Molybdenum-containing seamless small-diameter pipe, preparation method and application thereof

Abstract

The application provides a molybdenum-containing metal seamless thin-walled tube, a preparation method and application thereof. The method adopts a powder metallurgy method to prepare a rod blank, adopts a mechanical processing mode to process the rod blank into a tube blank, and then adopts a hot drawing mode to draw the tube blank after spinning and necking to obtain the molybdenum-containing metal seamless thin-walled tube, wherein the wall thickness is 0.3mm ±0.05mm ~0.8mm ±0.1mm , the outer diameter is 3.17mm ±0.05mm ~6.35mm ±0.05mm , and the molybdenum-containing metal seamless thin-walled tube can be used for preparing a thermocouple. The preparation method overcomes the characteristics of poor room temperature plasticity and large brittleness of molybdenum and molybdenum alloy, and realizes the preparation of the molybdenum-containing metal seamless thin-walled tube.

Description

TECHNICAL FIELD

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

[0002] The seamless thin-wall pipe has been widely adopted in the technical fields of precision detection and transportation due to its excellent characteristics such as toughening, light weight and high precision, and more and more hollow thin-wall components with new materials, new processes and new structures are emerging. The addition of rare earth elements (such as La2O3) in molybdenum powder can play a role of dispersion strengthening, and the oxide dispersion phase reduces the recrystallization tendency of pure metal, improves the high-temperature performance of the material, and the grain forms a dovetail lap joint structure after deformation processing and has good creep performance. The molybdenum-containing molybdenum alloy pipe can be widely used in fields requiring high-temperature resistant materials, such as as a hot thermocouple sheath pipe.

[0003] At present, the preparation methods of molybdenum and molybdenum alloy pipes mainly include extrusion, rolling and spinning, etc. Due to the characteristics of molybdenum and molybdenum alloy such as high melting point, high hot strength, poor room temperature plasticity and high brittleness, there are many defects in the preparation process, such as high extrusion temperature (about 1400-1500℃) leading to large crystal size, easy occurrence of scale and micro-cracks on the inner and outer surfaces during spinning, low rolling efficiency and small feed amount, etc. Therefore, the preparation of molybdenum and molybdenum alloy seamless thin-wall pipes is difficult, which further limits its application. SUMMARY

[0004] In view of the deficiencies in the prior art, one of the purposes of the present application is to provide a molybdenum-containing seamless thin-wall pipe and a preparation method thereof, which solves the technical problem that molybdenum and molybdenum alloy seamless thin-wall pipes are difficult to prepare due to the poor room temperature plasticity and high brittleness of molybdenum in the prior art.

[0005] In view of the deficiencies in the prior art, another purpose of the present application is to provide an application of the molybdenum-containing seamless thin-wall pipe for preparing a thermocouple, which solves the technical problem that the application of molybdenum and molybdenum alloy thin-wall pipes is limited due to the difficulty in preparing the pipes in the prior art.

[0006] In order to solve the above technical problems, the present application adopts the following technical solutions:

[0007] A preparation method of a molybdenum-containing seamless thin-wall pipe, which specifically comprises the following steps:

[0008] Step 1: preparing a rod blank

[0009] The molybdenum powder or rare earth element molybdenum alloy powder is pressed into a rod blank, and then sintered to obtain the rod blank.

[0010] Step 2: preparing a pipe blank

[0011] The rod blank prepared in step one is forged to be dense, and then is subjected to spinning, sawing of head and tail and annealing treatment to prepare a finished rod blank, and then the finished rod blank is punched, and after annealing treatment and hot rolling, a pipe blank is prepared.

[0012] In step three, the pipe blank is spun to be necked:

[0013] In the pipe blank prepared in step two, an inner plug is coaxially arranged, the pipe blank with the inner plug is heated to 500-600 DEG C for 1-3 min to perform first spinning, then an outer sleeve is coaxially arranged outside the pipe blank, the pipe blank with the inner plug and the outer sleeve is heated to 500-600 DEG C for 1-3 min to perform second spinning, and the necking pretreatment of the pipe blank is completed and a necked pipe blank is prepared.

[0014] In step four, drawing passes are designed:

[0015] According to the design size of the hot-rolled pipe blank and the molybdenum-containing seamless thin-wall pipe, the drawing requirement is determined, the drawing passes are designed, the drawing die is selected, and the drawing process parameters are determined.

[0016] In step five, on-line heating drawing and straightening are performed:

[0017] The necked pipe blank prepared in step three is preheated to 120-200 DEG C for 20-30 s, after preheating, continuous multiple drawing is performed, the drawing die and the short core are replaced after each drawing pass, and straightening is performed according to the straightness requirement, after the last straightening, sizing cutting, alkali washing, finishing and processing of the inner and outer surfaces are performed, and the molybdenum-containing seamless thin-wall pipe is prepared.

[0018] The specific process of straightening is that the drawn pipe is annealed, then the annealed pipe is preheated to 180-220 DEG C for 2-5 min, after preheating, the annealed pipe is sent into a multi-roll straightening machine with an oil bath pipe, and straightening is performed at a temperature of 180-220 DEG C.

[0019] The present application also has the following technical features:

[0020] Specifically, in step one, the rare earth element is lanthanum, and the content of lanthanum in the rare earth element molybdenum alloy powder is 0.2-0.5 wt.%.

[0021] Specifically, in step two, the outer diameter of the finished rod blank is 29-31 mm.

[0022] Specifically, in step three, the outer diameter of the flower port of the inner plug is 5-8 mm, and the length of the inner plug is 30-45 mm.

[0023] Specifically, in step three, the length of the outer sleeve is 50-60 mm.

[0024] Specifically, in step five, the preheating and drawing process uses a mixed atmosphere of hydrogen and compressed air for heating, wherein the flow rate of hydrogen is 0.2-0.5 m 3 / h, and the flow rate of compressed air is 2-5 m 3 / h.

[0025] Specifically, the oil bath pipe is located above the straightening roll of the multi-roll straightening machine, and the oil bath pipe is arranged along the transverse direction, and the vertical distance between the oil bath pipe and the straightening roll is 80 mm; the length of the oil bath pipe is 100 mm, a plurality of oil outlets are formed on the oil bath pipe along the transverse direction, the spacing between adjacent oil outlets is 10 mm, and the inner diameter of the oil outlet is 0.2 mm ±0.05mm .

[0026] Specifically, the oil bath pipe is connected with the oil tank through the oil conveying pipe, the oil conveying pipe is arranged along the vertical direction, the bottom end of the oil conveying pipe is fixed on the multi-roll straightening machine, and the top end of the oil conveying pipe is connected with the oil bath pipe.

[0027] The application also protects a molybdenum-containing metal seamless thin-walled pipe prepared by the above-mentioned method; the wall thickness of the molybdenum-containing metal seamless thin-walled pipe is 0.3 mm ±0.05mm -0.8 mm ±0.1mm , the outer diameter is 3.17 mm ±0.05mm -6.35 mm ±0.05mm .

[0028] The application also protects the use of the above-mentioned molybdenum-containing metal seamless thin-walled pipe for preparing a thermocouple.

[0029] Compared with the prior art, the application has the following technical effects:

[0030] (I) The preparation method of the molybdenum-containing metal seamless thin-walled pipe protects the pipe blank by using an inner plug and an outer sleeve during neck spinning, avoiding the adverse effects caused by the poor room temperature plasticity and high brittleness of molybdenum, and further avoiding the situation that pipe blank rupture leads to preparation failure; in addition, the oil bath pipe is arranged above the multi-roll straightening machine, which can ensure constant temperature control during pipe straightening and improve lubrication conditions to further avoid brittle cracks. According to the above analysis, the preparation method of the application overcomes the characteristics of poor room temperature plasticity and high brittleness of molybdenum and molybdenum alloy, and realizes the preparation of the molybdenum-containing metal seamless thin-walled pipe.

[0031] (II) The molybdenum-containing metal seamless thin-walled pipe has an average room temperature tensile strength of ≥722 MPa, a yield strength of ≥615 MPa, and an elongation after fracture of ≥28.5%, and has good mechanical properties.

[0032] (III) The thermocouple prepared by the molybdenum-containing seamless small-diameter pipe can withstand high-temperature environment, has the characteristics of fast response speed, high precision and good stability, and can meet the precise measurement requirement in high-temperature environment. BRIEF DESCRIPTION OF DRAWINGS

[0033] Fig. 1 (A) is a schematic diagram of the overall structure of the assembly of the pipe blank and the inner plug.

[0034] Fig. 1 (B) is a side view of the assembly of the pipe blank and the inner plug.

[0035] Fig. 1 (C) is a front view of the assembly of the pipe blank and the inner plug.

[0036] Fig. 2 (A) is a schematic diagram of the overall structure of the assembly of the pipe blank and the outer sleeve.

[0037] Fig. 2 (B) is a side view of the assembly of the pipe blank and the outer sleeve.

[0038] Fig. 2 (C) is a front view of the assembly of the pipe blank and the outer sleeve.

[0039] Fig. 3 (A) is a front view of the multi-roller straightening machine with an oil bath pipe.

[0040] Fig. 3 (B) is a top view of the multi-roller straightening machine with an oil bath pipe.

[0041] Fig. 3 (C) is a side view of the multi-roller straightening machine with an oil bath pipe.

[0042] Figure 4 Fig. 4 is a mechanical property curve diagram of the molybdenum-lanthanum alloy seamless small-diameter pipe numbered 1# in Example 2.

[0043] Figure 5 Fig. 5 is a mechanical property curve diagram of the molybdenum-lanthanum alloy seamless small-diameter pipe numbered 2# in Example 2.

[0044] Figure 6 Fig. 6 is a mechanical property curve diagram of the molybdenum-lanthanum alloy seamless small-diameter pipe numbered 3# in Example 2.

[0045] Figure 7 Fig. 7 is a macroscopic morphology diagram of the molybdenum-lanthanum alloy seamless small-diameter pipe of Example 2.

[0046] Figure 8 Fig. 8 is a macroscopic morphology diagram of the thermocouple prepared in Example 3.

[0047] The meanings of the various reference numbers and symbols in the drawings are as follows: 1-pipe blank, 2-inner plug, 3-outer sleeve, 4-oil bath pipe, 5-multi-roller straightening machine, 6-straightening roller, and 7-oil delivery pipe.

[0048] The specific content of the present application is further explained and described in detail in conjunction with the following examples. DETAILED DESCRIPTION

[0049] In the present application:

[0050] The upper index number with unit represents the tolerance, for example, the wall thickness of the seamless fine diameter tube containing molybdenum metal is 0.5mm ±0.05mm , which means that the wall thickness of the seamless fine diameter tube containing molybdenum metal is 0.5mm, and the tolerance is 0.05mm.

[0051] It should be noted that all the equipment and molds in the present application, if not specially stated, adopt the known equipment and molds in the prior art, for example:

[0052] The multi-roll straightening machine adopts the conventional multi-roll straightening machine known in the prior art.

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

[0054] According to the above technical solution, the specific embodiments of the present application are given below. It should be noted that the present application is not limited to the following specific embodiments, and any equivalent transformation based on the technical solution of the present application falls within the protection scope of the present application.

[0055] Example 1:

[0056] The present embodiment gives a preparation method of a seamless fine diameter tube containing molybdenum metal. The method uses a powder metallurgy method to prepare a rod blank, and adopts a mechanical processing method to process the rod blank into a tube blank, and then uses a hot drawing method to prepare the seamless fine diameter tube containing molybdenum metal after spinning necking of the tube blank.

[0057] Step one, preparing a rod blank:

[0058] The molybdenum lanthanum alloy powder is pressed into a shape by using a cold isostatic pressing (CIP) technology, and the content of lanthanum in the molybdenum lanthanum alloy powder is 0.5 wt.%; and then a molybdenum lanthanum alloy rod blank is prepared by sintering, and the theoretical density of the molybdenum lanthanum alloy rod blank is greater than or equal to 97%.

[0059] Step two, preparing a tube blank:

[0060] The molybdenum lanthanum alloy rod blank prepared in step one is forged to be dense, and then is subjected to spinning, sawing head and tail, and annealing treatment to prepare a finished molybdenum lanthanum alloy rod blank, and the outer diameter of the finished molybdenum lanthanum alloy rod blank is 31mm, and the straightness after spinning is 0.5mm / 1000mm; and then the finished molybdenum lanthanum alloy rod blank is punched, and then is subjected to annealing treatment and hot rolling to prepare a molybdenum lanthanum alloy tube blank.

[0061] Step three, spinning necking of the tube blank:

[0062] In step two, the inner plug 2 is coaxially arranged in the molybdenum lanthanum alloy pipe blank 1, the outer diameter of the inner plug 2 is 8 mm, the opening ensures that the inner plug is not slippage, the length of the inner plug 2 is 45 mm, the molybdenum lanthanum alloy pipe blank 1 with the inner plug 2 is heated to 600 DEG C, the heating time is 3 min, and the first spinning is carried out; then the outer sleeve 3 is coaxially arranged outside the molybdenum lanthanum alloy pipe blank 1, the length of the outer sleeve 3 is 60 mm, and then the molybdenum lanthanum alloy pipe blank 1 with the inner plug 2 and the outer sleeve 3 is heated to 600 DEG C, the heating time is 1 min, the second spinning is carried out, the necking pretreatment of the pipe blank is completed, and the molybdenum lanthanum alloy necking pipe blank is prepared.

[0063] In the embodiment, the inner plug 2 and the outer sleeve 3 are both made of conventional pipe material known in the prior art, preferably carbon steel pipe or stainless steel pipe, and the assembly relationship of the inner plug 2, the outer sleeve 3 and the molybdenum lanthanum alloy pipe blank 1 is shown in FIG. 1 and FIG. 2. The inner plug 2 is obtained by cutting, and the shape is cross-shaped horn. The inner plug 2 is plastically deformed at the same time as the pipe blank 1 when supporting the pipe blank, does not affect the necking effect of the pipe blank 1, the outer sleeve 3 can ensure repeated clamping of the necking head in multiple passes, the inner plug 2 and the outer sleeve 3 are deformed together with the spinning necking, can effectively play a protective role for the head end of the pipe blank 1, avoids the influence of the room temperature brittleness of the molybdenum lanthanum alloy pipe blank on the processing, and reduces the waste of the pipe blank. The specific necking length can be adjusted according to the drawing die and the mouthpiece specification, the outer diameter of the head end of the spinning necking pipe material is measured, and if it does not meet the requirements, the spinning necking can be carried out again.

[0064] Step four, design the drawing pass:

[0065] The outer diameter of the molybdenum lanthanum alloy necking pipe blank prepared in step three is 10 ±0.05 mm, and the wall thickness of the molybdenum lanthanum alloy necking pipe blank is 1.0 ±0.05 mm. The design size of the molybdenum lanthanum alloy seamless thin-walled pipe is: the outer diameter is 6.35 ±0.05 mm, and the wall thickness is 0.5 ±0.05 mm. The design outer diameter and wall thickness of the molybdenum lanthanum alloy seamless thin-walled pipe are different from the outer diameter and wall thickness of the molybdenum lanthanum alloy necking pipe blank, that is, the drawing requirement is to reduce the diameter and the wall thickness; 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.

[0066] The thermal expansion of the drawing die and the short core is calculated by formula I, and the drawing process is adjusted according to the thermal expansion result; formula I is as follows:

[0067] λ = α * l0 * (t-t0) formula I.

[0068] In the formula:

[0069] λ represents the thermal expansion of the drawing die and the short core.

[0070] a represents the linear expansion coefficient of the drawing die and the short core head, in mm / mm.

[0071] l0 represents the dimensional length of the drawing die and the short core head, in mm.

[0072] t represents the heating temperature of the drawing die and the short core head, in °C.

[0073] t0 represents the initial temperature of the drawing die and the short core head, in °C; t-t0 is the temperature rise difference.

[0074] 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°C), 15.6*10-6 (300°C), and 16.3*10-6 (400°C), respectively. -6 -6 -6 After calculation, 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°C. 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 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.

[0075] Step five, in-line heating, drawing and straightening:

[0076] The molybdenum lanthanum alloy necked pipe blank prepared in step three is preheated to 200°C in a hydrogen and combustion-supporting gas multi-chamber heating furnace, and the preheating time is 30 s; after preheating, continuous drawing is carried out for three times, and new drawing dies and short core heads are replaced after each drawing pass, and straightening is carried out according to the straightness requirement; the whole preheating and drawing process is carried out in a mixed gas atmosphere composed of hydrogen and compressed air, wherein the flow rate of hydrogen is 0.5 m 3 / h, and the flow rate of compressed air is 5 m 3 / h; straightening is carried out after each drawing pass, and after the last straightening is completed, cutting is carried out by using an online cutting machine with a fixed size, and then after alkali washing, finishing and processing the inner and outer surfaces, a molybdenum lanthanum alloy seamless small-diameter pipe is prepared. The specific process of straightening is as follows: the drawn pipe is annealed, and then the annealed pipe is preheated to 200°C by using an electric heating furnace, and the preheating time is 3 min; after preheating is completed, the annealed pipe is sent into a multi-roller straightening machine 5 with an oil bath pipe 4, and straightening is carried out at a temperature of 200°C. Two repeated straightenings can be carried out after each drawing pass to ensure the straightness requirement.

[0077] ​​In this embodiment, the preheating time is generally 4 / 6 holes arranged uniformly in the circumferential direction, and the effective heating length of the furnace body is 1000 mm, so as to ensure uniform heating. The gas pressure and die temperature are adjusted at any time during the drawing stage to ensure the authenticity of the experimental data. In addition, since the molybdenum lanthanum alloy thin-walled tube has a rapid room temperature drop, in order to avoid the brittle splitting of the tube caused by the temperature drop, the outlet of the electric heating furnace needs to be close to the inlet of the multi-roll straightening machine.

[0078] As a specific solution of the embodiment, the oil bath tube 4 is made by punching a galvanized pipe, as shown in FIG. 3. The oil bath tube 4 is located above the straightening roll 6 of the multi-roll straightening machine 5, and the vertical distance between the oil bath tube 4 and the straightening roll 6 is 80 mm. The length of the oil bath tube 4 is 100 mm. A plurality of oil outlets are formed on the oil bath tube 4 along the transverse direction. The spacing between adjacent oil outlets is 10 mm, and the inner diameter of the oil outlet is 0.2 mm ± 0.05 mm. The oil bath tube 4 is connected in communication with the oil tank through the oil delivery pipe 7. The oil delivery pipe 7 is arranged along the vertical direction. The bottom end of the oil delivery pipe 7 is fixed on the multi-roll straightening machine 5, and the top end of the oil delivery pipe 7 is connected in communication with the oil bath tube 4.

[0079] In this embodiment, the straightening tube path can be covered by the oil sprayed from the oil outlet, achieving the purpose of high-temperature oil bath. Compared with the cold straightening of the unmodified multi-roll straightening machine, the oil bath straightening has the characteristics of straightening roll modification and oil bath nozzle design. The straightening roll is made of hot abrasive tool steel to meet the oil bath constant temperature requirement during the straightening process. The oil in the oil tank is selected from high-temperature heat-conducting oil with small viscosity and high flash point, preferably L-QB300-II GB23971 Great Wall heat-conducting oil. The oil bath can maintain a constant temperature during the straightening process. In addition, the oil can lubricate and seal the frictional parts of the machine, preventing the occurrence of brittle cracks.

[0080] Embodiment 2:

[0081] This embodiment gives a kind of molybdenum metal seamless thin-walled tube, which is made by the preparation method of the molybdenum metal seamless thin-walled tube of the embodiment. The wall thickness of the molybdenum metal seamless thin-walled tube is 0.5 mm ±0.05mm , the outer diameter is 6.35 mm ±0.05mm , the straightness is ≤0.5 mm / 1000 mm, the outer surface roughness is <0.5 microns, and the inner surface roughness is <0.8 microns. As can be seen from the above results, the actual size of the molybdenum lanthanum alloy seamless thin-walled tube meets the design size, and its appearance is shown in Figure 7 .

[0082] In this embodiment, the mechanical properties of the molybdenum lanthanum alloy seamless thin-walled tube are shown in Tables 1, Figure 4 , Figure 5 and Figure 6 . 1#, 2# and 3# in Table 1 are the numbers of three parallel tests, respectively.

[0083] Table 1, Mechanical property room temperature data table of molybdenum lanthanum alloy seamless small diameter pipe

[0084]

[0085] Example 3:

[0086] This example gives the application of the molybdenum-containing metal seamless small diameter pipe of Example 2 for preparing a thermocouple, and the finally prepared thermocouple is as shown in Figure 8 The thermocouple can withstand high temperature environment, has the characteristics of fast response speed, high precision and good stability, and can meet the accurate measurement demand under high temperature environment.

Claims

1. A method for preparing a seamless, narrow-diameter tube containing molybdenum metal, characterized in that, The method specifically includes the following steps: Step 1, Prepare the billet: Molybdenum powder or rare earth element molybdenum alloy powder is pressed into shape and then sintered to obtain a billet. Step 2, preparing the tube blank: The bar billet obtained in step one is forged into a dense state, and then subjected to rotary forging, sawing of the head and tail, and annealing to obtain a precision-machined bar billet. The precision-machined bar billet is then punched, annealed, and hot-rolled to obtain a tube billet. Step 3, tube blank spin compression neck: An inner plug (2) is coaxially placed inside the tube blank (1) obtained in step two. The tube blank (1) with the inner plug (2) is heated to 500-600°C for 1-3 minutes and the first spinning is performed. Then, an outer sleeve (3) is coaxially placed outside the tube blank (1). The tube blank (1) with the inner plug (2) and the outer sleeve (3) is heated to 500-600°C for 1-3 minutes and the second spinning is performed to complete the tube blank necking pretreatment and obtain the necked tube blank. Step 4, Design the pulling sequence: Based on the design dimensions of the hot-rolled tube billet and the seamless small-diameter tube containing molybdenum, determine the drawing requirements; design the number of drawing passes based on the drawing requirements, select the drawing die, and determine the drawing process parameters. Step 5: Online heating, drawing, and straightening: The necked tube blank obtained in step three is preheated to 120-200℃ for 20-30 seconds. After preheating, the tube is drawn repeatedly. After each drawing, a new drawing die and short mandrel are replaced. The tube is straightened according to the straightness requirements. After the last straightening, the tube is cut to length, washed with alkali, finished and treated on the inner and outer surfaces to obtain a seamless fine diameter tube containing molybdenum metal. The specific process of straightening is as follows: the drawn tube is annealed, and then the annealed tube is preheated to 180-220°C for 2-5 minutes. After preheating, the annealed tube is sent into a multi-roller straightener (5) with an oil bath tube (4) and straightened at a temperature of 180-220°C.

2. The method for preparing a seamless, narrow-diameter molybdenum-containing metal tube as described in claim 1, characterized in that, In step one, the rare earth element is lanthanum, and the lanthanum content in the rare earth element molybdenum alloy powder is 0.2-0.5 wt.%.

3. The method for preparing a seamless, narrow-diameter molybdenum-containing metal tube as described in claim 1, characterized in that, In step two, the outer diameter of the finished bar blank is 29-31 mm.

4. The method for preparing a seamless, narrow-diameter molybdenum-containing metal tube as described in claim 1, characterized in that, In step three, the outer diameter of the flower-shaped opening of the inner plug is 5-8 mm, and the length of the inner plug is 30-45 mm.

5. The method for preparing a seamless, narrow-diameter molybdenum-containing metal tube as described in claim 1, characterized in that, In step three, the length of the outer garment is 50-60mm.

6. The method for preparing a seamless, narrow-diameter molybdenum-containing metal tube as described in claim 1, characterized in that, In step five, the preheating and drawing processes are heated using a mixed atmosphere of hydrogen and compressed air, with a hydrogen flow rate of 0.2–0.5 m³ / h. 3 / h, the flow rate of compressed air is 2-5m³ / h. 3 / h.

7. The method for preparing a seamless, narrow-diameter molybdenum-containing metal tube as described in claim 1, characterized in that, The oil bath pipe (4) is located above the straightening roller (6) of the multi-roller straightener (5). The oil bath pipe (4) is arranged in the transverse direction, and the vertical distance between the oil bath pipe (4) and the straightening roller (6) is 80 mm. The length of the oil bath pipe (4) is 100 mm, and multiple oil outlets are opened in the transverse direction on the oil bath pipe (4). The distance between adjacent oil outlets is 10 mm, and the inner diameter of the oil outlet is 0.2 mm. ±0.05mm .

8. The method for preparing a seamless, narrow-diameter molybdenum-containing metal tube as described in claim 7, characterized in that, The oil bath pipe (4) is connected to the oil tank through the oil delivery pipe (7). The oil delivery pipe (7) is set in the vertical direction. The bottom end of the oil delivery pipe (7) is fixed on the multi-roller straightener (5), and the top end of the oil delivery pipe (7) is connected to the oil bath pipe (4).

9. A seamless fine-diameter tube containing molybdenum, characterized in that, The molybdenum-containing seamless fine-diameter tube is manufactured using the method described in any one of claims 1 to 8; the wall thickness of the molybdenum-containing seamless fine-diameter tube is 0.3 mm. ±0.05mm ~0.8mm ±0.1mm The outer diameter is 3.17mm. ±0.05mm ~6.35 mm ±0.05mm .

10. The application of the seamless narrow-diameter molybdenum-containing metal tube as described in claim 9 for the manufacture of thermocouples.

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