A method for preparing zirconium alloy pipe

Abstract

A method for preparing a zirconium alloy tube comprises: obtaining a zirconium alloy tube blank; rolling the tube blank at least three times, and performing annealing after each rolling to obtain a zirconium alloy tube; the ratio of the relative wall reduction to the relative diameter reduction in the last rolling pass is 1.9 to 2.1, and the ratio of the relative wall reduction to the relative diameter reduction in the second to last rolling pass and the third to last rolling pass is 1.0 to 2.1. The present invention can effectively improve the orientation distribution of hydrides after hydrogen precipitation of zirconium alloy by reasonably distributing the ratio of the relative wall reduction to the relative diameter reduction in the last three rolling passes in the production process of zirconium alloy tubes, so as to overcome the phenomenon that the hydrides precipitated from zirconium alloys are brittle.

Description

Technical Field

[0001] The invention relates to the technical field of material metals, and in particular to a method for preparing a zirconium alloy tube. Background Art

[0002] Zirconium alloy is used as a key structural material for nuclear reactor fuel due to its small thermal neutron absorption cross section and excellent corrosion resistance. However, in water-cooled reactors, "hydrogen absorption" of zirconium alloy cladding components is an inevitable phenomenon. When the hydrogen content exceeds its solubility in zirconium alloy, the supersaturated hydrogen will form hydrides (ZrH1.66). The precipitation of hydrides will destroy the integrity of α-Zr grains, produce microcracks or increase in volume, resulting in a decrease in material toughness and strength. When the operating temperature is lower than 150°C, the hydrides precipitated in the matrix are brittle, which is called "hydrogen embrittlement." Summary of the invention

[0003] (I) Purpose of the invention

[0004] The purpose of the present invention is to provide a method for preparing a zirconium alloy tube which can reduce the "hydrogen embrittlement" phenomenon of the zirconium alloy.

[0005] (II) Technical solution

[0006] To solve the above problems, the present invention provides a method for preparing a zirconium alloy tube, comprising: obtaining a zirconium alloy tube blank; performing at least three rolling passes on the tube blank, and performing annealing after each rolling pass to obtain a zirconium alloy tube; the ratio of the relative wall reduction to the relative diameter reduction in the last rolling pass is 1.9 to 2.1, and the ratio of the relative wall reduction to the relative diameter reduction in the second to last rolling pass and the third to last rolling pass is 1.0 to 2.1.

[0007] Optionally, for the last three rolling passes, the cumulative annealing parameter value of the annealing treatment after each rolling pass is controlled at 3.2×10 -20 ~5.2×10 -19 h.

[0008] Optionally, the cumulative annealing parameter is: ∑A=∑[t i exp(-Q / RT i )];

[0009] Among them, ∑A is the cumulative annealing parameter, t i is the annealing time per pass (h), T i is the temperature of each annealing process (K), Q is the activation energy, and R is the gas constant.

[0010] Optionally, the raw material is subjected to vacuum consumable melting three times to obtain an ingot; the ingot is heated to a first preset temperature and kept warm for a first preset time, then forged to obtain a forged billet; the forged billet is induction quenched at a second preset temperature; the quenched forged billet is extruded and annealed to obtain the zirconium alloy tube billet.

[0011] Optionally, the size of the ingot is within 700mm-750mm; the first preset temperature is not less than 1030°C; the first preset time is 2-5h; the size of the forged billet is within 200mm-250mm; the second preset temperature is 1010-1100°C; the temperature of the extrusion treatment is not more than 650°C; the size of the zirconium alloy tube billet is 80×15mm-90×25mm.

[0012] Optionally, the raw material is a Zr-4 zirconium alloy raw material.

[0013] Optionally, the raw material includes: 1.20-1.70wt% tin, 0.18-0.24wt% iron, 0.07-0.13wt% chromium, 0.09-0.16wt% oxygen, less than 0.0200wt% carbon and less than 0.0120wt% silicon, and the balance is zirconium and impurities.

[0014] Optionally, the raw materials include: 1.30 wt% tin, 0.22 wt% iron, 0.12 wt% chromium, 0.12 wt% oxygen, 0.0070 wt% carbon and 0.010 wt% silicon.

[0015] Optionally, the ratio of the relative wall reduction to the relative diameter reduction in each rolling is obtained by the ratio of the tube wall deformation to the diameter deformation.

[0016] (III) Beneficial effects

[0017] The above technical solution of the present invention has the following beneficial technical effects:

[0018] The invention can effectively improve the orientation distribution of hydrides after hydrogen precipitation of zirconium alloy by reasonably distributing the ratio of the relative wall reduction to the relative diameter reduction in the last three rolling passes during the production process of zirconium alloy pipes, so as to overcome the phenomenon that the hydrides precipitated from the zirconium alloy are brittle. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of a zirconium alloy tube obtained by the method for making a zirconium alloy tube of the present invention under a microscope. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0021] In the description of the present invention, it should be noted that the terms “first”, “second” and “third” are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0022] The present embodiment provides a method for preparing a zirconium alloy tube, comprising: obtaining a zirconium alloy tube blank; rolling the tube blank at least three times, and performing annealing after each rolling to obtain a zirconium alloy tube; the ratio of the relative wall reduction to the relative diameter reduction in the last rolling pass is 1.9 to 2.1, and the ratio of the relative wall reduction to the relative diameter reduction in the second to last rolling pass and the third to last rolling pass is 1.0 to 2.1. Among them, the ratio of the last relative wall reduction to the relative diameter reduction (hereinafter referred to as the Q value) is 1.0 to 2.1, and the corresponding pass deformation is 69% to 83%. The present embodiment can effectively improve the orientation distribution of hydrides after hydrogen precipitation in the zirconium alloy by reasonably distributing the ratio of the relative wall reduction to the relative diameter reduction in the last three rolling passes during the production process of the zirconium alloy tube, so as to overcome the phenomenon that the hydrides precipitated from the zirconium alloy are brittle.

[0023] Research has shown that in order to overcome "hydrogen embrittlement", one is to minimize hydrogen absorption and the other is to improve the orientation distribution of hydrides after hydrogen absorption. The present invention uses Zr-4 alloy pipes because Zr-4 alloy pipes reduce the nickel component that causes hydrogen absorption and can effectively reduce "hydrogen embrittlement". Zr-4 alloy pipes for nuclear reactors generally use hydride orientation factor f n 40° To quantitatively characterize the hydride orientation, it is defined as the ratio of the number of hydride strips with an angle less than 40° to the radial direction to the total number of hydride strips in the field of view. For Zr-4 alloy recrystallization annealing tubes, f is generally required. n 40° ≤0.50. Since zirconium is a close-packed hexagonal structure with anisotropy, texture will be formed during processing. This directionality makes the hydride also directional. Usually, the precipitation of hydride has a so-called habit plane. The habit plane of Zr-4 alloy is The angle with the base surface is 15°, and it is approximately assumed that the hydride precipitates along the base surface. Therefore, in order to prevent the hydride distribution along the radial direction, which is not conducive to the performance of the pipe, the essence is to optimize the texture distribution during the processing. Studies have shown that there is a certain relationship between texture and rolling Q value. When only the rolling Q value of the finished pass is considered, the radial texture factor f r Correlation R with Q value 2is 0.33. When the Q value of the last three rolling passes is considered, the radial texture factor f r Correlation R with Q value 2 is 0.83, and it is generally believed that R 2 =1, the correlation is the best, so optimizing the texture distribution of the tube requires controlling the Q value distribution of the last three rolling passes. The zirconium alloy obtained by this embodiment has f n 40° Very small, visible Figure 1 .

[0024] In an optional embodiment, the Q value is calculated using the ratio of the tube wall deformation to the diameter deformation, where the tube wall deformation is the deformation of the tube length, and the diameter deformation is the deformation of the outer diameter of the tube.

[0025] In an optional embodiment, when annealing is performed above the recrystallization temperature, the higher the annealing temperature, the more chaotic the distribution of hydrides tends to be. Therefore, controlling the annealing parameters of the last three rolling passes is also very important for optimizing the distribution of hydrides. For the last three rolling passes, the cumulative annealing parameter value of the annealing treatment after each rolling pass is controlled at 3.2×10 -20 ~5.2×10 -19 h, only then can a tube with a lower hydride orientation factor be obtained. The cumulative annealing parameter is: ∑A=Σ[t i exp(-Q / RT i )]; where ∑A is the cumulative annealing parameter, t i is the annealing time per pass (h), T i is the temperature of each annealing treatment (K), Q is the activation energy, R is the gas constant, and generally for Zr-4 alloy, Q / R=40000K.

[0026] In an optional embodiment, the raw material is subjected to vacuum consumable melting three times to obtain an ingot; the ingot is heated to a first preset temperature and kept warm for a first preset time, then forged to obtain a forged billet; the forged billet is induction quenched at a second preset temperature; the quenched forged billet is extruded and annealed to obtain the zirconium alloy tube billet. Specifically, the size of the ingot is within Ф700mm-Ф750mm; the first preset temperature is not less than 1030℃; the first preset time is 2 to 5h; the size of the forged billet is within Ф200mm-Ф250mm; the second preset temperature is 1010 to 1100℃; the temperature of the extrusion treatment is not more than 650℃; the size of the zirconium alloy tube billet is Ф80×15mm-Ф90×25mm.

[0027] In an optional embodiment, the raw material is a raw material of Zr-4 zirconium alloy, which includes: 1.20-1.70wt% tin, 0.18-0.24wt% iron, 0.07-0.13wt% chromium, 0.09-0.16wt% oxygen, less than 0.0200wt% carbon and less than 0.0120wt% silicon, and the balance is zirconium and impurities.

[0028] In an optional embodiment, this embodiment defines preferred values ​​based on an embodiment of the valley, wherein the raw materials include: 1.30wt% tin, 0.22wt% iron, 0.12wt% chromium, 0.12wt% oxygen, 0.0070wt% carbon and 0.010wt% silicon (see Table 1).

[0029] Table 1

[0030]

[0031] Example 1

[0032] Obtain the raw materials in Table 1 and perform the following steps:

[0033] S1: Obtain a 720 mm ingot through three vacuum consumable smeltings;

[0034] S2: heating the ingot to above 1030° C. in a box-type heating furnace, keeping the temperature for 2 to 5 hours, and then forging the ingot to obtain a 225 mm Ø forging ingot;

[0035] S3: Induction hardening of the 225 mm diameter forging blank at 1010-1100°C;

[0036] S4: extruding the Ø225 mm quenched billet at ≤650°C to obtain an extruded tube billet of Ø86×19 mm;

[0037] S5: annealing the Ø86×19 mm extruded tube blank at ≤700° C. for 1 to 1.5 hours to obtain a zirconium alloy tube blank;

[0038] S6: Φ86×19mm zirconium alloy tube billet is cold rolled to Φ63.5×10.92mm, annealed at ≤650℃, and the holding time is 1.5 to 3.5 hours;

[0039] S7: The annealed Φ63.5×10.92mm tube was subjected to the last three cold rolling passes. The Q values ​​(from front to back) of the last three passes were 1.284, 1.015, and 1.971, respectively; the deformation amounts (from front to back) were 71.80%, 69.41%, and 73.55%, respectively; the cumulative annealing parameter ∑A value of the last three passes was 5.18×10 -19 h.

[0040] The hydride test results show that f n 40° =0.18.

[0041] Example 2

[0042] Obtain the raw materials in Table 1 and perform the following steps:

[0043] S1: Obtain a 720 mm ingot through three vacuum consumable smeltings;

[0044] S2: heating the ingot to above 1030° C. in a box-type heating furnace, keeping the temperature for 2 to 5 hours, and then forging the ingot to obtain a 225 mm Ø forging ingot;

[0045] S3: Induction hardening of the 225 mm diameter forging blank at 1010-1100°C;

[0046] S4: extruding the Ø225 mm quenched billet at ≤650°C to obtain an extruded tube billet of Ø86×19 mm;

[0047] S5: annealing the Ø86×19 mm extruded tube blank at ≤700° C. for 1 to 1.5 hours to obtain a zirconium alloy tube blank;

[0048] S6: Φ86×19mm zirconium alloy tube billet is cold rolled to Φ63.5×10.92mm, annealed at ≤650℃, and the holding time is 1.5 to 3.5 hours;

[0049] S7: The annealed Φ63.5×10.92mm tube was subjected to the last three cold rolling passes. The Q values ​​(from front to back) of the last three passes were 1.284, 1.015, and 1.971, respectively; the deformation amounts (from front to back) were 71.80%, 69.41%, and 73.55%, respectively; the cumulative annealing parameter ∑A value of the last three passes was 3.2×10 -20 h.

[0050] The hydride test results show that f n 40° =0.17.

[0051] Example 3

[0052] Obtain the raw materials in Table 1 and perform the following steps:

[0053] S1: Obtain a 720 mm ingot through three vacuum consumable smeltings;

[0054] S2: heating the ingot to above 1030° C. in a box-type heating furnace, keeping the temperature for 2 to 5 hours, and then forging the ingot to obtain a 225 mm Ø forging ingot;

[0055] S3: Induction hardening of the 225 mm diameter forging blank at 1010-1100°C;

[0056] S4: extruding the Ø225 mm quenched billet at ≤650°C to obtain an extruded tube billet of Ø86×19 mm;

[0057] S5: annealing the Ø86×19 mm extruded tube blank at ≤700° C. for 1 to 1.5 hours to obtain a zirconium alloy tube blank;

[0058] S6: Φ86×19mm zirconium alloy tube billet is cold rolled to Φ63.5×10.92mm, annealed at ≤650℃, and the holding time is 1.5 to 3.5 hours;

[0059] S7: The annealed Φ63.5×10.92mm tube was subjected to the last three cold rolling passes. The Q values ​​(from front to back) of the last three passes were 1.127, 1.986, and 2.011, respectively; the deformation amounts (from front to back) were 76.40%, 78.46%, and 82.56%, respectively; the cumulative annealing parameter ∑A value of the last three passes was 2.47×10 -19 h.

[0060] The hydride test results show that f n 40° =0.14.

[0061] The present invention aims to protect a method for preparing a zirconium alloy tube, comprising: obtaining a zirconium alloy tube blank; rolling the tube blank at least three times, and performing annealing after each rolling to obtain a zirconium alloy tube; the ratio of the relative wall reduction to the relative diameter reduction in the last rolling pass is 1.9 to 2.1, and the ratio of the relative wall reduction to the relative diameter reduction in the second to last rolling pass and the third to last rolling pass is 1.0 to 2.1. The present invention can effectively improve the orientation distribution of hydrides after hydrogen precipitation of zirconium alloy by reasonably distributing the ratio of the relative wall reduction to the relative diameter reduction in the last three rolling passes in the production process of zirconium alloy tubes, so as to overcome the phenomenon that the hydrides precipitated from zirconium alloys are brittle.

[0062] It should be understood that the above specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, and do not constitute a limitation of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. In addition, the appended claims of the present invention are intended to cover all changes and modifications that fall within the scope and boundaries of the appended claims, or the equivalent forms of such scope and boundaries.

Claims

1. A method for preparing a zirconium alloy tube, characterized in that: include: Obtaining a zirconium alloy tube blank; The tube blank is rolled at least three times, and annealing is performed after each rolling, and the cumulative annealing parameter value is 2.47×10 -19 h, obtaining a zirconium alloy tube; The ratio of the relative wall reduction to the relative diameter reduction in the last rolling pass is 1.971 to 2.011, and the ratio of the relative wall reduction to the relative diameter reduction in the second to last rolling pass and the third to last rolling pass is 1.015 to 1.986; Wherein, the cumulative annealing parameters are: ∑A=Σ[t i exp(-Q / RT i )]; Among them, ∑A is the cumulative annealing parameter, t i is the annealing time per pass (h), T i is the temperature of each annealing process (K), Q is the activation energy, and R is the gas constant; The raw material of the zirconium alloy tube blank is the raw material of Zr-4 zirconium alloy.

2. The method for preparing the zirconium alloy tube according to claim 1, characterized in that: The method of obtaining the zirconium alloy tube blank comprises: The raw materials are subjected to vacuum consumable melting three times to obtain an ingot; The ingot is heated to a first preset temperature and kept at the temperature for a first preset time, and then forged to obtain a forged billet; Induction quenching the forging blank at a second preset temperature; The quenched forging blank is subjected to extrusion treatment and annealing to obtain the zirconium alloy tube blank.

3. The method for preparing the zirconium alloy tube according to claim 2, characterized in that: The size of the ingot is within Φ700mm-Φ750mm; The first preset temperature is not less than 1030°C; The first preset time is 2 to 5 hours; The size of the forging blank is within 200mm-250mm. The second preset temperature is 1010-1100° C.; The temperature of the extrusion treatment is not more than 650°C; The size of the zirconium alloy tube blank is Ф80×15mm-Ф90×25mm.

4. The method for preparing the zirconium alloy tube according to claim 1, characterized in that: The raw materials include: 1.20-1.70wt% tin, 0.18-0.24wt% iron, 0.07-0.13wt% chromium, 0.09-0.16wt% oxygen, less than 0.0200wt% carbon and less than 0.0120wt% silicon, the balance being zirconium and impurities.

5. The method for preparing the zirconium alloy tube according to claim 4, characterized in that: The raw materials include: 1.30 wt% tin, 0.22 wt% iron, 0.12 wt% chromium, 0.12 wt% oxygen, 0.0070 wt% carbon and 0.010 wt% silicon.

6. The method for preparing the zirconium alloy tube according to claim 1, characterized in that: The ratio of the relative wall reduction to the relative diameter reduction in each rolling is obtained by the ratio of the tube wall deformation to the diameter deformation.

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