Molybdenum alloy seamless tube hot rolling method

Abstract

The molybdenum alloy seamless tube hot rolling method comprises the steps that a hole pattern mold and a core rod mold are manufactured, the hole pattern mold comprises two rollers which are oppositely arranged, and a hole pattern defined by rolling grooves of the rollers is in a double-eccentric-circle opening ring shape; the defects of the inner surface and the outer surface of the molybdenum alloy pipe blank are treated; a rolling assembly with a hole pattern mold is arranged, the rolling assembly and the core rod mold are installed on a rolling mill, the hole pattern mold is preheated, and the molybdenum alloy pipe blank is arranged on the core rod mold in a sleeving mode; the gap between the two rollers in the pass mold is pre-adjusted to a first threshold value, the gap between the two rollers in the pass mold is adjusted to 0 after loading, the first threshold value is larger than or equal to 0, and the molybdenum alloy pipe blank is heated to a first preset temperature; and rolling the molybdenum alloy tube blank. According to the embodiment of the invention, high-precision hot rolling of the molybdenum alloy seamless tube can be carried out, molybdenum alloy rolling passes are reduced, zero-gap control of a rolling pass is realized, the rolling stability is improved, and the dimensional precision of a rolled thin-walled tube is guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of hot rolling, and in particular relates to a hot rolling method for a molybdenum alloy seamless pipe. Background Art

[0002] Molybdenum metal has excellent thermal and electrical conductivity and corrosion resistance. However, it is relatively brittle at room temperature, exhibits poor processing and welding properties, is easily oxidized, and exhibits recrystallization brittleness. Molybdenum tubes are manufactured by machining forgings or direct sintering. Due to their heat resistance and high pressure resistance, molybdenum tubes have a wide range of applications in the electronics and energy industries. Demand for high-precision, small-sized molybdenum alloy tubes is increasing year by year.

[0003] In the related art, molybdenum alloy seamless tubes are forged to obtain molybdenum cored rods, and then the molybdenum core is removed by machining to obtain molybdenum alloy tubes. This method has very low production yield and efficiency, and it is difficult to manufacture thin-walled molybdenum tubes by machining. Summary of the Invention

[0004] The present invention is based on the inventor's discovery and understanding of the following facts and problems:

[0005] The inventors recognized that hot-rolling seamless pipes using H13 molds is prone to collapse, sticking, cracking, and dimensional instability in high-temperature environments. These molds typically utilize a single-opening die and a single-cone core head, resulting in poor dimensional accuracy during hot-rolling. These molds are primarily used for the production of semi-finished pipes such as steel pipe and TC4. For small-diameter seamless molybdenum alloy pipes with low specific heat capacity, requiring dimensional accuracy within ±0.03mm, conventional hot-rolling techniques are difficult to achieve.

[0006] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0007] To this end, an embodiment of the present invention provides a method for hot rolling a molybdenum alloy seamless pipe to improve the straightness and precision of hot rolling.

[0008] The hot rolling method of a molybdenum alloy seamless pipe according to an embodiment of the present invention comprises:

[0009] Making a hole mold and a core rod mold, wherein the hole mold comprises two rollers arranged opposite to each other, and the hole defined by the rolling grooves of the rollers is in the shape of a double eccentric open ring;

[0010] Treat the defects on the inner and outer surfaces of molybdenum alloy tube blanks;

[0011] Configuring a rolling assembly with the pass die, installing the rolling assembly and the mandrel die on a rolling mill, preheating the pass die, and sleeve the molybdenum alloy tube onto the mandrel die;

[0012] Pre-adjusting the gap between the two rollers in the pass die to a first threshold value, adjusting the gap between the two rollers in the pass die to 0 after loading, wherein the first threshold value is greater than or equal to 0, and heating the molybdenum alloy tube blank to a first preset temperature;

[0013] The molybdenum alloy tube blank is rolled.

[0014] The hot rolling method of the molybdenum alloy seamless pipe in the embodiment of the present invention can perform high-precision hot rolling of the molybdenum alloy seamless pipe, reduce the number of molybdenum alloy rolling passes, achieve zero-gap control of the rolling pass, improve the rolling stability, and ensure the dimensional accuracy of the rolled thin-walled pipe.

[0015] In some embodiments, the steps of treating defects on the inner and outer surfaces of the molybdenum alloy tube include:

[0016] The molybdenum alloy tube blank is fixed on a lathe, an extension rod is arranged on a feeding device of the lathe, sandpaper is arranged on the extension rod, the extension rod is driven to rotate and extend into the interior of the molybdenum alloy tube blank, and the inner surface of the molybdenum alloy tube blank is mechanically polished;

[0017] The outer surface of the molybdenum alloy tube is ground using a centerless grinder.

[0018] In some embodiments, the rotation speed of the lathe is 500 r / min to 1000 r / min, and the feed speed of the lathe is 0.1 mm / r to 0.3 mm / r; the rotation speed of the grinding wheel of the centerless grinder is 1300 r / min to 1455 r / min, and the feeding speed of the molybdenum alloy tube relative to the grinding wheel in the centerless grinder is 0.3 m / min to 0.5 m / min;

[0019] And / or, the surface roughness of the inner surface and the outer surface of the molybdenum alloy tube blank after defect treatment is less than or equal to Ra0.8.

[0020] In some embodiments, the method for making the hole-shaped mold includes:

[0021] The material of the roll substrate is GH4169 nickel-based alloy steel;

[0022] Rough turning of the shape, rough milling of the transition section, deformation section, sizing section and release section of the rolling groove in the roll, and reserve a machining allowance of 0.15mm to 0.2mm;

[0023] Perform aging treatment on the rolls after rough milling;

[0024] Rough and fine grinding of the rolls.

[0025] In some embodiments, the step of performing an aging treatment on the roll after rough milling includes: heating the roll to 650° C. to 750° C. and keeping the temperature for at least 12 hours; cooling the roll to 615° C. to 625° C. and keeping the temperature for at least 12 hours; air cooling the roll to complete the aging treatment of the roll;

[0026] And / or, the roller is finely ground to a dimensional accuracy of 0.005 mm.

[0027] In some embodiments, the method for making the core rod mold includes:

[0028] Configure the mandrel base material with M42 high-speed steel and rough-turn the shape;

[0029] Heat treating the mandrel;

[0030] Straighten, rough grind and fine grind the mandrel.

[0031] In some embodiments, the step of heat treating the mandrel comprises:

[0032] Heating the mandrel to a first temperature and keeping it at that temperature for at least 20 minutes;

[0033] Heating the mandrel to a second temperature and maintaining the temperature for at least 20 minutes;

[0034] heating the mandrel to a third temperature and maintaining the temperature for at least 20 minutes, wherein the third temperature is 1180° C. to 1220° C., and the second temperature is greater than the first temperature and less than the third temperature;

[0035] Quenching and cooling the core rod;

[0036] Heat the mandrel to 530°C to 560°C and keep it warm for at least 120 minutes;

[0037] The core rod is air-cooled and tempered.

[0038] In some embodiments, the first temperature is 500° C. to 600° C., and the second temperature is 750° C. to 820° C.;

[0039] And / or, in the step of quenching and cooling the core rod, using air cooling at a pressure of more than 700Pa;

[0040] And / or, in the steps of straightening, rough grinding and fine grinding the mandrel, the circular runout of the straightened mandrel is less than or equal to 0.1 mm, and the dimensional accuracy of the fine grinding mandrel reaches 0.005 mm.

[0041] In some embodiments, the hole-shaped die is hot-fitted into the rolling assembly, and the hot-fitting temperature is less than or equal to 150° C.;

[0042] And / or, in the step of preheating the hole mold, the hole mold is sprayed with a hydrogen flame for 20 minutes to 30 minutes; the step of putting the molybdenum alloy tube blank on the mandrel mold includes: applying lubricating oil on the inner surface of the molybdenum alloy tube blank, passing the molybdenum alloy tube blank through the mandrel, and feeding the molybdenum alloy tube blank through the mandrel with a single feeding distance of 0.2 mm, and preheating the molybdenum alloy tube blank during the feeding process.

[0043] In some embodiments, the steps of pre-adjusting the gap between the two rollers in the pass mold to a first threshold value, and adjusting the gap between the two rollers in the pass mold to 0 after loading, include: applying grease to the circumference of the pass in the pass mold, adjusting the gap between the two rollers in the rolling assembly, adjusting the gap between the two rollers to the first threshold value when unloaded, judging whether the pass is installed in place based on the cleanliness and shape of the oil film, adjusting the gap between the two rollers to 0 after loading, and making the oil films corresponding to the two rollers uniform and symmetrical;

[0044] and / or, the first threshold is 0 to 0.1 mm;

[0045] And / or, the first preset temperature is 600 degrees Celsius to 900 degrees Celsius;

[0046] And / or, during the rolling of the molybdenum alloy tube billet, the gap between the gear in the rolling assembly and the rack on the rolling mill is adjusted to 0.2 mm to 0.3 mm, the rolling speed is 130 rpm to 150 rpm, the feed amount of the rolling mill is 0.8 mm / time to 1.1 mm / time, the outlet jaw pressure of the rolling mill is 0.1 to 0.5 MPa, and the rolling mill adopts a double-rotation single-feed method for continuous rolling.

[0047] In some embodiments, the rolling groove of the roll comprises a deformation section, a sizing section, and a release section, which are sequentially arranged along the circumference of the roll and with cross-sectional dimensions from large to small. The groove depths of the deformation section, the sizing section, and the release section are the same. The deformation section, the sizing section, and the release section each comprise a plurality of segment units sequentially arranged along the circumference of the roll and with cross-sectional dimensions from large to small.

[0048] Each of the segment units has a first cross-section located at one end of the segment unit, a second cross-section located in the middle of the segment unit, and a third cross-section located at the other end of the segment unit, and two adjacent cross-sections are smoothly transitioned and connected;

[0049] The radius of the groove bottom contour line of the second section is smaller than the radius of the groove bottom contour line of the first section and larger than the radius of the groove bottom contour line of the third section. The circles in which the groove bottom contour lines of the first section, the second section and the third section are located are eccentrically arranged in the radial direction of the rolling roller, so that the hole shape defined by the rolling groove is a double eccentric open ring. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 1 is a flow chart of a method for hot rolling a molybdenum alloy seamless tube according to an embodiment of the present invention.

[0051] Figure 2 Schematic diagram of the hole expansion in the embodiment of the present invention.

[0052] Figure 3 Schematic side view of a segment unit in an embodiment of the present invention.

[0053] Figure 4 It is a process curve diagram of aging treatment in an embodiment of the present invention.

[0054] Figure 5 It is a quenching process curve diagram in an embodiment of the present invention.

[0055] Figure 6 It is a tempering process curve diagram in an embodiment of the present invention. DETAILED DESCRIPTION

[0056] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0057] like Figures 1 to 6 As shown, the hot rolling method of the molybdenum alloy seamless pipe according to the embodiment of the present invention comprises:

[0058] S1. Make a die for the hole and a core rod. The die for the hole includes two rollers arranged opposite to each other. The groove of the rollers defines a hole in the shape of a double eccentric open ring. The groove of the rollers usually includes a transition section ( Figure 2 Middle section A), deformation section ( Figure 2 Middle section B), sizing section ( Figure 2 Middle segment C) and release segment ( Figure 2 Middle section D), wherein the deformation section, sizing section and release section serve as working sections to roll-form the tube blank.

[0059] S2. Treat the defects on the inner and outer surfaces of the molybdenum alloy tube. By eliminating the defects on the inner and outer surfaces of the molybdenum alloy tube and improving the roughness of the inner and outer surfaces of the molybdenum alloy tube, the subsequent rolling accuracy can be improved, ensuring the quality of the rolled molybdenum alloy seamless tube.

[0060] S3. Configure a rolling assembly with a hole-type die, install the rolling assembly and the mandrel die on the rolling mill, preheat the hole-type die, and put the molybdenum alloy tube blank on the mandrel die.

[0061] S4. Pre-adjust the gap between the two rollers in the pass mold to a first threshold value, and then adjust the gap between the two rollers in the pass mold to 0 after loading, where the first threshold value is greater than or equal to 0. Heat the molybdenum alloy tube billet to a first preset temperature. This embodiment can achieve zero gap control of the rolling pass, improve rolling stability, and ensure the dimensional accuracy of the rolled molybdenum alloy seamless tube. By heating the molybdenum alloy tube billet, it is more conducive to the plastic deformation of the molybdenum alloy tube billet during the rolling process, reducing deformation resistance, reducing energy consumption and the number of passes during the rolling process, making the rolling process smoother, and helping to improve the internal structure of the metal, eliminate internal defects, and improve the performance and quality of the molybdenum alloy seamless tube.

[0062] S5. Rolling of the molybdenum alloy tube billet is carried out. By setting the process parameters, continuous rolling can be achieved and the rolling quality can be guaranteed.

[0063] The hot rolling method of molybdenum alloy seamless pipe in some specific embodiments of the present invention is described below.

[0064] like Figures 1 to 6 As shown, the hot rolling method of the molybdenum alloy seamless pipe according to the embodiment of the present invention comprises:

[0065] S1. Fabricate a die for the pass and a mandrel die. The die comprises two rollers positioned opposite each other. The grooves of the two rollers define a pass in the shape of a double-eccentric open ring. The grooves of the rollers typically include a transition section, a deformation section, a sizing section, and a release section. The deformation section, sizing section, and release section serve as working sections for rolling the tube.

[0066] In this embodiment, the roll groove comprises a deformation section, a sizing section, and a release section, arranged in descending order of cross-sectional dimensions along the circumference of the roll. The groove depth of the deformation, sizing, and release sections is the same, and each section comprises a plurality of segment units arranged in descending order of cross-sectional dimensions along the circumference of the roll. For example, the deformation and sizing sections may comprise a total of 40 segment units, while the release section may comprise 5 or 6 segment units.

[0067] Each segment unit has a first cross section located at one end of the segment unit, a second cross section located in the middle of the segment unit and a third cross section located at the other end of the segment unit, and two adjacent cross sections are smoothly transitioned and connected.

[0068] The radius of the groove bottom contour line of the second section is smaller than the radius of the groove bottom contour line of the first section and larger than the radius of the groove bottom contour line of the third section. The circles in which the groove bottom contour lines of the first section, the second section and the third section are located are eccentrically arranged in the radial direction of the rolling roller, so that the hole shape defined by the rolling groove is a double eccentric open ring.

[0069] It can be understood that the groove depth of the rolling groove is the same. When the groove profile defined by the rolling groove is expanded, the bottom of the groove is on the same straight line. The groove profile expansion structure is as follows: Figure 2 As shown, the side view of the expanded segment unit is as follows Figure 3 As shown. The bottom contour line of the first section ( Figure 3 The center of the circle where the arc Z) is located is O", and the bottom contour line of the second section ( Figure 3 The center of the circle where the arc Y is located is O', and the bottom contour line of the third section ( Figure 3 The center of the circle where the arc X) is located is O. The three sections are arranged eccentrically in the circle.

[0070] The die manufacturing method includes: preparing a roll base made of GH4169 nickel-based alloy steel; rough turning the roll profile; and rough milling the transition, deformation, and sizing sections of the roll groove, leaving a machining allowance of 0.15mm to 0.2mm. The roll after rough milling is then aged.

[0071] like Figure 4 As shown, the aging treatment steps are as follows: heating the rolls to 650°C to 750°C and holding for at least 12 hours; furnace cooling the rolls to 615°C to 625°C and holding for at least 12 hours; and air cooling the rolls to complete the aging treatment. The aging treatment reduces the δ phase in the material, improving its strength and impact resistance. Finally, the rolls are rough-ground and fine-ground, achieving a dimensional accuracy of 0.005mm.

[0072] The manufacturing method of the core rod mold includes: preparing a core rod base material made of M42 high-speed steel, rough turning the shape, and heat treating the core rod.

[0073] like Figure 5 As shown, the heat treatment steps are as follows: heating the core rod to 500°C to 600°C and holding for at least 20 minutes; heating the core rod to 750°C to 820°C and holding for at least 20 minutes; and heating the core rod to 1180°C to 1220°C and holding for at least 20 minutes. The core rod is then quenched, for example, using air cooling at a pressure of 700 Pa or above, or oil cooling.

[0074] Then, the core rod is heated to 530°C to 560°C and kept at this temperature for at least 120 minutes, and the core rod is air-cooled and tempered.

[0075] The mandrel is straightened, rough-ground, and fine-ground. The circular runout of the straightened mandrel is less than or equal to 0.1mm, and the dimensional accuracy of the fine-ground mandrel reaches 0.005mm. This completes the production of the mandrel.

[0076] S2. Treat the defects on the inner and outer surfaces of the molybdenum alloy tube. By eliminating the defects on the inner and outer surfaces of the molybdenum alloy tube and improving the roughness of the inner and outer surfaces of the molybdenum alloy tube, the subsequent rolling accuracy can be improved, ensuring the quality of the rolled molybdenum alloy seamless tube.

[0077] Specifically, the molybdenum alloy tube blank is fixed on a lathe, and an extension rod is arranged on the lathe's feeding device. The extension rod can be made according to the length of the tube blank to ensure that the inner surface of the molybdenum alloy tube blank can be completely cleaned. Sandpaper is clamped at the end of the extension rod. After the lathe is started, the extension rod can be driven to rotate and extend into the interior of the molybdenum alloy tube blank. After the sandpaper contacts the inner surface of the molybdenum alloy tube blank, the inner surface of the molybdenum alloy tube blank can be mechanically polished. By driving the extension rod to rotate and reciprocate, multiple reciprocating cycles of cleaning are performed.

[0078] When performing defect treatment on the inner surface of the molybdenum alloy tube blank, the rotation speed of the lathe is 500r / min to 1000r / min, the feed speed of the lathe is 0.1mm / r to 0.3mm / r, and the surface roughness of the inner surface of the molybdenum alloy tube blank after defect treatment is less than or equal to Ra0.8. According to the needs of actual operation, the mesh number of the sandpaper can be reasonably selected. Of course, sandpaper with different mesh numbers can also be selected for multiple polishing.

[0079] The outer surface of the molybdenum alloy tube blank is ground using a centerless grinder. The grinding wheel speed of the centerless grinder is 1300 r / min to 1455 r / min, and the feed speed of the molybdenum alloy tube blank relative to the grinding wheel in the centerless grinder is 0.3 m / min to 0.5 m / min. The surface roughness of the outer surface of the molybdenum alloy tube blank after defect treatment is less than or equal to Ra0.8. For example, the grinding wheel of the centerless grinder can use an 80-grit grinding wheel. After grinding, the surface roughness of the outer surface of the molybdenum alloy tube blank after defect treatment is guaranteed to be less than or equal to Ra0.8.

[0080] S3. Prepare a rolling assembly with a die. The die is heat-fitted into the rolling assembly at a temperature of 150°C or less. Install the rolling assembly and mandrel die onto the rolling mill. Preheat the die. Specifically, the die can be sprayed with a hydrogen flame for 20 to 30 minutes. Place the molybdenum alloy tube over the mandrel die. Specifically, lubricate the inner surface of the molybdenum alloy tube. Pass the molybdenum alloy tube through the mandrel, feeding it a distance of 0.2 mm at a time. Preheat the molybdenum alloy tube continuously during feeding.

[0081] S4. Pre-adjust the gap between the two rollers in the hole mold to a first threshold value, and adjust the gap between the two rollers in the hole mold to 0 after loading. The first threshold value is greater than or equal to 0 and less than or equal to 0.1 mm. Specifically, grease is applied to the circumference of the hole in the hole mold (specifically, it can be the position where the deformation section and the transition section roughly intersect), and the gap between the two rollers in the rolling assembly is adjusted. When the roller is unloaded, the gap between the two rollers is adjusted to the first threshold value. The hole is installed in place based on the cleanliness and shape of the oil film. For example, when the roller is unloaded, lubricating oil is applied to both sides of the outer groove of the roller. Through reciprocating motion, the length, thickness and other shapes of the lubricating oil on both sides of the roller groove are observed to determine whether the hole is installed in place. After loading, adjust the gap between the two rollers to 0, and make the oil films corresponding to the two rollers uniform and symmetrical.

[0082] This embodiment can achieve zero-gap control of the rolling pass, improve the stability of rolling, and ensure the dimensional accuracy of the rolled molybdenum alloy seamless pipe.

[0083] The molybdenum alloy tube is heated to a first preset temperature of 600 to 900 degrees Celsius. The molybdenum alloy tube can be heated in a resistance furnace, with the temperature controlled within ±5 degrees Celsius. The tube is then held at this temperature for 20 to 30 minutes. Heating the molybdenum alloy tube facilitates plastic deformation during rolling, reduces deformation resistance, and reduces energy consumption and the number of passes during rolling, making the rolling process smoother. This helps improve the metal's internal structure, eliminate internal defects, and enhance the performance and quality of the molybdenum alloy seamless tube.

[0084] S5. Rolling of molybdenum alloy tube billets is carried out. Specifically, transmission gears are installed on both sides of the rolling assembly, and the rack is fixed to the frame of the rolling mill. The rolling assembly equipped with the gear is installed on the rack of the rolling mill frame. The gear and rack structure applies external force to the working frame equipped with the roller assembly, thereby driving the two rollers to perform reciprocating linear motion. The gap between the gear in the rolling assembly and the rack on the rolling mill is adjusted to 0.2mm to 0.3mm, the rolling speed is 130 rpm to 150 rpm, the feed rate of the rolling mill is 0.8mm / time to 1.1mm / time, the outlet clamping pressure of the rolling mill is 0.2Mpa, and the rolling mill adopts a double-rotation single-feed method for continuous rolling. By setting the process parameters, continuous rolling can be achieved and the rolling quality can be guaranteed.

[0085] Example 1:

[0086] This example provides a method for hot rolling a φ9×0.5mm molybdenum alloy seamless tube, comprising:

[0087] The pilger hot rolling production process is adopted, and the diameter ranges from φ13×1.2mm to φ9×0.5mm. After hot rolling, the inner and outer surfaces are treated, degreased and alkali washed, annealed, and finely ground.

[0088] Hot rolling dies with a pass length of φ12×1.2mm-φ9×0.5mm are manufactured according to the following process. The high-temperature resistant hole mold with double eccentric circular opening rings and curved mandrel mold required for the rolling process are manufactured. The hole mold is made of GH4169 material and undergoes rough turning, rough milling of the hole transition section, deformation section, sizing section and release section (leaving a 0.15-0.2mm margin), followed by aging treatment, rough grinding and fine grinding. Failure treatment is as follows: Figure 4 As shown in the figure, the hole mold with double eccentric circular opening ring with dimensional accuracy of 0.005mm is manually polished and inspected. The core rod is made of M42 material and undergoes rough turning, heat treatment, straightening (circular runout ≤ 0.1mm), rough grinding and fine grinding. The heat treatment process is as follows Figure 5 and Figure 6 As shown, the curved core rod with a dimensional accuracy of 0.005mm is manually polished and inspected.

[0089] Molybdenum alloy tubes (φ13×1.2mm) were subjected to internal and external surface defects removal. The inner surface of the tubes was mechanically ground on a lathe using an automatic lathe feed mechanism holding an extension rod with sandpaper at a speed of 800 rpm and a feed rate of 0.1 mm / min. The resulting inner surface was glossy and had a roughness of ≤ Ra0.8. The outer surface of the molybdenum alloy tubes was roughened using a centerless grinder with the following process parameters: a grinding wheel speed of 1455 rpm and a feed rate of 0.5 m / min. An 80-grit grinding wheel was used. The surface roughness of the molybdenum alloy tubes after grinding was ≤ Ra0.8.

[0090] The assembled rolling assembly is preheated. The rolling assembly consists of the roll shaft, gears, die, locating keys, bearing housing, and butterfly spring assembly. The die is installed using a heat-shrink mechanism, with a temperature not exceeding 150°C. After the rolling assembly is installed in the pilger mill, the die is preheated using a hydrogen flame spray for 20-30 minutes. After lubricating the inner surface of the billet, it is passed through a mandrel and fed at a rate of 0.2 mm / s, preheating the molybdenum alloy billet as it is fed.

[0091] After installing the die, apply grease to the outer diameter of the die at position 0. Verify the die is properly installed by observing the cleanliness and shape of the oil film. During pre-adjustment, adjust the upper and lower die clearances to 0-0.1mm without load. Adjust the clearance to 0 after loading. Adjust the rack and pinion clearance to 0.2-0.3mm. Rolling speed: 130-150 rpm, feed rate: 0.8-1.1mm / turn, exit jaw pressure: 0.1-0.5 MPa. Using a double-rotation, single-feed method, continuously roll molybdenum alloy seamless pipe with an outer diameter of φ9±0.03mm×0.5±0.02mm and a straightness of ≤0.1mm.

[0092] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0093] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0094] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection, or communication; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0095] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0096] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0097] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A method for hot rolling a molybdenum alloy seamless tube, characterized in that: include: Making a hole mold and a core rod mold, wherein the hole mold comprises two rollers arranged opposite to each other, and the hole defined by the rolling grooves of the rollers is in the shape of a double eccentric open ring; Treat the defects on the inner and outer surfaces of molybdenum alloy tube blanks; Configuring a rolling assembly with the pass die, installing the rolling assembly and the mandrel die on a rolling mill, preheating the pass die, and sleeve the molybdenum alloy tube onto the mandrel die; Pre-adjusting the gap between the two rollers in the pass die to a first threshold value, adjusting the gap between the two rollers in the pass die to 0 after loading, wherein the first threshold value is greater than or equal to 0, and heating the molybdenum alloy tube blank to a first preset temperature; The molybdenum alloy tube blank is rolled.

2. The hot rolling method of molybdenum alloy seamless pipe according to claim 1, characterized in that: The steps for treating defects on the inner and outer surfaces of the molybdenum alloy tube blank include: The molybdenum alloy tube blank is fixed on a lathe, an extension rod is arranged on a feeding device of the lathe, sandpaper is arranged on the extension rod, the extension rod is driven to rotate and extend into the interior of the molybdenum alloy tube blank, and the inner surface of the molybdenum alloy tube blank is mechanically polished; The outer surface of the molybdenum alloy tube is ground using a centerless grinder.

3. The hot rolling method of molybdenum alloy seamless pipe according to claim 2, characterized in that: The rotation speed of the lathe is 500 r / min to 1000 r / min, and the feed speed of the lathe is 0.1 mm / r to 0.3 mm / r; the rotation speed of the grinding wheel of the centerless grinder is 1300 r / min to 1455 r / min, and the feed speed of the molybdenum alloy tube relative to the grinding wheel in the centerless grinder is 0.3 m / min to 0.5 m / min; And / or, the surface roughness of the inner surface and the outer surface of the molybdenum alloy tube blank after defect treatment is less than or equal to Ra0.

8.

4. The hot rolling method of molybdenum alloy seamless pipe according to claim 1, characterized in that: The method for making the hole-shaped mold comprises: The material of the roll substrate is GH4169 nickel-based alloy steel; Rough turning of the shape, rough milling of the transition section, deformation section, sizing section and release section of the rolling groove in the roll, and reserve a machining allowance of 0.15mm to 0.2mm; Perform aging treatment on the rolls after rough milling; Rough and fine grinding of the rolls.

5. The hot rolling method of molybdenum alloy seamless pipe according to claim 4, characterized in that: The step of performing an aging treatment on the roll after rough milling includes: heating the roll to 650° C. to 750° C. and keeping the temperature for at least 12 hours; cooling the roll to 615° C. to 625° C. and keeping the temperature for at least 12 hours; and air cooling the roll to complete the aging treatment of the roll; And / or, the roller is finely ground to a dimensional accuracy of 0.005 mm.

6. The hot rolling method of molybdenum alloy seamless pipe according to claim 1, characterized in that: The manufacturing method of the core rod mold comprises: Configure the mandrel base material with M42 high-speed steel and rough-turn the shape; Heat treating the mandrel; Straighten, rough grind and fine grind the mandrel.

7. The hot rolling method of molybdenum alloy seamless pipe according to claim 6, characterized in that: The steps of heat treating the core rod include: Heating the mandrel to a first temperature and keeping it at that temperature for at least 20 minutes; Heating the mandrel to a second temperature and maintaining the temperature for at least 20 minutes; heating the mandrel to a third temperature and maintaining the temperature for at least 20 minutes, wherein the third temperature is 1180° C. to 1220° C., and the second temperature is greater than the first temperature and less than the third temperature; Quenching and cooling the core rod; Heat the mandrel to 530°C to 560°C and keep it warm for at least 120 minutes; The core rod is air-cooled and tempered.

8. The hot rolling method of molybdenum alloy seamless pipe according to claim 7, characterized in that: The first temperature is 500° C. to 600° C., and the second temperature is 750° C. to 820° C.; And / or, in the step of quenching and cooling the core rod, using air cooling at a pressure of more than 700Pa; And / or, in the steps of straightening, rough grinding and fine grinding the mandrel, the circular runout of the straightened mandrel is less than or equal to 0.1 mm, and the dimensional accuracy of the fine grinding mandrel reaches 0.005 mm.

9. The hot rolling method of molybdenum alloy seamless pipe according to claim 1, characterized in that: The hole-shaped die is hot-fitted into the rolling assembly, and the hot-fitting temperature is less than or equal to 150° C. And / or, in the step of preheating the hole mold, the hole mold is sprayed with a hydrogen flame for 20 minutes to 30 minutes; the step of putting the molybdenum alloy tube blank on the mandrel mold includes: applying lubricating oil on the inner surface of the molybdenum alloy tube blank, passing the molybdenum alloy tube blank through the mandrel, and feeding the molybdenum alloy tube blank through the mandrel with a single feeding distance of 0.2 mm, and preheating the molybdenum alloy tube blank during the feeding process.

10. The hot rolling method of molybdenum alloy seamless pipe according to claim 1, characterized in that: The step of pre-adjusting the gap between the two rollers in the pass mold to a first threshold value, and adjusting the gap between the two rollers in the pass mold to 0 after loading, includes: applying grease to the circumference of the pass in the pass mold, adjusting the gap between the two rollers in the rolling assembly, adjusting the gap between the two rollers to the first threshold value when no-load, judging whether the pass is installed in place based on the cleanliness and shape of the oil film, adjusting the gap between the two rollers to 0 after loading, and making the oil films corresponding to the two rollers uniform and symmetrical; and / or, the first threshold is 0 to 0.1 mm; And / or, the first preset temperature is 600 degrees Celsius to 900 degrees Celsius; And / or, during the rolling of the molybdenum alloy tube billet, the gap between the gear in the rolling assembly and the rack on the rolling mill is adjusted to 0.2 mm to 0.3 mm, the rolling speed is 130 rpm to 150 rpm, the feed amount of the rolling mill is 0.8 mm / time to 1.1 mm / time, the outlet jaw pressure of the rolling mill is 0.1 to 0.5 MPa, and the rolling mill adopts a double-rotation single-feed method for continuous rolling.

11. The method for hot rolling a molybdenum alloy seamless tube according to any one of claims 1 to 10, characterized in that: The rolling groove of the roller comprises a deformation section, a sizing section, and a release section, which are arranged in descending order along the circumference of the roller, wherein the deformation section, the sizing section, and the release section have the same groove depth, and each of the deformation section, the sizing section, and the release section comprises a plurality of segment units, which are arranged in descending order along the circumference of the roller, wherein the cross-sectional dimensions are from large to small. Each of the segment units has a first cross-section located at one end of the segment unit, a second cross-section located in the middle of the segment unit, and a third cross-section located at the other end of the segment unit, and two adjacent cross-sections are smoothly transitioned and connected; The radius of the groove bottom contour line of the second section is smaller than the radius of the groove bottom contour line of the first section and larger than the radius of the groove bottom contour line of the third section. The circles in which the groove bottom contour lines of the first section, the second section and the third section are located are eccentrically arranged in the radial direction of the rolling roller, so that the hole shape defined by the rolling groove is a double eccentric open ring.

Images