A cobalt-based alloy UNS R30035 bar for processing fasteners and a manufacturing method thereof

Abstract

The invention provides a cobalt-based alloy UNS R30035 bar for processing fasteners and a manufacturing method thereof, wherein the composition of the bar includes C≤0.025%, Si≤0.15%, Mn≤0.15%, Cr: 19.0%-21.0%, Ni: 33.0%-37.0%, Mo: 9.00%-10.50%, Fe≤1.0%, Ti≤1.0%, B≤0.015%, and the remainder is Co and unavoidable impurities, and the manufacturing method includes the following steps: firstly, hot rolling of the steel ingot is performed to obtain the bar; then, high-temperature solid solution annealing heat treatment is performed, and then the bar is processed to the target specification by a cold drawing process, and the deformation amount and drawing speed of each pass are controlled; finally, after aging precipitation strengthening heat treatment, it is ensured that the final bar has ideal mechanical properties and surface quality. The method can effectively improve the strength and toughness of the bar, especially in the cold drawing process, surface defects are reduced by lubrication optimization, and the alloy is ensured to perform excellently in a high stress environment. The manufactured rods of the present invention can be widely used in the production of fasteners in the fields of medicine, ocean, oil field, gas field, chemistry, food processing, etc., and have significant market application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of high-strength alloy fasteners, and in particular to a cobalt-based alloy UNSR30035 bar for processing fasteners and a manufacturing method thereof. Background Art

[0002] As the core parts of mechanical connections, fasteners are widely used in many fields such as machinery and equipment, ships, aerospace, ocean, medicine, and oil and gas chemistry. These fields have strict requirements on the strength, corrosion resistance and processing performance of fastener materials. For example, in marine environments, fastener materials must have excellent seawater corrosion resistance; in high-stress working environments, such as aerospace and oil and gas field applications, materials are required to have high tensile strength and creep resistance.

[0003] Cobalt-based alloy UNS R30035 has become one of the ideal materials for producing fasteners due to its excellent corrosion resistance and high strength characteristics. The alloy provides excellent resistance to pitting and stress corrosion by adding chromium (Cr) and molybdenum (Mo), while its high nickel (Ni) content enhances the overall corrosion resistance, allowing the material to remain stable in acid, alkali and salt corrosion environments. In addition, the cobalt-based characteristics of UNS R30035 alloy give it excellent high-temperature strength and durability. However, despite the alloy's good performance foundation, traditional manufacturing processes have the following shortcomings in realizing its material potential:

[0004] Hot working stage: The high alloying characteristics of UNS R30035 alloy lead to poor hot working plasticity. In the traditional hot rolling process, coarse grains and uneven structure are prone to occur, which affects the subsequent processing performance. At the same time, due to the large deformation during hot working and the lack of reasonable deformation control measures in the process, the performance of the bar fluctuates greatly, affecting the consistency of the final product.

[0005] Cold working stage: Insufficient cold working deformation is the main bottleneck of traditional processes. In the common cold drawing process, in order to reduce the surface defects generated during the drawing process, the deformation is usually limited, resulting in insufficient cold working strengthening and difficulty in fully exerting the potential performance of the alloy. Larger deformation will cause surface cracks and processing defects due to insufficient material plasticity or increased friction between the die and the bar, thus affecting the surface quality and yield rate of the bar.

[0006] Heat treatment stage: In traditional processes, aging treatment has limited effect on optimizing the mechanical properties of alloys, especially it is difficult to achieve a good balance between tensile strength, ductility and plasticity. At the same time, the existing process has poor control over the precipitated phase, resulting in uneven distribution of the strengthening phase and failure to fully utilize the potential strength and toughness of the material.

[0007] Surface quality issues: Hot-rolled surface defects further expand during cold processing and become the main source of cracks on the bar surface. In addition, traditional lubrication measures are difficult to effectively reduce the friction between the die and the material, increasing the demand for pulling force and further weakening the surface quality and processing efficiency of the bar.

[0008] In summary, the existing technology faces the following problems when manufacturing cobalt-based alloy UNS R30035 bars for fasteners: insufficient control of the hot rolling process, limited cold working strengthening and poor surface quality, unsatisfactory aging treatment effect, and difficulty in stably achieving bar performance that meets high strength and high plasticity requirements. In order to solve the above technical problems, it is urgent to develop an optimized manufacturing process to significantly improve the mechanical properties and processing yield of the bars to meet the strict application requirements of fasteners in the fields of ocean, aerospace, medicine, oil and gas chemistry, etc. Summary of the invention

[0009] One of the technical problems to be solved by the present invention is to provide a cobalt-based alloy UNS R30035 bar for processing fasteners, so as to solve the problems of unstable mechanical properties, processing surface defects and difficulty in controlling cold processing deformation in conventional bars for processing fasteners in the prior art.

[0010] In order to overcome the defects of the above prior art, the present invention provides a cobalt-based alloy UNS R30035 bar for processing fasteners, comprising the following components in mass ratio: Cr: 19.0%-21.0%, Ni: 33.0%-37.0%, Mo:

[0011] 9.00%-10.50%, C≤0.025%, Si:≤0.15%, Mn:≤0.15%, S≤0.010%, P≤0.015%, Fe:≤1.0%, Ti:≤1.0%, B:≤0.015%, the balance is Co and unavoidable impurities.

[0012] Compared with the prior art, the cobalt-based alloy UNS R30035 bar material for processing fasteners of the present invention has the following advantages: the alloy of the present invention significantly improves the mechanical properties of the bar material by accurately regulating the composition, especially in terms of high strength, corrosion resistance and stress corrosion resistance, and the cobalt-based alloy UNS R30035 bar material for processing fasteners has high high-temperature strength, corrosion resistance, stress corrosion cracking resistance and good plasticity through the carefully designed composition in the bar material, and the alloy can maintain excellent mechanical properties and durability under high temperature environment, and is particularly suitable for key parts in the industries of medicine, ocean, oilfield chemistry and food processing, and specifically:

[0013] The Cr (chromium) content is between 19.0% and 21.0%, which helps to form a dense Cr2O3 protective film on the alloy surface, significantly improving the corrosion resistance of the material, especially the stability in corrosive media such as acid, alkali, and salt, ensuring its service life in extreme environments;

[0014] The Ni (nickel) content is between 33.0% and 37.0%, which works synergistically with Cr to further improve the corrosion resistance of the material and enhance the strength and toughness of the alloy;

[0015] The Mo (molybdenum) content is between 9.00% and 10.50%. In addition to enhancing corrosion resistance, it also improves the elastic limit, yield point and tensile strength of the alloy. Especially under high stress, the addition of Mo can effectively improve the alloy's resistance to pitting corrosion and reduce the risk of stress corrosion;

[0016] The trace addition of Ti (titanium) and B (boron) further enhances the structural stability and high-temperature performance of the material. Ti can refine the grains by forming a strengthening phase (such as TiC) and improve the high-temperature strength of the material. B helps to purify the grain boundaries and reduce the accumulation of harmful elements at the grain boundaries, thereby improving the corrosion resistance of the material and improving its overall performance;

[0017] The C (carbon) content is strictly controlled at ≤0.025%, avoiding the precipitation of excessive carbides, thereby ensuring that the toughness and strength of the alloy are not affected, especially in high temperature environments.

[0018] In a possible implementation, the mechanical properties of the cobalt-based alloy UNS R30035 bar for processing fasteners include: room temperature tensile strength Rm≥1793MPa, room temperature tensile yield strength Rp0.2≥1586MPa, room temperature tensile elongation A≥8%, and room temperature tensile section shrinkage≥35%.

[0019] Compared with the prior art, the rod of the present invention adopts the above technical solution, and can effectively improve the tensile strength and yield strength of the alloy by optimizing the alloy composition, especially adding elements such as Cr, Ni, and Mo, and ensure the stability of the material under high stress environment. The addition of Cr in the alloy improves the corrosion resistance, Ni further enhances the strength, and the addition of Mo improves the pitting resistance and high temperature strength, and improves the performance under extreme conditions. The trace addition of Ti and B further refines the grains, improves the high temperature stability of the alloy, and avoids the decrease in strength and toughness caused by grain growth.

[0020] Another technical problem to be solved by the present invention is to provide a method for manufacturing a rod material for processing fasteners of a cobalt-based alloy UNS R30035, so as to solve the problems of unstable mechanical properties, surface defects and low yield rate existing in the conventional method for manufacturing a rod material for processing fasteners in the prior art.

[0021] In order to overcome the above defects of the prior art, the present invention provides a method for manufacturing a bar material for processing fasteners of the cobalt-based alloy UNS R30035, comprising the following steps:

[0022] S1: hot rolling process: heating a square billet of a cobalt-based alloy UNS R30035 bar material for processing fasteners having the chemical composition of claim 1, and then rolling the billet to obtain a rolled bar;

[0023] S2: solution annealing heat treatment of rolled bars: cool the rolled bars obtained in step S1 and put them into an annealing furnace, keep them at 1050±15°C for 50 minutes, and then air cool them out of the furnace;

[0024] S3: cold drawing process: the rolled bar after being taken out of the furnace according to step S2 is cold drawn by a cold drawing machine, deformed by a fixed hole die, and the cold drawn bar is obtained by controlling the deformation amount and drawing speed of each pass;

[0025] S4: Heat treatment: The cold drawn bar obtained in step S3 is subjected to aging precipitation strengthening heat treatment to obtain a cobalt-based alloy UNS R30035 bar for processing fasteners.

[0026] Compared with the prior art, the method for manufacturing a rod material for processing fasteners of a cobalt-based alloy UNS R30035 of the present invention has the following advantages:

[0027] Optimize the cold drawing process: The manufacturing method of the present invention optimizes the cold drawing process by reasonably controlling the cold drawing deformation and drawing rate of each pass. The rod size and deformation of each pass are precisely controlled by the die. In combination with the innovative lubrication method between the rod and the die, the surface defects caused by excessive friction during the drawing process are effectively reduced. At the same time, a large deformation cold drawing deformation scheme is implemented during the cold drawing process, and a grain structure finer than level 8 is successfully obtained, which improves the mechanical properties of the material. Finally, the cold drawing process optimizes the surface quality while enhancing the strength and toughness of the material;

[0028] Hot rolling and solution annealing strengthening structure: The manufacturing method of the present invention controls the total rolling deformation to 76% in the hot rolling process, thereby obtaining a uniform and fine grain structure. Combined with the solution annealing heat treatment, the precipitation strengthening phases such as secondary carbides in the bar blank are dissolved, the cold working plasticity is further guaranteed, the processing performance of the bar is improved, and a good foundation is laid for the subsequent aging treatment;

[0029] Aging precipitation strengthening: The present invention ensures uniform distribution of precipitation phase in the alloy by precisely controlling the aging heat treatment temperature and time, further improving the strength and toughness of the bar, and meeting the application requirements in high temperature and high stress working environment;

[0030] In summary, the present invention successfully solves the problems of unstable mechanical properties, surface defects and low yield rate in the prior art by rationally designing and optimizing multiple process steps such as cold drawing, hot rolling, solution annealing and aging. Finally, the manufactured cobalt-based alloy UNS R30035 bar for processing fasteners has ultra-high strength, good toughness and excellent surface quality, which meets the needs of the field of high-end fasteners and has significant industrial application value.

[0031] In a possible implementation, in step S1, the heating treatment includes: charging the billet into a furnace at ≤600°C, heating the billet to 1160±10°C with the furnace, and keeping the temperature for 90 minutes.

[0032] Compared with the prior art, the above technical solution is adopted to charge the billet into the furnace at ≤600°C and heat it to 1160±10°C with the furnace, which helps to reduce the thermal stress of the material during the heating process and avoid cracks or local overheating of the alloy caused by excessively high initial temperature. Low-temperature heating also helps to gradually activate the internal structure of the material and prevent uneven temperature distribution due to drastic temperature differences, thereby reducing processing defects caused by uneven composition in the alloy. Further heat preservation for 90 minutes can ensure that the temperature inside the alloy is uniform, so that the grains of the alloy can complete the initial precipitation and dissolution process at a relatively uniform temperature, thereby providing ideal material properties for subsequent rolling and cold drawing. This time length can also ensure that some strengthening phases (such as carbides) in the alloy are fully dissolved, reducing problems such as hardening or uneven distribution of components in subsequent processing.

[0033] In a possible implementation, in the step S1, the starting rolling temperature is ≥1080°C, and the final rolling temperature is ≥920°C.

[0034] Compared with the prior art, the above-mentioned technical scheme is adopted, by designing the start rolling temperature to be greater than 1080°C, which helps to ensure that the material has sufficient plasticity at the initial stage of rolling, and reduces the phenomenon of increased deformation resistance caused by too low temperature. By increasing the start rolling temperature, it can promote the uniform distribution of the strengthening phase in the alloy, and avoid the occurrence of local poor plasticity, cracks or other defects caused by insufficient temperature; and the selection of the final rolling temperature determines the degree of grain refinement and organizational uniformity of the final product. The above-mentioned technical scheme of the present invention controls the final rolling temperature at ≥920°C, which can ensure that the material can maintain good plasticity after the final rolling, and avoid the situation where excessively high rolling temperature causes grain growth or uneven alloy structure. At the same time, it can effectively dissolve and distribute the strengthening phase in the alloy, and ensure that the final bar has good mechanical properties.

[0035] In a possible implementation, in step S1, the rolling conditions are: multiple rolling passes, and the deformation rate of each pass is 20%-35%, and the rolled rod is obtained by one-pass rolling.

[0036] Compared with the prior art, the above technical solution and the multi-pass rolling process are used to gradually reduce the cross-section of the material in stages, reduce the deformation of the material in each pass, and make the material more evenly stressed during the entire rolling process. The deformation rate of each pass is controlled within the range of 20%-35%, which can ensure that the plastic deformation of the alloy during the rolling process is within a reasonable range, and will not cause excessive local stress concentration, and can also achieve a sufficient deformation effect. A higher deformation rate is helpful for grain refinement and enhancing the uniformity of the material structure, while avoiding insufficient rolling caused by too low a deformation rate, and ensuring the strength and surface quality of the material; the one-fire rolling forming is used to avoid the temperature gradient problem that may be caused by multiple heating and cooling processes, thereby reducing the internal stress and deformation defects caused by temperature changes. At the same time, this method also improves production efficiency and reduces energy consumption.

[0037] In a possible implementation, in step S3, the cold drawing process further includes straightening the rolled rod, surface peeling and processing the rolled rod into a bright rod.

[0038] Compared with the prior art, the above technical scheme is adopted to correct the bending and irregular shapes of the hot-rolled bars caused by processing back to a straight shape through straightening, and then remove the oxide scale, surface impurities and potential surface defects generated during the hot rolling process through surface peeling. The removal of the oxide scale can reduce the friction that may be generated on the surface of the material during the cold drawing process, reduce the influence of friction, avoid uneven deformation or surface damage of the material, and further process it into a bright bar to ensure that the surface of the material is smooth and flawless, and reduce the surface roughness; through the pretreatment of straightening, surface peeling and bright bar processing, the surface quality and processing accuracy of the bar are effectively improved, the defects that may occur during the cold drawing process are reduced, and the stability and efficiency of the cold drawing process are improved.

[0039] In a possible implementation, in step S3, during the cold drawing process, a mixture of gasoline and graphite powder is evenly coated on the surface of the bright rod to reduce static friction between the rod and the mold.

[0040] Compared with the existing technology, the above-mentioned technical scheme can significantly reduce the static friction between the rod and the mold by applying a mixed coating of gasoline and graphite powder on the surface of the bright rod, thereby improving the smoothness and precision of the cold drawing process, improving the surface quality of the rod, and optimizing the mechanical properties of the material, ultimately making the cold drawing process more efficient and stable, and the final rod has better surface quality and mechanical properties, meeting high-standard industrial application requirements.

[0041] In a possible implementation, in step S3, the cold drawing treatment is performed in two passes, and the cold drawing deformation in the first pass is 20%, the cold drawing deformation in the second pass is 17%, and the drawing speed is 0.8 m / min.

[0042] Compared with the prior art, the above technical solution is adopted to carry out cold drawing deformation in two passes in the cold drawing process, which can effectively reduce the deformation amount of each pass, thereby avoiding surface defects and internal stress concentration caused by excessive deformation. In the first pass, the cold drawing deformation amount is 20%, which is moderate and helps to reduce the initial deformation resistance of the bar; while the deformation amount of the second pass is 17%, which further completes the final deformation. The two-pass design can balance the drawing force of each pass to ensure more uniform deformation, and through a slower drawing speed (0.8m / min), the friction between the material and the die can be effectively reduced, and the heat and surface damage caused by high friction can be reduced, thereby maintaining the surface smoothness of the bar. The lower drawing speed also helps to better control the strain rate of the bar during the cold drawing process, preventing surface defects caused by excessive speed; ultimately effectively improving the uniformity and stability of the cold drawing process.

[0043] In a possible implementation, in step S4, the conditions of the aging precipitation strengthening heat treatment are: heating the cold-drawn bar to 620±10°C at a rate of 75-100°C, keeping the temperature for 4 hours, and air-cooling after exiting the furnace.

[0044] Compared with the prior art, the above technical solution is adopted to heat the cold-drawn bar to 620±10°C at a rate of 75-100°C / h. The heating rate ensures the temperature uniformity of the alloy during the heating process, avoids excessive temperature difference or thermal stress caused by too fast heating, and maintains the stability and uniformity of the material. The heating rate is properly controlled to avoid excessive grain coarsening or uneven precipitation of strengthening phases caused by overheating, and ensures the uniformity and effect of the precipitated phase during the aging process; and the temperature is kept at 620±10°C for 4 hours. The selection of time and temperature allows the precipitated phase in the alloy to be fully dissolved and evenly distributed, which helps to improve the strength and hardness of the material and ensures that the mechanical properties of the final product are within the standard range. The time control of keeping warm for 4 hours can prevent excessive grain growth, thereby maintaining the toughness and strength of the material. The air cooling process after leaving the furnace controls the cooling rate of the material by natural cooling to avoid thermal stress caused by too fast cooling; through the above-mentioned aging precipitation strengthening heat treatment, the grain structure is further refined, the organizational structure of the material is optimized, and the uniformity and stability of the material are improved. DETAILED DESCRIPTION

[0045] First, those skilled in the art should understand that these implementations are only used to explain the technical principles of the embodiments of the present invention, and are not intended to limit the protection scope of the embodiments of the present invention. Those skilled in the art can make adjustments to them as needed to adapt to specific application scenarios.

[0046] The invention provides a cobalt-based alloy UNS R30035 bar for machining fasteners. The bar comprises the following components in mass ratio: Cr: 19.0%-21.0%, Ni: 33.0%-37.0%, Mo: 9.00%-10.50%, C≤0.025%, Si:≤0.15%, Mn:≤0.15%, S≤0.010%, P≤0.015%, Fe:≤1.0%, Ti:≤1.0%, B:≤0.015%, and the balance is Co and inevitable impurities.

[0047] Now with regard to the prior art, the cobalt-based alloy UNS provided by the present invention is R30035 bars for processing fasteners, the principle of its alloy composition system is analyzed: by adding Cr to improve the strength and corrosion resistance of the material, a dense Cr2O3 protective film is formed on the surface of the material to protect the inside of the material from oxidation and corrosion in the working environment, and increase the stability and service life of the material; adding Ni element and Cr synergistically can effectively enhance the effect of Ni element on improving the corrosion of the material; adding Mo element to improve the elastic limit, yield point and tensile strength of steel, and combining with C to produce MoC is conducive to recrystallization and refinement of the structure, which is conducive to uniform organization and improves the performance of the material; adding Ti and Al elements, by adding Ti element to refine the grain and uniform organization, at the same time, it can also form Ni3AlTi strengthening phase with Ni, further improving the strength of the material; adding B element, by combining B element with harmful elements to form crystallization points, reducing the aggregation of harmful elements at the grain boundary and purifying the grain boundary; in addition, controlling the content of impurity elements such as C, P, S, Fe, H, O, N at a low level to improve the purity of steel, is also conducive to reducing the generation of surface defects during cold working deformation, and is conducive to further improving the mechanical properties of the material.

[0048] As a preferred solution, the mechanical properties of the cobalt-based alloy UNS R30035 bar for processing fasteners include: room temperature tensile strength Rm≥1793MPa, room temperature tensile yield strength Rp0.2≥1586MPa, room temperature tensile elongation A≥8%, and room temperature tensile section shrinkage≥35%.

[0049] The present invention also provides a method for manufacturing a bar material for processing fasteners using the cobalt-based alloy UNS R30035, comprising the following steps:

[0050] S1: hot rolling process: heating a square billet of a cobalt-based alloy UNS R30035 bar material for processing fasteners having the chemical composition of claim 1, and then rolling the billet to obtain a rolled bar;

[0051] S2: solution annealing heat treatment of rolled bars: cool the rolled bars obtained in step S1 and put them into an annealing furnace, keep them at 1050±15°C for 50 minutes, and then air cool them out of the furnace;

[0052] S3: cold drawing process: the rolled bar after being taken out of the furnace according to step S2 is cold drawn by a cold drawing machine, deformed by a fixed hole die, and the cold drawn bar is obtained by controlling the deformation amount and drawing speed of each pass;

[0053] S4: Heat treatment: The cold drawn bar obtained in step S3 is subjected to aging precipitation strengthening heat treatment to obtain a cobalt-based alloy UNS R30035 bar for processing fasteners.

[0054] As a preferred solution, in step S1, the heating treatment comprises: charging the billet into a furnace at ≤600°C, heating the billet to 1160±10°C with the furnace, and keeping the temperature for 90 minutes.

[0055] As a preferred solution, in step S1, the starting rolling temperature is ≥1080°C, and the final rolling temperature is ≥920°C.

[0056] As a preferred solution, in step S1, the rolling conditions are: multiple rolling passes, and the deformation rate of each pass is 20%-35%, and the rolled rod is obtained by one-pass rolling.

[0057] As a preferred solution, in the step S3, the cold drawing process also includes straightening the rolled rod, surface peeling and processing the rolled rod into a bright rod.

[0058] As a preferred solution, in the step S3, during the cold drawing process, a mixture of gasoline and graphite powder is evenly coated on the surface of the bright rod to reduce the static friction between the rod and the mold.

[0059] As a preferred solution, in step S3, the cold drawing treatment conditions are: the cold drawing treatment is carried out in two passes, and the cold drawing deformation amount of the first pass is 20%, the cold drawing deformation amount of the second pass is 17%, and the drawing speed is 0.8 m / min.

[0060] As a preferred solution, in step S4, the conditions of the aging precipitation strengthening heat treatment are: heating the cold-drawn rod to 620±10°C at a rate of 75-100°C, keeping the temperature for 4 hours, and air-cooling after exiting the furnace.

[0061] The following provides a specific embodiment combined with data in combination with the above-mentioned technical solution to further expand the technical solution of the present invention:

[0062] Embodiment 1:

[0063] This embodiment provides a cobalt-based alloy UNS R30035 bar material for processing fasteners and a manufacturing method thereof. The cobalt-based alloy UNS R30035 bar material for processing fasteners includes the following components in mass ratio:

[0064] C: 0.015%, Si: 0.06%, Mn: 0.09%, S: 0.003%, P: 0.002%, Cr: 20.2%, Ni: 35.3%, Mo: 9.65%, Fe: 0.44%, Ti: 0.87%, B: 0.006%, Al: 0.215%, the balance is Co and unavoidable impurities;

[0065] The method for preparing the alloy comprises the following steps:

[0066] S1: hot rolling process: a 55 mm square billet of a cobalt-based alloy UNS R30035 fastener bar having the chemical composition is heated and sent to a 250 mm reciprocating rolling mill for multiple rolling to obtain a 32.2 mm Ø rolled bar;

[0067] S2: high temperature solution annealing heat treatment of rolled bars: the round bars rolled in step S1 are cooled and then placed in an annealing furnace at 1050±15°C for 50 minutes and then taken out of the furnace for air cooling;

[0068] S3: cold drawing process: after the high temperature solution annealing heat treatment is carried out in step S2, the bar is straightened, the surface is peeled, and the bar is processed into a 30.1 mm dia. bright bar. The bright bar is deformed through a fixed hole die under the tensile force of the cold drawing machine, and the 20.5 mm dia. cold drawn bar is obtained by controlling the deformation amount and drawing speed of each pass;

[0069] S4: Heat treatment: The bar material after the cold drawing process in step S3 is subjected to aging precipitation strengthening heat treatment to obtain a cobalt-based alloy UNS R30035 bar material for processing fasteners.

[0070] Embodiment 2:

[0071] This embodiment provides a cobalt-based alloy UNS R30035 bar material for processing fasteners and a manufacturing method thereof. The cobalt-based alloy UNS R30035 bar material for processing fasteners includes the following components in mass ratio:

[0072] C: 0.013%, Si: 0.045%, Mn: 0.103%, S: 0.0024%, P: 0.0028%, Cr: 20.45%, Ni: 35.55%, Mo: 9.85%, Fe: 0.47%, Ti: 0.85%, B: 0.0055%, Al: 0.224%, the balance is Co and unavoidable impurities;

[0073] The method for preparing the alloy comprises the following steps:

[0074] S1: hot rolling process: a 55 mm square billet of a cobalt-based alloy UNS R30035 fastener bar having the chemical composition is heated and sent to a 250 mm reciprocating rolling mill for multiple rolling to obtain a 32.18 mm Ø rolled bar;

[0075] S2: high temperature solution annealing heat treatment of rolled bars: the round bars rolled in step S1 are cooled and then placed in an annealing furnace at 1050±15°C for 50 minutes and then taken out of the furnace for air cooling;

[0076] S3: cold drawing process: after the high temperature solid solution annealing heat treatment is carried out in step S2, the bar is straightened, the surface is peeled, and the bar is processed into a 30.14 mm Φ bright bar. The bright bar is deformed by a fixed hole die under the tensile force of the cold drawing machine, and the 20.5 mm Φ cold drawn bar is obtained by controlling the deformation amount and the drawing speed of each pass;

[0077] S4: Heat treatment: The bar material after the cold drawing process in step S3 is subjected to aging precipitation strengthening heat treatment to obtain a cobalt-based alloy UNS R30035 bar material for processing fasteners.

[0078] Embodiment 3:

[0079] This embodiment provides a cobalt-based alloy UNS R30035 bar material for processing fasteners and a manufacturing method thereof. The cobalt-based alloy UNS R30035 bar material for processing fasteners includes the following components in mass ratio:

[0080] C: 0.011%, Si: 0.042%, Mn: 0.115%, S: 0.0019%, P: 0.0018%, Cr: 20.16%, Ni: 35.38%, Mo: 9.78%, Fe: 0.465%, Ti: 0.852%, B: 0.0049%, Al: 0.216%, the balance is Co and unavoidable impurities;

[0081] The method for preparing the alloy comprises the following steps:

[0082] S1: hot rolling process: a 55 mm square billet of a cobalt-based alloy UNS R30035 fastener bar having the chemical composition is heated and sent to a 250 mm reciprocating rolling mill for multiple rolling to obtain a 32.15 mm Ø rolled bar;

[0083] S2: high temperature solution annealing heat treatment of rolled bars: the round bars rolled in step S1 are cooled and then placed in an annealing furnace at 1050±15°C for 50 minutes and then taken out of the furnace for air cooling;

[0084] S3: cold drawing process: after the high temperature solid solution annealing heat treatment is carried out in step S2, the bar is straightened, the surface is peeled, and the bar is processed into a 30.14 mm Φ bright bar. The bright bar is deformed by a fixed hole die under the tensile force of the cold drawing machine, and the 20.5 mm Φ cold drawn bar is obtained by controlling the deformation amount and the drawing speed of each pass;

[0085] S4: Heat treatment: The bar material after the cold drawing process in step S3 is subjected to aging precipitation strengthening heat treatment to obtain a cobalt-based alloy UNS R30035 bar material for processing fasteners.

[0086] The rods prepared in Examples 1-3 were randomly sampled for analysis, and the room temperature tensile mechanical properties were tested in the laboratory.

[0087] According to the standard requirements of GB / T 228, tensile specimens were randomly cut from the bars prepared in Examples 1-3 to test their tensile strength, yield strength and elongation after fracture. The statistical analysis results are shown in Table 1, wherein the number of samples in the table is the number of actual bar samples taken, and a random sampling method is adopted. The test results are the average values ​​of the test results of each implementation case rounded off.

[0088] The existing UNS R30035 alloy was analyzed. The chemical composition of the existing UNS R30035 alloy is as follows: C: 0.016%, Si: 0.065%, Mn: 0.12%, S: 0.0033%, P: 0.0043%, Cr: 20.15%, Ni: 35.26%, Mo: 9.75%, Fe: 0.64%, Ti: 0.846%, B: 0.0055%, Al: 0.216%, and the balance is Co and unavoidable impurities.

[0089] The main production process is: 55mm square billet is hot rolled to obtain Ф25mm round bar, which is then subjected to high-temperature solution annealing heat treatment at 1050±15℃ and surface peeling to obtain Ф23.5mm, and then cold drawn to the target specification of Ф20mm, and finally subjected to aging precipitation strengthening heat treatment at 540-645℃ for 4 hours.

[0090] Comparative Example: Preparation method of existing UNS R30035 alloy:

[0091] S1: hot rolling process: a 55 mm square billet of a cobalt-based alloy UNS R30035 fastener bar having the chemical composition is heated and sent to a 250 mm reciprocating rolling mill for multiple rolling to obtain a 25 mm Ø rolled bar;

[0092] S2: high temperature solution annealing heat treatment of rolled bars: the round bars rolled in step S1 are cooled and then placed in an annealing furnace at 1050±15°C for 50 minutes and then taken out of the furnace for air cooling;

[0093] S3: cold drawing process: after the high temperature solution annealing heat treatment is carried out in step S2, the bar is straightened, the surface is peeled, and the bar is processed into a 23.5 mm dia. bright bar. The bright bar is deformed by a fixed hole die under the tensile force of the cold drawing machine. The cold drawing deformation is 15%, and the drawing speed is 0.9 m / min, so as to obtain a 20.5 mm dia. cold drawn bar;

[0094] S4: Heat treatment: The bar material after the cold drawing process in step S3 is subjected to aging precipitation strengthening heat treatment to obtain a cobalt-based alloy UNS R30035 bar material for processing fasteners.

[0095] The differences between the present invention and the manufacturing method include but are not limited to:

[0096] There are great differences in the control of cold and hot processing deformation: the hot rolling process of the preparation method of the present invention adopts a relatively small total deformation, hot rolling 30mm bar billets from 55mm square billets, and adopts two cold drawing processes in the cold drawing process to increase the control method of cold processing deformation, which is different from the existing process deformation control.

[0097] The following are the performance data of the UNS R30035 alloy bars prepared in the above-mentioned Examples 1-3 of the present invention and the existing UNS R30035 alloy bars, as shown in Table 1:

[0098] Table 1: Performance data of UNS R30035 rods prepared in Examples 1-3 and existing UNS R30035 rods

[0099]

[0100] Table 1 further proves that, compared with the existing UNS R30035 alloy bars, the square bars prepared in Examples 1-3 of the present invention have higher tensile strength. Although the elongation after fracture is reduced, the main performance indicators can meet the standard requirements. The bars manufactured by the existing UNS R30035 alloy bar process have an average tensile strength lower than the lower limit of the standard requirements, and there is a situation where the analysis results do not meet the standard requirements. Therefore, the manufacturing method of the present invention obtains a cobalt-based alloy UNS R30035 bar for processing fasteners with higher mechanical properties and more stable strength by controlling the deformation amount of hot working and cold working.

[0101] In summary, the present invention achieves the improvement of the performance of the cobalt-based alloy UNS R30035 bar for processing fasteners by accurately designing and optimizing the manufacturing process. The technical principle of the present invention is further explained from the aspects of manufacturing process and formula as follows:

[0102] Appropriately reduce the deformation amount of hot rolling: In the hot working stage, the final strengthening effect of the alloy mainly comes from the deformation during the cold working process, and the deformation amount in the hot working stage contributes less to the final strength of the material. Therefore, during the hot rolling process, the material only needs to be rolled to a size suitable for subsequent cold working to ensure that the subsequent processing can exert the maximum strengthening effect. In addition, the cobalt-based alloy UNS R30035 components (such as Cr, Ni, Mo and other elements) in the present invention make the alloy have higher strength and good corrosion resistance. Therefore, during the hot rolling process, it is not necessary to strengthen the material by excessive deformation, avoiding the degradation of material performance caused by excessive deformation.

[0103] Optimization of cold drawing process: The present invention effectively reduces the risk of surface defects caused by large deformation during cold working by reasonably controlling the deformation amount of each pass (20% for the first pass and 17% for the second pass) during the cold drawing process. This control method ensures the surface quality of the alloy while further enhancing the mechanical properties of the material. In addition, by improving the lubrication effect and reducing the drawing rate during the cold drawing process, it is ensured that the drawing force mainly acts on the deformation of the material rather than the surface, reducing material defects caused by uneven deformation. This process not only ensures the surface quality of the bar, but also refines the grains of the alloy, thereby improving the mechanical properties of the alloy.

[0104] Synergistic effect of alloy composition and manufacturing method: The composition of the cobalt-based alloy UNS R30035 of the present invention has been carefully optimized, especially in the addition of alloy elements such as Cr, Ni, Mo, Ti, B, etc., so that the alloy has excellent corrosion resistance, high temperature strength and good mechanical properties. Different from the traditional process, the present invention precisely controls the deformation amount during hot rolling and cold drawing, so that the alloy grains are uniform and the precipitation of strengthening phases (such as γ' phase and carbide) is more uniform, thereby further improving the strength, toughness and high temperature resistance of the alloy. In addition, the cooling rate control (especially rapid water cooling) in the aging heat treatment can effectively inhibit the growth of grains and retain fine strengthening phases after solution treatment, further optimizing the organization and performance of the alloy.

[0105] Through these optimized process steps, the present invention not only solves the problems of many surface defects and unstable mechanical properties in the cold drawing process in the prior art, but also significantly improves the strength, toughness and corrosion resistance of the final bar through the fine adjustment of the alloy composition and the synergy of the process. Finally, the manufactured cobalt-based alloy UNS R30035 bar for processing fasteners shows excellent performance in high stress and harsh working environments, meeting the high standard requirements for materials in the pharmaceutical, marine, oilfield chemical, food processing and other industries.

[0106] In the description of the present invention, the description with reference to the terms "one embodiment", "some embodiments", "in the present embodiment", "specific example", or "some examples" etc. means that the specific features, mechanisms, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, mechanisms, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0107] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A cobalt-based alloy UNS R30035 bar for processing fasteners, characterized in that: The invention comprises the following components in mass ratio: Cr: 19.0%-21.0%, Ni: 33.0%-37.0%, Mo: 9.00%-10.50%, C≤0.025%, Si:≤0.15%, Mn:≤0.15%, S≤0.010%, P≤0.015%, Fe:≤1.0%, Ti:≤1.0%, B:≤0.015%, and the balance is Co and unavoidable impurities.

2. The cobalt-based alloy UNS R30035 bar for processing fasteners according to claim 1, characterized in that: The mechanical properties of the cobalt-based alloy UNS R30035 bar for processing fasteners include: room temperature tensile strength Rm≥1793MPa, room temperature tensile yield strength Rp0.2≥1586MPa, room temperature tensile elongation after break A≥8%, and room temperature tensile section shrinkage≥35%.

3. A method for manufacturing a rod material for processing fasteners of cobalt-based alloy UNS R30035 as claimed in any one of claims 1 to 2, characterized in that: The following steps are involved: S1: hot rolling process: heating a square billet of a cobalt-based alloy UNS R30035 bar material for processing fasteners having the chemical composition of claim 1, and then rolling the billet to obtain a rolled bar; S2: solution annealing heat treatment of rolled bars: cool the rolled bars obtained in step S1 and put them into an annealing furnace, keep them at 1050±15°C for 50 minutes, and then air cool them out of the furnace; S3: cold drawing process: the rolled bar after being taken out of the furnace according to step S2 is cold drawn by a cold drawing machine, deformed by a fixed hole die, and the cold drawn bar is obtained by controlling the deformation amount and drawing speed of each pass; S4: Heat treatment: The cold drawn bar obtained in step S3 is subjected to aging precipitation strengthening heat treatment to obtain a cobalt-based alloy UNS R30035 bar for processing fasteners.

4. The method for manufacturing a rod for processing fasteners of cobalt-based alloy UNS R30035 according to claim 3, characterized in that: In the step S1, the heating treatment includes: charging the billet into a furnace at ≤600°C, heating the billet to 1160±10°C with the furnace, and keeping the temperature for 90 minutes.

5. The method for manufacturing a rod for processing fasteners of cobalt-based alloy UNS R30035 according to claim 3, characterized in that: In the step S1, the starting rolling temperature is ≥1080°C, and the final rolling temperature is ≥920°C.

6. The method for manufacturing a rod for processing fasteners of cobalt-based alloy UNS R30035 according to claim 3, characterized in that: In the step S1, the rolling conditions are: multiple rolling passes, and the deformation rate of each pass is 20%-35%, and the rolled rod is obtained by one-pass rolling.

7. The method for manufacturing a rod for processing fasteners of cobalt-based alloy UNS R30035 according to claim 3, characterized in that: In the step S3, the cold drawing process also includes straightening the rolled rod, surface peeling and processing the rolled rod into a bright rod.

8. The method for manufacturing a rod material for processing fasteners of cobalt-based alloy UNS R30035 according to claim 7, characterized in that: In the step S3, during the cold drawing process, the surface of the bright rod is evenly coated with a mixture of gasoline and graphite powder to reduce the static friction between the rod and the mold.

9. The method for manufacturing a rod for processing fasteners of cobalt-based alloy UNS R30035 according to claim 3, characterized in that: In step S3, the cold drawing treatment is performed in two passes, and the cold drawing deformation in the first pass is 20%, the cold drawing deformation in the second pass is 17%, and the drawing speed is 0.8 m / min.

10. The method for manufacturing a rod for processing fasteners of cobalt-based alloy UNS R30035 according to claim 3, characterized in that: In step S4, the conditions of the aging precipitation strengthening heat treatment are: heating the cold-drawn bar to 620±10°C at a rate of 75-100°C, keeping the temperature for 4 hours, and air-cooling after taking out of the furnace.

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