A shield alloy seamless pipe and a method for manufacturing the same

Abstract

The application discloses a kind of shielding alloy seamless pipes and preparation method thereof, preparation method includes the following steps: S1.casting blank preparation, according to the composition of alloy, and the raw materials are melted and cast to prepare casting blank;S2.forging blank preparation, the casting blank is heated and forged, and the forging blank is prepared, and the forging blank is heat treated;S3.tube blank preparation, the forging blank after heat treatment is processed, forms central hole, and tube blank is prepared;S4.tube blank hot extrusion, the tube blank is hot extruded, and extruded tube is prepared;S5.extruded tube processing, the extruded tube is cold-rolled, cold-drawn, hot-rolled and / or machined to design size, and finished pipe is obtained.The preparation method of shielding alloy seamless pipe provided by the application can be mass-produced into various specifications, is suitable for industrialized mass production, and the shielding alloy seamless pipe prepared simultaneously has excellent mechanical properties and comprehensive shielding performance.

Description

Technical Field

[0001] This invention relates to the field of shielding materials technology, and in particular to a seamless shielding alloy tube and its preparation method. Background Technology

[0002] With the development of national defense, nuclear physics research, and nuclear power technology, a large number of nuclear reactors have been built and put into use, placing increasingly higher demands on shielding materials and systems, especially shielding pipes used for radiation medium transmission. These materials require excellent gamma-ray and neutron shielding capabilities, along with superior mechanical and processing properties. Boron-containing steel, with iron as its matrix, inherently provides some shielding against gamma rays, and the boron it contains provides excellent shielding against thermal neutrons. Therefore, boron-containing steel has become one of the widely used comprehensive shielding materials. However, due to the very low solid solubility of boron in an iron matrix, excessive boron precipitates to form hard and brittle borides, Fe₂B, which form a continuous network, severely impacting the mechanical and processing properties of boron-containing steel.

[0003] Patent document CN116219268A discloses a method for preparing boron-containing super duplex stainless steel and seamless tubes. By optimizing the alloy composition and increasing the amount of boron, which can absorb neutrons, the method employs a process of smelting → forging → tube threading → solution heat treatment → cold rolling to finally obtain a high-strength, corrosion-resistant boron-containing super duplex stainless steel seamless tube. However, considering that low-melting-point phase (Fe,Cr)2B is easily formed at the grain boundaries in boron-containing duplex stainless steel, which leads to deterioration of high-temperature hot working performance, the boron content of this stainless steel is limited to the range of 0.020 to 0.035 wt%, which limits the improvement of the material's thermal neutron shielding performance. Patent document CN115921577A discloses a method for preparing seamless boron stainless steel tubes for thermal neutron absorption. Through a process of "vacuum induction melting + electroslag remelting," the size, morphology, and distribution of the initial solidification structure of the boron stainless steel ingot are effectively controlled, significantly improving the machinability of the ingot. "Hot forging + hot extrusion" with large reduction further refines the boride particles, improving the mechanical properties of the finished tube. However, the tubes prepared by this method still contain boride particles with a long axis greater than 20 μm, limiting further improvement in the mechanical properties of the seamless tube. Furthermore, the prepared tubes do not contain heavy elements (such as tungsten) that can effectively shield gamma rays and slow down fast neutrons, thus lacking excellent comprehensive shielding performance. Moreover, the addition of large amounts of heavy metal elements (such as tungsten) to steel inevitably leads to a deterioration in processing performance, increasing the difficulty of tube preparation, especially for thin-walled, small-diameter shielding tubes, which have not yet been reported.

[0004] In summary, there is an urgent need to develop a shielding alloy seamless tube and its preparation method. The seamless tube prepared has good gamma-ray and neutron shielding capabilities, as well as good comprehensive mechanical properties and cold and hot working properties, and can be used to prepare various sizes and thicknesses. Summary of the Invention

[0005] The purpose of this invention is to provide a shielding alloy seamless tube and its preparation method. The prepared seamless tube has good gamma-ray and neutron shielding capabilities, as well as good comprehensive mechanical properties.

[0006] In a first aspect, the present invention provides a method for preparing a seamless shielding alloy tubing, comprising the following preparation steps:

[0007] S1. Billet preparation: Weigh the raw materials according to the alloy composition, and melt and cast the raw materials to obtain a billet. The alloy composition includes: boron: 0.2-4.0 wt.%, chromium: 5.0-26.0 wt.%, nickel: 6.0-20.0 wt.%, tungsten: 2.0-20.0 wt.%, molybdenum: 0-4.0 wt.%, titanium: 0-10.0 wt.%, manganese: 0-4.0 wt.%, with the balance being iron;

[0008] S2. Forging billet preparation: The cast billet is heated and forged to obtain a forging billet. The final forging temperature is controlled to be above 850°C and the forging ratio is 2 to 12. The forging billet is then subjected to heat treatment at a temperature of 950 to 1250°C.

[0009] S3. Tube blank preparation: The heat-treated forging blank is processed to form a center hole, thus preparing a tube blank;

[0010] S4. Hot extrusion of tube blank: The tube blank is hot extruded to prepare an extruded tube. The hot extrusion temperature is 950-1250℃ and the extrusion ratio is 1.8-22.

[0011] S5. Extrusion tube processing: The extruded tube is cold-rolled, cold-drawn, hot-rolled and / or machined to the design dimensions to obtain the finished tube. The deformation amount of each cold rolling pass is less than 50%, and the tube after each cold rolling pass needs to be heat-treated at a temperature of 900℃~1200℃.

[0012] Optionally, in step S1, the alloy composition includes: boron: 0.2–2.2 wt.%, chromium: 6.0–17.0 wt.%, nickel: 6.0–18.0 wt.%, tungsten: 8.0–20.0 wt.%, molybdenum: 0–2.0 wt.%, titanium: 0–2.0 wt.%, manganese: 0–2.0 wt.%, with the balance being iron.

[0013] Optionally, in step S4, the hot extrusion rate is 90–200 mm / s.

[0014] Optionally, in step S5, the extruded tube is cold-rolled or hot-rolled to the design size to obtain the finished tube.

[0015] Optionally, step S4 further includes heat-treating the extruded tube at a temperature of 950–1250°C.

[0016] Secondly, the present invention provides a shielding alloy seamless tube, the composition of which includes: boron: 0.2-4.0 wt.%, chromium: 5.0-26.0 wt.%, nickel: 6.0-20.0 wt.%, tungsten: 2.0-20.0 wt.%, molybdenum: 0-4.0 wt.%, titanium: 0-10.0 wt.%, manganese: 0-4.0 wt.%, with the balance being iron;

[0017] The phase structure of the shielding alloy seamless tube includes a matrix phase and a boride phase, wherein the boride phase is granular and the particle size of the boride phase is less than 15 μm.

[0018] Optionally, the composition of the shielding alloy seamless tube includes: boron: 0.2-2.2 wt.%, chromium: 6.0-17.0 wt.%, nickel: 6.0-18.0 wt.%, tungsten: 8.0-20.0 wt.%, molybdenum: 0-2.0 wt.%, titanium: 0-2.0 wt.%, manganese: 0-2.0 wt.%, with the balance being iron.

[0019] Optionally, the matrix phase includes an austenitic phase.

[0020] Optionally, the boride phase is (Fe,Cr)W2B2 phase and / or TiB2 phase, and the particle size of the boride phase is less than 10 μm.

[0021] Optionally, the boride phase is (Fe,Cr)W2B2 phase.

[0022] Optionally, the particle size of the (Fe,Cr)W2B2 phase is 0.1–5 μm.

[0023] Optionally, the shielding alloy seamless tube has a tensile strength of 700–770 MPa, a yield strength of 330–380 MPa, and an elongation of 19–34%; the thermal neutron absorption rate of the shielding alloy seamless tube is 88–99.99%. 60 The linear attenuation coefficient of Co is 0.43–0.48 cm. -1 , 137 The linear attenuation coefficient of Cs is 0.63–0.68 cm⁻¹ -1 .

[0024] In summary, the present invention has at least one of the following beneficial effects:

[0025] 1. This invention provides a seamless shielding alloy tube capable of simultaneously shielding gamma rays and neutrons, and its preparation method. It balances both shielding performance and excellent mechanical properties. In the preferred embodiments, the shielding alloy seamless tube exhibits a tensile strength of 700–770 MPa, a yield strength of 330–380 MPa, an elongation of 19–34%, and a thermal neutron absorption rate of 88–99.99%. 60 The linear attenuation coefficient of Co can reach 0.43–0.48 cm. -1 , 137 The linear attenuation coefficient of Cs can reach 0.63–0.68 cm⁻¹ -1 .

[0026] 2. The method for preparing high-strength and tough shielded seamless tubes provided by this invention is applicable to outer diameters... We manufacture shielding alloy seamless tubes with wall thicknesses ranging from 1 to 30 mm. The tubes are available in a full range of specifications and have a wide range of applications.

[0027] 3. The shielding alloy seamless pipe provided by this invention can simultaneously shield gamma rays and neutrons, effectively reducing the radiation dose of radioactive sources, ensuring the life safety of staff and the normal operation of instruments and equipment, simplifying the design of nuclear power plant shielding systems, and can be applied to the preparation of pipelines or containers for nuclear reactors, shielded glove boxes, spent fuel transportation and storage, etc.

[0028] 4. The method for preparing shielded alloy seamless pipes provided by this invention only requires the melting and casting process when preparing billets of less than 1 ton, without the need for self-consumable remelting or electroslag remelting processes, which can greatly improve production efficiency and reduce production costs.

[0029] 5. The method for preparing the shielded alloy seamless tube provided by the present invention adopts processes such as melting and casting, forging, extrusion, and rolling. The process is simple, has a high yield, is stable and reliable, and has almost no environmental pollution. It is very suitable for large-scale industrial production and has a good prospect for development and application. Attached Figure Description

[0030] Figure 1 The image shows the XRD pattern of the ingot prepared in step S1 of Example 1.

[0031] Figure 2 The image shows the SEM image of the cast billet prepared in step S1 of Example 1.

[0032] Figure 3 The image shows the SEM image of the forging billet after heat treatment in step S2 of Example 1.

[0033] Figure 4 The image shows an SEM image of the extruded tube prepared in step S4 of Example 1.

[0034] Figure 5 The image shows an SEM image of the finished pipe obtained in step S5 of Example 1.

[0035] Figure 6 The image shows an SEM image of the finished pipe obtained in step S5 of Example 2.

[0036] Figure 7 The image shows the XRD pattern of the ingot prepared in step S1 of Example 8.

[0037] Figure 8 The image shows the XRD pattern of the ingot prepared in step S1 of Example 9.

[0038] Figure 9 The surface crack pattern of the extruded tube prepared in step S4 of Comparative Example 1 is shown.

[0039] Figure 10 The surface crack pattern of the cold-rolled tube obtained in step S5 of Comparative Example 6 is shown.

[0040] Figure 11 The image shows the surface crack pattern of the cold-rolled tube obtained in step S5 of Comparative Example 7. Detailed Implementation

[0041] This invention provides a shielded alloy seamless tube and its preparation method. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0042] Shielding tubing used for radiation medium transmission requires excellent shielding capabilities against both gamma rays and neutrons, as well as good hot and cold working properties, enabling it to be manufactured into various required sizes. Currently, the conventional materials used for shielding neutrons and gamma rays are metal-based boron alloys. However, in traditional boron alloys, boron (B) is distributed in a network along the grain boundaries in the form of low-melting-point eutectic borides, resulting in low ductility and toughness, high notch sensitivity, and a high susceptibility to cracking during forging. Furthermore, it is difficult to perform hot working and cannot be extruded, significantly limiting its application in the manufacture of shielding tubing.

[0043] During their extensive research, the inventors discovered that by employing specific alloy compositions and combining them with specific manufacturing processes, seamless shielding alloy tubing with specific phase structures and microstructures can be produced. In the shielding alloy seamless tubing uniquely provided by this invention, the high boron content ensures excellent neutron shielding performance. Furthermore, the high tungsten content effectively shields gamma rays, while the high chromium and nickel content is primarily dissolved in iron, forming a high-strength and ductile austenitic matrix phase. A unique M3B2 type boride ((Fe,Cr)W2B2) is formed between tungsten, boron, iron, and chromium. The inventors surprisingly found that, compared to hard and brittle borides such as M2B(FeB2 or (F... M3B2 type borides (e,Cr)B2) possess excellent deformability and a high degree of compatibility with the matrix, allowing them to deform along with the matrix during processing. In specific forging, hot extrusion, rolling, and heat treatment processes, the continuously distributed network of M3B2 type borides in the alloy billet transforms into dispersed, fine-grained M3B2 type borides, thereby improving the strength and plasticity of the shielding alloy seamless tubing. Simultaneously, the matrix phase further enhances the strength and plasticity of the shielding alloy seamless tubing during processing due to grain refinement. This invention is based on this research.

[0044] Specifically, in some embodiments of the present invention, the preparation method of the shielding alloy seamless tubing includes the following preparation steps:

[0045] S1. Billet Preparation: Weigh the raw materials according to the alloy composition, and melt and cast the raw materials to obtain a billet. The alloy composition includes: boron: 0.2-4.0 wt.%, chromium: 5.0-26.0 wt.%, nickel: 6.0-20.0 wt.%, tungsten: 2.0-20.0 wt.%, molybdenum: 0-4.0 wt.%, titanium: 0-10.0 wt.%, manganese: 0-4.0 wt.%, with the balance being iron; preferably, boron: 0.2-2.3 wt.%, chromium: 5.0-20.0 wt.%, nickel: 6.0-20.0 wt.%, tungsten: 4.0-20.0 wt.%, molybdenum: 0-4.0 wt.%, titanium: 0-10.0 wt. The composition is as follows: %, manganese: 0–4.0 wt.%, balance iron; more preferably, boron: 0.2–2.2 wt.%, chromium: 6.0–17.0 wt.%, nickel: 6.0–18.0 wt.%, tungsten: 8.0–20.0 wt.%, molybdenum: 0–2.0 wt.%, titanium: 0–2.0 wt.%, manganese: 0–2.0 wt.%, balance iron; even more preferably, boron: 0.7–1.3 wt.%, chromium: 11.0–15.0 wt.%, nickel: 9.0–11.0 wt.%, tungsten: 10.0–20.0 wt.%, molybdenum: 0–1.5 wt.%, titanium: 0–1.5 wt.%, manganese: 0–1.5 wt.%, balance iron. The smelting temperature is 1500–1750 °C, preferably 1600–1700 °C.

[0046] S2. Forging billet preparation: The cast billet is heated and forged to obtain a forging billet. The final forging temperature is controlled to be above 850°C, and the forging ratio is 2-12. The forging billet is then subjected to heat treatment at a temperature of 950-1250°C. Preferably, the forging temperature is 900-1250°C. More preferably, the forging temperature is 1000-1200°C. The forging ratio is 2-10. The heat treatment temperature is 950-1250°C, preferably 1000-1200°C, and the heat treatment time is 60-120 min, preferably 80-100 min.

[0047] S3. Tube blank preparation: The heat-treated forging blank is processed to form a center hole, thus preparing a tube blank.

[0048] S4. Hot extrusion of tube blank: The tube blank is hot extruded to prepare an extruded tube. The hot extrusion temperature is 950-1250℃, preferably 1000-1200℃, more preferably 1050-1200℃; the extrusion ratio is 1.8-22, preferably 2-20, more preferably 5-20; the hot extrusion rate is 90-200mm / s, preferably 100-180mm / s; preferably, the hot extrusion further includes heat treatment of the extruded tube, the heat treatment temperature is 950-1250℃, preferably 1000-1200℃, and the holding time is 30-120min, preferably 40-90min.

[0049] S5. Extrusion tube processing: The extruded tube is cold-rolled, cold-drawn, hot-rolled and / or machined to the design dimensions to obtain the finished tube. The deformation amount of each cold rolling pass is less than 50%, preferably 10-50%, more preferably 15-45%, and even more preferably 20-45%. The rolling passes are preferably 2-10. Each tube after cold rolling must undergo heat treatment at a temperature of 900℃-1200℃, preferably 900℃-1150℃, for a holding time of 20-90 minutes, preferably 30-60 minutes. The hot rolling temperature is 950–1250℃, preferably 1000–1200℃; the deformation per hot rolling pass is less than 75%, preferably 10–65%, more preferably 15–50%, and even more preferably 20–45%; the number of rolling passes is preferably 2–10; the pipe after each hot rolling pass needs to undergo heat treatment at a temperature of 900℃–1200℃, preferably 900℃–1150℃, for a holding time of 20–90 minutes, preferably 30–60 minutes. The dimensions of the finished pipe are designed according to requirements, and can be selected as the outer diameter. Wall thickness 1-30mm.

[0050] In some embodiments of the present invention, a shielding alloy seamless tube is provided, the composition of which includes: boron: 0.2-4.0 wt.%, chromium: 5.0-26.0 wt.%, nickel: 6.0-20.0 wt.%, tungsten: 2.0-20.0 wt.%, molybdenum: 0-4.0 wt.%, titanium: 0-10.0 wt.%, manganese: 0-4.0 wt.%, and the balance being iron; preferably, boron: 0.2-2.3 wt.%, chromium: 5.0-20.0 wt.%, nickel: 6.0-20.0 wt.%, tungsten: 4.0-20.0 wt.%, molybdenum: 0-4.0 wt.%, titanium: 0-10.0 wt.%, manganese: 0–4.0 wt.%, balance being iron; more preferably, boron: 0.2–2.2 wt.%, chromium: 6.0–17.0 wt.%, nickel: 6.0–18.0 wt.%, tungsten: 8.0–20.0 wt.%, molybdenum: 0–2.0 wt.%, titanium: 0–2.0 wt.%, manganese: 0–2.0 wt.%, balance being iron; even more preferably, boron: 0.7–1.3 wt.%, chromium: 11.0–15.0 wt.%, nickel: 9.0–11.0 wt.%, tungsten: 10.0–20.0 wt.%, molybdenum: 0–1.5 wt.%, titanium: 0–1.5 wt.%, manganese: 0–1.5 wt.%, balance being iron. The phase structure of the shielding alloy seamless pipe includes a matrix phase and a boride phase. The boride phase is granular, with a particle size of less than 15 μm, preferably less than 12 μm, and more preferably less than 10 μm. Preferably, the boride phase is (Fe,Cr)W2B2 phase and / or TiB2 phase. More preferably, the boride phase is (Fe,Cr)W2B2 phase or (Fe,Cr)W2B2 phase and a small amount of TiB2 phase. The particle size of the (Fe,Cr)W2B2 phase or TiB2 phase is 0.01 to 10 μm. Preferably, the particle size of the (Fe,Cr)W2B2 phase or TiB2 phase is 0.1 to 5 μm. More preferably, the boride phase is (Fe,Cr)W2B2 phase. The (Fe,Cr)W2B2 phase has better deformability and bonding ability with the matrix phase than the TiB2 phase, which can further improve the deformability and plasticity of the pipe. The matrix phase includes an austenitic phase or the matrix phase includes an austenitic phase and a small amount of ferrite phase.

[0051] In some embodiments of the present invention, the shielding alloy seamless tube has a tensile strength of 600-770 MPa, a yield strength of 330-380 MPa, and an elongation of 8-34%; preferably, the tensile strength is 700-770 MPa, the yield strength is 330-380 MPa, and the elongation is 19-34%; more preferably, the tensile strength is 730-770 MPa, the yield strength is 330-380 MPa, and the elongation is 19-31%.

[0052] In some embodiments of the present invention, the thermal neutron absorption rate of the shielding alloy seamless tubing is 88-99.99%; 60 The linear attenuation coefficient of Co is 0.39–0.48 cm. -1 The preferred size is 0.43–0.48 cm. -1 ; 137 The linear attenuation coefficient of Cs is 0.54–0.68 cm⁻¹ -1 The preferred size is 0.63–0.68 cm. -1 .

[0053] The present invention will be further described in detail below with reference to embodiments and comparative examples.

[0054] Example 1

[0055] This embodiment provides a shielding alloy seamless tube and its preparation method, specifically including the following steps:

[0056] S1. Billet preparation: Weigh the raw materials according to the alloy composition. The total weight of the raw materials is 500 kg. The designed composition of the alloy is: boron: 0.72 wt.%, chromium: 13 wt.%, nickel: 10 wt.%, tungsten: 12.24 wt.%, with the balance being iron. The raw materials used were pure iron (99.95% purity), nickel plate (99.98% purity), tungsten rod (99.99% purity), metallic chromium (99.6% purity), and ferroboron (19.59% boron content, 99.4% purity). The weighed pure iron, nickel plate, tungsten rod, and metallic chromium were placed in a crucible and then placed in a vacuum induction melting furnace. Ferroboron was placed in the furnace's feeder. The furnace was heated and melted under a vacuum of 15 Pa at 1650℃ until the raw materials in the crucible were completely melted. The vacuum was then closed, and argon gas was introduced at 7000 Pa. Ferroboron was then added back in the feeder, and the mixture was refined for 15 minutes to obtain molten metal. The molten metal was then poured into a vat at 1550℃. After cooling in the mold cavity, the sample is removed from the mold cavity, and after surface grinding, the desired product is obtained. The cast billet.

[0057] S2. Forging Billet Preparation: After heating the prepared billet to 1200℃ and holding it for 120 min, it is then subjected to multi-directional forging using a hydraulic high-speed forging machine. The final forging temperature is controlled to be ≥900℃, and the forging ratio of the billet is 2.32, which is the cross-sectional area before forging / the cross-sectional area after forging. The forging billet is then heated to 1000℃ for heat treatment and held for 90 minutes.

[0058] S3. Billet Preparation: The heat-treated forging billet is slit into forging bars with a length of 400mm. The outer surface of the forging bar is machined to be round and then processed. The center hole is used to prepare the outer diameter. The tube blank.

[0059] S4. Hot extrusion of tube blank: The prepared tube blank is heated to 1150℃ and held for 60 min, then hot extruded through an extrusion press at a speed of 136 mm / s to obtain the outer diameter... The extruded tube has a wall thickness of 15mm and an extrusion ratio of 6.0. The extrusion ratio is the cross-sectional area before extrusion / the cross-sectional area after extrusion.

[0060] S5. Cold rolling of extruded tubes: A total of 9 rolling passes are designed; the specific process for cold rolling deformation of extruded tubes is as follows. The deformation per pass is controlled between 40% and 45%; each tube after rolling requires an intermediate heat treatment at 1000℃ for 30 minutes to obtain the finished tube. The tube is then rolled in 9 passes using a rolling mill. The finished pipes have a good appearance and are free of cracks.

[0061] Figure 1 The XRD pattern of the cast billet prepared in step S1 of Example 1 is shown below. Figure 1 It can be seen that the phase composition of the billet is austenite phase, a small amount of ferrite phase and (Fe,Cr)W2B2 phase. No other boride phases were detected. Chromium and nickel are dissolved in both the austenite and ferrite phases. Figure 2 The image shows the SEM image of the cast billet prepared in step S1 of Example 1. Figure 2 It can be seen that the (Fe,Cr)W2B2 phase is distributed in a continuous network in the austenitic matrix phase.

[0062] Figure 3 The image shown is a SEM image of the forging billet after heat treatment in step S2 of Example 1. Figure 3 It can be seen that the (Fe,Cr)W2B2 phase in the forging billet is mainly distributed in a network, but it has changed from a continuous distribution to a discontinuous granular distribution. The particle size of the (Fe,Cr)W2B2 phase is 5-10 μm.

[0063] Figure 4 The image shows a SEM image of the extruded tube prepared in step S4 of Example 1. Figure 4 It can be seen that the (Fe,Cr)W2B2 phase is transformed into a dispersed granular structure, and the particle size of the (Fe,Cr)W2B2 phase is 0.5-5 μm.

[0064] Figure 5The image shows a SEM image of the finished pipe obtained in step S5 of Example 1. Figure 5 It can be seen that the (Fe,Cr)W2B2 phase is a dispersed granular structure, and the particle size of the (Fe,Cr)W2B2 phase is 0.1-5 μm.

[0065] The mechanical properties of the finished pipe prepared in step S5 of Example 1 were measured as follows: tensile strength Rm was 733.5 MPa, yield strength Rp was... 0.2 The strength is 343.0 MPa, and the elongation after fracture (A) is 33.20%.

[0066] The shielding performance of the finished pipe prepared in Example 1 was measured as follows: thermal neutron absorptivity was 88.41% (theoretical calculation value for a 10mm thickness). 60 The linear attenuation coefficient of Co is 0.463 cm. -1 (Measured for boards of the same composition) 137 The linear attenuation coefficient of Cs is 0.678 cm. -1 (Actual measurement of boards with the same composition).

[0067] Example 2

[0068] The difference between Example 2 and Example 1 is that Example 2 increases the tungsten and boron content in the alloy. The designed composition of the alloy is: boron: 1.1 wt.%, chromium: 13 wt.%, nickel: 10 wt.%, tungsten: 18.7 wt.%, with the balance being iron. The raw materials are weighed according to the designed composition of the alloy, and the total weight of the raw materials is 500 kg. Steps S1 to S4 of Example 2 are the same as those of Example 1, but step S5 is different. Step S5 of Example 2 is as follows:

[0069] S5. Cold rolling of extruded tubes: A total of 2 rolling passes are designed; the deformation process of cold rolling extruded tubes is as follows: The deformation per pass is controlled between 40% and 45%; the tubes after each pass of rolling require an intermediate heat treatment at 1050℃ for 30 minutes. The tubes are rolled in two passes using a rolling mill. The finished pipes have a good appearance and are free of cracks.

[0070] The phase structure of the billet prepared in step S1 of Example 2 was found to be the same as that of Example 1. The phase composition of the billet was austenite phase, a small amount of ferrite phase and (Fe,Cr)W2B2 phase. Chromium and nickel were dissolved in both the austenite phase and the ferrite phase. No other boride phases were detected. The (Fe,Cr)W2B2 phase was distributed in a continuous network in the austenite matrix phase. Figure 6 The image shows the SEM image of the finished pipe obtained in step S5 of Example 2. Figure 6It can be seen that the (Fe,Cr)W2B2 phase has been transformed into a diffusely distributed granular form, and the particle size of the (Fe,Cr)W2B2 phase is 0.1-5 μm. Compared with Example 1, the amount of (Fe,Cr)W2B2 phase in Example 2 is significantly increased.

[0071] The mechanical properties of the finished pipe prepared in step S5 of Example 2 were measured as follows: tensile strength Rm was 755.0 MPa, yield strength Rp was... 0.2 The strength is 373 MPa, and the elongation after fracture (A) is 27.5%.

[0072] The shielding performance of the finished pipe prepared in Example 2 was measured as follows: thermal neutron absorptivity was 94.16% (theoretical calculation value for a 10mm thickness). 60 The linear attenuation coefficient of Co is 0.493 cm. -1 (Measured for boards of the same composition) 137 The linear attenuation coefficient of Cs is 0.698 cm⁻¹ -1 (Measured values ​​of boards with the same composition).

[0073] As can be seen from Examples 1 and 2, the increased content of W and B in the alloy composition is beneficial to improving strength and shielding performance, and the amount of (Fe,Cr)W2B2 phase increases significantly, while the machinability and plasticity decrease slightly.

[0074] Example 3

[0075] This embodiment provides a shielding alloy seamless tube and its preparation method, specifically including the following steps:

[0076] S1. Billet Preparation: Weigh the raw materials according to the alloy composition. The total weight of the raw materials is 3T. The designed alloy composition is: boron: 1.2wt.%, chromium: 13wt.%, nickel: 10wt.%, tungsten: 15.0wt.%, titanium: 1.25wt.%, with the balance being iron. The raw materials used are pure iron (purity 99.95%), nickel plate (purity 99.98%), tungsten rod (purity 99.99%), metallic chromium (purity 99.6%), metallic titanium (purity 99.5%), and ferroboron (boron...). With a content of 19.59% and a purity of 99.4%, weighed pure iron, nickel plates, tungsten rods, metallic chromium, and metallic titanium were placed in a crucible and then placed in a vacuum induction melting furnace. Boron ferrophosphate was placed in the furnace's feeder. The furnace was heated and melted under a vacuum of 15 Pa at 1650℃ until the raw materials in the crucible were completely melted. The vacuum was then closed, and argon gas was introduced at 7000 Pa. Boron ferrophosphate was then added back in, and the furnace was refined for 15 minutes to obtain molten metal. The molten metal was then poured at 1550℃. Due to the large size of the ingot, a consumable remelting method was used to improve the ingot's microstructure and compositional inhomogeneity. After consumable remelting, the following was obtained: Self-consumable ingots, after surface grinding, are prepared to obtain The cast billet.

[0077] S2. Forging Billet Preparation: After heating the prepared billet to 1200℃ and holding it for 120 min, it is then subjected to three-dimensional forging using a hydraulic high-speed forging machine. The final forging temperature is controlled to be ≥900℃, and the forging ratio of the billet is 2.0, thus preparing the billet into... The forging billet is then heated to 1100℃ for heat treatment and held for 90 minutes.

[0078] S3. Billet Preparation: The heat-treated forging billet is slit into 400mm long forging bars. The outer surface of the forging bars is machined to be round and then processed. The center hole is used to prepare the outer diameter. The tube blank.

[0079] S4. Hot extrusion of tube blank: The prepared tube blank is heated to 1150℃ and held for 90 min, then hot-extruded through an extrusion press at a speed of 100 mm / s to prepare the tube blank. The extrusion ratio is 2.0.

[0080] S5. Cold rolling of extruded tubes: A total of 3 rolling passes are designed; the deformation process of cold rolling extruded tubes is as follows: The deformation amount in each pass is controlled between 25% and 32%; the pipe after each rolling pass undergoes intermediate heat treatment, heated to 1100℃ for 30 minutes to obtain the finished pipe. The pipe is then rolled in three passes using a rolling mill. The finished pipes have a good appearance and are free of cracks.

[0081] The phase composition of the billet prepared in step S1 of Example 3 was determined to be austenite, a small amount of ferrite, and (Fe,Cr)W2B2 phase. No other boride phases were detected. With the addition of a small amount of Ti, Ti was mainly dissolved in the (Fe,Cr)W2B2 phase, which was distributed continuously in a network within the austenite matrix. The (Fe,Cr)W2B2 phase in the finished pipe of step S5 of Example 3 was determined to have been transformed into dispersed granular particles, with a particle size of 0.1–5 μm.

[0082] The mechanical properties of the finished pipe prepared in step S5 of Example 3 were measured as follows: tensile strength Rm was 760.0 MPa, yield strength Rp was... 0.2 The strength is 378.0 MPa, and the elongation after fracture (A) is 19.8%.

[0083] The shielding performance of the material prepared in Example 3 was measured as follows: thermal neutron absorption rate was 99.99% (theoretical calculation value for a thickness of 30 mm). 60 The linear attenuation coefficient of Co is 0.446 cm. -1 (Measured values ​​for boards of the same composition), the linear attenuation coefficient of 137Cs is 0.638cm. -1 (Measured values ​​of boards with the same composition).

[0084] As can be seen from Examples 2 and 3, adding Ti to replace part of W to reduce the alloy's specific gravity is beneficial for improving strength, but it reduces plasticity and gamma-ray shielding performance.

[0085] Example 4

[0086] This embodiment provides a shielding alloy seamless tube and its preparation method, specifically including the following steps:

[0087] S1. Billet Preparation: Weigh the raw materials according to the alloy composition. The total weight of the raw materials is 3T. The designed alloy composition is: boron: 0.72wt.%, chromium: 13wt.%, nickel: 10wt.%, tungsten: 12.24wt.%, with the balance being iron. The raw materials used are pure iron (purity 99.95%), nickel plate (purity 99.98%), tungsten rod (purity 99.99%), metallic chromium (purity 99.6%), and ferroboron (boron content 19.59%). (99.4% purity) Weighed pure iron, nickel plates, tungsten rods, and metallic chromium were placed in a crucible and then placed in a vacuum induction melting furnace. Boron ferrophosphate was placed in the furnace's feeder. The furnace was heated and melted under a vacuum of 15 Pa at 1650℃ until the raw materials in the crucible were completely melted. The vacuum was then closed, and argon gas was introduced at 7000 Pa. Boron ferrophosphate was then added back in, and the furnace was refined for 15 minutes to obtain molten metal. The molten metal was then poured at 1550℃. Due to the large size of the ingot, a consumable remelting method was used to improve the ingot's microstructure and compositional inhomogeneity. After consumable remelting, the following was obtained: Self-consumable ingots, after surface grinding, are prepared to obtain The cast billet.

[0088] S2. Forging Billet Preparation: After heating the prepared billet to 1200℃ and holding it for 120 min, it is then subjected to bidirectional forging using a hydraulic high-speed forging machine to improve production efficiency. The final forging temperature is controlled to be ≥950℃, and the forging ratio of the billet is 10. The outer diameter of the forged billet after forging is... Subsequently, the forging billet is heated to 1000℃ and held for 90 minutes for heat treatment to obtain the heat-treated forging billet.

[0089] S3. Billet Preparation: The heat-treated forging billet is slit into 400mm long forging bars. The outer surface of the forging bars is machined to be round and then processed. The central hole was prepared to obtain Tube blank.

[0090] S4. Hot extrusion of tube blank: The tube blank is heated to 1150℃ and held for 60 minutes, then hot-extruded through an extrusion press at a speed of 180 mm / s to obtain... The extruded tube has a wall thickness of 15mm and an extrusion ratio of 5.8.

[0091] S5. Cold rolling of extruded tubes: A total of 9 rolling passes are designed; the deformation process of cold rolling of extruded tubes is as follows: The deformation per pass is controlled between 40% and 45%; each tube after rolling requires an intermediate heat treatment at 1000℃ for 30 minutes to obtain the finished tube. The tube is then rolled in 9 passes using a rolling mill. The finished pipes have a good appearance and are free of cracks.

[0092] The phase structure of the billet prepared in step S1 of Example 4 was found to be the same as that in Example 1. The phase composition of the billet was austenite, a small amount of ferrite, and (Fe,Cr)W2B2 phase. Chromium and nickel were dissolved in both the austenite and ferrite phases. No other boride phases were detected. The (Fe,Cr)W2B2 phase was distributed continuously in a network in the austenite matrix. The (Fe,Cr)W2B2 phase in the finished pipe of step S5 of Example 4 was found to have been transformed into dispersed granular particles, and the particle size of the (Fe,Cr)W2B2 phase was 0.1-5 μm.

[0093] The mechanical properties of the finished pipe from step S5 of Example 4 were measured as follows: tensile strength Rm was 741.0 MPa, yield strength Rp was... 0.2 The strength is 355.0 MPa, and the elongation after fracture (A) is 30.2%.

[0094] The shielding performance of the finished pipe prepared in Example 4 was measured as follows: thermal neutron absorptivity was 88.41% (theoretical calculation value for a 10mm thickness). 60 The linear attenuation coefficient of Co is 0.463 cm. -1 (Measured for boards of the same composition) 137 The linear attenuation coefficient of Cs is 0.678 cm. -1 (Actual measurement of boards with the same composition).

[0095] Example 5

[0096] The difference between Example 5 and Example 1 is that the extrusion ratio of the tube blank in step S4 is increased to 20. Steps S1 to S3 of Example 5 are the same as those in Example 1. Steps S4 and S5 of Example 5 are different from those in Example 1. Steps S4 and S5 of Example 5 are as follows:

[0097] S4. Hot extrusion of tube blank: The prepared tube blank is heated to 1150℃ and held for 60 minutes, then hot extruded through an extrusion press at a speed of 180 mm / s to obtain the outer diameter... The extruded tube has a wall thickness of 8mm and an extrusion ratio of 20.

[0098] S5. Cold rolling of extruded tubes: A total of 7 rolling passes are designed; the deformation process is as follows: The deformation per pass is controlled between 40% and 45%; the tubes after each pass of rolling must undergo an intermediate heat treatment at 1000℃ for 30 minutes, and then the extruded tubes are cold rolled to [the desired temperature] using a rolling mill. Cold-rolled tubes with a wall thickness of 1mm are used to obtain finished tubes.

[0099] It was found that the (Fe,Cr)W2B2 phase in the finished pipe prepared in step S5 of Example 5 was transformed into a dispersed granular form, and the particle size of the (Fe,Cr)W2B2 phase was 0.1-5 μm.

[0100] The mechanical properties of the finished pipe prepared in Example 5 were measured as follows: tensile strength Rm was 763.0 MPa, yield strength Rp0.2 was 374.0 MPa, and elongation after fracture A was 28.4%.

[0101] The shielding performance of the finished pipe prepared in Example 5 was measured as follows: thermal neutron absorptivity was 88.41% (theoretical calculation value for a 10mm thickness). 60 The linear attenuation coefficient of Co is 0.463 cm. -1 (Measured for boards of the same composition) 137 The linear attenuation coefficient of Cs is 0.678 cm. -1 (Actual measurement of boards with the same composition).

[0102] Example 6

[0103] The difference between Example 6 and Example 1 is that the extrusion temperature of the tube blank in step S4 is reduced to 1000 degrees Celsius. Steps S1-S3 of Example 6 are the same as those in Example 1. Steps S4 and S5 of Example 6 are different from those in Example 1. Steps S4 and S5 of Example 6 are as follows:

[0104] S4. Hot extrusion of tube blank: The prepared tube blank is heated to 1000℃ and held for 60 min, then hot extruded through an extrusion press at a speed of 136 mm / s to obtain the outer diameter... The extruded tube has a wall thickness of 15mm and an extrusion ratio of 6.0.

[0105] S5. Cold rolling of extruded tubes: A total of 2 rolling passes are designed; the deformation process is as follows: The deformation per pass is controlled between 40% and 45%; the pipe after each pass rolling requires an intermediate heat treatment at 1000℃ for 30 minutes to obtain the finished pipe. The pipe is then rolled in two passes using a rolling mill. The finished pipes have a good appearance and are free of cracks.

[0106] It was found that the (Fe,Cr)W2B2 phase in the finished pipe prepared in step S5 of Example 6 was transformed into a dispersed granular form, and the particle size of the (Fe,Cr)W2B2 phase was 0.1-5 μm.

[0107] The mechanical properties of the finished pipe prepared in step S5 of Example 6 were measured as follows: tensile strength Rm was 752.0 MPa, yield strength Rp0.2 was 360 MPa, and elongation after fracture A was 28%.

[0108] The shielding performance of the finished pipe prepared in step S5 of Example 6 was measured as follows: the thermal neutron absorption rate was 88.41% (theoretical calculation value for a thickness of 10 mm). 60 The linear attenuation coefficient of Co is 0.463 cm. -1 (Measured for boards of the same composition) 137 The linear attenuation coefficient of Cs is 0.678 cm. -1 (Actual measurement of boards with the same composition).

[0109] Example 7

[0110] The difference between Example 7 and Example 1 is that the cold rolling deformation in each pass is reduced to about 30% in step S5. Steps S1 to S4 of Example 7 are the same as those of Example 1, but step S5 of Example 7 is different from that of Example 1. Step S5 of Example 7 is as follows:

[0111] S5. Cold rolling of extruded tubes: A total of 2 rolling passes are designed; the specific process for cold rolling deformation of extruded tubes is as follows: Each rolled tube undergoes an intermediate heat treatment at 1100℃ for 30 minutes, resulting in a finished tube with dimensions of [missing value].

[0112] The mechanical properties of the finished pipe prepared in step S5 of Example 7 were measured as follows: tensile strength Rm is 700MPa, yield strength Rp0.2 is 330MPa, and elongation after fracture A is 34%.

[0113] The shielding performance of the finished pipe prepared in Example 7 was measured as follows: thermal neutron absorptivity was 88.41% (theoretical calculation value for a 10mm thickness).60 The linear attenuation coefficient of Co is 0.463 cm. -1 (Measured for boards of the same composition) 137 The linear attenuation coefficient of Cs is 0.678 cm. -1 (Actual measurement of boards with the same composition).

[0114] Example 8

[0115] This embodiment provides a shielding alloy seamless tube and its preparation method, specifically including the following steps:

[0116] S1. Billet Preparation: Weigh the raw materials according to the alloy composition. The total weight of the raw materials is 500 kg. The designed alloy composition is: boron: 2.25 wt.%, chromium: 18 wt.%, nickel: 12 wt.%, tungsten: 7.0 wt.%, titanium: 5.3 wt.%, manganese: 1.0 wt.%, with the balance being iron. The raw materials used are pure iron (purity 99.95%), nickel plate (purity 99.98%), tungsten rod (purity 99.99%), metallic chromium (purity 99.6%), metallic manganese (purity 99.9%), and metallic titanium (purity 99.9%). 9.5% boron (boron content 19.59%, purity 99.4%), weighed pure iron, nickel plate, tungsten rod, metallic chromium, and metallic titanium were placed in a crucible and then placed in a vacuum induction melting furnace. Metallic manganese and ferroboron were placed in the feeder of the vacuum induction melting furnace. The furnace was heated and melted under a vacuum of 15 Pa at 1680℃ until the raw materials in the crucible were completely melted. The vacuum was then closed, and argon gas was introduced at 7000 Pa. The metallic manganese and ferroboron were then added back in, and the mixture was refined for 15 minutes to obtain a liquid alloy. The liquid alloy was then poured into a container at 1580℃. After cooling in the mold cavity, the sample is removed from the mold cavity, and after surface grinding, the desired product is obtained. The cast billet.

[0117] S2. Forging Billet Preparation: After heating to 1180℃ and holding for 120 min, the billet is forged in three directions using a hydraulic high-speed forging machine. The final forging temperature is controlled at ≥900℃, and the forging ratio of the billet is 2.32, thus preparing the billet into... The forging billet is then heated to 1100℃ and held for 90 minutes for heat treatment.

[0118] S3. Billet Preparation: The heat-treated forging billet is slit into 430mm long forging bars. The outer surface of the forging bars is machined to be round and then processed. The central hole was prepared to obtain Tube blank.

[0119] S4. Hot extrusion of tube blank: The tube blank is heated to 1150℃ and held for 90 minutes, then hot extruded using an extrusion press at a speed of 100 mm / s to prepare the tube blank. The extrusion ratio is 2.85, and the extruded tube undergoes heat treatment at 1100℃ for 40 minutes.

[0120] S5. Hot rolling of extruded tubes: The extruded tubes are heated to 1150℃ and held for 90 minutes before hot rolling, with a total of 3 rolling passes designed. The hot rolling deformation process of the heat-treated extruded tubes is as follows: The deformation per pass is controlled between 10% and 15%; the tubes after each pass of rolling must undergo an intermediate heat treatment at 1150℃ for 45 minutes, and the extruded tubes are then hot-rolled using a rolling mill to... The hot-rolled pipe is used to obtain the finished pipe.

[0121] Figure 7 The image shows the XRD pattern of the ingot prepared in step S1 of Example 8. The phase composition of the ingot is austenitic phase, (Fe,Cr)W2B2 phase, and a small amount of TiB2 phase. The (Fe,Cr)W2B2 and TiB2 phases in the finished pipe prepared in step S5 of Example 8 were found to be dispersedly distributed, with particle sizes ranging from 1 to 10 μm.

[0122] The mechanical properties of the finished pipe prepared in Example 8 were measured as follows: tensile strength Rm was 625.2 MPa, yield strength Rp was... 0.2 The strength is 378.0 MPa, and the elongation after fracture (A) is 8.5%.

[0123] The shielding performance of the material prepared in Example 8 was measured as follows: thermal neutron absorption rate was 98.95% (theoretical calculation value for a 10mm thickness). 60 The linear attenuation coefficient of Co is 0.416 cm. -1 (Theoretical calculation) The linear attenuation coefficient of 137Cs is 0.583 cm. -1 (Theoretical calculation value)

[0124] Example 9

[0125] This embodiment provides a shielding alloy seamless tube and its preparation method, specifically including the following steps:

[0126] S1. Billet Preparation: Weigh the raw materials according to the alloy composition. The total weight of the raw materials is 500 kg. The designed alloy composition is: boron: 4.0 wt.%, chromium: 18 wt.%, nickel: 10 wt.%, tungsten: 4 wt.%, titanium: 9.3 wt.%, manganese: 1.0 wt.%, with the balance being iron. The raw materials used are pure iron (purity 99.95%), nickel plate (purity 99.98%), tungsten rod (purity 99.99%), metallic chromium (purity 99.6%), metallic manganese (purity 99.9%), and metallic titanium (purity 99%). Manganese and ferroboron (boron content 19.59%, purity 99.4%) were used. Weighed pure iron, nickel plates, tungsten rods, metallic chromium, and metallic titanium were placed in a crucible and then placed in a vacuum induction melting furnace. Metallic manganese and ferroboron were placed in the furnace's feeder. The furnace was heated and melted under a vacuum of 15 Pa at 1680°C until the raw materials in the crucible were completely melted. The vacuum was then closed, and argon gas was introduced at 7000 Pa. The manganese and ferroboron were then added back in, and the mixture was refined for 15 minutes to obtain a liquid alloy. The liquid alloy was then poured into a vat at 1580°C. After cooling in the mold cavity, the sample is removed from the mold cavity, and after surface grinding, the desired product is obtained. The cast billet.

[0127] S2. Forging Billet Preparation: After heating to 1180℃ and holding for 120 min, the billet is forged in three directions using a hydraulic high-speed forging machine. The final forging temperature is controlled at ≥900℃, and the forging ratio of the billet is 2.32, thus preparing the billet into... The forging billet is then heated to 1150℃ and held for 90 minutes for heat treatment.

[0128] S3. Billet Preparation: The heat-treated forging billet is slit into 430mm long forging bars. The outer surface of the forging bars is machined to be round and then processed. The central hole was prepared to obtain Tube blank.

[0129] S4. Hot extrusion of tube blank: After heating the tube blank to 1150℃ and holding it at that temperature for 90 minutes, hot extrusion is performed using an extrusion press at a speed of 100 mm / s to obtain the outer diameter... The extruded tube has an extrusion ratio of 2.85. After the extruded tube is heat-treated at 1150℃ for 40 minutes, the finished tube is obtained.

[0130] Figure 8 The image shows the XRD pattern of the ingot prepared in step S4 of Example 9. The phase composition of the ingot is austenite, a small amount of ferrite, and TiB2 phase, with the added tungsten dissolved into the matrix phase. The TiB2 phase in the finished pipe prepared in step S4 of Example 9 was found to be dispersed, with a particle size of 1–10 μm.

[0131] The mechanical properties of the finished pipe prepared in Example 9 were measured as follows: tensile strength Rm was 674.7 MPa, yield strength Rp was... 0.2 The strength is 370.0 MPa, and the elongation after fracture (A) is 8.0%.

[0132] The shielding performance of the material prepared in Example 9 was measured as follows: thermal neutron absorption rate was 99.91% (theoretical calculation value for a 10mm thickness). 60 The linear attenuation coefficient of Co is 0.384 cm. -1 (Theoretical calculation) The linear attenuation coefficient of 137Cs is 0.527 cm. -1 (Theoretical calculation value)

[0133] Comparative Example 1

[0134] The difference between Comparative Example 1 and Example 1 is that the alloy design composition of Comparative Example 1 is: boron: 0.72 wt.%, chromium: 13 wt.%, nickel: 10 wt.%, tungsten: 2 wt.%, with the balance being iron. Steps S1-S4 of Comparative Example 1 are the same as those of Example 1.

[0135] In Comparative Example 1, obvious cracks were formed on the extruded tube prepared in step S4, such as... Figure 9 As shown, further rolling cannot be carried out. The phase composition of the billet prepared in step S1 of Comparative Example 1 was measured to include austenite phase, a small amount of ferrite phase, and (Fe,Cr)W2B2 phase, as well as (Fe,Cr)2B phase, which led to a significant reduction in the alloy's ductility and toughness.

[0136] Comparative Example 2

[0137] The difference between Comparative Example 2 and Example 1 is that the alloy design composition of Comparative Example 2 is: boron: 0.72 wt.%, chromium: 13 wt.%, nickel: 10 wt.%, tungsten: 24 wt.%, with the balance being iron (Fe). Steps S1-S4 of Comparative Example 2 are the same as those of Example 1.

[0138] The extruded tube prepared in step S4 of Comparative Example 2 showed obvious cracks and could not be rolled further. The phase composition of the cast billet prepared in step S1 of Comparative Example 2 was measured to contain austenite, a small amount of ferrite, and (Fe,Cr)W2B2 phase, as well as (Fe,Cr)2W phase, indicating a significant decrease in the alloy's ductility and toughness.

[0139] Comparative Example 3

[0140] Comparative Example 3 provides a shielding alloy seamless tube and its preparation method, specifically including the following steps:

[0141] S1. Billet Preparation: Weigh the raw materials according to the alloy composition. The total weight of the raw materials is 500 kg. The designed alloy composition is: boron: 0.72 wt.%, chromium: 13 wt.%, nickel: 10 wt.%, tungsten: 12.24 wt.%, with the balance being iron. The raw materials used are pure iron (purity 99.95%), nickel plate (purity 99.98%), tungsten rod (purity 99.99%), metallic chromium (purity 99.6%), and ferroboron (boron content 19.5%). 9% purity (99.4%), weighed pure iron, nickel plate, tungsten rod, and metallic chromium were placed in a crucible and then placed in a vacuum induction melting furnace. Boron ferrophosphate was placed in the furnace's feeder. The furnace was heated and melted under a vacuum of 15 Pa at 1650°C until the raw materials in the crucible were completely melted. The vacuum was then closed, and argon gas was introduced at 7000 Pa. Boron ferrophosphate was then added back in, and the furnace was refined for 15 minutes to obtain molten metal. The molten metal was then poured into a container at 1550°C. After cooling in the mold cavity, the sample is removed from the mold cavity, and after surface grinding, the desired product is obtained. The cast billet.

[0142] S2. Forging billet preparation: After heating to 1200℃ and holding for 120 min, it is forged in two directions using a hydraulic high-speed forging machine, with the final forging temperature controlled at 900℃ and the forging ratio of the billet being 1.5; subsequently, the billet is heated to 1000℃, held for 90 min, and then heat-treated.

[0143] S3. Billet Preparation: The heat-treated forging billet is slit into 400mm long forging bars. The outer surface of the forging bars is machined to be round and then processed. The central hole was prepared to obtain Tube blank.

[0144] S4. Hot extrusion of tube blank: The prepared tube blank is heated to 1150℃ and held for 60 min, then hot extruded through an extrusion press at a speed of 136 mm / s to prepare the tube blank. The extruded tube has a wall thickness of 15mm and an extrusion ratio of 6.0.

[0145] The extruded tube prepared in step S4 of Comparative Example 3 showed obvious cracks and could not be rolled further.

[0146] It was found that the continuously distributed (Fe,Cr)W2B2 in the forging blank prepared in step S2 of Comparative Example 3 was not sufficiently broken into discontinuous particles, resulting in poor plasticity and toughness.

[0147] Comparative Example 4

[0148] The difference between Comparative Example 4 and Example 1 is that the extrusion ratio in step S4 of Comparative Example 4 is increased to 25. Steps S1 to S3 of Comparative Example 4 are the same as those in Example 1. Step S4 of Comparative Example 4 is as follows:

[0149] S4. Hot extrusion of tube blank: After heating the tube blank to 1150℃ and holding it at that temperature for 60 minutes, hot extrusion is performed through an extrusion press at a speed of 180 mm / s to obtain the outer diameter... The extruded tube has a wall thickness of 6.8 mm and an extrusion ratio of 25.

[0150] In Comparative Example 4, the extrusion deformation exceeded the hot deformation limit of the alloy, resulting in obvious cracks during extrusion, making it impossible to proceed to the next rolling step.

[0151] Comparative Example 5

[0152] The difference between Comparative Example 5 and Example 1 is that the forging billet prepared in step S2 of Comparative Example 5 is heated to 900°C and held for 90 minutes for heat treatment, while the tube blank is heated to 900°C and held for 60 minutes in step S4 of Comparative Example 5 and then hot extruded through an extrusion unit. Steps S1-S4 of Comparative Example 5 are the same as those in Example 1.

[0153] The extruded tube prepared in step S4 of Comparative Example 5 showed obvious cracks and could not be rolled further. It was found that the forging billet after heat treatment in step S2 of Comparative Example 5 contained not only austenite phase, a small amount of ferrite phase and (Fe,Cr)W2B2 phase, but also (Fe,Cr)2W brittle phase, which led to a significant decrease in the alloy's plasticity and toughness.

[0154] Comparative Example 6

[0155] The difference between Comparative Example 6 and Example 1 is that step S5 of Comparative Example 6 increases the cold rolling deformation per pass to 57%. Steps S1-S4 of Comparative Example 6 are the same as those of Example 1. Step S5 of Comparative Example 6 is as follows:

[0156] S5. Cold rolling of extruded tubes: The specific process for cold rolling deformation of extruded tubes is as follows:

[0157] Comparative Example 6: Due to excessive deformation in the first cold rolling pass, numerous cracks appeared on the surface of the tube, such as... Figure 10 As shown, the next rolling step cannot be performed.

[0158] Comparative Example 7

[0159] The difference between Comparative Example 7 and Example 1 is that step S5 in Comparative Example 7 lowers the heat treatment temperature after each rolling pass. Steps S1-S4 in Comparative Example 7 are the same as in Example 1. Step S5 in Comparative Example 7 is as follows:

[0160] S5. Cold rolling of extruded tubes: The specific process for cold rolling deformation of extruded tubes is as follows: Each rolled tube must undergo an intermediate heat treatment at 800℃ for 30 minutes.

[0161] The mechanical properties of the pipe after the first rolling pass in Comparative Example 7 are as follows: tensile strength Rm is 740 MPa, yield strength Rp0.2 is 560 MPa, and elongation after fracture A is only 16%. The pipe after the second rolling pass shows obvious cracking. Figure 11 As shown, the next rolling step cannot be performed.

[0162] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a shielding alloy seamless tube, characterized in that, The preparation steps include the following: S1. Billet preparation: Weigh the raw materials according to the alloy composition, and melt and cast the raw materials to obtain a billet. The alloy composition includes: boron: 0.2~4.0 wt.%, chromium: 5.0~26.0 wt.%, nickel: 6.0~20.0 wt.%, tungsten: 2.0~20.0 wt.%, molybdenum: 0~4.0 wt.%, titanium: 0~10.0 wt.%, manganese: 0~4.0 wt.%, with the balance being iron; S2. Forging billet preparation: The cast billet is heated and forged to obtain a forging billet. The final forging temperature is controlled to be above 850°C and the forging ratio is 2~12. The forging billet is then subjected to heat treatment at a temperature of 950~1250°C. S3. Tube blank preparation: The heat-treated forging blank is processed to form a center hole, thus preparing a tube blank; S4. Hot extrusion of tube blank: The tube blank is hot extruded to prepare an extruded tube. The hot extrusion temperature is 950~1250℃ and the extrusion ratio is 1.8~22. S5. Extrusion tube processing: The extruded tube is cold-rolled or hot-rolled to the design size to obtain the finished tube. The deformation of each cold rolling pass is less than 50%, and the tube after each cold rolling pass needs to be heat-treated at a temperature of 900℃~1200℃. The phase structure of the prepared shielding alloy seamless tube includes a matrix phase and a boride phase. The matrix phase includes an austenitic phase, and the boride phase is granular. The boride phase is (Fe,Cr)W2B2 phase and TiB2 phase, and the particle size of the boride phase is less than 10 μm.

2. The method for preparing the shielding alloy seamless tubing according to claim 1, characterized in that, Step S4 also includes heat-treating the extruded tube at a temperature of 950~1250℃.

3. A shielding alloy seamless tube, prepared by the method for preparing the shielding alloy seamless tube according to claim 1 or 2.

4. The shielding alloy seamless tubing according to claim 3, characterized in that, The particle size of the (Fe,Cr)W2B2 phase is 0.1~5μm.

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