step of the entire processing, the probability of ingot / blank cracking is very small. The resulting modified CoCrMo alloy rod has fine grains, a uniform and stable microstructure, and good mechanical properties, meeting the requirements of the biomedical field for the microstructure and properties of CoCrMo alloys.

[0056] Example 2:

[0057] According to another preferred embodiment of the method for preparing modified CoCrMo alloy rods of the present invention, the preparation process, equipment used, technical principles, and beneficial effects are basically the same as those in Embodiment 1, except that:

[0058] In step one, the chemical composition of the cylindrical CoCrMo alloy ingot, by mass percentage, includes Cr 26.0wt%, Mo 7.0wt%, Ni 1.0wt%, C 0.35wt%, Fe 0.75wt%, Si 1.0wt%, Mn 1.0wt%, N 0.35wt%, with the balance being Co; the cylindrical CoCrMo alloy ingot has a length of 1.5m and a diameter of 480mm; the cylindrical CoCrMo alloy ingot is prepared by a dual-melting process, namely, vacuum induction melting and protective atmosphere electroslag remelting; the key parameters of the vacuum induction melting process are: a vacuum pressure of 30Pa for the purification stage, a vacuum pressure of 10Pa for the refining stage, and a pouring temperature of 1510℃; the key parameters of the protective atmosphere electroslag remelting process are: a melting speed of 4.5kg / min, an argon flow rate of 5L / min, and a feeding weight of 85kg.

[0059] In step two, the homogenization process for the cylindrical CoCrMo alloy ingot is as follows: the cylindrical CoCrMo alloy ingot is placed in a heat treatment furnace and heated from room temperature to 500°C at a rate of 5°C / min, and held at that temperature for 2 hours; then the temperature is further increased from 500°C to 900°C at a rate of 5°C / min, and held at that temperature for 2 hours; then the temperature is further increased from 900°C to 1150°C at a rate of 5°C / min, and held at that temperature for 6 hours; no protective atmosphere is required during the homogenization process.

[0060] In step three, after the homogenization treatment is completed, the cylindrical CoCrMo alloy ingot is removed from the heat treatment furnace and transferred to a press within 3 minutes. The process for the first forging is as follows: the cylindrical CoCrMo alloy ingot is placed horizontally on the platform of the press, and the press head performs the first forging from one end of the ingot to the other. After the first forging, the ingot is rotated 60° axially, and the press head continues to perform the second forging from one end of the ingot to the other. After the second forging, the ingot is rotated 60° axially, and the press head continues to perform the third forging from one end of the ingot to the other, and so on, until the total deformation reaches 12%, thus completing the first forging and producing a billet. The deformation of each adjacent forging is 1.2%. After the tenth forging, the temperature of the billet is 900℃. The process for the first annealing is as follows: annealing temperature 1180℃, annealing time 3 hours, and no protective atmosphere is required during the first annealing process.

[0061] In step four, after the first annealing treatment, the billet is removed from the heat treatment furnace and transferred to the press within 3 minutes. The process for the second forging is as follows: the billet is placed horizontally on the platform of the press, and the press head performs the first forging from one end of the billet to the other. After the first forging, the billet is rotated 60° axially, and the press head continues to perform the second forging from one end of the billet to the other. After the second forging, the billet is rotated 60° axially, and the press head continues to perform the third forging from one end of the billet to the other, and so on, until the total deformation reaches 42%. The second forging is then completed, and the billet is further produced. The deformation of each adjacent forging is 4%. After the ninth forging, the temperature of the billet is 900℃. The process for the second annealing treatment is as follows: annealing temperature 1160℃, annealing time 3 hours, and no protective atmosphere is required during the second annealing treatment.

[0062] In step five, after the second annealing process, the billet is removed from the heat treatment furnace and transferred to the press within 3 minutes. The process for the third forging is as follows: the billet is placed horizontally on the platform of the press, and the press head performs the first forging from one end of the billet to the other. After the first forging, the billet is rotated 60° axially, and the press head continues to perform the second forging from one end of the billet to the other. After the second forging, the billet is rotated 60° axially, and the press head continues to perform the third forging from one end of the billet to the other, and so on, until the total deformation reaches 19%. The third forging is then completed, and the billet is further produced. The deformation of each adjacent forging is 2%. After the ninth forging, the temperature of the billet is 900℃. The process for the third annealing is as follows: annealing temperature 1170℃, annealing time 4 hours, and no protective atmosphere is required during the third annealing process.

[0063] In step six, after the third annealing treatment is completed, the billet is removed from the heat treatment furnace and transferred to the precision forging machine within 3 minutes. The radial forging process is as follows: the billet is installed on the precision forging machine, and the forging hammer performs the first radial forging from one end of the billet to the other to obtain an elliptical billet. After the first radial forging, the forging hammer performs the second radial forging from one end of the elliptical billet to the other to obtain a circular billet. After the second radial forging, the forging hammer performs the third radial forging from one end of the circular billet to the other to obtain an elliptical billet again. After the third radial forging, the forging hammer performs the fourth radial forging from one end of the elliptical billet to the other to obtain a circular billet again. After the fourth radial forging, the forging hammer performs the fifth radial forging from one end of the circular billet to the other to obtain a square billet. The deformation amount of each adjacent radial forging is 9%. After the fifth radial forging, the temperature of the square billet is 930℃. The process for the fourth annealing treatment is as follows: annealing temperature 1150℃, annealing time 4h, and no protective atmosphere is required during the fourth annealing treatment.

[0064] In step seven, after the fourth annealing treatment is completed, the billet is removed from the heat treatment furnace and transferred to the hot rolling mill within 3 minutes. The hot rolling process involves at least two hot rolling cycles, with a deformation of 10% for each of the two adjacent hot rolling cycles. The final deformed CoCrMo alloy bar has a diameter of 35 mm.

[0065] Example 3:

[0066] According to another preferred embodiment of the method for preparing modified CoCrMo alloy rods of the present invention, the preparation process, equipment used, technical principles, and beneficial effects are basically the same as those in Embodiment 1, except that:

[0067] In step one, the chemical composition of the cylindrical CoCrMo alloy ingot, by mass percentage, includes Cr 30.0wt%, Mo 5.0wt%, Ni 1.0wt%, C 0.35wt%, Fe 0.75wt%, Si 1.0wt%, Mn 1.0wt%, N 0.35wt%, with the balance being Co; the cylindrical CoCrMo alloy ingot has a length of 1.5m and a diameter of 480mm; the cylindrical CoCrMo alloy ingot is prepared by a dual-melting process, namely, vacuum induction melting and protective atmosphere electroslag remelting; the key parameters of the vacuum induction melting process are: a vacuum pressure of 30Pa for the purification stage, a vacuum pressure of 10Pa for the refining stage, and a pouring temperature of 1550℃; the key parameters of the protective atmosphere electroslag remelting process are: a melting speed of 4.5kg / min, an argon flow rate of 5L / min, and a feeding weight of 85kg.

[0068] In step two, the homogenization process for the cylindrical CoCrMo alloy ingot is as follows: the cylindrical CoCrMo alloy ingot is placed in a heat treatment furnace and heated from room temperature to 500°C at a rate of 10°C / min, and held at that temperature for 1 hour; then the temperature is further increased from 500°C to 900°C at a rate of 10°C / min, and held at that temperature for 1 hour; then the temperature is further increased from 900°C to 1250°C at a rate of 10°C / min, and held at that temperature for 1 hour; no protective atmosphere is required during the homogenization process.

[0069] In step three, after the homogenization treatment is completed, the cylindrical CoCrMo alloy ingot is removed from the heat treatment furnace and transferred to a press within 3 minutes. The process for the first forging is as follows: the cylindrical CoCrMo alloy ingot is placed horizontally on the platform of the press, and the press head performs the first forging from one end of the ingot to the other. After the first forging, the ingot is rotated 60° axially, and the press head continues to perform the second forging from one end of the ingot to the other. After the second forging, the ingot is rotated 60° axially, and the press head continues to perform the third forging from one end of the ingot to the other, and so on, until the total deformation reaches 12%, thus completing the first forging and producing a billet. The deformation of each adjacent forging is 2%. After the sixth forging, the temperature of the billet is 900℃. The process for the first annealing is as follows: annealing temperature 1220℃, annealing time 1 hour, and no protective atmosphere is required during the first annealing process.

[0070] In step four, after the first annealing treatment, the billet is removed from the heat treatment furnace and transferred to the press within 3 minutes. The process for the second forging is as follows: the billet is placed horizontally on the platform of the press, and the press head performs the first forging from one end of the billet to the other. After the first forging, the billet is rotated 60° axially, and the press head continues to perform the second forging from one end of the billet to the other. After the second forging, the billet is rotated 60° axially again, and the press head continues to perform the third forging from one end of the billet to the other, and so on, until the total deformation reaches 42%, thus completing the second forging and further producing the billet. The deformation of each adjacent forging is 4%. After the ninth forging, the temperature of the billet is 900℃. The process for the second annealing treatment is as follows: annealing temperature 1180℃, annealing time 1 hour, and no protective atmosphere is required during the second annealing treatment.

[0071] In step five, after the second annealing treatment, the billet is removed from the heat treatment furnace and transferred to the press within 3 minutes. The process for the third forging is as follows: the billet is placed horizontally on the platform of the press, and the press head performs the first forging from one end of the billet to the other. After the first forging, the billet is rotated 60° axially, and the press head continues to perform the second forging from one end of the billet to the other. After the second forging, the billet is rotated 60° axially again, and the press head continues to perform the third forging from one end of the billet to the other, and so on, until the total deformation reaches 19%, thus completing the third forging and further producing the billet. The deformation of each adjacent forging is 3%. After the sixth forging, the temperature of the billet is 900℃. The process for the third annealing treatment is as follows: annealing temperature 1200℃, annealing time 1 hour, and no protective atmosphere is required during the third annealing treatment.

[0072] In step six, after the third annealing treatment is completed, the billet is removed from the heat treatment furnace and transferred to the precision forging machine within 3 minutes. The radial forging process is as follows: the billet is installed on the precision forging machine, and the forging hammer performs the first radial forging from one end of the billet to the other to obtain an elliptical billet. After the first radial forging, the forging hammer performs the second radial forging from one end of the elliptical billet to the other to obtain a circular billet. After the second radial forging, the forging hammer performs the third radial forging from one end of the circular billet to the other to obtain an elliptical billet again. After the third radial forging, the forging hammer performs the fourth radial forging from one end of the elliptical billet to the other to obtain a circular billet again. After the fourth radial forging, the forging hammer performs the fifth radial forging from one end of the circular billet to the other to obtain a square billet. The deformation amount of each adjacent radial forging is 10%. After the fifth radial forging, the temperature of the square billet is 930℃. The process for the fourth annealing treatment is as follows: annealing temperature 1220℃, annealing time 1 hour, and no protective atmosphere is required during the fourth annealing treatment.

[0073] In step seven, after the fourth annealing treatment, the billet is removed from the heat treatment furnace and transferred to the hot rolling mill within 3 minutes. The hot rolling process involves at least two hot rolling cycles, with a deformation of 15% for each of the two adjacent hot rolling cycles. The final deformed CoCrMo alloy bar has a diameter of 35 mm.

[0074] Under the same test conditions and environment, the mechanical properties of the modified CoCrMo alloy bars prepared in the above three embodiments were tested. The test environment was 23℃, 48%RH, and the loading rate was 0.00025mm / s before yielding. The test results are shown in Table 1.

[0075] Table 1. Test results of mechanical properties of modified CoCrMo alloy bars

[0076] Example 1 1376 980 44.5 40.2 Example 2 1381 990 45.2 39.5 Example 3 1410 1089 45.1 40.1

[0077] As can be seen from Table 1, the mechanical properties of the processed CoCrMo alloy bar with a diameter of 35 mm are significantly improved, especially the tensile strength and yield strength. At the same time, the elongation and shrinkage of the alloy bar are also significantly improved.

[0078] Special Note: The technical solution of this invention involves numerous parameters, and the synergistic effects between these parameters must be comprehensively considered to achieve the beneficial effects and significant progress of this invention. Furthermore, the value ranges of each parameter in the technical solution were obtained through extensive experimentation. For each parameter and the combinations thereof, the inventors have recorded a large amount of experimental data; however, due to space limitations, the specific experimental data is not disclosed here.

[0079] Those skilled in the art will readily understand that the method for preparing the modified CoCrMo alloy rod of the present invention includes any combination of the inventive content and specific embodiments described in the above specification and the parts shown in the accompanying drawings. Due to space limitations and for the sake of brevity, not all of these combinations have been described in detail. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing modified CoCrMo alloy rods, characterized in that, The preparation method includes the following steps in sequence: Step 1: Prepare cylindrical CoCrMo alloy ingots according to design requirements; Step 2: Place the cylindrical CoCrMo alloy ingot into a heat treatment furnace for homogenization treatment; Step 3: After homogenization, place the cylindrical CoCrMo alloy ingot horizontally on the platform of the press. The press head performs the first forging from one end of the ingot to the other. After the first forging, rotate the ingot 60° axially and perform the second forging from one end of the ingot to the other. After the second forging, rotate the ingot 60° axially and perform the third forging from one end of the ingot to the other. Continue this process until the total deformation reaches 8-20%, thus completing the first forging and producing a billet. The deformation of each adjacent forging is 1-2%. Place the billet obtained from the first forging in a heat treatment furnace for the first annealing treatment. Step 4: After the first annealing treatment, place the billet horizontally on the platform of the press. The press head performs the first forging from one end of the billet to the other. After the first forging, rotate the billet 60° axially and the press head continues to perform the second forging from one end of the billet to the other. After the second forging, rotate the billet 60° axially and the press head continues to perform the third forging from one end of the billet to the other. This process is repeated until the total deformation reaches 25-45%, at which point the second forging is completed and the billet is further obtained. The deformation of each adjacent forging is 2-4%. Place the billet obtained from the second forging into a heat treatment furnace for the second annealing treatment. Step 5: After the second annealing process, place the billet horizontally on the platform of the press. The press head performs the first forging from one end of the billet to the other. After the first forging, rotate the billet 60° axially and perform the second forging from one end of the billet to the other. After the second forging, rotate the billet 60° axially and perform the third forging from one end of the billet to the other. Continue this process until the total deformation reaches 10-30%, thus completing the third forging and obtaining the billet. The deformation of each adjacent forging is 2-4%. Place the billet obtained from the third forging into a heat treatment furnace for the third annealing process. Step 6: After the third annealing process is completed, the billet is transferred to the precision forging machine for radial forging to obtain a square billet. The square billet obtained by radial forging is then placed in the heat treatment furnace for the fourth annealing process. Step 7: After the fourth annealing process, the billet is transferred to a hot rolling mill for hot rolling to obtain a bar. After the hot rolling is completed, the modified CoCrMo alloy bar can be obtained.

2. The method for preparing the modified CoCrMo alloy rod according to claim 1, characterized in that, In step one, the chemical composition of the cylindrical CoCrMo alloy ingot, by mass percentage, includes Cr 26.0-30.0wt%, Mo 5.0-7.0wt%, Ni≤1.0wt%, C≤0.35wt%, Fe≤0.75wt%, Si≤1.0wt%, Mn≤1.0wt%, N≤0.35wt%, with the balance being Co. The cylindrical CoCrMo alloy ingot is prepared by dual melting, namely, vacuum induction melting and protective atmosphere electroslag remelting. The key parameters of the vacuum induction melting process are: vacuum pressure not exceeding 30Pa during the cleaning stage, vacuum pressure not exceeding 10Pa during the refining stage, and pouring temperature of 1500-1550℃. The key parameters of the protective atmosphere electroslag remelting process are: melting speed not exceeding 4.5 kg / min, argon flow rate not less than 5 L / min, and feeding weight not less than 85 kg.

3. The method for preparing the modified CoCrMo alloy rod according to claim 2, characterized in that, In step two, the homogenization process for the cylindrical CoCrMo alloy ingot is as follows: the cylindrical CoCrMo alloy ingot is placed in a heat treatment furnace and heated from room temperature to 500°C at a rate of 5-10°C / min, and held for 1-2 hours; the temperature is then increased from 500°C to 900°C at a rate of 5-10°C / min, and held for 1-2 hours; the temperature is then increased from 900°C to 1150-1250°C at a rate of 5-10°C / min, and held for 1-6 hours; no protective atmosphere is required during the homogenization process.

4. The method for preparing the modified CoCrMo alloy rod according to claim 3, characterized in that, In step three, after the homogenization treatment is completed, the cylindrical CoCrMo alloy ingot is taken out of the heat treatment furnace and transferred to the press within 3 minutes; after the last forging of the first forging, the temperature of the billet is not lower than 900℃.

5. The method for preparing the modified CoCrMo alloy rod according to claim 4, characterized in that, In step three, the process of the first annealing treatment is as follows: annealing temperature 1150-1220℃, annealing time 1-3h, and no protective atmosphere is required during the first annealing treatment.

6. The method for preparing the modified CoCrMo alloy rod according to claim 5, characterized in that, In step four, after the first annealing treatment is completed, the billet is taken out of the heat treatment furnace and transferred to the press within 3 minutes; after the final forging of the second forging, the temperature of the billet shall not be lower than 900℃.

7. The method for preparing the modified CoCrMo alloy rod according to claim 6, characterized in that, In step four, the process of the second annealing treatment is as follows: annealing temperature 1100-1180℃, annealing time 1-3h, and no protective atmosphere is required during the second annealing treatment.

8. The method for preparing the modified CoCrMo alloy rod according to claim 7, characterized in that, In step five, after the second annealing process is completed, the billet is removed from the heat treatment furnace and transferred to the press within 3 minutes; after the final forging of the third forging process, the temperature of the billet shall not be lower than 900℃. The process for the third annealing treatment is as follows: annealing temperature 1120-1200℃, annealing time 1-4h, and no protective atmosphere is required during the third annealing treatment.

9. The method for preparing the modified CoCrMo alloy rod according to claim 8, characterized in that, In step six, after the third annealing treatment is completed, the billet is taken out from the heat treatment furnace and transferred to the precision forging machine within 3 minutes. The radial forging process is as follows: the billet is installed on the precision forging machine, and the forging hammer performs the first radial forging from one end of the billet to the other to obtain an elliptical billet. After the first radial forging, the forging hammer performs the second radial forging from one end of the elliptical billet to the other to obtain a circular billet. After the second radial forging, the forging hammer performs the third radial forging from one end of the circular billet to the other to obtain an elliptical billet again. After the third radial forging, the forging hammer performs the fourth radial forging from one end of the elliptical billet to the other to obtain a circular billet again. After the fourth radial forging, the forging hammer performs the fifth radial forging from one end of the circular billet to the other to obtain a square billet. The deformation amount of each adjacent radial forging is 6-12%. After the fifth radial forging, the temperature of the square billet is not lower than 930℃. The process for the fourth annealing treatment is as follows: annealing temperature 1150-1220℃, annealing time 1-4h, and no protective atmosphere is required during the fourth annealing treatment.

10. The method for preparing the modified CoCrMo alloy rod according to claim 9, characterized in that, In step seven, after the fourth annealing process is completed, the billet is taken out of the heat treatment furnace and transferred to the hot rolling mill within 3 minutes; the hot rolling process is as follows: at least two hot rollings, and the deformation amount of each of the two adjacent hot rollings is 10-30%.

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