Preparation method of niobium rod with uniform grain fragmentation and the obtained niobium rod

Abstract

This invention relates to a method for preparing niobium rods with uniformly broken grains. First, alloy raw materials are melted and cast to obtain an ingot, which is then preheated to obtain a first billet. Next, the first billet undergoes multiple axial forgings and a first heat treatment to obtain a second billet. Then, the second billet undergoes surface treatment to remove surface defects and is radially forged to obtain a third billet. Subsequently, the third billet undergoes oxidation treatment to form an oxide film on its surface, protecting it. The third billet with the oxide film is then subjected to multiple roll forming processes to obtain a first rod. Next, the first rod is rotary forged and polished to obtain a second rod. Finally, the second rod undergoes a second heat treatment to obtain a finished rod. Through multiple axial forgings, radial rotary forgings, and roll forming processes, the resulting finished rod has a uniform and fine grain structure, a grain size GS=7-9, an elongation ≥40%, and a hardness (HV / 2.9N) ≤60.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of niobium rod preparation, and particularly relates to a preparation method of a niobium rod with uniform grain breakage and the prepared niobium rod. BACKGROUND

[0002] In the Nb3Sn superconducting wire, the core wire diameter is usually less than 10 μm, and the niobium rod is the most important basic raw material of the Nb3Sn superconducting wire material. The niobium rod needs to be processed for multiple times in the manufacturing process of the Nb3Sn superconducting wire material, so that the processing rate of the niobium rod is very large. Therefore, a niobium rod with a diameter of Φ5-Φ17 mm is needed, which has the performance of uniform grain breakage, grain size reaching more than 6 levels, low hardness and high plasticity. SUMMARY

[0003] The application aims to provide a preparation method of a niobium rod with uniform grain breakage, and the niobium rod obtained by the preparation method has uniform grain breakage, grain size reaching more than 6 levels, low hardness and high plasticity.

[0004] It is also necessary to provide a niobium rod.

[0005] To achieve the above-mentioned purpose, the application provides a preparation method of a niobium rod with uniform grain breakage, which comprises the following steps:

[0006] Step 1: melting and casting the alloy raw material to obtain an ingot, and preheating the ingot to improve the cutting processing performance of the ingot to obtain a first blank;

[0007] Step 2: performing multiple axial forging and first heat treatment on the first blank to obtain a second blank;

[0008] Step 3: performing surface treatment on the second blank to remove defects on the surface of the second blank, and performing radial forging on the second blank to obtain a third blank;

[0009] Step 4: performing oxidation treatment on the third blank to generate an oxide film on the surface of the third blank to protect the third blank, and performing multiple pass rolling on the third blank with the generated oxide film to obtain a first rod;

[0010] Step 5: performing rotary forging and polishing on the first rod to obtain a second rod;

[0011] Step 6: performing second heat treatment on the second rod to obtain a finished rod.

[0012] Preferably, the step 2 is specifically as follows:

[0013] A1: performing multiple axial upsetting and axial elongation on the first blank after preheating treatment, and rounding;

[0014] A2: Put the first blank after rounding into a mixed acid solution for surface cleaning to remove surface impurities and oil stains;

[0015] A3: The first blank after cleaning in the mixed acid solution is subjected to first heat treatment in a vacuum environment of nitrogen, heated to 450-550°C in 25-35 minutes, kept for 25-35 minutes, then heated to 750-850°C in 25-35 minutes, kept for 25-35 minutes, then heated to 900-1000°C in 10-20 minutes, kept for 95-105 minutes, and then cooled down and discharged naturally;

[0016] A4: The first blank after heat treatment is subjected to axial upsetting and axial elongation again, and is rounded to obtain a second blank.

[0017] Preferably, the step A1 specifically comprises: the first blank after preheating is subjected to first axial upsetting and axial elongation, the first blank is upset by 245-255 mm and elongated by 175-185 mm, then the first blank is subjected to second axial upsetting and axial elongation, the first blank is upset by 215-225 mm and elongated by 175-185 mm, and finally the first blank is rounded to obtain a first blank with a diameter error of 5 mm.

[0018] Preferably, the step 3 specifically comprises:

[0019] B1: The surface of the second blank is turned, polished and cleaned;

[0020] B2: The second blank after cleaning is subjected to radial forging, and the outer diameter is reduced by 5-8 mm to obtain a third blank.

[0021] Preferably, the step 4 specifically comprises:

[0022] C1: The surface of the third blank is turned;

[0023] C2: The turned third blank is placed in an oxidation solution formed by mixing H2O and H2SO4 and is electrified for oxidation treatment, wherein the volume ratio of H2O to H2SO4 is (96-99) : (1-3), so that an oxide film is formed on the surface of the third blank;

[0024] C3: The third blank after oxidation treatment is subjected to multiple pass rolling to obtain a first rod.

[0025] Preferably, the step 5 specifically comprises:

[0026] D1: The first rod is subjected to rotary forging processing;

[0027] D2: The first rod after rotary forging processing is subjected to surface polishing treatment to obtain a second rod.

[0028] Preferably, the step 6 is specifically: placing the second bar into a vacuum environment of nitrogen for a second heat treatment, heating to 450-550 DEG C in 25-35 minutes, holding for 110-130 minutes; then heating to 750-850 DEG C in 25-35 minutes, holding for 50-70 minutes; then heating to 800-1000 DEG C in 25-35 minutes, holding for 85-95 minutes, and then cooling down, naturally cooling out of the furnace, to obtain the finished bar.

[0029] Preferably, the preheating treatment in the step 1 is specifically: placing the ingot into a high-temperature environment of 400-550 DEG C for constant temperature for 90-180 minutes, to obtain the second blank.

[0030] Preferably, the step 1 is specifically:

[0031] The alloy raw material comprises the following elements: carbon 0.002-0.005 wt%, oxygen 0.01-0.03 wt%, nitrogen 0.003-0.005 wt%, hydrogen 0.0015-0.0018 wt%, iron 0.002-0.005 wt%, tantalum 0.1-0.3 wt%, silicon 0.002-0.005 wt%, nickel 0.005-0.007 wt%, molybdenum 0.003-0.005 wt%, tungsten 0.01-0.04 wt%, titanium 0.002-0.005 wt%, zirconium 0.02-0.04 wt%, hafnium 0.02-0.05 wt%, and the rest is niobium.

[0032] Another aspect of the present application provides a niobium bar prepared by the method of the previous aspect.

[0033] From the above technical solution, the preparation method of the niobium bar with uniform grain crushing provided by the present application first melts and casts the alloy raw material to obtain an ingot, and preheats the ingot to improve the cutting processing performance of the ingot, to obtain a first blank; then performs multiple axial forging on the first blank to fully crush the grains and performs a first heat treatment to eliminate micro-defects, to obtain a second blank; then performs surface treatment on the second blank to remove defects on the surface of the second blank, and performs radial forging on the second blank to improve the grain structure, to obtain a third blank; then performs oxidation treatment on the third blank to form an oxide film on the surface of the third blank to protect the third blank, and performs multiple pass rolling on the third blank with the oxide film to change the direction of the grain structure, to obtain a first bar; then performs rotary forging on the first bar to make the grain structure dense and polished, to obtain a second bar; finally performs a second heat treatment on the second bar to stabilize the size, to obtain a finished bar; through multiple axial forging+radial rotary forging+pass rolling, the finished bar has uniform and small grain structure, grain size GS=7-9, elongation ≥40%, and hardness (HV / 2.9N) ≤60, which meets the demand for high processing rate of the niobium bar in the manufacturing process of Nb3Sn superconducting wire. Attached Figure Description

[0034] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a flowchart illustrating a method for preparing a uniformly grained niobium rod according to an embodiment of the present invention.

[0036] Figure 2 The image shows the results of grain size testing in an embodiment of the method of the present invention.

[0037] Figure 3 The image shows the results of a hardness test in an embodiment of the method of the present invention.

[0038] Figure 4 This is a graph showing the results of an elongation test in an embodiment of the method of the present invention. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] Please refer to Figure 1 The present invention provides a method for preparing a niobium rod with uniformly broken grains, comprising the following steps:

[0041] Step 1: Melt and cast the alloy raw materials to obtain an ingot, and preheat the ingot to improve its machinability, thus obtaining the first billet;

[0042] Step 2: Perform multiple axial forgings and a first heat treatment on the first billet to obtain the second billet;

[0043] Step 3: Perform surface treatment on the second billet to remove defects on the surface of the second billet, and then perform radial forging on the second billet to obtain the third billet;

[0044] Step 4: Oxidize the third billet to form an oxide film on its surface to protect it, and then roll the oxide film-coated third billet multiple times through a pass to obtain the first bar.

[0045] Step 5: Rotary forging and polishing the first bar to obtain the second bar;

[0046] Step 6: performing a second heat treatment on the second bar to obtain a finished bar.

[0047] Compared with the prior art, the present application has the following beneficial effects:

[0048] The preparation method of the grain-crushed uniform niobium bar provided by the present application first melts and casts an alloy raw material to obtain an ingot, and preheats the ingot to improve the cutting processing performance of the ingot, to obtain a first blank; then performs multiple axial forging on the first blank to fully crush the grains and performs a first heat treatment to eliminate micro-defects, to obtain a second blank; then performs surface treatment on the second blank to remove defects on the surface of the second blank, and performs radial forging on the second blank to improve the grain structure, to obtain a third blank; then performs oxidation treatment on the third blank to generate an oxide film on the surface of the third blank to protect the third blank, and performs multiple pass rolling on the third blank with the generated oxide film to change the direction of the grain structure, to obtain a first bar; then performs rotary forging on the first bar to make the grain structure dense and to polish, to obtain a second bar; finally performs a second heat treatment on the second bar to stabilize the size, to obtain a finished bar; through multiple axial forging + radial rotary forging + pass rolling rotary forging, the finished bar obtained has uniform and small grain structure, grain size GS = 7-9, elongation ≥40%, and hardness (HV / 2.9N) ≤60, which meets the demand for high processing rate of niobium bars in the manufacturing process of Nb3Sn superconducting wires.

[0049] In one embodiment, in order to eliminate bubbles, cracks and porosity formed during melting and casting of the alloy raw material and to fully crush the grains of the first blank, the step 2 is specifically:

[0050] A1: performing multiple axial upsetting and axial elongation on the first blank after the preheating treatment to fully crush the grains of the first blank, and rounding the first blank;

[0051] A2: placing the rounded first blank into a mixed acid solution for surface cleaning to remove surface impurities and oil stains;

[0052] A3: performing a first heat treatment on the first blank after the cleaning in the mixed acid solution in a vacuum environment of nitrogen, heating to 450-550℃ within 25-35 minutes, keeping warm for 25-35 minutes; heating to 750-850℃ within 25-35 minutes, keeping warm for 25-35 minutes; then heating to 900-1000℃ within 10-20 minutes, keeping warm for 95-105 minutes, and then cooling down and discharging, to eliminate bubbles, cracks and porosity and other micro-defects generated during melting and casting of the alloy raw material;

[0053] A4: the first blank after heat treatment is again subjected to axial upsetting and axial elongation to eliminate the voids generated in the grain crushing process in step A1, to make the grain distribution more uniform, and to round the second blank.

[0054] In an embodiment, step A1 is specifically: the first blank after preheating is subjected to first axial upsetting and axial elongation, the first blank is axially upset by 245-255 mm and axially elongated by 175-185 mm, then the first blank is subjected to second axial upsetting and axial elongation, the first blank is axially upset by 215-225 mm and axially elongated by 175-185 mm, and finally the first blank is rounded to obtain a first blank with a diameter error of 5 mm.

[0055] In an embodiment, after the grains are fully crushed, in order to improve the distribution of the grain structure and improve the cutting performance, step 3 is specifically:

[0056] B1: the surface of the second blank is turned, polished and cleaned to remove surface impurities and oil stains;

[0057] B2: the second blank after cleaning is subjected to radial forging, and the outer diameter is reduced by 5-8 mm to obtain a third blank.

[0058] In an embodiment, step 4 is specifically:

[0059] C1: the surface of the third blank is turned;

[0060] C2: the turned third blank is placed in an oxidation solution formed by mixing H2O and H2SO4 and is electrified for oxidation treatment, wherein the volume ratio of H2O to H2SO4 is (96-99): (1-3), so that an oxidation film with lubricating effect is formed on the surface of the third blank to prevent damage to the third blank during the process of hole type rolling;

[0061] C3: the third blank after oxidation treatment is subjected to multiple hole type rolling to reduce the risk of damage to the third blank, to obtain a first rod.

[0062] In an embodiment, in order to make the grain structure of the first rod obtained by hole type rolling dense, step 5 is specifically:

[0063] D1: the first rod is subjected to swaging processing to further crush the grain structure of the first rod and eliminate the voids between the grain structures of the first rod;

[0064] D2: the first rod after swaging processing is subjected to surface polishing treatment to obtain a second rod.

[0065] In one embodiment, in order to stabilize the size of the second rod, reduce deformation and crack tendency, the step 6 is specifically: placing the second rod into a vacuum environment of nitrogen for second heat treatment, heating to 450-550℃ within 25-35 minutes, holding for 110-130 minutes; then heating to 750-850℃ within 25-35 minutes, holding for 50-70 minutes; then heating to 800-1000℃ within 25-35 minutes, holding for 85-95 minutes, and then cooling, naturally cooling out of the furnace to obtain the finished rod.

[0066] In one embodiment, the preheating treatment in the step 1 is specifically: placing the ingot into a high-temperature environment of 400-550℃ for constant temperature for 90-180 minutes to obtain the second blank.

[0067] In one embodiment, the step 1 is specifically:

[0068] In order to improve the purity of the grain broken uniform niobium rod, the alloy raw material comprises the following elements: carbon 0.002-0.005 wt%, oxygen 0.01-0.03 wt%, nitrogen 0.003-0.005 wt%, hydrogen 0.0015-0.0018 wt%, iron 0.002-0.005 wt%, tantalum 0.1-0.3 wt%, silicon 0.002-0.005 wt%, nickel 0.005-0.007 wt%, molybdenum 0.003-0.005 wt%, tungsten 0.01-0.04 wt%, titanium 0.002-0.005 wt%, zirconium 0.02-0.04 wt%, hafnium 0.02-0.05 wt%, and the rest is niobium.

[0069] Another aspect of the present application provides a niobium rod prepared by the method of the previous aspect.

[0070] The preparation process of the grain broken uniform niobium rod with a diameter of Φ5-Φ17mm is shown by the following embodiment of the method of the present application.

[0071] Step 1:

[0072] (1) Melting: using EB smelting furnace to smelt alloy raw materials, wherein the alloy raw materials include the following elements: carbon 0.002-0.005 wt%, oxygen 0.01-0.03 wt%, nitrogen 0.003-0.005 wt%, hydrogen 0.0015-0.0018 wt%, iron 0.002-0.005 wt%, tantalum 0.1-0.3 wt%, silicon 0.002-0.005 wt%, nickel 0.005-0.007 wt%, molybdenum 0.003-0.005 wt%, tungsten 0.01-0.04 wt%, titanium 0.002-0.005 wt%, zirconium 0.02-0.04 wt%, hafnium 0.02-0.05 wt%, and the rest is niobium, and pouring into a φ190x1360-1380mm ingot;

[0073] (2) Sawing: sawing the φ190x1360-1380mm ingot into a φ190x420mm round ingot;

[0074] (3) Preheating treatment: heating to 400-550℃ in a box resistance furnace, and placing the round ingot into the box resistance furnace, and after constant temperature at 400-550℃ for 90-180min, a first blank is obtained;

[0075] Step 2:

[0076] A1: vertically placing the first blank after preheating treatment between the upper and lower anvils of a rapid forging machine to perform first axial upsetting and axial elongation on the first blank, first upsetting the first blank by 245-255mm, then elongating the first blank by 175-185mm between the two anvils, chamfering eight sides, then performing second axial upsetting and axial elongation on the first blank, upsetting by 215-225mm and elongating by 175-185mm, chamfering eight sides, and finally rounding to obtain a φ190-195mm second blank;

[0077] A2: placing the first blank after rounding into a mixed acid solution of HF, HCl and NHO3 to clean the surface and remove surface impurities and oil stains, and the staff observes the tantalum metal luster without impurities and stains, and the volume ratio of HF, HCl and NHO3 in the mixed acid solution is 1:2:3;

[0078] A3: placing the first blank after mixed acid cleaning into a vacuum degree ≤3.0x10 -3 Pa under the environment of filling nitrogen, performing first heat treatment, heating to 500℃ within 30min, holding for 30min; heating to 800℃ within 30min, holding for 30min; then heating to 950℃ within 15min, holding for 90min, and then cooling, stopping filling argon during the cooling process, and naturally cooling to ≤80℃ to discharge;

[0079] A4: After the first heat treatment, the first blank is placed vertically between the upper and lower anvils of the rapid forging machine at room temperature, the second blank is axially upset to 245-255 mm, axially elongated to 175-185 mm, chamfered and octagonal, and then rounded to φ 135-140 mm. Then the second blank is placed between the two half-round anvils and is rounded to φ 110-114 mm to obtain the second blank;

[0080] Step 3:

[0081] B1: The surface of the second blank is turned using a CW6163C lathe, with a turning amount of 2-2.5 mm. Then the surface of the turned second blank is polished using a grinding machine. Then the polished second blank is placed in the mixed acid solution of HF, HCl, and NHO3 in step A2 for surface cleaning to remove defects left on the surface of the second blank;

[0082] B2: The second blank after mixed acid cleaning is radially forged at room temperature using a precision forging machine, with a hammer head striking 450-550 times per minute, an outer diameter reduction of 5-8 mm, and a φ 38 mm second blank is obtained. Then the surface of the second blank is turned using a CW6163C lathe, with a single turning amount of 1-1.5 mm, a rotation speed of 720 rpm, and a feed amount of 0.8-1.0 mm, to obtain a φ 35.2 mm third blank;

[0083] Step 4:

[0084] C1: The third blank is placed in an oxidation solution formed by mixing H2O and H2SO4 and is electrified for oxidation treatment, with a volume ratio of H2O to H2SO4 of 99:1, a current of 10-30 A, and a voltage of 120-180 V, to form an oxide film on the surface of the fourth blank;

[0085] C2: The third blank after oxidation treatment is subjected to elliptical-round hole type rolling using a 2LG-10L flat-stand roller type rolling mill to obtain a φ 21.5-22.5 mm rod, and then subjected to elliptical-round hole type rolling using a 2LG-8L flat-stand roller type rolling mill to obtain a φ 13.5-14.5 mm first rod;

[0086] Step 5:

[0087] D1: The first rod is subjected to rotary forging using a DH7-4 rotary forging machine, with a pressing amount of 0.8-1.2 mm each time, to obtain a φ 11.80 mm second rod;

[0088] D2: using GB40 band sawing machine to cut the second bar, sawing down 2mm / min, sawing into the second bar with the length of 500-575mm, then using the outer circle polishing equipment to polish the surface of the second bar, polishing thickness 0.02-0.04mm, after polishing, the second bar with the diameter of 11.76-11.78mm is obtained;

[0089] Step 6:

[0090] Put the second bar into the vacuum degree ≤3.0×10 -3 Under the environment of filling nitrogen, the second heat treatment is carried out, the temperature is increased to 500℃ within 30min, the temperature is kept for 120min, then the temperature is increased to 800℃ within 30min, the temperature is kept for 60min, then the temperature is increased to 970℃ within 30min, the temperature is kept for 90min, then the temperature is decreased, the filling of argon is stopped in the process of decreasing, and the temperature is naturally cooled to ≤60℃, the finished bar is obtained;

[0091] Inspection: first, the inspector observes the surface of the finished bar (whether smooth, whether there is wrinkle, whether there is crack, whether there is inclusion), then the grain size of the finished bar is tested by using the metallographic instrument of "Olympus GX51f", then the hardness is tested by using the hardness tester, finally, the tensile strength and yield strength are tested by using the INSTRON4505 testing machine, in the process of testing, the non-proportional tensile sample with the gauge length of 25mm is selected, the elongation rate = ((the length after testing-the length before testing) / the length before testing)×100%;

[0092] The grain size test results are shown in Table 1. Figure 2 The grain structure of the finished bar is uniform and small, the grain size GS=7-8 grade (the difference ≤1.5 grade), the hardness test results are shown in Table 2. Figure 3 The hardness (HV / 2.9N) of the finished bar is ≤60, the elongation test results are shown in Table 3. Figure 4 The elongation rate of the finished bar is ≥40%.

[0093] Finally, the finished bar which needs to be packed and shipped is put into the mixed solution of HNO3, HF and H3PO4 for surface cleaning, the tantalum metal luster is observed and there is no impurity spot, the volume ratio of HNO3, HF and H3PO4 in the mixed solution is 1:1:1.

[0094] The above only discloses the preferred embodiments of the present application, of course, cannot limit the scope of the present application, the person skilled in the art can understand that the whole or part of the above-mentioned embodiments are implemented, and the equivalent changes made according to the claims of the present application still belong to the scope covered by the present application.

Claims

1. A method for producing a niobium rod having a uniform grain size, characterized by, The method comprises the following steps: Step 1: alloy raw materials are melted and cast to obtain ingots, and the ingots are preheated to improve the cutting performance of the ingots, thereby obtaining first blanks; Step 2: the first blanks are subjected to multiple axial forging and first heat treatment to obtain second blanks; Step 3: the second blanks are subjected to surface treatment to remove defects on the surface of the second blanks, and the second blanks are subjected to radial forging to obtain third blanks; Step 4: the third blanks are subjected to oxidation treatment to form an oxide film on the surface of the third blanks to protect the third blanks, and the third blanks with the oxide film are subjected to multiple pass rolling to obtain first rods; Step 5: the first rods are subjected to rotary forging and polishing to obtain second rods; Step 6: the second rods are subjected to second heat treatment to obtain finished rods; The step 2 specifically comprises: A1: the first blanks after preheating are subjected to multiple axial upsetting and axial elongation, and are rounded; A2: the first blanks after rounding are placed in a mixed acid solution for surface cleaning to remove surface impurities and oil stains; A3: the first blanks after cleaning in the mixed acid solution are subjected to first heat treatment in a vacuum environment of nitrogen, are heated to 450-550 DEG C within 25-35 minutes, are kept warm for 25-35 minutes, are then heated to 750-850 DEG C within 25-35 minutes, are kept warm for 25-35 minutes, are then heated to 900-1000 DEG C within 10-20 minutes, are kept warm for 95-105 minutes, and are then cooled and discharged naturally; A4: the first blanks after heat treatment are subjected to axial upsetting and axial elongation again, and are rounded to obtain second blanks; The step 3 specifically comprises: B1: the surface of the second blanks is subjected to turning, polishing and cleaning; B2: the second blanks after cleaning are subjected to radial forging, and the outer diameter is reduced by 5-8 mm to obtain third blanks; The step 5 specifically comprises: D1: the first rods are subjected to rotary forging; D2: the first rods after rotary forging are subjected to surface polishing to obtain second rods; The step 6 specifically comprises: the second rods are placed in a vacuum environment of nitrogen and subjected to second heat treatment, are heated to 450-550 DEG C within 25-35 minutes, are kept warm for 110-130 minutes, are then heated to 750-850 DEG C within 25-35 minutes, are kept warm for 50-70 minutes, are then heated to 800-1000 DEG C within 25-35 minutes, are kept warm for 85-95 minutes, and are then cooled and discharged naturally to obtain finished rods; In the step 1, The alloy raw materials comprise the following elements: carbon 0.002-0.005 wt%, oxygen 0.01-0.03 wt%, nitrogen 0.003-0.005 wt%, hydrogen 0.0015-0.0018 wt%, iron 0.002-0.005 wt%, tantalum 0.1-0.3 wt%, silicon 0.002-0.005 wt%, nickel 0.005-0.007 wt%, molybdenum 0.003-0.005 wt%, tungsten 0.01-0.04 wt%, titanium 0.002-0.005 wt%, zirconium 0.02-0.04 wt%, hafnium 0.02-0.05 wt%, and the rest is niobium.

2. The method of claim 1, wherein the method is characterized by: The step A1 is specifically: the first blank after preheating is subjected to first axial upsetting and axial elongation, the first blank is upset by 245-255mm and elongated by 175-185mm, then the first blank is subjected to second axial upsetting and axial elongation, the first blank is upset by 215-225mm and elongated by 75-185mm, and finally the first blank is circularized to obtain the first blank with a diameter error of 5mm.

3. The method of claim 1 or 2, wherein the method is characterized by: The step 4 is specifically: C1: turning the surface of the third blank; C2: the turned third blank is put into an oxidizing solution formed by mixing H2O and H2SO4 and subjected to electrolysis to perform oxidation treatment, wherein the volume ratio of H2O and H2SO4 is (96-99):(1-3), so that an oxide film is formed on the surface of the third blank; C3: the third blank after oxidation treatment is subjected to multiple pass rolling to obtain the first rod.

4. The method of claim 1 to 3, wherein The preheating in the step 1 is specifically: the ingot is put into a high-temperature environment of 400-550℃ and kept at a constant temperature for 90-180min to obtain the second blank. 5.A niobium rod prepared by the preparation method of the grain-crushed uniform niobium rod according to any one of claims 1 to 4.

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