Annealing method of zirconium alloy pipe

Abstract

The present application belongs to the technical field of metal material processing. Specifically, it relates to an annealing method for zirconium alloy pipes, comprising the following steps: laying a padding layer at the bottom of an annealing furnace, placing the zirconium alloy pipe to be annealed in parallel on the padding layer, and then laying a padding layer on the zirconium alloy pipe, and laying in a manner of alternating one layer of padding layer and one layer of zirconium alloy pipe, and after the laying is completed, the annealing furnace is sealed for annealing. The beneficial effects of the present application include: the annealing method for zirconium alloy pipes described in the present application lays a padding layer between two adjacent layers of zirconium alloy pipes, so that the upper and lower line contact pressures of the zirconium alloy pipes in the axial direction are expanded into upper and lower curved surface pressures under the action of the padding layer, and the local point contact pressure originally received by the pipe is extended into surface contact pressure, which can reduce the maximum pressure that the pipe can be locally contacted with, prevent the local collapse and deformation of the pipe at high temperature, and the annealing efficiency is relatively high.

Description

Technical Field

[0001] The invention belongs to the technical field of metal material processing, and in particular relates to an annealing method for a zirconium alloy pipe. Background Art

[0002] The dimensions of conventional nuclear-grade zirconium alloy cladding tubes are 9.5mm in outer diameter × 0.57mm in wall thickness × 4700mm in length. The finished tubes are crystallized and annealed in a vacuum horizontal furnace. During annealing, the tubes are placed in parallel layer by layer in the annealing furnace bin, with a height of 6 to 10 layers. Because each layer of tubes is placed in parallel, each tube is in tangential contact with the surrounding six tubes (except the edges). The tubes are subjected to uniform pressure in six directions along the axial direction, with the pressure on both sides being smaller. However, due to the actual slight deflection of the tubes, the pressure on the tubes along the axial direction is not uniformly distributed. Moreover, the tubes in the lower layer of the annealing bin will be subject to the gravity of all the tubes in the upper layer, that is, they will bear the maximum compressive stress in the up and down directions. When the pressure on some points of the tubes in the lower layer of the annealing bin at high temperature exceeds the support yield strength of the tubes, the tubes will undergo local collapse and flattening deformation, the ovality will increase, and the wall thickness will not change. After the annealing is completed, the permanent deformation will be retained. To solve this problem, the existing technology adopts the solution of loading the zirconium alloy cladding tubes one by one or several into the metal sleeve and then putting them into the horizontal vacuum annealing furnace for annealing. However, the following problems will occur: the production efficiency is reduced when the zirconium tube is loaded into the metal sleeve, and the zirconium tube is easily scratched on the outer surface of the zirconium tube when it is loaded into the metal sleeve. In addition, the large volume of the sleeve wastes the space of the vacuum annealing silo; and in order to save the silo space, different cladding tubes need to be equipped with sleeves of different inner diameters. Another solution is to punch holes at the end of the tube and hoist the tube in a vertical vacuum annealing furnace for annealing. This method can ensure the quality of the annealed tube, but the production efficiency is lower. Summary of the invention

[0003] The present application provides an annealing method for a zirconium alloy tube, aiming to solve the problems of low annealing efficiency and difficulty in ensuring annealing quality of existing zirconium alloy tubes.

[0004] The present application provides an annealing method for a zirconium alloy pipe, comprising the following steps: laying a padding layer at the bottom of an annealing furnace, placing a zirconium alloy pipe to be annealed in parallel on the padding layer, and then laying the padding layer on the zirconium alloy pipe in a manner of alternatingly laying a layer of padding layer and a layer of zirconium alloy pipe, and after the laying is completed, sealing the annealing furnace for annealing.

[0005] The annealing method of the zirconium alloy tube described in the present application is to lay a cushion layer between two adjacent layers of zirconium alloy tubes, so that the upper and lower line contact pressures of the zirconium alloy tube in the axial direction are expanded into upper and lower curved surface pressures under the action of the cushion layer, and the local point contact pressure originally received by the tube is extended into surface contact pressure, which can reduce the maximum pressure that the tube can be locally contacted with, and prevent the local collapse and deformation of the tube at high temperature.

[0006] In addition, the annealing method of the zirconium alloy tube described in the present application saves annealing bin space compared to the annealing method of the zirconium tube being loaded with a metal sleeve. When the same number of zirconium alloy tubes are loaded, the annealing method described in the present application can save 40% of the annealing bin space compared to the method of annealing in a metal sleeve.

[0007] According to some embodiments of the annealing method of the zirconium alloy tube described in the present application, the method further includes the step of laying a gasket tube at the bottom of the annealing furnace.

[0008] According to some embodiments of the annealing method of the zirconium alloy tube described in the present application, the gasket tube includes a zirconium alloy gasket tube, and more preferably, the tube wall thickness of the zirconium alloy gasket tube is ≥1 mm.

[0009] According to some embodiments of the method for annealing a zirconium alloy tube of the present application, the outer diameter of the zirconium alloy gasket tube is greater than the outer diameter of the zirconium alloy tube.

[0010] According to some embodiments of the annealing method of the zirconium alloy tube described in the present application, the outer diameter of the zirconium alloy gasket tube is 0.04 mm-0.06 mm larger than the outer diameter of the zirconium alloy tube.

[0011] According to some embodiments of the annealing method of the zirconium alloy tube described in the present application, the number of layers of the gasket tube is two, and the two layers of zirconium alloy gasket tubes are alternately arranged in parallel.

[0012] According to some embodiments of the annealing method of the zirconium alloy tube described in the present application, the gasket layer includes a stainless steel fiber cloth layer.

[0013] According to some embodiments of the annealing method of the zirconium alloy tube described in the present application, the thickness of the gasket layer is ≤1 mm, preferably 0.4-0.6 mm.

[0014] According to some embodiments of the annealing method of the zirconium alloy tube of the present application, the density of the stainless steel fiber cloth is less than 1 kg / m 2 , preferably 0.5-0.7kg / m 2 .

[0015] According to some embodiments of the method for annealing a zirconium alloy tube described in the present application, two adjacent layers of the zirconium alloy tubes are arranged alternately in parallel.

[0016] According to some embodiments of the annealing method of the zirconium alloy tube described in the present application, the outer diameter of the zirconium alloy tube is 8-14 mm, the wall thickness of the zirconium alloy tube is 0.4-0.6 mm, and the length of the zirconium alloy tube is 500-5000 mm.

[0017] According to some embodiments of the method for annealing a zirconium alloy tube described in the present application, the number of layers of the zirconium alloy tube laid is 8-10.

[0018] According to some embodiments of the annealing method of the zirconium alloy tube described in the present application, a stainless steel filter screen is also installed on the inner wall of the annealing furnace.

[0019] According to some embodiments of the annealing method of the zirconium alloy tube described in the present application, the annealing temperature of the zirconium alloy tube is 500-600° C., and the annealing time is 3-8 hours.

[0020] According to some embodiments of the annealing method of the zirconium alloy tube described in the present application, the furnace temperature of the zirconium alloy tube is ≤200°C.

[0021] According to some embodiments of the annealing method of the zirconium alloy tube of the present application, the annealing vacuum degree of the zirconium alloy tube is less than 1.333×10 -2 Pa. DETAILED DESCRIPTION

[0022] Embodiments of the present invention are described in detail below. The embodiments described below are exemplary and intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0023] The technical solution of the present application is described in detail below in conjunction with specific embodiments.

[0024] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0025] The embodiment of the present application provides an annealing method for a zirconium alloy pipe, comprising the following steps: laying a padding layer at the bottom of an annealing furnace, placing a zirconium alloy pipe to be annealed in parallel on the padding layer, and then laying the padding layer on the zirconium alloy pipe, in a manner of alternatingly laying a layer of padding layer and a layer of zirconium alloy pipe, and after the laying is completed, sealing the annealing furnace for annealing.

[0026] A padding layer is laid between two adjacent layers of zirconium alloy pipes. In this way, the upper and lower line contact pressures on the zirconium alloy pipes in the axial direction are expanded into upper and lower curved surface pressures under the action of the padding layer. The local point contact pressure originally on the pipes is extended into surface contact pressure, which can reduce the maximum pressure that the pipes can be locally exposed to, and prevent the local collapse and deformation of the pipes at high temperatures.

[0027] In some embodiments, the method further includes laying a gasket pipe at the bottom of the annealing furnace.

[0028] In some embodiments, the gasket tube includes a zirconium alloy gasket tube. In some embodiments, the wall thickness of the zirconium alloy gasket tube is ≥1 mm, such as 1 mm, 1.05 mm, 1.08 mm, 1.1 mm, 1.2 mm, etc. In some embodiments, the outer diameter of the zirconium alloy gasket tube is larger than the outer diameter of the zirconium alloy tube. In some embodiments, the outer diameter of the zirconium alloy gasket tube is 0.04 mm-0.06 mm larger than the outer diameter of the zirconium alloy tube, such as 0.04 mm, 0.05 mm, 0.06 mm, etc. Selecting that the outer diameter of the gasket tube is larger than the outer diameter of the zirconium alloy tube can reserve a certain gap between the two sides of each layer of annealed zirconium alloy tube and the inner wall of the annealing furnace, such as a gap of 0.04-0.06 mm, so as to reserve space for movement for the lateral expansion of the tube during annealing, and also prevent deformation of adjacent tubes due to extrusion. In addition, since a gap is reserved between the annealed zirconium alloy pipe and the inner wall of the annealing furnace, the discharging of the zirconium alloy pipe is facilitated, the labor efficiency is improved, and the outer surface of the zirconium alloy pipe is effectively protected.

[0029] In some embodiments, the gasket tubes have two layers, and the two layers of zirconium alloy gasket tubes are arranged in parallel and alternately.

[0030] In some embodiments, the padding layer includes a stainless steel fiber cloth layer.

[0031] In some embodiments, the thickness of the padding layer is ≤1 mm, preferably 0.4-0.6 mm;

[0032] In some embodiments, the density of the stainless steel fiber cloth is less than 1 kg / m 2 , preferably 0.5-0.7kg / m 2 .

[0033] In some embodiments, the two adjacent layers of zirconium alloy tubes are arranged alternately in parallel, that is, any one of the zirconium alloy tubes in the upper layer is placed between the two zirconium alloy gasket tubes in the lower layer adjacent to it. This placement method can ensure that the tubes subsequently placed thereon are parallel, and the upper and lower layers of tubes will not be staggered. If the upper and lower layers of tubes are staggered, the gravity of the upper tube will affect the intersection of the upper and lower layers, resulting in severe deformation due to high temperature during annealing.

[0034] In some embodiments, the outer diameter of the zirconium alloy tube is 8-14 mm, the wall thickness of the zirconium alloy tube is 0.4-0.6 mm, and the length of the zirconium alloy tube is 500-5000 mm.

[0035] In some embodiments, the zirconium alloy pipe is laid in 8-10 layers, such as 8 layers, 9 layers, or 10 layers.

[0036] In some embodiments, a stainless steel filter is also installed on the inner wall of the annealing furnace. The number of layers of the stainless steel filter can be 1 layer, 2 layers, 3 layers, etc., which can reduce the deformation of the zirconium alloy pipe caused by vibration when the annealing silo is hot in and out of the annealing silo, and can also provide a certain buffer space between the pipe and the inner wall of the silo after the pipe expands due to heat.

[0037] In some embodiments, a stainless steel foil is covered on the surface of the uppermost zirconium alloy tube, and the tubes at both ends of the silo are also covered with stainless steel foil to prevent the zirconium alloy tube from being oxidized during the annealing process.

[0038] In some embodiments, the annealing temperature of the zirconium alloy tube is 500-600°C, such as 500°C, 550°C, 580°C, 600°C, etc., and the annealing time is 3-8h, such as 3h, 5h, 8h, etc.

[0039] In some embodiments, the furnace temperature of the zirconium alloy tube is ≤200°C, such as 200°C, 190°C, 185°C, 180°C, 160°C, 150°C, etc.

[0040] In some embodiments, the annealing vacuum degree of the zirconium alloy tube is less than 1.33×10 -2 Pa, for example 1.32×10 - 2 Pa, 1.30×10 -2 Pa, 1.28×10 -2 Pa, 1.25×10 -2 Pa, 1.20×10 -2 Pa, 1.15×10 -2 Pa, 1.10×10 - 2 Pa, 1.0×10-2 Pa.

[0041] The annealing method of the zirconium alloy tube described in the present application is further described below with reference to the embodiments.

[0042] The zirconium alloy tube to be annealed described in the examples and comparative examples of the present application has an outer diameter of 9.5 mm, a wall thickness of 0.57 mm, and a length of 4700 mm.

[0043] Example 1

[0044] A zirconium alloy pipe annealing method comprises the following steps: paving two layers of stainless steel filter screens on the inner wall of a silo of a vacuum annealing furnace, and then paving two layers of zirconium alloy padding tubes at the bottom of the vacuum annealing furnace, wherein the two layers of zirconium alloy padding tubes are laid in parallel, and any one of the zirconium alloy padding tubes located in the upper layer is placed between two zirconium alloy padding tubes in the lower layer adjacent thereto, the outer diameter of the laid zirconium alloy padding tube is 0.05 mm larger than the outer diameter of the zirconium alloy pipe, the wall thickness of the zirconium alloy padding tube is 1 mm, and then a 0.4 mm thick and 0.6 kg / m thick zirconium alloy padding tube is laid on the zirconium alloy padding tube. 2 A stainless steel fiber cloth is provided, a zirconium alloy pipe to be annealed is placed on the stainless steel fiber cloth in parallel, and then the stainless steel fiber cloth is laid on the zirconium alloy pipe, that is, a layer of stainless steel fiber cloth and a layer of zirconium alloy pipe are laid alternately, two adjacent layers of zirconium alloy pipes are arranged in parallel, and any one of the zirconium alloy pipes in the upper layer is arranged between two adjacent zirconium alloy pipes in the lower layer, and loading is stopped when the loading height of the zirconium alloy pipes approaches the height of the silo. At this time, the number of laid layers of the zirconium alloy pipes is 10, and a layer of stainless steel foil is covered on the surface of the zirconium alloy pipe in the top layer to prevent oxidation of the zirconium alloy pipe during annealing.

[0045] Close the door of the annealing furnace and evacuate the pressure to less than 1.33×10 -2 After Pa, the annealing furnace starts to heat up at a rate of 90℃ per hour to 596℃ and then keeps warm for 3.5h. Then the vacuum system is turned off and filled with 99.998% pure argon for cooling. After the temperature in the furnace cools to 200℃, the furnace door is opened, the silo is pulled out from the annealing furnace, and the pipes and stainless steel fiber cloth are taken out from the silo layer by layer.

[0046] The ovality of the zirconium alloy tube obtained by the method described in this embodiment is unchanged compared with the ovality before annealing, which can effectively prevent the tube from being flattened and partially collapsed during annealing.

[0047] Example 2

[0048] A zirconium alloy pipe annealing method comprises the following steps: paving two layers of stainless steel filter screens on the inner wall of a silo of a vacuum annealing furnace, and then paving two layers of zirconium alloy gasket tubes at the bottom of the vacuum annealing furnace, wherein the two layers of zirconium alloy gasket tubes are laid in parallel, and any one of the zirconium alloy gasket tubes located on the upper layer is placed between two zirconium alloy gasket tubes located on the lower layer adjacent thereto, and the outer diameter of the laid zirconium alloy gasket tube is 0.06 mm larger than the outer diameter of the zirconium alloy pipe, and then laying a 0.5 mm thick and 0.6 kg / m 2 A stainless steel fiber cloth is provided, a zirconium alloy pipe to be annealed is placed on the stainless steel fiber cloth in parallel, and then the stainless steel fiber cloth is laid on the zirconium alloy pipe, that is, a layer of stainless steel fiber cloth and a layer of zirconium alloy pipe are laid alternately, two adjacent layers of zirconium alloy pipes are arranged in parallel, and any one of the zirconium alloy pipes in the upper layer is arranged between two adjacent zirconium alloy pipes in the lower layer, and loading is stopped when the loading height of the zirconium alloy pipes approaches the height of the silo. At this time, the number of laid layers of the zirconium alloy pipes is 10, and a layer of stainless steel foil is covered on the surface of the zirconium alloy pipe in the top layer to prevent oxidation of the zirconium alloy pipe during annealing.

[0049] Close the door of the annealing furnace and evacuate the pressure to less than 1.33×10 -2 After Pa, the annealing furnace starts to heat up at a rate of 90℃ per hour to 600℃ and then keeps warm for 3.5h. Then the vacuum system is turned off and filled with 99.998% pure argon for cooling. After the temperature in the furnace cools to 200℃, the furnace door is opened, the silo is pulled out from the annealing furnace, and the pipes and stainless steel fiber cloth are taken out from the silo layer by layer.

[0050] The ovality of the zirconium alloy tube obtained by the method described in this embodiment is unchanged compared with the ovality before annealing, which can effectively prevent the tube from being flattened and partially collapsed during annealing.

[0051] Example 3

[0052] A zirconium alloy pipe annealing method comprises the following steps: laying two layers of stainless steel filter screens on the inner wall of a silo of a vacuum annealing furnace, and then laying two layers of zirconium alloy padding tubes at the bottom of the vacuum annealing furnace, wherein the two layers of zirconium alloy padding tubes are laid in parallel, and any one of the zirconium alloy padding tubes located on the upper layer is placed between two zirconium alloy padding tubes located on the lower layer adjacent thereto, the outer diameter of the laid zirconium alloy padding tube is 0.04 mm larger than the outer diameter of the zirconium alloy pipe, the wall thickness of the zirconium alloy padding tube is 1 mm, and then laying a 0.6 mm thick and 0.5 kg / m2 density zirconium alloy padding tube on the zirconium alloy padding tube. 2A stainless steel fiber cloth is provided, a zirconium alloy pipe to be annealed is placed on the stainless steel fiber cloth in parallel, and then the stainless steel fiber cloth is laid on the zirconium alloy pipe, that is, a layer of stainless steel fiber cloth and a layer of zirconium alloy pipe are laid alternately, two adjacent layers of zirconium alloy pipes are arranged in parallel, and any one of the zirconium alloy pipes in the upper layer is arranged between two adjacent zirconium alloy pipes in the lower layer, and loading is stopped when the loading height of the zirconium alloy pipes approaches the height of the silo. At this time, the number of laid layers of the zirconium alloy pipes is 10, and a layer of stainless steel foil is covered on the surface of the zirconium alloy pipe in the top layer to prevent oxidation of the zirconium alloy pipe during annealing.

[0053] Close the door of the annealing furnace and evacuate the pressure to less than 1.33×10 -2 After Pa, the annealing furnace starts to heat up at a rate of 90℃ per hour to 550℃ and then keeps warm for 5h. Then the vacuum system is turned off and filled with 99.998% pure argon for cooling. After the temperature in the furnace cools to 200℃, the furnace door is opened, the silo is pulled out from the annealing furnace, and the pipes and stainless steel fiber cloth are taken out from the silo layer by layer.

[0054] The ovality of the zirconium alloy tube obtained by the method described in this embodiment is unchanged compared with the ovality before annealing, which can effectively prevent the tube from being flattened and partially collapsed during annealing.

[0055] Comparative Example 1

[0056] The only difference between Comparative Example 1 and Example 1 is that the annealing method described in Comparative Example 1 does not lay stainless steel fiber cloth between two adjacent layers of zirconium alloy tubes.

[0057] Because stainless steel fiber cloth was not laid between two adjacent layers of zirconium alloy tubes, the tubes at the bottom of the silo would be locally flattened and deformed during annealing, with an ellipticity greater than 0.05 mm, making them unusable later (the nuclear fuel core blocks made from them could not be inserted into the cladding tubes).

[0058] Comparative Example 2

[0059] The difference between Comparative Example 2 and Example 1 is that the annealing method described in Comparative Example 2 does not lay a zirconium alloy gasket tube at the bottom of the annealing furnace.

[0060] When the pipe is annealed and enters the cooling chamber, the guide at the bottom of the silo will cause the silo to vibrate, which will affect the pipes in the silo. The bottom pipes are prone to flattening and deformation under high temperature, gravity, and vibration.

[0061] Although the above embodiments have been shown and described, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. Changes, modifications, substitutions and variations of the above embodiments by those of ordinary skill in the art are all within the scope of protection of the present invention.

Claims

1. A method for annealing a zirconium alloy tube, characterized in that: The following steps are involved: A padding layer is laid at the bottom of the annealing furnace, and the zirconium alloy pipe to be annealed is placed parallel to the padding layer. Then, a padding layer is laid on the zirconium alloy pipe in an alternating manner of laying a layer of padding layer and a layer of zirconium alloy pipe. After the laying is completed, the annealing furnace is sealed for annealing.

2. The annealing method of the zirconium alloy tube according to claim 1, characterized in that: The step of laying a gasket pipe at the bottom of the annealing furnace is also included: Preferably, the gasket tube comprises a zirconium alloy gasket tube, and more preferably, the tube wall thickness of the zirconium alloy gasket tube is ≥1 mm; Further preferably, the outer diameter of the zirconium alloy gasket tube is larger than the outer diameter of the zirconium alloy tube, and further preferably, the outer diameter of the zirconium alloy gasket tube is 0.04 mm-0.06 mm larger than the outer diameter of the zirconium alloy tube; Preferably, the number of layers of the gasket tubes is two, and the two layers of zirconium alloy gasket tubes are arranged alternately in parallel.

3. The annealing method of the zirconium alloy tube according to claim 1, characterized in that: The padding layer includes a stainless steel fiber cloth layer.

4. The annealing method of the zirconium alloy tube according to claim 3, characterized in that: The thickness of the padding layer is ≤1 mm, preferably 0.4-0.6 mm; Preferably, the density of the stainless steel fiber cloth is less than 1 kg / m 2 , preferably 0.5-0.7kg / m 2 .

5. The annealing method of zirconium alloy tube according to claim 1, characterized in that: The two adjacent layers of zirconium alloy tubes are arranged in parallel and alternately.

6. The annealing method of zirconium alloy tube according to claim 1, characterized in that: The outer diameter of the zirconium alloy tube is 8-14 mm, the wall thickness of the zirconium alloy tube is 0.4-0.6 mm, and the length of the zirconium alloy tube is 500-5000 mm.

7. The annealing method of zirconium alloy tube according to claim 1, characterized in that: The number of layers of the zirconium alloy pipes laid is 8-10.

8. The annealing method of zirconium alloy tube according to claim 1, characterized in that: The method also includes installing a stainless steel filter on the inner wall of the annealing furnace.

9. The annealing method of zirconium alloy tube according to claim 1, characterized in that: The annealing temperature of the zirconium alloy tube is 500-600°C, and the annealing time is 3-8h; And / or, the furnace temperature of the zirconium alloy tube is ≤200°C.

10. The annealing method of zirconium alloy tube according to claim 1, characterized in that: The annealing vacuum degree of the zirconium alloy tube is less than 1.333×10 -2 Pa.