Method for manufacturing cold-rolled tubular products from zirconium alloys

Abstract

The invention relates to the manufacture of corrosion-resistant cold-rolled tubular products from zirconium alloy for use as constructional elements in the core of water-cooled nuclear reactors. A method for manufacturing cold-rolled tubular products from a zirconium-based alloy includes preparing a charge, melting an ingot, hot forging the ingot, producing and tempering tubular workpieces, applying a protective coating and lubrication, hot pressing, removing the lubrication and the protective coating, vacuum heat treating the tubular workpieces, carrying out cold rolling in four stages interspersed with vacuum heat treatment to produce cold-rolled tubular products, and carrying out a final vacuum heat treatment and finishing operations. Before the first and second cold-rolling steps, the tubular workpieces are coated with a protective undercoat followed by a lubricant, which are subsequently removed after rolling. According to a first embodiment, the charge prepared contains powdered alloying components, zirconium-niobium and zirconium-molybdenum binary master alloys and a powdered zirconium-containing base alloy. According to a second embodiment, the charge prepared contains powdered alloying components, a zirconium-niobium master alloy, vanadium in the form of turnings or powder and a powdered zirconium-containing base alloy. This results in tubular workpieces with a high level of corrosion resistance.

Description

[0001] METHOD OF MANUFACTURING COLD-ROLLED TUBE PRODUCTS

[0002] FROM ZIRCONIUM ALLOYS

[0003] AREA OF TECHNOLOGY

[0004] The invention relates to the field of nuclear engineering and metallurgy, in particular to the production of corrosion-resistant cold-rolled tubular products made of zirconium alloy, used as structural elements of the fuel assembly of water-cooled nuclear reactors, in particular for WWER and PWR type reactors.

[0005] PRIOR ART

[0006] There are many requirements for products used in the active zone of water-cooled thermal power reactors, including requirements for resistance to oxidation and hydrogenation in high-temperature water and steam, radiation growth, thermal and radiation-thermal creep. Zirconium alloys, due to a combination of unique physical, chemical, functional and technological properties, are the main structural material for fuel assembly components. The manufacturability of zirconium alloy products and the set of required properties are determined by the alloy composition, alloying and charge preparation method, ingot smelting technology, hot and cold deformation parameters and modes, heat treatment modes at intermediate and finished sizes, and methods of applied finishing works.

[0007] The “Method for manufacturing tubular products from zirconium alloys (variants)” RU 2123065C1 (published 10.12.1997, class C22F1 / 18) is known, which includes, for a multi-component zirconium alloy, hot preliminary deformation of the smelted ingot, obtaining a tubular blank by hot molding (extrusion), hardening, mechanical treatment and tempering, cold deformation with intermediate heat treatments and final annealing.

[0008] The disadvantage of this method is that no protective coating is applied to the blanks before hot extrusion, which leads to oxidation of the metal during heating and adhesion of the metal to the tool during deformation, which ultimately reduces the manufacturability and yield in the production of tubular products. Also, no finishing operations are provided, which allow removing residual process contaminants from the surface of tubular products, reducing roughness and ensuring a uniform surface morphology. Contaminants and increased roughness of the surface of tubular products worsen the corrosion resistance of the products. The "Method for producing products from zirconium alloys" RU 2110600C1 (published 10.05.1998, cl.C22F1 / 18), which includes the production of an initial blank from an ingot by hot forming (extrusion), then subsequent hot forming to obtain an intermediate blank, then the cut-to-length blanks are quenched and tempered, then hot forming, tempering and cold rolling are carried out.

[0009] The disadvantages of the method are that no protective coating is applied to the blanks before hot extrusion, which leads to oxidation of the metal during the process, which reduces the technological efficiency of tubular products; there are no finishing operations that allow removing residual technological contaminants from the surface of tubular products and reducing the surface roughness. Contaminants and increased surface roughness of tubular products worsen the corrosion resistance of the products.

[0010] The patent "Tubes from zirconium-based alloys and the method of their manufacture" RU 2298042C2 (published 27.04.2004, class C22F1 / 18C21D1 / 18, C22C16 / 00) is known. The manufacturing method includes homogenizing treatment of extruded tube sleeves, quenching them in water, stress-relieving annealing, two-stage cold rolling with intermediate and final annealing.

[0011] The disadvantage of the method, firstly, is that no protective lubricating coating is applied before hot extrusion, which leads to oxidation of the metal during heating and adhesion of the metal to the tool during deformation, which ultimately leads to a decrease in manufacturability and yield in the production of tubular products. The second disadvantage is the use of a two-roll cold processing scheme using finishing homogenizing treatment in the (a+)- region, which does not allow for high strength of the product, while annealing in the (a+P)- region leads to the appearance of a metastable P-Zr phase in the product structure. Another disadvantage is that the process scheme does not provide for finishing operations that allow removing residual process contaminants from the surface of tubular products and reducing surface roughness. The presence of the P-Zr phase in the structure, contaminants and increased surface roughness reduce the corrosion resistance of the products.

[0012] The patent "Zirconium alloy having excellent corrosion resistance for fuel element cladding and the method of its production" KR100831578B1 (published on 21.05.2008, class C22C16 / 00, C22F1 / 186, G21C3 / 07) is known. The patent specifies the composition of the corrosion-resistant zirconium alloy and the method of producing fuel element cladding from it, including smelting an ingot, coating the ingot with a protective steel casing, heat treating the ingot with the casing before hot rolling, hot rolling, removing the protective steel coating, heat treating hot-rolled tubular blanks, three passes of cold rolling, intermediate heat treatments after each rolling and finishing heat treatment.

[0013] The disadvantage of the method is the use of a steel casing containing carbon, which at the hot rolling temperature can interact with the zirconium alloy to form carbides. The second disadvantage is that hot rolling of the ingot does not provide a uniform processing of the cast structure and is characterized by axial porosity of the blanks. The number and size of pores increases from the periphery to the center of the blanks, which leads to deterioration in the processability of the material and the appearance of continuity defects in finished products. The use of three-stage long-term finish annealing (stage 1 460-470 °C, stage 2 510-520 °C, stage 3 580-590 °C) does not allow obtaining an increased level of material strength. In addition, the use of hot rolling at T= 630-650 °C in combination with a small number of cold deformation stages and low annealing temperatures does not allow the process of grinding and disintegration of the metastable P-Zr phase to be completed, which leads to a deterioration in the corrosion resistance of the products.The process flow chart also does not provide for finishing operations that allow removing residual process contaminants from the surface of tubular products, reducing the surface roughness. In the absence of these operations, the corrosion resistance of the products decreases.

[0014] The patent "Zirconium-based alloy for nuclear fuel assemblies" CN103898368A (published 02.07.2014, class C22C 16 / 00, C22F 1 / 18) is known. The patent specifies the composition of a multicomponent complex alloy, as well as a method for manufacturing products, including smelting an ingot, forging, homogenization and tempering of the blank, cold deformation with intermediate and finishing heat treatments.

[0015] The disadvantage of the method is that the products manufactured under the above patent do not have the required level of mechanical characteristics. The main structural products used in nuclear reactors are thin-walled pipes (shell pipes, guide channel pipes, etc.). The process of manufacturing tubular products necessarily includes the manufacture of tubular blanks (drilling, piercing), as well as multiple cold plastic deformation along the wall and diameter, the parameters of which significantly affect the characteristics and operation of tubular products, these operations are not described in the patent. Also, the patent does not provide for finishing operations that allow removing residual process contaminants from the surface of tubular products, reducing the surface roughness. Without finishing operations, the corrosion resistance of the products is reduced.

[0016] The closest to the claimed method is the “Method for producing tubular products from a zirconium-based alloy”, patent application WO2021 / 133195 (published on 01.07.2021, IPC B21B37 / 00, C22C 16 / 00, C21D8 / 10).The application specifies the alloy composition and the method for producing tubular products from a zirconium-based alloy, including smelting an ingot by multiple vacuum-arc remelting, mechanical processing of the ingot, heating, multi-stage hot forging of the ingot to produce a forging, subsequent mechanical processing of the forging to produce a round blank, producing tubular blanks, hardening and tempering them, applying a protective coating to them and heating to a hot pressing temperature, hot pressing, removing the protective coating from the surface of the sleeves, vacuum heat treatment, multiple cold rolling to produce tubular products, after each cold rolling an intermediate vacuum heat treatment is carried out, the final vacuum heat treatment is carried out on the finishing size, with subsequent finishing operations.

[0017] The disadvantage of the method, firstly, is that the alloy composition does not contain molybdenum or vanadium, which increase the corrosion resistance of the alloy. Another disadvantage is the use of multi-stage hot forging, which leads to an increase in the duration of the forging process of ingots into forgings due to the use of repeated heating. Another disadvantage of the patent application is that the tubular blank is hardened without further mechanical treatment, and then tempered, as a result of which an oxide film is formed on the side surface of the tubular blank, which is pressed into the metal during hot pressing, which leads to deterioration in the processability of the material, an increase in defects and a decrease in the corrosion resistance of tubular products. Another disadvantage is the lack of lubrication during hot pressing and a protective coating and lubrication in the first two stages of cold rolling, which leads to an increase in surface roughness and a decrease in corrosion resistance.The use of jet etching in finishing operations leads to greater roughness and lower corrosion resistance compared to the claimed method of batch etching. The combination of the above disadvantages of the method leads to the production of cold-rolled tubular products with lower corrosion resistance compared to the claimed method.

[0018] DISCLOSURE OF INVENTION

[0019] The objective of the present invention is to develop a technological method for producing cold-rolled tubular products used as structural elements of the active zone of water-cooled nuclear reactors of the WWER and PWR types, with higher corrosion resistance.

[0020] The technical result of the first and second variants of the proposed invention is the manufacturability of the material at all stages of hot and cold pressure treatment used in the manufacture of cold-rolled tubular products from an alloy additionally alloyed with molybdenum or vanadium, which improve the corrosion resistance of the products, as well as a reduction in the defectiveness and roughness of the surface of cold-rolled tubular products, which also ensures their high corrosion resistance.

[0021] The technical result in the proposed method according to the first variant is achieved by manufacturing cold-rolled tubular products from zirconium alloys, including smelting an ingot by multiple vacuum-arc remelting, mechanical processing of the ingot, heating, hot forging of the ingot to obtain a forging, subsequent mechanical processing of the forging, obtaining tubular blanks and tempering them, applying a protective coating to the tubular blanks and heating the tubular blanks to the temperature required for hot pressing, hot pressing of the tubular blanks, removing the protective coating from them, vacuum heat treatment, multi-stage cold rolling with intermediate heat treatments to obtain tubular products, final vacuum heat treatment at the finishing size with subsequent finishing operations, characterized in that before smelting the ingot, double ligatures of zirconium-niobium (Zr + Nb) and zirconium-molybdenum are smelted (Zr+Mo) and prepare the batch,containing powders of alloying components, the above-mentioned double ligatures and a zirconium-containing alloy base, an ingot is smelted containing % by 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, molybdenum 0.002-0.2, zirconium and impurities - the rest, hot forging of the ingot is carried out by drawing in one heating with partial deformations from 10 to 20% and tilting to obtain forgings, mechanical processing of the forging is carried out to obtain a tubular blank with allowances for their further mechanical processing, hardening of the tubular blanks is performed, then mechanical processing with the removal of allowances, then chemical treatment of the pipe blanks and their vacuum tempering are carried out, before heating to the temperature of hot pressing, a protective coating and additional lubricant are applied to the pipe blanks, then after hot pressing, the lubricant is removed and then the protective coating,and cold rolling is carried out in four stages with partial deformations of no more than 5%, total deformation per pass of 44.9-58.6% and with a ratio of deformation along the wall (ss) to deformation along the diameter (SD) of the tubular blank as / SD = 1.36-1.95, whereby before the first and second cold rolling a protective lubricating coating and lubricant are applied to the tubular blanks with subsequent removal after rolling, final finishing operations are carried out by straightening, grinding, batch etching and alkali treatment.

[0022] In double ligatures zirconium-niobium (Zr+Nb) and zirconium-molybdenum (Zr+Mo), the content of the main components (Zr+Nb or Zr+Mo) should be more than 99.2% by weight.

[0023] Powders of alloying components or chips from compact material have a fraction size of less than 1 mm.

[0024] Zirconium powder or zirconium sponge is used as the zirconium-containing base of the alloy.

[0025] Hot forging of the ingot is carried out at a temperature from 950 °C to 860 °C.

[0026] When manufacturing tubular blanks, drilling of the axial central hole is carried out before their hardening, and boring of the axial central hole is carried out after hardening.

[0027] Hardening of the tubular blank is carried out at a temperature of 1050-1090 °C in water.

[0028] The tempering of the tubular blank is carried out at a temperature of 600-640 °C.

[0029] Hot pressing of the tubular blank is carried out at a temperature from 640 °C to 600 °C with a drawing coefficient of c=12.3 and a pressing speed of 7-15 mm / s.

[0030] Vacuum heat treatment of tubular blanks after hot pressing is carried out before cold rolling at a temperature of 575-600 °C.

[0031] Vacuum heat treatment of tubular blanks in the intervals between cold rollings is carried out at a temperature of 565-590 °C.

[0032] The final vacuum heat treatment of tubular products is carried out at a temperature of 555-565°C.

[0033] The technical result in the proposed method according to the second variant is achieved by manufacturing cold-rolled tubular products from zirconium alloys, including smelting an ingot by multiple vacuum-arc remelting, mechanical processing of the ingot, heating, hot forging of the ingot to obtain a forging, subsequent mechanical processing of the forging, obtaining tubular blanks and tempering them, applying a protective coating to the tubular blanks and heating the tubular blanks to the temperature required for hot pressing, hot pressing of the tubular blanks, removing the protective coating from them, vacuum heat treatment, multi-stage cold rolling with intermediate heat treatments to obtain tubular products, final vacuum heat treatment at the finishing size with subsequent finishing operations, characterized in that before smelting the ingot, a double zirconium-niobium ligature (Zr+Nb) is smelted and a charge is prepared,containing vanadium in the form of chips from compact material or powder, powders of alloying components, double zirconium-niobium ligature and zirconium-containing alloy base, an ingot is smelted containing % by 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 - the rest, hot forging of the ingot is carried out by drawing in one heating with partial deformations from 10 to 20% and turning to obtain forgings, mechanical processing of the forging is carried out to obtain a tubular blank with allowances for their further mechanical processing, hardening of the tubular blanks is performed, then mechanical processing with the removal of allowances, then chemical treatment of the tubular blanks and their vacuum tempering are carried out, before heating to the temperature of hot pressing, a protective coating and additional lubrication are applied to the tubular blanks,then after hot pressing the lubricant and then the protective coating are removed, and cold rolling is carried out in four stages with partial deformations of no more than 5%, a total deformation per pass of 44.9-58.6% and with a ratio of deformation along the wall (ss) to deformation along the diameter (SD) of the tubular blank £s / ED - 1.36-1.95, and before the first and second cold rolling a sub-lubricating protective coating and lubricant are applied to the tubular blanks with subsequent removal after rolling, the final finishing operations are carried out by straightening, grinding, batch etching and alkali treatment.

[0034] In the double ligature zirconium-niobium (Zr+Nb) the content of the main components (Zr+Nb) should be more than 99.2% by weight.

[0035] The vanadium content in the chips or powder should be more than 99.2% by weight.

[0036] Powders of alloying components or chips from compact material have a fraction size of less than 1 mm.

[0037] Zirconium powder or zirconium sponge is used as the zirconium-containing base of the alloy.

[0038] Hot forging of the ingot is carried out at a temperature from 950 °C to 860 °C.

[0039] When manufacturing tubular blanks, drilling of the axial central hole is carried out before their hardening, and boring of the axial central hole is carried out after hardening.

[0040] Hardening of the tubular blank is carried out at a temperature of 1050-1090 °C in water.

[0041] The tempering of the tubular blank is carried out at a temperature of 600-640 °C.

[0042] Hot pressing of the tubular blank is carried out at a temperature from 640 °C to 600 °C with a drawing coefficient of p=12.3 and a pressing speed of 7-15 mm / s.

[0043] Vacuum heat treatment of tubular blanks after hot pressing is carried out before cold rolling at a temperature of 575-600 °C.

[0044] Vacuum heat treatment of tubular blanks in intervals between cold rollings is carried out at a temperature of 565-590 °C. The final vacuum heat treatment of tubular products is carried out at a temperature of 555-565 °C.

[0045] High corrosion properties and mechanical characteristics are provided by the technology of manufacturing tubular products, as well as the composition and range of contents of alloying elements. Zirconium alloy contains:

[0046] - niobium 0.8-1.7% by weight - to ensure mechanical and corrosion properties of cold-rolled tubular products; increasing the niobium content to more than 1.7% by weight increases the likelihood of the formation of a metastable phase of the F-phase type, which negatively affects the technological properties; a niobium content of less than 0.8% by weight does not allow achieving the required mechanical characteristics of cold-rolled tubular products;

[0047] - tin in the amount of 0.5-2.0% by weight - to neutralize the harmful effect of interstitial impurity elements and have a positive effect on the corrosion resistance of cold-rolled tubular products, an increase in the tin content of more than 2.0% by weight increases the resistance to deformation, worsens the processability of the alloy in the manufacture of cold-rolled tubular products, with a tin content of less than 0.5% by weight there is a decrease in the corrosion resistance of cold-rolled tubular products;

[0048] - iron in the amount of 0.3-1.0% by weight - to increase the alloy resistance to nodular corrosion in water and steam, increasing the iron content to more than 1.0% by weight promotes the formation of large T-phase particles that embrittle the material of cold-rolled tubular products, with an iron content of less than 0.3% by weight the resistance to nodular corrosion of cold-rolled tubular products decreases;

[0049] - chromium in the amount of 0.001-0.020% by weight - to form finely dispersed intermetallic phases in the structure, which lead to an increase in mechanical characteristics and stabilization of the corrosion resistance of cold-rolled tubular products; with an increase in the chromium content of more than 0.020% by weight, phases are formed that embrittle the material of cold-rolled tubular products; with a chromium content of less than 0.020% by weight, there is no stabilization of the corrosion resistance of cold-rolled tubular products;

[0050] - carbon in the amount of 0.003-0.040% by weight and oxygen in the amount of 0.04-0.15% by weight - to ensure solid-solution strengthening and improve the mechanical properties of cold-rolled tubular products, an increase in the carbon content of more than 0.040% by weight causes increased corrosion due to the formation of carbide phases at the grain boundaries; and an increase in the oxygen content of more than 0.15% by weight leads to increased defects of ingots and cold-rolled tubular products in the form of discontinuities, an oxygen content of less than 0.040% by weight and carbon less than 0.003% by weight does not ensure the required mechanical properties of cold-rolled tubular products; - oxygen in the amount of 0.04-0.15% by weight - to strengthen the alloy by the solid-solution mechanism; an increase in the oxygen content of more than 0.15% by weight leads to a decrease in the processability of the material at all stages of its pressure processing and the plastic characteristics of tubular products; reduction of oxygen content to less than 0.10 mass.% does not allow achieving the required level of mechanical characteristics of tubular products;

[0051] - silicon in the amount of 0.002-0.015% by weight - to stabilize the corrosion resistance of the alloy in water and steam at 400 °C, while reducing hydrogen absorption, an increase in the silicon content of more than 0.015% by weight worsens the processability of the alloy in the manufacture of cold-rolled tubular products, with a silicon content of less than 0.002% by weight the corrosion resistance of cold-rolled tubular products in water and steam at 400 °C worsens;

[0052] - molybdenum or vanadium in the amount of 0.002-0.2% by weight - to improve the corrosion properties of cold-rolled tubular products, an increase in the molybdenum content of more than 0.2% by weight worsens the processability of the alloy in the manufacture of cold-rolled tubular products, and an increase in the vanadium content of more than 0.2% by weight worsens the corrosion properties of cold-rolled tubular products, with a molybdenum or vanadium content of less than 0.002% by weight, the corrosion properties of cold-rolled tubular products are reduced.

[0053] To solve the problem, the first option proposes a technology for manufacturing tubular products from an alloy containing molybdenum, and the second option proposes a technology for manufacturing vanadium-containing tubular products from an alloy containing molybdenum.

[0054] According to the first variant, it is proposed to introduce refractory components of the niobium and molybdenum alloy in the form of double ligatures of zirconium-niobium (Zr+Nb) and zirconium-molybdenum (Zr+Mo). The method of preparing the charge ensures guaranteed dissolution and averaging of all components of the alloy during vacuum-arc melting of ingots specified in the invention of compositions. The following requirements have been established: for the content of the main components in double ligatures (Zr+Nb or Zr+Mo) more than 99.2% by weight. In order to prevent contamination of ingots of the claimed alloy with impurity elements that worsen the corrosion properties of cold-rolled tubular products.

[0055] According to the second variant, it is proposed to introduce into the alloy a refractory component of niobium in the form of a double ligature of zirconium-niobium (Zr+Nb), vanadium is introduced in the form of chips from a compact material or powder. The method for preparing the charge ensures guaranteed dissolution and averaging of all components of the alloy during vacuum-arc melting of ingots specified in the invention of compositions. The following requirements are established: for the content of the main components in the double ligature (Zr+Nb) more than 99.2% by weight and for the content of vanadium in vanadium powder or chips more than 99.2% by weight to prevent contamination of ingots of the claimed alloy with impurity elements that worsen the corrosion properties of cold-rolled tubular products.

[0056] Hot forging is carried out mainly in the 0-region, which allows for intensive processing of the cast structure without the formation of defects in one heating, which increases the processability of the material. This helps to increase the resource of plasticity and reduce the gas-saturated layer, the forging structure is uniform in cross-section. Forging in the range of partial deformations from 10 to 20% is due to the fact that a decrease in the value of partial deformations increases the temperature range of forging, reduces the degree of processing of the cast structure and the processability of the material and leads to the need to introduce an additional forging heating operation. An increase in partial deformations of more than 20% leads to the formation of defects on the surface of the forging, as well as to the ingress of the gas-saturated layer deep into the forging.The tilting operation (rotation) is carried out to ensure the required geometry and increase the homogeneity of the cast structure processing, this is due to the fact that hot forging by drawing is carried out with the application of a compressive load only along one axis. Rotation of the forging changes the direction of deformation and, as a result, ensures the production of a homogeneous structure of the forging material and the required shape of the forging.

[0057] The order of operations in the manufacture of pipe blanks is as follows: mechanical processing to obtain a pipe blank for hardening with allowances for further mechanical processing, hardening of pipe blanks, subsequent mechanical processing with allowance removal to obtain pipe blanks without an oxidized layer, chemical treatment of pipe blanks and their vacuum tempering, which allows obtaining pipe blanks without oxidized surfaces, which leads to improved processability of the material, reduced defects and increased corrosion resistance of pipe products. Chemical treatment of pipe blanks after hardening is carried out to remove residual process contaminants from the surface. Vacuum tempering prevents oxidation of the surface of pipe blanks before hot pressing.

[0058] Before hot pressing, a protective coating is applied to the surface of the tubular blanks to protect them from oxidation and gas saturation, and then a lubricant. The lubricant improves the conditions of tribocontact interaction (interaction of solid deformable bodies during their relative movement) during hot pressing and cold rolling, which eliminates the formation of defects on the outer and inner surfaces, thereby increasing the processability of the material. The lubricant also intensifies the hot pressing process, namely, increases the elongation coefficient (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.

[0059] Before the first and second cold rolling, a protective lubricating coating and lubricant are applied to the tubular blanks, with subsequent removal after rolling to improve tribu-contact interaction during cold rolling, to eliminate sticking and to minimize defects on the outer and inner surfaces of the tubular blanks. Cold rolling is carried out in four stages with a gradual increase in deformation from stage to stage and a given ratio of deformation along the wall ES to deformation along the diameter £D to ensure uniform refinement of the grain structure and second-phase inclusions, and to increase the homogeneity of the structure. Rolling of tubular blanks should be carried out with partial deformations of no more than 5%.Increasing partial deformations by more than 5% leads to a decrease in the number of alternating loads, a decrease in the influence of the Bauschinger effect on the reduction of the yield strength, an increase in the thermal effect of plastic deformation and, as a result, to an earlier onset of an unstable flow of plastic deformation - localization. As a result, this significantly reduces the manufacturability of the metal and leads to the appearance of continuity defects in finished pipes. The total deformation per pass in the range of 44.9-59.6% ensures defect-free manufacturing with a minimum number of rolling passes (4 rolling passes). The ratio of the deformation along the wall £s to the deformation along the diameter ED of the pipe blank 8s / ED = 1.36-1.95 ensures maximum use of the Bauschinger effect and, as a result, an increase in the manufacturability of the processed material. In addition, deformation is mainly carried out along the wall, which ensures refinement of the material structure and, as a result, increases corrosion resistance.The formation of a favorable radial texture fr up to 0.6 occurs, which provides the required mechanical strength.

[0060] The order of finishing operations has been changed, namely straightening, grinding, batch etching, alkali treatment. Using the grinding operation before batch etching allows to reduce the roughness of the outer surface, reduce defects and increase the corrosion resistance of tubular products. Batch etching instead of jet etching allows to provide the required morphology, surface cleanliness inside and outside, which increases the corrosion resistance of tubular products.

[0061] IMPLEMENTATION OF THE INVENTION

[0062] The method is carried out as follows:

[0063] Example 1 (first option) According to the first option of the technical solution, the technology for manufacturing tubular products includes the following operations.

[0064] The following alloys were smelted: zirconium-molybdenum (Zr+Mo) with an average molybdenum content of 37.1% by weight, the zirconium and molybdenum content in the alloy is 99.35% by weight, and zirconium-niobium (Zr+Nb) with an average niobium content of 52.6% by weight, the zirconium and niobium content in the alloy is 99.4% by weight. Double alloys are produced in the form of chips with a fraction size of less than 1 mm. Powders of alloying components: zirconium dioxide, iron and tin are sifted through a sieve with a cell size of 1 mm, the powder fraction of less than 1 mm is used as a batch. Zirconium powder with an average impurity content, % by weight is used as a zirconium-containing base of the alloy: 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-the rest. Zirconium powder is mixed with shavings from double ligatures Zr+Nb and Zr+Mo and powders of alloying components.Then consumable electrodes are formed, which are remelted twice by vacuum-arc remelting. An ingot is obtained with the following composition, % by weight: 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; 0 - 0.082-0.086; Si -0.003; Zr and impurities - the rest. The side surface of the ingot is mechanically processed. The ingot is heated in a resistance electric furnace to a temperature of 950 °C, the ingot forging is carried out in one heating by drawing with partial deformations of 10-20% and tilting to obtain forgings. Forging is completed at a forging temperature of 860 °C.

[0065] Mechanical processing of forgings is carried out with allowances for further mechanical processing. When manufacturing tubular blanks, drilling of the axial central hole is carried out before their hardening.

[0066] Hardening of tubular blanks is performed at a temperature of 1050-1090 °C in water.

[0067] Mechanical processing is carried out by turning the outer surface and boring the axial central hole to remove oxidized metal (allowance) and tubular blanks with dimensions for hot pressing are obtained.

[0068] After which, chemical treatment of the pipe blanks is carried out (degreasing and chemical etching). Then, vacuum tempering of the pipe blanks is carried out at a temperature of 600-640 °C. Vacuum furnaces with a vacuum of 1 ■ 10' are used. 4 -1 • 10' 5 mm Hg

[0069] Next, a protective copper coating and lubricant are applied to the tubular blanks using a galvanic method to improve tribocontact interaction and protect against gas saturation during heating and hot pressing.

[0070] Heating of tubular blanks for hot pressing is carried out in a furnace with an air atmosphere. The heating temperature of tubular blanks before pressing is in the range from 600 to 640 °C. Pressing is carried out with a drawing coefficient of c = 12.3 and a pressing speed of 7-15 mm / s. Then the lubricant and protective coating are removed.

[0071] Then the tubular blanks are sent for vacuum heat treatment at T=575-600 °C. Vacuum furnaces with a vacuum of 1 10' are used. 4 -1 10' 5 mm Hg

[0072] Before the first two stages of cold rolling, a protective copper coating is applied by galvanic means and lubricant is applied to improve tribocontact interaction and eliminate defects on the outer and inner surfaces; after cold rolling with a protective coating and lubricant, the lubricant and protective coating are removed from the tubular blanks by chemical etching.

[0073] Pipe blanks are rolled on cold rolling mills of the HPT, KPW type in 4 rollings with partial deformations of 4-4.5%:

[0074] 1 rolling - total deformation 44.9% with the ratio of deformation along the wall (8s) to deformation along the diameter (SD) of the tubular blank 8s / SD = 1.36;

[0075] 2 rolling - total deformation 47.6% with the ratio of deformation along the wall (8s) to deformation along the diameter (SD) of the tubular blank ss / SD = 1.51;

[0076] 3 rolling - total deformation 53.8% with the ratio of deformation along the wall (ss) to deformation along the diameter (SD) of the tubular blank ss / SD = 1.41;

[0077] 4 rolling - total deformation 58.6% with the ratio of deformation along the wall (ss) to deformation along the diameter (SD) of the tubular blank ss / SD = 1.92.

[0078] Intermediate vacuum heat treatments between cold rollings are carried out in the temperature range from 565 °C to 590 °C. Vacuum furnaces with a vacuum of 1 • 10' are used.4 -1 • 10' 5 mm Hg

[0079] The final vacuum heat treatment is carried out at T=555-565 °C. Vacuum furnaces with a vacuum of 1 • 10' are used. 4 -1 • 10' 5 mm Hg

[0080] After final annealing, tubular products undergo finishing operations by straightening, grinding, batch etching and alkali treatment.

[0081] Cold-rolled tubular products 012.9x10.9 mm made of alloy, manufactured according to the declared technical solution, are characterized by the following properties (table, example 1). Additionally, the ultrasonic testing (UT) method is used to check the continuity of cold-rolled tubular products; during testing, a standard one with a defect depth of 0.05 mm is used, respectively, the signal corresponds to a defect of 0.05 mm in depth in 100%. To determine suitable pipes, the signal level is determined. The UT results are presented in the table. The table shows that the developed method allows to reduce the signal level by ~ two times and, accordingly, the defect depth. Studies of corrosion resistance (weight gain relative to the prototype during corrosion tests) of cold-rolled tubular products in an environment with steam at a temperature of 400 °C, in water at temperatures of 330 °C, 360 °C with and without the addition of 70 ppm Li, showed a smaller weight gain relative to the prototype in percentage in all autoclave test modes.

[0082] Example 2 (first option)

[0083] Carry out the same procedure as in example 1.

[0084] Alloy composition in % by weight: 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 - the rest.

[0085] Cold-rolled tubular products 012.9x10.9 mm made of alloy, manufactured according to the declared technical solution, are characterized by the following properties (table, example 2).

[0086] Example 3 (first option)

[0087] Carry out the same procedure as in example 1.

[0088] The zirconium-containing base of the alloy is made of zirconium sponge with an average impurity content, % by weight: 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 - the rest.

[0089] Powders of alloying components were sifted through a sieve with a cell size of 1 mm; the fraction of powders less than 1 mm was mixed with shavings from double ligatures Zr+Nb and Zr+Mo and zirconium sponge (the base of the alloy).

[0090] Alloy composition in % by weight: 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 - the rest.

[0091] Cold-rolled tubular products 012.9x10.9 mm made of alloy, manufactured according to the declared technical solution, are characterized by the following properties (table, example 3).

[0092] Example 4 (second option)

[0093] According to the second version of the technical solution, the technology for manufacturing tubular products includes the following operations.

[0094] A zirconium-niobium (Zr+Nb) ligature with an average niobium content of 52.6 wt.% was smelted, the zirconium and niobium content in the ligature was 99.4 wt.%, respectively. Chips with a fraction size of less than 1 mm were obtained by mechanical treatment of the double ligature. A powder with an average impurity content, % by weight, was used as a zirconium-containing base for the alloy: 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 - the rest.

[0095] Vanadium (with a vanadium content of 99.4% by weight), powders of alloying components: zirconium dioxide, iron and tin are sifted through a sieve with a cell size of 1 mm, the fraction of powders less than 1 mm is used as a batch. Zirconium powder (zirconium-containing base of the alloy) is mixed with shavings from a double ligature Zr + Nb and powders of alloying components. Then consumable electrodes are formed, which are remelted by double vacuum-arc remelting. An ingot with the composition, % by weight is 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 - the rest.

[0096] The side surface of the ingot is machined. The ingot is heated in a resistance electric furnace to a temperature of 950 °C, the ingot is forged in one heating by drawing with partial deformations of 10-20% and turning to obtain forgings. Forging is completed at a forging temperature of 860 °C.

[0097] Mechanical processing of forgings is carried out with allowances for further mechanical processing. When manufacturing tubular blanks, drilling of the axial central hole is carried out before their hardening.

[0098] Hardening of tubular blanks is performed at a temperature of 1050-1090 °C in water.

[0099] Mechanical processing is carried out by turning the outer surface and boring the axial central hole to remove oxidized metal (allowance) and tubular blanks with dimensions for hot pressing are obtained.

[0100] After which, chemical treatment of the pipe blanks is carried out (degreasing and chemical etching). Then, vacuum tempering of the pipe blanks is carried out at a temperature of 600-640 °C. Vacuum furnaces with a vacuum of 1 ■ 10' are used. 4 -1 • 10' 5 mm Hg

[0101] Next, a protective copper coating and lubricant are applied to the tubular blanks using a galvanic method to improve tribocontact interaction and protect against gas saturation during heating and hot pressing.

[0102] Heating of tubular blanks for hot pressing is carried out in a furnace with an air atmosphere. The heating temperature of tubular blanks before pressing is in the range from 600 to 640 °C. Pressing is carried out with a drawing coefficient of c = 12.3 and a pressing speed of 7-15 mm / s. Then the lubricant and protective coating are removed.

[0103] Then the tubular blanks are sent for vacuum heat treatment at T=575-600 °C. Vacuum furnaces with a vacuum of 1 - 10' are used. 4 -1 10' 5mm Hg. Before the first two stages of cold rolling, a protective copper coating is applied by galvanic means and lubricant is applied to improve tribocontact interaction and eliminate defects on the outer and inner surfaces; after cold rolling with a protective coating and lubricant, the lubricant and protective coating are removed from the tubular blanks by chemical etching.

[0104] Pipe blanks are rolled on cold rolling mills of the HPT, KPW type in 4 rollings with partial deformations of 4-4.5%:

[0105] 1 rolling - total deformation 44.9% with the ratio of deformation along the wall (ss) to deformation along the diameter (ED) of the tubular blank ES / ED = 1.36;

[0106] 2 rolling - total deformation 47.6% with the ratio of deformation along the wall (ES) to deformation along the diameter (ED) of the tubular blank ES / ED = 1.51;

[0107] 3 rolling - total deformation 53.8% with the ratio of deformation along the wall (ES) to deformation along the diameter (ED) of the tubular blank ES / d = 1.41;

[0108] 4 rolling - total deformation 58.6% with the ratio of deformation along the wall (ES) to deformation along the diameter (ED) of the tubular blank ES / £D = 1.92.

[0109] Intermediate vacuum heat treatments between cold rollings are carried out in the temperature range from 565 °C to 590 °C. Vacuum furnaces with a vacuum of 1 10' are used. 4 -1 10' 5 mm Hg

[0110] The final vacuum heat treatment is carried out at T=555-565 °C. Vacuum furnaces with a vacuum of 1 • 10' are used. 4 -1 • 10' 5 mm Hg

[0111] After final annealing, tubular products undergo finishing operations by straightening, grinding, batch etching and alkali treatment.

[0112] Cold-rolled tubular products 012.9x10.9 mm made of alloy, manufactured according to the declared technical solution, are characterized by the following properties (table, example 4). Additionally, the continuity of cold-rolled tubular products is controlled by the ultrasonic testing (UT) method; during testing, a standard one with a defect depth of 0.05 mm is used, respectively, the signal corresponds to a defect of 0.05 mm in depth in 100%. To determine suitable pipes, the signal level is determined. The UT results are presented in the table. The table shows that the developed method allows to reduce the signal level by ~ two times and, accordingly, the defect depth.

[0113] Studies of corrosion resistance (weight gain relative to the prototype during corrosion tests) of cold-rolled tubular products in an environment with steam at a temperature of 400 °C, in water at temperatures of 330 °C, 360 °C with and without the addition of 70 ppm Li, showed a smaller weight gain relative to the prototype in percentage in all autoclave test modes. Example 5 (second option)

[0114] Carry out the same procedure as in example 4.

[0115] The zirconium-containing base of the alloy is made of zirconium sponge with an average impurity content, % by weight: 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 - the rest.

[0116] Mechanical processing of compact vanadium (with a vanadium content of 99.5% by weight) produces chips with a fraction size of less than 1 mm.

[0117] Powders of alloying components: zirconium dioxide, iron and tin are sifted through a sieve with a cell size of 1 mm; a fraction of powders less than 1 mm is used as a batch.

[0118] Zirconium sponge (zirconium-containing base of the alloy) is mixed with shavings from the double Zr+Nb ligature and vanadium shavings, as well as with powders of alloying components.

[0119] The composition of the obtained alloy in % by weight: 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 - the rest.

[0120] Cold-rolled tubular products 012.9x10.9 mm made of alloy, manufactured according to the declared technical solution, are characterized by the following properties (table, example 5).

[0121] Table Properties of tubular products according to the prototype and the declared technical solution

[0122] INDUSTRIAL APPLICABILITY

[0123] Thus, the presented method for manufacturing cold-rolled tubular products (options) ensures the manufacturability of the material at all stages of hot and cold pressure treatment used in the manufacture of cold-rolled tubular products, with additional alloying with molybdenum (first option) or vanadium (second option), which improve the corrosion resistance of the products, and also ensures a decrease in the defectiveness and roughness of the surfaces of cold-rolled tubular products, which improves their corrosion resistance in various environments (with steam at a temperature of 400 °C, in water at temperatures of 330 °C, 360 °C with the addition of 70 ppm Li and without).

Claims

Invention formula 1. A method for producing cold-rolled tubular products from zirconium alloys, comprising smelting an ingot by repeated vacuum-arc remelting, mechanical processing of the ingot, heating, hot forging of the ingot to produce a forging, subsequent mechanical processing of the forging, producing tubular blanks and tempering them, applying a protective coating to the tubular blanks and heating the tubular blanks to a temperature required for hot pressing, hot pressing of the tubular blanks, removing the protective coating from them, vacuum heat treatment, multi-stage cold rolling with intermediate heat treatments to produce tubular products, final vacuum heat treatment at the finishing size with subsequent finishing operations, characterized in that before smelting the ingot, double ligatures of zirconium-niobium (Zr+Nb) and zirconium-molybdenum (Zr+Mo) are smelted and a charge is prepared, containing powders of alloying components,the above-mentioned double ligatures and a zirconium-containing alloy base, an ingot is smelted containing % by 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, molybdenum 0.002-0.2, zirconium and impurities - the rest, hot forging of the ingot is carried out by drawing in one heating with partial deformations from 10 to 20% and tilting to obtain forgings, mechanical processing of the forging is carried out to obtain a tubular blank with allowances for their further mechanical processing, hardening of the tubular blanks is performed, then mechanical processing with removal allowances, then chemical treatment of the tubular blanks and their vacuum tempering are carried out, before heating to the temperature of hot pressing, a protective coating and additional lubricant are applied to the tubular blanks, then after hot pressing the lubricant is removed and then the protective coating, and cold rolling is carried out in four stages with partial deformations of no more than 5%,with a total deformation per pass of 44.9-58.6% and with a ratio of deformation along the wall (ss) to deformation along the diameter (SD) of the tubular blank es / 8D = 1.36-1.95, and before the first and second cold rolling, a protective lubricating coating and lubricant are applied to the tubular blanks with subsequent removal after rolling, the final finishing operations are carried out by straightening, grinding, batch etching and alkali treatment.

2. The method according to item 1, characterized in that in the double ligatures zirconium-niobium (Zr+Nb) and zirconium-molybdenum (Zr+Mo) the content of the main components (Zr+Nb or Zr+Mo) must be more than 99.2% by weight.

3. The method according to paragraph 1, characterized in that the powders of alloying components or chips from compact material have a fraction size of less than 1 mm.

4. The method according to paragraph 1, characterized in that zirconium powder or zirconium sponge is used as the zirconium-containing base of the alloy.

5. The method according to paragraph 1, characterized in that hot forging of the ingot is carried out at a temperature from 950 °C to 860 °C.

6. The method according to paragraph 1, characterized in that when manufacturing tubular blanks, drilling of the axial central hole is carried out before their hardening, and boring of the axial central hole is carried out after hardening.

7. The method according to item 1, characterized in that the hardening of the tubular blank is carried out at a temperature of 1050-1090 °C in water.

8. The method according to paragraph 1, characterized in that the tempering of the tubular blank is carried out at a temperature of 600-640 °C.

9. The method according to item 1, characterized in that hot pressing of the tubular blank is carried out at a temperature from 640 °C to 600 °C with a drawing coefficient of c=12.3 and a pressing speed of 7-15 mm / s.

10. The method according to paragraph 1, characterized in that vacuum heat treatment of tubular blanks after hot pressing is carried out before cold rolling at a temperature of 575-600 °C.

11. The method according to paragraph 1, characterized in that the vacuum heat treatment of tubular blanks in the intervals between cold rollings is carried out at a temperature of 565-590 °C.

12. The method according to paragraph 1, characterized in that the final vacuum heat treatment of tubular products is carried out at a temperature of 555-565°C.

13. A method for producing cold-rolled tubular products from zirconium alloys, comprising smelting an ingot by repeated vacuum-arc remelting, mechanical processing of the ingot, heating, hot forging of the ingot to produce a forging, subsequent mechanical processing of the forging, producing tubular blanks and tempering them, applying a protective coating to the tubular blanks and heating the tubular blanks to a temperature required for hot pressing, hot pressing of the tubular blanks, removing the protective coating from them, vacuum heat treatment, multi-stage cold rolling with intermediate heat treatments to produce tubular products, final vacuum heat treatment at the finishing size with subsequent finishing operations, characterized in that before smelting the ingot, a double zirconium-niobium ligature (Zr+Nb) is smelted and a charge is prepared containing vanadium in the form of chips from a compact material or powder, powders of alloying components,a double ligature of zirconium-niobium and a zirconium-containing alloy base, an ingot containing % by weight is smelted. 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 - the rest, hot forging of the ingot is carried out by drawing in one heating with partial deformations from 10 to 20% and tilting to obtain forgings, mechanical processing of the forging is carried out to obtain a tubular blank with allowances for their further mechanical processing, hardening of the tubular blanks is performed, then mechanical processing with removal of allowances, then chemical treatment of the tubular blanks and their vacuum tempering are carried out, before heating to the temperature of hot pressing at the tubular blanks are coated with a protective coating and additionally with lubricant, then after hot pressing the lubricant is removed and then the protective coating, and cold rolling is carried out in four stages with partial deformations of no more than 5%, the total deformation per pass is 44.9-58,6% and with a ratio of wall deformation (ss) to diameter deformation (SD) of the tubular blank es / £D = 1.36-1.95, and before the first and second cold rolling, a protective lubricating coating and lubricant are applied to the tubular blanks with subsequent removal after rolling, the final finishing operations are carried out by straightening, grinding, batch etching and alkali treatment.

14. The method according to item 13, characterized in that in the double zirconium-niobium ligature (Zr+Nb) the content of the main components (Zr+Nb) must be more than 99.2% by weight.

15. The method according to item 13, characterized in that the vanadium content in the shavings or powder must be more than 99.2% by weight.

16. The method according to paragraph 13, characterized in that the powders of alloying components or chips from compact material have a fraction size of less than 1 mm.

17. The method according to paragraph 13, characterized in that zirconium powder or zirconium sponge is used as the zirconium-containing base of the alloy.

18. The method according to paragraph 13, characterized in that hot forging of the ingot is carried out at a temperature from 950 °C to 860 °C.

19. The method according to paragraph 13, characterized in that when manufacturing tubular blanks, drilling of the axial central hole is carried out before their hardening, and boring of the axial central hole is carried out after hardening.

20. The method according to paragraph 13, characterized in that the hardening of the tubular blank is carried out at a temperature of 1050-1090 °C in water.

21. The method according to paragraph 13, characterized in that the tempering of the tubular blank is carried out at a temperature of 600-640 °C.

22. The method according to item 13, characterized in that hot pressing of the tubular blank is carried out at a temperature from 640 °C to 600 °C with a drawing coefficient of c=12.3 and a pressing speed of 7-15 mm / s.

23. The method according to paragraph 13, characterized in that vacuum heat treatment of tubular blanks after hot pressing is carried out before cold rolling at a temperature of 575-600 °C.

24. The method according to paragraph 13, characterized in that the vacuum heat treatment of tubular blanks in the intervals between cold rollings is carried out at a temperature of 565-590 °C.

25. The method according to paragraph 13, characterized in that the final vacuum heat treatment of tubular products is carried out at a temperature of 555-565°C.

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