A method for producing a thin-walled molybdenum alloy tube

Abstract

The application provides a preparation method of a thin-walled molybdenum alloy pipe, which comprises five steps of designing a drawing pass, preparing a molybdenum alloy pipe blank, pipe blank necking, drawing and post-drawing treatment. The application adopts a ring-shaped heat conduction device to preheat a drawing die, lengthens a heating work belt in the drawing process, makes the molybdenum alloy pipe more uniformly heated, and realizes constant temperature control. In combination with reasonable processing pass design, the size of the molybdenum alloy pipe, especially the wall thickness, can be precisely controlled, and the pipe yield is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of molybdenum metal products, and relates to a molybdenum alloy pipe, in particular to a preparation method of a thin-wall molybdenum alloy pipe. BACKGROUND

[0002] With the development of industrial heating furnaces in the direction of large-scale and precise temperature measurement, higher requirements are put forward for the specifications and properties of the molybdenum alloy sleeve for thermocouples. However, due to the intrinsic defects of molybdenum alloy, such as large room temperature brittleness, low strength, poor ductility and insufficient creep resistance, the processing of the molybdenum alloy is difficult, the wall thickness of the pipe is difficult to accurately control, and the pipe yield is low. SUMMARY

[0003] In view of the problems in the prior art, the purpose of the present application is to provide a preparation method of a thin-wall molybdenum alloy pipe, which solves the technical problem that the yield of the thin-wall molybdenum alloy pipe needs to be improved due to the difficulty in accurately controlling the wall thickness of the molybdenum alloy pipe in the prior art.

[0004] In order to solve the above technical problems, the present application adopts the following technical solutions:

[0005] A preparation method of a thin-wall molybdenum alloy pipe, which adopts a ring-shaped heat conduction device to preheat the drawing die; the ring-shaped heat conduction device comprises a small heating ring arranged on one side of the drawing die and a large heating ring arranged on the other side of the drawing die, a stainless steel pressing plate is fixedly arranged on one side of the small heating ring, and a stainless steel pressing plate is fixedly arranged on the other side of the large heating ring; a terminal post and a temperature sensor are arranged on the small heating ring and the large heating ring.

[0006] The method specifically comprises the following steps:

[0007] Step 1: design the drawing pass

[0008] According to the design size of the molybdenum alloy pipe blank and the thin-wall molybdenum alloy pipe, the drawing requirement is determined; the drawing pass is designed according to the drawing requirement, and the drawing die and the short core are selected.

[0009] Step 2: prepare the molybdenum alloy pipe blank.

[0010] Step 3: pipe blank necking

[0011] The inner sleeve is arranged coaxially in the molybdenum alloy pipe blank in step 1, the outer sleeve is arranged coaxially outside the molybdenum alloy pipe blank, the molybdenum alloy pipe blank is heated and necked.

[0012] Step 4: drawing

[0013] Step 4.1: install the ring-shaped heat conduction device

[0014] Assemble the large heating ring and the small heating ring on both sides of the first-pass drawing die of the center heating furnace, and then install the stainless steel pressing plates on both sides of the large heating ring and the small heating ring; and install the first-pass short core on the drawing rod.

[0015] Step 4.2, lubrication of the pipe blank:

[0016] Soak the molybdenum alloy pipe blank in the ultrasonic cleaning tank containing the lubricating liquid to ensure that the inner and outer walls of the pipe are fully lubricated, and then drain and cover the core rod.

[0017] Step 4.3, first-pass drawing:

[0018] Preheat the first-pass drawing die to 100-220℃ by using the annular heat conduction device; preheat the molybdenum alloy pipe blank to 100-220℃; after the preheating of the drawing die and the molybdenum alloy pipe blank is completed, perform the first-pass drawing at a speed of 10-15m / min, and obtain the first-pass drawn pipe material after the first-pass drawing is completed.

[0019] Step 4.4, second-pass drawing:

[0020] Replace the first-pass drawing die with the second-pass drawing die; replace the first-pass short core with the second-pass short core; then preheat the second-pass drawing die to 100-220℃ by using the annular heat conduction device; preheat the first-pass drawn pipe material to 100-220℃; after the preheating of the drawing die and the pipe material is completed, perform the second-pass drawing at a speed of 10-15m / min, and obtain the second-pass drawn pipe material after the second-pass drawing is completed.

[0021] Step 4.5, stress relief annealing.

[0022] Step 4.6, third-pass drawing:

[0023] Replace the second-pass drawing die with the third-pass drawing die; replace the second-pass short core with the third-pass short core; then preheat the third-pass drawing die to 100-220℃ by using the annular heat conduction device; preheat the third-pass drawn pipe material to 100-220℃; after the preheating of the drawing die and the pipe material is completed, perform the third-pass drawing at a speed of 10-15m / min, and obtain the third-pass drawn pipe material after the third-pass drawing is completed.

[0024] Step five, post-drawing treatment:

[0025] After the drawing process of step four is completed, straighten, finish and acid-alkali wash the pipe material to obtain the thin-walled molybdenum alloy pipe material.

[0026] The present application also has the following technical features:

[0027] Specifically and optionally, step four further comprises the following steps:

[0028] Step 4.7, four-pass drawing:

[0029] The three-pass drawing die is replaced by a four-pass drawing die; the three-pass short core is replaced by a four-pass short core head, and then the four-pass drawing die is preheated to 120-180℃ by using a ring-shaped heat conduction device; the four-pass drawing pipe is preheated to 120-180℃; after the preheating of the drawing die and the pipe is completed, four-pass drawing is performed at a speed of 12-15 m / min, and a four-pass drawn pipe is obtained after the four-pass drawing is completed.

[0030] Step 4.8, stress relief annealing.

[0031] Step 4.9, five-pass drawing:

[0032] The four-pass drawing die is replaced by a five-pass drawing die; the four-pass short core is replaced by a five-pass short core head; then the five-pass drawing die is preheated to 120-180℃ by using a ring-shaped heat conduction device; the five-pass drawing pipe is preheated to 120-180℃; after the preheating of the drawing die and the pipe is completed, five-pass drawing is performed at a speed of 12-15 m / min, and a five-pass drawn pipe is obtained after the five-pass drawing is completed.

[0033] Specifically, the wall thickness of the thin-walled molybdenum alloy pipe is (0.3-0.8) ± 0.05 mm, and the outer diameter is (6-9.5) ± 0.05 mm.

[0034] Specifically, in step two, the outer diameter of the molybdenum alloy pipe blank is 9.5-12 mm, the wall thickness of the molybdenum alloy pipe blank is 0.5-1.0 mm, and the length of the molybdenum alloy pipe blank is 1000 mm.

[0035] Specifically, in step three, the heating temperature of the molybdenum alloy pipe blank is 500-700℃, and the heating time is 1-5 min.

[0036] Specifically, in step 4.1, the inner diameter of the first-pass drawing die is 8-11 mm, and the outer diameter of the first-pass short core head is 6.76-9 mm; in step 4.4, the inner diameter of the second-pass drawing die is 7-10 mm, and the outer diameter of the second-pass short core head is 5.76-8.5 mm; in step 4.6, the inner diameter of the third-pass drawing die is 6.0-9.5 mm, and the outer diameter of the third-pass short core head is 4.76-7.9 mm.

[0037] Specifically, step 4.5 specifically refers to: using a hydrogen protective atmosphere, stress relief annealing the second-pass drawn pipe at 800-1000℃ for 1-3 h.

[0038] Specifically, in step 4.7, the inner diameter of the four-pass drawing die is 5.0 mm.

[0039] Specifically, step 4.8 involves: using a hydrogen protective atmosphere to perform stress-relief annealing on the second-pass drawn tube at 800–1000°C for 1–3 hours.

[0040] Specifically, in step 4.9, the inner diameter of the five-pass drawing die is 4.76 mm.

[0041] Compared with the prior art, the present invention has the following technical effects:

[0042] (I) The method for preparing thin-walled molybdenum alloy tubes of the present invention uses an annular heat-conducting device to preheat the drawing die, which lengthens the heating working zone during the drawing process, making the molybdenum alloy tubes heat more uniformly and achieving constant temperature control. With the reasonable design of processing passes, the dimensions of the molybdenum alloy tubes, especially the wall thickness, can be precisely controlled, thereby improving the tube yield.

[0043] (II) The method for preparing thin-walled molybdenum alloy tubing of the present invention uses an annular heat-conducting device to preheat the drawing die, which can also effectively avoid material deformation caused by the temperature difference between the inside and outside of the die, resulting in large deviations in the drawing test data.

[0044] (II) The thin-walled molybdenum alloy tube prepared by the present invention can have a minimum wall thickness of 0.3±0.05mm, which can be used in high-precision temperature control equipment. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the overall structure of the annular heat-conducting device.

[0046] Figure 2 This is a schematic diagram of the small heating coil.

[0047] Figure 3 This is a cross-sectional view of the small heating coil.

[0048] Figure 4 This is a schematic diagram of the large heating coil.

[0049] Figure 5 This is a cross-sectional view of the large heating coil.

[0050] The meanings of the labels and symbols in the figure are as follows: 1-drawing die, 2-small heating coil, 3-large heating coil, 4-stainless steel pressure plate, 5-terminal, 6-temperature sensor.

[0051] The specific content of the present invention will be further explained in detail below with reference to the embodiments. Detailed Implementation

[0052] It should be noted that all the instruments, molds and reagents in the present application, if not specially stated, adopt the instruments, molds and reagents known in the prior art, for example:

[0053] The drawing die 1 adopts a conventional drawing die known in the prior art, for example, a drawing die made of TG8 carbon tool steel, die casting tool steel and 3W2Cr8V.

[0054] The temperature sensor 6 adopts a conventional infrared temperature sensor known in the prior art.

[0055] The lubricating liquid adopts a conventional lubricating liquid known in the prior art.

[0056] In accordance with the above technical solution, the specific embodiments of the present application are given below, and it should be noted that the present application is not limited to the following specific embodiments, and any equivalent transformation made on the basis of the technical solution of the present application falls within the protection scope of the present application.

[0057] Example 1:

[0058] This embodiment gives a ring-shaped heat conduction device, as shown in Figures 1 to 5 The small heating ring 2 is arranged on one side of the drawing die 1, and the large heating ring 3 is arranged on the other side of the drawing die 1; a stainless steel pressing plate 4 is fixedly arranged on one side of the small heating ring 2, and a stainless steel pressing plate 4 is fixedly arranged on the other side of the large heating ring 3; a terminal post 5 and a temperature sensor 6 are arranged on the small heating ring 2 and the large heating ring 3.

[0059] In this embodiment, the inside of the small heating ring 2 and the large heating ring 3 is a nickel-chromium alloy heating wire, which has the characteristics of high strength under high temperature conditions, material not brittle after high temperature cooling, no magnetism and corrosion resistance; the nickel-chromium alloy heating wire is processed into a ring after insulation treatment, which can effectively increase the stability of the heating system and reduce the use cost.

[0060] In this embodiment, the outside of the small heating ring 2 and the large heating ring 3 is poured into a ring shape by H62 brass, which has good mechanical properties, good shaping, and good electrical conductivity and corrosion resistance, which can further increase the heat conduction efficiency.

[0061] In this embodiment, the thickness of the stainless steel pressing plate 4 is about 2mm, which is used to fix the small heating ring 2 and the large heating ring 3.

[0062] In this embodiment, the terminal post 5 is used to connect the power supply for the nickel-chromium alloy heating wire of the heating ring.

[0063] In this embodiment, the temperature sensor 6 is a known contact thermocouple temperature sensor 6. The principle of this temperature sensor 6 is to connect one end of two metals of different materials. When one end of the thermocouple is heated, a potential difference exists in the thermocouple circuit, which can then be used to calculate the temperature. This temperature sensor 6 can accurately detect the real-time temperature and, in conjunction with a temperature controller, adjust the voltage to control the current, thereby achieving temperature regulation of the heating wire and keeping the heating temperature of the nickel-chromium alloy heating wire below 800°C in real time.

[0064] As an optional solution in this embodiment, a guide tube (not shown in the figure) is also provided on the other side of the axial direction of the large heating coil 3. The guide tube is shaped like a horn and is detachably installed in the elongated slot of the back plate (not shown in the figure) by bolts.

[0065] In this embodiment, the guide tube guides the tube as it enters the working zone of the drawing die 1. When installing the guide tube, its position within the elongated slot needs to be adjusted to ensure it is directly aligned with the tube. This guide tube replaces the traditional method of manually clamping and preheating the tube before placing it into the biting opening of the drawing die 1, achieving automated continuous feeding, effectively improving work efficiency and reducing tube temperature drop.

[0066] Example 2:

[0067] This embodiment provides a method for preparing thin-walled molybdenum alloy tubing. The method uses the annular heat-conducting device from Embodiment 1 to preheat the drawing die. The method specifically includes the following steps:

[0068] Step 1, Design the pulling sequence:

[0069] In this embodiment, the outer diameter of the molybdenum alloy tube blank is 9.5 mm, the wall thickness is 0.5 mm, and the length is 1000 mm. The design dimensions of the thin-walled molybdenum alloy tube are: outer diameter 8.0 mm and wall thickness 0.3 mm. The outer diameter and wall thickness of the thin-walled molybdenum alloy tube are different from those of the molybdenum alloy tube blank, i.e., the drawing requirement is to reduce the diameter and wall thickness. Based on the drawing requirements, a three-stage drawing process was designed, and the first-stage drawing die and short mandrel, the second-stage drawing die and short mandrel, and the third-stage drawing die and short mandrel were selected.

[0070] Equation I is used to calculate the thermal expansion of the drawing die and the short mandrel, and the drawing process is adjusted based on the thermal expansion results; Equation I is as follows:

[0071] λ=α*ℓ0*(t-t0) Formula I.

[0072] In the formula:

[0073] λ represents the thermal expansion of the drawing die and the short mandrel.

[0074] a represents the linear expansion coefficient of the drawing die and the short core head, in mm / mm.

[0075] l0 represents the size length of the drawing die and the short core head, in mm.

[0076] t represents the heating temperature of the drawing die and the short core head, in ℃.

[0077] t0 represents the initial temperature of the drawing die and the short core head, in ℃; t-t0 is the temperature rise difference.

[0078] In this embodiment, the linear expansion coefficients of the first-pass drawing die and the short core head, the second-pass drawing die and the short core head, and the third-pass drawing die and the short core head are 14.7*10-6 (200 ℃), 15.6*10-6 (300 ℃) and 16.3*10-6 (400 ℃) respectively. -6 -6 -6 After calculation, it is obtained that the thermal expansion of the drawing die is 0.22-0.26 mm and the thermal expansion of the short core head is 0.02-0.025 mm under the temperature rise difference of 200 ℃. According to actual requirements, the processing route and the die material can be adjusted according to the above calculation results, and the wall thickness control pass can be reasonably designed according to the theoretical deformation amount combined with the influence of the thermal expansion of the drawing die and the fixed short core head, so as to realize the precise control of the wall thickness pass processing of the pipe.

[0079] Step two, prepare the molybdenum alloy pipe blank:

[0080] Check whether the molybdenum alloy pipe blank has a leak point by water pressure test, and check the uniformity of the outer diameter and wall thickness at three different positions by caliper, and visually check whether there is a defect in the appearance.

[0081] Step three, pipe blank necking:

[0082] An inner sleeve is coaxially arranged in the molybdenum alloy pipe blank in step one, the outer diameter of the inner sleeve is 8.0 mm, the wall thickness of the inner sleeve is 1.0 mm, and the length of the inner sleeve is 40 mm; an outer sleeve is coaxially arranged outside the molybdenum alloy pipe blank, the outer diameter of the outer sleeve is 10.0 mm, the wall thickness of the outer sleeve is 1.0 mm, and the length of the outer sleeve is 50 mm; the materials of the inner sleeve and the outer sleeve are both stainless steel; the molybdenum alloy pipe blank is heated to 600 ℃, the heating time is 3 min, and the necking is performed twice on the necking machine for standby.

[0083] Step four, perform drawing:

[0084] Step 4.1, install the annular heat conduction device:

[0085] ​​The large heating ring 3 and the small heating ring 2 are assembled on both sides of the first-pass drawing die located in the central heating furnace. The inner diameter of the first-pass drawing die is 9.0 mm. Then, stainless steel pressure plates 4 are installed on both sides of the large heating ring 3 and the small heating ring 2. The first-pass short mandrel is installed on the tie rod. The outer diameter of the first-pass short mandrel is 8.0 mm.

[0086] Step 4.2, Lubrication of the tube blank:

[0087] The molybdenum alloy tube blank is immersed in an ultrasonic cleaning tank containing lubricating fluid to ensure that the inner and outer walls of the tube are fully lubricated. After draining, the core rod is manually inserted.

[0088] Step 4.3, First pull-out:

[0089] The first-pass drawing die is preheated to 200–220°C using a ring-shaped heat-conducting device for 30–120 seconds. The molybdenum alloy tube blank is preheated to 200–220°C using a resistance wire heating furnace or a gas furnace for 30–120 seconds. After the drawing die and the molybdenum alloy tube blank are preheated, the first-pass drawing is performed at a speed of 10–12 m / min. The first-pass drawn tube is then obtained.

[0090] Step 4.4, Second-pass drawing:

[0091] The first-pass drawing die is replaced with a second-pass drawing die, with an inner diameter of 8.5 mm. The first-pass short mandrel is replaced with a second-pass short mandrel, with an outer diameter of 7.6 mm. Then, the second-pass drawing die is preheated to 200–220°C using an annular heat-conducting device for 30–120 seconds. The first-pass drawn tube is preheated to 200–220°C using a resistance wire heating furnace or a gas furnace for 30–120 seconds. After the drawing die and tube are preheated, the second-pass drawing is performed at a speed of 10–12 m / min. The second-pass drawn tube is obtained after the second-pass drawing is completed.

[0092] Step 4.5, Stress-relief annealing:

[0093] A hydrogen protective atmosphere is used, with a hydrogen pressure of 4.8–5.2 MPa and a hydrogen flow rate of 0.2–0.5 m³ / s. 3 / h, stress-relief annealing of the second-pass drawn tubes is carried out at 900℃ for 1h.

[0094] Step 4.6, three-stage pulling:

[0095] The second-pass drawing die is replaced by a third-pass drawing die, the inner diameter of the third-pass drawing die is 8.0 mm; the second-pass short core is replaced by a third-pass short core head, the outer diameter of the third-pass short core head is 7.2 mm; then the third-pass drawing die is preheated to 200-220 ℃ by using the annular heat conduction device, the preheating time is 30-120 s; the third-pass drawing pipe is preheated to 200-220 ℃ by using the resistance wire heating furnace or the gas furnace, the preheating time is 30-120 s; after the preheating of the drawing die and the pipe is completed, the third-pass drawing is carried out, the third-pass drawing speed is 10-12 m / min, and the third-pass drawing pipe is prepared after the third-pass drawing is completed.

[0096] Step five, drawing post-processing:

[0097] After the drawing process of step four is completed, the pipe is straightened, finished and washed with acid and alkali to prepare the thin-walled molybdenum alloy pipe.

[0098] In this embodiment, after each drawing is completed, the size of the pipe is measured by using a caliper, and the results are as follows: the wall thickness of the first-pass drawing pipe is 0.38±0.05 mm, and the outer diameter is 9.0±0.05 mm; the wall thickness of the second-pass drawing pipe is 0.33±0.05 mm, and the outer diameter is 8.5±0.05 mm; the wall thickness of the third-pass drawing pipe is 0.3±0.05 mm, and the outer diameter is 8±0.05 mm.

[0099] Effect verification of example 2:

[0100] In this embodiment, the finally prepared thin-walled molybdenum alloy pipe has a wall thickness of 0.3±0.05 mm, an outer diameter of 8±0.05 mm, an outer diameter cumulative deformation of 16.5%, a wall thickness cumulative deformation of 49.17%, a straightness of 0.5 mm / 1000 mm, an outer surface roughness of 0.4 microns and an inner surface roughness of 0.6 microns. From the above results, it can be seen that the actual size of the thin-walled molybdenum alloy pipe meets the design size.

[0101] Example 3:

[0102] This embodiment gives a method for preparing a thin-walled molybdenum alloy pipe, which preheats the drawing die by using the annular heat conduction device in example 1, and the method specifically includes the following steps:

[0103] Step one, design the drawing pass:

[0104] In the embodiment, the design size of the thin-walled molybdenum alloy pipe is: the outer diameter is 6.0 mm, and the wall thickness is 0.5 mm. The design wall thickness of the thin-walled molybdenum alloy pipe is the same as the wall thickness of the molybdenum alloy pipe blank, and the design outer diameter is smaller than the outer diameter of the molybdenum alloy pipe blank, that is, the drawing requirement is to reduce the diameter without reducing the wall; three drawing passes are designed according to the drawing requirement, and the first drawing die and the short core, the second drawing die and the short core, and the third drawing die and the short core are selected.

[0105] Step two, prepare the molybdenum alloy pipe blank:

[0106] In the embodiment, step two is exactly the same as step two of embodiment 2.

[0107] Step three, pipe blank necking:

[0108] In the embodiment, step three is exactly the same as step three of embodiment 2.

[0109] Step four, drawing:

[0110] Step 4.1, install the annular heat conduction device:

[0111] The large heating ring 3 and the small heating ring 2 are assembled on both sides of the first drawing die of the center heating furnace, the inner diameter of the first drawing die is 8.0 mm, and then the stainless steel pressing plate 4 is installed on both sides of the large heating ring 3 and the small heating ring 2; the first short core is installed on the draw bar, and the outer diameter of the first short core is 6.76 mm.

[0112] Step 4.2, lubrication of the pipe blank:

[0113] In the embodiment, step 4.2 is exactly the same as step 4.2 of embodiment 2.

[0114] Step 4.3, first drawing:

[0115] The annular heat conduction device is used to preheat the first drawing die to 120-160℃, and the preheating time is 30-120s; the resistance wire heating furnace or gas furnace is used to preheat the molybdenum alloy pipe blank to 120-160℃, and the preheating time is 30-120s; after the preheating of the drawing die and the molybdenum alloy pipe blank is completed, the first drawing is carried out, the first drawing speed is 12-15 m / min, and the first drawing pipe is obtained after the first drawing is completed.

[0116] Step 4.4, second drawing:

[0117] The first pass drawing die is replaced by the second pass drawing die, and the inner diameter of the second pass drawing die is 7.0 mm; the first pass short core is replaced by the second pass short core, and the outer diameter of the second pass short core is 5.76 mm. Then the second pass drawing die is preheated to 120-160°C by using the annular heat conduction device, and the preheating time is 30-120 s; the first pass drawing pipe is preheated to 120-160°C by using the resistance wire heating furnace or gas furnace, and the preheating time is 30-120 s; after the preheating of the drawing die and the pipe is completed, the second pass drawing is carried out, and the second pass drawing speed is 12-15 m / min, and the second pass drawing pipe is obtained after the second pass drawing is completed.

[0118] Step 4.5, stress relief annealing:

[0119] In this embodiment, step 4.5 is exactly the same as step 4.5 of embodiment 2.

[0120] Step 4.6, three-pass drawing:

[0121] The second pass drawing die is replaced by the third pass drawing die, and the inner diameter of the third pass drawing die is 6.0 mm; the second pass short core is replaced by the third pass short core, and the outer diameter of the third pass short core is 4.76 mm. Then the third pass drawing die is preheated to 120-160°C by using the annular heat conduction device, and the preheating time is 30-120 s; the third pass drawing pipe is preheated to 120-160°C by using the resistance wire heating furnace or gas furnace, and the preheating time is 30-120 s; after the preheating of the drawing die and the pipe is completed, the third pass drawing is carried out, and the third pass drawing speed is 12-15 m / min, and the third pass drawing pipe is obtained after the third pass drawing is completed.

[0122] Step five, post-drawing treatment:

[0123] In this embodiment, step five is exactly the same as step five of embodiment 2.

[0124] In this embodiment, the size of the pipe is measured by using the caliper after each drawing is completed. The wall thickness of the first pass drawing pipe is 0.5±0.05 mm, and the outer diameter is 8.0±0.05 mm; the wall thickness of the second pass drawing pipe is 0.5±0.05 mm, and the outer diameter is 7.0±0.05 mm; the wall thickness of the third pass drawing pipe is 0.5±0.05 mm, and the outer diameter is 6.0±0.05 mm.

[0125] Effect verification of embodiment 3:

[0126] In the embodiment, the wall thickness of the thin-walled molybdenum alloy pipe finally prepared is 0.5±0.05 mm, the outer diameter is 6±0.05 mm, the straightness is 0.5 mm / 1000 mm, the outer surface roughness is 0.4 microns, and the inner surface roughness is 0.8 microns. It can be known from the above results that the actual size of the thin-walled molybdenum alloy pipe conforms to the design size.

[0127] Embodiment 4:

[0128] The embodiment provides a preparation method of a thin-walled molybdenum alloy pipe. The method adopts the annular heat conduction device in the embodiment 1 to preheat the drawing die. The method specifically comprises the following steps:

[0129] Step 1: design the drawing pass

[0130] In the embodiment, the design size of the thin-walled molybdenum alloy pipe is that the outer diameter is 4.76 mm and the wall thickness is 0.5 mm. The design outer diameter of the thin-walled molybdenum alloy pipe is small, that is, the drawing requirement is a thin-diameter pipe. Five drawing passes are designed according to the drawing requirement, and the first-pass drawing die and short core, the second-pass drawing die and short core, the third-pass drawing die and short core, the fourth-pass drawing die and short core and the fifth-pass drawing die and short core are selected.

[0131] Step 2: prepare the molybdenum pipe blank

[0132] In the embodiment, step 2 is completely same as step 2 in the embodiment 3.

[0133] Step 3: neck the pipe blank

[0134] In the embodiment, step 3 is completely same as step 3 in the embodiment 3.

[0135] Step 4: perform drawing

[0136] In the embodiment, steps 4.1 to 4.6 are completely same as 4.1 to 4.6 in the embodiment 3.

[0137] Step 4.7: fourth-pass drawing

[0138] The third-pass drawing die is replaced by the fourth-pass drawing die, and the inner diameter of the fourth-pass drawing die is 5.0 mm. The third-pass short core is removed, and then the annular heat conduction device is used to preheat the fourth-pass drawing die to 120-160 ℃, and the preheating time is 30-120 s. The resistance wire heating furnace or gas furnace is used to preheat the fourth-pass drawing pipe to 120-160 ℃, and the preheating time is 30-120 s. After the preheating of the drawing die and the pipe is completed, the fourth-pass drawing (empty drawing) is performed, the fourth-pass drawing speed is 12-15 m / min, and the fourth-pass drawing pipe is prepared after the fourth-pass drawing is completed.

[0139] Step 4.8, stress relief annealing:

[0140] The four-pass drawn tube is subjected to stress relief annealing at 900℃ for 1h under a hydrogen atmosphere with a hydrogen pressure of 4.8-5.2Mpa and a hydrogen flow rate of 0.2-0.5m 3

[0141] Step 4.9, five-pass drawing:

[0142] The four-pass drawing die is replaced by a five-pass drawing die with an inner diameter of 4.76mm, and the five-pass drawing die is preheated to 120-160℃ for 30-120s using a ring-shaped heat conduction device, and the five-pass drawn tube is preheated to 120-160℃ for 30-120s using an electric resistance wire heating furnace or a gas furnace. After the preheating of the drawing die and the tube is completed, five-pass drawing (empty drawing) is performed at a speed of 12-15m / min, and a five-pass drawn tube is obtained after the five-pass drawing is completed.

[0143] Step five, post-drawing treatment:

[0144] In this embodiment, step five is identical to step five of embodiment 3.

[0145] In this embodiment, the size of the tube is measured after each drawing using a caliper. The wall thickness of the first-pass drawn tube is 0.5±0.05mm, and the outer diameter is 8.0±0.05mm; the wall thickness of the second-pass drawn tube is 0.5±0.05mm, and the outer diameter is 7.0±0.05mm; the wall thickness of the third-pass drawn tube is 0.5±0.05mm, and the outer diameter is 6.0±0.05mm; the wall thickness of the fourth-pass drawn tube is 0.5±0.05mm, and the outer diameter is 5.0±0.05mm; and the wall thickness of the fifth-pass drawn tube is 0.5±0.05mm, and the outer diameter is 4.76±0.05mm.

[0146] Effect verification of embodiment 4:

[0147] In this embodiment, the final thin-walled molybdenum alloy tube has a wall thickness of 0.5±0.05mm and an outer diameter of 4.76±0.05mm. From the above results, it can be seen that the actual size of the thin-walled molybdenum alloy tube conforms to the design size.

[0148] Embodiment 5:

[0149] This embodiment provides a method for preparing a thin-walled molybdenum alloy tube, which uses the ring-shaped heat conduction device in embodiment 1 to preheat the drawing die. The method specifically comprises the following steps:

[0150] Step one, design the drawing passes:​

[0151] In the embodiment, the outer diameter of the molybdenum alloy tube blank is 12 mm, the wall thickness of the molybdenum alloy tube blank is 1.0 mm, and the length of the molybdenum alloy tube blank is 1000 mm. The design size of the thin-walled molybdenum alloy tube is: the outer diameter is 9.5 mm, and the wall thickness is 0.8 mm. The design wall thickness and the design outer diameter of the thin-walled molybdenum alloy tube are smaller than the wall thickness and the outer diameter of the molybdenum alloy tube blank, and the design outer diameter is larger, that is, the drawing requirement is to reduce the diameter and wall thickness of the thick tube. Three drawing passes are designed according to the drawing requirement, and the first drawing die and the short core, the second drawing die and the short core, and the third drawing die and the short core are selected.

[0152] Step two, prepare the molybdenum alloy tube blank:

[0153] In the embodiment, step two is exactly the same as step two of embodiment 2.

[0154] Step three, tube blank necking:

[0155] In the embodiment, step three is exactly the same as step three of embodiment 2.

[0156] Step 4.1, install the annular heat conduction device:

[0157] The large heating ring 3 and the small heating ring 2 are assembled on both sides of the first drawing die of the center heating furnace, the inner diameter of the first drawing die is 11 mm, and then the stainless steel pressing plate 4 is installed on both sides of the large heating ring 3 and the small heating ring 2; the first short core is installed on the pull rod, and the outer diameter of the first short core is 9.0 mm.

[0158] Step 4.2, lubrication of the tube blank:

[0159] In the embodiment, step 4.2 is exactly the same as step 4.2 of embodiment 2.

[0160] Step 4.3, first drawing:

[0161] The annular heat conduction device is used to preheat the first drawing die to 140-180℃, and the preheating time is 30-120s; the resistance wire heating furnace or gas furnace is used to preheat the molybdenum alloy tube blank to 140-180℃, and the preheating time is 30-120s; after the preheating of the drawing die and the molybdenum alloy tube blank is completed, the first drawing is carried out, the first drawing speed is 10-12m / min, and the first drawing tube is prepared after the first drawing is completed.

[0162] Step 4.4, second drawing:

[0163] The first-pass drawing die is replaced by a second-pass drawing die, the inner diameter of the second-pass drawing die is 10 mm; the first-pass short core is replaced by a second-pass short core, the outer diameter of the second-pass short core is 8.4 mm; then the second-pass drawing die is preheated to 140-180 DEG C by using a ring-shaped heat conduction device, the preheating time is 30-120 s; the first-pass drawing pipe is preheated to 140-180 DEG C by using a resistance wire heating furnace or a gas furnace, the preheating time is 30-120 s; after the preheating of the drawing die and the pipe is completed, the second-pass drawing is carried out, the second-pass drawing speed is 10-12 m / min, and the second-pass drawing pipe is obtained after the second-pass drawing is completed.

[0164] Step 4.5, stress relief annealing:

[0165] In this embodiment, step 4.5 is completely same as step 4.5 of embodiment 2.

[0166] Step 4.6, three-pass drawing:

[0167] The second-pass drawing die is replaced by a third-pass drawing die, the inner diameter of the third-pass drawing die is 9.5 mm; the second-pass short core is replaced by a third-pass short core, the outer diameter of the third-pass short core is 7.9 mm; then the third-pass drawing die is preheated to 140-180 DEG C by using a ring-shaped heat conduction device, the preheating time is 30-120 s; the third-pass drawing pipe is preheated to 140-180 DEG C by using a resistance wire heating furnace or a gas furnace, the preheating time is 30-120 s; after the preheating of the drawing die and the pipe is completed, the third-pass drawing is carried out, the third-pass drawing speed is 10-12 m / min, and the third-pass drawing pipe is obtained after the third-pass drawing is completed.

[0168] Step five, post-drawing treatment:

[0169] In this embodiment, step five is completely same as step five of embodiment 2.

[0170] In this embodiment, after each drawing is completed, the size of the pipe is measured by using a caliper, and the results are as follows: the wall thickness of the first-pass drawing pipe is 1.0±0.05 mm, and the outer diameter is 11±0.05 mm; the wall thickness of the second-pass drawing pipe is 0.8±0.05 mm, and the outer diameter is 10±0.05 mm; the wall thickness of the third-pass drawing pipe is 0.8±0.05 mm, and the outer diameter is 9.5±0.05 mm.

[0171] Effect verification of embodiment 5:

[0172] In this embodiment, the wall thickness of the finally obtained thin-walled molybdenum alloy pipe is 0.8±0.05 mm, and the outer diameter is 9.5±0.05 mm. It can be known from the above results that the actual size of the thin-walled molybdenum alloy pipe conforms to the design size.

Claims

1. A method for preparing a thin-walled molybdenum alloy tube, characterized in that, The method uses an annular heat-conducting device to preheat the drawing die (1); the annular heat-conducting device includes a small heating ring (2) set on one side of the drawing die (1) and a large heating ring (3) set on the other side of the drawing die (1). A stainless steel pressure plate (4) is fixedly set on one side of the small heating ring (2) and a stainless steel pressure plate (4) is fixedly set on the other side of the large heating ring (3); a terminal block (5) and a temperature sensor (6) are set on the small heating ring (2) and the large heating ring (3); The method specifically includes the following steps: Step 1, Design the pulling sequence: Based on the design dimensions of the molybdenum alloy tube blank and the thin-walled molybdenum alloy tube, the drawing requirements are determined; the number of drawing passes is designed according to the drawing requirements, and the drawing die (1) and short mandrel are selected; Step 2: Prepare molybdenum alloy tube blanks; Step 3, tube blank shrinkage: In step one, an inner sleeve is coaxially installed inside the molybdenum alloy tube blank, and an outer sleeve is coaxially installed outside the molybdenum alloy tube blank. The molybdenum alloy tube blank is then heated and its head is reduced. Step 4, perform the pulling: Step 4.1, Install the annular heat-conducting device: Assemble the large heating ring (3) and the small heating ring (2) on both sides of the first drawing die located in the central heating furnace, and then install stainless steel pressure plates (4) on both sides of the large heating ring (3) and the small heating ring (2); install the first short core head on the tie rod; Step 4.2, Lubrication of the tube blank: The molybdenum alloy tube blank is immersed in an ultrasonic cleaning tank containing lubricating fluid to ensure that the inner and outer walls of the tube are fully lubricated. After draining, the core rod is inserted. Step 4.3, First pull-out: The first-pass drawing die is preheated to 100-220°C using a ring-shaped heat-conducting device; the molybdenum alloy tube blank is preheated to 100-220°C; after the preheating of the drawing die and the molybdenum alloy tube blank is completed, the first-pass drawing is performed at a speed of 10-15 m / min; after the first-pass drawing is completed, the first-pass drawn tube is obtained. Step 4.4, Second-pass drawing: Replace the first-pass drawing die with the second-pass drawing die; replace the first-pass short mandrel with the second-pass short mandrel; then use an annular heat-conducting device to preheat the second-pass drawing die to 100-220℃; preheat the first-pass drawn tube to 100-220℃; after the drawing die and tube are preheated, perform the second-pass drawing at a speed of 10-15 m / min; after the second-pass drawing is completed, the second-pass drawn tube is obtained. Step 4.5, stress-relief annealing; Step 4.6, three-stage pulling: Replace the second-pass drawing die with a third-pass drawing die; replace the second-pass short mandrel with a third-pass short mandrel head; then use an annular heat-conducting device to preheat the third-pass drawing die to 100-220℃; preheat the three-pass drawn tube to 100-220℃; after the preheating of the drawing die and tube is completed, perform three-pass drawing at a speed of 10-15 m / min; after the three-pass drawing is completed, a three-pass drawn tube is obtained. Step 5, Post-pull processing: After the drawing process in step four is completed, the tube is straightened, finished and acid-alkali washed to obtain thin-walled molybdenum alloy tube. Step four also includes the following steps: Step 4.7, four-stage pulling: Replace the three-pass drawing die with a four-pass drawing die; replace the three-pass short mandrel with a four-pass short mandrel head; then use an annular heat-conducting device to preheat the four-pass drawing die to 120-180℃; preheat the four-pass drawn tube to 120-180℃; after the drawing die and tube are preheated, perform four-pass drawing at a speed of 12-15 m / min; after the four-pass drawing is completed, a four-pass drawn tube is obtained. Step 4.8, stress-relief annealing; Step 4.9, five pull-out cycles: The four-pass drawing die is replaced with a five-pass drawing die; the four-pass short mandrel is replaced with a five-pass short mandrel head; then, the five-pass drawing die is preheated to 120-180℃ using an annular heat-conducting device; the tube is preheated to 120-180℃ after five passes of drawing; after the drawing die and tube are preheated, five passes of drawing are performed at a speed of 12-15 m / min; after the five passes of drawing are completed, a five-pass drawn tube is obtained. The wall thickness of the thin-walled molybdenum alloy tube is (0.3~0.8)±0.05mm; In step two, the outer diameter of the molybdenum alloy tube blank is 9.5-12 mm, the wall thickness of the molybdenum alloy tube blank is 0.5-1.0 mm, and the length of the molybdenum alloy tube blank is 1000 mm. In step three, the heating temperature of the molybdenum alloy tube blank is 500–700℃, and the heating time is 1–5 min; In step 4.1, the inner diameter of the first drawing die is 8–11 mm, and the outer diameter of the first short mandrel is 6.76–9 mm; in step 4.4, the inner diameter of the second drawing die is 7–10 mm, and the outer diameter of the second short mandrel is 5.76–8.5 mm; in step 4.6, the inner diameter of the third drawing die is 6.0–9.5 mm, and the outer diameter of the third short mandrel is 4.76–7.9 mm. Step 4.5 specifically involves: using a hydrogen protective atmosphere, stress-relief annealing is performed on the second-pass drawn tube at 800–1000°C for 1–3 hours; In step 4.7, the inner diameter of the four-pass drawing die is 5.0 mm; Step 4.8 specifically involves: using a hydrogen protective atmosphere, stress-relief annealing is performed on the second-pass drawn tube at 800–1000°C for 1–3 hours; In step 4.9, the inner diameter of the five-pass drawing die is 4.76 mm.

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