A high purity corrosion resistant alloy and preparation method thereof

Abstract

The present invention provides a high-purity corrosion-resistant alloy and a preparation method thereof, which are suitable for the field of low-temperature superconductivity. The composition of the alloy includes: C < 0.008%, Mn < 0.50%, S < 0.010%, Co < 0.90%, Mo, Cr, Fe, Ni and other elements, and the sum of Cr, Fe, Ni, Mo and W is greater than 99.0%. By optimizing the alloy composition and smelting process, its corrosion resistance and purity are improved. The preparation method adopts steps such as vacuum induction smelting, argon protection electroslag remelting and high vacuum consumable remelting to effectively remove impurities and gases, further improve the purity and performance of the alloy, and further improve the purity, low gas content and corrosion resistance of the alloy by accurately controlling the temperature, vacuum degree and alloy composition during the smelting process. The alloy of the present invention has excellent corrosion resistance and mechanical properties, can be widely used in high-end precision electronic equipment and low-temperature superconducting technology, replace imported materials, and has good market prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of corrosion-resistant alloy preparation, and in particular to a high-purity corrosion-resistant alloy and a preparation method thereof. Background Art

[0002] Corrosion-resistant alloys are important materials widely used in many fields, especially in the pharmaceutical, chemical, hydrometallurgical, marine engineering, flue gas desulfurization equipment for pollution control, and oil and gas extraction industries. Their excellent corrosion resistance makes them an indispensable structural material in these fields. In the field of low-temperature superconducting materials, corrosion-resistant alloys also have important applications. At present, the technical level of corrosion-resistant alloys is relatively mature. However, the corrosion-resistant alloys commonly used in the market, especially C-276 alloy, still have some technical bottlenecks, which are mainly reflected in the following aspects.

[0003] First, the existing corrosion-resistant alloy materials have certain deficiencies, especially in terms of purity. Traditional corrosion-resistant alloy materials are usually produced through conventional smelting processes, but these processes are prone to introduce high impurity and gas contents, especially elements such as nitrogen, oxygen and hydrogen. These impurities will significantly affect the mechanical properties and corrosion resistance of the alloy. For example, in the production process of C-276 alloy, the nitrogen and oxygen contents are relatively high. The presence of these elements not only affects the strength and corrosion resistance of the alloy, but also easily causes problems such as intergranular corrosion.

[0004] Secondly, the existing corrosion-resistant alloys have a high level of inclusions, especially non-metallic inclusions, which have a negative impact on the overall performance of the material. The presence of inclusions will increase the brittleness of the material and reduce its stability and reliability in extreme working environments. Therefore, how to reduce inclusions in the alloy, especially non-metallic inclusions, becomes the key to improving the performance of corrosion-resistant alloys.

[0005] In addition, although existing corrosion-resistant alloys have been widely used in many application fields, due to technical limitations, most corrosion-resistant alloys still rely on imports, resulting in high prices and long delivery cycles. Especially in the field of low-temperature superconducting materials, my country still relies heavily on high-purity corrosion-resistant alloys and cannot meet the domestic market's demand for such materials. This not only restricts the development of related technologies, but also affects the competitiveness of domestic products in the international market.

[0006] The corrosion-resistant alloys of the prior art, such as C-276 alloy, have certain corrosion resistance, but due to insufficient process control during the smelting process, their impurity content (such as C, S, P, etc.) and gas element content (such as O, N, H) are relatively high, resulting in high inclusion levels and poor processing plasticity, making it difficult to meet high purity requirements in special application fields such as low-temperature superconductivity. In addition, its alloy design cannot effectively inhibit the precipitation of harmful phases, resulting in the material showing insufficient performance in complex corrosive environments.

[0007] In summary, the corrosion-resistant alloy materials in the existing technology have problems such as insufficient purity, excessive inclusion content, impurity elements affecting performance, and domestic market dependence on this material. These problems need to be solved urgently to improve the performance of corrosion-resistant alloys, reduce production costs, break the dependence on imports, and achieve domestic substitution. Summary of the invention

[0008] The technical problem to be solved by the present invention is to provide a high-purity corrosion-resistant alloy to solve the problems of insufficient purity, high inclusion level, high impurity content and unstable corrosion resistance of conventional corrosion-resistant alloys in the prior art.

[0009] In order to overcome the defects of the above-mentioned prior art, the present invention provides a high-purity corrosion-resistant alloy, whose components include by weight percentage: Mo: 15.00-19.00%, Cr: 14.50-18.00%, Fe: 4.70-7.00%, W: 3.00-4.50%, C: <0.008%, Mn: <0.50%, S: <0.010%, Co: <0.90%, V: <0.35%, P: <0.025%, the remainder is Ni and unavoidable impurities, and the sum of Cr, Fe, Ni, Mo and W components is greater than 99.0%.

[0010] Compared with the prior art, the high-purity corrosion-resistant alloy of the present invention has the following advantages: the pitting and crevice corrosion resistance of the alloy is significantly improved by precisely controlling the content of Mo and W (15.00-19.00% and 3.00-4.50%, respectively); the Cr content (14.50-18.00%) is controlled to ensure the formation of a dense Cr2O3 protective film on the surface of the alloy, effectively inhibiting the corrosion of the base metal by the corrosive environment, and improving the stability and service life; the synergistic effect of the base Ni and Cr enhances the corrosion resistance, and the appropriate amount of Fe (4.70-7.00%) is added, The method not only reduces the cost of raw materials, but also inhibits the precipitation of harmful phase Ni4Mo, and improves the crack sensitivity of the alloy during hot and cold processing; controls the C and Si contents within an extremely low range (C < 0.008%, Si < 0.05%), and improves the alloy's resistance to intergranular corrosion and pitting corrosion; through the above-mentioned component optimization, the alloy of the present invention successfully solves the problems of high impurity content, high inclusion level, insufficient corrosion resistance and poor mechanical processing performance in the prior art, making the high-purity corrosion-resistant alloy not only suitable for conventional corrosion environments, but also particularly suitable for the corrosion resistance requirements of low-temperature superconducting fields, marine engineering and high-end equipment.

[0011] In a possible embodiment, its components include by weight percentage: Mo: 16.80-16.90%, Cr: 17.10-17.30%, Fe: 6.15-6.25%, W: 4.10-4.20%, C: <0.0070%, Mn: <0.25%, S: <0.0030%, Co: <0.070%, V: <0.020%, P: <0.0020%, the remainder is Ni and unavoidable impurities, and the sum of Cr, Fe, Ni, Mo, and W components is greater than 99.0%.

[0012] Compared with the prior art, by adopting the above technical scheme and through the design of the above optimized components, the high-purity corrosion-resistant alloy significantly improves the corrosion resistance, purity and hot working performance of the material, and contains fewer inclusions in the alloy, overcoming the problems of insufficient corrosion resistance, high impurity content and high inclusion level in the prior art. It is particularly suitable for the field of low-temperature superconductivity and occasions with extremely high requirements for corrosion resistance and purity.

[0013] Another technical problem to be solved by the present invention is to provide a method for preparing the high-purity corrosion-resistant alloy, so as to solve the problems of insufficient purity, lax impurity control, difficulty in effectively removing inclusions, high gas content and low process efficiency existing in the conventional corrosion-resistant alloy preparation methods in the prior art.

[0014] In order to overcome the above defects of the prior art, the present invention provides a method for preparing the high-purity corrosion-resistant alloy, comprising the following steps:

[0015] S1: mixing the raw materials in proportion, smelting and casting the electrode rod in a vacuum induction furnace, wherein the chemical composition of the electrode rod is the same as the chemical composition of the high-purity corrosion-resistant alloy;

[0016] S2: remelting the electrode rod ingot in step a through electroslag in an argon protective atmosphere, and filtering and purifying the molten slag to obtain an electroslag ingot;

[0017] S3: subjecting the electroslag ingot obtained in step S2 to consumable remelting in a high vacuum atmosphere, further degassing by consumable remelting, and removing inclusions to obtain a high-purity corrosion-resistant alloy.

[0018] Compared with the prior art, the preparation method of a high-purity corrosion-resistant alloy in the present application has the following advantages: the preparation method of the present invention changes the single vacuum smelting process in the prior art into a multi-stage vacuum extraction and argon filling process, ensuring that the oxygen and nitrogen contents in the smelting process are greatly reduced (O≤0.0015%, N≤0.0030%), and at the same time, through the precise addition of metal Al and Mn, strict control of impurities such as C, S, and P is achieved, and ultimately the purity of the alloy is improved, and the argon-protected electroslag remelting in S2 ensures the removal of large-particle inclusions through the combined filtration of molten slag and optimizes the grain refinement effect; while the high-vacuum consumable remelting in S3 is further degassed, arc vibration is used as It can effectively remove fine inclusions and improve the overall cleanliness of the alloy; in the preparation process of the present invention, the content of gas impurities such as H, O, and N is reduced to the industry's limit level (H≤0.0003%, O≤0.0015%, N≤0.0030%) through a combination of high vacuum and protective atmosphere, ensuring the corrosion resistance and hot working performance of the material in an extreme corrosive environment, greatly improving the accuracy of process control and smelting efficiency, while ensuring the uniformity of the final alloy's structure and performance stability; the present invention has achieved breakthrough improvements in smelting, impurity control, and inclusion removal through a multi-stage optimized preparation process, solving the problem of preparing high-purity corrosion-resistant alloys in the prior art. The high-purity corrosion-resistant alloy finally prepared has more excellent corrosion resistance, mechanical properties, and processing properties, and is particularly suitable for the field of low-temperature superconductivity and other high-end application scenarios with extremely high requirements for purity and performance.

[0019] In a possible implementation, in step S1, the conditions for smelting in the vacuum induction furnace are as follows: the vacuum induction furnace is filled with argon after the first vacuuming, and then vacuumed for the second time. The material can be oxidized only after the second vacuuming is completed. After more than 50% of the material is oxidized, metal Cr is added to the vacuum induction furnace. After all the raw materials are oxidized, the vacuum induction furnace is evacuated for the third time, and when the oxygen content in the vacuum induction furnace is lower than 15PPM and the nitrogen content is lower than 30PPM, metal Al, Ni-Mg alloy and metal Mn are added.

[0020] Compared with the prior art, the above technical solution can gradually discharge the residual gas in the furnace through multiple vacuuming processes combined with argon filling steps, reduce the content of oxygen, nitrogen and other volatile impurities, and reduce the oxidation risk caused by the contact between molten steel and air. In addition, through multiple vacuuming and the addition of key elements, the weakening of alloy properties by low-melting-point inclusions (such as FeS) and gas inclusions (such as H2, O2) is minimized, and the purification efficiency of inclusions by subsequent electroslag remelting and consumable remelting is improved. Finally, the material purity, corrosion resistance and comprehensive mechanical properties of high-purity corrosion-resistant alloys are significantly improved, and it has obvious advantages over the prior art in terms of process controllability and product performance. .

[0021] In a possible implementation, in step S1, the first vacuuming condition is: evacuating the air pressure in the vacuum induction furnace to ≤0.67Pa, the second vacuuming condition is: after the argon filling is completed, the air pressure in the vacuum induction furnace is evacuated again to ≤0.67Pa, and the third vacuuming condition is: evacuating the vacuum induction furnace to ≤0.5Pa and maintaining it for 60-90min.

[0022] Compared with the existing technology, the above technical scheme can effectively improve the quality of high-purity corrosion-resistant alloys and reduce the content of impurities and gas by further optimizing the vacuum induction furnace vacuum pumping process, thereby obtaining excellent corrosion resistance and mechanical properties, and providing a more controllable and efficient smelting process for alloy production.

[0023] In a possible implementation, in step S1, after adding metal Al, Ni-Mg alloy and metal Mn, the impurity content in the molten steel in the furnace is: C≤0.008%, S≤0.010%, P≤0.010%, H≤0.0003%, O≤0.0015%, N≤0.0030%.

[0024] Compared with the prior art, the above technical solution can significantly reduce the impurity content in the molten steel, especially in controlling the content of elements such as C, S, P, H, O and N. By precisely controlling the added metal Al, Ni-Mg alloy and metal Mn, the efficiency of deoxidation, desulfurization, dephosphorization and removal of impurities such as nitrogen in the smelting process is optimized, thereby improving the purity of the molten steel.

[0025] In a possible embodiment, in the step S2, the operation of electroslag remelting the electrode rod ingot in an argon protective atmosphere includes: grinding the surface of the electrode rod to remove surface impurities, removing shrinkage defects, using a low melting rate of 3.5-2.8kg / min, the water temperature is controlled at 28±2°C, and the flow rate of Ar gas is stabilized at 80PLM to ensure that most of the inclusions in the electrode rod are removed and refined after combined filtration of the molten slag.

[0026] Compared with the prior art, the above technical solution can make the molten steel fully contact with the slag at a slower cooling rate by controlling the low melting rate (3.5-2.8kg / min), thereby accelerating the removal of impurities and inclusions; by grinding the surface of the electrode rod and removing the shrinkage defects, the accumulation of impurities caused by surface irregularities and defects is reduced, and the filtering effect of the slag on inclusions is enhanced. By controlling the water temperature (28±2℃) and the Ar gas flow (stable at 80PLM), the smelting process can be stabilized, avoiding the influence of temperature fluctuations and unstable airflow on the smelting quality that may occur during the smelting process. The precise control of water temperature helps to maintain the stability of the cooling rate during the smelting process, avoids the precipitation of harmful phases and uneven smelting process that may be caused by excessive cooling, and ultimately improves the purity of the alloy, improves the performance of the material, and solves the problem of low impurity removal efficiency during the smelting process in the prior art.

[0027] In a possible implementation, in step S3, the high vacuum atmosphere consumable remelting includes: smelting at a low melting rate of 3.5-2.8 kg / min under the condition of a vacuum degree of ≤0.5 Pa, using the arc to vibrate the molten steel to discharge inclusions to the edge of the liquid surface, and performing subsequent heat processing after the surface impurities and defects of the consumable ingot are polished.

[0028] Compared with the prior art, by adopting the above-mentioned technical scheme, through the consumable remelting treatment in the above-mentioned high vacuum atmosphere, the purity of the alloy is significantly improved, and impurities such as inclusions and gas content are reduced, so that the alloy performs better in terms of corrosion resistance and strength, removes impurities in the alloy, and optimizes its performance.

[0029] In a possible implementation, in the steps S2 and S3, the electrode rod ingot is subjected to pretreatment of the electroslag ingot before being subjected to electroslag remelting in an argon protective atmosphere and consumable remelting in a high vacuum atmosphere, and the pretreatment includes: polishing the surface of the electroslag ingot and cutting off the head and tail.

[0030] Compared with the prior art, the above-mentioned technical scheme can effectively remove coarse inclusions and defective areas on the surface of the electroslag ingot by pre-treating the electroslag ingot. The polishing treatment uses mechanical processing to remove the uneven and defective parts of the surface, thereby ensuring the uniformity of the alloy quality in the subsequent smelting process, significantly improving the purity of the alloy, and enhancing its subsequent processing performance and stability in use, solving the problems of insufficient alloy purity and many surface defects in the prior art. DETAILED DESCRIPTION

[0031] 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 application, and are not intended to limit the protection scope of the embodiments of the present application. Those skilled in the art can make adjustments to them as needed to adapt to specific application scenarios.

[0032] The invention provides a high-purity corrosion-resistant alloy, which comprises, by weight percentage, Mo: 15.00-19.00%, Cr: 14.50-18.00%, Fe: 4.70-7.00%, W: 3.00-4.50%, C: <0.008%, Mn: <0.50%, S: <0.010%, Co: <0.90%, V: <0.35%, P: <0.025%, the remainder is Ni and unavoidable impurities, and the sum of Cr, Fe, Ni, Mo and W components is greater than 99.0%.

[0033] The composition of the high purity corrosion resistant alloy in the present invention is mainly designed based on the following ideas:

[0034] C in the corrosion-resistant alloy mainly forms carbides with the added Cr and Fe, enhancing the strength and corrosion resistance of the material. However, the higher the C content, the more chromium carbides will be formed, resulting in a decrease in the Cr content in the solid solution and the formation of a chromium-poor area around the carbides, thereby reducing the corrosion resistance of the steel. Therefore, in the present invention, C is controlled to be ≤ 0.015%, and the smaller the better. However, during the vacuum smelting process, C will combine with O to produce CO that overflows the molten steel and is discharged with vacuum. Therefore, during the vacuum smelting process, C is added according to the upper limit value of 0.008.

[0035] Cr can improve the corrosion resistance and strength of steel materials. In the present invention, the Cr content is controlled within 16.50%≤Cr≤17.50%, which improves the corrosion resistance of steel and the strength of the material. Therefore, in the present invention, the Cr content is controlled according to the standard upper limit value.

[0036] Ni is an alloying element that forms austenite. In the present invention, Ni is a matrix element, and Ni can improve the corrosion resistance of steel materials. Compared with ferrite, martensite, bainite and other structures, austenite steel materials have more stable structures and more stable performance. Therefore, the material has better corrosion resistance and stable mechanical properties in the use environment.

[0037] Mn and Al are both elements that are easy to combine with O. The addition of these elements ensures that the steel liquid is fully deoxidized during the smelting process, so that the O content in the material is lower and the hot processing performance of the material is ensured. On the other hand, the material is strengthened to make the material have higher strength. Mn can also combine with S to produce MnS, which has a higher melting point than FeS, reduces the hot brittleness of the material, and improves the hot processing plasticity of the material. Therefore, the Mn element in the present invention is controlled at 0.2-0.3%; the main role of Al is the deoxidation effect during the smelting process, and its strengthening effect is that it can combine with Ni in the material to precipitate Ni3Al strengthening phase, which greatly improves the strength of the material. However, in the present invention, the formation of the alloy phase will form a basin chromium area, which reduces the material's pitting resistance. At the same time, the combination of Al and O is the main source of impurities in the corrosion-resistant alloy involved in the present invention, and excessive addition should be avoided. Therefore, the content of Al in the present invention is controlled at 0.03-0.05%.

[0038] Mo is the main strengthening element in the alloy and is also an important element that is indispensable for the alloy to have good corrosion resistance, but its cost is relatively high. Therefore, the alloy of the present invention contains Mo element at a controlled rate of 16.5-17.5%.

[0039] As a strengthening element in the alloy, W, similar to Mo, mainly improves the local corrosion resistance of the alloy, such as pitting corrosion resistance and crevice corrosion resistance. In the alloy involved in the present invention, W is added in an amount of 3.80-4.20%.

[0040] The Fe element is mainly used to reduce the raw material cost of the alloy, and at the same time to inhibit the precipitation of harmful phase Ni4Mo and reduce the crack sensitivity of the alloy during processing. In the alloy involved in the present invention, Fe is controlled to be added at 5.50-6.50%.

[0041] Co, V, P, S, H, O, N and the like are impurity elements. The main purpose of the present invention is to reduce the content of these elements in the material as much as possible through vacuum induction smelting, protective atmosphere electroslag remelting and consumable remelting, thereby improving the purity of the material, ensuring the thermal processing performance of the material and making the material have better corrosion resistance.

[0042] As a preferred solution, its components include by weight percentage: Mo: 16.80-16.90%, Cr: 17.10-17.30%, Fe: 6.15-6.25%, W: 4.10-4.20%, C: <0.0070%, Mn: <0.25%, S: <0.0030%, Co: <0.070%, V: <0.020%, P: <0.0020%, the remainder is Ni and unavoidable impurities, and the sum of Cr, Fe, Ni, Mo and W components is greater than 99.0%.

[0043] The present invention also provides a method for preparing the high-purity corrosion-resistant alloy, comprising the following steps:

[0044] S1: mixing the raw materials in proportion, smelting and casting the electrode rod in a vacuum induction furnace, wherein the chemical composition of the electrode rod is the same as the chemical composition of the high-purity corrosion-resistant alloy;

[0045] S2: remelting the electrode rod ingot in step a through electroslag in an argon protective atmosphere, and filtering and purifying the molten slag to obtain an electroslag ingot;

[0046] S3: subjecting the electroslag ingot obtained in step S2 to consumable remelting in a high vacuum atmosphere, further degassing by consumable remelting, and removing inclusions to obtain a high-purity corrosion-resistant alloy.

[0047] The preparation method and the formula of the present invention also have a synergistic effect:

[0048] The element ratio design in the composition formula and the process control of the preparation method are highly matched and work synergistically with each other to jointly ensure the purity, corrosion resistance and mechanical properties of the final alloy.

[0049] Synergistic effect of Cr, Mo, W and vacuum smelting: High content of Cr (14.50-18.00%) and Mo (15.00-19.00%) in the formula can form dense oxide (such as Cr2O3) and molybdate passivation film on the alloy surface, significantly improving the corrosion resistance of the material.

[0050] During the vacuum induction furnace smelting (S1), the oxygen content is effectively reduced by staged vacuum extraction and precise addition of deoxidizers (such as Al and Mn), avoiding the formation of oxide inclusions of Cr and Mo, and improving the utilization rate of Cr and Mo in the alloy and its corrosion resistance.

[0051] Synergistic effect of low-impurity formula and vacuum remelting: Impurities such as C, S, P, H in the formula are strictly controlled in an ultra-low range (such as C < 0.008%, S < 0.010%, etc.), which is the basis for ensuring the high purity and intergranular corrosion resistance of the alloy.

[0052] Vacuum consumable remelting (S3) further removes trace gases (such as H, O, N) and inclusions through high vacuum conditions and low melting rate operation, minimizes the content of impurity elements, and synergizes with the low impurity design of the formula to ensure the purity and corrosion resistance of the final alloy.

[0053] The control of Fe and the coordination of strengthening process: the Fe content in the formula is strictly controlled at 4.70-7.00%, which not only reduces the cost, but also inhibits the precipitation of harmful phases (such as Ni4Mo) through optimization in the vacuum melting process, reduces the sensitivity of processing cracks, and improves the processing performance in combination with precise heat treatment.

[0054] Argon-shielded electroslag remelting (S2) refines the grains and evenly distributes alloying elements such as Fe, which complements this ratio design.

[0055] Synergistic effect of W ratio and inclusion removal process: W, as an anti-corrosion element, enhances the resistance to pitting and crevice corrosion by precisely controlling its content (3.00-4.50%) in the formula.

[0056] During the vacuum consumable remelting process, the inclusions are discharged to the surface of the molten pool through the action of the vibrating arc, which effectively avoids the deterioration effect caused by the combination of W and inclusions and improves the local corrosion resistance of the alloy.

[0057] The steps are also closely synergized through reasonable division of labor and technical connection, which greatly improves the purity and performance of the alloy.

[0058] The synergy of S1 vacuum induction smelting and S2 argon-protected electroslag remelting: S1 smelting removes raw material impurities (such as O, N, S) initially, and improves the purity of molten steel by adding deoxidizers (such as Al, Mn), while controlling the content of impurities such as C and P; S2 electroslag remelting further removes large-particle inclusions and non-metallic inclusions through the filtering effect of molten slag, and evenly distributes alloy elements. This process effectively makes up for the limited removal rate of inclusions in vacuum induction smelting, and significantly improves the purity and uniformity of the alloy.

[0059] The synergy of S2 electroslag remelting and S3 vacuum consumable remelting: S2 electroslag remelting mainly targets large-particle inclusions to ensure the first step of purification; S3 consumable remelting further degasses and removes fine inclusions (such as sulfide and oxide inclusions) and gas impurities (such as H, O, N) under high vacuum conditions to achieve the final high purity. The combination of the two greatly reduces the gas and inclusion content in the finished alloy, and ultimately achieves excellent corrosion resistance and mechanical properties; S3 vacuum consumable remelting and subsequent processing synergy: In S3, high vacuum and low melting rate smelting is used to optimize grain distribution and reduce the weakening effect of inclusions on grain boundaries. This process significantly improves the plasticity and processing properties of the alloy in subsequent hot processing (such as forging and heat treatment), while reducing crack sensitivity.

[0060] Coordination of vacuum control and impurity removal at each stage: impurities (such as C, S, P, O, N) are gradually reduced in S1, S2 and S3. The impurity control and removal efficiency of each step are superimposed to ensure the purity of the final alloy, including S1 preliminary control of C≤0.008%, S2 removal of large particle inclusions, and S3 removal of gas impurities and fine inclusions, achieving the best effect step by step.

[0061] As a preferred scheme, in step S1, the conditions for smelting in the vacuum induction furnace are: the vacuum induction furnace is filled with argon after the first vacuuming, and then vacuumed for the second time. The material can be oxidized only after the second vacuuming is completed. After the material is oxidized by more than 50%, metal Cr is added to the vacuum induction furnace. After all the raw materials are oxidized, the vacuum induction furnace is evacuated for the third time, and when the oxygen content in the vacuum induction furnace is lower than 15PPM and the nitrogen content is lower than 30PPM, metal Al, Ni-Mg alloy and metal Mn are added.

[0062] As a preferred scheme, in step S1, the condition for the first vacuuming is: the air pressure in the vacuum induction furnace is evacuated to ≤0.67Pa, the condition for the second vacuuming is: after the filling of argon gas is completed, the air pressure in the vacuum induction furnace is evacuated again to ≤0.67Pa, and the condition for the third vacuuming is: the vacuum induction furnace is evacuated to ≤0.5Pa and maintained for 60-90min.

[0063] As a preferred solution, in step S1, after adding metal Al, Ni-Mg alloy and metal Mn, the impurity content in the molten steel in the furnace is: C≤0.008%, S≤0.010%, P≤0.010%, H≤0.0003%, O≤0.0015%, N≤0.0030%.

[0064] As a preferred solution, in step S2, the operation of electroslag remelting the electrode rod ingot in an argon protective atmosphere includes: grinding the surface of the electrode rod to remove surface impurities, removing shrinkage defects, using a low melting rate of 3.5-2.8kg / min, the water temperature is controlled at 28±2°C, and the flow rate of Ar gas is stabilized at 80PLM to ensure that most of the inclusions in the electrode rod are removed and refined after combined filtration of the molten slag.

[0065] As a preferred solution, in step S3, the high vacuum atmosphere consumable remelting includes: adopting a low melting rate of 3.5-2.8 kg / min for smelting under the condition of vacuum degree ≤ 0.5 Pa, using the arc to vibrate the molten steel to discharge inclusions to the edge of the liquid surface, and polishing the surface of the consumable ingot to remove surface impurities and defects before subsequent heat processing.

[0066] As a preferred solution, in the steps S2 and S3, the electrode rod ingot is subjected to pretreatment of the electroslag ingot before being subjected to electroslag remelting in an argon protective atmosphere and consumable remelting in a high vacuum atmosphere, and the pretreatment includes: polishing the surface of the electroslag ingot and cutting off the head and tail.

[0067] In combination with the above embodiments, embodiments combined with specific data are provided below to further describe the above technical solutions of the present invention:

[0068] Embodiment 1:

[0069] The present embodiment provides a high-purity corrosion-resistant alloy and a preparation method thereof. The chemical composition of the alloy is: C: 0.006%, Mn: 0.24%, P: 0.002%, S: 0.0013%, Si: 0.06%, Cr: 17.27%, Fe: 6.12%, Mo: 16.92%, Co: 0.072%, V: 0.017%, P: 0.025%, W: 4.16%, and the remainder is Ni and unavoidable impurities, and the sum of Cr, Fe, Ni, Mo, and W components is greater than 99.0%.

[0070] The method for preparing the high-purity corrosion-resistant alloy comprises the following steps:

[0071] S1: Mix the raw materials in proportion and perform vacuum induction furnace smelting. In the vacuum induction furnace smelting process, start to charge the materials in the vacuum induction furnace at ≤1.0Pa, add metal chromium when the materials are more than 50% charged, keep the vacuum induction furnace at ≤1.0Pa for 75min after all the materials are charged, add metal aluminum and metal Mn when the oxygen content is less than 15PPM and the nitrogen content is less than 30PPM, so that C≤0.008%, S≤0.010%, P≤0.010%, H≤0.0003%, O≤0.0015%, N≤0.0030% in the molten steel; and cast to obtain a Φ260mm electrode rod, the chemical composition of the electrode rod is the same as that of the above alloy;

[0072] S2: cutting off the head and tail of the electrode rod ingot, polishing off the surface impurities, and then electroslag remelting in an argon protective atmosphere, using a low melting rate of 3kg / min, the water temperature is maintained at 28°C, and the Ar gas flow rate is stabilized at 80PLM to obtain an electroslag ingot of Φ360mm;

[0073] S3: After the surface of the electroslag ingot is polished and the head and tail are cut off, consumable remelting is carried out in a high vacuum atmosphere, the vacuum degree is controlled at ≤0.5Pa, a low melting rate of 3kg / min is adopted, and the inclusions are discharged to the edge of the liquid surface by arc vibration of the molten steel, and finally a Φ400mm consumable ingot is obtained.

[0074] Embodiment 2:

[0075] The present embodiment provides a high-purity corrosion-resistant alloy and a preparation method thereof. The chemical composition of the alloy is: C: 0.0065%, Mn: 0.25%, P: 0.0025%, S: 0.0016%, Si: 0.065%, Cr: 17.14%, Fe: 6.21%, Mo: 16.85%, Co: 0.064%, V: 0.015%, P: 0.025%, W: 4.14%, and the remainder is Ni and unavoidable impurities, and the sum of Cr, Fe, Ni, Mo, and W components is greater than 99.0%.

[0076] The method for preparing the high-purity corrosion-resistant alloy comprises the following steps:

[0077] S1: Mix the raw materials in proportion and carry out smelting in a vacuum induction furnace. In the smelting process of the vacuum induction furnace, start to charge the materials in the vacuum induction furnace at ≤1.0Pa, add metal chromium when the materials are more than 50% charged, keep the vacuum induction furnace at ≤1.0Pa for 60min after all the materials are charged, add metal aluminum and metal Mn when the oxygen content is lower than 15PPM and the nitrogen content is lower than 30PPM, so that C≤0.008%, S≤0.010%, P≤0.010%, H≤0.0003%, O≤0.0015%, N≤0.0030% in the molten steel; and cast to obtain a Φ260mm electrode rod, and cast to obtain a Φ260mm electrode rod. The chemical composition of the electrode rod is the same as that of the above alloy;

[0078] S2: the electrode rod ingot is cut off from the head and tail, and the surface impurities are polished off, and then electroslag remelting is carried out in an argon protective atmosphere, with a low melting rate of 2.8 kg / min, the water temperature is maintained at 26° C., and the Ar gas flow rate is stabilized at 80 PLM to obtain an electroslag ingot of Φ360 mm;

[0079] S3: After the surface of the electroslag ingot is polished and the head and tail are cut off, consumable remelting is carried out in a high vacuum atmosphere, the vacuum degree is controlled at ≤0.5Pa, a low melting rate of 2.8kg / min is adopted, and the molten steel is vibrated by electric arc to discharge the inclusions to the edge of the liquid surface, and finally a consumable ingot of Φ400mm is obtained.

[0080] Embodiment 3:

[0081] The present embodiment provides a high-purity corrosion-resistant alloy, whose chemical composition is: C: 0.006%, Mn: 0.23%, P: 0.0024%, S: 0.0015%, Si: 0.058%, Cr: 17.33%, Fe: 6.15%, Mo: 17.13%, Co: 0.068%, V: 0.0165%, P: 0.025%, W: 4.17%, and the remainder is Ni and unavoidable impurities, and the sum of Cr, Fe, Ni, Mo, and W components is greater than 99.0%.

[0082] The method for preparing the high-purity corrosion-resistant alloy comprises the following steps:

[0083] S1: Mix the raw materials in proportion and carry out vacuum induction furnace smelting. In the vacuum induction furnace smelting process, start to charge the vacuum induction furnace below ≤1.0Pa, add metal chromium when the charge is more than 50%, keep the vacuum induction furnace at ≤1.0Pa for 90min after all the charge is charged, add metal aluminum and metal Mn when the oxygen content is lower than 15PPM and the nitrogen content is lower than 30PPM, so that C≤0.008%, S≤0.010%, P≤0.010%, H≤0.0003%, O≤0.0015%, N≤0.0030% in the molten steel; and cast to obtain a Φ260mm electrode rod. The chemical composition of the electrode rod is the same as that of the above alloy;

[0084] S2: cutting off the head and tail of the electrode rod ingot, polishing off the surface impurities, and then electroslag remelting in an argon protective atmosphere, using a low melting rate control of 3.5kg / min, the water temperature is maintained at 30°C, and the Ar gas flow rate is stabilized at 80PLM to obtain an electroslag ingot of Φ360mm;

[0085] S3: After the surface of the electroslag ingot is polished and the head and tail are cut off, consumable remelting is carried out in a high vacuum atmosphere, the vacuum degree is controlled at ≤0.5Pa, a low melting rate of 3.5kg / min is adopted, and the molten steel is vibrated by electric arc to discharge the inclusions to the edge of the liquid surface, and finally a consumable ingot of Φ400mm is obtained.

[0086] Comparative Example:

[0087] Preparation method of C-276 alloy: step a, weighing and mixing raw materials according to the designed proportion of chemical components, and casting by vacuum induction melting to obtain a Φ260mm steel ingot; wherein the chemical composition of the steel ingot meets the chemical composition requirements of the above-mentioned existing C-276 alloy;

[0088] Step b, polishing the electrode rod to remove surface defects, cutting off the shrinkage holes at the head and tail, and electroslag remelting to obtain the existing C-276 alloy Φ230mm electroslag ingot. In the electroslag remelting process, the electrode rod is cut off at the head and tail, polished to remove surface impurities and defects, and then electroslag remelted in a protective atmosphere to obtain a Φ360mm electroslag ingot.

[0089] Among them, the existing C-276 vacuum induction melting process is specifically as follows: the vacuum induction furnace starts to melt the materials below ≤1.0Pa, and metallic chromium is added when the materials are more than 50% melted. After all the materials are melted, the vacuum induction furnace is kept at ≤1.0Pa for 60-90min, and metallic aluminum and metallic Mn are added when the oxygen content is lower than 30PPM and the nitrogen content is lower than 40PPM, so that C≤0.010%, S≤0.020%, P≤0.030%, H≤0.0003%, O≤0.0030%, and N≤0.0040% in the molten steel.

[0090] The alloys of Examples 1-3 and the comparative example were subjected to composition testing and related testing, and the results are as follows:

[0091] Table 1: Test data of C-276 consumable ingots prepared in Example 1-3 and existing C-276 electroslag ingots

[0092]

[0093] It can be seen from Table 1 that, compared with the existing C-276 alloy, the consumable ingots prepared in Examples 1-3 of the present invention have lower impurity elements and gas contents, higher inclusion levels, and higher purity, which further illustrates that, compared with the C-276 alloy in the prior art, the control of impurity content in the molten steel is relatively loose, such as: S: ≤0.020%, P: ≤0.030%, H: ≤0.0003%, O: ≤0.0030%, N: ≤0.0040%. In addition, the chemical composition range is wide, and the restrictions on impurities (such as Mn, Si, Co, V, etc.) in the composition are relatively broad, which may have a certain impact on the corrosion resistance and material processing performance of the alloy; the alloy of the present invention has stricter impurity control: C: <0.008%, S: <0.010%, P: <0.010%, H: ≤0.0003%, O: ≤0.0015%, N: ≤0.0030%, and the composition system is optimized, which significantly reduces the impact of impurities on corrosion resistance and mechanical properties, and improves Material purity; and in terms of preparation method, the existing C-276 alloy: adopts simple vacuum control (≤1.0Pa), and adds metal chromium when the material is more than 50%. The preparation method of the present invention includes more complex vacuum operation, including adding metal aluminum, Ni-Mg alloy and metal manganese when the vacuum degree and impurity concentration reach higher standards (oxygen content is less than 15PPM, nitrogen content is less than 30PPM) to ensure that the impurity content in the molten steel reaches a higher purity, and three vacuuming: the first vacuuming: the vacuum degree is drawn to

[0094] Fill with argon after ≤0.67Pa; second vacuuming: vacuum again to ≤0.67Pa; third vacuuming: control the vacuum degree to ≤0.5Pa and keep it for 60-90 minutes, and use argon protective atmosphere for electroslag remelting. The key parameters are controlled more refined, and a vacuum consumable remelting process and its specific processes are added, which ultimately achieves performance improvement.

[0095] In summary, the high-purity corrosion-resistant alloy of the present invention has an optimized component system, advanced smelting process, and excellent purity. It can be used to replace imported C-276 alloy in the field of low-temperature superconductivity, and has broad market prospects and technological advancement.

[0096] In the description of the present application, 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 application. 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.

[0097] The above is only a specific implementation of the present application, but the protection scope of the present application 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 in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A high purity corrosion resistant alloy, characterized in that: Its components include by weight percentage: Mo: 15.00-19.00%, Cr: 14.50-18.00%, Fe: 4.70-7.00%, W: 3.00-4.50%, C: <0.008%, Mn: <0.50%, S: <0.010%, Co: <0.90%, V: <0.35%, P: <0.025%, the remainder is Ni and unavoidable impurities, and the sum of Cr, Fe, Ni, Mo and W components is greater than 99.0%.

2. The high purity corrosion resistant alloy according to claim 1, characterized in that: Its components include by weight percentage: Mo: 16.80-16.90%, Cr: 17.10-17.30%, Fe: 6.15-6.25%, W: 4.10-4.20%, C: <0.0070%, Mn: <0.25%, S: <0.0030%, Co: <0.070%, V: <0.020%, P: <0.0020%, the remainder is Ni and unavoidable impurities, and the sum of Cr, Fe, Ni, Mo and W components is greater than 99.0%.

3. A method for preparing a high-purity corrosion-resistant alloy as claimed in any one of claims 1 to 2, characterized in that: The following steps are involved: S1: mixing the raw materials in proportion, smelting and casting the electrode rod in a vacuum induction furnace, wherein the chemical composition of the electrode rod is the same as the chemical composition of the high-purity corrosion-resistant alloy; S2: remelting the electrode rod ingot in step a through electroslag in an argon protective atmosphere, and filtering and purifying the molten slag to obtain an electroslag ingot; S3: subjecting the electroslag ingot obtained in step S2 to consumable remelting in a high vacuum atmosphere, further degassing by consumable remelting, and removing inclusions to obtain a high-purity corrosion-resistant alloy.

4. The method for preparing a high-purity corrosion-resistant alloy according to claim 3, characterized in that: In step S1, the conditions for smelting in the vacuum induction furnace are as follows: the vacuum induction furnace is filled with argon after the first vacuuming, and then vacuumed for the second time. The material can be oxidized only after the second vacuuming is completed. After more than 50% of the material is oxidized, metal Cr is added to the vacuum induction furnace. After all the raw materials are oxidized, the vacuum induction furnace is evacuated for the third time, and when the oxygen content in the vacuum induction furnace is lower than 15PPM and the nitrogen content is lower than 30PPM, metal Al, Ni-Mg alloy and metal Mn are added.

5. The method for preparing a high-purity corrosion-resistant alloy according to claim 4, characterized in that: In the step S1, the condition for the first vacuuming is: the air pressure in the vacuum induction furnace is evacuated to ≤0.67Pa, the condition for the second vacuuming is: after the filling of argon gas is completed, the air pressure in the vacuum induction furnace is evacuated again to ≤0.67Pa, and the condition for the third vacuuming is: the vacuum induction furnace is evacuated to ≤0.5Pa and maintained for 60-90min.

6. The method for preparing a high-purity corrosion-resistant alloy according to claim 4, characterized in that: In the step S1, after adding the metal Al, Ni-Mg alloy and metal Mn, the impurity content in the molten steel in the furnace is: C≤0.008%, S≤0.010%, P≤0.010%, H≤0.0003%, O≤0.0015%, N≤0.0030%.

7. The method for preparing a high-purity corrosion-resistant alloy according to claim 3, characterized in that: In the step S2, the operation of electroslag remelting the electrode rod ingot in an argon protective atmosphere includes: grinding the surface of the electrode rod to remove surface impurities, removing shrinkage defects, using a low melting rate of 3.5-2.8kg / min, the water temperature is controlled at 28±2°C, and the flow rate of Ar gas is stabilized at 80PLM to ensure that most of the inclusions in the electrode rod are removed and refined after combined filtration of the molten slag.

8. The method for preparing a high-purity corrosion-resistant alloy according to claim 3, characterized in that: In step S3, the high vacuum atmosphere consumable remelting includes: smelting at a low melting rate of 3.5-2.8 kg / min under the condition of vacuum degree ≤ 0.5 Pa, using the arc to vibrate the molten steel to discharge inclusions to the edge of the liquid surface, and polishing the surface of the consumable ingot to remove surface impurities and defects before subsequent heat processing.

9. The method for preparing a high-purity corrosion-resistant alloy according to claim 8, characterized in that: In the steps S2 and S3, the electrode rod ingot is subjected to pretreatment before the electroslag remelting in an argon protective atmosphere and the consumable remelting in a high vacuum atmosphere, and the pretreatment includes: polishing the surface of the electroslag ingot and cutting off the head and tail.

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