Method for manufacturing cold-rolled tubular products from zirconium alloys

Abstract

This invention relates to the manufacture of corrosion-resistant, cold-rolled tubular products made of zirconium alloys for use as structural elements in the core of water-cooled nuclear reactors. A method for manufacturing cold-rolled tubular products from zirconium-based alloys includes: preparing a charge, melting an ingot, hot forging the ingot, producing and tempering the tubular workpiece, applying a protective coating and lubricant, hot pressing, removing the lubricant and protective coating, subjecting the tubular workpiece to vacuum heat treatment, cold rolling in four stages (interspersed with vacuum heat treatment) to produce the cold-rolled tubular product, and performing a final vacuum heat treatment and finishing operation. Prior to the first and second cold rolling steps, the tubular workpiece is coated with a protective undercoat, followed by a lubricant, which is removed after rolling. According to a first embodiment, the prepared charge contains powdered alloy components, zirconium-niobium and zirconium-molybdenum binary master alloys, and powdered zirconium-containing matrix alloys. According to a second embodiment, the prepared charge contains powdered alloy components, a zirconium-niobium master alloy, vanadium in chip or powder form, and powdered zirconium-containing matrix alloys. This results in a high level of corrosion resistance in the tubular workpiece.

Description

Technical Field

[0001] This invention relates to the fields of nuclear engineering and metallurgy, and in particular to the manufacture of corrosion-resistant cold-rolled tubular products made of zirconium alloys, which are used as structural components in fuel assemblies of water-cooled nuclear reactors, especially VVER and PWR reactors (pressurized water reactors). Background Technology

[0002] Products used in the active zone of water-cooled thermal neutron reactors must meet a wide range of requirements, including resistance to oxidation and hydrogenation in high-temperature water and steam, radiative growth, and thermal and radiation-induced thermal creep. Zirconium alloys are a primary structural material used in fuel assembly components due to their unique combination of physical, chemical, functional, and technical properties. The feasibility and range of desired properties for zirconium alloy products depend on the alloy composition, alloying methods and charge preparation, ingot melting processes, hot forming and cold forming parameters and conditions, heat treatment conditions at intermediate and final dimensions, and the finishing processes employed.

[0003] "A method for manufacturing tubular products from zirconium alloys (in the form of the present invention)" is known in RU 2123065 C1 (published on December 10, 1997, IPC C22F1 / 18), which discloses hot pre-deformation of molten ingots, obtaining tubular billets by hot forming (extrusion), quenching, machining and tempering, cold deformation by intermediate heat treatment, and final annealing to obtain multi-component zirconium alloys.

[0004] The drawback of this method is the lack of a protective coating applied to the billet prior to hot extrusion, leading to metal oxidation during heating and metal adhesion to the tooling during deformation; this ultimately reduces the feasibility and yield of the produced tubular products. Furthermore, no finishing operations are designed to remove residual process contaminants from the surface of the tubular products, reduce surface roughness, and ensure a uniform surface finish. Contamination and excessive surface roughness in the tubular products reduce their corrosion resistance.

[0005] A method for manufacturing zirconium alloy products is known in RU 2110600C1 (published May 10, 1998, IPC C22F1 / 18), which involves manufacturing an initial billet from an ingot by hot forming (extrusion), and then obtaining an intermediate billet by subsequent hot forming. The billets are then cut to the required size, quenched and tempered, and then hot-formed, tempered and cold-rolled.

[0006] The drawback of this method is that no protective coating is applied to the billet prior to hot extrusion, leading to metal oxidation during the process and reducing the viability of tubular products; no finishing operations are provided to remove residual process contaminants from the surface of the tubular products and reduce surface roughness. The increased contamination and surface roughness in the tubular products reduce their corrosion resistance.

[0007] The patent “Zirconium Alloy Tube and Manufacturing Method Thereof” is known in RU 2298042C2 (published April 27, 2004, IPC С22F1 / 18С21D1 / 18, C22C16 / 00). The manufacturing process involves homogenization of extruded tube blocks, water quenching, stress-relief annealing, and two-stage cold rolling with intermediate and final annealing.

[0008] The main drawback of this method is the lack of a protective lubricating coating prior to hot extrusion, which leads to metal oxidation during heating and metal adhesion to the tooling during deformation; this ultimately reduces the feasibility and yield of tubular product production. A second drawback is the use of a two-pass cold working process involving a final homogenization treatment in the (α+β) region, which prevents the product from achieving high strength; annealing in the (α+β) region results in the formation of a metastable β-Zr phase in the product's microstructure. Another drawback is that the process flow diagram does not include any finishing operations to remove residual process contaminants from the surface of the tubular product and reduce surface roughness. The presence of the β-Zr phase, contaminants, and excessive surface roughness reduces the product's corrosion resistance.

[0009] The following patent is known: "Zirconium alloy with excellent corrosion resistance for fuel rod cladding and method for producing the same" KR100831578B1 (published May 21, 2008, IPC C22C16 / 00, C22F1 / 186, G21C3 / 07). This patent specifies the composition of a corrosion-resistant zirconium alloy and a method for producing fuel rod cladding from it. The method includes melting an ingot, coating the ingot with a protective steel sleeve, heat-treating the sleeved ingot before hot rolling, hot rolling, removing the protective steel coating, heat-treating the hot-rolled tubular billet, three-pass cold rolling, intermediate heat treatment after each rolling pass, and final heat treatment.

[0010] The disadvantages of this method are the use of a carbon-containing steel shell, which can react with zirconium alloys at hot rolling temperatures to form carbides. A second disadvantage is that hot rolling of the ingot cannot ensure uniform refinement of the cast structure and results in axial porosity in the billet. The number and size of the pores increase from the edges of the billet towards the center, leading to deterioration of material viability and a discontinuous appearance in the finished product. Using a three-stage, extended final annealing process (Stage 1: 460-470°C, Stage 2: 510-520°C, Stage 3: 580-590°C) does not increase the material strength level. Furthermore, using hot rolling at T=630-650°C, combined with a small number of cold working stages and low annealing temperatures, hinders the complete refinement and decomposition of the metastable β-Zr phase, leading to deterioration of the product's corrosion resistance. Additionally, the process flow diagram does not include any finishing operations aimed at removing residual process contaminants from the surface of the tubular product, which reduces surface roughness. Without these processes, the product's corrosion resistance is reduced.

[0011] "Zirconium alloy for nuclear fuel assemblies" is known in CN103898368A (published July 2, 2014, IPC C22C 16 / 00, C22F 1 / 18). This patent specifies the composition of a multi-component composite alloy and methods for manufacturing the product, including casting, forging, homogenization and tempering of ingots, and cold working with intermediate and final heat treatments.

[0012] A drawback of this method is that products manufactured according to the aforementioned patent do not possess the required level of mechanical properties. The main structural components used in nuclear reactors are thin-walled tubes (cladding tubes, guide tubes, etc.). The manufacturing process of tubular products necessarily involves the production of tubular blanks (through drilling or piercing) and repeated cold plastic deformation through changes in wall thickness and diameter; these parameters significantly affect the characteristics and performance of the tubular products. These operations are not described in this patent. Furthermore, the patent does not provide any finishing operations aimed at removing residual process contaminants from the surface of the tubular products, which would reduce surface roughness. Without finishing operations, the corrosion resistance of the product is reduced.

[0013] The closest prior art to the claimed method is "Method for producing tubular products from zirconium alloys," WO2021 / 133195 (published July 1, 2021, IPC B21B37 / 00, C22C16 / 00, C21D8 / 10). This application details the composition of the alloy and a method for producing tubular products from zirconium alloys, including melting an ingot by repeated vacuum arc melting, machining the ingot, heating, performing multi-stage hot forging of the ingot to produce forgings, subsequently machining the forgings to produce round cross-section billets, producing tubular billets, quenching and tempering them, applying a protective coating to them and heating them to a hot-pressing temperature, hot-pressing, removing the protective coating from the surface of the tube, vacuum heat treatment, multiple cold rolling to produce tubular products; intermediate vacuum heat treatment after each cold rolling pass; final vacuum heat treatment at the final dimensions, followed by finishing operations.

[0014] A disadvantage of this method is that the alloy composition does not contain molybdenum or vanadium, which enhance the corrosion resistance of the alloy. Another disadvantage is the use of multi-stage hot forging, which increases the time spent forging the ingot into a forging due to the need for repeated heating. Another disadvantage of this patent application is that the tubular billet is quenched and then tempered without further machining, thus forming an oxide film on the side surfaces of the tubular billet. This oxide film is pressed into the metal during hot pressing, leading to a deterioration in the material viability of the tubular product, an increase in defects, and a reduction in corrosion resistance. Another disadvantage is the lack of lubrication during hot pressing and the absence of a protective coating and lubrication during the first two stages of cold rolling, resulting in excessive surface roughness and reduced corrosion resistance. Compared to the claimed batch pickling method, the use of jet etching in the finishing operation results in a rougher surface and lower corrosion resistance. In summary, these disadvantages of this method result in cold-rolled tubular products with lower corrosion resistance than those produced by the claimed method. Summary of the Invention

[0015] The purpose of this invention is to develop a manufacturing method for producing cold-rolled tubular products that are used as structural components in the core of VVER and PWR type water-cooled nuclear reactors and have enhanced corrosion resistance.

[0016] The technical effect of the first and second embodiments of the claimed invention is that the feasibility of the materials used in the manufacture of cold-rolled tubular products made of alloys (further alloyed with molybdenum or vanadium) at all stages of the hot and cold pressing process improves the corrosion resistance of the products and reduces defects and surface roughness of the cold-rolled tubular products, which also ensures their high corrosion resistance.

[0017] According to a first embodiment of the present invention, the technical effect of the claimed method is achieved by manufacturing cold-rolled tubular products from zirconium alloys, comprising melting an ingot by multiple vacuum arc remeltings, machining the ingot, heating and hot forging the ingot to produce a forging, further machining the forging, producing a tubular billet and tempering it, applying a protective coating to the tubular billet and heating the tubular billet to a temperature required for hot pressing, hot pressing the tubular billet, removing the protective coating from the tubular billet, vacuum heat treatment, multi-stage cold rolling with intermediate heat treatment to produce a tubular product, performing a final vacuum heat treatment at the final dimensions, and then performing a finishing operation. The method is characterized in that, before melting the ingot, a zirconium-niobium (Zr+Nb) and zirconium-molybdenum (Zr+Mo) binary alloy is melted, and a charge containing alloy components, the aforementioned binary master alloy, and a zirconium-containing alloy matrix is ​​prepared; the ingot is melted containing the following weight percentages: 0.8-1.7% niobium and 0.5-2% tin. 0.0, iron 0.3-1.0, chromium 0.001-0.020, carbon 0.003-0.040, oxygen 0.04-0.15, silicon 0.002-0.015, molybdenum 0.002-0.2, zirconium and impurities - balance, the ingot is hot forged to produce forgings by drawing in a single heating cycle with a reduction of 10% to 20% per stand, and turning; the forgings are then machined to produce forgings with further machining allowance. A quantity of tubular billet; the tubular billet is quenched, then machined to remove excess material, and then chemically treated and vacuum tempered; a protective coating and additional lubricant are applied to the tubular billet before heating to the hot pressing temperature; after hot pressing, the lubricant is removed, followed by the removal of the protective coating; cold rolling is performed in four stages, with a reduction rate of no more than 5% per stand, a total deformation of 44.9-58.6% per pass, and the wall thickness deformation (ε) of the tubular billet... S ) and diameter deformation (ε D The ratio of ε to ε S / ε D =1.36-1.95, wherein a pre-lubricating protective coating and lubricant are applied to the tubular billet before the first and second cold rolling passes, and are subsequently removed after rolling; finishing operations are performed by straightening, grinding, batch pickling and alkaline treatment.

[0018] In zirconium-niobium (Zr+Nb) and zirconium-molybdenum (Zr+Mo) binary alloys, the content of the main component (Zr+Nb or Zr+Mo) must be greater than 99.2% by weight.

[0019] The powder of the alloying element or the chips from the compacted material have a particle size of less than 1 mm.

[0020] Zirconium powder or sponge zirconium is used as the zirconium-containing matrix in the alloy.

[0021] The hot forging of the ingot is carried out at a temperature of 950℃-860℃.

[0022] When manufacturing tubular blanks, an axial center hole is drilled before quenching, and the axial center hole is enlarged after quenching.

[0023] The tubular blank is quenched in water at a temperature of 1050-1090℃.

[0024] The tubular billet is annealed at a temperature of 600-640℃.

[0025] The hot pressing of the tubular blank is carried out at a temperature of 640℃-600℃, with an elongation of μ=12.3 and a pressing speed of 7-15mm / sec.

[0026] The hot-pressed tubular billet is subjected to vacuum heat treatment before cold rolling at a temperature of 575-600℃.

[0027] Vacuum heat treatment of tubular billets between cold rolling operations is carried out at a temperature of 565-590℃.

[0028] The final vacuum heat treatment of the tubular products is carried out at a temperature of 555-565℃.

[0029] According to a second embodiment of the present invention, the technical effect of the claimed method is achieved by manufacturing cold-rolled tubular products from zirconium alloys, comprising melting an ingot by multiple vacuum arc remeltings, machining the ingot, heating and hot forging the ingot to produce a forging, further machining the forging, producing a tubular billet and tempering it, applying a protective coating to the tubular billet and heating the tubular billet to a temperature required for hot pressing, hot pressing the tubular billet, removing the protective coating from the tubular billet, vacuum heat treatment, multi-stage cold rolling with intermediate heat treatment to produce a tubular product, performing a final vacuum heat treatment at the final dimensions, and then performing a finishing operation, characterized in that, before melting the ingot, a zirconium-niobium (Zr+Nb) binary alloy is melted, and a charge containing vanadium in the form of chips or powder from compacted material, a powder of alloy components, a zirconium-niobium binary master alloy, and a zirconium-containing alloy matrix is ​​prepared; then, an ingot containing the following weight %: niobium 0.8-1.7%, Tin 0.5-2.0, iron 0.3-1.0, chromium 0.001-0.020, carbon 0.003-0.040, oxygen 0.04-0.15, silicon 0.002-0.015, vanadium 0.002-0.2, zirconium, and impurities - balance, are hot-forged from the ingot to produce forgings by drawing in a single heating cycle with a reduction of 10% to 20% per stand, and turning; the forgings are then machined to produce forgings with further mechanical properties. The tubular billet with a machining allowance is processed; the tubular billet is quenched, then machined to remove the allowance, and then chemically treated and vacuum tempered; a protective coating and additional lubricant are applied to the tubular billet before heating to the hot pressing temperature; after hot pressing, the lubricant is removed, followed by the removal of the protective coating; cold rolling is performed in four stages, with a reduction rate of no more than 5% per stand, a total deformation of 44.9-58.6% per pass, and the wall deformation (ε) of the tubular billet is... S ) and diameter deformation (ε D The ratio of ε to ε S / ε D =1.36-1.95, wherein a pre-lubricating protective coating and lubricant are applied to the tubular billet before the first and second cold rolling passes, and are subsequently removed after rolling; finishing operations are performed by straightening, grinding, batch pickling and alkaline treatment.

[0030] In zirconium-niobium (Zr+Nb) binary alloys, the content of the main component (Zr+Nb) must exceed 99.2% by weight.

[0031] The vanadium content in the chips or powder must exceed 99.2% by weight.

[0032] The powder of the alloying element or the chips from the compacted material have a particle size of less than 1 mm.

[0033] Zirconium powder or sponge zirconium is used as the zirconium-containing matrix in the alloy.

[0034] The hot forging of the ingot is carried out at a temperature of 950℃-860℃.

[0035] When manufacturing tubular blanks, an axial center hole is drilled before quenching, and the axial center hole is enlarged after quenching.

[0036] The tubular billet is quenched in water at a temperature of 1050-1090℃.

[0037] The tubular billet is annealed at a temperature of 600-640℃.

[0038] The hot pressing of the tubular blank is carried out at a temperature of 640℃-600℃, with an elongation of μ=12.3 and a pressing speed of 7-15mm / sec.

[0039] The tubular billet after hot pressing is subjected to vacuum heat treatment before cold rolling at a temperature of 575-600℃.

[0040] Vacuum heat treatment of tubular billets between cold rolling operations is carried out at a temperature of 565-590℃.

[0041] The final vacuum heat treatment of the tubular products is carried out at a temperature of 555-565℃.

[0042] High corrosion resistance and mechanical properties are ensured through manufacturing techniques used in tubular products and through the composition and range of alloying elements. Zirconium alloys contain:

[0043] - 0.8-1.7% wt% niobium — to ensure the mechanical and corrosion properties of cold-rolled tubular products; increasing the niobium content to more than 1.7% wt% increases the likelihood of forming metastable phases of the α phase type, which has a negative impact on technical properties; a niobium content of less than 0.8% wt% does not allow the achievement of the mechanical characteristics required for cold-rolled tubular products.

[0044] - 0.5-2.0% by weight of tin — used to neutralize the adverse effects of interstitial elements and improve the corrosion resistance of cold-rolled tubular products; tin content exceeding 2.0% by weight increases resistance to deformation and impairs the processability of the alloy during the manufacture of cold-rolled tubular products; when the tin content is less than 0.5% by weight, the corrosion resistance of cold-rolled tubular products decreases.

[0045] - 0.3-1.0% by weight of iron — used to improve the alloy’s resistance to knot corrosion in water and steam; iron content exceeding 1.0% by weight promotes the formation of large T-phase particles, which embrittle the material of cold-rolled tubular products; when the iron content is less than 0.3% by weight, the resistance of cold-rolled tubular products to knot corrosion is reduced.

[0046] - 0.001-0.020% by weight of chromium — used to form a fine-grained intermetallic phase within the structure, which improves mechanical properties and stabilizes the corrosion resistance of cold-rolled tubular products; if the chromium content exceeds 0.020% by weight, a phase that embrittles the material of cold-rolled tubular products will be formed; when the chromium content is less than 0.020% by weight, the corrosion resistance of cold-rolled tubular products is unstable.

[0047] - 0.003-0.040 wt% carbon and 0.04-0.15 wt% oxygen — Used to ensure solid solution strengthening and improve the mechanical properties of cold-rolled tubular products. Increasing the carbon content to more than 0.040 wt% will lead to accelerated corrosion due to the formation of carbide phases at grain boundaries; and increasing the oxygen content to more than 0.15 wt% will lead to an increase in the defect rate in the ingot and cold-rolled tubular products in a discontinuous form; oxygen content less than 0.040 wt% and carbon content less than 0.003 wt% cannot ensure the mechanical properties required for cold-rolled tubular products.

[0048] - 0.04-0.15% by weight of oxygen — strengthens the alloy through a solid solution mechanism; an increase in oxygen content to greater than 0.15% by weight will result in reduced processability of the material and reduced plasticity of tubular products at all stages of pressure treatment; a decrease in oxygen content to less than 0.04% by weight will prevent the achievement of the required mechanical properties for tubular products.

[0049] - 0.002-0.015% by weight of silicon — used to stabilize the corrosion resistance of the alloy in water and steam at 400°C, while reducing hydrogen absorption; increasing the silicon content above 0.015% by weight will impair the feasibility of the alloy during the manufacture of cold-rolled tubular products; if the silicon content is less than 0.002% by weight, the corrosion resistance of the cold-rolled tubular products in water and steam at 400°C is compromised.

[0050] - 0.002-0.2% by weight of molybdenum or vanadium — used to improve the corrosion resistance of cold-rolled tubular products; increasing the molybdenum content to more than 0.2% by weight will impair the feasibility of the alloy in the production of cold-rolled tubular products, while increasing the vanadium content to more than 0.2% by weight will degrade the corrosion resistance of cold-rolled tubular products; if the molybdenum or vanadium content is less than 0.002% by weight, the corrosion resistance of cold-rolled tubular products will decrease.

[0051] To address the current task, a first embodiment of the present invention provides a method for manufacturing a tubular product made of a molybdenum-containing alloy, while a second embodiment of the present invention provides a vanadium-containing tubular product.

[0052] The first embodiment of the present invention proposes the addition of refractory alloying elements niobium and molybdenum in the form of binary alloys: zirconium-niobium (Zr+Nb) and zirconium-molybdenum (Zr+Mo). The method of preparing the charge ensures complete dissolution and homogenization of all alloy components during the vacuum arc melting of the ingot of the composition specified in the present invention. The following requirement has been set: the content of the major component (Zr+Nb or Zr+Mo) in the binary alloy is greater than 99.2% by weight to prevent contamination of the ingot of the specific alloy by impurity elements that impair the corrosion resistance of cold-rolled tubular products.

[0053] A second embodiment of the invention proposes adding niobium (the refractory component) to the alloy in the form of a zirconium-niobium (Zr+Nb) binary alloy; and adding vanadium in the form of chips from the compacted material or as powder. The method of preparing the charge ensures complete dissolution and homogenization of all alloy components during the vacuum arc melting of the ingot of the composition specified in this invention. The following requirements have been set: the content of the major component in the binary alloy (Zr+Nb) is greater than 99.2% by weight, and the vanadium content in the vanadium powder or chips is greater than 99.2% by weight, to prevent contamination of the ingot of the specific alloy by impurity elements that impair the corrosion properties of cold-rolled tubular products.

[0054] Hot forging primarily occurs in the β region, allowing the cast microstructure to be concentratedly machined without defects during a single heating cycle, thus improving material viability. This helps increase the ductility limit and reduce the gas saturation layer, resulting in forgings with a uniform cross-sectional structure. Forging is performed with a reduction rate of 10-20% per stand, as reducing the reduction rate per stand increases the forging temperature range, reduces the machinability of the cast microstructure and material viability, and requires additional preheating operations for forging. Increasing the reduction rate per stand by more than 20% leads to surface defects in the forging and causes the gas saturation layer to penetrate deeper into the forging. Turning operations are performed to ensure the desired geometry and improve the uniformity of machining on the cast microstructure; this is because hot forging by drawing is performed by applying a compressive load along only a single axis. Turning the forging changes the deformation direction and thus ensures that the forging has a uniform structure and the desired shape.

[0055] The manufacturing process for tubular billets follows this sequence: machining to produce tubular billets ready for quenching, allowing for subsequent machining allowances; quenching the tubular billets; and subsequent machining to remove the allowances, resulting in tubular billets without an oxide layer; chemical treatment and vacuum tempering of the tubular billets allow for the production of tubular billets with an oxide-free surface, leading to improved material processability, reduced defect rates, and increased corrosion resistance of the tubular products. The tubular billets undergo chemical treatment after quenching to remove any residual process contaminants from the surface. Vacuum tempering prevents oxidation of the tubular billet surface before hot pressing.

[0056] Prior to hot pressing, a protective coating is applied to the surface of the tubular blanks to protect them from oxidation and gas absorption, followed by lubrication. Lubrication improves the conditions of frictional contact interactions (interactions of deformable solids during their relative motion) during hot pressing and cold rolling, preventing the formation of defects on both the outer and inner surfaces, thus enhancing the material's viability. Lubrication also enables the enhancement of the hot pressing process, particularly by increasing the elongation μ (the ratio of the cross-sectional area before pressing to the cross-sectional area after pressing) from 8.5-9.0 in the prior art to 12.3.

[0057] Before the first and second cold rolling operations, a pre-lubricated protective coating and lubricant are applied to the tubular billet and then removed after rolling to improve frictional contact interactions during cold rolling, prevent adhesion, and minimize defects on the outer and inner surfaces of the tubular billet. Cold rolling is performed in four stages, with deformation gradually increasing from one stage to the next, and the wall deformation ε... S With diameter deformation ε D The ratio is specific to ensure uniform refinement of the grain structure and second-phase inclusions, and to improve structural homogeneity. The rolling of tubular billets must be performed with a reduction rate of no more than 5% per stand. Increasing the reduction rate per stand beyond 5% leads to a reduction in the amount of alternating load, a decrease in the influence of the Bauschinger effect on yield strength, an increase in the thermal effects of plastic deformation, and therefore, an earlier onset of unstable plastic deformation (zoning). This significantly reduces the viability of the metal and results in continuous defects in the finished tubular product. A total reduction rate of 44.9%–59.6% per pass ensures defect-free production with a minimum number of rolling passes (4 rolling passes). The wall deformation ε of the tubular billet... S With diameter deformation ε D The ratio of ε S / ε D=1.36-1.95 ensures maximum utilization of the Bauschinger effect and thus improves the feasibility of processing the material. Furthermore, deformation occurs primarily along the wall, which refines the material's microstructure and thus improves its corrosion resistance. A favorable radial texture fr of up to 0.6 is produced, ensuring the required mechanical strength.

[0058] The sequence of finishing operations has been changed (i.e., straightening, grinding, batch pickling, and alkaline treatment). Grinding, performed before batch pickling, reduces surface roughness, minimizes defects, and improves the corrosion resistance of the tubular product. In contrast to jet etching, batch pickling ensures the required surface finish and cleanliness for both the interior and exterior, thereby improving the corrosion resistance of the tubular product. Detailed Implementation

[0059] The method is as follows:

[0060] Example 1 (First Embodiment of the Invention)

[0061] According to a first embodiment of the technical solution of the present invention, the manufacturing process of the tubular product includes the following operations.

[0062] Zirconium-molybdenum (Zr+Mo) alloys with an average molten molybdenum content of 37.1 wt% (Zr and Mo in the alloy are 99.35 wt%) and zirconium-niobium (Zr+Nb) alloys with an average niobium content of 52.6 wt% (Zr and niobium in the alloy are 99.4 wt%) were produced. The binary alloys were manufactured in the form of chips with a particle size less than 1 mm. Powders of the alloying elements (zirconia, iron, and tin) were sieved through a 1 mm sieve; the fraction of powder smaller than 1 mm was used as the charge. Zirconium powder with the following average impurity content (wt%) was used as the zirconium-containing matrix: oxygen 0.063; iron 0.0066; carbon 0.0085; chromium 0.0023; silicon 0.003%; hafnium, nickel <0.01%; aluminum <0.02%; titanium <0.005%; chlorine <0.009%; fluorine <0.06%; potassium <0.05%; Zr - balance. Zirconium powder is mixed with chips and alloying element powder from Zr+Nb and Zr+Mo binary master alloys. A consumable electrode is then formed via a two-stage vacuum arc remelting process. An ingot with the following composition (wt%) is obtained: Nb, 1.01–1.04; Sn, 0.793–0.800; Fe, 0.339–0.347; Mo, 0.104–0.106; Cr, 0.002–0.0024; C, 0.0076–0.009; O, 0.082–0.086; Si, 0.003; Zr and impurities – balance. The side surfaces of the ingot are machined. The ingot is heated to 950°C in a resistance furnace; in a single heating process, the ingot is drawn and forged, partially deformed by 10–20%, and then turned to produce a forging. Forging is completed at a forging temperature of 860°C.

[0063] Forgings are machined and have allowances for subsequent machining. When manufacturing tubular blanks, axial center holes are drilled before they are quenched.

[0064] The tubular billet is quenched in water at a temperature of 1050-1090℃.

[0065] Machining is performed by turning the outer surface and reaming the axial hole at the center to remove the oxide metal (blank), thereby producing a tubular blank with dimensions suitable for hot pressing.

[0066] The tubular blank is then chemically treated (degreasing and chemical etching). Next, it is vacuum annealed at 600-640°C. A vacuum level of 1×10⁻⁶ is used. -4 - 1×10 -5 A vacuum furnace with a capacity of mmHg.

[0067] The tubular blank is then electroplated with a protective copper coating and lubricated to improve frictional contact interactions and prevent gas saturation during heating and hot pressing.

[0068] The tubular billet for hot pressing is heated in an air atmosphere furnace. The heating temperature of the tubular billet before pressing is 600-640℃. Pressing is carried out with an elongation of μ=12.3 and a pressing speed of 7-15mm / s. The lubricant and protective coating are then removed.

[0069] The tubular billet is then conveyed for vacuum heat treatment at 575-600°C. The operating pressure is 1×10⁻⁶. -4 - 1×10 -5 A vacuum furnace with a capacity of mmHg.

[0070] Before the first two stages of cold rolling, a protective copper coating is applied and lubricated by electroplating to improve frictional interactions and prevent defects on the outer and inner surfaces; after cold rolling, the lubricating and protective coatings are removed from the tubular billet by chemical etching.

[0071] The tubular billet is cold rolled on HPT and KPW type cold reduction tube mills, in four rolling passes, with a reduction rate of 4-4.5% per stand.

[0072] First rolling pass - total deformation 44.9%, wall deformation of tubular billet (ε S ) and diameter deformation (ε D The ratio of ε to ε S / ε D =1.36;

[0073] Second rolling – Total deformation 47.6%, wall deformation of tubular billet (ε S ) and diameter deformation (ε D The ratio of ε to ε S / ε D =1.51;

[0074] Third rolling pass - total deformation 53.8%, wall deformation of tubular billet (ε S ) and diameter deformation (ε D The ratio of ε to ε S / ε D =1.41;

[0075] Fourth rolling pass - total deformation 58.6%, wall deformation of tubular billet (ε) S ) and diameter deformation (ε D The ratio of ε to ε S / ε D =1.92;

[0076] Intermediate vacuum heat treatment between cold rolling is carried out at a temperature of 565℃-590℃. A vacuum level of 1×10⁻⁶ is used. -4 - 1×10 -5 A vacuum furnace with a capacity of mmHg.

[0077] The final vacuum heat treatment was performed at T = 555-565℃. A vacuum level of 1.10 was used. -4 - 1.10 -5 A vacuum furnace with a capacity of mmHg.

[0078] After final annealing, the tubular products undergo finishing operations, including straightening, grinding, batch pickling, and alkaline treatment.

[0079] A cold-rolled tubular product, made of alloy and measuring Ø12.9 × 10.9 mm, manufactured according to specified technical specifications, possesses the following characteristics (Table, Example 1). Furthermore, the continuity of the cold-rolled tubular product was inspected using ultrasonic testing (UT); during this test, a standard probe with a defect depth of 0.05 mm was used, meaning that 100% of the signal corresponds to a defect 0.05 mm deep. The signal level was measured to identify suitable tubes. The results of the ultrasonic testing are shown in the table. This table demonstrates that the developed method allows the signal level to be reduced by half, thus reducing the depth of the defect.

[0080] Studies of the corrosion resistance (weight increase relative to the prototype during corrosion testing) of cold-rolled tubular products in a steam environment at 400°C and in water at 330°C and 360°C, with and without the addition of 70 ppm Li, showed that the percentage weight increase relative to the prototype was low under all autoclave test conditions.

[0081] Example 2 (First Embodiment of the Invention)

[0082] Perform similarly to Example 1.

[0083] Alloy composition (wt%): Nb, 1.03-1.04; Sn, 1.19-1.20; Mo, 0.103-0.105; Fe, 0.323-0.347; Cr, 0.002-0.0027; C, 0.0093-0.0116; O, 0.094-0.095; Si, 0.003; Zr and impurities - balance.

[0084] A cold-rolled tubular product made of alloy, measuring Ø12.9×10.9mm, manufactured according to specific technical specifications, has the following characteristics (Table, Example 2).

[0085] Example 3 (First Embodiment of the Invention)

[0086] Perform similarly to Example 1.

[0087] Sponge zirconium with the following average impurity content (wt%) was used as a zirconium-containing matrix: oxygen 0.05; iron 0.065; carbon 0.0075; chromium 0.0028; silicon 0.003%; hafnium, nickel <0.01%; aluminum <0.02%; titanium <0.005%; chlorine, fluorine <0.0035%; potassium <0.05%; Zr balance.

[0088] The alloy component powder is sieved through a 1 mm sieve; the powder fraction smaller than 1 mm is mixed with chips from the Zr+Nb and Zr+Mo binary alloys and sponge zirconium (alloy matrix).

[0089] Alloy composition (wt%): Nb, 1.00-1.09; Sn, 1.16-1.18; Fe, 0.333-0.364; Mo, 0.148-0.152; Cr, 0.002-0.0023; C, 0.0065-0.0077; O, 0.086-0.088; Si, 0.003; Zr and impurities - balance.

[0090] A cold-rolled tubular product made of alloy, measuring Ø12.9×10.9mm, manufactured according to specified technical specifications, has the following characteristics (Table, Example 3).

[0091] Example 4 (Second Embodiment of the Invention)

[0092] According to the second embodiment of the present invention, the manufacturing process of the tubular product includes the following operations.

[0093] Zirconium-niobium (Zr+Nb) alloys with an average niobium content of 52.6% by weight have been produced; the total content of zirconium and niobium in the alloy is 99.4% by weight. The binary alloy is machined to produce chips with a particle size of less than 1 mm.

[0094] Powders with the following average impurity content (wt%) were used as zirconium-containing matrices: oxygen 0.063; iron 0.0066; carbon 0.0085; chromium 0.0023; silicon 0.003%; hafnium, nickel <0.01%; aluminum <0.02%; titanium <0.005%; chlorine <0.009%; fluorine <0.06%; potassium <0.05%; Zr balance.

[0095] Vanadium (99.4 wt%) and alloy component powders (zirconia, iron, and tin) were sieved through a 1 mm sieve; the powder fraction smaller than 1 mm was used as the charge. Zirconium powder (containing a zirconium matrix) was mixed with chips from a binary Zr+Nb alloy and powders of alloying elements. Then, a consumable electrode was formed by a two-stage vacuum arc remelting process. An ingot with the following composition (wt%) was obtained: Nb, 1.04–1.06; Sn, 1.20–1.26; Fe, 0.339–0.356; V, 0.099–0.104; Cr, 0.0015; C, 0.0044–0.0076; O, 0.091; Si, 0.003; Zr and impurities—balance.

[0096] The side surfaces of the ingot are machined. The ingot is heated to 950°C in a resistance furnace; it is forged in a single heating process by drawing a portion deformed by 10-20%, and then turned to produce forgings. Forging is completed at a forging temperature of 860°C.

[0097] Forgings are machined and have allowances for subsequent machining. When manufacturing tubular blanks, axial center holes are drilled before they are quenched.

[0098] The tubular blank is quenched in water at a temperature of 1050-1090℃.

[0099] Machining is performed by facing the outer surface and boring a central axial hole to remove oxide metal (residue), thereby producing a tubular blank with dimensions suitable for hot pressing.

[0100] The tubular blank is then chemically treated (degreasing and chemical etching). Next, it is vacuum tempered at 600-640°C. A vacuum level of 1×10⁻⁶ is used. -4 - 1×10 -5 A vacuum furnace with a capacity of mmHg.

[0101] The tubular blank is then electroplated with a protective copper coating and lubricated to improve frictional contact interactions and prevent gas saturation during heating and hot pressing.

[0102] The tubular billet for hot pressing is heated in an air atmosphere furnace. The heating temperature of the tubular billet before pressing is 600-640℃. Pressing is carried out with an elongation of μ=12.3 and a pressing speed of 7-15mm / s. The lubricant and protective coating are then removed.

[0103] Then, the tubular blank is subjected to vacuum heat treatment at a temperature of 575-600℃. The pressure used is 1×10⁻⁶. -4 - 1×10 -5 A vacuum furnace with a capacity of mmHg.

[0104] Before the first two stages of cold rolling, a protective copper coating is applied and lubricated by electroplating to improve frictional interactions and prevent defects on the outer and inner surfaces; after cold rolling, the lubricating and protective coatings are removed from the tubular billet by chemical etching.

[0105] The tubular billet is cold rolled on HPT and KPW type cold reducing tube mills, in four rolling passes, with a reduction rate of 4-4.5% per stand.

[0106] First rolling pass - total deformation 44.9%, wall deformation of tubular billet (ε S ) and diameter deformation (ε D The ratio of ε to ε S / ε D =1.36;

[0107] Second rolling – Total deformation 47.6%, wall deformation of tubular billet (ε S ) and diameter deformation (ε D The ratio of ε to ε S / ε D =1.51;

[0108] Third rolling pass - total deformation 53.8%, wall deformation of tubular billet (ε S ) and diameter deformation (ε D The ratio of ε to ε S / ε D =1.41;

[0109] Fourth rolling pass - total deformation 58.6%, wall deformation of tubular billet (ε) S ) and diameter deformation (ε D The ratio of ε to ε S / ε D =1.92;

[0110] Intermediate vacuum heat treatment between cold rolling is carried out at a temperature of 565℃-590℃. A vacuum level of 1×10⁻⁶ is used. -4 - 1×10 -5 A vacuum furnace with a capacity of mmHg.

[0111] After final annealing, the tubular products undergo finishing operations, including straightening, grinding, batch pickling, and alkaline treatment.

[0112] A cold-rolled tubular product, made of alloy and measuring Ø12.9 × 10.9 mm, manufactured according to specified technical specifications, possesses the following characteristics (Table, Example 4). Furthermore, the continuity of the cold-rolled tubular product was inspected using ultrasonic testing (UT); during this test, a standard probe with a defect depth of 0.05 mm was used, meaning that 100% of the signal corresponds to a defect 0.05 mm deep. The signal level was measured to identify suitable tubes. The results of the ultrasonic testing are shown in the table. This table demonstrates that the developed method allows the signal level to be reduced by half, thus reducing the depth of the defect.

[0113] Studies of the corrosion resistance (weight increase relative to the prototype during corrosion testing) of cold-rolled tubular products in a steam environment at 400°C and in water at 330°C and 360°C, with and without the addition of 70 ppm Li, showed that the percentage weight increase relative to the prototype was low under all autoclave test conditions.

[0114] Example 5 (Second Embodiment of the Invention)

[0115] Perform similarly to Example 4.

[0116] Sponge zirconium with the following average impurity content (wt%) was used as a zirconium-containing matrix: oxygen 0.05; iron 0.065; carbon 0.0075; chromium 0.0028; silicon 0.003%; hafnium, nickel <0.01%; aluminum <0.02%; titanium <0.005%; chlorine, fluorine <0.0035%; potassium <0.05%; Zr balance.

[0117] Compacted vanadium (vanadium content 99.5% by weight) is machined to produce chips with a particle size of less than 1 mm.

[0118] The powders of the alloying elements—zirconium dioxide, iron, and tin—are sieved through a 1mm sieve; the fraction of powder smaller than 1mm is used as raw material.

[0119] Sponge zirconium (containing zirconium matrix) is mixed with chips from a Zr+Nb binary master alloy, chips from vanadium, and powders of alloying elements.

[0120] The composition (wt%) of the resulting alloy: Nb, 1.02-1.05; Sn, 1.18-1.24; Fe, 0.335-0.350; V, 0.096-0.102; Cr, 0.0017-0.0025; C, 0.0050-0.0067; O, 0.093-0.098; Si, 0.0042-0.0048; Zr and impurities - balance.

[0121] A cold-rolled tubular product made of alloy with dimensions of Ø12.9×10.9mm, manufactured according to specified technical specifications, has the following characteristics (Table, Example 5).

[0122] Table: Characteristics of tubular products based on prototypes and proposed technical solutions

[0123]

[0124]

[0125] Industrial applicability

[0126] Therefore, the method for manufacturing cold-rolled tubular products proposed in this invention (implementation method) ensures material feasibility at all stages of the hot-pressing and cold-pressing processes used to manufacture cold-rolled tubular products, and additionally alloys with molybdenum (first embodiment of the invention) or vanadium (second embodiment of the invention), which improves the corrosion resistance of the product and also ensures a reduction in defects and surface roughness of the cold-rolled tubular products, thereby improving their corrosion resistance in various environments (in steam at 400°C, in water at 330°C and 360°C, with and without the addition of 70 ppm Li).

Claims

1. A method for manufacturing cold-rolled tubular products from zirconium alloy, comprising melting an ingot by multiple vacuum arc remelting processes, machining the ingot, heating and hot forging the ingot to produce a forging, further machining the forging, producing a tubular billet and tempering it, applying a protective coating to the tubular billet and heating the tubular billet to a temperature required for hot pressing, hot pressing the tubular billet, removing the protective coating from the tubular billet, vacuum heat treatment, multi-stage cold rolling with intermediate heat treatment to produce the tubular product, final vacuum heat treatment at the final dimensions, and subsequent finishing operations, characterized in that... Before melting the ingot, zirconium-niobium (Zr+Nb) and zirconium-molybdenum (Zr+Mo) binary alloys are melted, and powders containing the alloy components, the aforementioned binary master alloys, and a zirconium-containing alloy matrix are prepared. The ingot is melted containing the following weight percentages: niobium 0.8-1.7, tin 0.5-2.0, iron 0.3-1.0, chromium 0.001-0.020, carbon 0.003-0.040, oxygen 0.04-0.15, silicon 0.002-0.015, molybdenum 0.002-0.2, zirconium, and impurities. - The allowance is used to hot forge the ingot to produce forgings by drawing in a single heating cycle with a reduction of 10% to 20% per stand, and by turning; the forgings are machined to produce tubular blanks with further machining allowances; the tubular blanks are quenched, then machined to remove the allowances, and then chemically treated and vacuum tempered; a protective coating and additional lubricant are applied to the tubular blanks before heating to the hot pressing temperature; After hot pressing, the lubricant is removed, followed by the removal of the protective coating; Cold rolling is carried out in four stages, with a reduction rate of no more than 5% per stand, a total deformation of 44.9-58.6% per pass, and the wall deformation (ε) of the tubular billet. S ) and diameter deformation (ε D The ratio of ε to ε S / ε D =1.36-1.95, wherein a pre-lubricating protective coating and lubricant are applied to the tubular billet before the first and second cold rolling passes, and are subsequently removed after rolling; finishing operations are performed by straightening, grinding, batch pickling and alkaline treatment.

2. The method according to claim 1, characterized in that, In zirconium-niobium (Zr+Nb) and zirconium-molybdenum (Zr+Mo) binary alloys, the content of the main component (Zr+Nb or Zr+Mo) must be greater than 99.2% by weight.

3. The method according to claim 1, characterized in that, The alloy component powder or chips from pressed material have a particle size of less than 1 mm.

4. The method according to claim 1, characterized in that, Zirconium powder or sponge zirconium is used as the zirconium-containing matrix.

5. The method according to claim 1, characterized in that, The hot forging of the ingot is carried out at a temperature of 950℃-860℃.

6. The method according to claim 1, characterized in that, During the manufacturing of the tubular blank, an axial center hole is drilled before quenching and the axial center hole is enlarged after quenching.

7. The method according to claim 1, characterized in that, The tubular blank is quenched in water at a temperature of 1050℃-1090℃.

8. The method according to claim 1, characterized in that, The tubular blank is annealed at a temperature of 600℃-640℃.

9. The method according to claim 1, characterized in that, The hot pressing of the tubular blank is carried out at a temperature of 640℃-600℃, with an elongation of μ=12.3 and a pressing speed of 7-15mm / s.

10. The method according to claim 1, characterized in that, The tubular billet, after hot pressing, undergoes vacuum heat treatment before cold rolling at a temperature of 575℃-600℃.

11. The method according to claim 1, characterized in that, Vacuum heat treatment of tubular billets between cold rolling operations is carried out at a temperature of 565℃-590℃.

12. The method according to claim 1, characterized in that, The final vacuum heat treatment of the tubular product is carried out at a temperature of 555℃-565℃.

13. A method for manufacturing cold-rolled tubular products from zirconium alloy, comprising melting an ingot by multiple vacuum arc remelting, machining the ingot, heating and hot forging the ingot to produce a forging, further machining the forging, producing a tubular billet and tempering it, applying a protective coating to the tubular billet and heating the tubular billet to a temperature required for hot pressing, hot pressing the tubular billet, removing the protective coating from the tubular billet, vacuum heat treatment, multi-stage cold rolling with intermediate heat treatment to produce the tubular product, final vacuum heat treatment at the final dimensions, and subsequent finishing operations, characterized in that... Before melting the ingot, a zirconium-niobium (Zr+Nb) binary alloy is melted, and a charge containing vanadium in the form of chips or powder from the compacted material, a powder of alloy components, a zirconium-niobium binary master alloy, and a zirconium-containing alloy matrix is ​​prepared; then, an ingot containing the following weight percentages is melted: niobium 0.8-1.7, tin 0.5-2.0, iron 0.3-1.0, chromium 0.001-0.020%, carbon 0.003-0.040%, oxygen 0.04-0.15%, silicon 0.002-0.015%, vanadium 0.002- 0.2%, zirconium and impurities - balance, the ingot is hot forged to produce forgings by drawing in a single heating cycle with a reduction of 10% to 20% per stand, and by turning; the forgings are machined to produce tubular blanks with further machining allowances; the tubular blanks are quenched, then machined to remove the allowances, and then chemically treated and vacuum tempered; a protective coating and additional lubricant are applied to the tubular blanks before heating to the hot pressing temperature; After hot pressing, the lubricant is removed, followed by the removal of the protective coating; Cold rolling is carried out in four stages, with a reduction rate of no more than 5% per stand, a total deformation of 44.9-58.6% per pass, and the wall deformation (ε) of the tubular billet. S ) and diameter deformation (ε D The ratio of ε to ε S / ε D =1.36-1.95, wherein a pre-lubricating protective coating and lubricant are applied to the tubular billet before the first and second cold rolling passes, and are subsequently removed after rolling; finishing operations are performed by straightening, grinding, batch pickling and alkaline treatment.

14. The method according to claim 13, characterized in that, In zirconium-niobium (Zr+Nb) binary alloys, the content of the main component (Zr+Nb) must be greater than 99.2% by weight.

15. The method according to claim 13, characterized in that, The vanadium content in the chips or powder must be greater than 99.2% by weight.

16. The method according to claim 13, characterized in that, The alloy component powder or chips from pressed material have a particle size of less than 1 mm.

17. The method according to claim 13, characterized in that, Zirconium powder or sponge zirconium is used as the zirconium-containing matrix.

18. The method according to claim 13, characterized in that, The hot forging of the ingot is carried out at a temperature of 950℃-860℃.

19. The method according to claim 13, characterized in that, During the manufacturing of the tubular blank, an axial center hole is drilled before quenching and the axial center hole is enlarged after quenching.

20. The method according to claim 13, characterized in that, The tubular blank is quenched in water at a temperature of 1050℃-1090℃.

21. The method according to claim 13, characterized in that, The tubular blank is annealed at a temperature of 600-640°C.

22. The method according to claim 13, characterized in that, The hot pressing of the tubular blank is carried out at a temperature of 640℃-600℃, with an elongation of μ=12.3 and a pressing speed of 7-15mm / s.

23. The method according to claim 13, characterized in that, The hot-pressed tubular blank is subjected to the vacuum heat treatment before cold rolling at a temperature of 575℃-600℃.

24. The method according to claim 13, characterized in that, Vacuum heat treatment of tubular billets between cold rolling operations is carried out at a temperature of 565℃-590℃.

25. The method according to claim 13, characterized in that, The final vacuum heat treatment of the tubular product is carried out at a temperature of 555℃-565℃.

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